JP2006290589A - Conveying passage switching mechanism and image forming apparatus having it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conveying passage switching mechanism simply constructed at low cost for switching a conveying passage for a sheet without using any solenoid or the like and to provide an image forming apparatus having the conveying passage switching mechanism. <P>SOLUTION: A first pinch roller 31 and a second pinch roller 32 are brought into pressure contact with a paper feed roller 30. In one end of a flapper rotational shaft 34 parallel to a roller rotational shaft 30a, a first gear 38 having gear teeth only in a part of the outer circumferential face is fixed to mesh with a second gear 39 fixed to the roller rotational shaft 30a. A tension spring 40 is fixed to the first gear 38, and another end of the tension spring 40 is fixed on the inside of an apparatus main body, which is not shown in the figure. In this way, the flapper rotational shaft 34 is rotated by a predetermined amount in the opposite direction to the direction of the paper feed roller 30, and according to the rotational direction of the paper feed roller 30, the flapper 33 is held in the position turned by a predetermined angle in the arrow DD' direction. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a paper used in an image forming apparatus such as a copying machine or a printer, a paper discharge unit of a paper post-processing device that performs paper binding processing or punching processing, a switchback device that reverses the front and back of the paper, and the like. The present invention relates to a transport direction switching mechanism.

  2. Description of the Related Art Conventionally, in an image forming apparatus using an electrophotographic system such as a copying machine or a printer, after forming an image on one side of a sheet, the sheet is conveyed again to the image forming unit without being discharged, and also on the other side. A double-sided printing method for forming an image is widely used. Such a double-sided printing type image forming apparatus includes a reversing unit for reversing a sheet on which an image is formed on one side, and a reconveying unit for reconveying the reversed sheet to the image forming unit. FIG. 11 shows a schematic configuration of a double-sided printing type image forming apparatus.

  In FIG. 11, reference numeral 1 denotes an image forming apparatus. Here, a digital multi-function peripheral is shown as an example. In the image forming apparatus 1, when performing a copy operation, the photosensitive drum 4 that rotates clockwise (in the direction of arrow A in the figure) is uniformly charged by the charging unit 3 in the image forming unit 2 in the MFP main body. An electrostatic latent image is formed on the photosensitive drum 4 by a laser beam from an exposure unit (laser scanning unit or the like) 8 based on the document image data read by the image reading unit 5, and an electrostatic latent image is formed by the developing unit 7. A developer (hereinafter referred to as toner) is attached to form a toner image. The toner is supplied to the developing unit 7 from the toner container 6.

  The sheet 9 is conveyed from the sheet feeding mechanism 10 to the image forming unit 2 via the sheet feeding roller 11, the sheet conveying path 12, and the resist roller pair 13 toward the photosensitive drum 4 on which the toner image is formed as described above. Then, the toner image formed on the surface of the photosensitive drum 4 by the transfer roller 14 in the image forming unit 2 is transferred onto the paper 9. Then, the sheet 9 on which the toner image is transferred is separated from the photosensitive drum 4 and conveyed to the fixing unit 15 to fix the toner image. The toner (residual toner) remaining on the surface of the photosensitive drum 4 after the toner image is transferred to the sheet is removed by the cleaning device 16.

  The paper 9 that has passed through the fixing unit 15 is distributed in the conveyance direction at a branching unit 17 that branches in a plurality of directions. When an image is formed only on one side of the sheet, the image is directly discharged onto the first discharge tray 19 with the image surface facing upward (hereinafter referred to as face-up) from the first discharge roller pair 18 or by the branching unit 17. The paper is distributed to the paper conveyance path 20, passes through the conveyance roller pair 21, and is discharged onto the second discharge tray 23 with the image surface facing downward (hereinafter referred to as face-down) from the second discharge roller pair 22. The paper transport path 20, the transport roller pair 21, and the second discharge roller pair 22 also function as a switchback device that switches the paper transport direction.

  On the other hand, when images are formed on both sides of the sheet, the sheet 9 that has passed through the fixing unit 15 is distributed to the sheet conveyance path 20 by the branching unit 17. Then, after the trailing edge of the sheet has passed through the branching portion 17, the conveying roller pair 21 and the second discharge roller pair 22 are reversely rotated to switch the conveying direction. Then, the image forming unit 2 is re-conveyed with the surface on which the image is not formed facing up. The re-conveyed paper 9 forms the next image in the image forming unit 2 and is conveyed to the fixing unit 15 to fix the toner image. Then, the first discharge roller pair 18 or the second discharge roller pair 22 is used to fix the toner image. It is discharged outside.

  Although not shown, a static elimination device that removes residual charges on the surface of the photosensitive drum 4 is provided on the downstream side of the cleaning device 16. Further, the paper feed mechanism 10 is detachably attached to the image forming apparatus 1 and includes a plurality of paper feed cassettes 10a, 10b, and 10c for storing paper, and a stack bypass (manual feed tray) 10d provided thereabove. These are connected to the image forming unit 2 including the photosensitive drum 4 and the developing unit 7 through the paper conveyance path 12.

  In such an image forming apparatus, conventionally, the sheet conveyance direction in the branching portion 17 is switched by switching the position of a plate-like gate member (hereinafter referred to as a flapper) by operating a solenoid or the like. However, in that case, there is a problem that a solenoid and a control mechanism for controlling the operation of the solenoid are required, which complicates the mechanism of the branching portion 17 and increases the cost.

  In view of this, a method of switching the sheet conveyance direction with a simple configuration has been proposed. For example, Patent Document 1 discloses that a discharge roller that can rotate forward and reverse and two discharge pinch rollers that are in pressure contact with the discharge roller. There is disclosed a sheet sorting mechanism that discharges paper from one of the discharge ports by gate means that forms two discharge ports and is switched in association with the rotation direction of the discharge roller. Further, Patent Document 2 includes a first and third roller pair including a discharge roller and two discharge pinch rollers pressed against the discharge roller, and a second roller pair that can rotate forward and backward. 1. A sheet material reversing device is disclosed in which a second conveyance path between a third roller pair and a second roller pair has a predetermined shape, thereby switching the conveyance path without using a flapper.

  However, in the method of Patent Document 1, since the arrangement of the gate means is switched using a fixed shaft, a hollow shaft, a friction ring, and the like, the structure of the gate switching mechanism becomes complicated and the number of parts increases. Also, friction is generated because the gear to which the driving force of the gate means is input and the friction ring are slid to limit the movable range of the gate means, and there is a risk that parts such as gears deteriorate due to changes over time.

In the method of Patent Document 2, the first and third roller pairs are rotated in opposite directions, so that the sheet can be switched back. However, both the first and third roller pairs are used as discharge roller pairs. The paper could not be discharged by switching between face-up and face-down. Furthermore, in order to switch the paper transport direction, it is necessary to separately provide a second roller pair that can rotate forward and backward.
JP-A-6-107366 JP 2001-328759 A

  SUMMARY An advantage of some aspects of the invention is that it provides a conveyance path switching mechanism that switches a conveyance path of a sheet with a simple and low-cost configuration without using a solenoid or the like, and an image forming apparatus including the conveyance path switching mechanism. .

  In order to achieve the above object, the present invention provides a paper feed roller that can rotate forward and reverse, a first pinch roller that is in pressure contact with the paper feed roller to form a first transport roller pair, and paper that is fed to the first transport roller pair. A first conveyance path that conveys, a second conveyance path that reversely conveys a sheet whose conveyance direction has been switched by reversing the sheet feed roller from the first conveyance roller pair, and the first and second conveyance paths. A conveyance position that is provided in the branching section and guides a sheet from the first conveyance path to the first conveyance roller pair, with a flapper rotation axis parallel to the roller rotation axis of the paper feed roller as a rotation center; and the first conveyance A flapper that is selectively disposed at a reverse conveyance position for guiding a sheet from the roller pair to the second conveyance path; and a flapper rotation mechanism that is fixed to the flapper rotation shaft and is part of the outer peripheral surface. A first gear formed with toothed teeth, a second gear fixed to the roller rotation shaft and transmitting a driving force to the first gear, and driving the first gear from the second gear. An urging means for urging in the direction opposite to the force transmission direction is provided, and the flapper is selectively arranged at the conveyance position and the reverse conveyance position in accordance with the rotation direction of the paper feed roller. .

  According to another aspect of the present invention, there is provided a paper feed roller that can rotate forward and backward, a first pinch roller that is pressed against the paper feed roller to form a first transport roller pair, and a pressure contact with the paper feed roller at a different contact point from the first pinch roller. A second pinch roller constituting a second transport roller pair, a first transport path for transporting paper to the first and second transport roller pair, and a roller for the paper feed roller provided upstream of the paper feed roller A first conveyance position for guiding a sheet to the first conveyance roller pair and a second conveyance position for guiding a sheet to the second conveyance roller pair with a flapper rotation axis parallel to the rotation axis as a rotation center. In a conveyance path switching mechanism comprising a selectively arranged flapper, a first gear fixed to the flapper rotation shaft and having gear teeth formed on a part of its outer peripheral surface, and fixed to the roller rotation shaft A second gear for transmitting a driving force to the first gear, and a biasing means for biasing the first gear in a direction opposite to a driving force transmission direction from the second gear. The flapper is selectively arranged at the first transport position and the second transport position in accordance with the rotation direction of the paper feed roller.

  Further, according to the present invention, in the conveyance path switching mechanism having the above-described configuration, a sheet that has passed through one of the first and second conveyance roller pairs is discharged with an image surface facing upward, and a sheet that has passed through the other is an image. It is characterized by being discharged with the surface facing down.

  According to the present invention, in the transport path switching mechanism configured as described above, a second transport path for reversely transporting the paper whose transport direction has been switched by reversing the first transport roller pair is provided. When in the second transport position, the sheet reversely transported from the first transport roller pair is guided to the second transport path.

  Further, the present invention is an image forming apparatus provided with the transport path switching mechanism having the above-described configuration.

  According to the first and second configurations of the present invention, the first gear fixed to the flapper rotation shaft and having gear teeth formed on a part of the outer peripheral surface, and fixed to the roller rotation shaft and driven to the first gear. The flapper is moved in accordance with the rotation direction of the paper feed roller by using a second gear for transmitting the force and an urging means for urging the first gear in a direction opposite to the driving force transmission direction from the second gear. Since it can be selectively arranged at the transport position and the reverse transport position, or the first transport position and the second transport position, it is not necessary to provide a solenoid or the like conventionally used as a flapper switching means, and the configuration of the transport path switching mechanism is eliminated. It will be easy. In addition, since a mechanism with high friction such as a torque limiter is not used for the flapper switching mechanism, it contributes to the extension of the service life and cost of the parts.

  According to the third configuration of the present invention, in the transport path switching mechanism of the second configuration, the sheet that has passed through one of the first and second transport roller pairs is discharged with the image surface facing upward. The sheet that has passed through the other side is discharged with its image surface facing downward, so that only one of the rotation direction of the paper feed roller is switched, and either the first conveyance roller pair or the second conveyance roller pair is faced up. Can be used for face-down, and the mechanism for switching the front and back of the discharged paper can be simplified.

  Further, according to the fourth configuration of the present invention, in the transport path switching mechanism of the second or third configuration, the first transport roller pair reversely transports the sheet whose transport direction is switched by reversing the first transport roller pair. When the second conveyance path is provided and the flapper is at the second conveyance position, the sheet conveyed backward from the first conveyance roller pair is guided to the second conveyance path, whereby the first conveyance roller pair. Is used to switch back the paper on which the image on the first side is formed, and at the same time, the paper on which the image on the second side is formed can be discharged using the second conveying roller pair. A switchback mechanism that improves image processing efficiency can be provided.

  Further, according to the fifth configuration of the present invention, by including the transport path switching mechanism having any one of the first to fourth configurations, the face-up, face-down discharge and switch can be realized with a simple and low-cost configuration. An image forming apparatus that performs a back operation can be provided, and at the same time, the life of parts can be extended.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a partial cross-sectional view illustrating a schematic configuration of an image forming apparatus including a conveyance path switching mechanism according to the first embodiment of the present invention. Portions common to FIG. 11 of the conventional example are denoted by the same reference numerals and description thereof is omitted. In the present embodiment, the paper feed roller 30 that can rotate forward and backward, the first pinch roller 31 and the second pinch roller 32 that are driven to rotate while being pressed against the paper feed roller 30 are switched to the branch portion 17, and the paper transport direction is switched. A flapper 33 is provided. The paper feed roller 30 and the first pinch roller 31 constitute a first transport roller pair 36, and the paper feed roller 30 and the second pinch roller 32 constitute a second transport roller pair 37.

  The flapper 33 is disposed so as to swing up and down around the flapper rotation shaft 34. The flapper rotation shaft 34 is connected to the paper feed roller 30 via a gear (described later), and the flapper 33 guides the paper to the first transport roller pair 36 according to the rotation direction of the paper feed roller 30 (hereinafter referred to as the first transport roller 36). 1 and a position where the sheet is guided to the second conveyance roller pair 37 (hereinafter referred to as a second conveyance position). In FIG. 1, the first transport position is indicated by a solid line, and the second transport position is indicated by a broken line.

  When the sheet (not shown) that has passed through the fixing unit 15 is discharged from the sheet conveyance path 35 (first conveyance path) in a face-up state, the sheet feed roller 30 is rotated clockwise (in the direction of arrow A). Accordingly, the first pinch roller 31 rotates counterclockwise (arrow B direction). At this time, the flapper 33 is disposed at the first transport position (solid line in the figure) by the rotation of the paper feed roller 30 in the direction of arrow A, and the paper passes through the first transport roller pair 36 and is fed from the first discharge roller pair 18. The face is discharged onto the first discharge tray 19.

  On the other hand, when the paper (not shown) that has passed through the fixing unit 15 is discharged in a face-up state, the paper feed roller 30 is rotated counterclockwise (in the direction of arrow B). Accordingly, the second pinch roller 31 rotates clockwise (in the direction of arrow A). At this time, the flapper 33 is disposed at the second transport position (broken line in the figure) by the rotation of the paper feed roller 30 in the direction of arrow B, and the paper passes through the second transport roller pair 37 and then is carried into the paper transport path 20. Then, the sheet is discharged face-down onto the second discharge tray 23 from the second discharge roller pair 22 via the conveying roller pair 21.

  When performing duplex printing, the paper feed roller 30 is rotated clockwise (in the direction of arrow A) to pass most of the paper from the first transport roller pair 36 toward the first discharge roller pair 18, and then the paper. The sheet feed roller 30 is rotated counterclockwise (arrow B direction) in a state where the rear end is nipped by the first conveying roller pair 36. At this time, the flapper 33 is disposed at the second transport position (broken line in the figure) by the rotation of the paper feed roller 30 in the direction of arrow B, and the paper is guided along the flapper 33 to the double-sided recording path 24 (second transport path). Is done.

  FIG. 2 is a schematic perspective view of the conveyance path switching mechanism of the present embodiment. Portions common to FIG. 1 are denoted by the same reference numerals and description thereof is omitted. The paper feed rollers 30 are provided at two locations in the paper width direction (the direction of arrow C in the figure), and the first pinch roller 31 and the second pinch roller 32 are pressed against each paper feed roller 30. A roller rotation shaft 30a is fixedly passed through the rotation center of the paper feed roller 30, and a driving force in a clockwise direction (arrow A direction) or counterclockwise (arrow B direction) is transmitted from a driving unit (not shown).

  A first gear 38 is fixed to one end of the flapper rotating shaft 34, and a second gear 39 that engages with the first gear 38 is fixed to one end of the roller rotating shaft 30a. When the roller rotation shaft 30a rotates in the direction of arrow A or B, the second gear 39 also rotates in the same direction, so the first gear 38 rotates in the opposite direction to the second gear 39, that is, the paper feed roller 30. To do. As a result, the flapper rotation shaft 34 also rotates in the opposite direction to the paper feed roller 30, and the flapper 33 can be rotated in the direction of the arrow DD ′ according to the rotation direction of the paper feed roller 30.

  One end of a tension spring 40 is fixed to the first gear 38, and the other end of the tension spring 40 is fixed inside the apparatus main body (not shown). In FIG. 2, the flapper 33 and the flapper rotation shaft 34 are shown separately for convenience of explanation, but in actuality, they are integrally formed.

  3 to 6 are side views of the transport path switching mechanism of the first embodiment. The conveyance path switching mechanism of this embodiment will be described in detail with reference to FIGS. As shown in FIG. 3, the second gear 39 is a normal gear having gear teeth 39a formed on the entire outer peripheral surface, but the first gear 38 has gear teeth 38a formed only on a part of the outer peripheral surface. Has been. Now, assuming that the second gear 39 rotates in the direction of arrow A, the first gear 38 rotates in the direction of arrow B due to the meshing of the gear teeth 38a and the gear teeth 39a. Accordingly, the flapper 33 connected to the first gear 38 via the flapper rotation shaft 34 also rotates in the arrow D direction.

  When the first gear 38 rotates by a predetermined amount, the gear teeth 38a disappear in the engaging portion between the first gear 38 and the second gear 39, as shown in FIG. Therefore, even if the second gear 39 continues to rotate in the direction of arrow A, the first gear 38 does not rotate any more, and the flapper 33 is held at a predetermined angle regardless of the amount of rotation of the second gear 39. Is done.

  The tension spring 40 is fixed at a position deviated from the rotation center of the first gear 38. Further, the other end of the tension spring 40 is in the gear teeth 38a in a state where no driving force (rotational force) is transmitted from the second gear 39. Is fixed at a position where it meshes with the gear teeth 39a. As a result, when the first gear 38 rotates in the arrow B direction, the tension spring 40 applies a rotational force in the direction opposite to the driving force transmission direction from the second gear 39 (arrow A direction) to the first gear 38. To do. Since the urging force of the tension spring 40 is weaker than the driving force from the second gear 39, the first gear 38 is in the state shown in FIG. 4 while the paper feed roller 30 is rotating in the arrow A direction. Is retained.

  Next, when the rotation direction of the paper feed roller 30, that is, the second gear 39 is reversed and begins to rotate in the direction of arrow B, the gear teeth 38a are again rotated by the urging force of the tension spring 40 as shown in FIG. The first gear 38 rotates in the reverse direction (arrow A direction) to the paper feed roller 30 because it meshes with 39a. As a result, the flapper 33 connected to the first gear 38 via the flapper rotation shaft 34 also rotates in the direction of the arrow D ′.

  When the first gear 38 rotates by a predetermined angle, as shown in FIG. 6, the gear teeth 38a do not mesh with the gear teeth 39a. Therefore, even if the second gear 39 continues to rotate in the arrow B direction, The first gear 38 does not rotate any more, the amount of rotation of the flapper 33 is limited, and the flapper 33 is held at a predetermined angle regardless of the amount of rotation of the second gear 39.

  Thereafter, when the paper feed roller 30 is rotated again in the direction of arrow A, the first gear 38 is moved in the direction opposite to the direction in which the driving force is transmitted from the second gear 39 (in the direction of arrow B) by the urging force of the tension spring 40. Since the rotational force is applied, the gear teeth 38a mesh with the gear teeth 39a again, and the first gear 38 rotates in the opposite direction (arrow B direction) to the paper feed roller 30 as shown in FIGS. 33 also rotates a predetermined amount in the direction of arrow D again. With the configuration described above, the flapper 33 swings by a predetermined angle in the direction of the arrow DD ′ according to the rotation direction of the paper feed roller 30.

  The range in which the gear teeth 38 a are formed on the outer peripheral surface of the first gear 38 is appropriately set according to the swing range of the flapper 33. That is, when the flapper 33 is swung largely, the formation range of the gear teeth 38a is widened. When the swinging range of the flapper 33 is small, the formation range of the gear teeth 38a is narrowed. On the other hand, if the urging force of the tension spring 40 is too strong, when the flapper 33 is held at a predetermined angle, the friction generated between the gear teeth 38a and the gear teeth 39a located at both ends by the rotation of the second gear 39 is large. Become. Therefore, the tension spring 40 only needs to have an urging force such that the gear teeth 38a mesh with the gear teeth 39a when the second gear 39 rotates in the reverse direction.

  Next, a method for discharging a sheet in a face-up or face-down state using the transport path switching mechanism of the present embodiment will be described. FIG. 7A is a side view showing a driving state of the conveyance path switching mechanism when the sheet is discharged in a face-up state, and FIG. In FIG. 7, the description of the second gear 39 is omitted.

  When discharging the paper face up, the paper feed roller 30 is rotated in the direction of arrow A as shown in FIG. As a result, the second gear 38 rotates by a predetermined amount in the direction of arrow B, and the flapper 33 also rotates by a predetermined angle in the direction of arrow D and is disposed at the first transport position (see FIGS. 3 and 4). Accordingly, the sheet 9 conveyed through the sheet conveyance path 35 is guided to the first conveyance roller pair 36 along the lower surface of the flapper 33. Thereafter, after passing through the first conveying roller pair 36, the sheet 9 is discharged from the first discharge roller 18 onto the first discharge tray 19 (see FIG. 1) in a face-up state.

  On the other hand, when the paper is discharged in a face-down state, the paper feed roller 30 is rotated in the direction of arrow B as shown in FIG. As a result, the second gear 38 rotates by a predetermined amount in the direction of arrow A, and the flapper 33 also rotates by a predetermined angle in the direction of arrow D ′ and is disposed at the second transport position (see FIGS. 5 and 6). . Accordingly, the sheet 9 conveyed through the sheet conveyance path 35 is guided to the second conveyance roller pair 37 along the upper surface of the flapper 33. Thereafter, the sheet 9 passes through the second conveying roller pair 37 and is then carried into the sheet conveying path 20, passes through the conveying roller pair 21, and then passes from the second discharging roller pair 22 to the second discharging tray 23 (both see FIG. 1). Ejected face down.

  Next, a method for switching back the paper during duplex printing using the conveyance path switching mechanism of the present embodiment will be described. 8 and 9 are side views showing a driving state of the transport path switching mechanism when the paper is switched back using the transport path switching mechanism of the first embodiment. Note that the description of the second gear 39 is omitted as in FIG.

  After the first image is fixed by the fixing unit 15 (see FIG. 1), the first gear 38 is moved to the arrow B by rotating the paper feed roller 30 in the direction of arrow A as shown in FIG. The flapper 33 is also rotated by a predetermined angle in the direction of the arrow D and is held at the first transport position for guiding the sheet 9a to the first transport roller pair 36. At this time, the sheet 9a that has been transported through the sheet transport path 35 is transported from the first transport roller pair 36 in the left direction of the drawing (the direction of arrow E).

  Then, most of the sheet 9a passes through the first conveying roller pair 36 from the state of FIG. 8A, and the rear end of the sheet 9a is disposed between the first conveying roller pair 36 and the flapper 33 as shown in FIG. 8B. , The rotation direction of the paper feed roller 30 is switched to the arrow B direction. As a result, as shown in FIG. 9A, the conveyance direction of the sheet 9a is switched to the arrow E ′ direction. At this time, since the first gear 38 rotates by a predetermined amount in the direction of arrow A, the flapper 33 also rotates by a predetermined angle in the direction of arrow D ′ and moves to the second transport position. Accordingly, the sheet 9 a conveyed from the first conveying roller pair 36 in the direction of the arrow E ′ is smoothly guided to the double-sided recording path 24 along the lower surface of the flapper 33. Thereafter, in order to form an image on the second side, the sheet 9a is conveyed again to the image forming unit 2 (see FIG. 11) with the side on which no image is formed facing up.

  Next, as shown in FIG. 9B, the sheet 9b on which the image on the second surface is fixed is conveyed from the sheet conveyance path 35 during the switchback of the sheet 9a. Here, since the flapper 33 is held at the second conveyance position, the sheet 9b is guided not in the direction of the first conveyance roller pair 36 but in the direction of the second conveyance roller pair 37 along the upper surface of the flapper 33. Since the sheet feed roller 30 rotates in the direction of arrow B and the second pinch roller rotates in the direction of arrow A, the sheet 9b passes through the second conveyance roller pair 37 and then is carried into the sheet conveyance path 20 (see FIG. 1). The Thereafter, the sheet 9b is discharged from the second discharge roller pair 22 onto the second discharge tray 23 (both see FIG. 1) via the conveying roller pair 21.

  By using the transport path switching mechanism of this embodiment for face-up and face-down discharge of the paper, it is possible to switch either the first transport roller pair 36 or the second transport roller pair 37 by simply switching the rotation direction of the paper feed roller 30. Can be used for face-up and the other for face-down, and the configuration of the front / back switching mechanism for the unloaded paper can be simplified.

  Further, a pair of conveying rollers to be used is determined according to the rotation direction of the sheet feeding roller 30, and the flapper 33 is disposed at the first conveying position or the second conveying position where the sheet 9 is guided to the conveying roller pair. Therefore, it is not necessary to provide a solenoid or the like that has been conventionally required for switching the flapper. Further, since a mechanism with high friction such as a torque limiter is not used for switching the flapper 33, it contributes to a longer life of parts and a lower running cost.

  In addition, when the sheet switching operation of the sheet at the time of double-sided printing is performed using the conveyance path switching mechanism of the present embodiment, the sheet 9a on which the first image is formed is switched back using the first conveyance roller pair 36. At the same time, since the sheet 9b on which the image on the second side is formed can be discharged using the second conveying roller pair 37, the switchback mechanism can be simplified and the image processing efficiency at the time of duplex printing can be improved.

  FIG. 10 is a schematic cross-sectional view of a transport path switching mechanism according to the second embodiment of the present invention. Portions common to FIG. 3 of the first embodiment are denoted by the same reference numerals and description thereof is omitted. In the present embodiment, the second pinch roller 32 of the first embodiment is not provided, and only the first conveying roller pair 36 including the paper feed roller 30 and the first pinch roller 31 is provided. Since other configurations are the same as those of the first embodiment, description thereof is omitted. Note that the description of the second gear 39 is omitted as in FIGS.

  A method of switching back the paper during duplex printing using the transport path switching mechanism of the present embodiment will be described. The sheet 9 on which the first image is fixed by the fixing unit 15 (see FIG. 1) and is conveyed through the sheet conveyance path 35 rotates the sheet feed roller 30 in the direction of arrow A as shown in FIG. As a result, the sheet is conveyed from the first conveying roller pair 36 in the left direction of the drawing (arrow E direction). At this time, since the first gear 38 rotates by a predetermined amount in the direction of arrow B, the flapper 33 also rotates by a predetermined amount in the direction of arrow D and is held at the transport position where the paper 9 is guided to the first transport roller pair 36. .

  When most of the sheet 9 passes through the first conveying roller pair 36 from the state shown in FIG. 10A and the rear end of the sheet 9 reaches between the first conveying roller pair 36 and the flapper 33, the sheet is fed. The rotation direction of the roller 30 is switched to the arrow B direction. As a result, as shown in FIG. 10B, the conveyance direction of the sheet 9 is switched to the arrow E ′ direction. At this time, since the first gear 38 rotates by a predetermined amount in the direction of arrow A, the flapper 33 also rotates by a predetermined amount in the direction of arrow D ′ and moves to the reverse conveyance position for guiding the sheet to the double-sided recording path 24. Accordingly, the sheet 9 conveyed in the direction of the arrow E ′ from the first conveying roller pair 36 is smoothly guided to the duplex recording path 24 along the lower surface of the flapper 33. Thereafter, in order to form an image on the second side, the sheet 9 is conveyed again to the image forming unit 2 (see FIG. 11) with the side on which no image is formed facing up.

  By performing a paper switchback operation during double-sided printing using the transport path switching mechanism of the present embodiment, the switchback mechanism can be simplified and the paper feed roller 30 can be rotated according to the direction of rotation, as in the first embodiment. Thus, the flapper 33 may be disposed at a transport position for guiding the paper from the paper transport path 35 to the first transport roller pair 36 or at a reverse transport position for guiding the paper 9 from the first transport roller pair 36 to the double-sided recording path 24. Therefore, it is not necessary to provide a solenoid or the like that has been conventionally required for switching the flapper.

  In addition, since a mechanism with high friction such as a torque limiter is not used for switching the flapper 33, it contributes to a longer life and cost reduction of parts. Note that the range in which the gear teeth 38a are formed in the first gear 38 and the setting of the biasing force of the tension spring 40 are the same as in the first embodiment, and thus description thereof is omitted.

  In addition, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the meaning of this invention. For example, in each of the above-described embodiments, the conveyance path switching mechanism is provided in the branch section 17 (see FIG. 1) on the upstream side of the paper discharge section, and is used as a face-up / face-down switching device or a switchback device during duplex printing. However, it can also be provided at another branching portion inside the image forming apparatus that switches the paper conveyance direction to two directions.

  In each of the above embodiments, only the example in which the first gear 38 is urged by using the tension spring 40 is described. However, instead of the tension spring 40, other springs such as a compression spring, a torsion spring, and a leaf spring are used. A biasing means can also be used. In the above embodiment, only the case where the transport path switching mechanism is mounted on a digital monochrome copying machine has been described. However, other types such as a tandem color copying machine, an analog monochrome copying machine, or a laser printer are used. It can also be used as a transport path switching mechanism of the image forming apparatus, and a sheet post-processing apparatus that performs sheet punching processing and stapling processing.

  The present invention includes a paper feed roller that can rotate forward and backward, a first pinch roller that is pressed against the paper feed roller to form a first transport roller pair, a first transport path that transports the paper to the first transport roller pair, A roller rotation shaft of the paper feed roller is provided in a second conveyance path that reversely conveys the paper whose conveyance direction is switched by reversing the paper feed roller from the first conveyance roller pair, and a branch portion of the first and second conveyance paths. A conveyance position for guiding the sheet from the first conveyance path to the first conveyance roller pair, and a reverse conveyance position for guiding the sheet from the first conveyance roller pair to the second conveyance path. In the transport path switching mechanism having a flapper selected and arranged, a first gear fixed to the flapper rotation shaft and having gear teeth formed on a part of its outer peripheral surface, and a first gear fixed to the roller rotation shaft To drive A second gear for transmitting force, and a biasing means for biasing the first gear in a direction opposite to the driving force transmission direction from the second gear, and depending on the rotation direction of the paper feed roller The flapper is selectively arranged at the transport position and the reverse transport position.

  The present invention also provides a paper feed roller that can rotate forward and reverse, a first pinch roller that is pressed against the paper feed roller to form a first transport roller pair, and a pressure contact with the paper feed roller at a different contact point from the first pinch roller. A second pinch roller constituting the second conveying roller pair, a first conveying path for conveying the sheet to the first and second conveying roller pairs, and provided upstream of the sheet feeding roller and parallel to the roller rotation axis of the sheet feeding roller. A flapper that is selectively disposed at a first conveyance position that guides the sheet to the first conveyance roller pair and a second conveyance position that guides the sheet to the second conveyance roller pair, with the rotation axis of the flapper as a rotation center A first gear that is fixed to the flapper rotation shaft and has gear teeth formed on a part of its outer peripheral surface, and a first gear that is fixed to the roller rotation shaft and transmits a driving force to the first gear. And an urging means for urging the first gear in the direction opposite to the direction in which the driving force is transmitted from the second gear are provided. The position is selectively arranged at the position and the second transport position.

  Thereby, since it becomes possible to selectively arrange the flapper at the transport position and the reverse transport position, or the first transport position and the second transport position using the engagement between the first gear and the second gear, There is no need to provide a solenoid or the like conventionally used as a flapper switching means, and a conveyance path switching mechanism with a simple structure and low cost can be provided. In addition, since a mechanism with high friction such as a torque limiter is not used for the flapper switching mechanism, it contributes to a longer life and lower running cost of the parts constituting the transport path switching mechanism.

  Further, the sheet that has passed through one of the first and second transport roller pairs is discharged with the image surface facing upward, and the sheet that has passed the other is discharged with the image surface facing downward. By simply switching the rotation direction of the paper feed roller, one of the first transport roller pair or the second transport roller pair can be used for face-up discharge and the other can be used for face-down discharge. The mechanism can be simplified.

  In addition, a second transport path for reversely transporting the paper whose transport direction has been switched by reversing the first transport roller pair is provided, and when the flapper is at the second transport position, it is transported reversely from the first transport roller pair. Since the sheet to be conveyed is guided to the second conveyance path, it is possible to simultaneously perform the switchback of the sheet on which the image is formed on the first side and the discharge of the sheet on which the image is formed on both sides. It is possible to provide a switchback mechanism that has a simple configuration and improves the image processing efficiency during double-sided printing.

  In addition, by installing the transport path switching mechanism of the present invention, it is possible to realize an image forming apparatus capable of face-up, face-down discharge and switchback operation with a simple and low-cost configuration, and a long service life of the apparatus. This contributes to a reduction in running costs.

1 is a partial cross-sectional view illustrating a schematic configuration of an image forming apparatus including a transport path switching mechanism according to a first embodiment of the present invention. These are the schematic perspective views of the conveyance path switching mechanism of 1st Embodiment. These are side views which show the state which the flapper rotates in the arrow D direction in the conveyance path switching mechanism of 1st Embodiment. These are side views which show a mode that a flapper is hold | maintained in the state rotated in the arrow D direction. These are side views which show the state which a flapper rotates in the arrow D 'direction. These are side views which show a mode that a flapper is hold | maintained in the state rotated in arrow D 'direction. In the case of discharging the paper in a face-up state using the transport path switching mechanism of the first embodiment (FIG. 7A) and the case of discharging the paper in a face-down state (FIG. 7B) It is a side view which shows the drive state of a path switching mechanism. FIG. 5 is a side view showing a state in which a sheet on which an image is formed on the first surface is conveyed in the direction of arrow E from the first conveying roller pair when the sheet is switched back using the conveyance path switching mechanism of the first embodiment. . FIG. 4 is a side view showing a state in which a sheet on which an image is formed on the first side is reversely conveyed from a first conveying roller pair in the direction of arrow E ′ and a sheet on which an image is formed on the second side is discharged from a second conveying roller. . These are the side views which show the drive state of the conveyance path switching mechanism in the case of switching back a paper at the time of duplex printing using the conveyance path switching mechanism which concerns on 2nd Embodiment of this invention. FIG. 2 is a schematic cross-sectional view showing the overall configuration of a conventional double-sided printing type image forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Image forming part 15 Fixing part 17 Branching part 24 Duplex recording path (2nd conveyance path)
DESCRIPTION OF SYMBOLS 30 Paper feed roller 30a Roller rotating shaft 31 1st pinch roller 32 2nd pinch roller 33 Flapper 34 Flapper rotating shaft 35 Paper conveyance path (1st conveyance path)
36 1st conveyance roller 37 2nd conveyance roller 38 1st gear 39 2nd gear 40 Tension spring (biasing means)

Claims (5)

A paper feed roller that can rotate forward and reverse, and a first pinch roller that is pressed against the paper feed roller to form a first transport roller pair;
A first transport path for transporting paper to the first transport roller pair;
A second conveyance path that reversely conveys the paper whose conveyance direction is switched by reversing the paper feed roller from the first conveyance roller pair;
Guided from the first conveyance path to the first conveyance roller pair, with a flapper rotation axis parallel to the roller rotation axis of the paper feed roller provided at a branch portion of the first and second conveyance paths. A conveyance path switching mechanism comprising: a conveyance position to perform; and a flapper that is selectively disposed at a reverse conveyance position for guiding the sheet from the first conveyance roller pair to the second conveyance path.
A first gear fixed to the flapper rotation shaft and having gear teeth formed on a part of its outer peripheral surface; a second gear fixed to the roller rotation shaft and transmitting a driving force to the first gear; Urging means for urging the first gear in a direction opposite to the direction in which the driving force is transmitted from the second gear is provided, and the flapper is moved to the transport position and the direction according to the rotation direction of the paper feed roller. A transport path switching mechanism that is selectively disposed at a reverse transport position. A paper feed roller that can rotate forward and backward, a first pinch roller that is pressed against the paper feed roller to form a first transport roller pair, and a second transport roller that is pressed against the paper feed roller at a different contact point from the first pinch roller A second pinch roller constituting a pair;
A first transport path for transporting paper to the first and second transport roller pairs;
A first conveying position provided on the upstream side of the sheet feeding roller and guiding a sheet to the first conveying roller pair about a rotation axis of a flapper parallel to the roller rotation axis of the sheet feeding roller; and the second In a conveyance path switching mechanism comprising a flapper that is selectively disposed at a second conveyance position for guiding a sheet to a conveyance roller pair,
A first gear fixed to the flapper rotation shaft and having gear teeth formed on a part of its outer peripheral surface; a second gear fixed to the roller rotation shaft and transmitting a driving force to the first gear; There is provided an urging means for urging the first gear in a direction opposite to the direction in which the driving force is transmitted from the second gear, and the flapper is moved in the first conveyance according to the rotation direction of the paper feed roller. A transport path switching mechanism, wherein the transport path switching mechanism is selectively arranged at a position and the second transport position.   The sheet that has passed through one of the first and second transport roller pairs is discharged with the image surface facing upward, and the sheet that has passed the other is discharged with the image surface facing downward. The conveyance path switching mechanism according to claim 2.   A second transport path for reversely transporting the paper whose transport direction has been switched by reversing the first transport roller pair is provided, and the first transport when the flapper is at the second transport position. The conveyance path switching mechanism according to claim 2 or 3, wherein the sheet reversely conveyed from the pair of rollers is guided to the second conveyance path.   An image forming apparatus comprising the transport path switching mechanism according to claim 1.

Images