Image forming system

Abstract

To quickly discharge a paper sheet after an image is formed on both sides by discharging the paper sheet subjected to double-sided printing in a paper surface direction similar to face-up in which a first surface on which the image is first formed is turned upward.SOLUTION: In an image forming system Sy, a control unit 68 causes an image forming apparatus 2 to form an image of an Nth (N is an odd number) page on an upward facing front surface of a sheet, when the sheet whose front and back surfaces are reversed is returned to the image forming apparatus 2, causes the image forming apparatus 2 to form an image of an (N+1)-th page on an upward facing back surface of the sheet and causes the sheet to be discharged from a sheet conveying apparatus 3 with the front surface of the sheet facing downward, or causes the image forming apparatus 2 to form an image of the (N+1)-th page on the upward facing front surface of the sheet, when the sheet whose front and back surfaces are reversed is returned to the image forming apparatus 2, causes the image forming apparatus to form an image of the Nth page on an upward facing back surface of the sheet and causes the sheet to be discharged from the sheet conveying apparatus 3 with the back surface of the sheet facing upward.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an image forming system including an image forming apparatus that forms an image on a sheet of paper, and a sheet transporting device that receives and transports the sheet of paper transported from the image forming apparatus. [Background technology]

[0002] Some image forming devices use an inkjet system in which ink is ejected onto paper to form an image on the paper. For example, the inkjet recording device described in Patent Document 1 includes a transport path that transports paper from a cassette through a recording head to an output tray and then ejects it, and another transport path that transports paper from the output tray in the opposite direction, turns the paper over, and transports the paper again to the recording head. By appropriately selecting one of the two transport paths, the device transports paper and enables back-side ejection, in which the paper is ejected face-down onto the output tray, or front-side ejection, in which the paper is ejected face-up onto the output tray, and enables recording on both sides of the paper. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-72998 Summary of the Invention [Problem to be solved by the invention]

[0004] In Patent Document 1, it is possible to select between back-side ejection, in which paper is ejected face-down onto the ejection tray, and front-side ejection, in which paper is ejected face-up onto the ejection tray. Furthermore, paper that has been recorded on both sides can be ejected by back-side ejection or front-side ejection.

[0005] However, when selecting backside or frontside ejection after recording on both sides of a sheet of paper, if the path the sheet must travel before being ejected after both sides of the sheet have become wet with ink is long, the frequency of jams and other problems increases.

[0006] The present invention has been made in consideration of the above circumstances, and aims to discharge double-sided printed paper in a paper orientation similar to face-up, with the first side on which the image is first formed facing upward, and to quickly discharge the paper after images have been formed on both sides. [Means for solving the problem]

[0007] An image forming system according to one aspect of the present invention includes an image forming device having an image forming unit that forms an image on an upward facing front side of a sheet of paper, discharges the sheet, and when the sheet is returned after being inverted, forms an image on the upward facing back side of the sheet of paper; a paper transporting device that receives the sheet of paper discharged from the image forming device, transports and discharges the sheet, and inverts the sheet and transports it towards the image forming device; and a control unit that controls the operation of the image forming device, wherein the control unit causes the image forming device to print on both the front and back sides of the sheet of paper, and when the sheet of paper is transported and discharged by the paper transporting device, causes the image forming device to form an image of an Nth page (N is an odd number) on the upward facing front side of the sheet of paper, and when the sheet of paper is returned to the image forming device after being inverted by the paper transporting device, When the image forming unit 100 is turned over, the image of page N is formed on the back side of the paper that is facing up, and the paper is discharged from the image forming device through the paper conveying device with the front side of the paper on which the image of page N has been formed facing down (a first conveyance); or when the image forming unit 100 forms the image of page N on the front side of the paper that is facing up and the paper is returned to the image forming device, the image forming unit 100 forms the image of page N on the back side of the paper that is facing up, and the paper is conveyed from the image forming device to the paper conveying device with the back side of the paper on which the image of page N has been formed facing up without being turned over by the paper conveying device, and the paper is discharged from the paper conveying device with the back side of the paper on which the image of page N has been formed facing up (a second conveyance). [Effects of the Invention]

[0008] According to the present invention, double-sided printed paper can be discharged in a face-up orientation, with the first side, on which the image is formed first, facing upward, and the paper can be quickly discharged after images have been formed on both sides. By quickly discharging the paper after double-sided image formation in this way, the present invention reduces the occurrence of jams on the paper transport path. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view showing a schematic configuration of an image forming system according to an embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram showing the configuration of a control system of the image forming system. [Figure 3] FIG. 2 is a cross-sectional view schematically illustrating a paper transport device in the image forming system. [Figure 4] 10A and 10B are diagrams showing the order of the transport paths through which a sheet is transported in a sheet transport device, turned over, and discharged. [Figure 5] 10A and 10B are diagrams showing the order of the transport paths along which a sheet is transported in the sheet transport device and returned to the image forming device. [Figure 6] (A) to (D) show the state in which five pages of images are printed on the front of each sheet of paper in either a forward printing order or a reverse printing order, and each sheet is discharged face up or face down onto the output tray. [Figure 7] (A) to (D) show the state in which five pages of images are printed on both sides of each sheet of paper in either a forward printing order or a reverse printing order, and each sheet is discharged face up or face down onto the output tray. [Figure 8] 10 is a flowchart showing paper transport control according to single-sided printing or double-sided printing, paper discharge face-down or face-up, and forward printing order or reverse printing order. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view that schematically shows an image forming system according to this embodiment. As shown in FIG. 1, the image forming system Sy has a paper feeder 1, an image forming device 2, and a paper transport device 3. The paper feeder 1 supplies paper to the image forming device 2. The image forming device 2 receives the paper from the paper feeder 1 and forms an image on the paper. The paper transport device 3 receives the paper from the image forming device 2, transports the paper and ejects it onto an ejection tray (not shown), and also transports the paper back to the paper feeder 1 via the image forming device 2.

[0011] The paper feed device 1 includes paper feed cassettes 12 each containing a plurality of sheets of paper, a paper feed transport path 13, a reversing transport path 14, and a plurality of transport rollers 18 that transport the paper along the paper feed transport path 13 or the reversing transport path 14. The paper feed transport path 13 pulls out a sheet of paper from one of the paper feed cassettes 12 and transports the sheet to the image forming device 2. The reversing transport path 14 receives a sheet of paper that has been returned to the paper feed device 1 via the image forming device 2, turns the sheet over, and transports the sheet to the image forming device 2 again.

[0012] The image forming device 2 includes a conveyor belt 24 that receives and conveys paper from the paper feed device 1, an image forming section 25 that forms an image on the paper, a conveying path 26 that conveys paper to the paper conveying device 3, a conveying path 27 that receives paper returned from the paper conveying device 3 and conveys it to the paper feed device 1, and a plurality of conveying rollers 28 that convey paper along each of the conveying paths 26 and 27.

[0013] The image forming unit 25 forms an image on paper using an inkjet system. The image forming unit 25 has an ink cartridge, a pump, a head, nozzles, and electrodes. The ink cartridge stores ink of each color, for example, Y (yellow), M (magenta), C (cyan), and K (black). The pump supplies ink from the ink cartridge to the head. The head has a large number of nozzles that form pixels. Based on image data, ink of a color corresponding to the image data is supplied to the head from the ink cartridge. Ink is ejected from the nozzles of the head toward the paper. The electrodes have, for example, a charging electrode and a deflection electrode. The charging electrode charges the ink ejected from the nozzle. The deflection electrode controls the flight direction of the charged ink.

[0014] The paper transport device 3 includes a main transport path 31 that receives and transports paper transported through the transport path 26 of the image forming device 2, a branch transport path 32 branching off from the main transport path 31, a second connecting transport path 33 connected to the branch transport path 32, a second drum-shaped transport path 34 and a first connecting transport path 35 branching off from the second connecting transport path 33, a first drum-shaped transport path 36 connected to the first connecting transport path 35, a first switchback transport path 37 branching off from the first drum-shaped transport path 36, a second switchback transport path 38 branching off from the second drum-shaped transport path 34, a third connecting transport path 39 connecting the second connecting transport path 33 to the second switchback transport path 38, a relay transport path 40 connecting the first switchback transport path 37 and the second switchback transport path 38 to the transport path 27 of the image forming device 2, and a sub-transport path 41 connecting the first switchback transport path 37 and the second switchback transport path 38 to the main transport path 31.

[0015] Furthermore, the paper transport device 3 is provided with a plurality of transport rollers 42 that are arranged along each of the transport paths 31 to 41 and transport the paper.

[0016] The paper conveying device 3 also includes a branch claw 51 provided at the branch point of the main conveying path 31 and the branch conveying path 32, a branch claw 52 provided at the branch point from the second connecting conveying path 33 to the second drum-shaped conveying path 34 or the first connecting conveying path 35, a branch claw 53 provided at the branch point from the first drum-shaped conveying path 36 to the first switchback conveying path 37, a branch claw 54 provided at the branch point from the second drum-shaped conveying path 34 to the second switchback conveying path 38, a branch claw 55 provided at the branch point from the first switchback conveying path 37 or the second switchback conveying path 38 to the relay conveying path 40 or the auxiliary conveying path 41, and a branch claw 56 provided at the branch point from the second connecting conveying path 33 to the third connecting conveying path 39.

[0017] The paper transport device 3 also includes a heat generating unit 61 disposed above the main transport path 31. The heat generating unit 61 irradiates the upper surface of the paper transported on the main transport path 31 with infrared rays to promote drying of the ink adhering to the upper surface of the paper.

[0018] In this paper transport device 3, an image is formed on the upward surface (front side; the same applies below) of the paper by the image forming device 2, and when this paper is transported from the transport path 26 of the image forming device 2 to the main transport path 31, each branch claw 51 to 56 is switched appropriately to transport the paper through several transport paths, and the paper is discharged from the main transport path 31 face up (paper is discharged with the first side on which the image was first formed facing upward) or face down (paper is discharged with the first side on which the image was first formed facing downward)).

[0019] Furthermore, in the paper transport device 3, when images are formed on both sides of a paper by the image forming device 2, an image is first formed on the upward facing surface of the paper, and when this paper is transported from the transport path 26 of the image forming device 2 to the main transport path 31, the branch claws 51 to 56 are switched appropriately to transport the paper to the relay transport path 40 via several transport paths, and the paper is transported from the relay transport path 40 to the transport path 27 of the image forming device 2. The paper is transported to the reversal transport path 14 of the paper feeder 1 via the transport path 27 of the image forming device 2.

[0020] In the paper feeder 1, the paper is conveyed through the reversing conveyance path 14, the paper is turned over, and the paper is conveyed to the image forming device 2 again.

[0021] In the image forming device 2, the paper is transported to the image forming section 25, which forms an image on the upward facing back side of the paper, and the paper with the images formed on both sides is transported from the transport path 26 to the main transport path 31 of the paper transport device 3.

[0022] In the paper transport device 3, when a paper sheet is transported to the main transport path 31, the paper sheet is discharged from the main transport path 31 face up (first side facing upward) or face down (first side facing downward) onto an output tray (not shown).

[0023] Fig. 2 is a block diagram showing the configuration of a control system of the image forming system Sy. As shown in Fig. 2, the image forming system Sy is configured to include a paper feeder 1, an image forming device 2, a paper transport device 3, a heat generating unit 61, an operation unit 62, a display unit 63, a touch panel 64, a communication unit 65, a storage unit 66, and a control unit 67. These components are capable of transmitting and receiving data or signals to and from each other via a bus.

[0024] The operation unit 62 includes hard keys such as a numeric keypad, a decision key, and a start key.

[0025] The display unit 63 is configured by a liquid crystal display (LCD) or an organic light-emitting diode (OLED) display.

[0026] A touch panel 64 is superimposed on the screen of the display unit 63. The touch panel 64 detects contact (touch) with the user's finger or the like on the touch panel 64 together with the contact position, and outputs a detection signal indicating the coordinates of the contact position to a control unit 68 of a control unit 67. This makes it possible to operate a GUI (Graphical User Interface) or the like displayed on the screen of the display unit 63 through the touch panel 64. Therefore, the touch panel 64 functions as an operation unit into which user operations are input to the screen of the display unit 63.

[0027] The communication unit 65 is a communication interface equipped with a communication module such as a LAN chip. The communication unit 65 is connected to an external information processing device 71 through a network (such as an intranet) N, and performs data communication with the information processing device 71. For example, the information processing device 71 is a DFE (Digital Front End) device, and transmits image data representing an image to the communication unit 65 of the image forming system Sy.

[0028] The storage unit 66 is a large-capacity storage device such as an SSD (Solid State Drive) or an HDD (Hard Disk Drive), and stores various application programs and various data.

[0029] The control unit 67 is composed of a processor, a RAM (Random Access Memory), a ROM (Read Only Memory), etc. The processor is, for example, a CPU (Central Processing Unit), an ASIC (Application Specific Integrated Circuit), or an MPU (Micro Processing Unit). The control unit 67 functions as a control unit 68 when a control program stored in the ROM or the storage unit 66 is executed by the processor.

[0030] The control unit 67 controls the paper feeder 1, the image forming device 2, and the paper transport device 3. The control unit 67 is also connected to the heat generating unit 61, the operation unit 62, the display unit 63, the touch panel 64, the communication unit 65, and the storage unit 66, and controls each of the above components and transmits and receives signals or data to and from each of the components. The control unit 68 is provided, for example, in the image forming device 2.

[0031] The control unit 68 serves as a processing unit that executes various processes. For example, when image data transmitted from the information processing device 71 is received by the communication unit 65, the control unit 68 controls the paper feed device 1 to transport a sheet from the paper feed device 1 to the image forming device 2, causes the image forming device 2 to form an image represented by the received image data on the sheet, and transports the sheet from the image forming device 2 to the paper transport device 3.

[0032] At this time, instructions such as single-sided printing or double-sided printing, and paper ejection face-down or face-up are received by the operation unit 62 by the user operating the operation unit 62, for example, a GUI displayed on the screen of the display unit 63. The control unit 68 performs control in accordance with the instructions received by the operation unit 62 via the touch panel 64.

[0033] For example, when a user instructs that single-sided printing and face-down ejection of paper be performed, control unit 68 controls paper feeder 1 based on the instruction to transport the paper from paper feeder 1 to image forming device 2, cause image forming device 2 to form an image on the upward facing surface of the paper, and transport the paper from image forming device 2 to paper transport device 3. Then, control unit 68 drives and controls motors (not shown) that rotate each transport roller 42 in paper transport device 3, actuators (not shown) that reciprocate each branch claw 51 to 57, and the like, to transport the paper along the path shown in Figures 3 and 4(A) or 3 and 4(B), and eject the paper face-down from main transport path 31.

[0034] 4A and 4B show the order of the transport paths through which paper printed on its upward surface is transported from image forming device 2 to paper transport device 3 and discharged face down (first side, in this case, the surface facing downward). In Fig. 4A, when paper printed on its upward surface is transported from transport path 26 of image forming device 2 to main transport path 31, the paper is transported in the order of main transport path 31 → branch claw 51 → branch transport path 32 → second connecting transport path 33 → branch claw 52 → first connecting transport path 35 → first drum-shaped transport path 36, where it is temporarily stopped, and the rear end of the paper passes branch claw 53. Next, the conveying roller 42 of the first drum-shaped conveying path 36 is rotated in the reverse direction, and the paper is conveyed in the opposite direction (called switchback conveying), and the paper is conveyed in the following order: first drum-shaped conveying path 36 → branch claw 53 → first switchback conveying path 37 → branch claw 55 → auxiliary conveying path 41, the paper is turned over, and the paper is discharged face down from the auxiliary conveying path 41 through the main conveying path 31.

[0035] 4(B), when a face-up sheet of paper is transported from the transport path 26 of the image forming device 2 to the main transport path 31, the sheet is transported in the order of the main transport path 31 → branch claw 51 → branch transport path 32 → second connecting transport path 33 → branch claw 52 → second drum-shaped transport path 34, and is then temporarily stopped, and the rear end of the sheet passes through the branch claw 54. Subsequently, the transport roller 42 of the second drum-shaped transport path 34 is rotated in the reverse direction, and the sheet is transported in the order of the second drum-shaped transport path 34 → branch claw 54 → second switchback transport path 38 → branch claw 55 → sub-transport path 41, whereupon the sheet is turned over and discharged face-down from the sub-transport path 41 through the main transport path 31 (FIGS. 6(A)(C)).

[0036] 3 shows the order of the transport paths through which a sheet of paper with a printed surface facing up is transported from the image forming device 2 to the paper transport device 3 and discharged face-up (first surface, in this case, facing up). In FIG. 3, when the face-up sheet of paper is transported from the transport path 26 of the image forming device 2 to the main transport path 31, the sheet is transported through the main transport path 31 and discharged as is (FIGS. 6(B)(D)).

[0037] When printing is performed only on the front side of the paper in this way, in the face-up case, the paper with the printed side facing up is transported through the main transport path 31 as shown in Figure 3 and discharged as is, or in the face-down case, the paper with the printed side facing up is turned over using the transport shown in Figure 4(A) or 4(B) and the paper is discharged face-down (the first side, in this case the front side facing down) through the main transport path 31.

[0038] In the paper transport device 3 configured as described above, the first drum-shaped transport path 36 and the second drum-shaped transport path 34 are linked together to transport each paper sheet alternately to each drum-shaped transport path 36, 34, thereby increasing the job processing volume per unit time and achieving high productivity compared to operating only the first drum-shaped transport path 36. Furthermore, because the first drum-shaped transport path 36 and the second drum-shaped transport path 34, through which paper sheets are evacuated, are drum-shaped, the paper transport device 3 can be made smaller than when a direct transport path through which paper sheets are evacuated is provided.

[0039] On the other hand, when the user instructs to print on both sides and discharge the paper face down, control unit 68 controls paper feeder 1 based on the instruction to transport the paper from paper feeder 1 to image forming device 2, cause image forming device 2 to form an image on the upward facing surface of the paper, and transport the paper from image forming device 2 to paper transport device 3. Then, control unit 68 drives and controls motors (not shown) that rotate each transport roller 42 in paper transport device 3, actuators (not shown) that reciprocate each branch claw 51 to 57, and the like, to transport the paper to relay transport path 40 via several transport paths as shown in FIG. 5(A) or 5(B), and transports the paper from relay transport path 40 through transport path 27 of image forming device 2 to reversal transport path 14 of paper feeder 1.

[0040] 5A, when a sheet of paper with its front side printed and set to be double-sided and face-down is conveyed from conveyance path 26 of image forming device 2 to main conveyance path 31, the sheet is conveyed in the order of main conveyance path 31 → diverter claw 51 → diverter conveyance path 32 → second connecting conveyance path 33 → diverter claw 52 → first connecting conveyance path 35 → first drum-shaped conveyance path 36, where it is temporarily stopped, and the rear end of the sheet passes diverter claw 53. Next, conveyance roller 42 of first drum-shaped conveyance path 36 is reversely rotated, and the sheet is conveyed in the order of first drum-shaped conveyance path 36 → diverter claw 53 → first switchback conveyance path 37 → diverter claw 55 → relay conveyance path 40, and the sheet is conveyed from relay conveyance path 40 to reversal conveyance path 14 of sheet feeding device 1 through conveyance path 27 of image forming device 2 with its front side facing up.

[0041] 5B, when a sheet of paper with its front side printed and set to be double-sided and face-down is conveyed from conveyance path 26 of image forming device 2 to main conveyance path 31, the sheet is conveyed in the order of main conveyance path 31 → diverter 51 → diverter conveyance path 32 → second connecting conveyance path 33 → diverter 52 → second drum-shaped conveyance path 34, where it is temporarily stopped, and the rear end of the sheet passes diverter 54. Next, conveyance roller 42 of second drum-shaped conveyance path 34 is reversely rotated, and the sheet is conveyed in the order of second drum-shaped conveyance path 34 → diverter 54 → second switchback conveyance path 38 → diverter 55 → relay conveyance path 40, and the sheet is conveyed from relay conveyance path 40 to reversal conveyance path 14 of paper feeder 1 through conveyance path 27 of image forming device 2 with its front side facing up.

[0042] 5(A) or 5(B), in the paper feeder 1, when the paper is transported from the transport path 27 of the image forming device 2 to the reversing transport path 14, the paper is inverted in the reversing transport path 14 and transported again to the image forming device 2. In the image forming device 2, an image is formed on the paper with the back side facing up, and the paper with both sides printed is transported from the image forming device 2 to the paper transport device 3.

[0043] Thereafter, if the paper is transported through the main transport path 31 as shown in FIG. 3 and discharged as is, the paper can be discharged face down.

[0044] On the other hand, if the user has input into the operation unit 62 a command to perform double-sided printing and discharge of the paper face-up, the control unit 68 controls the paper feeder 1, the image forming device 2, and the paper transport device 3 based on that command, so that the image forming device 2 forms an image on the front side (first side) of the paper, then the paper is turned over using the path shown in Figure 5(A) or Figure 5(B), and the image forming device 2 again forms an image on the back side (second side) of the paper, and then the paper is turned over again using the transport shown in Figure 4(A) or Figure 4(B) before being discharged from the sub-transport path 41. As a result, the paper is discharged face-up.

[0045] However, if the transport path for paper after double-sided printing is long because both sides of the paper are wet with ink, jams and other problems will occur more frequently. Therefore, it is desirable to shorten the transport path for paper after images have been formed on both sides so that the paper can be quickly discharged.

[0046] Therefore, in this embodiment, when a user instructs double-sided printing and face-up ejection of paper, control unit 68 causes image forming device 2 to first form an image of the (N+1)th page on the upward facing front side of the paper, and then causes the paper to be transported from image forming device 2 to paper transport device 3, and as shown in FIG. 5(A) or 5(B), the paper is transported from relay transport path 40 to transport path 27 of image forming device 2, and the paper is returned to reversal transport path 14 of paper feeder 1 via transport path 27, where it is turned over and transported again to image forming device 2, where image forming device 2 forms an image of page N on the back side of the paper, which is now facing upward, and then causes the double-sided printed paper to be transported again from image forming device 2 to paper transport device 3, and the paper is ejected via only main transport path 31 along the path shown in FIG. 3. This type of paper transport is adopted in this embodiment.

[0047] 5(A) or 5(B), which would normally result in face-down discharge, the printing order of images formed on the front and back of a sheet of paper is reversed from that for face-down discharge by forming the image of page (N+1) first on the front side of the paper facing up, followed by the image of page N on the back side of the paper facing up, thereby discharging the paper with both sides printed in the same state as face-up, i.e., with the first side on which the image was formed first facing up, through only the main transport path 31 without transporting the paper for reversing as shown in FIG. 4(A) or 4(B). This shortens the transport path for the paper after images have been formed on both sides, and allows it to be discharged in the same way as face-up discharge.

[0048] In addition, when the user operates the printer to input instructions for double-sided printing, face-down or face-up paper ejection, and specifying the printing order of the images to be printed when printing multiple pages of images to be printed on multiple sheets of recording paper, the control unit 68 causes the image forming device 2 to form images in accordance with the specified printing order.

[0049] The printing order of the images of each page can be a forward direction in which images are formed in the original page order indicated by the data to be printed received by the communication unit 65 of the image forming system Sy from the information processing device 71, or a reverse direction in which images are formed in an order opposite to the original page order. An instruction to select the forward direction or the reverse direction is input to the operation unit 62 by the user's operation, and is accepted by the control unit 68.

[0050] When the user inputs instructions for double-sided printing, paper face-down ejection, and forward printing, the control unit 68 causes the image forming device 2 to form images in the specified printing order, i.e., the printing order indicated by the data to be printed.

[0051] In this case, the control unit 68 causes image formation to be performed on each sheet, with the front image being the Nth page (N is an odd number) and the back image being the (N+1)th page.

[0052] The control unit 68 causes the paper to be transported from the paper feeder 1 to the image forming device 2, causes the image forming unit 25 of the image forming device 2 to form the image of the Nth page on the upward facing front side of the paper, and causes the paper after the image formation to be transported toward the paper transport device 3. The control unit 68 causes the paper to be inverted along the path shown in FIG. 5(A) or 5(B) and then transported again toward the image forming device 2. The control unit 68 causes the image forming unit 25 of the image forming device 2 to form the image of the (N+1)th page on the back side of the paper, which is now facing upward. The control unit 68 causes the paper to be transported from the image forming device 2 to the paper transport device 3 and discharged from the paper transport device 3 by transporting only along the main transport path 31 shown in FIG. 3.

[0053] For example, as shown in Figure 7(A), when printing five pages of images according to instructions specifying double-sided printing, face-down, and forward printing, the image of page 1 is formed on the front side of the first sheet, the image of page 2 is formed on the back side of the first sheet, the image of page 3 is formed on the front side of the second sheet, the image of page 4 is formed on the back side of the second sheet, and the image of page 5 is formed on the front side of the third sheet. In this case, the sheets are stacked one on top of the other and ejected from the main transport path 31 to an ejection tray (not shown) with the front side of each sheet facing downwards and the back side of each sheet facing upwards. Therefore, each sheet is ejected face-down.

[0054] Next, when performing image formation in the printing order indicated by the print target data in accordance with double-sided printing, face-up, and forward printing instructions, the control unit 68 causes paper to be transported from the paper feeder 1 to the image forming device 2, causes the image forming unit 25 of the image forming device 2 to form the image of the (N+1)th page on the upward facing front side of the paper, and causes the paper after the image formation to be transported toward the paper transport device 3. The control unit 68 causes the paper to be inverted along the path shown in FIG. 5(A) or 5(B) and then transported again toward the image forming device 2. The control unit 68 causes the image forming unit 25 of the image forming device 2 to form the image of the Nth page on the back side of the paper, which is now facing upward. The control unit 68 causes the paper to be transported from the image forming device 2 to the paper transport device 3 and discharged from the paper transport device 3 by transporting only along the main transport path 31 shown in FIG. 3.

[0055] 7(B), when printing an image of page 5 in accordance with instructions specifying double-sided printing, face-up, and forward printing, the image of page 2 is formed on the front of the first sheet, the image of page 1 is formed on the back of the first sheet, the image of page 4 is formed on the front of the second sheet, the image of page 3 is formed on the back of the second sheet, the front of the third sheet is blank, and the image of page 5 is formed on the back of the third sheet, but as a result, the sheets are stacked one on top of the other and ejected from the main transport path 31 to an ejection tray (not shown) with the front of each sheet facing downwards and the back of each sheet facing upwards. Therefore, each sheet is ejected in the same orientation as face-up, with the first side facing upwards.

[0056] Furthermore, when forming images in accordance with double-sided printing, face-down printing, and reverse printing instructions, the control unit 68 forms images on each sheet in the reverse order to the printing order indicated by the data to be printed, with the front image being the Nth page (N is an odd number) and the back image being the (N+1)th page.

[0057] In this case, the control unit 68, in accordance with the instruction for the reverse printing order, forms the images of each page in an order that is the reverse of the original page order indicated by the data to be printed. The control unit 68 causes the image forming unit 25 of the image forming device 2 to form the image of page N on the front side of the paper, starting with the image of the last page indicated by the data to be printed, and conveys the paper after the image formation toward the paper conveying device 3. The control unit 68 then inverts the paper along the path shown in FIG. 5(A) or 5(B) and conveys it again toward the image forming device 2. The control unit 68 causes the image forming unit 25 of the image forming device 2 to form the image of page (N+1) on the back side of the paper, which is now facing up. The control unit 68 conveys the paper from the image forming device 2 to the paper conveying device 3 and ejects it from the paper conveying device 3 by conveying it only along the main conveying path 31 shown in FIG. 3.

[0058] For example, as shown in Figure 7(C), when printing an image of page 5 according to instructions indicating double-sided printing, face-down, and reverse printing order, the image of page 5 is printed on the front side of the first sheet and the back side of the first sheet is blank, the image of page 3 is printed on the front side of the second sheet and the image of page 4 is printed on the back side of the second sheet, the image of page 1 is printed on the front side of the third sheet, and the image of page 2 is printed on the back side of the third sheet. In this case, the sheets are stacked one on top of the other and ejected from the main transport path 31 to an ejection tray (not shown) with the front side of each sheet facing down and the back side of each sheet facing up. Therefore, each sheet is ejected face-down.

[0059] Furthermore, when forming images in accordance with double-sided printing, face-up printing, and reverse printing instructions, the control unit 68 forms images on each sheet in the reverse order to the printing order indicated by the data to be printed, with the front image being the Nth page (N is an odd number) and the back image being the (N+1)th page.

[0060] In this case, the control unit 68, in accordance with the instruction for the reverse printing order, forms the images of each page in an order that is the reverse of the original page order indicated by the data to be printed. The control unit 68 causes the image forming unit 25 of the image forming device 2 to form the image of the (N+1)th page on the front side of the paper, starting from the image of the last page indicated by the data to be printed, and conveys the paper after the image formation toward the paper conveying device 3. The control unit 68 then inverts the paper along the path shown in FIG. 5(A) or 5(B) and conveys it again toward the image forming device 2. The control unit 68 causes the image forming unit 25 of the image forming device 2 to form the image of the Nth page on the back side of the paper, which is now facing up. The control unit 68 conveys the paper from the image forming device 2 to the paper conveying device 3 and ejects it from the paper conveying device 3 by conveying it only along the main conveying path 31 shown in FIG. 3.

[0061] For example, as shown in Figure 7(D), when printing an image of page 5 according to instructions specifying double-sided printing, face-up, and reverse printing order, the image of page 5 is printed on the front side of the first sheet and the back side of the first sheet is blank, the image of page 3 is printed on the front side of the second sheet and the image of page 4 is printed on the back side of the second sheet, the image of page 1 is printed on the front side of the third sheet and the image of page 2 is printed on the back side of the third sheet. In this case, the sheets are stacked one on top of the other and ejected from the main transport path 31 to an ejection tray (not shown) with the front side of each sheet facing downward and the back side of each sheet facing upward. Therefore, each sheet is ejected in the same orientation as face-up, with the first side facing upward.

[0062] Next, the image formation and paper transport performed in accordance with instructions specifying single-sided or double-sided printing, face-down or face-up, and forward or reverse direction as described above will be explained in detail with reference to the flowchart shown in FIG.

[0063] The control unit 68 receives instructions from the user via the operation unit 62 to specify single-sided or double-sided printing, face-down or face-up, and forward or reverse direction (S101).

[0064] When the control unit 68 determines that the received instruction indicates single-sided printing (S102 "single-sided"), it determines whether the received instruction indicates forward printing or reverse printing (S103).

[0065] When the control unit 68 determines that the received instruction indicates the forward direction (S103 "Forward direction"), it causes the image forming unit 25 to form the image indicated by the data to be printed in the original page order indicated by the data to be printed received by the communication unit 65 of the image forming system Sy from the information processing device 71 (S104).

[0066] Furthermore, if the control unit 68 determines that the received instruction indicates the reverse direction (S103 "reverse direction"), it rearranges the data to be printed received by the communication unit 65 of the image forming system Sy from the information processing device 71 in the reverse page order of the original page order indicated (S105), and causes the image forming unit 25 to form the images indicated by the data to be printed in the reverse printing order of the image data indicating each image (S104).

[0067] The image forming device 2 forms an image indicated by the print target data on a sheet of paper, and sends the sheet of paper out to the paper transport device 3.

[0068] The control unit 68 determines whether the received instruction indicates face-down or face-up (S106), and if it determines that the instruction indicates face-down (S106 "down"), it causes the paper transport device 3 to transport the paper along the path shown in Figure 4(A) or 4(B), and discharges the paper face-down from the main transport path 31 (S107).

[0069] Furthermore, if the control unit 68 determines that face-up is indicated (S106 "Up"), it causes the paper transport device 3 to transport the paper along the path shown in FIG. 3, and discharges the paper face-up from the main transport path 31 (S108).

[0070] On the other hand, if the control unit 68 determines that the received instruction indicates double-sided printing (S102 "Double-sided"), it determines whether the last page of each image indicated by the data to be printed is an even-numbered page or an odd-numbered page (S109), and if it determines that the last page is an odd-numbered page (S109 "Odd"), it adds image data indicating a blank image to the end of each image indicated by the data to be printed, so that each image indicated by the data to be printed consists of an even-numbered page (S110). Also, if the control unit 68 determines that the last page is an even-numbered page (S109 "Even"), it does not perform S110 and leaves each image indicated by the data to be printed as is.

[0071] Next, the control unit 68 determines whether the received instruction indicates forward or reverse printing (S111), and if it determines that the instruction indicates forward printing (S111 "forward printing"), it selects the image of page N and the image of page (N+1) in forward printing order (S112).

[0072] The control unit 68 determines whether the received instruction indicates face-down or face-up (S113), and if it determines that the instruction indicates face-down (S113 "Down"), it assigns the image of page N and the image of page (N+1) selected in the forward printing order to one sheet of paper, and causes the image forming device 2 to form the image of page N on the upward facing front side of the paper, and transports the paper to the paper transport device 3. The control unit 68 causes the paper transport device 3 to transport the paper along the path shown in FIG. 5(A) or 5(B), and then causes the paper to be returned to the image forming device 2 via the paper feeder 1. The control unit 68 causes the image forming device 2 to form the image of page (N+1) on the upward facing back side of the returned paper (S114).

[0073] The control unit 68 transports the paper again from the image forming device 2 to the paper transport device 3, and discharges the paper face down only through the main transport path 31 as shown in Figure 3 (S115). S114 and S115 are performed for all images indicated by the data to be printed.

[0074] Furthermore, when the control unit 68 determines that the received instruction indicates face-up (S113 "up"), it assigns the image of page N and the image of page (N+1) selected in the forward printing order to one sheet of paper, and causes the image forming device 2 to form the image of page (N+1) on the upward facing front side of the paper, and transports the paper to the paper transport device 3. The control unit 68 causes the paper transport device 3 to transport the paper along the path shown in FIG. 5(A) or 5(B), and returns the paper to the image forming device 2 via the paper feeder 1. The control unit 68 causes the image forming device 2 to form the image of page N on the upward facing back side of the returned paper (S116).

[0075] The control unit 68 transports the paper from the image forming device 2 again to the paper transport device 3, and discharges the paper in a state equivalent to face-up through only the main transport path 31, as shown in Figure 3 (S117). S116 and S117 are performed for all images indicated by the data to be printed.

[0076] Furthermore, when the control unit 68 determines that the received instruction indicates the reverse direction (S111 "reverse direction"), it prints each image indicated by the data to be printed in the reverse order to the original order, and selects the image of page N and the image of page (N+1) in the reverse printing order (S118).

[0077] The control unit 68 determines whether the received instruction indicates face-down or face-up (S113), and if it determines that the instruction indicates face-down (S113 "Down"), it assigns the image of page N and the image of page (N+1), selected in reverse printing order, to one sheet of paper, and causes the image forming device 2 to form the image of page N on the front side of the paper facing up, and transports the paper to the paper transport device 3. The control unit 68 causes the paper transport device 3 to transport the paper along the path shown in FIG. 5(A) or 5(B), and returns the paper to the image forming device 2 via the paper feeder 1. When the paper is returned, the control unit 68 causes the image forming device 2 to form the image of page (N+1) on the back side of the paper facing up (S114).

[0078] The control unit 68 transports the paper again from the image forming device 2 to the paper transport device 3, and discharges it face down only through the main transport path 31 as shown in Figure 3 (S115). S114 and S115 are performed for all images indicated by the data to be printed.

[0079] Furthermore, when the control unit 68 determines that the received instruction indicates face-up (S113 "up"), it assigns the image of page N and the image of page (N+1) selected in the forward printing order to one sheet of paper, and causes the image forming device 2 to form the image of page (N+1) on the front side of the paper facing up, and transports the paper to the paper transport device 3. The control unit 68 causes the paper transport device 3 to transport the paper along the path shown in FIG. 5(A) or 5(B), and returns the paper to the image forming device 2 via the paper feeder 1. When the paper is returned, the control unit 68 causes the image forming device 2 to form the image of page N on the back side of the paper facing up (S116).

[0080] The control unit 68 transports the paper from the image forming device 2 back to the paper transport device 3, and ejects the paper in a state equivalent to face-up through only the main transport path 31, as shown in Figure 3 (S117). S116 and S117 are performed for all images indicated by the data to be printed.

[0081] In this manner, in this embodiment, depending on whether or not the page order of the images formed on the front and back of a single sheet of paper is reversed, double-sided printed paper is discharged in a state equivalent to face-down or face-up without the need for conveying the paper to turn it over as shown in Figure 4(A) or 4(B), and therefore the frequency of jams and the like can be reduced by the amount of the omission of the reversal conveyance. Therefore, according to this embodiment, double-sided printed paper is discharged in a paper orientation similar to face-up, with the first side on which the image was first formed facing upward, and the paper can be quickly discharged after images have been formed on both sides.

[0082] In the above embodiment, infrared rays from the heating unit 61 are irradiated onto the top surface of the paper being transported along the main transport path 31 to promote drying of the ink adhering to the top surface of the paper. This causes the paper to expand and contract as it is heated, and the image formed on the paper also expands and contracts. When forming images on both sides of the paper, the image formed on the front side expands and contracts before the image formed on the back side. This results in a mismatch between the size of the image on the front side and the size of the image on the back side of the paper. Therefore, when forming images on both sides of the paper, the control unit 68 enlarges or reduces the image formed on the front or back side of the paper at an appropriate enlargement or reduction ratio, and causes the image forming device 2 to form the enlarged or reduced image on the front or back side of the paper, thereby matching the size of the image on the front side and the size of the image on the back side of the paper. The enlargement or reduction ratio is preset based on the expansion or contraction ratio measured by heating the paper.

[0083] In addition, in the above embodiment, an example is shown in which the user operates the operation unit 62 to input instructions specifying single-sided printing or double-sided printing, ejecting paper face-down or face-up, and the printing order of images on multiple pages, but the information processing device 71 may send the instructions together with the data to be printed to the communication unit 65 of the image forming system Sy, and the control unit 68 may, in accordance with the instructions, cause the image forming device 2 to form images of each page indicated by the data to be printed on the front or front and back of each sheet of paper, and cause each sheet of paper to be transported by the paper transport device 3.

[0084] Furthermore, when forming images on both sides of a sheet of paper, the information processing device 71 may enlarge or reduce the image formed on the front or back of the sheet of paper as described above at an appropriate enlargement or reduction ratio, and transmit image data representing this enlarged or reduced image to the communication unit 65 of the image forming system Sy.

[0085] Furthermore, the configurations and processes of the above-described embodiment explained with reference to FIGS. 1 to 8 are merely examples of the present invention, and the present invention is not limited to these configurations and processes. [Explanation of symbols]

[0086] 1 Paper feeder 2. Image forming device 3 Paper transport device 61 Heat generating part 62 Operation section 63 Display section 64 Touch Panel 65 Communications Department 66 Memory section 67 Control Unit 68 Control Unit Sy Image Forming System

Claims

1. an image forming device having an image forming unit that forms an image on an upward facing front surface of a sheet of paper, carries out the sheet of paper, turns the sheet over, and when the sheet of paper is returned, forms an image on the upward facing back surface of the sheet of paper; a paper transport device that receives the paper discharged from the image forming device, transports and discharges the paper, and inverts the paper and transports it toward the image forming device; a control unit for controlling an operation of the image forming apparatus; The control unit When the image forming device prints on the front and back sides of a sheet of paper and the sheet is transported and discharged by the sheet transport device, a first transport in which an image of page N (N is an odd number) is formed on the upward facing surface of the paper by the image forming device, the paper transport device inverts the paper, and when the paper is returned to the image forming device, an image of page (N+1) is formed on the back surface of the upward facing paper, and the paper on which the image of page N has been formed is turned downward and discharged from the image forming device through the paper transport device; an image forming system in which the image forming unit forms an image of the (N+1)th page on the upward facing front side of the paper, and when the paper is turned over and returned to the image forming device, the image forming device forms an image of the Nth page on the back side of the upward facing paper, the back side of the paper on which the image of the Nth page has been formed is turned upward and the paper is transported from the image forming device to the paper transport device, and the paper is not turned over by the paper transport device, but is discharged from the paper transport device with the back side of the paper on which the image of the Nth page has been formed facing upward, a second transport.

2. a communication unit that receives print data including images for a plurality of pages from the information processing device; The image forming system described in claim 1, wherein when the printing target data is received by the communication unit, the control unit reverses the printing order of each image indicated by the printing target data from the original order indicated by the printing target data, and causes the image forming device to form each image indicated by the printing target data sequentially on the front and back sides of paper.

3. further comprising an operation unit into which instructions are input by a user; 2. The image forming system according to claim 1, wherein the control unit executes the first transport when an instruction to eject paper face down is input to the operation unit, and executes the second transport when an instruction to eject paper face up is input to the operation unit.

4. 2. The image forming system according to claim 1, wherein the image forming device forms an image on a sheet by an inkjet method.

Images