JPH0671926A - Thermal recording apparatus - Google Patents

Abstract

PURPOSE:To provide a highly safe thermal recording apparatus which can positively stop the power supply to a heat generating resistor at the occurrence of an abnormal state and prevent the generation of emission of smoke or fire surely. CONSTITUTION:A white data transferring part 8 is provided to generate an image data W-DATA which is a data indicating that all the data form no dot. The abnormality of the heat generating temperature and the state of an enable signal are monitored by a TPH temperature monitoring part 9 and an EN line monitoring part 10, respectively. A selector 7 is provided to select and output either of a general image data T-DATA output from a TPH controlling part 4 and the image data W-DATA generated from the white data transferring part 8. That is, when no abnormality is detected by the TPH temperature monitoring part 9 and EN line monitoring part 10, the selector 7 selects the image data T-DATA. If an abnormality is present, the selector 7 selects the image data W-DATA. The data is fed to a heat-sensitive head 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention records an image by using a thermal head composed of a large number of heating resistors arranged.
For example, the present invention relates to a thermal recording device such as a thermal printer or a thermal transfer printer.

[0002]

2. Description of the Related Art A thermal recording apparatus records an image using a thermal head having a large number of heating resistors arranged one-dimensionally or two-dimensionally. That is, the heat-sensitive recording paper is colored by heating the plurality of heat-generating resistors,
Alternatively, the ink is melt-transferred to form dots on the recording paper. Then, by appropriately selecting a heating resistor for generating heat in accordance with image data, dot formation / non-formation is controlled to obtain an image.

As described above, the thermal recording apparatus records an image by the heat generated from the heating resistor. Therefore, if some abnormality occurs and the heating resistor is constantly energized, the heating resistor is abnormally heated, and there is a risk of smoking, ignition, and the like.

Therefore, it is necessary to monitor abnormal heating of the heating resistor and abnormalities that cause it, and to forcibly stop energization to the heating resistor when an abnormality occurs. Conventionally, such stoppage of energization has been done by software by a microcomputer. That is, the microcomputer confirms various monitoring results, and when an abnormality occurs, the original image data (image data of the image to be recorded) is stopped from being supplied to the thermal head, and instead, all data does not form dots. Image data (white data) indicating As a result, the thermal head is driven by the white data, and the power supply to the heating resistor is stopped.

However, there are cases where the operation of the microcomputer becomes abnormal due to abnormal heating of the heating resistor and the abnormality that causes it, and in this case, abnormal heating of the heating resistor cannot be prevented. .

[0006]

As described above, in the conventional thermal recording apparatus, since the control of stopping the energization of the heating resistor when an abnormality occurs is performed by software by the microcomputer, the abnormality of the heating resistor occurs. If the operation of the microcomputer becomes abnormal due to heating or the abnormality that causes it, it is not possible to prevent abnormal heating of the heating resistor, and smoke or ignition may occur. It was

The present invention has been made in consideration of such circumstances, and an object thereof is to appropriately stop the power supply to the heating resistor when an abnormality occurs, and to emit smoke or fire. It is an object of the present invention to provide a highly safe thermal recording device capable of reliably preventing the occurrence of heat generation.

[0008]

SOLUTION: A white image generating means such as a white data transfer section for generating image data in which all data are data indicating non-formation of dots, and an abnormality of a heat generation temperature or a state of an enable signal, for example. An abnormality detection unit such as a TPH temperature monitoring unit or an EN line monitoring unit for detecting an abnormality relating to the thermal head such as an abnormality is provided, and when no abnormality is detected by the abnormality detection unit, for example, TP
Normal image data generated by a driving unit such as an H control unit, and image data generated by the white image generation unit when an abnormality is detected by the abnormality detection unit are selected and given to the thermal head. did.

[0009]

By taking such means, an abnormality relating to the thermal head such as an abnormality in heat generation temperature or an abnormality in the state of the enable signal is monitored by abnormality detection means such as a TPH temperature monitoring section or an EN line monitoring section. It When the abnormality is not detected by the abnormality detecting means, normal image data generated by the driving means such as the TPH controller is generated, and when the abnormality is detected by the abnormality detecting means, the white image generating means is generated. Image data in which all data are data indicating non-formation of dots are selected and given to the thermal head. Therefore, when an abnormality occurs, all the data generated by the white image generating means is given to the thermal head as data indicating the non-formation of dots, and the energization of the heating resistor is forcibly stopped.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a main configuration of a thermal recording apparatus according to this embodiment. In the figure, reference numeral 1 is a CPU that controls the present thermal recording apparatus as a whole. The CPU 1 controls each part based on the operation program stored in the ROM 2.
The CPU 1 is connected to a RAM 3 for storing various data necessary for the CPU 1 to perform various processes.

Reference numeral 4 is a thermal head controller (TPH controller). The TPH control unit 4 is connected to the CPU 1, and image data for driving the thermal head 5 based on various signals and data given under the control of the CPU 1.
It outputs T-DATA, clock signal T-CK, latch signal T-LA, and enable signal EN, respectively. Image data T-DA
The TA, clock signal T-CK, and latch signal T-LA are signals used when performing a normal recording operation according to the image data of the image to be recorded. Further, the TPH control section 4 turns ON / OFF the voltage supply from the power supply circuit 6 to the thermal head 5.
Generates a control signal POW that controls The power supply circuit 6 supplies a drive voltage of a predetermined voltage (here, +24 V) to the thermal head 5.

By the way, the image data T-DATA, the clock signal T-CK and the latch signal output from the TPH controller 4
The T-LA is input to the selector 7. The image data W-DATA, the clock signal W-CK and the latch signal W-LA output from the white data transfer unit 8 are also input to the selector 7, and either the image data T-DATA or the image data W-DATA is input. Of the clock signal T-CK or the clock signal W-CK as the image data DATA for actually supplying the thermal head 5 to the thermal head 5.
Either CK or the latch signal T-LA or the latch signal W-LA is selected as the latch signal LA for actually supplying the thermal head 5. The image data DATA, the clock signal CK and the latch signal LA selected by the selector 7 are supplied to the thermal head 5. The image data W-DATA output by the white data transfer unit 8 is white data indicating that all dots are not formed. The latch signal W-LA is a signal in which pulses are generated in the same cycle as the clock signal W-CK and the phase of pulse generation is different from that of the clock signal W-CK.

The thermal head 5 includes n (n is the number of pixels in one line of an image to be recorded) heat generating resistors R-1 to.
It is constructed by arranging Rn one-dimensionally. The thermal head 5 includes a shift register 51, a latch circuit 52, AND gates 53-1, 53-2 ..., 53-n, switch amplifiers 54-1 and 54-2.
, 54-n, a thermistor 55 and a pull-up resistor 56. The shift register 51 is an n-bit shift register, transfers and holds the image data DATA output from the selector 7, and outputs the image data DATA in n-bit parallel. The latch circuit 52 captures and holds the n-bit output of the shift register 51 in synchronization with the input latch signal LA. The n-bit output of the latch circuit 52 is input to one of the input ends of the AND gates 53-1 to 53-n with its logic inverted. The enable signal EN is input to the other input terminals of the AND gates 53-1 to 53-n.
The output of the latch circuit 52 is applied to the switch amplifiers 54-1 to 54-n only when is at "H" level. The switch amplifiers 54-1 to 54-n are heating resistors R-1 to Rn, respectively.
+ 24V supplied from the power supply circuit 6 only when the input is at "H" level.
Drive voltage is applied to the corresponding heating resistor. The thermistor 55 is arranged near the heating resistors R-1 to Rn. One end of the thermistor 55 is grounded. The other end of the thermistor 55 is pulled up by a pull-up resistor 56, and the thermal head temperature monitoring unit (TP
H temperature monitoring unit) 9.

The TPH temperature monitoring unit 9 monitors the voltage value V _TH of the thermistor 55 to generate heating resistors R-1 to R-.
The heat generation temperature of n is monitored, and when the heat generation temperature of the heat generating resistors R-1 to Rn exceeds a predetermined temperature, the output is set to the "H" level. The output of the TPH temperature monitoring unit 9 is the OR gate 10
Is input to one of the input terminals. The output of the enable line monitoring unit (EN line monitoring unit) 11 is input to the other input terminal of the OR gate 10. EN line monitoring unit 1
1 monitors the state of the enable signal EN, and sets the output to the "H" level when the enable signal becomes abnormal. The output of the OR gate 10 is given to the selector 7 as the select signal SEL.

Next, the operation of the thermal recording apparatus configured as described above will be described. First, when no abnormality has occurred, the TPH temperature monitoring unit 9 and the EN line monitoring unit 1
The outputs of 1 are both at "L" level, and the select signal SEL output from the OR gate 10 is at "L" level. Selector 7 has select signal SEL "L"
When the level is set, the image data T-DATA, the clock signal T-CK, and the latch signal T-LA output from the TPH controller 4 are output.
Are selectively output as the image data DATA, the clock signal CK, and the latch signal LA.

As shown in FIG. 2, the TPH control section 4 synchronizes with a clock signal T-CK in which a pulse is generated at a predetermined cycle, and an "L" level portion indicating dot formation (black dot) and dot non-formation. The image data T-DATA in which the "H" level portion indicating (white dot) is mixed is output. The selector 7 converts the image data T-DATA to the image data DATA as described above.
The image data T-DATA is supplied to the thermal head 5 as the image data DATA. Therefore, in the thermal head 5, the energization control of the heating resistors R-1 to Rn is performed based on the image data T-DATA, and the image recording is performed as usual.

Now, as described above, the heating resistors R-1 to Rn
When the heat generating resistors R-1 to Rn generate heat by controlling the energization of the above, the temperature of the thermistor 55 changes. Thermistor 55
As is well known, is an element whose electric resistance value changes with temperature, and the voltage value V _TH changes with temperature change. T
The PH temperature monitoring unit 9 monitors the heat generation temperature of the heating resistors R-1 to Rn by monitoring the change in the voltage value. In addition, the EN line monitoring unit 11 enables the enable signal.
Monitoring EN.

Here, the enable signal is generated for some reason.
When the period during which the EN is at the “H” level becomes a predetermined value or more (for example, the “H” state at all times), the EN line monitoring unit 11 determines that an abnormality has occurred in the enable signal EN, and outputs “H”. Level. This is because if the enable signal EN is abnormally at the "H" level, the heating resistors R-1 ~
This is because the energization time of Rn may increase and the heat generation temperatures of the heating resistors R-1 to Rn may rise. Also,
The heating resistor is caused by a cause other than the abnormality of the enable signal EN.
When the exothermic temperatures of R-1 to Rn rise, the TPH temperature monitoring unit 9 detects this and sets the output to the "H" level. In this way, the TPH temperature monitoring unit 9 or the EN line monitoring unit 11
When the output level of the OR gate becomes "H" level, the OR gate 10
The select signal SEL output from is also at "H" level.

When the select signal SEL becomes "H" level, the selector 7 outputs the image data W-DATA, the clock signal W-CK, and the latch signal W-LA output from the white data transfer section 8.
Selectively output as image data DATA, clock signal CK, and latch signal LA. Here, the image data W-DATA output by the white data transfer unit 8 is a signal in which the "H" level indicating non-dot formation (white dots) continues, as shown in FIG. The clock signal W-CK is a signal equivalent to the clock signal T-CK as shown in FIG. And the latch signal W-LA is
As shown in FIG. 2, it is a signal that is equivalent to the clock signal W-CK but has a different phase.

Thus, after the selector signal SEL becomes "H" level as shown in FIG. 2, the image data DATA output from the selector 7 becomes "H" level continuously as shown in FIG. . Therefore, the shift register 51 sequentially receives the "H" level data.

At this time, since the latch circuit 52 is supplied with the latch signal W-LA having the same frequency as the clock signal W-CK, the shift register 51 is loaded every time one bit of data is fetched. The n-bit output of is input to the latch circuit 52. The data taken in by the latch circuit 52 in this way enables the enable signal EN.
Is at "H" level, the energization of the heating resistors R-1 to Rn is controlled. That is, the AND gates 53-1 to 53-n are sequentially supplied with "H" level data for each cycle of the clock signal W-CK.

Thus, when n cycles of the clock signal W-CK and the latch signal W-LA have passed since the selector 7 was switched, all n-bit outputs of the latch circuit 52 are set to the "H" level. Therefore, even if the enable signal EN goes to "H" level after this, the outputs of the AND gates 53-1 to 53-n all go to "L" level. Therefore, the switch amplifiers 54-1 to 54-n are not turned on, and the heating resistors R-1 to Rn are not energized. In this way, the energization of the heating resistors R-1 to Rn is forcibly stopped, and the heat generation is stopped.

As described above, according to this embodiment, when the heating temperature of the heating resistors R-1 to Rn is abnormally increased or the EN signal is abnormally generated, the white data transfer section 8 independent of the CPU 1 is generated. Image data W-DATA, heating resistor R-1
Since energization of ~ Rn is forcibly stopped, energization of the heating resistors R-1 ~ Rn can always be stopped accurately regardless of the state of the CPU1, and it is possible to reliably prevent smoking or ignition. can do.

Further, in this embodiment, the latch signal W-LA used when the energization of the heating resistors R-1 to Rn is forcibly stopped by the image data W-DATA is a signal having the same frequency as the clock signal W-CK. Therefore, it takes an n-bit data transfer period to surely stop the energization of the heating resistor Rn, but since the other heating resistors are sequentially stopped energizing before that, the stop timing is the latch signal. It is faster than when a normal latch signal such as T-LA is given. Therefore, it is possible to reduce the amount of heat generated by the thermal head 5 as a whole from the occurrence of an abnormality to the time when the energization of the heating resistors R-1 to Rn is completely stopped.

The present invention is not limited to the above embodiment. For example, in the above embodiment, the latch signal W-LA generated by the white data transfer unit 8 may be a general signal such as the latch signal T-LA output by the TPH control unit 4. Further, in the above embodiment, the white data transfer unit 8 outputs the clock signal W-
Although the CK and the latch signal W-LA are output, the clock signal T-CK and the latch signal T-LA generated by the TPH control unit 4 may be used without generating them in the white data transfer unit 8. .

In the above embodiment, the TPH temperature monitoring section 9 and the EN line monitoring section 11 are provided as abnormality detecting means, and the temperature of the heating resistors R-1 to Rn and the state of the enable signal are monitored as abnormality. , For example, power supply circuit 6
Other abnormalities such as the output voltage of the above may be monitored. In addition, various modifications can be made without departing from the scope of the present invention.

[0027]

According to the present invention, a white image generating means such as a white data transfer section for generating image data, in which all data is data indicating non-formation of dots, and a thermal head, for example, a heat generation temperature or enable. It is provided with an abnormality detecting means such as a TPH temperature monitoring section or an EN line monitoring section for detecting an abnormality such as a signal state, and when the abnormality is not detected by the abnormality detecting means, normal image data generated by the driving means is displayed. Further, when an abnormality is detected by the abnormality detecting means, the image data generated by the white image generating means is selected and given to the thermal head, so that the energization of the heating resistor is stopped when the abnormality occurs. The thermal recording device is highly safe and can be appropriately performed, and can reliably prevent smoke and ignition.

[Brief description of drawings]

FIG. 1 is a diagram showing a main configuration of a thermal recording apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing signals of respective parts in FIG.

[Explanation of symbols]

1 ... CPU, 4 ... Thermal head control unit (TPH control unit),
5 ... Thermal head, R-1 to Rn ... Heating resistor, 55 ... Thermistor, 7 ... Selector, 8 ... White data transfer section, 9 ... Thermal head temperature monitoring section (TPH temperature monitoring section), 10 ... OR gate, 11 ... Enable line monitoring unit (EN line monitoring unit).

Claims (1)

[Claims] 1. A plurality of heat generating resistors constituting a thermal head are selectively energized by a driving means based on image data indicating dot formation / non-formation, thereby selectively selecting the plurality of heat generating resistors. In a thermal recording apparatus that heats up the image and records an image by this heat generation, a white image generation unit that generates image data in which all data is data indicating non-dot formation, and an abnormality detection that detects an abnormality related to the thermal head. Means and image data generated by the drive means when no abnormality is detected by the abnormality detecting means, and image data generated by the white image generating means when the abnormality is detected by the abnormality detecting means. And a selection unit for supplying the thermal head to the thermal recording head.