JP2012092694A - Driving device for compressor and refrigerator using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow a compressor to be operated with high efficiency and low vibration.SOLUTION: A driving device for a compressor includes: the compressor 6 including a brushless DC motor 4; an inverter 3; a duty computing device 14; a current detection device 16; and a duty correcting device 17. In the driving device for a compressor, the duty correcting device 17 adds a correction value to a duty that is determined by the duty computing device 14 so that an envelope curve of the current circulating through the inverter is kept within a predetermined range, thereby reducing the loss of the brushless DC motor 4 and accordingly enhancing the efficiency of the compressor 6.

Description

  The present invention relates to an inverter-driven compressor mainly used in a refrigerator-freezer, and more particularly to a reciprocating compressor driving device having a compression element by reciprocating motion in which a load torque greatly varies during one rotation.

  Conventionally, this type of compressor drive device detects the mechanical position of the rotor, that is, the mechanical process position of the compressor, from the magnetic pole position detection signal of the brushless DC motor, and is preset according to the detected mechanical process. By correcting the PWM duty width with a value, vibration during driving is suppressed by suppressing speed fluctuations accompanying load fluctuations during the compressor process (see, for example, Patent Document 1).

FIG. 6 shows a conventional compressor driving apparatus described in Patent Document 1. In FIG.
In FIG. 6, the commercial power source 100 is an AC power source of 100 V 50 Hz or 60 Hz in the case of Japan.

  The rectifier circuit 101 includes a rectifier diode and a smoothing capacitor, converts the commercial power supply 100 into a direct current, and obtains a voltage of 140V direct current.

  The inverter 102 is composed of six switching elements connected in a three-phase bridge and six diodes connected in reverse parallel to the switching elements. By controlling these six switching elements, the DC power can be changed to an arbitrary voltage, arbitrary To three-phase AC power with a frequency of.

  The brushless DC motor 103 has a stator having three-phase windings and a rotor having permanent magnets, and is driven by the three-phase AC output of the inverter 102.

  The compression element 104 is a reciprocating type and is driven by a brushless DC motor 103. Moreover, the reciprocating compressor 105 is comprised by accommodating these in an airtight container.

  The reciprocating compressor performs compression by reciprocating movement of the piston. During one rotation, half is divided into the suction process, and half is completely divided from the compression process. Are concentrated on the compression process side, so that the load torque varies greatly.

  The driving device 109 drives the inverter 102. The output drives the six switching elements of the inverter 102 via the drive means 110.

  The position detector 111 detects the rotational position of the rotor of the brushless DC motor 103 from the back electromotive voltage generated in the stator winding of the brushless DC motor.

  The commutation means 112 determines the timing for energizing the six switching elements of the inverter 102 based on the output of the position detection means 111.

  The rotational position determination unit 113 analyzes the output signal of the position detection unit 111 and detects the mechanical rotational position of the rotor of the brushless DC motor 103.

  The first PWM generation means 114 determines a predetermined duty width by speed feedback control of the brushless DC motor and outputs a PWM signal.

  The second PWM generation unit 115 generates a duty (for example, 10%) obtained by adding a predetermined amount of duty to the duty determined by the first PWM generation unit 114.

  The selection means 116 selects the first PWM generation means 114 when the rotation speed is high, and selects the first PWM generation means or the second PWM generation means according to the rotation position by the rotation position determination means 113 when the rotation speed is low. .

  The synthesizing unit 117 synthesizes the output of the commutation unit 112 and the output of the selection unit, and outputs the combined result to the drive unit 110 to control the inverter 102.

JP 2006-2732 A

  However, in the conventional configuration, in order to correct a predetermined amount of duty, a predetermined value corresponding to the driving speed state and driving state of the compressor needs to be prepared in advance in ROM data or the like. is there. However, in order to provide an optimum correction amount according to the state, it can be realized by dividing the driving state of the compressor and assigning the correction amount, but this involves an increase in cost such as an increase in ROM capacity of the microcomputer and use of an EEPROM.

  On the other hand, in order to set the correction amount with the limited ROM, it becomes difficult to give the optimal correction amount according to the load state, and the optimum load range (for example, load state, pressure state, speed state, etc.) is deviated. In this case, there is a problem that the vibration of the compressor cannot be sufficiently suppressed.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and an object thereof is to provide a compressor driving device that can realize low-vibration and high-efficiency driving in any compressor driving state at low cost.

  In order to solve the above-described conventional problems, a compressor driving apparatus according to the present invention drives a compressor having a brushless DC motor at a variable speed by a PWM-controlled inverter, and detects current flowing through the inverter as current detection means. The PWM duty is corrected so that the detected current is always constant.

  Thereby, the pulsation of the electric current accompanying the load fluctuation | variation of a compression process can be suppressed, and it can improve a motor efficiency, ie, the efficiency of a compressor, by flowing a fixed electric current through a motor.

  In order to keep the current flowing through the inverter (ie, the compressor current) constant, the PWM duty is increased (ie, the applied voltage is increased) in a section where the current is low, that is, a section before the position where the maximum load is applied in the compression process. And increase the flowing current. Here, since the compressor is a load having a relatively large moment of inertia, the point that affects the angular velocity is delayed from the position where the applied voltage increases or decreases. Therefore, by increasing the current at the machine process position where the flowing current is relatively small (increasing the PWM duty and increasing the applied voltage), the speed reduction at the machine process position where the load torque is large can be suppressed. Vibration can be reduced.

The compressor driving device of the present invention can reduce the loss of the brushless DC motor when the compressor is driven, thereby improving the efficiency of the compressor (that is, improving the COP) and realizing low vibration and noise.

  Furthermore, by using the compressor driving device of the present invention for the cooling cycle of the refrigerator, it is possible to provide a product with low noise consumption and low power consumption by suppressing the driving vibration of the compressor.

1 is a block diagram of a compressor driving device according to Embodiment 1 of the present invention. The flowchart which shows the operation | movement in Embodiment 1 of this invention. Graph showing torque and angular velocity per compressor rotation (A) Current waveform diagram of U phase when duty correction of brushless DC motor is not performed (b) Current waveform diagram of U phase when duty correction of brushless DC motor is performed (1) Graph showing inverter current waveform and position detection timing when duty correction is not performed (2) Graph showing inverter current waveform and position detection timing when duty correction is performed Block diagram of a conventional compressor drive device

  According to a first aspect of the present invention, there is provided a compressor having a compression element, a brushless DC motor having a permanent magnet for driving the compression element in a rotor, and a DC voltage converted into a three-phase alternating current to supply power to the brushless DC motor. An inverter to be supplied, a duty calculating means for controlling a voltage applied to the brushless DC motor, calculating a PWM duty for changing a rotation speed to make a refrigeration capacity of the compressor variable, and an inverter Compression having current detection means for detecting the flowing current and duty correction means for correcting the voltage applied to the brushless DC motor determined by the duty calculation means so that the envelope of the current flowing through the inverter falls within a certain range. It is a drive device of the machine. As a result, current pulsation flowing through the inverter can be suppressed, so that the efficiency of the brushless DC motor can be increased, and a highly efficient compressor drive device can be provided.

  According to a second aspect of the invention, in particular, in the first aspect of the invention, the section for duty correction does not include at most 30 degrees before and after the position where the current flowing through the inverter is maximum. As a result, the loss of the brushless DC motor can be reduced, the speed fluctuation of the compressor due to the load torque fluctuation during one rotation of the compressor can be suppressed, and the compressor vibration can be suppressed.

  According to a third invention, in the first or second invention, the current detecting means detects a voltage generated in a resistor provided in series between the rectifier circuit and the inverter circuit, and detects an overcurrent of the inverter. It also serves as a protection circuit. As a result, it is not necessary to provide a new current detection circuit, and the circuit can be reduced in size and cost.

  According to a fourth invention, in any one of the first to third inventions, the commutation means outputs a waveform having an energization angle of 120 or more and less than 150 degrees, and drives the inverter, so that it can be flexibly adapted to the application. It is possible to select a proper conduction angle. In addition, because of the very simple control, an inexpensive processor can be used, so that the price of the apparatus can be reduced.

  According to a fifth invention, in any one of the first to fourth inventions, the compressor is a reciprocating compressor. As a result, it is possible to reduce the vibration of the reciprocating compressor that has a relatively large vibration due to driving.

6th invention is the refrigerator which used the compressor drive device of any one of 1st to 5th invention for the cooling cycle. This makes it possible to realize a refrigerator with low driving noise, to reduce power consumption by increasing efficiency, and to reduce the cost of the cooling system by suppressing vibration accompanying driving of the compressor.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a block diagram of a compressor driving apparatus according to Embodiment 1 of the present invention.

  In FIG. 1, electric power necessary for driving is supplied from a commercial power source 1. For example, in the case of Japan, it is an AC power supply, and is a power supply of 100 V 50 Hz or 60 Hz.

  The rectifier circuit 2 converts the commercial power source 1 into direct current. Here, the rectifier circuit 2 is shown as a full-wave rectifier circuit. A full-wave rectifier circuit is generally composed of four diodes and a smoothing capacitor connected in a bridge. With this circuit, a DC voltage of 140 V is obtained from the AC 100 V of the commercial power source 1.

  The inverter 3 converts the DC voltage of the rectifier circuit 2 again into three-phase AC. The inverter 3 generally includes six switching elements (indicated by IGBT in the drawing) connected in a three-phase bridge and six diodes connected in reverse to the switching elements in parallel. By controlling these six switching elements, a three-phase alternating current having an arbitrary voltage and an arbitrary frequency can be obtained.

  The brushless DC motor 4 is driven by the three-phase AC output of the inverter 3. It consists of a stator (not shown) with three-phase windings and a rotor (not shown) with permanent magnets. For example, the stator is a 9-slot tooth wound directly through insulating paper, and a 3-phase 6-pole winding is star-connected. The rotor has 6 permanent magnets on the surface side with N and S poles. And embedded magnet type rotors arranged alternately.

  The output from the inverter 3 can be set to an arbitrary voltage / arbitrary frequency, and the brushless DC motor 4 has 6 poles. Therefore, the brushless DC motor 4 has a frequency (rotational speed) that is one third of the output frequency of the inverter 3. Driven. For example, when the output frequency of the inverter 3 is 60 Hz, the rotation speed of the brushless DC motor 4 can be driven at 20 r / s, and when the output frequency of the inverter 3 is 240 Hz, the rotation speed of the brushless DC motor 4 can be driven at 80 r / s. .

  The compression element 5 is driven by a brushless DC motor 4 and performs compression work. Here, the compression element 5 is a reciprocating compression element whose load torque varies greatly during one rotation. In the case of a reciprocating type compression element, compression is performed by reciprocating movement of the piston. During one rotation, half is divided into the suction process, and half is completely divided from the compression process. These two processes are necessary. Since a large load torque is concentrated on the compression process side, the load torque varies greatly. This variation in load torque has a characteristic that it becomes larger as driving at low speed, and vibration increases at driving at low speed.

  The compressor 6 stores the brushless DC motor 4 and the compression element 5 in a sealed container. It goes without saying that any refrigerant gas may be used, and any refrigerant gas such as an alternative refrigerant (R-134a, etc.) or a natural refrigerant (R-600a, CO2, etc.) may be used.

The compressor has a discharge pipe for discharging the compressed refrigerant and a suction pipe for sucking the refrigerant. A condenser 7, a decompressor 8, an evaporator 9, etc. are connected in series to the discharge pipe, and finally the refrigerant gas returns from the suction pipe to the compressor 6. By assembling such a refrigerating and air-conditioning system, heat can be radiated on the condenser 7 side and heat absorbed on the evaporator 9 side, so that heating or cooling can be performed. Further, by attaching a fan motor to the condenser 7 or the evaporator 9 and sending air, the efficiency of heat exchange can be increased, so that these heats can be used effectively and heated or cooled efficiently.

  The control device 10 drives the inverter 3. The output drives the six switching elements of the inverter 3 via the drive means 11.

  In general, when driving a brushless DC motor 4 having a permanent magnet as a rotor, the six switching elements of the inverter 3 are commutated at optimum positions while detecting the rotational position of the rotor. The brushless DC motor 4 is moved optimally.

  Further, the contents of the control device 10 will be described in detail.

  The position detector 12 detects the rotational position of the rotor of the brushless DC motor 4. In general, a method for detecting the counter electromotive voltage generated in the stator winding of the brushless DC motor 4 is well known, but a method for estimating the rotational position from the motor current or the current of the DC section is also often used. ing. Of course, there is a method of directly detecting the position using a magnetic sensor such as a Hall element. However, since it is difficult to attach such a sensor to the compressor, the former method (position sensorless method) is often used. Yes.

  In such a position sensorless system, since position detection is impossible at the time of startup, a predetermined phase (for example, between U and W) of the brushless DC motor 4 called positioning is forcibly energized before starting the rotor. A control circuit such as a method of rotating to a predetermined position or a forcible drive system for forcibly applying an AC waveform of a predetermined frequency and a predetermined voltage to drive the rotor is also necessary, but is omitted here.

  The commutation means 13 determines the timing of energization of the six switching elements of the inverter 3 based on the output of the position detection means 12. In general, the timing is determined so that the phase of the counter electromotive voltage coincides with the phase. However, in the case of a magnet-embedded motor (generally called an IPM motor), the reluctance torque is also taken into consideration, and the motor current is slightly increased. There are also cases in which the operation is advanced with respect to the phase of the counter electromotive voltage. Although this phase advance changes depending on the type of motor (especially the amount of reluctance component used), it is common to have an advance angle of about 0 to 15 degrees. Further, the conduction angle of the commutation means 13 is set to 120 degrees or more and less than 150 degrees, and the conduction angle is set according to the application. For example, when driving at a relatively high speed or when the load torque is high, the load range where the brushless DC motor can be driven can be expanded by increasing the energization angle, and the driving is performed with high efficiency. In this case, in the case of 120-degree energization or silent drive, it may be arbitrarily set such as driving that suppresses the sound accompanying the cogging torque of the motor by widening the energization angle.

  In the duty calculation means 14, in order to make the rotation speed of the brushless DC motor 4 constant at a predetermined rotation speed, the duty of PWM (pulse width modulation) control (predetermined period, called carrier period) Calculated) and output.

  The current detector 15 detects a current flowing through the inverter 3 and is a current sensor or a fixed resistor having a very small resistance value.

The current detecting means 16 detects the current flowing through the inverter 3 from the output of the current detector 15. Specifically, it can be easily configured by A / D conversion using, as an input, an output voltage of a current sensor used as the current detector 15 or a voltage generated in a fixed resistor having a small resistance value (for example, about 100 mΩ). In the embodiment of the present invention, a fixed resistor having a very small resistance value is used as the current detector, and it is also used as a shunt resistor of an overcurrent protection detection circuit for detecting an overcurrent of the inverter. As a result, the current detection circuit can be realized without adding a new circuit, so that the cost and size of the circuit can be reduced.

  The duty correction means 17 adds a predetermined value to the duty calculated by the duty calculation means 14 and corrects it according to the current flowing through the inverter 3.

  The synthesizing unit 18 synthesizes the commutation output from the commutation unit 13 and the PWM signal having the duty determined by the duty calculation unit 14 and the duty correction unit 17 and outputs the synthesized signal to the drive unit 11 to control the inverter 3.

  The operation of the compressor driving apparatus configured as described above will be described with reference to FIGS.

  FIG. 2 is a flowchart showing the operation in the first embodiment of the present invention.

  In FIG. 2, first, the driving speed of the brushless DC motor is detected in STEP1. Since the motor used in the present invention is a synchronous motor, the electrical frequency output from the inverter 3 and the rotational operation of the brushless DC motor 4 coincide with each other. The number can be detected. Although the number of rotations is used here, it may be the same as the number of rotations, for example, a rotation cycle or an angular velocity.

  Next, it is determined whether or not the speed detected in STEP 2 is equal to or lower than a predetermined speed. The predetermined speed here is set to a low rotational speed, and is set to a rotational speed (for example, 20 r / s) at which vibration of the reciprocating compressor due to torque pulsation of the load torque becomes large.

  At a rotational speed greater than this predetermined speed, the inertial force due to the inertia of the compressor is sufficiently large, so the influence on the speed fluctuation due to the pulsation of the load torque is small, and the resulting compressor vibration is also small. Accordingly, the process proceeds to STEP 3 at this time, and the inverter 3 is driven with a duty necessary for maintaining the predetermined speed calculated by the duty calculating means (that is, duty correction is not performed). The predetermined speed is determined by the configuration of the refrigeration air-conditioning system, the type and capacity of the compressor, inertia of the rotor of the motor, and the like, and it is desired to suppress vibration due to load torque pulsation generated at a low speed of the compressor. Set the rotation speed. Of course, a predetermined value that varies depending on the surrounding environment state (temperature, etc.) and the driving state may be determined.

  On the other hand, if the speed is equal to or lower than the predetermined speed, the process proceeds to STEP 4 to determine whether the operation is stable. The determination of the stable operation may be made from the temperature condition of each part in the refrigeration air-conditioning system control device (not shown) or the elapsed time. Since it is important that the operation is stable when it is determined that it is not stable, that is, in a transition period, the process proceeds to STEP 3 and the inverter 3 is driven with the duty width set by the duty calculation means 14 (that is, duty correction is not performed). ).

  If it is determined in STEP4 that the operation is stable, the process proceeds to STEP5, and the inverter is driven by adding the duty correction amount obtained by the duty correction means 17 to the duty calculated by the duty calculation means 14.

By operating as described above, when the brushless DC motor is driven at a speed lower than the predetermined speed, the duty necessary for driving at the target speed when the driving state is stabilized (that is, the duty calculated by the duty calculating means). ) Is corrected, and in other cases, the duty determined by the duty calculation means is set.

  Here, the torque and speed state during one rotation of the compressor will be described. FIG. 3 is a graph showing a torque and speed state per one rotation of the compressor. In FIG. 3, the load torque is indicated by a solid line, the motor torque is indicated by a broken line, and the angular speed of the compressor motor rotor is indicated by a one-dot chain line.

  In FIG. 3, since the compressor is a reciprocating compressor, the mechanical process changes at the top and bottom dead center (from the suction process to the compression process, or from the suction process to the compression process), and the load torque state changes. In particular, after the transition from the suction process to the compression process, the load torque increases rapidly. On the other hand, the motor torque generates a substantially constant torque per rotation. (Strictly speaking, the motor torque automatically changes according to the change of the load torque, especially when the inertia moment due to the low-speed driving is small, but here it is assumed to be a constant torque for the sake of simplicity of explanation).

  As shown in FIG. 3, when the instantaneous timing during one rotation of the compressor is seen, the load torque and the motor torque do not coincide with each other, so the motor torque is larger than the load torque as in the change of the angular velocity in FIG. In the section, the compressor is in an acceleration state, and the compressor is in a deceleration state in a section where the motor torque is small relative to the load torque. That is, the compressor repeatedly accelerates and decelerates during one rotation even when the compressor is in a stable driving state.

  FIG. 4 is a three-phase current waveform of the brushless DC motor. FIG. 4A shows a current waveform when duty correction is not performed, and it can be seen that the phase current waveform varies greatly during one rotation of the compressor. This is almost synchronized with the load fluctuation state of the compressor, and the current in the section where the load torque is large is large and the current in the section where the load torque is small is small. The fluctuation of the current accompanying the fluctuation of the load torque during one rotation leads to an increase in the loss of the brushless DC motor, and the motor efficiency is reduced as compared with the case where the brushless DC motor is driven at a constant speed. That is, when the brushless DC motor is used for driving the compressor, the efficiency is lowered due to the load fluctuation of the compressor.

  FIG. 5 is a graph showing the current waveform of the inverter 3 and the position detection timing. FIG. 5A shows a case where duty correction is not performed. The waveform (a) in FIG. 5 is the waveform of the output of the current detector 15 (that is, the current flowing through the inverter 3). For simplicity, the current is detected at the timing when the PWM signal is on, and the instantaneous value is plotted in the inverter. The flowing current is represented as an envelope. The actual current waveform includes a high-frequency switching waveform synchronized with PWM on or off. FIG. 2B shows the detection timing of the induced voltage zero cross by the position detecting means 12. Assuming that the brushless DC motor 4 in this embodiment uses a 6-pole motor, 18 position detection signals can be obtained per rotation. That is, by measuring the time at which the position detection signal is generated, the time of 1/18 rotation of the motor (that is, the angular velocity at a mechanical angle of 20 degrees) can be obtained.

  In the waveform of the inverter current shown in FIGS. 5A and 5A, since the sum of the currents flowing through the three-phase windings of the brushless DC motor 4 appears, the fluctuation of the current for three phases appears. That is, the positive current of the three phases of the brushless DC motor shown in FIG. 4 appears. Therefore, it is possible to suppress fluctuations in all three phases of the brushless DC motor 4 by keeping the envelope of the current flowing through the inverter 3 within a predetermined range (that is, suppressing fluctuations in the current flowing through the inverter). It is possible to suppress increase in motor loss due to current fluctuation.

Now, a method for suppressing fluctuations in the current flowing through the inverter 3 will be described. The PWM control inverter can control the voltage applied to the brushless DC motor 4 and adjust the current flowing through the brushless DC motor 4 by changing the PWM ON time. In the first embodiment of the present invention, the correction amount obtained by the duty correction means is added to the duty required to maintain the target speed calculated by the duty calculation means, so that the current flowing through the inverter is I try to suppress fluctuations.

  The duty correction by the duty correction means is, for example, an average current or target current per rotation and a current flowing every PWM ON, and an amount obtained by adding a constant gain to the difference between the target (or average) current is a correction amount As a method to make the flowing current close to the target (or average) current, or to correct the difference between the current in each section and the maximum current by correcting with a predetermined gain in a section where the detected current with respect to the maximum current is smaller than a predetermined ratio , A method of correcting the next PWM ON width from the difference between the current detection value at the previous PWM ON and the current detection value, and eliminating the difference in the current detected at each PWM cycle, a predetermined A method of integrating the current for each section (for example, every position detection interval) and correcting so that the integrated current for each section becomes constant, or between the 1/18 rotation time of the target speed and each position detection signal And a method of correction from the difference between, can be implemented in a variety of ways. In addition, these methods do not need to perform high-level arithmetic using a high-speed arithmetic processor in real time and can be realized by a very simple method, thereby realizing cost reduction of the apparatus.

  Note that by correcting the duty, the duty is driven with a duty width that is determined by the duty calculating means, and there is a possibility that the speed becomes transiently higher than the temporary target speed. Then, as the speed becomes higher than the target speed, the duty calculating means 14 operates so as to decrease the duty and drive at a predetermined speed, so that stable driving at the target speed is continued. Furthermore, since the duty near the maximum current (near the maximum load torque) decreases at this time, the current near the maximum load torque (maximum current) also decreases.

  FIG. 5B shows the current (a) envelope of the inverter 3 and the position detection timing (b) when the duty correction is performed. As shown to (a), it turns out that the amplitude of the envelope of the electric current which flows into the inverter 3 is suppressed by performing duty correction. Further, the phase current waveform at this time is shown in FIG. 4B, and it can be seen that the fluctuation of the phase current per one rotation can be suppressed.

  Thus, by correcting the duty, it is possible to suppress a reduction in efficiency when the compressor is driven by the brushless DC motor 4. That is, by performing duty correction, the efficiency (generally COP) of the compressor can be increased as compared with a conventional compressor control device.

  Next, the position detection timing (b) will be described with reference to FIG. 5 (1) and 5 (b), the position detection timing is a section where the inverter current (a) is large (ie, the compression process where the load torque is high), the position detection timing interval is coarse, and a section where the inverter current is small (ie, the load torque is small). It is dense in the inhalation process. Since the position detection timing interval corresponds to a 1 / 18th rotation cycle of the motor, it can be seen that the speed of the compressor fluctuates during one rotation.

  On the other hand, in FIGS. 5B and 5B in which duty correction is performed, the difference in position detection timing interval is small during one rotation. That is, the speed fluctuation of the compressor during one rotation is suppressed.

This is because the compressor has a very large moment of inertia, so even if the duty correction amount is added to the base duty obtained by the duty calculation means (that is, the inverter output is increased), the compressor motor reacts immediately. It does not (i.e. accelerates) but reacts (i.e. accelerates) from a position delayed by a certain mechanical angle. Therefore, by performing duty correction in the section where the inverter current is low before the load torque becomes maximum, the compressor is accelerated in the section where the load torque becomes maximum, and as a result, 1
The fluctuation of the driving speed of the rotating motor was suppressed.

  Since the speed fluctuation of the motor with respect to the load torque fluctuation in the compressor process is a major factor in the generation of the vibration of the compressor, the driving vibration of the compressor can be suppressed by performing the duty correction according to the present embodiment.

  As described above, in the present embodiment, a compressor having a compression element, a brushless DC motor having a permanent magnet for driving the compression element in a rotor, and a brushless DC motor by converting a DC voltage into a three-phase AC. An inverter for supplying electric power to the DC motor, and a duty calculating means for controlling a voltage applied to the brushless DC motor, and calculating a PWM duty for making the refrigeration capacity of the compressor variable by varying the rotation speed Current detecting means for detecting the current flowing through the inverter, and duty correcting means for correcting the voltage applied to the brushless DC motor determined by the duty voltage calculating means so that the current detected by the current detecting means is constant. It is the control apparatus of the compressor which has. As a result, the envelope of the current flowing through the inverter can fall within a predetermined range, so that the efficiency of the brushless DC motor can be increased, and a highly efficient compressor drive device can be provided.

  Further, the maximum of the duty correction section by the duty correction means is a section that does not include 30 degrees before and after the position where the current flowing through the inverter 3 is maximum, so that the speed of the compressor due to load fluctuations during one rotation of the compressor. The fluctuation can be suppressed and the vibration of the compressor can be suppressed.

  Moreover, the current detection means detects the voltage generated in the resistor provided in series between the rectifier circuit and the inverter circuit, and it is not necessary to newly provide a current detection circuit by using it also as the overcurrent detection circuit of the inverter. Therefore, the circuit can be reduced in size and cost.

  In addition, the commutation means has an energization angle of 120 or more and less than 150 degrees, and by driving the inverter, it is possible to select a flexible energization angle according to the application and for very simple control. Since an inexpensive processor can be used, the price of the apparatus can be reduced.

  Further, by driving the reciprocating compressor, it is possible to realize low vibration of the reciprocating compressor having relatively large vibration.

(Embodiment 2)
FIG. 1 is a configuration diagram of a refrigerator using a compressor driving device according to a second embodiment of the present invention.

  In FIG. 1, in this embodiment, the drive unit of the reciprocating compressor is used in the refrigeration cycle of the refrigerator, and the evaporator 9 cools the inside 21 of the refrigerator 20 surrounded by the heat insulating wall 19. Yes.

  By using the reciprocating compressor of the present invention for a refrigerator, it is possible to reduce the power consumption of the refrigerator by improving the compressor COP.

  Furthermore, noise accompanying compressor drive vibration can be reduced by reducing compressor vibration, and the refrigerator can be silenced.

Further, since the refrigerator is in a stable state of cooling in the refrigerator most of the day, the compressor is often driven at a low speed. Driving the compressor at a low speed leads to the system efficiency of the refrigeration cycle, and has a great effect on reducing the power consumption of the refrigerator. However, with a reciprocating compressor, the lower the drive, the greater the variation in load torque during one rotation, and the drive vibration increases significantly. For this reason, in the reciprocating compressor, it is necessary to take measures such as suppressing the minimum rotational speed to sacrifice the energy saving effect or adding a vibration suppressing member at the expense of cost.

  However, in the compressor driving device of the present invention, since the compressor drive vibration is reduced, the compressor can be driven at a lower speed than before, and the power consumption of the refrigerator can be reduced by increasing the system efficiency of the refrigeration cycle. realizable.

  Moreover, the suppression of the driving vibration of the compressor does not require the addition of a vibration suppressing member, and the cost of the refrigerator can be reduced.

  Furthermore, suppression of compressor drive vibration can also reduce noise caused by vibration, so that the refrigerator can be quiet.

  As described above, the compressor drive device according to the present invention is a device such as a refrigerator, an air conditioner, a dehumidifier, a heat pump water heater, a pump, or the like that has a large load fluctuation per one rotation of the motor and the load torque fluctuates periodically. Widely applicable to.

DESCRIPTION OF SYMBOLS 2 Rectifier circuit 3 Inverter 4 Brushless DC motor 5 Compression element 6 Compressor 10 Control apparatus 13 Commutation means 14 Duty calculation means 15 Current detector (resistance)
16 Current detection means 17 Duty correction means

Claims (6)

A compressor having a compression element, a brushless DC motor having a permanent magnet for driving the compression element in a rotor, an inverter for converting a DC voltage into a three-phase AC and supplying electric power to the brushless DC motor, Duty calculation means for calculating a PWM duty for controlling the voltage applied to the brushless DC motor and varying the rotational speed to vary the refrigeration capacity of the compressor, and a current for detecting the current flowing through the inverter A compressor driving apparatus comprising: a detection unit; and a duty correction unit that corrects a voltage applied to the brushless DC motor determined by the duty calculation unit so that an envelope of a current flowing through the inverter falls within a predetermined range. The compressor driving device according to claim 1, wherein the section for performing duty correction does not include 30 degrees before and after the position where the current flowing through the inverter is maximum. The compression according to claim 1 or 2, wherein the current detection means detects a voltage generated in a resistor provided in series between the rectifier circuit and the inverter circuit, and is also used as a circuit for detecting an overcurrent of the inverter. Machine drive. The compressor driving device according to any one of claims 1 to 3, wherein the commutation means has a conduction angle of 120 degrees or more and less than 150 degrees. The compressor driving device according to any one of claims 1 to 4, wherein the compressor is a reciprocating compressor having a reciprocating compression element. The refrigerator which has the drive device of the said compressor of at least 1 of Claims 1-5.

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