JPH02277650A - Thermal recorder - Google Patents

Abstract

PURPOSE:To enable a data to be printed by imaging to be corrected following variation of a resistant value of each thermal resistor even though the resistant value of each thermal resistor is varied due to repetition of a number of printing by a method wherein an image data in which only a part to be printed with a thermal resistor to be measured is taken as a black data and the other part is taken as a white data while specific voltage is being impressed to the thermal resistor, is supplied to a thermal head, and a resistant value of a heating element to be measured is calculated. CONSTITUTION:When printing of a specific number of sheets is performed, a control part 6 turns a relay 41 off to stop printing of an image data 100 once, and rewrites a resistant value correcting table 31. Firstly, when an image data in which only a data to be printed is taken as a black data and the other one is taken as a black data is supplied to a thermal head 1 with a thermal resistor 15-1, a current from a +24V power source flows to the resistor 15-1 via a resistance Rret. The control part 6 reads impressed voltage Vout of the thermal head 1 at that time as a digital value via an A/D converter 5, calculates a resistant value of the resister 15-1, rewrites data concerning the resistor 15-1 in a resistant value correcting table 3, and performs the same operation for the other resistors 15-2 to 15-n.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Field of Application) The present invention relates to a thermal recording device that prints on thermal recording paper or the like by generating heat from a heating resistor of a thermal head, and particularly relates to a thermal recording device that prints on thermal recording paper, etc. during recording. Regarding correction of image data.

(Prior Art) The main structure of a conventional thermal recording device of this type is as shown in FIG. 5, for example. After the image data (8 bits) 100 is corrected by the data correction section 3, it is sent to the head controller 2.
is supplied to the thermal head 1 via. The head controller 2 supplies the corrected data to the thermal head 1, and also supplies the thermal head 1 with a clock signal CK, a latch signal LA, and an enable signal EN for operating the thermal head 1.

FIG. 6 is a block diagram showing a detailed example of the thermal head 1 shown in FIG. 5. Thermal head 1 has image data 1
It has D-flip-flops 11-1 to 11-n forming a shift register that sequentially holds 00, and the contents held by these D-flip-flops 11-1 to 11-n are latch circuits 12-1 to 12-n. latched to. 13-1~1
3-n is an AND gate and latch circuits 12-1 to 12-n
The data latched to switch amplifiers 14-1 to 14
This is an AND gate that controls whether or not to apply to -n.

Switch amplifiers 14-1 to 14-n are heating resistors 15-
A current is caused to flow through latch circuits 1 to 15-n according to the contents of latch circuits 12-1 to 12-n.

The head controller 2 supplies the image data 100, the clock CK, the latch signal LA, and the enable signal EN to the thermal head 1 at the timing shown in FIG. 7(A). That is, one line of data 100 is sequentially held in the D-flip-flops 111 to 11-n shown in FIG. 6 by the clock CK. When one line of data is held in the D-flip-flops 11-1 to 11-n, the latch signal LA becomes low level, and the latch circuits 12-1 to 12-n transfer to the D-flip-flops 11-n.
The contents of 1 to 11-n are latched. After that, when the enable signal EN becomes low level, this inverter 6
The signal is inverted and input to AND gates 13-1 to 13-n, opening these gates. As a result, the content held in the latch circuits 12-1 to 12-n changes to the switch amplifier 1.
4-1 to 14-n, heating resistors 15-1 to 15-1
A current corresponding to image data 100 flows through 5-n, and thermal printing is performed.

By the way, the switch amplifiers 14-1 to 14-n store the image data 100 latched by the latch circuits 12-1 to 12-n.
As shown in FIG. 7(A), during the time Ten when the enable signal EN is at a low level, the heating resistor 15-1
~15-n. Therefore, the energy E supplied to each heating resistor is as follows, where V is the supply voltage and R is the resistance value of each heating resistor.

E=(V/R)T...(1)n Therefore, in order to reproduce halftones with the above thermal recording device, the energy E expressed by the above equation (1) must be adjusted to the image data 10.
0, specifically the time T.

This is done by modulating 0.

This modulation is performed by the head controller 2 shown in FIG. 5, and this head controller 2 controls the timing of each signal shown in FIG. The 8-bit signal of , time T for each bit. Perform control to assign from no to Ten7,
The above energy modulation is realized.

Here, the heating resistors 15-1 to 15-n are shown in FIG.
), there are variations in the resistance value R.

Therefore, if recording is performed as is without taking this variation into account, there will be variation in the energy supplied to each heating resistor, resulting in variation in recording density as shown in FIG. 8(B).

Therefore, the resistance value is determined in advance for each of the heating resistors 15-1 to 15-n, and the image data 100 is corrected based on the measured resistance value to absorb the variations in the heating resistors. This is done in the data correction section 3 shown in FIG. This data correction section 3 has a resistance value correction table 31 as shown in FIG. The above correction is performed for each corresponding portion. This resistance value correction table 31 is prepared for each heating resistor 15-1 to 15-1 before installing the thermal head 1 into the device.
It is created based on data obtained by measuring the resistance value of 5-n in advance.

However, as shown in FIG. 9, each heating resistor has a characteristic that its resistance value changes when the energy E is applied many times. Therefore, the resistance values measured in advance to create the resistance value correction table 31 as described above are:
The problem is that the data changes due to multiple printings, and even though the data is corrected by the data correction section 3 as described above, the original correction effect cannot be obtained.

(Problem to be Solved by the Invention) As described above, in the conventional thermal recording device, in order to correct the variation in the resistance value of the heating resistor, the resistance value is corrected by measuring the resistance value of each heating resistor in advance. The image data to be printed is corrected based on the table. However, the resistance value of the heating resistor changes from the previously measured resistance value as printing is repeated, so even though the image data is corrected, the initial correction effect is lost. The drawback was that it became impossible to obtain it. Therefore, the present invention eliminates the above-mentioned drawbacks, and even if the resistance value of each heating resistor that makes up the thermal head changes as the number of times of printing is repeated, the printed image data is corrected by following this change. The purpose of the present invention is to provide a thermal recording device that can perform thermal printing with stable image quality at all times.

[Structure of the Invention] (Means for Solving the Problems) In order to correct variations in the resistance values of a plurality of heating resistors constituting a thermal head, the present invention corrects recorded image data and then A thermal recording device that performs recording by supplying corrected image data to the thermal head, comprising: voltage applying means for applying a predetermined voltage to a heating resistor constituting the thermal head via a resistor having a predetermined value; During a period when the predetermined voltage is applied to the heat generating resistor by the voltage applying means, image data is supplied to the thermal head, with only the part to be printed by the heat generating resistor to be measured being set as black data and the rest being set as white data. a control means for causing a recording operation to be performed by the control means; and an arithmetic means for calculating a resistance value of the heat generating element to be measured by reading a voltage applied to the heat generating resistor to be measured when the recording operation is performed by the control means; The image forming apparatus is configured to include correction data updating means for rewriting correction data necessary for correcting the image data based on the resistance value calculated by the calculation means.

(Function) In the thermal recording device of the present invention, the voltage applying means applies a predetermined voltage to the heating resistor constituting the thermal head via a resistor having a predetermined value. The control means outputs image data to the thermal image data in which only the part to be printed by the heat generating resistor to be measured is set as black data and the other parts are set as white data during a period in which the predetermined voltage is applied to the heat generating resistor by the voltage applying means. It is supplied to the head to perform a recording operation. The calculation means reads the voltage applied to the heating resistor to be measured when the recording operation is performed by the control means and calculates the resistance value of the heating element to be measured. The correction data updating means rewrites the correction data necessary for correcting the image data based on the resistance value calculated by the calculation means.

(Example) An example of the present invention will be described below with reference to the drawings, in which the same parts as those of the conventional example are denoted by the same reference numerals. The first side is a block diagram showing one embodiment of the thermal recording device of the present invention. 1 is a thermal head having a plurality of heating resistors (not shown) and prints on thermal recording paper; 2 is various control signals CK, LA, EN and print image data ioo for driving the thermal head 1; The head controller 3 that supplies the thermal head 1 with a resistance value correction table 31 is a data correction section that corrects the printed image data 100 in order to correct variations in the resistance values of the heating resistors. Reference numeral 4 denotes a switch circuit section for measuring each heating resistor constituting the thermal head 1, and is composed of a relay 41 and a resistor RR6.degree. 5 is an A/D converter that digitizes the analog voltage; 6 is a control unit that calculates the resistance value of each heating resistor and rewrites the resistance value correction table 31 in the data correction unit 3.

Next, the operation of this embodiment will be explained. During recording, the relay 41 of the switch circuit section 4 is closed, and the power supply +24■ is directly applied to the thermal node 1 via this relay 41, so that the thermal power ? The card 1 is in a state where it can be driven. Further, the initial resistance value of the heating resistor in the thermal head 1 is written in the resistance value correction table 31 of the data correction unit 3.

In this state, the image data 100 is input to the data correction section 3, where the data portion corresponding to the heating resistor is corrected using the resistance value correction table 31, and then output to the head controller 2.

The head controller 2 supplies the image data 100 clocks CK, the latch signal LA, and the enable signal EN to the thermal head 1 at the timing shown in FIG. 7(A).

FIG. 2 is a block diagram showing a detailed example of the thermal head 1 shown in FIG. 1. The image data 100 sent from the head controller 2 is transferred to the D-flip-flop 11-.
1 to 11-n, the latch circuits 12-1 to 12-1
2-n latches the contents (image data) held in the D-flip-flops 11-1 to 11-n. Next, the enable signal EN is inverted and the AND gates 13-1 to 13
-n is opened, switch amplifiers 14-1 to 14-n are turned on and off according to the latched contents of latch circuits 12-1 to 12-n, and current flows to heating resistors 15-1 to 15-n. , swear words are printed.

Next, when a predetermined number of sheets have been printed, the control unit 6 turns off the relay 41 via the interface 7, temporarily stops printing the image data 100, and performs an operation to rewrite the resistance value correction table 31.

First, image data in which only the data to be printed by the heating resistor 15-1 is black data is supplied to the thermal head 1 via the head controller 2, and the D-flip-flop 11
-1 to 11-n hold this image data. Next, the head controller 2 outputs a latch signal LA to cause the latch circuits 12-1 to 12-n to latch the image data.

Thereafter, the head controller 2 sets the enable signal EN to a low level and opens the AND gates 13-1 to 13-n. As a result, the output side of the switch amplifier 14-1 is approximately 0.
Therefore, the output sides of the other switch amplifiers 14-2 to 14-n remain at high level. Therefore, the current from the +24■ power supply flows to the heating resistor 15-1 via the resistor Rref. Here, the voltage applied to the heating resistor 15-1 is
, and its resistance value is R, then the following equation holds.

(3), and the resistance value of the heating resistor 15-1 can be determined. Therefore, the control unit 6 controls the voltage V applied to the thermal head 1 at this time. , t are read as digital values via the A/D converter 5, and the calculation shown in the above equation (3) is performed to calculate the resistance value of the heating resistor 15-1. Based on the resistance value of the heating resistor 15-1 obtained in this way, the control unit 6 adjusts the heating resistor 15-1 in the resistance value correction table 3.
Rewrite the related data. The control unit 6 performs the same operation as above for the heating resistors 15-2 to 15-n,
The contents of the resistance value correction table 31 are sequentially rewritten. In this way, when the rewriting of the resistance value correction table 31 is completed, the control unit 6 again controls the relay 41 via the interface 7.
After closing, normal recording operation begins.

According to this embodiment, when the thermal head 1 is used to some extent, the control unit 6 measures the resistance values of the heating resistors 15-1 to 15-n, and the resistance value correction table is created based on the obtained resistance values. Since the contents of 31 are rewritten, the data correction section 3 can always correct the image data 100 in accordance with changes in the resistance values of the heating resistors 15-1 to 15-n. Therefore, it is possible to print swear words with stable quality from the start to the end of printing.

In the above embodiment, the resistance value correction table 31 is rewritten every time a predetermined number of sheets are printed, but it may be rewritten by a user's manual instruction when turning on the power. Furthermore, although multiple energy modulations were written in the above embodiments, the present invention can also be applied to a driver that drives a heating element that has the function of performing the energy modulation to obtain the same effect. can.

FIG. 3 is a block diagram showing another embodiment of the present invention. In this example, the switch circuit section 4 consists of a transistor T and a resistor R6゜f, and the transistor T only performs the function of the relay 41 of the previous embodiment, and the other configurations are exactly the same as the previous embodiment. . During recording, the control unit 6 increases the base voltage B of the transistor T by +2 via the interface 7.
This transistor is turned on at a voltage ten tenths of a volt below 4V.

As a result, +24cm power is applied to the thermal head 1 via the transistor T, and a normal recording operation is performed. On the other hand, when rewriting the resistance value correction table 31, the control unit 6 sets the base side voltage By of the transistor T to +24V via the interface 7 to turn off the transistor T, and connects the +24cm power supply to the resistor R6°f. The measurement operation of the resistance value of the heating element resistance is started by applying the voltage to the thermal head 1 through the heating element resistor. This embodiment also has the same effect as the above embodiment. Note that the transistor Tr is not limited to a transistor, and may be any semiconductor element that has a switching function.

FIG. 4 is a block diagram showing still another embodiment of the present invention. In this example, a relay 41 constituting the switch circuit section 4
A +24V power supply is applied to the other end, and a +12V power supply is applied to the other end of the resistor R6°f.

Also in this example, the relay 41 is turned on during recording, and +24
V power is applied to the thermal head 1, and thermal recording is performed by the thermal head 1.

On the other hand, when rewriting the resistance value correction table, the relay 41 is turned off and +12㎜ power is applied to the thermal head 1 via the resistor R6°f. Therefore, in this example, if the voltage applied to the thermal head 1 at this time is Vout, the following equation holds true.

The resistance value of the heating resistor in the thermal head 1 can be determined. In this example, the voltage applied to the heating resistor during resistance measurement is 172 12V compared to that in Figure 1, so the energy applied to the heating resistor is 1/4; It is possible to prevent printing on thermal recording paper due to body heat generation. Also, +12
(2) By using a stabilized power source as the power source, it is possible to measure resistance with higher accuracy than in the previous embodiment, and the quality of printing can be improved accordingly.

[Effects of the Invention] As described above, according to the thermal recording device of the present invention, even if the resistance value of each heating resistor constituting the thermal head changes as the number of printing is repeated, this change can be followed. By correcting the printed image data, it is possible to always perform thermal printing with stable image quality.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the thermal recording device of the present invention, FIG. 2 is a block diagram showing a detailed example of the thermal head shown in FIG. 1, and FIG. 4 is a block diagram showing another example of the present invention, FIG. 5 is a block diagram showing an example of a conventional thermal recording device, and FIG. 6 is a block diagram showing another example of the present invention. A block diagram showing a detailed example of the shown thermal head, FIG. 7 is a time chart showing the output timing of various control signals output from the head controller 2, and FIG. 8 shows variations in resistance values of heating resistors, FIG. 9 is a diagram showing variations in recording density, and FIG. 9 is a diagram showing resistance value change characteristics of a heating resistor with respect to applied energy. 1... Thermal head 2... Head controller 3... Data correction section 4... Switch circuit section 5...
・A/D converter 6...control section 15-1 to 15-n・
...Heating resistor 41...Relay Rref...Resistance Tr...
・Transistor agent patent attorney book 1) Takashi 4V Figure 1 Figure 4 Figure 3 Figure 5 Figure 4V Figure 6

Claims (1)

[Claims] In a thermal recording device that corrects recorded image data and then supplies the corrected image data to the thermal head for recording in order to correct variations in the resistance values of a plurality of heat generating resistors constituting the thermal head. , a voltage applying means for applying a predetermined voltage to the heat generating resistor constituting the thermal head via a resistor having a predetermined value; and the predetermined voltage is applied to the heat generating resistor by the voltage applying means. a control means for supplying image data to the thermal head so as to perform a recording operation by supplying image data to the thermal head, in which a portion to be printed by the heat generating resistor to be measured is printed as black data and white data for the other portion; calculation means for calculating the resistance value of the heating element to be measured by reading the voltage applied to the heating resistor to be measured when the voltage is applied to the heating element to be measured; and correction of the image data based on the resistance value calculated by the calculation means. 1. A thermal recording device comprising: correction data updating means for rewriting correction data necessary for the thermal recording device.