JP2000108396A - Printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform controlling of divisional printing without causing a lower ing of printing quality due to density variation. SOLUTION: There is disclosed a printer wherein a plurality of heaters provided on a thermal head 5 are divided into plural groups and the heaters in each group are driven in a time-sharing manner, thereby performing one line of printing. One line of generation data corresponding to each of first to fourth energization is generated based on data for dividing stored in a ROM 32 on the basis of whether a line of real data stored in a printing data memory 33b to be printed in an odd number or an even number and the generated data is stored in a real printing data memory 33c. The printing is performed such that the driving order of the first to fourth energization in the plural groups of the heaters is changed corresponding to the printing of each line.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method of manufacturing a plurality of heating elements.
The present invention relates to a printing apparatus having a line-type thermal head arranged in a line.

[0002]

2. Description of the Related Art Generally, in a printing apparatus having a line-type thermal head, image data to be printed is converted into dot pattern data, and the dot data is read out one by one and sequentially printed out.

[0003] In a low-power printing apparatus driven by a battery power supply or the like, the power consumption accompanying the heat generation driving of the thermal head imposes a heavy burden. For this reason, in such a printing apparatus, the plurality of heating elements of the thermal head are divided into a plurality of groups, and the timing is shifted by one dot line data for each data corresponding to each of the plurality of divided groups. 2. Description of the Related Art A divided printing control method (divided printing control method) has been widely used in which current output is instantaneously limited to reduce the load on a power supply by dividing and printing output.

That is, in the divided printing control method in the conventional printing apparatus, while the recording paper is conveyed with a width of one dot in a sub-scanning direction orthogonal to the line direction (main scanning direction) of the thermal head, Printing output is sequentially performed for each of the plurality of divided heating element groups, and printing of one dot line data is performed.

FIG. 12 shows an example of a divided print control method of 4
This shows division printing control. The printing timing by the thermal head is controlled by a strobe signal via a printing control line, and one printing row is formed in one printing cycle.

[0006] The energizing time for the heating element is determined by the first to fourth times.
As shown in FIG. 12, in the first energization, the heating elements of numbers R1, R5, R9,... Are energized (corresponding to dots denoted by "1" in the figure), and so on. In the second energization, the numbers R2, R6, R10... In the third energization, the numbers R3, R7, R11.
Electric power is supplied to the heating elements 4, R8, R12,... (Corresponding to the dots with numerals in the figure).

[0007]

However, while the recording paper is conveyed at a width of one dot in the sub-scanning direction, print output is sequentially performed for each of a plurality of divided heating element groups of the thermal head. In the division printing control, since the heating element that generates heat by the second energization receives the residual heat of the adjacent heating element that generates heat by the first energization, the generated heat is greater than the heat generated by the first energization. Similarly, the heating element that generates heat by the third power supply becomes larger than the heat generated by the second power supply due to the residual heat of the adjacent heating element that generates heat by the second power supply, and the heat generator that generates heat by the fourth power supply The heat generated by the third energization is larger than the heat generated by the third energization due to the residual heat generated by the adjacent heating element that generates heat by the third energization.

As a result, in printing by a direct thermal method using thermal recording paper or a fusion transfer method using an ink ribbon, the color density on the recording paper by the second current becomes larger than the color density on the recording paper by the first current.
Similarly, the color density on the recording paper by the third energization becomes the second color.
The color density becomes higher than the color density due to energization, and the color density on the recording paper by the fourth energization becomes higher than the color density due to the third energization. That is, as represented by the size of the circle in the print sequence shown in FIG. 12, the color density of each dot differs for each group of the heating elements.

As shown in FIG. 12, when dots of the same color density continue in the sub-scanning direction of the thermal head,
The density of a line pattern that is continuous in the sub-scanning direction becomes uneven and is visually recognized. Therefore, in particular, when performing density gradation control for expressing the gradation by the color density of the recording paper,
The print quality deteriorates due to the density unevenness.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-described problems, and has as its object to provide a printing apparatus capable of performing divided printing control without causing a decrease in print quality due to uneven density.

[0011]

A printing apparatus according to the present invention divides a plurality of heating elements provided in a thermal head into a plurality of groups, and drives the heating elements in a time-division manner for each of the plurality of groups. A printing apparatus that prints one line by using a printing control unit that changes a driving order among the plurality of groups of the heating elements that are driven in a time-division manner every time a predetermined number of lines are printed.

According to such a printing apparatus, since the driving order among a plurality of groups of heating elements is not constant,
The effect of the residual heat of the heating element has no regularity, and dots having different shades are appropriately arranged on the recording paper. Therefore, the density of the continuous line pattern becomes uneven and becomes difficult to be visually recognized. Even when the density gradation control for expressing the gradation is performed, the print quality does not significantly deteriorate.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a side sectional view showing a configuration of a printer unit of a printing apparatus according to an embodiment of the present invention.

This printing apparatus has a small hexahedral main body case 1, and a front face 1a is provided with a key portion 12 and a recording paper discharge port 2 to be described later.

Inside the printing apparatus, a platen roller 4, a thermal head 5, and a pair of transport rollers 6 and 7 are provided opposite to each other at positions on both sides along the recording paper transport path. A cutter 8 is provided immediately before the outlet 2.

A plurality of dot heating elements 5a are provided in a line at a contact portion of the thermal head 5 with the platen roller 4, and the thermal head 5 has a head driving motor 3a.
9 (see FIG. 2), a structure in which an end of the heating element 5a can move in a direction in which it contacts the platen roller 4 and in a direction in which it is separated. The thermal head 5 has a power supply OF
In the state of F and the printing operation state, the heating element 5a is moved and set in the separating direction only in the printing operation state, and is moved and set in the direction in which the heating element 5a contacts the platen roller 4.

The transport rollers 6 and 7 are rotated by driving one of the rollers 6 by a paper feed motor 37 (see FIG. 2) described later. The transport rollers 6 and 7 transport the recording paper 9b. When they are set in the printer unit, they are separated from each other.

The printing apparatus according to the present embodiment can use a roll paper 9a as a thermal recording paper or a recording paper 9b of a predetermined size as a printing medium (FIG. 1 shows the recording paper 9b).
Is shown). When the roll paper 9a is used, it is arranged at a position indicated by a broken line above the printer unit. The roll paper 9 is mounted in a power-off state, pulled out to a recording paper transport path between the platen roller 4 and the thermal head 5, and between the transport rollers 6 and 7, and further to a cutter 8 and a recording paper discharge port. Set through 2.

During the printing operation of the thermal head 5 on the roll paper 9a, the roll paper 9a is conveyed and discharged in the direction shown by the arrow A with the rotation of the conveying rollers 6 and 7 in the direction of the arrow i. As the roll paper is wound, the paper is conveyed backward in the direction indicated by arrow B and pulled back.

When the recording paper 9b is used, when the recording paper 9b is inserted from the recording paper outlet 2, the leading end of the recording paper 9b is detected by the paper sensor 15, and the transport rollers 6, 7 are driven. The recording paper 9b is conveyed in the direction of arrow B. After the leading edge of the recording paper 36 is detected, the recording paper 9
The recording paper 9b is conveyed by a predetermined length until the rear end of the recording paper 9b reaches the position of the cutter 8. This state is the start position, and the conveyance is performed in the same manner as in the case of the roll paper 9a. In the printing start state, the leading end of the recording paper 9b projects outside through the opening 3 provided on the back side 1b of the main body case 1. In the following description, it is assumed that printing is performed using the recording paper 9b.

Here, the transport distance of the recording paper 9b by the transport rollers 6, 7 accompanying the driving of the paper feed motor 37 is determined by the dot width of one line printing by the heating element 5a of the thermal head 5 in accordance with the division printing control. It is set equal to the divided pitch. For example, in the case of performing four-division printing control, the dot width of one-line printing is divided into four and transported in quarter pitch units.

FIG. 2 is a block diagram showing the configuration of the electronic circuit of the printing apparatus.

The electronic circuit of the printing apparatus includes a control unit 31 including a CPU.

The control unit 31 includes the key unit 12 and the paper sensor 15
A system program stored in advance in the ROM 32 is started in response to an input signal from the CPU 32, and the operation of each section of the circuit is controlled using the RAM 33 as a work memory.

The control unit 31 includes a key unit 12, a paper sensor 1
5, an input / output control unit (I / O) 34 for inputting image data from an external device and the like, in addition to the ROM 32 and the RAM 33, and a thermal head 5 for printing.
A head driver 35 for driving the heating element 5a, a motor driver 36 for driving a paper feed motor (step motor) 37, and a motor driver 38 for driving a head moving motor (DC motor) 39 are connected.

The heating elements 5a of the thermal head 5 are arranged in a line (m) (for example, 128) in a direction (main scanning direction) orthogonal to the transport direction (sub scanning direction) of the roll paper 9a or recording paper 9b. Provided. The heating element 5a provided in the thermal head 5 is driven by a divided printing control method and is divided into a plurality of groups. One dot line data (one line of actual data) is divided into a plurality of groups. Driving is performed with the timing shifted for each data corresponding to each group.

An electronic circuit of the printing apparatus includes a battery power supply 40.
It is driven by the power supply from.

The ROM 32 stores, in addition to the system program, logical product data for divided printing, font patterns, and the like for generating print data in accordance with the divided print control based on image data at the time of print processing. I have. As the logical product data for divided printing, data representing the number of patterns corresponding to the divided printing is prepared. For example, when performing the four-divided printing, four patterns are prepared.

The RAM 33 stores an image data memory 33a in which original image data (actual data) is stored, and prints one line of actual data to be printed in the image data stored in the image data memory 33a. Data memory 3
3b (printer buffer), an actual print data memory 33c for storing one line of generation data used for actual printing corresponding to each of the plurality of groups of the heating elements 5a
(Line buffer), a print address memory 33d indicating the position of a line to be printed of the image data stored in the image data memory 33a, and the like.

FIG. 3 is a block diagram for explaining the flow and control of data until the printing apparatus performs printing.

The image data memory 33a stores one image data (actual data) to be printed as dot pattern data.

In printing the dot pattern data (actual data) stored in the image data memory 33a, the print data memory 33b sequentially prints the last row of dot pattern data from the top row of dot pattern data for each transport operation for one printing cycle. Are sequentially read out and stored one by one line data (actual data for one line) up to the dot pattern data. The position of the line to be read is managed by data stored in the print address memory 33d.

FIG. 4 shows how one line of actual data is read. For example, when a screen display of 120 dots vertically and 160 dots horizontally is performed as shown in FIG. 4B, the origin (0, 0) is used as a reference in the image data memory 33a as shown in FIG. The data of each dot is successively stored for each column. That is, the first column (0,
0) to (0,120), second column (1,0) to (1,12)
, (160, 0) to (160, 120) are stored in the image data memory 33a.

The image data stored in the image data memory 33a is read in the direction (1) taken from the origin (0, 0) of the image shown in FIGS.
(A) A point (12) that is diagonal to the origin of the image shown in (d)
0, 160).
Actual data for one line is sequentially read in the order indicated by any of the fetching directions and stored in the print data memory 33b.

The control section 31 performs an AND operation on the logical product data for division printing (hereinafter, abbreviated as division data) stored in the ROM 32 with respect to the actual data for one line stored in the print data memory 33b. The heating element 5a
The one-line generation data used for actual printing corresponding to each of the plurality of groups is generated and stored in the actual print data memory 33c.

FIG. 5 is a diagram showing an example of the division data stored in the ROM 32. The printing apparatus according to the present embodiment performs four-division printing control, and generates data for one line corresponding to each of the first to fourth energizations, ie, drives the heating element 5a of the thermal head 5 in four divisions. There are four patterns for generating the print data. FIG. 5A shows one-byte data “88”.
FIG. 5B is a diagram showing a pattern A represented by “h”, and FIGS. 5B to 5D similarly show “44h” and “2”, respectively.
Patterns B, C, D represented by "2h" and "11h"
FIG. In the patterns A, B, C, and D, black data for two dots is provided at positions different from each other.

While the recording paper 9b is conveyed by one dot in the sub-scanning direction, one line of actual data (dot pattern data) read from the top row of the image data memory 33a is divided into division data (four patterns). A to D) are logically multiplied by 8 dots each to generate print data (one-line generation data) to be used in each energization of the four-part printing.

FIG. 6 shows an example in which the actual data for one line stored in the print data memory 33b is obtained by using the division data.
The example which produces | generates the production | generation data for a line is shown. However, FIG. 6 shows only one byte of real data of one line of real data for the sake of simplicity.

In the printing apparatus according to the present embodiment, the first to fourth energizations in one printing cycle depend on whether the actual data for one line read from the image data memory 33a is odd or even. In accordance with the above operation, the use order of the division data for generating the print data (generation data for one line) corresponding to each energization is switched.

The CPU 31 has a print address memory 33d.
It is determined whether the read actual data for one line is an odd-numbered line or an even-numbered line, based on the position of the line to be printed, which is managed in.

If the data is odd-numbered one-line actual data, the divided data is used in the order of patterns A, B, C, and D to generate one-line generated data for the first to fourth energizations. Are sequentially generated. If the data is even-numbered one-line actual data, one-line generated data for the first to fourth energization is sequentially generated using the divided data in the order of patterns D, C, B, and A. I do.

The generated data for one line is sequentially stored in the line buffer 33c, read out by the head driver 35 as follows, and each heating element 5a of the thermal head 5 is driven.

That is, as shown in FIG. 3, the generated data for one line stored in the line buffer 33c is transmitted through the shift register 50a of the gate array (G / A) 50 of the head driver 35 to the timing of the clock signal. Are sequentially stored one bit at a time in the shift register 51, and furthermore, a latch circuit 52 according to a latch signal from the CPU 31.
Is latched.

The latch circuit 52 includes the thermal head 17
The plurality of AND gates 53-1 to 53-128 corresponding to each of the plurality of heating elements 5a arranged in a direction orthogonal to the conveying direction of the recording paper P (128 heating elements 5a (R1
To R128) are connected). AND gates 53-1 to 53-128 are CPU
Time-division driving is controlled for each of a plurality of groups of the heating elements 5a in accordance with a strobe signal from 31. Although not shown, when performing the four-split printing control, the strobe signals 1 to 4 corresponding to the first to fourth energizations are sent to the CPU 31.
Output from

The strobe signal 1 drives the heating elements 5a belonging to the first group in order to perform printing with one line of generated data generated using the pattern A of the division data. Similarly, the strobe signal 2 drives the heating elements 5a belonging to the second group in order to print with one line of generated data generated using the pattern B of the division data, and the strobe signal 3 The heating element 5a belonging to the third group is driven in order to perform printing using the generated data for one line using the pattern C of the data for use, and the strobe signal 4 is generated using the pattern D of the data for division. The heating elements 5a belonging to the fourth group are driven to perform printing using the generated data for one line.

In the printing operation of one line (one printing cycle),
If the actual data for one line read from the image data memory 33a to be printed is an odd number, the strobe signals 1, 2, 2,.
The heating elements 5a are output in the order of 3, 4 and are driven in the order of the first to fourth groups. When the generated data for one line is an even number, the heating elements 5a are output in accordance with the first to fourth energizations. The heating elements 5a are output in the order of the strobe signals 4, 3, 2, and 1 and are driven in the order of the fourth to first groups.

When the time-division (four-division) printing operation for one line is completed, the printing of the next line is performed in the same manner, and the operation is continued until the last line of the actual data. The recording paper 9b is conveyed by a predetermined distance in accordance with printing of the thermal head 5 for each line. As a result, an image corresponding to the image data stored in the image data memory 33a is printed on the recording paper 9b.

As described above, the plurality of heating elements 5a provided on the thermal head 5 have four patterns A, B, C, and D.
By driving the generated data for one line generated by using the data for division by the first to fourth energization, the heating elements 5a are driven in a time-division manner for each of a plurality of groups, and the image data memory By changing the use order of the divisional data of the four patterns in accordance with whether the line of the actual data for one line read from the line 33a is an even-numbered line or an odd-numbered line, and by performing drive control by a strobe signal, The driving order of the plurality of groups of the heating elements 5a to be time-divisionally driven is changed for each line.

FIG. 7 shows a sequence for printing by driving the heating element 5a based on the one-line generation data stored in the actual print data memory (line buffer) 33c shown in FIG. 3, and transporting the recording paper 9b. FIG. 6 is a diagram illustrating the timing of excitation of the paper feed motor 37 for one printing cycle.

As shown in FIG. 7, the generated data for one line stored in the actual print data memory (line buffer) 33c includes first to fourth data generated by each of the patterns A to D of the division data. Data is stored in the shift register 51 according to the timing of the clock signal,
The data is latched by the latch circuit 52 at the timing of the latch signal from the CPU 31. The strobe signal includes first to fourth strobe signals.
The heating elements 5a are output according to the timing of energization, and drive the heating elements 5a for each group of the heating elements 5a according to the first to fourth data. Accordingly, in each of the first to fourth energizations, the corresponding first latched by the latch circuit 52 is performed.
Printing is performed using the fourth to fourth data.

The excitation of the paper feed motor 37 is switched in accordance with the first to fourth energization timings, and the recording paper 9b is shifted by １ ／ pitch every energization in one printing cycle for printing one line. It is controlled to be transported.

Next, the operation of the printing apparatus according to the present embodiment will be described.

FIG. 8 is a flowchart showing a printing process by the printing apparatus.

First, when the "print" key provided on the key section 12 is operated, the CPU 31 clears the print data memory 33b, the actual print data memory 33c, and the print address memory 33d of the RAM 33, and also executes a print process. Initial processing for execution is executed (step A1).

Here, when the recording paper 9b is inserted from the recording paper discharge port 2, when the paper sensor 15 detects the leading end of the recording paper 9b, the motor driver 36 controls the paper feed motor (step motor) 37. Driven transport rollers 6, 7
Is rotated, the recording paper 9b is pulled in and conveyed (step A3).

Thereafter, the rear end of the recording paper 9b is
(Step A4), the head driver motor 39 is driven by the motor driver 38 to move the thermal head 5 in the direction of the platen 4 (head down).
The heating element 5a of the thermal head 5 is pressed against the lower surface of the recording paper 9b (step A5).

The CPU 31 sets a print address C indicating the line position of the image data in the print address memory 33d, and prints one line (one line of actual data) of the image data stored in the image data memory 33a.
Is read from the first column and stored in the print data memory 33b (step A6).

Here, the actual data for one line stored in the print data memory 33b is divided as described above according to whether it is an odd-numbered line or an even-numbered line of the image data. Data (patterns A, B,
C, D), and the generated data for one line to be actually printed is generated and stored in the actual print data memory (line buffer) 33c (see FIG. 3). The printing is performed by driving only the corresponding heating element 5a (steps A8 and A9).

If the actual data for one line is the odd-numbered line, the first divided printing control (step A8) shown in the flowchart of FIG. 9 is executed, and if it is the even-numbered line, Then, the second divided printing control (step A9) shown in the flowchart of FIG. 10 is executed.

The first divided printing control will be described with reference to the flowchart shown in FIG.

First, the CPU 31 sets the print data memory 3
ROM for the actual data for one line stored in 3b
Then, an AND process for performing a logical product with the pattern A of the division data stored in the memory 32 is performed to generate one line of generated data, and the generated data is stored in the actual print data memory 33c (step B1). In the AND processing, when the pattern A of the division data is one byte as shown in FIG. 5, logical data is obtained for each byte of the actual data for one line to generate generated data for one line.

The 1 stored in the actual print data memory 33c
The line generation data (first data) is supplied to the latch circuit 5 of the head driver 35 by a latch signal from the CPU 31.
2 (see FIG. 3). The CPU 31 outputs the strobe signal 1 and drives the thermal head 5 by executing the first energization.
Execute printing using the line generation data (step B
2, B3). Here, the CPU 31 controls the motor driver 3
6 to switch the excitation of the paper feed motor 37 to convey a quarter pitch of the conveyance amount for one-line printing (step B).
4).

Next, the CPU 31 sets the print data memory 3
ROM for the actual data for one line stored in 3b
Then, an AND process for performing a logical AND operation with the pattern B of the division data stored in 32 is performed to generate one line of generated data, and stored in the actual print data memory 33c (step B5). In the AND processing, when the pattern B of the division data is one byte as shown in FIG. 5, the logical product is calculated for each byte of the actual data for one line to generate the generated data for one line.

The 1 stored in the actual print data memory 33c
The line generation data (second data) is supplied to the latch circuit 5 of the head driver 35 by a latch signal from the CPU 31.
2 (see FIG. 3). The CPU 31 outputs the strobe signal 2 and drives the thermal head 5 by executing the second energization, and the 1
Execute printing using the line generation data (step B
6, B7). Here, the CPU 31 controls the motor driver 3
6 to switch the excitation of the paper feed motor 37 to convey a quarter pitch of the conveyance amount for one-line printing (step B).
8).

Next, the CPU 31 sets the print data memory 3
ROM for the actual data for one line stored in 3b
Then, an AND process for performing an AND operation with the pattern C of the division data stored in the memory 32 is performed to generate one line of generated data, and the generated data is stored in the actual print data memory 33c (step B9). In the AND processing, when the pattern C of the division data is one byte as shown in FIG. 5, logical data is obtained for each byte of the actual data for one line to generate generated data for one line.

The 1 stored in the actual print data memory 33c
The line generation data (third data) is supplied to the latch circuit 5 of the head driver 35 by a latch signal from the CPU 31.
2 (see FIG. 3). The CPU 31 outputs the strobe signal 3 and drives the thermal head 5 by executing the third energization, and the 1 latched by the latch circuit 52
Execute printing using the line generation data (step B
10, B11). Here, the CPU 31 switches the excitation of the motor of the paper feed motor 37 by the motor driver 36, and causes the motor to carry a １ ／ pitch of the carry amount of one-line printing (step B12).

Next, the CPU 31 sets the print data memory 3
ROM for the actual data for one line stored in 3b
Then, an AND process for performing an AND operation with the pattern D of the division data stored in the memory 32 is performed to generate one line of generated data, and the generated data is stored in the actual print data memory 33c (step B13). In the AND processing, the pattern D of the division data
Is 1 byte as shown in FIG. 5, the logical product is calculated for each byte of the actual data for one line to generate the generated data for one line.

The 1 stored in the actual print data memory 33c
The line generation data (fourth data) is supplied to the latch circuit 5 of the head driver 35 by a latch signal from the CPU 31.
2 (see FIG. 3). The CPU 31 outputs the strobe signal 4, drives the thermal head 5 by executing the fourth energization, and outputs the one latched by the latch circuit 52.
Execute printing using the line generation data (step B
14, B15). Here, the CPU 31 switches the excitation of the motor of the paper feed motor 37 by the motor driver 36, and causes the motor to carry a 印刷 pitch of the carry amount of one-line printing (step B16).

With the above processing, the print data memory 33
The four-division printing for the odd-numbered one-line actual data stored in b is completed.

The second divided printing control will be described with reference to the flowchart shown in FIG.

First, the CPU 31 sets the print data memory 3
ROM for the actual data for one line stored in 3b
Then, an AND process for performing an AND operation with the pattern D of the division data stored in the memory 32 is performed to generate generated data for one line, and stored in the actual print data memory 33c (step C1). In the AND process, when the pattern D of the division data is one byte as shown in FIG. 5, the logical product is obtained for each byte of the actual data for one line to generate the generated data for one line.

The 1 stored in the actual print data memory 33c
The line generation data (first data) is supplied to the latch circuit 5 of the head driver 35 by a latch signal from the CPU 31.
2 (see FIG. 3). The CPU 31 outputs the strobe signal 4, drives the thermal head 5 by executing the first energization, and outputs the 1 latched by the latch circuit 52.
Execute printing using the line generation data (step C
2, C3). Here, the CPU 31 controls the motor driver 3
6 to switch the excitation of the paper feed motor 37 to convey 1/4 pitch of the conveyance amount for one-line printing (step C).
4).

Next, the CPU 31 sets the print data memory 3
ROM for the actual data for one line stored in 3b
Then, an AND process for performing a logical AND operation with the pattern C of the division data stored in 32 is performed to generate generated data for one line, and stored in the actual print data memory 33c (step C5). In the AND processing, when the pattern C of the division data is one byte as shown in FIG. 5, logical data is obtained for each byte of the actual data for one line to generate generated data for one line.

The 1 stored in the actual print data memory 33c
The line generation data (second data) is supplied to the latch circuit 5 of the head driver 35 by a latch signal from the CPU 31.
2 (see FIG. 3). The CPU 31 outputs the strobe signal 3 and drives the thermal head 5 by executing the second energization.
Execute printing using the line generation data (step C
6, C7). Here, the CPU 31 controls the motor driver 3
6 to switch the excitation of the paper feed motor 37 to convey 1/4 pitch of the conveyance amount for one-line printing (step C).
8).

Next, the CPU 31 sets the print data memory 3
ROM for the actual data for one line stored in 3b
Then, an AND process for performing a logical product with the pattern B of the division data stored in the memory 32 is performed to generate generated data for one line, and the generated data is stored in the actual print data memory 33c (step C9). In the AND processing, when the pattern B of the division data is one byte as shown in FIG. 5, the logical product is calculated for each byte of the actual data for one line to generate the generated data for one line.

The 1 stored in the actual print data memory 33c
The line generation data (third data) is supplied to the latch circuit 5 of the head driver 35 by a latch signal from the CPU 31.
2 (see FIG. 3). The CPU 31 outputs the strobe signal 2, drives the thermal head 5 by executing the third energization, and outputs the signal 1 latched by the latch circuit 52.
Execute printing using the line generation data (step C
10, C11). Here, the CPU 31 switches the excitation of the motor of the paper feed motor 37 by the motor driver 36 and causes the paper to be conveyed by ピ ッ チ pitch of the conveyance amount for one-line printing (step C12).

Next, the CPU 31 sets the print data memory 3
ROM for the actual data for one line stored in 3b
Then, an AND process for performing a logical AND operation with the pattern A of the division data stored in the memory 32 is performed to generate one line of generated data, and the generated data is stored in the actual print data memory 33c (step C13). In the AND processing, the pattern A of the division data
Is 1 byte as shown in FIG. 5, the logical product is calculated for each byte of the actual data for one line to generate the generated data for one line.

The 1 stored in the actual print data memory 33c
The line generation data (fourth data) is supplied to the latch circuit 5 of the head driver 35 by a latch signal from the CPU 31.
2 (see FIG. 3). The CPU 31 outputs the strobe signal 1, drives the thermal head 5 by executing the fourth energization, and outputs the signal 1 latched by the latch circuit 52.
Execute printing using the line generation data (step C
14, C15). Here, the CPU 31 switches the excitation of the motor of the paper feed motor 37 by the motor driver 36 and causes the motor to carry a １ ／ pitch of the carry amount of one-line printing (step C16).

With the above processing, the print data memory 33
The four-division printing for the even-numbered one-line actual data stored in b is completed.

Here, the CPU 31 counts up (+1) the print address C in the print address memory 33d (step A10), and prints one line of the actual data of the last line of the image data stored in the image data memory 33a. It is determined whether or not Cn has been completed (step A11).

If the CPU 31 determines that the print address C is not the same as Cn and that printing for one line of the last line of the actual data has not been completed, the CPU 31 proceeds to step A.
Returning to the processing of step 6, the generated data for one line corresponding to the counted print address is read out, and one line is printed by the four-division printing control in the same manner as described above.

The printing apparatus according to the present embodiment executes the first print control on the actual data for one line indicated by the print address in the print address memory 33d if it is an odd number (step A8), and executes an even number. If so, the second divided printing control is executed (step A9). Therefore, every time one line is printed, C is set at each of the first to fourth energization timings.
The order of the strobe signals output from the PU 31 is reversed, and the driving order among a plurality of groups of the heating elements 5a disposed on the thermal head 5 is changed.

As a result, the print sequence of each line is as shown in FIG. In other words, in the printing of the odd-numbered line and the even-numbered line, the direction of the dot at which the color density on the recording paper increases due to the effect of the residual heat of the heating element 5a that generates heat by each energization. For this reason, the density of the line pattern continuous in the sub-scanning direction does not become uneven, and the print quality is not deteriorated by the density unevenness.

When printing of all lines of the image data stored in the image data memory 33a is completed (step A11), the CPU 31 stops driving the thermal head 5 by the head driver 35 and stops printing.

The paper feed motor 37 is continuously driven by the motor driver 36, and the transport rollers 6, 7 and the platen roller 4 are rotated in the direction of discharging the recording paper 9b, so that the recording paper 9b is discharged. It is discharged from the outlet 2 (step S12).

Then, the rear end of the recording paper 9b passes from the platen roller 4 to the position of the conveying rollers 6 and 7, and further passes the position of the paper sensor 15, so that the paper sensor 15
Detects that the recording paper 9b has been discharged from the recording paper discharge port 2 to the outside (step A13).
Stops the driving of the transport roller 37 by the motor driver 36, stops the paper feed by the transport rollers 6, 7 and the platen roller 4, and further drives the head moving motor 39 by the motor driver 38 to move the thermal head 5 to the platen roller. 4 (head-up) (step A15).

Thus, the image data memory 33a
The first print processing (FIG. 9) or the second print processing (FIG. 10) is executed depending on whether the actual data for one line read from the first line is an odd-numbered data or an even-numbered data. Since the driving order among the plurality of groups 5a is not constant, the effect of the residual heat of the heating element 5a does not have regularity, and dots having different shades are appropriately arranged on the recording paper 9b. . Therefore, the density of the continuous line pattern becomes uneven and becomes difficult to be visually recognized. Even when the density gradation control for expressing the gradation is performed, the print quality does not significantly deteriorate.

In the above description, the case where four-division printing control is performed is described as an example. However, any case where two or more division printing control is performed can be applied. is there.

[0090]

As described above, according to the printing apparatus of the present invention, the driving order between a plurality of groups of heating elements driven in a time-division manner is changed every time a predetermined number of lines are printed. Since the driving order among the plurality of groups of the heating elements is not constant, the influence of the residual heat of the heating elements does not have a regularity, and dots having different shades are appropriately arranged on the recording paper. Therefore, the density of the continuous line pattern becomes uneven and becomes difficult to be visually recognized. Even when the density gradation control for expressing the gradation is performed, the print quality does not significantly deteriorate.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a configuration of a printer unit of a printing apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of an electronic circuit of the printing apparatus.

FIG. 3 is a block diagram for explaining the flow and control of data until the printing apparatus performs printing.

FIG. 4 is a diagram showing a state of reading actual data for one line.

FIG. 5 is a view showing an example of division data stored in a ROM 32;

FIG. 6 is a diagram showing an example in which generated data for one line is generated by using division data for real data for one line stored in a print data memory 33b.

FIG. 7 shows a sequence for printing by driving the heating element 5a based on the one-line generation data stored in the actual print data memory (line buffer) 33c shown in FIG.
FIG. 9 is a diagram showing the excitation timing of the paper feed motor 37 for conveying b for one printing cycle.

FIG. 8 is a flowchart illustrating a printing process performed by the printing apparatus.

FIG. 9 is a flowchart for describing first divided printing control.

FIG. 10 is a flowchart for explaining a second divided print control.

FIG. 11 is a view showing an example of printing by four-division printing control in the embodiment.

FIG. 12 is a diagram showing a printing example by conventional four-division printing control.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Body case, 2 ... Recording paper discharge port, 3 ... Opening, 4 ... Platen roller, 5 ... Thermal head, 5a ... Heating element, 6, 7 ... Conveying roller, 6a ... Conveying roller rotating shaft, 8 ... Cutter, 9b ... Recording paper, 15 ... Paper tip sensor, 31 ... Control unit (CPU), 32 ... ROM, 33 ... RAM, 33a ... Image data memory, 33b ... Print data memory, 33c ... Actual print data memory, 33d ... Print address memory 34, an input / output control unit (I / O), 35, a head driver, 36, a step motor driver, 37, a paper feed motor, 38, a motor driver, 39, a head moving motor, 40, a battery power supply.

Claims (3)

[Claims] 1. A printing apparatus which divides a plurality of heating elements provided in a thermal head into a plurality of groups, and drives one of the plurality of heating elements in a time-division manner to print one line. A printing apparatus, comprising: a printing control unit that changes a driving order among the plurality of groups of the heating elements that are divided and driven each time a predetermined number of lines are printed. 2. The printing apparatus according to claim 1, wherein adjacent heating elements of the thermal head belong to different groups. 3. The printing apparatus according to claim 1, wherein the predetermined line is one line.