JPH0832465B2 - Thermal head - Google Patents

Description

The present invention relates to a thermal head having a heating resistance element array in which a plurality of heating resistance elements are arranged in a row on a substrate.

(B) Conventional technology In a well-known thermal head, heating resistance elements for printing are arranged in a line on a substrate, and a driver IC for controlling the energization of these heating resistance elements is also included. It is mounted on the board. This driver IC has a shift register that captures data to be printed bit-serially, a latch circuit that captures each dot data stored in the shift register in parallel, and heating resistor elements individually according to the output data of the latch circuit. It has a built-in drive circuit for energization. In this thermal head, the data to be printed is first bit-sequentially input to the shift register together with the clock signal, and at the timing when all the data is stored, the bit outputs of the shift register are simultaneously output in parallel and latched in the latch circuit. When a print command is input, the drive circuit energizes the corresponding heating resistor to generate heat according to the data to be printed in the latch circuit, thereby performing printing. Such a printing operation is performed every time a print command is input.
It is repeated in sequence.

(C) Problems to be Solved by the Invention In recent years, when a thermal head is used in a bar code printer or the like that prints many bar codes, it is required to have a high-speed printing function. However, since the applied energy differs depending on the print cycle and the temperature of the thermal head, the thermal history, print cycle, and temperature will not be printed when the normal thermal head with the conventional thermal print control system described above is used for high speed. Quality is affected and high-precision printing cannot be performed. Therefore, for high-speed printing, it is necessary to perform control according to the print cycle and control that considers the thermal history, but when the user of the thermal head designs an external control circuit to achieve this purpose, the control circuit is extremely In addition to the complexity, there is a problem that when manufacturing a printer having a different printing speed, a control circuit suitable for the printer must be designed each time.

The present invention has been made in view of the above-mentioned problems, and a user who incorporates a thermal head into a printer does not need to design any special control circuit for any printing cycle, and the thermal head It is an object of the present invention to provide a thermal head capable of highly accurate printing in consideration of temperature and heat history.

(D) Means and Actions for Solving the Problems A thermal head according to the present invention responds to print data each time a print command is input, and a heat generating resistance element array in which a plurality of heat generating resistance elements are arranged in series. A heating resistance element drive circuit for individually energizing the heating resistance elements to print dots, a temperature sensor for measuring the temperature, a print cycle measuring means for measuring the cycle of an input print command, and a past for each bit. Thermal history control for detecting a thermal history level suitable for each heating resistor element from a plurality of thermal history levels set in advance based on the presence / absence of printing twice and the presence / absence of printing of both adjacent bits this time. Means, the temperature measured by the temperature sensor, the print cycle measured by the print cycle measuring means, and the heat history level detected by the heat history control means, to control the energization time of each heating resistance element. And a current control means, are integrally unit configured to each circuit of the drive circuit and each means a thermal head apparatus.

In this thermal head, the temperature is measured by the temperature sensor, the printing cycle is measured by the printing cycle measuring means, and further, the printing has been performed twice in the past for each bit and the presence or absence of the current printing of the bits on both sides. From a plurality of preset thermal history levels, the thermal history control means detects the thermal history level suitable for each heating resistance element, and the optimum energization time corresponding to these temperatures, printing cycles, and thermal history levels. Selected by the energization control means or calculated for each heating resistance element,
The heating resistance element is energized for the energization time. Therefore, even if the user inputs a print command of any print cycle, it is possible to automatically perform proper printing in accordance with the print cycle.

(E) Examples Hereinafter, the present invention will be described in more detail with reference to Examples. FIG. 1 is a circuit block diagram of a thermal head showing an embodiment of the present invention. In the figure, the thermal head device 1 includes a thermal head 11 and a thermal head 11
Temperature sensor 12 that detects the temperature of the temperature sensor and A / D converter 13 that converts the temperature signal detected by the temperature sensor 12 into a digital signal
, Oscillator 14, counter 15 for print cycle measurement, CPU1
6. A microcomputer 19 including a memory 17 and an I / O circuit 18, and a heat history control circuit 20. These circuits are integrally configured as a thermal head device.

The thermal head 11 is already well known, and a plurality of heat generating resistance elements for print dots are lined up in a line on the upper surface of the substrate, and a driver IC for energizing and driving each of these heat generating resistance elements. Is installed.

The driver IC has a built-in shift register for storing input data, a latch circuit, and a drive circuit for energizing and driving each heating resistance element.

The thermistor 12 is a sensor for detecting the temperature of the thermal head 11. The temperature signal detected by the thermistor 12 is converted into a digital signal by the A / D converter 13 and the CPU 16
Has been taken into.

The counter 15 counts the pulse signal from the oscillator 14 after the print command PRC (LA1) is input, and the next print command
It has the function of counting the number of pulses up to the 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 this and further outputs a latch signal LA2,
The stroke signal STR is controlled to be output to the thermal head 11.

The memory 17 stores the energization time table shown in FIG. This energization time table takes temperature on the horizontal axis,
The printing cycle is taken on the vertical axis, and the energization time corresponding to each column is stored. The address according to the measured temperature is directly specified by the 8-bit temperature signal 00 to FF output from the CPU 16,
The print cycle is designated by the start address depending on which of the print cycles 1 to 7 the measured print cycle belongs to and which additional pulse width corresponds to each print cycle. Therefore, when the print cycle and the 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, whereby the thermal head 11 Data corresponding to each pulse width is input and printed.

The thermal history control circuit 20 is composed of a gate array, receives the input data DA1 with the clock signal CLK, and takes in the data. For each bit data, the presence / absence of previous and previous printing, and the left and right adjacent bit printing conductors are printed. The thermal history for each bit is detected depending on the presence or absence of the signal, and a level signal corresponding to the thermal history is output.

Regarding the heat history, as shown in FIG. 4, the heat history states of level 1 to level 6 are defined. Level 1 indicates that the print state of the bit in the past two times is 0, and the print state of the adjacent bit this time is also 0, and indicates the highest level that requires a lot of energy for heating. In level 2, one or both of the adjacent bits are in the print state, but the print state in the previous and last two prints is 0, and the energy level required this time is the second. Showing the second highest level,
Similarly, in the case of level 6, the bit is printed the last time or the time before the last time, and the bit is further added to print one adjacent bit or both adjacent bits.
In such a case, the print energy in that bit at this time is relatively small, which is a good level.

In this thermal head device, the energization time is controlled in accordance with the detection of the thermal history from level 1 to level 6 shown in FIG.

When the heat history control circuit 20 detects that the heat history in the bit is level 1, the heating resistance element is energized for the longest time, and conversely, in the case of level 6,
It will be energized for the shortest time.

Example thermal head device 1 configured as described above
Measures the temperature of the thermal head 11 with the thermistor 12, measures the print cycle of the print command PRC with the counter 15, and detects the heat history state with the heat history control circuit 20. Memory 17 according to history
The corresponding energization time is read out, and energization of the heating resistance element for each bit of the thermal head 11 is controlled according to the energization time.

Next, the operation of the thermal head device of the above embodiment will be described with reference to the flow chart shown in FIG. 3 and the time chart shown in FIG. CPU16, as shown in FIG. 3, print command PRC
It is determined whether or not is input (step ST1). As shown in FIG. 5, when the data DA1 to be printed is input by the clock pulse CLK1 and then the print command PRC is input,
The CPU 16 applies a start signal to the heat history control circuit 20. C
After receiving the print command PRC, the PU 16 measures the temperature by the signal from the thermistor 12 and the print cycle by the signal from the counter 15 (step ST2, step ST3), which is measured by the thermistor 12. The address of 00 to FF on the horizontal axis of the energization time table of the memory 17 is directly specified by the temperature of the memory 17, and the printing cycle of the counter 15 can be any of the printing cycles 1 to 7 in FIG. Whether or not it belongs to a cycle is extracted, and a rough range of energization time in the printing cycle 1 to the printing cycle 7 is specified.

On the other hand, when a start signal is applied to the heat history control circuit 20, in response to this, the heat history control circuit 20 determines whether or not each bit input this time is printed, and at the same time, two times before the bit cell and on both sides. In consideration of the presence or absence of the printing of the bit, the level to be printed this time corresponds to any of the levels 1 to 6 shown in FIG. Then, the level of each bit is added as data DA2 to the thermal head 11.

If the print level of a specific bit in the thermal history control circuit 20 corresponds to level 1, the print energy is required to be relatively large this time, so DA2 in FIG.
The print data is output from A shown in FIG. Then, the printing is continuously continued during the period A, B, C, D, E, and F for each next start signal at which the printing is completed.

On the other hand, when the level of the bit extracted by the thermal history control circuit 20 is level 6, it means that the thermal energy of the bit cell at this time may be relatively small. In this case, FIG. It is sufficient to energize only during the period corresponding to the final pulse width F indicated by DA2. This F indicates the basic pulse width.

Therefore, assuming that the print cycle detected by the counter 15 now belongs to the print cycle 2 and the level of the heat history extracted by the heat history control circuit 20 is 3, the address according to the temperature measured by the thermistor 12 is 01. Then, the thermal head 11
The energization time of the dot bit that is added to is read at the energization time stored at the intersection of the address 1800 of the additional pulse width 3 of the printing cycle 2 and the temperature 01.
11 will be energized.

Next, it is assumed that the print cycle measured by the counter 15 belongs to the width of the print cycle 3 and the temperature measured by the thermistor 12 is addressed by 03, and is extracted by the heat history control circuit 20. If the level is level 4,
The energization time stored at the intersection of the applied pulse width 4 of the printing cycle 3 and the temperature address 03 is read and applied to the thermal head 11. Now, for example, if the print cycle 2 is shorter than the print cycle 3, the shorter the print cycle is, the better the influence of the thermal history and the temperature is. The printing cycle 2 is shorter than the printing cycle 3.

On the other hand, even if the printing cycle 2 is the same, when the measured temperature is high, it is more affected by heat than when it is low.
In this case also, the higher the temperature, the shorter the energization time as compared to the case where the temperature is low. In this way, the most suitable energizing time corresponding to each printing cycle and temperature is stored in the table shown in FIG.

Assuming that the thermal history level extracted by the thermal history control circuit 20 is level 3 as described above, and 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 applied pulse width 4, the applied pulse width 5, and the energizing time at the intersection of each address of the basic pulse width and the measured temperature are sequentially read, and the total time is energized. Will be.

As described above, when the temperature measurement by the thermistor and A / D converter and the print cycle measurement by the counter are completed, the corresponding energization time control ratio is read from the memory table from the table according to this temperature and print cycle (step ST
4) Finally, according to the read energization time, energization printing is performed for each bit (step ST5).

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

(F) Effect of the Invention According to the present invention, the temperature and the printing cycle are measured, and the thermal history level suitable for each bit is extracted from the plurality of preset thermal history levels. Since the energization time of each heating resistance element is controlled by the heat history level, the most suitable energization time can be controlled even if the user inputs a command signal of any printing cycle. High-speed printing can be realized with a free printing cycle. Moreover, since the control of the energization time by the temperature and the control of the energization time by the heat history level are also provided, the user can use this thermal head without worrying in any environment. As a result, it is possible to always perform high-speed printing of appropriate quality.

Further, since the drive circuit and the circuits of the respective means are integrally unitized in the thermal head device, the thermal head can be easily manufactured, and simplification, miniaturization and cost reduction can be realized.

[Brief description of drawings]

FIG. 1 is a circuit block diagram showing a thermal head device showing an embodiment of the present invention, FIG. 2 is a diagram showing an energization time table stored in a memory of the thermal head device, and FIG. FIG. 4 is a flow chart for explaining the schematic 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 diagram for explaining the operation of the thermal head device. It is a time chart for. 11: Thermal head, 12: Thermistor, 15: Counter, 16:
CPU, 17: memory, 20: thermal history control circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 62-282956 (JP, A) JP 63-109654 (JP, A) JP 63-209955 (JP, A) JP 62- 164565 (JP, A)

Claims (1)

[Claims] 1. A heating resistance element array in which a plurality of heating resistance elements are arranged in a row, and each time a print command is input, the heating resistance elements are individually energized according to print data to perform dot printing. Heating resistor element drive circuit, temperature sensor for measuring temperature, print cycle measuring means for measuring the cycle of the input print command, presence / absence of past two prints for each bit, and print of both adjacent bits this time The heat history control means for detecting a heat history level suitable for each of the heating resistance elements from a plurality of heat history levels preset based on the presence or absence of the temperature, the temperature measured by the temperature sensor, and the printing. The drive circuit and the circuit of each means are provided with an energization control means for controlling the energization time of each heating resistance element by the print history measured by the cycle measurement means and the heat history level detected by the heat history control means. So Thermal head, characterized in that it is integrally unit configured to respectively the thermal head apparatus.