JP2606614B2 - Print control device for thermal printer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing control device for a thermal printer, which prints directly on thermal paper or through a thermal transfer film by applying a current to a heating element, and more particularly to a thermal history control of a thermal printer. is there.

[0002]

2. Description of the Related Art Conventionally, there has been a printing control apparatus of a thermal printer which performs a heat history control for storing past application histories of heating elements and determining the next energy of each heating element.

In these conventional examples, the next energization time is reduced by a predetermined time according to the past heat history.

[0004]

In these conventional techniques, when the conditions such as the environmental temperature and the temperature of the thermal head and the condition of the voltage supplied to the heating element fluctuate, the energizing time of the first dot is generally reduced. It is corrected and adjusted to an energization time that meets the conditions. However, since the energization time reduced by the thermal history control was constant without considering the fluctuating factors, the ratio of the applied energy obtained by the basic energization time fluctuated, and the energization time was continuous with voltage fluctuations and temperature changes. Good printing quality was not obtained with the dots.

An object of the present invention is to eliminate such disadvantages of the prior art, and to reduce the applied energy by the history even when the applied energy to the heating element is changed by the voltage condition or the temperature condition when performing the thermal history control. Of the present invention is to provide a control device for a thermal printer which makes the ratio of the thermal printer approximately constant and always obtains good print quality.

[0006]

SUMMARY OF THE INVENTION According to the present invention, even if the printing energization time changes to correct the fluctuation of the voltage of the heating element, the value is subtracted from the next dot of each heating element or the subsequent dots. By setting the amount of energy to a substantially constant ratio with respect to the initial total energy, good printing quality can be obtained in continuous dots even if the power supply voltage fluctuates. A charge / discharge circuit connected to a power supply used for driving the heater and initialized in synchronization with the drive timing of the heating element;
Comparing the charge level of the capacitor with a different reference level, and a plurality of voltage comparison circuits that obtain a plurality of mutually different timings, which are timings from the start of operation by initialization of the charge and discharge circuit, A thermal printer, comprising: a power supply width control circuit that is used for setting the basic power supply time of the heating element at the latest timing, and for setting a reduction amount when the power supply time is reduced according to the driving history. Print control device.

Further, the present invention is characterized in that a thermo-sensitive resistance element whose resistance value changes in response to a temperature change is added to the components of the resistor for determining the time constant of the charge / discharge circuit.

[0008]

FIG. 1 is a schematic diagram showing an embodiment of a conduction width control circuit of a print control device of a thermal printer according to the present invention. 1 is a resistor for adjustment, 2 is a resistor, 3 is a thermosensitive resistor, 5 is a capacitor for determining the pulse width according to the time for accumulating electric charge, 4 is a capacitor which discharges the electric charge of the capacitor 5 instantaneously, and triggers pulse output. And a discharge circuit for forming the charge / discharge circuit. Reference numeral 6 denotes a first voltage comparison circuit for comparing the voltage of the capacitor 5 with a reference voltage VREF1, and reference numeral 7 similarly denotes a second voltage comparison circuit for comparing the voltage of the capacitor 5 with the reference voltage VREF2. is there.

FIG. 2 is an explanatory diagram showing the operation principle of one embodiment of the present invention.

When TRIG is input from the TRIGIN terminal, the transistor 4 is momentarily turned on, and then the capacitor 5 is charged from the power supply Vc via the resistor 2, the thermosensitive resistor 3, and the variable resistor 1. When the charge level of the capacitor 5 reaches the comparison reference voltage VREF2 of the second voltage comparison circuit 7,
Inverted output of the voltage comparator circuit 7, the pulse width t ₂ is obtained. Thereafter, when the charge level of the capacitor 5 increases and reaches the comparison reference voltage VREF1 of the first voltage comparison circuit 6,
Similarly, the output of the first voltage comparison circuit 6 is inverted, the pulse width t1 is set to the basic energizing time of the dot, and the pulse width t2
Is set as the time of the energization width in which the second and subsequent dots are reduced when driven continuously. Point J indicates a capacitor 5 charging terminal.

FIG. 2 shows the relationship between the voltage VJ at point J and the charging time t in FIG.
Shows the characteristic at 20 ° C., and the time at the point P when the charge level of the capacitor 5 reaches VREF2 is indicated by t ₂ , and the time at the point Q when the charge level reaches VREF1 is indicated by t ₁ . At this time, when the resistance value of the thermosensitive resistance element 3 changes according to the environmental temperature condition, and the relationship between VJ and t, that is, the time constant of the charging and discharging circuit changes, Vc changes according to the voltage condition of the heating element.
Even when the relationship between VJ and t changes, the set time t2 for reducing the energization time also changes with the change of t1.

At this time, t1 / t2 and t3 / t4 become substantially constant.

That is, the ratio of the energizing time reduced in accordance with the history data to the basic energizing time becomes substantially the same with respect to the temperature change, and the print density can be controlled to be equal between 20 ° C. and 0 ° C. It becomes possible.

Similarly, when the voltage of the charge / discharge circuit changes, if the voltage increases, both values of t1 / t2 decrease while maintaining a substantially constant relationship, and conversely, if the voltage decreases, the value decreases. Will increase.

These operating principles are not limited to an energization control device in which the energization time reduced by the heat history is one step, and the number of voltage comparison circuits is three or more, and the energization width 2 reduced according to the heat history data is more than one. The method is also applicable.

Since the input pulse width of TRIGIN is extremely small, the influence on the output pulse widths t1 and t2 can be neglected.

FIG. 3 is a schematic view of a thermal printer according to the present invention, wherein the same components as those in FIG. 1 are denoted by the same reference numerals.

The charge / discharge circuit including the capacitor 5 as a component is connected to the same power supply as the power supply of the heating element 8, and the influence of the fluctuation of the power supply voltage of the heating element is reflected on the output pulse width of the voltage comparison circuits 6 and 7. It has become so.

Reference numeral 21 denotes a CPU for controlling the entire thermal printer, reference numeral 22 denotes a reference voltage generation circuit for determining reference voltages VREF1 and VREF2, and reference numeral 23 denotes a zener diode for keeping the reference voltage unchanged even when the power supply Vc changes. It is.

8 is a heating element, 9 is a head drive IC,
Reference numeral 24 denotes a power supply transistor for turning on and off a power supply terminal of the head drive IC. The power supply transistor 24 is connected to the first voltage comparison circuit 6, and as an example, the head drive IC becomes operable at 20 ° C. for a time t2.

The output of the second voltage comparison circuit 7 is
The dot which reduces the energization time based on the history data and outputs the head data to the head drive IC is delayed by t2 time from the start of t1.

The dots requiring the basic energizing time output the TRIG output to the discharging transistor 4 almost simultaneously with the output of the head data to the head drive IC.

In the embodiment shown in FIG. 3, due to the power supply fluctuation of the heating element, t1 and t2 change while maintaining substantially the same ratio,
As the change just compensates for the fluctuation of the power supply, the energization time is extended when the power supply voltage is decreased, and the energization time is reduced when the power supply voltage is increased.

As the thermal resistance element, a thermistor having a negative characteristic with respect to temperature is generally used, and a fixed resistor or the like can be installed in parallel with the thermistor to correct this characteristic.

[0025]

As described above, in the print control apparatus for a thermal printer according to the present invention, the charge / discharge circuit included in the power supply width control circuit has at least a capacitor, and is initially synchronized with the print timing at which printing is to be performed. Charge and discharge are performed with a target corresponding to the voltage of the power supply used to drive the heating element. Therefore, if the power supply voltage fluctuates or is set to a different potential value, the charge and discharge circuit If the charge level of the middle capacitor is a predetermined potential, the output pulse width is small when the power supply voltage is high, and the output pulse width is large when the voltage is low. Will be compensated. The charge levels of the capacitors are compared with different reference levels by a plurality of voltage comparison circuits of the conduction width control circuit. Therefore, the timings obtained from the outputs of the plurality of voltage comparison circuits, that is, the plurality of different timings from the initialization of the charging / discharging circuit, correspond to the change in the power supply voltage and are substantially mutually reciprocal. It will have a certain ratio.
Therefore, the energization width control circuit sets the latest one of these timings to the setting of the basic energization time of the heating element, and the other to the setting of the amount of reduction when the energization time is reduced according to the drive history. If you use each,
It is possible to easily obtain an appropriate energization time corresponding to the fluctuation and change of the power supply voltage and a reduction amount of the energization time.

Further, a thermal resistance element for detecting the ambient temperature or the temperature of the print head is connected in series with the capacitor of the charge / discharge circuit, and the time constant of the charge / discharge circuit is determined by the thermal resistance element. If the ambient temperature or the temperature of the print head fluctuates or changes, the time constant of the charging / discharging circuit is changed accordingly. Thus, the plurality of timings are automatically set to values corresponding to the ambient temperature or the print head temperature while maintaining a substantially constant ratio with each other. Accordingly, by setting the basic energizing time and the amount of reduction thereof based on these timings as described above, it is possible to easily obtain an appropriate energizing time and the amount of reduction of the energizing time corresponding to the fluctuation and change of the ambient temperature. it can.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an embodiment of a conduction width control circuit of a print control device of a thermal printer according to the present invention.

FIG. 2 is an explanatory diagram showing a relationship between a charging voltage and a charging time of a capacitor of the charge / discharge circuit of the present invention.

FIG. 3 is a schematic diagram of the thermal printer of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Adjusting resistor 3 Thermal resistance element 5 Capacitor 6, 7 Voltage comparison circuit 8 Heating element

Claims (2)

(57) [Claims] 1. A thermal printer which forms dots by a plurality of heating elements arranged on a print head and performs printing on thermal paper directly or on plain paper via a transfer film, and records the driving history of each heating element. A print control device of a thermal printer for reducing the energization time of each of the heating elements of the next dot or subsequent dots based on the stored driving history and having the stored driving history, comprising at least a capacitor, which is used for driving the heating element. A charge / discharge circuit connected to a power supply connected to the heating element and initialized in synchronization with the drive timing of the heating element; and comparing the charge level of the capacitor with a reference level different from each other to start operation by initializing the charge / discharge circuit. And a plurality of voltage comparison circuits for obtaining a plurality of timings different from each other, and A thermal printer having a power-on width control circuit for setting the basic power-on time of the heating element at a later timing, and for setting the amount of reduction when reducing the power-on time according to the driving history. Printing control device. 2. A print control device for a thermal printer according to claim 1, wherein a thermo-sensitive resistance element whose resistance value changes according to temperature is added to a component of the resistor for determining a time constant of said charging / discharging circuit. .