JP2011095569A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent, at low cost without providing a fan or the like, a situation in which water vapor generated by a fixing unit is not discharged out of an image forming apparatus and then the water vapor is changed into water droplets to drip on a paper ejection portion. <P>SOLUTION: The image forming apparatus has: a paper ejection guide 45 for guiding paper, which is ejected after passing through the fixing unit 38, from a higher position; and a paper ejection cover 46 provided at the position higher than the paper ejection guide 45. The paper ejection guide 45 is provided with a first exhaust hole 49, and the paper ejection cover 46 is provided with a second exhaust hole 50 at the position not to vertically overlap the first exhaust hole 49 of the paper ejection guide 45. The water vapor generated by the fixing unit 38 is discharged out of the image forming apparatus from the second exhaust hole 50 of the paper ejection cover 46 through an exhaust passage S formed between the paper ejection guide 45 and paper ejection cover 46, from the first exhaust hole 49 of the paper ejection guide 45. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly, to an image forming apparatus in which water vapor generated from a fixing device is not discharged outside the apparatus, and water vapor does not drop into a paper discharge section.

  If the water vapor generated from the fixing unit of the image forming apparatus is discharged out of the apparatus as it is, there is a possibility that the user may misunderstand that smoke is generated. If the water vapor is not discharged outside the apparatus, the water vapor is condensed in the apparatus to form water droplets, and the water droplets adhere to the paper, resulting in a decrease in image quality.

  Therefore, conventionally, in order to discharge water vapor generated from the fixing device of the image forming apparatus, Patent Document 1 discloses an exhaust hole 103 of the discharge cover 102 by a fan 101 above the fixing unit 100 as shown in FIG. An image forming apparatus has been proposed in which an air flow is generated from the outside to the outside of the apparatus, and the air around the fixing unit 100 is sucked from the exhaust hole 105 of the paper discharge guide 104 by the air flow. Further, in Patent Document 2, as shown in FIG. 6, an image is provided in which a discharge hole 106 is provided in the discharge guide 106 above the fixing device 100 and an exhaust hole 109 is provided in the discharge cover 108 to release water vapor upward. A forming apparatus has been proposed.

  However, in the case where the fan 100 is provided as in Patent Document 1, there is a problem that the arrangement space of the fan 100 is required and the cost of the fan 100 itself is increased, which increases the cost. Further, in Patent Document 2, since the exhaust hole 107 is provided in the paper discharge guide 106 above the sheet, water vapor passing through the exhaust hole 107 is condensed at or around the edge of the exhaust hole 107 to form the sheet from the exhaust hole 107. There was a problem of water drops falling.

JP-A-5-27534 JP 2004-90221 A

  The present invention has been made in view of the above-described conventional problems, and at low cost without providing a fan or the like, the water vapor generated from the fixing device is not discharged outside the apparatus, and the water vapor becomes water droplets to form a paper discharge unit. It is an object of the present invention to provide an image forming apparatus that does not drop on the screen.

In order to solve the above problems, the present invention provides:
In an image forming apparatus having a paper discharge guide for guiding paper discharged from the fixing device from above and a paper discharge cover provided above the paper discharge guide, a first exhaust hole is provided in the paper discharge guide. A second exhaust hole is provided in the discharge cover so as not to overlap the first exhaust hole of the discharge guide in the vertical direction, and water vapor generated by the fixing device is discharged from the first exhaust hole of the discharge guide. The sheet is discharged out of the apparatus through a second exhaust hole of the sheet discharge cover through an exhaust path formed between the sheet discharge guide and the sheet discharge cover.

  The water vapor generated from the paper heated by the fixing device is condensed on the wall surface of the exhaust passage while passing through the exhaust passage between the discharge guide and the discharge cover from the first exhaust hole of the discharge guide to form water droplets. And become attached. Therefore, the water vapor discharged from the second exhaust hole is in a state where it cannot be visually recognized, and flows out of the apparatus. On the other hand, the water droplets adhering to the wall surface of the exhaust path do not fall from the first exhaust hole to the sheet discharge path, but accumulate on the upper surface of the wall of the sheet discharge guide and naturally evaporate due to the heat of the wall surface.

  The first exhaust hole is preferably formed at a position between the fixing device and a paper discharge roller disposed on the downstream side of the fixing device and excluding the upper side of the fixing device.

  It is preferable to provide a plurality of ribs on the exhaust path between the first exhaust hole of the discharge guide and the second exhaust hole of the discharge cover so that water vapor passing through the exhaust path contacts.

  It is preferable that the first exhaust hole is not provided below the plurality of ribs.

  According to the present invention, the water vapor generated from the paper heated by the fixing device is condensed on the wall surface of the exhaust path of the exhaust path and adheres as water droplets, and the water vapor discharged from the second exhaust hole cannot be visually recognized. Since it enters a state and flows out of the apparatus, it is not mistaken for the user that smoke is generated. Further, since water droplets adhering to the wall surface of the exhaust path do not fall from the first exhaust hole to the paper discharge path, the image quality is not deteriorated.

1 is a schematic front view of an image forming apparatus of the present invention. FIG. 2 is an enlarged sectional view above a fixing device of the image forming apparatus of FIG. 1. Sectional drawing which shows the modification of FIG. Sectional drawing which shows the other modification of FIG. FIG. 6 is an enlarged cross-sectional view above a fixing device of a conventional image forming apparatus. FIG. 6 is an enlarged cross-sectional view above a fixing device of another conventional image forming apparatus.

  Next, embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 shows an image forming apparatus 11 which is a tandem color laser printer. The image forming apparatus 11 includes a main body 11a, a process cartridge 12, a transfer unit 13, an exposure unit 14, a paper feed unit 15, and a cleaning unit 16.

  The process cartridges 12 are arranged at four locations along the intermediate transfer belt 18 of the transfer unit 13, and image formation of yellow (Y), magenta (M), cyan (C), and black (Bk) is performed from the cleaning unit 16 side, respectively. As a result, a color image is formed on the surface of the intermediate transfer belt 18.

  The transfer unit 13 bridges the intermediate transfer belt 18 between the pair of support rollers 27 and 28, drives the support roller 27 by a power transmission device (not shown), and drives the intermediate transfer belt 18 in the arrow A direction. The transfer unit 13 is opposed to a primary transfer roller 31 that constitutes a primary transfer portion facing the photosensitive drum 20 and a support roller 27, as typically shown by a yellow photosensitive drum 20. And a secondary transfer roller 33 constituting a secondary transfer portion.

  The exposure unit 14 irradiates the photosensitive drum 20 with a laser beam to form an electrostatic latent image corresponding to image data sent from a personal computer (not shown).

  The sheet feeding unit 15 sequentially conveys the recording medium S accommodated in the sheet feeding cassette 35 and the manual sheet feeding cassette 36 to the secondary transfer unit via the conveyance roller 37. The toner image formed on the intermediate transfer belt 18 is transferred to the recording medium S transported to the secondary transfer unit, and the toner image transferred by the fixing unit 38 is fixed, and then transferred to the discharge tray 39. The

  The cleaning unit 16 can come into contact with and separate from the intermediate transfer belt 18, and collects and cleans toner remaining on the intermediate transfer belt 18 when approaching.

  Each process cartridge 12 includes a charging device 21, a developing device 22, and a cleaning device 23 around the photosensitive drum 20, as typically shown by a yellow process cartridge 12.

  The charging device 21 gives a predetermined charge to the surface of the photosensitive drum 20. This surface potential becomes an electrostatic latent image when exposed by the exposure unit 14.

  The developing device 22 supplies toner to the photosensitive drum 20 to develop the electrostatic latent image. A toner cartridge 26 that replenishes toner to the developing device 22 is detachably installed above the developing device 22.

  The cleaning device 23 collects and cleans the toner remaining on the surface after the transfer to the photosensitive drum 20.

  FIG. 2 shows details above the fusing unit 38. The fixing unit 38 includes a pressure roller 40 and a heating roller 41, and a toner image is fixed by inserting a sheet onto which a toner image has been transferred into a fixing nip portion 42 therebetween. A lower discharge guide 44 and an upper discharge guide 45 that guide the fixed sheet to the discharge roller 43 are provided on the downstream side of the fixing unit 38. A paper discharge cover 46 is mounted above the upper paper discharge guide 45 with a space therebetween.

  The upper paper discharge guide 45 extends obliquely upward from the fixing unit 38. A plurality of sheet passing ribs 47 extending along the sheet passing direction are formed on the lower surface of the upper sheet discharge guide 45. A reinforcing rib 48 is formed on the upper surface of the upper paper discharge guide 45. A first exhaust hole 49 is provided between the fixing unit 38 and the paper discharge roller 43 of the upper paper discharge guide 45 and on the downstream side in the paper conveyance direction except for the upper side of the fixing unit 38, preferably in the vicinity of the paper discharge roller 43. Is formed. The first exhaust holes 49 may have any shape such as a plurality of holes and slits, and the size thereof is not limited as long as air and water vapor can pass therethrough.

  The paper discharge cover 46 is formed in a box shape integrally with the upper paper discharge guide 45 so that the fixing unit 38 and the paper discharge roller 43 can be opened at the time of jam processing or inspection. The paper discharge cover 46 is positioned so as not to overlap the first exhaust hole 49 of the upper paper discharge guide 45 in the vertical direction, preferably at a position farthest upstream from the first exhaust hole 49 in the sheet conveyance direction. Two exhaust holes 50 are formed. The second exhaust hole 50 may have any shape such as a plurality of holes and slits, and the size is not limited as long as air and water vapor can pass therethrough. An exhaust path S is formed between the upper discharge guide 45 and the discharge cover 46 from the first exhaust hole 49 of the upper discharge guide 45 to the second exhaust hole 50 of the discharge cover 46. A plurality of ribs 51 projecting from the inner surface of the paper discharge cover 46 are in contact with water vapor flowing through the exhaust path S. These ribs 51 extend in a direction perpendicular to the flow direction of water vapor flowing through the exhaust path S.

  An operation of discharging the steam generated in the fixing unit 38 of the image forming apparatus 11 having the above configuration will be described.

  The paper that has been fixed by passing through the fixing roller 38 of the fixing unit 38 and the pressure roller 41 is heated by the heating roller 40, and the water contained in the paper evaporates to generate water vapor. The water vapor flows along the upper discharge guide 45 as indicated by an arrow in FIG. 2 and flows into the exhaust path S from the first exhaust hole 49 of the upper discharge guide 45. While flowing through the exhaust path S, the water vapor collides with and comes into contact with the rib 51 of the paper discharge cover 46, dew condensation on the surface of the rib 51, and drops as water droplets onto the upper surface of the upper paper discharge guide 45. Therefore, the water vapor in the exhaust path S becomes dry water vapor and is discharged out of the apparatus through the second exhaust hole 50 of the paper discharge cover 46 in an invisible state. For this reason, it is not mistaken that the user generates smoke. Further, water droplets adhering to the wall surface of the exhaust path S naturally evaporate due to the heat of the wall surface of the upper paper discharge guide 45.

  Further, since there are no first discharge holes 49 and other holes below the ribs 51, water drops falling from the ribs 51 do not enter the paper discharge path, and the water drops adhere to the paper and the image quality deteriorates. There is nothing.

  In FIG. 3, the rib 51 is not provided on the paper discharge cover 46 as in FIG. 2, but the rib 51 extending in the direction perpendicular to the flow direction of the water vapor flowing through the exhaust path S is provided on the upper surface of the upper paper discharge guide 45. It is a thing. Although not shown, the ribs 51 may be alternately provided on both the upper discharge guide 45 and the discharge cover 46.

  In FIG. 4, ribs 51 are provided on the paper discharge cover 46 as shown in FIG. 2, but the ribs 51 extend to the vicinity of the upper paper discharge guide 45, and a large number of passages through which steam passes through each rib 51. The pores 52 are formed.

  The operation and effect of the rib 51 of FIGS. 3 and 4 are the same as those of the rib 51 of FIG.

11 Image forming apparatus 38 Fixing unit 43 Paper discharge roller 45 Upper discharge guide 46 Paper discharge cover 49 First exhaust hole 50 Second exhaust hole 51 Rib S Exhaust path S

Claims (4)

  In an image forming apparatus having a paper discharge guide for guiding paper discharged from the fixing device from above and a paper discharge cover provided above the paper discharge guide, a first exhaust hole is provided in the paper discharge guide. A second exhaust hole is provided in the discharge cover so as not to overlap the first exhaust hole of the discharge guide in the vertical direction, and water vapor generated by the fixing device is discharged from the first exhaust hole of the discharge guide. An image forming apparatus, wherein an image is discharged out of the apparatus through a second exhaust hole of the discharge cover through an exhaust path formed between the discharge guide and the discharge cover.   The first exhaust hole is formed between the fixing unit and a paper discharge roller disposed on the downstream side of the fixing unit, and is formed at a position excluding the upper side of the fixing unit. The image forming apparatus according to 1.   2. A plurality of ribs are provided in an exhaust path between a first exhaust hole of the discharge guide and a second exhaust hole of the discharge cover so that water vapor passing through the exhaust path contacts. Or the image forming apparatus according to 2;   The image forming apparatus according to claim 3, wherein the first exhaust hole is not provided below the plurality of ribs.

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