JP3716558B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electronic device such as a copying machine, a printer, or a fax machine in which a charging unit, an image exposure unit, and a developing unit are arranged around an image carrier to transfer and fix a toner image formed on the image carrier onto a transfer material. The present invention relates to a photographic image forming apparatus, and more particularly to a method of conveying a transfer material to a transfer unit.
[0002]
[Prior art]
Conventionally, in double-sided copying, an image on one side formed on an image carrier is transferred and fixed on a transfer material, which is once stored in a double-sided reversing paper feeder and formed on the image carrier again. In this method, a transfer material is fed from a double-sided reversing paper 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 the double-sided copying apparatus, as described above, the transfer material is conveyed such as feeding to the double-sided reversing paper feeding device and passing through the fixing device twice. Therefore, the reliability of the transfer material conveyance is low, causing jamming and the like. It was the cause. On the other hand, a toner image is formed on both sides of a transfer material according to Japanese Patent Publication Nos. 49-37538, 54-28740, Japanese Laid-Open Patent Publication No. 1-444457, Japanese Laid-Open Patent Publication No. 4-214576, and the like. In particular, JP-A-1-44457 and JP-A-4-214576 disclose a plurality of image forming units including an image carrier, a charging unit, an image exposing unit, a developing unit, and the like. There has been proposed a method of forming a double-sided copy of a color image by arranging them in parallel on a combined toner image receiver.
[0004]
[Problems to be solved by the invention]
In contrast, the inventors of the present application once transferred the toner image formed on the image carrier (first image carrier) to the belt-like toner image receiver (second image carrier) in a batch. A double-sided image formation method is considered in which a toner image is formed again on the image carrier, and the toner image on the toner image receiver and the toner image formed on the image carrier are transferred to both sides of the recording paper (transfer material). However, depending on the type of transfer material, the transfer material separated from the belt-shaped toner image receiver is not uniformly conveyed, but is unevenly conveyed, and the toner image on the transfer material is disturbed or the transfer material is When sandwiched between the fixing means, wrinkles are generated on the transfer material, and there is a problem that good fixing is not performed.
[0005]
For this reason, a conveyance unit having a spur is provided between the toner image receiver and the fixing unit to try to convey the transfer material to the fixing unit. However, the toner image on the transfer material conveyed by the spur is spurted. There is a problem that marks are generated.
[0006]
SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus that solves the above-described problems and prevents the occurrence of spur marks on a toner image on a transfer material.
[0007]
Further, when the transfer material is conveyed by a spur, there is a problem that the toner on the transfer material adheres to the spur and the spur is contaminated, and the transfer material conveyed by the spur is contaminated with toner.
[0008]
SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus that solves the above-mentioned problems and prevents the transfer material from being contaminated by spurs.
[0009]
[Means for Solving the Problems]
  The object is to transfer a toner image carried on the first image carrying means, the first image carrying means carrying the toner image formed by the toner image forming means, and to transfer the transferred toner image to the surface. A belt-like second image carrying means carried on the toner image and a toner image carried on the first image carrying means., On the side facing the first image bearing meansTransfer materialFace ofA first transfer means for transferring the toner image and a toner image carried on the second image carrying means., On the side facing the second image bearing meansTransfer materialFace ofA second transfer means for transferring the toner image to the toner image, and a fixing means for fixing the toner image transferred onto both surfaces of the transfer material by sandwiching and transporting the transfer material by a fixing member that rotates in pairs. In the image forming apparatus in which the transfer material is transported by the second image carrying means, the transfer material is separated from the second image carrying means, and then fixed by the fixing means, the second image carrying means and the fixing From the extended surface of the transfer material conveying surface of the second image bearing means., On the side facing the second image bearing meansTransfer materialFace ofOn the side,A conveying unit having a spur for conveying the transfer material, and feeding the transfer material to the fixing unit through the conveying unit; at the end of the second image carrying unit on the fixing unit side, the belt; The transfer material is separated from the second image-bearing unit having a shape, and is moved to the fixing unit along the spurs of the conveying unit, and at the nip portion formed by the pair of fixing members of the fixing unit. The image forming apparatus is characterized in that when the leading edge of the transfer material is clamped, the transfer material is separated from the spur, and the fixing member is conveyed in a state of being separated from the spur. IsThe
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below. The description in this section does not limit the technical scope of the claims or the meaning of terms, but the assertive explanation below indicates the best mode, and limits the meaning and technical scope of the terms of the present invention. Not what you want. In the following description of the embodiment, the surface of the transfer material on the side facing the first image carrying means in the transfer area is the surface, the other side of the transfer material, that is, the side facing the second image carrying means. The surface of the transfer material is referred to as the back surface, the image transferred to the surface of the transfer material is referred to as the front surface image, and the image transferred to the other surface of the transfer material is referred to as the back surface image.
[0012]
An image forming process and each mechanism of an embodiment of an image forming apparatus according to the present invention 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 according to the present invention, and FIG. 2 is a side cross-sectional view of the first image carrying means of FIG. FIG. 3 is a diagram showing a state of toner image formation on both sides of the image forming apparatus according to the present invention, and FIG. 3A shows a transfer of the toner image formed on the first image carrying unit onto the second image carrying unit. FIG. 3B is a diagram for forming a front image on the first image carrying means in synchronization with the back image on the second image carrying means, and FIG. C) is a diagram showing double-sided image formation on a transfer material.
[0013]
In FIG. 1, 10 is a photosensitive drum as a first image carrier, 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 for each color. 14a is a toner image receiver that is a second image carrying means, 14c is a transfer device that is a first transfer means, 14g is a back surface transfer device that is a second transfer means, and 150. A paper charger as a transfer material charging unit, 14h is a paper separation AC static eliminator as a transfer material separation unit, 160 is a transport unit, and 17 is a fixing device as a fixing unit.
[0014]
The photosensitive drum 10 which is the first image carrying means includes, for example, a transparent conductive layer, an a-Si layer or an organic photosensitive layer on the outer periphery of a cylindrical base formed by a transparent member made of optical glass or transparent acrylic resin. A photosensitive layer such as (OPC) is formed, and is rotated clockwise as indicated by an arrow in FIG. 1 with the conductive layer grounded.
[0015]
As shown in FIG. 2, the photosensitive drum 10 has a bearing with respect to a drum shaft 30 that is installed and fixed to the apparatus main body by bearings B1 and B2 fitted into flange members 10a and 10b at both ends for engaging and fixing the photosensitive drum. The gear G, which is rotatably supported and integrated with the flange member 10b, is engaged with a drive gear (not shown) on the apparatus main body side and is driven at a constant speed in a predetermined direction. WA is a lead wire from a light emitting element (LED) of an image exposure means described later.
[0016]
In the present embodiment, 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 set as one set. Four sets are provided for the image forming process of each color of yellow (Y), magenta (M), cyan (C), and black (K), and with respect to the rotation direction of the photosensitive drum 10 indicated by an arrow in FIG. Arranged in the order of Y, M, C, K.
[0017]
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.
[0018]
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. Note that 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. Since it is a system, it may have a shorter wavelength of 400 to 780 nm, which is not sufficiently transmissive to the color toner.
[0019]
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, and yellow (Y), magenta (M), cyan (C), and black (K) are contained therein. 1-component or 2-component developer). 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.
[0020]
The toner image receiver 14a as the second image carrier means has a volume resistivity of 10¹²-10¹⁵An 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 0.1 to 1.0 mm in which a conductive material is dispersed in silicon rubber, urethane rubber, or the like can also be used. The toner image receiver 14a is stretched in contact with the driving roller 14d, the driven roller 14e, and the tension roller 14i, and is rotated counterclockwise as indicated by an arrow in FIG. The driven roller 14e, the driving roller 14d, and the tension roller 14i are provided in this order according to the rotation direction of the toner image receiver 14a. The driven roller 14e and the driving roller 14d are fixed and rotated. Therefore, the drive roller 14d is rotated by being driven by a drive motor (not shown), and the toner image receiver 14a is driven to rotate. The driven roller 14e and the tension roller 14i are driven and rotated by the rotation of the toner image receiver 14a. The slack of the belt of the rotating toner image receiver 14a is tensioned by the tension roller 14i.
[0021]
The transfer device 14c, which is a first transfer means, is provided to face the photosensitive drum 10 with the toner image receiver 14a interposed therebetween, and forms a transfer area 14b between the toner image receiver 14a and the photosensitive drum 10. To do. 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 to form a transfer electric field in the transfer area 14b, whereby the toner image on the photosensitive drum 10 is transferred to the toner image receiver. 14a or on the surface of the transfer material.
[0022]
The back transfer device 14g as the second transfer means is provided to face the conductive driving roller 14d grounded with the toner image receiver 14a interposed therebetween, and has a polarity opposite to that of the toner (in this embodiment, a positive polarity). A DC voltage is applied to transfer the toner image on the toner image receiver 14a to the back surface of the transfer material.
[0023]
The paper charger 150 serving as a transfer material charging unit is provided to face the driven roller 14e that is grounded with the toner image receiver 14a interposed therebetween, and contacts and contacts the toner image receiver 14a with the support shaft 152 as a rotation fulcrum. The transfer material is charged and adsorbed to the toner image receiver 14a.
[0024]
A paper separating AC neutralizer 14h as a transfer material separating unit is arranged with the back surface transfer device 14g as necessary, and is electrically conductive with a grounding at the fixing device 17 side end portion of the toner image receiver 14a with the toner image receiver 14a interposed therebetween. An AC voltage, which is provided facing the driving roller 14d and superimposes a DC voltage having the same or opposite polarity as the toner, is applied to neutralize the transfer material conveyed by the toner image receiver 14a.
[0025]
The conveyance unit 160 is provided between the toner image receiver 14 a and the fixing device 17, and a spur 162 is provided on the upper surface of the conveyance unit 160. The spur 162 scoops up the transfer material that is to be bent and conveyed in the direction of the toner image receiver 14a when the transfer material is separated from the toner image receiver 14a, and transfers the transfer material having the toner image on the back surface to the back surface toner image. Then, the sheet is conveyed to the fixing device 17 while preventing the disturbance.
[0026]
The fixing device 17 serving as fixing means is composed of two roller-shaped fixing members, a fixing roller 17a having a heater inside both rollers and a pressure roller 17b, and between the fixing roller 17a and the pressure roller 17b. The toner image on the transfer material is fixed by applying heat and pressure.
[0027]
Next, the image forming process will be described.
[0028]
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.
[0029]
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.
[0030]
The latent image is reversely developed in a non-contact state by the Y developing unit 13 and a yellow (Y) toner image is formed in accordance with the rotation of the photosensitive drum 10.
[0031]
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. .
[0032]
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).
[0033]
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 the images corresponding to the second, third, and fourth color signals is performed without any influence of the toner image formed earlier, and is equivalent to the image corresponding to the first color signal. It is possible to form an electrostatic latent image.
[0034]
The superimposed color toner image, which is the back image formed on the photosensitive drum 10 as the first image carrying means by the above image forming process, is transferred by the transfer device 14c as the first transfer means in the transfer area 14b. Then, the toner images are transferred onto the toner image receiver 14a which is the second image carrying means (FIG. 3A). At this time, uniform exposure is performed by the simultaneous transfer exposure unit 12d provided inside the photosensitive drum 10 so that good transfer is performed.
[0035]
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 as the photosensitive drum cleaning means or comes into contact with the photosensitive drum 10. It is cleaned by a cleaning blade 19a made of a rubber material and collected by a screw 19b in a waste toner container (not shown). 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.
[0036]
After the superimposed color toner image to be the back surface image is formed on the toner image receiver 14a as described above, the superimposed color toner image to be the front surface image is continuously formed in the same manner as the above color image forming process. It is formed on the drum 10 (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.
[0037]
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. The color toner image of the front image carried on the photosensitive drum 10 and the color toner image of the back image carried on the toner image receiver 14a are synchronized by driving the timing roller 15b. To the transfer area 14b. At this time, the tip of the recording paper P that is brought into contact with the recording paper P and is applied with a DC voltage having the same polarity as the toner (negative polarity in this embodiment) is fed by the brush-shaped paper charger 150, and the recording paper P is the same as the toner. The paper is charged to the polarity, and is attracted to the toner image receiver 14a and fed 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 toner image receiver 14a or the toner image on the photosensitive drum 10, thereby preventing the toner image from being disturbed. Simultaneously with the passage of the recording paper P, the paper charger 150 is separated from the toner image receiver 14a, and the contact is released.
[0038]
The paper charger 150 is released from contact with the toner image receiver 14 a immediately before or simultaneously with the passage of the trailing edge of the recording paper P and is separated from the recording paper P. Further, the voltage is applied to the paper charger 150 only when the recording paper P is being fed, and the voltage applied to the paper charger 150 is cut off simultaneously with the separation from the recording paper P.
[0039]
Further, as the transfer material charging means, a conductive roller, a semiconductive film member, or a blade member that can be contacted and released from the toner image receiver 14a and to which a DC voltage having the same polarity as the toner is applied is used. Is also possible.
[0040]
In the transfer area 14b, the surface image on the photosensitive drum 10 is collectively collected on the recording paper P by a transfer device 14c as a first transfer means to which a voltage having a polarity opposite to that of the toner (plus polarity in the present embodiment) is applied. Transferred to the surface. At this time, the back surface image on the toner image receiver 14a is not transferred to the recording paper P and exists on the toner image receiver 14a. Uniform exposure by a simultaneous transfer exposure device 12d using, for example, a light emitting diode provided inside the photosensitive drum 10 so as to face the transfer region 14b so that a good transfer can be performed at the time of transfer by the transfer device 14c. 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 second 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 surface image on the peripheral surface of the toner image receiver 14a is collectively transferred to the back surface of the recording paper P by the container 14g (FIG. 3C).
[0042]
The recording paper P is a paper separating member serving as a transfer material separating means provided opposite to the driving roller 14d at the end of the toner image receiving member 14a and the curvature of the driving roller 14d for driving the toner image receiving member 14a. The toner is electrostatically separated from the toner image receiver 14a by the charge eliminating action of the AC charge remover 14h, and is conveyed to the fixing device 17 as a fixing unit through a conveyance unit 160 provided with a spur 162 described later. At this time, the paper separating AC static eliminator 14h to which a voltage is applied is disposed opposite to the grounded driving roller 14d so that good separation is achieved.
[0043]
The recording paper P on which the color toner images are formed on both sides is conveyed to a fixing device 17 as fixing means composed of two roller-shaped fixing members having heaters inside both rollers, and a surface image ( The fixing roller 17a, which is a fixing member disposed on the upper side for fixing the toner image on the upper surface side), and the fixing disposed on the lower side for fixing the toner image on the rear surface image (lower surface image). Heat and pressure are applied at the nip T formed by the pressure roller 17b, which is a member, so that the attached toner images on the front and back of the recording paper P are fixed, and the recording paper P on which double-sided image recording has been performed is fixed. The recording paper P is reversed and conveyed through the paper discharge roller 17e, the conveyance rollers 18a and 18b, and the paper discharge roller 18, and is discharged to the upper part of the apparatus with the toner image of the front image as the lower surface. Further, as shown by a one-dot chain line in FIG. 1, a switching member (not shown) is provided at the rear of the fixing discharge roller 17e at the outlet of the fixing device 17, and the toner image of the surface image is straightly discharged to the tray outside the device. You may make it do.
[0044]
The toner remaining on the peripheral surface of the toner image receiver 14a after the transfer is provided facing the driven roller 14e with the toner image receiver 14a interposed therebetween, and contacts the toner image receiver 14a with the support shaft 142 as a rotation fulcrum. Cleaning is performed by a toner image receiver cleaning device 140 having a toner image receiver cleaning blade 141 that can be contacted and released.
[0045]
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 the residual toner is removed by the cleaning device 19, and the uniform exposure unit 12e before charging is removed. Thus, the history of the photosensitive drum 10 in the previous image formation is canceled, and the next image formation cycle is started.
[0046]
By using the above method, the superimposed color toner images are collectively transferred, so that color misregistration of the color image on the toner image receiver 14a, toner scattering and rubbing hardly occur, and good double-sided color with little image deterioration. Image formation is performed.
[0047]
The conveyance part which has a spur concerning this invention is demonstrated using FIG.4, FIG.5 and FIG.1. FIG. 4 is a diagram illustrating the transport unit, and FIG. 5 is a perspective view of a spur provided in the transport unit.
[0048]
A conveyance unit 160 provided with a spur 162 below the transfer material conveyance surface of the toner image receiver 14a is disposed between the toner image receiver 14a and the fixing device 17, and is separated from the toner image receiver 14a. The recording paper P is transported up and down through a transport unit 160 to a fixing device 17 provided with a fixing roller 17a and a pressure roller 17b.
[0049]
A central shaft 162a provided integrally with the spur 162 is inserted into a hole of a semicircular stopper 163b opposite to the guide surface 163a of the conveyance guide member 163, and the tip of the central shaft 162a is stopped by an E ring E. Thus, the spur 162 is rotatably attached to the conveyance guide member 163. A plurality of conveyance guide members 163 to which the spurs 162 are attached are attached to the conveyance unit housing 161 to constitute the conveyance unit 160.
[0050]
The guide surface 163 a of the conveyance guide member 163 is provided closer to the transfer material conveyance surface than the rotation center of the spur 162. As a result, even when the leading end of the recording paper P separated from the toner image receiver 14a comes into contact with the guide surface 163a, it is scooped up by the guide surface 163a and sent to the spur 162, and the protruding portion 162b of the spur 162 is applied to the recording paper P. The spur 162 is driven and rotated in the state of contact or piercing, and the recording paper P is conveyed to the fixing device 17 without rubbing the toner image.
[0051]
The spur 162 has a thickness of 0.05 to 0.5 mm and an outer diameter of 5 to 25 mm etched from a metal plate such as a stainless steel plate or a copper plate, or a thickness of 0.5 to 2.0 mm and an outer diameter of 5 to 25 mm. These are made of a polygonal member having a sharp protrusion 162b at the tip, for example, a hexagonal plate-shaped member.
[0052]
A roller configuration used in the fixing unit and a transfer material conveyance method using the roller configuration will be described with reference to FIGS. 6 is a diagram illustrating a first example of a roller configuration used in the fixing unit, and FIG. 7 is a diagram illustrating a first example of a transfer material conveyance method using the roller configuration of FIG. 8 is a diagram showing a second example of a transfer material conveyance method using the roller configuration of FIG. 6, and FIG. 9 is a second example of a roller configuration used for the fixing unit and a transfer material conveyance using the second example. FIG. 10 is a diagram illustrating a third example of a roller configuration used in the fixing unit and a transfer material conveyance method using the third example.
[0053]
According to FIGS. 6 and 7, the recording paper P is intermittently passed through the fixing device 17 at the time of double-sided image formation that requires heat capacity at the time of fixing, and at the time of surface image formation on only one side by the photosensitive drum 10. The recording paper P is continuously passed, but in any case, it is preferable that the fixing roller 17a for fixing the surface image has a good thermal conductivity and a large heat capacity. As shown in FIG. As the respective roller members, the fixing roller 17a as the upper roller member is a hard roller using a metal roller member 171a such as a steel material or aluminum material having a surface coated with Teflon, for example, and the lower roller member. For example, a rubber roller 172b using, for example, a silicon material is formed on a metal pipe 172a using, for example, an aluminum material. Soft roller which has been subjected to over the door is used. An arc-shaped nip portion T is formed by the pressure roller 17b using a soft roller by pressure bonding of both rollers. Halogen heaters 171c and 172c for fixing heat are provided inside each roller member.
[0054]
As shown in FIG. 7, the recording paper P on which the color toner images are formed on both sides is driven by the curvature of the driving roller 14d for driving the toner image receiver 14a and, if necessary, the end of the toner image receiver 14a. Separation from the toner image receiver 14a is performed by the neutralization action of a paper separation AC neutralizer 14h serving as a transfer material separation unit provided facing the roller 14d.
[0055]
The recording paper P separated from the toner image receiver 14a as the second image carrying means is conveyed by a spur 162 provided below the transfer material conveyance surface PL1 of the toner image receiver 14a, and serves as the fixing roller 17a. The hard roller is fed to the nip portion T of the fixing device 17 serving as fixing means using upper and lower rollers having a configuration in which a soft roller is used as the pressure roller 17b.
[0056]
When the leading edge of the recording paper P as a transfer material is nipped by the arc-shaped nip portion T of the fixing device 17, the recording paper P is tangential to the fixing roller 17a at the point P1 on the recording paper P entry side of the nip portion T. As shown by a thick arrow in FIG. 7, the back surface of the recording paper P is separated from the spur 162, and the recording paper P is conveyed from the upper part of the conveying unit 160 in a state of being separated from the spur 162, The recording paper P is fixed by the fixing device 17. At this time, the extended surface of the transfer material conveyance surface PL1 of the toner image receiver 14a is in the vicinity of the nip portion T of the fixing roller 17a as a roller member on the upper portion of the fixing device 17, for example, on the entry side of the recording paper P in the nip portion T. It is preferable to contact 1 to 3 mm above the point P1. Thereby, the recording paper P smoothly enters the nip portion T.
[0057]
As described above, since the surface image fixing roller is a hard roller, even if the recording paper or OHT used as a transfer material hits the surface image fixing roller, the surface image fixing roller is not damaged. . Further, by using a soft roller as the back surface image fixing roller, the width of the nip portion becomes large, and good fixing is performed.
[0058]
Further, a plate-like entry guide member 165 is provided between the transport unit 160 and the fixing device 17 as shown by a one-dot chain line in FIG. 7, and the leading end of the recording paper P is fixed as an upper roller member through the entry guide member 165. It is also possible to contact the roller 17a. At this time, it is preferable that the leading end portion of the entry guide member 165 is disposed below the point P1 of the nip portion T so that the toner image of the back surface image of the recording paper P is not rubbed by the leading end portion of the entry guide member 165.
[0059]
As a result, the occurrence of spur marks on the toner image on the transfer material is prevented.
[0060]
According to FIG. 8, in this example, the conveying unit 160 described in FIG. 7 is arranged at an upper portion than the arrangement in FIG. 7, and the roller configuration of the fixing unit is the same as that described in FIG. Is used.
[0061]
A recording sheet P on which color toner images are formed on both sides is provided to face the drive roller 14d at the end of the toner image receiver 14a and, if necessary, the curvature of the drive roller 14d that drives the toner image receiver 14a. The toner is separated from the toner image receiver 14a by the neutralization action of the paper separation AC neutralizer 14h as the transfer material separation means.
[0062]
The recording paper P separated from the toner image receiver 14a as the second image carrying means is conveyed by a spur 162 provided below the transfer material conveyance surface PL1 of the toner image receiver 14a, and serves as the fixing roller 17a. The hard roller is fed to the arc-shaped nip portion T of the fixing device 17 serving as fixing means using an upper and lower roller having a configuration in which a soft roller is used as the pressure roller 17b.
[0063]
When the leading edge of the recording paper P as a transfer material is nipped by the arc-shaped nip portion T of the fixing device 17, the recording paper P is tangential to the fixing roller 17a at the point P1 on the recording paper P entry side of the nip portion T. As shown by a thick arrow in FIG. 8, the back surface of the recording paper P is separated from the spur 162, and the recording paper P is conveyed from the upper part of the conveying unit 160 in a state of being separated from the spur 162. The recording paper P is fixed by the fixing device 17.
[0064]
An extension surface PL2 of the conveyance surface of the recording paper P along the spur 162 is in the vicinity of the nip portion T of the fixing roller 17a as a roller member on the upper portion of the fixing device 17, for example, a point on the entry side of the recording paper P in the nip portion T. The recording paper P is smoothly brought into the nip portion T by contacting the upper portion of 0.5 to 2.5 mm from P1.
[0065]
As described above, since the surface image fixing roller is a hard roller, even if the recording paper or OHT used as a transfer material hits the surface image fixing roller, the surface image fixing roller is not damaged. . Further, by using a soft roller as the back surface image fixing roller, the width of the nip portion becomes large, and good fixing is performed.
[0066]
As a result, the occurrence of a spur mark on the toner image on the transfer material is prevented, and image rubbing with the second image carrier means due to the transfer material being pulled when the transfer material is held by the fixing means. Transfer deviation in the second transfer means is prevented.
[0067]
According to FIG. 9, as a roller member of the fixing device 17 of this example, a fixing roller 17c using a soft roller is used instead of the upper fixing roller 17a using the hard roller described in FIGS. Used as a roller.
[0068]
As each roller member of the fixing device 17, a fixing roller 17c as an upper roller member is a soft roller in which a rubber roller 173b made of, for example, silicon is formed on a metal pipe 173a made of, for example, aluminum, and a lower roller is used. Similarly to the upper roller member, the pressure roller 17b as a member is a soft roller in which a rubber roller 172b made of, for example, silicon is formed on a metal pipe 172a made of, for example, aluminum, and the surface thereof is coated with, for example, Teflon coating. A nip portion T is formed by the upper and lower rollers using a soft roller by pressure bonding of both rollers. Since the upper and lower rollers are soft rollers, the nip portion T is provided in a straight line substantially orthogonal to a plane PL3 passing through the central axis of the fixing roller 17c and the central axis of the pressure roller 17b. Halogen heaters 173c and 172c for fixing heat are provided inside each roller member.
[0069]
Since the nip portion T is formed in a straight line, the surface PL3 so that the upper roller is inclined toward the discharge side of the recording paper P with respect to the transfer material conveyance surface PL1 of the toner image receiver 14a as the second image carrier. The fixing roller 17c and the pressure roller 17b are inclined, and the inlet of the nip portion T is inclined upward from the outlet.
[0070]
The recording paper P on which the color toner images are formed on both surfaces is provided with a curvature of the driving roller 14d for driving the toner image receiver 14a and a transfer material provided opposite to the driving roller 14d at the end of the toner image receiver 14a. The toner image receiving member 14a is electrostatically separated by the charge removing action of the paper separating AC charge remover 14h as the separating means.
[0071]
The recording paper P separated from the toner image receiver 14a as the second image bearing means is conveyed by a spur 162 provided below the transfer material conveyance surface PL1 of the toner image receiver 14a, and the fixing roller 17c and The pressure roller 17b is fed to the nip portion T of the fixing device 17 as fixing means using upper and lower rollers having a configuration in which a soft roller is used.
[0072]
When the leading edge of the recording paper P as a transfer material is nipped by the nip portion T of the fixing device 17, a force that lifts the recording paper P in the extending direction of the linear nip portion T provided in an inclined manner works. 9, the back surface of the recording paper P is separated from the spur 162, and the recording paper P is transported over the transport unit 160 in a state of being separated from the spur 162. Fixing is performed. At this time, the extended surface of the transfer material conveying surface PL1 of the toner image receiver 14a is in the vicinity of the nip portion T of the fixing roller 17c as the upper roller member of the fixing device 17, for example, on the entry side of the recording paper P of the nip portion T. It is preferable to contact 1 to 3 mm above the point P1. Thereby, the recording paper P smoothly enters the nip portion T.
[0073]
As a result, the occurrence of a spur mark on the toner image on the transfer material is prevented, and image rubbing with the second image carrier means due to the transfer material being pulled when the transfer material is held by the fixing means. Transfer deviation in the second transfer means is prevented.
[0074]
According to FIG. 10, as a roller member of the fixing device 17 of this example, instead of the upper fixing roller 17a described in FIGS. 6 and 7, a heat fixing film 17d acting as a hard roller described below is provided on the upper side. Used as a roller member.
[0075]
The heat fixing film 17d as an upper roller member is composed of, for example, a thin fixing film 174a having a thickness of 40 to 100 μm, a plate-like heating element (ceramic heater) 174b, and a heater holder 174c for holding the ceramic heater 174b. Is done. The seamless fixing film 174a includes an internal base material, an intermediate conductive layer, and a surface release layer. The pressure roller 17b as the lower roller member is a soft roller in which a rubber roller 172b made of, for example, silicon is formed on a metal pipe 172a made of, for example, aluminum, as described in FIG. A halogen heater 172c for fixing heat is provided inside the member. An arc-shaped nip portion T is formed by the pressure roller 17b using a soft roller by pressure bonding of both rollers.
[0076]
The base material of the fixing film 174a can withstand high temperatures and is rotationally driven while sliding with the ceramic heater 174b at the high temperatures. Even in such an environment, it is preferable to use a polyimide resin as a material that has a small dimensional change and maintains a high elastic modulus, and a 5 to 15 μm thick carbon is dispersed on the surface of a 20 to 80 μm polyimide resin. It is preferable to increase the thickness to about 40 to 100 μm. By increasing the thickness to about 40 μm, the strength and rigidity are improved, and the fixing film 174a can be regulated at the end without buckling the rotating side of the fixing film 174a. On the other hand, if the thickness is more than 100 μm, the heat conduction is deteriorated, and the heat conduction is increased, so that it is difficult to heat instantaneously and the electric power used is increased. In order to prevent offset, it is preferable to adopt a two-layer structure in which, for example, a fluororesin (PFA or PTFE) layer is provided as a release layer. Further, the inner surface of the base material of the fixing film 174a and the surface of the ceramic heater 174b A conductive layer is provided and grounded to eliminate the influence of triboelectric charges generated by sliding between and.
[0077]
In addition, a conductive filler is placed in the release layer to reduce the resistance so as to release the charge off the trailing edge of the recording paper P in a low humidity environment, thereby preventing offset. However, if the resistance value is too low, the transfer charge leaks and causes an offset.^Ten~ 5x10¹¹Ω / cm²The resistance value is preferable.
[0078]
The recording paper P on which the color toner images are formed on both surfaces is provided with a curvature of the driving roller 14d for driving the toner image receiver 14a and a transfer material provided opposite to the driving roller 14d at the end of the toner image receiver 14a. The toner image receiving member 14a is electrostatically separated by the charge removing action of the paper separating AC charge remover 14h as the separating means.
[0079]
The recording paper P separated from the toner image receiver 14a as the second image carrying means is transported by a spur 162 provided below the transfer material transport surface PL1 of the toner image receiver 14a and functions as the hard roller. Then, the sheet is fed to the nip portion T of the fixing device 17 as a fixing means by an upper and lower roller having a configuration in which a soft roller is used as the heat fixing film 17d and the pressure roller 17b.
[0080]
When the leading edge of the recording paper P as a transfer material is sandwiched by the arc-shaped nip portion T of the fixing device 17, the recording paper is tangential to the thermal fixing film 17d at the point P1 on the recording paper P entry side of the nip portion T. The force by which P is lifted works, and the back surface of the recording paper P is separated from the spur 162 as shown by the thick arrow in FIG. Then, the fixing of the recording paper P by the fixing device 17 is performed. At this time, the extended surface of the transfer material conveying surface PL1 of the toner image receiver 14a is in the vicinity of the nip portion T of the heat fixing film 17d as a roller member on the upper portion of the fixing device 17, for example, the recording paper P entrance side of the nip portion T. It is preferable to contact 1 to 3 mm above the point P1. Thereby, the recording paper P smoothly enters the nip portion T.
[0081]
As described above, since the surface image fixing roller is a hard roller, even if the recording paper or OHT used as a transfer material hits the surface image fixing roller, the surface image fixing roller is not damaged. . Further, by using a soft roller as the back surface image fixing roller, the width of the nip portion becomes large, and good fixing is performed.
[0082]
As a result, the occurrence of a spur mark on the toner image on the transfer material is prevented, and image rubbing with the second image carrier means due to the transfer material being pulled when the transfer material is held by the fixing means. Transfer deviation in the second transfer means is prevented.
[0083]
The spur cleaning member and the arrangement thereof will be described with reference to FIGS. 11 to 14, 4, 5, and 1. FIG. 11 is a view showing a first example of a method of attaching the cleaning member to the spur, FIG. 12 is a perspective view showing the cleaning member, and FIG. 13 is a second method of attaching the cleaning member to the spur. FIG. 14 is a diagram illustrating an example, and FIG. 14 is a diagram illustrating a third example of the method of attaching the cleaning member to the spur.
[0084]
As shown in FIGS. 4, 5 and 1, the conveying section 160 having a spur 162 is provided between the toner image receiver 14a as the second image carrying means and the fixing device 17 as the fixing means. .
[0085]
A recording sheet P on which color toner images are formed on both sides is provided to face the drive roller 14d at the end of the toner image receiver 14a and, if necessary, the curvature of the drive roller 14d that drives the toner image receiver 14a. The toner is separated from the toner image receiver 14a by the neutralization action of the paper separation AC neutralizer 14h serving as a transfer material separation means.
[0086]
The recording paper P separated from the toner image receiver 14a as the second image carrying means is conveyed by a spur 162 provided in the conveyance section 160, and the fixing device 17 as a fixing means by the fixing roller 17c and the pressure roller 17b. The paper is fed to the nip portion T and the toner images on both sides are fixed.
[0087]
As shown in FIGS. 11 and 12, a central shaft 162 a integrated with the spur 162 is attached to the transport guide member 163, so that the spur 162 can be rotated by the transport guide member 163. The recording paper P on which the toner image is formed is conveyed on the spur 162, but the protrusion 162b of the spur 162 driven to rotate by the recording paper P is soiled by the toner image of the back image, and the toner attached to the protrusion 162b. As a result, the recording paper P transported by the image smears. For this reason, a cleaning member 210 is provided for cleaning the toner adhering to the protrusion 162b. Further, the guide surface 163a of the conveyance guide member 163 is provided on the passing side of the recording paper P from the center of the spur 162 so that the leading edge of the recording paper P after separation from the toner image receiver 14a described in FIG. Let him scoop up. This prevents the toner image from being rubbed due to the trailing edge of the transfer material when it enters the conveyance section or the trailing edge of the transfer material when it is removed from the conveyance section.
[0088]
As shown in FIG. 12, the cleaning member 210 includes a cleaning brush 211 and a brush holder 212 for holding the cleaning brush 211. In FIG. 12, the cleaning brush 211 is provided at a position corresponding to the spur 162, but the brush portion may be provided continuously.
[0089]
By using a brush member as the cleaning member, the rotation of the spur is kept good and the spur is cleaned well.
[0090]
Further, as shown in FIG. 11, the downstream side of the spur 162 in the rotation direction on the side opposite to the recording paper P passing side is the tip of the cleaning brush 211, and the tip of the cleaning brush 211 is brought into contact with the protruding portion 162b. 210 is arranged. By arranging the brush eyes of the cleaning brush 211 in parallel, the rotation of the spur 162 is not hindered, and the toner attached to the protrusion 162b is cleaned. A brush with a rough eye is preferable in order to satisfactorily clean the adhered toner. Further, when the protruding portion 162b is in deep contact with the brush of the cleaning brush 211, the spur 162 becomes defective in rotation, so it is preferable that the spur 162 be shallow to the brush, for example, about 0.5 to 1.5 mm.
[0091]
As described above, the cleaning member is disposed without hindering the transfer of the transfer material.
[0092]
In addition, as shown in FIG. 13, the cleaning member 210 stands substantially vertically below the rotating portion of the spur 162 on the side opposite to the recording paper P passing side, and the tip of the cleaning brush 211 is brought into contact with the protruding portion 162b. It is also possible to dispose the cleaning member 210 and clean the toner attached to the protrusion 162b. Although this can be brought into deeper contact with the brush rather than being disposed horizontally, the spur 162 becomes defective in rotation when the projecting portion 162b is in deep contact with the brush of the cleaning brush 211. It is preferable that the contact is about 0 mm.
[0093]
As described above, the cleaning member is disposed without hindering the transfer of the transfer material.
[0094]
Further, as shown in FIG. 14, the cleaning member 210 is disposed on the guide surface 163 a of the conveyance guide member 163 on the recording paper P passing side, and the tip of the cleaning brush 211 of the cleaning member 210 is placed on the protruding portion 162 b of the spur 162. It is also possible to clean the toner adhering to the projecting portion 162b by contact. The brush surface of the cleaning brush 211 may be disposed on the same surface as the guide surface 163a. In FIG. 14, the cleaning member 210 is arranged on the downstream side in the rotation direction of the spur 162 with respect to the contact position with the recording paper P. However, on the upstream side, the cleaning member 210 is on the guide surface 163a of the transport guide member 163 or on the same surface as the guide surface 163a. The cleaning member 210 may be disposed and disposed so that the brush tip of the cleaning brush 211 is in contact with the protruding portion 162b.
[0095]
As described with reference to FIGS. 11 to 14 above, the spur is cleaned well and the spur is prevented from being contaminated.
[0096]
Further, although the color image forming apparatus has been described as an embodiment of the above double-sided image forming apparatus, the present invention is not necessarily limited to this, and monochrome double-sided image formation by the same process as described in FIG. This also applies to the device.
[0097]
Furthermore, in the image forming apparatus of the present invention, in addition to the double-sided image formation for forming images on both sides of the transfer material as described in the above embodiment, one side for forming an image on only one side of the front or back surface of the transfer material. Of course, image formation can also be performed.
[0098]
【The invention's effect】
According to the first to fifth aspects, it is possible to prevent the occurrence of a spur mark on the toner image on the transfer material and to prevent image rubbing when the transfer material is sandwiched between the fixing means.
[0099]
According to the sixth aspect, the spur is well cleaned and the spur is prevented from being contaminated.
[0100]
According to the seventh aspect, the rotation of the spur is kept good and the spur is cleaned well.
[0101]
According to the eighth aspect of the present invention, the toner image is prevented from being rubbed due to the trailing edge of the transfer material when the transfer material enters the conveyance section or the trailing edge when the transfer material comes out of the conveyance section.
[0102]
According to the ninth aspect, the cleaning member is disposed without hindering the transfer of the transfer material.
[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 according to the present invention.
FIG. 2 is a side sectional view of the first image bearing means of FIG.
FIG. 3 is a diagram illustrating a toner image forming state on both sides of the image forming apparatus according to the present invention.
FIG. 4 is a diagram illustrating a transport unit.
FIG. 5 is a perspective view of a spur provided in the transport unit.
FIG. 6 is a diagram illustrating a first example of a roller configuration used in the fixing unit.
7 is a diagram showing a first example of how a transfer material is conveyed by the roller configuration of FIG. 6; FIG.
FIG. 8 is a diagram illustrating a second example of a transfer material conveyance method using the roller configuration of FIG. 6;
FIG. 9 is a diagram illustrating a second example of a roller configuration used in the fixing unit and a transfer material conveyance method using the second example.
FIG. 10 is a diagram illustrating a third example of a roller configuration used in the fixing unit and a transfer material conveyance method using the third example.
FIG. 11 is a diagram showing a first example of a method for attaching a cleaning member to a spur.
FIG. 12 is a perspective view showing a cleaning member.
FIG. 13 is a diagram showing a second example of a method for attaching a cleaning member to a spur.
FIG. 14 is a diagram showing a third example of a method for attaching a cleaning member to a spur.
[Explanation of symbols]
10 Photosensitive drum
11 Scorotron charger
12 Exposure optics
13 Developer
14a Toner image receiver
14c Transfer device
14d Driving roller
14g Back transfer device
14h Paper separation AC static eliminator
17 Fixing device
17a, 17c fixing roller
17b Pressure roller
17d heat fixing film
160 Conveying section
162 Spur
163 Transport guide member
165 Entrance guide member
211 Cleaning brush
P Recording paper
T Nip part

Claims (9)

First image carrying means for carrying a toner image formed by the toner image forming means;
A belt-like second image carrying means for transferring the toner image carried on the first image carrying means and carrying the transferred toner image on the surface;
A first transfer means for transferring a toner image carried on the first image carrying means to a surface of a transfer material on the side facing the first image carrying means ;
A second transfer means for transferring a toner image carried on the second image carrying means to a surface of a transfer material facing the second image carrying means ;
Fixing means for fixing and fixing the toner images transferred to both surfaces of the transfer material by sandwiching and conveying the transfer material by a fixing member that rotates in pairs;
After the transfer material is conveyed by the second image carrying means and the transfer material is separated from the second image carrying means,
In the image forming apparatus fixed by the fixing unit,
Between the fixing means and the second image bearing means, from the extended surface of the transfer material conveying surface of the second image carrying means, the surface side of the transfer material on the side opposite to the second image bearing means in a transport unit having a spur to convey the transfer material is provided, it intended for feeding to the fixing means the transfer material through the transfer section,
The transfer material is separated from the belt-like second image carrying means at the end of the second image carrying means on the fixing means side, and moves to the fixing means along the spur of the transport section. As
The transfer material is separated from the spur and the transfer material is separated from the spur when the leading end of the transfer material is sandwiched between nip portions formed by the pair of fixing members of the fixing unit. An image forming apparatus transported by a fixing unit. The nip portion when the fixing member is brought into the deforming pressure contact state has a convex shape on the surface side of the transfer material facing the second image carrier , or the inclination between the inlet and the outlet is the transfer The image forming apparatus according to claim 1, wherein the image forming apparatus is set to be inclined to the surface side of the transfer material on the side facing the second image carrying unit with respect to the conveyance direction of the material. Those in the nip portion near the fixing member surface side of the transfer material on the side opposite to the first image bearing means of the extension surface the fixing means of the conveying surface of the transfer material of the second image bearing means The image forming apparatus according to claim 1, wherein the image forming apparatus is in contact with the image forming apparatus. That extension plane of the conveying surface of the transfer material along the spur comes into contact with the nip portion near said first of said fixing member surface side of the side of the transfer material opposite the image carrying means of the fixing means The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   2. An entry guide member is provided between the conveyance unit and the fixing unit, and a leading end of the transfer material is brought into contact with a roller member above the fixing unit via the entry guide member. 4. The image forming apparatus according to any one of items 3 and 3. The image forming apparatus according to claim 1, further comprising a cleaning member that contacts the tip end portion of the spur and cleans the spur.   The image forming apparatus according to claim 6, wherein the cleaning member is a brush-like member.   8. The image forming apparatus according to claim 6, wherein a conveyance guide member for the transfer material is provided in the conveyance unit on a passage side of the transfer material from a center of the spur. 9.   The image forming apparatus according to claim 6, wherein the cleaning member is provided on the same surface as the conveyance guide member or on the opposite side of the transfer material passage side.

Images