JPH0784067B2 - Line thermal printer - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a line thermal printer that protects the line thermal head by stopping the operation of the printer depending on the temperature of the line thermal head.

2. Description of the Related Art Generally, when the thermal head exceeds the operating temperature range, the applied energy to the head becomes large at low temperature and the head is destroyed, and at high temperature, the head itself may be destroyed due to the temperature rise of the head itself. is there. In particular, since the line thermal head is expensive, it is necessary to prevent its destruction in the control circuit of the head in the control circuit of the line thermal printer. With the conventional temperature protection function, the value of the thermistor built in the head is read into the microcomputer by the A / D converter, and the value that stops the operation of the printer is stored in the memory of the microcomputer. Had stopped working. Further, the temperature of the head is not protected. On the other hand, for the temperature correction, a conversion table of temperature and energy applied to the head is prepared in the microcomputer and energy is applied to the head.

However, in the temperature protection function of the prior art, when the line thermal printer exceeds the operating temperature range, the head is destroyed or a value for stopping the operation of the printer is stored in the memory of the microcomputer. It is wasteful in terms of time, because it is necessary to check each time whether or not the value has exceeded. Also, the capacity of the software will increase. Further, since the temperature correction is a table, the magnitude of the energy applied to the head is stepwise with respect to the temperature, and the magnitude of the energy applied changes at the boundary of the table, resulting in uneven print density.

In order to solve the above problems, the present invention confirms on a hardware whether the line thermal printer exceeds or does not exceed the operating temperature range, and when the operating temperature range is exceeded, the operation of the line thermal printer is stopped and the line thermal head is An object of the present invention is to provide a line thermal printer that protects and can apply energy suitable for the temperature of the line thermal printer to the head linearly with respect to the temperature within the operating temperature range and that does not cause uneven density. To do.

Means for Solving the Problems In order to achieve the above object, a line thermal printer according to the present invention includes an oscillating means for changing an oscillation cycle by a resistance value change of a thermistor for detecting a temperature of the line thermal head, and a line thermal head. A head coloring time determining means for determining the coloring time by counting the number of input pulses from the oscillating means with a counter; a low temperature side integrating means and a high temperature side primary integrating means for integrating the input voltage from the oscillating means. , Integrating the input voltage generated by the high temperature side primary voltage comparing means and the low temperature side voltage comparing means and the high temperature side primary voltage comparing means for comparing the obtained voltage with a preset reference voltage. A high temperature side second integrating means and a high temperature side second comparing means for comparing a voltage generated by the high temperature side secondary integrating means with a reference voltage set in advance. The secondary voltage comparing means and the low temperature side voltage comparing means or the high temperature side second
Temperature protection means for stopping the control when the next voltage comparison means determines that the comparison side voltage is higher than the reference voltage; and control continuation means for continuing the control when the comparison side voltage is lower than the reference voltage. It is a configuration provided with.

With the above-described structure, the present invention controls the line thermal printer by the low temperature side voltage comparing means or the high temperature side secondary voltage comparing means while the head color development time determining means corrects the temperature of the energy applied to the head of the line thermal printer. If it is determined to stop, the temperature protection means stops the control of the printer, and if it is determined to continue, the control continuation means continues the control of the printer.

Embodiment FIG. 1 is a block diagram showing an embodiment of the present invention, in which 1 is a line thermal head, 2 is a thermistor for detecting the temperature of the line thermal head, and 3 is oscillation due to a change in resistance value due to the temperature of the thermistor 2. This is an oscillator circuit whose period changes. Reference numeral 4 denotes a head coloring time determining means, which is an oscillation circuit 3
The input pulse from is counted using a counter and the head is colored for the count time. Further, the low temperature side integrating means 5 and the high temperature side primary integrating means 7 for integrating the voltage generated in the oscillation circuit 3 and the low temperature side comparing the voltage integrated by the low temperature side integrating means 5 with a preset reference voltage. Generated by the side voltage comparison means 6, the high temperature side primary voltage comparison means 8 for comparing the voltage integrated by the high temperature side primary integration means 7 with the reference voltage, and the high temperature side primary voltage comparison means 8. A high temperature side secondary integrating means 9 for integrating the generated voltage, and a high temperature side secondary voltage comparing means 10 for comparing the voltage integrated by the high temperature side secondary integrating means 9 with a preset reference voltage. , Low temperature side voltage comparing means 6 or high temperature side secondary voltage comparing means 10
There is provided a temperature protection means 11 for deciding to stop the control of the printer and a control continuation means 12 for deciding to continue the control of the printer.

FIG. 2 shows the relationship between the temperature of the oscillator circuit 3 and the oscillation pulse period.

FIG. 3 shows an example of a specific circuit of a main part, and the line thermal printer control circuit is composed of a microcomputer 13 and peripheral circuits. The microcomputer 13 shown here is a so-called one-chip microcomputer having a CPU, ROM, RAM and an input / output unit. The oscillation circuit 3 is one in which the cycle of the output pulse changes due to the change in the resistance value of the thermistor built in the head, and this output pulse changes with the counter 16 and the low temperature protection circuit 14.
And is input to the high temperature protection circuit 15. At the counter 16, the oscillation pulse from the oscillation circuit 3 is sent to the microcomputer 13
Counts from the value set in to the overflow. This counting time is the time when the head is coloring, and when the temperature is high, the oscillation pulse cycle becomes short and the coloring time of the head becomes short as shown in FIG. The opposite is true for low temperatures. Further, the voltage generated in the oscillation circuit 3 is monitored by the low temperature protection circuit 14 and the high temperature protection circuit 15 while performing various controls such as the above operation. FIG. 4 shows a timing chart of the A, B, C parts of the low temperature protection circuit 14, and FIG. 5 shows a timing chart of the A, D, E, C parts of the high temperature protection circuit 15. In the low temperature protection circuit 14, when the oscillation pulse period from the oscillation circuit 3 becomes long, the charging time in the B section becomes long, and when the reference voltage V or more is charged, the output C section of the voltage comparator is displayed.
The LOW signal is output, and the microcomputer 13 stops controlling the printer. Oscillation circuit 3 in high temperature protection circuit 15
When the oscillation pulse period from is shortened, the charging time in the D section is shortened, and when the reference voltage V is no longer charged, the HIGH signal continues to be output to the output F section of the voltage comparator, so that only the G section is charged. When the voltage becomes equal to or higher than the reference voltage V, a LOW signal is output to the output H of the voltage comparator, and the microcomputer 13 stops the control of the printer. When the temperature returns to the operating temperature range, the printer control is continued.

Effects of the Invention As is clear from the above description, the applied energy setting of the head using the normal A / D converter is 0 to 5 ° C.
At x1 [mj], 5 to 10 ° C, the setting is stepwise like x2 [mj], and there is a density difference at the step boundary, or 0
Even if x1 [mj] at 1 ° C and x2 [mj] at 1 ° C, an energy table for the operating temperature range of the printer is required, and the system software capacity could not be reduced. With the input pulse from the oscillation circuit whose oscillation pulse period changes, the head coloring time determining means can apply energy suitable for the temperature of the head at that time to the head linearly with respect to the temperature, so that the print density is not uneven. Also, while controlling the printer, without using an expensive A / D converter, it is possible to inexpensively prevent the thermal head from being destroyed at low and high temperatures by means of temperature protection means, eliminating the waste of software capacity and time. It is possible to realize a line thermal printer having excellent effects.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a control circuit of a line thermal printer according to an embodiment of the present invention, and FIG. 2 is an oscillation pulse period temperature characteristic diagram showing a relation between a head temperature and a pulse period output from an oscillation circuit. FIG. 3 is a circuit diagram of a main part of this embodiment,
FIG. 4 is a timing chart of the low temperature protection circuit, and FIG. 5 is a timing chart of the high temperature protection circuit. 1 ... Line thermal head, 2 ... Thermistor, 3 ...
... oscillation circuit, 4 ... head coloring means determining means, 5 ... low temperature side integrating means, 6 ... low temperature side voltage comparing means, 7 ... high temperature side primary integrating means, 8 ... high temperature side primary voltage Comparison means,
9 ... High temperature side secondary integration means, 10 ... High temperature side secondary voltage comparison means, 11 ... Temperature protection means, 12 ... Control continuation means.

Claims (1)

[Claims] 1. An oscillating means for changing an oscillating cycle by changing a resistance value of a temperature detecting means for detecting a temperature of a line thermal head, a low temperature side integrating means and a high temperature side for repeating charging and discharging by an input pulse from the oscillating means. Low temperature side voltage comparing means and high temperature side primary voltage comparing means for comparing the voltage generated by the integrating means with a preset reference voltage, and the high temperature side primary voltage comparing means High temperature side secondary voltage comparing means for comparing the voltage generated by the high temperature side secondary integrating means with a preset reference voltage and the high temperature side secondary integrating means for repeating charging and discharging by the input pulse generated in Means, a temperature protection means for stopping the control when it is determined by the low temperature side voltage comparison means or the high temperature side secondary voltage comparison means that the comparison side voltage is higher than the reference voltage, and the reference Control continuation means for continuing the control when it is determined that the voltage on the comparison side is smaller than the pressure, and head energy application means for linearly applying energy to the line thermal head by the oscillation cycle from the oscillation means are provided. Line thermal printer characterized by.