Image forming apparatus

Abstract

To provide an image forming apparatus that can reduce the occurrence of paper feeding failures. [Solution] The image forming apparatus comprises an image forming unit, a paper feeding unit, a paper discharge unit, a paper transport path, a branch transport path, a transport guide, and an assist roller. The transport guide forms part of the transport surface of the paper transport path at the intersection of the paper transport path and the branch transport path. The assist roller pair transports the recording medium along the paper transport path. The transport guide is supported so as to be able to swing about a pivot axis in a direction away from the transport surface of the paper transport path. One of the assist roller pair is fixed to a shaft extending parallel to the pivot axis and is rotatably supported by the transport guide.

Description

Technical Field

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[0001] The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a multi-functional device using an electrophotographic method.

Background Art

[0002] A conventional image forming apparatus is disclosed in Patent Document 1. This image forming apparatus includes an image forming unit, a paper feeding unit, a discharging unit, a paper conveyance path, a branch conveyance path, and a conveyance guide. The image forming unit forms an image on a recording medium. The paper feeding unit supplies the recording medium to the image forming unit. The discharging unit discharges the recording medium on which the image is formed by the image forming unit. The paper conveyance path connects the image forming unit, the paper feeding unit, and the discharging unit. The branch conveyance path branches from the paper conveyance path. The conveyance guide constitutes a part of the conveyance surface of the paper conveyance path at the intersection of the paper conveyance path and the branch conveyance path. The conveyance guide is supported so as to be swingable about a swing axis in a direction retreating from the conveyance surface of the paper conveyance path. When a jam (paper jam) occurs in the paper conveyance path, the side cover and the conveyance guide are opened to perform jam processing.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the configuration of Patent Document 1, the conveyance force of the recording medium in the conveyance guide is reduced, and there is a possibility of occurrence of paper feeding failure.

[0005] In view of the above problems, an object of the present invention is to provide an image forming apparatus capable of reducing the occurrence of paper feeding failure.

Means for Solving the Problems

[0006] To achieve the above objective, the first configuration of the present invention comprises an image forming unit, a paper feeding unit, an output unit, a paper transport path, a branch transport path, a transport guide, and a pair of assist rollers. The image forming unit forms an image on a recording medium. The paper feeding unit supplies the recording medium to the image forming unit. The output unit outputs the recording medium on which the image has been formed in the image forming unit. The paper transport path connects the image forming unit, the paper feeding unit, and the output unit. The branch transport path branches off from the paper transport path. The transport guide constitutes a part of the transport surface of the paper transport path at the intersection of the paper transport path and the branch transport path. The pair of assist rollers transport the recording medium along the paper transport path. The transport guide is supported so as to be able to swing about a pivot axis in a direction away from the transport surface of the paper transport path. One of the assist rollers is fixed to a shaft extending parallel to the pivot axis and is rotatably supported by the transport guide. [Effects of the Invention]

[0007] According to the first configuration of the present invention, an image forming apparatus that can reduce the occurrence of paper feeding failures can be provided. [Brief explanation of the drawing]

[0008] [Figure 1] A schematic cross-sectional view showing the overall configuration of an image forming apparatus 100 according to one embodiment of the present invention. [Figure 2] A partial cross-sectional view showing an enlarged view of the area around the transport guide 65 of the image forming apparatus 100 according to one embodiment of the present invention. [Figure 3] A partial cross-sectional view showing an enlarged view of the area around the transport guide 65 of the image forming apparatus 100 according to one embodiment of the present invention. [Figure 4] A perspective view showing the transport guide 65 of an image forming apparatus 100 according to one embodiment of the present invention. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described below with reference to the drawings. Figure 1 is a cross-sectional view showing the internal structure of an image forming apparatus 100 according to one embodiment of the present invention. For convenience of explanation, the vertical direction is defined as the up-down direction (Z1-Z2) when the image forming apparatus 100 is in a usable installation state (as shown in Figure 1). The front-to-back direction (Y1-Y2) is defined with the front side of the image forming apparatus 100 shown in Figure 1 as the front (front). The left-to-right direction (X1-X2) is defined with reference to the front of the image forming apparatus 100 in its installed state. In this embodiment, the left-to-right direction (X1-X2) is orthogonal to the up-to-down direction (Z1-Z2) and the front-to-back direction (Y1-Y2). The left-to-right direction (X1-X2) is defined as the opposing direction of the pair of side surfaces 102 of the image forming apparatus 100, and the front-to-back direction (Y1-Y2) is defined as the axial direction of the pivot axis 65a. Note that this definition of the up-to-down direction does not limit the orientation and positional relationship of the image forming apparatus 100 when it is in use.

[0010] The image forming apparatus 100 comprises an image forming section Pa to Pd, a paper feeding section 60, a transfer section 50, a fixing section 14, an ejection section 17, a transport roller pair 40, a paper transport path 19, and branch transport paths 20 and 21.

[0011] The image forming apparatus 100 (in this case, a color printer) has four image forming units Pa, Pb, Pc, and Pd arranged in order from the upstream side in the transport direction (left side in Figure 1). The image forming units Pa to Pd form an image on the transfer paper (recording medium) P.

[0012] More specifically, the image forming sections Pa to Pd are provided to correspond to images of four different colors (yellow, cyan, magenta, and black). The image forming sections Pa to Pd sequentially form images of yellow, cyan, magenta, and black through the processes of charging, exposure, development, and transfer, respectively.

[0013] The image forming sections Pa to Pd form visible images (toner images) of each color on the photoreceptor drums (image carriers) 1a to 1d. In addition, an intermediate transfer belt (intermediate transfer body) 8, which rotates counterclockwise in Figure 1, is provided adjacent to each image forming section Pa to Pd. The toner images formed on the photoreceptor drums 1a to 1d are sequentially transferred and superimposed onto the intermediate transfer belt 8, which moves while in contact with each photoreceptor drum 1a to 1d.

[0014] The transfer unit 50 transfers the toner image formed in the image forming units Pa to Pd onto the transfer paper P (recording medium). The transfer unit 50 includes a drive roller 11 and a secondary transfer roller 9. Specifically, the toner image that has been primary transferred onto the intermediate transfer belt 8 is secondary transferred onto the transfer paper P, which is an example of a recording medium, by the secondary transfer roller 9. Furthermore, the transfer paper P on which the toner image has been secondary transferred is discharged from the main body of the image forming apparatus 100 after the toner image has been fixed in the fixing unit 14.

[0015] The paper feeding unit 60 supplies transfer paper P to the image forming units Pa to Pd. Specifically, the paper feeding unit 60 includes a paper cassette 61, a pickup roller 62, and a pair of feed rollers 63. The paper cassette 61 is located at the bottom of the main body of the image forming apparatus 100 and contains the transfer paper P on which the toner image is secondarily transferred. The pickup roller 62 presses against the upper surface of the transfer paper P with a predetermined pressure. The feeding of the transfer paper P is started by rotating the pickup roller 62.

[0016] The feed roller pair 63 includes a feed roller 63a and a retard roller 63b. The retard roller 63b is pressed against the feed roller 63a and rotates in its own direction. The retard roller 63b also has a built-in torque limiter. Furthermore, a drive force transmission gear 66 is positioned between the feed roller 63a and the pickup roller 62 to transmit the rotation of the feed roller 63a to the pickup roller 62 (see Figure 2).

[0017] As a result, when multiple sheets of transfer paper P are fed simultaneously by the pickup roller 62, the feed roller 63a and retard roller 63b separate the transfer paper P, and only the top sheet is sent towards the paper transport path 19. The feed roller pair 63 separates only the top sheet of transfer paper P from the multiple sheets and transports it towards the paper transport path 19. After passing through the paper transport path 19, the transfer paper P reaches the register roller pair 13 and is transported to the nip section between the secondary transfer roller 9 and the drive roller 11 of the intermediate transfer belt 8 in accordance with the image formation timing.

[0018] The intermediate transfer belt 8 is made of a dielectric resin sheet, and a seamless belt is mainly used. In addition, a blade-shaped belt cleaner 25 is positioned downstream of the secondary transfer roller 9 to remove toner and other residues remaining on the surface of the intermediate transfer belt 8.

[0019] Around and below the rotatably mounted photoreceptor drums 1a to 1d are charging devices 2a, 2b, 2c, and 2d, an exposure device 5, developing devices 3a, 3b, 3c, and 3d, and cleaning devices 7a, 7b, 7c, and 7d. The charging devices 2a, 2b, 2c, and 2d charge the photoreceptor drums 1a to 1d. The exposure device 5 exposes each photoreceptor drum 1a to 1d with image information. The developing devices 3a, 3b, 3c, and 3d form toner images on the photoreceptor drums 1a to 1d. The cleaning devices 7a, 7b, 7c, and 7d remove any remaining developer (toner) from the photoreceptor drums 1a to 1d.

[0020] When image data is input from a host device such as a personal computer, first, the charging devices 2a to 2d uniformly charge the surfaces of the photoreceptor drums 1a to 1d. Next, the exposure device 5 irradiates light according to the image data, and an electrostatic latent image corresponding to the image data is formed on each of the photoreceptor drums 1a to 1d. The developing devices 3a to 3d are each filled with a predetermined amount of a two-component developer containing yellow, cyan, magenta, and black toners. When the ratio of the toner in the two-component developer filled in each of the developing devices 3a to 3d falls below a specified value due to the formation of the toner image, toner is replenished from the toner containers 4a to 4d to each of the developing devices 3a to 3d.

[0021] The toner in the developer is supplied onto the photoreceptor drums 1a to 1d by the developing devices 3a to 3d and adheres electrostatically. Thereby, a toner image corresponding to the electrostatic latent image formed by the exposure from the exposure device 5 is formed.

[0022] Then, an electric field is applied at a predetermined transfer voltage between the primary transfer rollers 6a to 6d and the photoreceptor drums 1a to 1d by the primary transfer rollers 6a to 6d, and the yellow, cyan, magenta, and black toner images on the photoreceptor drums 1a to 1d are primarily transferred onto the intermediate transfer belt 8. These images are formed with a predetermined positional relationship. Thereafter, in preparation for the formation of a new electrostatic latent image that is subsequently performed, toner and the like remaining on the surfaces of the photoreceptor drums 1a to 1d after the primary transfer are removed by the cleaning devices 7a to 7d.

[0023] The intermediate transfer belt 8 is stretched between the upstream driven roller 10 and the downstream driving roller 11. When the intermediate transfer belt 8 starts to rotate counterclockwise as the driving roller 11 rotates by a belt driving motor (not shown), the transfer paper P is conveyed from the registration roller pair 13 to the secondary transfer nip portion N between the driving roller 11 and the secondary transfer roller 9 provided adjacent thereto at a predetermined timing. Then, the toner image on the intermediate transfer belt 8 is secondarily transferred onto the transfer paper P passing through the secondary transfer nip portion N.

[0024] The transfer paper P on which the toner image has been secondarily transferred is transported to the fuser unit 14. The fuser unit 14 has a fuser belt 14a and a pressure roller 14b. The fuser belt 14a is heated by a heating device (not shown), such as a heater or an induction heating unit. The pressure roller 14b is pressed against the fuser belt 14a to form a fuser nip, and imparts rotational driving force to the fuser belt 14a.

[0025] The transfer paper P, transported to the fixing unit 14, is heated and pressurized by the fixing belt 14a and pressure roller 14b, fixing the toner image to the surface of the transfer paper P and forming a predetermined full-color image.

[0026] The transfer paper P on which the full-color image has been formed is directed in a different direction by a transport guide member 15 located at the branching point of the paper transport path 19, after passing through a transport roller pair 40. It is then discharged into the discharge tray 18 by a discharge roller pair (discharge section) 17 (or after being sent to the branching transport path 20 where images are formed on both sides).

[0027] In other words, the discharge roller pair (discharge unit) 17 discharges the transfer paper (recording medium) P on which the toner image has been formed in the image forming unit Pa to Pd. The transport roller pair 40 feeds the transfer paper (recording medium) P from the fixing unit 14 to the discharge roller pair (discharge unit) 17. The transport roller pair 40 consists of a driven transport roller 40a and a driven transport roller 40b. The driven transport roller 40a is driven by a motor (not shown), and the driven transport roller 40b rotates in conjunction with the driven transport roller 40a.

[0028] The paper transport path 19 connects the paper feeding section 60, the transfer section 50, the fixing section 14, and the discharge section 17. The branch transport path 20 branches off from the paper transport path 19 downstream of the transport roller pair 40 and communicates with the paper transport path 19 upstream of the registration roller pair 13. The branch transport path 20 extends vertically (Z1-Z2) along the side surface 102 of the image forming apparatus 100 and is curved in a roughly C-shape. The branch transport path 21 branches off from the paper transport path 19 upstream of the intersection of the branch transport path 20 and the paper transport path 19 and extends vertically (Z1-Z2) along the side surface 102 of the image forming apparatus 100.

[0029] The side cover 91 constitutes the side surface 102 of the image forming apparatus 100 and is rotatably supported, for example, by a cover support shaft (not shown) located below the main body of the image forming apparatus 100.

[0030] The inner surface of the side cover 91 constitutes the outer surface of the branch transport paths 20 and 21. By opening the side cover 91, the branch transport paths 20 and 21 can be exposed.

[0031] Figures 2 and 3 are enlarged views of the area around the transport guide 65. In Figure 2, the transport direction of the transfer paper P is indicated by a dashed line. Figure 2 shows the transport guide 65 in a position that constitutes part of the transport surface of the paper transport path 19, while Figure 3 shows the transport guide 65 retracted from the transport surface of the paper transport path 19. Figure 4 is a perspective view of the transport guide 65.

[0032] The image forming apparatus 100 further comprises a transport guide 65 and a pair of assist rollers 64. The transport guide 65 is, for example, a resin molded product and constitutes a part of the transport surface of the paper transport path 19 and the branch transport path 21 at the intersection 22 of the paper transport path 19 and the branch transport path 21. The transport guide 65 is supported so as to be able to swing about a pivot axis 65a in a direction that retracts from the transport surface of the paper transport path 19.

[0033] More specifically, in a cross-section perpendicular to the axial direction of the pivot shaft 65a, the left side X1 of the transport guide 65, side 651, constitutes part of the transport surface of the paper transport path 19. The right side X2 of the transport guide 65, side 652, also constitutes part of the transport surface of the branch transport path 21. The pivot shaft 65a is configured to protrude from both ends of the transport guide 65 in the axial direction (Y1-Y2), and the pivot shaft 65a is pivotably supported by a bearing portion (not shown) of the main body of the device.

[0034] The assist roller pair 64 transports the transfer paper P (recording medium) along the paper transport path 19. In this embodiment, the assist roller pair 64 consists of a driven assist roller 64a (the other of the assist roller pair 64) and a driven assist roller 64b (one of the assist roller pair 64). The driven assist roller 64a is connected to the main body of the device.

[0035] On the other hand, the driven assist roller 64b (one of the assist roller pair 64) is fixed to a shaft 64c that extends parallel to the oscillating axis 65a and is rotatably supported on the transport guide 65. By arranging the assist roller pair 64 on the transport guide 65, the transport force of the transfer paper P on the transport guide 65 is improved.

[0036] By pressing the driven assist roller 64b (one of the assist roller pair 64) against the driven assist roller 64a (the other of the assist roller pair 64) with a predetermined pressure, the transport force of the transfer paper P is improved. The shaft 64c is, for example, a cylindrical object made of metal, and the transport guide 65 is reinforced by the shaft 64c, improving its strength. As a result, the transport guide 65 is less likely to bend convexly in the direction away from the driven assist roller 64a (the other of the assist roller pair 64). Therefore, the pressing force on the assist roller pair 64 is kept constant, and a decrease in the transport force of the transfer paper P can be suppressed.

[0037] The side surface 651 of the transport guide 65 has a recess 651a in the axial direction (Y1-Y2), and a driven assist roller 64b is positioned inside the recess 651a. That is, the driven assist roller 64b (one of the assist roller pair 64) is located in the axial direction (Y1-Y2) of the oscillating axis 65a, in the central part of the transport guide 65. This stabilizes the transport force of the transfer paper P in the transport guide 65 and suppresses the occurrence of jams.

[0038] Furthermore, the shaft 64c is positioned between the side surfaces 651 and 652 of the transport guide 65 and extends across the entire width of the transport guide 65 in the axial direction (Y1-Y2) of the pivot axis 65a. As a result, the transport guide 65 is strengthened by the shaft 64c and deformation can be further suppressed.

[0039] Furthermore, the shaft 64c is located above the pivot axis 65a at Z1, and the pivot axis 65a and the center of gravity are set such that the transport guide 65 generates a moment that causes it to swing in a direction away from the transport surface of the paper transport path 19 due to its own weight.

[0040] When the side cover 91 is rotated in the opening direction relative to the image forming apparatus 100, the branch transport path 21 is exposed over a wide area. At this time, by swinging the transport guide 65 in a direction that retracts it from the transport surface of the paper transport path 19, a portion of the paper transport path 19 is opened.

[0041] The transport guide 65 has its pivot axis 65a and center of gravity set such that it generates a moment that causes it to swing away from the transport surface of the paper transport path 19 by its own weight, and it rotates easily. As a result, when a jam (paper jam) occurs near the intersection 22 of the paper transport path 19, the side cover 91 and the transport guide 65 can be opened to improve the efficiency of jam removal.

[0042] Furthermore, the rotation axes of each assist roller pair 64 and the oscillating axis 65a are aligned on a straight line L in a cross-section perpendicular to the oscillating axis 65a (see Figure 2). When the side cover 91 is opened, the transport guide 65 is easily subjected to a force that moves it away from the transport surface of the paper transport path 19 due to the repulsive force between the assist roller pairs 64. This makes it easier for the transport guide 65 to rotate. Therefore, the efficiency of jam handling can be further improved by opening the transport guide 65.

[0043] On the other hand, by rotating the side cover 91 in the closing direction, the transport guide 65 is pressed against the side cover 91 and rotates in the closing direction. As a result, the driven assist roller 64b (one of the assist roller pair 64) is pressed against the driven assist roller 64a (the other of the assist roller pair 64). Therefore, by returning the side cover 91 to the closed state, the transport guide 65 can also be returned to the closed state at the same time.

[0044] Furthermore, the present invention is not limited to the above embodiments, and various modifications are possible without departing from the spirit of the invention. For example, although the above embodiment described the transport guide 65, the same effect can be obtained by arranging a pair of assist rollers on the transport guide member 15, which constitutes a part of the feeding surface of the paper transport path 19, at the intersection of the paper transport path 19 and the branch transport path 20. Also, by fixing the driven assist rollers to the shaft and rotatably supporting them on the transport guide member 15, the transport guide member 15 is reinforced and its strength is improved. This provides the same effect as the transport guide 65 described above. [Industrial applicability]

[0045] The present invention is not limited to color copiers, but can also be used in other vertical transport type image forming devices such as analog copiers, digital multifunction printers, monochrome and color printers, and facsimile machines. [Explanation of Symbols]

[0046] 1a~1d Photoconductor drum 2a~2d Charging device 3a~3d developing device 4a~4d Toner container 5. Exposure apparatus 6a~6d Primary transfer roller 7a~7d Cleaning equipment 8. Intermediate transfer belt 9. Secondary transfer roller 10 Driven rollers 11 Drive rollers 12 Paper feed rollers 13 Resist Roller vs 13b Roller 14 Fixing section 14a Fixing belt 14b Pressure Roller 15 Conveyor guide member 16 paper cassettes 17 Discharge roller pair (discharge section) 18 Output tray 19. Paper transport path 20, 21 Branching transport routes 22 Intersection 25 Belt Cleaner 33 Side cover 38 Conveyor Unit 40 Conveyor Rollers 40a Driven conveyor roller 40b Driven conveyor roller 50 Transfer section 60 Paper feed section 61 Paper Cassette 62 Pickup Roller 63 Feeding roller pair 63a Feed Roller 63b Retard Roller 64 Assist Roller vs 64a Drive assist roller 64b Driven assist roller 64c shaft 65 Conveyor Guide 65a Oscillating shaft 66 Power transmission gear 91 Side cover 100 Image forming apparatus 102 Side view 651, 652 Side view of the transport guide 651a Recess L straight line N Secondary transfer nip section P Transfer paper (recording medium) Pa~Pd Image Forming Unit

Claims

1. An image forming unit that forms an image on a recording medium, A paper feeding unit that supplies a recording medium to the image forming unit, An ejection unit for ejecting the recording medium on which an image has been formed in the image forming unit, A paper transport path connecting the image forming unit, the paper feeding unit, and the paper discharge unit, A branch transport path that branches off from the aforementioned paper transport path, At the intersection of the aforementioned paper transport path and the aforementioned branch transport path, a transport guide that constitutes a part of the transport surface of the aforementioned paper transport path, The system includes a pair of assist rollers that transport a recording medium along the aforementioned paper transport path, The transport guide is supported so as to be able to swing about a pivot axis in a direction that retracts from the transport surface of the paper transport path, An image forming apparatus in which one of the assist roller pair is fixed to a shaft extending parallel to the pivot axis and rotatably supported by the transport guide.

2. The image forming apparatus according to claim 1, wherein the shaft extends in the axial direction of the pivot axis over the entire width of the transport guide.

3. The image forming apparatus according to claim 1 or claim 2, wherein one of the assist roller pair is located in the central part of the transport guide in the axial direction of the pivot axis.

4. The image forming apparatus according to claim 1 or claim 2, wherein the pivot axis and center of gravity of the transport guide are set such that a moment is generated that causes the transport guide to pivot in a direction away from the transport surface of the paper transport path by its own weight.

5. The image forming apparatus according to claim 1 or claim 2, wherein each rotation axis of the assist roller pair and the oscillating axis are aligned in a straight line in a cross section perpendicular to the oscillating axis.

Images