JPH01122456A - Thermal head driver - Google Patents

Abstract

PURPOSE:To eliminate completely the occurrence of density irregularity or the like by performing uniform heat history control, by a method wherein in a thermal head driver having a heating resistor, preheating printing and main printing are performed at each divided block. CONSTITUTION:One line is divided into a plurality of terms and printing is successively performed by each divided block, preheating printing and main printing are performed by each divided block. That is, just after preheating printing block W1 has passed, main printing term W3 comes immediately at a specific term W2 interval. After execution of those preheating printing and main printing, the preheating printing and main printing in the following divided block are executed. This procedure is successively repeated with a specific period T. Therefore, when the number of division (m) is set as 4, a divided period T of one line will be constant for all divided heads H1-H4 as shown in A-D. Consequently, preheating block will not differ at each divided block. Thereby, preheating effect at each head becomes the same, and density irregularily after printing can be completely eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thermal head driving device suitable for application to a recording means built into a facsimile machine.

[Background of the Invention] In a facsimile machine, the transmitted image information signal is converted into a visible image by a recording means, and the image information is recorded.

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 30 used in such recording means.

In this example, a resistance heating element 40 is provided. As for the resistance heating element 40, one row is shown as being composed of n dots, and therefore, it is composed of n resistance heating elements 40a to 40n (n=2048) arranged in a line.

Therefore, a 2048-bit shift register is used as the shift register 32, 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 stored in this shift register 32 is transferred to the latch circuit 3.
It is latched to 5. After that, the corresponding resistance heating element 40a~
By simultaneously supplying print data to 4on, printing for one line is executed.

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 is divided into n/m units, and the n/m resistance heating elements can be sequentially divided and printed as one unit.

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

By the way, when the resistance heating element is divided into a plurality of parts and printed separately in this way, the amount of heat generated by the resistance heating element that is driven for printing is different from that of the resistance heating element that is not. Density unevenness may occur due to line 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 40 (FIGS. 6A and 6B).

The strobe pulses 81 to S4 are sequentially obtained immediately after the 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),
Preheating printing is performed 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 in consideration of how printing pulses were applied in the past to each resistance heating element.

The simplest method is to print on the resistance heating element 40 that did not print in the previous printing line.
The purpose is to apply print data for a longer time than when printing is made to the resistance heating element 40 that printed in the immediately previous print line.

[Problems to be Solved by the Invention] Incidentally, in the head driving device 30 that performs such thermal history control, as shown in FIG. Then, for the first time, the actual print data is sequentially added to each resistance heating element 40.

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 preheating print data is stored in one head H1 to H4.
In a conventional thermal head drive device, which performs divided printing in one stroke, and then sends the main print data one line at a time to the head for printing, the preheating print data and main print data are A disadvantage arises in that the spacing differs depending on the subsection of the head.

This has the disadvantage that thermal history control cannot be sufficiently effective for heads that are off for a long time.

Therefore, in this invention, such conventional problems are configured and easily solved, and in a thermal head drive device that uses a divided printing method with thermal history control, equal thermal history is applied to each divided head. This makes it possible to achieve control.

[Technical means for solving the problem] In order to solve the above-mentioned problem, the present invention uses a resistance heating element that divides one line into a plurality of sections and prints sequentially in each divided section. A thermal head drive device having the following is characterized in that preheating printing and main printing are performed for each divided section.

[Function] The composite print data applied to each split head is the preheat print data followed by the main print data, as in the past.

However, instead of sending preheating print data to all of the resistance heating elements, the configuration is such that preheating print data and main print data are sent to each of the divided heads H1 to H4.

That is, immediately after being driven by preheating print data, main print data is supplied to execute printing, and thermal history control for the next divided head is performed only after this is completed (
(See Figures 4A-B).

As a result, the interval between preheating printing and main printing becomes constant (=T), and uniform thermal history control is performed for each of the heads H1 to H4.

As a result, the effect of thermal history control appears uniformly in each splitting head, so that it is possible to eliminate the occurrence of density unevenness and the like.

[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, a document table 3 is provided that projects from the upper left to the lower right. These papers (collectively referred to as manuscripts) are optical reading means 10
Paper is fed to

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 disposed 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, the optical image information is converted into an electrical signal, that is, an image signal. Although the image signal is not shown, it can be stored in a memory or sent to a communication line through an image processing system.

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

17 shows the mounting of the CCD 15 on the board.

The original is conveyed downward at a speed corresponding to the original.
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 can be 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.
is rotatably provided, and this recording paper 21 is sent 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 may be used.

Therefore, when the recording paper 21 that has been completely 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 is recorded is conveyed for a predetermined length, the automatic cutter device 24 is driven to automatically cut the rear end of the recording paper 21. Therefore, although not shown, the automatic cutter device 24 includes a blade for cutting paper and a drive means for moving the blade up and down.

The automatically 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 image information signal that has been completely transmitted 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 and stored therein.

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

By supplying this composite print data to the head visiting circuit 30, desired printing can be executed.

Everything from the main memory 51 to the head drive device 30 is controlled based on instructions from the microcomputer 7o.

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 desired switching control is performed for each divided head to form composite print data. . 6
6 indicates its output terminal.

A control signal obtained from the microcomputer 7o is supplied to the terminal 67, and composite print data as shown in FIG. 4F is formed based on this control signal.

Incidentally, in the data processing circuit 60 shown in FIG. 3, composite print data as shown in FIG. 4 is formed, and this composite print data is supplied to the head drive circuit 30 to perform necessary thermal history control. The accompanying printing process is executed.

Next, an example of the operation of the divided printing process involving thermal history control will be explained with reference to FIG.

This invention is characterized in that when one line is divided into a plurality of periods and each divided section is sequentially printed, preheat 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, the preheating section will not be different 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, as the main print data in that divided printing section, the data latched in that divided printing section is used.

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 clock length of the transfer lock CK applied to the shift register 32 differs depending on each divided printing section, as shown in FIG.

Here, the preheat printing data is a. -do and the main print data is An=Dn, the number and contents of the composite print data supplied to the shift register 32 differ depending on which split head is driven next.

That is, the strobe pulse S1 causes the dividing head H
1 is driven, the dividing head H2 is driven by the strobe pulse S2, and the dividing head H3 is driven by the strobe pulse S3. Therefore, at the timing when the strobe pulse S3 is obtained, printing is performed for all dividing heads H1 to H4. If the data is not updated, the next strobe pulse S4 will cause the corresponding dividing head H to
4 cannot be printed using the corresponding print data.

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.

In this way, since the preheating print data differs depending on the immediately preceding preheating state, the data processing circuit 60 as shown in FIG.
, the current print data Ln and the previous print data Ln
The contents of the preheating print data will differ depending on the contents of -1.

Note that the above-mentioned preheating printing section W1 is 0 in this example.
, 15m5ec, main printing section W3 is 0°53m
5ec, and the blank interval W2 is selected to be slightly wider than the width of the latch pulse RP, and in this example, is selected to be about 10 μsec.

[Effects of the Invention] As explained above, in the present invention, in a thermal head drive device of a division printing method in which one line is divided into a plurality of sections and printing is performed sequentially in each divided printing section, each division is Preheat printing and main printing are executed for each section.

According to this, since the length of each divided printing section is equal, the preheating time becomes constant. This makes the preheating effect the same for each head, which has the practical benefit of eliminating density unevenness after printing.

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

[Brief explanation of the drawing]

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...Facsimile device 10...Optical reading means 20...Recording means 30...Head drive circuit 32...Shift register 35...Latch circuit 40...Resistive heating element 50...Thermal Head drive device 60...Data processing circuits H1 to H4...Divided head Patent applicant Konica Corporation

Claims (1)

[Claims] (1) In a thermal head drive device that has a resistance heating element that divides one line into multiple sections and prints sequentially in each divided section, preheat printing and main printing are performed for each divided section. A thermal head drive device characterized by: