JP2021008034A - Printing apparatus and printing method - Google Patents

Abstract

To provide a printing apparatus and a printing method which can suppress the reduction in the productivity by shortening the time to the printing resumption while preventing the contact between a medium in which the floating is generated and a recording head, and can perform the alignment of front and rear images when performing the two-sided printing in the variable printing.SOLUTION: A printing apparatus according to one aspect of the present invention retreats a recording head from a printing position at a position facing a medium support surface of a medium conveyance unit when the floating of a medium is detected by a medium floating detection unit, continues the medium conveyance to temporarily suspend the printing, and resumes the printing by returning the recording head to the printing position after the floating of the medium is resolved. The printing apparatus changes an image to be printed on a succeedingly-printing surface of the medium at the printing resumption in a case where the medium floating avoidance control is executed in the printing of the succeedingly-printing surface in the variable printing in accordance with a precedingly-printed image that has been printed on a precedingly-printing surface of the medium at the printing resumption.SELECTED DRAWING: Figure 7

Description

The present invention relates to a printing apparatus and a printing method, and more particularly to a digital printing apparatus capable of variable printing and a printing control technique thereof.

An inkjet printing device, which is an example of a digital printing device, includes a recording head for ejecting ink droplets and a paper transport mechanism for transporting paper, transports paper in a certain direction, and transfers ink from the recording head. An image is formed on the paper by ejecting. Paper transported using the paper transport mechanism may have paper floats such as wrinkles and bends. If the amount of floating paper exceeds the permissible range, the floating paper may collide with the recording head and damage the recording head.

The inkjet printing apparatus disclosed in Patent Document 1 is provided with a paper float sensor for detecting paper float on the upstream side of a recording head in a paper transport path, and when the paper float sensor detects paper float exceeding an allowable range, By urgently stopping the paper transport drum and retracting the recording head to a maintenance position outside the drum, it is possible to prevent the paper from colliding with the recording head.

In the inkjet printing apparatus disclosed in Patent Document 2, when the amount of floating of paper is light, the recording head is temporarily retracted in a direction away from the paper conveying surface without stopping the paper conveying, and the floating occurs. After passing through the paper, the position of the recording head is returned to the original printing position, and printing is restarted.

In Patent Document 3, when printing is resumed after the printing process is interrupted due to an error in the middle of a job being executed, duplicate printing of pages that have been printed at the time of interruption is avoided, and the interrupted pages are avoided. A print control device that identifies a print resume page so as to resume printing from is disclosed.

Japanese Unexamined Patent Publication No. 2010-11174 International Publication No. 2016/009941 Japanese Unexamined Patent Publication No. 10-177464

As described in Patent Document 1, when paper floating occurs, if the control is performed to uniformly stop the paper transport to avoid the collision between the paper and the recording head, it takes time to restart printing and the productivity is improved. descend.

In this regard, as described in Patent Document 2, when the amount of floating paper is light, the recording head is temporarily retracted upward without stopping the paper transport, and the floating paper is placed under the recording head. By adopting a configuration that automatically returns to printing after passing through, the time until returning to printing can be shortened.

Patent Document 1-3 refers to the process of resuming printing after interrupting printing. However, Patent Documents 1-3 do not describe variable printing, which is one of the strengths of digital printing devices, and mention processing when printing is resumed from a state in which printing is interrupted during double-sided printing. Absent.

A digital printing device represented by an inkjet printing device can perform non-variable printing in which the same image is repeatedly printed and variable printing in which different images are printed on each sheet.

In Patent Documents 2 and 3, when printing is resumed after printing is interrupted, printing is uniformly resumed from the image in which printing is interrupted. However, since the image on the back side in double-sided printing is a set with the image on the front side, in the case of variable printing, especially when printing is restarted uniformly from the image interrupted in the printing on the post-printing side, the images on the front side and the back side are displayed. There is a problem that the consistency of the set is broken. Patent Documents 2 and 3 do not consider the consistency of the front and back image sets of double-sided printing by variable printing.

The above-mentioned problem is not limited to the inkjet printing device, but is a problem common to digital printing devices that use a recording head to form an image in a non-contact manner with respect to various media. In the present specification, the term "paper" includes the meaning of "medium" on which an image is formed regardless of the material or form.

The present invention has been made in view of such circumstances, solves the above-mentioned problems, prevents contact between the medium in which floating occurs and the recording head, and shortens the time until printing is resumed to improve productivity. It is an object of the present invention to provide a printing apparatus and a printing method capable of suppressing deterioration and matching front and back images when double-sided printing is performed by variable printing.

In order to solve the problem, the following aspects of the invention are provided.

The printing apparatus according to the first aspect has a medium supporting surface that supports the medium, and forms an image on a medium conveying section that conveys the medium supported by the medium supporting surface and a medium that is conveyed using the medium conveying section. With respect to the head elevating part and the recording head, which move the recording head with respect to the medium support surface at a position facing the medium support surface of the medium transport unit to change the distance between the medium support surface and the recording head. When the medium float detection unit is located upstream of the medium transport direction and detects the float of the medium transported by the medium transport unit, and the medium float detection unit detects the float of the medium. The recording head is retracted from the printing position facing the medium support surface of the medium transfer section to a retracted position farther from the medium support surface than the print position by using the head elevating section, and the medium using the medium transfer section is used. With a control unit that performs media floating avoidance control that resumes printing by returning the recording head from the retracted position to the printing position using the head elevating unit after the printing is temporarily interrupted and the floating of the medium is resolved. When resuming printing by executing the medium floating avoidance control in printing the post-printing surface of variable printing, the control unit prints an image printed on the post-printing surface of the medium when resuming printing. The image is changed to the image corresponding to the printed preprinted image according to the preprinted image printed on the preprinted surface of the medium.

According to the printing apparatus according to the first aspect, when the conveyed medium floats, the recording head is temporarily moved from the printing position to the retracted position while continuing the conveying of the medium, and the temporary printing is interrupted. In the state, let the medium in which the float occurs pass. Then, after the floating medium passes through the position of the recording head and the floating of the medium is eliminated, the recording head is returned from the retracted position to the original printing position to perform the medium floating avoidance control for restarting printing. By executing such a medium floating avoidance control, it is possible to suppress a decrease in productivity while preventing contact between the floating medium and the recording head.

Further, according to the printing apparatus according to the first aspect, when the medium floating avoidance control is executed in the printing of the post-printing surface of the variable printing and the printing is restarted, the preprinted surface of the medium at the time of resuming printing is already printed. The image to be printed on the post-printing surface of the medium when printing is resumed is changed according to the pre-printed image. In the case of double-sided printing, the front side image and the back side image are a set (pair), and it is necessary to print the image of the back print surface in accordance with the preprinted image that has been printed. The “image corresponding to the printed preprinted image” refers to an image of the postprinted surface defined as an image set to be paired with the image of the preprinted surface in double-sided printing.

According to the printing apparatus according to the first aspect, even if the medium floating avoidance control is executed and the printing is temporarily interrupted when double-sided printing is performed by variable printing, the front and back images are automatically aligned after the medium floating is eliminated. It can be realized and printing can be resumed.

Aspect 2 is a printing device in which the control unit switches the image to be printed at the time of resuming printing of the medium floating avoidance control according to the printing type of the job being executed in the printing device of the first aspect.

Depending on the print type of the job, there are cases where the consistency of the front and back images becomes a problem, and there are cases where it does not become a problem. For example, in the case of a job that prints the preprinted surface of variable printing, since the postprinted surface is not printed at the time of printing the preprinted surface, the printing of the medium floating avoidance control when printing the preprinted surface is performed. When resuming, there is no problem that the image on the post-printing surface is out of alignment. Further, in non-variable printing, since the same image is printed continuously, there is no problem that the front and back images are out of alignment when the printing of the medium floating avoidance control is restarted regardless of the pre-printed surface and the post-printed surface.

According to the printing apparatus according to the second aspect, for example, during printing of the preprinted surface of variable printing, when the medium floating occurs and the medium floating avoidance control is executed, the image to be printed at the time of resuming printing has the floating. It can be an image that was supposed to be printed on the printed medium, that is, an image that failed to be printed due to the occurrence of floating. On the other hand, the image to be printed at the time of resuming printing when the medium floating occurs and the medium floating avoidance control is executed during the printing of the post-printing surface of the variable printing is printed on the pre-printed surface of the medium at the time of resuming printing. The image corresponds to the preprinted image that has already been printed. In this way, it is preferable to switch the image to be printed when the printing of the medium floating avoidance control is resumed according to the print type of the job being executed.

In the printing apparatus of the third aspect, the printing type includes at least one of non-variable printing and variable printing preprinted surface printing and at least two types of variable printing post-printed surface printing. A printing device included.

In the case of non-variable printing or printing of the preprinted surface of variable printing, the image printed when the printing of the medium floating avoidance control is restarted may be the same image as the image that should have been printed on the medium in which the medium floating has occurred. it can. On the other hand, in the case of printing on the post-printing surface of variable printing, the image printed when printing is restarted under the medium floating avoidance control is changed to an image corresponding to the pre-printed image printed on the medium when printing is restarted.

Aspect 4 is a printing apparatus according to aspect 3, wherein the printing type includes three types of printing: non-variable printing, printing of the pre-printed surface of variable printing, and printing of the post-printing surface of variable printing. is there.

Aspect 5 is in the printing apparatus of Aspect 3 or Aspect 4, in which the control unit controls media floating avoidance control when the print type of the job being executed is non-variable printing or printing of the preprinted surface of variable printing. This is a printing device that performs a process of printing an image that was supposed to be printed on a medium in which the medium floats when printing is resumed.

For non-variable printing or printing on the preprinted surface of variable printing, the front and back images are aligned with each other for the image printed when printing is resumed when the medium floating occurs during printing and the medium floating avoidance control is executed. Since this is not a problem, the image printed when printing is resumed can be an image that should have been printed on a medium in which floating has occurred.

Aspect 6 includes a storage unit for storing image data of an image printed on a medium using a recording head in the printing apparatus of any one of aspects 2 to 5, and the control unit has a floating medium. When it occurs, the process of holding the image data stored in the storage unit and the image data stored in the storage unit are synchronized with the transport of the medium for each print area of the medium according to the print type. It is a printing device that switches between the update process and the update process.

The medium may be a single-wafer medium or a continuous medium. "For each print area of the medium" includes the meaning of "for each medium" when a sheet-fed medium is used.

In the seventh aspect, when the printing type of the job being executed in the printing apparatus of the sixth aspect is non-variable printing or printing on the preprinted surface of variable printing, the storage unit is stored during the medium floating avoidance control. It is a printing device that holds stored image data.

According to the printing apparatus according to the seventh aspect, since the image data of the image that was supposed to be printed on the medium in which the medium floating has occurred is held in the storage unit, the storage unit promptly releases the image data after the medium floating is eliminated. The image data can be read out and printing can be resumed.

In the eighth aspect, when the printing type of the job being executed in the printing device of the sixth aspect or the seventh aspect is the printing of the post-printing surface of the variable printing, the aspect 8 is stored in the storage unit during the medium floating avoidance control. By updating the existing image data for each print area of the medium, the printing apparatus changes the image to be printed on the post-printing surface of the medium at the time of resuming printing to an image corresponding to the printed preprinted image.

According to the printing apparatus according to the eighth aspect, when the medium floats during the printing of the post-printing surface of the variable printing, the medium is stored in the storage unit while continuing the transport of the medium by the medium float avoidance control. By updating the image data for printing for each print area of the medium in synchronization with the transport of the medium, an image of the post-printing surface corresponding to the printed pre-printed image is prepared in the storage unit. As a result, after the medium floating is eliminated, the image data can be quickly read from the storage unit and printing can be resumed. According to the printing apparatus according to the eighth aspect, the amount of waste paper required for resuming printing can be reduced, and the productivity can be improved. The amount of waste paper required to resume printing refers to the number of media that could not be printed.

Aspect 9 comprises a print timing signal generation unit that generates a print timing signal corresponding to a print area of the medium in synchronization with the transfer of the medium by the medium transfer unit in the printing apparatus according to any one of aspects 3 to 8. In the case of non-variable printing or printing of the preprinted surface of variable printing, the print timing signal generation unit prints for each print area of the medium synchronized with the transfer of the medium during the print interruption period by the medium floating avoidance control. This is a printing device that pauses the output of timing signals.

According to the printing apparatus according to the ninth aspect, the processing and updating of the image data synchronized with the transport of the medium should be stopped during the period when the output of the print timing signal is suspended, and the image data should be printed on the medium in which the floating occurs. The image data of the existing image can be stored in the storage unit. The print timing signal generation unit resumes the output of the print timing signal corresponding to the print area of the medium after the floating of the medium is eliminated.

In aspect 10, in the printing apparatus of aspect 9, the print timing signal generation unit is the printing area of the medium synchronized with the transfer of the medium during the printing interruption period by the medium floating avoidance control in the case of printing the post-printing surface of variable printing. It is a printing device that continues to output each print timing signal.

According to the printing apparatus according to the tenth aspect, by continuing the output of the print timing signal during the printing interruption period by the medium floating avoidance control, it is possible to continue the processing and updating of the image data synchronized with the transport of the medium. The image data of the image to be printed when printing is resumed can be prepared in the storage unit.

Aspect 11 includes a storage unit for storing image data of an image printed on a medium using a recording head in the printing apparatus of Aspect 1, and a control unit avoids floating of the medium in printing a post-printing surface of variable printing. This is a printing device that updates the image data stored in the storage unit for each print area of the medium in synchronization with the transfer of the medium when the control is executed.

According to the eleventh aspect, the image printed when printing is resumed after the medium floating is eliminated can be changed to an image corresponding to the printed preprinted image.

Aspect 12 includes, in the printing apparatus of Aspect 1 or Aspect 11, a print timing signal generation unit that generates a print timing signal corresponding to a print area of the medium in synchronization with the transfer of the medium by the medium transfer unit, and includes a print timing signal. The generation unit is a printing device that continues to output a print timing signal for each print area of the medium, which is synchronized with the transfer of the medium, during the print interruption period by the medium floating avoidance control in the case of printing on the post-printing surface of variable printing. ..

Aspect 13 is a printing device according to any one of aspects 1 to 12, wherein the control unit prints an image that could not be printed due to execution of the medium floating avoidance control after a series of printing according to the job is completed. It is a printing device that performs processing.

According to the printing apparatus according to the thirteenth aspect, it is possible to collectively reprint the images that could not be printed due to the occurrence of the medium floating after the series of printing is completed.

Aspect 14 is an identification information reading unit that reads image identification information attached to a medium in order to identify a preprinted image printed on the preprinted surface of the medium in the printing apparatus of any one of aspects 1 to 13. The control unit is a printing device that determines an image to be printed on the post-printing surface of the medium based on the image identification information read by the identification information reading unit.

Aspect 15 is a printing apparatus according to any one of aspects 1 to 14, wherein the recording head is an inkjet head.

In the 16th aspect, in the printing apparatus of any one of the 1st to 15th aspects, the medium floating detection unit detects the floating of the medium with a floating amount exceeding a preset allowable floating amount and not more than a specified amount. However, the control unit is a printing device that executes medium float avoidance control when a float of a medium having a float amount exceeding the allowable float amount and not more than a specified amount is detected.

Aspect 17 is a printing apparatus for stopping the transfer of a medium using the medium transfer unit when a float amount exceeding a specified amount occurs in the printing device of the aspect 16.

The printing method according to aspect 18 is a printing method in which double-sided printing is performed using a printing device capable of variable printing, and the printing method is supported on the medium supporting surface by using a medium conveying portion having a medium supporting surface for supporting the medium. A recording head of a printing apparatus when a medium float detection step for transporting a medium, a medium float detection step for detecting the float of the medium to be conveyed using the medium transport unit, and a medium float detection step for detecting the float of the medium are detected. From the printing position, the recording head is moved from the printing position by using a head elevating part that changes the distance between the medium supporting surface and the recording head by moving the material to the medium supporting surface at a position facing the medium supporting surface of the medium conveying part. The recording head is moved after the printing is temporarily interrupted by retracting the medium to a retracted position farther from the medium supporting surface than the printing position and continuously conveying the medium using the medium conveying section to eliminate the floating of the medium. The step of performing the medium floating avoidance control for returning from the retracted position to the printing position and restarting printing, and the rear of the medium when resuming printing when the medium floating avoidance control is executed in the printing of the post-printing surface of variable printing and the printing is restarted. It includes a step of changing the image printed on the printing surface to an image corresponding to the printed preprinted image according to the preprinted image printed on the preprinted surface of the medium at the time of resuming printing.

In the printing method of the 18th aspect, the same items as the specific items of the printing apparatus specified in the 2nd to 17th aspects can be appropriately combined. In that case, the elements of the processing unit and the functional unit as means for carrying out the processing and operation specified in the printing apparatus can be grasped as the elements of the corresponding processing and operation steps (processes).

By carrying out the printing method of aspect 18, it is possible to obtain a printed matter in which the front and back images are matched. The printing method of aspect 18 can be understood as a method of manufacturing a printed matter in which images are printed on both sides of a medium.

According to the present invention, when a floating medium occurs, it is possible to prevent contact between the recording head and the medium, shorten the time until printing is resumed, and suppress a decrease in productivity. Further, according to the present invention, it is possible to realize matching of front and back images when double-sided printing is performed by variable printing.

FIG. 1 is an overall configuration diagram of an inkjet printing apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram showing a schematic configuration of a control system of an inkjet printing apparatus. FIG. 3 is a schematic view schematically showing a main part of a drawing unit in an inkjet printing apparatus. FIG. 4 is an explanatory diagram of a measure example 1 for avoiding contact between the paper in which the paper floats and the recording head. FIG. 5 is an explanatory diagram of a measure example 2 for avoiding contact between the paper in which the paper floats and the recording head. FIG. 6 is a chart showing examples of images printed on each paper during normal printing without paper floating for each print type. FIG. 7 is a chart showing an example of an image printed on each paper when the paper floats, for each print type. FIG. 8 is a flowchart of a process for determining a return image in the case of variable printing. FIG. 9 is an explanatory diagram showing an example of the printing order of collating printing. FIG. 10 is a conceptual diagram of a pre-printing process including printing of an image identification pattern. FIG. 11 is a conceptual diagram of a post-printing process performed after the pre-printing process described with reference to FIG. FIG. 12 is a block diagram showing a main part of the configuration of the inkjet printing apparatus. FIG. 13 is a block diagram showing an example of image data handling carried out in an inkjet printing apparatus. FIG. 14 is an example of a timing chart for printing the preprinted surface by variable printing. FIG. 15 is an example of a timing chart for variable printing and printing on the post-printing surface.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<< Configuration example of an inkjet printing device >>
FIG. 1 is an overall configuration diagram of an inkjet printing apparatus 1A according to an embodiment of the present invention. The inkjet printing apparatus 1A includes line-type inkjet heads 46K, 46C, 46M, and 46Y as recording heads of the drawing unit 40, and black (K), cyan (C), and magenta (M) are printed on paper P, which is a sheet of paper. This is a single-pass inkjet type color digital printing apparatus that prints a desired image by a single-pass method using four color inks of yellow (Y) and yellow (Y).

In this example, water-based ink is used as the drawing ink. Aqueous ink refers to an ink in which a coloring material such as a pigment or a dye is dissolved or dispersed in water and / or a solvent soluble in water. In addition, UV curable ink may be used instead of water-based ink.

The inkjet printing device 1A includes a paper feeding unit 10, a processing liquid applying unit 20, a processing liquid drying unit 30, a drawing unit 40, an ink drying unit 50, and an integrating unit 60.

The paper feed unit 10 includes a paper feed device 12, a feeder board 14, and a paper feed drum 16. The paper P is placed on the paper feed tray 12A in a bundle in which a large number of sheets are stacked. The type of paper P is not particularly limited, but for example, printing paper mainly composed of cellulose such as high-quality paper, coated paper, and art paper can be used.

The paper feeding device 12 takes out the bundled paper P set in the paper feeding table 12A one by one from the top and feeds the paper P to the feeder board 14. The feeder board 14 conveys the paper P received from the paper feeding device 12 to the paper feeding drum 16.

The paper feed drum 16 receives the paper P to be fed from the feeder board 14, and conveys the received paper P to the processing liquid application unit 20.

The treatment liquid application unit 20 applies the treatment liquid to the paper P. The treatment liquid is a liquid having a function of aggregating, insolubilizing, or thickening the color material components in the ink. The treatment liquid application unit 20 includes a treatment liquid application drum 22 and a treatment liquid application device 24.

The processing liquid application drum 22 receives the paper P from the paper feed drum 16 and conveys the received paper P to the processing liquid drying unit 30. The processing liquid application drum 22 is provided with a gripper 23 on the peripheral surface, and the paper P is wound around the peripheral surface and conveyed by rotating the gripper 23 by gripping the tip portion of the paper P.

The treatment liquid coating device 24 applies the treatment liquid to the paper P conveyed by the treatment liquid application drum 22. The treatment liquid is applied by a roller. The method of applying the treatment liquid is not limited to the roller coating method. Other methods may be applied to the treatment liquid coating device 24. Examples of other methods of the treatment liquid coating device 24 include coating using a blade, ejection by an inkjet method, spraying by a spray method, and the like.

The treatment liquid drying unit 30 dries the paper P coated with the treatment liquid. The treatment liquid drying unit 30 includes a treatment liquid drying drum 32 and a warm air blower 34. The processing liquid drying drum 32 receives the paper P from the processing liquid application drum 22, and conveys the received paper P to the drawing unit 40. The treatment liquid drying drum 32 is provided with a gripper 33 on the peripheral surface. The processing liquid drying drum 32 conveys the paper P by gripping the tip end portion of the paper P with the gripper 33 and rotating the paper P.

The hot air blower 34 is installed inside the processing liquid drying drum 32. The warm air blower 34 blows warm air onto the paper P conveyed by the processing liquid drying drum 32 to dry the processing liquid.

The drawing unit 40 includes a drawing drum 42, a head unit 44, a paper float sensor 45, and an image reading device 48. The drawing drum 42 receives the paper P from the processing liquid drying drum 32, and conveys the received paper P to the ink drying unit 50. The drawing drum 42 is provided with a gripper 43 on the peripheral surface of the drum, and the paper P is wound around the peripheral surface and conveyed by gripping and rotating the tip of the paper P using the gripper 43. The drawing drum 42 is provided with a suction mechanism (not shown), and the paper P wound around the peripheral surface is sucked onto the peripheral surface of the drum and conveyed. Negative pressure is used for adsorption. The drawing drum 42 is provided with a large number of suction holes on the peripheral surface, and the paper P is attracted to the peripheral surface of the drawing drum 42 by sucking from the inside of the drawing drum 42 through the suction holes. The peripheral surface of the drawing drum 42 on which the paper P is suction-supported corresponds to the paper support surface that supports the paper, and is an example of the “medium support surface”. The peripheral surface of the drawing drum 42 corresponds to the paper transport surface. The drawing drum 42 is an example of a “medium carrier”. The step of transporting the paper using the drawing drum 42 is an example of the “media transport step”.

The paper float sensor 45 is a means for detecting the paper float of the paper P conveyed by the drawing drum 42. Paper lift is lift due to wrinkles and / or bending of the paper. The amount of floating of the paper may be evaluated by the height from the paper supporting surface of the drawing drum 42, or by the height from the reference printing surface which is the surface of the paper P supported by the paper supporting surface. May be good.

The paper float sensor 45 is arranged on the upstream side of the head unit 44 of the paper transport path in the drawing drum 42, and detects the paper float at a position in front of the head unit 44. The paper float sensor 45 is preferably a non-contact sensor that detects paper float without contacting the paper P.

The paper float sensor 45 is composed of, for example, a pair of a floodlight and a receiver. Although the detailed configuration of the paper float sensor 45 is not shown, as an example, the floodlight and the receiver are divided on both sides of the drawing drum 42 in the axial direction of the drawing drum 42 and are arranged so as to face each other. The axial direction of the drawing drum 42 is a direction parallel to the rotation axis of the drawing drum 42.

As the floodlight, various light emitting elements such as a light emitting diode or a laser diode can be used. As the light receiver, a photoelectric conversion element that outputs an electric signal according to the amount of light received can be used.

The optical axis of the inspection light emitted from the floodlight is substantially parallel to the axial direction of the drawing drum 42, and the luminous flux of the inspection light passes near the surface of the drawing drum 42.

When the paper P floats from the drawing drum 42 in excess of the specified amount, a part of the inspection light is blocked and the amount of light incident on the receiver (light receiving amount) is reduced. Therefore, the signal obtained from the receiver reduces the amount of light incident on the receiver. Floating can be detected. By adjusting the height of the inspection light from the peripheral surface of the drawing drum 42, the amount of paper float to be detected can be set.

The paper float sensor 45 is configured to irradiate light from one end of the paper support surface of the drawing drum 42 in the width direction and receive the reflected light from the reflection surface arranged at the other end to detect the float of the paper P. May be good. The width direction of the paper support surface is a direction parallel to the axial direction of the drawing drum 42.

The head unit 44 includes inkjet heads 46K, 46C, 46M, and 46Y. The inkjet head 46K is a recording head that ejects droplets of black (K) ink. The inkjet head 46C is a recording head that ejects droplets of cyan (C) ink. The inkjet head 46M is a recording head that ejects droplets of magenta (M) ink. The inkjet head 46Y is a recording head that ejects droplets of yellow (Y) ink. In addition, in this specification, the term "head" may be simply described as a term indicating "inverter head" or "recording head".

Ink is supplied to each of the inkjet heads 46K, 46C, 46M, and 46Y from an ink tank (not shown), which is an ink supply source of the corresponding color, via a piping path (not shown).

Each of the inkjet heads 46K, 46C, 46M, and 46Y is composed of line heads that can be printed by one scan on the paper P conveyed by the drawing drum 42, that is, by a single pass method. The nozzle surfaces of the inkjet heads 46K, 46C, 46M, and 46Y are arranged so as to face the peripheral surface of the drawing drum 42. The inkjet heads 46K, 46C, 46M, and 46Y are arranged at regular intervals along the transport path of the paper P by the drawing drum 42.

Although not shown in FIG. 1, a plurality of nozzles, which are ink ejection ports, are two-dimensionally arranged on the nozzle surfaces of the inkjet heads 46K, 46C, 46M, and 46Y. The “nozzle surface” refers to an ejection surface on which a nozzle is formed, and is synonymous with terms such as “ink ejection surface” or “nozzle forming surface”. The nozzle arrangement of a plurality of nozzles arranged in two dimensions is called a "two-dimensional nozzle arrangement". A water-repellent film is formed on each nozzle surface of the inkjet heads 46K, 46C, 46M, and 46Y.

Each of the inkjet heads 46K, 46C, 46M, and 46Y can be configured by connecting a plurality of head modules in the paper width direction. The paper width referred to here refers to a paper width in a direction orthogonal to the transport direction of the paper P. Each of the inkjet heads 46K, 46C, 46M, and 46Y is a nozzle capable of recording an image at a specified recording resolution in the entire recording area of the paper P in a single scan with respect to the paper width direction orthogonal to the transport direction of the paper P. A line-type recording head having rows. Such a recording head is also called a "full-line recording head" or a "page wide head". In this specification, the specified recording resolution may be a recording resolution predetermined by the inkjet printing apparatus 1A, or is set by the user's selection or by automatic selection by a program according to the printing mode. It may be the recording resolution to be performed. The recording resolution can be, for example, 1200 dpi. “Dpi” means dot per inch and is a unit notation representing the number of dots (dots) per inch. One inch is 25.4 millimeters [mm].

The paper width direction orthogonal to the paper P transport direction may be referred to as the nozzle row direction of the line head, and the paper P transport direction may be referred to as the nozzle row vertical direction.

In the case of an inkjet head having a two-dimensional nozzle arrangement, the projected nozzle row in which each nozzle in the two-dimensional nozzle arrangement is projected (normally projected) so as to line up along the nozzle row direction achieves the maximum recording resolution in the nozzle row direction. It can be considered to be equivalent to a row of nozzles in which each nozzle is arranged at approximately equal intervals according to the nozzle density. "Approximately evenly spaced" means that the drip points that can be recorded by an inkjet printing device are substantially evenly spaced. For example, the concept of "equal spacing" also includes those with slightly different spacing in consideration of manufacturing errors and / or movement of droplets on the medium due to landing interference. The projected nozzle array corresponds to a substantial nozzle array. Considering the projection nozzle array, it is possible to associate each nozzle with a nozzle number indicating the nozzle position in the order in which the projection nozzles are arranged along the nozzle array direction.

The arrangement form of the nozzles in each of the inkjet heads 46K, 46C, 46M, and 46Y is not limited, and various nozzle arrangement forms can be adopted. For example, instead of the form of a matrix-like two-dimensional array, a line-shaped nozzle array, a V-shaped nozzle array, a polygonal line-shaped nozzle array such as a W-shaped array having a V-shaped array as a repeating unit, etc. are also possible. Is.

Ink droplets are ejected from at least one of the inkjet heads 46K, 46C, 46M, and 46Y toward the paper P conveyed by the drawing drum 42, and the ejected droplets adhere to the paper P. , An image is formed on the paper P.

The drawing drum 42 functions as a means for relatively moving the inkjet heads 46K, 46C, 46M, 46Y and the paper P. The drawing drum 42 corresponds to a form of a medium transport mechanism that transports the paper P to the inkjet heads 46K, 46C, 46M, and 46Y. The ejection timings of the inkjet heads 46K, 46C, 46M, and 46Y are synchronized with the encoder signal obtained from the encoder installed on the drawing drum 42. Illustration of the encoder is omitted in FIG. The ejection timing is a timing for ejecting ink droplets, and is synonymous with a droplet ejection timing.

In this example, a configuration using four colors of CMYK ink is illustrated, but the combination of the ink color and the number of colors is not limited to this embodiment, and if necessary, light ink, dark ink, special color ink, etc. May be added. For example, it is possible to add an inkjet head that ejects light ink such as light cyan or light magenta, or add an inkjet head that ejects a special color ink such as green or orange. Further, the arrangement order of the inkjet heads of each color is not particularly limited.

The image reading device 48 is a device that optically reads an image recorded on the paper P by the inkjet heads 46K, 46C, 46M, and 46Y and generates electronic image data indicating the read image. The image reading device 48 includes an imaging device that captures an image recorded on the paper P and converts it into an electric signal indicating image information. In addition to the image pickup device, the image reader 48 may include an illumination optical system that illuminates the reading target and a signal processing circuit that processes signals obtained from the image pickup device to generate digital image data.

The image reading device 48 preferably has a configuration capable of reading a color image. In the image reading device 48 of this example, for example, a color CCD (Charge-Coupled Device) linear image sensor is used as the image pickup device. The color CCD linear image sensor is an image sensor in which light receiving elements equipped with color filters of R (red), G (green), and B (blue) are linearly arranged. A color CMOS (Complementary Metal Oxide Semiconductor) linear image sensor can also be used instead of the color CCD linear image sensor.

The image reading device 48 reads the image on the paper P while the drawing drum 42 conveys the paper P. The image reading device installed in the paper transport path in this way may be called an "in-line scanner" or an "in-line sensor". Further, the image reading device 48 may be a camera.

The paper P on which the image is recorded using at least one of the inkjet heads 46K, 46C, 46M, and 46Y reads the image on the paper P when passing through the reading area of the image reading device 48. The image recorded on the paper P includes a user image to be printed specified by the job, a defective nozzle detection pattern for inspecting the ejection state of each nozzle, a test pattern for print density correction, and various other tests. Patterns can be included.

Based on the data of the scanned image read by the image reading device 48, the printed image is inspected and the presence or absence of an image quality abnormality is determined. Further, based on the data of the scanned image read by the image reading device 48, information such as image density and ejection failure of the inkjet heads 46K, 46C, 46M, and 46Y can be obtained.

The ink drying unit 50 dries the paper P on which the image is formed by the drawing unit 40. The ink drying unit 50 includes a chain gripper 70, a paper guide 80, and a heat drying processing unit 90.

The chain gripper 70 receives the paper P from the drawing drum 42, and conveys the received paper P to the accumulating unit 60. The chain gripper 70 includes a pair of endless chains 72 that travel on a specified travel path, and conveys the paper P in a state where the tip of the paper P is gripped by the grippers 74 provided on the pair of chains 72. Transport along the route. A plurality of grippers 74 are provided on the chain 72 at regular intervals.

The chain gripper 70 of this example is configured to include a first sprocket 71A, a second sprocket 71B, a chain 72, and a plurality of grippers 74, and is paired with a pair of the first sprocket 71A and a pair of the second sprocket 71B. It has a structure in which an endless chain 72 is wound around. FIG. 1 shows only one of the pair of first sprockets 71A and second sprockets 71B and the pair of chains 72.

The chain gripper 70 has a structure in which a plurality of grippers 74 are arranged at a plurality of positions in the feed direction (length direction) of the chain 72. Further, the chain gripper 70 has a structure in which a plurality of grippers 74 are arranged between the pair of chains 72 along the width direction in the paper width direction. FIG. 1 shows only one gripper 74 out of a plurality of grippers 74 arranged between a pair of chains 72.

The transport path of the paper P by the chain gripper 70 includes a horizontal transport region for transporting the paper P along the horizontal direction and an inclined transport region for transporting the paper P diagonally upward from the end of the horizontal transport region. The horizontal transport area is referred to as a first transport section, and the inclined transport region is referred to as a second transport section.

The paper guide 80 is a mechanism for guiding the transport of the paper P by the chain gripper 70. The paper guide 80 includes a first paper guide 82 and a second paper guide 84. The first paper guide 82 guides the paper P transported in the first transport section of the chain gripper 70. The second paper guide 84 guides the paper to be conveyed in the second conveying section after the first conveying section.

Although the detailed structure of the first paper guide 82 is not shown in FIG. 1, a suction belt transfer device is used as the first paper guide 82. The suction belt transport device is a device that transports the paper P by feeding the transport belt in a state where the paper P is sucked on the endless transport belt.

The heat-drying treatment unit 90 applies heat to the paper P on which the image is formed by the drawing unit 40 to evaporate the solvent of the ink and dry the paper P. The heat-drying treatment unit 90 is, for example, a warm air blowing unit, which is arranged so as to face the first paper guide 82, and blows warm air onto the paper P conveyed by the chain gripper 70.

A detailed description of the configuration of the drying device including the first paper guide 82 using the suction belt transport device and the heat-drying processing unit 90 will be described later.

The accumulating unit 60 includes an accumulating device 62 that receives and accumulates the paper P conveyed from the ink drying unit 50 by the chain gripper 70. The chain gripper 70 releases the paper P at a predetermined stacking position. The stacking device 62 includes a stacking tray 62A, receives the paper P released from the chain gripper 70, and stacks the paper P on the stacking tray 62A in a bundle. The collecting unit 60 corresponds to a paper ejection unit.

In addition to the above-described configuration, although not shown in FIG. 1, in the inkjet printing apparatus 1A, each of the inkjet heads 46K, 46C, 46M, and 46Y can be individually moved in the normal direction of each nozzle surface. Equipped with an elevating part. The head elevating portion is described as reference numeral 200 in FIG. The head elevating portion 200 can be used to change the distance (gap) between the nozzle surface of each head and the outer peripheral surface of the drawing drum 42.

Each of the inkjet heads 46K, 46C, 46M, and 46Y can be moved from the print position to the upper retracted position by the head elevating portion 200, and can be returned from the retracted position to the printed position. The term "upper" as used herein refers to a direction away from the peripheral surface of the drawing drum 42 as a paper support surface to the outside of the drawing drum 42. The printing position is the head position when each of the inkjet heads 46K, 46C, 46M, and 46Y forms an image on the paper P. The retracting position is a position where the drawing drum 42 above the printing position is far from the paper supporting surface, and when the paper floats, each head is retracted in order to avoid contact with the paper P. Is.

Although not shown in FIG. 1, the inkjet heads 46K, 46C, 46M, and 46Y of each color in the drawing unit 40 are supported by a common head support frame. The inkjet printing device 1A moves the entire head unit 44 including the inkjet heads 46K, 46C, 46M, and 46Y attached to the head support frame together with the head support frame above the drawing drum 42. It has a part.

Further, the inkjet printing apparatus 1A includes a head horizontal moving portion capable of horizontally moving the entire head unit 44 including the inkjet heads 46K, 46C, 46M, and 46Y together with the head support frame in the axial direction of the drawing drum 42. The head horizontal moving portion not shown in FIG. 1 is designated as reference numeral 202 in FIG.

Further, although not shown in FIG. 1, the inkjet printing apparatus 1A includes a maintenance unit that performs maintenance processing on the inkjet heads 46K, 46C, 46M, and 46Y. The maintenance unit is installed side by side with the drawing drum 42 in the axial direction of the drawing drum 42. The maintenance unit is described as reference numeral 240 in FIG.

<< Explanation of control system of inkjet printing equipment >>
FIG. 2 is a block diagram showing a schematic configuration of a control system of the inkjet printing apparatus 1A. The inkjet printing device 1A includes a system controller 100. The system controller 100 includes a CPU (Central Processing Unit) 100A, a ROM (Read Only Memory) 100B, and a RAM (Random Access Memory) 100C. Storage units such as ROM 100B and RAM 100C may be provided outside the system controller 100.

The system controller 100 functions as an overall control unit that collectively controls each unit of the inkjet printing apparatus 1A. Further, the system controller 100 functions as a calculation unit that performs various calculation processes. Further, the system controller 100 functions as a memory controller that controls reading and writing of data in memories such as ROM 100B and RAM 100C.

The inkjet printing device 1A includes a communication unit 102, an image memory 104, an image processing unit 106, a transport control unit 110, a paper feed control unit 112, a processing liquid application control unit 114, a processing liquid drying control unit 116, a drawing control unit 118, and a head. It includes an elevating control unit 120, a head horizontal movement control unit 122, an ink drying control unit 124, a paper discharge control unit 126, and a maintenance control unit 128. The elements of each of these parts can be realized by one or more computers. That is, each element of the control unit including the system controller 100 can be configured by a combination of computer hardware and software. Further, a part or all of the processing functions required for control may be realized by using an integrated circuit typified by a DSP (Digital Signal Processor) or an FPGA (Field Programmable Gate Array).

The communication unit 102 includes a communication interface (not shown), and can transmit and receive data between the communication interface and the connected host computer 300.

The image memory 104 functions as a temporary storage unit for various data including image data. The image data taken in from the host computer 300 via the communication unit 102 is temporarily stored in the image memory 104.

The image processing unit 106 generates dot data from the input image data. The image processing unit 106 includes a color separation processing unit, a color conversion processing unit, a correction processing unit, and a halftone processing unit. In the image processing unit 106, color separation processing for separating the input image data into each RGB color, color conversion processing for converting RGB data into CMYK data, various correction processing such as gamma correction and unevenness correction, and pixels of each color. Halftone processing is performed to convert each gradation value into a gradation value less than the original gradation value. The correction process performed by the image processing unit 106 includes a defect correction process for suppressing an image defect caused by a defective nozzle.

The input image data is continuous gradation image data. As an example of the input image data, raster data represented by a digital value from 0 to 255 can be mentioned. The dot data obtained as a result of the halftone processing may be a binary value, or may be a multi-valued value of ternary value or more and less than the gradation value before the halftone processing. A part or all of the processing functions of the image processing unit 106 may be included in the system controller 100 or the drawing control unit 118.

The transfer control unit 110 controls the operation of the transfer system 11 of the paper P in the inkjet printing apparatus 1A. The transport system 11 includes a paper transport mechanism such as the paper feed drum 16, the processing liquid application drum 22, the processing liquid drying drum 32, and the drawing drum 42 shown in FIG. Further, the transport system 11 includes a motor as a power source (not shown) and a drive unit such as a motor drive circuit.

The paper feed control unit 112 shown in FIG. 2 operates the paper feed unit 10 in response to a command from the system controller 100. The paper feed control unit 112 controls the paper P supply start operation, the paper P supply stop operation, and the like.

The processing liquid application control unit 114 operates the processing liquid application unit 20 in response to a command from the system controller 100. The treatment liquid application control unit 114 controls the application amount of the treatment liquid, the application timing, and the like.

The drawing control unit 118 controls the drawing operation of the head unit 44 in response to a command from the system controller 100. The drawing control unit 118 includes a waveform generation unit, a waveform storage unit, and a drive circuit. The waveform generation unit, waveform storage unit, and drive circuit are not shown. The waveform generation unit generates a waveform of a drive voltage for ejecting each ink jet head of the head unit 44. The waveform of the drive voltage is stored in the waveform storage unit. The drive circuit generates a drive voltage having a drive waveform corresponding to the dot data. The drive circuit supplies a drive voltage to the ink jet head of the head unit 44.

The inkjet printing device 1A includes an encoder 206 as a means for detecting the rotation angle of the drawing drum 42 in the transport system 11. The encoder 206 is provided on the drawing drum 42, and outputs a signal according to the amount of paper P conveyed by the drawing drum 42. Here, a rotary encoder that outputs a pulse signal for each unit rotation angle of the rotation axis of the drawing drum 42 is used. The ejection timing of each of the inkjet heads 46K, 46C, 46M, and 46Y is controlled according to the ejection timing signal generated from the encoder signal output by the encoder 206.

Based on the dot data generated through processing by the image processing unit 106, the ejection timing and ink ejection amount of each pixel position are determined, and the ejection timing of each pixel position, the drive voltage according to the ink ejection amount, and each pixel A control signal that determines the discharge timing of the ink is generated. The drive voltage generated by the drawing control unit 118 is supplied to the inkjet head, and dots are formed by the ink ejected from the inkjet head.

The head elevating control unit 120 operates the head elevating unit 200 in response to a command from the system controller 100. The head elevating unit 200 includes a mechanism for moving each of the inkjet heads 46K, 46C, 46M, and 46Y up and down in the normal direction of the nozzle surface, and a motor as a power source thereof.

The inkjet printing device 1A includes a paper float detection unit 208. The paper float detection unit 208 includes the paper float sensor 45 described with reference to FIG. The paper float detection unit 208 may include a circuit for determining whether or not the paper P has passed through the detection area of the paper float sensor 45 based on the output signal of the paper float sensor 45.

The paper float detection unit 208 sends the detection information of the paper P in which the float has occurred to the system controller 100. The detection information of the paper P includes information on the floating amount of the paper P. The step of detecting the float of the paper P by using the paper float detection unit 208 is an example of the “media float detection step”.

When the system controller 100 acquires the detection information of the floating paper P, it sends a command to the head elevating control unit 120 to move each of the inkjet heads 46K, 46C, 46M, and 46Y to the retracted position. The paper float detection unit 208 is an example of a medium float detection unit.

When the paper float detection unit 208 detects the paper float, the head elevating unit 200 is driven to move the inkjet heads 46K, 46C, 46M, and 46Y from the printing position to the upper retracted position. Further, when the paper P on which the paper floats has occurred passes under the inkjet heads 46K, 46C, 46M, 46Y, the respective inkjet heads 46K, 46C, 46M, 46Y are returned from the retracted position to the printing position.

The head horizontal movement control unit 122 operates the head horizontal movement unit 202 in response to a command from the system controller 100. The head horizontal movement unit 202 includes a mechanism for horizontally moving the head unit 44 in the axial direction of the drawing drum 42 and a motor serving as a power source thereof. The head horizontal movement unit 202 moves the inkjet heads 46K, 46C, 46M, and 46Y between the drawing unit 40 and the maintenance unit 240.

The ink drying control unit 124 operates the ink drying unit 50 in response to a command from the system controller 100. The ink drying control unit 124 controls the temperature of the dry gas, the flow rate of the dry gas, the injection timing of the dry gas, and the like.

The paper discharge control unit 126 operates the integration unit 60 in response to a command from the system controller 100. When the integrating device 62 shown in FIG. 1 includes an elevating mechanism, the paper discharge control unit 126 controls the operation of the elevating mechanism according to the increase or decrease of the paper P. The stacking unit 60 may stack the normally printed paper P and the printing-failed paper P as they are in the paper transport order without distinguishing them, or select the paper P that failed to print. Paper P that has been normally printed and paper P that has failed to print may be stacked separately. The output control unit 126 may control the sorting of the normally printed paper P and the paper P determined to be a waste paper that failed to print.

The maintenance control unit 128 controls the operation of the maintenance unit 240 in response to a command from the system controller 100. The maintenance unit 240 is a processing unit that performs maintenance processing such as cleaning and / or capping for moisturizing the nozzle surfaces of the inkjet heads 46K, 46C, 46M, and 46Y. Examples of the maintenance process include pressurized purge, dummy jet, nozzle suction, nozzle surface wiping, or an appropriate combination thereof. "Dummy jet" is synonymous with preliminary discharge. In the maintenance unit 240, for example, a cap that covers the nozzle surfaces of the inkjet heads 46K, 46C, 46M, and 46Y, and a wiping member such as a web that wipes the nozzle surface are arranged.

The inkjet printing device 1A includes an operation unit 130, a display unit 132, a parameter storage unit 134, and a program storage unit 136.

The operation unit 130 includes an operation member such as an operation button, a keyboard, a mouse, and a touch panel, a voice input device, or an input device including an appropriate combination thereof. The information input via the operation unit 130 is sent to the system controller 100. The system controller 100 executes various processes according to the information input from the operation unit 130. The operation unit 130 may include a plurality of types of operation members. The illustration of the operating member is omitted. The information input via the operation unit 130 is sent to the system controller 100. The system controller 100 executes various processes according to the information sent from the operation unit 130.

The display unit 132 includes a display device (display) such as a liquid crystal panel. The display unit 132 can display various information such as various setting information of the device or abnormality information in response to a command from the system controller 100. A user interface is composed of an operation unit 130 and a display unit 132. The user can set various parameters and input and edit various information by using the operation unit 130 while observing the contents displayed on the screen of the display unit 132.

The parameter storage unit 134 stores various parameters used in the inkjet printing apparatus 1A. Various parameters stored in the parameter storage unit 134 are read out via the system controller 100 and set in each unit of the device.

The program storage unit 136 stores programs used in each unit of the inkjet printing apparatus 1A. Various programs stored in the program storage unit 136 are read out via the system controller 100 and executed in each unit of the device. The parameter storage unit 134 and the program storage unit 136 are configured by using a storage device such as a hard disk device and / or a semiconductor memory.

<< Example 1 of measures to avoid contact between the paper on which the paper floats and the recording head >>
FIG. 3 is a schematic view schematically showing a main part of the drawing unit 40 in the inkjet printing apparatus 1A. In FIG. 3, the same elements as those described in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted. FIG. 3 shows that the paper does not float and printing is normally performed. Each of the inkjet heads 46K, 46C, 46M, and 46Y is arranged at a printing position facing the drawing drum 42 during printing.

FIG. 4 is a schematic view showing a state in which the paper floats during printing and the rotation of the drawing drum 42 is stopped. In FIG. 4, the raised convex portion 210 of the paper float has a large amount of float to a level where contact cannot be avoided by the head retracting operation using the head raising / lowering portion 200 described in FIG. 2, for example. As shown in FIG. 4, when a paper float with a large amount of float occurs and the paper float is detected by the paper float sensor 45, the rotation of the drawing drum 42 is urgently stopped and the inkjet heads 46K and 46C are stopped. , 46M, 46Y are retracted to the maintenance position. The maintenance position is the position of the maintenance unit 240 described with reference to FIG. 2, which is a position away from the drawing drum 42 in the axial direction of the drawing drum 42. The maintenance position is a position not facing the peripheral surface of the drawing drum 42.

Since it takes time to resume printing in the contact avoidance measure according to the measure example 1 described with reference to FIG. 4, when the floating amount of the paper P is light, the contact avoidance measure as shown in the measure example 2 shown in FIG. 5 is used. Will be executed.

<< Example 2 of measures to avoid contact between the paper on which the paper floats and the recording head >>
FIG. 5 is an explanatory diagram schematically showing an outline of a measure example 2 of a contact prevention measure to be executed when a paper float occurs. (A) in FIG. 5 shows the state of FIG. In FIG. 5B, the drawing drum 42 is continuously rotated in a state where the paper floats with a slight amount of float, and each head is retracted upward so that the convex portion 210 of the paper float does not come into contact with the heads. It shows the situation.

When the amount of floating paper generated during printing is slight, each head is temporarily retracted upward at a position facing the drawing drum 42 without stopping the paper transport, and the floating paper is passed.

That is, when the paper floating is detected, the ink ejection from the head is stopped and the printing operation is temporarily interrupted, but the paper transport by the rotation of the drawing drum 42 is continued, and is shown in FIG. 5 (b). As described above, the heads are retracted upward in order from the inkjet head 46K on the upstream side in the paper transport direction in accordance with the movement of the convex portion 210 of the paper float accompanying the rotation of the drawing drum 42. Then, after the paper P in which the paper floats has passed under the head, the head is automatically returned from the retracted position to the printing position. FIG. 5C in FIG. 5 shows that the inkjet head 46K and the inkjet head 46K are in the process of returning to the printing position, and the inkjet head 46M is in the process of returning to the printing position.

In this way, after passing the paper P on which the paper floats have occurred, printing is automatically restarted. In FIG. 5, the arrow returning from (c) to (a) indicates that printing is restarted after the head is returned to the printing position. The operation of returning the head from the retracted position to the printing position and automatically restarting printing is called "automatic return". In the present specification, the term "return" may be used to mean restarting printing that has been suspended, that is, returning to the operation of printing.

When the contact avoidance measure of the measure example 2 is adopted, the "mild floating amount" means that the floating amount is relatively small to a level where contact can be avoided by the head retracting operation using the head raising / lowering portion 200. means. For example, the upper limit of the allowable float amount at a level that the paper float sensor 45 does not detect as "paper float" is set in advance as the first reference float amount h1, and the contact is made by the head retracting operation using the head elevating unit 200. The upper limit of the floating amount at a level that can avoid the above is set as the second reference floating amount h2. In this case, the case where the floating amount of the paper exceeds the first reference floating amount h1 and is equal to or less than the second reference floating amount h2 corresponds to "mild" paper floating. The first reference float amount h1 corresponds to the "allowable float amount". The second reference floating amount h2 corresponds to the "specified amount".

When the paper float sensor 45 detects a float amount exceeding the second reference float amount h2, the contact prevention measure according to the first measure described in FIG. 4 is executed, and the first reference float amount h1 or more is the second reference. When a float amount of the float amount h2 or less is detected, the contact avoidance measure according to the measure example 2 described with reference to FIG. 5 is executed.

The paper float sensor 45 may be configured to include a first sensor that detects a paper float that exceeds the first reference float amount h1 and a second sensor that detects a paper float that exceeds the second reference float amount h2. A configuration may be configured in which one sensor is used to perform the functions of the first sensor and the second sensor.

In the measure example 2, the time until the print return can be shortened as compared with the measure example 1, and the productivity can be improved. As illustrated in FIG. 5, in the case of a device configuration in which a plurality of recording heads are arranged side by side in the paper conveying direction and each recording head sequentially drops ink on the conveyed paper, the paper floats. When is detected, each recording head retracts upward at the same position (each printing position) in the paper transport direction on the paper, and each recording head is at the same position in the paper transport direction on the paper. By returning to the printing position, it is possible to further increase the productivity. The control of the paper floating avoidance operation according to the policy example 2 is called "paper floating avoidance control". Paper float avoidance control is an example of "media float avoidance control". The step in which the system controller 100 performs the paper float avoidance control of the measure example 2 is an example of the “medium float avoidance control step”.

<< Processing to determine the image to be printed when printing is resumed >>
In the present embodiment, the image printed on the paper when printing is automatically restarted after the paper floating is eliminated when the paper floating avoidance control is executed according to the measure example 2 is produced according to the printing type. Then, control for switching to an appropriate image is performed. For this control, the image printed on the paper when printing is resumed when the paper floating avoidance control is executed in the printing of the post-printing surface of variable printing is printed on the preprinted surface of the paper when printing is resumed. A process of changing to an image corresponding to the printed preprinted image according to the finished preprinted image is included.

The inkjet printing apparatus 1A is capable of variable printing and non-variable printing. Variable printing is a printing mode in which a different image is printed for each sheet. Non-variable printing is a printing mode in which a specified number of the same images are continuously printed. The specified number can be specified by the user as the number of prints. The inkjet printing device 1A illustrated in FIG. 1 is a single-sided printing device that prints one side of paper P. However, the paper on which the first side is printed is returned to the paper feed unit 10, and the second side is the back side of the first side. Double-sided printing is possible by performing additional printing on the surface. A double-sided printing device may be used instead of the single-sided printing device.

When double-sided printing is performed, of the first and second sides of the paper, there are a preprinted surface to be printed first and a postprinted surface to be printed on the back side of the paper on which the preprinted surface is printed. To do.

Therefore, as the classification of printing types, it is possible to classify into four types in total from the viewpoint of whether it is variable printing or non-variable printing and the viewpoint of whether it is a pre-printed surface or a post-printed surface. That is, there are four types of printing, including printing of the preprinted surface of non-variable printing, printing of the post-printing surface of non-variable printing, printing of the pre-printing surface of variable printing, and printing of the post-printing surface of variable printing. Print type is included. The single-sided printing of non-variable printing can be regarded as the printing mode of the pre-printed surface of non-variable printing. Single-sided printing of variable printing can be regarded as a printing mode of the preprinted surface of variable printing.

FIG. 6 shows an example of an image printed on each paper during normal printing without paper floating. The chart shown in FIG. 6 shows what kind of pattern images are shown for each of the four types of non-variable printing pre-printed surface, non-variable post-printed surface, variable-printed pre-printed surface, and variable-printed post-printed surface. It is a symbol indicating whether it will be printed. In FIG. 6, the images from the first sheet to the seventh sheet are shown as a part of continuous printing of a plurality of sheets.

As for the preprinted surface of non-variable printing, the same preprinted image A is printed from the first to the seventh sheet.

For the post-printing surface of non-variable printing, the same post-printing image a is printed from the first to the seventh sheets.

In the case of the preprinted surface of variable printing, the preprinted image A is printed on the first sheet, the preprinted image B on the second sheet, the preprinted image C on the third sheet, and the preprinted image D on the fourth sheet. A preprinted image E is printed on the eyes, a preprinted image F is printed on the sixth sheet, and a preprinted image G is printed on the seventh sheet.

In the case of the post-printing surface of variable printing, the image a is printed on the first sheet, the image b on the second sheet, the image c on the third sheet, the image d on the fourth sheet, the image e on the fifth sheet, and the sixth sheet. The image f and the image g are printed on the seventh sheet, respectively. The image a is a post-printed image that is a set with the pre-printed image A. The image b is a post-printed image that is a set with the pre-printed image B. The image c is a post-printed image that is a set with the pre-printed image C. The image d is a post-printed image that is a set with the pre-printed image D. The image e is a post-printed image that is a set with the pre-printed image E. The image f is a post-printed image that is a set with the pre-printed image F. The image g is a post-printed image that is a set with the pre-printed image G.

FIG. 7 shows an example of an image printed on each paper when the paper floats. Here, an example is shown in which the paper floats on the third sheet and printing is restarted on the fifth sheet. The notation method of the chart shown in FIG. 7 is the same as that in FIG.

In FIG. 7, in the case of the pre-printed surface of non-variable printing, the image to be printed on the fifth sheet of resuming printing is the same image A as the third sheet that failed to print due to the occurrence of paper floating. The same preprinted image A is printed on the fifth and subsequent sheets.

In the case of the post-printing surface of non-variable printing, the image to be printed on the fifth sheet of resuming printing is the same image a as the third sheet that failed to print due to the occurrence of paper floating. The same image a is printed on the fifth and subsequent sheets.

In the case of the preprinted surface of variable printing, the preprinted image A is printed on the first sheet, and the preprinted image B is printed on the second sheet. When printing of the preprinted image C fails on the 3rd sheet and printing is resumed from the 5th sheet, the image to be printed on the 5th sheet after resuming printing is printed due to the occurrence of the sheet floating. It is the same preprinted image C as the third failed image. After that, the preprinted image D is printed on the sixth sheet, and the preprinted image E is printed on the seventh sheet.

In the case of the post-printing surface of variable printing, the image a is printed on the first sheet and the image b is printed on the second sheet. When the paper floats on the 3rd sheet and the printing of the image c fails and the printing is restarted from the 5th sheet, the image to be printed on the 5th sheet of the resuming printing is changed to the 5th sheet preprinted image E. It is the corresponding image e. After that, the image f is printed on the sixth sheet, and the image g is printed on the seventh sheet.

<< Explanation of the process for determining the return image during variable printing >>
The image printed when printing is resumed (at the time of return) after the paper float avoidance control is executed and the paper float is eliminated is called a "return image". The return image in the example of FIG. 7 refers to the image printed on the fifth sheet.

As shown in FIG. 7, in the inkjet printing apparatus 1A of the present embodiment, an image (return image) to be printed when printing is resumed is prepared in the following three patterns.

[Pattern 1] In the case of non-variable printing, an image is prepared so that the same image is printed on all papers regardless of whether it is a preprinted surface or a postprinted surface.

[Pattern 2] In the case of variable printing and a preprinted surface, image data is prepared so that an image that fails to be printed due to the occurrence of paper floating is printed when printing is resumed.

[Pattern 3] In the case of variable printing and the post-printing surface, image data is prepared so that the corresponding image is printed at the time of resuming printing according to the printed image printed on the pre-printing surface.

That is, in the inkjet printing apparatus 1A according to the present embodiment, it is possible to switch what kind of image is printed as the return image at the time of resuming printing according to the printing types classified into the above three patterns.

FIG. 8 is a flowchart of a process for determining a return image in the case of variable printing. The flowchart shown in FIG. 8 is a process of determining what kind of image is to be printed when the head is moved to the retracted position and then returned to the printing position to resume printing due to the occurrence of paper floating. .. When the paper float occurs and the paper float sensor 45 detects the paper float, the return image determination process shown in FIG. 8 is started.

In step S12, the system controller 100 determines whether or not printing has been restored. If the print is not restored, the determination in step S12 becomes a NO determination, and the process proceeds to step S14.

In step S14, the system controller 100 determines whether or not the print area of the paper has been added. In the case of this embodiment, since sheet-fed paper is used, the addition of the “paper printing area” corresponds to the supply of new paper. That is, the system controller 100 determines whether or not new paper has been supplied to the drawing unit 40. When a new sheet arrives at the drawing unit 40, the determination in step S14 is a YES determination.

If the system controller 100 determines in the determination process of step S14 that a new paper print area has not been added, the system controller 100 returns to step S12. On the other hand, when it is determined in the determination process of step S14 that the paper is switched to a new sheet and the print area of the new sheet is added, the process proceeds to step S16.

In step S16, the system controller 100 determines whether the current job is printing the preprinted surface or printing the postprinted surface. When the system controller 100 determines in the determination process of step S16 that the preprinted surface is to be printed, the system controller 100 proceeds to step S18.

In step S18, the system controller 100 holds the current image at the time of printing interruption. In the example of FIG. 7, it corresponds to holding the image A.

On the other hand, if the system controller 100 determines that the post-printing surface is to be printed in the determination process of step S16 of FIG. 8, the process proceeds to step S20.

In step S20, the system controller 100 switches to the next image. That is, in the case of the post-printing surface, each time the paper is switched, the images are sequentially switched to prepare the image data for printing. In the example of FIG. 7, it corresponds to switching to the image d at the timing of switching to the fourth sheet of paper and switching to the image e at the timing of switching to the fifth sheet of paper. The process of step S20 shown in FIG. 8 is as follows: "The image printed on the post-printing surface of the medium when printing is resumed is printed according to the pre-printed image printed on the pre-printing surface of the medium when printing is resumed. This is an example of "step to change to an image corresponding to the preprinted image".

After the processing of step S18 or step S20, the process returns to step S12. The loop of steps S12 to S20 described above is repeated until printing is resumed.

When each head that has been retracted to the retracted position is returned to the printing position and printing is resumed, a YES determination is made in the determination process in step S12, and the flowchart of FIG. 8 ends.

In the case of printing on the preprinted surface, the image printed when printing is resumed is the current image held in step S18. In the case of printing on the post-printing surface, the image to be printed when printing is resumed is the next image switched and held in step S20.

According to the flowchart shown in FIG. 8, the return image is switched depending on whether the printing is on the pre-printed surface or the printed surface of the variable printing.

In the case of non-variable printing, the image to be printed has one pattern, and the image that should have been printed on the paper on which the paper floats has occurred and the image to be printed when printing is resumed are the same image. Therefore, in the case of non-variable printing, the image data for printing is retained during the printing interruption period due to the paper floating avoidance control, and the same image is printed when printing is resumed.

Non-variable printing and variable printing on the preprinted surface are common in that the image that was supposed to be printed on the paper on which the paper floats occurred and the image that is printed when printing is resumed are the same image. That is, in the case of non-variable printing and variable printing on the preprinted surface, the image data of the image that was supposed to be printed on the paper in which the paper floated is retained during the printing interruption period and printed when printing is resumed. It is common in that it is used as image data.

<< About variable printing >>
Variable printing is a printing mode in which an image different from the image printed on the immediately preceding paper is printed, and another image is printed on the next paper. Variable printing includes printing different images one by one from the beginning to the end of printing, or printing images in order from the first page to the last page like collation printing, and then again at the beginning. Includes those that repeat printing in order from the image on the page. The concept of "variable printing" includes collating printing.

FIG. 9 is an explanatory diagram showing an example of the printing order of collating printing. Here, an example of collating printing in the case of printing a plurality of copies of a 4-page image set is shown. The images are printed in the order of "Page02", "Page03", "Page04" from the image of "Page01" which is the first page of the image set, and after printing the image of "Page04" which is the last page, the first Repeat printing of each image in the same order from the image of "Page 01" in.

Note that variable printing is not limited to the mode of forming an image on a sheet-fed medium, but may also be a mode of forming an image on a continuous medium such as roll paper. In variable printing when a continuous medium is used, an image different from the image printed in the immediately preceding print area is printed for each of a plurality of print areas continuously arranged in the medium transport direction, and the next print area is printed. Is a printing form for printing another image.

<< Example of means for matching the image of the pre-printed surface and the image of the post-printed surface of variable printing >>
Image matching between the pre-printed surface and the post-printed surface is performed, for example, based on an image identification pattern printed on the pre-printed surface together with the pre-printed image. The image identification pattern is identification information for identifying a pattern of an image printed on a preprinted surface. The image identification pattern may be, for example, a barcode, a number, a letter, or a symbol, or an appropriate combination thereof.

An image identification pattern is determined according to the pattern of each image to be printed on the preprinted surface of variable printing, and the corresponding image identification pattern is preprinted when printing the preprinted image on the preprinted surface of each paper. Print on the side. For example, the inkjet printing device 1A according to the present embodiment uses at least one of the inkjet heads 46K, 46C, 46M, and 46Y of the drawing unit 40 to print an image identification pattern in a margin area outside the printed image area of the paper P. To do. The image identification pattern is not limited to the configuration in which at least one of the inkjet heads 46K, 46C, 46M, and 46Y is used for printing, and the image identification pattern is different in place of or in combination with the inkjet heads 46K, 46C, 46M, and 46Y. It may be attached to the paper P by using the recording head or other marking part of the above. The inkjet printing apparatus 1A may include a marking portion for attaching an image identification pattern to the paper P.

The inkjet printing device 1A includes an identification pattern reading unit as a means for reading an image identification pattern printed on paper P. The identification pattern reading unit reads the image identification pattern from the paper P on the paper transport path after printing the preprinted surface and before printing the postprinted surface.

The inkjet printing apparatus 1A identifies the image of the post-printing surface that is set with the image of the pre-printing surface based on the image identification pattern read through the identification pattern reading unit, and refers to the post-printing surface. Print an image that matches the preprinted image.

Further, for example, when paper floating occurs during printing on the preprinted surface and the image on the preprinted surface fails to be printed, the system controller 100 stores the number of sheets for which printing has failed, and this printing is performed. Based on the failure information, when printing the post-printing surface, control is performed so that the image is not printed on the corresponding printing failure paper. Then, with respect to the sheets before and after the sheet of printing failure, image matching of the pre-printed surface and the post-printed surface is performed based on the above-mentioned image identification pattern.

FIG. 10 is a conceptual diagram of a pre-printing process including printing of an image identification pattern. In FIG. 10, the printing result of the preprinted surface of each of the first to sixth sheets is schematically shown.

In FIG. 10, the preprinted image A and the image identification pattern 1 are printed on the preprinted surface of the first sheet of paper. The preprinted image B and the image identification pattern 2 are printed on the preprinted surface of the second sheet. The third and fourth sheets are sheets that failed to be printed due to the detection of paper floating. The pre-printed surfaces of the third and fourth sheets remain unprinted.

In FIG. 10, printing is restarted from the fifth sheet of paper. The image (preprinted image C) that was supposed to be printed on the third sheet and the image identification pattern 3 are printed on the preprinted surface of the fifth sheet. Further, the preprinted image D and the image identification pattern 4 are printed on the preprinted surface of the sixth sheet. The image identification patterns 1 to 4 shown in FIG. 10 are examples of image identification information.

FIG. 11 is a conceptual diagram of a post-printing process performed after the pre-printing process described with reference to FIG. In FIG. 11, the printing results of the first to sixth sheets are schematically shown. The post-printing process shown in FIG. 11 is an example in which the process shifts to the post-printing process including the third and fourth sheets of paper that failed to be printed in the pre-printing process described with reference to FIG.

In FIG. 11, a post-print image a corresponding to the pre-print image A is printed on the post-print surface of the first sheet of paper based on the reading result of the image identification pattern 1.

A post-print image b corresponding to the pre-print image B is printed on the post-print surface of the second sheet based on the reading result of the image identification pattern 2. Since the third and fourth sheets have failed to print on the pre-printed surface, respectively, the post-printed surface is not printed.

In FIG. 11, printing is restarted from the fifth sheet. When printing is resumed, the post-printed image corresponding to the pre-printed image is specified based on the image identification pattern printed on the pre-printed surface, and the post-printed image is printed on the post-printed surface. That is, a post-print image c corresponding to the pre-print image C is printed on the post-print surface of the fifth sheet based on the reading result of the image identification pattern 3. A post-print image d corresponding to the pre-print image D is printed on the post-print surface of the sixth sheet based on the reading result of the image identification pattern 4.

<< Main part configuration of inkjet printing device 1A >>
FIG. 12 shows a main part of the configuration of the inkjet printing apparatus 1A capable of carrying out the printing operation described with reference to FIGS. 10 and 11. In FIG. 12, the same elements as those described in FIG. 2 are designated by the same reference numerals, and the description thereof will be omitted. The inkjet head 46 shown in FIG. 12 represents each of the inkjet heads 46K, 46C, 46M, and 46Y arranged in the head unit 44 shown in FIG.

The head elevating unit 200 includes an elevating mechanism 212 and an elevating motor 214. The elevating mechanism 212 is a mechanism that supports the inkjet head 46 so that it can be moved up and down between the printing position and the retracted position. The elevating motor 214 is a power source for operating the elevating mechanism 212.

The inkjet printing device 1A includes a motor driver 216 for driving the elevating motor 214. The head elevating control unit 120 controls the elevating motor 214 via the motor driver 216. The motor driver 216 may be included in the head elevating control unit 120 or may be included in the head elevating unit 200.

The head horizontal movement unit 202 includes a horizontal movement mechanism 222 and a horizontal movement motor 224. The horizontal movement mechanism 222 is a mechanism unit that supports the inkjet head 46 so as to be horizontally movable between a position facing the drawing drum 42 and a maintenance position. The horizontal movement motor 224 is a power source for operating the horizontal movement mechanism 222.

The inkjet printing device 1A includes a motor driver 226 for driving the horizontal moving motor 224. The head horizontal movement control unit 122 controls the horizontal movement motor 224 via the motor driver 226. The motor driver 226 may be included in the head horizontal movement control unit 122, or may be included in the head horizontal movement unit 202.

The inkjet printing device 1A includes a paper sensor 250, an identification pattern reading unit 252, and a printing timing signal generation unit 254.

The paper sensor 250 is a sensor provided in the transport path of the paper P and detects the position of the paper P. The paper sensor 250 detects that the paper P has arrived and outputs a detection signal. The detection signal output from the paper sensor 250 is sent to the system controller 100. The system controller 100 can grasp the position of the paper P on the paper transport path based on the detection result of the paper sensor 250. The detection signal of the paper sensor 250 may be sent to the print timing signal generation unit 254.

The identification pattern reading unit 252 is a means for reading the image identification pattern printed on the preprinted surface of the paper P. The identification pattern reading unit 252 is configured by using, for example, a barcode reader, an imaging device, or a combination thereof. The identification pattern reading unit 252 is an example of the “identification information reading unit”.

The print timing signal generation unit 254 calculates the transfer position of the paper P conveyed by the drawing drum 42 based on the encoder signal from the encoder 206, and the printable position corresponding to each of the inkjet heads 46K, 46C, 46M, and 46Y. A print timing signal indicating the timing at which the paper P is passing is generated. For example, the print timing signal generation unit 254 sets the timing at which the paper P passes under the head as the low (L) level and the other timings as the high (H) level based on the encoder signal from the encoder 206. Generates and outputs a print timing signal. The print timing signal is also called a PageSync signal (page synchronization signal).

The print timing signal generation unit 254 changes the output form of the print timing signal according to the print type when the paper floats. When paper floating occurs during printing on the post-printing surface of variable printing, the print timing signal generation unit 254 switches between high (H) and low (L) at a timing synchronized with the transfer of paper P as usual. Outputs the print timing signal. That is, the print timing signal generation unit 254 continues to output the print timing signal for each paper P synchronized with the transfer of the paper P during the print interruption period due to the paper floating avoidance control in the case of printing on the post-print surface of variable printing. To do.

On the other hand, when paper floating occurs during printing on the preprinted surface of non-variable printing or variable printing, the print timing signal generation unit 254 synchronizes with the feeding of paper P until the paper floating is eliminated. Pause switching from high (H) to low (L). That is, the print timing signal generation unit 254 is a print timing signal for each paper that is synchronized with the paper transport during the print interruption period due to the paper floating avoidance control in the case of non-variable printing or printing of the preprinted surface of variable printing. Pauses the output of. When the paper floating is eliminated, the print timing signal generation unit 254 outputs a print timing signal that switches between high (H) and low (L) at a timing synchronized with the feeding of the paper P as usual.

The print timing signal (PageSync signal) generated by the print timing signal generation unit 254 is sent to the drawing control unit 118 and the image processing unit 106. The function of the print timing signal generation unit 254 may be included in the system controller 100.

<< Processing of image data >>
After detecting the paper float using the paper float sensor 45, it takes only a short period of time to actually move the head to the retracted position to avoid the paper float and return to printing. For example, it takes about 1 to several seconds for the head to be retracted to the retracted position and returned to printing. Therefore, as illustrated in the flowchart of FIG. 8, in order to switch the image according to the print type, the image is selected, re-transferred, and corrected by the image processing unit 106 from a higher-level system such as the host computer 300 when printing is resumed. If the processing or the like is performed from the beginning, it is assumed that the processing of the image data to be printed when printing is resumed may not be in time.

Therefore, in the inkjet printing apparatus 1A according to the present embodiment, the handling of the image data is performed in synchronization with the PageSync signal without stopping even when the paper floats. Then, the image data for printing that has been subjected to the correction processing and the like actually used for printing is conveyed according to the printing type (that is, according to the printed image at the time of restoration) when the paper floats. By switching the process of holding in the memory or discarding in synchronization with the above, the preparation of the restored image within a short period of time until the restoration of printing is realized.

As described above, there are three patterns [Pattern 1] to [Pattern 3] in the inkjet printing apparatus 1A for preparing an image (return image) to be printed when printing is resumed when the paper floating avoidance control is executed. .. Of these three patterns, in the case of pattern 1 and pattern 2, the image data for printing that has undergone the correction processing actually used for printing is stored in the memory in synchronization with the paper transfer when the paper floats. Realized by holding.

On the other hand, in the case of pattern 3, the image data for printing that has undergone the correction processing actually used for printing is discarded in synchronization with the paper transport when the paper floats, and the correction of the next image is performed. This is achieved by storing the image data for printing that has been processed or the like in the memory (updating the image data).

FIG. 13 is a block diagram showing an example of image data handling carried out in the inkjet printing apparatus 1A. In FIG. 13, the data processing process in the image processing unit 106 is described as a first correction process, a second correction process, and printing in order to roughly show that the data processing proceeds step by step in synchronization with the paper transfer. An example simplified to three processes of output image generation processing is shown. The first correction process includes, for example, a density correction process. The second correction process includes, for example, a ejection failure correction process for correcting an image defect caused by the ejection failure nozzle. The print output image generation process includes, for example, a halftone process for generating dot data.

The image processing unit 106 includes a first correction processing unit 262, a second correction processing unit 264, and a print output image generation processing unit 266.

Further, the storage areas of the memory 270 provided in the inkjet printing apparatus 1A include an unprocessed data storage area 272, a first correction processing data storage area 274, a second correction processing data storage area 276, and a print output image data storage. Includes region 278 and. The memory 270 may be the image memory 104 shown in FIG. 2, the RAM 100C, or a combination thereof. Further, a part or all of the storage area of the memory 270 may be included in the image processing unit 106.

The unprocessed data storage area 272 is an area for storing image data input to the inkjet printing apparatus 1A. The image data input to the inkjet printing apparatus 1A from the higher-level system may be, for example, image data represented in a PDF (Portable Document Format) file format. In the unprocessed data storage area 272, the image data in the unprocessed state before the processing by the image processing unit 106 is stored.

The image data stored in the unprocessed data storage area 272 is sent to the first correction processing unit 262. The first correction processing unit 262 performs the first correction processing on the image data acquired from the unprocessed data storage area 272. The first corrected image data generated by the first correction processing unit 262 is stored in the first correction processing data storage area 274.

The first correction processed image data stored in the first correction processing data storage area 274 is sent to the second correction processing unit 264. The second correction processing unit 264 performs the second correction processing on the image data acquired from the first correction processing data storage area 274. The second corrected image data generated by the second correction processing unit 264 is stored in the second correction processing data storage area 276.

The second corrected image data stored in the second corrected data storage area 276 is sent to the print output image generation processing unit 266. The print output image generation processing unit 266 generates the final print output image data from the image data acquired from the second correction processing data storage area 276. The print output image data generated by the print output image generation processing unit 266 is stored in the print output image data storage area 278. The ink ejection operation of each head is controlled based on the print output image data generated in this way. The print output image data storage area 278 is a storage area for storing image data for printing for which correction processing and the like have been completed. The print output image data storage area 278 is an example of "a storage unit for storing image data of an image printed on a medium using a recording head".

In the case of variable printing, new image data is sequentially input in synchronization with the paper transfer, and the first correction process, the second correction process, and the print output image generation process are performed in synchronization with the paper transfer. The image data processing progresses step by step in order. In the inkjet printing apparatus 1A of the present embodiment, the first correction process, the second correction process, and the print output image generation process proceed step by step in synchronization with the print timing signal.

When N represents an integer of 1 or more and the pattern of the image to be printed on the Nth sheet is expressed as an image (N), when the data of the image (N) is stored in the print output image data storage area 278, the second Image (N + 1) data is stored in the correction processing data storage area 276, image (N + 2) data is stored in the first correction processing data storage area 274, and image is stored in the unprocessed data storage area 272. The data of (N + 3) will be stored.

The step of holding the current image described in step S18 of FIG. 8 corresponds to holding the image data stored in the print output image data storage area 278 of FIG.

Further, in the step of switching to the next image described in step S20 of FIG. 8, the step discards the image data stored in the print output image data storage area 278 of FIG. 13 and stores the image data in the print output image data storage area 278. It corresponds to updating the image data to be stored, that is, storing the image data of the next image in the print output image data storage area 278.

《Timing chart for printing on the preprinted surface》
FIG. 14 is an example of a timing chart for variable printing and printing on the preprinted surface. The paper float occurrence notification signal shown in FIG. 14 changes from the low (L) level to the high (H) level when the paper float occurs, and changes from the high (H) level to the low (L) when the paper float is released. Become a level state. The timing at which the paper float is released is the timing after the convex portion of the paper float passes under the head.

The paper float generation notification signal may be generated by the system controller 100 or the print timing signal generation unit 254 based on the signal obtained from the paper float detection unit 208. The timing at which the paper float is released can be determined based on the timing at which the paper float is detected, the paper transport speed, and the position of the head in the paper transport direction.

The print timing signal (PageSync signal) switches from the high (H) level to the low (L) level at the timing of printing. Normally, the low (L) level is reached when the paper P is under the head. When paper floating occurs, the PageSync signal remains at the high (H) level until the paper floating is released during non-variable printing or printing on the preprinted surface of variable printing. Then, after the paper float is released, the PageSync signal returns to the normal output in which the high (H) level is switched to the low (L) level for each paper in synchronization with the paper transfer. On the other hand, in the printing of the post-printing surface of variable printing, the PageSync signal when the paper floats occurs switches from the high (H) level to the low (L) level for each paper in synchronization with the paper transport as usual ( (See FIG. 15).

The Jetting Trigger indicates the ejection operation timing for each nozzle of the inkjet head 46. The jetting trigger (Jetting Trigger) changes from a low (L) level to a high (H) level at the discharge operation timing.

The image data shown in FIG. 14 indicates print output image data for which necessary processing such as correction processing has been completed. As shown in FIG. 14, in the case of printing on the preprinted surface of variable printing, the printing interruption period of the paper floating avoidance control due to the occurrence of paper floating should have been printed on the paper in which the paper floating occurred (N). Image data is retained. As a result, the image printed when printing is resumed after the paper float is released becomes the same image (N) as the image (N) when the paper float occurs.

<< Timing chart for printing on the post-printing surface >>
FIG. 15 is an example of a timing chart for variable printing and printing on the post-printing surface. In the case of post-printing of variable printing, the print timing signal (PageSync) is generated as usual even after the paper floats, and the image data is sequentially processed in synchronization with the paper transport.

As shown in FIG. 15, in the case of printing on the post-printing surface of variable printing, the printing interruption period of the paper floating avoidance control due to the occurrence of paper floating is also synchronized with the printing timing signal, and the stepwise image processing is sequentially advanced. , The image data prepared in the print output image data storage area 278 of the memory 270 is sequentially updated. Therefore, the image printed at the time of returning to printing by releasing the paper floating after the printing is interrupted due to the occurrence of the paper floating is an image (N + 3) corresponding to the image of the preprinted surface that has already been printed.

<< Reprinting of pages that could not be printed due to paper floating >>
In the case of "variable printing and post-printing" shown in the bottom line of FIG. 7, the image set of "post-printing image c and pre-printing image C" that should have been printed on the third and fourth sheets was printed. The printed matter and the printed matter on which the image set of "post-printed image d and pre-printed image D" are printed are not obtained. Therefore, the system controller 100 stores the page of the image that could not be printed (cannot be printed) due to the occurrence of paper floating, and can print at the end when a series of printing of the specified number of prints is completed. You may want to control the printing of the missing image.

For example, in the case of "variable printing and post-printing" shown in the bottom line of FIG. 7, the third and fourth sheets have failed to be printed, and the specified number of printed sheets is 10 in total. , The image that was supposed to be printed on the 11th and 12th sheets (the image that could not be printed) and the image that was supposed to be printed on the 4th sheet (the image that could not be printed) Are printed respectively.

Further, for example, in the cases illustrated in FIGS. 10 and 11, when the printing of the third and fourth sheets has failed and the specified number of printed sheets is 10 in total, the 11th sheet is displayed. The process of printing the pre-printed image and the post-printed image that should have been printed on the third sheet, and printing the pre-printed image and the post-printed image that should have been printed on the fourth sheet on the twelfth sheet. Will be done.

<< Printing method using an inkjet printing device 1A >>
The operation of printing using the inkjet printing apparatus 1A can be grasped as a printing method or a printing control method for realizing the operation. For example, the printing method including the paper floating avoidance operation of the measure example 2 described with reference to FIG. 5 and the printing operation described with reference to FIGS. 7 to 11 is grasped as a print control method for realizing such an operation. You may.

The operations of the inkjet printing apparatus 1A described above include a medium transport step of transporting the paper P supported on the peripheral surface of the drawing drum 42 and a medium float detection step of detecting the float of the paper P transported by using the drawing drum 42. When the floating of the paper P is detected, the step of performing the medium floating avoidance control described with reference to FIG. 5, the example shown in the bottom row of the chart of FIG. 7, and the process shown in step S20 of FIG. Further, as in the example described with reference to FIG. 11, in the printing of the post-printing surface of variable printing, the image printed on the post-printing surface of the paper P when the printing of the medium floating avoidance control is restarted is printed on the paper P when the printing is restarted. It can be grasped as a printing method including a step of changing to an image corresponding to the printed preprinted image according to the finished preprinted image.

<< Hardware configuration of each processing unit and control unit >>
System controller 100, image processing unit 106, transfer control unit 110, paper feed control unit 112, processing liquid application control unit 114, processing liquid drying control unit 116, drawing control unit 118, head elevating control unit 120, described with reference to FIG. Head horizontal movement control unit 122, ink drying control unit 124, paper ejection control unit 126, maintenance control unit 128, print timing signal generation unit 254 described with reference to FIG. 12, and first correction processing unit 262 described with reference to FIG. The hardware structure of various control units such as the second correction processing unit 264 and the print output image generation processing unit 266 and the processing unit that executes processing is, for example, various processors as shown below. (Processor).

Various processors include CPUs (Central Processing Units) and FPGAs (Field Programmable Gate Arrays), which are general-purpose processors that execute programs and function as various processing units, and whose circuit configurations can be changed after manufacturing. A programmable logic device (PLD), a dedicated electric circuit which is a processor having a circuit configuration specially designed for executing a specific process such as an ASIC (Application Specific Integrated Circuit), and the like are included.

One processing unit may be composed of one of these various processors, or may be composed of two or more processors of the same type or different types. For example, one processing unit may be composed of a plurality of FPGAs or a combination of a CPU and an FPGA. Further, a plurality of processing units may be configured by one processor. As an example of configuring a plurality of processing units with one processor, first, one processor is configured by a combination of one or more CPUs and software, as represented by a computer such as a client or a server. There is a form in which the processor functions as a plurality of processing units. Secondly, as typified by System On Chip (SoC), there is a form in which a processor that realizes the functions of the entire system including a plurality of processing units with one IC (Integrated Circuit) chip is used. is there. As described above, the various processing units are configured by using one or more of the above-mentioned various processors as a hardware-like structure.

Further, the hardware structure of these various processors is, more specifically, an electric circuit (circuitry) in which circuit elements such as semiconductor elements are combined.

<< About the ejection method of the inkjet head >>
The ejector of the inkjet head includes a nozzle for discharging a liquid, a pressure chamber leading to the nozzle, and a discharge energy generating element for supplying discharge energy to the liquid in the pressure chamber. Regarding the discharge method of discharging droplets from the nozzle of the ejector, the means for generating discharge energy is not limited to the piezoelectric element, and various discharge energy generating elements such as a heat generating element and an electrostatic actuator can be applied. For example, a method of ejecting droplets by utilizing the pressure of film boiling due to heating of a liquid by a heat generating element can be adopted. A corresponding ejection energy generating element is provided in the flow path structure according to the ejection method of the inkjet head.

<< Advantages of the Inkjet Printing Device and Its Printing Control Method According to the Present Embodiment >>
(1) According to the present embodiment, when double-sided printing is performed by variable printing, even if the paper floating avoidance control is executed and printing is temporarily interrupted, the front and back images are automatically aligned after the paper floating is eliminated. It can be realized and printing can be resumed.

(2) According to the present embodiment, during the printing interruption period of the paper floating avoidance control, the image data of the image to be printed can be prepared at the time of resuming printing in synchronization with the paper transport, so that printing can be resumed in a short period of time. Is.

(3) According to the present embodiment, when paper floating occurs, it is possible to reduce the number of waste paper (paper that cannot be printed) required for continuous printing to resume printing, and to improve productivity. it can.

<< Modification 1 >>
The present invention can be applied not only to the inkjet printing apparatus 1A described with reference to FIG. 1 but also to various types of printing apparatus. For example, the present invention can be applied to a double-sided printing apparatus. The double-sided printing device includes a first drawing unit for printing the preprinted surface and a second drawing unit for printing the postprinted surface, and after printing the preprinted surface of the paper with the first drawing unit, the second drawing is performed. The paper is fed to the unit, and the post-printing surface of the paper is printed at the second drawing unit. Each of the first drawing unit and the second drawing unit may adopt the same configuration as the drawing unit 40 described with reference to FIG. Further, a reversing mechanism for reversing the front and back of the paper is provided between the first drawing unit and the second drawing unit of the double-sided printing apparatus.

<< Modification 2 >>
As described with reference to FIG. 7, regarding double-sided printing, the printing types include non-variable printing pre-printing surface printing, non-variable printing post-printing surface printing, variable printing pre-printing surface printing, and variable printing post-printing surface. There can be four types of printing. Of these four types, the alignment of the front and back images becomes a particular problem when resuming printing after the paper float is released in the case of printing on the post-printing surface of variable printing.

Both non-variable printing and printing on the preprinted surface of variable printing are images when printing is interrupted (images that should be printed on paper with paper floating) as images to be printed when printing is resumed after the paper floating is released. can do. Therefore, for the print type including at least one of non-variable printing and variable printing preprinted surface printing and at least two types of variable printing post-printed surface printing, the print type of the job being executed is set. Correspondingly, the control for switching the image to be printed when the printing of the paper floating avoidance control is restarted may be performed.

<< Modification 3 >>
In the above-described embodiment, the inkjet printing apparatus has been described as an example of a printing apparatus capable of variable printing and double-sided printing, but the present invention can be applied to various types of printing apparatus. For example, the present invention is also applied to a printing device that records an image using a thermal print head as a recording head, or a printing device that records an image using an LED (Light Emitting Diode) print head. Is possible.

<< Modification 4 >>
The configuration of the control unit including the system controller 100, the image processing unit 106, the print timing signal generation unit 254, and the drawing control unit 118 described with reference to FIGS. 2 and 12 is printing that controls the operation of the inkjet printing device 1A. It can be grasped as a control device.

<< About the medium >>
"Paper" is a general term for what is called by various terms such as recording paper, printing paper, recording medium, printing medium, printing medium, printed medium, image forming medium, image forming medium, image receiving medium, and ejection medium. The material and shape of the medium are not particularly limited, and various sheet bodies can be used regardless of the material and shape, such as seal paper, resin sheet, film, cloth, non-woven fabric, and the like. The medium is not limited to a sheet-fed medium, and may be a continuous medium such as continuous paper. Further, the sheet-fed medium is not limited to cut paper prepared in advance to a specified size, and may be obtained by cutting a continuous medium to a specified size at any time.

The concept of "multiple sheets" printing when using a continuous medium means that printing is performed multiple times on different areas of the continuous medium. Further, when a continuous medium is used, the inter-image area formed between the user image area and the user image area corresponds to a margin portion, and the inter-image area can be an area for printing a test chart for detecting defective nozzles. ..

<< About the medium transport mechanism >>
The medium transport mechanism for transporting the medium is not limited to the drum transport method, and various forms such as a suction belt transport method, a nip transport method, a chain transport method, and a pallet transport method can be adopted. When a continuous medium is used, a so-called roll-to-roll type transport mechanism such as a web transport method is used. When a continuous medium is used, the medium supporting surface may be the surface of a platen that supports the medium.

<< About terms >>
The term "printing device" includes the concept of terms such as a printing machine, a printer, a printing device, an image forming device, an image output device, or a drawing device. Further, the term "printing device" includes the concept of a printing system in which a plurality of devices are combined. "Printing" is used as a term that includes the meaning of recording, printing, printing, drawing, or image formation.

"Image" shall be interpreted in a broad sense, and includes color images, black-and-white images, single-color images, gradation images, uniform density (solid) images, and the like. "Image" is not limited to a photographic image, but is used as a comprehensive term including a pattern, characters, symbols, line art, mosaic pattern, color-coded pattern, various other patterns, or an appropriate combination thereof.

The term "recording head" is synonymous with terms such as print head, print head, print head, and drawing head, and is used for an inkjet head, an ink ejection head, a liquid ejection head, a droplet ejection head, or a droplet ejection head. Including the concept.

The term "orthogonal" or "vertical" as used herein refers to the case where the intersections are made at an angle of less than 90 ° or an angle of more than 90 ° and intersect at an angle of substantially 90 °. A mode in which the same action and effect as the above is generated is included. The term "parallel" as used herein includes aspects that are strictly non-parallel and can be regarded as substantially parallel to obtain substantially the same effects as in the case of parallel.

<< Application example of printing equipment >>
In the above embodiment, an inkjet printing device for graphic printing has been described as an example, but the scope of application of the present invention is not limited to this example. For example, a wiring drawing device that draws a wiring pattern of an electronic circuit, a manufacturing device for various devices, a resist printing device that uses a resin liquid as a functional liquid for ejection, a color filter manufacturing device, and a fine material that uses a material for material deposition. The present invention can be widely applied to an image forming apparatus for forming various shapes and patterns by using a liquid functional material (liquid) such as a microstructure forming apparatus for forming a structure.

<< Combination of control example and embodiment example >>
The various control examples and the technical matters of the embodiment described above can be used in combination as appropriate, or some matters can be replaced.

[Other]
In the embodiment of the present invention described above, the constituent requirements can be appropriately changed, added, or deleted without departing from the spirit of the present invention. The present invention is not limited to the embodiments described above, and many modifications can be made by a person having ordinary knowledge in an equivalent related field within the technical idea of the present invention.

1A Inkjet printing device 10 Paper feed unit 11 Transport system 12 Paper feed device 12A Paper feed stand 14 Feeder board 16 Paper feed drum 20 Treatment liquid application unit 22 Treatment liquid application drum 23 Gripper 24 Treatment liquid coating device 30 Treatment liquid drying unit 32 Processing Liquid drying drum 33 Gripper 34 Warm air blower 40 Drawing unit 42 Drawing drum 43 Gripper 44 Head unit 45 Paper floating sensor 46, 46K, 46C, 46M, 46Y Inkjet head 48 Image reader 50 Ink drying unit 60 Integration unit 62 Accumulator 62A Stacking tray 70 Chain gripper 71A 1st sprocket 71B 2nd sprocket 72 Chain 74 Gripper 80 Paper guide 82 1st paper guide 84 2nd paper guide 90 Heat drying processing unit 100 System controller 102 Communication unit 104 Image memory 106 Image processing unit 110 Transport Control unit 112 Paper feed control unit 114 Processing liquid application control unit 116 Processing liquid drying control unit 118 Drawing control unit 120 Head elevating control unit 122 Head horizontal movement control unit 124 Ink drying control unit 126 Paper discharge control unit 128 Maintenance control unit 130 Operation Unit 132 Display unit 134 Parameter storage unit 136 Program storage unit 200 Head elevating unit 202 Head horizontal movement unit 206 Encoder 208 Paper floating detection unit 210 Convex part 212 Elevating mechanism 214 Elevating motor 216 Motor driver 222 Horizontal movement mechanism 224 Horizontal movement motor 226 Motor Driver 240 Maintenance unit 250 Paper sensor 252 Identification pattern reading unit 254 Print timing signal generation unit 262 First correction processing unit 264 Second correction processing unit 266 Print output image generation processing unit 270 Memory 272 Unprocessed data storage area 274 First correction processing Data storage area 276 Second correction processing Data storage area 278 Print output image Data storage area 300 Host computer P Paper S12 to S20 Steps for determining the return image

Claims (18)

A medium transport unit having a medium support surface that supports the medium and transporting the medium supported by the medium support surface,
A recording head that forms an image on the medium that is conveyed using the medium transfer unit, and
A head elevating unit that moves the recording head with respect to the medium support surface at a position facing the medium support surface of the medium transport unit to change the distance between the medium support surface and the recording head.
A medium float detection unit, which is arranged at a position upstream of the recording head in the transport direction of the medium and detects the float of the medium transported by using the medium transport unit,
When the floating of the medium is detected by the medium floating detecting unit, the recording head is moved from the printing position facing the medium supporting surface of the medium conveying unit by using the head elevating unit, and the medium is more than the printing position. After retracting to a retracted position far from the support surface, continuing the transport of the medium using the medium transport section, temporarily suspending printing, and eliminating the floating of the medium, the head elevating section is lifted. A control unit that controls the media floating avoidance by returning the recording head from the retracted position to the printing position and restarting printing.
With
When the control unit executes the medium floating avoidance control in printing the post-printing surface of variable printing and restarts printing, the control unit prints an image printed on the post-printing surface of the medium at the time of resuming printing. A printing device that changes an image corresponding to the printed preprinted image according to the preprinted image printed on the preprinted surface of the medium. The printing device according to claim 1, wherein the control unit switches an image to be printed when printing is restarted in the medium floating avoidance control according to a print type of a job being executed. The printing apparatus according to claim 2, wherein the printing type includes at least one of non-variable printing and variable printing preprinted surface printing, and at least two types of variable printing post-printed surface printing. .. The printing apparatus according to claim 3, wherein the printing type includes three types: non-variable printing, printing of a pre-printed surface of variable printing, and printing of a post-printed surface of variable printing. In the control unit, when the print type of the job being executed is non-variable printing or printing of the preprinted surface of variable printing, the medium in which the medium floating occurs when the printing of the medium floating avoidance control is restarted is performed. The printing apparatus according to claim 3 or 4, which performs a process of printing an image that was supposed to be printed in. A storage unit for storing image data of an image printed on the medium using the recording head is provided.
When the medium floats, the control unit performs a process of holding the image data stored in the storage unit and the image data stored in the storage unit according to the print type. The printing apparatus according to any one of claims 2 to 5, which switches between a process of updating each print area of the medium in synchronization with the transfer of the medium. When the print type of the job being executed is non-variable printing or printing on the pre-printed surface of variable printing, the image data stored in the storage unit is retained during the medium floating avoidance control. The printing apparatus according to claim 6. When the print type of the job being executed is printing on the post-printing surface of variable printing, the image data stored in the storage unit is stored for each print area of the medium during the medium floating avoidance control. The printing apparatus according to claim 6 or 7, wherein the image to be printed on the post-printing surface of the medium at the time of resuming printing is changed to an image corresponding to the printed pre-printed image by updating to. A print timing signal generation unit that generates a print timing signal corresponding to a print area of the medium in synchronization with the transfer of the medium by the medium transfer unit is provided.
The print timing signal generation unit is used for each print area of the medium that is synchronized with the transfer of the medium during the print interruption period due to the medium floating avoidance control in the case of non-variable printing or printing of the preprinted surface of variable printing. The printing apparatus according to any one of claims 3 to 8, wherein the output of the printing timing signal is suspended. The print timing signal generation unit receives the print timing signal for each print area of the medium that is synchronized with the transfer of the medium during the print interruption period due to the medium floating avoidance control in the case of printing on the post-print surface of variable printing. The printing apparatus according to claim 9, wherein the output is continued. A storage unit for storing image data of an image printed on the medium using the recording head is provided.
When the control unit executes the medium floating avoidance control in printing the post-printing surface of variable printing, the control unit transmits the image data stored in the storage unit to the print area of the medium in synchronization with the transfer of the medium. The printing apparatus according to claim 1, which is updated every time. A print timing signal generation unit that generates a print timing signal corresponding to a print area of the medium in synchronization with the transfer of the medium by the medium transfer unit is provided.
The print timing signal generation unit receives the print timing signal for each print area of the medium that is synchronized with the transfer of the medium during the print interruption period due to the medium floating avoidance control in the case of printing on the post-print surface of variable printing. The printing apparatus according to claim 1 or 11, wherein the output is continued. The method according to any one of claims 1 to 12, wherein the control unit performs a process of printing an image that could not be printed due to the execution of the medium floating avoidance control after a series of printing according to a job is completed. Printing equipment. An identification information reading unit for reading the image identification information attached to the medium for identifying the preprinted image printed on the preprinted surface of the medium is provided.
The printing according to any one of claims 1 to 13, wherein the control unit determines an image to be printed on the post-printing surface of the medium based on the image identification information read by the identification information reading unit. apparatus. The printing apparatus according to any one of claims 1 to 14, wherein the recording head is an inkjet head. The medium float detection unit is
A floating amount of the medium that exceeds a preset allowable floating amount and is equal to or less than a specified amount is detected.
Any of claims 1 to 15, wherein the control unit executes the medium floating avoidance control when the floating of the medium with a floating amount exceeding the allowable floating amount and equal to or less than the specified amount is detected. The printing apparatus according to paragraph 1. The printing apparatus according to claim 16, wherein when a floating amount exceeding the specified amount occurs, the transport of the medium using the medium transport unit is stopped. It is a printing method that performs double-sided printing using a printing device capable of variable printing.
A medium transporting step of transporting the medium supported on the medium supporting surface by using a medium transporting unit having a medium supporting surface for supporting the medium.
A medium floating detection step for detecting the floating of the medium conveyed by using the medium conveying unit, and
When the floating of the medium is detected by the medium floating detection step, the recording head of the printing apparatus is moved with respect to the medium supporting surface at a position facing the medium supporting surface of the medium conveying section to move the medium. Using the head elevating part that changes the distance between the support surface and the recording head, the recording head is retracted from the printing position to a retracted position that is farther from the media support surface than the printing position. , The medium that continues the transfer of the medium using the medium transfer unit, temporarily suspends printing, returns the recording head from the retracted position to the printing position, and resumes printing after the floating of the medium is resolved. Steps to control floating avoidance and
In the printing of the post-printing surface of variable printing, the image printed on the post-printing surface of the medium when the printing is restarted by executing the medium floating avoidance control is printed on the pre-printing of the medium when the printing is restarted. A step of changing to an image corresponding to the printed preprinted image according to the preprinted image printed on the surface, and
Printing methods including.

Images