JPH05137370A - Motor controller - Google Patents

Abstract

PURPOSE:To perform a constant-speed control of a variable target speed and to effectively and rapidly interrupt power supply at the time of locking by so controlling to negatively feed back a PWM modulation factor that a deviation between an actual rotting speed and a target rotating speed becomes zero. CONSTITUTION:A transistor 7 is turned ON, OFF by a PWM signal V6, a PWM voltage is applied to a battery 10 or a DC motor 8, which starts to be rotated. The PWM voltage rises in proportion to the rise of a modulation factor control signal V4. Then, a mean voltage V1 to be output from a differential integrator 11 also rises in proportion to the rise of the signal V4. Since the voltage V1 is fed back to a b terminal of a deviation integrator 5, a deviation input of the integrator 5 is reduced, and the rising of the voltage V1 to be output from the integrator 11 is smoothed. A difference between a command voltage V0 and the fed-back mean output V1 becomes zero, an increase in the voltage V4 is stopped, and it is stabilized at a predetermined level necessary to obtain a desired speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention, in a DC motor controller using PWM, performs stable speed control by feeding back the average voltage of the applied voltage.
The present invention relates to a device that ensures cutoff of power supply when a motor is locked by using an average voltage detected for feedback.

[0002]

2. Description of the Related Art Conventionally, a DC motor (permanent magnet excitation) has been used as a blower motor used in an on-vehicle air conditioner. The speed control of the DC motor is performed by continuously changing the applied DC voltage in an analog manner by using a transistor in a non-saturation region.

On the other hand, in order to prevent the armature coil of the DC motor from being burnt out, it is necessary to immediately cut off the power supply when the motor is locked. For this purpose, the motor is provided with a temperature sensitive fuse so that when the motor is heated, the power supply is cut off by the breaking action of the fuse.

[Problems to be Solved by the Invention]

The above-mentioned control of the applied voltage by the base voltage of the transistor has a problem that the power consumption of the battery is large for use in electric components of automobiles because the collector loss of the transistor is large. In order to solve this, a method of controlling the average value of the applied voltage of the motor by performing on / off control of the transistor by PWM control is used in the speed control of a general motor not mounted on a vehicle. However, in this PWM control, generally, the current value is fed back to control the torque, or the rotational speed of the motor is detected by the tacho generator to perform the speed feedback control. Therefore, there is a problem that a speed detector such as a tacho-generator is required to precisely perform variable constant speed control like a blower motor.

On the other hand, in an apparatus for preventing burnout of a motor by detecting the temperature, the current is not cut off until some time has elapsed after the motor was locked, so that burnout may not be effectively prevented.

The present invention has been made to solve the above problems, and an object thereof is to achieve constant speed control in which a target speed can be varied in PWM control, and an average voltage value used in the constant speed control. By accurately detecting the locked state by using, the power supply can be cut off reliably and at high speed at the time of locking.

[0007]

The structure of the invention for solving the above-mentioned problems is a motor control device for controlling the rotation speed of a direct-current motor by applying a PWM control voltage to a constant-excitation type direct-current motor. The average voltage detection circuit that detects the average value of the voltage applied to the motor and the PWM control of the voltage applied to the DC motor so that the deviation between the speed command value and the average voltage value output by the average voltage detection circuit decreases. A PWM control circuit, a current detection circuit for detecting a load current of a DC motor, a threshold value changing means for changing a threshold value proportionally to an average voltage value output from the average voltage detection circuit, and a current detection circuit. A power supply stop circuit is provided for stopping power supply to the DC motor when the output current value exceeds the threshold value set by the threshold value changing means.

[0008]

The average value of the voltage applied to the motor is detected by the average voltage detection circuit. For a DC motor of constant excitation type (a DC motor of a type in which the excitation magnetic field does not change with the load current, that is, a motor that is not a direct-winding DC motor, such as a permanent magnet excitation, shunt winding, or compound winding DC motor) The voltage value represents the rotation speed of the DC motor during rotation. Therefore, P is set so that the average voltage value, that is, the deviation between the actual rotation speed and the command value (target rotation speed) becomes zero.
The WM modulation rate is negatively feedback controlled. By this control, the actual rotation speed will stably follow the command value,
In PWM control of a DC motor, stable and precise speed control is possible.

Further, the threshold value of the load current for judging the lock state of the motor is proportionally varied according to the detected average voltage value of the applied voltage of the motor. Then, when the current value output from the current detection circuit exceeds the variably determined threshold value, it is determined that the motor is locked. Then, depending on the determination result, the power supply to the motor is cut off.

When the rotational speed command value increases, the detected average voltage value also increases. The detected average voltage value is the average value of the voltage applied by the PWM control, and therefore does not change even when the motor is in the lock state. Therefore, the load current when the motor is locked increases in proportion to the average voltage value applied to the motor. The load current when not locked also increases in proportion to the average voltage value applied to the motor. Therefore, by accurately changing the threshold value between the load current in the locked state and the load current in the non-locked state with respect to the average voltage value, it is possible to accurately detect whether or not the motor is in the locked state. It becomes possible.

[0011]

According to the present invention, the average voltage detection circuit for detecting the average value of the voltage applied to the DC motor and the deviation between the speed command value and the average voltage value output by the average voltage detection circuit are reduced. P for PWM controlling the voltage applied to the DC motor
Since the WM control circuit is provided, the stability of the rotation speed of the motor and the control accuracy of the rotation speed are improved. Further, according to the present invention, the average voltage value detected by the above-mentioned PWM feedback control is used to change the threshold value proportionally to the average voltage value, and the output of the current detection circuit. When the current value to be applied exceeds the threshold value set by the threshold value changing means, a power supply stop circuit for stopping the power supply to the DC motor is provided, so that the threshold value is relative to the average value of the applied voltage. Therefore, the lock determination can be accurately performed regardless of the rotation speed of the motor before the lock, and the current can be interrupted without delay during the lock.

[0012]

EXAMPLES The present invention will be described below based on a specific example. In FIG. 1, the armature of a permanent magnet excitation type DC motor 8 is fed from a battery 10 via a commutator 21. The power supply circuit to the armature has a transistor 7 (MOS FET) that operates on and off and a current detection circuit 12
Has been inserted. The current detection circuit 12 is composed of a current detection resistor 12a through which a load current flows and an operational amplifier 12b with a large input impedance that amplifies a voltage across its terminals. The output voltage V2 of the operational amplifier 12b is the DC motor 8
Represents the magnitude of the load current flowing through the armature. Hereinafter, the output voltage V2 will be referred to as the load current value V2.

The PWM signal V6 output from the comparator 6 is input to the base of the transistor 7 that PWM-controls the voltage applied to the DC motor 8. The inverting input terminal of the comparator 6 receives the triangular wave voltage V5 output from the triangular wave generating circuit 4, and the non-inverting input terminal receives the output voltage V4 of the deviation integrating circuit 5. Since the PWM modulation rate (duty ratio) of the voltage applied to the DC motor 8 is proportional to this output voltage V4, this output voltage V4 is hereinafter referred to as modulation rate control voltage V4. The command voltage VO relating to the rotation speed is input from the terminal a to the deviation integration circuit 5, and the voltage V1 output from the differential integration circuit 11 is input from the terminal b. The triangular wave generation circuit 4, the deviation integration circuit 5, the comparator 6, and the transistor 7 constitute a PWM control circuit. The inductor 2 and the resistor 3 are circuits that convert the speed command value input from the signal input terminal 1 into a command voltage V0 of the rotation speed of the DC motor 8 by the terminal voltage of the resistor 3.

On the other hand, both terminals of the DC motor 8 are connected to the terminals a and b of the differential integration circuit 11. The differential integration circuit 11 (average voltage detection circuit) is a pulse-width-modulated voltage applied to the DC motor 8 (hereinafter referred to as PWM voltage).
Voltage V1 proportional to the average value of (hereinafter referred to as average voltage V1)
Is a circuit for outputting. The average voltage V1 output from the differential integration circuit 11 is input to the terminal b of the deviation integration circuit 5 and the terminal a of the motor lock determination circuit 13.

The average voltage V1 output from the differential integration circuit 11 is input to the motor lock determination circuit 13 from the a terminal,
The load current value V2 output from the current detection circuit 12 is input from the b terminal. The motor lock determination circuit 13 includes an amplifier 22 (threshold variable means for generating a threshold voltage Vt (hereinafter, this voltage Vt is referred to as a threshold Vt)) proportional to the average voltage V1 output from the differential integration circuit 11. ), And a comparator 23 (power feeding cutoff means) that outputs a power feeding cutoff signal V3 according to the load current value V2 and the threshold value Vt. The power supply cutoff signal V3 output from the comparator 23 is input to the gate of the transistor 7, and when the power supply cutoff signal V3 is at the L level, the transistor 7 is turned off regardless of the output of the comparator 6. Reference numeral 9 is a flywheel diode for returning the current flowing in the DC motor 8 when the transistor 7 is turned off, 14 is a ferrite bead for noise removal, and 15 is a temperature rise reduction and noise reduction of the transistor 7. It is a capacitor for reduction.

The operation of this apparatus will be described below. (1) At the time of starting the DC motor 8 and rotating at a constant speed In the timing chart of FIG.
The average voltage V1 output from the differential integration circuit 11 is 0V,
The b terminal of the deviation integration circuit 5 is 0V. When a speed command value corresponding to a desired speed is input from the signal input terminal 1 at time t1, a command voltage V0 that rises at time t1.
Is input to the deviation integration circuit 5. Then, at time t1, the deviation input of the deviation integration circuit 5 becomes the command voltage V1, and the time integration value of the command voltage V1 becomes the modulation factor control voltage V4 output by the deviation integration circuit 5. Therefore, the modulation rate control voltage V4 input to the non-inverting input terminal of the comparator 6 gradually rises from the time t1. The comparator 6 compares the levels of the modulation rate control voltage V4 and the triangular wave voltage V5, and while the modulation rate control voltage V4 is higher than the triangular wave voltage V5, the PWM signal V6 output from the comparator 6 becomes the H level and the modulation rate. While the control voltage V4 is lower than the triangular wave voltage V5, the PWM signal V6 is at L level. Therefore, the modulation rate of the PWM signal V6 changes in proportion to the modulation rate control voltage V4.

The transistor 7 is turned on / off by the PWM signal V6, and the PWM is supplied from the battery 10 to the DC motor 8.
A voltage is applied, a current flows through the armature, and the DC motor begins to rotate. This PWM voltage rises in proportion to the rise of the modulation rate control signal V4. Then, the average voltage V1 output from the differential integration circuit 11 is averaged by the integration operation of the differential integration circuit 11 to output the average voltage V1. The average voltage V1 also rises in proportion to the rise of the modulation rate control signal V4.

Since this average voltage V1 is fed back to the terminal b of the deviation integration circuit 5, the deviation input of the deviation integration circuit 5 is reduced. As a result, the rate of increase of the deviation integration value decreases, and the level of the modulation rate control signal V4 gradually increases. As a result, the increase in the average voltage of the PWM voltage applied to the DC motor 8 also moderates, and the increase in the average voltage V1 output from the differential integration circuit 11 also moderates. Then, the difference between the command voltage V0 and the fed-back average voltage V1 becomes zero, and the modulation rate control signal V4 stops increasing and stabilizes at a constant level required to obtain a desired speed. And the average voltage V1
Also stabilizes at a level equal to the command voltage V0. After that,
Even if the average voltage V1 or the like changes due to disturbance, the modulation rate control signal V4 changes in the direction in which the average voltage V1 becomes equal to the command voltage V0. Therefore, the DC motor 8 is always stable at the commanded constant rotation speed. It will rotate.

Even when the command voltage V0 is changed in order to change the rotation speed of the DC motor 8, the rotation speed of the DC motor 8 becomes equal to the commanded rotation speed by the same operation as at the time of starting. It will follow stably.

(2) When the DC motor 8 is locked It is assumed that the DC motor 8 is locked for some reason while the PWM voltage is being applied to the DC motor 8 as described above. At this time, since the command voltage V0 and the average voltage V1 do not change, the modulation rate control voltage V4 also does not change.

The average voltage V1 is input to the amplifier 22, and the threshold value Vt is output from the amplifier 22. This threshold Vt
The gain of the amplifier 22 is adjusted so that the characteristic of the average voltage V1 becomes the characteristic shown by the straight line C in FIG. The comparator 23 compares the load current value V2 with the threshold value Vt,
When the load current value V2 becomes higher than the threshold value Vt, the power cutoff signal V3 of L level is output. On the other hand, when the load current value V2 is lower than the threshold value Vt, the power feeding cutoff signal V3 is at the H level. When the power interruption signal V3 is at the H level, the transistor 7 is turned on / off according to the PWM signal V6 output from the comparator, and the PWM voltage is supplied to the DC motor 8.

When the DC motor 8 is rotating, the relationship between the average voltage V1 (which can be regarded as a speed command value) and the load current is as shown by the straight line A in FIG. When the DC motor 8 is locked, the relationship between the average voltage V1 and the load current is as shown by the straight line B in FIG. In FIG. 3, when the DC motor 8 is rotating,
Since a speed electromotive force is generated in the armature, the load current flowing in the armature is smaller than that in the locked state. However, both increase in proportion to the average voltage V1 (or speed command value). Therefore, if it is judged from the magnitude of the load current whether the DC motor 8 is in the rotating state or the locked state,
The lock state cannot be determined unless the threshold value Vt that increases proportionally to the average voltage V1 (or the speed command value) is set.

In this embodiment, this threshold value Vt is set to the average voltage.
It is changed in proportion to V1 (or speed command value). still,
The characteristic of this threshold value Vt-average voltage V1 is as shown in FIG.
In the operating range of the average voltage V1, it suffices if the load current during lock and the load current during rotation can be distinguished.
It may be a characteristic that increases in a stepwise manner with respect to the increase of. In short,
It is sufficient for the threshold value Vt to increase proportionally in a broad sense with respect to the increase of the average voltage V1.

When the DC motor 8 is locked, the load current suddenly increases. At this time, when the load current value V2 detected by the current detection circuit 12 becomes higher than the threshold value Vt, the power supply cutoff signal V3 output from the comparator 23 becomes L level. Therefore, the gate of the transistor 7 is grounded regardless of the voltage level of the PWM signal V6 output from the comparator 6, and the transistor 7 is immediately turned off. Therefore, even if the speed command value is continuously input from the signal input terminal 1, the power supply to the DC motor 8 is instantaneously stopped with respect to the lock, and the DC motor 8 is prevented from being burned due to the lock.

The differential integration circuit 11 may have the configuration shown in FIG. Also in this configuration, it is possible to detect the average voltage of the PWM voltage applied to the DC motor 8. Also, when locked, the power supply to the motor is not stopped immediately, it is maintained for a while, torque is generated in order to remove the cause of the lock, and the power supply is stopped after a certain period of time. You may let me. In this case, it goes without saying that the power supply is not stopped if the normal rotation is returned in the middle. Furthermore, by adding an appropriate delay circuit, it is possible to limit the current flowing through the motor.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of a motor control device according to a specific embodiment of the present invention.

FIG. 2 is a timing chart illustrating the operation of the control device.

FIG. 3 is a characteristic diagram showing a relationship between an average voltage (or speed command value) applied to a DC motor, a load current, and a threshold value.

FIG. 4 is a circuit diagram showing a circuit for detecting an average voltage of a PWM voltage related to a DC motor according to another embodiment.

[Explanation of symbols]

 4 ... Triangular wave generation circuit (PWM control circuit) 5 ... Deviation integration circuit (PWM control circuit) 6 ... Comparator (PWM control circuit) 7 ... Transistor (PWM control circuit) 8 ... DC motor 11 ... Differential integration circuit (average voltage detection) Circuit) 12 ... current detection circuit 13 ... lock determination circuit 22 ... amplifier (threshold variable means) 23 ... comparator (power supply stopping means)

Claims (1)

[Claims] 1. A motor control device for controlling the rotation speed of a DC motor by applying a PWM control voltage to a constant excitation DC motor, wherein an average voltage for detecting an average value of the voltage applied to the DC motor. A detection circuit; a PWM control circuit for PWM-controlling the voltage applied to the DC motor so that the deviation between the speed command value and the average voltage value output by the average voltage detection circuit is reduced; A current detection circuit for detecting, a threshold value varying means for varying a threshold value in proportion to an average voltage value output by the average voltage detection circuit, and a current value output by the current detection circuit is the threshold value. A motor control circuit comprising a power supply stop circuit for stopping power supply to the DC motor when a threshold value set by the value changing means is exceeded.