JPS61277465A - Printing controller for thermal printer - Google Patents

Abstract

PURPOSE:To suppress a heat-accumulating effect and enable printing quality to be enhanced, by providing a means for reducing the quantity of energy subsequently applied to each heating element according to the driving hysteresis of the element, and a means for regulating the quantity of energy applied to all heating elements in accordance with the ratio of the number of driven dots to the total number of dots in a fixed section previously printed. CONSTITUTION:A controlling circuit 5 for the thermal printer outputs output data to a driver 2 through the first and second buffers 3, 4, and drives a thermal head 1 by pulses supplied from an energization width controlling circuit 8. The circuity 5 stores the driving hysteresis of each of the heating elements and the ratio of the number of driven dots to the total number of dots in the fixed section previously printed, into a RAM 6. Based on a program stored in a ROM 7, a command is sent to the circuit 8 so as to reduce the quantity of energy subsequently applied to each of the heating elements in accordance with the driving hysteresis and regulate the quantity of energy applied to all of the elements in accordance with said ratio. Accordingly, heat accumulation in each of the heating elements and the entire body of the head can be suppressed, and higher printing quality can be contrived.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a print control device for a thermal printer that prints on printing paper by energizing a heating element, and particularly to thermal history control.

[Conventional technology]

Conventionally, various ideas have been made for thermal history control of thermal printers. A typical example is Special Publication No. 55-48631.
and Japanese Patent Publication No. 57-18507, both of which store the history of each heating element and determine the energization time for the next song.

However, with these conventional technologies, when performing solid printing that uses all the heating elements to cover the paper surface, heat gradually accumulates in the thermal head and heat sink where the heating elements are installed. A difference in print density occurs between the print start position and the print end due to this heat storage effect. Furthermore, in serial printers, the difference in density is not only a problem, but also causes a shortening of the lifespan of the thermal head.

As a measure against heat accumulation in the thermal head, there was a method of placing a thermistor on the thermal head and reducing the applied energy according to the temperature rise, but this method was complicated and the thermal response of the thermistor was slow. It wasn't a complete solution.

[Problem that the invention seeks to solve]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for driving a heating element that eliminates the drawbacks of the prior art, suppresses the heat storage effect of a thermal head in a thermal printer, and provides high print quality.

Means for Solving Problem C] The present invention suppresses the heat storage effect of the thermal head by:
means for storing the drive history of each heat generating element; control means for reducing the energy applied to each of the next heat generating elements based on the drive history; means for storing the ratio of the number of driven dots to the total number of dots in a certain period in the past; It has a means for increasing or decreasing the energy applied to all the heat generating elements according to the ratio of the number of dots, suppressing heat accumulation in each heat generating element, and also suppressing heat accumulation in the entire thermal head, thereby achieving good printing quality. It's something you get.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of a print control device for a thermal printer according to the present invention. 1 is a thermal head, 2 is a head driver for the thermal head, 3 is a first buffer for storing output data of each heating element, and 4 is a similar second buffer.

5 is a central processing unit (hereinafter referred to as cptr) that controls various operations of the thermal printer. Reference numeral 6 denotes a random access memory (hereinafter abbreviated as RAM) that stores the driving history of each heating element, the ratio of the number of driven dots to the total number of dots in a certain section that has already been printed, and various data. 7 is a read-only memory (hereinafter referred to as RO) that stores CPH control programs, character patterns, etc.
Abbreviated as M. ). Reference numeral 8 denotes an energization width control circuit that supplies a reference pulse width to the heating element on the thermal head, and mainly detects the ambient temperature and converts it into a pulse width.

The second factor is an explanatory diagram showing an embodiment of the present invention. 10
indicates the previous printing data, with the drive dot set to 1,
Otherwise, it is indicated by 'f:0.

The previous data 10 is stored in the RAM 6.

Reference numeral 11 indicates current data, and reference numeral 12 indicates current correction data. 15 shows a printing timing chart for the first dot, and 14 shows a printing timing chart for the second dot.

〔motion〕

At least R that stores data from one timing ago
The previous data 10 is called from AM6, compared with the current data 11, and correction data 12 is created in which continuous drive data is corrected to 0. Before the printing timing comes, the correction data 12 is stored in the first buffer 5 and the current data 11 is stored in the second buffer 4. When the printing timing comes, the correction data 12 is outputted and applied to the thermal head 1. After t8 hours, the data in the second buffer 4 is sent to the first buffer 3, and the current data is outputted to the thermal head 1. The trailing edge of the current application time to the thermal head is determined by the current application width control circuit.

13 is the timing diagram for the first dot, when the previous data and current data are consecutively driven dots, the previous (b) timing T
If the energization time is t in ml, the current timing Tm
1 in l. -1. The energization time will be .

T indicates the printing cycle. 14 is a timing diagram of the second dot, and when the previous data is a space, it is the energization time of tl.

In addition to such history control for each heating element, when the ratio of drive dots to the total number of dots in the previous data exceeds a predetermined ratio, for example, the total number of dots of 50 data x 8 dots If there are 200 or more driving dots, assuming a 2/1t-predetermined ratio, the second
By reducing the energy applied to all heat generating elements by the time t4 shown in the shaded area in the figure, it is possible to suppress the temperature rise of the entire thermal head. The energization width control circuit 8 normally outputs a pulse width of t, but when the CPU outputs information that a predetermined ratio has been exceeded, it outputs a pulse width of t2.

At this time, the reference value of the ratio of the number of driven dots is t-28 or more.
By doing this, you can control the energization width! II (If the g circuit can output two or more types of pulse widths, the heat accumulation countermeasures will be even more effective.

FIG. 3 shows an embodiment of the pulse width control circuit used in the present invention. When TRIG is input from the TRI()IN@ child, 1 is applied to the capacitor 31 from the source Vc to the resistor 33, heat sensitive resistance element 34. Charging is started via the variable resistor 65.

Capacitor 310 photoelectric level is VB of transistor 66
When the voltage reaches K, the transistor 36 turns on and the waveform shaping t
gI#l! r37, a predetermined pulse @t output is obtained. The heat-sensitive resistance element 34 compensates for the ambient temperature and completely suppresses the influence of the ambient temperature, which is a disadvantage of thermal printers.

A low level signal is input from the RAT1C N terminal depending on the ratio of the number of driven dots. It has resistors 39 connected to the transistors 38, respectively.
By selectively applying a low level input to the transistor 1, each transistor 68 is turned on. By turning on the transistor 38, the charging speed of the capacitor 61 becomes faster, and the output pulse width t becomes smaller. In the example shown in FIG. 5, it is possible to output up to eight types of pulses by selecting the resistance value of the resistor 39. Note that the heat-sensitive resistance element 54 may be unnecessary because the VBIC of the transistor 36 has a role of temperature compensation.

The control means for increasing or decreasing the energy applied to all the heating elements according to the ratio of the number of driven dots is not limited to the above-described pulse width control path, but may also be a means for increasing or decreasing the voltage of the power supply to the heating elements. Furthermore, in addition to the above-mentioned analog method, the pulse width control circuit can also be a digital counter that counts clocks and increases or decreases this count.
VXt- has.

In the present invention, printing refers to printing not only characters, numbers, alphabets, etc., but also graphs, figures, etc.

〔Effect of the invention〕

In the conventional history control for each heating element,
When printing on the paper surface, there were problems such as the pulse width being fixed at a certain constant pulse width, but in the print control device of the thermal printer according to the present invention, the Since the applied energy is determined using the ratio of the number of dots, the optimum applied energy can be determined by an extremely simple method. Furthermore, in the conventional method, 24
In order to store the entire history of 24 dot heating elements in the dot head, we assume that 10 dot rows (1 bit row refers to data driven at one timing) are stored at 1 before 8 dots.
While 30 bit registers are required, in the present invention, in order to perform the same level of history control, there are 5 registers that store the entire washing history of each heating element, and 5 registers that store the ratio of 1 drive dot. However, if the ratio of the number of dots processed by lXAm at one timing is stored as 1 or 0 with 1/2 as a threshold value, an 8-bit register can store 8-bit string data. Also, if you divide it into quarters, 2 bits equals 1
Bit string data can be stored, and 4 bits can be stored in an 8-bit register.
The bit string data is stored. That is, since data of 10 dot rows is stored, 3/4 is set as the threshold value.
This register is fine. Combined with this and the three registers that store the history of each heating element one timing before, there are six registers. This difference will become even larger if more detailed MIFM control is attempted.

Moreover, as the number of registers increases, the processing by the CPU and the like becomes more complicated, and this has an effect on the printing speed of printers, which are moving toward higher speeds.

The present invention is thus extremely useful in enabling high-speed printing of thermal printers and improving print quality, and can be applied not only to serial printers but also to line printers.

The pulse width control circuit used in the present invention is 1! In battery drive where the source voltage fluctuates, voltage compensation can also be achieved by changing to a system in which the pulse width is inversely proportional to the square of the power source in response to power source fluctuations.

It is also possible to use a timer built into the cpυ as a control means for increasing or decreasing the energy applied to all the heating elements.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a printing control device for a thermal printer according to the present invention. 1...Thermal head 6...Read-only memory 3.4...Buffer 8...Electrification width control-path FIG. 2 is an explanatory diagram showing one embodiment of the print control fefl of the present invention. FIG. 3 shows an embodiment of the energization width control circuit used in the present invention. Above tkUIIR person Egunun Co., Ltd. Figure 2

Claims (1)

[Claims] In a thermal printer that has multiple heating elements and prints on plain paper directly or via a transfer film,
means for storing the drive history of each heat generating element; a control means for reducing the energy applied to each heat generating element for the next dot based on the stored drive history; and a number of drive dots relative to the total number of dots in a certain section that has already been printed. 1. A printing control device for a thermal printer, comprising: means for storing a ratio of the number of driven dots; and a control means for increasing or decreasing the energy applied to all heating elements according to the stored ratio of the number of driven dots.