JP5765057B2 - Image forming apparatus - Google Patents

Description

The present invention relates to images forming apparatus and, more particularly, to a cleaning mechanism of the charging equipment.

In addition to a configuration using an image forming unit for a single color image, an image forming apparatus using an electrophotographic system can receive a multicolor image such as a full color image by using an image forming unit capable of forming a multi-color image. There are configurations to form.
The image forming unit is provided with a charging device for uniformly charging the latent image carrier. However, the charging member used in the charging device is configured so as to be in contact with the surface of the latent image carrier or in close proximity. A configuration that maintains a contact state is known.

Since the untransferred toner may adhere to the surface of the latent image carrier that has been transferred to the recording medium, the surface of the latent image carrier is cleaned.
In the case of a charging member using a configuration that contacts the surface of the latent image carrier, the charging member moves while contacting the surface of the latent image carrier, so that the toner that has still adhered even after cleaning is scraped off the charging member. May be. When the toner adhering to the charging member is deposited, the surface characteristics of the charging member may change, and the charging characteristics may be deteriorated.

On the other hand, in the case of a charging member using a non-contact configuration, toner is not scraped off, so that toner adhesion to the surface of the charging member is reduced.
However, in the case of a charging member using a non-contact configuration, the toner or the external additive of the toner depends on the bias polarity when a charging bias in which alternating current is superimposed on direct current is applied in order to make the charging on the surface of the latent image carrier uniform. Even if it is slight, it may fly and adhere to the charging member.

2. Description of the Related Art Conventionally, a configuration for removing toner by bringing a cleaning member into contact with the surface of the charging member is known as a configuration for removing the toner and foreign matters adhering to the charging member and maintaining the charging characteristics appropriately.
When removing the toner by bringing the cleaning member into contact with the surface of the charging member, if the cleaning member is always in contact, the toner removed from the charging member will accumulate on the cleaning member and the dirt will be transferred to the charging member to remove the dirt. There is a possibility that the cleaning characteristic of the cleaning member itself is deteriorated.

In view of this, a configuration has been proposed in which a cleaning member can be brought into and out of contact with a charging member and intermittent cleaning is performed in a predetermined cycle (for example, Patent Document 1).
For intermittent cleaning, instead of simply setting a predetermined cycle, a method for determining the actual toner removal amount based on the history of use environment, image area, etc., and executing cleaning according to the calculated amount has been proposed. (For example, Patent Document 2).

The configuration in which the cleaning member is brought into contact with and separated from the charging member has the following problems.
In the case of an image forming apparatus capable of forming images of a plurality of colors, a charging device is provided in each color image forming unit, and a configuration in which a cleaning member can contact and separate is used for this charging device.
When a plurality of image forming units are used, since each image forming unit, in other words, the image area for each color is different, the cleaning time to be executed for each image forming unit is also different. However, depending on the situation of use, cleaning may be performed in a plurality of image forming units at the same time, and the cleaning member may come in contact with or separate from the charging member.

  When the cleaning members are simultaneously brought into contact with and separated from each other in a plurality of image forming units in this way, a large operation sound is generated at that time, which may be recognized as so-called noise.

An object of the present invention, the view of the problems in the cleaning of the case of using the multiple image forming section that put the conventional image forming apparatus, which can suppress the generation of noise in the case of using a plurality of charging members configured It is to provide the images forming apparatus provided with.

In order to achieve this object, the present invention has the following configuration.
(1) It has a plurality of image forming units capable of forming images of different colors, and each image forming unit is in contact with the charging unit in order to remove toner and foreign matters adhering to the charging unit. A charging device including a detachable cleaning unit, and a control unit that individually contacts and separates each cleaning unit provided in the charging device. The control unit is stored in the image forming unit. When the operation of the cleaning unit is controlled based on the image forming history and the use environment condition for the image forming unit, and the operation timing of the cleaning unit is determined to be the same as the operation timing of the cleaning unit provided in another charging device And an image forming apparatus that operates the cleaning means at different timings .

(2) When the control unit determines that the operation timing of the cleaning unit is simultaneous, the control unit sets the operation timing of the cleaning unit according to the order of image transfer from the image forming unit. (1) The image forming apparatus according to (1).

(3) The image according to (1) or (2), wherein the cleaning unit is configured such that a state apart from the charging unit is set as an initial state, and is in contact with the charging unit at a cleaning operation timing. Forming equipment.

(4) The image forming apparatus according to any one of (1) to (3), wherein the charging unit has a roller shape, and the charging region is disposed in a non-contact manner on the image carrier.

(5) The image forming apparatus according to any one of (1) to (4), wherein the charging unit applies a charging bias in which AC is superimposed on DC.

(6) The roller used in the charging unit includes at least a core as a support, a charging member that is provided on the core and charges the image carrier used for image formation, and the image carrier. (5), wherein the charging member and the gap forming member are made of a resin member. The gap forming member forms a gap between the image bearing member and the image bearing member. Image forming apparatus.

(7) The image forming apparatus according to any one of (1) to (3), wherein the cleaning unit includes a roller in which a core metal and a melamine resin foam as a cleaning member are stacked. .

  According to the present invention, when cleaning for a plurality of charging means is performed at the same time, the operation noise is reduced by shifting each cleaning operation, unlike when the cleaning means is simultaneously in contact with the charging means. Can do. As a result, it is possible to suppress the generation of noise due to an increase in operating sound.

In particular, when the operation timing is shifted, the shift is made in accordance with the transfer order of the images. Therefore, since the cleaning means comes in contact with the image forming unit after the image transfer is completed , one of the sounds generated at the time of image formation is reduced. And the occurrence of inadvertent noise can be prevented.

Further, by using a charging bias obtained by superimposing AC on DC in a non-contact state with respect to the charging unit, it is possible to suppress the adhesion of toner and foreign matter to the charging unit, thereby reducing the cleaning operation. In addition, it is possible to reduce the occurrence of operation noise due to the operation of the cleaning means .

1 is a schematic diagram for explaining an overall configuration of an image forming apparatus using a charging device according to the present invention. FIG. 2 is a schematic diagram illustrating an example of a charging device used in the image forming apparatus illustrated in FIG. 1. FIG. 6 is a schematic diagram illustrating another example of a charging device used in the image forming apparatus illustrated in FIG. 1. It is sectional drawing for demonstrating the structure of the blood transmission means used for the charging device by this invention. It is a figure for demonstrating the structure of the cleaning means used for the charging device by this invention. It is a figure for demonstrating the structure used for the charging device by this invention. It is a block diagram for demonstrating the structure of the control part used for the charging device by this invention. It is a flowchart for demonstrating the effect | action of the control part shown in FIG.

Hereinafter, embodiments for carrying out the present invention will be described with reference to illustrated embodiments.
FIG. 1 is an overall configuration diagram showing an example in which the present invention is applied to a tandem intermediate transfer type full-color copying machine.
In FIG. 1, the full-color copying machine includes an apparatus main body 100, a paper feed table 200 on which the main body is mounted, a scanner 300 mounted on the copying apparatus main body, an automatic document feeder (ADF) 400 mounted on the scanner, and the like.

The full-color copying machine is configured as a tandem image forming apparatus 20 in which four image forming units 18Y, 18C, 18M, and 18Bk of Y, C, M, and Bk are arranged side by side in the center of the main body.
Each image forming unit of the tandem image forming apparatus includes photoreceptors 40Y, 40C, 40M, and 40Bk on which toner images of respective colors Y, C, M, and Bk are formed.

An exposure device 21 is provided above the tandem image forming apparatus.
The exposure apparatus includes four laser diode (LD) light sources prepared for each color, a pair of polygon scanners composed of a six-surface polygon mirror and a polygon motor, and fθ arranged in the optical path of each light source. It is composed of a lens, a lens such as a long WTL, and a mirror. Laser light emitted from the LD in accordance with the image information of each color is deflected and scanned by a polygon scanner and applied to the photoconductor of each color.

An endless belt-shaped intermediate transfer belt 10 is installed below the tandem image forming apparatus.
In the illustrated example, the intermediate transfer belt 10 is wound around three support rollers 14, 15, and 16 and can be rotated and conveyed in the clockwise direction in the figure. The support roller 14 is a drive roller that rotationally drives the intermediate transfer belt. Further, between the first support roller 14 and the second support roller 15, primary transfer rollers 62 Y, C, M, and Bk are intermediate transfer as primary transfer means for transferring the toner image from the photosensitive member of each color to the intermediate transfer belt. It is provided so as to face each photoconductor with the belt 10 in between.

An intermediate transfer belt cleaning device 17 that removes residual toner remaining on the intermediate transfer belt 10 after image transfer is provided downstream of the third support roller 16.
As the material of the intermediate transfer belt 10, a resin material such as polyvinylidene fluoride, polyimide, polycarbonate, polyethylene terephthalate, etc. can be molded into a seamless belt and used. These materials can be used as they are, or the resistance can be adjusted with a conductive material such as carbon black. Further, using these resins as a base layer, a surface layer may be formed by a method such as spraying or dipping to form a laminated structure.

A secondary transfer device 22 is provided below the intermediate transfer belt 10.
In the illustrated embodiment, the secondary transfer device 22 is arranged with a secondary transfer belt 24, which is an endless belt, spanned between two rollers 23, and is connected to the third support roller 16 via the intermediate transfer belt 10. The image on the intermediate transfer belt 10 is transferred to a transfer material by being pressed.
As the secondary transfer belt 24, the same material as that of the intermediate transfer belt 10 can be used.

Next to the secondary transfer device 22, a fixing device 25 for fixing an image on the transfer material is provided.
The fixing device 25 is configured by pressing a pressure roller 27 against a fixing belt 26 that is an endless belt.
The secondary transfer device 22 described above is also provided with a sheet transport function for transporting the transfer material after image transfer to the fixing device 25. Of course, a transfer roller or a transfer charger may be disposed as the secondary transfer device 22, and in such a case, it is necessary to provide this transfer material conveying function separately.

In the illustrated example, a transfer material is disposed below the secondary transfer device 22 and the fixing device 25 in parallel with the above-described tandem image forming device so as to reversely discharge the transfer material or to form an image on both sides of the transfer material. And a reversing device 28 for re-feeding and refeeding.
When a copying operation is performed using such a tandem image forming apparatus, a document is set on the document table 30 of the ADF. Alternatively, the ADF is opened, an original is set on the contact glass 32 of the scanner, the ADF is closed, and the original is pressed.
When the start switch of the operation unit (not shown) is pressed, when the document is set on the ADF, the document is transported and moved onto the contact glass, and when the document is set on the contact glass, immediately drives the scanner, Ru is run first carriage 33 and second carriage 34. The first traveling body emits light from the light source, further reflects reflected light from the document surface toward the second traveling body, reflects by the mirror of the second traveling body, and passes through the imaging lens 35 to read sensor 36. And read the document contents. Thereafter, when the mode setting is set in the operation unit or the automatic mode selection is set in the operation unit, the image forming operation is started in the full color mode or the monochrome mode according to the reading result of the original.

  When the full color mode is selected, each photoconductor rotates in the counterclockwise direction in FIG. Then, the surface of each photoconductor is uniformly charged by a charging roller which is a charging device. Each color photoconductor is irradiated with laser light corresponding to the image of each color from the exposure device, and a latent image corresponding to the image data of each color is formed. Each latent image is developed with the toner of each color by the developing devices 60Y, 60C, 60M, and 60B of each color as the photoconductor rotates. The toner images of the respective colors are sequentially transferred onto the intermediate transfer belt 10 along with the conveyance of the intermediate transfer belt 10 to form a full color image on the intermediate transfer belt. After the transfer, the photosensitive member is subjected to light neutralization by a static elimination lamp, and the residual toner is removed by a cleaning unit.

  On the other hand, one of the paper feed rollers 42 is selectively rotated, the transfer material is sent out from one of the paper feed cassettes 44 provided with the paper feed tables 43 in multiple stages, and separated one by one by the separation roller 45 to the paper feed path 46. Then, the sheet is conveyed by a conveying roller 47 and guided to a sheet feeding path 48 in the main body, and is abutted against a registration roller 49 and stopped. Alternatively, the transfer roller 50 is rotated to feed the transfer material on the manual feed tray 51, separated one by one by the separation roller 52, put into the manual feed path 53, and abutted against the registration roller 49 and stopped. Then, the registration roller 49 is rotated in synchronization with the full-color image on the intermediate transfer belt 10, the transfer material is fed between the intermediate transfer belt 10 and the secondary transfer device 22, and transferred by the secondary transfer device 22. A toner image is collectively transferred onto a transfer material.

  The transfer material onto which the toner image has been transferred is conveyed by the secondary transfer device 22 and sent to the fixing device 25, where it is fixed to the transfer material by applying heat and pressure in the fixing device 25. The paper is switched and discharged by a discharge roller 56 and stacked on a discharge tray 57. Alternatively, it is switched by the switching claw 55 and put into the sheet reversing device 28, where it is reversed and fed again to the transfer position. After the image is also recorded on the back side, it is ejected onto the sheet ejection tray by the ejection roller 57. . Thereafter, when the formation of two or more images is instructed, the above-described image forming process is repeated.

After the formation of a predetermined number of images, the rotation of the photosensitive member is stopped after post-image forming processing.
In the post-image forming process, the photosensitive member is rotated one or more times with the charging bias and transfer bias turned off. At that time, the charge on the surface of the photosensitive member is discharged by the discharging means, and the photosensitive member is left uncharged and exposed to light. Prevent the body from deteriorating.

  When the monochrome mode is selected, the support roller 15 moves downward, and the intermediate transfer belt is separated from the photoreceptors Y, C, and M. Only the Bk photoconductor rotates counterclockwise in FIG. 1, the surface of the Bk photoconductor is uniformly charged by the charging roller, and a laser beam corresponding to the Bk image is irradiated to form a latent image, The toner image is developed with Bk toner. This toner image is transferred onto the intermediate transfer belt. At this time, the three color photoconductors 40Y, 40C, 40M other than Bk and the developing devices 60Y, 60C, 60M are stopped, and unnecessary wear of the photoconductor and the developer is prevented.

  On the other hand, the transfer material is fed from the paper feed cassette 44 and conveyed by the registration roller 49 at a timing that coincides with the toner image formed on the intermediate transfer belt 10. The transfer material onto which the toner image has been transferred is fixed by the fixing device 25 as in the case of a full-color image, and is processed through a paper discharge system corresponding to a designated mode. Thereafter, when the formation of two or more images is instructed, the above-described image forming process is repeated.

Next, the image forming unit will be described in detail. The image forming units 18Y, 18C, 18M, 18B, and 18B have the same configuration except that the color of the stored toner is different.
FIG. 2 is a schematic configuration diagram of the image forming unit.
In the figure, around the photoconductor 40, a charging roller 70 as a charging means for uniformly charging the photoconductor 40, a potential sensor 71 for detecting the potential of the photoconductor 40, and an electrostatic latent image formed on the photoconductor 40 A developing device 60 for developing the toner, a neutralizing lamp 72 for neutralizing the surface of the photoconductor 40 after the toner image is transferred, and a photoconductor cleaning device for cleaning the transfer residual toner are arranged. The case of the image forming unit 18 is provided with an opening for allowing the exposure light 76 from the exposure device 21 to pass therethrough.

  The developing device 60 contains a two-component developer composed of toner and carrier. The developing device 60 includes a developing roller 61 facing the photoreceptor 40, screws 62 and 63 for conveying and stirring the developer, a toner concentration sensor 64, and the like. The developing roller 61 includes an outer rotatable sleeve and an inner fixed magnet. The developer frictionally charged by being agitated by the screws 62 and 63 is carried by the magnetic force of the developing roller 61, conveyed to a portion facing the photoreceptor 40, and supplying toner to the latent image on the photoreceptor 40. Develop it. Further, the toner concentration of the developer that has consumed the toner is detected by the toner concentration sensor 64, and a necessary amount of toner is supplied from a toner supply device (not shown) provided at the upper portion of the developing device 60 according to the detection result.

  The toner supply device transports and stores toner from a toner storage container (not shown) that stores toner. Further, the toner supply device is provided with a supply port for communicating with the developing device 60 and a screw for moving the stored toner to the supply port. When a toner supply command to the developing device 60 is issued by the toner density sensor 64, a clutch (not shown) is turned on to operate the screw and move an amount of toner according to the rotation time toward the supply port. The toner is supplied by dropping it into the developing device 60 from the supply port.

The photoconductor cleaning device includes two brush rollers 73 and 74 and a cleaning blade 75. Further, a solid lubricant 78 is in contact with the brush roller 74, and has a function as a lubricant supply member.
Examples of solid lubricants include zinc stearate, barium stearate, iron stearate, nickel stearate, cobalt stearate, copper stearate, strontium stearate, calcium stearate, magnesium stearate, zinc oleate, oleic acid Fatty acid metal salts such as cobalt, magnesium oleate, and zinc palmitate, natural waxes such as carnauba wax, and fluorine-based resins such as polytetrafluoroethylene can be used. Further, other materials can be mixed as required. The solid lubricant can be produced by melting and solidifying the lubricant particles or by compression molding.
The toner scraped off from the photoreceptor 40 by the brush rollers 73 and 74 and the cleaning blade 75 made of polyurethane rubber is collected by the toner transport coil 79 and transported to a waste toner storage unit (not shown).

  The image forming unit 18 is configured to clean the photoreceptor 40 that has been neutralized after the transfer, but may be configured to neutralize the photoreceptor 40 that has been cleaned after the transfer.

  In the image forming unit 18 of FIG. 2, the lubricant supply member is disposed in the photosensitive member cleaning device. However, in this configuration, the supply of the lubricant is easily affected by the amount of toner input to the cleaning. was there. In contrast, by arranging a lubricant supply member downstream of the photoconductor cleaning device as shown in FIG. 3, even if the input amount of transfer residual toner or reverse transfer toner changes depending on the image area to be formed, the photoconductor The lubricant can be stably supplied to 40.

FIG. 4 shows a schematic configuration of the charging roller.
In the figure, the charging roller 70 is composed of a cored bar 101 that is a conductive support, a resin layer 102 as a charging member, and a gap holding member 103 that holds a gap between the photoreceptor 40. The metal core 101 is made of metal such as stainless steel. If the core metal 101 is too thin, the influence of the deflection when the charging member is cut or when the photosensitive member 40 is pressed cannot be ignored, and the required gap accuracy is difficult to obtain. Further, when the core metal 101 is too thick, there is a problem that the charging roller 70 becomes large or the mass becomes heavy. Therefore, the diameter of the core metal 101 is preferably about 6 to 10 [mm].

  The resin layer 102 of the charging roller 70 is preferably made of a material having a volume resistance of 104 to 109 [Ω · cm]. If the resistance is too low, charging bias leaks easily when there is a defect such as a pinhole in the photoconductor 40. If the resistance is too high, the discharge is not sufficiently generated and a uniform charging potential cannot be obtained. A desired volume resistance can be obtained by blending a conductive material with a resin as a base material.

  As the base resin, resins such as polyethylene, polypropylene, polymethyl methacrylate, polystyrene, acrylonitrile-butadiene-styrene copolymer, and polycarbonate can be used. Since these base resins have good moldability, they can be easily molded. As the conductive material, an ion conductive material such as a polymer compound having a quaternary ammonium base is preferable. Examples of polyolefins having a quaternary ammonium base include polyethylene, polypropylene, polybutene, polyisoprene, ethylene-ethyl acrylate copolymer, ethylene-methyl acrylate copolymer, ethylene-vinyl acetate copolymer, ethylene- Polyolefins such as propylene copolymer and ethylene-hexene copolymer. In the present embodiment, the polyolefin having a quaternary ammonium base is exemplified, but a high molecular compound other than the polyolefin having a quaternary ammonium base may be used. The ion conductive material is uniformly blended with the base resin by using means such as a biaxial kneader or a kneader. The blended material can be easily molded into a roller shape by injection molding or extrusion molding on the core metal. The blending amount of the ion conductive material and the base resin is desirably 30 to 80 parts by weight of the ion conductive material with respect to 100 parts by weight of the base resin.

  The thickness of the resin layer 102 of the charging roller 70 is desirably 0.5 to 3 [mm]. If the resin layer 102 is too thin, it is difficult to mold and there is a problem in terms of strength. If the resin layer 102 is too thick, the charging roller 70 is increased in size and the actual resistance of the resin layer 102 is increased, so that the charging efficiency is lowered.

  After the resin layer 102 is molded, the gap holding member 103 molded in advance on both ends of the resin layer 102 is fixed to the cored bar 101 by press-fitting, bonding, or both. In this way, the resin layer 102 and the gap holding member 103 are integrated, and then the outer diameter of the charging roller 70 is adjusted by performing processing such as cutting and grinding, so that the phase of the flare between the resin layer 102 and the gap holding member 103 is obtained. And the fluctuation of the charging gap can be reduced.

As the material of the gap holding member 103, a resin such as polyethylene, polypropylene, polymethyl methacrylate, polystyrene, acrylonitrile-butadiene-styrene copolymer, polycarbonate and the like can be used in the same manner as the base material of the charging member. However, since the gap holding member 103 is brought into contact with the photoconductor 40, it is desirable to use a grade having a lower hardness than the charging member in order to prevent the photoconductor 40 from being damaged.
Further, as a resin material having excellent slidability and hardly damaging the photoreceptor 40, polyacetal, ethylene-ethyl acrylate copolymer, polyvinylidene fluoride, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexa Resins such as a fluoropropylene copolymer can also be used. In addition, a surface layer on which the toner or the like hardly adheres can be formed on the resin layer 102 or the gap holding member 103 with a thickness of about several tens [μm] by coating or the like.

A gap is formed between the resin layer 102 of the charging roller 70 and the photoreceptor 40 by applying the gap holding member 103 to the outside of the image area of the photoreceptor 40. In the charging roller 70, a gear attached to the end of the core metal 101 is engaged with a gear formed on the flange of the photosensitive member 40, and when the photosensitive member 40 is rotated by a photosensitive member driving motor (not shown), the charging roller 70 is also in the photosensitive member 40. Rotate in the follow-up direction at a linear speed almost equal to
Since the resin layer 102 and the photoconductor 40 are not in contact with each other, even when a hard resin material and an organic photoconductor are used as the charging roller 70, the photoconductor in the image region is not damaged. Further, if the gap is too wide, abnormal discharge occurs and it becomes impossible to uniformly charge, so the maximum gap needs to be suppressed to about 100 [μm] or less. When such a charging roller 70 having a gap between the photoreceptor 40 and the charging roller 70 is used, it is desirable to superimpose an AC voltage on a DC voltage as a charging bias.

  The charging means that can be used in the image forming unit 18 is not limited to the charging roller 70 arranged in the proximity, but may be a charging roller or a charging brush arranged in contact. When the charging roller 70 is disposed in contact with the photosensitive member 40, dirt on the surface of the photosensitive member 40 is rubbed against the charging roller 70 when the charging roller 70 rotates along with the photosensitive member 40. Dirt is easy to adhere and sticks more easily. On the other hand, by disposing the charging roller 70 close to the photoreceptor 40 in a non-contact manner, the surface of the charging roller 70 is not rubbed against the photoreceptor 40, so that the contamination of the charging roller 70 can be greatly reduced. it can.

  However, since the AC voltage is superimposed to uniformly charge the photoconductor 40, a slight amount of toner, toner external additive, and the like on the photoconductor 40 fly to the charging roller 70 even when arranged in a non-contact manner. Will adhere. For this reason, it is necessary to provide the charging cleaning member 77 as a cleaning unit for cleaning the charging roller 70 and remove the contamination of the charging roller 70 even in the charging roller 70 in the close arrangement, as well as the charging roller 70 in the close arrangement.

However, when such a charging cleaning member 77 is always brought into contact with the charging roller 70, the surface of the charging roller 70 can be removed initially, but accumulated on the surface of the charging cleaning member 77 over a long period of time. The toner or the like is rubbed against the surface of the charging roller 70, and the charging roller 70 is soiled.
In addition, since the AC bias is applied to the charging roller 70, dirt on the photoconductor 40 is electrostatically attracted, but conversely, the dirt adhering to the charging roller 70 is electrostatically returned to the photoconductor 40. Power also works. Therefore, cleaning is performed by intermittently abutting the charge cleaning member 77 to reduce the amount of toner or the like that accumulates on the charge cleaning member 77, thereby suppressing deterioration of the charge cleaning member 77 and charging with the charging roller 70. The lifetime with the cleaning member 77 is extended.

Therefore, the present invention is characterized in that the cleaning members provided in the respective image forming units are not simultaneously brought into and out of operation.
Hereinafter, a configuration related to the feature will be described.

FIG. 5 is a schematic configuration diagram of a contact / separation mechanism that contacts and separates the charging cleaning member 77 from the charging roller 70.
The charging cleaning member 77 has a roller shape and is supported by arms 80 at both ends.
The arm 80 is swingably provided with the support shaft 80A as a fulcrum, and the state in which the cleaning member 77 is separated from the charging roller 70 by the habit of an urging member (not shown) other than during cleaning is the initial state. ing.
In the initial state, the arm 80 is charged by depressing the protrusion 82 located on the swing end side of the arm 80 by a solenoid (not shown) installed on the main body side (in the direction opposite to the arrow A in FIG. 5). The cleaning member 77 is brought into contact with the charging roller 70.
Thereby, the charging cleaning member 77 cleans the surface of the charging roller 70 while rotating around the charging roller 70. After the cleaning is finished, a solenoid (not shown) installed on the main body side is released to move the protrusion 82 of the arm 80 in the direction of arrow A in FIG. 5 and the charging cleaning member 77 is separated from the charging roller 70. In FIG. 5, reference numeral 70 </ b> A indicates a charging frame that supports the charging roller 70.

  Since the state in which the cleaning member 77 is separated from the charging roller 70 is the initial state, the chance of toner adhesion from the charging roller 70 to the cleaning member 77 is reduced, so the toner on the cleaning member It is possible to suppress the accumulation amount and prevent the charging roller 70 from being soiled.

  If such a contact / separation operation of the charging cleaning member 77 is executed during the image forming operation, vibrations due to the operation of the solenoid may be transmitted to the exposure device 21 or the like to disturb the image. For this reason, it is necessary to perform the charging roller cleaning operation by the charging cleaning member 77 other than during the image forming operation. Further, if the charging roller cleaning operation is frequently executed, the waiting time of the user increases. Therefore, it is desirable to reduce the execution frequency of the charging roller cleaning operation as much as possible.

  Various materials such as sponges and brushes can be used as the charging cleaning member 77. However, when the charging cleaning member 77 is fixedly brought into contact with the charging roller 70, the toner or the like accumulated on the contact surface is changed. It is desirable that the cleaning member be rotated with the charging roller 70 as a roller shape.

FIG. 6 is a schematic configuration diagram of the roller-shaped charging cleaning member 77.
The charging cleaning member 77 has a configuration in which a core metal 86 is covered with a melamine resin foam (porous material) 87, and the melamine resin foam (porous material) 87 is brought into contact with the surface of the charging roller 70 to charge the charging roller. Remove 70 stains. Melamine resin foam 87 is superior in strength to other sponge-like materials, and since there are many spaces in the foam, it is possible to retain a large amount of dirt such as toner and maintain cleaning performance over a long period of time. .

The charging cleaning member 77 having the above configuration is controlled by the control unit shown in FIG. 7 so that the operation timings in the respective image forming units are not the same based on the image forming history and the use environment described below. It has become.
FIG. 7 is a block diagram for explaining the configuration of the control unit. In the figure, the control unit 1000 uses a processor that executes an image forming process sequence program.

On the input side of the control unit 1000, a memory 1001 that stores and stores image forming histories in each image forming unit, so-called use histories of the photoreceptors 40Y, C, M, and Bk, as members related to the present embodiment. A temperature sensor 1002 for detecting the temperature in the apparatus, and a humidity sensor 1003 for detecting humidity, and a solenoid drive unit 1004 used as a contact / separation drive source for the cleaning member 77 is connected to the output side. .
The use history described above also stores information about the amount of toner attached to the photosensitive drum, in other words, the image area that affects the residual toner amount.

  The control unit 100 controls the contact / separation operation of the cleaning member 77 on the premise of the following conditions. When it is determined that the contact / separation operations need to be performed simultaneously under these conditions, the control unit 100 individually performs the cleaning member 77's operation according to the procedure described later. It is designed to perform contact and separation operations.

In an image forming apparatus using a plurality of image forming units 18Y, C, M, and Bk, when forming a full-color image, all the image forming units 18Y, C, M, and Bk are used to form a monochrome image. Uses only the black image forming unit 18Bk. For this reason, the usage time of the charging roller 70 included in the image forming unit 18 is different between black and color.
In addition, each image forming unit 18 is replaced depending on the lifetime, but the replacement cycle does not match because the use time is different. In addition, one of the plurality may be replaced due to a failure or the like. Thus, since the usage time of the charging roller 70 of each image forming unit 18 is generally not the same, the contamination of each charging roller 70 is different.

  Accordingly, the operation of the contact / separation mechanism of each charging cleaning member 77 is estimated from the usage history of each photoconductor 40 so that the contamination of each charging roller 70 is estimated and the charging roller cleaning operation is performed at an appropriate interval according to this. Conditions can be set individually. Specifically, when the usage history of each photoconductor 40 reaches a predetermined value, the contact / separation solenoid of the corresponding color is operated to bring the corresponding charging cleaning member 77 into contact with the corresponding charging roller 70. Perform charging roller cleaning operation.

  Further, when the usage environment is a low temperature and low humidity environment, the resistance of the charging roller 70 itself or dirt attached to the charging roller 70 is increased, and charging failure is likely to occur. Therefore, the operation interval of the contact / separation mechanism individually set based on the use history can be changed depending on the use environment. Specifically, the usage history of each photoconductor 40 is corrected by the output of the temperature and humidity sensor, and when the corrected usage history reaches a predetermined value, the contact / separation solenoid of the corresponding color is operated, and the corresponding charging cleaning is performed. The charging roller cleaning operation is performed by bringing the member 77 into contact with the corresponding charging roller 70. Thereby, cleaning at a more suitable interval can be performed, and the charging performance of each charging roller 70 can be maintained over a long period of time.

  In a full-color image forming apparatus, the image area is generally different for each color, and it is very rare that the image area of each color is the same. When a large number of images with a large image area are output, the toner input to the photoconductor cleaning device increases, so that the charging roller 70 is likely to become dirty. Therefore, the operation interval of the contact / separation mechanism set individually based on the use history of each photoconductor can be changed by the image area of each color. Specifically, the usage history of each photoconductor 40 is corrected based on the image area ratio, and when the corrected usage history reaches a predetermined value, the contact / separation solenoid of the corresponding color is operated, and the corresponding charging cleaning is performed. The charging roller cleaning operation is performed by bringing the member 77 into contact with the corresponding charging roller 70. As a result, it is possible to perform cleaning at intervals suitable for contamination of each charging roller 70.

  In addition, depending on the conditions of the apparatus, toner may be consumed in addition to image formation, which increases the amount of toner input to the photoconductor cleaning apparatus, so that the charging roller 70 is likely to become dirty. Therefore, the toner supply amount replenished to each developing device 60 is detected, and the operation interval of the contact / separation mechanism set individually based on the usage history of each photoconductor can be changed based on each toner supply amount. Specifically, the toner supply amount replenished to each developing device 60 is calculated from the rotation time of the replenishment motor that drives the screw of the toner supply device as detection means for detecting the toner supply amount replenished to each developing device 60. To do. The usage history of each photoconductor 40 is corrected by the amount of toner supplied to each developing device 60. When the corrected usage history reaches a predetermined value, the contact / separation solenoid of the corresponding color is operated to The charging cleaning member 77 is brought into contact with the corresponding charging roller 70 to execute the charging roller cleaning operation. As a result, it is possible to perform cleaning at intervals suitable for contamination of each charging roller 70.

  Further, as the number of sheets used increases, the deterioration of the photosensitive member cleaning device (specifically, wear of the cleaning blade 75, etc.) progresses, so that the toner passes through more easily and the charging roller 70 is likely to become dirty. When the charging roller 70 and the cleaning blade 75 are individually replaced, it is difficult to accurately grasp the usage status of the cleaning blade 75, but the photoconductor 40, the charging roller 70, and the photoconductor cleaning means can be replaced together. With this process cartridge configuration, if the process cartridge replacement time is stored, the operation interval of the contact / separation mechanism set individually based on the usage history of each photoconductor is changed according to the number of photoconductor cleaning units used. Make it possible.

  Based on the above conditions, the contact / separation operation of the cleaning member 77 is executed. As a result of determining the contact / separation operation timing in the control unit 1000, it is necessary to perform the contact / separation operation between the image forming units at the same time. When the determination is made, the contact / separation operation timing of the cleaning member 77 is shifted between the image forming units.

As a method of shifting the operation time, a method is used in which a preset time is assigned to the contact timing of the cleaning member in each image forming unit and the contact time is sequentially delayed between the image forming units. .
Further, as a method of starting the contact / separation operation with the contact / separation timing set, the contact / separation operation of the cleaning member 77 is performed in the order of Y, C, M, Bk, for example, in the order in which the image forming unit units are arranged. I do.
In addition, in the process in which the image of each color is transferred, the contact operation of the cleaning member 77 is performed using the timing when the photosensitive drum is cleaned in the order in which the transfer of each color is completed. It is also possible.

FIG. 8 is a flowchart for explaining the operation of the control unit 1000.
In the figure, the control unit 1000 reads a use history for each color image forming unit and determines whether it is the cleaning time of the charging roller 70 based on the history (ST1, ST2).
If it is determined in step ST2 that it is not the cleaning time, temperature and humidity detection information around or inside the image forming unit is captured, and it is determined whether or not it is the cleaning time from the captured detection results (ST3 to ST6).
If it is determined in the history and the detection result that the cleaning time is the same, it is determined whether or not the image forming units have the same cleaning time (ST7), and if it is determined that the time is the same, a shift process is executed. Then, the solenoid is driven based on this shifting process (ST8, ST9).
As described above, the shifting process sets a method for delaying the contact / separation start time by assigning a preset time between the image forming units to the contact / separation start time of the cleaning member 77, and the contact / separation order. The

In this way, by shifting the contact / separation operation timing of the cleaning member 77 in accordance with the arrangement order of the image forming units or the transfer order, the operation sound is not increased when performing the contact / separation operation simultaneously.
In addition, when the location where the operation sound is generated is different from the image forming unit, the operation sound is generated in the order of the image formation processing, so that the operation sound is not generated randomly and from various places in the device. As one of the operation sounds, the generation of abnormal sounds can be eliminated. That is, it is possible to reduce a sense of incongruity when listening to the operation sound during the contact / separation operation by setting the order.

Since the present embodiment is configured as described above, experimental examples are given below.
(Experimental example 1)
As the charging roller, the resin non-contact charging roller shown in FIG. 4 was used, and as the charging roller cleaner, a roller composed of a metal core and melamine resin foam was used.
Normally, the charging roller cleaner is separated from the charging roller, and when a predetermined condition is reached, the charging roller cleaning operation is performed after the job.
The charging roller cleaning operation repeats the operation of bringing the charging roller cleaner into contact with the charging roller for 3 seconds while rotating the charging roller and then separating the cleaning roller for 1 second three times.
When performing cleaning of the four color charging rollers at the same time, the control for the contact for 3 seconds and the separation for 1 second are the same, but the contact / separation solenoids for 4 colors are not operated simultaneously, but have a delay of 0.1 second. Let
That is, the solenoid of C is operated 0.1 second after the operation of the Y solenoid, the solenoid of M is operated 0.1 second after the operation of the C solenoid, and K is operated 0.1 second after the operation of the M solenoid. The solenoid was operated.
By setting it as such operation | movement, generation | occurrence | production of the noise by a several solenoid operating simultaneously can be prevented.

(Experimental example 2)
When performing two-color charging roller cleaning at the same time, for example, to simultaneously perform Y and C, the C solenoid is operated 0.1 seconds after the Y solenoid is operated, and the M and Bk solenoids are not operated.
In order to perform C and K simultaneously, the solenoid of K is operated 0.1 seconds after the operation of the solenoid of C, and the solenoids of Y and M are not operated.

DESCRIPTION OF SYMBOLS 10 Intermediate transfer bell 18Y, C, M, Bk Image forming unit 40CY, C, M, Bk Photoconductor 70 Charging roller 77 Cleaning member 80 Arm 82 Arm protrusion 87 Melamine resin foam 100 Image forming apparatus main body 101 Core metal 102 Resin layer 103 Gap Holding Member 1000 Control Unit 1001 Usage History Storage Memory 1002 Temperature Sensor 1003 Humidity Sensor 1004 Solenoid Drive Unit

Japanese Patent Laid-Open No. 06-250504 JP 2009-58559 A

Claims (7)

It has a plurality of image forming units capable of forming images of different colors, and each image forming unit can be brought into contact with and separated from the charging unit in order to remove toner and foreign matters adhering to the charging unit. A charging device including a cleaning unit, and a control unit that individually contacts and separates each cleaning unit provided in the charging device. The control unit stores the image forming unit stored in the image forming unit. Based on the history and operating environment conditions for the image forming unit, the operation of the cleaning unit is controlled, and each cleaning is performed when it is determined that the operation timing of the cleaning unit is the same as the operation timing of the cleaning unit provided in another charging device. An image forming apparatus that operates by shifting the operation timing of the means . 2. The control unit according to claim 1, wherein when the operation time of the cleaning unit is determined to be simultaneous, the control unit sets the operation time of the cleaning unit in accordance with an image transfer order from the image forming unit. The image forming apparatus described. 3. The image forming apparatus according to claim 1, wherein the cleaning unit is configured such that a state apart from the charging unit is set as an initial state, and is in contact with the charging unit at a cleaning operation timing. 4. 4. The image forming apparatus according to claim 1, wherein the charging unit has a roller shape, and the charging area is disposed in a non-contact manner on the image carrier. The image forming apparatus according to claim 1, wherein the charging unit applies a charging bias in which AC is superimposed on DC. The roller used in the charging means includes at least a core as a support, a charging member that is provided on the core and charges the image carrier used for image formation, and contacts the image carrier. 6. The image forming apparatus according to claim 5, further comprising: a gap forming member that forms a gap between the image bearing member and the charging member, wherein the charging member and the gap forming member are made of a resin member. . The image forming apparatus according to claim 1, wherein the cleaning unit includes a roller in which a core metal and a melamine resin foam as a cleaning member are stacked.

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