JPS63186283A - Image forming device - Google Patents

Abstract

PURPOSE:To suppress toner adhesion to a separating claw by setting a heating means to the same or higher value as/than that of single fixing operation at the time of 1st fixing and setting the heating means to a fixing temperature higher than a 1st fixing temperature. CONSTITUTION:In case of executing image formation plural time on a single sheet, a heat roller 41 is controlled by a control part 44 so as to be heated and maintained at the same or higher temperature as/than that of single fixing operation at the time of 1st fixing. The sheet is supplied again to a transfer means 30 by a refeeding means 50. A 2nd latent image formed on an image carrier 2 by an image forming means 10 is developed by a developing device 20 and transferred to the refed sheet by a transfer means 30, and then the sheet is sent to a fixing device 40. At that time, the heating means 43 is controlled by a control part so as to heat and maintain the heat roller 41 at a prescribed temperature higher than the 1st fixing in an area generating no toner adhesion to the separating claw.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image forming apparatus used in an electronic copying machine or the like equipped with editing functions such as automatic double-sided copying and composite copying.

Conventional technology] 2. Description of the Related Art Image forming devices have been conventionally used in copying machines, for example.

In recent years, copying machines have been enriched with editing functions such as automatic double-sided copying and composite copying, and in this case, the process of forming an image on one sheet of paper is performed multiple times. Such a conventional image forming apparatus includes an image forming means for forming a latent image on an image carrier, a developing device for developing the latent image formed by the image forming means, and a developing device for developing the latent image formed by the developing device. a transfer means for transferring the image of the image carrier-hi onto a sheet of paper; a fixing device for fixing the image on the sheet transferred by the transfer means;
a re-feeding means for again supplying the paper fixed by the fixing device to the transfer means; It is composed of a pressure roller that rotates in circumferential contact and presses the paper, and a heating means that heats the heating roller.

[Problems to be Solved by the Invention] In the above-mentioned conventional image forming apparatus, the separability when the paper is sent out from both sides of the fixing device is limited to the fact that the paper is normally copied only once for one sheet of paper. Compared to the case where paper at room temperature is separated, as in the case of double-sided copying or composite copying, when a single sheet of paper is copied multiple times, the 1r! The problem tended to be worse when the paper heated by the L heating roller was separated. As a result, toner adheres to the spine of the separation claw provided to separate the paper from the heating roller (the surface that guides the paper backward), resulting in loss of images on the paper. A problem has arisen in which paper jams and the like occur.

Therefore, the inventor of the present invention has developed
The state of occurrence of toner adhesion to the back of the separating claw was investigated in relation to this, and the results are shown in FIGS. 6 and 7.

Figure 6 shows the results of one normal copying process.
The lower the ID and the higher the temperature of the heating roller, the less likely it is that the separation claw will receive a 1 to ner signal. This is because when the IQ is low, there is less adhesion of toner (that is, adhesive) on the paper, making it easier to peel off. Also, if the temperature of the heating roller is high, the temperature of the toner during fixing will also be high and the temperature of the toner will increase. ) As the JfJ force decreases, the toner becomes moist and follows the behavior of the paper well, and after the paper is separated from the heating roller, the toner image comes into contact with the separation claw whose temperature is lower than that of the heating roller. This is because even when the toner is cooled, the cohesive force of the toner does not increase to the extent that the toner adheres to the back of the separating claw.

Figure 7 shows the results of the second fixing after the paper is warmed by the first fixing, such as double-sided copying and composite copying, and toner adhesion occurs compared to normal one-time copying. easy. The reason for this is that heat curls occur on the paper, making it difficult to separate as it wraps around the heating roller, or because the paper is warmed up during the second fixing process, the cohesive force distribution within the toner is distorted, causing an inflection point. It is inferred that this occurs and breaks near the inflection point when separated from the heating roller, making it easier to adhere to the separating claw. This is similar to, for example, when two plates pasted with adhesive are peeled off, the warmed side is more likely to peel off, and if both sides are heated, it is uncertain which side will peel off.

From the above, in order to prevent toner from adhering to the separating claw, it is possible to increase the temperature of the heating roller using the characteristics shown in Figures 6 and 7, but if the temperature of the heating roller is When the temperature is constant and high, the curl of the paper becomes large, and paper jams are likely to occur when the paper is transported to the sorter or during the second copying.

The present invention is intended to solve the above problems, and its purpose is to improve the separation of paper after fixing even in double-sided copying and composite copying, to prevent toner from adhering to the separation claw, and to prevent toner from adhering to the separation claw. It is an object of the present invention to provide an image forming apparatus that is less likely to cause inconveniences such as paper jams due to curling.

[Means for Solving the Problems] The image forming apparatus of the present invention includes an image forming means for forming a latent image on an image bearing member, and a developing device for developing the latent image formed by the image forming means. a transfer device that transfers the image on the image carrier developed by the development device onto a sheet of paper; a fixing device that fixes the image on the paper transferred by the transfer device; and an image fixed by the fixing device. an image forming apparatus that selectively forms an image once or multiple times on one sheet of paper; a heating roller in contact with the surface to which the image is transferred; a pressure roller that rotates in circumferential contact with the heating roller and presses the paper; a heating means that heats the heating roller; and a control unit that sets the fixing temperature to be the same or higher than that when performing the first fixing during the first fixing, and sets the fixing temperature to a higher fixing temperature than the first fixing temperature during the second fixing. There is a patent that characterizes it.

[Function] In the image forming apparatus of the present invention, one
Single or multiple imaging is selectively performed. When image formation is performed only once, a latent image is first formed on an image carrier by an image forming means, and after being developed by a developing device, the latent image is transferred onto a supplied paper by a transfer means. . Then, the paper is sent to a fixing device, and the image on the paper is heated and pressed by a heating roller heated to a predetermined temperature by a heating means and a pressure roller, thereby being fixed on the paper. During this fixing, the heating means is controlled by the controller so that the heating roller is heated and maintained at a predetermined temperature within a region where toner does not adhere to the separating claw.

In addition, when image formation is performed multiple times on the same sheet of paper, the first
A second image formation is performed. During fixing at this time, the heating means is controlled by the control unit so that the heating roller is heated and maintained at the same or higher temperature than when performing the one-time fixing. After that, the paper is fed again to the feeding means. is again supplied to the transfer means. Then, the second latent image formed on the image carrier by the image forming means is developed by the developing device, transferred onto the above-mentioned re-supplied paper by the transfer means, and then sent to the fixing device where it is fixed. . At this time, the heating means is controlled so that the heating roller is heated and maintained at a predetermined temperature higher than that during the first fixing in an area where toner does not adhere to the separating claw. There is.

[Embodiments] Specific embodiments of the image forming apparatus of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 schematically shows a copying machine main body 1 equipped with an image forming apparatus according to Embodiment 1. This image forming apparatus includes an image forming means 10, a developing bag W120, a transfer device [30, and a developing bag W120.
It consists of a device 40 and a supply means 50 again.

The image forming means 10 forms a latent image on the outer peripheral surface of the photoreceptor 2, and performs exposure scanning on a document set on a glass document table 3 fixed to the top surface of the copying machine main body 1. It consists of an optical system consisting of a lamp 11, mirrors 12, 13, 14, 15, and a copying lens 16. The optical system moves back and forth along the lower surface of the original m mounting table 3, and performs exposure scanning during forward movement (movement in the direction of arrow a).In this case, the mirrors 13 and 14 are designed to keep the optical path length constant. The mirror 12 moves at 1/2 the speed of the mirror 12. In this optical system, during exposure scanning, the irradiation light from the exposure lamp 11 hits the original, mirrors 12, 13, and 14 in that order and is reflected, and after passing through the copying lens 16, it is further reflected by the mirror 15 and is used as a photosensitive image carrier. The image of the document is guided to the photoreceptor 1
It is arranged so that an image is formed on the outer peripheral surface of 1. The photoreceptor 2 is configured to rotate in the direction indicated by the arrow. First, the main charger 4 charges the surface of the photoreceptor 2, and the image of the document is exposed to slit light to form an electrostatic latent image.

The developing bag M 20 is attached to the photoreceptor 2 by the image forming means 1o.
The m-image formed on the surface of the image is developed with toner. This developing device 20 includes a magnet roller 21,
It is composed of a bucket section 22. The magnet roller 21 is arranged so that its outer circumferential surface faces the outer circumferential surface of the photoreceptor 2 and is close to it. The bucket portion 22 stores toner mixed with a carrier, and this toner is attracted to the outer circumferential surface of the magnet [1-ra 21 by magnetic force, and is attached to the outer circumferential surface of the opposing photoreceptor 2 due to the potential difference. The latent image is then developed.

The transfer means 3o is for transferring the latent image on the photoreceptor 2 developed by the developing device 2o onto the supplied paper, and in this embodiment, this is performed by a transfer charger 31. This transfer charger 31 is placed near the photoreceptor 2, and the paper fed between the transfer charger 31 and the rotating photoreceptor 2 is brought into close contact with the surface of the photoreceptor 2 by electrostatic adsorption. A predetermined voltage is applied when the device is being transported in a state where the Note that the paper P is in the paper feed cassette 32.
After being sent out one by one by a paper feed roller 33, the paper is guided through a paper guide path 34 to a registration roller 35, aligned by the registration roller 35, and sent to the transfer means 30. In this way, the transfer means 3
0, the toner image is transferred from the photoreceptor 2 by the transfer charger 31, and immediately after that, the paper is transferred to the peeling charger 3.
6, it is peeled off from the surface of the photoreceptor 2 and transferred to the conveyor belt 3.
7 to the fixing device 40.

The fixing device 40 fixes the image on the paper transferred by the transfer means 30. In this embodiment, the fixing device 40 includes, as shown in FIG. 2, a heating roller 41 that contacts the surface of the paper P on which the toner image has been transferred, and a pressure roller that rotates in circumferential contact with the heating roller 41 and presses the paper. 42, a heater 43 that heats the heating roller 41, and a heater 43.
and a control section 44 that controls the. The heating roller 41 has a cylindrical shape with a diameter of 60 nm and a thickness of 5 mm, the surface of which is coated with Teflon, and a heater 43 is disposed inside the roller. Also, the heating roller 41
A separating claw 45 whose tip end is biased is provided on the outer peripheral surface of the heating roller 41 on the paper P feeding side. Further, a thermistor Th1 as a temperature adjustment element is provided on the surface of the heating roller 41. On the other hand, the pressure roller 42 is
Silicone rubber with a thickness of 6 mm is provided on the surface of a roll-shaped aluminum core metal.

The paper P carrying the toner image sent to the fixing device 40 is moved from its leading edge to a heating roller 41 and a pressure roller 42.
After the toner image is fixed on the paper by being heated and pressurized, it is separated from the heating roller 41 by a separation claw 45 and sent out. At this time, the heating setting temperature of the heater 43 is switched by the control unit 44, and the temperature of the heating roller 41 is set to 1.
Approximately 18 mm at the time of first fixing of double copying and multiple copying
The temperature is set at 5°C, and at the second fixing of multiple copies, the temperature is set at approximately 200°C. In this embodiment, the control section 44 is constituted by a temperature control circuit shown in FIG. This temperature control circuit is connected to the comparator A when a signal is output from the ICI's ■0 output port.
The voltage divided by the combined resistance of RI and R2 and Th1 is input to the e input terminal of , and the switching transistor B is controlled by the output signal of the comparator A, and as a result, the temperature of the heater 43 is approximately 185°C. controlled.

On the other hand, when a signal is output from the 1+ output port of ICI, the e input terminal of comparator A has R2 and T
A voltage resistance-divided by h1 is input, and the switching transistor B is controlled by the output signal of the comparator A, and as a result, the temperature of the heater 43 is controlled to approximately 200°C.

Note that the signal from the 11 output ports of IC1 is set so that it is output at the first copy end signal when multiple copies are made, and is switched to the output signal from the IO output boat at the second copy end signal. There is.

Again, the supply means 50 is connected to the fixing device @40 as shown in FIG.
The paper set by the guide selector 51, 57 and the paper guide path 5
2 and an intermediate stacker 53. One of the guide selectors 51 is swingably provided, and is at the position shown by the solid line in FIG.
is guided to a paper guide path 52 and an intermediate stacker 53. Further, during the second fixing and the fixing for normal one-time copying, the paper P sent out from both rollers 41 and 42 is located at the position shown by the broken line in FIG.
55 and then to a paper discharge tray 56-hi.

The other guide selector 57 is also swingably provided, and in the case of double-sided copying, it is in the position shown by the solid line in FIG. Paper P conveyed by
When the trailing edge passes the guide selector 57, the guide roller 58 rotates in the opposite direction and guides the paper P to the intermediate stacker 53.In addition, in the case of composite copying, the guide roller 58 is located at the position shown by the broken line in FIG. , the paper P is guided directly from the paper guide path 52 to the intermediate stacker 53.

The image forming apparatus of this embodiment configured as described above operates as follows. First, when the copying machine main body 1 is powered on, the heater 43 is turned on to maintain the surface temperature of the heating roller 41 at approximately 185° C. in preparation for copying operation. Next, a selection key (not shown) on the operation panel provided on the copying machine body 1
When, for example, the composite copy mode is specified, the guide selector 51 of the supply means 50 is set again to the position shown by the solid line in FIG. 1, and the guide selector 57 is set to the position shown by the broken line in FIG. Then, the copying operation is started by pressing the print key on the operation panel, and the image of the first original placed on the original placing table 3 is slit-exposed by the image forming means 10 and is projected onto the surface of the rotating photoreceptor 2. A latent image is formed. After that, the developing device 20 is activated, and the rotating photoreceptor 2
Toner is attached to the latent image and the latent image is developed as a toner image. At this time, paper P is sent out from the paper feed cassette 32, and 1
It is guided and aligned by a pair of registration rollers 35 and is on standby. After the development is completed, the photoreceptor 2 continues to rotate, and the paper P is supplied between the photoreceptor 2 and the transfer charger 31. At this time, the paper P is brought into close contact with the surface of the photoreceptor 2 by electrostatic adsorption, and in this state, the transfer charger 31 is operated to transfer the toner image from the surface of the photoreceptor 2 to the paper P. Immediately thereafter, the paper P is peeled off from the surface of the photoreceptor 2 by the peeling charger 36 and sent to the fixing device 40. Fixing device 40
Then, the toner image on the paper P is heated and pressed by the heating roller 41 and the pressure roller 42 and fixed on the paper P.
is separated from the heating roller 41 by a separating claw. During this first fixing, the heating roller 541 is maintained at a temperature of approximately 185° C., so that even if the ID of the toner image shows a value of 1°4 as shown in FIG. adhesion is unlikely to occur. Then, at the same time as the first fixing is completed, the heater 43 that heats the heating roller 41 is switched from low temperature adjustment to high m adjustment, so that the temperature of the heating roller 41 will be approximately 200° C. during the second fixing. . The paper P separated from the heating roller 41 after the first fixing is guided by the guide selector 51 from the paper guide path 52 via the intermediate stacker 53 to the registration rollers 35, aligned, and then transferred for the second time. Prepare for settlement to take place. Then, a second original is set on the original placing table 3, and by pressing the print key, a WI image is formed on the surface of the photoreceptor 2 in the same manner as in the case of the first original, and is developed with toner. Note that when the print key is pressed, the guide selector 51 is switched to a position not shown by the broken line in FIG. Then, as the photoconductor 2 rotates, the paper P that was waiting on the registration rollers 35 is sent out, and the toner image on the surface of the photoconductor 2 is transferred to the paper P in the same manner as the first time, and then peeled off. The image is sent to the fixing device 40 and fixed. At this time, the heating roller 41 of the fixing device 40 is heated and maintained at a temperature of approximately 200'C.
As shown in FIG. 7, even when the ID of the toner image shows a value of 1.4, toner is unlikely to adhere to the separating claw. Second
The paper P that has been fixed for the first time is guided from the roller 54 to the paper discharge roller 55 and is discharged to the tray 56-L to complete the composite copying. On the other hand, when the second fixing is completed, the heater 43 that heats the heating row 541 is switched from high temperature T14 to low temperature adjustment in preparation for the next copying operation. Incidentally, the setting temperature change of the heater 43 and the temperature characteristics of the heating roller 41 in the first embodiment are as shown in FIG. Further, after the toner image is transferred to the paper P, the photoreceptor 2 rotates one more time, and after the latent image is erased by an eraser lamp, it is cleaned by a cleaner device in preparation for the next image formation.

As described above, in the image forming apparatus of the first embodiment, the heating roller 541 is adjusted such that the temperature of the heating roller 41 becomes approximately 185° C. during the first fixing and approximately 200° C. during the second fixing. A heater 43 for heating is controlled by a control section 44. Therefore, the separation of the paper P from the heating roller 41 after fixing was good, and it was possible to prevent toner from adhering to the separation claw 45. Therefore, inconveniences such as image defects and paper jams due to toner adhesion to the separating claws 45 can be prevented.

In addition, compared to the case where the heating roller 41 is constantly maintained at a constant high temperature, there is less heat curling of the paper, which eliminates inconveniences such as paper jams during the second copy or paper jams in the sorter. I was able to do that.

Furthermore, it was possible to eliminate the occurrence of wrinkles during double-sided copying and composite copying.

(Example 2) The image forming apparatus of Example 2 is installed in a copying machine in the same manner as in Example 1, and differs from Example 1 in that the image forming apparatus is equipped with 1IlII [1 part The switching timing is different. That is, the control section turns on the heater to adjust the low temperature when the copying machine is powered on, switches from low temperature adjustment to high m adjustment when double-sided copying or composite copying mode is specified by pressing the selection key, and roughly adjusts the low temperature. The setting is such that the high temperature adjustment is switched to the low temperature adjustment when the second fixing is completed. In this case, the surface temperature of the heating roller is
As in Example 1, the temperature is maintained at approximately 185° C. during low temperature adjustment and approximately 200° C. during high temperature adjustment. The switching of the set temperature of the heater and the temperature characteristics of the heating roller in Example 2 are as shown in FIG. Note that the other configurations and the like are the same as in the first embodiment, so explanations will be omitted.

The image forming apparatus of this embodiment 2 may terminate the first fixing when the outer diameter of the heating roller is large as in a high-speed copying machine, when the core metal is thick, or when there is not enough power for the heater. Suitable when switching the heater to high temperature control sometimes lacks quick response.

The point is to set the surface temperature of the heating roller to appropriate conditions during fixing, for example approximately 185°C during the first fixing and approximately 200°C during the second fixing, as shown in Figures 6 and 7. The separation claw may be set within an effective area where toner does not adhere to the separation claw.

[Effects of the Invention] As explained above, in the image forming apparatus of the present invention, the fixing device includes a heating roller that contacts the surface of the paper onto which the image is transferred, and a heating roller that rotates in circumferential contact with the heating roller and presses the paper. A pressure roller that heats the heating roller, a heating means that heats the heating roller, and a heating means that is set to the same or higher fixing humidity as when fixing is performed only once at tJ41st fixing, and and a control section that sets the fixing humidity higher than the first constant II temperature.

For this reason, even in the case of double-sided copying and composite copying, the separation of the paper from the heating roller after constant S is improved, and it is possible to prevent toner from adhering to the minute-1 nail.

Therefore, it is possible to eliminate problems such as image defects and paper jams caused by toner adhering to the separating claw.

Also, compared to the case where the heating roller is always set at a high temperature during fusing, there is less heat curling of the paper.
It is possible to eliminate problems such as paper jams during double-sided copying or composite copying or paper jams in the sorter. Furthermore, it is possible to reduce the occurrence of paper wrinkles during double copying and composite copying.

[Brief explanation of the drawing]

1 to 4 relate to Embodiment 1 of the image forming apparatus of the present invention, in which FIG. 1 is a schematic diagram of the copying machine main body, FIG. 2 is a schematic diagram of the fixing device, and FIG. is a temperature control circuit diagram of the control unit, Figure m4 is a diagram showing switching of heating means and temperature characteristics of the heating roller, Figure 5 is a diagram showing switching of heating means and temperature characteristics of the heating roller according to Example 2, Figures 6 and 7 show the occurrence of toner adhesion to the back of the separating claw due to the relationship between the heating roller and the image fa density. Figure 6 is a diagram during the first fixing, and Figure 7 is a diagram at the second fixing time. 1... Copying machine main body 2... Photoreceptor (image carrier)
10... Image forming means 20... Developing device 30...
・Transfer means 40... Fixing device 41... Heat roller 42... Pressure roller 43... Heater
44...Control unit 50...Re-supplying means Figure 1 Figure 3 Figure 6 Figure 7 Katana Ro-cho Korala Star Degree

Claims (1)

[Claims] (1) An image forming means for forming a latent image on an image carrier, a developing device for developing the latent image formed by the image forming means, and an image on the image carrier developed by the developing device. The image forming apparatus includes a transfer means for transferring the image onto the paper, a fixing device for fixing the image on the paper transferred by the transfer means, and a re-feeding means for again supplying the paper fixed by the fixing device to the transfer means. In an image forming apparatus that selectively forms an image once or multiple times on a sheet of paper, the fixing device includes a heating roller that contacts the surface of the sheet on which the image is transferred, and a heating roller that contacts the surface of the sheet on which the image is transferred. A pressure roller that rotates in circumferential contact with the roller and presses the paper, a heating means that heats the heating roller, and a fixing temperature that is the same or higher than when fixing is performed only once during the first fixing. An image forming apparatus comprising: a control section that sets a fixing temperature higher than a first fixing temperature during a second fixing.