KR20010020667A - Refrigerator - Google Patents

Abstract

PURPOSE: To obtain a suitable PAM control function by providing a first control mode wherein the number of revolution of a motor is controlled by means of a pulse width modulation function of an inverter and a second control mode wherein the number of revolution of the motor is controlled by means of a voltage variable function of a converter. CONSTITUTION: In the refrigerator, either a PAM control or a PWM control is selected by a PWM/PAM selector 150, as a means for controlling the number of revolution of a motor, while a switch in a selector 152 is changed over according to the result decided by a decision instrument 151. The PWM control is changed over to the PAM control when a duty of an inverter PWM duty command generator 195 is judged to be a predetermined value by the decision instrument 151. For changing over from the PAM control to the PWM control, a DC stage voltage command value to be outputted to the converter generated by a converter PAM voltage command generator 106 is made an object for judgment as a substitute for an actual DC voltage. Thus, a PAM control function suitable as a motor control device for a refrigerator can be obtained.

Description

Refrigerator {REFRIGERATOR}

The present invention relates to an inverter refrigerator comprising a power supply circuit for rectifying alternating current and outputting a desired direct current voltage, and an electric motor drive circuit for driving an electric motor.

Conventionally, the use of so-called PAM control means for controlling a DC voltage as an electric motor control device for driving a compressor for refrigerators is described in Japanese Patent Application Laid-Open Nos. 7-260309 (Patent 1) and 7-218097 (Document 2). have. In addition, Japanese Patent Application Laid-Open No. 63-224698 (Patent 3) is known as using a PAM control means as a control device for an electric motor. In this document 3, the motor speed is controlled by controlling the output pulse width of the pulse width modulation inverter by keeping the DC voltage constant in the low speed region of the motor rotation speed. In the high speed region, the DC voltage boosting of the converter is performed by only operating the inverter with current. The so-called linear PAM control for driving control of an electric motor by a function is described, and switching between drive control (PWM control) of an electric motor by an inverter and drive control (PAM control) of an electric motor by a converter is performed. It is described that switching is performed when the flow rate of control reaches a predetermined value, and when the converter output real DC voltage reaches a predetermined value from PAM control to PWM control.

Documents 1 and 2 describe energy saving by using a PAM inverter as a control device for a compressor driving motor for a refrigerator. However, nothing is described about implementing PAM control as a control device for a compressor driving motor for a refrigerator. It is not. In addition, in the structure like document 3, it is not savored for a refrigerator.

In addition, the power supply voltage (voltage of the alternating current supplied to the household outlet) for driving the electric motor is ± 7.5% of the reference value in consideration of the allowable fluctuation amount and the voltage drop in the home determined by the Electricity Business Law. In the conventional motor control apparatus using a double voltage circuit, the DC voltage is 260V to 303V, and the difference between the maximum value and the minimum value may be 43V. When the DC voltage is low, the motor may not start.

An object of the present invention is to provide a refrigerator having a PAM control function suitable as an electric motor control device for a refrigerator.

The 2nd object of this invention is to provide the refrigerator which can start a compressor even if the voltage of a power supply changes.

The first object of the present invention is a refrigerator having an electric motor for driving a compressor, an inverter for controlling rotation of the electric motor, and a converter for inputting alternating current to supply a direct current of a variable voltage to the inverter, wherein the temperature in the refrigerator and the set temperature are provided. A first control mode in which the rotational speed of the motor is controlled in accordance with the pulse width modulation function of the inverter, and the rotational speed of the motor is controlled according to the voltage varying function of the converter so as to approach a speed command generated based on It is achieved by having a second control mode of.

The first object of the present invention is a refrigerator including an electric motor for driving a compressor, an inverter for rotationally controlling the electric motor, and a converter for inputting alternating current to supply a direct current of a variable voltage to the inverter. A first control mode in which the rotational speed of the motor is controlled by the pulse width modulation function of the inverter so as to approach a speed command generated based on a set temperature, and the rotational speed of the motor is controlled by a voltage varying function of the converter. And a second control mode for controlling the control, and when the flow rate in the pulse width modulation function of the inverter reaches a predetermined value, the control unit switches to the second control mode from the first control mode, and When the direct current voltage command reaches a predetermined value, it is provided with a function of switching from the second control mode to the first control mode. It is sex.

The second object of the present invention is a refrigerator including an electric motor for driving a compressor, an inverter for rotationally controlling the electric motor, and a converter for inputting alternating current to supply a direct current of a variable voltage to the inverter. In this case, it is achieved by providing a means for raising the DC voltage supplied to the inverter higher than the value obtained by converting the AC to DC.

1 is a control block diagram of a refrigerator according to the present embodiment;

2 is a diagram showing a direct current voltage and a flow rate.

3 shows details of the PWM / PAM selector 150.

4 is a diagram showing details of the speed command generator 140. FIG.

5 is a block diagram illustrating an insulation structure of a refrigerator.

Fig. 6 is a diagram showing the transition of the DC voltage at the time of starting the motor.

7 shows power device characteristics of an inverter;

8 shows the superposition characteristics of the reactor.

9 shows the structure of a reactor.

10 is a longitudinal sectional view for explaining a schematic structure of a freezer refrigerator according to the present embodiment.

Fig. 11 is a diagram showing the current when the pulse width at the time of pulse width modulation is changed.

12 shows details of the adder 208.

<Description of the code | symbol about the principal part of drawing>

1: commercial power

2: converter

3: inverter

4: compressor

7: electric motor

140: speed command generator

150: PWM / PAM selector

105: Inverter PWM Duty Command Generator

106: Converter PAM Voltage Command Generator

132: suppression circuit

134: quench circuit

151: Determinator

152: selector

137: PAM / PWM selection circuit

As a demand for refrigerators, frozen frozen foods are rapidly frozen, such as rapid freezing, rapid ice making to make ice in a short time. Low annual power consumption) is an example of energy saving. In the case of rapid freezing and rapid deicing, it is achieved by increasing the rotational speed of the compressor to increase the refrigerant circulation in the refrigeration cycle. However, in order to save energy, it is necessary to operate the compressor at low speed. There are the following problems when trying to make both the compressor run at high speed and the compressor run at low speed.

BACKGROUND ART Motors operating a refrigerator compressor (mainly a reciprocating type) are often used as brushless motors for rotating a rotor as permanent magnets are embedded in the rotor and a magnetic field is generated by the inverter in the stator. The rotation speed of this brushless electric motor is shown by the following formula.

N = (V-IR) / kΦ

Where N is the rotation speed of the motor, V is the motor applied voltage, I is the motor current, R is the internal resistance of the motor, k is the 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 rotation speed. The DC voltage input to the inverter can be doubled to 288V (approximately 250V when the load is connected) using the double voltage circuit.However, the internal resistance R of the motor can be set at high speed or low speed. It is different whether it is a high-speed rotation specification, for example, The value of the internal resistance R is made small by setting the number of turns which is the winding number of the stator of an electric motor to 120 turns, for example. However, when the specification of the motor is set to the high speed side in this way, there is a problem that the efficiency of the motor is remarkably lowered in the low speed region.

On the other hand, since the specifications of the motor are matched to the low speed range (the efficiency of the low speed range is increased), when the number of windings of the stator winding line is 140 turns, for example, the motor applied voltage V is constant and the motor internal resistance R becomes large. Therefore, there is a problem in that the rotation speed necessary for rapid freezing or rapid ice making cannot be obtained.

Therefore, in the present embodiment, the high speed rotation of the motor is realized by increasing the inverter input voltage in the high speed region in accordance with the specifications of the motor. In order to increase the inverter input voltage, that is, the DC stage voltage, a step-up chopper (or a PWM controllable converter) is provided at the rear end of the converter for converting AC into direct current, and the step-up chopper is subjected to pulse amplitude modulation, that is, PAM control, by chopping control. Is achieved.

Hereinafter, one embodiment of the present invention described above will be described with reference to the drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 illustrates a control device of a refrigerator, and is an overall configuration diagram of a motor control device including a converter circuit using a rectifier circuit and a boost chopper circuit, and an motor drive circuit including an inverter circuit and a compressor motor.

The AC power source 1 is generally an outlet and supplies electricity to the refrigerator by inserting an insertion plug on the refrigerator side. The energized alternating current is connected to the converter circuit 2 and converted into direct current. The converter circuit 2 includes a boost chopper circuit composed of switching elements 27 which are power elements such as diodes 21, 22, 23, 24, reactor 25, diode 26, and transistors constituting a rectifier circuit. It is output as a direct current voltage through. The boost chopper circuit in the converter circuit 2 is connected to the output side of the rectifier circuit in the converter circuit 2, and forcibly flows an input current according to the switching operation of the power element and the energy accumulation effect of the reactor 25 described above. Step up. The boosted DC voltage is supplied to the smoothing capacitor 5 to output a stable DC voltage. The structure of the boost is known, but will be explained briefly. When the diode 21 side is positive and the switching element 27 is on, the current is alternating with the AC power source 1, the diode 21, the reactor 25, the switching element 27, the diode 24, Electronic energy flows in the order of the AC power supply 1 and accumulates in the reactor 25. At this time, when the switching element 27 is turned off, a current flows from the reactor 25 to the smoothing capacitor 5 through the backflow prevention diode 26, and the electron energy is transferred to the capacitor 5 to condense the capacitor 5. ) Voltage rises. This raises the DC stage voltage. In addition, the resistor 28 in the converter 2 is a resistor for current detection.

The capacitor 5 is connected to an inverter 3 which converts a direct current into an alternating current which generates a rotating magnetic field for rotating the electric motor. The inverter driving motor 7 is connected to the inverter 3. Although the compressor 4 which this electric motor 7 drives is not shown in detail, it is accommodated in the airtight container with the electric motor 7, and is mainly a reciprocating type compressor. In addition, it may be a rotary type or a scroll type compressor.

The inverter 3 is a three-phase inverter, and in this embodiment, IGBTs (Insulated Gate Bipolar Transistors: 31a to 32c) are used as the switching elements. The reflux diodes 33a to 34c are connected to these switching elements in parallel, respectively. Then, 120 degrees of flow is performed based on the output of the rotation position detection of the electric motor 7 so that the direct current supplied from the capacitor 5 is set to the set number of revolutions, and control of the flow rate (pulse width control) in the flow period of each phase is performed. The rotation speed of the electric motor 7 is controlled.

In addition, the resistor 6 is a current detection resistor, and this current detection value is sent to the overcurrent protection device 111, and when this current detection value exceeds the threshold level, a signal for turning off all the switching elements constituting the inverter 3 is exceeded. Is output to the driver 110, the driver 110 turns off the switching element. This is because the inverter does not have a current minor loop in control.

Control performed using such a main circuit configuration will be described based on FIG. 2. As described above, the electric motor 7 is a DC brushless motor, and the rotation speed of the electric motor 7 can be controlled by controlling the voltage applied to the electric motor 7. The electric motor 7 in this embodiment is designed so that the motor efficiency in a low speed rotation area | region may improve. This is due to the fact that the compressor driven by this electric motor is built in a refrigeration cycle used in the refrigerator, and is mainly used as a refrigerator in a general home, and the opening and closing of the door is not frequent all day. That is, through the day, the door of the refrigerator is almost closed, and thus, the refrigeration cycle may only generate cool air suitable for heat intrusion into the refrigerator through the heat insulating material when the door is closed. Since heat intrusion in this refrigerator is very small, the operation of the compressor is a low speed rotation of approximately 2000 revolutions per minute. Therefore, if the motor efficiency of this low speed rotation area | region is designed to be good, power consumption can be made small.

However, as shown in FIG. 2, only the pulse width modulation (PWM) control by the inverter 3 allows rapid freezing or rapid deicing when a large load of food is entered into the refrigerator, or when the door is frequently opened and closed. When the compressor needs to be driven at high speed, for example, the flow rate is about 2400min ⁻¹ to 100%. Therefore, the voltage applied to the electric motor 7 is 150V or more, which is the input DC voltage of the inverter 3. This doesn't work.

Therefore, in the present embodiment, the input of the inverter 3 by the converter 2 is controlled from the pulse width control of the inverter 3 to control the voltage provided to the electric motor 7, that is, the rotation speed control of the electric motor 7. This was done by controlling the direct current voltage, which is the voltage (in this case, the inverter 3 maintains a flow rate of 100%). In this way, even an electric motor designed to improve efficiency in the low speed region can be driven at high speed rotation. In the present specification, the control of controlling the rotation speed of the electric motor 7 by controlling the voltage provided to the electric motor 7 by adjusting the width of the pulse train applied to the electric motor 7 by the inverter 3 controls the PWM (pulse width). Modulation) control and control of controlling the rotational speed of the electric motor 7 by adjusting the amplitude of the pulse applied to the electric motor 7 by controlling the DC voltage of the converter 2 are called PAM (pulse amplitude modulation) control.

In the embodiment shown in Fig. 2, the motor rotation speed is set between 1800min ^-1 to 2400min-1 for PWM control (at this time, DC voltage is 150V), and 2400min-1 or more for PAM control (these values are examples, and the present invention). Are not limited to these values).

By the way, in the present embodiment, the minimum value of the voltage of the DC stage is set to 150V slightly higher than the output voltage 144V of the rectifier circuit constituted by the diodes 21, 22, 23, and 24. The reason is explained below.

When the minimum set voltage of the DC stage is set high, for example, 180 V, the area controlled by the PWM control is enlarged, but the following problem occurs in the low speed area frequently used in the refrigerator.

In order to make the electric motor 7 rotate at low speed in the state where the voltage of the DC stage is high, it is necessary to narrow the pulse width which is a PWM waveform. At this time, the magnitude of the current flowing in the on-period of the inverter 3 increases (the maximum value of the current flowing in the period during which the switching element is on), and in the reflux mode (period in which the current flows in the reflux diode on the phase). The difference with the minimum current becomes large. The difference between the maximum value and the minimum value is in proportion to the pulsating magnetic flux density of the electric motor 7, and the larger this value is, the larger the iron loss of the electric motor 7 becomes.

In order to solve this problem, in the present embodiment, the DC voltage is set to 150 V, which is a value close to the rectified voltage, in the PWM region including the low speed region. By lowering the voltage of the DC stage in this way, the pulse width of the PWM of the inverter becomes wider as it is lowered, and the difference between the maximum current value and the minimum current value in one cycle of the inverter switching element can be reduced. As a result, the pulsating magnetic flux density can be reduced, and the iron loss of the electric motor 7 can be reduced.

It demonstrates based on FIG. 11A is a PWM waveform of the switching element of the inverter 3 in a state where the DC stage voltage is high. When the switching element is on, the motor current flows from the capacitor 5, and when it is off, the motor current is refluxed and attenuated through the reflux diode. This amplitude value is set to ΔIM. Similarly, Fig. 11 (b) is a case where the DC stage voltage is decreased and the same voltage as in (a) is used as the flow rate applied to the electric motor 7. Since the DC stage voltage is low at this time, the rate of rise of the current is small even when the switching element is turned on, so that ΔIM is small as compared with (a). This ΔIM represents the pulsating magnetic flux density of the motor, which means that the smaller the iron loss of the motor. Therefore, the larger the flow rate, the better the motor efficiency.

The reason why the boosting operation by the converter 2 is not turned off in the PWM control area is to maintain the function as a kerbrate improving circuit.

An embodiment for realizing such control will be described based on FIG. 1. In this embodiment, either the PAM control or the PWM control is selected by the PWM / PAM selector 150 as a means for controlling the rotation speed of the electric motor 7. The speed command Np according to the temperature control in the refrigerator of the refrigerator generated by the speed command generator 140 described below is input to the PWM / PAM selection circuit 150.

On the other hand, the induced voltage of the electric motor 7 is input to the position detector 102, the magnet position of the rotor is calculated from this induced voltage, and the speed calculator 103 uses the speed calculator 103 based on this position signal. Actual speed) is output and input to the PWM / PAM selector 150 as the inverter converter control means.

As will be described in detail later, in the PWM / PAM selector 150, the speed command Np and the actual speed of the electric motor 7 are input, and the next control command is generated for the converter 2 and the inverter 3. .

When it is determined that it is a PWM control area, a control command for outputting a constant DC voltage (150 V in the present embodiment) to the converter 2 is sent to the inverter 2 based on the deviation between the speed command value and the actual motor speed. The flow rate command (in this embodiment, the pulse train based on the flow rate command) is sent out, respectively.

In the case where it is determined that the PAM control area is determined, the DC stage voltage command based on the deviation between the speed command value and the actual motor speed is given to the converter 2, and the command for setting the flow rate to 100% for the inverter 2 (in this embodiment, And pulse trains with a flow rate of 100%). At this time, since the inverter has a PWM duty of 100%, the inverter 3 only performs current output without chopper.

The DC stage voltage command output from the PWM / PAM selector 150 is added by the reference voltage 150V and the adder 208 to become a DC voltage command (when the command value from the PWM / PAM selector 150 is 0, If it is determined that it is a PWM control area and this command value has a certain value, it means that it is determined in the PAM control area, and although the reference voltage is used here, the sum value may be output from the PWM / PAM selector 150. ). The voltage between the output of the adder 208 and the terminals of the capacitor 5 detected by the DC voltage detection circuit 50 is compared with the comparator 207, and the deviation is obtained by digging the DC current through the proportional integrator 206. The command is input to the multiplier 201. The voltage (wave current) rectified and rectified by the diodes 21, 22, 23, and 24 is detected by the voltage detector 29, and the pulse current and the DC current crest value command are multiplied by the multiplier 201 to generate the instantaneous current command. do. The instantaneous current command and the real time current detected by the current detection resistor 28 are compared with the comparator 202, the deviation is input into the comparator 204, and the sawtooth wave (triangle wave) generated by the transmitter 203. Is compared to obtain a pulse width modulated signal. This signal is input to the drive circuit 205 and amplified to become a gate signal of the boost chopper 27. By comparing the instantaneous current command and the instantaneous current in this way and controlling the direction in which the deviation is eliminated, the phases of the input voltage and the input current are almost equal to each other and the ratio becomes close to one. In this way, by making the current into a sinusoidal wave, harmonics can be suppressed.

Each element enclosed by the dotted line A is packaged as one integrated circuit. In addition, the converter control circuit described above has recently been made into a control IC, and a large number of products having a method of controlling a DC voltage by controlling an analog voltage have been commercialized.

On the other hand, the PWM signal, which is the flow rate for switching the inverter 3 generated by the PWM / PAM selector 150, is switched to the AND circuit 109 as a pulse train. In addition, the output signal of the position detector 102 is also input to the current outputter 108, and a pulse train which is a current timing (a pulse train shifted by 120 degrees per phase) of the 120 degree current flow of the switching elements of each phase is outputted for each switching element ( The figure shows one switching element). The switching elements 32a, 32b and 32c constituting the lower arm of each phase are turned on during the period of this current timing, and the switching elements 31a, 31b and 31c constituting the upper arm have a pulse train and a front indicative of the current timing. The AND with the pulse train representing the PWM signal is taken by the AND circuit 109 and controlled on and off via the driver 110.

The converter operation determiner 107 stops the drive circuit 205 for switching the step-up chopper 27 when the speed command Np, which is the output of the speed command generator 140, is zero. This is because the output from the PWM / PAM selector to the converter 2 side is 0 and the speed command is 0, so that the command becomes 0, which is the result of the speed command being sent but it is determined to be a PWM control area or the converter 2 This is because there is no distinction in the side.

Next, the details of the PWM / PAM selector will be described with reference to FIG. 3.

The speed command Np from the speed command generator 140 is input to the selector 152. According to the result determined by the determiner 151, the switch in the selector 152 is switched to the A side or the B side. The A side is the PAM control region and the B side is the PWM control region.

When the B side is determined by the determiner 151, the switch in the selector 152 is switched to the B side. The speed command Np is compared with the actual speed from the speed calculator 103 by the comparator 153, the deviation is input to the proportional integrator 155, and the calculated control amount is input to the inverter PWM duty command generator 105. Through these calculations, the flow rate at which the speed deviation becomes 0 (close to) is calculated, and a pulse train having a pulse width of this flow rate is sent to the AND circuit 109. On the other hand, the converter side outputs 0, which is a command for setting the converter output voltage to 150 V, from the selector 152 to the converter PAM voltage command generator 106, and also determines the result of selecting B of the determiner 151. It is output to the voltage command generator 106. The 0 command, which is a command for maintaining the DC voltage at 150 V, is output to the adder 208.

On the other hand, when the A side is determined by the determiner 151, the switch in the selector 152 is switched to the A side. The speed command Np is compared with the actual speed from the speed calculator 103 by the comparator 154, the deviation is input to the proportional integrator 156, and the calculated control amount is output to the converter PAM voltage command generator 106. By these calculations, a DC voltage command at which the speed deviation becomes 0 (close) is calculated and output to the adder 208. On the other hand, on the inverter side, an infinite speed command value is input to the comparator 153, the deviation is input to the proportional integrator 155, and the calculation result is output to the inverter PWM duty command generator 105. In this case, the speed command value is set to infinity because the speed variation is large when it is set to infinity, so the flow rate is expected to be 100%. Then, a pulse train having a flow rate of 100% is sent from the inverter PWM duty command generator 105 to the AND circuit 109.

Next, the determination operation of the determiner 151 will be described.

The determiner 151 inputs the flow rate from the inverter PWM duty command generator 105 and the DC stage voltage command from the converter PAM voltage command generator 106. If the flow rate (duty) of the inverter PWM duty command generator 105 is equal to or less than a predetermined value (for example, 100%), it is determined to be a PWM control region, and the selector 152 is instructed to select the B side. When the flow rate reaches a predetermined value, it is determined that the PAM control area is made, and the selector 152 is instructed to select the A side.

Therefore, switching from the PWM control to the PAM control determines with the determiner 151 whether the duty of the inverter PWM duty command generator 105 is a predetermined value (for example, 100%).

In contrast, switching from the PAM control to the PWM control is performed in accordance with the value of the DC stage voltage command which is the output of the converter PAM voltage command generator 106. When the voltage command value of the DC stage reaches a value lower than the predetermined value 150V, the determiner 151 sends a command for switching the selector 152 from the A side to the B side.

In addition, since the DC voltage corresponds to 150 V and the PWM pass rate of the inverter 3 corresponds to 100%, it is possible to cause hunting when there is a speed command near this side. In order to prevent this, when switching from PWM control to PAM control, the end condition is whether the speed increase command (decided to increase speed when the speed deviation is greater than the predetermined value) is set, and when the speed increase command is not increased, the switching is not performed. When switching to PWM control, whether the same deceleration command is added or not is added to the determination condition.

Here, when switching from PAM control to PWM control, a technique for switching when the DC voltage (DC voltage of the main circuit, real DC voltage) output by the boost chopper circuit becomes lower than the set voltage is disclosed in Japanese Patent Application Laid-Open No. 63-224698. Known. In this case, the DC voltage input to the microcomputer divides the voltage of several 100V with a resistance and lowers it below 5V which can detect a microcomputer. For this reason, the ground of the microcomputer drive voltage and the ground of the power system (main circuit) DC voltage must be common.

However, in a refrigerator, a signal system of direct current voltage and a signal system of a microcomputer driving unit should be insulated and grounded separately. The reason is explained using the insulation structural diagram of the refrigerator of FIG.

The refrigerator is installed indoors and is provided with operation buttons as described below. As described above, when the direct current voltage meter, the direct current voltage meter and the microcomputer drive unit signal system have a common ground, the operation button is exposed to some problem and the user touches or touches the surface of the refrigerator. There is a concern.

For this reason, the converter circuit 2, the inverter circuit 3, various heaters, etc. are insulated by an optical semiconductor element (photo coupler), a relay, etc. In addition, the power supply of the microcomputer drive unit generally uses a switching power supply, but the power supply of the microcomputer driver must be constructed to insulate the primary side and the secondary side with a transformer.

For example, a microcomputer constituting a temperature control system having an operation unit in a room air conditioner and a microcomputer for controlling an electric motor exist independently, and the connection between them is a compressor rotation command from a microcomputer constituting the temperature control system. It only transfers to the microcomputer constituting the motor control system. This part can be insulated using a photocoupler or the like. For this reason, it is possible to detect the DC voltage of the main circuit in a room air conditioner and switch from PAM control to PWM control according to the value. In addition, this electric motor control is completed only by an outdoor unit.

On the other hand, since a refrigerator does not want to narrow the capacity | capacitance in the refrigerator in which food was put, it performs a temperature control system and an electric motor control system by one microcomputer. In this case, dividing the DC voltage of the main circuit and inputting it to the microcomputer should not be made in terms of insulation. In this state, switching from PAM control to PWM control cannot be performed.

Therefore, in the present embodiment, when switching from the PAM control to the PWM control as described above, the direct current voltage is substituted with the DC stage voltage command value output to the converter 2 side generated by the converter PAM voltage command generator 106. By making it an object of determination, it is possible to switch from PAM control to PWM control without directly inputting a DC voltage to a microcomputer after voltage division.

Moreover, even in a refrigerator, in the method of receiving and controlling the main circuit DC voltage, a dedicated microcomputer for controlling only the converter circuit 2 or the inverter circuit 3 is provided, such as a room air conditioner, to detect the temperature of the refrigerator and the fan motor. It is possible to separate it from the microcomputer which controls the damper, control button and so on. However, although each microcomputer performs control by communication, insulation of an optical semiconductor element etc. is required here.

In addition, since a direct current voltage can be detected even if a commercially available isolated analog / digital converter is used, the control of receiving a direct current voltage and switching from PAM control to PWM control becomes possible. However, the cost is expensive.

Next, generation | occurrence | production of speed command Np is demonstrated using FIG. The basic speed command is the speed command N output by the temperature setter 130, the freezer compartment temperature detector 138, the comparator 100, and the speed command calculator 101. That is, the freezer compartment set temperature which is the signal from the temperature setter 130 and the actual freezer compartment temperature from the freezer compartment temperature detector 138 are compared by the comparator 100, and the temperature deviation is output to the speed command calculator 101. Up to the maximum speed command, the speed command is output in proportion to the temperature deviation. However, the speed command is constant for the deviation above that. Although this is a general method of generating a speed command, in this embodiment, by adding various functions, an easy-to-use and energy-saving refrigerator is provided.

The rapid freezing operation, the rapid ice making operation and the suppression operation will be described. The home freezing performance in a home refrigerator is characterized by the fact that ice crystals in the tissue at the time of freezing can be shortened by shortening the passage time of the maximum ice crystal producing zone (-l ° C. to -5 ° C.) where most of the moisture in the food is frozen. The growth can be suppressed, and the outflow of the drips (the soup containing taste and nutrients) at the time of thawing due to cell destruction can be suppressed, and high-quality freezing can be suppressed. To realize this, a quick freezing button (quick deicing button: 134) is provided on the door of the refrigerator, and the quick freezing button 134 is pressed to start quick freezing (ice making).

This quick freezing button may be a relay contact or an electronic switch provided in the refrigerator but closed by another remote control.

When the quick freezing button 134 is pressed, the timer in the quenching circuit 133 is started, and a quick freezing operation is performed for a maximum of two hours until the quick freezing button 134 is manually released or the timer is turned off. In the quench circuit 133, a speed command for setting the motor rotational speed to 4200 revolutions per minute (fixed) is sent to the selection circuit 137 (this state becomes a PAM control region), and the selection circuit 130 quenches it. The speed command from the circuit 133 is selected and output to the comparator 104. In addition, when the motor speed command is fixed, the temperature deviation at the time of return may become large and unstable. Therefore, the temperature command is set to a value lower than -7 ° C than usual. For this reason, -7 degreeC is added to the output from the temperature setter 130 with the adder 135, and it is set as a temperature command. The deviation between this temperature and the actual temperature is output from the comparator 100. The quench circuit 133 inputs this temperature deviation, and when the freezer compartment temperature is lower than the temperature set in the refrigerator by 7 ° C lower than the temperature setting (normally -18 ° C) during the rapid freezing operation, the speed command is 4200 revolutions / of the fixed value. It is set to 0 rotation / min from minute, and the temperature of refrigerator rooms or vegetable rooms other than a freezer compartment falls too much. When the freezer temperature rises and exceeds the set temperature lower by 7 ° C (has hysteresis), the motor speed command is returned to resume operation. This operation continues until the timer is off.

By the above-mentioned quick freezing (ice-making) operation function, the maximum ice crystal generating zone passage time can be set within 30 minutes, and high-quality freezing is possible.

In recent years, energy saving of refrigerators has been on the rise in response to social requests as measures to prevent global warming. In order to answer this request, in the refrigerator which concerns on a present Example, the "inhibition button" 132 which implements an energy saving mode was provided in the door.

When the "suppress button" 132 is pressed, the "suppression circuit" 131 starts. In order to increase the temperature setting (temperature command) by 1 ° C, the "suppression circuit" 131 outputs a signal to be added by 1 ° C to the output of the temperature setter 130 and adds it to the adder 135, and adder 135 ) Is the temperature command at the time of suppression operation. In addition, the "suppression circuit" 131 outputs a signal to the speed command limiter 136, and receives a speed command of 3000 revolutions / minute or more even if the speed command that is the output of the speed command generator 101 exceeds 3000 revolutions / minute. The output was not made at the rear end. For this reason, even when the temperature deviation is very large, the maximum speed is suppressed at 3000 revolutions / minute, and thus, while the "suppression button" 132 is pressed, the high speed rotation is not arbitrarily performed, and thus the power consumption can be reduced. In this restraint operation, since most of the operating states are PWM control regions, the efficiency of the motor is good and the power consumption is low.

By the way, the "inhibition circuit" 131 inputs the output of the freezer compartment temperature detector 138, detects that the temperature of the freezer compartment is -10 ° C or higher, and releases the "inhibition control". This means that the load is larger as the temperature in the refrigerator rises even if the operation continues at the motor rotation speed 3000 revolutions / minute, and at this time, in order to maintain the temperature of the food stored in the refrigerator at an appropriate temperature, the "inhibition control" This is because the refrigerator is released to return to normal operation to cool the inside of the refrigerator.

In addition, since rapid freezing operation and "suppression control" are not compatible, when one function is performed, it is configured to be invalid even if the other button is pressed.

Next, control at the start of the compressor (motor) will be described. In general, the voltage range of electricity transmitted to homes is allowed to vary based on the Electricity Business Law, and considering the voltage drop caused by indoor wiring, the variation range of 281 ± 7.5% (260V to 303V) is displayed in the double voltage display. do. For this reason, when the voltage is low, the starting torque of the compressor may be large, and the starting torque may be difficult due to the lack of the rotating torque of the electric motor. In the present embodiment, when the compressor is stopped, when the start command is received, the DC voltage command is controlled to a high voltage for the first time, and after the DC voltage with less variation is obtained, the motor is started. By doing in this way, since it becomes 281 +/- 3%, a stable DC voltage is supplied and start is assured.

That is, the converter PAM voltage command generator 106 inputs the actual speed, which is the output of the speed calculator 103, and the speed command Np, and determines that the compressor is started even when the actual speed is 0, and the DC voltage command is determined. A high voltage command is used (not shown in FIG. 3). As shown in Fig. 6, under this voltage, the inverter switches and starts the electric motor. Thereafter, control is performed by the above-described PAM control or PWM control so that the electric motor 7 rotates appropriate to the deviation of the freezer compartment temperature and the temperature set value.

7 shows the relationship between the PWM duty and the Ic peak current of the inverter 3. Ic peak current is the collector current of each IGBT with reference numerals 31a-31c and 32a-32c. The limit line is the guarantee of the Ic peak current for the PWM duty, and the smaller the PWM duty, the higher the guarantee.

Starting torque is required at the time of starting the electric motor 7, and therefore the current of Ic also increases. Since the starting current is determined according to the DC voltage applied to the inverter 3, when the DC voltage is high, the current at startup can reduce the PWM duty.

In this embodiment, the current at startup requires a current of 4A with a PWM duty of about 15%. In this case, the DC voltage is 280V. Therefore, if the direct current voltage at start-up is performed at a high voltage, the PWM duty can be reduced, so that the capacity of the IGBT can also be reduced.

It is also possible to start by lowering the DC voltage applied to the inverter 3 within the guaranteed value of Ic. In this case, however, it is necessary to increase the PWM duty.

Next, the reactor 25 is described. 8 shows the reactor characteristics of the converter circuit 2. In refrigerators, the harmonic regulation guidelines are Class D. Since the curvature improvement is performed by controlling the DC voltage through the boosting chopper 27 over the entire range of the rotation speed control range of the electric motor 7, the value of the reactor 25 ends at about 1 mH.

9 shows a structural diagram of a reactor. The core of the reactor 25 of the PAM control is generally amorphous, which has good frequency characteristics, but an air gap must be provided in the core to obtain the reactor touch. However, as the air gap is provided, there is a factor in which the air gap part vibrates and noise is generated. In this embodiment, the reactor can be obtained without using a gap by using a core of a special material. The material uses permalloy and iron.

Next, the outline of the freezer refrigerator will be described with reference to FIG. 10. Reference numeral 301 denotes a blowing direction changer, reference numeral 302 denotes a circulating fan motor in a refrigerating chamber, reference numeral 303 denotes a step motor for changing a blowing direction, and reference numeral 304 denotes a fan motor for cooling air circulation in a refrigerator, Reference numeral 305 denotes an evaporator, reference numerals 306a to 306c denote temperature sensors, reference numeral 307 denotes a refrigerator compartment, reference numeral 308 denotes a vegetable compartment, and reference numeral 309 denotes a freezer compartment. When the "quick refrigerating button" installed in the refrigerator compartment door (not shown) is pressed, the blowing direction changer 301 provided in the refrigerator compartment 307 performs a 90 degree reciprocation rotation, and the motor 302 for the circulation fan in the refrigerator compartment operates. The inside of the refrigerating chamber 307 is equalized. As a result, the refrigerating chamber 307 may be rapidly cooled when it is homogenized and warm food is entered.

Moreover, the temperature sensors 306a to 306c (one not shown) provided on both sides of the refrigerating chamber 307 detect the temperature of the food placed on the left and right, and the blowing direction changer 301 in the direction where the food temperature is high. It is also possible to quench toward.

By the way, in the above embodiment, when switching from PAM control to PWM control, the DC stage voltage command value is detected without detecting the real DC voltage, thereby insulating between the main circuit (power system) and the microcomputer directly wired to the operation unit. Could. A surrounded by a dotted line in FIG. 1 is a package IC that receives a real DC voltage and configures a voltage feedback control system to control the DC voltage near a DC stage voltage command. In other words, this package IC is also directly connected to the power system. In order to send out the DC stage voltage command from the PWM / PAM selector 150 constituted by a microcomputer connected to the operation unit, it is necessary to be connected to the wiring and to insulate it again. An embodiment in which insulation is performed will be described with reference to FIG. 12. FIG. 12 shows an example in which insulation is applied to the adder 208 shown in FIG.

Since the DC stage voltage command transmitted from the converter PAM voltage command generator 106 in the PAM / PWM selector 150 converts the digital voltage command into an analog value, the input voltage may be input to the base of the photocoupler for signal isolation. Since the photocoupler has no voltage amplifying action, if the base voltage exceeds the on-voltage of the photocoupler, only two values of low are output if the base voltage exceeds the on-voltage, and the subtle DC stage voltage command cannot be transmitted to the step-up chopper control system at the next stage. .

Thus, in the present embodiment, the signal transfer is possible at the rear end by replacing the DC stage voltage command from the converter PAM voltage command generator with a pulse train and making the pulse width of the pulse train the width corresponding to the DC stage voltage command. By converting the DC stage voltage command into a pulse train, the pulse generation unit made the 150V command (PWM control area) the case where the pulse width was zero, and the maximum 280V command the case of 100%.

Pulse width is zero (PWM control area). Since the base voltage of the photo coupler is zero, the photocoupler does not turn on. For this reason, the voltage which divided | segmented the fixed voltage determined by the voltage-division ratio of resistor R2 and resistor R3 is output to the comparator 207 of FIG. 1 (FIG. 1). This corresponds to the reference voltage Vp shown in FIG.

When a pulse train including the width is output (PAM control area). Since the photocoupler is turned on during the period in which the pulse is output, the output of the adder outputs a voltage obtained by dividing a constant voltage determined by the voltage divider ratio between the parallel resistance of the resistor R1 and the resistor R2 and the resistor R3 to the analog converter. In the analog converter, the pulse train output from the adder is shifted with the time constant determined by the resistor R4 and the capacitor C, and the average voltage of the on-period and the off-period is output. The output of the adder outputs a voltage lower than the period during which the photocoupler is on, and therefore the analog voltage with the wider pulse width is output to the rear stage. That is, the maximum DC stage voltage command value (100% duty) in the PAM control region is the lowest analog voltage, and the highest DC stage voltage command in the PWM control region is output the highest. This configuration allows the DC stage voltage command to be transmitted while maintaining the insulation. In the comparator 207 of FIG. 1, since the reference for the magnitude of the DC voltage command and the real DC voltage is inverted, it is necessary to invert either.

In addition, a pulse generator may be provided in the converter PAM voltage command generator 106 in FIG. In this case, the signal to the determiner 151 becomes a pulse train.

In the above-described embodiment, various numerical values are shown and described, but these numerical values are examples and other numerical values are acceptable as long as they are consistent with the control idea.

In addition, although the present embodiment has been described with a control block diagram for ease of understanding, the speed command generator 140, the position detector 102, the speed calculator 103, the current output device 108, and the PWM / PAM selector 150 are described. Can be realized by software.

As described above, the present embodiment has the following effects. The design of the motor for a compressor is designed at the highest utilization rate (for example, at the lowest rotational speed), so that the motor can be highly efficient, resulting in energy saving of the system. When the heat load of the refrigerator is high, it switches to PAM control, so that the compressor motor can be operated at high speed, and the voltage is increased compared to the so-called staircase PAM in which the DC voltage is increased stepwise to control the motor by PWM control of the inverter. Since the motor can be controlled only by the chopper switching control (the inverter simply operates as a brush of the motor), there is an effect that the switching loss is small. In addition, since the PAM control can be performed at a reactor capacity of about 1 mH, the size of the reactor can be reduced and the board can be mounted.

According to the present invention, in addition to the effect that a refrigerator having a suitable PAM control function can be provided as an electric motor control device for a refrigerator, a refrigerator capable of starting a compressor even when the voltage of the power source fluctuates can be provided. It works.

Claims (16)

A refrigerator comprising an electric motor for driving a compressor, an inverter for rotationally controlling the electric motor, and a converter for inputting alternating current to supply a direct current of a variable voltage to the inverter, A first control mode in which the rotation speed of the electric motor is controlled by the pulse width modulation function of the inverter to approach a speed command generated based on the temperature in the refrigerator and the set temperature; A second control mode in which the rotation speed of the motor is controlled according to the voltage varying function of the converter Refrigerator comprising a. A refrigerator comprising an electric motor for driving a compressor, an inverter for rotationally controlling the electric motor, and a converter for inputting alternating current to supply a direct current of a variable voltage to the inverter, A first control mode in which the rotation speed of the electric motor is controlled by the pulse width modulation function of the inverter to approach a speed command generated based on the temperature in the refrigerator and the set temperature; A second control mode in which the rotation speed of the electric motor is controlled by a voltage varying function of the converter And When the flow rate in the pulse width modulation function of the inverter reaches a predetermined value, when switching from the first control mode to the second control mode and the DC voltage command for the converter reaches a predetermined value, And a function of switching from the second control mode to the first control mode. A refrigerator comprising an electric motor for driving a compressor, an inverter for rotationally controlling the electric motor, and a converter for inputting alternating current to supply a direct current of a variable voltage to the inverter, Speed command generation means for generating a speed command of the electric motor based on a temperature in the refrigerator and a set temperature; Inverter converter control means for generating a flow rate for the inverter and a DC voltage command for the converter based on the speed command; And And said inverter and converter, said speed command generation means and said inverter converter control means are electrically insulated from each other. A refrigerator comprising an electric motor for driving a compressor, an inverter for rotationally controlling the electric motor, and a converter for inputting alternating current and supplying a direct current of a variable voltage to the inverter, Means for making the DC voltage supplied to the inverter higher than the value obtained by converting the AC into DC when starting the motor. Refrigerator comprising a. The refrigerator according to claim 4, further comprising a mode for driving the electric motor with a voltage lower than the direct current voltage at the time of starting the electric motor. An electric motor for driving a compressor, a rectifier circuit for converting alternating current into a direct current, a boost chopper for boosting the direct current, a reactor provided between the rectifier circuit and the boost chopper, and a rear end of the boost chopper, In the refrigerator provided with the inverter which converts a direct current into alternating current, The reactor is a refrigerator characterized in that the coil is wound around the annular core having no gap. A refrigerator comprising an electric motor for driving a compressor, an inverter for rotationally controlling the electric motor, and a converter for inputting alternating current to supply a direct current of a variable voltage to the inverter, Means for adjusting the rotation speed of the electric motor by controlling the chopping operation of the switching elements constituting the inverter or converter based on a deviation between a set temperature and a refrigerator freezer temperature; Operation mode which raises the said set temperature and makes the rotation speed of the said electric motor below the predetermined value in an operation area. Refrigerator comprising a. A refrigerator comprising an electric motor for driving a compressor, an inverter for rotationally controlling the electric motor, and a converter for inputting alternating current and supplying a direct current of a variable voltage to the inverter, Means for adjusting the rotation speed of the electric motor by controlling the chopping operation of the switching elements constituting the inverter or converter based on a deviation between a set temperature and a refrigerator freezer temperature; An operation mode in which the set temperature is raised to make the rotational speed of the electric motor less than or equal to a predetermined value in an operation region; A switch for operating the operation mode Refrigerator comprising a. A refrigerator comprising an electric motor for driving a compressor, an inverter for rotationally controlling the electric motor, and a converter for inputting alternating current and supplying a direct current of a variable voltage to the inverter, Means for adjusting the rotation speed of the electric motor by controlling the chopping operation of the switching elements constituting the inverter or converter based on a deviation between a set temperature and a refrigerator freezer temperature; An operation mode in which the set temperature is raised to make the rotational speed of the electric motor less than or equal to a predetermined value in an operation region; Means for terminating the operation mode when the freezer compartment temperature reaches a predetermined value higher than the set temperature; Refrigerator comprising a. A refrigerator comprising an electric motor for driving a compressor, an inverter for rotationally controlling the electric motor, and a converter for inputting alternating current to supply a direct current of a variable voltage to the inverter, Means for adjusting the rotation speed of the electric motor by controlling the chopping operation of the switching elements constituting the inverter or converter based on a deviation between a set temperature and a refrigerator freezer temperature; Operation mode which lowers the said set temperature and makes the rotation speed of the said electric motor a predetermined value in an operation area. Refrigerator comprising a. A refrigerator comprising an electric motor for driving a compressor, an inverter for rotationally controlling the electric motor, and a converter for inputting alternating current to supply a direct current of a variable voltage to the inverter, Means for adjusting the rotation speed of the electric motor by controlling the chopping operation of the switching elements constituting the inverter or converter based on a deviation between a set temperature and a refrigerator freezer temperature; An operation mode in which the set temperature is lowered to set the rotation speed of the electric motor to a predetermined value in an operation region; A switch for operating the operation mode Refrigerator comprising a. A refrigerator comprising an electric motor for driving a compressor, an inverter for rotationally controlling the electric motor, and a converter for inputting alternating current to supply a direct current of a variable voltage to the inverter, Means for adjusting the rotation speed of the electric motor by controlling the chopping operation of the switching elements constituting the inverter or converter based on a deviation between a set temperature and a refrigerator freezer temperature; An operation mode in which the set temperature is lowered to set the rotation speed of the electric motor to a predetermined value in an operation region; A switch for operating the driving mode; Means for ending the operation mode after a predetermined time has elapsed in association with the switching of the switch; Refrigerator comprising a. A refrigerator comprising an electric motor for driving a compressor, an inverter for rotationally controlling the electric motor, and a converter for inputting alternating current to supply a direct current of a variable voltage to the inverter, Means for adjusting the rotation speed of the electric motor by controlling the chopping operation of the switching elements constituting the inverter or converter based on a deviation between a set temperature and a refrigerator freezer temperature; An operation mode in which the set temperature is lowered to set the rotation speed of the electric motor to a predetermined value in an operation region; Means for stopping rotation of the motor when the freezer compartment temperature reaches the lowered set temperature Refrigerator comprising a. A refrigerator comprising an electric motor for driving a compressor, an inverter for rotationally controlling the electric motor, and a converter for inputting alternating current to supply a direct current of a variable voltage to the inverter, Means for adjusting the rotation speed of the electric motor by controlling the chopping operation of the switching elements constituting the inverter or converter based on a deviation between a set temperature and a refrigerator freezer temperature; A first operation mode in which the set temperature is raised to make the rotational speed of the electric motor less than or equal to a predetermined value in an operation region; A second operation mode in which the set value temperature is lowered to set the rotation speed of the electric motor to a predetermined value in the operation region; Refrigerator comprising a. A refrigerator comprising an electric motor for driving a compressor, an inverter for rotationally controlling the electric motor, and a converter for inputting alternating current to supply a direct current of a variable voltage to the inverter, Means for adjusting the rotation speed of the electric motor by controlling the chopping operation of the switching elements constituting the inverter or converter based on a deviation between a set temperature and a refrigerator freezer temperature; A first operation mode in which the set temperature is raised to make the rotational speed of the electric motor less than or equal to a predetermined value in an operation region; A switch for operating the first driving mode; A second operation mode in which the set value temperature is lowered to set the rotation speed of the electric motor to a predetermined value in an operating region; A switch to operate the second operation mode Refrigerator comprising a. A refrigerator comprising an electric motor for driving a compressor, an inverter for rotationally controlling the electric motor, and a converter for inputting alternating current to supply a direct current of a variable voltage to the inverter, Means for adjusting the rotation speed of the electric motor by controlling the chopping operation of the switching elements constituting the inverter or converter based on a deviation between a set temperature and a refrigerator freezer temperature; A first operation mode in which the set temperature is raised to make the rotational speed of the electric motor less than or equal to a predetermined value in an operation region; Means for ending the first operation mode when the freezer compartment temperature reaches a predetermined value that is higher than the set temperature; A second operation mode in which the set value temperature is lowered to set the rotation speed of the electric motor to a predetermined value in an operating region; Means for stopping rotation of the electric motor when the freezer compartment temperature reaches the reduced set temperature during the second operation mode period Refrigerator comprising a.