JP7040182B2 - Droplet ejection device, transfer control device, transfer control method, transfer control program - Google Patents

Description

The present invention relates to a droplet ejection device, a transfer control device, a transfer control method, and a transfer control program.

Entities with large printing demands use production printers. A production printer is a high-speed printer used for mass printing of printed matter (for example, 100 pages or more per minute). As one form of this production printer, there is a continuous paper printer that prints on a large roll-shaped printing medium (this is called the web).

Production printers typically have a printing engine (sometimes referred to as an "imaging engine" or "marking engine"), and a localized print controller that controls the overall operation of the printing system. The print engine includes one or more printhead assemblies, each assembly including a printhead controller and a printhead (or printhead array). Each printhead contains a plurality of very small (eg, hundreds) nozzles capable of ejecting ink controlled by a printhead controller. The printhead array consists of a plurality of printheads spaced in series in the width direction of the web.

While the production printer is printing, the web is fast-fed under the nozzle, paused, and ink is ejected at regular intervals to form pixels on the web. The web is tensioned in the transport direction to ensure that the web is consistently and in the same position under the nozzle.

However, an error in the position of image formation may occur also in the transport direction of the web. As an example, the encoder signal of the transport roller located upstream of the printhead array is used to generate the ink ejection timing. However, if the position of the web in the transport direction by the encoder signal does not match the actual position of the web, a state may occur in which the upstream printhead array and the downstream printhead array form images at different positions.

A technique for controlling the position of the web in the transport direction is known for such inconvenience (see, for example, Patent Document 1). In Patent Document 1, a non-contact displacement sensor is arranged under each print head, so that the encoder signal arranged on the transfer roller can be used for thermal expansion of the transfer roller, slippage between the web and the transfer roller, and elongation of the web itself. A printing device that cancels a factor that causes a displacement of the landing position such as the above is disclosed.

Further, in order to prevent the web from bending when the web is conveyed by the drive roller, Patent Document 1 describes the torque of the motor that drives the drive roller when the continuous paper is conveyed by the drive roller and the ink is ejected. A technique for applying tension to continuous paper by performing management is disclosed.

However, although the conventional web transport method can control the position in the transport direction by suppressing bending, there is a problem that the print quality deteriorates due to the fluctuation of the distance between the print head and the web at the ink ejection position. It cannot be resolved. That is, it is not possible to deal with the variation in the landing position caused by the fluctuation of the gap between the web and the head under the printhead, which is caused by the local tension of the web under the printhead due to the influence of solid printing or the like. In addition, the web may vibrate simply by landing the ink, and in this case as well, the landing position varies. Fluctuations in the gap between the web and head may cause misalignment of landing, which may cause deterioration of print quality.

In view of the above problems, it is an object of the present invention to provide a droplet ejection device that suppresses deterioration of print quality due to a change in the position of an object to which droplets are ejected in the droplet ejection direction.

The present invention comprises a transport motor that transports an object in a transport direction, a droplet ejection head that ejects a liquid toward the object, and a droplet of the object at a position where the liquid is ejected in the object. It has a sensor capable of detecting fluctuations in the ejection direction, and a control means for controlling the tension of the object according to the amount of the fluctuations in the droplet ejection direction of the object detected by the sensor. The control means controls the tension of the object according to the amount of the fluctuation of the droplet ejection direction of the object detected by the sensor while operating in the print density adjustment mode for adjusting the density of the droplet. Provided is a droplet ejection device characterized by the above.

It is possible to provide a droplet ejection device that suppresses deterioration of print quality due to a change in the position of an object to which droplets are ejected in the droplet ejection direction.

It is an example of the figure explaining the control of the tension of the web by a printing system. This is an example of a schematic external view of a continuous paper printing system. It is a figure which shows the configuration example of the printing system which suppresses the variation of the landing position due to the fluttering of the web. It is a figure which shows an example of the patch pattern of Y, C, M, K formed on the web. This is an example of the hardware configuration diagram of the control board. This is an example of a functional block diagram illustrating the function of the fluttering amount adjustment control unit. This is an example of a flowchart showing the operation procedure of the fluttering amount adjustment control unit that adjusts the fluttering amount of the web and reduces the ink landing position deviation. It is a figure which shows an example of the error message displayed on the display device. This is an example of a diagram showing the relationship between the amount of web fluttering and tension for each type of web. This is an example of a diagram showing the amount of landing position deviation at each printhead position by the conventional technique of generating the ink ejection timing from the encoder signal. This is an example of a diagram schematically showing an error between the encoder signal and the actual paper transfer amount when the eccentricity of the transfer roller in which the encoder is arranged, the thermal expansion of the roller, and the slip between the web and the transfer roller occur. It is a figure which shows the configuration example of the printing system which suppresses the variation of the landing position due to the fluttering of the web. This is an example of a functional block diagram of the controller. It is an example of the flowchart which shows the procedure which the controller controls the position of the web in the transport direction in an exemplary embodiment.

Hereinafter, as an example of the embodiment for carrying out the present invention, the printing system 500 and the transport control method performed by the printing system 500 will be described with reference to the drawings.
<First Embodiment>
FIG. 1 is an example of a diagram illustrating control of tension of the web 120 by the printing system 500 of the present embodiment. Although one print head 210 is shown in FIG. 1, the print heads 210 of each color are actually arranged in the transport direction of the web 120.

A non-contact fluttering amount detection displacement sensor 540 that detects a gap (distance) with the web 120 is arranged directly below each print head 210. At the start of printing or at the time of adjustment printing before the start of printing, the fluttering amount adjustment control unit 521 detects the gap fluctuation between the web and the head due to the fluttering of the web 120 at the time of solid printing (hereinafter, simply referred to as gap fluctuation). Further, the fluttering amount adjustment control unit 521 detects the tension applied to the web by the tension detecting unit 240, and controls the motor that drives the transport roller 230 so that the tension falls within the set range. In the present embodiment, the tension is further adjusted by controlling the motor that drives the transport roller 230 so that the gap fluctuation falls within a preset range. For example, if the tension is small, the fluttering becomes large, so if the gap fluctuation is large, the tension is increased.

Therefore, the printing system 500 of the present embodiment can optimize the tension applied to the web and the amount of fluttering. As a result, the amount of gap fluctuation is kept within the specified range even during solid printing, so that gap fluctuation due to fluttering of the web 120 can be reduced and deterioration of print quality can be suppressed.

<Terminology>
Image formation, recording, printing, printing, printing, modeling, etc. in the terms of the present application are all synonymous.

The liquid droplet ejection device includes a droplet ejection head (print head 210) or a droplet ejection unit, and drives the droplet ejection head to eject the liquid. An inkjet device dedicated to textile printing may be used. In this embodiment, the term printing system 500 will be used.

The object is an object from which droplets are ejected. Objects include those that expand and contract due to droplets, and those that expand and contract due to the impact of droplets even if they do not actually expand and contract. The case where not only the droplet but also the gas is ejected, or the case where the gas is caught by the ejection of the droplet and lands on the object is also within the scope of the application of this embodiment. Further, the case where only the gas is discharged and the object shakes is also within the scope of the application of this embodiment.

<Configuration example>
FIG. 2A shows an example of a schematic external view of the continuous paper printing system 100. The continuous paper printing system 100 forms an image on a continuous printing medium (for example, paper), and applies ink on the web 120, which is continuous paper. Further, the continuous paper printing system 100 includes a so-called production printer 110 capable of high-speed printing.

In addition, in the description of this embodiment, the word "ink" is used to refer to any suitable marking fluid (for example, water-soluble ink, oil-based paint, etc.). The production printer 110 is a form of an inkjet printer because it applies inks of each color of cyan (C), magenta (M), yellow (Y), and black (K). The web 120 is conveyed in the direction of the arrow in FIG. 1A, and the roller 130 applies a conveying force to the web 120 to convey the inside of the continuous paper printing system 100.

FIG. 2B shows a schematic configuration of the production printer 110 according to the present embodiment. As shown in FIG. 2B, the production printer 110 includes a carry-in unit 1 that carries in (carries) a web (roll paper) 120 as a print medium along a transport path, and a transport device 2 that transports the web. It has a pre-coating processing unit 3 that performs a pre-coating process as a pre-treatment on the carried-in web 120, and a printing system 500 that forms an image on the surface of the pre-processed web 120. These devices may be connected to each other to form a system as a whole, or may be apparently one printing device housed in the same housing. Further, when configured as a printing system, a control unit that controls the whole or a part of the system may be included in any of the devices, or may be provided in an independent separate housing.

The printing system 500 has an inkjet recording unit 5 that forms an image on the web 120 by an inkjet method. Further, the printing system 500 may include a post-processing unit 6 that post-processes the web 120 on which the image is formed. Further, the production printer 110 may have a drying unit 7 for drying the post-processed web 120 and a carry-out unit 8 for carrying out the image-formed (including further post-processed) web 120. good. Further, the printing system 500 has a controller 520 that controls the operation of each part.

Of the configurations shown in FIG. 2B, the pre-coating processing unit 3, the post-processing unit 6, and the drying unit 7 may not be provided. Further, the place where the controller 520 is arranged is only an example, and the controller 520 is arranged at an appropriate place. Further, a plurality of controllers 520 may be distributed and arranged, and they may cooperate to control the printing system 500.

<Example of a printing system configuration that can suppress variations in landing position due to web fluttering>
FIG. 3 is a diagram showing a configuration example of a printing system that suppresses landing position variation due to fluttering of the web 120. The printing system 500 includes a system, a component, or a device that can operate to form an image on the web 120, which is a printing medium.

In the figure, each printhead 210 provides one color plane of cyan, magenta, yellow, and black (each color when expressing a color with a plurality of colors of ink).

On the lower side of each print head 210, transport rollers 220 are arranged on the upstream side and the downstream side of the print head 210, respectively, to suppress paper fluttering directly under the print head 210. The rotating shaft of the transport roller 230 on the upstream side of the print head 210 is rotated by a motor, and an encoder 241 is arranged on this rotating shaft. When the web is transported, the transport roller 230 rotates to detect the encoder 241. The signal is transmitted to the controller 520. The controller 520 generates the ink ejection timing in each printhead 210 based on the detection signal of the encoder 241.

The controller 520 can be realized, for example, as a custom circuit, as a processor that executes a programmed instruction stored in an associated program memory, or as a specific combination thereof. The controller 520 is built on a control board described later.

The printing system 500 of FIG. 3 has motors 401 and 402 that come into contact with the nip roller 250 via the web 120, a tension detection unit 240, and a fluttering amount detection displacement sensor 540 that can detect the fluttering amount under the head. ing. The motors 401 and 402, the tension detection unit 240, and the fluttering amount detection displacement sensor 540 are connected to the fluttering amount adjustment control unit 521. The fluttering amount adjustment control unit 521 receives a signal of the gap fluctuation from the fluttering amount detection displacement sensor 540 and controls at least one of the motors 401 and 402 to adjust the tension.

The fluttering amount adjustment control unit 521 is provided in the control board 522 together with the controller 520. The control board 522 will be described with reference to FIG.

The amount of fluttering means the amount of fluctuation in the gap between the web and the head. The fluttering amount detection displacement sensor 540 is arranged within a range directly below each print head 210. Directly below is between two transport rollers 220 arranged so as to sandwich the print head 210 on both sides of the print head 210 in the transport direction of the web 120 (range in which the gap fluctuates), or the print head. It means a range that overlaps with the print head 210 when 210 is projected in parallel in the direction of the web 120. By arranging the fluttering amount detection displacement sensor 540 between the two transport rollers 220, the fluttering amount can be detected. Further, by arranging the fluttering amount detection displacement sensor 540 in the range overlapping with the print head 210, the fluttering amount at the landing position can be detected.

However, since the amount of fluttering (amplitude) is the largest at the center of the transfer rollers 220 adjacent to each other on the upstream side and the downstream side, the fluttering amount (amplitude) is arranged at a position close to the center of the transfer rollers 220 on the upstream side and the downstream side with respect to the print head 210. It is desirable to be done. Alternatively, since the landing position shifts at the ink ejection position due to fluttering, it is desirable to arrange the ink at a position close to the ink ejection position.

When there are a plurality of print heads 210, the transport roller 220 on the upstream side of a certain print head 210 and the transport roller 220 on the downstream side of the print head 210 on the upstream side of the print head 210 may be common. As a result, the number of transport rollers 220 can be reduced.

Further, the transport roller 220 may be a support member that supports the web instead of the roller. That is, a shaft or the like that does not rotate may be used.

The fluttering amount detection displacement sensor 540 can detect the position of the web 120 in the droplet ejection direction with reference to the state where the gap fluctuation is zero. The droplet ejection direction is a direction substantially perpendicular to the transport direction of the web 120. Alternatively, it may be said that the direction is perpendicular to the surface of the web 120. Since the fluttering amount detection displacement sensor 540 is arranged at positions close to the center of the transport roller 220 on the upstream side and the downstream side, the fluttering amount is detected at the ink ejection position.

The fluttering amount detection displacement sensor 540 may be any method as long as it can detect the distance between the fluttering amount detecting displacement sensor 540 and the web 120 in a non-contact manner. The amount of fluttering of the web 120 is measured based on the detected amount before the start.

First, a general method of transporting the web 120 will be described with reference to FIG. For example, the speed of the motor 401 (downstream in the transport direction) that comes into contact with the nip roller 250 is used as the speed reference, and the speed of the other motor 402 that comes into contact with the nip roller 250 is such that the tension detected by the tension detection unit 240 is the fluttering amount adjustment control unit 521. There is a feedback control in which the fluttering amount adjustment control unit 521 controls the speed of the motor 402 so that the tension is set in 1.

In the configuration of FIG. 3, tension is applied to the web 120 so that it can be stably conveyed in the printing system, but tension fluctuation may occur under the print head 210. When a large amount of liquid such as ink is ejected, such as solid printing, the web 120, which easily absorbs water, stretches under the head by absorbing the water of the ink, and the tension of the web 120 is localized due to the effect. May go down to. It has been found that the resulting fluttering of the web 120 under the head adversely affects print quality.

FIG. 4 shows an example of a patch pattern 602 of Y, C, M, K formed on the web 120. The patch patterns 602Y, 602C, 602K, and 602M of Y, C, M, and K are formed on the web 120 in the transport direction of the web 120 without overlapping each other. The Y, C, M, and K patch patterns 602 have lower concentrations toward the front in the transport direction, respectively.

The optical sensor unit 600 is arranged so as to face the web 120. The optical sensor unit 600 has a plurality of reflective photo sensors 600a, 600b, 600c, 600d arranged at predetermined intervals in the width direction of the web 120. Each of the reflective photo sensors 600a, 600b, 600c, and 600d is arranged directly above the patch pattern 602, and outputs a signal corresponding to the light reflectance of the patch pattern formed on the web 120.

Each patch of such a patch pattern 602 (a portion of each rectangle in FIG. 4) is in a state called solid printing because a range of a predetermined value or more is formed with a density of a predetermined value or more.

Therefore, the fluttering amount adjustment control unit 521 uses the signal of the fluttering amount detection displacement sensor 540 so that the fluttering amount is within the specified range (or may be only below the upper limit value of this range) at least one of the motors 401 and 402. To adjust the tension.

<Control board>
The control board 522 will be described with reference to FIG. The control board 522 is an electronic circuit or the like, is in charge of the feedback control, and has at least a storage means and a calculation means. The storage means referred to here is a so-called memory or the like, and the calculation means is, for example, a microcomputer, a CPU (Central Processing Unit), an FPGA (Field Programmable Gate Array), an electronic circuit, or the like.

FIG. 5 is an example of a hardware configuration diagram of the control board 522. The control board 522 has the function of an information processing device and is also called a microcomputer or the like. It may also be called a control device, a control unit, or the like. The control board 522 includes a CPU 21, a RAM 22, a ROM 23, an ASIC 24, an input IF 25, an output IF 26, an input device 27, and a display device 28.

The CPU 21 comprehensively controls the operation of the control board 522. The ROM 23 is a non-volatile memory for storing various data such as a program (transport control program). The RAM 22 is a volatile memory that functions as a work area (work area) for various processes executed by the CPU 21. The ASIC 24 is a processor having a specific function of performing image processing for changing print data into data formed by inkjet. The input IF 25 is an input unit or an input means that receives input of a detection signal from various sensors such as a fluttering amount detection displacement sensor 540. The output IF 26 is an output unit or output means that outputs a control signal generated by the flutter amount adjustment control unit 521 to the print head 210 and the motors 401 and 402.

The input device 27 is an input receiving means such as a hard key or a soft key (touch panel) used for inputting various settings by a user. The display device 28 is a liquid crystal display, an LED, or the like that displays various information such as a print state and an alarm. The input device 27 and the display device 28 may not be provided.

<About the function of the fluttering amount adjustment control unit>
FIG. 6 is an example of a functional block diagram illustrating the function of the fluttering amount adjustment control unit 521. The function of the fluttering amount adjustment control unit 521 is realized by utilizing the resources of the control board 522. For example, it is realized by the CPU 21 executing a program (transfer control program) expanded from the ROM 23 to the RAM 22 to control the hardware resources of the control board 522. Further, each function of FIG. 6 can be realized by one or a plurality of processing circuits. In this case, the hardware resources of FIG. 5 may include a DSP (digital signal processor), an FPGA (field programmable gate array), a SOC (System on a chip), a GPU (Graphics Processing Unit), and the like.

The fluttering amount adjustment control unit 521 includes two motor drivers 555 and 556 that control the rotation speeds of the motors 401 and 402, a set fluttering amount holding unit 555, and a calculation unit 524. The calculation unit 524 is a control means that optimizes the tension according to the amount of fluttering of the web. The calculation unit 524 further includes a solid print determination unit 554 at the time of adjustment, a fluttering amount comparison unit 552, a tension value setting unit 551, and a tension control unit 550. The two motor drivers 555 are connected to the motor 401 and the motor 402, respectively. The flutter amount comparison unit 552 is connected to the flutter amount detection displacement sensor 540, and the tension control unit 550 is connected to the tension detection unit 240. There are as many fluttering amount detection displacement sensors 540 as there are printheads 210.

The solid print determination unit 554 at the time of adjustment determines whether or not solid printing of the patch pattern for adjusting the print density is performed. Further, if it is performed, the fluttering amount suppressing unit 525 is enabled, and if it is not performed, the fluttering amount suppressing unit 525 is disabled. Since the print density adjustment mode is performed at a predetermined timing before or after the start of printing, it is known to the solid print determination unit 554 at the time of adjustment. Since the print density adjustment mode is used, it can be determined whether solid printing is performed by whether or not ink is ejected. Alternatively, the determination may be made based on, for example, image data. It can be determined by the ratio of the number of pixels in a predetermined range (the number of pixels from which ink is ejected).

The fluttering amount suppressing unit 525 includes a fluttering amount comparison unit 552, a fluttering amount detection displacement sensor 540, and a set fluttering amount holding unit 553. When the fluttering amount suppressing unit 525 becomes effective, it means that the fluttering amount suppressing unit 525 is operated or the function is turned on. To become invalid means to stop, turn off the function, and the like.

The fluttering amount suppressing unit 525 sends the tension value setting value data to the tension value setting unit 551 so that the fluttering amount of the web is within the set range. The set fluttering amount holding unit 553 holds the fluttering amount set by the operator or the fluttering amount set by default by the ROM 23 or the like.

The fluttering amount is input to the fluttering amount comparison unit 552 as a signal of the fluttering amount detection displacement sensor 540, and the fluttering amount is compared with the set fluttering amount set in the set fluttering amount holding unit 553, and the detected fluttering amount is set. When the upper limit of the fluttering amount range is exceeded, the tension value data is updated so as to increase the tension value of the tension value setting unit 551. When the detected fluttering amount is below the lower limit of the set fluttering amount range, the fluttering amount comparison unit 552 updates the tension value data so as to reduce the tension value of the tension value setting unit 551. The fluttering amount comparison unit 552 repeatedly updates the tension value data. The update may be performed by increasing or decreasing the tension value data by a certain amount, or may increase or decrease a fixed percentage of the current tension value data.

When the fluttering amount detected by the fluttering amount detection displacement sensor 540 is within the range of the fluttering amount set in the set fluttering amount holding unit 553, the fluttering amount comparing unit 552 performs the tension value data to the tension value setting unit 551. Will not be updated. If the print density adjustment is completed, the tension adjustment is completed.

As a result, the solid print determination unit 554 at the time of adjustment invalidates the flutter amount suppression unit 525, and the calculation unit 524 returns to the normal print mode with the current set tension. That is, the tension control unit 550 controls the motor 401 using the motor driver 555 and the motor using the motor driver 556 so that the tension detected by the tension detection unit 240 becomes the tension set by the tension value setting unit 551. Feedback control is performed to control the speed of the 402.

In this way, the fluttering amount adjustment control unit 521 can reduce the fluttering of the web under the print head, so that the ink landing position shift can be reduced.

<Operation procedure>
FIG. 7 is an example of a flowchart showing an operation procedure of the fluttering amount adjustment control unit 521 that adjusts the fluttering amount of the web 120 and reduces the ink landing position deviation. The procedure of FIG. 7 starts when the power of the printing system 500 is turned on.

First, the solid print determination unit 554 at the time of adjustment determines whether or not the print density adjustment mode is in progress (S110).

When the print density adjustment mode is not set (No in S110), the tension for suppressing the fluttering amount is not adjusted, so the process proceeds to step S210, and the tension is controlled by the current tension value data.

It is conceivable that the print density adjustment here is performed every time the web 120 is changed, but the set tension value can be stored for each type of the web 120, and the print density is adjusted every time the type of the web 120 is changed. You may.

When the print density adjustment mode is in effect (Yes in S110), the solid print determination unit 554 at the time of adjustment determines whether or not the solid print portion is being printed (S120). When the solid printing portion is not being printed (No in S120), the tension for suppressing the amount of fluttering is not adjusted, so the process proceeds to step S150.

When the solid printing portion is being printed (Yes in S120), the solid printing determination unit 554 at the time of adjustment enables the fluttering amount suppressing unit 525 (S130). This makes it possible to set the tension so that the fluttering of the web caused by the elongation of the web during solid printing can be set within an appropriate range.

In the fluttering amount suppressing unit 525, the fluttering amount detected by the fluttering amount detection displacement sensor 540 is within the range of the set fluttering amount held by the set fluttering amount holding unit 553 (greater than or equal to the second threshold value which is the lower limit and the upper limit is the first). The set value data is sent to the tension value setting unit 551 so as to be (below the threshold value of).

First, the fluttering amount comparison unit 552 determines whether or not the fluttering amount detected by the fluttering amount detection displacement sensor 540 is within the range of the set fluttering amount held by the set fluttering amount holding unit 553 (S140).

The signal of the fluttering amount detection displacement sensor 540 used here may take the average value of the fluttering amount for each page, or may take the average value of the fluttering amount for each finer transport distance (for example, every 1 inch). Further, a moving average value may be used instead of the average value. In the case of continuous paper, one page is, for example, an area sandwiched between perforations at predetermined intervals.

If the determination in step S140 is No, the fluttering amount comparison unit 552 determines whether or not the print density adjustment mode has ended (S160).

Even though the fluttering amount is not within the range of the set fluttering amount held in the set fluttering amount holding unit 553 (less than the second threshold value which is the lower limit and exceeds the first threshold value which is the upper limit), the print density adjustment mode When is completed, the fluttering amount comparison unit 552 performs error processing such as notifying the operator that the tension setting is not completed (S170). This makes it possible to prevent the transition to normal printing without completing the tension optimization. FIG. 8 shows a display example displayed by error processing.

Until the print density adjustment mode ends (No in S160), the fluttering amount comparison unit 552 determines whether or not the fluttering amount is below the lower limit of the range held by the set fluttering amount holding unit 553 (S180).

If the determination in step S180 is Yes, the current tension is too large, so the fluttering amount comparison unit 552 updates the tension value data so as to reduce the tension value of the tension value setting unit 551 (S190). It is possible to prevent the web from breaking or stretching due to excessive tension applied to the web.

If the determination in step S180 is No, the upper limit of the range of the fluttering amount set in the set fluttering amount holding unit 553 is exceeded, and the current tension is too small. Therefore, the fluttering amount comparing unit 552 is the tension value setting unit 551. The tension value data is updated so as to increase the tension value of (S200). By increasing the tension value data, it is possible to reduce the fluctuation of the position in the transport direction due to the fluttering of the web and the variation of the ink landing position.

If the tension value data is too large, the paper may be broken or stretched. Therefore, it is preferable that the tension value data is increased within a range not exceeding a predetermined maximum tension value data. In addition, it is effective that this tension value data is defined for each type of web. However, in FIG. 7, since there is a mechanism in which the excessive tension is reduced by the process of step S190, there is little risk of breakage or elongation of the paper.

When it is determined in step S140 that the fluttering amount detected by the fluttering amount detection displacement sensor 540 is within the range of the fluttering amount set in the set fluttering amount holding unit 553, the fluttering amount comparing unit 552 has a tension value. The tension value data is not updated to the setting unit 551.

In this case, the fluttering amount comparison unit 552 determines whether or not the operation in the print density adjustment mode is completed (S150). When operating in the print density adjustment mode, the process returns to step S110, and it is determined whether or not the fluttering amount is within the set fluttering amount.

When not operating in the print density adjustment mode, the fluttering amount comparison unit 552 ends the tension adjustment. The solid printing determination unit 554 at the time of adjustment invalidates the fluttering amount suppressing unit 525. As a result, the calculation unit 524 returns to the normal print mode with the current set value data (S210).

FIG. 8 shows an example of an error message displayed on the display device 28. In FIG. 8, the message "Tension adjustment based on the detection of the amount of fluttering has not been completed" is displayed. By confirming such an error message, the operator can prevent the transition to normal printing in a state where the tension optimization is not completed.

In addition to displaying an error message, the output to the effect that the tension adjustment has not been completed may be performed at least one of the lighting of the lamp and the sounding of the alarm sound. The operator may also be notified by e-mail.

<Relationship between web fluttering amount and tension for each type of web>
FIG. 9 is an example of a diagram showing the relationship between the amount of fluttering of the web 120 and the tension for each type of the web 120. In FIG. 9, the horizontal axis is the tension setting value of the web 120, and the vertical axis is the amount of fluttering of the web 120. In FIG. 9, tension and fluttering amount are shown as a graph for two webs 120, web A and web B.

Web A is a paper that is easy to flutter, and Web B is a paper that is hard to flutter. The amount of fluttering differs depending on the web 120 depending on the thickness of the paper and the ease with which moisture permeates. Generally, the thicker the web 120, the easier it is to stretch due to the permeation of moisture (the tension tends to decrease), and the amount of fluttering. The fluctuation of the web-head gap due to fluttering also increases. The fluttering allowance is predetermined or can be experimentally determined by the user.

On the other hand, if the tension is too large for the paper, the paper may be broken or stretched. Therefore, each user decides and uses the optimum tension setting value depending on the paper.

According to this embodiment, it is possible to select a tension setting in which fluttering is within an allowable range and is not excessive. In FIG. 9, the setting range of the fluttering amount is P to Q [mm]. Q is the upper limit of the range of the fluttering amount set in the set fluttering amount holding portion 553 (first threshold value), and P is the lower limit of the range of the fluttering amount set in the set fluttering amount holding portion 553 (second threshold value). ). Therefore, in the case of Web B, 100 to 150 [N] is an appropriate value, and in the case of Web A, 150 to 200 [N] is an appropriate value. The fluttering amount adjustment control unit 521 can determine an appropriate tension for each web 120 by the above control procedure.

<Summary>
As described above, the printing system 500 of the present embodiment detects the amount of fluttering of the web and optimizes the tension applied to the web, so that the distance between the print head and the web fluctuates at the ink ejection position. It can be suppressed and the deterioration of print quality can be suppressed. For example, even during solid printing, the amount of gap fluctuation is kept within the specified range, so that deterioration of print quality can be suppressed.
<Second Embodiment>
In the above embodiment, the controller 520 generates the ink ejection timing in each printhead 210 based on the detection signal of the encoder 241.

When each print head 210 is arranged at a position that is an integral multiple of the peripheral length of the transfer roller 230 from the transfer roller 230 in which the encoder 241 is arranged, the transfer is performed by the eccentricity of the transfer roller 230 synchronized with the rotation cycle of the transfer roller 230. It is easy for the controller 520 to cancel the error in the position of the direction. That is, the controller 520 may cancel the error in the position in the transfer direction due to the eccentricity of one rotation of the transfer roller 230 (since the error in the position in the transfer direction due to the eccentricity does not accumulate, the print head 210 transfers from the transfer roller 230. Even if it is arranged at a position that is an integral multiple of the circumference of the roller 230, the error is within one rotation).

Further, regarding the fact that the mechanically generated mounting position of the print head 210 does not become the ideal position in the design, the ink ejection timing is corrected from the result of the test print performed by the controller 520 before the start of printing, and the ink ejection timing is canceled.

However, at the position of the web 120 directly under the print head 210 for ejecting ink and the position calculated from the encoder signal, thermal expansion of the transport roller 230, slippage between the web 120 and the transport roller, elongation of the web 120 itself, etc. Since it is normal for an error in the position in the transport direction to occur due to the above factors, the ink ejected by each print head 210 actually lands at a position on the web 120 deviated from the target position. This will be described in detail with reference to FIGS. 10 and 11.

FIG. 10 is an example of a diagram showing the amount of landing position deviation at the position of each print head 210 by the technique of generating the ink ejection timing from the encoder signal. In FIG. 10, the horizontal axis indicates the transport time, and the vertical axis indicates the web position. Two graphs are drawn, showing the actual paper position P1 and the paper position P2 calculated from the encoder signal, respectively. The paper position P2 calculated from the encoder signal is exactly proportional to the transport time. The actual paper position P1 is substantially proportional to the transport time, but periodically fluctuates depending on the amount of landing position shift due to the eccentricity of the transport roller 230.

Normally, the landing position shift due to the eccentricity of the transport roller 230 fluctuates with a cycle synchronized with the rotation cycle of the transport roller 230, and the same shift occurs for each cycle. In addition, the amount of landing position shift increases in proportion to the amount of eccentricity, but does not accumulate.

In FIG. 10, the landing position deviation amount δ at the position of the print head 210 of K is shown. Since the landing position deviation amount δ based on the eccentricity amount is reproducible and can be measured before the start of printing, the controller 520 can correct the ejection timing and cancel it.

However, as described above, the displacement of the landing position from the target position due to the thermal expansion of the transport roller 230, the slip between the web 120 and the transport roller, the elongation of the web 120 itself, etc., is caused by the generation of the ink ejection timing from the encoder signal. It is difficult to cancel.

FIG. 11 schematically shows an error between the encoder signal and the actual paper transfer amount when the eccentricity of the transfer roller 230 in which the encoder is arranged, the thermal expansion of the roller, and the slip between the web 120 and the transfer roller occur. It is a thing. In FIG. 11, the horizontal axis is the rotation angle of the transport roller 230, and the vertical axis is the error amount. In FIG. 11, three graphs are drawn, which are the landing position deviation Z1 due to eccentricity (0.01 mm), the landing position deviation Z2 due to eccentricity + temperature change (-10 degrees), and eccentricity + slip (0.1), respectively. %) Indicates the landing position shift Z3.

As shown in the figure, the landing position shift due to the eccentricity of the transport roller 230 usually has a cycle synchronized with the rotation cycle of the transport roller 230, and the landing position shift occurs in the same manner each time. In addition, the amount of landing position shift increases in proportion to the amount of eccentricity, but does not accumulate. In addition, it can be seen that the amount of landing position shift increases due to temperature changes and slippage.

The linear expansion of the transport roller 230 and the slippage between the web 120 and the transport roller are cumulative, and the landing position shift cannot be corrected by the printing system 500 having a configuration in which the state is different for each printing and the encoder is arranged on the transport roller 230. In addition, the amount of landing position shift due to the elongation of the web 120 caused by applying tension to suppress the meandering of the web 120 also differs depending on the thickness of the web 120, the width of the web 120, and the amount of ink applied, and is a state for each printing. Is different.

<Example of a printing system configuration that suppresses the landing position deviation from the target position due to thermal expansion of the transport roller, slippage between the web and the transport roller, and elongation of the web itself>
FIG. 12 is a diagram showing a configuration example of a printing system 500 that suppresses a landing position deviation from a target position due to thermal expansion of a transport roller, slippage between a web and a transport roller, and elongation of the web itself. In the description of FIG. 12, since the components having the same reference numerals in FIG. 3 perform the same function, only the main components of the present embodiment may be mainly described.

Immediately below the print head 210, a web position sensor 530 that can detect the position of the web 120 in the transport direction is arranged. Directly below is between two transport rollers 220 arranged so as to sandwich the printhead 210 on both sides of the printhead 210 in the transport direction of the web 120, or the printhead 210 is parallel to the direction of the web 120. It means a range that overlaps with the print head 210 when projected.

The printing system 500 includes a printer 510 and a controller 520 with one or more printheads 210 used to form an image with ink on the web 120.

The web position sensor 530 is a sensor that can detect the position and the amount of movement of the web 120 in the transport direction of the web 120 in a non-contact manner. The web position sensor 530 includes, for example, a laser, a sound wave, a CCD camera, infrared rays, light, or a detection device by another suitable detection method. In one embodiment, the web position sensor 530 detects the web position by the speckle pattern of the web 120. The speckle pattern is an interference pattern obtained by irradiating two moving laser beams on a moving rough surface, and the distance between these interference fringes is determined by the original surface, so the amount of movement of the web can be measured by counting the number of fringes. Can be measured. In another embodiment, the web position sensor 530 detects the equidistant marks formed on the web by the upstream printhead 210 and positions the number of marks based on the marks made by the upstream printhead 210 (eg, the upstream printhead 210 detects the equidistant marks formed on the web. Detects the position of the web 120 (converted to).

The web position sensor 530 located directly below the print head 210 on the most upstream side generates a reference ink ejection timing. In the printing system 500, two printers 510 for the front side and a printer 510 for the back side may be arranged in the transport path of the web 120 in order to print on both sides of the web. In this case, the web position sensor 530 located directly below the print head 210 on the most upstream side in each printer 510 generates a reference ink ejection timing.

The ejection timing of the ink generated by the web position sensor 530 in the print head 210 on the most upstream side is different from the ejection timing generated by the encoder arranged in the transport roller 230, and the rotation cycle is caused by the eccentricity of the transport roller 230. Since the landing position shift synchronized with the above does not occur, it is not necessary to make the distance between the print heads 210 an integral multiple of the peripheral length of the transport roller 230, and it is possible to reduce the restrictions on the arrangement.

Further, since the web position is directly detected, the configuration is not affected by the above-mentioned slip between the web 120 and the transport roller and the thermal expansion of the transport roller 230.

Further, by arranging the web position sensor 530 directly under each print head 210, it is possible to detect the position of the web 120 without being affected by the elongation of the web 120 between the print heads 210. It is clear that the closer the printhead 210 and the web position sensor 530 are, the more accurate the correction is possible.

The controller 520 controls the ejection timing of the printhead 210 based on the web position detected by the web position sensor 530. For example, the controller 520 is the most upstream from the time required to convey a predetermined amount of the web 120 by the web position sensor 530 located directly below the printhead 210 most upstream in the conveying direction of the web 120 in the printer 510. Generates ink ejection timing at the side printhead 210.

Further, at the same time that the ink ejection timing in the print head 210 on the most upstream side is generated, the web position sensor 530 on the downstream side detects and integrates the amount of ink conveyed by the web 120. The web position sensor 530 on the downstream side notifies the controller 520 when the web 120 transport amount equal to the distance between the web position sensors 530 is reached. The controller 520 executes printing after correcting the ink ejection timing in the print head 210 on the downstream side. That is, the specified amount of web 120 measured by the downstream web position sensor 530 is conveyed with respect to the ink ejection timing of the downstream print head 210 obtained from the conveying speed of the web 120 measured by the most upstream web position sensor 530. Correct by the time required to do. Specifically, the time when the web position sensor 530 on the downstream side reaches the same amount of web 120 conveyed as the distance between the web position sensors 530 is determined as the printing timing of the print head 210 on the downstream side.

FIG. 13 shows an example of a functional block diagram of the controller 520. The controller 520 has an upstream discharge timing generation unit 11 and a downstream discharge timing generation unit 12. The upstream ejection timing generation unit 11 is connected to the most upstream web position sensor 530 and is connected to the most upstream print head 210. The downstream discharge timing generation unit 12 is connected to the remaining web position sensor 530 on the downstream side, and is also connected to the print head 210 on the downstream side.

The upstream ejection timing generation unit 11 receives a notification that a predetermined amount of the web 120 has been conveyed by the web position sensor 530 directly below the printhead 210 most upstream in the direction of the web 120, and the printhead on the upstream side is the most upstream. Generates the ink ejection timing at 210. The upstream discharge timing generation unit 11 notifies the downstream discharge timing generation unit 12 that the most upstream web position sensor 530 has required to convey the specified amount of the web 120. The downstream discharge timing generation unit 12 causes each downstream web position sensor 530 to start measuring the conveyed amount of the web 120. The downstream ejection timing generation unit 12 obtains a notification that the web position sensor 530 on the downstream side has measured the amount of ink transferred to the web 120, which is the same as the distance between the web position sensors 530, and the ink in the print head 210 on the downstream side. Generate discharge timing. For example, the discharge timing is generated at the same time as the notification.

<Controller operation>
FIG. 14 is an example of a flowchart showing a procedure in which the controller in an exemplary embodiment controls the position of the web in the transport direction. The flowchart of FIG. 14 will be described with reference to the printing system 500 of FIG. However, the process of FIG. 14 can also be performed in other printing systems. The steps in the flowchart of the present embodiment do not include all the steps performed by the controller 520, and the controller 520 may include other steps not shown. Further, the steps of the present embodiment may be performed in an alternative order in addition to the order of the steps shown in the figure.

In step S10, the web position sensor 530 of the printhead 210 on the most upstream side of the printer 510 measures the time during which a specified amount of web 120 is transported based on the transport amount of the web 120. The upstream ejection timing generation unit 11 of the controller 520 generates the ink ejection timing by the notification that this time has been measured. The time during which the specified amount of the web 120 is conveyed may be used as the ink ejection timing as it is, or the ink ejection timing may be set by adding a predetermined time.

In step S20, the downstream ejection timing generation unit 12 of the controller 520 notifies the web position sensor 530 of each printhead 210 on the downstream side of the ink ejection timing of the printhead 210 on the most upstream side. The web position sensor 530 starts accumulating the amount of web transport, compares it with the distance between the sensors of each print head 210 on the downstream side, and when both become equal, the controller 520 notifies that the specified amount of web 120 has been transported. Notify the downstream discharge timing generation unit 12 of the above.

The downstream ejection timing generation unit 12 of the controller 520 generates ink ejection timing in each print head 210 on the downstream side based on this time before performing the printing operation.

The controller 520 may acquire and integrate the amount of the web 120 conveyed from the web position sensor 530 of each print head 210 on the downstream side, and compare it with the distance of each print head 210 on the downstream side.

The process of FIG. 14 is performed continuously during printing so that the web position is consistently identified and the ink ejection timing can be generated. This makes it possible for the printing system 500 to reduce an error in the transport direction of the web 120 of the printing medium. The print quality is improved by ejecting the ink ejection timing to the web 120 more accurately, and in the printing system 500 using a plurality of ink colors, the color of the image is accurately reproduced on the print medium. Also contributes.

When the fluttering amount adjustment control shown in FIG. 7 is performed on the printing system shown in FIGS. 12 to 14, not only the gap fluctuation due to the fluttering of the web 120 can be reduced and the deterioration of print quality can be suppressed, but also the web position can be suppressed. It can also contribute to the improvement of the position reading performance by the sensor 530, for example, the reading performance of the speckle pattern of the paper. As a result, the ink ejection timing in each print head 210 can be generated more accurately, and the deterioration of print quality can be suppressed.

<Other application examples>
Although the best mode for carrying out the present invention has been described above with reference to examples, the present invention is not limited to these examples, and various modifications are made without departing from the gist of the present invention. And substitutions can be made.

For example, the content of this embodiment is not limited to a printing device, but is a technique applicable to all devices such as a laser processing machine and an inspection device, which convey a long medium while applying tension.

Further, in the present embodiment, it has been described that the print head 210 ejects ink, but the print head 210 may be a droplet ejection head that ejects / ejects a liquid from a nozzle. The liquid to be discharged may have a viscosity and surface tension that can be discharged from the head, and is not particularly limited, but has a viscosity of 30 mPa · s or less at room temperature, under normal pressure, or by heating or cooling. Is preferable. More specifically, solvents such as water and organic solvents, colorants such as dyes and pigments, polymerizable compounds, resins, functionalizing materials such as surfactants, biocompatible materials such as DNA, amino acids and proteins, and calcium. , Solvents, suspensions, emulsions, etc. containing edible materials such as natural pigments, such as inks for inkjets, surface treatment liquids, components of electronic and light emitting elements, and formation of electronic circuit resist patterns. It can be used in applications such as liquids and material liquids for three-dimensional modeling.

Piezoelectric actuators (laminated piezoelectric elements and thin-film piezoelectric elements), thermal actuators that use electric heat conversion elements such as heat-generating resistors, and electrostatic actuators that consist of a vibrating plate and counter electrodes are used as energy sources for discharging liquid. Includes what to do.

Further, the web is not limited to paper and may be any one to which a liquid can adhere. A liquid to which a liquid can adhere means a liquid to which the liquid can adhere at least temporarily, such as one that adheres and adheres, and one that adheres and permeates. Specific examples include paper, recording paper, recording paper, film, recorded media such as cloth, electronic substrates, electronic components such as piezoelectric elements, powder layers (powder layers), organ models, and media such as inspection cells. Yes, and includes everything to which the liquid adheres, unless otherwise specified. These may be collectively referred to as an object.

The material of the above-mentioned "material to which a liquid can adhere" may be paper, thread, fiber, cloth, leather, metal, plastic, film, glass, wood, ceramics or the like as long as the liquid can adhere even temporarily.

Further, in the present embodiment, the production printer 110 has been described as an example, but the optimization of the tension based on the amount of fluttering can be applied not only to the production printer 110. For example, it can be applied to an inkjet printer.

Further, the droplet ejection device may be referred to as a printing system, an image forming apparatus, a three-dimensional modeling apparatus, a processing liquid coating apparatus, an injection granulation apparatus, or the like.

Further, the control board 522 or the fluttering amount adjustment control unit 521 is an example of a transfer control device. The motors 401 and 402 are examples of transfer motors.

500: Printing system 524: Calculation unit 530: Web position sensor 540: Amount detection displacement sensor 550: Tension control unit 551: Tension value setting unit 552: Amount comparison unit 552: Amount holding unit 554: Solid printing judgment unit during adjustment

Japanese Unexamined Patent Publication No. 2016-28983

Claims (9)

A transport motor that transports an object in the transport direction,
A droplet ejection head that ejects a liquid toward the object,
A sensor capable of detecting a change in the droplet ejection direction of the object at a position where the liquid is ejected in the object, and a sensor.
It has a control means for controlling the tension of the object according to the amount of the fluctuation in the droplet ejection direction of the object detected by the sensor.
The control means controls the tension of the object according to the amount of the fluctuation in the droplet ejection direction of the object detected by the sensor while operating in the print density adjustment mode for adjusting the density of the droplet. A droplet ejection device characterized by The position where the liquid is discharged in the object is between two support members arranged on both sides of the droplet ejection head in the transport direction of the object, or the droplet ejection head is the object. The droplet ejection device according to claim 1, wherein the droplet ejection device is in a range that overlaps with the droplet ejection head when projected in parallel in the direction of. The control means is characterized in that when the amount of the fluctuation in the droplet ejection direction of the object exceeds the first threshold value, the transfer motor is controlled so that the tension of the object becomes large. The droplet ejection device according to 1 or 2. The control means is characterized in that when the amount of the fluctuation in the droplet ejection direction of the object is less than the second threshold value, the transfer motor is controlled so that the tension of the object becomes small. 3. The droplet ejection device according to 3. The control means is operating in the print density adjustment mode, and further, when the droplet ejection head performs solid printing to eject a liquid at a predetermined density or higher in a predetermined range or higher, the sensor performs solid printing. The droplet ejection device according to claim 1 , wherein the tension of the object is controlled according to the amount of the change in the droplet ejection direction of the object. When the print density adjustment mode is terminated, but the amount of the fluctuation in the droplet ejection direction of the object detected by the sensor exceeds the first threshold value or falls below the second threshold value. The droplet ejection device according to claim 4, wherein the control means outputs that the tension adjustment has not been completed. A transport control device that controls a transport motor that transports an object in the transport direction.
Information on the fluctuation is acquired from a sensor capable of detecting a fluctuation in the droplet ejection direction at the position of the object to which the liquid droplet ejection head ejects the liquid.
It has a control means for controlling the tension of the object by controlling the transfer motor according to the amount of the fluctuation of the position of the object.
The control means controls the tension of the object according to the amount of the fluctuation in the droplet ejection direction of the object detected by the sensor while operating in the print density adjustment mode for adjusting the density of the droplet. A transport control device characterized by It is a transport control method of a transport control device that controls a transport motor that transports an object in the transport direction.
A step in which the sensor detects a change in the droplet ejection direction at the position of the object to which the droplet ejection head ejects the liquid, and
The control means has a step of acquiring information about the fluctuation from the sensor and controlling the tension of the object by controlling the transfer motor according to the amount of the fluctuation of the position of the object. death,
The control means controls the tension of the object according to the amount of the fluctuation in the droplet ejection direction of the object detected by the sensor while operating in the print density adjustment mode for adjusting the density of the droplet. A transport control method characterized by performing. A transport control device that controls a transport motor that transports an object in the transport direction.
Information on the fluctuation is acquired from a sensor capable of detecting the fluctuation of the droplet ejection direction of the object at the position where the droplet ejection head ejects the liquid.
It functions as a control means for controlling the tension of the object by controlling the transfer motor according to the amount of the fluctuation of the position of the object.
The control means controls the tension of the object according to the amount of the fluctuation in the droplet ejection direction of the object detected by the sensor while operating in the print density adjustment mode for adjusting the density of the droplet. A transport control program characterized by

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