JP4211294B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine to which an electrophotographic system is applied, and in particular, a developing unit formed on an image carrier such as an intermediate transfer member. The present invention relates to an image forming apparatus of a type that transfers onto a transfer material using.
[0002]
[Prior art]
Conventionally, as an image forming apparatus such as a copying machine, a printer, a facsimile, or a composite machine using this type of electrophotographic method, a developed image formed on a photosensitive drum is directly transferred onto a transfer material by a transfer member. After transfer, or after primary transfer of developed images of different colors such as yellow, magenta, cyan, black, etc. formed on a single or multiple photosensitive drums onto an intermediate transfer member in the form of a belt or drum In some cases, a black-and-white or full-color image is formed by performing secondary transfer from the belt-shaped or drum-shaped intermediate transfer body onto a transfer material at once by a transfer member.
[0003]
In such an image forming apparatus, a guide member for guiding a transfer material is provided at a nip portion between the photosensitive drum and the transfer member and a nip portion between the belt-shaped or drum-shaped intermediate transfer member and the transfer member. However, if the transfer material is not guided to the nip portion in an appropriate posture by the guide member, the transfer material is transported to the transfer member side and an excessive transfer electric field acts, or the rear end of the transfer material is the guide member When it passes through, the rear end of the transfer material jumps up, and the image is disturbed.
[0004]
Therefore, in order to solve such problems, as disclosed in JP-A-6-3974 and the like, the most downstream end of the transfer material guide on the transfer member side is arranged on the image carrier side including the tangent line of the transfer nip. Thus, a technique for reducing image scattering (blurring) due to gap transfer immediately before the transfer nip has been proposed.
[0005]
More specifically, as shown in FIG. 10, the image forming apparatus according to the above-mentioned Japanese Patent Application Laid-Open No. 6-3974 has an image carrier 100 and an image carrier 100 for electrostatically transferring a toner image on the image carrier 100 to a transfer material. In an image forming apparatus having a transfer charging member 101 that contacts and a guide member 102 that guides a transfer material to a transfer position, an end 102 a on the most downstream side that guides the transfer material of the guide member 102 has an image bearing The tangent L of the image carrier 100 at the point on the most upstream side in the transfer material moving direction in the contact portion between the body 100 and the transfer charging member 101₁The angle formed between the transfer material guide surface of the guide member 102 and the horizontal direction is L₁And the angle formed by the horizontal direction.
[0006]
[Conspiracy to be solved by the invention]
However, the above prior art has the following problems. That is, in the case of the image forming apparatus according to the above-mentioned Japanese Patent Application Laid-Open No. 6-3974, the distance between the most downstream end 102a of the guide member 102 and the transfer nip is not defined. When the most downstream end 102a of the guide member 102 on the transfer charging member side is disposed at a position far away from the nip, the rear end of the transfer material 103 is transferred as shown in FIGS. After leaving the most downstream end 102a of the guide member 102 on the charging member side, it falls to the transfer charging member 101 side, image scattering (blurring) occurs due to the drop of the transfer material 103, and the transfer material 103 is charged by transfer charging. There is a problem in that the member 101 receives an excessive transfer electric field locally, and the toner is charged to a reverse polarity, resulting in a transfer leak (missing white point).
[0007]
More specifically, as shown in FIG. 13, when the posture of the transfer material 102 entering the transfer nip portion is closer to the transfer charging member 101 side than the nip tangent, the transfer material 103 is transferred to the transfer charging member 101 immediately before the nip portion. As a result, the image is scattered due to gap transfer (blurring), or the transfer material 103 is locally subjected to an excessive transfer electric field by the transfer charging member 101 and is directed from the transfer material 103 toward the image carrier 100. As a result, local discharge (transfer leakage) occurs, and the toner exposed to the discharge is charged with a reverse polarity and cannot be transferred, resulting in white spot missing. In particular, as shown in FIG. 12, when the rear end of the transfer material 103 falls and the posture changes suddenly as shown in FIG. 12, an electric field change in the vicinity of the transfer nip portion occurs abruptly. .
[0008]
As shown in FIG. 11, this problem is remarkable in an image forming apparatus that employs a layout in which the conveying roller 104 that conveys the transfer material 103 to the transfer nip is positioned closer to the transfer charging member 101 than the tangent to the transfer nip. is there. In addition, when an image carrier having a large outer diameter is used, the clearance necessary for the entry and transfer of the transfer material into the nip portion is set at the most downstream end of the guide member on the image carrier and the transfer charging member side. If an attempt is made to secure the gap between them, the most downstream end of the guide member on the transfer charging member side must be arranged at a position far away from the nip portion, and the above-described image scattering (blur) or transfer leak (white point missing) The problem that it is easy to occur.
[0009]
When the image carrier is an elastic member and the transfer charging member is made of a high hardness member, the transfer nip portion has a high hardness photoconductor drum and a low hardness transfer charging member. Therefore, after the transfer material has a posture in which the transfer material is easily wound around the transfer charging member side and the rear end of the transfer material leaves the most downstream end of the guide on the transfer charging member side, the transfer charging member side And the problem of image splattering (blur) and transfer leakage (missing white spots) easily occurs.
[0010]
Furthermore, when printing an image on both sides of the transfer material, if the image is transferred to the second side of the transfer material, if the first side is curled to the image side, the trailing edge of the transfer material will drop drastically, This problem occurs remarkably.
[0011]
Further, in the case of a layout in which the most downstream end of the transfer material guide member is closer to the image carrier side than the nip tangent, the rebound when the rear end of the transfer material leaves the most downstream end of the guide member becomes large. For this reason, the above-mentioned problems such as image scattering (blur) and transfer leakage (missing white spots) occur remarkably.
[0012]
Accordingly, the present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is to provide a posture of a transfer material guided to a transfer nip formed by an image carrier and a transfer member. By controlling the diameter, the diameter of the image carrier and the relationship between the hardness of the image carrier and the transfer member can be arbitrarily set to increase the degree of design freedom. Another object of the present invention is to provide an image forming apparatus capable of preventing image quality defects such as image scattering (blurring) and transfer leakage (white spot missing).
[0013]
[Means for Solving the Problems]
  In order to solve the above problems, the invention described in claim 1 is
  An image carrier that carries a toner image; a transfer member that presses against the image carrier to form a transfer nip portion that transfers the toner image carried on the image carrier to a transfer material; and transfers the transfer material A guide member that guides to the nip portion, and a conveyance member that is disposed closer to the transfer member than a tangent line of the transfer nip portion, and that conveys the transfer material to the transfer nip portion.,In an image forming apparatus comprising:
  The guide member includes an image carrier side guide member disposed on the image carrier side with respect to the transfer material, and a transfer member side guide member disposed on the transfer member side with respect to the transfer material,
  The image carrier side guide member is arranged such that the most downstream end of the image carrier side guide member in the transfer material conveyance direction is spaced apart from the tangent line of the transfer nip portion toward the transfer member side,
  The transfer member side guide member lowers the front end portion side between a front end portion located downstream of the transfer member side guide member in the transfer material conveyance direction and an intermediate portion located in front of the front end portion. And forming a bent portion facing the transfer member at the downstream end of the transfer member side guide member in the transfer agent conveying direction.
  A film is affixed to the transfer material side surface at the tip, and the film tip of the film is disposed closer to the image carrier than the tangent to the transfer nip,
A space was formed between the leading end of the film and the bent portion by a notched portion that was cut obliquely.An image forming apparatus characterized by the above.
[0015]
further,Claim 2The invention described in (1) is characterized in that the surface of the image carrier is an intermediate transfer member having elasticity.Claim 1The image forming apparatus described.
[0016]
Furthermore,Claim 3In the invention described in the item 1, the transfer member is composed of a transfer roller having an Asker C hardness of 70 degrees or more.Claim 1 or 2The image forming apparatus described in the above.
[0017]
or,Claim 4The invention described in the aboveTransfer member side guide memberThe distance between the guide surface and the image carrier is set to 1.5 mm or more.Claims 1 to 3The image forming apparatus according to any one of the above.
[0018]
Furthermore,Claim 5The invention described in the aboveTransfer member side guide memberThe guide surface of the image carrier is closest to the image carrier, or the bent portion is formed concentrically with the surface of the image carrier.Claims 1 to 4The image forming apparatus according to any one of the above.
[0020]
further,Claim 6The invention described in the aboveTransfer member side guide memberAt least a part from the most upstream part of the sheet to the tangent line of the transfer nip part or a part located on the image carrier side with respect to the tangent line is constituted by an elastic film that can be elastically deformed by passing the transfer material.Claims 1 to 5The image forming apparatus according to any one of the above.
[0021]
or,Claim 7The invention described in the aboveTransfer member side guide memberOf the guide surface, the volume resistance of the portion where the back surface of the transfer material rubs is 10⁷  -10^TenIt is formed of a semiconductive member of Ω · cmClaims 1 to 6The image forming apparatus according to any one of the above.
[0022]
further,Claim 8The invention described in the aboveTransfer member side guide memberOf the guide surface, the volume resistance of the portion where the back surface of the transfer material rubs is 10⁶  It is formed of a conductive member of Ω · cm or less, and a portion where the back surface of the transfer material is rubbed is grounded via a high resistance element or a constant voltage element.Claims 1 to 6The image forming apparatus according to any one of the above.
[0023]
Furthermore,Claim 9The invention described in the aboveTransfer member side guide memberOf the guide surface, a portion where the back surface of the transfer material rubs is formed by a member that is charged to the same polarity as the toner by rubbing with the transfer material.Claims 1 to 8The image forming apparatus according to any one of the above.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0025]
Embodiment 1
FIG. 2 shows a tandem type full-color printer as an image forming apparatus according to Embodiment 1 of the present invention.
[0026]
In FIG. 2, 01 indicates the main body of a tandem type full-color printer. The printer main body 01 is roughly divided into a print head device (Print Head Device) 02 for forming a full-color image, and this. ROS (Raster Output Scanner) (exposure device) 03 for performing image exposure on the four photosensitive drums (image carriers) 11, 12, 13 and 14 of the print head device 02, and developing devices for the respective colors of the print head device 02 Four toner boxes 04Y, 04M, 04K, 04C that supply toners of colors corresponding to 41, 42, 43, and 44, and a paper feed cassette 05 that supplies transfer paper P as a transfer material to the print head device 02, The fixing device 06 that performs a fixing process on the transfer paper P onto which the toner image is transferred from the print head device 02, and the transfer paper P on which the image is fixed on one side by the fixing device 06 are In the reversed state, the double-sided conveyance path 07 for conveying again to the transfer unit of the print head device 02, the manual sheet feeding means 08 for feeding desired transfer paper P from the outside of the printer main body 01, and the operation of the printer. A controller 09 including a control circuit for controlling, an image processing circuit for performing image processing on an image signal, and the like, and an electric circuit 10 including a high-voltage power supply circuit are provided. In FIG. 2, T indicates a discharge toilet for discharging the transfer paper P on which an image is formed. The discharge toilet T is integrally disposed on the upper portion of the printer main body 01.
[0027]
Of the various members arranged in the printer main body 01, ROS03 as an exposure device is image data corresponding to each color of yellow (Y), magenta (M), black (K), and cyan (C). From four semiconductor lasers that are driven to light based on the above, four laser beams emitted from these four semiconductor lasers, f-θ lenses for deflecting scanning, polygon mirrors, or a plurality of reflection mirrors It is configured.
[0028]
FIG. 3 shows a print head device of a tandem type full-color printer as an image forming apparatus according to Embodiment 1 of the present invention. In addition, the arrow in FIG. 3 has shown the rotation direction of each rotation member.
[0029]
As shown in FIG. 3, the print head device 02 includes yellow (Y), magenta (M), black (K), and cyan (C) photosensitive drums (image carriers) 11, 12, 13, and the like. Image forming units 1, 2, 3, 4 having 14 and charging rolls (contact-type charging devices) 21, 22, 23, 24 for primary charging that are in contact with the photosensitive drums 11, 12, 13, 14; ROS (exposure device) 03 (see FIG. 2) for irradiating laser light 31, 32, 33, 34 of each color of yellow (Y), magenta (M), black (K), cyan (C), and the above photoreceptor Developing devices 41, 42 for developing the electrostatic latent images formed on the drums 11, 12, 13, 14 with toners of yellow (Y), magenta (M), black (K), and cyan (C). , 43, 44 and a first primary intermediate as an intermediate transfer member that contacts two of the four photosensitive drums 11, 12, 13, and 14 A second primary intermediate transfer drum (image carrier) 52 in contact with the transfer drum (image carrier) 51 and the other two photosensitive drums 13 and 14, and the first and second primary intermediate transfer drums 51, A secondary intermediate transfer drum (image carrier) 53 as an intermediate transfer member that contacts 52 and a final transfer roll (transfer electric field applying rotator) 60 that contacts the secondary intermediate transfer drum 53, the main part of which is It is configured.
[0030]
The photosensitive drums 11, 12, 13, and 14 are arranged at a constant interval so as to have a common tangential plane M.sub.2. Further, the first primary intermediate transfer drum 51 and the second primary intermediate transfer drum 52 are surfaces whose rotational axes are parallel to the photosensitive drums 11, 12, 13, and 14 and have predetermined symmetry planes as boundaries. They are arranged in a symmetrical relationship. Further, the secondary intermediate transfer drum 53 is arranged so that the rotation axis thereof is parallel to the photosensitive drums 11, 12, 13, and 14.
[0031]
A signal corresponding to the image information for each color is rasterized by an image processing circuit disposed in the electric circuit 10 (see FIG. 2) and input to the ROS03. In this ROS03, the laser beams 31, 32, 33, and 34 of yellow (Y), magenta (M), black (K), and cyan (C) are modulated, and the corresponding photosensitive drums 11, 12, and 12 are modulated. 13 and 14 are irradiated.
[0032]
Around each of the photosensitive drums 11, 12, 13, and 14, an image forming process for each color is performed by a known electrophotographic method. First, as the photoconductor drums 11, 12, 13, and 14, for example, photoconductor drums using an OPC photoconductor with a diameter of 30 mm are used. These photoconductor drums 11, 12, 13, and 14 are, for example, It is rotationally driven at a rotational speed of 104 mm / sec. As shown in FIG. 3, a DC voltage of about −1000 V is applied to the surfaces of the photosensitive drums 11, 12, 13, and 14 to charging rolls 21, 22, 23, and 24 as contact type charging devices. For example, it is charged to about -500V. The contact-type charging device includes a roll type, a film type, a brush type, and the like, but any type may be used. In this embodiment, a charging roll generally used in an electrophotographic apparatus in recent years is employed. Further, in order to charge the surfaces of the photosensitive drums 11, 12, 13, and 14, in this embodiment, a charging method in which only DC is applied is used, but a charging method in which AC + DC is applied may be used.
[0033]
Thereafter, laser light 31 corresponding to each color of yellow (Y), magenta (M), black (K), and cyan (C) is formed on the surfaces of the photosensitive drums 11, 12, 13, and 14 by ROS03 as an exposure device. , 32, 33, and 34 are irradiated, and an electrostatic latent image corresponding to input image information for each color is formed. When the electrostatic latent image is written by ROS03, the surface potential of the image exposure portion of the photosensitive drums 11, 12, 13, and 14 is discharged to about -100V or less.
[0034]
In addition, the electrostatic latent images corresponding to the respective colors of yellow (Y), magenta (M), black (K), and cyan (C) formed on the surfaces of the photosensitive drums 11, 12, 13, and 14 Are developed by the developing devices 41, 42, 43, and 44, and the yellow (Y), magenta (M), black (K), and cyan (C) colors are formed on the photosensitive drums 11, 12, 13, and 14, respectively. Visualized as a toner image.
[0035]
In this embodiment, as the developing devices 41, 42, 43, 44, a magnetic brush contact type two-component developing method is adopted, but the scope of application of the present invention is not limited to this developing method, Needless to say, the present invention can be sufficiently applied to a non-contact type developing system.
[0036]
The developing devices 41, 42, 43, and 44 are filled with different yellow (Y), magenta (M), black (K), and cyan (C) color toners and a developer. Yes. As shown in FIG. 2, when toner is supplied from the corresponding color toner boxes 04Y, 04M, 04K, 04C to these developing devices 41, 42, 43, 44, the supplied toner is augered. 401 and 402 are sufficiently agitated with the carrier and triboelectrically charged. Inside the developing roll 403, a magnet roll (not shown) having a plurality of magnetic poles arranged at a predetermined angle is fixed. The amount of developer conveyed to the vicinity of the surface of the developing roll 403 is regulated by the developer amount regulating member 404 by the auger 402 that conveys the developer to the developing roll 403. In this embodiment, the amount of the developer is about 30-50 g / m.²At this time, the charge amount of the toner existing on the developing roll 403 is about -20 to -50 μC / g.
[0037]
The toner supplied onto the developing roll 403 is in the form of a magnetic brush composed of a carrier and toner by the magnetic force of the magnet roll, and this magnetic brush comes into contact with the photosensitive drums 11, 12, 13, and 14. ing. A developing bias voltage of AC + DC is applied to the developing roll 403, and the toner on the developing roll 403 is developed into an electrostatic latent image formed on the photosensitive drums 11, 12, 13, and 14 to obtain a toner image. Is formed. In this embodiment, for example, the AC component of the developing bias voltage is set to 4 kHz, 1.6 kVpp, and the DC component is set to about −300V.
[0038]
In this embodiment, in the developing devices 41, 42, 43, and 44, so-called “spherical toner” that is a substantially spherical toner is used, and an average particle diameter of about 3 to 10 μm is used. For example, the average particle diameter of the black toner is set to 8 μm, and the average particle diameter of the color toner is set to 7 μm.
[0039]
As the toner, for example, a toner having PS (polystyrene) as a main component and formed into a spherical shape by a polymerization method is used. The toner used in the present embodiment has a toner shape factor defined by the following formula of 120 or less.
Toner shape factor =
((Maximum length of toner particle size)²× π / (4 × toner projected area)) × 100
[0040]
Next, the yellow (Y), magenta (M), black (K), and cyan (C) toner images formed on the photosensitive drums 11, 12, 13, and 14 are first primary images. The primary transfer is electrostatically performed on the intermediate transfer drum 51 and the second primary intermediate transfer drum 52. The yellow (Y) and magenta (M) toner images formed on the photosensitive drums 11 and 12 are formed on the first primary intermediate transfer drum 51 on the black ( The toner images of K) and cyan (C) are transferred onto the second primary intermediate transfer drum 52, respectively. Therefore, on the first primary intermediate transfer drum 51, the single color image transferred from either the photosensitive drum 11 or 12 and the two color toner images transferred from both the photosensitive drums 11 and 12 are superimposed. A double color image is formed. In addition, similar single-color images and double-color images are also formed on the second primary intermediate transfer drum 52 from the photosensitive drums 13 and 14.
[0041]
The surface potential necessary for electrostatically transferring the toner image from the photosensitive drums 11, 12, 13, 14 onto the first and second primary intermediate transfer drums 51, 52 is about +250 to 500V. It is. This surface potential is set to an optimum value depending on the charged state of the toner, the ambient temperature, and the humidity. The ambient temperature and humidity can be easily known by detecting the resistance value of a member having a characteristic that the resistance value varies depending on the ambient temperature and humidity. As described above, the surface of the first and second primary intermediate transfer drums 51 and 52 when the charge amount of the toner is in the range of −20 to −50 μC / g and is in a normal temperature and humidity environment. The potential is preferably about + 400V.
[0042]
For example, the first and second primary intermediate transfer drums 51 and 52 used in this embodiment are formed to have an outer diameter of 60 mm and a resistance value of 10 mm.⁸It is set to about Ω. The first and second primary intermediate transfer drums 51 and 52 are single-layered or multiple-layered cylindrical rotating bodies whose surfaces are elastic, and generally include Fe or Al as shown in FIG. On the metal pipes 51a and 52a as the metal cores made of, etc., low resistance base elastic rubber layers 51b and 52b represented by conductive silicone rubber or the like (R = 10)²~Ten^FourΩ) is provided in a thickness of about 0.1 to 10 mm, and intermediate layers 51c and 52c made of acrylic rubber having a thickness of 10 to 100 μm are formed on the surfaces of the low resistance base elastic rubber layers 51b and 52b. Is provided. Further, the outermost surfaces of the first and second intermediate transfer drums 51 and 52 are typically high release layers 51d and 52d (ρv = p = 3) having a thickness of 3 to 100 μm made of fluororubber in which fluororesin fine particles are dispersed. Ten¹¹~Ten¹³Ω · cm). The first and second intermediate transfer drums 51 and 52 have an Asker C hardness of about 45 °. What is important here is the resistance value and the releasability of the surface. The resistance value of the intermediate transfer drums 51 and 52 is R = 10.⁶~Ten⁹The material is not particularly limited as long as it is about Ω and the high release layers 51d and 52d have a high release property with respect to the toner.
[0043]
The single-color or double-color toner images formed on the first and second primary intermediate transfer drums 51 and 52 in this way are electrostatically secondary-transferred onto the secondary intermediate transfer drum 53. Therefore, a final toner image from a single color image to a quadruple color image of yellow (Y), magenta (M), black (K), and cyan (C) is formed on the secondary intermediate transfer drum 53. Will be.
[0044]
In FIG. 3, a magenta toner image is first transferred from a magenta photosensitive drum 12 onto a first primary intermediate transfer drum 51, and then a yellow toner image is transferred to a yellow photosensitive drum. The toner image is transferred from 11 and superimposed on the magenta toner image transferred earlier. On the second primary intermediate transfer drum 52, a cyan toner image is first transferred from the cyan photosensitive drum 14, and then a black toner image is transferred from the black photosensitive drum 13. The cyan toner image transferred previously is superimposed and transferred.
[0045]
In the embodiment according to the present invention shown in FIG. 3, the process distance from the formation of the electrostatic latent image to the transfer of the full color toner image onto the paper is different for each color. Therefore, in the embodiment shown in FIG. 3, since images are not written by laser light in the order of magenta image, yellow image, cyan image, and black image, the first and second primary intermediate transfer drums 5 1, 52 are The order of the toner images to be overlaid is determined.
[0046]
As described above, the toner images formed on the first and second primary intermediate transfer drums 51 and 52 are transferred from the first primary intermediate transfer drum 51 to yellow and magenta with respect to the secondary intermediate transfer drum 53. After being collectively transferred in order, the second primary intermediate transfer drum 52 is collectively transferred in the order of black and cyan.
[0047]
The surface potential necessary for electrostatically transferring the toner image from the first and second primary intermediate transfer drums 51 and 52 onto the secondary intermediate transfer drum 53 is about +600 to 1200V. This surface potential is the same as when the toner is transferred from the photosensitive drums 11, 12, 13, 14 to the first primary intermediate transfer drum 51 and the second primary intermediate transfer drum 52. Will be set to the optimum value. Further, since what is necessary for the transfer is a potential difference between the first and second primary intermediate transfer drums 51 and 52 and the secondary intermediate transfer drum 53, the first and second primary intermediate transfer drums 51 and 52 have different potentials. It is necessary to set the value according to the surface potential. As described above, the toner charge amount is in the range of −20 to −50 μC / g, the room potential is normal temperature and humidity, and the surface potentials of the first and second primary intermediate transfer drums 51 and 52 are In the case of about +400 V, the surface potential of the secondary intermediate transfer drum 53 is about +850 V, that is, the potential difference between the first and second primary intermediate transfer drums 51 and 52 and the secondary intermediate transfer drum 53 is It is desirable to set to about + 450V.
[0048]
For example, the secondary intermediate transfer drum 53 used in this embodiment has an outer diameter of 60 mm, which is the same as the first and second primary intermediate transfer drums 51 and 52, and has a resistance value of 10 mm.⁷-10¹¹It is set to about Ω. Similarly to the first and second primary intermediate transfer drums 51 and 52, the secondary intermediate transfer drum 53 is a single-layered or cylindrical rotating body having a surface with elasticity, and FIG. As shown, a low resistance base elastic rubber layer 53a (R = 10) typified by conductive silicone rubber or the like is generally formed on a metal pipe 53a as a metal core made of Fe, Al or the like.²~Ten^FourΩ) is provided in a thickness of about 0.1 to 10 mm, and an intermediate layer 53c made of acrylic rubber having a thickness of 10 to 100 μm is provided on the surface of the low resistance base elastic rubber layer 53b. . Further, the outermost surface of the secondary intermediate transfer drum 53 is typically a high release layer 53d (ρv = 10) having a thickness of 3 to 100 μm of fluororubber in which fluororesin fine particles are dispersed.¹¹~Ten¹³Ω · cm). The secondary intermediate transfer drum 53 has an Asker C hardness of about 45 °. Here, the resistance value of the secondary intermediate transfer drum 53 needs to be set higher than that of the first and second primary intermediate transfer drums 51 and 52. Otherwise, the secondary intermediate transfer drum 53 will charge the first and second primary intermediate transfer drums 51, 52, making it difficult to control the surface potential of the first and second primary intermediate transfer drums 51, 52. Become. The material is not particularly limited as long as the material satisfies such conditions.
[0049]
Next, a final toner image from a single color image to a quadruple color image formed on the secondary intermediate transfer drum 53 is printed on a sheet by a final transfer roll 60 to which a transfer voltage of about +2000 V is applied. Tertiary transfer is performed on the paper P passing through the conveyance path. The paper P passes through a paper transporting roll 90 through a paper feeding process (not shown), and is fed into the nip portion between the secondary intermediate transfer drum 53 and the final transfer roll 60. After this final transfer step, the final toner image formed on the paper is fixed by the fixing device 06, and a series of image forming processes is completed.
[0050]
The final transfer roll 60 as a transfer electric field application roll is a cylindrical rotating body having elasticity, and as shown in FIG. 6, on a metal core 60a as a metal core made of SUS or the like having a diameter of about 12 mm, The elastic layer 60b made of solid urethane having a thickness of about 2 mm and the surface layer 60C made of fluorine-based resin having a thickness of about 10 μm are covered. The final transfer roll 60 is rotated by a driving force transmitted from the secondary intermediate transfer drum 53 via a gear or driven by a frictional driving force with the secondary intermediate transfer drum 53.
[0051]
Note that after being transferred at the transfer nip portion between the secondary intermediate transfer drum 53 and the final transfer roll 60, the residual toner is electrostatically or physically removed by a cleaner. The cleaner 62 has a rotating cylindrical shape and ρv = 10.²~Ten^ThreeIt is a conductive roll having a resistance of about Ω · cm. An applied voltage of about +1200 V is applied to electrostatically attract and remove residual toner.
[0052]
Similarly, the first and second primary intermediate transfer drums 51 and 52 are also provided with a cleaner, and an applied voltage of about +800 V is applied. Residual toner after the secondary transfer performed between the first and second primary intermediate transfer drums 51 and 52 and the secondary intermediate transfer drum 53 is removed by electrostatic and physical rotational sliding force. The material of the cleaners 63 and 64 is the same as that of the cleaner 62.²~Ten^ThreeIt is a conductive roll having a resistance of about Ω · cm.
[0053]
By the way, an image forming apparatus according to this embodiment includes an image carrier that carries a toner image, and a transfer nip that presses the image carrier and transfers the toner image carried on the image carrier to a transfer material. A transfer member that forms a transfer portion, a guide member that guides the transfer material to the transfer nip portion, a transfer member that is disposed closer to the transfer member than a tangent to the transfer nip portion, and that transports the transfer material to the transfer nip portion; In the image forming apparatus, the guide surface of the guide member disposed on the transfer member side among the guide members is at least one or more in a portion other than the most upstream end and the most downstream end in the transfer material conveyance direction. It is configured to be arranged on the tangent line of the transfer nip portion or on the image carrier side of the tangent line.
[0054]
Further, in this embodiment, a bent portion that is bent toward the transfer member side is provided at a tip portion of the guide member that is disposed on the transfer member side among the guide members, and at least a part of the bent portion is provided. Are arranged on the tangent line of the transfer nip portion or closer to the image carrier side than the tangent line.
[0055]
Further, in this embodiment, the closest portion of the guide surface of the guide member arranged on the transfer member side with the image carrier is formed concentrically with the surface of the image carrier. Yes.
[0056]
Furthermore, in this embodiment, the guide member arranged on the image carrier side is arranged on the transfer member side with respect to the tangent line of the transfer nip portion.
[0057]
FIG. 1 is a block diagram showing a main part of a tandem type full-color printer as an image forming apparatus according to Embodiment 1 of the present invention.
[0058]
That is, in the tandem type full color printer according to this embodiment, as shown in FIG. 1, a final transfer roll 60 as a transfer member is pressed against the surface of a secondary intermediate transfer drum 53 as an image carrier, Between the secondary intermediate transfer drum 53 and the final transfer roll 60, a transfer nip portion 70 in which the secondary intermediate transfer drum 53 side is deformed into a concave shape is formed.
[0059]
Further, on the upstream side of the transfer nip portion 70 between the secondary intermediate transfer drum 53 and the final transfer roll 60, a resist roll 90 as a conveying means for conveying the transfer material P to the transfer nip portion is provided on the transfer nip portion 70. Is positioned closer to the final transfer roll 60 than the tangent line L at a position separated by a predetermined distance.
[0060]
Further, on the upstream side of the transfer nip portion 70 between the secondary intermediate transfer drum 53 and the final transfer roll 60, the transfer material P conveyed by the resist roll 90 between the resist roll 90 and the transfer nip portion 70. Guide members 71 and 72 for guiding the toner to the transfer nip portion 70 are provided.
[0061]
These guide members 71 and 72 are arranged on the front surface side of the transfer material P, that is, on the secondary intermediate transfer drum 53 side, and on the back surface side of the transfer material P, that is, on the final transfer roll 60 side. And a guide member 72. Further, the guide member 71 disposed on the secondary intermediate transfer drum 53 side is formed of, for example, a metal plate-like member (sheet metal), and the most downstream end 71a of the guide member is the transfer nip portion 70. Is located farther from the tangent line L to the final transfer roll 60 side. As a result, when the transfer material P enters the transfer nip portion 70 and curves, the transfer material P curves in the space formed at the most downstream end 71a of the guide member 71. The guide member 71 is set so that the front end of the transfer material P guided by the guide member 71 enters a position at a predetermined angle θ from the horizontal direction of the secondary intermediate transfer drum 53.
[0062]
Further, the guide member 72 disposed on the final transfer roll 60 side is formed of, for example, a thick plate-like member made of synthetic resin, and the guide surface 73 of the guide member 72 is in the transfer material conveyance direction. At a portion other than the most upstream end 72a and the most downstream end 72b, the bent portion 74, which is an intermediate portion, is arranged so as to be positioned slightly closer to the secondary intermediate transfer drum 53 side than the tangent line L of the transfer nip portion 70. ing. Note that the guide surface 73 of the guide member 72 is a portion other than the most upstream end 72a and the most downstream end 72b in the transfer material conveyance direction, and the bent portion 74, which is an intermediate portion, is tangent L of the transfer nip portion 70 only at one place. You may arrange | position so that it may be located on. Further, the guide member 72 has a bent portion in which a portion 74 in the vicinity of the most downstream end 72b is bent at an angle larger than approximately 90 degrees toward the transfer material side. The curved portion 74 is formed such that a guide surface 73 b on the secondary intermediate transfer drum 53 side is curved concentrically with the surface of the secondary intermediate transfer drum 53. Further, the gap between the guide surface 72b of the guide member 72 on the secondary intermediate transfer drum 53 side and the surface of the secondary intermediate transfer drum 53 is set to 1.5 mm, for example. The gap between the most downstream end 72b of the guide member 72 and the final transfer roll 60 is set to 1.0 mm, for example.
[0063]
The guide member 72 disposed on the final transfer roll 60 side is formed of, for example, ABS resin. The guide member 72 is a transfer surface among the guide surfaces 73 of the guide member 72 disposed on the transfer roll 60 side. The volume resistance is 10 including the part where the back surface of the material P rubs.⁷-10^TenIt may be formed of a semiconductive member of Ω · cm.
[0064]
Further, the guide member 72 has a volume resistance of 10 on the portion of the guide surface 73 of the guide member 72 disposed on the transfer roll 60 side where the back surface of the transfer material P rubs.⁶The conductive member may be formed of a conductive member of Ω · cm or less, and the portion where the back surface of the transfer material P rubs may be grounded via a high resistance element or a constant voltage element.
[0065]
Further, the guide member is configured such that a portion of the guide surface 73 of the guide member 72 arranged on the transfer member side that the back surface of the transfer material P rubs is rubbed with the transfer material P by toner (negative charging property). It may be configured to be formed of a member (for example, PP or PE) that is charged with the same polarity.
[0066]
Further, the guide member 72 disposed on the final transfer roll 60 side is provided with a step 77 having a lower end portion 76 side between the intermediate portion 75 and the end portion 76, and the end portion. On the surface of 76, a Mylar film 78 (trade name) made of PET for reducing the frictional resistance with the transfer material P is attached. The tip of the mylar film 78 is positioned slightly closer to the secondary intermediate transfer drum 53 side than the tangent line L of the transfer nip portion 70 as the guide surface 73a of the guide member 72. Further, the intermediate portion 75 of the guide member 72 is formed by a plurality of ribs formed along the conveyance direction of the transfer material P. The intermediate portion 75 only guides the front end portion of the transfer material P. It is desirable that the back surface of the transfer material P be disposed at a position where it does not rub as much as possible.
[0067]
In the above configuration, in the image forming apparatus according to this embodiment, the image carrier is controlled by controlling the posture of the transfer material guided to the transfer nip formed by the image carrier and the transfer member as follows. Even when the diameter of the body or the relationship between the hardness of the image carrier and the transfer member is arbitrarily set, image scattering (blurring) or transfer is possible even when the degree of freedom of design is expanded or when printing on both sides. It is possible to prevent image quality defects such as leakage (missing white spots) from occurring.
[0068]
That is, in the tandem-type full-color printer, as shown in FIG. 1, the guide surface 73 of the guide member 72 that guides the transfer material P to the transfer nip portion 70 is other than the most upstream end and the most downstream end in the transfer material transport direction. In the portion, the intermediate portion 73a is arranged so that it is located at a position slightly closer to the secondary intermediate transfer drum 53 side than the tangent line L of the transfer nip portion 70. Therefore, the transfer material P guided to the transfer nip 70 by the guide member 72 is slightly secondary intermediate transfer than the tangent L of the transfer nip 70 by the guide surface 73 of the guide member 72 on the final transfer roll 60 side. Since it is once located on the drum 53 side, when the transfer material P enters the transfer nip portion 70, the transfer material P is not too close to the final transfer roll 60 side, and the transfer electric field becomes excessive or gap transfer occurs. In addition, troubles such as image scattering (blurring) and transfer leakage (missing white spots) can be prevented.
[0069]
The transfer material P is guided by the guide surface 73 of the guide member 72 on the side of the final transfer roll 60 to the secondary intermediate transfer drum 53 side slightly from the tangent L of the transfer nip portion 70, and then the guide member 72. Since the second intermediate transfer drum 53 is guided at a predetermined distance by the bent portion 74 up to the most downstream end 72b, after being guided to the secondary intermediate transfer drum 53 side once, the final transfer roll 60 side It is also possible to prevent problems such as image scattering (blur) and transfer leakage (missing white spots) due to the trailing edge of the transfer material P falling to the final transfer roll 60 side. .
[0070]
The inventors made a prototype printer as shown in FIGS. 2 and 3 and set the gap between the guide surface 73 on the secondary intermediate transfer drum 53 side of the guide member 72 and the surface of the secondary intermediate transfer drum 53 to 0. An experiment was conducted to check whether or not a jam occurred when transferring a toner image onto an A4 size paper (P paper, Fuji Xerox Co., Ltd.) by changing from 0.5 mm to 2.0 mm every 0.5 mm.
[0071]
FIG. 7 shows the result of the above experiment. As is clear from FIG. 7, the gap between the guide surface 73 of the guide member 72 on the secondary intermediate transfer drum 53 side and the surface of the secondary intermediate transfer drum 53 is shown as follows. By setting it to 1.5 mm or more, it is possible to transfer the image satisfactorily without causing a jam.
[0072]
FIG. 8 shows a modification of the first embodiment of the present invention. The same reference numerals are given to the same parts as those in the above-described embodiment. In this modification, the tip of the mylar film 78 is shown. A notched portion 79 that is obliquely cut out is provided on the back surface side of the guide member 72 located at a position where the Mylar film 78 is deformed when the transfer material P passes through, thereby improving the running performance of the transfer material P. It is configured as follows.
[0073]
Further, in FIG. 9, the intermediate portion 76 of the guide member 72 is configured to be set longer than the embodiment shown in FIG.
[0074]
【The invention's effect】
As described above, according to the present invention, by controlling the posture of the transfer material guided to the transfer nip formed by the image carrier and the transfer member, the diameter of the image carrier and the image carrier and transfer can be controlled. Even if the degree of freedom of design is expanded by arbitrarily setting the relationship with the hardness of the material, image quality defects such as image scattering (blur) and transfer leakage (white spot missing) are also observed during double-sided printing. An image forming apparatus capable of preventing the occurrence can be provided.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a main part of a tandem full-color printer as an image forming apparatus according to Embodiment 1 of the present invention.
FIG. 2 is a configuration diagram showing a tandem type full-color printer as an image forming apparatus according to Embodiment 1 of the present invention.
FIG. 3 is a block diagram showing a tandem type full-color printer as an image forming apparatus according to Embodiment 1 of the present invention.
FIG. 4 is a cross-sectional view showing a primary intermediate transfer drum.
FIG. 5 is a cross-sectional view showing a secondary intermediate transfer drum as an image carrier.
FIG. 6 is a cross-sectional view showing a final transfer roll as a transfer member.
FIG. 7 is a chart showing experimental results.
FIG. 8 is a block diagram showing a main part of a tandem type full color printer as an image forming apparatus according to a modification of the first embodiment of the present invention.
FIG. 9 is a block diagram showing a main part of a tandem type full color printer as an image forming apparatus according to a modification of the first embodiment of the present invention.
FIG. 10 is a configuration diagram showing a main part of a conventional image forming apparatus.
FIG. 11 is a configuration diagram showing a main part of a conventional image forming apparatus.
FIG. 12 is a configuration diagram showing a main part of a conventional image forming apparatus.
FIG. 13 is a configuration diagram showing a main part of a conventional image forming apparatus.
[Explanation of symbols]
53: secondary intermediate transfer drum (image carrier), 60: final transfer roll (transfer means), 70: transfer nip, 71: guide member (guide member), 72: guide member (guide member).

Claims (9)

An image carrier that carries a toner image; a transfer member that presses against the image carrier to form a transfer nip portion that transfers the toner image carried on the image carrier to a transfer material; and transfers the transfer material a guide member for guiding the nip portion than the tangent of the transfer nip is arranged on the transfer member, in an image forming apparatus and a conveying member that conveys the transfer material to the transfer nip portion,
The guide member includes an image carrier side guide member disposed on the image carrier side with respect to the transfer material, and a transfer member side guide member disposed on the transfer member side with respect to the transfer material,
The image carrier side guide member is arranged such that the most downstream end of the image carrier side guide member in the transfer material conveyance direction is spaced apart from the tangent line of the transfer nip portion toward the transfer member side,
The transfer member side guide member lowers the front end portion side between a front end portion located downstream of the transfer member side guide member in the transfer material conveyance direction and an intermediate portion located in front of the front end portion. And forming a bent portion facing the transfer member at the downstream end of the transfer member side guide member in the transfer agent conveying direction.
A film is affixed to the transfer material side surface at the tip, and the film tip of the film is disposed closer to the image carrier than the tangent to the transfer nip,
An image forming apparatus, wherein a space is formed between the film front end portion and the bent portion by a notched portion cut obliquely . 2. The image forming apparatus according to claim 1, wherein a surface of the image carrier is made of an intermediate transfer member having elasticity. The image forming apparatus according to claim 1, wherein the transfer member includes a transfer roller having an Asker C hardness of 70 degrees or more. 4. The image forming apparatus according to claim 1 , wherein a distance between a guide surface of the transfer member side guide member and a closest portion between the image carrier is set to 1.5 mm or more. . The closest portion or bent portion of the image bearing member of the guide surface of the transfer member side guide member, any one of claims 1 to 4, characterized in that formed concentrically with respect to the surface of the image bearing member The image forming apparatus described in 1. At least part of the transfer member side guide member from the most upstream part to the tangent line of the transfer nip part or the part located on the image carrier side with respect to the tangent line is constituted by an elastic film that can be elastically deformed by passing the transfer material. The image forming apparatus according to claim 1 , wherein the image forming apparatus is an image forming apparatus. Of the guide surface of the transfer member side guide member, according to claim 1, wherein the back surface of the transfer material is a portion to rubbing, the volume resistivity was formed of a semi-conductive member ^{10 7} ~10 10 Ω · cm 7. The image forming apparatus according to any one of items 6 to 6 . Of the guide surface of the transfer member side guide member , a portion where the back surface of the transfer material rubs is formed of a conductive member having a volume resistance of 10 ⁶ Ω · cm or less, and the back surface of the transfer material is rubbed. 7. The image forming apparatus according to claim 1, wherein a portion to be grounded is grounded through a high resistance element or a constant voltage element. Of the guide surface of the transfer member side guide member, to claim 1, characterized in that the back surface of the transfer material is a portion to rubbing were formed by member charged by friction with the transfer material to the toner of the same polarity The image forming apparatus according to claim 8 .

Images