JP2005266248A - Cleaning device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prolong a service life of an image carrier by suppressing a friction coefficient on a front surface of the image carrier while suppressing the waste of lubricants, and reducing the quantity of the front surface of the image carrier to be shaved in vain. <P>SOLUTION: In a cleaning device comprising a cleaning brush (8) for cleaning a front surface of an image carrier (3) and a lubricant mechanism (10) capable of connecting to and disconnecting from the brush, the connection and disconnection of the lubricant mechanism (10) to and from the cleaning brush are controlled in accordance with a motive current value of the cleaning brush (8) with respect to the image carrier. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

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

  An electrophotographic image forming apparatus forms an electrostatic latent image on an image carrier with an exposure means (for example, a laser), visualizes it with toner, and transfers the toner image onto a transfer material (paper). The image forming process is performed, and the image forming member including the image carrier deteriorates with time by repeatedly executing the process.

  Normally, even when a toner image is transferred to a transfer material, not all of the toner is transferred to the transfer material, and some percent of the toner remains on the image carrier (the remaining toner is referred to as “transfer residual toner”). ) Must be cleaned by a cleaning mechanism. When a document having a large image area ratio is copied, a large amount of toner remains that is not transferred to the transfer material. For example, when the transfer rate is 90%, the transfer residual toner is 5% when the image area ratio of the original is 50%, and the transfer residual toner is 1% when the image area ratio of the original is 10%. The transfer residual toner is cleaned by a brush or blade of a cleaning unit. Here, it is well known that the toner acts like an abrasive at the contact portion between the image carrier, the cleaning brush, and the blade. Therefore, the more toner that enters the cleaning unit, the greater the amount of surface abrasion of the image carrier over time. Further, there is a correlation between the image carrier surface scraping amount and the image carrier surface friction coefficient. Naturally, the smaller the image carrier surface friction coefficient, the less the friction between the cleaning brush or blade and the image carrier, and the smaller the scraping amount.

  From the above, when the image forming apparatus outputs a large amount of a document with a high image area ratio and when a large amount of development with a low image area ratio is output, the image carrier surface scraping amount becomes clear over time. There will be a difference.

  Basically, the image carrier is composed of a total of four layers, with three layers of UL, charge generation layer (CGL), and charge transport layer (CTL) present on the substrate. The surface of the image carrier is uniformly charged with negative charges, for example, by being charged in the charging step. It is considered that a positive charge for this is injected from the substrate and has been increased to the vicinity of the UL surface. However, it is considered that the hole blocking ability in the UL is not uniform and there is a non-uniform portion. Holes are injected into the upper layer from such local non-uniform portions, thereby canceling the negative charges in the upper layer. As a result, it is considered that nonuniformity of the charged potential on the CTL surface is generated. When the potential of the portion where the charge is locally dropped on the CTL surface becomes equal to or lower than the developing bias, it is considered that the toner is developed in that portion and the background becomes dirty. When the film thickness of the image carrier is reduced, that is, when the CTL layer is reduced, holes in the UL are more easily injected into the upper layer, and the background contamination increases. From the above, it is desirable that the film thickness of the image carrier is not reduced as much as possible over time. Conversely, by preventing the image carrier from being reduced in film thickness, the life of the image carrier can be increased.

  Also, when the transfer residual toner is recycled while the lubricant is fixed at a predetermined position and applied to the image carrier with a brush or the like, the lubricant is mixed in the recycled toner. That is, the lubricant is mixed in the developing device. Then, when the amount of the lubricant is large, for example, a two-component developer has a side effect that the toner charging ability is lowered. As a result, the developing ability decreases, and problems such as a decrease in ID and background contamination occur. Therefore, when a mechanism for applying the fixed lubricant to the image carrier is provided, it is necessary to suppress the amount of the lubricant mixed in the recycled toner.

  The present invention realizes a long life of an image carrier by reducing the amount of scraping on the surface of the image carrier by reducing the friction coefficient of the surface of the image carrier while preventing the consumption of the wasteful lubricant. This is the issue.

  In the cleaning device including a cleaning brush for cleaning the surface of the image carrier and a lubricant mechanism that can come into contact with and separate from the brush, according to the starting current value of the cleaning brush with respect to the image carrier. This can be solved by controlling the contact and separation of the lubricant mechanism to and from the cleaning brush.

  In addition to the starting current value, it is preferable to use the number of copies as a control factor. It is more effective if a toner recycling mechanism and means for enabling on / off switching of toner recycling are provided, and toner recycling on / off control is performed along with contact / separation of the lubricant mechanism.

  According to the present invention, it is configured to control the contact / separation of the lubricant mechanism with respect to the cleaning brush in accordance with the starting current value of the cleaning brush with respect to the image carrier, so that wasteful lubricant consumption can be prevented. Further, the amount of surface abrasion of the image carrier can be reduced, and the life of the image carrier is increased.

  If the number of copies is used as a control factor in addition to the start-up current value, the amount of cleaning brush falling over time can be compensated. By providing the toner recycling mechanism, it is possible to prevent the toner yield from being lowered. A means for enabling on / off switching of toner recycling is provided. Toner scattering by recycling toner containing excessive lubricant by controlling on / off of toner recycling along with contact / separation of the lubricant mechanism. In addition, problems such as a decrease in toner concentration can be prevented.

  In the image forming apparatus shown in FIG. 1, there are a charging device 4 for charging the surface of the photosensitive drum around the photosensitive drum 3 serving as an image carrier, a latent beam on the uniformly charged surface of the photosensitive drum 3 with a laser beam or the like. Toner image formed on the photoconductive drum 3 using the photo-writing system 2 that forms an image, the developing device 1 that forms a toner image by attaching charged toner to the latent image on the photoconductive drum 3, and the charger. Are arranged in this order: a transfer belt 5 for transferring the toner onto the recording paper; a cleaning device 6 for removing the toner remaining on the photosensitive drum 3 after the transfer; and a neutralizing device 7 for removing the residual potential on the photosensitive drum 3. Reference numeral 8 denotes a cleaning brush.

  In such a configuration, the photosensitive member 3 whose surface is uniformly charged by the charging device 4 forms an electrostatic latent image by the optical writing system 2 and forms a toner image by the developing device 1. The toner image is transferred on the transfer belt 5 from the surface of the photosensitive drum 3 to a recording sheet conveyed from a paper supply tray (not shown). Thereafter, the toner image on the recording paper is transferred to the recording paper by a fixing device (not shown). On the other hand, the toner remaining on the photosensitive drum without being transferred is collected by the cleaning brush 6 and the cleaning blade 9 (FIG. 2). The photosensitive drum 3 from which the residual toner has been removed is initialized by the static eliminator 7 and used for the next image forming process.

  Details of the cleaning brush used in this example are shown in Table 1 (the photoconductor for this has a diameter of 100 mm). The image carrier to which the lubricant is applied has a smaller coefficient of surface friction of the image carrier than the image carrier to which the lubricant is not applied. When the coefficient of friction of the image carrier decreases, the torque value of the cleaning brush with respect to the image carrier also decreases. For example, when the cleaning brush of Table 1 is used, the static torque value at the start is 0.408 kgf · cm when the lubricant is not applied, whereas it is 0.323 kgf · cm when the lubricant is applied. 0.085 kgf · cm is also reduced. Here, since the current value and the static torque value have the relationship shown in FIG. 2, the driving of the cleaning brush is performed when controlling whether or not the fixed lubricant is applied to the surface of the image carrier according to the amount of change in the static torque value. It can be captured by changes in the current value.

  Details of the cleaning device 6 are shown in FIG. A cleaning brush 8 and a cleaning blade 9 are disposed facing the photosensitive drum 3. An application roller 11 for applying a lubricant to the cleaning brush 8 is provided. In order to supply the lubricant to the application roller 11, a fixed lubricant 10 made of zinc stearate is a solenoid (lubricant solenoid) (not shown). It contacts and separates from the application roller 11 according to ON / OFF. When ON, the fixed lubricant 10 comes into contact with the application roller 11 so as to have a predetermined contact pressure. FIG. 3 shows a state where the lubricant solenoid is ON. Then, the application roller 11 polishes the fixed lubricant 10 to form a lubricant film on the application roller, and the cleaning brush 8 applies it to the photosensitive drum 3. When the solenoid is OFF, the application roller 11 and the fixed lubricant 8 are completely separated from each other, and no lubricant is applied to the photosensitive drum.

  In this example, whether or not the lubricant is applied to the surface of the photosensitive drum is controlled according to the current value of a brush drive motor (not shown) that drives the cleaning brush 8 alone. This is done by turning the solenoid on / off. Specifically, when the current value of the cleaning brush with respect to the photoreceptor becomes an intermediate value between when the lubricant is applied and when the lubricant is not applied (hereinafter referred to as “reference value”), the lubricant is detected on the photoreceptor. It is determined that the amount is insufficient on the surface, and a lubricant is applied to the surface of the photosensitive member during the job, immediately before the start of the job, after the end of the job, or the like. As a specific operation, the current value of the brush drive motor at the time of starting the job is detected, and if the detected value is larger than the reference value, the solenoid is turned on, and if it is smaller, the current is turned off.

  FIG. 4 illustrates current values and reference values when the lubricant is applied to the photosensitive member at the start of the job and when the lubricant is not applied. At this time, when the current value reaches the reference value of 0.36 A, the solenoid is turned on, so that the lubricant is applied to the surface of the photoconductor, the friction coefficient is lowered, and the amount of abrasion of the photoconductor is also reduced. Can extend the service life. In this example, the activation current detection and solenoid ON / OFF operations are performed at the time of each copy output.

  When using a cleaning brush as described above, the brush may fall over time. In such a case, since the lubricant is detected on the surface of the photoconductor even when the starting current value decreases due to the brush falling over time, the surface of the photoconductor is actually lubricated. Even if the agent is insufficient, there is a problem that the lubricant is not applied and the surface of the photoreceptor is scraped more than necessary.

  FIG. 5 shows the starting current value when 0 to 300K sheets (1K = 1000 sheets) of lubricant is applied and not applied. When brush fall is not considered, the application / non-application of the lubricant to the surface of the photoconductor was determined based on the reference value only as shown in the above example. In consideration of hair fall, whether to apply the lubricant to the surface of the photoconductor is determined according to the value of the starting current (hereinafter referred to as “threshold”) in FIG. Therefore, the relationship between application and non-application is determined as shown in Table 2 depending on the number of sheets to be passed and the current value. The solenoid ON / OFF shown in Table 2 is performed when the current value reaches each threshold value.

  With the above configuration, if the image forming process is repeated without recycling the toner, the toner yield decreases and the amount of waste toner increases. Therefore, as shown in FIG. 6, a toner recycling device 13 is provided from the cleaning device 6 to the developing device 1 to reduce the toner consumption. In this case, when the surface roughness of the application roller 11 is small, for example, when Rz = 0 to 1 μm, the amount of the fixed lubricant 10 scraped off by the application roller 11 is small, and the lubricant is applied to the photoreceptor 3. However, since the amount of the lubricant mixed in the recycled toner is small and the influence of the lubricant on the developer in the developing device is small, it is not necessary to have a noticeable influence on the charge amount of the toner. However, when the surface roughness Rz of the application roller increases to, for example, 1 μm or more, the amount of the fixed lubricant 10 scraped off by the application roller 11 increases, and the amount of lubricant mixed in the recycled toner increases. In some cases, the charge amount of the developer in the developing device is lowered (the charge amount is lowered regardless of whether the toner is charged + or-). Therefore, a shutter 14 is provided in the toner recycling device 13 (recycled toner transport path), and a part of the recycled toner (toner in which a lot of lubricant is mixed) is discarded, so that the toner can be removed without lowering the toner charging capability of the developing device. Make it recyclable. The shutter 14 is ON / OFF controlled by a solenoid (recycle solenoid) (not shown) (not recycled when the solenoid is ON).

  The following is assumed as specific control. It takes a certain amount of time (the number of processed images) until the toner in the cleaning device is recycled to the developing device through the recycling path. In this example, the number of sheets corresponding to this recycle time (the number of images processed until the transfer residual toner when a certain sheet is output reaches the developing device from the cleaning device via the toner recycling path) is, for example, 10,000. A sheet. This value naturally depends on the length of the recycling path and the number of turns / speed of the coil of the recycling apparatus.

  The recycle solenoid is turned on when 10,000 sheets are output from when the lubricant solenoid is turned on. The number of images processed while the recycle solenoid is on is from the time when the recycle solenoid is turned on until 100 sheets are output. Therefore, even if the lubricant solenoid is ON at the time of output of the first sheet and the ON and OFF are repeated until the 2nd to 100th sheets, the recycle solenoid is in the ON state during the output of 10001 to 10100 sheets. That is, when the solenoid for the lubricant is turned on at the first sheet, when the output of 10001 to 10100 sheets is performed, the recycle solenoid is turned on regardless of the ON / OFF of the 2nd to 100th sheets of the lubricant solenoid. The same control is performed for the second and subsequent sheets. Also, when the first solenoid lubricant is ON, the second to 98th sheets are OFF, the 99th sheet is ON, and the 100th and subsequent sheets are OFF, the recycle solenoid is turned on until the 1000th to 10198th sheets. The first and subsequent sheets are turned off. FIG. 7 shows a simple example.

1 is a schematic configuration diagram of an image forming apparatus according to the present invention. It is a graph which shows the relationship between the starting current value and static torque value between an image carrier and a cleaning brush. It is a schematic block diagram which shows a lubricant application mechanism. It is a graph which shows the relationship between the presence or absence of lubricant application and a starting current value (static torque value). It is a graph which shows the change (time-dependent change) by the copy number progress of a starting electric current value by the presence or absence of lubricant application. It is the schematic which shows a toner recycling mechanism. It is a figure which shows the example of ON / OFF control of the solenoid for lubricants, and a recycle solenoid.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Developing device 2 Optical writing system 3 Photoconductor 4 Charging device 5 Transfer belt 6 Cleaning device 8 Cleaning brush 10 Fixed lubricant 11 Application roller

Claims (5)

In a cleaning device including a cleaning brush for cleaning the surface of an image carrier and a lubricant mechanism that can contact and separate from the brush,
A cleaning device configured to control contact and separation of the lubricant mechanism with respect to the cleaning brush in accordance with an activation current value of the cleaning brush with respect to the image carrier.   An image forming apparatus comprising the cleaning device according to claim 1.   3. The image forming apparatus according to claim 2, wherein the number of copies is used as a control factor in addition to the starting current value.   The image forming apparatus according to claim 2, further comprising a toner recycling mechanism.   The image forming apparatus according to claim 4, further comprising means for enabling on / off switching of toner recycling, and performing on / off control of toner recycling together with contact and separation of the lubricant mechanism.

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