JPH0292554A - Thermal head driving device - Google Patents

Abstract

PURPOSE:To restrain irregularity in density from being generated by uniformizing control of thermal hysteresis by a method wherein a resistance heating element is divided, printing is performed for each division and besides, an input state of an image data to a shift register is controlled for a period from first latch timing to following second latch timing. CONSTITUTION:For a remaining heating printing data in each printing division, a data latched in a just before printing division is used and for main printing data in a printing division, the data latched in said printing division is used. Therefore, strobe pulses S1 to S4 establish a specific blank section W2 between a preliminary printing division W1 and a main printing division W3, and perform latch operation of data in this section. That is, an input state of an image data to a shift register containing a case wherein the image data to be inputted to a shift register 32 for a period from first latch timing to second latch timing does not yet reach a position of the shift register in a division to be driven initially after the second latch timing just after the second latch timing, is controlled.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a thermal head drive device suitable for application to a recording means that can be used in a facsimile machine, and in particular a thermal head drive device that performs divided printing while controlling thermal history. The present invention relates to a thermal head driving device.

[Background of the Invention] A facsimile machine converts a transmitted image information signal into a visible image by a built-in recording means, and records the image information.

A thermal head is usually used as this recording means, especially its recording section.

FIG. 5 shows an example of a thermal head drive circuit 3o used in such a recording means.

In this example, a resistance heating element 4o is provided. The resistive heating element 4o is constructed of n dots in one row, and is therefore composed of n resistive heating elements 40a to 40n (n=2048) arranged in a line.

The shift register 32 is a 2048-bit shift register, and the print data supplied to the terminal 33 is sequentially transferred by the transfer lock CK applied to the terminal 34.

After transferring the print data up to 2048 bits, the print data for one line stored in the shift register 32 is latched by the latch circuit 35.

Thereafter, printing data for one line is completed by simultaneously supplying the printing data to the corresponding resistance heating elements 40a to 40n.

By the way, this resistance heating element 40 consumes a considerable amount of power, so in relation to the power supply capacity, normally all 2048 resistance heating elements 40 are not driven at the same time.
A divided printing method is used in which one line is divided into multiple sections and each divided section is printed sequentially.

For example, if the number of divisions is m, it will be divided into n / m units, and these n / m resistance heating elements will be divided into one unit (
This will result in printing as a flock) and sequentially divided printing.

Therefore, the strobe pulses 31 to S4 are completely supplied to the resistance heating element 4o, respectively, and these strobe pulses 81 to
The configuration is such that the corresponding resistance heating element 40 is driven only when S4 is supplied.

By the way, when a resistance heating element is driven in a short cycle, the next heating is performed before the heating element has cooled down, and the difference between the resistance heating element that was driven for printing immediately before and the resistance heating element that was not driven for printing is different.
The amount of heat generated is different. Therefore, density unevenness may occur in the next line of printing.

In order to improve such density unevenness, preheating printing is usually performed.

Figure 6 shows an example of this preheating printing, in which one line of printing data (composite printing data) is divided into preheating printing data and main printing data, and these two printing data form one data. It will be printed. Prior to the transfer of the main print data, preheat print data is first supplied to the resistance heating element 4o (FIGS. 6A and 6B).

Each of the strobe pulses 81 to S4 is sequentially obtained immediately after this preheating print data. Strobe pulses 81 to S4 are supplied to corresponding divided resistance heating element groups (hereinafter referred to as heads H1 to H4),
Preheat printing can be executed before the actual printing data.

The main printing process is executed only after the preheating printing for all the resistance heating elements 40 is completed.

Here, the thermal history control method for preheating printing is to adjust the length of the next printing pulse to be applied, taking into consideration how printing pulses have been applied in the past to each resistance heating element.

The simplest method is to print on the resistance heating element 40 that was not printed in the previous printing line,
The purpose is to apply print data for a longer period of time than when printing is done on the resistance heating element 40 that was printed in the immediately preceding print line.

In the head driving device 30 that performs such thermal history control, all the resistance heating elements 4 are
When the preheating printing for 0 is completed, the main printing data is sequentially applied to each resistance heating element 40 for the first time.

Therefore, the period from preheating printing to actual printing differs depending on the divided heads H1 to H4.

For example, as shown in FIG. 6, if the interval between preheating print data and main print data applied to head H1 is T1, then head H4
The interval between the preheating print data added to the main print data and the main print data is T4.
In this case, the period T4 becomes much longer.

In this way, the preheated print data is added to one line by Rad I (1 to H
In a conventional thermal head drive device, the main print data is sent to the head one line at a time and printed while performing divided printing on all lines. The spacing differs depending on the divided section of the head.

Therefore, in divided sections where the off period is long, the effect of thermal history control cannot be sufficiently exerted.

This problem is discussed in, for example, ``Japanese Patent Application Laid-Open No. 63-21152''.
This can be solved by performing printing control as shown as a conventional example.

By using a thermal head that has four serial inputs for each divided printing section and a corresponding shift register for each divided section, it is possible to print the current line image signal and print the corrected image for thermal history control immediately after that. This allows printing of signals to be performed independently for each divided section.

The gist of the invention disclosed in this publication is the W! , 111. The present invention shows a method of replacing the shift register of 1 with a single shift register, thereby reducing the image signal interface with the thermal head to only one wire, and still enabling thermal history control.

However, in the method shown therein, the timings of printing the current line image signal and printing the corrected image signal for thermal history control are different for each divided printing section. Therefore, there still remains the problem that the effect of thermal history control differs depending on the divided printing section.

[Problems to be Solved by the Invention] In the above case, the shift register that inputs the image signal for one line, and the image signal input and latch input that latch the image signal for one line at a time, each have one thermal input. However, in order to perform preheating printing for thermal history control and main printing of the current line image signal at equal time intervals in each divided printing section using the head, image signal transfer becomes a problem.

The image signal on the shift register is sequentially moved from the serial input terminal side by a clock. Therefore, in order to rewrite the latched data on the divided section farthest from the serial input end, it is necessary to send one line of data to the shift register together with a clock and then latch it. This made it difficult to change data during divisional printing.

Below, we will take four-part printing as an example. The four divided printing sections are A, B, C, D in order from the farthest from the serial input.
Let's call it a block.

#1. Preheat printing of A block 112, A block main printing #3.8 block preheat printing 64.8 block book printing t$5. C block preheat printing $116. C block book printing 117, D block preheat printing 18. Main printing of D block Consider doing the following in order.

To rewrite the data in block A, it is necessary to send 4 blocks (1 line) of data to the shift register.
Hereinafter, data for 3 blocks, 2 blocks, and 1 block are required for each of the B block, C block, and D block, respectively.

As a simple method, if you send the necessary data to the serial input each time, latch it, and print it, in each of the cases from 21 to 8 above, - Preheat printing data for A block and dummy data for 3 blocks.・Actual printing data for A block and dummy data for 3 blocks ・Preheating printing data for B block and 2 blocks of dummy data ・Actual printing data for B block and dummy data for 2 blocks ・Preheating for C block Data for a total of 20 blocks, including print data and 1 block of dummy data, C block's main print data and 1 block's worth of dummy data, D block's preheat printing data, and D block's main print data, or Dummy data consisting only of the shift register transfer clock regardless of the contents is required. This takes time to transfer the image information, which hinders high-speed printing.

In a thermal head having only one shift register and one latch input, printing in the order shown from 111 to #8 has never been seen before.

Therefore, the present invention presents an efficient control method that can uniformly perform thermal history control for each divided printing section without delay using a thermal head using one shift register.

[Means for Solving the Problems] In order to solve the above-mentioned problems, in this invention, 1.
In a thermal head drive device consisting of a shift register that transfers image data within a line, a latch circuit that latches the image data output from the shift register, and a plurality of resistance heating elements arranged in a line, a resistor is used. The heating element is divided into a plurality of parts, and printing is performed for each divided section, and the image data input to the shift register during the period from the first latch timing to the next second latch timing is transferred to the second latch timing. Immediately after the second latch timing, the input state of the image data to the shift register is controlled so that it does not reach the position of the shift register of the first divided section driven after the second latch timing. This is characterized by the fact that it includes cases where

[Function J The data sent to the thermal head while printing the first line of the nth line according to the order from #1 to #8 described above from *2 to *17 described later is 8 blocks, and redundant data is It is very efficient and can evenly control the thermal history of each divided section without interfering with high-speed printing.

As a result, since main printing is performed immediately after preheating printing in each divided printing section, thermal history control becomes uniform and occurrence of density unevenness is suppressed.

Moreover, serial input and latch input of image information can each be carried out with one thermal head, so a painter interface can be easily provided compared to a thermal head consisting of a plurality of shift registers.

[Embodiment] Next, a case in which an example of the thermal head driving device according to the present invention is applied to the recording means in the above-mentioned facsimile machine will be described in detail with reference to FIG. 1 and subsequent figures.

FIG. 1 is a block diagram of essential parts of an example of a facsimile machine to which the present invention is preferably applied.

As is well known, the facsimile machine 1 includes a document optical reading means 10 in a rectangular parallelepiped-shaped housing (main body) 2.
Recording means 20 for recording received image data on recording paper
is stored.

The image signal read by the optical reading means 10 is transmitted to the other party using a communication line.

At the top of the housing 2, in the illustrated example, there is provided a document table 3 protruding from the upper left side to the lower right side. These papers are collectively referred to as manuscripts) are optical reading means 1
Paper is fed to 0.

The original that has entered the inside of the housing through the original insertion hole is fed downward by a feed-in roller 4. Then, the paper ejection roller 5
, 6, the paper type is determined and the document image is read.

Therefore, the feeding roller 4 and the pair of paper ejection rollers 5.6
A fluorescent lamp 11 is provided between the two and illuminates the surface of the document with its light. The reflected light (optical image information) thus obtained is transmitted to a pair of mirrors 12 arranged on the bottom side of the housing 2,
13, the light is guided to an image reading element 15 via a lens system 14.

In the image reading element 15, optical image information is converted into an electrical signal, that is, an image signal. The image signal passes through an image processing system (not shown), is stored in memory, or is sent out to a communication line.

As the image reading element 15, a line sensor made of a charge transfer element such as a COD or the like can be used.

Reference numeral 17 indicates a board on which the CCD 15 is mounted.

The original is conveyed downward at a speed corresponding to the original, and in the embodiment, image information is read line by line and sequentially converted into image signals.

The document fed out at a predetermined speed is passed through a pair of paper ejection rollers 5 and 6.
In this example, the document is ejected from the front bottom side of the housing 2 to a tray (not shown) for the document tray.

Although not shown, the upper front side of the casing 2 serves as an operation panel surface on which various operation keys and a display section are formed.

Next, the recording means 20 will be explained.

The recording means 20 is means for reproducing the information as a visible image on recording paper based on the received image signal. The recording means 20 is provided above the rear of the housing 2.

Therefore, roll paper (recording paper) 21 is placed in the center of the housing 2.
The recording paper 21 is fed out to the platen roller 22 side.

A recording element 23 is arranged on the upper surface of the platen roller 22 so as to be in sliding contact with the outer peripheral surface of this roller. As the recording element 23, a linear thermal head or the like can be used.

Therefore, when the recording paper 21 that has been conveyed to the upper surface of the platen roller 22 passes the thermal head 23, the incoming image information is recorded.

When the recording paper 21 on which image information has been recorded has been conveyed for a predetermined length, the automatic cutter device 24 is driven to automatically cut the rear end of the recording paper 21. Therefore, this automatic cutter device 24 is composed of a blade for cutting paper and a driving means for moving the blade up and down.

The cut recording paper 21 is discharged onto a paper discharge tray 25 attached to the rear of the housing 2.

FIG. 2 shows a thermal head driving device 50 according to the present invention.
It is a system diagram of the main part showing an example.

The transmitted image information signal is temporarily stored in the main memory 51. Among the image information signals stored in the main memory 51, one line or several lines of image information signals are supplied to the line memory 52.

The output is supplied to a data processing circuit 60 to form composite print data as shown in FIG.

The composite print data is supplied to the head drive circuit 30, and desired print is executed based on this data.

Everything from the main memory 51 to the head drive device 30 is controlled based on commands from the microcomputer 70.
1 will be given.

FIG. 3 shows an example of the data processing circuit 60, in which the image information signal read from the line memory 52 is once converted from parallel data to serial data in a parallel-to-serial conversion circuit 61.

From the image information signal converted into serial data, the image data of the current line Ln and the immediately preceding line Ln-1 are outputted, and the image data of the immediately preceding line Ln-1 is inverted by the inverter 62. It is supplied to the AND circuit 63 together with the image data of the current line Ln.

As a result, preliminary print data is formed, and this preliminary print data and the image data of the current line Ln are supplied to the switching circuit 65, and the desired switching control is performed for each divided section to form composite print data. Ru. 66
indicates its output terminal.

A control signal obtained from the microcomputer 70 is supplied to the terminal 67, and composite print data as shown in FIG. 4F is formed based on this control signal.

The head drive circuit 30 executes printing processing accompanied by necessary thermal history control based on the supplied composite printing data.

In this printing process, when one line is divided into a plurality of periods and each divided section is sequentially printed, preheating printing and main printing are performed for each divided section.

That is, as shown in FIG. 4, immediately after the preheating printing period W1 has elapsed, a predetermined period W2 has elapsed, and the main printing period W3 immediately begins. After this preheating printing and main printing are performed, preheating printing and main printing in the next divided section are performed. This is sequentially repeated at a predetermined period T.

Therefore, when the number of divisions m is 4 as shown in Figure 4,
As shown in figures A to D, the division period T of one row is constant for each division head H1 to H4. As a result of -C, the preheating section does not differ for each divided section.

Next, let's explain a concrete example.

First, as the preheating print data in each divided printing section, the data latched in the immediately preceding divided printing section is used. Then, the data latched in the divided printing section can be used as the main print data in the divided printing section.

Therefore, in the strobe pulses 81 to S4, a predetermined blank section W2 is provided between the preliminary printing section W1 and the main printing section W3, and the data latching operation is performed in this section. That is, as shown in FIG. 4E, the latch pulse RP is obtained during a period corresponding to section W2.

By this latch pulse RP, both the main print data in the divided print section and the preliminary print data in the next divided print section are latched.

Therefore, the composite print data is data as shown in FIG. Accordingly, the number of clocks of the transfer lock CK applied to the shift register 32 differs depending on each divided printing section, as shown in FIG.

In order to achieve high-speed printing with a thermal head that has only one shift register and one latch input, the data sent to the thermal head between one latch and the next latch must be sent immediately after the latch. It is sufficient to create a sequence that includes the case where the divided printing section to be printed is not reached.

The following symbols will be used for explanation below.

The n-th line preheat printing data of blocks A, B, C, and D are set as an, bn, Cn+dn in order, and A, B, C,
The data for main printing of the n-th line of the D block is sequentially An,
Bn, Cn+Dn.

Assuming that the current line is n lines, the previous line can be represented by n-1, and the next line can be represented by n+1.

In order to perform printing in the order from ttl to #8 above, printing is performed in the following sequence. This will be explained with reference to FIG.

*1 The data is input to the shift register 32 of the thermal head in the order of (an, An, bn, Dn 1) and latched.

The arrangement on the shift register 32 is (a n , A n
+bn*Dn1).

(The order is written in order starting from block A. The same applies below.) When all the contents of the shift register 32 are transferred to the latch circuit 35, the latched data is arranged as (an, An+ bn,
Dn -1).

*2. Enter Bn. This need only be completed by the time of processing *4 shown below, during which time processing *3 can be performed simultaneously.

The arrangement on the shift register 32 is such that when the input Bn enters the D block, the data on the D block moves to the C block, the data on the C block moves to the B block, and the data on the B block moves to the A block. In order to continue
When the input of Bn is completed (An, bn.

Dn-1, , Bn).

*3. A strobe pulse S1 is applied to the A block (Fig. 4A).

Since it is latched in A block by processing an or *1,
Preheat printing of block A is performed (F in the same figure).

*4. Apply the latch.

The contents of the shift register 32 are transferred to the latch circuit 35, and the latched data is arranged as (An, bn, Dn −
1*Bn).

*5. Input an and Cn. This only needs to be completed by the time of the process in *8 below, during which time each process in *6 and *7 can be performed simultaneously.

The arrangement on the shift register 32 is (Dn-1°Bn, c
n, Cn).

*6. Apply strobe pulse S1 to A block.

Since An is latched to the A block at *4, actual printing of the A block is performed (FIG. F).

*7. A strobe pulse S2 (B in the same figure) is applied to the B block.

Since bn is *4 and latched to the B block, eight blocks of preheat printing are performed (FIG. F).

*8. Apply the latch.

*9 The latched data arrangement is (Dn-1°Bn, cn
, Cn).

Enter dn. This need only be completed by the time of the process in *12 below, during which time each process in *10 and 11 can be performed simultaneously.

The arrangement on the shift register 32 is (Bn, cn.

Cn, dn).

*10. Apply strobe pulse S2 to B block.

Since Bn is latched to the B block in the process of *8, the actual printing of the B block is performed.

*11. Strobe pulse 33 to C block (C in the same figure)
multiply.

Since it is latched to the C block by the process of Cn or *8, preheat printing of the C block is performed.

*12. Apply the latch.

The latched data sequence is (Bn, On.

Cn, dn).

*13. (an + 1 + An + 1 + bn
+ 1 + Dn). This is the following *1
It only needs to be completed by the processing in step 6, and during that time *14.15
Each process can be performed simultaneously.

The arrangement on the shift register 32 is (bn+1).

An+1, bn+1+Dn).

*14. Apply strobe pulse S3 to C block.

Since Cn is fully latched to the C block in the process of *12, actual printing of the C block is performed.

*15. Strobe pulse S4 to D block (D in the same figure)
multiply.

Since dn is latched to the C block in the process of *12, preheat printing of the C block is performed.

*16. Apply the latch.

The latched data sequence is (an+l.

Δn+1, bn+1, Dn).

*17. Apply strobe pulse S4 to D block.

Since Dn is latched to the C block in the process of *16, actual printing of the C block is performed.

*181 For printing on the next line (n+1), return to the process in *2. However, consider replacing n in the sentence with n+1.

In the above, the only data sent to the shift register 32 of the thermal head between the latch pulses *1 and *4 is Bn at *2. This is latched to the C block in latch *4, and immediately after latch *4 *6
, 7 does not reach the shift register of the divided printing section.

Also, the data sent to the shift register 32 of the thermal head between the latch pulses *4 and *8 is *5.
n, Cn only. This is latched to the C block and C block in the latch of *8, and does not reach the shift register of the divided printing section printed in *10 immediately after the latch of *8.

Further, the data sent to the shift register 32 of the thermal head between the latch pulses *8 and *12 is only the dn at *9. This is C for latch *12.
It is latched in the block and has not reached the shift register of the divided section where printing can be completed at *14 immediately after the latch of *12.

*The C block at 17 is the closest block to the serial input side, so it must be printed before the latch at 16*13
The data entered will be output immediately.

Therefore, image data input to the shift register 32 during the period from an arbitrary latch timing (first latch timing) to the next latch timing (second latch timing) is not immediately after the second latch timing. The input state of the image data to the shift register 32 is controlled so as to include the case where the image data does not reach the position of the shift register 32 in the divided section that can be driven first after the second latch timing.

Therefore, the contents of the print data transferred to the shift register 32 and the contents of the print data applied to the divided heads H1 to H4 at that time have a relationship as shown in FIG. 4H and I.

[Effects of the Invention] As explained above, in the present invention, in the thermal head drive device of the divided printing method, preheating printing and main printing are executed for each divided section, and the content of transfer printing data to the shift register is , the contents of the print data applied to the dividing head at that time are selected as desired.

According to this, the thermal history control of each divided printing section becomes constant, which has the practical benefit of eliminating density unevenness after printing.

Furthermore, since all the image data input to the shift register is used as main print data or preliminary print data, there is no image data that does not contribute as print data. Therefore, it is possible to perform high-speed printing processing with a reduction in printing time.

Therefore, the thermal head driving device according to the present invention is extremely suitable for application to a recording means built into a facsimile machine as described above.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an outline of a preferred facsimile machine using a thermal head driving device according to the present invention, and FIG.
FIG. 3 is a system diagram showing an example of a thermal head drive device according to the present invention, FIG. 3 is a system diagram showing an example of a data processing circuit, FIG. 4 is a waveform diagram for explaining its operation, and FIG. 5 is a head drive circuit. FIG. 6 is a system diagram showing an example of the system, and FIG. 6 is a waveform diagram for explaining its operation. 1 ・ 10 ・ 20 ・ 30 ・ 32 ・ 35 ・ 40 ・ 50 ・ 60 ・ H1 to H4・・Facsimile device・Optical reading means・Recording means・Head drive circuit・Shift register・Latch circuit・Resistive heating element・Thermal head drive Equipment/data processing circuit/dividing head

Claims (1)

[Claims] (1) A thermal head drive consisting of a shift register that transfers image data for one line or less, a latch circuit that latches the image data output from the shift register, and a plurality of resistance heating elements arranged in a line. In the apparatus, the resistive heating element is divided into a plurality of sections, printing is performed for each divided section, and image data input to the shift register during the period from the first latch timing to the next second latch timing. However, immediately after the second latch timing, the second
Thermal image forming apparatus includes a case where the input state of the image data to the shift register is controlled so that it does not reach the position of the shift register of the divided section that is first driven after the latch timing of the image data. Head drive device.