JP2932668B2 - Thermal recording device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal recording apparatus, and more particularly, to an improvement in recording quality of a light line in an apparatus for color-recording the magnitude of a waveform on thermal recording paper. It is about.

<Prior Art> As a recorder for recording the magnitude of a waveform, a plurality of heating elements arranged at regular intervals so as to constitute a line thermal head are selectively driven according to the magnitude of the waveform to generate heat. There is a type in which a thermosensitive recording paper is colored and recorded based on the heat generation.

FIG. 12 is a block diagram showing an example of such a conventional apparatus, and FIG. 13 is a timing chart showing an example of the operation of the circuit of FIG. In the shift register 1, data of m dots for one line shown in (a) is sequentially stored according to m clocks CLK shown in (b). Shift register 1
Is stored in the latch 2 by the latch pulse LAT shown in FIG. The output data of these latches 2 is applied to one input terminal of each NAND gate 3. An enable signal EN 'shown in (d) is commonly applied to the other input terminals of these NAND gates 3 via an inverter 16. Note that a dash “′” indicates that the operation is performed by negative logic. The output terminal of the NAND gate 3 is connected to one end of a heating element 5 constituting a thermal head, and the other end of the heating element 5 is commonly connected to a plus terminal of a DC power supply 6.

In such a configuration, as the recording data of each line, for example, from the heating element corresponding to the maximum value to the heating element corresponding to the minimum value, the maximum value and the minimum value of the measurement value in each measurement cycle are recorded in a line. The data interpolated so as to simultaneously drive a plurality of heating elements continuous in the arrangement direction up to are added.

Thus, the enable signal EN 'is between t ₀ which is the L level, the recording based on the recording data of 1 line driving current flows through the heating element 5 from the DC power supply 6 is carried out. The recording paper (not shown) is fed one line at a time every time the recording operation of one line is completed.

By the way, such a thermal recording apparatus is configured so as to select between dark line recording for coloring deeply in a saturated portion and light line recording for coloring lightly in an unsaturated portion by utilizing the γ characteristic of the thermal recording paper. There are things.

However, in the case of light line recording in which the color is lightly colored in the unsaturated portion of the γ characteristic, the color density changes due to a slight change in energy, and the influence of the adjacent heating element cannot be ignored.

Specifically, for example, as shown in FIG.
When recording is performed simultaneously with the same recording density set to the same recording density as that of the linear waveform B, the adjacent heating elements are also in the recording state when recording the sine wave waveform A, but in the recording of the linear waveform B, only the single heating element is in the recording state. become.

<Problems to be Solved by the Invention> As a result, the recording density of the linear waveform B is lower than the recording density of the sine wave waveform A even though the recording density is set to be equal. If the recording density of the linear waveform B is set to be lighter than the recording density of the sine wave waveform A, the recording density of the linear waveform B may be too light to be distinguished.

As a countermeasure to solve such inconvenience, it has been proposed to perform thermal history control in consideration of the influence of an adjacent heating element, but a complicated matrix-like operation is required and the circuit scale becomes large. There is a problem.

The present invention pays attention to such a point, and an object of the present invention is to provide a thermal recording apparatus capable of automatically increasing the density when straight lines having a low density continue.

<Means for Solving the Problems> The thermal recording apparatus of the present invention selectively drives a plurality of heating elements which are arranged at regular intervals and constitute a line thermal head according to the size of a waveform to generate heat. In a thermal recording apparatus that records the magnitude of a waveform on thermal recording paper based on heat generation, stored temperature data related to the recording operation of the heating element is stored in advance, and the current stored temperature data and the address of the presence or absence of recording are stored as the next time. A first memory for reading the heat storage temperature data of the first memory, a second memory for temporarily storing the heat storage temperature data read from the first memory, and a heat storage temperature data temporarily stored in the second memory. And a switch element for controlling the recording operation of the heating element according to the comparison result, wherein the same heating element is provided in the first memory. In this case, trap data for forming an inner loop for driving the heating element so as to increase the color density when the pixel is continuously driven at a light color density is stored.

<Operation> When the same heating element is continuously driven at a light color density, trap data stored so as to form a minor loop as heat storage temperature data is read, and the heating element increases the color density. Driven.

<Example> Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention. In the figure, A is a digital one-shot unit that generates print data for driving the heating element, and B is a heat history control unit that controls the heating temperature of the heating element.

In the digital one-shot unit A, the input data D _i to be recorded is added as a selection signal to the data selector 7. The data selector 7 determines whether the input data _Di is "1" or "0".
Outputs ₁ to the subtractor 9 and outputs the data conversion unit 8 - predetermined data P _i to be selected in accordance with. When the data P _{i -1} added from the data selector 7 is other than "0", the data converter 8 converts the data d _i 'of "1" to the heat history controller B.
Is added to one input terminal of the AND gate 18 which constitutes the above. For example, an OR gate is used. Subtractor 9 is the input data P _i - performing subtraction of P _i = P _i -1 for _one. However, the subtractor 9 performs subtraction only on natural numbers, for example,
P _i - ₁ is directly outputs 0 as P _i in the case of zero.
The operation result _Pi is temporarily stored in the dual port memory 11 via the latch 10. Output data _Pi - ₁ of the dual port memory 11 is applied to the data selector 7 via the latch 12.

In the heat history control section B, the memory 13 previously stores heat storage temperature data relating to the recording operation of a plurality of heating elements constituting the thermal head 19, and a part of the heat storage temperature data includes the same heating element as a pale color. Also stored are trap data for forming a minor loop for driving the heating element so as to increase the color density when driven continuously at the density.
Table 1 shows an example of the heat storage temperature data read when the temperature is lowered, and Table 2 shows an example of the heat storage temperature data read when the temperature is raised. These heat storage temperature data are sequentially stored from the top data to the lower order of the address, such as the first data at address 0, the next data 0 at address 1, and the subsequent data 1 at address 2. The trap data is underlined.

The heat storage temperature data stored in the memory 13 is stored in a thermal head 19 measured by a temperature sensor 20 such as a thermistor.
Predetermined current heat storage temperature data R _i according to the ambient temperature of
- ₁ and in the address output data of the AND gate 18 associated with the presence of the recording, is read out as the next thermal storage temperature data R _i. Heat storage temperature data R _i to be read from the memory 13 is a dual port memory 15 via the latch 14
Is stored temporarily. The accumulated temperature data R _i is the current heat storage temperature data described above that is temporarily stored in the memory 15
It is read out as R _{i -1 and} applied as an address to the memory 13 via the latch 16 and to one input terminal of the comparator 17. Preset set temperature data SD is added to the other input terminal of the comparator 17. This comparator
The output signal of 17 is applied to the other input terminal of AND gate 18.

Together with the output data O _i of the AND gate 18 is applied as an address to the memory 13 as described above, is added as a drive signal to the heat generating elements of the thermal head 19. Reference numeral 21 denotes a heat-sensitive recording paper on which color recording is performed by the heat generated by a plurality of heating elements constituting the thermal head 19;
At a predetermined speed. Reference numeral 23 denotes a timing control circuit that outputs a control signal for controlling the operation of each unit. Note that the thermal head 19 can be configured as shown in FIG.

The operation of the device configured as described above will be described with reference to the timing chart of FIG.

In FIG. 2, m-dot data DATA is transferred four times to thermahead 20, and one-line recording is performed by adding a fourth-order enable signal EN '. Where the enable signal
The pulse width t ₀ ′ of EN ′ is / 4 of the pulse width t ₀ in FIG. That is, the energy applied to the heating element 5 in one drive is 1/4 of the energy in the case of FIG.
By sending A and the enable signal EN ', one line is recorded. The feeding of the recording paper 21 is also divided into quarter steps in FIG.

In such a driving method, since the pulse width t ₀ ′ of the enable signal EN ′ is constant, for example, the recording conditions of the recording sequence of the line up to the data D ₄ starting from the data D ₁ and the data D ₂ starting from the data D ₂ and the recording condition of the recording sequence of the line to the data D ₅ are equal. Therefore, the feeding speed of the recording paper 21 is equal, that is, the data transfer period Dn in FIG.
If the data transfer period is 1/4 in FIG. 13, the resolution along the time axis direction is four times that of the driving method in FIG. 12 according to the driving method in FIG.

FIG. 3 is a diagram showing an example of recording by such a recording method. The recording paper is fed in the direction of arrow Y by 1/4 of the pitch P in FIG. The heating element 5 is driven four times in synchronism with the paper feed pitch as shown in a to c. a represents the operating state of the heating element 5 _4, b represents the operating state of the heating element 5 _5, c indicates a driving state of the heating elements 5 _6. Heating element
5 ₄ data selector 7 in the recording pattern PTa the time t ₁ by
4 by adding input data D _i “1” to
Recorded by rotating the drive, the input data D _i to the data selector 7 in the recording pattern PTb the time t ₂ due to heat generation elements 5 ₅ "1"
Recorded by four driving continuous due to is applied, the recording pattern PTc the consecutive four driving due to the input data D _i "1" is added to the data selector 7 at time t ₃ by heating element 5 ₆ Recorded by Similarly, each recording pattern is recorded by continuously driving the corresponding heating element four times in synchronization with the paper feed pitch. When the input data D _i “1” is added to the data selector 7 of the heating element being driven again, driving is performed four times again from that point, and the recording pattern becomes longer.

As is apparent from the recording result of FIG. 3, since the resolution of the paper feed pitch is higher than that of the conventional recording result, the maximum stepped portion caused by the paper feed pitch when the paper is fed at the same speed is obtained. The height is smaller than before, and the result of the waveform curve recording is smoother. Since the input data is taken in synchronism with the paper feed timing, a signal waveform having a higher frequency than in the related art can be faithfully recorded.

FIG. 4 is a timing chart for explaining the operation of the digital one-shot section A. The memory 11 stores trigger data corresponding to each dot.
Trigger data corresponding to the (ml) -th dot in Al
P _i-1 and _l are stored. By adding an address A _l in the l-th clock of the internal clock CLK as shown from the timing control circuit 23 (a), the trigger data corresponding to m-l-th dot as shown from the memory 11 in (b) _Pi-1 and _l are read. The trigger data read from the memory 11 is latched by the latch 12 at the rise of the (l + 1) -th clock as shown in FIG. When the input data d _i , _l is “0”, the data selector 7 outputs the input data P _i−1 , _l as it is, and when the input data d _i , _l is “1”, the data selector 7 outputs the input data P _i−1 , _l.
The data CD in which _i-1 and _l are set in the data selector 7 in advance is output. In the case of the present embodiment, "4" is output because one line is recorded four times. The data of the data selector 7 is applied to a data converter 8 and a subtractor 9. The data converter 8 is a data selector 7
When the data P _i-1 , _l added from
d _i ′ is set to “1” and is added to the AND gate 18 of the thermal history control section B. The subtracter 9 performs the operation of _{Pi -1} , _{l -1} and outputs the operation result _Pi , _l to the latch 10 as shown in (d). The latch 10 latches the operation result P _i , _l of the subtractor 9 at the rising edge of the (l + 2) th clock, as shown in (e), and stores the data as the address Al in the memory 11 during the clock cycle.
Outputs P _i and _l .

Such a series of operations the data D ₁ ~ of FIG. 2 (a)
It is repeated m times for D ₅ interval.

Next, it will be described how the data at an address Al in the memory 11 changes in accordance with the repetition of the interval cycle.

FIG. 5 shows a data change of each part when a certain address Al of the memory 11 is fixed.

It is assumed that the data _Di , _l input to the data selector 7 at the interval k shown in FIG. 7A becomes "1" as shown in FIG. At this time, "4" is set as the output data of the data selector 7 as shown in (d). On the other hand, since the output data of the data selector 7 is not "0", the output data of the data conversion unit 8 becomes "1" as shown in FIG. In the subsequent intervals k + 1, k + 2, k + 3, the data is subtracted by “1” by the subtracter 9 as shown in FIG.

In this way, the data D _i , _{l at} interval k
Triggered by input of “1” at interval k to k + 3
From the data conversion unit 8 to the history control unit B
Will be added to the recording data.

Such a series of operations includes the interval k + 5 and k +
Data D _i at 8, a same when "1" is input as _l, a digital one-shot unit A is operated as if re triggerable monostable multivibrator, the data conversion unit 8 data D _i , _l , the recording data is output to the history control unit B in the fourth floor interval starting from the interval in which “1” is input.

That is, the digital one-shot section A receives the input data
The input data is used as a data selector 7 by using D _i and _l as triggers.
The operation is performed so as to increase the number of times of the predetermined interval set by the above.

 Next, the operation of the heat history control unit B will be described.

For example, in the interval k + 5~k + 10 periods of FIG. 5 recording data d _i outputted from the data converting unit 8 'have become continuously "1", such a recording data d _i' the thermal head 19 as it is , The drive current flows continuously to the corresponding heating element. As a result,
Not only does the temperature of the heating element significantly increase so that uniform recording quality cannot be maintained, but in the worst case, the heating element may be burned.

Therefore, the heat history control unit B performs the recording data based on the heat storage temperature data stored in the memory 13 as described above.
After performing data processing such as thinning out d _i ′, the recording data O _i is transferred to the thermal head 19.

By performing one line recording at four times the data transfer as in the present embodiment, the pattern of drive pulses applied to the heat generating element 5 by way of taking each time the data D ₁ to D _4, as shown in FIG. 6 One of 15 ways (2 ⁴ -1 = 15). That is, the driving of the heating element 5 is controlled according to the heat storage temperature, and as a result, the heating element 5 is driven according to any one of these 15 patterns.

In FIG. 2, one line is recorded by sending the data DATA and the enable signal EN 'four times. However, the number of times is not limited to four, and n times (n is an integer of 2 or more). ). The driving pattern for n times is
2 ⁿ -1 ways.

 Details of such heat storage control will be described.

At the address Ax of the memory 15, the heat storage temperature data corresponding to the (mx) th heating element in the main scanning direction to be recorded is stored as shown in FIG. Timing control circuit
23 sends the address Al to the memory 15 which temporarily stores the heat storage temperature data at the 1st clock of the internal clock CLK shown in (a) of the timing chart of FIG. As a result, the memory 15 outputs the heat storage temperature data R _i−1 , _l corresponding to the (m−1) th heating element as shown in FIG. 8 (b).

In the 1 + 1 cycle of the internal clock CLK, the latch 16 is turned on by the rise of the clock CLK, as shown in FIG.
As shown in ( ₁₎ , the heat storage temperature data R _i−1 , _l is latched. The heat storage temperature data R _i−1 , _l latched by the latch 16 is applied to the comparator 17 and compared with the initially set temperature data SD. The heat storage temperature data R _i−1 , _l and the temperature data SD are quantized by a plurality of s bits. Comparator 17
For example, if the temperature data SD is set to 200 ° C. and the heat storage temperature data R _i−1 , _l is 100 ° C., “1” is output to the AND gate 18 and the temperature data SD is set to 200 ° C. If the heat storage temperature data R _i−1 , _l is 250 ° C., “0” is output to the AND gate 18. In this 1 + 1 clock cycle, the recording data d' _i , _l
Is read out by the AND gate 18 and the logical product with the relatively 17 output data as shown in FIG. The output data _Ol of the AND gate 18 is applied to the heating element 5 of the thermal head 19 as data to be actually recorded. That is, the heating element 5 of the thermal head 19 enters the recording state because the recording data d ′ _i , _l is “1” and the heat storage temperature data R _i−1 ,
Only when _l is lower than the temperature data SD.

In the l + 1 cycle, the following control is performed simultaneously with the above-described process. That is, the heat storage temperature data R _i−1 , _l and the output data O _l of the AND gate 18 are input to the memory 13 as addresses. Here, the comparator 17 and the AND gate 18
Because it consists of a high speed gate elements, settling of the output data O _l of the AND gate 18 becomes about several 10 ns, the memory 13 within one clock if the clock cycle and the number 100ns
Can complete reading of data.

The memory 13 stores (d) according to the addresses _Ri-1 , _l and _Ol.
As shown in (1), the next heat storage temperature data R _i , _l is output. For example, when the heat storage temperature data R _i−1 , _l is 100 ° C., if _Ol is 1, the bit data of 180 ° C. is output as the heat storage temperature data R _i , _l , and if _Ol is 0, the heat storage temperature is output. 50 ° C as data R _i , _l
Is output.

In the l + 2 cycle, the latch 14 stores the memory 13 at the rising edge of the clock CLK in the 1 + 2 cycle as shown in FIG.
Heat storage temperature data R _i output from the latches _l. The data latched by the latch 14 is applied to the other port of the memory 15 and written to the address Al.

These series of operations are pipelined in parallel,
In l + 1 clock cycle heat storage temperature data R _{i-1, l} l from the memory 15 is read out.

By executing such an operation m times, the thermal head 19 receives m print data. After the m data transfer, the timing control circuit 23 activates the latch pulse LAT as shown in FIG.
As shown in (1), the enable signal EN 'is activated once only for the time t', and the drive current flows through the heating element 5. These m
The data transfer and transmission of the latch pulse LAT and the enable signal EN 'are repeated a plurality of times. FIG. 2 shows an example of repeating four times.

Next, the setting of the heat storage temperature data of the memory 13 will be described.

Temperature change of the heating elements 5 of the thermal head 19 can be simulated by the vibration and the pulse width of the drive pulses to the initial temperature T ₀ as a reference. That is, the thermal head
The structure of 19 is known, and the physical properties of each part are also known. From these, the thermal response of the thermal head 19 can be modeled and described using a heat conduction equation. By giving the initial temperature to this heat conduction equation as the initial condition and the amplitude and pulse width of the drive pulse as the input energy to the system, the thermal head at each time can be calculated numerically.
The temperature of the 19 heating elements 5 can be simulated. In addition, since the heat conduction equation is non-linear, a numerical operation is performed by a computer using a one-dimensional finite element method,
The temperature state after the data transfer is predicted by simulation, and is stored in the memory 13 as a table.

In the configuration described above Figure 1, the pulse width of the transfer period and the enable signal EN 'of data m dots to the thermal head 19 is constant, the temperature after the data transfer Knowing the initial temperature T ₀ by Shi shoe Configuration Can be predicted. Ninth
The figure is an explanatory diagram of such a simulation state,
(A) shows a temperature change state when a drive pulse is applied for a time t ', and (b) shows a temperature change state when a drive pulse is not applied.

In the memory 13, the initial temperature T ₀ as a parameter in advance a table as data the temperature T 'after transfer period if not added with the case of adding the drive pulse. That is, the heat storage temperature data R _i−1 , _{l is set} to the initial temperature T ₀ , and the output signal _Ol of the AND gate 18 is input to the address of the memory 13 as an ON / OFF signal of the drive pulse, thereby making the memory 13
Outputs the temperature T 'after the transfer cycle as bit data R _i , _l .

By storing such data in the memory 13, the heat storage temperature is sequentially calculated. Then, the heat storage temperature data and the set temperature are compared one by one in the comparator 17, and as a result, a pulse train corresponding to the past heat storage temperature data is selected from the plurality of pulse trains in FIG. Heat history control is performed.

In the above description, the temperature control is in an open loop. Also, an error occurs in the simulation data depending on the periodic temperature. Therefore, the temperature of the heat radiating plate of the thermal head 19 is measured by the temperature sensor 20, the measured data TD is added to the memory 13 as an address, and the data in the memory 13 is switched. If the temperature of the heat radiating plate of the thermal head 19 rises excessively, the drive pulse is cut so that the temperature does not rise any more.

Further, the pulse width of the driving pulse may be variable in order to improve the recording quality according to the change in the chart feed speed or the ambient temperature. In this case, the address of the memory 13 is switched according to the chart feed speed and the ambient temperature to
What is necessary is just to change the data read from 13.

According to such a configuration, the application pattern of the driving pulse of the thermal head can be finely set basically by a simple combination of one read-only memory and a comparator, and the recording quality can be improved.

FIG. 10 is a block diagram showing a modified example of the present invention,
This shows a case where there are two types of recording lines, and portions common to those in FIG. 1 are denoted by the same reference numerals to which ₁ and ₂ are added in accordance with the types of recording lines.

That is, in FIG. 10, a digital one-shot section A has two systems of digital one-shots including a data selector 7, a data conversion section 8, a subtractor 9, latches 10, 12 and a memory 11 to which subscripts ₁ and ₂ are added. A shot loop is provided. on the other hand,
The heat history control unit B has a comparator 17 for processing data output from each of these digital one-shot loop systems.
And an AND gate 18 is provided two systems constitute these two systems of AND gates 18 _1, 18 ₂ of the output data to apply to the thermal head 19 via the OR gate 24.

In such a configuration, recording with different line types is performed as follows. Note that one data selector
The 7 ₁ "4" is set as the set value CD _1, the other of the data selector 7 _2, "6" is set as the set value CD _2.

FIG. 11 is a timing chart for explaining the operation, which corresponds to FIG. 5 described above, and shows a change in data corresponding to one arbitrary dot during a transfer interval by focusing on the dot. It is.

When the data D _1i inputted to the data selector ₇₁ of one of the strains of the digital one-shot portion A in the interval k shown in (a) becomes "1" as shown in (c), the output data of the data selector 7 ₁ As shown in (d) CD
A value of ₁ “4” is set. Output data d _'1i of the data conversion unit ₈₁ becomes "1" as shown since the output data of the data selector 7 is "4" (e), one of the AND gates 18 ₁ in the history control unit B To the input terminal. In a subsequent interval k + 1, k + 2, k + 3, as the data is indicated by the subtractor 9 ₁ (f) "1"
Is subtracted by one. By this process, data "1" is input to the data selector 7 ₁ in interval k
4 from interval k to k + 3 triggered by D _1i
So that recording data in the history control unit B is applied from the data conversion unit ₈₁ over time.

Such a series of operations is performed at intervals k + 7 and k +
A true even if "1" as the data D _1i is input at 9, the digital one-shot unit A is operated as if re triggerable monostable multivibrator, the data conversion unit ₈₁ as the data D _1i thereby outputting recording data to the aND gates 18 ₁ in the history control unit B in the four intervals that the top "1" is input, "interval.

Such an operation is also performed in the other system with the subscript ₂ shown in (g) to (k). However, the data selector 7 ₂ as data CD ₂ since "6" is set, from the interval k in the trigger data D _2i of "1" is input to the data selector 7 ₂ in interval k to k + 5 recorded data will be applied from the data converter ₈₂ to the aND gate 18 ₂ of the history control unit B for 6 times.

A same when "1" as the data D _2i is input in the interval k + 7 and k + 8, the digital one-shot unit A is operated as if re triggerable monostable multivibrator, the data conversion unit ₈₂ is data thereby outputting recording data to the aND gate 18 ₂ of the history control unit B in six intervals "1" at the beginning of interval entered as D _2i.

That is, the digital one-shot section A receives the input data
Input data triggered by D _1i and D _2i is used as a data selector 7 ₁ ,
7 ₂ sets data CD _1, operates to stretch the predetermined interval times arguments set by CD _2, set data CD
₁ , the recording line width varies depending on CD ₂ .

Temperature data SD ₁ and SD ₂ of the comparators 17 ₁ and 17 ₂ of the heat history control unit B
Sets the recording densities of the data d' _1i and d' _2i output from each system of the digital one-shot section A individually. For example, when the temperature data SD ₁ of relatively 17 ₁ is set to 0.99 ° C., the comparator 17 ₁ temperature data R ₁ applied from latch 16 - ₁ only if less than 0.99 ° C. "1" and outputs to the aND gate 18 _1. AND gate 18 ₁ uses this comparator 17
It will be for outputting a logical product of the _first output data and the output data of the data converter ⁸¹ to the OR gate 24, the heat storage temperature of the heating element will be suppressed to a value of the temperature data SD ¹ neighborhood. Here, the level of the heat storage temperature is related to the level of the recording temperature. As the heat storage temperature increases, the recording density increases. That is, the recording density can be set individually by the temperature data SD ₁ and SD ₂ of the comparators 17 ₁ and 17 ₂ .

Thus, according to the configuration of FIG. 10, the data selector
The recording line width can be set by the data CD ₁ and CD ₂ of 7 ₁ and 7 ₂ , and the recording density can be set by the data SD ₁ and SD ₂ of the comparators 17 ₁ and 17 ₂ . Therefore, for example, by setting CD ₁ = 4, CD ₂ = 6, SD ₁ = 200 ° C., and SD ₂ = 150 ° C., the system of the input data d _1i can be recorded with a thin and dark line, and the input data d _2i Lines can be recorded with thick and thin lines. In the part where two types of lines intersect, the dark line is preferentially recorded by the operation of the OR gate 24.

FIG. 10 shows an example of two types of recording lines, but three or more types of recording lines can be simultaneously recorded by adding a system of the digital one-shot section and a system of the thermal history control section as necessary.

Further, the memories 11 ₁ and 11 ₂ may be configured to allocate higher-order plural bits and lower-order plural bits of one memory respectively.

In addition, by controlling the break of the recording line,
The types of recording lines such as broken lines and chain lines can be further increased. In this case, the data input to the AND gate 18 system and the data externally input to the data selector 7 system may be controlled to be on and off by the gate.

Next, a density correction operation in the case of recording a linear waveform with a light line will be described with reference to FIG.

The data of the first table stored in the memory 13 is selected when the output data O _i of the OR gate 24 is “0”, and the data of the second table is selected when the output data O _i of the OR gate 24 is “1”. You.

It is assumed that linear image data is input as input data _d1i . That is, "1" is input to the heating elements with a line thermal head 19, the output data d _'1i of the data conversion section ₈₁ also becomes "1".

First, a set of "203" in order to set the dark lines as, for example, temperature data SD ₁ of the comparator 17 _1. It is assumed that the data in the memory 15 has been cleared to “0”. Table 3 shows the operation state of the heat history control unit B at this time. Here, A represents the order of the processing loop, i represents the output data d _'1i of the data conversion section _81, c represents the heat storage temperature data R _i-1, d is the output data O _i of the OR gate 24 shows, o denotes the thermal storage temperature data R _i.

That is, in the loop 1, the heat storage temperature data R _i-1 with respect to temperature data SD ₁ "203" of the comparator 17 ₁ is "0", is applied to one input of the AND gate 18 _first comparator 17 the output of the ₁ becomes "1". Output data d _'1i of the data conversion unit ₈₁ applied to the other input terminal of the AND gate 18 ₁ is also "1", output data O _i of the OR gate 24 to be added as an address of the memory 13 to "1" Become. Thereby, the above-mentioned second table is selected. Then, the memory 13
Since the heat storage temperature data R _i-1 input as the address is "0", the heat storage temperature data "111" in the address 0 in Table 2 is output as a heat storage temperature data R _i. In the subsequent loop 2, the heat storage temperature data “111” read out in loop 1 is used as the heat storage temperature data R _i−1 , and the heat storage temperature data “161” of the 111 address in Table 2 is used as the heat storage temperature data R _1. Is output. The same procedure is repeated from loop 3 onward, and the output data O _i applied to the thermal head 19 from the OR gate 24 when the linear image data is recorded as a dark line is “1” until loop 4 and thereafter “1”. 011011....

Next, Awasen when recording, the comparator 17 _first temperature data SD ₁ as a dark line value lower than the set value of the recording, for example, "1
40 ". Table 4 shows the operation state of the heat history control unit B at this time. (A) to (e) are the same as in Table 3.

OR gate 24 when recording straight line image data with light lines
, The output data O _i applied to the thermal head 19 becomes “1” in the loops 1 and 2 and “0” in the loop 3 and thereafter becomes “100100” until the loop 9. Output data in loop 10
O _i becomes “1”, and the trap heat storage temperature data 250 stored at the address 120 in the second table is read out.
Then, the output data O _i becomes “1” and the address 250
It will be trapped heat storage temperature data 120 stored in the read, since the output data O _i becomes repetition of "101010". As a result, the energy applied to the thermal head 19 after the loop 10 changes from the loop 3 to the loop 9
Up to "100100" up to "11" for dark line recording
01110... ”, And the density of light line recording can be prevented from becoming too light.

<Effects of the Invention> As described above, according to the present invention, it is possible to realize a thermal recording apparatus capable of automatically increasing the density when straight lines with low density continue.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a timing chart for explaining the operation of FIG. 1, FIG. 3 is an example of recording by the apparatus of FIG. 1, and FIG. FIG. 5 is a timing chart for explaining the operation of the digital one-shot unit shown in FIG. 5, FIG. 5 is a diagram for explaining a change in data in the digital one-shot unit shown in FIG. 1, and FIG. 7, FIG. 7 is a perspective view of a main part of FIG. 1, FIG. 8 is a timing chart for explaining the operation of the heat history control unit of FIG. 1, FIG. 9 is an explanatory view of simulation data used in the present invention, FIG. 10 is a block diagram showing an application example of the present invention, FIG. 11 is an explanatory diagram of data change in the digital one-shot section of FIG. 10, FIG. 12 is a block diagram showing an example of such a conventional device, FIG. Fig. 13 shows the operation of the circuit in Fig. 12. Timing chart showing,
FIG. 14 and FIG. 15 are examples of conventional recording. 1 shift register, 2, 10, 12, 14, 16 ... latch, 3
... NAND gate, 4 ... inverter, 5 ... heating element, 7 ... data selector, 8 ... data conversion section, 9 ...
… Subtractor, 11,15 …… Memory (dual port RAM), 13
…… Memory (ROM), 17 …… Comparator, 18 …… And gate, 19 …… Thermal head, 20 …… Temperature sensor, 21 ……
Recording paper, 22 ... Motor, 23 ... Timing control circuit, 24
... Ao gate.

Claims (1)

(57) [Claims] A plurality of heating elements, which are arranged at regular intervals and constitute a line thermal head, are selectively driven in accordance with the magnitude of a waveform to generate heat, and the magnitude of the waveform is recorded on a thermosensitive recording paper based on the generated heat. A first memory for storing heat storage temperature data related to the recording operation of the heating element in advance, and reading out the next heat storage temperature data using the current heat storage temperature data and the presence / absence of recording as an address; A second memory for temporarily storing heat storage temperature data read from the first memory, a comparator for comparing the heat storage temperature data temporarily stored in the second memory with a preset temperature, A switch element for controlling a recording operation of the heating element according to the result; Thermal recording apparatus characterized by trap data forming the minor loop is stored for driving the heat generating element to increase.