JPS6028799A - Control system for pulse motor - Google Patents

Abstract

PURPOSE:To prevent the improper rotation of a pulse motor due to a decrease in the torque and to enable to suppress the heat generation of the motor by detecting the temperature of a motor coil, reducing the voltage when the temperature increases, and increasing the period of a pulse. CONSTITUTION:When a pulse motor 4 is driven continuously for a long period so that the heat generating temperature of the motor rises to become the prescribed temperature or higher, the resistance of a thermistor varies, it is detected by a detector 6, and the output of the detector 6 becomes ON. Thus, the output signal to a driver 7 becomes ON, and a transistor Q2 is turned ON. Thus, the supply voltage to the motor 4 becomes low voltage. Further, to normally rotate the motor 4, the pulse width of the drive pulse to the pulse motor is increased to decrease the rotating speed.

Description

TECHNICAL FIELD The present invention relates to a pulse motor control system, and more particularly to a pulse motor control system that changes the pulse motor drive voltage depending on the pulse motor heat generation temperature.

BACKGROUND OF THE INVENTION Conventional dot type printers print characters, symbols, etc. by driving dots corresponding to a dot matrix pattern in synchronization with the feeding of a print head. Therefore, in order to obtain a desired character pattern, it is essential to accurately move the print head to a predetermined position. For this reason, a pulse motor is generally used to move the print head.

In this case, in order to increase the printing speed, the rotational speed of the pulse motor must be increased, and the pulse width of the pulse motor drive pulse must be shortened. However, if only the pulse width of the pulse motor drive pulse is shortened, the pulse motor drive torque decreases and normal rotation becomes impossible, so the supply current has been increased by increasing the drive voltage or the like.

For this reason, the electric power applied to the pulse motor increases, the amount of heat generated by the pulse motor increases, and if the pulse motor continues to rotate continuously, it causes an abnormal temperature rise and even burnout.

In order to prevent this, a large and expensive pulse motor had to be installed.

Purpose The present invention has been made in view of the above-mentioned points, and its object is to provide a pulse motor temperature detection means and to control the pulse motor drive current and drive pulse width according to the heat generation temperature of the pulse motor. The purpose of this invention is to propose a pulse motor control method that achieves efficient high-speed rotation using a pulse motor without reducing torque.

Example An embodiment of the present invention will be described below based on the drawings.

FIG. 1 is a pulse motor drive circuit diagram of an embodiment of the present invention, and FIG. 2 is a timing chart of drive pulses of the pulse motor of the present invention.

In FIG. 1, 1 is a controller that controls various signals with the pulse motor, and 2 is a stepping motor pulse φl, φ2, . φ3. φ4
5 is a thermistor that detects the temperature of the stepping motor, 6 is a detector that detects whether the temperature data from the thermistor 5 is within a specified value, 11 is a power supply for the stepping motor, and 12 is a pulse generator.

The operation of the circuit will be explained using as an example the operation of a printer that has a built-in stepping motor drive circuit shown in Fig. 1 and uses the stepping motor to move the print head.6 When a print command is given to the printer, the print head In order to move the motor, the controller l outputs a pulse motor drive signal to the latch circuit based on the P1 pulse among the pulses from the pulse generator 12. In this embodiment, the pulse motor is a four-phase motor, and the driving method is two-phase excitation in which adjacent phases are constantly excited.

Based on the drive signal from the controller 1, the latch circuit generates the stepping motor drive pulses φ1 to φ1 shown in FIG. 2(A).
Connect φ4 to each phase of pulse motor 4 with drivers 3-1 to 3-4.
Output through and rotate the pulse motor. Here φ
The l signal goes to phase l via driver 3-1, the φ2 signal goes to phase 2 via driver 3-2, and the φ3 signal goes to driver 3-1.
The φ4 signal is applied to phase 3 via driver 3-4, and the φ4 signal is applied to phase 4 via driver 3-4. Phase l~ due to drive pulses φ1~φ4
The procedure for rotating the motor by applying a drive signal to phase 4 is well known and will not be described here.

As shown in FIG. 2(A), the stepping motor 4 rotates in synchronization with the basic pulse PI for driving the stepping motor. The printer only needs to drive the print dots of the print head in synchronization with this Pi pulse.

When the stepping motor 4 first starts rotating, the heat generation temperature of the stepping motor 4 is low, there is no output from the detector 6, the controller 1 does not output an output signal to the driver 7, and the transistor Q2 (8) is in an off state. Yes, the power supply VM to the pulse motor 4 is a Zener diode ZDI.
(9-1) is set to V by the Zener voltage. This power supply VM is supplied to the pulse motor through resistors R3 and R4, and these resistors R3 and R4 are intended to improve the rise and fall characteristics of the current supplied to the pulse motor.

Now, if the pulse motor 4 is driven continuously for a long time and the motor's heat generation temperature rises and exceeds the specified temperature, the pulse motor 4
The resistance value of the thermistor mounted in close contact with the thermistor changes, this resistance value change becomes large, and is detected by the detector 6, and the output of the detector 6 is turned on. When the controller 1 detects that the output of the detector 6 has turned on and the motor heat generation temperature has become high, it turns on the output signal to the driver 7, and outputs a transistor Q2 (8) connected to the driver 7 via a resistor.
) rises and transistor Q2 (8) turns on. Therefore, Zener diode ZD2 (9-2
).

In this embodiment, the Zener potential v 1 due to the Zener diode ZDI (9-1) is
Zener potential V 2 ) + due to D2 (9-2)
(Transistor Q2 (8) V of Q2 (8) when on
potential) is set lower. Therefore, by turning on the transistor Q2 (8), the pulse motor 4
The supply voltage to is 7M2, which is lower than vMl. When the supply voltage decreases from VMI to 7M2, the current supplied to the pulse motor 4 also decreases, so the driving torque of the pulse motor decreases. Therefore, with this driving torque, the pulse motor 4
In order to rotate the motor normally, the pulse width of the drive pulse to the pulse motor may be increased and the rotation speed may be reduced.

In order to rotate the motor at the pulse period P2 of the maximum rotation speed within the normal rotation range of the pulse motor 4 at the power supply voltage VIJ2 supplied to the pulse motor 4, the controller l uses the output pulse P2 of the pulse generator PG12 to rotate the motor. The drive signal for the pulse motor 4 is output to the latch circuit 2, and the latch circuit 2 generates pulse motor drive pulses φ1 to φ4 as shown in FIG. 2(B), and the drivers 3-1 to φ4.
3-4 to phase 1 to phase 4 of the pulse motor 4 to rotate the pulse motor 4. Good printing can be achieved by synchronizing the dot drive pulse of the print head with R2.

The switching timing during this period is shown in FIG.

The periods T1 and T2 of the basic pulses P1 and R2 are T1 and T2
It becomes.

As shown in Figure 3, the voltage supplied to the pulse motor 4 decreases from vMl to V1A2, so the current supplied to the pulse motor 4 decreases, and the temperature of the pulse motor 4 gradually decreases until it falls below the specified temperature again. The output of the driver 6 is turned off, the output of the driver 7 is also turned off, and the transistor Q2 (
8) Turn off L and raise the supply voltage to VM□, and the drive timing of the pulse motor 4 also returns to the timing shown in FIG. 2(A).

As described above, in this embodiment, the power supply voltage supplied to the pulse motor 4 is controlled by the Zener voltage of the Zener diode, but another example of power supply voltage control is shown in FIG.

Components common to those in FIG. 1 are given the same numbers.

Driver 7' is an innoheter type of driver 7 of FIG. When the temperature of the stepping motor 4 is below the specified temperature, the driver 7' output is at a high level, the transistor Q3 (14) and the transistor Q4 (15) are in the on state, and the resistor R3 connected to the stepping motor 4 is in the on state. and to R4 (power supply 11' (7) power supply voltage)
A voltage V of -(Q3V or Q4V), 4□ is applied. The motor drive pulse is based on the PI pulse of the pulse generator 12.

If the stepping motor 4 rotates continuously and the motor heat generation temperature exceeds the specified temperature, the driver 7
' input becomes low level, transistor Q3 (14
) and Q4 (15) are turned off, and power is supplied to the stepping motor 4 from the power supply 11' through the resistors R1 and R2.

3 Therefore, the power supply voltage to the pulse motor 4 is controlled by the resistor R1,
The voltage drop across R2 is reduced, and the current supplied to the motor is also reduced.

When the voltage supplied to the pulse motor 4 is vI, 2 when the transistors Q3 (14) and Q4 (15) are off, the motor drive torque is reduced compared to when the supply voltage is V, 2. Therefore, in order to make the pulse motor rotate normally with this drive torque, as in the circuit of Fig. 1, the pulse generator 1
A motor drive pulse is generated based on the R2 pulse of 2. This timing is as shown in FIGS. 2 and 3.

As described above, when the pulse motor 4 is used to move the print head of a printer, etc., the print dot drive timing of the print head is synchronized with the P1 pulse or R2 pulse of the pulse generator 12, thereby changing the print head movement speed. 4 can be easily dealt with.

Effects As explained above, according to the present invention, when the pulse motor is normally rotated at the highest speed it has and the motor is continuously rotated for a long time, the heat generation temperature of the motor is high. If there is a risk of burnout of the motor coil, lower the drive power voltage of the pulse motor,
By reducing the supply current S and lengthening the period of the dry pulse of the pulse motor accordingly, it is possible to prevent rotation failure due to a reduction in the drive torque of the pulse motor, and also to suppress heat generation of the motor.

As a result, a very efficient pulse-smoke control system has been realized which does not require the use of a large and expensive pulse motor as in the past, and which causes almost no reduction in rotational speed during normal operation.

5 It is an energizer.

It is also possible to prevent motor burnout due to abnormal heat generation of the pulse motor.

[Brief explanation of drawings]

Fig. 1 is a pulse motor drive circuit diagram of an embodiment of the present invention, Fig. 2 (A) is a pulse motor drive timing chart when the motor heat generation temperature is below the set temperature, and Fig. 2 (B) is above the motor heat generation temperature set temperature. FIG. 3 is a pulse motor drive circuit operation timing chart when the motor heat generation temperature rises. FIG. 4 is a pulse motor drive circuit diagram according to another embodiment of the present invention. In the figure, l... controller, 2... latch circuit, 4... pulse motor, 5... thermistor, 6...
...Detector, 11.11'...Power supply circuit, 12...
pulseji 6

Claims (7)

[Claims] (1) Voltage control means for controlling the voltage supplied to the pulse motor drive power supply unit and the pulse motor; pulse width control means for controlling the pulse motor drive pulse width according to the control voltage of the voltage control means; temperature detection means for detecting the temperature of the motor, the voltage control means and pulse width control means controlling the pulse motor drive voltage and pulse motor drive pulse width according to the temperature detected by the temperature detection means. Motor control method. (2) The pulse smoke control method according to claim 1, wherein the voltage control means lowers the control voltage by a certain amount when the temperature detection means detects a specific temperature or higher. (3) The pulse motor control method according to claim 1 or 2, wherein the pulse width control means controls the drive pulse width so that the pulse motor can rotate normally. (4) The voltage control means is characterized in that a resistor is provided in series between the power supply unit and the pulse motor, and the resistance value of the resistor is controlled to control the voltage supplied to the pulse motor. The pulse motor control method described in Section 3. (5) The resistor comprises a resistor and a control transistor connected in parallel with the resistor, and the resistance value is controlled by turning on and off the control transistor. pulse motor control method. (6) The voltage control means includes a voltage control transistor and a reference voltage generation section that generates at least two types of reference voltages, and the voltage control is performed by changing the reference voltage of the reference voltage generation section. A pulse motor control method according to claims 1 to 3, characterized in that the pulse motor control method is controlled. (7) The reference voltage generator generates at least two reference voltages.
7. The pulse motor control method according to claim 6, wherein the pulse motor control method is performed using Zener diodes having different Zener voltages.