JPH06269192A - Dc brushless motor - Google Patents

Abstract

PURPOSE:To provide a DC brushless motor which can be driven with high efficiency without requiring any position detecting element. CONSTITUTION:The DC brushless motor comprises a frequency generator 1 generating frequency signals for a plurality of phases in proportion to the r.p.m. of a rotor 20, a circuit 3 for detecting the rotational direction of the rotor 20 based on the frequency signals for the plurality of phases and outputting a directional signal, a circuit 4 for counting the number of pulses of at least one frequency signal generated from the frequency generator 1 depending on the directional signal, a phase detection circuit 10 outputting a phase signal corresponding to the phase of voltage or current of at least one phase of stator winding having a plurality of phases, a phase regulation circuit 5 for adding/ subtracting the count of the count circuit 4 by a predetermined value corresponding to the rotational direction command and outputting a command value obtained through regulation depending on a phase signal, and a circuit 6 generating waveform signals for the plurality of phases corresponding to the command value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless DC motor which does not require a position detecting element for detecting the rotational position of a permanent magnet rotor.

[0002]

2. Description of the Related Art A brushless DC motor has a longer life and less electrical noise than a DC motor with a brush because it has no mechanical contacts. Therefore, in recent years, it has been widely applied to industrial equipment and video / audio equipment that require high reliability.

Conventionally, this type of brushless DC motor has been
A position detecting element (for example, a hall element) corresponding to a brush is used for switching the energizing phase of the stator winding. However, the position detection element itself is not inexpensive at all, and the brushless DC motor has a drawback that the cost is significantly increased as compared with the brushed DC motor due to the complexity of adjusting the mounting position of the element and the increase in the number of wires. Also,
Since the position detection element has to be mounted inside the motor, structural restrictions of the motor often occur. In recent years, the motors used have become smaller and thinner along with the downsizing of equipment, and the actual situation is that there is no room for mounting a position detecting element such as a Hall element. Therefore, some brushless DC motors having no position detecting element such as a Hall element have been proposed.

As a brushless DC motor having no position detecting element of this kind, there is a brushless DC motor which utilizes an output pulse of a frequency generator attached to the motor. The counter counts the output pulses of a frequency generator that generates pulses according to the rotation of the rotor, and the driving current of a preset current pattern corresponding to the count value is applied to the three-phase stator winding. In order to rotate the permanent magnet rotor (see, for example, JP-A-63-262088).

[0005]

However, in the above structure, the initial position of the rotor cannot be known when the power is turned on. Therefore, in the brushless DC motor shown in the above-mentioned prior art, a special reset signal generation circuit is provided, and when the power is turned on, the counter is reset by using the reset signal, and at the same time, a predetermined reset current is supplied to the stator winding. In advance, the rotor and the stator winding are arranged in a predetermined positional relationship.

However, when a predetermined reset current is supplied to the stator winding in order to determine the initial position, the rotor starts to rotate and the position of the rotor becomes oscillatory around the predetermined position, so that the predetermined position is maintained for a short time. Does not stand still. Therefore, from the reset mode in which a predetermined reset current is supplied to the stator winding when the power is turned on and the rotor is stopped at a predetermined position, a regular generator that counts the output pulse of the frequency generator according to the rotation of the rotor is used. It cannot move to the position detection mode in a short time. As a result, there is a problem that the startup time becomes long.

Therefore, the brushless DC motor shown in the prior art cannot be used for applications where it is necessary to start up in a short time by frequently repeating rotation and stop.

Further, in the brushless DC motor shown in the above-mentioned prior art, in order to detect the initial position of the rotor when the power is turned on, a reset current is supplied to the stator winding to rotate the rotor and the stator winding. Even if the and are configured to have a predetermined positional relationship, when the rotor is under a load, the positional relationship between the rotor and the stator winding largely changes depending on the magnitude of the load. Therefore, the rotor cannot be fixed at a predetermined position in the reset mode.

Therefore, in the brushless DC motor shown in the above-mentioned prior art, the mode is changed from the reset mode to the normal position detection mode in which the output pulse of the frequency generator is counted according to the rotation of the rotor. However, since the phase of the current supplied to the stator winding deviates greatly from the normal phase, highly efficient driving cannot be realized.

Therefore, the brushless DC motor shown in the prior art has a problem that it can be applied only to applications where the motor is in a no-load state when the power is turned on.

Further, as shown in the above-mentioned prior art, the counter counts the output pulses of the frequency generator that generates the pulses according to the rotation of the rotor, and the drive currents corresponding to the counted values are divided into three phases. In a brushless DC motor that sequentially energizes the stator windings of the above to rotate the permanent magnet rotor, when noise is superimposed on the output of the frequency generator for some reason during continuous driving, an error occurs in the count value of the counter. This counting error reduces the motor efficiency and increases the torque ripple. Further, if the count error accumulates, it may cause a worst case of stopping the motor, and the brushless DC motor described in the above-mentioned prior art has a problem of lack of reliability.

According to the present invention, the positional relationship between the rotor and the stator winding when the power is turned on can be detected in a short time.
An object of the present invention is to provide a brushless DC motor capable of promptly switching from a phase matching mode when the power is turned on to a normal position detection mode performed by counting output pulses output according to the rotation of a rotor.

Further, the present invention is a brushless DC motor capable of detecting the position of the rotor with extremely high accuracy regardless of the magnitude of the load even when the motor is already under load when the power is turned on. The purpose is to provide.

Further, according to the present invention, the phase of the induced voltage induced in the stator winding while the motor is normally rotating and the phase of the current supplied to the stator winding of each phase match. An object of the present invention is to provide a brushless DC motor that can always drive a motor with high efficiency by performing a phase correction process.

[0015]

In order to solve the above problems, a brushless DC motor according to the present invention comprises a frequency generator that generates frequency signals of a plurality of phases proportional to the number of revolutions of a permanent magnet rotor, and a plurality of the frequency generators. Direction detecting means for detecting the rotation direction of the permanent magnet rotor from the phase frequency signal and outputting a direction signal, and the number of pulses of at least one frequency signal of the frequency generator is up-counted or down-counted according to the direction signal. Counting means, waveform generating means for generating a plurality of phase waveform signals according to the count value of the counting means, and electric power is supplied to the stator windings according to the plurality of phase waveform signals to generate a rotating magnetic field. The power supply means, the initial position detection means for detecting the initial position of the magnetic poles of the permanent magnet rotor by rotating the rotating magnetic field in the forward and reverse directions, and the multi-phase stator winding Detecting means for detecting the current phase or the phase of the induced voltage induced in the stator winding, and the phase of the rotating magnetic field is shifted from the initial position in the forward or reverse direction by a predetermined value according to the rotation direction command. And a phase adjusting means for correcting the phase of the current applied to the stator winding and the induced voltage induced in the stator winding according to the output of the phase detecting means, and the stator is generated when the power is turned on. Rotate the rotating magnetic field in the forward and reverse directions to match the initial phase of the permanent magnet rotor so that during normal rotation, the phase of the current flowing in the stator winding and the phase of the induced voltage induced in the stator winding will always match. It is equipped with a configuration for phase correction.

[0016]

According to the present invention, the brushless DC motor of the present invention has the above-described structure, and the output pulse of the frequency generator generated according to the rotation of the rotor is counted by the counting circuit. Since the position signal is created based on the count value, the position detecting element required in the conventional brushless DC motor is not necessary. Therefore, the complexity of adjusting the mounting position of the element and the number of wires are reduced, and the cost of the motor is significantly reduced. Furthermore, because it is not necessary to mount a position detection element inside the motor, the motor is not constrained by the structure and can be made compact.
Thinning is possible.

Further, during normal rotation, the phase is constantly corrected so that the phase of the current applied to the stator winding and the phase of the induced voltage induced in the stator winding match, so the motor can be driven with high efficiency. Becomes

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A brushless DC motor according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the structure of a brushless DC motor according to an embodiment of the present invention. In FIG. 1, 20 is a permanent magnet rotor and 11, 12, 13 are three-phase stator windings. Reference numeral 1 is a frequency generator, which generates two-phase frequency signals m1 and m2 having different phases proportional to the rotation of the permanent magnet rotor 20. The two-phase frequency signals m1 and m2 are input to the waveform shaping circuit 2 and converted into rectangular wave signals s1 and s2, and then input to the direction detection circuit 3. The direction detection circuit 3 outputs a direction signal d according to the forward and reverse rotation directions of the permanent magnet rotor 20. Reference numeral 4 denotes a count circuit, which receives the rectangular wave signal s1 output from the waveform shaping circuit 2 and the direction signal d output from the direction detection circuit 3 and generates a pulse of the rectangular wave signal s1 generated according to the rotation of the permanent magnet rotor 20. The number is counted up or down depending on the direction of rotation. Reference numeral 8 denotes an initial position detection circuit, which receives the count value c of the counting circuit 4 and rotates the rotating magnetic field generated by the stator in the forward and reverse directions during phase matching to obtain the initial position of the permanent magnet rotor. Counting circuit 4
Output to. The initial position detection circuit 8 not only outputs the initial value q to the count circuit 4, but also outputs the address command b to the selection circuit 9 during phase matching. Reference numeral 10 denotes a phase detection circuit, which compares the magnitudes of the two-phase voltages applied to the stator windings 11, 12, and 13 and outputs a phase signal g. Reference numeral 5 denotes a phase adjustment circuit, which adds or subtracts a predetermined value from the count value c of the count circuit 4 in accordance with the direction command r input to the input terminal 14, and outputs the phase signal g output from the phase detection circuit 10. After performing the phase correction accordingly, the address signal a is output to the selection circuit 9. The selection circuit 9 selects either the address signal a or the address command b according to the phase adjustment command t input to the terminal 15 and outputs the address f to the waveform generation circuit 6. The waveform generation circuit 6 includes a selection circuit 9
Position signals p1 and p of three phases according to the address f output by
2 and p3 are output. A power supply circuit 7 amplifies the input three-phase position signals p1, p2, p3,
The current i proportional to the magnitude of the position signals p1, p2, p3
1, i2 and i3 are respectively connected to stator windings 11, 12, 13
Supply to.

The operation of the brushless DC motor of the present invention will be described in detail with reference to the embodiment constructed as described above.

First, the case where the permanent magnet rotor 20 is rotating in a normal state will be described. 2 is a circuit configuration diagram of an embodiment of the direction detection circuit 3, and FIG. 3 shows a signal waveform diagram of each part thereof.

In FIG. 2, reference numeral 21 is a data input type flip-flop circuit to which the two-phase rectangular wave signals s1 and s2 output from the waveform shaping circuit 2 are input. The rectangular wave signal s1 is input to the data input terminal D of the flip-flop circuit 21, and the rectangular wave signal s2 is input to the clock input terminal CK.

FIG. 3 (a) shows the waveforms of the rectangular wave signals s1 and s2 when the permanent magnet rotor 20 is rotating in the positive direction, and FIG. The waveforms of the rectangular wave signals s1 and s2 when rotating in the direction are shown.
The data input type flip-flop circuit 21 receives the rising edge of the signal input to the clock input terminal CK at each rising edge.
Since the state of the data input terminal D is held and the state is output from the output terminal Q, when the permanent magnet rotor 20 is rotating in the positive direction as shown in FIG. The output Q of the pull-up circuit 21 is always in a high potential state (hereinafter referred to as "H" state). On the other hand, when the permanent magnet rotor 20 is rotating in the opposite direction, the phase of the rectangular wave signal s1 lags behind the rectangular wave signal s2 by 90 degrees as shown in FIG. (Less than,"
This is called the L "state).

As is clear from the above, the direction of rotation of the permanent magnet rotor 20 can be detected by the direction detection circuit 3 of FIG. That is, the direction signal d output from the direction detection circuit 3 is in the "H" state when the permanent magnet rotor 20 is rotating in the forward direction, and is in the "L" state when rotating in the reverse direction. Becomes The rectangular wave signal s1 output from the waveform shaping circuit 2 and the direction signal d from the direction detection circuit 3 are input to the count circuit 4, and the count circuit 4 receives the direction signal d.
The rectangular wave signal s1 is up-counted or down-counted according to That is, the number of pulses of the rectangular wave signal s1 generated according to the rotation of the permanent magnet rotor 20 is up-counted or down-counted according to the rotation direction. The amount of rotational movement can be obtained. However, the count circuit 4 is undefined in the initial state when the power is turned on,
The method of giving the initial value will be described in detail in the phase matching operation described in FIGS. 10 and 11.

FIG. 4 is a circuit configuration diagram of an embodiment of the phase detection circuit 10, and FIG. 5 shows a signal waveform diagram of each part thereof.

In FIG. 4, reference numeral 31 denotes a comparator, which is a comparator 3.
The two input terminals 1 are connected to both ends of the stator winding 11. The stator winding 11 is connected to the non-inverting input (+) of the comparator 31.
Of the three-phase stator windings 11, 12, and 13 is connected to the inverting input (-) of the comparator 31. The comparator 31 outputs a phase signal g corresponding to the phase voltage of the stator winding 11 to the phase adjustment circuit 5.

In FIG. 5, a shows the respective voltage waveforms of the three-phase terminal voltages v1, v2, v3 when the permanent magnet rotor 20 is rotating. The terminal voltage v1 is connected to the non-inverting input (+) of the comparator 31, the three-phase stator winding 11,
Since the neutral points O of 12 and 13 are connected to the inverting input (-) of the comparator 31, the comparator 31 has detected the sign of the phase voltage generated in the stator winding 1. As is clear from the waveform b, the rising edge of the phase signal g coincides with the zero cross point with the neutral point potential O of the terminal voltage v1. That is, the phase signal g output from the phase detection circuit 10 outputs the timing of the zero-cross point of the phase voltage of one phase of the stator windings 11, 12, and 13. The phase of the phase voltage on line 11 can be detected. The operation performed based on the phase signal g will be described in detail in the phase correction operation described in FIGS. 12 and 13.

First, the operation when the brushless DC motor of the present invention is rotating in a steady state will be described.

FIG. 6 is a signal waveform diagram of each part during steady rotation of the brushless DC motor of the present invention. In FIG. 6, a is the waveform of the induced voltages e1, e2, e3 induced in the stator windings 11, 12, 13, respectively. b is a three-phase position signal p1, p2, p3 generated by the waveform generation circuit 6, which is output according to the rotational position of the permanent magnet rotor 20,
It has the same phase as the induced voltages e1, e2, e3. c
Is supplied to each phase of the stator windings 11, 12, 13
The phase drive currents i1, i2, i3 are used to generate a sinusoidal position signal p
1, p2 and p3 are amplified by the power supply circuit 7, respectively. d is the terminal voltage v1, v2, v3 of each phase of the stator windings 11, 12, 13 and
Induced voltages e1 and e induced in 12 and 13 respectively
2 and e3 are waveforms in which a voltage drop due to the winding resistance generated by the drive currents i1, i2, and i3 flowing in each phase (a portion in which only the voltage waveform v1 is shaded) is combined.

As is apparent from FIG. 6, the induced voltage e1,
e2, e3, position signals p1, p2, p3, drive current i
1, i2, i3 and terminal voltages v1, v2, v3 are all in phase, and when the induced voltages e1, e2, e3 and drive currents i1, i2, i3 are in phase, the motor is driven with maximum efficiency. . A rotating magnetic field is generated in the stator windings 11, 12, 13 by the three-phase drive currents i1, i2, i3, and the magnetic poles of the permanent magnet rotor 20 and the stator windings 11, 1 are generated.
By the interaction with the rotating magnetic field generated by 2 and 13,
The permanent magnet rotor 20 receives a rotational force and starts rotating.

FIG. 7 is a vector diagram showing the phase relationship between the magnetic poles of the permanent magnet rotor 20 and the rotating magnetic fields generated by the stator windings 11, 12, and 13. In FIG. 7, Φ is a magnetic pole vector indicating the magnetic pole of the permanent magnet rotor 20, I is a magnetomotive force vector indicating the rotating magnetic field generated by the stator windings 11, 12, and 13, and E is the stator windings 11, 12, and 13 is an induced voltage vector indicating an induced voltage induced in No. 13.

In FIG. 7A, the motor is in the forward direction (clockwise direction).
7B is a vector diagram showing that the motor is rotating in the reverse direction (counterclockwise direction), and the magnetomotive force vector I and the magnetic pole vector Φ are shown respectively. Rotate in the direction. As is clear from the figure,
In order to rotate the permanent magnet rotor 20 continuously, the phase of the magnetomotive force vector I generated in the stator windings 11, 12, 13 is always 90 degrees from the phase of the magnetic pole vector Φ of the permanent magnet rotor 20. Just proceed in the direction of rotation. That is, the magnetomotive force vector I may be advanced by 90 degrees in the clockwise direction to rotate in the positive direction, and the magnetomotive force vector I may be advanced by 90 degrees in the counterclockwise direction to rotate in the opposite direction.

As is apparent from FIG. 7, the magnetomotive force vector I and the induced voltage vector E are in phase with each other regardless of the rotation direction of the motor. In this state, the motor will be driven with maximum efficiency.

The operation of each part of the embodiment of the present invention that performs such signal processing will be described in detail.

FIG. 8 is a block diagram showing an embodiment of the phase adjusting circuit 5, the waveform generating circuit 6, the initial position detecting circuit 8 and the selecting circuit 9 which constitute the brushless DC motor of the present invention.

In this embodiment, the phase adjusting circuit 5, the waveform generating circuit 6, the initial position detecting circuit 8 and the selecting circuit 9 are the arithmetic unit 6
1, memory 62, and digital / analog converters 63 and 6
4, 65. The arithmetic unit 61 operates according to a predetermined internal program stored in a ROM (Read Only Memory) area of the memory 62, and a direction command r input to the terminal 14 and a phase adjustment command t input to the terminal 15 are operated. Then, the phase signal g output from the phase correction circuit 10 and the count value c of the count circuit 4 are taken into a RAM (random access memory) area, and a predetermined calculation is performed to obtain an address f. Next, the computing unit 61 refers to the function table of the sine wave for one cycle, which is stored in advance in the ROM area of the memory 62, according to the address f, and thereby the three-phase digital position signal dp1 corresponding to the address f. , Dp
2 and dp3 are obtained and output to the digital / analog converters 63, 64 and 65, respectively. The digital / analog converters 63, 64, 65 convert the three-phase digital position signals dp1, dp2, dp3 into analog values and output three-phase position signals p1, p2, p3.

Next, a built-in program stored in the ROM area of the memory 62 will be described.

First, the normal mode in which processing is performed during normal rotation will be described with reference to the basic flow chart shown in FIG.

In process 71, the count value c of the count circuit 4
Waiting for an interrupt when it changes. When an interrupt occurs, the process proceeds to process 72.

In the process 72, the count value c of the count circuit 4
And the direction command r input to the terminal 14 are fetched and the memory 6
2 RAM area.

In process 73, it is determined whether the direction command r is a forward direction command or a reverse direction command. When the direction command r is a forward direction command, a predetermined value (corresponding to 90 degrees in terms of phase) is added to the count value c of the count circuit 4 in step 74 to calculate the address f. When the direction command r is a reverse direction command, a predetermined value (corresponding to 90 degrees in terms of phase) is subtracted from the count value c of the counting circuit 4 to calculate the address f. Processes 71, 72, 73, 74, and 75 are arithmetic processes performed by the phase adjustment circuit 5.

The processing 76 is based on the address f obtained in the processing 74 or the processing 75, and the required 3 in the next processing 77.
The phase addresses f1, f2, f3 are determined.

That is, since the phases of the position signals p1, p2 and p3 are shifted by 120 degrees (FIG. 6), and from the following (Equation 1), (Equation 2), (Equation 3), f
The respective address values of the three phases of 1, f2 and f3 are calculated.

[0044]

[Equation 1]

[0045]

[Equation 2]

[0046]

[Equation 3]

In (Equation 1) and (Equation 2), (12
The value 0) is an address count value equivalent to 120 degrees when converted into a phase.

In process 77, the RO of the memory 62 is RO based on the three-phase address values f1, f2 and f3 obtained in process 76.
Referring to the sine wave function table stored in the M region, the three-phase digital position signals dp1, dp2, dp3
Ask for.

In process 78, the three-phase digital position signals dp1, dp2, dp3 obtained in process 77 are output to the digital / analog converters 63, 64, 65 shown in FIG. Digital / analog converters 63, 64, 65
Converts the digital position signals dp1, dp2, dp3 into analog values, and outputs the position signals p as shown in FIG.
1, p2 and p3 are output. Processes 76, 77 and 78 are arithmetic processes performed by the waveform generation circuit 6. After this process,
The process moves to process 71 and the above process is repeated.

By performing the above processing in the phase adjusting circuit 5 and the waveform generating circuit 6, the position signals p1, p2 and p3 are output to the power supply circuit 7 according to the rotation of the permanent magnet rotor 20. The power supply circuit 7 supplies the stator windings 1, 12, 13 with sinusoidal drive currents i1, i2, i3. That is, the amount of rotation of the permanent magnet rotor 20 is detected, and the magnetic field generated by the stator windings 11, 12, and 13 is rotated by that amount of rotation. As a result, the stator windings generate a rotating magnetic field, and the magnetomotive force vector I of the rotating magnetic field causes the permanent magnet rotor 2 to rotate.
As shown in FIG. 7, the magnetic pole vector Φ of 0 is always formed so as to have a phase difference of 90 degrees. Then, due to the interaction between the magnetic pole vector I and the magnetic pole vector Φ, the permanent magnet rotor 20 receives the rotational force and continues to rotate.

However, the count value of the count circuit 4 is indefinite in the initial state such as power-on, and it is necessary to give the initial value cs of the count value.

Next, the phase matching operation for giving the initial value to the counting circuit 4 in the brushless DC motor of the present invention will be described in detail.

When the power is turned on, the terminal 1 of the selection circuit shown in FIG.
A phase alignment command t is input to 5, and an output b of the initial position detection circuit 8 is selected and input to the waveform generation circuit 6 as an address f. Then, the initial position detection circuit 8 forcibly rotates the rotating magnetic fields generated by the stator windings 11, 12, and 13 in the forward and reverse directions, and the magnetic poles of the permanent magnet rotor 20 and the stator windings 11 and 12 are rotated. , 13 to detect the phase relationship with the rotating magnetic field.

FIG. 10 shows the relationship between the magnetic pole vector Φ generated by the permanent magnet rotor 20 and the magnetomotive force vector I generated by the stator windings 11, 12, 13 in order to explain the phase matching operation of the present invention. It is a vector diagram represented by a vector.

At the time of phase matching, the selection circuit 9 inputs the address command b of the initial position detection circuit 8 to the waveform generation circuit 6, so the address f input to the waveform generation circuit 6 is not the rotation of the permanent magnet rotor 20. Forced to change regardless of
The direction of the magnetomotive force vector Φ of the stator winding is changed accordingly. As a result, the magnetic pole vector I and the magnetic pole vector Φ
Due to the interaction with the permanent magnet rotor 20, the permanent magnet rotor 20 receives a rotational force and accordingly starts to move. Assuming that the motor is unloaded, the magnetomotive force vector I and the magnetic pole vector Φ
And are exactly the same (at that time, the torque generated by the motor is zero). The situation is shown in FIG.

However, when the motor is in a loaded state, the magnetomotive force vector I and the magnetic pole vector Φ do not match, and a certain phase angle θ is maintained according to the magnitude of the load. Moreover, the direction of the phase shift is such that when the motor is rotated in the forward direction (clockwise direction), the magnetic pole vector Φ is as shown in FIG.
Deviates from the magnetomotive force vector I in the counterclockwise direction by an angle θ,
When the motor is rotated in the opposite direction (counterclockwise),
As shown in FIG. 10C, the magnetic pole vector Φ is displaced from the magnetomotive force vector I by the angle θ in the clockwise direction. However, since the count circuit 4 counts up or counts down the rectangular wave signal s1 according to the direction signal d, it means that the rotation amount of the permanent magnet rotor 20 from the initial value is always detected. . Now, assuming that the initial value of the count circuit 4 is cs and the magnetomotive force vector I of the stator winding is rotated in the positive direction by Δf, the count value of the count circuit 4 is

[0057]

[Equation 4]

It becomes However, h is converted to the phase in Fig. 1.
It is a count value corresponding to a phase angle θ of 0.

If the magnetomotive force vector I of the stator winding is rotated in the opposite direction by Δf, the count value of the counting circuit 4 becomes

[0060]

[Equation 5]

It becomes Therefore, the initial value of the count circuit 4 is given by the following equations (4) and (5):

[0062]

[Equation 6]

It can be calculated by Regarding the operation of one embodiment of the present invention that performs such phase matching processing,
This will be described in more detail.

The phase matching mode in which the phase matching process is performed will be described with reference to the flowchart shown in FIG.

In FIG. 11, in the process 91, the address f input to the waveform generating circuit 6 is incremented by 1, and the process 9 is performed.
Move to 2. The initial value of the address f at the time of phase matching is zero.

In the process 92, it is determined whether the address f exceeds the predetermined value Δf. When the address f is within Δf,
The process shifts to the process 91 again, and the address f is further increased by 1. When the address f exceeds Δf, the process 93 is entered.

In the process 93, the count value c of the count circuit 4
Is taken in and RA is stored in the memory 62 as the first count value c1.
After storing in the M area, the processing shifts to the processing 94.

In process 94, the address f input to the waveform generating circuit 6 is decremented by 1 this time, and the process shifts to process 95.

In process 95, it is determined whether the address f exceeds -Δf. When the address f is within -Δf, the processing shifts to the processing 94 again, and the address f is further decreased by 1. Then, when the address f exceeds −Δf, the processing shifts to processing 96.

In process 96, the count value c of the count circuit 4
Is stored in the memory 62 as the second count value c2.
After storing in the M area, the processing shifts to the processing 97.

In process 97, the first count value c1 and the second count value c2 obtained in process 93 and process 96, respectively.
Based on the above, the calculation of (Equation 6) is performed to obtain the initial value cs of the count circuit 4. After the calculation process of process 97 ends, process 98
Move to.

In process 98, c obtained by the calculation of process 97
The value s is transferred to the count circuit 4 as an initial value.

The above processings 91 to 98 are generated by the magnetic pole vector Φ of the permanent magnet rotor 20 and the stator windings 11, 12 and 13 in the operation of the phase matching mode in the initial state when the power is turned on. The phase matching of the magnetomotive force vector I is completed (FIG. 10A).

After the phase matching is completed, the normal mode described with reference to FIG. 9 is entered to rotate the permanent magnet rotor 20.

Next, a detailed description will be given of the phase correction operation performed during normal rotation in the brushless DC motor of the present invention.

FIG. 12 shows the induced voltages e1, e2, e3 induced in the stator windings 11, 12, 13 and the voltage of each part when the drive currents i1, i2, i3 applied to each phase are out of phase. Current waveform and phase signal g output from the phase detection circuit 10
It is the waveform diagram which showed.

In FIG. 12, a is a stator winding 11, 1.
The induced voltages e1, e2, e3, and b induced in 2 and 13 are sinusoidal position signals p1 and p output from the waveform generation circuit 6.
2, p3, c are drive currents i1, i2, i3 which are supplied to the stator windings 11, 12, 13. Position signals p1, p
2 and p3 have a sinusoidal signal waveform, and the power supply circuit 7
Respectively amplify each of these to generate a sinusoidal three-phase drive current i
1, i2, i3 are converted and supplied to the respective phases of the stator windings 11, 12, 13, so that the position signals p1, p2, p3 and the drive currents i1, i2, i3 have the same phase relationship. v of d
1, v2, v3 are terminal voltages of each phase of the stator windings 11, 12, 13 and are induced voltages e1, e2, e induced in each phase.
3 is a waveform obtained by synthesizing the voltage drop amount of the winding resistance (the voltage waveform v1 is indicated by hatching) generated by the driving currents i1, i2, and i3 flowing in each phase. As is clear from FIG. 12, the induced voltages e1, e2, e3 and the drive current i
1, i2, i3 and terminal voltages v1, v2, v3 all have different phases. In particular, since the induced voltages e1, e2, e3 and the drive currents i1, i2, i3 are out of phase with each other, the motor cannot be driven at maximum efficiency. e represents the phase signal g output from the phase detection circuit 10 shown in FIG. 4, and the rising edge of the position signal g is a zero-cross point at which the neutral point potential O of the terminal voltage v1 crosses from the bottom to the top as in FIG. Match and
The falling edge of the phase signal g coincides with the zero-cross point where the neutral point potential O of the terminal voltage v1 crosses from the top to the bottom. As is clear from FIG. 12, the rising edge of the phase signal g is out of phase with the zero cross point of the position signal p1 (or the drive current i1) by Δg.

Next, based on the phase signal g output from the phase detection circuit 10, the induced voltages e1, e2, e3 and the drive current i
The operation of the embodiment of the present invention for performing the phase correction process for matching the phases of 1, 1, 2 and i3 as shown in FIG. 6 will be described in detail.

FIG. 13 is a flowchart of an embodiment of the phase correction mode for performing the phase correction processing. Below, FIG.
A description will be given along the flowchart shown in FIG.

In FIG. 13, the process 131 waits for an interrupt due to the occurrence of the rising edge of the phase signal g output from the phase detection circuit 10. If the rising edge of the phase signal g has not occurred, the processing shifts to the normal mode, and if the rising edge of the phase signal g has occurred, shifts to the processing 132. In process 132, the difference between the address value f input to the waveform generating circuit 6 and the address value fp corresponding to the zero cross point of the position signal p1 output from the waveform generating circuit 6 at the time when the rising edge of the phase signal g occurs ( Δg = f−fp) is calculated to obtain the phase difference Δg,
It is stored in the RAM area of the memory 62, and the processing shifts to the processing 133. In process 133, it is determined whether or not the magnitude of the phase difference Δg obtained in process 132 is within the range of the predetermined value G.
When the magnitude of the phase difference Δg is smaller than the predetermined value G, the processing shifts to the normal mode, and the magnitude of the phase difference Δg is the predetermined value G.
When it is larger, the processing shifts to processing 134. In process 134, the sign of the phase difference Δg obtained in process 132 is determined. When the sign of the phase difference Δg is positive, the processing shifts to the processing 135, the address value f is incremented by 1, and then shifts to the normal mode. When the sign of the phase difference Δg is not positive in the process 134, the process shifts to the process 136, the address value f is subtracted by 1, and then the normal mode is shifted.

The above processing 131 to processing 136
This is the operation in the phase correction mode. By performing the processing shown in the flowchart of FIG. 13, the terminal voltages v1, v2, v
The processing is performed so that the zero-cross point with the neutral point potential O of 3 coincides with the zero-cross points of the position signals p1, p2, p3 output from the waveform generating circuit 6. That is, as shown in e of FIG. 12, when the zero cross point of the terminal voltage v1 is at a position advanced from the address value fp corresponding to the zero cross point of the position signal p1, the address value of the position signal output from the waveform generation circuit 6 is reached. By reducing f, the position signal p
Advance the phase of 1, p2, p3. On the contrary, when the zero-cross point of the terminal voltage v1 is at a position delayed from the address value fp corresponding to the zero-cross point of the position signal p1, the address value f of the position signal output from the waveform generation circuit 6 is increased, The phase of the position signals p1, p2, p3 is delayed. As a result, the phases of the position signals p1, p2, p3 output from the waveform generation circuit 6 (in phase with the drive currents i1, i2, i3) and the terminal voltages v1, v2, v3 match, and the induced voltage e1, e2, e3 phase and drive current i1,
Since the phases of i2 and i3 match as shown in FIG. 6, the motor is driven with maximum efficiency.

Therefore, even if the accurate initial position cannot be detected in the phase matching mode of FIG. 11, the phase and driving of the induced voltages e1, e2, and e3 during normal rotation of the motor by the phase correction mode of FIG. Current i1, i2, i
The phases of 3 can be matched. In addition, noise is superimposed on the frequency generator 1 for some reason while the motor is being driven.
Even if an error occurs in the count value of the count circuit 4, the phase of the induced voltages e1, e2, e3 and the drive currents i1, i2, i are automatically generated during normal rotation of the motor by the phase correction mode of FIG.
The phases of 3 can be matched. Therefore, it is possible to prevent a worst case in which the error of the count value of the count circuit 4 is accumulated due to the noise superimposed on the frequency generator 1 and the motor stops.

In the above description, the power supply circuit 7 is a so-called current control type power supply circuit that generates a three-phase drive current proportional to the position signals p1, p2, p3 output from the waveform generation circuit 6. However, a current amplifier circuit that generates a current having a magnitude proportional to each of the input position signals p1, p2, and p3 is generally prone to phase-to-phase variation, and the circuit configuration is complicated as compared with a simple voltage amplifier circuit. Have. The input position signal p1,
When a so-called voltage control type power supply circuit that generates three-phase drive voltages proportional to p2 and p3 is used, the phase detection circuit shown in FIG. 14 is used instead of the phase detection circuit 10 shown in FIG. Should be used.

FIG. 14 is a circuit configuration diagram of another embodiment of the phase detection circuit 10, and FIG. 15 shows a signal waveform diagram of each part thereof.

In FIG. 14, reference numeral 41 denotes a current detection resistor connected in series to the one-phase stator winding 11 to convert the phase current i1 supplied to the stator winding 11 into a voltage. Reference numeral 42 is a comparator, and two input terminals of the comparator 42 are connected to both ends of the resistor 41. The comparator 42 outputs the phase signal g to the phase adjustment circuit 5 according to the direction of the current flowing through the resistor 41.

In FIG. 15, a is a permanent magnet rotor 20.
Three-phase stator windings 11, 12, 1 when rotating
3 shows the respective current waveforms of the currents i1, i2, i3 flowing in No. 3. The current i1 flowing through the stator winding 11 is converted into a voltage corresponding to the current by the resistor 41, and the voltage across the resistor 41 is connected to the non-inverting input (+) and the inverting input of the comparator 42. The container 42 has detected the sign of the phase current passed through the stator winding 1. As is clear from the waveform b, the rising edge of the position signal g coincides with the zero cross point of the current i1. That is, the phase signal g output from the phase detection circuit 10 outputs the timing of the zero crossing point of the current of one phase of the stator windings 11, 12, and 13. The phase of the current of 11 can be detected.

Based on the phase signal g output from the phase detection circuit 10, the induced voltages e1, e2, e3 and the drive currents i1, i
The phase correction process for matching the phases of 2 and i3 is shown in FIG.
Since the operation is almost the same as in the case of the current control type power supply circuit shown in FIG.

As described above, since the brushless DC motor of the present invention creates the three-phase position signals based on the two-phase frequency signals output from the frequency generator and having different phases, a position detecting element such as a Hall element is used. Need not be provided.

In the waveform generating circuit 6 according to the present invention, the function table of the sine wave of only one cycle is stored in the memory, and the address table is changed by the amount corresponding to the difference in phase to refer to the function table. Figure 8 shows the phase position signals.
3 digital / analog converters 63,
It outputs to 64 and 65, but after sequentially converting into an analog value using one digital / analog converter, the obtained analog value is held by three sample hold circuits (not shown). It goes without saying that it is also possible to output as a three-phase position signal.

Further, since the sine wave function is a symmetric periodic function, it is not necessary to store all one cycle in the function table, but only one half cycle or one quarter cycle. After that, appropriate processing may be performed according to the address value to obtain a digital value corresponding to the three-phase position signal. In this case, there is an advantage that the memory required for the function table can be reduced. On the contrary, not only the function table of the sine wave having only one cycle is stored in the memory, but the sine waves for the three phases are stored in the function table respectively and correspond to the position signals of the three phases directly. It goes without saying that the digital value can be output to the three digital / analog converters 63, 64, 65.

Further, although the embodiment of the present invention is limited to the three-phase motor, it goes without saying that the number of phases is not limited to three and may be any number of phases. Besides, various modifications can be made without changing the gist of the present invention.

[0092]

As described above, according to the present invention, since the position detecting element such as the conventional brushless DC motor is unnecessary, the complexity of adjusting the mounting position of the element and the number of wirings are reduced, and the cost is greatly reduced. . Further, since it is not necessary to mount a position detection element inside the motor, the motor can be downsized and thinned without structural restrictions.

Furthermore, the brushless DC motor of the present invention is
With the above configuration, there is no particular need for a no-load state during the phase matching operation, and the positional relationship between the permanent magnet rotor and the stator winding can be accurately detected even when the motor is under load. In addition, after the power is turned on, the frequency generator detects the rotation of the permanent magnet rotor even when the motor is not being driven, so the magnetic pole position is always maintained even if the permanent magnet rotor is externally rotated for some reason. As can be seen, the phase matching operation only needs to be performed when the power is turned on. Therefore, after the completion of the phase matching operation, the starting and stopping operations are the same as those of the conventional brushless DC motor with the position detecting element.

Further, the phase correction operation is performed so that the phase of the induced voltage induced in the stator winding while the motor is rotating and the phase of the current supplied to the stator winding of each phase match. By doing so, even if noise is superimposed on the output of the frequency generator for some reason while the motor is being driven, the phase of the induced voltage and the phase of the drive current can be automatically matched, and the motor will stop. It is possible to prevent such a worst situation and to always drive the motor with high efficiency.

Therefore, it is possible to provide a brushless DC motor which does not require a position detecting element, can be driven with high efficiency, and can be applied to a wide range of purposes.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of a brushless DC motor of the present invention.

FIG. 2 is a circuit configuration diagram showing an embodiment of a direction detection circuit according to the present invention.

3 is a signal waveform diagram of each part of the direction detection circuit shown in FIG.

FIG. 4 is a circuit configuration diagram showing an embodiment of a phase detection circuit according to the present invention.

5 is a signal waveform diagram of each part of the phase detection circuit shown in FIG.

FIG. 6 is a signal waveform diagram of each part during steady rotation of the brushless DC motor of the present invention.

FIG. 7 shows the relationship between the magnetic pole vector Φ of the permanent magnet rotor, the magnetomotive force vector I generated by the stator winding, and the induced voltage E induced in the stator winding during steady rotation of the brushless DC motor of the present invention. Vector illustration

FIG. 8 is a block diagram showing the configurations of a phase adjusting circuit, a waveform generating circuit, an initial position detecting circuit, and a selecting circuit which constitute the brushless DC motor of the present invention.

FIG. 9 is a flow chart for explaining the processing in the normal mode of the brushless DC motor of the present invention.

FIG. 10 is a vector diagram showing the relationship between the magnetic pole vector Φ of the permanent magnet rotor and the magnetomotive force vector I generated by the stator winding during the phase matching operation of the brushless DC motor of the present invention.

FIG. 11 is a flow chart of an embodiment for performing a phase matching operation of the brushless DC motor of the present invention.

FIG. 12 is a signal waveform diagram of each part when the phase detection circuit shown in FIG. 4 is used and the phase of the induced voltage induced in the stator winding and the phase of the drive current supplied to each phase are deviated.

FIG. 13 is a flowchart of one embodiment for performing a phase correction operation of the brushless DC motor of the present invention.

FIG. 14 is a circuit configuration diagram showing another embodiment of the phase detection circuit according to the present invention.

FIG. 15 is a signal waveform diagram of each part of the phase detection circuit shown in FIG.

[Explanation of symbols]

 1 frequency generator 2 waveform shaping circuit 3 direction detection circuit 4 count circuit 5 phase adjustment circuit 6 waveform generation circuit 7 power supply circuit 8 initial position detection circuit 9 selection circuit 10 phase detection circuit

Claims (10)

[Claims] 1. A rotor having a plurality of magnetic poles, a plurality of phases of stator windings arranged in the rotor with a predetermined air gap, and a plurality of phases proportional to the rotational speed of the rotor. A frequency generator for generating a frequency signal, a direction detecting means for detecting a rotation direction of the rotor from the frequency signals of the plurality of phases and outputting a direction signal, and at least one of the frequency generators according to the direction signal. Counting means for up-counting or down-counting the pulses of one frequency signal, and phase detecting means for outputting a phase signal according to the phase of the voltage or current of at least one phase of the stator windings of the plurality of phases,
Phase adjustment means for adding and subtracting the count value of the counting means by a predetermined value according to the rotation direction command, and further outputting a command value obtained by adjusting according to the phase signal, and according to the command value A brushless DC motor comprising: waveform generating means for generating waveform signals of a plurality of phases; and power supply means for supplying a driving current or a driving voltage according to the waveform signals of the plurality of phases to a stator winding. 2. A rotor having a plurality of magnetic poles, a plurality of phases of stator windings arranged in the rotor with a predetermined gap, and a plurality of phases proportional to the rotational speed of the rotor. A frequency generator for generating a frequency signal, a direction detecting means for detecting a rotation direction of the rotor from the frequency signals of the plurality of phases and outputting a direction signal, and at least one of the frequency generators according to the direction signal. Counting means for up-counting or down-counting pulses of one frequency signal; initial position detecting means for calculating an initial value of the rotor from the count value of the counting means and outputting the initial value to the counting means;
The phase detection means for outputting a phase signal corresponding to the phase of at least one phase voltage or current of the stator windings of the plurality of phases, and the count value of the counting means are set to a predetermined value according to the rotation direction command. Phase adjusting means for adding and subtracting, and further outputting a command value obtained by adjusting according to the phase signal,
Brushless composed of waveform generating means for generating waveform signals of a plurality of phases according to the command value and power supply means for supplying a driving current or a driving voltage according to the waveform signals of the plurality of phases to the stator winding. DC motor. 3. The initial position detecting means detects a first count value of the counting means when it is rotated in the forward direction and a second count value of the counting means when it is rotated in the opposite direction, The brushless DC motor according to claim 2, wherein an average value of the count value of 1 and the second count value is used as an initial value of the counting means. 4. The brushless DC motor according to claim 1, wherein the initial position detecting means operates only when the power is turned on. 5. The phase adjusting means does not adjust the count value of the counting means according to the phase signal when the magnitude of the phase difference between the voltage and the current of the stator winding is smaller than a predetermined value. The brushless DC motor according to claim 1 or 2. 6. The phase adjusting means adds or subtracts a predetermined value from a count value of the counting means in response to a rotation direction command, so that the phase of the rotating magnetic field generated by the stator winding is electrically changed from the phase of the magnetic pole of the rotor. The brushless DC motor according to claim 1 or 2, wherein the brushless DC motor is rotated at an angle of 90 degrees. 7. The waveform generating means includes a memory means for storing a sinusoidal signal in advance and a digital / analog converter for converting a digital value read from the memory means into an analog value. 2. The brushless DC motor described in 2. 8. The brushless DC motor according to claim 1, wherein the waveform generating means stores a sinusoidal signal having only one cycle in advance. 9. The waveform generating means comprises 1/2 cycle or 1 / cycle.
The sinusoidal signal having only four cycles is stored in advance.
Alternatively, the brushless DC motor according to claim 2. 10. An initial position detecting means, a counting means, a phase adjusting means and a waveform generating means, a memory means for storing program data according to processing contents, and the program.
The brushless DC motor according to claim 1 or 2, which is configured to include an arithmetic processing unit that executes processing in accordance with data.