JP2009136149A - Brushless DC motor driving apparatus, refrigerator compressor, and brushless DC motor driving method - Google Patents

Abstract

An object of the present invention is to prevent fluctuations in motor behavior when switching from a waveform output means at low speed to a waveform output means at high speed, or vice versa, for a brushless DC motor.
Waveform generating means for outputting a rectangular wave having an energization angle of 120 degrees or more and less than 180 degrees or a waveform corresponding thereto, and a rectangular wave / sine wave having an energization angle exceeding 120 degrees and less than 180 degrees or a waveform corresponding thereto are predetermined. It is possible to suppress fluctuations in motor behavior when switching according to operating conditions, with waveform generation means that changes only the predetermined frequency with a constant duty while outputting at a frequency, suppressing noise generation / step-out, By reducing the instantaneous peak current, it is possible to eliminate the influence on refrigerator non-cooling / blunt cooling and motor life reliability.
[Selection] Figure 1

Description

  More particularly, the present invention relates to a brushless DC motor comprising a rotor having a permanent magnet and a stator having a three-phase winding. More particularly, the present invention relates to a method and apparatus for driving a brushless DC motor that is optimal for driving a compressor such as a refrigerator or an air conditioner.

In recent years, large-scale models of 350L or more have become mainstay refrigerators, and most of these refrigerators are inverter-controlled refrigerators with highly efficient variable compressor rotation speed. These refrigerator compressors generally employ a brushless DC motor including a rotor having a permanent magnet and a stator having a three-phase winding for high efficiency. In addition, since the brushless DC motor is installed in an environment of high temperature, high pressure, refrigerant atmosphere, and oil atmosphere in the compressor, a position detection sensor such as a hall element normally used in a brushless DC motor cannot be used. Therefore, generally, a method of detecting the rotational position of the rotor from the counter electromotive voltage of the motor is often used. (For example, see Patent Document 1)
FIG. 10 is a block diagram of a conventional brushless DC motor driving apparatus.

  In FIG. 10, a commercial power source 101 is an AC power source having a frequency of 50 Hz or 60 Hz and a voltage of 100 V in Japan.

  The rectifier circuit 102 converts the AC voltage of the commercial power supply 101 into a DC voltage. The rectifier circuit 102 includes bridge-connected rectifier diodes 102a to 102d and smoothing electrolytic capacitors 102e and 102f. In the circuit shown in FIG. 10, the voltage rectifier circuit is a voltage doubler rectifier circuit, and a DC voltage 280V is input from the AC100V input of the commercial power supply 101. Obtainable.

  The inverter circuit 103 has a three-phase bridge configuration including six switch elements 103a, 103b, 103c, 103d, 103e, and 103f. Each switch element includes a diode for return current in the reverse direction of each switch element, but this is omitted in the figure.

  The brushless DC motor 104 includes a rotor 104a having a permanent magnet and a stator 104b having a three-phase winding. When the three-phase alternating current generated by the inverter 103 flows through the three-phase winding of the stator 104b, the rotor 104a can be rotated. The rotational movement of the rotor 104a is changed to a reciprocating movement by a crankshaft (not shown), and a piston (not shown) reciprocates in a cylinder (not shown) to compress the refrigerant. Drive.

  The counter electromotive voltage detection circuit 105 detects the rotational relative position of the rotor 104a from the counter electromotive voltage generated by the rotation of the rotor 104a having the permanent magnet of the brushless DC motor 104.

  The commutation circuit 106 performs logical signal conversion based on the output signal of the back electromotive voltage detection circuit 105, and generates a signal to be driven by sequentially switching the switch elements 103a, 103b, 103c, 103d, 103e, and 103f of the inverter 103.

  The synchronous drive circuit 107 forcibly outputs an output of a predetermined frequency from the inverter 103 and drives the brushless DC motor 104, and forcibly outputs a signal having the same shape as the logical signal generated by the commutation circuit 106. It is generated at a predetermined frequency.

  The load state determination circuit 108 determines a load state in which the compressor 104 is operated.

  The switching circuit 109 switches whether the brushless DC motor of the compressor 104 is driven by the commutation circuit 106 or the synchronous driving circuit 107 according to the output of the load state determination circuit 108.

  The drive circuit 110 drives the switch elements 103a, 103b, 103c, 103d, 103e, and 103f of the inverter 103 by the output signal from the switching circuit 109.

  Next, the operation of the above configuration will be described.

  When the load detected by the load state determination circuit 108 is a normal load, driving by the commutation circuit 106 is performed. The back electromotive voltage detection circuit 105 detects the relative position of the rotor 104 a of the brushless DC motor 104. Next, the commutation circuit 106 creates a commutation pattern for driving the inverter 103 from the relative position of the rotor 104a. This commutation pattern is supplied to the drive circuit 110 through the switching circuit 109, and drives the switch elements 103a, 103b, 103c, 103d, 103e, and 103f of the inverter 103. By this operation, the brushless DC motor 104 is driven in accordance with its rotational position.

  Next, the operation when the load increases will be described.

The load of the brushless DC motor increases, and the rotational speed decreases due to the characteristics of the brushless DC motor. The load state determination circuit 108 determines that this state is a high load state, and switches the output of the switching circuit 109 to the signal from the synchronous drive circuit 107. By driving in this way, it is intended to suppress a decrease in the rotational speed at the time of high load.
Japanese Patent Laid-Open No. 9-88837

  However, the conventional configuration has the following problems.

  According to the output signal of the load state determination circuit 108, the switching circuit 109 switches to the commutation circuit 106 when the load is low, and the switching circuit 109 switches to the synchronous drive circuit 107 when the load is high. However, the commutation timing before and after the switching cannot be matched, or conversely, it cannot be intentionally changed in order to realize smooth switching, so that it flows to the stator 104b immediately after switching. There is a high possibility that the current will be disturbed. Further, the current is disturbed to generate a large peak current, thereby shortening the lifetime of the permanent magnet included in the rotor 104a. In addition, current disturbance may appear as noise or vibration, or the brushless DC motor 104 may stop stepping out.

  The present invention solves the above-described conventional problems, and provides a driving method and apparatus for a brushless DC motor that can suppress disturbance of current flowing in the stator by matching the commutation timing before and after switching the driving method. The purpose is to provide.

  It is another object of the present invention to provide a brushless DC motor driving method and apparatus capable of suppressing disturbance of current flowing in the stator by intentionally changing the commutation timing before and after switching the driving method. Objective.

  The brushless DC motor driving apparatus according to the present invention includes an I waveform generator that generates a waveform according to the rotational position of the motor, and an II waveform generator that generates a waveform synchronized with the frequency while changing only a predetermined frequency. And before and after the switching determination unit switches according to the motor operating state, the timing for outputting the waveform can be made equal.

  As a result, stable operation can be maintained, noise and vibration can be reduced, step-out stop can be prevented, and generation of instantaneous peak current can be suppressed.

  In addition, a frequency calculation unit that calculates the output frequency of the waveform from the timing detected by the position detection circuit, a predetermined frequency setting unit that determines a predetermined frequency of the second waveform generation unit, and a frequency equal to the frequency calculated by the frequency calculation unit A frequency command unit that commands the predetermined frequency setting unit as the predetermined frequency.

  This makes it possible to keep the waveform output timing equal before and after switching from the first waveform generation unit to the second waveform generation unit.

  Also, it is determined whether the timing detected by the position detection circuit is coincident with the timing output by the II waveform generator, and if they coincide, a coincidence determination is made to output a predetermined frequency to the I waveform generator. Part.

  This makes it possible to maintain the same waveform output timing before and after switching from the II waveform generator to the I waveform generator.

  Also, switching determination between the first waveform generator that generates a waveform in accordance with the rotational position of the motor and the second waveform generator that generates a waveform synchronized with the frequency while changing only a predetermined frequency is made according to the operating state of the motor. It is possible to make a difference in the timing of outputting the waveform before and after the switching of the units.

  As a result, when unstable driving is detected, it is possible to prevent further unstable driving and improve the driving state to be more stable.

  In addition, a frequency calculation unit that calculates the output frequency of the waveform from the timing detected by the position detection circuit, a predetermined frequency setting unit that determines the predetermined frequency of the second waveform generation unit, and a frequency obtained by correcting the frequency calculated by the frequency calculation unit And a frequency correction unit that commands the predetermined frequency setting unit as a predetermined frequency.

  As a result, it is possible to make a difference in the timing of outputting the waveform before and after switching from the I waveform generation section to the II waveform generation section.

  Also, it is compared whether or not the timing detected by the position detection circuit is within the allowable range with respect to the timing output by the II waveform generator, and if it is within the allowable range, the predetermined frequency is generated. And a deviation comparison unit that outputs to the unit.

  This makes it possible to make a difference in the timing for outputting the waveform before and after switching from the II waveform generator to the I waveform generator.

  The brushless DC motor of the present invention can exhibit effects such as noise and vibration reduction, step-out stop prevention, and instantaneous peak current generation suppression. This prevents the compressor from stepping out and prevents the occurrence of uncooled and slow-cooling phenomena in the refrigerator, and suppresses the peak current to avoid the reduction in motor life, thereby reducing the life of the refrigerator itself. Can be secured.

  The invention described in claim 1 is a brushless DC motor comprising a rotor having a permanent magnet and a stator having a three-phase winding, and three switch elements for supplying power to the three-phase winding. A phase bridge connection, and each switch element is connected in parallel with a diode for return current in the opposite direction, and the rotation position of the rotor is detected, and the connection between the three-phase winding and the inverter A position detection circuit for detecting the operating state of the brushless DC motor from the waveform information at the point, an I waveform generator for outputting a waveform according to the rotational position, and a waveform synchronized with the frequency while changing only a predetermined frequency A second waveform generator that outputs a predetermined frequency, a predetermined frequency setting unit that determines a predetermined frequency of the second waveform generator, and a timing at which the position detection circuit detects the rotational position A frequency calculation unit that calculates an output frequency of the waveform, and a switching determination unit that determines whether to switch the output waveform by the first waveform generation unit or the second waveform generation unit according to the operation state information output. It is a brushless DC motor driving device, and can exhibit effects such as reduction of noise and vibration, prevention of step-out stop, and suppression of instantaneous peak current generation.

  According to the second aspect of the present invention, in addition to the first aspect of the present invention, the stability and phase of the behavior of the brushless DC motor are appropriately determined from the variation and the length of time that the position detection circuit flows through the return current diode. After the determination is made, the frequency is transmitted to the switching determination unit, and after the switching determination unit determines that switching to the output waveform by the second waveform generation unit is possible, a frequency equal to the frequency calculated by the frequency calculation unit is obtained. Instructing the predetermined frequency setting unit as a predetermined frequency and switching the output waveform generation unit from the I waveform generation unit to the II waveform generation unit reduces noise and vibration, prevents step-out stop, and suppresses peak current generation The effects such as can be demonstrated.

  According to a third aspect of the present invention, in addition to the first aspect of the present invention, since the position detection circuit can detect the rotational position after the current has flown through the return current diode, the position detection can be reliably performed. After confirming the characteristics, it is determined whether the timing for detecting the rotational position is coincident with the output timing of the second waveform generating unit. If they coincide, the predetermined frequency determined by the predetermined frequency setting unit is determined. By including the coincidence determination unit that commands the output frequency of the I-th waveform generation unit, it is possible to exhibit effects such as noise and vibration reduction, prevention of step-out stop, and suppression of peak current generation.

  According to a fourth aspect of the present invention, in addition to the first aspect of the invention, the phase of the brushless DC motor may be inappropriate due to the length of time that the position detection circuit flows through the return current diode. If found, a frequency correction unit that corrects the frequency calculated by the frequency calculation unit so that the phase is appropriate and outputs the frequency to the predetermined frequency setting unit as a predetermined frequency, thereby reducing noise / vibration and stepping out. It is possible to exhibit effects such as prevention of stop and further suppression of instantaneous peak current generation.

According to a fifth aspect of the present invention, in addition to the first aspect of the present invention, since the position detection circuit can detect the rotational position after the current has flown through the return current diode, the position detection can be reliably performed. After confirming the characteristics, a comparison is made as to whether or not the timing detected by the position detection circuit is within the allowable range with respect to the timing output by the second waveform generator. By having a deviation comparison unit that commands the predetermined frequency determined by the predetermined frequency setting unit as an output frequency to the I waveform generation unit, and having a frequency correction unit that outputs the predetermined frequency as a predetermined frequency to the constant frequency setting unit, The effects of reducing noise and vibration, preventing step-out stop, and suppressing instantaneous peak current generation can be exhibited.

  The invention according to claim 6 is a compressor of a refrigerator equipped with the brushless DC motor operated by the drive device according to any one of claims 1 to 5, and prevents the compressor from stepping out by preventing the compressor from stepping out. It is extremely important to prevent the occurrence of uncooled and slow-cooling phenomena and to prevent a decrease in motor life by suppressing the peak current, and thus to ensure the life of the refrigerator itself.

  The invention according to claim 7 is a brushless DC motor comprising a rotor having a permanent magnet and a stator having a three-phase winding, an inverter for supplying electric power to the three-phase winding, and a rotational position of the rotor. An I waveform generator that outputs a waveform according to the frequency, a II waveform generator that outputs a waveform in synchronization with the frequency while changing only a predetermined frequency, and a connection point between the three-phase winding and the inverter. A position detection circuit that detects the rotational position and operating state of the rotor from the waveform information, and an output to the first waveform generation unit or the second waveform generation unit according to the operation state information output from the position detection circuit A switching determination unit for switching waveforms, and the operation of the switching determination unit from the I waveform generation unit to the II waveform generation unit or the II waveform during operation of the brushless DC motor. Increase in current flowing to the brushless DC motor by enabling switching from the raw part to the I waveform generating part and confirming from the operating state information that the current of the brushless DC motor is not disturbed after switching. The brushless DC motor driving method capable of suppressing the noise can exhibit effects such as noise / vibration reduction, step-out stop prevention, and suppression of instantaneous peak current generation.

Hereinafter, embodiments of a refrigerator according to the present invention will be described with reference to the drawings. The present invention is not limited to the embodiments. (Embodiment 1)
FIG. 1 is a block diagram of a brushless DC motor driving apparatus when switching from an I waveform generator to an II waveform generator according to Embodiment 1 of the present invention. In FIG. 1, a commercial power source 1 is an AC power source having a frequency of 50 Hz or 60 Hz and a voltage of 100 V in Japan.

  The rectifier circuit 2 converts the AC voltage of the commercial power source 1 into a DC voltage. The rectifier circuit 2 comprises bridge-connected rectifier diodes 2a to 2d, smoothing electrolytic capacitors 2e and 2f, and a voltage regulator circuit 2g. When the circuit shown in FIG. From this, a DC voltage of 280V can be obtained. Although voltage doubler rectification is used here, the voltage adjustment circuit 2g corresponds to a DC voltage variable chopper circuit or voltage doubler rectification / full wave rectification switching type circuit.

  The inverter circuit 3 has a three-phase bridge configuration including six switch elements 3a, 3b, 3c, 3d, 3e, and 3f. Each switch element includes a diode for return current in the reverse direction of each switch element, but this is omitted in the figure.

  The brushless DC motor 4 includes a rotor 4a having a permanent magnet and a stator 4b having a three-phase winding. When the three-phase alternating current generated by the inverter 3 flows in the three-phase winding of the stator 4b, the rotor 4a can be rotated. The rotary motion of the rotor 4a is changed to a reciprocating motion by a crankshaft (not shown), and a piston (not shown) reciprocates in a cylinder (not shown) to compress the refrigerant. Drive.

The position detection circuit 5 can detect the rotational relative position of the rotor 4 a from the back electromotive voltage generated by the rotation of the rotor 4 a having the permanent magnet of the brushless DC motor 4. In addition to detecting the rotation relative position, it is also possible to detect disturbances in the motor current and changes in the load state by detecting an increase or decrease in the time during which the current flows through the return current diode.

  Here, the rotation relative position of the rotor 4a is detected from the counter electromotive voltage generated by the rotation of the rotor 4a. However, any means for detecting the position of the rotor may be used as long as it is a means for detecting the rotor position. The configuration used may be used.

  The frequency calculation unit 6 detects the rotation speed of the brushless DC motor 4 from the output signal of the position detection circuit 5. The rotation speed can be detected by counting the output signal of the position detection circuit 5 for a certain time or measuring the period.

  The I-th waveform generation unit 7 performs logical signal conversion based on the position detection signal of the position detection circuit 5 to generate a signal for driving the switch elements 3a, 3b, 3c, 3d, 3e, and 3f of the inverter 3. This driving signal is based on rectangular wave energization, and generates a rectangular wave with an energization angle of 120 degrees or more and less than 180 degrees. In addition to the rectangular wave, a trapezoidal wave having a slight inclination in rising / falling may be used as a waveform conforming thereto. Furthermore, in order to keep the rotation speed constant, duty control of PWM control is also performed. According to the rotational position, the most efficient operation is possible because the operation can be performed with the optimum duty.

  The second waveform generator 8 generates a signal for driving the switching elements 3a, 3b, 3c, 3d, 3e, and 3f of the inverter 3 based on the output signal of the predetermined frequency setting unit 9. This driving signal creates a rectangular wave with a conduction angle exceeding 120 degrees and less than 180 degrees. In addition to the rectangular wave, a waveform conforming thereto such as a sine wave or a distorted wave may be used. Furthermore, it is operating here with a constant duty.

  The predetermined frequency setting unit 9 changes only the output frequency while keeping the duty of the waveform output by the second waveform generation unit 8 constant.

  The frequency command unit 10 instructs the predetermined frequency setting unit 9 to use the frequency calculated by the frequency calculation unit 6 as a predetermined frequency when switching the output waveform generation unit from the I waveform generation unit 7 to the II waveform generation unit 8. . Further, while the switching determination unit 11 selects the I-th waveform generation unit 7, the frequency detected by the frequency calculation unit 6 is output to the frequency command unit 10.

  The switching determination unit 11 operates the brushless DC motor 4 based on factors such as the number of rotations detected by the frequency calculation unit 6, the duty controlled by the first waveform generation unit 7, and temperature data in applications such as a refrigerator. The state is determined, and the waveform for operating the inverter 3 is switched between the first waveform generation unit 7 and the second waveform generation unit 8. For example, when the rotational speed is low, the signal from the I waveform generator 6 is selected, and when the rotational speed is high, the signal from the II waveform generator 8 is selected to operate the inverter 3.

  The drive unit 12 drives the switch elements 3a, 3b, 3c, 3d, 3e, and 3f of the inverter 3 based on the output signal from the switching determination unit 11. By this driving, an optimal AC output can be applied from the inverter 3 to the brushless DC motor 4, so that the rotor 4a can be rotated.

  The microcomputer 13 realizes the aforementioned functions. These functions can be realized by a microcomputer program.

  Next, the operation in FIG. 1 will be described with reference to FIGS.

FIG. 2 is a flowchart showing the operation at the time of switching from the I waveform generator to the II waveform generator in the first embodiment.

  First, in STEP 21, it is determined whether or not the waveform generation means selected by the switching determination unit 11 is the I-th waveform generation unit 7. As a result of the determination, if the I-th waveform generator 7 is being selected, the process proceeds to STEP22.

  Next, in STEP 22, the calculation result of the frequency calculation unit 6 is output to the frequency command unit 10, and the process proceeds to STEP 23.

  Further, in STEP 23, it is determined whether or not the waveform generating means needs to be switched to the second waveform generating unit 8. This determination is made by the switching determination unit 11 according to the operating state of the brushless DC motor 4. Here, the determination of the operating state is performed based on data such as the rotational speed and the duty. As a result of determining whether or not the switching is necessary, if it is determined that it is necessary to switch to the second waveform generator 8, the process proceeds to STEP24.

  In STEP 24, the calculation result output to the frequency command unit 10 in STEP 22 is output to the predetermined frequency setting unit 9.

  Finally, in STEP 25, the frequency determination unit 11 switches the waveform generation means from the I waveform generation unit 7 to the II waveform generation unit 8.

  As described above, in the present embodiment, by having the frequency command unit 10, the waveform generation timing (commutation timing and brushless timing before and after switching from the I waveform generation unit 7 to the II waveform generation unit 8). The operating frequency of the DC motor 4 can be kept equal, and effects such as reduction of noise and vibration, prevention of step-out stop, and suppression of peak current generation can be exhibited.

  10, when the switching circuit 109 switches the waveform generating means from the commutation circuit 106 to the synchronous drive circuit 107, the commutation timing in the commutation circuit 106 is transmitted to the synchronous drive circuit 107. Because there was no means to do so, the commutation timing could not be kept equal before and after switching. Therefore, by having the frequency command unit 10, the commutation timing and the operating frequency of the brushless DC motor 4 can be kept equal before and after switching from the first waveform generation unit 7 to the second waveform generation unit 8. -It brings about effects such as vibration reduction, prevention of step-out stop, and suppression of peak current generation.

  FIG. 3 is a block diagram of a brushless DC motor driving apparatus when switching from the II waveform generator to the I waveform generator according to the first embodiment of the present invention. 3 that are the same as those in FIG. 1 have already been described, and will not be described.

  When the coincidence determination unit 30 switches the output waveform generation unit from the II waveform generation unit 8 to the I waveform generation unit 7, the frequency calculated by the frequency calculation unit 6 is equal to the predetermined frequency determined by the predetermined frequency setting unit 9. If they match, the frequency determined by the predetermined frequency setting unit 9 is commanded to the I-th waveform generation unit 7 as the waveform output timing.

  Next, the operation in FIG. 3 will be described with reference to FIGS.

  FIG. 4 is a flowchart showing the operation at the time of switching from the II waveform generator to the I waveform generator in the first embodiment.

First, in STEP 41, it is determined whether or not the waveform generation means selected by the switching determination unit 11 is the second waveform generation unit 8. If it is determined that the second waveform generator 8 is being selected, the process proceeds to STEP42.

  Next, in STEP 42, it is determined whether or not the waveform generating means needs to be switched to the I-th waveform generating unit 7. This determination is made by the switching determination unit 11 according to the operating state of the brushless DC motor 4. Here, the determination of the operating state is performed based on data such as the rotational speed and the duty. As a result of determining whether or not the switching is necessary, if it is determined that switching to the I-th waveform generation unit 7 is necessary, the process proceeds to STEP 43.

  Further, in STEP 43, it is determined whether or not the frequency calculated by the frequency calculation unit 6 matches the predetermined frequency determined by the predetermined frequency setting unit 9. This determination is performed by the coincidence determination unit 30. As a result of the determination, if they match, the process proceeds to STEP44.

  In STEP 44, the coincidence determination unit 30 instructs the I-th waveform generation unit 7 using the predetermined frequency determined by the predetermined frequency setting unit 9 as the waveform output timing.

  Finally, in STEP 45, the frequency determination unit 11 switches the waveform generation unit from the II waveform generation unit 8 to the I waveform generation unit 7.

  As described above, in the present embodiment, by having the coincidence determination unit 30, the waveform generation timing (commutation timing and brushless timing) before and after switching from the second waveform generation unit 8 to the first waveform generation unit 7. The operating frequency of the DC motor 4 can be kept equal, and a stable motor control state can be maintained, and effects such as reduction of noise and vibration, prevention of step-out stop, and suppression of peak current generation can be exhibited. it can.

  10, when the switching circuit 109 switches the waveform generating means from the synchronous drive circuit 107 to the commutation circuit 106, the commutation timing in the synchronous drive circuit 107 is transmitted to the commutation circuit 106. Because there was no means to do so, the commutation timing could not be kept equal before and after switching. Therefore, by having the coincidence determination unit 30, the commutation timing and the operation frequency of the brushless DC motor 4 can be kept equal before and after switching from the II waveform generation unit 8 to the I waveform generation unit 7. -It brings about effects such as vibration reduction, prevention of step-out stop, and suppression of peak current generation.

  In addition, it is extremely important to exhibit noise and vibration reduction effects in compressors for products that have a quiet need such as refrigerators and air conditioners, and this need is maintained by maintaining equal commutation timing and operating frequency before and after the waveform generation means. Can be controlled.

(Embodiment 2)
FIG. 5 is a block diagram of a brushless DC motor driving apparatus when the first waveform generation unit is switched to the second waveform generation unit according to the second embodiment of the present invention. Note that the same components in FIG. 5 as those in FIG. 1 have already been described and are omitted.

  When switching the output waveform generation means from the I waveform generation section 7 to the II waveform generation section 8, the frequency correction section 50 calculates a frequency that has been appropriately corrected based on the frequency calculated by the frequency calculation section 6. Commands the predetermined frequency setting unit 9 as a predetermined frequency. For example, when the switching determination unit 11 is accelerating at the time of switching the waveform generating means, when it is known that the delay control is performed after the acceleration, the correction is made to the timing at which the phase advances in advance. . Needless to say, a correction that predicts the advance control and delays the phase in advance is one specific example. Further, while the switching determination unit 11 selects the I-th waveform generation unit 7, the frequency detected by the frequency calculation unit 6 is output to the frequency correction unit 50.

  Next, the operation in FIG. 5 will be described with reference to FIGS.

  FIG. 6 is a flowchart showing the operation at the time of switching from the I waveform generator to the II waveform generator in the second embodiment.

  First, in STEP 61, it is determined whether or not the waveform generation means selected by the switching determination unit 11 is the I-th waveform generation unit 7. As a result of the determination, if the I-th waveform generator 7 is being selected, the process proceeds to STEP62.

  Next, in STEP 62, the calculation result of the frequency calculation unit 6 is output to the frequency correction unit 50, and the process proceeds to STEP 63.

  Further, in STEP 63, it is determined whether or not the waveform generation means needs to be switched to the second waveform generation unit 8. This determination is made by the switching determination unit 11 according to the operating state of the brushless DC motor 4. Here, the determination of the operating state is performed based on data such as the rotational speed and the duty. As a result of determining whether or not the switching is necessary, if it is determined that it is necessary to switch to the second waveform generator 8, the process proceeds to STEP64.

  In STEP 64, the calculation result output to the frequency correction unit 50 in STEP 62 is corrected to an appropriate value, and then output to the predetermined frequency setting unit 9 as a predetermined frequency.

  Finally, in STEP 65, the frequency determination unit 11 switches the waveform generation means from the I waveform generation unit 7 to the II waveform generation unit 8.

  As described above, in the present embodiment, by having the frequency correction unit 50, before and after switching from the I waveform generation unit 7 to the II waveform generation unit 8, the waveform generation timing (commutation timing and brushless timing). It is possible to make a difference in the operating frequency of the DC motor 4, preventing deterioration of the unstable state of the motor control, and further improving to a stable control state, thereby reducing noise and vibration and stepping out. Effects such as prevention of stop and suppression of peak current generation can be exhibited.

  10, when the switching circuit 109 switches the waveform generating means from the commutation circuit 106 to the synchronous drive circuit 107, the commutation timing in the commutation circuit 106 is transmitted to the synchronous drive circuit 107. Because there was no means to do so, it was not possible to make a difference in the timing of commutation before and after switching. Therefore, by having the frequency correction unit 50, it is possible to cause a difference in the commutation timing and the operation frequency of the brushless DC motor 4 before and after switching from the first waveform generation unit 7 to the second waveform generation unit 8. By preventing deterioration of the unstable state of the motor control and further improving to a stable control state, effects such as noise and vibration reduction, prevention of step-out stop, and suppression of peak current generation are brought about.

  FIG. 7 is a block diagram of a brushless DC motor driving apparatus when switching from the II waveform generator to the I waveform generator according to the second embodiment of the present invention. 7 that are the same as those in FIG. 1 have already been described, and will not be described.

  The deviation comparing unit 70 switches the frequency calculated by the frequency calculating unit 6 and the predetermined frequency determined by the predetermined frequency setting unit 9 when switching the output waveform generating unit from the II waveform generating unit 8 to the I waveform generating unit 7. Is within the predetermined allowable range, the frequency calculated by the frequency calculation unit 6 is commanded to the I waveform generation unit 7 as the waveform output timing.

  Next, the operation in FIG. 7 will be described with reference to FIGS.

  FIG. 8 is a flowchart showing an operation at the time of switching from the II waveform generator to the I waveform generator in the second embodiment.

  First, in STEP 81, it is determined whether or not the waveform generation means selected by the switching determination unit 11 is the second waveform generation unit 8. If it is determined that the second waveform generator 8 is being selected, the process proceeds to STEP 82.

  Next, in STEP 82, it is determined whether or not the waveform generating means needs to be switched to the I-th waveform generating unit 7. This determination is made by the switching determination unit 11 according to the operating state of the brushless DC motor 4. Here, the determination of the operating state is performed based on data such as the rotational speed and the duty. As a result of determining whether the switching is necessary, when it is determined that the switching to the I-th waveform generation unit 7 is necessary, the process proceeds to STEP83.

  Further, in STEP 83, it is determined whether or not the deviation between the frequency calculated by the frequency calculation unit 6 and the predetermined frequency determined by the predetermined frequency setting unit 9 is within a predetermined allowable range. This determination is performed by the deviation comparison unit 70. As a result of the determination, if the deviation is within the allowable range, the process proceeds to STEP84.

  In STEP 84, the deviation comparison unit 70 instructs the I waveform generation unit 7 using the frequency calculated by the frequency calculation unit 6 as the waveform output timing.

  Finally, in STEP 85, the frequency determination unit 11 switches the waveform generation means from the second waveform generation unit 8 to the first waveform generation unit 7.

  As described above, in the present embodiment, by having the deviation comparison unit 70, the timing of generating a waveform (commutation timing and brushless timing) before and after switching from the II waveform generation unit 8 to the I waveform generation unit 7 is provided. It is possible to make a difference in the operating frequency of the DC motor 4, preventing deterioration of the unstable state of the motor control, and further improving to a stable control state, thereby reducing noise and vibration and stepping out. Effects such as prevention of stop and suppression of peak current generation can be exhibited.

  10, when the switching circuit 109 switches the waveform generating means from the synchronous drive circuit 107 to the commutation circuit 106, the commutation timing in the synchronous drive circuit 107 is transmitted to the commutation circuit 106. Because there was no means to do so, it was not possible to make a difference in the timing of commutation before and after switching. Therefore, by having the deviation comparison unit 70, it is possible to cause a difference in the commutation timing and the operation frequency of the brushless DC motor 4 before and after switching from the second waveform generation unit 8 to the first waveform generation unit 7. By preventing deterioration of the unstable state of the motor control and further improving to a stable control state, effects such as noise and vibration reduction, prevention of step-out stop, and suppression of peak current generation are brought about.

  In addition, it is extremely important to exhibit noise and vibration reduction effects in compressors for products that have a quiet need such as refrigerators and air conditioners. The motor control corresponding to this need can be realized by suppressing the progress of the state deterioration or improving the control deterioration state.

FIG. 9 is an example of a characteristic diagram showing the relationship between the load state of the refrigerator and the appropriate frequency in the second embodiment. In the figure, the horizontal axis represents the load state of the refrigerator, and the vertical axis represents an appropriate frequency. It can be seen from the figure that the optimum frequency is low in the high load region and the appropriate frequency is high in the low load region. It can also be seen that the appropriate frequency under the same load condition decreases as the duty decreases.

  Next, the operation of the refrigerator will be described with reference to FIGS. When a compressor is used for cooling in a limited space that is sufficiently insulated from the outside environment, such as a refrigerator, if the compressor is operating for a long time with a high operating frequency, the space is higher than the initial state. The required torque for operating the brushless DC motor 4 at the same frequency decreases, that is, changes to a low load state. As shown in the figure, under the high load state such as the load state A, the switching determination unit 11 sets the time point to the second waveform generation unit 8 as an initial state while setting the appropriate frequency a to a predetermined frequency. The second waveform generator 8 continues the operation of the compressor with a constant predetermined frequency, and the load state decreases to B as time elapses. At this time, it is sufficient if the duty is β% (α> β), but the compressor is operated with α% (α> β) without performing duty control during commutation in the second waveform generator. Then, although it is appropriate for the compressor to operate at the frequency b, the compressor is forced to operate at a frequency a lower than b. In other words, it can be said that the vehicle is decelerated (braking) by | b−a |, that is, in a delayed control state.

  In such a load state B, during operation at the frequency a, when the operation state of the motor changes and the switching determination unit 11 switches to the I-waveform generation unit 7, it is in the delay control state, so the calculation of the frequency calculation unit 6 It can be said that there is a deviation c−a between the result c (a <c ≦ b) and the predetermined frequency a. When the predetermined allowable deviation is ba, the deviation ca is within the range of the allowable deviation ba, and the process proceeds to STEP 84, where the correction determination unit 70 determines the frequency to be output to the first waveform generation unit 7. Correction is made so as to advance from a to c, and the switching determination unit 11 switches the waveform generation means to the I-th waveform generation unit 8 in STEP 85.

  As described above, in the present embodiment, by including the deviation comparison unit 70, the timing of generating a waveform (commutation timing and brushless timing before and after switching from the II waveform generation unit 8 to the I waveform generation unit 7). It is possible to make a difference in the operating frequency of the DC motor 4, preventing deterioration of the unstable state of the motor control, and further improving the stable control state, thereby preventing the refrigeration employment compressor from being stopped, As a result, non-cooling and blunt cooling of the refrigerator can be reduced.

  10, when the switching circuit 109 switches the waveform generating means from the synchronous drive circuit 107 to the commutation circuit 106, the commutation timing in the synchronous drive circuit 107 is transmitted to the commutation circuit 106. Because there was no means to do so, it was not possible to make a difference in the timing of commutation before and after switching. Therefore, by having the deviation comparison unit 70, it is possible to cause a difference in the commutation timing and the operation frequency of the brushless DC motor 4 before and after switching from the second waveform generation unit 8 to the first waveform generation unit 7. By preventing the deterioration of the unstable state of the motor control and further improving the stable control state, the effect of stabilizing the refrigerator control state is brought about.

  As described above, the brushless DC motor driving method and apparatus according to the present invention can exhibit effects such as noise and vibration reduction, prevention of step-out stop, and suppression of peak current generation. It can be applied to various applications equipped with brushless DC motors regardless of whether they are for industrial use or industrial use.

1 is a block diagram of a brushless DC motor driving apparatus when switching from an I waveform generator to an II waveform generator according to Embodiment 1 of the present invention; The flowchart which showed the operation | movement at the time of switching from the 1st waveform generation part to the 2nd waveform generation part in Embodiment 1 of this invention 1 is a block diagram of a brushless DC motor driving apparatus when switching from a second waveform generator to an first waveform generator according to Embodiment 1 of the present invention; The flowchart which showed the operation | movement at the time of 1st waveform generation part switching from the II waveform generation part in Embodiment 1 of this invention Block diagram of a brushless DC motor driving apparatus when switching from the I waveform generator to the II waveform generator according to the second embodiment of the present invention. The flowchart which showed the operation | movement at the time of the 2nd waveform generation part switching from the 1st waveform generation part in Embodiment 2 of this invention Block diagram of the brushless DC motor driving apparatus when switching from the II waveform generator to the I waveform generator according to the second embodiment of the present invention. The flowchart which showed the operation | movement at the time of switching from the II waveform generator to the I waveform generator in Embodiment 2 of this invention The characteristic view which showed the load condition of the refrigerator in Embodiment 2 of this invention, and the relationship of a suitable frequency Block diagram of a conventional brushless DC motor drive device

DESCRIPTION OF SYMBOLS 3 Inverter 4 Brushless DC motor 4a Rotor 4b Stator 5 Position detection part 6 Frequency calculation part 7 1st waveform generation part 8 1st waveform generation part 9 Predetermined frequency setting part 10 Frequency command part 11 Switching determination part 30 Match determination part 50 Frequency correction unit 70 Deviation comparison unit

Claims (7)

A brushless DC motor including a rotor having a permanent magnet and a stator having a three-phase winding, and six switch elements for supplying power to the three-phase winding are connected in a three-phase bridge. In the reverse direction, a reverse current diode is connected in parallel, and the rotational position of the rotor is detected. From the waveform information at the connection point of the three-phase winding and the inverter, the brushless DC motor A position detection circuit for detecting an operating state; an I waveform generator for outputting a waveform in accordance with the rotational position; an II waveform generator for outputting a waveform in synchronization with the frequency while changing only a predetermined frequency; A predetermined frequency setting unit for determining a predetermined frequency of the second waveform generation unit, and a waveform output frequency from the timing at which the position detection circuit detects the rotational position. A frequency calculating unit for, in response to the driving state information output, a brushless DC motor driving device having the above determining switching determination unit Come to switch the output waveform according to I waveform generator or the second II waveform generator. The position detection circuit determines the stability of the behavior of the brushless DC motor and the appropriateness of the phase from the variation and the length of time flowing through the return current diode, and then transmits the determination to the switching determination unit. After determining that the output waveform can be switched to the output waveform by the second waveform generation unit, the predetermined frequency setting unit is instructed as a predetermined frequency to be equal to the frequency calculated by the frequency calculation unit, and the output waveform generation unit is 2. The brushless DC motor driving apparatus according to claim 1, wherein the waveform generator is switched to the second waveform generator. Since the position detection circuit can detect the rotational position after the current has flown through the return current diode, the timing of detecting the rotational position after confirming the reliability of the position detection is the second waveform generator. And a coincidence determination unit that commands the predetermined frequency determined by the predetermined frequency setting unit as the output frequency of the I-waveform generation unit. 2. A brushless DC motor drive device according to 1. When it is determined that the phase of the brushless DC motor is in an inappropriate state from the length of time that the position detection circuit flows through the return current diode, the phase calculated from the frequency calculated by the frequency calculation unit is made appropriate. The brushless DC motor drive device according to claim 1, further comprising: a frequency correction unit that corrects the output to a predetermined frequency and outputs the predetermined frequency to the predetermined frequency setting unit. Since the position detection circuit can detect the rotational position after the current has passed through the return current diode, the position detection circuit detects the second waveform after confirming the reliability of the position detection. A comparison is made as to whether or not the deviation within a permissible range remains with respect to the timing output by the generation unit, and if within the permissible range, the predetermined frequency determined by the predetermined frequency setting unit is output to the I-th waveform generation unit The brushless DC motor drive device according to claim 1, further comprising a deviation comparison unit that commands the frequency. The compressor of the refrigerator carrying the brushless DC motor operated with the drive device in any one of Claims 1-5. A brushless DC motor comprising a rotor having a permanent magnet and a stator having a three-phase winding, an inverter for supplying electric power to the three-phase winding, and a waveform I corresponding to the rotational position of the rotor A waveform generation unit, a second waveform generation unit that outputs a waveform in synchronization with the frequency while changing only a predetermined frequency, and a rotational position of the rotor from waveform information at a connection point of the three-phase winding and the inverter And a position detection circuit that detects an operation state, and a switching determination unit that switches an output waveform to the first waveform generation unit or the second waveform generation unit according to the operation state information output from the position detection circuit. During the operation of the brushless DC motor, the switching determination unit causes the I waveform generation unit to transfer the I waveform generation unit from the I waveform generation unit to the II waveform generation unit. It is possible to switch to a part, and after switching from the operating state information to confirm that the current of the brushless DC motor is not disturbed, switching is performed, thereby suppressing an increase in current flowing through the brushless DC motor. Driving method for brushless DC motor.