JP2006258885A - Cleaning device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cleaning device which improves durability of a photoreceptor as well as decreases cleaning failure or image disturbance in any environment. <P>SOLUTION: The cleaning device 010 is provided with a planar elastic blade 011 which touches a photoreceptor 01 and cleans off toner on the surface of the photoreceptor 01. The coefficient of friction on the surface of the elastic blade 011 is specified to 1.0 or less under the conditions that the average circularity of the toner used is 0.970 or more and the pressing force of the elastic blade 011 on the photoreceptor 01 is 60 N/m or more. A contact angle formed by a tangential line from a contact point with the elastic blade 011 on the surface of the photoreceptor 01, and the surface of the elastic blade 011 opposing the photoreceptor 01 is 5° or more. The elastic blade 011 to be in contact with an image carrier shows JIS-A hardness of 60° or more; the coefficient of friction on the surface of the photoreceptor 01 ranged from 0.1 to 0.4; and the average particle size of the toner used is 7.0 μm or less. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a cleaning device mounted on an image forming apparatus using an electrophotographic process such as a copying machine, a printer, and a facsimile, and more particularly to a cleaning device in an image forming apparatus that provides a low friction coefficient cleaning member.

The electrophotographic process is composed of charging, exposure, development, transfer / fixing, and cleaning processes. In the final cleaning process, a blade cleaning system is usually employed.
The blade for blade cleaning is a structure in which an elastic member made of a material such as a plate-like polyurethane is attached to a support, and is configured to press contact with the surface of the electrophotographic photosensitive member. Accordingly, in order to increase the toner cleaning accuracy, it is necessary to increase the contact pressure of the blade to the electrophotographic photosensitive member. In addition, the contact form of the blade to the electrophotographic photosensitive member includes a forward direction with respect to the rotation direction of the electrophotographic photosensitive member and a counter direction. From the standpoint of cleaning accuracy, the latter counter direction contact form is more preferable.

However, the counter-direction contact method that improves the cleaning accuracy simultaneously increases the contact pressure of the blade to the electrophotographic photosensitive member, causing an increase in the frictional force between the two. As a result, durability decreases due to an increase in the amount of abrasion of the electrophotographic photosensitive member, scratches on the electrophotographic photosensitive member occur, cleaning failure occurs due to turning of the contact portion between the blade and the photosensitive member, and the blade entrains in the downstream direction of the photosensitive member. This may lead to problems such as stoppage and damage of the device.

In order to solve the above problems, it is known that it is effective to reduce the friction coefficient of the electrophotographic photosensitive member. Conventionally, as a method for reducing the coefficient of friction of an electrophotographic photosensitive member, many methods for incorporating a lubricant into the surface layer or protective layer of the electrophotographic photosensitive member have been proposed. As the lubricant, fluorine atoms such as polytetrafluoroethylene are proposed. Known resin, resin powder such as spherical acrylic resin and polyethylene resin, metal oxide powder such as silicon oxide and aluminum oxide, and the like are known. As a means for reducing the coefficient of friction on the photosensitive member in the initial stage, an application mechanism for applying toner or a lubricant or the like is provided near the contact portion between the elastic blade and the photosensitive member, and a lubricating layer is provided on the surface of the photosensitive member. The installation is also in practical use.

However, with the recent trend toward higher image quality, the average particle size of toners is also decreasing, and in addition, the use of uniform and high-circularity toners is increasing, as represented by toners produced by polymerization. As a result, the pressing force on the surface of the photosensitive member by the elastic blade that has been used for the toner by the conventional pulverization method cannot obtain a sufficient passage blocking force, so that a larger pressing force is required. Yes.
However, the increase in the pressing force on the surface of the photosensitive member by the elastic blade further increases the frictional force between the elastic blade and the surface of the photosensitive member. The situation is likely to occur.

For this reason, for example, Patent Document 1 discloses a system that suppresses the rolling-up of the cleaning blade and the noise. In this system, the electrophotographic photosensitive member has a photosensitive layer and a surface protective layer on a conductive support, and the surface protective layer is a fluorine atom-containing resin having 15.0 to 40.0% by mass based on the total mass of the protective layer. It contains particles, has a 10-point average surface roughness of 0.1 to 5.0 μm, a surface hardness of 0.1 to 20.0 by Taber abrasion test, and a surface friction coefficient of 0. 0.001 to 1.2, the cleaning means is a rubber elastic blade, the linear pressure of the blade against the electrophotographic photosensitive member is 12.5 to 25.0 g / cm, and the glass transition of the toner used This is a system in which the point (Tg) is 40 ° C. to 55 ° C., the blade physical property tensile modulus (Young's modulus) is 50 to 70 kgf / cm 2, and the impact resilience value is 20% to 35%. .

JP 2002-82468 A

However, in order to cope with an increase in the circularity and a reduction in the diameter of the toner used, when the pressing force applied to the elastic blade is further increased, the blade-photosensitive member contact portion increases between the two. The frictional force cannot be counteracted, the contact becomes nonuniform, and the problem of causing defective cleaning remains.

The present invention has been made in view of the above problems, and its object is to improve the durability of the electrophotographic photosensitive member and improve durability from the beginning even when the circularity of the toner used is increased or reduced in diameter. It is an object of the present invention to provide a cleaning apparatus and an image forming apparatus that can obtain an excellent image without defective cleaning and image disturbance under the entire environment.

As means for solving the above problems, the present invention has the following features.
The cleaning device according to claim 1, wherein an average circularity of the toner to be used is 0. 0 in the cleaning device in contact with the image carrier and a plate-like elastic blade for cleaning the toner on the surface of the image carrier. The surface friction coefficient of the elastic body blade is 1.0 or less when the force that the elastic body blade presses against the image carrier is 60 N / m or more.
According to a second aspect of the present invention, the cleaning device according to the first aspect is formed by a tangent from a contact point with the elastic blade on the surface of the image carrier and a side surface of the image carrier on the elastic blade. The contact angle is 5 ° or more.
According to a third aspect of the present invention, in the cleaning device according to the first aspect, the hardness of the elastic blade contacting the image carrier is JIS-A 60 ° or more.
According to a fourth aspect of the present invention, in the cleaning device according to the first aspect, the resilience of the elastic blade contacting the image carrier is in the range of 10% to 40%.
According to a fifth aspect of the present invention, in the cleaning apparatus according to the first aspect, the surface friction coefficient of the image carrier is 0.1 or more and 0.4 or less.
The cleaning device according to claim 6 is characterized in that, in the cleaning device according to claim 1, the average particle size of the toner used is 7.0 μm or less.
The image forming apparatus according to claim 7, based on image data on an image carrier that carries a latent image, charging means that uniformly charges the surface of the image carrier, and the surface of the charged image carrier. An exposure means for exposing and writing a latent image; a developing means for supplying toner to the latent image formed on the surface of the image carrier to make it visible; and a visible image on the surface of the image carrier; In an image forming apparatus comprising a transfer means for transferring to an intermediate transfer body and a cleaning means for cleaning the surface of the image carrier after transfer,
The cleaning means is the cleaning device according to any one of claims 1 to 6.

The image forming apparatus of the present invention has the following effects.
According to the first aspect of the present invention, the frictional force acting between the blade and the photoconductor is obtained by selecting a low friction coefficient material having a coefficient of friction of 1.0 or less as the blade and using it together with the low friction coefficient photoconductor. And the behavior at the contact portion is stabilized, and the toner blocking force spreads evenly, thereby preventing the toner from passing therethrough.
According to the second aspect of the present invention, by ensuring the contact angle of 5 ° or more, it is possible to reduce unnecessary contact and obtain a toner distribution blocking force with a sharp distribution from the applied pressing force.
According to the invention described in claim 3, by setting the hardness of the elastic blade to JIS-A 60 ° or more, unnecessary elastic deformation at the blade contact portion is suppressed, and sharply distributed toner passage is prevented from the applied pressing force. It becomes possible to gain power.
According to the fourth aspect of the present invention, by keeping the rebound resilience in the range of 10 to 40%, it is possible to cope with the frictional force unevenness generated in the longitudinal direction of the blade by elastic deformation and maintain stable contact. Is possible.
According to the fifth aspect of the present invention, by setting the coefficient of friction on the surface of the photosensitive member to 0.1 to 0.4, toner releasability is improved, and operation with a lower pressing force is possible.
According to the invention described in claim 6, by making the toner having a volume average particle diameter of 7 μm or less practical, it is possible to improve the image quality and reduce the running cost by reducing the amount of adhesion.
According to the seventh aspect of the invention, even when the circularity of the toner to be used is increased or the diameter is reduced, the durability of the electrophotographic photosensitive member is improved, and the cleaning failure or It is possible to provide an image forming apparatus that can obtain an excellent image without image distortion.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the description, specific member names are used to facilitate understanding of the invention, but it should be clearly stated that the scope of the present invention is not limited thereby.

FIG. 1 is a diagram schematically showing an image forming unit 100 in the image forming apparatus. In addition to the image forming unit 100, the image forming apparatus includes at least a paper feed unit, a document reading unit, a document transport unit, a duplex reversing unit, and a sheet discharge tray (not shown).
The image forming unit 100 includes an exposure unit, a transfer unit, and a fixing unit, and includes four units that respectively form toner images of four colors of black (Bk), cyan (C), magenta (M), and yellow (Y). Prepare in parallel. In the center of each image forming unit 100, photoconductors 01K, 01C, 01M, and 01Y that are image carriers are provided, and around each photoconductor 01, a charging device 02, a developing unit 04, and a cleaning device 010 are provided. ing.

The exposure unit converts the data read by the reading unit or an image signal sent from the outside such as a PC (not shown), scans the laser beam with a polygon motor, and on the photoconductor 01 based on the image signal read through the mirror. An electrostatic latent image is formed on the surface.
The transfer unit includes a transfer roller 07 that sequentially holds the toner images formed on the respective photoconductors 01, and transfers the color toner image formed on the transfer roller 07 onto a recording sheet. It has a configuration. In addition, the recording paper may be conveyed by a transfer conveyance belt, and the toner image formed on each photoconductor 01 may be directly transferred to the recording paper.
The fixing means is composed of a belt stretched around a roller having a halogen heater or the like inside and a pressure roller, and applies heat and pressure to the toner on the recording paper at the nip formed by the both. Fix the image. In addition, a pair of rollers or a pair of belts may be used.

With reference to FIG. 1, the operation of the transfer to the recording paper and the conventional blade cleaning method will be described.
The charging device 02 uniformly charges the surface of the photoconductor 01 on the photoconductor 01 that can be freely rotated. Next, a laser beam is irradiated by an exposure optical system to expose the surface of the photoconductor 01 to form an electrostatic latent image on the image carrier, and then the developer 05 in the developing unit 04 is applied to the surface of the photoconductor 01. A visible image is formed on the photoconductor 01 by moving it.
Next, at the contact portion between the intermediate transfer device 06 and the photoconductor 01, the developer 05 on the surface of the photoconductor 01 is removed from the surface of the intermediate transfer device 06 by a transfer roller 07 provided inside the intermediate transfer device 06 at the contact portion. Transcript to. The transferred developer 05 is transferred to the recording paper by the secondary transfer unit 08 and then supplied to the fixing device 09 to fix the toner image on the recording paper. On the other hand, the developer 05 remaining on the surface of the photoconductor 01 is removed by the cleaning blade 011 in the cleaning device 010.

FIG. 2 is a view showing the positional relationship between the embodiment of the cleaning device of the present invention and the image carrier, FIG. 3 is a detailed explanatory view of the cleaning device of the embodiment, and FIG. It is a detailed explanatory view.
In FIG. 2, a cleaning device 010 used for cleaning toner adhering to the surface of the photoconductor 01 is supported by a toner collection case 012 and a fulcrum shaft 013 provided in the toner collection case 012. A movable member 014 that can be rotated in a direction and that can be mounted with a cleaning blade 011 and a fulcrum shaft 013 are mounted at the end of the movable member 014 on the opposite side of the cleaning blade 011 mounting position. A tension spring 015 for supplying a rotational force and a pressing force to the photosensitive member 01 to the cleaning blade 011 and a screw 016 for transferring the toner scraped off from the surface of the photosensitive member 01 by contact with the cleaning blade 011 in the toner recovery case. It has.

  As shown in FIGS. 3 and 4, the cleaning blade 011 is composed of a plate-like elastic blade 017 and a support member 018 that supports the elastic blade 017. The cleaning blade 011 is elasticized by a biasing means such as a spring. The free-end-side tip portion 017c of the body blade 017 rotates and moves together with the movable member 014 to which the cleaning blade 011 is mounted and is pressed against the surface of the photoreceptor 01 that rotates in the direction of the arrow (clockwise) at a predetermined contact angle θ. Used.

As the material used for the elastic blade 017, the hardness [JIS-A type] is 60 to 80, the elongation is 300 to 350%, the permanent elongation is 1.0 to 5.0%, and the 300% modulus is 100 to 350 kg. / Cm ² , those having a resilience in the range of 10 to 40% are used, and resins conventionally used in plate blade members, such as urethane, styrene, olefin, vinyl chloride, polyester, A thermoplastic resin such as a polyamide-based resin or a fluorine-based resin can be appropriately selected and used, but a lower elastic blade friction coefficient is particularly desirable.
The material of the support member 018 is not particularly limited. For example, metal, plastic, ceramic, or the like can be used, but a metal plate is preferable because a certain degree of strength is applied. In particular, a steel plate such as SUS, an aluminum plate, a phosphor bronze plate, or the like is preferably used.

Regarding the toner, the trend toward smaller diameter is progressing in consideration of higher image quality, and the volume average particle diameter is 7.0 μm or less (measured by Coulter Multisizer III), and the toner transfer performance is improved. Since the circularity is preferably 0.970 (measured value of FPIA-2100 manufactured by SYSMEX) or higher, a material having a volume average particle diameter of 6.7 μm and a circularity of 0.98 is used. Further, in the photoconductor 01, the static friction coefficient is set to be 0.1 in order to suppress the frictional force and vibration at the contact portion between the elastic blade 017 and the photoconductor 01 by the Euler-belt type friction coefficient measuring method as shown in FIG. A photoconductor of 4 or less is used.
When using the above toner, the conventional blade cleaning system easily passes through the elastic blade-photoconductor contact portion and appears as noise on the image, so the pressing force on the surface of the photoconductor by the elastic blade is increased, In this case, it is necessary to apply a pressing force of 50 N / m or more to the elastic blade.
At that time, the contact portion between the elastic body blade 017 and the surface of the photoconductor 01 is enlarged, and the tangent line at the contact point with the elastic body blade 017 on the surface of the photoconductor and the elasticity are prevented so that the toner passage blocking force is not dispersed. The contact angle formed with the surface on the photoconductor 01 side of the body blade 017 is set to 5 ° or more.

That is, in the cleaning device of the present invention, when a toner having a circularity of 0.97 or more and a volume average particle size of 7.0 μm or less is used, in order to obtain a toner passage blocking force necessary to enable the cleaning, It is necessary to apply a strong pressing force of 50 N / m or more to the elastic blade 017 so as to contact the surface of the photoconductor 01. At this time, as the pressing force increases, the frictional force increases at the contact portion between the elastic blade 017 and the surface of the photoconductor 01, and the contact end of the elastic blade 017 moves in the rotation direction of the photoconductor as the photoconductor 01 rotates. In this case, the amplitude of the repetitive movement from compression due to entanglement to elastic recovery increases at least at the contact portion, the adhesion to the surface of the photoreceptor is reduced, and poor cleaning due to toner slippage occurs. For example, the influence of frictional force, which has been difficult to become a problem in the past, becomes significant.

FIG. 6 is a diagram illustrating a relationship in which cleaning failure occurs in the photoconductor friction coefficient and the friction coefficient of the elastic blade in the present embodiment.
In these systems, the friction coefficient of the elastic blade 017 is dominant, and even if the friction coefficient of only the photoconductor 01 is reduced as shown in FIG. Therefore, a low friction coefficient material having a friction coefficient of 1.0 or less is selected as the elastic body blade 017 and used in combination with the low friction coefficient photoconductor. As a result, the frictional force acting between the elastic body blade 017 and the photoconductor 01 is reduced, the behavior at the contact portion is stabilized, and the toner blocking force is evenly distributed, so that the passage of toner can be suppressed. .

Further, when the pressing force is increased, the elastic deformation of the elastic blade 017 around the contact portion with the photosensitive member 01 increases and the contact area tends to increase, but the elastic blade 017 on the surface of the photosensitive member tends to increase. The contact angle formed between the tangent line at the contact point and the surface of the elastic blade 017 on the photoconductor 01 side is set to 5 ° or more, so unnecessary contact is reduced and the distribution is sharp from the applied pressing force. It is possible to obtain a toner passage blocking force.

In addition, since the hardness of the elastic blade 017 is set to JIS-A 60 ° or more, unnecessary elastic deformation at the blade contact portion can be suppressed, and a toner distribution blocking force with a sharp distribution can be obtained from the applied pressing force. ing.
Further, by keeping the rebound resilience in the range of 10 to 40%, it is possible to cope with the frictional force unevenness generated in the blade longitudinal direction by elastic deformation and keep stable contact.

In addition, by setting the coefficient of friction on the surface of the photoreceptor to 0.1 to 0.4, toner releasability is improved, and operation with a lower pressing force is possible.
Further, by making the toner having a volume average particle diameter of 7 μm or less practical, it is possible to improve the image quality and reduce the running cost by reducing the adhesion amount.

As a measuring means, in the conventional method for measuring the friction force between the photosensitive member and the elastic blade, since the influence of the blade viscosity and the like appears strongly, vibration occurs at the contact portion, and an accurate numerical value cannot be obtained. 7, with a 100 gf load applied between the elastic blade 017 and the PTFE tape (Nitto Flon No. 903UL manufactured by Nitto Denko), the elastic blade 017 is moved with a digital force gauge (SHGCPO FGC-2B). The static friction force when the elastic blade 017 started to move was read from the digital force gauge and obtained by a method of converting to a friction coefficient. As a result, an elastic body having a friction coefficient of 1.0 or less is selected and evaluated.

FIG. 2 is a schematic configuration diagram illustrating an image forming unit according to the present embodiment. FIG. 2 is a schematic configuration diagram showing a positional relationship between a photoconductor and a cleaning device in the present embodiment. The schematic block diagram which showed the structure of the cleaning apparatus in this embodiment. The schematic block diagram which showed the structure of the cleaning blade which concerns on this embodiment. The schematic block diagram which showed the measurement means in this embodiment. The figure which showed the relationship which the cleaning defect generate | occur | produces in the photoconductor friction coefficient in this embodiment, and the friction coefficient of an elastic body blade. The figure which showed the friction coefficient of the elastic body blade and photoconductor in this embodiment.

Explanation of symbols

01 photoconductor 02 charging device 04 developing unit 05 developer 06 intermediate transfer device 07 transfer roller 08 secondary transfer unit 010 cleaning device 011 cleaning blade 012 toner collection case 013 fulcrum shaft 014 movable member 015 tension spring 016 screw 017 elastic blade 018 Support member 100 Image forming unit

Claims (7)

In a cleaning device in contact with an image carrier and arranged with a plate-like elastic blade for cleaning toner on the surface of the image carrier, the average circularity of the toner used is 0.970 or more, and the elastic blade The cleaning device according to claim 1, wherein a surface friction coefficient of the elastic blade is 1.0 or less when a force to press the image carrier is 60 N / m or more. 2. The cleaning according to claim 1, wherein a contact angle formed by a tangent from a contact point with the elastic blade on the surface of the image carrier and a side surface of the image carrier on the elastic blade is 5 ° or more. apparatus. 2. The cleaning device according to claim 1, wherein the hardness of the elastic blade contacting the image carrier is JIS-A 60 [deg.] Or more. 2. The cleaning device according to claim 1, wherein the resilience of the elastic blade contacting the image carrier is in the range of 10% to 40%. 2. The cleaning device according to claim 1, wherein the surface friction coefficient of the image carrier is 0.1 or more and 0.4 or less. 2. The cleaning device according to claim 1, wherein the toner used has an average particle size of 7.0 [mu] m or less. An image carrier for carrying a latent image;
Charging means for uniformly charging the surface of the image carrier;
Exposure means for exposing the surface of the charged image carrier based on image data and writing a latent image;
Developing means for supplying toner to the latent image formed on the surface of the image bearing member to visualize the latent image;
Transfer means for transferring the visible image on the surface of the image carrier to transfer paper or an intermediate transfer member;
In an image forming apparatus comprising a cleaning means for cleaning the surface of the image carrier after transfer,
The image forming apparatus according to claim 1, wherein the cleaning unit is the cleaning apparatus according to claim 1.

Images