JP2019130840A - Double-sided printing system - Google Patents

Abstract

To improve productivity.SOLUTION: A double-sided printing system 1 performs double-sided printing by use of: an upstream side printing device 10 which executes printing processing by discharging an ink from an ink jet head unit 134 onto one surface of a sheet which is transported on a transport path; an intermediate reversing device 20 which reverses the front and rear of the sheet; and a downstream side printing device 30 which executes printing processing by discharging an ink from an ink jet head unit 334 onto the other surface of the sheet of which the front and rear are reversed by the intermediate reversing device 20. In this system, a job allocation part 43 allocates front face image data and rear face image data, which are included in a double-sided printing job, respectively to either the upstream side printing device 10 or the downstream side printing device 30 so as to reduce a difference between a temperature Ti of the ink jet head unit 134 and a temperature of the ink jet head unit 334.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a duplex printing system that improves productivity by appropriately assigning image data to be printed to an image forming unit.

  Conventionally, a circulation conveyance path including a sheet reversing path has been provided, and printing is performed on one side of a sheet fed from a sheet feeding table, and the sheet printed on this one side is conveyed on the sheet reversing path. There is a double-sided printing apparatus that performs double-sided printing by reversing the front and back and performing printing on the other side (for example, Patent Document 1).

  In such a double-sided printing apparatus, the paper fed from the paper feed tray and the paper that has been turned upside down by the paper reversing path are alternately conveyed, so the printing time is longer than when printing on one side. It was.

  Therefore, as in Patent Document 2, the first image forming unit and the second image forming unit are arranged in series, and the sheet printed on one side by the first image forming unit is turned upside down by a reversing device. A technology related to a tandem inkjet recording apparatus that performs printing on the other surface by a two-image forming unit is disclosed.

JP 2014-91304 A JP 2011-51342 A

  Here, the ink used in the inkjet printing apparatus has a temperature characteristic in which the viscosity changes depending on temperature conditions, such that the viscosity is high at a low temperature and the viscosity is low at a high temperature. Depending on the viscosity of the ink, the size of the ink droplets and the discharge speed may vary, or the amount of mist generated by the discharge may increase, making it impossible to obtain a high-definition printed matter. . Therefore, it is necessary to adjust the temperature of the ink so as to have an appropriate viscosity.

  In the tandem inkjet recording apparatus described in Patent Document 2, when one of the first image forming unit and the second image forming unit becomes unusable due to, for example, an increase in the ink temperature, the conveyance for circulation is performed. Printing is continued using an image forming unit that can be used via a path.

  As described above, printing is continued until one of the image forming units becomes unusable, and when one of the image forming units becomes unusable, printing is continued in the remaining image forming units, so that productivity is lowered.

  For example, when form printing, in which letters are printed on the front side and photographic advertisements are printed in color on the back side, is continuously executed in units of tens of thousands of sheets, the image forming unit that prints the back side increases the temperature of the inkjet head. Along with this, the ink temperature tends to rise.

  Therefore, although the image forming unit printing the front surface can still continue printing sufficiently, it becomes unusable due to the rise in ink temperature of the image forming unit printing the back side. Will be reduced.

  SUMMARY An advantage of some aspects of the invention is that it provides a duplex printing system that improves productivity by appropriately assigning image data to be printed to an image forming unit.

In order to achieve the above object, the feature of the duplex printing system according to the present invention is as follows:
An upstream printing apparatus that performs a printing process on a conveyed sheet by a first printing unit, an intermediate reversing apparatus that reverses the front and back of the sheet that has been printed by the upstream printing apparatus, and the intermediate reversing apparatus A double-sided printing system that performs double-sided printing on the paper whose front and back are reversed by using a downstream printing device that executes printing processing by a second printing unit,
In order to reduce the difference between the temperature of the first printing unit and the temperature of the second printing unit, the front side image data and the back side image data included in the double-sided printing job are respectively sent to the upstream printing apparatus or the downstream side. Job assignment means for assigning to any of the printing devices;
It is in having.

  According to the feature of the duplex printing system according to the present invention, productivity can be improved by appropriately assigning image data to be printed to an image forming unit.

1 is a schematic configuration diagram of a double-sided printing system according to a first embodiment of the present invention. It is a block diagram which shows the function of the double-sided printing system which concerns on 1st Embodiment of this invention. It is the flowchart which showed the processing content of the mode selection process in the double-sided printing system which concerns on 1st Embodiment of this invention. 6 is a flowchart showing the processing content of a printing rate calculation mode execution process when a printing rate calculation mode is set in the mode selection process in the duplex printing system according to the first embodiment of the present invention. 6 is a flowchart showing the processing contents of final inversion control of the final inversion device when a printing rate calculation mode is set in the mode selection processing in the duplex printing system according to the first embodiment of the present invention. It is explanatory drawing which showed the processing content of the predetermined space | interval switching mode execution process in case the predetermined space | interval switching mode is set in the mode selection process in the duplex printing system which concerns on 1st Embodiment of this invention. It is a state transition diagram showing the processing content of the temperature measurement mode execution process when the temperature measurement mode is set in the mode selection process in the duplex printing system according to the first embodiment of the present invention.

  Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.

(Schematic configuration of the duplex printing system)
First, the configuration of the double-sided printing system 1 according to the first embodiment of the present invention will be described. The duplex printing system 1 receives a duplex printing job transmitted from a terminal device such as a PC, and prints an image on both sides of a sheet as a printing medium based on the received printing job.

  The double-sided printing system 1 according to the present embodiment is a tandem printing system in which two printing apparatuses each performing predetermined printing processing on a sheet are arranged in series along a sheet conveyance path.

  FIG. 1 is a schematic configuration diagram of a duplex printing system 1 according to the first embodiment of the present invention. As shown in FIG. 1, the duplex printing system 1 according to the first embodiment includes an upstream printing device 10, an intermediate reversing device 20, a downstream printing device 30, a final reversing device 50, and an overall control device 40. Is provided.

  In the present embodiment, the predetermined printing process is a process for completing the printing of the requested image, and the upstream printing apparatus 10 executes the predetermined printing process on one side of the paper, The downstream printing apparatus 30 performs a printing process on the other side of the paper. The predetermined printing process includes monochrome printing or color printing process.

  In FIG. 1, a path indicated by a double line or a thick line is a conveyance path through which the sheet is conveyed. The conveyance path includes a conveyance path R1 in the upstream printing apparatus 10, a conveyance path R2 in the intermediate reversing apparatus 20, a conveyance path R3 in the downstream printing apparatus 30, and conveyance paths R4 and R5 in the final reversing apparatus 50. .

  As shown in FIG. 1, the upstream printing apparatus 10 includes a side paper feed unit 110, an internal paper feed unit 120, a printing unit 130, a paper discharge unit 140, and a reversing unit 150.

  The side paper feed unit 110 includes a paper feed tray 111 on which the paper P is stacked, a pickup roller 112 that transports only the uppermost paper P from the paper feed base 111 onto the paper feed transport path FR1, and the pickup roller 112. And a registration roller 114 for carrying the skew correction by temporarily slackening the paper P conveyed by, and then conveying it onto the circulation conveyance path CR1.

  The internal paper feed unit 120 includes paper feed trays 121a to 121d on which the paper P is stacked, and pickup rollers 122a to 122d that transport only the uppermost paper P from the paper feed stands 121a to 121d onto the paper feed transport path FR1. And.

  Further, an intermediate conveyance roller 123 that conveys the paper P conveyed from the pickup rollers 122a to 122d onto the paper feed conveyance path FR1 to the registration roller 114 on the paper feed conveyance path FR1 is provided.

  In this way, the sheet P is conveyed to the registration roller 114 from the pickup roller 112 of the side paper feeding unit 110 and the intermediate conveyance roller 123 of the internal paper feeding unit 120, and also from a conveyance roller 153 of the reversing unit 150 described later. The paper P is transported, and after the transported paper P is slackened, skew correction is performed, and then transported onto the circulation transport path CR1.

  Therefore, a junction point where the conveyance path of the fed paper P and the path through which the paper on which one side is printed is circulated is merged exists in front of the registration roller 114 in the conveyance direction. . Based on this merging point, the path on the sheet feeding mechanism side is referred to as a sheet feeding conveyance path FR1, and the other path is referred to as a circulation conveyance path CR1.

  The printing unit 130 includes an inkjet head unit 134 in which a plurality of print heads are incorporated, and an annular conveyance belt 133 provided on the opposite surface of the inkjet head unit 134, and is a sheet fed by a registration roller 114. P is printed on the paper P by the ink ejected from the inkjet head unit 134 while being transported at a predetermined transport speed. Further, a thermometer 137 for measuring the temperature of the ink inside the inkjet head unit 134 is provided.

  The paper P printed by the printing unit 130 is conveyed on the circulation conveyance path CR1 in the housing by a conveyance roller or the like disposed on the circulation conveyance path CR1. A switching mechanism 135 is provided on the circulation conveyance path CR1 to switch between guiding the sheet P conveyed on the circulation conveyance path CR1 to the intermediate reversing device 20 or recirculating on the circulation conveyance path CR1. . Further, a switching mechanism 143 is provided for switching between guiding the sheet P conveyed on the circulation conveyance path CR1 to the paper discharge unit 140 or recirculating on the circulation conveyance path CR1.

  The paper discharge unit 140 includes a face-down paper discharge table 141 having a tray shape protruding from the casing of the upstream printing apparatus 10. Then, the paper P guided to the paper discharge unit 140 by the switching mechanism 143 is conveyed and stacked on the face-down paper discharge table 141.

  The reversing unit 150 includes a reversing table 151 for reversing the paper P.

  The sheet P guided to the reversing unit 150 by the switching mechanism 143 is transported from the circulation transport path CR1 to the reversing table 151, and after a predetermined time, is transported from the reversing table 151 to the circulation transport path CR1. The front and back are reversed with respect to CR1. Then, the sheet P with the front and back reversed is conveyed toward the printing unit 130 on the circulation conveyance path CR1.

  The apparatus control unit 160 is configured to perform a side sheet feeding unit 110, an internal sheet feeding unit 120, a printing unit 130, and a sheet discharging unit based on front surface image data or back surface image data transmitted from the overall control device 40 described later. 140 and the reversing unit 150 are controlled to print an image on the paper P, and the printed paper P is conveyed to the intermediate reversing device 20 or discharged to the face-down paper discharge table 141.

  The intermediate reversing device 20 is disposed on the downstream side in the transport direction of the upstream printing device 10. The intermediate reversing device 20 reverses the front and back of the paper P carried out from the upstream printing device 10 and then conveys it to the downstream printing device 30. The intermediate reversing device 20 includes a transport unit 210 and a device control unit 260.

  The transport unit 210 includes transport rollers 211, 212, and 213, and transports the paper P along the transport path R2 by driving the transport rollers 211, 212, and 213.

  The device control unit 260 controls various functions of the intermediate inverting device 20. As a result, the paper P is transported on the transport path R <b> 2, and when the paper P hits the reversal plate 221, the transport roller 212 is reversely rotated to be reversed and transported to the downstream printing apparatus 30 by the transport roller 213.

  The downstream printing apparatus 30 includes an intermediate conveyance unit 310, an internal paper feeding unit 320, a printing unit 330, a paper discharge unit 340, and a reversing unit 350.

  The intermediate transport unit 310 temporarily loosens the transport roller 312 that transports the paper P whose front and back are reversed by the intermediate reversing device 20 onto the paper feed transport path FR3 and the paper P transported by the transport roller 312. Thus, after performing skew correction, there is provided a registration roller 314 that is conveyed onto the circulation conveyance path CR3.

  The internal paper feed unit 320 includes paper feed bases 321a to 321d on which the paper P is stacked, and pickup rollers 322a to 322d for transporting only the uppermost paper P from the paper feed base 321a onto the paper feed transport path FR3. I have.

  Then, an intermediate transport roller 323 is provided that transports the paper P transported from the pickup rollers 322a to 322d onto the paper feed transport path FR3 to the registration roller 314 on the paper feed transport path FR3.

  In this way, the paper P is transported to the registration rollers 314 from the transport roller 312 of the intermediate transport unit 310 and the intermediate transport roller 323 of the internal paper feed unit 320, and also from the transport roller 353 of the reversing unit 350 described later. P is transported, and after the transported paper P is slackened, skew correction is performed and then transported onto the circulation transport path CR3.

  Therefore, a junction point where the conveyance path of the fed paper P and the path through which the paper on which one side is printed is circulated is merged exists in front of the registration roller 314 in the conveyance direction. . Based on this merging point, the path on the sheet feeding mechanism side is referred to as a sheet feeding conveyance path FR3, and the other path is referred to as a circulation conveyance path CR3. In the downstream printing apparatus 30, the paper P is transported from the intermediate reversing apparatus 20, so the internal paper feed unit 320 and the paper feed transport path FR <b> 3 are not necessarily provided, and are used when printing only one side. .

  The printing unit 330 includes an ink jet head unit 334 in which a plurality of print heads are incorporated, and an annular conveyance belt 333 provided on the opposite surface of the ink jet head unit 334, and paper fed by a registration roller 314. P is printed on the paper P by ink ejected from the inkjet head unit 334 while being transported at a predetermined transport speed. Further, a thermometer 337 for measuring the temperature of the ink inside the inkjet head unit 334 is provided.

  The paper P printed by the printing unit 330 is conveyed on the circulation conveyance path CR3 in the housing by a conveyance roller or the like disposed on the circulation conveyance path CR3. On the circulation conveyance path CR3, a switching mechanism 335 is provided for switching whether the paper P conveyed on the circulation conveyance path CR3 is guided to the final reversing device 50 or recirculated on the circulation conveyance path CR3. Yes. In addition, a switching mechanism 343 that switches between guiding the sheet P conveyed on the circulation conveyance path CR3 to the paper discharge unit 340 or recirculating on the circulation conveyance path CR3 is provided.

  The paper discharge unit 340 includes a face-down paper discharge table 341 having a tray shape protruding from the casing of the downstream printing apparatus 30. Then, the paper P guided to the paper discharge unit 340 by the switching mechanism 343 is conveyed and stacked on the face-down paper discharge table 341.

  The reversing unit 350 includes a reversing table 351 for reversing the paper P.

  The sheet P guided to the reversing unit 350 by the switching mechanism 343 is transported from the circulation transport path CR3 to the reversing table 351, and after a predetermined time has passed, is transported from the reversing table 351 to the circulation transport path CR3. The front and back are reversed with respect to CR3. Then, the paper P whose front and back are reversed is conveyed toward the printing unit 330 on the circulation conveyance path CR3.

  The device control unit 360 is based on the front image data or the back image data sent from the overall control device 40 to be described later, the intermediate transport unit 310, the internal paper feed unit 320, the printing unit 330, and the paper discharge unit 340. Then, the reversing unit 350 is controlled to print an image on the paper P, and the printed paper P is conveyed to the final reversing device 50 or discharged to the face-down paper discharge tray 341.

  The final reversing device 50 is disposed on the downstream side in the transport direction of the downstream printing device 30. The final reversing device 50 includes a transport unit 510 and a device control unit 560.

  The transport unit 510 includes transport rollers 511, 512, and 513, and the paper P is transported by driving the respective transport rollers. A switching mechanism 514 is provided on the downstream side of the transport roller 511 for switching whether the paper P transported by the transport roller 511 is guided to the reverse path R4 or directly to the paper discharge path R5.

  The paper P guided to the reversing path R4 is conveyed to the paper discharge table 345 after the front and back are reversed. The sheet P guided directly to the sheet discharge path R5 is conveyed to the sheet discharge table 345 without being inverted.

  The device control unit 560 controls various functions of the final reversing device 50. For example, when the switching mechanism 514 is switched and the paper P is transported on the reversing path R 4, the paper P hits the reversal plate 521, and the transport roller 512 rotates reversely so that the front and back are reversed. Be transported.

  The overall control device 40 controls various functions in the duplex printing system 1. The overall control device 40 controls the upstream printing device 10, the intermediate reversing device 20, the downstream printing device 30, and the final reversing device 50 so as to execute a printing process based on the print job. To do.

(Configuration of overall control device 40)
Next, the configuration of the overall control device 40 will be specifically described. FIG. 2 is a block diagram illustrating functions of the duplex printing system 1.

  As shown in FIG. 2, the overall control device 40 includes a job reception unit 41, a mode selection unit 42, a job allocation unit 43, a storage unit 44, and a communication unit 47.

  The job receiving unit 41 transmits / receives information to / from the terminal device 100. Specifically, the job receiving unit 41 receives a print job (double-sided print job) from the terminal device 100 used by the user. The communication here includes, for example, an intranet (in-house network), a home network, and the like, and may be either wired communication or wireless communication.

  The mode selection unit 42 selects any one of a printing rate calculation mode, a predetermined interval switching mode, a temperature measurement mode, and a normal mode.

  The printing rate calculation mode is a mode in which the upstream printing device 10 or the downstream printing device 30 is assigned based on the printing rates of the front surface image data and the back surface image data included in the duplex printing job.

  The predetermined interval switching mode is a mode in which the front surface image data and the back surface image data are alternately assigned to either the upstream printing device 10 or the downstream printing device 30 in turn, for example, every 10 pages.

  In the temperature measurement mode, the temperature of the ink inside the inkjet head unit 134 detected by the thermometer 137 or the temperature of the ink inside the inkjet head unit 334 detected by the thermometer 337 exceeds the near temperature Th1. In this mode, the upstream printing apparatus 10 or the downstream printing apparatus 30 is switched with respect to the front surface image data and the back surface image data. Here, the near temperature Th1 is a threshold temperature set lower than the upper limit temperature Th2 at which the apparatus is to be stopped.

  The job allocation unit 43 reduces the difference between the temperature of the inkjet head unit 134 and the temperature of the inkjet head unit 134 based on the printing rate calculation mode, the predetermined interval switching mode, and the temperature measurement mode selected by the mode selection unit 42. As described above, the front surface image data and the back surface image data included in the duplex printing job are assigned to either the upstream printing apparatus 10 or the downstream printing apparatus 30, respectively.

  The storage unit 44 is configured by a hard disk, a memory, or the like, and stores the received double-sided print job and various information used for processing of the overall control device 40.

  The communication unit 47 transmits and receives various types of information to and from the upstream printing apparatus 10, the intermediate reversing apparatus 20, the downstream printing apparatus 30, and the final reversing apparatus 50.

<Operation of duplex printing system 1>
Next, the operation of the double-sided printing system 1 which is an embodiment of the present invention will be described.

≪Mode selection process≫
FIG. 3 is a flowchart showing the contents of the mode selection process in the duplex printing system 1.

  When the overall control device 40 receives a double-sided print job from the terminal device 100 (step S101; YES), the mode selection unit 42 determines whether the double-sided print job includes a large number of pages (step S103). For example, the page number threshold is set to 10,000 (pages) in advance, and it is determined whether or not the double-sided print job includes data with a page number exceeding 10,000 (pages).

  If the double-sided print job does not include a large number of pages (step S103; NO), the mode selection unit 42 sets the normal mode because there is no need to consider the temperature rise of the inkjet head unit (step S105). When this normal mode is set, for example, the upstream printing apparatus 10 prints one side of the paper P based on the surface image data without switching the upstream printing apparatus 10 or the downstream printing apparatus 30, and downstream The side printing apparatus 30 prints the other side of the paper P based on the back side image data.

  When the duplex printing job includes a large number of pages (step S103; YES), the mode selection unit 42 determines whether or not a fixed format condition is satisfied (step S107). Here, the fixed format condition is, for example, as in the form data, the variation in the difference between the printing rate of the front surface image data for each page of both sides and the printing rate of the back side image data is small, and The condition that the average of the difference between the printing rate of the front surface image data and the printing rate of the back surface image data is equal to or greater than a predetermined average printing rate threshold value. For this reason, information indicating that the data is form data is stored in advance in the header of the duplex print job, and the mode selection unit 42 may determine that the fixed format condition is satisfied when this information is included. Alternatively, it may be determined whether or not the fixed format condition is satisfied based on the front surface image data and the back surface image data included in the duplex printing job. Note that one page on both sides refers to a set of one page of front image data and one page of back image data.

  If it is determined that the fixed format condition is satisfied (step S107; YES), since the variation in the difference between the printing rate of the front surface image data and the printing rate of the back surface image data for each page on both sides is small, the temperature of the inkjet head unit 134 And the temperature of the inkjet head unit 134 are likely to rise at a constant temperature gradient. In addition, since the average of the difference between the printing rate of the front surface image data and the printing rate of the back surface image data for each page on both sides is equal to or greater than a predetermined value, the temperature gradients are different from each other, based on the image data with the higher printing rate. The temperature of the inkjet head unit that is printing is likely to rise.

  Therefore, the mode selection unit 42 sets a predetermined interval switching mode (step S109).

  When it is determined that the fixed format condition is not satisfied (step S107; NO), the mode selection unit 42 determines whether or not the job data size of the duplex printing job is equal to or smaller than a predetermined value (step S111).

  If the job data size is equal to or smaller than the predetermined value (step S111; YES), even if the printing rate of the front surface image data and the printing rate of the back surface image data are calculated, it can be assumed that the calculation load is small. Then, the printing rate calculation mode is set (step S113).

  On the other hand, when the job data size exceeds a predetermined value (step S111; NO), calculating the printing rate of the front surface image data and the printing rate of the back surface image data has a large calculation load and requires a considerable time to start printing. Then, since it can be assumed, the mode selection part 42 sets temperature measurement mode (step S115).

≪Print rate calculation mode execution processing≫
FIG. 4 is a flowchart showing the processing content of the printing rate calculation mode execution process when the printing rate calculation mode is set in the mode selection process.

  When the printing rate calculation mode is set, the job allocation unit 43 initializes the variable n (step S201), and then prints the printing rate A (n) of the nth block front image data and the nth block backside image data. The printing rate B (n) is calculated (step S203). Here, the block refers to a unit divided by a predetermined number of pages, such as double-sided 10 (page).

  Then, the job allocation unit 43 calculates AT (n) indicating the integrated value of A (n) up to n blocks and calculates BT (n) indicating the integrated value of B (n) up to n blocks. (Step S205).

  If n exceeds the total number of blocks N, the process is terminated (step S207; YES). If n does not exceed the total number of blocks N, the job allocation unit 43 prints the print rate integrated value AT (n). Whether or not the absolute value of the difference between the print rate integrated value BT (n) exceeds a predetermined print rate difference threshold Thc is determined (step S209).

  If it is determined that the printing rate difference threshold value Thc is equal to or less than the printing rate difference threshold Thc (step S209; NO), it can be predicted that there is not much difference between the temperature increase of the inkjet head unit 134 and the temperature increase of the inkjet head unit 134. Alternatively, n is incremented without switching the downstream printing apparatus 30 (step S219), and the process proceeds to step S203.

  On the other hand, if it is determined that the printing rate difference threshold Thc has been exceeded (step S209; YES), the temperature of the inkjet head unit that is printing based on the image data with the higher printing rate is likely to rise.

  Therefore, the job allocation unit 43 turns on the flag (step S211) and switches the upstream printing apparatus 10 or the downstream printing apparatus 30 with respect to the front surface image data and the back surface image data (step S213). For example, when the upstream printing device 10 is assigned to the front image data and the downstream printing device 30 is assigned to the back image data, the job assignment unit 43 prints the downstream printing to the front image data. The apparatus 30 is allocated, and the upstream printing apparatus 10 is allocated to the back surface image data.

  Then, after assigning “0” to the print rate integrated value AT (n) and the print rate integrated value BT (n) (step S215), the job assigning unit 43 increments n (step S219), and the process To step S203.

  As described above, when the printing rate calculation mode is set in the mode selection process, the job allocation unit 43 prints the printing rate in order from the top of each of the front and back surfaces based on the front surface image data and the back surface image data included in the duplex printing job. The upstream printing apparatus 10 or the downstream printing apparatus 30 is located at a position where the difference between the integrated value of the print ratio of the front surface image data and the integrated value of the print ratio of the back surface image data exceeds the print ratio difference threshold Thc. By repeating the process of switching to the entire duplex printing job, the front surface image data and the back surface image data are assigned to either the upstream printing apparatus 10 or the downstream printing apparatus 30, respectively.

  As a result, the upstream printing apparatus 10 or the downstream printing apparatus 30 can be switched on the assumption that the temperature of the inkjet head unit is more accurately estimated based on the printing rate, so that the temperature of one of the inkjet head units is increased. By preventing this, productivity can be improved.

≪Final inversion process≫
When the printing rate calculation mode is set in the mode selection process, a position for switching the upstream printing device 10 or the downstream printing device 30 is determined in advance based on the printing rate.

  When switching to the upstream printing apparatus 10 or the downstream printing apparatus 30, each time the switching is performed, the paper P printed on the upper surface based on the front surface image data and the paper P printed on the upper surface based on the back surface image data Will be mixed.

  Therefore, after printing, the paper P printed based on one of the image data of the front image data and the back image data is reversed by the final reversing device 50, so that the top surface of the discharged paper P is discharged. It is necessary to unify the image printed on the front side image or the back side image.

  FIG. 5 is a flowchart showing the processing contents of the final inversion control of the final inversion device when the printing rate calculation mode is set in the mode selection processing.

  When the printing rate calculation mode is set and printing start is requested, the overall control device 40 initializes the variable n (step S301) and then starts printing of the nth block (step S303).

  When printing of the nth block is completed (step S305), the apparatus control unit 560 determines whether or not the flag is set to ON (step S307).

  When the flag is set to ON (step S307; YES), both the front surface image data and the back surface image data are assigned to the downstream printing apparatus 30. For this reason, on / off switching of the front and back by the final reversing device 50 is performed so that the paper P printed on the upper surface based on the front image data and the paper P printed on the upper surface based on the back image data are not discharged together. Are switched (step S309). Specifically, when the paper P is guided to the reverse path R4, the switching mechanism 514 is switched so as to be guided directly to the paper discharge path R5. On the other hand, when the paper P is directly guided to the paper discharge path R5, the switching mechanism 514 is switched so as to be guided to the reverse path R4.

  Then, the overall control device 40 ends the process when n exceeds the total number of blocks N (step S311; YES), and increments n when n does not exceed the total number of blocks N ( In step S313), the process proceeds to step S303.

  In this way, it is determined whether both the front surface image data and the back surface image data are assigned to the downstream printing apparatus 30 for each duplex printing job, and both the front surface image data and the back surface image data are assigned. In addition, the paper reversed on the basis of any one of the image data by the downstream printing device 30 is reversed by the final reversing device 50.

  Thereby, the image printed on the upper surface of the discharged paper P can be unified as either the front image or the back image.

  In addition, instead of reversing the front and back of the paper P, which has been printed by the downstream printing apparatus 30, the reversing unit 350 may reverse the front and back.

  When the front and back are reversed by the final reversing device 50, the conveyance distance is short, so that the productivity is increased accordingly. On the other hand, when reversing the front and back by the reversing unit 350, it is not necessary to newly provide the final reversing device 50, so that the manufacturing cost can be reduced.

≪Predetermined interval switching mode execution process≫
FIG. 6 is an explanatory diagram showing the processing content of the predetermined interval switching mode execution processing when the predetermined interval switching mode is set in the mode selection processing.

  When the predetermined interval switching mode is set, the job allocation unit 43 initializes the variable n (step S401) and then starts printing of the nth block (step S403).

  When the printing of the nth block is completed (step S405), the job allocation unit 43 switches the upstream printing apparatus 10 or the downstream printing apparatus 30 for the front surface image data and the back surface image data (step S407). For example, when the upstream printing device 10 is assigned to the front image data and the downstream printing device 30 is assigned to the back image data, the job assignment unit 43 prints the downstream printing to the front image data. The apparatus 30 is allocated, and switching is performed so that the upstream printing apparatus 10 is allocated to the back surface image data.

  Next, the apparatus control unit 560 performs the final inversion so that the paper P printed on the upper surface based on the front image data and the paper P printed on the upper surface based on the back image data are not discharged together. The on / off of the front / back inversion by the device 50 is switched (step S409). Specifically, when the paper P is guided to the reverse path R4, the switching mechanism 514 is switched so as to be guided directly to the paper discharge path R5. On the other hand, when the paper P is directly guided to the paper discharge path R5, the switching mechanism 514 is switched so as to be guided to the reverse path R4.

  Then, the overall control device 40 ends the process when n exceeds the total number of blocks N (step S411; YES), and increments n when n does not exceed the total number of blocks N ( In step S413), the process proceeds to step S403.

  As described above, the job allocation unit 43 satisfies the fixed format condition, that is, the variation in the difference between the printing rate of the front surface image data and the printing rate of the back surface image data included in the duplex printing job is small, and the printing rate When the average difference is equal to or greater than a predetermined average printing rate threshold value, by executing the predetermined interval switching mode, the front side image data and the back side image data are respectively sent from the top to the upstream printing apparatus 10 or downstream for each predetermined page. Alternatingly assigned to any one of the side printing apparatuses 30.

  As a result, when the duplex printing job has a fixed format such as a form, the upstream printing apparatus 10 or the downstream printing apparatus 30 can be switched on the assumption that the temperature of the inkjet head unit is increased without calculating the printing rate. Therefore, productivity can be improved by preventing the temperature of any one of the inkjet head units from rising.

≪Temperature measurement mode execution process≫
FIG. 7 is a state transition diagram showing the processing contents of the temperature measurement mode execution process when the temperature measurement mode is set in the mode selection process.

  When the ink temperature T1 inside the inkjet head unit 134 detected by the thermometer 137 and the ink temperature T2 inside the inkjet head unit 334 detected by the thermometer 337 are both below the near temperature Th1, the upstream printing apparatus Printing is continued without switching between 10 and the downstream printing apparatus 30 (601).

  When either the ink temperature T1 or the ink temperature T2 exceeds the near temperature Th1, the job assignment unit 43 causes the upstream printing apparatus 10 or the downstream printing apparatus 30 to be used for the front surface image data and the back surface image data. Switching is continued and printing is continued (603). Thereby, productivity can be improved by preventing the temperature of any one of the inkjet head units from rising.

  Further, when the temperature of the ink jet head unit rises and both the ink temperature T1 and the ink temperature T2 exceed the near temperature Th1, printing is continued without switching the upstream printing apparatus 10 and the downstream printing apparatus 30. (605).

  When either the ink temperature T1 or the ink temperature T2 exceeds the upper limit temperature Th2, if the printing is continued further, the viscosity of the ink decreases, the amount of mist generated due to ejection increases, and a high-definition printed matter can be obtained. You may not be able to get it.

  Therefore, the overall control device 40 stops printing (607).

  Thus, when the temperature measurement mode is set in the mode selection process, the temperature of the ink inside the inkjet head unit 134 detected by the thermometer 137 or the ink inside the inkjet head unit 334 detected by the thermometer 337 is detected. When the temperature exceeds the near temperature Th1, the upstream printing apparatus 10 or the downstream printing apparatus 30 is switched with respect to the front surface image data and the back surface image data.

  Therefore, since the upstream printing apparatus 10 or the downstream printing apparatus 30 can be switched more accurately based on the actually measured temperature rise of the inkjet head unit, the temperature of either one of the inkjet head units rises. By preventing this, productivity can be improved.

  As described above, according to the duplex printing system 1 according to an embodiment of the present invention, the job allocation unit 43 reduces the difference between the temperature T1 of the inkjet head unit 134 and the temperature of the inkjet head unit 334. The front side image data and the back side image data included in the duplex printing job are assigned to either the upstream printing apparatus 10 or the downstream printing apparatus 30, respectively. Therefore, productivity can be improved by preventing the temperature of any one of the inkjet head units from rising.

  The upstream printing apparatus 10 and the downstream printing apparatus 30 have been described as an inkjet printing apparatus including an inkjet head unit. However, the printing unit is not limited to this, and other types of printing such as a stencil printing apparatus, for example. It may be a device.

(Appendix)
The present application discloses the following inventions.

(Appendix 1)
An upstream printing apparatus that performs a printing process on a conveyed sheet by a first printing unit, an intermediate reversing apparatus that reverses the front and back of the sheet that has been printed by the upstream printing apparatus, and the intermediate reversing apparatus A double-sided printing system that performs double-sided printing on the paper whose front and back are reversed by using a downstream printing device that executes printing processing by a second printing unit,
In order to reduce the difference between the temperature of the first printing unit and the temperature of the second printing unit, the front side image data and the back side image data included in the double-sided printing job are respectively sent to the upstream printing apparatus or the downstream side. Job assignment means for assigning to any of the printing devices;
A double-sided printing system comprising:

(Appendix 2)
The job allocating means has a small variation in a difference between a printing rate of the front surface image data and a printing rate of the back surface image data included in the double-sided printing job, and an average of the difference of the printing rates is a predetermined average printing. When the ratio is equal to or greater than a rate threshold value, the front surface image data and the back surface image data are sequentially and alternately assigned to either the upstream printing apparatus or the downstream printing apparatus for each predetermined page from the top. The double-sided printing system according to (Appendix 1).

(Appendix 3)
The job allocating unit accumulates the printing rate sequentially from the top of the front and back surfaces based on the front surface image data and the back surface image data included in the double-sided print job, and accumulates the accumulated printing rate of the front surface image data. A process in which a position where a difference between a value and an integrated value of the printing rate of the back surface image data exceeds a predetermined printing rate difference threshold is set as a switching position of the upstream printing apparatus or the downstream printing apparatus, The double-sided printing according to (Appendix 1), wherein the front-side image data and the back-side image data are assigned to either the upstream-side printing device or the downstream-side printing device, respectively, by repeating over the whole. system.

(Appendix 4)
First temperature detecting means for detecting the temperature of the first printing unit;
A second temperature detecting means for detecting the temperature of the second printing unit,
When the temperature detected by the first temperature detection unit or the temperature detected by the second temperature detection unit exceeds a predetermined temperature set lower than the temperature at which the apparatus is to be stopped, The duplex printing system according to (Appendix 1), wherein the upstream printing device or the downstream printing device assigned to the front surface image data and the back surface image data is switched.

(Appendix 5)
The double-sided printing system further comprising a final reversing unit that reverses the front and back of the paper that has been subjected to the printing process by the downstream printing apparatus,
The double-sided printing system according to (Appendix 1), further comprising control means for reversing the paper printed on the basis of any one of the image data by the downstream printing apparatus using the final reversing unit.

DESCRIPTION OF SYMBOLS 1 Duplex printing system 10 Upstream printing apparatus 20 Intermediate inversion apparatus 30 Downstream printing apparatus 40 Overall control apparatus 41 Job receiving part 42 Mode selection part 43 Job allocation part 44 Storage part 47 Communication part 50 Final inversion apparatus (final inversion part)
100 Terminal device 130, 336 Printing unit 133 Conveying belt 134 Inkjet head unit (first printing unit)
334 Inkjet head unit (second printing unit)
137,337 Thermometer 160,260,360,560 Device control unit 350 Inversion unit (final inversion unit)
514 switching mechanism

Claims (5)

An upstream printing apparatus that performs a printing process on a conveyed sheet by a first printing unit, an intermediate reversing apparatus that reverses the front and back of the sheet that has been printed by the upstream printing apparatus, and the intermediate reversing apparatus A double-sided printing system that performs double-sided printing on the paper whose front and back are reversed by using a downstream printing device that executes printing processing by a second printing unit,
In order to reduce the difference between the temperature of the first printing unit and the temperature of the second printing unit, the front side image data and the back side image data included in the double-sided printing job are respectively sent to the upstream printing apparatus or the downstream side. Job assignment means for assigning to any of the printing devices;
A double-sided printing system comprising: The job allocating means has a small variation in a difference between a printing rate of the front surface image data and a printing rate of the back surface image data included in the double-sided printing job, and an average of the difference of the printing rates is a predetermined average printing. When the ratio is equal to or greater than a rate threshold value, the front surface image data and the back surface image data are sequentially and alternately assigned to either the upstream printing apparatus or the downstream printing apparatus for each predetermined page from the top. The double-sided printing system according to claim 1. The job allocating unit accumulates the printing rate sequentially from the top of the front and back surfaces based on the front surface image data and the back surface image data included in the double-sided print job, and accumulates the accumulated printing rate of the front surface image data. A process in which a position where a difference between a value and an integrated value of the printing rate of the back surface image data exceeds a predetermined printing rate difference threshold is set as a switching position of the upstream printing apparatus or the downstream printing apparatus, 2. The duplex printing system according to claim 1, wherein the front side image data and the back side image data are assigned to either the upstream side printing apparatus or the downstream side printing apparatus, respectively, by repeating over the whole. . First temperature detecting means for detecting the temperature of the first printing unit;
A second temperature detecting means for detecting the temperature of the second printing unit,
When the temperature detected by the first temperature detection unit or the temperature detected by the second temperature detection unit exceeds a predetermined temperature set lower than the temperature at which the apparatus is to be stopped, The duplex printing system according to claim 1, wherein the upstream printing apparatus or the downstream printing apparatus assigned to the front surface image data and the back surface image data is switched. The double-sided printing system further comprising a final reversing unit that reverses the front and back of the paper that has been printed by the downstream printing apparatus,
The double-sided printing system according to claim 1, further comprising a control unit that reverses a sheet printed by the downstream printing apparatus based on any one of the image data using the final reversing unit.

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