JPH02155666A - line thermal printer - Google Patents

Abstract

PURPOSE:To make it possible to prevent a thermal head from being broken by judging whether the current temperature is a temperature at which a line thermal head is to be operated for color development, based on an output pulse from an oscillation circuit the oscillational pulse period of which varies with temperature. CONSTITUTION:Before starting color development by operating a line thermal head 1, it is necessarily judged by a high temperature discriminating means 4 whether the color development by the head is to be performed. When it is judged that the color development is not to be performed, the color development by the head is stopped by a head color development stopping means 5, and the color development is suspended by a head color development suspending means 6 until it is judged by the means 4 that the color development by the head is to be performed. When it is judged by the means 4 that the color development by the head is to be performed, a color developing time for the head is determined by a head color development time determining means 7, and the color development by the head 1 is effected by a head color developing means 8.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a line thermal printer that stops the operation of the printer depending on the temperature of the line thermal head to protect the line thermal head.

Conventional Technology Generally speaking, when a thermal head exceeds its high-temperature usage limit, the heating element of the head may be destroyed.
In particular, since line thermal heads are expensive, it is necessary to prevent the head control circuit from being destroyed in the control circuit of the line thermal printer. For this reason, conventional line thermal printers are required to be used within high temperature limits, or the head temperature is read into a microcomputer using a thermistor and an expensive A/D converter, and a table set inside the microcomputer is used to record the print head temperature. The energy applied to the thermal head is adjusted, and for high-temperature protection, the microcomputer has a value that stops coloring the head, and when that value is exceeded, the head stops coloring, protecting the line thermal head. Ta.

Problems to be Solved by the Invention However, in the conventional technology, if the line thermal printer exceeds the high temperature range, the heating element of the line thermal head will be destroyed, or the method using a thermistor and A/D converter will not work. Since the energy applied to the line thermal head is adjusted by a table set inside the microcomputer, the magnitude of the energy applied to the head becomes step-like with respect to the temperature, and the magnitude of the energy applied to the line thermal head changes at the boundary of the table. There were problems such as variations in the print density and uneven print density.

In order to solve the above-mentioned problems, the present invention protects the line thermal head by stopping coloring of the line thermal head of the line thermal printer when the line thermal printer exceeds the high temperature use limit, and also protects the line thermal head within the high temperature use limit. If it is within the range, energy that matches the temperature of the line thermal head at that time can be applied to the line thermal head linearly with respect to the temperature, there will be no uneven density, and the above content can be applied without using an expensive A/D converter. The purpose is to provide a line thermal printer that performs.

Means for Solving the Problems In order to achieve the above object, the line thermal printer of the present invention includes an oscillation means that changes the oscillation period by a change in the resistance value of a thermistor that detects the temperature of the line thermal head, and a line thermal printer that detects the temperature of the line thermal head. A head coloring time determining means that determines the coloring time by counting the number N of input pulses from the oscillation means and a number M of input pulses that is different from the number N of input pulses that determines the coloring time of the line thermal head; A high temperature determination means that starts a timer to determine whether or not the count has increased within a certain period of time before the line thermal head develops color, starts a counter at the same time, and determines whether or not the count has increased during the timer amplifier; head coloring stopping means for stopping coloring of the line thermal head if the determining means determines that the count is up, and in that case, repeating the stopping of coloring of the line thermal head until it is determined by the high temperature protection means that the count is not up. The apparatus is configured to include a head color development stop continuation means, and a head color development means for coloring the line thermal head when the high temperature determination means determines that the count has not increased.

Effect of the Invention With the above-described configuration, the present invention always uses the high temperature determination means to determine whether or not to color the line thermal head before starting coloring of the line thermal head, and when it is determined not to color the line thermal head, the head The coloring stopping means stops the coloring of the line thermal head, and in this case, the head coloring stopping continuation means stops the coloring of the line thermal head until the high temperature determining means determines that the line thermal head should color. When the determining means determines that the line thermal head should be colored, the head coloring time determining means determines the coloring time of the line thermal head, and the head coloring means colors the line thermal head.

Embodiment FIG. 1 is a configuration diagram showing an embodiment of the present invention, in which 1 is a line thermal head, 2 is a thermistor that detects the temperature of the line thermal head 1, and 3 is an oscillation caused by a change in resistance value of the thermistor 2 due to temperature. This is an oscillation circuit whose period changes.

Then, the high temperature determination means 4 starts a timer,
Next, a counter is started, and it is determined whether or not the input pulse number M from the oscillation circuit 3 is counted up during the timer amplifier, and if it is determined that the count is counted up, the coloring of the line thermal head 1 is completely stopped. The head color development stop means 6, in which case, the head color development stop continuation means 6 which repeats the stop of color development of the line thermal head until the high temperature determination means determines that the count has not increased, and the high temperature determination means 4 determine that the count has not increased. If it is determined, head coloring time determining means 7 sets the coloring time of the line thermal head 1 by counting the number N of input pulses from the oscillation circuit 3, and head coloring means 7 performs coloring of the line thermal head for the set time. It consists of

Next, to explain the relationship between temperature and the high temperature determination function from Figures 2, 3, and 4, the output pulse period from the oscillation circuit 3, which uses the resistance value change of the thermistor due to temperature, becomes smaller as the temperature rises. Become. In other words, the number of input pulses increases within a certain period of time. The number of output pulses is counted within a certain period of time by a timer, and if it is larger than the set number of input pulses, the line thermal head stops coloring, and if it is smaller, the line thermal head starts coloring.

FIG. 6 is a diagram showing an example of a specific circuit of the main part.

The control circuit of the line thermal printer is composed of a microcomputer 9 and peripheral circuits. The microcomputer 9 shown here includes a CPU, ROM, and RA.
This is a so-called one-chip microcomputer that has an M and an input/output section. The oscillation circuit 3 changes the cycle of its output pulses due to changes in resistance due to temperature of a thermistor built into the head, and these output pulses are input to the microcomputer 9. On the other hand, an output signal from the microcomputer 9 for controlling the line thermal head is input to the thermal head via the head control device C1o.

Therefore, when the microcomputer 9 determines to stop the color generation of the line thermal head based on the input pulse from the oscillation circuit, it outputs an "off" signal to the head control IC to stop the color generation of the line thermal head, and all other operation also stops.

Also, when the microcomputer 9 determines that the line thermal head is to be colored, the number of human pulses N from the oscillation circuit is
Throat control I to the time until counting up
is configured to output an "on" signal to C. Incidentally, the time it takes to count up the number N of input pulses, the time during which the reline thermal head is colored, is the amount of energy applied to the head.

Next, the operation of the control circuit of the line thermal printer configured as described above will be explained using the flowchart shown in FIG. The line thermal printer operates according to the procedure of the high temperature judgment and magnitude determination program of the energy applied to the head, which is stored in the ROM in the microcomputer 9 and shown in the flowchart of FIG. 6 immediately before starting the printing operation.

By inputting the output pulses of the oscillation circuit 3 to the microphone computer 9, the number of human pulses V in step 11 is first calculated.
The number M to be counted with a counter in a set (for example, 1oO
), and a counter that counts the number of manual pulses M is started in step 12. Next, in step 13, a timer time (for example, 70
0 usec), the timer is started in step 14, and the timer is set in step 16 to wait until the timer is reached. When the set timer time has passed, it is determined in step 16 whether or not the counter started in step 12 has counted up. If it is determined that the counter has counted up, in step 17 the line thermal head is colored. is stopped and the process returns to step 11. On the other hand, if it is determined in step 16 that the count has not increased, the line thermal head is caused to develop color in step 18. Next, the output cover pv y of the oscillation circuit 3
, f The number N to be counted by the counter (for example, 171) is set by inputting the number N of input pulses in step 19 to the microcomputer 9, and the counter that counts the number N is started in step 20. Then, the process waits in step 21 until the counter started in step 20 counts up.

Thereafter, when the counter counts up the set count number N, the line thermal head that has been colored in step 18 is stopped in step 22, and the printing operation is completed. Incidentally, the amount of time the head is colored is the amount of energy applied to the head. For example, even if a line thermal head is used in which the heating element of the line thermal head is destroyed when the temperature of the line thermal head becomes high (for example, +70°C), the structure of the above embodiment allows the temperature to rise to +60°C. If you want to stop the printer's operation, check the pulse period output from the oscillation circuit 3 when the temperature is +60'C, and divide the timer time by that number and set the quotient as the number of input pulses M, then you can determine the high temperature. By means of means 4, color development of the line thermal head stops at temperatures above +60° C., and destruction of the line thermal head can be prevented. Further, according to the above configuration, the applied energy suitable for the temperature of the head is supplied to the head each time the temperature of the line thermal head changes, so that it is possible to prevent uneven printing density from occurring.

Effects of the Invention As is clear from the above explanation, the present invention uses a high temperature determination means to cause the line thermal head to develop color using the output pulse from an oscillation circuit whose oscillation pulse period changes with temperature changes immediately before entering the printing operation. If it is determined that the temperature is such that the line thermal head does not develop color, the head color stop means stops the line thermal head from producing color, and the head color stop continuation means continues to operate the line until the temperature reaches a temperature that causes the line thermal head to develop color again. This can stop the thermal head from coloring and prevent the thermal head from being destroyed. Furthermore, if the high temperature determining means determines that the temperature is such that the line thermal head develops color, the head coloring time determining means determines the coloring time of the head suitable for the temperature of the line thermal head at that time, that is, the amount of energy applied to the head. It is possible to realize a thermal line printer that has an excellent effect of not causing print density unevenness because the head coloring means is used to color the head.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing a control circuit of a line thermal printer according to an embodiment of the present invention, Fig. 2 is a thermistor resistance temperature characteristic diagram showing an example of the relationship between the head temperature and the thermistor, and Fig. 3 is a head FIG. 4 is an oscillation pulse period temperature characteristic diagram showing the relationship between the temperature and the pulse period output from the oscillation circuit; FIG. FIG. 6 is a circuit diagram of the main part of this embodiment, and FIG. 6 is a flowchart showing an example of a program for determining low temperature and determining the magnitude of energy applied to the head. 1...Line thermal head, 2°゛・passer mister, 3...Oscillation circuit, 4...High temperature determination means, 5...Head color stop means, 6... . . . Head color development stop continuation means, 7 . . . Head color development time determining means, 8 . . . Head color development means.

Claims (1)

[Claims] An oscillation means that changes the oscillation cycle by a change in the resistance value of a temperature detection means that detects the temperature of the line thermal head, and a head coloring means that determines the coloring time of the line thermal head by counting the number N of input pulses from the oscillation means. The time setting means and the number M of input pulses, which is different from the number N of input pulses that determines the head color development time, are set, and a timer is started before the head color development to determine whether or not the count has counted up within a certain time. At the same time, there is a high temperature determination means that starts a counter and determines whether or not the input pulse number M has counted up when the timer is up, and a head that stops coloring of the line thermal head if the high temperature determination means determines that the count has increased. a color development stop means; in that case, a head color development stop continuation means that repeats the head color development stop until the high temperature determination means determines that the count has not increased; and a line thermal head when the high temperature determination means determines that the count has not increased; A line thermal printer comprising a head coloring means for coloring.