Image forming device

Abstract

To insert an insert sheet while suppressing reduction in productivity.SOLUTION: An image forming apparatus comprises: a main conveyance path that reaches an ejection position through a printing position and an insertion position; a printing unit that feeds a sheet to the main conveyance path to convey the sheet and prints an image on the sheet passing through the printing position; and an inserter that feeds an insert sheet from the insertion position to insert the insert sheet between the sheets sequentially conveyed along the main conveyance path. During print job involving insert processing, between a preceding sheet being a sheet immediately before the insert sheet and a subsequent sheet being a sheet immediately after the insert sheet, the printing unit sequentially conveys the preceding sheet and the subsequent sheet with an insertion interval, and the printing unit automatically changes the insertion interval according to a length in a conveyance direction of the insert sheet.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus equipped with an inserter. [Background technology]

[0002] Conventionally, there is known an image forming apparatus that can insert an insert sheet (sometimes called a partition sheet) among multiple sheets of paper to be printed in a print job. Such an image forming apparatus is disclosed, for example, in Patent Document 1. The image forming apparatus of Patent Document 1 inserts the insert sheet while sequentially transporting multiple sheets of paper to be printed in the print job. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-26344 Summary of the Invention [Problem to be solved by the invention]

[0004] When inserting an insert sheet while sequentially conveying multiple sheets of paper, the gap between the sheet immediately preceding the insert sheet (the preceding sheet) and the sheet immediately following the insert sheet (the following sheet) is set larger than the gap between the other sheets, allowing the insert sheet to be inserted between the preceding and following sheets.

[0005] Here, insert paper sizes vary: the size of an insert paper for one print job may be different from the size of an insert paper for another print job, and multiple insert paper sizes may be used in a single print job.

[0006] Therefore, in a conventional configuration, when a print job involves inserting insert sheets, for example, a gap corresponding to the maximum size of the insert sheet is left between the leading and trailing sheets. In this configuration, if the size of the insert sheet is relatively small, a gap larger than necessary is left between the leading and trailing sheets, which causes the inconvenience of reduced productivity.

[0007] The present invention has been made to solve the above-mentioned problems, and has an object to provide an image forming apparatus that is capable of inserting insert sheets while suppressing a decrease in productivity. [Means for solving the problem]

[0008] To achieve the above object, an image forming apparatus according to one aspect of the present invention includes a main transport path that runs from a cassette in which paper sheets are set to an ejection position via a printing position and an insert position; a printing unit that, during a print job, feeds paper sheets from the cassette to the main transport path and transports them, printing images on the paper sheets that pass the printing position; and an inserter that performs an insert process that feeds insert paper sheets from the insert position to the main transport path and inserts the insert paper sheets between sheets that are sequentially transported along the main transport path. During a print job that includes insert processing, the printing unit sequentially transports the leading and trailing sheets, leaving an insert space between the leading sheet that is the sheet immediately before the insert sheet and the trailing sheet that is the sheet immediately after the insert sheet. The printing unit automatically changes the insert space depending on the length of the insert paper in the transport direction. [Effects of the Invention]

[0009] In the configuration of the present invention, it is possible to insert insert sheets while suppressing a decrease in productivity. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic diagram of an image forming apparatus according to an embodiment of the present invention. [Figure 2] 1 is a block diagram of an image forming apparatus according to an embodiment of the present invention. [Figure 3] 5 is a diagram showing the timing of paper feeding by the printing unit of the image forming apparatus according to one embodiment of the present invention (timing in the case of a single-sided print job). FIG. [Figure 4] 10 is a diagram showing the timing of paper feeding by the printing unit of the image forming apparatus according to one embodiment of the present invention (timing in the case of a normal double-sided printing job). FIG. [Figure 5] 10 is a diagram showing the timing of paper feeding by the printing unit of the image forming apparatus according to one embodiment of the present invention (timing in the case of a high-speed double-sided printing job). FIG. [Figure 6] 10 is a diagram showing the positional relationship between a front sheet and a rear sheet traveling on a main transport path of an image forming apparatus according to an embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0011] <Configuration of image forming device> As shown in FIG. 1, the image forming apparatus 100 has a printing unit 11 in a main body 1. The printing unit 11 includes a reversing unit UN. In a print job executed by the image forming apparatus 100, an image is printed on a sheet S by the printing unit 11. The image forming apparatus 100 also has an inserter 2 and a finisher 3. When viewed from the front of the image forming apparatus 100, the main body 1, inserter 2, and finisher 3 are arranged in this order from right to left.

[0012] The image forming apparatus 100 includes a main transport path 1A. In Fig. 1, the main transport path 1A is indicated by a thick solid arrow. During a print job, a sheet of paper S is transported along the main transport path 1A. An image is printed on the sheet of paper S while it is being transported.

[0013] The main transport path 1A runs from the paper feed position P1, through the printing position P2 and the inserting position P3 in that order, and to the discharging position P4. The main body 1 is provided with a portion of the main transport path 1A that includes the paper feed position P1 and the printing position P2. The inserter 2 is provided with a portion of the main transport path 1A that includes the inserting position P3. The finisher 3 is provided with a portion of the main transport path 1A that includes the discharging position P4.

[0014] The image forming apparatus 100 also includes a reverse conveying path 1B. The reverse conveying path 1B is provided in the reversing unit UN. The reverse conveying path 1B is used in a print job that prints images on both sides of the paper S. Hereinafter, a print job that prints an image on only one side of the paper S may be referred to as a single-sided print job, and a print job that prints images on both sides of the paper S may be referred to as a double-sided print job, to distinguish between the two.

[0015] The reverse conveyance path 1B branches off from the main conveyance path 1A at a position BP (hereinafter referred to as the branching position BP) downstream of the printing position P2 in the paper conveyance direction, and connects to the main conveyance path 1A at a position CP (hereinafter referred to as the connecting position CP) upstream of the printing position P2 in the paper conveyance direction. The branching position BP is located upstream of the insert position P3 in the paper conveyance direction. The connecting position CP is located downstream of the paper feed position P1 in the paper conveyance direction.

[0016] The printing unit 11 feeds paper S from a paper feed position P1 to a main transport path 1A. A cassette CA is disposed at the paper feed position P1. That is, the main transport path 1A extends from the cassette CA and passes through a printing position P2 and an insert position P3. Paper S is set in the cassette CA.

[0017] Although not shown, the printing unit 11 includes a paper feed roller. The paper feed roller abuts against the paper S in the cassette CA and rotates in that state. This causes the paper S to be drawn out of the cassette CA and fed into the main transport path 1A.

[0018] Although not shown, the printing unit 11 also includes pairs of transport rollers. The pairs of transport rollers are provided on the main transport path 1A and the reverse transport path 1B. The pairs of transport rollers rotate to transport the paper S. The number and positions of the pairs of transport rollers on the main transport path 1A can be changed depending on the shape and length of the main transport path 1A. The number and positions of the pairs of transport rollers on the reverse transport path 1B can be changed depending on the shape and length of the reverse transport path 1B.

[0019] The printing unit 11 includes a photosensitive drum 111 and a transfer roller 112. The photosensitive drum 111 and the transfer roller 112 are pressed against each other, thereby forming a transfer nip between the photosensitive drum 111 and the transfer roller 112. The position of the transfer nip is the printing position P2.

[0020] Although not shown, the printing unit 11 includes a charging device, an exposure device, and a developing device. The charging device charges the circumferential surface of the photosensitive drum 111. The exposure device forms an electrostatic latent image on the circumferential surface of the photosensitive drum 111. The developing device develops the electrostatic latent image into a toner image.

[0021] The paper S being conveyed enters the transfer nip, whereby a toner image is transferred onto the paper S. The paper S onto which the toner image has been transferred continues to be conveyed.

[0022] The printing unit 11 includes a fixing roller pair 113. The fixing roller pair 113 has a fixing nip located downstream of the printing position P2 in the paper transport direction. The paper S onto which the toner image has been transferred enters the fixing nip. The fixing roller pair 113 fixes the toner image to the paper S by applying heat and pressure to the paper S that has entered the fixing nip.

[0023] In a single-sided print job, the printing unit 11 transports a sheet S with an image printed on one side (herein referred to as a single-sided print sheet S) along the main transport path 1A. The single-sided print sheet S is transported into the inserter 2.

[0024] During a double-sided print job, the printing unit 11 switches back the single-sided printed paper S that has passed through the fixing nip, and pulls the switched-back single-sided printed paper S from branch position BP into the reverse conveying path 1B. The printing unit 11 then conveys the single-sided printed paper S along the reverse conveying path 1B, returning the single-sided printed paper S to a position upstream of printing position P2 on the main conveying path 1A in the paper conveying direction. In other words, the printing unit 11 re-feeds the paper S on the reverse conveying path 1B from the connection position CP to the main conveying path 1A.

[0025] Furthermore, in a double-sided printing job, the printing unit 11 transports the paper S that has been re-fed to the main transport path 1A to the printing position P2. When the paper S that has been re-fed to the main transport path 1A passes through the printing position P2, the orientation of the front and back sides of the paper S has been reversed, so an image is printed on the unprinted side of both sides of the paper S. The paper S with images printed on both sides is transported along the main transport path 1A and carried into the inserter 2.

[0026] The inserter 2 is equipped with a set tray 21 on which the paper S is set. The inserter 2 also has an insert conveying path 2A. In FIG. 1, the insert conveying path 2A is indicated by a thick dashed line to distinguish it from the main conveying path 1A. The insert conveying path 2A leads from the set tray 21 to the insert position P3. The insert conveying path 2A connects to the main conveying path 1A at the insert position P3.

[0027] The inserter 2 transports the paper S set on the set tray 21 along the insert transport path 2A. The inserter 2 then feeds the paper S from the insert transport path 2A to the main transport path 1A from the insert position P3. In other words, the insert position P3 is the feed position for the paper S fed from the inserter 2 to the main transport path 1A.

[0028] The inserter 2 feeds the sheet S from the insert conveyance path 2A to the main conveyance path 1A, and then conveys the sheet S along the main conveyance path 1A. As a result, the sheet S is conveyed from the inserter 2 to the finisher 3.

[0029] The inserter 2 performs the insert process. When a print job requires the insert process, the inserter 2 receives the paper S from the printing unit 11. The inserter 2 also transports the paper S set in the set tray 21 along the insert transport path 2A. The inserter 2 then feeds the paper S on the insert transport path 2A from the insert position P3 to the main transport path 1A.

[0030] In a print job that involves insert processing, the sheets S to be inserted before, after, or both before and after the sheets S already printed by the printing unit 11 are set in the set tray 21. Various types of sheets S, such as cardboard and index paper, can be inserted. Hereinafter, the sheets S set in the inserter 2 (set tray 21) may be referred to as insert sheets SS to distinguish them from the sheets S on which images are printed by the printing unit 11.

[0031] The finisher 3 receives the sheets S from the inserter 2 and transports them along the main transport path 1A. For example, the finisher 3 has a function of performing post-processing such as punching on the sheets S. The finisher 3 discharges the sheets S to a discharge tray 31.

[0032] 2, the image forming apparatus 100 includes a main control unit 10. The main control unit 10 includes processing circuits such as a CPU and an ASIC. The main control unit 10 controls the image forming apparatus 100. The main control unit 10 also performs various processes such as image processing on image data.

[0033] The main control unit 10 controls the printing unit 11. The main control unit 10 also controls the inserter 2 and the finisher 3.

[0034] The image forming apparatus 100 includes a storage unit 101. The storage unit 101 includes storage devices such as a ROM, a RAM, and an HDD. The storage unit 101 is connected to a main control unit 10. The main control unit 10 reads information from the storage unit 101. The main control unit 10 also writes information to the storage unit 101.

[0035] The image forming apparatus 100 includes a communication unit 102. The communication unit 102 includes a communication circuit. The communication unit 102 is communicably connected to an external device (not shown) via a network. The external device includes a personal computer (user terminal) used by a user. For example, print data (e.g., PDL data) of a print job is transmitted from the user terminal to the image forming apparatus 100.

[0036] The printing unit 11 includes a print control unit 110. The print control unit 110 includes a CPU, a memory, and the like. The print control unit 110 is connected to the main control unit 10. The main control unit 10 issues control instructions regarding print jobs (including feeding and transporting paper S) to the print control unit 110. Based on the control instructions from the main control unit 10, the print control unit 110 controls the printing operation of the printing unit 11.

[0037] For example, the print control unit 110 controls the timing of feeding paper S from cassette CA to main transport path 1A. The print control unit 110 also controls the timing of re-feeding paper S from reversing transport path 1B of reversing unit UN to main transport path 1A. By controlling the timing of feeding paper S (including the timing of re-feeding), an appropriate gap is provided between the previously fed paper S and the next fed paper S.

[0038] The inserter 2 includes an inserter control unit 20. The inserter control unit 20 includes a CPU, memory, and the like. The inserter control unit 20 is connected to the main control unit 10. The main control unit 10 issues control instructions related to the insert process to the inserter control unit 20. Based on the control instructions from the main control unit 10, the inserter control unit 20 controls the insert process. For example, the inserter control unit 20 controls the timing of feeding the sheet S from the insert conveyance path 2A to the main conveyance path 1A.

[0039] <Paper feed control> Based on information indicating the paper feed source of each sheet S fed in a print job, the main control unit 10 gives the printing unit 11 (print control unit 110) control instructions regarding the feeding of sheets S. In a print job involving insert processing, sheets S fed from cassette CA and sheets S fed from inserter 2 are mixed.

[0040] The printing unit 11 recognizes the paper feed source of each sheet S to be fed in a print job based on a control instruction from the main control unit 10. Then, the printing unit 11 performs paper feed control for a print job involving insert processing.

[0041] First, a description will be given of a case where the paper source for the Nth sheet in a single-sided print job is the inserter 2. When the paper source for the Nth sheet is the inserter 2, this means that the Nth sheet is an insert sheet SS.

[0042] In a single-sided print job, when the paper feed source for the Nth sheet is the inserter 2 (when the Nth sheet is an insert sheet SS), the main control unit 10 sets the timing for feeding the (N+1)th sheet S from cassette CA to main conveyance path 1A as the feed timing for the (N+1)th sheet S from cassette CA to main conveyance path 1A, based on the timing when a sheet S corresponding to the insert sheet SS (a sheet S having the same length in the conveyance direction as the insert sheet SS) is fed from cassette CA to main conveyance path 1A. Then, the main control unit 10 gives an instruction to the printing unit 11 (print control unit 110) to feed the (N+1)th sheet S from cassette CA to main conveyance path 1A at the set feed timing.

[0043] Here, the main control unit 10 sets the feed timing of the (N+1)th sheet S based on the length of the insert sheet SS in the transport direction. The longer the length of the insert sheet SS in the transport direction, the later the main control unit 10 sets the feed timing of the (N+1)th sheet S. The shorter the length of the insert sheet SS in the transport direction, the earlier the main control unit 10 sets the feed timing of the (N+1)th sheet S. In other words, the main control unit 10 changes the feed timing of the (N+1)th sheet S depending on the length of the insert sheet SS in the transport direction.

[0044] If the paper feed source for the Nth sheet is the inserter 2, the printing unit 11 does not feed the Nth sheet from the cassette CA. In this case, the printing unit 11 feeds the (N+1)th sheet S from the cassette CA to the main transport path 1A at the timing (feed timing instructed by the main control unit 10) when the printing unit 11 feeds the (N+1)th sheet S from the cassette CA to the main transport path 1A after feeding the sheet S corresponding to the insert sheet SS from the cassette CA to the main transport path 1A. In other words, the printing unit 11 does not actually feed the insert sheet SS from the cassette CA to the main transport path 1A. However, the printing unit 11 controls the feed timing of the next sheet S to be fed from the cassette CA to the main transport path 1A, assuming that the insert sheet SS has been fed from the cassette CA to the main transport path 1A.

[0045] For example, as shown in Figure 3, the source of the first sheet S1, the second sheet S2, and the fourth sheet S4 is cassette CA, and the source of the third sheet S3 is inserter 2. In other words, the third sheet S3 is an insert sheet SS, and is inserted between sheets S2 and S4.

[0046] 3, first, the printing unit 11 feeds paper S1 from cassette CA to main transport path 1A (prints an image on paper S1). Thereafter, the printing unit 11 feeds paper S2 from cassette CA to main transport path 1A (prints an image on paper S2) at a timing when the distance in the transport direction (paper interval) between the rear end in the transport direction of paper S1 fed from cassette CA to main transport path 1A and the front end in the transport direction of paper S2 becomes a predetermined distance.

[0047] After feeding sheet S2 from cassette CA to main transport path 1A, printing unit 11 does not actually feed sheet S3 from cassette CA to main transport path 1A. However, printing unit 11 feeds sheet S4 from cassette CA to main transport path 1A at the same timing as when printing unit 11 feeds sheet S4 from cassette CA to main transport path 1A after feeding sheet S3 from cassette CA to main transport path 1A.

[0048] Next, a description will be given of a double-sided printing job in which the paper source for the Nth sheet is the inserter 2. Double-sided printing jobs include normal double-sided printing jobs and high-speed double-sided printing jobs.

[0049] In a normal double-sided printing job, an image is printed on one side of a sheet of paper S fed from cassette CA to main conveyance path 1A, and the sheet of paper S is then pulled into reverse conveyance path 1B. Then, the sheet of paper S with the image printed on one side is fed again from reverse conveyance path 1B to main conveyance path 1A, and then the next sheet of paper S on which an image should be printed is fed from cassette CA to main conveyance path 1A.

[0050] In a normal double-sided printing job, when the paper feed source for the Nth sheet is the inserter 2, the main control unit 10 sets the timing for feeding the (N+1)th sheet S from cassette CA to main conveyance path 1A to be the timing when the Nth sheet S corresponding to the insert sheet SS is fed from cassette CA to main conveyance path 1A and then the (N+1)th sheet S is fed from cassette CA to main conveyance path 1A. Then, the main control unit 10 gives an instruction to the printing unit 11 (print control unit 110) to feed the (N+1)th sheet S from cassette CA to main conveyance path 1A at the set paper feed timing.

[0051] Here, as with a single-sided print job, the main control unit 10 sets the feed timing of the (N+1)th sheet S based on the length of the insert sheet SS in the transport direction. The longer the length of the insert sheet SS in the transport direction, the later the main control unit 10 sets the feed timing of the (N+1)th sheet S. The shorter the length of the insert sheet SS in the transport direction, the earlier the main control unit 10 sets the feed timing of the (N+1)th sheet S. In other words, the main control unit 10 changes the feed timing of the (N+1)th sheet S depending on the length of the insert sheet SS in the transport direction.

[0052] If the paper feed source for the Nth sheet is the inserter 2, the printing unit 11 does not feed the Nth sheet from cassette CA. In this case, the printing unit 11 feeds the N+1th sheet S from cassette CA to main conveyance path 1A at the timing (feed timing instructed by main control unit 10) when the printing unit 11 re-feeds sheet S corresponding to insert sheet SS as the Nth sheet from reverse conveyance path 1B to main conveyance path 1A and then feeds the (N+1)th sheet S from cassette CA to main conveyance path 1A. In other words, the printing unit 11 does not actually feed insert sheet SS from cassette CA to main conveyance path 1A (does not re-feed insert sheet SS from reverse conveyance path 1B to main conveyance path 1A). However, the printing unit 11 controls the timing of feeding the next sheet S from the cassette CA to the main conveying path 1A, assuming that the insert sheet SS has been fed from the cassette CA to the main conveying path 1A (assuming that the insert sheet SS has been re-fed from the reverse conveying path 1B to the main conveying path 1A).

[0053] For example, as shown in Figure 4, suppose that the source of the first sheet S1, the second sheet S2, and the fourth sheet S4 is cassette CA, and the source of the third sheet S3 is inserter 2. In other words, the third sheet S3 is an insert sheet SS, and is inserted between sheets S2 and S4.

[0054] In the example shown in FIG. 4, first, the printing unit 11 feeds sheet S1 from cassette CA to main conveyance path 1A (prints an image on one side of sheet S1). Next, the printing unit 11 transports sheet S1 into reverse conveyance path 1B and re-feeds sheet S1 from reverse conveyance path 1B to main conveyance path 1A (prints an image on the other side of sheet S1). Thereafter, the printing unit 11 feeds sheet S2 from cassette CA to main conveyance path 1A (prints an image on one side of sheet S2) at a timing when the distance in the conveyance direction between the rear end of sheet S1 in the conveyance direction and the front end of sheet S2 in the conveyance direction (sheet interval) becomes a predetermined distance for double-sided printing. Like sheet S1, sheet S2 is transported into reverse conveyance path 1B and re-fed from reverse conveyance path 1B to main conveyance path 1A (prints an image on the other side of sheet S2).

[0055] After re-feeding sheet S2 from reversing conveyance path 1B to main conveyance path 1A, printing unit 11 does not actually feed sheet S3 from cassette CA to main conveyance path 1A. In other words, printing unit 11 does not actually re-feed sheet S3 from reversing conveyance path 1B to main conveyance path 1A. However, at the same timing as when printing unit 11 re-feeds sheet S3 from reversing conveyance path 1B to main conveyance path 1A and then feeds sheet S4 from cassette CA to main conveyance path 1A (an image is printed on one side of sheet S4). Like sheet S1, sheet S4 is transported into reversing conveyance path 1B and is re-fed from reversing conveyance path 1B to main conveyance path 1A (an image is printed on the other side of sheet S4).

[0056] In a normal double-sided printing job, multiple sheets of paper S do not circulate through the reverse conveying path 1B at the same time. On the other hand, in a high-speed double-sided printing job, multiple sheets of paper S circulate through the reverse conveying path 1B at the same time. This allows the high-speed double-sided printing job to be completed quickly.

[0057] In a high-speed double-sided printing job, an image is printed on one side of a sheet of paper S (herein referred to as first sheet of paper S) fed from cassette CA to main conveyance path 1A, and the first sheet of paper S is switched back and pulled into reverse conveyance path 1B from branch position BP. Then, before the first sheet of paper S is fed again from reverse conveyance path 1B (connection position CP) to main conveyance path 1A, a sheet of paper S (herein referred to as second sheet of paper S) following the first sheet of paper S is fed from cassette CA to main conveyance path 1A, and an image is printed on one side of the second sheet of paper S.

[0058] The second sheet S is drawn into the reverse conveying path 1B from the branching position BP and circulates through the reverse conveying path 1B together with the first sheet S. Subsequently, the first sheet S is fed again from the reverse conveying path 1B (connecting position CP) to the main conveying path 1A, and an image is printed on the other side of the first sheet S. Then, after the first sheet S is fed again from the reverse conveying path 1B (connecting position CP) to the main conveying path 1A and before the second sheet S is fed again from the reverse conveying path 1B (connecting position CP) to the main conveying path 1A, the sheet S following the second sheet S (referred to here as the third sheet S) is fed from the cassette CA to the main conveying path 1A, and an image is printed on one side of the third sheet S.

[0059] The third sheet S is drawn into the reverse conveying path 1B from the branching position BP and circulates through the reverse conveying path 1B together with the second sheet S. Thereafter, printing is performed on the other side of the second sheet S, as with the first sheet S, and then printing is performed on the other side of the third sheet S. If there is a sheet S (referred to here as the fourth sheet S) on which an image should be printed next to the third sheet S, the fourth sheet S is fed from the cassette CA to the main conveying path 1A after the second sheet S has been refed from the reverse conveying path 1B (connecting position CP) to the main conveying path 1A and before the third sheet S is refed from the reverse conveying path 1B (connecting position CP) to the main conveying path 1A.

[0060] In this way, in a high-speed double-sided printing job, after the Nth sheet S is fed from cassette CA to main conveying path 1A, the (N-1)th sheet S is refed from reverse conveying path 1B to main conveying path 1A. Also, after the Nth sheet S is refed from reverse conveying path 1B to main conveying path 1A, the (N+2)th sheet S is fed from cassette CA to main conveying path 1A.

[0061] In a high-speed double-sided printing job, when the paper feed source for the Nth sheet is the inserter 2, the main control unit 10 sets the timing for re-feeding the N-1th sheet S from the reversing conveyance path 1B to the main conveyance path 1A as the timing when, after feeding the Nth sheet S corresponding to the insert sheet SS from the cassette CA to the main conveyance path 1A, the N-1th sheet S is re-fed from the reversing conveyance path 1B to the main conveyance path 1A.The main control unit 10 then gives the printing unit 11 (print control unit 110) an instruction to re-feed the N-1th sheet S from the reversing conveyance path 1B to the main conveyance path 1A at the set re-feed timing.

[0062] Furthermore, in a high-speed double-sided printing job, when the paper feed source for the Nth sheet is the inserter 2, the main control unit 10 sets the timing for feeding the (N+2)th sheet S from cassette CA to main conveyance path 1A as the feed timing for the (N+2)th sheet S from cassette CA to main conveyance path 1A, based on the timing when the Nth sheet S corresponding to the insert sheet SS is re-fed from reverse conveyance path 1B to main conveyance path 1A and then the (N+2)th sheet S is fed from cassette CA to main conveyance path 1A. Then, the main control unit 10 gives an instruction to the printing unit 11 (print control unit 110) to feed the (N+2)th sheet S from cassette CA to main conveyance path 1A at the set feed timing.

[0063] Here, the main control unit 10 sets the refeed timing of the N-1th sheet S and the feed timing of the N+2th sheet S based on the length of the insert sheet SS in the transport direction. The longer the length of the insert sheet SS in the transport direction, the later the main control unit 10 sets the refeed timing of the N-1th sheet S and the feed timing of the N+2th sheet S. The shorter the length of the insert sheet SS in the transport direction, the earlier the main control unit 10 sets the refeed timing of the N-1th sheet S and the feed timing of the N+2th sheet S. In other words, the main control unit 10 changes the refeed timing of the N-1th sheet S and the feed timing of the N+2th sheet S depending on the length of the insert sheet SS in the transport direction.

[0064] If the paper feed source for the Nth sheet is the inserter 2, the printing unit 11 does not feed the Nth sheet from the cassette CA. In this case, the printing unit 11 feeds a sheet S corresponding to an insert sheet SS as the Nth sheet from the cassette CA to the main transport path 1A, and then refeds the N-1th sheet S from the reverse transport path 1B to the main transport path 1A at the timing (the refeed timing instructed by the main control unit 10) when refeding the N-1th sheet S from the reverse transport path 1B to the main transport path 1A. In other words, the printing unit 11 does not actually feed the insert sheet SS from the cassette CA to the main transport path 1A. However, the printing unit 11 controls the refeed timing of the next sheet S to be refed from the reverse transport path 1B to the main transport path 1A, assuming that the insert sheet SS has been fed from the cassette CA to the main transport path 1A.

[0065] Furthermore, the printing unit 11 feeds the (N+2)th sheet S from cassette CA to main conveyance path 1A at the timing (feed timing instructed by main control unit 10) when, after re-feeding sheet S corresponding to insert sheet SS as the Nth sheet from reversing conveyance path 1B to main conveyance path 1A, the (N+2)th sheet S is fed from cassette CA to main conveyance path 1A. In other words, the printing unit 11 does not actually re-feed insert sheet SS from reversing conveyance path 1B to main conveyance path 1A. However, the printing unit 11 controls the feed timing of the next sheet S to be fed from cassette CA to main conveyance path 1A, assuming that insert sheet SS has been re-fed from reversing conveyance path 1B to main conveyance path 1A.

[0066] For example, as shown in Figure 5, the source of the first sheet S1, the second sheet S2, the fourth sheet S4, and the fifth sheet S5 is cassette CA, and the source of the third sheet S3 is inserter 2. In other words, the third sheet S is an insert sheet SS, and is inserted between sheets S2 and S4.

[0067] In the example shown in FIG. 5, first, the printing unit 11 feeds sheet S1 from cassette CA to main transport path 1A (prints an image on one side of sheet S1). Next, the printing unit 11 transports sheet S1 into reverse transport path 1B. Before re-feeding sheet S1 from reverse transport path 1B to main transport path 1A, the printing unit 11 feeds sheet S2 from cassette CA to main transport path 1A (prints an image on one side of sheet S2). The printing unit 11 also transports sheet S2 into reverse transport path 1B.

[0068] Next, the printing unit 11 re-feeds the sheet S1 from the reverse conveying path 1B to the main conveying path 1A (printing an image on the other side of the sheet S1). After re-feeding the sheet S1, the printing unit 11 does not actually feed the sheet S3 from the cassette CA to the main conveying path 1A. However, the printing unit 11 re-feeds the sheet S2 from the reverse conveying path 1B to the main conveying path 1A (printing an image on the other side of the sheet S2) at the same timing as when the printing unit 11 re-feeds the sheet S2 from the reverse conveying path 1B to the main conveying path 1A after feeding the sheet S3 from the cassette CA to the main conveying path 1A.

[0069] After re-feeding sheet S2, printing unit 11 feeds sheet S4 from cassette CA to main conveying path 1A (prints an image on one side of sheet S4). After feeding sheet S4, printing unit 11 does not actually re-feed sheet S3 from reverse conveying path 1B to main conveying path 1A. However, printing unit 11 feeds sheet S5 from cassette CA to main conveying path 1A (prints an image on one side of sheet S5) at the same timing as when printing unit 11 re-feeds sheet S3 from reverse conveying path 1B to main conveying path 1A and then feeds sheet S5 from cassette CA to main conveying path 1A. In addition, printing unit 11 transports sheet S5 into reverse conveying path 1B.

[0070] Next, the printing unit 11 re-feeds the sheet S4 from the reverse conveying path 1B to the main conveying path 1A (prints an image on the other side of the sheet S4). If the sheet S5 is the last, the printing unit 11 re-feeds the sheet S5 from the reverse conveying path 1B to the main conveying path 1A (prints an image on the other side of the sheet S5).

[0071] By performing paper feed control for a print job involving insert processing, as shown in Fig. 6, the printing unit 11 sequentially conveys the leading sheet S10, which is the sheet S immediately before the insert sheet SS, and the trailing sheet S20, which is the sheet S immediately after the insert sheet S, with an insert interval S0 between them. The printing unit 11 changes the insert interval S0 depending on the length of the insert sheet SS in the conveying direction. Note that the insert interval S0 is greater than the length of the insert sheet SS inserted between the leading sheet S10 and the trailing sheet S20 in the conveying direction.

[0072] The inserter 2 inserts an insert sheet SS between the leading sheet S10 and the trailing sheet S20. Specifically, in a print job that involves insert processing, the inserter 2 feeds the insert sheet SS from the insert position P3 to the main conveyance path 1A after the trailing end in the conveyance direction of the leading sheet S10 being conveyed along the main conveyance path 1A passes through the insert position P3. Here, the inserter 2 completes feeding of the insert sheet SS to be inserted between the leading sheet S10 and the trailing sheet S20 after the trailing end in the conveyance direction of the leading sheet S10 passes through the insert position P3 and before the leading end in the conveyance direction of the trailing sheet S20 reaches the insert position P3.

[0073] In this embodiment, as described above, the main control unit 10 provides the printing unit 11 (printing control unit 110) with a control signal related to a print job involving insert processing. For example, the control signal related to a print job involving insert processing includes a signal indicating the length in the transport direction of the insert sheet SS. Based on this control signal, the printing unit 11 recognizes the length in the transport direction of the insert sheet SS to be inserted among the multiple sheets S to be printed in the print job involving insert processing.

[0074] The printing unit 11 then automatically changes the insert spacing S0 according to the length of the insert sheet SS in the transport direction. The longer the length of the insert sheet SS in the transport direction, the larger the insert spacing S0 is set by the printing unit 11. The shorter the length of the insert sheet SS in the transport direction, the smaller the insert spacing S0 is set by the printing unit 11. In other words, the printing unit 11 sets the insert spacing S0 to a spacing appropriate for the length of the insert sheet SS in the transport direction.

[0075] The configuration of this embodiment can prevent the insert spacing S0 from becoming too large unnecessarily. Even when insert sheets SS of different sizes are used in a single print job, the insert spacing S0 changes each time depending on the size of the insert sheet SS in the transport direction. As a result, insert sheets SS can be inserted while preventing a decrease in productivity.

[0076] In addition, in the configuration of this embodiment, the inserter 2 feeds the insert sheet SS from the insert position P3 to the main transport path 1A after the rear end of the leading sheet S10 being transported along the main transport path 1A has passed the insert position P3. Here, the insert interval S0 is set according to the length of the insert sheet SS in the transport direction. Therefore, feeding of the insert sheet SS can be completed by the time the leading end of the trailing sheet S20 reaches the insert position P3. This makes it possible to prevent the insert sheet SS from colliding with other sheets S being transported along the main transport path 1A.

[0077] In addition, in the configuration of this embodiment, for a single-sided printing job that involves insert processing, the paper feed control shown in Fig. 3 is performed. For a normal double-sided printing job that involves insert processing, the paper feed control shown in Fig. 4 is performed. For a high-speed double-sided printing job that involves insert processing, the paper feed control shown in Fig. 5 is performed. This makes it possible to insert insert sheets SS in each printing job while suppressing a decrease in productivity.

[0078] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims rather than the description of the above embodiments, and further includes all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0079] 1A Main transport path 1B Reversing conveyance path 2 Inserter 11 Printing Department 100 Image forming device BP branch position CA cassette CP connection position P2 print position P3 insert position P4 Ejection position S paper S0 Insert Spacing S10 Front Sheet S20 Rear Paper SS Insert Paper

Claims

1. a main transport path extending from a paper feed position where a cassette in which paper is set is disposed, through a print position and an insert position in that order, to an ejection position; a printing unit that, during a print job, feeds and transports paper from the cassette to the main transport path and prints an image on the paper as it passes through the printing position; an inserter that performs an insert process of feeding an insert sheet from the insert position to the main transport path to insert the insert sheet between sheets that are sequentially transported along the main transport path, The printing unit is provided on a main body, the main body is provided with a portion of the main transport path that includes the paper feed position and the print position, and the inserter is provided with a portion of the main transport path that includes the insert position; the printing unit includes a print control unit that controls timing of feeding paper from the cassette to the main transport path; the inserter includes an inserter control unit that controls the inserting process; When the print job involves the insert process, the printing unit sequentially conveys the leading sheet and the trailing sheet, leaving an insert space between the leading sheet that is one sheet before the insert sheet and the trailing sheet that is one sheet after the insert sheet, the printing unit automatically changes the insert interval in accordance with the length of the insert paper in the transport direction; In an image forming device, when the print job involves the insert processing, the inserter feeds the insert sheet from the insert position to the main transport path after the rear end of the front sheet being transported along the main transport path has passed the insert position.

2. The print job includes a single-sided print job in which an image is printed on only one side of a sheet of paper, The image forming device of claim 1, wherein in the single-sided printing job involving the insert processing, when the Nth sheet is the insert sheet, the printing unit does not feed the Nth sheet from the cassette, but feeds the N+1th sheet from the cassette to the main transport path at the timing when a sheet having the same length in the transport direction as the insert sheet is fed from the cassette to the main transport path as the Nth sheet, and then feeds the N+1th sheet from the cassette to the main transport path.

3. a reverse conveyance path that branches off from the main conveyance path at a branching position downstream of the printing position in a paper conveyance direction and connects to the main conveyance path at a connecting position upstream of the printing position in the paper conveyance direction, The print job includes a normal double-sided print job in which images are printed on both sides of a sheet of paper, the print control unit controls timing for re-feeding paper from the reverse transport path to the main transport path; In the case of the normal double-sided printing job, the printing unit the paper fed from the cassette to the main transport path is switched back and drawn into the reverse transport path from the branch position; After the sheet on the reverse transport path is re-fed from the connection position to the main transport path, a process of feeding the next sheet from the cassette to the main transport path is performed; The image forming device of claim 1, wherein in the normal double-sided printing job involving the insert processing, when the Nth sheet is the insert sheet, the printing unit does not feed the Nth sheet from the cassette, but feeds a sheet having the same length in the transport direction as the insert sheet from the reverse transport path to the main transport path as the Nth sheet, and then feeds the N+1th sheet from the cassette to the main transport path at the same time as feeding the N+1th sheet from the cassette to the main transport path.

4. a reverse conveyance path that branches off from the main conveyance path at a branching position downstream of the printing position in a paper conveyance direction and connects to the main conveyance path at a connecting position upstream of the printing position in the paper conveyance direction, The print job includes a high-speed double-sided print job that prints images on both sides of a sheet of paper, the print control unit controls timing for re-feeding paper from the reverse transport path to the main transport path; During the high-speed double-sided printing job, the printing unit: a first sheet of paper fed from the cassette to the main transport path is switched back and pulled from the branch position into the reverse transport path; before the first sheet is re-fed from the connection position to the main transport path, a second sheet that is the next sheet to the first sheet is fed from the cassette to the main transport path; After feeding the second sheet, the second sheet is switched back and pulled from the branch position into the reverse transport path, and the first sheet is re-fed from the connection position to the main transport path; after the first sheet is re-fed and before the second sheet is re-fed from the connection position to the main transport path, a third sheet that is the next sheet after the second sheet is fed from the cassette to the main transport path; After the third sheet has been fed, a process is performed to re-feed the second sheet from the connection position to the main transport path; The image forming device of claim 1, wherein in the high-speed double-sided printing job involving the insert processing, when the Nth sheet is the insert sheet, the printing unit does not feed the Nth sheet from the cassette, but feeds a sheet having the same length in the transport direction as the insert sheet from the cassette to the main transport path as the Nth sheet, and then refeds the N-1th sheet from the reverse transport path to the main transport path at the same time as refeding the N-1th sheet from the reverse transport path to the main transport path.

5. The image forming device of claim 4, wherein the printing unit feeds the N+2th sheet of paper from the cassette to the main transport path at the same timing as when the Nth sheet of paper, which has the same length in the transport direction as the insert sheet, is re-fed from the reverse transport path to the main transport path, and then the N+2th sheet of paper is fed from the cassette to the main transport path.

Images