JPH06270452A - Serial printer - Google Patents

Abstract

PURPOSE:To prevent a black line from generating on a piled up part of dots, by a method wherein a plurality of elements are electrified so that printing density of dots obtained by piling-up printing is not different from printing density of dots which is printed by not using the piling-up printing. CONSTITUTION:A head driver circuit 8 driving a printing head having a plurality of elements which are heated when they are electrified to print an image constituted of a plurality of dots is formed. In the head driver circuit 8, at the time of piling-up printing of one line running along a printing direction and the other line continuing to the one line in relation to the dots by a printing head, a plurality of elements are electrified so that printing density of dots obtained by piling-up printing is not different substantially from printing density of dots which is printed by not using the piling-up printing. With this construction, even if the dots of the printed image are piled up or each other, generation of a black line on a piled-up part of the dots can be prevented. Then a letter free from printing irregularity can be printed by performing neither an improvement in accuracy of paper feed nor correction of a quantity of paper feed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a serial printer, and more particularly to a serial thermal printer. It can be used for thermal printers and ink jet printers.

[0002]

2. Description of the Related Art FIG. 6 is a diagram showing a hiragana "a" printed in double-width or image by a conventional method, and FIG. 7 is a partially enlarged view of FIG. 6 (enlarged view of a portion surrounded by a circle in FIG. 6). FIG. 8 is a diagram for explaining the dot overlapping state, and FIG. 8 is a diagram for explaining the details of the dot overlapping state of two rows during printing.

An example of the prior art will be described with reference to FIGS. 6 to 8 in the case of printing with a serial type thermal printer.

In the case of a serial type thermal printer, in double-width printing or image printing in which printing is performed by connecting a plurality of lines, the double-width characters and the image angle are printed due to variations in the paper feed due to variations in the diameter of the paper feed roller. May become empty.

In order to prevent the occurrence of a gap there, the last few dots of the first to previous lines and the first few dots of the next line are printed in an overlapping manner. As is apparent from the partially enlarged view shown in FIG. 7, the double-width character “A” in FIG. 6 has a high print density in the overlapping portion of the first line and the second line (portion where shaded lines overlap).

FIG. 8 shows the details of the overlapping state of the print area 20 on the first line and the print area 21 on the second line. When the print head is n dots, the number of overlapping dots is 3 dots. . The lower 3 dots (n-2nd dot, n-1th dot, nth dot) of the 1st line and the upper 3 dots (1st dot, 2nd dot, 3rd dot) of the 2nd line are overlapped. When the density of dots is represented by the shaded area, the dot overlap area becomes the density of the mesh line (the overlapping area of the shaded area), and in the overall image, the three-dot line appears as black streaks.

[0007]

As described above, when a plurality of dots are overlapped and printed, the density of the part is overprinted and the density of the part is increased. It looks like black streaks.

Therefore, even if the print quality of each line is good, the print quality of the entire image is poor.

It is an object of the present invention to maintain an optimum print density without unevenness in the entire image in double-width character printing or image image printing without leaving a gap between print lines and improve the overall print quality of the image. The purpose is to provide a serial printer that can do this.

[0010]

According to the present invention, there is provided a head which includes a plurality of elements which are energized and generate heat to print an image composed of a plurality of dots and which is movable in a printing direction.
When the head prints one line along the printing direction and another line following the one line with respect to the dot, the print density of the dot printed in the overlapped manner is the print density of the dot not printed in the overlapped manner. A head driver circuit for energizing the plurality of elements so that there is substantially no difference.

[0011]

When the head driver circuit prints one row along the printing direction by the head and another row following the one row in an overlapping manner with respect to dots, the print densities of the printed dots are overlapped and printed. Since multiple elements are energized so that there is substantially no difference in the print density of the unprinted dots, even if the dots of the printed images overlap, it is possible to prevent the generation of black streaks in the overlapping parts of the dots, and to feed the paper in the printer. Characters without print unevenness can be printed without improving accuracy or correcting the paper feed amount, and the manufacturing cost of the printer can be significantly reduced.

[0012]

1 is a block diagram showing a drive circuit of a serial printer, and FIG. 2 is a schematic perspective view of the serial printer.

In FIG. 2, 1 is a carriage for mounting a ribbon cassette, 2 is a print head mounted on a carriage that is movable in the printing direction, 3 is platen rubber for receiving the print head, 4 is a paper feed roller for feeding paper, and 5 is a paper feed roller. Is a gear that transmits the drive of the carriage drive motor 6 that drives the carriage to the left and right, and 7 is a belt that transmits the drive of the motor.

In FIG. 1, reference numeral 8 is a head driver circuit for driving the print head 2, and reference numeral 9 is a circuit for moving the print head 2 up.
Motor driver circuit down, 10 paper feed motor driver circuit, 11 carriage motor driver
A circuit, 12 is a CPU for controlling the driving of the printer of FIG.
Reference numeral 13 is a ROM for storing a control program, and 14 is a RAM for updating data.

FIG. 3 is a diagram showing details of the head driver circuit.

In FIG. 3, the signals DATA IN 1,
2 is high during printing and low during non-printing. The clock signal (CLOCK) is a positive edge trigger, the latch signal (LATCH) is a negative edge trigger, and GN.
DH is a heater driving ground, and GNDL is an IC logic ground. R1 to R64 are resistors of the thermal head, and printing can be performed by causing a current to flow in this portion to generate heat. Data is transferred from DATA IN 1 and DATA IN 2 to the shift registers (S / R) 24 and 25 and stored therein in synchronization with a clock. LA
Shift register 2 by pulling TCH low
The data stored in 4 and 25 are latched in the 64-bit latch 23. Then signal STROB 1 bar and ST
ROB 2 bar low and individual resistors R1 to R64
Current is supplied from the power supply VH to the resistors R1 to R6
The head driver circuit is driven by the heat generated by the motor 4.

FIG. 4 is a time chart showing the driving sequence of the head driver circuit. The same signals as those in FIG. 3 are denoted by the same symbols.

In FIG. 4, N, N + 1, and N + 2 mean energization per column, respectively. That is, 400 dpi
If the printer has 9-inch print data, it has an energization cycle of 3600 columns. DATA
It is shown that data is input to the 32-bit shift register 24 from IN 1 and data is input to the 32-bit shift register 25 from DATA IN 2 respectively.

Data 31 is original print data, 32 is correction data for density correction, data 31 and 32 are the same data when no correction is made, and heater numbers corresponding to correction when correction is made. By making the data of (Rn) null data, only the pulse width of the period P1 is actually applied, and the density becomes light.

FIG. 5 is a time chart showing a sequence of a specific example of density correction. In FIG. 5, the same signals as those in FIG. 3 have the same symbols as in FIG.

When it is attempted to correct the print density of the dots corresponding to the resistors R1 to R3, it is assumed that the pattern is solid black (the resistors R1 to R32 are all energized) and the preceding stage is synchronized with the rising of the clock signal. , DATA
IN 1 is all "high" (energization data), D in the latter stage
ATA IN 1 is "low" for resistors R1 to R3
In the (null data) resistors R4 to R32, "high" (energization data) is stored in the shift registers 24 and 25. In this way, for one column, the resistors R1 to R3 have a pulse width P1 and the resistors R4 to R32 have P1 + P2, so that the correction can be performed by performing this correction on all columns. As a matter of course, the dots to be corrected can be set arbitrarily.

[0022]

When the head driver circuit prints one line along the printing direction by the head and another line following the one line, the print densities of the printed dots overlap. Since multiple elements are energized so that there is substantially no difference in the print density of the dots that are not printed, even if the dots of the printed images overlap, it is possible to prevent the generation of black streaks in the overlapping parts of the dots, and the printer It is possible to print characters without print unevenness without improving the paper feed accuracy and correcting the paper feed amount, and it is possible to greatly reduce the manufacturing cost of the printer.

[Brief description of drawings]

FIG. 1 is a block diagram showing a drive circuit of a serial printer.

FIG. 2 is a schematic perspective view of a serial printer.

FIG. 3 is a diagram showing details of a head driver circuit.

FIG. 4 is a time chart showing a driving sequence of a head driver.

FIG. 5 is a time chart showing a sequence of a specific example of density correction.

FIG. 6 is a diagram showing a hiragana “A” printed by double-width printing or image printing by a conventional method.

FIG. 7 is a partially enlarged view of FIG. 6 and is a diagram illustrating a dot overlapping state.

FIG. 8 is a diagram illustrating details of a dot overlapping state of two rows at the time of printing.

[Explanation of symbols]

 1 Carriage 2 Print Head 3 Platen Rubber 4 Paper Feed Roller 5 Gear 6 Motor 7 Belt 8 Head Driver-Circuit 9 Motor Driver-Circuit 10 Paper Feed Motor Driver-Circuit 11 Carriage Motor Driver-Circuit 12 CPU 13 ROM 14 RAM

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location 8703-2C B41J 3/12 G

Claims (1)

[Claims] 1. A head having a plurality of elements that are energized and generate heat to print an image composed of a plurality of dots, and a head that is movable in the printing direction, and one row along the printing direction by the head. The plurality of elements so that when one dot is printed over another line following the one line, the print density of the dot printed in the overlap is not substantially different from the print density of the dot not printed in the overlap. A serial printer including a head driver circuit for energizing the printer.