JPH0412695A - Motor control method - Google Patents

Abstract

PURPOSE:To control the temperature of a motor, without requiring a temperature detecting element such as a thermister, by predicting current temperature based on temperature rise characteristics during operation of motor and temperature drop characteristics during pause of motor and then comparing thus predicted temperature with the dangerous temperature, i.e., a prescribed temperature, of motor thereby controlling the motor. CONSTITUTION:A monitor circuit 4 adds the count in a counter 5 with a rate correlative to temperature rise characteristics when a drive signal (DR signal) fed from a control circuit 3 is 'H', whereas decreases the count in the counter 5 with a rate correlative to temperature drop characteristics when the DR signal is 'L' thus predicting current temperature of a motor 1. When the output from a first comparator circuit 6 is 'H', the control circuit 3 outputs an 'L' DR signal to disable a motor drive circuit 2 so as to stop operation of the motor 1 while furthermore provides an alarm from an alarm unit 7. When the output from a second comparator circuit 9 is 'O', the control circuit 3 outputs an 'H' DR signal to restart the motor 1 and to interrupt provision of an alarm from the alarm unit 7.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a motor control method for preventing abnormal overheating of the motor.

(Prior art) Conventional methods for preventing abnormal overheating caused by long-term use of a motor include measuring the temperature near the heat generating part using a thermistor to regulate motor operation, and installing a cooling fan to prevent abnormal overheating from occurring near the heat generating part. or use high-grade motors with self-cooling functions to prevent themselves from overheating.

(Problems to be Solved) All of the conventional methods described above result in high costs, which is a factor in increasing the cost of equipment that employs them.

An object of the present invention is to provide a motor control method that allows the temperature of the motor to be controlled without using a temperature detection element such as a thermistor.

(Means for Solving the Problem) In order to achieve the following two objects, the motor control method according to the present invention monitors the operating time and rest time of the motor, and monitors the temperature rise characteristic during motor operation and the above-mentioned temperature rise characteristic. Predict the current temperature of the motor based on the temperature drop characteristics when the motor is at rest,
When the predicted temperature exceeds the first specified temperature, the operation of the motor is stopped, and based on this stop, the predicted temperature falls to a second specified temperature that is lower than the first specified temperature. to restart the above motor.

(Function) The operating time and rest time of the motor are monitored, and the current temperature of the motor is predicted from the temperature rise characteristics when the motor is operating and the temperature drop characteristics when the motor is stopped.

This predicted temperature is compared with a first specified temperature which is a dangerous temperature of the motor, and when this predicted temperature exceeds the specified temperature, the operation of the motor is stopped.

Based on this stop, the motor is restarted when the predicted temperature falls to a second specified temperature lower than the first specified temperature. Therefore, abnormal overheating of the motor can be prevented without using a temperature detection element such as a thermistor. Furthermore, since the motor operation is restarted after the motor temperature has fallen below the dangerous temperature by a predetermined temperature, there is a long period of time before the predicted temperature exceeds the first specified temperature, and the motor can be operated continuously during this time.

(Example) An example of the present invention will be described below with reference to the drawings.

The circuit for realizing the second control method is shown in FIG. 1 as a motor drive circuit 2. Control circuit 3. Monitoring circuit 4. Counter 5. First comparison circuit 6. Alarm device such as a buzzer7.
It is configured by a second comparison circuit 9.

The control circuit 3 outputs a drive signal (DR multiplied signal) that controls the operation/pause of the motor 1, and also controls the alarm device 7, and when the DR multiplied signal is at a low level "H", the motor 1 is activated, and the DR double signal low level “L”
When , the motor 1 rotates one turn.

The monitoring circuit 4 monitors whether the DR multiplied signal is “H” or “L”,
When "H', the count value of the counter 5 is added at a rate correlated to the temperature rise characteristic of curve a shown in the second diagram, while "L
When o, the count value of the counter 5 is subtracted at a rate correlated to the temperature drop characteristic due to natural cooling of the curve shown in the third figure. Therefore, the current temperature of the motor 1 can be predicted based on the count value of the counter 5.

A first specified temperature corresponding to the dangerous temperature of the motor 1 is preset in the first comparison circuit 6, and the counted value (predicted temperature) of the counter 5 is constantly compared with this specified temperature.

The output of the first comparator circuit 6 becomes "H" when the count value of the counter 5 exceeds the first specified temperature. Further, when the above-mentioned count value is equal to or lower than the first specified temperature, the output becomes "0".

The second comparison circuit 9 compares the count value of the counter 5 after the motor is stopped with a second specified temperature that is lower than the first specified temperature. The second comparator circuit 9 determines that the count value of the counter 5 is the second one.
When the temperature is higher than the specified temperature, the output becomes “H”, and when the above count value is below the second specified value, the output becomes “0”.
” becomes.

The outputs of the first and second comparison circuits 6.9 cause the control circuit 3 to control the motor drive circuit 2.9. Controls the alarm device 7.

That is, when the output of the first comparison circuit 6 is "H",
The control circuit 3 outputs the DR signal "L" and the motor drive circuit 2
stops the operation, stops the operation of the motor 1, and causes the alarm device 7 to issue a warning.

When the output of the second comparison circuit 9 is "O", the control circuit 3 outputs the DR multiplied signal "H", restarts the motor 1, and stops the alarm device 7 from issuing a warning.

Next, the control operation of the present invention will be explained with reference to the flowchart of FIG.

DR multiplied signal of control circuit 3, or "H'" Lo
The monitoring circuit 4 monitors whether this is the case. When the DR multiplication signal is H'', that is, when the motor 1 is being operated by the motor drive circuit 2, the counter 5 is successively added at a rate correlated to the temperature rise characteristic of the curve a shown in FIG.
When the DR multiplication signal is "Lo", that is, when the motor 1 is operated or stopped by the motor drive circuit 2, the counter 5 is sequentially subtracted at a rate correlated to the temperature drop characteristic of the curve shown in FIG. The counted value (predicted temperature) of motor 1 is compared with the specified temperature of No. 1 depending on luck by the first comparator circuit 6, and if this counted value exceeds the first specified temperature, that is, the current temperature of motor 1 (predicted temperature) When the temperature (I temperature) reaches the dangerous temperature, the output from the first comparator circuit 6 becomes "H", the control circuit 3 outputs the DR double signal Lo, and the operation of the motor 1 is stopped.At the same time, an alarm is activated. The device 7 generates a warning sound.

While the motor 1 is at rest, the motor 1 is naturally cooled.
Similarly to the above, the counter 5 is subtracted at a rate correlated to the temperature drop characteristic of the curve shown in the third diagram.

The second comparison circuit 9 compares the count value of the counter 5 with a second specified temperature, and when the count value is larger than the second specified value, the output of the second comparison circuit 9 is high. It is.

Eventually, when the count value of the counter 5 falls to the second specified temperature, the output from the second comparator circuit 9 is reversed to "0", and in response to this, the control circuit 3 stops the alarm device 7 and generates a warning sound. Then, the DR double signal becomes "H" and the mode 1 is restarted. At this time, the count value of the counter 5 is sufficiently smaller than the first specified temperature.

As described above, according to the present invention, the motor is restarted after the count value of the counter becomes sufficiently smaller than the first specified temperature which is the dangerous temperature of the motor.

In other words, since the motor starts operating after the motor temperature has fallen sufficiently below the dangerous temperature, there is a long period of time before the counter count value exceeds the first specified temperature again, and it is possible to operate the motor continuously during this time. be.

Note that the alarm device may be a light emitting device such as an LED that lights up or flashes instead of a device that generates a warning sound such as a buzzer, or the alarm device does not need to be provided.

(Effects) The operating time and rest time of the motor are monitored, and the current temperature of the motor is predicted from the temperature rise characteristics when the motor is operating and the temperature drop characteristics when the motor is stopped.

This predicted temperature is compared with a first specified temperature which is a dangerous temperature of the motor, and when this predicted temperature exceeds the specified temperature, the operation of the motor is stopped.

Based on the second stop, the motor is restarted when the predicted temperature drops to a second specified temperature that is lower than the first specified temperature.

Therefore, it is possible to prevent the motor from overheating without using an expensive high-quality motor, thermistor, or cooling fan. This makes it possible to reduce the cost of equipment that uses the motor.

Further, since the motor operation is restarted after the motor temperature has fallen below the dangerous temperature by a predetermined temperature, there is a long period of time before the predicted temperature exceeds the first specified temperature, and the motor can be operated continuously during this time.

[Brief explanation of the drawing]

The drawings show an embodiment according to the present invention. Fig. 1 is a circuit block diagram, Fig. 2 is a temperature rise characteristic diagram showing the relationship between motor operating time and temperature rise, and Fig. 3 is a diagram showing the relationship between motor operating time and temperature rise. A temperature drop characteristic diagram showing the relationship with temperature drop, and FIG. 4 is a flowchart showing the control operation. DESCRIPTION OF SYMBOLS 1...Motor, 2...Motor drive circuit, 3...Control circuit, 4...Monitoring circuit, 5...Counter, 6.9...Comparison circuit. that's all

Claims (1)

[Claims] The operating time and rest time of the motor are monitored, and the current temperature of the motor is predicted based on the temperature rise characteristic when the motor is operating and the temperature drop characteristic when the motor is stopped, and this predicted temperature is the first temperature. When the predetermined temperature is exceeded, the operation of the motor is stopped, and based on this stop, the motor is restarted when the predicted temperature falls to a second predetermined temperature lower than the first predetermined temperature. A method for controlling a motor, characterized in that: