JP2005351946A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which ensures high durability by greatly reducing filming of an image carrier and wear and chipping of a cleaning blade. <P>SOLUTION: The image forming apparatus includes: the image carrier for carrying a toner image formed on the basis of image data; the cleaning blade which is in press-contact with the surface of the image carrier and removes toner sticking to the surface of the image carrier; and a screw for discharging the toner removed by the cleaning blade, by rotating. The screw is provided with a flying means for attaching some of toner stored near the screw, to the image carrier by flying it thereto. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus using an electrophotographic system such as a copying machine, a printer, and a facsimile, and more particularly to a cleaning device that removes toner remaining on an image carrier.

  A configuration in which a toner image is formed on a photosensitive drum having charging, exposure, and development means around it, and the toner image is transferred to a transfer material (paper), or a toner image formed on a plurality of photosensitive drums is intermediate In an image forming apparatus configured to perform secondary transfer of a toner image on an intermediate transfer belt to a transfer material after primary transfer to a transfer belt, a transferred photosensitive drum or intermediate transfer belt (also referred to as an image carrier) In order to remove residual toner, a blade cleaning method is known in which an elastic cleaning blade made of urethane rubber or the like is brought into contact with the running direction of the image carrier in the counter direction to perform cleaning.

  In recent years, high speed and high durability of image forming apparatuses have been demanded. With conventional blade cleaning methods, image streaks due to filming of the photosensitive drum or intermediate transfer belt, unevenness, and poor cleaning due to wear or chipping of the edge of the cleaning blade are caused. It is a problem. In particular, when an intermediate transfer belt is used, filming and chipping of the edge of the cleaning blade tend to occur more than the photosensitive drum. In the case of the intermediate transfer belt, the surface is harder than the photosensitive drum and is not easily scraped off, and a lot of toner substance is easily accumulated on the surface, so that more filming is likely to occur. As a result, the frictional resistance between the intermediate transfer belt and the cleaning blade where filming has occurred increases, and the edge of the cleaning blade is caught on the surface of the intermediate transfer belt, resulting in turning. Chipping occurs. Also, the transferability is lowered at the place where filming occurs, resulting in image streaks and unevenness.

  As a countermeasure against this problem, consideration has been given to strengthening the material of the cleaning blade to prevent chipping and polishing the intermediate transfer belt with the cleaning blade, but the countermeasure has not yet been achieved.

As a countermeasure against this problem, a toner band is created on the intermediate transfer belt during non-image formation, and toner is supplied to the cleaning blade to improve the lubricity and polishing effect between the intermediate transfer belt and the cleaning blade. There is an image forming apparatus in which the frictional resistance is reduced (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 8-115030

  In the above-described measures, there is a problem that the toner consumption is increased by that amount because the toner band is formed on the intermediate transfer belt other than the image formed based on the image data. Further, in the case of transfer contact such as a transfer roller method, a toner band adheres to the transfer roller, which causes a problem that the back surface of the transfer material becomes dirty. In order to prevent contamination of the back surface of the transfer material, it is necessary to provide a transfer roller cleaning unit or to relieve the transfer roller by retracting it when the toner band passes. However, if the transfer roller cleaning means is provided, the cost increases and there is a problem of durability. In addition, with the method of retracting the transfer roller, in the case of a high-speed machine, sufficient time for releasing between normal images cannot be taken, so normal image formation is interrupted to create a toner band. It is necessary to reduce the number of copies per unit time.

  The present invention has been made in view of such a problem, and by reattaching the cleaned waste toner to the image carrier and supplying it again to the cleaning blade, filming of the image carrier, wear and chipping of the cleaning blade are prevented. An object of the present invention is to provide an image forming apparatus which is greatly reduced and has high durability.

  The above object is achieved by the following means.

  By rotating an image carrier that carries a toner image formed based on image data, a cleaning blade that presses against the surface of the image carrier and removes toner adhering to the surface of the image carrier, and A screw for discharging the toner removed by the cleaning blade, and the screw is provided with flying means for causing a part of the toner stored in the vicinity of the screw to fly and adhere to the image carrier. An image forming apparatus.

  According to the image forming apparatus of the present invention, the toner removed by the cleaning blade is caused to fly by the flying means provided on the screw for discharging the toner, is again attached to the image carrier, and is supplied again to the cleaning blade. The filming of the carrier and the wear and chipping of the cleaning blade are greatly reduced, and the durability can be enhanced.

  First, an embodiment of an image forming apparatus provided with a cleaning device according to the present invention will be described with reference to FIG.

  FIG. 1 is a cross-sectional configuration diagram of an image forming apparatus that forms a color image. The cleaning apparatus according to the present invention can also be applied to an image forming apparatus that forms a monochrome image.

  This image forming apparatus is called a tandem color image forming apparatus, and a plurality of sets of image forming units 10Y, 10M, 10C, and 10K arranged in a vertical column and an intermediate transfer belt arranged on the left side thereof. The unit 7 includes a sheet feeding / conveying means (no reference) and a fixing means 24. A document image reading device B is arranged on the upper part of the main body A of the image forming apparatus.

  The image forming unit 10Y that forms a yellow image includes a photosensitive drum 1Y as a first image carrier, a charging unit 2Y disposed around the photosensitive drum 1Y, an exposure unit 3Y, a developing unit 4Y, a primary transfer unit. It comprises a primary transfer roller 5Y as a means, a cleaning means 6Y and the like.

  The image forming unit 10M that forms a magenta color image includes a photosensitive drum 1M as a first image carrier, a charging unit 2M disposed around the photosensitive drum 1M, an exposure unit 3M, a developing unit 4M, and a primary transfer. It comprises a primary transfer roller 5M as a means, a cleaning means 6M and the like.

  The image forming unit 10C for forming a cyan image includes a photosensitive drum 1C as a first image carrier, a charging unit 2C disposed around the photosensitive drum 1C, an exposure unit 3C, a developing unit 4C, and a primary transfer. It comprises a primary transfer roller 5C as a means, a cleaning means 6C, and the like.

  The image forming unit 10K that forms a black image includes a photosensitive drum 1K as a first image carrier, a charging unit 2K disposed around the photosensitive drum 1K, an exposure unit 3K, a developing unit 4K, and a primary transfer unit. Primary transfer roller 5K and cleaning means 6K.

  Developing means 4Y, 4M, 4C and 4K are yellow (Y), magenta (M), cyan (C) or black (K) charged to the same polarity as the charging polarity of the photosensitive drums 1Y, 1M, 1C and 1K. The two-component developer (which may be a one-component developer) made of each color toner is accommodated, and is formed of, for example, a cylindrical nonmagnetic stainless steel or aluminum material having a thickness of 0.5 to 1 mm and an outer diameter of 15 to 25 mm. And developing rollers 4Y1, 4M1, 4C1, and 4K1, which are developer carriers.

  The developing rollers 4Y1, 4M1, 4C1, and 4K1 are kept in contact with the photosensitive drums 1Y, 1M, 1C, and 1K with a predetermined gap, for example, 100 to 1000 μm, by a butting roller (not shown). The drums 1Y, 1M, 1C, 1K rotate in the forward and reverse directions.

  By applying a developing bias voltage that superimposes an AC voltage on the DC voltage or DC voltage having the same polarity as the toner to the developing rollers 4Y1, 4M1, 4C1, and 4K1 during development, the photosensitive drums 1Y, 1M, 1C, and 1K are Reversal development is performed on the electrostatic latent image.

  Generally, so-called external additives are added to toners for the purpose of improving fluidity and cleaning properties. Among these, as a lubricant related to the present invention, for example, zinc stearate is used. Salt of aluminum, copper, magnesium, calcium, zinc oleate, salt of manganese, iron, copper, magnesium, etc., zinc of palmitic acid, salt of copper, magnesium, calcium, etc., zinc of linoleic acid, calcium, etc. And salts of higher fatty acids such as salts, zinc of ricinoleic acid, salts of calcium, and the like.

  The amount of these external additives added is about 0.01 to 10% by mass with respect to the toner.

  The intermediate transfer belt unit 7 includes a plurality of rollers 71, 72, 73, 74, and 75, a semiconductive endless belt, and an intermediate transfer belt 70 as a second image carrier.

  The intermediate transfer belt 70 is stretched in contact with a drive roller 73 connected to a drive motor (not shown), support rollers 71 and 72, a secondary transfer backup roller 74, and a backup roller 75, and the intermediate transfer belt 70 rotates. The direction is arranged so as to be clockwise in FIG.

  Opposite to the photosensitive drums 1Y, 1M, 1C, and 1K, primary transfer rollers 5Y, 5M, 5C, and 5K are provided for the respective colors via an intermediate transfer belt 70.

  The primary transfer rollers 5Y, 5M, 5C, and 5K are formed on the photosensitive drums 1Y, 1M, 1C, and 1K by applying a DC voltage having a polarity opposite to that of the toner to form a transfer electric field in the transfer area. The toner images of the respective colors are primarily transferred onto the intermediate transfer belt 70.

  A secondary transfer roller 5 </ b> A is provided opposite to the secondary transfer backup roller 74 via an intermediate transfer belt 70.

  A DC voltage having a polarity opposite to that of the toner is applied to the secondary transfer roller 5A, and a transfer electric field is formed in the transfer area, so that the superimposed toner image carried on the intermediate transfer belt 70 is transferred onto the transfer material (paper) P. Secondary transfer to the surface of

  The transfer material P is fed from the sheet feeding cassette 20 by the sheet feeding means 21 and is conveyed to the secondary transfer position via the plurality of intermediate rollers 22A, 22B, 22C, 22D and the registration roller 23, and the color image is collectively transferred. Is done.

  When the size of the transfer material P is changed, the length (paper width) in the direction orthogonal to the transport direction is configured to change with the center reference of the intermediate transfer belt 70.

  The transfer material P onto which the color image has been transferred is subjected to fixing processing by the fixing unit 24, sandwiched by the paper discharge roller 25, and placed on the paper discharge tray 26.

  A cleaning device 60 that removes toner remaining on the intermediate transfer belt 70 is provided on the downstream side of the secondary transfer position in the rotational direction of the intermediate transfer belt 70. The details of the cleaning device 60 will be described later.

  Here, materials of the intermediate transfer belt, the transfer roller, and the like in the present embodiment will be described.

The intermediate transfer belt 70 is an endless belt having a volume resistance of 10 ⁶ to 10 ¹² Ω · cm. For example, polycarbonate (PC), polyimide (PI), polyamideimide (PAI), polyvinylidene fluoride (PVDF), and etrafluoro A resin material such as ethylene-ethylene copolymer (ETFE) or a rubber material such as EPDM, NBR, CR, polyurethane, etc., in which a conductive filler such as carbon is dispersed or an ionic conductive material is contained. The thickness used is preferably about 50 to 200 μm in the case of a resin material and about 300 to 700 μm in the case of a rubber material.

The primary transfer rollers 5Y, 5M, 5C, and 5K, for example, disperse a conductive filler such as carbon in a rubber material such as polyurethane, EPDM, or silicone on the peripheral surface of a conductive core metal such as stainless steel having an outer diameter of 8 mm. In addition, an ionic conductive material is contained, and the volume resistance is about 10 ⁵ to 10 ⁹ Ω · cm in a solid state or a foamed sponge state, the thickness is 5 mm, and the rubber hardness is about 20 to 70 ° (Asker hardness C) is formed by coating a semiconductive elastic rubber.

For example, the secondary transfer roller 5A is formed by dispersing a conductive filler such as carbon in a rubber material such as polyurethane, EPDM, or silicone on a peripheral surface of a conductive core metal such as stainless steel having an outer diameter of 8 mm. A semiconducting material with a volume resistance of about 10 ⁵ to 10 ⁹ Ω · cm in a solid state or foamed sponge state, a thickness of 5 mm, and a rubber hardness of about 20 to 70 ° (Asker-C) It is formed by covering an elastic rubber.

  Unlike the primary transfer rollers 5Y, 5M, 5C, and 5K, the secondary transfer roller 5A may be coated with a material having good releasability such as semiconductive fluorine resin or urethane resin because the toner contacts. The secondary transfer backup roller 74 is made of a conductive core such as stainless steel, and a conductive filler such as carbon is dispersed in a rubber or resin material such as polyurethane, EPDM, or silicone, or an ionic conductive material is used. It is formed by coating a semiconductive material that is contained or having a thickness of about 0.05 to 0.5 mm.

  Next, the image forming process will be described.

  When the image recording is started, a drive motor (not shown) of the photosensitive drum 1Y is started, and the photosensitive drum 1Y of the yellow (Y) image forming unit 10Y is rotated counterclockwise as indicated by an arrow in FIG. Application of a potential to the photosensitive drum 1Y is started by the charging action of the charging unit 2Y.

  After a potential is applied to the photosensitive drum 1Y, image writing is started by the exposure means 3Y using an electrical signal corresponding to the first color signal, that is, yellow (Y) image data, and a document is formed on the surface of the photosensitive drum 1Y. An electrostatic latent image corresponding to the yellow (Y) image of the image is formed.

  The electrostatic latent image is reversely developed in a contact or non-contact state by the developing roller 4Y1, and a yellow (Y) toner image is formed on the photosensitive drum 1Y according to the rotation of the photosensitive drum 1Y.

  The yellow (Y) toner image thus formed on the photosensitive drum 1Y is transferred onto the intermediate transfer belt 70 by the primary transfer roller 5Y.

  Subsequently, the yellow (Y) toner image on the intermediate transfer belt 70 is synchronized, and magenta (M), cyan (C), and black (K) toner images are sequentially superimposed to form a color. A toner image is obtained.

  The transfer residual toner remaining on the peripheral surfaces of the photosensitive drums 1Y, 1M, 1C, and 1K after the transfer is removed by the cleaning units 6Y, 6M, 6C, and 6K.

  In synchronization with the formation of the color toner image on the intermediate transfer belt 70, the transfer material P separated and conveyed one by one from the sheet feeding cassette 20 is conveyed through the registration roller 23, and is intermediately transferred by the secondary transfer roller 5A. The color toner images on the transfer belt 70 are collectively transferred onto the transfer material P.

  The transfer material P onto which the color toner image has been transferred is neutralized by a separation means (not shown), conveyed to the fixing device 24, and after the toner image is fixed, it is discharged to the discharge tray 26 by the discharge roller 25. .

  On the other hand, residual toner remaining on the peripheral surface of the intermediate transfer belt 70 after the transfer is removed by the cleaning device 60.

  Next, the details of the cleaning device 60 will be described with reference to FIG.

  FIG. 2 is a cross-sectional view of a main part of the cleaning device 60.

  Reference numeral 601 denotes a casing, which has a waste toner storage portion S in which each member constituting the cleaning device 60 is mounted and which stores waste toner removed from the intermediate transfer belt 70.

  A cleaning blade 602 is made of an elastic material such as urethane rubber, and is fixed to the blade holder 603 with an adhesive or the like. The blade holder 603 is rotatably attached to a support shaft 604 provided in the casing 601.

  Reference numeral 605 denotes a tension spring that urges the blade holder 603 to rotate counterclockwise about the support shaft 604, and causes the edge 602A of the cleaning blade 602 to move in a direction opposite to the rotation direction of the intermediate transfer belt 70 (counter direction). ) In a state of being in contact with the intermediate transfer belt 70 supported by the backup roller 75.

  Reference numeral 606 denotes a cleaning auxiliary brush having a brush on the surface, which contacts the intermediate transfer belt 70 at a position upstream of the contact position between the edge 602A of the cleaning blade 602 and the intermediate transfer belt 70 in the rotation direction of the intermediate transfer belt 70. Touch. The cleaning auxiliary brush 606 is configured to rotate in the forward direction with the intermediate transfer belt 70 by a rotating unit (not shown), and its peripheral speed is faster than the peripheral speed of the intermediate transfer belt 70.

  Reference numeral 607 denotes a flicker made of a resin plate, a stainless steel plate, or the like. One end of the flicker is in contact with the cleaning auxiliary brush 606 at a position opposite to the contact position between the cleaning auxiliary brush 606 and the intermediate transfer belt 70, and the other end is the casing 601. Fixed with double-sided tape.

  Reference numeral 608 denotes a seal plate fixed to the casing 601, which contacts the intermediate transfer belt 70 to prevent waste toner from leaking.

  Reference numeral 609 denotes a screw provided at the bottom of the casing 601, which rotates counterclockwise in the figure by a drive source (not shown).

  A paddle (flying means) 610 is formed from a thin plate such as PET (polyethylene terephthalate) and has elasticity, and is attached to the shaft 609A of the screw 609 at a predetermined interval. By rotating, the waste toner reservoir S A part of the toner stored on the bottom of the toner is allowed to fly.

Here, the specifications of the cleaning blade 602, the cleaning auxiliary brush 606, the screw 609, and the paddle 610 in the present embodiment are shown below.
(1) Cleaning blade 602
・ Material: Polyurethane rubber, JISA hardness 75 °, rebound resilience 50%
・ Shape: Thickness 1.7-2.3mm, Free length 7-11mm,
-Counter contact: Contact angle 12-23 °
・ Spring load method: Load 13 ~ 20N / m
(2) Cleaning auxiliary brush 606
・ Material: Conductive nylon system ・ Loop shape: 320d / 32, 567 loops / inch ²
-Hair length: 4-6mm
・ Outer diameter: 16-20mm
・ Belt bite amount: 0.3-1.5mm
Rotational speed: 1.0 to 1.2 times the intermediate transfer belt (3) Screw 609
・ Outer diameter: 10mm
・ Pitch: 10mm
・ Rotation speed: 100-200 rpm
(4) Paddle 610
・ Material: PET
・ Thickness: 80-200 μm
Next, the operation of the cleaning device 60 will be described.

  After the toner image on the intermediate transfer belt 70 is transferred to the transfer material P at the secondary transfer position, the toner remaining on the intermediate transfer belt 70 is scraped off and removed by the cleaning blade 602, and the intermediate transfer belt 70 is cleaned. . The removed toner (hereinafter referred to as waste toner) T adheres to the waste toner supply brush 606 that rotates in contact with the intermediate transfer belt 70, is further scraped off by the flicker 607, and is stored in the waste toner storage portion S.

  The waste toner T stored at the bottom of the waste toner storage S is transported in the direction perpendicular to the paper surface by the rotation of the screw 609 and discharged out of the casing 601, and is collected in a waste toner collection box (not shown).

  Further, the paddle 610 is tipped on an arcuate inner wall 601A (contact portion) of the casing 601 that is located in the vicinity of the outer periphery of the screw 609 and formed in an arc concentric with the outer diameter of the screw 609 during rotation performed together with the screw 609. The parts abut and bend so that the tip is positioned upstream of the root in the rotational direction. Eventually, the paddle 610 that continues to rotate is pulled out of the arc-shaped inner wall 601A and jumped up, so that the bent state is rapidly released. By the restoring force at this time, the paddle 610 causes a part of the waste toner T stored in the vicinity of the screw 609 to fly to the upper right of the screw 609. As a result, the waste toner T adheres again on the intermediate transfer belt 70.

  As a result, the waste toner T is supplied again to the edge 602A of the cleaning blade 602, so that the lubricity between the intermediate transfer belt 70 and the cleaning blade 602 is improved and the frictional resistance is reduced. Wear and chipping can be reduced. In addition, the polishability is improved and filming can be prevented.

  Further, there is no need to re-supply toner using a brush roller or the like, and there is no need to provide a storage part for storing toner for re-supply. Therefore, the above effect can be obtained with the cleaning device 60 having a simple configuration. Can be achieved.

  Next, Table 1 shows an example of optimum design values in which a predetermined amount of waste toner T uniformly adheres to the intermediate transfer belt 70 and is smoothly conveyed by the screw 609 without clogging the waste toner T.

  In Table 1, the number of paddles is the number in the circumferential direction at a predetermined position of the shaft 609A of the screw 609.

  Further, since the outer diameter of the screw is 10 mm, the shaft diameter is 4 mm, and the length of the paddle is 5 mm, the paddle protrudes 2 mm from the outer periphery of the screw.

  A cleaning device manufactured based on the above design values was incorporated into an image forming apparatus, and a running test was performed.

Experimental conditions ・ Paddle: When not attached to screw ・ Image printing rate: 30% for high printing rate and 5% for low printing rate
・ Paper size: A4R
-Number of copies: 100,000-Experiment environment: High temperature and high humidity (30 ° C, 80% RH)
The test results are shown in Table 2.

  In Table 2, the edge chipping rate is the chipping rate of the edge of the cleaning blade and is calculated by the following mathematical formula.

Edge chip ratio = chip width × 100 / measurement length of cleaning blade Further, the chip width is as shown in FIG.

  By this test, waste paper is ejected using a paddle and is reattached to the intermediate transfer belt, thereby using a sheet on which an image is formed only at the center with respect to the width direction of the intermediate transfer belt, such as A4R, and It was proved that the edge defect of the cleaning blade was greatly reduced even when an image having a low printing rate was formed and passed.

  In addition, the paddle 610 described with reference to FIG. 2 is configured to bend while the tip is in contact with the arc-shaped inner wall 601A of the casing 601, but as shown in FIG. May be slightly different.

  That is, in FIG. 4A, a semicircular protrusion 611B (contact portion) is provided near the outer periphery of the screw 609 in the casing 611, and the paddle 620 rotates along the arcuate inner wall 611A of the casing 611. Sometimes it is not bent, and the tip of the paddle 620 is bent by coming into contact with the protrusion 611B, and then the protrusion 611B is lifted by further rotation, and the bent state is released. The waste toner T is caused to fly to the upper right of the screw 609 by the restoring force of.

  4B, the casing 621 is provided with a protrusion 621B (contact portion) formed so that the dimension from the center of the screw 609 is gradually reduced.

  The protrusions 611B and 621B are intermittently provided at axial positions where only the paddle 620 is in contact with the screw 609.

1 is a cross-sectional configuration diagram of an image forming apparatus. It is principal part sectional drawing of a cleaning apparatus. It is a figure which shows an edge missing width. It is a figure of the paddle of a different structure.

Explanation of symbols

60 Cleaning device 70 Intermediate transfer belt 601, 611, 621 Casing 601 A, 611 A Arc-shaped inner wall 602 Cleaning blade 606 Cleaning auxiliary brush 607 Flicker 609 Screw 610 Paddle 611 B, 621 B Protrusion S Waste toner reservoir

Claims (4)

An image carrier that carries a toner image formed based on image data;
A cleaning blade that presses the surface of the image carrier and removes toner adhering to the surface of the image carrier;
A screw for discharging the toner removed by the cleaning blade by rotating, and
An image forming apparatus, wherein the screw is provided with flying means for causing a part of the toner stored in the vicinity of the screw to fly and adhere to the image carrier. The image forming apparatus according to claim 1, wherein the flying unit is an elastic thin plate. The flying means is bent by contacting a contact portion located near the outer periphery of the screw during rotation, and a part of the toner is recovered by a restoring force generated when the bent state is released after further rotation. The image forming apparatus according to claim 1, wherein the image forming apparatus is caused to fly. The image forming apparatus according to claim 1, wherein the image carrier is an intermediate transfer belt.

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