JP2573075B2 - Starting method of sensorless motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a starting method of a sensorless DC motor.

(Prior Art) Conventionally, a Hall motor using a Hall element has been known as a so-called brushless motor. The Hall motor incorporates a Hall element for detecting the position of the rotor (rotor pole position, rotor rotation angle).

On the other hand, a sensorless motor without such a rotor position detecting element has been developed.

In order to rotate these motors in a predetermined rotation direction, it is necessary to control the rotation direction at the time of starting. In the above-described Hall motor, the position of the rotor can be detected by the Hall element. Therefore, based on the detection result, each excitation winding can be driven so that the rotor rotates in a predetermined direction. However, the position of the sensorless motor cannot be detected when the rotor is stopped. Therefore, conventionally, the rotor is slightly moved in a predetermined step at the time of starting, and the starting position of the rotor is obtained by detecting the starting force generated in the exciting winding by the slight rotation of the rotor. Each excitation winding was driven to rotate.

Furthermore, as a start-up method of a sensorless motor,
There is a technique disclosed in JP-A-63-69489. In this starting method, one of a plurality of excitation windings in a state where the rotor is stopped is used.
A current pulse is sequentially supplied, and a peak amplitude value of the current pulse is measured and stored. Then, after the measurement and storage of the peak amplitude values for all the excitation windings are completed, the stored maximum amplitude values are read and compared. Then, according to the comparison result, the rotor is started so as not to reverse.

(Problems to be Solved by the Invention) Incidentally, in the above-described Hall motor, it is easy to control rotation in a predetermined direction, but it is difficult to reduce the size of the motor because the Hall element is incorporated. However, there is a drawback that high temperature characteristics are poor, such as deterioration of Further, according to the sensorless motor starting method, in which the rotor is slightly moved at the time of starting and the position of the rotor is detected, the rotor may be rotated reversely at the time of starting. This is because, when used for rotating a disk medium of a Winchester type hard disk drive (which performs writing / reading while the head is not in contact with a magnetic medium and floated), the head is damaged by reverse rotation. This is a major drawback.

Further, the starting method disclosed in Japanese Patent Application Laid-Open No. 63-69489 has high reliability because the rotor does not rotate in the reverse direction, but requires a microcomputer, the configuration of the motor drive circuit is complicated, and the precision of parts is required. However, there is a disadvantage that the cost is high.

The present invention has been made in view of the above-described problems in the conventional example, and has as its object to provide a sensorless motor start-up method that does not cause the rotor to reverse at start-up, has high cost performance, has few start-up failures, and has high reliability. .

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, in the starting method of the sensorless motor according to the present invention, a plurality of soft magnetic material magnetic pole teeth are wound around each of the magnetic pole teeth. A starting method of a sensorless motor having a stator including a plurality of excitation windings and a rotor including a permanent magnet, wherein each of the permanent magnets is controlled so that rotation of the rotor is suppressed during starting. A direct current is simultaneously supplied to all the excitation windings magnetically biased by the magnetic poles to store energy between the terminals of the excitation windings, and thereafter, the energy stored in the excitation windings is released. A potential difference between the excitation windings at the time of the discharge is detected, and a relative position between the stator and the rotor is detected based on the detection result, and the rotor is rotated so that the rotor rotates in a predetermined direction. A turning control signal is generated and output.

Further, in order to achieve the above object, in a starting method of a sensorless motor according to the present invention, a stator including a plurality of soft magnetic material magnetic pole teeth and a plurality of excitation windings wound around each of the magnetic pole teeth, A starting method of a sensorless motor having a rotor including a permanent magnet, wherein a capacitor is connected between the plurality of excitation windings, and at the time of starting, the rotation of the rotor is suppressed. A direct current is simultaneously supplied to all the excitation windings magnetically biased by the respective magnetic poles of the permanent magnet to store energy between the terminals of the excitation windings, and then the energy stored in the excitation windings And stores charge in the capacitor based on the difference in energy stored in each of the excitation windings, and detects the relative position between the stator and the rotor based on the polarity of the capacitor. Rutotomoni said rotor and said rotating direction control signal to generate an output so as to rotate in a predetermined direction.

Further, in order to achieve the above object, in a starting method of a sensorless motor according to the present invention, a stator including a plurality of soft magnetic material magnetic pole teeth and a plurality of excitation windings wound around each of the magnetic pole teeth, A starting method of a sensorless motor having a rotor including a permanent magnet, wherein a parallel circuit of a capacitor and a resistor is connected between the plurality of exciting windings, and at the time of starting, rotation of the rotor is suppressed. As described above, a direct current is simultaneously supplied to all the excitation windings magnetically biased by the respective magnetic poles of the permanent magnet to store energy between terminals of the respective excitation windings, and thereafter, the respective excitation windings are stored. The energy stored in the wire is released, and a current flows through the resistor based on the difference in energy stored in each of the excitation windings. Storing a charge in a capacitor, detecting a relative position between the stator and the rotor based on the charge in the capacitor, and generating and outputting a rotation direction control signal so that the rotor rotates in a predetermined direction. I do.

(Operation) According to the above starting method, the DC current is simultaneously applied to the plurality of excitation windings so that the rotation of the rotor (rotor) is temporarily suppressed (stopped) before the normal motor starting period. Is added. By supplying this DC current, energy is stored between the terminals of each excitation winding. Normally, a plurality of excitation windings (and a soft magnetic material around which these excitation windings are wound) are configured to have the same electrical characteristics, but in a sensorless motor, the rotor The effective electric characteristics of each excitation winding change due to the influence of the magnetic flux of the magnet. Therefore, the energy stored in each excitation winding during the rotation suppression period is:
This will be different for each excitation winding. According to the present invention, a predetermined electrical characteristic of the exciting winding is detected in a correlated manner based on the energy difference, and a rotation direction control signal is provided so that the rotor rotates in a predetermined direction based on the detected electrical characteristic of the exciting winding. Generate and output

One of the effective electrical characteristics of each excitation winding that is changed by the influence of the magnetic flux of the rotor permanent magnet is the inductance of the excitation winding. If there is a magnetic pole (S-pole or N-pole) of the rotor near the soft magnetic material around which the exciting winding is wound, the B-
The H characteristic is biased. Therefore, the effective inductance of the exciting winding is affected and changes.

When the same direct current is simultaneously supplied to the plurality of excitation windings, energy is stored in each excitation winding. However, as described above, since the effective inductances of the respective excitation windings are different, there is a difference in stored energy.
This energy difference causes, for example, the DC current to be cut off and the energy stored in each of the excitation windings to be released. At this time, in any one of the excitation windings, the current flows in a direction opposite to the DC current It can be known by detecting the flow. The obtained energy difference indicates a change in the inductance value of each excitation winding due to the influence of the permanent magnet of the stator. Therefore, by this, the positional relationship between the rotor and the stator (stator) (that is, when the starting current is supplied and the rotor rotates forward) can be known while the rotor is not rotating, and the rotor can be rotated in a desired direction. It can be understood how to apply the starting current to the exciting winding.

The difference in energy stored in the exciting winding can be obtained by measuring electric characteristics such as the terminal potential of the exciting winding in addition to the current value of the current flowing through the exciting winding. These electrical characteristics can be accumulated and detected over time by, for example, a capacitor.

(Example) Hereinafter, an example of the present invention will be described in detail.

First, a method of detecting the rotation direction of the rotor at the time of starting will be described.

The exciting coil of the motor is formed by winding a winding around a soft magnetic material. Usually, each excitation coil is adjusted to have substantially the same BH characteristics and inductance if the influence of the magnet is ignored. However, the excitation coil has N
When the pole or the south pole approaches, the BH characteristic of the exciting coil is affected by the magnetic field from the pole, so that the effective inductance and the hysteresis characteristic are different from the original ones.

For example, each excitation coil has its BH curve biased according to the polarity (N or S) of the adjacent pole, the strength of the magnetic pole, and the distance to the adjacent pole, as shown in FIG. The zero (0) level line of the BH curve corresponds to the phase (u, v,
w) (the u phase is close to the S pole of the rotor, w
Phase close to the north pole). Therefore, when a current flows in a certain direction, the effective inductance of each exciting coil also differs.

For example, in the two-phase excitation circuit shown in FIG. 2A, when the power switch S is turned on, each excitation coil (each phase) is turned on.
The currents I ₁ and I ₂ flowing through L ₁ and L ₂ increase exponentially. Exciting coil L rotor N pole to _1, the exciting coil L ₂ rotor of S poles in the, if in close proximity respectively, the B-H characteristic of the exciting coils L _1, L ₂ symbolically When written, it looks like G ₁ , G ₂ . Accordingly, the effective inductance of the exciting coils L _1, L ₂ are different from each other, stored energy ^{_{(L 1 I 1 2/2}} , L 2 I 2 2/2) are different from each other.

Next, as shown in FIG. 2B, the power switch S is opened to release the energy stored in each of the exciting coils L ₁ and L ₂ . At this time, since there is a difference between the energies stored in the excitation coils L ₁ and L ₂ , the current value of the current flowing through each phase
A difference occurs between i ₁ and i ₂ , and a potential difference occurs between terminals P ₁ and P _{2 of} each phase,
Depending on the energy stored in each excitation coil, damped oscillating currents i ₁ -i ₂ having different polarities flow through the resistor r. By detecting and comparing the current difference and the potential difference, that is, the energy difference, the relative position of the rotor pole with respect to the exciting winding can be detected. If the direction of the exciting current and the exciting polarity are associated in advance, the polarity of the magnetic pole can be detected.

The potential difference between the terminals of each phase may be detected, for example, at a certain moment after the power switch is opened. As shown in FIG. 2 (b), the terminals P ₁ and P ₂ of each phase
A capacitor C may be connected between the terminals and the potential difference between the terminals P ₁ and P ₂ (representing the difference in energy stored in each excitation coil) may be detected over time and cumulatively. As a result, it is possible to avoid the influence of noise and the influence of variations in coil characteristics, etc., and to perform measurement more accurately.

Further, an integrating circuit as shown in FIG. 3A may be used in place of the capacitor C, and a circuit for rectifying a current flowing according to a potential difference and holding the current in a capacitor as shown in FIG. 3B. May be used.

The case where the present invention is applied to a three-phase excitation circuit will be described with reference to FIG. In the circuit of the figure, the switching transistor _{T A, T B, T C} , and on the T _D, the excitation from the terminal A ₁ coil a, b, and c, and the position detection voltages of the rotor shown in FIG. 5 Apply. In the period from T1 to T2 in FIG. 5, a positive current flows simultaneously in all the exciting coils a, b, and c, and energy is accumulated. At this time, each exciting coil a, b,
Vector diagrams of magnetic fluxes φ ₂ , φ _b , φ _c generated in c
It looks like the figure. As can be seen from this vector diagram, 3
The two magnetic fluxes φ _a , φ _b , φ _c cancel each other, and no rotational force is generated in the rotor.

Next, the voltage applied to the excitation coils a, b, and c is set to 0 at the timing of T2. At this time, the exciting coils a, b, the energy accumulated in the c is released, the transistors _{T A, T B, T C} , if you turn the T _D, the exciting coils a, b, resistance from c r _a , r _b , r
Current flows toward _c (same resistance value). Excitation coil
a, b, because the energy stored in the c a difference as described above, unlike the potentials of the terminals P _a, P _b, P _c, the position of the rotor can be seen by detecting this potential difference.

FIG. 7 is a block diagram showing a starting and driving circuit of a two-phase sensorless motor according to one embodiment of the present invention.
The two-phase sensorless motor shown in FIG. 1 includes a stator (stator) 1, a rotor (rotor) 2, and excitation windings 11 and 12. 3 is the direction in which the rotor 2 should rotate (forward direction)
It is an arrow showing.

Now, it is assumed that the motor is not driven and the rotor 2 is stopped at a position as shown in the figure. At this time, the south pole of the rotor 2 is located near the exciting coil 11 and the rotor 2 is located near the exciting coil 12.
Are located respectively, the BH characteristics of each pole of the stator 1 are as shown by G ₁ and G ₂ , respectively.

To start the motor, first, the switch S is turned on. The timer 5 detects that the switch S is turned on, and switches the switching circuit 6
A switch-on detection signal is sent to Switching circuit 6
Receives this signal and sends a signal to all conduction instruction circuit 7 to activate the circuit. Full conduction instruction circuit 7 is a gate circuit
Instruct the switching transistors Q ₁₀ and Q ₂₀ to conduct all the signals to ₁₀ . In response to this, the gate circuit 10 supplies a base voltage that simultaneously turns on the switching transistors Q ₁₀ and Q ₂₀ . As a result, the resistance r ₁ from the power supply E and the transistor
Exciting current to the exciting coil 11 through Q ₁₀ energy is supplied is accumulated. At the same time, the resistance r ₂ (resistance r ₁
The same resistance value), the exciting coil 12 through the transistor Q ₂₀
Is supplied with an exciting current to store energy. At this time, the magnetic fluxes of the exciting coils 11 and 12 cancel each other as described above,
No rotational force is generated on the rotor 2. Also, due to the BH characteristics G ₁ and G ₂ of each pole of the stator 1, the excitation coil 11 has less stored energy than the excitation coil 12.

Next, the switch S is turned off. At this time, the gate circuit
The base voltage from 10 is kept supplied, and the switching transistors Q ₁₀ and Q ₂₀ are turned on. As a result, the energy stored in the exciting coils 11 and 12 is released, and a current flows through the resistors r ₁ and r ₂ and the transistors Q ₁₀ and Q ₂₀ , respectively. A current flowing through the resistor r ₁ by the energy difference described above, unlike the current through the resistor r _2, a potential difference occurs charges are accumulated between the for capacitor C ₁ terminal.

By repeating switch suitable number of times on / off of S as described above, over time, cumulatively it detects a potential difference between the terminal capacitor C _1. That is, both terminals of the capacitor C ₁ are input to the comparator 4, and the comparison result (+/− signal) is input to the normal signal output circuit 8. The forward signal output circuit 8 outputs a +/- signal (N, S of the rotor) from the comparator 4.
A forward rotation signal is output to the gate circuit 10 so that the rotor rotates in the predetermined direction 3 based on the position of the pole.

After a predetermined time (a time sufficient for outputting the normal rotation signal), the timer 5 sends a signal to the switching circuit 6, and the switching circuit 6 receives the signal and invalidates the output of the full conduction instruction circuit 7. The normal signal output of the normal signal output circuit 8 is made valid.
As a result, the gate circuit 10 inputs the non-inversion signal, and turns on / off the transistors Q ₁₀ and Q ₂₀ based on the input.

As described above, the motor is started in a predetermined direction. Inverted signal output circuit 8 based on the signal from the sensorless signal circuit 9 after the start on / off the transistor Q _10, Q ₂₀ through a gate circuit, the motor will sustain forward.

FIG. 8 is a circuit diagram of a sensorless motor starting and driving device according to a second embodiment of the present invention. The device shown in the figure is an example in which the present invention is applied to a three-phase (u, v, w) sensorless motor having excitation coils Lu, Lv, Lw.

When the power is turned on, the energization switching circuit 23 informs the phase switching circuit 25 that a phase current as shown in FIG.
To instruct. In accordance with this instruction, the phase switching circuit 25 outputs a signal instructing to turn on the Darlington-connected transistors Q ₁ , Q ₃ , Q ₅ and to turn off the transistors Q ₂ , Q ₄ , Q ₆ . The control circuit 27 is configured to respectively ON / OFF controlling the base voltage of each transistor in response to this signal, the transistor Q ₇ is also turned on. Thus, the transistor Q _1, the exciting coils Lu, resistor R _4, and through the transistor Q _7,
A current is supplied from a power supply E. Similarly, the excitation coil
Power is also supplied to Lv and Lw. Therefore, the exciting coil L
The current shown in FIG. 5 flows through u, Lv, and Lw, but no rotational torque is generated in the rotor by this current as described above.

On the other hand, a reference clock is generated from the clock generator 21 after the power is turned on, and the ring counter 22 counts this reference clock, and notifies that the predetermined time has passed by the energization switching circuit 23
To instruct. The energization switching circuit 23 receives this, and instructs the phase switching circuit 23 to stop supplying current to the excitation coils Lu, Lv, Lw.
Instruct 25. In accordance with this instruction, the phase switching circuit 25 outputs a signal instructing to turn off the Darlington-connected transistors Q ₁ , Q ₃ , Q ₅ and to turn off the transistors Q ₂ , Q ₄ , Q ₆ .
The control circuit 27 turns off all the transistors Q ₁ to Q ₆ controls the base voltage of each transistor in response to this signal, the transistor Q ₇ is also turned off.

Thereby, the energy stored in the exciting coils Lu, Lv, Lw is released, and a current flows through the resistors R ₁ , R ₂ , R ₃ based on the difference between the stored energies. Resistance due to this current
The potential difference between each terminal of R ₁ , R ₂ , R ₃ is determined by capacitors C ₁ , C
To charge the _2, C _3.

Repeating the above described operation, once reliably sufficient charge to detection is stored in the capacitor _{C 1, C 2, C 3} , to detect this by the comparator CP1, CP2, CP3. The detection result is input to the rotation direction detection circuit 29, and the rotation direction detection circuit 29 outputs a rotation direction instruction signal to the phase switching circuit 25 based on the result. The phase switching circuit 25 is based on this rotation direction instruction signal,
The phase is switched so that the rotor starts rotating in a desired direction without reversing, and starting is started.

When the rotor starts rotating, a back electromotive force is generated in the excitation windings Lu, Lv, Lw of each phase by the rotation of the rotor. This back electromotive force is supplied to comparators COM1 to COM3. In response to the back electromotive force, the comparators COM1 to COM3 output signals corresponding to the rotational position of the rotor. This comparator
Output signals from COM1 to COM3 are delayed by a predetermined angle by a delay circuit 31 and supplied to a conduction switching circuit 23. Energization switching circuit 23
Switches the current of each phase during the activation period according to the signal supplied from the delay circuit 31.

 As described above, the motor is started without reverse rotation.

After the end of the activation period, a pause period is arranged. After the elapse of the pause period, a generally known acceleration period occurs. During this acceleration period, the power supply switching path 23 outputs a phase current switching signal to switch the phase current so as to accelerate the rotation speed of the rotor. In response to this instruction signal, the phase switching circuit 25, and operates the control circuit 27, the transistor Q ₁ to Q ₇ is turned on / off, it is energized while being switched phase current. As a result, the speed of the rotor gradually increases.

When the rotation speed of the rotor reaches a predetermined ratio (for example, 95%) of the rated rotation speed according to the output signal from the delay circuit 31, a normal rated rotation period is set.

During this period, the power supply switching circuit 23 instructs to supply a phase current so that the rotor rotates in the rated state. In response to this instruction, the phase switching circuit 25, and operates the control circuit 27, the transistors Q ₁ to Q ₇ is turned on / off, it is supplied while being switched phase current. As a result, the rotor rotates at a substantially constant speed.

In the above embodiment, an example of a two-phase or three-phase motor has been described. However, the present invention is not limited to this. Applicable.

Furthermore, as long as the position and polarity of the magnetic pole are determined based on the accumulation of energy in the soft magnetic material and its function,
It goes without saying that other applications also fall within the scope of the present invention.

[Effects of the Invention] As described above, according to the present invention, the same direct current is simultaneously supplied to each phase of the sensorless motor to accumulate energy in the exciting coil, and a difference in the energy is detected to control the rotation direction. Since the signal is generated, the rotor can always be rotated in a desired direction without reversing at startup. Further, since the circuit is not complicated, the cost performance is high, the starting failure is small, and the reliability is high.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining the effect of the poles of the rotor on the exciting coil, FIG. 2 is a circuit diagram for explaining the principle of detecting the rotation direction of the rotor, and FIG. FIG. 4 is a circuit diagram showing another example of detecting accumulated energy with time and cumulatively. FIG. 4 is a circuit diagram showing an example in which the present invention is applied to a three-phase excitation circuit. FIG. FIG. 6 is a diagram showing an exciting current supplied to each phase of the circuit of FIG. 6, FIG. 6 is a diagram showing a magnetic flux generated by the exciting current of FIG. 5, and FIG. FIG. 8 is a circuit diagram of a starting and driving device of the sensorless motor according to the second embodiment of the present invention. 1 ... stator (stator), 2 ... rotor (rotor),
3 forward rotation direction 5 timer 6 switching circuit 7
··· Full conduction instruction circuit, 8 ··· forward rotation signal output circuit, 10 ··· gate circuit, 11, 12 ··· excitation coil, G ₁ , G ₂ ··· BH characteristics,
S ...... switches, Q _10, Q ₁₂ ...... transistor, E ...... power, r1, r2 ...... resistance ,, C1 ...... capacitor, 23 ...... energization switching circuit 25 ...... phase switching circuit 27 ...... control circuit, 29 ...... rotation direction detection circuit, 31 ...... delay circuit ,, Lu, Lv, Lw ...... exciting coil, R ₁ to R ₄ ...... resistance, Q ₁ to Q ₇ ...... transistor, C ₁
~ C ₃ …… Capacitors, CP1 to CP3 …… Comparators.

Claims (4)

(57) [Claims] 1. A sensorless motor having a stator including a plurality of soft magnetic material magnetic pole teeth, a plurality of excitation windings wound around each of the magnetic pole teeth, and a rotor including a permanent magnet. At startup, the rotation of the rotor is suppressed,
A direct current was simultaneously supplied to all of the excitation windings magnetically biased by the magnetic poles of the permanent magnet to store energy between the terminals of the excitation windings, and then stored in the excitation windings. Energy is emitted to detect a potential difference between the excitation windings at the time of the emission, and based on the detection result, a relative position between the stator and the rotor is detected, and the rotor rotates in a predetermined direction. And generating and outputting a rotation direction control signal. 2. A method for starting a sensorless motor having a stator including a plurality of soft magnetic material magnetic pole teeth and a plurality of excitation windings wound around each of the magnetic pole teeth, and a rotor including a permanent magnet. A capacitor is connected between the plurality of excitation windings, and at the time of startup, all the magnetic poles of each of the permanent magnets are magnetically biased so that rotation of the rotor is suppressed. The DC current is simultaneously supplied to the excitation windings to store energy between the terminals of the excitation windings, and then the energy stored in the excitation windings is released, and the energy stored in the excitation windings is released. And stores a charge in the capacitor based on the difference between the two, and detects a relative position between the stator and the rotor based on the polarity of the capacitor and generates a rotation direction control signal so that the rotor rotates in a predetermined direction. A sensorless motor startup method characterized by output. 3. A starting method of a sensorless motor having a stator including a plurality of soft magnetic pole teeth and a plurality of excitation windings wound around each of the pole teeth, and a rotor including a permanent magnet. A parallel circuit of a capacitor and a resistor is connected between the plurality of excitation windings, and the magnetic poles of the permanent magnet are magnetically controlled by the respective magnetic poles of the permanent magnet so that the rotation of the rotor is suppressed during startup. DC current is simultaneously supplied to all of the excitation windings biased to store energy between the terminals of the respective excitation windings, and thereafter, the energy stored in the respective excitation windings is released, and the respective excitation windings are released. A current flows through the resistor based on a difference in energy stored in the wire, and a charge is accumulated in the capacitor in parallel with the resistor due to a potential difference between terminals of the resistor, and the stator and the rotor are charged by the charge of the capacitor. A sensorless motor start-up method for detecting a relative position of the motor and generating and outputting a rotation direction control signal so that the rotor rotates in a predetermined direction. 4. The method according to claim 1, wherein said synchronous energization and said energy release are repeated a plurality of times, and the accumulation of electric charges in said capacitor is accumulated with time. The method according to claim 2 or 3, wherein a relative position is detected.