JP2007089322A - Controller for brushless dc motors and ventilator blower - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a reliable controller for brushless DC motors for ventilating fans, range hood fans, and the like and brushless DC motors for heat exchange cooling devices used for cooling equipment in cellular phone base stations or the like, wherein the commutation timing for motor current is controlled properly in a sensorless manner, without the use of a position sensor. <P>SOLUTION: The controller 12 for brushless DC motors 2 is so constructed that the phase of voltage applied to the winding of the stator 4 of a brushless DC motor 2 is deduced relative to induced voltage induced in the winding of the stator 4 and stored beforehand, based on the rate of change in the value of current supplied from a direct-current power supply 5 to an inverter circuit 1, and timing for commutation is determined so that the deduced phase follows a predetermined target phase. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a brushless DC motor such as a ventilation fan or a range hood, and a brushless DC motor control device of a heat exchange type cooler used for cooling equipment such as a mobile base station. The motor is controlled by sensorless control without using a position sensor. The present invention relates to suitably controlling the current commutation timing.

  Conventionally, this type of ventilation blower, for example, a heat exchange type cooler, takes in the air in the heating element storage box, passes through the heat exchange element, exchanges heat, and returns to the heating element storage box again. The internal air path to be circulated and the outside air are taken in through the heat exchange element, passed through the heat exchange element, and then exhausted to the outside air. In each of the air passages, one in which a blower for conveying each air is installed is known (for example, see Patent Document 1).

  Usually, the heat exchange type cooler having such a configuration is used for cooling mobile base stations and the like, and a DC low voltage power source is supplied to the heat exchange type cooler from the mobile base station body side, and a brushless DC motor is mounted. A blower or the like is driven.

  Hereinafter, the operation of the heat exchange type cooler will be described with reference to FIG.

  As shown in the drawing, the heated air in the heating element storage box 101 (hereinafter referred to as “inside air”) is a chamber in which the indoor brushless DC motor 104 is mounted from the inside air inlet 103 of the heat exchange type cooler 102. The air is sucked by the inner blower 105, passes through the heat exchange element 106, and then circulates in a circulation air path that returns from the inside air discharge port 107 into the heating element storage box 101. On the other hand, the outside air sucked from the outside air inlet 110 by the outside fan 109 equipped with the outside brushless DC motor 108 passes through the heat exchange element 106 and then is discharged again to the outside air from the outside air outlet 111. . The inside air passage and the outside air passage are partitioned in a substantially airtight state by the partition plate 112 so that the two air passages are independent, and a heat exchange element that exchanges sensible heat of the outside air and the inside air at the intersection of the inside air passage and the outside air passage. 106 is arranged. With the above configuration, the heat exchange type cooler 102 takes in the low temperature outside air, exchanges heat with the warm air inside the heating element storage box 101 by the heat exchange element 106, exhausts the warm outside air, and cools it. The air that has become is supplied into the box.

  The indoor brushless DC motor 104 and the outdoor brushless DC motor 108 normally use brushless DC motors with built-in magnetic pole sensors such as Hall elements, and the control device 113 that drives the brushless DC motor has a base station installed. In order not to be affected by low-temperature outside air or dust at the place where the heat is applied, the outdoor brushless DC motor 108 installed in the inside air path of the heat exchange type cooler 102 and exposed to the outside air is connected to a power lead 114 having a long relay. And the sensor signal lead wire 115. Drive power is supplied to the control device 113 from a low-voltage DC power supply 116 installed in the heating element storage box 101 or the like.

  Sensorless control of a brushless DC motor is a control method that determines the commutation timing of the motor based on the induced voltage, focusing on the correlation between the induced voltage induced in the stator winding during motor driving and the field. A sensorless control method is known that determines the commutation timing of the motor by estimating the magnetic pole position of the rotor based on the rate of change of the current value supplied from the power source to the inverter circuit with respect to time (for example, Patent Documents). 2).

  The operation of the brushless DC motor control device will be described below with reference to FIG.

  As shown in FIG. 18, the inverter circuit 117 has a three-phase inverter bridge configuration, Q1, Q2, and Q3 are U, V, and W phase upper arm switching elements. Similarly, Q4, Q5, and Q6 are respectively It is a U, V, W phase lower arm switching element. The switching diodes D1, D2, D3, D4, D5, and D6 are connected to each switching element in parallel. The brushless DC motor 118 includes a rotor 119 and a stator 120, and stator windings L1, L2, and L3 are arranged on the stator 120 so as to have a phase difference of 120 degrees in electrical angle. Between the DC power supply 116 and the switching element, a current detection resistor 121 for detecting the output current of the DC power supply 116 is disposed as shown in the figure. The voltage between the terminals of the current detection resistor 121 is input to an A / D converter 123 built in the microcomputer 122. The computing unit 124 calculates the phase commutation timing of the motor current with reference to the current value digitized by the A / D converter 123, and controls switching signals U +, V +, W +, U−, V−, W- is output. The drive circuit 125 is driven by energizing the switching elements Q1, Q2, Q3, Q4, Q5, and Q6 every 120 degrees based on the switching signal output from the computing unit 124.

The polarity of the rate of change of the current output from the DC power supply 116 with respect to time is detected, the magnetic pole position of the rotor is estimated based on the time when the polarity changes, and the polarity reversal time is measured based on the detection signal. From this time, the magnetic pole position of the rotor is estimated and the commutation timing is obtained.
JP 2001-156478 A JP-A-8-126379

  In such a conventional configuration, when a magnetic sensor is mounted, the magnetic sensor built in the outdoor brushless DC motor and the control device are connected by a long relay lead, so the relay lead of the sensor signal is affected by noise. It is easy to receive and malfunction, and there are restrictions on the temperature conditions of the installation location depending on the operating temperature range of the magnetic sensor, and the wiring work in the heat exchange type cooler is complicated and laborious, and it becomes a high cost cooler In the case of a brushless DC motor with sensorless driving, the commutation timing is determined by estimating the magnetic pole position on the assumption that the current value is the minimum, that is, where the induced voltage is the maximum. When there is a sudden load fluctuation due to disturbance, etc., the phase difference from the induced voltage becomes large, and the point where the current value becomes minimum cannot be found. Ri, it becomes difficult to accurately grasp the pole position, causing step-out, there is a problem that the possibility of the motor stop increases.

  The present invention solves such a conventional problem, eliminates the influence of noise, and is highly reliable and highly efficient brushless DC without stepping out even when the load fluctuation is large due to disturbance or the like. The object is to realize a motor control device.

  In order to achieve the above object, the brushless DC motor control device of the present invention is induced in the stator winding of the brushless DC motor stored in advance based on the rate of change of the current value supplied from the DC power supply to the inverter circuit. A control device for a brushless DC motor that estimates the phase of a voltage applied to the stator winding with respect to the induced voltage and determines the commutation timing so that the estimated phase follows a predetermined target phase It is.

  By this means, the current flowing through the inverter circuit can be detected and the phase can be estimated, and the position can be reliably detected, and a control device for a brushless DC motor capable of sensorless driving can be obtained.

  Further, the other means calculates the ratio of the current values at the first and second timings of the commutation cycle determined as the current change rate, and applies the position detection means to the current change rate and the stator winding. The correlation curve with the phase with the voltage is stored in advance.

  Thus, by storing the correlation curve in advance, the phase can be detected without requiring a complicated calculation, and an inexpensive microcomputer can be used, and a low-cost brushless DC motor control device can be obtained.

  The other means is that the first current value at the time when one-fourth of the commutation cycle has elapsed from the commutation timing, and three-fourths of the commutation cycle has elapsed from the commutation timing. The second current value at the time is obtained, and the ratio of the second current value to the first current value is calculated as the current change rate.

  This makes it possible to sample the current value at a position where the current change changes relatively greatly in the phase estimation within the commutation cycle, and obtain a larger current change rate, improving the phase estimation accuracy. A highly reliable brushless DC motor drive device can be obtained.

  Further, the other means stores the current change rate in a mechanical angle for one rotation period to obtain an average value of the current change rate of one rotation so that the phase can be estimated from the average value of the current change rate of one rotation. It is a thing.

  As a result, it is possible to reduce the effects of current variations due to variations in switching elements, rotor magnets, load imbalance, etc., and drive highly reliable brushless DC motors that can improve phase estimation accuracy. A device is obtained.

  Another means is to store the current change rate for one rotation at a mechanical angle, obtain an average value of the current change rate for one rotation, and compare the latest current change rate with the current change rate before one rotation. When the difference is smaller than a predetermined value, the phase is estimated from the average value of the current change rate of one rotation, while when larger than the predetermined value, the phase is calculated from the latest current change rate. Can be estimated.

  As a result, the magnitude of the load fluctuation can be detected, a more accurate current detection rate can be obtained according to the load fluctuation, and a highly reliable brushless DC motor control device that can improve the phase estimation accuracy is obtained. .

  Further, the other means obtains a current value at each time when one-fourth of the commutation period has elapsed from the commutation timing, and sets the ratio of the third to the fourth to the first current. When the phase obtained by the first current change rate is a lagging phase, the ratio of the four quarters to the two quarters is calculated as the second current change rate. The energization timing is determined based on the phase obtained from the rate of change, while the commutation timing is determined based on the phase obtained from the second current rate of change in the advanced phase.

  As a result, a more accurate current change rate can be detected in accordance with the phase, and a highly reliable brushless DC motor drive device that can improve the estimation accuracy of the phase and improve the followability to the load fluctuation can be obtained. .

  In addition, other means shall perform time correction according to the phase difference between the target phase and the actual phase from the previous commutation cycle, calculate the next commutation cycle, and determine the commutation timing. It is.

  As a result, an optimal commutation timing can always be obtained for each commutation cycle with respect to load fluctuation, and a highly reliable brushless DC motor control device that can improve followability to load fluctuation is obtained.

  Another means divides the previous commutation cycle into four and corrects the target phase by time-correcting only a predetermined quarter time interval according to the phase difference between the target phase and the actual phase. It is intended to follow.

  As a result, an optimal commutation timing can always be obtained for each commutation cycle with respect to load fluctuation, and a highly reliable brushless DC motor control device that can improve followability to load fluctuation is obtained.

  Other means compares the target phase with the actual phase, and if it is larger than the predetermined phase difference, it corrects the time according to the phase difference between the target phase and the actual phase from the previous commutation cycle. The next commutation cycle is calculated and the commutation timing is determined. On the other hand, when it is small, only a quarter of the predetermined commutation cycle is corrected for time. It is.

  This makes it possible to detect the magnitude of load fluctuations, obtain the optimum energization timing according to the load fluctuation at each commutation timing, and improve the followability to the load fluctuation with high reliability. A control device for the DC motor is obtained.

  Further, the other means compares the target phase with the actual phase, and when it is smaller than the predetermined phase difference, corrects only the time section of a quarter of the commutation period and corrects the phase obtained next time. If the number of times that the current phase is the same as the previous phase is greater than or equal to a predetermined number, the time is corrected according to the phase difference between the target phase and the actual phase from the previous commutation cycle. The next commutation cycle is calculated.

  As a result, the estimated phase can be accurately detected, so that it is possible to determine that the estimated phase is the same, it is possible to determine that the phase is about to step out, and the time correction amount of the next commutation cycle is changed. Thus, a highly reliable brushless DC motor control device that can reduce the occurrence of step-out can be obtained.

  Another means is to correct the commutation timing so as to follow the target phase by changing the amount of time correction during startup and during operation.

  As a result, the rotation is unstable at start-up, so an error is likely to occur in the phase estimation.By changing the amount of time correction between start-up and operation, it is possible to reduce instability of rotation and step-out. Thus, a highly reliable brushless DC motor control device that can improve the followability to load fluctuations can be obtained.

  Another means is that the control device for the brushless DC motor is mounted on the ventilation fan.

  This eliminates the need for sensor signal relay lead wires and magnetic sensors used to connect to the control means installed on the side of the inside air path, so there is no malfunction caused by noise on the sensor signal lines, and the temperature of the installation location. It is possible to provide a highly reliable brushless DC motor control device that eliminates restrictions on conditions, eliminates the need for lead wires, and eliminates the work of connecting relay wires, thus providing a low-cost heat exchange type cooler. .

  According to the present invention, even when the load size such as a light load or a heavy load changes, it is possible to always obtain an optimum phase according to the load, to eliminate the influence of noise, and to change the load due to disturbance or the like. Even in a large case, it is possible to provide a highly reliable and highly efficient brushless DC motor control device without stepping out.

  In addition, even when the load size changes, such as a light load or a heavy load, it is possible to always have an optimum phase according to the load, and the brushless DC motor is effective in that it can always be operated with high efficiency. A control device can be provided.

  In addition, a highly reliable brushless DC motor control device can be provided which has the effect of not stepping out even when the load fluctuation is large due to disturbance or the like.

  The invention according to claim 1 of the present invention relates to the induced voltage induced in the stator winding of the brushless DC motor stored in advance based on the rate of change of the current value supplied from the DC power supply to the inverter circuit. Phase estimation means for estimating the phase of the voltage applied to the stator winding, and commutation timing determination means for determining the commutation timing so that the phase estimated by the phase estimation means follows a predetermined target phase. A brushless DC motor that can detect the current flowing through the inverter circuit and estimate the phase, eliminates the effects of noise, and enables reliable magnetic pole position detection without stepping out The control device can be realized.

  According to the second aspect of the present invention, the ratio of the current values at the first and second timings of the commutation cycle determined in advance is calculated as the current change rate and applied to the current change rate and the stator winding. The correlation curve between the voltage and the phase is stored in advance. By storing the correlation curve in advance, the phase can be detected without the need for complicated calculations, and an inexpensive microcomputer can be used. It has the effect that a control device for a low-cost brushless DC motor can be manufactured.

  According to the third aspect of the present invention, the first current value at the time when one-fourth of the commutation period has elapsed from the commutation timing, and three-fourths of the commutation period from the commutation timing. The second current value at the time when the time has passed is obtained, and the ratio of the second current value to the first current value is calculated as a current change rate. In the estimation of the phase in the commutation cycle, The current value can be sampled at a position where the current change changes relatively greatly, a larger current change rate can be obtained, and a highly reliable drive with improved phase estimation accuracy can be realized.

  In the invention according to claim 4 of the present invention, the current change rate is memorized in the mechanical angle for one rotation period, the average value of the current change rate of one rotation is obtained, and the phase is calculated from the average value of the current change rate of one rotation. It can be estimated, and can reduce the influence of current variation due to variation of switching elements, variation of rotor magnets, variation due to load imbalance, etc., and improved reliability of phase estimation. High driving can be realized.

  In the invention according to claim 5 of the present invention, the current change rate is memorized for one rotation in mechanical angle, the average value of the current change rate of one rotation is obtained, and the latest current change rate and the current change before one rotation are obtained. When the difference is smaller than a predetermined value, the phase is estimated from the average value of the current change rate of one rotation, and when it is larger than the predetermined value, the latest current The phase can be estimated from the rate of change, the magnitude of the load fluctuation can be detected, a more accurate current detection rate can be obtained according to the load fluctuation, and the reliability with improved phase estimation accuracy High drive can be realized.

In the invention according to claim 6 of the present invention, a current value is obtained every time when one-fourth of the commutation period has elapsed from the commutation timing, and the ratio of the three-fourths to the one-fourth is obtained. As the first current change rate, the ratio of the four quarters to the two quarters is calculated as the second current change rate, and when the phase obtained by the first current change rate is a lagging phase, The energization timing is determined based on the phase obtained from the first current change rate. On the other hand, in the advance phase, the commutation timing is determined based on the phase obtained from the second current change rate. Accordingly, it is possible to detect a more accurate current change rate, and it is possible to realize a highly reliable drive that can improve the phase estimation accuracy and improve the followability to load fluctuations.

  The invention according to claim 7 of the present invention performs time correction according to the phase difference between the target phase and the actual phase from the previous commutation cycle, calculates the next commutation cycle, and determines the commutation timing. Therefore, the optimum commutation timing can always be obtained for each commutation cycle with respect to the load variation, and a highly reliable drive capable of improving the followability to the load variation can be realized.

  In the invention according to claim 8 of the present invention, the previous commutation cycle is divided into four, and only a predetermined quarter time section is time-corrected according to the phase difference between the target phase and the actual phase. Therefore, the optimum commutation timing can always be obtained for each commutation cycle with respect to the load variation, and a highly reliable drive capable of improving the followability to the load variation can be realized.

  The invention according to claim 9 of the present invention compares the target phase with the actual phase, and when the phase difference is larger than a predetermined phase difference, the phase difference between the target phase and the actual phase is changed from the previous commutation cycle. The time is corrected accordingly, the next commutation cycle is calculated, and the commutation timing is determined. On the other hand, when it is small, only the time section of a quarter of the predetermined commutation cycle is corrected. This makes it possible to detect the magnitude of load fluctuations, obtain the optimum energization timing according to the load fluctuation at each commutation timing, and improve the followability to the load fluctuation with high reliability. Drive can be realized.

  The invention according to claim 10 of the present invention compares the target phase with the actual phase, and when the phase difference is smaller than a predetermined phase difference, only the time section of a quarter of the commutation period is corrected for time, When the number of times that the obtained phase is the same as the previous phase is greater than or equal to a predetermined number of times, from the previous commutation cycle, depending on the phase difference between the target phase and the actual phase Time correction is performed and the next commutation cycle is calculated. Since the estimated phase can be accurately detected, it can be determined that the estimated phase is the same step out. It becomes possible to realize a highly reliable drive that can reduce the occurrence of step-out by changing the time correction amount of the next commutation cycle.

  According to the eleventh aspect of the present invention, the time correction amount is changed at the time of start-up and during operation. Since rotation is unstable at the time of start-up, an error is likely to occur in phase estimation. By changing the amount of time correction depending on the time, it is possible to reduce the instability of rotation and the occurrence of step-out, and it is possible to realize a highly reliable drive that can improve the followability to load fluctuations.

  The invention according to claim 12 of the present invention is a ventilation blower equipped with a brushless DC motor control device, and is a relay lead wire for sensor signals used for connection with a control device installed on the inside air path side. And a magnetic sensor are no longer required, so there is no influence of malfunction due to noise on the sensor signal line, and there is no restriction on the temperature condition of the installation location. This eliminates the need to connect the trunk line and eliminates the need to connect the trunk line, thus making it possible to manufacture a low-cost heat exchange type cooler.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
As shown in FIG. 1, the inverter circuit 1 has a three-phase inverter bridge configuration, Q1, Q2, and Q3 are U, V, and W-phase upper arm switching elements. Similarly, Q4, Q5, and Q6 are respectively It is a U, V, W phase lower arm switching element. The switching diodes D1, D2, D3, D4, D5, and D6 are connected to each switching element in parallel. The brushless DC motor 2 includes a rotor 3 and a stator 4, and stator windings L1, L2, and L3 are arranged on the stator 4 so as to have a phase difference of 120 degrees in electrical angle. Between the DC power supply 5 and the switching element, a current detection resistor 6 for detecting the output current of the DC power supply 5 is disposed as shown in the figure. The voltage between the terminals of the current detection resistor 6 is input to an A / D converter 8 built in the microcomputer 7. The phase estimation means 9 calculates a current change rate with respect to time of the current from the current value digitized by the A / D converter 8, and fixes the current change rate of the current value supplied to the inverter circuit 1 stored in advance. The phase is estimated from the phase relationship between the induced voltage induced in the child winding and the voltage applied to the stator winding. The commutation timing determination means 10 compares the phase obtained from the phase estimation means 9 with the target phase, calculates the phase commutation timing of the motor current based on the phase difference, and switching signals for controlling the inverters U +, V + , W +, U−, V−, W−. The drive circuit 11 is driven by energizing the switching elements Q1, Q2, Q3, Q4, Q5, and Q6 every 120 degrees based on the switching signal output from the commutation timing determining means 10.

  The phase estimation means 9, the commutation timing determination means 10, and the drive circuit 11 are built in the microcomputer 7.

  The control device 12 includes an inverter circuit 1, a current detection resistor 6, and a microcomputer 7.

  Next, a phase estimation method will be described. FIG. 2 (a) shows a current waveform at 120 degrees energization. In the figure, A / D conversion is performed on current values at two arbitrary points of the commutation cycle, that is, I1 and I2, and the ratio of the current value of I2 to the current value of I1 is obtained as a current change rate Ihi by Formula 1. .

Ihi = current value of I2 / current value of I1 (Expression 1)
The current change rate when the phase of the voltage applied to the stator winding with respect to the induced voltage induced in the stator winding is changed from, for example, -30 degrees to 30 degrees with the torque being constant is obtained by Equation 1. Then, the phase relationship between the current change rate and the voltage applied to the stator winding as shown in FIG. 3 is obtained.

  From this phase relationship, in order to reduce the processing load, the phase relationship between the current change rate and the voltage applied to the stator winding as shown in FIG. 4 is simplified and stored in advance. Therefore, the current phase can be obtained from the current change rate obtained by Equation 1 using FIG.

  FIG. 2B shows a current waveform when the commutation timing is early with respect to the target phase. In this case, if the current change rate Ihi obtained by Equation 1 is 1.223, it can be estimated from FIG. 4 that the phase is −5 degrees, and if the target phase is 0 degrees, the phase difference with respect to the target phase is − It is 5 degrees, and it can be determined that the phase is an advance phase with respect to the target phase. By delaying the next commutation timing in accordance with the phase difference, the current waveform is brought closer to a broken line, and operation at the target phase is enabled.

  On the other hand, FIG. 2C shows a current waveform when the commutation timing is late with respect to the target phase. A broken line indicates a current waveform in the case of a target phase. In this case, if the current change rate Ihi obtained by Equation 1 is 1.255, it can be estimated from FIG. 4 that the phase is 5 degrees, and if the target phase is 0 degrees, the phase difference with respect to the target phase is 5 degrees. It can be determined that the phase is delayed with respect to the target phase, and the current commutation timing is advanced according to the phase difference, thereby making the current waveform closer to the dashed waveform and enabling operation at the target phase. To do.

  As a result, it is possible to detect the current flowing through the inverter circuit 1 and estimate the phase, and even if the motor and the control device are separated and the motor lead wire becomes long, it is not affected by the voltage drop due to the lead wire. Highly reliable sensorless driving is possible. Further, as in this embodiment, when the heating element is a mobile base station, the DC power source is often a low-voltage DC power source such as 24V or 48V, and in that case, it is driven with a large current. Therefore, the reliability of current detection is increased and the accuracy of phase estimation is further increased.

  In this embodiment, the sensorless driving method based on the current change rate in the 120-degree energization method has been described. However, the energization method does not have to be 120-degree energization, and may be 150 degrees, 180 degrees, or other energization methods. , No difference in its effects.

  Moreover, although the phase memorize | stored beforehand was made into the range of -30 degree | times to 30 degree | times, what is necessary is just to set according to a motor, and a difference does not produce the effect.

(Embodiment 2)
FIG. 5 shows a current waveform at 120 degrees energization. In the figure, A / D conversion is performed on current values at two arbitrary points in the predetermined first and second timing regions of the commutation period, that is, I1 and I2, and the current of I2 is compared with the current value of I1. The ratio of the values is obtained from Equation 1 as the current change rate Ihi.

  Similarly, when the torque is constant and the phase of the voltage applied to the stator winding with respect to the induced voltage induced in the stator winding is changed, the current change rate is obtained by Equation 1, and the current change rate And the phase relationship between the voltage applied to the stator winding and stored in advance, and based on the obtained phase, the commutation timing is advanced or delayed, so that Enable driving.

  In this way, by storing the correlation curve in advance, the current phase can be easily obtained from the obtained current change rate, the phase can be detected without requiring complicated calculation, and an inexpensive microcomputer is used. This makes it possible to manufacture a control device for a brushless DC motor that is inexpensive and highly reliable.

(Embodiment 3)
FIG. 6 shows a current waveform at 120 degrees energization. In the figure, the previous commutation timing is t0, the current commutation timing is t1, and the commutation period from t0 to t1 is T1. Assuming that the time obtained by dividing the commutation cycle T1 into four is T1a, the commutation cycle starts from the first current value I1 and the commutation timing t0 at time t11 when a quarter of the commutation cycle has elapsed from the commutation timing t0. A / D conversion is performed on the second current value I2 at time t13 when three-quarters of the time has elapsed, and the ratio of the current value of I2 to the current value of I1 is obtained as a current change rate Ihi by Formula 1. .

  The relationship with the current change rate in each phase at this time is shown by a solid line in FIG. The dotted curve shows the first current value I1 at time t12 when the time of two-fourths of the commutation cycle has elapsed from the commutation timing t0 and the time of four-fourths of the commutation cycle from the commutation timing t0. The second current value I2 at the elapsed time t14 is A / D converted, and the ratio of the current value of I2 to the current value of I1 is defined as the current change rate Ihi. The relationship is shown.

  Therefore, the rate of current change is larger in each phase in the characteristics indicated by the solid line. Thus, it can be seen that the larger the current change rate, the smaller the phase estimation error.

  This makes it possible to sample the current value at a position where the current change is relatively large in the phase estimation within the commutation cycle, and obtain a larger current change rate, improving the phase estimation accuracy. Enables highly reliable driving that can be performed.

  In the present embodiment, the current change rate is obtained from the current value at the time when one-fourth and three-fourths of the commutation period has elapsed, and the phase is estimated. Alternatively, the current value at the time when four quarters have elapsed may be used. In short, the current change rate may be obtained at the time when the current change becomes large, and there is no difference in the effect.

(Embodiment 4)
FIG. 8 shows a current waveform in 120-degree energization when driving at a constant rotation speed without load fluctuation. In the figure, the amplitude of the current waveform varies due to the influence of switching element variation, rotor magnet variation, load imbalance, and the like. These variations in current have periodicity and are repeated every rotation at a mechanical angle.

  Therefore, the current change rate for one rotation is stored as a mechanical angle, and the average value is used as the current change rate to estimate the phase.

  For example, in the case of an 8-pole 12-slot brushless DC motor, energization switching corresponding to one rotation in mechanical angle is 24 times. Therefore, the current change rate for 24 times is stored, and the average value Ihia is obtained by Equation 2.

Ihia = (Ihi1 + Ihi2 + Ini3 +... + Ihi24) / 24 (Formula 2)
This can reduce the influence of current variation due to variation in switching elements, variation in rotor magnets, variation due to load imbalance, etc., and enables highly reliable driving that can improve phase estimation accuracy. .

  In the present embodiment, the current change rate for one rotation is stored as a mechanical angle, and the phase is estimated based on the average value, but it may be two rotations or 0.5 rotations. In short, it is only necessary to reduce the influence of variation, and there is no difference in the effect.

(Embodiment 5)
FIG. 9 shows a current waveform in 120-degree energization when the load gradually increases.

  In the figure, since the load becomes heavier every commutation cycle, the phase gradually becomes a lagging phase. When the current waveform one revolution before (indicated by a broken line) is overlapped with the mechanical angle, the shape of the current waveform gradually becomes a lagging phase, and the commutation cycle is delayed more remarkably.

  Therefore, the current change rate is stored in the mechanical angle for one rotation period, the average value of the current change rate for one rotation is obtained by Equation 2, and the latest current change rate is compared with the current change rate before one rotation. When this difference is a predetermined value, for example, when the current change rate is smaller than ± 0.02, it is determined that the load fluctuation is small, and the phase is estimated from the average value of the current change rate of one rotation. On the other hand, when the current change rate is larger than ± 0.02, it is determined that the load fluctuation is large, and the phase is estimated from the latest current change rate.

  For example, when the latest current change rate is 1.255, the average value of the current change rates is 1.220.

  The difference between the two is 0.035, which is larger than a predetermined threshold value ± 0.02, so that it is determined that the load fluctuation is large, and the phase is estimated from the latest current change rate. On the other hand, when the latest current change rate is 1.230, similarly, the difference between the two is 0.01, and it is determined that the load fluctuation is small, and the phase is estimated from the average value of the current change rates. Become.

  As a result, the magnitude of the load fluctuation can be detected, a more accurate current detection rate can be obtained according to the load fluctuation, and a highly reliable brushless DC motor control apparatus capable of improving the phase estimation accuracy can be obtained. .

  In the present embodiment, the difference between the latest current change rate and the current change rate before one rotation is ± 0.02, but a numerical value may be determined according to the motor load, such as ± 0.01 or ± Even if it is 0.03, the effect does not produce a difference.

(Embodiment 6)
A method for estimating the phase based on FIGS. 10A and 10B will be described.

  The previous commutation timing is t0, the current commutation timing is t1, and the commutation period from t0 to t1 is T1. The time when the commutation cycle T1 is divided into four is T1a, and the current value is A / D converted every time the T1a time elapses from the commutation timing t0. The first current value I1 at time t11 when the quarter time of the commutation cycle has elapsed from the commutation timing t0 and the second at time t13 when the time of three quarters of the commutation cycle has elapsed from the commutation timing t0. Current value I2 is A / D-converted, and the ratio of the current value of I2 to the current value of I1 is obtained as a current change rate Ihi by Equation 1.

  Similarly, the phase with the voltage applied to the stator winding is estimated from the current change rate, and when the obtained phase is the lag phase or the target phase, the estimated phase is adopted, and at the lead phase, The first current value I1 at time t12 when two-fourths of the commutation cycle has elapsed from the commutation timing t0, and the first current value I1 at time t14 when four-fourths of the commutation cycle has elapsed from commutation timing t0. The current value I2 of 2 is A / D-converted, and the ratio of the current value of I2 to the current value of I1 is determined as a current change rate Ihi by Formula 1.

  Similarly, the phase with the voltage applied to the stator winding is estimated from the current change rate, and the obtained phase is adopted.

  For example, in FIG. 4, the current value I1 at time t11 when a quarter time of the commutation cycle has elapsed from the commutation timing t0 and the time t13 when the time of three quarters of the commutation cycle has elapsed from the commutation timing t0. When the current change rate of the second current value I2 is 1.255, the phase is 5 degrees, and when the target phase is 0 degrees, it can be determined that the phase is a delayed phase. Therefore, assuming that the phase is 5 degrees, control is performed so that the commutation timing is advanced so as to approach the target phase of 0 degrees.

  On the other hand, when the current change rate is 1.223, the phase is −5 degrees, and when the target phase is 0 degrees, it can be determined that the current phase is the leading phase. Accordingly, the first current value I1 at time t12 at which two-fourths of the commutation cycle has elapsed from the commutation timing t0 and the time t14 at which four-fourths of the commutation cycle has elapsed from the commutation timing t0. The current change rate is obtained from the second current value I2, and when the current change rate at this time is 1.234, the phase is −5 degrees, and based on this phase, the commutation is performed so as to approach the target phase. Control to delay the timing.

  Based on the phase thus obtained, the current commutation timing t1 is advanced or delayed to enable operation at the target phase.

  This makes it possible to detect the current change rate more accurately according to the phase, such as the leading phase and the lagging phase, improve the estimation accuracy of the phase, and improve the followability to the fluctuation of the load. A motor drive device is obtained.

(Embodiment 7)
Based on FIG. 11, a method for determining the next commutation timing from the current commutation timing will be described.

  The previous commutation timing is t0, the current commutation timing is t1, and the commutation period from t0 to t1 is T1. The phase of the current change rate and the voltage applied to the stator winding is estimated based on FIG. 12, and the correction value α is obtained from the obtained phase. Assuming that the next commutation timing is t2, the commutation cycle T2 until the next commutation timing is obtained by Equation 3.

T2 = T1 + α × T1 (Formula 3)
For example, when the commutation cycle T1 is 1 ms and the phase is 5 degrees, the correction value α is −1/16, and from Equation 3, the commutation cycle T2 is 0.9375 ms, and the next commutation timing t2 is set to the current commutation timing t2. Control is performed so as to approach the target phase by making it earlier than the flow timing t1.

  On the other hand, the correction value α when the phase is −5 degrees is 1/16, and similarly, the commutation cycle T2 is 1.0625 ms according to Equation 5, and the next commutation timing t2 is delayed from the current commutation timing. Thus, control is performed so as to approach the target phase.

  Based on the correction value thus obtained, the next commutation timing is advanced or delayed to enable operation at the target phase.

  As a result, an optimal commutation timing can always be obtained for each commutation cycle with respect to load fluctuations, and a highly reliable brushless DC motor control device that can improve followability to load fluctuations can be obtained.

  In this embodiment, the phase relationship between the rate of change of current and the voltage applied to the stator winding and the correction value α as shown in FIG. 12 are simplified, but these values are matched to the characteristics of the motor. It only has to be decided, and there will be no difference in its effects.

(Embodiment 8)
Based on FIG. 13, a method for determining the next commutation timing from the current commutation timing will be described.

  FIG. 13A shows a current waveform when the phase is advanced by advancing the commutation timing. FIG. 13B shows a current waveform when the commutation timing is delayed and the phase is delayed. A broken line indicates a current waveform in the target phase. The previous commutation timing is t0, the current commutation timing is t1, the commutation cycle from t0 to t1 is T1, and the time obtained by dividing the commutation cycle T1 into four is T1a. Based on FIG. 14, the phase with the voltage applied to the stator winding is estimated from the current change rate, and the correction value β is obtained based on the obtained phase.

  Assuming that the next commutation timing is t2, the commutation cycle T2 until the next commutation timing is obtained by Equation 4.

T2 = 3 × T1a + (T1a + β × T1a) (Formula 4)
At this time, the next commutation timing t2 is advanced or delayed by correcting the time T1a from the commutation timing until three-quarters of the commutation cycle T1 elapses until four-fourths elapses. This enables operation at the target phase.

  For example, the correction value β when the commutation period T1 is 1 ms and the phase is 5 degrees is −1/32, and the commutation period T2 is 0.992 ms according to Equation 4, and the next commutation timing t2 is set to the current commutation timing t2. Control is performed so as to approach the target phase by making it earlier than the flow timing t1.

  On the other hand, the correction value β when the phase is −5 degrees is 1/32, and similarly, the commutation cycle T2 is 1.008 ms according to Equation 4, and the next commutation timing t2 is delayed from the current commutation timing. Thus, control is performed so as to approach the target phase.

  Based on the correction value thus obtained, the next commutation timing is advanced or delayed to enable operation at the target phase.

  As a result, an optimal commutation timing can always be obtained for each commutation cycle with respect to load fluctuations, and a highly reliable brushless DC motor control device that can improve followability to load fluctuations can be obtained.

  In the present embodiment, the phase relationship between the current change rate and the voltage applied to the stator winding and the correction value β as shown in FIG. 14 are simplified, but these numerical values are matched to the characteristics of the motor. It only has to be decided, and there will be no difference in its effects.

(Embodiment 9)
A method for determining the next commutation timing from the current commutation timing will be described.

  When the target phase is compared with the actual phase and is larger than the predetermined phase difference, the next commutation cycle is calculated according to Equation 5 according to the phase difference between the target phase and the actual phase from the previous commutation cycle. And time correction is performed to determine the commutation timing. On the other hand, when it is smaller than the phase difference, the next commutation cycle is calculated by Equation 6, and the time from the commutation timing until 3/4 of the commutation cycle elapses until 4/4 of the commutation is corrected Then, the operation at the target phase is made possible by advancing or delaying the next commutation timing.

  For example, when the target phase and the actual phase difference are larger than 10 degrees, the calculation is performed by Expression 3, and when the phase difference is less than 10 degrees, the next commutation cycle is obtained by Expression 6. Therefore, when the phase difference from the target phase is 10 degrees, the commutation period T1 is 1 ms, and the correction value α when the phase is 10 degrees is −1/16, and the commutation period T2 is 0.9375 ms from Equation 3. Thus, the next commutation timing t2 is controlled so as to approach the target phase by making it earlier than the current commutation timing t1.

  On the other hand, when the phase difference from the target phase is less than 10 degrees, the commutation period T1 is 1 ms, and when the phase is 5 degrees, the correction value β is −1/32. 992 ms, and the next commutation timing t2 is controlled to be closer to the target phase by making the next commutation timing t1 earlier than the current commutation timing t1.

  Based on the correction value thus obtained, the next commutation timing is advanced or delayed to enable operation at the target phase.

  As a result, it is possible to detect the magnitude of the load fluctuation, obtain the optimum energization timing according to the load fluctuation at each commutation timing, and improve the followability to the load fluctuation with high reliability. A control device for the DC motor is obtained.

(Embodiment 10)
A method for determining the next commutation timing from the current commutation timing will be described.

  When the target phase is compared with the actual phase and is smaller than a predetermined phase difference, the next commutation cycle is calculated by Equation 6, and after three-fourths of the commutation cycle has elapsed from the commutation timing. Correct the time until 4/4. When it is more than the predetermined number of times that the phase obtained next time is different from the previous phase, it is converted from the previous commutation cycle according to Equation 5 according to the phase difference between the target phase and the actual phase. By calculating the flow period, performing time correction, and calculating the next commutation period, the next commutation timing is advanced or delayed, thereby enabling operation at the target phase.

  For example, when the phase difference from the target phase is less than 10 degrees, the commutation period T1 is 1 ms, and when the phase is 5 degrees, the correction value β is −1/32. 992 ms, and the next commutation timing t2 is controlled to be closer to the target phase by making the next commutation timing t1 earlier than the current commutation timing t1.

  On the other hand, when the control is performed so that the commutation cycle is advanced and the control is performed so as to approach the target phase, the commutation is similarly performed when the obtained phase does not change three times or more. When the period T1 is 1 ms and the phase is 5 degrees, the correction value α is −1/16, and the commutation period T2 is 0.9375 ms from Equation 3, and the next commutation timing t2 is determined from the current commutation timing t1. The control is performed so as to approach the target phase by speeding up.

  Based on the correction value thus obtained, the next commutation timing is advanced or delayed to enable operation at the target phase.

  As a result, the estimated phase can be accurately detected, so that the estimated phase is the same, it can be determined that the phase is about to step out, and the time correction amount of the next commutation cycle can be changed. Thus, a highly reliable brushless DC motor control device that can reduce the occurrence of step-out can be obtained.

(Embodiment 11)
Based on FIG. 15, a method of determining the next commutation timing from the current commutation timing will be described.

  At startup and during operation, the commutation timing is corrected so as to follow the target phase by changing the correction value α as shown in FIG.

  For example, when the commutation period T1 is 1 ms and the phase is 10 degrees at the time of start-up, the correction value α is −2/16, and the commutation period T2 is 0.875 ms from Equation 3, and the next commutation timing t2 Is made closer to the target phase by advancing the current commutation timing t1.

  On the other hand, during operation, the correction value α when the phase is 10 degrees is 1/16. Similarly, the commutation cycle T2 is 0.9375 msms according to Equation 3, and the next commutation timing t2 is set to the current commutation timing. The control is performed so as to approach the target phase by making it earlier.

  Based on the correction value thus obtained, the next commutation timing is advanced or delayed to enable operation at the target phase.

  As a result, the rotation is unstable at start-up, so errors are likely to occur in the phase estimation.By changing the time correction value between start-up and operation, it is possible to reduce instability of rotation and step-out. Thus, a highly reliable brushless DC motor control device that can improve the followability to load fluctuations can be obtained.

  In the present embodiment, the phase relationship between the current change rate and the voltage applied to the stator winding and the correction value α as shown in FIG. 15 are simplified, but these values are matched to the characteristics of the motor. It only has to be decided, and there will be no difference in its effects.

(Embodiment 12)
As shown in FIG. 16, a brushless DC motor control device is mounted on a ventilation fan.

  In the figure, reference numeral 2 denotes an outdoor sensorless DC brushless motor. By rotating the outdoor blower 13, the ambient air around which a heating element storage box 14 such as a mobile phone exchange base station is installed is cooled by heat exchange cooling. The air is sucked from the outside air inlet 16 at the lower part of the machine 15, passed through the heat exchange element 16, and then discharged from the outside air outlet 18 at the upper part of the heat exchange type cooler 15. Reference numeral 19 denotes an indoor brushless DC motor, which rotates the indoor blower 20 to suck the heated inside air inside the heating element storage box 4 from the inside air inlet 21 at the top of the heat exchange type cooler 15, After passing through the exchange element 17, the air is discharged from the inside air discharge port 22 below the heat exchange type cooler 15. The movement of the outside air due to the rotation of the outdoor blower 13 is indicated by a solid line arrow, and the movement of the indoor air due to the rotation of the indoor blower 20 is indicated by a broken line arrow. Heat is exchanged when the cooled outside air and the heated indoor air pass through the heat exchange element 17, the outside air is heated and discharged into the atmosphere, and the indoor air is cooled and returned to the indoor side. The inside of the body storage box 14 can be cooled. In the heat exchange element 17, the outside air passage and the inside air passage are blocked, and the air in the outside air passage does not flow into the inside air passage of the heat exchange type cooler 15. The control box 23 is installed in the inside air path of the heat exchange type cooler 15, and a control device 12 for driving the outdoor sensorless DC brushless motor 2 is installed therein. The control device 12 is supplied with low-voltage DC power from the low-voltage DC power source 5 installed in the heating element storage box 15, and the control device 12 passes the driving lead wire 24 to drive the sensorless DC brushless motor 2 on the outdoor side. Driving. The control box 23 is also provided with an indoor inverter circuit (not shown) that drives the indoor brushless DC motor 19 to operate the indoor fan 20.

  This eliminates the need for sensor signal relay leads and magnetic sensors used to connect to the control device installed on the side of the inside air path, so there is no effect of malfunction due to noise on the sensor signal line, and the temperature of the installation location. It is possible to provide a highly reliable brushless DC motor control device that eliminates restrictions on conditions, eliminates the need for lead wires, and eliminates the work of connecting relay wires, thus providing a low-cost heat exchange type cooler. .

  In the present embodiment, the brushless DC motor control device is mounted on the heat exchange type cooler. However, the control device may be mounted on a ventilation fan, a range hood, or the like, and there is no difference in operational effects.

1 is a block diagram of a brushless DC motor control device according to a first embodiment of the present invention. An explanatory diagram of a phase estimation method by the same phase estimation means ((a) a diagram showing a current waveform at a target phase, (b) a diagram showing a current waveform at a leading phase, and (c) a diagram showing a current waveform at a lagging phase. ) Correlation characteristics diagram showing in-phase and current change rate Correlation diagram with simplified phase and current change rate Explanatory drawing of the phase estimation method by the phase estimation means of Embodiment 2 of this invention (The figure which shows the current waveform at the time of a target phase) Explanatory drawing of the phase estimation method by the phase estimation means of Embodiment 3 of this invention (The figure which shows the current waveform at the time of a target phase) Correlation characteristics diagram showing in-phase and current change rate Explanatory drawing of the phase estimation method by the phase estimation means of Embodiment 4 of this invention Explanatory drawing of the phase estimation method by the phase estimation means of Embodiment 5 of this invention Explanatory drawing of the phase estimation method by the phase estimation means of Embodiment 6 of this invention ((a) The figure which shows the current waveform at the time of a lead phase, (b) The figure which shows the current waveform at the time of a lagging phase) Explanatory drawing of the determination method of the commutation timing by the commutation timing determination means of Embodiment 7 of this invention (The figure which shows the current waveform at the time of a target phase) Correlation diagram with simplified phase and current change rate Explanatory drawing of the determination method of the commutation timing by the commutation timing determination means of Embodiment 8 of this invention ((a) The figure which shows a current waveform when advancing the phase by advancing commutation timing, (b) Commutation timing Figure showing the current waveform when the phase is delayed by delaying Correlation diagram with simplified phase and current change rate The figure which shows the determination method of the commutation timing by the commutation timing determination means of Embodiment 11 of this invention Schematic sectional view showing the structure of a ventilation blower equipped with a control device for a brushless DC motor according to a twelfth embodiment of the present invention. Schematic sectional view showing the structure of a conventional heat exchange type cooler Block diagram of a conventional brushless DC motor control device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inverter circuit 2 Brushless DC motor 3 Rotor 4 Stator 5 DC power supply 6 Current detection resistance 7 Microcomputer 8 A / D converter 9 Phase estimation means 10 Commutation timing determination means 11 Drive circuit 12 Controller

Claims (12)

A control device for rotating a brushless DC motor having a rotor and a stator winding connected via an inverter circuit in which a plurality of switching elements are bridge-connected to a DC power source by turning on and off the switching elements of the inverter circuit The voltage applied to the stator winding with respect to the induced voltage induced in the stator winding of the brushless DC motor stored in advance based on the rate of change of the current value supplied from the DC power supply to the inverter circuit And a commutation timing determining means for determining commutation timing so that the phase estimated by the phase estimating means follows a predetermined target phase. Control device for DC motor. The phase estimating means calculates the ratio of the current values at the first and second timings determined in advance of the commutation cycle as the current change rate, and calculates the current change rate and the phase of the voltage applied to the stator winding. 2. The brushless DC motor control device according to claim 1, wherein a correlation curve is stored in advance. The phase estimation means includes a first current value at a time when one-fourth of the commutation cycle has elapsed from the commutation timing, and a time at which three-fourths of the commutation cycle has elapsed from the commutation timing. 3. The brushless DC motor control device according to claim 1, wherein a second current value is obtained, and a ratio of the second current value to the first current value is calculated as a current change rate. The phase estimation means stores the current change rate in a mechanical angle for one rotation period, obtains an average value of the current change rate of one rotation, and can estimate the phase from the average value of the current change rate of one rotation. The brushless DC motor control device according to claim 1 or 3. The phase estimation means stores the current change rate in a mechanical angle for one rotation period, obtains an average value of the current change rate of one rotation, compares the latest current change rate with the current change rate before one rotation, When the difference is smaller than a predetermined value, the phase is estimated from the average value of the current change rate of one rotation, while when larger than the predetermined value, the phase is estimated from the latest current change rate. 4. The brushless DC motor control device according to claim 1, wherein the control device is configured to be able to perform the control. The phase estimation means obtains a current value at each time when one-fourth of the commutation period has elapsed from the commutation timing, and the ratio of the three-fourths to the one-fourth is a first current change rate. And the ratio of the fourth quarter to the second quarter is calculated as the second current change rate, and the first current change rate is obtained when the phase obtained by the first current change rate is a lagging phase. The commutation timing is determined based on the phase obtained from the second current change rate when the energization timing is determined based on the phase obtained by the step (2). Control device for brushless DC motor. The commutation timing determining means performs time correction according to the phase difference between the target phase and the actual phase from the previous commutation cycle, calculates the next commutation cycle, and determines the commutation timing. The brushless DC motor control device according to any one of claims 1 to 6. The commutation timing determining means divides the previous commutation period into four, and only corrects a predetermined time period of one quarter according to the phase difference between the target phase and the actual phase. The brushless DC motor control device according to any one of claims 1 to 6. The commutation timing determination means compares the target phase with the actual phase, and if it is greater than the predetermined phase difference, corrects the time according to the phase difference between the target phase and the actual phase from the previous commutation cycle. The next commutation cycle is calculated and the commutation timing is determined. 7. The brushless DC motor control apparatus according to claim 1, wherein when it is small, only a quarter of a predetermined commutation period is time-corrected. The commutation timing determination means compares the target phase with the actual phase, and when it is smaller than a predetermined phase difference, corrects the time of only a quarter of the commutation period, and obtains the phase obtained next time Is equal to the previous phase or more than a predetermined number, the time is corrected according to the phase difference between the target phase and the actual phase from the previous commutation cycle. The brushless DC motor control device according to claim 9, wherein the next commutation cycle is calculated. The brushless DC motor control device according to any one of claims 7 to 10, wherein the commutation timing determining means changes a time correction amount at the time of startup and during operation. A ventilation blower equipped with the brushless DC motor control device according to any one of claims 1 to 11.

Images