JP2015189580A - Image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image formation apparatus capable of double-sided printing and shortening an interval of the printing.SOLUTION: An image formation apparatus comprises: an apparatus body 2 having a body paper discharge tray 21 and an image formation unit 4; a body paper discharge path 71 for discharging a sheet S conveyed form the image formation unit 4 to the body paper discharge tray 21; and a re-conveyance path 80 branched from the body paper discharge path 71 for conveying the sheet S to the image formation unit 4 again. A paper discharge unit 200 having an option tray 220 and a paper discharge unit inside path 240 for discharging the sheet S to the option tray 220 can be attached to the apparatus body 2. The image formation apparatus is configured so that the paper discharge unit inside path 240 is connected to the re-conveyance path 80 by attaching the paper discharge unit 200 to the apparatus body 2.

Description

  The present invention relates to an image forming apparatus capable of forming images on both sides of a sheet.

  2. Description of the Related Art Conventionally, in an image forming apparatus capable of forming images on both sides of a sheet, a sheet discharge path for discharging a sheet carried out from an image forming unit to a discharge tray and a branch from the discharge path are formed. A sheet having a re-conveying path for conveying a sheet unloaded from the unit to the image forming unit again is known (for example, see Patent Document 1). In this image forming apparatus, when an image is formed on both sides of a sheet, the sheet on which an image is formed on one side by the image forming unit is conveyed to a certain extent by a discharge roller provided in a discharge path toward a discharge tray. After that, the sheet is conveyed to the re-conveying path by rotating the paper discharge roller in the reverse direction.

JP 2012-220870 A

  By the way, in the configuration as described above, when a sheet on which an image is formed on one side is conveyed to the re-conveying path, a sheet discharge roller is used, and during this time, subsequent sheets cannot be discharged. For this reason, when images are formed on both sides of the sheet, it is necessary to leave a gap between the conveyed sheets, and the time until the end of printing becomes long.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of forming an image on both sides of a sheet and shortening the time until the end of printing.

In order to achieve the above-described object, an image forming apparatus of the present invention includes a main body having a first paper discharge tray and an image forming unit, and a sheet discharged from the image forming unit to the first paper discharge tray. A first discharge path and a re-transport path that branches from the first discharge path and transports the sheet to the image forming unit again. The apparatus main body is provided in the second discharge tray and the second discharge tray. A paper discharge unit having a second paper discharge path for discharging the sheet can be attached.
The image forming apparatus is configured such that the second paper discharge path is connected to the re-transport path by attaching the paper discharge unit to the apparatus main body.

  According to the image forming apparatus configured as described above, when performing double-sided printing, a sheet on which an image is formed on one side is temporarily sent to the paper discharge unit without passing through the first paper discharge tray and then re-conveyed. Since the sheet can be sent to the path, the subsequent sheet can be discharged to the first discharge tray immediately after the sheet is sent to the discharge unit. Accordingly, the interval between the conveyed sheets can be shortened as compared with the configuration in which the sheet is once discharged to the first discharge tray and then pulled in, so that the time until the end of printing can be shortened. Further, since the re-transport path and the second paper discharge path are connected, it is possible to suppress dust from entering the re-transport path.

  In the above-described image forming apparatus, the apparatus main body has an opening on the upper surface, and the re-transport path is branched from the first transport path and connected to the opening, and the first path is branched from the first path to form an image. And a second path extending toward the part.

  In this case, the image forming apparatus is detachable from the apparatus main body to which the paper discharge unit is not attached, and includes a cover that covers the opening from above while attached to the apparatus main body, and the cover discharges from the opening. It is desirable to have a cover side guide for guiding the formed sheet in a direction along the upper surface of the apparatus main body.

  According to this, it can suppress that a dust penetrate | invades in an apparatus main body from opening by a cover. Even if a cover that covers the opening from above is provided, the cover has a cover-side guide, so that the sheet that comes out of the opening can be smoothly conveyed.

The cover-side guide may include a first guide portion that guides one surface of the sheet and a second guide portion that guides the other surface of the sheet.
In this case, the apparatus main body can be configured to have an insertion part into which the first guide part and the second guide part are inserted when the cover is attached to the apparatus main body.

  In the image forming apparatus having the insertion portion in the apparatus main body, when the paper discharge unit has a paper discharge unit side guide constituting the second paper discharge path, the paper discharge unit side guide is It is desirable that it can be inserted into the insertion portion.

  According to this, since the cover side guide and the paper discharge unit side guide are connected to the same part of the reconveying path, the cover side guide and the paper discharge unit side guide are connected to the reconveying path at different parts. The configuration can be simplified.

  The second path described above preferably extends vertically downward from the first path or inclined downward toward the image forming unit.

  According to this, the apparatus main body can be reduced in size compared with the case where the second path has a shape that projects.

The image forming unit described above may include a fixing unit and a curl removing roller that corrects curling of the sheet discharged from the fixing unit.
In this case, the image forming apparatus is disposed on the downstream side of the decurling roller in the sheet conveyance direction in the first sheet discharge path, and is a flapper that switches the sheet conveyance direction at a branch portion between the first sheet discharge path and the re-conveyance path. May be further provided.

  In the image forming apparatus including the curl removal roller, the sheet discharge roller provided at a position facing the first sheet discharge tray of the apparatus main body, and the intermediate discharge provided between the curl removal roller and the sheet discharge roller in the transport direction. When the paper roller is provided, the flapper may be provided between the curl removal roller and the intermediate paper discharge roller in the transport direction.

In the image forming apparatus described above, the first paper discharge tray is provided on the image forming unit, and the first paper discharge path is configured to transfer the sheet conveyed away from the image forming unit to the first paper discharge tray. You may have a U-turn guide comprised so that it may make a U-turn so that it may go to.
In this case, it is desirable that the re-conveying path is branched from the bottom of the U-turn guide.
The re-conveying path may be branched from the first paper discharge path at a position closer to the first paper discharge tray than the bottom of the U-turn guide.

  According to the present invention, when performing double-sided printing, a sheet on which an image is formed on one side can be sent once to the paper discharge unit and then sent to the re-conveying path without passing through the first paper discharge tray. Immediately after the sheet is sent to the sheet discharge unit, the subsequent sheet can be discharged to the first sheet discharge tray. Accordingly, the interval between the conveyed sheets can be shortened as compared with the configuration in which the sheet is once discharged to the first discharge tray and then pulled in, so that the time until the end of printing can be shortened.

1 is a diagram illustrating a schematic configuration of a laser printer according to an embodiment of the present invention to which a paper discharge unit is attached. It is an enlarged view showing a paper discharge path and a re-transport path. It is a figure which shows the laser printer with which the cover was attached. It is a figure explaining operation | movement of a laser printer during double-sided printing execution, Comprising: It is a figure which shows the state which conveyed the 1st sheet | seat to the path | route in a paper discharge unit. FIG. 10 is a diagram for explaining the operation of the laser printer during execution of double-sided printing, and is a diagram showing a state in which a second sheet is conveyed to a path inside the paper discharge unit. FIG. 10 is an enlarged view showing a paper discharge path and a re-transport path in a first modified example. FIG. 10 is an enlarged view showing a paper discharge path and a re-transport path in a second modified example. FIG. 10 is an enlarged view showing a paper discharge path and a re-transport path in a third modified example.

Next, an embodiment of the present invention will be described in detail with reference to the drawings as appropriate.
In the following description, the direction will be described with reference to the user who uses the laser printer 1. That is, the right side in FIG. 1 is “front (front)”, the left side is “rear (back)”, the front side is “left”, and the back side is “right”. Also, the vertical direction in FIG.

  As shown in FIG. 1, the laser printer 1 is an example of an image forming apparatus capable of forming images on both sides of a sheet S as an example of a sheet. In the laser printer 1, a paper discharge unit 200 can be attached to the upper part of the apparatus main body 2 as an optional component.

  The apparatus main body 2 mainly includes a paper feeding unit 3, an image forming unit 4, and a conveying unit 7 inside. In addition, the apparatus main body 2 has a main body discharge tray 21 as an example of a first discharge tray on which the paper S on which an image is formed is placed. The main body discharge tray 21 is provided on the image forming unit 4.

  The paper feed unit 3 is configured to supply the paper S to the image forming unit 4, and includes a paper feed cassette 31 that stores the paper S, a paper feed mechanism 32 that includes various rollers that transport the paper S, and the like. A paper feed path 33 for conveying the paper S supplied from the paper feed cassette 31 to the image forming unit 4 and a pair of registration rollers 34 are provided.

  The sheets S stored in the sheet feeding cassette 31 are separated one by one by the sheet feeding mechanism 32 and sent to the sheet feeding path 33, passing through the pair of registration rollers 34, and conveyed to the image forming unit 4. The pair of registration rollers 34 are provided in the vicinity of the exit of the paper feed path 33, and the paper S is temporarily stopped by being abutted before the paper S is supplied to the image forming unit 4. And the timing of image formation on the paper S is adjusted.

  The image forming unit 4 is configured to form an image on the fed paper S. The image forming unit 4 is disposed above the paper feeding cassette 31 and includes a scanner unit 41, a process cartridge 5, a fixing unit 6, and curl removal. And a roller 42.

  The scanner unit 41 is provided in the upper part of the apparatus main body 2, and laser light based on image data passes through a polygon mirror, a lens, a reflecting mirror, and the like that are omitted from the reference numerals, and passes through a photosensitive drum 51 included in the process cartridge 5. Irradiated on the surface by high-speed scanning.

  The process cartridge 5 is attachable to and detachable from the apparatus main body 2 through a mounting opening that is opened and closed by a front cover 22 rotatably provided on the front wall of the apparatus main body 2. The process cartridge 5 includes a drum cartridge 5A and a developing cartridge 5B that can be attached to and detached from the drum cartridge 5A.

  The drum cartridge 5 </ b> A includes a photosensitive drum 51 on which an electrostatic latent image is formed, a charger 52, and a transfer roller 53.

  The developing cartridge 5B includes a developing roller 54 that supplies toner contained therein to the photosensitive drum 51, a supply roller 55 that supplies toner to the developing roller 54, a layer thickness regulating blade, an agitator, and the like that are omitted from the reference numerals. Have.

  In the process cartridge 5, the surface of the rotating photosensitive drum 51 is uniformly charged by the charger 52 and then exposed by high-speed scanning of the laser beam from the scanner unit 41. As a result, the potential of the exposed portion is lowered, and an electrostatic latent image based on the image data is formed on the surface of the photosensitive drum 51.

  Next, the toner in the developing cartridge 5 </ b> B is supplied to the electrostatic latent image on the photosensitive drum 51 by the rotationally driven developing roller 54, and a toner image is formed on the surface of the photosensitive drum 51. Thereafter, the sheet S is conveyed between the photosensitive drum 51 and the transfer roller 53, so that the toner image carried on the surface of the photosensitive drum 51 is transferred onto the sheet S.

  The fixing unit 6 is disposed behind the process cartridge 5 and mainly includes a heating unit 61 having a heating element and a pressure roller 62 that sandwiches the paper S between the heating unit 61. In the fixing unit 6, the toner image transferred onto the paper S is thermally fixed while the paper S passes between the heating unit 61 and the pressure roller 62.

  The curl removing roller 42 is disposed behind the fixing unit 6 and configured to correct curling of the paper S discharged from the fixing unit 6.

  The transport unit 7 has a discharge function for discharging the paper S carried out from the image forming unit 4 to the main body paper discharge tray 21 or the paper discharge unit 200, and the paper S carried out from the image forming unit 4 is again formed in the image forming unit. 4 is provided with a re-transporting function. The detailed configuration of the transport unit 7 will be described later.

  The paper discharge unit 200 includes an option tray 220 as an example of a plurality of second paper discharge trays arranged vertically, and the paper S sent from the apparatus main body 2 can be sorted and discharged to each option tray 220. It is configured.

  Specifically, the paper discharge unit 200 includes a plurality of option trays 220, a casing 210 that supports the plurality of option trays 220, and a paper discharge unit-side paper discharge roller 230 provided corresponding to each option tray 220. In addition, a sheet discharge unit path 240 as an example of a second sheet discharge path for discharging the sheet S conveyed from the apparatus main body 2 to the option tray 220 is provided.

  The discharge unit inner path 240 includes a first discharge unit inner path 241 connected to the uppermost option tray 220 and a plurality of branch branches from the first discharge unit inner path 241 to the other option trays 220. And a second discharge unit path 242. Note that a swingable switching member 260 is provided at a branch portion between the first paper discharge unit inner path 241 and each second paper discharge unit inner path 242. The transport direction of the paper S can be switched.

Next, a detailed configuration of the transport unit 7 will be described.
As shown in FIG. 2, the transport unit 7 includes a main body discharge path 71 as an example of a first discharge path, a main body discharge roller 72 as an example of a discharge roller, an intermediate discharge roller 73, A conveyance path 80, a plurality of pairs of re-conveyance rollers 74 (see FIG. 1) for conveying the paper S in the re-conveyance path 80, a flapper 75 configured to swing back and forth, and an unloading roller 77 are mainly used. I have.

  The main body discharge path 71 is a path for discharging the paper S carried out from the image forming unit 4 to the main body discharge tray 21, and has a U-turn guide 76.

  The U-turn guide 76 constitutes the rear side of the main body discharge path 71, and comes into contact with the paper S conveyed rearwardly away from the image forming unit 4 by the curl removal roller 42. It has a guide surface that is curved so as to make a U-turn forward toward the paper discharge tray 21.

  The main body discharge roller 72 is provided at a position facing the main body discharge tray 21 of the apparatus main body 2 in the vicinity of the exit of the main body discharge path 71, and rotates the paper S that has passed through the main body discharge path 71 to the main body. The paper is discharged to the paper discharge tray 21.

  The intermediate paper discharge roller 73 is disposed between the curl removal roller 42 and the main body paper discharge roller 72 in the conveyance direction of the paper S in the main body paper discharge path 71 so as to convey the paper S in the main body paper discharge path 71. Is provided.

  The re-transport path 80 is a path for branching from the main body discharge path 71 and transporting the paper S to the image forming unit 4 again. The re-conveying path 80 includes a first path 81 that branches from the main body discharge path 71 and leads to the outside of the apparatus main body 2, and a second path 82 that branches from the first path 81 and extends toward the image forming unit 4. doing.

  Here, the apparatus main body 2 has a main body side communication port 23 as an example of an opening and an insertion portion 24 at the rear portion of the upper surface.

The insertion portion 24 is a recess that is recessed from the upper surface of the apparatus main body 2, and a main body side communication port 23 is formed at the bottom thereof.
The main body side communication port 23 is formed so that the paper S can pass therethrough, and is provided at a position closer to the rear side than the main body discharge path 71.

  The first path 81 branches from the bottom portion 76 </ b> A of the U-turn guide 76 of the main body discharge path 71 and extends upward, and is connected to the main body side communication port 23. In the present embodiment, the bottom portion 76A of the U-turn guide 76 is provided at a portion of the guide surface of the U-turn guide 76 that is farthest from the image forming unit 4 in the front-rear direction, that is, a position that is closest to the rear side. It is a part to be.

  In this way, by branching the first path 81 from the bottom portion 76A of the U-turn guide 76, it is not necessary to make the first path 81 curved to the rear side so as to bypass the bottom portion 76A of the U-turn guide 76. Since the main body side communication port 23 can be extended straight, the apparatus main body 2 can be downsized.

  The second path 82 extends vertically downward from the first path 81 through the rear side of the U-turn guide 76 and then bends forward to extend between the image forming unit 4 and the paper feed cassette 31 forward. It extends further below the pair of registration rollers 34 and joins the paper feed path 33 on the front side of the pair of registration rollers 34 (see FIG. 1).

  In this way, by forming the second path 82 so as to extend vertically downward from the first path 81, for example, the apparatus main body 2 can be downsized as compared with the case where the second path is formed to project backward. It is possible to do.

  The carry-out roller 77 is provided at a position below the main body side communication port 23 on the first path 81. The carry-out roller 77 is a roller configured to be rotatable in both forward and reverse directions, and carries out the sheet S conveyed through the first path 81 from the main body side communication port 23 to the outside of the apparatus main body 2 by rotating forward. The paper S is transported so as to be drawn into the apparatus main body 2 by rotating in the reverse direction.

  The flapper 75 is a member that switches the transport direction of the paper S at a branch portion between the main body discharge path 71 and the re-transport path 80 (first path 81). It is disposed downstream of the roller 42, more specifically, between the intermediate paper discharge roller 73 and the main body paper discharge roller 72.

  The flapper 75 is swingably supported on the upper wall of the apparatus main body 2 so that the lower end moves back and forth. As shown in FIG. 1, the flapper 75 assumes a first position that swings backward when the paper S carried out from the image forming unit 4 is guided to the main body discharge tray 21 (see a two-dot chain line). When the sheet S carried out from the image forming unit 4 is guided to the re-conveying path 80, the second position is configured to swing forward (see the solid line).

  As shown in FIG. 2, the paper discharge unit 200 is attached to the apparatus main body 2 with respect to the transport unit 7 configured as described above, so that the paper discharge unit path 240 becomes the re-transport path 80. It is configured to be connected to.

  Specifically, the housing 210 of the paper discharge unit 200 has an engaging portion 250 that protrudes from the lower surface and can be inserted into the insertion portion 24 of the apparatus main body 2. The engaging portion 250 constitutes a lower end portion of the paper discharge unit side guide 270 constituting the paper discharge unit inner path 240, and the paper discharge unit side communication port 251 connected to the paper discharge unit inner path 240 at the lower end surface. have.

  When the paper discharge unit 200 is attached to the apparatus main body 2, the engagement portion 250 is inserted into the insertion portion 24, so that the paper discharge unit side communication port 251 faces the main body side communication port 23. It has become.

  In this way, by connecting the paper discharge unit path 240 to the re-transport path 80, it is possible to prevent dust from entering the re-transport path 80 from the main body side communication port 23.

  In the present embodiment, the discharge unit side discharge roller disposed at the uppermost position of the first discharge unit inner path 241 from the branch portion of the first path 81 (reconveying path 80) with the main body discharge path 71. The distance to 230 is longer than the length of the paper S.

  As shown in FIG. 3, the laser printer 1 includes a cover 100 that can be attached to and detached from the apparatus main body 2 to which the paper discharge unit 200 is not attached. The cover 100 is configured to cover the main body side communication port 23 from above while being attached to the apparatus main body 2. The cover 100 is configured to guide the conveyance of the paper S carried out from the main body side communication port 23.

  Specifically, the cover 100 is a cylindrical member having an L-shaped cross section that can be inserted into the insertion portion 24. The cover 100 includes a first guide portion 110 that extends upward from the rear side of the main body side communication port 23 and then extends to the front side of the main body side communication port 23. The cover 100 has a second guide portion 120 that extends upward from the front side of the main body side communication port 23 so as to face the first guide portion 110 and then extends forward. The two guide portions 120 constitute a cover side guide 130 that guides the paper S discharged from the main body side communication port 23 in a direction along the upper surface of the apparatus main body 2, specifically, forward. When the cover 100 is attached to the apparatus main body 2, the first guide part 110 and the second guide part 120 are inserted into the insertion part 24.

Next, the operation of the laser printer 1 will be described.
As shown in FIG. 1, when the paper S on which an image is formed by the image forming unit 4 is discharged to the option tray 220 of the paper discharge unit 200, the flapper 75 swings forward and moves to the second position. Then, the first path 81 is opened, and the downstream portion of the main body discharge path 71 from the branching portion with the first path 81 is closed. Accordingly, the sheet S carried out from the image forming unit 4 is conveyed from the main body discharge path 71 to the first path 81. Then, the sheet S conveyed to the first path 81 is carried out by the carry-out roller 77 to the discharge unit inner path 240 of the discharge unit 200 through the main body side communication port 23 and the discharge unit side communication port 251.

  In the paper discharge unit 200, each switching member 260 swings to open the second paper discharge unit path 242 corresponding to the target option tray 220. As a result, the paper S transported through the paper discharge unit path 240 is transported toward the target option tray 220 and is discharged onto the option tray 220 by the paper discharge unit-side paper discharge roller 230.

  When double-sided printing is executed by the laser printer 1 to which the paper discharge unit 200 is attached, the flapper 75 first swings forward and moves to the second position, as shown in FIG. Is opened, and the downstream portion of the main body discharge path 71 with respect to the first path 81 is closed. Thus, the first sheet S1 on which an image is formed on one side by the image forming unit 4 is conveyed from the main body discharge path 71 to the first path 81. Then, the first sheet S1 conveyed to the first path 81 passes through the main body side communication port 23 and the paper discharge unit side communication port 251 by the carry-out roller 77 that rotates in the forward direction, and the inside of the paper discharge unit of the paper discharge unit 200. It is carried out to the route 240.

  When the trailing edge of the first sheet S1 carried out in the paper discharge unit path 240 passes through the main body paper discharge path 71, the carry-out roller 77 rotates in the reverse direction. As a result, the first sheet S1 is conveyed toward the second path 82 with the trailing edge at the top, and is conveyed to the image forming unit 4 with the front and back sides reversed.

  On the other hand, the second sheet S2 is supplied from the sheet feeding unit 3 to the image forming unit 4 while the first sheet S1 is being conveyed through the reconveying path 80 and the discharge unit inner path 240, and is fed to one side. An image is formed. The second sheet S2 is unloaded from the image forming unit 4 until the first sheet S1 reaches the image forming unit 4 from the second path 82. Then, as shown in FIG. 5, the second sheet S2 passes through the first path 81 from the main body discharge path 71 through the first path 81, as in the first sheet S1, and the path inside the discharge unit 200. It is carried out to 240.

  When the trailing edge of the second sheet S2 passes through the main body discharge path 71, the flapper 75 swings backward and moves to the first position, and from the branch portion of the main body discharge path 71 with the first path 81. The downstream portion is opened and the first path 81 is closed. As a result, the first sheet S1 on which images are formed on both sides conveyed behind the second sheet S2 is discharged to the main body discharge tray 21 through the main body discharge path 71.

  In this manner, the first sheet S1 is discharged to the main body discharge tray 21, while the carry-out roller 77 rotates in the reverse direction, so that the second sheet S2 carried out to the discharge unit path 240 is discharged. However, it is conveyed toward the second path 82 with the rear end at the top, and is conveyed to the image forming unit 4 with the front and back sides reversed. Then, the second sheet S <b> 2 on which the image is formed again on both sides of the image forming unit 4 is discharged to the main body discharge tray 21 through the main body discharge path 71.

  As described above, in the laser printer 1 according to the present embodiment, when performing double-sided printing, the paper S printed on one side is temporarily sent to the paper discharge unit 200 without passing through the main body discharge roller 72 and then the image. Since the sheet S can be conveyed to the forming unit 4, the subsequent sheet S can be discharged to the main body discharge tray 21 by the main body discharge roller 72 immediately after the sheet S is sent to the discharge unit 200. As a result, the printing interval can be shortened as compared with the configuration in which the sheet S is once discharged by the main body discharge roller 72 and then drawn into the apparatus main body 2 and conveyed to the image forming unit 4.

  Further, if the configuration is such that the paper S is once discharged by the main body discharge roller 72 and then drawn into the apparatus main body 2, the paper S for which printing has not been completed will go out of the apparatus main body 2. However, there is a risk that the paper S will be taken out of the print job. However, in the present embodiment, the discharge unit-side discharge roller disposed at the uppermost position of the first discharge unit inner path 241 from the branch portion of the first path 81 (reconveying path 80) with the main body discharge path 71. Since the distance to 230 is equal to or longer than the length of the sheet S, the sheet S that has not been printed does not go out of the apparatus main body 2, and therefore the user takes the sheet S that has not been printed. Can be suppressed.

  In the case where the paper discharge unit 200 is not attached to the apparatus main body 2, the laser printer 1 is used with the cover 100 attached to the apparatus main body 2 as shown in FIG. Since the cover 100 covers the main body side communication port 23 from above while attached to the apparatus main body 2, it is possible to prevent dust from entering the apparatus main body 2 from the main body side communication port 23.

  When double-sided printing is executed by the laser printer 1 to which the cover 100 is attached, first, the flapper 75 swings forward to open the first path 81 and the first path of the main body discharge path 71. A portion downstream of the branching portion with 81 is closed. As a result, the sheet S on which an image is formed on one side by the image forming unit 4 is conveyed from the main body discharge path 71 to the first path 81. Then, the paper S conveyed to the first path 81 is carried out of the apparatus main body 2 through the main body side communication port 23 by the carry-out roller 77 that rotates forward. Then, the sheet S carried out of the apparatus main body 2 from the main body side communication port 23 is guided by the cover side guide 130 and conveyed forward.

  When the trailing edge of the sheet S passes through the main body discharge path 71, the carry-out roller 77 rotates in the reverse direction. As a result, the sheet S is conveyed toward the second path 82 with the trailing edge at the top, and is conveyed to the image forming unit 4 with the front and back sides reversed.

  As described above, even when the paper discharge unit 200 is not attached, the laser printer 1 according to the present embodiment passes the paper S printed on one side through the main body discharge roller 72 when performing double-sided printing. Instead, it can be reversed and conveyed to the image forming unit 4, so that the printing interval can be shortened.

  Further, since the cover 100 is provided with the cover side guide 130 for guiding the conveyance of the paper S, the paper S can be smoothly fed even if the cover 100 covers the upper side of the main body side communication port 23. Can be transported.

  In the present embodiment, the cover side guide 130 of the cover 100 and the paper discharge unit side guide 270 of the paper discharge unit 200 can both be inserted into the insertion portion 24 of the apparatus body 2. And the paper discharge unit side guide 270 are connected to the same part (main body side communication port 23) of the re-conveyance path 80, so that the cover side guide 130 and the paper discharge unit side guide 270 are connected to the re-conveyance path 80 at different parts. Compared to the configuration, the configuration can be simplified.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. About a concrete structure, it can change suitably in the range which does not deviate from the meaning of this invention. In the following description, components that are substantially the same as those in the above-described embodiment are given the same reference numerals, and descriptions thereof are omitted.

  In the embodiment, the re-transport path 80 (first path 81) is branched from the bottom 76A of the U-turn guide 76, but the configuration of the re-transport path is not limited to this. For example, as shown in FIG. 6, the re-conveying path 80 may be branched from the main body discharge path 71 at a position closer to the main body discharge tray 21 than the bottom 76 </ b> A of the U-turn guide 76. Even in this case, it is not necessary to make the first path 81 curved to the rear side so as to bypass the bottom portion 76A of the U-turn guide 76, as in the above-described embodiment, and it is directed toward the main body side communication port 23. Therefore, the apparatus main body 2 can be miniaturized.

  For example, as shown in FIG. 7, the re-conveying path 90 may be branched from the main body discharge path 71 at a position closer to the curl removal roller 42 than the bottom portion 78 </ b> A of the U-turn guide 78.

  Specifically, the U-turn guide 78 has a guide surface extending from the rear oblique upper side to the front oblique upper side of the curl removing roller 42. Further, a flapper 75 for switching the transport direction of the paper S is supported at the lower end of the U-turn guide 78 so as to be swingable so that the lower end moves back and forth. The tip of the flapper 75 is provided near the curl removal roller 42 and swings backward to guide the paper S conveyed by the curl removal roller 42 to the main body discharge path 71 and swing forward. By moving, the sheet S conveyed by the decurling roller 42 is guided to the re-conveying path 90.

  The re-transport path 90 is branched from the main body discharge path 71 and passes through the rear side of the U-turn guide 78 and extends upward, and the second path 92 branches from the first path 91 and extends vertically downward. And have.

  In this modification, the intermediate paper discharge roller 79 is disposed downstream of the flapper 75 in the conveyance direction of the paper S in the main body discharge path 71. That is, the flapper 75 is disposed between the curl removal roller 42 and the intermediate paper discharge roller 79 in this transport direction.

  In the embodiment, the second path 82 extends vertically downward from the first path 81, but the configuration of the second path 82 is not limited to this. For example, as shown in FIG. 8, the second path 82 may extend downward from the first path 81 so as to be inclined toward the image forming unit 4 side, that is, the front side. Even if the second path 82 is formed in this way, the apparatus main body 2 can be reduced in size as compared with the case where the second path is formed so as to protrude rearward, as in the above-described embodiment.

DESCRIPTION OF SYMBOLS 1 Laser printer 2 Apparatus main body 4 Image formation part 6 Fixing part 21 Main body discharge tray 23 Main body side communication opening 24 Insertion part 42 Curling roller 71 Main body discharge path 72 Main body discharge roller 73 Intermediate discharge roller 75 Flapper 76 U Turn guide 80 Re-conveying path 81 1st path 82 2nd path 100 Cover 110 1st guide part 120 2nd guide part 130 Cover side guide 200 Paper discharge unit 220 Option tray 240 Paper discharge unit path 270 Paper discharge unit side guide S Paper

Claims (10)

An apparatus body having a first paper discharge tray and an image forming unit;
A first paper discharge path for discharging the sheet carried out from the image forming unit to the first paper discharge tray;
A re-transport path that branches from the first paper discharge path and transports the sheet to the image forming unit again.
The apparatus main body can be attached with a paper discharge unit having a second paper discharge tray and a second paper discharge path for discharging the sheet to the second paper discharge tray.
The image forming apparatus, wherein the two paper discharge paths are connected to the re-transport path by attaching the paper discharge unit to the apparatus main body. The apparatus main body has an opening on the upper surface,
The re-conveying path includes a first path that branches from the first transport path and connects to the opening, and a second path that branches from the first path and extends toward the image forming unit. The image forming apparatus according to claim 1. It is detachable from the apparatus main body to which the paper discharge unit is not attached, and includes a cover that covers the opening from above in a state of being attached to the apparatus main body,
The image forming apparatus according to claim 2, wherein the cover includes a cover-side guide that guides a sheet discharged from the opening in a direction along an upper surface of the apparatus main body. The cover-side guide has a first guide portion that guides one surface of the sheet, and a second guide portion that guides the other surface of the sheet,
The apparatus main body has an insertion part into which the first guide part and the second guide part are inserted when the cover is attached to the apparatus main body. The image forming apparatus according to claim 3. The paper discharge unit has a paper discharge unit side guide constituting the second paper discharge path,
The image forming apparatus according to claim 4, wherein the paper discharge unit side guide is insertable into the insertion portion.   The image forming apparatus according to claim 2, wherein the second path extends vertically downward from the first path or tilted downward toward the image forming unit. The image forming unit includes a fixing unit, and a curl removing roller that corrects curling of the sheet discharged from the fixing unit,
A flapper that is disposed downstream of the curl removal roller in the sheet conveyance direction in the first sheet discharge path and switches the sheet conveyance direction at a branch portion between the first sheet discharge path and the re-conveyance path; The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. A paper discharge roller provided at a position facing the first paper discharge tray of the apparatus body;
An intermediate paper discharge roller provided between the curl removal roller and the paper discharge roller in the transport direction,
The image forming apparatus according to claim 7, wherein the flapper is provided between the curl removal roller and the intermediate paper discharge roller in the transport direction. The first paper discharge tray is provided on the image forming unit,
The first paper discharge path has a U-turn guide configured to U-turn the sheet conveyed away from the image forming unit toward the first paper discharge tray,
The image forming apparatus according to claim 1, wherein the re-conveying path is branched from a bottom portion of the U-turn guide. The first paper discharge tray is provided on the image forming unit,
The first paper discharge path has a U-turn guide configured to U-turn the sheet conveyed away from the image forming unit toward the first paper discharge tray,
9. The re-conveying path is branched from the first sheet discharging path at a position closer to the first sheet discharging tray than the bottom portion of the U-turn guide. 2. The image forming apparatus according to item 1.

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