JP2851976B2 - Motor control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor control device for controlling a motor to rotate or stop in response to an external rotation or stop instruction signal, and more particularly to overload protection control.

[0002]

2. Description of the Related Art When an overload or a locked state continues due to an abnormal mechanical load, a motor rotating while receiving power is damaged by the heat generated by the motor itself or its control circuit. Therefore, the control device includes an overload protection device that detects an overload or a locked state of the motor and shuts off power supply to the motor before the motor is destroyed to protect the motor and the control circuit. A general overload protection device detects a load current flowing through a motor, compares the detected load current with a preset current value (overcurrent determination reference value), and monitors the load state of the motor. When the power exceeds the limit, the power supply to the motor is cut off to stop the motor, and this state is stored and maintained. The operator clears the stored state after removing the cause of overload or lock. , The rotation control can be restarted.

Devices such as printers and copiers incorporating such a motor and its control device generate a rotation control signal for instructing rotation or stop of the motor from a main control device for controlling the entire motor, thereby controlling the rotation of the motor. Although the control is performed, if the above-described overload protection device is provided, once the protection function has been activated, the operation of the device cannot be resumed without the assistance of an operator. That is, it is not possible to attempt control to automatically restart the operation after the main controller checks the state of the device.

In particular, this type of motor control in a device such as a paper feed mechanism which is charged with static electricity by friction or a device using a brush motor which generates a relatively large amount of noise (eg, a printer or a copying machine). In the device,
The protection device may malfunction due to noise and cause the device to stop. Also, a malfunction may occur when the power is turned on or when there is a momentary interruption. Also in such a case, there is an inconvenience that the operator must assist in restarting the operation of the device.

[0005] This type of motor control device is disclosed in
No. 43413 or Japanese Patent Application Laid-Open No. 61-74293, none of which has a configuration in which the main controller can automatically attempt to restart the rotation control of the stopped motor.

[0006]

As described above, the overload protection device in the conventional motor control device is liable to malfunction at the moment of instantaneous interruption or startup of the power supply or due to noise.
When the overload protection device operates, there is an inconvenience that even if the operation is a malfunction due to noise or the like, the rotation control of the motor cannot be restarted without the assistance of an operator.

Accordingly, an object of the present invention is to prevent the overload protection device from malfunctioning due to instantaneous interruption or start-up of the power supply, noise, or the like. Is to be able to resume.

[0008]

SUMMARY OF THE INVENTION The present invention provides control means for rotating or stopping a motor in response to an externally applied rotation control signal, and an overcurrent when a load current of the motor exceeds a preset current value. Overcurrent detection means for generating a detection signal, time management means for managing the output time of the overcurrent detection signal, storage means for storing an output signal of the time management means, and output of the storage means to the control means In the motor control device that returns to and stops the motor,
Clear means for clearing the storage means is provided while the rotation control signal instructs stop of rotation of the motor, or the storage means is cleared at the moment when the rotation control signal instructs rotation of the motor. A clearing means for performing the operation.

[0009]

The storage means for storing the overcurrent detection is controlled to the clear state while the rotation control signal supplied from the outside indicates the rotation stop, so that the chance of malfunction due to noise or the like is reduced. Once the external rotation control signal is set to the rotation stop instruction state, the storage means can be cleared, so
The memory of the malfunction state can be cleared. Further, when the rotation control signal instructs the rotation of the motor, the storage in the storage unit is cleared, so that the control of restarting the rotation of the motor can be automatically attempted according to the rotation instruction from the main control device.

[0010]

1 is a block diagram of a motor control device according to the present invention, and FIG. 2 is a time chart showing various signals during the operation.

In the motor control device, the rotation or stop of the DC motor 5 is instructed by a rotation control signal 10 from an external main control device 30 which controls the entire apparatus. This motor control device uses a general PWM (pulse width modulation)
Execute drive control. For this purpose, the rotation detector 21 such as an encoder outputs a speed detection pulse signal 19 corresponding to the rotation of the DC motor 5. The speed comparator 1 compares the speed detection pulse signal 19 with a reference clock pulse signal 28 provided from the main controller 30 and outputs the difference as an analog speed difference signal 12. On the other hand, the waveform generator 3 generates and outputs a reference waveform signal 13 for PWM drive control. The comparison device 2 compares the speed difference signal 12 with the reference waveform signal 13 and outputs a drive pulse signal 14. The driver 4 controls the drive current supplied to the DC motor 5 on / off in response to the drive pulse signal 14, and rotates the DC motor 5 at a predetermined speed. The control system constituted by this closed loop is a general PWM drive control system.

Here, the speed comparator 1 outputs the rotation control signal 10
The function is set to an operating state or a stopped state, and finally the DC motor 5 is set to a rotation control state and a stop control state. The high level (off) of the rotation control signal 10 indicates an instruction to control the motor 5 to be in a stopped state, and the low level (on) indicates an instruction to control the motor 5 to be in a rotated state.

The load current of the DC motor 5 is a current detection resistor 6
Flows through to the ground. The overcurrent detection circuit 7 detects the load current flowing through the DC motor 5 based on the voltage generated at the terminal of the current detection resistor 6, and when the value exceeds a preset value (overcurrent determination reference value), the overcurrent is detected. Current detection signal 1
Set 6 to high level. When the overcurrent detection signal 16 goes to a high level, the timer circuit 8 serving as a time management means operates an internal timer function. When the high level state continues for a certain period of time t or more, the overload detection signal 17 goes to a low level. When the overload detection signal 17 becomes low level, the storage circuit 9 as protection means makes the protection output signal 18 high level and stores the state. The inverting circuit 23 inverts the signal level of the protection output signal 18, converts the high-level protection output signal 18 to a low level, and fixes the input circuit of the driver 4 to a low level. Accordingly, the driver 4 is not driven, the current supply to the DC motor 5 is cut off, and the rotation of the DC motor 5 is stopped. This is the protection operation.

By the way, generally, an overcurrent of the DC motor 5 instantaneously flows at the time of start-up, as much as at the time of motor lock.
However, it is necessary that the above-mentioned protection function does not work with the overcurrent flowing at the time of starting. The set time t of the timer circuit 8 is set to be longer than the continuation time of the overcurrent flowing at the time of starting, so that the overload detection signal 17 is not output in the overcurrent detection signal 16 having a time width equal to or less than the set time t. I do.

An input terminal CLR for clearing the storage state of the storage circuit 9 is supplied with a clear signal 20 obtained by inverting the signal level of the rotation control signal 10 by an inversion circuit 24. Since the clear signal is input to the input terminal CLR of the storage circuit 9 while the rotation control signal 10 is at the high level indicating that the rotation of the motor is stopped, even if there is external noise or momentary interruption of the power supply during this period, the clear signal is input. The storage circuit 9 does not malfunction and enter a storage state similar to the overload detection state. Therefore, when the rotation control signal 10 given from the main control circuit 30 becomes low level (motor rotation instruction), the motor control device enters a control state in which the DC motor 5 is reliably rotated.

In a general DC motor control system, a microcomputer or the like of the main control device 30 that controls the DC motor in many cases instructs the rotation or stop control of the motor. Then, after instructing the rotation of the motor by the rotation control signal (after a specific time), main controller 30 confirms whether or not the motor has started to a specified rotation state. The speed comparator 1 determines whether or not the rotation of the motor has risen to a specified value based on the pulse interval of the speed detection pulse signal 19 input from the encoder 21, and returns a ready signal 11 to the main controller 30. The main control device 30
By checking the ready signal 11, it can be detected that the DC motor 5 has risen to a specified rotation state.

When the motor control device enters a protection operation state due to an overload or a motor lock, the pulse interval of the speed detection pulse signal 19 is widened, so that the speed comparator 1 detects this and changes the ready signal 11 to a high level. The main controller 30 can detect that the load of the DC motor 5 is abnormal and is stopped by checking the ready signal 11. In this case, if the load side is abnormal, this protection operation is correct, but is often due to temporary overload or noise. Such a state is a state where it is possible to return to the normal rotation control state again by instructing re-rotation. In order to return the stopped DC motor 5 to the normal rotation control state, the main control device 30 sends the rotation control signal 10
If the state is once instructed to stop the rotation and then the state is again instructed to rotate, the storage state of the storage circuit 9 is cleared, and the maintenance of the protection operation is released. 5 can be controlled to rotate.

FIG. 2 is a time chart showing various signals in such a series of control operations.
Is started (rotated). During this rotation, the lock of the motor occurs, and after t time, the protection function is activated.
This is an operation of trying to restart (retry) and returning to the normal rotation control state again.

Here, the signal timing at the start of the retry is the rotation control signal 1 given from main controller 30.
0 activates the drive pulse signal 14 after passing through the speed comparator 1 and the comparison device 2, but clears the storage circuit 9 earlier than this and releases the input circuit of the driver 4, so that
The restart operation is not hindered.

Next, a description will be given of an embodiment in which a malfunction due to noise or an instantaneous interruption of the power supply is further reduced with reference to FIG. This embodiment is obtained by connecting the capacitor 25 between the inverting output terminal Q ₃ and clear input terminals CLR of the memory circuit 9 is constituted by a flip-flop with respect to the embodiment of FIG.

In the embodiment of FIG. 1, while the rotation control signal 10 indicates the stop of rotation, the memory circuit 9 is in a clear state because a low-level signal is input to the clear input terminal CLR. No malfunction occurs due to noise or momentary power interruption. However, during rotation, the storage circuit 9 may malfunction due to external noise or momentary interruption of the power supply. Avoiding this malfunction can be achieved by AC to return to their own clear input terminal CLR of the output signal of the inverting output terminal Q ₃ of the memory circuit 9 via a capacitor 25.
That is, malfunction due to the output signal is fed back to the clear input terminal CLR the storage circuit 9 to clear the inversion output terminal Q ₃ when the storage circuit 9 is inverted output terminal Q ₂ from the protection output signal 18 is generated Acts to return. Therefore, it is possible to prevent a malfunction due to a temporary noise or a momentary power interruption. Of course, the power supply to the DC motor 5 is momentarily cut off by the operation, but since this is an instant, the DC motor 5 continuously rotates by the rotational inertia.

In this embodiment, a one-shot pulse generating circuit can be used instead of the capacitor 25. On the other hand, in the case of normal motor lock or overload, the overload detection signal 17 continues, and the set input of the storage circuit 9 is continuously fixed at the low level. protection terminal Q ₂ from the protection output signal 18 is generated is reliably work it.

The time chart of FIG. 4 is a variety of signals at the time of such a series of control operations, the protection output signal storage circuit 9 by external noise during motor rotation control malfunctions from its output terminal Q ₂ 18 is generated, the output signal of the inverting output terminal Q ₃ is fed back to the clear input terminal CLR via the capacitor 25 mis-operation is restored automatically,
Thereafter, a state in which the protection function normally operates after a time t after the motor is locked due to the abnormality is shown.

FIG. 5 shows a time chart in the control operation when chattering occurs at power-on. In the conventional device, when chattering occurs at power-on, the storage circuit 9 malfunctions and the protection output signal 1
8 is often output as shown by the broken line. When inconvenience occurs during use of equipment using the motor and maintenance work is performed by opening a part of the equipment, power is often shut off in conjunction with the opening for safety reasons.
When the maintenance work is completed and closed, the power supply is often started in conjunction with the closure. In such a case, if chattering occurs and a malfunction occurs, the motor control device is in a state where the protection function is activated from the time of power-on, and the rotation control signal 10 given from the main control device 30 instructs rotation. However, the rotation of the motor cannot be controlled. However, by setting the rotation control signal 10 to the high level, the clear input terminal CLR of the storage circuit 9 is input to the low level to be in the clear state, so that the storage circuit 9 does not store the malfunction state, and Can be resumed.

FIG. 6 shows another embodiment, in which the inverting circuit 24 in the above-described embodiment is replaced with the one-shot pulse generating circuit 2.
6 instead of 6. In this embodiment, the memory circuit 9 is cleared by generating a clear signal for clearing the memory circuit 9 at the moment when the rotation control signal 10 instructs the rotation of the motor. 9
Even if the motor becomes malfunctioning, the motor can be brought into the rotation control state by the rotation instruction.

[0026]

According to the present invention, the storage means for storing the overcurrent detection is controlled to the clear state while the rotation control signal supplied from the outside is instructing the stop of the rotation. To reduce the power supply and to be resistant to instantaneous power interruptions and noise.In addition, once the external rotation control signal is set to the rotation stop instruction state, the storage means can be cleared, so that the storage of the malfunction state is cleared and the rotation control is performed. Or when the rotation control signal instructs the rotation of the motor, the storage in the storage means is cleared and the rotation can be controlled. Therefore, the control of restarting the rotation of the motor by the rotation instruction from the main controller is performed. Can be automatically attempted.

[Brief description of the drawings]

FIG. 1 is a block diagram of a motor control device according to the present invention.

FIG. 2 is a time chart showing operation signals in the motor control device of FIG. 1;

FIG. 3 is a block diagram showing another embodiment of the motor control device according to the present invention.

FIG. 4 is a time chart showing operation signals in the motor control device of FIG. 3;

FIG. 5 is a time chart showing operation signals in the motor control device of FIG. 3;

FIG. 6 is a circuit diagram showing another embodiment of the storage circuit clear means.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Speed comparator 2 Comparator 4 Driver 5 DC motor 6 Current detection resistor 7 Overcurrent detection circuit 8 Timer circuit 9 Storage circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H02H 7/08-7/097 H02P 5/04-5/26

Claims (5)

(57) [Claims] 1. A control means for rotating or stopping a motor according to a rotation control signal supplied from outside, and an overcurrent detection for generating an overcurrent detection signal when a load current of the motor exceeds a preset current value. Means, time management means for managing the output time of the overcurrent detection signal, storage means for storing the output signal of the time management means, and the output of the storage means fed back to the control means to stop the motor. The motor control device, further comprising: a clear unit that clears the storage unit while the rotation control signal instructs the motor to stop rotating. 2. The motor control device according to claim 1, wherein said clear means couples an output of said storage means and a clear input in an alternating manner. 3. A control means for rotating or stopping a motor according to a rotation control signal given from outside, and an overcurrent detection for generating an overcurrent detection signal when a load current of the motor exceeds a preset current value. Means, time management means for managing the output time of the overcurrent detection signal, storage means for storing the output signal of the time management means, and the output of the storage means fed back to the control means to stop the motor. The motor control device, further comprising: a clear unit that clears the storage unit at a moment when the rotation control signal instructs rotation of the motor. 4. The motor control device according to claim 3, wherein said clear means couples an output of said storage means and a clear input in an alternating manner. 5. A control means for rotating or stopping a motor according to a rotation control signal supplied from outside, and an overcurrent detection for generating an overcurrent detection signal when a load current of the motor exceeds a preset current value. Means, storage means for storing an overload state, and a motor control device for returning an output of the storage means to the control means to stop the motor, wherein the rotation control signal indicates that the rotation of the motor is to be stopped. A motor control device provided with clear means for clearing a storage means.