Electricity: motive power systems – Limitation of motor load – current – torque or force
Reexamination Certificate
1999-03-22
2001-02-20
Ip, Paul (Department: 2837)
Electricity: motive power systems
Limitation of motor load, current, torque or force
C318S254100, C318S132000, C318S599000
Reexamination Certificate
active
06191545
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a control apparatus for a brushless motor and to a machine and apparatus using a brushless motor. The invention relates in particular to a control apparatus for controlling the speed of rotation of a brushless motor to a desired speed. This control apparatus may be used in an air conditioner for performing air conditioning in a room by controlling a brushless motor for driving a compressor and a blower in the air conditioner, a refrigerator for carrying out refrigeration by controlling a brushless motor for driving a compressor and a blower in the refrigerator, and a washing machine for carrying out the washing of clothes by controlling a brushless motor for driving an agitator and a spinning basket in the washing machine.
A brushless motor in which a permanent magnet rotor and a stator winding are combined typically is employed in an air conditioner, a refrigerator and a washing machine, etc. from an aspect of ease of maintenance.
In a drive control of the above stated brushless motor, it is necessary to carry out control in close relationship with the magnetic pole position of the rotor and the position of the stator winding to which electric power is suppled. To detect the magnetic pole position of the rotor, without use of a rotor position detection sensor, such as a Hall element etc, a sensorless position detection system is employed using a counter electromotive voltage, which is induced in the stator winding according to a mutual operation with the magnetic pole of the rotor, allowing the magnetic pole position of the rotor to be detected.
As a brushless drive apparatus in which the above stated rotor position detection system is employed, for example, there is a brushless motor drive apparatus described in Japanese application patent laid-open publication No. Hei 7-147793. In this brushless motor drive apparatus, a direct current voltage, which is outputted from a direct current power supply, is supplied to a stator winding of a brushless motor through an inverter circuit. A terminal voltage detection means produces a detection voltage by voltage dividing the terminal voltage of the stator winding of the brushless motor, and the detection voltage is inputted to a comparison circuit. The comparison circuit outputs a phase signal by comparing the detection voltage with a standard voltage.
And, on the basis of a pulse width modulation (PWM) signal PS generated from a pulse width modulation (PWM) signal generation circuit, a control apparatus generates a latch timing signal LS according to a latch signal generation circuit to perform a latch operation after a timing in which the above stated PWM signal PS changes from an “on” condition to an “off” condition. Even when an oscillation is generated in the terminal voltage of the stator winding, without being affected by such oscillation, the phase signal from the comparison circuit is latched in a latch circuit and the position detection signal can be obtained.
SUMMARY OF THE INVENTION
In the above stated conventional brushless motor drive apparatus, an output signal from the latch circuit is delayed with time from the phase signal which is outputted from the comparison circuit and, accordingly, the detection position of the rotor magnetic pole which is obtained becomes displaced widely from the actual position of the magnetic pole of the rotor.
As stated above, when the detection timing of the position detection signal deviates widely, the commutation (electric supply) phase of the stator winding current of the brushless motor is delayed, resulting in an increase in current delays, and the current rises up immediately prior to a change-over of the winding current. This places an increased burden on the drive circuit due to a lowering of the operating efficiency and a sharp rise-up by the current, with a result that an increase of the current capacity of the circuit elements is necessary, which results in an increase in the manufacturing cost. Or, during the latch timing, the noises overlap with the output signal of the comparison circuit due to the disturbance noises, and, when a phase signal which deviates widely in position from an original position detection signal is latched, the brushless motor can not be driven normally, resulting in a problem in which the brushless motor vibrates or stops.
Further, in the above stated conventional brushless motor drive apparatus, since the latch operation is carried out after the timing in which the PWM signal PS changes from the “on” condition to the “off” condition, when the conduction ratio during PWM control is 100%, there is an problem in that a gate signal of the latch circuit can not be defined or the gate signal in the conduction ratio at 100% of PWM control etc. can not be defined.
An object of the present invention is to provide a control apparatus for a brushless motor wherein the magnetic pole position detection accuracy of a rotor in the brushless motor can be heightened and an accurate control can be carried out.
Another object of the present invention is to provide a control apparatus for a brushless motor wherein the position detection error due to noises can be reduced.
A further object of the present invention is to provide a control apparatus for a brushless motor wherein an electric supply error operation due to noises can be reduced.
A still further object of the present invention is to provide a control apparatus for a brushless motor wherein the control range can be enlarged.
A further object of the present invention is to provide a control apparatus for a brushless motor wherein the operation of a brushless motor can be controlled by an efficiency importance characteristic or can be controlled by a high speed importance characteristic.
Yet another object of the present invention is to provide a control apparatus for a brushless motor wherein a wide control range can be attained.
Still another object of the present invention is to provide a control apparatus for a brushless motor wherein, when the period of return flow current after an electric supply change-over is very long without stopping the brushless motor, a good control can be carried out.
A further object of the present invention is to provide a machine and apparatus, in which a brushless motor controlled as stated above becomes a power source, in particular, for an apparatus such as an air conditioner, a refrigerator, or a washing machine.
One feature according to the present invention resides in the fact that in a control apparatus for use in a brushless motor in which, by detecting a position of a magnetic pole of a rotor according to a terminal voltage of a stator winding of a respective phase, an electric supply to the stator winding is controlled, and an “on” period and an “off” period of the PWM signal is extracted in accordance with a comparison result information signal in which a detection voltage in response to the terminal voltage is compared with a standard voltage.
Another feature according to the present invention resides in the fact that, during the “on” period of the PWM signal, extracted according to the terminal voltage of the stator winding, the above stated comparison result information signal, which is output as a phase signal as it is during the “off” period by holding an immediately prior comparison result information signal, is output as a phase signal.
Another feature according to the present invention resides in the fact that the position of the rotor is detected in accordance with a pattern of the comparison result information signal of the stator winding of plural phases.
A further feature according to the present invention resides in the fact that an electric supply pattern to the stator winding is determined in accordance with a pattern of the comparison result information signal of the stator winding of plural phases.
Another feature according to the present invention resides in the fact that the period in which a return flow current flows after an electric supply change-over is detected in accordance with a pa
Kawabata Yukio
Notohara Yasuo
Tahara Kazuo
Antonelli, Terry Stout & Kraus, LLP.
Hitachi , Ltd.
Ip Paul
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