JPS63254060A - Driving control circuit for thermal head - Google Patents

Abstract

PURPOSE:To obtain excellent printing quality, by dividing the frequency of a driving signal for performing the driving of the heat generating element groups of a printing head to drive each of the heat generating element groups in a time sharing manner. CONSTITUTION:Drive signals DV1-DV4 are respectively, simultaneously, brought to an ON- state in order to perform printing operation and it is necessary to change the ON-time thereof at every heat generating element groups according to the characteristic of a thermal head. For example, the high resistance heat generating element group of the thermal head is made long timewise and the low resistance heat generating element group thereof is made short timewise. When either one of the driving signals DV1-DV4 is in an ON-state, the input signals at the ENB terminal and CLR terminal of a divide-by-4 system counter 41 are turned ON and the divide-by-4 system counter 41 performs counting operation in synchronous relation to a clock signal and outputs QA, QB are successively changed over. The AND results of the output of the divide-by-4 counter and the driving signals DV1-DV4 are supplied to the terminals STB 1 - STB 4 of the thermal head. That is, the pulses obtained by dividing the frequencies of the driving signals DV1-DV4 by 4 are applied to STB 1 - STB 4 in a time sharing manner. Therefore, the heat generating element groups can be driven at an extremely short cycle and become almost simultaneous in the rising of temp.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a thermal head drive control circuit for controlling the drive of a line-type thermal head in a direct thermal type or thermal transfer recording apparatus, particularly in a thermal transfer type color recording apparatus.

(Prior Art) The configuration of a conventional thermal transfer color recording apparatus is shown in a perspective view in FIG. The apparatus shown in the figure is a so-called field-sequential swing system, and will be explained below.

In the figure, 1 is a print head (line thermal head) equipped with a plurality of heating resistors arranged in a line, and this print head is supplied from a paper roll 3 between it and a platen 2 in the direction of arrow A. Thermal transfer recording is performed by sandwiching the paper 4 running along the ink ribbon 7, which runs together with the recording paper 4 supplied and wound up by the supply roll 5 and the take-up roll 6. Reference numeral 8 denotes a greso shear roller facing the platen 2.

The ink ribbon 7 has a width equivalent to the paper width, and has a dimension L' slightly larger than the recording area 9 in which transfer inks of three primary colors for printing yellow, magenta, and cyan are preset. It is coated. This device is
First, yellow is transferred to the recording area 9, then the paper 4 is sent backwards to the initial position and set, then magenta is transferred, and then cyan is transferred in the same manner as above. This is to record multiple screens. Here, in order to sequentially record yellow, magenta, and cyan, the ink ribbon 7 has a mark 10a corresponding to the printing start position of each color.
, 10b, and 10c are printed in advance, and the sensor 11 detects them.

Normally, the print head 1 rotates about a fulcrum 13 attached to a bracket 12 and is kept pressed against the platen 2 by a spring 14 to perform recording. During standby or when the ink ribbon 7 is running to set the printing start position of each color, the motor 15 and cam 16 move the head down to separate the print head 1 from the platen 2.

In such a configuration, if it is predetermined to print in the order of yellow, magenta, and cyan, the mark 10a corresponding to the yellow printing start position is placed on the sensor 1 when the power is turned on.
After the initial setting of running until detection in step 1 and positioning,
Start printing.

Next, FIG. 4 shows the configuration of the head control circuit of the thermal transfer type color recording apparatus. In the same figure, 20 is a ROM, R
A control section consisting of an AM, a timer, a microprocessor, etc., controls each part; 21 is an interface line for inputting commands and print data from an external host device; 22 is a control section for controlling input/output with the line thermal head 1; I10 port 23 is an I10 port that controls output to the paper feed motor 26, ribbon feed motor 27, and head motor 15 via the motor driver 25, and controls input of detection information from the paper sensor 28 and ribbon sensor 29. This I10 boat 22.23 and control unit 20
and are connected by a common control bus 24.

FIG. 5 is a circuit diagram showing the configuration of the line thermal head 1. In the figure, the thermal head 1 includes a shift register circuit 30, a latch circuit 31, a logic element 32, and a heating element 33.

First, the DATA section of the shift register 30 contains CLOC.
Data to be printed is input in synchronization with the clock signal input to section K. When one line of print data has been input to the shift register circuit 30, the shift register circuit 3
In order to transfer data from 0 to the latch circuit 31, a latch signal is applied to the LATCH section from the control section 20 shown in FIG. By transferring the print data to the latch circuit 31, the shift register circuit 30 can transfer the print data of the next line. The data of the latch circuit 31 can selectively energize the heating element 33 based on the drive signals of STBs (strobes) 1 to STB 4 and the logic conditions of the logic element 32.

The terminals of STB 1 to STB 5TB4 are I5TBfi, D2 because the heating elements 33 are divided into heating element groups and driven separately.
Approximately 56 dots are driven at once, and the power supply capacity can be reduced by driving the heating element groups corresponding to 5TB1 to 5TB4 with a temporal shift.

FIG. 6 shows a time chart when the above-mentioned series of operations are carried out by this recording apparatus. In the figure, the paper feed motor and the ribbon feed motor are advanced by one step, then one line of print data is transferred from the DATA section and the CLOCK section of the thermal head 1, and then the LATCH
A pulse is applied to 5TBI to 5TB4 to transfer data to the latch circuit 31, and then a signal with a constant pulse width is sequentially applied to 5TBI to 5TB4 to energize the heating element 33, and the - line printing operation is completed. By repeating these series of operations, one screen of operations is completed.

(Problems to be Solved by the Invention) However, the thermal head control circuit in the thermal transfer type color recording apparatus has the following problems.

As shown in Fig. 6, since the drive signal with a constant pulse width is temporally divided to drive the heat generating element group, when the drive of the heat generating element group is switched, that is, when the drive signal is adjacent to the heat generating element group to be driven, Due to the influence of heat from the heating elements in the heating element groups, density differences occur at the boundaries of the heating element groups in the printed image, resulting in a significant deterioration in print quality. This is not so much of a problem when printing characters or data related to combo graphics, but it is particularly noticeable when printing natural image information or the like using the area gradation method. In order to solve the above problem, it is possible to simultaneously generate drive signals and drive each heating element group at the same time, but the power supply capacity would be four times that of the conventional four-division case. There is a problem.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and provide a thermal head drive control circuit with excellent print quality.

(Means for Solving the Problems) In order to solve the problems of the prior art, the present invention includes a print head having a plurality of heating elements, and thermally prints on a recording medium by driving each heating element. The thermal head drive control circuit for this purpose includes the following means.

The thermal head drive control circuit divides and drives a plurality of heat generating elements into each heat generating element group, and therefore includes a control means for outputting a plurality of drive signals corresponding to the number of heat generating element groups, and a control means for outputting a plurality of drive signals corresponding to the number of heat generating element groups; Divide the signal by the number of heating element groups,
The apparatus is configured to include drive signal frequency dividing means for supplying frequency-divided drive signals to the print head so that each heating element group is sequentially driven in a time-division manner.

(Function) Since the thermal head drive control circuit is configured as described above, each technical means functions as follows.

When performing thermal printing in the thermal head drive control circuit according to the present invention, the control means divides and drives the plurality of heating elements of the print head into each heating element group, so the number of heating elements corresponding to the number of heating element groups, For example, the same number of drive signals as the number of element groups are output.

'The drive signal frequency dividing means divides the frequency of the drive signal by the number of heat generating element groups, and supplies each frequency divided drive signal to the print head so that each heat generating element group is driven in a time division manner.

Therefore, each heating element group can be driven in an extremely short cycle, so the temperature rise of each heating element is almost the same.1. Thermal printing can be performed between the groups of heating elements to be driven without being affected by heat from each heating element. Therefore, the problems of the prior art can be solved.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram showing the main part configuration of the thermal head drive control circuit according to this embodiment. In the figure, the same components as those in FIG. 4 used in the conventional explanation are designated by the same reference numerals. It is attached.

In FIG. 1, the thermal head drive control circuit according to this embodiment includes an OR circuit 40.
It is constructed by providing a quaternary counter 41, inversion circuits 42 and 43, and AND circuits 44 to 47.

The I10 port 22 is connected to the thermal head 1 as before.
Transfer print data to DATA.

This is done using the CLOCK and LATCH signals. Drive signals DV1~ for driving each heating element group of the thermal head 1
Dv4 is supplied from the control unit (not shown) to the I10 port and connected to the OR circuit 40 and the AND circuits 44 to 47. The output of the OR circuit 40 is the EN of the quaternary counter 41.
Connected to B terminal and CLR terminal. Quaternary counter 41
If the output of the OR circuit 40 is at the "herb (high) level", a counting operation is performed in synchronization with a clock (CLOCK) supplied from a control section (not shown).
If it is "LOW level", the counting operation is stopped and cleared.

The output QA + QB of this quaternary counter 41 is CLK
Every time a clock pulse is input to the terminal, 00°0
The state 1, 10, 11, 00, 01, . . . is repeated.

The inverting circuits 42 and 43 output QA of the quaternary counter 41.
Invert yQB and output QA and QB. AND circuits 44 to 47 output drive signal DV, to DV4. Output QA r QB % of quaternary counter 41 and output QA of inverter 42.43.

A logical AND operation is performed with QB, and the output is supplied to 5TB1 to 5TB4 of the thermal head 1.

Next, the operation of this embodiment will be explained with reference to FIG.

FIG. 2 is a time chart showing the operation of the thermal head drive control circuit according to this embodiment. As shown in the figure, drive signals DV1 to DV4 are turned on at the same time to perform a printing operation. The on time needs to be changed for each heating element group depending on the characteristics of the thermal head.

For example, depending on the resistance value characteristics of each heating element of the thermal head, a group of heating elements with high resistance takes a long time, and a group of elements with a low resistance takes a short time. If any of the drive signals DV, to DV4 is on, the input signals to the ENB terminal and CLR terminal of the quaternary counter 41 are not on.
1 performs the above-mentioned counting operation in synchronization with the clock signal, and sequentially switches the outputs QA and QB. The logical product results of the output of the quaternary counter 41 and the drive signals DV1 to DV4 are supplied to terminals 5TBI to 5TB4 of the thermal head 1. That is, for 5TBI to 5TB4,
Pulses obtained by frequency-dividing the drive signals DV1 to DV are applied in a time-division manner.

In this way, by time-divisionally inputting drive pulses to 5TBI to 5TB4, each heating element group can be driven in an extremely short period, and the temperature of each heating element increases almost simultaneously. Therefore, since the heat generation conditions of each heating element group are almost the same, ls! There is no thermal influence between the heating elements in the heating element groups that are in contact with each other, and it is possible to obtain high-quality printing results with no difference in density between the heating element groups.

Further, in this embodiment, the heating elements of the thermal head 1 are divided into four element groups and driven, but the present invention is not limited to this. For example, in the case of dividing and driving six heat generating element groups, the drive signal may be set to DV, .about.DV, and this drive signal may be frequency-divided and input to the thermal head.

It goes without saying that the method for driving a line thermal head described in this embodiment can be applied to printers using a line thermal head such as a direct thermal type or a thermal transfer type.

(Effects of the Invention) As described above in detail, according to the present invention, each heating element group is time-divisionally driven by dividing the frequency of the 1@ motion signal for driving the heating element groups of the print head. Therefore, each heating element group can be driven in an extremely short cycle.

Therefore, the temperature rise of each heating element is almost the same, thermal printing can be performed with no density difference between heating element groups without being affected by the heat of adjacent heating elements, and printing with excellent print quality can be achieved. As a result, printing results such as natural image information can be provided.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a thermal head drive control circuit according to an embodiment of the present invention, FIG. 2 is a time chart showing the operation of FIG. 1, and FIG. 3 is a perspective view showing the configuration of a thermal transfer color recording device. 4 is a diagram showing the configuration of a conventional thermal head drive control circuit, FIG. 5 is a diagram showing the configuration of the thermal head, and FIG. 6 is a time chart showing the operation of FIG. 4. 1...Thermal head, 22...I10 port, 4
0...OR circuit, 41...Quadary counter, 42.
43... Inverter, 44, 45, 46.47... AND circuit.

Claims (1)

[Claims] In a thermal head drive control circuit that includes a print head having a plurality of heating elements and performs thermal printing on a recording medium by driving each heating element, the plurality of heating elements are arranged in each heating element group. In order to drive the heating elements separately, the control means outputs a plurality of drive signals corresponding to the number of heating element groups, and the frequency of each of the plurality of driving signals is divided by the number of heating element groups so that each heating element group is 1. A thermal head drive control circuit comprising drive signal frequency dividing means for supplying each drive signal frequency-divided to the print head so as to be driven in divisions.