JP2007151305A - Inverter system, control method thereof and refrigiration cycle system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inverter system, a control method thereof and a refrigeration cycle system capable of accurately recognizing the rotational speed of a DC motor, regardless of the number of poles of a DC motor, thus enabling the DC motor to constantly perform appropriate drive. <P>SOLUTION: This system determines the number of poles of a brushless DC motor M based on load fluctuations generated during one turn of the brushless DC motor M. If the determination result shows four poles, an output of a switching circuit 4 is controlled using, without any change, a target rotational speed Ns given by a rotational-speed command. If the determination result shows six poles, on the other hand, the output of the switching circuit 4 is controlled using a value of two-thirds of the target rotational speed Ns as the appropriate target rotational speed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an inverter device for driving a DC motor for driving a compressor at a variable speed, a control method therefor, and a refrigeration cycle device.

Conventionally, an inverter device that drives a DC motor of a compressor includes a controller in which a dedicated control program corresponding to the operation of the DC motor is incorporated. As the DC motor, a 4-pole or 6-pole DC motor is mainly used (for example, Patent Document 1). In the DC motor, the relationship between the number of poles and the number of concentrated winding slots is set to pole number: slot number = 2: 3. A 4-pole motor has 6 slots and a 6-pole motor has 9 slots.
JP 2004-194454 A

  The 4-pole motor makes one rotation when the cycle of the output of the inverter device (voltage changing in a sine wave shape) is repeated twice. The 6-pole motor rotates once when the output cycle of the inverter device is repeated three times. Therefore, when a 6-pole motor is driven using a controller for a 4-pole motor, the 6-pole motor can be rotated, but the rotational speed recognized by the controller is a low value of 2/3 of the actual rotational speed. .

  For example, when an inverter device having a controller for a four-pole motor is mounted on a refrigeration cycle device such as an air conditioner or a refrigerator, the compressor motor is 6 even if the controller recognizes a rotational speed of 60 rps. In the case of a pole motor, the actual rotational speed is 40 rps. In the case of this mismatch, there is a problem that proper control becomes difficult in the case of a refrigeration cycle apparatus that performs temperature control based on the rotational speed.

  On the other hand, it is desirable for the inverter device to be as versatile as possible. In other words, an inverter device that has been conventionally manufactured individually according to the number of poles of the DC motor can be used as long as it is an inverter device that can always recognize and drive the rotational speed of the DC motor regardless of the number of poles of the DC motor. Can be unified into one type. As a result, inventory management or the like becomes unnecessary.

  In general, the compressor repeats suction, compression, and discharge operations during one rotation of the DC motor. For this reason, the load concerning a DC motor fluctuates periodically during one rotation of the DC motor. The load fluctuation is small in the scroll compressor and the helical compressor, but is large in the reciprocating compressor and the rotary compressor. Along with this load fluctuation, the speed during one rotation of the DC motor fluctuates, which is a major cause of mechanical vibration and noise.

  Therefore, in the example of Patent Document 1 described above, the voltage induced in each phase winding of the DC motor is detected, and one cycle of the output of the inverter device is divided into six sections based on the induced voltage, and the load fluctuations for each section. Is detected, and the output of the inverter device is changed in accordance with the detected load fluctuation, thereby suppressing the speed fluctuation of the DC motor and reducing noise and vibration. As described above, a means for dividing one cycle of the output of the inverter device into a plurality of sections and detecting a load fluctuation for each section is known.

  In addition, as an example of a rotary type compressor or a reciprocating type compressor, there is one in which two or more compression mechanisms are provided to reduce load fluctuation.

  In consideration of the above circumstances, the present invention can accurately recognize the rotational speed of a direct current motor regardless of the number of poles of the direct current motor, thereby enabling an inverter device to always drive the direct current motor appropriately. Another object is to provide a control method thereof and a refrigeration cycle apparatus.

  An inverter device according to a first aspect of the invention drives a DC motor for driving a compressor at a variable speed, and has a discriminating means for discriminating the number of poles of the DC motor based on a load fluctuation during one rotation of the DC motor. And a control means for controlling the driving of the compressor based on the determination result of the determination means.

  According to the inverter device, the control method thereof, and the refrigeration cycle device of the present invention, it is possible to accurately recognize the rotational speed of the DC motor regardless of the number of poles of the DC motor. Is possible.

[1] A first embodiment of the present invention will be described below with reference to the drawings.
As shown in FIG. 1, a rectifier circuit 2 is connected to a commercial AC power supply 1, and a switching circuit 4 is connected to an output terminal of the rectifier circuit 2 via a smoothing capacitor 3.

  The switching circuit 4 has a series circuit of a pair of switching elements on the upstream side and the downstream side along the direction of the DC voltage applied from the rectifier circuit 2 for three phases U, V, and W. A transistor 5u + is provided on the upstream side, a transistor 5u− is provided on the downstream side, a transistor 5v + is provided on the upstream side of the V phase, a transistor 5v− is provided on the downstream side, a transistor 5w + is provided on the upstream side of the W phase, and a transistor 5w− is provided on the downstream side. ing. A freewheeling diode D is connected in antiparallel to each transistor. The interconnection point between the transistors 5u + and 5u− becomes the output terminal Qu, the interconnection point between the transistors 5v + and 5v− becomes the output terminal Qv, and the interconnection point between the transistors 5w + and 5w− becomes the output terminal Qw.

  The phase windings Lu, Lv, and Lw of a DC motor, for example, a three-phase brushless DC motor M, are connected to the output terminals Qu, Qv, and Qw of the switching circuit 4. The brushless DC motor M includes a stator having three phase windings Lu, Lv, and Lw connected in a star shape and a rotor having a permanent magnet. The rotor rotates due to the interaction between the magnetic field generated by the current flowing through the phase windings Lu, Lv, and Lw and the magnetic field generated by the permanent magnet fixed to the rotor.

  This brushless DC motor M is mounted on a refrigeration cycle apparatus, for example, a compressor 31 of an air conditioner 30. The compressor 31 sucks, compresses, and discharges the refrigerant by the operation of the brushless DC motor M. During cooling, the refrigerant discharged from the compressor 31 flows through the four-way valve 32 to the outdoor heat exchanger 33 that functions as a condenser, and the refrigerant that has passed through the outdoor heat exchanger 33 is shown by a solid line arrow in the figure. It flows to the indoor heat exchanger 35 that functions as an evaporator via an expansion valve 34 that is a pressure reducing device. The refrigerant that has passed through the indoor heat exchanger 35 is sucked into the compressor 31 through the four-way valve 32. Note that the compressor 31, the four-way valve 32, the outdoor heat exchanger 33, the expansion valve 34, and the indoor heat exchanger 35 are connected by a refrigerant pipe made of a copper pipe or the like. During heating, the refrigerant discharged from the compressor 31 flows through the four-way valve 32 to the indoor heat exchanger 35 that functions as a condenser, and the refrigerant that has passed through the indoor heat exchanger 35 is, as indicated by the dashed arrows in the figure. It flows to the outdoor heat exchanger 33 that functions as an evaporator via the expansion valve 34. The refrigerant that has passed through the outdoor heat exchanger 33 is sucked into the compressor 31 through the four-way valve 32.

  The air conditioner 30 includes a device control unit 36 in addition to the refrigeration cycle. The device control unit 36 controls the compressor 31, the four-way valve 32, the expansion valve 34, an outdoor fan (not shown), an indoor fan, and the like according to operating conditions and room temperature set by the user. Among these, a signal for controlling the compressor 31 including the rotation speed command value is supplied to the inverter control unit 10. A rotation position detection unit 11 is connected to the inverter control unit 10.

  The rotational position detector 11 detects a voltage induced in the non-energized phase winding among the phase windings Lu, Lv, Lw of the brushless DC motor M, and the brushless DC motor M is detected based on the change in the induced voltage. The rotational position of the rotor is detected. This detection result is supplied to the inverter control unit 10.

  The inverter control unit 10 generates three sine wave voltages whose frequencies change according to the rotation position detected by the rotation position detection unit 11 and whose phase angles are different from each other by 120 degrees, and these sine wave voltages and carriers are generated. Three drive signals (pulse width modulation signals) for turning on and off each transistor of the switching circuit 4 are generated and output by pulse width modulation (PWM) by voltage comparison with a triangular wave signal of a predetermined frequency F. The three drive signals sequentially switch the multi-phase energization in which at least one of the series circuit transistors in the switching circuit 4 is turned on and off and the at least one other series circuit transistor is turned on. By switching the multi-phase energization (so-called commutation), three inter-phase voltages (voltages changing in a sine wave) at levels according to the on / off duty of the transistor are generated between the output terminals Qu, Qv, Qw. . When these interphase voltages are applied to the phase windings Lu, Lv, Lw, a sinusoidal current flows through the phase windings Lu, Lv, Lw, and the rotor of the brushless DC motor M rotates.

  The on / off duty of the transistor changes according to the voltage levels of the three generated sine wave voltages. This voltage level is adjusted according to a rotation speed command signal supplied from the device control unit 36 of the air conditioner 30. That is, when the air conditioning load is large and the compression function force needs to be increased, the voltage level of each sine wave voltage is adjusted in the increasing direction, and the on / off duty is increased (the on period becomes longer and the off period becomes longer). Becomes shorter). As the on / off duty increases, the level of the interphase voltage increases, and the phase winding current increases. Along with this, the rotation speed of the brushless DC motor M increases. When the air conditioning load is small and the compression function needs to be reduced, the voltage level of each sine wave voltage is adjusted in the downward direction to reduce the on / off duty (the on period is shortened and the off period is lengthened). Become). When the on / off duty decreases, the level of each interphase voltage decreases and the phase winding current decreases. Along with this, the rotation speed of the brushless DC motor M decreases.

  Thus, a so-called 120-degree energization from the switching circuit 4 to the brushless DC motor M is performed. In this 120-degree energization, when the brushless DC motor M is a 4-pole motor, the brushless DC motor M makes one rotation when the cycle of the interphase voltage (360 degrees of electrical angle) output from the switching circuit 4 is repeated twice. To do. When the brushless DC motor M is a 6-pole motor, the brushless DC motor M rotates once when the cycle of the interphase voltage output from the switching circuit 4 is repeated three times.

  On the other hand, the detection result of the rotational position detection unit 11 is supplied to the pole number determination unit 20. The pole number discriminating unit 20 discriminates the number of poles of the brushless DC motor M based on the load fluctuation during one rotation of the brushless DC motor M. The pole number discriminating unit 20 includes a heavy load detecting unit 21, a timer 22, and a discriminating unit 23. ing.

  Based on the detection result of the rotational position detector 11, the heavy load detector 21 sets each cycle of the output (sinusoidal interphase voltage) of the switching circuit 4 (360 degrees of electrical angle = 180 degrees of rotation mechanical angle of a 4-pole motor). Each of which is divided into 6 sections (corresponding to a rotating machine angle of 30 degrees of a 4-pole motor), and the load on the compressor 31 becomes heavy in each section (36 sections) within at least 6 cycles of the same output. A section (compression period of the compressor 31) is detected. The six sections set within one period correspond to the respective energization modes of the above-described multiphase energization. In a section where the load on the compressor 31 is heavy (referred to as a heavy load section), the speed of the rotor of the brushless DC motor M is slow. The time from the start to the end of each section is counted by the timer 22 and the difference between two adjacent time counts in each time count is sequentially calculated, and the calculated difference turns from increasing to decreasing (Peak section) is detected as a heavy load section.

  The determination unit 23 counts the number of heavy load sections detected by the heavy load detection unit 21, and the number of poles of the brushless DC motor M is 4 or 6 depending on the number of counts in 6 cycles. And whether the compressor 31 is a 1-cylinder rotary type or a 2-cylinder rotary type.

  The relationship between the load fluctuation during one rotation of the 4-pole motor and the energization mode is shown in FIG. 2 separately for the case of the 1-cylinder rotary type and the case of the 2-cylinder rotary type. The load becomes heaviest during the compression stroke before discharge. Therefore, in the 1-cylinder rotary type, the number of heavy load sections (also referred to as peak sections) during one rotation of the motor is “1”, whereas in the 2-cylinder rotary type, two compression / discharge strokes are performed during one rotation of the motor. Therefore, the number of heavy load sections is “2”.

  FIG. 3 shows the relationship between the load fluctuation and the energization mode in the 6 output cycles of the inverter device, divided into the case of 1-cylinder rotary type, 2-cylinder rotary type, 4-pole motor, and 6-pole motor. ing. In the case of a 1-cylinder rotary type and a 4-pole motor, the number of heavy load sections (peak sections) (number of peaks) is “3”. In the case of a 1-cylinder rotary type and a 6-pole motor, the number of heavy load sections is “2”. In the case of a 2-cylinder rotary type and a 4-pole motor, the number of heavy load sections is “6”. In the case of a 2-cylinder rotary type and a 6-pole motor, the number of heavy load sections is “4”. Therefore, the determination unit 23 determines the form of the compressor and the number of poles of the motor based on the number of heavy load sections in the output device 6 cycles of the inverter device.

  The rectifier circuit 2, the smoothing capacitor 3, the switching circuit 4, the inverter control unit 10, the rotational position detection unit 11, and the pole number determination unit 20 constitute an inverter device that drives the brushless DC motor M at a variable speed.

Next, the operation will be described with reference to the flowchart of FIG.
When the brushless DC motor M is started (YES in step 101), the frequency F of the triangular wave signal for pulse width modulation, the so-called PWM carrier frequency F, is set to Fb higher than the normal value Fa used during operation (step 102). . This is a measure for more accurately detecting the rotational position during the energization period for pole number discrimination than during normal operation. Regardless of the rotational position of the rotor of the brushless DC motor M, the switching circuit 4 is driven to perform so-called forced commutation for forcibly switching the multi-phase energization to the brushless DC motor M (step 103). At this time, the ON / OFF duty of each transistor in the switching circuit 4 is kept constant (step 104). The brushless DC motor M is started by this forced commutation and constant duty control.

  When the brushless DC motor M is activated, a rotational position signal corresponding to the rotational position of the rotor of the brushless DC motor M is output from the rotational position detector 11. The time from the detection of this rotational position signal to the detection of the next rotational position signal is sequentially detected by the timer 22, and based on this time, the heavy load section 21 is detected (step 105). When the output for six cycles of the switching circuit 4 is completed (YES in Step 106), the number of poles of the brushless DC motor M is determined according to the number of heavy load sections detected by the determination unit 23 (Step 107). .

  Thereafter, normal operation is started, and a rotation speed command corresponding to the air conditioning load emitted from the device control unit 36 of the air conditioner 30 is taken into the inverter control unit 10 (step 108).

  In the inverter control unit 10, if the number of poles determined by the determination unit 23 is four (YES in step 109), the target rotation speed Ns based on the rotation speed command is determined as it is as the target rotation speed Ns ( Step 110). If the determined number of poles is 6 (NO in step 109), a value of 3/2 of the target speed Ns based on the speed command is set as the target speed Ns in this case (step) 111).

  In the inverter control unit 10, the rotation speed N of the brushless DC motor M is calculated in accordance with the rotation position signal from the rotation position detection unit 11 (step 112). In this case, the calculation of the rotation speed N in the inverter control unit 10 is performed with 4 poles as a default, and N = 1 / [6 × (time from rotation position detection to next rotation position detection (s)) ] Or N = 1 / (time from rotational position detection to rotational position detection 6 times later (s))].

  Subsequently, the calculated rotation speed N is compared with the determined target rotation speed Ns (step 113). Then, with the PWM frequency F set to the normal value Fa (step 114), the on / off duty of each transistor in the switching circuit 4 is controlled according to the comparison result (step 115). That is, when the rotational speed N is lower than the target rotational speed Ns, the on / off duty is increased, and when the rotational speed N is higher than the target rotational speed Ns, the on / off duty is decreased, and the rotational speed N and the target rotational speed Ns are obtained. If they are almost the same, the on / off duty at that time is maintained. When the operation described above is completed, unless an operation stop instruction is input, the process returns to step 108 and steps 108 to 115, which are the rotational speed control, are repeated.

  As described above, the number of poles of the brushless DC motor M is determined from the load fluctuation during one rotation of the brushless DC motor M, and if the determination result is four poles, the target rotational speed Ns based on the rotational speed command is directly used as the target. The output of the switching circuit 4 is controlled using the rotational speed Ns. If the determination result is 6 poles, the output of the switching circuit 4 is controlled by setting the value of 3/2 of the target rotational speed Ns to an appropriate target rotational speed Ns. . Therefore, even if a program for a 4-pole motor is used as the actual rotational speed calculation program in the inverter control unit 10, proper driving is always performed for both the 4-pole brushless DC motor M and the 6-pole brushless DC motor M. It becomes possible.

  The process for determining the number of poles of the brushless DC motor M, that is, steps 102 to 107, is performed only once at the time of startup, and only a very short time is required, so there is almost no influence on the temperature control of the air conditioner 30.

  In the above embodiment, only the discrimination between the 4-pole motor and the 6-pole motor has been described. However, since the mainstream of the DC motor is 4 poles and 6 poles, the discrimination between the 4 poles and 6 poles is sufficient for practical use. Is. Further, although the rotational position is detected from the induced voltage of each phase winding, the present invention can also be applied to the case where the rotational position is estimated by calculating the current flowing through each phase winding.

[2] A second embodiment of the present invention will be described.
In the first embodiment, the target rotational speed Ns is corrected based on the discrimination result between the 4-pole motor and the 6-pole motor. In the second embodiment, the actual rotational speed side on the motor side is used. The method has been changed to add correction. Here, as shown in FIG. 5, the processes of steps 201 to 206 are executed instead of the processes of steps 108 to 113 of the first embodiment.

That is, in the inverter control unit 10, based on the rotational position signal of the rotational position detection unit 11, the period of each energization mode of the multiphase energization, that is, the time from the rotational position detection to the next rotational position detection (referred to as the energization period) Is obtained (step 201). If the determined number of poles is four (YES in step 202), the determined energization period t is determined as it is as the energization period t (step 203). If the determined number of poles is six (NO in step 202), a value 2/3 of the determined energization period t is newly determined as the energization period t (step 204). Then, the rotational speed N (rps) of the brushless DC motor M is calculated by the following equation using the determined energization period t.
N = 1 / (6 × t)
A rotation speed command corresponding to the air conditioning load is issued from the device control unit 36 of the air conditioner 30, and the target rotation speed Ns according to the rotation speed command is compared with the calculated rotation speed N (step). 206). Then, with the PWM frequency F set to the normal value Fa (step 114), the on / off duty of each transistor in the switching circuit 4 is controlled according to the comparison result (step 115).

  Other configurations, operations, and effects are the same as those in the first embodiment. Therefore, the description is omitted.

  [3] It should be noted that the present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiments. You may delete a some component from all the components shown by each embodiment.

The block diagram which shows the structure of each embodiment of this invention. The figure which shows the relationship between the load fluctuation | variation in 1 rotation of 4 pole motor and energization mode in each embodiment separately in the case of 1 cylinder rotary type, and the case of 2 cylinder rotary type. The figure which shows separately the relationship between the load fluctuation | variation and energization mode in each embodiment in the case of a 1-cylinder rotary type, a 2-cylinder rotary type, a 4-pole motor, and a 6-pole motor. The flowchart for demonstrating the effect | action of 1st Embodiment. The flowchart for demonstrating the effect | action of 2nd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Commercial AC power supply, 2 ... Rectifier circuit, 3 ... Smoothing capacitor, 4 ... Switching circuit, 5u +, 5u-, 5v +, 5v-, 5w +, 5w -... Transistor (switching element), M ... Brushless DC motor (DC motor) ), Lu, Lv, Lw ... phase winding, 10 ... control unit, 11 ... rotational position detection unit, 20 ... pole number determination unit, 21 ... heavy load detection unit, 22 ... timer, 23 ... determination unit, 30 ... air Harmonic machine 31 ... Compressor 36 ... Control unit

Claims (4)

In an inverter device that drives a DC motor for driving a compressor at a variable speed, a discriminating unit that discriminates the number of poles of the DC motor based on a load fluctuation during one rotation of the DC motor, and a discrimination result of the discriminating unit An inverter device comprising: control means for controlling driving of the compressor. 2. The inverter device according to claim 1, wherein the determination unit divides one cycle of the output of the device into six sections, and each of the sections within at least six cycles of the output has a section where the load of the compressor is heavy. Depending on the number of detected sections, whether the number of poles of the DC motor is 4 poles or 6 poles, whether the compressor is a one-cylinder rotary type or a two-cylinder rotary type An inverter device characterized by being distinguished regardless. A refrigeration cycle apparatus comprising a compressor, an evaporator, a decompression device, and a condenser, which are driven by the inverter device according to claim 1 or 2, connected by a refrigerant pipe. In the control method of the inverter device that drives the DC motor for driving the compressor at a variable speed, the number of poles of the DC motor is determined based on a load fluctuation during one rotation of the DC motor, and based on the determination result, A method for controlling an inverter device, comprising: calculating a rotational speed of a DC motor.

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