JPH11187690A - Inverter device and brushless fan motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inverter device and a bruhless fan motor, which is capable of detecting rotation state of a brushless motor before the start and select a proper starting method, even with a sensorless driving method. SOLUTION: When a brushless motor 8 is rotated by an external force such as the force of wind, etc., applied to a fan, revolutions SS of the brushless motor 8 is detected based on the polarity changes of currents which are applied to respective windings 8u, 8v and 8w through the action of a current application signal generating unit 10 based on the voltages induced in the windings 8u, 8v and 8w. If the revolutions SS exceed a reference number of revolution, a starting method determination unit 9a leaves the start of the brushless motor 8 at that time over, but if the revolution SS is smaller than the reference revolution, the starting method determination unit 9a starts the operation of the brushless motor 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter device for forming an energization signal based on the polarity of a current flowing in a three-phase winding of a brushless motor and energizing the three-phase winding of the brushless motor by an inverter main circuit. The present invention relates to a brushless fan motor that rotationally drives a fan with a brushless motor.

[0002]

2. Description of the Related Art In recent years, fan motors for air conditioners and the like and motors for driving electric vehicles have been used for a wide range of variable speed control and to save power consumption. A brushless motor has been adopted for improvement, and is driven by an inverter device.

In the field of home appliances and electric vehicles, reduction of power consumption, vibration and noise is required, and it is effective to improve motor efficiency and reduce torque fluctuation. There is a demand for a technology capable of realizing an inverter device capable of supplying a voltage waveform of (1) to a motor at low cost.

As a prior art responding to such a demand, for example, as disclosed in Japanese Patent Application Laid-Open No. Hei 7-224299, a Hall IC having a simple structure and the lowest cost is used as a position sensor. There are motors that supply a brushless motor by supplying a sine wave voltage waveform.

For example, in the case of a fan motor for an air conditioner or the like, before the fan motor is started, the fan of the outdoor unit is rotated at a relatively high speed in the reverse direction by natural wind, and the fan motor is suddenly turned forward. Attempting to start in the wrong direction can adversely affect the fan motor. Therefore, for such an application, before starting the motor, it is necessary to obtain in advance information about the direction and how many revolutions the fan motor is rotating, and then select the motor starting method. Is desirable.

Therefore, assuming that the above-mentioned prior art is applied to a fan motor of an air conditioner, if the fan motor is rotating as described above before starting, a position detection signal from a Hall IC can be obtained. Thus, the number of rotations and the direction of rotation of the motor can be detected, and the method of starting the motor can be selected based on the detection result.

On the other hand, for the purpose of further lowering the cost, reducing the size and expanding the use environment, for example, Japanese Patent Application No. 9-863.
As proposed in Japanese Patent No. 25, a sensorless drive type inverter device capable of sine-wave driving a motor without using a position sensor has been considered.

[0008]

However, in the sensorless drive system, when the fan motor is rotating before starting, there is no means for determining the number of rotations and the direction of rotation. It has been difficult to apply these applications. The present invention has been made in view of the above circumstances, and its purpose is to
Also in a sensorless drive system, an object is to provide an inverter device and a brushless fan motor capable of detecting a rotation state of a brushless motor before starting and selecting an appropriate starting system.

[0009]

In order to achieve the above object, an inverter device according to a first aspect of the present invention includes an inverter main circuit that energizes a three-phase winding of a brushless motor, and an inverter main circuit that supplies current to the three-phase winding. Current polarity detecting means for detecting a polarity and outputting a polarity signal; energizing signal forming means for forming an energizing signal based on the polarity signal output by the current polarity detecting means and outputting the energizing signal to the inverter main circuit; At the time of starting the brushless motor, by referring to the polarity signal output by the current polarity detection unit, the rotation speed detection unit detects the rotation speed of the brushless motor based on a cycle in which the current polarity changes. Starting method determining means for determining the starting method of the brushless motor based on the number of rotations of the brushless motor detected by the means.

With this configuration, the rotation speed detecting means changes the current polarity by referring to the polarity signal output by the current polarity detecting means detecting the polarity of the current flowing through the three-phase winding of the brushless motor. Since the rotation speed of the brushless motor is detected based on the cycle, the starting method determination means can determine an appropriate startup method of the brushless motor based on the rotation speed of the brushless motor detected by the rotation speed detection means.

[0011] In this case, as described in claim 2, when the rotation speed of the brushless motor detected by the rotation speed detection means is equal to or more than a predetermined value, the starting method determination means is provided.
If the brushless motor is not started and the rotation speed of the brushless motor detected by the rotation speed detecting means is less than a predetermined value, the current polarity detection is performed after the energization signal forming means performs DC excitation on the brushless motor. It is preferable to output an energization signal based on the polarity signal output by the means.

With this configuration, when the rotation speed of the brushless motor is equal to or higher than the predetermined value, starting the brushless motor from that state imposes a heavy burden on the brushless motor. . When the rotation speed of the brushless motor is less than the predetermined value, the brushless motor can be relatively easily stopped by performing DC excitation on the brushless motor. Thereafter, the brushless motor can be started smoothly by outputting, for example, a sine wave energization signal to the inverter main circuit based on the polarity signal output by the current polarity detection means.

According to a third aspect of the present invention, at the time of starting the brushless motor, a rotation signal for detecting the rotation direction of the brushless motor based on a change in the current polarity with reference to a polarity signal output by the current polarity detection means. Direction detecting means is provided, and the starting method determining means determines the starting method of the brushless motor based on the rotational speed of the brushless motor detected by the rotational speed detecting means and the rotational direction of the brushless motor detected by the rotating direction detecting means. It is good to configure.

With this configuration, for example, if the brushless motor is rotating in a direction opposite to the normal driving state before starting, and if the brushless motor is driven in the normal rotation direction from that state, The burden on the brushless motor increases. Therefore, a more appropriate starting method can be selected by determining the rotation direction of the brushless motor before starting.

According to a fourth aspect of the present invention, when the rotation speed of the brushless motor detected by the rotation speed detecting means is equal to or higher than a predetermined value, the starting method determining means does not start the brushless motor. If the number of rotations of the brushless motor detected by the number detection means is less than a predetermined value and the direction of rotation of the brushless motor detected by the rotation direction detection means is a positive direction, the current polarity An energization signal based on the polarity signal output by the detection means is output, and the rotation speed of the brushless motor detected by the rotation speed detection means is less than a predetermined value, and the rotation of the brushless motor detected by the rotation direction detection means If the direction is reverse, the current polarity detection means outputs the current after making the energization signal formation means perform DC excitation for the brushless motor. Preferably configured to output the energization signal based on that the polarity signal.

With this configuration, when the rotation speed of the brushless motor before starting is less than the predetermined value and the rotation direction is the forward direction, even if the brushless motor starts to be driven, There is no burden. On the other hand, when the rotation speed of the brushless motor is less than the predetermined value and the rotation direction of the brushless motor detected by the rotation direction detecting means is the reverse direction, the rotation is performed by performing DC excitation on the brushless motor. Is relatively easily stopped, and thereafter, a brushless motor can be started smoothly by outputting, for example, a sine wave energization signal to the inverter main circuit based on the polarity signal output by the current polarity detection means.

According to a fifth aspect of the present invention, when the starting method determining means determines the starting method of the brushless motor at the time of starting the brushless motor, the energizing signal forming means is used for all three-phase windings of the brushless motor. The same energization signal may be formed and output, and the rotation speed detecting means may detect the rotation speed of the brushless motor based on a cycle in which the polarity of the current flowing through the three-phase winding changes.

According to this structure, when the energization signal forming means applies the same energization signal to all three-phase windings of the brushless motor, if the brushless motor is rotating before starting, the three-phase winding is controlled. An alternating current having a phase difference of 120 degrees between the phases flows through the phase winding due to the generation of the induced voltage.
Therefore, the rotation speed detecting means can easily detect the rotation speed of the brushless motor based on the cycle in which the polarity of the alternating current changes.

According to a sixth aspect of the present invention, when the starting method determining means determines the starting method of the brushless motor at the time of starting the brushless motor, the energizing signal forming means may be one of the three-phase windings of the brushless motor. The same energization signal is formed and output to the two-phase windings, and the rotation speed detecting means is
The rotation speed of the brushless motor may be detected based on a cycle in which the polarity of the current flowing through the two-phase winding changes.

With this configuration, if the brushless motor is rotating before starting, an alternating current having a phase difference of 180 degrees flows through the two-phase windings. Therefore, the rotation speed of the brushless motor can be easily detected based on the cycle in which the polarity of the alternating current changes.

According to a seventh aspect of the present invention, the energization signal forming means is provided for all three-phase windings of the brushless motor when the starting method determining means determines the starting method of the brushless motor when starting the brushless motor. The same energization signal is formed and output, and the rotation direction detecting means is configured to control the current of the other two-phase winding at the time when the current polarity of one of the three-phase windings changes. A configuration in which the rotation direction of the brushless motor is detected based on the polarity may be adopted.

With this configuration, when the brushless motor is rotating before starting, the phase difference between each phase is 120 V in the three-phase winding of the brushless motor by the energization signal output by the energization signal forming means. AC current flows.
At this time, if the AC current flowing through one of the three-phase windings is used as a reference, the leading and lagging phases of the AC current flowing through the other two-phase windings are determined by the rotation direction of the brushless motor. (Forward rotation, reverse rotation).

Then, the rotation direction detecting means detects the two-phase winding based on the current polarity of the other two-phase winding when the current polarity of one of the three-phase windings changes. Since the lead and lag of the phase of the alternating current flowing through the line are determined, the rotation direction of the brushless motor can be reliably detected.

According to an eighth aspect of the present invention, when the starting method determining means determines the starting method of the brushless motor at the time of starting the brushless motor, the energizing signal forming means may be any one of the three-phase windings of the brushless motor. After forming and outputting the same energization signal to the two-phase winding, at the timing when the polarity of the current flowing through the two-phase winding changes, any one of the remaining one-phase winding and the two-phase winding is used. Or the same energizing signal is formed by switching the energizing phase to the one-phase winding, and the same energizing signal is formed and output. May be configured to detect the rotation direction of the brushless motor based on

With this configuration, when the brushless motor is rotating before starting, any one of the two-phase windings of the three-phase winding of the brushless motor is operated according to the energizing signal output by the energizing signal forming means. , An alternating current having a phase difference of 180 degrees between the phases flows. Thereafter, when the energization signal forming means switches the energization phase at the above timing, the current polarities of the two-phase windings immediately after the switching change according to the rotation direction (forward rotation, reverse rotation) of the brushless motor. The rotation direction detection means can reliably detect the rotation direction of the brushless motor based on the current polarities of the two-phase windings immediately after the switching of the energized phase.

According to a ninth aspect of the present invention, there is provided a brushless fan motor comprising: a brushless motor for driving a fan; an inverter main circuit for energizing a three-phase winding of the brushless motor; and a polarity of a current flowing through the three-phase winding. Current polarity detection means for detecting and outputting a polarity signal, current supply signal formation means for forming an energization signal based on the polarity signal output by the current polarity detection means and outputting the energization signal to the inverter main circuit, and the brushless motor At the time of starting, when the fan is rotated by an external force, the rotation signal for detecting the rotation speed of the brushless motor based on a cycle in which the current polarity is changed with reference to the polarity signal output by the current polarity detection means. Number detection means, and a brushless motor starting method based on the number of rotations of the brushless motor detected by the rotation number detection means. Characterized in that a starting method determination means determined.

According to this structure, when the fan is rotating by external force, the current polarity detecting means detects the polarity of the current flowing through the three-phase winding of the brushless motor and outputs the detected current. Since the rotation speed of the brushless motor is detected based on the cycle in which the current polarity changes with reference to the polarity signal, the starting method determining unit determines the rotation speed of the brushless motor based on the rotation speed of the brushless motor detected by the rotation speed detection unit. An appropriate starting method can be determined.

In this case, as described in claim 10,
When the rotation speed of the brushless motor detected by the rotation speed detection unit is equal to or greater than a predetermined value, the start method determination unit does not start the brushless motor, and the rotation speed of the brushless motor detected by the rotation speed detection unit. Is smaller than a predetermined value, it is preferable that the energization signal forming means perform DC excitation on the brushless motor and then output an energization signal based on the polarity signal output by the current polarity detection means.

With this configuration, the fan is rotating by an external force such as wind, and when the rotation speed of the brushless motor is equal to or higher than a predetermined value, the brushless motor is started from that state. In this case, a heavy load is applied to the brushless motor. When the rotation speed of the brushless motor is less than the predetermined value, the brushless motor can be relatively easily stopped by performing DC excitation on the brushless motor. Thereafter, the brushless motor can be started smoothly and the fan can be driven to rotate by outputting, for example, a sine wave energization signal to the inverter main circuit based on the polarity signal output by the current polarity detection means.

According to the eleventh aspect, when the brushless motor is started, the polarity signal output by the current polarity detection means when the fan is rotating by an external force is referred to, and the change in the current polarity is determined. A rotation direction detecting means for detecting a rotation direction of the brushless motor, and a starting method determining means for detecting a rotation speed of the brushless motor detected by the rotation speed detection means and a rotation direction of the brushless motor detected by the rotation direction detection means. It is preferable to determine the starting method of the brushless motor based on the brushless motor.

According to this structure, for example, when the brushless motor is rotating in a direction opposite to the normal driving state before starting by the fan rotating by an external force such as wind, the state is changed from that state. If the brushless motor is driven in the forward rotation direction, the load on the brushless motor increases. Therefore, by determining the rotation direction of the brushless motor before starting,
A more appropriate starting method can be selected.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment in which the present invention is applied to a fan motor installed in an outdoor unit of an air conditioner will be described below with reference to FIGS. FIG.
, Both terminals of the AC power supply 1 are connected to the reactor 2
To the AC input terminal of the full-wave rectifier circuit 3. The smoothing capacitor 4 is connected between the DC output terminals of the full-wave rectifier circuit 3, and the DC power supply circuit 5 is connected to the reactor 2, the full-wave rectifier circuit 3, and the smoothing capacitor 4.
Is composed. The DC output terminals of the DC power supply circuit 5 are connected to the positive and negative DC buses 6a and 6b.

The inverter main circuit 7 includes transistors (IGBT) T1 to T6 connected in a three-phase bridge between the positive and negative DC buses 6a and 6b, and flywheel diodes connected in parallel to the transistors T1 to T6, respectively. D1 to D6. Output terminals 7u, 7v, 7w of the inverter main circuit 7 are connected to star-connected phase windings 8u, 8v, 8w of a three-phase brushless motor (hereinafter simply referred to as a motor) 8, respectively.

When a start command signal for the motor 8 is given from outside, the start control unit 9 converts the voltage command V into an energizing signal forming unit (energizing signal forming means) 10 and an induced voltage phase difference calculating unit 1.
1 and outputs the frequency command fs to the command selector 12.

The start control section 9 includes a start method determining section (start method determining means) 9a and a rotational speed detecting section (rotation speed detecting means) 9b. The rotation speed detection unit 9b
The number of rotations Ss of the motor 8 is determined based on current polarity signals Su, Sv and Sw given by a current polarity detection circuit 17 described later.
Is detected, and the rotation speed Ss is given to the starting method determining unit 9a. The starting method determining unit 9a determines the rotation speed S
The starting method of the motor 8 is determined according to the value of s, and the DC excitation command signal Br is output to the energization signal forming unit 10 according to the determined starting method.

Further, the start control unit 9 outputs to the command selection unit 12 a selection signal Sk output after a predetermined time has elapsed after the start method is determined.
2 is the frequency command f according to the output of the selection signal Sk.
s and the frequency command fe output by the frequency command determination unit 13 are switched and output as the frequency command f. The frequency command f is given to the energization signal forming unit 10, the induced voltage phase difference calculating unit 11, and the frequency command determining unit 13.

Regarding the internal configuration of the energization signal forming unit 10,
It is described below. The clock generator 10a outputs the frequency command f
And outputs a clock signal of a frequency corresponding to
The clock signal is provided to the counter 10b. The counter 10b counts up the input number of the clock signal pulse, and outputs the count value to the ROM 10c as an address signal.

The ROM 10c stores level data of an energizing signal having an amplitude of a voltage ratio corresponding to a sine wave, reads out level data of a phase corresponding to an address signal supplied from a counter 10b, and generates a level signal. Vessel 1
0d is output. The level signal generator 10d generates a U-phase energization signal Du by multiplying the level data given from the ROM 10c by the voltage command V, and shifts the energization signal Du by 120 or 240 degrees to V.
Phase and W-phase conduction signals Dv and Dw,
Each is output to the WM circuit 14 (FIG. 6).
(A)).

The energization signal forming section 10 detects a zero-cross point when these energization signals Du, Dv, Dw are AC signals, and any one of the energization signals Du, Dv, Dw passes through the zero-cross point. Each time the current phase difference signal is inverted, a current-carrying phase signal Sp that repeats inversion of the high and low levels is formed (see FIG. 6B), and is output to the current phase difference detection unit 15.

In addition, when the frequency command f given by the command selecting section 12 is f = 0, the energization signal forming section 10 determines the starting method of the motor 8 as described later. The energization signals Du, Dv and Dw of the PWM
The signal is output to the circuit 14. Further, the energization signal forming unit 10 receives a DC excitation command signal Br from the start control unit 9.
Is given, a signal for exciting the motor 8 by DC is
The signal is output to the inverter main circuit 7 via the M circuit 14.

Although not specifically shown, the PWM circuit 14 has the level of a carrier (triangular wave) output from an internal carrier generator and the supplied energization signals Du, Dv, and Dw.
Are compared with each other to form positive drive signals Dup, Dvp, and Dwp by PWM control, which are at a high level during a period in which the level of each energization signal is higher. Also, the inverted ones of these positive drive signals are formed as negative drive signals Dun, Dvn, Dwn, and output to the drive circuit 16.

The drive circuit 16 is composed of a photocoupler or the like, and is supplied with positive and negative drive signals Dup to Dup.
Gate signals corresponding to wp, Dun to Dwn are output to the transistors T1 to T3, T4 to T6. Details of the operation will be described later.

Current polarity detection circuit (current polarity detection means) 1
7 detects the polarity of each of the U, V, and W phase currents flowing in the inverter main circuit 7, and outputs the current polarity signals Su, Sv, Sw.
Is output to the current phase difference detection unit 15.
The current phase difference detector 15 outputs the current polarity signals Su,
Based on Sv, Sw and energization phase signal Sp output from energization signal forming unit 10, windings 8u, 8v,
8w, and detects the phase difference θi of the winding current with respect to the voltage applied to each end of 8w, and outputs the current phase difference θi to the induced voltage phase difference calculation unit 11 and the frequency command determination unit 13. ing.

Based on the voltage command V, the frequency command f, and the current phase difference θi, the induced voltage phase difference calculation unit 11 calculates the windings 8 u, 8 of the motor 8 with respect to the output voltage of the inverter main circuit 7.
The phase difference θe of the voltage induced in v, 8w is calculated, and the induced voltage phase difference θe is output to the frequency command determination unit 13. The frequency command determination unit 13 determines the frequency command fe from the frequency command f, the current phase difference θi, and the induced voltage phase difference θe, and as described above,
Output to

FIG. 2 shows a current polarity detection circuit 1 for the U phase.
7u shows a detailed electric configuration of 7u. In FIG. 2, the drive circuit 16un applies a positive voltage for gate drive from a drive power supply (not shown) between the base and the emitter of the transistor T1 when the drive signal Dun is at a high level, and when the drive signal Dun is at a low level. The gate signal Gun is applied so as to apply a negative gate driving voltage between the base and the emitter of the transistor T1.

The emitter of the transistor T4 and the DC bus 6
b, a resistor 18u is interposed. And
A common connection point between the emitter of the transistor T4 and the resistor 18u is connected to the non-inverting input terminal of the comparator 19u.
The common connection point between the resistor 18u and the DC bus 6b is connected to the inverting input terminal of the comparator 19u. The output terminal of the comparator 19u is connected to the input terminal D of the latch circuit 20u.
It is connected to the. The output terminal of the driving circuit 16un is connected to the input terminal ck of the latch circuit 20u.
A gate signal Gun is provided.

The latch circuit 20u latches (sets) the data applied to the input terminal D at the falling edge of the signal applied to the input terminal ck. The negative logic output terminal / Q of the latch circuit 20u outputs a current polarity signal Su via a photocoupler or the like (not shown). As described above, the current polarity detection circuit 17u is configured by the resistor 18u, the comparator 19u, and the latch circuit 20u. In addition, about the V and W phases,
The current polarity detection circuits 17v and 17w are configured in exactly the same manner, and output current polarity signals Sv and Sw, respectively. The above constitutes the inverter device and the brushless fan motor.

Next, the operation of the first embodiment will be described with reference to FIGS. The start control unit 9 receives a voltage command V
(For example, a voltage ratio of 50%) to the energization signal forming unit 10 and a frequency command fs (= 0) to the command selecting unit 12.
Output to The command selecting unit 12 outputs the frequency command fs as it is to the energization signal forming unit 10 as the frequency command f.

Since the frequency command f is f = 0, the energization signal forming section 10 applies energization signals Du, Dv, Dw having the same waveform and a duty of approximately 50% to the PWM circuit 1.
4 (see FIGS. 3A and 4A). Then, in the inverter main circuit 7, the energization signals Du, D
gate signals Gup to Gwp, Gun to G given via the PWM circuit 14 and the drive circuit 16 based on the signals v and Dw.
Depending on wn, transistors T1 to T3, T4 to T6
Are turned on and off (FIGS. 3B and 3C and FIG. 4).
(See (b) and (c)).

In this case, when the transistors T1 to T3 are turned on and the transistors T4 to T6 are turned off, the transistors T1 and T6 are turned off.
A closed loop is formed between T2 and T3 and the windings 8u, 8v and 8w of the motor 8, and when the transistors T1 to T3 are off and the transistors T4 to T6 are on, the transistors T4 and T4 are turned on.
A closed loop is formed between T5, T6 and the windings 8u, 8v, 8w of the motor 8.

At this time, the wind naturally blowing outdoors hits the fan installed in the outdoor unit of the air conditioner, and the fan rotates, so that the motor 8 mounted for driving the fan rotates. Then, a power generating action is generated in the motor 8, and an induced voltage is generated in the windings 8u, 8v, 8w.

In this state, when the transistors T1 to T3 and T4 to T6 are turned on and off as described above,
Sinusoidal winding currents Iu, Iv, Iw having a phase difference of 120 degrees flow through the windings 8u, 8v, 8w.
For example, FIGS. 3D to 3F show that the motor 8 rotates forward (U →
V → W → U → V →...)
FIGS. 4D to 4F show waveforms of the winding currents Iu, Iv, Iw when the motor 8 is rotating in reverse (U → W → V → U → W →...). It is a waveform.

Current polarity detection circuits 17u, 17v, 17w
Detects the polarity of the winding currents Iu, Iv, Iw and outputs current polarity signals Su, Sv, Sw (FIG. 3 (g) to (g)).
(I), see FIGS. 4 (g) to (i)). Then, the rotation speed detecting unit 9b performs the operation from the time when any one of the current polarity signals Su, Sv, Sw rises to a high level to the time when any one signal subsequently falls to a low level. Time Tm is set by a built-in timer (not shown)
Measured by For example, in FIGS. 3G to 3I, the time from when the signal Su rises to when the signal Sw falls is measured as Tm.

In this case, even if the time Tm is measured between any two signals, both times are equivalent to the armature angle of 60 degrees. When measuring the time Tm, the rotation speed detector 9b calculates and detects the rotation speed Ss of the motor 8 according to the equation (1). Ss = 1 / (6 × Tm) (1)

Then, the starting method determining unit 9a determines the starting method of the motor 8 as follows based on the rotational speed Ss detected by the rotational speed detecting unit 9b. The rotation speed Ss is a reference rotation speed (predetermined value, for example, 300 to
In the case of 400 rpm or more, the motor 8 does not start at that time, and after a certain time elapses, the same process as above is repeated again, and the same judgment is made based on the rotation speed Ss. When the rotation speed Ss is lower than the reference rotation speed In this case, the start control unit 9 outputs the DC excitation signal Br to the energization control unit 10. Then, the energization control unit 10 continuously turns on only the transistors T1 and T5, for example, and applies DC current to the windings 8u and 8v, thereby exciting the motor 8 with DC and stopping the rotation. After the positioning of the rotor is performed in this state, a voltage command value V and a frequency command value fs are output as described later to start the motor 8.

Here, the significance of dividing the starting method into two according to the rotation speed Ss of the motor 8 will be described. That is,
In the case of (1), the fan of the outdoor unit and the motor 8 are blown by natural wind and rotate at a relatively high speed, and it is not easy to stop the motor 8. Attempting to start the motor 8 suddenly in such a state places a heavy burden on the motor 8. Therefore, in this case, the start of the motor 8 is postponed, and after a certain period of time, the same process is repeated again to determine whether or not the motor 8 can be started.

In this case, since the fan of the outdoor unit and the motor 8 are rotating at a relatively low speed, the rotation of the motor 8 can be easily stopped by performing DC excitation. If the positioning of the rotor is performed in a state where the rotation of the motor 8 is stopped, the start of the motor 8 can be easily started.

In this case, when starting the motor 8 (by sine wave drive), the start control unit 9
Outputs the voltage command value V and the frequency command value fs according to the time function shown in FIG. That is, a relatively small command value is output as an initial value, and after the command value is linearly increased with time, the command value is made constant after a predetermined time has elapsed.

The energization signal forming unit 10 receives the frequency command f
The level data of the energization signal is sequentially read out while the address is cyclically increased at a frequency corresponding to the energization signal Du, and the energization signals Du, each having a phase difference of 120 electrical degrees by multiplying by the voltage command V
Dv and Dw are output.

The PWM circuit 14 supplies the energization signals Du, Dv,
When Dw is given, the positive and negative drive signals Dup to Dw
Based on these drive signals, the drive circuit 16 generates positive and negative gate signals Gup to Gwp,
Gun to Gwn are replaced by transistors T1 to T3, T4 to T
6 is output. Then, each phase winding 8u, 8
A substantially sinusoidal phase current iu, iv, iw is supplied to v, 8w to drive the motor 8 (see FIG. 6C, only the current iu is shown).

The operation of the current polarity detection circuit 17u at this time will be described below. FIGS. 7A and 7B show the driving circuit 1.
Drive signals Dup and D output to U-phase transistors T1 and T4 of inverter main circuit 7 via 6up and 16un.
un, and shows a case where the polarity of the U-phase current iu changes from negative to positive (see FIG. 7C).

When the polarity of the U-phase current iu is negative, a collector current flows through the transistor T4, and the current iun flows through the resistor 18u in such a direction that the potential of the non-inverting input terminal of the comparator 19u becomes higher than the potential of the inverting input terminal. Flows (Fig. 7
(D)). Therefore, the output signal of the comparator 19u goes high as the drive signal Dun goes high.

When the polarity of the U-phase current iu is positive,
Since the forward current of the diode D4 indicated by a dotted line in FIG. 2 flows at the off timing (low level) of the drive signal Dup, the resistor 18u flows in the direction in which the potential of the inverting input terminal of the comparator 19u increases (see FIG. 2). 7 (d)), the output signal of the comparator 19u is always at the low level (see FIG. 7 (e)).

The inverted output terminal / Q of the latch circuit 20u latches the signal supplied from the comparator 19u at the falling edge of the gate signal Gun and inverts the level of the signal, and outputs the inverted signal. When the polarity of the current iu is negative, it becomes a low level signal, and when it is positive, it becomes a high level signal (see FIG. 7F). Note that the current polarity detection circuit operates in exactly the same manner for the V and W phases, and the current polarity signals Sv and Sw together with the current polarity signal Su are changed as shown in FIG.
Is output as shown.

As shown in FIG. 6, the current phase difference detector 15
Measures the time Tp (corresponding to an electrical angle of 60 degrees) between the rising edge and the falling edge of the energization phase signal Sp provided from the energization signal forming unit 10 by a timer. Also, the timer measures the time Ti from the rising edge of the conduction phase signal Sp to the rising edge of the current polarity signal Su, and calculates and detects the phase difference θi of the winding current iu with respect to the conduction signal Du by Expression (1). I do. θi = 60 × Ti / Tp (2)

Next, the operation of the induced voltage phase difference calculating section 11 will be described with reference to FIGS. FIG.
2 shows an equivalent circuit for one phase of the motor 8. That is,
Output voltage (phase voltage) V of inverter main circuit 7 (= V's)
in (θ)), the reactance L and resistance R of the winding of the motor 8, and the induced voltage E (= E′sin) of the motor 8.
(Θ−θe)) are connected in series. Here, V 'and E' indicate the maximum values. For the induced voltage E,
The output voltage V of the inverter main circuit 7 is advanced by the phase θe (see FIG. 9).

At this time, a difference voltage (V−E) between the output voltage V of the inverter main circuit 7 and the induced voltage E is applied to both ends of the series circuit of the reactance L and the resistor R, The current I (= I'si) delayed from the time constant and the frequency command f by the phase θv determined as in equation (3)
n (θ−θi)) flows (see FIG. 9). Here, I 'indicates the maximum value. θv = tan ⁻¹ (2πfL / R) (3)

FIG. 9 is a waveform diagram showing the phase relationship between output voltage V, induced voltage E and current I of inverter main circuit 7 described above. As is apparent from FIG. 9, the phase difference between the output voltage V of the inverter main circuit 7 and the difference voltage (VE) is
(Θv−θi). As shown by the point A in FIG. 9, at the zero cross point of the difference voltage, the level of the output voltage V and the induced voltage E of the inverter main circuit 7 become equal, so that the equation (4) is established. V′sin (θi−θv) = E′sin (θi−θv−θe) (4) When the induced voltage constant of the motor 8 is K, the induced voltage E
Is represented by equation (5). E = K · f (5)

From these equations, the induced voltage phase difference θe is calculated as follows. Equation (3) is a function of the frequency command f using the reactance L and the resistance R as constants. FIG. 10 shows a case where the time constant (L / R) of the winding of the motor 8 is, for example, “1/20”. It is shown by the middle broken line. Considering the range of the number of rotations (frequency) actually used for the motor 8, the function shown by the broken line in FIG. 10 can be approximated by a straight line as shown by the equation (6), which is shown by the solid line. . θv = Ka × f + Kb (6) By storing the data Ka and Kb of the linear function in a memory or the like, the phase difference θv of the current I with respect to the difference voltage (V−E) can be obtained by a simple calculation. still,
It goes without saying that θv may be obtained by directly calculating equation (3).

Next, equation (4) can be modified as equation (7). V′sin (θv−θi) = E′sin (θv−θi + θe) sin (θv−θi + θe) = (V ′ / E ′) sin (θv−θi) (7)

FIG. 11 shows sine wave level data for 90 electrical degrees. By storing the sine wave data in the memory in the same manner, the induced voltage phase difference θ
Find e. First, the phase differences θi, θ obtained from the equations (2) and (6)
Since (θv−θi) is obtained from v, sin (θv−θi) = X on the right side of equation (7) is obtained. Next, assuming that (V ′ / E ′) · X = Y is obtained by multiplying the constant (V ′ / E ′) by “X”, since “Y” is the right side of the equation (7), sin ^{− 1} (Y) = θv−θi + θe (8), and (θv−θi + θe) can be obtained. From the equation (9), the induced voltage phase difference θe is obtained. (Θv−θi + θe) − (θv−θi) = θe (9)

The above-described calculation in the induced voltage phase difference calculation unit 11 is executed each time the current phase difference detection unit 15 detects the current phase difference θi for each of the U, V, and W phases. The phase of the induced voltage E with respect to the output voltage V can be obtained. Since the phase of the induced voltage E has a fixed relationship with the rotational position of the rotor of the motor 8,
Obtaining the phase of the induced voltage E is equivalent to detecting the rotational position of the rotor.

The frequency command determiner 13 determines and outputs the frequency command fe by the equation (10) every time the induced voltage phase difference θe is obtained. fe = Kz (θi−θe) + f (10) where Kz is a constant. That is, in the case of θi> θe, the frequency command fe is increased, energization is performed so as to accelerate the motor 8, and the phase of the rotor (induced voltage phase difference θe) is relatively shifted in the delay direction. vice versa,
When θi <θe, the frequency command fe is reduced, and the phase of the rotor is relatively shifted in the leading direction. Although the above description has mainly been given of the U phase, V and W
The same applies to the phases.

By repeating the above processing, finally, the frequency command fe, that is, the frequency command f is determined so that the current phase difference θi becomes equal to the induced voltage phase difference θe. The start control unit 9 outputs a selection signal Sk when a predetermined time has elapsed from the start of the start of the motor 8 and the voltage command V and the frequency command fs shown in FIG. Then, the frequency command is switched from fs to fe. At that time, the expression (10) is expressed as: fe = Kz (θi−θe) + fs (11). From the expression (11) as an initial value, control is thereafter performed with the frequency command f = fe. As described above, the inverter device of the present embodiment is based on the current polarity signals Su, Sv, Sw output by the current polarity detection circuit 17.
The motor 8 is driven by a sine wave.
A so-called sensorless drive system that does not use a position sensor such as C is adopted.

As described above, according to the present embodiment, when the motor 8 is being rotated by an external force such as wind received by the fan before the start of the start of the motor 8, the rotation speed detecting unit 9 b is used.
energization signal forming unit 1 in accordance with the induced voltage generated in
0, the rotation speed Ss of the motor 8 is detected based on the change in the polarity of the current flowing through each of the windings 8u, 8v, 8w, and the starting method determining unit 9a determines if the rotation speed Ss is equal to or greater than the reference rotation speed. Start of motor 8 at
When s is less than the reference rotation speed, the motor 8 is started to start.

Therefore, even when the sensorless drive system is adopted, the rotation state of the motor 8 before starting can be determined. Then, the motor 8 is started in a state where the motor 8 is rotating at a relatively high speed, and the rotation of the motor 8 can be easily stopped without putting a mechanical burden on each part of the motor 8. By starting the motor 8 only when the position detection can be reliably performed, the life of the motor 8 can be extended. Also,
Occurrence of vibration at the time of starting can be prevented.

That is, the inverter device of the sensorless drive system can be applied to the drive of a fan arranged in an outdoor unit of an air conditioner, and the cost and size of the air conditioner system can be reduced. Further, the usage environment of the inverter device can be expanded.

FIG. 12 shows a second embodiment of the present invention. The same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. Only different parts will be described below. In FIG. 12 showing the electrical configuration, the configuration of the second embodiment is different from the startup control unit 9 in that a rotation direction detection unit (rotation direction detection unit) 9 c
Is different. The rotation direction detector 9c
Detecting the rotation direction Ds of the motor 8,
Starting method determining unit (starting method determining means) 9a 'instead of a
Output. Other configurations are the same as in the first embodiment.

Next, the operation of the second embodiment will be described with reference to FIGS. 3 and 4 again. When a start command signal for the motor 8 is given from outside, the energization signal forming unit 10
Outputs the energization signals Du, Dv, and Dw having the same waveform and a duty of about 50% to the PWM circuit 14 to turn on and off the transistors T1 to T3 and T4 to T6 in the same manner as in the first embodiment (FIG. a) to (c) and FIGS.
(C)). Then, when the motor 8 is rotating before the start of the start, the rotation speed detector 9b measures the time Tm, and calculates and detects the rotation speed Ss of the motor 8 according to the equation (1).

At this time, the rotation direction detecting section 9 c
The rotation direction Ds of the motor 8 is detected by referring to the current polarity signals Su, Sv, Sw output in different patterns according to the rotation direction of the motor 8. Various methods can be considered as a detection method. For example, the rotation direction Ds can be detected by referring to the levels of the current polarity signals Sv and Sw at the time when the current polarity signal Su falls.

For example, as shown in FIGS. 3G to 3I, when the motor 8 is rotating forward, the current polarity signal Su
Polarity signal S at the falling point of time (time point A)
The levels of v and Sw are high (H) and low (L), respectively. Further, as shown in FIGS.
Are reversed, the levels of the current polarity signals Sv and Sw at the falling time point (time point B) of the current polarity signal Su are low and high, respectively.

As described above, the rotation direction detector 9c
Detects the rotation direction Ds of the motor 8 and outputs it to the starting method determining unit 9a '. The starting method determining unit 9a 'determines the starting method of the motor 8 as follows based on the rotational direction Ds of the motor 8 and the rotational speed Ss detected by the rotational speed detecting unit 9b. When the rotation speed Ss is equal to or higher than the reference rotation speed At this point, the motor 8 does not start, and after a certain period of time, the same process is repeated again, and the same judgment is made based on the rotation speed Ss. . In this case, the start of the motor 8 is forgotten at this point because there is a possibility that a load is imposed on the motor 8 as in the first embodiment.

The rotation speed Ss is less than the reference rotation speed, and
When the rotation direction Ds is the forward rotation direction, the motor 8 is started to start in that state. In this case, since the motor 8 is rotating forward at a relatively low speed, there is no risk that the motor 8 will be burdened, and since the rotational position information of the rotor is also obtained, the motor 8 can be started without any problem. .

The rotation speed Ss is less than the reference rotation speed, and
When the rotation direction Ds is the reverse rotation direction, a DC excitation command signal Br is output to the energization signal forming unit 10,
The rotation of the motor 8 is stopped by DC excitation. After positioning the rotor in that state, the start of the motor 8 is started. In this case, since the motor 8 is rotating in the reverse direction, the motor 8 is DC-excited to stop the rotation and then starts (in the normal rotation direction).

The rotation speed Ss is less than the reference rotation speed, and
In the case where the rotation direction Ds cannot be detected In this case, it is determined that the motor 8 is stopped. Therefore, the DC is excited to perform the positioning of the rotor, and then the start of the motor 8 is started. The subsequent drive control of the motor 8 is the same as in the first embodiment.

As described above, according to the second embodiment, the rotation direction detector 9c determines the rotation direction Ds of the motor 8 rotating by an external force such as wind before the start, at the time of the fall of the current polarity signal Su. And by detecting the levels of the current polarity signals Sv and Sw in the starting method determining section 9a '.
Determines the starting method of the motor 8 according to the rotation direction Ds and the rotation speed Ss detected by the rotation speed detection unit 9b.

Therefore, after grasping the rotation state of the motor 8 before starting in more detail, for example, as described above, when the rotation speed Ss is less than the reference rotation speed and the rotation direction Ds is the normal rotation direction, In this state, it is possible to start the motor 8 and to start the motor 8 more quickly, so that a more appropriate starting method can be selected.

FIGS. 13 and 14 show a third embodiment of the present invention. The same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. Only different parts will be described below. In FIG. 13 showing the electrical configuration, the rotation speed detector 9b of the first embodiment is replaced by a rotation speed detector (rotation speed detector).
9b 'and the energization signal forming unit 10
Are replaced by an energization signal forming section (energization signal forming means) 10 '. Other configurations are the same as those of the first embodiment.

Next, the operation of the third embodiment will be described with reference to FIG. When a start command signal for the motor 8 is given from the outside, the start control unit 9 outputs a voltage command V (for example, a voltage ratio of 50%) to the energization signal forming unit 10 and a frequency as in the first embodiment. Command fs (= 0)
Is output to the energization signal forming unit 10 ′ via the command selecting unit 12.

Since the frequency command f is f = 0, the energization signal forming unit 10 'outputs energization signals Du and Dv having the same waveform and a duty of approximately 50% to the PWM circuit 14 (FIG. 14 (a)). )reference). Note that the energization signal Dw is not output. Then, in the inverter main circuit 7, the gate signals Gup, Gvp, and Gun provided through the PWM circuit 14 and the drive circuit 16 based on the energization signals Du and Dv.
And Gvn turn on / off the transistors T1 and T2, T4 and T6 (see FIGS. 14B and 14C).

In this case, when the transistors T1 and T2 are turned on and the transistors T4 and T5 are turned off, the transistors T1 and T5 are turned off.
A closed loop is formed between T2 and the windings 8u and 8v of the motor 8, and the transistors T1 and T2 are turned off, T4 and T4
5 is on, the transistors T4, T5 and the motor 8
A closed loop is formed between the windings 8u and 8v.

In this state, as described above, the motor 8
Is rotating, sinusoidal winding currents Iu and Iv having a phase difference of 180 degrees flow through the windings 8u and 8v due to induced voltages generated in the windings 8u and 8v. When the current is supplied to the two-phase windings among the three phases, the winding currents Iu and Iv regardless of whether the rotation direction of the motor 8 is normal or reverse.
Have the same waveform pattern.

Current polarity detecting circuits 17u, 17v, 17w
Detects the polarity of the winding currents Iu, Iv, Iw and outputs current polarity signals Su, Sv, Sw (FIG. 14 (g) to (g)).
(See (i)). In this case, the current polarity signal Sw is not output. Then, the rotation speed detecting section 9b 'outputs the current polarity signal S
The time Tm from the time when one of the signals u and Sv rises to a high level to the time when the other signal subsequently falls to a low level is measured by a built-in timer (not shown). I do. For example, FIG.
, The signal Sv from the time when the signal Su rises
Is measured as Tm until the time when falls.

In this case, even if the time Tm is measured between any two signals, both times are equivalent to the armature angle of 180 degrees. When measuring the time Tm, the rotation speed detecting unit 9b 'calculates the rotation speed Ss of the motor 8 according to the equation (12).
Is calculated and detected. Ss = 1 / (2 × Tm) (12) Then, based on the rotation speed Ss detected by the rotation speed detecting unit 9b ', the starting method determining unit 9a performs the starting method of the motor 8 in the same manner as in the first embodiment. To determine.

As described above, according to the third embodiment, when the motor 8 is rotating by an external force such as wind applied to the fan before the start of the motor, the rotation speed detecting unit 9b '
u, 8v according to the induced voltage generated
0, the rotation speed Ss of the motor 8 is detected based on the change in the polarity of the current flowing through each of the windings 8u, 8v, and the starting method determination unit 9a determines the starting method of the motor 8 according to the rotation speed Ss. The same effects as those of the first embodiment can be obtained.

FIGS. 15 to 17 show a fourth embodiment of the present invention. The same parts as those in the second and third embodiments are denoted by the same reference numerals, and the description thereof will be omitted. explain. In FIG. 15 showing the electrical configuration, the fourth
The configuration of the embodiment is obtained by adding a rotation direction detector (rotation direction detector) 9c 'instead of the rotation direction detector 9c of the second embodiment to the configuration of the third embodiment.

The rotation direction detector 9c 'supplies an energization switching signal Ch to the energization signal generator 10'. The energization signal generator 10 'outputs the energization switching signal Ch.
Is given, the energizing phases to the windings 8u, 8v, 8w of the motor 8 are switched as described later.

Next, the operation of the fourth embodiment will be described with reference to FIGS. When a start command signal for the motor 8 is given from outside, the energization signal forming unit 10 '
Outputs the energization signals Du and Dv having the same waveform and a duty of approximately 50% to the PWM circuit 14 to turn on and off the transistors T1 and T2, T4 to T6, similarly to the third embodiment (FIG. 16A). -(C) and FIG. 17 (a)-
(C)). Then, when the motor 8 is rotating before the start of the start, the rotation speed detector 9b 'measures the time Tm and calculates and detects the rotation speed Ss of the motor 8 according to the equation (12).

At this time, only the current polarity signals Su and Sv are detected by the rotation direction detector 9c ', and as described in the third embodiment, regardless of the rotation direction of the motor 8, both waveform patterns are detected. Are the same.

The rotation direction detector 9c 'outputs, for example, the fall of the current polarity signal Su (= the current polarity signal S
17 (time A in FIG. 16, FIG. 17)
At time B), the energization switching signal Ch is output to the energization signal forming unit 10 '. Then, the energization signal forming unit 10 '
Switches the energization phase of the energization signal from the U and V phases to the U and W phases.

The current polarity signals Su and Sw immediately after the switching of the energized phase indicate different levels according to the rotation direction of the motor 8. That is, when the motor 8 is rotating forward as shown in FIG. 16, the levels of the current polarity signals Su and Sw are high and low, respectively, and as shown in FIG. 17, the motor 8 is rotating reversely. In this case, the levels of the current polarity signals Su and Sw are low and high, respectively.

Here, description will be made again with reference to FIGS. First, pay attention to the waveform of the winding current Iu (FIG. 3D).
4 (d)), after the fall of the current polarity signal Su,
That is, the waveforms of the winding currents Iu, Iv, Iw at the time point C in FIG. 3 (in the case of normal rotation) and at the time point D in FIG. 4 (in the case of reverse rotation) after the zero crossing of the winding current Iu from positive to negative are shown. Let's compare.

Then, the polarities of the respective winding currents at the time point C in FIG. 3 are Iu (-), Iv (+), and Iw (-). That is, as in the first embodiment, the three-phase windings 8u, 8v,
If all 8w are energized, at this point
Current flows from the V phase to the U and W phases, and the phase of the current is V → W, that is, the polarity is Iu (−), Iv (−), I
It is moving in the direction of changing to w (+). That is, the W-phase current Iw is on the way to the zero-cross point from negative to positive.

Therefore, time A in FIG. 16 (time C in FIG. 3)
When the current-carrying phase is switched from the U and V phases to the U and W phases at the time, the current supplied from the V phase at that time is supplied from the U phase, and Iu (+): Su (high),
Iw (−): Sw (low), and current flows from the U phase to the W phase.

On the other hand, the polarity of each winding current at the time point D in FIG. 4 is Iu (-), Iv (-), Iw (+).
That is, when the three-phase windings 8u, 8v, and 8w are all energized, at this time, current flows from the W phase to the U and V phases, and the phase of the current is W → V, that is, The polarity is moving in the direction of changing to Iu (-), Iv (+), Iw (-). That is, the W-phase current Iw is on the way to the zero-cross point from positive to negative.

Therefore, time point B in FIG. 17 (time point D in FIG. 4)
When the current-carrying phase is switched from the U and V phases to the U and W phases in, all of the current supplied from the W phase to the U and V phases at that time flows to the U phase, and Iu (-): Su
(Low), Iw (+): Sw (high).

As described above, the rotation direction detector 9
c ′ refers to the level of the current polarity signals Su and Sw immediately after the energization switching signal Ch is output to the energization signal forming unit 10 ′ at the timing of zero crossing where the polarity of the winding current Iu changes from positive to negative. The rotation direction Ds of the motor 8 is detected.
The determination of the starting method after the detection is performed by the starting method determining unit 9a in the same manner as in the second embodiment.

As described above, according to the fourth embodiment, when the motor 8 is rotated by an external force such as wind received by a fan before the start of the motor 8, the energization signal forming unit 10 ′
The currents Iu and Iv are caused to flow through the two-phase windings 8u and 8v by the induced voltages generated at u, 8v and 8w, and the energized phases are switched when the energization switching signal Ch is given from the rotation direction detecting unit 9c '. The phase is switched from the U and V phases to the U and W phases, and the rotation direction detector 9c 'outputs the energization switching signal Ch to the energization signal generator 1
Since the rotation direction Ds of the motor 8 is detected by referring to the levels of the current polarity signals Su and Sw immediately after the output to 0 ', the same effect as in the second embodiment can be obtained.

The present invention is not limited to the embodiment described above and shown in the drawings, and the following modifications or extensions are possible. When the motor 8 is rotating before the start, the transistor T1 is turned on as in the first and second embodiments.
T3, T4 to T6 are turned on and off at the same timing, and the transistors T1, T2, T4 and T5 are turned on and off at the same timing as in the third and fourth embodiments. (Short circuit braking), the rotation speed detector 9b or 9
In practice, the rotation speed Ss detected by b 'is slightly lower than the rotation speed of the motor 8 before the braking is applied. Therefore, the actual rotation speed of the motor 8 and the rotation speed detection unit 9b are determined in advance.
Alternatively, a correlation with the rotation speed Ss detected by 9b 'is obtained and stored as a data table for correction.
After obtaining s, the motor 8
May be obtained. Also, formulas,
Or you may make it correct by calculation by an approximate expression.
With this configuration, it is possible to obtain a rotation speed of the motor 8 closer to the actual value.

The detection of the rotation direction Ds in the second embodiment is determined by, for example, the levels of the current polarity signals Sv and Sw at the time of rising of the current polarity signal Su (low, high for normal rotation, high, low for reverse rotation). May be. Alternatively, the determination may be made based on the levels of the remaining two phases at the time of rising or falling of another phase. Also in the fourth embodiment, the energized phase is switched by selecting any two of the three phases, and when the energization switching signal Ch is given, one of the two phases is switched to the remaining one. What should I do? The induced voltage phase difference calculation means is not limited to a calculation based on a mathematical formula or a calculation using an approximation formula.
i, a voltage command V, and a frequency command f are calculated in advance as parameters and stored as a data table,
It may be read out and obtained. It is preferable that the reactance L, the resistance R, and the induced voltage constant K, which are constants of the motor 8, are not fixed values but corrected according to the ambient temperature or the like. In this case, the accuracy can be further improved.

Frequency command f in frequency command determination means
The determination of e is not limited to the equation (10).
The change amount of the frequency command fe may be changed according to the immediately preceding frequency command f or voltage command V. The current polarity detection circuit 17 is provided for three phases, and the processes in the current phase difference detection unit 15, the induced voltage phase difference calculation unit 11, and the frequency command determination unit 13 are executed six times in one electric cycle, that is, every 60 electrical degrees. However, the number of processes may be reduced according to the inertia of the motor and the load. Further, the number of times of processing may be changed according to the level of the frequency. The drive circuit 16 and the current polarity detection circuit 17 may be configured as a one-chip IC. Further, an inverter main circuit 7 is further added to the one-chip IC.
May be configured. With this configuration, the number of components can be reduced, and the inverter device can be downsized. Instead of the resistor 18u, diodes connected in anti-parallel to each other may be used. Positive transistors T1 to T3
May be provided with current polarity detection means. The signal applied to the clock input terminal ck of the latch circuit 20u is not limited to the gate signals Gun, Gvn, and Gwn, but may be any signal such as the drive signals Dun, Dvn, and Dwn that can obtain the ON / OFF timing of the transistor T4. Energization signal forming unit 10
Is not limited to the voltage rate corresponding to the sine wave, but may be changed as appropriate as long as the voltage rate corresponds to the waveform that reduces the torque fluctuation of the motor 8.

[0112]

The present invention is as described above. The starting method determining means can determine an appropriate starting method of the brushless motor based on the rotational speed of the brushless motor detected by the rotational speed detecting means. Specifically, if the rotation speed of the brushless motor is equal to or higher than a predetermined value, the brushless motor is not started, and if the rotation speed of the brushless motor is lower than the predetermined value, DC excitation is performed on the brushless motor. After the rotation is stopped, the brushless motor can be started smoothly without generating vibration by outputting, for example, a sine wave energization signal to the inverter main circuit based on the polarity signal output by the current polarity detection means. Can be. In addition, since no load is applied to the brushless motor at the time of starting, the life can be extended.

The rotation direction detecting means can also determine the rotation direction of the brushless motor before starting, so that a more appropriate starting method can be selected. For example, the number of rotations of the brushless motor before starting can be determined to a predetermined value. If it is less than the value and the rotation direction is forward rotation, by starting driving the brushless motor as it is,
It is possible to start the brushless motor more quickly.

Further, when a brushless motor is used to drive a fan disposed in, for example, an outdoor unit of an air conditioner, if the fan is rotated by receiving an external force such as wind when the brushless motor is started, the rotation state is determined. , The brushless motor and the fan can be started smoothly.

[Brief description of the drawings]

FIG. 1 is a functional block diagram of an electric configuration showing a first embodiment of the present invention.

FIG. 2 is a diagram showing a detailed electrical configuration of a current polarity detection circuit.

FIG. 3 is a timing chart of each part when the motor is rotating forward.

FIG. 4 is a timing chart of each part when the motor is rotating in reverse.

FIG. 5 is a diagram illustrating a voltage command and a frequency command output by a start control unit as a time function.

FIG. 6 is a diagram illustrating a phase relationship between a signal waveform output by a conduction signal forming unit and a current polarity signal;

FIG. 7 is a timing chart of a current polarity detection circuit.

FIG. 8 is a diagram showing an equivalent circuit for one phase of a brushless motor.

FIG. 9 is a diagram showing a phase relationship between a voltage and a current between the inverter device and the brushless motor.

FIG. 10 is a diagram showing an approximation of a voltage phase difference θv as a linear function of a frequency f used in an operation performed by an induced voltage phase difference calculation unit.

FIG. 11 is a diagram showing sine wave level data for an electrical angle of 90 degrees used in the calculation performed by the induced voltage phase difference calculation unit.

FIG. 12 is a view corresponding to FIG. 1, showing a second embodiment of the present invention;

FIG. 13 is a view corresponding to FIG. 1, showing a third embodiment of the present invention.

FIG. 14 is a diagram corresponding to FIG. 3;

FIG. 15 is a view corresponding to FIG. 1, showing a fourth embodiment of the present invention.

FIG. 16 is a diagram corresponding to FIG. 3;

FIG. 17 is a diagram corresponding to FIG. 4;

[Description of References] 7 is an inverter main circuit, 8 is a brushless motor, 8u,
8v and 8w are windings, 9a and 9a 'are starting method determining units (starting method determining means), 9b and 9b' are rotation speed detecting units (rotating speed detecting means), and 9c and 9c 'are rotation direction detecting units (rotation direction). Direction detecting means), 10 and 10 'are energization signal forming units (energization signal forming means), 17 (17u, 17v, 17
w) shows a current polarity detection circuit (current polarity detection means).

Claims (11)

[Claims] An inverter main circuit for energizing a three-phase winding of a brushless motor; current polarity detecting means for detecting a polarity of a current flowing in the three-phase winding and outputting a polarity signal; Means for forming an energization signal based on the polarity signal output by the means, and outputting the energization signal to the inverter main circuit; and referencing the polarity signal output by the current polarity detection means when the brushless motor is started. A rotation speed detecting means for detecting a rotation speed of the brushless motor based on a cycle in which a current polarity changes; anda starting method of the brushless motor based on a rotation speed of the brushless motor detected by the rotation speed detection device. An inverter device comprising: a starting method determining means for determining. 2. The method according to claim 1, wherein the starting method determining means does not start the brushless motor when the rotation speed of the brushless motor detected by the rotation speed detecting means is equal to or higher than a predetermined value. When the rotation speed of the brushless motor is less than a predetermined value, the energizing signal forming unit is configured to perform DC excitation on the brushless motor, and then output an energizing signal based on the polarity signal output by the current polarity detecting unit. The inverter device according to claim 1, wherein: 3. A method for determining a starting method, comprising: detecting a rotation direction of a brushless motor based on a change in current polarity by referring to a polarity signal output by a current polarity detection unit when starting the brushless motor; 2. The brushless motor starting method according to claim 1, wherein said means determines a brushless motor starting method based on a rotation speed of said brushless motor detected by said rotation speed detection means and a rotation direction of said brushless motor detected by said rotation direction detection means. Inverter device. 4. The starting method determining means does not start the brushless motor when the rotation speed of the brushless motor detected by the rotation speed detecting means is equal to or higher than a predetermined value, and detects the rotation by the rotation speed detecting means. When the rotation speed of the brushless motor is less than a predetermined value and the rotation direction of the brushless motor detected by the rotation direction detection means is the positive direction, the polarity signal output by the current polarity detection means to the energization signal formation means. Output the energization signal based on the rotation speed, the rotation speed of the brushless motor detected by the rotation speed detection means is less than a predetermined value, and the rotation direction of the brushless motor detected by the rotation direction detection means is in the opposite direction. After the energization signal forming means performs DC excitation on the brushless motor, the current based on the polarity signal output from the current polarity detecting means is used. The inverter apparatus according to claim 3, wherein the outputting the signal. 5. An energization signal forming means for generating the same energization signal for all three-phase windings of the brushless motor when the starting method determining means determines the starting method of the brushless motor when starting the brushless motor. The rotation speed detection means detects the rotation speed of the brushless motor based on a cycle in which the polarity of the current flowing through the three-phase winding changes. Inverter device. 6. The brushless motor according to claim 6, wherein the energization signal forming unit is configured to determine whether the brushless motor is to be started by the start mode determination unit when starting the brushless motor. The rotation number detecting means detects the rotation number of the brushless motor based on a period in which the polarity of the current flowing through the two-phase winding changes. Item 5. The inverter device according to any one of Items 1 to 4. 7. The energization signal forming means forms all the same energization signals for the three-phase windings of the brushless motor when the starting method determination means determines the starting method of the brushless motor when starting the brushless motor. The rotation direction detecting means detects the rotation direction of the brushless motor based on the current polarity of the other two-phase winding at the time when the current polarity of one of the three-phase windings changes. The inverter device according to claim 3 or 4, wherein the inverter device detects (i). 8. The brushless motor according to claim 1, wherein the energization signal forming means is configured to determine whether the brushless motor is to be started by the start method determining means to determine the start method of the brushless motor. After forming and outputting the same energization signal, the remaining one-phase winding and one of the two-phase windings are applied to the timing at which the polarity of the current flowing through the two-phase winding changes. The energization phase is switched to generate and output the same energization signal, and the rotation direction detection means changes the rotation direction of the brushless motor based on the current polarities of the two-phase windings immediately after the energization phase is switched by the energization signal formation means. The inverter device according to claim 3, wherein the detection is performed. 9. A brushless motor for rotating a fan, an inverter main circuit for energizing a three-phase winding of the brushless motor, and detecting a polarity of a current flowing through the three-phase winding to output a polarity signal. Current polarity detecting means, an energizing signal forming means for forming an energizing signal based on the polarity signal output by the current polarity detecting means, and outputting the energizing signal to the inverter main circuit; Rotation speed detecting means for detecting the rotation speed of the brushless motor based on a cycle in which the current polarity changes by referring to the polarity signal output by the current polarity detection means when the motor is rotating by an external force; Starting method determining means for determining a starting method of the brushless motor based on the number of revolutions of the brushless motor detected by the detecting means. Brushless fan motor, wherein the door. 10. The method according to claim 1, wherein the starting method determining means does not start the brushless motor when the rotation speed of the brushless motor detected by the rotation speed detecting means is equal to or more than a predetermined value. When the rotation speed of the brushless motor is less than a predetermined value, the energizing signal forming unit is configured to perform DC excitation on the brushless motor, and then output an energizing signal based on the polarity signal output by the current polarity detecting unit. The brushless fan motor according to claim 9, characterized in that: 11. When starting the brushless motor,
Reference is made to a polarity signal output by the current polarity detection means when the fan is rotated by an external force, and a rotation direction detection means for detecting the rotation direction of the brushless motor based on a change in the current polarity is provided. 10. The brushless motor according to claim 9, wherein a starting method of the brushless motor is determined based on a rotation speed of the brushless motor detected by the rotation speed detection means and a rotation direction of the brushless motor detected by the rotation direction detection means. Fan motor.