JPS59207269A - Monitoring circuit for operating time of thermal recording head - Google Patents

Abstract

PURPOSE:To prevent the occurrence of hindrance and destruction due to an overheat caused by a continuous operation of a heating element, by monitoring an operation stop time of a thermal recording head as well as an operating time thereof so as to control the driving of the heating element. CONSTITUTION:An operating-time monitoring circuit 2, which is provided between a program timer 1 setting a time for a write instruction and a thermal recording head 3, is composed of an operating-time monitoring monostable multivibrator 21 monitoring an operating time of the head, a time-constant circuit 210 setting the operating time thereof, a stop-time monitoring monostable multivibrator 22 monitoring an operation stop time of the head, a time-constant circuit 220 setting the stop time thereof, an AND gate 23 delivering a control signal to the head based on the coincidence of the outputs from said two monostable multivibrators 21 and 22, and an inverter 24 inverting a write instruction pulse.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field The present invention relates to an operating time monitoring circuit for a thermal recording head used in a thermal printer.

(2) Technical background In the field of non-impact printers, thermal printers do not rely on mechanical movement during printing, so the printing mechanism is simple, and therefore they are small and lightweight devices with low noise and high reliability. is possible. Due to this feature, it is widely used as a portable device.

However, since this method selectively heats the heat-generating confectionery in the thermal recording head until it takes the shape of the letters and records it on thermal paper, there is always a problem if the thermal recording head deteriorates due to heat and shortens its lifespan. Improvements in dust are requested.

(3) Prior Art and Problems Conventionally, in a time monitoring circuit that monitors the operation time of a thermal recording head used in a thermal printer, the pulse is generated based on a write command pulse output from a program timer according to a predetermined program. A method has been used in which a monostable multi-vibrator (mono-multi) activated by the rising part of the motor is used to monitor the operating time for a certain period of time determined by a circuit constant, for example, 2m5ec. However, although this circuit can monitor the operating time of 2m5ec, it does not monitor the operating stop time of the head, so if the circuit goes into an abnormal state due to thermal runaway of the element, for example, the operating time cannot be controlled and the program Since the write command pulses are no longer controlled, the head is forced to adjust to the next operating state after one page, which causes the head to overheat and shorten its lifespan.

(4) Purpose of the Invention The purpose of the present invention is to monitor not only the operation time of the thermal recording head but also the operation stop time. An object of the present invention is to provide an operating time monitoring circuit that protects the operating time from occurring.

(5) Structure of the Invention According to the present invention, the present invention provides a thermal recording head operating time monitoring circuit for a thermal printer, which circuit is configured to monitor the rising edge of a write command pulse from a program timer. A monostable multivibrator for monitoring operating time includes a time constant circuit that starts depending on the V section and sets the operating time, and a time constant circuit that starts depending on the V lower part of the write command pulse and sets the stopping time. A monostable Marna bibrake for monitoring stop time, and an AND gate that outputs an output based on a match between the outputs of the monostable multivibrator for monitoring operation time and the monostable multivibrator for monitoring stop time. This is achieved by providing a complete operating time monitoring circuit for a thermal recording head with a % characteristic.

(6), Embodiment FIG. 1 is a circuit quotient showing an example of an operating time monitoring circuit for a thermal recording head according to the present invention. In Figure 1, l
2 shows a program timer that sets up the entire time for a write command, 2 shows an operating time monitoring circuit according to the present invention, and 3
The thermal recording head shows gold. The operating time monitoring circuit 2 includes an operating time monitoring monomulti 21 that monitors the operating time of the head, a time constant circuit 210 that sets the operating time, a stop time monitoring monomulti 22 that monitors the operating stop time of the head, and a time constant circuit 210 that sets the operating time. It is fully equipped with a time constant circuit 220 that sets the entire stop time, an AND gate 23 that sends the matching value of both outputs 21 and 22 and a control value number 9 to the head, and an inverter 24 that inverts the write command pulse. .

FIG. 2 shows signal lines A and B of the circuit of FIG.

This is a waveform diagram showing the signal waveforms at C and D. In this example, the diagram shows the case where the operating time of 2m5ec and the stop time of lm5er: are changed, and ■ is the output drum of the program timer in A. The shape, ■ is the output drum shape of the operating time monitoring monomulti 21 at B, and ■ is the (
Output waveform of stop time monitoring monomulti 22, and ■
shows the output waveform of the AND gate 23 at D and the head control signal.

In such a combination, conventionally, the program timer 1 outputs a drum-shaped pulse shown in ■ in Fig. 2, and the mono multi 21 detects the full rise of the pulse, starts operation, and divides the operation time into the waveform ■. The signal shown was being supplied to head 3. In this case, during the period T1, the output of the program timer is determined by the output of the program timer, for example, an operating time of 2 m5e and a stop time of 1 m5e.
c is maintained, but since the stop time is not monitored during period T2, the 9th operation is entered by the next write command pulse when the stop time is within 1 m.Please note that the operation time The reason why is less than 2 m (8) is because the clear command is supplied within 2 m (8) of the write command.

In this way, since a sufficient stopping time (in this case, 1 m5 ec or more) was not maintained, the heating element of the thermal recording head overheated, causing deterioration. In the operating time monitoring circuit 2 according to the present invention, the output waveform of the program timer 1 is converted into the waveform shown in (2) by the stop time monitoring monomulti 22, its time constant circuit 220, and the inverter 24. In this case, in period T, a predetermined stop time (1 m5ec or more in this case) is secured against the time constant circuit 220, and even if it is 1 m5ec in order to detect only the falling edge of the waveform [F],
Even if there is a next write command within 5ec, 1m5ec should be secured. Mono multi 21 and mono multi 22 output ■ and ■
is input to the AND gate 23, the two swords are matched, and from its output, the pulse 1 shown in the shape of an hourglass (■) is supplied to the head 3. As is clear from the output waveform (2), a predetermined stopping time is ensured, so that the heating element is prevented from heating up, and the head can be preserved.

(7) Effects of the Invention The operating time monitoring circuit according to the present invention prevents the heating element of the thermal recording head from overheating, thereby preventing deterioration of the head and extending its life.

[Brief explanation of the drawing]

Figure M1 is a circuit diagram showing the entire operating time timing circuit according to an embodiment of the present invention, and Figure 2 is a tentative diagram showing waveforms at each point of the circuit shown in Figure 1. Explanation of symbols) 1...Program swimmer 2...Operating time monitoring circuit 3...Thermal recording head 2''...Mono-J during operation 22...Stop time mono-multi 23...And gate 24...Inverter 210...Operating time time constant circuit 220...Stop time time constant circuit Patent applicant Fujitsu Kiden Ltd. Patent application agent Akira Yoiki Patent attorney Kazuyuki Nishidate Patent attorney Yukio Uchida Akira Yamaguchi

Claims (1)

[Claims] 1. An operating time monitoring circuit for a thermal recording head of a thermal printer, which circuit includes a time constant circuit that is activated by the rising edge of a write command pulse from a program timer and sets an operating time. It includes a monostable multivibrator and a time constant circuit that is activated by the falling portion of the write command pulse and sets a stop time. All features include a monostable multivibrator for monitoring stop time, and an AND gate that outputs based on the coincidence of the respective outputs of the monostable multivibrator for monitoring operating time and the monostable multivibrator for monitoring stop time. An operating time monitoring circuit for a thermal recording head.