JPH0429857A - Electrification control method of thermal head - Google Patents

Abstract

PURPOSE:To prevent faulty printing of blurred printing, stained printing, etc. by a method wherein only in the case where when a number o f total electrified dots reaches a certain value, a printing pattern of which a printing rate is high exists in a plurality of printing lines printed so far, electrifying time of a heating cell hereinafter is shortened. CONSTITUTION:Since when printing on a first page of paper is started (heating cell electrified time at that time is taken as T0), a counted value of a counter 15A is read into a first register R1 and a second register R2 to be added, values in both registers increase. Every time a counted value of an l line counter CNT reaches 'l', whether a value of the second register R2 reaches a specific value N (<<M) or not is judged. When the value of the first register R1 reaches a specific value M, a state of a flag 1 is checked. Only in the case where the flag 1 is set, the flag 1 is reset, and an MCPU converts a time width of a printing pulse P to a time width corresponding to To-Tk ( constant) to be sent out.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of controlling current supply to a thermal head in a thermal transfer line printer.

[Conventional technology]

The thermal head of this type of printer has an array of heat generating cells that generate heat when energized, and sequentially reads print data from the print data memory according to an address signal from the read address control circuit in the print control unit (including the microcomputer MCPU). The print pattern (dot data) for each line sent out is stored in the register of the head drive circuit, and the head drive circuit is given a print pulse from the control section to print on a specific heat generating cell based on the stored dot data. Turn on electricity and generate heat. The heated cell melts the ink applied to the color transfer ribbon and transfers it to the transfer paper, but the temperature of the thermal head is detected to prevent defective printing (bleeding printing) due to heat accumulation in the thermal head. A thermistor is provided, and temperature data is obtained from the output of the thermistor, and based on the temperature data, the printing control section controls the width of the printing pulse (current application time) to prevent overheating of the thermal head.

[Problem to be solved by the invention]

However, the method using a thermistor cannot be applied to high-speed printing printers due to its slow response.This type of printer requires a method that counts the total number of energized dots, and this total number of energized dots determines the set value. A method has been adopted in which the above-mentioned energization time is reduced when the current is exceeded.

However, although this method using the total number of energized dots can solve the above-mentioned problem when using a thermistor, the printing pattern after reducing the energization time is
100% when all dots on the line are energized and printed
There is a problem in that blurred printing occurs when the printing pattern is low (as shown in FIG. 1).

The present invention has been made in order to solve the above problems, and an object of the present invention is to provide a thermal head energization control method that can prevent defective printing such as blurred printing and blurred printing even when high-speed printing is performed. shall be.

[Means to solve the problem]

In order to achieve the above object, the present invention includes an ON dot number counter that keeps the number of printed dots as a constant, and a first ON dot number counter that is cleared when the count value of this counter is input and reaches a first predetermined value.
a storage section, a second storage section for inputting the count value, and a line number counter that counts the number of printed lines and is cleared every time a predetermined number of lines is counted and also clears the second storage section. and each time the first storage unit reaches the first specified value, the content history of the second storage unit during this period is checked, and the second storage unit is smaller than the first specified value. The configuration is such that the energization time is shortened if the second specified value is ever reached.

[Effect]

In the present invention, each time the total number of energized dots after the start of printing reaches the first specified value, it is determined whether or not to shorten the energization time. This is based on whether or not the number of energized dots in a predetermined number of print lines exceeds a second predetermined value before reaching the predetermined value. In such a case, the energizing time will be shortened, but if a printing line with a low printing rate continues, the energizing time will not be shortened, so the total number of energized dots will reach the first specified value. After that, even if there is a printing pattern with a low printing rate, it is possible to prevent blurred printing.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

In FIG. 1, 10 is a print control unit (MCPU);
12 is a print data memory, 12 is a head drive circuit, 13 is a thermal head, and 14 is an ON dot number counter, which is composed of a counter 15A and an AND circuit 15B. 16 is a motor drive circuit, and 17 is a step motor that drives the platen roller 18.

The hard copy device takes in a video signal transmitted from a host computer (not shown) via an input interface, and the video signal is A/D converted and temporarily stored in the print data memory 11 as print data.

The print data (dot data) D stored here is sent to the head drive circuit 12 in response to a command from the print control section 10 every time one line is accumulated.

In this embodiment, this print data is also taken out to the AND circuit 15B, and is input to the counter 15A under an AND condition with the strobe signal STB generated within the print control unit IO. This counter 15A is print data (shown in FIG. 2)
The number of ON dots is counted and the count value is input to the MCPU in the print control section 10. The MCPU stores the input count value in the first register R in the working area.
1 and stored in the second register R2, and an internal counter CNT (line number counter, hereinafter referred to as !line counter) counts the number of printed lines. This l line counter CNT is 1547 from the print data memory 11.
It is cleared every time the minute dot data D is output.

The first register R1 has the count value set to the first specified value M.
The second register R2 is cleared every time the l line counter CNT becomes !. Cleared each time a line is counted and cleared.

Next, the throat operation of the above embodiment will be explained with reference to the time chart of FIG. 3 and the flowcharts of FIGS. 4 to 7.

In this embodiment, when printing on the first page of paper starts (
The heating cell energization time at this time is To), counter 1
Since the count value of 5A is read into the first register R1 and the second register R2 and added, the values in both registers increase (see FIG. 7). ! line counter CNT
Each time the count value of Rll reaches rll, , it is determined whether the value of the second register R2 has reached the specified value N (<<M), as shown in FIG. If not, the l line counter CNT is cleared.

Now, after this clearing, in which the value of the second register R2 does not reach the specified value N, has been repeated m-1 times, the value of the second register R2 has reached the specified value N. If it exceeds the limit, flag 1 will be set at the mth time of the above judgment! line counter CNT
is cleared, and the second register R2 is also cleared.

After that, printing continues and when the value of the first register R1 reaches the specified value M (Fig. 5), the state of flag 1 is checked, and only if flag 1 is set, flag 1 is reset. Then, the energization time is changed based on the following formula, and the new energization time T=To-Tk (constant)...(1
) Thereafter, the MCPU changes the time width of the print pulse P to the time width corresponding to this newly determined energization time T and sends it out. In this way, the main routine shown in FIG. 4 is repeated.

As described above, in this embodiment, each time the total number of energized dots after the start of printing reaches the first specified value M, it is determined whether or not to shorten the energization time. It is based on whether or not the number of energized dots in a predetermined number of printing lines exceeds the second specified value N before the number of energized dots reaches the first specified value M. For example, the printing rate is 100.
% printing line continues for the specified printing line, the energizing time will be shortened, but if the printing line with a low printing rate continues, the energizing time will not be shortened, so the total energizing dots will be reduced. After the number reaches the first specified value,
Even if there is a printing pattern with a low printing rate, it is possible to prevent blurred printing.

〔Effect of the invention〕

As explained above, in the present invention, when the total number of energized dots reaches a certain value, multiple print lines printed so far are
In the conventional case, the energization time is shortened every time the total number of energized dots reaches a certain value, since the subsequent energization time of the heating cells is shortened only when there is a printing press with a high printing rate. The occurrence of defective printing can be reduced compared to the above.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a signal time chart for explaining the operation of the ON dot number counter in the above embodiment, and FIG. 3 is for explaining the overall operation of the above embodiment. 4 to 7 are flowcharts of the above embodiment. 10-print control unit, 11-print data memory 12-head drive circuit, 13-thermal head, 14...-O
N dot number counter, 15A--Power output, 15B--
- AND circuit, R1, R2 - register, CN T - line number counter.

Claims (1)

[Claims] Image data sent from the host computer,
It has a print control unit that stores the print data in the print data memory and then reads it out to the head drive circuit, and turns on the heat generating cells of the thermal head for a period of time instructed by the print control unit according to the print pattern given by the head drive circuit. /O to count the number of printed dots in a thermal transfer printer that is turned off.
N dot number counter, a first memory section that is cleared when the count value of this counter is input and reaches a first specified value, a second memory section that inputs the count value, and a second memory section that counts the number of printing lines. has a line number counter that is cleared every time a predetermined number of lines are counted and also clears the second storage section, and each time the first storage section reaches the first specified value, The content history of the second storage section is checked, and if the second storage section has reached a second specified value that is smaller than the first specified value, the shortening change of the energization time is performed. 1. A method for controlling energization time of a thermal head, characterized in that: