JP2010262093A - Transfer device and image forming apparatus - Google Patents

Abstract

Provided is a transfer device capable of preventing abnormal discharge due to charging of a transfer facing member.
In the present invention, a belt 10 for carrying an image on a surface, a transfer member 12 to which a transfer voltage is applied from a power source 24, and a transfer member 12 are arranged so as to face each other via the belt 10. In the transfer device including the transfer facing member 8. The transfer device includes a conductive contact member 25 that contacts the surface of the transfer facing member 8 and grounds the contact member 25.
[Selection] Figure 2

Description

  The present invention relates to a transfer device for transferring an image to a recording medium, and an image forming apparatus including the transfer device.

  As an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a complex machine of these, a so-called direct transfer system that directly transfers a toner image formed on the surface of a photoconductor onto a recording paper or the like, and a toner on the photoconductor A so-called indirect transfer method is known in which an image is transferred onto a recording sheet or the like via an intermediate transfer belt as an intermediate transfer member.

FIG. 10 shows an example of a direct transfer type image forming apparatus.
This direct transfer type image forming apparatus 1A has a photoreceptor belt 2A composed of an endless belt member, a charging device 3A, a developing device 4A, an exposure device 5A, and a photoreceptor belt 2A so as to face each other. A transfer roller 6A and a transfer counter roller 7A are provided.

An image forming process and a transfer process of the image forming apparatus shown in FIG. 10 will be described.
First, the photosensitive belt 2A is run in the direction of the arrow in the figure, and the surface of the photosensitive belt 2A is charged by the charging device 3A. Next, the exposure device 5A exposes the charged surface of the photoreceptor belt 2A to form an electrostatic latent image on the photoreceptor belt 2A. Then, toner is supplied from the developing device 4A to the electrostatic latent image, and a toner image is formed on the photoreceptor belt 2A. Further, the recording paper P is sent out from a paper feeding unit (not shown), and the recording paper P is conveyed to a transfer position between the transfer roller 6A and the transfer counter roller 7A in synchronization with the toner image on the photosensitive belt 2A. Is done. A toner image on the photosensitive belt 2A is electrostatically transferred onto the recording paper P by applying a transfer voltage to the transfer roller 6A from a power source (not shown).

FIG. 11 shows an example of an indirect transfer type image forming apparatus.
This indirect transfer type image forming apparatus 1B includes a plurality of photosensitive drums 2B formed in a drum shape, a plurality of charging devices 3B and a plurality of developing devices 4B arranged corresponding to the respective photosensitive drums 2B. The exposure device 5B, the intermediate transfer belt 6B, a plurality of primary transfer rollers 7B disposed to face the photosensitive drums 2B via the intermediate transfer belt 6B, and the intermediate transfer belt 6B face each other. A secondary transfer roller 8B and a transfer counter roller 9B.

An image forming process and a transfer process of the image forming apparatus shown in FIG. 11 will be described.
First, each photosensitive drum 2B is rotated in the direction of the arrow in the figure, and the surface of each photosensitive drum 2B is charged by each charging device 3B. Next, the exposure device 5B exposes the charged surface of each photoconductive drum 2B to form an electrostatic latent image on each photoconductive drum 2B. Then, toner is supplied from each developing device 4B to each electrostatic latent image, and a toner image is formed on each photosensitive drum 2B. The toner image on each photoconductive drum 2B is electrostatically primary-transferred onto the intermediate transfer belt 6B running in the direction of the arrow by applying a transfer voltage from a power source (not shown) to each primary transfer roller 7B. The Further, the recording paper P sent out from a paper supply unit (not shown) is conveyed to the secondary transfer position between the secondary transfer roller 8B and the transfer counter roller 9B in synchronization with the toner image on the intermediate transfer belt 6B. Is done. The toner image on the intermediate transfer belt 6B is electrostatically secondary-transferred onto the recording paper P by applying a transfer voltage to the secondary transfer roller 8B from a power source (not shown).

  In the direct transfer image forming apparatus shown in FIG. 10, a part of the transfer current generated by the transfer voltage applied to the transfer roller 6A flows into the ground via the transfer counter roller 7A. In the indirect transfer type image forming apparatus shown in FIG. 11, a part of the transfer current generated by the transfer voltage applied to the secondary transfer roller 8B flows into the ground via the transfer counter roller 9B. Yes.

  However, at the end of the endurance life of the photosensitive belt and the intermediate transfer belt, the belt components, foreign matter and toner mixed in the belt adhere to the surface of the transfer counter roller, and the surface of the transfer counter roller is thin. A phenomenon called filming that is covered with a film occurs. As a result of filming on the transfer counter roller, if the electrical resistance of the transfer counter roller increases, the transfer current from the transfer counter roller cannot flow to the ground well, the surface of the transfer counter roller is charged, and abnormal discharge occurs at some time. Wake up. When such abnormal discharge occurs during image transfer, there is a risk that a discharge mark will be formed in the transferred image and an image defect will occur. In addition, there is a possibility that the power supply board may be abnormal because current due to abnormal discharge flows back to the power supply via the transfer roller.

  On the other hand, some conventional image forming apparatuses include a brush as a cleaning unit that removes foreign matters or the like attached to the surface of the transfer counter roller (see, for example, Patent Document 1 below). In this case, the brush comes into sliding contact with the surface of the transfer counter roller along with the rotation of the transfer counter roller, and the brush can physically and mechanically remove foreign matters on the surface of the transfer counter roller. .

  However, since the filming occurs when the electrically exuding belt component adheres to the surface of the transfer counter roller, the physical and mechanical cleaning means such as a brush cannot remove the filming. Have difficulty. In addition to filming, the electrical resistance of the surface of the transfer counter roller may also increase due to a change in characteristics as a result of the surface layer portion of the transfer counter roller being deteriorated by energization. In this case, even if the surface of the transfer counter roller is cleaned, charging of the transfer counter roller cannot be prevented.

  Accordingly, in view of such circumstances, the present invention is intended to provide a transfer device capable of preventing abnormal discharge due to charging of a transfer counter roller, and an image forming apparatus including the transfer device.

  The invention according to claim 1 is a belt for carrying an image on a surface, a transfer member to which a transfer voltage is applied from a power source, and a transfer counter member disposed to face the transfer member via the belt. The transfer apparatus includes a conductive contact member that contacts the surface of the transfer facing member, and the contact member is grounded.

  Since a conductive contact member is brought into contact with the surface of the transfer counter member and grounded, a transfer voltage is applied to the transfer member even if the electrical resistance of the transfer counter member increases due to filming or deterioration. The transfer current generated by this can flow to the ground via the contact member. As a result, charging of the surface of the transfer facing member and abnormal discharge caused thereby can be prevented, and problems such as occurrence of discharge traces in the transferred image and reverse current flowing to the power source can be prevented. it can.

According to a second aspect of the present invention, in the transfer device according to the first aspect, an electrical resistance of the contact member is set to 10 ⁵ Ω or less.

By setting the electrical resistance of the contact member to 10 ⁵ Ω or less, it becomes possible to prevent the transfer counter member from being charged or abnormally discharged even under conditions where the transfer counter member is easily charged or abnormally discharged. .

  According to a third aspect of the present invention, in the transfer device according to the first or second aspect, when the transfer counter member is a rotating body, a cleaning unit is provided for removing foreign matter on the surface of the rotating body.

  When foreign matter adheres to the surface of the rotating body as the transfer facing member, the foreign matter is sandwiched between the rotating body and the contact member as the rotating body rotates, and a gap is formed at the contact portion between the rotating body and the contact member. May occur. As a result, if the contact of the contact member with the rotating body (transfer facing member) becomes poor, the function of passing the transfer current to the ground through the contact member may be reduced, or the function may not be performed.

  Therefore, by providing a cleaning means for removing the foreign matter on the surface of the rotating body, it is possible to prevent foreign matter from being caught between the rotating body and the contact member, and the contact of the contact member with the rotating body is good. Can be maintained. Thereby, the antistatic effect of the rotating body (transfer facing member) can be stably exhibited.

  According to a fourth aspect of the present invention, in the transfer device according to any one of the first to third aspects, when the transfer counter member is a rotating body and the contact member is formed of a conductive sheet, the rotation is performed. The direction in which the conductive sheet is brought into contact with the body is the trailing direction with respect to the rotation direction of the rotating body.

  When the conductive sheet is brought into contact with the rotating direction of the rotating body in the trailing direction, the conductive sheet is less likely to bend and entangled with the rotation of the rotating body. By preventing the conductive sheet from curling or entraining, the conductive sheet can be prevented from being damaged (scratched, etc.) or from poor contact with the rotating body (transfer facing member).

  According to a fifth aspect of the present invention, in the transfer device according to any one of the first to third aspects, when the transfer counter member is a rotating body and the contact member is formed of a conductive sheet, the rotation is performed. The direction in which the conductive sheet is brought into contact with the body is a counter direction with respect to the rotation direction of the rotating body.

  When the conductive sheet is contacted in the counter direction, the contact position of the contact member with respect to the rotating body (transfer facing member) is different from that when the conductive sheet is contacted in the trailing direction. It is far from the contact start position with the member. For this reason, the space which arrange | positions a belt back surface cleaning member etc. can be ensured in the upstream of the belt running direction of the said contact start position.

  According to a sixth aspect of the present invention, in the transfer device according to the fifth aspect, the contact pressure of the conductive sheet against the rotating body is 1 N / m or more.

  The contact direction of the conductive sheet is set to the counter direction with respect to the rotation direction of the rotating body, and the contact pressure of the conductive sheet to the rotating body is set to 1 N / m or more. Foreign matter adhering to the surface can be removed. In other words, in this case, the conductive sheet also functions as an antistatic means and a cleaning means for the rotating body. Accordingly, there is no need to provide a separate cleaning means for removing foreign matter on the surface of the rotating body, so that the number of parts can be reduced to reduce the size and cost.

  According to a seventh aspect of the present invention, in the transfer device according to any one of the first to sixth aspects, the contact member is formed of a conductive sheet, and the conductive sheet has a contact assistance with higher rigidity than that. A member is attached.

  By attaching a contact assisting member having higher rigidity to the conductive sheet, it is possible to improve the apparent rigidity of the conductive sheet. Thereby, even if the conductive sheet is formed of a member having low rigidity, the contact pressure of the conductive sheet with respect to the transfer facing member can be sufficiently ensured, and the transfer current is passed to the ground via the conductive sheet. be able to. This also makes it possible to apply a material having a low rigidity to the material of the conductive sheet, so that the selection range of the material is expanded.

  According to an eighth aspect of the present invention, in the transfer device according to any one of the first to seventh aspects, the contact member is formed of a conductive double-sided adhesive tape on a support member that forms at least a part of the grounding path. It is attached via.

  By attaching the abutting member to the support member with a double-sided adhesive tape, it is easier to install than the abutting member using a fastening member such as a screw. Can be realized. Furthermore, since the double-sided adhesive tape is inexpensive, it is possible to reduce the manufacturing cost.

  According to a ninth aspect of the present invention, in the transfer device according to the eighth aspect, a slit is formed in the conductive double-sided adhesive tape.

  By forming a slit in the double-sided adhesive tape, it is possible to absorb the difference in expansion and contraction due to the difference in linear expansion coefficient between the contact member and the double-sided adhesive tape, and it is possible to prevent the contact member from being deformed. . As a result, the contact of the contact member with the transfer facing member can be maintained satisfactorily, and the antistatic effect of the transfer facing member can be stably exhibited.

  A tenth aspect of the present invention is the transfer apparatus according to any one of the first to ninth aspects, wherein the transfer facing member is configured by a roller having a middle resistance surface layer disposed on an outer periphery of a core metal. is there.

  As a result of filming or energization deterioration in the surface layer portion of the medium resistance, if the electrical resistance of the surface layer portion increases, abnormal discharge may occur. Even in such a case, it is possible to flow to the transfer current ground through the contact member by bringing the conductive contact member into contact with the surface of the surface layer portion and grounding it. As a result, abnormal discharge caused by charging of the surface layer portion can be prevented, and problems such as occurrence of discharge traces in the transferred image and backflow of current due to discharge to the power source can be prevented.

  An eleventh aspect of the invention is the transfer apparatus according to the tenth aspect, wherein the cored bar is grounded.

  By grounding both the surface layer part and the cored bar of the transfer counter member, a transfer current can flow from both the surface layer part and the cored bar to the ground, and charging and abnormal discharge of the transfer counter member can be reliably prevented. it can.

  A twelfth aspect of the present invention is an image forming apparatus including the transfer device according to any one of the first to eleventh aspects.

  The transfer device of the present invention can be applied to an image forming apparatus.

  According to the present invention, abnormal discharge due to charging of the transfer facing member can be prevented, so that a good transfer image without discharge traces can be obtained, and abnormalities caused by the backflow of current due to discharge to the power source can be obtained. Can be prevented.

1 is a schematic configuration diagram of an image forming apparatus according to the present invention. It is a figure which shows the structure which concerns on Example 1 of this invention. It is a figure which shows the structure which concerns on Example 2 of this invention. It is a figure which shows the structure which concerns on Example 3 of this invention. It is a figure which shows the structure which concerns on Example 4 of this invention. It is a figure which shows the structure which concerns on Example 5 of this invention. It is a figure which shows the structure which concerns on Example 6 of this invention. It is a figure which shows the structure which concerns on Example 7 of this invention. It is a figure which shows the structure which concerns on Example 8 of this invention. 1 is a schematic configuration diagram of a direct transfer type image forming apparatus. 1 is a schematic configuration diagram of an indirect transfer type image forming apparatus.

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to the present invention.
The image forming apparatus illustrated in FIG. 1 includes four process units 1Y, 1C, 1M, and 1Bk configured to be detachable from the image forming apparatus main body 100. The process units 1Y, 1C, 1M, and 1Bk have the same configuration except that they contain toners of different colors of yellow, cyan, magenta, and black corresponding to the color separation components of the color image. Therefore, the configuration of one process unit 1Y will be described as an example.

  The process unit 1Y includes a photosensitive member 2 as an image carrier, a charging roller 3 as a charging unit that charges the surface of the photosensitive member 2, and a developing unit that supplies toner (developer) to the surface of the photosensitive member 2. A developing device 4 and a cleaning blade 5 as a cleaning means for cleaning the surface of the photoreceptor 2 are provided.

  The photoreceptor 2 is a photoreceptor drum formed in a cylindrical shape. This photosensitive drum is configured to rotate at a peripheral speed of 100 to 180 mm / s in the clockwise direction in the drawing. The charging roller 3 is in pressure contact with the surface of the photoreceptor 2, and the charging roller 3 is driven to rotate as the photoreceptor 2 rotates. Further, the charging roller 3 is applied with DC or a bias in which AC is superimposed on DC by a high voltage power source (not shown). The developing device 4 is configured to transfer toner as a developer to the photosensitive member 2 by a developing bias supplied from a high voltage power source (not shown). Here, a one-component developer containing a magnetic material is used as a developer, but a two-component developer having a toner and a carrier can also be used.

  In FIG. 1, an exposure device 7 as an exposure means for exposing the surface of the photoreceptor 2 is disposed above each process unit 1Y, 1C, 1M, 1Bk. The exposure device 7 can be a laser beam scanner using a laser diode, an LED, or the like. On the other hand, a transfer device 6 is disposed below the process units 1Y, 1C, 1M, and 1Bk. The transfer device 6 has an intermediate transfer belt 10 constituted by an endless belt. The intermediate transfer belt 10 is stretched around a driving roller 8 and a driven roller 9 and is configured to be able to run around in the direction of the arrow in the figure. Further, the driven roller 9 also has a function as a tension roller for applying tension to the intermediate transfer belt 10. The rollers 8 and 9 that stretch the intermediate transfer belt 10 are rotatably supported at both axial ends by side plates (not shown).

  Materials used for the intermediate transfer belt 10 include PVDF (vinylidene fluoride), ETFE (ethylene-tetrafluoroethylene copolymer), PI (polyimide), PC (polycarbonate), TPE (thermoplastic elastomer), and carbon. A resin film-like endless belt in which a conductive material such as black is dispersed can be used. In this embodiment, the belt tensile elastic modulus is 1000 to 2000 [MPa] (tensile elastic modulus: measured in accordance with ISOR1184-1970. Test piece: width 15 [mm], length 150 [mm], tensile speed: 1 [ A belt having a thickness of 90 to 160 [μm] and a belt width of 230 [mm] was used in a single-layer structure in which carbon black was added to TPE with a distance of 100 mm [mm / min].

  Four primary transfer rollers 11 as primary transfer means are disposed at positions facing the four photoconductors 2. In this embodiment, a metal roller is used as the primary transfer roller 11, but in addition to this, a conductive blade, a conductive sponge roller, or the like can also be applied as the primary transfer unit. Each primary transfer roller 11 is pressed against the photoreceptor 2 via the intermediate transfer belt 10, and a primary transfer nip N <b> 1 is formed between each photoreceptor 2 and the intermediate transfer belt 10. The primary transfer roller 11 is applied with a predetermined transfer voltage (transfer bias) from a single high-voltage power source (not shown).

  Further, a secondary transfer roller 12 as a secondary transfer unit is disposed at a position facing the driving roller 8. In other words, in this embodiment, the driving roller 8 is a transfer counter roller disposed to face the secondary transfer roller 12 with the intermediate transfer belt 10 interposed therebetween. Hereinafter, the driving roller 8 is referred to as a transfer counter roller 8. The secondary transfer roller 12 is pressed against the transfer counter roller 8 via the intermediate transfer belt 10, and a secondary transfer nip N <b> 2 is formed between the secondary transfer roller 12 and the intermediate transfer belt 10. A predetermined transfer voltage (transfer bias) is applied to the secondary transfer roller 12 from a high voltage power source (not shown).

The secondary transfer roller 12 is configured by coating an elastic layer made of urethane or the like prepared so as to have a resistance value of 10 ⁶ to 10 ¹⁰ [Ω] with a conductive material on a metal core such as SUS. Has been. As the material, an ion conductive roller (urethane + carbon dispersion, NBR, hydrin), an electronic conductive type roller (EPDM), or the like can be used. In the present embodiment, a urethane roller is used as a foaming roller having a diameter of 20 [mm] and an Asker C hardness of 35 to 50 [°]. The resistance value of the secondary transfer roller 12 is such that the secondary transfer roller 12 is installed on a conductive metal plate and 4.9 [N] on one side at both ends of the core metal (total of 9.8 [N] on both sides). ) Is applied from the value of the current that flows when a voltage of 1000 [V] is applied between the metal core and the metal plate.

  A belt cleaning device 21 is disposed on the outer peripheral surface of the intermediate transfer belt 10. The belt cleaning device 21 has a belt cleaning blade 21 a that contacts the outer peripheral surface of the intermediate transfer belt 10. The belt cleaning blade 21 a is disposed in the counter direction with respect to the traveling direction of the intermediate transfer belt 10. A waste toner transfer hose (not shown) extending from the belt cleaning device 21 is connected to the entrance of a waste toner container 22 disposed below the transfer device 6.

  A lower part of the image forming apparatus main body 100 is provided with a paper feed cassette 23 that stores recording paper P as a recording medium, a paper feed roller 14 that carries the recording paper P out of the paper feed cassette 23, and the like. Further, a conveyance path R for conveying the recording paper P to the stock unit 20 provided on the upper surface of the image forming apparatus main body 100 is formed in the image forming apparatus main body 100. In the transport path R, a pair of registration rollers 15 a and 15 b are disposed between the paper feed roller 14 and the secondary transfer roller 12. Further, a fixing device 16 for fixing an image on the recording paper P is disposed downstream of the secondary transfer roller 12 in the transport direction of the transport path R (upward in the drawing). The fixing device 16 includes a heating roller 17 and a pressure roller 18. The heating roller 17 and the pressure roller 18 are pressed against each other, and a fixing nip N3 is formed between them. A pair of paper discharge rollers 19a and 19b for discharging the recording paper P to the outside of the apparatus is disposed at the downstream end of the transport path R in the transport direction.

The basic operation of the image forming apparatus will be described below with reference to FIG.
When the image forming operation is started, the photosensitive members 2 of the respective process units 1Y, 1C, 1M, and 1Bk are rotationally driven clockwise by a driving device (not shown), and the surface of each photosensitive member 2 is predetermined by the charging roller 3. It is uniformly charged to the polarity. The surface of each charged photoconductor 2 is irradiated with laser light from the exposure device 7 to form an electrostatic latent image on the surface of each photoconductor 2. At this time, the image information to be exposed on each photoconductor 2 is monochromatic image information obtained by separating a desired full-color image into color information of yellow, cyan, magenta, and black. In this way, toner is supplied to each electrostatic latent image formed on each photoconductor 2 by each developing device 4, whereby the electrostatic latent image is visualized as a toner image.

  When the transfer counter roller 8 as a driving roller is rotationally driven counterclockwise in the figure, the intermediate transfer belt 10 runs in the direction indicated by the arrow in the figure. Further, a constant voltage or a constant current controlled voltage having a polarity opposite to the toner charging polarity is applied to each primary transfer roller 11. As a result, a transfer electric field is formed in the primary transfer nip N <b> 1 between each primary transfer roller 11 and each photoconductor 2. The toner images of the respective colors formed on the photoreceptors 2 of the process units 1Y, 1C, 1M, and 1Bk are sequentially superimposed on the intermediate transfer belt 10 by the transfer electric field formed in the primary transfer nip N1. Electrostatically transferred (primary transfer). Thus, the intermediate transfer belt 10 carries a full-color toner image on its surface.

  Residual toner adhering to the surface of each photoconductor 2 after the toner image is transferred is removed from the surface of the photoconductor 2 by each cleaning blade 5, and then the surface is subjected to static elimination action by a static eliminator (not shown). Then, the surface potential is initialized to prepare for the next image formation.

  Further, the recording paper P is sent out from the paper feed cassette 23 to the transport path R by the rotation of the paper feed roller 14. The recording paper P sent out to the transport path R is timed by the registration rollers 15a and 15b and sent to the secondary transfer nip N2 between the secondary transfer roller 12 and the transfer counter roller 8. At this time, a transfer voltage having a polarity opposite to the toner charging polarity of the toner image on the intermediate transfer belt 10 is applied to the secondary transfer roller 12, and a transfer electric field is formed in the secondary transfer nip N2. Then, the toner image on the intermediate transfer belt 10 is electrostatically transferred (secondary transfer) collectively onto the recording paper P by the transfer electric field formed in the secondary transfer nip N2. The recording paper P to which the toner image has been transferred is conveyed to the fixing means 16, and heat and pressure are applied to the recording paper P as it passes through the fixing nip N 3 between the heating roller 17 and the pressure roller 18. The image is melted and fixed. The recording sheet P on which the toner image is fixed is discharged to the stock unit 20 by the discharge rollers 19a and 19b. Further, the toner remaining on the intermediate transfer belt 10 after the transfer is removed by the belt cleaning blade 21a. The removed toner is transported to the waste toner container 22 and collected.

  The above description is an image forming operation when a full-color image is formed on the recording paper P, and a single-color image is formed using any one of the four process units 1Y, 1C, 1M, and 1Bk. Two or three process units may be used to form a two or three color image.

  The configuration of the transfer device 6 provided in the image forming apparatus of the present invention will be described below.

  FIG. 2 shows a configuration according to Embodiment 1 of the present invention. FIG. 2 is a schematic configuration diagram showing a peripheral region of the transfer nip N2 of the transfer device 6 of the present invention. In FIG. 2, the same reference numerals as those in FIG. 1 denote the same members.

As shown in FIG. 2, the transfer counter roller 8 includes a metal core 81 and a surface layer portion 82 disposed so as to cover the surface of the core 81. The surface layer portion 82 is formed of a rubber material or the like having a high friction coefficient in order to improve the grip performance with respect to the intermediate transfer belt 10 and improve the transportability. Furthermore, the rubber material or the like by mixing a conductive material such as carbon or titanium, are set the electrical resistance of the surface layer portion 82 to 10 4 ^{to 10} within the range of 8 ^[Omega]. Thus, by setting the surface layer portion 82 as an intermediate resistance, a part of the transfer current generated when the transfer voltage is applied from the power source 24 (high voltage power source) to the secondary transfer roller 12 passes through the secondary transfer nip N2. The recording paper P (not shown) in the middle and the intermediate transfer belt 10 are passed from the transfer counter roller 8 to the ground.

Further, a conductive contact member 25 is brought into contact with the outer peripheral surface of the transfer counter roller 8. Here, a conductive sheet 26 is used as the contact member 25. As a material of the conductive sheet 26, in particular, it is preferable that the electric resistance to apply a 10 ⁵ Omega following materials. In addition, as the contact member 25, it is also possible to use a conductive cloth (static discharge cloth) or the like.

  In this case, the contact direction of the conductive sheet 26 is set to the trailing direction with respect to the rotation direction of the transfer counter roller 8. That is, the conductive sheet 26 is disposed so that the direction in which the tip of the conductive sheet 26 that contacts the transfer counter roller 8 faces and the rotation direction of the transfer counter roller 8 are the same.

  The conductive sheet 26 is grounded. Specifically, the conductive sheet 26 is attached to a metal support member 27 that forms a part of the grounding path 30. The support member 27 is also a member that supports the left and right side plates of the transfer device 6.

FIG. 3 shows a configuration according to Embodiment 2 of the present invention.
The second embodiment is basically configured in the same manner as the first embodiment, but in the second embodiment, the inner peripheral surface of the cored bar 81 of the transfer counter roller 8 is further grounded via the grounding path 31. . Since the other configuration is the same as that of the first embodiment, description thereof is omitted. 3, the same reference numerals as those in FIG. 2 denote the same members as those in FIG. 2.

FIG. 4 shows a configuration according to Embodiment 3 of the present invention.
The third embodiment is basically configured in the same manner as the first embodiment, but in the third embodiment, a cleaning member 29 is further provided as a cleaning unit for cleaning the surface of the transfer counter roller 8. The cleaning member 29 is formed of a blade-like member, but a brush roller, a sponge roller, or the like may be used as the cleaning member. Since the other configuration is the same as that of the first embodiment, description thereof is omitted. 4, the same reference numerals as those in FIG. 2 indicate the same members as those in FIG. 2.

FIG. 5 shows a configuration according to Embodiment 4 of the present invention.
In Example 4 shown in FIG. 5, a belt back surface cleaning member 32 that contacts the back surface (inner peripheral surface) of the intermediate transfer belt 10 is provided. In this case, the belt back surface cleaning member 32 is disposed near the contact start position E between the intermediate transfer belt 10 and the transfer counter roller 8 (or upstream in the traveling direction of the intermediate transfer belt 10 with respect to the contact start position E). Has been. In this case, the contact direction of the conductive sheet 26 is the counter direction with respect to the rotation direction of the transfer counter roller 8. In other words, the conductive sheet 26 is disposed so that the direction in which the tip of the conductive sheet 26 that contacts the transfer counter roller 8 faces and the rotation direction of the transfer counter roller 8 are opposite to each other. The fourth embodiment shown in FIG. 5 is the same as the first embodiment except for the configuration described above, and a description thereof will be omitted. 5, the same reference numerals as those in FIG. 2 indicate the same members as those in FIG. 2.

FIG. 6 shows a configuration according to the fifth embodiment. 6, the conductive sheet 26 (contact member 25), the support member 27, and the like are shown in an enlarged manner, and the intermediate transfer belt 10, the secondary transfer roller 12, the transfer counter roller 8, and the like are not shown.
In Example 5 shown in FIG. 6, a contact assisting member 33 having higher rigidity than the conductive sheet 26 is attached to the upper surface of the conductive sheet 26 in the figure. On the other hand, the lower surface of the conductive sheet 26 is attached to a support member 27. In this embodiment, a PET (polyethylene terephthalate) sheet is applied as the contact assisting member 33, but other members are also applicable. Thus, by attaching the contact assisting member 33 having higher rigidity to the conductive sheet 26, the apparent rigidity of the conductive sheet 26 is improved. Further, the apparent rigidity of the conductive sheet 26 can be changed by changing the thickness of the PET sheet as the contact assisting member 33. Here, a PET sheet having a thickness of 0.1 mm is used. The surface of the transfer facing roller 8 is brought into contact with the conductive sheet 26 as in the above embodiments. The fifth embodiment shown in FIG. 6 is the same as the first embodiment except for the configuration described above, and a description thereof will be omitted.

FIG. 7 shows a configuration according to Embodiment 6 of the present invention.
A contact assisting member 33 is attached to the conductive sheet 26 shown in FIG. 7 as in the fifth embodiment shown in FIG. In Example 6 shown in FIG. 7, the contact direction of the conductive sheet 26 is the counter direction with respect to the rotation direction of the transfer counter roller 8. Furthermore, in this case, the contact pressure (contact line pressure) of the conductive sheet 26 against the transfer facing roller 8 is set to 1 N / m or more. The sixth embodiment shown in FIG. 7 is the same as the first embodiment except for the configuration described above, and a description thereof will be omitted. 7, the same reference numerals as those in FIG. 2 indicate the same members as those in FIG. 2.

FIG. 8 shows a configuration according to Embodiment 7 of the present invention. In FIG. 8, the conductive sheet 26 (contact member 25), the support member 27, and the like are shown in an enlarged manner, and the intermediate transfer belt 10, the secondary transfer roller 12, the transfer counter roller 8, and the like are not shown.
As shown in FIG. 8, here, the conductive sheet 26 is attached to the support member 27 via a double-sided adhesive tape 28. The double-sided adhesive tape 28 is made of a conductive member so that the conductive sheet 26 is grounded satisfactorily. Since the other configuration is the same as that of the first embodiment, description thereof is omitted.

FIG. 9 shows a configuration according to Embodiment 8 of the present invention.
In Example 8 shown in FIG. 9, as in Example 7 shown in FIG. 8, the conductive sheet 26 is attached to the support member 27 via a conductive double-sided adhesive tape 28. However, unlike the adhesive tape 28 shown in FIG. 8, the adhesive tape 28 shown in FIG. 9 has a plurality of slits 28a penetrating in the thickness direction. The number of slits 28a is not particularly limited as long as at least one slit 28a is formed. Since the other configuration is the same as that of the first embodiment, description thereof is omitted.

  Hereinafter, the operation and effect of each embodiment of the present invention will be described.

  In the transfer apparatus according to the present invention, when filming occurs in the surface layer portion 82 of the transfer counter roller 8 or the characteristics of the surface layer portion 82 are deteriorated due to energization deterioration, the electrical resistance of the surface layer portion 82 increases, and the transfer is performed. It may be difficult for the current to flow from the cored bar 81 to the ground via the surface layer part 82. However, even in such a case, in each of the above embodiments, the conductive sheet 26 is brought into contact with the outer peripheral surface of the transfer counter roller 8 and grounded, so that the transfer current is passed through the conductive sheet 26. It can flow to the ground, and charging of the transfer counter roller 8 and abnormal discharge caused thereby can be prevented. Therefore, according to each embodiment of the present invention, it is possible to prevent a trace of discharge from being generated on a transfer image on a recording sheet and to form a good image, and a current caused by the discharge causes a power supply 24 of the secondary transfer roller 12 to be generated. It is possible to prevent an abnormality of the power supply 24 due to the reverse flow.

In addition, depending on the transfer device, in order to remove the toner adhering to the surface of the secondary transfer roller 12, a bias having a polarity opposite to that applied at the time of image transfer is applied to the secondary transfer roller 12. There is something. That is, by applying a bias having the same polarity as the charging polarity of the toner to the secondary transfer roller 12 and generating a repulsive force (repulsive force) between the secondary transfer roller 12 and the toner, The adhered toner is transferred to the intermediate transfer belt 10, and the toner is removed from the intermediate transfer belt by a belt cleaning device or the like. As described above, when the positive and negative biases are alternately applied to the secondary transfer roller 12, there is a possibility that charging and abnormal discharge of the transfer counter roller 8 may be remarkably generated. By applying a material having an electric resistance of 10 ⁵ Ω or less as the material, it is possible to prevent the transfer facing roller 8 from being charged or abnormally discharged.

  Further, as in the second embodiment shown in FIG. 3, both the surface layer portion 82 and the cored bar 81 of the transfer counter roller 8 may be grounded. In this case, a transfer current can flow from both the surface layer portion 82 and the cored bar 81 to the ground, and charging and abnormal discharge of the transfer counter roller 8 can be reliably prevented.

  When foreign matter such as toner adheres to the surface of the transfer counter roller 8, the foreign matter is sandwiched between the transfer counter roller 8 and the conductive sheet 26 as the transfer counter roller 8 rotates. There may be a gap at the point of contact with 26. As a result, if the contact of the conductive sheet 26 with the transfer facing roller 8 becomes poor, the function of passing the transfer current to the ground through the conductive sheet 26 may be reduced or the function may not be performed.

  Therefore, as in the third embodiment shown in FIG. 4, by providing a cleaning member 29 for cleaning the surface of the transfer counter roller 8, foreign matters on the surface of the transfer counter roller 8 can be removed. It is possible to prevent foreign matter from being caught between the conductive sheet 26 and the conductive sheet 26. Thereby, the contact of the conductive sheet 26 with the transfer counter roller 8 can be maintained satisfactorily, and the antistatic effect of the transfer counter roller 8 can be stably exhibited.

  In addition, foreign matter attached to the back surface of the intermediate transfer belt 10 may enter between the intermediate transfer belt 10 and the transfer counter roller 8 as the intermediate transfer belt 10 travels. When the foreign matter that has entered between the intermediate transfer belt 10 and the transfer counter roller 8 aggregates and grows, a convex portion is formed on the surface of the intermediate transfer belt 10 due to the grown foreign matter. As described above, when the convex portion is formed on the surface of the intermediate transfer belt 10, the contact of the secondary transfer roller 12 and the contact of the belt cleaning member with the intermediate transfer belt 10 are not satisfactorily performed, and the image transfer is performed. There is a risk that defects such as defects and cleaning defects may occur.

  In order to solve the above problem, as shown in Example 4 shown in FIG. 5, a belt back surface cleaning member 32 is provided on the back surface of the intermediate transfer belt 10, and foreign matter adhered to the back surface of the intermediate transfer belt 10 by the belt back surface cleaning member 32. It is desirable to remove. Further, in order to prevent foreign matters from entering between the intermediate transfer belt 10 and the transfer counter roller 8 more effectively, the belt back surface cleaning member 32 is arranged so that the contact start position between the intermediate transfer belt 10 and the transfer counter roller 8 is reached. It is preferable to be disposed near E (see FIG. 5).

  Therefore, in Example 4 shown in FIG. 5, the contact direction of the conductive sheet 26 is set to the counter direction with respect to the rotation direction of the transfer counter roller 8. That is, when the conductive sheet 26 is contacted in the counter direction, the contact position of the conductive sheet 26 with respect to the transfer counter roller 8 is set to the intermediate position compared to the case where the conductive sheet 26 is contacted in the trailing direction (see FIG. 2). The distance from the contact start position E between the transfer belt 10 and the transfer counter roller 8 can be increased, and a space for arranging the belt back surface cleaning member 32 and the like can be secured.

  As in the first embodiment shown in FIG. 2, the conductive sheet 26 is brought into contact with the rotation direction of the transfer counter roller 8 in the trailing direction, compared with the case where the conductive sheet 26 is brought into contact with the counter direction. Further, there is an advantage that the conductive sheet 26 is less likely to be twisted or rolled up due to the rotation of the transfer counter roller 8. By preventing the conductive sheet 26 from being twisted or entangled, it is possible to prevent the conductive sheet 26 from being damaged (scratched, etc.) or from being poorly contacted with the transfer facing roller 8. However, even when the conductive sheet 26 is brought into contact with the counter direction, for example, by applying a material having a small friction coefficient to the material of the conductive sheet 26, the conductive sheet 26 is interposed between the conductive sheet 26 and the transfer counter roller 8. If the generated frictional resistance is reduced, it is possible to prevent the conductive sheet 26 from curling or getting caught.

  As described above, in order for the transfer current to flow through the conductive sheet 26 to the ground, the contact pressure of the conductive sheet 26 against the transfer counter roller 8 needs to be a certain value or more. However, when the conductive sheet 26 is formed of a member having low rigidity (soft), it may be considered that necessary contact pressure cannot be secured.

  Therefore, the apparent rigidity of the conductive sheet 26 can be improved by attaching the contact assisting member 33 having higher rigidity to the conductive sheet 26 as in the fifth embodiment shown in FIG. is there. Thereby, even if the conductive sheet 26 is formed of a member having low rigidity, the contact pressure against the transfer facing roller 8 can be sufficiently secured by providing the contact assisting member 33. Furthermore, by improving the apparent rigidity of the conductive sheet 26, the conductive sheet 26 can be prevented from curling or entraining as the transfer counter roller 8 rotates. In addition, by adopting such a configuration, it is possible to apply a material having low rigidity to the material of the conductive sheet 26, so that the selection range of the material is expanded.

  In Example 6 shown in FIG. 7, the contact direction of the conductive sheet 26 is a counter direction with respect to the rotation direction of the transfer counter roller 8, and the contact pressure (contact point) of the conductive sheet 26 with respect to the transfer counter roller 8. The linear pressure is set to 1 N / m or more. By setting the contact direction and the contact pressure of the conductive sheet 26 in this way, foreign matter attached to the surface of the transfer facing roller 8 by the conductive sheet 26 can be removed. That is, the conductive sheet 26 also functions as an antistatic means and a cleaning means for the transfer counter roller 8. Accordingly, in the sixth embodiment shown in FIG. 7, it is not necessary to separately provide the cleaning member 29 for cleaning the transfer facing roller 8 unlike the third embodiment shown in FIG. Reduction can be achieved. In FIG. 7, the contact assisting member 33 is attached to the conductive sheet 26. However, if the contact pressure of the conductive sheet 26 against the transfer facing roller 8 can be secured to 1 N / m or more, the contact assisting member 33 is provided. It can be omitted.

  Further, as in Example 7 shown in FIG. 8, when the conductive sheet 26 is attached to the support member 27 by the double-sided adhesive tape 28, the conductive sheet 26 is attached using a fastening member such as a screw. As compared with the case of performing the mounting, the mounting work is simplified, and space saving and miniaturization can be achieved. Furthermore, since the double-sided adhesive tape 28 is inexpensive, it is possible to reduce the manufacturing cost.

  Further, depending on the use environment of the image forming apparatus, the temperature, humidity, etc. in the apparatus may change significantly. Therefore, the expansion and contraction amounts of the conductive sheet 26 and the double-sided adhesive tape 28 are different from each other. As a result, there is a case where waving or twisting occurs at the tip of the conductive sheet 26. When the leading end of the conductive sheet 26 is deformed, for example, undulated or twisted, and a gap is generated between the leading end of the conductive sheet 26 and the transfer counter roller 8, the transfer current is grounded through the conductive sheet 26. There is a possibility that the function of flowing through the battery will deteriorate or that the function cannot be performed.

  Therefore, as in Example 8 shown in FIG. 9, by forming slits 28a in the double-sided adhesive tape 28, the difference in expansion and contraction due to the difference in linear expansion coefficient between the conductive sheet 26 and the double-sided adhesive tape 28 is absorbed. Therefore, it is possible to prevent deformation of the conductive sheet 26 such as undulation or twisting. Thereby, the contact of the conductive sheet 26 with the transfer counter roller 8 can be maintained satisfactorily, and the antistatic effect of the transfer counter roller 8 can be stably exhibited.

  Although the present invention has been described above, the present invention is not limited to the above-described embodiments, and it is needless to say that various modifications can be made without departing from the gist of the present invention. For example, a member such as a non-rotating pad may be applied as the transfer counter member in addition to the transfer counter roller that is a rotating body. In the above embodiment, the configuration of the present invention is applied to an indirect transfer type image forming apparatus as an example. However, the direct transfer type image forming apparatus as shown in FIG. Configuration can be applied. Specifically, charging and abnormal discharge of the transfer counter roller 7A can be prevented by bringing a conductive contact member into contact with the transfer counter roller 7A shown in FIG. The configuration of the present invention can also be applied to other copiers, printers, facsimiles, or multifunction peripherals thereof.

6 Transfer device 10 Intermediate transfer belt (belt)
12 Secondary transfer roller (transfer member)
24 Power supply 25 Contact member 26 Conductive sheet 27 Support member 28 Double-sided adhesive tape 28a Slit 29 Cleaning member (cleaning means)
30 Grounding path 31 Grounding path 33 Contact assisting member 81 Core metal 82 Surface layer part

JP 2008-209602 A

Claims (12)

In a transfer apparatus comprising a belt for carrying an image on the surface, a transfer member to which a transfer voltage is applied from a power source, and a transfer counter member disposed to face the transfer member via the belt,
A transfer apparatus comprising a conductive contact member that contacts the surface of the transfer facing member, and the contact member is grounded. The transfer device according to claim 1, wherein the contact member has an electric resistance of 10 ⁵ Ω or less.   The transfer device according to claim 1, further comprising a cleaning unit that removes foreign matter on the surface of the rotating body when the transfer facing member is a rotating body.   When the transfer facing member is a rotating body and the contact member is formed of a conductive sheet, the direction in which the conductive sheet is brought into contact with the rotating body is trailing with respect to the rotation direction of the rotating body. The transfer device according to claim 1, wherein the transfer device is in a direction.   When the transfer counter member is a rotating body and the contact member is formed of a conductive sheet, the direction in which the conductive sheet is brought into contact with the rotating body is a counter direction with respect to the rotation direction of the rotating body. The transfer device according to any one of claims 1 to 3.   The transfer device according to claim 5, wherein a contact pressure of the conductive sheet against the rotating body is 1 N / m or more.   The transfer device according to claim 1, wherein the contact member is formed of a conductive sheet, and a contact assisting member having higher rigidity than the conductive sheet is attached to the conductive sheet.   The transfer device according to any one of claims 1 to 7, wherein the contact member is attached to a support member that forms at least a part of a grounding path via a conductive double-sided adhesive tape.   The transfer device according to claim 8, wherein a slit is formed in the conductive double-sided adhesive tape.   The transfer device according to claim 1, wherein the transfer counter member is configured by a roller having a middle resistance surface layer portion disposed on an outer periphery of a cored bar.   The transfer device according to claim 10, wherein the core metal is grounded.   An image forming apparatus comprising the transfer device according to claim 1.

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