JP4558364B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an electrophotographic image forming apparatus.

  Patent Documents 1 and 2 disclose means for heat insulation from a fixing device to an image forming unit in an electrophotographic image forming apparatus.

JP 2000-227730 A JP 2001-183959 A

  Many of today's electrophotographic apparatuses can form color images, such as color copiers and color printers, in accordance with market demands. Such a color electrophotographic apparatus is provided with a developing device of a plurality of colors around one photosensitive member, and a toner is attached by these developing devices to form a composite toner image on the photosensitive member. A so-called one-drum type that transfers and records a color image on a sheet, and a plurality of photoconductors arranged side by side are each provided with a developing device, and a monochromatic toner image is formed on each photoconductor. A so-called tandem type is known in which a single color toner image is sequentially transferred to record a composite color image on a sheet.

  Comparing such a one-drum type and a tandem type, since the former has one photoconductor, there is an advantage that the apparatus can be reduced in size relatively easily and the manufacturing cost can be reduced. Since a full-color image is formed by repeating image formation a plurality of times (usually four times) using a photoconductor, there is a problem that it is difficult to increase the speed of image formation. On the other hand, the latter has the advantage that it is easy to speed up image formation, although there is a problem that the apparatus becomes large and the manufacturing cost increases.

  In recent years, tandem type has been attracting attention because full-color is required to have the same high speed as monochrome image formation.

  The tandem type electrophotographic apparatus includes a direct transfer system in which images on each photoconductor are sequentially transferred to a sheet conveyed by a sheet conveying belt by a transfer device, and an image on each photoconductor by a primary transfer device. There is an indirect transfer type in which images are sequentially transferred to an intermediate transfer belt once, and then images on the intermediate transfer belt are collectively transferred to a sheet by a secondary transfer device. The secondary transfer device in this case is generally in the shape of a roller, but a transfer transfer belt shape is also used.

  Comparing the direct transfer type and the indirect transfer type, the former is the case where the conveyance sheet fluctuates on the sheet conveyance belt in order to transfer the conveyance sheet directly from each photosensitive element. There is a problem that the image written in is shifted. On the other hand, in the latter, the secondary transfer position can be set relatively freely, and even when the conveyed sheet fluctuates, the image written by each photoconductor is used when transferring the image to the sheet. Already match, and there is an advantage that the image does not shift even if the sheet fluctuates.

  In view of the above, recently, an indirect transfer type of tandem type electrophotographic apparatus has attracted attention.

  In such an indirect transfer type electrophotographic apparatus, in order to reduce the lateral size of the apparatus, the internal density of the apparatus is increased and the fixing device is also pulled under the intermediate transfer belt. The fixing device comes close to the intermediate transfer belt. In addition, the amount of heat generated inside the apparatus is increasing as the speed of the electrophotographic apparatus increases. Therefore, the intermediate transfer belt is thermally affected by the fixing device that is a heating element. Therefore, when transferring the toner image of each color to the intermediate transfer belt by the heat generated from the fixing device, the intermediate transfer is performed in each image forming device (device that forms the image of each color around the photosensitive member). Since the belt stretches and contracts, there is a problem in that the elongation ratio of the pixels of each color does not match, which causes color misregistration and banding, which is one of the image degradations of the tandem color image forming apparatus.

  An object of the present invention is to prevent thermal factors from being applied to an image carrier from a fixing device in an electrophotographic image forming apparatus having an image carrier such as an intermediate transfer belt.

The present invention provides an image carrier on which a toner image is formed, a transfer device that transfers the toner image on the image carrier onto a medium, and the toner image on the medium that is disposed below the image carrier. A fixing device for fixing the heat, a first heat exhaust member comprising a heat pipe for discharging the heat generated by the fixing device to a heat radiating portion at a predetermined position, and heat generated by the medium after passing through the fixing device. And the second exhaust heat member that forms an exhaust flow path that guides and discharges water vapor to an exhaust port adjacent to the heat radiating portion at the predetermined position, and insulates the first exhaust heat member and the exhaust flow path. A first heat insulating member, and a second heat insulating member provided on an outer wall of the second heat exhausting member opposite to the first heat exhausting member side, facing the exhaust flow path No, respectively inner walls respectively of the first inner wall of the heat insulating member and the second insulation <br/> members are In part, a electrophotographic image forming apparatus wherein the medium after passing through the fixing device is emitted steam is receiving member for receiving the water droplets generated by dew condensation are provided.

  According to the present invention, by insulating the space between the first heat exhaust member and the second heat exhaust member, the influence of heat from the fixing device on the image carrier can be reduced without increasing the size of the device. It can be reduced that the heat load other than the fixing device that wants to carry away heat is applied to the first exhaust heat member and the heat carrying efficiency is deteriorated.

  The best mode for carrying out the present invention will be described.

  FIG. 1 is an explanatory diagram illustrating a schematic configuration of an image forming apparatus 1 according to the present embodiment, FIG. 2 is a perspective view of a main part of the image forming apparatus 1, and FIG. 3 is a front view of a main part of the image forming apparatus 1. is there.

  The image forming apparatus 1 is a tandem type electrophotographic apparatus using an indirect transfer method. The image forming apparatus 1 includes image forming apparatuses 2Y, 2C, 2M, and 2K that form toner images of each color of Y (yellow), C (cyan), M (magenta), and K (black) by a known electrophotographic method. It is provided side by side. An intermediate transfer belt 3 is provided below the image forming devices 2Y, 2C, 2M, and 2K, and toner images formed on the respective photosensitive drums 4Y, 4C, 4M, and 4K of the image forming devices 2Y, 2C, 2M, and 2K. Are primarily transferred to the endless intermediate transfer belt 3, and a plurality of color toners are superimposed on the intermediate transfer belt 3 to form a color image. The color image is transferred to a medium P such as transfer paper at the nip portion between the counter rotator 5 and the final transfer body 6 pressurized against the counter rotator 5. Is fixed.

  The image forming apparatus 1 is configured such that the fixing device 7 is arranged in a direction closer to the final transfer body 6 due to the limitation of the lateral size of the apparatus, and is recessed under the intermediate transfer belt 3. Accordingly, the heat generated in the fixing device 7 rises directly above by convection and is easily transmitted in the direction of the intermediate transfer belt 3.

  Therefore, the intermediate transfer belt 3 is heated and expanded in the vicinity of the fixing device 7, and the intermediate transfer belt 3 is contracted by being cooled as the distance from the fixing device 7 is increased. Furthermore, since the expansion rate of the intermediate transfer belt 3 at the time of primary transfer of each color at a certain image position is different, the primary transfer position with respect to the intermediate transfer belt 3 varies with the toner of each color, and color misregistration occurs.

  Therefore, a heat pipe 11 serving as a first exhaust heat member is provided between the fixing device 7 and the intermediate transfer belt 3, and heat generated in the direction of the intermediate transfer belt 3 by radiation and convection is generated from the fixing device 7. 3 is led from the space between the high fixing device 7 and the intermediate transfer belt 3 to the left side of the device in FIG. The heat of the fixing device 7 is diffused.

  Further, a flow path 13 serving as a second heat exhaust member is provided to discharge the air A containing a large amount of hot air and water vapor generated from the medium P such as transfer paper, which is heated by the fixing device 7, and includes hot air and water vapor. Air is guided through the flow path 13 and forcedly discharged outside the apparatus by a cooling fan 14 that is a forced exhaust device.

  At this time, the flow path 13 through which the air A containing a large amount of heat and moisture generated from the medium P and the heat pipe 11 are insulated by the heat insulating member 15 serving as the first heat insulating member. As a result, it is possible to prevent the efficiency of transporting the heat generated from the fixing device 7 that should be transported originally from being lowered because the heat pipe 11 is heated in the course of heat transport.

  The heat insulating member 15 is a partition wall on the heat pipe 11 side of the flow path 13 through which air A containing a large amount of heat and water vapor flows, and is made of a material having a heat insulating effect. Examples of the material having the heat insulating effect include hard urethane and polystyrene. Accordingly, it is possible to effectively insulate without increasing the size of the apparatus and without newly adding parts, and to efficiently exhaust the medium P with low manufacturing cost and space saving. it can.

  A vacuum space 16 is provided between the heat pipe 11 and the partition wall (heat insulating member) 15 on the heat pipe 11 side of the flow path 13 through which the air A containing a large amount of heat and water vapor flows. Thereby, the contact area of the partition 15 and the heat pipe 11 becomes small, and the contact area where heat conduction is performed becomes small. Therefore, it can be further reduced that the heat of the heated air A flowing through the flow path 13 is slightly conducted to the heat pipe 11 through the partition wall 15 which is a heat insulating material and the surrounding air.

  Further, the airflow 19 for cooling the medium P flowing through the flow path 13 by the cooling fan 14 is changed to an upward airflow flowing from the lower side to the upper side of the apparatus, so that the gas due to heat when the medium P is heated by the fixing device 7 is changed. The buoyancy caused by the decrease in density can be used to assist the force of flowing the air flow in the flow path 13 of the medium P, so that more efficient exhaust heat can be performed.

  The outer wall 17 on the side opposite to the heat pipe 11 side of the flow path 13 for cooling the medium P is made of a material having a heat insulating effect and serves as a second heat insulating member. Examples of the material having a heat insulating effect include hard urethane and polystyrene. As a result, the heated air A containing water vapor is rapidly cooled by the outer wall 17 outside the apparatus of the flow path 13 cooled by the outside air when passing through the flow path 13, and water droplets are generated due to condensation. Can be prevented from falling.

  A water drop receiving member 18 is provided below the flow path 13 for cooling the medium P (FIG. 4), and it is possible to prevent water drops generated by condensation from falling on the medium P.

  In the present embodiment, an indirect transfer type electrophotographic apparatus has been described as an example. However, the present invention is not limited to this, and a photosensitive drum or other image carrier is disposed above the fixing device. The present invention can be applied to various types of image forming apparatuses.

1 is an explanatory diagram showing a schematic configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a perspective view of a main part of an image forming apparatus. 2 is a front view of a main part of the image forming apparatus. FIG. It is a longitudinal cross-sectional view of a flow path.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2Y, 2C, 2M, 2K Image forming apparatus 3 Image carrier, intermediate transfer belt 4Y, 4C, 4M, 4K Photoconductor 7 Fixing apparatus 11 First heat exhausting member 13 Flow path 14 Forced exhaust apparatus 15 First 1 heat insulating member 16 space 17 second heat insulating member 18 receiving member

Claims (6)

An image carrier on which a toner image is formed;
A transfer device for transferring a toner image on the image carrier onto a medium;
A fixing device that is disposed below the image carrier and fixes the toner image on the medium;
A first heat exhaust member comprising a heat pipe that guides and discharges the heat generated by the fixing device to a heat radiating portion at a predetermined position;
A second heat exhaust member that forms a discharge flow path that guides and discharges heat and water vapor generated by the medium after passing through the fixing device to a discharge port adjacent to the heat radiating portion at the predetermined position;
A first heat insulating member that insulates the first heat exhaust member and the exhaust flow path;
A second heat insulating member provided on an outer wall opposite to the first heat exhausting member side of the second heat exhausting member;
With
The lower inner wall, respectively each of the inner wall and the second insulating member of the first heat insulating member facing the discharge passage, the medium is water vapor condensing emitted after passing through the fixing device An electrophotographic image forming apparatus provided with a receiving member for receiving water droplets generated in this manner. An image forming device that forms toner images of different colors on a plurality of photoconductors;
The image forming apparatus according to claim 1, wherein the image carrier is an endless intermediate transfer belt onto which the toner images are transferred in an overlapping manner.   The image forming apparatus according to claim 1, further comprising a forced exhaust device that forcibly exhausts the heat and water vapor discharge flow path from the second exhaust heat member to the outside of the discharge port.   The image forming apparatus according to claim 1, wherein the first heat insulating member is a partition wall on the first heat exhausting member side of the second heat exhausting member.   The image forming apparatus according to claim 1, wherein a vacuum space is provided between the second heat exhaust member and the first heat exhaust member.   The image forming apparatus according to claim 1, wherein the discharge flow path takes a rising path.

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