JP2012186876A - Compressor drive unit and refrigerator using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain generation of driving oscillation during low-speed driving of a compressor.SOLUTION: The present invention includes: a compressor 105; an inverter 102 that varies the driving speed of the brushless DC motor 103; position detection means 111 that detects the position of a rotor of the brushless DC motor; commutation means 112 that switches an energization phase according to the position detection means; synchronization signal generation means 115 that switches the energization phase of the inverter in a fixed period; and selection and switching means 203 that selects and switches either of an output by the position detection means or an output by the synchronization signal generation means. When a position signal by the position detection means does not occur within a predetermined time, the energization phase of the inverter is switched by the output by the synchronization signal generation means.

Description

  The present invention relates to an inverter-driven compressor mainly used in a refrigerator-freezer or an air conditioner, and more particularly, a compressor having a compression element whose load torque fluctuates during one rotation (for example, a reciprocating type or a one-piston type rotary). And the like.

  Conventionally, this main compressor drive device uses a highly efficient brushless DC motor to drive the compressor element, and is variable by pulse width modulation control (hereinafter referred to as PWM control) of the motor applied voltage, and the rotational speed of the motor. To change the refrigeration capacity of the compressor. Thus, in a refrigerator-freezer (hereinafter referred to as a refrigerator) or an air conditioner, when the temperature is stable, the compressor is driven at a low speed, thereby improving the efficiency of the entire refrigeration system and realizing energy saving.

  In a reciprocating compressor often used in a refrigerator, half of the rotation is a refrigerant suction process with a small load torque, and the other half of the rotation is a compression / discharge process with a large load torque. It is known that the load torque varies greatly.

  Since the motor torque of the brushless DC motor generates a substantially constant torque during one rotation, the angular velocity fluctuates during one rotation from the relationship with the load torque. This fluctuation in angular velocity causes the drive vibration of the compressor. In particular, the vibration increases in the low-speed drive region where the energy due to the moment of inertia of the compressor rotation system (rotor, shaft, piston, etc.) is small. The low-speed drive has large vibrations and has practical problems.

  The same applies to rotary compressors often used in air conditioners. Even if not as much as reciprocating compressors, there are similar load torque pulsations due to the relationship between the suction process and compression / discharge process during one rotation. Due to the same principle as described above, a large vibration is generated in low-speed driving.

  In response to these phenomena, a synchronous drive that switches the current-carrying pattern of the inverter at a constant time at low-speed rotation has been performed so that the phase of the current and voltage changes according to the angular speed. Efforts have been made to suppress fluctuations in angular velocity and reduce vibration (see, for example, Patent Document 1).

  FIG. 7 shows a conventional compressor driving apparatus described in Patent Document 1. In FIG. As shown in FIG. 7, the commercial power source 100 is a 50 or 60 Hz AC power source having an effective value of 100 V in Japan, and the rectifier circuit 101 is a rectifying / smoothing circuit composed of four diodes connected to the bridge and a smoothing capacitor. It is a circuit and converts the AC voltage of the commercial power supply 100 into a DC voltage. The inverter 102 is composed of six switching elements (indicated by IGBT in the drawing) connected in a three-phase bridge and six diodes connected in parallel in the reverse direction to the switching elements, and the rectifier circuit 101 is controlled by controlling the switching elements. Is converted into a three-phase AC output.

  The brushless DC motor 103 includes a stator (not shown) having a three-phase winding and a rotor (not shown) having a permanent magnet, and is driven by an inverter 102.

The compression element 104 driven by the brushless DC motor 103 is a reciprocating type or a rotary type, and the load torque varies during one rotation. In the case of the reciprocating type in particular, the gas is compressed by the reciprocating motion of the piston, so half of one rotation is a suction process with a small load torque, and the other half is a compression / discharge process with a large load torque. Large load torque fluctuations occur. Also, the rotary type has a suction process and a compression / discharge process during one rotation, and thus there is a large load torque fluctuation during one rotation, although not as much as in the reciprocating type.

  The compressor 105 houses the brushless DC motor 103 and the compression element 104 in a hermetic container, and has a discharge pipe for discharging the compressed refrigerant and a suction pipe for sucking the refrigerant. The discharge pipe includes a condenser 106. The refrigerating and air-conditioning system is configured such that the decompressor 107 and the evaporator 108 are connected in series and the refrigerant gas is returned to the suction pipe of the compressor again. As a result, the heat dissipation action occurs on the condenser 106 side and the heat absorption action occurs on the evaporator 108 side, so that heating or cooling can be performed.

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

  In general, when driving a brushless DC motor 103 having a permanent magnet as a rotor, optimal switching is achieved by commutating the switching element of the inverter 102 at an appropriate position while detecting the rotational position of the rotor. Realize.

  Next, the configuration of the control device 109 will be described in detail.

  The position detector 111 detects the rotational position of the rotor of the brushless DC motor 103. As a method of detecting the rotational position of the rotor, a method of detecting an induced voltage generated in the stator winding by rotating a rotor having a permanent magnet of the brushless DC motor 103, a motor current or a current of a DC section A method for estimating the rotational position from the above is generally used. Of course, there is a method of directly detecting the position using a magnetic sensor such as a Hall element, but it is difficult to attach such a sensor to the compressor, so the former method (position sensorless method) is common. .

  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. Generally, the timing is determined so that the phase of the induced voltage coincides with that of the induced voltage. However, in the case of an embedded magnet motor (generally called an IPM motor), the reluctance torque is taken into consideration, and the motor current is slightly In some cases, the phase is advanced from the phase of the induced voltage. Although this phase advance varies 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 10 degrees.

  Since the output of the position detection unit 111 detects the rotational position of the rotor of the brushless DC motor 103, the speed detection unit 113 analyzes the signal of the position detection unit 111 to drive the brushless DC motor 103. Speed (or rotation period, number of rotations, angular speed, etc.) can be detected.

  Depending on the state of the refrigerating and air conditioning system, a target speed is instructed from the refrigerating and air conditioning system control device (not shown). The PWM voltage setting means 114 indicates the duty of the PWM control (predetermined period, called the carrier period, the ratio of the ON width in the middle) so that this target speed and the actual drive speed detected by the speed detection means 113 coincide. ).

  The brushless DC motor 103 is driven by driving the six switching elements of the inverter 102 via the drive means 110 by the output of the PWM voltage setting means 114 and the output of the commutation means 112, and the optimum Highly efficient operation is achieved with the motor current phase.

  The synchronization signal generation means 115 generates a signal that is synchronized with the drive speed detected by the speed detection means 113. For example, when the driving speed detected by the speed detecting means 113 is 20 r / s, the driving signal is the driving speed and the number of pole pairs of the brushless DC motor (for example, the driving speed is 3 when the number of pole pairs of the brushless DC motor is three pairs). (Synchronizing signal of 60 Hz) is output from the synchronizing signal generating means 115.

  Further, when the driving speed detected by the speed detecting means 113 is lower than a predetermined speed, the selecting means 116 selects a signal from the synchronization signal generating means 115 as a signal to be sent to the driving means 110. When the driving speed detected by the speed detecting means 113 is higher than a predetermined driving speed number, a signal from the commutating means 112 is selected as a signal to be sent to the driving means 110.

  The compressor driving apparatus configured as described above is constant regardless of the position information of the brushless DC motor detected by the position detecting means 111 when the compressor is in a stable driving state at a speed lower than a predetermined speed. By performing commutation (that is, synchronous driving) at the time of, the phase of the motor current changes according to the torque fluctuation generated per one rotation of the compressor. As a result, in the suction process with a small load torque, a lagging phase occurs, the rotor speed decreases, and in the compression / discharge process with a large load torque, a leading phase occurs and the rotor speed increases. As a result, the vibration during driving of the compressor is suppressed.

JP 2005-86911 A

  However, the conventional configuration has a problem that the brushless DC motor is always driven in a synchronous manner during low-speed driving, so that it is liable to be unstable due to disturbance such as an instantaneous power failure. Further, in the suction process where the load torque is small, the motor is driven with a lagging phase current, so that there is a problem that the step-out stop is likely to occur due to a rapid decrease in the motor torque.

  A compressor having a compression element whose torque varies during one rotation, a brushless DC motor having a permanent magnet for driving the compression element in a rotor, and a driving speed of the brushless DC motor are varied to change the compressor. An inverter that varies the refrigeration capacity, a position detection unit that detects a position of the rotor of the brushless DC motor, a commutation unit that switches a conduction phase of the inverter according to the position detection unit, and a constant conduction phase of the inverter. Synchronization signal generating means for switching over time, and selection switching means for selecting whether to use the commutation means or the synchronization signal generation means for switching the conduction phase of the inverter. When the position signal is not generated within a predetermined time, the selection switching means selects the synchronization signal generating means, and the position detection signal is predicted. If this occurred within prescribed time is obtained so as to select said commutation means.

  As a result, commutation according to the position of the brushless DC motor is performed in the suction process with a low load, and the current phase is added with an appropriate advance angle and stable driving is performed. In the compression process with a large load, the current phase is an angular velocity. An advance angle corresponding to the reduced state is added, and the weakening magnetic flux increases, so that the decrease in angular velocity is suppressed.

  The compressor drive device of the present invention suppresses the drive vibration of the compressor and suppresses the drive vibration at a low speed by suppressing the decrease in the angular speed of the brushless DC motor in the compression process, particularly when the compressor is driven at a low speed. Stability can be improved.

  Furthermore, since the compressor drive device of the present invention can be used in a refrigerator refrigeration cycle, the practical low-speed drive range of the compressor can be expanded, so that the power consumption of the refrigerator is reduced as the efficiency of the entire refrigeration cycle system is improved. be able to.

The block diagram which shows the drive device of the compressor in Embodiment 1 of this invention (A) Flow chart showing operation in the first embodiment of the present invention (B) Flow chart showing operation in the first embodiment of the present invention. Timing chart of control in Embodiment 1 of the present invention Control principle explanatory diagram at the time of driving by commutation means in Embodiment 1 of the present invention Explanatory drawing of the principle at the time of the drive by the synchronizing signal generation means in Embodiment 1 of this invention Characteristic diagram of advance angle, rotation speed, and motor current in Embodiment 1 of the present invention Block diagram showing a conventional compressor drive device

  According to a first aspect of the present invention, a compressor having a compression element whose torque varies during one rotation, a brushless DC motor having a permanent magnet for driving the compression element in a rotor, and a driving speed of the brushless DC motor are varied. An inverter that varies the refrigeration capacity of the compressor, a position detection unit that detects a position of a rotor of the brushless DC motor, a commutation unit that switches an energized phase of the inverter according to the position detection unit, and the inverter There is provided a synchronizing signal generating means for switching the energized phases of the inverter at a constant time, and a selection switching means for selecting whether to use the commutation means or the synchronizing signal generating means for switching the energized phases of the inverter. When the position signal from the position detecting means is not generated within a predetermined time, the selection switching means selects the synchronization signal generating means, When the detection signal is generated within a predetermined time, the commutation means is selected to perform commutation according to the position of the brushless DC motor in the low load suction process, and the current phase is set to an appropriate advance angle. Is added, and stable driving is performed. In the compression process with a large load, the current phase is added with an advance angle corresponding to the state of decrease in angular velocity, and the weakening magnetic flux is increased, so that the decrease in angular velocity is suppressed.

  Thus, by suppressing the decrease in the angular velocity of the brushless DC motor in the compression process, it is possible to suppress the drive vibration of the compressor and improve the driving stability at a low speed.

  According to a second aspect of the present invention, in the compressor driving device according to the first aspect of the present invention, the AC current flowing through the brushless DC motor and the rotation of the brushless DC motor in the section where the energization phase of the inverter is switched by the synchronization signal generating means. By setting the phase difference from the induced voltage generated by the above in a predetermined phase difference range, it is possible to suppress an increase in current due to an advance angle more than necessary, and to drive with high efficiency even at low speed driving.

  According to a third aspect of the present invention, the output voltage of the inverter when the compressor drive device of the first and second aspects of the invention is switched by the synchronization signal generating means is the current supply phase of the inverter according to the commutation means. By setting the output voltage to be equal to or higher than the output voltage at the time of switching, by applying a high voltage to the brushless DC motor in a section where the load torque is high, the vibration of the compressor can be suppressed by suppressing the decrease in angular velocity in the high load region.

According to a fourth aspect of the present invention, in the compressor driving apparatus according to any one of the first to third aspects, the phase of the alternating current of the brushless DC motor when the energized phase of the inverter is switched by the synchronization signal generating means is the brushless By increasing or decreasing the inverter output voltage or current in the section where the energization phase of the inverter is switched by the synchronization signal generating means so that the phase difference from the induced voltage of the DC motor and a predetermined phase difference range are obtained. Even in a section where the torque is large and the energized phase is switched by the synchronization signal generating means, the current flowing through the brushless DC motor can be suppressed as low as possible, and the low loss can be achieved along with the low vibration and noise at the time of low speed driving.

  In a fifth aspect of the present invention, the compressor of the compressor driving device according to any one of the first to fourth aspects is a reciprocating compressor having a reciprocating compression element. As a result, even with a reciprocating compressor in which the load torque is concentrated in half of one rotation and the angular velocity fluctuation during one rotation is large, the angular velocity fluctuation can be suppressed, so a low-vibration, low noise reciprocating compressor drive device is provided. it can.

  In a sixth aspect of the invention, the compressor of the compressor driving device according to any one of the first to fourth aspects is a rotary compressor having a rotary compression element. As a result, although the load torque fluctuation during one rotation is over the whole area, the rotary compressor with low vibration and low noise can be controlled because the fluctuation of the angular speed of the rotary compressor that is greatly affected by the fluctuation of the load torque is suppressed. A compressor driving device can be provided.

  In a seventh aspect of the invention, a compressor, a decompressor, an evaporator, or the like is connected to the compressor of the compressor driving device of any one of the first to sixth aspects, and the refrigerant is circulated to cool or heat the refrigerant. This is a refrigeration air conditioning system configuration. As a result, the angular speed fluctuation can be suppressed even when the compressor having a large load torque fluctuation is driven at a low speed, and therefore a cooling system that realizes low vibration and low noise even during the low speed driving can be provided.

  An eighth invention is a refrigerator equipped with the compressor driving device according to any one of claims 1 to 7. As a result, the practical low-speed driving region of the refrigerator can be expanded, and the efficiency of the entire refrigeration cycle can be improved. Therefore, energy saving of the refrigerator can be achieved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected about the same structure as the past, the detailed description is abbreviate | omitted, and only a different part is described. Further, the present invention is not limited to the present embodiment.

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

  In FIG. 1, a commercial power source 100 is an AC power source, which is input to a rectifier circuit 101 and converted into a DC voltage. The inverter 102 has six switching elements, and controls these to convert the DC output of the rectifier circuit 101 into a three-phase AC output.

  The brushless DC motor 103 includes a stator (not shown) having a three-phase winding and a rotor (not shown) having a permanent magnet, and is driven by an inverter 102.

  The brushless DC motor 103 and the compression element 104 driven by the brushless DC motor 103 are accommodated in the same sealed container to constitute the compressor 105.

  Further, the refrigerant compressed by the compressor 105 is sent out from the discharge pipe and connected in series so as to return to the suction pipe of the compressor 105 via the condenser 106, the decompressor 107, and the evaporator 108, so that the refrigeration air conditioning system Is configured.

The output of the inverter driving device 200 for driving the inverter 102 is the drive means 1
The six switching elements of the inverter 102 are driven via 10.

  Here, details of the inverter driving apparatus 200 will be described. The position detector 111 detects the rotational position of the rotor of the brushless DC motor 103. In the present embodiment, the zero cross point of the induced voltage generated by the rotation of the rotor of the brushless DC motor is detected.

  The commutation unit 112 determines energization timings of the six switching elements of the inverter 102 based on the rotational position of the brushless DC motor detected by the position detection unit 111. For example, in the case where the induced voltage and current phase of the brushless DC motor are made the same at an energization angle of 120 degrees, if commutation is performed at the timing when 30 degrees of electrical angle has elapsed from the zero cross point of the induced voltage detected by the position detecting means 111, good.

  The speed detector 113 detects the driving speed of the brushless DC motor from the output of the position detector 111.

  Depending on the state of the refrigerating and air-conditioning system, the target speed is instructed from the rotation speed setting means 201, and the PWM voltage setting means 114 performs PWM control so that the target speed matches the actual driving speed detected by the speed detection means 113. The PWM duty and the output of the commutation means 112 are input to the drive means 110, the switching element of the inverter is energized, and the brushless DC motor 103 is driven.

  The synchronization signal generator 115 generates a signal that is synchronized with the driving speed detected from the speed detector 113.

  The timer unit 202 starts counting from a predetermined timing, and measures the generation timing of the position detection signal by the position detection unit 111. In this embodiment, the start of the timer count is synchronized with the commutation timing, and the time from the commutation to the generation timing of the position detection signal is measured. Note that the position detection signal may be measured.

  The selection switching unit 203 sends the position detection signal measured by the timer unit 202 to the drive unit 110 based on the generation timing of the position detection signal (that is, the time until the position detection signal is generated after commutation in this embodiment). A signal to be output is selected and switched between commutation means and synchronization signal generation means. Specifically, when the time counted by the timer means, that is, the time from commutation to the generation of the position detection signal is within a predetermined time, when the signal from the commutation means 112 is selected and longer than the predetermined time Selects a signal from the synchronization signal generating means 115. For example, when the driving angle is 120 degrees and the current advance angle is 0 degrees with respect to the induced voltage of the brushless DC motor and the driving is stable, the position detection signal is an electrical angle and is generated around 30 degrees after commutation. Therefore, the switching timing by the selection switching means may be set to a time of about 32 degrees, for example, as a time slightly longer than 30 degrees in electrical angle. Of course, this time should be arbitrarily taken into consideration depending on the characteristics of the system and the compressor.

  The synchronous PWM setting unit 204 sets a PWM duty when the selection switching unit 203 selects a signal from the synchronous signal generating unit 115. Therefore, the synchronous PWM setting means cancels the PWM duty set by the PWM voltage setting means 114 and outputs the PWM duty set by itself to the drive means when driven by the signal from the synchronous signal generating means. On the other hand, when driven by the commutation means, the PWM duty set by the PWM voltage setting means 114 is output as it is.

  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. FIG. 2 (A) shows the operation when the position is detected in the position detecting means 111. FIG. 2 (B) is the selection switching means 203. Shows the operation for determining the commutation method.

  2A, the rotational position of the brushless DC motor is detected by the position detector 111 in STEP1, and the speed detector 113 detects the driving speed based on the output of the position detector 111 in STEP2. An angular velocity, a rotation speed, a rotation cycle, or the like that can be regarded as synonymous with the driving speed may be used.

  In STEP3, the commutation means 112 calculates the timing for performing commutation based on the position detection means. The method for determining the commutation timing is commutation by sensorless driving of a general brushless DC motor. For example, in the case of 120-degree energization, 30 degrees elapses in electrical angle after obtaining the position detection signal (induced voltage zero cross point). When commutation is performed later, the phases of the induced voltage and the current flowing through the brushless DC motor can be matched.

  In STEP 4, the selection switching means calculates a reference time for selecting a commutation method (that is, whether to perform commutation by the synchronization signal generating means or to perform commutation by the commutation means). This reference time defines the time from commutation until the position detection signal is generated, and determines the commutation method depending on whether this time is longer or shorter than the prescribed time (described later). The reference time is calculated based on the driving speed detected by the speed detecting means 113 and the electrical angle is set to a time equivalent to a predetermined angle. Specifically, when the brassless DC motor is in a stable driving state with a 120-degree energization and an advance angle (the advance angle of the current phase with respect to the induced voltage) of 0 degrees, the position detection signal (zero cross point of the induced voltage) is converted by an electrical angle. It can be expected to occur around 30 degrees after flowing. Therefore, in this embodiment, the reference time is set to a time of about 32 degrees that is slightly larger than the electrical angle of 30 degrees.

  Next, the commutation method determination operation will be described with reference to FIG.

  First, at STEP 10, the system waits until the commutation timing. When the commutation timing is reached, the commutation is performed at STEP 11, and at the same time, a timer for measuring the time from the commutation to the generation of the position detection signal is started at STEP 12.

  In STEP 13, it is monitored whether or not the position detection signal is generated within the reference time set in STEP 4 in the timer count. If the position detection signal is generated within the reference time, the selection switching means uses the signal from the commutation means 112 in STEP 114. Is selected to be sent to the drive means 110, and the commutation control (general sensorless control) based on the position detection signal by the commutation means 112 is performed in STEP15.

  On the other hand, if the position detection signal is not generated in STEP 13 even after the reference time has passed, the driving based on the output of the synchronization signal generator 115 is selected in STEP 16 and the process proceeds to STEP 17. In STEP 17, the commutation (switching of energized phases) is performed at a fixed time corresponding to the driving speed at a timing unrelated to the position detection signal.

Next, in STEP 18, the phase difference between the induced voltage phase of the brushless DC motor detected by the position detector 111 and the synchronous commutation signal generated by the synchronous signal generator 115 is adjusted. Specifically, the synchronous PWM generator increases or decreases the PWM duty so that the phase difference between the induced voltage phase and the synchronous commutation signal is within a predetermined range. When the advance angle (advance phase) of the synchronization signal generation means relative to the output signal phase of the position detection means is larger (advance) than the predetermined range, the PWM duty is increased and the advance phase is smaller than the predetermined range. Decreases the PWM duty. For example, in this embodiment, the energization angle is 120 degrees, and the predetermined phase range is an advance angle (for example, 10 degrees) added during driving by the commutation means 112 and less than 30 degrees, and the advance angle is less than 10 degrees. In this case, the PWM duty is decreased, and when it is 30 degrees or more, it is increased.

  Thereby, in the commutation by the synchronization signal generating means, an advance angle larger than the advance angle at the time of sensorless driving by the commutation means 112 is added to promote the suppression of the speed reduction of the brushless DC motor by the weak magnetic flux, and further less than 30 degrees. Thus, the position detection unit 111 can easily and reliably detect the induced voltage phase (zero cross point in the present embodiment) of the brushless DC motor. The reason for setting the maximum advance angle to 30 degrees is that when 120 degrees energization is performed as in this embodiment, the position signal (that is, the zero cross point) cannot be detected by commutation at an advance angle of 30 degrees or more. It is. Therefore, when driving at an energization angle exceeding 120 degrees, it is desirable to set the maximum advance angle at which the zero cross point can be reliably detected with respect to the energization angle.

  Furthermore, by adjusting the PWM duty during driving using the synchronization signal, the duty in the compression process with a large load torque (that is, the output voltage of the inverter) becomes larger than that during driving by the commutation means, and the motor current increases in the compression process. Thus, the loss of the inverter 102 can be reduced.

  Next, the actual operation will be described with reference to FIG. FIG. 3 is a control timing chart according to Embodiment 1 of the present invention.

  In FIG. 3, the horizontal axis indicates the movement of the brushless DC motor 103 during one rotation. The broken line indicated on the horizontal axis indicates the mechanical rotation state detected by the position detection means 111. In the present embodiment, as a 6-pole brushless DC motor, one segment indicates 1/18 rotation, and further, a mechanical rotation state per one electrical angle cycle (1/3 rotation and 2/3 rotation). ) Is shown using a one-dot chain line.

  As for torque, load torque and motor torque are shown, and since the compressor 105 is a reciprocating compressor, the load torque enters the compression / discharge process after a half rotation of the mechanical rotation state. The torque increases rapidly as shown. On the other hand, the motor torque generates a substantially constant torque per rotation. Strictly speaking, the motor torque also fluctuates in accordance with the change in the load torque, particularly in low-speed driving with a small moment of inertia.

  As shown in FIG. 3, the angular velocity fluctuates during one rotation, and increases in the range of “motor torque> load torque”, and decelerates when “motor torque <load torque”. The change in the angular velocity during one rotation is a factor of the drive vibration of the compressor in the low speed driving.

  The position signals X, Y, and Z are generated in accordance with the positive and negative states of the induced voltage generated in the U, V, and W phase windings of the brushless DC motor. That is, when the induced voltage is positive, H is output as the position signal, and when the induced signal is negative, L is output. Therefore, the point where the position signal changes from H to L or from L to H is the zero cross point of the induced voltage, and this point is detected as the position signal. In the six-pole motor in the present embodiment, a position signal is generated 18 times (that is, every mechanical angle of 20 degrees) during one rotation.

  The position signal is generated every mechanical angle of 20 degrees. However, when the angular velocity changes, the generation cycle changes.

  Normally, in the drive by the commutation means based on the position signal (sensorless drive), the timing for switching the energization pattern is determined based on this position signal, and changes every 1 / 18th rotation (that is, mechanical angle 20 degrees). Drive signals U (upper arm and lower arm), V (upper arm and lower arm), and W (upper arm and lower arm) are generated in accordance with a predetermined logical signal.

  However, in the present embodiment, in the “synchronous commutation” section shown in FIG. 3 (the section in which the position signal cycle is longer than the commutation method switching level in FIG. 3), the relationship with the output timing of the position signals X, Y, and Z is related. Instead, the energized phase is switched at a fixed time t1 set by the synchronization signal generating means.

  In this way, a mechanism that can suppress fluctuations in angular velocity by performing synchronous commutation during one rotation will be described in more detail.

  FIG. 4 is an explanatory diagram of the control principle at the time of driving by the commutation means 112 in Embodiment 1 of the present invention, and FIG. 5 is an explanatory diagram of the principle of drive control by the synchronization signal generating means 115 in the same embodiment. The waveforms shown in FIG. 4 and FIG. 5 show the drive voltage supplied from the inverter 102 and the induced voltage generated in the brushless DC motor 103 for a predetermined phase (for example, U phase).

  In the driving by the commutation means 112 based on the position detection shown in FIG. 4, the energized phase is switched based on the position detection signal (that is, the zero cross signal of the induced voltage), so the phase of the induced voltage is brushless. The voltage and current applied to the DC motor maintain a constant phase relationship. For the fixed phase relationship, select a value that can drive the brushless DC motor optimally. For embedded magnet motors with permanent magnets embedded in the rotor, reluctance torque can be used effectively by adding a slight advance angle. Therefore, driving with the highest efficiency is possible. Naturally, this optimum angle varies depending on the characteristics of the brushless DC motor.

  When the brushless DC motor is driven at a stable speed, the position signal is generated at a constant cycle, and commutation is performed at a constant cycle. However, as shown in FIG. 3, when the brushless DC motor drives the compressor, the angular velocity during one rotation varies due to the variation of the load torque generated during one rotation.

  In the driving by the synchronization signal generating means, when position detection does not occur within a certain time from the reference timing (that is, a section where the angular velocity is reduced in a section where the load torque is large), the energized phase is forcibly switched. . In the present embodiment, when a position detection signal is not generated within a certain time after the previous commutation, the commutation is forcibly performed. The relationship between the induced voltage and the drive signal at this time is shown in FIG. As shown in FIG. 5, in synchronous commutation, commutation is performed at a fast timing with respect to the position of the rotor (that is, in the compression process with a large load torque, the rotor speed decreases with respect to the commutation speed, Therefore, the applied voltage of the brushless DC motor becomes a leading phase with respect to the induced voltage phase, and a current advance angle is added. This current advance angle gives a flux weakening control (acts to suppress the induced voltage caused by the permanent magnets of the rotor and to reduce the apparent amount of magnetic flux. The action which tries to raise angular velocity by this action works.

  Therefore, since the commutation is performed by the synchronizing signal generating means at a constant cycle of t1, the current advance angle increases as the load torque increases and the speed decrease increases, and the action of suppressing the speed decrease increases by the weakening magnetic flux. That is, the advance angle is automatically added according to the load torque during one rotation, and the fluctuation of the angular velocity during one rotation of the brushless DC motor is remarkably suppressed.

Further description will be made with reference to FIG. FIG. 6 is a characteristic diagram showing changes in drive speed and motor current when the advance angle is changed in the first embodiment of the present invention. The horizontal axis represents the current advance angle, and the vertical axis represents the drive speed and motor current. The driving speed is indicated by a broken line, and the motor current is indicated by a solid line. As shown in FIG. 6, when the advance angle is 30 degrees or more, the motor current rapidly increases. Therefore, if the applied voltage is controlled so that this current phase is less than 30 degrees, the fluctuation suppression of the angular velocity is minimized. This can be realized with an increase in current (ie, low loss). Therefore, in the drive by the synchronous drive signal generating means, when the phase relationship between the synchronous drive signal and the induced voltage by the position detecting means is 30 degrees or more, the phase difference is less than 30 degrees so that the duty is increased and the angular velocity is increased. Control to be If the advance angle is smaller than the drive angle by the commutation means, the voltage is excessively applied, so the motor torque is small and the risk of out-of-step is high, so the PWM duty is reduced to increase the advance angle. To do.

  Thus, by controlling the PWM duty during driving by the synchronization signal generating means, a current advance angle larger than that during the suction process is added in the compression process with a large load torque in accordance with the load state. A decrease in angular velocity accompanying an increase in torque can be greatly suppressed.

  As described above, in the present embodiment, a compressor having a compression element whose torque varies during one rotation, a brushless DC motor having a permanent magnet in the rotor for driving the compression element, and driving of the brushless DC motor. An inverter that varies the refrigeration capacity of the compressor by varying the speed, a position detection means that detects the position of the rotor of the brushless DC motor, and a commutation means that switches the energized phase of the inverter according to the position detection means And a selection method for switching the current-carrying phase of the inverter by selecting whether to use the commutation unit or the synchronization-signal generation unit. Switching means, and when the position signal from the position detection means is not generated within a predetermined time, the selection switching means generates the synchronization signal. When the position detection signal is generated within a predetermined time, the commutation means is selected, and in the suction process with a low load, commutation according to the position of the brushless DC motor is performed. Appropriate advance angle is added and stable driving is performed.In the compression process with a large load, the current phase is added according to the reduced state of the angular velocity, and the magnetic flux is weakened and the angular velocity is reduced. It is suppressed. Thus, by suppressing the decrease in the angular velocity of the brushless DC motor in the compression process, it is possible to suppress the drive vibration of the compressor and improve the driving stability at a low speed.

  Further, in a section in which the energized phase of the inverter is switched by the synchronization signal generating means, the phase difference between the alternating current flowing through the brushless DC motor and the induced voltage generated by the rotation of the brushless DC motor is a predetermined phase difference range. By doing so, it is possible to suppress an increase in current due to an advance angle more than necessary, and to drive with high efficiency even during low-speed driving.

  Further, in the compressor drive device, when the inverter energization phase is switched by the synchronization signal generating means, the output voltage of the inverter is equal to or higher than the output voltage when the inverter energization phase is switched according to the commutation means, so that the load torque By applying a high voltage to the brushless DC motor in a high section, the vibration of the compressor can be suppressed by suppressing the decrease in angular velocity in the high load region.

  The phase of the alternating current of the brushless DC motor when the compressor driving device switches the energization phase of the inverter by the synchronization signal generating means is different from the phase difference between the induced voltage of the brushless DC motor and a predetermined phase difference range. The current phase deviates from the predetermined phase range with respect to the induced voltage phase by increasing or decreasing the inverter output voltage or current in the section where the energization phase of the inverter is switched by the synchronization signal generating means. At this time, by keeping the voltage or current within a predetermined range by increasing / decreasing, high-efficiency driving can be realized by always ensuring an appropriate phase relationship.

  In addition, if the compressor drive device drives a reciprocating compressor with concentrated load torque and large fluctuations in angular velocity during one rotation, the fluctuations in angular velocity during one rotation can be greatly suppressed, so that it is compared with the conventional compressor drive device. Thus, it is possible to provide a driving device for a reciprocating compressor with low vibration and low noise.

  In addition, if the compressor drive device drives a rotary compressor having a rotary compression element, it is possible to suppress fluctuations in the angular speed of a rotary compressor that is greatly affected by fluctuations in load torque due to its structure. A drive device for a rotary compressor can be provided.

  In addition, by connecting a condenser, a decompressor, an evaporator, etc. to the compressor and circulating a refrigerant, a refrigeration air conditioning system that cools or heats is configured, so that the compressor with a large load torque fluctuation can be driven at low speed. However, since the fluctuation of the angular velocity can be suppressed, it is possible to provide a cooling system that realizes low vibration and low noise even when driving at low speed.

(Embodiment 2)
In FIG. 1, in this embodiment, the compressor driving device is used in the refrigeration cycle of the refrigerator 205, and the evaporator 108 cools the interior 207 of the refrigerator 205 surrounded by the heat insulating wall 206. .

  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 an improvement in system efficiency of the refrigeration cycle, and has a great effect on reducing the power consumption of the refrigerator. However, as the compressor is driven at a lower speed, the fluctuation of the load torque during one rotation is larger, the driving vibration is significantly increased, and noise is increased.

  Since most refrigerators are installed in living spaces such as kitchens, it is essential to reduce vibration and noise. For this reason, it is necessary to give priority to low vibration and low noise when driving the compressor of the refrigerator, and it is necessary to reduce the minimum number of revolutions and sacrifice the energy saving effect, or add vibration suppression members at the expense of cost. Met.

  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 can reduce the drive vibration when driving the compressor at a particularly low speed and the noise caused by the vibration. The present invention can also be applied to any apparatus using a compressor such as a heat pump type selective dryer, a showcase, and a vending machine.

DESCRIPTION OF SYMBOLS 102 Inverter 103 Brushless DC motor 105 Compressor 106 Condenser 107 Decompressor 108 Evaporator 111 Position detection means 112 Commutation means 115 Synchronization signal generation means 203 Selection switching means 205 Refrigerator

Claims (8)

A compressor having a compression element whose torque varies during one rotation, a brushless DC motor having a permanent magnet for driving the compression element in a rotor, and a driving speed of the brushless DC motor are varied to change the compressor. An inverter that varies the refrigeration capacity, a position detection unit that detects a position of the rotor of the brushless DC motor, a commutation unit that switches a conduction phase of the inverter according to the position detection unit, and a constant conduction phase of the inverter. Synchronization signal generating means for switching over time, and selection switching means for selecting whether to use the commutation means or the synchronization signal generation means for switching the conduction phase of the inverter. When the position signal is not generated within a predetermined time, the selection switching means selects the synchronization signal generating means, and the position detection signal is predicted. Drive device when generated in the predetermined time compressor so as to select said commutation means. In the section in which the energization phase of the inverter is switched by the synchronization signal generating means, the phase difference between the alternating current flowing through the brushless DC motor and the induced voltage generated by the rotation of the brushless DC motor is within a predetermined phase difference range. The compressor driving device according to claim 1, wherein the compressor driving device is provided. 3. The compression according to claim 1, wherein an output voltage of the inverter when the energization phase of the inverter is switched by the synchronization signal generating means is equal to or higher than an output voltage when the energization phase of the inverter is switched according to the commutation means. Machine drive. The synchronizing signal generation means that the phase of the alternating current of the brushless DC motor when the energization phase of the inverter is switched by the synchronizing signal generating means is within a predetermined range from the phase difference from the induced voltage of the brushless DC motor. The compressor drive device according to any one of claims 1 to 3, wherein the inverter output voltage or current in the section in which the inverter energization phase is switched by means is increased or decreased. The compressor driving device according to any one of claims 1 to 3, wherein the compressor is a reciprocating compressor having a reciprocating compression element. The compressor drive device according to any one of claims 1 to 4, wherein the compressor is a rotary compressor having a rotary compression element. The compressor is for driving a refrigerating and air-conditioning system for cooling or heating by connecting a condenser, a decompressor, an evaporator and the like to circulate the refrigerant. The compressor driving device according to claim 1. The refrigerator which has the drive device of the compressor of at least any one of Claims 1-7.

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