JP5953859B2 - Transfer device and image forming apparatus - Google Patents

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 carrier onto the sheet surface, and the toner image transferred onto the sheet surface by the transfer device is fixed on the sheet in the fixing process which is the next process. The

  A conventional transfer apparatus will be described with reference to the drawings. FIG. 7 is a model diagram showing a configuration in the vicinity of the transfer device of the image forming apparatus according to the prior art, and FIG. 8 is an enlarged model diagram in the vicinity of the guide plate conveying surface 81.

  This 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 plate conveyance surface 81 of the transfer outlet guide member 8 that is in contact with the sheet is made of a high-resistance resin.

  On the guide plate conveyance surface 81, a slit that is long in the width direction of the conveyed sheet is provided as a slit portion 82. A plurality of neutralizing members 9 for neutralizing when the surfaces of the sheets are close to each other are provided on the transfer outlet guide plate 10 with a plurality of tips 9a in the slit portion 82 and at a depth of about 2 mm from the guide plate conveying surface 81. And grounded.

  The sheet is conveyed by the endless belt 2 to the transfer outlet guide plate 10 through a nip portion composed of a photosensitive drum (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 at the nip portion.

  When the sheet conveyed to the transfer outlet guide plate 10 comes into contact with the plurality of tips 9 a of the charge removal member 9, the residual charge is removed. Thereafter, the sheet from which the residual charge has been removed 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.

  Here, the toner image on the sheet forms an image by applying a bias having a polarity opposite to that of the toner to electrostatically attract the toner to the sheet. For this reason, even after being neutralized by the neutralizing member 9, electric charges accumulate in the sheet conveyance direction downstream region 8b (see FIG. 8) of the guide plate conveyance surface 81 with respect to the slit portion 82 due to friction with the sheet. When the subsequent sheet passes, the toner electrostatically attracted to the sheet due to abnormal discharge may move, causing image disturbance (hereinafter referred to as “conveying dust”).

  In the technique proposed by the cited document 1, a roller having conductivity in a middle resistance region grounded via a variable resistor on the conveyance surface upstream of the neutralization mechanism of the transfer outlet guide plate on the upstream side in the sheet conveyance direction. The rotating member is provided so that a part thereof protrudes from the conveying surface. With this configuration, the sheet transportability is improved, and the resistance of the variable resistor is changed in accordance with the sheet characteristics, so that the sheet is gradually discharged and delivered to the discharging member. Is prevented.

  However, in this method, since the charged sheet before passing through the static elimination mechanism is in contact with the rotating member having conductivity in the middle resistance region, the sheet is not applied to the rotating member itself. There is a risk of image disturbance due to the flow of electric charge.

  In addition, since the rotation of the rotation member is rotation by rotation using friction with the sheet, the sheet may not rotate the rotation member due to differences in the type of sheet, for example, smoothness, resistivity, Clark stiffness, etc. is there. In that case, there is a possibility that the sheet does not effectively contact the surface of the rotating member, and the charge removal work by the rotating member cannot be sufficiently obtained. Thus, depending on the type of sheet, the effect of improving the transportability by the rotating member and the effect of removing static electricity cannot be stably obtained. The contact is also unstable. As described above, when the technique described in the cited document 1 is actually applied, the neutralization of the sheet by the neutralization mechanism that should be performed is not stably performed, and the image of the image due to the discharge is discharged when the sheet contacts the rotating member. There remains a concern that disturbance will occur.

  SUMMARY An advantage of some aspects of the invention is that it provides a transfer device that can transport a toner image formed on a sheet to a subsequent process without disturbing the toner image.

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, wherein a guide plate conveying surface made of a resin is provided. A transfer outlet guide means for guiding the discharge and conveyance of the sheet by bringing the guide plate conveyance surface into contact with the surface of the sheet when the sheet is discharged and conveyed from the inside of the transfer device to the outside; and on the guide plate conveyance surface A sheet neutralizing unit that neutralizes the sheet when the surface of the sheet approaches the slit portion provided in the transfer unit, wherein the downstream region in the sheet conveyance direction is defined with respect to the slit on the guide plate conveyance surface. the material constituting is constituted by a conductive resin of medium-resistance region, the material constituting the sheet conveyance direction upstream side region with respect to the slit of the guide plate conveyance plane, an insulating resin Made is, and the guide plate conveyance plane, ridged rib portion protruding from the guide plate conveying surface is provided with a plurality of said ribs, in the sheet conveyance direction, wherein the said sheet conveying direction upstream area The transfer device is provided so as to extend beyond the slit portion to the downstream region in the sheet conveyance direction .

According to the transfer device of the present invention, the material constituting the downstream region in the sheet conveyance direction with respect to the slit on the guide plate conveyance surface is composed of the conductive resin in the medium resistance region, and downstream of the guide plate conveyance surface. With the configuration in which the region other than the side region is made of the insulating resin, the toner image formed on the sheet can be conveyed to the subsequent process without being disturbed.
In addition, a plurality of rib-shaped rib portions protruding from the guide plate conveyance surface are provided on the guide plate conveyance surface, and the rib portions are arranged in the sheet conveyance direction from the upstream region in the sheet conveyance direction. With the configuration provided so as to extend to the downstream area in the sheet conveying direction beyond the slit portion, the sheet and the guide plate conveying surface are in contact with each other only by the rib portion, so that the contact area is small. It will be a scale.

It is a model figure which shows the transfer apparatus which concerns on one Embodiment of this invention. It is a model top view of the vicinity of the transfer outlet guide member 8 of the apparatus shown in FIG. FIG. 10 is a model view of the vicinity of a transfer outlet guide member 8 showing another embodiment in which a sheet 13 made of insulating resin is attached to the upstream region 8a. FIG. 4 is a model top view of the vicinity of a transfer outlet guide member 8 of the apparatus shown in FIG. 3. FIG. 6 is a model diagram illustrating an example of a transfer device in which a rib portion 14 is provided on a guide plate conveyance surface 81. FIG. 6 is a model top view of the vicinity of a transfer outlet guide member 8 of the apparatus shown in FIG. 5. It is a model figure which shows the transfer apparatus which concerns on a prior art. FIG. 8 is a model diagram in the vicinity of a transfer outlet guide member 8 of the apparatus shown in FIG. 7. It is a model top view of a polisher.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a model view showing the vicinity of a transfer device as an example of an image forming apparatus according to the present invention, and FIG. 2 is a top view of the vicinity of a transfer outlet guide member 8.

  The example of this transfer device is unitized, and the lower part 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. Be transported. The endless belt 2 is in contact with the photosensitive drum 1 by forming a nip portion 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.

  On the guide plate conveyance surface 81, a slit that is long in the width direction of the conveyed sheet is provided as a slit portion 82. A neutralizing member 9 is provided in the slit portion 82 as a sheet neutralizing means for receiving a discharge from the sheet and neutralizing the sheet when the sheet surfaces approach each other. The neutralizing member 9 is made of stainless steel, has a rectangular shape with a thickness of 0.2 mm, and is processed into a saw blade shape so that the distance between two adjacent tooth tips is 2 mm. The neutralizing member 9 is provided so that the plurality of sawtooth-shaped tips 9a are located at a depth of about 2 mm from the guide plate conveying surface 81, and is grounded.

  On the downstream side of the transfer outlet guide member 8 in the sheet conveyance direction, there is 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.

  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 from the sheet conveyed to the transfer outlet guide plate 10 when the back surface thereof is close to the plurality of tips 9 a of the charge removal member 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.

  In this transfer apparatus, a guide in the sheet conveyance direction downstream area 8b (hereinafter referred to as “downstream area 8b”) with respect to the slit portion of the guide plate conveyance surface 81 that contacts the sheet of the transfer outlet guide member 8. The material which comprises the board conveyance surface 81 is comprised with the conductive resin of a middle resistance area | region. Furthermore, in this example, the guide plate conveyance surface 81 other than the downstream region 8b is made of an insulating resin having a higher volume resistivity than the conductive resin in the middle resistance region. Specifically, the transfer outlet guide member 8 is made of an insulating resin, and is made of a conductive resin in the intermediate resistance region in the downstream region 8b in the sheet conveying direction with respect to the slit portion 82 of the transfer outlet guide member 8. A sheet 12 is affixed.

  With such a configuration, the sheet can be removed without causing image disturbance while maintaining a state in which the toner image on the sheet surface and the positive charge applied from the transfer bias roller 6 are electrically balanced. It is conveyed to 9. After the static elimination by the sheet neutralizing member 9, the transfer outlet guide member 8 is prevented from being charged due to the friction between the back surface of the sheet and the guide member conveying surface 81. The risk of toner image disturbance due to inflow is kept low.

  In the above description, the transfer outlet guide member 8 is made of an insulating resin, and the sheet 12 made of a conductive resin in the middle resistance region is attached to the downstream region 8b. It may be configured.

  In other words, the transfer outlet guide member 8 is formed of a conductive resin in the middle resistance region, and the downstream region 8a in the sheet conveyance direction with respect to the slit portion 82 (hereinafter referred to as “upstream region 8a”) is formed of an insulating resin. The sheet 13 may be pasted.

  Further, at the time of forming the transfer outlet guide member 8, the downstream region 8b may be formed with a conductive resin in the middle resistance region, and the other portion may be formed with an insulating resin. Alternatively, the upstream region 8a may be formed from an insulating resin, and the other portions may be formed from a conductive resin in the middle resistance region.

  Further, as shown in the model cross-sectional view in FIG. 3 and the model top view in FIG. 4, the transfer outlet guide member 8 is formed of a material other than the conductive resin and the insulating resin in the middle resistance region, and is upstream. A sheet 13 made of insulating resin may be attached to the side region 8a, and a sheet made of conductive resin in the middle resistance region may be attached to the downstream region 8b.

When the volume resistivity of the conductive resin in the middle resistance region constituting the downstream region 8b of the guide plate conveyance surface 81 in the present invention is 10 ⁶ Ω · cm or more and 10 ⁹ Ω · cm or less, the downstream region 8b Self-discharge of charges charged on the surface is sufficiently promoted. At this time, a particularly high image disturbance prevention effect is obtained, which is preferable. If the volume resistivity is higher than this range, the surface potential of the downstream region 8b composed of the conductive resin in the middle resistance region is not self-discharged due to friction with the sheet, so that the surface potential gradually increases. Therefore, it is difficult to obtain a sufficient effect. If the volume resistivity is lower than the above range, when the sheet comes into contact with the downstream area 8b, positive charges on the back side of the transfer paper that is electrically balanced with the toner on the sheet surface flow into the downstream area 8b. At this time, the toner adsorption by the sheet may become unstable and the image may be disturbed.

  It is preferable that the conductive resin in the middle resistance region is made of polyethylene as a base resin because charging due to friction with the sheet is particularly reduced. If the volume resistivity is higher than this region, the downstream region 8b may be charged due to friction with the sheet.

Further, if the volume resistivity of the insulating resin used in the present invention is 10 ¹³ Ω · cm or more and 10 ¹⁵ Ω · cm or less, the image is disturbed due to the flow of the sheet charge into the upstream region 8a. Can be prevented more reliably. When the volume resistivity is lower than the above range, the sheet charge easily flows into the upstream region 8a, and at this time, image disturbance is likely to occur.

  When the insulating resin used in the present invention is an insulating resin from polycarbonate, polyethylene terephthalate, or a mixed resin of polycarbonate and polyethylene terephthalate, since these resins have a high volume resistivity, the charge of the sheet to the upstream region 8a is reduced. It is possible to more reliably prevent occurrence of image disturbance due to inflow, and to obtain an accurate and highly reliable molded product. Here, among the three insulating resins, polyethylene terephthalate is more preferable.

  Next, another example of the transfer apparatus according to the present invention will be described with reference to FIGS.

  FIG. 5 is a structural view schematically showing an example of a transfer device in which the rib portion 14 is provided on the guide plate conveying surface 81, and FIG. 6 is a top view of the transfer outlet guide member 8 of the transfer device shown in FIG. It is.

  The transfer device shown in FIGS. 5 and 6 has all of the configuration of the transfer device shown in FIG. 1, and the guide plate conveyance surface 81 has a sheet conveyance direction in FIG. As shown by the arrows), the upstream region 8a of the guide plate conveying surface 81 is made of a sheet 13 made of an insulating resin, and the downstream region 8b is made of a conductive resin in a medium resistance region. Each sheet 12 is affixed.

  Further, in this transfer apparatus, a plurality of hook-shaped rib portions 14 protruding from the guide plate conveyance surface 81 are provided on the guide plate conveyance surface 81. With such a configuration, since the sheet and the guide plate conveying surface 81 are in contact with each other only by the rib portion 14 (14a), the contact area is small, so that charging due to friction becomes a small scale.

  Further, the plurality of rib portions 14 are provided so as to spread from the upstream side toward the downstream side in the sheet conveying direction toward the outer side in the width direction of the guide plate conveying surface 81. With such a configuration, the generation of wrinkles by the plurality of rib portions 14 is prevented in advance. Here, forming the rib portion so that the angle formed by the conveyance direction of the sheet and the rib portion 14 has an inclination of 15 to 25 ° can achieve both good sheet conveyance performance and high conveyance wrinkle generation prevention effect. Therefore, it is preferable.

  In this example, among the plurality of rib portions 14, the upstream ends in the sheet conveyance direction of the two rib portions 14a provided near the center in the width direction of the guide plate conveyance surface 81 are in contact with each other in a V shape. Further, the end on the upstream side in the sheet conveyance direction of the rib portion 14 other than the two rib portions 14a whose upstream end in the sheet conveyance direction is in contact with the V shape is a rib portion adjacent to the center side in the width direction of the guide plate conveyance surface 81. 14 (or 14a) is located closer to the center side in the width direction of the guide plate conveyance surface 81 than the downstream end in the conveyance direction of the sheet.

  With such a configuration, any part on the back side of the sheet comes into contact with the guide plate conveyance surface 81, and the contact points between the sheet and the guide plate conveyance surface 81 are dispersed and are not partially biased to a specific portion of the sheet. There is no portion where the charge increases. With such a configuration, charging of the transfer outlet guide member 8 due to friction between the sheet after static elimination by the sheet static elimination unit and the guide member conveyance surface 81 (the rib portion 14 (14a) thereof) is extremely effectively prevented. Thus, the risk of toner image disturbance due to the inflow of charges from the sheet to the guide member 8 is effectively suppressed.

  In addition, it is possible to always obtain a stable conveyance state for various sizes of transfer materials such as overseas paper sizes and irregular sizes.

  By making the material of the rib portion 14 the same material as the transfer outlet guide member 8, the rib portion 14 can be formed at the same time when the transfer outlet guide member 8 is formed. When the width of the rib portion is about 2 to 4 mm and the height is about 0.5 to 2 mm, good sheet transportability can be obtained. Further, in order to reduce the contact area with the transfer material as much as possible while accommodating various paper sizes, it is desirable to arrange them at a pitch of 3 to 5 mm. Further, the arrangement of the plurality of rib portions 14 need not be equal pitches.

  The central position of the arrangement of the plurality of ribs 14 (14a), that is, the position of the V-shaped tips of the two ribs 14a in contact with the V shape in the width direction of the conveyed sheet is, for example, A4 or B5 It is preferable that a plurality of ribs 14 (14a) are provided so that the inside of the sheet is placed 2 to 3 mm from the position where the end portion when the standard size sheet is conveyed is positioned. It is preferable because of its property.

  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.

  As shown in FIG. 3, the transfer device shown in a model in FIG. 1 has an upstream region 8a of the guide plate conveyance surface 81 made of insulating resin. An image was actually formed using an image forming apparatus provided with a sheet 13 and a sheet 12 made of a conductive resin in a medium resistance region attached to the downstream region 8b.

At this time, instead of the sheet 12 made of the conductive resin in the middle resistance region, polyethylene is used as the base resin, and a conductive resin is added to the polyethylene resin to adjust the volume resistivity to various values. The resin sheet made was used. At this time, a sheet made of polyethylene having a volume resistivity of 10 ¹⁵ Ω · cm is used as the sheet 13 made of insulating resin in the upstream region 8a of the guide plate conveying surface 81, and 2000 sheets of images are formed respectively. went. Then, the presence or absence of conveyance dust was visually evaluated with respect to the obtained image.

  Moreover, it replaced with the sheet | seat 12 comprised with the conductive resin of the middle resistance area | region, and image formation was performed using the metal sheet | seat (copper foil), and the presence or absence of conveyance dust was evaluated similarly.

  Here, when the conveyance dust is visually in a state where there is no image disturbance, it is assumed that the effect of preventing the generation of conveyance dust is sufficient, and when the level at which the image distortion can be confirmed is considered insufficient, “×” was evaluated.

  At that time, Table 1 shows the volume resistivity of the resin constituting the used sheet and the evaluation result of the conveyance dust.

From Table 1, it is understood that when the conductive resin in the middle resistance region has a volume resistivity of 10 ⁶ Ω · cm or more and 10 ⁹ Ω · cm or less, a high conveyance dust generation preventing effect can be obtained.

Further, in the same manner as described above, except that a sheet made of polyethylene having a volume resistivity of 10 ⁹ Ω · cm is used as the sheet 12 made of the conductive resin in the middle resistance region, and replaced with the sheet 13 made of the insulating resin. A resin sheet formed of a polyethylene terephthalate resin adjusted to various volume resistivity by adding polyethylene terephthalate as a base resin and adding a conductive component thereto (including those without adding a conductive component). Then, image formation was performed, and the presence or absence of conveyance dust was evaluated on the obtained image in the same manner as described above. At this time, the volume resistivity of the resin constituting the used sheet and the evaluation result of the conveyance dust are shown in Table 2.

From Table 2, it is understood that when an insulating resin having a volume resistivity of 10 ¹³ Ω · cm or more and 10 ¹⁵ Ω · cm or less is used, a high conveyance dust generation preventing effect is obtained.

1 Photosensitive drum (image carrier)
2 Endless Belt 3 Casing 4 Driven Roller 5 Drive Roller 6 Bias Roller 7 High Voltage Power Supply 8 Transfer Exit Guide Member 81 Guide Plate Conveying Surface 82 Slit 8a Upstream Region 8b Downstream Region 9 Discharge Member 9a Tip 10 Transfer Exit Guide Plate 12 Sheet made of conductive resin in middle resistance region 13 Sheet made of insulating resin

JP 2009-237522 A

Claims (7)

A transfer device for electrostatically transferring a toner image formed on an image carrier image to a sheet, having a guide plate conveyance surface made of resin, and discharging and conveying the sheet from the transfer device to the outside When the surface of the sheet comes close to the transfer outlet guide means that guides the discharge and conveyance of the sheet by the guide plate conveyance surface sometimes contacting the surface of the sheet, and the slit portion provided on the guide plate conveyance surface In a transfer device having a sheet neutralizing means for neutralizing the sheet,
The material constituting the sheet conveyance direction downstream region with respect to the slit of the guide plate conveyance surface is composed of a conductive resin in a medium resistance region ,
The material constituting the upstream region in the sheet conveyance direction with respect to the slit of the guide plate conveyance surface is composed of an insulating resin , and
The guide plate conveyance surface is provided with a plurality of rib-shaped rib portions protruding from the guide plate conveyance surface, and the rib portions extend from the upstream region in the sheet conveyance direction to the slit portion in the sheet conveyance direction. A transfer device provided to extend to a downstream side region in the sheet conveying direction 2. The transfer device according to claim 1, wherein the volume resistivity of the conductive resin in the medium resistance region is 10 ⁶ Ω · cm or more and 10 ⁹ Ω · cm or less.   The transfer apparatus according to claim 1, wherein the conductive resin in the middle resistance region is configured by using polyethylene as a base resin.   The transfer according to any one of claims 1 to 3, wherein the insulating resin is an insulating resin selected from polycarbonate, polyethylene terephthalate, and a mixed resin of polycarbonate and polyethylene terephthalate. apparatus. The volume resistivity of the insulating resin, the transfer device according to any one of claims 1 to 4, wherein the 10 [Omega ¹³ · cm or more 10 or less ^{15 Ω} · cm.   The transfer device according to claim 5, wherein the upstream region in the sheet conveying direction is made of polyethylene terephthalate. Out of the plurality of rib portions, the upstream ends of the two rib portions in the sheet conveyance direction are in contact with each other in a V shape,
Rib portions other than the two rib portions are provided so as to spread from the upstream side in the conveyance direction of the sheet toward the downstream side with respect to the two rib portions toward the outside in the width direction of the guide plate conveyance surface,
An end on the upstream side in the sheet conveyance direction of the rib portion other than the two rib portions whose upstream end in the sheet conveyance direction is in a V shape is adjacent to the center side in the width direction of the guide plate conveyance surface. The transfer device according to claim 1 , wherein the transfer device is located on the center side in the width direction of the guide plate with respect to the downstream end of the sheet in the conveyance direction.

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