JPH05330118A - Thermal printer - Google Patents

Abstract

PURPOSE:To lighten the shift degree of a printing position within an one-dot row by providing a means controlling the time lag between the point of time when the supply of a current to a thermal line head is started and the point of time when the driving of a paper feed mechanism is started. CONSTITUTION:When a printing cycle is T', the shift DELTA of a printing position is generated between a third block and a fourth block in the setting of the thermal head current supply period (printing period) shown by D. For example, when the printing region of a bar code stretches over the third and fourth blocks, this shift of the printing position becomes a problem. Therefore, when a paper feed start pulse is changed from A to F and the time lag with printing start timing is set to tau, the movement of paper becomes the state shown by G and the third and fourth blocks become a movement stop period during a printing period. The problem can be avoided by the generation of the shift of a printing position between first and second blocks. That is, by controlling the time lag tau, a place where the shift of a printing position is generated can be changed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printer using a thermal line head, and more particularly to a thermal printer suitable for a printer that prints barcodes such as barcode labels.

[0002]

2. Description of the Related Art In a thermal printer using a thermal line head, a block energization method is used. In 1-dot line printing, when the entire line head is energized at once, the amount of temporary current is large, and if the capacity of the power supply is adjusted to that, the power supply becomes large, so the line head is divided into several blocks. By sequentially energizing in block units, the maximum value of the current that should be energized at one time is kept low. However, in this block energization method, energization is performed several times for printing one dot line, so the printing speed is reduced. On the other hand, there is a strong demand for improving the printing speed in the thermal printer, and the printing cycle, that is, the time from the start of printing of one dot line to the start of printing of the next one dot line must be made as short as possible. Therefore, the following problems occur.

In a printer using a thermal line head, paper feeding is stopped during printing of one dot line, and the paper is fed by one pitch of one dot line before starting printing of the next one dot line. However, since the paper is stretchable, the paper feed mechanism has play and friction, and also has inertia, the paper actually starts to move after the paper feed pulse is applied, and there is a slight delay before the paper stops moving. There is a time delay. This relationship is shown in FIG. This figure A shows the paper feed start pulse.
By applying this pulse, a drive pulse for one step is applied to the stepping motor for paper feeding. B indicates the amount of movement at the print line position of the paper, and the movement of the paper starts after a time t from the pulse of A. It takes time t'from the pulse of A to stop the movement of the paper. ing. T is the printing cycle of one dot line, and C is the energization period of the thermal head in the case where one dot line is energized once. Normally, this period is set so as to be within the period in which the movement of the paper is stopped as shown in the figure. D is an energization period in which one dot line is divided into four blocks and energized by block energization, which takes four times as long as in C. On the other hand, when the printing cycle is set to T'to increase the printing speed, the paper movement becomes as shown in E, and the block is energized in D, and during the energization period of the later fourth block, the paper starts to move at the beginning portion. Come on. Therefore, a printing position shift of Δ occurs between the third block and the fourth block.

The deviation of the printing position as described above appears as a slight step difference in the horizontal line on the printing surface and is not a serious problem in a normal document, but when printing a bar code as shown in FIG. If the scanning line for reading runs at an angle to the bar code and crosses this step difference, erroneous reading will occur. In such a case, misalignment of printing is a serious problem.

[0005]

SUMMARY OF THE INVENTION According to the present invention, a position where a print position shift occurs within one dot line which occurs when a block line is energized by a thermal line head, or a position where a print position is not hindered, or a shift amount. It is intended to be a level that does not hinder.

[0006]

[Means for Solving the Problems] The time difference between the print start timing and the paper feed start timing, that is, time τ in FIG. 1, can be adjusted.

[0007]

When the print cycle is T'in FIG. 1, a print position shift of Δ occurs between the third block and the fourth block in the setting of the thermal head energization period (print period) shown in FIG. Now, for example, when the print area of the above-mentioned bar code extends over the third block and the fourth block, this print position deviation Δ becomes a problem. Therefore, the pulse to start feeding is
If the time difference from the print start timing is changed from τ to τ ′ by changing from A to F, the paper movement becomes as shown in FIG. 1G.
During the printing period, the movement of the paper is stopped between the third block and the fourth block, and the printing position shift occurs between the first block and the second block, and the problem is avoided. That is, by adjusting the time difference τ, it is possible to change the place where the print position shift occurs. As shown in FIG. 1H, the print position shift is between the third and fourth blocks by setting the time difference as τ ″, but the shift can be reduced to Δ ′. When the print position shift occurs at a location that is not convenient, the adjustment of τ makes it possible to move the print position shift to a place that does not hinder or reduce the shift value.

[0008]

FIG. 3 shows an embodiment of the present invention. 1 in this figure
Is a CPU for controlling the printer, 2 is a thermal line head, and is composed of a shift register R for receiving data for one dot row, a latch circuit L, a switch circuit S, and a heating resistance element P. In this example, 4 It is divided into blocks and energized. A thermal line head controller 3 inputs print data for one dot row to the shift register R, sends a latch signal to the latch circuit to hold the parallel output of the shift register R, and causes the switch circuit S to output 4 dots per dot row. A strobe signal is sent to energize the heating element P. Four
Is an operation panel, 5 is an R0M storing a printer operation program, 6 is a RAM for inputting print data and the like, 7
Is a character generator that forms character dot pattern data from character codes, and 8 is an interface that connects a host computer and this printer. Document data is sent from the host computer in the form of a list signal such as a character code. This document data is taken into the RAM 6, formed into print pattern data, sent to the thermal line head controller 3, and printed one dot row at a time. Reference numeral 9 is a paper feed stepper, and 10 is a drive circuit thereof. The above components and operations are the same as those of the conventional thermal line printer.

The feature of the present invention resides in that the delay circuit 11 is provided in the preceding stage of the stepper driving circuit 10. This delay circuit is, for example, the preceding one-shot circuit and the stepper driving circuit 10 at the fall of the output pulse of the circuit. It is composed of a rear one-shot circuit that outputs a starting pulse, and the width of the output pulse of the front one-shot circuit can be adjusted by a variable resistor r. With this configuration, the CPU sends the paper feed start pulse indicated by E in FIG. 1 to the delay circuit 11. Conventionally, this pulse was directly input to the stepper drive circuit 10, but in the present invention, the pulse of FIG. 1E is input to the delay circuit 11,
11 after the A pulse as shown in FIG. 1F or H
The paper output is started by the pulse output from. The variable resistance r is adjusted by trial printing of a document so that the printing position shift is generated at a position or at a position where it does not hinder the printing.

[0010]

It is unavoidable that a printing position shift occurs in one dot row when the thermal line printer is energized in blocks and the printing speed is increased, but according to the present invention, the thermal line head By adjusting the time difference between the power-on timing and the paper feed start timing, more specifically, by adjusting only one variable resistor, the degree of this print position deviation can be reduced, or the location of the position deviation does not hinder the document. It can be moved to a place, which does not complicate the structure of the device and is easy to operate. In particular, when barcode printing is performed by a thermal line printer that performs block energization, the positional deviation of the printing that appears at the block boundary is a fatal problem as described above, but the present invention solves this problem.

[Brief description of drawings]

FIG. 1 is a time chart explaining the operation of the device of the present invention.

FIG. 2 is a diagram of a print pattern in which a print position is displaced.

FIG. 3 is a block diagram of an apparatus according to an embodiment of the present invention.

[Explanation of symbols]

 1 CPU 2 Thermal line head 3 Thermal head controller 4 Operation panel 9 Stepper 10 Stepper drive circuit 11 Delay circuit r Variable resistance

Claims (3)

[Claims] 1. A thermal printer in which a thermal line head is divided into a plurality of blocks and sequentially energized for each block, the time difference between the energization start time of the thermal line head and the drive start time of the paper feed mechanism is adjusted. A thermal printer provided with means. 2. The thermal printer according to claim 1, wherein means for adjusting the time difference is provided on the paper feed mechanism side. 3. In a thermal printer in which a block of a thermal line head is set to print a bar code in which a bar is orthogonal to the paper feed direction, the thermal printer starts the energization of the thermal line head and the paper feed. When the bar of the bar code straddles two adjacent blocks of the thermal line head, the time difference between the start of driving the mechanism and the timing at which the two blocks are energized corresponds to the stop period in the middle of the drive before and after the paper. A thermal printer characterized by being set so that