JP2005083683A - Refrigerator and its operation control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To save energy, while having the function required as a refrigerator, by miniaturizing a motor, by controlling a weak field in a dehydrating process, by designing the motor by a rotating speed and a load in a washing process, in a fully automatic washer and a fully automatic washing drier. <P>SOLUTION: This refrigerator has an electric motor for driving a compressor, an inverter for rotatably controlling this electric motor, and a converter for supplying a direct current of variable voltage to this inverter by inputting an alternating current. The refrigerator has a first operation mode for operating a rotating speed of the electric motor in a speed area not more than a first rotating speed, and a second operation mode for operating the rotating speed of the electric motor at a second speed larger than the first rotating speed, and has a third operation mode for operating the rotating speed of the electric motor at a third speed larger than a second rotating speed. The refrigerator is constituted so as to control the rotating speed of the electric motor, by controlling the weak field in the third operation mode. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an inverter refrigerator including a power supply circuit that rectifies AC and outputs a desired DC voltage, and an electric motor drive circuit that drives an electric motor.

  As a method for controlling the rotation speed of an electric motor that drives a compressor provided in the refrigerator, there is a refrigerator described in Patent Document 1 that uses so-called PWM control. In this example, when controlling the rotation speed of a brushless motor, which is often used as an electric motor for operating a refrigerator compressor (mainly reciprocating type), the rotation speed is controlled by changing the conduction ratio by PWM control. doing.

  On the other hand, Patent Document 2 discloses a method for performing field-weakening control as a method for controlling the rotational speed of a motor.

  In the example described in Patent Document 2, washing is performed by a fully automatic washing machine and a fully automatic washing and drying machine, dehydration is performed, and a motor is driven by a variable frequency control device having a vector control function. During washing, the motor voltage is varied to control the rotation speed of the motor, and during dehydration, field weakening control is performed from the washing time to control the rotation speed of the motor.

  When the motor is driven by an inverter, it can be set to an arbitrary number of revolutions because it can be set to a variable frequency. There is a method of drying.

  Table 1 shows the torque with respect to the required rotational speed and the output at that time when the induction motor is driven by a brushless motor or a V / F constant control inverter of a fully automatic washing machine and a fully automatic washing dryer in which the reduction gear ratio of the reduction gear is constant. The relationship between the motor voltage and current for outputting the output is shown. The motor voltage and current are shown as approximate calculated values assuming that the motor efficiency is 100%.

  From Table 1, when the reduction ratio is constant, if the motor voltage of the dehydration process with the highest rotation speed is set to the maximum 200 V with a constant V / F control inverter, the current increases to 29.3 V and 9.3 A in the washing process. . In the drying process, the motor voltage is minimized to 12.2 V, but the current is a relatively large value of 4.6 A. That is, the motor current varies greatly in each process, and the motor must be designed so that the motor can withstand the motor current 9.3A in the washing process from the design of the motor.

  On the other hand, Table 2 shows an example in which the required motor rotation speed of 1200 min-1 in the washing process is set to the specified rotation speed. From Table 2, if the motor rotation speed for washing is the specified rotation speed, the rated voltage is reached at 1200 min-1, and the voltage at this time is 200 V, so the current is 1.23 A. Since 9000 min-1 during dehydration, field weakening control is performed, so the voltage is maintained at the rated voltage of 200V.

  On the other hand, since the drying process is performed at a rotational speed equal to or lower than the specified rotational speed, the voltage is reduced by a ratio with respect to the specified rotational speed to 92 V and the current is 0.61 A. As described above, the difference in the current value of the motor current in each step can be reduced, so that the motor can be miniaturized.

JP 2001-50625 A

Japanese Patent Laid-Open No. 4-126192

  Considering the usage pattern of refrigerators in general households, it is considered that doors are not frequently opened and closed throughout the day. Therefore, assuming that the refrigerator is almost closed when viewed throughout the day, it is sufficient for the refrigeration cycle to generate cold air commensurate with heat intrusion from the outside when the door is closed. The operation of the compressor at this time may be low speed rotation. Therefore, if the electric motor is designed so as to improve the efficiency in the low-speed rotation region, the power consumption can be reduced and energy saving can be achieved.

  However, refrigerators require sufficient cooling capacity for quick freezing and quick ice making, etc., and motors require high-speed rotation, but increasing the motor efficiency in the low-speed rotation region as described above will increase the number of rotations sufficient for quick freezing etc. There was a problem that could not get.

  Patent Document 2 describes that in a fully automatic washing machine and a fully automatic washing / drying machine, the motor is designed with the rotation speed and load in the washing process, and the motor is miniaturized by performing field weakening control during the dehydration process. However, there is no description of a specific configuration that saves energy while having the functions required for a refrigerator. Moreover, since it is not examined for refrigerators, no further energy saving is disclosed.

  The objective of this invention is providing the refrigerator which can achieve energy saving, having the function requested | required as a refrigerator.

  The second object of the present invention is to provide a refrigerator capable of securing cooling power such as quick freezing while achieving energy saving.

The object includes, for example, an electric motor that drives a compressor, an inverter that inputs a direct current and outputs a pulse train for driving the electric motor, and a direct current generation circuit that changes a direct current voltage input to the inverter. A refrigerator,
This is achieved by controlling the conduction rate of the inverter to control the rotation speed of the electric motor, and performing field-weakening control when the conduction rate reaches a predetermined value.

In addition, the DC voltage that achieves the rotational speed command for the electric motor is calculated,
The calculated DC voltage is compared with a preset threshold voltage,
This is achieved by providing a function of performing field-weakening control when the calculated DC voltage is higher than the threshold voltage.

  In addition, when the DC voltage that achieves the rotation speed command of the electric motor is higher than the maximum voltage that can be generated by the DC generation circuit, this is achieved by providing a function to weaken the electric motor and perform field control.

  Further, when the rotational speed of the electric motor is increased to a predetermined rotational speed, the predetermined rotational speed is compared with a predetermined rotational speed, and the predetermined rotational speed is higher than the predetermined rotational speed. In some cases, this is achieved by providing a function of performing field weakening control.

  Further, in a refrigerator including an electric motor that drives a compressor and an inverter that controls the rotation of the electric motor, a first operation mode in which the rotational speed of the electric motor is operated in a speed region equal to or lower than a first rotational speed; A second operation mode in which the rotation speed of the electric motor is operated at a second speed greater than the first rotation speed, and the rotation speed of the electric motor is operated at a third speed greater than the second rotation speed. And a third operation mode, and in the third operation mode, the field-weakening control is performed to control the rotation speed of the electric motor.

  In the refrigerator, when the pulse width modulation control of the inverter reaches a predetermined value, the speed control function in the first operation mode is switched to the second control function, while the pulse width modulation control is performed. Has a function of switching from the speed control function of the second operation mode to the first control function when the pulse width modulation control of the inverter reaches a predetermined value. This is achieved by providing a function for switching from the speed control function in the second operation mode to the third control function.

  In the above refrigerator, when the quick freezing switch is pressed and an operation command is set, the speed control function in the second operation mode is switched to the third control function, and the quick freezing operation time is reached or This is achieved by providing a function of switching from the speed control function of the third operation mode to the second control function when the operation command is canceled by the quick freezing switch.

  Further, means for adjusting the number of revolutions of the electric motor by controlling a chopping operation of the switching element constituting the inverter based on a deviation between the set temperature and the refrigerator freezer temperature, and the set temperature is increased to increase the set temperature. A first operation mode in which the number of revolutions is equal to or less than a predetermined value in the operation region; and a means for ending the first operation mode when the freezer temperature reaches a predetermined value higher than the set temperature; The second operation mode in which the set temperature is lowered and the rotation speed of the electric motor is set to a predetermined value in the operation region, and when the refrigerating capacity is further required during the second operation mode period, This is achieved by providing a function for switching to the third control function.

Also, a refrigerator operation control method for controlling the temperature in the refrigerator by controlling the number of revolutions of the electric motor that drives the compressor in response to a signal of an external quick freeze operation command,
When the quick freeze operation command signal is received, a voltage to be applied to the electric motor to rotate the electric motor at a predetermined rotational speed is compared with a preset threshold voltage,
This is achieved by performing field-weakening control when the voltage to be applied exceeds the threshold voltage to control the rotation of the motor.

  In the above operation control method, the threshold voltage is achieved by setting the threshold voltage to a maximum voltage that can be generated by the DC generation circuit.

  According to the present invention, it is possible to provide a refrigerator that can significantly reduce the refrigeration and ice making time, and that can design a motor at a low speed, thereby increasing motor efficiency and reducing power consumption. Moreover, the refrigerator which can ensure cooling power, such as quick freezing, can achieve providing energy saving.

  Demand for refrigerators includes quick freezing, such as quick freezing when cooking foods are stored frozen, quick ice making to make ice in a short time, and since refrigerators are always used with ordinary power plugs in ordinary households, there is an annual electricity bill It is energy saving that it is cheap (low annual power consumption). For quick refrigeration and quick ice making, it is achieved by increasing the number of revolutions of the compressor and increasing the amount of refrigerant circulating in the refrigeration cycle. However, in order to save energy, it is necessary to operate the compressor at a low speed. . There are the following problems when trying to achieve both the operation of the compressor at high speed and the operation of the compressor at low speed.

Currently, a motor for operating a compressor for a refrigerator (mainly a reciprocating type) is often used as a brushless motor in which a permanent magnet is embedded in a rotor and a rotor is rotated by generating a rotating magnetic field by an inverter. Yes. The rotation speed of the brushless motor is expressed by the following equation.
N = (V-IR) / kΦ
Here, N is the rotational speed of the motor, V is the voltage applied to the motor, I is the motor current, R is the internal resistance of the motor, k is a coefficient, and Φ is the magnetic flux density.

  As understood from this equation, the higher the motor applied voltage V and the smaller the motor internal resistance R, the higher the rotation speed. When the voltage doubler circuit is used, the DC voltage input to the inverter is 288V (about 250V when the load is connected), which is twice 144V. However, the internal resistance R of the motor can be either high-speed or low-speed. For example, in the case of high-speed rotation specifications, the value of the internal resistance R is reduced by setting the number of turns, which is the number of windings of the stator of the motor, to 120 turns (one example). However, when the specification of the electric motor is set to the high speed side as described above, there is a problem that the efficiency of the electric motor is remarkably lowered in a low speed region.

  On the other hand, if the number of windings of the stator winding is 140 turns (one example) in order to match the motor specifications to the low speed range (increase the efficiency in the low speed range), the motor applied voltage V is constant and the motor internal resistance R is Since it becomes large, there exists a problem that the rotation speed required for quick freezing and quick ice making cannot be obtained.

  Therefore, in the present embodiment, the motor specifications are adjusted to the low speed range, and the high speed rotation of the motor is realized by field weakening control in the high speed range.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 illustrates a control device for a refrigerator, and is an overall configuration diagram of an electric motor control device including a converter circuit that converts an AC voltage into a DC voltage, and an electric motor drive unit that includes an inverter circuit and an electric motor for a compressor. .

  An inverter that converts direct current into alternating current that generates a rotating magnetic field for rotating the electric motor is connected to the capacitor. A compressor driving motor is connected to the inverter. The compressor driven by the electric motor is housed in a sealed container together with the electric motor, and is mainly a reciprocating type compressor. In addition, a rotary type or scroll type compressor may be used.

  The inverter circuit is a three-phase inverter, and an IGBT (insulated gate bipolar transistor) is used as a switching element in this embodiment. These switching elements are each connected in parallel with a reflux diode. Then, the conduction ratio in the conduction period of each phase is controlled (pulse width control) based on the output of the rotational position detection of the motor so that the direct current supplied from the capacitor is set by the control unit. The number of rotations is controlled.

  This system is configured to amplify the voltage across the shunt resistor provided in the inverter and take in the DC voltage Idc into the control system using an A / D converter built in the microcomputer. Neither the magnetic pole position sensor nor the motor current sensor is provided.

  The shunt resistor is a current detection resistor, and this current detection value is sent to the overcurrent detection circuit. When this current detection value exceeds the threshold level, a signal is output to the driver that turns off all the switching elements that make up the inverter. Then, the driver turns off the switching element. This is provided because there is no current minor loop in the inverter control.

  Next, means for controlling the rotation speed of the compressor motor will be described below. The control of the DC voltage of the converter circuit will be described. The converter circuit is a direct current generating circuit that changes the direct current voltage input to the inverter. The direct current voltage in the present embodiment is equal to the first operation mode of full wave rectification and voltage doubler rectification by a semiconductor element of the converter circuit, for example, SSR. Switch to the second operation mode.

  A temperature deviation is calculated by comparing the freezer compartment set temperature with the actual freezer compartment temperature from the temperature detector installed in the freezer compartment. On the other hand, the induced voltage of the motor is input to the position detector, the magnet position is calculated from the induced voltage, and the rotational speed (speed) of the motor is output from the control unit via the driver based on this position signal.

  Next, the rotation speed mode switching of the compressor will be described based on the motor applied voltage and the conduction ratio in FIG. The solid line indicates the DC voltage applied to the compressor motor, and the dotted line indicates the duty (current ratio) of the inverter circuit. When the pulse width modulation control of the inverter reaches a predetermined value (for example, 100%), the full-wave rectifier circuit in the first operation mode is switched to the voltage doubler rectifier circuit in the second operation mode, and the pulse When the width modulation control reaches a predetermined value (for example, 50%), the voltage doubler rectifier circuit in the second operation mode is switched to the full-wave rectifier circuit in the first operation mode.

  Next, when the pulse width modulation control of the inverter reaches a predetermined value (for example, 100%) in the state of the voltage doubler rectifier circuit in the second operation mode, switching to field weakening control as the third control function is performed. During field-weakening control, which is the third operation mode, the number of revolutions is varied by controlling the induced voltage of the compressor motor.

In the present embodiment, in the full-wave rectifier circuit that is the first operation mode, 2400 min ⁻¹ is the first rotation speed and the conduction rate is 100%. Further, in the voltage doubler rectifier circuit that is the second operation mode, 3800 min ⁻¹ is the second rotation speed, and in the voltage doubler rectifier circuit, the energization rate is 100%.

That is, the rotational speed of the brushless motor is expressed by the following equation as described above.
N = (V-IR) / kΦ
Here, N is the rotational speed of the motor, V is the voltage applied to the motor, I is the motor current, R is the internal resistance of the motor, k is a coefficient, and Φ is the magnetic flux density.

  As can be understood from this equation, the higher the motor applied voltage V and the smaller the motor internal resistance R, the higher the speed of rotation, but the motor applied voltage is the maximum during field weakening control in the third operation mode. is there. Therefore, the rotational speed cannot be changed unless the portion of the induced voltage (V-IR) is controlled.

  When the quick freeze button, which is a function of the refrigerator, is pressed, the rotation speed of the compressor motor is set to the maximum rotation speed, so that the mode for field weakening control, which is the third operation mode described above, is set. The quick freezing operation is performed for a maximum of 2 hours until the quick freezing button is manually released or the timer is turned off.

  With the above quick freezing (ice making) operation function, the maximum ice crystal formation zone passage time can be made within 30 minutes, and high quality freezing has become possible.

  Further, the mode becomes the field-weakening control that is the third operation mode not only when the rotation speed is high speed but also when the cycle load is large, such as when the refrigerator internal temperature is not cold. For example, when warm food is put in, when the door is opened for a long time, when the outside air temperature is very high, the cycle load becomes large.

  In PWM control, the lower the DC voltage, the better the motor efficiency. The reason for this will be described with reference to FIG. FIG. 3A shows a PWM waveform of the switching element of the inverter when the DC stage voltage is high. When the switching element is on, the motor current flows from the capacitor. When the switching element is off, the motor current is circulated and attenuated via the freewheeling diode. Let this amplitude value be ΔIM. Similarly, FIG. 3B shows a case where the DC stage voltage is decreased and the same voltage as that shown in FIG. 3A is applied to the electric motor 7. At this time, since the DC stage voltage is low, even if the switching element is turned on, the rate of increase in current is small, so ΔIM is small compared to (a). This ΔIM is a value representing the pulsation magnetic flux density of the electric motor, and a smaller value means that the iron loss of the electric motor is smaller. Therefore, the motor efficiency is improved as the conduction ratio is increased.

FIG. 4 shows the motor efficiency characteristics of the present invention. As described above, in PWM control, the motor efficiency is improved when the DC voltage is lower. As in the normal motor design, the DC voltage is designed so that the maximum rotation of 4800 min ⁻¹ can be operated at 280 V at the time of voltage doubler rectification. However, motor efficiency generally decreases.

  Therefore, the first operation mode is designed so that the motor efficiency is improved, and the problem that the applied voltage of the motor is insufficient and the rotation does not increase during high-speed rotation is compensated by field control.

  FIG. 5 shows a field-weakening control flowchart during the quick freezing operation as an example of the third operation mode. When an external quick freezing operation command signal is input, the quick freezing operation is started. That is, when the quick freezing operation is set by the quick freezing switch (101), the quick freezing operation time is set by the timer (102), and the rotation speed of the compressor is increased (103). When increasing the voltage, if the DC voltage V1 obtained by rectifying the AC voltage is equal to or higher than a predetermined threshold voltage Vlim, field weakening control is performed, and high-speed operation is possible.

  In this example, the threshold voltage Vlim is determined from the voltage applied to the electric motor when the commercial power supply is converted to direct current, and is 280 V in this example. In this case, the voltage V1 required for operation at the set rotational speed is compared with the threshold voltage Vlim (104), and control is performed so that the third operation mode is established when V1 is greater than Vlim ( 105). In other words, the third operation mode is entered when the Vlim value, which is the voltage actually applied to the motor, is lower than the voltage V1 required for operation at the set rotational speed.

  In this example, V1 uses a value calculated by the control unit as a voltage necessary for the set rotation speed. Therefore, Vlim is a voltage that is actually applied to the motor as a value obtained by converting a commercial power source into a direct current by a converter circuit. In other words, this threshold voltage Vlim is a maximum voltage generated by a converter circuit that is a direct current generation circuit. . When V1> Vlim, that is, when the actually applied voltage is lower than the required voltage, field-weakening control is performed.

  In this embodiment, the threshold voltage Vlim is set to the maximum voltage generated by the converter circuit, so that the reduction in motor efficiency that is lowered during field-weakening control can be reduced.

  In the above example, whether or not the third operation mode is set is determined by comparing V1 and Vlim. However, it may be determined by comparing the rotation speeds corresponding to them.

  Thereafter, it is determined whether or not a signal for canceling the quick freezing operation is input by the quick freezing switch (106), and when it is canceled by the signal or whether the quick freezing set time set by the reference numeral 102 has elapsed is determined. (107) When the time has elapsed, the compressor rotational speed is decreased (108), and the field weakening control is canceled (109).

  In addition, when V1 <Vlim, that is, in the case of “No” of reference numeral 104, does not enter the third operation mode, is the quick freezing operation performed in the second operation mode, and is the quick freezing operation released? When the set time has elapsed, the voltage is controlled to reduce the rotational speed of the compressor. At this time, step 109 is omitted.

  In the embodiment described above, various numerical values are shown and described. However, these numerical values are merely examples, and other numerical values may be used as long as they match the control concept.

  As described above, the present embodiment has the following effects. The compressor motor is designed with the highest utilization factor (for example, at the minimum rotation speed), so that the motor efficiency can be improved, and the system energy can be saved. When the quick freeze button of the refrigerator is pressed and the compressor motor operates at high speed or when the load is high, the compressor motor can be operated at high speed by the field weakening control as described above.

The control apparatus block diagram of the refrigerator which concerns on this Embodiment. The figure showing a motor applied voltage and a conduction rate. The figure which shows the electric current when changing the pulse width at the time of pulse width modulation. Motor efficiency characteristics of the present invention. The weak field control flowchart during a quick freezing operation.

Claims (10)

A refrigerator including an electric motor for driving a compressor, an inverter for inputting a direct current and outputting a pulse train for driving the electric motor, and a direct current generating circuit for changing a direct current voltage input to the inverter,
A refrigerator having a function of controlling the current passing rate of the inverter to control the rotation speed of the electric motor and performing field-weakening control when the current passing rate reaches a predetermined value. A refrigerator including an electric motor for driving a compressor, an inverter for inputting a direct current and outputting a pulse train for driving the electric motor, and a direct current generating circuit for changing a direct current voltage input to the inverter,
Calculate the DC voltage to achieve the rotational speed command for the electric motor,
The calculated DC voltage is compared with a preset threshold voltage,
A refrigerator having a function of performing field-weakening control when the calculated DC voltage is higher than the threshold voltage. A refrigerator including an electric motor for driving a compressor, an inverter for inputting a direct current and outputting a pulse train for driving the electric motor, and a direct current generating circuit for changing a direct current voltage input to the inverter,
A refrigerator having a function of performing field control by weakening the motor when the DC voltage that achieves the rotation speed command of the motor exceeds a maximum voltage that can be generated by the DC generation circuit. A refrigerator including an electric motor for driving a compressor, an inverter for inputting a direct current and outputting a pulse train for driving the electric motor, and a direct current generating circuit for changing a direct current voltage input to the inverter,
When increasing the rotational speed of the electric motor to a predetermined rotational speed, the predetermined rotational speed is compared with a predetermined rotational speed,
A refrigerator having a function of performing field-weakening control when the predetermined rotational speed is higher than the predetermined rotational speed.   In a refrigerator including an electric motor that drives a compressor and an inverter that controls rotation of the electric motor, a first operation mode in which the rotational speed of the electric motor is operated in a speed region equal to or lower than a first rotational speed, and the electric motor A second operation mode in which the rotational speed is operated at a second speed greater than the first rotational speed, and a third rotational speed of the electric motor is operated at a third speed greater than the second rotational speed. The refrigerator is characterized in that, in the third operation mode, field-weakening control is performed to control the rotational speed of the electric motor.   When the pulse width modulation control of the inverter reaches a predetermined value, the speed control function of the first operation mode is switched to the second control function, while the pulse width modulation control reaches a predetermined value. A function of switching from the speed control function of the second operation mode to the first control function, and when the pulse width modulation control of the inverter reaches a predetermined value, the speed control of the second operation mode The refrigerator according to claim 5, further comprising a function for switching from a function to the third control function.   When the quick freezing switch is pressed and an operation command is set, the speed control function in the second operation mode is switched to the third control function, and when the quick freezing operation time is reached or the operation command is issued by the quick freezing switch. The refrigerator according to claim 6, comprising a function of switching from the speed control function of the third operation mode to the second control function when released.   Means for adjusting the number of revolutions of the motor by controlling the chopping operation of the switching elements constituting the inverter based on the deviation between the set temperature and the refrigerator freezer temperature; and the number of revolutions of the motor by increasing the set temperature. A first operation mode in which the operating temperature is equal to or less than a predetermined value in the operation region, means for ending the first operation mode when the freezer compartment temperature reaches a predetermined value higher than the set temperature, and the setting A second operation mode in which the value temperature is lowered and the rotation speed of the electric motor is set to a predetermined value in the operation region; and during the second operation mode period, when the refrigerating capacity is further required, the third operation mode The refrigerator according to claim 6, further comprising a function of switching to the control function. A refrigerator operation control method for controlling the temperature in the refrigerator by controlling the number of revolutions of an electric motor that drives the compressor according to a signal of an external quick freeze operation command,
When the quick freeze operation command signal is received, a voltage to be applied to the electric motor to rotate the electric motor at a predetermined rotational speed is compared with a preset threshold voltage,
An operation control method for a refrigerator, in which field weakening control is performed to control rotation of the electric motor when the voltage to be applied exceeds the threshold voltage. 10. The refrigerator operation control method according to claim 9, wherein the threshold voltage is a maximum voltage that can be generated by the DC generation circuit.

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