JPS58151898A - Driving method for pulse motor - Google Patents

Abstract

PURPOSE:To reduce power sonsumption, and to cheapen the manufacturing cost by selecting and controlling exciting methods in response to the frequency of input pulse signals applied to each phase of a pulse motor. CONSTITUTION:A CPU 14 outputs driving-system informations to the pulse motor 8 through a driver 16 while bringing frequency to 1500PPS by two-phase excitation in a carriage return instruction 19 and frequency to 500PPS by one- phase excitation in a printing instruction 18. According to said driving method for the pulse motor, since one-phase excitation is executed during printing revolving torque is weak though time per one step is long, thus resulting in no vibration. Since two-phase excitation is executed during the return of a carriage, revolving torque is strong though time per one step is short, thus resulting in the state of smooth drive through which vibration is not generated. Power consumed in the pulse motor and a printing head is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for driving a pulse motor, and more particularly to a method for driving a pulse motor used, for example, to drive a carriage of a printing device.

Generally, the characteristics of a pulse motor are greatly influenced by the current pattern (energization method) commanded to each phase winding and the drive circuit. The 1-phase excitation method, the 2-phase excitation method, and the 1.2-phase excitation method are widely known as energization methods for this pulse motor, and the energization method is determined depending on the application. For example, when comparing the 1-phase excitation method and the 2-phase excitation method, the 2-phase excitation method requires approximately twice the drive current as the 1-phase excitation method, but the response frequency is 2 rotational torque, the static angle error is In addition, the one- and two-phase excitation method has the characteristic that the number of steps (resolution) is doubled (the step angle per pulse is halved) compared to other methods.

Therefore, since it is necessary to move the carriage accurately at high speed, such as when driving a carriage in a printing device, a two-phase excitation method that can obtain a relatively strong rotational torque in a high frequency range has generally been adopted.

However, when the two-phase excitation method is adopted, the characteristic of a pulse motor is that when driven near the maximum response frequency, it rotates sufficiently smoothly, as is clear from the curve shown in Figure 1 (A). As can be seen, when driving in a low frequency range, there is a characteristic that it rotates while vibrating as is clear from curve a shown in Figure 1 (B), and when mechanical parts etc. are driven in such a state, noise is generated. It is clear that this not only causes the occurrence of damage, but also causes wear and tear on various parts.

Therefore, in conventional printing devices and the like, when driving a pulse motor for driving a carriage using the two-phase excitation method, a drive circuit as shown in FIG. 2 has been adopted. According to a circuit with such a configuration, when driving a pulse motor in a high frequency range, transistor 1 is turned on and current flows to the collector emitter, driving voltage Vcc is applied to the pulse motor, and when driving a pulse motor in a low frequency range. When driving the motor, transistor 1 is turned off and no current flows to the collector-emitter side, and voltage is applied to the pulse motor through resistor 2, which has the effect of weakening the rotational torque and reducing vibration. . That is, by appropriately setting the resistance value of the resistor 2, vibrations were suppressed as shown by the curve shown in FIG. 1 (Bl).

However, in this conventional circuit configuration, the resistor 2
For example, if the resistance value of one phase of a pulse motor is set to 30Ω and the drive voltage is set to 15V, and the pulse motor is driven using the two-phase excitation method, the power consumption of the pulse motor will decrease in the high frequency range. In the case of low frequency range, it becomes 7.5W, which is about half, but the resistance value of resistor 2 needs to be about 6.4Ω, so a resistor with a large resistance value is required, and heat dissipation must also be taken into consideration. There was a drawback that it had to be done.

Also, as mentioned above, the power consumption in the high frequency range is 15W, while the power consumption in the low frequency range is 4.5W on the resistor side and 75W on the pulse motor side, for a total of 12W.
This has the disadvantage that there is almost no significant difference from the case in the high frequency range.

Furthermore, when changing direction, such as the return of a pulse motor for driving a carriage, for example from print 1 drive to print drive, or vice versa, or when transitioning from an operating state to a stopped state, inertial force is generated. Conventionally, in order to prevent missteps, a method has been used in which the first pulse is made about twice as long as the normal pulse width. However, since it is natural to generate pulses with different pulse widths, a separate pulse generation circuit is required, which, like the drive circuit described above, also contributes to high manufacturing costs. Ta.

Therefore, the present invention has been made to overcome these conventional drawbacks, and it is an object of the present invention to provide an extremely stable method of driving a pulse motor that does not require the above-mentioned circuit and consumes less power.

In order to achieve this objective, the present invention employs a method of increasing the number of phases simultaneously driven when driven in a high frequency range compared to when driven in a low frequency range.

The present invention will be explained in detail below based on the drawings.

Fig. 3 shows the drive mechanism of the pulse motor for driving the carriage of a thermal printer that employs the drive method of the present invention. be. This carriage 3
is fitted to the guardrail 4, and is fitted to be slidable in the width direction of the thermal recording paper 5 (hereinafter referred to as the recording paper). Also, one end 3' of the carriage 3 is connected to a pulley 10.
12. When the pulse motor 8 is driven counterclockwise, the pulley 12 rotates through the shaft, and the carriage 3 moves to the width of the recording paper 5. Timing belt 9 on the left side
Move through.

On the other hand, an arm 6 is attached to one end of the guardrail 4, and one end of this arm 6 is connected to a print head 1 by a spring 7 fixed to a part (not shown) of the main body of the device.
1 is pressed against the recording paper 5.

Further, in addition to the spring 7 described above, a solenoid 11 is connected to one end of the arm 6, and the solenoid 11 is a means for separating the print head 14 from the recording paper 5.

The thermal printing pulse motor 8, print head 14#, and solenoid 11 having the above-mentioned drive mechanism are as follows:
Each of them is driven and controlled by a control section shown in FIG. That is, in the figure, when a print command 18 is input to a CPU (Central Processing Unit) 14, the CPU 14 processes it and outputs print information to the print head 13 via the driver 11, and at the same time, the CPU 14 performs arithmetic processing and outputs print information to the print head 13 via the driver 11. The drive method information is output to the pulse motor 8 via the driver 16.

Further, when the carriage return command 19 is input to the CPU 14, the CPU 14 outputs the carriage return information to the solenoid 11 via the driver 17, and at the same time outputs the drive method information to the pulse motor 8 via the driver 16.
Output to.

Here, this drive method information is the frequency of pulses given to the pulse motor 8 and the energization method. For example, the frequency of pulses applied to the pulse motor during printing is generally determined by the relationship between the printing to rad characteristics and the starting torque required to move the carriage 3. In other words, the print head must move as slowly as possible while printing.
For this purpose, a frequency as low as possible is required.

Next, when the carriage returns, it is desired to move the carriage as fast as possible, so the frequency of the pulses applied to the pulse motor 8 is determined by the performance of the pulse motor.

For example, if the performance of the pulse motor 8 used in this embodiment is set to an input voltage of 5 V and a maximum response frequency of 1500 PPS, it will normally drive at a frequency of 1500 PPS using the two-phase excitation method during carriage return, but during printing, for example, As mentioned above, based on the relationship between the print head characteristics and the starting torque, if the frequency of the pulses given to the pulse motor 8 is set to, for example, 500 PPS, if the motor is driven with two-phase excitation, vibrations will occur as shown in Figure 1 fB]. Therefore, in the present invention, the energization method during printing is a one-phase excitation method.

That is, the CPU 14 inputs the drive method information with two-phase excitation at a frequency of 1500 PPS in the carriage return command 19.
In the print command 18, the signal is output to the pulse motor 8 via the driver 16 at a frequency of 500 PPS with one-phase excitation.

The driving state of the pulse motor 8 at this time is shown in FIG.

In the same figure, it can be seen that during printing, vibration does not occur because the rotational torque is weak, even though the time per step (in this example, the number of rotations of 10 degrees per step) is long because of one-phase excitation. . Furthermore, since two-phase excitation is used during carriage return, the rotational torque is strong even though the time per step is short, so it can be seen that the driving state is smooth without vibration.

Here, the pulse motor rotates 10 degrees per step during carriage return, but the rotation angle of the first step SS at the start of the carriage return and the final step SH at the end of the carriage return is 5 degrees each. ing. This is to make it difficult for the pulse motor 8 to make a misstep, as will be described later.

To explain in more detail with reference to FIGS. 6(A) and [F]), this figure shows the timing of input pulse signals applied to each phase AD of the pulse motor 8. In the figure, when the print head 13 is printing, the pulse motor
The eight phases are excited in the order of a phase → b phase → C phase → d phase → a phase and are driven by one-phase excitation. Next, as shown by the one-dot chain line, when printing is completed, each phase of the pulse motor 8 is activated in the opposite order to that during printing (2 DAC phase → c11b-+b11a phase →
a11d phase - + d @ (excited with the phase and driven by two-phase excitation. At this time, the first pulse d 1 + c 1 applied to the d phase and C phase is applied at the same time, and moreover, it is applied to the d phase. The pulse width of the first pulse d1 is half of the normal pulse width.As a result, as mentioned above, the rotation angle of the first step at the start of carriage return is half the normal one, or 5 degrees.Also, in the same figure (I3), At the stage where the carriage return is completed as shown by the one-dot chain line, the pulse motor 8
The final pulse be applied to the b-phase and a-phase of
The pulse width 1 of the final pulse a-end of the a phase is half the normal pulse width so that excitation of nd and a end ends at the same time, and as a result, the rotation angle of the final step at the end of carriage return is 5 degrees.

In this manner, when the rotation of the pulse motor changes direction or when it transitions from a stopped state to an operating state, the pulse width of the first pulse is reduced to half of the normal pulse width, thereby making it possible to avoid missteps of the pulse motor.

Although the present invention has been described as an embodiment of a pulse motor for driving a carriage of a printing device to which the driving method of the present invention is applied, the present invention is not particularly limited to carriage driving, and can be applied to a wide range of applications.

In addition, in this embodiment, the frequency of the manual pulse is changed only when the rotation direction of the pulse motor changes, and the corresponding excitation method is selected and controlled, but it can also be adopted when changing the speed in the forward direction. .

As is clear from the above description, according to the present invention, there is no need for a drive circuit or a pulse generation circuit for preventing missteps, which were required in conventional printing devices. The total power consumed by the print head is approximately 125W, and the total power consumed by the pulse motor and solenoid during carriage return is approximately 165W, which is a significant power consumption saving compared to conventional models. be done.

Therefore, by applying the present invention, a stable method for driving a pulse motor with extremely low power consumption and low manufacturing cost can be obtained.

[Brief explanation of drawings]

Figure 1 (Al, Q3) both explain the characteristics of general pulse motors, and Figure 1 shows the time and rotation angle when driving a pulse motor with two-phase excitation in the highest response frequency range. Figure 1 is a diagram showing the relationship between time and rotation angle when a pulse motor is driven with two-phase excitation in a low frequency range. Figure 2 is a diagram showing the relationship between the carriage of a conventional printing device. The drive circuit diagrams used in the drive pulse motor, FIGS. 3 to 6, all explain the carriage drive system of a thermal printer, which is an embodiment of the present invention. 4 is a control circuit diagram showing the control section of the thermal printer, and FIG. 5 is a pulse motor for driving the carriage.
Figure 6 (Al and (Bl) are timing charts of the input pulse signals excited in each phase of the carriage drive pulse motor. 3 ... Carriage 8 ... Pulse motor -1
3...Print head 14...CPU16...
・Driver Figure 1 (A) Figure 1 (B) Darkness □ Figure 3 Figure 4

Claims (2)

[Claims] (1) In a drive method for a pulse motor driven by at least two or more types of excitation methods, the excitation method is selected and controlled according to the frequency of an input pulse signal applied to each phase of the pulse motor. pulse motor
driving method. (2) The method for driving a pulse motor according to claim 1, wherein the number of excitation phases is increased when the frequency is high compared to when the frequency is low.