JPS63309472A - Thermal head energization control device for hand copy - Google Patents

Abstract

PURPOSE:To eliminate a persistent thermal effect and enable sufficient color development when a hand copy is used under temperature environment by shortening the pulse width of a strobe signal in accordance with an increase in detection temperature. CONSTITUTION:A variable clock signal from an oscillation circuit 18 is input to CPU 30 as an interruption signal whereby the pulse widths of strobe signals STR1, 2, 3, 4 from a control part 14 are controlled so that these pulse widths may coincide with the wavelength of the variable clock signal. That is, an increase in the temperature of a thermal head causes the oscillation frequency of the oscillation circuit 18 to increase, and subsequently the pulse width of the strobe signals STR1, 2, 3, 4 is reduced. The energization time of the thermal head is determined by the pulse width of the strobe signals. Therefore, the thermal head can always be maintained at a proper color developing temperature (sensitive paper) by decreasing the pulse width of the strobe signal according to an increase in the temperature of the thermal head. At the same time, power consumption can be minimized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a portable copying machine, so-called hand copy, and more specifically, a method for controlling a thermal head by adjusting the pulse width of a strobe signal output to the thermal head. The present invention relates to a hand copy thermal head energization control device that controls energization.

[Conventional technology]

2. Description of the Related Art Portable copying machines, so-called hand copy machines, have been attracting attention in recent years for their ability to easily copy a portion of a newspaper, magazine, or the like by tracing the surface of the paper.

This type of hand copying basically consists of an image reading section that optically reads image information from the image of the FII reproduction section and converts it into an electrical image signal, and an electrical signal obtained by this image reading section. a comparator that processes a target image signal to generate binary image data; an image recording section that records an image based on the binary image data; and controls operations of the image reading section and the image recording section. It consists of a control section. Note that, in the control section, a microcomputer is used.

The image reading section includes a light source (for example, LE) that illuminates the copying area.
D) and an image sensor (for example, a CCD) that reads the reflected light from the copying area as image information and converts it into electrical image information.

The image sensor is configured as a one-line sensor, and when a hand copy is traced over the copying area, it reads the image on the copying area one line at a time based on the control signal from the control unit. The electrical image signals for one line obtained by The electrical image signals for 20 minutes are converted into binary image data.

The image recording section is equipped with a thermal head, and this thermal head is configured as a one-line printer (one unit pixel is recorded one line at a time).For this reason, the thermal head is equipped with a linear heating element. In this case, heating resistive elements corresponding to the number of pixels corresponding to the line (ie, the number of binarized image data corresponding to the line) are embedded. The thermal head also includes a shift register that sequentially stores -line binarized image data processed by the above-mentioned comparator based on a clock signal from the control unit, and a binarized image stored in this shift register. A latch is provided that takes in data based on a latch signal from the control section. When recording an image, when a strobe signal is input from the control unit to the heating resistor element for one line described above,
Based on the -line's worth of binary image data taken into the latch, a predetermined one of the -line's heating resistive elements is energized and generates heat. On the other hand, the image recording section is provided with a roll of thermal paper, and the thermal paper is pulled out from the hand copy while in contact with the heating element of the thermal head during image recording.

Therefore, when the heating element of the thermal head generates heat based on the binary image data in the latch as described above, the read images are sequentially reproduced on the thermal paper as the hand copy moves.

[Problem that the invention seeks to solve]

By the way, the coloring temperature of the above-mentioned thermal paper is 80 to 90°C in terms of -a, and when recording on the thermal paper, the heating element of the thermal head is raised to the coloring temperature of 80 to 90°C. The temperature of the heating element depends on the time during which current is applied to the heating resistor element. To be more specific, the energization time for the heating resistor element is determined by the pulse of the strobe signal, and in the conventional case, the temperature of the heating element is appropriately selected so that the coloring temperature is obtained during the pulse of the strobe signal. There is. However, if hand copying is continuously operated at a high room temperature, the heating element of the thermal head will accumulate heat due to residual heat, and the temperature will exceed the coloring temperature even after the electricity is applied to the heating resistor element. It may happen. In this case, a so-called "tailing phenomenon" occurs in the colored areas on the thermal paper, making it impossible to obtain a clear image. Of course, the thermal head is equipped with a heat sink,
This allows the heat from the thermal head to be dissipated quickly, but especially when the room temperature is high or when there are many colored areas in the recorded image, the heat dissipation from the heating element of the thermal head may not be sufficient. The above-mentioned trailing phenomenon often occurs. When such a trailing phenomenon occurs, not only the thermal paper but also the electric power is wasted.

Therefore, in order to eliminate such tailing phenomenon and eliminate wasteful consumption of thermal paper and power, a temperature detector is applied to the thermal head so that the temperature detected by this temperature detector reaches a predetermined temperature, that is, a tail. It has been proposed to disable the hand copy when the temperature exceeds the temperature that causes the pull phenomenon. However, such a solution is undesirable in various respects:
This is because, as mentioned above, when the temperature is high or when there are many colored parts in the recorded image, the hand copy often becomes inoperative, and the hand copy becomes inoperative during the copying process. In this case, the recording paper previously obtained by copying and the power required for copying would be wasted.

Contrary to the above case, when the thermal head is exposed to a low-temperature environment, the temperature of the thermal head is not raised to the appropriate coloring temperature, and in this case, sufficient coloring of the thermal paper cannot be obtained. A clear image will not be reproduced.

In short, in the conventional case, the energization time is determined regardless of the temperature of the thermal head, and if the hand copy is used when the environmental temperature is too high or too low than the normally expected environment temperature, the above-mentioned As shown above, a trailing phenomenon may occur, or the color development may be insufficient.

Therefore, an object of the present invention is to provide a structure that eliminates the above-mentioned trailing phenomenon without interrupting the copying operation of a hand copy machine, and also allows sufficient color development to be obtained even when using a hand copy machine in a low temperature environment. An object of the present invention is to provide a thermal head energization control device for hand copying.

[Means for solving problems]

The thermal head power supply control device for hand copying according to the present invention detects the temperature of the thermal head to control the power supply to the thermal head by adjusting the pulse width of the strobe signal output to the thermal head. A strobe signal control means is provided for adjusting the pulse width of the strobe signal according to the detected temperature, and the adjustment during the pulse of the strobe signal is performed such that the pulse width of the strobe signal becomes shorter as the detected temperature becomes higher. be exposed.

In a preferred embodiment of the present invention, the strobe signal control means comprises an oscillation circuit for controlling strobe signals,
A part of the resistance of the 7-way oscillation port for controlling the strobe signal is replaced with a thermistor, and this thermistor is applied to the thermal head as a temperature detector, and when the temperature of the thermal head increases, the electrical resistance of the thermistor increases. The oscillation frequency of the strobe signal control oscillation circuit is increased, and the pulse width of the strobe signal is adjusted to a length corresponding to one wavelength of the oscillation frequency.

[For production]

In the present invention, by controlling the pulse width of the strobe signal, the time during which electricity is applied to the thermal head is controlled, and the temperature is adjusted so that the temperature always becomes an appropriate coloring temperature for the thermal paper. In other words, as the temperature of the thermal head increases, the pulse width of the strobe signal becomes shorter, and the time for which electricity is applied to the thermal head becomes shorter.

〔Example〕

Referring to FIG. 1, there is shown as a block diagram the configuration of a hand copy device incorporating a hand copy thermal head energization control device according to the present invention. As shown in FIG. 1, the hand copy system includes an image reading unit 10, an image recording unit 12, and a control unit 14 as basic components.
and equipped with.

The hand copy is also provided with a thermal head energization control device according to the present invention, which in this embodiment is comprised of a transmitting circuit 16 adapted to generate a variable clock.

The image reading unit 10 is provided with an image sensor, and such an image sensor is formed by a photoelectric conversion element 18 made of, for example, COD, and a shift register 20. The image reading unit 10 is also provided with illumination means (not shown), such as an LED, so that the area to be copied is illuminated by this illumination means. The image sensor is configured as a one-line sensor with a pixel density of, for example, 5 dots/mark, and when a hand copy is traced over the copying object to make a copy, the image sensor scans the object one line at a time. Read the image on the copy section. To be more specific, when the reflected light from the to-be-copied area illuminated by the illumination means is made incident on the photoelectric conversion element 18 as optical image information for the - line, the optical image information for the - line is input to the photoelectric conversion element 18. is changed into an electrical image signal, and this -line electrical image signal is stored in the shift register 20. The electrical image signal is stored in the shift register 20 based on the reading start signal R3S from the control unit 14, and the electrical image signal is stored in the shift register 20 until the next reading start signal R3S is output. The electrical image signal is never rewritten. Next, the -line electrical image signals stored in the shift register 20 are sequentially outputted to the comparator 22 based on the tarlock signal CLKI from the control section, where they are subjected to binarization processing. - Lines of digitized binary image data are sequentially output.

The image recording unit 12 is provided with a thermal head, and this thermal head includes a shift register 24, a latch 26,
It is formed by the heating element 28.

The digitized binary image data output from the comparator 22 is sequentially stored in the shift register 24 based on the clock signal CLK2 from the control section 14. - When all of the digitized binary image data for the line is stored in the shift register 24, the latch signal LAT is inputted to the latch 26 from the control unit 14, whereby the digitized binary image data for the - line is stored in the shift register 24. latch 26
will be incorporated into. The heating element 28 is embedded with a number of heating resistive elements (not shown) corresponding to the number of digitized binary image data (number of pixels) for the - line,
When a strobe signal is output from the control unit 14 to the heating element 28, a predetermined one of the heating resistive elements in the heating element 28 is energized based on the digitized binary image data stored in the latch 26. This will cause heat to be generated.

On the other hand, the image recording section 12 has a roll of thermal paper (
(not shown) is also provided, and the thermal paper is pulled out from the hand copy while in contact with the heating element 28 of the thermal head.

To be more specific, when copying by hand copying, when the hand copy is traced on the part to be copied with a finger pressed against the part to be copied and the edge of the thermal paper pulled out from there is fixed. , the thermal paper will be gradually pulled out from the hand copy. In short, while a hand copy is traced over the copying area and image information is sequentially read line by line by the image reading unit 10, an image record based on the image information is recorded line by line on thermal paper by the image recording unit 12. This will be done sequentially.

In this embodiment, the digitized binary image data for -line is divided into four groups and recorded. That is, the heating resistive elements within the heating element 28 are divided into four groups and are individually operated.

Therefore, the control unit 14 outputs four slobe signals (5T).
RI, 2,3°4 is outputted to the heating element 28. Note that the strobe signals 1.2.3.4 and the above-mentioned latch signals are generated based on a variable clock from the oscillation circuit 16, which is referred to as LAT and will be described later.

In this embodiment, the control unit 14 is configured as a microcomputer, which includes a central processing unit (CPU) 3G, a read-only memory (ROM) 32 that stores hand copy operating programs, etc., and a data storage system that temporarily stores data. A read/write memory (RAM) 34 for storing data, an input/output interface (Ilo) 36, and a clock 38 are provided. As already mentioned, the control section 14 outputs various signals to the image reading section 10 and the image recording section 12, which control the operations during image reading and image recording. .

The oscillation circuit 16 has a configuration as shown in FIG. 1, and a part of its resistance is replaced by a thermistor 40. Thermistor 40 is applied to the thermal head as a temperature detector. To explain in detail with reference to FIG. 2, there is shown a specific example of a thermal head, which includes a thermal head main body 42 having a heating element 28, and a thermal conductive grease layer on this thermal head main body 42. A heat dissipation plate 44 is provided. Reference number 46 indicates a control circuit printed board, and this control circuit printed board 46 includes the control section 14 and the oscillation circuit 16. A pair of lead wires 48, 48 are drawn out from the control circuit printed board 46, and a thermistor 40 is connected thereto. Thermistor 4
0 is adhered with thermally conductive grease 50.

The resistance value of a thermistor changes depending on the temperature, and as the temperature rises, the resistance value decreases.

Here, the resistance value of the thermistor is "TH", and the resistance value of the resistor of the oscillation circuit 18 is "R1", "
R2'' and the capacitance of the capacitor of the oscillation circuit 18 is C° as shown in the figure, the oscillation frequency “fo” of the oscillation circuit 18 can be expressed by the following equation.

f =0.45/ ((R, //TFl+R2)
C) (Hz) Here, R1//TH= (R, xT
II)/(RI+TI), as is clear from this equation, as the resistance value of "T H" decreases (that is, as the temperature of the thermal head increases), the oscillation frequency "f" increases. In short, the oscillation circuit outputs a variable clock signal whose pulse width changes depending on the temperature of the thermal head. As shown in FIG. 1, the variable clock signal from the oscillation circuit 18 is input as an interrupt signal to the central processing unit (CPU) 30, thereby causing the strobe signal 5TR from the control unit 14 to be input to the central processing unit (CPU) 30.
The pulses I, 2, 3.4 are controlled to match the wavelength of the variable clock signal.

That is, when the temperature of the thermal head rises, the oscillation frequency of the oscillation circuit 18 increases, and the slope 1-lobe signal 5 increases.
The pulse widths of TR1, 2, 3, and 4 will be reduced. As mentioned above, the energization time of the thermal head is determined by the duration of the strobe signal pulse. therefore,
By reducing the pulse width of the strobe signal as the temperature of the thermal head increases, the temperature of the thermal head can always be maintained at the appropriate coloring temperature (for thermal paper) and power consumption can be minimized. Can be done.

Next, the operation of the hand copying thermal head energization control device according to the present invention will be explained with reference to the timing chart of FIG. 3 and the flow sheet of FIG. 4.

In FIG. 3, the variable clock signal is generated from the oscillation circuit 16, and its wavelength is shortened as the temperature of the thermal head increases, as described above.

When this variable clock signal rises, it becomes v1.
When the central control unit (CI'U) 30 is interrupted as an interrupt signal (step 401), the central control unit (CP
At U) 30, a rising edge interrupt routine is initiated.

In step 402, the interrupt signal (the "rising edge" of the variable clock signal) is counted. In step 402, "N" is a counter indicating the number of counts of the interrupt signal, and it is incremented by +1. It is assumed that the number "°N" has been cleared in advance.

In steps 403 and 418, when the interrupt signal count exceeds "5", the counter "N" is cleared.

In step 404, it is determined whether "N" is "1" or not. Initially, since N=1, the flow proceeds to steps 405 and 406. In step 405, the strobe signal 4 is turned off. A command is issued, but since none of the strobe signals are output at the start of hand copying, the "off" command of strobe signal 4 is ignored without any meaning. Next, in step 406, the latch signal LAT is output, and the latch signal LAT causes the latch 26 to capture one line of digitized binary image data from the shift register 24, as described above. Therefore, this routine ends once.

Next, when this routine is executed again, since N=1, the flow is set to N=2 in step 402 and proceeds to step 408 via step 407.

That is, in step 408, strobe signal 1 is
゛It is turned on. At this point, this routine ends once.

Next, when this routine is executed again, since N=2, the flow is set to N=3 in step 402 and proceeds to steps 410 and 411 via step 409.
That is, in step 410, strobe signal 1 is “
Then, in step 411, the strobe signal 2 is turned on. At this point, this routine ends once.

Next, when this routine is executed again, since N=3, the flow is set to N=4 in step 402 and proceeds to steps 413 and 414 via step 412.
That is, in step 413, strobe signal 2 becomes “
Then, in step 414, the strobe signal 3 is turned on. At this point, this routine ends once.

Next, when this routine is executed again, since N=4, the flow is set to N=5 in step 402 and proceeds to steps 416 and 417 via step 415.

That is, in step 415, strobe signal 3 is “
Then, in step 417, strobe signal 4 is turned on. At this point, this routine ends once.

When the sixth interrupt signal is input, the counter "N" is cleared in step 418 so that N=O, and the flow proceeds to steps 405 and 406. In step 405, strobe signal 4 is turned "off", Also step 4
At 06, the latch signal LAT signal is output again, and the latch 26 takes in the next line of digitized binary image data from the shift register 24.

By sequentially repeating this operating cycle,
The image recording section 12 sequentially records images based on the image information read by the image reading section 10.

What should be noted here is that, as is clear from the timing chart in FIG. be. Therefore, as mentioned above, when the temperature of the thermal head increases, the duration of the pulse of the strobe signals 1, 2, 3, 4, in other words, the energization time of the thermal head is shortened accordingly. temperature is always maintained at the appropriate color development temperature (thermal paper). Note that by appropriately selecting the resistance values R3 and R2 of the oscillation circuit 16, the capacitance value C of the capacitor, and the resistance characteristics of the thermistor, it is possible to appropriately determine the pulse width of the strobe signal with respect to temperature changes in the thermal head. It's obvious what you'll get.

In the above-described embodiment, four strobe signals are used to record -line digitized binary image data divided into four groups, but it goes without saying that the present invention is not limited to this. If necessary, -line worth of digitized image data can be recorded using four or more strobe signals.

Further, in the above embodiment, an oscillation circuit is used as the strobe signal control means, but the relationship between the temperature of the thermal head and the pulse of the strobe signal is stored in a ROM in advance as a function table, and the detected temperature of the thermal head is A strobe signal having a predetermined pulse width may be output based on.

〔effect〕

As is clear from the above explanation, according to the present invention, the energization time is controlled according to the temperature of the thermal head, so that the hand copy is disabled in order to prevent the occurrence of trailing phenomenon as in the conventional case. It is no longer necessary to set the temperature in the state, and at the same time, wasteful consumption of thermal paper and electric power can be eliminated. In addition, sufficient color development can be obtained even when hand copying is used in a low-temperature environment.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a hand copy device incorporating a hand copy thermal head energization control device according to the present invention;
FIG. 2 is a perspective view showing a specific example of the thermal head shown in FIG. 1, FIG. 3 is a timing chart illustrating the operation of the thermal head energization control device for hand copying according to the present invention, and FIG. 4 is a diagram according to the present invention. 3 is a flowchart illustrating the operation of the hand copy thermal head energization control device. 10... Image reading section, 12... Image recording section, 1
4... Control unit, 16... Oscillation circuit, 18.
...Photoelectric conversion element, 20...Shift register, 22...Comparator,
24...Shift register, 26...Latch, 28...
...Heating element, 30...Central processing unit, 32.
...Write-only memory, 34...Writable/readable memory, 36...I/O interface, 38...Clock, 40...Thermistor, 4
2... Thermal head body, 43... Thermal conductive grease layer, 44... Heat sink, 46...
... Control circuit printed board, 48... Lead wire, 50... Thermal conductive grease. Figure 2 Figure 3

Claims (1)

[Claims] 1. A thermal head energization control device for hand copying that controls energization to a thermal head by adjusting the pulse width of a strobe signal output to the thermal head, which controls the temperature of the thermal head. The strobe signal control means detects and adjusts the pulse width of the strobe signal according to the detected temperature, and the pulse width of the strobe signal is shortened as the detected temperature becomes higher. A thermal head energization control device for hand copying. 2. In the hand copying thermal head energization control device according to claim 1, the strobe signal control means is composed of an oscillation circuit for controlling a strobe signal, and a part of the resistance of the oscillation circuit for controlling a strobe signal is provided. is replaced with a thermistor, and this thermistor is applied to the thermal head as a temperature detector, and when the temperature of the thermal head increases, the electrical resistance of the thermistor is reduced, and the oscillation frequency of the strobe signal control oscillation circuit increases. A thermal head energization control device for hand copying, wherein the pulse width of the strobe signal is adjusted to a length corresponding to one wavelength of the oscillation frequency.