JP3687334B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a copying machine, a printer, a fax machine, etc., in which a charging unit, an image writing unit, and a developing unit are arranged around an image forming body to transfer and fix a toner image formed on the image forming body onto a transfer material. The present invention relates to an electrophotographic image forming apparatus, and more particularly to an image forming apparatus capable of forming images on both sides of a transfer material.
[0002]
[Prior art]
Conventionally, in double-sided image formation, an image on one side formed on an image forming body is transferred and fixed on a transfer material, which is once stored in a double-sided reversal feeding device and formed again on the image forming body. A method is used in which a transfer material is fed from a double-sided reversal feeding device in synchronization with the transferred image, and the image on the other surface is transferred and fixed on the transfer material.
[0003]
In this double-sided image forming apparatus, as described above, the transfer material is conveyed such as feeding to the double-sided reversal feeding device and passing through the fixing device twice. It was the cause of jams and wrinkles.
[0004]
On the other hand, according to Japanese Patent Publication Nos. 49-37538, 54-28740, JP-A-1-44457, and 4-214576, etc., a transfer material can be formed using an image forming body and an intermediate transfer body. It has been proposed to fix the toner image once after forming toner images on both sides.
[0005]
In addition, the inventors of the present application have arranged a plurality of toner image forming means including charging means, image writing means, developing means, etc. around the photosensitive drum (image forming body), and overlaid on the photosensitive drum. The combined color toner image is temporarily transferred (primary transfer) to the intermediate transfer belt (endless belt-shaped intermediate transfer member) once by the first transfer unit, and then the superimposed color toner image is formed again on the photosensitive drum. Then, the transfer material fed in synchronism with the toner image on the photosensitive drum and the toner image on the intermediate transfer belt is charged by the transfer material charging means and is electrostatically brought into close contact with the intermediate transfer member to perform intermediate transfer. Transfer (secondary transfer) the toner image on the photosensitive drum to both surfaces of the transfer material conveyed by the belt as a surface image by a second transfer unit (using the same one as the first transfer unit), Also intermediate After the toner image on the belt is transferred as the back image by the third transfer means (tertiary transfer), the curvature of the roller member that is provided on the fixing device (fixing means) side and stretches the intermediate transfer belt, and if necessary An image forming apparatus and an image forming method are disclosed in which a transfer material is separated from an intermediate transfer belt by static elimination by a transfer material separating unit provided and a toner image on the transfer material is fixed by a fixing device to form a double-sided color image. No. 9-258492 and JP-A-9-258516.
[0006]
[Problems to be solved by the invention]
However, in a double-sided image forming apparatus that forms a double-sided image by transferring a toner image onto both sides of a transfer material using the above-described image-forming body and an endless belt-like intermediate transfer body, the width of the belt-like intermediate transfer body is If the width is larger than the width of the image forming member, the intermediate transfer member is damaged at both ends of the image forming member, and the end of the intermediate transferring member is damaged when used for a long time. Further, when the charging width of the first, second, and third transfer units is made larger than the width of the intermediate transfer member, the toner adheres to the end of the intermediate transfer member, and the attached toner wraps around the back surface of the intermediate transfer member. There arises a problem that a stable running of the transfer body cannot be obtained.
[0007]
The present invention improves the above-described problems, prevents damage to the end of the endless belt-shaped intermediate transfer member, and prevents toner from wrapping around the back of the intermediate transfer member due to toner adhesion to the end of the intermediate transfer member. An object of the present invention is to provide an image forming apparatus which prevents the intermediate transfer member from running stably.
[0008]
[Means for Solving the Problems]
The object is to form an image forming body, a means for forming a toner image on the image forming body, a toner image on the image forming body is transferred, and the transferred toner image is carried on the surface and a transfer material. An endless belt-shaped intermediate transfer member for conveying the toner, first transfer means for transferring the toner image on the image forming member to the intermediate transfer member, and the toner image on the image forming member on the surface of the transfer material. A second transfer means for transferring, a third transfer means for transferring the toner image on the intermediate transfer member to the back surface of the transfer material, and the transfer material sandwiched and conveyed by a fixing member that rotates in pairs. And a fixing means for fixing the toner image on the transfer material, the width in a direction perpendicular to the moving direction of the intermediate transfer member is set to a width of the image forming member. Axis of rotation The width of the intermediate transfer body, and provided with a detent member at both ends of the inner peripheral surface of the intermediate transfer body, There is provided a transfer material charging means for charging the transfer material and electrostatically adhering to the intermediate transfer body, and the image forming body has a charge width in a direction perpendicular to the moving direction of the intermediate transfer body by the transfer material charging means. Increased the width of the photoconductive layer formed on the outer periphery of the rotating shaft This is achieved by an image forming apparatus characterized in that (first invention).
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below. The description in this column does not limit the technical scope of the claims or the meaning of terms. In addition, the following assertive description in the embodiment of the present invention shows the best mode, and does not limit the meaning or technical scope of the terms of the present invention. In the following description of the embodiments, the surface of the transfer material facing the image forming body in the transfer area is referred to as the front surface, and the other surface of the transfer material, that is, the surface of the transfer material facing the intermediate transfer body is referred to as the back surface. An image transferred onto the surface of the transfer material is referred to as a front image, and an image transferred onto the back surface of the transfer material is referred to as a back image.
[0011]
An image forming process and mechanisms of an embodiment of an image forming apparatus common to the inventions of the claims will be described with reference to FIGS. FIG. 1 is a cross-sectional configuration diagram of a color image forming apparatus showing an embodiment of an image forming apparatus common to the inventions of each claim, and FIG. 2 is a side cross-sectional view of the image forming body of FIG. FIG. 3 is a diagram illustrating a toner image forming state in the image forming apparatus of FIG. 1, and FIG. 3A illustrates a toner image forming state when a back image formed on the image forming body is transferred onto an intermediate transfer body. FIG. 3B is a diagram illustrating a toner image forming state when a front surface image is formed on the image forming body in synchronization with the back surface image on the intermediate transfer body, and FIG. FIG. 3 is a diagram showing double-sided image formation on a transfer material.
[0012]
In FIG. 1, 10 is a photosensitive drum as an image forming body, 11 is a scorotron charger as charging means for each color, 12 is an exposure optical system as image writing means for each color, and 13 is developing means for each color. 14a is an intermediate transfer belt as an intermediate transfer member, 14c is a transfer device as first and second transfer means, 14g is a back surface transfer device as third transfer means, and 150 is a transfer material charging means. 14h, a paper separating AC static eliminator 14h as a transfer material separating means, 160 a conveying portion having a separation claw 210 as a claw member and a spur 162 as a spur member, and 17 a fixing device as a fixing means. It is.
[0013]
A photosensitive drum 10 as an image forming body is formed on a cylindrical base formed by a transparent member such as optical glass or transparent acrylic resin, on a transparent conductive layer, an a-Si layer, or an organic photosensitive layer (OPC). ) And the like, and is rotated clockwise as indicated by an arrow in FIG. 1 with the conductive layer grounded.
[0014]
As shown in FIG. 2, the photosensitive drum 10 is fixed to a drum shaft 30 installed and fixed to the apparatus main body by bearings BE1 and BE2 fitted into flange members 10A and 10B at both ends for engaging and fixing the photosensitive drum. The gear G, which is supported by the bearing and rotatably supported, and is integrated with the flange member 10B is engaged with a drive gear (not shown) on the apparatus main body side and driven to rotate in a predetermined direction at a constant speed.
[0015]
A scorotron charger 11 that is a charging unit for each color, an exposure optical system 12 that is an image writing unit for each color, and a developing unit 13 that is a developing unit for each color are yellow, yellow, and magenta. Four sets are provided for the image forming process of each color of (M), cyan (C), and black (K), and Y, M, C, and R with respect to the rotation direction of the photosensitive drum 10 indicated by arrows in FIG. Arranged in the order of K.
[0016]
A scorotron charger 11 serving as a charging means for each color has a control grid held at a predetermined potential and a discharge electrode 11a made of, for example, a sawtooth electrode, and is mounted opposite to the photosensitive layer of the photosensitive drum 10. Then, a charging action (negative charging in the present embodiment) is performed by corona discharge having the same polarity as the toner, and a uniform potential is applied to the photosensitive drum 10. As the discharge electrode 11a, other wire electrodes or needle electrodes can be used.
[0017]
In the exposure optical system 12, which is an image writing unit for each color, the exposure position on the photosensitive drum 10 is located downstream in the rotation direction of the photosensitive drum 10 with respect to the aforementioned scorotron charger 11 for each color. In this way, it is arranged inside the photosensitive drum 10. As shown in FIG. 2, each exposure optical system 12 is a line in which a plurality of LEDs (light emitting diodes) as light emitting elements for image exposure light arranged in the main scanning direction in parallel with the drum shaft 30 are arranged in an array. Exposure unit 12a, a light focusing optical transmission body (trade name: Selfoc lens array) 12b as an imaging element, and a lens holder 12c, and is attached to the holding member 20. . In addition to the exposure optical system 12 for each color, a simultaneous transfer exposure device 12 d and a uniform exposure device 12 e are attached to the holding member 20, and are integrally accommodated in the translucent substrate of the photosensitive drum 10. The exposure optical system 12 for each color image-exposes the photosensitive layer of the photosensitive drum 10 from the back according to the image data of each color read by a separate image reading device and stored in the memory, and electrostatically is applied on the photosensitive drum 10. A latent image is formed. As the exposure element 12a, a plurality of light emitting elements such as FL (phosphor light emission), EL (electroluminescence), and PL (plasma discharge) arranged in an array can be used in addition to the LED. The emission wavelength of the image exposure light-emitting element is usually in the range of 780 to 900 nm, which is highly transmissive to Y, M, and C toners. In this embodiment, image exposure is performed from the back side. For this reason, a wavelength of 400 to 780 nm, which is not sufficiently transparent to the color toner, may be used. In FIG. 2, WA is a lead wire from a light emitting element (LED) for image exposure light.
[0018]
The developing device 13 which is a developing unit for each color maintains a predetermined gap with respect to the peripheral surface of the photosensitive drum 10 and rotates in the forward direction and the rotating direction of the photosensitive drum 10, for example, a thickness of 0.5 to 1 mm, an outer diameter. A developing sleeve 131 made of 15-25 mm cylindrical non-magnetic stainless steel or aluminum material and a developing casing 138 are provided. Inside the developing casing 138, yellow (Y), magenta (M), Contains one-component or two-component developer of cyan (C) and black (K). Each developing device 13 is kept in contact with the photosensitive drum 10 with a predetermined gap, for example, 100 to 500 μm, by an abutting roller (not shown), and a DC voltage and an AC voltage are superimposed on the developing sleeve 131. By applying the developed bias, non-contact reversal development is performed, and a toner image is formed on the photosensitive drum 10.
[0019]
The intermediate transfer belt 14a, which is an intermediate transfer body, has a volume resistivity of 10 ¹² -10 ¹⁵ An endless belt of Ω · cm, for example, a conductive material dispersed in engineering plastics such as modified polyimide, thermosetting polyimide, ethylene tetrafluoroethylene copolymer, polyvinylidene fluoride, nylon alloy, and the thickness of 0.1-1. A seamless belt having a two-layer structure, in which a fluorine coating having a thickness of 5 to 50 μm is preferably applied to the outside of a 0 mm semiconductive film substrate as a toner filming prevention layer. In addition to this, a semiconductive rubber belt having a thickness of 0.5 to 2.0 mm in which a conductive material is dispersed in silicon rubber, urethane rubber, or the like can also be used. The intermediate transfer belt 14a is stretched in contact with a driving roller 14d, a driven roller 14e, and a tension roller 14i, which are roller members, and is rotated counterclockwise as indicated by an arrow in FIG. The driven roller 14e and the driving roller 14d are fixed and rotated, and the tension roller 14i is supported and rotated by an elastic force of a spring (not shown). The drive roller 14d is rotated by driving from a drive motor (not shown), and drives and rotates the intermediate transfer belt 14a. The driven roller 14e and the tension roller 14i are driven and rotated by the rotation of the intermediate transfer belt 14a. The slack of the rotating intermediate transfer belt 14a is tensioned by the tension roller 14i. The intermediate transfer belt 14a carries a toner image and conveys a recording paper P as a transfer material. The recording paper P is supplied to a position where the intermediate transfer belt 14a is stretched around the driven roller 14e, and the intermediate transfer belt 14 at the curvature portion KT at the end on the fixing device 17 side of the intermediate transfer belt 14a stretched around the drive roller 14d. 14a.
[0020]
The transfer device 14c, which is the first and second transfer means, is a corona discharge device provided opposite to the photosensitive drum 10 with the intermediate transfer belt 14a interposed therebetween, and between the intermediate transfer belt 14a and the photosensitive drum 10. The transfer area 14b is formed on the substrate. A DC voltage having a polarity opposite to that of the toner (plus polarity in the present embodiment) is applied to the transfer device 14c, and the toner image on the photosensitive drum 10 is transferred onto the intermediate transfer belt 14a or the surface of the recording paper P as a transfer material. Transcript.
[0021]
The back transfer device 14g, which is the third transfer means, is preferably constituted by a corona discharge device, and is provided facing the drive roller 14d that is grounded with the intermediate transfer belt 14a interposed therebetween, and has a polarity opposite to that of the toner (in this embodiment) Is applied with a positive polarity), and the toner image on the intermediate transfer belt 14a is transferred to the back surface of the recording paper P.
[0022]
The paper charger 150 serving as a transfer material charging unit is preferably constituted by a corona discharger, and is provided to face the driven roller 14e that is grounded with the intermediate transfer belt 14a interposed therebetween, and has the same polarity as the toner (in this embodiment, A negative polarity) DC voltage is applied to charge the recording paper P and attract it to the intermediate transfer belt 14a. As the paper charger 150, in addition to the corona discharger, it is also possible to use a paper charging brush, a paper charging roller, or the like that can be brought into contact with and released from the intermediate transfer belt 14a.
[0023]
The paper separating AC static eliminator 14h, which is a transfer material separating means, is preferably constituted by a corona discharger, and if necessary, a driving roller that is grounded with the intermediate transfer belt 14a sandwiched between ends of the intermediate transfer belt 14a on the fixing device 17 side. An AC voltage is provided opposite to 14d and superimposed with a DC voltage having the same or opposite polarity as that of the toner as necessary, and the recording paper P conveyed by the intermediate transfer belt 14a is neutralized to remove the intermediate transfer belt 14a. Separate from.
[0024]
The transport unit 160 includes a separation claw 210 that is a claw member and a spur 162 that is a spur member, and is provided between the curvature portion KT at the end of the intermediate transfer belt 14 a on the fixing device 17 side and the fixing device 17. The transport unit 160 may cause the intermediate transfer belt 14a to be deformed by heat from the fixing device 17, or the toner image carried on the intermediate transfer belt 14a may become fused and difficult to transfer, or may be on the intermediate transfer belt 14a. The toner is prevented from adhering to the toner.
[0025]
The separation claw 210 as a claw member is provided close to the curvature portion KT of the intermediate transfer belt 14a and fixed to the support shaft 221 with a predetermined distance, preferably 0.1 to 2.0 mm, from the intermediate transfer belt 14a. When the recording paper P is separated from the intermediate transfer belt 14a, the recording paper P comes into contact with the leading end of the recording paper P to be bent and conveyed in the moving direction of the intermediate transfer belt 14a, and assists in the separation of the recording paper P.
[0026]
The spur 162, which is a spur member, has a plurality of protrusions 162a on the peripheral surface, and is provided so as to be rotatable about the rotation support shaft 165. The spur 162 guides the back side of the recording paper P and conveys the recording paper P to prevent the back side toner image of the recording paper P having a toner image on both sides from being disturbed and to fix the recording paper P to the fixing device 17. The recording paper P is stably conveyed to the fixing device 17 while keeping the entering direction constant.
[0027]
The separation claw 210 and the spur 162 are disposed on the opposite side of the photosensitive drum 10 with respect to the transfer material conveyance surface of the intermediate transfer belt 14a or its extended surface PL1 (hereinafter referred to as transfer material conveyance surface PL1). It is also possible to provide a spur 162 that is a spur member on both sides of the transfer material conveyance surface PL1.
[0028]
The fixing device 17 serving as a fixing unit includes two roller-shaped fixing members including a first fixing roller 17a and a second fixing roller 17b each having a heater therein, and the first fixing roller 17a and the second fixing roller 17b. The toner image on the recording paper P is fixed by sandwiching the recording paper P at the nip portion T between the two and applying heat and pressure.
[0029]
Next, the image forming process will be described.
[0030]
The photosensitive drum 10 is rotated in the clockwise direction indicated by the arrow in FIG. 1 by starting the photosensitive member driving motor (not shown) by the start of image recording, and at the same time, the photosensitive drum 10 is charged by the yellow (Y) scorotron charger 11. Application of a potential is started.
[0031]
After the photosensitive drum 10 is applied with an electric potential, image writing by an electric signal corresponding to the first color signal, that is, Y image data is started by the Y exposure optical system 12, and a document is formed on the surface of the photosensitive drum 10. An electrostatic latent image corresponding to the Y image of the image is formed.
[0032]
The latent image is reversely developed in a non-contact state by the Y developing device 13 to form a yellow (Y) toner image on the photosensitive drum 10.
[0033]
Next, a potential is applied to the photosensitive drum 10 from above the Y toner image by the charging action of the magenta (M) scorotron charger 11, and the M exposure optical system 12 applies a second color signal, that is, M image data. Image writing is performed by a corresponding electric signal, and a magenta (M) toner image is formed on the yellow (Y) toner image by non-contact reversal development by the M developing unit 13. .
[0034]
By a similar process, a cyan (C) toner image corresponding to the third color signal is further superimposed by a cyan (C) scorotron charger 11, a C exposure optical system 12, and a C developer 13. Further, a black (K) toner image corresponding to the fourth color signal is successively superimposed on the black (K) scorotron charger 11, the K exposure optical system 12, and the K developing device 13. Then, a superposed color toner image of four colors of yellow (Y), magenta (M), cyan (C) and black (K) is formed on the peripheral surface within one rotation of the photosensitive drum 10 (toner image). Forming means).
[0035]
Image writing to the photosensitive layer of the photosensitive drum 10 by the Y, M, C, and K exposure optical systems 12 is performed from the inside of the drum through the above-described translucent substrate. Therefore, writing of images corresponding to the second, third, and fourth color signals is performed without any influence from the previously formed toner image, and is equivalent to the image corresponding to the first color signal. It is possible to form an electrostatic latent image.
[0036]
The superimposed color toner image, which is the back image formed on the photosensitive drum 10 as an image forming body by the above image forming process, is intermediately transferred by the transfer device 14c as the first transfer means in the transfer area 14b. The images are collectively transferred (primary transfer) onto the intermediate transfer belt 14a (FIG. 3A). At this time, uniform exposure may be performed by the simultaneous transfer exposure unit 12d provided inside the photosensitive drum 10 so that good transfer is performed.
[0037]
The toner remaining on the peripheral surface of the photosensitive drum 10 after the transfer is subjected to static elimination by the photosensitive drum AC static eliminator 16, and then enters the cleaning device 19 which is an image forming body cleaning unit or abuts on the photosensitive drum 10. It is cleaned by the cleaning blade 19a made of the rubber material and collected in a waste toner container (not shown) by the screw 19b. Further, the history of the photosensitive drum 10 in the previous image formation is eliminated on the peripheral surface of the photosensitive drum 10 by exposure by the uniform exposure device 12e before charging using, for example, a light emitting diode.
[0038]
After the superimposed color toner image to be the back image is formed on the intermediate transfer belt 14a as described above, it is continuously superimposed on the surface of the photosensitive drum 10 in the same manner as the color image forming process described above. A combined color toner image is formed (FIG. 3B). At this time, the image data is changed so that the front surface image formed on the photoconductive drum 10 becomes a mirror image with respect to the back image formed on the photoconductive drum 10.
[0039]
Along with the surface image formation on the photosensitive drum 10, the recording paper P as a transfer material is sent out by a feed roller 15a from a paper feed cassette 15 as a transfer material storage means, and a timing roller 15b as a transfer material feeding means. By driving the timing roller 15b, the color toner image of the front image formed on the photosensitive drum 10 and the color toner image of the back image carried on the intermediate transfer belt 14a are synchronized. It is fed to the transfer area 14b. At this time, the fed recording paper P is charged to the same polarity as the toner by a paper charger 150 which is a transfer material charging means provided on the surface side of the recording paper P, and is attracted to the intermediate transfer belt 14a to be transferred to the transfer area. 14b. By charging the paper with the same polarity as the toner, the toner image is prevented from being attracted by being attracted to the toner image on the intermediate transfer belt 14a or the toner image on the photosensitive drum 10, thereby preventing the toner image from being disturbed.
[0040]
In the transfer area 14b, the surface image on the photosensitive drum 10 is collectively collected on the recording paper P by the transfer device 14c as the second transfer means to which a voltage having a polarity opposite to that of the toner (plus polarity in the present embodiment) is applied. Transfer (secondary transfer) to the surface. At this time, the back image on the intermediate transfer belt 14a is not transferred to the recording paper P and exists on the intermediate transfer belt 14a. In the secondary transfer by the transfer device 14c as the second transfer means, for example, a light emitting diode provided inside the photosensitive drum 10 so as to be opposed to the transfer area 14b is used so that a good transfer can be performed. Uniform exposure by the simultaneous transfer exposure device 12d may be performed.
[0041]
The recording paper P on which the color toner image is transferred on the front surface is conveyed to a back surface transfer device 14g as a third transfer means to which a voltage having a polarity opposite to that of the toner (a positive polarity in the present embodiment) is applied. The back image on the peripheral surface of the intermediate transfer belt 14a is collectively transferred (third transfer) to the back surface of the recording paper P by the transfer device 14g (FIG. 3C).
[0042]
The recording paper P on which the color toner images are formed on both sides is removed from the curvature of the curvature portion KT of the intermediate transfer belt 14a and paper separation AC removal as a transfer material separation means provided at the end of the intermediate transfer belt 14a as necessary. The fixing means is separated from the intermediate transfer belt 14a by a charge eliminating action by the electric device 14h and a separation claw 210 provided in the conveyance unit 160 at a predetermined interval from the intermediate transfer belt 14a, and through a spur 162 provided in the conveyance unit 160. The toner image on the recording paper P is fixed by applying heat and pressure to the nip T between the first fixing roller 17a and the second fixing roller 17b. The recording paper P on which double-sided image recording has been performed is sent with its front and back reversed and discharged by a paper discharge roller 18 to a tray outside the apparatus. 1, a switching member (not shown) may be provided at the outlet of the fixing device 17, and the sheet may be discharged to a tray (not shown) outside the device without reversing the front and back.
[0043]
The toner remaining on the peripheral surface of the intermediate transfer belt 14a after the transfer is provided to face the driven roller 14e with the intermediate transfer belt 14a interposed therebetween, and abuts against and contacts the intermediate transfer belt 14a with the support shaft 142 as a rotation fulcrum. Cleaning is performed by an intermediate transfer body cleaning device 140 that is an intermediate transfer body cleaning unit having an intermediate transfer body cleaning blade 141 that can be contacted and released.
[0044]
The toner remaining on the peripheral surface of the photosensitive drum 10 after the transfer is discharged by the photosensitive drum AC static eliminator 16 and then cleaned by the cleaning device 19, and is further cleaned by the uniform exposure unit 12e before charging. The history of the photoconductive drum 10 in the image formation is canceled, and the next image formation cycle is started.
[0045]
By using the above method, the superimposed color toner images are collectively transferred, so that color misregistration of the color image on the intermediate transfer belt 14a, toner scattering and rubbing are unlikely to occur, and good double-sided color image with little image deterioration Formation is made.
[0046]
The invention according to claim 1 will be described with reference to FIGS. FIG. 4 is a diagram showing the relationship between the width of the image forming member and the width of the intermediate transfer member and the stopper member provided on the intermediate transfer member. FIG. 5 shows the interval between the stopper members and the first, second, It is a figure which shows the unpreferable setting of the relationship with the charging width by a 3rd transfer means.
[0047]
In the present invention, as shown in FIG. 4, the width BD (hereinafter referred to as the intermediate transfer belt width BD) in the direction orthogonal to the moving direction of the intermediate transfer belt 14a, which is an intermediate transfer body, is a photosensitive drum 10 that is an image forming body. Is smaller than the width PD in the direction orthogonal to the moving direction (hereinafter referred to as the photosensitive drum width PD). This prevents damage to the end of the intermediate transfer belt 14a. If the intermediate transfer belt width BD is larger than the photosensitive drum width PD, the intermediate transfer belt 14a is damaged at both end positions of the photosensitive drum 10 as described above, and the end of the intermediate transfer belt 14a is damaged when used for a long time. Problem arises.
[0048]
Further, in the present invention, a detent member 14A that engages with step portions 14C and 14D at both ends of the driving roller 14d, driven roller 14e, and tension roller 14i, which are roller members, at both ends of the inner peripheral surface of the intermediate transfer belt 14a, respectively. , 14B are provided to prevent the intermediate transfer belt 14a from shifting.
[0049]
The stopper members 14A and 14B are preferably made of a rubber material having a hardness of 50 to 90 degrees. The stopper members 14A and 14B have a width L1 of 5 to 10 mm and a height L2 of 2 to 8 mm. The width L3 of the stepped portions 14C and 14D engaged with the members 14A and 14B is set to about 0 to 15 mm, the height L4 is set to 0.1 to 0.5 mm larger than the height L2 of the detent members 14A and 14B, and the step is further increased. Making the distance between the portions 14C and 14D smaller by 0.1 to 0.5 mm than the distance A between the stopper members 14A and 14B prevents the intermediate transfer belt 14a from coming off the roller member, thereby preventing the intermediate transfer belt 14a from being offset. This is preferable because the intermediate transfer belt 14a can be run stably.
[0050]
Further, in the present invention, a direction orthogonal to the moving direction of the intermediate transfer belt 14a by the transfer device 14c as the first transfer device, the transfer device 14c as the second transfer device, and the back transfer device 14g as the third transfer device. Charging widths B1, B2, and B3 (hereinafter referred to as primary transfer width B1, secondary transfer width B2, and tertiary transfer width B3) are smaller than the distance A between the detent members 14A and 14B of the intermediate transfer belt 14a (B1 < A, B2 <A, B3 <A) are set. This prevents toner from adhering to the end of the intermediate transfer belt 14a. When the primary transfer width B1, the secondary transfer width B2, and the tertiary transfer width B3 are larger than the distance A between the detent members 14A and 14B, toner adheres to the end of the intermediate transfer belt 14a as shown in FIG. Eventually, the adhering toner goes around to the back surface of the intermediate transfer belt 14a, and when used over a long period of time, the toner accumulates on the step portions 14C and 14D of the roller member and the detent members 14A and 14B of the intermediate transfer belt 14a. There arises a problem that stable running of the transfer belt 14a cannot be obtained.
[0051]
As described above, by making the width of the intermediate transfer member smaller than the width of the image forming member, damage to the belt end is prevented, and by providing a detent member at both ends of the inner peripheral surface of the intermediate transfer member, The deviation of the intermediate transfer member is prevented, and the charging width by the first, second, and third transfer means is made smaller than the distance between the detent members of the intermediate transfer member, thereby causing the toner to adhere to the belt end. The toner can be prevented from wrapping around the back of the belt, and the belt can travel stably.
[0052]
The invention of claim 2 will be described with reference to FIGS. FIG. 6 is a diagram for explaining the supply of the transfer material to the intermediate transfer member and the charging of the transfer material by the transfer material charging unit, and FIG. 7 shows the charging width by the transfer material charging unit and the charging width by the first transfer unit. 7A is a diagram showing the setting of the invention of claim 2, FIG. 7B is a diagram showing an unfavorable setting, and FIG. FIG. 9 is a diagram for explaining the transfer (secondary transfer) of the surface toner image by the second transfer means, and FIG. 9 is an unfavorable setting of the relationship between the charge width by the transfer material charging means and the charge width by the second transfer means. FIG.
[0053]
After the back surface toner image is transferred (primary transfer) from the photosensitive drum 10 as the image forming body to the intermediate transfer belt 14a as the intermediate transfer body by charging by the transfer device 14c as the first transfer means, FIG. As shown, recording paper P, which is a transfer material, is fed to the intermediate transfer belt 14a in synchronization with the leading edge of the back surface toner image carried on the intermediate transfer belt 14a, and a paper charger 150, which is transfer material charging means. The recording paper P is charged to the same polarity as the back surface toner image on the intermediate transfer belt 14a by the charging, and is attracted to the intermediate transfer belt 14a via the back surface toner image and conveyed. In this case, in the present invention, as shown in FIG. 7A, the primary transfer width B1 is set to a charge width C in a direction orthogonal to the moving direction of the intermediate transfer belt 14a by the paper charger 150 (hereinafter referred to as transfer material charge width C). ) Set below (B1 ≦ C). As a result, the toner at the end of the recording paper P is pressed to the center so that the toner is not scattered at both ends. As shown in FIG. 7B, when the primary transfer width B1 is larger than the transfer material charging width C, the polarity of the back toner image is the same as that of the paper charger 150 (in this embodiment, negative polarity). Therefore, the toner at the end on the recording paper P is scattered at both ends and adheres to the end of the intermediate transfer belt 14a.
[0054]
The recording paper P charged by the charging of the paper charger 150 is adsorbed and conveyed by the intermediate transfer belt 14a via the back surface toner image, and then, as shown in FIG. 8, the transfer device 14c as the second transfer means. The surface toner image carried on the photosensitive drum 10 as an image forming body is transferred onto the surface of the recording paper P (secondary transfer). At this time, in the present invention, the secondary transfer width B2 for transferring the surface toner image from the photosensitive drum 10 to the recording paper P is set to be equal to or smaller than the transfer material charging width C by the paper charger 150 (B2 ≦ C). As a result, the toner on the edge of the photosensitive drum 10 or on the recording paper P can be pressed to the center so that the toner is not scattered at both ends, and toner adhesion to the belt edge of the intermediate transfer member is further prevented. In addition, the toner can be prevented from wrapping around the back of the belt due to the toner adhering to the belt end, and the belt can be more stably run.
[0055]
As shown in FIG. 9, when the secondary transfer width B2 is larger than the transfer material charging width C, the polarity of the surface toner image and the charging polarity by the paper charger 150 are the same (in this embodiment, negative polarity). Therefore, the toner at the end on the photosensitive drum 10 is attracted to the positive transfer charge of the secondary transfer on the back surface of the intermediate transfer belt 14a, and the toner is transferred to both ends of the intermediate transfer belt 14a or is temporarily transferred. There arises a problem that the toner on the recording sheet P is repelled by the electric charge of the paper charger 150 and scattered at both ends and adheres to the end of the intermediate transfer belt 14a.
[0056]
The invention of claim 3 will be described with reference to FIGS. FIG. 10 is a perspective view of the image forming body, and FIG. 11 is a diagram showing an unfavorable setting of the relationship between the width of the photoconductive layer and the charging width of the transfer material charging unit.
[0057]
As shown in FIG. 10, a photoconductive drum 10 as an image forming body is formed by forming a photoconductive layer on the outer periphery of a grounded conductive layer, and is usually photoconductive in a direction perpendicular to the moving direction of the photoconductive drum 10. Since the layer width D (hereinafter referred to as the photoconductive layer width D) is set to be smaller than the photosensitive drum width PD, when the conductive layers exposed at both ends of the photosensitive drum 10 come into contact with the intermediate transfer belt 14a, the intermediate transfer is performed. The charge on the belt 14a will be leaked. Therefore, in the present invention, the photoconductive layer width D is set larger than the transfer material charging width C (C <D). As a result, toner adhesion to the belt end portion of the intermediate transfer member is further prevented, and toner wraparound to the belt back surface due to toner adhesion to the belt end portion is prevented, and the belt can travel more stably. As shown in FIG. 11, when the photoconductive layer width D of the photosensitive drum 10 is smaller than the transfer material charging width C, the charge at both ends on the intermediate transfer belt 14a by the paper charger 150 indicated by a thick line in the figure is It leaks to the conductive layer of the photosensitive drum 10 and disappears, and eventually becomes the same as when the transfer material charging width C is reduced, and is similar to that described with reference to FIGS. 7B and 9 on the intermediate transfer belt 14a. There arises a problem that the back surface toner image and the front surface toner image on the photosensitive drum 10 are scattered on both ends and adhere to the end of the intermediate transfer belt 14a.
[0058]
The invention of claim 4 will be described with reference to FIGS. FIG. 12 is a diagram for explaining the transfer (third transfer) of the back surface toner image by the third transfer unit, and FIG. 13 shows the relationship between the charging width by the transfer material charging unit and the charging width by the third transfer unit. It is a figure which shows the setting which is not preferable.
[0059]
As shown in FIG. 12, after being charged with the same polarity as the toner image by a paper charger 150 as a transfer material charging means, the intermediate transfer belt 14a is transferred to the back surface of the recording paper P to which the surface toner image is transferred and conveyed. The back toner image carried thereon is transferred by charging by the back transfer device 14g as the third transfer means (third transfer). At this time, in the present invention, the tertiary transfer width B3 for transferring the back surface toner image from the intermediate transfer belt 14a to the recording paper P is set to be equal to or larger than the transfer material charging width C by the paper charger 150 (C ≦ B3). As a result, toner adhesion to the belt end portion of the intermediate transfer member is further prevented, and toner wraparound to the belt back surface due to toner adhesion to the belt end portion is prevented, and the belt can travel more stably. As shown in FIG. 13, when the transfer material charging width C is larger than the tertiary transfer width B3, the surface toner image on the recording paper P is reversed by the discharge of the back surface transfer device 14g when passing through the back surface transfer device 14g. The surface toner image converted into polarity (in this embodiment, plus polarity) is attracted to the charged charge (minus polarity) of the paper charger 150 remaining at both ends and scattered at both ends, and the end of the intermediate transfer belt 14a. The problem of adhering to the part occurs.
[0060]
The invention of claim 5 will be described. After the back surface toner image is transferred (tertiary transfer) to the back surface of the recording paper P by the discharge of the back surface transfer device 14g, the charge due to the tertiary transfer on the front surface of the recording paper P and the intermediate transfer belt 14a is used as a transfer material discharging means. The paper is removed by the paper separation AC neutralizer 14h. In this case, in the present invention, when the neutralization width in the direction orthogonal to the moving direction of the intermediate transfer belt 14a by the paper separation AC neutralizer 14h as the transfer material neutralization means is E (hereinafter referred to as transfer material neutralization width E), the transfer material. The charge removal width E is set to be equal to or greater than the tertiary transfer width B3 (B3 ≦ E), and the charge on the surface of the recording paper P and both ends of the intermediate transfer belt 14a is reliably discharged. Accordingly, toner adhesion to the belt end portion of the intermediate transfer member is further prevented, and toner wraparound to the belt back surface due to toner adhesion to the belt end portion is prevented, and the belt can be more stably run. If the transfer material neutralization width E is smaller than the tertiary transfer width B3, the tertiary transfer charge at both ends of the intermediate transfer belt 14a is not neutralized. Therefore, when the recording paper P passes through the paper separation AC neutralizer 14h, The back toner image (minus polarity) is attracted to the charged charge (plus polarity) of the third transfer remaining at both ends of the intermediate transfer belt 14a and scattered at both ends to adhere to the end of the intermediate transfer belt 14a. Problems arise.
[0061]
Further, when the cleaning width in the direction orthogonal to the moving direction of the intermediate transfer belt 14a of the intermediate transfer body cleaning device 140, which is an intermediate transfer body cleaning means, is F (hereinafter referred to as cleaning width F), the charging or discharging of the intermediate transfer belt 14a is performed. The cleaning width F is set to the primary transfer width B1, the secondary transfer width B2, the tertiary transfer width B3, and the transfer material charging so as to clean all the portions where the toner may adhere to the intermediate transfer belt 14a due to charging by It is preferable that the width C is larger than the transfer material static elimination width E (B1 <F, B2 <F, B3 <F, C <F, E <F). This ensures that the toner on the intermediate transfer belt 14a is cleaned.
[0062]
Another example of the image forming apparatus will be described with reference to FIG. FIG. 14 is a schematic explanatory diagram of a color image forming apparatus showing another example of the image forming apparatus.
[0063]
In the image forming apparatus, first, four sets of developing units 13 (developing means) of yellow (Y), magenta (M), cyan (C) and black (K) are provided on the photosensitive drum 10 (image forming body), scorotron. A toner image forming means comprising a charger 11 (charging means) and an exposure optical system 12 (image writing means) is used to form a toner image to be a back image and temporarily transfer it onto the intermediate transfer belt 14a (intermediate transfer member). Subsequently, a toner image to be a surface image is formed on the same photosensitive drum 10, and the toner image on the photosensitive drum 10 is transferred onto the surface of the recording paper P (transfer material) and the toner on the intermediate transfer belt 14a. The image is transferred to the back side of the recording paper P to obtain a double-sided image. In the image forming apparatus of this example, as shown in FIG. 14, the second image formation for forming a toner image to be the back side image is performed. Photoconductor drum 10 as a body And a photosensitive drum 10a, which is a first image forming body that forms a toner image to be a front surface image, are provided separately, and the back toner image formed on the photosensitive drum 10b has a polarity opposite to that of the toner (in this embodiment, Is transferred (primary transfer) onto the intermediate transfer belt 114a, which is an intermediate transfer member, by the primary transfer unit 114b, which is a first transfer unit to which a positive polarity voltage is applied, and then the photosensitive drum 10b and the photosensitive member. The recording paper P, which is a transfer material, is supplied to the intermediate transfer belt 114a between the drum 10a, the recording paper P is adsorbed to the intermediate transfer belt 114a by the charging of the paper charger 150, and is transported to the photosensitive drum 10a. The surface toner image formed on the recording sheet P is transferred by a secondary transfer unit 114c which is a second transfer unit to which a voltage having a polarity opposite to that of the toner (a positive polarity in the present embodiment) is applied. After the transfer to the front surface (secondary transfer), the back surface toner image on the intermediate transfer belt 114a is a third transfer means that is a third transfer means to which a voltage having a polarity opposite to that of the toner (in this embodiment, a positive polarity) is applied. Transfer (tertiary transfer) is performed on the back surface of the recording paper P by the transfer device 114g, and the recording paper P on which the front and back toner images are transferred is separated by a paper separation AC static eliminator 14h, which is a transfer material separating means, and then fixed (not shown) It is fixed by means to obtain a double-sided image. The photosensitive drums 10a and 10b and the intermediate transfer belt 114a have the same functions and structures as the photosensitive drum 10 and the intermediate transfer belt 14a described in the image forming apparatus. As described above, the intermediate transfer belt is used. 114a is stretched in contact with a driving roller 14d, a driven roller 14e, and a tension roller 14i, which are roller members.
[0064]
A toner image forming means (second toner image forming means) for forming a toner image to be a back image on the photosensitive drum 10b as a second image forming body and a toner image to be a front image with the first image forming body. As the toner image forming means (first toner image forming means) formed on a certain photosensitive drum 10a, yellow (Y), magenta (M) similar to those used in the image forming apparatus described above with reference to FIG. ), Cyan (C) and black (K), four sets of developing units 13 (developing unit), scorotron charger 11 (charging unit), and exposure optical system 12 (image writing unit) are included in the photosensitive drums 10a and 10b. Used for each of them, a toner image of the front image and a toner image of the back image are formed respectively.
[0065]
As described with reference to FIG. 4, the width BD (hereinafter referred to as the intermediate transfer belt width BD) in the direction orthogonal to the moving direction of the intermediate transfer belt 114a, which is an intermediate transfer body, is the first and second image forming bodies. It is made smaller than the width PD (hereinafter referred to as the photoconductor drum width PD) in the direction orthogonal to the moving direction of the photoconductor drums 10a and 10b concerned. As described above with reference to FIG. 4, step portions 14C and 14D (FIG. 14) at both ends of the driving roller 14d, driven roller 14e, and tension roller 14i, which are roller members, are provided at both ends of the inner peripheral surface of the intermediate transfer belt 114a. 4) is provided to prevent the intermediate transfer belt 114a from shifting.
[0066]
Further, as described with reference to FIG. 5, the primary transfer unit 114b as the first transfer unit, the secondary transfer unit 114c as the second transfer unit, and the tertiary transfer unit 114g as the third transfer unit. Charge widths B1, B2, and B3 (hereinafter referred to as primary transfer width B1, secondary transfer width B2, and tertiary transfer width B3) in directions orthogonal to the moving direction of the intermediate transfer belt 14a are provided at both ends of the intermediate transfer belt 14a. The distance is set smaller than the distance A (see FIG. 5) between the stopper members 14A and 14B (B1 <A, B2 <A, B3 <A).
[0067]
As described above, by making the belt width of the intermediate transfer member smaller than the width of the image forming member, damage to the belt end is prevented, and the widths of the first, second, and third transfer means are made to be the intermediate transfer member. By making the distance smaller than the distance between the detent members, the toner can be prevented from wrapping around the back of the belt caused by the toner adhering to the end of the belt, and the belt can travel stably.
[0068]
Further, the primary transfer width B1 is set to be equal to or less than the charge width C (hereinafter referred to as transfer material charge width C) in the direction orthogonal to the moving direction of the intermediate transfer belt 114a by the paper charger 150 (B1 ≦ C). The toner at the end of the toner is pressed to the center so that the toner is not scattered at both ends.
[0069]
Further, the secondary transfer width B is set to be equal to or smaller than the transfer material charging width C by the paper charger 150 (B2 ≦ C), and the toner on the edge of the photosensitive drum 10 or on the recording paper P is pressed down to the center to remove the toner. Make sure that it is not scattered at both ends.
[0070]
As a result, toner adherence to the belt end of the intermediate transfer member is further prevented, and toner wraparound to the back of the belt due to toner adherence to the belt end is prevented, so that the belt can travel more stably.
[0071]
Further, the width D1 (not shown, hereinafter referred to as photoconductive layer width D1) of the photoconductive layer in the direction orthogonal to the moving direction of the photosensitive drum 10a that forms the toner image of the front image is larger than the transfer material charging width C ( C <D1) Set.
[0072]
As a result, toner adherence to the belt end of the intermediate transfer member is further prevented, and toner wraparound to the back of the belt due to toner adherence to the belt end is prevented, so that the belt can travel more stably.
[0073]
Further, the tertiary transfer width B3 is set to a transfer material charging width C or more (C ≦ B3).
[0074]
As a result, toner adherence to the belt end of the intermediate transfer member is further prevented, and toner wraparound to the back of the belt due to toner adherence to the belt end is prevented, so that the belt can travel more stably.
[0075]
Further, when the charge removal width in the direction orthogonal to the moving direction of the intermediate transfer belt 14a by the paper separation AC charge remover 14h as the transfer material charge removal means is E (hereinafter referred to as transfer material charge removal width E), the transfer material charge removal width E is set to 3. The next transfer width is set to B3 or more (B3 ≦ E), and the charge at both ends of the intermediate transfer belt 14a is surely discharged.
[0076]
As a result, toner adherence to the belt end of the intermediate transfer member is further prevented, and toner wraparound to the back of the belt due to toner adherence to the belt end is prevented, so that the belt can travel more stably.
[0077]
【The invention's effect】
By making the belt width of the intermediate transfer member smaller than the width of the image forming member, damage to the belt end is prevented, and by providing detent members at both ends of the inner peripheral surface of the intermediate transfer member, Is prevented, and further ,During The toner is prevented from wrapping around the back surface of the belt caused by the toner adhering to the belt end portion of the intermediate transfer member, and the belt can be stably driven.
[Brief description of the drawings]
FIG. 1 is a cross-sectional configuration diagram of a color image forming apparatus showing an embodiment of an image forming apparatus common to the inventions of the claims.
FIG. 2 is a side sectional view of the image forming body of FIG.
3 is a diagram illustrating a toner image forming state in the image forming apparatus of FIG. 1; FIG.
FIG. 4 is a diagram illustrating a relationship between a width of an image forming member and a width of an intermediate transfer member, and a detent member provided on the intermediate transfer member.
FIG. 5 is a diagram illustrating an unfavorable setting of the relationship between the interval between the stopper members and the charging width by the first, second, and third transfer units.
FIG. 6 is a diagram for explaining transfer material supply to an intermediate transfer member and transfer material charging by a transfer material charging unit.
FIG. 7 is an explanatory diagram showing a relationship between a charging width by a transfer material charging unit and a charging width by a first transfer unit.
FIG. 8 is a diagram for explaining transfer (secondary transfer) of a surface toner image by a second transfer unit;
FIG. 9 is a diagram illustrating an unfavorable setting of the relationship between the charging width by the transfer material charging unit and the charging width by the second transfer unit.
FIG. 10 is a perspective view of an image forming body.
FIG. 11 is a diagram showing an unfavorable setting of the relationship between the width of the photoconductive layer and the charging width of the transfer material charging unit.
FIG. 12 is a view for explaining transfer (third transfer) of a back surface toner image by a third transfer unit;
FIG. 13 is a diagram illustrating an unfavorable setting of a relationship between a charging width by a transfer material charging unit and a charging width by a third transfer unit.
FIG. 14 is a schematic explanatory diagram of a color image forming apparatus showing another example of the image forming apparatus.
[Explanation of symbols]
10, 10a, 10b Photosensitive drum
11 Scorotron charger
12 Exposure optics
13 Developer
14A, 14B Stop stopper
14a, 114a Intermediate transfer belt
14c Transfer device
14g Back transfer device
14h Paper separation AC static eliminator
17 Fixing device
114b Primary transfer device
114c secondary transfer device
114g tertiary transfer device
150 Paper charger
P Recording paper

Claims (1)

An image forming body;
Means for forming a toner image on the image forming body;
An endless belt-shaped intermediate transfer body that transfers the toner image on the surface to which the toner image on the image forming body has been transferred and carries the transferred toner image;
First transfer means for transferring a toner image on the image forming body to the intermediate transfer body;
A second transfer means for transferring a toner image on the image forming body to the surface of the transfer material;
Third transfer means for transferring the toner image on the intermediate transfer member to the back surface of the transfer material;
In an image forming apparatus, the image forming apparatus includes a fixing unit that sandwiches and conveys the transfer material by a fixing member that rotates as a pair, and fixes a toner image on the transfer material.
While making the width in the direction perpendicular to the moving direction of the intermediate transfer body smaller than the width in the rotation axis direction of the image forming body,
A detent member is provided at both ends of the inner peripheral surface of the intermediate transfer member,
Furthermore, there is provided a transfer material charging unit that charges the transfer material and electrostatically adheres to the intermediate transfer member,
Image formation characterized in that the width of the photoconductive layer formed on the outer periphery of the image forming body in the rotation axis direction is larger than the charging width in the direction perpendicular to the moving direction of the intermediate transfer member by the transfer material charging means. apparatus.

Images