JP2000134984A - Motor controlling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to obtain a constant torque even if the rise in temperature of the magnet of a motor causes a demagnetizing action. SOLUTION: This device comprises a magnet temperature sensor 4 and a current controlling and calculating part. The magnet temperature sensor 4 is structured by providing a thermistor 41 in the proximity of the magnet 21 of a motor 2. The current controlling and calculating part receives the signals from the magnet temperature sensor 4 as temperature signals and supplies current signals to the motor. It generates correcting operation signals from the temperature and current signals, and by comparing the signals with present command value signals, generates current controlling signals which control the driving part which controls the amount of currents to the motor.

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 which can obtain an appropriate torque in response to a temperature rise of a magnet.

[0002]

2. Description of the Related Art In a general motor, if a rotating motion is continued for a long period of time, a wire, which is a winding, generates heat and the resistance of the wire increases. If the power to be supplied to the motor is directly connected to the conductor from the battery, the value of the current flowing through the conductor decreases accordingly and the torque of the motor naturally decreases. Therefore, as a measure to keep the motor torque constant, there has conventionally been a motor that measures a current value flowing through a conductive wire and controls the current so that the current value supplied to the motor becomes constant.

[0003]

However, the entire motor of the motor is heated by the heat generated from the conductive wire, and the magnet also generates heat. When commonly used ferrite magnets are used at high temperatures, a demagnetizing action occurs and the magnetic force decreases. As a result, the following fundamental torque of the motor has been reduced. Therefore, in the conventional motor control using only the current, the motor torque cannot be reliably kept constant. Theoretical formula T = k × Φ × I (k is a proportional constant: Φ is a magnetic flux amount: I is a motor current value)

An object of the present invention is to solve the above-mentioned problem, and an object of the present invention is to provide a motor control device capable of reliably obtaining a constant torque even with a continuously operated motor.

[0005]

In order to achieve the above object, a motor control device according to the present invention has a motor having a magnet, a drive unit for controlling the amount of current supplied from a power supply to the motor, and A command value generation unit that generates a command signal determined to flow a current amount set in the above, a magnet temperature sensor that is partially provided near the magnet and generates a temperature signal according to a temperature rise of the magnet, A current detection unit that detects a supply current of the current signal and generates a current signal; and a driving unit that outputs a current increase signal that increases a current amount to the motor when the correction operation signal of the current signal and the temperature signal is lower than the command value signal. Current control calculation for providing a drive with a current decrease signal for reducing the amount of current to the motor when the current signal and the correction calculation signal of the signal are higher than the command signal. Door is provided.

According to a second aspect of the present invention, the magnet temperature sensor comprises a thermistor disposed between a constant voltage portion and a ground portion and a plurality of resistors, and a voltage value between the resistors is used as a generated signal. Is provided in addition to the configuration of the first aspect.

[0007]

According to the first aspect of the motor control device of the present invention, the current supplied to the motor body is detected by the current detecting section to generate a current signal. This current signal is a signal that increases or decreases in accordance with an increase or decrease in the amount of current. The temperature of the magnet is detected by a magnet temperature sensor provided near the magnet, and a temperature signal is generated. This temperature signal is a signal that rises as the temperature of the magnet rises. The correction operation signal is a signal having a value obtained by subtracting the temperature signal from the current signal by a certain operation. Therefore, the correction operation signal is a signal that increases and decreases with the increase and decrease of the current signal and increases and decreases with the increase and decrease of the temperature signal. The command signal generated by the command value generator corresponds to the amount of torque required by the motor user, and if the torque is lower than the required torque, the amount of current to the motor body is increased to increase the amount of the required torque. When it is high, the amount of current to the motor body is reduced. According to the above configuration, the temperature rise of the magnet is corrected to include the torque decrease due to the demagnetization, and the torque of the motor can be reliably maintained.

Further, according to a second aspect of the motor control device of the present invention, the magnet temperature sensor is composed of a thermistor and a plurality of resistors, which are arranged between a fixed voltage and a ground portion, and a terminal between them has a voltage. It measures the value and generates a temperature signal. This means that the resistance value of the thermistor changes when the temperature rises, so that the voltage output from the terminal changes due to the arrangement of the plurality of resistors. With the above configuration, a temperature signal can be obtained with a simple configuration.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention shown in the drawings will be described. FIG. 1 is a block diagram showing an embodiment of a motor control device according to the present invention. FIG. 2 is a circuit diagram of the magnet temperature sensor shown in FIG.

First, a description will be given with reference to FIG. The main components of the motor control device 1 according to the present invention include the motor 2 and the circuit board 3. A magnet 21 is mounted on the motor 2, and a thermistor 41 for measuring the temperature is provided in close contact with the magnet 21. The circuit board 3 includes a driving unit 5 for controlling the amount of current supplied from a power supply (not shown) for driving the motor 2, a resistor network 42, and a current detecting unit 6 for detecting a current supplied to the motor.
A command value generating unit 7 for generating a signal that is set so that a current amount set to the motor flows, and a current control calculating unit 8 as a CPU. The resistance network 42 plays the role of the magnet temperature sensor 4 by being connected to the thermistor 41. In addition, the current control calculation unit 8 includes the current detection unit 6
The analog signal from the magnet temperature sensor 4 is converted into a digital signal by the A / D conversion element 9, the two digital signals are compared, and a correction operation is performed to generate a correction operation signal.

Next, the operation of the above configuration will be described. The following describes each of the current value and the state of the magnet.

[When the current value is constant and the temperature of the magnet is also a flat temperature] A current is stably supplied from a power source (not shown) to a conductor which is a winding of the motor through a driving unit.
The current value that enters the current detection unit from the conductor provided immediately before the motor is supplied to the motor is stable and constant. as a result,
A constant analog signal is input to the CPU as a current signal generated from the current detection unit. On the other hand, if the temperature of the magnet is also in the normal temperature state, the thermistor indicates the resistance value in the normal temperature state. Therefore, the temperature signal generated from the magnet temperature sensor (the constant voltage of the thermistor and a plurality of resistance networks in the circuit board and the ground). Voltage value) is a constant analog signal from the CPU
Is input to The CPU, which is a current control operation unit, converts the above-mentioned stable current signal and stable temperature signal into an analog signal as a digital signal, performs a correction operation, and generates a correction operation signal. (For example, a digital current signal in which the numerical value of the current value of the current detection unit is directly converted into a digital value by analog / digital conversion, and the current value obtained from the magnet temperature sensor is converted into the digital value of the current value of the current detection unit by analog / digital conversion. If the digital temperature signal is used as a digital value, the digital temperature signal is converted to the outside air temperature 2 in the correction operation.
A temperature signal at 5 ° C. is set as a zero reference, and a numerical value obtained by multiplying the numerical value by a certain coefficient (coefficients vary depending on the type of magnet) by adding or subtracting the numerical value above and below the zero signal is used as a digital temperature correcting signal. The result of subtraction becomes the correction operation signal. In this correction operation, since the current signal and the temperature signal are both in a normal state, a value closest to the command value generator can be obtained. For example, if the temperature of the magnet is 25 ° C., the correction operation signal matches the current signal. Next, since the command value signal sets the current value required by the motor in advance, if the rotation of the motor is in a normal state in a steady state, the correction operation signal matches the value of the command value generation unit. That is, the current control calculation unit continues to issue an instruction such that the current is directly applied to the motor without issuing a special instruction to the drive unit.

[When the current value increases and decreases and the temperature of the magnet is at a normal temperature] A current is supplied from a power source (not shown) to the conductor, which is the winding of the motor, through the drive unit in an unstable state. The value of the current entering the current detection unit from the conductor provided immediately before being supplied to the motor becomes unstable. As a result, the current signal generated from the current detector is
Input to PU. On the other hand, if the temperature of the magnet is in a normal temperature state, an unstable analog signal is input to the CPU as a temperature signal (a voltage value between a constant voltage in the thermistor and the resistor network and ground) generated from the magnet temperature sensor. . The CPU, which is a current control calculation unit, converts the unstable current signal and the stable temperature signal into analog signals, and then performs a correction calculation to generate a correction calculation signal. In this correction operation, since the current signal is unstable and the temperature signal is stable, a value obtained by changing only the unstable portion of the current around the command value generating section is obtained. For example, if the temperature of the magnet is a normal temperature of 25 ° C., the correction calculation signal changes from the command value signal only in the portion where the current signal decreases or increases. Next, since the command value signal sets the current value required by the motor in advance, the CPU that is the current control calculation unit performs control such that the rotation of the motor matches the value of the command value generation unit. . In other words, the current control calculation unit controls the drive unit so that the current easily flows from the power supply to the motor when the current value of the current detection unit decreases, and conversely, when the current value of the current detection unit increases, the drive unit The drive unit is controlled so that current does not easily flow.

[When the current value is stabilized and the temperature of the magnet rises and falls] A current is stably supplied from a power source (not shown) to the conductor, which is the winding of the motor, through the drive unit. The current value that enters the current detection unit from the conductor provided immediately before the motor is supplied to the motor is stable and constant. As a result, a constant analog signal is input to the CPU as a current signal generated from the current detection unit. On the other hand, when the temperature of the magnet rises and falls, the thermistor also shows the resistance value of rise and fall. Therefore, the temperature signal generated from the magnet temperature sensor (the voltage between the constant voltage of the thermistor and a plurality of resistance networks in the circuit board and the ground) Value) is input to the CPU as a rising and falling analog signal. CPU that is a current control calculation unit
Converts a stable current signal and an unstable temperature signal into an analog signal as a digital signal, and then performs a correction operation to generate a correction operation signal. In this correction operation, the current signal is stable and the temperature signal is unstable. Therefore, a value obtained by changing only the unstable portion of the current around the command value generating section is obtained. For example, the correction operation signal changes to a command value signal that vibrates so that only the portion where the temperature signal increases or decreases increases or decreases in reverse. Next, the command value signal sets the current value required by the motor in advance, so
Control such that the rotation of the motor matches the value of the command value generation unit is performed by the CPU, which is the current control calculation unit. In other words, the current control calculation unit controls the drive unit so that the current easily flows from the power supply to the motor when the current value of the temperature detection unit increases and the magnetic flux of the magnet decreases, and conversely, the current value of the temperature detection unit decreases. The drive unit is controlled so that current does not easily flow from the power supply to the motor when the magnetic flux of the magnet becomes larger than necessary.

[When the current value increases / decreases and the temperature of the magnet rises / falls] An unstable current is supplied from a power source (not shown) to the conductor, which is the winding of the motor, through the drive unit. The value of the current entering the current detection unit from the conductor provided immediately before being supplied to the motor becomes unstable. as a result,
An unstable analog signal is input to the CPU as a current signal generated from the current detection unit. On the other hand, when the temperature of the magnet rises and falls, the thermistor also shows the resistance value of rise and fall, so the temperature signal (the voltage value between the constant voltage of the thermistor and the resistor network and the ground) generated from the magnet temperature sensor rises and falls. An analog signal is input to the CPU. The CPU, which is a current control operation unit, converts the unstable current signal and the unstable temperature signal into analog signals, and then performs a correction operation to generate a correction operation signal. In this correction operation, since both the current signal and the temperature signal are unstable, a value obtained by changing only the respective unstable portions of the current signal and the temperature signal around the command value generating section is obtained. For example, the correction operation signal similarly increases and decreases only in the portion where the current signal increases and decreases, and changes to a command value signal that vibrates so that only the portion where the temperature signal increases or decreases reversely decreases and increases. At this time, the instability of the temperature signal is an extremely small value because the instability of the current signal is multiplied by a coefficient corresponding to the magnet. Next, since the current value required by the motor is set in advance for the command value signal, the CPU that is the current control calculation unit performs control such that the rotation of the motor matches the value of the command value generation unit. Become.

FIG. 2 shows a magnet temperature sensor.
It will be described according to the following. One terminal V is a terminal to which a constant voltage is supplied, and the other terminal is a ground terminal. A plurality of resistors (Ra, Rb, Rc, R1) and a thermistor (Rc) are provided therebetween. And the resistance R
A voltage is output between 1 and Rc. This voltage value is affected by the resistance value of the thermistor that changes due to a temperature change near the thermistor and changes.

A thermistor typically varies logarithmically with temperature according to the following equation:

[0018]

(Equation 1)

Around the thermistor, as shown in FIG.
Rb and Rc are arranged. Then, two levels of temperatures are set in the temperature range to be used. For example, 75 ° C and 125
When the temperature of the thermistor is 75 ° C., the resistance values are set to Rs 75 ° C. and Rs 125 ° C. The combined resistance of Rs, Ra, Rb, and Rc at this time is represented by R2 (75
° C) and R2 (125 ° C) can be expressed by the following equations, respectively.

[0020]

(Equation 2)

[0021]

(Equation 3)

[0022]

(Equation 4)

The voltage output is represented by the following equation. A = (R1 / (R1 + R2)) × V R2 (75 ° C.) and R2 (125 ° C.) are determined so that this change in the voltage output matches the high-temperature demagnetization of the magnet. Is calculated by calculating back. The motor torque T can be represented by T = k × Φ × I, where Φ is the amount of magnetic flux of the magnet and I is the current of the motor. (K is a proportional constant) The motor current is
Even if the winding resistance increases due to the feedback loop of FIG. 1, a constant current flows. Further, the value of the high temperature demagnetization is input from the A / D converter, and the motor current value to be corrected and fed back is reduced by the input. As a result, the motor current increases by an amount corresponding to the demagnetization of the magnet, and the torque becomes constant.

[0024]

As is apparent from the above description, according to the present invention, even if a demagnetizing action occurs due to an increase in the temperature of the magnet, the current value for compensating for the demagnetizing action further increases in the conductive wire. , The torque of the motor can be kept constant.

[Brief description of the drawings]

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

FIG. 2 is a circuit diagram of a magnet temperature sensor in a motor control device according to an embodiment of the present invention.

[Explanation of symbols]

1 ... motor control device, 2 ... motor, 21 ... magnet,
3 Circuit board 4 Magnet temperature sensor 41 Thermistor 42
Resistance network, 5: drive unit, 6: current detection unit, 7: command value generation unit, 8: current control calculation unit

Claims (2)

[Claims] 1. A motor having a magnet, a drive unit for controlling an amount of current supplied from a power supply to the motor, and a command value generating unit for generating a command signal for flowing a set amount of current to the motor. A magnet temperature sensor that is provided in the vicinity of the magnet and generates a temperature signal in accordance with a rise in temperature of the magnet; a current detection unit that detects a supply current to the motor and generates a current signal; When the correction operation signal of the temperature signal is lower than the command value signal, a current increase signal for increasing the amount of current to the motor is provided to the driving unit, and the correction operation signal of the current signal and the signal is higher than the command signal. A motor control device comprising: a current control operation unit that supplies a current reduction signal for reducing a current amount to a drive unit in the case. 2. The magnet temperature sensor according to claim 1, wherein said magnet temperature sensor comprises a thermistor disposed between a constant voltage section and a ground section, and a plurality of resistors, and uses a voltage value between the resistors as a generated signal. The motor control device according to any one of the preceding claims.