JPS6072758A - Drive control for thermal head - Google Patents

Abstract

PURPOSE:To enable a high-speed printing without lowering the printing quality by applying a pulse with a uniformly set pulse width to a heat generating body at the position of a dot under a specified condition. CONSTITUTION:The printing pulse Px shall have the pulse width t3 the same when a printing pulse P(x-3) exists at the dot position D(x-3) three dots ahead of the dot position Dx for printing and when a printing pulse P(x-2) exists at the dot position D(x-2) two dots ahead of the Dx. The pulse is applied to each heat generating body with the pulse width t3 in the almost middle (t1<t3>t2) between the pulse width t1 determined when the printing pulse P(x-2) two dots ahead of Dx by a 2-stage control system and the pulse width t2 determined when the printing pulse P(x-3) exists three dots ahead of Dx by 3-stage control system. Thus, though a printing pulse exists two dots ahead of the dot position for printing with respect to the heat generating body 1 and it exists three dots ahead of Dx for the heat generating body 2, both are applied with the pulse width equivalant to application time t3 uniformly thereby enabling the printing with an equalized printing density.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a drive control method for a thermal spatula r in which a plurality of heating elements are arranged in a row.

[Technical background of the invention and its problems]

For example, in a printer using a thermal head in which a plurality of heating elements are arranged in a line in the vertical direction, one heating element and the recording paper are moved relative to each other in a direction perpendicular to the arrangement direction of the heating elements,
Dot matrix printing is performed by selectively adding markings to each heating element.

What is the problem with the above thermal head?

Even after the electricity is turned off to the heating element, residual heat remains in the heating element for a certain period of time, and due to the presence of this residual heat, unevenness (shading) occurs in the print density when the dots are continuous, so a cooling period is required. , the printing speed will be limited.

However, in recent years, the amount of information has increased and the operating speed of other digital systems has improved, and printers are also required to be faster. As a way to solve this problem of increasing the printing speed, the pulse width of the printing pulse applied to the heating element at the position of the dot to be printed is adjusted depending on whether or not there was a printing pulse at the dot position before the dot. An Ω step control method is known as a drive control method for controlling to an appropriate value. The difference in the number of stages is caused by how many dots in front of the dot position to be printed are considered.

First, the Ω step control method will be explained (Fig. 1 (A)
, (B), (0)), Figure 1 (A) shows an example of printing, in which three heating elements are arranged in the vertical direction.
3 are arranged in a straight line and are fed in the direction of the arrow with respect to the recording paper. At each dot position in rows 8 to 1, the hatched area indicates the dot printed by the heat generated by the luth when printed on the heating element, and the cross-hatched area indicates the area stretched by residual heat. It shows. Note that the following explanation assumes high-speed printing without considering low-speed printing. For high-speed printing, the same heating element can be used to generate heat continuously.

Since unevenness occurs in the print density due to the influence of the above-mentioned residual heat, it is common to print every other dot. for example,
If we look at the heating element / in Fig. 7fA), it does not print in the 0th column following Dbl in column b, but always prints Ddl.

Now, the one-step control method means that when printing consecutive dots (when the same heating element is made to generate heat continuously), the pulse width during printing at the dot position to be printed is
When a printing nozzle ξ pulse exists at the dot position before the dot, the pulse width is made narrower by an appropriate width than the pulse width of the printing/Q pulse before the dot and gutter to equalize the amount of heat generated. That is, as shown in FIG. 1(B), when printing DdI following dot Dbt, the pulse width t of dot Dd1 (11 is r) generates more heat than the pulse width tb of dot Db. It should be narrowed depending on the degree of residual heat in the body. The degree of narrowing can be adjusted experimentally so that the printing density is the same as that of the heating element in the absence of residual heat.This aspect is the same for the heating element 3.On the other hand, the zero heating element Since the dots Dc and Fog are separated by three dots, the pulse width tf2 of the applied pulse Pf of the dot Df to be printed is the same as the pulse width tag of the applied pulse Fog of the dot Dc2. Figure 1 (C1) shows the heat generation waveform in each heating element. In this figure, the dotted line S indicates the heat generation temperature at which one heating element can print. From Figure 7 (0) As can be seen, since the pulse width tal of the applied pulse Pdl is narrower than the pulse width tbl of the applied pulse Pbl, the peaks of the heat generation of the 5 heating elements 1 and 3 coincide, making it possible to print with the same density. However, in terms of heating elements.

Pulse width ta2 of applied pulse Pct and applied pulse Pf
Since the pulse width tf2 of 2 is the same, when printing Dfl, due to the action of residual heat remaining in the heating element.

The peak of heat generation due to the applied pulse Pf is the applied pulse P.
It was higher than the exothermic peak due to c2 by the difference H.

For this reason, the dot Df is printed darker than the dot DO2, and moreover, there is a high amount of residual heat K at the end of printing on the dot Dfi, and this residual heat causes the unevenness that occurs on Pv)Df2 to occur on Ptsu)Dog. It was larger than the unevenness and the printed characters were distorted.

Next, the three-stage control system will be explained (see Figure 3 (Multiple).
, (Bl, (see 01)) is a method that considers whether or not a printing pulse exists at a dot position three dots before the dot position to determine the pulse width during printing at the dot position to be printed. Of course, the above-mentioned Ω step control method is also used.That is, as shown in Fig. 1 (B), focusing on 1 heating element, dots Dc, 3,
Dot on the dot Df! exists, so the printing pulse Pf of dot Df! The pulse width tf of Dc2 is made narrower than the pulse width tc* of the printing pulse PCIlI of Dc2.・Zorusu width tf! The method for determining is the same as the Ω step control method.

This three-stage control method is superior to the two-stage control method in that it takes into account the presence or absence of dots in front of the dot, and also improves printing quality because the influence of residual heat can be kept away by the amount of printing radius. be able to. However, since a large amount of information is handled to determine the printing/glue width of the dots to be printed, the control circuit and control program become complex, and there is a limit to high-speed printing.

[Purpose of the invention]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a thermal head drive control method that enables high-speed printing with a simple device configuration and without deteriorating print quality.

[Summary of the invention]

In order to achieve the above object, a thermal head drive control method according to the present invention is configured as follows.

First, the present invention moves a thermal head in which a plurality of heating elements are arranged in a line relative to the recording paper in a direction perpendicular to the direction in which the heating elements are arranged, so as to move the thermal head in front of the do and dot positions where printing is to be performed. The present invention assumes a drive control method for a thermal spatula r that performs high-speed printing using the P dot matrix method by individually applying voltage to each heating element that has a pulse width determined according to the continuous state of printing pulses at the dot position. shall be.

As shown in Fig. 3, the main feature is that the printing pulse P
When there is a printing nozzle P(x-a) at the P point position X-s which is three dots before the dot position Dx to be printed, and when there is a printing nozzle P(x-a) at the position D(X −
The pulse width t3 is the same as in the case where the printing pulse P(x2), 6ζ exists in 2), and this pulse width t3 is the same as when the printing pulse P(x- 2
) is determined when the pulse width t1 and the three-step control method are used to print three or more blocks in front of the pulse width t1 (x-3).
is applied to each heating element as a pulse width tl<ts>t-) which is approximately the middle of the pulse width t2 determined when .

[Embodiments of the invention]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a thermal head drive control method according to the present invention will be described below with reference to the drawings.

FIG. 9 shows a control and drive circuit for implementing the drive control method according to the present invention. 1, print data l sent from a host device (not shown) is input to a control circuit S. The control circuit S is for developing the input print data into print head data (dot pattern) and sequentially sending it to the memory circuit B, as well as determining the print pulse width.

1 is a counter circuit for controlling the printing pulse width (current application time) applied to one heating element, and its output is sent to the output circuit g. The output circuit g is a circuit for driving the first and second parts 9.

Next, the drive control method according to the present invention will be explained with reference to FIGS. IA), (B), and (0). First, we will focus on the heating element 1. When a print data tag is input from the host device, the print data is developed into a dot pattern by the control circuit and stored in the memory circuit B.Next, when a print start command is input, the control circuit S A count value corresponding to the width tbl of the printing pulse pbl for the th t'=z)Dbl is set in the counter circuit 7. Then, the counter circuit allows the output circuit to operate by the set count value, and the printing pulse PBL is applied to the heating element for a predetermined period of time. When the first-order dot (which prohibits the application of In this case, the molding is continued for a predetermined minimum application time. As shown in FIG. 3, this minimum application time is determined by the pulse width t1 determined by the two-stage control method and the pulse width t2 determined by the three-stage control method.
<ts>t2). In the example of FIG. In the next r dot Dhl, since there is no applied pulse to the dot or third dot in front of it, a pulse width thl corresponding to one normal application time is applied.

Next, let's focus on the heating element. As for the heating element-D
c2 is the first, and therefore the pulse width ξ of the printing A pulse Pop for this dot Da2 corresponds to the normal application time. In the case of dot Df2 to be printed next, 3
There is a printing pulse Peg at the dot position in front of the dot,
Therefore, in this case the pulse width tf corresponds to the minimum application time ts (FIG. 3).

The count value is set in the counter circuit.

In this way, 1 heating element 1 is before codot.

As for the heating element, even if there is a printing pulse before the 3P point, by uniformly applying a pulse width of 9 pulses with a minimum application time t3 to both, the average printing density can be achieved for each heating element and each dot. Furthermore, the control circuit is simple and the control circuit is simple as it applies an applied pulse with a uniformly set minimum time pulse width to the heating element at the dot position under the above predetermined conditions. Programming is also easier.

Furthermore, the signal transmission time delay is reduced for simplicity.

Contributes to faster printing. For 1 heating element 3, l
Since this is the same pattern, the explanation will be omitted.

〔Effect of the invention〕

As described above, according to one aspect of the present invention, it is possible to provide a drive control method for a thermal spatula F that enables high-speed printing without degrading printing quality with a simple device configuration.

[Brief explanation of drawings]

Figure 1 is for explaining the conventional one-step control system. Figure 1 is an explanatory diagram showing a heating element and an example of printing dots, (B) is a timing chart of printing pulses, and (0) is the heat generated by the heating element. It is a diagram showing a waveform. Figure 1 is for explaining the conventional three-stage control system. (A) is an explanatory diagram showing a heating element and an example of printing dots, (B) is a timing chart of printing pulses), '=((1) 3 is a diagram showing a heat generation waveform of a heating element. FIG. 3 is a timing chart for explaining the present invention in detail, FIG. FIG. 3A is an explanatory diagram for explaining the drive control method of the present invention, showing an example of a heating element and printing. (Bl C printing pulse timing chart), (0
) is a diagram showing a heat generation waveform of a heating element. 7-3... Heating element, lI... Print data, S...
control circuit, 6... memory circuit, 7... counter circuit,
g...Output circuit, 9...Print head. (13) Figure ( ( (

Claims (1)

[Scope of Claims] A thermal head in which a plurality of heating elements are arranged in a line is moved relative to the recording paper in a direction perpendicular to the direction in which the heating elements are arranged, and the thermal head is placed in front of the dot position to be printed. In a drive control method for a thermal spatula P that performs dot matrix printing by individually applying a printing pulse having a pulse width determined depending on the presence or absence of a printing pulse at a dot position to each heating element, the printing pulse 3 from the dot position you want to print.
The pulse width is the same when there is a print pulse at the previous one dot position and when there is a print pulse at the previous dot position, and. This pulse width is the optimum pulse width that is determined when there is a trace in the printing line before the above-mentioned point, and the optimum pulse width that is determined when there is a lupus in the printing line before the above-mentioned point.
1. A method for controlling the drive of a thermal head, characterized in that a voltage is applied to each heating element at a magnitude approximately midway between the optimal pulse width determined when a pulse width exists.