JP2019116019A - Image forming device - Google Patents

Abstract

An object of the present invention is to prevent the tip of a sheet from being stained. A determining unit (81b) determines whether or not image data of a page to be printed is generated by a printing unit (30) at a timing of being transported on a circulation transport path (CR) to a printing unit (30). When it is determined that the image data of the page to be generated has not been generated, the transport control unit 81c feeds the sheet P from one of the sheet feeding tables 11, 21a, 21b, 21c, and 21d at a predetermined sheet interval L1. However, when the image is conveyed on the circulating conveyance path CR without being printed by the printing unit 30 and the determination unit 81b determines that the image data of the page to be printed has been generated, the conveyance control unit 81c outputs the corresponding page of the generated page. The paper P printed by the printing unit 30 based on the image data is conveyed on the circulation conveyance path CR at a predetermined sheet interval L1. [Selection diagram] FIG.

Description

  BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to an image forming apparatus that prevents the contamination of the leading edge of a sheet.

  The inkjet type image forming apparatus develops an image of the received print job, and the ink jet head discharges ink droplets based on the image data obtained by the image expansion to print on a sheet. In such an image forming apparatus, the conveyance belt for conveying the sheet is provided below the ink jet head, and the suction fan installed in the conveyance belt conveys the sheet at a predetermined conveyance speed while suctioning the sheet onto the conveyance belt. There is also a full line type in which printing is performed using ink ejected from an inkjet head.

  For example, Patent Document 1 discloses a technique related to an image forming apparatus in which a suction fan is provided on the back surface (of a transport surface for transporting a recording medium) under a transport belt for transporting a recording medium (paper). In this image forming apparatus, by rotating the suction fan, negative pressure is applied to the recording medium through the plurality of holes provided at equal intervals in the conveyance belt, and the recording medium is attracted to the conveyance surface side of the conveyance belt. In this state, the recording head is conveyed below the recording head in the order of printing, and ink is ejected from the recording head based on the image data for printing.

JP, 2014-79977, A

  Here, the image forming apparatus develops an image of a print job in page order in page units to generate image data for each page, and sequentially performs printing based on the image data generated in the printing order. Therefore, if the image data includes, for example, high-definition data, multiple page allocation data, a photo image, etc., the data amount of the print job becomes large, and it may take considerable time for the image expansion processing.

  As described above, in the technique of Patent Document 1, a negative pressure is applied to the recording medium (sheet) by rotating the suction fan (suction fan), and the recording medium is attracted to the conveyance surface side of the conveyance belt. The recording head is conveyed in the order of printing to the lower side of the recording head, and the ink is ejected from the recording head based on the image data for printing.

  Therefore, according to the technique of Patent Document 1, when the image expansion process requires a considerable amount of time, when the sheet is transported to the lower side of the recording head and printing is performed based on the image data, the image expansion of the print job is not in time. In some cases, the paper interval (paper interval) may increase. When the distance between the conveyed sheets (paper interval) becomes long, the influence of the suction force by the suction fan becomes large, and the ink on the surface of the ink jet head gathers on the mask plate by the air flow (suction wind) by the suction fan. Ink reservoirs may be formed. Then, when an ink reservoir is formed on the mask plate, the ink reservoir may come in contact with the leading edge of the conveyed sheet, which may cause the leading edge contamination.

  The present invention has been made in view of the above problems, and an object thereof is to provide an image forming apparatus capable of preventing the contamination of the leading end of a sheet.

In order to achieve the above object, a first feature of the image forming apparatus according to the present invention is
The image data of each page is generated in the printing order by developing the print job, and the sheet is printed by the printing unit based on the generated image data of each page with respect to the sheet adsorbed and transported by air suction on the transport path. An image forming apparatus for printing on
A sheet feeding unit configured to feed the sheet with a predetermined sheet interval in the conveyance path;
A determination unit that determines whether or not image data of a page to be printed is generated by the printing unit in time for printing by the printing unit;
When it is determined by the determination unit that the image data of the page to be printed is not generated, the sheet fed by the sheet feeding unit is conveyed on the conveyance path without being printed by the printing unit.
A control unit for conveying the sheet printed by the printing unit based on the generated image data of the corresponding page when it is determined that the image data of the page to be printed is generated by the determination unit; is there.

  According to the first aspect of the image forming apparatus of the present invention, the leading edge of the sheet can be prevented from being soiled.

FIG. 1 is a configuration diagram showing a configuration of an image forming apparatus as an embodiment of the present invention. (A) shows a view from below of a part of an ink jet unit provided in an image forming apparatus according to an embodiment of the present invention, and (b) to (c) show the structure of the ink jet unit in the prior art. FIG. 7 is a view schematically showing an example in the case where a sheet interval (a sheet interval) conveyed downward is long. FIG. 1 is a diagram showing a functional configuration of an image forming apparatus according to an embodiment of the present invention. (A) is explanatory drawing which looked at the paper P conveyed from the upper surface of the conveyance belt in, when the data amount of image data is small in the image forming apparatus which is one Example of this invention, (b) And FIG. 7C is a view for explaining the prior art for comparison, and FIG. It is explanatory drawing seen from. It is the flowchart which showed the processing contents of the picture formation device which is one execution example of this invention.

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

  Further, the embodiment shown below is an example of an apparatus etc. for embodying the technical idea of the present invention, and the technical idea of the present invention is the arrangement of each component, etc. Not specific to Various changes can be added to the technical idea of the present invention within the scope of the claims.

(Overall Configuration of Image Forming Apparatus 1)
The configuration of an image forming apparatus 1 according to an embodiment of the present invention will be described in detail. FIG. 1 is a block diagram showing the configuration of an image forming apparatus 1 according to an embodiment of the present invention.

  As shown in FIG. 1, the image forming apparatus 1 is an apparatus for forming an image on a sheet P by discharging an ink according to image data to the sheet P which is a printing medium conveyed on a conveyance path. A side paper feed unit 10, an internal paper feed unit 20, a printing unit 30, a paper discharge unit 40, and a reversing unit 50 are provided.

  The side sheet feeding unit 10 includes a sheet feeding table 11 on which sheets P are stacked, a pickup sheet feeding unit 12 that conveys only the sheet P at the uppermost position from the sheet feeding table 11 onto a sheet feeding conveyance path FR, and the pickup The registration unit 14 includes a registration unit 14 that corrects the skew of the sheet P conveyed by the sheet feeding unit 12 and conveys the sheet P onto the circulation conveyance path CR at a predetermined conveyance timing. A registration sensor 141 is provided in front of the registration unit 14 in the transport direction, and detects the leading end or the rear end of the sheet P to be transported.

  The internal sheet feeding unit 20 feeds only the topmost sheet P from the sheet feeding bases 21a, 21b, 21c and 21d on which the sheets P are stacked and the sheet feeding bases 21a, 21b, 21c and 21d. There are provided pickup sheet feeding units 22a, 22b, 22c, and 22d which are conveyed upward.

  As described above, the sheet P is conveyed to the registration unit 14 from the side sheet feeding unit 10 and the internal sheet feeding unit 20, and the sheet P is also conveyed from the reversing unit 50 described later. Therefore, in front of the registration unit 14 in the transport direction, there is a junction where the transport path of the fed sheet P and the transport path through which the sheet having one surface printed is transported are merged. Do. Based on this junction point, the path on the side of the sheet feeding mechanism is referred to as a sheet feeding conveyance path FR, and the other conveyance paths are referred to as a circulation conveyance path CR. A printing unit 30 is provided on the conveying direction side of the registration unit 14.

  The printing unit 30 includes an inkjet unit 31 in which a plurality of inkjet heads are incorporated, an annular conveyance belt 133 provided on the opposing surface of the inkjet unit 31 and sliding along a circulation conveyance path CR, and an annular conveyance belt 133 A suction fan 131 is provided corresponding to the back surface of the conveyance road surface of the sheet P, and suctions the sheet P on the upper surface of the conveyance belt 133 by air suction. A large number of suction holes are formed in the conveyance belt 133, air is sucked by the suction fan 131 through the suction holes, and an attraction force is generated in the suction holes. The sheet P fed by the registration unit 14 is adsorbed onto the conveyance belt 133 by the suction force generated in the suction hole of the conveyance belt 133 by the drive of the suction fan 131, and is conveyed at a predetermined conveyance speed. Is printed on the sheet P by the ink ejected from the above.

  A top edge sensor 32 is provided on the upstream side of the inkjet unit 31 of the circulation conveyance path CR, and detects the sheet P conveyed by the conveyance belt 133.

  The sheet P printed by the printing unit 30 is transported on the circulation transport path CR in the housing by a transport roller or the like disposed on the circulation transport path CR. On the circulation conveyance path CR, a switching mechanism 43 is provided which switches whether the sheet P conveyed on the circulation conveyance path CR is guided to the paper discharge unit 40 or recirculated on the circulation conveyance path CR. .

  The switching mechanism 43 switches the sheet P in order to guide the sheet P to the sheet discharge unit 40 or the reversing unit 50 described later. The paper discharge unit 40 has a paper discharge tray 41 having a tray shape protruding from the casing of the image forming apparatus 1 and a pair of paper discharge rollers 42 for guiding the sheet P to the paper discharge tray 41. Then, the sheet P guided to the paper discharge unit 40 by the switching mechanism 43 is conveyed to the paper discharge tray 41 by the paper discharge roller 42 and stacked on the paper discharge tray 41 with the printing surface down.

  The reversing unit 50 reverses the sheet P, reverses the sheet P, and conveys the sheet P from the circulation conveyance path CR to the inversion block 51 or conveys the sheet P from the inversion table 51 onto the circulation conveyance path CR. Is equipped.

  The sheet P guided to the reversing unit 50 by the switching mechanism 43 is conveyed from the circulation conveyance path CR to the inversion stand 51 by the inversion roller 52, and is conveyed from the inversion stand 51 to the circulation conveyance path CR after a predetermined time has elapsed. The front and back are reversed with respect to the circulating conveyance path CR. Then, the sheet P whose front and back is reversed is conveyed toward the printing unit 30 on the circulation conveyance path CR by a plurality of rollers such as the conveyance roller 53 provided on the circulation conveyance path CR.

  The image forming apparatus 1 further includes a control unit 80 that controls the entire image forming apparatus 1. The control unit 80 is configured by a processor such as a CPU or DSP (Digital Signal Processor), a memory, hardware such as another electronic circuit, software such as a program having a function thereof, or a combination thereof. It is a calculation module. The control unit 80 virtually constructs various functional modules by reading and executing a program as appropriate, and performs various processing for processing of image data, operation control of each part, and user operation by each constructed functional module. I do.

  FIG. 2A shows a part of the ink jet unit 31 as viewed from below, and FIGS. 2B to 2C show paper sheets conveyed under the ink jet unit 31 in the prior art. It is a figure showing typically an example in case an interval (paper interval) becomes long. Here, among the plurality of inkjet heads of the inkjet unit 31, two inkjet heads 31a and 31b are shown.

  As shown in FIG. 2A, the inkjet heads 31a and 31b are provided in series adjacent to each other in the transport direction, and eject ink of the same color here. Since the two inkjet heads 31a and 31b have the same function, the inkjet head 31a will be described.

  The inkjet head 31a includes a mask plate 311 for protecting the ink ejection side of the inkjet head main body, and a plate-like nozzle plate 313 in which a plurality of nozzles 314 for ejecting ink are arranged.

  Here, in the prior art, when it takes a considerable amount of time for image expansion processing, when printing on the basis of image data by conveying the sheet P, the image expansion of the print job is not in time, and the interval of the conveyed sheet P There was a case that (the interval between sheets) became long.

  When the sheet interval (sheet interval) to be conveyed becomes long, as shown in FIG. 2B, the suction force by suction fan 131 installed corresponding to the back surface of the conveyance road surface of sheet P in conveyance belt 133 The impact is greater. Then, the ink may be collected on the mask plate 311 on the surface of the inkjet head 31 a on the upstream side in the transport direction by the air flow (suction wind) by the suction fan 131, and the ink reservoir Q may be formed on the mask plate 311.

  Then, when an ink reservoir is formed on the mask plate 311, as shown in FIG. 2C, the ink reservoir Q comes in contact with the leading edge of the sheet P conveyed on the conveyance belt 133, and the leading edge becomes dirty. Could have been the cause of

  Therefore, in the image forming apparatus 1 according to an embodiment of the present invention, the contamination of the leading edge of the sheet P is prevented by suppressing the formation of the ink reservoir Q.

(Functional Configuration of Image Forming Apparatus 1)
Next, the functional configuration of the image forming apparatus 1 according to an embodiment of the present invention will be described. FIG. 3 is a diagram showing a functional configuration of an image forming apparatus 1 according to an embodiment of the present invention.

  As shown in FIG. 3, the image forming apparatus 1 includes a side paper feed unit 10, an internal paper feed unit 20, a printing unit 30, a paper discharge unit 40, a reversing unit 50, an operation panel 70, and a control unit. And 80. Among these configurations, the side paper feed unit 10, the internal paper feed unit 20, the printing unit 30, the paper discharge unit 40, and the reversing unit 50 have been described above, and thus the description thereof is omitted.

  The control unit 80 includes a CPU 81, a ROM 82 storing an operation program of the CPU 81, various tables, and the like, and the number of pages, the number of copies, the sheet size, the sheet orientation, etc. A print job including various print conditions and a RAM 83 for storing image data of each page generated by developing the print job are provided.

  As shown in FIG. 3, the CPU 81 executes the operation program stored in the ROM 82, thereby the entire apparatus, that is, the side paper feed unit 10, the internal paper feed unit 20, the printing unit 30, and the paper discharge unit. The operations of the control unit 40, the reversing unit 50, the operation panel 70 and the like are controlled. In addition, the CPU 81 functionally includes an image developing unit 81a, a determination unit 81b, and a conveyance control unit 81c.

  When receiving the print job, the image developing unit 81a develops the received print job to generate bitmapped image data in page units in the printing order, and sequentially generates the image data generated for each page in the RAM 83. Remember.

  The determination unit 81 b is configured to use the printing unit 30 so that the fed sheet P is printed in time by the printing unit 30 at the sheet feeding timing when the pickup sheet feeding unit 12 or the conveyance roller 53 feeds the sheet P. It is determined whether image data of a page to be printed has been generated. The sheet feeding timing is predetermined to be a predetermined sheet interval depending on the sheet size to be printed and the sheet orientation. Further, the fed sheet P is conveyed on the circulation conveyance path CR, and reaches immediately below the ink jet unit 31. Therefore, whether or not the fed sheet P is in time for printing by the printing unit 30 depends on whether the sheet P is fed by the pick-up sheet feeding unit 12 or the conveyance roller 53, The sheet feeding timing is determined after subtracting the time to reach immediately below.

  If it is determined by the determination unit 81 b that the image data of the page to be printed is generated, printing can be performed immediately. Therefore, the conveyance control unit 81 c conveys the sheet P printed by the printing unit 30 on the basis of the generated image data of the corresponding page between the predetermined sheets on the circulation conveyance path CR.

  FIGS. 4A to 4C are explanatory diagrams for explaining the operation of the conveyance control unit 81c. FIG. 4A is an explanatory view of the sheet P conveyed on the circulating conveyance path CR when viewed from above in the case where the data amount of the image data is small in the image forming apparatus 1 according to an embodiment of the present invention. .

  As shown in FIG. 4A, the sheets P1 to P6 are sequentially transported in the transport direction while being attracted to the upper surface of the transport belt 133 by the suction force of the suction fan 131. Here, for the sake of explanation, the sheets P will be described in order from the top to the sheets P1 to P6.

  The amount of image data to be printed on sheets P1 to P6 is small. Therefore, after the sheet P1 is conveyed by the registration unit 14, when the sheet feeding timing of the sheet P2 is reached, the expansion processing of the image data to be printed on the sheet P2 is already completed, and the image data is stored in the RAM 83.

  Therefore, as shown in FIG. 4A, the conveyance control unit 81c causes the registration unit 14 to convey the next sheet P2 with a predetermined sheet interval L1, and the sheet P2 is generated based on the generated image data of the corresponding page. Are printed by the printing unit 30 and conveyed on the circulation conveyance path CR. Then, the conveyance control unit 81 c sequentially conveys the sheet P printed based on the image data by the conveyance belt 133. As described above, when the data amount of the image data to be printed is small, it is possible to print based on the image data that has been subjected to the expansion processing while conveying with a predetermined sheet interval L1. Therefore, since printing can be continued without unnecessarily lengthening the sheet interval, formation of an ink reservoir on the mask plate of the inkjet unit 31 can be prevented.

  FIG. 4 (b) is a description of the prior art for comparison. Here, the conveyance state of the sheet P conveyed on the circulation conveyance path CR in the case where the data amount of the image data is large and the feeding timing is delayed until the image data whose expansion processing is completed is generated is described. .

  As shown in FIG. 4B, in the prior art, when the data amount of the image data to be printed on the sheet P2 is large, it takes a considerable amount of time for the image expansion processing, so when the sheet feed timing of the sheet P2 is reached Image data to be printed on paper P2 is not generated. Therefore, the sheet feeding timing is delayed until the image data to be printed on the sheet P2 is generated.

  Therefore, the sheet interval L2 between the sheet P1 and the sheet P2 is longer than the sheet interval L1. When the paper interval L2 is long, the suction force of the suction fan 131 is susceptible to the influence. Specifically, as described in FIG. 2, the air in the vicinity of the mask plate 311 of the inkjet unit 31 is sucked by the suction fan 131 immediately below, and the air flow (suction wind) by the suction fan 131 causes the ink to be on the mask plate 311. And may form an ink reservoir on the mask plate 311. Then, when an ink reservoir is formed, the ink reservoir may come in contact with the leading edge of the sheet P2 being conveyed, which may cause the leading edge contamination.

  Therefore, in the embodiment of the present invention, when it is determined that the image data of the page to be printed is not generated by the determination unit 81b, the conveyance control unit 81c performs sheet feeding so as not to lengthen the sheet interval more than necessary. The sheet P is fed from any one of the platforms 11, 21a, 21b, 21c, and 21d, and the sheet P is conveyed on the circulation conveyance path CR without being printed by the printing unit 30.

  FIG. 4C is an explanatory view of the sheet P conveyed on the circulation conveyance path CR when viewed from above in the image forming apparatus 1 according to an embodiment of the present invention when the data amount of the image data is large. .

  As shown in FIG. 4C, the sheet P1 is transported in the transport direction while being attracted to the upper surface of the transport belt 133 by the suction force of the suction fan 131.

  Thereafter, if the data amount of the image data to be printed on the sheet P2 is large, it takes a considerable amount of time for the image expansion processing, so when the sheet P2 feed timing is reached, the expansion processing is not complete and the sheet P2 is used. Image data to be printed has not been generated.

  Therefore, the conveyance control unit 81c selects a sheet feeding base on which the sheet P of the corresponding sheet size is placed among the sheet feeding bases 11, 21a, 21b, 21c, and 21d, and selects the sheet from the selected sheet feeding base. Feed the Q1. Then, the registration unit 14 conveys the sheet Q1 on the circulation conveyance path CR with a predetermined sheet interval L1. Here, for the sake of explanation, the sheets P not to be printed are numbered as the sheets Q1 to Q4 in order from the top.

  The sheet Q1 conveyed on the circulation conveyance path CR by the registration unit 14 is circulated on the circulation conveyance path CR by the switching mechanism 43 without being printed by the printing unit 30. Then, the sheet Q1 conveyed on the circulation conveyance path CR is conveyed by the conveyance roller 53 toward the printing unit 30 on the circulation conveyance path CR at the sheet feeding timing.

  As described above, even when the data amount of the image data to be printed is large, the sheet P (Q1) is conveyed in the sheet interval L1. Therefore, since it is possible to prevent the paper interval from being unnecessarily increased, the influence of the suction force of the suction fan 131 can be suppressed, and the formation of the ink pool on the mask plate of the ink jet unit 31 can be prevented.

  In the example shown in FIG. 4C, after the conveyance of the sheet Q1, the image data to be printed on the sheet P2 is not generated even when the sheet feeding timing of the sheet P2 is reached again.

  Accordingly, similarly, the transport control unit 81c transports the sheets Q2, Q3, and Q4 in the sheet interval L1 until the image data to be printed on the sheet P2 is generated. As described above, since the sheets Q1 to Q4 are conveyed in the sheet interval L1 on the circulation conveyance path CR until the image data to be printed on the sheet P2 is generated, the influence of the suction force by the suction fan 131 can be suppressed. it can.

  After transporting the sheet Q4, when the sheet feeding timing is reached, the expansion processing of the image data to be printed on the sheet P2 is completed, and the image data is stored in the RAM 83.

  Therefore, the conveyance control unit 81c causes the registration unit 14 to convey the next sheet P2 in the predetermined sheet interval L1, and the printing unit 30 prints on the sheet P2 based on the generated image data of the corresponding page. Transport on the circulating transport path CR. At this time, the sheet Q <b> 1 previously fed is conveyed on the circulation conveyance path CR and reaches the registration unit 14. Therefore, the conveyance control unit 81c corrects the skew of the sheet Q1 previously fed by the registration unit 14 and conveys it as the sheet P2 in the sheet interval L1, and the sheet P2 is formed based on the generated image data of the corresponding page. On the other hand, printing is performed by the printing unit 30 and conveyed on the circulation conveyance path CR.

  As described above, even when the data amount of the image data to be printed is large, printing can be performed based on the image data that has been subjected to the expansion processing while being conveyed at the predetermined inter-sheet distance L1. Therefore, printing can be continued without unnecessarily lengthening the sheet interval, so that the influence of the suction force of the suction fan 131 can be suppressed, and the formation of an ink reservoir on the mask plate of the inkjet unit 31 can be prevented.

(Operation of image forming apparatus 1)
Next, the operation of the image forming apparatus 1 according to an embodiment of the present invention will be described.

  FIG. 5 is a flowchart showing the processing contents of the image forming apparatus 1 according to an embodiment of the present invention.

  As shown in FIG. 5, the determination unit 81b determines whether or not the sheet feeding timing has been reached (step S101).

  If it is determined that the paper feed timing has been reached (step S101; YES), the determination unit 81b determines whether or not the image data of the page to be printed by the printing unit 30 for the sheet P is generated (step S103).

  When it is determined that the image data of the page to be printed is generated by the printing unit 30 on the sheet P (step S103; YES), the conveyance control unit 81c causes the registration unit 14 to print a predetermined sheet of paper. The sheet P is transported in the interval L1 (step S105).

  Then, when the sheet P is detected by the top edge sensor 32 (step S105; YES), the conveyance control unit 81c causes the printing unit 30 to print on the sheet P based on the generated image data of the corresponding page. The sheet is conveyed on the circulating conveyance path CR (step S109).

  On the other hand, when it is determined that the image data of the page to be printed is not generated by printing unit 30 for paper P (step S103; NO), conveyance control unit 81c determines that the image data to be printed by the print job is It is determined whether the number of remaining pages is equal to or more than the number of unprinted sheets conveyed by the circulation conveyance path CR (step S111).

  As described above, the sheet P circulated on the circulation conveyance path CR without being printed is again subjected to skew correction by the registration unit 14 and conveyed toward the printing unit 30 on the circulation conveyance path CR. At this time, if printing is completed if the remaining number of pages of image data to be printed by the print job is less than the number of unprinted sheets transported by the circulation transport path CR, it is transported by the circulation transport path CR. The unprinted paper P (blank paper not to be printed) remains in the apparatus.

  Therefore, the conveyance control unit 81c is configured such that the remaining number of pages of the image data to be printed by the print job is not conveyed by the circulation conveyance path CR so that the unprinted paper P does not remain in the apparatus when printing is completed. If it is less than the number of sheets for printing (step S111; NO), it is determined whether printing has been completed without feeding sheets P from sheet feeding tables 11, 21a, 21b, 21c, 21d newly (step S111) S117).

  When the printing is not completed (step S117; NO), the process is returned to step S101, and the process waits until the next sheet feeding timing is reached. As a result, printing is performed using the sheet P circulating in the circulation conveyance path CR, and it is possible to prevent the unprinted sheet P from remaining in the apparatus when printing is completed.

  On the other hand, when the remaining number of pages of the image data to be printed by the print job is equal to or more than the number of unprinted sheets conveyed by the circulation conveyance path CR (step S111; YES), the conveyance control unit 81c determines that It is determined whether the upper limit number has been exceeded (step S113).

  The number of sheets of paper P circulated in the circulation conveyance path CR is determined by the path length of the circulation conveyance path CR, the sheet size, and the direction of the paper P. For example, when printing in A4 size sideways, the number of sheets of paper P circulated in the circulation conveyance path CR is set to "5".

  Therefore, when it is determined that the upper limit number of sheets in the apparatus has been exceeded (YES in step S113), the conveyance control unit 81c does not newly feed the sheet P from the sheet feeding trays 11, 21a, 21b, 21c, and 21d. It is determined whether printing has been completed (step S117). As a result, it is possible to feed unprinted sheets P (blank sheets not to be printed) within the range of the upper limit number of sheets in the apparatus.

  On the other hand, when it is determined that the number of sheets is equal to or less than the upper limit number in the apparatus (step S113; NO), the sheet P is fed from any of the sheet feeding trays 21a, 21b, 21c, 21d, and printing is not performed by the printing unit 30 The sheet P is conveyed in a blank state.

  As described above, according to the image forming apparatus 1 which is an embodiment of the present invention, the image data of the page to be printed by the printing unit 30 in time for the determination unit 81 b to be printed by the printing unit 30 If it is determined by the determination unit 81b that the image data of the page to be printed is not generated, the conveyance control unit 81c determines that the paper feed trays 11, 21a, 21b, 21c, and 21d are generated. The sheet P fed from any of the above is conveyed on the circulation conveyance path CR without being printed by the printing unit 30.

  Therefore, when the data amount of the image data to be printed is large, the unprinted sheet P (a blank sheet which is not a print target) is conveyed, so that the sheet interval is not unnecessarily extended. As a result, the influence of the suction force by the suction fan 131 can be suppressed, so that the formation of the ink reservoir Q on the mask plate 311 of the ink jet unit 31 can be prevented.

  When it is determined that the image data of the page to be printed is generated by the determination unit 81b, the transport control unit 81c transports the sheet P printed by the printing unit 30 based on the generated image data of the corresponding page.

  Therefore, when the data amount of the image data to be printed is small, it is possible to print based on the expanded image data while conveying the sheet P. Therefore, printing can be continued without unnecessarily lengthening the sheet interval, and therefore, the formation of the ink reservoir Q on the mask plate 311 of the inkjet unit 31 can be prevented.

  Further, the conveyance control unit 81 c re-sends the sheet P which has passed the printing unit 30 without being printed, to the printing unit 30 via the circulation conveyance path CR.

  Therefore, printing can be performed using the sheet P circulating in the circulation conveyance path CR, and the unprinted sheet P can be prevented from remaining in the apparatus when printing is completed.

  Further, when the conveyance control unit 81c determines that the image data of the page to be printed is not generated by the determination unit 81b, the remaining number of pages of the image data to be printed by the print job is conveyed by the circulation conveyance path CR. If the number of unprinted sheets is equal to or less than the number of unprinted sheets, the sheet P is fed to any one of the sheet feeding tables 11, 21a, 21b, 21c, and 21d.

  Therefore, the unprinted sheet P can be prevented from remaining in the apparatus when printing is completed.

  In step S111, the conveyance control unit 81c determines whether the number of remaining pages of image data to be printed by the print job is equal to or more than the number of unprinted sheets conveyed by the circulation conveyance path CR. This process can be omitted. When this process is omitted, the unprinted sheet P remaining on the circulation conveyance path CR may be discharged onto the discharge tray 41 after the printing is completed.

(Supplementary note)
The present application discloses the following invention.

(Supplementary Note 1)
The image data of each page is generated in the printing order by developing the print job, and the sheet is printed by the printing unit based on the generated image data of each page with respect to the sheet adsorbed and transported by air suction on the transport path. An image forming apparatus for printing on
A sheet feeding unit configured to feed the sheet with a predetermined sheet interval in the conveyance path;
A determination unit that determines whether or not image data of a page to be printed is generated by the printing unit in time for printing by the printing unit;
When it is determined by the determination unit that the image data of the page to be printed is not generated, the sheet fed by the sheet feeding unit is conveyed on the conveyance path without being printed by the printing unit.
A control unit that conveys a sheet printed by the printing unit based on the generated image data of the corresponding page when it is determined that the image data of the page to be printed is generated by the determination unit;
An image forming apparatus comprising:

(Supplementary Note 2)
The transport path includes a circulation transport path for circulating the sheet.
The determination means
It is determined whether or not image data of a page to be printed is generated by the printing unit in time for the sheet transported on the circulation transport path to be printed by the printing unit.
The image forming apparatus according to (Appendix 1), wherein the control unit re-sends the sheet which has passed through the printing unit without being printed, to the printing unit through the circulation conveyance path.

(Supplementary Note 3)
The control means
When the determination unit determines that the image data of the page to be printed is not generated, the remaining number of pages of the image data to be printed by the print job is the unprinted sheet being conveyed by the circulating conveyance route (Supplementary Note 2) The image forming apparatus according to Supplementary Note 2, wherein the sheet is fed by the sheet feeding unit when the number is equal to or less than the number of sheets.

Reference Signs List 1 image forming apparatus 10 side sheet feeding unit 11, 21a, 21b, 21c, 21d sheet feeding table 12 pickup sheet feeding unit 14 registration unit 20 internal sheet feeding unit 22a, 22b, 22c, 22d pickup sheet feeding unit 30 printing unit 31 inkjet Unit 32 top edge sensor 40 discharge unit 50 reverse unit 70 operation panel 80 control unit 81 a image developing unit 81 b determination unit 81 c transport control unit (control means)
131 suction fan 133 conveyance belt 141 registration sensor

Claims (3)

The image data of each page is generated in the printing order by developing the print job, and the sheet is printed by the printing unit based on the generated image data of each page with respect to the sheet adsorbed and transported by air suction on the transport path. An image forming apparatus for printing on
A sheet feeding unit configured to feed the sheet with a predetermined sheet interval in the conveyance path;
A determination unit that determines whether or not image data of a page to be printed is generated by the printing unit in time for printing by the printing unit;
When it is determined by the determination unit that the image data of the page to be printed is not generated, the sheet fed by the sheet feeding unit is conveyed on the conveyance path without being printed by the printing unit.
A control unit that conveys a sheet printed by the printing unit based on the generated image data of the corresponding page when it is determined that the image data of the page to be printed is generated by the determination unit;
An image forming apparatus comprising: The transport path includes a circulation transport path for circulating the sheet.
The determination means
It is determined whether or not image data of a page to be printed is generated by the printing unit in time for the sheet transported on the circulation transport path to be printed by the printing unit.
The image forming apparatus according to claim 1, wherein the control unit re-sends the sheet which has passed through the printing unit without being printed, to the printing unit via the circulation conveyance path. The control means
When the determination unit determines that the image data of the page to be printed is not generated, the remaining number of pages of the image data to be printed by the print job is the unprinted sheet being conveyed by the circulating conveyance route 3. The image forming apparatus according to claim 2, wherein the sheet is fed by the sheet feeding unit when the number is equal to or less than the number of sheets.

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