JP2004354778A - Transfer material separation mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent image staining caused by the adhesion of toner to a separation pawl even in the case of using a separation needle to which separation charge is imparted and the separation pawl for performing mechanical separation in the case of separation. <P>SOLUTION: The transfer separation mechanism is equipped with a transfer means for transferring a toner image formed on an image carrier to transfer material, a separation means for separating or assisting to separate the transfer material carried to pass through the transfer means from the surface of a latent image carrier by applying specified voltage from the back of the transfer material, and a plurality of separation pawl means whose edges come into contact with the rotating latent image carrier and are arranged in the rotary shaft direction of the latent image carrier. The separation means is the separation needle where a plurality of needle-shaped parts whose edge part is pointed are arranged in a line, and the needle-shaped part having positional relation facing to the separation pawl means out of a plurality of needle-shaped parts is removed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer material separating mechanism used in an image forming apparatus such as a copying machine, a printer, a facsimile and the like.
[0002]
[Prior art]
2. Description of the Related Art In an image forming apparatus such as a copying machine, a printer, and a facsimile, a mechanism having a separation needle and a separation claw is known as a mechanism for separating a transfer material after a toner image is transferred from a photosensitive drum (for example, see Document No. 1). . This is because the transfer material conveyed when the toner image is transferred to the transfer material is charged with electrostatic charge to attract the toner electrostatically from the opposite side of the photoconductor drum. The transfer material is electrostatically attracted and conveyed, so that the transfer material is electrostatically and mechanically separated in order to be conveyed to fixing means for fixing the toner located on the downstream side of the conveyance path to the transfer material. belongs to.
Specifically, the end of the transfer material contacts the surface of the photoconductor, and the transfer material is mechanically separated from the surface of the transfer material holding the toner by a separation claw for separating the transfer material from the photoconductor. In addition, in order to effectively prevent discharge generated when the transfer material is peeled off from the photosensitive drum attracted by the electrostatic charge, a separation needle (static elimination needle) for removing electric charge from the transfer material after the transfer is completed. Is provided.
A plurality of the separation claws are provided at predetermined intervals along the longitudinal direction of the photoconductor, and separation needles are also arranged in rows along the width direction of the transfer material to be conveyed. There is also known a separation needle in which a predetermined AC charge is positively applied in order to effectively remove the charge accumulated in the transfer material (Reference No. 2).
[0003]
[Reference number 1]
JP-A-7-104584 [Reference number 2]
Japanese Patent Application Laid-Open No. 2000-3081
On the other hand, in such an apparatus using both the separation claw and the separation needle, if the separation claw is continuously used, the toner may adhere to the separation claw and the amount of toner adhered may gradually accumulate. Then, since the accumulated toner is also transferred to the transfer material, band-like toner stain corresponding to the position of the separation claw or scattered dust-like stain causes image deterioration.
[0005]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and it is an object of the present invention to provide a transfer material separating mechanism capable of performing stable transfer even when a separating claw and a separating needle are used together.
[0006]
[Means for Solving the Problems]
According to a first aspect of the present invention, as a transfer separation mechanism, a transfer unit that transfers a toner image formed on an image carrier to a transfer material, and a transfer material that is conveyed through the transfer unit A separating means for applying a predetermined voltage from the back surface of the latent image carrier to separate or assist the separation of the transfer material from the surface of the latent image carrier, and rotating the latent image carrier by contacting the latent image carrier whose tip rotates. A plurality of separation claws arranged in the axial direction, wherein the separation means is a separation needle in which a plurality of needle-like portions having sharpened distal ends are arranged in a row, and the separation claw and the separation claw among the plurality of needle-like portions are provided. It is characterized in that needle-like portions having a facing positional relationship have been removed.
[0007]
According to the first aspect of the present invention, since the needle-like portion of the separating means corresponding to the separating claw is removed, it is possible to prevent the charge from being injected into the separating claw and to suppress the adhesion of the toner. You. As a result, there is no occurrence of image deterioration due to band-like toner stain corresponding to the position of the separation claw, or scattered dust-like stain.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0009]
FIG. 1 shows an example of an image forming apparatus according to the present invention. The image forming apparatus shown in FIG. 1 is a copying machine having a reader unit (image reading unit) and a printing unit (printing unit), and FIG. 1 is a longitudinal sectional view showing a schematic configuration thereof.
[0010]
First, an overall configuration of the copying machine 10 will be described with reference to FIG.
[0011]
A copying machine 10 shown in FIG. 1 includes a copying machine main body 11 constituting an entire framework, and a reader unit 12 for reading image surfaces (image information) G of originals D1 and D2 is provided above the copying machine main body 11. A printing unit 13 is provided below the printing unit 13 for forming a toner image on a transfer material P such as paper in accordance with image information read by the reader unit 12.
[0012]
The former reader unit 12 includes a transparent document table 14 on which the document D1 is placed with its image surface G facing down, and an openable and closable document for bringing the image surface G of the document D1 into close contact with the upper surface of the document table 13. A scanning unit 18 having a pressing plate 15, a light source 16 for irradiating light from below onto the image surface G of the document D1 on the document table 14 and a first reflecting mirror 17, and a light reflected from the first reflecting mirror 17. Further, there are provided second and third reflecting mirrors 20 and 21 for reflecting light, a lens array 22 for forming an image of light from the third reflecting mirror 21, and a CCD 23 to which light from the lens array 22 is incident. I have. The above-described scanning unit 18 is configured to scan the image surface G of the document D1 with the light source 16 while moving rightward from the home position HP shown in FIG. 1, and to return to the home position HP after the scanning is completed. I have. The above is a configuration for performing the so-called fixed reading, in which the document D1 is fixed and the scanning unit 18 is moved to read the image surface G.
[0013]
The reader unit 12 further includes an automatic document feed mechanism 24 for moving the document D2, fixing the scanning unit 18 and reading the document surface G, that is, performing a so-called drift reading. The automatic document feeder 24 transports the document D2 on the paper feed table 25 leftward toward the scanning unit 18 disposed at the home position HP, and a paper feed table 25 that supports the leading end side of the document D2 from below. And a discharge roller pair 27 that carries out the document D2 read by the scanning unit 18 to the left from the scanning unit 18. The automatic document feed mechanism 24 conveys the document D2 to the left in FIG. 1 by the above-described paper feed roller pair 26 and paper discharge roller pair 27, and after reading the document D2, discharges the document D2 to the document discharge tray 28. [0014]
The fixed reading and the flow reading are selectively used, for example, while a document D1 such as a bound book is placed on the platen 14 to perform fixed reading, while a cut sheet-shaped document D2 is The document is placed on the paper feed table 25 and read.
[0015]
The print unit 13 includes a cylindrical photoconductor (hereinafter, referred to as a “photoconductor drum”) 30 as an electrostatic latent image carrier (subject to be charged), which is disposed substantially at the center in the vertical direction on the left side in FIG. Have. The photoreceptor drum 30 is rotatably supported by the copying machine main body 11 in the direction of the arrow (clockwise in the figure), and its primary charger (charging means) 31 is arranged around the photoconductor drum 30 substantially in the rotation direction. , An exposure unit (exposure unit) 32, a development unit (development unit) 33, a transfer charger (transfer unit) 34, and a cleaning unit 35 are provided. Further, along a transport path 36 (indicated by a two-dot chain line in FIG. 1) of a transfer material P such as paper to be image-formed, from the upstream side to the downstream side (from substantially lower to upper in FIG. 1), A paper feed cassette 37, a paper feed roller 38, a transport roller pair 40, a registration roller pair 41, a transport guide 42, a fixing device (fixing unit) 43, a paper discharge roller pair 44, and a paper discharge tray 45 are provided.
[0016]
The photosensitive drum 30 is configured by providing a photosensitive layer such as OPC (organic optical semiconductor) or amorphous silicon on the outer peripheral surface of a conductive drum base such as aluminum. The photoconductor drum 30 is driven to rotate at a predetermined process speed (peripheral speed) in the direction of the arrow by a driving unit (not shown).
[0017]
In the present embodiment, a scorotron type corona charger is used as the primary charger 31. The primary charger 31 is configured to uniformly charge the surface of the photosensitive drum 30 to a predetermined polarity / potential by applying a charging bias from a charging bias application power supply (not shown).
[0018]
The exposing device 32 has a laser oscillator, a polygon mirror, and the like (both not shown), and forms an electrostatic latent image on the surface of the photosensitive drum 30. The image information of the document D1 (or D2) read by the reader unit 12 is appropriately converted by an image processing unit (not shown) provided in the printing unit 13 into A / D conversion, density correction, shading correction, and the like. After the processing, the image signal is input to the laser oscillator as an image signal. The laser oscillator exposes the charged surface of the photosensitive drum 30 via a polygon mirror or the like with a laser beam whose ON / OFF is controlled based on the image signal, and removes the charge of the exposed portion to remove the electrostatic latent image. Is formed.
[0019]
The developing device 33 includes a developing container 46 that stores the developer and a developing roller that conveys the developer carried on the surface to a developing position facing the surface of the photosensitive drum 30 by rotating the developer in the direction of the arrow (counterclockwise). 47. A developing bias is applied to the developing roller 47 by a developing bias application power supply (not shown), whereby toner in the developer adheres to the electrostatic latent image on the surface of the photosensitive drum 30, and this electrostatic latent image is removed. The image is developed as a toner image.
[0020]
The transfer charger 34 is formed by a roller-shaped member provided so as to face the surface of the photosensitive drum 30. To the transfer charger 34, a transfer bias having a polarity opposite to that of the toner image on the photosensitive drum 30 is applied by a transfer bias application power supply (not shown), whereby the toner on the photosensitive drum 30 is applied to the surface of the transfer material P. This is for transferring an image. Here, the transfer material P on which the toner image is transferred is stored in the paper feed cassette 37, is fed by the paper feed roller 38, is transported by the transport roller pair 40, and is temporarily transferred by the registration roller pair 41. After being stopped, the toner image is sent out from the pair of registration rollers 41 so as to match the timing with the toner image on the photosensitive drum 30.
[0021]
The cleaning device 35 has a cleaning blade 48 in contact with the surface of the photoconductor drum 30 to remove residual toner remaining on the surface of the photoconductor drum 30 without being transferred onto the transfer material P during the above-described transfer.
A plurality of separation claws 60 each having a tip abutting on the surface of the photoconductor drum 30 are arranged at predetermined intervals along the longitudinal direction of the photoconductor drum 30 on the lower surface side (conveyance path side) of the cleaning device 35. The details of the separation claw 60 will be described later.
[0022]
A transport guide 42 that guides the transfer material P after the transfer of the toner image to the fixing device 43 is provided downstream of the transfer charger 34.
On the transfer charger 34 side of the transport guide 42, separation needles 70 having a sharp tip as separating means are arranged in a row in the width direction of the transport path. Details of the separation needle 70 will be described later.
[0023]
The fixing device 43 has a fixing roller 51 heated by a heater 50 disposed inside, and a pressure roller 52 pressing the transfer material P against the fixing roller 51, and an unfixed toner image is formed on the surface. The transfer material P carried and transported is heated and pressed to fix a toner image on the surface of the transfer material P.
[0024]
The discharge roller pair 44 discharges the transfer material P on which the toner image has been fixed onto a discharge tray 45 as a completed product.
[0025]
In the copying machine 10 having the configuration described above, when forming an image, first, the photosensitive drum 30 is driven to rotate in the direction of the arrow by the driving unit, and the surface thereof is set to a predetermined polarity and potential by the primary charger 31. Charged uniformly. An electrostatic latent image corresponding to the image information is formed on the surface of the charged photosensitive drum 30 by irradiation of laser light from an exposure device 32 that operates according to the image information of the document D1 (or D2) read by the reader unit 12. It is formed. The electrostatic latent image is developed with a toner by a developing device 33 as a toner image. The toner image formed on the surface of the photoconductor drum 30 is transferred to the transfer material P conveyed at a predetermined timing by the registration roller pair 41 and the like, and a transfer bias is applied to the transfer charger 34 so that the transfer material P Transferred to the surface. The residual toner remaining on the surface of the photosensitive drum 30 after the transfer of the toner image is removed by the cleaning device 35, and the photosensitive drum 30 is provided for the next image formation. On the other hand, the transfer material P after the transfer of the toner image is transported to the fixing device 43 along the transport guide 42, where the toner image is fixed on the surface by receiving heat and pressure. The transfer material P after the toner image is fixed is discharged onto the paper discharge tray 45 by the paper discharge roller pair 44 with the image surface (the surface on which the toner image is fixed) facing downward, that is, in a face-down state. Thus, the image forming (printing) by the copying machine 10 is completed.
[0026]
In the above-described image forming apparatus, the quality of the final print quality depends on the performance of each component. Therefore, it also depends on the transfer material separating performance of a transfer material separating mechanism (described later), which is one of the constituent members.
[0027]
Next, a transfer material separating mechanism according to the present invention will be described with reference to FIGS.
FIG. 3 is a schematic view of the separation needle and the separation claw viewed from the downstream side in the transport direction of the transfer material P. Four separation claws are arranged along the longitudinal direction of the photoconductor drum. The separation claw 60 is formed of an insulating material (for example, an insulating synthetic resin or ceramic), is pivotally attached to the frame 35a constituting a part of the cleaning device 35, and is provided with a biasing means such as a spring. The end 60a of the photosensitive drum 30 is in contact with the surface of the photosensitive drum 30 (not shown). The four separating claws are arranged at predetermined intervals corresponding to the width of the sheet conveyed on the conveying path of the copying machine. The outside corresponds to the large size (the case where the paper is passed with the long side of A4 as the leading end, or the paper passing of A3).
On the other hand, a separation needle 70 as a separation unit is provided below in FIG. 3 in a positional relationship facing the separation claw 60 with respect to the transfer surface M of the transfer material P. The separation needle 70 in this embodiment is provided with a plurality of needle-like portions 70a having a sharp tip, and has a shape like a saw blade as a whole. Electrode member. The separation needle 70 has a needle-like portion 70 a at the tip provided with a gap of, for example, about 5 mm from the photosensitive drum 30, and is disposed slightly upstream of the tip 60 a of the separation claw 60 with respect to the transfer direction of the transfer material P. In addition, the transfer material P is arranged slightly below the sheet conveying surface (indicated by a broken line in FIG. 2) M so as not to hinder the conveyance of the transferred transfer material P.
Then, as shown in FIG. 3, the positional relationship corresponding to the separation claw 60, specifically, of the needle-like portions 70 a arranged in a row of the separation needles 70, is positioned immediately below the position of the separation claw 60. The needle-like portion 70b thus removed is removed, and the release of charges for separation is suppressed.
[0028]
Regarding the operation and effect of the transfer material separating mechanism according to the present invention described above, the amorphous silicon photoconductor having a positive (plus) charging characteristic is used as the photoconductor drum 30, and reversal development is performed using toner having a positive charge. An example will be described again with reference to FIG.
[0029]
First, the surface of the photoconductor drum 30 is uniformly charged to a predetermined positive potential (for example, +250 V in the case of a silicon photoconductor having a film thickness of 20 μm) by the primary charger 31. The surface of the charged photosensitive drum 30 is subjected to image exposure in accordance with image information by an exposure device 32, and charges on exposed portions are removed to form an electrostatic latent image. A toner having a positive charge is attached to the portion from which the charge has been removed by a developing device 33 to which a bias voltage for reversal development (for example, Vpp 1.7 KV / Vdc 160 V) is applied, and reversal development is performed as a toner image. On the other hand, the transfer material P conveyed from the lower sheet cassette 37 is temporarily stopped by the registration roller pair 41, and the registration roller pair 41 is rotated so as to match the timing with the toner image on the photosensitive drum 30. The transfer material P is passed through a transfer nip portion N1 (see FIG. 2) between the photosensitive drum 30 and a transfer roller (hereinafter, referred to as a "transfer roller 34") as a transfer charger (transfer member) 34. At this time, a negative charging bias (−2 KV in this embodiment) having a polarity opposite to that of the toner image on the photosensitive drum 30 is applied to the transfer roller 34. By applying the charging bias, a negative charge is applied to the back surface of the transfer material P, whereby the positive toner image on the photosensitive drum 30 is transferred to the surface of the transfer material P. The transfer material P on which the toner image has been transferred by the reversal development is negatively charged by the transfer bias at the time of transfer. On the other hand, the surface of the photosensitive drum 30 after the transfer of the toner image remains positive because the polarity at the time of charging is positive. Therefore, the transfer material P after the transfer of the toner image is electrically attracted to the surface of the photosensitive drum 30.
[0030]
The transfer material P after the transfer of the toner image electrostatically attracted to the photosensitive drum 30 in this manner is transferred to the photosensitive drum 30 by the leading end of the separating member 60 which is a main component of the transfer and separation mechanism. 30 mechanically separated from the surface. At the time of this separation, a DC bias charge is applied to the separation needle 70 (for example, +3.5 KV), so that the transfer material P and the photoconductor drum 30 are neutralized. At this time, since the tip (70b) of the separation needle 70 located immediately below the separation claw 60 on the transport surface side is removed, such discharge is not performed. However, since the discharge from the distal end portion (needle-shaped portion 70a) of the separation needle 70 is a somewhat widespread discharge, the discharge from the needle-shaped portion 70a of the adjacent separation needle removes the charge of the photosensitive drum and the transfer material. Is substantially performed, but no charge is injected into the separation claw 60 because there is no separation claw 60 immediately above where the charges are concentrated. As a result, toner contamination of the separation claw 60 can be prevented with a simple configuration in which the needle-like portion 70b immediately below the position of the separation claw 60 is removed.
The transfer material P thus well separated is guided to the downstream fixing device 43 through the transport path.
[0031]
In the above description, an example in which the transfer material separating mechanism according to the present invention is applied to an electrophotographic image forming apparatus (copier) has been described. The present invention can also be applied to a recording type image forming apparatus. Further, the present invention can be applied not only to a monochrome image forming apparatus but also to a color image forming apparatus.
[0032]
【The invention's effect】
As described above, according to the transfer material separation mechanism of the present invention, the separation claw 60 as the separation means has a simple configuration in which the needle-like portion 70b immediately below the separation claw 60 corresponding to the position of the separation claw 60 is removed. Toner contamination can be prevented. As a result, it is possible to realize a stable separation mechanism that does not cause dust on the transferred toner image or dust-like stain due to toner scattering over a long period of time.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an image forming apparatus according to the present invention.
FIG. 2 is a schematic configuration diagram of a transfer material separating mechanism according to the present invention.
FIG. 3 is a schematic diagram illustrating a relationship between a separation claw and a separation needle in the transfer separation mechanism according to the present invention.
[Explanation of symbols]
Reference numeral 10: copying machine (image forming apparatus), 30: photosensitive drum, 31: primary charger (charging unit), 32: exposure unit (exposure unit), 33: developing unit (developing unit), 34 ... Transfer roller (transfer means, transfer charger),..., Conveyance guide, 42a, guide surface, 43, fixing device (fixing means), 60, separating claw, 70, separating means (separating needle) , 70a ... needle-like portion, N1 ... transfer nip portion, N2 ... fixing nip portion, P ... transfer material,

Claims (1)

Transfer means for transferring the toner image formed on the image carrier to a transfer material,
A separation unit for applying a predetermined voltage from the back surface of the transfer material conveyed through the transfer unit to separate the transfer material from the surface of the latent image carrier or to assist the separation,
A plurality of separation claws arranged in the rotation axis direction of the latent image carrier in contact with the latent image carrier whose tip rotates.
The separating means is a separating needle in which a plurality of needle-like portions having sharpened tips are arranged in a row, and that the needle-like portion of the plurality of needle-like portions facing the separation claw has been removed. Characteristic transfer material separation mechanism.

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