JPS63268667A - Thermal recorder - Google Patents

Abstract

PURPOSE:To protect a thermal recording head from overheating troubles, by providing a temperature sensor for detecting the temperature of the head, independently of a controlling part, and inhibiting the supply of an ENABLE signal to the head on the basis of the result of the comparison of the temperature detected by the sensor with a preset temperature, by a part provided independently from a controlling part. CONSTITUTION:An ENABLE inhibition controlling part 5 supplied with a detection output of a thermistor 10 and being independent from a controlling part 2 is connected between an ENABLE signal output terminal of a head-controlling part 21 and an ENABLE signal input terminal of a thermal recording head 1. A comparator 50 compares a temperature detected by the thermistor 10 with a preset temperature, and generates a control output only when the detected temperature exceeds the preset temperature, whereby a control is performed so as to close an AND gate 51 having been opened. By such a control, the supply of a continuous ENABLE signal from the head-controlling part 21 to the head 1 is cut off, and abnormal heating of the head 1 is restrained.

Description

Detailed Description of the Invention [Objective of the Invention] (Industrial Field of Application) The present invention relates to a thermal recording device used in a recording section of a facsimile machine R11, etc., and specifically relates to a thermal recording head constituting this thermal recording device. Concerning improvements to protect against overheating damage.

(Prior Art) As is well known, many facsimile machines use a thermal recording device as a recording section. □Figure 7 is a block diagram showing the main components of this type of thermal recording device. 1 is a thermal recording head, 2 is a control unit, and 3 is a
is the power supply circuit.

Of these, the thermal recording head 1 has a thermistor 10 that detects sa of a heating resistor (not shown), and the control section 2 includes a power supply circuit control section 20, a head control section 21, and a pulse width control section 22. .

In FIG. 7, the power supply circuit control section 20 has a
The power supply circuit 3 having a power supply capacity of V is 0N10FFb.
IJIIl.

The power supply circuit control unit 20 controls the power supply circuit 3 to be ON only when the facsimile machine is performing a sending/receiving operation or a copying operation, so that the
Supply a power supply voltage of V.

The thermal recording head 1, which is brought into an operation compensation state by this power supply voltage, becomes capable of driving a heating resistor (not shown) to generate heat according to image information by an enable signal (EN) supplied from the head control unit 21. .

By driving the heating resistor to generate heat, an image corresponding to the image information can be recorded on a thermal recording paper or the like.

At this time, the pulse width control section 22 receives the temperature detection output of the heating resistor by the thermistor 10, and controls the pulse width applied to the thermal recording head 1 based on the detection output so that the recording density is constant.

In a thermal recording device having such a configuration, facsimile 'J
When the temperature detected by the thermistor 10 exceeds a preset temperature in addition to the period in which the AM does not perform transmission/reception or copying operations, the power supply circuit controller 20 turns the power supply circuit 3 off.
By controlling to FF, troubles such as damage to the thermal recording head due to overheating can be avoided.

However, in such a configuration, 0N10FFIF! ! power supply circuit 3 having the function or this power supply circuit 3 as 0N10FIJ
The power supply circuit control section 20 that controls illumination is required, which increases the size of the device and increases the manufacturing cost.

In order to eliminate this inconvenience, as shown in Figure 8,
There has been a proposal for a thermal recording device comprising a power supply circuit 4 configured to supply 24V.

In the case of this thermal recording device, a temperature fuse 11 is provided in the thermal recording head 1, and when the temperature of the thermal recording head 1 exceeds a certain level, the WA temperature fuse 11 is cut off and the power supply from the power supply circuit 4 is cut off. This makes it possible to prevent the thermal recording head 1 from overheating.

Although it is possible to downsize the device and reduce manufacturing costs in this type of thermal recording device, it is difficult to attach the humidity fuse 11 to the first base plate of the thermal recording head 1. There were disadvantages such as loss of efficiency in the manufacturing process.

Therefore, in the end, in this type of conventional thermal recording device, the temperature fuse 11 is not provided, and the temperature detected by the thermistor 10 is taken into the head control section 21, and when the detected temperature becomes abnormally high, the software It has been customary to stop the supply of the enable signal to prevent overheating of the thermal recording head.

However, in such a conventional thermal recording apparatus, if an abnormality such as the CPU going out of control occurs in the control unit 2, the supply stop control of the enable signal cannot be performed, and In some cases, accidents could not be avoided.

(Problems to be Solved by the Invention) In this way, in the conventional thermal recording device described above, the supply of the enable signal is controlled to be stopped by software based on the temperature detected by the thermistor. There is a problem in that it is not possible to prevent the recording head from overheating, and accidents such as damage may not be avoided.

The present invention has been made in view of the above-mentioned circumstances, and is applicable to a thermal recording device configured to perform control to stop the supply of an enable signal based on the temperature detected by a thermistor, regardless of whether an abnormality such as a runaway of the CPU has occurred. It is an object of the present invention to provide a thermal recording device which can prevent overheating of a thermal recording head and head and can reliably protect the thermal recording head from accidents such as 1-meter scratches caused by the overheating.

(Structure of the Invention) (Means for Solving the Problems) A thermal recording device of the present invention includes a thermal recording head and a control unit that controls the thermal recording head. A temperature sensor for detecting temperature and the control section are provided independently, and a comparison means compares the temperature detected by the temperature sensor and a preset temperature, and the temperature sensor detects the temperature based on the comparison result of the comparison means. and an enable prohibition control means for prohibiting supply of an enable signal to the recording head.

(Function) Since the thermal recording device of the present invention has an enable prohibition control means independent of the control section, even if an abnormality such as runaway of the CPU occurs in the control section, the temperature sensor detects m degrees exceeding a certain value. If this happens, the supply of the enable signal to the thermal recording head can be reliably cut off.

(Example) Hereinafter, an example of the present invention will be described in detail based on the accompanying drawings.

FIG. 1 is a block diagram showing the configuration of main parts of a thermal recording device according to an embodiment of the present invention, which performs the same functions as each part of the conventional thermal recording device shown in FIGS. 7 and 8. The same reference numerals are used.

The thermal recording device of the present invention inputs the detection output of the thermistor 10 between the enable signal output terminal of the head control section 21 and the enable signal input terminal of the thermal recording head 1, and has an enable prohibition function independent of the control section 2. By connecting the control unit 5.

configured.

This enable prohibition control section 5 is for stopping the supply of an enable signal to the thermal recording head 1 when the temperature detected by the thermistor 10 exceeds a set value, and specifically, as shown in FIG. 50 and an AND gate 51.

Normally, the thermal recording head 1 is powered by a +2.
The heating resistor is driven to generate heat by receiving a power supply of V.

In this state, it is assumed that an abnormality such as a runaway of the CPU occurs in the control section 2 and the operation of the head control section 21 is stopped while outputting the enable signal.

In such a case, since power of +24V is continuously supplied from the power supply circuit 4 to the thermal recording head 1, the temperature of the thermal recording head 1 gradually rises and is heated.

The temperature of the thermal recording head 1 is detected by the thermistor 10, and is input to the pulse width control section 22 and the comparator 50 as an electric signal (detected at 8 degrees) corresponding to the temperature.

Among these, the comparator 50 is preset with a temperature that must not be exceeded in order to maintain normal operation of the thermal recording head 1.

Therefore, the comparator 50 compares the temperature detected by the thermistor 10 with the preset temperature of 8 degrees, generates a control output only when the detected temperature exceeds the preset temperature, and closes the AND gate 51, which has been open until now. Control as follows.

Through such control, the continuous supply of enable signals from the head control unit 21 to the thermal recording head 1 is cut off,
Abnormal heating of the thermal recording head 1 can be suppressed.

By the way, the enable prohibition control section 5 according to the present invention can be provided not only outside the thermal recording head 1 but also inside it, as long as it is independent from the control section 2 and configured as a hardware.

FIG. 3 shows an example of a thermal recording device constructed based on this method, in which a comparator 12 and an AND gate 13 corresponding to the comparator 50 and AND gate 51 in FIG. 2 are mounted in the thermal recording head 1. has been done.

However, in this case, ICs such as drivers, comparators, gate circuits, etc. that constitute the enable prohibition 1lIIID section 5
type is the high temperature (100°C) associated with driving the thermal recording head 1.
It is essential to operate stably even during heating, and from the viewpoint of a wide operating temperature range, a CMO8II structure is preferable.

Further, the enable prohibition control section 9 according to the present invention can also be configured using a comparator 50 having a hysteresis characteristic as described later.

A schematic configuration of such a comparator 50 is shown in FIG. 4, and includes a comparator C that uses the temperature detected by the thermistor 10 as a comparison voltage 1N, and a resistor that variably sets the value of the reference voltage v8 based on the output of the comparator C2. R1 and R2 are provided.

The operation of this comparator 50 will be simply explained with reference to the hysteresis characteristic diagram in FIG.

First, in FIG. 4, the detected temperature of thermistor 0 is inputted to the comparator CH as a comparison voltage VIN.

In the comparator CH, the comparison voltage V1N is the reference voltage ■
When the comparison voltage VIN exceeds the base l\thunder pressure ■8, the output ■ changes from ■ to ■1, for example.
H Turn.

The AND gate 51 is closed by the output of the comparator C, and the enable signal is turned OFF.

Further, the inverted output V[ of the comparator C11 is converted into a reference voltage 8 by a voltage dividing resistor composed of resistors R1 and R2, and is fed back into the comparator CH.

At this time, the reference voltage ■ is the output of the comparator CH
With the reversal of , I/1 changes from, for example, ■81 to VS2 (■0υ■81>■S2').

Thereafter, the comparator CH compares the newly set reference voltage ■ with the comparison voltage ■1N, and when the comparison voltage ■ becomes lower than the reference voltage V82, the output ■N is inverted from ■ to ■1 again.

OUT L The AND gate 51 is closed by the output VH of this comparator CH, and the enable signal is turned ON.

By changing the reference voltage ■ or ■82 based on the output ■oU■ of the comparator C in this way, it is possible to maintain a certain temperature difference between the temperature at which the enable signal is turned off and the temperature at which it is turned on again. can.

Therefore, for example, as shown in FIG.
In order to have a hysteresis characteristic that turns OFF at ℃ and turns ON at 80℃, the output of comparator C
Based on u■, the values of the resistors Ri and R2 may be determined so that the reference voltage V and VS2 become the output voltages when the temperatures of 100° C. and 80° C. are detected by the thermistor 0, respectively.

By providing such a hysteresis characteristic, the [
As the temperature of the thermal recording head 1 rises and falls near the preset threshold level of 1 degree, the enable signal is turned ON and OFF repeatedly, thereby making it possible to eliminate "developing".

Furthermore, the thermal recording apparatus of the present invention can also be configured as shown in FIG.

This thermal recording device prohibits the supply of an enable signal from the head control unit 6 to the thermal recording head 1 based on the output of the comparator 50, and at the same time prohibits the supply of an enable signal from the power supply circuit 4 to the
It also cuts off the 4V power supply, and the thermal recording head 1
This makes it possible to further improve the reliability of protection against heating damage.

In the thermal recording apparatus of the present invention, as described above, the thermistor 10, which is used for the function of inhibiting the enable signal when the temperature of the thermal recording head 1 exceeds a set value, is controlled by the conventional pulse width control section 22. Since it is used in common with what constitutes the recording density inter-am function depending on the pulse width given to the recording head 7, the increase in the hardware configuration can be kept to a minimum.

〔Effect of the invention〕

As explained above, according to the thermal recording device of the present invention, the enable prohibition control section is provided with a hardware configuration independent from the control section, and the enable signal prohibition control is performed based on the temperature detected by the thermistor. This has the excellent advantage that even in the event of an abnormality such as running, the thermal recording head can be reliably protected from various troubles such as damage caused by overheating.

4. Brief explanation of the drawings FIGS. 1, 2, 3, and 6 are block diagrams showing the main structure of each thermal recording apparatus according to an embodiment of the present invention, and FIG. A block diagram showing an example of a hysteresis comparator used in the thermal recording device of the invention, FIG.
Figures 7 and 8, which show the hysteresis characteristics of the hysteresis comparator shown in the figure, are block diagrams showing the main structure of each conventional thermal recording device.

1... Thermal recording head, 2... Control section, 3.4...
- Power supply circuit, 5... Enable prohibition control section, 10...
・Thermistor, 11...Temperature fuse, 12.50・
...Comparator, 13.51...AND gate, 2
0... Power supply circuit control section, 21... Head control section, 2
2... Pulse width control section Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6

Claims (4)

[Claims] (1) In a thermal recording device having a thermal recording head and a control section that controls the thermal recording head, a temperature sensor that detects the temperature of the thermal recording head and the control section are provided independently, and the The apparatus further comprises an enable prohibition control means for comparing the detected temperature of the temperature sensor and a preset temperature by a comparison means, and for prohibiting the supply of an enable signal to the thermal recording head based on the comparison result of the comparison means. Features of thermal recording device. (2) The enable prohibition control means is implemented in the thermal recording head, as claimed in claim 1 (1).
) The heat-sensitive recording device described in item 2. (3) The thermal recording device according to claim (1) or (2), wherein the comparison means is constituted by a comparator having hysteresis characteristics. (4) The temperature sensor is also used as a temperature sensor for recording density control that controls recording density according to the print pulse width applied to the thermal recording head. The thermal recording device according to any one of the items (3).