JP6993264B2 - Printing equipment - Google Patents

Description

The present invention relates to a printing device that prints on the web.

There is known a printing device that prints an image by ejecting ink from an inkjet head to the web while transporting a long web as a printing medium.

Further, as such a printing device, a printing unit for the front surface of the web and a printing unit for the back surface arranged on the downstream side of the printing unit for the front surface in the transport direction of the web are provided, and printing can be performed on both sides of the web. (See Patent Document 1).

Further, as a printing device capable of double-sided printing as described above, there is one in which a printing unit for the front surface and a printing unit for the back surface have a plurality of inkjet heads that eject inks of different colors from each other. Here, a plurality of inkjet heads in each printing unit are arranged in parallel in the transport direction of the web.

In such a printing apparatus, the ink ejection timing in each inkjet head is controlled based on the output pulse signal of the encoder connected to the roller that rotates synchronously with the conveyed web.

Japanese Patent Application Laid-Open No. 2003-63072

In the ejection timing control as described above, the farther the inkjet head is from the encoder, the lower the accuracy of the ink landing position due to the influence of expansion and contraction of the web. For this reason, for example, when the encoder is arranged near the upstream side of the printing portion for the front surface, the ink landing position shifts between the inkjet heads due to a decrease in the landing accuracy of the ink in the printing portion for the back surface far from the encoder. May occur. That is, color shift may occur in the printed image on the back surface, and the print image quality may deteriorate.

On the other hand, if encoders are installed on the rollers near each of the front side printing part and the back side printing part, and the ink ejection timing in each printing part is controlled by using those encoders, the above-mentioned It is possible to suppress color shift on the back surface.

When two encoders for the front surface and the back surface are provided in this way, usually, the two rollers provided with the encoders have the same diameter. However, the outer peripheral lengths of the two rollers may differ from each other due to mechanical tolerances.

Therefore, the amount of web transport according to the number of output pulses of the encoder corresponding to each of the position of the printed portion for the front surface and the position of the printed portion for the back surface may differ from each other. This causes a difference in the print length of the image between the front and back surfaces of the web, which may cause a gradual misalignment of the printed image between the front and back surfaces of the web as printing progresses.

The present invention has been made in view of the above, and an object of the present invention is to provide a printing apparatus capable of reducing misalignment of a printed image between the front surface and the back surface of a web while suppressing deterioration of print image quality.

In order to achieve the above object, the printing apparatus of the present invention has a plurality of printing mechanisms arranged in parallel in the conveying direction of the web, and prints an image on the first surface of the conveyed web by each of the printing mechanisms. A first printing unit for printing, a second printing unit having a plurality of printing mechanisms arranged in parallel in the transport direction, and printing an image on the second surface of the web to be transported by each of the printing mechanisms, and a transport unit. A first roller and a second roller that rotate in synchronization with the web, a first encoder that outputs a pulse signal according to the rotation angle of the first roller, and a pulse signal according to the rotation angle of the second roller. The printing timing in each printing mechanism of the first printing unit is controlled based on the output pulse signal of the first encoder and the second encoder that outputs The control unit includes a control unit that controls the printing timing in each of the printing mechanisms, and the control unit uses the difference information indicating the difference in the outer peripheral length between the first roller and the second roller to indicate the difference in the outer peripheral length between the first roller and the second roller. It is characterized in that the print length in at least one of the first and second print portions is adjusted so that the difference between the print length of the first side and the print length of the second side is reduced.

According to the printing apparatus of the present invention, it is possible to reduce the misalignment of the printed image between the front surface and the back surface of the web while suppressing the deterioration of the print image quality.

It is a schematic block diagram of the printing system provided with the printing apparatus which concerns on 1st Embodiment. It is a control block diagram of the printing system shown in FIG. It is explanatory drawing of the position shift of the printed image between the front surface and the back surface of a web. It is a flowchart for demonstrating the adjustment table generation operation in 1st Embodiment. It is explanatory drawing of the method of setting the adjustment flag in the adjustment table generation operation. It is a figure which shows an example of the adjustment table. It is explanatory drawing of the adjustment method of a print length. It is a flowchart of the process which adjusts a print length in 2nd Embodiment. It is explanatory drawing of the method of counting the output pulse number of the encoder in the process of adjusting the print length of 2nd Embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same or equivalent parts and components are designated by the same or equivalent reference numerals throughout the drawings.

The embodiments shown below exemplify an apparatus or the like for embodying the technical idea of the present invention, and the technical idea of the present invention includes the material, shape, structure, arrangement, etc. of each component. Is not specified as the following. The technical idea of the present invention can be modified in various ways within the scope of claims.

[First Embodiment]
FIG. 1 is a schematic configuration diagram of a printing system including the printing apparatus according to the first embodiment of the present invention. FIG. 2 is a control block diagram of the printing system shown in FIG. In the following description, the direction orthogonal to the paper surface of FIG. 1 is defined as the front-back direction. Further, the vertical and horizontal directions of the paper surface in FIG. 1 are defined as the vertical and horizontal directions.

As shown in FIGS. 1 and 2, the printing system 1 according to the first embodiment includes an unwinding device 2, a printing device 3, and a winding device 4.

The unwinding device 2 unwinds the web W, which is a long printing medium made of a film, paper, or the like, to the printing device 3. The unwinding device 2 includes a web roll support shaft 11, a brake 12, and an unwinding device control unit 13.

The web roll support shaft 11 rotatably supports the web roll 16. The web roll 16 is a roll of the web W.

The brake 12 brakes the web roll support shaft 11. As a result, tension is applied to the web W between the web roll 16 and the transport roller 43 of the printing apparatus 3 described later.

The unwinding device control unit 13 controls the brake 12. The unwinding device control unit 13 includes a CPU, a memory, a hard disk, and the like.

The printing device 3 prints an image on the web W while transporting the web W unwound from the web roll 16. The printing device 3 includes a transport unit 21, encoders 22A and 22B (corresponding to the first or second encoder, respectively), printing units 23A and 23B (corresponding to the first or second printing unit, respectively), and an operation panel 24. , A printing device control unit (corresponding to a control unit) 25. In addition, the subscripts of the alphabet in the codes of the encoders 22A, 22B and the like may be omitted and described collectively.

The transport unit 21 transports the web W unwound from the web roll 16 toward the take-up device 4. The transport unit 21 includes guide rollers 31 to 40, 20 under-head rollers 41, a meandering control unit 42, a pair of transport rollers 43, and a transport motor 44.

The guide rollers 31 to 40 guide the web W conveyed in the printing apparatus 3. The guide rollers 31 to 40 rotate in a driven manner according to the conveyed web W. The guide rollers 31 to 40, the under-head roller 41, the transport roller 43, and the meandering control rollers 46 and 47 of the meandering control unit 42 described later form a transport path for the web W in the transport unit 21.

The guide rollers 31 and 32 guide the web W between the unwinding device 2 and the meandering control unit 42. The guide roller 31 is arranged at the left end of the lower part of the printing apparatus 3. The guide roller 32 is arranged between the guide roller 31 and the meandering control roller 46 of the meandering control unit 42 described later.

The guide rollers 33 to 39 guide the web W between the meandering control unit 42 and the transport roller 43. The guide roller 33 is arranged slightly above the left side of the meandering control roller 47 of the meandering control unit 42, which will be described later. The guide roller 34 is arranged above the guide roller 33. The guide roller 35 is arranged at substantially the same height as the guide roller 34 and to the right of the guide roller 34. The guide roller 36 is located below the guide roller 35 and higher than the guide roller 33. The guide roller 37 is located on the left side of the guide roller 36, near the right side of the web W between the guide rollers 33 and 34, and at a position substantially the same as the guide roller 36. The guide roller 38 is arranged on the lower right side of the guide roller 37. The guide roller 39 is arranged slightly below the right side of the guide roller 38.

The guide roller 40 guides the web W between the transport roller 43 and the take-up device 4. The guide roller 40 is arranged at the lower right end of the printing apparatus 3.

The lower head roller 41 supports the web W under the head unit 51, which will be described later, between the guide rollers 34 and 35 and between the guide rollers 36 and 37. Ten under-head rollers 41 are arranged between the guide rollers 34 and 35 and between the guide rollers 36 and 37, respectively. Two rollers 41 under the head are arranged directly under each head unit 51. The roller 41 under the head rotates drivenly according to the conveyed web W.

The meandering control unit 42 corrects meandering, which is a change in position in the width direction (front-back direction) orthogonal to the transport direction of the web W. The meandering control unit 42 includes meandering control rollers 46 and 47 and a meandering control motor 48.

The meandering control rollers 46 and 47 are rollers for guiding the web W and correcting the meandering of the web W. The meandering control rollers 46 and 47 drive the web W to be conveyed and rotate. The meandering control rollers 46 and 47 rotate so as to be tilted with respect to the width direction of the web W when viewed from the left-right direction, thereby moving the web W in the width direction to correct the meandering. The meandering control roller 46 is arranged to the right of the guide roller 32. The meandering control roller 47 is arranged above the meandering control roller 46.

The meandering control motor 48 rotates the meandering control rollers 46 and 47 around a rotation axis parallel to the left-right direction.

The pair of transfer rollers 43 convey the web W toward the take-up device 4 while niping the web W. The pair of transport rollers 43 are arranged between the guide rollers 39 and 40.

The transfer motor 44 rotates and drives the transfer roller 43.

The encoder 22A is installed on the guide roller 34 (corresponding to the first or second roller), and outputs a pulse signal according to the rotation angle of the guide roller 34 that is driven (synchronically rotated) by the web W to be conveyed. .. The encoder 22B is installed on the guide roller 36 (corresponding to the first or second roller) and outputs a pulse signal according to the rotation angle of the guide roller 36 that is driven (synchronically rotated) by the web W to be conveyed. ..

The printing unit 23A prints an image on the surface (corresponding to the first or second surface) of the web W. The printing unit 23A is arranged near the upper side of the web W between the guide rollers 34 and 35. The printing unit 23A includes head units 51K, 51C, 51M, 51Y, 51P.

Each of the head units 51K, 51C, 51M, 51Y, and 51P has an inkjet head (corresponding to a printing mechanism) 56K, 56C, 56M, 56Y, 56P, respectively. The head units 51K, 51C, 51M, 51Y, and 51P are arranged in parallel in the sub-scanning direction (left-right direction), which is the transport direction of the web W. Therefore, the inkjet heads 56K, 56C, 56M, 56Y, and 56P are also arranged in parallel in the sub-scanning direction.

The inkjet heads 56K, 56C, 56M, 56Y, and 56P eject black (K), cyan (C), magenta (M), yellow (Y), and preliminary ink colors to the web W to print an image, respectively. .. As the preliminary ink color, red, light cyan, or the like is used.

The inkjet head 56 has a plurality of nozzles (not shown) that are open to the ink ejection surface facing the web W and are arranged along the main scanning direction (front-back direction), and eject ink from the nozzles.

The printing unit 23B prints an image on the back surface (corresponding to the first or second surface) of the web W. The printing unit 23B is arranged near the upper side of the web W between the guide rollers 36 and 37. That is, the printing unit 23B is arranged on the downstream side of the printing unit 23A in the transport direction of the web W. The printing unit 23B includes head units 51K, 51C, 51M, 51Y, and 51P, similarly to the printing unit 23A.

The printing unit 23B has a configuration in which the printing unit 23A is horizontally inverted. The printing unit 23B has the same configuration as the printing unit 23A except that it is flipped horizontally.

The operation panel 24 displays various input screens and the like, and accepts input operations by the user. The operation panel 24 includes a display unit (not shown) having a liquid crystal display panel or the like, and an input unit (not shown) having various operation keys, a touch panel, or the like.

The printing device control unit 25 controls the operation of each unit of the printing device 3. The printing device control unit 25 includes a CPU, a memory, a hard disk, an FPGA (Field Programmable Gate Array), and the like.

When printing, the printing device control unit 25 drives the inkjet heads 56 of the printing units 23A and 23B to print the image on the web W while driving the transport roller 43 to transport the web W.

At this time, the printing device control unit 25 controls the ink ejection timing (printing timing) in each inkjet head 56 of the printing unit 23A based on the output pulse signal of the encoder 22A. Further, the printing device control unit 25 controls the ink ejection timing in each inkjet head 56 of the printing unit 23B based on the output pulse signal of the encoder 22B.

Further, the printing device control unit 25 uses the difference information indicating the difference in the outer peripheral length between the guide roller 34 in which the encoder 22A is installed and the guide roller 36 in which the encoder 22B is installed, and uses the difference information indicating the difference in the outer peripheral length of the surface of the surface of the web W in the transport direction. The print length in at least one of the print units 23A and 23B is adjusted so that the difference between the print length and the print length on the back side is reduced. Here, the print length is the length of the print area of the image in the transport direction of the web W.

Specifically, the printing device control unit 25 is a difference value of the number of output pulses of the encoders 22A and 22B per page as the difference information indicating the difference in the outer peripheral lengths of the guide rollers 34 and 36, which will be described later. The pulse difference Db per per is used. The printing device control unit 25 generates an adjustment table 71, which will be described later, using the pulse difference Db per page. At the time of printing, the printing apparatus control unit 25 adjusts the print length in at least one of the printing units 23A and 23B on a page-by-page basis with reference to the adjustment table 71.

The take-up device 4 winds up the web W printed by the printing device 3. The take-up device 4 includes a take-up shaft 61, a take-up motor 62, and a take-up device control unit 63.

The take-up shaft 61 winds up and holds the web W.

The take-up motor 62 rotates the take-up shaft 61 in the clockwise direction in FIG. By the rotation of the take-up shaft 61, the web W is taken up by the take-up shaft 61.

The take-up device control unit 63 controls the drive of the take-up motor 62. The take-up device control unit 63 includes a CPU, a memory, a hard disk, and the like.

Next, the adjustment table generation operation in the printing system 1 will be described.

The adjustment table generation operation is an operation of generating an adjustment table 71 used for adjusting the print length for the web W.

The print length adjustment using the adjustment table 71 is to suppress the misalignment of the printed image between the front surface and the back surface of the web W due to the difference in the outer peripheral length due to the mechanical tolerance of the guide rollers 34 and 36. It is what is done.

Here, the guide rollers 34 and 36 are rollers having the same diameter. However, due to mechanical tolerances, the guide rollers 34 and 36 have a difference in outer peripheral length. If there is a difference in the outer peripheral lengths of the guide rollers 34 and 36, there will be a difference in the amount of web W conveyed according to the number of output pulses of the encoders 22A and 22B corresponding to each. As a result, between the front surface of the web W printed by the printing unit 23A based on the output pulse signal of the encoder 22A and the back surface of the web W printed by the printing unit 23B based on the output pulse signal of the encoder 22B. There is a difference in the print length of the image. Then, as printing progresses, the position of the printed image gradually shifts between the front surface and the back surface of the web W.

For example, when the outer peripheral La of the guide roller 34 is larger than the outer peripheral Lb of the guide roller 36, the printed length of the front surface is longer than that of the back surface as shown in FIG. The page shifts to the upstream side.

The adjustment table 71 is used to adjust the print length in order to suppress the positional deviation of the printed image between the front surface and the back surface of the web W.

The adjustment table generation operation is performed when the printing apparatus 3 is completed, when the guide rollers 34 and 36 are replaced, and the like. FIG. 4 is a flowchart for explaining the adjustment table generation operation.

In step S1 of FIG. 4, the printing device control unit 25 starts the transmission of the web W. Specifically, the printing device control unit 25 starts the drive of the transfer roller 43 by the transfer motor 44, and instructs the unwinding device control unit 13 and the winding device control unit 63 to start the transfer of the web W. When the web W is instructed to start transporting, the unwinding device control unit 13 causes the brake 12 to start outputting the braking force, and the winding device control unit 63 causes the winding motor 62 to start driving the winding shaft 61. ..

As a result, unwinding and transport of the web W from the web roll 16 are started. By applying the brake to the web roll support shaft 11 by the brake 12, the web W is conveyed while tension is applied to the web W between the web roll 16 and the transfer roller 43. When the transmission of the web W is started, the output of the pulse signal from the encoders 22A and 22B is started in response to the start of rotation of the guide rollers 34 and 36.

After the start of transporting the web W, in step S2, the printing device control unit 25 determines whether or not the transport speed of the web W has reached the specified transport speed.

Here, the printing device control unit 25 performs the transfer control to shift to the constant speed transfer at the specified transfer speed when the transfer speed of the web W is accelerated to the specified transfer speed after the transfer of the web W is started. The specified transport speed is set to, for example, the same speed as the transport speed of the web W (print transport speed) at the time of printing.

When it is determined that the transport speed of the web W has not reached the specified transport speed (step S2: NO), the printing device control unit 25 repeats step S2. When it is determined that the transport speed of the web W has reached the specified transport speed (step S2: YES), in step S3, the printing device control unit 25 starts counting the number of output pulses of the encoders 22A and 22B.

Next, in step S4, the printing device control unit 25 determines whether or not the transport distance of the web W from the start of counting the number of output pulses of the encoders 22A and 22B has reached the specified transport distance Lm. Here, since the web W is transported at a constant speed at a specified transport speed, the printing device control unit 25 defines the transport distance of the web W by the elapsed time from the start of counting the output pulses of the encoders 22A and 22B. It can be determined whether or not the transport distance Lm has been reached.

The specified transport distance Lm is set in advance as the transport distance of the web W for measuring the difference in the number of output pulses of the encoders 22A and 22B due to the difference in the outer peripheral lengths of the guide rollers 34 and 36. The specified transport distance Lm is set to a relatively long distance, for example, for 20 laps of the guide rollers 34 and 36, in order to suppress the influence of an error in the number of output pulses of the encoders 22A and 22B on the measurement result.

When it is determined that the transport distance of the web W from the start of counting the output pulses of the encoders 22A and 22B has not reached the specified transport distance Lm (step S4: NO), the printing device control unit 25 performs step S4. repeat.

When it is determined that the transport distance of the web W from the start of counting the output pulses of the encoders 22A and 22B has reached the specified transport distance Lm (step S4: YES), in step S5, the printing device control unit 25 uses the encoder. The counting of the number of output pulses of 22A and 22B is completed. As a result, the count value Ca of the number of output pulses of the encoder 22A and the count value Cb of the number of output pulses of the encoder 22B while the web W is transported by the specified transport distance Lm can be obtained.

Next, in step S6, the printing device control unit 25 ends the transfer of the web W. Specifically, the printing device control unit 25 stops the transfer motor 44 and instructs the unwinding device control unit 13 and the winding device control unit 63 to end the transfer of the web W. When the end of transporting the web W is instructed, the unwinding device control unit 13 stops the brake 12, and the winding device control unit 63 stops the winding motor 62.

Next, in step S7, the printing device control unit 25 calculates the pulse difference Dm. The pulse difference Dm is the difference in the number of output pulses of the encoders 22A and 22B with respect to the specified transport distance Lm, and is calculated by the following equation (1).

Dm = | Ca-Cb | ... (1)
Next, in step S8, the printing device control unit 25 determines whether or not the pulse difference Dm is less than the threshold value Dth. Here, the threshold value Dth is such that the pulse difference Dm, which is a value corresponding to the difference in the outer peripheral lengths of the guide rollers 34 and 36, can adjust the print length while suppressing the influence on the printed image. It is set as a value for determining whether or not.

When it is determined that the pulse difference Dm is less than the threshold value Dth (step S8: YES), the printing device control unit 25 calculates the pulse difference Db per page in step S9. Assuming that the length of one page in the transport direction of the web W is Ln, the pulse difference Db per page is calculated by the following equation (2).

Db = (Ln / Lm) × Dm ... (2)
Here, the printing device control unit 25 calculates the pulse difference Db per page for the length Ln of one page of each of the plurality of page sizes that can be printed by the printing device 3.

Next, in step S10, the printing device control unit 25 calculates the cumulative difference Dsum (n). The cumulative difference Dsum (n) is the cumulative value of the pulse difference Db per page from the first page on the nth page. The calculation of the cumulative difference Dsum (n) may be performed up to a predetermined page set as sufficient for extracting the periodic pattern of the adjustment flag described later. The cumulative difference Dsum (n) is calculated by the following equation (3).

Dsum (n) = Db × n ... (3)
Here, for example, in the case of Lm = 5000 mm, Ln = 420 mm, Ca = 21600, Ca = 21595, Dm = 5, Db = 0.42. In this case, the cumulative difference Dsum (n) is calculated as shown in FIG.

The printing device control unit 25 calculates the cumulative difference Dsum (n) from the calculated pulse difference Db per page for the length Ln of each page of the plurality of page sizes that can be printed by the printing device 3. ..

Next, in step S11, the printing device control unit 25 converts the cumulative difference Dsum (n) into an integer. Specifically, the printing device control unit 25 calculates INT (Dsum (n)). INT (Dsum (n)) indicates an integer part of the cumulative difference Dsum (n). INT (Dsum (n)) is calculated, for example, as shown in FIG.

The printing device control unit 25 converts the calculated cumulative difference Dsum (n) into an integer for each page length Ln of a plurality of page sizes that can be printed by the printing device 3.

Next, in step S12, the printing device control unit 25 generates the adjustment table 71 based on the value of INT (Dsum (n)).

Specifically, first, as shown in the example of FIG. 5, the printing apparatus control unit 25 sets the adjustment flag of the page where the value of INT (Dsum (n)) increases to "1", and adjusts the other pages. Set the flag to "0".

Then, the printing device control unit 25 generates and stores the adjustment table 71 in which the page and the adjustment flag are associated with each other, as shown in FIG. The adjustment flag "1" in the adjustment table 71 indicates that the page is a page for which the print length is adjusted.

Here, the printing device control unit 25 extracts the pattern for one cycle from the adjustment flag of each page and generates the adjustment table 71. In the example of FIG. 6, the adjustment table 71 holds the adjustment flag for one cycle consisting of 5 pages. Even if the adjustment flag does not form a strictly periodic pattern, a pattern for one cycle may be extracted within a range that can be regarded as a periodic pattern. The adjustment of the print length at the time of printing on the web W is performed by repeatedly using the adjustment flag for one cycle of the adjustment table 71.

The printing device control unit 25 generates an adjustment table 71 based on the value of INT (Dsum (n)) for each page length Ln of a plurality of page sizes that can be printed by the printing device 3. That is, the adjustment table 71 corresponding to each of the plurality of types of length Ln of one page is generated.

When the printing device control unit 25 generates and stores the adjustment table 71, the adjustment table generation operation ends.

When it is determined in step S8 that the pulse difference Dm is equal to or greater than the threshold value Dth (step S8: NO), in step S13, the printing device control unit 25 sends a warning message to the operation panel 24 to notify the user of the abnormality. Display. This ends the adjustment table generation operation.

Here, the fact that the pulse difference Dm is equal to or greater than the threshold value Dth indicates that the difference in the outer peripheral lengths of the guide rollers 34 and 36 is excessive. Therefore, the printing device control unit 25 displays a message or the like indicating that the guide rollers 34 and 36 are abnormal and needs to be replaced on the operation panel 24 as a warning.

When the guide rollers 34 and 36 are replaced according to the warning, the above-mentioned adjustment table generation operation is executed.

Next, the operation at the time of printing in the printing system 1 will be described.

When the print job is input, the printing device control unit 25 starts the transmission of the web W. After the start of transporting the web W, when the transport speed of the web W is accelerated to a predetermined print transport speed, the printing device control unit 25 shifts to constant speed transport at the print transport speed.

After the constant speed transfer of the web W at the print transfer speed is started, the printing apparatus control unit 25 starts printing on the surface of the web W by the printing unit 23A. After that, the printing device control unit 25 starts printing on the back surface of the web W by the printing unit 23B. Here, the printing device control unit 25 controls the printing start position on the back surface of the web W by the printing unit 23B to match the printing start position on the front surface by the printing unit 23A based on the output pulse signal of the encoder 22B. ..

After the start of printing, the printing device control unit 25 sets the landing position of each color of ink in the sub-scanning direction for each line of the image along the main scanning direction on the surface of the web W based on the output pulse signal of the encoder 22A. In addition, the ink ejection timing of each inkjet head 56 of the printing unit 23A is controlled. Further, the printing device control unit 25 sets the landing position of the ink of each color in the sub-scanning direction for each line of the image along the main scanning direction on the back surface of the web W based on the output pulse signal of the encoder 22B. The ink ejection timing of each inkjet head 56 of the printing unit 23B is controlled.

During printing, the printing device control unit 25 adjusts the print length in at least one of the printing units 23A and 23B on a page-by-page basis with reference to the adjustment table 71. At this time, the printing device control unit 25 refers to the adjustment table 71 corresponding to the length Ln of one page in the printing job being executed.

Specifically, the printing device control unit 25 adjusts the print length of the page in at least one of the printing units 23A and 23B on the page where the adjustment flag is "1" in the adjustment table 71.

The adjustment value for reducing the difference between the print length of the front surface and the print length of the back surface at the time of adjusting the print length is the number of lines per pulse of the output pulse signal of the encoder 22. When the adjustment flag is "1", it means that the number of lines per pulse of the output pulse signal of the encoder 22 is set as the adjustment value for the page. Further, when the adjustment flag is "0", it means that the adjustment value for the page is "0".

The number of lines per pulse of the output pulse signal of the encoder 22 is the number of lines according to the print resolution in the sub-scanning direction. For example, when the number of lines per pulse of the output pulse signal of the encoder 22 is "1", the adjustment value is "1". Further, when the number of lines per pulse of the output pulse signal of the encoder 22 is "2", the adjustment value is "2". Since the adjustment value is calculated according to the adjustment flag determined as described above, it is calculated using the cumulative difference Dsum (n) which is the cumulative value of the pulse difference Db per page for each page. It can be said that it is a thing.

The print length adjustment is realized by increasing or decreasing the number of lines for the page whose adjustment flag is "1" in at least one of the printing units 23A and 23B.

For example, the printing device control unit 25 sets one of the front surface and the back surface of the web W as a reference surface and the other surface as an adjustment surface, and in the printing unit 23 corresponding to the adjustment surface, the number of lines for the page whose adjustment flag is “1”. Is increased or decreased by the adjustment value.

In this case, the printing surface by the printing unit 23 corresponding to the encoder 22 having the larger count value of the number of output pulses corresponding to the specified transport distance Lm of the web W measured in the above-mentioned adjustment table generation operation is the reference surface. And. In this case, on the page where the adjustment flag is "1", the printing device control unit 25 adds a number of lines for the adjustment value to the page image of the adjustment surface as shown in FIG. 7A, and prints the print length. The printing unit 23 corresponding to the adjustment surface is controlled so as to extend by the adjustment value. The addition of the number of lines for the adjustment value is performed, for example, by copying the final line for the adjustment value.

Contrary to the above case, it is assumed that the printing surface by the printing unit 23 corresponding to the encoder 22 having the smaller count value of the number of output pulses corresponding to the specified transport distance Lm of the web W is the reference surface. In this case, on the page where the adjustment flag is "1", the printing device control unit 25 deletes the number of lines corresponding to the adjustment value in the page image of the adjustment surface as shown in FIG. 7B, and prints the print length. The printing unit 23 corresponding to the adjustment surface is controlled so as to reduce the size by the adjustment value. At this time, for example, the line corresponding to the adjustment value is deleted from the final line.

The reference plane may not be fixed, and the adjustment flag may be switched for each page of "1". Further, when the adjustment value is 2 or more, the print length of each page may be adjusted in both the printing units 23A and 23B without setting the reference plane so that the print lengths are made uniform.

When the printing based on the print job is completed, the printing device control unit 25 ends the transfer of the web W. This ends a series of operations.

As described above, in the printing device 3, the printing device control unit 25 controls the ink ejection timing in the printing units 23A and 23B based on the output pulse signals of the encoders 22A and 22B, respectively. As a result, the deviation of the ink landing position between the inkjet heads 56 in both the printing units 23A and 23B can be suppressed. As a result, deterioration of print quality can be suppressed.

Further, the printing device control unit 25 uses the difference information indicating the difference in the outer peripheral lengths of the guide rollers 34 and 36 so that the difference between the printing length on the front surface and the printing length on the back surface of the web W is reduced. The print length in at least one of 23A and 23B is adjusted. As a result, the difference in the print length of the image between the front surface and the back surface of the web W, which is caused by the difference in the outer peripheral lengths of the guide rollers 34 and 36, can be suppressed. As a result, the positional deviation of the printed image between the front surface and the back surface of the web W can be reduced.

Therefore, according to the printing apparatus 3, it is possible to reduce the positional deviation of the printed image between the front surface and the back surface of the web W while suppressing the deterioration of the print image quality.

Further, in the first embodiment, the printing apparatus control unit 25 uses the pulse difference Db per page as the difference information. Specifically, the printing device control unit 25 generates the adjustment table 71 using the cumulative difference Dsum (n), which is the cumulative value of the pulse difference Db per page. Then, the printing device control unit 25 adjusts the printing length in at least one of the printing units 23A and 23B in page units based on the adjustment value of the printing length in page units according to the adjustment flag of the adjustment table 71. ..

In this way, by using the pulse difference Db per page due to the difference in the outer peripheral lengths of the guide rollers 34 and 36 as the difference information, the difference in the print length of the image between the front surface and the back surface of the web W is used. It is possible to realize the adjustment of the print length to suppress the problem with high accuracy.

[Second Embodiment]
Next, a second embodiment in which a part of the first embodiment described above is modified will be described.

In the second embodiment, the printing device control unit 25 uses the printing device control unit 25 as a specified value which is the number of output pulses per page of the number of output pulses in the encoders 22A and 22B as the difference information indicating the difference in the outer peripheral lengths of the guide rollers 34 and 36. The difference time ΔT (n), which is the difference value of the time until reaching K, is used. The printing device control unit 25 calculates the difference time ΔT (n) for each page, and uses the calculated difference time ΔT (n) to reduce the difference between the print length of the front surface and the print length of the back surface. The print length adjustment value X (n) for the next page is calculated. Then, the printing device control unit 25 adjusts the print length of the next page in any of the printing units 23A and 23B based on the calculated adjustment value X (n).

Next, the process of adjusting the print length in the second embodiment will be described with reference to the flowchart of FIG.

Here, in the process of adjusting the print length, the printing device control unit 25 sets one of the front and back surfaces of the web W as a reference surface and the other as an adjustment surface, and adjusts the print length of the adjustment surface. Here, it is assumed that the surface is a reference plane.

The processing of the flowchart of FIG. 8 is started when a print job is input to the printing device 3. In step S21 of FIG. 8, the printing device control unit 25 determines whether or not it is time to start printing on the surface of the web W. Here, printing on the surface of the web W is started after the transport of the web W is started and the transport speed of the web W reaches the print transport speed. When it is determined that the printing start timing of the front surface has not been reached (step S21: NO), the printing device control unit 25 repeats step S21.

When it is determined that the printing start timing of the front surface has come (step S21: YES), in step S22, the printing apparatus control unit 25 starts counting the number of output pulses of the encoders 22A and 22B for adjusting the printing length.

That is, as shown in FIG. 9, the printing device control unit 25 starts counting the number of output pulses of the encoders 22A and 22B for adjusting the printing length from the timing when the surface printing signal is turned on.

Here, the front side printing signal and the back side printing signal in FIG. 9 are signals supplied to the FPGA that controls the ink ejection of the inkjet head 56 in the printing device control unit 25. When the surface printing signal is turned on, printing on the surface of the web W by the printing unit 23A starts. Further, when the back side printing signal is turned on, printing on the back side of the web W by the printing unit 23B starts. The back side printing signal is turned on at the timing when the printing start position on the back surface of the web W by the printing unit 23B coincides with the printing start position on the front surface by the printing unit 23A.

After the start of printing, the printing device control unit 25 uses the output pulse signal of the encoder 22A to match the landing positions of the inks of each color in the sub-scanning direction for each line of the image along the main scanning direction on the surface of the web W. As described above, the ink ejection timing of each inkjet head 56 of the printing unit 23A is controlled. Further, the printing device control unit 25 sets the landing position of the ink of each color in the sub-scanning direction for each line of the image along the main scanning direction on the back surface of the web W based on the output pulse signal of the encoder 22B. The ink ejection timing of each inkjet head 56 of the printing unit 23B is controlled.

Returning to FIG. 8, in step S23, the printing apparatus control unit 25 reaches the specified value K at least one of the count values Cta and Ctb of the respective output pulses of the encoders 22A and 22B that started counting in step S22. Determine if you did. When it is determined that neither of the count values Cta and Ctb has reached the specified value K (step S23: NO), the printing device control unit 25 repeats step S23.

When it is determined that at least one of the count values Cta and Ctb has reached the specified value K (step S23: YES), in step S24, the printing apparatus control unit 25 determines whether the count value Cta has reached the specified value K. Judge whether or not.

When it is determined that the count value Cta has reached the specified value K (step S24: YES), in step S25, the printing device control unit 25 resets the count value Cta.

Next, in step S26, the printing device control unit 25 determines whether or not the count value Ctb has reached the specified value K. When it is determined that the count value Ctb has not reached the specified value K (step S26: NO), the printing device control unit 25 repeats step S26.

When it is determined that the count value Ctb has reached the specified value K (step S26: YES), in step S27, the printing device control unit 25 resets the count value Ctb. After that, the process proceeds to step S31.

In step S24, when it is determined that the count value Cta has not reached the specified value K, that is, the count value Ctb has reached the specified value K (step S24: NO), in step S28, the printing device control unit. 25 resets the count value Ctb.

Next, in step S29, the printing device control unit 25 determines whether or not the count value Cta has reached the specified value K. When it is determined that the count value Cta has not reached the specified value K (step S29: NO), the printing device control unit 25 repeats step S29.

When it is determined that the count value Cta has reached the specified value K (step S29: YES), in step S30, the printing device control unit 25 resets the count value Cta. After that, the process proceeds to step S31.

By the processing of steps S23 to S30 described above, the count values Cta and Ctb are reset when they reach the specified values K, respectively. When the count values Cta and Ctb are reset, counting from 0 is started respectively.

In step S31, the printing device control unit 25 determines whether or not there is a next page to be printed in the print job. Here, the next page is the next page ((n + 1)) of the page on the surface of the Web W (nth page) corresponding to the counting period (nth counting period) until the count value Cta becomes K this time. ) Page).

When it is determined that there is a next page (step S31: YES), in step S32, the printing device control unit 25 calculates the difference time ΔT (n). The difference time ΔT (n) is calculated by the following equation (4).

ΔT (n) = At (n) -Bt (n) ... (4)
Here, At (n) is the time from 0 to K in the count value Cta in the nth count period of the number of output pulses of the encoder 22A. Further, Bt (n) is the time from 0 to K in the count value Ctb in the nth count period of the number of output pulses of the encoder 22B. At (n) and Bt (n) are measured by the internal clock of the FPGA included in the printing device control unit 25.

By the way, in the printing apparatus 3, since the printing units 23A and 23B are separated from each other in the sub-scanning direction, the timing of printing the corresponding pages differs between the front surface and the back surface. On the other hand, in counting the output pulses of the encoders 22A and 22B for adjusting the print length, it is sufficient that the difference time ΔT (n) can be measured, so that the counts of the output pulses of the encoders 22A and 22B corresponding to each page are performed at the same time. It is done in parallel.

Next, in step S33, the printing device control unit 25 determines whether or not the difference time ΔT (n) is less than the threshold value ΔTth. Here, the threshold value ΔTth is large enough that the difference time ΔT (n), which is a value corresponding to the difference in the outer peripheral lengths of the guide rollers 34 and 36, can adjust the print length while suppressing the influence on the printed image. It is set as a value for determining whether or not it is.

When it is determined that the difference time ΔT (n) is less than the threshold value ΔTth (step S33: YES), the printing apparatus control unit 25 calculates the line deviation amount G (n) in step S34. The line deviation amount G (n) indicates the difference between the print length of the front surface and the print length of the back surface per page in terms of the number of lines. The line deviation amount G (n) is calculated by the following equation (5).

G (n) = (ΔT (n) / Tl) + Y (n-1) ... (5)
Here, Tl is a line period. The line period Tl is the printing period of the line along the main scanning direction. The line period Tl is determined according to the print resolution in the sub-scanning direction and the print transfer speed. T (n) / Tl in the formula (5) corresponds to the number of lines printed with the difference time ΔT (n).

Y (n-1) is a fractional part of the line deviation amount G (n-1) corresponding to the previous ((n-1) th time) count period.

Next, in step S35, the printing device control unit 25 calculates the adjustment value X (n). The adjustment value X (n) is an integer part of the line deviation amount G (n) and is represented by the following equation (6).

X (n) = INT (G (n)) ... (6)
Here, the fractional part of the line deviation amount G (n) is represented by the following equation (7).

Y (n) = G (n) -INT (G (n)) ... (7)
The fractional part Y (n) of the line deviation amount G (n) is included in the line deviation amount G (n + 1) used for the calculation of the next adjustment value X (n + 1). Therefore, as shown in the above equation (5), the line deviation amount G (n) is T (n) / Tl, and the fractional part Y (n-1) of the previous line deviation amount G (n-1) is set to T (n) / Tl. ) Is added.

In this way, the fractional part Y (n) of the line deviation amount G (n) is carried over to the calculation of the next adjustment value X (n + 1), so that the line deviation amount G (n) and the adjustment value X (n) are obtained. Accumulation of errors between is prevented.

Next, in step S36, the printing device control unit 25 corrects the image data on the next page ((n + 1) page) of the adjustment surface based on the adjustment value X (n). Here, since the back surface is the adjustment surface as described above, the printing device control unit 25 corrects the image data on the next page of the back surface.

Specifically, the printing device control unit 25 adjusts the number of lines in the image data on the next page on the back surface based on the adjustment value X (n). When the adjustment value X (n) is a positive value, the printing device control unit 25 adds a line with the number of adjustment values X (n) to the image data on the next page on the back surface. Lines are added, for example, by copying the final line. When the adjustment value X (n) is a negative value, the printing device control unit 25 deletes the number of lines of the adjustment value X (n) from the image data on the next page on the back surface. For example, the printing apparatus control unit 25 deletes the number of lines having the adjustment value X (n) from the final line.

By printing based on the image data corrected as described above, the print length of the adjustment surface is adjusted as shown in FIGS. 7A and 7B.

After step S36, the printing device control unit 25 returns to step S23 and repeats the subsequent processing.

If it is determined in step S31 that there is no next page (step S31: NO), the printing device control unit 25 ends a series of processes.

When it is determined in step S33 that the difference time ΔT (n) is equal to or greater than the threshold value ΔTth (step S33: NO), in step S37, the printing device control unit 25 operates a warning message for notifying the user of the abnormality. It is displayed on the panel 24. Further, the printing device control unit 25 ends printing by the printing unit 23 and the transfer of the web W. As a result, a series of processes is completed.

Here, the fact that the difference time ΔT (n) is equal to or greater than the threshold value ΔTth indicates that the difference in the outer peripheral lengths of the guide rollers 34 and 36 is excessive. Therefore, the printing device control unit 25 displays a message or the like indicating that the guide rollers 34 and 36 are abnormal and needs to be replaced on the operation panel 24 as a warning.

Also in the second embodiment as described above, similarly to the first embodiment, it is possible to reduce the positional deviation of the printed image between the front surface and the back surface of the web W while suppressing the deterioration of the print image quality.

Further, in the second embodiment, the printing device control unit 25 uses the difference time ΔT (n), which is the difference value of the time until the specified value K is reached, of the number of output pulses in the encoders 22A and 22B as the difference information. Use. The printing device control unit 25 calculates the difference time ΔT (n) for each page, and uses the calculated difference time ΔT (n) to reduce the difference between the print length of the front surface and the print length of the back surface. The print length adjustment value X (n) for the next page ((n + 1) th page) is calculated. Then, the printing device control unit 25 adjusts the print length of the next page in any of the printing units 23A and 23B based on the calculated adjustment value X (n).

In this way, by using the difference time ΔT (n) caused by the difference in the outer peripheral lengths of the guide rollers 34 and 36 as the difference information, the difference in the print length of the image between the front surface and the back surface of the web W can be obtained. It is possible to adjust the print length to suppress it with high accuracy.

Further, the printing device control unit 25 calculates the line deviation amount G (n) using the difference time ΔT (n) and the line period Tl, and adjusts the integer part of the line deviation amount G (n) to the adjustment value X (n). Calculated as. Then, the printing apparatus control unit 25 includes the fractional part Y (n) of the line deviation amount G (n) in the line deviation amount G (n + 1) used for the calculation of the next adjustment value X (n + 1). This prevents the error between the line deviation amount G (n) and the adjustment value X (n) from accumulating, so that the difference in the print length of the image between the front surface and the back surface of the web W is prevented. Can be further suppressed.

[Other embodiments]
As mentioned above, the invention has been described by the first and second embodiments, but the statements and drawings that form part of this disclosure should not be understood as limiting the invention. This disclosure will reveal to those skilled in the art various alternative embodiments, examples and operational techniques.

In the first and second embodiments described above, the printing apparatus provided with the inkjet head as the printing mechanism has been described, but the printing mechanism may be another type such as an electrophotographic method.

Further, in the first and second embodiments described above, the unwinding device and the winding device are connected to the printing device as separate devices, but the unwinding unit and the winding unit are incorporated in the printing device. It may be configured.

Further, in the above description of the second embodiment, one of the front surface and the back surface of the web W is set as a reference surface and the other surface is set as an adjustment surface, and the print length of the page of the adjustment surface by either the printing unit 23A or 23B is set. It was decided to adjust. However, both the printing units 23A and 23B may adjust the printing length of each page to make the printing lengths uniform.

As described above, it goes without saying that the present invention includes various embodiments not described here. Therefore, the technical scope of the present invention is defined only by the matters specifying the invention relating to the reasonable claims from the above description.

[Additional Notes]
This application discloses the following inventions.

(Appendix 1)
A first printing unit that has a plurality of printing mechanisms arranged in parallel in the transport direction of the web and prints an image on the first surface of the transported web by each of the printing mechanisms.
A second printing unit having a plurality of printing mechanisms arranged in parallel in the transport direction and printing an image on the second surface of the transported web by each of the printing mechanisms.
A first roller and a second roller that rotate synchronously with the transported web,
A first encoder that outputs a pulse signal according to the rotation angle of the first roller, and
A second encoder that outputs a pulse signal according to the rotation angle of the second roller, and
The printing timing of each printing mechanism of the first printing unit is controlled based on the output pulse signal of the first encoder, and the printing timing of each printing mechanism of the second printing unit is controlled based on the output pulse signal of the second encoder. Equipped with a control unit to control
The control unit uses the difference information indicating the difference in the outer peripheral length between the first roller and the second roller, and uses the difference information between the print length of the first surface and the print length of the second surface in the transport direction. A printing apparatus characterized in that the printing length in at least one of the first and second printing units is adjusted so as to reduce the size of the printing device.

(Appendix 2)
The difference information is a difference value between the number of output pulses of the first encoder and the number of output pulses of the second encoder per page.
The control unit has a page-based print length for reducing the difference between the print length of the first side and the print length of the second side, which is calculated by using the cumulative value of the difference value for each page. The printing apparatus according to Appendix 1, wherein the printing length in at least one of the first and second printing units is adjusted on a page-by-page basis based on the adjustment value.

(Appendix 3)
The difference information is a difference value of the number of output pulses between the first encoder and the second encoder in the time required to reach the number of output pulses per page.
The control unit calculates the difference value for each page, and uses the calculated difference value to reduce the difference between the print length of the first side and the print length of the second side, the next page. The description in Appendix 1 is characterized in that an adjustment value of the print length is calculated for, and the print length of the next page in at least one of the first and second printing units is adjusted based on the calculated adjustment value. Printing equipment.

(Appendix 4)
The control unit
Using the difference value and the print cycle of the line of the image, the line deviation amount indicating the difference between the print length of the first side and the print length of the second side per page is calculated in terms of the number of lines.
The integer part of the line deviation amount is calculated as an adjustment value, and the print length is adjusted by adjusting the number of lines in the image based on the calculated adjustment value.
The printing apparatus according to Appendix 3, wherein a fractional part of the line deviation amount is included in the line deviation amount used for the calculation of the next adjustment value.

1 Printing system 2 Unwinding device 3 Printing device 4 Winding device 21 Transport section 22, 22A, 22B Encoder 23, 23A, 23B Printing section 24 Operation panel 25 Printing device control section 31-40 Guide roller 41 Head bottom roller 42 Serpentine control Part 43 Conveying roller 44 Conveying motor 46, 47 Serpentine control roller 48 Serpentine control motor 51, 51K, 51C, 51M, 51Y, 51P Head unit 56, 56K, 56C, 56M, 56Y, 56P Inkjet head 71 Adjustment table

Claims (4)

A first printing unit that has a plurality of printing mechanisms arranged in parallel in the transport direction of the web and prints an image on the first surface of the transported web by each of the printing mechanisms.
A second printing unit having a plurality of printing mechanisms arranged in parallel in the transport direction and printing an image on the second surface of the transported web by each of the printing mechanisms.
A first roller and a second roller that rotate synchronously with the transported web,
A first encoder that outputs a pulse signal according to the rotation angle of the first roller, and
A second encoder that outputs a pulse signal according to the rotation angle of the second roller, and
The printing timing of each printing mechanism of the first printing unit is controlled based on the output pulse signal of the first encoder, and the printing timing of each printing mechanism of the second printing unit is controlled based on the output pulse signal of the second encoder. Equipped with a control unit to control
The control unit uses the difference information indicating the difference in the outer peripheral length between the first roller and the second roller, and uses the difference information between the print length of the first surface and the print length of the second surface in the transport direction. A printing apparatus characterized in that the printing length in at least one of the first and second printing units is adjusted so as to reduce the size of the printing device. The difference information is a difference value between the number of output pulses of the first encoder and the number of output pulses of the second encoder per page.
The control unit has a page-based print length for reducing the difference between the print length of the first side and the print length of the second side, which is calculated by using the cumulative value of the difference value for each page. The printing apparatus according to claim 1, wherein the printing length is adjusted on a page-by-page basis in at least one of the first and second printing units based on the adjustment value. The difference information is a difference value of the number of output pulses between the first encoder and the second encoder in the time required to reach the number of output pulses per page.
The control unit calculates the difference value for each page, and uses the calculated difference value to reduce the difference between the print length of the first side and the print length of the second side, the next page. The first aspect of the present invention is to calculate an adjustment value of the print length with respect to, and to adjust the print length of the next page in at least one of the first and second printing units based on the calculated adjustment value. The printing device described. The control unit
Using the difference value and the print cycle of the line of the image, the line deviation amount indicating the difference between the print length of the first side and the print length of the second side per page is calculated in terms of the number of lines.
The integer part of the line deviation amount is calculated as an adjustment value, and the print length is adjusted by adjusting the number of lines in the image based on the calculated adjustment value.
The printing apparatus according to claim 3, wherein a fractional part of the line deviation amount is included in the line deviation amount used for the calculation of the next adjustment value.

Images