JP2858902B2 - Driving method of thermal head - Google Patents

Description

The present invention relates to a method for driving a thermal head in a thermal recording apparatus.

(B) Conventional technology A plurality of heating resistors are arranged in an array on a thermal head of a thermal recording apparatus, and these heating resistors are arbitrarily energized and heated to print on a recording medium. The thermal recording device is disclosed in
No. 60-151074.

It is assumed that printing as shown in FIG. 4 is performed using this thermal recording apparatus. The numbers in the figure correspond to the dots on the recording medium, and a horizontal row of dots 1 to 5, dots 6 to 10, etc., matches the arrangement direction of the heating resistors, and is line by line like Line 1, Line 2, etc. Printing is performed. A horizontal direction parallel to the arrangement direction of the heating resistors in FIG.
The vertical direction is called a sub-scanning direction.

Usually, in adjacent dots, in order not to leave a portion that is not printed between the dots, the printing is controlled so that a part of the dots overlaps. Based on the printing control, FIG. FIG. 5 shows the result of printing as shown in FIG.

In the figure, in Line 1 and Line 2, the dots are slightly overlapped and printed. Immediately after that, in Line 3, there is no printing section 1
Because only 3 is not printed, the temperature of the unprinted section 13 on the recording medium is lower than the temperature of the dots 12 and 14. Therefore, the heat on the recording medium in the portions of the dots 12 and 14 is transmitted to the non-printing section 13 and is printed to a part in the non-printing section 13, and the heating dots of the dots 12 and 14 are generated. The diameter becomes larger than the heat generation dot diameter of the dots 11 and 15. Similarly, also in Line 4, the heat of the dot 18 immediately after the non-printing section 13 is transmitted to the non-printing section 13, and the dot diameter of the dot 18 becomes larger than the heating dot diameter of the dots 17 and 19. Would.

As a result, even if an attempt is made to perform the printing as shown in FIG. 4, the dots 12, 14, and 18 around the non-printing section 13 heat transfer on the recording medium, as shown in FIG. , Unprinted section
There is a problem that 13 is almost filled and printed.

(C) Problems to be Solved by the Invention The present invention has been made in view of the above-mentioned problem, and is intended to prevent heat from being generated around a dot when an arbitrary section in a printing line is not printed. The purpose is to prevent the above-mentioned section from being painted out due to the influence.

(D) Means for Solving the Problems The present invention drives a thermal head having a plurality of heating resistors arranged in parallel to drive a thermal head for printing one line at a time on a recording medium. In the method, for the heating resistor corresponding to the non-printing section on the recording medium, and for the heating resistors located on both sides in the arrangement direction of the heating resistor, a printing line including the non-printing section, At the time of printing each of the three lines immediately before and immediately after, the heating resistors corresponding to the non-printing section on the recording medium and the heating resistors existing on both sides in the arrangement direction of the heating resistors. It is characterized in that applied energy is reduced.

(E) action A heating resistor corresponding to the non-printing section on the recording medium,
And the heating medium existing on both sides in the direction of the sequence of the heat generation antibody and the recording medium at the time of printing each of three printing lines including a printing line including a non-printing section, a line immediately before and after this line. By reducing the applied energy to the heating resistor corresponding to the upper non-printing section and the heating resistor existing on both sides in the arrangement direction of the heating resistor,
Thermal effects on the unprinted section are suppressed.

(F) Embodiment One embodiment of the present invention is shown in FIG. 1 to FIG.

In FIG. 1, a microprocessor MPU applies printing data for each one of four consecutive lines to arbitrary data buffers DB1 to DB4. These data buffers DB1 to DB4 are connected to the respective line buffers LB1.
LB4 to transfer the print data by one byte.

These line buffers LB1 to LB4 are used to transfer one byte of print data from one line of print data to a line switch.
Transfer to shift registers SR1 to SR4 through LI. The line switch LI has a function of sequentially rearranging the print data of four consecutive lines in the line buffers LB1 to LB4 in the order of each line to be printed and applying the data to the shift registers SR1 to SR4.

The data transferred to the shift registers SR1 to SR4 is further transferred to the shift registers SR5 to SR8 for each dot, and then written to the history control table ROM. The history control table ROM converts the printing data for each dot into four signals, that is, a main pulse signal MP, a sub-pulse signal SP1, a sub-pulse signal SP2, or a sub-pulse signal SP3, and these signals are sent to the pulse switch PI. Apply. The signal applied to the pulse switch PI is subsequently applied to the thermal head SH.

Next, the control circuit C exchanges control signals and the like with the microprocessor MPU, and further applies a count clock signal CC and a clear signal CS to the address counter AC. The address counter AC designates addresses for temporarily storing the print data for the four line buffers LB1 to LB4.

Further, the control circuit C sends the chip select signal TS and the write signal WS to the line buffers LB1 to LB4, respectively,
RP is applied to shift registers SR1 to SR4, and shift clock signal SC is applied to shift registers SR1 to SR4 and shift register SR5.
To SR8.

Further, the control circuit C sends the pulse selection signal PS to the pulse switch PI, the read clock signal YC, and the heat control signal HC.
Is applied to the thermal head SH.

 Next, the operation of the above configuration will be described.

The control circuit C applies a clear signal CS to the address counter AC in order to erase the contents of the address counter AC before writing the printing data of each of the continuous four lines, and thereafter applies the clear signal CS to the count clock signal CC. Based on this, the address to which data is to be written is specified for the line bumpers LB1 to LB4. Then, the control circuit C applies a signal for writing the print data to the data buffers DB1 to DB4 to the microprocessor MPU.

According to the signal, the microprocessor MPU
The printing data of four consecutive lines are written to the data buffers DB1 to DB4 line by line. The control circuit C which has detected the writing writes the print data in the data buffers DB1 to DB4 into the line buffers LB1 to LB4 one byte at a time.
A write signal WS and a chip select signal TS are applied to B4. Then, one byte of the print data of one line of the print data written in the data buffers DB1 to DB4 is transferred to the line buffers LB1 to LB4, respectively.

The line buffers LB1 to LB4 always hold one byte of print data of one line in four consecutive lines.

Then, in four consecutive lines transferred to the line buffers LB1 to LB4, the print data for one byte is
In accordance with the count clock signal CC applied from the control circuit C, the data is sequentially read out according to the address specified by the address counter AC. Then, the line buffers LB1 to LB
Due to the line switching operation of the line switch L1 connected to B4, the print data of one byte of the first line is always stored in the shift register SR1 among the continuous four lines.
The shift register SR2 stores the 1-byte printing data of the second line, and the shift register SR3 stores the 1-byte printing data of the third line.
The byte data is further stored in the shift register SR4 by 4
One byte of data in the line is written.

The one-byte data held in the shift registers SR1 to SR4 is sequentially transferred to the shift registers SR5 to SR8 in units of one dot based on a shift clock signal SC applied from the same control circuit C thereafter.

After that, the shift registers SR5 to SR8 respectively store the print data corresponding to, for example, five dots (the horizontal direction shown in FIG. 3) in the main scanning direction, and then store them in the history control table.
Transfer to ROM.

The history control table ROM stores the data as main pulse signal MP and sub-pulse signal SP as information for each dot.
1. The signal is converted into a sub-pulse signal SP2 or a sub-pulse signal SP3, and is sequentially transferred to the pulse switch PI for each signal.

Here, the control circuit C determines which of the four signals transferred to the pulse switch PI is to be combined with the main pulse signal MP and which of the sub-pulse signals SP1, SP2, SP3 to generate heat. Is applied to the pulse switch PI as a pulse selection signal PS. The four signals have different pulse lengths from the main pulse signal MP and the sub-pulse signals SP1, SP2, SP3, as shown in FIG. 2 (a).
As shown in the figure, the main pulse signal MP and the sub pulse signal SP
1, the combination of SP2 and SP3, the information that combines them as data for each dot, the pulse switch PI
Is transferred to the thermal head SH.

That is, the control circuit C prints the heating resistors corresponding to the unprinted sections on the recording medium and the heating resistors existing on both sides in the arrangement direction of the heating resistors, including the unprinted sections. A pulse switch according to the print data signal of the line, the line immediately before and after the line,
The print data signal ID to be transferred from the PI to the thermal head SH is determined. Therefore, by changing the combination of the above-mentioned signals, the pulse length transferred to the thermal head SH changes, and accordingly, the heating time of the heating resistor changes, thereby adjusting the dot diameter on the recording medium. It becomes possible.

In the present embodiment, when heat is generated only by the main pulse signal MP, the dot becomes a dot having the minimum diameter, and when heat is generated by all four signals, a dot becomes the dot having the maximum diameter. I always use it to generate heat.

For example, when printing is to be performed as shown in FIG. 3, when dots 1 to 5 of Line 1 are to be printed, all dots of Line 2 of the next line are printed. Reads the signal (i) of FIG. 2 (b) in which the main pulse signal MP and the sub-pulse signal SP1 are combined as a print data signal ID and transfers the read signal to the thermal head SH according to the clock signal YC. Next, when trying to print dots 6 to 10 of Line2,
Since the dots 13 of Line 3 are not printed, the heating resistors corresponding to the dots 6 and 10 are printed with the signal of FIG. 2B (i) combining the main pulse signal MP and the sub-pulse signal SP1. The read data signal ID is transferred to the thermal head SH in accordance with the read clock signal YC, and the heating resistors corresponding to the dots 7, 8, 9 are supplied with a main pulse signal.
The signal of (ii) in FIG. 2 (b) combined by only MP is read as the print data signal ID and transferred to the thermal head SH according to the clock signal YC.

Further, when the dots 16 to 20 of Line 3 are to be printed, the dots 13 of that line are not printed, and the main pulse signal MP is applied to the heating resistors corresponding to the dots 12 and 14.
The signal (ii) in FIG. 2 (b) is read as the print data signal ID and transferred to the thermal head SH in accordance with the clock signal YC. The heating resistors corresponding to the dots 16 and 20 have the main pulse signal MP and the sub pulse signal.
The signal of (i) in FIG. 2 (b) combined with SP1 is
The print data signal ID is transferred to the thermal head SH in accordance with the read clock signal YC. In addition, dots 17, 1
The signals of (ii) in FIG. 2 (b) based on only the main pulse signal MP are read into the heating resistors corresponding to 8 and 19 as the printing data signal ID and transferred to the thermal head SH in accordance with the clock signal YC.

 Hereinafter, the operation after Line 5 is the same as the above operation.

Thereafter, the printing data signal ID transferred to the heating resistor of the thermal head SH forms a desired dot diameter on the recording paper by the ON / OFF signal of the heating control signal HC applied from the control circuit C, Finally, the stencil diagram shown in FIG. 3 is obtained.

In this embodiment, the pulse length is set to a length as shown in FIG. 2 (a), but the pulse length is not limited to this.

As described above, after the printing data of the first continuous four lines is transferred to the data buffers DB1 to DB4, the printing data of the fifth line is changed to the first line of the first four lines. Is written to the data buffer in which the print data is stored. Therefore, four lines of continuous print data are always written in the data buffers DB1 to DB4 while performing print.

In the above, the flow of data of the first byte of the printing data of the continuous four lines has been described.
When the transfer is completed, the flow as described above is repeated.

By repeating printing for each line in this manner, printing for one screen is completed.

(G) Effects of the Invention According to the present invention, the heating resistors corresponding to the portions not printed on the recording medium, and the heating resistors existing on both sides in the arrangement direction of the heating resistors, include the non-printing section. At the time of printing each of the printing line and the three lines immediately before and after this line, the heating resistor corresponding to the non-printing section on the recording medium, and the heating resistor existing on both sides in the arrangement direction of the heating resistor By determining the applied energy to be applied to the heating resistor, the unprinted section is not filled, and the printing quality is improved.

[Brief description of the drawings]

FIG. 1 is a block diagram of a control circuit used in a method of driving a thermal head according to the present invention. FIGS. 2A and 2B are pulse waveform diagrams showing pulse lengths of a main pulse signal and a sub-pulse signal according to the present invention. FIG. 3 is a transcript showing printing using the thermal head driving method according to the present invention, and FIG.
Imprint model drawing for printing all except one section, 5th
The figure is an imprint diagram obtained by imprinting using a conventional method. MPU: microprocessor, DB1 to DB4: data buffer, LB1 to LB4: line buffer, C: control circuit,
SR1 to SR8: Shift register, PI: Pulse switch, SH
…… Thermal head, LI …… Line switcher.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁶ , DB name) B41J 2/36 H04N 1/23

Claims (1)

(57) [Claims] 1. A method of driving a thermal head for printing one line at a time on a recording medium by driving a thermal head having a plurality of heating resistors arranged in parallel. Regarding the heating resistor corresponding to the imaging section and the heating resistors existing on both sides in the arrangement direction of the heating resistor, three lines including a printing line including a non-imaging section, a line immediately before and after this line, At the time of each printing, the energy applied to the heating resistors corresponding to the non-printing section on the recording medium and the heating resistors existing on both sides in the arrangement direction of the heating resistors are reduced. Driving method of thermal head.