JPH0416365A - Thermal head - Google Patents

Abstract

PURPOSE:To realize an appropriate conduction duration for a command signal having any printing period by a method wherein the conduction time of exothermic resistive elements is controlled, based on the temperature and the printing period. CONSTITUTION:As printing data DA are inputted by clock pulses CLK into a thermal head 11 and as printing commands PRC are inputted into a CPU 16 afterward, the CPU 16 measures the temperature based on signals outputted from a thermistor 12 and, at the time, counts 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 directly based on the temperature measured by the thermistor 12. A head address is specified out of the printing periods 1-7 based on the printing period of the counter 15 and the conduction time corresponding to the head address is read out of the table. Then strobe signals STR corresponding to thus-read out conduction time are inputted into the thermal head 11 for execution of the electrification and the printing.

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 element array in which a plurality of heat generating resistor elements are arranged in a row on a substrate.

(B) Conventional Technology A generally well-known thermal head has heating resistive elements for printing arranged in a line on a substrate, and a driver IC for controlling the energization of these heating resistive elements is also mounted on the substrate. It is installed on top. This driver IC has
A shift register that captures the data to be printed in a bit-sorial format, a latch circuit that captures all the don't data stored in the shift register in parallel, and a drive circuit that individually drives the heating resistor elements according to the output data of the latch circuit. etc. are built-in. In this thermal head, first, the data to be printed is input bit-sequentially into a shift register along with a clock signal, and at the timing when all the data is stored, each focus output of the shift register is output simultaneously in parallel, launched into a latch 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. This kind of printing operation is performed every time a printing command is input.
It is repeated in sequence.

(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 the 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 heating resistor element will not radiate heat sufficiently. The next printing command is given to the printer, and this residual heat affects the thermal printing quality, making it impossible to print with high precision. Therefore, appropriate energization according to the printing cycle is required for high-speed printing.

Therefore, if a user of a thermal head were to design an external control circuit that matches the printing cycle specified by the user, the control circuit would become extremely complex, and if printers with different printing speeds were to be manufactured, There is a problem in that a control circuit must be designed to suit the printer.

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 purpose is to provide a thermal head that is capable of high-precision printing that takes temperature into consideration.

(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 drive 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; and energization control means for controlling the energization time of the heating resistor element based on the temperature measured and the printing cycle measured by the printing cycle measuring means.

In this thermal head, when the temperature is measured by the temperature sensor and the printing cycle is measured by the printing cycle measuring means, the optimum energization time is selected or calculated by the energization control means according to the temperature and printing cycle. , the heating resistor element is energized for the energization time. Therefore, even if the user manually issues a printing command for any printing cycle, appropriate printing can be automatically performed that matches the printing cycle and temperature.

(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 1 and a thermal head 11.
a thermistor (temperature sensor) 12 that detects the temperature of the thermistor 12, an A/D converter 13 that converts the temperature signal detected by the thermistor 12 into a digital signal, an oscillator 14, a counter 15 for measuring the printing cycle, a CPU 16, and a memory. 17 and r1
Microcomputer (microcomputer) consisting of 0 circuits and 18
19, and each of these circuits is integrally configured as a unit as a thermal head device.

The thermal heater 11 is already well known, and has a plurality of heating resistive elements for printing dots arranged in a line on the top surface of the substrate, and each of these heating resistive elements is driven by four electric currents. It is equipped with a driver IC for this purpose.

The driver IC includes a shift register for storing input data, a sub circuit, and a drive circuit for driving each heat generating resistor element.

The thermistor 12 is a sensor for detecting the temperature of the thermal head 11, and the temperature signal detected by the thermistor 12 is converted into a digital signal by an A/D converter 13 and then input to the CPU 16. .

The counter 15 counts the pulse signals from the oscillator 14 after the print command PRC (latch signal LA) is input, and counts the number of pulses until the next print command PRC.
It has a function to count the printing cycle.

When the CPU 16 receives a printing command PRC from the outside, it calculates the temperature based on the signal from the thermistor 12 and measures the printing cycle based on the count value of the counter 15.The CPU 16 calculates the temperature based on the signal from the thermistor 12, and measures the printing cycle based on the count value of the counter 15. It has a function of reading the energization time from the memory 17 and outputting a strobe signal corresponding to the energization time to the thermal radar 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 set on the joint shaft, and the corresponding energization time is stored in each column.The address according to the measured temperature is stored in the CPU 16.
The printing cycle is directly specified by the 8-bit temperature signal 0O-FF output from the 8-bit temperature signal 00-FF, and the printing cycle is determined by the first address 1000,
... 1600 is specified. Therefore, when the printing cycle and temperature are measured, the energization time is read out by specifying the corresponding start address and reading address on the horizontal axis, and the strobe signal STR corresponding to this is input to the thermal head 11 and printed. It has become so.

Next, the operation of the thermal head device of the above embodiment will be explained with reference to the flowchart shown in FIG. As shown in FIG. 3, the CPU 16 determines whether a print command PRC has been input (step 5TI). When the print command PRC is input after the print data DA is input to the thermal head 11 in accordance with the clock pulse CLK, the determination in step STl becomes YES, and the CPU 16 measures the temperature based on the signal from the thermistor 12. At the same time, the printing cycle is measured based on the signal from the counter 15 (step ST2,
Step 5T3). The temperature measured by this thermistor 12 determines the O on the horizontal axis of the energization time table of the memory 17.
The addresses O to FF are directly specified, and the counter 15
The print cycle specifies the start address of one of the print cycles 1 to 7 to which the print cycle belongs, and
The corresponding energization time is read out (step 5T4).

Then, the strobe signal STR corresponding to the read energization time is applied to the thermistor 11 (step 5T5).
), the heating resistor element of the thermistor 11 is energized and printed in accordance with the pulse width of the strobe signal STR.

Therefore, if the printing cycle currently detected by the counter 15 belongs to, for example, printing cycle 2, and the reading address according to the temperature measured by the thermistor 12 is 01, the current application time applied to the thermal head 11 is the beginning of the printing cycle FJJ 2. The energization time stored at the intersection of address 1100 and temperature 01 is read out, and the thermal head 11 is energized during that time.

Next, for example, if the printing cycle measured by the counter 15 belongs to the middle white of printing cycle 3, and the temperature measured by the thermistor 12 is addressed by 03, then the first address 1200 of printing cycle 3 The energization time stored at the intersection of temperature reading address 03 is read out and applied to the thermal head 11.

For example, if printing period 2 is smaller than printing period 3, the shorter printing period is more affected by the residual heat of the heating resistor element. This means that the printing cycle 2 is shorter than the above.

On the other hand, even if the printing cycle is the same, if the measured temperature is high, it will be more affected by the heat than if it is low, so in this case too, the energization time will be shorter if the temperature is higher than if it is lower. Become. 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.

In the above embodiment, the energization time is read from the memory table based on the temperature and printing cycle, but C
If the PU 16 has the ability, these may be calculated using a conversion formula.

(F) Effects of the Invention According to the present invention, the temperature and printing cycle are measured, and the energization time of the heating resistor element is controlled based on these temperatures and printing cycles, so that the user can input any printing cycle command signal. Since the most appropriate energization time can be controlled by inputting , high-speed printing can be achieved with a free printing cycle. What's more, since it also has the ability to control the energization time based on temperature, users can always use this thermal head at high speed and with appropriate quality even in harsh environments. can be printed.

[Brief explanation of the drawing]

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. 2 is a flowchart illustrating the general operation of the head device. 11: Thermal head, 12: Thermistor, 15: Counter, 15: cPU. 17: Memory. Patent Applicant: ROHM Co., Ltd. Agent, Patent Attorney: Shigeru Nakamura, Number 1 Data, J-Use, etc.

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 means that measures the cycle of an input printing command, and the temperature measured by the temperature sensor and the printing cycle measured by the printing cycle measuring means. and energization control means for controlling the energization time of the heating resistor element.