JP3239025B2 - Brushless motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless motor, and more particularly to the detection of a rotational position of a rotor of a sensorless brushless motor.

[0002]

2. Description of the Related Art As a conventional technique, Japanese Patent Publication No. 5-100
There was one described in JP-A-39. In this publication, the continuous rotation of the rotor is performed by sequentially switching the energization pattern to two of the three-phase stator windings based on the change in the induced voltage generated in the non-energized stator winding. The rotor position detection method is based on when the magnitude relationship between the induced voltage generated in the non-energized stator winding and the three-phase neutral point voltage is reversed. To obtain the switching timing.

[0003]

In the conventional motor having such a structure, the current supply pattern to the stator winding is 120
Current, 60-degree non-current, 120-degree current, and 60-degree current are sequentially repeated, and current is applied to the stator winding by a semiconductor switching element such as a transistor or FET.
N / OFF was controlled.

Accordingly, the output of the brushless motor depends on the current capacity of the switching element which can be continuously supplied, and the output of the brushless motor is substantially several tens of watts.

As a method of increasing the output of the brushless motor, a method of shortening the continuous energization time of the switching element by turning on / off the switching element with a high-frequency signal during the 120-degree energization period, that is, applying the voltage to the stator windings A method of chopping DC power to be used has been considered.

When such chopping is used, 12
Since the DC voltage applied during the 0-degree energization period is chopped, it is induced in the non-energized stator winding due to a circuit loss, a limit on the transmission speed of parts, and the like in a place where the chopping frequency, that is, the ON duty is small. The induced voltage also has a distorted waveform according to the chopping cycle.

When the distorted induced voltage waveform is compared with the reference voltage, the reversal of the comparison output shifts back and forth depending on the degree of the distortion, and the timing of switching the energization pattern to the stator winding shifts. there were.

[0008] The deviation of the energization timing causes irregular braking and acceleration with respect to the rotation of the rotor, which is the main cause of vibration and noise of the brushless motor, and in the worst case, causes problems such as loss of synchronism and locking. Was something.

[0009] In particular, such a problem appears greatly in a brushless motor requiring a large output such as a refrigerant compressor.

The present invention provides a brushless motor in which the distortion of the induced voltage is canceled to solve such a problem.

[0011]

SUMMARY OF THE INVENTION The present invention provides a stator winding for an electric motor having a rotating rotor having magnetism and a plurality of stator windings forming a magnetic field for rotating the rotor. In a brushless motor, in which a rotor is controlled to supply DC power to a wire, means for forming DC power supplied to a stator winding into a predetermined switching voltage waveform, and the stator is rotated by rotation of the rotor. Comparing means for comparing the magnitude of the induced voltage generated in the winding with the reference voltage; energizing control means for controlling energization to the stator winding based on the comparison result of the comparing means; and ON duty of the voltage waveform Correction means for correcting the reference voltage so as to increase as the width decreases according to the width, wherein the reference voltage is adjusted according to the distortion of the induced voltage when the DC power applied to the stator winding is chopped. To Correct, is obtained so as to prevent the time shift of the output inversion of the comparison means by this strain.

[0012]

[0013] The present invention also relates to a motor for rotating a rotor having magnetism and a plurality of stator windings forming a magnetic field for rotating the rotor. In a brushless motor in which power supply is controlled so that a rotor rotates, means for forming a DC voltage supplied to a stator winding into a predetermined switching voltage waveform, and a rotation of the rotor is generated in the stator winding. Comparison means for comparing the magnitude of the induced voltage and the reference voltage, energization control means for controlling energization to the stator winding based on the comparison result of the comparison means, and all terminal voltages of the stator winding Correction means for correcting the reference voltage with a smoothed voltage obtained based on the reference voltage, and corrects the reference voltage according to the distortion of the induced voltage when the DC power applied to the stator winding is chopped. Output of comparison means It is obtained so as to prevent the time shift of the reversal.

[0014]

In the brushless motor constructed as described above, the reference voltage is corrected in accordance with the distortion of the induced voltage when the DC power applied to the stator winding is chopped, and the time lag of the output inversion of the comparison means due to the distortion is corrected. Can be prevented.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an electric circuit diagram for detecting a rotational position of a rotor. In the figure, R1, R2, and R3 are directly connected to voltage applying terminals of a stator winding (star-connected three-phase winding) of a motor described later. The connected resistors, together with the resistors R4 and R5, divide the total voltage of the respective terminal voltages of the stator winding to supply the total voltage to one input terminal of the comparator CMP.

R6, R7 and R8 are resistors connected to the voltage application terminals of the stator windings, respectively, and divide the total voltage of the respective terminal voltages of the stator windings together with the resistor R9, and smooth the voltage with the capacitor C1. After that, a resistor R1 is connected via a diode D1.
The voltage is applied to a reference voltage set by 0 and the resistor R11 to correct the reference voltage. The corrected reference voltage is supplied to the other input terminal of the comparator CMP.

On the other hand, the energization to the three-phase stator winding is generally applied in an energization pattern as shown in FIG. In this energization pattern, voltages of different polarities and equal magnitudes are always applied to the terminals of the two-phase stator windings energized in any section (based on the center voltage). . Therefore, the voltages between the two phases cancel each other out and become a voltage of 0 V in theory, so that only the induced voltage generated in the non-conducting stator winding is the resistor R1 (for example, the non-conducting stator winding is set to the U phase). ), Divided by the resistors R4 and R5, and applied to one terminal of the comparator CMP.

Similarly, the induced voltage is divided by a resistor R6 (for example, a non-energized stator winding is set to a U phase) and a resistor R9.
After being smoothed by the capacitor C1, the voltage is applied to the reference voltage determined by the resistors R10 and R11 via the diode D1, and the corrected reference voltage is applied to the other terminal of the comparator CMP. That is, these resistances R6 to R
7, a correction means for correcting the reference voltage by the capacitor C1 and the diode D1.

The voltage applied to one terminal of the comparator CMP is an induced voltage and a divided voltage which changes as shown in the waveform of FIG. Intersect. This center voltage is a reference voltage determined by the resistors R10 and R11. Since a voltage of about 280 V DC is applied to the terminals U, V, and W of the stator winding, in an actual circuit, the voltage is dropped to the input allowable range of one terminal of the comparator CMP and the other terminal. I have.

The voltage corrected to the reference voltage is 1 of the induced voltage.
/ 2, which is optimally set according to the chopping frequency of the voltage applied to the stator winding. Further, the magnitude of the voltage to be corrected is not limited to this magnitude. For example, if the reference voltage is set small, the correction is made large, and if the reference voltage is set large, the correction is made small.

In FIG. 1, PC is a photocoupler whose output changes according to the output of the comparator CMP, and its output is given to a microcomputer described later via a switching transistor Tr1. By using this photocoupler, the large voltage side (motor side) and the various voltage sides (microcomputer side) are electrically insulated. Next, the rotation control of the brushless motor using this electric circuit diagram will be described.

In FIG. 3, reference numeral 3 denotes an inverter for obtaining a rotating magnetic field in the stator 4 using a DC output (DC 280 V) rectified by the rectifier circuit.

The elements constituting the inverter 3 may be thyristors, FETs or other elements as long as they can perform switching control in response to a signal from a microcomputer 8 which will be described later, but are connected as shown in the following description. Six transistors Tr1 to Tr6 will be described as representative examples. The microcomputer 8 outputs a signal for controlling ignition of the transistors constituting the inverter 3 in a predetermined order, and inputs the rotational position of the rotor 7 detected by the electric circuit shown in FIG. It has a configuration for determining the firing order of the transistors Tr1 to Tr6 of the inverter 3 as a signal. N and S shown on the rotor 7 indicate magnetic poles magnetized on the surface of the rotor 7.

An outline of the operation of the commutatorless DC motor having such a configuration will be described. The inverter 3 supplied with DC power from the single-phase AC power supply via the rectifier circuit receives the signal of the rotational position of the rotor 7 as an input and supplies the signal to the transistors Tr1 to Tr6 of the inverter 3, for example, as shown in FIG. Is giving a good signal. That is, when a control potential is applied to each transistor in the first mode so that the transistors Tr1 and Tr5 are turned on and the other transistors Tr2 to Tr4 and Tr6 are turned off, a voltage between the windings U and V of the stator is as shown in FIG. A current as shown by an arrow I flows, and then (second mode) the transistors Tr1 and Tr6 are turned on, and the other transistors Tr2
When each transistor is controlled so that Tr5 is turned off, the current between the windings U and W as shown by the arrow II in the figure, and the transistors Tr2 and Tr6 are turned on and the others are turned off in the third mode. When controlled, the stator windings V, W
Between them, a current flows as indicated by arrow III in the figure. Similarly, the transistor Tr1 is sequentially changed from the third mode to the sixth mode.
2 to 6 are controlled to fire as shown in FIG. 2B, and the cycle of the first to sixth modes is repeated.

By the output of the ignition control from the microcomputer 8, a current flows in the stator 4 in the above-described direction, and the relationship with each mode is schematically shown in FIG. 2C. A chart is obtained. In each of U, V, and W phases in the figure, the conduction display above the center line indicates that a current flows from the entrance of each phase toward the neutral point N in the stator 4 of FIG. Indicates that a current is flowing from the neutral point N toward the entrances U, V, W of the windings of each phase.

When a current flows through the stator windings U, V, W in this manner, a rotating magnetic field is formed in the stator 4, so that, for example, one point M of the rotor 7 is shifted from the point P in FIG. ,
One rotation is made in accordance with R, X, Y, Z and each ignition mode, and thereafter, the rotor 7 is rotated in accordance with the sequentially repeated mode, so that the operation as the electric motor can be continued.

In general, when the motor shown in FIG. 3 is started and in a steady operation state, the rotor 7 having magnetism is used. Therefore, during operation of the motor, each stator winding U,
Back electromotive force is induced in V and W. In particular, in the embodiment of FIG. 3, since there is a stator winding that is not energized in each ignition mode, when the conductor 10 connecting the neutral point N of the stator winding and the microcomputer 8 is used, The potential due to the back electromotive force directly appears between the stator winding and the non-energized stator winding. The curves u, v, w shown by dotted lines in FIG. 2d are thus the respective stator windings U, V, W
FIG. 4 is a model diagram showing a voltage induced between the motor and the conductor 10, and the relationship between this waveform and the mode of energizing each of the stator windings U, V, and W is as follows. In the state shown in the figure, when the motor is started or when the load on the motor is increasing, the waveform of the induced voltage is also shown because the rotation of the rotor 7 cannot follow the conduction of each stator winding and is delayed. If the width of the horizontal axis of FIG. 2 is not changed, it will lag behind the waveform shown by the dotted line in FIG. 2D.

The present invention thus provides for the stator windings U,
With the back electromotive force generated in V and W as an input, the rotational position of the rotor 7 is detected, and an optimal ignition output is given to the inverter 3 in relation to the rotational state of the rotor 7.

That is, regarding the U phase in FIG. 2 showing the operating state of the motor, an intermediate point between the point where the second ignition mode ends and the point where the fourth ignition mode starts, in other words,
The direction of the potential of the back electromotive force is reversed at the middle point E (the position of 150 ° on the scale in the figure) in which the U-phase is not energized (third) firing mode. The direction of the back electromotive force is reversed at the midpoint F (at the position of 330 °). When a load is applied to the rotor 7, the points E and F gradually move to the second ignition mode (or the fifth mode), and when the motor starts, the point E and the point F are set to the second point. Before the end of the ignition mode (or the fifth mode), for example, 120 on the scale in the figure.
Since the direction of the potential of the back electromotive force changes at the position of .degree. Or 280.degree., A deviation occurs between the ignition mode and the actual rotation of the rotor 7, the inverter 3 is controlled by the control device 8 such as a microcomputer. Is made to correspond to the rotation state of the rotor 7, and a signal of an optimum mode is given to the stator winding 4 for a necessary time.

In the embodiment shown in FIG. 3, the change point of the direction of the potential of the back electromotive force (hereinafter referred to as the change point of the potential direction) is shifted by 120 ° from the U phase in the embodiment of FIG. , The V1 phase E1 point and the F1 point, and the W phase
In the same manner, the phase can be detected as points E2 and F2. In the present invention, the operation is performed based on the potential direction change point from each phase, and the timing of energizing each stator winding according to the result, in other words, each mode And the time for energizing the inverter 3 is controlled.

However, the rotor has inertia unless the load is excessively heavy, and it is not necessary to detect the rotor position every 60 ° rotation. Therefore, in the following description, the apparatus will be simplified to 1
Even if a method of determining the firing output timing to the inverter 3 based on the potential direction change point every 20 ° is used, there is no practical problem.

When the load on the motor is lighter, 36
Every 0 °, that is, every one rotation of the rotor,
The signal may be detected by any one of the phase, V-phase, and W-phase windings, and the inverter may be controlled based on this signal. However, in the following description, the rotation position every one third rotation (120 ° rotation) will be described. A case will be described in which the ignition control for each of the transistors Tr1 to Tr6 constituting the inverter 3 is performed based on the detection signal.

In FIG. 3, terminals 11, 12, 13, and 14 are terminals to which stator windings U, V, W and a conductor N are connected.
C is a circuit for detecting a position change point based on the back electromotive force generated in each of the stator windings U, V and W and supplying the detected position change point to the input terminal I1 to the microcomputer 8 as a position signal of the rotor 7. This is shown in FIG. 15 is a stator winding U, V,
A protection circuit for protecting the transistors Tr1 to Tr6 from a back electromotive force generated at the time of switching of W;
The inverting amplifiers 7 and 18 have one ends connected to the bases of the transistors Tr1, Tr2 and Tr3 and the other ends connected to the output ports O1, O2 and O3 of the microcomputer 8, respectively.
5, 26 and 27 are output ports O of the microcomputer.
4, O5, O6, and transistors Tr4, Tr5,
A transistor constituting a Darlington connection together with Tr6, a power supply input 24 for applying a base bias to the transistors 25, 26 and 27, and the transistors Tr1 to Tr6 are turned on in response to H signals from the output ports O1 to O6. You. Reference numeral 19 denotes a reset input port to the microcomputer 8, and reference numeral 20 denotes a clock input port for inputting an oscillation pulse from the vibrator 21 to the microcomputer 8 and controlling the inside thereof.

FIG. 4 shows a change in the voltage of the terminal 11 shown in FIG. In this figure, I is a period in which the first mode and the second mode shown in FIG. 2 are continuously maintained, and during this period, the rotor rotates 120 °. II is a period in which the third mode is also maintained, and the rotor is 60
° rotate. III is a period in which the fourth mode and the fifth mode are continuously maintained, and the rotor rotates 120 °. IV is the period during which the sixth mode is maintained,
The rotor rotates 60 °. Therefore, the rotor makes one rotation (360 °) by changing from I → II → III → IV. After IV, I is again followed by I → II → III → IV → I
Are repeated in order.

In the period I, the first mode and the second mode are maintained. Therefore, during this period, the transistor Tr1 is continuously ON, the transistor Tr4 is continuously OFF, and the transistors Tr5 and Tr6
Is ON, a DC voltage for driving the electric motor is applied to the terminal 11 via the transistor Tr1. That is, since a DC voltage is applied to the terminal 11 during the period I, a change in the back electromotive force cannot be detected, and the voltage at the terminal 11 becomes the voltage level of the DC power supply. In the period II, the third mode is maintained. Therefore, since the transistors Tr1 and Tr4 are continuously OFF, the terminal 11 is substantially open and the stator winding U is non-conductive. That is, since the input impedance of the comparator CMP shown in FIG. 1 is sufficiently high, a change in the back electromotive force generated in the stator winding U can be detected at the terminal 11 in accordance with the rotation of the rotor. The intersection of the back electromotive force and the neutral point voltage is point E in this period. As shown in FIG. 2, the output of the comparator CMP is inverted at the point E.

In the period III, the fourth mode and the fifth mode are maintained. Therefore, in this period, the transistor Tr1 is continuously OFF, and the transistor Tr4
Are continuously ON and the transistors Tr2, T
Since either of r3 is ON, the terminal 11 is connected to the minus side of the DC voltage for driving the electric motor via the transistor Tr2 or Tr3. That is, in the period III, since a DC voltage is applied to the terminal 11, a change in the back electromotive force cannot be detected, and the voltage at the terminal 11 becomes a negative voltage of the DC power supply.

In the period IV, the sixth mode is maintained. Therefore, since the transistors Tr1 and Tr4 are continuously OFF, the terminal 11 is substantially open and the stator winding U is non-conductive. That is,
Since the input impedance of the comparator CMP is sufficiently high, a change in the back electromotive force generated in the stator winding U can be detected at the terminal 11 in accordance with the rotation of the rotor. The intersection of the back electromotive force and the neutral point voltage is point F in this period. FIG.
As shown in the figure, the output of the comparator CMP is inverted at the point F.

During the period II and the period IV, the polarity of the magnet changes due to the rotation of the rotor, and the direction of change of the back electromotive force is reversed between negative and positive.

In FIG. 4, T1, T2, and T3 are referred to as a reversal time, a restart time, and a standby time, respectively.
As can be seen from this figure, the time T1 + T3 is the time from the start of the period II to the point E, and the time T2 is the time from the point E to the end of the period II. T2 time after the point E (when the output of the comparator CMP is inverted), the current supply mode to the stator winding is changed from the third mode to the fourth mode. The point of the present invention is that the current supply mode to the stator winding is changed after T2 time from the inversion of the output of the comparator.

As can be seen from the second d, the comparator C
When MP is used, each of the energizing modes (first mode to sixth mode)
Mode), the output of the comparator changes once. That is, in the first mode, E2 point,
Point F1 in the second mode, point E in the third mode, fourth point
The mode is the F2 point in the mode, the E1 point in the fifth mode, and the F point in the sixth mode.

Therefore, in the current energizing mode,
By repeating the operation of changing the energization mode to the next energization mode after T2 time from the time when the output of the comparator is inverted, the energization mode changes continuously, and the rotor of the electric motor can be rotated.

The time of T1, T2 and T3 is logically (when there is no load) (T1 + T3) = T2. That is, as can be seen from FIG. 2, the time when the output of the comparator is inverted is an intermediate time in each mode. However, when the load is actually driven by the electric motor, (T1 + T3)> T2, as can be seen from FIG. That is, (T1 + T
3) = kT2. The value of k is set to an optimum value according to the size of the load connected to the motor, the number of rotations of the motor, the operating efficiency of the motor in terms of structure, and the like. At the time of actual operation, a value obtained according to the magnitude of the load or the like is corrected based on the actual rotation speed and used. As a result, the operation efficiency of the motor during acceleration or deceleration can be improved. K is a value in a range in which T2 is set substantially equal to T1 and equal to or less than T1. The time T2 is calculated by the microcomputer 8 based on the time T1 + T3.

Therefore, the time of T2 is the time of T1 + T3,
That is, if the time from the start of energization in the current mode to the change of the output of the comparator is obtained, the time T2 can be obtained. The time from the start of the current mode until the output of the comparator changes is measured by a built-in timer of the microcomputer 8. The microcomputer 8 changes the energization mode by turning on / off the transistors.
Since the FF combination is changed, the microcomputer stores the start time of the energization mode, and the change of the output of the comparator can be known by the change of the voltage of the input ports 11 to 13 of the microcomputer 8. The computer 8 can measure the time.

T3 is a standby time, which is used when the motor is started, and has an initial value set when the motor is started. When the motor is stopped, the rotor is not rotating and no back electromotive force is generated. That is, since the output of the comparator does not change and the time cannot be obtained, the value is set in a pseudo manner. Therefore, the T3 time is 0 after the start of the motor. That is, in the steady state, T2
= KT1 holds.

Next, the operation at the time of startup will be described. T
The time 3 needs to be longer as the output of the electric motor is larger, and it is necessary to shorten the time as the designed rotation speed at the time of starting is higher. That is, it is necessary to set an optimum value for each motor. In the following description, the standby time T3 is temporarily set to one second. When energization is started, the time from the start of the energization mode until the output of the comparator changes (T
1 + T3) is secured for at least one second or more. When the change in the output of the comparator cannot be detected, the upper limit value of T1 is used, and (T1 + T3) = 1 + α
As described above, even when a change in the output of the comparator cannot be detected, the time T2 can be obtained by calculation as described above. At this time, when the timing of the time T1 reaches the upper limit value, for example, the time at the point E is reached, and the timing of the time T2 is started. Therefore, the energization mode can be changed to the next mode at the end of the time measurement of the T2 time. A state in which a change in the output of the comparator cannot be detected corresponds to a state in which the rotor is not rotating. In this way, when the motor is started, the energization mode changes even if the rotor does not rotate. This state is continued until the stop rotation position of the rotor and the energization mode match (at most within 6 energization modes). Generally, in a DC motor, the rotor does not rotate unless an appropriate energization mode is made to correspond to the rotation angle of the rotor (distribution of the magnetic field by the permanent magnet). In other words, when the motor is started, the rotor does not start unless the rotational position of the rotor matches the energization mode. In the present invention, the energization mode is forcibly changed until the rotational position of the rotor matches the energization mode.
The time for changing the energization mode is set based on T3.

Hereinafter, a description will be given of a period from when the rotation position of the rotor coincides with the energization mode and when the rotor starts rotating to when the rotor shifts to a steady state (end of startup). From the start of energization in this mode, the timer starts measuring the time T3, and the time T from the time UP of the time T3 to the point E (the output of the comparator changes).
Measure 1. At the time of point E, time measurement of T2 starts, and T
The current supply mode is changed to the next mode after a time UP of 2 hours. Thereafter, this operation is repeated while decreasing the value of T3.

FIG. 5 is a flowchart showing the operation when the above operation is adopted in an actual motor. In the flowchart on the left side of FIG. 5, first, initial setting (initial setting of the microprocessor) is performed, and then the transistor is energized in mode 1 (first energizing mode). Next, timer processing described later is performed, and then the transistor is energized in mode 2 (second energizing mode). Then, a timer process described later is performed to energize the transistor in mode 6 (sixth energization mode). ………. The operation of changing the energization mode after performing the timer process in this manner is repeated thereafter. In the flowchart of the timer processing shown on the right side of FIG. 5, first, the timer T3 starts counting time to secure the time T3. Then, when the timer T3 ends after the time T3 has elapsed, the timer T1 starts counting. Then, the time T1 of the input of the comparator (until the output of the comparator changes) is measured. At this time, T
3 = (T3-1) is performed to reduce the value of T3. (T3 = 1
Second = 1000 msec. Also, the subtraction amount is not limited to 1 and is 20
It may be in the 50th place. Note that an upper limit value (about three times the time period T3) is set for the time counted by the timer T1, and when there is no input from the comparator, the timer T1 ends counting at this upper limit value and the next step. Proceed to. Therefore, the timer T2 is started to measure the time either by the input from the comparator or by the end of the timer T1. The time measured by the timer T2 is calculated by the microprocessor by multiplying the time measured by the timer T1 (or the upper limit time of the timer T1) by k, and is set in the timer T2. At the time of start-up, it is preferable that the time of T2 be shorter than at the time of steady state to advance the phase of the rotating magnetic field with respect to the rotation of the rotor.
Therefore, by setting the time of T2 to kT1 (not k (T1 + T3)), it is possible to change the amount of phase advance between the startup and the steady state without changing the value of k. That is, the time T2 is shortened by the addition of the time T3, and the phase of the rotating magnetic field can be advanced. When the counting of the timer T2 ends, the timer processing ends, and the energizing mode for the transistor is changed to the next energizing mode.

In the flowchart shown in FIG. 5, the time T3 is subtracted even before the rotor starts rotating. However, the amount of the subtraction is smaller than the value of T3, and this subtraction is performed at most six times. Since the predetermined energization time is always secured in each energization mode, there is no problem at the time of actual startup, and the flowchart can be simplified.

Since the energization mode is switched in this way, the standby time T3 is gradually reduced with the start-up, and the rotor 7
The standby time T3 becomes zero by the time when the rotation becomes a steady speed. Further, after the motor is started, the speed of the rotor 7 gradually increases until the rotation speed reaches the steady rotation speed, so that the time T1 until the potential direction change point E at which the direction of the back electromotive force generated in the winding of the stator changes, that is, The restart time T2 also becomes shorter and shorter, so that the energization time (T1 + T2 + T3) to the winding in each mode is determined by the time that gives the rotating speed at which the magnitude of the load applied to the rotor and the current flowing through the winding are balanced. Each phase 120
Forward rotation for 60 ° rotation, pause for 60 ° rotation, 120 °
The cycle of the reverse direction energization for the rotation and the pause for the 60 ° rotation is repeated.

In the above description, the energization of the motor was performed by continuous energization as shown in FIG. 2 for the sake of simplicity. However, in practice, a chopping waveform (PWM) as shown in FIG. 6 or FIG. (A waveform based on the theory).

[0051]

In the brushless motor configured as described above, since the potential of the capacitor C1 changes according to the duty of the chopped voltage waveform, the reference voltage can be corrected according to this voltage.

That is, the reference voltage can be corrected to be high where the duty of the voltage waveform is small, and the deviation of the position detection signal can be corrected.

[0053]

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram showing a main part of an embodiment of the present invention.

FIG. 2 is a timing chart showing ON / OFF conduction waveforms of transistors.

FIG. 3 is an electric circuit diagram showing an embodiment of the entire electric motor to which the present invention is applied.

FIG. 4 is an explanatory diagram of ignition timing control.

FIG. 5 is a flowchart illustrating an example of control according to the present invention.

FIG. 6 is a waveform diagram of energization of an electric motor.

FIG. 7 is a waveform diagram of energization of an electric motor.

[Explanation of symbols]

 7 Rotor 8 Microcomputer CMP comparator

──────────────────────────────────────────────────の Continued on the front page (72) Inventor Hirotaka Murata 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Inventor Mitsuru Toyoda 2-5-2 Keihanhondori, Moriguchi-shi, Osaka No. 5 Sanyo Electric Co., Ltd. (72) Inventor Hisashi Tokizaki 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (56) References JP-A-3-198688 (JP, A) JP-A-6-261159 (JP, A) JP-A-1-321189 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02P 6/18

Claims (2)

(57) [Claims] An electric motor comprising a rotor which rotates with magnetism and a plurality of stator windings for forming a magnetic field for rotating the rotor, supplies DC power to respective stator windings. In a brushless motor controlled to rotate a rotor, a means for forming a DC voltage supplied to a stator winding into a predetermined switching voltage waveform, an induced voltage generated in the stator winding due to rotation of the rotor and a reference voltage. Comparing means for comparing the magnitude with the voltage, energizing control means for controlling energization to the stator winding based on the comparison result of the comparing means, and ON of the voltage waveform
Bei and correcting means for correcting so as to increase as said reference voltage said width decreases in accordance with the width of the duty
The DC power applied to the stator winding is chopped.
The reference voltage is corrected according to the distortion of the induced voltage when
It is possible to prevent a time lag of the output inversion of the comparing means due to this distortion.
Brushless motor, characterized in that that. 2. An electric motor comprising a rotor which rotates with magnetism and a plurality of stator windings forming a magnetic field for rotating the rotor, supplies DC power to respective stator windings. In a brushless motor controlled to rotate a rotor, a means for forming a DC voltage supplied to a stator winding into a predetermined switching voltage waveform, an induced voltage generated in the stator winding due to rotation of the rotor and a reference voltage. Comparison means for comparing the magnitude with the voltage, energization control means for controlling energization to the stator winding based on the comparison result of the comparison means, and a current control means obtained based on all terminal voltages of the stator winding. Correction means for correcting the reference voltage with a smoothed voltage, and applying the voltage to the stator winding.
Of induced voltage when chopping DC power
The reference voltage is corrected in accordance with the
A brushless motor characterized by preventing a time lag of output reversal .