JPH04109151U - thermal head - Google Patents

Abstract

(57) [Summary] [Purpose] To prevent abnormal overheating of the heating element due to abnormality in the control unit. [Configuration] Strobe signal and N in the thermal head 15
A timer circuit 16 connected to the AND circuit 15 is provided.
The timer circuit 16 is triggered by a strobe signal, keeps the input of the NAND circuit 15 at a "High" level for a certain period of time, and then switches to a "Low" level. Therefore, the strobe signal makes the input of the NAND circuit 15 "High".
Even if the level is continued, the timer circuit 16
As a result, the input of the NAND circuit 15 becomes "Low", and no current flows through the heating element 9.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

This invention relates to a thermal head equipped with a heating element, and is particularly aimed at preventing abnormal heat generation. Regarding thermal heads.

0002

[Conventional technology]

Traditionally, thermal heads equipped with heating elements have been widely used in thermal printers, etc. It is widely used. The configuration of the thermal printer is shown in FIG. same In the figure, a rolled thermal paper 1 is passed through a guide roller 2 to a platen 3. wrapped around. At this time, the thermal surface of thermal paper 1 is on the opposite side of platen 3. There is. A line thermal head 4 is provided in contact with the platen 3, and a line thermal head 4 is provided in contact with the platen 3. By selectively driving a plurality of heating elements provided in the thermal head 4, Characters, figures, etc. are recorded on thermal paper 1.

0003 FIG. 5 is a circuit diagram showing the inside of a conventional line thermal head 4. As shown in FIG. The same figure Therefore, the shift register circuit 5 receives one line of data input in synchronization with the clock signal. This is used to temporarily store recorded data. Latch circuit 6 becomes shift register circuit 5 It takes in the stored recorded data into itself. The inverter circuit 7 is The strobe signal input to the thermal head 5 is inverted and input to the NAND circuit 8. Strengthen. The NAND circuit 8 is a driver circuit that drives the heating element 9 with electricity.

Next, the recording operation will be explained according to the time chart shown in FIG. The platen 3 is rotated by a pulse motor (not shown) and the thermal paper 1 is moved by one line. Next, the recording data is transferred to the line thermal head 4 in synchronization with the clock signal. As a result, the recording data is accumulated in the shift register circuit 5 shown in FIG. Thereafter, when a pulse is input to the latch terminal, the recording data is transferred from the shift register circuit 5 to the latch circuit 6. Next, the strobe signal is set to "Low" level for a certain period of time. The strobe signal is inverted by the inverter circuit 7 and input to the NAND circuit 8 at "High" level. As a result, the input terminals of the NAND circuit 8 corresponding to the "High" level recording data of the latch circuit 6 both become "High" level, and the output becomes "Low" level. As a result, current flows from the power supply terminal V _H to the heating element 9 . The temperature of the heating element 9 rises rapidly due to Joule heat, and recording is performed on the thermal paper 1.

[0005]

[Problem that the idea aims to solve]

However, in the conventional line thermal head mentioned above, some kind of Failure (CPU runaway due to static noise, etc., failure of control unit components, mechanical damage) The strobe terminal becomes “Low” level due to malfunction due to If this happens, current will continue to flow through the heating element. This causes the heating element to generate abnormal heat. The heating element itself may burn out, or other parts may remain in an overheated state. There is a risk of thermal damage to the thermal paper and even a flame. this Such problems can be prevented to some extent by providing a protection circuit within the control unit. However, the protection circuit itself may fail, and sufficient protection is provided. I couldn't say that.

[0006] This invention was devised in view of the above problems, and its purpose is to energize the heating element. Prevents abnormal heat generation by forcibly turning off the power after a certain period of time. The objective is to provide an excellent thermal head.

[0007]

[Means to solve the problem]

In order to solve the above problems, this invention distinguishes recorded data using a strobe signal. A heat-generating element is connected to a logic element, and the heat-generating element is selectively energized to record heat. In the multihead, input a strobe signal and detect the leading edge of the strobe signal. A timer that is triggered by a logic element and stops energizing the heat generating element by the logic element after a certain period of time. It is equipped with a circuit.

[0008]

[Effect] If the strobe signal continues to excessively energize the heating element due to a fault, etc., A timer circuit triggered by this strobe signal activates the logic element after a certain period of time. In response, a signal is issued to stop the energization. This stops the power supply to the heating element, Abnormal overheating can be prevented.

[0009]

【Example】

Embodiments of the present invention will be described below with reference to the drawings. Note that this is common to each drawing. Elements are given the same reference numerals.

0010 Figure 1 is a circuit diagram showing an embodiment of the present invention, and Figure 2 is a schematic diagram of a line thermal printer. FIG. This invention is a line-up device equipped with a thermal head. This will be explained using a thermal printer.

[0011] In FIG. 2, the control unit 11 connects the line thermal head via the I/O port 12. 13. The control unit 11 and the I/O port 12 are connected by a common control bus 14. , a strobe signal and a lamp signal from the I/O port 12 to the line thermal head 13. switch signals, recording data, and clock signals are sent.

0012 Next, the inside of the line thermal head 13 will be explained according to FIG. In the same figure The line thermal head 13 includes a shift register circuit as in the conventional example. 5 and a latch circuit 6 are provided. That is, the shift register circuit 5 has one line. The latch circuit 6 temporarily stores the recorded data for each time in the shift register circuit 5. Latch the recorded data. In addition, the inverter circuit 7 inverts the strobe signal. and inputs it to the NAND circuit 15. The NAND circuit 15 energizes and drives the heating element 9. This is a 3-input driver circuit. A straw is connected to the other input terminal of the NAND circuit 15. A signal and an output signal of a timer circuit, which will be described later, are input.

[0013] In this embodiment, a timer circuit 16 is provided in addition to the above configuration. timer circuit 16 is composed of a capacitor 17, a resistor 18 and a timer 19. timer 19 is a dedicated device that generates a constant pulse width with the time constant of a capacitor 17 and a resistor 18. IC (for example, manufactured by Texas Instruments, model number SN74123, etc.) ) is used. The timer 11 receives the strobe signal inverted by the inverter circuit 7. is input, and the output of the timer 19 is input to the NAND circuit 15 as described above. It will be done. That is, the timer circuit 16 is triggered by the rising edge of the strobe signal. After keeping the output TMout at “High” level for a certain period of time, it becomes “Low” level. It is something to return to.

[0014] Next, the operation of this embodiment will be further explained according to the time chart shown in FIG. .

First, recording data is transferred to the line thermal head 13 in synchronization with a clock signal from the control section 11 . As a result, one line of recording data is stored in the shift register circuit 5. Next, when a pulse is input to the latch terminal, the recording data is transferred from the shift register circuit 5 to the latch circuit 6. Next, the strobe signal is set to "Low" level and this state is maintained for a certain period of time. The strobe signal is inverted by the inverter circuit 7 and input to the NAND circuit 15 at a "High" level. This causes the input of the NAND circuit 15 to become "High". When the inverted strobe signal switches to the "High" level, the timer 19 is activated and the output TMout becomes the "High" level for a certain period of time (time t shown in FIG. 3). As a result, the input of the NAND circuit 15 becomes "High" for time A. Here, the output of the latch circuit 6 becomes "High" level depending on the presence or absence of recorded data. All inputs of the NAND circuit 15 become "High" level, and current flows from the power supply terminal V _H to the corresponding heating element 9. flows and generates heat.

[0016] If an abnormality occurs in the control unit 11 and the strobe signal changes as shown by the broken line in FIG. If the state remains “Low” for a long time, the output TMout of timer 19 returns to “Low” level after time t, and as a result, the input of the NAND circuit 15 becomes “ Therefore, the output of the NAND circuit 15 is shown by the broken line in FIG. The level becomes “High”. As a result, no current flows through the heating element 9. , can prevent abnormal overheating.

[0017] The present invention is not limited to the above embodiments, and various modifications are possible. Ta For example, as shown in FIG. 7, the timer circuit 16 is connected to an inverter circuit 7 and The object of the present invention can also be achieved even if the device is connected in series with the circuit. And this By doing as follows, the conventional 2-input NAND circuit 8 can be used as the heat generating element. It can also be used. Also, use a digital timer as a timer circuit. You can also do it.

[0018] Furthermore, although the above embodiment has been explained with respect to a line thermal head, it is The present invention can also be applied to a mall head.

[0019]

[Effect of the idea]

As explained in detail above, according to the present invention, after a certain period of time after the heating element is energized, We have installed a timer circuit that forcibly stops the power supply after a certain period of time has passed, so that it will not occur due to an abnormality in the control section. A highly reliable thermal head that prevents thermal element burnout and thermal effects on other parts. You can get

[Brief explanation of drawings]

[Fig. 1] Circuit diagram showing an embodiment of the present invention

[Figure 2] Block diagram showing the main parts of a line thermal printer

[Figure 3] Time chart showing the operation of the embodiment

[Figure 4] Configuration diagram showing a thermal printer

[Figure 5] Circuit diagram showing a conventional line thermal head

[Figure 6] Time chart showing the operation of the conventional example

[Figure 7] Circuit diagram showing a modification of the present invention

[Explanation of symbols]

5 Shift register circuit 6 Latch circuit 9 Heating element 13 Line thermal head 15 NAND circuit 16 Timer circuit

Claims (1)

[Scope of utility model registration request] 1. A thermal head that connects a heating element to a logic element that discriminates recording data using a strobe signal, and performs thermal recording by selectively energizing the heating element. A thermal head characterized by being provided with a timer circuit that is triggered by an edge and stops energizing a heat generating element by a logic element after a certain period of time.