JPS59150767A - Control system of thermal printing head - Google Patents

Abstract

PURPOSE:To make it possible to enhance printing quality, by controlling heat generating tming so that the heat generation of a head at the starting of printing operation is increased corresponding to the operation stopping time to a printing operation time. CONSTITUTION:A pulse signal T1 having large pulse amplitude is generated from a timing generating circuit 23a while a pulse signal T2 having small pulse amplitude is generated from a timing generating circuit 23b in synchronous relation to a printing timing signal T. In addition, printing data D enters a latch circuit 20 similarily operated as a shift register in synchronous relation to the signal T and printing data before one cycle, two cycles and three cycles are respectively latched in flip-flops 21a, 21b, 21c. In this state, an AND circuit 22 outputs H when data is not continuously blank and outputs L when continuously blank over three dots or more while a change-over circuit 24 selects T1 in H and selects T2 in L to output a heat generating timing signal H corresponding to the selected one. By this method, sufficient printing density is obtained and printing quality is enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] This invention relates in particular to a thermal print head control system for thermal printers and the like.

[Technical background of the invention and its problems]

Thermal printers generally have a thermal print head (
A head (hereinafter simply referred to as a head) scans the paper and prints characters and the like made up of a dot matrix. Conventionally, in such a thermal printer, when printing characters, etc., the printing density of the initially printed dot 10 is lower than that of the dot 12 (arrow 1) after the printing operation has elapsed, as shown in Figure 1.
The density may be lower than that in the printing direction).

This occurs when the entire head heats up from a cold state, and
This is because the peak value of the temperature differs depending on when heat is generated from a state where there is residual heat.

Various countermeasures have been considered in the past to address these problems, but none of them have yielded sufficient results. For example, there is no control over long-term temperature changes that takes into account heat accumulation in the head itself. Therefore, if the density at the time of connected dots □ is appropriate, it is difficult to obtain a sufficient density for the dots immediately after the start of printing, which has the disadvantage of causing a decrease in printing quality.

[Purpose of the invention]

This invention has been made in view of the above circumstances, and its purpose is to always obtain sufficient print density by controlling the heat generation timing of the head in accordance with the print operation time of the head in a thermal printer or the like. Overview] According to the present invention, a pulse signal for controlling heat generation timing of a head is generated from a pulse generating means as a plurality of pulse signals having at least two types of pulse widths. On the other hand, by synchronizing the print data with the print timing signal,
For example, it is latched using multiple stages of flip-flops. In this case, the latched print data is output at a predetermined period. The output of this print data is searched, and a predetermined pulse width is selected from among the plurality of pulse signals generated from the pulse generation means in synchronization with the print timing signal according to the extraction signal of a pattern with continuous blank dots. The pulse signal is selected and outputted using a multi-bleph sensor or the like. Based on both the selected pulse signal and print data, a heat generation timing signal for the head is created and output. This makes it possible to create and output a heat generation timing signal that increases the heat generation time of the head when no print data is output for a certain period of time.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a block diagram showing the configuration of a head control circuit according to the present invention. In the figure, 20 is a latch circuit, which is composed of a plurality of stages of seven lip flow circuits 21a to 21c. This latch circuit 20 latches the print data D in the first-stage flip-flop 21a in synchronization with the print timing signal T (pulse shown in FIG. 3), and sequentially
The way in which the signals a and 21b come out are latched by the seven subsequent lip-flops 21b and 21c, respectively. Each output of the 7-rig flops 21a to 21c is connected to an AND circuit 2.
2 input terminals b.

On the other hand, each timing generation circuit 23m, 23b outputs a pulse signal TI and a pulse signal T2 having different pulse widths in synchronization with the print timing signal T. Both of these signal signals TI+T2 are applied to a switching circuit 24 such as a multiplexer. This switching circuit 24 outputs a signal T11T2 according to the output signal G of the AND circuit 22.
Select one of the output dart circuits (e.g. AND circuit)
output to one input terminal of 25. The output dirt circuit (hereinafter referred to as output gate) 25 receives print data D at the other input terminal and outputs a heat generation timing signal (hereinafter referred to as a timing signal) H for printing that controls the heat generation timing of the head. .

The operation of this configuration will be explained. Now, suppose that in synchronization with the print timing signal T as shown in FIG.
3b has a smaller pulse width than T1, -e pulse signal T,
Assume that each occurs. Further, print data D is latched in the latch circuit 2° in synchronization with the print timing signal T. The latch circuit 2o operates in the same way as a shift reno star (i.e., the signal T becomes a shift clock pulse)
7 lip flops 21h to 21c each
latches the print data D at different cycles.

That is, the flip-flop 7° 21a is busy with print data from one cycle before, the flip-flop 21b is latched with print data from two cycles before, and the flip-flop 21c is latched with print data from three cycles before.

Therefore, since the outputs of each of the seven printers f2xa to f21c are supplied to the AND circuit 22, the AND circuit 22 continuously determines that when the print data D is not a blank dot,
Outputs an output signal G that becomes "1". That is, when the print data D includes three or more consecutive blank dots, an output signal G of "0" is applied from the AND circuit 22 to the switching circuit 24. The switching circuit 24 is switched to i4 by the signal G (roj).
The pulse signal T1 is selected from the pulse signal TIIT2 and output to the output dart 25. Output dart 25 is printed data D and /? after three or more consecutive blank spaces in print data D and /? Based on the pulse signal T1, a heat generation timing signal H corresponding to the pulse signal Tl is output as shown in FIG. This reduces the heat generated by the head during printing.
In the normal case, that is, the heat generated by the heat generation timing signal H corresponding to the pulse signal T2 is increased.

Further, when the signal G that is "1" is output from the AND circuit 22 to the switching circuit 24, the switching circuit 24 selects the A' pulse signal T2 and outputs it to the output dart 25. Accordingly, the output dart 25 is a pulse signal T as shown in FIG.
A heat generation timing signal H corresponding to 2 is output.

In this way, in the present invention, for example, after three or more blank spaces in the print data D continue as shown in FIG.
In the case of printed dots 10, the heat generation timing of the head is controlled by a heat generation timing signal H (corresponding to the Cruz signal T1) with a large nof pulse width. For this,
Conventionally, the dot 10 printing results in a decrease in density due to insufficient heat generation in the head, but since the head heat generation can be increased, sufficient density can always be obtained in dot IQ printing. In addition, in a printing operation in which the blank space of the print data D is less than 3 consecutive dots (for example, at the scanning position of the head shown by 12 in Fig. 1, the heat generation timing signal (pulse The heat generation timing of the head is controlled by the signal H (corresponding to signal T2).

In the above embodiment, the heat generation timing signal H is set to 2.
Although we have described the case where the
According to the present invention, it is possible even for cases of 3s class or higher. In this case, the number of timing generation circuits does not increase accordingly, and the switching circuit becomes a circuit that selects three or more types of pulse signals based on a plurality of control signals.

Further, in the above embodiment, when there are three or more consecutive blank spaces in the print data D, the heat generation timing signal H is changed from normal to normal. However, the present invention is not limited to this. It is also possible to change the heat generation timing signal H when a blank space of more than one dot or more than two dots continues. In this case, the number of stages of the flip 70 may be increased or decreased.

〔Effect of the invention〕

As detailed above, according to the present invention, in a thermal printer or the like, the heat generation timing is controlled so as to increase the heat generation of the head at the start of the printing operation in accordance with the operation stop time with respect to the print operation time of the head. Can be done. Therefore, sufficient print density can always be obtained even at the beginning of printing, and thereby print quality can be greatly improved. In addition, since the heat generation timing of the head can be controlled over a wide range, it is possible to provide a margin in the design for the heat generation characteristics of the head itself and the thermal characteristics of thermal paper, heat-sensitive resin, etc., which improves the overall yield of the device. Effects such as improved performance and reduced costs can also be obtained.

[Brief explanation of drawings]

FIG. 1 shows dot printing using a conventional thermal printer. FIG. 3 is a timing chart for explaining the operation of the circuit shown in FIG. 21a to 21c... Frizzoflo, f, 22... AND circuit, 23h, 23b... Timing generation circuit,
24...Switching circuit, 25...Output dirt circuit.

Claims (1)

[Claims] pulse generating means for respectively generating pulse signals having at least two different pulse widths in synchronization with the print timing signal; and a pulse generation means for generating pulse signals having at least two types of pulse widths in synchronization with the print timing signal, and predetermined of the print data latched at a predetermined period in synchronization with the print timing signal. latch means for outputting a switching control signal in response to a dart output that detects that a portion of data is not printed continues for the number of times; A selection means for selecting and outputting a pulse signal with a predetermined pulse width, and an output means for outputting a heating timing signal for printing based on both the pulse signal selected by the selection means and the printing data. Thermal print head control method featuring