JP2013195943A - Transfer device, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transfer device capable of conveying a toner image formed on a sheet to a subsequent process without causing disturbance on the toner image.SOLUTION: A transfer device includes: transfer exit guide means that has a guide surface formed of resin, and guides, when a sheet is conveyed and ejected from the transfer device to the outside, conveyance and ejection of the sheet by the guide surface contacting the surface of the sheet; sheet discharge means that discharges the sheet when the surface of the sheet comes in the proximity of the inside of the slit part provided to the guide surface; and guide surface discharge means for discharging the guide surface.

Description

  The present invention relates to a transfer device for transferring a toner image formed on an image carrier to a sheet, which is used in an image forming apparatus such as a copying machine, a printer, or a facsimile machine that forms an image in an electrophotographic process, and such a transfer. The present invention relates to an image forming apparatus having the apparatus.

  The transfer device is a device that electrostatically transfers the toner image formed on the image bearing member to the sheet surface, and the toner image transferred to the sheet surface by the transfer device is fixed to the sheet in a fixing process which is the next process. . FIG. 7 shows a configuration of a conventional transfer apparatus, and FIG. 8 shows a configuration in the vicinity of the transfer outlet guide member 8 as a model.

  The sheet on which the toner image formed on the surface of the photosensitive drum 1 serving as an image carrier is transferred is transferred from right to left in the figure by an endless belt 2 suspended between a driving roller 5 and a driven roller 4 that are both grounded. Be transported. The endless belt 2 is in contact with the photosensitive drum 1 from below. A bias roller 6 for applying a transfer bias necessary for transferring a toner image to a sheet conveyed by the endless belt 2 is in contact with the endless belt 2 from the inside on the downstream side in the sheet conveying direction with respect to the photosensitive drum 1. And connected to a high voltage power source 7.

  The transfer outlet guide plate 10 installed on the downstream side of the endless belt 2 in the sheet conveying direction is composed of a transfer outlet guide member 8 and a charge removal member 9. In this example, the guide surface 8a of the transfer outlet guide member 8 that is in contact with the sheet is made of an insulating resin such as polycarbonate resin or polyester resin. The neutralizing member 9 for neutralizing when the sheet surface comes close is positioned so that the tip is located at a depth of about 2 mm from the guide surface 8a inside the slit portion 8b provided on the guide surface 8a of the transfer outlet guide member 8. It is provided on the transfer outlet guide plate 10 and is grounded.

  The sheet is conveyed by the endless belt belt 2 to the transfer outlet guide plate 10 through the nip portion constituted by the photosensitive member (which is also an image carrier in this example) 1 and the endless belt 2. During this conveyance, the toner image carried on the photoreceptor 1 is transferred to the sheet. Thereafter, the sheet is conveyed to the fixing inlet guide plate 11 while being discharged by discharging the charge held when approaching the discharging member 9 to the discharging member 9, and then fixed as shown in FIG. It is conveyed to the device 20. The lower part of the transfer device is covered with a casing 3 as a cover, and is unitized.

  In this transfer device, the toner image formed on the image bearing member is electrostatically attracted and transferred to the sheet surface by applying a bias having a polarity opposite to that of the toner during development of the sheet. For this reason, when the transfer outlet guide member 8 is charged by friction between the guide surface 8a of the transfer outlet guide member 8 and the sheet, and then abnormal discharge occurs when the subsequent sheet passes, the sheet is electrostatically attracted to the sheet. In some cases, the toner that has been moved moves, causing image distortion.

  In particular, when using a sheet having a high electrical resistance and electrostatically adhering to the guide surface 8a of the transfer outlet guide member 8, or when using a sheet with low moisture content in a low temperature and low humidity environment such as winter In this case, the toner image is easily disturbed (hereinafter referred to as “transfer dust”). That is, under such conditions, the sticking of the sheet to the guide surface 8a is strengthened, and as shown in FIG. 8, the sheet P and the guide surface 8a are in close contact with each other and the contact area is increased. At this time, since the guide surface 8a is more easily charged, abnormal discharge is likely to occur when a subsequent sheet having unfixed toner adsorbed on the surface passes.

  Here, Patent Document 1 proposes a technique in which a mechanism for removing static electricity is provided in a conveyance path vicinity member that faces a sheet conveyance path in the vicinity of a transfer position. This mechanism has a configuration in which a resistor having a predetermined resistance value and a ground switch are grounded with a conductive material through a static elimination circuit in which the resistor is electrically connected in parallel. The earth switch is turned off to prevent the transfer bias from leaking when a transfer bias is applied to the sheet. Then, at an appropriate time other than the time when the transfer bias is applied, the ground switch is turned on for a predetermined time, and the static electricity accumulated in the member near the transport path is grounded to eliminate the static electricity. As described above, Patent Document 1 discloses that a transfer device can be provided that does not leak the transfer bias and can prevent image quality deterioration of the transferred image due to charging.

  When such a technique described in Patent Document 1 is applied to the transfer device having the structure shown in FIG. 8, the guide surface 8a is made of a high-resistance resin such as polycarbonate or polyester resin. Then, it is difficult to completely remove the charged charges on the guide surface 8a. Further, in the technique described in Patent Document 1, a member in the vicinity of the conveyance path cannot be neutralized when a transfer bias is applied, and a potential increase due to charging of the guide surface cannot be prevented when images are continuously transferred. There remains a risk of image quality degradation.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to perform a post-process in a state in which a toner image formed on a sheet is not disturbed even at the time of continuous image transfer. It is an object of the present invention to provide a transfer device that can be conveyed.

  According to a first aspect of the present invention, there is provided a transfer device for electrostatically transferring a toner image formed on an image carrier image onto a sheet, and having a guide surface made of resin. Transfer exit guide means for guiding the discharge and conveyance of the sheet by the guide surface coming into contact with the surface of the sheet during the discharge and conveyance of the sheet from the inside of the transfer device, and the inside of the slit portion provided on the guide surface And a sheet neutralizing unit that neutralizes the sheet when the surface of the sheet comes close to the sheet. The transfer unit further includes a guide surface neutralizing unit for neutralizing the guide surface.

  According to the transfer device of the present invention, since it has the guide surface neutralizing means for neutralizing the guide surface that contacts the surface of the sheet, the post-process is performed without disturbing the toner image formed on the sheet. Can be transported. Furthermore, since the potential of the conveyance guide plate can be prevented from increasing even when a large number of sheets are continuously fed, the image quality is always stable.

FIG. 1 is a model diagram showing a configuration in the vicinity of a transfer device as an example of the image forming apparatus of the present invention. FIG. 2 is a model diagram showing the configuration in the vicinity of the transfer device in another example of the image forming apparatus according to the present invention. It is a model perspective view which shows the ionized air generator and the nozzle part 18 with a brush in which the static elimination brush 12 was provided. It is a model bottom view of the nozzle part 18 with a brush. It is a model figure explaining the division path of the up-down direction of the nozzle part 18 with a brush by the actuator 20. FIG. It is a figure explaining selection of the static elimination control condition by the electric current detection static elimination control means. It is a model figure which shows the structure of the transfer apparatus which concerns on a prior art. FIG. 9 is a model diagram showing a configuration in the vicinity of a transfer outlet guide member 8 of the transfer apparatus of FIG. 8.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a model diagram showing the vicinity of a transfer apparatus as an example of an image forming apparatus according to the present invention.

  This example of the transfer device is unitized, and the lower part thereof is covered with a casing 3.

  The sheet on which the toner image formed on the surface of the photosensitive drum 1 serving as an image carrier is transferred is transferred from right to left in the figure by an endless belt 2 suspended between a driving roller 5 and a driven roller 4 that are both grounded. It is conveyed to. The endless belt 2 is in contact with the photosensitive drum 1 from below. A bias roller 6 for applying a transfer bias necessary for transferring a toner image to a sheet conveyed by the endless belt 2 is in contact with the endless belt 2 from the inside on the downstream side in the sheet conveying direction with respect to the photosensitive drum 1. And connected to the high voltage power source 7.

  The transfer outlet guide plate 10 installed on the downstream side of the endless belt 2 in the sheet conveying direction is composed of a transfer outlet guide member 8 and a charge removal member 9. In this example, the guide surface 8a that contacts the sheet of the transfer outlet guide member 8 is made of a polycarbonate resin (the guide surface 8a is formed of a polyester resin such as polyethylene terephthalate, or a mixture of a polyester resin and polycarbonate. May be)

  In the guide surface 8a, a slit that is long in the width direction of the conveyed sheet is provided as a slit portion 8b. In the slit portion 8b, the tips 9a of a plurality of static elimination needles 9 for removing charges in contact with the surface of the sheet are arranged at a depth of about 2 mm from the guide surface 8a in the longitudinal direction of the slit portion 8b. Are provided on the transfer outlet guide plate 10 and these static elimination needles 9 are grounded.

  The sheet is conveyed by the endless belt 2 to the transfer outlet guide plate 10 through the nip portion constituted by the photosensitive member (which is also an image carrier in this example) 1 and the endless belt 2. During this conveyance, the toner image carried on the photoreceptor 1 is transferred to the sheet.

  Residual charges are removed when the back surface of the sheet conveyed to the transfer outlet guide plate 10 is brought close to the tip 9 a of the static elimination needle 9. Thereafter, the sheet is conveyed to the fixing inlet guide plate 11 and then conveyed to a fixing device (not shown), and the toner image is fixed on the sheet by the fixing device.

  A fixing inlet guide plate 11 for guiding the conveyance of the sheet to a fixing device (not shown) for fixing the toner image transferred on the sheet surface to the sheet is provided downstream of the transfer outlet guide member 8 in the sheet conveyance direction. It has been.

  In this example, ionized air supply means composed of an ionized air generator 15 and a nozzle portion 18a connected to the ionized air generator 15 by a tube 15a as guide surface charge eliminating means for removing the guide surface 8a in a plane. have.

  The ionized air generator 15 alternately applies positive and negative high voltages to the air taken in by the air pump by the electrode needles provided therein, thereby generating ionized air having both polarities, Send it out. The nozzle part 18a has an air supply port (not shown) on the lower surface for supplying ionized air supplied from the ionized air generator 15 via the tube 15a to the lower guide surface 8a.

  With such a configuration, even when the guide surface 8a is charged due to friction with the sheet or the like, the charging of the guide surface 8a is mitigated by the ionized air supplied from the nozzle portion 18a, and the transfer dust in the formed image is reduced. Can be effectively suppressed.

  In this example, nozzle holes (not shown) provided on the lower surface of the nozzle portion 18a are provided so that the supply of ionized air from the nozzle portion 18 is evenly discharged in the sheet width direction perpendicular to the sheet conveyance direction on the guide surface 8a. It has been adjusted.

  In the above apparatus, the supply of ionized air is always performed. For this reason, when the sheet on which the toner image is electrostatically transferred to the surface passes through the transfer outlet guide plate 10, the ionized air is also supplied to the sheet. There is a concern about the negative effect on the toner image.

  For this purpose, the transfer apparatus shown in FIG. 1 is further provided with a sheet detection sensor 16 and a charge removal control means 17a. In other words, the sheet detection sensor 16 is an optical sensor in this example, and is provided upstream of the photosensitive drum 1 in the sheet conveyance direction as sheet detection means for detecting the presence or absence of a sheet in contact with the guide surface 8a as shown in FIG. ing.

  The static elimination control unit 17a includes a CPU as an arithmetic circuit, a ROM in which a control program and various constants are stored, a RAM for storing temporary data, a timer, and various input / output ports. This static elimination control means 17a is connected to the sheet detection sensor 16 and the ionized air generator 15 by a signal control line.

  The static elimination control means 17a receives the sheet detection signal from the sheet detection sensor 16 and activates the ionized air generator 15 of the guide surface static elimination means when the sheet detection sensor 16 does not detect a sheet. The ionized air generator 15 supplies the ionized air from the nozzle portion 18a toward the guide surface 8a to neutralize the guide surface 8a. When the sheet is detected by the sheet detection sensor 16, the static elimination control unit 17 a stops the supply of ionized air by the ionized air generator 15. By adding such a configuration, it is possible to eliminate in advance the adverse effects on the toner image caused by the airflow and its ions. There is no particular limitation on the amount of ionized air supplied, but in order to effectively reduce the charging of the guide surface within the time when the sheet does not exist on the guide surface 8a during continuous transfer, the amount of ionized air supplied is set at 0. It is preferably 5 to 1 L / min.

  Next, another embodiment of the transfer device according to the present invention will be described with reference to FIGS. In this example, all of the functions of the transfer apparatus shown in FIG. 1 are provided, and in addition to the charge removal control means 17a, a charge removal current detection means for detecting a current value at the time of sheet charge removal by the sheet charge removal means is provided. With this static elimination current detecting means, the transfer device can more effectively neutralize the guide surface 8a using the detected current value. 2 to 6, common members are denoted by the same reference numerals as the removal transmission values illustrated in FIG. 1, and descriptions of common functions are omitted.

  FIG. 2 is a model diagram showing a configuration in the vicinity of the transfer device according to another embodiment of the image forming apparatus of the present invention. The static elimination needle 9 is grounded via an ammeter 14 which is a static elimination current detecting means for detecting a current value flowing from the sheet to the static elimination needle 9 when the sheet is neutralized due to proximity to the static elimination needle 9. And instead of the nozzle part 18a shown in FIG. 1, the nozzle part 18 with a brush is connected to the ionized air generator 15 via the tube 15a. As shown in FIG. 3 as a model, the brushed nozzle portion 18 is provided with a neutralizing brush 12 made of a conductive material such as a fine metal wire or carbon fiber on its lower surface. Is installed.

  FIG. 4 schematically shows the lower surface of the brushed nozzle portion 18. In addition to the static eliminating brush 12, a plurality of air supply ports 13 for supplying ionized air supplied from the ionized air generator 15 to the lower guide surface 8a are provided on the lower surface of the nozzle portion 18 with the brush. The air supply port 13 allows the brushed nozzle portion 18 to uniformly supply ionized air to the guide surface 8a.

  The transfer device is further provided with an actuator 20 as a neutralizing brush contact means for bringing the neutralizing brush 12 into contact with the guide surface 8a. As schematically shown in FIG. 5, the actuator 20 lowers the brushed nozzle portion 18 to contact the guide surface 8a, and pulls it upward so as not to interfere with the conveyance of the sheet.

  The nozzle portion 18 with the brush, the actuator 20, and the ionized air generator 15 function as a guide surface static elimination unit.

  The transfer apparatus shown in FIG. 2 further has a current detection / elimination control means 17. The current detection and neutralization control means 17 includes a CPU that is an arithmetic circuit, a ROM that stores control programs and various constants, a RAM that stores temporary data, a timer, and various input / output ports. The static elimination control means 17a is connected to each of the sheet detection sensor 16, the ionized air generation device 15, and the actuator 20 through these input / output ports via signal control lines.

  The current detection neutralization control means 17 is configured to guide the guide surface by the guide surface neutralization means when no sheet is detected by the sheet detection means after the current value when the sheet detected by the ammeter 14 is neutralized exceeds a predetermined value. 8a is neutralized.

  Specifically, in this example, the current detection and neutralization control means 17 selects the static elimination control condition (1) when the current value when the sheet is neutralized becomes −1 μA or more and less than −2 μA as shown in FIG. . Then, the neutralization control condition (2) is selected when the current value becomes −2 μA or more and less than −3 μA, and the static elimination control condition (3) is selected when the current value becomes −3 μA or more, respectively, and the guide surface 8a is neutralized. .

  Under the charge removal control condition (1), the current detection charge removal control unit 17 operates the ionized air generator 15 to supply the ionized air to the guide surface 8a to discharge the guide surface 8a. Under the charge removal control condition (2), the actuator 20 is controlled to lower the brushed nozzle portion 18 so that the charge removal brush 12 is brought into contact with the guide surface 8a to discharge the guide surface 8a. In the charge removal control condition (3), the ionized air generator 15 and the actuator 20 are controlled to perform both charge removal by the contact of the charge removal brush 12 and charge removal by the ionized air.

  By such a charge removal control operation by the current detection charge removal control means 17, it is possible to remove the sufficient guide surface 8a as necessary, and the occurrence of transfer dust on the succeeding sheet is effectively prevented.

  Although the present invention has been described with reference to the preferred embodiment, the transfer device and the image forming apparatus of the present invention are not limited to the configuration of the above embodiment.

  A person skilled in the art can appropriately modify the transfer device and the image forming apparatus of the present invention in accordance with conventionally known knowledge. Of course, such modifications are included in the scope of the present invention as long as the configuration of the polishing apparatus of the present invention is provided.

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Endless belt 3 Casing 4 Driven roller 5 Drive roller 6 Bias roller 8 Transfer exit guide member 8a Guide surface 8b Slit part 9 Static elimination needle 10 Transfer exit guide plate 11 Fixing entrance guide plate 12 Static elimination brush 13 Air supply port DESCRIPTION OF SYMBOLS 15 Ionized air generator 15a Tube 17 Current detection static elimination control means 17a Static elimination control means 18 Brushed nozzle part 18a Nozzle part 20 Actuator

JP 2009-128481 A

Claims (6)

A transfer device that electrostatically transfers a toner image formed on an image carrier image to a sheet, the guide device having a guide surface made of resin, and when the sheet is discharged and conveyed from the transfer device to the outside Transfer exit guide means for guiding the discharge and conveyance of the sheet by the guide surface coming into contact with the surface of the sheet, and discharging the sheet when the surface of the sheet comes close to the inside of the slit portion provided on the guide surface In a transfer device having a sheet neutralizing means,
A transfer device comprising: a guide surface neutralizing means for neutralizing the guide surface.   2. The transfer apparatus according to claim 1, further comprising ionized air supply means for supplying ionized air to the guide surface as the guide surface neutralizing means. A sheet detection unit configured to detect the presence or absence of the sheet in contact with the guide surface; and a discharge control unit configured to discharge the guide surface by the guide surface discharge unit when the sheet is not detected by the sheet detection unit. The transfer device according to claim 2. Sheet detecting means for detecting the presence or absence of the sheet in contact with the guide surface;
Static elimination current detection means for detecting a current value at the time of static elimination by the sheet static elimination means, and
A current detection and neutralization control unit that neutralizes the guide surface by the guide surface neutralization unit when the sheet is not detected by the sheet detection unit after the current value detected by the neutralization current detection unit exceeds a predetermined value. The transfer apparatus according to claim 2, further comprising:   The guide surface neutralizing means has ionized air supply means for supplying ionized air to the guide surface and / or neutralizing brush contact means for bringing a neutralizing brush into contact with the guide surface. The transfer device according to claim 3 or 4.   An image forming apparatus comprising the transfer device according to claim 1.

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