JP6394245B2 - Image forming apparatus - Google Patents

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 object, an image forming apparatus according to the present invention includes an apparatus main body having a first paper discharge tray and an image forming unit, a main body transport path for transporting a sheet carried out from the image forming unit, and a main body transport path And a main body re-conveying path that branches from the main body conveying path and conveys 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 sheets to the second paper discharge tray.
The image forming apparatus is configured such that the second paper discharge path is connected to the first paper discharge path when the paper discharge unit is attached to the apparatus main body.

  According to the image forming apparatus configured as described above, when printing on both sides of the sheet, after the sheet is sent to the main body re-transport path, the subsequent sheet is immediately transferred to the first discharge path or the second discharge path. It can be conveyed to the path and discharged to the first discharge tray or the second discharge tray. Accordingly, the interval between the conveyed sheets can be shortened as compared with the configuration in which the sheet is once exposed to the first discharge tray and then pulled in, so that the time until the end of printing can be shortened.

In the image forming apparatus described above, the paper discharge unit may have a paper discharge unit re-conveying path.
In this case, the image forming apparatus may be configured such that the paper discharge unit re-transport path is connected to the main body re-transport path when the paper discharge unit is attached to the apparatus main body.

  According to this, since the re-conveyed sheet is sent into the paper discharge unit, exposure to the outside can be reduced. Therefore, it is possible to prevent the user from accidentally taking this sheet by exposing the sheet being re-conveyed to the outside.

  In the image forming apparatus described above, it is desirable that the paper discharge unit re-conveyance path is provided so as to extend along the second paper discharge path.

  According to this, the enlargement of the paper discharge unit can be suppressed.

  In the image forming apparatus described above, when the first paper discharge tray is provided above the image forming unit, the conveyance path formed by the main body conveyance path and the first paper discharge path is separated from the image forming unit. After extending, it has a U-shape that makes a U-turn toward the first paper discharge tray, and the second paper discharge path is a U-shaped bottom of the conveyance path formed by the main body conveyance path and the first paper discharge path. It can be provided so as to be connected to the first conveyance path on the downstream side in the sheet conveyance direction from the portion.

  In this case, the image forming apparatus includes a guide unit that forms a part of the first paper discharge path outside the U-shape of the transport path formed by the main body transport path and the first paper discharge path. A guide in which a communication port through which a sheet can pass is formed at a position where the two paper discharge paths are connected, and a flapper that opens and closes the communication port and switches the sheet conveyance direction.

  In the image forming apparatus described above, the main body re-transport path is a U of the transport path formed by the main body transport path and the first paper discharge path from the main body transport path in a state where the paper discharge unit is not attached to the apparatus main body. A temporary discharge path formed in a U-shape that extends toward the first discharge tray and then U-turns toward the first discharge tray. It can be configured to connect to a temporary discharge path on the upstream side in the transport direction.

  In the image forming apparatus described above, the flapper closes the communication port and guides the sheet conveyed through the first paper discharge path to the first paper discharge tray side, and opens the communication port and the first paper discharge route. The flapper positioned at the first position is movably provided at a second position for guiding the sheet conveyed to the communication port. Can be configured.

  According to the present invention, when printing on both sides of a sheet, after the sheet is sent to the main body re-conveying path, the subsequent sheet is immediately conveyed to the first paper discharge path or the second paper discharge path to be the first. Paper can be discharged to a paper discharge tray or a second paper 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. FIG. 5 is an enlarged view showing a conveyance unit, and is a diagram showing a state where a sheet is conveyed to a main body re-conveyance path. FIG. 6 is an enlarged view showing a transport unit, and is a diagram showing a state where a second sheet is being transported to a first paper discharge path. FIG. 5 is an enlarged view showing a transport unit when a cover is attached to the apparatus main body, and is a diagram showing a state where a sheet is transported to a main body re-transport path. FIG. 6 is an enlarged view showing a transport unit when a cover is attached to the apparatus main body, and is a diagram showing a state in which a second sheet is being transported to a first paper discharge path. It is a figure which shows schematic structure of the laser printer which concerns on the reference example to which the paper discharge unit was attached. It is an enlarged view showing a paper discharge route and a re-transport route in a reference example. It is a figure which shows the laser printer which concerns on the reference example with which the cover was attached. It is a figure explaining operation | movement of the laser printer of a reference example 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. It is a figure explaining operation | movement of the laser printer of a reference example during double-sided printing execution, Comprising: It is a figure which shows the state which conveyed the 2nd sheet | seat to the path | route in a paper discharge unit. It is an enlarged view showing a paper discharge route and a re-transport route in a first modification of the reference example. It is an enlarged view showing a paper discharge route and a re-transport route in a second modification of the reference example. It is an enlarged view showing a paper discharge route and a re-transport route in a third modification of the reference 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 left side in FIG. 1 is “front (front)”, the right side is “rear (back)”, the front side is “right”, and the back side is “left”. 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 conveyance unit 300 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 sheet feed path 33 for conveying the sheet S supplied from the sheet 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, and a fixing unit 6. Yes.

  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 unit 5A and a developing cartridge 5B that can be attached to and detached from the drum unit 5A.

  The drum unit 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 has a supply roller, a layer thickness regulating blade, an agitator and the like (not shown) in addition to the developing roller 54 that supplies the toner contained therein to the photosensitive drum 51.

  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 mainly includes a heating roller 61 that is disposed behind the process cartridge 5 and has a heating element, and a pressure roller 62 that holds the paper S between the heating roller 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 roller 61 and the pressure roller 62.

  The transport unit 300 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 300 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, the configuration of the transport unit 300 will be described in detail.
As shown in FIG. 2, the transport unit 300 branches from the main body transport path 310 for transporting the paper S carried out from the fixing unit 6 and the main body transport path 310, and transports the paper S to the main body discharge tray 21. 1 discharge path 320 and a main body re-transport path 330 that branches from the main body transport path 310 and transports the paper S to the image forming unit 4 again. Further, the transport unit 300 includes a guide 350 that guides the transported paper S, and a first flapper 360 and a second flapper 370 for switching the transport path of the paper S.

  The main body conveyance path 310 extends obliquely upward from the rear of the fixing unit 6. In the main body conveyance path 310, a first conveyance roller 341 for conveying the paper S is provided.

  The first paper discharge path 320 extends obliquely upward from the upper end of the main body conveyance path 310. Thus, the conveyance path formed by the main body conveyance path 310 and the first paper discharge path 320 has a U shape that extends away from the fixing unit 6 and then makes a U-turn toward the main body discharge tray 21. ing. The first paper discharge path 320 is provided with a second transport roller 342 and a main body paper discharge roller 343.

  The second transport roller 342 is a roller for transporting the paper S sent from the main body transport path 310 to the first paper discharge path 320. In the present embodiment, the second transport roller 342 is formed by the main body transport path 310 and the first paper discharge path 320. It is provided in the bottom part of the U shape of the conveyance path.

  The main body discharge roller 343 is a roller disposed at the exit of the first discharge path 320 and is provided to discharge the paper S to the main body discharge tray 21.

  The main body re-transport path 330 extends upward from the main body transport path 310 through the rear side of the first paper discharge path 320 and branches from the apparatus main body 2 to the outside of the apparatus main body 2 and the first path 331 branches off the image. A second path 332 extending toward the formation portion 4.

  Here, the apparatus main body 2 has an opening 25 at the rear part of the upper surface. The opening 25 is formed so that the paper S can pass therethrough. The opening 25 is provided from a position overlapping the first paper discharge path 320 to a position behind the first paper discharge path 320 when viewed in the vertical direction. The first path 331 of the main body re-conveying path 330 has an upper end connected to the opening 25.

A third transport roller 344 is provided in the first path 331.
The third transport roller 344 is configured to be rotatable in both forward and reverse directions, so that the paper S transported through the first path 331 is transported from the opening 25 to the outside of the apparatus main body 2 and rotated in reverse. Thus, the sheet S is conveyed so as to be drawn into the apparatus main body 2.

  The second path 332 extends downward from the first path 331 and then bends forward to extend between the image forming unit 4 and the paper feed cassette 31 as shown in FIG. It extends further below 34 and joins the paper feed path 33 on the front side of the pair of registration rollers 34.

  Returning to FIG. 2, the guide 350 is a member constituting part of the first paper discharge path 320 and the main body re-transport path 330. The guide 350 is outside the U-shape of the conveyance path formed by the main body conveyance path 310 and the first paper discharge path 320 and between the first paper discharge path 320 and the first path 331 of the main body re-conveyance path 330. Is provided. The guide 350 extends in a curved manner so as to go forward as it goes upward from the rear obliquely upward of the first conveying roller 341, and is connected to the front edge of the opening 25.

  A first surface 351 as an example of a guide portion facing the front side of the guide 350 is a rear side of the sheet S (see FIG. 1) conveyed through the first paper discharge path 320, that is, the main body conveyance path 310 and the first paper discharge. It is arranged outside the U-shape of the transport path formed by the path 320, forms a part of the first paper discharge path 320, and guides the paper S transported through the first paper discharge path 320. Yes. The second surface 352 facing the rear side of the guide 350 is disposed on the front side of the sheet S conveyed through the first path 331 of the main body reconveying path 330 and guides the sheet S conveyed along the first path 331. It is like that.

  The guide 350 is a communication port 353 penetrating in the vertical direction at a portion located downstream of the U-shaped bottom portion of the conveyance path formed by the main body conveyance path 310 and the first paper discharge path 320 in the conveyance direction of the paper S. Is provided. The communication port 353 is formed in a size that allows the sheet S to pass therethrough. As a result, the first paper discharge path 320 is connected to the opening 25 through the communication port 353.

  The first flapper 360 is a member that switches the transport direction of the paper S at a branching portion between the main body transport path 310 and the main body re-transport path 330 (first path 331), and is swingably provided on the apparatus main body 2. When the first flapper 360 guides the paper S carried out from the fixing unit 6 to the first paper discharge path 320, the first flapper 360 becomes a paper discharge position (see a two-dot chain line) that closes the main body re-transport path 330. When the paper S transported from the paper is guided to the main body re-conveying path 330, the main body re-conveying path 330 is swung forward from the paper discharge position to open the main body re-conveying path 330 and the first paper discharge path 320 is closed. (See the solid line).

  The second flapper 370 is an example of a flapper that opens and closes the communication port 353 and switches the transport direction of the paper S transported through the first paper discharge path 320. The second flapper 370 is supported such that the upper end of the second flapper 370 can swing on the apparatus main body 2 on the front side of the communication port 353 and the lower end swings back and forth. The second flapper 370 closes the communication port 353 and opens the communication port 353 at a first position (see the solid line) for guiding the sheet S conveyed through the first paper discharge path 320 to the main body discharge tray 21 side. It is provided so as to be movable to a second position (refer to a two-dot chain line) for guiding the paper S conveyed through the first paper discharge path 320 to the communication port 353.

  The second flapper 370 positioned at the first position has a surface facing the first path 331 provided at a position substantially along the second surface 352 of the guide 350 to form the first path 331.

  With respect to the transport unit 300 configured as described above, the paper discharge unit 200 attaches the paper discharge unit 200 to the apparatus main body 2, so that the paper discharge unit path 240 passes through the communication port 353 to the first paper discharge path 320. It is configured to be connected. That is, with the paper discharge unit 200 attached to the apparatus main body 2, the paper discharge unit path 240 is downstream of the U-shaped bottom portions of the main body transfer path 310 and the first paper discharge path 320 in the transport direction of the paper S. It is connected to the first paper discharge path 320 on the side.

  The paper discharge unit 200 has a paper discharge unit re-transport path 290 that is connected to the first path 331 of the main body re-transport path 330 when the paper discharge unit 200 is attached to the apparatus main body 2. The paper discharge unit re-transport path 290 extends in the vertical direction along a portion of the paper discharge unit path 240 that extends in the vertical direction of the first paper discharge unit path 241 (see also FIG. 1). The paper discharge unit re-transport path 290 is the rear side of the communication port 353 in a state where the paper discharge unit 200 is attached to the apparatus main body 2, that is, the third transport roller 344 is rotating forward. The first path 331 is connected to the first path 331 (a temporary discharge path 333 to be described later) on the upstream side in the conveyance direction of the sheet S in the first path 331.

  Specifically, the paper discharge unit 200 includes a partition 280 between the paper discharge unit inner path 240 and the paper discharge unit re-transport path 290. The partition 280 extends in the vertical direction, and guides the paper S that is transported through the paper discharge unit path 240 on the front side, and guides the paper S that is transported on the paper discharge unit re-transport path 290 on the back side. It is like that.

  When the paper discharge unit 200 is attached to the apparatus main body 2, the lower end portion of the partition 280 enters the opening 25 of the apparatus main body 2, and faces the guide 350 behind the communication port 353. As a result, the paper S sent from the first paper discharge path 320 to the communication port 353 is conveyed to the paper discharge unit internal path 240, and the paper S conveyed through the main body reconveyance path 330 to the paper discharge unit reconveyance path 290. Be transported.

  Further, the discharge unit re-transport path 290 has a length from a branch portion of the main body re-transport path 330 to the main body transport path 310 to the upper end of the discharge unit re-transport path 290, which is described later. It is formed so as to be longer than the temporary discharge path 333.

  As shown in FIG. 4, the laser printer 1 includes a cover 400 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 400 is configured to cover the opening 25 from above while being attached to the apparatus main body 2. The cover 400 is configured to guide the conveyance of the paper S carried out from the opening 25.

  Specifically, the cover 400 has a guide surface 410 that extends upward from the rear end edge of the opening 25 and then extends forward from the opening 25 to the front side of the opening 25 in a state of being attached to the apparatus main body 2. The guide surface 410 and the upper wall 26 of the apparatus body 2 are configured to form an in-cover path 420.

  The cover 400 is attached to the apparatus main body 2 when the paper discharge unit 200 is not attached to the apparatus main body 2, so that the main body re-conveyance path 330 is configured by the first path 331 and the in-cover path 420. A temporary discharge path 333 is formed. The temporary discharge path 333 extends along the first discharge path 320 outside the first discharge path 320. More specifically, the temporary discharge path 333 extends from the main body transfer path 310 toward the outside of the U-shape of the transfer path formed by the main body transfer path 310 and the first discharge path 320, and then the main body discharge tray. It is formed in a U-shape that U-turns toward the 21st side, that is, the front side.

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 main body discharge tray 21, the first flapper 360 swings backward and moves to the discharge position. At the same time, the second flapper 370 swings backward and moves to the first position. As a result, the first paper discharge path 320 is opened, and the main body re-transport path 330 and the communication port 353 are closed. When the sheet S is unloaded from the image forming unit 4 in this state, the sheet S is transported from the main body transport path 310 to the first discharge path 320 and discharged to the main body discharge tray 21 by the main body discharge roller 343. Is done.

  When the sheet S on which an image is formed by the image forming unit 4 is discharged to the option tray 220 of the discharge unit 200, the first flapper 360 swings backward to move to the discharge position, and The entrance of one paper discharge path 320 is opened, and the main body re-transport path 330 is closed. Further, the second flapper 370 swings forward to move to the second position, the communication port 353 is opened, and the downstream side in the transport direction of the sheet S from the communication port 353 of the first paper discharge path 320 is. Closed. When the sheet S is unloaded from the image forming unit 4 in this state, the sheet S is transported from the main body transport path 310 to the first sheet discharge path 320, passes through the communication port 353, and is discharged from the sheet discharge unit 200. It is carried out to the inner path 240.

  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 with the paper discharge unit 200 attached to the apparatus main body 2, first the first flapper 360 first swings and moves to the re-conveying position as shown in FIG. As a result, the first paper discharge path 320 is closed and the main body re-transport path 330 is opened. As a result, the first sheet S1 on which the image is formed on the first surface by the image forming unit 4 is conveyed from the main body conveyance path 310 to the first path 331 of the main body re-conveyance path 330. Then, the first sheet S1 transported to the first path 331 is carried out to the paper discharge unit re-transport path 290 through the opening 25 by the third transport roller 344 that rotates forward.

  As shown in FIG. 3, when the trailing edge of the first sheet S1 conveyed to the main body reconveying path 330 passes through the main body conveying path 310, the first flapper 360 swings backward and moves to the discharge position. . As a result, when viewed from the main body transport path 310 side, the first paper discharge path 320 is opened and the entrance of the main body re-transport path 330 is closed.

  Then, when the rear end of the first sheet S1 conveyed to the main body reconveying path 330 reaches the branch portion of the first path 331 and the second path 332, the third conveying roller 344 rotates in the reverse direction. As a result, the first sheet S1 is conveyed toward the second path 332 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, after the rear end of the first sheet S1 passes through the main body conveyance path 310 and the first flapper 360 moves to the discharge position, the second sheet S2 is unloaded from the fixing unit 6. The second sheet S2 is transported from the main body transport path 310 to the first paper discharge path 320, and is discharged to the main body paper discharge tray 21 or the option tray 220 of the paper discharge unit 200.

  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 sent to the main body re-transport path 330 without passing through the first paper discharge path 320. Since the sheet S can be transported to the forming unit 4, after the sheet S is sent to the main body re-transport path 330, the subsequent sheet S is immediately sent to the first paper discharge path 320 to be sent to the main body paper discharge tray 21 and the paper discharge unit 200. Can be discharged to the optional tray 220. This makes it possible to shorten the printing interval as compared with the configuration in which the sheet S is once exposed by the main body discharge roller 343 and then drawn into the apparatus main body 2 and conveyed to the image forming unit 4.

  In the laser printer 1 according to the present embodiment, the sheet S conveyed from the opening 25 to the outside of the apparatus main body 2 by the main body re-conveying path 330 is conveyed to the paper discharge unit re-conveying path 290 of the paper discharge unit 200. It is possible to reduce a portion where the paper S that has not been printed is exposed. Thereby, it is possible to suppress the user from taking the paper S that has not been printed.

  Even if the paper discharge unit 200 is provided with the paper discharge unit re-transport path 290 in addition to the paper discharge unit internal path 240, the paper discharge unit re-transport path 290 extends along the paper discharge unit internal path 240. Therefore, it is possible to prevent the paper discharge unit 200 from becoming large.

  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 400 attached to the apparatus main body 2 as shown in FIG. Since the cover 400 covers the opening 25 of the apparatus main body 2 from above while attached to the apparatus main body 2, dust can be prevented from entering the apparatus main body 2 from the opening 25.

  When double-sided printing is executed by the laser printer 1 with the cover 400 attached to the apparatus main body 2, the first flapper 360 first swings forward and moves to the re-transport position. As a result, the first paper discharge path 320 is closed and the main body re-transport path 330 is opened. Further, the second flapper 370 moves to the first position, closes the communication port 353 and forms the temporary discharge path 333. In this state, the first sheet S1 on which the image is formed on the first surface by the image forming unit 4 is transported from the main body transport path 310 to the temporary discharge path 333 of the main body re-transport path 330. The first sheet S1 transported to the temporary discharge path 333 is transported by the third transport roller 344 that rotates in the forward direction, and is guided forward by the guide surface 410 of the cover 400.

  Then, as shown in FIG. 5, when the trailing edge of the first sheet S1 passes through the main body conveyance path 310, the first flapper 360 swings backward and moves to the paper discharge position. As a result, when viewed from the main body transport path 310 side, the first paper discharge path 320 is opened and the entrance of the main body re-transport path 330 is closed.

  When the rear end of the first sheet S1 conveyed to the main body reconveying path 330 reaches the branching portion of the temporary discharge path 333 (first path 331) and the second path 332, the third conveying roller 344 is moved. Reverse rotation. As a result, the first sheet S1 is conveyed toward the second path 332 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, after the rear end of the first sheet S1 passes through the main body conveyance path 310 and the first flapper 360 moves to the discharge position, the second sheet S2 is unloaded from the fixing unit 6. The second sheet S2 is transported from the main body transport path 310 to the first paper discharge path 320 and discharged to the main body discharge tray 21.

  As described above, even when the paper discharge unit 200 is not attached to the apparatus main body 2, the laser printer 1 uses the first paper discharge for the paper S printed on the first surface when performing double-sided printing. Since the succeeding paper S can be sent to the first paper discharge path 320 immediately after being sent to the main body re-transport path 330 without passing through the path 320, the printing interval can be shortened.

  Further, since the cover 400 is provided with a guide surface 410 for guiding the conveyance of the paper S, the paper S can be smoothly fed even when the cover 400 covers the upper portion of the opening 25 of the apparatus main body 2. Can be transported.

  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 embodiment, the paper discharge unit 200 includes the paper discharge unit re-transport path 290, and the paper discharge unit re-transport path 290 is connected to the main body re-transport path 330 with the paper discharge unit 200 attached to the apparatus main body 2. However, the configuration of the laser printer is not limited to this. For example, after the paper discharge unit 200 does not include the paper discharge unit re-transport path 290 and the paper S sent from the main body transport path 310 to the main body re-transport path 330 is once discharged out of the apparatus main body 2 from the opening 25, The third conveying roller 344 may be configured to be drawn into the apparatus main body 2 by rotating in the reverse direction.

  Hereinafter, a laser printer 1A that has the same configuration as the present invention but can obtain the same effect as the present invention will be introduced as a reference example. 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 following description, the direction will be described with reference to the user who uses the laser printer 1A. That is, the right side in FIG. 6 is “front (front)”, the left side is “rear (back)”, the front side is “left”, and the back side is “right”. In addition, the vertical direction in FIG.

  As shown in FIG. 6, the laser printer 1 </ b> A can form images on both sides of the paper S, and the laser printer 1 </ b> A can attach a paper discharge unit 200 as an optional component on the upper part of the apparatus main body 2. .

  The apparatus main body 2 mainly includes a paper feeding unit 3, an image forming unit 4, and a conveying unit 7 inside. Further, the apparatus main body 2 has a main body discharge tray 21 on which the paper S on which an image is formed is placed on the upper surface. The main body discharge tray 21 is provided on the image forming unit 4.

  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 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 a plurality of option trays 220 arranged vertically, and is configured to be able to distribute and discharge the paper S sent from the apparatus main body 2 to each option tray 220.

Next, a detailed configuration of the transport unit 7 will be described.
As shown in FIG. 7, the transport unit 7 transports the sheet S in the main body discharge path 71, the main body discharge roller 72, the intermediate discharge roller 73, the re-transport path 80, and the re-transport path 80. A plurality of pairs of re-conveying rollers 74 (see FIG. 6), a flapper 75 configured to swing back and forth, and a carry-out roller 77 are mainly provided.

  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 and an insertion portion 24 at the rear part 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 this reference example, the bottom portion 76A of the U-turn guide 76 is provided in 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 that is

  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. 6).

  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. 6, 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. 7, 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 this reference example, 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. 8, the laser printer 1 </ b> A 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 1A will be described.
As shown in FIG. 6, when 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 1A 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. As shown in FIG. 10, the second sheet S <b> 2 passes through the first path 81 from the main body discharge path 71 through the first path 81 as in the first sheet S <b> 1. 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 1A according to the present reference example, 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 paper discharge roller 72, and then the image is printed. 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 this reference example, 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 (reconveyance 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.

  When the paper discharge unit 200 is not attached to the apparatus main body 2, the laser printer 1A 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 1A 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 1A in the present reference example 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 this reference example, 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 main 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.

  In the reference example described above, the re-transport path 80 (first path 81) branches off from the bottom 76A of the U-turn guide 76. For example, as shown in FIG. The main body discharge path 71 may branch off at a position closer to the main body discharge tray 21 than the bottom 76A of 76. Even in this case, similarly to the above-described reference example, 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, The apparatus main body 2 can be downsized because it can be extended straight.

  For example, as shown in FIG. 12, 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 reference example described above, 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. 13, 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 to the rear side as in the above-described reference example. .

DESCRIPTION OF SYMBOLS 1 Laser printer 2 Apparatus main body 4 Image forming part 21 Main body paper discharge tray 200 Paper discharge unit 220 Option tray 240 Path in paper discharge unit 290 Paper discharge unit re-transport path 310 Main body transport path 320 First paper discharge path 330 333 Temporary discharge path 350 Guide 353 Communication port 360 First flapper S Paper

Claims (7)

An apparatus main body having a first paper discharge tray and an image forming unit;
A main body conveyance path for conveying the sheet carried out from the image forming unit;
A first paper discharge path that branches from the main body conveyance path and conveys the sheet to the first paper discharge tray;
A main body re-conveying path that branches off from the main body conveying path and conveys the sheet to the image forming unit again.
The apparatus main body is attachable to the discharge unit and a second discharge path and the discharge unit re-feeding path for discharging the sheet to the second sheet discharge tray and said second tray,
Wherein when the sheet discharge unit mounted on the apparatus main body, the second discharge path is Rutotomoni connected to the first discharge path, the discharge unit re-conveying path leading to the main re-transport path,
The main body re-conveying path is a U-shape of a conveying path formed by the main body conveying path and the first paper discharging path from the main body conveying path in a state where the paper discharge unit is not attached to the apparatus main body. A temporary discharge path formed in a U-shape that extends outward and then U-turns toward the first discharge tray;
The paper discharge unit has a partition provided between the second paper discharge path and the paper discharge unit re-transport path,
The lower end of the partition is disposed below the upper surface of the apparatus main body when the paper discharge unit is attached to the apparatus main body. The sheet discharge unit re-transport path, the image forming apparatus according to claim 1, characterized in that extending along the second discharge path. The first paper discharge tray is provided above the image forming unit,
The conveyance path formed by the main body conveyance path and the first paper discharge path has a U-shape that extends away from the image forming unit and then makes a U-turn toward the first paper discharge tray.
The second sheet discharge path is connected to the first sheet discharge path on the downstream side in the sheet conveyance direction from the U-shaped bottom portion of the conveyance path formed by the main body conveyance path and the first sheet discharge path. The image forming apparatus according to claim 1 , wherein the image forming apparatus is an image forming apparatus. There is a guide part that forms a part of the first paper discharge path outside the U-shape of the transport path formed by the main body transport path and the first paper discharge path, and the second paper discharge path is connected. A guide formed with a communication port through which the sheet can pass;
The image forming apparatus according to claim 3 , further comprising: a flapper that opens and closes the communication port and switches a sheet conveyance direction. The flapper closes the communication port and guides a sheet conveyed through the first paper discharge path to the first paper discharge tray, and opens the communication port to open the first paper discharge path. Provided so as to be movable to a second position for guiding the conveyed sheet to the communication port;
The image forming apparatus according to claim 4 , wherein the flapper located at the first position forms part of the temporary discharge path in a state where the discharge unit is not attached to the apparatus main body. apparatus. An apparatus main body having a first paper discharge tray and an image forming unit;
A main body conveyance path for conveying the sheet carried out from the image forming unit;
A first paper discharge path that branches off from the main body conveyance path and conveys the sheet to the first paper discharge tray;
A main body re-conveying path that branches off from the main body conveying path and conveys the sheet to the image forming unit again.
The apparatus main body is attachable to the discharge unit and a second discharge path and the discharge unit re-feeding path for discharging the sheet to the second sheet discharge tray and said second tray,
The main body re-conveying path is a U-shape of a conveying path formed by the main body conveying path and the first paper discharging path from the main body conveying path in a state where the paper discharge unit is not attached to the apparatus main body. A temporary discharge path formed in a U-shape that extends outward and then U-turns toward the first discharge tray;
In the upper part of the apparatus main body, when the paper discharge unit is attached to the apparatus main body, a first opening that connects the second paper discharge path and the first paper discharge path, and the paper discharge unit re-conveyance An image forming apparatus comprising: a second opening that connects the path and the main body re-transport path . The paper discharge unit has a partition provided between the second paper discharge path and the paper discharge unit re-transport path,
The image forming apparatus according to claim 6, wherein a lower end portion of the partition enters the apparatus main body to form the first opening and the second opening.

Images