JPH01227698A - Stepping motor controller - Google Patents

Abstract

PURPOSE:To drive a motor with a suitable torque even when the speed of the motor is varied by determining the current value on the basis of the rotating speed. CONSTITUTION:A value responsive to the pulse internal of the driving pulse of a motor is held in a latch circuit 14, and input to a D/A converter 15. The converter 15 outputs a preset voltage in response to the input value. When the driving pulse is short, i.e., when the speed of the motor is fast, it outputs a high reference voltage, and when the pulse is long, i.e., when the speed of the motor is slow, it outputs a low reference voltage. This output is used as the reference voltage of a comparator 9. That is, when the motor is desired to be accelerated, the reference voltage of the comparator 9 is raised, i.e., and the winding voltage is increased, while when the motor is desired to be decelerated, the reference voltage is reduced, and the winding current is decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application 1] The present invention relates to a stepping motor control circuit, and more specifically to a stepping motor control circuit for a device that is driven at a frequency higher than the self-starting frequency of a stepping motor, such as a stepping motor used to drive a printer carriage. Regarding control circuits.

[Prior Art] A stepping motor control circuit for driving a carriage in a conventional printer is configured as shown in FIG. Stepping motor control will be briefly explained using FIG. 4. This is an example of a circuit that drives a stepping motor with a constant current. In the figure, 1 is a power supply, 2 is a chopper transistor that turns on the power supply to the motor windings, 3 is a stepping motor winding, and 4 is a flywheel diode, 5 is a Zener diode for absorbing back electromotive force, 6 is a flyback diode, 7 is a winding drive transistor, 8 is a current detection resistor,
9 is a comparator that changes the logic of the output signal according to the potential difference across the resistor 8; 16 is a reference power source; 17 and 18;
are motor drive pulse input terminals corresponding to each of the windings 3.

When a drive pulse is applied to the drive pulse input terminal 17 or 18, the transistor 2 is initially in the "ON" state, so the current flows through the path of the power supply 11 - transistor 2 - winding 3 - transistor 7 - resistor 8 - power supply 1. flows. As the speed of the carriage increases, the current flowing through this path increases,
The potential difference across the resistor 8 increases. This potential difference is compared with the voltage from the reference power supply 16 by the comparator 9, and when it exceeds the reference voltage, the logic of the output signal of the comparator 9 is inverted, and the state of the transistor 2 is turned "OFF". As a result, the current flowing through the winding 3 decreases, the potential difference between both ends of the resistor 8 decreases, the output signal of the comparator 9 is inverted again, and the transistor 2 becomes 'ON'.By repeating this operation, the circuit operates as a constant current circuit,
The stepping motor is driven by a constant current determined by the voltage of the reference power source 16.

[Problem to be solved by the invention] However, in printers, there is no need to drive the carriage.
In the conventional example described above, the current value is a constant value predetermined by the reference power source 16, although it changes depending on the recording speed or the recording mode, which causes the following problems.

In other words, since the current value remains constant even when the motor speed is changed, if the current value is set so that the optimum torque can be obtained when the motor is operated at the highest speed, the torque or the large clearance will be obtained when the motor is operated at low speed. There were also problems such as excessive heat generation. On the other hand, if you set the current value corresponding to the slowest speed, you may lose synchronization when the speed is set to high speed.
There was a problem with the lack of torque.

The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to provide a stepping motor control circuit that can flow a drive current of a value corresponding to the speed of the motor. .

[Means for Solving the Problems] To achieve this, the present invention includes a motor speed signal generating means that generates a pulse signal related to the rotational speed of the motor, and a motor speed signal generating means that generates a pulse signal corresponding to the rotational speed of the motor. The present invention is characterized by comprising a current value determination circuit that determines the drive current value of the drive current.

[Function] According to the above configuration, the current value of the motor drive current is determined based on the signal related to the rotational speed of the motor.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

Fig. 1 is a circuit diagram of a stepping motor control circuit showing an embodiment of the present invention. speed signal, 12 is a clock signal that is sufficiently fast compared to the motor drive pulse, 10
1 is an ant gate which outputs a signal by human power to the drive pulse input terminal 17 and human power to the motor constant speed signal IX;
3 is a counter circuit, 14 is a latch circuit, 15 is I)-A
It is a conversion circuit. Note that elements similar to those shown in FIG. 4 are designated by the same reference numerals, and their explanations will be omitted.

When a drive pulse is manually input to the motor drive pulse input terminal 17, a signal is output from the ANDKET 10 if the motor is operating at a constant speed, and the signal is input to the counter circuit 13. The counter circuit 13 starts counting the clock pulses of the clock signal 12 at the rising edge of this signal, and latches the counted value at the falling edge.
Hold at 4. The value held in the latch circuit 14 is D-A
The conversion circuit 15 is manually inputted and outputs a preset voltage according to the input value, which is used as a reference voltage for the comparator 9.

This situation will be explained in more detail with reference to the signal chart shown in FIG. First, motor drive pulse or input terminal 1
7 (A in the figure), the motor constant speed signal 11 is enabled (E in the figure) and an anchor output signal is obtained from the anchor 10 (B in the figure). Note that the constant speed signal 11 is in a disabled state when the motor is stopped or during slow-up/down operation. The ant gate output signal is input to the counter circuit 13, and its rising edge starts counting the clock pulses of the clock signal 12 (C in the figure). At the falling edge of the ANDKATE output signal, the counted value is held in the latch circuit 14 (D in the figure) and input to the DA conversion circuit 15. The DA conversion circuit 15 outputs a preset voltage according to the manually input value (F in the figure). As is clear from the chart of the DA conversion circuit output voltage, a high reference voltage is used when the drive pulse is short, that is, when the motor speed is high, and when the drive pulse is long (G in the figure), that is, when the motor speed is slow. outputs a low reference voltage. Since this output is the reference voltage of the comparator 9, the current value of the constant current circuit is determined according to this value as explained in the conventional example (H in the figure).

By using the circuit shown above, when you want to make Chiyu operate faster, you can use the base of comparator 9! (When the voltage increases and the winding current increases, and when you want to operate at low speed, the reference voltage of comparator 9 becomes low and the winding current decreases.In other words, even if the motor speed changes, it will adjust to the speed.) The optimum constant current value is automatically set.

As a result, problems such as the lack of torque and step-out due to changing the speed, the excessive torque that causes the motor to make a loud operating noise, and the motor's heat generation increasing, as in the conventional example, are avoided. It will be resolved.

FIG. 3 is a circuit diagram of a stepping motor control circuit showing a second embodiment. Elements similar to those shown in FIG. 1 are denoted by the same reference numerals and their explanations will be omitted. In the figure 1
9 is a motor, 20 is a slit plate, 21 is) an odometer,
22 is a sensor drive circuit that drives the photosensor 21 and shapes its waveform.

A slit plate 20 is attached to the rotating shaft of the motor 19, and the slit plate 20 rotates as the motor 19 rotates, and the sensor 21 generates a predetermined signal every time it detects light passing through the slit of the slit plate 20. arise. Sensor drive circuit 22
waveform-shapes the signal from the photosensor 21 and supplies it to one input terminal of the AND gate 10. This waveform-shaped signal plays a role similar to that of the motor drive pulse shown in FIG. Based on this signal, the pulse width of the signal is changed to the clock signal 12 as described in the first embodiment.
By measuring this, the reference voltage of the comparator 9 is determined via the DA conversion circuit 15, and the current value in the constant current circuit is determined.

According to the present invention, if there is a signal that relatively represents the speed of the carriage (motor) during constant speed operation, that signal is input to the AND gate lO, and a value corresponding to the signal is input to the D-A converter circuit. It is clear that if the current value is set to 15, the current value can be changed in accordance with the speed change. That is, the present invention can be implemented with any signal indicating the speed of the motor.

[Effects of the Invention] As is clear from the above description, according to the present invention, the current value of the motor drive current is determined based on the signal related to the rotational speed of the motor.

As a result, even when the motor was driven at varying speeds, the motor could be driven with appropriate torque.

Furthermore, it was also possible to prevent heat generation, step-out, and noise of the motor caused by mismatch between speed and current value.

[Brief explanation of the drawing]

Fig. 1' is a circuit diagram of a stepping motor control circuit showing one embodiment of the present invention, Fig. 2 is a chart of signal waveforms in the circuit shown in Fig. 1, and Fig. 3 is a stepping motor control circuit showing a second embodiment. Circuit diagram of motor control circuit FIG. 4 is a circuit diagram of a conventional stepping motor control circuit. DESCRIPTION OF SYMBOLS 11... Motor constant speed signal, 12... Clock signal, 13... Counter circuit, 14... Latch circuit, 15... D-A conversion circuit, 20... Slit plate, 21... - Photo sensor, 22... sensor drive circuit. Circuit diagram of the motor control circuit according to the conventional example (- Fig. 4)

Claims (1)

[Scope of Claims] 1) Motor speed signal generation means for generating a pulse signal related to the rotational speed of the motor, and a drive current value of the motor according to the pulse width of the pulse signal generated by the motor speed signal generation means. A stepping motor control circuit comprising: a current value determining circuit for determining a current value.