JP2010175861A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus for suppressing occurrence uneven brightness even when the temperature of a sheet having passed a fixing section is high. <P>SOLUTION: A lower guide 9 is disposed on the downstream side of the sheet conveying direction of the fixing section for fixing, to the sheet, a toner image that is formed in an image forming section and then transferred on the sheet, and the sheet to which the toner image is fixed by the fixing section. The lower guide 9 is provided with a small guide 13 for passing the sheet conveyed from the fixing section in a separated state from the lower guide 9, and a clearance C1 constituting a thermal insulation section between the small guide 13 and the lower guide 9. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to a configuration of a guide member that is provided on a downstream side of a fixing unit in a sheet conveying direction and guides a sheet on which a toner image is fixed.

  2. Description of the Related Art Conventionally, some image forming apparatuses such as copying machines and printers form images by an electrophotographic method. In such an image forming apparatus, when an image is formed on a sheet, a toner image is first formed in the image forming unit, the toner image is transferred to the sheet by the transfer unit, and then the sheet is guided to the fixing unit. Yes.

  In this fixing unit, unfixed toner on the sheet is fixed to the sheet. As such a fixing section, a fixing roller and a pressure roller are provided, and heat and pressure fixing that fixes a toner image on the sheet by simultaneously applying heat and pressure to the sheet by the fixing roller and the pressure roller. There is a department.

  By the way, in recent years, in image forming apparatuses, colorization has been promoted along with higher speed and higher image quality. Here, as a feature of the color image formed by colorization, that is, the feature of color print, when printing photographs and graphics, high-quality and high-gloss prints using a dedicated glossy sheet with high smoothness Image quality is mentioned.

  In general, in order to obtain high gloss image quality, it is necessary to perform sufficient heating in the fixing unit to fix the toner image transferred to the glossy sheet. That is, when fixing the toner image transferred to the glossy sheet, it is necessary to sufficiently dissolve the toner at a temperature higher than that of the sheet normally used.

  However, since the sheet fixed at a high temperature in the fixing unit is naturally delayed in cooling, it contacts the sheet conveying roller or the like located downstream of the fixing unit while maintaining the temperature above the glass transition temperature of the toner. To do. At this time, only the contact portion with the sheet conveying roller or the like is locally cooled to a temperature equal to or lower than the glass transition temperature of the toner, so that gloss unevenness occurs.

  In order to prevent this, conventionally, for example, a leveling roller is disposed in an area where the fixed toner is in a soft state downstream of the fixing unit in the sheet conveying direction, and the leveled roller makes the fixed toner soft. There is one in which a certain sheet is conveyed (see Patent Document 1). Here, since the leveling roller conveys the sheet while being in pressure contact with the sheet over the entire width direction of the sheet, the entire image area of the sheet is uniformly cooled, and the sheet is removed without causing uneven gloss. Can be transported.

  Also, in order to prevent the occurrence of uneven glossiness, as a discharge roller provided on the downstream side of the fixing unit, the sheet is sandwiched between the rollers and the sheet is waved in the width direction, so that a good discharge performance with a so-called waist is attached. There is one in which an elastic layer is applied to the roller outer peripheral layer while maintaining the above (see Patent Document 2). In such a discharge roller, the surface layer of the roller, which is a roller outer peripheral layer, is formed of, for example, an elastic layer of foamed silicon rubber.

  Here, in the case of the elastic layer of foamed silicon rubber, small holes due to a large number of bubbles are generated on the roller surface in the rubber foaming process, and when the sheet is discharged, the small holes on the roller surface come into contact with the toner surface and the back surface of the sheet. To do. In this case, the contact area of the roller with the sheet becomes small, and the heat capacity of the roller itself is small, so the amount of heat taken from the toner surface of the roller is small, and the occurrence of uneven gloss can be suppressed.

  By the way, in the conventional image forming apparatus, with the recent digitization and combination, for example, an image reading apparatus is arranged above the image forming apparatus main body, and a sheet is placed in a space between the image forming apparatus main body and the image reading apparatus. There is a so-called in-cylinder discharge method. Further, in such an in-cylinder discharge type image forming apparatus, a relay conveyance device that conveys a sheet after image formation to a paper discharge tray is arranged in a cylinder discharge space on the downstream side of the fixing unit.

  Here, in such a relay conveyance device, there is one configured to convey the sheet while changing the sheet passing time of the relay conveyance device according to the type of sheet (see Patent Document 3). For example, when a glossy sheet is conveyed, the toner image is solidified by temporarily stopping and cooling the sheet in the relay conveying apparatus, and then conveying the sheet to obtain uneven glossiness. Is to prevent the occurrence of.

JP 2003-195663 A JP 2008-030892 A JP 2007-062970 A

  By the way, in such a conventional image forming apparatus, when a leveling roller or a roller having an outer peripheral layer is used, it is possible to suppress the occurrence of uneven gloss when the sheet passes through the roller. However, a guide member for guiding the sheet to the roller is provided on the upstream side in the sheet conveying direction of the roller, and a guide member for guiding the sheet fed by the roller is provided on the downstream side of the roller in the sheet conveying direction. ing.

  Here, in order to prevent jamming in the vicinity of the roller, the sheet and the guide member have to come into contact with each other. When the sheet comes into contact with the guide member in this way, the toner image is locally generated by heat transfer at the contact portion. It is cooled and uneven gloss occurs at the contact portion.

  In addition, when a leveling roller is used, the toner surface can be leveled uniformly, but in general, a roller with a rubber elastic layer formed on a metal shaft has a small heat capacity and a sufficient cooling effect on the sheet itself. is not. For this reason, when passing through the leveling roller, the toner surface is leveled uniformly, but since the toner still maintains a high temperature, when the sheet comes into contact with the guide member downstream of the roller, uneven glossiness is generated on the sheet. May occur. In this way, by using a leveling roller or a roller having an elastic layer on the outer peripheral layer, it is possible to prevent the occurrence of uneven gloss when passing through the roller, but it is possible to prevent the occurrence of uneven gloss in the guide member. Can not.

  Further, when the toner is solidified by stopping and cooling the sheet once in the relay conveyance device, a sufficient cooling time is required. However, because of recent downsizing of image forming apparatuses, there is a tendency that the fixing unit and the discharge rollers and the relay conveyance device are arranged close to each other, and the sheets are conveyed to the discharge rollers and the relay conveyance device in a state where the sheets are not sufficiently cooled. End up.

  Further, as the speed increases, the amount of heat applied to the sheet from the fixing unit tends to increase, and along with the downsizing of the image forming apparatus, the temperature of the sheet downstream of the fixing unit tends to become even higher. For this reason, in order to sufficiently cool the toner on the sheet, it is necessary to stop for a long time. However, if the sheet is stopped for a long time in this way, the throughput is lowered.

  Therefore, the present invention has been made in view of such a current situation, and an object of the present invention is to provide an image forming apparatus capable of suppressing occurrence of uneven glossiness even when the temperature of a sheet that has passed through a fixing unit is high. It is what.

  The present invention provides an image forming apparatus comprising: an image forming unit that forms a toner image; and a fixing unit that fixes the toner image formed on the image forming unit and then transferred to the sheet to the sheet. And a guide member that guides a sheet on which a toner image is fixed by the fixing unit, and a sheet that protrudes from the guide member and that is conveyed from the fixing unit, is separated from the guide member. And a sheet contact portion having heat insulating properties to be passed in the state.

  As in the present invention, by passing the sheet from the fixing unit in a state of being separated from the guide member by the sheet contact unit having heat insulation properties, even when the temperature of the sheet that has passed through the fixing unit is high, uneven gloss occurs. Can be suppressed.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings.

  FIG. 1 is a perspective view of a full-color laser printer that is an example of an image forming apparatus according to a first embodiment of the present invention, and FIG. 2 is a diagram illustrating a schematic configuration thereof.

  1 and 2, reference numeral 1 denotes a full-color laser beam printer, and 1A denotes a full-color laser beam printer main body (hereinafter referred to as a printer main body). Reference numeral 1B denotes an image forming unit that forms a toner image, 2 denotes a sheet feeding device that feeds the sheet S to the image forming unit 1B, and 22 denotes a fixing device that constitutes a fixing unit.

  Reference numeral 3 denotes an image reading device installed substantially horizontally above the printer main body 1A. Reference numeral 5 denotes a relay conveying device which is a sheet conveying device that receives an image-formed sheet S from the printer main body 1A and conveys it to the paper discharge tray 4. It is. The relay conveyance device 5 is disposed in a space G between the upper surface of the printer main body 1A that is the main body of the image forming apparatus and the image reading device 3 that is the upper device.

  The image forming unit 1B is of a four-drum full color type, and includes four process cartridges 14 (for forming toner images of four colors of yellow (Y), magenta (M), cyan (C), and black (Bk). 14Y, 14M, 14C, and 14K) are detachably provided. The process cartridge 14 is for developing a photosensitive drum (not shown), charging means for applying a predetermined voltage to the photosensitive drum for charging, and attaching a toner to a latent image formed on the photosensitive drum. Development means and the like. The image forming unit 1B includes a laser scanner 15 (15YM, 15CK) and an intermediate transfer unit 16 disposed above the process cartridge 14.

  The intermediate transfer unit 16 includes an intermediate transfer belt 16a wound around a driving roller 16b and a tension roller 16c. The intermediate transfer unit 16 includes a primary transfer roller 16d that is provided inside the intermediate transfer belt 16a and contacts the intermediate transfer belt 16a at a position facing a photosensitive drum (not shown) provided in the process cartridge 14. ing.

  Here, the intermediate transfer belt 16a is composed of a film-like member and is disposed so as to be in contact with each photosensitive drum, and is rotated in the arrow direction by a driving roller 16b driven by a driving unit (not shown). Yes. Then, by applying a positive transfer bias to the intermediate transfer belt 16a by the primary transfer roller 16d, each color toner image having a negative polarity on the photosensitive drum is sequentially transferred to the intermediate transfer belt 16a. As a result, a full-color image is formed on the intermediate transfer belt.

  A secondary transfer roller 20 constituting a secondary transfer unit that transfers a full-color image formed on the intermediate transfer belt to the sheet S is provided at a position facing the drive roller 16b of the intermediate transfer unit 16. .

  Further, a fixing device 22 is disposed above the secondary transfer roller 20, and a discharge roller pair 24 and a double-side reversing unit 1C are disposed at the upper left portion of the fixing device 22. The double-side reversing unit 1C is provided with a reversing roller pair 26 capable of forward / reverse rotation, a re-conveying path R3 for conveying a sheet on which an image is formed on one surface to the image forming unit 1B again, and the like.

  Next, an image forming operation of the full color laser beam printer 1 configured as described above will be described.

  First, when image information of a document is read by the image reading device 3, the image information is subjected to image processing, converted into an electric signal, and transmitted to the laser scanner 15 of the image forming unit 1B. The image information may be input to the image forming unit 1B from an external device such as a personal computer (not shown).

  In the image forming unit 1B, the surface of the photosensitive drum is scanned with a laser beam corresponding to the image information emitted from the laser scanner 15, and the photosensitive drum is uniformly charged with a predetermined polarity and potential. The surface is sequentially exposed to form an electrostatic latent image on the photosensitive drum. Thereafter, the electrostatic latent image is developed with toner and visualized.

  For example, first, the photosensitive drum of the process cartridge 14Y is irradiated with laser light based on the image signal of the yellow component color from the laser scanner 15Y to form a yellow electrostatic latent image on the photosensitive drum. The yellow electrostatic latent image is developed with yellow toner from a developing device, and visualized as a yellow toner image.

  Next, when the yellow toner image arrives at the primary transfer portion where the photosensitive drum and the intermediate transfer belt 16a come into contact with the rotation of the photosensitive drum, the primary transfer bias applied to the primary transfer roller 16d causes The yellow toner image is transferred to the intermediate transfer belt 16a.

  Next, when the portion carrying the yellow toner image on the intermediate transfer belt 16a moves, the magenta toner image formed on the photosensitive drum of the process cartridge 14M by the same method as described above is transferred from the yellow toner image. It is transferred to the intermediate transfer belt 16a. Similarly, as the intermediate transfer belt 16a moves, the cyan toner image and the black toner image are transferred onto the yellow toner image and the magenta toner image, respectively, in the primary transfer portion. As a result, a full-color toner image is formed on the intermediate transfer belt 16a.

  In parallel with this toner image forming operation, a sheet S accommodated in a sheet feeding cassette (not shown) is sent out by a pickup roller 17, and the sheet S is separated one by one by a feed / retard roller pair 18. It is conveyed to the registration roller pair 19. Then, the skew feeding is corrected by the pair of registration rollers 19 and conveyed to the secondary transfer unit so that the position of the full color toner image on the intermediate transfer belt and the sheet S is aligned at the secondary transfer unit. Thereafter, the full-color toner image is collectively transferred onto the sheet S by the secondary transfer bias applied to the secondary transfer roller 20 in the secondary transfer unit. At this time, waste toner that has not been secondarily transferred to the sheet S is collected by a cleaning device 21 as a cleaning unit provided on the intermediate transfer belt.

  Next, the sheet S on which the full-color toner image has been transferred in this manner is conveyed to the fixing device 22, and the toner of each color is melted and mixed by receiving heat and pressure in the fixing device 22, so that a full-color image is formed on the sheet S. It is fixed. Thereafter, the sheet S on which the image has been fixed is conveyed to the relay conveying device 5 by a discharge roller pair 24 provided downstream of the fixing device 22.

  Next, the sheet S passes through a paper discharge conveyance path R1 provided substantially horizontally above the relay conveyance apparatus 5, and a first conveyance roller pair 10 and a second conveyance roller provided in the paper discharge conveyance path R1. The pair 11 and the relay discharge roller pair 12 are discharged onto the sheet discharge tray 4 with the image forming surface down.

  By the way, the full-color laser beam printer 1 of the present embodiment can form images on both sides of a sheet. When an image is formed on both sides of the sheet, the sheet on which the image is formed on one side (one side) passes through the fixing device 22 and is then relayed and conveyed to the image reading device 3 by the switching member 30 and the reverse roller pair 26. It is introduced into the reverse conveyance path R2, which is a re-conveyance path installed between the devices 5.

  Next, when the trailing edge of the sheet S passes through the fixing device 22, the reversing roller pair 26 is reversed at a predetermined timing and the switching member 30 is rotated, whereby the sheet S is reversed to the re-conveyance path R3. Be transported. Thereafter, the first re-feed roller pair 31 and the second re-feed roller pair 32 provided in the re-transport path R <b> 3 are transported again to the registration roller pair 19 with the transport direction reversed upside down. Then, image formation and fixing are performed again on the back surface, and thereafter, the paper passes through the paper discharge conveyance path R1 and is delivered to the paper discharge tray 4.

  By the way, the image reading device 3 includes an image reading device main body 3a and an automatic document feeding device 3b which is disposed above the image reading device main body and can be opened and closed via a hinge (not shown) on the back side of the image reading device main body. Has been. The image reading apparatus 2 is installed so that the front side of the printer main body is opened.

  On the other hand, a reversing upper guide 6 constituting a reversing conveyance path R2 that can be opened and closed together with an upper guide 8 constituting the upper surface of the relay conveying device 5 shown in FIG. Yes. A guide sheet metal 7 that also serves as a reinforcing member during rotation of the image reading device 3 is installed in a shape orthogonal to the sheet conveying direction at a substantially central portion of the reversing upper guide 6 indicated by an arrow D1. ing. That is, the reverse conveyance path R <b> 2 is formed by the upper surface of the reverse upper guide 6, the guide sheet metal 7, and the upper guide 8 of the relay conveyance device 5 of the image reading device 3.

  Further, as shown in FIG. 4, the relay conveyance device 5 located downstream of the fixing device 22 in the sheet conveyance direction has an upper guide 8 whose upper surface forms the lower surface of the reverse conveyance path R <b> 2 and a sheet conveyance that can be opened and closed together with the upper guide 8. And a lower guide 9 constituting a discharge conveyance path R1 which is a path. The upper guide 8 has a guide shape that is paired with the reversing upper guide 6 and the guide metal plate 7, and is provided on the lower guide 9 with respect to the lower guide 9. It can be opened and closed around the center. As described above, the relay conveyance device 5 can be opened and closed by dividing the upper guide 8 and the lower guide 9 by the discharge conveyance path for conveying to the discharge tray 4, and the front side of the printer main body is opened like the image reading device 3. It is installed to do. Further, by adopting such a configuration, it is possible to reduce the height of the entire relay transfer device, and consequently, it is possible to reduce the size of the entire relay transfer device.

  By the way, on the lower surface of the upper guide 8 and the upper surface of the lower guide 9, rollers 10a to 12a, 10b constituting the first conveying roller pair 10, the second conveying roller pair 11, and the relay discharge roller pair 12 from the upstream in the sheet conveying direction, respectively. ~ 12b are arranged.

  Further, downstream of the first conveying roller pair 10 in the vicinity of the fixing device 22, the lower guide 9 is separated from the lower guide 9 at a plurality of positions in the width direction orthogonal to the sheet conveying direction, and at three positions in the present embodiment. A small guide 13 that constitutes the sheet contact portion is projected. That is, three small guides 13 are provided in the width direction on the upstream side portion of the lower guide 9 that is a guide member for guiding (guiding) a sheet from the fixing device 22 in the sheet conveyance direction.

  In the present embodiment, the first conveyance roller pair 10 and the second conveyance roller pair 11 can form a nip N over substantially the entire width W of the sheet S as shown in FIG. It has a full width roller configuration having a length L in the width direction. The first conveying roller pair 10 and the second conveying roller pair 11 form a nip N by rubber rollers in which elastic rubber is press-fitted or bonded on a roller shaft, and the sheet S is nipped and conveyed by the nip N. It is like that.

  By configuring the first and second transport roller pairs 10 and 11 in this way, even if the sheet is transported to the relay transport device 5, the toner image on the sheet is leveled over the entire area. For this reason, even if the sheet is conveyed to the relay conveying device 5 in a state where the temperature of the toner image is higher than the glass transition temperature, uneven glossiness due to the first and second conveying roller pairs 10 and 11 does not occur.

  In the present embodiment, the rollers 12a and 12b constituting the relay discharge roller pair 12 are alternately brought into contact with the sheet S in the width direction as shown in FIG. This makes it possible to transport (discharge) while avoiding this. Therefore, the relay discharge roller pair 12 can stack the sheets S on the discharge tray (see FIG. 1) as a kicking roller.

  Further, each of the rollers 12a and 12b constituting the relay discharge roller pair 12 is formed of heat-resistant flexible foamed silicon rubber, and a skin layer formed at the time of mold molding is removed by a polishing process. . As a result, small holes due to a large number of bubbles generated during foaming are exposed on the surface of each roller. The small holes on the roller surface come into contact with the toner surface and the back surface of the sheet, so that the toner image is not cooled by the relay discharge roller pair 12 as described above, and gloss unevenness occurs. There is no.

  By the way, as shown in FIG. 7, the upper surface of the small guide 13 that contacts the sheet, that is, the sheet contact surface 25 is higher than the rib 9 c provided on the guide surface 9 b of the lower guide 9 in the relay conveyance device 5. Only H1 protrudes. Here, the height H1 of the sheet contact surface 25 is set to a height that allows the sheet conveyed from the fixing device 22 to pass through in a state of being separated from the rib 9c of the lower guide 9.

  Thereby, when passing the upstream portion of the discharge conveyance path R1 in the sheet conveyance direction, the sheet S is in contact with only the small guide 13, in other words, the lower guide 9 is separated from the upstream portion of the lower guide 9 in the sheet conveyance direction. Pass 9 A tapered surface 13a is formed on the upstream side of the small guide 13 in the sheet conveying direction so that the sheet passes through the small guide 13 without being caught.

  Here, since the small guide 13 has a sufficiently small volume with respect to the lower guide 9, the heat capacity is also small, and the temperature can be increased more quickly than the lower guide 9. Further, since the sheet contact surface 25 of the small guide 13 contacts the sheet S with a predetermined size, the contact surface pressure with the sheet S can be set low. Thus, even when the sheet S contacts the sheet contact surface 25 of the small guide 13 when passing through the discharge conveyance path R1, uneven glossiness of the toner image does not occur.

  FIG. 8 is a view showing a state where a small guide 13 made of a material that is separate from the lower guide 9, for example, has a smaller heat capacity than the lower guide 9 and is easily heated, is attached to the lower guide 9. And in this Embodiment, as shown in FIG. 8, the space | gap C1 which comprises a heat insulation part is provided between the lower guide 9 and the small guide 13. As shown in FIG. Further, only the downstream locking portion 26 and the upstream locking portion 27 are in contact with the lower guide 9 and the small guide 13.

  Thereby, most of the heat accumulated in the small guide 13 is once transmitted to the air in the gap C <b> 1 and then transmitted from the air to the lower guide 9. At this time, since the heat transfer efficiency is very small, the heat accumulated in the small guide 13 is not lost to the lower guide 9. As a result, the small guide 13 is kept at a high temperature, and the sheet contact surface 25 does not cool the toner image, so that gloss unevenness does not occur.

  In this way, by providing the lower guide 9 with the small guide 13 that allows the sheet to pass away from the lower guide 9, the sheet comes into contact with only the small guide 13. It will never be. Furthermore, by providing the gap C1 between the small guide 13 and the lower guide 9, the heat insulating property of the small guide 13 is enhanced, and as a result, the heat accumulated in the small guide 13 is not taken away by the lower guide 9, The temperature of the small guide 13 can be maintained in a high state.

  In the present embodiment, since the heat capacity of the small guide 13 is made smaller than that of the lower guide 9, the temperature of the small guide 13 can be increased more quickly than the lower guide 9. Yes. As a result, the temperature rise of the small guide 13 can be accelerated, and the small guide 13 can be heated to a high temperature from the initial printing operation of the full-color laser beam printer 1.

  As described above, when the small guide 13 having heat insulation is provided in the lower guide 9 and the sheet is passed by the small guide 13 while being separated from the lower guide 9, the temperature of the sheet passing through the fixing device 22 is high. However, the occurrence of uneven gloss can be suppressed. A good image can be obtained by suppressing the uneven glossiness caused by the lower guide 9 contacting the sheet.

  Next, a second embodiment of the present invention will be described.

  FIG. 9 is a perspective view illustrating the configuration of the relay conveyance device provided in the image forming apparatus according to the present embodiment. 9, the same reference numerals as those in FIG. 4 indicate the same or corresponding parts.

  In FIG. 9, reference numeral 28 denotes a small guide that is formed integrally with the lower guide 9 at three positions in the sheet width direction downstream of the first conveying roller pair 10 and constitutes a sheet contact portion. Here, since the volume of the small guide 28 is sufficiently smaller than that of the lower guide 9, the small guide 28 has a small heat capacity. Therefore, the temperature can be increased more quickly than the lower guide 9.

  As shown in FIG. 10, the upper surface of the small guide 28 that contacts the sheet, that is, the sheet contact surface 29 protrudes from the rib 9 c of the lower guide 9 in the relay conveyance device 5 by the height H <b> 2. Here, the height H2 of the sheet contact surface 25 is set to a height that allows the sheet conveyed from the fixing device 22 to pass through in a state of being separated from the rib 9c of the lower guide 9. As a result, when passing through the discharge conveyance path R1, the sheet S contacts only the small guide 28 and does not contact the lower guide 9.

  Further, since the sheet contact surface 29 of the small guide 28 contacts the sheet S with a predetermined size, the contact surface pressure with the sheet S can be set low. Thereby, even when the sheet S contacts the sheet contact surface 29 of the small guide 28 when passing through the discharge conveyance path R1, uneven glossiness of the toner image does not occur.

  In the present embodiment, as shown in FIG. 11, a gap C <b> 2 that constitutes a heat insulating portion is provided below the small guide 28. Further, only the rib root 30 is in contact with the lower guide 9 and the small guide 28.

  Thereby, most of the heat accumulated in the small guide 13 is once transmitted to the air in the gap C <b> 2 and then transmitted from the air to the lower guide 9. At this time, since the heat transfer efficiency is very small, the heat accumulated in the small guide 28 is not lost to the lower guide 9. As a result, the small guide 28 is kept at a high temperature, and the sheet contact surface 29 does not cool the toner image, so that gloss unevenness does not occur. Therefore, by providing the small guide 28 integrally with the lower guide 9 as in the present embodiment, the same effects as those of the first embodiment described above can be obtained.

1 is a perspective view of a full-color laser printer that is an example of an image forming apparatus according to a first embodiment of the present invention. The figure which shows schematic structure of the said full color laser printer. FIG. 3 is a first perspective view illustrating a configuration of a relay conveyance device provided in the full color laser printer. The 2nd perspective view explaining the composition of the above-mentioned relay conveyance device. The perspective view explaining the structure of the 1st and 2nd conveyance roller pair provided in the said relay conveyance apparatus. The perspective view explaining the structure of the relay discharge roller pair provided in the said relay conveyance apparatus. The perspective view explaining the structure of the small guide provided in the said relay conveyance apparatus. Sectional drawing which shows a state when the said small guide is attached to a lower guide. FIG. 6 is a perspective view illustrating a configuration of a relay conveyance device provided in an image forming apparatus according to a second embodiment of the present invention. The perspective view explaining the structure of the small guide provided in the said relay conveyance apparatus. Sectional drawing explaining the structure of the said small guide.

DESCRIPTION OF SYMBOLS 1 Full color laser beam printer 1A Full color laser beam printer main body 1B Image formation part 5 Relay conveyance apparatus 8 Upper guide 9 Lower guide 13 Small guide 22 Fixing device 25 Small guide sheet contact surface 28 Small guide 29 Small guide sheet contact surface C1 Space | gap C2 Cavity R1 Paper discharge conveyance path R2 Reverse conveyance path S Sheet

Claims (6)

An image forming apparatus comprising: an image forming unit that forms a toner image; and a fixing unit that fixes the toner image formed on the image forming unit and then transferred to the sheet to the sheet.
A guide member that is provided downstream of the fixing unit in the sheet conveying direction and guides a sheet on which a toner image is fixed by the fixing unit;
An image forming apparatus comprising: a sheet contact portion that protrudes from the guide member and has a heat insulating property that allows a sheet conveyed from the fixing portion to pass through the sheet in a state of being separated from the guide member.   The image forming apparatus according to claim 1, wherein a heat insulating portion is provided between the sheet contact portion and the guide member so that the sheet contact portion has a heat insulating property.   The image forming apparatus according to claim 2, wherein the heat insulating portion is a gap provided between the sheet contact portion and the guide member.   The image forming apparatus according to claim 1, wherein a heat capacity of the sheet contact portion is smaller than a heat capacity of the guide member.   The sheet contact portion projects from the upstream portion of the guide member in the sheet conveyance direction, and the sheet conveyed from the fixing portion is allowed to pass in a state of being separated from the upstream portion of the guide member in the sheet conveyance direction. The image forming apparatus according to any one of claims 1 to 4. An image forming apparatus main body having the image forming unit and the fixing unit;
A sheet conveying apparatus provided in a space between the image forming apparatus main body and the upper apparatus, and having a reconveying path for conveying a sheet on which an image is formed on one surface to the image forming unit again,
The image forming apparatus according to claim 2, wherein the guide member, the sheet contact portion, and the heat insulating portion are provided in a re-conveyance path of the sheet conveying device.

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