Image forming apparatus

Abstract

To provide an image forming device capable of eliminating paper length limitation in double-sided printing.SOLUTION: A paper conveying path 90 connected to a first discharge port 91e and a second discharge port 92e has: a first conveying path 91; a second conveying path 92 connecting the downstream side of a fixing part 17 in a conveying direction and a second discharge port; a third conveying path 93 connecting the upstream side in the conveying direction from a second discharge port and the upstream side in the conveying direction from an image formation part 10 of the first conveying path; a first switching part 94 provided at a connection part of the second conveying path with the first conveying path; and a second switching part 95 provided at a connection part of the third conveying path with the second conveying path. In the case of double-sided printing, the first switching part and the second switching part are controlled so that one end side of the paper with a toner image fixed on one side is conveyed to the second discharge port, and when the one end side is discharged from the second discharge port to the outside, the second switching part is controlled so that the paper is reversed and the other end side opposite to the one end side is directed to the image formation part via the third conveying path and the first conveying path.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus suitable for double-sided printing of long sheets of paper.

Background Art

[0002] As a conventional image forming apparatus, for example, Patent Document 1 discloses an apparatus having a paper feed conveyance path and a reverse conveyance path inside the apparatus body. During double-sided printing of paper, the paper with a toner image formed on one side is sent to the reverse conveyance path, and the paper is conveyed from the reverse conveyance path through the paper feed conveyance path to the image forming unit (secondary transfer unit) so that a toner image is also formed on the other side where no toner image is formed. More specifically, the reverse conveyance path has a first reflux conveyance path connecting a downstream side of the fixing unit in the paper feed conveyance path and an upstream side of the image forming unit in the paper feed conveyance path, and a second reflux conveyance path connecting an intermediate position of the first reflux conveyance path and an upstream side of the image forming unit in the paper feed conveyance path. During double-sided printing, after one end side in the conveyance direction of the paper with a toner image formed on one side is sent to the first reflux conveyance path and stopped, the other end side in the conveyance direction of the paper is conveyed from the second reflux conveyance path through the paper feed conveyance path to the image forming unit to form a toner image on the other side.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a configuration where paper is reversed within the apparatus main body for duplex printing as in Patent Document 1, if the paper is long and its length is sufficiently longer than the reverse conveyance path, the other end side may collide with the paper itself during paper reversal and it may become impossible to advance, thus requiring a length limit for the paper. Such duplex printing of long paper is performed, for example, to create concertina-folded printed matter such as pamphlets and menus, horizontal or vertical pop advertisements, etc. The present invention has been made in consideration of the above circumstances, and an object thereof is to provide an image forming apparatus capable of eliminating the length limit of paper during duplex printing.

Means for Solving the Problems

[0005] The present invention includes an image forming unit that forms a toner image on paper, a fixing unit that fixes the toner image formed on the paper, a paper conveyance path that conveys the paper to the image forming unit and the fixing unit, a first discharge port and a second discharge port connected to the paper conveyance path so that the paper on which the toner image is fixed can be discharged to the outside, and a control unit. The paper conveyance path includes a first conveyance path that conveys the paper to the image forming unit and the fixing unit and conveys the paper on which the toner image is fixed to the first discharge port, a second conveyance path that connects the downstream side in the conveyance direction of the fixing unit in the first conveyance path and the second discharge port, a third conveyance path that connects the upstream side in the conveyance direction of the second conveyance path from the second discharge port and the upstream side in the conveyance direction of the image forming unit in the first conveyance path, a first switching unit provided at the connection portion of the second conveyance path with the first conveyance path, and a second switching unit provided at the connection portion of the third conveyance path with the second conveyance path. In the case of duplex printing, the control unit controls the switching operation of the first switching unit so as to convey one end side of the paper on which the toner image is fixed on one side to the second discharge port, and controls the switching operation of the second switching unit so as to reverse the paper when the one end side is being discharged from the second discharge port to the outside and direct the other end side opposite to the one end through the third conveyance path and the first conveyance path to the image forming unit. An image forming apparatus is provided which is characterized by this.

Effects of the Invention

[0006] According to the image forming apparatus of the present invention, when double-sided printing is performed on a sheet of paper, one end side in the conveyance direction of the sheet of paper on which a toner image has been formed on one side is passed through a second conveyance path and discharged to the outside from a second discharge port. When most of the sheet of paper has been temporarily discharged to the outside from the second discharge port, the other end side in the conveyance direction of the sheet of paper is sent to the first conveyance path via the third conveyance path, and the sheet of paper is sent to the image forming unit and the fixing unit to form a toner image on the other side on which the toner image has not been formed. Since most of the sheet of paper can be temporarily discharged to the outside during such sheet inversion, double-sided printing is possible even for a long sheet of paper having a length exceeding the total length of all the conveyance paths, and the length limitation of the sheet of paper can be eliminated.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9A

Figure 9B

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Mode for Carrying Out the Invention

[0008] Hereinafter, the present invention will be described in more detail with reference to the drawings. Note that the following description is illustrative in all respects and should not be construed as limiting the present invention. (First Embodiment) FIG. 1 is a perspective view of the image forming apparatus according to the first embodiment of the present invention, FIG. 2 is a plan view of the image forming apparatus according to the first embodiment, and FIG. 3 is a schematic configuration diagram for explaining the internal structure of the image forming apparatus according to the first embodiment. As shown in FIG. 1, this image forming apparatus (multifunction machine) 1 includes a housing 1x having a printing unit 10 as an image forming unit, and an operation unit 70 provided above the housing 1x. The image forming apparatus 1 also includes a control unit, a communication interface circuit, an image processing circuit, etc. (not shown) in the housing 1x. The control unit includes an operation recognition unit, a display control unit, a job control unit, and a memory.

[0009] This image forming apparatus (hereinafter also referred to as MFP: Multifunction Peripheral, or composite machine) 1 is a device that processes image data, and is, for example, an electronic device equipped with functions such as a copying function, a printing function, an original reading (scanning) function, an original editing function, an original sending (fax, FAX) function, and a communication function.

[0010] In the housing 1x, a storage space for removably storing a plurality of upper and lower paper feed trays 21 is provided below the printing unit 10. Above the printing unit 10, a first discharge port tray 31 (hereinafter sometimes referred to as the "first discharge tray 31") as a discharge unit is provided. Above the first discharge tray 31, a scanner unit 40 is provided. A USB connection terminal 61 is provided on the left side of the operation unit 70 on the front surface (the front surface of the scanner unit 40) of the upper part of the housing 1x. Also, in the housing 1x, the upper right side of the printing unit 10 is a discharge unit 30 that discharges printed paper to the first discharge tray 31 or the second discharge port tray 32 (hereinafter sometimes referred to as the "second discharge tray 32").

[0011] With the discharge unit 30 in between, the first discharge tray 31 is arranged on the left side and the second discharge tray 32 is arranged on the right side. Also, a first discharge port 91e of a paper conveyance path 90 (see FIG. 3) described later is provided on the inner surface of the discharge unit 30 on the side of the first discharge tray 31, and a second discharge port 92e of the paper conveyance path 90 is provided on the outer surface of the discharge unit 30 on the side of the second discharge tray 32.

[0012] In this image forming apparatus 1, a manual feed tray 22 is provided on the right side surface of the printing unit 10 of the housing 1x. Above the manual feed tray 22 on the right side surface of the housing 1x, the second discharge tray 32 is provided. An automatic document feeder (also referred to as ADF: Automatic Document Feeder) 50 is connected via a hinge part to the upper rear edge of the image input unit (scanner unit) 40 of the housing 1x.

[0013] The operation unit 70 includes a display unit (display unit) 71 that displays an operation screen, an operation unit (touch panel unit) 72 provided on the display unit 71 to receive the user's operation on the operation screen of the display unit 71, and a support frame 73 that supports the periphery of the display unit 71 and the operation unit 72. The display unit 71 is a part that displays information, and displays information necessary for the execution of each function, the result of the execution of the function, etc. to notify the user. For example, an LCD, an organic EL display, etc. are used. When a touch panel is used as the operation unit 72, the display unit 71 and the touch panel are arranged so as to overlap each other.

[0014] On the display unit 71, for example, settings of setting items used for printing of an image forming apparatus, information necessary for executing a document reading function, etc., an operation screen of a selected function, a function proposal screen, etc. are displayed using characters, symbols, graphics, images, icons, animations, videos, etc. The operation unit 72 is an input device for a user of the image forming apparatus to perform a predetermined input operation. The operation unit 72 is, for example, a part for inputting information such as characters and for selecting and inputting functions, and a keyboard, a mouse, a touch panel, etc. are used. As keys operated by the user, there are item selection keys, operation start keys, function selection keys, setting keys, etc.

[0015] The upper surface of the image input unit 40 serves as a document table 41 on which a document to be read is placed, and the document on the document table 41 can be pressed by an automatic document feeder 50. Also, it is assumed to have a function (document presence / absence detection function) for detecting that a document is placed on the document table 41. Furthermore, it is preferable to have a function (document size detection function) for detecting the size of the document placed on the document table 41. However, it does not necessarily have to have a function for detecting the size of the document placed on the document table 41. When it does not have a function for detecting the size of the document, it is assumed to have a function for the user to input the size of the document placed on the document table 41.

[0016] The automatic document feeder 50 may be a device that reads only one side of the document, or it may be a device that reads both sides of the document. Also, assume that the automatic document feeder 50 has a function of detecting the document size when a plurality of documents are placed.

[0017] Assume that it has a function of detecting that printing paper is placed on the manual feed tray 22 (paper presence / absence detection function) and a function of detecting the size of the printing paper placed on the manual feed tray 22 (paper size detection function).

[0018] As shown in FIG. 3, the printing unit (image forming unit) 10 includes four photoreceptor drums 3a, 3b, 3c, 3d, four chargers (charging devices) 5a, 5b, 5c, 5d for charging the surfaces of the respective photoreceptor drums 3a to 3d, an exposure unit (exposure device) 19 for forming an electrostatic latent image on the surfaces of the respective photoreceptor drums 3a to 3d, four developing devices 2a, 2b, 2c, 2d for individually storing black, cyan, magenta, and yellow toners and developing the electrostatic latent images on the surfaces of the respective photoreceptor drums 3a to 3d to form toner images, four cleaner units 4a, 4b, 4c, 4d for removing residual toner remaining on the surfaces of the respective photoreceptor drums 3a to 3d after development and image transfer, four toner cartridges (toner supply devices) 6a, 6b, 6c, 6d for individually supplying the four-color toners to the respective developing devices 2a to 2d, an intermediate transfer belt unit (transfer device) 7 for transferring the toner images on the surfaces of the respective photoreceptor drums 3a to 3d to a recording medium, an intermediate transfer belt cleaning unit 8, and the like.

[0019] Here, the symbols a to d indicate that a is a member for forming a black image, b is a member for forming a cyan image, c is a member for forming a magenta image, and d is a member for forming a yellow image. In this image forming apparatus 1, based on the image data for each of the four color components of black (K), cyan (C), magenta (M), and yellow (Y), a black toner image, a cyan toner image, a magenta toner image, and a yellow toner image are selectively formed on the surfaces of the respective photosensitive drums 3a to 3d. Then, these formed toner images are superimposed on the intermediate transfer belt unit 7, and one color image is formed on a sheet of paper as a recording medium.

[0020] Since the photosensitive drums 3a to 3d corresponding to each color have the same configuration, in the following description, the reference numerals are unified as 3. Similarly, the developing device is described with the reference numeral unified as 2, the charger is described with the reference numeral unified as 5, the cleaner unit is described with the reference numeral unified as 4, and the toner cartridge is described with the reference numeral unified as 6.

[0021] The photosensitive drum 3 is composed of a conductive substrate and a photosensitive layer formed on its surface, and is a cylindrical member responsible for charging and latent image formation by exposure. The photosensitive drum 3 exhibits conductivity when irradiated with light, and an electrical image called an electrostatic latent image is formed on its surface. Also, the photosensitive drum 3 is supported by a driving means (not shown) so as to be rotatable around its axis. Below each photosensitive drum 3, four developing devices 2 for forming images of different colors are arranged.

[0022] The cleaner unit 4 removes and collects the toner remaining on the surface of the photosensitive drum 3 after the developing and image transfer processes.

[0023] The charger 5 uniformly charges the surface of the photosensitive drum 3 to a predetermined potential. As the charger 5, in addition to the contact roller type shown in FIG. 1, chargers such as a contact brush type or a non-contact charger type are used.

[0024] The developing device 2 mainly includes a developing tank that houses a developer (two-component developer) containing toner and a magnetic carrier, a developing roller that supplies the developer to the photosensitive drum 3, and a toner transfer mechanism.

[0025] The developing device 2 has a developing roller disposed in the developing tank so as to face the photosensitive drum 3, and supplies toner to the surface of the photosensitive drum 3 by the developing roller to develop (visualize) the electrostatic latent image formed on the surface of the photosensitive drum 3. The carrier contained in the developer used in this embodiment is a magnetic carrier having magnetism, and for example, a ferrite carrier is used.

[0026] The exposure unit 19 irradiates light corresponding to image data from below the charger 5 and the developing device 2 onto the surface of the charged photosensitive drum 3 to perform exposure, thereby forming an electrostatic latent image corresponding to the image data on the surface of the photosensitive drum 3. In this embodiment, when the light corresponding to the image data is emitted from the exposure unit 19, it passes through the light guide path provided in the developing device 2 and is irradiated onto the surface of the rotating photosensitive drum 3. In this embodiment, as shown in FIG. 3, the exposure unit 19 is a laser scanning unit (LSU) including a laser irradiation unit and a reflection mirror. However, an EL (electroluminescence) or an LED writing head in which light emitting elements are arranged in an array can also be used. The exposure unit 19 is disposed below the developing device 2.

[0027] Also, in this embodiment, without reducing the size of the developing device 2 itself, the light (illustrated by a dotted line) emitted from the exposure unit 19 is passed through the light guide path provided inside the developing device 2 and irradiated onto the surface of the photosensitive drum 3 so that the image forming apparatus 1 can be miniaturized. The light guide path is a space penetrating the inside of the developing device 2. Since the optical path of the light emitted from the exposure unit 19 is provided inside the developing device 2, it becomes possible to arrange the four developing devices 2 closer to each other, contributing to the miniaturization of the image forming apparatus 1.

[0028] The intermediate transfer belt unit 7 includes an intermediate transfer roller 9 (9a, 9b, 9c, 9d), an intermediate transfer belt 80, an intermediate transfer belt driving roller 81, an intermediate transfer belt driven roller 82, and an intermediate transfer belt tension mechanism (not shown). The intermediate transfer roller 9, the intermediate transfer belt driving roller 81, the intermediate transfer belt driven roller 82, and the intermediate transfer belt tension mechanism stretch the intermediate transfer belt 80 and rotationally drive the intermediate transfer belt 80 in the direction of arrow B in FIG. 3.

[0029] The intermediate transfer roller 9 is rotatably supported by an intermediate transfer roller mounting portion in the intermediate transfer belt tension mechanism of the intermediate transfer belt unit 7. A transfer bias for transferring the toner image on the photosensitive drum 3 onto the intermediate transfer belt 80 is applied to the intermediate transfer roller 9.

[0030] The intermediate transfer belt 80 is provided so as to contact each photosensitive drum 3. A color toner image (multi-color toner image) is formed on the intermediate transfer belt 80 by sequentially and superposedly transferring the toner images of respective color components formed on the photosensitive drum 3. The intermediate transfer belt 80 is formed in an endless shape using a film having a thickness of, for example, about 100 μm to 150 μm.

[0031] The driving roller 81 and the driven roller 82 are arranged outside the straight-ahead direction of the intermediate transfer belt 80 with respect to the photosensitive drums (3a, 3d) arranged at both ends among the four photosensitive drums 3. Further, as shown in FIG. 3, the intermediate transfer belt cleaning unit 8 is arranged so as to contact a portion on the side of the driven roller 82 in the intermediate transfer belt unit 7. Furthermore, a transfer roller 83 is arranged in proximity to the side of the driving roller 81. The conveyed paper passes between the transfer roller 83 and the driving roller 81.

[0032] The transfer of the toner image from the photoreceptor drum 3 to the intermediate transfer belt 80 is performed by the intermediate transfer roller 9 that is in contact with the back side of the intermediate transfer belt 80. A high-voltage transfer bias (a high voltage with a polarity opposite to the charging polarity (-) of the toner (+)) is applied to the intermediate transfer roller 9 in order to transfer the toner image. The intermediate transfer roller 9 is formed based on a metal (e.g., stainless steel) shaft having a diameter of, for example, 8 to 10 mm, and the surface is covered with a conductive elastic material (e.g., EPDM, foamed urethane, etc.). Due to this conductive elastic material, the intermediate transfer roller 9 can uniformly apply a high voltage to the intermediate transfer belt 80. In the present embodiment, a roller-shaped member (intermediate transfer roller 9) is used as the transfer electrode, but a brush or the like can also be used instead.

[0033] As described above, the electrostatic latent images on the respective photoreceptor drums 3 are visualized with toner corresponding to each color component to become toner images, and these toner images are superimposed and laminated on the intermediate transfer belt 80. Thus, the laminated toner images are moved by the rotation of the intermediate transfer belt 80 to the contact position (transfer portion) between the conveyed paper and the intermediate transfer belt 80, and are transferred onto the paper by the transfer roller 83 disposed at this position. In this case, the intermediate transfer belt 80 and the transfer roller 83 are pressed against each other with a predetermined nip, and a voltage for transferring the toner image to the paper is applied to the transfer roller 83. This voltage is a high voltage with a polarity opposite to the charging polarity (-) of the toner (+).

[0034] In order to constantly obtain the above nip, either the transfer roller 83 or the intermediate transfer belt driving roller 81 is formed of a hard material such as metal, and the other is formed of a soft material such as an elastic roller (elastic rubber roller or foamed resin roller, etc.). The toner attached to the intermediate transfer belt 80 due to the contact between the intermediate transfer belt 80 and the photoreceptor drum 3, and the toner remaining on the intermediate transfer belt 80 without being transferred during the transfer of the toner image from the intermediate transfer belt 80 to the paper are removed and recovered by the intermediate transfer belt cleaning unit 8 because they cause toner color mixing in the next process.

[0035] The intermediate transfer belt cleaning unit 8 is provided with a cleaning blade (cleaning member) that contacts the intermediate transfer belt 80. The portion of the intermediate transfer belt 80 that is in contact with the cleaning blade is supported by the intermediate transfer belt driven roller 82 from the back side.

[0036] Furthermore, the printing unit 10 includes a paper feed tray 21 that houses a plurality of recording media disposed at the lowermost part thereof, a manual feed tray 22 disposed on one side surface on which an irregular-sized paper is set, and a paper conveyance path 90 or the like for conveying the paper from the paper feed tray 21 or the manual feed tray 22 to the intermediate transfer belt unit 7. Note that a regular-sized paper may be set on the manual feed tray 22.

[0037] As shown in FIG. 3, the paper conveyance path 90 guides the paper from the paper feed tray 21 and the manual feed tray 22 through the transfer portion and the fixing portion 17 to the first paper discharge tray 31 or the second paper discharge tray 32. Here, the transfer portion is located between the intermediate transfer belt driving roller 81 and the transfer roller 83. Furthermore, a pickup roller 16a, a plurality of pairs of conveyance rollers 16b, a registration roller 16c, a transfer portion (transfer roller 83), a fixing portion 17, etc. are disposed in the paper conveyance path 90.

[0038] The paper conveyance path 90 includes a first conveyance path 91 that conveys the paper to the printing unit (image forming unit) 10 and the fixing unit 17 and conveys the paper with the toner image fixed thereto to the first discharge port 91e, a second conveyance path 92 that connects a downstream side in the conveyance direction from the fixing unit 17 in the first conveyance path 91 and the second discharge port 92e, a third conveyance path 93 that connects an upstream side in the conveyance direction from the second discharge port 92e in the second conveyance path 92 and an upstream side in the conveyance direction from the transfer unit (transfer roller 83) of the printing unit 10 in the first conveyance path 91, a first switching unit 94 provided at a connection portion between the first conveyance path 91 and the second conveyance path 92, and a second switching unit 95 provided at a connection portion between the third conveyance path 93 and the second conveyance path 92. Note that the first conveyance path 91 is divided into an upstream side portion from the transfer unit (transfer roller 83), a portion between the transfer unit and the fixing unit 17, and a downstream portion from the fixing unit 17.

[0039] Further, the paper conveyance path 90 includes a regular paper conveyance path 96 that connects the plurality of paper feed trays 21 and the upstream side portion of the first conveyance path 91, and an irregular paper conveyance path 97 that connects the manual feed tray 22 and the upstream side portion of the first conveyance path 91.

[0040] The first switching unit 94 has a first switching plate 94a that is swingable to switch the conveyance direction so as to communicate the first conveyance path 91 and the first discharge port 91e, or to communicate the first conveyance path 91 and the second conveyance path 92. This first switching plate 94a is swung by a first actuator (not shown) that is driven and controlled by the control unit. The second switching unit 95 has a second switching plate 95a that is swingable to switch the conveyance direction so as to communicate the first conveyance path 91 and the second discharge port 92e, or to communicate the second discharge port 92e and the third conveyance path 93. This second switching plate 95a is swung by a second actuator (not shown) that is driven and controlled by the control unit.

[0041] The conveyance roller 16b is a small roller for promoting and assisting the conveyance of the sheet, and a plurality of pairs are provided along the paper conveyance path 90. The pickup roller 16a is provided at the ends of the paper feed tray 21 (see FIG. 1) and the manual feed tray 22, and is a calling roller that supplies sheets (recording media) one by one from the paper feed tray 21 or the manual feed tray 22 to the paper conveyance path 90. The registration roller 16c temporarily holds the sheet being conveyed through the paper conveyance path 90, and conveys the sheet to the transfer unit at a timing when the leading edge of the toner image on the intermediate transfer belt 80 and the leading edge of the sheet are aligned.

[0042] As shown in FIG. 3, the fixing unit 17 includes a heat roller 17a and a pressure roller 17b that rotate in opposite directions with the sheet having the toner image transferred therebetween. The heat roller 17a is controlled by a control unit (not shown) so as to reach a predetermined fixing temperature. This control unit controls the temperature of the heat roller 17a based on a detection signal from a temperature detector (not shown).

[0043] The heat roller 17a and the pressure roller 17b, which have been heated to the fixing temperature, are pressed against the sheet to melt the toner, thereby fixing the toner image on one side of the sheet. The sheet on which the toner image has been fixed is conveyed by the conveyance roller 16b to the first discharge port 91e of the paper conveyance path 90 and discharged onto the first paper discharge tray 31, or is conveyed to the second discharge port 92e and discharged onto the second paper discharge tray 32. When discharging the sheet onto the first paper discharge tray 31, the first switching unit 94 opens the downstream portion of the first conveyance path 91 (closes the connection portion with the second conveyance path 92) to communicate with the first discharge port 91e. When discharging the sheet onto the second paper discharge tray 32, the first switching unit 94 opens the connection portion with the second conveyance path 92, and the second switching unit 95 closes the connection portion with the third conveyance path 93 to communicate the second conveyance path 92 with the second discharge port 92e.

[0044] [Regarding the operation during double-sided printing of the sheet] According to the image forming apparatus 1 configured as described above, double-sided printing can be performed on the sheet as follows. At this time, this image forming apparatus 1 can perform double-sided printing without limiting the length of the long sheet (long paper). Figs. 4 to 7 are the first to fourth operation explanatory diagrams for explaining double-sided printing by the image forming apparatus of the first embodiment. In the following description, the case of double-sided printing on a long sheet S as the paper is exemplified. However, the double-sided printing operation of the image forming apparatus 1 is generally the same even when using a regular-sized paper.

[0045] As shown in Figs. 1 to 4, in the case of double-sided printing on a long sheet S (or a regular-sized paper), the control unit controls the switching operation of the first switching unit 94 so as to convey one end s1 side of the long sheet S on which the toner image is fixed on one side to the second discharge port 92e, and when discharging the one end s1 side from the second discharge port 92e to the outside, reverses the long sheet S and controls the switching operation of the second switching unit 95 so that the other end s2 side opposite to the one end s1 is directed to the printing unit 10 via the third conveyance path 93 and the first conveyance path 91.

[0046] Explaining the double-sided printing procedure in detail, as shown in Figs. 1 to 4, first, set the long sheet S on the manual feed tray 22. At this time, it is desirable to set one end of the long sheet S at the position of the pickup roller 16a, and the other end side of the long sheet S should not hang down on the floor surface. For example, place it on a table installed on the right side of the image forming apparatus 1. In the case of this embodiment, the length of the long sheet S is longer than the sum of the lengths of the first conveyance path 91, the second conveyance path 92, and the third conveyance path 93.

[0047] Next, the user operates the operation unit 72 of the operation unit 70 to set it to the long sheet double-sided printing mode. Alternatively, set it to the long sheet double-sided printing mode on a PC (personal computer) connected to the image forming apparatus 1 via a LAN. As a result, in the paper conveyance path 90, the first switching unit 94 and the second switching unit 95 operate the first switching plate 94a and the second switching plate 95a so that the second conveyance path 92 communicates with the first conveyance path 91.

[0048] Next, the user inputs the image data to be double-sided printed on the long paper S into the storage unit of the image forming apparatus 1 by connecting a USB memory to the USB connection terminal 61 of the image forming apparatus 1, or accepts the selection of print data stored in the storage unit of the image forming apparatus 1, or inputs it to the storage unit of the image forming apparatus 1 using a PC. Further, the print data may be read from both sides of a long document by the reading unit of the automatic document feeder 50. Also, the size of the long paper S to be used is input, the images to be printed on one side and the other side of the long paper S are selected, and inputs such as the print area on the long paper S are made. When the preparation for double-sided printing is thus completed, an operation to start double-sided printing is performed on the operation unit 72 or the PC. As a result, as shown in FIG. 4, one end s1 side of the long paper S on the manual feed tray 22 is sent from the irregular paper conveyance path 97 to the first conveyance path 91 by the pickup roller 16a and the conveyance roller 16b, and the long paper S passes through the transfer unit (transfer roller 83) and the fixing unit 17, whereby a toner image is formed on one side thereof.

[0049] Note that when the operation to start double-sided printing of the long paper S is performed, before starting the printing operation of the long paper S, the control unit may cause the display unit 71 to display an inquiry content asking the user whether the second paper discharge tray 32 is in a usable peripheral environment. According to this configuration, for example, it is possible to prompt the user in advance to check whether there is anything around that may obstruct the movement of one end s1 side of the long paper S discharged and hanging down on the second paper discharge tray 32. In this case, for example, printing starts by pressing the "Print" key displayed on the display unit 71.

[0050] Thereafter, as shown in FIG. 4, one end s1 side of the long paper S advances along the second conveyance path 92 and reaches the second discharge port 92e. As shown in FIG. 5, the one end s1 side slides on the second paper discharge tray 32 and droops downward. When the other end s2 of the long paper S passes through the second switching section 95 and reaches before the conveyance roller (paper discharge roller) 16b near the second discharge port 92e, the conveyance roller (paper discharge roller) 16b stops. At this time, the control unit stops the conveyance roller (paper discharge roller) 16b at the timing when the sensor provided at a predetermined position of the paper conveyance path 90 detects one end s1 and the other end s2 of the long paper S and the other end s2 approaches the conveyance roller (paper discharge roller) 16b. In this case, for example, the following method may be adopted. The length of the long paper may be calculated by detecting the passage of one end s1 and the other end s2 of the long paper with a sensor provided at a predetermined position of the paper conveyance path 90, or simply by detecting the passage of the other end s2 of the long paper, and the control unit may stop the conveyance roller (paper discharge roller) 16b at the timing when the other end s2 approaches the conveyance roller (paper discharge roller) 16b from the conveyance speed in the conveyance path. Alternatively, a sensor may be provided in front of the conveyance roller (paper discharge roller) 16b to detect the rear end of the other end s2, and the control unit may stop the conveyance roller (paper discharge roller) 16b at the timing when the other end s2 approaches the conveyance roller (paper discharge roller) 16b.

[0051] Thereafter, as shown in FIG. 6, the control unit swings the second switching plate 95a of the second switching unit 95 so that the second discharge port 92e communicates with the third conveyance path 93, and swings the first switching plate 94a of the first switching unit 94 so that the first discharge port 91e communicates with the first conveyance path 91. Then, the conveyance roller (paper discharge roller) 16b is rotated reversely to convey the other end s2 side of the long paper S to the third conveyance path 93, and the other end s2 side enters the first conveyance path 91. As shown in FIG. 7, the long paper S passes through the transfer unit (transfer roller 83) and the fixing unit 17, and a toner image is formed on the other surface thereof. Then, the long paper S with toner images formed on both surfaces is discharged from the first discharge port 91e onto the first paper discharge tray 31. At this time, the other end s2 side of the long paper S is slid on the first paper discharge tray 31 so as not to stay on the first paper discharge tray 31, and the other end s2 side of the long paper S is accommodated in a cardboard box installed on the left side of the image forming apparatus 1 as necessary.

[0052] As described above, according to the image forming apparatus 1 of the first embodiment, the one end s1 side of the long paper S printed on one side is temporarily discharged to the outside, the one end s1 side is temporarily discharged to the outside from the second discharge port 92e different from the first discharge port 91e for finally discharging the long paper S, and after temporarily discharging the one end s1 side to the outside, the one end s1 side of the long paper S does not obstruct the progress of the other end s2 side while the other end s2 side of the long paper S is conveyed to the first discharge port 91e. Different from Patent Document 1, therefore, double-sided printing can be performed without limiting the length of the long paper S.

[0053] (Modification Example 1 of the First Embodiment) FIG. 8 is a plan view showing a modification example 1 of the paper discharge tray in the image forming apparatus of the first embodiment. In FIG. 8, the same elements as those in FIGS. 1 to 7 are denoted by the same reference numerals. As shown in FIG. 8, in the above-described first embodiment, a guide mechanism unit 33 for guiding a long sheet of paper may be provided on the second paper discharge tray 32 provided on the outer surface of the discharge unit 30 of the housing 1x and receiving the paper discharged from the second discharge port 92e.

[0054] In the case of this Modification 1, the guide mechanism portion 33 is composed of a pair of parallel guide plates 33a and 33b, and the second paper discharge tray 32 is provided with four mounting holes 32a for the pair of guide plates 33a and 33b. The pair of guide plates 33a and 33b are in sliding contact with a pair of long sides of the long paper S (see FIGS. 5 and 6) to guide the long paper S straight, and two projecting pieces (not shown) to be fitted into the two mounting holes 32a are provided at their lower ends.

[0055] In addition, the ends of the pair of guide plates 33a and 33b on the second paper discharge port 92e side are bent portions 33aa and 33ba that bend away from each other as they go toward the second paper discharge port 92e. One end s1 of the long paper S discharged from the second paper discharge port 92e can smoothly enter between the pair of guide plates 33a and 33b due to the pair of bent portions 33aa and 33ba. By providing this guide mechanism portion 33 on the second paper discharge tray 32, it is possible to temporarily discharge the one end s1 side of the long paper S to the outside from the second paper discharge port 92e and perform diagonal correction of the long paper S when it is reversed and returned to the second paper discharge port 92e.

[0056] (Modification 2 of the First Embodiment) FIG. 9A is a plan view showing Modification 2 of the paper discharge tray in the image forming apparatus of the first embodiment, and FIG. 9B is a front view of the paper discharge tray in FIG. 9A. In FIGS. 9A and 9B, the same elements as those in FIGS. 1 to 7 are denoted by the same reference numerals. As shown in FIGS. 9A and 9B, in the above-described first embodiment, another guide mechanism portion 34 different from Modification 1 may be provided on the second paper discharge tray 32 provided on the outer surface of the discharge portion 30 of the housing 1x.

[0057] In the case of this Modification Example 2, the guide mechanism portion 34 includes a top plate 34a, a pair of side plates 34b provided along an edge of the top plate 34a in a direction orthogonal to the paper conveyance direction (the direction of arrow A), an inclined plate portion 34c provided at an end portion of the top plate 34a on the second discharge port 92e side, and bent portions 34d provided at end portions of the pair of side plates 34b on the second discharge port 92e side, respectively. Note that two protruding pieces (not shown) to be fitted into the four mounting holes 32a of the second paper discharge tray 32 are provided at the lower ends of the pair of side plates 34b, respectively.

[0058] The inclined plate portion 34c and the pair of bent portions 34d are bent in a direction away from each other as they go toward the second discharge port 92e. As a result, one end s1 of the long paper S discharged from the second discharge port 92e can smoothly enter the flat guide slit formed by the second paper discharge tray 32 and the guide mechanism portion 34. Further, by providing this guide mechanism portion 34 on the second paper discharge tray 32, it is possible to temporarily discharge the one end s1 side of the long paper S to the outside from the second discharge port 92e, and to perform oblique correction of the long paper S when it is reversed and returned to the second discharge port 92e, and to prevent the one end s1 of the long paper S discharged from the second discharge port 92e from going upward.

[0059] (Modification Examples 3 and 4 of the First Embodiment) FIG. 10 is a front view showing Modification Example 3 of the paper discharge tray in the image forming apparatus of the first embodiment, and FIG. 11 is a front view showing Modification Example 4 of the paper discharge tray in the image forming apparatus of the first embodiment. In FIGS. 10 and 11, the same elements as those in FIGS. 1 to 7 are denoted by the same reference numerals. As in Modification Example 3 shown in FIG. 10, in the above-described first embodiment, a curved surface portion 32b may be provided at an end portion of the second paper discharge tray 32 provided on the outer surface of the discharge portion 30 of the housing 1x in the paper conveyance direction (the direction of arrow A1). Alternatively, as in Modification Example 4 shown in FIG. 11, in the above-described first embodiment, a roller 32c may be rotatably provided at an end of the second paper discharge tray 32 in the paper conveyance direction (arrow A1 direction). Further, in this case, the roller 32c may be rotated forward and backward by a motor (not shown) according to the direction of arrow A1 in which the long paper S is discharged or the direction of arrow A2 in which the long paper S travels backward. According to Modification Examples 3 and 4, the unprinted other side of the long paper S printed on one side can smoothly move along the curved surface portion 32b or the roller 32c.

[0060] (Modification Example 5 of the First Embodiment) FIG. 12 is a front view showing Modification Example 5 of the paper discharge tray in the image forming apparatus of the first embodiment. In FIG. 12, the same elements as those in FIGS. 1 to 7 are denoted by the same reference numerals. As in Modification Example 3 shown in FIG. 10, in the above-described first embodiment, a storage cylinder portion 35 capable of temporarily storing the long paper S from one end s1 side may be provided at an end of the second paper discharge tray 32 in the paper conveyance direction (arrow A1 direction).

[0061] This storage cylinder portion 35 has a cylindrical portion 35a and a pair of arm portions 35b provided at both ends in the axial direction of the cylindrical portion 35a. Further, a plurality of projecting pieces (not shown) to be fitted into a plurality of mounting holes 32a (see FIG. 8) provided in the second paper discharge tray 32 are provided at the lower ends of the pair of arm portions 35b. An opening 35aa is provided at a location where the cylindrical portion 35a faces the upper surface of the second paper discharge tray 32.

[0062] According to this Modification Example 5, while receiving the one end s1 side of the long paper S temporarily and partially discharged from the second discharge port 92e during double-sided printing by the second paper discharge tray 32, it can be stored while being wound up by the storage cylinder portion 35. Therefore, a receiving container such as a tray or a box placed on the floor surface for receiving the one end s1 side of the discharged long paper S becomes unnecessary. Further, the pair of arm portions 35b of the storage cylinder portion 35 also function as guide members for guiding the long paper S to the opening 35aa of the cylindrical portion 35a.

[0063] (Second Embodiment) FIG. 13 is a schematic configuration diagram for explaining the internal structure of the image forming apparatus according to the second embodiment. In FIG. 13, the same elements as those in FIGS. 1 to 7 are denoted by the same reference numerals. As shown in FIG. 13, the image forming apparatus 201 according to the third embodiment is substantially the same as that of the first embodiment except that the configuration of the paper conveyance path 290 and the second paper discharge tray is different from that of the first embodiment. Hereinafter, the differences from the first embodiment in the second embodiment will be mainly described.

[0064] In the case of the second embodiment, the first paper discharge tray 31, which is the paper discharge unit, is provided on the upper surface of the printing unit 10, and the second paper discharge tray 232, which is the other paper discharge unit, is provided above the first paper discharge tray 31. Also, both the first paper discharge port 91e and the second paper discharge port 292e are provided on the inner surface of the discharge unit 230, and the second paper discharge port 292e is provided at a position higher than the first paper discharge port 91e. Therefore, the second conveyance path 292 bends to the left from the connection portion with the first conveyance path 91 and connects to the second paper discharge port 292e, and the third conveyance path 293 bends to the left from the connection portion with the first conveyance path 91 and connects to the middle portion of the second conveyance path 292. Note that a first switching unit 94 is provided at the connection portion of the second conveyance path 292 with the first conveyance path 91, and a second switching unit 95 is provided at the connection portion of the third conveyance path 293 with the second conveyance path 292, which is the same as in the first embodiment.

[0065] FIGS. 14 to 17 are first to fourth operation explanatory diagrams for explaining double-sided printing by the image forming apparatus according to the second embodiment. Next, the operation of the image forming apparatus 201 according to the second embodiment during double-sided printing of the long paper S will be described. After the preparation for double-sided printing is completed in the same manner as in the first embodiment, an operation to start double-sided printing is performed on the operation unit 72 or the PC (see FIG. 1). As a result, as shown in FIG. 14, one end s1 side of the long paper S on the manual feed tray 22 is sent from the irregular paper conveyance path 97 to the first conveyance path 91 by the pickup roller 16a and the conveyance roller 16b, and the long paper S passes through the transfer unit (transfer roller 83) and the fixing unit 17, whereby a toner image is formed on one surface thereof.

[0066] Thereafter, as shown in FIG. 14, one end s1 side of the long paper S advances along the second conveyance path 92 and reaches the second discharge port 292e. As shown in FIG. 15, the one end s1 side slides on the second paper discharge tray 232 and hangs downward along the left side surface of the housing 1x. When the other end s2 of the long paper S passes through the second switching portion 95 and reaches in front of the conveyance roller (paper discharge roller) 16b near the second discharge port 292e, the conveyance roller (paper discharge roller) 16b stops. Also in this case, the sensor provided at a predetermined position of the paper conveyance path 290 detects one end s1 and the other end s2 of the long paper S, and the control unit stops the conveyance roller (paper discharge roller) 16b at the timing when the other end s2 approaches the conveyance roller (paper discharge roller) 16b.

[0067] Thereafter, as shown in FIG. 16, the control unit swings the second switching plate 95a of the second switching portion 95 so that the second discharge port 292e and the third conveyance path 293 communicate with each other, and swings the first switching plate 94a of the first switching portion 94 so that the first discharge port 91e and the first conveyance path 91 communicate with each other. Then, the conveyance roller (paper discharge roller) 16b is rotated reversely to convey the other end s2 side of the long paper S to the third conveyance path 293, and the other end s2 side enters the first conveyance path 91. As shown in FIG. 17, the long paper S passes through the transfer portion (transfer roller 83) and the fixing portion 17, and a toner image is formed on the other surface thereof. Then, the long paper S with toner images formed on both surfaces is discharged from the first discharge port 91e onto the first paper discharge tray 31. At this time, the other end s2 side is slid on the first paper discharge tray 31 so that the other end s2 side of the long paper S does not stay on the first paper discharge tray 31, and the other end s2 side of the long paper S is accommodated in the cardboard box installed on the left side of the image forming apparatus 1 as necessary.

[0068] Thus, similar to the first embodiment, the image forming apparatus 201 of the second embodiment also temporarily discharges one end s1 side of the long paper S with one side printed to the outside, temporarily discharges the one end s1 side to the outside from a second discharge port 292e different from the first discharge port 91e that finally discharges the long paper S, and, different from Patent Document 1, the one end s1 side of the long paper S passes through a route that does not obstruct the progress of the other end s2 side while the other end s2 side of the long paper S is conveyed to the first discharge port 91e after the one end s1 side is temporarily discharged to the outside. Therefore, double-sided printing can be performed without restricting the length of the long paper S. In the case of the second embodiment, as shown in FIG. 15, since the length of the second paper discharge tray 232 in the paper conveyance direction is the same as or greater than the length of the first paper discharge tray 31 in the paper conveyance direction, one end s1 of the long paper S temporarily discharged from the second discharge port 292e does not hang down from the second paper discharge tray 232 and land on the first paper discharge tray 31. That is, if the horizontal protruding dimension from the upper discharge port of one tray arranged in the upper stage is the same as or greater than the horizontal protruding dimension from the lower discharge port of the other tray arranged in the lower stage, the long paper hanging down from the upper tray will not land on the lower tray.

[0069] (Third Embodiment) The image forming apparatus of the present invention may include upper and lower two-stage paper discharge trays in which both the first discharge port and the second discharge port are provided on the outer surface of the apparatus. In this case, the first discharge port on the upstream side is in the upper stage, and the second discharge port on the downstream side is in the lower stage. In this configuration, the protruding dimension of the tray body of the first discharge port from the outer surface of the apparatus is the same as or greater than the protruding dimension of the tray body of the second discharge port from the outer surface of the apparatus, so that it is possible to avoid the long paper with double-sided printing completed being discharged from the first discharge port and the long paper hanging down from the tray body of the first discharge port contacting the tray body of the second discharge port. That is, if the horizontal protruding dimension from the upper discharge port of one tray arranged in the upper stage is the same as or greater than the horizontal protruding dimension from the lower discharge port of the other tray arranged in the lower stage, the long paper hanging down from the upper tray will not land on the lower tray.

[0070] (Fourth Embodiment) The first to fifth modification examples of the first embodiment (see FIGS. 8 to 12) are limited to the second paper discharge tray 32 provided on the outer surface of the housing 1x of the first embodiment, but these first to fifth modification examples may be applied to the first paper discharge tray 31 provided on the inner surface of the first embodiment. Similarly, they may be applied to the first and second paper discharge trays of the second and third embodiments.

[0071] As described above, (i) The image forming apparatus according to the present invention includes an image forming unit that forms a toner image on a sheet, a fixing unit that fixes the toner image formed on the sheet, a sheet conveyance path that conveys the sheet to the image forming unit and the fixing unit, a first discharge port and a second discharge port connected to the sheet conveyance path so that the sheet on which the toner image is fixed can be discharged to the outside, and a control unit. The sheet conveyance path includes a first conveyance path that conveys the sheet to the image forming unit and the fixing unit and conveys the sheet on which the toner image is fixed to the first discharge port, a second conveyance path that connects a downstream side in the conveyance direction of the fixing unit in the first conveyance path and the second discharge port, a third conveyance path that connects an upstream side in the conveyance direction of the second conveyance path from the second discharge port and an upstream side in the conveyance direction of the image forming unit in the first conveyance path, a first switching unit provided at a connection portion of the second conveyance path and the first conveyance path, and a second switching unit provided at a connection portion of the third conveyance path and the second conveyance path. In the case of double-sided printing, the control unit controls the switching operations of the first switching unit and the second switching unit so as to convey one end side of the sheet on which the toner image is fixed on one side to the second discharge port, and when the one end side is discharged from the second discharge port to the outside, controls the switching operation of the second switching unit to reverse the sheet and direct the other end side opposite to the one end through the third conveyance path and the first conveyance path to the image forming unit.

[0072] According to this configuration, during double-sided printing of the paper, one end side in the conveyance direction of the paper with a toner image formed on one side is passed through the second conveyance path and discharged to the outside from the second discharge port. When most of the paper is temporarily discharged to the outside from the second discharge port, the other end side in the conveyance direction of the paper is sent to the first conveyance path via the third conveyance path, and the paper is sent to the image forming unit and the fixing unit to form a toner image on the other side where the toner image has not been formed. Since most of the paper can be temporarily discharged to the outside during such paper inversion, even if the paper is a long sheet having a length exceeding the total length of all the conveyance paths, double-sided printing is possible, and the length limit of the paper can be eliminated.

[0073] Furthermore, a preferred embodiment of the present invention will be described. (ii) The control unit may control the switching operation of the first switching unit so as to discharge the paper with toner images fixed on one side and the other side from the first discharge port. According to this configuration, since the other end of the paper after double-sided printing can be discharged from the first discharge port, when the paper is a long sheet, it is possible to surely control so as to form a conveyance path that avoids the other end after double-sided printing from intersecting with the paper during conveyance before double-sided printing. Note that if the length of the paper is such that the other end after double-sided printing does not collide with the one end side, the other end of the paper after double-sided printing may be discharged from the second discharge port.

[0074] (iii) The image forming unit, the fixing unit, and the paper conveyance path are provided in a housing, the housing has a discharge portion provided on the image forming unit, the first discharge port is provided on the outer surface of the discharge portion in the discharge portion, the second discharge port may be provided at a position below the first discharge port on the outer surface in the discharge portion. According to this configuration, the first discharge port and the second discharge port can be provided on the same outer surface of the housing.

[0075] (iv) The image forming unit, the fixing unit, and the paper conveyance path are provided in a housing, The housing has a paper discharge unit provided on the image forming unit and a discharge unit provided on the image forming unit so as to be adjacent to the paper discharge unit. The first discharge port is provided on the inner surface of the discharge unit on the paper discharge unit side. The second discharge port may be provided at a position above the first discharge port on the inner surface of the discharge unit. According to this configuration, the paper discharge unit is configured in two upper and lower stages, and the printed paper from the first discharge port can be received by the lower paper discharge unit, and the printed paper from the second discharge port can be received by the upper paper discharge unit. That is, an image forming apparatus in which two upper and lower paper discharge units are intensively arranged above the image forming unit can be obtained. (v) The image forming unit, the fixing unit, and the paper conveyance path are provided in the housing. The housing has a paper discharge unit provided on the image forming unit and a discharge unit provided on the image forming unit so as to be adjacent to the paper discharge unit. The first discharge port is provided on the inner surface of the discharge unit on the paper discharge unit side. The second discharge port may be provided on the outer surface of the discharge unit of the housing on the side opposite to the paper discharge unit. According to this configuration, since the second discharge port is provided on the outer surface of the discharge unit of the housing, an image forming apparatus with an increased loadable volume of the printed paper in the paper discharge unit can be obtained. In addition, the second discharge port can be used as a discharge port for printed paper during, for example, FAX reception, other than during double-sided printing.

[0076] (vi) A first discharge port tray for receiving the paper discharged from the first discharge port and a second discharge port tray for receiving the paper discharged from the second discharge port are provided in two upper and lower stages. Of the first discharge port tray and the second discharge port tray, the horizontal protruding dimension from the upper discharge port of the upper one of the trays may be the same as or larger than the horizontal protruding dimension from the lower discharge port of the lower one of the trays. According to this configuration, the long paper hanging down from the upper tray does not fall onto the lower tray.

[0077] (vii) It has a discharge port tray for receiving the paper discharged from at least one of the first discharge port and the second discharge port, A guide mechanism portion for guiding the long paper may be provided on the discharge port tray. According to this configuration, when single-sided printing is completed, during double-sided printing, or when double-sided printing is completed, the long paper (including the case of being temporarily and partially discharged) discharged from at least one of the first discharge port and the second discharge port can be guided by the guide mechanism portion so as to be discharged straight while being received by the discharge tray. Further, by providing the discharge port tray, for example, it is possible to prevent one end side of the long paper from accumulating on the hand tray provided below the discharge port tray. In this case, it is preferable to place a receiving container on the floor surface so that one end side of the long paper hanging down from the discharge port tray is not soiled.

[0078] (viii) It has a discharge port tray for receiving the paper discharged from at least one of the first discharge port and the second discharge port, A curved surface portion or a roller may be provided at an end portion in the conveyance direction of the discharge port tray. According to this configuration, by providing the discharge port tray, for example, it is possible to prevent one end side of the long paper from accumulating on the hand tray provided below the discharge port tray. Also, the unprinted other surface of the long paper printed on one side can move smoothly along the curved surface portion or the roller. In this case, it is preferable to place a receiving container on the floor surface so that one end side of the discharged long paper is not soiled.

[0079] (ix) It has a discharge port tray for receiving the paper discharged from at least one of the first discharge port and the second discharge port, A storage cylinder portion capable of temporarily storing the long paper from the one end side may be provided at an end portion in the conveyance direction of the discharge port tray. According to this configuration, it is possible to store the long paper discharged from at least one of the first discharge port and the second discharge port (including the case of temporarily and partially discharging) while receiving it in the discharge port tray and winding it up in the storage cylinder part. Therefore, there is no need for a receiving container such as another tray or box placed on the floor surface to receive one end side of the discharged long paper.

[0080] (x) Further include a display unit capable of displaying the driving state, When double-sided printing is performed on the long paper, the control unit may cause the display unit to display an inquiry content asking the user whether it is a surrounding environment where the tray can be used. According to this configuration, for example, it is possible to prompt the user in advance whether there is anything around that may prevent the movement of one end side of the long paper discharged and hanging down on the tray.

[0081] Preferred embodiments of the present invention also include combinations of any of the above-described embodiments. In addition to the above-described embodiments, there can be various modifications to the present invention. These modifications should not be construed as not belonging to the scope of the present invention. The present invention should include meanings equivalent to the claims and all modifications within the scope.

Explanation of Reference Numerals

[0082] 1. 201: Image forming apparatus (multifunction device), 1x: Housing, 2, 2a, 2b, 2c, 2d: Developing device, 4, 4a, 4b, 4c, 4d: Cleaner unit, 3, 3a, 3b, 3c, 3d: Photoconductor drum, 5, 5a, 5b, 5c, 5d: Charger (charging device), 6, 6a, 6b, 6c, 6d: Toner cartridge (toner supply device), 7: Intermediate transfer belt unit (transfer device), 8: Intermediate transfer belt cleaning unit, 9, 9a, 9b, 9c, 9d: Intermediate transfer roller, 10: Printing unit (image forming section), 16a: Pickup roller, 16b: Conveyor roller, 16c: Registration roller, 17: Fixing section, 17a: Heat roller, 17b: Pressure roller, 19: Exposure unit (exposure device), 21: Paper feed tray, 22: Manual feed tray, 30, 230: Discharge section, 31: First paper discharge tray (first paper discharge opening tray, paper discharge section), 32, 232: Second paper discharge tray (second paper discharge opening tray, paper discharge section), 32a: Mounting hole, 32b: Curved surface portion, 32c: Roller, 33, 34: Guide mechanism section, 33a, 33b: Guide plate, 33aa, 33ba: Bent portion, 34a: Top plate, 34b: Side plate, 34c: Inclined plate section, 34d: Bent portion, 35: Storage cylinder section, 35a: Cylindrical section, 35aa: Opening, 35b: Arm section, 40: Image input section (scanner unit), 41: Document table, 50: Automatic document feeder, 61: USB connection terminal, 70: Operation unit, 71: Display section (display unit), 72: Operation section (touch panel unit), 73: Support frame body, 80: Intermediate transfer belt, 81: Driving roller, 82: Driven roller, 83: Transfer roller, 90, 290: Paper conveyance path, 91: First conveyance path, 91e: First paper discharge opening, 92, 292: Second conveyance path, 92e, 292e: Second paper discharge opening, 93, 293: Third conveyance path, 94: First switching section, 94a: First switching plate, 95: Second switching section, 95a: Second switching plate, 96: Regular paper conveyance path, 97: Irregular paper conveyance path, A, A1, A2, B: Arrow, S: Long paper, s1: One end, s2: The other end

Claims

1. An image forming unit that forms a toner image on a sheet, a fixing unit that fixes the toner image formed on the sheet, a sheet conveyance path that conveys the sheet to the image forming unit and the fixing unit, a first discharge port and a second discharge port connected to the sheet conveyance path so that the sheet on which the toner image is fixed can be discharged to an external discharge tray, and a control unit, The sheet conveyance path includes a first conveyance path that conveys the sheet to the image forming unit and the fixing unit and conveys the sheet on which the toner image is fixed to the first discharge port, a second conveyance path that connects the downstream side in the conveyance direction of the fixing unit in the first conveyance path and the second discharge port, and a third conveyance path that connects the upstream side in the conveyance direction of the second discharge port in the second conveyance path and the upstream side in the conveyance direction of the image forming unit in the first conveyance path. The sheet conveyance path also has a first switching unit provided at a connection portion between the second conveyance path and the first conveyance path, and a second switching unit provided at a connection portion between the third conveyance path and the second conveyance path. When double-sided printing is performed on a long sheet whose length exceeds the total length of the first, second, and third conveyance paths, the control unit controls the switching operations of the first switching unit and the second switching unit so as to convey one end side of the long sheet on which the toner image is fixed on one side to the second discharge port, and when the one end side is being discharged from the second discharge port to the outside, controls the switching operation of the second switching unit to reverse the long sheet and direct the other end side, which is opposite to the one end, toward the image forming unit via the third conveyance path and the first conveyance path. After fixing an image on the other side of the long sheet, the control unit controls the switching operation of the first switching unit to restrict the discharge of the long sheet to the discharge tray downstream of the second discharge port and not convey it to the second discharge port. An image forming apparatus characterized by this.

2. The image forming apparatus according to claim 1, wherein the control unit controls the switching operation of the first switching unit so as to discharge the long sheet on which the toner image is fixed on one side and the other side from the first discharge port.

3. The image forming unit, the fixing unit, and the sheet conveyance path are provided inside a housing, The housing has a discharge portion provided above the image forming unit, The first discharge port is provided on an outer surface of the discharge portion, The image forming apparatus according to claim 1 or 2, wherein the second discharge port is provided at a position below the first discharge port on the outer surface of the discharge portion.

4. The image forming unit, the fixing unit, and the paper conveyance path are provided inside the housing. The housing has a paper discharge unit provided above the image forming unit, and a discharge unit provided above the image forming unit so as to be adjacent to the paper discharge unit. The first discharge port is provided on the inner surface of the discharge unit on the paper discharge unit side. The second discharge port is provided at a position above the first discharge port on the inner surface of the discharge unit. The image forming apparatus according to claim 1 or 2.

5. The image forming unit, the fixing unit, and the paper conveyance path are provided inside the housing. The housing has a paper discharge unit provided above the image forming unit, and a discharge unit provided above the image forming unit so as to be adjacent to the paper discharge unit. The first discharge port is provided on the inner surface of the discharge unit on the paper discharge unit side. The second discharge port is provided on the outer surface of the discharge unit on the side opposite to the paper discharge unit. The image forming apparatus according to claim 1 or 2.

6. A first discharge port tray for receiving the paper discharged from the first discharge port and a second discharge port tray for receiving the paper discharged from the second discharge port are provided in two upper and lower stages. Among the first discharge port tray and the second discharge port tray, the horizontal protruding dimension from the upper discharge port of one tray arranged in the upper stage is the same as or larger than the horizontal protruding dimension from the lower discharge port of the other tray arranged in the lower stage. The image forming apparatus according to any one of claims 1 to 4.

7. It has a discharge port tray for receiving the paper discharged from at least one of the first discharge port and the second discharge port. A guide mechanism unit for guiding the long paper is provided on the discharge port tray. The image forming apparatus according to any one of claims 1 to 6.

8. It has a discharge port tray for receiving the long paper discharged from the second discharge port. A curved surface portion or a roller is provided at an end in the conveyance direction of the discharge port tray. The image forming apparatus according to any one of claims 1 to 6.

9. It has a discharge port tray for receiving the long paper discharged from the second discharge port. A storage cylinder portion capable of temporarily storing the long paper from one end side is provided at an end in the conveyance direction of the discharge port tray. The image forming apparatus according to any one of claims 1 to 6.

10. further comprising a display unit capable of displaying a driving state; The image forming apparatus according to any one of claims 6 to 9, wherein when double-sided printing is performed on the long paper, the control unit causes the display unit to display an inquiry content for asking a user whether the surrounding environment in which the tray can be used.

Images