JP2002023584A - Cleaning device, image forming device and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cleaning device which enables continuously and satisfactorily cleaning image carriers even when toner has average high roundness, an image forming device equipped with the cleaning device and an image forming method thereof. SOLUTION: This cleaning device cleans image carriers which performs image formation by using a toner having the mean sphericity of >=0.96. Therein, the cleaning device is provided with a cleaning blade which brings the end part into pressurized contact with the imager carrier and cleans the same, a cleaning roller which is positioned on the upstream of the cleaning blade, is brought into contact with the image carrier and cleans the same, and a biased voltage applying means which applies a biased voltage to the cleaning roller. The image forming device which is arranged with this cleaning device and the image forming method are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleaning apparatus for cleaning an image carrier of an electrophotographic image forming apparatus such as a copying machine, a laser printer, a facsimile, etc., an image forming apparatus provided with the cleaning apparatus, and an image forming method therefor. In particular, the present invention relates to a cleaning device useful when the circularity of the toner used is as high as 0.96 or more, an image forming apparatus provided with the cleaning device, and an image forming method thereof.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus,
Various cleaning devices have been proposed for cleaning the surface of the image carrier, which are disposed on the periphery of the image carrier.

In a normal image forming process, after forming an electrostatic latent image on an image carrier, the electrostatic latent image is developed with toner to form a toner image, and after transferring the toner image, the image carrier is Paper dust attached to the surface and residual toner not transferred are cleaned by a cleaning device.

An irregular toner (average circularity of 0.95 or less) produced by a conventional pulverization method only scrapes off an end of an elastic plate-like member called a cleaning blade by pressing against an image carrier surface. Cleaning was possible.

[0005]

However, with the recent demand for higher image quality, polymerized toner having a small particle size and a substantially spherical shape with a high average circularity has been adopted.
It has been found that it is difficult to continuously and sufficiently remove the polymerized toner having a high average circularity by scraping and cleaning with a cleaning blade. In the case of a polymer toner having a high average circularity, there is no problem if the cleaning blade is a new one that has just been replaced, but the cleaning blade gradually wears and the pressure contact with the image carrier deteriorates. It is presumed that when the specific pressure between the cleaning blade and the image carrier deteriorates, it passes through a slight gap between the tip of the cleaning blade and the surface member of the image carrier, so that the cleaning blade easily passes through because of the substantially spherical shape. It is also considered that the shape and the particle size are uniform, and the affinity for the image carrier or between the toners is high.

To improve the image quality, it is desirable to use a toner having a high average circularity. However, if the image carrier is not sufficiently cleaned, the attached paper dust and residual toner adversely affect the next image formation. The image quality will be degraded.

In view of the above problems, an object of the present invention is to provide a toner which has a high average circularity continuously and sufficiently.
A cleaning device capable of cleaning the image carrier,
An object of the present invention is to provide an image forming apparatus provided with the cleaning device and an image forming method thereof.

[0008]

The object of the present invention is as follows.
This has been achieved by the following configuration.

1. A cleaning device for cleaning an image carrier that forms an image with toner having an average circularity of 0.96 or more, comprising: a cleaning blade that presses an end of the image carrier against the image carrier to clean the image carrier; and a cleaning blade that is positioned upstream of the cleaning blade. A cleaning roller that contacts and cleans the image carrier; and a bias voltage applying unit that applies a bias voltage to the cleaning roller.

[0010] 2. The cleaning device according to claim 1, wherein the cleaning roller is a conductive elastic roller.

3. 3. The cleaning apparatus according to the above item 1 or 2, further comprising control means for applying the bias voltage by the bias voltage applying means by DC constant current control.

4. An image forming apparatus provided with the cleaning device according to the above 1, 2 or 3. 5. A plurality of developing means are arranged around the first image carrier, and the toner image formed on the first image carrier is primarily transferred to a second image carrier, and the first transferred toner image is transferred to the second image carrier. 2. An image forming apparatus for secondary-transferring a toner image on an image carrier to a recording material, wherein the cleaning device for the first image carrier or the second image carrier comprises An image forming apparatus, which is the cleaning apparatus according to any one of the preceding claims.

6. A developing step of forming a toner image on the image carrier with a toner having an average circularity of 0.96 or more, a transfer step of transferring the toner image on the image carrier, and a step of transferring the toner image on the image carrier after the transfer step. The cleaning step of applying a bias voltage to contact the image carrier to clean it, and then pressing the tip of a cleaning blade against the image carrier. An image forming method comprising cleaning.

7. 7. The image forming method according to the above item 6, wherein the cleaning roller is a conductive elastic roller.

[8] 8. The image forming method according to the above item 6 or 7, wherein the application of the bias voltage applied to the cleaning roller is a DC constant current control.

[0016]

Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited thereto.

FIG. 1 is a schematic diagram showing the relationship between the cleaning device of the present invention and an image carrier. In the figure, reference numeral 2 denotes a photosensitive drum as an image carrier, 4 denotes a cleaning device, 41 denotes a cleaning blade for cleaning the end by pressing the photosensitive drum 2 against the end, and 42 denotes a cleaning blade 41. And a spring 43 for applying an urging force for pressing against the photosensitive drum 2,
A cleaning roller 4 that contacts the photosensitive drum 2 while rotating and removes and cleans the photosensitive drum 2 electrostatically;
Reference numeral 4 denotes a blade for scraping off the toner adhered to the cleaning roller 43, and reference numeral 45 denotes a toner collection roller for collecting the toner scraped by the blade 44 from the cleaning roller 43 and sending it to a recycling pipe (not shown) connected to a developing device. , 46 is a housing of the cleaning device 4, 47 is a power supply as bias voltage applying means for applying a bias voltage to the cleaning roller 43,
Reference numeral 8 denotes a power supply controller as control means for controlling the power supply 47 at a constant current.

Since the cleaning roller 43 comes into contact with the photosensitive drum 2 to electrostatically attract and remove the toner, the bias voltage applied to the cleaning roller 43 is applied to the photosensitive member at the position where the cleaning roller 43 is in contact with the cleaning roller 43. It is necessary that the polarity of the toner on the drum 2 is opposite to that of the toner on the drum 2. That is, the power supply 47 applies a positive bias voltage to the cleaning roller 43 when the toner is negatively charged, and applies a negative bias voltage when the toner is positively charged. For example, when the photoconductor drum 2 is an OPC photoconductor (organic photoconductor), the bias voltage to be applied is positive because the toner has a negative potential. The bias voltage applied at this time is
The constant current control is performed by the power supply controller 48.
With the constant current control, a constant voltage can be applied to the toner per unit amount regardless of the amount of the residual toner adhering on the photosensitive drum 2, so that the toner adhering portion can be reduced. Even if there is a small portion, it is preferable because the toner can be removed by suction without unevenness. The constant current value in the case of the constant current control depends on the performance and characteristics of the image carrier and the cleaning device, but is preferably about 5 μA to 30 μA.

When the photosensitive drum 2 rotates in the direction of the arrow, the cleaning roller 43 located upstream in the cleaning device 4 and applied with a bias voltage comes into contact with the photosensitive drum 2. The cleaning roller 43 rotates in the direction of the arrow not opposing the rotation of the photosensitive drum 2 and electrostatically attracts and adheres to the surface of the foreign matter such as residual toner and paper dust attached to the photosensitive drum 2. . The toner and the like adhering to the cleaning roller 43 further rotate,
When the toner reaches the position of the blade 44, the toner is scraped off by the blade 44, and the scraped toner and the like are guided to a recycling pipe (not shown) by rotation of the toner collecting roller 45, and are reused as toner for development. Will be. When the photosensitive drum 2 further rotates and reaches a position where the tip of the cleaning blade 41 comes into pressure contact with the photosensitive drum 2, the residual toner and the like are rubbed off at once, and the scraped-off toner and the like are the same as in the case of the cleaning roller 43. Is guided to the recycling pipe by the toner collecting roller 45. Then, even if the cleaning blade 41 wears and deteriorates and a gap is formed between the cleaning blade 41 and the photosensitive drum 2, even if toner or the like passes through the gap, the suction is again performed by the cleaning roller 43 located upstream of the cleaning blade 41. Since the cleaning device 4 is removed, the cleaning ability of the cleaning device 4 does not decrease over time, and the image carrier can be sufficiently cleaned continuously.

The cleaning roller 43 is preferably a conductive elastic roller. Cleaning roller 4
In order to efficiently apply electrostatic bias to the toner and the like on the photosensitive drum 2 by applying a bias voltage to the cleaning roller 3, the surface resistance of the cleaning roller 43 is preferably 10 ⁵ Ω to 10 ⁸ Ω. preferable.

Furthermore, if the cleaning roller 43 is elastic, it is possible to carry the cleaning roller 4 into the cleaning device 4 without damaging the surface of the photoreceptor drum 2 even if a foreign object is caught between the cleaning roller 43 and the photoreceptor drum 2. I do. When the cleaning roller 43 is elastic, the photosensitive drum 2
As a result, not only the removal of toner and the like on the photosensitive drum 2 by electrostatic suction but also a wiping effect can be expected, so that the cleaning ability is further enhanced. Cleaning roller 43
The hardness of the surface when is elastic is preferably Asker C 20 ° to 40 °.

Specifically, as a preferred conductive elastic roller, a ruby cell roller (having a hardness of Asker C of 32 °) manufactured by Toyo Polymer Co., Ltd. or the like can be mentioned.

FIG. 2 is a schematic diagram showing a laser printer as an example of an image forming apparatus provided with the cleaning device of the present invention.

In the drawing, reference numeral 1 denotes a charger, 2 denotes a photosensitive drum as a first image carrier, 3 denotes a developing drum having four developing devices (developing means), and 4a denotes a photosensitive drum. A photoconductor cleaning device for cleaning; 4b, an intermediate transfer belt cleaning device for cleaning the intermediate transfer belt;
Is a primary transfer roller, 7 is a secondary transfer roller, 8 is a backup roller, 9, 10, 11 and 12 are support rollers,
14 is a laser exposure device, 15 is an intermediate transfer belt as a second image carrier, 30 is a paper feed cassette for storing the transfer paper P, 31 is a pickup roller for feeding out the transfer paper P, 3
Reference numeral 2 denotes a registration roller, reference numeral 33 denotes a fixing device for thermally fixing the toner image on the transfer paper P on which the secondary transfer has been completed, and reference numeral 34 denotes a discharge tray 34 for discharging the transfer paper P on which an image has been formed. Here, the photoconductor cleaning device 4a and the intermediate transfer belt cleaning device 4b are the cleaning device 4 of the present invention described with reference to FIG.

Around the photosensitive drum 2, a charger 1 for uniformly charging the surface of the photosensitive drum 2 with a charge of a predetermined polarity, and an electrostatic latent image on the photosensitive drum 2 imagewise. , A developing drum 3 for attaching toner to the electrostatic latent image to form a toner image, and a primary transfer roller 6 for transferring the toner image on the photosensitive drum 2 to an intermediate transfer belt 15 ( Conductive) are arranged in this order.

The photosensitive drum 2 is rotated in a direction indicated by an arrow in FIG. Charger 1
Is a band electrode such as a corotron, which can uniformly charge the photosensitive drum 2. When the photoconductor drum 2 is an OPC photoconductor (organic photoconductor), the photoconductor drum 2 is uniformly charged to a negative polarity.

An image signal transmitted from an image reading unit such as a scanner (not shown) or a personal computer is
A required process is performed in an image processing unit (not shown), and the image processing unit is sent to a laser exposure unit 14, which scans and exposes the photosensitive drum 2 with a laser beam corresponding to the image signal. The negative potential of the photosensitive drum 2 attenuates imagewise to form an electrostatic latent image.

The electrostatic latent image formed on the photosensitive drum 2 is developed with the toner in the first color developing unit of the developing drum 3 having four developing units, and the first color toner image is formed. To form At this time, the toner is charged to a negative polarity in the developing device, and the toner is visualized by attaching to the portion of the photosensitive drum 2 where the charged potential is attenuated. The toner image carried on the photoconductor drum 2 is further rotated by the photoconductor drum 2, reaches a primary transfer portion where the primary transfer roller 6 is disposed, and is primarily transferred to the intermediate transfer belt 15. The intermediate transfer belt 15 is moving at substantially the same speed as the photosensitive drum 2 in the direction of the arrow in FIG.
At the primary transfer site, the toner is primarily transferred to the intermediate transfer belt 15 by a transfer electric field applied to the primary transfer roller and having a characteristic opposite to that of the toner (plus in this case).

Thereafter, the process from the formation of the latent image to the primary transfer of the toner image is repeated for the second color, the third color, and the fourth color, so that the multicolor toner is superimposed on the intermediate transfer belt 15. Form an image. Normally, the colors of the toner are four colors of black, yellow, magenta, and cyan, which are included in four developing units in the developing drum 3, respectively. Until the color toner image is completed, the secondary transfer roller 7 and the intermediate transfer belt cleaning device 4b are retracted from the intermediate transfer belt 15 and are in a non-contact state. In the present embodiment, a developing drum provided with a plurality of developing means is used for forming a color toner image. However, a photosensitive drum and a developing device and other image forming units are formed for each color, and a plurality of developing units are formed. A so-called tandem type in which the image forming units are arranged in a line on the intermediate transfer belt 15 and each of the image forming units primarily transfer the toner image to the intermediate transfer belt 15 may be used.

After the transfer of the toner image to the intermediate transfer belt 15 at the primary transfer site in this way, the residual toner is scraped off by the photosensitive member cleaning device 4a, and the photosensitive drum 2 is exposed to light by a neutralizer (not shown). The potential on the body drum 2 is cancelled, and preparations are made for the next image formation.

On the other hand, when the primary transfer of the color toner image to the intermediate transfer belt 15 is completed and the color toner image reaches the secondary transfer portion where the secondary transfer roller 7 is disposed, the recording material is transferred from the sheet cassette 30 to the recording material. Is picked up by the pickup roller 31. The transfer paper P thus taken out is sent out in a timely manner by the registration roller 32, and is conveyed to a secondary transfer portion sandwiched between the intermediate transfer belt 15 supported by the backup roller 8 and the secondary transfer roller 7. Left side in the figure). A bias potential having a polarity opposite to that of the toner on the intermediate transfer belt 15 is applied to the secondary transfer roller 7 (not shown), and the backup roller 8 is grounded (not shown). When the transfer paper P passes between the intermediate transfer belts 15, the toner image carried on the intermediate transfer belt 15 by the transfer electric field formed by the transfer voltage having the polarity opposite to the charging polarity of the toner image is transferred onto the transfer paper P. The secondary transfer is performed. At this time, the relationship between the bias application and the grounding of the secondary transfer roller 7 and the backup roller 8 may be reversed. The transfer paper P on which the toner image has been secondarily transferred is further fixed to a fixing device 33 composed of a pair of heat rollers.
, And is heated, pressurized and fixed, and is discharged to a discharge tray 34.

On the other hand, the intermediate transfer belt 15 on which the secondary transfer has been completed is cleaned of residual toner or paper dust by the intermediate transfer belt cleaning device 4b to prepare for the next image formation.

The above-described operations and sequence control of image formation are performed by a control unit (not shown).

Next, the toner having an average circularity of 0.96 or more, which is to be cleaned and removed by the cleaning device of the present invention, will be described.

As a toner having a circularity of 0.96 or more,
So-called polymerization toners are known. Above all, JP 6
The method for producing a polymerization toner in which resin particles and colorant particles are associated with each other as disclosed in JP-A-3-186253 is an excellent technique.

Various other toner techniques in which resin particles are associated (fused) with each other have been disclosed. The measurement of the circularity of the polymerized toner is not particularly limited, but it is preferable to use a flow type particle image analyzer FPIA-2000 (manufactured by Toa Medical Electronics Co., Ltd.). This apparatus is suitable because the shape can be monitored by performing image processing in real time while passing the sample liquid.

FIG. 3 shows a configuration diagram of a main part of a measuring device for particle shape and shape distribution of toner. FIG. 4 is a perspective view illustrating the flow of the sample solution and the imaging unit in FIG. FIG. 5 is a diagram for explaining how to determine the circularity.

3 and 4, arrows indicate the flow of the sample liquid 101 or the sheath liquid, and 102 indicates the sheath liquid (coating liquid), whereby the particles flow to the imaging unit 103 without overlapping. The sample liquid 101 is photographed by the high-speed video camera 105 in accordance with the emission of the strobe light 104. 1
06 represents particles in the sample solution, and Y, X, and Z represent
3 represents the vertical and horizontal lengths and thicknesses. FIG. 5 shows the “circumferential length of the circle obtained from the equivalent circle diameter” of the particles photographed thereby.
7 and a method of obtaining the “peripheral length of the particle projection image” 108.

The circularity can be defined as follows. Circularity = (Circumferential length of circle obtained from equivalent circle diameter) / (Circumferential length of particle projected image) In the present invention, the average value of circularity of toner (average circularity) is in the range of 0.96 to 0.99. It is preferably within. If the degree of circularity is too low, grinding occurs due to stress caused by agitation inside the developing device, adhesion to the carrier and the developing device may occur, and durability may be reduced, and the degree of circularity is too high. This is because the shape may be spherical, so that the cleaning property may be reduced.

Further, the standard deviation based on the number is preferably 0.05 or less. When the standard deviation exceeds 0.05, the distribution of the shape is expanded, so that a distribution is generated in the developing property, selective development occurs, and long-term development cannot be stabilized. It is possible that so-called fog or a change in image density occurs.

The particle size of the toner is measured on a volume basis, and can be obtained by a method of measuring a frequency distribution around a scale converted logarithmically using a circle equivalent diameter. The volume average particle size is preferably 3 to 9 μm. The particle size distribution can also be measured by the above-mentioned measuring device at the same time.

The method for producing a toner having a circularity of 0.96 or more is not particularly limited as described above, but is preferably a method disclosed in JP-A-5-265252 or JP-A-6-329.
No. 947 and Japanese Patent Application Laid-Open No. 9-15904 are preferable.

[0043]

(Embodiment 1) The present invention in which the cleaning device 4 shown in FIG. 1 is used as the photoconductor cleaning device 4a of the laser printer shown in FIG. 2 using polymerized toner having an average circularity of 0.973. An image forming test using the image forming apparatus described above, and a conventional cleaning apparatus using a polymerized toner having an average circularity of 0.973, having no cleaning roller, and using only a cleaning blade, is also a laser printer shown in FIG. An image forming test was performed using a comparative image forming apparatus provided as the photoconductor cleaning device 4a. A running print test was performed with the number of prints set to zero when each cleaning device was newly installed, and whether or not the cleaning performance deteriorated with time was evaluated.

The cleaning device of the comparative image forming apparatus is the same as the cleaning device of FIG. 1 except that the cleaning device 4 of FIG. 1 does not include the cleaning roller 43, the blade 44, the power supply 47 and the power supply controller 48. is there.

In the image forming apparatus of the present invention, the cleaning roller 43 of the cleaning device is a ruby cell roller (Asker C hardness 32 °) manufactured by Toyo Polymer Co., Ltd. Constant current control was performed with a current value of 20 μA.

In the image forming apparatus of the present invention and the comparative image forming apparatus, the evaluation of the cleaning performance of the photosensitive drum 2 by the photosensitive body cleaning device was performed as follows. That is, the operation of cleaning the untransferred toner image of the entire A4 size (solid) (not primary-transferred to the intermediate transfer belt) formed on each photosensitive drum 2 by each cleaning device is performed 10 times ( This is referred to as one set). Thereafter, it was visually confirmed whether or not the toner remained on the photosensitive drum 2. When the toner remained, the evaluation was ×, and when the cleaning was sufficiently completed without the toner, the evaluation was ○.

The total number of images formed from the number of prints when the cleaning device is newly installed to the actual transfer to the transfer paper is defined as the total number of prints, and after reaching the total number of prints shown in Tables 1 and 2. The formation and cleaning of the untransferred toner image on the entire surface of the A4 size sheet with the toner adhesion amount changed as shown in Tables 1 and 2 were performed for each of 2 to 4 sets in accordance with the evaluation method described above. The results are shown in Tables 1 and 2. Table 1 shows the evaluation results of the comparative image forming apparatus, and Table 2 shows the evaluation results of the image forming apparatus of the present invention.

[0048]

[Table 1]

[0049]

[Table 2]

As is clear from the above table, in forming an image with toner having an average circularity of 0.96 or more, a cleaning roller to which a bias voltage is applied is disposed upstream of the cleaning blade in combination with the cleaning blade. It has been found that the cleaning device of the present invention continuously shows stable high cleaning performance.

[0051]

According to the present invention, a cleaning device capable of continuously and sufficiently cleaning an image carrier even with a toner having a high average circularity, an image forming apparatus provided with the cleaning device, and image forming of the image forming device. A method could be provided.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a relationship between a cleaning device of the present invention and an image carrier.

FIG. 2 is a schematic configuration diagram showing a laser printer as an example of an image forming apparatus provided with the cleaning device of the present invention.

FIG. 3 is a configuration diagram of a main part of a toner particle shape and shape distribution measuring device.

FIG. 4 is a perspective view illustrating a flow of a sample solution and an imaging unit in FIG. 3;

FIG. 5 is a diagram illustrating a method of obtaining a circularity.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Charger 2 Photoreceptor drum 3 Developing drum 4 Cleaning device 6 Primary transfer roller 7 Secondary transfer roller 8 Backup roller 9, 10, 11, 12 Supporting roller 14 Laser exposure device 15 Intermediate transfer belt 30 Feed cassette 33 Fixing device 34 Discharge tray 41 Cleaning blade 42 Spring 43 Cleaning roller 44 Blade 45 Toner recovery roller 46 Housing 47 Power supply 48 Power supply controller

Claims (8)

[Claims] 1. A cleaning device for cleaning an image carrier on which an image is formed with toner having an average circularity of 0.96 or more, wherein the cleaning blade cleans the image carrier by pressing an end thereof against the image carrier. A cleaning roller that is located upstream of the cleaning device and that contacts and cleans the image carrier, and a bias voltage applying unit that applies a bias voltage to the cleaning roller. 2. The cleaning device according to claim 1, wherein the cleaning roller is a conductive elastic roller. 3. The cleaning apparatus according to claim 1, further comprising control means for applying the bias voltage by said bias voltage applying means by DC constant current control. 4. An image forming apparatus provided with the cleaning device according to claim 1. 5. A method according to claim 1, wherein a plurality of developing means are arranged around the first image carrier, and a toner image formed on the first image carrier is primarily transferred to a second image carrier. An image forming apparatus for secondary-transferring a primary-transferred toner image on a second image carrier to a recording material, wherein the first image carrier or the second image carrier cleaning device includes: An image forming apparatus comprising the cleaning device according to claim 1. 6. A developing step of forming a toner image on an image bearing member with a toner having an average circularity of 0.96 or more, a transferring step of transferring a toner image on the image bearing member, and after the transferring step, A cleaning step of cleaning the image bearing member, wherein the cleaning step includes: contacting the image bearing member with a cleaning roller to which a bias voltage has been applied to clean the cleaning roller; An image forming method, wherein the cleaning is performed by pressing against a body. 7. The image forming method according to claim 6, wherein the cleaning roller is a conductive elastic roller. 8. The image forming method according to claim 6, wherein the application of the bias voltage applied to the cleaning roller is a DC constant current control.