JPH0576909B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thermal recording device using a plurality of line-type thermal heads arranged in a staggered manner.

[Summary of the invention]

The present invention uses a plurality of line-type thermal heads (hereinafter referred to as thermal heads) arranged in a staggered manner to record on long, wide recording paper of large size, such as A1 or A0. In order to prevent printing overlap or gaps that occur due to expansion and contraction of the thermal head in the width direction of the recording paper due to temperature changes, each thermal head independently adjusts the printing area of adjacent thermal heads according to temperature changes. This allows the printed characters to match.

[Conventional technology]

Conventionally, there have been several line-type thermal heads that are connected in the width direction of the recording paper to record with recording widths such as A0 and A1. For example, a thermal head in which the heating resistors are arranged in a straight line, and a thermal head in which the thermal heads are arranged in a staggered manner as in the present invention have been proposed. However, recording apparatuses using these heads are often used for printing records that do not require high image quality and precision, and have a resolution of 6 dots/mm or less.

[Problem that the invention seeks to solve]

With the recent development of image processing technology, there is a demand for recording devices that can record with high image quality and high precision, and high-performance products with thermal heads with a resolution of 16 dots/mm have appeared. However, the thermal head
Heat is emitted from a heating resistor, and the higher the printing rate, the higher the temperature of the thermal head itself becomes, and the thermal head expands. These are
0.1mm at the junction of adjacent thermal head prints
There was a problem in that a gap of ~0.3 mm that could not be recorded or an overlapping area was generated. Currently, the resolution of thermal recording devices is 16 dots/mm.
However, in this case, the length of 0.2 mm to 0.3 mm is equivalent to 4 to 5 dots, which is important in achieving high image quality, high precision, and high resolution of thermal recording devices using multiple thermal heads. It was a problem.

[Means for solving problems]

In order to solve these conventional drawbacks, the present invention arranges a plurality of thermal heads in a staggered manner in the direction of the recording paper, and has line-shaped heating resistors of the thermal heads in the front row and the rear row with respect to the recording paper running direction. However, each thermal head is placed so that it partially overlaps,
The temperature of each thermal head is measured using a thermistor or the like in order to adjust the print position in the width direction of the recording paper by controlling the amount of data printed by the heating resistor in the overlapping area and the blank data that is not printed. As a result, the amount of expansion and contraction relative to the reference temperature is calculated, and the printing area of each thermal head is determined in accordance with the amount of expansion and contraction described above.

[Effect]

According to the present invention, the temperature of each thermal head and its support mechanism is measured by a thermistor,
Based on the temperature measurement results, the amount of expansion and contraction of each thermal head relative to the reference temperature is calculated. This calculation formula is naturally determined by the shape, material, and structure of the thermal head. Based on this calculation result, print data is distributed and recorded to each thermal head so that the print images are best joined.

〔Example〕

Embodiments of the present invention will be described below based on the drawings. FIG. 1 is a block diagram of the present invention, and a case will be explained in which three line type thermal heads are used. Thermistors 9, 10, and 11 are attached to the thermal heads 1, 2, and 3 to measure the temperature of each thermal head. The temperature signal detected by each thermistor is
The signal is inputted to the temperature detection circuit 5, A/D converted, and inputted to the control circuit 6 as temperature information. Based on the input temperature information, the control circuit 6 determines the printing area of each of the thermal heads 1 to 3 so that the joints of the thermal heads in the output image do not overlap or have no gaps. On the other hand, the raster data transferred for image output is stored in the line memory 7, and the line memory 7 transfers the stored raster data to the data distribution control circuit 8 according to a command from the control circuit 6. The data distribution control circuit 8 transfers the divided raster data and blank data to each of the thermal heads 1 to 3 based on the information on the print assignment area of each of the thermal heads 1 to 3 determined by the control circuit 6, and then transfers the divided raster data and blank data to each of the thermal heads 1 to 3. Drive and output images.

An example in which three thermal heads are actually arranged will be described below. FIG. 2 is a plan view of the thermal head, and FIG. 3 is an enlarged view of the overlapping portion of the heating resistors. Thermal heads 1 and 3 are arranged so that their heating resistors are aligned in a straight line, and the heating resistors of thermal heads 1 and 3 and thermal head 2 are arranged in parallel. Further, the printable areas of adjacent thermal heads overlap in the A2 and B1 portions and the B2 and C1 portions. The heating resistors of thermal heads 1, 2, and 3 are bonded to a ceramic substrate elongated in the width direction of the recording paper, and because the ceramic substrate is fixed to the thermal head base at only one point in the center, expansion and contraction due to heat generation progresses to both ends. . Corrections due to temperature changes in the printing area are determined by expansion and contraction of the ceramic substrate of each thermal head. The thermistors 9, 10, and 11 attached to the thermal head measure the temperature of the ceramic substrate. Thermal head 1,
Assuming that the printing areas 2 and 3 are equal in width to A, B, and C, and each width is L, the origin is assumed to be the center where the ceramic substrate of thermal head 2 is fixed in Fig. 2. In this case, the degree of joining of the printed images on thermal heads 1 and 2 is determined by the expansion and contraction of the ceramic substrate from the center of thermal head 2 to the joining part of the printed images on the thermal head 1 side, and the printed image from the center of thermal head 1 on the thermal head 2 side. is determined by the expansion and contraction of the ceramic substrate up to the joint. Now, let us assume that the amount of change in the image joining portion of thermal heads 1 and 2 is X, assuming that the change in which the printing assigned areas overlap is positive. The coefficient of thermal expansion of the ceramic substrate is α, the temperature of thermal head 1 when the printed images are best bonded is T ₁ , similarly the temperature of thermal head 2 is T ₂ , the current temperature of thermal head 1 is T′ ₁ , If the current temperature of the thermal head 2 is _T'2 , the following equation holds.

X=αL(T' ₁ -T ₁ )/2+αL(T' ₂ -T ₂ )/2 The first term of this equation is the expansion and contraction of the thermal head 1,
The second term represents the expansion and contraction of the thermal head 2.

In addition, the movement of the print area actually used by the thermal head is performed based on digital values, and if the number of correction dots is Y and the resolution of the thermal head is β, then Y=X/B, rounded to the nearest whole number. Calculated based on the value.

Next, the procedure for moving the printing area of the printing assignment area will be explained. As shown in the enlarged view of the overlapping part of the heating resistors at the ideal printing position in Figure 3A, for example, in actual printing between thermal heads 1 and 2, an unnatural printing position shift may occur at the joint spanning different adjacent thermal heads. Suppose it doesn't exist. At this point, because of printing, the thermal head 1
Assuming that the temperatures of thermal heads 1 and 2 rise, the ceramic substrate of each thermal head will thermally expand and the current junction of the printed images of thermal heads 1 and 2 will become as shown in Figure 3B.
When the position of the thermal head is deviated, the enlarged view of the overlapping portion of the heating resistor becomes the state a before correction.
Therefore, temperature information signals of the thermal heads 1 and 2 are obtained by thermistors 11 and 12. This signal is sent to the thermal heads 1 and 2 by the temperature detection circuit 5.
Convert to temperature information. The control circuit 6 uses the above-mentioned formula to calculate the overlapping amount of the joints due to the temperature rise between the thermal heads 1 and 2, and further calculates the corrected number Y of dots. It is sufficient to shift the dots toward the thermal head 3 by the number of correction dots. A command for the printing use area of each thermal head is sent to the data distribution control circuit 8. On the other hand, the raster data of the printed image is transferred to the line memory 7 and further transferred to the data distribution control circuit 8. The data distribution control circuit 8 distributes the transferred data to each thermal head based on the information of the printing area of each thermal head sent from the control circuit 7. Initially, the data is distributed between the printing areas of thermal heads 1 and 2 before printing starts, that is, before the temperature rises, as shown in the enlarged view of overlapping heating resistors at the ideal printing position in Figure 3A. The heating resistor of thermal head 2 is blank data from 1*o to 1*e, and the heating resistor of thermal head 2 is *2a.
~*2e will be blank data.

In fact, if there is a two-dot shift as shown in Figure 3A before correction in the enlarged view of the overlapping part of the heat generating resistor when the thermal head is misaligned, the data distribution control circuit 8 will control the print area from the control circuit 7. Based on the information, operate the printing area B of thermal head 2 and change the printing area B that was used up to *2f.*
Prepare blank data in *2f and *2g by 2h. As described above, the printing areas A, B, and C of each thermal head 1, 2, and 3 are determined, data is transferred to each thermal head 1, 2, and 3 for printing, and the printing area is determined based on the temperature information of the thermal head. By changing the area, the joint portions of adjacent thermal heads will not cause unnatural printing misalignment.

It goes without saying that the above-mentioned formula changes depending on the structure of the thermal head. Further, in the present invention, a thermistor is used as a temperature detecting element, but it is not limited to a thermistor as long as it is a temperature-electric element.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to automatically correct the misalignment of the printing joint part due to expansion and contraction due to temperature changes in the recording paper width direction of each thermal head, and the gap between the printing assigned areas of the joint parts of adjacent thermal heads. and over-rough can be kept within 1/2 dot. Therefore, a thermal recording device that uses multiple short-sized thermal heads (A4 size, B4 size, etc.) outputs high-quality, high-precision printed images on long-width recording paper (A1 size, A0 size, etc.). It is something that can be done.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the present invention, Fig. 2 is a plan view of a line-type thermal head, Fig. 3A is an enlarged view of the overlapping portion of heating resistors at the ideal printing position, and Fig.
Figure B is an enlarged view of the overlapping portion of the heating resistors when the thermal head is misaligned. 1, 2, 3... Line type thermal head, 5...
...Temperature detection circuit, 6...Control circuit, 7...Line memory, 8...Data distribution control circuit, 9,1
0,11...Thermistor.

Claims (1)

[Claims] 1. In a thermal recording device in which a plurality of line-type thermal heads are arranged in a staggered manner in the width direction of the recording paper, and the heating resistors of the thermal heads are arranged in series in the running direction of the recording paper, the temperature of the thermal head is measured. . A thermal recording apparatus, comprising: a control circuit that calculates the amount of expansion and contraction, and shifts the printing use area of each of the thermal heads in accordance with the expansion and contraction of the thermal heads in the width direction of the recording paper.