JP2011059483A - Paper carrying device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a failure image or a trouble such as the waving or jam of paper which is caused by an effect that water drops due to the steam condensation of moisture contained in paper which is evaporated by the heat of a fixing device which is adhered to a guide plate or a carrying roller, and thus absorbed by paper to be carried. <P>SOLUTION: The paper carrying device includes a carrying guide plate which forms a paper carrying path for carrying paper and a condensation means which contacts with air containing moisture to condense the moisture. The carrying guide plate includes an opening, and the condensation means contacts with the air containing moisture in the paper carrying path through the opening, and the thermal capacity of the condensation means is larger than that of the carrying guide plate. The condensation means is provided in a position separated from the carrying surface of the carrying guide plate so as not to contact with the paper to be carried. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a sheet conveying device for an image forming apparatus such as a copying machine, a printer, and a facsimile, and an image forming apparatus including the sheet conveying device.

  In recent image forming apparatuses such as copiers and printers, energy saving has been promoted, and a function to shift to an energy saving mode / sleep mode is generally added when there is no print job for a certain period of time. It is essential to shorten the rise time of the machine. In particular, color machines, for which demand is increasing, have a tendency to increase the amount of heat required for the fixing device, so a mechanism for rapid heating is provided. In this case, the fixing device is at a high temperature, but the other parts are cooled to the outside temperature.

  When printing is performed in a state where the temperature inside the apparatus is not sufficiently warm, the water contained in the paper evaporates when the paper passes through the fixing device, and a large amount of water vapor is generated on the downstream side of the fixing device. If the generated water vapor exceeds the amount of saturated water vapor, it adheres to the guide plate on the conveyance path as condensation, and the conveyed paper picks up the condensed water droplets, causing an abnormal image, or the paper Problems such as waving and jamming occur.

In recent years, in order to save space, an increasing number of copiers, printers, and the like are configured to form images by sending paper in a substantially vertical direction to the side of the machine. For this reason, the water vapor generated in the fixing device rises together with the paper and easily flows to the downstream conveyance path, and the guide plate is likely to condense. In addition, the number of equipment equipped with double-sided equipment as standard is increased for environmental reasons, and there are a wide variety of transport paths after fixing, including diversification of paper discharge trays. The fact is that it is configured with a curve. Therefore, if the guide plate in such a conveyance path is condensed, the sheet may pick up condensed moisture when the sheet passes and an abnormal image may be generated.
To solve this problem, it is better to sufficiently warm the fixing device and its vicinity. However, since it is necessary to warm up the fixing device by spreading the rise time sufficiently, the user's request is met from the viewpoint of speed. It will not be possible.

  Conventionally, a guide plate after fixing may be provided with a slit to allow water vapor to escape to the outside of the machine. Resulting in. Further, if it is attempted to increase the flow rate, it is necessary to add a fan or rotate at a high speed, which causes disadvantages such as an increase in cost and a decrease in the temperature of the fixing unit and noise.

Patent Document 1 discloses a technique in which a fixing device is provided with a cooling device, and water vapor generated by the fixing device is condensed on the entire surface of the cooling unit to remove moisture. Since the water is transported while evaporating / diverging, the water vapor reaches the transport path after fixing, and does not prevent the condensation on the paper in the transport path after fixing.
In Patent Document 2, a heater H using a heating resistor is provided on a paper guide in the fixing device, and heat is generated to heat the guide plate, thereby preventing the occurrence of condensation in the fixing device. There is no detailed description on prevention of dew condensation on the paper in the subsequent transport path.

  Further, Patent Document 3 discloses a device that contacts a cooled conveying roller after fixing an image on a sheet with the sheet and removes moisture condensed on the cooled conveying roller. The load torque is increased to prevent moisture that is condensed later from re-adhering to the paper, or a large removing device is required near the conveyance path, and space saving is hindered. Further, in recent low melting point toner, the toner adheres to the cooled transport roller and may cause problems such as image peeling, and moisture removal is incomplete due to the toner attached to the transport roller.

  Therefore, according to the present invention, the water vapor contained in the paper evaporated by the heat of the fixing device is condensed on the guide plate and the transport roller after the fixing device, and water droplets are attached. An object of the present invention is to prevent an abnormal image from being picked up by water droplets, or a problem such as paper waving or jamming.

  This object is achieved by installing a member that condenses moisture prior to the member that contacts the paper in the vicinity of the portion where the saturated water vapor amount increases. According to the present invention, there is provided a paper transport device having a transport guide plate that forms a paper transport path for transporting a paper, and dew condensation means that contacts and condenses moisture-containing air, wherein the transport guide plate has an opening. The condensation means is in contact with moisture-containing air in the paper conveyance path through the opening, and the heat capacity of the condensation means is larger than the heat capacity of the conveyance guide plate so that the condensation means does not contact the conveyed paper. It is achieved by a sheet conveying device characterized in that it is provided at a position separated from the conveying surface of the conveying guide plate.

In the sheet conveying device, it is preferable that the dew condensation member is disposed in an annular flow path that recirculates the air flowing in from the conveying path to the conveying path.
Further, in the sheet conveying apparatus, it is preferable that the dew condensation member has a moisture moving means for moving the condensed moisture to a predetermined location.

Further, it is preferable that the paper transport device is provided with a moisture removing unit that removes moisture condensed on the condensation member.
Further, it is preferable that the sheet conveying device is provided with a cooling unit for cooling the dew condensation member.

Further, it is preferable that the sheet conveying device is provided in a portion immediately after the conveying downstream side of the fixing device in the image forming apparatus.
Further, it is preferable that the paper transport device is provided in the vicinity of the paper discharge roller pair of the paper discharge unit in the image forming apparatus.

Further, it is preferable that the sheet conveying device is provided in a switchback conveying path that reverses the sheet in the image forming apparatus.
The image forming apparatus according to the present invention includes the paper transport device described above, thereby preventing the occurrence of abnormal images due to water droplets adhering to the transported paper and the occurrence of problems such as paper waving and jamming.

  According to the present invention, the paper evaporated by the heat of the fixing device is installed near the portion where the saturated water vapor amount is high, by installing a member that condenses moisture prior to the member in contact with the paper and lowering the ambient humidity. The water vapor contained in the water does not condense on the guide plate and the transport roller after the fixing device and the water droplets adhere to it. Therefore, the transported paper picks up the water droplets and generates abnormal images and corrugated paper. The occurrence of defects such as jams and jams is prevented.

1 is a schematic cross-sectional view of a full-color printer that is an example of an image forming apparatus according to the present invention. FIG. 2 is a diagram illustrating a sheet conveyance path in the full-color printer illustrated in FIG. 1. It is a figure which shows a mode that the duplex unit in the full-color printer shown in FIG. 1 was open | released. It is a schematic sectional drawing of the full-color printer which is another example of the image forming apparatus which concerns on this invention. It is a figure which shows a mode that the duplex unit in the full-color printer shown in FIG. 4 was open | released. It is a schematic sectional drawing of 1st Example of the paper conveying apparatus which concerns on this invention. It is the schematic front view which looked at the paper conveying apparatus shown in FIG. 6 from the conveyance path side. It is a schematic sectional drawing of 2nd Example of the paper conveying apparatus which concerns on this invention. It is the schematic front view which looked at the paper conveying apparatus shown in FIG. 8 from the conveyance path side. It is a figure which shows the modification of the dew condensation member as a roller member which concerns on this invention. FIG. 3 is an enlarged view of a fixing device and a branch discharge portion in the image forming apparatus according to the present invention.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a cross-sectional configuration diagram showing an outline of a full-color printer which is a first embodiment of an image forming apparatus according to the present invention. In the full-color printer 100, an intermediate transfer belt 11 wound around a plurality of rollers is disposed at a substantially central portion of the apparatus main body 50, and four pieces are formed along the lower running side of the intermediate transfer belt 11. An image unit 10 is provided.

  Each image forming unit 10 includes a photosensitive drum 1 as an image carrier. A charging unit, a developing device, a cleaning unit, and the like are disposed around the photosensitive drum 1, and a transfer roller 12 serving as a primary transfer unit is disposed inside the intermediate transfer belt 11 at a position facing each photosensitive drum 1. Is provided. In the present embodiment, the four image forming units 10 have the same structure, but the developer colors handled by the developing devices of the respective image forming units are magenta (M), cyan (C), yellow (Y ) And black (Bk). As shown in the figure, the four image forming units 10 are arranged in the order of colors of magenta, cyan, yellow, and black from the left. Each image forming unit 10 is detachably attached to the apparatus main body 50 as a process cartridge.

  An optical writing device 14 is provided below the image forming unit 10. The optical writing device 14 includes a polygon mirror, a group of mirrors (not shown), and the like, and irradiates the surface of the photosensitive drum 1 of each color image forming unit 10 with light-modulated laser light. The optical writing device may be provided individually for each image forming unit 10, but using a common optical writing device is advantageous in terms of cost. In this embodiment, the intermediate transfer belt 11 and the optical writing device 14 are also unitized, and are configured to be detachable from the apparatus main body 50.

  Two stages of paper feed cassettes 15a and 15b are set in the lower part of the apparatus, and paper feed means 16a and 16b corresponding to the respective paper feed cassettes are provided. Each of the sheet feeding means 16a and 16b includes a calling roller, a supply roller, and a separation roller. Conveying roller pairs 17 and 17 are provided for conveying a recording medium such as transfer paper (hereinafter referred to as paper) fed by the paper feeding means 16a and b. A registration roller pair 18 is provided above the upper conveyance roller pair 17 (on the downstream side in the paper conveyance direction). Above the pair of registration rollers 18, a transfer roller 19 as a secondary transfer unit is provided to face a transfer counter roller 13 that is one of the rollers around which the intermediate transfer belt 11 is stretched.

  A fixing device 20 is provided above the secondary transfer unit. Above the fixing device 20, first, second, and third switching claws 21, 22, and 23 for switching the paper transport direction are provided. Has been placed. Each switching claw 21, 22, 23 is switched to a position indicated by a solid line and a broken line in FIG. 2 by an actuator such as a solenoid (not shown). Reference numerals 24, 25, 26, and 27 indicate conveyance roller pairs that are appropriately disposed in the sheet conveyance path. Reference numerals 35, 36, 37, 38, 39, 40, and 41 denote paper sensors that are appropriately disposed in the paper transport path. Note that the paper conveyance path is appropriately guided by a member (not labeled) such as a guide plate.

The upper surface of the apparatus main body 50 is configured as a paper discharge tray 30, and a paper discharge roller pair 29 for discharging paper to the paper discharge tray 30 is provided at the upper left of the fixing device 20.
A switchback transport path 61 and a refeed path 62 are formed in the duplex unit 60. A first reverse roller pair 31 is provided at the inlet (upper side of the apparatus) of the switchback conveyance path 61, and a second reverse roller pair 32 is provided in the middle of the switchback conveyance path 61. The first and second reversing roller pairs 31 and 32 are configured to be rotatable forward and backward. A pair of conveying rollers 26 and 27 is arranged at a position where the refeeding path 62 is divided into approximately three equal parts. The third switching claw 23 is disposed right next to the first reversing roller pair 31 and at an entry portion from the switchback conveyance path 61 to the refeed path 62.

  A manual feed tray 33 is provided on the side surface of the duplex unit 60 so that it can be pulled out and stored. FIG. 1 shows a state where the manual feed tray 33 is pulled out. In order to feed a sheet from the manual feed tray 33, a sheet feeding unit 34 including a calling roller, a supply roller, and a separation roller is provided. A re-feed roller 28 is disposed on the side of the paper feed means 34 and inside the apparatus. The driven rollers are in pressure contact with the upper and lower sides of the refeed roller 28, respectively. The re-feed roller 28 is configured to be able to rotate forward and backward. When the paper is re-feeded from the re-feed path 62, the re-feed roller 28 is rotated counterclockwise in the drawing to feed the paper from the manual feed tray 33. In this case, it is rotated clockwise in the figure.

Next, an image forming operation in the full color printer 100 of the present embodiment configured as described above will be briefly described.
The photosensitive drum 1 of the image forming unit 10 is rotated in the clockwise direction in the figure by a driving means (not shown), and the surface of the photosensitive drum 1 is uniformly charged to a predetermined polarity by the charging means. The charged photoconductor surface is irradiated with laser light from the optical writing device 14, whereby an electrostatic latent image is formed on the photoconductor drum 1 surface. At this time, the image information exposed to each photosensitive drum 1 is single-color image information obtained by separating a desired full-color image into magenta, cyan, yellow, and black color information. Each color toner is applied from the developing device to the electrostatic latent image formed in this way, and visualized as a toner image.

Further, the intermediate transfer belt 11 is driven to run counterclockwise in the drawing as indicated by an arrow, and each color toner image is sequentially transferred from the photosensitive drum 1 to the intermediate transfer belt 12 by the action of the primary transfer roller 12 in each image forming unit 10. Overprinted. In this way, the intermediate transfer belt 11 carries a full-color toner image on the surface thereof.
Note that any one of the image forming units 10 can be used to form a single-color image or a two-color or three-color image. In the case of monochrome printing, image formation is performed using the black image forming unit 10Bk on the rightmost side of the drawing among the four image forming units.
The residual toner adhering to the surface of the photosensitive drum after the toner image is transferred is removed from the surface of the photosensitive drum by the cleaning device, and then the surface is subjected to the action of the static eliminator to initialize the surface potential. Ready for image formation.

  On the other hand, the paper is selectively fed from the paper feed cassettes 15a and 15b or the manual feed tray 33, and the registration roller pair 18 takes the timing with the toner image carried on the intermediate transfer belt 11 to the secondary transfer position. Sent out. In this embodiment, a transfer voltage having a polarity opposite to the toner charging polarity of the toner image on the surface of the intermediate transfer belt is applied to the transfer roller 19, whereby the toner image on the surface of the intermediate transfer belt is collectively transferred onto the paper. When the sheet on which the toner image has been transferred passes through the fixing device 20, the toner image is fused and fixed to the sheet by heat and pressure. The sheet on which the toner image is fixed is discharged by a pair of discharge rollers 29 to a discharge unit 30 formed on the upper surface of the apparatus main body 50. A sheet conveyance path during single-sided printing (when the sheet is fed from the sheet feeding cassettes 15a and 15b) is indicated by a solid line [1] in FIG.

  An optional paper discharge tray (for example, a 4-bin tray having a sorting function) can be mounted on the upper surface of the apparatus above the second switching claw 22, and the fixed sheet can be discharged to the optional tray (not shown). It is. A paper transport path (after passing through the fixing device) when paper is discharged to the option tray is indicated by a broken line [2] in FIG.

  When printing on both sides of the sheet, the sheet having the toner image fixed on one side of the sheet is caused to enter the switchback conveyance path 61 by appropriately switching the first to third switching claws 21 to 23. In this case, the first and second switching claws 21 and 22 are switched to the positions indicated by broken lines in FIG. Moreover, the 3rd switching nail | claw 23 is switched to the position of the continuous line of FIG. The first and second reversing roller pairs 31 and 32 are rotated clockwise. A conveyance path (however, after the conveyance roller pair 25) when the sheet enters the switchback conveyance path 61 is indicated by a two-dot chain line [3] in FIG.

  When the sensor 40 detects the trailing edge of the paper that has entered the switchback conveyance path 61, the first and second reversing roller pairs 31, 32 are rotated counterclockwise to reverse the paper. At this time, by switching the third switching claw 23 to the position of the broken line in FIG. 2, the reversed paper is sent to the refeed path 62.

  The sheet re-feeding path 62 joins with the sheet conveying path from the manual feed tray 33 at the lower end thereof, and further merges with the sheet conveying path from the sheet feeding cassettes 15 a and 15 b on the back side of the sheet re-feeding roller 28. . The sheet is transported in the refeed path 62 by the transport roller pairs 26 and 27 and further sent to the registration roller 18 by the refeed roller 28. A sheet conveyance path (however, from the third switching claw 23 to a portion joining the solid line [1]) passing through the refeed path 62 is indicated by a one-dot chain line [4] in FIG. Further, a sheet conveyance path (up to a position after the refeed roller 28 is removed) when the sheet is fed from the manual feed tray 33 is indicated by a dotted line [5] in FIG.

  By passing the paper reversed by the switchback conveyance path 61 through the refeed path 62, the front and back of the paper are reversed, and the toner image is transferred from the intermediate transfer belt 11 to the back of the paper, and the back image is fixed to the fixing device. By fixing at 20, the paper carrying the images on both the front and back sides is discharged to the paper discharge tray 30 or an optional tray (not shown), whereby double-sided printing is completed.

  In the printer 100 of the present embodiment, the duplex unit 60 is provided so as to be swingable about a rotation shaft 63 provided at the lower part thereof, and the duplex unit 60 is provided so as to be openable and closable with respect to the apparatus main body 50. . FIG. 3 shows a state where the duplex unit 60 is opened. The duplex unit 60 is supported by the apparatus main body 50 by a link mechanism (not shown), and stops at a predetermined position when opened. Further, in order to reduce the opening / closing force of the double-sided unit 60, it is preferable to provide a damper means in the link mechanism that supports the double-sided unit 60. As the damper means, one using a spring, an oil damper or the like can be used.

  Included in the duplex unit 60 and opened and closed with respect to the apparatus main body 50 are a guide plate that forms a switchback conveyance path 61, a part of a guide plate 66 that forms a refeed path 62, and a sub-rotation unit. In addition to 64, there are a third switching claw 23, first and second reversing roller pairs 31 and 32, a manual feed tray 33, its paper feed means 34, a refeed roller 28, and the like. The driven rollers 17 b and 17 b of the two transport roller pairs 17 and 17 are members included in the duplex unit 60.

The sub-rotation unit 64 supports the secondary transfer roller 19, the driven roller 27 b of the conveyance roller pair 27, the driven roller 28 b of the refeed roller 28, and the paper sensor 41, and swings about the rotation shaft 65 as a fulcrum. It is configured to be movable. The rotation shaft 65 of the sub-rotation unit is supported by the structural member (side plate) of the duplex unit and the conveyance guide plate.
Further, the sub-rotation unit is provided with a stopper member (not shown), and the sub-rotation unit 64 is opened more than the angle shown in FIG. 3 (rotates counterclockwise from the illustrated state in FIG. 3). There is nothing.

  One side (outside of the apparatus) of the refeed path 62 is defined by a guide plate 66, and the opposite side (inside of the apparatus) is sequentially arranged on one side of the guide member 42, one side of the fixing device 20, and the sub-rotation unit 64. When the duplex unit 60 is closed, a refeed path 62 is formed by the above-described members.

  In the full color printer 100 of this embodiment, when a paper jam occurs during the printing operation, the duplex unit 60 is opened as shown in FIG. At this time, as described above, the two sheet conveyance paths 43 of the normal sheet conveyance path 43 and the refeed path 62 are simultaneously opened by the action of one action that only opens the duplex unit 60, so that the jammed sheet can be easily removed. In addition, since the pressure contact between the conveying roller pair 17, 17, 26, 27, the transfer roller 19 and the intermediate transfer belt 11, the refeed roller 28, and the upper driven roller 28b is released, jam processing is performed. Has become very easy.

  In addition, both the jam processing during single-sided printing and the jam processing during double-sided printing are performed by removing the jammed paper by performing the same operation of opening the duplex unit 60. Units to be released will be unified. Therefore, the user is not confused during the jam processing and has an excellent jam processing property. In addition, since the duplex unit is provided with a switchback conveyance path and a refeed path, even when a jam occurs between the switchback conveyance path and the refeed path, the jammed paper is removed by opening the duplex unit 60. It will not be cut by being pulled.

  Next, the second image forming apparatus according to the present invention is configured such that a plurality of image forming units 10 are arranged side by side along the paper conveyance path, and a toner image is directly transferred from each image forming unit 10 onto the conveyed paper. Examples will be described with reference to FIGS. 4 and 5. FIG. In addition, the same code | symbol is attached | subjected to the part which is the same as that of the said 1st Example, and the overlapping description is abbreviate | omitted.

  FIG. 4 is a diagram schematically illustrating the configuration of the full-color printer 200 according to the second embodiment. In this embodiment, four image forming units 10 are arranged in the order of magenta (M), cyan (C), yellow (Y), and black (Bk) from the bottom in the approximate center of the apparatus main body 50. . On the left side of the four image forming units 10, an optical writing device 14 is provided in each image forming unit, and writing light is irradiated from the optical writing device 14 to the photosensitive drum 1 of each image forming unit 10. Further, a conveyor belt 11 ′ is disposed so as to face the photosensitive drum 1 of each image forming unit 10. A transfer roller 12 is disposed in the transport belt 11 ′ so as to face each photosensitive drum.

  In this embodiment, at the time of single-sided printing, the paper fed from the paper feeding unit 15 is sent out in a timely manner by the registration roller pair 18, and is nipped between the conveyance belt 11 ′ and each photosensitive drum 1 and conveyed. On the other hand, the toner images of the respective colors are directly transferred from the photosensitive drums 1 onto the paper. After the toner image is transferred, the toner is fixed by the fixing device and is discharged to a paper discharge tray on the upper surface of the device. The sheet conveyance path at this time is indicated by a solid line [1] in FIGS.

  In the duplex unit 60, a switchback conveyance path and a refeed path are formed in the same manner as in the first embodiment, and the conveyance path when the paper enters the switchback conveyance path is shown in FIGS. This is indicated by a two-dot chain line [3]. Further, the sheet conveyance path passing through the refeed path is indicated by a one-dot chain line [4] in FIGS. A pair of conveyance rollers and sensors are arranged in each sheet conveyance path in the same manner as in the first embodiment, but illustration and description thereof are omitted here.

  FIG. 5 is a schematic diagram showing a state where the duplex unit 60 is opened in the full-color printer 200 of the second embodiment. As shown in the figure, a sub-rotation unit 64 ′ is rotatably supported by the double-sided unit 60. When the double-sided unit 60 is opened, it is always recharged in the same way as the sub-rotating unit 64 of the first embodiment. The sub-rotation unit 64 'biased in the direction of opening the paper path rotates counterclockwise in the figure as indicated by the arrow, and the normal paper transport path and the refeed path are simultaneously opened. This is the same as the embodiment. In the present embodiment, the conveyance belt 11 'is mounted on the sub-rotation unit 64'.

  Even in the image forming apparatus configured to transfer toner images directly from a plurality of image forming units onto a sheet to be transported configured as described above, the normal sheet transport path 43 and the refeed path are opened by opening the duplex unit 60. Since 62 can be released at the same time, jam processing can be facilitated by unifying units to be released during jam processing regardless of the recording mode. Other operations are the same as those in the first embodiment.

  Further, in this embodiment, since the pressure contact between the photosensitive drums 1 arranged in the paper transport path and the transport belt 11 ′ is released by opening the duplex unit 60, the paper removability at the time of jam processing is improved. It is done. Further, since each photosensitive drum 1 and the conveying belt 11 'are pressed against each other by closing the unit, it can be automatically returned to an operable state.

  Further, in the present embodiment, since the transport belt 11 'is supported by the sub-rotation unit 64', maintenance of the transport belt unit having a complicated structure and a high frequency of adjustment work is facilitated. Further, since the transfer means is arranged in the conveying belt, the maintenance of the transfer portion is facilitated.

Next, a first embodiment of the paper conveying apparatus according to the present invention is shown in FIGS.
As shown in the drawing, an opening 302 is provided in a conveyance guide plate 300 in a conveyance path formed between arbitrary conveyance roller pairs A and B for conveying a sheet in the above-described image forming apparatus, and conveyance is usually made of resin. A dew condensation member 303 made of a metal having a larger heat capacity than the guide plates 300 and 301 is disposed. The conveyance roller pair A, B is rotated in the direction of the arrow in the figure by a driving source (not shown), and the sheet is conveyed from the lower side to the upper side. The dew condensation member 303 is formed by a plate-like cooling part 304 and a plurality of extending parts extending up and down in a substantially vertical direction therefrom, and the part of the extending part closest to the conveying path is conveyed by the conveying guide plate 300. It is set apart from the surface by a gap α in the concave direction. Since the dew condensation member 303 is exposed to the air in the conveyance path, the dew condensation member 303 having a larger heat capacity than the conveyance guide plates 300 and 301 is positively preceded by the conveyance guide plate when the humidity in the conveyance path is high. Condensation causes the humidity in the transport path to decrease. Therefore, the dew condensation on the conveyance guide plates 300 and 301 can be suppressed, and the dew condensation is prevented from adhering to the paper.
Here, an example of a dew condensation member formed by a plate-like cooling part and a plurality of extending parts extending vertically up and down from the plate-like cooling part in the straight conveyance path is shown. May be.

  The gap α is set so that even if water droplets adhere to the surface of the dew condensation member 303, the paper does not pick up water droplets. If the openings 302 are slit-like openings arranged at a plurality of locations in the conveyance path width direction, the entry of paper is reduced. If the dew condensation member 303 protrudes between the slits, the gap α can be set smaller, and the surface area of the dew condensation member 303 is also increased, so that it becomes easier to touch the air in the conveyance path.

  The condensation member 303 is provided with a gradient in which the condensed moisture moves in a direction away from the conveyance surface by its own weight. Due to the gradient functioning as the moisture moving means, the moisture is prevented from moving to the conveyance path side when the amount of dew condensation increases, and moisture adhesion to the paper is prevented.

The dew condensation member 303 is provided with a cooling unit 304 and is cooled by a cooling fan 305. Thereby, the temperature rise of the dew condensation member 303 can be prevented and the dew condensation effect can be maintained. The cooling fan 305 also serves as a fan for the airflow in the image forming apparatus, and the cost increase can be suppressed by extending the cooling unit 304 of the dew condensation member 303 to the airflow fan in the apparatus. If a heat pipe is used, the cooling efficiency is good.
Further, a recovery container 306 that recovers water droplets falling by its own weight may be provided below the tapered lower end of the dew condensation member 303. The collected water droplets are prevented from evaporating and diverging out of the collection container, and are periodically discarded by maintenance, for example.

  FIG. 7 is a schematic front view of the dew condensation member 303 of FIG. 6 as viewed from the conveyance path side. A plurality of slit-shaped openings 302 are provided in the conveyance guide plate 300 in the width direction, and the extended portions of the dew condensation member 303 are separated from the conveyance surface of the conveyance guide plate 300 by a gap α in the concave direction. Projecting at the portion 302.

Next, a second embodiment of the paper conveying apparatus according to the present invention is shown in FIGS.
As shown in the figure, an opening 312 is provided in a conveyance guide plate 310 in a conveyance path formed between any pair of conveyance rollers C and D for conveying a sheet in the above-described image forming apparatus, and a conveyance made of ordinary resin is provided there. A dew condensation member 313 made of a metal having a larger heat capacity than the guide plates 310 and 311 is disposed. The conveyance roller pairs C and D are rotated in the direction of the arrow in the drawing by a driving source (not shown), and the sheet is conveyed from the lower side to the upper side. As shown in FIG. 9, the dew condensation member 313 is a roller member in which a plurality of large-diameter protrusions 319 are provided on a small-diameter shaft portion, and can be rotated in the direction of the arrow in the drawing by a drive source (not shown). The large-diameter protruding portion 319 closest to the conveyance path is disposed away from the conveyance surface of the conveyance guide plate 310 by a gap β in the concave direction. Since the dew condensation member 313 is exposed to the air in the conveyance path, when the humidity in the conveyance path is high, the dew condensation member 313 having a larger heat capacity than the conveyance guide plates 310 and 311 preferentially dew condensation and Since the humidity is lowered, dew condensation on the conveyance guide plates 310 and 311 can be suppressed.
Here, an example of a dew condensation member as a roller member in the bent conveyance path is shown, but this may be used in a straight conveyance path.

  The gap β is set so that even if water droplets adhere to the surface of the condensation member 313, the conveyed paper does not pick up water droplets. If the openings 312 are slit-like openings arranged in a plurality of locations in the conveyance path width direction, the entry of paper is reduced. If the dew condensation member 313 protrudes between the slits, the gap β can be set smaller, and the dew condensation member 313 can easily touch the air in the conveyance path.

  The dew condensation member 313 is rotatably supported, and is rotated clockwise so that the portion facing the conveyance path moves in the same direction as the sheet conveyance direction. As a result, the dew condensation member 313 functions as a water movement unit that moves the dew condensation water to a predetermined location. Therefore, when the amount of dew condensation increases, the dew condensation member 313 prevents the water from moving to the conveyance path side, and moisture adheres to the paper. Is prevented. A scraper 314 comes into contact with the dew condensation member 313 to remove moisture condensed on the surface of the dew condensation member, and the removed water is collected in the collection container 315. If the scraper 314 is arranged on the upstream side of the opening 312, for example, on the lower side in the vertical direction passing through the axis of the dew condensation member 313, moisture is always removed on the side where the dew condensation member faces the conveyance path, and the amount of dew condensation increases. In this case, it is possible to prevent moisture from flowing out to the conveyance path side and dripping into the apparatus.

In the case of this embodiment, it is also possible to increase the moisture absorption effect by causing the dew condensation member 313 to protrude into the conveyance path. However, when the toner is disposed immediately after the fixing device, the low melting point toner adheres, so that a dew condensation member is preferably disposed on the non-image surface side. Needless to say, if the peripheral speed of the dew condensation member 313 is set to be the same as the transport speed, there is no problem in the transport.
The moisture removing means may be a water absorbing member such as a web in addition to the scraper 314. Also in this embodiment, as in FIG. 6, if a cooling device that extends a part of the dew condensation member 313 and cools it by air is formed, the dew condensation effect can be maintained.

Further, in FIG. 8, an annular flow path 316 is provided behind the dew condensation member 313 to recirculate the air that has flowed in from the conveyance path to the conveyance path, and the air that has touched the dew condensation member 313 is opened in the downstream conveyance guide plate 318. The annular flow path 316 is configured to flow from 317 to the conveyance path. Thereby, the air from which moisture has been removed by the dew condensation member 313 can be supplied to other parts of the transport path to reduce the humidity, and dew condensation there can also be prevented.
Here, natural convection caused by the rise of warm air, or when the fan for discharging outside the machine can also be used as a fan for generating the in-machine airflow, the in-machine airflow is used as the airflow in the reflux path 316, so that the blower fan Cost up can be avoided without the need to add.

  FIG. 9 is a schematic front view of the dew condensation member 313 of FIG. 8 viewed from the conveyance path side. A plurality of slit-shaped openings 312 are provided in the conveyance guide plate 310 in the width direction, and the large-diameter protruding portions 319 of the dew condensation member 313 are individually separated from the conveyance surface of the conveyance guide plate 310 by a gap β in the concave direction. Projecting at the opening 312. The scraper 314 is in contact with the lower side of the large-diameter projecting portion 319 and removes moisture condensed on the surface of the large-diameter projecting portion 319. The collection container 315 is provided further below the scraper 314 and collects moisture.

FIG. 10 shows a modification of the dew condensation member 323 as a roller member. The dew condensation member 323 can be rotated in the direction of the arrow in the figure by a drive source (not shown). As shown in the drawing, a jagged wing-like member 325 extending outward from the small-diameter shaft portion is provided between the large-diameter protrusions 324. As a result, when the dew condensation member 323 rotates, the wing-like member 325 pushes air to the downstream side in the rotation direction, that is, the reflux path side, so that ventilation in the reflux path is promoted. Further, since the surface area of the dew condensation member 323 increases, dew condensation is also promoted. The scraper 326 is in contact with the lower side of the large-diameter protruding portion 324, and removes moisture condensed on the surface of the large-diameter protruding portion 324. The recovery container 327 is provided further below the scraper 326 and recovers moisture.
The right side view of FIG. 10 is a cross-sectional view of the shaft portion. The small-diameter shaft portion may be provided with a wing-like member extending outward, or the shape of the shaft portion itself may be configured to protrude outward.

FIG. 11 is an enlarged view of the fixing device and the branch discharge portion in the image forming apparatus 100 according to the present invention.
The portion immediately after the downstream side in the conveyance direction of the fixing device 20 is a portion having the largest amount of water vapor, and the humidity can be effectively reduced by disposing the dew condensation members 330 and 331 here. Since the conveyance guide plate 332 is provided with slit openings 333 at a plurality of locations in the conveyance width direction, air is taken in from these slit openings 333 and is absorbed by dew condensation by the dew condensation members 330 and 331. Thereafter, the air absorbed by the dew condensation member 330 returns to the downstream conveyance path through the upper opening 334. As shown in FIG. 8, if the air that has been absorbed is recirculated to a portion where the branching claws and sensors are densely packed and the dew condensation member cannot be installed, an increase in humidity can be effectively suppressed.

  Further, the dew condensation members 335 and 336 may also be disposed in the vicinity of the paper discharge roller pair 29 in the paper discharge unit. The dew condensation member 335 on the upper side of the conveyance path can capture the water vapor that rises and positively condense it, and the lower dew condensation member 334 can efficiently capture the water vapor that is retained by the sheet. It can be actively condensed. As a result, the amount of water vapor in the air decreases, condensation on the conveyance guide plate can be prevented, and water droplet adhesion to the paper can be prevented until the paper is discharged. The dew condensation members 330, 331, and 335 can be rotated in the direction of the arrow in the figure by a drive source (not shown), and a scraper and a recovery container as moisture removing means may be provided as appropriate.

Although not shown, if a dew condensation member is similarly arranged in the switchback conveyance path 61 that is a reversing unit for reversing the paper, the water vapor generated from the conveyed paper is captured to reduce the amount of water vapor in the air, and the manual feed table For example, it is possible to prevent condensation on the transport guide plate in the switchback transport path where it is difficult to form an opening. Since the dew condensation member is provided in the reversing part, adverse effects due to dew condensation on the double-sided second-side printing can be prevented.
These dew condensation members may be installed alone, or may be combined and arranged in a plurality of effective portions.

Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto.
For example, the present invention can be applied to a monochrome apparatus having a single image carrier as an image forming apparatus. Of course, the image forming apparatus is not limited to a printer, and may be a copying machine or a facsimile, or a multi-function machine having a plurality of functions. Further, the image forming method is not limited to the electrophotographic method, and the present invention can be applied to an apparatus of an arbitrary image forming method.
Moreover, the member etc. which are mounted in the double-sided unit side can be set as appropriate. The configuration of the fixing device is also arbitrary. In the fixing device, an arbitrary configuration can be adopted as the configuration for releasing the applied pressure between the fixing member and the pressure member.
Further, one or a plurality of paper transport devices may be provided on the upstream side of transport of the fixing device.

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 10 Image forming unit 11 Intermediate transfer belt 11 'Conveyor belt 12 Transfer roller 14 Optical writing device 18 Registration roller pair 19 Secondary transfer roller 20 Fixing device 21, 22, 23 Switching claw 24, 25, 26, 27 Conveyance Roller pair 28 Refeed roller 60 Duplex unit 61 Switchback transport path 62 Refeed path 64, 64 'Sub-rotation unit 100, 200 Full color printer

Japanese Patent Application Laid-Open No. 2007-293111 Japanese Unexamined Patent Publication No. 2000-89594 Japanese Patent Application Laid-Open No. 2007-86310

Claims (9)

A paper transport device having a transport guide plate that forms a paper transport path for transporting paper, and dew condensation means that contacts and condenses moisture-containing air,
An opening is provided in the transport guide plate, and the dew condensation means is in contact with moisture-containing air in the paper transport path through the opening,
The heat capacity of the dew condensation means is larger than the heat capacity of the transport guide plate,
The paper transporting apparatus, wherein the dew condensation means is provided at a position separated from the transport surface of the transport guide plate so as not to contact the transported paper.   2. The sheet conveying device according to claim 1, wherein the dew condensation member is disposed in an annular flow path that recirculates air flowing in from the conveying path to the conveying path again. 3.   3. The sheet conveying apparatus according to claim 1, wherein the dew condensation member includes a moisture moving unit that moves the condensed moisture to a predetermined location.   The paper conveying apparatus according to claim 1, further comprising a water removing unit that removes water condensed on the dew condensation member.   The sheet conveying apparatus according to claim 1, further comprising a cooling unit that cools the dew condensation member.   The sheet conveying device according to any one of claims 1 to 5, wherein the sheet conveying device is provided in a portion of the image forming apparatus immediately after the downstream side in the conveying direction of the fixing device.   The paper conveying device according to claim 1, wherein the paper conveying device is provided in the vicinity of a pair of paper discharge rollers of a paper discharge unit in the image forming apparatus.   The sheet conveying apparatus according to claim 1, wherein the sheet conveying apparatus is provided in a switchback conveying path that reverses the sheet in the image forming apparatus.   An image forming apparatus comprising the sheet conveying device according to claim 1.

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