Image forming device

Abstract

To provide an image forming device that enables a sheet being conveyed by a re-conveying part to be smoothly conveyed, while suppress the sheet from dropping off.SOLUTION: An image forming device comprises: a conveying part 20 that has an endless conveying belt 223, and conveys a sheet-like recording medium; an image forming part 30 that forms an image on a surface of the recording medium; a re-conveying part 50 that receives the recording medium from the conveying part 20 on the downstream side of the image forming part 30 and re-conveys the recording medium to the upstream side of the image forming part 30 of the conveying part 20; a suction part 55 arranged inside a lower-side placement surface 223b of the conveying belt 223; a separating part 56 that separates the recording medium conveyed while being placed on the lower-side placement surface 223b of the conveying belt 223 from the conveying belt 223; and a recording medium guide part 57 that supports the recording medium separated from the conveying belt 223 by the separating part 56 from below to suppress the recording medium from being curved.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an image forming apparatus. [Background technology]

[0002] Conventionally, among image forming devices such as copiers and printers, there are known ones capable of double-sided printing, in which an image is formed on one side of a sheet of paper, and then the sheet is transported back to the image forming section without being ejected, and an image is formed on the other side (see, for example, Patent Document 1).

[0003] In this type of image forming device capable of double-sided printing, a re-conveying unit is generally provided, separate from a conveying unit that conveys paper to the image forming unit, that reverses the conveying direction of the paper conveyed from the conveying unit, turns the paper over relative to the conveying unit, and then sends it again to the upstream side of the image forming unit from the conveying unit. In this image forming device, the conveying direction of the paper is divided by a branching member provided downstream of the conveying unit, and when an image is formed on only one side, the paper is divided into an output tray once the image has been formed on one side, and when an image is formed on both sides, the paper is divided into the re-conveying unit and conveyed again to the image forming unit after the image has been formed on one side. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-144830 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, in image forming apparatuses according to the prior art, a method is adopted in which the transport path of a re-conveyance unit that returns paper that has been printed on one side to the upstream side of the image forming unit in the transport path of the transport unit is configured with a large number of guide rollers or the like (see re-conveyance unit 50 in FIG. 3 described later). However, if the long transport path of the re-conveyance unit is configured with components separate from the components of the transport unit, it leads to an increase in the size of the image forming apparatus and an increase in the production cost of the image forming apparatus.

[0006] Therefore, the inventors of the present application have considered using the endless conveyor belt that constitutes the conveyance path of the conveyor unit to also constitute the conveyance path of the re-conveyor unit (see re-conveyor unit 50 in FIG. 1 , described later). Specifically, the conveyance path of the conveyor unit is constituted by the upper support surface of the conveyor belt, and the conveyance path of the re-conveyor unit is constituted by the lower support surface of the conveyor belt (the lower support surface moves in the opposite direction from the upper support surface). By adopting this structure, it is not necessary to provide a separate conveyor belt for the re-conveyor unit in addition to the conveyor belt for the conveyor unit, which prevents the image forming apparatus from becoming larger and reduces the manufacturing cost of the image forming apparatus. Additionally, this structure simplifies the structure of the re-conveyor unit, thereby improving the stability of paper conveyance.

[0007] However, if the transport path of the re-conveying unit is configured on the lower loading surface of the conveyor belt, there is a risk that the paper placed on the lower loading surface of the conveyor belt and transported thereon may fall off the lower loading surface of the conveyor belt during transport. In this regard, a mechanism that strongly suctions the paper to the lower loading surface of the conveyor belt can be provided to prevent the paper from falling off the lower loading surface of the conveyor belt. However, the transport path of the re-conveying unit cannot be configured solely on the lower loading surface of the conveyor belt; it must also be designed to include the transport path to the downstream processing device (for example, the back steering unit 53 and the reversing unit 52 in FIG. 1, which will be described later). In other words, the re-conveying unit must be designed to ensure smooth paper transport, including the area from the lower loading surface of the conveyor belt to the downstream processing device where the paper is transferred.

[0008] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide an image forming apparatus that can achieve smooth transport of paper while preventing the paper from falling out when transported in the re-transport section. [Means for solving the problem]

[0009] The present disclosure mainly solves the above-mentioned problems by: a conveying section having an endless conveying belt and configured to convey a sheet-shaped recording medium by placing it on an upper side of the conveying belt; an image forming unit that forms an image on the surface of the recording medium conveyed by the conveying unit; a re-conveying unit that receives the recording medium from the conveying unit downstream of the image forming unit, places the recording medium on a lower placement surface of the conveying belt, conveys the recording medium in a direction opposite to the conveying direction of the conveying unit, and sends the recording medium again to the upstream side of the image forming unit from the conveying unit; a suction unit that adsorbs the recording medium, which is placed on the lower placement surface of the conveyor belt and conveyed, to the lower placement surface; a separation unit that is disposed downstream of the suction unit on the lower placement surface of the conveyor belt and separates the recording medium, which is placed on the lower placement surface of the conveyor belt and conveyed, from the conveyor belt; a recording medium guide section that supports the recording medium separated from the conveyor belt by the separation section from below and suppresses curvature of the recording medium; The image forming apparatus includes: [Effects of the Invention]

[0010] According to the image forming apparatus according to the present disclosure, it is possible to prevent the paper being transported by the re-transport unit from dropping off, and to realize smooth transport of the paper. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 2]FIG. 1 is a block diagram showing the main functional configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 3] FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus according to a conventional technique. [Figure 4] FIG. 1 is a diagram illustrating an example of the configuration of a paper guide unit of an image forming apparatus according to an embodiment of the present invention. [Figure 5A] FIG. 10 is a diagram showing the behavior of paper during transport when a paper guide unit is not provided; [Figure 5B] FIG. 10 is a diagram showing the behavior of paper during transport when a paper guide unit is provided; [Figure 6] FIG. 10 is a diagram showing a schematic configuration of an image forming apparatus according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functions are designated by the same reference numerals, and redundant description will be omitted.

[0013] [Overall configuration of image forming device] The configuration of an image forming apparatus according to one embodiment of the present invention (hereinafter referred to as "image forming apparatus 1") will be described below with reference to Figures 1 and 2. The image forming apparatus 1 according to this embodiment is an inkjet type image forming apparatus.

[0014] Fig. 1 is a diagram showing a schematic configuration of image forming apparatus 1. Fig. 2 is a block diagram showing the main functional configuration of image forming apparatus 1. In Fig. 1, the upward direction in the drawing corresponds to the vertically upward direction when image forming apparatus 1 is in use, and the downward direction in the drawing corresponds to the vertically downward direction when image forming apparatus 1 is in use.

[0015] Fig. 3 is a diagram showing a schematic configuration of an image forming apparatus 1a according to the prior art, and is presented here for the convenience of explanation to enable comparison between the configuration of the image forming apparatus 1 according to this embodiment and the configuration of the image forming apparatus 1a according to the prior art.

[0016] The image forming apparatus 1 includes a paper feed section 10, a conveying section 20, an image forming section 30, a fixing section 40, a re-conveying section 50, a paper discharge section 60, and a control section 100.

[0017] Under the control of the control unit 100, the image forming apparatus 1 transports paper P stored in the paper feed unit 10 to the image forming unit 30 using the transport unit 20, and the image forming unit 30 ejects ink onto the paper P to form an image. The image forming apparatus 1 transports the paper P on which the image has been formed to the fixing unit 40, fixes the image on the paper P, and then transports the paper P to the paper discharge unit 60. Furthermore, when double-sided printing is to be performed on the paper P, the image forming apparatus 1 transports the paper P that has been printed on one side and is transported by the transport unit 20 again to the upstream side of the image forming unit 30 in the transport unit 20 using the re-transport unit 50.

[0018] In this embodiment, paper P such as plain paper or coated paper is shown as an example of a recording medium on which an image is formed by the image forming device 1, but in addition to paper, various sheet-like recording media such as fabric or sheet-like resin, on whose surface ink can be fixed, can also be used as the recording medium to which the image is applied.

[0019] The paper feed unit 10 has a paper feed tray 11 that stores paper sheets P, and a supply unit 12 that supplies paper sheets P from the paper feed tray 11 to the conveyance unit 20. In the paper feed unit 10, the supply unit 12 conveys the paper sheets P stacked in the paper feed tray 11, thereby supplying the paper sheets P to the conveyance unit 20.

[0020] The transport unit 20 includes an aligner unit 21, a transport path unit 22, a branching unit 23, a heating unit 24, and an upper suction unit 25.

[0021] The aligner unit 21 adjusts the position of the paper P supplied from the paper supply unit 10 in the width direction on the transport path unit 22 .

[0022] The transport path section 22 constitutes a transport path from when the paper P is supplied from the paper feed section 10 to when it passes through the image forming section 30 and is discharged to the paper discharge section 60. The transport path section 22 is constituted by an endless transport belt 223 stretched over a driven roller 221 and a drive roller 222 that are arranged in parallel at a predetermined distance. In the transport path section 22, the drive roller 222 is rotated at a predetermined speed by the rotational drive of a sub-scanning motor (not shown), thereby rotating the transport belt 223. By this operation, the paper P placed on the upper placement surface 223a of the transport belt 223 is transported in the direction of arrow A.

[0023] Here, the front side of the conveyor belt 223 is a placement surface on which the paper P is placed in close contact, and the conveyor belt 223 has an upper placement surface 223a located above the driven roller 221 and the drive roller 222, and a lower placement surface 223b located below the driven roller 221 and the drive roller 222. When the conveyor belt 223 rotates, the upper placement surface 223a of the conveyor belt 223 moves in the direction of arrow A, and the lower placement surface 223b of the conveyor belt 223 moves in the direction of arrow B, which is opposite to the direction of arrow A.

[0024] In the image forming apparatus 1 according to this embodiment, the upper side loading surface 223a of the conveying belt 223 forms part of the conveying path section 22 of the conveying section 20, and the lower side loading surface 223b of the conveying belt 223 forms part of the re-conveying path section 51 of the re-conveying section 50.

[0025] Hereinafter, when referring to the "conveying direction," it means the direction of arrow A in the conveying path section 22, and it means the direction of arrow B in the re-conveying path section 51. Furthermore, when referring to the "upstream side" and the "downstream side," it means the "upstream side" and the "downstream side" based on the "conveying direction" of the conveying path section 22 and the re-conveying path section 51, respectively.

[0026] In addition, the conveying belt 223 (including the upper side loading surface 223a and the lower side loading surface 223b) is provided with openings (not shown) to allow the air sucked by the upper side suction section 25 and the lower side suction section 55 to pass through.

[0027] In FIG. 1, the transport path section 22 uses separate transport belts for the image forming section 30 and the fixing section 40, but these may be configured with a single transport belt.

[0028] The branching processing unit 23 is disposed downstream of the conveying path unit 22 in the conveying direction (direction of arrow A) of the fixing unit 40, and distributes the paper P conveyed to the conveying unit 20 to either the printed paper output tray 61 of the paper output unit 60, the unsuccessfully printed paper output tray 62 of the paper output unit 60, or the re-conveying unit 50. The branching processing unit 23 is configured, for example, by a branching member (for example, a claw member) that can distribute the conveying direction of the paper P.

[0029] The branching processing unit 23 operates under the control of the control unit 100. For example, in the single-sided printing mode, the branching processing unit 23 forms an image on one side of the paper P, and then sends the paper P to the printed paper output tray 61. In the double-sided printing mode, the branching processing unit 23 first forms an image on one side of the paper P, and then sends the paper P to the re-conveying unit 50, and then, after images are formed on both sides of the paper P, sends the paper P to the printed paper output tray 61. In the paper output mode, the branching processing unit 23 sends the paper P transported by the transporting unit 20 to the failed print paper output tray 62 of the paper output unit 60.

[0030] The heating unit 24 is disposed upstream of the conveying path unit 22 in the conveying direction (direction of arrow A) of the image forming unit 30, and heats the printing surface (i.e., the upper surface) of the paper P fed to the paper feed unit 10. The heating unit 24 is configured, for example, by a heating roller that heats the paper P while applying pressure to it.

[0031] The upper suction section 25 adsorbs the paper P, which is placed on the upper placement surface 223a of the conveyor belt 223 and is conveyed, to the upper placement surface 223a of the conveyor belt 223. The upper suction section 25 is configured by, for example, an air suction mechanism disposed inside the upper placement surface 223a of the conveyor belt 223.

[0032] The operation of the upper suction unit 25 is controlled under the control of the control unit 100. The upper suction unit 25 is typically controlled to maintain an ON state not only during printing operation but also when printing operation is stopped (for example, during an emergency stop based on a user command). This is because the image forming apparatus 1 controls the operation of the conveyor belt 223 so that it continues to operate even when printing operation is stopped. That is, the image forming apparatus 1 is configured such that the upper suction unit 25 maintains an ON state even when printing operation is stopped, thereby preventing the paper P conveyed by the conveyor unit 20 from colliding with the image forming unit 30, such as an inkjet head.

[0033] The image forming unit 30 is disposed opposite the upper placement surface 223a of the conveyor belt 223, and forms an image on the surface of the paper P conveyed by the conveyor unit 20. The image forming unit 30 has a plurality of (four in this case) head units 31, and is disposed so as to be spaced a predetermined distance from the upper placement surface 223a of the conveyor belt 223 in the conveyance path unit 22. The four head units 31 are configured to be able to eject different types of ink, and in this case, the ink ejected by each of the four head units 31 corresponds to one of four colors of ink: yellow (Y), magenta (M), cyan (C), and black (K).

[0034] The head unit 31 forms an image by, for example, a single-pass method in which ink is sequentially ejected at predetermined intervals to different positions in the transport direction in accordance with the transport of the paper P. Note that the image forming unit 30 is not limited to the single-pass method, and may be one that forms an image by a scanning method using a carriage that can scan in the width direction of the paper P.

[0035] The fixing unit 40 is disposed downstream in the conveying direction (direction of arrow A) of the image forming unit 30 on the conveying path unit 22. The fixing unit 40 irradiates the paper P placed on the conveying belt 223 with activation energy light such as ultraviolet light, thereby curing and fixing the ink ejected onto the paper P.

[0036] The re-conveying unit 50 is a conveying unit that switches the conveying direction of the paper P conveyed from the conveying unit 20 to the opposite direction (the direction of arrow B) and sends it again to the upstream side of the image forming unit 30 of the conveying unit 20 in order to form an image on the back side of the paper P that has already been printed on one side during double-sided printing. The re-conveying unit 50 is configured so that the image forming apparatus 1 can convey the paper P to the image forming unit 30 twice in total, once when printing on the front side and once when printing on the back side, from the time when a single paper P is supplied to the image forming unit 30 until it is discharged.

[0037] The re-conveying section 50 has a re-conveying path section 51 , a reversing section 52 , a back steering section 53 , a heating section 54 , a lower suction section 55 , a separating section 56 , and a paper guide section 57 .

[0038] The re-conveying path section 51 constitutes a re-conveying path for re-conveying the paper P that has passed through the image forming section 30 in the conveying path section 22 to the upstream side of the image forming section 30 in the conveying path section 22.

[0039] In the image forming apparatus 1 according to this embodiment, at least a part of the re-conveying path section 51 is configured by the lower side mounting surface 223b of the conveyor belt 223. That is, in the image forming apparatus 1 according to this embodiment, the conveyor belt 223 that configures the conveying path of the conveying section 20 is also used to configure the conveying path of the re-conveying section 50.

[0040] For example, the re-conveying path section 51 according to the present embodiment is provided so as to branch off from the conveying path section 22 at the position of the branching processing section 23 (the downstream end position of the conveying path section 22), and is configured to pass through the lower side loading surface 223b of the conveying belt 223, the back steering section 53, the inverting section 52, and the heating section 54 in this order, and then merge with the conveying path section 22 on the upstream side of the aligner section 21. That is, the paper P conveyed through the re-conveying path section 51 is conveyed by the conveying belt 223 (lower side loading surface 223b), and then delivered from the conveying belt 223 (lower side loading surface 223b) to the back steering section 53, the inverting section 52, the heating section 54, and the conveying path section 22 in this order.

[0041] Furthermore, within the re-conveying path section 51, the paths between the lower side loading surface 223b of the conveying belt 223, the back steering section 53, the inversion section 52, and the heating section 54 are each composed of a conveying roller, a conveying roller, a conveying belt, or the like.

[0042] The reversing unit 52 is a switchback device that guides the sheet P being conveyed along the re-conveying path unit 51 toward the reversing unit 52 and switches back the sheet P, thereby reversing the front and back of the sheet P. The reversing unit 52 is provided in the re-conveying path unit 51 near the junction of the re-conveying path unit 51 and the conveying path unit 22. As a result, the sheet P is conveyed to the junction with the conveying path unit 22 with the back side, on which no image is formed, facing the image forming unit 30.

[0043] The back surface steering unit 53 (corresponding to the "processing device" of the present invention) is a steering device that adjusts the widthwise position of the sheet P transported along the re-conveying path unit 51. The back surface steering unit 53 is disposed, for example, in the re-conveying path unit 51, downstream of the path formed by the lower-side loading surface 223b of the conveying belt 223 and upstream of the reversing unit 52. In other words, the back surface steering unit 53 is disposed at a position that receives, from the conveying belt 223, the sheet P that is placed on the lower-side loading surface 223b of the conveying belt 223 and transported.

[0044] The heating unit 54 is disposed downstream of the reversing unit 52 within the re-conveying path 51, and heats the back surface (the surface on which no image is formed) of the paper P being transported through the re-conveying path 51. The heating unit 54 is configured, for example, by a heating roller that heats the paper P while applying pressure to it.

[0045] In the image forming apparatus 1a according to the prior art, the re-conveying path section 51a of the re-conveying section 50 is not constructed using the lower side loading surface 223b of the conveying belt 223, but is constructed by a plurality of rollers 51a arranged continuously from one end side to the other end side of the re-conveying path section 51 (see Figure 3).

[0046] In this regard, in the image forming apparatus 1 according to this embodiment, the re-conveying path portion 51a of the re-conveying unit 50 is configured using the lower placement surface 223b of the conveyor belt 223, and therefore, the image forming apparatus 1 is smaller in size than the image forming apparatus 1a according to the prior art. However, due to this configuration, the image forming apparatus 1 according to this embodiment needs the re-conveying unit 50 to include the lower suction portion 55, the separation portion 56, and the paper guide portion 57. The detailed configurations of the lower suction portion 55, the separation portion 56, and the paper guide portion 57 will be described later.

[0047] The paper output section 60 is a section where the paper P that has passed through the image forming section 30 and the fixing section 40 by the conveying section 20 is output, and has a printed paper output tray 61 on which the paper P is placed, and an unsuccessfully printed paper output tray 62 on which paper P that has not been printed is placed. The sorting of paper from the conveying section 20 to the printed paper output tray 61 or the unsuccessfully printed paper output tray 62 is performed by the branching processing section 23 of the conveying section 20.

[0048] The control unit 100 includes a CPU 101 (Central Processing Unit), a RAM 102 (Random Access Memory), a ROM 103 (Read Only Memory), and a storage unit 104. The CPU 101 reads a program corresponding to the processing content from the ROM 103, loads it into the RAM 102, and centrally controls the operation of each block of the image forming apparatus 1 in cooperation with the loaded program. At this time, various data stored in the storage unit 104 is referenced. The storage unit 104 is configured, for example, with a non-volatile semiconductor memory (so-called flash memory) or a hard disk drive.

[0049] The control unit 100 generates print data that defines, for example, the amount of ink ejected for each of the four head units 31, and issues operation instructions to drivers (not shown) that control the operation of the four head units 31. The control unit 100 then controls the operation of the four head units 31 so that ink is ejected sequentially at predetermined intervals at different positions in the transport direction as the paper P is transported.

[0050] Furthermore, the control unit 100 controls the operation of the drive roller 222 that rotates the conveyor belt 223, other conveyor rollers (for example, conveyor rollers of the aligner unit 21 and the back surface steering unit 53), etc., in order to control the conveyance of the paper P by the conveyance unit 20 and the re-conveyance unit 50. The control unit 100 also controls the operation of the branching unit 23, and performs a process of allocating the conveyance destination of the paper P.

[0051] In addition, the control unit 100 controls the on / off operation of the upper suction unit 25 and the lower suction unit 55, and controls the adsorption state of the paper P to the upper loading surface 223a of the conveying belt 223, and the adsorption state of the paper P to the lower loading surface 223b of the conveying belt 223.

[0052] The control unit 100 has modes in which the image forming apparatus 1 operates, for example, a single-sided printing mode and a double-sided printing mode.

[0053] In the single-sided printing mode, the control unit 100 transports the paper P using the transport unit 20, forms an image on one side of the paper P using the image forming unit 30, and then sends the paper P to the printed paper output tray 61 using the branching processing unit 23.

[0054] In the double-sided printing mode, the control unit 100 sends out the paper P, which has been printed on one side, from the transport unit 20 to the re-transport unit 50, and re-transports the paper P upside down to the upstream side of the image forming unit 30, where the image forming unit 30 performs printing processing again on the paper P. Then, the control unit 100 sends out the paper P, which has been printed on both sides, to the printed paper output tray 61 using the branching processing unit 23.

[0055] In addition, in the paper discharge mode, the control unit 100 operates the conveying unit 20 and the re-conveying unit 50 to send the paper P present in the conveying unit 20 and / or the re-conveying unit 50 to the failed printing paper discharge tray 62 of the paper discharge unit 60 without performing printing processing by the image forming unit 30.

[0056] [Detailed Configuration of Re-conveying Unit 50 (Lower Suction Unit 55, Separation Unit 56, and Paper Guide Unit 57)] The following describes in detail the configuration of the lower suction section 55, separation section 56, and paper guide section 57 of the re-conveyance section 50. Note that FIG.

[0057] The lower suction section 55 (corresponding to the "suction section" of the present invention) adsorbs the paper sheet P, which is placed on the lower loading surface 223b of the conveyor belt 223 and conveyed, to the lower loading surface 223b of the conveyor belt 223. In other words, the lower suction section 55 prevents the paper sheet P, which is placed on the lower loading surface 223b of the conveyor belt 223 and conveyed, from falling off the lower loading surface 223b during conveyance.

[0058] The lower suction section 55 is configured, for example, by an air suction mechanism disposed inside the lower placement surface 223b of the conveyor belt 223. The lower suction section 55 is disposed, for example, so as to extend over substantially the entire area from the upstream end to the downstream end of the lower placement surface 223b of the conveyor belt 223, and applies suction force to the paper P at each position while the paper P is placed on the lower placement surface 223b of the conveyor belt 223 and conveyed.

[0059] The separation section 56 is disposed at a position downstream of the lower suction section 55 on the lower loading surface 223b of the conveying belt 223, and separates the paper P that is placed on the lower loading surface 223b of the conveying belt 223 and conveyed from the conveying belt 223.

[0060] The separating section 56 is configured by, for example, an air blowing section 56a disposed inside the lower-side loading surface 223b of the conveyor belt 223, and a belt bending section 56b formed at the downstream end of the lower-side loading surface 223b of the conveyor belt 223. Both the air blowing section 56a and the belt bending section 56b are disposed at positions downstream of the lower-side suction section 55.

[0061] The belt bending portion 56b forms an area that bends the conveyor belt 223 in a convex shape outward at the downstream end of the lower loading surface 223b of the conveyor belt 223. As a result, the leading edge of the sheet P moves downward from the lower loading surface 223b of the conveyor belt 223 due to the elastic force of the sheet P itself, starting from the position of the belt bending portion 56b.

[0062] The belt bending portion 56b is, for example, disposed inside the lower path of the conveyor belt 223 so as to come into contact with the inner surface of the conveyor belt 223, and is configured by a roller member that rotates together with the rotation of the conveyor belt 223.

[0063] The air blowing section 56a is disposed, for example, near the downstream end of the lower placement surface 223b of the conveyor belt 223, downstream of the belt bending section 56b, so as to blow air downward from the inside of the lower placement surface 223b of the conveyor belt 223. The air blowing section 56a applies a downward external force by air to the paper sheet P being placed on the lower placement surface 223b of the conveyor belt 223 and conveyed. As a result, the leading edge of the paper sheet P separates downward from the lower placement surface 223b of the conveyor belt 223, starting from the position of the air blowing section 56a.

[0064] It is preferable that the air blowing section 56a is configured, for example, integrally with the lower suction section 55, and uses the air sucked by the lower suction section 55 to blow out air.

[0065] In this way, the paper P placed on the lower loading surface 223b of the conveying belt 223 and transported is transported in an approximately flat state along the surface shape of the lower loading surface 223b of the conveying belt 223 up to the position of the separation section 56, but after progressing to the position of the separation section 56, the leading edge of the paper P will detach downward from the lower loading surface 223b of the conveying belt 223.

[0066] At this time, to achieve smooth delivery from the conveyor belt 223 to a downstream processing device (here, the back steering unit 53), it is ideal for the sheet P to maintain a flat posture even after it leaves the conveyor belt 223. However, in reality, when the sheet P is delivered from the conveyor belt 223 to the processing device, the sheet P tends to assume a curved posture so that the leading edge of the sheet P that has left the conveyor belt 223 points downward due to the sheet P's own weight and the air blown onto the sheet P from the air blowing unit 56a (i.e., a downward external force). In particular, the air blowing unit 56a is useful as a function of the separation unit 56 because it forcibly separates the sheet P from the conveyor belt 223 by the external force of the air, but it is prone to inducing a curve in the sheet P.

[0067] From this perspective, the image forming apparatus 1 according to this embodiment is provided with a paper guide section 57, which forcibly maintains the posture of the paper P flat when smoothly transferred from the conveying belt 223 to the downstream processing device (here, the back steering section 53).

[0068] 5A and 5B are diagrams illustrating the function of paper guide unit 57. Fig. 5A is a diagram illustrating the behavior of paper P during transport when paper guide unit 57 is not provided. Fig. 5B is a diagram illustrating the behavior of paper P during transport when paper guide unit 57 is provided.

[0069] The paper guide section 57 is disposed so as to form a flat section below the lower placement surface 223b of the conveyor belt 223, and supports the paper P separated from the conveyor belt 223 by the separation section 56 from below, thereby suppressing the curvature of the paper P when the paper P is handed over from the conveyor belt 223 to a downstream processing device (in this embodiment, the back surface steering section 53). That is, the paper guide section 57 supports the paper P from below to keep the paper P flat when the paper P separated from the conveyor belt 223 tries to change into a curved position due to forces acting on the paper P (here, the external force of air from the air blowing section 56a and the weight of the paper P itself).

[0070] When the paper P is transferred from the conveyor belt 223 to a downstream processing device (here, the back steering unit 53), for example, a nip conveyance (roller nip or belt nip) is used.

[0071] The paper guide section 57 is configured, for example, by a plate member extending in the extension direction of the lower placement surface 223b at a position spaced downward from the lower placement surface 223b of the conveyor belt 223 (see FIG. 4). The paper guide section 57 is disposed, for example, so that its plate surface is approximately parallel to the lower placement surface 223b. In particular, the paper guide section 57 is preferably disposed close to the lower placement surface 223b while being spaced downward from the lower placement surface 223b of the conveyor belt 223, and is preferably disposed so that the flat surface formed by the paper guide section 57 is continuous with the flat surface formed by the lower placement surface 223b. This makes it possible to more reliably maintain the posture of the paper P flat.

[0072] 1 shows a preferred form of the paper guide section 57, which is arranged to straddle from the position of the lower suction section 55 to the position of the separation section 56. The paper guide section 57 is also arranged to extend from the position of the separation section 56 to the position of the downstream processing device (in this embodiment, the back surface steering section 53). This makes it possible to maintain the paper P flat from the conveyor belt 223 to the position where it is handed over to the back surface steering section 53.

[0073] Here, the reason why the paper guide section 57 is disposed away from the lower loading surface 223b of the conveyor belt 223 is to prevent the image formed on the front side of the paper P from being deteriorated due to friction with the paper guide section 57. From the viewpoint of reliably preventing friction with the paper guide section 57, the paper guide section 57 may have a variable mechanism that changes the distance (i.e., the distance in the vertical direction) between itself and the lower loading surface 223b of the conveyor belt 223.

[0074] Preferably, paper guide section 57 has opening 57a (see FIG. 4) that allows passage of air sucked by lower suction section 55. This prevents paper guide section 57 from interfering with the suction action of lower suction section 55.

[0075] As described above, in the image forming apparatus 1 according to this embodiment, the sheet P to be transported to the re-transport section 50 is first placed on the lower loading surface 223b of the transport belt 223 while being attracted to the lower loading surface 223b of the transport belt 223 by the lower suction section 55, and then transported. Then, as the sheet P reaches the separation section 56 at the downstream end of the lower loading surface 223b of the transport belt 223, the action of the separation section 56 causes the leading edge of the sheet P to fall downward from the transport belt 223.

[0076] At this time, if paper guide section 57 is not provided, paper sheet P, which is gradually separated from lower loading surface 223b of conveyor belt 223 by the action of separator 56, changes to a curved posture so that the leading edge hangs downward as it is conveyed due to the forces acting on paper sheet P (here, the external force of air from air blowing section 56a and the weight of paper sheet P itself). As a result, as shown in Figure 5A, when the leading edge of paper sheet P is handed over to the downstream processing device, it is significantly displaced from the originally intended handover position, and paper sheet P may fall off re-conveyance path section 51 when handed over to the downstream processing device.

[0077] In this regard, in the image forming apparatus 1 according to this embodiment, the leading edge of the sheet P, which is gradually separated from the lower loading surface 223b of the conveyor belt 223 by the action of the separation unit 56, comes into contact with the sheet guide unit 57 and is supported from below, as shown in Fig. 5B. This maintains the posture of the sheet P flat, and the sheet P is delivered to the processing device on the downstream side in this posture. This allows the sheet P to be delivered to the processing device smoothly without falling off the re-feed path unit 51.

[0078] [effect] As described above, the image forming apparatus 1 according to this embodiment: a conveying section (corresponding to the conveying section 20 in the above embodiment) that has an endless conveying belt and that places a sheet-like recording medium (e.g., paper P) on an upper side placement surface of the conveying belt and conveys the recording medium; an image forming unit (corresponding to the image forming unit 30 in the above embodiment) that forms an image on the surface of the recording medium transported by the transport unit; a re-conveying unit (corresponding to the re-conveying unit 50 in the above embodiment) that receives the recording medium from the conveying unit downstream of the image forming unit, places the recording medium on a lower placement surface of the conveying belt, conveys the recording medium in a direction opposite to the conveying direction of the conveying unit, and sends the recording medium again to the upstream side of the image forming unit from the conveying unit; a suction section (corresponding to the lower suction section 55 in the above embodiment) that adsorbs the recording medium, which is placed on the lower placement surface of the conveyor belt and conveyed, to the lower placement surface; a separation unit (corresponding to separation unit 56 in the above embodiment) that is disposed at a position downstream of the suction unit on the lower placement surface of the conveyor belt and separates the recording medium, which is placed on the lower placement surface of the conveyor belt and conveyed, from the conveyor belt; a recording medium guide section (corresponding to the paper guide section 57 in the above embodiment) that supports the recording medium separated from the conveyor belt by the separation section from below and suppresses curvature of the recording medium; Equipped with.

[0079] Therefore, according to the image forming apparatus 1 of this embodiment, when the re-conveying section 50 is configured using the lower side loading surface 223b of the conveying belt 223, the recording medium (paper P) can be reliably transferred from the conveying belt 223 to a downstream processing device (in the above embodiment, the back steering section 53) without falling off the lower side loading surface 223b of the conveying belt 223.

[0080] (Variation) FIG. 6 is a diagram showing a schematic configuration of an image forming apparatus 1 according to a modified example.

[0081] 1 in that the separation section 56 is composed of an air suction section 56c disposed below and facing the lower-side loading surface 223b of the conveyor belt 223, and a belt bending section 56b formed at the downstream end of the lower-side loading surface 223b of the conveyor belt 223. That is, the image forming apparatus 1 according to this modification is provided with an air suction section 56c instead of the air blowing section 56a.

[0082] The air suction unit 56c is a mechanism for forcibly separating the paper P from the conveyor belt 223 by the external force of air, but unlike the air blowing unit 56a, it forcibly separates the paper P from the conveyor belt 223 by the air suction action.

[0083] The air suction unit 56c is disposed, for example, near the downstream end of the lower placement surface 223b of the conveyor belt 223, downstream of the belt bending portion 56b, so as to suck air from above downward. More specifically, the air suction unit 56c is disposed, for example, below the paper guide unit 57, and sucks air through an opening 57a formed in the paper guide unit 57.

[0084] As a result, air suction section 56c applies a downward external force due to the suction force of air to paper P being placed on and transported on lower loading surface 223b of conveyor belt 223. As a result, the leading edge of paper P is released downward from lower loading surface 223b of conveyor belt 223, starting from the position of air blowing section 56a.

[0085] In this way, even with the image forming apparatus 1 of this modified example, it is possible to reliably transfer the recording medium (paper P) from the conveying belt 223 to the downstream processing device (in the above embodiment, the back steering section 53) without the recording medium falling off midway on the lower side loading surface 223b of the conveying belt 223.

[0086] The image forming apparatus 1 according to the present disclosure is not limited to the above embodiment, but can be applied to various modified aspects.

[0087] For example, in the above embodiment, a steering device (rear steering unit 53 in the above embodiment) that adjusts the widthwise position of the paper P being transported through the re-transport unit 50 is shown as an example of a processing device to which the paper P is transferred from the transport belt 223 to the re-transport unit 50. However, the configuration of the re-transport unit 50 can be changed in various ways, and for example, the processing device to which the paper P is transferred from the transport belt 223 may be a switchback device (reversal unit 52 in the above embodiment) that switches back the paper P to reverse the front and back of the paper P relative to the transport unit 20.

[0088] Although specific examples of the present invention have been described above in detail, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above. [Industrial Applicability]

[0089] According to the image forming apparatus according to the present disclosure, it is possible to prevent the paper being transported by the re-transport unit from dropping off, and to realize smooth transport of the paper. [Explanation of symbols]

[0090] 1. Image forming device 10 Paper feed section 20 Conveying section 21 Aligner section 22 Conveying path section 23 Branching section 24 Heating section 25 Upper side suction part 30 Image forming unit 31 Head Unit 40 Fixing section 50 Re-feeding section 51 Re-transport path section 52 Reversing section (switchback device) 53 Back steering section (steering device) 54 Heating section 55 Lower side suction part 56 Separation part 56a Air outlet 56b Belt bend 56c Air suction part 57 Paper guide section (recording medium guide section) 57a opening 60 Paper output section 61 Printed paper output tray 62 Printing failure paper output tray 100 control section 223 Conveyor Belt 223a Upper side mounting surface 223b Lower side mounting surface P Paper (recording medium)

Claims

1. a conveying section having an endless conveying belt and configured to convey a sheet-shaped recording medium by placing it on an upper side of the conveying belt; an image forming unit that forms an image on the surface of the recording medium conveyed by the conveying unit; a re-conveying unit that receives the recording medium from the conveying unit downstream of the image forming unit, places the recording medium on a lower placement surface of the conveying belt, conveys the recording medium in a direction opposite to the conveying direction of the conveying unit, and sends the recording medium again to the upstream side of the image forming unit from the conveying unit; a suction unit that adsorbs the recording medium, which is placed on the lower placement surface of the conveyor belt and conveyed, to the lower placement surface; a separation unit that is disposed downstream of the suction unit on the lower placement surface of the conveyor belt and separates the recording medium, which is placed on the lower placement surface of the conveyor belt and conveyed, from the conveyor belt; a flat recording medium guide portion that supports the recording medium separated from the conveyor belt by the separation portion from below and suppresses curvature of the recording medium; a processing device constituting a steering unit or a reversing unit disposed downstream of the separating unit; Equipped with the separation unit has an air blowing unit disposed inside the lower placement surface of the conveyor belt, The recording medium guide section is disposed at a position spaced downward from the lower loading surface of the conveyor belt, along the extending direction of the lower loading surface, so as to straddle from the position of the suction section to the position of the processing device, and guides the recording medium so that the recording medium reaches the position of the processing device in a planar posture. Image forming device.

2. a conveying section having an endless conveying belt and configured to convey a sheet-shaped recording medium by placing it on an upper side of the conveying belt; an image forming unit that forms an image on the surface of the recording medium conveyed by the conveying unit; a re-conveying unit that receives the recording medium from the conveying unit downstream of the image forming unit, places the recording medium on a lower placement surface of the conveying belt, conveys the recording medium in a direction opposite to the conveying direction of the conveying unit, and sends the recording medium again to the upstream side of the image forming unit from the conveying unit; a suction unit that adsorbs the recording medium, which is placed on the lower placement surface of the conveyor belt and conveyed, to the lower placement surface; a separation unit that is disposed downstream of the suction unit on the lower placement surface of the conveyor belt and separates the recording medium, which is placed on the lower placement surface of the conveyor belt and conveyed, from the conveyor belt; a recording medium guide section that supports the recording medium separated from the conveyor belt by the separation section from below and suppresses curvature of the recording medium; Equipped with the separation unit has an air suction unit disposed below and facing the lower-side loading surface of the conveyor belt. Image forming device.

3. a conveying section having an endless conveying belt and configured to convey a sheet-shaped recording medium by placing it on an upper side of the conveying belt; an image forming unit that forms an image on the surface of the recording medium conveyed by the conveying unit; a re-conveying unit that receives the recording medium from the conveying unit downstream of the image forming unit, places the recording medium on a lower placement surface of the conveying belt, conveys the recording medium in a direction opposite to the conveying direction of the conveying unit, and sends the recording medium again to the upstream side of the image forming unit from the conveying unit; a suction unit that adsorbs the recording medium, which is placed on the lower placement surface of the conveyor belt and conveyed, to the lower placement surface; a separation unit that is disposed downstream of the suction unit on the lower placement surface of the conveyor belt and separates the recording medium, which is placed on the lower placement surface of the conveyor belt and conveyed, from the conveyor belt; a recording medium guide section that supports the recording medium separated from the conveyor belt by the separation section from below and suppresses curvature of the recording medium; Equipped with the recording medium guide portion has an opening portion through which air sucked by the suction portion can pass; Image forming device.

4. the separation unit further includes an air blowing unit disposed inside the lower placement surface of the conveyor belt.

4. The image forming apparatus according to claim 2 or 3.

5. The air blowing unit is configured to blow out air using the air sucked by the suction unit. The image forming apparatus according to claim 4 .

6. the separating section further includes a belt bending portion formed at a downstream end of the lower placement surface of the conveying belt. The image forming apparatus according to claim 1 .

7. the image forming unit forms an image on the surface of the recording medium by an inkjet printing method; The image forming apparatus according to claim 1 .

8. the re-conveying unit receives the recording medium from the conveying unit downstream of the image forming unit, places the recording medium on a lower placement surface of the conveying belt, and conveys the recording medium in a direction opposite to the conveying direction of the conveying unit, delivers the recording medium from the conveying belt to the processing device, and then sends the recording medium again to the upstream side of the conveying unit of the image forming unit. The image forming apparatus according to claim 1 .

Images