JPH0416364A - Thermal head - Google Patents

Abstract

PURPOSE:To realize an appropriate conduction time control for a command signal having any printing period by a method wherein each of exothermic resistive elements is controlled, based on data of the temperature, the printing cycles and thermal hysteresis level for each of bits. CONSTITUTION:A CPU 16 inputs start signals into a thermal hysteresis control circuit 20 as printing data DA1 are inputted therein by clock pulses CLK1 and printing commands PRC are inputted therein. After receiving the printing commands PRC, the CPU 16 measures the temperature based on signals from a thermistor 12, and measures printing period based on signals from a counter 15. Addresses on the axis of abscissa 00-FF in a conduction time table stored in a memory 17 are specified based on the measured temperature, and printing period necessary for operation is extracted out of the printing cycles 1-7 based on the print period of the counter 15. On the other hand, the thermal hysteresis control circuit 20, with the start signals inputted therein, specifies the conduction time by outputting level signals (additional level amplitude) in accordance with the thermal hysteresis of each of bits.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a thermal head that is provided with a heat generating resistor array in which a plurality of heat generating resistive elements are arranged in a row on a substrate.

(0) Prior Art In the generally well-known thermal system, heating resistive elements for printing are arranged in a line on a substrate, and a driver I is used to control the illumination of these heating resistive elements.
C is also mounted on the board. This driver IC includes a shift register that captures the data to be printed into a pinto serial, a latch circuit that captures all dot data stored in the soft register all at once in parallel, an output data register of the launch circuit, and a heating resistor that individually controls the output data. It has a built-in drive circuit, etc. that drives the energization. In this thermal head, the data to be printed is first input into the shift register together with a clock signal in focus order, and at the timing when all the data has been stored, the outputs of each focus of the shift register are output simultaneously in parallel, latched into the launch circuit, and then When a print command is input, the drive circuit energizes the corresponding heating resistor to generate heat according to the data to be printed on the launch circuit, thereby printing. Such printing operations are sequentially and repeatedly performed each time a printing command is input.

(c) Problems to be Solved by the Invention In recent years, when a thermal head is employed in a code printer or the like that prints a large number of bar codes, it is required to have a high-speed printing function. However, since the energy applied to thermal heads differs depending on the printing cycle and temperature of the thermal head, if a normal thermal head using the conventional thermal printing control method described above is used for high-speed printing, the thermal history, printing cycle, and temperature will be This affects the quality and makes it impossible to print with high precision. Therefore, for high-speed printing, it is necessary to control the printing cycle, control accordingly, and control that takes thermal history into consideration.If the user of the thermal head were to design an external control circuit to achieve this purpose, the control circuit would be extremely complicated. In addition to being complicated, when producing printers with different printing speeds, there is a problem in that a control circuit suitable for each printer must be designed each time.

The present invention has been made in view of the above-mentioned problems, and does not require a user who incorporates a thermal head into a printer to design any special control circuit no matter what printing cycle is used. The objective is to provide a thermal head that is capable of high-precision printing that takes temperature and thermal history into account.

(d) Means and operation for solving the problems The thermal head of the present invention has a heating resistor array in which a plurality of heating resistors are arranged in a row, and a heating resistor array that responds to print data each time a printing command is input. , a heating resistance element driving circuit that individually energizes the heating resistance elements to print dots; a temperature sensor that measures temperature; a printing cycle measuring means that measures the cycle of input printing commands; heat history control means for detecting the heat history level of each of the above-mentioned heat generation by the temperature measured by the temperature sensor, the printing cycle measured by the printing cycle measurement means, and the heat history level detected by the heat history control means; and energization control means for controlling the energization time of the resistance element.

In this thermal head, the temperature is measured by the temperature sensor, the printing cycle is measured by the printing cycle measuring means, and the thermal history level of the heating resistor element is detected by the thermal history control means. The optimum energization time corresponding to the level is selected or calculated by the energization control means for each heating resistor element, and the heating resistor element is energized for the selected energization time. Therefore, even if the user inputs a printing command for any printing cycle, appropriate printing can be automatically performed in accordance with the printing cycle.

(E) Examples The present invention will be explained in more detail with reference to Examples below. FIG. 1 is a circuit block diagram of a thermal head showing an embodiment of the present invention. In the figure, a thermal head device 1 includes a thermal head 11 and a thermal head 1.
1, an A/D converter 13 that converts the temperature signal detected by the temperature sensor 12 into a digital signal, an oscillator 14, a counter 15 for measuring printing cycle, a CPU 16, and a memory 17. and an I10 circuit 18, and a thermal history control circuit 29, and these circuits are integrated into a unit as a thermal head device.

Thermal head 1 is already well known, and includes a plurality of heating resistive elements for printing donts arranged in a line on the top surface of the substrate, and a driver for driving each of these heating resistive elements with current. It is equipped with an IC.

The driver rC includes a shift register for storing input data, a launch circuit, and a drive circuit for driving each heating resistor element with electricity.

The thermistor 12 is a sensor for detecting the temperature of the thermal spatula Fil, and the temperature signal detected by the thermistor 12 is converted into a digital signal by an A/D converter 13 and then taken into the CPU 16.

The counter 15 has a function of counting pulse signals from the oscillator 14 after the printing command PRC (LAI) is input, counting the number of pulses until the next printing command PRC, and counting the printing cycle.

When the CPU 16 receives a print command PRC from the outside, it outputs a start signal in synchronization with the print command PRC, and further performs control to output a latch signal LA2 and a stroke signal STR to the thermal head 11.

The memory 17 stores an energization time table shown in FIG. This energization time table takes temperature on the horizontal axis and
The printing cycle is plotted on the vertical axis, and the corresponding energization time is stored in each column.The address according to the measured temperature is the CPU 16.
The printing cycle is directly specified by the 8-bit temperature signal 00 to FF output from the 8-bit temperature signal, and the printing cycle is determined depending on which of printing cycles 1 to 7 the measured printing cycle belongs to, and to which additional pulse width in each printing cycle. The start address is specified depending on whether the address corresponds to the address. Therefore, when the printing cycle and temperature are measured and the additional pulse width from the thermal history control circuit is determined, the energization time is read from the corresponding address and the designation on the horizontal axis. , data corresponding to each pulse width is input and printed.

The thermal history control circuit 20 is composed of a gate array, receives input data DAI together with a clock signal CLK, takes in the data, and checks for each bit data whether or not there was printing in the previous and two previous times, and whether or not there is a printed conductor for adjacent bits on the left and right. The thermal history of each bit is detected and a level signal corresponding to the thermal history is output.

Regarding heat history, heat history states from level 1 to level 6 are defined as shown in FIG. Level 1 is past 2
The printing status of that bit is 0, and the printing status of the adjacent bit is also 0, indicating the highest level that requires a lot of energy to heat. One or both bits are in the printing state, but the printing state of that bit in the previous two times was 0, and the degree of energy required this time is the second highest level. Similarly, in the case of level 6, the bit has been printed in the previous time or the time before the previous time, and the bit on one side or the bits on both sides are additionally printed. In this case, it indicates a level where the printed ball name rugi for that bit at this time is relatively small.

In this thermal head device, by detecting the thermal history from level 1 to level 6 shown in FIG. 4, the energization time is controlled accordingly.

When the thermal history control circuit 20 detects that the thermal history at that bit is at level 1, the heating resistor element is energized for the longest time; conversely, when the thermal history is at level 6,
It will be energized for the shortest time.

The embodiment thermal head device 1 configured as described above detects and measures the temperature of the thermal head 11 with the thermistor 12, measures the printing cycle of the print command PRC with the counter 15, and further measures the temperature with the thermal history control circuit 20. The history state is detected, the corresponding energization time is read from the memory 17 according to the temperature, printing cycle, and thermal history, and the energization of the heating resistor element for each bit of the thermal hand 11 is controlled according to the energization time. It looks like this.

Next, the operation of the thermal device of the above embodiment will be explained with reference to the flow diagram shown in FIG. 3 and the time chart shown in FIG. 5. As shown in FIG. 3, the CPU 16 determines whether a print command PRC is input or not (step 5TI).
. As shown in the 5th episode, the data DAI to be printed is input by clock pulse CLK 1, and then the print command P
When RC is input, the CPU 16 applies a start signal to the thermal history control circuit 20. The CPU 16 issues a print command P.
After receiving RC, the temperature is measured based on the signal from the thermistor 12, and the printing cycle is measured based on the signal from the counter 15 (step ST2, step 5T).
3), depending on the temperature measured by this thermistor 12,
Addresses from 00 to FF on the horizontal axis of the energization time table in the memory 17 are directly specified, and the print cycle of the counter 15 determines which print cycle from print cycles l to 7 in FIG. 2 the print cycle belongs to. Extract and print cycle 1
From this, a rough range of energization time in printing cycle 7 is specified.

On the other hand, when a start signal is applied to the thermal history control circuit 20, in response to this, the thermal history control circuit 20 determines whether or not each bit input this time is printed, and also determines whether or not each bit that has been input this time is printed, and also determines whether the bit cell is printed twice before and on both sides of the bit cell. Considering the presence or absence of printing in focus, it is extracted which level from level 1 to level 6 shown in FIG. 4 corresponds to the level to be printed this time. Then, the level for each focus is added to the thermal radar 11 as data DA2.

If the printing level of a specific bit in the thermal history control circuit 20 corresponds to level 1, relatively large printing energy is required this time, so the DA in FIG.
Print data is output from A shown in 2. Then, A, B, C, D, E, F for each start signal after printing ends.
Printing will continue continuously during this period.

On the other hand, if the level of the bit extracted by the thermal history control circuit 20 is level 6, it means that the thermal energy of the current bit cell may be relatively small. It is sufficient to apply electricity only for a period corresponding to the final pulse width F indicated by DA2. 20F indicates the basic pulse width.

Therefore, assuming that the printing cycle currently detected by the counter 15 belongs to printing cycle 2 and the level of thermal history extracted by the thermal history control circuit 20 is 3, the address based on the temperature measured by the thermistor 12 is Then, the energization time of the dot bit applied to the thermal head 11 is
The energization time stored at the intersection of the address 1800 and the temperature 01 in the third additional pulse of the printing cycle 2 is read, and the thermal radar 11 is energized during that time.

Next, for example, assume that the printing cycle measured by the counter 15 belongs to the middle white of printing cycle 3, and that the temperature measured by the thermistor 12 is addressed by 03, and the temperature is extracted by the thermal history control circuit 20. Assuming that the level is level 4, the applied pulse width 4 of the printing cycle 3 and the temperature address 03
The energization time stored at the intersection is read out and applied to the thermal head 11. Now, for example, if printing circumference M2 is smaller than printing period 3, the smaller printing period is more affected by thermal history and temperature, so if the same thermal history and temperature are used, i! ! This means that the printing cycle 2 is shorter than the character cycle 1iA3.

On the other hand, even if the printing cycle 2 is the same, if the measured temperature is high, it will be more affected by heat than if it is low, so in this case too, the higher the temperature, the longer the energization time will be than the lower one. becomes smaller. In this way, the most appropriate energization times corresponding to each printing period and temperature are stored in the table shown in FIG. 2, respectively.

Note that if the level of the thermal history extracted by the thermal history control circuit 20 is, for example, level 3 as described above, and if the printing cycle is 2 as in the above example,
The temperature corresponding to the position 1800 of the additional pulse width 3, then the i[l open time of the intersection of each address of the applied pulse width 4, the applied pulse width 5, the basic pulse width, and the measured temperature are read out in sequence, and the total time is read out. will be illuminated.

As described above, when the temperature measurement by the thermistor and A/D converter and the printing cycle measurement by the counter are completed, the corresponding energization time control ratio is determined from the table based on the temperature and printing cycle by the step 5T.
4) Finally, energization printing is performed for each bit according to the illll open time read out (Stenbu 5T5
).

In the above embodiment, the energization time of the heat control ratio is read from the table based on the temperature and printing cycle, but if the CPU 16 has the ability, these may be calculated using a conversion formula.

(F) Effects of the Invention According to this invention, the temperature and printing cycle are measured, and the thermal history level of each bit is extracted, and the current-carrying time of each heating resistor element is determined based on these temperatures, printing cycle, and heat level. Therefore, no matter what print cycle command signal the user inputs, the most appropriate energization time can be controlled, making it possible to achieve high-speed printing with a free print cycle. . Moreover, since it also has the ability to control the energization time based on temperature and the thermal history level, users can use this thermal head without worrying about it in any environment. This makes it possible to always print at high speed and with appropriate quality.

[Brief explanation of drawings]

FIG. 1 is a circuit block diagram showing a thermal head device according to an embodiment of the present invention, FIG. 2 is a diagram showing an energization time table stored in the memory of the thermal head device, and FIG. FIG. 4 is a flowchart for explaining the general operation of the head device, FIG. 4 is a diagram for explaining the thermal history level of the thermal history control circuit of the thermal head device, and FIG. 5 is a flow diagram for explaining the operation of the thermal head device. This is a time chart for 11: Thermal head, 12: Thermistor, 15: Counter, 16: CPtJ, 17: Memory,
20: Thermal history control circuit. mouth diagram

Claims (1)

[Claims] (1) A heating resistor array consisting of a plurality of heating resistive elements arranged in a row, and a heating resistor that individually energizes the heating resistive elements to print dots each time a print command is input, according to print data. an element drive circuit, a temperature sensor that measures temperature, a printing cycle measuring unit that measures the cycle of input printing commands, a thermal history control unit that detects the thermal history level of each of the heating resistor elements, and the temperature sensor. energization control means for controlling the energization time of each heating resistor element based on the temperature measured by the temperature, the printing cycle measured by the printing cycle measuring means, and the heat history level detected by the heat history control means. A thermal head featuring