JP2001211682A - Controller for brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent overvoltage and overcurrent from occurring in respective cases of current recovery from power failure, reversing command, and start-up from inertial rotation. SOLUTION: A speed control circuit 7 PI-computes a difference between command rotational speed cob from an acceleration adjusting circuit 6 and detected rotational speed Ωc from a speed detecting circuit 5 to output command voltage Va. When current recovers after the power failure occurs, the acceleration adjusting circuit 6 increases the command rotational speed Ωb from 0 to external command rotational speed Ωa gradually with a soft start function. A switch circuit 8 selects inductive voltage Vb from a voltage converting circuit 9 instead of the command voltage Va from the speed control circuit 7 until the command circuit rotational speed Ωb after current recovery becomes almost equal to the detected rotational speed Ωc which reduces gradually, and gives it to a drive circuit 2 as drive voltage Vc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a brushless motor having speed control means for generating a command voltage based on a difference between a command rotation speed and a detected rotation speed.

[0002]

SUMMARY OF THE INVENTION A brushless motor is
It is widely used in various fields because of its high efficiency and operability up to the high speed range, long life and high reliability. The brushless motor control device includes a position signal detection circuit (for example, a Hall element) for detecting a position signal indicating the rotation position of the rotor, a rotation speed detection circuit for detecting the rotation speed using the position signal, and the like. A speed control circuit that generates a command voltage for the brushless motor based on the difference between the rotation speed and the detected rotation speed, a drive circuit that controls energization of the windings of the brushless motor based on the command voltage, the command rotation direction, and the position signal It is composed of

In this conventional configuration, in order to prevent a failure of the brushless motor from starting at the time of starting or at the time of power recovery from a power failure state in which the voltage input to the brushless motor is cut off, the command rotation speed is gradually increased from 0. A soft start to raise is performed.

However, when the power failure time is relatively short, the power is restored before the brushless motor decelerates sufficiently, so that the difference between the detected rotation speed and the command rotation speed increases in the negative direction, and the speed control circuit generates The command voltage output to the drive circuit becomes extremely small. If the command voltage is extremely small,
When the drive circuit is performing sine wave PWM control or the like, a mode in which all the upper arm switching elements or lower arm switching elements of the drive circuit having, for example, a three-phase bridge configuration are turned on frequently occurs. As a result, excessive regenerative current flows from the winding of the brushless motor to the input side DC power supply of the drive circuit, and the DC voltage of the input side DC power supply becomes excessive.

Also, when an inversion command for changing the rotation direction in a stepwise manner is given during operation, or when an operation command in the direction opposite to the rotation direction is given when the brushless motor is coasting. Also, an excessive current flows through the drive circuit. When such an excessive current or voltage is generated, the protection circuit of the control device functions and the brushless motor may stop.

The present invention has been made in view of the above circumstances, and has as its object to prevent the occurrence of overcurrent and overvoltage in each case of power recovery from a power failure, inversion command, and startup from a coasting state. An object of the present invention is to provide a control device for a brushless motor in which the control is prevented.

[0007]

According to another aspect of the present invention, there is provided a control device for a brushless motor, comprising: a rotation speed detecting means for detecting a rotation speed of the brushless motor; a command rotation speed; A brushless motor control device comprising: a speed control unit that outputs a command voltage to the brushless motor based on a difference from a speed; and a driving unit that outputs a sinusoidal AC voltage to the brushless motor in accordance with the command voltage. A power failure detection means for detecting that the AC voltage input to the brushless motor has been interrupted, and a predetermined period after the power failure detection means has detected a power recovery from the interruption, with respect to the drive means. Voltage switching means for applying a voltage corresponding to the detected rotation speed in place of the command voltage output from the speed control means. The features.

According to this configuration, the command rotation speed suddenly changes due to the power failure, and the difference between the suddenly changed command rotation speed and the rotation speed (detection rotation speed) of the brushless motor that is gradually decelerating when power is restored is increased. In this case, a voltage (for example, an induced voltage) according to the detected rotational speed is applied to the drive means in place of the command voltage that changes transiently for a predetermined period until the transient state of the speed control means due to the increased difference is stabilized. . Thereby, the drive means can continue the operation in a stable state for a predetermined period after the power recovery, and thereafter, the transient state converges and the operation is stabilized using the command voltage from the stable speed control means. Can continue.

As a result, the drive means does not perform the energization control by the command voltage temporarily excessively or excessively reduced, so that the current flowing from the winding of the brushless motor to the drive means is suppressed to a small value. The energy regenerated by the input-side DC power supply is also reduced, and the occurrence of overvoltage in the input-side DC power supply can be prevented. This allows
When the power is restored, the overcurrent / overvoltage protection function does not operate, and continuous operation becomes possible.

In this case, it is preferable that the predetermined period is terminated when the command rotational speed and the detected rotational speed become substantially equal (claim 2). According to this configuration, it is possible to return to the speed feedback operation using the command voltage in a more stable state after a predetermined period has elapsed after the power recovery.

According to a third aspect of the present invention, there is provided a brushless motor control device, comprising: a rotating speed detecting means and a speed controlling means similar to those described above; and an AC voltage applied to the brushless motor based on the command voltage and the command rotating direction. A brushless motor control device comprising:
When the command rotation direction is reversed during operation, the command rotation direction before the reversal is given to the drive means, and the command rotation speed for decelerating the brushless motor is given to the speed control means, and the detected rotation speed is given. After the rotation speed becomes equal to or less than a predetermined rotation speed, the rotation control means for giving a command rotation direction after the reversal to the driving means and the command rotation speed for accelerating the brushless motor to the speed control means. It is characterized by having.

According to this configuration, when the command rotation direction is reversed, the reversal command is given in a state where the speed is reduced to the predetermined rotation speed at which the speed electromotive force becomes sufficiently small while maintaining the command rotation direction before the reversal command. In addition, the current flowing through the drive circuit due to the induced voltage is suppressed. As a result, even when the brushless motor is rotating at high speed, stable and smooth reversal can be performed without generating excessive current or voltage.

The control device for a brushless motor according to a fourth aspect of the present invention further comprises a rotation direction detecting means for detecting a rotation direction of the brushless motor, and when the commanded rotation direction is different from the detected rotation direction, the drive is performed. Means, the detected rotation direction is given in place of the commanded rotation direction, and a commanded rotation speed for decelerating the brushless motor is given to the speed control means, and the detected rotation speed becomes equal to or less than a predetermined rotation speed. And a rotation control unit for giving the command rotation direction to the drive unit and giving a command rotation speed for accelerating the brushless motor to the speed control unit.

According to this configuration, when the command rotation direction is different from the detection rotation direction, the detection rotation direction is switched from the detection rotation direction to the command rotation direction while being reduced to a predetermined rotation speed at which the speed electromotive force becomes sufficiently small. The current flowing through the drive circuit is suppressed by the voltage. In addition, since the rotation direction detecting means is provided, it is possible to smoothly start in the command rotation direction not only during rotation driving but also during startup when the brushless motor is coasting.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment (corresponding to claims 1 and 2) of the present invention will be described below with reference to FIGS. FIG. 1 is a block diagram showing an electrical configuration of a control device for a brushless motor. In this FIG.
The control device 1 includes a drive circuit 2, a pulse encoder 4 connected to a rotating shaft of a brushless motor 3, a speed detection circuit 5,
It comprises an acceleration adjustment circuit 6, a speed control circuit 7, a switching circuit 8, a voltage conversion circuit 9, and an instantaneous interruption detection circuit 10.
In the present embodiment, each of these circuits is configured by hardware.

The driving circuit 2 corresponds to a driving means in the present invention, and for example, a DC voltage generating circuit for rectifying and smoothing an AC voltage input from a three-phase AC power supply 11 to generate a DC voltage, I connected to the subsequent stage of the generation circuit
An inverter main circuit in which switching elements such as GBTs are connected in a three-phase bridge, generating a sine wave PWM signal based on a driving voltage Vc input from a switching circuit 8 and generating the IG signal;
It is composed of a PWM control circuit (both circuits are not specifically shown) for switching the BT. The output terminal of the drive circuit 2 is connected to each phase terminal of the three-phase winding of the brushless motor 3. The PWM control circuit uses the pulse signal from the pulse encoder 4 to determine the rotor position and determine the timing of energizing the winding.

The instantaneous power failure detection circuit 10 detects the occurrence of an instantaneous power failure (instantaneous power failure) based on the AC voltage of the AC power supply 11, and outputs the detection result to the instantaneous power failure signal Sa.
To the switching circuit 8.

Pulse encoder 4 and speed detection circuit 5
Corresponds to a rotation speed detecting means. The pulse encoder 4 outputs a pulse signal every time the rotating shaft of the brushless motor 3 rotates by a predetermined angle. The speed detection circuit 5 is configured as, for example, an FV conversion circuit, and detects the rotation speed of the brushless motor 3 based on the pulse signal.
The detected rotation speed ωc is multiplied by the induced voltage constant KE of the brushless motor 3 in the voltage conversion circuit 9 and is converted into the induced voltage Vb of the brushless motor 3.
Is input to

The acceleration adjusting circuit 6 is a circuit for a so-called soft start function, and is constituted by, for example, a charging circuit including a capacitor and a resistor. The acceleration adjustment circuit 6 is configured to control an external command rotational speed ωa input from the outside.
Is gradually increased according to the time constant of the charging circuit, and is output to the speed control circuit 7 as the commanded rotational speed ωb.

The speed control circuit 7 corresponds to speed control means, and includes a subtraction circuit (not shown) and a proportional / integral controller (P
I controller). The subtraction circuit calculates the difference between the command rotation speed ωb from the acceleration adjustment circuit 6 and the detection rotation speed ωc from the speed detection circuit 5, and the PI controller integrates the calculated difference with the proportional controller. A command voltage Va for the brushless motor 3 is obtained by inputting the signal to a controller.

The switching circuit 8 corresponds to a voltage switching means. As will be described in detail later, the switching circuit 8 receives a command voltage V from the speed control circuit 7 based on the operation command signal Sb and the instantaneous stop signal Sa.
a, and the induced voltage Vb from the voltage conversion circuit 9 is selected, and the selected voltage is output to the drive circuit as the drive voltage Vc.

Next, the operation of this embodiment will be described with reference to FIG. FIG. 2 shows waveforms of various parts at the time of start-up and at the time of a momentary stop, and shows, in order from the top, the operation signal, the external command rotation speed ωa, the command rotation speed ωb, the detection rotation speed ωc, the drive voltage Vc, and the switching signal. ing.

The switching circuit 8 generates an operation signal by calculating a logical product of the instantaneous stop signal Sa and the operation command signal Sb. This operation signal becomes an L level (low level) indicating a non-driving state during a period in which a stop command is input or a period during which a power failure occurs, and is a period during which the operation command is input and during a period during which no power failure occurs. It becomes H level (high level) indicating the driving state. Further, the switching circuit 8
Is, when the operation command changes from L level to H level,
A switching signal which becomes H level for a predetermined time is generated.

The time width of the switching signal is from the time when the operation command changes from the L level to the H level from the command rotation speed ωb
And the detected rotational speed ωc are set to be substantially equal to each other. That is, at the time of startup (time t1) shown in FIG. 2, the command rotation speed ωb is 0 due to the soft start function of the acceleration adjustment circuit 6, and the detected rotation speed ωc is also 0, so the width of the switching signal is Set short.

On the other hand, after the momentary stop occurs at time t2, time t
3, when the power is restored, the switching signal includes a command rotation speed ωb gradually increasing from 0 and a detection rotation speed ωc gradually decreasing by the soft start function of the acceleration adjustment circuit 6.
Are set to be at the H level until time t4 at which the values are substantially equal to each other.

The switching circuit 8 supplies the command voltage Va from the speed control circuit 7 when the switching signal is at the L level.
Is selected as the driving voltage Vc, and when the switching signal is at the H level, the induced voltage Vb from the voltage conversion circuit 9 is selected and set as the driving voltage Vc.

When a power failure occurs at time t2 when the control device 1 drives the brushless motor 3 at a high rotational speed, the respective circuits stop operating, the operation signal is at L level, the command rotational speed ωb and the drive voltage. Vc becomes 0. In this state, the brushless motor 3 enters an inertia rotation state, and the rotation speed gradually decreases.

Thereafter, when the power is restored at time t3, the command rotation speed ωb gradually increases from 0 to the external command rotation speed ωa by the soft start function. If the power failure period from time t2 to time t3 is short, the brushless motor 3 is not sufficiently decelerated and is driven again at a high speed. Therefore, the difference between the command rotation speed ωb and the detected rotation speed ωc at the time of power restoration becomes large on the negative side (deceleration side), and the command voltage Va output from the speed control circuit 7 becomes extremely small. In the conventional configuration, the sine wave PWM drive is performed using the command voltage Va as the drive voltage Vc.
The excessive regenerative current flows in the inverter main circuit, and the DC voltage of the DC voltage generating circuit becomes excessive.

On the other hand, the control device 1 according to the present embodiment uses the switching circuit 8 as described above to
Control. In other words, during the period when the switching signal after the power recovery is at the H level, the induced voltage Vb of the brushless motor 3 itself is used as the drive voltage Vc instead of the command voltage Va from the speed control circuit 7. Therefore, when the drive circuit 2 drives the brushless motor 3 again after the power is restored, no regenerative current flows through the drive circuit 2, and the brushless motor 3 gradually decelerates according to the size of the load.

At time t4 when the detected rotation speed ωc and the command rotation speed ωb gradually increasing from 0 become substantially equal.
, The switching signal changes from the H level to the L level, and the drive circuit 2 continues driving the brushless motor 3 using the command voltage Va as the drive voltage Vc instead of the induced voltage Vb. Also, at this time t4, the integral controller in the speed control circuit 7 is set to a predetermined value (for example, the induced voltage Vb), so that no excessive current flows through the drive circuit 2 after time t4, and the brushless motor 3 In accordance with the command rotation speed ωb, the vehicle smoothly accelerates to the external command rotation speed ωa.

As described above, the control device 1 of this embodiment
In the case of a change from the non-drive state to the drive state such as at the time of start-up or power recovery from a power failure state, the command rotation speed ωb gradually increased from 0 by the soft start function becomes substantially equal to the detected rotation speed ωc. During this period, the speed feedback loop is cut off and a voltage (induced voltage Vb) corresponding to the rotation speed of the brushless motor 3 is set as the drive voltage Vc. This prevents an excessive regenerative current from flowing such that the overcurrent protection circuit operates or an excessive DC voltage from causing the overvoltage protection circuit to operate at the time of start-up or power restoration, and the control device 1 Thus, the brushless motor 3 can be started or operated stably.

Next, a second embodiment (corresponding to claim 3) of the present invention will be described with reference to FIGS.
FIG. 3 is a block diagram showing the electrical configuration of the control device of the brushless motor, and the same components as those of the control device 1 shown in FIG. The control device 12
A drive circuit 13 is provided in place of the drive circuit 2 in the control device 1, and an acceleration / deceleration command circuit 14 is provided in place of the acceleration adjustment circuit 6. Further, the control device 12 includes a speed comparison circuit 1
5 and an acceleration / deceleration determination circuit 16 are added. With this configuration, the control device 12 can perform the forward and reverse rotation operation of the brushless motor 3.

The drive circuit 13 corresponds to the drive means in the present invention, and receives the drive voltage Vc from the switching circuit 8 and the command rotation direction Sf from the acceleration / deceleration determination circuit 16. Then, the drive circuit 13 outputs the command rotation direction S
By performing a switching operation of the IGBT of the inverter main circuit so as to generate a torque in the forward rotation direction or the reverse rotation direction in accordance with f, the energization control for the winding of the brushless motor 3 is performed. The energization control is
The control is not limited to the sine wave PWM control, and may be, for example, a 120-degree conduction control.

The acceleration / deceleration command circuit 14, speed comparison circuit 15, and acceleration / deceleration determination circuit 16 correspond to the rotation control means in the present invention. The speed comparison circuit 15 compares the detected rotation speed ωc with a predetermined switching rotation speed ωd. When the detected rotation speed ωc is higher than the switching rotation speed ωd, the H level is set. L when
A level comparison signal Sc is output (see FIG. 4). In this embodiment, the rotation speed is represented by an absolute value.

The acceleration / deceleration determination circuit 16 calculates the speed comparison signal Sc.
And an external command rotation direction Sd, and a command inversion signal which becomes H level when the external command rotation direction Sd changes is generated. Then, the acceleration / deceleration determination circuit 16
During the period in which the command inversion signal is at the L level, the external command rotation direction Sd is used as the command rotation direction Sf for the drive circuit 13 as it is, and after the command inversion signal goes to the H level, it is based on the speed comparison signal Sc. External command rotation direction Sd
Is inverted to be the command rotation direction Sf. The acceleration / deceleration determination circuit 16 outputs an acceleration / deceleration command signal Se for instructing the acceleration / deceleration command circuit 14 to accelerate or decelerate in response to the delay operation.

The acceleration / deceleration command circuit 14 is configured as a charge / discharge circuit including, for example, a capacitor and a resistor. When the acceleration / deceleration command signal Se is an acceleration command, the acceleration / deceleration command circuit 14 sets the external command speed ωa as a target value and outputs a command speed ωb that gradually increases according to the time constant of the charge / discharge circuit. When a deceleration command is issued, a command rotation speed ωb that gradually decreases in accordance with the time constant of the charge / discharge circuit is output.

Next, the operation of the present embodiment will be described with reference to FIG. FIG. 4 shows waveforms of the respective parts when the external command rotation direction Sd is reversed from the normal rotation direction to the reverse rotation direction during the normal rotation drive. The operation signal, the external command rotation speed ωa, and the detected rotation speed are shown in order from the top. ωc, speed comparison signal Sc, external command rotation direction Sd, command reversal signal, acceleration / deceleration command signal Se, command rotation direction Sf, and command rotation speed ωb
Is shown.

Here, the operation signal indicates that the L level indicates the non-drive state and the H level indicates the drive state, and the external command rotation direction Sd
And the command rotation direction Sf, the L level indicates the forward rotation direction and the H level indicates the reverse rotation direction. The acceleration / deceleration command signal Se is L
The level indicates an acceleration command, and the H level indicates a deceleration command.

When the external command rotation direction Sd is the normal rotation direction when the brushless motor 3 is stopped and the operation command changes from the non-drive state to the drive state (time t1).
1) The acceleration / deceleration determination circuit 16 gives the drive circuit 13 a command in the same normal rotation direction as the external command rotation direction Sd. At the same time, the acceleration / deceleration determination circuit 16
Command, the command rotational speed ωb is 0
Gradually increase from. At this time, unlike the control device 1 described above, since the switching circuit 8 selects the command voltage Va from the speed control circuit 7 as the drive voltage Vc, the brushless motor 3 gradually rotates in the forward direction according to the command rotation speed ωb. To a constant speed in the normal rotation direction equal to the external command rotation speed ωa.

At time t12, the external command rotation direction S
When d changes from the normal rotation direction to the reverse rotation direction, the command inversion signal which is an internal signal of the acceleration / deceleration determination circuit 16 becomes H level. Therefore, the acceleration / deceleration determination circuit 16 maintains the command rotation direction Sf in the normal rotation direction regardless of the external command rotation direction Sd, and gives a deceleration command to the acceleration / deceleration command circuit 14. Thus, the acceleration / deceleration command circuit 14 gradually reduces the command rotation speed ωb to decelerate the brushless motor 3.

At time t13, when the rotation speed falls to or below the switching rotation speed ωd, the speed comparison signal Sc changes from H level to L level. The acceleration / deceleration determination circuit 16
In response to this level change, the command rotation direction Sf given to the drive circuit 13 is set to the reverse direction in accordance with the external command rotation direction Sd, and an acceleration command is given to the acceleration / deceleration command circuit 14. As a result, the acceleration / deceleration command circuit 14 outputs the external command rotation speed ω
Since the command rotational speed ωb is gradually increased with the target value a, the brushless motor 3 accelerates in the reverse direction, and eventually reaches a constant speed in the reverse direction equal to the external command rotational speed ωa.

As described above, when the external command rotation direction Sd is reversed while the brushless motor 3 is being driven, the control device 12 maintains the command rotation direction Sf at that time and gradually switches the brushless motor 3 to the switching rotation speed ωd. After decelerating to
The command rotation direction Sf is reversed so that the brushless motor 3 is gradually accelerated (in the reverse direction). Moreover, since the switching rotation speed ωd is set sufficiently low, an excessive current or an excessive voltage due to the induced voltage does not occur in the drive circuit 13 at the time of inversion, and the overcurrent
Smooth inversion is possible without operating the overvoltage protection circuit.

Next, a third embodiment (corresponding to claim 4) of the present invention will be described with reference to FIGS.
FIG. 5 is a block diagram showing the electrical configuration of the control device of the brushless motor. The same components as those of the control device 12 shown in FIG. 3 are denoted by the same reference numerals. Control device 17
Includes an acceleration / deceleration determination circuit 18 in place of the acceleration / deceleration determination circuit 16 in the control device 12, and further includes a rotation direction detection circuit 1
9 (corresponding to rotation direction detecting means) and rotation direction comparison circuit 20
And Here, the acceleration / deceleration command circuit 14, the speed comparison circuit 15, the acceleration / deceleration determination circuit 18, and the rotation direction comparison circuit 20 correspond to the rotation control means in the present invention.

The rotation direction detection circuit 19 detects the rotation direction of the brushless motor 3 based on a pulse signal (for example, an A signal and a B signal whose phases differ by 90 degrees) output from the pulse encoder 4, and outputs the detection result as L. The detected rotation direction Sg is output at the level (forward rotation direction) or the H level (reverse rotation direction). However, the rotation direction detection circuit 19 has a slight detection delay.

The rotation direction comparison circuit 20 outputs an operation command signal S
b, an external command rotation direction Sd and a detected rotation direction Sg are input, and a rotation direction comparison signal Sh is output. The acceleration / deceleration determination circuit 18 determines whether the external command rotation direction S
d, a speed comparison signal Sc and a rotation direction comparison signal Sh are input, and an acceleration / deceleration command signal Se and a command rotation direction Sf are output.

Next, the operation of this embodiment will be described with reference to FIG. FIG. 6 shows waveforms when the brushless motor 3 is started in the normal rotation direction from the state in which it is coasting in the reverse rotation direction. The waveforms are, in order from the top, an operation command signal Sb, an operation command pulse signal, an external command rotation direction Sd,
A detected rotation direction Sg, a rotation direction comparison signal Sh, an external command rotation speed ωa, a detection rotation speed ωc, a speed comparison signal Sc, an acceleration / deceleration command signal Se, a command rotation direction Sf, and a command rotation speed ωb are shown.

When the operation command signal Sb changes from L level to H level at time t21, the rotation direction comparison circuit 20 generates an operation command pulse signal having a predetermined width. Although not shown, while the operation command pulse signal is at the H level,
The drive circuit 13 stops the drive operation.
Then, when the operation direction pulse signal is generated, the rotation direction comparison circuit 20 compares the external command rotation direction Sd with the detected rotation direction Sg. H-direction rotation direction comparison signal S
h is output (time t22). Note that the detection rotation direction Sg
Indicates that the L level indicates the normal rotation direction and the H level indicates the reverse rotation direction.

The acceleration / deceleration determination circuit 18 receives the H-level rotation direction comparison signal Sh from the rotation direction comparison circuit 20 and sends a deceleration command (H level) to the acceleration / deceleration command circuit 14.
And outputs to the drive circuit 13 a direction opposite to the external command rotation direction Sd, that is, the actual coasting rotation direction (here, the reverse rotation direction) as the command rotation direction Sf.

The acceleration / deceleration command circuit 14 increases the command rotation speed ωb to the detected rotation speed ωc during the detection delay of the rotation direction detection circuit 19 described above.
8 receives the deceleration command, the command rotation speed ωb is gradually reduced. Thus, the drive circuit 13 gradually decelerates while driving the brushless motor 3 that is coasting in the reverse direction in the reverse direction after the operation command pulse signal changes to the L level at time t23.

When the detected rotation speed ωc falls below the switching rotation speed ωd at time t24, the speed comparison signal Sc changes from the H level to the L level. The acceleration / deceleration determination circuit 18 receives the level change, and
3 is set to the normal rotation direction in accordance with the external command rotation direction Sd, and an acceleration command is given to the acceleration / deceleration command circuit 14. As a result, the acceleration / deceleration command circuit 14 gradually increases the command rotation speed ωb with the external command rotation speed ωa as a target value, so that the brushless motor 3 accelerates in the normal rotation direction, and eventually has a positive speed equal to the external command rotation speed ωa. The rotation speed becomes constant and the start is completed.

As described above, the control device 1 of the present embodiment
7 is provided with a rotation direction detection circuit 19 for detecting the rotation direction of the brushless motor 3. When the rotation direction (detection rotation direction Sg) in which the brushless motor 3 is coasting and the external command rotation direction Sd are different at the time of startup, the brushless motor 3 is set to the command rotation direction Sf as the coast rotation direction at that time. After gradually reducing the rotation speed to the switching rotation speed ωd, the command rotation direction Sf is changed to the external command rotation direction Sd.
And the brushless motor 3 is gradually accelerated.

Thus, even when the brushless motor 13 is started from a state rotating in the direction opposite to the external command rotation direction Sd, an excessive current or an excessive voltage due to the induced voltage is generated in the drive circuit 13. This does not occur, and a smooth start-up becomes possible without operating the overcurrent / overvoltage protection circuit.

It should be noted that the present invention is not limited to the embodiments described above and shown in the drawings, and the following expansions or modifications are possible. In the embodiment described above, the rotation speed of the brushless motor 3 is
Although the rotation direction, the rotation position of the rotor, and the like are detected, the detection may be performed using a plurality of Hall elements.

The change rate of the command rotation speed ωb at the time of soft start in the first embodiment, or the change rate of the command rotation speed ωb at the time of deceleration and acceleration in the second and third embodiments is
It is preferable that the rated rotation speed of the brushless motor 3 be set to N [rpm] or less per second (N / 2) [rpm].

In the third embodiment, the rotation direction comparing circuit 2
For 0, an operation signal which is an internal signal of the switching circuit 8 may be given instead of the operation command signal Sb. Thus, the same operation and effect as at the time of startup can be obtained even at the time of an instantaneous stop.

In the first embodiment, the case of the power failure of the AC power supply 11 has been described.
The present invention is not limited to the case of the power outage 1 but also includes a case where an AC voltage applied to the brushless motor 3 is cut off due to, for example, occurrence of an overcurrent or an overvoltage.

[0057]

The control device for a brushless motor according to the present invention uses a command voltage output from the speed control means to the drive means for a predetermined period after detecting a power recovery from a power failure according to the detected rotation speed. Since the power supply is configured so as to apply the voltage, when the power is restored, the driving means does not perform the energization control by the excessively large or small instruction voltage,
The generation of an excessive current and an excessive voltage due to regeneration can be suppressed. As a result, the overcurrent / overvoltage protection function does not operate when the power is restored, and the brushless motor can be smoothly operated.

When the command rotation direction is reversed during operation, the brushless motor is decelerated in a state where the command rotation direction before the reversal is given to the driving means, and the detected rotation speed becomes lower than a predetermined rotation speed. Later, since the brushless motor is accelerated by giving the command rotation direction after the reversal to the driving means, the current flowing through the drive circuit by the induced voltage at the time of the reversal is suppressed, and the overcurrent / overvoltage protection function operates. Smooth reversal is possible without any problem.

Further, when a rotation direction detecting means is provided and the command rotation direction is different from the detection rotation direction, the brushless motor is decelerated in a state where the detection rotation direction is given to the driving means, and the detection rotation speed becomes a predetermined rotation speed. After the speed becomes lower than the speed, the command rotation direction is given to the driving means to accelerate the brushless motor, so that it is possible to smoothly start and reverse without driving the drive circuit with excessive current due to induced voltage. Become.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an electric configuration of a control device according to a first embodiment of the present invention.

FIG. 2 is a waveform diagram of each part of the control device at the time of startup and at the time of occurrence of a momentary power failure.

FIG. 3 is a view corresponding to FIG. 1, showing a second embodiment of the present invention.

FIG. 4 is a waveform diagram of each part of the control device at the time of an inversion command.

FIG. 5 is a view corresponding to FIG. 1, showing a third embodiment of the present invention.

FIG. 6 is a waveform diagram of each part of the control device at the time of startup.

[Explanation of symbols]

1, 12, 17 are control devices, 2, 13 are drive circuits (drive means), 3 is a brushless motor, 4 is a pulse encoder (rotation speed detection means), 5 is a speed detection circuit (rotation speed detection means), 7 is Speed control circuit (speed control means), 8 is a switching circuit (voltage switching means), 10 is a momentary power failure detection circuit (power failure detection means), 14 is an acceleration / deceleration command circuit (rotation control means), 1
5 is a speed comparison circuit (rotation control means), 16 and 18 are acceleration / deceleration determination circuits (rotation control means), 19 is a rotation direction detection circuit (rotation direction detection means), and 20 is a rotation direction comparison circuit (rotation control means). is there.

Claims (4)

[Claims] A rotational speed detecting means for detecting a rotational speed of the brushless motor; a speed control means for outputting a command voltage to the brushless motor based on a difference between the command rotational speed and the detected rotational speed; A drive unit that outputs a sine-wave AC voltage to the brushless motor in accordance with the following, wherein a power failure detection unit for detecting that the AC voltage input to the brushless motor has been interrupted, A voltage for giving a voltage corresponding to the detected rotation speed to the drive means in place of a command voltage output from the speed control means for a predetermined period after the power failure detection means detects power recovery from the interruption. A control device for a brushless motor, comprising: switching means. 2. The brushless motor control device according to claim 1, wherein the predetermined period ends when the command rotational speed and the detected rotational speed become substantially equal. 3. A rotation speed detection means for detecting a rotation speed of the brushless motor; a speed control means for outputting a command voltage to the brushless motor based on a difference between the command rotation speed and the detected rotation speed; And a drive unit for outputting an AC voltage to the brushless motor based on the command rotation direction and the command rotation direction, wherein when the command rotation direction is reversed during operation, the drive unit is reversed. After giving the previous command rotation direction and giving a command rotation speed for decelerating the brushless motor to the speed control means, after the detected rotation speed falls below a predetermined rotation speed, And a command rotation speed for accelerating the brushless motor is given to the speed control means. A control device for a brushless motor, comprising: a rotation control means. 4. A rotation speed detection means for detecting a rotation speed of the brushless motor; a speed control means for outputting a command voltage to the brushless motor based on a difference between the command rotation speed and the detected rotation speed; A brushless motor control device comprising: a driving unit that outputs an AC voltage to the brushless motor based on the command rotation direction; and a rotation direction detection unit that detects a rotation direction of the brushless motor; and the command rotation direction. And the detected rotation direction is different,
The drive means is provided with the detected rotation direction in place of the command rotation direction, and the speed control means is provided with a command rotation speed for decelerating the brushless motor, and the detected rotation speed is equal to or less than a predetermined rotation speed. A rotation control means for giving the command rotation direction to the drive means and for giving a command rotation speed for accelerating the brushless motor to the speed control means. apparatus.