JP2006076667A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device capable of performing face down delivery or face up delivery when forming images on both faces of a paper sheet and forming image on one face of a paper sheet to realize stable paper conveyance. <P>SOLUTION: The paper sheet P coming out of a fixation part 60 is fed to a pair of face down delivery rollers 73 by a paper delivery roller 21 and a face down conveyance roller 23. When printing on both faces of the paper sheet, the paper sheet P switched back by the pair of face down delivery rollers 73 is fed to a paper conveyance path 74 for inversion by a paper conveyance roller 21 and a paper conveyance roller 24 for inversion. When opening a face up tray 13, a paper guide 22 guides the paper sheet P between the paper conveyance roller 21 inverting the direction of rotation and the paper conveyance roller 24 for inversion moving below it, and the paper sheet P is delivered to a face up tray 21. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus capable of forming images on both sides of a sheet and capable of face-down discharge or face-up discharge when forming an image on one side of a sheet.

  2. Description of the Related Art Image forming apparatuses are widely used in which an image is formed on both sides of a sheet by conveying a sheet having an image formed on one side to an image forming unit again.

  On the other hand, in an image forming apparatus that forms an image only on one side of a sheet, a face that is ejected with the side on which the image of the sheet is formed facing down in order to ensure that the discharged sheets are in the document order. Down discharge is common. However, in face-down discharge, when a sheet is transported, it often passes through a path with a large curvature, and when a thick sheet is used, the sheet may be wrinkled. In order to cope with this, an image forming apparatus that makes the path through which a sheet passes straight and enables face-up discharge that discharges with the surface on which the image is formed upward is also widely used.

An image forming apparatus having both the image forming function on both sides of the paper and the face-up discharge function has been proposed in Patent Document 1.
Japanese Patent Application Laid-Open No. 2002-104707 (pages 5 to 7, FIGS. 1 and 2)

  However, the image forming apparatus proposed in Patent Document 1 performs both face-down paper discharge and face-up paper discharge with a pair of transport rollers. In order to perform face-up paper discharge, the paper transport direction of this pair of transport rollers is substantially horizontal. Therefore, it is necessary to prevent the sheet from being bent in the paper transport path for face-down paper discharge directed upward, and the paper transport path has a certain horizontal section or a curved section with a large curvature radius from the exit of the transport roller. As a result, the horizontal dimension of the image forming apparatus is increased.

  Further, when images are formed on both sides of a sheet, in a reversing path in which a sheet having an image formed on one side is conveyed, between the discharge roller for switching back the sheet and the pair of reversing sheet conveying rollers. There are no rollers to support and transport the paper. For this reason, a short sheet is not supported by the discharge roller or the pair of reverse sheet transport rollers in the reverse path, and may not be transported well.

  Therefore, in the present invention, in an image forming apparatus capable of forming an image on both sides of a sheet and capable of face-down discharge or face-up discharge when forming an image on one side of the sheet, 1 Provided is an image forming apparatus capable of reducing the horizontal dimension of the apparatus with a simple configuration comprising two rollers and two rollers in contact therewith, and capable of stably transporting even a short sheet. For the purpose.

  (1) In order to achieve the above object, an image forming apparatus according to the present invention includes a main body, an image forming section and a fixing section provided in the main body, and paper provided downstream of the fixing section in the paper transport direction. A conveying roller, a face-down conveying roller rotated in contact with the sheet conveying roller, and the fixing unit for guiding the sheet sent from the fixing unit between the sheet conveying roller and the face-down conveying roller. A sheet guide provided between the sheet conveying roller and the sheet conveying roller, and a face-down tray provided on the upper surface of the main body to receive the sheet sent by the sheet conveying roller and the face-down conveying roller in a face-down state. The face-down tray that ejects the paper onto the face-down tray or switches back the paper to form an image on both sides. In order to send out a sheet whose conveyance direction has been switched by the roller pair and the face-down discharge roller pair to the lower side of the image forming unit and the fixing unit, the sheet conveyance roller is brought into contact with the sheet conveyance roller on the side opposite to the face-down conveyance roller. In the image forming apparatus provided with a reversing paper conveyance roller that is rotated and rotated, a face-up tray provided on the side surface of the main body so as to be openable and closable around a lower end, and the paper conveyance roller in conjunction with opening and closing of the face-up tray A rotation direction reversing mechanism for switching the rotation direction of the paper, and the reversing paper transport roller is provided on the face-up tray and is displaced about the axis of the paper transport roller simultaneously with the opening of the face-up tray. When the face-up tray is opened, the paper guide is The paper transport roller is displaced to a posture for guiding it between the paper transport roller and the displaced reverse paper transport roller, and the rotational direction of the paper transport roller is switched by the rotational direction reversing mechanism. The sheet fed from the fixing unit together with the conveying roller is discharged onto the face-up tray.

  According to this configuration, when face-down discharge is performed, the sheet guided and fed from the fixing unit to the sheet guide is sent out toward the face-down tray by the sheet transport roller and the face-down transport roller, and the face-down discharge roller pair To discharge the paper onto the face-down tray. The direction in which the paper transport roller and the face-down transport roller feed the paper is obliquely upward, so that the subsequent paper transport path can be made almost vertical, such as a horizontal section or an outer curvature radius as in Patent Document 1. Since the curve section is unnecessary, the horizontal dimension of the apparatus can be reduced. Similarly, when forming images on both sides of the paper, the paper fed in the face-down tray direction is switched back by a pair of face-down discharge rollers, and the fixing unit is connected by a paper transport roller and a reverse paper transport roller. It is only necessary to feed it downward and transport it again to the image forming unit and the fixing unit to form an image on the surface where no image is formed. At this time, since there is a reverse sheet conveyance roller between the face-down discharge roller pair and below the fixing unit, even a short sheet can be reliably conveyed. For further face-up discharge, open the face-up tray to displace the reversing paper transport roller below the paper transport roller and place the paper guide in the nip formed by the paper transport roller and the reversing paper transport roller. The sheet is displaced to the guiding posture, and the rotation direction of the sheet conveying roller is reversed by the rotation direction reversing mechanism. As a result, the direction in which the paper transport roller and the reverse paper transport roller feed the paper is almost horizontal and the face-up tray direction, and the paper does not bend toward the face-down discharge roller by the paper guide, and the paper is reliably bent from the fixing unit. The sheet is discharged with the surface on which the image is formed on the up tray. In this way, a roller for face-down discharge and a roller for face-up discharge are provided by a roller that is applied with a driving force, two rollers in contact with the roller, and a rotation direction reversal mechanism that reverses the rotation direction of the roller. By separating the pair, the size of the apparatus is reduced, the paper is conveyed in the face-down tray direction, and the paper is stably conveyed below the fixing unit when images are formed on both sides of the paper. And transporting paper to the face-up tray.

  (2) Further, in the image forming apparatus having the above-described configuration, the rotation direction reversing mechanism includes a rotation direction reversing gear train composed of a plurality of gears rotatably attached to a gear base, and a starting gear is a motor. The gear base is attached to the main body so as to be rotatable about the rotation shaft of the starting gear, and the face-up tray is closed. Sometimes one of the gears constituting the rotational direction reversing gear train meshes with a roller driving gear attached to the shaft of the paper transport roller, and rotates in a direction to transport the paper to the face down tray toward the paper transport roller. When the face-up tray is opened, the gear base rotates and another rotation direction reversing gear train is connected to the roller drive gear. Ya engages, characterized in that transmits rotation in the direction of conveying the paper to said paper transport rollers to the face-up tray direction.

  According to this configuration, the rotation direction reversing mechanism can be realized with a simple configuration including a plurality of gears attached to the gear base that is interlocked with the opening and closing of the face-up tray. Further, since the driving gear only needs to rotate in a certain direction, the driving force can be taken out from a gear train such as an image forming unit or a fixing unit.

  According to the present invention, conveyance of a sheet relating to face-down discharge, face-up discharge, and image formation on both sides of the sheet is performed by one roller with a driving force, two rollers in contact with the roller, and rotation. This can be performed stably by the direction reversal mechanism. Further, the rotation direction reversing mechanism can be realized with a simple configuration including a plurality of gears attached to the main body and the gear base, and can be easily interlocked with the operation of the face-up tray by the biasing means and the engaging portion.

  An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic configuration diagram of a printer 10 that is an image forming apparatus according to an embodiment of the present invention, FIG. 2 is a partially enlarged view around a face-up tray 13 in a closed state, and FIG. 3 is a face-up tray 13 in an opened state. FIG. 4 is a schematic configuration diagram of the rotation direction reversing mechanism 30 with the face-up tray 13 closed, and FIG. 5 is a schematic configuration of the rotation direction reversing mechanism 30 with the face-up tray 13 open. FIG.

  The printer 10 is provided with a face-down tray 12 on the upper surface of the main body 11, a manual feed tray 44 that can be opened and closed on the right side, and a face-up tray 13 that can be opened and closed on the left side. In addition, a paper feeding unit 40 is provided on the right side of the main body 11 and a lower portion inside, and an image forming unit 50, a fixing unit 60, and a paper transporting direction switching unit 20 are formed in the middle middle of the main body 11, and an image forming unit is formed on the inner upper part. A control device 90 is provided for controlling the operation and the sheet transport operation.

  First, the paper feed unit 40 will be described. The paper feed unit 40 includes a paper feed cassette 41, a paper feed roller 42, a paper feed roller 43, and a manual paper feed tray 44 provided on the right side. The paper feed cassette 41 accommodates the paper P and is disposed at the lower part of the main body 11. The paper P stored in the paper feed cassette 41 is sent one by one to the paper transport path 71 by the paper feed roller 42 and transported by the transport roller pair group 72. The manual paper feed tray 44 is supported by the main body 11 so as to be opened and closed by a lower support shaft. By placing the paper P on the open manual paper feed tray 44 shown by a solid line in FIG. 1, the paper P is fed one by one by the paper feed roller 43, like the paper P in the paper feed cassette 41. It is sent out to the conveyance path 71 and conveyed by a plurality of conveyance roller pairs 72. One of the rollers constituting the conveying roller pair 72 may be a driven roller.

  Next, the image forming unit 50 will be described. The image forming unit 50 includes a photosensitive drum 51 and a charger 52, an optical scanning unit 53, a developing device 54, a transfer roller 55, and a cleaning device 56 disposed around the photosensitive drum 51. When a user issues an image formation instruction from an external computer (not shown) connected to the main body 11 directly or via a network, the control device 90 receives the instruction, and the photosensitive drum 51 rotates clockwise in FIG. First, the surface of the photosensitive drum 51 is uniformly charged by the charger 52. Next, the surface of the photosensitive drum 51 is irradiated with laser light from the optical scanning unit 53, and the charge corresponding to the portion of the image formed on the paper P or the portion other than the image is erased. An electrostatic latent image is formed on the surface. Then, the developing device 54 supplies toner to the electrostatic latent image on the photosensitive drum 51, and the electrostatic latent image is visualized.

  When the photosensitive drum 51 further rotates and the toner image comes to a position facing the transfer roller 55, the paper P is conveyed between the photosensitive drum 51 and the transfer roller 55 accordingly. At this time, the toner image on the photosensitive drum 51 is transferred onto the paper P by applying a voltage having a polarity opposite to the charging polarity of the toner to the transfer roller 55. Residual toner that has not been transferred onto the photosensitive drum 51 is removed from the photosensitive drum 51 by the cleaning device 56. On the other hand, the paper P onto which the toner image has been transferred is conveyed to a fixing unit 60 in which a fixing roller 61 and a pressure roller 62 are in pressure contact, and the toner image is heated and pressurized to be fixed on the paper P.

  Next, the paper transport direction switching unit 20 will be described. The paper transport direction switching unit 20 switches the transport direction of the paper P sent from the fixing unit 60 to the face-down tray direction or the face-up tray direction, and when forming images on both sides of the paper P, the paper P is sent to the reverse sheet conveyance path 74.

  The paper transport direction switching unit 20 includes a paper transport roller 21, a paper guide 22, a face-down transport roller 23, a reverse paper transport roller 24, and a rotation direction reversing mechanism 30. The rotation direction reversing mechanism 30 is not shown in FIGS. 1 and 2, but will be described later. The paper transport roller 21 is attached to the main body 11 so as to freely rotate, and a driving force from a motor (not shown) is transmitted through a rotation direction reversing mechanism 30 described later. Both ends of the sheet guide 22 are fixed to the side wall 13 a of the face-up tray 13, and the posture of the sheet guide 22 is displaced according to the opening / closing operation of the face-up tray 13. The face-down conveyance roller 23 is attached to the main body 11 so as to freely rotate, and is in contact with the sheet conveyance roller 21 to form a nip. The sheet conveying roller 21 and the face-down conveying roller 23 are provided in a direction for conveying the sheet obliquely upward. The reverse paper conveyance roller 24 is attached to the side wall 13a of the face-up tray 13 so as to freely rotate, and is in contact with the paper conveyance roller 21 to form a nip. The paper transport roller 21 and the reverse paper transport roller 24 are attached in a direction to transport the paper perpendicular to the floor surface.

  Here, a shaft hole 13 b is provided in the side wall 13 a of the face-up tray 13, and the shaft of the paper transport roller 21 is passed therethrough. Thus, the face-up tray 13 is supported by the shaft of the paper transport roller 21 so as to be opened and closed with the shaft hole 13b as an axis. As shown in FIG. 3, when the face-up tray 13 is opened, the reversing paper transport roller 24 is also displaced about the axis of the paper transport roller 21 accordingly. Therefore, the distance between the axis of the sheet conveying roller 21 and the axis of the reverse sheet conveying roller 24 is constant regardless of the opening angle of the face-up tray 13, and the nip state is the same. In addition, the sheet guide 22 is configured to guide the sheet P sent from the fixing unit 60 toward the nip formed by the sheet conveying roller 21 and the face-down conveying roller 23 when the face-up tray 13 is closed. When the up tray 13 is opened, the sheet P sent from the fixing unit 60 is displaced to a posture for guiding it toward the nip formed by the sheet conveying roller 21 and the reverse sheet conveying roller 24.

  The rotation direction reversing mechanism 30 is provided inside the wall surface on the back side of the main body 11, and is located on the other side of the sheet conveying roller 21 and the like in FIG. 1. 4 and 5 are views of the rotation direction reversing mechanism 30 as viewed from the front of the printer 10, that is, from the same direction as FIG.

  As shown in FIG. 4, the rotation direction reversing mechanism 30 includes a driving gear 31, a rotation direction changing gear train 32, a roller drive gear 33, and a gear base 34. The driving gear 31 is rotatably attached to the main body 11 and is driven so as to be rotated clockwise (in the direction of arrow A) in FIG. The rotation direction changing gear train 32 includes three rotation direction changing gears 32 a, 32 b, and 32 c that are rotatably attached to the gear base 35, and the rotation direction changing gear 32 a is engaged with the driving gear 31. The gear base 34 is attached to the main body 11 so as to be rotatable about the position where the shaft of the rotation direction changing gear 32a is attached. When the face-up tray 13 is closed, the rotation direction changing gear 32b is a roller driving gear. It is urged counterclockwise (in the direction of arrow B1) by an urging means (not shown) such as a torsion coil spring attached around the shaft so as to engage with the shaft 33. The roller drive gear 33 is attached to the shaft of the paper transport roller 21 so as to rotate together with the paper transport roller 21. When the face-up tray 13 is closed, the driving force from the driving gear 31 is transmitted to the roller driving gear 33 by the rotation direction changing gear train 32 and rotates counterclockwise (in the direction of the arrow C1). Also rotates counterclockwise.

  When the face-up tray 13 is opened, as shown in FIG. 5, the gear base 34 is rotated clockwise (in the direction of arrow B2) against the urging means by the engaging portion 13c provided in the face-up tray 13, and rotated. The direction change gear 32 b is disengaged from the roller drive gear 33, and the rotation direction change gear 32 c is engaged with the roller drive gear 33. As a result, the roller drive gear 33 rotates clockwise (in the direction of the arrow C2), whereby the sheet transport roller 21 also rotates clockwise as viewed from the front as shown in FIG.

  Next, a paper transport operation will be described. When an image is formed only on one side of the sheet and the sheet is discharged with the side down, that is, when the face-down discharge is performed, the face-down tray 13 is closed as shown in FIG. The sheet P is guided toward the nip formed by the sheet conveying roller 21 and the face-down conveying roller 23 by the sheet guide 22 and rotated counterclockwise in accordance with the sheet conveying roller 21 that rotates counterclockwise in FIGS. It is sent out in the direction of the face-down tray 12 by the rotating face-down conveying roller 23, and then discharged onto the face-down tray 12 by the face-down discharge roller pair 73. One of the rollers constituting the face-down discharge roller pair 73 may be a driven roller. Here, since the paper transporting roller 21 and the face-down transport roller 23 are transported obliquely upward, the paper transport path from the paper transport roller 21 and the face-down transport roller 23 to the face-down discharge roller pair 73 is almost the same. The printer 10 can be vertical, and the printer 10 can be downsized.

  When forming images on both sides of the paper, the paper P is transported to the face-down discharge roller pair 73 in the same manner as the face-down discharge, and the paper P is separated from the paper transport roller 21 and the face-down transport roller 23 and discharged face-down. When the state is supported only by the roller pair 73, the rotation direction of the face-down discharge roller pair 73 is reversed, and the paper P is transported toward the nip portion formed by the paper transport roller 21 and the reverse paper transport roller 24. . In FIG. 1 and FIG. 2, the sheet conveyance roller 21 rotating counterclockwise and the reversing sheet conveyance roller 24 rotating clockwise according to the rotation are conveyed to the reverse sheet conveyance path below the image forming unit 50 and the fixing unit 60. 74. The paper P is transported toward the paper transport path 71 by a plurality of transport roller pairs 75 in the reverse paper transport path 74, and then the surface on which no image is formed faces the photosensitive drum 51 again to the image forming unit 50. An image is formed on the surface on which the image has not been formed. Thereafter, the paper is discharged onto the face-down tray 12 in the same manner as the face-down discharge. Here, one of the rollers constituting the conveying roller pair 75 may be a driven roller.

  When an image is formed only on one side of the paper and is discharged with the side facing up, that is, when face-up discharge is performed, the face-up tray 13 is first opened by hand as shown in FIG. At the same time, as described above, the reverse sheet conveyance roller 24 is displaced about the axis of the sheet conveyance roller 21 and moves below the sheet conveyance roller 21 to convey the sheet P substantially horizontally toward the face-up tray 13. become. Further, the paper guide 22 is displaced to a posture for guiding the paper P sent from the fixing unit 60 between the paper transport roller 21 and the reverse paper transport roller 24. Further, as described above, the rotation direction of the sheet conveying roller 21 is switched by the rotation direction reversing mechanism 30 and the sheet conveying roller 21 rotates clockwise as viewed from the front. As a result, the paper P is sent from the fixing unit 60 between the paper transport roller 21 and the reverse paper transport roller 24 by the paper guide 22 and discharged onto the face-up tray 13. At this time, by placing the paper P on the manual paper feed tray 44 with the paper P opened, the path through which the paper P is conveyed becomes linear, and folds and wrinkles are less likely to occur during the conveyance.

  As described above, the sheet conveyance roller 21 to which the drive of the motor is transmitted, the two rollers of the face-down conveyance roller 23 and the reverse sheet conveyance roller 24 that are in contact therewith, and the rotation direction that reverses the rotation direction of the sheet conveyance roller 21 The configuration of the reversing mechanism 30 with a small number of parts enables the printer 10 to be miniaturized, and enables stable conveyance of paper for face-down ejection, face-up ejection, and image formation on both sides of the paper. . In particular, when forming an image on both sides of a sheet, the sheet conveying roller 21 and the reversing sheet conveying roller 24 are provided between the face-down discharge roller pair 73 and the reversing sheet conveying path 74, so that even a short sheet is stable. And can be transported.

  The present invention can be used for a printer, a copying machine, or a complex machine of these and an image forming apparatus such as a facsimile.

1 is a schematic configuration diagram of a printer that is an image forming apparatus according to an embodiment of the present invention. Partial enlarged view around the face-up tray with the printer closed Enlarged view of the area around the face-up tray with the printer open Schematic configuration diagram of rotation direction reversing mechanism with face-up tray closed Schematic configuration diagram of rotation direction reversing mechanism with face-up tray open

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Main body 12 Face down tray 13 Face up tray 13c Engagement part 20 Paper conveyance direction switching part 21 Paper conveyance roller 22 Paper guide 23 Face down conveyance roller 24 Reverse paper conveyance roller 30 Rotation direction inversion mechanism 31 Drive transmission gear 32 Rotation direction change Gear train 32a Rotation direction change gear 32b Rotation direction change gear 32c Rotation direction change gear 33 Roller drive gear 34 Gear base 60 Fixing portion 73 Face down discharge roller pair

Claims (2)

A main body, an image forming section and a fixing section provided in the main body, a paper transport roller provided downstream of the fixing section in the paper transport direction, and a face-down transport roller rotated in contact with the paper transport roller. A sheet guide provided between the fixing unit and the sheet conveying roller for guiding the sheet sent from the fixing unit between the sheet conveying roller and the face-down conveying roller, and the sheet The face-down tray provided on the upper surface of the main body and the paper are discharged onto the face-down tray or images are formed on both sides to receive the paper sent by the transport roller and the face-down transport roller in a face-down state. The face-down discharge roller pair that switches back the paper and the conveyance direction by this face-down discharge roller pair In order to send out the switched paper to the lower side of the image forming unit and the fixing unit, the image forming unit includes a reversing paper transport roller that is rotated in contact with the paper transport roller on the side opposite to the face-down transport roller In the device
A face-up tray provided on the side surface of the main body so as to be openable and closable around a lower end; and a rotation direction reversing mechanism that switches a rotation direction of the paper conveyance roller in conjunction with opening and closing of the face-up tray. A roller is provided on the face-up tray and is displaced about the axis of the paper transport roller simultaneously with the opening of the face-up tray. When the face-up tray is opened, the paper guide is fixed to the fixing roller. The paper transport roller is displaced to a posture for guiding the paper between the paper transport roller and the displaced reversing paper transport roller, and the rotation direction of the paper transport roller is switched by the rotation direction reversing mechanism, and the reversal is performed. A sheet fed from the fixing unit together with a sheet conveying roller is discharged onto the face-up tray. An image forming apparatus comprising and. The rotation direction reversing mechanism comprises a rotation direction reversing gear train composed of a plurality of gears rotatably attached to a gear base, and a gear at the starting end meshes with a driving gear to which the drive of the motor is transmitted, Is attached to the main body so as to be rotatable about the rotation shaft of the starting gear,
When the face-up tray is closed, one of the gears constituting the rotational direction reversing gear train meshes with a roller driving gear attached to the shaft of the paper transport roller, and the paper is faced down to the paper transport roller. The rotation of the conveying direction in the tray direction is transmitted, and when the face-up tray is opened, the gear base is rotated, and another gear of the rotation direction reversing gear train is engaged with the roller driving gear, and the sheet conveying roller is loaded with the sheet. The image forming apparatus according to claim 1, wherein a rotation in a conveying direction toward the face-up tray is transmitted.

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