JPH0126873B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for driving a horizontally or vertically aligned thermal head of a thermal printer, and particularly to a method for driving a thermal head of a thermal printer in which a plurality of heating elements arranged in a horizontal or vertical line are improved. The present invention relates to a method for driving a thermal head for high-speed, high-quality printing, which enables printing on thermal printing paper as a set of accurate printing spots, respectively, using a thermal driving method.

Conventional devices of this type have the following drawbacks. That is, the temperature of each heating element is
As shown in the energization-temperature characteristic curve shown in the figure (when there is a break in energization), as the energization is applied, the temperature gradually rises according to the a curve, and after reaching the coloring temperature Tc of the thermal printing paper and reaching a ₁ , When the energization is stopped, it gradually decreases according to the b curve until it reaches b ₁ , and the next energization starts. When the same temperature cycle is performed from now on, the shaded area is sensitive to heat on the thermal printing paper and prints. A high-quality printing effect can be obtained with the same amount of heat and in fact with the same size, shape, etc. of the printing spot.

In this way, if the energization pause time ts is made sufficiently larger than the energization time ta, the amount of residual heat will be small and the print reproduced on thermal printing paper will be of good quality, but if high-speed printing is required, , it is necessary to reduce ts/ta, and in such a case, as shown in Figure 2 (when energization occurs at each printing timing), the temperature b ₁ at the end of energization of the heating element will still be The next energization starts before it remains high and has not cooled down, and after reaching a ₂ it follows the same rising curve as the previous one and repeats the same process as before.
It gradually rises as a ₁ → a ₂ → a ₃ →...(b ₁ → b ₂ → b ₃ →...), and the area of the shaded area also gradually increases. This means that the coloring time applied to the thermal printing paper becomes gradually longer with each energization, so that the printed spot will move in the direction of travel of the thermal head, as shown in Figure 3b, for example. It has an elongated shape,
It has the disadvantage of being difficult to read.

That is, Figure 3a is the same as in Figure 1.
This shows a case where ts/ta is sufficiently large and printing on paper is performed normally.

In addition, Part 4 shows the energization-temperature characteristics of heating elements when the energization stop time ts is irregular. The example is shown when printed. Now, as shown in the same figure, add characters of this shape to column 7.
For example, if we consider the printing spot in the 3rd row of the vertical column, the first printing spot in the horizontal row
It can be seen that there are spots that should be printed only at numbers 3, 3, and 4.

Therefore, in this case, it is only necessary to apply electricity as shown in Fig. 4c, and it is clear from the explanation of Figs. 1 and 2 that in this case the temperature of the heating element changes as shown in Fig. 4a. The area of the shaded area is large only in the case of the fifth horizontal line, so when the printing spot of the fifth horizontal line is longer in the direction of travel, as shown in Figure 3b, the printed shape is distorted and it is difficult to read. This has been a drawback as a thermal print head.

The present invention eliminates the above drawbacks, and detects whether or not the head is energized one print timing before the printing spot, and if energization occurs, shortens the energization time for the printing spot. energized-
By making the area _a3 of the shaded part of the temperature characteristic curve the same as the area _a2 immediately before, deformation of the print spot in the direction of head movement is prevented. The output of the monostable multivibrator is operated by the output of a plurality of printing spots from the character generator into which the output and print data are input, and the output of the monostable multivibrator for generating a printing time, and the output of a monostable multivibrator for generating a cut signal to shorten the printing time. A thermal circuit comprising a group of AND circuits operated by the output from a group of data flip-flops reset by a differential signal of , a clock pulse Q of the monostable multivibrator for generating printing time, and a group of drivers thereof. A thermal head capable of high-quality printing that reduces printing time by resetting the data flip-flop circuit using the above differential signal when there is an output at the previous printing timing. The present invention provides a driving method.

The invention will now be explained in detail with reference to the drawings.

FIG. 5 is a block diagram showing one embodiment of the present invention, in which 1 is a column counter that selects and outputs printing spots in a column from among the print data input, and 3 is a circuit that causes the character generator 2 to select and output printing spots, and 3 is a circuit that generates printing time. 4 is a monostable multivibrator for generating a cut signal to shorten printing time, 5 is a differentiation circuit, and 6 is the rise of the output (F) of character generator 2 and the clock pulse (C) from printing time generation circuit 3. The data flip-flop circuit group 7, which operates at
Reference numeral 8 denotes a driver group of AND circuits that operate only when the output (F) of the generator 2 and the output (G) of the data flip-flop 6 are input simultaneously.

Next, the operation of the present invention will be explained.

FIG. 6 is a waveform chart at each part of FIG. This means that it is composed of printing spots numbered 1, 4, and 5 in the rows. (B) shows the printing timing pulse, (C) shows the clock pulse group with the printing time Q, (D) shows the pulse group for cutting to shorten the printing time, and (E) shows the (D) waveform passed through the differentiating circuit. (F) is the output waveform of the character generator in the third column in Figure 3 a and c, (G)
is the side output waveform of data flip-flop 6, (H)
is the output waveform of the AND circuit 7. By the way, if printed characters, etc. are displayed as a group of printing spots consisting of 7 vertical columns and 5 horizontal lines as shown in Figure 3, the thermal print head consisting of a single vertical column of heating elements will It is clear that among the seven heating elements arranged in a vertical line, it is sufficient to thermally drive only the heating element corresponding to the required printing spot group of the desired printed characters, etc. The operation of the printing spots shown in FIGS. 3a and 3c above, that is, the case of the transverse spots in the third row in the column, will be described below with reference to FIG. 6 as a representative example.

(1) First, considering the driving operation of the first horizontal printing spot, the data flip-flop 6 receives the output (F ₃ ) from the character generator 2 shown in (F) and the printing time. The output shown in waveform (C) from generation circuit 3 is input, and with the rise of clock pulse ₁ ,
Data flip-flop side output (Figure 5)
is set to 0 as shown in waveform (G).

(2) Since there is no spot to be printed on the second horizontal line, the circuit 6 is reset by the differential pulse _d1 slightly later than the printing timing _t1 , and the side
(G) output is obtained, and (3) there is no spot to print on the third row, so the data flip-flop circuit is the same as (2) (G)
Continue to retain output.

(4) However, since there is a spot to be printed in the fourth row, there is an output (F ₄ ), and the output (G) is set to 0 by the rising edge of _{the 4th} pulse in (C).

(5) Also, since there is a spot to be printed in row No. 5, there is an (F ₅ ) output, and the (G) output of the data flip-flop continues to be 0, so the data flip-flop 6 is reset by the differential pulse _d4 with a slight delay from the printing timing _t4 , and the (G) output is generated, but the (G) output becomes 0 by the rise of the clock pulse _Q5 in (C).

From the above explanation and waveform diagram, 3 to AND circuit 7
If there are inputs at the same time, the print timing t ₀ ,
It is clear that the printing timing is limited to t ₃ and t ₄ , and among these, the AND output (H ₁ ) at printing timing t ₀ and t ₃ ,
(H ₄ ) is the same time as the printing time Q, but only the AND output at printing timing t ₄ has a printing time shorter by the width of the printing time reduction cut pulse.

This means that when the output (Gt ₃ ) is applied to the data flip-flop circuit at time t ₃ , one print timing before, the output (Gt ₄ ) at time t ₄ is slightly shorter than the output (Gt ₃ ). With this AND output (H), the energization-temperature characteristic curve becomes as shown in Figure 7, and since the area of the shaded part is equal, the transverse first
No. 4, No. 5, and No. 5 are all the same, and therefore the printing effect on the thermal printing paper is the same, so the drawback of the energization-temperature characteristic curve in Fig. 4 obtained by the conventional drive system is eliminated. This makes it possible to prevent a bad phenomenon in which the printing spot extends in the direction of travel as shown in FIG. 3b.

As explained above, according to the present invention, in addition to the printing time generation circuit, there is also a printing time reduction cut signal generation circuit, a differentiation circuit connected in series with this, and the output from these and the output from the character generator. By providing a data flip-flop that operates, it is possible to detect the data flip-flop output one print timing before, that is, the presence or absence of a print spot immediately before the relevant print spot, and when that output occurs, the printing time is shortened. To provide a method for driving a thermal head capable of high-quality printing, which can easily prevent deformation of the printing spot in the advancing direction simply by shortening the printing time using a cut signal and limiting the heat amount of the heating element. This can have an extremely large effect.

[Brief explanation of drawings]

Figure 1 is a waveform diagram when there is a break in energization, Figure 2
The figure is a waveform diagram when energization occurs at each printing timing, Figures 3a and b are diagrams showing the normal state and deformed state of the printing spot, Figure 4 is a waveform diagram when energization is irregular, and Figure 5 6 is a block diagram of an embodiment of the present invention, FIG. 6 is a waveform diagram of each part of FIG. 5, and FIG. 7 is a waveform diagram when the present invention is implemented in the case of FIG. 4. DESCRIPTION OF SYMBOLS 1...Column counter, 2...Character generator, 3...Print time generation circuit, 4...Print time reduction cut signal generation circuit, 5...Differential circuit, 6...Data flip-flop circuit, 7... …
AND circuit, 8...driver.

Claims (1)

[Claims] 1. In a thermal head that thermally prints on thermal paper by energizing a predetermined heating element of the heating element corresponding to a group of printing spots that form a predetermined character, etc. to be printed, A column counter operated by a print timing pulse is connected to the character generator, and the character generator selects and outputs a print spot in a predetermined horizontal row of a predetermined column in a predetermined column from among the print data. The data flip-flop circuit group connected to the stage output is set to 0 at the rise of one output of the printing time generating circuit operated by the printing timing pulse.
At the same time, by inputting the output of a printing time reduction cut signal generation circuit operated by the printing timing pulse to the reset terminal of the data flip-flop circuit via a differentiating circuit, When there is a printing spot, the differential signal of the differential circuit
The data flip-flop circuit is reset, and the printing time of the printing spot is shortened by the pulse width of the printing time reduction cut signal circuit. Thermal generator is characterized in that it is driven by its driver via an AND circuit that operates based on simultaneous inputs from the data flip-flop circuit and the printing time generation circuit.
How to drive the head.