JPH01278352A - Printer - Google Patents

Abstract

PURPOSE:To accurately obtain a slippage at the time of feeding a printing paper by a unit quantity, namely, skewing characteristics, by detecting variations in the ratio of the time for which a paper side edge position sensor is opposed to the upper side of the printing paper and the other times. CONSTITUTION:When a paper side edge position sensor 50 is periodically displaced by +5--5mm relative to a normal position 0, an output from the sensor 50 is repeatedly turned ON and OFF each time the sensor 50 crosses a side edge 3b of a paper. When the position of the side edge of the paper is constantly located at such a position that a sensor displacement on a graph is 0, the ratio of the ON time to the OFF time of the sensor output is 1. When the side edge position of the paper is deviated, the ON time of the sensor output [paper present range (b)] is logner than the OFF time of the sensor output [paper absent range (a)]. The time ratio is measured on the basis of the number of printing lines. When the time ratio b/a is represented by the number of lines and it is made to be skew quantity, skewing characteristics can be obtained by determining the skew quantity 3 or 4 times during the feeding of the printing paper by a one-screen amount and plotting the skew quantities determined.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a printing apparatus having a function of determining the skew characteristics of printing paper.

(Prior Art) In an apparatus that performs printing while transporting printing paper in a predetermined direction at a constant speed, it is required to transport the printing paper accurately and linearly along a transport path.

However, due to mechanical play in the conveying device, the printing paper may be conveyed slightly tilted. This state is called skew, and this skew characteristic is an important problem in printing apparatuses that are required to print at predetermined positions with high precision.

For example, printing images of two or more colors on printing paper,
In so-called multi-color printing devices, when overlaying images of other colors on top of the initially printed image of a certain color, the printing paper must be conveyed accurately and the overlapping of images must be controlled with high precision. , the quality of printed images deteriorates due to color misregistration.

FIG. 2 shows a perspective view of the main parts of a conventional general multicolor printing apparatus, and its operation will be specifically explained. This printing device is a multicolor printing device that employs a method called a field sequential swing method.

The print head 1 of this device is equipped with a so-called line-type heating resistor, and an ink ribbon 4 is conveyed in an overlapping manner with respect to a printing paper 3 conveyed by a platen 2, and heat is applied from the back side of the ink ribbon 4. A pulse is applied to transfer the ink to the printing paper 3.

The ink ribbon 4 is drawn out from the supply roll 5 and conveyed to be wound up on the take-up roll 6, and the surface facing the printing paper 3 has an area that is larger than the printing area 3a of the printing paper 3. An ink application area 4a is provided in which ink is applied. In this ink application area 4a, yellow, magenta,
The three primary colors for printing, such as cyan, are applied periodically.

Note that the printing paper 3 is sandwiched between the platen 2 and the pressure roller 7, and when these are rotated, it is conveyed back and forth in the direction of arrow 8, and is repeatedly conveyed so that the same printing surface 3a faces the print head 1. The configuration is as follows.

In this device, printing is first performed with the yellow ink application area 4a facing the printing surface 3a of the printing paper 3,
Next, the print surface 3a is made to face the print head 1, and then the magenta ink application area 4a is made to face the print head 1, and then printing is performed. Similarly, when printing is finally performed with the cyan ink application areas 4a facing each other, the printing operation for three colors is completed.

In order to perform such an operation, identification marks 10a and 10b are provided on the edge of the ink ribbon 4 along its longitudinal direction to identify the printing start position.

10c is provided. A ribbon sensor 11 is arranged to read these marks. As the ribbon sensor detects the identification mark, the ink ribbon 4 is repeatedly conveyed and stopped intermittently.

Further, the print head 1 is fixed to a bracket 12 and is supported so as to swing around a shaft 13 implanted in the side surface of the bracket 12. This bracket 1
2 is biased toward the platen 2 by the force of a spring 14. On the other hand, when the cam 16 is rotationally driven by the head drive motor 15 via the gear, the bracket 12 swings in the direction of the arrow 17, and the print head 1 is moved away from the platen 2. In this state, the platen 2 and pressure roller 7 rotate to convey the printing paper 3 to the printing start position.

FIG. 3 shows a block diagram of a control circuit of the printing apparatus as described above.

As shown in the figure, the print head 1 includes a print data output section 20.
Print data 20a is supplied from the printer and printing is performed. The print head 1 includes a large number of heating resistors 1a, driver gates 1b connected to these, a latch circuit 1c connected to one terminal of these driver gates 1b, and a printing circuit connected to the latch circuit 1c. The shift register ld supplies data.

Note that a power source 25 is connected to the power line of the heating resistor 1a. Furthermore, a strobe signal 1e is input to the other terminal of the driver gate 1b, and a strobe signal 1e is input to the other terminal of the driver gate 1b.
The reference clock signal 34 is connected to the reference clock signal 34 .

The print data output unit 2o also has an I10 port 22.23.2 that serves as an interface between the control unit 21 and an external circuit.
4 is provided. And on I10 boat 22,
A shift register 1d is connected. Further, a paper conveyance motor 31 , an ink ribbon feed motor 32 , and a head swing motor 15 are connected to a motor driver 26 connected to the I10 boat 23 . Further, a paper sensor 33 and a ribbon sensor 11 are connected to the I10 boat 24.

In this device, the controller 2 is connected to an external circuit (not shown).
When the print data input to 1 is supplied to the shift register 1d via the I10 port 22 one line at a time,
A latch circuit IC latches one line of printing data at a predetermined timing, selectively turns on and off the driver gate 1b, and selectively causes the heating resistor 1a to generate heat. Further, the control unit 21 drives the paper transport motor 31 to transport the paper 3 shown in FIG. 2 via the work/○ boat 23 and the motor driver 26, and drives the ink ribbon feed motor 32 to transport the ink ribbon. 4 is transported intermittently. In this case, the conveyance of the printing paper 3 is stopped by the paper sensor 3.
It is controlled by the input timing of the detection signal No. 3. Note that this paper sensor 33 is not shown in FIG.

On the other hand, the timing of conveying and stopping the ink ribbon 4 is controlled by the detection signal of the bond sensor 11 as shown in FIG.

That is, in the above-mentioned printing apparatus, print data that is serially input to the shift register 1d of the print head 1 in synchronization with the reference clock signal 34 is stored in the shift register 1d for one line. Then, the latch circuit 1c latches it, and printing for one line is performed. Then, while the next line of print data is being supplied to the shift register 1d, the printing paper 3
is transported for one line.

FIG. 4 shows an operational flowchart of multicolor printing using such a printing device.

First, the control unit 21 shown in FIG. 2 receives print data for one screen from an external circuit or the like (step Sl). next,
Rotate the ribbon feed motor 32 (step S2
). Then, the ribbon sensor 11 detects the yellow mark (step S3). When the yellow mark is detected, the yellow ink application area 4a faces the printing surface 3a of the printing paper 3. after that,
Do a heads-up. As a result, the print head 1 shown in FIG. 2 is pressed against the platen 2. First, one line is printed (step S5). Here, if the number of lines required to print one screen is n, then the counter's n
is decremented (step S6). And n is O
It is determined whether or not, and printing is repeated for n942 minutes (step S7). When printing for n942 minutes is completed, the head is lowered (step S8). As a result, the print head 1 is separated from the platen 2. Then print paper 3 to n9
Backfeed by 42 minutes (step S9). As a result, the printing surface 3a of the printing paper faces the print head 1 again. After that, print magenta (step 5).
IO). The procedure is exactly the same as steps 31 to S8. After magenta printing is completed, the paper is back-fed by n lines (step 511).
). Finally, cyan printing is performed (step 512). This is also done in the same manner as magenta printing. After this printing is completed, the paper is fed to a position where it can be easily taken out (step 513). Multicolor printing is performed in the manner described above.

(Problem to be Solved by the Invention) By the way, in the above-mentioned device 1, as explained at the beginning, if there is mechanical play or eccentricity in the conveyance mechanism of the printing paper 3, the printing paper may become skewed. Occur.

For example, if there is eccentricity in the outer diameters of the platen 2 and the pressure roll 7 shown in FIG. 2, the printing paper 3 will not be conveyed straight. That is, when feeding and pack feeding are repeated back and forth as shown by the arrow 8, a slight positional shift occurs in the axial direction of the platen 2.

On the other hand, since the position of the print head 1 is fixed, images of two or more colors to be superimposed may be misaligned with each other, resulting in a significant deterioration of print image quality. Although such deviation can be solved to some extent by high-precision machining of the platen 2 or the like, a satisfactory result is not necessarily obtained.

Another problem is that the more precisely the parts are machined, the higher the cost becomes.

The need to prevent such skew is not limited to multicolor printing devices. For devices that need to control the printing position with high precision, it is necessary to determine the skew characteristics of the printing paper,
Some kind of countermeasure must be taken.

An object of the present invention is to provide a printing apparatus having a function of determining such skew characteristics of printing paper.

Another object of the present invention is to provide a printing device that can eliminate color misregistration caused by misalignment of the printing paper 3 in the axial direction of the platen 2 and maintain the quality of the printed image at a high level. It is something to do.

(Means for Solving the Problems) The printing device of the present invention synchronizes with the conveyance of printing paper.
A paper side edge position sensor that periodically moves back and forth in a direction that intersects the conveying direction of the printing paper and crosses the side edge of the printing paper, and a time period during which the paper side edge position sensor faces the top surface of the printing paper, and The present invention is characterized by comprising a calculation section that calculates the skew characteristic of the printing paper by calculating the ratio of times other than the above.

Further, the device of the present invention can synchronize with the conveyance of printing paper.
A paper side edge position sensor that periodically moves back and forth in a direction that intersects with the conveyance direction of the printing paper and traverses its side edge, and a calculation for determining the skew characteristic of the printing paper based on the detection signal of this paper side edge position sensor. a print head that prints images of two or more colors one line at a time on the printing paper that is repeatedly conveyed to the printing section; and a print head that prints images of two or more colors one line at a time on the printing paper that is repeatedly conveyed to the printing section; The present invention is characterized by comprising a print position correction section that generates correction data according to the above data and combines it with the print data to correct the print start position of the print head in the line direction.

(For B) The above-described apparatus includes a paper side edge position sensor that periodically reciprocates across the side edge of the printing paper, intersecting the conveying direction of the printing paper in synchronization with the conveyance of the printing paper. When printing paper is skewed, its side edge position gradually shifts in a predetermined direction as it is transported. In this case, the ratio of the time when the paper side edge position sensor faces the top surface of the printing paper to the other time changes. If we capture this change,
It is possible to accurately determine the amount of deviation when printing paper is conveyed by a unit amount, that is, the skew characteristics.

Furthermore, when images of two or more colors are printed one line at a time, one line at a time, when printing of the first color is completed and the second and subsequent colors are printed, the amount of deviation of the printing paper can be determined from the skew characteristics. When printing the second color, the printing start position in the line direction can be corrected by combining the print data with correction data corresponding to the amount of deviation. This allows the next printed image to be accurately superimposed on the printing paper that has been slightly misaligned due to skew.

(Example) Hereinafter, the present invention will be explained in detail using embodiments shown in the drawings.

FIG. 1 is a block diagram showing an embodiment of a printing apparatus of the present invention.

In FIG. 1, the printing paper 3 is conveyed in the direction of arrow 8, and in synchronization with the conveyance of the printing paper 3, it is periodically reciprocated in the direction across the side edge 3b of the printing paper 3, that is, in the direction of arrow 9. A paper side edge position sensor 50 is provided to do so. The output of this paper side edge position sensor 50 is
Further, a skew characteristic storage section 52 is connected to the calculation section 51 .

Further, the output of the calculation section 51 is connected to be inputted to a print position correction section 60, and the print data output from this print position correction section 60 is connected to be inputted to the print data output section 20. .

Further, the output of this print data output section 20 is wired so as to be supplied to the print head 1 arranged opposite to the printing paper 3. This print head 1 is arranged to face the printing paper 3 by a mechanism as explained in FIG.

The printing position correction section 6o includes a correction data output section 61,
It is composed of a counter 62 and a comparison section 63.

The correction data output unit 61 is a circuit that takes in data output from the calculation unit 51 and outputs it to the comparison unit 63.

Further, the counter 62 is a circuit that receives and counts the reference clock signal 34 and outputs the count value to the comparator 63.

Incidentally, this reference clock signal 34 is also supplied to the printing radar 1 and is used to control the timing of supplying the image signal. In addition, the output of the comparison section 63 is sent to the print data output section 2.
0, and this signal is used to control the timing at which the print data output section 20 starts supplying print data to the print head 1.

FIG. 5 shows a specific embodiment of the paper side edge position sensor 50 shown in FIG. That is, FIG. 5 is a front view of the main part of the paper side edge position sensor 50. As shown in FIG.

In the figure, the rotating shaft 53 of the pressure roll 7 that presses the printing paper 3 against the platen 2 is extended in the axial direction. An endless screw-shaped groove 53a is provided on the outer peripheral surface of the rotating shaft 53. Further, a guide shaft 54 is provided parallel to this shaft 53. A sensor carriage 55 is attached so as to be able to reciprocate in the direction of arrow 9 so as to fit into these shafts 53 and guide shafts 54.

A reflective optical sensor 56 is fixed to the lower part of the sensor carriage 55. This reflective optical sensor 56 has a light emitting element 56a and a light receiving element 56b, and the light emitting element 50
The light emitted from a is reflected on the printing paper 3 and is received by the light receiving element 56b. The flexible wire 57 is provided for transmitting a drive signal and a detection signal for driving the reflective optical sensor 56.

FIG. 6 shows a side view of the main part of FIG. 5.

As shown in the figure, the pressure roll 7, which is pressed against the platen 2 with the printing paper 3 in between,
Rotates by rotation in direction a.

Further, a print head 1 for supplying heat pulses from the back surface of the ink ribbon 4 is arranged on the lower surface of the platen 2.

As is clear from this figure, when the printing paper 3 is present on the side facing the reflective optical sensor 56, the light receiving element 5
When a strong reflected light enters the printing paper 6b and the printing paper 3 runs out, the light is absorbed by the black platen 2, and the detection signal level of the light receiving element 56b decreases.

When the sensor carriage 55 reciprocates in the direction of the arrow 9 shown in FIG. will receive reflected light from the surface of the platen 2.

FIG. 7 is an exploded perspective view of essential parts of the apparatus of FIG. 6.

As described above, in order to reciprocate the sensor carriage 50, as shown in the figure, the shaft 53 of the pressure roll 7 is
A screw-shaped groove 53a is cut in the groove. and,
The sensor carriage 55, which is loosely inserted into the shaft 53 and the guide shaft 54, periodically reciprocates in the direction of the arrow 9 as the guide pin 58 screwed into the upper surface traces the screw-shaped groove 53a. It is preferable that this reciprocating movement is performed, for example, three to four times while the printing paper 3 is transported for one screen in synchronization with the transport of the printing paper.

The screw-shaped groove 53a is formed at such a pitch.

FIG. 8 shows the relationship between the displacement of the paper side edge position sensor 50 and its output signal, and its specific operation will be explained based on this.

The graph in the figure shows time on the horizontal axis and displacement of the paper side edge position sensor 50 on the vertical axis.

Here, when the output of the paper side edge position sensor 50 is periodically displaced from +5 mm to -5 mm with respect to the normal position O, it repeats on and off every time it crosses the side edge 3b of the paper. If the paper side edge position is always at the position where the sensor displacement is 0 in this graph, the time ratio of the sensor output on and off signals will be 1. However, if the side edge position of the printing paper shifts as shown by the dashed line in the figure, the sensor output becomes longer when it is on (range b with paper) than when it is off (range a without paper). This time ratio may be measured based on the number of printing lines shown in step S6 of the flowchart of FIG. 4.

Here, if the above time ratio b/a is expressed using this number of lines and this is the skew amount, then if the skew amount is measured and calculated 3.4 times while the printing paper is conveyed for one screen and plotted, the skew Characteristics can be determined. The calculation section 51 shown in FIG. 1 performs such calculation of the skew characteristic and stores it in the skew characteristic storage section 52.

Here, when printing is actually performed using the apparatus shown in Figure 2, the skew amount of the printing paper b / a
usually varies linearly.

Figure 9 is a graph showing the change in the skew amount b/a.If the printing start position of the yellow image is A, then the skew amount will change when the printing paper is fed from there to the printing end position. becomes B, and if the printing paper is then back-fed, the skew amount becomes C.

Then, printing of a cyan image is started from this state, and when the printing is finished, the skew amount increases to D. Then, the paper is back-fed again and the skew amount becomes E, and when the printing of the last magenta image is completed, the skew amount becomes F.

This change in the amount of skew, that is, the skew characteristic, is the first
When stored in the skew characteristic storage unit 52 shown in the figure, the calculation unit 5
1 creates correction data according to the skew characteristics and outputs it to the correction data output section 61. The correction data output section 61 is composed of, for example, a latch circuit, and temporarily holds the correction data and outputs it to the comparison section 63. for example,
When the number of dots in one line is 2048, normally about 8 dots at both ends are left as a margin where no print data is supplied. On the other hand, the deviation caused by the skew is usually about 0.2 to 0.3 mm.

Here, if a print head with a resolution of 8 dots per 1 mm is used, this deviation corresponds to a deviation of about 2 to 3 dots. Therefore, for example, when printing a yellow image and then printing a magenta 1 color image, the printing start position of one line of print data should be adjusted to match the shift (C-A) caused by the above skew. Once corrected, the next color can be accurately layered on top of the yellow image. This can be done by advancing or delaying the timing at which print data is supplied from the print data output section 20 to the print head 1 by 2 to 3 dots relative to the reference timing in FIG. 1.

For example, in the case of shifting two-dot print data, numerical data of 2 is stored in the correction data output section 61.

On the other hand, the force 2 counter 62 is cleared every time one line of print data is printed by the print head 1.
Start counting the reference clock signal 34. here,
When the counter 62 counts the reference clock signal 34 up to the value stored in the correction data output section 61, the output of the counter 62 and the output of the correction data output section 61 match, and the comparison section 63 then outputs the output from the print data output section 2o. Outputs tie and mink pulses.

The print data output unit 20 receives the timing pulse and starts outputting one line of print data. As a result, blank data is accumulated in the print head 1 by an amount corresponding to the delay in the input of print data, and the position of the print data is relatively shifted.

In this way, by replacing the correction data stored in the correction data output section 61 when printing an image of each color starts, the printing position of each image can be corrected with high precision, and high-quality images without color shift can be printed. can be done.

The present invention is not limited to the above embodiments.

The configuration of the paper side edge position sensor 50 is not limited to the above-described embodiment, and various mechanisms capable of reciprocating movement in synchronization with the conveyance of the printing paper may be employed. Further, the reciprocating direction of the paper side edge position sensor 5o does not necessarily have to be exactly orthogonal to the side edge of the printing paper.

Furthermore, the method of calculating the skew characteristics from the skew amount detected by the paper side edge position sensor 50 may be such that the calculation is performed by capturing only the timing at which this sensor turns off or from off to on. .

Furthermore, the device of the present invention is not necessarily limited to multicolor printing devices, but can be applied to devices that require extremely high precision printing position control, and can be used to control printing paper according to the skew characteristics determined by the above method. The print image quality may be corrected according to the skew characteristics by moving the print head position, moving the print head position, or using various other methods.

Further, the device of this invention is a serial type circle printer. It can be similarly applied to thermal transfer printers, wire dot impact printers, etc.

(Effects of the Invention) The apparatus of the present invention described above determines the amount of skew of printing paper while it is being conveyed, and takes measures according to the skew characteristics, so that printing quality can be improved. Furthermore, if this is applied to multicolor printing, correction control of the printing position can be automatically performed in order to perform high quality printing without color shift.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the printing apparatus of the present invention;
Figure 2 is a perspective view of the main parts of a conventional general multicolor printing device;
The figure is a circuit block diagram of the printing apparatus, FIG. 4 is a flowchart explaining the multicolor printing operation of the printing apparatus, FIG. 5 is a front view of the main part of the printing apparatus of the present invention, and FIG. 6 is a side view of the main part. 7 is an exploded perspective view of the main parts thereof, FIG. 8 is an explanatory diagram of the operation of the paper side edge position sensor of the apparatus of the present invention, and FIG. 9 is a graph showing the skew characteristics determined by the apparatus of the present invention. . 3...Printing paper, 3b...Side edge of printing paper, 8...
- Conveyance direction, 9... Reciprocating direction, 20... Print data output unit, 50... Paper side edge position sensor, 51... Calculation unit, 5
2... Skew characteristic storage section, 60... Print position correction section. Embodiment Block diagram of the printing device of the present invention FIG. 1 FIG. 4 Upper front view of main parts of the printing device of the invention FIG. Cutting drawing, paper conveyance direction □ Nuki 1 - Indicating characteristics, 77 Figure 9

Claims (1)

[Scope of Claims] 1. A paper side edge position sensor that periodically reciprocates in a direction that intersects the conveying direction of the printing paper and crosses the side edge thereof in synchronization with the conveyance of the printing paper, and a side edge of the paper; A printing apparatus comprising: a calculation unit that calculates a skew characteristic of the printing paper by calculating a ratio between the time when the position sensor faces the top surface of the printing paper and the other time. 2. A paper side edge position sensor that periodically reciprocates in a direction that intersects the conveyance direction of the printing paper and crosses its side edge in synchronization with the conveyance of the printing paper, and a detection signal of this paper side edge position sensor. a calculation unit that calculates the skew characteristic of the printing paper based on the printing unit; a print head that prints images of two or more colors in an overlapping manner one line at a time on the printing paper that is repeatedly conveyed to the printing unit; In this case, the present invention further includes a print position correction unit that generates correction data according to the skew characteristics of the printing paper in advance, and combines it with the print data to correct the print start position of the print head in the line direction. Characteristic printing device.