JPH028063A - Stabilization of printing quality of thermal recorder - Google Patents

Abstract

PURPOSE:To make it possible to maintain a constantly uniform printing quality through applying optimum energy to heat generating elements by digitizing variations in a power supply voltage, individual differences in the resistance of heat generating elements and variations in ambient temperature, processing the digital data by a microprocessor, and regulating the pulse duration of a strobe signal for printing. CONSTITUTION:An MPU system 2 performs a process for receiving printing data for a thermal head 1 from the exterior, converting the printing data into data on a line basis for an actual printing operation, and transferring the converted data. Further, the MPU system 2 digitize inputs of three parameters having effects on printing quality, namely, a driving voltage A of a power supply 4, a voltage B controlled according to the intrinsic heat generating element resistance of the thermal head 1 and an output voltage C of a thermistor 6 according to the temperature of the head, by an A/D converter 3, then processes the digital parameters, and regulate the pulse duration of a strobe signal. The thermal head 1 is thereby supplied constantly with optimum energy, so that printing is conducted with a constantly stable printing quality, without any dispersion of printed density.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for always ensuring stable printing quality in a thermal recorder.

[Summary of the invention]

The present invention digitizes three variable factors that affect the print quality of a thermal recorder, namely, fluctuations in power supply voltage, individual differences in heating element resistance, and changes in ambient temperature, and converts these into numerical values using a microprocessor (MPU). By processing and changing the pulse width of the printing strobe and applying optimal energy to the heating element, it is possible to maintain uniform printing quality at all times.

[Conventional technology]

A thermal recorder prints dots on thermal recording paper using a heating element of a thermal head, and there are the following three variables that affect the print quality at this time. In other words, when driving a thermal head using a power source with voltage fluctuations such as a battery, the energy supplied to the heating element changes due to the voltage fluctuations, and the quality of the print drawn on thermal recording paper changes. Can't keep it uniform.

fb) Due to individual differences in the electrical resistance of the heating elements of each thermal head, variations in print density occur for each thermal head.

(C) Even if uniform energy is always applied to the heating element of the thermal head, if the ambient temperature changes, the temperature transferred to the thermal recording paper will change, and the print density will also change.

Conventionally, several measures have been developed to deal with the variable factors that affect the print quality of thermal recorders, but each method still has technical issues.

That is, to deal with the fluctuation of the power supply voltage in ta) above, there is a method of changing the duty factor applied to the heating element according to the power supply voltage, as shown in Japanese Patent Publication No. 55-24432, for example. Although it has been proposed, this content is
This is simply a circuit that has an inverse characteristic to the change in energy applied to the heating element with the change in power supply voltage as a parameter, and correction is performed using that characteristic curve. In addition, for boat fishing, there is a method to absorb fluctuations by configuring a stabilized power supply circuit of some kind from a power source that has fluctuating elements, but the loss in this part is large and the power usage efficiency is poor, and the circuit configuration is complicated. There is a drawback.

In addition, methods such as adjusting the output voltage of the stabilized power supply mentioned above according to the resistance value specific to the thermal head are adopted to deal with individual differences in the resistance value of the heating element (BL). This results in loss and circuit complexity.

In addition, methods are being explored to compensate for changes in the ambient temperature of the tel, such as correcting the output voltage of the stabilized power supply mentioned above based on the output voltage of a thermistor etc. attached to the radiator of the thermal heater. However, this still leaves problems such as loss and circuit complexity.

The present invention has been made in view of the above, and an object of the present invention is to solve the above-mentioned problems by making it possible to maintain uniform print quality on a thermal dot recorder using simple hardware.

[Means to solve the problem]

In order to achieve the above-mentioned object, the method of the present invention quantifies three variable factors that affect the print quality of a thermal recorder: 1. variation in power supply voltage, 1. individual difference in heating element resistance value, 9. variation in ambient temperature. The MPU (microprocessor unit) (2) performs processing to change the pulse width of the print strobe signal G.

[Effect]

In this way, by processing the MPU system (2) and changing the pulse width of the strobe signal G according to the variable factors, the optimum energy is always supplied to the heating element of the thermal head. Density is constant and stable print quality is always maintained.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of a configuration for implementing the method of the present invention, in which +1) is a thermal head having a heating element for dot printing, (2) is a microprocessor unit (hereinafter referred to as MPU) system, (3) is this M
Multi-channel input A arranged in PLI system (2)
/D converter. In addition to the A/D converter (3), the MPIJ system (2) also includes an internal event timer,
-fiIlo, Serial ■ A one-chip CPU equipped with 10° RAM, ROM, etc. is used.

A driving voltage A is directly applied to the thermal head (11) as a head voltage VH from a power source (4) having voltage fluctuations.At the same time, driving voltage A is applied to the MPU system 12.
) is input to the A/D converter (3).

Further, (5) is a variable resistor, and this variable resistor (5) is adjusted according to the resistance value of each unique heating element of the thermal head, and the voltage B is applied to the A/D converter of the MPU system (2). (
3) is input. In addition, a thermistor (6) as a temperature sensing element for measuring the temperature of the heating element is arranged near the heating element in the No. 1-maru head (1), and the output voltage C of this thermistor (6) is also connected via the amplifier (7). MPLI system (2)
It is configured such that it is input to the A/D converter (3) of.

A clock D is used to serially transfer print data from the MPU system (2) to the thermal head (1).
, print data E, data ruff F, and a strobe signal G that defines printing time are output.

And this MPU system (2) is a thermal head +
It receives print data for 11 from the outside, converts it into data for each line and transfers it for actual printing, and also inputs the parameters of the three elements that affect print quality, namely the above-mentioned parameters. Driving voltage A of the power source (4), voltage B adjusted according to the inherent resistance value of the heating element of the thermal head +1).

A predetermined process is performed based on the input of the output voltage C of the thermistor (6) according to the temperature of the thermal head, and as a result,
It operates to obtain printing of constant quality by changing the pulse width of the strobe signal G to the thermal head (1).

Generally, in order to obtain uniform print quality from a thermal head, if the thermal temperature of the thermal recording paper and the ambient salinity are constant, it is sufficient to always apply equal electrical energy to the heating element. W)l) can be expressed as follows using the head voltage (VH), the resistance value (RH) of the heating element, and the print factor (1).

Note that the printing death factor (t) is the time t during which the heating element of the thermal head is in the on state. N and ON ′″7tn4ifi′″l> 611 rJ top”
6゛゛. . ,. .

is expressed by

In the configuration of this example, the A
The /D converter (3) continuously converts the head voltage (VH) into a numerical value, and the variable grinder (5) adjusts the voltage corresponding to the heating element resistance value (RH), and converts the value into MP.
It can be input into the tJ system (2). MPLI
System (2) naturally has the ability to calculate these numerical data, so once the energy (WH) given to the heating element is specified to obtain the optimal print density, the head voltage ( VH), heating element resistance value (RH
Even if the parameters of ) change, the energy (
The print duty factor (1) can be accurately processed and output so as to give WH).

Further, even if a constant amount of energy is always applied to the heating element of the thermal head, a large change in ambient temperature will affect the print density. Therefore, in the configuration of this example, the MPU system (
2) can be digitized as continuous data by the A/D converter (3), and based on this data, the MPU system (2) calculates the printing duty factor (t) calculated by the method described above. By multiplying by a coefficient, changes in print density due to ambient temperature can be absorbed.

Next, to explain a specific processing example of thermal to rad control using the method described above, in actual processing,
The MPU system performs interrupt-driven operation at the timing of printing one line of the thermal head.

In addition, in order to speed up the processing, a table of the strobe width to be output is created based on the input parameters considered in advance using Equation 11 above, and processing is performed using a table search method that searches this table. .

Figure 2 shows the procedure of this process. First, the power is turned on and initialization is performed, and then the A/D of the thermal head resistance is adjusted by the IJJ variable resistor.
Conversion value is input. Incidentally, this head resistance value basically does not change if it is measured by -degrees, so it only needs to be set once. Thereafter, as described above, the preset usage table is registered and the device enters a standby state.

Then, when a line interrupt is performed at the timing of printing one line of the thermal head, the A/D conversion value of the thermal head drive voltage is input, and then the thermistor (6)
The A/D conversion value of the output voltage of Data is retrieved.

The obtained strobe data is then sent to the event counter, and then the strobe output terminal is activated and the event timer is activated to generate the required pulse width to apply optimal energy to the thermal head (1). strobe signal is output.

As described above, in the configuration of this example, there are three variable factors that affect the print quality of the thermal head, namely, the power supply voltage variation,
Individual differences in heating element resistance values and changes in ambient temperature are digitized by an A/D converter (31) and converted into numerical values by an MPU system (31).
By processing 2) and changing the pulse width of the strobe signal, the optimum energy is always supplied to the thermal head t1), so there is no variation in the print density of the thermal head and the print quality is always stable. Printing is done with .

〔Effect of the invention〕

As described above, according to the present invention, there are three
Since it can absorb two different variables, uniform and stable printing quality can always be obtained.

Furthermore, according to the present invention, since a conversion circuit such as a converter is not required in the power supply section, there is no loss in this part and the efficiency of power usage is good, and especially when operating on a battery, the operating time can be extended. Furthermore, hardware can be simplified by not requiring a conversion circuit such as a converter in the power supply section and by using an MPU system. Furthermore, M
By using the PU system to quantify and process variable factors, it is possible to strictly control print quality.Also, since it is controlled by the MPU system, the software will not change even if the power supply or thermal head characteristics change. It has various effects, such as being able to cope with changes.

[Brief explanation of the drawing]

Fig. f31 is a block diagram showing an embodiment of the present invention, and Fig. 2 is a flow chart showing a processing procedure by a microprocessor. In the figure, (1) is a thermal head, (2) is an MPU system, (3) is an A/D converter, (4) is a power supply, (5) is a variable resistor, and (6) is a thermistor. The same Matsukuma Hidemori book #B Tsuki no Mihikima・1 Figure 1 Flow of work by b+ya-[ Figure 2

Claims (1)

[Claims] The three variables that affect the print quality of thermal recorders are quantified: fluctuations in power supply voltage, individual differences in heating element resistance, and changes in ambient temperature. Printing is performed by a microprocessor in order to apply optimal energy to the heating element. A method of stabilizing print quality in a thermal recorder that consistently achieves uniform print quality by changing the strobe pulse width.