JPS62128281A - Printing pulse generating circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Table of contents] Overview Industrial field of application Prior art (Figures 5 and 6) Problems to be solved by the invention Means for solving the problems (Figure 1) Effects Embodiment (Figs. 2 to 4) Effects of the invention [Summary] The power supply voltage applied to the thermal head of a facsimile is integrated, and the thermal head is adjusted according to the time it takes for this integrated output to reach a predetermined basic value. By controlling the energization time, it is possible to prevent the print density from being affected by fluctuations in the power supply voltage applied to the thermal head.

[Industrial application field]

The present invention relates to a method for controlling the print density of a recording part of a facsimile, and more particularly to a power supply voltage generation circuit for controlling the power supply voltage inside the facsimile to a predetermined value in order to keep the print density constant at a predetermined density.

C. Prior Art] A thermal head as a heating element used when recording on thermal recording paper in a facsimile machine has heating resistors 81 arranged in an array as shown in FIG. 5, one of which is connected to a common power source. 1, and the other end is connected to each switching element 82. Only the heating element 81 connected to the switching element 82 to which the print pulse is input generates heat, and prints or figures are output on the corresponding thermal paper (not shown).

The print density printed on the thermal paper depends on the amount of heat generated (ie, temperature) of the heating element 81, and the power supply voltage fluctuates due to voltage drop due to load fluctuation. Since the amount of heat generated by the heating element is Joule heat, the fluctuation in the voltage has an effect equal to the square of the amount of heat generated by the heating element.

Here, the calorific value J can be expressed by the following equation.

J=(V”/R)t V: voltage, R: resistance, t: time.

Therefore, in the case of thin printing, even slight voltage fluctuations lead to fluctuations in print density, causing deterioration in facsimile image quality.

Conventionally, in order to prevent such unevenness in print density, excessive energy was applied to the heating element. In other words, there is a correlation between the temperature of the heating element and the print density as shown in Figure 6 (al), and when the temperature exceeds a certain temperature T3, the print density is saturated and the density does not change even with slight energy fluctuations. However, a power supply voltage was applied so that the temperature was higher than T1.

Further, in the case of actual printing, since the application time of the printing pulse is very short, it is devised to instantaneously heat the heating element to a high temperature (for example, T2) to ensure that the temperature around the heating element is around T1.

[Problem that the invention seeks to solve]

The method of applying extra energy as described above is effective in the case of binary recording in which only black and white images are obtained. However, there are a lot of demands for middle school these days! When printing 11 (half tone), it is necessary to control the print density by controlling the temperature change of the heating element, that is, the printing energy.

For halftone printing, as shown in Figure 6 (bl), intermediate color images with densities corresponding to several temperatures, that is, printing energy, are created between all white with no printing at all and all black with saturated printing density. It is necessary to control the temperature of the heating element to a certain constant temperature.However, when unexpected fluctuations in the power supply voltage occur, such as when printing with a large amount of black, it is necessary to control the heating element to a certain temperature in order to obtain a printed image with a certain density. Even if a printing pulse with a pulse width corresponding to the applied voltage is applied, the voltage may fluctuate due to load fluctuations and a predetermined density corresponding to the desired applied voltage may not be obtained.

Conventionally, in the case of a halftone facsimile as described above, the density has been controlled by using a power supply with little voltage fluctuation, but such a power supply is very expensive, leading to an increase in the cost of the facsimile.

SUMMARY OF THE INVENTION In order to solve these problems, it is an object of the present invention to provide a printing pulse generation circuit that is capable of printing almost unaffected by fluctuations in power supply voltage.

[Means for solving problems]

In order to achieve the above object, the printing pulse generation circuit of the present invention is provided with a power supply voltage monitoring section 2 in addition to a printing processing section 3 such as a thermal head as shown in FIG. When the input is input to the print processing section 3, the information is transmitted to the print processing section 3 and printing processing starts.At the same time, the power supply voltage is integrated and monitored to reach a certain reference value, and when the specified reference value is reached, the output is sent to the printing processing section 3. The printing time is controlled so that electricity is stopped and a certain amount of printing energy is applied to the thermal head.

[Effect]

In this way, by providing the power supply monitoring unit 2 in the common type tA1 of the thermal head, even if there is voltage fluctuation due to load fluctuation, it is possible to prevent fluctuations in printing energy by adjusting the printing time and to adjust the printing density to a constant level. .

〔Example〕

The present invention will be explained in detail with reference to FIGS. 2 to 4. In the figure, the same reference numerals as in FIG. 1 indicate the same parts, 4 is an integrating circuit, 5 is a reference voltage generation circuit, 6 is a comparator, 7 is a block control, 8 is a thermal head, 81 is a heating element, and 82 is a switching element. , 83 is a gate circuit such as an AND circuit, 84 is a flip-flop, and 85 is a shift register for print data.

The power source monitoring section 2 integrates the power source voltage to determine the time required to reach the reference voltage, and includes an integrating circuit 4, a reference voltage generating circuit 5, and a comparator 6. Integrating circuit 4
is a circuit that integrates the power supply voltage at the same time as the print pulse signal A is input, and the reference voltage generation circuit 5 outputs a predetermined reference voltage. This reference voltage is selected depending on, for example, the density of halftone data or the maximum density. The comparator 6 constantly compares the voltage integrated and output from the integration circuit 4 and the reference voltage output from the reference voltage generation circuit 5, detects a signal when the two match (tB in FIG. 3), and outputs the signal to the thermal head. It generates a signal that determines the energization time. That is, the integration circuit 4
A voltage shown in FIG. 3 is applied to the voltage, and the time e.g. t (B-A) until the integrated value reaches the reference voltage is detected.

As shown in Figure 3, this time is long as t (B-A) when the power supply voltage is small, and t (B'-
It will be shortened as shown in A').

The printing processing section 3 performs printing processing by applying electricity to the thermal head, and includes a block control 7 and a thermal head 8. The block control 7 controls the start or stop of printing, which is to start energizing the thermal head, based on the signal from the comparator 6.

The thermal head 8 prints on thermal paper, and as shown in FIG.
, a gate circuit 83, a flip-flop 84, and a shift register 85.

When printing, print data is first sequentially input to the shift register 85 of the thermal head 8 according to a clock.

When the print start signal A is applied to the integrating circuit 4 and the comparator 6 at LA in FIG. 3, for example, a print pulse is transmitted from the comparator 6 to the block control 7.

The block control 7 transmits the data to the gate circuit 83 of the thermal head, and the print data of the shift register transmitted via the flip-flop 84 is also input to the gate circuit 83 to start printing. Then from comparator 6,
The time t(A-B) until the voltage integrated by the integrating circuit 4 reaches the reference voltage is output to the block control 7. The block control 7 controls the time t (B-A
) instructs the gate circuit 83 to energize the heating element 81, that is, to print, but since the energization to the heating element is simultaneously performed according to the print data input to the shift register 85, the print data is blocked by the flip-flop 84. Control is performed so that only a predetermined heating element is energized in synchronization with a signal from the control 7, thereby obtaining a predetermined printed image.

If the number of black dots in the print data is small and the power supply voltage is high, the time width of the print pulse is t(B'-
As shown in A'), since it is short, control is performed in accordance with the magnitude of the power supply voltage in this way.

〔Effect of the invention〕

According to the present invention, a power supply monitoring unit is provided in the common power supply of the thermal head, and the energization time can be adjusted depending on the magnitude of the power supply voltage.This makes it possible to produce high-quality images with uniform print density that are not affected by load fluctuations. You can get it.

[Brief explanation of drawings]

Fig. 1 is a diagram of the inventive principle of the present invention, Fig. 2 is a schematic configuration diagram of an embodiment, Fig. 3 is an explanatory diagram of the operation of the embodiment, Fig. 4 is an explanatory diagram of the thermal head in the present invention, and Fig. 5 is a thermal head diagram. A schematic diagram of the head, FIG. 6 is an explanatory diagram of the temperature dependence of print density. 1-Electric power supply 2-Power supply monitoring section 3-・-
-Print processing section 4-Integrator circuit 5-Reference voltage generation circuit 6-Comparator 7゛°''--Block control 8--Thermal head 81--Heating element 82--Switching element 83--Gate circuit 84...Flip flow, 7bu 85--Shift register

Claims (1)

[Claims] A recording circuit using a thermal head includes an integrating circuit (4) that integrates a power supply voltage that is energized to the thermal head, a reference voltage generation circuit (5) that outputs a reference voltage, and a comparator (6). ), integrates the power supply voltage applied to the thermal head, compares it with a reference voltage, controls the energization time based on this, and performs printing.