JP4468273B2 - Sheet conveying apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a sheet conveying apparatus and an image forming apparatus, and more particularly to a sheet conveying apparatus in which a toner image is fixed and sequentially conveyed to a re-fixing processing unit at a predetermined interval to obtain a high gloss image.

  Conventionally, an image forming apparatus using an electrophotographic method such as a copying machine, a printer, a facsimile, and a multifunction machine of these is widely known, and many products that form full color images as well as black and white have been commercialized. . In addition, as electrophotographic image forming apparatuses are used in various fields, the demand for image quality has become higher and higher.

  Here, smoothness of the output image can be cited as one of the factors that determine the image quality, particularly the glossiness of the full-color image. In response to such needs, for example, there is an image forming method for forming a color image by transferring a color toner made of a thermoplastic resin onto a sheet provided with a transparent resin layer made of a thermoplastic resin, and heating and melting the sheet. (For example, refer to Patent Document 1 and Patent Document 2).

  As a fixing device employed in these image forming methods, a belt fixing device using a fixing belt has been proposed. Here, the belt fixing device presses and heats the sheet on which the toner image is transferred with a fixing belt made of a heat-resistant film, and then cools the sheet while keeping the sheet in close contact with the fixing belt to solidify the toner image. I have to.

  As a result, the toner image is fixed on the sheet. After the toner image is fixed on the sheet in this way, the sheet is peeled off from the fixing belt (see, for example, Patent Documents 3 to 5).

  Here, in such a fixing device, the toner image is fixed while being embedded in the transparent resin layer of the sheet, so that the transparent resin layer on the surface of the recording sheet and the toner image are solidified according to the belt surface shape. To do. Thereby, the entire surface of the sheet becomes a smooth surface, and as a result, a color image having excellent gloss can be obtained.

  Accordingly, such a fixing device is disposed in the main body as a second fixing device for performing the fixing process again on the sheet fixed by the first fixing device that performs the normal fixing process, In some cases, the image forming apparatus is provided as an optional fixing device.

Japanese Patent Application Laid-Open No. 64-35542 JP-A-5-216322 JP-A-4-216580 JP-A-4-362679 JP 2002-99168 A

  By the way, such a conventional image forming apparatus includes a sheet conveying apparatus that sequentially conveys the sheets on which the image fixing process has been performed to the second fixing apparatus at predetermined intervals. Here, when a belt fixing device is used in the second fixing device, a cooling time for solidifying the toner image (a temperature difference of about 100 ° C.) is required. Therefore, the sheet conveyance speed (processing speed) is decreased. Yes. In general, the sheet conveyance speed of the sheet discharged (output) from the main body of the image forming apparatus is about 200 mm / sec to 300 mm / sec, whereas the sheet conveyance speed (processing speed) of the second fixing apparatus is about 40 mm / sec. sec to 60 mm / sec.

  Here, when the sheet conveyance speed is different as described above, when the re-fixing process of the previous sheet is performed at a low sheet conveyance speed, when the next sheet is conveyed at a high sheet conveyance speed by the sheet conveyance device, The next sheet collides with the previous sheet that has been re-fixed. The collision may damage the two front and rear sheets.

  Therefore, in order to prevent damage to the sheet due to such a speed difference, for example, in an optional fixing device, the sheet is temporarily placed in order to adjust the speed difference between the sheet discharge speed from the image forming apparatus main body and the processing speed. A standby means for stopping is necessary.

  Further, the timing of discharging the sheet from the image forming apparatus main body differs depending on the image forming method. For example, in an apparatus for forming an image by superimposing a plurality of images on an intermediate transfer member, sheets are output intermittently for each of a plurality of sheets. Further, for such a sheet that is output intermittently, a standby unit that temporarily stops the sheet is necessary to cope with the conveyance speed between the apparatuses.

  Here, as such a waiting unit, a switchback method that reverses the front and back of the sheet and matches the conveyance timing, and a refeeding method that temporarily accumulates the sheets discharged from the image forming apparatus and feeds them again. Etc. are known. However, in such a conventional standby unit, damage such as scratches or rubbing marks on the sheet image is unavoidable due to switching of the sheet conveyance direction or refeeding.

  Accordingly, the present invention has been made in view of such a situation, and an object of the present invention is to provide a sheet conveying apparatus and an image forming apparatus that can prevent occurrence of damage to a sheet and a sheet image. .

The present invention, a sheet fixing process of the image is performed, the sheet conveying device for conveying the sequential re-fixing unit, and the sheet conveying path sheet passes to be transported to the re-fixing unit, the sheet conveying provided in the passage, the sheet conveying speed of the first sheet conveying speed, and the first sheet slower than the conveying speed second sheet conveying means which can be switched to a sheet conveying speed, the sheet in the re-fixing process unit Control means for controlling the sheet conveying means so as to switch the sheet conveying speed from the first sheet conveying speed to the second sheet conveying speed when performing the re-fixing process on the sheet conveying path, the length, the time of the sheet conveying speed is switched to the second sheet conveying speed from the first sheet conveying speed, and then re-fixing process of the sheet re-fixing process is carried out is performed It is characterized in that the rear end of the sheet is Satoshi long as present in the sheet conveyance passage.

As in the present invention, the sheet length of the conveyance path, a sheet conveying speed from the first sheet conveying speed in the re fixing process unit of the second sheet conveying speed for conveying the re-fixing process unit sheets are sequential transport When switching to , the length is set such that the trailing edge of the next sheet to be re-fixed exists in the sheet conveyance path. As a result, collision of sheets sequentially conveyed to the re-fixing processing unit can be prevented, and damage to the sheet and sheet image can be prevented.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the best embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of a color copying machine which is an example of an image forming apparatus according to an embodiment of the present invention.

  In FIG. 1, reference numeral 200A denotes a color copying machine, and reference numeral 200 denotes a color copying machine main body (hereinafter referred to as an apparatus main body). An image reading unit 61 for reading a document D placed on a platen glass 206 as a document placement table by an automatic document feeder 60 is provided on the upper part of the apparatus main body 200. The image reading unit 61 is provided with a light source 207a, a lens system 207b, and a CCD unit 207c.

  Below the image reading unit 61, an image forming unit 202 and a paper feeding unit 209 that feeds the sheet S to the image forming unit 202 are provided. Further, an external fixing device 1 is provided on one side of the apparatus main body 200 for fixing the image-formed sheet discharged from the apparatus main body 200 again.

Here, the image forming unit 202 includes a photosensitive drum 213, a primary charger 214, a black developing device 203 configured independently, a rotary developing device 201 including a plurality of developing devices 215 integrated with a toner cartridge, A post charger 216 for adjusting the image quality after development is provided.
Further, the four-color toner images are superimposed and transferred to the image forming unit 202, and then the endless transfer belt 217 that transfers the multicolor image to the sheet S, and the toner image is transferred from the transfer belt 217 to the sheet S. A secondary transfer roller 219 is provided.

  The transfer belt 217 is generally set to an integral multiple of the circumferential length of the photosensitive drum 213 and a circumferential length capable of transferring a plurality of sheets (for example, twice the A4 size plus the transfer interval). ing. Reference numeral 218 denotes a drum cleaner for cleaning residual toner on the photosensitive drum, and 220 denotes a belt cleaner for cleaning residual toner on the transfer belt.

  The sheet feeding unit 209 is provided with cassettes 210 and 211 and a manual cassette 212 that store the sheet S and can be attached to and detached from the apparatus main body 200. The cassette 210 and 211 and the manual cassette 212 are transferred to the image forming unit 202. The sheet S is supplied toward the head.

  A registration roller 221 is provided on the upstream side of the image forming unit 202 to increase the posture position accuracy of the sheet S and to feed the sheet S in a timely manner according to the toner image on the transfer belt. Further, on the downstream side of the image forming unit 202, a transfer conveyance device 222 that conveys the sheet S to which the toner image is transferred, a first fixing unit 204 that fixes an unfixed image on the sheet, and a sheet on which the image is fixed A discharge roller pair 205 and the like for discharging S to the outside of the apparatus main body are provided. Reference numeral 62 denotes a control device that controls the overall image forming operation of the apparatus main body 200.

  Next, the operation of the color copying machine 200A having such a configuration will be described.

  When a paper feed signal is output from the control device 62 provided in the apparatus main body 200, for example, light is applied from the light source 207a to the document D placed on the platen glass 206 by the automatic document feeder 60 and reflected. To do. The light reflected from the document D is once read by the CCD unit 207c through the lens system 207b and converted into an electric signal. Thereafter, a laser beam corresponding to this electrical signal or a laser beam corresponding to data from an image memory (not shown) is irradiated on the photosensitive drum 213 from the laser scanner unit 208.

  At this time, the photosensitive drum 213 is charged in advance by the primary charger 214, and an electrostatic latent image is formed by irradiation with light. Next, a plurality of photosensitive drums 213 disposed in the black developing unit 203 and the rotary developing unit 201 are provided. The developing device 215 forms a toner image of the selected color. Thereafter, the potential of the toner image formed on the photosensitive drum is adjusted by the post charger 216, and is eventually transferred onto the transfer belt 217 at the transfer position.

  Here, in the color mode, the transfer belt 217 to which the toner image is transferred further rotates so that the next toner image is formed and transferred. During this time, the rotary developing device 201 rotates the next designated color developing device in the counterclockwise direction so as to face the photosensitive drum 213 and prepares to develop the next electrostatic latent image.

  Thus, in the full color mode, electrostatic latent image formation, development, and transfer are repeated until a predetermined number of toner images (the number of transfer material surfaces within the circumference of the transfer belt 217) have been transferred. Therefore, for example, when an A4 size image is transferred, the image is formed and transferred on both sides simultaneously, and after the toner image is transferred to the sheet, the next image is formed.

  On the other hand, when a paper feed signal is output from the control device 62, the sheet S is supplied from the cassettes 210 and 211 or the manual feed cassette 212. Thereafter, the sheet S fed from the paper feeding unit 209 is corrected in skew by the registration roller 221, and is further timed to be sent to the secondary transfer unit constituted by the transfer belt 217 and the secondary transfer roller 219. It is done.

  Next, after the toner image is transferred by the secondary transfer roller 219, the sheet S thus sent to the secondary transfer unit is conveyed to the first fixing unit 204 by the transfer conveyance device 222. Thereafter, the unfixed transfer image is permanently fixed on the sheet S by being heated and pressed by the first fixing unit 204.

  Then, the sheet S on which the image is fixed in this manner is discharged from the apparatus main body 200 by the discharge roller 205 and is delivered to the external fixing device 1. In this way, the sheet S fed from the paper feeding unit 209 is formed with an image and discharged.

  The color copying machine 200A has a double-sided image forming function. Next, the double-sided image forming operation will be described mainly based on the conveyance state of the sheet S. The sheet S after the fixing process of the first surface by the first fixing unit 204 described above is first branched downward by the reverse flapper mechanism 111 and then to the reverse conveyance path 101 disposed downstream of the reverse branch point P. It is conveyed and switched back by this reverse conveyance path 101.

  Next, the sheet S that has been switched back by the reversal conveyance path 101 in this manner is drawn into the double-sided conveyance path 102 by the double-sided flapper mechanism 112 in a state where the front and back sides are reversed, and then passes through the registration rollers 221 and the image forming unit. Retransmitted to 202. The sheet S re-conveyed to the image forming unit 202 in this way forms a toner image on the second surface of the sheet S by the image forming process described above. If the sheet is discharged by the discharge roller 205 while being reversed from the reverse conveyance path 101, the sheet S is reversely discharged.

  FIG. 2 is a diagram showing a schematic configuration of the external fixing device 1 connected to the apparatus main body 200. The external fixing device 1 can selectively perform high gloss processing or non-gloss processing. .

  In FIG. 2, reference numeral 5 denotes a second fixing unit that is a re-fixing processing unit, and 2 denotes an upper conveyance path that is provided on the upper portion of the external fixing device 1 and receives and conveys the sheet S discharged from the apparatus main body 200. Note that when the high gloss process is selected, the second fixing unit 5 has a higher temperature than the sheet S on which the toner image has been fixed by the first fixing unit 204 provided in the apparatus main body 200. The pressure is applied and the fixing process is performed again, thereby smoothing the toner image.

  Reference numeral 4 denotes a paper discharge conveyance path for discharging the sheet S as it is or for transferring it to a subsequent finishing unit (not shown) when non-gloss processing is selected. Reference numeral 6 denotes a pre-fixing conveyance path, which is a sheet conveyance path for inverting the sheet S to the second fixing unit 5 when the high gloss processing is selected, and is curved toward the second fixing unit. The guide surface 6a is provided.

  A branch flapper 3 switches the transport path to the paper discharge transport path 4 or the pre-fixing transport path 6 in accordance with the selected processing type, that is, the high gloss process or the non-gloss process. Reference numeral 7 denotes a post-fixing transport path that reverses and conveys the sheet S fixed by the second fixing unit 5 in a substantially U-shape. The post-fixing transport path 7 is in a direction opposite to the guide surface 6 a of the pre-fixing transport path 6. It has a curved guide surface 7a.

  8 is a stack provided on the downstream side of the second fixing unit, and after the high-gloss image is finally fixed by the second fixing unit 5, the sheets S conveyed through the post-fixing conveyance path 7 are stacked. It is a stack tray.

  As described above, in the external fixing device 1, the fixing process is performed in the pre-fixing conveyance path 6 for reversing the sheet S substantially U-shaped and conveying the sheet S to the second fixing unit 5 and the second fixing unit 5. And a post-fixing conveyance path 7 that conveys the subsequent sheet S with a substantially U-shaped inversion. As a result, the sheet S is reversed substantially U-shaped by the pre-fixing conveyance path 6 and conveyed to the second fixing unit 5, and after the re-fixing process in the second fixing unit 5, by the post-fixing conveyance path 7. The paper is reversed to a substantially U shape and conveyed to the stack tray 8.

  That is, in the external fixing device 1, a substantially S-shaped path is formed as a whole by the guide surface 6 a of the pre-fixing transport path 6 and the guide surface 7 a of the post-fixing transport path 7. In this way, a substantially S-shaped path is formed, and the pre-fixing transport path 6, the second fixing unit 5, and the pre-fixing transport path 6 are arranged in the vertical direction, so that the external fixing device 1 can be used. The width can be shortened. As a result, the installation area of the apparatus can be suppressed and the height can be reduced.

  In the present embodiment, the second fixing unit 5 is configured to perform fixing with the high-gloss image forming surface, which is the image fixing surface of the sheet S, facing downward. When the external fixing apparatus 1 receives the sheet S from the apparatus main body 200, the image fixing surface is received in the upper state, and is reversed by the pre-fixing conveyance path 6 so that the high gloss image forming surface is received. The sheet S is received downward.

  With this configuration, the sheet conveyance sequence on the apparatus main body 200 side can be prevented from becoming complicated, and various external connection units can be easily handled. Further, the apparatus main body 200 can deliver the sheet S to the external fixing apparatus 1 with the surface on which the image is formed (fixed) facing upward, and there is a need to perform reverse paper discharge within the apparatus main body. Therefore, damage to the image forming (fixing) surface of the sheet S can be suppressed as much as possible.

  On the other hand, the configuration of the second fixing unit 5 in the external fixing device 1 employs a system in which the high-gloss image forming surface is in close contact and conveyed, so that the sheet S received inside the fixing device is reversed. It is necessary to transport to the second fixing unit 5. However, the external fixing device 1 is not so-called switchback reversal in which conveyance is stopped once and then conveyed in the opposite direction, and substantially U-shaped reversal in which the conveyance direction is not different is mounted, so there is almost no damage to the image surface. Good high-quality images can be obtained.

  In the case where the sheet S discharged from the apparatus main body 200 is discharged to the stack tray 8 through the second fixing unit 5 as in the external fixing apparatus 1, the sheet S is conveyed in consideration of the installation area of the entire apparatus. It is desirable to bend the paths 6 and 7 in different directions. Further, by arranging and configuring in this way, the curling direction of the sheet S does not have to be one direction, so that the occurrence of curling can be prevented, and a suitable result article can be obtained.

  On the other hand, in general, when the sheet S immediately after fixing is passed through the bending path, if the image forming surface is conveyed outward in the radial direction, the image fixing surface of the sheet S is easily creased by the guide surface, and fine conveyance scratches are caused. May remain on the image plane.

  Here, the sheet S once fixed by the apparatus main body 200 as in the external fixing apparatus 1 passes through the guide surface 6a of the pre-fixing conveyance path 6 and is subjected to a fixing process. When the guide surface 7a is passed, the sheet S passes through the bending path twice. That is, if the sheet S is passed through the pre-fixing and post-fixing conveyance paths 6 and 7 having the guide surfaces 6a and 7a bent in different directions, curling can be prevented, but the sheet S after fixing is prevented. Will be bent twice.

  Further, when the sheet S is conveyed in the pre-fixing and post-fixing conveyance paths 6 and 7 having the guide surfaces 6a and 7a bent in different directions as described above, the image forming surface is radially outward. There are cases. In this case, fine conveyance scratches may remain on the image fixing surface of the sheet S as described above.

  However, in the present embodiment, a bending path (guide surface 6a) with the image fixing surface on the outside is arranged upstream of the second fixing unit 5, and a bending path (guide surface 7a) with the image fixing surface on the inside. ) Is arranged downstream of the second fixing unit 5. As a result, it is possible to minimize damage to the image forming (fixing) surface on which the fixing process has been performed again by the second fixing unit 5.

  That is, as described above, the second fixing unit 5 in the present embodiment smoothes the image surface once fixed by the first fixing unit 204 provided in the apparatus main body 200 by high-temperature pressure bonding again. Create a face. For this reason, even when the sheet S from the apparatus main body 200 passes through the guide surface 6a with the image fixing surface on the outside, even if the image forming (fixing) surface is finely scratched, the second fixing unit. 5 can be eliminated when creating a smooth surface.

  Next, the operation of the external fixing device 1 configured as described above will be described.

  First, an operation when outputting a sheet having a normal non-gloss (or low gloss) image will be described. In this case, when the sheet S on which the non-gloss (or low gloss) image created by the apparatus main body 200 is placed is sent to the external fixing device 1, the sheet S is conveyed and discharged by the branch flapper 3. It is sent to pass 4 and discharged as it is. Or it is handed over to the finishing unit which is a subsequent unit.

  Next, a case where a sheet having a high gloss image is output will be described. In this case, when the sheet S on which a high gloss image formed by the apparatus main body 200 is formed is sent to the external fixing device 1, the branch flapper 3 is switched, and the sheet S is conveyed to the conveyance path 6 before fixing. Thereafter, re-fixing is performed by the second fixing unit 5, and after passing through the post-fixing conveyance path 7, the sheet is discharged to the stack tray 8.

  Note that when passing through the pre-fixing conveyance path 6, the image surface fixed by the first fixing unit 204 may be slightly scratched. This is caused by the second fixing unit 5 as described above. It disappears when creating a smooth surface. Further, since the high gloss image forming surface of the sheet S is transported inside in the post-fixing transport path 7, in other words, the surface opposite to the image fixing surface passes along the guide surface 7a. Hard to stick. Accordingly, it is possible to supply a high-gloss image with high image quality even when the guide surfaces 6a and 7a curved in the conveyance paths 6 and 7 before and after fixing are used.

  FIG. 3 is a diagram showing a configuration of the second fixing unit 5 of the external fixing device 1. In FIG. 3, 11 is a pressure roller, 12 is a heating roller, and 15 is a pressure roller 11 and a heating roller 12. It is an endless belt that is nipped and conveyed. The pressure roller 11 presses the heating roller 12 via the endless belt 15 to form a nip, and pressurizes and heats the sheet S on the endless belt. The pressure roller 11 includes a metal cylindrical roll having high thermal conductivity, an elastic layer (for example, a silicone rubber layer having a JIS-A rubber hardness of about 40 °), and a release layer (for example, a fluororesin tube such as PFA). ).

  Further, the heating roller 12 is formed by coating a release layer (for example, a fluororesin tube such as PFA) on a metal cylindrical roll having high thermal conductivity, and disposing a halogen heater 12a inside the roll. Here, in the present embodiment, the temperature adjustment temperature of the heating roller 12 is set to 200 ° C., and good fixability is ensured even when a four-color toner image is fixed. The temperature control temperature of the heating roller 12 is not limited to this, and the number of developing devices (type of toner) is not limited to this.

  The endless belt 15 is formed by coating a belt base material made of a thermosetting polyimide endless film (75 μm or more) or the like with a surface layer (30 μm or more) such as silicone rubber having a smooth surface. It is rotationally driven in the direction of arrow b in the figure. In the fixing processing operation, the endless belt 15 is heated by the heating roller 12 together with the sheet S while pressing the image fixing surface of the sheet S by the pressure roller 11, thereby ensuring good fixability. To be able to.

  In FIG. 3, reference numeral 13 denotes a peeling roller for peeling the sheet S from the endless belt 15 with its own rigidity. The outer dimensions of the peeling roller 13 are the adhesion force between the endless belt 15 and the sheet S and the endless belt 15. Is determined by the wrapping angle around the peeling roller 13.

  Reference numeral 14 denotes a steering roller for preventing the end portion of the belt from being damaged due to the offset running that occurs when the endless belt 15 rotates. The steering roller 14 adjusts the traveling direction of the endless belt 15. . Here, the steering roller 14 is configured to adjust the traveling direction of the endless belt 15 by displacing one of the shafts so as to be inclined with respect to the axis of the heating roller 12 by a displacement mechanism (not shown).

  The endless belt 15 is wound around the heating roller 12 that is one roller of the fixing roller pair 11A constituted by the pressure roller 11 and the heating roller 12, and the steering roller 14 and the peeling roller 13 that are downstream rollers. It has been.

  Reference numeral 16 denotes a cooling device that is a cooling unit that is in close contact with the inner peripheral surface that is the side surface opposite to the sheet pressing surface of the endless belt 15 between the heating roller 12 and the peeling roller 13. 15, the heat of the sheet S is absorbed. In addition, this cooling device 16 is comprised by the heat sink etc., for example. The cooling target temperature of the cooling device 16 varies depending on the type of toner used, the image receiving layer of the sheet, and the like, but is generally a temperature at which the temperature of the sheet S on the endless belt 15 is 60 to 80 ° C. is there.

  By providing such a cooling device 16, it is possible to reduce the degree of thermal influence on the sheet on which the high-gloss image is cooled and fixed by the heat of the sheet passing through the upper pre-fixing conveyance path 6. . Further, conventionally, a cooling means separately provided for temperature control inside the apparatus is not necessary. The cooling device 16 may be configured to cool the sheet S using a cooling fan.

  Further, in the present embodiment, as shown in FIG. 3, at least the stretched surface from the heating roller 12 to the cooling device 16 in the endless belt 15 is arranged to be inclined downward from the horizontal plane. That is, by setting the sheet delivery section of the pre-fixing conveyance path 6 and the second fixing section 5 to a position higher than the delivery section of the post-fixing conveyance path 7, the cooling device 16 is more than the fixing roller pair 11 </ b> A. The endless belt 15 is inclined so that the one is positioned below.

  As a result, unnecessary heat transfer to the cooling device 16 can be eliminated, a decrease in the capacity of the cooling device 16 can be prevented, and the entire device can be downsized. In the present embodiment, by setting the angle of the belt tension surface to approximately 30 degrees, a good cooling capacity can be obtained, and the temperature control of the heating roller 12 and the temperature control of the cooling device 16 can be performed. A balance is achieved.

  Next, the operation of creating a high gloss image by the second fixing unit 5 will be described.

  First, in the present embodiment, the following method is adopted as one method for obtaining a high gloss image. When an operator who requests output requests output of a high gloss image, a high gloss image output sheet is preferably used.

  As the high-gloss image output sheet, a gloss output sheet S1 in which a transparent image receiving layer 52 made of a thermoplastic resin is provided on one surface of a sheet-like substrate 51 as shown in FIG. Such a gloss output sheet S1 has a uniform gloss feeling on the entire surface on which the image receiving layer 52 is formed.

  In the special output mode for outputting an image with high glossiness, such a gloss output sheet S1 is used. In addition to such a gloss output sheet S1, even if coated paper or the like is used, an image with a certain degree of gloss can be output.

  On the other hand, in the normal output mode, if non-glossy image output is performed, a sheet of plain paper or the like having a specified size such as A4 plate or B5 plate is used which has almost no gloss. If low gloss image output is to be performed, a coated paper sheet or the like that has a smooth surface and is slightly glossy is used.

  Here, in the special output mode, when the sheet S on which the low-gloss and non-gloss images are fixed is sent to the external fixing device 1, the sheet S is heated by the heating roller 12 and the pressure roller 15 and the pressure roller. 11 is heated and pressurized by passing through the nip between 11. Further, even after passing through the nip, the sheet is conveyed while being in close contact with the endless belt 15.

  Next, the sheet S in close contact with the endless belt 15 is cooled to a predetermined temperature (60 to 80 ° C.) by the cooling device 16, and then peeled off from the endless belt 15 at a portion where the peeling roller 13 is located.

  Incidentally, the toner image of the sheet S subjected to the fixing process in the first fixing unit 204 of the apparatus main body 200 is slightly buried in the surface of the image receiving layer 52 as shown in FIG. Yes.

  However, in this embodiment, in the re-fixing process, the image receiving layer 52 of the sheet S1 is first melted by heating in the second fixing unit 5. Thereafter, the cooling device 16 cools the image receiving layer 52 and the toner image Ta after the first fixing, which is also melted and pushed into the image receiving layer 52. Thereafter, the entire surface of the image receiving layer 52 including the toner image Ta is solidified in a smooth surface state following the surface of the endless belt 15.

  Then, by performing the fixing process again, the toner image Ta is almost completely buried in the image receiving layer 52 along the smooth surface of the endless belt 15 as shown in FIG. The toner image Tb is given a smooth glossiness. The sheet S that has been subjected to the fixing process again by the second fixing unit 5 as described above passes through the post-fixing conveyance path 7 and is discharged onto the stack tray 8 as described above.

  FIG. 5 is a control block diagram of the external fixing device 1. In FIG. 5, reference numeral 70 denotes a controller that controls the operation of the external fixing device 1, and the controller 70 includes a microcomputer that includes a CPU, ROM, RAM, and the like. The controller 70 executes a control operation in accordance with a control program stored in a memory such as a ROM, the operation unit 71, and the contents of selection instruction information input from another OA device. A control program related to each operation described later is also stored in a memory such as a ROM.

  Further, the controller 70 sends necessary control signals to the upper conveyance motor M1 that drives the conveyance rollers 120 and 121 that are sheet conveyance means provided in the paper discharge conveyance path 4 and the solenoid SL that drives the branch flapper 3. It is supposed to be sent out.

  Further, necessary control signals are sent to the upper bending path motor M2 for driving the conveying rollers 122 to 124, which are sheet conveying means provided in the pre-fixing conveying path 6, and to the fixing motor M3 for driving the pressure roller 11. It has become. Further, a required control signal is sent to the fixing heater H which is the halogen heater 12a inside the heating roller. Furthermore, when a cooling fan is used as the lower bending path motor M4 and the cooling device 16 that drive the conveyance roller 125 and the like provided in the conveyance path 7 after fixing, a necessary control signal is sent to the cooling fan F. It has become. The paper discharge transport path 4 and the pre-fixing transport path 6 constitute a common path between the transport roller 120 and the transport roller 121.

  In FIG. 5, reference numeral 1A denotes a sheet conveying apparatus provided with conveying rollers 120 to 124 and a pre-fixing conveying path 6. The sheets on which image fixing processing has been performed by the sheet conveying apparatus 1A are sequentially specified. The sheet is conveyed to the second fixing unit 5 with an interval.

  The operation unit 71 is provided at a predetermined position of the external fixing device 1 or the apparatus main body 200. The operation unit 71 includes keys for inputting instructions for setting, selecting, determining, and executing various conditions when the external fixing device 1 is used, a setting menu for the external fixing device 1, an operating state, and a selection menu for various conditions. A display unit for displaying input information and the like is provided.

  Here, the display unit may be a general liquid crystal display screen or a lamp, but in general, a touch panel type liquid crystal display screen that can also perform information selection instruction and input in addition to information display is used. Is done. Note that the instruction information input by the operation unit 71 is transmitted to the controller 70, and predetermined display is performed on the display unit according to the control operation from the controller 70, the output status from other OA devices, and the like.

  Then, the external fixing device 1 performs a normal output mode in which image output (copy or print) with a general image quality (low-gloss, non-gloss image quality) is performed according to a predetermined selection instruction, and an image output with high glossiness. One of the special output modes (gloss imparting modes) can be selected. This selection instruction is performed directly by displaying a predetermined input screen or the like from the operation unit 71 having a touch panel type liquid crystal display screen, or in combination with a selection input operation from another OA device.

  In the apparatus main body 200, the sheet S corresponding to each output mode described above is set to be used from the viewpoint of surely outputting an image having a desired image quality. For example, the gloss output sheet S1 is stored in the paper feed cassette 211 shown in FIG. 1, and the sheet S such as plain paper or coated paper is stored in the paper feed cassette 210 shown in FIG.

  Hereinafter, main operations of the external fixing device 1 when each mode is selected will be described.

  When there is a sheet reception request from the apparatus main body 200, the controller 70 first turns on the upper conveyance motor (M1) (step 1) and instructs rotation. As a result, the external fixing device 1 can receive the sheet S from the apparatus main body 200. Next, information communication is performed with the control device 62 on the apparatus body side, and it is determined whether the output mode of the sent sheet S is the special output mode or the normal output mode (step 2).

  Here, in the present embodiment, when the controller 70 sets the gloss output sheet S1 stored in the sheet cassette 211, for example, by the operation unit 71, the special output mode (gloss imparting mode) is set. ) Is selected. In this case, in order to transfer the toner image to the image receiving layer surface side, it is necessary to feed the gloss output sheet S1 so that the image receiving layer 52 is positioned on the transfer surface side. The paper cassette 211 is accommodated with the image receiving layer 52 facing down.

  Next, when the output mode is determined to be the special output mode (N in step 2), the fixing heater H of the second fixing unit 5 that has been temperature-controlled in advance by a standby mode such as the energy saving mode is turned on in full. (Step 3). Further, when a cooling fan is used as the cooling device, the cooling fan is turned on (step 4).

  Next, by a series of image forming processes in the apparatus main body 200, a permanent toner image is formed on the sheet S1 determined to be highly glossy. When it is determined that the sheet S1 has been sent to the external fixing device 1, the solenoid is turned on. (Step 5). As a result, the branch flapper 3 in the branching section is switched to the lower conveyance side, and the sheet S1 is conveyed to the conveyance path 6 before fixing. During this time, the controller 70 is turned on at any time, such as the upper bending path motor (M2), the fixing motor (M3), and the lower bending path motor (M4) (step 6).

  As a result, the sheet S1 fed from the apparatus main body 200 is conveyed from the pre-fixing conveyance path 6 to the second fixing unit 5, and then the second fixing unit 5 performs another fixing process with improved smoothness. Thereafter, the sheet is discharged from the post-fixing conveyance path 7 to the stack tray 8 (step 7).

  At this time, as described above, the fixed toner image on the image surface side once normally fixed is pushed in while being melted again on the endless belt 15 side, so that a smooth and high-gloss image is fixed. The In addition, as described above, in the post-fixing conveyance pass 7, the sheet S is conveyed with the high-gloss image forming surface on the inside, so that the image is hardly damaged, and a high-gloss image without deterioration in image quality is thereby obtained. Formed on the sheet.

  Next, it is determined whether or not the continuous conveyance sequence has been completed (step 8). If it is determined that the continuous conveyance sequence has been completed (Y in step 8), various M (motor) / H (heater) / F (fan) Is turned off (step 9), and the control sequence is terminated.

  On the other hand, when the operation unit 71 sets the feeding from the sheet feeding cassette 210 containing the sheet S such as plain paper or coated paper, the controller 70 determines that the output mode is the normal output mode. When the output mode is thus determined to be the normal output mode (Y in step 2), the solenoid is turned off (or kept in the off state) (step 10). As a result, the branch flapper 3 switches to the upper conveyance side, and conveys the sheet S2 to the paper discharge conveyance path 4.

  Next, the sheet S thus transported to the paper discharge transport path 4 is eventually delivered to a paper discharge tray or another finishing system which is a connected subsequent unit (not shown) (step 11). During this time, it is determined whether or not the continuous conveyance sequence has ended (step 12). If it is determined that the continuous conveyance sequence has ended (Y in step 12), the control sequence ends. Thereby, a non-glossy or low-gloss image is formed on the sheet S.

  As described above, when the sheet S that has been subjected to the fixing process again by the second fixing unit 5 is transported by the transport path 7 after fixing, the sheet S faces along the guide surface 7a with the surface opposite to the image fixing surface. By making it pass, a high gloss image can be formed. Further, as described above, a substantially S-shaped path is formed, and the pre-fixing transport path 6, the second fixing unit 5, and the pre-fixing transport path 6 are arranged in the vertical direction, so that an external fixing device is provided. The width of 1 can be shortened and the height can be lowered.

  As a result, it is possible to reduce the installation area while achieving high image quality of high-gloss images, and supply high-quality images with high gloss to a wide range of users without limiting the number of users. Is possible. Thereby, the introduction destination which can introduce this system can be expanded greatly.

  Furthermore, it is necessary to provide a cutting unit for impressing image information on the sheet, passing the second fixing unit 5 and cutting the sheet on which the final image has been fixed to a desired size, up to a large size sheet. Even in this case, the apparatus can be easily arranged without increasing the size.

  In addition, it can be installed compactly to obtain high-gloss images of silver-salt photographic tone, even at copy shops where there is a request for printing on the back side of high-gloss silver-salt photos, such as installation locations and equipment installation costs. At the same time, it has become possible to provide a popular image forming apparatus capable of printing on the back side.

  Also in this case, the sheet S is conveyed to the second fixing unit 5 by the conveyance path 6 before fixing, and the sheet S after fixing is conveyed by the conveyance path 7 after fixing by the second fixing unit 5. A path is formed in the apparatus main body 200 in a substantially S shape as a whole. Thereby, the enlargement of the apparatus main body 200 can be prevented.

  By the way, the conveyance rollers 120 to 124 are driven by an upper conveyance motor M1 and an upper bending path motor M2 controlled by a controller 70 as control means, and convey the sheet. That is, the sheet is conveyed at the first sheet conveyance speed that is the sheet discharge speed of the apparatus main body 200 until the sheet reaches a predetermined position upstream of the second fixing unit 5. Further, when the sheet reaches a predetermined position, the sheet is switched to the second sheet conveying speed that is the same as the second fixing speed, which is the fixing speed of the second fixing unit 5 that is slower than the first sheet conveying speed, and the sheet is moved to the second position. The sheet is conveyed to the second fixing unit 5 at the sheet conveyance speed.

  Here, in the present embodiment, when the sheet conveyance speed is switched from the first sheet conveyance speed to the second sheet conveyance speed, it is assumed that the next sheet enters the conveyance path 6 before fixing. Yes. For this reason, at least the length of the pre-fixing conveyance path 6 (the length from the conveyance roller 120 to the second fixing unit 5) is equal to or greater than the sum of the circumferential length of the transfer belt 217 and the conveyance direction length of the sheet. .

  Then, by setting the length of the pre-fixing conveyance path 6 to such a length, when the preceding sheet S1 reaches the second fixing unit 5 as shown in FIG. Sheet S2 is present in the sheet conveyance path 6. As a result, it is possible to prevent the next sheet (not shown) of the next sheet S2 from colliding with the next sheet S2.

  As described above, when the sheet conveying speed is switched from the first sheet conveying speed to the second sheet conveying speed, the second sheet S2 is sequentially fixed by making the next sheet S2 exist in the pre-fixing conveying path 6. The collision of the sheet conveyed to the unit 5 can be prevented. Thereby, the occurrence of damage to the sheet and the sheet image can be prevented.

  Further, with this configuration, the external fixing device 1 (the first fixing device) (the first fixing device) is not provided without affecting the image forming speed without providing a standby unit for temporarily stopping the sheet in order to adjust the difference in sheet conveyance speed. The sheet can be conveyed in accordance with the fixing speed of the second fixing unit 5). As a result, the sheet conveyance path and conveyance control are simplified, and stable sheet conveyance with little damage to the image becomes possible.

  When the trailing edge of the previous sheet S1 reaches the second fixing unit 5, the sheet conveyance speed is conveyed from the second sheet conveyance speed to the first sheet conveyance speed. Thereby, the sheet conveyance time in the second fixing unit 5 can be shortened.

  In the above description, the controller 70 is provided in the external fixing device 1 and the external fixing device 1 is controlled by the controller 70. However, the control of the external fixing device 1 is controlled by the control device 62 on the apparatus main body side. You may comprise so that it may perform.

1 is a diagram illustrating a schematic configuration of a color copier that is an example of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a diagram showing a schematic configuration of an external fixing device connected to the main body of the color copying machine. FIG. 3 is a diagram illustrating a configuration of a second fixing unit of the external fixing device. (A) is a diagram showing the configuration, (b) is a diagram showing a state after the first fixing, and (c) is a state after the second fixing, of the image output sheet for high gloss used in the color copying machine. FIG. FIG. 3 is a control block diagram of the external fixing device. 7 is a flowchart for explaining fixing control of the external fixing device. FIG. 4 is a diagram for explaining fixing control of the external fixing device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 External fixing device 1A Sheet conveyance device 3 Branch flapper 5 Second fixing unit 6 Pre-fixing conveyance path 6a Curved guide surface 7 Post-fixation conveyance path 7a Curved guide surface 8 Stack tray 11 Pressure roller 11A Fixing roller pair 12 Heating Roller 15 Endless belt 16 Cooling device 62 Controller 70 Controller 120, 121 Conveying rollers 122-124 Conveying roller 200A Color copier 200 Color copier main body 202 Image forming unit 204 First fixing unit S, S1, S2 Sheet

Claims (7)

A sheet fixing process of the image is performed, the sheet conveying device for conveying the sequential re-fixing process unit,
A sheet conveyance path through which a sheet conveyed to the re-fixing processing unit passes;
A sheet conveying means provided in the sheet conveying path and capable of switching a sheet conveying speed between a first sheet conveying speed and a second sheet conveying speed slower than the first sheet conveying speed;
When performing the re-fixing process to the sheet in the re-fixing process unit, and control means for controlling the sheet conveying means so as to switch the sheet conveying speed from the first sheet conveying speed in the second sheet conveying speed,
With
When the length of the sheet conveying path is changed from the first sheet conveying speed to the second sheet conveying speed, the sheet on which the refixing process is performed next to the sheet on which the refixing process is performed. A sheet conveying apparatus having a length such that a rear end thereof exists in the sheet conveying path.   The control means controls the sheet conveying means so as to switch the sheet conveying speed from the second sheet conveying speed to the first sheet conveying speed after completion of the sheet re-fixing process. The sheet conveying apparatus according to 1.   The sheet conveying apparatus according to claim 1, wherein the second sheet conveying speed is the same as a fixing speed of the re-fixing processing unit.   The sheet conveying apparatus according to claim 1, wherein a curved guide surface is provided in the sheet conveying path. An apparatus main body, the sheet according the image forming unit having an intermediate transfer member the toner image on the image bearing member and the image bearing member toner image is formed is transferred to any one of 請 Motomeko 1 to 4 An image forming apparatus comprising: a conveyance device, wherein the length of the sheet conveyance path is equal to or greater than a total length of a peripheral length of the intermediate transfer member and a sheet.   The image forming apparatus according to claim 5, wherein the intermediate transfer member has a peripheral length to which a plurality of toner images can be transferred. The image forming apparatus according to claim 5 or 6, wherein the provision of said control means to said apparatus main body.

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