Refrigeration – Automatic control – Refrigeration producer
Reexamination Certificate
1999-11-24
2001-04-24
Tanner, Harry B. (Department: 3744)
Refrigeration
Automatic control
Refrigeration producer
C062S229000
Reexamination Certificate
active
06220045
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus and method for controlling a resonance frequency of an inverter refrigerator and, in particular, to an apparatus and method for controlling a resonant frequency of an inverter refrigerator whereby, in a compressor of an inverter refrigerator, when a current rotation frequency is converted to a target rotation frequency in the rotor detecting operation mode, an operation of the compressor is implemented in a frequency band higher or lower than a resonance frequency band.
2. Description of the Conventional Art
An inverter refrigerator rectifies a frequency(60 Hz) of an AC power source by a direct current and changes a supplied frequency(PWM) at the same time, whereby a rotation frequency of a compressor motor is adjusted and the amount of coolant compressed according to the adjusted frequency is controlled. Thus, in the case that there is much food in a refrigerator which food must be stored at a lower temperature as shown in
FIG. 1
, that is, in the case that the temperature in the refrigerator is higher than a set temperature, the rotation speed of a compressor is increased(usually, at a rotation frequency of higher than 60 Hz) for thereby taking much quantity of heat away. In the case that the amount of food is small or there is no food, that is, the temperature detected in the refrigerator is the same as the set temperature or is lower than the set temperature, the operation is performed at a lower speed(usually, at a speed of higher than 60 Hz) so that a small quantity of heat can be taken away from the foods, thereby reducing the energy consumed for compressing an unnecessary coolant.
The operation control of the compressor motor of the inverter refrigerator for performing the operation described above can be divided into three segments. As shown in
FIG. 3
, a first segment is an initial positioning mode for setting the rotor to a regular phase all the time by providing an electric current before starting the operation, a second segment is a synchronous operation mode for forcibly applying a current corresponding to a set starting torque, thereby accelerating the motor, because the initial rotation frequency of the motor is low and thus an induced electromotive force cannot be sensed, and a third segment is a rotor detecting operation mode for distributing a current appropriate for each phase of a stator according to a position information generated by an induced electromotive force and controlling the same when enough induced electromotive force can be detected based on an increased rotation frequency of the motor.
FIG. 2
is an example of a rotor position sensor of a conventional inverter refrigerator. The description thereof will be provided as follows.
There are two kinds of rotor position sensors; one is a hall sensor, and the other is a sensorless type. In a conventional inventor refrigerator motor, a stator
220
has an extra hall element for sensing an electric magnetic field when a magnet of a rotor
210
approaches the extra hall element. At present, the sensorless type is being generally used, considering a high pressure and current leakage in the compressor. The sensing principle thereof is that as a permanent magnet of the rotor is rotated near a coil wound on the stator
220
, an induced electromotive force is generated at the coil based on the operation of an electric generator, thereby detecting the position of the rotor
210
. In this way, the position of the rotor
210
is detected, whereby the current is flown to two phases(AB-BC-CA) of three phases(A, B, C) for sensing the induced electromotive force and supplying power, thus generating a rotation force, so that the rotor
210
is rotated.
FIG. 3
is a graph showing a frequency characteristic in the operation control mode of a compressor of a conventional inverter refrigerator. As shown in
FIG. 2
, the rotor
210
has a certain phase obtained by applying a current to three phases of the stator
220
, respectively, for a certain time before starting the motor. The rotor is operated at the same phase for thereby obtaining a certain rotation. The above described operation is called as an initial positioning mode.
Thereafter, by selecting a starting pattern(a certain voltage and current), which is capable of generating a certain starting torque among a plurality of starting patterns according to the power voltage supplied when a start-up command signal is outputted to a semiconductor switching element having a certain phase, a current corresponding to the starting torque is supplied to thereby start the motor. Before performing the above starting operation, the rotor
210
must always be located at a certain position in the stator
210
. The rotor
210
is located at a certain position based on an electric magnetic field formed by supplying a current corresponding to a certain phase of the stator. When the start-up operation is thusly prepared, a starting current is supplied for thereby driving the motor, so that the motor is operated in the synchronous operation mode.
Next, the rotor detecting operation mode will be described as follows referring to FIG.
4
.
As shown in
FIG. 3
, when a transition segment is passed over, the position of the rotor is detected by a position detector
410
based on the induced electromotive force. The thusly detected position is outputted to a rotation frequency detector
440
to detect a rotation frequency. Then, the interior temperature of the refrigerator is judged by a set rotation frequency command unit
430
for thereby determining whether the rotor is operated at a lower RPM or a higher RPM. The current ratio supplied to each phase is differently set using a duty setting unit
450
according to a result of the determination. Six semiconductor switching elements each connected to a corresponding phase by a chopping signal generator
460
are controlled to thereby control the RPM of the compressor motor at a certain frequency.
In the above described conventional art, there is a problem that, as shown in
FIG. 5
, when an operating frequency passes through a frequency band in which a resonance occurs at the compressor or when the operating frequency is set in a resonance frequency band, the operating frequency is resonated, so that strong noises and vibrations occur.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an apparatus and method for implementing an operation of an inverter refrigerator in a higher or lower frequency band than a resonance frequency band when the current rotation frequency is converted to a target rotation frequency in the rotor detecting operation mode.
To achieve the above object, a resonance frequency controller of an inverter refrigerator of the present invention includes: a temperature sensing unit for sensing an interior temperature of a refrigerator; a desired operating frequency determination unit for determining the desired operating frequency by checking the state of the refrigerator based on the temperature sensed in the above temperature sensing unit; an initial operating frequency setting unit for setting a first operating frequency during an initial start-up of a compressor; a resonance band judgement unit for judging whether a set resonance frequency band(hereinafter, called as a “resonance band”) exists between the operating frequency and the initial operating frequency, which are inputted from the desired operating frequency determination unit and the initial operating frequency setting unit; an operating frequency control unit for varying the operating frequency determined by the desired operating frequency determination unit according to a result of the determination by the resonance band judgement unit and outputting the varied operating frequency; and a compressor driving unit for driving the compressor in accordance with the operating frequency outputted from the operating frequency control unit.
The operating frequency control unit includes a variable speed setting unit for deviati
Fleshner & Kim LLP
LG Electronics Inc.
Tanner Harry B.
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