JP2009003019A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of preventing transfer failure by suppressing the undesired charging of a transfer material caused by the charging of resist rollers. <P>SOLUTION: The image forming apparatus includes: a transfer roller 102 rotating in contact with an image carrier 100 of a belt form; and the pair of resist rollers 22 and 23 for conveying a transfer material 104 to the area where the transfer roller 102 and the image carrier 100 of the belt form are in contact with each other. The image forming apparatus transfers a toner image, formed on the image carrier 100, to the transfer material 104 by the application of current or voltage to the transfer roller 102. Each of the resist rollers 22 and 23 is formed of an insulator, and a charge removal member 24 is disposed so as to be brought into contact with the resist rollers 22 and 23 or separated therefrom. When the transfer material 104 is in contact with the resist rollers 22 and 23, the charge removal member is separated from the rollers 22 and 23. When the transfer material 104 is not in contact with the resist rollers 22 and 23, the charge removal member 24 is brought into contact with them. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, or a printer, and more particularly to an image forming apparatus that transfers a toner image carried on an endless belt-like image carrier onto a transfer material using a transfer belt. Is.

  In the transfer-type image forming apparatus, in order to perform appropriate transfer, it is necessary to apply an appropriate transfer current to the toner. If the transfer current is insufficient, the toner cannot be transferred to the transfer material, causing a transfer failure. Conversely, if the transfer current is excessive, the toner is charged to a polarity opposite to the original charge polarity, For this reason, the toner cannot be transferred to the transfer material, resulting in transfer failure.

  Therefore, an appropriate transfer current is applied to the toner, but the resistance value of the transfer material varies greatly due to changes in the environment and the like. In particular, the resistance value of the transfer material decreases under high humidity. For this reason, there is a problem in that a transfer current flows toward the registration roller that conveys the transfer material via the transfer material, and an appropriate transfer current cannot be applied to the toner, resulting in a transfer failure.

  In order to solve this problem, a means for detecting an applied current with respect to an applied voltage at the time of transfer is provided, and when the value of applied voltage / applied current is a certain value or less, an appropriate transfer current is applied to the toner. A method for adjusting the applied voltage has been proposed (for example, Patent Document 1).

  In addition, a method has been proposed in which a current leaking through a transfer material is suppressed by grounding a portion that seems to leak through a resistance of 200 MΩ or more to prevent a transfer failure due to the leak (for example, Patent Document 2). Further, there is a configuration in which a charge is removed by contacting both the back surface of the sheet and the lower registration roller with a neutralizing brush provided on the downstream side of the registration roller pair with respect to the sheet conveyance direction (for example, Patent Document 3). .

  However, the following problems can be considered in the conventional technology. That is, the method of controlling the transfer voltage after detecting the transfer voltage and the transfer current before performing the transfer as in Patent Document 1 does not provide time for performing the control in high-speed printing. Since the detection apparatus and the control are performed, the configuration is complicated and the cost is increased.

  Further, in the system in which the registration roller is not grounded directly via a resistor as in Patent Document 2, when the transfer material passes, frictional charging occurs every time the transfer material and the registration roller come into contact with each other. The charge is accumulated in the. As a result, the next transfer material is charged, causing transfer failure.

Furthermore, if the static elimination brush is always in contact with the registration roller as in Patent Document 3, the transfer current may leak to the registration roller through the transfer material.
JP-A-5-40418 JP 7-129000 A JP 2002-372874 A

  In view of this, the present invention solves the above-described conventional problems, suppresses transfer current flowing into the registration roller, and prevents transfer defects by suppressing unnecessary charging to the transfer material caused by charging of the registration roller. An object of the present invention is to provide an image forming apparatus capable of performing the above.

  In order to solve the above-mentioned problem, the invention described in claim 1 is an endless belt-shaped image carrier, a counter roller that is wound around the endless belt-shaped image carrier, and is wound around the counter roller. A transfer roller that contacts the belt-shaped image carrier and rotates in the same direction as the opposing roller, and transports the transfer material to transport the transfer material to a region where the transfer roller and the belt-shaped image carrier contact. A pair of registration rollers arranged upstream in the direction, and applying a current or voltage from the transfer roller to the opposing roller, the toner image formed on the belt-shaped image carrier is used as a transfer material. In the image forming apparatus that performs the transfer, the registration roller is formed of an insulator, and includes a charge removal member that can contact and separate from the registration roller, and when the transfer material is in contact with the registration roller, Conductive member away from the registration roller, the transfer material when not in contact with the registration roller is characterized by that the discharging member into contact with the registration roller.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the neutralizing member is a neutralizing brush or a neutralizing roller.

  The present invention is as described above, wherein the registration roller is formed of an insulator, and includes a static elimination member that can contact and separate from the registration roller. When the transfer material is in contact with the registration roller, the static elimination member is used as the registration roller. When the transfer material is not in contact with the registration roller, the charge removing member is in contact with the registration roller, so that the transfer current does not flow into the registration roller and the transfer failure caused by the charging of the registration roller is suppressed. be able to. In other words, the transfer voltage and transfer current are detected before transfer as in the prior art, and the current flowing into the registration roller via the transfer material under high humidity can be suppressed without performing the process of controlling the transfer voltage. Appropriate transfer current can be applied to the toner, and by passing the transfer material, the charging of the registration roller due to frictional charging and the unnecessary charge to the transfer material caused by it can be suppressed, and the transfer material is unnecessary. There is an effect that it is possible to prevent a transfer failure caused by a simple charge.

  Hereinafter, an embodiment in which the present invention is applied to a color copier as an image forming apparatus will be described with reference to the drawings.

  FIG. 2 is a schematic configuration diagram of the entire color copying machine. First, the configuration and operation of an image forming unit and a transfer unit, which are main parts of a color copying machine, will be described with reference to FIG.

  The image forming unit and the primary transfer unit include chargers 10a to 10d, exposure units 11a to 11d, developing units 12a to 12d, static eliminators 13a to 13d, cleaners 14a to 14d, photosensitive drums 15a to 15d, and primary transfer rollers. The intermediate transfer belt 100 is an endless belt-shaped image carrier 16a to 16d.

  The photosensitive drums 15a to 15d rotate in the direction of the arrow. Further, the intermediate transfer belt 100 is stretched by rollers 30, 31 and the like, and is in contact with the photosensitive drums 15a to 15d. The members constituting the image forming unit are arranged around the photosensitive drums 15a to 15d and the neutralizers 13a to 13d and the cleaners 14a to 14d with respect to the rotation direction of the photosensitive drum 15 from the point of contact with the intermediate transfer belt 100. The chargers 10a to 10d, the exposure devices 11a to 11d, and the developing devices 12a to 12d are arranged in this order. The primary transfer rollers 16a to 16d constituting the primary transfer portion are arranged so as to be pressed from the back side of the region where the photosensitive drums 15a to 15d and the intermediate transfer belt 100 are in contact with each other. In the present embodiment, the roller for driving the belt is the roller 30, and the intermediate transfer belt 100 is rotated in the direction of the arrow by the roller 30.

  Next, an image forming method and a primary transfer method will be described. The photosensitive drum 15 is charged by the charger 10. Thereafter, an electrostatic latent image is generated on the charged photosensitive drum 15 by irradiating a laser beam from the exposure device 11 based on image data from the scanner and the PC. Thereafter, the toner charged by the developing device 12 is developed on the photosensitive drum 15. The toner image formed on the photosensitive drum 15 is transferred onto the intermediate transfer belt 100 by applying a transfer electric field with a current or voltage controlled by a constant current or a constant voltage to the primary transfer roller 16.

  After the toner image is transferred onto the intermediate transfer belt 100, the photosensitive drum 15 removes the remaining charge remaining on the photosensitive drum 15 by the static eliminator 13, and removes the toner remaining on the photosensitive drum 15 by the cleaner 14. The process of removing and returning to the charger 10 is repeated.

  In the present embodiment, an image forming unit is arranged for each of the four colors of cyan, magenta, yellow, and black, and the toner image formed on the photosensitive drum 15a is primarily transferred onto the intermediate transfer belt 100. Thereafter, the intermediate transfer belt 100 moves to the photosensitive drum 15b, and transfers the toner image formed on the photosensitive drum 15b onto the toner image transferred on the photosensitive drum 15a. Thereafter, the photosensitive drums 15c and 15d and the toner image are sequentially superimposed and transferred.

  The toner image transferred onto the intermediate transfer belt 100 is transferred by the registration rollers 22 and 23 at the secondary transfer portion formed by the secondary opposing roller 103 and the secondary transfer roller 102 that hold the intermediate transfer belt 100. Transferred to the material 104. The registration rollers 22 and 23 temporarily stop the transfer material 104 conveyed from a paper supply unit (not shown) and are driven to rotate at the timing when the toner image on the intermediate transfer belt 100 reaches the transfer position of the transfer material 104. Further, a transfer material detection sensor (not shown) is provided downstream of the registration rollers 22 and 23 in the transport direction of the transfer material 104 to detect the passage of the front and rear ends of the transfer material 104.

  In the secondary transfer unit, current is applied to the secondary transfer roller 102, and the transfer current flows into the secondary opposing roller 103, whereby the toner on the intermediate transfer belt 100 is transferred to the transfer material 104. The secondary transfer material 104 is then fixed by the fixing rollers 20 and 21.

  However, since the resistance value of the transfer material 104 decreases in a high humidity environment, the transfer current does not flow into the opposing roller 103 as shown in FIG. 3, and the registration roller 22 passes through the transfer material 104 as indicated by a broken line. , 23 may occur. In this case, a transfer current is not applied to the toner on the intermediate transfer belt 100, and a transfer failure occurs in which the toner is not transferred to the transfer material 104.

  Therefore, in this embodiment, as shown in FIG. 1, the registration rollers 22 and 23 are made of an insulator so that the transfer current does not flow into the registration rollers 22 and 23. However, since the registration rollers 22 and 23 are made of an insulator, every time the transfer material 104 passes through the registration rollers 22 and 23, the charge is charged to the registration rollers 22 and 23 due to frictional charging, and the next transfer material 104 is transferred. Then, the charge accumulated on the previous registration roller moves to the transfer material 104, and the charged transfer material 104 is conveyed to the secondary transfer portion. Therefore, the transfer material 104 in a charged state causes transfer defects such as being attracted to the intermediate transfer belt 100 or attracting toner on the intermediate transfer belt 100 to the transfer point.

  For this reason, a static elimination brush 24, which is a static elimination member, is attached to the resist roller 23, which is an insulator, so as to be able to come in contact with and separate from it. The charge is removed to suppress transfer defects. In the present embodiment, the neutralizing brush 24 is employed as the neutralizing member, but the neutralizing member is not limited to a brush shape, and may be a roller shape such as a neutralizing roller. Further, in order to prevent the transfer current from flowing into the registration rollers 22 and 23 via the transfer material 104, when the transfer material 104 is in contact with the secondary transfer point and the registration rollers 22 and 23 at the same time, the static elimination brush 24. Is removed from the registration roller 23, and when it is not in contact with the registration roller 23, the neutralization brush 24 is brought into contact with the registration roller 23 to neutralize the registration rollers 22 and 23.

  As the contact / separation mechanism of the static elimination brush 24, for example, a mechanism that connects a movable part of a solenoid (not shown) to both ends of the static elimination brush 24, and the movable part of the solenoid moves so It is done. Furthermore, cam receiving portions that receive an eccentric cam (not shown) are provided at both ends of the static elimination brush 24, and when the eccentric cam is rotated by a driving means such as a stepping motor, the cam receiving portion comes into contact with the large diameter portion of the eccentric cam. When the neutralizing brush 24 is in contact with the registration roller 23 and the cam receiving portion is in contact with the small diameter portion of the eccentric cam, the neutralizing brush 24 may be separated from the registration roller 23.

  That is, the static eliminating brush 24 is separated from the registration roller 23 before the transfer material 104 enters the secondary transfer portion, and the static elimination brush 24 is in contact with the registration roller 23 after the transfer material 104 passes through the registration roller pairs 22 and 23. You can do it. Specifically, it is conceivable that the separation operation of the static elimination brush 24 is performed in synchronization with the drive timing of the registration rollers 22 and 23 and the application timing of the secondary transfer bias. Further, it is conceivable that the contact operation of the charge eliminating brush 24 is performed after elapse of a predetermined time from the timing when the passage of the rear end of the transfer material 104 is detected by the transfer material detection sensor.

  As described above, the registration rollers 22 and 23 are made of an insulator, and the static elimination brush 24 is attached to the registration roller 23 so as to be able to contact and separate, thereby detecting the transfer voltage and the transfer current before transfer and controlling the transfer voltage. Therefore, the current flowing into the registration rollers 22 and 23 via the transfer material 104 under high humidity can be suppressed without performing the process, and it is possible to apply an appropriate transfer current to the toner. By passing, it is possible to suppress charging of the registration rollers 22 and 23 due to frictional charging and unnecessary charging to the transfer material 104 caused by the charging.

  The configuration of the image forming unit described in the above embodiment is merely a preferred example, and other configurations are not excluded. Within the scope of the invention specific matter described in claim 1 of the claims, a slight change in configuration is allowed. The intermediate transfer belt 100 is only an example of an endless belt, and other belts may be used. Furthermore, it goes without saying that the arrangement of the registration roller pair with respect to the secondary transfer portion, the arrangement of the neutralizing brush with respect to the registration roller pair, and the like can be appropriately changed and corrected for the implementation.

FIG. 3 is an enlarged view showing a secondary transfer portion and a registration roller pair of a color copying machine according to an embodiment of the present invention. It is a schematic block diagram of the whole color copying machine same as the above. It is an enlarged view for explaining the operation of the secondary transfer portion in a high humidity environment.

Explanation of symbols

10a to 10d Charger 11a to 11d Exposure unit 12a to 12d Developer 13a to 13d Static eliminator 14a to 14d Cleaner 15a to 15d Photosensitive drum 16a to 16d Primary transfer roller 20, 21 Fixing roller 22, 23 Registration roller 24 Static elimination brush (Charging member)
30, 31 Tension roller 100 Intermediate transfer belt 102 Secondary transfer roller 103 Secondary counter roller 104 Transfer material

Claims (2)

  An endless belt-shaped image carrier, a counter roller that rotates around the endless belt-shaped image carrier, and contacts the belt-shaped image carrier wound around the counter roller in the same direction as the counter roller A transfer roller that rotates, and a pair of registration rollers disposed upstream of the transfer material in order to convey the transfer material to a region where the transfer roller and the belt-shaped image carrier contact each other, In an image forming apparatus that transfers a toner image formed on the belt-shaped image carrier onto a transfer material by applying a current or voltage from a transfer roller to a counter roller, the registration roller is formed of an insulator. A static elimination member that can contact and separate from the registration roller, and when the transfer material is in contact with the registration roller, the static elimination member is separated from the registration roller, and the transfer material is registered. When not in contact with the controller, the image forming apparatus characterized by that the discharging member into contact with the registration roller.   2. The image forming apparatus according to claim 1, wherein the charge eliminating member is a charge eliminating brush or a charge eliminating roller.

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