JP2007086282A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the temperature rise of a photoreceptor drum in an image forming apparatus of an electrographic system. <P>SOLUTION: Reverse paths 9, 11, and 13 are formed to invert the recording medium 3 having a toner image already fixed in the fixing section 7 and to transfer it again to the image forming section 6. Further, first and second hollow rollers 15, 14 open at both sides are provide with the reverse paths 9, 11, and 13 between them. The roller 15 has fins formed in its insides and air is blown in its inside from one end to the other. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a laser printer, and a facsimile machine, and more particularly to an image forming apparatus that performs duplex printing on a recording medium.

  Conventionally, in an image forming apparatus that employs an electrophotographic method in which toner is electrostatically adsorbed to a photosensitive drum and transferred onto a recording medium, and the double-sided printing is performed, the image formed on one side of the recording medium is fixed by a fixing device. Then, the image is reversed and image formation is performed again on the other surface by the photosensitive drum.

  At this time, since the recording medium on which the image formed on one side by the fixing device is fixed is received from the fixing device and conveyed again to the photosensitive drum in a high temperature state, the photosensitive drum is heated by the high temperature recording medium. It will be.

  It is known that a photosensitive layer for forming an electrostatic latent image is coated on the outer peripheral surface of the photosensitive drum, and when this photosensitive layer is heated, its characteristics change to cause problems in image formation. Yes.

  Therefore, it is conceivable that a fan for cooling the photosensitive drum is provided in the image forming apparatus to blow air to the photosensitive drum. However, in this case, the toner electrostatically attracted to the outer peripheral surface of the photosensitive drum and the toner transferred to the recording medium before fixing are peeled off by the wind of the fan. As a result, the printing state of the recording medium deteriorates, and the peeled toner scatters inside the image forming apparatus and gives image noise to other recording media.

  In order to cope with such a problem, a technology is provided in which a fan is provided in a conveyance path for reversing a recording medium having a toner image fixed on one side and sending it to the image forming unit again, and the recording medium conveyed by blowing is cooled. It has been known. Japanese Patent Application Laid-Open No. 2004-228561 discloses a technique in which a wind for separating recording media loaded in a sheet feeding cassette one by one is used instead of a fan.

JP 2004-272079 A

  However, when using the technology for blowing and cooling the recording medium as described above, if the recording medium is blown with strong air so that the cooling is performed satisfactorily, the recording medium is deformed and the recording medium is conveyed. Problems such as obstruction may occur.

  An object of the present invention is to prevent an increase in the temperature of a photosensitive drum by efficiently cooling a recording medium on which a toner image is fixed and conveyed to an image forming unit again in an image forming apparatus that performs double-sided printing. It is.

  An image forming apparatus according to the present invention includes an image forming unit that transfers a toner image formed on the outer peripheral surface of a photosensitive drum by electrophotography to a recording medium, and a fixing that fixes the toner image transferred onto the recording medium. A reversing path for reversing the recording medium on which the toner image has been fixed by the fixing apparatus and transporting the recording medium again toward the image forming unit, and provided on the reversing path, with both side surfaces opened. A hollow first roller having fins formed on the inner peripheral surface, a second roller disposed opposite to the first roller via the reverse path, and from one end side to the other end side in the first roller An air blowing section for blowing air toward.

  An image forming apparatus according to the present invention includes an image forming unit that transfers a toner image formed on the outer peripheral surface of a photosensitive drum by electrophotography to a recording medium, and a fixing that fixes the toner image transferred onto the recording medium. A reversing path for reversing the recording medium on which the toner image has been fixed by the fixing apparatus and transporting the recording medium again toward the image forming unit, and provided on the reversing path, with both side surfaces opened. A hollow first roller having fins formed on the inner peripheral surface, a guide blade provided on the inner peripheral surface and sending air in the axial direction of the first roller by the rotation of the first roller, and the reverse path And a second roller disposed opposite to the first roller.

  According to the present invention, when the recording medium on which the toner image is fixed and heated is transported again to the image forming unit, it is possible to cool the recording medium without applying air to the recording medium. It is possible to prevent the temperature rise of the photosensitive drum without impairing the toner.

  An embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a longitudinal side view schematically showing an image forming apparatus according to the present embodiment. The image forming apparatus 1 includes a main body case 2. A paper feed cassette 4 on which a recording medium 3 is placed is attached to one end of the main body case 2, and image formation is performed on the other end of the main body case 2. A paper discharge tray 5 on which the recording medium 3 is discharged is attached.

  In the main body case 2, there are a photosensitive drum 17 and a transfer device 22, which will be described later, an image forming unit 6 that transfers a toner image onto the recording medium 3 by an electrophotographic process, and a toner transferred onto the recording medium 3. A fixing device 7 for fixing an image and a conveyance path 8 through which the recording medium 3 is conveyed from the paper feed cassette 4 to the paper discharge tray 5 through the image forming unit 6 and the fixing device 7 are provided. .

  Further, a branch path 9 branched from a transport path 8 from the fixing device 7 to the paper discharge tray 5 is provided in the main body case 2, and the transport direction of the recording medium 3 is set at the branch position at the paper discharge tray 5. Alternatively, a switching unit 10 that selectively switches to the inversion path 11 is provided.

  A reversing path 11 for switching back the recording medium 3 conveyed through the branch path 9 is provided at the front end side of the branch path 9. In the reversing path 11, there is provided a reversing roller 12 that is movable to the contact / separation position and that switches the recording medium 3 when the recording medium 3 is sandwiched and rotated.

  In front of the recording medium 3 switched back in the reversing path 11 in the transport direction, a refeed path 9 for transporting the recording medium 3 to the image forming unit 6 side again for duplex printing is provided. . The refeed path 9 is disposed below the reversing path 11 and is connected to a transport path 8 from the paper feed cassette 4 to the image forming unit 6. Here, in the refeed path 13, a driving roller 14 and a driven roller 15 that are arranged to face each other via the refeed path 13 are provided as means for transporting the recording medium 3.

  FIG. 2 is a longitudinal sectional view showing the image forming unit 6. The image forming unit 6 is formed on a photosensitive drum 17 that is rotationally driven around a support shaft 16 integrally formed with a gear (not shown) driven by a motor (not shown), and on the outer peripheral surface of the photosensitive drum 17. A charger 19 that uniformly charges the photosensitive layer 18; an exposure device 20 that forms an electrostatic latent image by exposing the outer peripheral surface of the photosensitive drum 17 according to image information; and a toner for the electrostatic latent image. The developer 21 that forms a toner image by adhering, the transfer device 22 that contacts the photosensitive drum 17 to transfer the toner image onto the recording medium 3, and remains on the photosensitive drum 17 after the toner image is transferred. A cleaning blade 23 that removes the toner that is present, a registration roller 24 that measures the timing of feeding the recording medium 3 to the transfer position, and the like. The recording medium 3 sent to the transfer position between the photoconductor drum 17 and the transfer device 22 is rotated by the photoconductor drum 17 to transfer the toner image and conveyed to the fixing device 7 side.

  FIG. 3 is a vertical side view showing the fixing device 7. The fixing device 7 includes a fixing roller 25 and a pressure roller 26. The fixing roller 25 generates heat when energized and is rotationally driven by a driving unit (not shown). The pressure roller 26 is disposed so as to be rotatable about an axis having an axis parallel to the axis of the fixing roller 25. The pressure roller 26 transfers the recording medium 3 onto which the toner image has been transferred and conveyed from the image forming unit 6 side. Press to 25. When the recording medium 3 to which the toner image has been transferred passes between the fixing roller 25 and the pressure roller 26, heat from the fixing roller 25 and pressure from the pressure roller 26 are applied to the recording medium 3, and recording is performed. The toner image on the medium 3 is fixed on the recording medium 3. Then, the recording medium 3 sandwiched between the fixing roller 25 and the pressure roller 26 is conveyed toward the paper discharge tray 5.

  Next, the driving roller 14 and the driven roller 15 will be described with reference to FIGS.

  FIG. 4 is a perspective view showing the driving roller 14 and the driven roller 15, and FIG. 5 is a longitudinal side view thereof. The driving roller 14 and the driven roller 15 are disposed to face each other via the refeed path 13, and the driven roller 15 is fitted to the duct 27 via the bearings 28 and is held rotatably around the center line. ing.

  The drive roller 14 includes a support shaft 29 and a rubber layer 30 formed of a rubber material having a high thermal resistance on the outer periphery thereof, and the recording medium 3 is moved around the support shaft 29 by a motor (not shown) as a drive source. It is rotated in the direction of conveyance.

  The driven roller 15 is a hollow cylindrical base formed of a metal material such as aluminum having a high thermal conductivity and having both sides opened. In addition, a plate-like fin 31 that is parallel to the axial direction from the inner peripheral surface toward the axial center is integrally formed in the driven roller 15. A plurality of fins 31 are provided and are formed at equal intervals. The driven roller 15 is in contact with the driving roller 14 and is driven to rotate according to the rotation of the driving roller 14.

  Here, the driving roller 14 and the driven roller 15 are arranged to face each other via the refeed path 13, and the driven roller 15 is provided on the surface side on which the toner image of the recording medium 3 is fixed. Then, the recording medium 3 sandwiched between the driving roller 14 and the driven roller 15 is conveyed toward the image forming unit 6.

  The duct 27 that holds the driven roller 15 is an air passage provided in the main body case 2. The duct 27 a that sends the air blown from the fan 32 or the like into the hollow driven roller 15, and the driven roller 15. It comprises a duct 27b for exhausting the internal air to the outside of the main body case 2. The side surface of the driven roller 15 on the side fitted in the duct 27a is referred to as an intake port 15a, and the side surface of the driven roller 15 on the side fitted in the duct 27b is referred to as an exhaust port 15b.

  FIG. 6 is an enlarged perspective view showing the intake port 15 a of the driven roller 15. As described above, the fin 31 is formed on the inner peripheral surface of the driven roller 15 in parallel with the axial direction. Further, on the inner peripheral surface of the driven roller 15, a plate-shaped guide vane 33 is integrally formed at the end of the fin 31 on the intake port 15 a side, and is provided obliquely with respect to the axial direction of the driven roller 15. It has been. Here, when the driven roller 15 is rotated in the direction of arrow A, air is scooped by the guide vanes 33 and pushed out along the fins 31 in the direction of arrow B.

  In such a configuration, in the image forming apparatus 1, when performing single-sided printing, the recording medium 3 fed from the paper feed cassette 4 is transported along the transport path 8, and in the transport process, in the image forming unit 6. The toner image is transferred, the transferred toner image is fixed by the fixing device 7, and the recording medium 3 on which the toner image is fixed is discharged onto the discharge tray 5.

  When double-sided printing is performed by the image forming apparatus 1, a toner image is fed from the paper feed cassette 4 and transferred to one surface by the image forming unit 6, and the toner image transferred by the fixing device 7 is fixed. The recorded recording medium 3 is conveyed to the branch path 9 by the switching unit 10. Then, the recording medium 3 is sent again to the image forming unit 6 and the fixing device 7 through the branching path 9, the reversing path 11, and the refeeding path 9, and the toner image is fixed to the other surface. The recording medium 3 on which the toner images are fixed on both sides is discharged onto a discharge tray 5.

  Here, the recording medium 3 conveyed through the refeed path 13 is nipped between the driving roller 14 and the driven roller 15 and conveyed toward the image forming unit 6. At this time, the recording medium 3 receives heat from the fixing device 7 and is in a high temperature state, but the driven roller 15 is cooled by air flowing through the duct 27 from the intake port 15a to the exhaust port 15b. Therefore, the recording medium 3 comes into contact with the driven roller 15 and is deprived of heat to be cooled. According to the cooling by this configuration, since it is not necessary to directly apply wind to the recording medium 3, there is no deformation of the recording medium 3 due to the wind. Therefore, it is possible to prevent a conveyance failure due to this deformation. Since the drive roller 14 is made of a rubber material having a large thermal resistance, most of the heat of the recording medium 3 moves to the driven roller 15 side, so that the heat of the recording medium 3 can be taken more effectively. .

  Since the driven roller 15 has a plurality of fins 31 formed therein and has a high surface area, it is easy to dissipate heat. Therefore, even when the recording medium 3 is continuously conveyed, the heat that has moved from the recording medium 3 is detected. Is easily dissipated and the cooling effect on the recording medium 3 can be maintained.

  Moreover, since the driven roller 15 is formed of aluminum having high thermal conductivity, it is easier to radiate heat. The material of the driven roller 15 is not limited to this, and may be formed of other metals having high thermal conductivity such as gold or copper.

  When the driven roller 15 is rotated in the direction in which the recording medium 3 is conveyed, the guide vane 33 pushes out air in the direction of the exhaust port 15b, so that the air sent into the driven roller 15 from the duct 27a 33 is caused to flow along the fin 31 and exhausted from the duct 27b. Therefore, more air flowing in the driven roller 15 can be used for heat dissipation of the fins 31, and the driven roller 15 can be efficiently cooled. Note that the duct 27 and the fan 32 are not necessarily required if the airflow sufficient for cooling can be guided into the driven roller 15 by the action of the guide vanes 33 due to the rotation of the driven roller 15.

  By the way, when the recording medium 3 is paper, its thermal conductivity is low and it is difficult for heat to move. Therefore, the heat received by the recording medium 3 from the fixing device 7 is biased to the surface of the recording medium 3 on which the toner image is fixed. ing. At this time, since the driven roller 15 is provided on the toner image fixing surface side of the recording medium 3 as described above, the heated toner image fixing surface of the recording medium 3 is in contact with the driven roller 15. It is cooled efficiently. By the way, in order to convey paper as the recording medium 3, it is desirable to form the surface of the driving roller 14 with rubber having a high frictional resistance. According to the configuration of the present embodiment, the roller made of a material having a thermal conductivity is used as the driven roller 14 in order to dissipate heat, so that the driving roller 15 can be formed of rubber, and the conveyance and cooling of the recording medium 3 can be performed. Both can be performed satisfactorily.

  As described above, according to the present embodiment, the recording medium 3 on which the toner image is fixed and heated on one surface is cooled by the driven roller 15, and is therefore conveyed again to the image forming unit 6. When the toner image is transferred to the other surface, the photosensitive drum 17 is prevented from being heated.

In the present embodiment, an example in which the driving roller 14 and the driven roller 15 are arranged in the refeed path 13 has been described. However, the present invention is not limited to this, and it may be arranged on the branch path 9 or the inversion path 11. Moreover, the arrangement | positioning location of the drive roller 14 and the driven roller 15 is not restricted to one, You may arrange | position in multiple places.

1 is a longitudinal side view schematically showing an image forming apparatus of the present embodiment. It is a longitudinal cross-sectional view which shows an image formation part. It is a vertical side view showing a fixing device. It is a perspective view which shows a drive roller and a driven roller. It is a vertical side view which shows a drive roller and a driven roller. It is a perspective view which expands and shows the inlet of a driven roller.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 3 Recording medium 6 Image forming part 7 Fixing device 9, 11, 13 Reverse path (branch path, reverse path, re-feed path)
14 Second roller (drive roller)
15 First roller (driven roller)
27, 32 Air blower (duct, fan)
31 Fin 33 Guide wing

Claims (4)

An image forming unit for transferring a toner image formed on the outer peripheral surface of the photosensitive drum by electrophotography to a recording medium;
A fixing device for fixing the toner image transferred onto the recording medium;
A reversing path for reversing the recording medium on which the toner image is fixed by the fixing device and transporting the recording medium again toward the image forming unit;
A hollow first roller provided in the reversing path, having side surfaces at both ends opened and fins formed on the inner peripheral surface;
A second roller disposed opposite the first roller via the reverse path;
An air blowing section for blowing air from one end side to the other end side in the first roller;
An image forming apparatus. An image forming unit for transferring a toner image formed on the outer peripheral surface of the photosensitive drum by electrophotography to a recording medium;
A fixing device for fixing the toner image transferred onto the recording medium;
A reversing path for reversing the recording medium on which the toner image is fixed by the fixing device and transporting the recording medium again toward the image forming unit;
A hollow first roller provided in the reversing path, having side surfaces at both ends opened and fins formed on the inner peripheral surface;
A guide vane provided on the inner peripheral surface and sending air in the axial direction of the first roller by the rotation of the first roller;
A second roller disposed opposite the first roller via the reverse path;
An image forming apparatus. The second roller is rotated by a driving source;
The first roller is in contact with the outer peripheral surface of the second roller and driven to rotate;
The image forming apparatus according to claim 1. The image forming apparatus according to claim 1, wherein the first roller is provided on a toner image fixing surface side of the recording medium.

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