JP2015042465A - Printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten a period when a printing part is occupied by a sheet while keeping a page order of a printed matter in two-sided printing.SOLUTION: A control part 9 controls each part so as to perform, in the case where there are sheets not requiring reverse printing during two-sided printing, surface printing on the sheets in vacant time between sheets to be printed, convey the sheets printed on the surface to a bulk sheet discharge path RD2 without circularly conveying, guide to a sheet discharge invert path RR2 to stock, and return from the sheet discharge invert path RR2 to the bulk sheet discharge path RD2 at a timing of moving into a position where the sheets are arranged in a sheet discharge page order to a plurality of sheets printed in two sides and conveyed to a bulk sheet discharge stand 63 along the bulk sheet discharge path RD2. Furthermore, in the case where there are sheets to be printed only in the reverse face in a printing page order according to face-up/face-down sheet discharge setting, the control part 9 changes the face-up/face-down sheet discharge setting so as to change the sheets to be printed only in the reverse face to sheets not requiring reverse printing.

Description

  The present invention relates to a printing apparatus capable of duplex printing.

  2. Description of the Related Art There is known a printing apparatus that has a circulation path including a reversal path, reverses the front and back by circulating and conveying paper printed on the front surface along the circulation path, and performs duplex printing by printing on the back surface.

  As a double-sided printing method in the printing apparatus as described above, an interleaf method is known. The interleaf system is a system that alternately prints the front surface of an unprinted paper and the back surface of a surface-printed paper while circulating and conveying a plurality of paper sheets (see, for example, Patent Document 1). Thereby, high productivity double-sided printing can be realized.

JP 2012-63642 A

  By the way, there is a case where a sheet on which double-sided printing is required does not require printing on the back side (the back side is blank). For example, when performing double-sided printing on an original with an odd total number of pages, it is not necessary to print the back side of the last sheet.

  In the interleaf double-sided printing, paper that does not require backside printing is circulated and conveyed in the same manner as other papers. That is, a sheet that does not require backside printing is printed on the front side by the printing unit, is circulated and reversed, and passes through the printing unit without backside printing, and is then discharged.

  Here, in the interleaf double-sided printing, immediately after the start of double-sided printing, there is a period in which a plurality of front side printings continue with a vacant time corresponding to the printing time for one sheet between sheets. Further, immediately before the end of double-sided printing, there is a period in which a plurality of backside printings continue with a vacant time corresponding to the printing time for one sheet between sheets.

  Therefore, if the front side printing of the paper that does not require the back side printing is performed during the above-mentioned idle time, and the paper is discharged without being circulated, the period during which the printing unit is occupied by the paper during double-sided printing is shortened. It becomes possible. If the period during which the printing unit is occupied is shortened, it is possible to quickly start changing the print settings such as the head gap and the print conveyance speed in the inkjet printing apparatus. As a result, when there is a next print job that needs to be changed, the execution of the print job can be started quickly. As a result, productivity when the print job is continued can be improved.

  However, as described above, when the front side printing of a sheet that does not require backside printing is performed in the idle time and the paper is discharged without being circulated, the page order in the discharged printed matter is changed from the original page order.

  The present invention has been made in view of the above, and an object of the present invention is to provide a printing apparatus capable of shortening a period during which a printing unit is occupied by paper while maintaining the page order of printed matter in double-sided printing.

  In order to achieve the above object, the first feature of the printing apparatus according to the present invention is that a circulation path including a first inversion path for reversing the front and back sides of the paper, and a paper discharge path branched from the circulation path and heading to a paper discharge tray. A paper transport unit that transports the paper along the paper discharge path, a paper discharge reversing unit that reverses the paper back and forth by returning the paper delivered from the paper discharge path to the paper discharge path by reciprocating the second reverse path, and A printing unit that prints on paper conveyed along a circulation path, a paper feeding unit that feeds unprinted paper to the circulation path, and a plurality of unprinted sheets to the circulation path during double-sided printing Paper is fed sequentially, and a plurality of unprinted sheets fed are sent to the printing unit with a predetermined time interval between the sheets to be printed on the surface, and the surface-printed sheets are circulated and conveyed along the circulation path. The front and back are reversed and the front and back are printed. The paper feeding section, the transport section, and the like so that the paper is sent to the printing section and printed on the back side, and the double-side printed paper that has been printed on the back side is transported to the paper discharge tray along the paper discharge path and discharged. And a control unit that controls the printing unit, and when there is a sheet that does not require backside printing in double-sided printing, the control unit determines that the backside printing is not required in a free time between sheets to be printed. Feeding unprinted paper and performing front side printing on the paper, transporting the paper that has been printed on the front side and does not require reverse printing to the paper discharge path without being circulated, and from the paper discharge path A plurality of double-sided papers that are led to the second reversing path and stocked, and the sheets that have been printed on the second reversing path and that do not require printing on the back surface are transported along the paper ejection path to the paper ejection tray. The output page is printed on the printed paper. The feeding unit, the transport unit, the printing unit, and the discharge reversing unit are controlled so as to return to the discharge path from the second reversing path at the timing of entering the matching position in order. If there is paper to be printed only on the back side in the print page order according to the set discharge page order, the back side printing is not required for the paper to be printed only on the back side by changing the ascending order or descending order of the discharge page order. Is to change the paper.

  A second feature of the printing apparatus according to the present invention is that the control unit discharges the paper, which is printed on the second reversing path and does not require the reverse side printing, onto a plurality of double side printed papers. It is to perform the front side printing on the paper that does not require the back side printing at the latest timing within a range where the page can be put in a position that matches the page order.

  According to the first feature of the printing apparatus according to the present invention, the control unit performs the front surface printing on the paper that does not require the back surface printing in the idle time between the printed papers, and does not require the back surface printing after the front surface printing. Paper is transported to the paper discharge path without being circulated. Thereby, the period during which the printing unit is occupied by the paper can be shortened.

  In addition, when there is a sheet to be printed only on the back side in the print page order corresponding to the discharge page order set in ascending order or descending order in advance, the control unit changes the ascending order or descending order of the discharge page order to change the order on the back side. Change the paper to be printed only to paper that does not require backside printing. As a result, even if there is no paper that does not require reverse side printing under the preset discharge page order setting, if there is paper that is printed only on the back side (no front side printing is required), the printing section is placed on the paper. The occupied period can be shortened.

  In addition, the control unit guides the paper that has been printed on the front surface and does not require the back surface printing to the second reversing path to be stocked. After that, the control unit enters the paper discharge path at a timing when the stocked paper enters the position where the plurality of double-sided printed sheets conveyed along the paper discharge path are aligned in the order of the discharge pages. Control to return. Thereby, the page order of printed matter can be maintained.

  Therefore, according to the first feature of the printing apparatus, in double-sided printing, the period during which the printing unit is occupied by the paper can be shortened while maintaining the page order of the printed matter.

  According to the second feature of the printing apparatus according to the present invention, the position where the sheets printed on the second reversing path that do not require the front-side printed backside printing are aligned with the plurality of double-sided printed sheets in the order of the discharged pages. The front side printing is performed on the paper that does not require the back side printing at the latest timing within the range that can be included. Thereby, it is possible to reduce the waste of paper when a paper jam or the like occurs.

1 is a schematic configuration diagram of a printing apparatus according to an embodiment. FIG. 2 is a control block diagram of the printing apparatus shown in FIG. 1. It is explanatory drawing of double-sided printing of an interleaf system. FIG. 5 is a diagram illustrating printing timing in an interleaf printing schedule. It is a figure which shows the timing which can insert the front surface printing of the paper which does not require back surface printing. It is a figure which shows the timing of printing in the printing schedule of the interleaf system in a specific example. It is a figure which shows the timing which can insert the front surface printing of the paper which does not require the back surface printing in a specific example. It is a figure which shows the timing which can insert the front surface printing of the paper which does not require the back surface printing in another specific example. FIG. 10 is a table summarizing the relationship between face-up / face-down paper discharge settings, pages to be printed on paper printed on only one side, and whether or not face-up / face-down paper discharge settings have been changed. 6 is a flowchart for explaining the operation of the printing apparatus during duplex printing. It is a figure which shows the timing of printing in the changed printing schedule. FIG. 6 is a diagram illustrating the page order of printed materials discharged face-down on a large-capacity discharge table. FIG. 6 is a diagram illustrating the page order of printed materials that are discharged face-up on a large-capacity discharge table.

  Embodiments of the present invention will be described below with reference to the drawings. Throughout the drawings, the same or equivalent parts and components are denoted by the same or equivalent reference numerals. However, it should be noted that the drawings are schematic and different from the actual ones. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  Further, the embodiment described below exemplifies an apparatus or the like for embodying the technical idea of the present invention, and the technical idea of the present invention includes the material, shape, structure, The layout is not specified as follows. The technical idea of the present invention can be variously modified within the scope of the claims.

  FIG. 1 is a schematic configuration diagram of a printing apparatus according to an embodiment of the present invention. FIG. 2 is a control block diagram of the printing apparatus shown in FIG. In the following description, the paper surface direction in FIG. In addition, the vertical and horizontal directions in FIG.

  In FIG. 1, a path indicated by a thick line is a transport path through which the paper P that is a print medium is transported. Of the transport routes, the route indicated by the solid line is the normal route RC. The paths indicated by broken lines are the main body side discharge path RD1 and the large capacity discharge path RD2. The paths indicated by the alternate long and short dash line are the reverse refeed path RR1 and the paper discharge reverse path RR2. A path indicated by a two-dot chain line is a paper feed path RS. In the following description, upstream and downstream mean upstream and downstream in the transport path.

  The normal route RC and the reverse refeeding route RR1 constitute a circulation route in the claims. The reverse refeed path RR1 corresponds to the first reverse path in the claims. The large-capacity paper discharge path RD2 corresponds to the paper discharge path in the claims. The paper discharge reverse path RR2 corresponds to the second reverse path of the claims.

  As shown in FIGS. 1 and 2, the printing apparatus 1 according to the present embodiment includes a paper feeding unit 2, a conveyance printing unit 3, an upper surface conveyance unit 4, a main body-side paper discharge unit 5, and reverse refeeding. A paper unit 6, a communication unit 7, a large-capacity paper discharge unit 8, a control unit 9, a main body-side housing 10 that stores or holds each unit on the main body side excluding the large-capacity paper discharge unit 8, and a large-capacity discharge unit A large-capacity paper discharge unit housing 11 that houses the paper unit 8 is provided.

  The paper feed unit 2 feeds the unprinted paper P to a circulation path composed of the normal path RC and the reverse refeed path RR1. The paper feed unit 2 is arranged on the most upstream side of the transport path. The paper feed unit 2 includes an external paper feed stand 21, an external paper feed roller 22, a plurality of internal paper feed stands 23, a plurality of pairs of internal paper feed rollers 24, a plurality of pairs of vertical transport rollers 25, and an external feed. A paper motor 26 and an internal paper feed motor 27 are provided.

  The external paper feed tray 21 is used for stacking unprinted paper P used for printing. The external paper feed tray 21 is partly exposed outside the main body side housing 10.

  The external paper feed roller 22 takes out the paper P one by one from the external paper feed tray 21 and conveys the paper P toward a later-described registration roller 31 along the paper feed path RS. The external paper feed roller 22 is disposed on the upper side of the external paper feed table 21.

  The internal paper feed table 23 is used for stacking unprinted paper P used for printing. The internal paper feed table 23 is disposed inside the main body side housing 10.

  The internal paper feed roller 24 takes out the paper P one by one from the internal paper feed tray 23 and sends it out to the paper feed path RS. The internal paper feed roller 24 is provided on the upper side of the internal paper feed table 23.

  The vertical conveyance roller 25 conveys the paper P taken out from the internal paper feed table 23 toward a registration roller 31 described later. The vertical conveyance roller 25 is disposed along the paper feed path RS.

  The external paper feed motor 26 rotationally drives the external paper feed roller 22 and the most downstream vertical transport roller 25. The external paper feed motor 26 is connected to the external paper feed roller 22 and the most downstream vertical transport roller 25 via a one-way clutch (not shown). As a result, the external paper feed roller 22 is driven by the one-way rotational drive of the external paper feed motor 26, and the most downstream vertical transport roller 25 is driven by the other-direction rotational drive of the external paper feed motor 26. Yes.

  The internal paper feed motor 27 rotationally drives the vertical paper feed rollers 25 other than the internal paper feed roller 24 and the most downstream vertical feed roller 25. The internal paper feed motor 27 can be connected / released to / from the internal paper feed roller 24 and other vertical transport rollers 25 via a clutch (not shown). The internal feed roller 24 and the vertical transport roller 25 that are driven to rotate are switched by the clutch.

  The transport printing unit 3 prints an image on the paper P while transporting the paper P. The transport printing unit 3 is disposed on the downstream side of the paper feeding unit 2. The conveyance printing unit 3 includes a registration roller 31, a registration motor 32, a belt conveyance unit 33, a belt motor 34, and an inkjet head unit (corresponding to a printing unit in claims) 35.

  The registration roller 31 temporarily stops the sheet P conveyed from the sheet feeding unit 2 or the reverse refeed unit 6 and corrects the skew feeding, and then conveys the sheet P toward the belt conveying unit 33. The registration rollers 31 are arranged on a normal route RC in the vicinity of the junction point between the paper feed route RS and the reverse route RR. The registration roller 31 corresponds to a part of the conveyance unit in the claims.

  The registration motor 32 rotates the registration roller 31.

  The belt conveyance unit 33 adsorbs and holds the paper P conveyed from the registration roller 31 on the belt and conveys it. The belt conveyance unit 33 is disposed on the downstream side of the registration roller 31. The belt conveyance unit 33 corresponds to a part of the conveyance unit in the claims.

  The belt motor 34 drives the belt conveyance unit 33.

  The inkjet head unit 35 has a plurality of line-type inkjet heads (not shown) in which a plurality of nozzles are arranged in a direction (front-rear direction) substantially orthogonal to the transport direction of the paper P. The inkjet head unit 35 is disposed above the belt conveyance unit 33. The ink jet head unit 35 prints an image by ejecting ink from the ink jet head onto the paper P transported by the belt transport unit 33.

  The upper surface transport unit 4 transports the paper P transported by the belt transport unit 33 so as to make a U-turn from the right direction to the left direction. The upper surface transport unit 4 includes a plurality of pairs of ascending transport rollers 36, a lift transport motor 37, a plurality of pairs of horizontal transport rollers 38, and a horizontal transport motor 39.

  The ascending conveyance roller 36 conveys the sheet P conveyed by the belt conveyance unit 33 to the upper horizontal conveyance roller 38 while nipping it. The ascending conveyance roller 36 is disposed along the ascending portion of the midstream area of the normal route RC. The ascending conveyance roller 36 corresponds to a part of the conveyance unit in the claims.

  The ascending conveyance motor 37 rotates a plurality of pairs of ascending conveyance rollers 36.

  The horizontal transport roller 38 transports the paper P transported by the ascending transport roller 36 to the main body-side paper discharge unit 5 or the reverse refeed unit 6 while niping it. The most downstream horizontal conveyance roller 38 is disposed along the upstream portion of the reverse refeed path RR1. The other horizontal conveyance rollers 38 are arranged along the horizontal portion in the downstream area of the normal route RC. The horizontal conveyance roller 38 corresponds to a part of the conveyance unit in the claims.

  The horizontal conveyance motor 39 rotates a plurality of pairs of horizontal conveyance rollers 38.

  The main body-side paper discharge unit 5 discharges the printed paper P. The main body-side paper discharge unit 5 includes a switching unit 41, a solenoid 42, a paper discharge roller 43, a paper discharge motor 44, and a paper discharge table 45.

  The switching unit 41 switches the transport path of the paper P between the main body side paper discharge path RD1 and the reverse refeed path RR1. The switching unit 41 is disposed at a branch point between the main body side paper discharge path RD1 and the reverse refeed path RR1.

  The solenoid 42 drives the switching unit 41.

  The paper discharge roller 43 conveys the paper P guided to the main body side paper discharge path RD1 by the switching unit 41 and discharges it to the paper discharge tray 45. The paper discharge roller 43 is disposed between the switching unit 41 and the paper discharge table 45 along the main body-side paper discharge path RD1.

  The paper discharge motor 44 rotates the paper discharge roller 43.

  The paper discharge tray 45 is for stacking printed paper P discharged by the paper discharge roller 43.

  The reverse refeed unit 6 reverses the surface-printed paper P and conveys it to the registration rollers 31 during double-sided printing. The reverse refeed unit 6 includes a reverse roller 46, a reverse motor 47, a refeed roller 48, a refeed motor 49, and a switching gate 50.

  The reversing roller 46 switches back the sheet P conveyed by the horizontal conveying roller 38 of the upper surface conveying unit 4 and conveys it to the refeed roller 48. The reverse roller 46 is configured to be able to rotate forward and backward in order to perform switchback conveyance of the paper P. The reverse roller 46 is disposed between the most downstream horizontal conveyance roller 38 and the refeed roller 48 along the reverse refeed path RR1. The reversing roller 46 corresponds to a part of the conveyance unit in the claims.

  The reverse motor 47 drives the reverse roller 46 to rotate forward and backward.

  The re-feed roller 48 conveys the paper P switched back by the reverse roller 46 to the registration roller 31. The refeed roller 48 is disposed between the reverse roller 46 and the registration roller 31 along the reverse refeed path RR1. The re-feed roller 48 corresponds to a part of the conveyance unit in the claims.

  The refeed motor 49 rotates the refeed roller 48.

  The switching gate 50 guides the sheet P conveyed by the horizontal conveyance roller 38 to the reverse roller 46. The switching gate 50 guides the paper P switched back by the reversing roller 46 to the refeed roller 48. The switching gate 50 is disposed in the vicinity of the center of gravity at the three positions of the most downstream horizontal conveyance roller 38, the reverse roller 46, and the refeed roller 48.

  The communication unit 7 sends the printed paper P to the large-capacity paper discharge unit 8. The communication unit 7 includes a switching unit 51, a solenoid 52, a communication roller 53, and a communication motor 54.

  The switching unit 51 switches the transport path of the paper P between the normal path RC and the large-capacity paper discharge path RD2. The switching unit 51 is disposed at a branch point between the normal route RC and the large-capacity paper discharge route RD2. The large-capacity paper discharge route RD2 is a route that branches from the normal route RC and goes to the large-capacity paper discharge tray 63 described later.

  The solenoid 52 drives the switching unit 51.

  The contact roller 53 transports the paper P transported from the belt transport unit 33 and sends it to the large-capacity paper discharge unit 8. The contact roller 53 is disposed on the downstream side of the switching unit 51 along the large-capacity paper discharge route RD2. The contact roller 53 corresponds to a part of the conveyance unit in the claims.

  The contact motor 54 drives the contact roller 53 to rotate.

  The large-capacity paper discharge unit 8 discharges the printed paper P. The large-capacity paper discharge unit 8 includes a paper discharge transport unit 61, a paper discharge reversing unit 62, a large-capacity paper discharge table (corresponding to the paper discharge table in the claims) 63, a lift drive unit 64, and a pair of side fences 65A, 65B, an end fence 66, a fence drive unit 67, and a carriage 68 are provided.

  The paper discharge conveyance unit 61 conveys the printed paper P sent out by the communication unit 7 and discharges it to the large-capacity paper discharge tray 63. The paper discharge transport unit 61 includes two pairs of introduction rollers 71, an introduction motor 72, a lift transport roller 73, a lift transport motor 74, two pairs of paper discharge rollers 75, and a paper discharge motor 76.

  The introduction roller 71 introduces the printed paper P sent out by the communication unit 7 to the large-capacity paper discharge unit 8. The introduction roller 71 is disposed on the downstream side of the communication roller 53 along the large-capacity paper discharge path RD2. The introduction roller 71 corresponds to a part of the conveyance unit in the claims.

  The introduction motor 72 rotationally drives two pairs of introduction rollers 71 and an upstream reverse approach roller 83 described later.

  The ascending conveyance roller 73 conveys the sheet P conveyed by the introduction roller 71 or the intermediate roller 86 described later to the upper discharge roller 75. The ascending conveyance roller 73 is disposed along the large-capacity discharge path RD2 in the vicinity of the downstream side of the junction between the large-capacity discharge path RD2 and the downstream portion of the discharge reversal path RR2. The ascending conveyance roller 73 corresponds to a part of the conveyance unit in the claims.

  The ascending conveyance motor 74 drives the ascending conveyance roller 73 to rotate.

  The paper discharge roller 75 conveys the paper P conveyed by the ascending conveyance roller 73 and discharges it to the large-capacity paper discharge tray 63. The paper discharge roller 75 is disposed along the most downstream part of the large-capacity paper discharge path RD2. The paper discharge roller 75 corresponds to a part of the conveyance unit in the claims.

  The paper discharge motor 76 rotates the two pairs of paper discharge rollers 75.

  The paper discharge reversing unit 62 reverses the paper P by turning the paper P delivered from the large-capacity paper discharge path RD2 back and forth along the paper discharge reverse path RR2 and returning it to the large-capacity paper discharge path RD2. The paper discharge reversing unit 62 includes a switching unit 81, a solenoid 82, two pairs of reverse approach rollers 83, a reverse roller 84, a reverse motor 85, two pairs of intermediate rollers 86, and an intermediate motor 87.

  The switching unit 81 switches the transport path of the paper P between the large-capacity paper discharge path RD2 and the paper discharge reverse path RR2. The switching unit 81 is disposed at a branch point between the large-capacity paper discharge route RD2 and the paper discharge reversal route RR2.

  The solenoid 82 drives the switching unit 81.

  The reverse approach roller 83 conveys the paper P guided from the large-capacity paper discharge path RD2 to the paper discharge reverse path RR2 by the switching unit 81 to the reverse roller 84. The reverse approach roller 83 is disposed along the upstream portion of the paper discharge reverse path RR.

  The reverse roller 84 switches back the paper P conveyed by the reverse approach roller 83 and conveys it to the intermediate roller 86. The reverse roller 84 is configured to be able to rotate forward and backward in order to perform switchback conveyance of the paper P. The reverse roller 84 is disposed on the downstream side of the reverse approach roller 83 along the paper discharge reverse path RR2.

  The reversing motor 85 drives the reversing roller 84 to rotate forward and backward.

  The intermediate roller 86 conveys the paper P switched back by the reverse roller 84 to the ascending conveyance roller 73. The intermediate roller 86 is disposed along the downstream portion of the paper discharge reversing path RR2.

  The intermediate motor 87 rotationally drives the reverse approach roller 83 and the two pairs of intermediate rollers 86 on the downstream side.

  The large-capacity paper discharge tray 63 is a stack on which printed paper P discharged by the paper discharge transport unit 61 is stacked. The large-capacity paper discharge tray 63 is disposed below the downstream side of the paper discharge roller 75. The large-capacity paper discharge tray 63 is configured to be able to move up and down, and can stack a large number of sheets P.

  The raising / lowering drive unit 64 raises and lowers the large-capacity paper discharge tray 63. The raising / lowering drive part 64 has a motor etc.

  The pair of side fences 65 </ b> A and 65 </ b> B regulates the position in the width direction (front-rear direction) of the paper P discharged on the large-capacity paper discharge tray 63. The side fences 65 </ b> A and 65 </ b> B are provided in a state of being suspended from the fence driving unit 67 above the large-capacity paper discharge tray 63, and are separated from the large-capacity paper discharge tray 63. The side fences 65A and 65B are arranged side by side in the front-rear direction.

  The end fence 66 regulates the position of the front end (right end) of the paper P discharged to the large-capacity paper discharge tray 63. The end fence 66 is provided in a state of being suspended from the fence drive unit 67 above the large-capacity paper discharge tray 63 and is separated from the large-capacity paper discharge tray 63.

  The fence driving unit 67 moves the pair of side fences 65A and 65B in a direction in which the pair of side fences 65A and 65B are brought closer to each other or in a direction in which the side fences are separated from each other. In addition, the fence drive unit 67 moves the end fence 66 in the left-right direction. The fence driving unit 67 is provided above the large-capacity paper discharge tray 63.

  The carriage 68 is for pulling out the large-capacity paper discharge tray 63 on which the paper P is loaded from the large-capacity paper discharge unit housing 11. When the large capacity discharge tray 63 is lowered to the lower limit position, it is placed on the carriage 68.

  The control unit 9 controls the operation of each unit of the printing apparatus 1. The control unit 9 includes a CPU, a RAM, a ROM, and the like.

  At the time of duplex printing, the control unit 9 performs interleaf duplex printing. When there is a sheet P that does not require reverse printing during duplex printing, the control unit 9 changes the printing schedule in the interleaf method. Details thereof will be described later.

  Next, the operation of the printing apparatus 1 will be described.

  When printing is started, unprinted paper P is transported to the transport printing unit 3 from one of the external paper feed tray 21 and the plurality of internal paper feed trays 23 of the paper feed unit 2. In the transport printing unit 3, the paper P is transported to the belt transport unit 33 by the registration rollers 31. The paper P is printed by the inkjet head unit 35 while being transported by the belt transport unit 33.

  When single-sided printing is performed and the paper discharge destination is the paper discharge tray 45 of the main-body-side paper discharge unit 5, the single-side printed paper P is guided to the upper surface transport unit 4 by the switching unit 51 of the communication unit 7. In the upper surface transport unit 4, the paper P is transported to the switching unit 41 of the main body-side paper discharge unit 5 by the ascending transport roller 36 and the horizontal transport roller 38, and is guided by the switching unit 41 from the normal path RC to the main body-side paper discharge path RD 1. It is burned. Then, the paper P is discharged to a paper discharge tray 45 by a paper discharge roller 43.

  In the case of single-sided printing, when the paper discharge destination is the large-capacity paper discharge tray 63, the single-side printed paper P is guided from the normal route RC to the large-capacity paper discharge route RD2 by the switching unit 51 of the communication unit 7. The sheet P guided to the large-capacity paper discharge path RD2 is conveyed by the contact roller 53 and the upstream introduction roller 71, and downstream along the large-capacity paper discharge path RD2 by the switching unit 81 of the paper discharge reversing unit 62. To the introduction roller 71. Then, the paper P is transported along the large-capacity paper discharge path RD2 by the introduction roller 71, the ascending transport roller 73, and the paper discharge roller 75, and is discharged to the large-capacity paper discharge tray 63.

  When the single-side printed paper P is discharged to the large-capacity paper discharge tray 63 with the printing surface facing downward, the paper P guided to the large-capacity paper discharge path RD2 by the switching unit 51 is connected to the contact roller 53 and the upstream side. While being transported by the introduction roller 71, it is guided to the paper discharge reverse path RR <b> 2 by the switching unit 81 of the paper discharge reverse unit 62. The paper P guided to the paper discharge reverse path RR2 is conveyed to the reverse roller 84 by the reverse approach roller 83 and switched back by the reverse roller 84. The switched-back paper P is conveyed by the intermediate roller 86 and returns from the paper discharge reverse path RR2 to the large capacity paper discharge path RD2. Thereby, the upper and lower sides of the paper P are reversed. Then, the paper P is transported along the large-capacity paper discharge path RD2 by the ascending transport roller 73 and the paper discharge roller 75, and is discharged onto the large-capacity paper discharge tray 63.

  In the case of duplex printing, the surface-printed paper P is guided to the upper surface transport unit 4 by the switching unit 51 of the communication unit 7, transported by the upper surface transport unit 4, and then switched by the switching unit 41 of the main body side discharge unit 5. It is guided to the reverse refeed path RR1. Here, a surface printed first in double-sided printing is a front surface, and a surface printed later is a back surface. The paper P guided to the reverse refeed path RR1 is guided to the reverse roller 46 by the switching gate 50 and switched back by the reverse roller 46 in the reverse refeed section 6. Thereafter, the sheet P is guided to the refeed roller 48 by the switching gate 50 and is transported to the transport printing unit 3 by the refeed roller 48. In the transport printing unit 3, the paper P is transported to the belt transport unit 33 by the registration rollers 31. Here, the paper P is turned upside down (front and back) by switchback, and the unprinted back surface is directed to the inkjet head unit 35. The paper P is printed on the back side by the ink ejected from the inkjet head unit 35 while being transported by the belt transport unit 33.

  In double-sided printing, when the paper discharge destination is the paper discharge tray 45 of the main body-side paper discharge unit 5, the double-side printed paper P is the ascending conveyance roller 36 and horizontal conveyance roller 38 as in the case of single-sided printing described above. And is discharged by a paper discharge roller 43 onto a paper discharge tray 45.

  In double-sided printing, when the paper discharge destination is the large-capacity paper receiving tray 63, the double-sided printed paper P is the same as in the case of single-sided printing described above. The paper is conveyed by a paper roller 75 and discharged to a large-capacity paper discharge tray 63.

  Here, in the printing apparatus 1, when printing a plurality of sheets, the sheets P are sequentially fed from the sheet feeding unit 2, and the plurality of sheets P are simultaneously conveyed on the circulation path.

  In the case of multiple-sided single-sided printing, the control unit 9 sequentially feeds a plurality of unprinted sheets P from the sheet feeding unit 2, and the sheet P is fed between predetermined sheets by the registration rollers 31 and the inkjet unit 33 and the inkjet. It is sent out to the head part 35. Then, the control unit 9 causes the inkjet head unit 35 to print on the paper P while transporting the paper P by the belt transport unit 33. As a result, a plurality of sheets P are printed while being conveyed between predetermined sheets. Here, the interval between sheets is the interval between the trailing edge of the preceding sheet P and the leading edge of the succeeding sheet P.

  In the case of a plurality of double-sided printings, the control unit 9 performs double-sided printing by an interleaf method. In this case, the control unit 9 sequentially feeds a plurality of unprinted sheets P from the sheet feeding unit 2, and the registration rollers 31 allow the plurality of sheets P to be fed between sheets for a printing time T corresponding to one sheet. It is vacated and sent out to the belt conveyance unit 33 and the inkjet head unit 35. The controller 9 causes the ink jet head unit 35 to print the front surface of the paper P while transporting the unprinted paper P by the belt transport unit 33.

  The control unit 9 circulates and conveys the paper P with the front surface printed, and reverses the front and back by the reverse refeed unit 6. Then, the control unit 9 inserts the front-side-inverted paper P, which is turned upside down, between the unprinted papers fed from the paper feeding unit 2, and the belt conveyance unit 33 and the inkjet head unit by the registration rollers 31. 35, and the back side is printed. Here, the control unit 9 makes the space between the front-side printed paper P inserted between the unprinted papers and the unprinted paper P before and after the same to be the same as the paper space in single-sided printing. The registration roller 31 is controlled.

  By the control as described above, in the interleaf method, printing is performed in the order and timing as shown in FIG. In FIG. 3, dot-hatched paper P indicates that the paper P has been printed on the front side and printed on the back side after inversion. Also, the numbers in the paper indicate what number of paper. The Nth sheet is the last sheet.

  In the example of FIG. 3, after the surface of the first sheet P is printed, the surface of the second sheet P is printed after a printing time T for one sheet, and then the printing time for one sheet is printed. The surface of the third sheet P is printed with a T interval. Next, the back side printing of the first sheet P that is circulated and reversed is performed. Then, the front surface of the fourth sheet P is printed, and then the back surface of the second sheet P that is circulated and reversed is printed. Thereafter, similarly, the front surface printing of the newly fed unprinted paper P and the back surface printing of the front surface printed paper P that is circulated and reversed are alternately performed. When the feeding of the unprinted paper P is completed immediately before the end of the double-sided printing, the back side printing of the paper P that is circulated and reversed is performed three times continuously with a printing time T left.

  Here, the printing time T is a value obtained by dividing the distance obtained by adding the sheet interval to the length in the conveyance direction of the paper P by the conveyance speed in the belt conveyance unit 33. In the interleaf duplex printing, the printing time T is the same as that for simplex printing. Thereby, double-sided printing is performed with the productivity per side equivalent to that during single-sided printing.

  As shown in FIG. 3, in the interleaf method, there is a free time between unprinted sheets that are printed on the front side in the period immediately after the start of double-sided printing and before the back side printing on the front side printed paper P starts. In the example of FIG. 3, the idle time of the printing time T is between the first surface printing and the second surface printing and between the second surface printing and the third surface printing. is there.

  In addition, there is a free time between the front-side printed sheets that are printed on the back side in the period immediately after the front-side printing on the unprinted paper P is completed just before the end of double-sided printing. In the example of FIG. 3, between the (N-2) th backside printing and the (N-1) th backside printing, and the (N-1) th backside printing and the Nth backside printing In the meantime, there is an idle time of the printing time T.

  In the example of FIG. 3, there are two idle times immediately after the start and end of double-sided printing. The number of idle times depends on the number of sheets P that are simultaneously conveyed to the circulation path. change. The number of circulating sheets varies depending on the length of the paper P in the transport direction. FIG. 3 shows an example in which the number of circulating sheets is five.

  By the way, the paper P for double-sided printing may include paper P that does not require backside printing (the backside is blank). In the printing apparatus 1, the front side printing of the paper P that does not require the back side printing is performed during an empty time between sheets to be printed in the interleaf double-sided printing.

  Then, the paper P that is printed on the front side and does not require backside printing is transported to the large-capacity paper discharge path RD2 without being circulated and stocked by the paper discharge reversing unit 62. Thereafter, the stocked paper P enters a position that is aligned with the plurality of double-side printed paper P transported to the large-capacity paper ejection tray 63 along the large-capacity paper ejection path RD2 in the order of the ejected pages. Thus, it is returned to the large-capacity paper discharge route RD2.

  This is performed in order to shorten the period during which the inkjet head unit 35 is occupied by the paper P while maintaining the page order of the printed matter. Here, the period during which the inkjet head unit 35 is occupied by the sheet P is from the start of printing of the first sheet P to the end of printing of the last sheet P until the sheet P passes through the inkjet head unit 35. Means period.

  As described above, in the printing apparatus 1, the front side printing of the paper P that does not require the back side printing is performed during the idle time between the printed papers. The paper P that has been printed on the front side and does not require backside printing is stocked by the paper discharge reversing unit 62, and then returned to the large-capacity paper discharge path RD2 at the timing of entering the position aligned with the other paper P in page order. Are ejected. Therefore, it is necessary to insert the front side printing of the paper P, which does not require the back side printing, in the idle time at which it is possible to discharge the paper with the page order aligned.

  The idle time in which the front side printing of the paper P that does not require the back side printing can be inserted will be described.

  Here, the number of double-sided printing is N. Assume that the Kth sheet in the page order of the document is a sheet P that does not require backside printing. Similarly to the example of FIG. 3, it is assumed that the circulation number is five. Here, K ≠ N. In other words, it is assumed that the paper P that does not require backside printing is not the paper P of the last page.

  In the normal printing schedule of the interleaf system, printing is performed at the timing as shown in FIG. 4 as in the example of FIG. In FIG. 4, for example, “front 1” indicates the first surface printing, and “front 1” indicates the first back surface printing. One square in FIG. 4 represents a unit time, which corresponds to the printing time T. The time when neither front side printing nor back side printing is performed is idle time.

  In the printing apparatus 1, when the Kth sheet is a sheet P that does not require backside printing, printing of the (K + 1) th sheet is advanced as shown in FIG. Then, the K-th surface print is inserted in a vacant time at which the pages can be discharged with the page order aligned.

  In order to align the order of discharged pages, the front-side printed Kth sheet must be discharged before the (K + 1) th sheet printed on both sides is discharged to the large-capacity discharge table 63.

  Here, in the printing apparatus 1, the time from when the paper P is printed by the transport printing unit 3 to when the paper P is transported through the large-capacity discharge path RD2 and discharged to the large-capacity discharge tray 63 is 5T. And

  In addition, the time from when the paper P is printed by the transport printing unit 3 until the paper P is transported through the large-capacity paper discharge path RD2 and discharged through the discharge reverse path RR2 to the large-capacity paper tray 63 is also 5T. Suppose that

  Therefore, in order for the Kth sheet to be ejected before the (K + 1) th sheet is ejected in the order of the pages, the Kth sheet is used in the idle time before the (K + 1) th rear surface printing. It is only necessary to perform surface printing. The idle time before the (K + 1) th sheet backside printing is the idle time between the first surface printing and the second surface printing, and the second surface printing and the third surface printing. Free time between printing. Therefore, the K-th surface print can be inserted at the timing indicated by the oblique lines in FIG.

  Here, in the case of K + 1 ≦ N−2, the idle time before the (K + 1) th backside printing is a period immediately after the start of double-sided printing and before the backside printing on the front-side printed paper P starts. There is only. On the other hand, in the case of K + 1> N−2, the idle time in the period after the front surface printing on the unprinted paper P immediately before the end of the double-sided printing is also the timing before the (K + 1) th back surface printing. Included in free time.

  As a specific example, a case where N = 4 and K = 3 will be described. When N = 4, printing is performed at the timing shown in FIG. 6 in the normal printing schedule of the interleaf method. When the third sheet is a sheet P that does not require reverse side printing, the fourth sheet is advanced as shown in FIG. The idle times before timing of printing the back side of the fourth sheet are all idle times. Therefore, the third surface printing can be inserted at the timing indicated by the oblique lines in FIG.

  When K = N, that is, when the paper P that does not require backside printing is the paper P of the last page, the front surface of the paper P that does not require backside printing in the empty time in the (N-1) printing schedule. Insert a print. In this case, it is only necessary to finally discharge the paper P that does not require the back side printing on the front side, so that the front side printing of the paper P that does not require the back side printing can be inserted in any idle time. For example, in the case of N = 5 and K = 5, as shown in FIG. 8, it is possible to insert the fifth surface print in all the idle times in the four-sheet printing schedule.

  When the paper P that does not require backside printing is included in the paper P that is to be printed on both sides, the control unit 9 determines the timing at which the front side printing of the paper P that does not require backside printing is inserted as described above. Select from.

  Here, in the printing apparatus 1, the control unit 9 can set a face-up discharge setting or a face-down discharge setting, which will be described later, as a discharge method at the time of duplex printing. The face-up discharge setting or the face-down discharge setting can be specified by the user.

  The face-up discharge setting is a setting for discharging the paper P so that the paper P is stacked with the younger pages facing up. That is, in the face-up discharge setting, in the plurality of sheets P that are printed by duplex printing, the top surface of the top sheet P is the first page, and the bottom surface of the bottom sheet P is the last page. The upper surface is an odd page, and the lower surface is an even page.

  The face-down paper discharge setting is a setting for discharging the paper P so that the paper P is stacked with the young page down. In other words, in the face-down paper discharge setting, among the plurality of sheets P that are printed by duplex printing, the bottom surface of the bottom sheet P is the first page, the top surface of the top sheet is the last page, and the top surface of each sheet P Is an even page and the bottom is an odd page.

  In the face-up discharge setting, when the paper P to be printed only on one side is included, if the paper P is printed only on even pages, the paper P does not need the above-described back side printing. Assuming that the paper is P, the print can be inserted in the idle time as described above.

  In this case, the sheet P to be printed on both sides has even pages printed on the front surface (the surface to be printed first) and odd pages printed on the back surface (the surface to be printed later). Printing is performed on each sheet P from a page with a large page number. The double-side printed paper P is sequentially discharged to the large-capacity paper discharge tray 63 without being turned upside down. Since the odd-numbered pages are printed on the back side, the paper P on which only even-numbered pages are printed (the odd-numbered pages are white paper) is a paper P that does not require back-side printing. The sheet P is printed with an even-numbered page image on the front surface in the idle time, stocked by the sheet discharge reversing unit 62, and then returned to the large-capacity sheet discharge path RD2 and discharged at a timing according to the sheet discharge page order. The

  Further, in the face-down paper discharge setting, when the paper P to be printed only on one side is included, if the paper P is printed only on odd pages, the paper P is subjected to the back side printing described above. Assuming that the paper P is unnecessary, the print can be inserted in the idle time as described above.

  In this case, the sheet P to be printed on both sides has an odd page on the front side and an even page on the back side. Printing is performed on each sheet P from a young page with a small page number. The double-side printed paper P is sequentially discharged to the large-capacity paper discharge tray 63 without being turned upside down. Since even-numbered pages are printed on the back side, the paper P on which only odd-numbered pages are printed (even-numbered pages are blank) is a paper P that does not require back-side printing. The sheet P is printed with an odd-numbered page image on the front surface in the idle time, stocked by the sheet discharge reversing unit 62, and then returned to the large-capacity sheet discharge path RD2 at a timing corresponding to the sheet discharge order. The

  On the other hand, if the paper P printed on only one side is printed on only one side with the face-up discharge setting, the paper P is printed on the back side. It is what is done. Therefore, since the paper P is not the paper P that does not require the back side printing, the method of inserting the front side printing of the paper P that does not require the back side printing as described above cannot be applied.

  Further, if the paper P printed only on one side in the face-down paper discharge setting is printed on even-numbered pages (odd pages are blank), the paper P is printed on the back side. Is. Therefore, since the paper P is not the paper P that does not require the back side printing, the method of inserting the front side printing of the paper P that does not require the back side printing as described above cannot be applied.

  Here, the print page order is reversed between the face-up discharge setting and the face-down discharge setting.

  Therefore, in the face-up discharge setting, when the paper P printed on only one side is printed on only odd pages (even pages are blank), the control unit 9 sets the face-down discharge setting. Change to As a result, assuming that the paper P on which only odd-numbered pages are printed is the paper P that does not require reverse-side printing, it is possible to insert the printing into the idle time as described above.

  Further, in the face-down discharge setting, when the paper P printed only on one side is printed on even-numbered pages (odd pages are blank), the control unit 9 sets the face-up discharge setting. Change to As a result, assuming that the paper P on which only even pages are printed is the paper P that does not require backside printing, it is possible to insert the printing into the idle time as described above.

  The face-up / face-down discharge setting, the page to be printed (odd page or even page) on the paper P printed only on one side, and whether the face-up / face-down discharge setting has been changed as described here 9 is summarized as shown in FIG.

  Next, the operation of the printing apparatus 1 during duplex printing will be described with reference to the flowchart of FIG.

  The process of the flowchart of FIG. 10 starts when print data for duplex printing is input to the printing apparatus 1. In step S1 of FIG. 9, the control unit 9 expands the image data of each page from the print data.

  Next, in step S2, the control unit 9 determines whether there is a sheet P to be printed only on one side based on the image data of each page. In the image data corresponding to each sheet P, the control unit 9 determines that there is a sheet P to be printed only on one side when there is image data in which one of the front side and the back side is blank page data. .

  Next, in step S3, the control unit 9 determines whether or not the preset paper discharge method is face-up paper discharge.

  If it is determined that the face-up discharge setting is set (step S3: YES), in step S4, the controller 9 prints an odd page on the paper P printed only on one side. Judge whether or not.

  If it is determined that an odd page is printed on the paper P printed on only one side (step S4: YES), in step S5, the control unit 9 sets the discharge method to face up. Change the paper discharge setting to the face-down paper discharge setting. Thereafter, the control unit 9 proceeds to step S8.

  If there are a plurality of sheets P to be printed only on one side, the control unit 9 determines “YES” in step S4 if all of them print only odd pages, and then step S4. The process of S5 is performed.

  Here, as described above, in the face-up discharge setting, if the paper P printed only on one side is printed on only odd pages (even pages are blank), the paper P is It is printed on the back side. Therefore, by changing to the face-down paper discharge setting, as described above, it is possible to insert the printing into the idle time, assuming that the paper P on which only odd-numbered pages are printed is the paper P that does not require reverse-side printing. become.

  In step S4, when it is determined that even-numbered pages are printed on the paper P printed on only one side (step S4: NO), the control unit 9 omits step S5 and performs step S8. Proceed to

  If there are a plurality of sheets P printed on only one side, the control unit 9 determines “NO” in step S4 if some of them print only even pages. .

  If it is determined in step S3 that the face-down paper discharge setting is set (step S3: NO), in step S6, the control unit 9 prints even numbers on the paper P printed on only one side. It is determined whether it is a page.

  If it is determined that even-numbered pages are printed on the paper P printed only on one side (step S6: YES), in step S7, the control unit 9 sets the paper discharge method face down. Change the paper discharge setting to the face-up paper discharge setting. Thereafter, the control unit 9 proceeds to step S8.

  If there are a plurality of sheets P printed only on one side, the control unit 9 determines “YES” in step S6 if all of them print only even pages. The process of S7 is performed.

  Here, as described above, if the paper P printed only on one side is printed even-numbered pages (odd pages are blank) in the face-down paper discharge setting, the paper P is It is printed on the back side. Therefore, by changing to the face-up discharge setting, as described above, it is possible to insert the printing in the idle time, assuming that the paper P on which even-numbered pages are printed is the paper P that does not require reverse-side printing. become.

  If it is determined in step S6 that the odd-numbered pages are printed on the paper P printed on only one side (step S6: NO), the control unit 9 omits step S7 and performs step S8. Proceed to

  When there are a plurality of sheets P printed only on one side, the control unit 9 determines “NO” in step S6 if any of them includes a sheet on which only odd pages are printed. .

  In step S8, the control unit 9 selects the timing for inserting the front side printing of the paper P that does not require the back side printing.

  Specifically, the control unit 9 prints the front surface of the paper P that does not require backside printing, as described above, based on the number of the sheet P from the start of double-sided printing. The timing at which can be inserted is obtained. Then, the control unit 9 selects the latest timing among the timings at which the front side printing of the paper P that does not require backside printing can be inserted as the timing at which the front side printing of the paper P that does not require backside printing is inserted.

  Here, in the face-up discharge setting, the paper P on which only even-numbered pages are printed (the odd-numbered pages are white paper) becomes the paper P that does not require reverse-side printing. The face-up discharge setting is set when the face-up discharge setting is set in advance and step S5 is omitted, and when the face-up discharge setting is changed at step S7.

  In the face-down paper discharge setting, the paper P on which only odd-numbered pages are printed (the even-numbered pages are white paper) becomes the paper P that does not require reverse-side printing. The face-down paper discharge setting is set when the face-down paper discharge setting is set in advance and step S7 is omitted, and when the face-down paper discharge setting is changed at step S5.

  When there are a plurality of sheets P that do not require back side printing, the control unit 9 selects one of them as a target to insert front side printing during the idle time, and otherwise, both sides are printed. It is handled in the same way as the paper P.

  When the timing for inserting the front side printing of the paper P that does not require the back side printing is selected in step S8, the control unit 9 executes the printing with a printing schedule corresponding to the timing in step S9. For example, in the example of FIG. 7, in step S <b> 9, the control unit 9 performs the interval between the second back surface printing and the fourth back surface printing, which is the latest timing among the timings at which the front surface printing can be inserted. Is selected as the timing for inserting the third surface printing. In step S9, the control unit 9 executes printing according to the print schedule as shown in FIG. Thereby, the control unit 9 changes the normal print schedule as shown in FIG. 6 to the print schedule as shown in FIG. 11 and executes printing.

  When performing front side printing of the paper P that does not require backside printing, the control unit 9 feeds the unprinted paper P during the selected idle time and causes the inkjet head unit 35 to perform front side printing. Thereafter, the control unit 9 guides the paper P, which is printed on the front surface and does not require reverse printing, to the large-capacity paper discharge route RD2 by the switching unit 51 of the communication unit 7 without circulating the paper P.

  Next, the control unit 9 guides the paper P, which is printed on the front side and does not require backside printing, to the paper discharge reversing path RR2 by the switching unit 81 of the paper discharge reversing unit 62, and the paper discharge reversing unit 62 passes the paper to the paper discharge reversing path RR2. P is stocked. Specifically, the control unit 9 stops the reverse roller 84 in a state where the rear end portion of the paper P is nipped by the reverse roller 84.

  The other paper P to be printed on both sides is printed on the back side according to the printing schedule, and is then transported along the large-capacity discharge path RD2 with the front side facing down, and is discharged to the large-capacity discharge tray 63. The control unit 9 enters a position where the paper P stocked by the paper discharge reversing unit 62 is aligned with the plurality of double-side printed paper P transported along the large-capacity paper discharge path RD2 in the order of the discharge pages. The reverse roller 84 and the intermediate roller 86 are driven so as to return to the large-capacity paper discharge path RD2 at the timing. The paper P returned from the paper discharge reversing path RR2 to the large-capacity paper discharge path RD2 is conveyed toward the large-capacity paper discharge tray 63 with the front side facing down. As a result, the sheets P are stacked on the large-capacity discharge tray 63 in the order of the discharged pages with the front side facing down.

  If it is determined in step S2 that there is no paper P printed on only one side (step S2: NO), the control unit 9 proceeds to step S9 and executes interleaf duplex printing with a normal printing schedule. To do.

  Here, a specific example in which the above-described face-up / face-down paper discharge setting is changed or not is described.

  First, an example 1 in which the preset paper discharge method is face-up paper discharge, the number of double-sided printed sheets is four, and the sixth page is blank paper will be described.

  In this case, the paper P printed only on one side is the paper P corresponding to the fifth and sixth pages. The fifth page, which is an odd page, is printed on the paper P. Therefore, in this case, “YES” is determined in step S4, and the face-up discharge setting is changed to the face-down discharge setting in step S5.

  In the face-down paper discharge setting, the first page is printed on the front side of the first sheet and the second page is printed on the back side. The third page is printed on the front side of the second sheet, and the fourth page is printed on the back side. The fifth page is printed on the front side of the third sheet, and the sixth page is printed on the back side. The seventh page is printed on the front side of the fourth sheet, and the eighth page is printed on the back side. In the case of Example 1, the sixth page is a blank sheet, and the third sheet is a sheet P that does not require backside printing.

  Therefore, printing is executed according to the printing schedule of FIG. 11, and the printed paper P is discharged to the large-capacity paper discharge tray 63. On the large-capacity paper receiving tray 63, as shown in FIG.

  After the image of the fifth page is printed on the front surface of the third sheet P, the third sheet P is sent out to the large-capacity paper discharge path RD2 with the front surface facing up without being circulated. The paper is reversed and inserted between the third and fourth sheets and discharged. Thereby, as shown in FIG. 12, the page order of the printed matter is matched.

  Next, an example 2 in which the preset paper discharge method is face-down paper discharge, the number of double-sided printed sheets is four, and the third page is blank paper will be described.

  In this case, the paper P printed on only one side is the paper P corresponding to the third and fourth pages. The fourth page, which is an even page, is printed on the paper P. Accordingly, in this case, “YES” is determined in the step S6, and the face-down paper discharge setting is changed to the face-up paper discharge setting in a step S7.

  In the face-up discharge setting, the eighth page is printed on the front side of the first sheet and the seventh page is printed on the back side. The sixth page is printed on the front side of the second sheet, and the fifth page is printed on the back side. The fourth page is printed on the front side of the third sheet, and the third page is printed on the back side. The second page is printed on the front side of the fourth sheet, and the first page is printed on the back side. In the case of Example 2, since the third page is a blank sheet, the third sheet is a sheet P that does not require backside printing.

  Therefore, printing is executed according to the printing schedule of FIG. 11, and the printed paper P is discharged to the large-capacity paper discharge tray 63. On the large-capacity paper discharge tray 63, as shown in FIG.

  After the fourth page image is printed on the front surface of the third sheet P, the third sheet P is not circulated and sent to the large-capacity paper discharge path RD2 with the front surface facing up. The paper is reversed and inserted between the third and fourth sheets and discharged. Thereby, as shown in FIG. 13, the page order of the printed matter is matched.

  Next, an example 3 in which the preset paper discharge method is face-up paper discharge, the number of double-sided printed sheets is four, and the third page is blank paper will be described.

  In this case, the paper P printed on only one side is the paper P corresponding to the third and fourth pages. The fourth page, which is an even page, is printed on the paper P. Accordingly, in this case, “NO” is determined in the step S4, and the face-up discharge setting is maintained.

  In this case, the situation is the same as the situation in which the face-up discharge setting is changed in Example 2 described above. Therefore, printing is executed according to the print schedule of FIG. 11, and the sheets P are stacked on the large-capacity discharge table 63 as shown in FIG. 13.

  Next, an example 4 in which the preset paper discharge method is face-down paper discharge, the number of double-sided printed sheets is four, and the sixth page is blank paper will be described.

  In this case, the paper P printed only on one side is the paper P corresponding to the fifth and sixth pages. The fifth page, which is an odd page, is printed on the paper P. Therefore, in this case, “NO” is determined in the step S4, and the face-down paper discharge setting is maintained.

  In this case, the situation is the same as in the case where the face-down paper discharge setting is changed in Example 1 described above. Therefore, printing is executed according to the print schedule of FIG. 11, and the sheets P are stacked on the large-capacity paper discharge tray 63 as shown in FIG.

  As can be seen from the above description, in face-up discharge, the order of discharge pages to the large-capacity discharge tray 63 is descending, and in face-down discharge, the order of discharge pages to the large-capacity discharge tray 63 is Ascending order. Accordingly, the face-up discharge setting corresponds to setting the discharge page order in descending order, and the face-down discharge setting corresponds to setting the discharge page order in ascending order. Further, changing the face-up / face-down paper discharge setting corresponds to changing the ascending order or descending order of the paper discharge page order.

  Further, as described above, when there is a sheet P on which only odd pages are printed in the face-up discharge setting, the face-down discharge setting is changed. If there is a sheet P on which only even pages are printed in the face-down paper discharge setting, the face-up paper discharge setting is changed. That is, when there is a sheet P to be printed only on the back side in the print page order corresponding to the preset face-up / face-down discharge setting (discharge page order), the control unit 9 performs face-up / face-down discharge. Change paper settings. As a result, the paper P that is printed only on the back surface is changed to a paper P that does not require back surface printing (printed only on the front surface).

  As described above, in the printing apparatus 1, when there is a sheet P that does not require the back side printing at the time of double-sided printing, the control unit 9 does not need the back side printing in the empty time between sheets printed by the interleaf method. Insert the surface print of the paper P. The control unit 9 conveys the paper P that has been printed on the front surface and does not require backside printing to the large-capacity paper discharge path RD2 without circulating it. Thereby, the period for which the inkjet head part 35 is occupied by the paper P can be shortened.

  In addition, when there is a sheet P that is printed only on the back side in the print page order according to the face-up / face-down discharge setting, the control unit 9 changes the face-up / face-down discharge setting to Only the paper P to be printed is printed on the front surface, and the paper P is changed to a paper P that does not require backside printing. As a result, even if there is no paper P that does not require backside printing under the preset face-up / face-down paper discharge setting, if there is paper P that is printed only on the backside (no front side printing is required), the inkjet The period during which the head portion 35 is occupied by the paper P can be shortened.

  In addition, the control unit 9 guides the paper P that has been printed on the front side and does not require backside printing from the large-capacity paper discharge route RD2 to the paper discharge reversal route RR2, and causes the paper discharge reversing unit 62 to stock. Thereafter, the control unit 9 aligns the stocked paper P with the plurality of double-side printed papers P transported to the large-capacity paper ejection tray 63 along the large-capacity paper ejection path RD2 in the order of the ejected pages. At the timing of entering the position, the control to return to the large-capacity paper discharge route RD2 is performed. Thereby, the page order of printed matter can be maintained.

  Therefore, according to the printing apparatus 1, in double-sided printing, the period during which the inkjet head unit 35 is occupied by the paper P can be shortened while maintaining the page order of the printed matter. If the period during which the inkjet head unit 35 is occupied by the paper P is shortened, it is possible to quickly start changing the print settings such as the head gap and the print conveyance speed in the conveyance printing unit 3. As a result, when there is a next print job that needs to be changed, the execution of the print job can be started quickly. As a result, productivity when the print job is continued can be improved.

  Further, the control unit 9 selects the latest timing among the timings at which the front side printing of the paper P that does not require the back side printing can be inserted as the timing at which the front side printing of the paper P that does not require the back side printing is inserted. That is, the control unit 9 prints the back surface at the latest timing within a range in which the paper P that does not require front surface printing and that does not require back surface printing can be placed in a position that matches the plurality of double-sided printed papers P in page order. Is printed on the paper P that does not require printing.

  When the operation of the printing apparatus 1 is stopped due to the occurrence of a paper jam or the like, if the paper P that has been printed on the front side and does not require the back side printing is stocked in the paper discharge reversing unit 62, the paper P becomes a jam paper. It becomes useless. By setting the timing of inserting the front side printing of the paper P that does not require the back side printing as the latest timing among the insertable timings, it is possible to reduce such waste of the paper P.

  Of the timings at which the front side printing of the paper P that does not require backside printing can be inserted, timings other than the latest timing may be selected as the timing for inserting the front side printing of the paper P that does not require backside printing. Even in this case, the period during which the inkjet head unit 35 is occupied by the paper P can be shortened while maintaining the page order of the printed matter.

  The present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiments. For example, some components may be deleted from all the components shown in the embodiment.

DESCRIPTION OF SYMBOLS 1 Printing apparatus 2 Paper feed part 3 Conveyance printing part 4 Upper surface conveyance part 5 Main body side paper discharge part 6 Reverse refeed part 7 Contact part 8 Large capacity paper discharge part 9 Control part 61 Paper discharge conveyance part 62 Paper discharge reverse part 63 Large-capacity output tray RC Normal path RR1 Reverse refeed path RD2 Large-capacity discharge path RR2 Discharge reverse path

Claims (2)

A circulation path that includes a first reversing path for reversing the front and back of the paper, and a transport section that transports the paper along a paper discharge path that branches from the circulation path and travels toward the paper discharge tray;
A paper discharge reversing unit for reversing the paper from the front and back by reciprocating a second reversing path and returning the paper delivered from the paper discharge path to the paper discharge path;
A printing unit for printing on paper conveyed along the circulation path;
A paper feed unit for feeding unprinted paper to the circulation path;
During double-sided printing, a plurality of unprinted sheets are sequentially fed to the circulation path, and a plurality of unprinted sheets fed are sent to the printing unit with a predetermined time interval between the sheets. Printed, surface-printed paper is circulated and transported along the circulation path and turned upside down, and the front printed paper that has been turned upside down is sent to the printing section, printed on the back side, and printed on both sides. A control unit that controls the sheet feeding unit, the transport unit, and the printing unit so that the sheet is conveyed to the sheet discharge table along the sheet discharge path and discharged.
The controller is
When there is paper that does not require backside printing during double-sided printing, unprinted paper is fed as paper that does not require backside printing during the idle time between the printed papers, and surface printing is performed on the paper.
The front-side-printed paper that does not require backside printing is transported to the paper discharge path without being circulated, and is guided from the paper discharge path to the second reversing path to be stocked,
The paper that has been printed on the second reversing path and that has not been printed on the back side is printed on the plurality of double-side printed sheets that are transported along the paper discharge path to the paper discharge table in the order of the discharged pages. Controlling the paper feeding unit, the transport unit, the printing unit, and the paper discharge reversing unit so as to return from the second reversing path to the paper discharging path at the timing of entering the alignment position;
If there is paper to be printed only on the back side in the print page order according to the discharge page order set in advance in ascending or descending order, the paper to be printed only on the back side can be changed by changing the ascending or descending order of the discharge page order. A printing apparatus that changes to a sheet that does not require the backside printing.   In the range in which the control unit can put the paper that has been printed on the second reversal path and that does not require the back-side printing into a position that is aligned with the plurality of double-sided printed sheets in the order of the discharged pages. The printing apparatus according to claim 1, wherein front side printing is performed on paper that does not require the back side printing at the latest timing.