Image formation device and program

Abstract

To provide an image formation device that can suppress printing failure due to sheet adsorption failure, and a program.SOLUTION: An image formation device 1 comprises: a conveyance part 22 which comprises a plurality of conveyance surfaces 221 on which a sheet P can be placed, and conveys the sheet P placed on the conveyance surfaces 221; an adsorption part 223 which adsorbs the sheet to the conveyance surface 221 by sucking air from a plurality of suction holes H formed in the conveyance surface 221; an image formation part 23 which forms an image on the sucked and conveyed sheet P; and a control part 40 functioning as a conveyance control part which causes a print job sheet Pa to be continuously adsorbed to the conveyance surface 221 and conveyed after causing one or more non-print job sheets Pb to be adsorbed to the conveyance surface 221 and conveyed if a prescribed condition is satisfied in which a suction force by the adsorption part 223 decreases when executing a print job, and as an image formation control part which does not perform image formation of the print job on the non-print job sheet Pb and performs image formation of the print job on the print job sheet Pa.SELECTED DRAWING: Figure 7A

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus and a program. [Background technology]

[0002] Conventionally, there has been known an image forming apparatus that forms an image on a sheet of paper transported by a transport unit. The image forming apparatus includes a transport unit that transports the sheet of paper by rotating a rotating body while sucking air from a transport surface on the front side to adsorb the sheet of paper to the transport surface.

[0003] In such a transport section, it is necessary to control the transport surface so that it has an appropriate suction force according to the paper being transported. If the suction force is too weak, the paper will float up, causing paper transport problems and printing problems. If the suction force is too strong, the paper will be sucked into the suction holes in the transport surface, causing the paper to become dented and deformed.

[0004] For example, Patent Document 1 describes a configuration of a transport surface that can move and change shape depending on the size of the paper placed on it. Patent Document 1 also describes a configuration in which multiple transport surfaces and multiple negative pressure sources are connected by multiple air pipes. With this configuration, the paper can be attracted with an appropriate suction force depending on the paper being transported. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2017-007865 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, in order to accommodate large-sized paper, it is necessary to make the suction part and air pipe wider. This creates negative pressure in the air pipe, and it takes time for the conveying surface to have sufficient suction power. As a result, there is a problem that poor suction can cause printing defects, especially at the start of printing.

[0007] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an image forming apparatus and a program that are capable of suppressing printing defects caused by poor sheet adsorption. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention provides an image forming apparatus, comprising: a conveying unit that includes a plurality of conveying surfaces on which paper can be placed and conveys the paper placed on the conveying surfaces; a suction unit that sucks air through a plurality of suction holes formed on the conveying surface to adsorb the paper to the conveying surface; an image forming section for forming an image on the paper that is attracted and conveyed; a conveyance control unit that, when a predetermined condition is satisfied under which the suction force of the suction unit is reduced during execution of a print job, causes one or more non-print job sheets to be adsorbed to the conveyance surface and conveyed, and then causes a print job sheet to be adsorbed to the conveyance surface and conveyed in succession; an image forming control unit that does not form an image of the print job on the non-print job paper and forms an image of the print job on the print job paper; Equipped with.

[0009] The invention described in claim 2 is the image forming apparatus described in claim 1, The predetermined condition is the start of a print job.

[0010] The invention described in claim 3 is the image forming apparatus described in claim 2, The transport control unit determines the number of sheets of the non-print job sheets to be transported at the start of printing, depending on paper conditions including the paper type, basis weight, paper thickness, and paper size of the print job sheets.

[0011] The invention described in claim 4 is the image forming apparatus according to any one of claims 1 to 3, the predetermined condition is when an empty transport surface occurs during execution of a print job, and the transport surface does not attract paper; The transport control section adsorbs the non-print job paper onto the idle transport surface and transports the paper.

[0012] The invention described in claim 5 is the image forming apparatus described in claim 4, a reversing unit that turns over the paper that has passed through the image forming unit, and a circulating unit that returns the paper that has been turned over by the reversing unit to the conveying unit upstream of the image forming unit, the image formation control unit forms an image on a first side of a second sheet of paper for the print job between image formation on a first side of the first sheet of paper for the print job and image formation on a second side of the first sheet of paper for the print job that has been returned to the transport unit by the reversing unit and the circulating unit during double-sided printing; The empty transport surface occurs at the start and end of double-sided printing.

[0013] The invention described in claim 6 is the image forming apparatus described in claim 5, The transport control unit discharges the non-print job paper during double-sided printing without passing the paper through the reversing unit and the circulating unit.

[0014] The invention described in claim 7 is the image forming apparatus described in any one of claims 1 to 3, The transport control unit discharges the print job sheets and the non-print job sheets to different discharge destinations.

[0015] The invention described in claim 8 is the image forming apparatus according to any one of claims 1 to 3, The image formation control unit causes a marker to be applied to the non-print job papers to distinguish them from the print job papers.

[0016] The invention described in claim 9 is the image forming apparatus according to any one of claims 1 to 3, The predetermined conditions are when a print job is interrupted and when the interrupted print job is resumed.

[0017] The invention described in claim 10 is the image forming apparatus according to any one of claims 1 to 3, an acquisition unit that acquires information regarding a suction pressure of the suction unit, The predetermined condition is when the suction pressure is equal to or greater than a predetermined value.

[0018] The invention described in claim 11 is the image forming apparatus according to any one of claims 1 to 3, The transport control unit stores, as a print job, control for adsorbing the non-print job paper to the transport surface and transporting the paper.

[0019] The invention described in claim 12 is the image forming apparatus according to any one of claims 1 to 3, The print job paper and the non-print job paper have the same paper conditions including paper type, basis weight, paper thickness, and paper size.

[0020] The invention described in claim 13 is the image forming apparatus according to any one of claims 1 to 3, The transport surface is provided in a specific area of ​​the transport section.

[0021] The invention described in claim 14 is a program, a conveying unit that includes a plurality of conveying surfaces on which paper can be placed and conveys the paper placed on the conveying surfaces; a suction unit that sucks air through a plurality of suction holes formed on the conveying surface to adsorb the paper to the conveying surface; and an image forming unit that forms an image on the paper that is attracted to and transported. a conveyance control unit that, when a predetermined condition is satisfied under which the suction force of the suction unit is reduced when a print job is executed, causes one or more non-print job sheets to be adsorbed to the conveyance surface and conveyed, and then causes a print job sheet to be adsorbed to the conveyance surface and conveyed in succession; an image forming control unit that does not form an image of the print job on the non-print job paper and forms an image of the print job on the print job paper; Function as. Effect of the Invention

[0022] According to the present invention, it is possible to suppress printing defects caused by poor adsorption of paper. [Brief description of the drawings]

[0023] [Figure 1] 1 is a schematic cross-sectional side view of each component of an image forming apparatus. [Diagram 2] 1 is a block diagram of an image forming apparatus according to an embodiment of the present invention. [Diagram 3] 2A and 2B are diagrams illustrating the internal and peripheral configuration of a transport unit according to the embodiment. [Figure 4] 5A and 5B are diagrams illustrating a configuration of an adsorption unit according to the embodiment. [Diagram 5] 11 is a table summarizing the sheets placed on each transport surface from the start of single-sided printing in the image forming apparatus according to the present embodiment. [Figure 6A] 11 is a table summarizing paper sheets placed on each transport surface from the start of double-sided printing in a conventional image forming apparatus. [Figure 6B] 11 is a table summarizing the paper that is transported before double-sided printing is completed in a conventional image forming apparatus. [Figure 6C] 7 is a graph showing the suction pressure of each transport surface at each timing in FIGS. 6A and 6B. [Figure 7A] 11 is a table summarizing the sheets placed on each transport surface from the start of double-sided printing in the image forming apparatus according to the present embodiment. [Figure 7B]11 is a table summarizing the paper that is transported before double-sided printing is completed in the image forming apparatus according to the present embodiment. [Figure 7C] 7C is a graph showing the suction pressure of each transport surface at each timing in FIGS. 7A and 7B. [Figure 8A] 13 is a table summarizing sheets placed on each transport surface from the start of double-sided printing in an image forming apparatus according to another embodiment. [Figure 8B] 13 is a table summarizing sheets transported before double-sided printing is completed in an image forming apparatus according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings. However, the scope of the invention is not limited to the illustrated examples. In the following description, components having the same functions and configurations are given the same reference numerals and their description will be omitted.

[0025] [Overall configuration of image forming device] Fig. 1 is a diagram showing an example of a schematic configuration of an image forming apparatus 1. Fig. 2 is a block diagram showing a functional configuration of the image forming apparatus 1. The image forming apparatus 1 includes a paper feeder 10, an image forming apparatus main body 20, a paper discharge device 30, a control unit 40, and a suction device 50.

[0026] (Paper Feeding Device) The paper feed device 10 includes a paper feed tray 11 and a paper feed section 12. The paper feed tray 11 stores paper sheets P. The paper feed section 12 includes rollers and a belt. The belt is loop-shaped, and its inner side is supported by two rollers. The paper feed section 12 transports paper sheets P by rotating the two rollers with paper sheets P placed on the belt.

[0027] (Image forming device) The image forming apparatus main body 20 includes a delivery roller 21 , a transport section 22 , an image forming section 23 , a fixing section 24 , a transport roller 25 , a belt transport section 26 , and a swing arm section 27 .

[0028] {Delivery Roller} The delivery roller 21 is provided at a position between the paper feed unit 12 and the transport unit 22 of the paper feed device 10. The delivery roller 21 includes a claw portion 21a. The claw portion 21a is switched between an open and closed state under the control of the control unit 40. The delivery roller 21 holds the paper P on its transport surface by the claw portion 21a.

[0029] The delivery roller 21 delivers the paper P transported by the paper feed section 12 of the paper feed device 10 to the transport section 22. In detail, the delivery roller 21 holds and picks up a first end of the paper P transported from the paper feed section 12 with the swing arm section 21b and holds it with the claw section 21a. The delivery roller 21 then rotates in the clockwise direction indicated by the arrow in FIG. 1 to deliver the paper P to one of the claw sections 222a to 222c of the transport section 22.

[0030] {Transportation section} The transport unit 22 has a plurality of transport surfaces 221 on its outer circumferential surface on which one sheet of paper P is placed. The transport unit 22 transports the paper P delivered from the delivery roller 21 in the transport direction indicated by the arrow in Fig. 1. In this embodiment, the transport unit 22 is a large-diameter transport drum that is substantially cylindrical.

[0031] In this embodiment, the case where the transport unit 22 is a triple-sized transport drum is exemplified. Triple-sized means that the circumferential length of the transport unit 22 is a size that can simultaneously hold three sheets of paper P having the maximum length usable in the image forming apparatus 1. That is, in this embodiment, the transport unit 22 has three transport surfaces 221. In the following, the three transport surfaces 221 are respectively referred to as surface A 221a, surface B 221b, and surface C 221c (see FIG. 3).

[0032] The transport unit 22 is not limited to a triple-cylinder transport drum, but may be, for example, a quadruple or quintuple-cylinder transport drum.

[0033] The conveying unit 22 is also connected to a conveying drum motor (not shown). The control unit 40 rotates the conveying drum motor to rotate the conveying unit 22 by an angle proportional to the amount of rotation. Under the control of the control unit 40, the conveying unit 22 conveys the paper P in the conveying direction while facing the image forming unit 23.

[0034] Further, in order to hold the paper sheet P on the transport surface 221, the transport section 22 includes claws 222a to 222c and an adsorption section 223 (see FIG. 4).

[0035] <Claw section> The claw portions 222a to 222c are arranged on the A surface 221a, the B surface 221b, and the C surface 221c at intervals equal to the circumferential lengths of the delivery roller 21 and the transport roller 25, respectively. The claw portions 222a to 222c are switched between open and closed states under the control of the control unit 40. In the closed state, the claw portions 222a to 222c press a first end of the paper P delivered from the delivery roller 21 or the swing arm portion 27 with a predetermined pressing force, and hold the paper P on the transport surface 221. In the open state, the claw portions 222a to 222c are released from the pressing state, and deliver the paper P held on the transport surface 221 to the transport roller 25.

[0036] <Suction part> The suction section 223 creates a suction pressure that sucks air from the transport surface 221 into the inside of the transport section 22 , thereby causing the paper sheet P to be suctioned onto the transport surface 221 .

[0037] Fig. 3 is a diagram illustrating the configuration of the inside and periphery of the transport section 22. Fig. 4 is a diagram illustrating the configuration of the suction section 223. As shown in Fig. 3, the inside of the transport section 22 has a hollow structure. Chambers 2231 are formed below (inner side of) the A-side 221a to C-side 221c, respectively. A sheet S forming the outer surface of the chamber 2231 is disposed on each transport surface 221. A plurality of suction holes H are formed in the sheet S.

[0038] A plurality of chambers 2231 (three chambers 2231a, 2231b, and 2231c in this embodiment) are arranged between two claws 222, 222 of the transport section 22. As shown in Fig. 4, each chamber 2231 includes a plurality of small chambers 2231S that are further divided in the longitudinal direction of the rotation shaft 224. A communication hole 227 is provided in the bottom surface of each small chamber 2231S.

[0039] 4, side plates 225, 225 for holding the rotation shaft 224 of the transport unit 22 are provided on the front and rear sides of the transport unit 22. A substantially ring-shaped suction control plate 226 is configured not to rotate between the rear side plate 225 and the transport unit 22. Specifically, for example, as shown in FIG. 4, the suction control plate 226 is biased against the transport unit 22 by a spring B provided between the suction control plate 226 and the side plate 225.

[0040] On the surface of the suction control plate 226 facing the transport section 22, openings 226a to 226c corresponding to the chambers 2231a to 2231c are provided. The openings 226a to 226c are arc-shaped grooves, and a plurality of rows are provided according to the number of the chambers 2231. The openings 226a to 226c are provided at positions on the suction control plate 226 corresponding to the suction areas A1 where the paper P is sucked by the suction device 50. A communication section C of the suction device 50 is fixed to each of the openings 226a to 226c. The suction device 50 is a known blower equipped with a fan and a motor, and detailed description thereof will be omitted. The communication section C is, for example, a tube.

[0041] Furthermore, a connection hole 228 communicating with the openings 226a to 226c is provided on the surface of the transport section 22 facing the suction control plate 226. A pipe 229 is provided inside the transport section 22, which has a plurality of flow paths and communicates the connection hole 228 with the plurality of communication holes 227. A known solenoid valve (not shown) is provided in each of the flow paths in the pipe 229, which are connected to the plurality of communication holes 227. The solenoid valve opens and closes the flow path for each small chamber 2231S, or adjusts the opening degree thereof, individually, under the control of the control section 40.

[0042] With the above configuration, in the suction area A1, one air flow path is formed by the opening 226a of the suction control plate 226, the communication hole 227, the connection hole 228, and the pipe 229 of the transport section 22. The adsorption section 223 is formed by the air flow path and the suction device 50 connected to the air flow path by a communication part C. The suction pressure generated by the suction device 50 is propagated through the air flow path to generate negative pressure in the chamber 2231 whose upper surface is covered by the paper P. As a result, the paper P is adsorbed and held on the transport surface 221 having a plurality of suction holes H.

[0043] Furthermore, by controlling the opening and closing of the solenoid valve by the control unit 40, the range of the transport surface 221 where suction pressure is generated according to the size of the paper P can be appropriately adjusted.

[0044] {Image forming section} Returning to FIG. 1, the image forming unit 23 forms an image on the paper P transported by the transport unit 22. In this embodiment, the image forming unit 23 includes a plurality of head units each consisting of a plurality of inkjet heads. Each head unit forms an image by ejecting ink of each color from a nozzle opening facing the transport surface 221 at an appropriate timing according to the rotation of the transport unit 22 holding the paper P. The head unit is disposed such that the nozzle opening is spaced a predetermined distance from the transport surface 221.

[0045] {Fixing part} The fixing unit 24 fixes the image formed on the paper P by the image forming unit 23. The fixing unit 24 is, for example, an energy ray irradiation unit. Specifically, the fixing unit 24 includes a light emitting unit arranged across the width of the conveying unit 22 in the perpendicular direction. The light emitting unit irradiates the conveyed paper P with energy rays such as ultraviolet rays under the control of the control unit 40. This causes the ink on the paper P to harden and be fixed.

[0046] {Transport roller} The transport rollers 25 transport the paper P that has passed through the image forming unit 23 and the fixing unit 24, receiving the paper P from the transport unit 22. The transport rollers 25 include, for example, a first transport roller 251, a second transport roller 252, a third transport roller 253, and a fourth transport roller 254, as shown in FIG.

[0047] The first transport roller 251 is provided to face the transport section 22. The second transport roller 252 is provided to face the first transport roller 251. The third transport roller 253 and the fourth transport roller 254 are provided to face the second transport roller 252. Of these, the first transport roller 251, the third transport roller 253 and the fourth transport roller 254 rotate in the opposite direction to the transport direction. The second transport roller 252 rotates in the transport direction.

[0048] The first transport roller 251 to the fourth transport roller 254 are provided with claw portions 251a to 254a, respectively. The claw portions 251a to 254a open and close under the control of the control unit 40. In detail, the control unit 40 opens the claw portions 251a to 253a at the timing when the paper P is handed over to the second transport roller 252 to the fourth transport roller 254 on the downstream side, thereby handing over the first end of the paper P to the claw portions 252a to 254a. The control unit 40 holds the first end of the paper P by closing the claw portions 252a to 254a at the timing when the first end of the paper P is handed over from the upstream claw portions 251a to 253a.

[0049] {Belt conveyor} The belt conveying section 26 is provided to face the third conveying roller 253. The belt conveying section 26 includes a ring-shaped conveying belt whose inner side is supported by a plurality of rollers. The belt conveying section 26 includes a branching section 261 that is rotatable at a predetermined angle on the downstream side in the conveying direction. The control section 40 controls the branching section 261 to convey print job paper Pa (described later) received from the third conveying roller 253 to a first paper output tray 31a (described later). Alternatively, the control section 40 controls the branching section 261 to send non-print job paper Pb (described later) received from the third conveying roller 253 to a second paper output tray 31b (described later).

[0050] {Swing arm part} The swing arm portion 27 is provided downstream of the fourth transport roller 254. When the image forming apparatus 1 performs double-sided printing, the fourth transport roller 254 and the swing arm portion 27 invert the first and second sides of the paper P and return it to the transport section 22.

[0051] Specifically, when image formation on the first side of the paper P is completed, the control unit 40 transfers the first end of the paper P to the first transport roller 251, the second transport roller 252, and the fourth transport roller 254 in that order. When the second end of the paper P reaches a position facing the swing arm unit 27, the control unit 40 transfers the paper P from the fourth transport roller 254 to the swing arm unit 27. Then, when any of the transport surfaces 221 reaches a position facing the swing arm unit 27, the control unit 40 transfers the paper P to the transport unit 22.

[0052] In this way, the transport roller 25 functions as an inverting section that inverts the paper P that has passed through the image forming section 23. In addition, the swing arm section 27 functions as a circulating section that returns the paper P that has been inverted in the inverting section to the transport section 22.

[0053] In addition, the image forming apparatus main body 20 in the present invention executes so-called alternating circulation control when forming images on both the first and second sides of the paper P. Alternating circulation control is a control in which image formation on a second paper P is sandwiched between image formation on the first and second sides of the first paper P. When the image forming apparatus 1 employs alternating circulation control, the gap between the sheets is narrower than in the normal circulation method in which image formation on the first and second sides of the first paper P is performed consecutively, thereby improving the productivity of double-sided printing. Details of paper transport control in the image forming apparatus 1 will be described later.

[0054] (Paper output device) The paper discharge device 30 stores the paper P discharged from the image forming apparatus main body 20 until the user collects it. The paper discharge device 30 has a plurality of plate-shaped paper discharge trays 31. Of the plurality of paper discharge trays 31, the first paper discharge tray 31a is for placing paper Pa for a print job. Also, of the plurality of paper discharge trays 31, the second paper discharge tray 31b is for placing paper Pb for a non-print job.

[0055] (Control unit) The control unit 40 controls the operation of each device constituting the image forming apparatus 1. The control unit 40 includes a CPU (Central Processing Unit) 41, a RAM (Random Access Memory) 42, and a ROM (Read Only Memory) 43, as shown in FIG.

[0056] The CPU 41 executes various types of arithmetic processing. The CPU 41 also centrally controls the overall operation of the image forming apparatus 1. The RAM 42 provides a working memory space for the CPU 41 and stores temporary data. The ROM 43 stores various control programs and setting data executed by the CPU 41. Note that a rewritable non-volatile memory such as an EEPROM (Electrically Erasable Programmable Read Only Memory) or a flash memory may be used instead of the ROM 43.

[0057] (external device) The external device 2 is, for example, a personal computer. The external device 2 supplies the control unit 40 with image data of the image recorded by the image forming apparatus 1 and the like.

[0058] [Paper transport control; single-sided printing] The paper transport control in the image forming apparatus 1 configured as above will be described below. First, the description will be limited to the case where an image is formed only on the first side of the paper P.

[0059] The control unit 40, which has received print job data from the external device 2, first conveys the paper P from the paper feeder 10 to the image forming apparatus main body 20. The control unit 40 places the paper P on the conveying surface 221 of the conveying unit 22 and causes the paper P to be adsorbed by the adsorption unit 223. The control unit 40 then drives the conveying drum motor to rotate the conveying unit 22 and convey the paper P.

[0060] As described above, when the paper P is placed on the transport surface 221, the suction unit 223 creates a negative pressure in the chamber 2231 by the suction device 50 performing suction, and adsorbs the paper P to the transport surface 221. On the other hand, immediately after the start of a print job, the negative pressure in the chamber 2231 is not sufficiently created, and the suction pressure on the transport surface 221 becomes high (i.e., the suction force becomes weak). Therefore, immediately after the start of a print job, paper transport problems and printing problems due to paper floating are likely to occur.

[0061] 5, at the start of a print job, the control unit 40 causes non-print job paper Pb to be adsorbed to the conveying surface 221 and conveyed. Specifically, the control unit 40 does not operate the image forming unit 23 and the fixing unit 24 for the non-print job paper Pb, and passes the paper to the conveying rollers 25 and the belt conveying unit 26. The control unit 40 also controls the branching unit 261 in the belt conveying unit 26 to discharge the non-print job paper Pb to the second discharge tray 31b of the paper discharge device 30.

[0062] When a negative pressure is generated in the chamber 2231 and the suction pressure on the transport surface 221 becomes sufficiently low, the control unit 40 causes the print job paper Pa on which the image of the print job is formed to be transported.

[0063] In this way, when a predetermined condition for reducing the suction force of the suction unit 223 is satisfied, the control unit 40 functions as a transport control unit that, after suctioning and transporting the non-print job paper Pb, continuously suctions and transports the print job paper Pa to the transport surface 221. The control unit 40 also functions as an image formation control unit that does not form an image of the print job on the non-print job paper Pb, but forms an image of the print job on the print job paper Pa.

[0064] With this configuration, print job paper Pa can be transported only after the suction section 223 has a predetermined sufficient suction force. This makes it possible to prevent printing defects caused by poor suction of paper P. Note that with this configuration, non-print job paper Pb can become waste paper, but on the other hand, the generation of waste paper due to poor printing can be prevented.

[0065] 5, a case where two non-print job sheets Pb are transported from the start of a print job is illustrated, but this is not limited to this. The number of non-print job sheets Pb transported may be one, and may be determined arbitrarily.

[0066] For example, before the image forming apparatus main body 20 is shipped, the number of non-print job sheets Pb that need to be transported until the suction section 223 has a predetermined suction force may be measured and set in the ROM 43. In this way, if the transport control for non-print job sheets Pb is stored in the ROM 43, the preparation time can be reduced when performing print control under the same conditions.

[0067] Alternatively, an acquisition unit may be provided that acquires information related to the suction force of the suction unit 223 and transmits the acquired information to the control unit 40. The acquisition unit is, for example, a known pressure sensor. In this configuration, the control unit 40 may perform control so as to transport non-print job paper Pb at a timing other than the start of a print job, according to the acquired information.

[0068] The number of non-print job sheets Pb to be conveyed may be changed as appropriate according to the sheet conditions of the print job sheets Pa used in the print job, such as the type of paper, basis weight, thickness, and size.

[0069] For example, if the print job paper Pa has low rigidity, its flatness is easily lost due to ink. Therefore, when the print job paper Pa has low rigidity, it is preferable for the control unit 40 to increase the suction force by increasing the number of non-print job paper Pb to be conveyed.

[0070] Also, for example, when the size of print job paper Pa is large, it is necessary to adsorb the print job paper Pa over the entire surface of the transport surface 221. Then, it is necessary to create a sufficient negative pressure in the adsorption unit 223. Therefore, when the size of print job paper Pa is large, it is preferable that the control unit 40 increase the adsorption force by increasing the number of non-print job paper Pb that are transported.

[0071] [Paper transport control; double-sided printing] Next, a description will be given of a case where images are formed on both sides of the print job paper Pa. As described above, the image forming apparatus 1 according to this embodiment executes double-sided printing by so-called alternate circulation control.

[0072] Fig. 6A is a table summarizing the paper sheets P placed on each transport surface 221 from the start of a print job in a conventional image forming apparatus 1. Fig. 6B is a table summarizing the paper sheets P transported before the end of a print job in a conventional image forming apparatus 1. Fig. 6C is a graph measuring the suction pressure of each transport surface 221 at each timing in Figs. 6A and 6B. As shown in Fig. 6B, in the following example, it is assumed that double-sided printing is performed on n sheets of paper Pa for a print job.

[0073] In the alternating circulation control, the second side of the inverted paper P is placed on the transport surface 221 between the transport surfaces 221, 221 on which the first side of the paper P is placed. Therefore, when double-sided printing starts, it is necessary to provide a margin of transport surface 221 on which the second side of the inverted paper P can be placed, and as shown in Fig. 6A, paper P cannot be placed consecutively on consecutive transport surfaces 221. As a result, as shown in A2 and A3, and A4 and A5 in Fig. 6C, the suction pressure of the transport surface 221 on which the paper P is not placed (empty transport surface) increases, and the suction pressure of the subsequent transport surfaces 221 may not decrease completely.

[0074] 6B, when double-sided printing is completed under the alternating circulation control, the paper P is no longer transported. Therefore, the paper P cannot be continuously placed on the successive transport surfaces 221. As a result, as shown by A12 and A13, and also A14 and A15 in FIG. 6C, the suction pressure of the empty transport surface 221 increases, and the suction pressure of the subsequent transport surfaces 221 may not decrease completely.

[0075] Therefore, as shown in Figures 7A and 7B, at the start and end of double-sided printing, when an empty transport surface 221 that does not adsorb paper P is generated, the control unit 40 according to this embodiment adsorbs and transports non-print job paper Pb to the empty transport surface 221. With this configuration, as shown in B7 to B19 in Figure 7C, the suction pressure of the transport surface 221 on which print job paper Pa is placed is sufficiently reduced. As a result, printing defects caused by poor adsorption of paper can be suppressed.

[0076] 7A and 7B show an example in which non-print job paper Pb is inverted by transport rollers 25 and circulated to transport section 22 by swing arm section 27, similar to print job paper Pa, but the present invention is not limited to this. In other words, control section 40 may send non-print job paper Pb to belt transport section 26 without inverting it by transport rollers 25, and discharge it to paper discharge device 30.

[0077] 8A and 8B are tables summarizing the paper P that is transported after the start and before the end of a print job in this configuration. In this configuration, there is no need to provide a margin for the transport surface 221 on which the second side of the inverted non-print job paper Pb can be placed. Therefore, as can be seen particularly from a comparison of FIG. 7A and FIG. 8A, in this configuration, the print job can be progressed in a shorter time.

[0078] On the other hand, in this configuration, the control unit 40 needs to control the transport roller 25 to send print job paper sheets Pa with images formed on their first sides to the swing arm unit 27, and send print job paper sheets Pa with images formed on their second sides and non-print job paper sheets Pb to the belt transport unit 26. In other words, a configuration in which all of the paper sheets P are circulated and transported once by the transport unit 22 makes it easier for the control unit 40 to control the image forming apparatus main body 20.

[0079] [Other configurations] Although the present invention has been specifically described above based on the embodiment, the present invention is not limited to the above embodiment. Of course, the present invention can be modified in various ways within the scope of the invention described in the claims and its equivalents.

[0080] For example, in the above, the non-print job paper Pb is transported at the start and before the end of the print job, but this is not limited to the above. For example, when the control unit 40 interrupts the print job midway for calibration or the like, the print job paper Pa is no longer transported, just as it is before the end of the print job, and the suction pressure of the transport surface 221 increases. Also, when the print job is resumed after the interruption, the suction pressure of the transport surface 221 does not decrease completely, just as it was when the print job started. For this reason, it is preferable to adsorb the non-print job paper Pb to the transport surface 221 and transport it when the print job is interrupted intentionally or when the interrupted print job is resumed.

[0081] 1 illustrates an example of one paper feed device 10 having one paper feed tray 11, but the present invention is not limited to this. For example, one paper feed device 10 may be configured to have multiple paper feed trays 11. Furthermore, the image forming apparatus 1 may be configured to have multiple paper feed devices 10. In this way, when the image forming apparatus 1 is configured to have multiple paper feed trays 11, the print job paper sheets Pa and the non-print job paper sheets Pb may be supplied from different paper feed trays 11. Furthermore, the print job paper sheets Pa and the non-print job paper sheets Pb may be paper sheets P with different paper conditions.

[0082] 1 illustrates an example of one paper discharge device 30 including a plurality of paper discharge trays 31, but the present invention is not limited to this. That is, the image forming apparatus 1 may be configured to include a plurality of paper discharge devices 30.

[0083] Furthermore, the image forming apparatus 1 may be configured to include only one paper discharge tray 31. In particular, in this configuration, it is preferable that the image forming unit 23 forms a predetermined mark on the non-print job paper Pb so that the paper Pb can be distinguished from the print job paper Pa. With this configuration, the print job paper Pa and the non-print job paper Pb can be easily sorted from the single paper discharge tray 31.

[0084] In the above, the transport unit 22 is a transport drum having the transport surface 221 in a specific area, but the present invention is not limited to this. For example, the transport unit 22 may be an endless belt on whose entire surface the paper P can be placed.

[0085] In the above, examples have been disclosed in which a hard disk or a non-volatile semiconductor memory is used as a computer-readable medium for the program according to the present invention, but the present invention is not limited to these examples. Portable recording media such as CD-ROMs can be used as other computer-readable media. Furthermore, carrier waves can be used as a medium for providing data for the program according to the present invention via a communication line. [Explanation of symbols]

[0086] 1. Image forming device 22 Conveyor section 221 Conveying surface 223 Adsorption part 23 Image forming section 25 Conveyor roller (reversal section) 27 Swing arm section (circulation section) 40 Control unit (transport control unit, image formation control unit) H Suction hole P Paper Pa Print Job Paper Pb Non-print job paper

Claims

1. a conveying unit that includes a plurality of conveying surfaces on which paper can be placed and conveys the paper placed on the conveying surfaces; a suction unit that sucks air through a plurality of suction holes formed on the conveying surface to adsorb the paper to the conveying surface; an image forming section for forming an image on the paper that is attracted and conveyed; a conveyance control unit that, when a predetermined condition is satisfied under which the suction force of the suction unit is reduced during execution of a print job, causes one or more non-print job sheets to be conveyed by being suctioned to the conveyance surface, and then causes a print job sheet to be conveyed by being suctioned to the conveyance surface; an image forming control unit that does not form an image of the print job on the non-print job paper and forms an image of the print job on the print job paper; An image forming apparatus comprising:

2. The image forming apparatus according to claim 1 , wherein the predetermined condition is a start time of a print job.

3. The image forming apparatus according to claim 2 , wherein the transport control unit determines the number of sheets of the non-print job paper to be transported at the start of printing in accordance with paper conditions including paper type, basis weight, paper thickness, and paper size of the print job paper.

4. the predetermined condition is when an empty transport surface occurs during execution of a print job, and the transport surface does not attract paper; The image forming apparatus according to claim 1 , wherein the transport control unit transports the non-print job paper by adsorbing it to the empty transport surface.

5. a reversing unit that turns over the paper that has passed through the image forming unit, and a circulating unit that returns the paper that has been turned over by the reversing unit to the conveying unit upstream of the image forming unit, the image formation control unit forms an image on a first side of a second sheet of paper for the print job between image formation on a first side of the first sheet of paper for the print job and image formation on a second side of the first sheet of paper for the print job that has been returned to the transport unit by the reversing unit and the circulating unit during double-sided printing; The image forming apparatus according to claim 4 , wherein the empty transport surface occurs at the start and end of double-sided printing.

6. The image forming apparatus according to claim 5 , wherein the transport control section discharges the non-print job paper during double-sided printing without passing the paper through the reversing section and the circulating section.

7. The image forming apparatus according to claim 1 , wherein the transport control section discharges the print job paper and the non-print job paper to different discharge destinations.

8. The image forming apparatus according to claim 1 , wherein the image forming control unit applies a marker to the non-print job paper to distinguish it from the print job paper.

9. 4. The image forming apparatus according to claim 1, wherein the predetermined condition is when a print job is interrupted and when the interrupted print job is resumed.

10. an acquisition unit that acquires information regarding a suction pressure of the suction unit, The image forming apparatus according to claim 1 , wherein the predetermined condition is that the suction pressure is equal to or higher than a predetermined value.

11. The image forming apparatus according to claim 1 , wherein the transport control unit stores, as a print job, control for adsorbing the non-print job paper to the transport surface and transporting the paper.

12. 4. The image forming apparatus according to claim 1, wherein the print job sheets and the non-print job sheets have the same paper conditions including paper type, basis weight, paper thickness, and paper size.

13. The image forming apparatus according to claim 1 , wherein the transport surface is provided in a specific area of ​​the transport section.

14. a conveying unit that includes a plurality of conveying surfaces on which paper can be placed and conveys the paper placed on the conveying surfaces; a suction unit that sucks air through a plurality of suction holes formed on the conveying surface to adsorb the paper to the conveying surface; and an image forming unit that forms an image on the paper that is attracted to and transported. a conveyance control unit that, when a predetermined condition is satisfied under which the suction force of the suction unit is reduced during execution of a print job, causes one or more non-print job sheets to be adsorbed to the conveyance surface and conveyed, and then causes a print job sheet to be adsorbed to the conveyance surface and conveyed in succession; an image forming control unit that does not form an image of the print job on the non-print job paper and forms an image of the print job on the print job paper; A program that functions as a

Images