JP2014095774A - Cleaning device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cleaning device capable of providing good cleanability even when a large amount of toner is input to a contact part between the surface of an image carrier and a brush roller, and an image forming apparatus.SOLUTION: A cleaning device 6 includes a brush roller 63 that is rotatably provided to be in contact with the surface of an image carrier 3 to remove a toner attached to the surface of the image carrier 3, and bias applying means for applying a bias for electrostatically attaching the toner to the brush roller. The cleaning device 6 inserts a toner remaining on the surface of the image carrier after transfer of a toner image formed on the surface of the image carrier to a transfer target body 10, into a contact part between the surface of the image carrier and brush roller, so as to remove the toner from the surface of the image carrier with the brush roller. The thickness of bristles of the brush roller is six deniers or more.

Description

  The present invention relates to a cleaning device used in an image forming apparatus such as a printer, a facsimile machine, and a copying machine, and an image forming apparatus including the cleaning device.

  Conventionally, in an image forming apparatus, after a toner image is transferred from an image carrier such as a photoconductor onto a transfer target, transfer residual toner, which is attached on the surface of the image carrier, is removed by a cleaning device. doing.

  In the cleaning device described in Patent Document 1, a cleaning brush roller that is rotatably provided in contact with the surface of an image carrier, and a bias application that applies a bias for electrostatically attaching toner to the cleaning brush roller Means. After transferring the toner image from the image carrier onto the transfer target, the positive and negative transfer residual toner remaining on the surface of the image carrier enters the contact portion between the image carrier surface and the cleaning brush roller, It is removed from the surface of the image carrier by the electrostatic force and rubbing force of the cleaning brush roller.

  However, if a large amount of toner is input to the contact portion between the surface of the image carrier and the cleaning brush roller, there is a problem that the transfer residual toner cannot be completely removed from the image carrier by the cleaning brush roller and sufficient cleaning properties cannot be obtained. Arise.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a cleaning device capable of obtaining good cleaning properties even when a large amount of toner is input to the contact portion between the surface of the image carrier and the brush roller. And an image forming apparatus provided with the cleaning device.

  In order to achieve the above object, a first aspect of the present invention provides a brush roller rotatably provided to remove toner adhering to a surface of an image carrier while being in contact with the surface of the image carrier, and a toner on the brush roller. Bias applying means for applying a bias for electrostatically adhering the toner, and transferring the toner image formed on the surface of the image carrier to the transfer target, the toner remaining on the surface of the image carrier, In a cleaning device that enters the contact portion between the surface of the image carrier and the brush roller and removes it from the surface of the image carrier by the brush roller, the brush thickness of the brush of the brush roller is 6 denier or more. It is a feature.

  As described above, according to the present invention, there is an excellent effect that a good cleaning property can be obtained even when a large amount of toner is input to the contact portion between the surface of the image carrier and the brush roller.

Schematic explanatory drawing of an image forming apparatus. 1 is a schematic configuration diagram of a copier according to an embodiment. Explanatory drawing of the cleaning by the cleaning blade which contact | abutted to the counter. Explanatory drawing of the cleaning by an electrostatic cleaning brush. Explanatory drawing of the cleaning which combined the cleaning blade and the electrostatic cleaning brush. 6 is a graph showing the relationship between brush thickness and toner recovery rate. FIG. 5 is a diagram used for explaining a toner recovery rate calculation method. 6 is a graph showing the relationship between the torque applied to the brush and the toner recovery rate when the brush contacts and rotates with the photosensitive member. The figure used for description of the measurement conditions of the torque concerning a brush.

  Embodiments in which the present invention is applied to a tandem type color image forming apparatus will be described below.

  FIG. 2 is a schematic configuration diagram of a copying machine as an image forming apparatus according to the embodiment. The copying machine includes a printer unit 100 that is a copying apparatus main body, a paper feeding unit 200 that is a paper feeding table, a scanner unit 300 that is mounted on the printer unit 100, and an automatic document feeder (ADF) that is mounted on the scanner unit 300. The document conveying unit 400 is. A control unit (not shown) for controlling the operation of each device in the copying machine is also provided.

  The printer unit 100 includes an intermediate transfer belt 10 as an intermediate transfer member at the center thereof. The intermediate transfer belt 10 is wound around the first support roller 14, the second support roller 15, and the third support roller 16, and can move on the surface in the clockwise direction in the drawing. Then, four photosensitive drums 3Y, 3M, 3C, and 3D as latent image carriers each carrying a toner image of one of black, yellow, magenta, and cyan on the surface so as to face the intermediate transfer belt 10. K is provided.

  Around the photosensitive drums 3Y, 3M, 3C, and 3K, charging devices 4Y, 4M, 4C, and 4K that are charging means for uniformly charging the surfaces of the photosensitive drums 3Y, 3M, 3C, and 3K, and toner images Developing devices 5Y, 5M, 5C, and 5K, which are developing means for forming the. Further, cleaning devices 6Y, 6M, 6C, and 6K for removing toner remaining on the surfaces of the photosensitive drums 3Y, 3M, 3C, and 3K after the primary transfer, and lubricant application for applying a lubricant to the surface of the photosensitive drums. Devices 8Y, M, C, K are also provided.

  The toner image forming unit includes the photosensitive drums 3Y, 3M, 3C, and 3K, the developing devices 5Y, M, C, and K, the charging devices 4Y, M, C, and K, and the cleaning devices 6Y, M, C, and K. The image forming apparatuses 1Y, 1M, 1C, and 1K are configured. The tandem image forming unit 20 is configured by arranging the four image forming apparatuses 1Y, 1M, 1C, and 1K side by side.

  A belt cleaning device 17 that removes residual toner remaining on the intermediate transfer belt 10 after the toner image is transferred onto a transfer sheet as a recording medium so as to face the third support roller 16 and the intermediate transfer belt 10. I have. In addition, the printer unit 100 includes an exposure device 21 above the tandem image forming unit 20.

  Primary transfer rollers 9Y, 9M, 9C, and 9K are provided at positions on the inner side of the intermediate transfer belt 10 that face the photosensitive drums 3Y, 3M, C, and K with the intermediate transfer belt 10 therebetween. The primary transfer rollers 9Y, 9M, 9C, and 9K are provided by being pressed against the photoconductive drums 3Y, 3M, 3C, and 3K with the intermediate transfer belt 10 interposed therebetween to form a primary transfer portion.

  On the other hand, a secondary transfer device 29 is provided on the opposite side of the intermediate transfer belt 10 from the tandem image forming unit 20. The secondary transfer device 29 is configured such that a secondary transfer belt 24 is stretched between a secondary transfer roller 22 and a secondary transfer belt stretching roller 23. In the secondary transfer device 29, the secondary transfer belt 24 is pressed against the third support roller 16 via the intermediate transfer belt 10 at a position supported by the secondary transfer roller 22. A secondary transfer nip portion as a secondary transfer portion is formed between the secondary transfer belt 24 and the intermediate transfer belt 10.

  A fixing device 25 for fixing the transfer image on the transfer paper is provided on the left side of the secondary transfer device 29 in the drawing. The fixing device 25 is configured by pressing a pressure roller 27 against a fixing belt 26 that is an endless belt. Further, the above-described secondary transfer device is also provided with a transfer paper transport function for transporting the transfer paper that has received the transfer of the toner image to the fixing device 25 at the secondary transfer nip portion. As the secondary transfer device, a transfer roller or a non-contact charging charger may be arranged. In such a case, it is difficult to provide this transfer paper transport function together.

  Under the secondary transfer device and the fixing device 25, a transfer paper reversing device 28 for reversing the transfer paper so as to record an image on both sides of the transfer paper is provided in parallel with the tandem image forming unit 20 described above. As a result, after the image is fixed on one side of the transfer paper, the transfer paper path is switched to the transfer paper reversing device side with the switching claw, and the transfer paper is transferred again to the secondary transfer nip portion to transfer the toner image. After that, the paper can be discharged onto a paper discharge tray.

  The scanner unit 300 reads the image information of the document placed on the contact glass 32 by the reading sensor 36 and sends the read image information to the control unit.

  Based on the image information received from the scanner unit 300, a control unit (not shown) controls a laser, an LED (not shown) disposed in the exposure device 21 of the printer unit 100, and lasers toward the photosensitive drum 3. The writing light L is irradiated. By this irradiation, an electrostatic latent image is formed on the surface of the photosensitive drum 3, and this latent image is developed into a toner image through a predetermined development process.

  The paper feed unit 200 includes paper cassettes 44 provided in multiple stages in the paper bank 43, a paper feed roller 42 that feeds transfer paper from the paper feed cassette, a separation roller 45 that separates the fed transfer paper and sends it to the paper feed path 46, A conveyance roller 47 that conveys the transfer paper is provided in the paper path 48.

  In the copying machine according to the present embodiment, in addition to the paper feed unit 200, manual paper feed is also possible. The manual feed tray 51 for manual feed and the transfer paper on the manual tray 51 are directed toward the manual paper feed path 53. A separation roller 52 for separating the sheets one by one is also provided on the side of the apparatus.

  The registration roller 49 discharges only one sheet of transfer paper placed on the paper feed cassette 44 or the manual feed tray 51, and is positioned between the intermediate transfer belt 10 as an intermediate transfer member and the secondary transfer device. Send to the next transfer nip.

  In the copying machine according to the present embodiment, when copying a color image, an original is set on the original platen 30 of the original conveying unit 400 or the original conveying unit 400 is opened and the original is placed on the contact glass 32 of the scanner unit 300. Is set and the original conveying unit 400 is closed to hold the original.

  When a start switch (not shown) is pressed, when the document is set on the document transport unit 400, the document is transported onto the contact glass 32, and then the scanner unit 300 is driven to drive the first travel body 33 and the second travel. Travel through the body 34. On the other hand, when the document is set on the contact glass 32, the scanner unit 300 is immediately driven to travel the first traveling body 33 and the second traveling body 34. Then, the first traveling body 33 emits light from the light source and further reflects the reflected light from the document surface toward the second traveling body 34 and reflects by the mirror of the second traveling body 34 and passes through the imaging lens 35. The image information of the original is read by putting in the reading sensor 36.

  The surfaces of the photosensitive drums 3Y, 3M, 3C, and 3K are uniformly charged by the charging devices 4Y, 4M, 4C, and 4K, and the image information read by the scanner unit 300 is color-separated, and the exposure device 21 performs color separation for each color. In addition, laser writing is performed on the photosensitive drums 3Y, 3M, 3C, and 3K. Thereby, an electrostatic latent image is formed on the surface of the photosensitive drums 3Y, 3M, 3C, and 3K.

  As an example, description will be made by performing image formation of Y (yellow). The electrostatic latent image formed on the surface of the photosensitive drum 3C is developed by the developing device 5Y in accordance with the Y toner to form a single color toner image. Similarly, a monochrome toner image is formed on the photosensitive drum 3 in the same manner in each of the image forming apparatuses 1M, C, and K in the order of M (magenta), C (cyan), and K (black). In this way, a toner image is formed on each photosensitive drum 3 and one of the four paper feed rollers is operated to feed a transfer paper having a size corresponding to the image information.

  At the same time, one of the first support roller 14, the second support roller 15 or the third support roller 16 is rotationally driven by a drive motor (not shown), and the other two support rollers are driven to rotate. The intermediate transfer belt 10 is rotated and conveyed. Then, along with the conveyance of the intermediate transfer belt 10, monochromatic toner images on the photosensitive drums 3 Y, M, C, and K are sequentially transferred to form a composite color image on the intermediate transfer belt 10.

  On the other hand, in the paper feed unit 200, one of the paper feed rollers 42 is selectively rotated, the transfer paper is fed out from one of the paper feed cassettes 44, separated one by one by the separation roller 45, and put into the paper feed path 46, and the transport roller The transfer paper is guided to the paper feed path 48 at 47 and the transfer paper is abutted against the registration roller 49 and stopped.

  Alternatively, the transfer paper on the manual feed tray 51 is fed by rotating the paper feed roller 50, separated one by one by the separation roller 52, put into the manual paper feed path 53, and abutted against the registration roller 49 and stopped.

  When the transfer paper on the manual feed tray 51 is used, the paper feed roller 50 is rotated to feed out the sheets on the manual feed tray 51, separated one by one by the separation roller 52, and put into the manual feed path 53. Stop against the registration roller 49.

  Then, the registration roller 49 is rotated in synchronization with the composite color image on the intermediate transfer belt 10, and the transfer paper is fed into the secondary transfer nip portion where the intermediate transfer belt 10 and the secondary transfer roller 22 are in contact with each other. . The composite color image is secondarily transferred onto the transfer paper from the intermediate transfer belt 10 due to the influence of the transfer electric field and contact pressure formed at the secondary transfer nip, and the color image is recorded on the transfer paper. To do.

  The transfer paper after the color image is transferred at the secondary transfer nip portion is sent to the fixing device 25 by the secondary transfer belt 24 of the secondary transfer device 29, and the pressure roller 27 and the fixing belt are fixed by the fixing device 25. The color image is fixed by applying pressure and heat. Thereafter, the paper is discharged by a discharge roller 56 and stacked on a paper discharge tray 57. Further, after the color image is fixed, the transfer paper on which images are formed on both sides is switched by the switching claw 55 and conveyed to the transfer paper reversing device 28, where it is reversed and led again to the secondary transfer nip portion, After the image is also recorded on the back surface, the paper is discharged onto a paper discharge tray 57 by a discharge roller 56.

  On the other hand, the residual toner remaining on the surface of the intermediate transfer belt 10 after the color image is transferred onto the transfer paper at the secondary transfer nip portion is removed by the belt cleaning device 17, so that the tandem image forming unit 20 can form an image again. Prepare.

FIG. 1 is a schematic explanatory diagram of the image forming apparatus 1.
As shown in FIG. 1, the image forming apparatus 1 includes a photosensitive drum 3, a charging device 4, a developing device 5, a cleaning device 6, a static elimination lamp 7, a lubricant application device 8, and the like, and includes a process. The cartridge is removable from the apparatus main body. In the copying machine of this embodiment, the image forming apparatus 1 itself as a process cartridge is replaced. However, the configuration may be such that the photosensitive drum 3, the charging device 4, the developing device 5, the cleaning device 6, the static elimination lamp 7, and the lubricant application device 8 are replaced with new ones.

  As shown in FIG. 1, the lubricant application device 8 is an application for applying a lubricant on the surface of the photosensitive drum 3 as a solid lubricant 84 obtained by solidifying zinc stearate as a lubricant or as a lubricant applying member. A brush 82, a leveling blade 86, and the like are included.

  The cleaning device 6 includes an electrostatic cleaning brush roller 63 and a cleaning blade 61 in order from the upstream side of the surface movement direction of the photosensitive drum 3.

  The electrostatic cleaning brush roller 63 rotates in the counter direction as indicated by the arrow in the drawing with respect to the rotation direction of the photosensitive drum 3, but is accompanied by a linear speed difference with respect to the rotation direction of the photosensitive drum 3. It may be rotated in the circumferential direction. The cleaning blade 61 is fixed to the holder and is counter-supported with respect to the rotation direction of the photosensitive drum 3.

  In addition, a cleaning power source is provided as a bias applying unit that applies a bias for electrostatically attaching the toner to the electrostatic cleaning brush roller 63. After the toner image is transferred from the photosensitive drum 3 onto the intermediate transfer belt 10, the positive and negative transfer residual toners remaining on the surface of the photosensitive drum are in contact with the surface of the photosensitive drum and the electrostatic cleaning brush roller 63. Enter the club. Then, the transfer residual toner is removed from the surface of the photosensitive drum by the electrostatic force and the rubbing force of the electrostatic cleaning brush roller 63.

  After the surface of the photosensitive drum 3 that has passed through the primary transfer portion is neutralized by the neutralizing lamp 7, the cleaning device 6 first removes most of the transfer residual toner from the surface of the photosensitive drum with the electrostatic cleaning brush roller 63. Thereafter, the transfer residual toner remaining on the surface of the photosensitive drum is removed from the surface of the photosensitive drum by the cleaning blade 61.

  The toner adhering to the electrostatic cleaning brush roller 63 is recovered by an electrostatic force by a recovery roller 65 to which a bias is applied from a recovery power source, and recovered by a recovery blade 67 provided in contact with the surface of the recovery roller 65. It is removed from the surface of the roller 65.

  On the surface of the photosensitive drum 3 from which the transfer residual toner has been removed by the cleaning device 6, a lubricant is applied by the application brush 82 of the lubricant applying device 8, thereby protecting the surface of the photosensitive drum. The surface of the photosensitive drum 3 to which the lubricant has been applied is leveled by the leveling blade 86 that comes into contact with the counter system, so that the lubricant on the surface of the photosensitive drum 3 is in a dense application state.

  The application of the lubricant by the application brush 82 is performed by pressing the solid lubricant 84 held by the bracket onto the application brush 82 by the lubricant pressurizing spring 88. Then, the solid lubricant 84 is shaved by the application brush 82 that rotates in contact with the surface of the photosensitive drum 3 and applied onto the photosensitive drum 3.

  Heretofore, in an image forming apparatus such as a copying machine, it has been required to increase the life of replacement parts such as a photosensitive drum and a cleaning device. Especially in electrophotographic equipment used in the industry that produces a large amount of printing such as the production printing business, the service life of replacement parts is greatly influenced by the cost per printing (CPP). Improvement has a great effect on running cost reduction.

  In order to improve the life of the cleaning device, it is necessary to reduce the wear rate of the edge of the cleaning blade. The cleaning unit using the cleaning blade has a simple configuration and, particularly, as shown in FIG. 3, the minute amount of toner is almost completely cleaned by contacting the counter with respect to the rotation direction of the photosensitive drum. Can be widely used.

  The lifetime of the cleaning device using this cleaning blade is determined by the amount of wear of the cleaning blade edge that is in contact. When the amount of wear of the blade edge advances, a large amount of toner cannot be stopped and slips downstream of the cleaning blade in the rotation direction of the photosensitive drum, resulting in a vertical streak image and an abnormality.

  In particular, as an acceleration factor, when a large amount of image with a high image area ratio is printed continuously, a large amount of toner is input to the blade edge, and a small amount of toner and toner additive (silica) slip through the blade. . During the slipping, the toner or toner additive (silica) damages the cleaning blade, and the blade edge wears.

  As a method of reducing the progress of blade wear, there is optimization of the blade material prescription, but it does not fundamentally change the physical properties of the urethane rubber, so that it does not significantly improve the service life. As a method for dramatically reducing the progress of blade wear, it is effective to prevent a large amount of toner from being input to the blade edge.

  Furthermore, as another concern due to a large amount of toner input to the blade edge, there is a problem that the surface film of the photosensitive drum is scraped off. When toner and toner additives slip through the blade edge, they become abrasives and scrape the surface of the photosensitive drum, reducing the life of the photosensitive drum.

  On the other hand, it is conceivable to increase the wearable film thickness of the photosensitive drum, but by increasing the film thickness, residual charges remain on the photosensitive drum, and a desired photosensitive drum surface potential can be obtained. This is not possible, and there is a problem that repeat fluctuations in image density occur. Therefore, from this point of view, it is desirable to make the film thickness from the surface of the photosensitive drum to the charge generation layer as thin as possible. Therefore, also for this problem, it is effective to prevent a large amount of toner from being input to the edge of the cleaning blade.

  On the other hand, as another form of the cleaning device, there is an electrostatic cleaning brush device that electrically cleans the toner by applying a voltage to the electrostatic cleaning brush roller 63 as shown in FIG.

  The merit of this means is that, even when a large amount of toner is input, the ability to collect toner is higher than that of the cleaning blade, and the toner is not subjected to stress due to mechanical force. For example, it is difficult for sticking to occur.

  As a disadvantage of the electrostatic cleaning device, a single brush cannot collect a small amount of toner having different polarities. To that end, as shown in FIG. 4, a plurality of brushes are arranged to collect positive and negative toners, or toners are controlled to align the charging polarity of the toner upstream of the electrostatic cleaning brush roller. It is necessary to provide polarity control means. However, in this case, there is a problem that the apparatus becomes expensive.

  As means for complementing the disadvantages of the cleaning blade and the electrostatic cleaning brush, the means shown in FIG. 5 may be considered in which a single electrostatic cleaning brush is disposed upstream of the photosensitive drum and a cleaning blade is disposed downstream.

  The image forming apparatus described in Patent Document 1 includes an electrostatic cleaning brush roller and a cleaning blade provided downstream of the photosensitive drum rotation direction. When a large amount of toner is input, most of the toner is cleaned with an electrostatic cleaning brush roller with high recovery capability, and toner with different polarity is cleaned with a cleaning blade with high capability to completely clean a small amount of toner. . As a result, blade wear and photoconductor drum surface wear can be significantly reduced, and silica adherence of the photoconductor drum can be prevented.

  However, in the cleaning device described in Patent Document 1, since the toner polarity control means is not provided upstream of the electrostatic cleaning brush roller, the toner recovery rate by the electrostatic cleaning brush roller is used when toner with a small charge amount is used. Is small. Therefore, a large amount of toner is input to the cleaning blade, and there is a problem that blade edge wear proceeds.

  Therefore, in the cleaning device 6 provided in the copying machine of the present embodiment, the toner recovery rate by the electrostatic cleaning brush roller 63 is increased, the amount of toner input to the cleaning blade 61 is reduced, and blade edge wear progresses. I try to suppress it.

  As a result of intensive studies by the inventors of the present application, the brush thickness of the electrostatic cleaning brush roller 63 is equal to or greater than a predetermined thickness, so that the toner removal performance by the rubbing force of the electrostatic cleaning brush roller 63 is improved. It has been found that even when a large amount of toner is input to the contact portion, a good cleaning property can be obtained.

  In the present embodiment, since the brush thickness of the electrostatic cleaning brush roller 63 is 6 denier or more, the toner recovery rate of the electrostatic cleaning brush roller 63 is increased as will be clarified in an experiment described later. Enhanced. Thereby, even if a large amount of toner is input to the contact portion between the surface of the photosensitive drum and the electrostatic cleaning brush roller 63, good cleaning properties can be obtained.

[Experiment]
At the time of image formation, a large amount of toner is developed on the photosensitive drum 3, and transfer residual toner is generated after the toner is transferred to an intermediate transfer or the like. The transfer residual toner is first recovered by the electrostatic cleaning brush roller 63. In this embodiment, the ratio between the toner weight recovered by the electrostatic cleaning brush roller 63 and the transfer residual toner weight is defined as “toner recovery rate”. To do.

  Further, there is a relationship that the wear amount of the blade edge increases as the number of printed sheets increases. As a result of repeated experiments by the inventors of the present application, when the number of prints is taken on the horizontal axis and the inclination when the wear amount of the blade edge is taken on the vertical axis is defined as “blade edge wear rate”, the toner recovery rate is The higher the blade edge wear rate, the lower the result.

  FIG. 6 shows the relationship between the brush thickness of the electrostatic cleaning brush roller 63 and the toner recovery rate. Table 1 shows specific numerical values and measurement conditions for each plot in FIG. It is.

  In the “evaluation” column of the table, “◯” indicates “no problem”, “Δ” indicates “no problem in product”, and “x” indicates “product impact”.

The measurement conditions of the toner recovery rate are as follows.
-Applied bias V1: 400 [V] to 800 [V] to the collection roller 65
Printing conditions: 10 A4 solid images Cleaning blade 61: Urethane rubber, hardness 72 [°], rebound resilience 31 [%]
・ Recovery roller 65: Stainless steel

A method for calculating the toner recovery rate will be described with reference to FIG.
The toner recovery rate was calculated from the transfer residual toner weight T1 and the cleaning blade input toner weight T2 by the equation (T1-T2) / T2. Here, T1-T2 corresponds to the electrostatic cleaning brush collected toner weight.

  The transfer residual toner weight T1 is calculated as follows. First, the electrostatic cleaning brush roller 63 is changed to a metal rod that does not come into contact with the photosensitive drum 3 (the rod is used for driving transmission), and a toner container P1 is provided under the cleaning blade 61. When paper is passed by changing the electrostatic cleaning brush roller 63 to a metal rod, all the transfer residual toner attached to the surface of the photosensitive drum is directly input to the cleaning blade 61. Then, the toner scraped off from the surface of the photosensitive drum by the cleaning blade 61 is stored in the toner storage portion P1. The weight of the toner stored in the toner storage portion P1 in this way is set as a transfer residual toner weight T1. The cleaning blade 61 is in a state close to a new one so that toner does not slip through.

  The measurement principle of the cleaning blade input toner weight T2 is the same as that of the transfer residual toner weight T1. The difference is that the electrostatic cleaning brush roller 63 is not changed to a metal rod, but the transfer residual toner is removed from the surface of the photosensitive drum using the electrostatic cleaning brush roller 63. The toner remaining on the surface of the photosensitive drum without being removed by the electrostatic cleaning brush roller 63 is input to the cleaning blade 61, scraped off from the surface of the photosensitive drum by the cleaning blade 61, and stored in the toner storage portion P1. The weight of the toner stored in the toner storage portion P1 in this way is set as a cleaning blade input toner weight T2.

  Note that the resistance of the brush, specifically, the specific resistance of the yarn varies depending on the thickness of the hair. Therefore, in consideration of the influence of the magnitude of the current flowing between the photosensitive drum and the brush, in other words, the magnitude of the electrostatic force, the applied bias V1 is set to the toner between 400 [V] and 800 [V]. A plurality of recovery rates were measured, and the toner recovery rate with the highest toner recovery rate was plotted in FIG.

  As shown in FIG. 6 and Table 1, when the hair thickness is 6 denier, the toner recovery rate is satisfactory so that there is no problem in the product when the hair density is 70 [kF], and there is no problem when the hair density is 50 [kF]. Became a rate. Further, when the hair thickness was 10 denier and 14 denier, there was no problem in the toner recovery rate. On the other hand, when the hair thickness was 2 denier, the toner recovery rate was drastically lowered compared to the other products, and the toner recovery rate was such that the product was affected.

  From the above, it can be seen that a high toner recovery rate can be stably obtained by using the electrostatic cleaning brush roller 63 having a hair thickness of 6 denier or more, preferably 10 denier or more.

  FIG. 8 shows the relationship between the torque applied to the electrostatic cleaning brush roller 63 and the toner recovery rate when the electrostatic cleaning brush roller 63 rotates in contact with the photosensitive drum 3. Table 2 shows specific numerical values and measurement conditions for each plot in FIG.

  As a measurement condition of the torque applied to the electrostatic cleaning brush roller 63, as shown in FIG. 9, the brush of the electrostatic cleaning brush roller 63 bites into the photosensitive drum 3 by 1 [mm]. The conditions are the same as the conditions for measuring the toner recovery rate in FIG.

  The reason why the amount of biting of the electrostatic cleaning brush roller 63 with respect to the photosensitive drum 3 is 1 [mm] is as follows. That is, if the amount of biting is less than 1 [mm], the amount of the brush that contacts the surface of the photosensitive drum is reduced and the ability to scrape off the toner is reduced. On the contrary, if the amount of biting is greater than 1 [mm], the brush falls, and the ability to scrape off the toner by the mechanical force due to the stiffness of the brush at the tip of the brush is reduced. On the other hand, by setting the biting amount to 1 [mm], it is possible to scrape off the toner satisfactorily by mechanical force due to the stiffness of the brush.

  In addition, as a problem that occurs due to hair fall, the biggest problem is that the ability to scrape off toner by mechanical force due to the stiffness of the brush at the tip of the brush decreases, and the biggest problem is that it adversely affects the printed image. Can be mentioned. When the fall of the hair occurs, the load applied from the brush to the photosensitive drum varies between the fall of the hair and other places. As a result, the rotational speed of the photosensitive drum in contact with the brush fluctuates, resulting in a belt-like density change that appears in the printed image. Therefore, by making the amount of biting less than 1 [mm], it is possible to suppress the adverse effect on the printed image due to the falling of the brush.

  8 and Table 2, when the torque applied to the electrostatic cleaning brush roller 63 is 4.2 [mN · m], the toner recovery rate is drastically reduced, but the torque is 5.7 [mN · m] or more. In the results, a stable and high toner recovery rate was obtained.

  Next, the cleaning state of the surface of the photosensitive drum when a large amount of an image with a high image area ratio is printed using a toner with a small charge amount in the copying machine of the present embodiment will be described.

  When an image with a high image area ratio is formed, a large amount of toner is developed on the photosensitive drum 3, so that the transfer residual toner on the surface of the photosensitive drum after the toner is transferred to the intermediate transfer belt 10 is also generated. A considerable amount is generated. Thus, a large amount of untransferred toner existing on the surface of the photosensitive drum is first recovered from the surface of the photosensitive drum by the electrostatic cleaning brush roller 63.

  At this time, after transfer, most of the transfer residual toner charged to the positive polarity and the negative polarity inputted to the contact portion between the surface of the photosensitive drum and the electrostatic cleaning brush roller 63 is the negative polarity which is the normal charging polarity of the toner. The charge amount is small. Then, the brush thickness of the electrostatic cleaning brush roller 63 is 6 denier or more, preferably 10 denier or more, thereby assisting the toner recovery effect by electrostatic force by the mechanical force of the brush, Most of the negatively charged toner can be collected from the surface of the photosensitive drum 3 by the electrostatic cleaning brush roller 63. At this time, the torque applied to the electrostatic cleaning brush roller 63 when the electrostatic cleaning brush roller 63 rotates in contact with the photosensitive drum 3 is 5.7 [mN · m] or more, preferably 6.3. [MN · m] or more.

  A small amount of transfer residual toner charged to a positive polarity passes through the electrostatic cleaning brush roller 63 as the photosensitive drum 3 rotates, and is input to the contact portion between the photosensitive drum 3 and the cleaning blade 61. The amount of toner input at this time is very small because even when printing a large amount of high images, most of the toner is collected by the electrostatic cleaning brush roller 63 located upstream of the cleaning blade 61 in the rotation direction of the photosensitive drum. It will be slight. Therefore, it is possible to easily scrape off the toner with the edge of the cleaning blade 61 and clean the surface of the photosensitive drum 3.

  Further, since the amount of toner input to the contact portion between the photosensitive drum 3 and the cleaning blade 61 is small, the blade edge of the cleaning blade 61 is hardly damaged, and the stressed toner is also small. As a result, the progress of blade edge wear that may occur when a large amount of toner is input to the contact portion between the photosensitive drum 3 and the cleaning blade 61, and the photosensitive drum of an additive contained in a developer such as silica. 3 and the progress of the photoconductor film shaving can be suppressed.

  Therefore, the life of the photosensitive drum and the cleaning device can be improved even when a toner with a small charge amount is used or an image with a high image area ratio is formed.

DESCRIPTION OF SYMBOLS 1 Image forming device 3 Photoconductor drum 4 Charging device 5 Developing device 6 Cleaning device 7 Static elimination lamp 8 Primary transfer roller 8 Lubricant coating device 10 Intermediate transfer belt 14 First support roller 15 Second support roller 16 Third support roller 17 Belt Cleaning device 20 Tandem image forming unit 21 Exposure device 22 Secondary transfer roller 23 Secondary transfer belt stretching roller 24 Secondary transfer belt 25 Fixing device 26 Fixing belt 27 Pressure roller 28 Transfer paper reversing device 29 Secondary transfer device 30 Original Table 32 Contact glass 33 First traveling body 34 Second traveling body 35 Imaging lens 36 Reading sensor 42 Paper feed roller 43 Paper bank 44 Paper feed cassette 45 Separating roller 46 Paper feed path 47 Transport roller 48 Paper feed path 49 Registration roller 50 Paper feed roller 51 Bypass tray 5 Separating roller 53 Paper feed path 55 Switching claw 56 Discharge roller 57 Discharge tray 61 Cleaning blade 63 Electrostatic cleaning brush roller 65 Recovery roller 67 Recovery blade 82 Application brush 84 Solid lubricant 86 Leveling blade 88 Lubricant pressure spring 100 Printer Part 200 paper feeding part 300 scanner part 400 document conveying part

Japanese Patent No. 4597837

Claims (6)

A brush roller rotatably provided to remove toner adhering to the surface of the image carrier while in contact with the surface of the image carrier;
Bias application means for applying a bias for electrostatically attaching toner to the brush roller,
The toner remaining on the surface of the image carrier after the toner image formed on the surface of the image carrier is transferred to the transfer body is caused to enter the contact portion between the surface of the image carrier and the brush roller. In the cleaning device for removing from the surface of the image carrier by
A cleaning device, wherein the brush roller has a brush thickness of 6 denier or more. The cleaning device according to claim 1.
The positive and negative toners remaining on the surface of the image carrier after the toner image formed on the surface of the image carrier is transferred to the transfer body, are contacted between the surface of the image carrier and the brush roller. A cleaning device, wherein the cleaning device is removed from the surface of the image carrier by the brush roller. The cleaning device according to claim 1 or 2,
A cleaning apparatus, wherein the brush has a bristle thickness of 10 denier or more. The cleaning device according to claim 1, 2 or 3,
A cleaning apparatus comprising a cleaning blade that contacts the surface of the image carrier and removes toner from the surface of the image carrier, downstream of the brush roller in the rotation direction of the image carrier. The cleaning device according to claim 1, 2, 3 or 4.
The cleaning apparatus according to claim 1, wherein the amount of biting of the brush roller with respect to the image carrier is 1 [mm]. An image carrier for carrying a toner image;
Transfer means for transferring a toner image carried on the image carrier onto a transfer medium;
An image forming apparatus comprising: a cleaning unit that removes deposits adhering to the surface of the image carrier after the toner image is transferred from the image carrier to the transfer target;
An image forming apparatus comprising the cleaning device according to claim 1 as the cleaning unit.

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