JPH05297742A - Image forming device - Google Patents

Abstract

PURPOSE:To fix a toner image, transferred to an OHP film, a thick sheet, or etc., by means of a color image forming device, into a glossy image. CONSTITUTION:The color image forming device is provided with ungloss mode for ordinary fixing and gloss mode for fixing on an OHP film, a thick sheet, etc. When the gloss mode is selected as the fixing mode, a sheet material subjected to fixing by a fixing device 30 and ejected to a sheet ejection tray 32 via a sheet ejection roller 31 is again carried between the transfer unit 24 and the fixing device 30 to be subjected to refixing, and it is again ejected onto the sheet ejection tray 32 by the common sheet ejection roller 31.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus for transferring and fixing a toner image formed on an image carrier by an electrophotographic method on a transfer material, and especially for a demand for glossy image, OHP film or thick paper. The present invention relates to a color image forming apparatus such as a copying machine or a printer having a corresponding re-fixing unit.

[0002]

2. Description of the Related Art In a conventional color image forming apparatus,
When a color image is formed on a transfer material, particularly thick paper or an OHP film (tranpen film for overhead projects: synthetic resin recording sheet), in order to obtain excellent color reproducibility of the color toner image, the toner is used. Since it is necessary to melt the toner almost completely to eliminate unevenness on the surface of the toner layer and smooth the surface, the fixing conditions are changed to fix the color toner image.

As a method of changing the fixing condition, there are a method of changing the fixing temperature and a method of changing the fixing speed. In the former method of changing the fixing temperature, it takes time for the temperature to reach a predetermined temperature, and an offset due to the temperature change is apt to occur. Furthermore, the color reproducibility is insufficient only by increasing the temperature. Etc. have problems. On the other hand, in the latter method of changing the fixing speed, the distance from the transfer unit to the fixing unit needs to be longer than that of the transfer material, and the rear end of the front transfer material and the front end of the rear transfer material at the time of continuous image formation. There is a problem that the fixing speed can be slowed only to the extent that they do not overlap.

In any case, a color image having excellent color reproducibility cannot be obtained by image formation by the method of changing the fixing temperature or the fixing speed.

In consideration of such a problem, the applicant of the present invention discloses in Japanese Patent Laid-Open No. 2-141767 that the transfer material which has been once fixed is conveyed by the transfer material conveying means to be fixed again and is fixed again. , An image forming apparatus capable of obtaining a color image having excellent color reproducibility is proposed.

[0006]

However, in the image forming apparatus disclosed in the above publication, after the transfer material which has once been fixed is conveyed to the re-fixing conveyance path by the guide claw,
Since the fixing is performed again by the fixing means, the structure of the conveying path is complicated, and the apparatus also has to be upsized.

According to the present invention, such a problem is solved, and a transfer material which has been once fixed in correspondence with a request for a particularly glossy image or OHP film or thick paper is fixed again using the fixing means of the image forming apparatus. It is an object of the present invention to provide an image forming apparatus which has a simple structure and is compact in size, and which can also be used as a sheet discharging unit for re-fixing.

[0008]

[Means for Solving the Problems]
It is achieved by any of the following means.

(A) In an image forming apparatus for transferring and fixing a toner image formed on an image carrier onto a transfer material, the transfer material fixed in the normal fixing mode is fixed again in the image forming apparatus. An image forming apparatus having a re-fixing mode, wherein when the re-fixing mode is selected, the transfer material discharged after fixing is conveyed again between the transfer section and the fixing section and fixed again.

In (b) and (a), the discharging section for discharging the transfer material fixed in the normal fixing mode to the outside of the image forming apparatus and the discharging section for re-fixing in the re-fixing mode are commonly used. Image forming apparatus.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention is a side sectional view showing the structure of a color image forming apparatus equipped with a re-fixing device of FIG. 1 and a side sectional view showing the structure of a color image forming device in the re-fixing mode of FIG. 6 and FIG. 3, a side sectional view showing the configuration of the fixing device, FIG. 4 showing a heating temperature control circuit, FIG. 5 showing the operating conditions of each member of the fixing device, and FIG. 6 showing the material of the transfer material. 9 is a diagram showing another proper fixing temperature, a plan view showing an operating portion of the color image forming apparatus shown in FIG. 7, a block diagram showing a control circuit of the color image forming apparatus shown in FIG. 8, and another implementation of the re-fixing means shown in FIG. An example will be described with reference to a side sectional view showing a configuration of a color image forming apparatus. However, the present invention is not limited to this embodiment. As shown in FIG. 1, an apparatus main body 10 of a color image forming apparatus is surrounded by an operation panel 11, an openable upper cover 12, a toner supply cover 13, a front cover 14 and the like on the front surface, and a detachable process inside. A cartridge 15 and a paper feed cassette 16 are provided.

In FIG. 1, a photosensitive belt 17, which is an image carrier, is a flexible belt having a photosensitive layer coated on the surface thereof, and is stretched between a driving roller 18 and a driven roller 19. The drive roller 18 rotates (not shown) via a drive gear that meshes with a gear provided in the apparatus body 10, and conveys the photosensitive belt 17 in the clockwise direction. Further, the distance maintaining member 20 makes it possible to keep the distance between the developing device 23 and the photoconductor belt 17 constant and to stably form a good image. In this embodiment, the photoconductor belt is used as the image carrier.
However, the present invention is not limited to this, and can be applied to an existing image carrier having a photosensitive layer such as a photosensitive drum.

Around the photosensitive belt 17, charging means, exposure means, developing means, transfer means and cleaning means are arranged.

The charging means is provided to uniformly charge the photosensitive layer on the surface of the photosensitive belt 17 with a predetermined polarity, and is an existing charger 21 such as a corona charger or a scorotron charger. A scorotron charger is preferably used for the body.

The exposure means is a semiconductor laser writing system unit 22, and the photosensitive belt 17 charged by the charger 21.
The surface of is exposed to form an electrostatic latent image.

The developing means is composed of a plurality of developing devices 23a to 23a each containing a developer of a different color, for example, a toner (developer) of each color of yellow, magenta, cyan and black.
It is d. Each of the developing devices 23a to 23d is a photoconductor belt.
17, developing sleeves 231a to 231d for keeping a predetermined gap and stirring screws 232a to 232d for stirring the toner of each color,
It has a function of developing an electrostatic latent image on the photoreceptor belt 17 into a toner image by a non-contact developing method. Unlike the contact developing method, this non-contact developing method does not impair the previous toner image formed on the photoconductor belt 17 and does not hinder the movement of the photoconductor belt 17, so that a good color image can be obtained. You can The developing means is not limited to color development using four different color toners as in the present embodiment, but may be a single color, two colors or three colors.
Color toners may be used, and in this case, the developing means may be provided with as many developing units as the number of toner colors around the photosensitive belt 17.

The transfer means transfers the toner image formed on the photosensitive belt 17 onto a transfer material by a transfer device 24 such as a transfer corona discharger. As this transfer means, an existing transfer member such as a transfer drum may be used instead of the transfer device 24.

The cleaning means 25 has a cleaning blade 251, which is kept at a position separated from the surface of the photoconductor belt 17 during the image forming process, and is used only for cleaning after the toner image is transferred onto the transfer material. It is provided so as to clean the photosensitive belt 17 by pressing it against the surface of the belt 17.

The recovery box 26 is for recovering the residual toner on the photosensitive belt 17 removed by the cleaning means 25 through the toner recovery pipe 262 by the waste toner screw 261 and storing it.

In this embodiment, the photosensitive belt 17 constituting the image forming portion of the printer described above, the charging device 21, the developing devices 23a to 23d containing the toner of each color, and the cleaning means.
The process means portions of the toner collection box 26 and the toner collection box 26 are housed in the integrated process cartridge 15 to be unitized, and can be collectively attached to and detached from the apparatus main body 10. However, the process unit unitized in the process cartridge 15 is not limited to this, and at least the photosensitive belt 17 and the developing devices 23a to 23d may be unitized, and the other process units may be united together. May be done.

The process of forming a color image by the color image forming apparatus having the above structure is performed as follows.

First, the process cartridge 15 is loaded in the first position (which will be described later), and is in a state capable of forming an image. Then, when the image signal of the first color output from the image reading apparatus separate from the apparatus main body 10 is input to the laser writing unit 22, a semiconductor laser (not shown) in the laser writing system unit 22 is used. A laser beam is generated. The laser beam is rotationally scanned by a polygon mirror 221 rotated by a drive motor (not shown), and the fθ lens 222 and the cylindrical lens 224 are scanned.
Then, through the three mirrors 223, a bright line is formed by being projected onto the peripheral surface of the photoconductor belt 17, which has been uniformly charged to a predetermined electric charge by the charger 21 in advance.

On the other hand, in the sub-scanning direction, a belt index corresponding to a specific position of the photosensitive drum 17 is detected by a photo sensor (neither is shown), or a print command signal is received, and this detection or command is received. The main scanning line at which the modulation of the semiconductor laser by the image signal is started is determined based on the signal. When the scanning is started, the laser beam is detected by an index sensor (not shown) in the main scanning direction, and the semiconductor laser modulation by the image signal of the first color is started based on the detected signal. The modulated and modulated laser beam is applied to the photoreceptor belt 17
Scan over the surface of. Therefore, a latent image corresponding to the first color is formed on the surface of the photosensitive belt 17 which is uniformly charged by the main scanning by the laser beam and the sub scanning by the conveyance of the photosensitive belt 17. This latent image is developed by the developing device 23a of the developing means that contains the yellow toner corresponding to the first color, and a yellow toner image is formed on the surface of the photosensitive belt 17. After that, the photoconductor belt 17 passes under the cleaning blade 251 separated from the surface of the photoconductor belt 17 while holding the yellow toner image on the surface thereof, and then the image formation of the second color is started. That is, the photoreceptor belt 17 on which the yellow toner image is formed is
Then, the image signal of the second color is inputted to the laser writing system unit 22 again, and the photosensitive belt 17 is charged in the same manner as the image signal of the first color.
Writing is performed on the surface of the to form a latent image. The latent image is a developing device 23b containing magenta toner as the second color.
Developed by. The magenta toner image is formed in the presence of the already formed yellow toner image.

Similarly, after the latent image is formed by the image signal of the third color, a cyan toner image is formed by the developing device 23c containing the cyan toner, and further, after the latent image is formed by the image signal of the fourth color, black is formed. A black toner image is superimposed on the surface of the photoconductor belt 17 by the developing device 23d that contains toner, and a color toner image is formed on the surface of the photoconductor belt 17.

Developing sleeves of these developing devices 23a-23d
A direct current or an alternating current bias is applied to 231a to 231d, and reversal development (jumping development) is performed in a non-contact manner on the photoreceptor belt 17 whose base is grounded. For this non-contact development, either one-component developer or two-component developer can be used. Further, when the one-component developer is used, the toner hopper 35 described later is not required and the size can be reduced, but the developing method using the two-component developer is superior in terms of the stability of the developer. It is preferable for color reproduction.

The color toner image formed on the surface of the photoconductor belt 17 as described above is supplied from the paper feed cassette 16 by the paper feed roller 27 to the transfer material which is timed with the color toner image by the timing roller 28. Transcribed. The transfer unit 24 applies a high voltage source output having a polarity opposite to that of the toner to perform transfer.

The transfer material on which the color toner image has been transferred in this manner is reliably separated along the driving roller 18 by the photosensitive belt 17 which rapidly changes direction (small diameter curvature), and is conveyed upward by the conveying belt 29. It The conveyor belt 29 is provided with a suction means 291 to surely convey it upward while sucking. Then, after the toner is melted and fixed on the transfer material by the fixing roller 101 and the pressure roller 102 of the fixing device 30, the transfer material passes through the conveyance guide 7 and is discharged onto the upper surface of the upper cover 12 which also serves as the discharge tray 32 by the discharge roller 31. Is discharged.

On the other hand, after the transfer of the color toner image onto the transfer material, the photosensitive belt 17 is further conveyed in the clockwise direction,
The cleaning means 25 with the cleaning blade 251 in a pressure contact state removes and cleans the residual toner. After cleaning, clean the blade again.
251 is separated from the photosensitive belt 17, and a new image forming process is started.

In the color image forming apparatus constructed as described above, the timing roller 28 at the time of image formation in the above-mentioned normal mode, that is, the normal copy mode (image formation by control in the non-glossy mode described later) 28 A transfer speed of the transfer material by the transfer means such as the photosensitive belt 17, the transfer belt 29, the fixing roller 101 and the pressure roller 102, the discharge roller 3
The fixing speed of 1 is, for example, all 120 mm / sec, and
Fixing roller 101 by fixing roller 101 and pressure roller 102
Has a surface temperature of 130 ° C.

The toner used in the color copying machine of this embodiment is obtained by dispersing a dye and a pigment in a polyester resin and pulverizing the pigment into particles having a weight average particle diameter of 3 to 12 μm and having a softening point of about 110 ° C. I used the one.

As shown in FIG. 3, 101 of the fixing device 30 is a fixing roller rotatably supported by a bearing at a fixed position.
102 is rotated counterclockwise by a drive system of the image forming apparatus while being pressed against the fixing roller 101 located on the upper side from below, and at the same time, the fixing roller 101 is driven to rotate clockwise.
The fixing roller 101 and the pressure roller 102 have built-in heaters H1 and H2 of approximately 400 W each having substantially the same amount of heat generation, and the outer peripheral surface has a silicon rubber layer as a heat-resistant synthetic rubber layer. Is detected by temperature sensors TS1 and TS2 and managed at a prescribed temperature by the control system of the image forming apparatus.

Denoted at 3 is a separation claw for the transfer material, which is pressed against the peripheral surface of the fixing roller 101, and a plurality of separation claws are arranged in parallel with the axis of the fixing roller 101.

Reference numeral 4 is a cleaning roller of the fixing roller 101, which is brought into contact with the peripheral surface of the fixing roller 101 by the tip of a brush on the outer periphery and is rotated in the same direction following the rotation thereof.

Reference numeral 5 denotes an oil supply device, whose oil-impregnated portion 5A is always in contact with the peripheral surface of the fixing roller 101 and applies silicon oil to improve the releasing property of the fixing roller 101, that is, the separating property of the transfer material.

A transfer material having a toner image transferred on its upper surface is indicated by an arrow A.
When the transfer material is conveyed from the direction into the fixing device, the transfer material is simultaneously heated from the upper surface and the lower surface at the pressure contact Q by the fixing roller 101 and the pressure roller 102, and the toner is melted. As the toner is received, the toner in a melted state is sufficiently permeated into the transfer material and firmly adhered to it, so that a toner image having a high gloss without offset risk can be obtained.

Control of fixing temperature in the fixing device 30
Management is performed as follows.

FIGS. 4 and 5 show the circuit and process for controlling the temperature by the temperature sensors TS1 and TS2. The heater H1 is used when the apparatus is "warm up".
And H2 continue to be in the ON state, both the fixing roller 101 and the pressure roller 102 are in the stopped state (OFF), and therefore the pressure bonding action of the pressure roller 102 is also released (OFF).

Fixing roller after "warm up" is completed
101 and the pressure roller 102 each reach a predetermined peripheral surface temperature,
In the fixing ready state, that is, in the “ready” stage, the heaters H1 and H1 are used to keep the fixing temperature of the transfer material constant.
2 turns on and off repeatedly, and at the same time the fixing roller 1
01 and the pressure roller 102 start conveying and rotating, respectively.

When "printing" is performed in the image forming apparatus at the "ready" stage, the pressure roller 102 is in a pressure contact state (O
The transfer material conveyed as N) is conveyed and the toner image is fixed.

By setting the heating temperature for the lower surface of the transfer material, that is, the back surface, to a temperature slightly higher than the heating temperature for the toner image surface of the transfer material, the resolution is high and the gloss is high without so-called offset phenomenon. It is possible to obtain a fixed image.

The heating temperature for the toner image surface, that is, the peripheral surface temperature (T1) of the fixing roller 101 is limited to a temperature of 130 ° C. necessary for melting the toner, whereby excessive melting of the toner is avoided and bleeding occurs. A high-quality fixed image with high resolution is obtained.

On the other hand, the heating temperature for the back surface, that is, the peripheral surface temperature (T2) of the pressure roller 102 is set higher than the peripheral surface temperature (T1) of the fixing roller 101 according to the material of the transfer material. As a result, the melted toner is sufficiently melted and adsorbed on the transfer material, and the image is fixed more firmly. The attraction of the toner to the transfer material is promoted by increasing the nip width of the pressure roller 102 with respect to the fixing roller 101 described above.

The temperature difference between the peripheral surface temperature (T1) of the fixing roller 101 and the peripheral surface temperature (T2) of the pressure roller 102 is 10 ° C. or less except for thin plain paper and some thick paper, as described later.
It is controlled and managed by the temperature detection of the temperature sensors TS1 and TS2 so that it is set in the range of 60 ° C.

FIG. 6 shows an example of the appropriate peripheral surface temperatures T1 and T2 for the peripheral surface temperature at the time of fixing in the gloss mode and the non-gloss mode for each material of the transfer material.

In the color image forming apparatus described above, either the gloss mode or the non-gloss mode can be selected, and a desired copy image can be displayed on the operation panel 11 shown in FIG. 7 prior to the start of the copy operation. The mode corresponding to the glossiness is selected.

That is, the gloss button 11A is used to make the copy image a gloss image, and the non-gloss button is used to make the non-gloss image.
Select 11B and press.

As a result, as shown in FIG. 8, the gloss mode selection information is input to the control unit, and the CPU fixes the copy image fixed in accordance with the subsequent image forming process in either the gloss mode or the non-gloss mode. Is processed in the mode.

At this time, a non-glossy button for selecting a non-glossy mode
When 11B is selected, the normal copy mode (described above) is selected, and when the gloss button 11A for selecting the gloss mode is selected, the re-fixing mode (described later) is selected and controlled in each image forming process.

The control mechanism in the re-fixing mode will be described below (when the gloss mode is selected).

That is, a case where a glossy image is formed on a transfer material such as an OHP film or a thick paper by using a color copying machine according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2.

A discharge tray 32, which is a part of the upper cover 12.
Has one end rotatably supported by the upper cover 12 by a rotatable shaft 321 and the other end hung by a notch of a hooking member 322 rotatably supported by the upper cover 12. It has been stopped. Hereinafter, this state (FIG. 1) is referred to as the discharge tray 32 being in the first position. When the discharge tray 32 is in the first position, the discharge tray 32 accommodates the transfer material discharged from the discharge roller 31.

On the other hand, as shown in FIG. 2, the catch member 322 is rotated in the direction of the arrow to release the catch of the discharge tray 32, so that the discharge tray 32 is rotated in the direction of the arrow by its own weight. It rotates around 321 and engages with the positioning member 33. Hereinafter, this state (FIG. 2) is referred to as the paper ejection tray 32 being in the second position. When the paper ejection tray 32 is in the second position, the paper ejection tray 32 functions as a paper feed tray that feeds the transfer material to the refeed roller 34.

In the position detecting sensor 36, the discharge tray 32 is the second one.
It is possible to use a variety of existing sensors that are microsensors, photoelectric switches, magnetic switches, and the like, which are sensors for detecting that they are in the position.

Further, the transfer material detection sensor 37 is a sensor for detecting that the transfer material to be re-fixed is placed on the sheet discharge tray 32 at the second position, and is of a transmission type or a reflection type. Various existing sensors using a photo coupler, a non-contact reed switch, a contact micro switch, or the like can be used.

When the gloss button 11A on the operation panel 11 is pressed, the control means selects the gloss mode, and when the copy button is pressed, first, an image is formed on the transfer material in the same manner as in the normal mode described above. The transfer material is discharged onto the discharge tray 32 at the first position of the upper cover 12.

That is, the control means controls the heaters H1 and H2 of the fixing roller 101 and the pressure roller 102, which are fixing means, to change the outer peripheral temperature of the fixing roller 101 from 130 ° C. in the normal mode to 130 ° C. in the re-fixing mode. C., the outer peripheral temperature of the pressure roller 102 is raised to 180.degree. C. in the case of transparency (OHP) according to the type of transfer material. The re-fixing feeding roller 34, the fixing roller 101, the pressure roller 102, and The transfer material conveyance speed by the paper ejection roller 31 is set to 12 in the normal mode.
Set each drive system at 0 mm / sec.

In the re-fixing mode, the image forming process unit such as the charging unit, the exposing unit, the developing unit, the transferring unit and the cleaning unit and the conveying unit such as the sheet feeding roller 27, the timing roller 28 and the conveying belt 29 are not operated by the control unit. And That is, at the time of re-fixing, image formation is not performed, so that means necessary for image formation are inoperative, and the control means controls so that only means necessary for re-fixing is activated.

On the other hand, the catch member 322 is rotated to rotate the catch tray 32.
Is moved from the first position to the second position. The discharge tray 32 is located at the second position. That is, when one end of the sheet discharge tray 32 collides with the positioning member 33, the position detection sensor 36 outputs a signal to the control means that the sheet discharge tray 32 is located at the second position.

Then, the position detection sensor 36 confirms that the sheet discharge tray 32 is at the second position, and the transfer material detection sensor 37 confirms that the transfer material for re-fixing is set.
Re-fix. That is, the control means sets the fixing temperature to 180
C., re-feed roller 34, fixing roller 101, pressure roller 102,
The transfer speed of the transfer material that is re-fixed by the discharge roller 31 is set to 12
The re-fixing sequence (re-fixing condition) is operated with 0 mm / sec, and the transfer material is fed to the fixing roller 101 and the pressure roller 102 by the re-feeding roller 34 to perform re-fixing. After that, the paper is ejected by the paper ejection roller 31 through the conveyance guide 7.

As for temperature control in both modes, when the non-glossy button 11B is pressed to set the non-glossy mode as shown in FIG. 6, the temperature T1 of the outer peripheral portion of the fixing roller 101 is 130.degree. The outer peripheral temperature T2 of 102 is 130 depending on the type of transfer material.
The temperature is controlled by the information from the temperature sensors TS1 and TS2 so that the temperature becomes 150 ° C. or 150 ° C., and a matte image is fixed. Further, when the gloss button 11A is pressed to set the gloss mode, the T1 is 130 as already described.
℃ and T2 are also 160 ℃, 180 ℃, depending on the type of transfer material.
The temperature is controlled by the information from the temperature sensors TS1 and TS2 so that the front and back surfaces of the transfer material are heated by appropriately selecting 190 ° C or the like.

In the gloss mode, that is, in the re-fixing mode, the linear speed is set to 120 mm / sec in the normal copy mode, but the fixing speed may be reduced if necessary, for example, 60 mm.
/ sec, 80mm / sec, etc., depending on the type of transfer material, can be fixed and a glossy image can be obtained. Especially in the case of a transparency sheet etc., excellent transparency and glossy image fixing can be formed. ..

In this embodiment, the gloss button 11A is pressed,
After confirming all the position detection of the discharge tray 32 by the position detection sensor 36 and the transfer material detection by the transfer material detection sensor 37,
Although the re-fixing sequence is operated, the present invention is not limited to this, and the mode selection and the re-fixing sequence may be operated by detecting one or more of them. In this case, the gloss button 11A, position detection sensor
As a matter of course, as the transfer material detection sensor 37, only those necessary for the operation of the above-described mode selection and re-fixing sequence may be provided in the color image forming apparatus.

Further, the hooking member 32 for hooking the discharge tray 32
2 can be rotated manually, but the gloss button 11A first
The control means may rotate the latching member 322 by pressing to move the discharge tray 32 to the second position. Further, the hooking member 322 shown in the present embodiment is unnecessary, and the discharge tray 3
Install the gear and motor on the rotating shaft 321 of the 2nd, and place the discharge tray 32 first.
The position and the second position may be automatically moved.

Next, another embodiment of the re-fixing means incorporated in the color image forming apparatus will be described.

Since the color image forming process of the color image forming apparatus, the setting conditions of the transfer unit, the fixing unit, the sheet discharging unit and the like are the same as those described above, the description thereof will be omitted and different from the built-in re-fixing mechanism. The points will be described.

The above-mentioned sheet discharge tray 32 of the apparatus main body 10 shown in FIG.
Is fixed at a certain angle as shown
322 is abolished and the tip of the paper ejection tray 32 is fixed integrally with the upper cover 12. As shown in the figure, the transport belt 29 is a transport belt in which an upper drive roller 29a around which the transport belt 29 is wound is rotatably supported by a frame of an image forming apparatus and is stretched around the drive roller 29a as a fulcrum. It is designed to rotate 29 clockwise. The rotation of the conveyor belt 29 is performed by pressing the gloss button 11A of the operation panel 11 described above, for example, the magnet provided in the image forming apparatus is energized to connect the plunger of the magnet to the lower end portion of the conveyor belt 29. Is pulled by the operating stroke of the plunger, pivots clockwise, and is positioned at the position indicated by the chain line. The fixing roller 101 and the pressure roller 102
As shown in the figure, the upper part of
The conveyance guide 7 up to and the re-conveyance conveyance guide 302 that is curved and raised to the upper left are branched and provided. Then, the re-fixing conveyance guide 302 that is erected on the upper left side faces the space between the lower end portion of the conveyance belt 29 and the transfer portion indicated by the chain line while curving the left space of the image forming apparatus downward as shown in the figure. It is provided in. The re-fixing conveyance guide 302 is provided with a plurality of conveying roller pairs 303 with appropriate intervals so that the transfer material to be re-fixed can be reliably conveyed onto the conveying belt 29.

Above the fixing roller 101 and the pressure roller 102, a conveyance shaft 7 is rotatably supported at a predetermined position near a branch point where the conveyance guide 7 and the re-conveyance conveyance guide 302 branch. A switching gate 301 is provided so that when the non-gloss mode or the gloss mode is selected, the respective conveyance paths of the conveyance guide 7 or the re-fixing conveyance guide 302 are switched according to the selection.

For example, when the gloss mode is selected, the switching gate 301, which has been closing the conveyance path of the re-fixing conveyance guide 302, is rotated counterclockwise by driving a magnet or a cam. Moving and conveying guide 7
The conveyance path of the re-fixing conveyance guide 302 is opened while the conveyance path of (3) is closed. Then, the fixing device 30 is also set to the fixing condition corresponding to the above-described gloss mode.

Further, the transport belt 2 of the transport guide 302 for re-fixing
A transfer material detection sensor 304, such as a non-contact type photocoupler, for detecting the transfer material passing near the lower tip of
When the passage of the transfer material is detected by the sensor 304, the switching gate 301 is rotated in the clockwise direction by the control of the CPU stored in advance to open the transfer path of the transfer guide 7 and the re-fixed transfer material is transferred to the transfer path. The sheet is discharged onto the sheet discharge tray 32 through the sheet discharge roller 31 along the opened transport guide 7.

While the gloss mode is selected, the switching gate 301 is automatically rotated clockwise with a predetermined time lag after the transfer material passes through the switching gate 301 under the control of the CPU stored in advance. Then, the transport path of the re-fixing transport guide 302 is opened and stands by for the transfer material for the gloss mode that is subsequently transported.

When the fixing in the gloss mode is completed and the non-gloss button 11B is pressed to switch to the non-gloss mode, the conveyor belt 29 rotates counterclockwise to return to the position in the non-gloss mode and the switching gate. 301 also rotates in the clockwise direction to open the conveyance path of the conveyance guide 7.

Then, the fixing device 30 is also set to the above-mentioned fixing condition corresponding to the fixing in the non-glossy mode. Although two selection mode buttons described above are provided, only the gloss mode button is provided, and the re-fixing copy is made only when the gloss mode button is selected, and the normal mode copy state is always set. It is the main idea.

[0073]

By the re-fixing mechanism of the extremely simple and compact color image forming apparatus of the present invention, a toner image transferred onto an OHP film or a cardboard can be fixed to a beautiful image with abundant gloss.

[Brief description of drawings]

FIG. 1 is a side sectional view showing the configuration of a color image forming apparatus including a re-fixing device according to an embodiment of the present invention.

FIG. 2 is a side sectional view showing a configuration of a color image forming apparatus in a re-fixing mode according to an embodiment of the present invention.

FIG. 3 is a side sectional view showing a configuration of a fixing device.

FIG. 4 is a diagram showing a heating temperature control circuit.

FIG. 5 is an explanatory diagram showing an operating state of each member of the fixing device.

FIG. 6 is a chart showing an appropriate fixing temperature for each transfer material.

FIG. 7 is a plan view showing an operation unit of the color image forming apparatus.

FIG. 8 is a block diagram showing a control circuit of a color image forming apparatus according to an embodiment of the present invention.

FIG. 9 is a side sectional view showing the configuration of a color image forming apparatus having a re-fixing unit according to another embodiment of the present invention.

[Explanation of symbols]

 7 Transport Guide 10 Device Main Body 11 Operation Panel 11A Glossy Button 11B Non-Glossy Button 12 Upper Cover 15 Process Cartridge 17 Photosensitive Belt 21 Charging Device 22 Laser Writing System Unit 23 Developing Device 24 Transfer Device 29 Conveying Belt 30 Fixing Device 31 Ejection Paper roller 32 Paper ejection tray 34 Refeed roller 36 Position detection sensor 37 Transfer material detection sensor 101 Fixing roller 102 Pressure roller 301 Switching gate 302 Re-fixing conveyance guide 303 Conveying roller 304 Transfer material detecting sensor 322 Hooking member

Claims (2)

[Claims] 1. An image forming apparatus for transferring and fixing a toner image formed on an image carrier onto a transfer material, wherein the image forming apparatus is in a normal fixing mode and the transfer material is fixed again. An image forming apparatus having a fixing mode, wherein when the re-fixing mode is selected, the transfer material discharged after fixing is conveyed again between the transfer section and the fixing section and fixed again. 2. The discharging unit for discharging the transfer material fixed in the normal fixing mode to the outside of the image forming apparatus and the discharging unit for re-fixing in the re-fixing mode are used in common in claim 1. Image forming apparatus.