JP2927395B2 - How to apply the energizing pulse to the thermal head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for applying an energizing pulse to a thermal head in a thermal recording apparatus such as a facsimile machine.

[0002]

2. Description of the Related Art FIG. 7 shows an example of an energizing pulse for driving a heating resistor constituting a thermal head, which is disclosed in JP-A-63-256644. In this example, the gradation of the recording density is expressed by ³ bits, and the data corresponding to 20 bits is expressed.
The four unit pulses as data, 2 ¹ De corresponding to the bit - six individual pulses as data, 2 ² Bittode - De corresponding to the data - each successive seven individual pulses as data , So that seven levels of density gradation are represented.

[0003]

When the energizing pulse is applied as described above while the thermal head and the thermal paper are relatively moved, only the density gradation 3 and one gradation are applied to the same line. In the case of expressing a large density gradation 4, in the density gradation 3, the energization period is shifted to the front side of one line period, and in the density gradation 4, conversely, the energization period is shifted to the rear side. Are not aligned linearly, giving a sense of noise and deteriorating image quality.

Further, the above-described energizing pulse applying method has the following inconveniences in the manufacturing process of the device or when the density gradation characteristic is changed on the user side. For example, focusing on the gray scale 5 in FIG. 7 described above, first, the period corresponding to 2 ⁰ bit is supplied four unit pulses, the period corresponding to the next two ^1-bit, nothing It is not supplied and it is the cooling period of the heating resistor,
The density gradation 5 is supplied with seven unit pulse during a period corresponding to 2 ² bit of the most significant digit is expressed.

[0005] In this case, the manufacturing process when derided devices - The - on the side, in the case so as to change the number of pulses to be applied during the period corresponding to 2 ¹ bit driving pulse duration is changed accordingly In other words, the cooling period naturally changes, and even if the number of energizing pulses supplied before and after that, that is, the applied energy is the same, the recording density changes. Therefore, there is a problem that the number of steps for adjusting the gradation characteristics increases. SUMMARY OF THE INVENTION An object of the present invention is to provide a method for applying an energizing pulse to a thermal head which solves the above-mentioned problems.

[0006]

The object of the present invention is to provide a method for applying an energizing pulse to a thermal head by the following means (1) to (4). 1) An energizing pulse corresponding to each bit of digital data indicating a gradation of recording density consisting of a predetermined number of bits is applied to a thermal head composed of a plurality of heating resistors arranged in a row. Thus, in the method of applying the energizing pulse of the thermal head in the thermal recording apparatus that performs recording on the thermal paper relatively moving in opposition to the plurality of heating resistors, the energizing pulse corresponding to a predetermined bit is divided, A method for applying an energizing pulse to a thermal head, wherein an energizing pulse corresponding to another bit is applied in the meantime.

2) At least one of the predetermined energizing pulses to be divided is an energizing pulse corresponding to the most significant bit, and at least one of the pulses corresponding to the other bits interposed therebetween has at least one tone gradation signal. 2. A method according to claim 1, wherein the pulse is a pulse corresponding to a logical sum output between each bit of the thermal head.

3) The method of applying an energizing pulse to a thermal head according to claim 1, wherein the pulse widths of the predetermined energizing pulses to be divided are made different from each other in accordance with the gradation characteristics.

4) The energizing pulse of the thermal head according to claim 1, wherein the generation cycle of the energizing pulse corresponding to each bit is made constant with a cooling period for cooling the temperature of the heating resistor interposed therebetween. Application method.

[0010]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic block diagram for controlling a thermal head to which the method of the present invention is applied. In FIG. 1, reference numeral 10 denotes density gradation (hereinafter simply referred to as gradation) data. A terminal 11 is a memory (RA) for storing gradation data for one line (or one screen).
M) and 12 select predetermined bits of gradation data read from the memory 11 by the bit select signal BS,
Head data S is added to a heat generating resistor of a thermal head to be described later.
This is a data selector for supplying as D.

As shown in FIG. 4, the data selector 12 has terminals A0 to A2 to which 3-bit gradation data is inputted, and an input terminal SE for a bit select signal BS.
L and a terminal Y for outputting the head data SD are provided. A high level (printing) signal is supplied to the input terminal A6, and a low level (non-printing) signal is supplied to the terminal A7. The data selector 12 has an OR circuit 12a and an AND circuit 12b as necessary, as will be described later.
Are provided, and terminals A4 and A5 are used for their output signals.

Reference numeral 13 denotes a group of counters. The group of counters 13 supplies a memory address AA for reading out gradation data to the memory 11, and a ROM address indicating the number of times data is transferred from the memory 11 to the ROM 14. AB, a latch clock to the latch 15, and an enable address AC indicating the time axis of the enable pulse to the comparator 16, respectively. The comparator 16 comprises a pulse width data PD and an enable address AC.
And the enable pulse EN is applied to the thermal head.
This is a comparator that outputs 1 and EN2, respectively. As described above, the control circuit of the thermal head is schematically configured.

FIG. 2 is a schematic block diagram of a thermal head controlled by the above-described control circuit. The thermal head includes a group of heating elements 21 arranged in a line and a group of heating elements 21.
, A shift register for converting head data SD indicating a predetermined heating element to be driven to parallel data, and parallel data output from the shift register 23. And a gate group 25 for supplying a current to a heating element to be driven for the duration of the enable pulses EN1 and EN2 in accordance with the parallel data output from the latch 24. I have.

Next, a method of applying an energizing pulse with the above configuration will be described with reference to FIG. FIG.
(A) to (P) are timing charts of respective signals in the respective circuits shown in FIGS. 1, 2 and 4, and FIG.
(P) is a drive pulse for the heating element connected by the enable pulse EN1 and shows a pulse train for expressing density gradations 2 to 6.

Here, in order to simplify the description, the grayscale data is represented by 3 bits (D ₀ , D ₁ , D ₂ = 2 ⁰ , 2 ¹ , 2).
² ), the gradation data for one line (n pixels) has already been written in the memory 11, the transfer bits for each transfer cycle have been written in the ROM 14 as the bit selector signal BS, and the transfer has been performed. It is assumed that the energizing time for the bit has been written in advance as pulse width data PD. It is also assumed that “0” is latched in the latch 15 at the start of each line.

[0016] First of all, the first of the de - outputs a ROM address AB = 0 from the data transfer cycle T ₁ in the counter 13,
ROM14 is a bit select signal BS = 0 de - output to Taserekuta 12, de - Taserekuta 12 Heddode - de as data SD - is set to select the data D ^₀ (2 _0). As a result, from the memory 11, only the data D ₀ (2 ⁰ ) of the 3 bits of gradation data is supplied to the shift register 23. When the counter 13 reads data for one line from the memory 11, that is, when the memory address AA is counted up from 0 to n, it outputs a head latch pulse LT1 and thereby the latch 24 in the head for one line. data D ₀ is held - de of. Also, de - energizing pulse width de against data D ₀ - data PD ₀ is
Latch 15 is held by latch clock LT2 which is output at about the same time as head latch pulse LT1.

These head latch pulses LT1, LT2
Is output, the counter 13 counts up the ROM address AB to "1" and starts the second data transfer cycle T2. Now, BS = 2 is output as a bit select signal from the ROM 14, the de - Taserekuta 12 de - data D ₂ (2 ² bit) shift register 23
Will be supplied sequentially. At the same time, the counter 13 outputs an enable address AC and an enable switch flag EF to the comparator 16. The enable switch flag EF indicates that one data transfer cycle is about 1/2.
The switching flag is divided into

The enable address AC repeatedly counts up from 0 in synchronization or asynchronously with the memory address AA every time the flag EF is inverted. Comparator - motor 16, the rice - compares the output PD ₀ Bull address AC and latch 15, the output PD ₀ is rice - Buruparusu EN1, - rice becomes time only "H" is greater than Bull address AC Output EN2 respectively. When the enable switch flag EF is at "L" timing, the enable pulse EN1 is output, and the enable switch flag EF is output.
At an "H" timing, an enable pulse EN2 is output. Thus, the enable pulses EN1, EN
The reason why 2 is distributed twice is to reduce the number of heating elements that are energized at the same time and reduce the load on the power supply.

As a result, in the thermal head, the heating element indicated by the data D ₀ held by the latch 24
The energization is performed for a period of ₀ . Similarly, in this cycle, when one line of data is read from the memory 11, head latch pulses LT1 and LT2 are output, and the data D is output.
₂ and PD _{2 (1)} are held by latches 24 and 15, respectively.

[0020] Thereafter in the same manner, the third de - de In data transfer cycle T ₃ - transfer and data of data D ₁ - energization of motor D _2, 4 th de - data transfer cycle T ₄ in de - data D ₂
Second time transfer and de of - energization of motor D _1, 5 th de - data transfer cycle T ₅ in the non-printing de - data (SD =
"L") transfer and data of - energizes a second time for data D _2. Then, de - data transfer cycle T ₆ after a non-printing de -
The transfer operation and the non-energized state continue, and the printing operation for one line is completed.

As described above, in the present embodiment, the energization pulse corresponding to the other bit is inserted instead of the energization of one bit by a continuous pulse.
The bias of the energization time can be eliminated, and the displacement of the print dots as shown in the conventional example can be reduced. FIG.
(M), as shown in (N), de - de between the first and second times of energization of the motor D ₂ - for energizing pulse to the motor D ₁ is adapted to be inserted, the density gradation 3 and the density gradation 4, the bias of the energization time is small.

In this embodiment, the most significant digit is divided, and the most significant bit has a large data amount and a long energizing time. The effect of preventing dot displacement is obtained.

Further, in this embodiment, only the energization to the most significant digit is performed twice, but the number of bits of the grayscale data is increased, the types of bits to be divided, and the continuous The effect is obtained as the number of times of the pulse increases.

Further, since the energizing pulse corresponding to each bit of the gradation data has a constant period irrespective of the pulse width, the cooling period is interposed. The gradation characteristic can be easily changed without affecting the bit cooling period.

In the present embodiment, when the gradation to be actually printed is different from the desired gradation density due to the energy characteristics of the thermal paper or the transfer paper, it is necessary to correct this. For example, in the case of gradation characteristics as shown in FIG. 6, an OR circuit 12a as shown in FIG. 4 may be provided, and its output may be used as a pulse for low gradation correction. Its timing signal a timing chart of FIG. 5 - As shown in bets, a bit select signal BS and BS = 4, de - first energizing and de for data D ₂ - between the energization of motor D _1, floor tone de - providing the energizing period PD _L to a logical sum output between data each bit. By doing so, not only the characteristics of the low gradation portion are corrected, but also, as shown in FIGS.
As is clear from (M), the bias of the energization time can be reduced, and the displacement of the recording dots can be further reduced.

Further, in method 3, the difference between the number of pulses to represent a gray scale 6 and the gradation 7, since only whether PD ₀ is present, in fact high gradation as shown in FIG. 6 There may be cases where the difference in density between parts is not clear. In such a case, an AND circuit 12b may be provided as shown in FIG. 4, and its output may be used as a pulse for high gradation correction. FIG.
Timing Cha - as shown in bets, de - for data D ₂ after the second energization, further Kaichode - the conduction period PD _H provided to the logical product output between data each bit gradation 6 and floors The gradation characteristic can be improved by increasing the difference between the applied energy and the tone 7.

Further, for example, if attention is paid to the pulse expressing the gradation 4 in FIG. 4 (P), the pulse PD _{2 (1)} and the pulse PD _{2 (1)
2 (2)} is divided into the same ratio, but if the ratio between PD _{2 ( 1)} and PD _{2 (2)} is changed while maintaining this density gradation 4, this density gradation is not affected. No density gradation 5 and density gradation 6
Can be increased or decreased.

Further, in this embodiment, the recording apparatus using the thermal paper has been described. However, if the recording apparatus performs thermal recording while relatively moving the recording head and the recording paper, the head and the recording paper can be used. A similar effect can be obtained even in a transfer apparatus in which a transfer sheet having a melting property or a sublimation property is interposed between the transfer apparatus and the transfer apparatus.

[0029]

According to the energizing pulse application method for the thermal head of the present invention, energizing one bit is not performed by a continuous pulse, but a transfer cycle corresponding to another bit is inserted. Eliminate time bias,
It is possible to reduce the displacement of print dots on the same line as shown in the conventional example. In particular, according to the second aspect of the present invention, the displacement can be further reduced. Also,
According to the third aspect of the invention, more subtle gradation characteristics can be expressed. Further, according to the present invention, when the gradation characteristic is changed at the time of manufacturing the device or when the device is used on the user side, even if the pulse width of any bit is increased or decreased, the cooling period of other bits is reduced. Has an effect that it can be easily changed without any influence.

[Brief description of the drawings]

FIG. 1 shows a schematic block diagram for controlling a thermal head to which the method of the present invention is applied.

FIG. 2 is a schematic block diagram of a thermal head.

FIG. 3 is a timing chart of each signal in the circuits shown in FIGS. 1, 2 and 4;

FIG. 4 is a schematic configuration diagram of a data selector 12.

FIG. 5 is a timing chart corresponding to FIG. 3 when performing density correction.

FIG. 6 is a diagram illustrating an example of a gradation characteristic requiring density correction.

FIG. 7 is a diagram showing an example of an energizing pulse for driving a heating resistor constituting a conventional thermal head.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Terminal 11 Memory (RAM) 12 Data selector 13 Counter group 14 ROM 15 Latch 16 Comparator 21 Heating element group 22 Thermal head 23 Shift register 24 Latch 25 Gate group EN1, EN2 Enable pulse SD head data

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-320777 (JP, A) JP-A-61-108259 (JP, A) JP-A-1-128853 (JP, A) JP-A-4- 135763 (JP, A) JP-A-5-131667 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B41J 2/36

Claims (4)

(57) [Claims] An energizing pulse corresponding to each bit of digital data indicating a gradation of a recording density having a predetermined number of bits is applied to a thermal head composed of a plurality of heating resistors arranged in a row. Is applied, a method of applying an energizing pulse to a thermal head in a thermal recording apparatus that performs recording on thermal paper relatively moving in opposition to the plurality of heating resistors, wherein an energizing pulse corresponding to a predetermined bit is applied. A method for applying an energizing pulse to a thermal head, wherein the method is divided and applied with an energizing pulse corresponding to another bit interposed therebetween. 2. At least one of the predetermined energizing pulses to be divided is an energizing pulse corresponding to the most significant bit, and at least one of the pulses corresponding to the other bits interposed therebetween has at least one gray scale data. 2. A method according to claim 1, wherein the pulse is a pulse corresponding to a logical sum output between each bit of the thermal head. 3. The pulse width of a predetermined energizing pulse to be divided is
2. The method according to claim 1, wherein the pulse width is different from each other according to the gradation characteristics. 4. The energizing pulse of a thermal head according to claim 1, wherein the generation cycle of the energizing pulse corresponding to each bit is made constant with a cooling period for cooling the temperature of the heating resistor interposed therebetween. Application method.