JP2010252480A - Motor drive device and refrigerator using the same - Google Patents

Abstract

Provided is a highly reliable motor driving device capable of realizing high-efficiency driving at low speed of a brushless DC motor and capable of high-speed driving at high load.
At a low speed, a position signal of a brushless DC motor 4 is acquired by a position detection section 5 and sensorless driving by a first waveform generation section 7 is performed to improve efficiency. At a high speed, a signal from a second waveform generation section 9 is achieved. When the waveform is synchronized with the frequency fixed and the second waveform generator 9 shifts from the high-load high-speed drive state to the low-speed high-efficiency drive in the first waveform generator, the waveform corrector 12 performs the second waveform generator. Since the commutation based on the position signal can be performed immediately after the transition to the first waveform generation unit by correcting the waveform generated in step 1 to a waveform capable of acquiring the position signal of the brushless DC motor, a stable transition is achieved. It becomes possible.
[Selection] Figure 1

Description

  The present invention relates to a device for driving a brushless DC motor comprising a rotor having a permanent magnet and a stator having a three-phase winding by means of an inverter that supplies power to the three-phase winding. The present invention relates to a brushless DC motor driving apparatus that is optimal for driving a compressor such as an air conditioner.

  Conventionally, this type of motor driving apparatus realizes optimum driving according to the load by switching the waveform generation method according to the state of the driving load (see, for example, Patent Document 1).

  In FIG. 7, the AC power source 1 is a general commercial power source, and is AC 100 V, 50 or 60 Hz in Japan. The rectifying / smoothing circuit 2 includes a rectifying circuit in which four diodes are bridge-connected and two smoothing electrolytic capacitors, and is a voltage doubler rectifying circuit that inputs an AC 100V voltage and outputs a DC 280V.

  The inverter 3 has six switching elements connected in a three-phase bridge, converts the output of the rectifying / smoothing circuit 2 into three-phase AC power, and supplies it to the brushless DC motor 4.

  The brushless DC motor 4 includes a rotor 4a having a permanent magnet and a stator 4b having a three-phase winding, and a three-phase alternating current generated by the inverter 3 flows through the three-phase winding of the stator. Thus, the rotor can be rotated.

  The position detector 5 detects the relative rotational position of the rotor by detecting the induced voltage generated in the three-phase winding urged by the stator as the rotor of the brushless DC motor 4 rotates. It is.

  The first waveform generator 6 generates a signal for driving the switch element of the inverter 3 based on the position detection signal of the position detector 5. This driving signal is based on rectangular wave energization, and produces a rectangular wave with an energization angle of 120 degrees to 150 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. The first waveform generator 6 also controls the duty of PWM control in order to keep the rotational speed constant, and operates with the optimum duty according to the rotational position, so that the most efficient operation is possible.

  The rotation speed detector 7 detects the rotation speed of the brushless DC motor 4 from the output signal of the position detector 5. This rotation speed can be detected by counting the output signal of the position detector 5 for a certain period of time or measuring the period.

  The frequency setting unit 8 changes only the output frequency while keeping the output duty constant.

  The second waveform generation unit 9 generates a signal for driving the switch element of the inverter 3 based on the output signal of the frequency setting unit 8. This driving signal creates a rectangular wave with a conduction angle of 130 degrees or more 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. Further, here, the operation is performed at the maximum duty, and the operation is performed at a constant duty of 90 to 100%.

The switching determination unit 10 determines the low speed / high speed based on the rotational speed detected by the rotational speed detection unit 7 and switches the waveform for operating the inverter 3 between the first waveform generation unit 6 and the second waveform generation unit 9. is there. Specifically, when the rotational speed is low, the signal from the first waveform generator 6 is selected, and when the rotational speed is high, the signal from the second waveform generator 9 is selected to operate the inverter 3.

Here, the determination of whether the rotational speed is low or high is based on the actual rotational speed from the rotational speed detection unit 7, but the set rotational speed and duty may be determined. Duty is the maximum duty (generally 10
0%), the number of rotations by PWM duty control in position detection becomes maximum, so that the signal can be switched under this condition.

  The drive unit 11 drives the switch element of the inverter 3 by the output signal from the switching circuit 10. By this driving, an optimum AC output is applied from the inverter 3 to the brushless DC motor 4, so that the rotor can be rotated.

  The operation of the motor driving apparatus configured as described above will be described below.

  First, at a relatively low load and low speed, each switching element of the inverter 3 is driven by the first waveform generator 6 that operates based on the output timing of the position detector 5. At this time, the rotation speed of the brushless DC motor 4 is detected from the output signal of the position detection unit 5, and the first waveform generation unit 6 performs PWM duty control so that the driving speed approaches the target speed. The brushless DC motor 4 is efficiently driven by sensorless PWM control.

In the load state in which the drive speed of the brushless DC motor 4 does not reach the target speed even though the PWM duty is maximized (for example, 100%) in the driving by the first waveform generator 6, the switching determination unit 10 The second waveform generator 9 operated by the frequency setting unit 8 is selected to drive the inverter 3. The drive signal of each phase of the inverter 3 is commutated so as to output a predetermined frequency according to the output of the frequency setting unit 8. At this time, the duty phase is constant and the commutation frequency is increased stepwise by synchronous driving regardless of the rotor position, so that the current phase is advanced with respect to the induced voltage phase of the brushless DC motor 4, so-called “weakening magnetic flux control”. The state becomes the same as that of the first waveform generation unit 6 and can be driven at a significantly higher speed.
With the configuration as described above, the conventional motor driving device can improve the high-load high-speed performance of the brushless DC motor as compared with the general PWM feedback control based on the detection of the induced voltage in the first waveform generator 6. Also, when using a motor with a large amount of stator winding and reduced torque (number of rotations), the first waveform generator 6 performs high-efficiency driving at low speed and the high-speed driving performance is the second waveform generator 9. It can be ensured by driving at
JP 2004-282911 A

  However, the above-described conventional configuration requires commutation based on the rotor position when shifting from driving by the second waveform generation unit 9 to driving to the first waveform generation unit 6 such as when the driving speed is reduced. However, the output signal from the position detection unit 5 when performing synchronous driving may deviate from the induced voltage zero cross signal of the brushless DC motor 4, and the detected position signal is at an accurate timing. If the waveform generator is switched from the second waveform generator 9 to the first waveform generator 6 in such a state, the protection is stopped due to the occurrence of an overcurrent or the step is stopped due to a step-out. There is a problem that this may occur.

  Further, in the conventional configuration, in order to avoid problems such as generation of overcurrent and stop of step-out, the brushless DC motor 4 is once stopped and switched again when switching from the second waveform generator 9 to the first waveform generator 6. There is a practical problem that it is necessary to take measures such as driving by the first waveform generator 6 upon activation, and to stop once when decelerating from high speed to low speed.

  The present invention solves the above-described conventional problems, and realizes the reliability and practicality of a conventional motor driving device capable of realizing high efficiency and high speed driving by stably and smoothly switching the waveform generator. It aims to improve.

  In order to solve the above-described conventional problems, the motor driving apparatus of the present invention is a state in which the brushless DC motor is driven at a speed higher than a predetermined speed by the synchronous driving by the second waveform generator regardless of the rotor position. When shifting to driving at a predetermined speed or less while detecting the rotor position by the first waveform generator, part or all of the waveform generated by the second waveform generator at a predetermined timing in the waveform corrector By driving the inverter with an intermittent waveform via the drive unit, it is possible to detect the position during synchronous driving, and the position is switched based on the position information of the brushless DC motor immediately after the shift to the drive in the first waveform generation unit. The flow is possible.

  The commutation at the time of switching to the first waveform generation unit can be performed at an appropriate timing based on the rotor position information by the rotor position signal obtained in this way, and therefore accompanying the position shift at the time of switching the waveform generation unit Since the commutation phase shift can be prevented, the occurrence of an overcurrent at the time of switching or the occurrence of a stop due to a step-out or the like can be prevented.

  The motor driving device of the present invention can improve reliability and prevent practicality by preventing occurrence of overcurrent or stoppage due to step-out while ensuring high efficiency and high-speed driving performance.

  Moreover, the refrigerator using the motor drive device of the present invention can drive the compressor in an optimal state according to the load state in the warehouse, and can switch the driving state without stopping the compressor. Therefore, power consumption of the refrigerator and deterioration of food in the refrigerator can be suppressed.

The invention according to claim 1 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 drive for driving the inverter A position detection unit that detects a relative rotational position of the rotor based on an induced voltage generated in a three-phase winding of the stator of the brushless DC motor and outputs a position signal; and the position detection unit A first waveform generator that outputs a rectangular wave, a sine wave, or a waveform conforming thereto while performing duty control based on an output signal from the output, a frequency setting unit that changes only a predetermined frequency with a constant duty, and a rectangular A second waveform generator for outputting a wave, a sine wave or a waveform conforming thereto, at a predetermined frequency determined by the frequency setting unit, and the brushless DC motor has a predetermined rotation speed When rotating at a low speed below, the inverter is driven via the drive unit with the output of the first waveform generating unit, and when the brushless DC motor is rotating at a high speed exceeding a predetermined number of revolutions, A switching determination unit that switches the waveform generation unit to drive the inverter via the drive unit with the output of the second waveform generation unit, and a part of the waveform generated in the second waveform generation unit at a predetermined timing, or A waveform correction unit that corrects the waveform so as to be intermittent, and when the drive from the second waveform generation unit shifts to the drive by the first waveform generation unit, the waveform correction unit By correcting the waveform output from the generator and outputting it to the drive unit to drive the inverter, the rotor relative position of the brushless DC motor is detected, and the detected brush By determining the commutation timing based on the rotor position of the DC motor, commutation when switching to the first waveform generator can be performed at an appropriate timing based on the rotor position information, and waveform generation The commutation phase shift due to the position shift at the time of part switching can be prevented, and the occurrence of an overcurrent at the time of switching or the occurrence of a stop due to a step-out, etc. can be eliminated, and by improving the reliability of the motor drive device Practicality can be increased.

  According to a second aspect of the present invention, in the motor drive device according to the first aspect of the present invention, the energization angle of the inverter before and after switching from driving by the second waveform generating unit to driving by the first waveform generating unit. Are equal and 150 degrees or less, it is possible to reliably detect the position by detecting the induced voltage after the shift to the drive in the first waveform generator, and therefore the stability after the shift to the first waveform generator. Since the drive can be secured, the reliability of the motor drive device can be further increased.

  According to a third aspect of the present invention, in the first and second aspects of the present invention, the waveform correction section sets a conduction angle of at least one phase of a waveform generated by the second waveform generation section to 150 degrees or less. Thus, since the position detection by the induced voltage detection can be surely performed in the driving by the second waveform generator, the motor drive is performed in order to perform the transition to the first waveform generator more surely and stably. The reliability of the apparatus can be further increased and the utility can be improved.

  According to a fourth aspect of the present invention, in the first to third aspects of the present invention, a phase difference between a relative position of the rotor of the brushless DC motor and a waveform generated by the second waveform generating unit is detected. When the phase difference detected by the phase difference detection unit becomes a predetermined difference, the driving from the second waveform generation unit shifts to the driving by the first waveform generation unit. As a result, when the load state that can be driven by the first waveform generating unit is reached, the driving is shifted to the driving by the first waveform generating unit, and thus the load state in which the driving by the first waveform generating unit is impossible. Therefore, it is possible to prevent a step-out due to the shift in the motor and to realize a stable drive, and thus it is possible to improve the reliability and practicality of the motor drive device.

  According to a fifth aspect of the present invention, the motor driving device according to the first to fourth aspects of the present invention drives a compressor. Since the compressor is a load having a relatively large inertia due to its configuration, even when a brushless DC motor is driven in a pattern in which some or all of the motor applied voltage is intermittent to detect the induced voltage, the influence on the driving speed fluctuation is affected. This is one of the very suitable applications for the motor drive device of the present invention.

  According to a sixth aspect of the present invention, the compressor according to the seventh aspect of the present invention has a reciprocating configuration. Since the reciprocating compressor has a configuration in which the brushless DC motor 4 is suspended by a spring or the like inside the compressor, vibration and noise due to the driving of the brushless DC motor 4 are hardly leaked to the outside. Therefore, in the motor driving device of the present invention, even if a part of or all of the motor applied voltage is intermittently generated and a slight speed fluctuation occurs in the driving speed of the brushless DC motor 4, vibrations and noises accompanying the fluctuation are generated in the compressor 4. Therefore, the same level of noise and vibration can be maintained without greatly increasing vibration and noise.

  The invention according to claim 7 uses the motor driving device according to claim 5 or claim 6 for driving the compressor of the refrigerator, and the refrigerator has a relatively high internal temperature and rapidly enters the internal storage. High-load high-efficiency drive is performed in high-load conditions, such as when the compressor needs to be cooled, and then the compressor is stopped to high-efficiency drive at low speed when the interior is in a stable cooling state and the load decreases. The drive state can be switched without any change, so that it is possible to continuously switch to the optimum drive state according to the load state in the refrigerator, improve food freshness performance by suppressing fluctuations in the refrigerator temperature, and reduce the number of times the compressor is started. By reducing the power loss at startup, you can save energy in the refrigerator.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the same reference numerals are given to the same components as those in the related art, and detailed descriptions thereof will be omitted.

  The present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 shows a block diagram of a motor drive apparatus according to Embodiment 1 of the present invention.

  In FIG. 1, the waveform correction unit 12 outputs the waveform generated by the second waveform generation unit 9 to the switching determination unit 10, but outputs a waveform in which a part or all of the waveform is intermittent for a certain period at a predetermined timing. The position signal determination unit 13 determines whether or not the signal input from the position detection unit 5 is credible as a position detection signal when driven by the second waveform generation unit 9, and the accurate position of the brushless DC motor 4 is determined. Only a signal including information is extracted.

  The phase difference detection unit 14 detects a phase difference between the phase of the waveform generated by the second waveform generation unit 9 and the induced voltage phase of the brushless DC motor 4. Specifically, it can be detected from the time difference between the position signal output from the position signal determination unit 13 and the output timing of the waveform generated by the second waveform generation unit 9.

  The compression element 15 is connected to the shaft of the rotor 4a of the brushless DC motor 4, and sucks, compresses and discharges the refrigerant gas. The brushless DC motor 4 and the compression element 15 are accommodated in the same hermetic container to constitute the compressor 16. The discharge gas compressed by the compressor 16 constitutes a refrigerating and air-conditioning system that returns to the suction of the compressor 16 through the condenser 17, the decompressor 18, and the evaporator 19. Then, since endotherm is performed, cooling and heating can be performed. If necessary, a heat blower may be further promoted by using a blower or the like for the condenser 17 or the evaporator 19. Further, in the present embodiment, the refrigeration system is configured to cool the inside 21 of the refrigerator 20 by the evaporator 19.

  FIG. 2 shows a cross-sectional view of the compressor 16 according to the first embodiment. In FIG. 2, oil 23 is stored in a sealed container 22 of the compressor 16 and a refrigerant 24 of R600a is enclosed, and a brushless DC motor 4 including a stator 4b and a rotor 4a and a compression element 15 driven by the brushless DC motor 4 are provided. It is elastically supported by a spring or the like, and is configured such that vibration due to rotation of the brushless DC motor 4 is difficult to leak out of the compressor.

  The compression element 15 supports a main shaft portion 25 of a crankshaft 27 composed of a main shaft portion 25 to which the rotor 4 a is fixed and an eccentric shaft portion 26, and has a compression chamber 28 and a cylinder 29. A reciprocating compression mechanism is provided by including a reciprocating piston 30 and a connecting means 31 for connecting the eccentric shaft portion 26 and the piston 30. Accordingly, in the present embodiment, when the brushless DC motor 4 is driven with a waveform in which a part or all of the waveform for a certain period is intermittent when driven by the second waveform generator 9, the compressor 16 having a large inertia is used. In addition to having little influence on the rotational speed (for example, speed change), vibration and noise due to speed fluctuations are less likely to occur due to the characteristics and sealing structure of the reciprocating compressor, and noise is less likely to leak outside the compressor 16. It has a configuration.

  FIG. 3 is a timing chart showing a driving state at a low speed in the first embodiment, and shows a signal of the drive unit 11 and an output terminal voltage state of the inverter 3. This timing chart is a rectangular wave with an energization angle of 150 degrees and is driven with an advance angle of 15 degrees.

As shown in FIG. 3, in this state, when both the upper and lower switches of each UVW phase are in the OFF state, a dielectric voltage appears in the output terminal voltage. For example, as shown in the figure, for the U phase, when the output pattern is 11 and 5, both the U phase upper and lower switches are off and an induced voltage appears in the terminal voltage. In order to detect the zero cross point of the induced voltage from the terminal voltage as a position signal, the position detecting unit 5 determines a point where the magnitude relationship between the terminal voltage and 1/2 of the inverter input voltage is inverted (that is, the zero cross point of the induced voltage). Monitor. The detected zero cross point is set as a reference as the relative rotation position of the brushless DC motor rotor, and the next commutation timing is determined based on this reference position. In the first embodiment, 150 degrees energization advance angle is 15 degrees, so the next commutation is zero seconds after position detection (that is, at the same time), and commutation (output pattern from 11 to 0 or 5 to 6). Although FIG. 3 shows the position detection timing based on the U-phase terminal voltage and the U-phase, since the position detection is performed twice for each phase per electrical angle cycle, it is eventually 6 times in one electrical angle cycle. A position detection signal is generated, and an output voltage is sequentially switched each time this position signal is detected, thereby generating an AC voltage of an arbitrary frequency and applying it to the brushless DC motor 4 for driving.

  The speed of the brushless DC motor 4 is detected based on the position detection signal. When the detected speed is slower than the target speed, the first waveform generator 6 increases the voltage applied to the brushless DC motor 4 to increase the target speed. If it is faster, the PWM duty width is controlled so as to lower the voltage applied to the brushless DC motor 4 to ensure speed stability at the target speed.

  Here, even if the load of the brushless DC motor 4 is large and the PWM duty is 100%, no further voltage can be applied in a state where the driving speed does not reach the target speed, so further high speed driving is impossible. It is. Therefore, at this time, the switching determination unit 10 performs switching so that the brushless DC motor 4 is driven by the second waveform generation unit 9.

  The driving by the second waveform generation unit 9 performs synchronous driving at a frequency set by the frequency setting unit 8 with a waveform having a maximum duty (ie, 100%) and a conduction angle of 130 degrees or more and less than 180 degrees.

  FIG. 4 is a timing chart showing the driving state at high speed in the first embodiment of the present invention, and shows the state of the signal of the drive unit 11 and the U-phase terminal voltage. The timing chart of FIG. 4 is also a rectangular wave with a conduction angle of 150 degrees, similar to the timing chart of FIG.

  In the driving by the second waveform generation unit 9, synchronous driving is performed at an arbitrary frequency set by the frequency setting unit 8 regardless of the relative position of the rotor of the brushless DC motor 4, and the rotor follows the commutation. Since the terminal voltage advances with respect to the state, that is, the induced voltage, the current phase of the brushless DC motor 4 advances, and the driving state with the so-called weak magnetic flux is obtained. The lead phase angle of the terminal voltage and current at this time can be driven at high speed and with a high load by being in an equilibrium state in a state more appropriate than the load with respect to the applied voltage.

  Since the conduction angle in FIG. 4 is 150 degrees, the advance angle when the zero cross detection of the induced voltage coincides with the commutation timing (that is, the commutation is performed immediately after the zero cross detection) is 15 degrees. Then, the commutation occurs before the detection of the zero cross of the induced voltage, and it can be seen that the driving is performed at an advance angle of 15 degrees or more. In FIG. 4, when both the upper and lower switching elements of the U phase are off, an induced voltage of the brushless DC motor 4 is generated in the terminal voltage, but since the commutation occurs before the zero cross timing of the induced voltage, an inverter terminal near the zero cross The voltage is stuck to the input potential (when the upper switching element is on). Therefore, in such a driving state, it is difficult to accurately detect the zero crossing of the induced voltage, and in the driving by the first waveform generation unit 6 based on the output signal of the position detection unit 5, the commutation is performed at an appropriate timing. It is difficult to perform and stable driving is difficult.

Next, switching between driving by the first waveform generator 6 and driving by the second waveform generator 9 will be described. Since driving by the first waveform generator 6 is feedback control by detecting the induced voltage zero cross signal, it is necessary to detect the position reliably. Therefore, the energization angle before and after the switching of the waveform generation unit is set to 150 degrees or less so that the position can be reliably detected by driving with the first waveform generation unit 6. Further, in the driving by the second waveform generator 9 before the transition to the first waveform generator 6, 15
When the conduction angle is 0 degree or more, the conduction angle is decreased to a conduction angle of 150 degrees or less.

  Switching from driving by the first waveform generation unit 6 to driving by the second waveform generation unit 9 makes the commutation cycle before and after switching the same, and thereafter repeats the commutation at a predetermined cycle regardless of the position signal. Thus, it can be easily realized without causing problems such as current disturbance such as overcurrent and speed fluctuation.

  However, in the transition from the drive at the second waveform generator 9 to the drive at the first waveform generator 6, the drive at the first waveform generator 6 detects the rotor position and determines the commutation timing. Although it is necessary, when commutation is performed using the output signal of the position detection unit 5 immediately before the transition as the position detection signal, the output signal of the position detection unit during synchronous driving by the second waveform generation unit 9 is as described above. Since there is no credibility as a position signal, there is a possibility of commutation at an incorrect timing, which causes overcurrent generation or out-of-step stop.

  Therefore, in order to smoothly shift to the driving by the first waveform generator 6, it is necessary to accurately detect the rotor relative position of the brushless DC motor 4.

  FIG. 5 is a timing chart showing position detection at the time of synchronous driving in the first embodiment of the present invention, and shows a signal of the drive unit 11 and an output terminal voltage state of the inverter 3. FIG. 5 shows a state in which synchronous driving is performed at 150 ° energization, and when the terminal voltage states of the V phase and the W phase are seen, since commutation is performed before the zero cross point of the induced voltage, it is 15 ° or more. It turns out that it is an advance angle state. Further, the induced voltage zero cross point is buried in the input voltage or the GND level of the inverter 3 due to the energization of the switch element, and is in an undetectable state.

  However, in the first embodiment, the second waveform is forcibly turned off during a certain period when the waveform correcting means 12 is expected to generate a zero cross point of the induced voltage in the energized section on the upper side of the U phase. The waveform of the generator 9 is corrected.

  The conduction angle at the time of correction is set to 150 degrees or less so that the zero crossing of the induced voltage can be reliably detected (in the first embodiment, in the output pattern 0, the switching element on the upper side of the U phase is turned on, but forced And 150 degrees energization is 120 degrees). As a result, as shown in the U-phase terminal voltage waveform of FIG. 5, before the U-phase upper side commutates (that is, before switching to the output pattern 1), an induced voltage zero cross appears and can be detected. Therefore, the relative position of the rotor of the brushless DC motor 4 can be detected accurately even by synchronous driving by the second waveform generator, and when switching to driving by the first waveform generator 6, switching at the correct timing is performed by accurate position detection. Flow is possible.

  Here, the operation of the position signal determination means 12 will be described. In the first embodiment, the relative position of the rotor of the brushless DC motor 4 is detected as position information at the time when the magnitude relation is inverted by comparing the magnitude of the inverter input voltage with 1/2 of the inverter output terminal voltage. In the V-phase and W-phase terminal voltages of 5, the point at which the magnitude relationship between the inverter terminal voltage and 1/2 of the inverter input voltage is reversed is clearly deviated from the induced voltage zero cross point (in the U-phase terminal voltage, the inverter terminal voltage This also applies to the point where becomes smaller than the inverter input voltage 1/2). Therefore, in order to reliably detect the rotor relative position of the brushless DC motor 4, it is necessary to take out only the signal including the rotor position information from the output signal of the position detector.

Therefore, in the first embodiment, the position signal determination unit 13 selects the output signal of the position detection unit 5 and extracts only the signal including the position information of the brushless DC motor 4.
Specifically, it is realized by extracting only the signal obtained during the period when the switching element is forcibly stopped to acquire the induced voltage (in this embodiment, when the output pattern is 0) and recognizing it as a position signal. ing.

  However, at the time of synchronous driving by the second waveform generator 9, the state is in a stable state with an advance state corresponding to the speed and load. Therefore, depending on the relationship between the speed and the load, there may be a case of driving in a large advance state that cannot be realized by the first waveform generator 6.

  FIG. 6 is a timing chart showing changes in position detection timing depending on the load state in the first embodiment of the present invention. In FIG. 6, (A) and (B) show a low load (A) and a high load (B) when driving at the same speed. This chart is similar to the chart of FIG. 5 in that the energization angle is 150 degrees, and in the output pattern 0, the waveform correction unit 12 forcibly turns off the U-phase upper switching element of the waveform in the second waveform generation unit 9. It is corrected to.

  In the position detection in the low load state of FIG. 6A, the position detection timing is generated at the same time when the output pattern is switched from 11 to 0 (that is, commutation timing). That is, since this state is a state where the lead angle is 15 degrees with 150 degrees energization, it is a load state that can be driven by the first waveform generator. Therefore, in such a load state, the commutation commutation timing is determined based on the detected position signal, and a smooth transition to driving by the first waveform generating means 6 is possible.

  Further, in the high load state shown in FIG. 6B, since the driving is stable in a large advance angle state, the position detection timing is delayed from the timing at which the output pattern 11 is switched to 0 (that is, commutation timing). When energization is 150 degrees and the advance angle is 15 degrees, the commutation is performed simultaneously with the position detection (that is, the induced voltage zero cross timing), so that it is understood that the drive is performed with the advance angle of 15 degrees or more. In addition, when the induced voltage zero cross point is used as a position signal, the maximum advance angle at 150 degrees energization is 15 degrees. Therefore, in the state shown in FIG. 6B, the first waveform generator 6 cannot be driven. . Therefore, in such a load state, when shifting from the synchronous driving in the second waveform generator 9 to the driving by the first waveform generator, commutation at an appropriate timing cannot be performed, and overcurrent and out-of-step occurrence are caused. Cause.

  Next, the operation of the phase difference detection means 14 will be described. As described above, in the transition from the driving by the second waveform generator 9 to the driving by the first waveform generator 6, in a load state (high load) where the first waveform generator 6 cannot drive, In order to avoid problems such as adjustment, it is necessary to limit the shift to driving by the first waveform generator 6.

  In synchronous drive, the advance angle changes depending on the speed and load state (the advance angle increases as the load increases), so the phase relationship between the applied voltage and the induced voltage also changes depending on the load state (the larger the load, the greater the applied voltage to the induced voltage). Therefore, the state of the load at the driving speed can be known from the phase relationship between the applied voltage phase and the induced voltage phase.

  The phase difference detection means 14 detects a phase difference between the applied voltage phase and the induced voltage phase, detects a timing difference between the commutation timing and the position detection timing, and when the detected timing difference is larger than a predetermined difference. Since the load is large and the driving by the first waveform generation unit is impossible, it is output to the switching determination unit 10 so that the switching determination unit 10 selects the driving by the second waveform generation unit.

In the present embodiment, as shown in FIG. 6B, when the position detection timing comes later than the commutation timing, the load is large, and the second waveform generator 9 cannot be driven by the first waveform generator 6. The synchronous drive is continued. Further, as shown in FIG. 2A, when the position detection timing is coincident or early with respect to the commutation timing, the load is light enough to enable the first waveform generator 6 to be driven. Shifting from driving by the waveform generator 9 to driving by the first waveform generator 6 performs PWM feedback control based on position detection.

  As described above, in the embodiment of the present invention, the brushless DC motor 4 having a permanent magnet, the inverter 3 that supplies power to the brushless DC motor 4, the drive unit 11 that drives the inverter 3, and the brushless DC motor 4 A position detector 5 that detects the relative rotational position of the rotor from the induced voltage generated in the winding of the first coil, and a first waveform that outputs a waveform while performing PWM duty control based on an output signal from the position detector 5 When the generator 6, the second waveform generator 9 that outputs a rectangular wave or a sine wave to the brushless DC motor 4, or a waveform corresponding thereto, and the brushless DC motor 4 are rotating at a low speed equal to or less than a predetermined number of rotations. Drives the inverter 3 via the drive unit 11 with the output of the first waveform generation unit 6, and when rotating at a high speed exceeding a predetermined rotation number, the second waveform generation unit 9 A switching determination unit 10 that drives the inverter 3 via the drive unit 11 with force, and a waveform correction unit that corrects the waveform so that part or all of the waveform generated in the second waveform generation unit 9 is intermittent at a predetermined timing 12, the waveform correction unit 12 corrects the waveform output from the second waveform generation unit 9 when shifting from driving by the second waveform generation unit 9 to driving by the first waveform generation unit 6. 11 to drive the inverter 3 so that the rotor relative position of the brushless DC motor 4 can be detected, the commutation timing is determined based on the detected rotor position information, and the first waveform generator 6 Move on to drive. As a result, the rotor position of the brushless DC motor 4 can be reliably detected in the synchronous drive by the second waveform generator 9, and the commutation when shifting to the drive by the first waveform generator 6 can be detected. Therefore, the commutation phase shift at the time of switching the waveform generator can be prevented, and the occurrence of overcurrent and step-out can be eliminated. Practicality can be increased.

  Further, by setting the energization angle of the inverter 3 before and after switching from driving at the second waveform generator 9 to driving at the first waveform generator 6 to be equal to or less than 150 degrees, the first waveform generator 6 Position detection by detection of the induced voltage after shifting to driving can be performed reliably, and the reliability of the motor driving device can be further increased.

  Further, the waveform correction unit 12 corrects the conduction angle of at least one phase of the waveform generated by the second waveform generation unit 9 to 150 degrees or less, so that the zero cross point of the induced voltage can be obtained even in the synchronous drive by the second waveform generation unit 9. Since the detection can be performed reliably, the position can be detected during synchronous driving, and the transition to the first waveform generator 6 can be performed more reliably and stably. Can be improved.

  The phase difference detection unit 14 detects the phase difference between the relative position of the rotor of the brushless DC motor 4 and the waveform generated by the second waveform generation unit 9, and the detected phase difference becomes a predetermined difference. When the driving by the second waveform generating unit 9 is shifted to the driving by the first waveform generating unit 6, the first waveform generating unit 6 can be driven by the first waveform generating unit 6. Since the process shifts to driving by the waveform generation unit 6, it is possible to prevent a step-out due to a shift in a load state where the driving by the first waveform generation unit 6 is impossible, and to realize a stable drive. Can increase the sexiness and utility.

  In addition, when the brushless DC motor 4 drives the compressor 16 having a large inertia, even when the brushless DC motor 4 is driven in a pattern in which a part or all of the applied voltage is intermittent, there is almost no influence on the drive speed change. This is one of the very suitable loads for the motor drive device of the invention.

Further, if the compressor 16 is a reciprocating configuration, the brushless DC motor 4 is suspended by a spring or the like inside the compressor, so that vibration and noise associated with the driving of the brushless DC motor 4 are difficult to leak to the outside. is there. Therefore, by intermittently applying a part or all of the voltage applied to the brushless DC motor, even if a slight speed fluctuation occurs in the driving speed, vibration and noise accompanying the speed fluctuation are absorbed inside the compressor 16. The same low noise and low vibration can be achieved without greatly increasing vibration and noise.

  Further, when the compressor 16 equipped with the motor drive device of the present invention is used in a refrigerator, a high load high speed drive is performed in a high load state in which the refrigerator interior temperature is relatively high and the interior needs to be rapidly cooled. After that, when the inside of the warehouse is in a stable cooling state and the load is low, the driving state can be switched to high efficiency driving at low speed without stopping the compressor, so it is matched to the inside load state It is possible to continuously switch to the optimal driving state, reduce the power loss at the start-up by reducing the number of start-up of the compressor, improve the food storage stability by suppressing the temperature unevenness in the refrigerator, and consume the refrigerator Electric power can be reduced.

  The brushless DC motor drive device of the present invention realizes high-efficiency and low-noise operation at low speed, and also enables high-load high-speed drive by weakening magnetic flux control by current advance according to the load at high speed. In particular, it is suitable for applications such as driving a compressor such as a refrigerator or an air conditioner, or a fan or a vacuum cleaner such as a fan having a wide speed range or load range.

1 is a block diagram of a motor drive device according to Embodiment 1 of the present invention. Sectional drawing of the compressor of this Embodiment 1. Timing chart showing drive state at low speed in the first embodiment Timing chart showing driving state at high speed in the first embodiment Timing chart showing position detection during synchronous driving in the first embodiment Timing chart showing change in position detection timing according to load state in the first embodiment Block diagram of a conventional motor drive device

DESCRIPTION OF SYMBOLS 3 Inverter 4 Brushless DC motor 5 Position detection part 7 1st waveform generation part 8 Frequency setting part 9 2nd waveform generation part 10 Switching determination part 11 Drive part 12 Waveform correction part 14 Phase difference detection part 16 Compressor 20 Refrigerator

Claims (7)

A brushless DC motor comprising a rotor having a permanent magnet and a stator having a three-phase winding, an inverter for supplying power to the three-phase winding, a drive unit for driving the inverter, and the brushless DC motor A position detector that detects the relative rotational position of the rotor based on the induced voltage generated in the three-phase winding of the stator and outputs a position signal, and a duty control based on the output signal from the position detector A first waveform generator that outputs a rectangular wave or a sine wave or a waveform conforming thereto, a frequency setting unit that changes only a predetermined frequency with a constant duty, and a rectangular wave or a sine wave or a waveform conforming thereto. The second waveform generator that outputs at a predetermined frequency determined by the frequency setting unit and the brushless DC motor are rotating at a low speed equal to or less than a predetermined number of rotations. Drives the inverter through the drive unit with the output of the first waveform generation unit, and when the brushless DC motor rotates at a high speed exceeding a predetermined number of rotations, the output of the second waveform generation unit A switching determination unit that drives the inverter via the drive unit, and a waveform correction unit that corrects the waveform so that a part or all of the waveform generated by the second waveform generation unit is intermittent at a predetermined timing, When shifting from driving by the two waveform generation unit to driving by the first waveform generation unit, the waveform correction unit corrects the waveform output by the second waveform generation unit and outputs it to the drive unit to drive the inverter. The relative position of the rotor of the brushless DC motor is detected, the commutation timing is determined based on the detected relative position of the rotor of the brushless DC motor, and the process proceeds to driving by the first waveform generator. Motor drive device. 2. The motor drive device according to claim 1, wherein energization angles of the inverters before and after switching from driving by the second waveform generation unit to driving by the first waveform generation unit are equal and equal to or less than 150 degrees. The motor driving apparatus according to claim 1, wherein the waveform correction unit sets a conduction angle of at least one phase of a waveform generated by the second waveform generation unit to 150 degrees or less. A phase difference detection unit that detects a phase difference between the relative position of the rotor of the brushless DC motor and the waveform generated by the second waveform generation unit; and the phase difference detected by the phase difference detection unit is a predetermined value 4. The motor driving device according to claim 1, wherein when the difference is reached, the driving by the second waveform generation unit shifts to the driving by the first waveform generation unit. 5. The motor driving apparatus according to any one of claims 1 to 4, wherein the brushless motor drives a compressor. The motor driving device according to any one of claims 1 to 5, wherein the compressor has a reciprocating configuration. A refrigerator using the motor driving device according to claim 5 for driving a compressor.