JPS6398457A - Printing controller of thermal printer - Google Patents

Abstract

PURPOSE:To obtain good printing quality at all times, by a method wherein even when energy applied to a heating element is changed according to temperature and voltage conditions in controlling a heat history, the ratio of applied energy to be reduced is made constant. CONSTITUTION:A CPU 50 totally controls all the body of a thermal printer, outputs a trigger to a trigger input terminal 32 at each head current application timing according to the input of printing data and simultaneously, sends head data 48 out to a head driver 47. An inverter 43 is connected to the output terminal 14 of CTCC 40. The operating time of the head driver is determined and the reference current application time of a thermal element 45 is determined with a transistor 44. The output terminals 15, 16 of CTCC 40 are inputted to the CPU 50. The CPU determines the amount to be reduced from the reference current application time according to the drive history of the past and outputs the data being reduced synchronized with the timing of the output terminals 15, 16.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a print control device for a thermal printer that prints on thermal paper or plain paper via a transfer film by energizing a heating element. This relates to thermal history control.

[Conventional technology]

Conventionally, in the printing control device of thermal printers,
There is a thermal history control method that stores the past driving history of the heat generating elements and determines the next applied energy to each heat generating element.

In these conventional examples, the next energization time is reduced by a certain period of time depending on the past thermal history.

[Problem that the invention seeks to solve]

In these conventional technologies, when conditions such as the environmental temperature, the temperature of the thermal head, or the supply voltage to the heating element change, the energization time to the heating element is generally corrected and the energization time is adjusted to match the conditions. be done. However, since the energization time reduced by heat history control was constant, the ratio of reduction to the applied energy obtained by the basic energization time fluctuated, making it difficult to obtain good printing quality with respect to temperature changes and voltage fluctuations. There wasn't.

The purpose of the present invention is to eliminate the drawbacks of the prior art, such as
When performing thermal history control, even when the applied energy to the heating element is changed depending on the temperature and voltage conditions, a control device for a thermal printer that maintains a constant ratio of applied energy that decreases and achieves excellent printing quality is provided. It is about providing.

[Means for solving the problem] The printing control of the thermal printer according to the present invention is as follows:
The following measures are taken to solve these problems.

a. a thermal head or a heating resistor element for detecting ambient temperature; a resistor network including the heat-sensitive resistor; c; an amplifier circuit (!) for amplifying the potential at a predetermined voltage dividing point of the resistor network; A voltage divider circuit e that divides the output of the amplifier circuit using a plurality of resistors, a charging and discharging circuit f whose main component is a capacitor, and a charging and discharging time of the capacitor with each of the plurality of voltage dividing points of the output of the amplifier circuit as a reference potential. One of the voltage comparison circuits is used for setting the reference energization time of the heat generating element, and the others are used for setting the reference energization time of the heat generating element according to the drive history. This is a control device used to determine the amount of reduction when reducing the time.

[Example]

FIG. 1 shows a printing control device U of a thermal printer according to the present invention.
FIG. 3 is a circuit diagram of an embodiment of the energization width control circuit of FIG.

1 is a thermistor, which is a type of heat-sensitive resistance element, and 2 is a thermistor.
- A resistor network including Mister 1, 17 and 18 are resistors, and 28 are capacitors, respectively. The capacitor 28 is for noise prevention and has no relation to the characteristics at all.

3 is an amplifier circuit having an operational amplifier 10, and a predetermined voltage dividing point of the resistor network and a predetermined voltage dividing point of the voltage dividing circuit 30 which serves as the variable resistor 20 are used as operational amplifier inputs. The operational amplifier 10 also includes a feedback resistor 22, a diode 23, and an input resistor 24. The voltage dividing circuit 30 is composed of resistors 19 and 21 and a variable resistor 20, and forms a reference input section of the operational amplifier 10.

4 is a voltage dividing circuit that divides the voltage of the output of the amplifier circuit by a resistor, and 25, 26, and 27 are resistors that are its constituent elements.

Reference numeral 5 denotes a charging/discharging circuit having a capacitor 7 as a main component, a resistor 6, a variable resistor 29, and a transistor 9 forming a charging path, and a transistor 8 forming a discharging circuit.

Reference numerals 11, 12, and 13 are voltage comparison circuits, which are connected to the voltage dividing point of the voltage dividing circuit 4 that divides the output of the operational amplifier 10 as a reference input.
Each of L and M is used as a reference potential, and one end of a capacitor 7 is connected as an input to be compared. At the partial pressure point, L, M
Letting the potentials of Vk, V] and Vm be the following relationships.

Vm>V ]>Vk 31 is an output pulse width switching terminal, 32 is a trigger input terminal, and 14, 15, and 113 are output terminals of this current width control circuit, respectively.

〔motion〕

The resistance network 2 is a curve correction section that corrects the temperature characteristics of the thermistor.

The resistance value Rt of the thermistor is generally expressed by the following equation using the B constant, where R(20) is the value of 20°C, and T is the absolute temperature.

Rt = R(20) e x I) B (1/T
(t) 1/”r(20))・・・・・・・・・
Formula IT(t) = Absolute temperature T at any temperature (20
)=20°C Absolute temperature Equation 1 contains the term exp, so the reciprocal of temperature is log linear. In other words, the resistance value is the temperature -
decreases with increasing temperature, and the rate of change becomes smaller on the high temperature side.

In the case of a thermal head, reducing the applied energy when the temperature is high will result in better printing quality and will be safer for the heat generating element, so it is necessary to correct the characteristics of this thermistor.

Figure 2 shows the resistance value Rt of the 'S'-mister and the resistance network 2.
2 is a graph showing the characteristics of the output voltage at the voltage dividing point A, where the horizontal axis represents absolute temperature, and the vertical axis represents the resistance value Rt and the potential at the voltage dividing point A.

41 is a characteristic curve showing the temperature characteristic of the resistance value Rt of the thermistor, and 42 is a characteristic curve showing the temperature characteristic of the potential at the voltage dividing point A. Thermistors have negative characteristics with respect to temperature changes, as shown in the characteristic curve.

The following points can be cited as characteristics of such correction.

1. There are few peripheral elements, so there is little variation such as variation.

2. Linearity can be provided over a relatively wide range.

3. Changes in output voltage with respect to temperature outside the operating temperature range, for example below 0''C, above 40@C, etc., can be made small, and the thermal head can be protected from destruction.

The amplifier circuit 3 uses the corrected temperature characteristics to partially expand the temperature characteristics, and has one input as the voltage dividing point A at which the characteristic curve 42 is obtained, and the other input as a voltage dividing circuit using a resistor.

The magnification of this circuit is expressed as follows.

If the value of the resistor 24 is R24 and the value of the resistor 22 is R22, the magnification is K''(R'24+R22)/R24.

The functions of the diode 23 are as follows: 1. To suppress a sudden rise in the reference potential at low temperatures, as a result, it prevents the output pulse width of the voltage comparator circuits 11, 12, 13 from increasing at low temperatures.

2. The inflection point of partial enlargement can be changed.

Using the characteristics of 1 and 2, various characteristic curves can be created by changing or eliminating the number of diodes.

The variable resistor 20 in the voltage dividing circuit 30 is used to adjust Vop without changing the rate of change of the output potential Vop of the operational amplifier with respect to temperature changes, and sets the output pulse width of the voltage comparison section in the subsequent stage to a predetermined value. It is something.

The input terminal 31 is an input terminal for a signal that turns on and off the pulse width switching transistor 9 for switching the energy applied to the thermal head. The input terminal 32 is a terminal that supplies a trigger input to the discharging transistor 8 for instantaneously turning on the capacitor 7.

FIG. 3 is an explanatory diagram showing the charging characteristics of the capacitor 7,
The horizontal axis shows charging time, and the vertical axis shows charging level. 35
36 shows the charging curve of the capacitor 7 when the transistor 9 is on, and 36 shows the charging curve when the transistor 9 is off. Voltage comparator circuit 11 when the slice level VmsVl, Vk on the vertical axis is 20”C
．． At an input level of 12.13, Vm' % Vl'
, Vk' are the input levels at 0@C. The charging voltage of this capacitor 7 is cut at each slice level, converted into a pulse width, and outputted from the voltage comparator circuits 11, 12, and 13. At this time, the pulse width tg of the trigger input is extremely small and can be ignored.

In Fig. 3, tl, tt, and ts of the E1 group are the charging times when the energy is small at 20°C, and similarly, the E2 group (t4, ts, ta) is the charging time when the energy is large at 2.0°C, and the E3 group ( Ly, ta, j9) indicate the charging time when the O''CC energy is small, and the four groups (1, ., t++sj+*) indicate the charging time when the 0''C energy is large.

FIG. 4 is an explanatory diagram showing input and output waveforms of the voltage comparator circuit of the energization width control circuit of FIG. 1.

51 is a trigger input waveform applied to the input terminal 32 of the charging circuit, and its pulse width tg is extremely small, so it can be ignored in terms of characteristics. Reference numeral 52 indicates the waveform of the output terminal 14, 53 indicates the waveform of the output terminal 150, and 54 indicates the waveform of the output terminal 16.

The respective pulse widths are TW14, TW15, TW I
It is indicated by C3 and has the following relationship.

T Wl 4 > T W 15 > T W 16 The reference potential of the voltage comparison circuit 11 at 20"C is Vm (2
0), the value of capacitor 7 is C7, the resistance values of resistor 6 and variable resistor 29 are R6 and R29, respectively, and the power supply voltage is Vc, then the output of voltage comparator circuit II when transistor 9 is on is The pulse width T W is expressed by the following formula. 1m-natural logarithm R=R6 to T\'14=-C7XR]n (1-Vm
(20) /Vc) =T.

becomes.

Similarly, 'rwte' is TW'1e=-C7XR1n (1-Vk (20)/
Vc) = ts.

At 0°C, T W 14 = t.

TW1G=t.

As can be seen from FIG. 3, the initial stage of the capacitor charging process has a nearly linear characteristic, and increases linearly with the passage of time. Therefore, the following formula holds.

t, :t, #j4 : ta Also, when transistor 9 is off, R=R'6+
Simply substitute R29 into the above equation, and the pulse width ratio at this time is expressed as follows.

C7: j+ = j*: tz =R6: (R8
It can be seen that the other energization width control circuits always operate at a nearly constant ratio to the output pulse width of the energization width control circuit 11 that outputs the medium R2, that is, the maximum pulse width.

By controlling the thermal history of a thermal printer using a current width control circuit having such characteristics, extremely good printing quality can be achieved.

FIG. 5 is a schematic diagram, not showing one embodiment of the printing control device according to the present invention, in which numeral 40 is the current conduction width control circuit (hereinafter abbreviated as CTCC) shown in FIG. The thermal head and 47 indicate a head driver, respectively. The thermistor 1 in the CTCC is placed in contact with the thermal head 46 .

44 is a power supply control transistor that turns on and off the power terminal of the head driver 47, and 50 is a CPU that centrally controls the entire thermal link, and outputs a signal to the trigger input terminal 32 at each head energization timing in accordance with print data input. , sends the head data 48 to the head driver 47.

Reference numeral 43 denotes an inverter connected to the output terminal 14 of the CTCC 40, and a transistor 44 determines the operation time of the head driver and the reference energization time of the heating element 450.

The output terminals 15 and I6 of the CTCC 44 are input to the CPU 50, and the CPU determines the amount of reduction from the standard energization time according to the past driving history of the heating element 45, and calculates the timing of the output terminals 15 and 16 from the head data output 48. The subtracted data is output in synchronization with the .

FIG. 6 is an explanatory diagram showing the energization state of the goose track control method for the thermal head using the present invention, taking 20° C. as an example.

Reference numeral 61 indicates the state when energization continues, and the reduction time when two dots are continuous is C3, and when three dots are continuous, it is t2.

Reference numeral 62 indicates energization when every other dot is intermittent, and the reduction time at that time is t3.

The reference energization time is determined by the head driver, and the amount of reduction is determined by the transmission of herad data from the CPU 50.

Note that the number of voltage comparison circuits is not limited to three, and more fine-grained thermal history control can be achieved by increasing the number.

Further, by using the charging/discharging circuit 5 in common with the power supply to the thermal head 46, it is possible to compensate the energization width even for fluctuations in the power supply of the thermal head.

Furthermore, the heat-sensitive resistance element is not only a thermistor, but also a posister, which has a positive characteristic against temperature changes, and has a similar effect.

FIG. 7 is a schematic diagram showing another embodiment of the print control device for a thermal printer according to the present invention, and the same parts as those shown in FIG.

71, 72, and 73 are latch circuits similar to the TTL LS-374, which temporarily hold hepto energization data. 74. 75 is a differential circuit connected to the output terminal of the C, T CC 40; 76 is a decoder that latches the address information simultaneously with the output of the head energization data 48;
7 is the WR# child of the CPU, 78 is a gate that synchronizes the address information and the WR signal, 79 is a differentiation circuit, 74.75,
The signal of the gate 78 is combined and the latch circuit 71.72.7
The gates for obtaining the three clock signals are shown respectively.

This embodiment will be described in detail below using FIG.

The differentiating circuits 74 and 75 are for obtaining a trigger output synchronized with the falling timing of the output waveform shown in FIG.
A trigger output is generated from the differentiating circuit 7/1 simultaneously with the passage of time 15, and similarly, a trigger output is generated from the differentiating circuit 75 simultaneously with the passing of p++ at T W 1 B.

First, the CPU 50 outputs the energization data 48 including the history data three times. Gate 78 in synchronization with data output
A clock signal is output from the latch circuits 71, 72 .
Each data is stored in 73. Next, at the same time as the energization timing, a trigger is output to the input terminal 35, the head driver 47 is activated, and energization is performed to a predetermined heating element based on the data stored in the latch circuit 73.

T, W After 16 hours have elapsed, a trigger output is generated at the gate 79, using this as a clock, the data in the latch circuit 72 is moved to the latch circuit 73, a predetermined energization is performed, and after TW15 hours have elapsed, a trigger output is generated from the same gate 79. A trigger output is issued and the last data is sent to the head driver. Thereafter, when a predetermined dot is formed, the transistor 44 closes and the energization ends after TW14 hours have elapsed.

In the embodiment shown in FIG. 7, since the CPU is not involved in the timing of sending history data, the processing speed can be increased, and it can be applied to high-speed thermal printers.

In addition to thermal printers that print using a thermal head equipped with a heating resistor, there are other types of thermal printers. There is an electric thermal printer that generates heat in a resistive layer coated on the back side of a thermal transfer film using a print head having twelve poles.

[Effects of the Invention] As described above, the printing control device for a thermal printer according to the present invention can properly operate even when the standard energization time to the heating element is changed due to environmental temperature conditions and voltage fluctuations of the heating element. The applied energy during heat history control can be set, and extremely good printing quality can be achieved.

Furthermore, by increasing the number of voltage comparison circuits, it becomes possible to easily perform fine-grained thermal history control.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment of the energization width control circuit of the print control device for a thermal printer according to the present invention. FIG. 2 is a characteristic diagram showing the relationship between the resistance value of the thermistor and the output voltage at the voltage dividing point of the resistor network. FIG. 3 is an explanatory diagram showing charging characteristics of a capacitor in the current width control circuit of the present invention. FIG. 4 is an explanatory diagram showing input and output waveforms of the energization width control circuit of the present invention. FIG. 5 is a schematic diagram of an embodiment of a printing control device according to the present invention. FIG. 6 is an explanatory diagram of a printing control method for a thermal head using the present invention. FIG. 7 is a schematic diagram of another embodiment of the printing control device according to the present invention. 1... Thermistor 2... Resistance network 3... Amplifier circuit 11.1.2.13... Voltage comparison circuit 5... Charging/discharging circuit 46... Thermal head and above Applicant: Seiko Epson Agent Co., Ltd. Patent attorney Tsutomu Mogami and 1 other person 11th mother Figure 3 Figure 6 Figure 7

Claims (1)

[Scope of Claims] A thermal printer that forms dots using a plurality of heat-generating elements and prints them directly on thermal paper or on plain paper via a transfer film, which stores the drive history of each heat-generating element, and stores the drive history of each heat-generating element. In a thermal printer having a control means that reduces the energization time to each heat generating element of the next dot or subsequent dots based on the history, a. The temperature of the thermal head in which the heat generating element is arranged or its surrounding temperature. a heating resistance element b for detecting the temperature, a resistance circuit line c including the heat-sensitive resistance element, an amplifier circuit d for amplifying the potential at a predetermined voltage dividing point of the resistance network, and an output of the amplifier circuit being connected to a plurality of resistors. A voltage dividing circuit e that divides the voltage, a charging/discharging circuit f whose main component is a capacitor, and a plurality of circuits that convert the charging/discharging time of the capacitor into a pulse width using each of the plurality of voltage dividing points of the output of the amplifier circuit as a reference potential. one of the voltage comparison circuits is used for setting the standard energization time of the heat generating element, and the other is used for determining the amount of reduction when reducing the energization time of the heat generating element according to the driving history. 1. A printing control device for a thermal printer, characterized in that it has an energization width control circuit.