JP2008058564A - Cleaning device and image forming apparatus mounted with same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cleaning device that excellently cleans a surface of an image carrier by preventing an image defect due to irregular rotations of the image carrier and insufficient removal of discharge products resulting from that the image carrier and a cleaning roller comes into contact with each other on the same parts in every rotation. <P>SOLUTION: The cleaning roller 33 that a cleaning device 30 for a photoreceptor drum 21 is equipped with is such that a surface at a place of contact with the photoreceptor drum 21 rotates in a direction of movement in the same direction with a surface of the photoreceptor drum 21, the ratio of the peripheral speed of the cleaning roller 33 to the peripheral speed of the photoreceptor drum 21 is >0.4 and ≤1, and the rotation period of the photoreceptor drum 21 is not an integral multiple of the rotation period of the cleaning roller 33. Consequently, the photoreceptor drum 21 is prevented from irregularly rotating to avoid a state wherein the same part on the surface of the photoreceptor drum 21 comes into contact with the same part on the surface of the cleaning roller without fail each time they rotate. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a cleaning device that removes deposits remaining on the surface of an image carrier and cleans them after transferring a toner image onto a sheet. The present invention also relates to an image forming apparatus equipped with this cleaning device.

  In an electrophotographic image forming apparatus such as a copying machine or a printer, a photosensitive drum is widely used as an image carrier. A general image forming operation using the photosensitive drum is as follows. The surface of the photosensitive drum is uniformly charged with a predetermined potential by a charging device, and by irradiating the LED light or the like of the exposure device there, the potential is partially attenuated to form an electrostatic latent image of an original image. Is done. The electrostatic latent image is developed with a developing device, whereby a toner image is formed on the surface of the photosensitive drum. This toner image is transferred to the sheet when the sheet is inserted into a transfer region formed by bringing the photosensitive drum and the transfer member into contact with each other or close to each other.

  In such an image forming apparatus, after a toner image is transferred to a sheet, a small amount of toner may remain on the surface of the photosensitive drum without being transferred to the sheet. The residual toner adhering to the surface of the photosensitive drum becomes an obstacle to the next new image formation, so that it needs to be cleaned. As a cleaning method used for such a purpose, a method of moving and collecting residual toner on the rotating member by pressing a cleaning roller, a rotating brush, or the like that is a rotating member on the surface of the photosensitive drum, or a surface of the photosensitive drum A method of scraping residual toner by bringing a cleaning blade into contact therewith, or a cleaning method combining these methods is widely known.

  On the other hand, when an amorphous silicon photoconductor is used as the photoconductor, it is known that discharge products easily adhere to the surface of the photoconductor due to the discharge of the charging device. When this discharge product absorbs moisture, the electrical resistance on the surface of the photoreceptor is lowered, and a problem of image flow that disturbs the electrostatic latent image may occur. For this reason, a small amount of abrasive as an external additive is mixed in the toner, and the cleaning roller and the cleaning blade are used in combination to remove the residual toner adhering to the surface of the photosensitive member, and a small amount of toner is carried on the surface of the cleaning roller. A method is known in which the discharge product and moisture adhering to the surface of the photoreceptor are polished by this toner so as to be polished.

As described above, Patent Documents 1 to 3 show examples of cleaning methods for removing discharge products and moisture adhering to the surface of the photosensitive drum using a cleaning roller. In the image forming apparatus described in Patent Document 1, the cleaning roller is rotated in such a direction that the surface at the contact point with the photosensitive drum moves in a direction different from the drum surface or in the same direction, so that the circumferential speed of the photosensitive drum is increased. On the other hand, the peripheral speed of the cleaning roller is 120%. Similarly, in the image forming apparatus described in Patent Document 2, the cleaning roller is rotated in a direction in which the surface at the contact point with the photosensitive drum moves in a direction different from the drum surface, and the rotation speed of the cleaning roller is set to the photosensitive drum. The rotational speed of the drum is 0.3 to 0.5 times. In the image forming apparatus described in Patent Document 3, the rotation speed of the cleaning roller is set to 100% or more of the rotation speed of the photosensitive drum.
JP-A-7-234619 (page 3, FIG. 4) Japanese Patent Laying-Open No. 2004-361776 (5th page, FIG. 3) Japanese Patent Laying-Open No. 2005-345505 (page 6-7, FIG. 3)

  In the image forming apparatuses described in Patent Documents 1 to 3, the cleaning roller is rotated in a direction in which the surface at the contact point with the photosensitive drum moves in a different direction from the drum surface, or in a direction in which the cleaning roller moves in the same direction. It is trying to improve the removal efficiency of the discharge product by rotating it faster than the body drum. However, in these methods, the rotation of the cleaning roller places a load on the rotation of the photosensitive drum, and the photosensitive drum does not rotate smoothly, which may cause the rotation to become unstable. In this way, when rotation unevenness occurs in the photosensitive drum, there is a high possibility that an image defect called jitter noise will occur due to the rotational displacement. Here, “jitter” means that the value fluctuates (vibrates) around a predetermined speed or period, and a band-like or striped image (jitter noise) due to the speed fluctuation. Is generated.

  In addition, in the image forming apparatus described in Patent Document 2, the rotation speed of the cleaning roller is set to be low in order to prevent such rotation unevenness of the photosensitive drum, but the surface at the contact point with the photosensitive drum is low. Since it rotates in a direction that moves in a direction different from the drum surface, it is difficult to completely prevent the rotation unevenness. Even if cleaning can be performed while preventing the occurrence of rotation unevenness of the photoconductive drum, the surface of the photoconductive drum is changed for each rotation only by considering only the rotation speed ratio between the photoconductive drum and the cleaning roller. There is a possibility that the same part of the surface of the cleaning roller comes into contact with the same part and the discharge product cannot be removed effectively. Therefore, it is preferable to consider not only the rotation speed ratio but also the rotation period.

  Further, in the image forming apparatus described in Patent Document 2, in order to change the rotation direction of the cleaning roller between image formation and non-image formation, the image forming apparatus described in Patent Document 3 In order to change the rotational speed of the cleaning roller between non-image formation, a motor dedicated to the cleaning roller is prepared to improve the discharge product removal efficiency. However, this is not preferable because the cost for adding a dedicated motor increases.

  The present invention has been made in view of the above points, and is caused by the occurrence of an image defect due to the rotation unevenness of the image carrier and the contact between the image carrier and the cleaning roller at the same place for each turn. It is an object of the present invention to provide a cleaning device that can prevent the discharge product from being insufficiently removed and can exhibit a suitable cleaning performance for the surface of the image carrier. Another object of the present invention is to provide a high-performance image forming apparatus equipped with such a cleaning device.

  In order to solve the above-described problems, the present invention provides a cleaning blade that contacts an image carrier and removes deposits remaining on the surface thereof, and is provided on the upstream side of the image carrier in the rotational direction of the cleaning blade. In a cleaning device comprising a cleaning roller that rotates while contacting the carrier and cleans the surface thereof, the surface of the cleaning roller in contact with the image carrier moves in the same direction as the surface of the image carrier The ratio of the circumferential speed of the cleaning roller to the circumferential speed of the image carrier is greater than 0.4 and less than 1 and the ratio of the rotation cycle of the image carrier to the rotation cycle of the cleaning roller Is a non-integer multiple.

  In the cleaning device having the above-described configuration, the cleaning roller is rotated by a motor that rotates the image carrier.

  In the present invention, the cleaning device is mounted on the image forming apparatus.

  In the image forming apparatus having the above configuration, the image carrier includes an amorphous silicon photoconductor.

  According to the configuration of the present invention, the cleaning blade that comes into contact with the image carrier and removes the deposits remaining on the surface thereof is provided on the upstream side of the cleaning blade in the rotation direction of the image carrier, and contacts the image carrier. In the cleaning device provided with a cleaning roller that rotates while cleaning the surface, the cleaning roller rotates in such a direction that the surface in contact with the image carrier moves in the same direction as the surface of the image carrier. The ratio of the peripheral speed of the roller to the peripheral speed of the image carrier is greater than 0.4 and less than 1 and the ratio of the rotation cycle of the image carrier to the rotation cycle of the cleaning roller is a non-integer multiple. Therefore, uneven rotation of the image carrier can be prevented, and the same part of the surface of the cleaning roller always contacts the same part of the surface of the image carrier every rotation. It is possible to avoid the state, such as. This prevents the occurrence of image defects called jitter noise caused by uneven rotation of the image carrier and the insufficient removal of discharge products caused by contact of the same locations with each turn. Is possible. Therefore, it is possible to obtain a cleaning device capable of exhibiting suitable cleaning performance for the surface of the image carrier.

  Further, since the cleaning roller is rotated by a motor that rotates the image carrier, it is not necessary to separately prepare a motor dedicated to the cleaning roller, and complicated control is not required. Accordingly, the cleaning roller can be rotated at a predetermined rotation speed and rotation cycle with a simple configuration in which an increase in cost is suppressed. Therefore, it is possible to exhibit a suitable cleaning performance for the surface of the image carrier by the cleaning device in which the increase in cost is suppressed.

  In the present invention, since the cleaning device is mounted on the image forming apparatus, the occurrence of image defects due to the rotation unevenness of the image carrier and the image carrier and the cleaning roller are located at the same location for each turn. Obtaining a high-performance image forming apparatus capable of preventing insufficient removal of discharge products caused by contact and capable of exhibiting suitable cleaning performance for the surface of the image carrier be able to.

  Photoconductors made of amorphous silicon are used in many image forming apparatuses because of high hardness, excellent wear resistance, and a very long life. However, on the other hand, there is also a problem that image flow is likely to occur due to discharge products adhering to the surface of the photoreceptor. For such a problem, by combining the image forming apparatus of the present invention with a photoconductor composed of amorphous silicon, it is possible to prevent the adhesion of discharge products to the surface of the photoconductor, so that the image flow is reduced. Therefore, it is possible to form a high-quality image without causing occurrence of an image and to obtain an image forming apparatus having a longer life.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

  First, an image output operation of an image forming apparatus equipped with a paper conveyance device according to an embodiment of the present invention will be described while explaining the outline of the structure with reference to FIG. FIG. 1 is a left side view of a schematic vertical section showing a schematic structure of a color printer which is an example of an image forming apparatus. This color printer is a type using an intermediate transfer belt. In FIG. 1, the right side is the front side of the printer, and the left side is the back side.

  As shown in FIG. 1, a paper cassette 3 is disposed below the inside of the main body 2 of the printer 1. Inside the paper cassette 3, paper P is stacked and stored. Then, the sheets P are separated and sent one by one toward the upper right of the sheet cassette 3 in FIG. The paper cassette 3 can be pulled out horizontally from the front side of the main body 2, that is, from the right side in FIG.

  A paper feed path 4, a paper feed transport roller 5, a registration roller 6, an image forming unit 20, and a secondary transfer unit 50 are disposed downstream of the paper cassette 3 in the paper transport direction. The paper P sent out from the paper cassette 3 enters the paper feed paper transport path 4, is transported by the paper feed transport roller 5, and reaches the registration roller 6. The registration roller 6 corrects the oblique feeding of the paper P, measures the timing with the color toner image or black toner image formed by the image forming unit 20, and sends the paper P to the secondary transfer unit 50.

  The image forming unit 20 includes a photosensitive drum 21 which is a rotating image carrier at the center thereof. The photosensitive drum 21 rotates counterclockwise in FIG. Around the photosensitive drum 21, a charging device 22, a developing device 23, and a drum cleaning device 30 are sequentially arranged along the rotation direction.

  On the other hand, an optical unit 7 is provided above the image forming unit 20, and a laser beam L is emitted from the optical unit 7 toward the photosensitive drum 21. The two-dot chain line in the figure indicates the laser beam L. Image data signals such as characters, graphics, and patterns from an external computer (not shown) are transmitted to the printer 1, and the laser light L is controlled by the optical unit 7 based on the image data. As a result, an electrostatic latent image of the original image is formed on the surface of the photosensitive drum 21 in the image forming unit 20. For this electrostatic latent image, an electrostatic latent image corresponding to each color is formed in order for each color image forming process.

The developing device 23 of the image forming unit 20 is mainly composed of a rotary rack 23a that is a rotating body that rotates clockwise in FIG. 1, and a total of four developing devices are arranged at equal intervals in the circumferential direction on the rotary rack 23a. Has been placed. The four developing devices are a black developing device 23B, a cyan developing device 23C, a magenta developing device 23M, and a yellow developing device 23Y. The rotary rack 23a is rotated by driving means (not shown), and the four developing devices are sequentially moved to positions facing the photosensitive drum 21 to supply toner of each color to the surface of the photosensitive drum 21 to thereby generate electrostatic latent images. The image is developed to form a toner image. Each color toner contains titanium oxide (TiO ₂ ) as an external additive, that is, an abrasive.

  Of the respective colors of black, cyan, magenta, and yellow, first, a black toner image, which is the first color, is formed on the surface of the photosensitive drum 21, so that the black developing unit 23 </ b> B faces the photosensitive drum 21. The rack 23a rotates. The black developing device 23B develops the electrostatic latent image on the surface of the photosensitive drum 21 to form a black toner image.

  An intermediate transfer belt 40 using an intermediate transfer member in the form of an endless belt is disposed immediately below the photosensitive drum 21. The intermediate transfer belt 40 is pressed against the photosensitive drum 21 from below to form a primary transfer nip portion. The intermediate transfer belt 40 is supported by being wound around a plurality of rollers, and rotates clockwise in FIG. The toner image formed on the surface of the photosensitive drum 21 is primarily transferred to the surface of the intermediate transfer belt 40 at a primary transfer nip portion formed by press-contacting the photosensitive drum 21 and the intermediate transfer belt 40.

  After the primary transfer, the black toner remaining on the surface of the photosensitive drum 21 is removed by the drum cleaning device 30. The intermediate transfer belt 40 rotates once so as to coincide with a predetermined primary transfer position with respect to the photosensitive drum 21 in order to perform primary transfer of the next color. When the toner image to be formed is a black toner image, the primary transfer process ends here. When the toner image to be formed is a color toner image, the image forming process of development, transfer, and cleaning similar to the first color is continuously repeated for each color from the second color to the fourth color, and the surface of the intermediate transfer belt 40 A color toner image is formed by superimposing four color toner images of black, cyan, magenta, and yellow.

  A secondary transfer unit 50 is disposed at a position where the intermediate transfer belt 40 is suspended on the sheet conveyance path. The secondary transfer unit 50 includes a secondary transfer roller 51, and the sheet P is inserted into a secondary transfer nip portion formed by press-contacting the intermediate transfer belt 40 and the secondary transfer roller 51. The secondary transfer roller 51 is movable in the vertical direction in FIG. 1, and is brought into pressure contact with or separated from the intermediate transfer belt 40 as necessary. When a four-color color toner image or a black toner image is formed on the surface of the intermediate transfer belt 40, the paper P sent in synchronization by the registration roller 6 is transferred to the secondary transfer portion 50. By being inserted into the next transfer nip portion, the toner image is transferred by being brought into pressure contact with the intermediate transfer belt 40. The secondary transfer roller 51 is separated from the intermediate transfer belt 40 while the toner images of the respective colors are sequentially primary transferred to the intermediate transfer belt 40.

  A belt cleaning device 60 is provided downstream of the secondary transfer unit 50 in the sheet conveyance direction. The cleaning roller 61 of the belt cleaning device 60 is also pressed against or separated from the intermediate transfer belt 40 as necessary. After the secondary transfer, the toner remaining on the surface of the intermediate transfer belt 40 is removed by the cleaning roller 61 that is in pressure contact with the intermediate transfer belt 40. Note that the cleaning roller 61 is separated from the intermediate transfer belt 40 while the toner images of the respective colors are sequentially primary-transferred to the intermediate transfer belt 40.

  A fixing unit 8, a discharge paper transport path 9, and a paper discharge unit 10 are disposed downstream of the image forming unit 20 and the secondary transfer unit 50 in the paper transport direction. The paper P carrying an unfixed color toner image or black toner image is sent to the fixing unit 8 and the toner image is fixed by a heat roller and a pressure roller.

  The paper P discharged from the fixing unit 8 is sent upward through the discharge paper transport path 9 and is discharged to the paper discharge unit 10 provided on the upper surface of the main body 2. The paper discharge unit 10 is provided on the upper surface of the main body 2 at a position where the printed paper P can be taken out from the outside.

  A sheet conveyance path 11 for double-sided printing is disposed below the fixing unit 8 and the secondary transfer unit 50 and between the sheet cassette 3. The double-sided printing paper conveyance path 11 branches from the middle of the discharge paper conveyance path 9, passes under the fixing unit 8 and under the secondary transfer unit 50, and conveys the paper for paper feeding immediately upstream of the registration roller 6. It merges with Road 4.

  When performing double-sided printing, the paper P discharged from the fixing unit 8 is switched to the reverse direction and switched back immediately before being discharged to the paper discharge unit 10 through the discharge paper transfer path 9. The Then, the paper P is sent to the double-sided printing paper transport path 11, merged with the paper feed paper transport path 4 immediately upstream of the registration rollers 6, and sent again to the secondary transfer unit 50.

  Next, a detailed configuration around the image forming unit 20 of the printer 1 will be described with reference to FIGS. 2 and 3 in addition to FIG. 2 is a partially enlarged vertical sectional view showing the periphery of the image forming unit of the printer, and FIG. 3 is a partially enlarged top view showing a driving mechanism for the photosensitive drum and the cleaning roller.

  As shown in FIGS. 1 and 2, the image forming unit 20 includes a photosensitive drum 21 that is an image carrier at the center thereof. An intermediate transfer belt 40 using an intermediate transfer member in the form of an endless belt is disposed immediately below the photosensitive drum 21. With respect to the primary transfer nip portion where the photosensitive drum 21 and the intermediate transfer belt 40 are in pressure contact with each other, the developing device 23 described above is provided on the upstream side in the drum rotation direction, and the drum cleaning device 30 is provided on the downstream side. ing.

  The photoconductive drum 21 extends in the paper width direction perpendicular to the paper conveyance direction in the printer 1, that is, the paper surface depth direction in FIGS. 1 and 2, and is arranged with its axial direction horizontal. The photosensitive drum 21 is an inorganic photosensitive drum in which an amorphous silicon photosensitive layer, which is an inorganic photoconductive material, is provided on the outside of a conductive roller-shaped substrate made of aluminum or the like by vacuum deposition or the like, and has a diameter of 30 mm. It is. The photosensitive drum 21 is rotated by a driving device (not shown) so that the peripheral speed thereof is substantially the same as the paper conveyance speed (for example, 150 mm / s).

  As shown in FIGS. 1 and 2, the intermediate transfer belt 40 is wound around a primary transfer roller 41, a tension roller 42, a driving roller 43, and a guide roller 44. The intermediate transfer belt 40 is composed of a single-layer resin belt formed only of a synthetic resin such as polyimide, or an elastic belt in which a rubber layer is laminated on the surface of such a synthetic resin. The primary transfer roller 41 is provided in the primary transfer nip portion so as to contact the photosensitive drum 21 from below via the intermediate transfer belt 40. A primary transfer bias is applied to the primary transfer roller 41 as necessary.

  As shown in FIG. 2, the cleaning device 30 for the photosensitive drum 21 includes a cleaning blade 32, a cleaning roller 33, and a discharge screw 34 as a discharge member inside the housing 31.

  The cleaning blade 32 is made of a plate-like urethane rubber and has substantially the same axial length as the photosensitive drum 21. The cleaning blade 32 is provided so as to be brought into pressure contact with the photosensitive drum 21 so that the contact portion has a predetermined linear pressure. Then, after the primary transfer of the toner image to the intermediate transfer belt 40, the cleaning blade 32 scrapes and removes deposits such as toner remaining on the surface of the photosensitive drum 21.

  The cleaning roller 33 is provided in contact with the photosensitive drum 21 on the upstream side of the cleaning blade 32 in the drum rotation direction. The cleaning roller 33 is configured in a form in which foamed ethylene propylene rubber (EPDM) is provided around a core metal having a diameter of 8 mm. The roller portion has a diameter of 12 mm and a hardness of Asker C50. As the cleaning roller 33, a roller having a hardness in the range of Asker C30 to 60 can be used. When the hardness is less than Asker C30, an image defect called jitter noise appears conspicuously. When the hardness exceeds Asker C60, the contact state with the photosensitive drum 21 becomes non-uniform, and image flow is likely to occur. As a material, it is desirable to use a foamed rubber material in order to suppress the occurrence of jitter.

  The cleaning roller 33 is provided by being pressed against the photosensitive drum 21 with a predetermined force (6N) by urging means (not shown) provided at both ends of the shaft portion. When this pressing force is strong, jitter noise appears remarkably, and when it is weak, image flow tends to occur. The cleaning roller 33 collects the toner around the surface of the photosensitive drum 21 and the cleaning blade 32, cleans (polls) the surface of the photosensitive drum 21 with the toner adhering to the surface of the cleaning roller 33, and removes the toner from the discharge screw 34. It plays the role of sending it out.

  As shown in FIG. 2, the discharge screw 34 is provided in the housing 31 at a position further away from the photosensitive drum 21 with the cleaning roller 33 interposed therebetween. The discharge screw 34 is removed from the surface of the photosensitive drum 21 and serves to discharge the toner in the housing 31 used for cleaning (polishing) to the outside of the housing 31.

  Here, the cleaning roller 33 is rotated by a drive mechanism 70 having a motor 71 as shown in FIG. In the drive mechanism 70, a drive gear 72 is attached to the shaft portion of the motor 71, a drum driven gear 73 is attached to the shaft portion of the photosensitive drum 21, and a roller driven gear 74 is attached to the shaft portion of the cleaning roller 33. ing. The motor 71 is for rotating the photosensitive drum 21 by the drum driven gear 73 connected to the drive gear 72. The cleaning roller 33 is rotated through a roller driven gear 74 connected to the drum driven gear 73. The cleaning roller 33 rotates in such a direction that the surface at the contact point with the photosensitive drum 21 moves in the same direction as the surface of the photosensitive drum 21. That is, in FIG. 2, the photosensitive drum 21 rotates counterclockwise, whereas the cleaning roller 33 rotates clockwise.

  The ratio of the peripheral speed of the cleaning roller 33 to the peripheral speed of the photosensitive drum 21 is determined by the gear ratio of the drum driven gear 73 and the roller driven gear 74. By changing this gear ratio, the ratio of the peripheral speed of the cleaning roller 33 to the peripheral speed of the photosensitive drum 21 can be changed. In order to efficiently clean the surface of the photosensitive drum 21, it is necessary to rotate the cleaning roller 33 at a predetermined peripheral speed.

  Next, when the surface of the photosensitive drum 21 is cleaned using the cleaning device 30 for the photosensitive drum 21 having the above-described configuration, the peripheral speed ratio and the rotation cycle ratio between the photosensitive drum 21 and the cleaning roller 33 are determined. The effect of this difference on the occurrence of image flow and jitter noise will be described with reference to FIG. FIG. 4 is a table showing the influence of differences in peripheral speed ratio and rotation period ratio on the occurrence of image flow and jitter noise.

  4 indicates the ratio of the peripheral speed of the cleaning roller 33 to the peripheral speed of the photosensitive drum 21. The “period ratio” indicates the ratio of the rotation period of the photosensitive drum 21 to the rotation period of the cleaning roller 33, and is calculated from the diameter and peripheral speed ratio of each of the photosensitive drum 21 and the cleaning roller 33.

  First, the ratio of the peripheral speed of the cleaning roller 33 to the peripheral speed of the photosensitive drum 21 (peripheral speed ratio) is changed for the printer 1 to form a color image with a toner occupation ratio of 3% on the surface of the paper P. Continuous 10,000 sheets were printed. Then, after the printing was completed, evaluation of image flow and generation of jitter noise was performed.

  In order to make the image flow relatively easy to occur, the image is printed for 12 hours in a high temperature and high humidity environment with a temperature of 30 ° C. and a humidity of 85%, and the state of the image is visually checked. It was evaluated in three ranks. Rank A was a character flow that could hardly be confirmed, Rank B a character flow that could be confirmed a little but an acceptable level, and Rank C a character flow marked.

  As for jitter noise, halftone images of each color were printed in a room temperature and humidity environment, and the presence or absence of shading unevenness caused by the driving pitch of the cleaning roller 33 was visually evaluated in three ranks. Rank A where density unevenness could hardly be confirmed was ranked A, rank B where density unevenness was slightly confirmed but acceptable level, and rank C where density unevenness was remarkable.

  Regarding the overall evaluation, both image flow and jitter noise were rated as good (◯) when rank A, slightly good (Δ) when either was rank B, and poor (x) when either was rank C. And the case of (circle) or (triangle | delta) was adopted.

  In addition, as an Example and a comparative example, it experimented in eight cases and compared.

  In Examples 1 to 4, each peripheral speed is set so that the ratio of the peripheral speed of the cleaning roller 33 to the peripheral speed of the photosensitive drum 21 (peripheral speed ratio) is greater than 0.4 and less than one. This is an example. In this case, according to FIG. 4, the image flow when the peripheral speed ratio of Example 1 was 0.9 was substantially good although the jitter was slightly good when the peripheral speed ratio of Example 4 was 0.5, The overall evaluation was also good or slightly good.

  Comparative Example 1 is an example in which each peripheral speed is set so that the ratio of the peripheral speed of the cleaning roller 33 to the peripheral speed of the photosensitive drum 21 (peripheral speed ratio) is 0.4. In this case, according to FIG. 4, although the image flow is good, it can be seen that the density unevenness appears remarkably with respect to the jitter and is defective.

  Comparative Examples 2 and 3 are examples in which the respective peripheral speeds are set so that the ratio of the peripheral speed of the cleaning roller 33 to the peripheral speed of the photosensitive drum 21 (peripheral speed ratio) is 1.0 or more. In this case, according to FIG. 4, when the peripheral speed ratio of Comparative Example 2 is 1.0, the jitter is good, but the character flow is conspicuous and the image flow is poor. Further, it can be seen that when the peripheral speed ratio is 1.2 in Comparative Example 3, the image flow is good, but the density unevenness appears remarkably with respect to the jitter, resulting in failure.

  In Comparative Example 4, the ratio of the peripheral speed of the cleaning roller 33 to the peripheral speed of the photosensitive drum 21 (peripheral speed ratio) is in a range where the ratio is greater than 0.4 and less than one (peripheral speed ratio 0). .8), each peripheral speed is set such that the ratio (cycle ratio) of the rotation cycle of the photosensitive drum 21 to the rotation cycle of the cleaning roller 33 is an integer multiple of 2. In this case, according to FIG. 4, although the jitter is good, it can be seen that the character flow is conspicuous and the image flow is poor.

  As a result of overall judgment, as shown in the results of Examples 1 to 4, the ratio of the circumferential speed of the cleaning roller 33 to the circumferential speed of the photosensitive drum 21 is greater than 0.4 times and less than 1 time. In addition, the configuration of the printer 1 as the image forming apparatus of the present invention in which the ratio of the rotation cycle of the photosensitive drum 21 to the rotation cycle of the cleaning roller 33 is a non-integer multiple results in the most favorable evaluation. It was.

  In this way, the cleaning blade 32 that contacts the photosensitive drum 21 that is the image carrier and removes the deposits remaining on the surface of the photosensitive drum 21 and the upstream side of the cleaning blade 32 in the drum rotation direction are provided. In the cleaning device 30 provided with a cleaning roller 33 that rotates while in contact with the cleaning roller 21 and cleans the surface thereof, the surface of the cleaning roller 33 in contact with the photosensitive drum 21 is in the same direction as the surface of the photosensitive drum 21. The ratio of the peripheral speed of the cleaning roller 33 to the peripheral speed of the photosensitive drum 21 is greater than 0.4 and less than one, and the rotation cycle of the photosensitive drum 21 is the cleaning roller. Since the ratio of 33 to the rotation period is a non-integer multiple, uneven rotation of the photosensitive drum 21 can be prevented. Can and to avoid a situation such as the same portion of the same portion of the surface of the photosensitive drum 21 for each rotation cleaning roller surface is always in contact. This prevents the occurrence of image defects called jitter noise caused by uneven rotation of the photosensitive drum 21 and the insufficient removal of discharge products caused by contact of the same portions with each turn. It is possible. Therefore, it is possible to obtain a cleaning device 30 that can exhibit a suitable cleaning performance for the surface of the photosensitive drum 21.

  Since the cleaning roller 33 is rotated by the motor 71 that rotates the photosensitive drum 21, it is not necessary to separately prepare a motor dedicated to the cleaning roller 33, and complicated control is not required. Accordingly, the cleaning roller 33 can be rotated at a predetermined rotation speed and rotation cycle with a simple configuration in which an increase in cost is suppressed. Therefore, it is possible to exert a suitable cleaning performance on the surface of the photosensitive drum 21 by the cleaning device 30 in which cost increase is suppressed.

  In the present invention, since the cleaning device 30 is mounted on the printer 1, image defects due to rotation unevenness of the photosensitive drum 21, and the photosensitive drum 21 and the cleaning roller 33 are located at the same location for each turn. It is possible to prevent the discharge product due to contact from being insufficiently removed, and to obtain a high-performance printer 1 capable of exerting a suitable cleaning performance on the surface of the photosensitive drum 21. be able to.

  In addition, a photoconductor composed of amorphous silicon is used in many image forming apparatuses because it has high hardness, excellent wear resistance, and a very long life. However, on the other hand, there is also a problem that image flow is likely to occur due to discharge products adhering to the surface of the photoreceptor. In order to solve such a problem, it is possible to prevent adhesion of discharge products to the surface of the photosensitive member by combining the printer 1 which is the image forming apparatus of the present invention with a photosensitive member made of amorphous silicon. Therefore, it is possible to form a high-quality image with no image flow and to obtain the printer 1 having a longer life.

  Although the embodiments of the present invention have been described above, the scope of the present invention is not limited to these embodiments, and various modifications can be made without departing from the spirit of the invention.

  For example, in the above-described embodiment, the printer 1 is a color that includes the rotary rack 23a in which four developing devices are arranged at equal intervals in the circumferential direction in the developing device 23, and the endless intermediate transfer belt 40 as an intermediate transfer member. Although it is an image forming apparatus for printing, it may be an image forming apparatus for tandem color printing or an image forming apparatus for monochrome printing using only black toner without using an intermediate transfer member.

  Further, in each color toner, titanium oxide is mixed as an abrasive (external additive), but strontium titanate, cerium oxide, and alumina oxide may be mixed as an abrasive instead.

  The present invention can be used in general image forming apparatuses.

It is a model vertical cross-section left side view of a printer according to an embodiment of the present invention. FIG. 2 is a partially enlarged vertical cross-sectional view illustrating the periphery of an image forming unit of the printer of FIG. 1. FIG. 3 is a partially enlarged top view showing a driving mechanism for a photosensitive drum and a cleaning roller in FIG. 2. 4 is a table showing the influence of difference in peripheral speed ratio and rotation cycle ratio between a photosensitive drum and a cleaning roller on image flow and jitter noise generation.

Explanation of symbols

1 Printer (image forming device)
20 Image forming unit 21 Photosensitive drum (image carrier)
23 Developing device 30 Cleaning device (for photosensitive drum)
32 Cleaning blade 33 Cleaning roller 70 Drive mechanism 71 Motor

Claims (4)

A cleaning blade that contacts the image carrier to remove deposits remaining on the surface thereof, and is provided upstream of the cleaning blade in the rotation direction of the image carrier, and rotates while contacting the image carrier. In a cleaning device comprising a cleaning roller for cleaning,
The cleaning roller rotates in such a direction that the surface in contact with the image carrier moves in the same direction as the surface of the image carrier, and the ratio of the peripheral speed of the cleaning roller to the peripheral speed of the image carrier is 0. A cleaning apparatus, wherein the ratio is greater than 4 times and less than 1 time, and the ratio of the rotation period of the image carrier to the rotation period of the cleaning roller is a non-integer multiple.   The cleaning device according to claim 1, wherein the cleaning roller is rotated by a motor that rotates the image carrier.   An image forming apparatus comprising the cleaning device according to claim 1.   The image forming apparatus according to claim 3, wherein the image carrier includes an amorphous silicon photoconductor.

Images