JPH0493970A - Image forming device - Google Patents

Abstract

PURPOSE:To remove the curl of a transfer paper by inverting the transfer paper where an image is transferred and fixed and making the transfer paper pass a fixing device again without performing transfer. CONSTITUTION:An original placed on a contact glass 1 with its image surface downward is exposed and scanned by an optical unit 2 and a light image is projected to a photosensitive body 3. By projecting the light image, an electrostatic latent image is formed on the photosensitive body 3. After the electrostatic latent image is developed to be a toner image by a developing device 4, it is carried to a transfer charger 5a. The transfer papers P1 and P2 are housed in a paper feeding cassette and any paper is selected as necessary and fed toward the photosensitive body 3 by a paper feeding device 6a or 6b. The fed transfer paper is fed after adjusting timing so that it may be superposed on the toner image on the photosensitive body 3 by a resist roller 8, and superposed on the toner image at a position corresponding to the charger 5a. By the discharge of the charger 5a, the toner image is transferred to the transfer paper and then the transfer paper is separated from the photosensitive body 3 by the discharge of the separation charger 5b.

Description

[Detailed description of the invention] [i Retired Emperor Tomoru! The present invention includes a transfer device that transfers a toner image formed on an image carrier onto a transfer paper during operation, a pressure roller that contacts a fixing roller equipped with a heat source, and a transfer paper that passes through the contact portion. The present invention relates to an image forming apparatus such as a copying machine, which has a fixing device that applies heat to the fixing device, and a reversing unit that reverses the transfer paper that has passed through the fixing device. Conventional technology In image forming devices such as copying machines, when the machine is started or when the inside of the machine is low temperature, the difference in temperature between the fixing roller and the pressure roller causes the front side and back side of the transfer paper to Since the amount of heat received is different, the transfer paper tends to curl. Furthermore, even if the transfer paper absorbs moisture due to high humidity in the environment, the transfer paper is likely to curl because it is heated and dehumidified on the fixing roller side of the fixing device. Conventional decurling devices for correcting curls of transfer paper curled due to such causes include methods for removing curls using a decurling roller, guide plate, etc. (see Japanese Patent Laid-Open No. 6160554), A method of removing curl using a curved portion protruding in the opposite direction (see Japanese Patent Application Laid-Open No. 6050547), a method of reducing curl by applying water vapor to the transfer paper discharged from a heat fixing device (especially (Refer to Kaisho 60-182459)
, a method of reducing curl by installing a heating mechanism that heats the opposite surface to the heated surface (see Japanese Patent Application Laid-Open No. 51-47737), and other devices have been disclosed. Problems to be Solved by the Invention The conventional decurling methods described above all require additional equipment and have the problem of increasing the size of the apparatus. When a decurling roller, a guide plate, or the like is used to straighten the transfer paper after transfer, a problem arises in that if a non-curled transfer paper is passed through, the decurling device will curl the paper. In order to solve this problem, a method of detecting the amount of curl and changing the conditions of the decurling device has been considered, but this would further complicate the device. Furthermore, the method of spraying water vapor requires replenishment of water, and there is a problem in that the transferred transfer paper absorbs moisture, making it impossible to obtain good copies. Furthermore, if a heating device is provided, there will be a problem in that a large amount of extra power will be consumed and the temperature inside the device will rise. Therefore, the present invention solves the above problems in the prior art, and
To provide an image forming device that can remove curls from transfer paper with a simple configuration without increasing the size of the device or consuming excessive power, and without causing the transfer paper to absorb moisture or cause unnecessary curls. The challenge is to provide. In order to solve the above problems, the present invention includes a transfer device that transfers a toner image formed on an image carrier onto a transfer paper during operation, a fixing roller equipped with a heat source, and a pressure roller. In the image forming apparatus, the image forming apparatus includes a fixing device that applies heat to the transfer paper by bringing the transfer paper into contact with the contact portion and passing the transfer paper through the contact portion, and a reversing unit that flips the transfer paper that has passed through the fixing device from front to back. an operation in which the transfer paper is passed through the transfer device and the fixing device in a state in which the toner is fixed, the transfer paper is reversed by the reversing means, and the transfer paper is passed through the fixing device again in a state in which the transfer device is not operating; It is characterized by having a mode. Function According to the present invention, the transfer paper after transfer and fixing is reversed,
An operation mode is provided in which the transfer paper passes through the fixing device again without performing any transfer, so if the transfer paper is operated in a state where it is likely to curl, the curl of the transfer paper can be removed by executing this operation mode. I can do it. In other words, the transfer paper passes through the fixing device twice, once when the toner is fixed and when the toner is reversed, and both sides of the paper are heated equally by the fixing roller and the pressure roller. It is decaled as it passes through the device. According to this method, since the existing fixing device is used, the image forming apparatus does not need to be enlarged.
In addition, since heat is applied evenly to both sides of the transfer paper, uncurled transfer paper will not be curled, and the transfer paper is further dehumidified by heating, making it possible to create high-quality images. Support Ship-j FIG. 1 shows a schematic structure of a double-sided copying machine as an example of an image forming apparatus according to an embodiment of the present invention. First, a normal one-sided copying process will be explained. A document placed on contact glass 1 with the image surface facing downward is exposed and scanned by optical system unit 2, and a light image of the image is irradiated onto drum-shaped photoreceptor 3, which is an example of an image carrier. By this light image irradiation, an electrostatic latent image is formed on the photoreceptor 3. After this electrostatic latent image is developed into a toner image by the developing device W4, the electrostatic latent image is transferred to a toner image during transfer charging, which is an example of a transfer device.
It is carried to a. A paper feed cassette 6.7 is provided at the lower right portion of the double-sided copying machine. These paper feed cassettes contain transfer paper P,,P
, are stored therein, and one of them is selected as required and fed toward the photoreceptor 3 by the paper feeding device W6a or 6b. The fed transfer paper is sent out with timing adjusted by the registration roller 8 so that it overlaps with the toner image on the photoreceptor 3, and is overlapped with the toner image at a position corresponding to the transfer charger 5''a.Transfer charger The toner image is transferred onto the transfer paper by the discharge of the separation charger 5a, and then the transfer paper is separated from the photoreceptor 3 by the discharge of the separation charger 5b.The separated transfer paper is conveyed to the fixing device 10 by the conveyance unit 9. Fixing roller 10a that has a heat source inside
When passing through the nip between the pressure roller 10b and the pressure roller 10b that are in pressure contact with this, heat is applied to fix the toner image thereon. The copy image is completed. Next, when double-sided copying is performed, the process is as follows. For copying onto the first side (front surface) of transfer paper, use the fixing bag W.
The same steps as the one-sided copying process described above are performed up to the fixing process using lO. In the double-sided copying process, the conveyance path of the transfer paper is then switched by the switching claw 12, and the transfer paper exiting the fixing device 10 is sent not to the ejection roller 11 but to the reversing guide 13, and then to the approaching/separating roller 14 and the reversing roller. The zero reversing guide 13, contact roller 14, reversing roller 15, etc., which are conveyed to the intermediate tray 16 via the rollers 15, are also used as reversing means of the present invention. Thereafter, the image is fed again to the image forming section composed of the registration roller 8, the photoreceptor 3, the fixing device 10, etc., and the image is copied onto the second side (back side), which is the opposite side of the first side, and finally A double-sided copy is completed. In such a copying machine as described above, when starting the machine or when the inside of the machine is low temperature, the amount of heat received on the front side and the back side of the transfer paper increases due to the temperature difference between the fixing roller 10a and the pressure roller 10b. Because the paper is different, the transfer paper tends to curl. Further, even when the environment is humid and the transfer paper absorbs moisture, curling is likely to occur because the fixing roller 10a side of the fixing device 10 is heated and dehumidified. For this reason, the copying machine of this embodiment is provided with a decurl mode which is an operation mode for removing such curls. Here, the decal mode means that after the above-mentioned one-sided copying process is completed and the transfer paper is discharged from the fixing device 1O, a reversing means consisting of a reversing guide 13, a contact/separation roller 14, a discharge port 15, etc., an intermediate tray 16, This is an operation mode in which the transfer paper is reversed from the front to the back and is introduced into the fixing device 10 again via the registration roller 8, transfer charger 5a, separation charger 5b, and conveyance unit 9, and the transfer charger 5a is Refers to the operating mode when not in operation. Note that since the copying machine of this embodiment is a double-sided copying machine, its double-sided conveyance system is used for the decal mode, but the transfer paper is introduced into the fixing device 10 without passing through the transfer charger 5a or the like. You can also do this. Such a decal mode may be implemented, for example, by providing an operation key at a suitable location on the operation display panel 100 of the copying machine shown in FIG. 2, so that the operator can execute the decal mode at his/her discretion. However, in this embodiment, the following method is used so that the operator can easily judge and operate. That is, as shown in FIG. 1, a temperature/humidity sensor 17, for example, for detecting internal temperature and humidity is provided inside the main body of the copying machine. If the transfer paper is likely to curl due to the detected temperature and humidity, a message to that effect is displayed on the language display section 101 of the display section of the operation display panel 100 shown in FIG. . With this display, if the operator wants to correct the curl on the transfer paper, he/she can press the enter key 1, for example.
After pressing 2, the user presses the copy start key 103, and if the transfer paper may curl, the user presses the copy start key 103 immediately. That is, in this case, the language display section 10
1 display and enter key] 02, copy start key 1
Pressing 03 configures the copy process to execute decal mode. Note that since there is no need to execute the decal mode during double-sided copying, no display to that effect is displayed on the language display section 101. FIG. 3 shows a flowchart for setting the process for executing the decal mode or the normal mode, which is a normal copy mode. Step 1) Determine whether the power of the copying machine is turned on or not. If it is turned on, it means that the copying machine is starting up and the transfer paper is likely to curl.
01 displays the message "Press the enter key 102 to perform decal processing" (step 3). This display prompts the operator to press the enter key 102 if he or she wishes to perform decal processing. is determined (step 4), and if the key is pressed, the decal mode is executed (step 5), and if the key is not pressed, the normal mode is executed (step 8).
. On the other hand, if the power is not on, it is necessary to determine whether the temperature/humidity sensor I7 has detected high humidity (Step 2). When high humidity is detected, the transfer paper is in a state where it is easy to curl, so the steps from Step 3 described above are performed. Run the flow. If the humidity is not high, it is necessary to further determine whether the temperature is low and the paper is being fed continuously (step 6.7). In such a case, perform the flow from step 3 onwards to prevent curling.
In other cases, the normal mode is executed (step 8). Effects As described above, according to the present invention, since the fixing device is used for curl removal, there is no need for a special decurling device, and it is possible to avoid increasing the size of the image forming apparatus. In addition, it does not add moisture to the transfer paper or consumes a large amount of extra power.
Able to form high quality images.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a double-sided copying machine according to an embodiment, FIG. 2 is a plan view of an operation display panel, and FIG. 3 is a flowchart. ...Photoconductor (image carrier) ...Transfer charging (transfer device) 0 ...Fixing device Oa ...Fixing roller Ob ...Pressure roller 13 ...Reversing Guide (reversing means) 14-0--Contact/separation roller (reversing means) 15--Reversing roller (reversing means) P,,P,...Transfer paper

Claims (1)

[Claims] (1) During operation, there is a transfer device that transfers the toner image formed on the image carrier onto transfer paper, and a pressure roller that contacts a fixing roller equipped with a heat source, passes the transfer paper through the contact portion, and transfers the toner image to the transfer paper. In an image forming apparatus that includes a fixing device that applies heat and a reversing unit that reverses the transfer paper that has passed through the fixing device, the transfer paper is transferred between the transfer device and the fixing device while the transfer device is in operation. An image forming apparatus characterized in that the image forming apparatus has an operation mode in which the transfer paper is reversed by the reversing means after passing the toner therethrough and the toner is fixed thereon, and the transfer paper is caused to pass through the fixing device again with the transfer device not operating.