JPH06320779A - Thermal printer - Google Patents

Abstract

PURPOSE:To maintain printing quality in prominent condition by correcting an applied voltage value on a thermal head while considering a temperature difference between the thermal head, whose temperature is risen, and printing medium. CONSTITUTION:A thermal printer is provided with a head temperature sensor, detecting the head temperature of a thermal head, a temperature table, in which an applied voltage value is set in accordance with the head temperature of the thermal head, and a correcting table, in which correcting data are set in accordance with a temperature difference between the head temperature of the thermal head upon printing and the head temperature of the thermal head upon putting a power supply ON or a previously specified temperature. In mores 1, 2, the actual voltage value V is set by correcting the applied voltage value V1 obtained from the temperature table by a correcting voltage value Vx obtained from a correcting table while the voltage control of the thermal head is effected based on the applied voltage value V1 obtained from the temperature table in a mode 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal printer which controls a voltage applied to a thermal head to print on a print medium.

[0002]

2. Description of the Related Art Generally, in a thermal printer, a voltage is applied to a thermal head to heat a heating resistor constituting the thermal head to melt the ink of an ink ribbon to transfer print information to a paper or a thermal paper. Printing information is printed on a printing medium by changing the chemical applied to the surface.

Therefore, the voltage value applied to the thermal head has a great influence on the print quality such as the print density. Therefore, in the conventional thermal printer, for example, printing speed, direct printing using thermal paper or transfer printing using an ink ribbon, rank of the resistance value (head resistance) of the heating resistor forming the thermal head, thermal printing, The temperature table for determining the voltage applied to the thermal head according to the conditions such as the temperature of the head is provided in the memory.

That is, before printing, the printing speed,
Set the rank of the resistance value (head resistance) of the heating resistor that constitutes the thermal head, whether it is direct printing using thermal paper or transfer printing using an ink ribbon, and set the head temperature of the thermal head during printing. The detected applied voltage value corresponding to the detected head temperature is read from the temperature table, and the voltage is applied to the thermal head with the read applied voltage value.

[0005]

By the way, the temperature of the thermal head does not immediately drop to the ambient temperature even if the voltage application is stopped, and the heat that cannot be dissipated is stored in the thermal head. become. Therefore, when printing is continuously issued, the thermal head accumulates heat cumulatively, and the temperature of the thermal head rises.

That is, as shown in FIG. 6, the temperature t1 of the thermal head rises as the issuing time elapses. On the other hand, the temperature of the ink ribbon, the paper or the thermal paper is the ambient temperature t0. Head temperature t1
And the temperature of ink ribbon, paper and thermal paper (ambient temperature t
The temperature difference with 0) becomes large.

Therefore, even when a voltage is applied to the thermal head with the voltage value read from the temperature table during actual printing, a part of the amount of heat generated by the voltage is applied to the ink ribbon or the paper which is in contact with the thermal head. Therefore, there is a problem that the heat generation resistor of the thermal head does not reach the temperature required for printing and the printing becomes thin.
That is, there is a problem that the printing quality is gradually deteriorated when the printing is continuously issued.

Therefore, according to the present invention, the voltage value applied to the thermal head can be corrected in consideration of the temperature difference between the thermal head whose temperature rises due to printing and the ink ribbon, paper, etc. An object is to provide a thermal printer that can be maintained.

[0009]

SUMMARY OF THE INVENTION According to the present invention, in a thermal printer which is provided with a thermal head and controls a voltage applied to the thermal head to print print information on a print medium, a head temperature for detecting the temperature of the thermal head. Detecting means, a head temperature comparing means for comparing the temperature of the thermal head detected by the head temperature detecting means at power-on or a preset temperature with the current temperature of the thermal head detected by the head temperature detecting means, A correction unit for correcting the voltage applied to the thermal head based on the result of the comparison by the head temperature comparison unit is provided.

[0010]

In the present invention having such a structure, the head temperature comparing means detects the temperature of the thermal head detected by the head temperature detecting means when the power is turned on or a preset temperature and the current temperature detected by the head temperature detecting means. The temperature of the thermal head is compared, and the voltage applied to the thermal head is corrected by the correction means based on the comparison result.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a circuit configuration of essential parts of a thermal printer to which the present invention is applied.

Reference numeral 1 denotes a CPU (cent
ral processing unit).

A ROM (read only memory) 2 in which program data for the processing performed by the CPU 1 is stored, and the C
A RAM (random access memory) 3 in which areas of various memories used when the PU 1 performs processing and a communication interface 4 connected to a host computer via a line are respectively connected to the C bus via a system bus 5.
It is connected to PU1.

Further, a keyboard controller 7 for controlling the keyboard 6, a head controller 9 for controlling driving of the thermal head 8 such as energization and voltage control, and a motor controller for controlling a stepping motor 10 for carrying paper and the like. 11. I / O (input / ou) to which a detection signal from a head temperature sensor 12 as a head temperature detecting means for detecting the temperature of the thermal head 8 is input
tput) ports 13 are each connected to the CPU 1 via the system bus 5.

The ROM 2 is shown in FIG.
Direct printing or transfer printing, the rank of the head resistance of the thermal head 8, the thermal head 8
The temperature table 2a in which the data of the applied voltage value to the thermal head 8 is set in accordance with the temperature condition of FIG.
As shown in, for each reference head temperature T0 for which the head temperature at power-on or a preset head temperature is set,
A correction table 2b is formed in which correction data for the voltage applied to the thermal head 8 is set in correspondence with the difference between the current head temperature T1 detected by the head temperature sensor 12 and the reference head temperature T0. ing.

When the power is turned on, various initializations are performed as an initialization process, and when the mode is set to 1, the head temperature of the thermal head 8 when the power is turned on is detected by the detection signal from the head temperature sensor 12. It is read and this head temperature is set as the reference head temperature T0.

FIG. 4 shows the flow of the printing process performed by the CPU 1.

First, the number of issued sheets N is set in the storage area n formed in the RAM 3 by a command or the like previously received from the host computer via the communication interface 4, and the initial value 0 is set in the counter i formed in the RAM 3. Set.

Next, in step 1 (ST1), the current head temperature T1 is read from the detection signal from the head temperature sensor 12.

Next, it is determined whether the mode is 1, 2 or 3 based on a command or the like previously received from the host computer via the communication interface 4.

If the mode is 1, the head temperature sensor 12
It is confirmed whether the value obtained by subtracting the reference head temperature T0 set by the detection signal from the head temperature sensor 12 when the power is turned on is equal to 0 from the current head temperature T1 read by (head temperature Comparison means).

Here, when the subtraction value T1-T0 is equal to 0, the correction voltage value Vx is set to 0, and when the subtraction value T1-T0 is not equal to 0, the correction table 2b is used. The correction data (correction voltage) corresponding to the subtracted values T1-T0 is read and set to the correction voltage value Vx. Then, the process proceeds to step 2 (ST2) described later.

If the mode is 2, the temperature TA designated by the command or the like previously received from the host computer via the communication interface 4 is used as the reference head temperature T.
Set to 0. Next, based on the current head temperature T1 read by the head temperature sensor 12, the reference head temperature T0 is obtained.
Check whether the value obtained by subtracting is equal to 0.

If the subtraction value T1-T0 is equal to 0, the correction voltage value Vx is set to 0. If the subtraction value T1-T0 is not equal to 0, the subtraction value T1-T0 is set.
The correction data (correction voltage) corresponding to 0 is set in the correction table 2
It is read from b and set to the correction voltage value Vx. And
The process shifts to step 2 described later.

If the mode is 3, the correction voltage value Vx is set to 0, and the process proceeds to step 2 described later.

As the processing of step 2 (ST2) described above, the voltage value V applied to the thermal head 8 corresponding to the current head temperature T1 read by the head temperature sensor 12
1 is read from the temperature table 2a and the applied voltage value V1
A value obtained by adding the correction voltage value Vx to is set as the applied voltage value V (correction means).

Next, the applied voltage of the thermal head 8 is controlled based on the applied voltage value V to print one label, and when the printing of one label is completed, the counter value of the counter i is changed. +1 addition processing is performed, and it is determined whether or not the count value of the counter i resulting from this addition processing is equal to the number of issued sheets (N) set in the storage area n.

Here, if the count value of the counter i is not equal to the set value (N) of the storage area n, the process returns to the above-mentioned step 1 again.
If the count value of is equal to the set value (N) of the storage area n, the printing process is ended.

In the present embodiment having such a configuration, when the mode is set to 1, the head temperature of the thermal head 8 at power-on is detected by the detection signal from the head temperature sensor 12 at power-on. The head temperature is read and the read head temperature is set to the reference head temperature T0.

Each time one label is issued, the current head temperature T1 of the thermal head 8 is read by a detection signal from the head temperature sensor 12, and the present head temperature T1 is read.
From the correction table 2b, the correction data corresponding to the temperature difference T1 -T0 obtained by subtracting the reference head temperature T0 for which the head temperature at power-on is set is read from the table and the correction data is set as the correction voltage value Vx. .

Therefore, the voltage value V1 applied to the thermal head 8 corresponding to the current head temperature T1 is shown in the temperature table 2.
The read applied voltage value V1 is corrected by the correction voltage value Vx and set as the actual applied voltage value V actually applied to the thermal head 8.

Therefore, each time one label is issued, the thermal head 8 is sent to the thermal head 8 based on the applied voltage value V corrected by the correction voltage value Vx calculated from the head temperature T0 of the thermal head 8 when the power is turned on. The applied voltage is controlled.

FIG. 5 shows a graph of the reference head temperature T0 and the applied voltage value based on the temperature table 2a, and the relationship between the applied voltage value V1 corresponding to the current head temperature T1 and the actual applied voltage value V. That is, the voltage difference between the applied voltage value V and the applied voltage value V1 is the correction data (correction voltage value) Vx obtained from the correction table.

When the mode is set to 2, the temperature TA designated by a command from the host computer is set as the reference head temperature T0.

Each time one label is issued, the current head temperature T1 of the thermal head 8 is read by the detection signal from the head temperature sensor 12, and the present head temperature T1 is read.
The reference head temperature T set with the temperature TA specified by
The correction data corresponding to the temperature difference T1-T0 obtained by subtracting 0 is read from the correction table 2b, and the correction data is set as the correction voltage value Vx.

Therefore, the voltage value V1 applied to the thermal head 8 corresponding to the current head temperature T1 is shown in the temperature table 2.
The read applied voltage value V1 is corrected by the correction voltage value Vx and set as the actual applied voltage value V actually applied to the thermal head 8.

Therefore, each time one label is issued, the thermal head 8 is based on the applied voltage value V corrected by the correction voltage value Vx calculated from the temperature TA designated in advance.
The voltage applied to the control circuit is controlled.

Further, when the mode is set to 3, the current head temperature T1 of the thermal head 8 is read by the detection signal from the head temperature sensor 12 every time one label is issued. The voltage value V1 applied to the thermal head 8 corresponding to the head temperature T1 is read from the temperature table 2a. Here, the applied voltage value V1 is directly set as the applied voltage value V without being corrected.

Therefore, the voltage control to the thermal head 8 is performed based on the applied voltage value V1 read from the temperature table 2a as the applied voltage value V for each label printing.

As described above, according to this embodiment, the head temperature sensor 12 for detecting the head temperature of the thermal head 8 is used.
A temperature table 2a in which an applied voltage value is set corresponding to the head temperature of the thermal head 8;
A correction table 2b in which correction data is set corresponding to the temperature difference between the head temperature at the time of printing and the head temperature at power-on of the thermal head 8 or a temperature designated in advance is provided, and the modes are set to 1 and 2. If set, the applied voltage value V1 obtained from the temperature table 2a is corrected by the correction data (correction voltage value) Vx obtained from the correction table 2b as the voltage actually applied to the thermal head 8. When the value V is set and the mode is set to 3, by controlling the voltage of the thermal head 8 on the basis of the applied voltage value V1 obtained from the temperature table 2a, the thermal head 8 whose temperature is raised by printing is obtained. The voltage value V1 applied to the thermal head 8 can be corrected in consideration of the temperature difference between the ink ribbon and the paper.

Therefore, the applied voltage added by the correction data (correction voltage value) can be applied in consideration of the heat radiation amount when the thermal head 8 comes into contact with a low temperature print medium such as an ink ribbon or paper. The heating resistor of the thermal head 8 can be reliably heated to the temperature required for printing. As a result, the print quality can be maintained in a good state.

Further, in this embodiment, the head temperature T0 of the thermal head 8 obtained from the head temperature sensor 12 when the power is turned on is set as the reference head temperature, and the applied voltage value V1 obtained from the temperature table 2a is set in the correction table. Two
Compensation using the compensation data (correction voltage value) Vx obtained from b and the applied voltage value V1 obtained from the temperature table 2a by setting the preset temperature TA as the reference head temperature. Three types of modes, one for correcting with the data Vx and one for not correcting the applied voltage value V1 obtained from the temperature table 2a, are provided for easy selection, so that it can be selected according to the purpose of use of the operator. The mode can be selected, and the operability can be further improved.

[0044]

As described above in detail, according to the present invention,
A thermal printer that can correct the voltage value applied to the thermal head in consideration of the temperature difference between the thermal head and the temperature of the ink ribbon, paper, etc., whose temperature rises due to printing, and that can maintain good print quality. Can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit configuration of essential parts of an embodiment of the present invention.

FIG. 2 is a diagram showing a memory configuration of a temperature table of the embodiment.

FIG. 3 is a diagram showing a memory configuration of a correction table of the embodiment.

FIG. 4 is a diagram showing a flow of a printing process of the embodiment.

FIG. 5 is a diagram showing a relationship of data of a head applied voltage value with respect to a head temperature in the temperature table of the embodiment.

FIG. 6 is a diagram showing changes in head temperature with respect to issuing time.

[Explanation of Codes] 1 ... CPU, 2a ... Temperature table, 2b ... Correction table, 8 ... Thermal head, 12 ... Head temperature sensor.

Claims (1)

[Claims] 1. A thermal printer which is provided with a thermal head and controls a voltage applied to the thermal head to print print information on a print medium, and a head temperature detecting means for detecting a temperature of the thermal head, and a power source when the power is turned on. Head temperature comparison means for comparing the temperature of the thermal head detected by the head temperature detection means or a preset temperature with the current temperature of the thermal head detected by the head temperature detection means, and this head temperature comparison means And a correction unit that corrects the voltage applied to the thermal head based on the result of the comparison.