JPH0464458A - Printing head drive control system - Google Patents

Abstract

PURPOSE:To improve a printing quality by a method wherein the number of applying an electric current to a heating element is counted, and in accordance with this count value, an applied current value is controlled. CONSTITUTION:Printing data 9 held in a data buffer 20 are counted by an application number counter 16. In accordance with the count value, an electronic volume 17 is controlled, and a drive current value to a printing head part 4-1 is variably controlled. A resistance selection decoder 18 is provided in the electronic volume 17. A resistance value is selected in accordance with application number count data 15 from the application number counter 16. In this manner, an optimum drive current value can be applied to the printing head part 4-1. For example, when the count value is high, a resistance value is increased but a drive current value is decreased. In this manner, the deterioration of a printing quality caused by a heat accumulation in heating elements 40-1-40-n can be prevented, and an ideal printing quality can be maintained.

Description

TECHNICAL FIELD The present invention relates to a print head drive control system, and more particularly to a print head drive control system for a thermal transfer line printer.

BACKGROUND ART In general, in thermal transfer type line printers, when printing is performed continuously, the print quality deteriorates due to heat accumulation in the print head. In order to prevent the print quality from deteriorating, conventional printers divide the print area into a matrix, monitor the number of times each heat generating element in the print head is driven when printing on each part, and adjust the number of times each heat generating element of the print head is driven accordingly. A method of thinning out printing was adopted.

However, since this conventional method performs thinning printing, it has the disadvantage that printing quality deteriorates due to a reduction in dot density.

OBJECTS OF THE INVENTION The present invention has been made to solve the above-mentioned conventional drawbacks, and its purpose is to provide a print head drive control system that can improve print quality.

Structure of the Invention A print head drive control system according to the present invention is a drive current control system that controls a current applied to a heating element of a print head, and includes a counting means for counting the number of times the current is applied to the heating element, and a counter for counting the number of times the current is applied to the heating element. A special embodiment characterized in that it has a control means for controlling an applied current value in accordance with a numerical value.Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of a print head drive control system according to the present invention.

In the figure, the print head drive control system according to an embodiment of the present invention includes print quality compensation circuits 3-1 to 3-4 having print head drivers, and the same number of print head units 4 as these circuits 3-1 to 3-4. -1 to 4-4. The printing operation is performed by the encoder 6 based on the printing data 9 given from the microcomputer 2.
It is executed in synchronization with the encoder pulse signal 11 from .

The encoder 6 detects the rotation period of the motor 5 that drives the platen roller 12, and sends out an encoder pulse signal 11 synchronized with the rotation operation. Also,
The platen roller 12 conveys the print medium 7 in the direction of arrow Y.

The print quality compensation circuits 3-1 to 3-4 convert the print data 9 given from the microcomputer 2 into print heads 4-1 to 4- selected by the RAD select signal 10 from the RAD selector 1. 4. The internal structure of these printing quality compensation circuits 3-1 to 3-4 will be explained using FIG. 2. FIG. 2 is a block diagram showing the configuration of the print quality compensation circuit, and parts equivalent to those in FIG. 1 are designated by the same symbols.

In the figure, the print quality compensation circuit 3-1 is connected to the print head section 4.
-1, it applies a current for driving the heating element, and includes a data buffer 20, a parallel/serial conversion circuit 21, an application number counter 16, and an electronic volume 17.
and a print head tricycle 19. In addition, the printing button 9 is connected to the printing quality compensation circuit 3-2 in the subsequent stage.
Also given for 3-4.

The print head driver 19 outputs a print head select signal 1.
By controlling the internal transistors on and off according to the parallel format print data 9 held in the data buffer 20 in response to the input of 0, the heating elements 40-1 to 40-n of the print head section 4-1 are turned on and off. It is what drives the. However, if the heating elements continue to be driven one after another, the print quality will deteriorate due to heat accumulation in the heating elements. Therefore, in the present invention, the number of times the heating element is driven, that is, the number of times the driving current is applied, is counted, and the driving current value is controlled according to the counted value.

In order to perform this control, the print data 9 in parallel format held in the data buffer 20 is converted into serial format in the parallel/serial conversion circuit 21, and then counted by the application number counter 16. Then, the electronic volume 17 is controlled based on the counted value, and the print head section 4-1 is
The drive current value is controlled to change. Since the counted value is proportional to the amount of heat generated by the heating element of the print head, by changing the drive current value according to the counted value, it is possible to prevent the print quality from deteriorating due to heat accumulation.

Here, a resistance selection decoder 1 is included in the electronic volume 17.
8 is provided, and a resistance value is selected according to the application number count data 15 from the application number counter 16, whereby an optimal drive current is applied to the print head section 4-1. For example, when the count value is large, the resistance value may be increased to lower the drive current value.

Note that the printing quality compensation circuit 3-2. 3-3 and 3-4 are similarly constructed, and count the number of times the drive current is applied to the corresponding print head, and control the drive current value in accordance with the counted value.

Furthermore, control of the drive current value according to the count value is performed at predetermined intervals. That is, the drive current value for the next predetermined period is determined by the number of times the drive current is applied within the predetermined period. In this embodiment, the output of the encoder 6 mentioned above,
That is, the period is determined according to the rotation period of the platen roller.

Next, the period will be explained using FIG. 1 again.

As described above, the encoder 6 provides the encoder pulse signal 11 to each of the print quality compensation circuits 3-1 to 3-4 at every fixed cycle of the rotation of the motor 5, that is, the rotation of the platen roller 12. The timing at which this encoder pulse signal 11 is applied is such that the print area 8 shown by diagonal lines on the print medium 7 is divided into vertical widths of 3 as shown by broken lines.

Therefore, each time the printing operation for the vertical width 13 is completed, the drive current value of the print head section changes.

Furthermore, since the drive current values are controlled separately for the four print head units 4-1 to 4-4, different controls are performed for each width 14 as shown by the broken line. Therefore,
The printing area 8 is divided into a matrix having a vertical width of 13 and a horizontal width of 14, and the printing quality is reviewed for each divided portion, thereby preventing deterioration of the printing quality.

In this embodiment, the print area is divided into a matrix, and the print quality is reviewed for each divided portion, but the review may be performed for each page or line of the print medium. Alternatively, a temperature sensor may be provided and the review cycle may be changed depending on the temperature.

DETAILED DESCRIPTION OF THE INVENTION As described above, the present invention prevents deterioration of print quality due to heat accumulation in the heat generating element by controlling the current value to be changed depending on the number of times the current is applied to the heat generating element of the print head.
This has the effect of maintaining good print quality.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a print head drive control system according to an embodiment of the present invention, and FIG. 2 is a block diagram showing the internal configuration of a print quality compensation circuit. Explanation of symbols of main parts 3-1 to 3-4...Print quality compensation circuit 4-1 to
4-4...Print head section 6...Encoder 7...Print medium

Claims (1)

[Claims] (1) A drive current control system for controlling the current applied to a heating element of a print head, comprising a counting means for counting the number of times the current is applied to the heating element, and controlling the applied current value according to the counted value. A print head drive control system comprising a control means.