JP2014085405A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the time for adjusting peak-to-peak voltage.SOLUTION: An image forming apparatus includes: a power source part 92 for applying a charging bias to a charging roller 70; an AC current detection part 91 which detects an AC current output; peak-to-peak voltage adjustment means for adjusting peak-to-peak voltage of an AC voltage so that the detected AC current coincides with a predetermined control target value; an environment detection part 93 for detecting an environment condition; and adjustment start voltage setting means which stores the peak-to-peak voltage adjusted by the peak-to-peak voltage adjustment means and the environment condition, compares an environment condition for the next peak-to-peak voltage adjustment with the stored previous environment condition, starts peak-to-peak voltage adjustment from the adjusted peak-to-peak voltage when the environment condition changes within a predetermined range, and starts peak-to-peak voltage adjustment from an adjustment start voltage set according to the environment condition when the predetermined range is exceeded.

Description

  The present invention relates to an image forming apparatus. More specifically, the present invention relates to an electrophotographic image forming apparatus such as a copying machine, a printer, a scanner, a facsimile machine, and a multifunction machine of these.

  In an electrophotographic image forming apparatus, after charging a photoconductor as an image carrier, an electrostatic latent image is formed by exposure of an original image or light writing in accordance with an image signal, and a static image formed on the photoconductor. The electrostatic latent image is visualized by developing it with a developing device using a two-component developer in which toner and carrier are frictionally charged, and then the visible image (toner image) on the photosensitive member is transferred with a transfer means (recording). The toner image on the transfer material is fixed by a fixing device using pressure, heat, or the like to obtain an image.

  Conventionally, a corona discharge method has been widely used as a charging means of this image forming apparatus, but a proximity discharge method that generates less discharge products such as ozone has also been used. As one of charging means using this proximity discharge method, a charging roller is used.

  Conventionally, a charging roller has been used in contact with an image carrier, but recently, a charging roller (hereinafter also referred to as a non-contact charging roller) arranged in a non-contact manner on an image carrier (for example, a photoreceptor). Has also been put to practical use.

  In this non-contact charging roller, a gap holding member made of a spacer or a tape having a predetermined thickness is attached to both ends of the elastic roller portion of the charging roller, thereby removing the gap holding members at both ends of the charging roller. The portion is not in contact with the surface of the image carrier, and the image carrier is charged in this state. A charging method using proximity discharge such as a charging roller has an advantage that discharge products such as ozone are very small compared to a charging method using corona discharge.

  Further, according to the non-contact charging roller, the charging member is charged in a non-contact state on the surface of the image carrier, so that the transfer residual toner or the like remaining after the image transfer on the surface of the image carrier is transferred to the surface of the charging member. As a result, it is possible to make it difficult to cause stains due to the transfer to, and to prevent deterioration of charging performance caused by the contamination.

  By the way, in a charging roller in which an AC voltage is superimposed on a DC voltage, if the peak-to-peak voltage of the AC voltage is insufficient, the charging potential becomes non-uniform and an abnormal image may occur. Also, if the AC peak-to-peak voltage is too large and the discharge becomes excessive, the wear of the photoconductor is promoted and toner filming on the photoconductor is caused. Therefore, the peak-to-peak voltage is adjusted to an appropriate value. There is a need to.

  In this regard, Patent Document 1 discloses an image forming apparatus using a non-contact charging roller, in which an alternating current output from a high-voltage power supply is detected so that the alternating current becomes a predetermined target value. Discloses an image forming apparatus for adjusting a peak-to-peak voltage of an AC voltage.

  According to the image forming apparatus of Patent Document 1, it is possible to reduce the contamination of the charging roller and prevent the occurrence of abnormal discharge with the passage of time, thereby outputting a good image.

  However, since an image cannot be output during the adjustment of the peak-to-peak voltage, a standby time is required during the adjustment of the peak-to-peak voltage, which causes the user of the image forming apparatus to wait. For this reason, it is desirable that the adjustment time of the peak-to-peak voltage is as short as possible so that the user can use the image forming apparatus comfortably.

  Here, the appropriate peak-to-peak voltage is affected by the environment in which the image forming apparatus is installed, and is lower in the high-temperature and high-humidity environment and higher in the low-temperature and low-humidity environment than the normal-temperature and normal-humidity environment. However, in Patent Document 1, since adjustment of the peak-to-peak voltage is not performed in consideration of the installation environment of the image forming apparatus, there remains room for improvement in shortening the adjustment time of the peak-to-peak voltage.

  Therefore, in the present invention, when adjusting the peak-to-peak voltage, the peak-to-peak voltage adjustment time can be reduced and the standby time can be shortened by starting the peak-to-peak voltage adjustment operation from the adjustment start voltage according to the installation environment. It is an object of the present invention to provide an image forming apparatus that can be used.

  In order to achieve this object, an image forming apparatus according to the present invention includes an image carrier, a charging unit that charges the image carrier, and a high voltage that applies a charging bias in which an AC voltage is superimposed on a DC voltage to the charging unit. A power source, current detection means for detecting an alternating current output from the high-voltage power supply, and a peak-to-peak voltage for adjusting the peak-to-peak voltage of the AC voltage so that the alternating current detected by the current detection means becomes a predetermined control target value A voltage adjusting unit; an environment detecting unit that detects an environmental condition of the image forming apparatus; a peak-to-peak voltage adjustment result when the peak-to-peak voltage adjusting unit performs a peak-to-peak voltage adjusting operation; and the environment detecting unit. And the environmental conditions detected by the environmental detection means at the time when the peak-to-peak voltage adjustment means performs the peak-to-peak voltage adjustment operation next time. Compared with the previous environmental condition, if the environmental condition variation is within a predetermined range, the peak-to-peak voltage adjustment operation is started from the previous peak-to-peak voltage adjustment result, and the environmental condition variation is Adjustment starting voltage setting means for starting the peak-to-peak voltage adjusting operation from the adjustment starting voltage set according to the environmental condition when exceeding the predetermined range.

  According to the present invention, the standby time can be shortened by reducing the adjustment time of the peak-to-peak voltage.

1 is an overall configuration diagram of a tandem intermediate transfer type full-color copying machine as an embodiment of an image forming apparatus according to the present invention. It is an internal block diagram of an image forming unit showing a configuration of the image forming unit. It is a figure which shows the other example of the internal structure of the image forming unit which shows the structure of an image forming unit. It is a figure which shows the structure of a charging roller.

  Hereinafter, the configuration according to the present invention will be described in detail based on the embodiment shown in FIGS.

  The image forming apparatus (full-color copying machine) according to this embodiment includes an image carrier (photosensitive member 40), a charging unit (charging roller 70) for charging the image carrier, and a DC voltage applied to the charging unit. , A high-voltage power supply (power supply unit 92) that applies a charging bias superimposed thereon, a current detection unit (AC current detection unit 91) that detects an AC current output from the high-voltage power supply, and an AC current detected by the current detection unit A peak-to-peak voltage adjusting unit (control unit 90) that adjusts the peak-to-peak voltage of the AC voltage so that becomes a predetermined control target value, and an environment detecting unit (environment detecting unit 93) that detects an environmental condition of the image forming apparatus. And the adjustment result of the peak-to-peak voltage when the peak-to-peak voltage adjustment means performs the adjustment operation of the peak-to-peak voltage, and the environmental condition detected by the environment detection means, and then the peak-to-peak voltage adjustment means P When performing the inter-voltage adjustment operation, the environmental condition detected by the environmental detection means at that time point is compared with the previous environmental condition stored, and if the fluctuation of the environmental condition is within a predetermined range, The peak-to-peak voltage adjustment operation is started from the previous adjustment result of the peak-to-peak voltage, and when the fluctuation of the environmental condition exceeds the predetermined range, the peak-to-peak voltage adjustment operation is started from the adjustment start voltage set according to the environmental condition. Adjustment start voltage setting means (control unit 90). In addition, the code | symbol in embodiment and the example of application are shown in a parenthesis.

(Configuration of image forming apparatus)
FIG. 1 is an overall configuration diagram of a tandem intermediate transfer type full-color copying machine as an embodiment of an image forming apparatus of the present invention. The full-color copying machine includes a main body 100, a paper feeding unit 200 on which the main body 100 is placed, a scanner unit 300 attached on the main body 100, and an automatic document feeder (ADF) 400 attached on the scanner unit 300. It is composed of

  In the center of the main body 100, four image forming units 18Y, 18C, 18M, and 18BK of yellow (Y), cyan (C), magenta (M), and black (BK) are arranged side by side (intermediate transfer belt 10). The tandem image forming apparatus 20 is arranged so as to be opposed to each other and arranged in order in the moving direction of the intermediate transfer belt 10.

  Each of the image forming units 18Y, 18C, 18M, and 18BK of the tandem image forming apparatus 20 is a roller-shaped photoconductor (“photosensitive roller”) that is an image carrier on which each color toner image of Y, C, M, and BK is formed. 40Y, 40C, 40M, and 40BK.

  Further, charging devices are provided as charging means for uniformly charging the surfaces of the photoconductors 40Y, 40C, 40M, and 40BK. The charging device charges the surface of each photoconductor. In this embodiment, a gap holding member is attached to both ends of the elastic roller portion of the charging roller, and other portions except for the gap holding member at both ends of the charging roller are not in contact with the surface of the corresponding photoreceptor. A non-contact charging roller (hereinafter abbreviated as a charging roller).

  An exposure device 21 is provided above the tandem image forming apparatus 20. The exposure device 21 is arranged in four laser diode (LD) light sources prepared for each color, a set of polygon scanners composed of a six-sided polygon mirror and a polygon motor, and an optical path of each light source. It is composed of an fθ lens, a lens such as a long WTL, and a mirror.

  The laser beams emitted from the respective LDs according to the image information of the respective colors Y, C, M, and BK are deflected and scanned by the polygon scanner, and are irradiated to the respective photoreceptors 40Y, 40C, 40M, and 40BK. The

  Below the tandem image forming apparatus 20, an endless belt-like intermediate transfer belt 10 is installed. In the full-color copying machine of this embodiment, the intermediate transfer belt 10 can be wound around three support rollers 14 to 16 and rotated and conveyed clockwise in the drawing. The first support roller 14 moves the intermediate transfer belt 10 around the intermediate transfer belt 10. It is a drive roller that rotates.

  Further, a primary transfer roller 65Y is provided between the first support roller 14 and the second support roller 15 as a primary transfer means for transferring a toner image from the photoconductors 40Y, 40C, 40M, and 40BK of the respective colors to the intermediate transfer belt 10. , 65C, 65M, and 65BK are provided so as to face the photoreceptors 40Y, 40C, 40M, and 40BK with the intermediate transfer belt 10 interposed therebetween.

  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. The intermediate transfer belt 10 can be used by molding it into a seamless belt using a resin material such as polyvinylidene fluoride, polyimide, polycarbonate, or polyethylene terephthalate as a material. The resin material can be used as it is, or the resistance can be adjusted with a conductive material such as carbon black. Alternatively, a surface layer may be formed by a method such as spraying or dipping using a resin material as a base layer to form a laminated structure.

  A secondary transfer device 22 is provided below the intermediate transfer belt 10. The secondary transfer device 22 hangs an endless belt-like secondary transfer belt 24 between the two rollers 23 and 23 and is pressed against the third support roller 16 via the intermediate transfer belt 10. Then, the image on the intermediate transfer belt 10 is transferred to a transfer material including paper. The secondary transfer belt 24 can be made of the same material as that of the intermediate transfer belt 10 described above.

  A fixing device 25 for fixing an image on the transfer material is provided beside the secondary transfer device 22. The fixing device 25 presses a pressure roller 27 against an endless belt-like fixing belt 26. 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 when such a member is disposed, it is necessary to separately provide a transfer material transport function. Further, in a full-color copying machine, the transfer material is reversed and discharged under the secondary transfer device 22 and the fixing device 25 in parallel with the tandem image forming device 20 described above, or an image is formed on both surfaces of the transfer material. And a reversing device 28 for reversing and transferring the transfer material.

  In the copying operation in the full-color copying machine, first, the user sets a document on the document table 30 of the ADF 400, or the user opens the ADF 400 and sets the document on the contact glass 32 of the scanner unit 300. Next, after the ADF 400 is closed and the document is pressed, the user presses a start switch of an operation unit (not shown). Accordingly, when an original is set on the ADF 400, the original is transported and moved onto the contact glass 32. On the other hand, when an original is set on the contact glass 32, the scanner unit 300 is immediately driven to drive the first. The traveling body 33 and the second traveling body 34 are caused to travel.

  Then, the first traveling body 33 emits light from a light source (not shown) and further reflects the reflected light from the document surface toward the second traveling body 34, with a mirror (not shown) of the second traveling body 34. The light is reflected and put into the reading sensor 36 through the imaging lens 35 to read the original content.

  Thereafter, when the mode setting is set in the operation unit (not shown) 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 document.

  When the full color mode is selected, the photoconductors 40Y, 40C, 40M, and 40BK rotate in the counterclockwise direction in the drawing. Accordingly, the surface of each of the photoconductors 40Y, 40C, 40M, and 40BK is uniformly charged by a charging roller that is a charging device described in detail later.

  The Y, C, M, and BK photoconductors 40Y, 40C, 40M, and 40BK are irradiated with laser beams corresponding to the Y, C, M, and BK images from the exposure device 21, respectively. , C, M, and BK are formed as latent images corresponding to the image data.

  By rotating the photoconductors 40Y, 40C, 40M, and 40BK, the latent images of Y, C, M, and BK are respectively developed in the colors Y, C, M, and BK by the developing devices 60Y, 60C, 60M, and 60BK. The toner is developed.

  The toner images of each color of Y, C, M, and BK 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 10. Each of the photoreceptors 40Y, 40C, 40M, and 40BK after being transferred to the intermediate transfer belt 10 is subjected to light neutralization by a neutralization lamp, and residual toner is removed by a cleaning device that is also a cleaning unit described later.

  On the other hand, one of the paper feed rollers 42 of the paper feed unit 200 is selectively rotated, the transfer material is fed from one of the paper feed cassettes 44 provided in multiple stages to the paper feed table 43, and separated one by one by the separation roller 45. It is put in the paper feed path 46. Next, the sheet is conveyed by the conveyance roller 47 and guided to the paper feed path 48 in the apparatus main body 100, and is abutted against the 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 in the apparatus main body 100, and abutted against the registration roller 49. Stop.

  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. The toner image is transferred onto the transfer material.

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

  Then, after the predetermined number of image formations are completed, post-image formation processing is performed, and then the rotation of each of the photoconductors 40Y, 40C, 40M, and 40BK is stopped. In the post-image forming process, the photoconductors 40Y, 40C, 40M, and 40BK are rotated one or more times with the charging bias voltage and the transfer bias voltage turned off. Remove the charge. As a result, the photoreceptors 40Y, 40C, 40M, and 40BK are prevented from being deteriorated by being left without being neutralized.

  When the monochrome mode is selected, the support roller 15 moves downward to separate the intermediate transfer belt 10 from the photoreceptors 40Y, 40C, and 40M. Then, only the photoconductor 40BK is rotated counterclockwise in the figure, the surface of the photoconductor 40BK is uniformly charged by the charging roller, and the laser beam corresponding to the image on the photoconductor 40BK is irradiated. As a result, a latent image of a black and white image is formed on the photoreceptor 40BK, and is developed with toner of BK to become a toner image. The toner image is transferred onto the intermediate transfer belt 10. At that time, the three color photosensitive members 40Y, 40C, and 40M other than BK and the developing devices 60Y, 60C, and 60M are stopped, respectively, to prevent unnecessary consumption of the photosensitive member and the developer.

  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 coincident with the black toner image formed on the intermediate transfer belt 10. The transfer material on which the black 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.

(Configuration of image forming unit)
Next, the image forming units 18Y, 18C, 18M, and 18BK will be described in more detail. Each of the image forming units 18Y, 18C, 18M, and 18BK has a role of forming each of Y, C, M, and BK toner images, and the internal configuration thereof is common. Therefore, the image forming unit 18 showing a common configuration of the image forming units 18Y, 18C, 18M, and 18BK will be described.

  FIG. 2 is an internal configuration diagram of the image forming unit 18 showing a common configuration of the image forming units 18Y, 18C, 18M, and 18BK.

  Around the photosensitive member 40 that is an image carrier of toner images of Y, C, M, and BK, there are a charging roller 70 that uniformly charges the surface of the photosensitive member 40, and a potential sensor that detects the potential of the photosensitive member 40. 71, a developing device 60 for developing the electrostatic latent image formed on the photoreceptor 40 is disposed. In addition, a static elimination lamp 72 that neutralizes the surface of the photoreceptor 40 after the toner image is transferred, a brush roller 73, a cleaning blade 75, and a lubricant supply brush roller as a cleaning device (cleaning means) for cleaning the transfer residual toner. 74 is arranged.

  Further, the case 80 of the image forming unit 18 is provided with an opening 80a for allowing the exposure light 76 from the exposure device 21 to pass therethrough.

  A solid lubricant 78 is brought into contact with the lubricant supply brush roller 74, and the lubricant of the lubricant 78 is supplied to the photoreceptor 40 by rotation. That is, the lubricant supply brush roller 74 and the lubricant 78 function as a lubricant supply member (lubricant supply means).

  Solid lubricant 78 is, for example, 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.

  The toner scraped from the photoreceptor 40 by the brush roller 73 and the cleaning blade 75 made of polyurethane rubber is collected by the toner transport coil 79 and transported to a known waste toner storage unit (not shown). Yes.

  In the present embodiment, an image forming unit configured to clean the photoreceptor 40 that has been neutralized after transfer is shown. However, the photoreceptor 40 that has been cleaned after transfer may be configured to be neutralized.

  Next, when the brush roller 73 and the cleaning blade 75 are arranged as a cleaning device for cleaning the transfer residual toner, in such a configuration, the supply of the lubricant is easily affected by the amount of toner input to the cleaning device. .

  This is due to the fact that a lubricant supply means is provided in the cleaning device. That is, when the amount of toner input to the cleaning device (transfer residual toner or reverse transfer toner based on a toner image formed upstream in a full-color image forming apparatus) fluctuates, the supply efficiency of the lubricant is affected. Because it ends up.

  Therefore, the supply of the lubricant to the photoconductor 40 can be stabilized by changing the arrangement of a partial configuration inside the image forming unit 18. FIG. 3 is a diagram showing another example of the internal configuration of the image forming unit 18 showing the common configuration of the image forming units 18Y, 18C, 18M, and 18BK.

  That is, as shown in FIG. 3, a cleaning blade 75 is disposed downstream of the brush roller 73, and a lubricant 78 as a lubricant supply means, a lubricant supply brush roller 74, and lubricant application are provided downstream of the cleaning blade 75. The blade 81 is arranged. As a result, the lubricant can be stably supplied to the photoconductor 40 even if the input amount of the transfer residual toner or the reverse transfer toner varies depending on the area of the image formed on the photoconductor 40.

  Next, the charging roller 70 will be described in detail. The charging roller 70 plays a role of uniformly charging the photoreceptors Y40, 40C, 40M, and 40BK in each of the image forming units 18Y, 18C, 18M, and 18BK.

  FIG. 4 is a diagram illustrating a configuration of the charging roller 70. As shown in FIG. 4, the charging roller 70 includes a cored bar 101 that is a conductive support, a resin layer 102 that is a charging member, and a gap holding member 103.

  The metal core 101 is made of a metal such as stainless steel. If the core metal 101 is too thin, the influence of the deflection when the resin layer 102 is cut or when the photosensitive member 40 is pressed cannot be ignored, and it becomes difficult to obtain the required gap accuracy. On the other hand, if it is too thick, there arises a problem that the charging roller 70 itself becomes large or the mass becomes heavy. Therefore, the diameter of the cored bar 101 is desirably about 6 to 10 mm.

  Further, if the resistance of the resin layer 102 is too low, leakage of the charging bias voltage is likely to occur when the photoreceptor 40 has defects such as pinholes. If the resistance is too high, the discharge is not sufficiently generated and uniform. A charged potential cannot be obtained. For this reason, it is preferable to use a material having a volume resistance of 104 to 109 Ωcm.

  In the production of the resin layer 102, a desired volume resistance can be easily obtained by blending a conductive material as a resin serving as a base material (referred to as a base resin). As the base resin, for example, resins such as polyethylene, polypropylene, polymethyl methacrylate, polystyrene, acrylonitrile-butadiene-styrene copolymer, and polycarbonate can be used. Since the base resin has good moldability, it can be easily molded.

  As the conductive material, for example, an ion conductive material such as a polymer compound (polyolefin) having a quaternary (quaternary) ammonium base is preferably used. Examples of the polyolefin having a quaternary ammonium base include, for example, polyethylene having a quaternary ammonium base, polypropylene, polybutene, polyisoprene, ethylene-ethyl acrylate copolymer, ethylene-methyl acrylate copolymer, ethylene-vinyl acetate copolymer, ethylene- Examples thereof include propylene copolymerization and ethylene-hexene copolymerization. In the present embodiment, the polyolefin having a quaternary ammonium base has been exemplified, but the same effect can be obtained by using a polymer compound other than the polyolefin having a quaternary ammonium base. The ion conductive material can be uniformly blended into the base resin by using a means such as a biaxial kneader or a kneader.

  Then, the blended material can be easily molded into a roller shape by injection molding or extrusion molding on the core metal 101. 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.

  If the thickness of the resin layer 102 of the charging roller 70 is too thin, it is difficult to mold and a problem arises in terms of strength. If it is too thick, the charging roller 70 is enlarged and the actual thickness of the resin layer 102 is increased. The resistance increases and the charging efficiency decreases. For this reason, it is desirable to make the thickness into 0.5-3 mm.

  As for the manufacturing method of the charging roller 70, for example, after forming the resin layer 102, the gap holding member 103 previously formed on both ends of the resin layer 102 is press-fitted and bonded, or both are used together. Fix to gold 101.

  In this way, the resin layer 102 and the gap holding member 103, which are charging members, are integrated, and then the outer diameter of the charging roller 70 is adjusted by performing processing such as cutting and grinding. The phase of the 103 flare can be made uniform. In addition, fluctuations in the charging gap can be reduced.

  As a material of the gap holding member 103, a resin such as polyethylene, polypropylene, polymethyl methacrylate, polystyrene, acrylonitrile-butadiene-styrene copolymer, polycarbonate, or the like can be used as in the base material of the resin layer 102.

  However, since the gap holding member 103 is brought into contact with the photosensitive layer of the photoreceptor 40, it is desirable to use a grade having a lower hardness than the resin layer 102 in order to prevent the photosensitive layer from being damaged.

  Further, as the resin material of the gap holding member 103, resins such as polyacetal, ethylene-ethyl acrylate copolymer, polyvinylidene fluoride, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, etc. If it is used, it is excellent in slidability and can make it difficult to damage the photosensitive layer.

  Thus, since the resin layer 102 and the gap holding member 103 are made of a resin material, the charging roller 70 can be manufactured easily and with high accuracy. Moreover, it is preferable to form a surface layer with a thickness of about several tens of μm on the resin layer 102 and the gap holding member 103 so that toner or the like is difficult to adhere by coating or the like.

  The charging roller 70 forms a gap (charging gap) between the photosensitive layer 40 and the resin layer 102 that is the charging area of the charging roller 70 by applying the gap holding member 103 to the outside of the image area of the photosensitive body 40. To do.

  A gear (not shown) attached to the end of the core metal 101 is configured to mesh with a gear (not shown) formed on the flange of the photoreceptor 40. Thus, when the photoconductor 40 is rotated by a drive motor (not shown) of the photoconductor 40, the charging roller 70 is also rotated in the follower direction at a linear velocity substantially equal to that of the photoconductor 40.

  In this way, since the resin layer 102 and the photoreceptor 40 do not come into contact with each other, even when a hard resin material and an organic photoreceptor are used as the charging roller 70, the photosensitive layer in the image area 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 the 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 voltage.

  The charging roller 70 is in contact with a cleaning roller 77 for cleaning the roller surface. The cleaning roller 77 is a roller in which a melamine foam is mounted on a metal core 101, and is in contact with the charging roller 70 by its own weight. The charging roller 70 rotates while the charging roller 70 rotates. Removes dirt such as toner adhering to the surface.

  The cleaning roller 77 may be always in contact with the charging roller 70, but it is preferable to provide a contact / separation mechanism for the cleaning roller 77. Accordingly, it is possible to configure such that the surface of the charging roller 70 is intermittently cleaned by being normally separated by the contact / separation mechanism and periodically contacting the charging roller 70 as necessary.

  Next, the developing device 60 is a two-component developing type developing device in which each of the photoconductors 40Y, 40C, 40M, and 40BK has the same configuration, and only the color of the toner to be used is different. In the apparatus, a two-component developer composed of toner and carrier is accommodated.

  The developing device 60 includes various parts including a developing roller 61 facing the photoreceptor 40, screws 62 and 63 for conveying and stirring the developer, and a toner concentration sensor 64. The developing roller 61 is composed of an outer rotatable sleeve (not shown) and an inner magnet (not shown).

  Then, according to the output of the toner density sensor 64, a necessary amount of toner is supplied from a toner supply device (not shown). The toner includes a binder resin, a colorant, and a charge control agent as main components, and other additives are added as necessary.

  As the binder resin, for example, resins such as polystyrene, styrene-acrylic acid ester copolymer, and polyester resin can be used. As coloring materials (for example, yellow, magenta, cyan and black) used for the toner, those known for toner can be used. The amount of the coloring material is suitably 0.1 to 15 parts by weight with respect to 100 parts by weight of the binder resin, for example.

  As the charge control agent, for example, a nigrosine dye, a chromium-containing complex, a quaternary ammonium salt or the like can be used, and these are properly used depending on the polarity of the toner particles. The amount of the charge control agent is preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of the binder resin.

Further, a fluidity imparting agent may be added to the toner particles. Examples of the fluidity-imparting agent include fine particles of metal oxide containing silica, titania and alumina, and those fine particles whose surface is treated with a silane coupling agent, titanate coupling agent, etc., polystyrene, polymethyl methacrylate Polymer fine particles such as polyvinylidene fluoride are used. The fluidity imparting agent preferably has a particle size in the range of 0.01 to 3 μm. The addition amount of the fluidity imparting agent is 0.1 to 7.0 with respect to 100 parts by weight of the toner particles.
It is preferable to be in the range of parts by weight.

  As a method for producing a toner for two-component developer, it can be produced by various known methods or a combination thereof. For example, in the kneading and pulverization method, a binder resin and a coloring material such as carbon black and the like are required. Additives are dry-mixed, heated, melted and kneaded with an extruder or two-roll, three-roll, etc., cooled and solidified, pulverized with a pulverizer such as a jet mill, and classified with an airflow classifier to obtain a toner. It is done. In addition, a toner can be directly produced from a monomer, a colorant, and an additive by suspension polymerization or non-aqueous dispersion polymerization.

  The carrier is generally composed of the core material itself, or a core material provided with a coating layer. Generally, ferrite or magnetite is preferably used as the core material of the resin-coated carrier. An appropriate particle size of the core material is about 20 to 60 μm.

  Examples of the material used for forming the carrier coating layer of the resin-coated carrier include, for example, vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ether, vinyl ether obtained by substituting fluorine atoms, and substituting fluorine atoms. There are vinyl ketones.

  As a method for forming the coating layer, a resin may be applied to the surface of the carrier core material particles by a spraying method, a dipping method, or the like, as in the conventional case.

  Next, as an example of the photoreceptor 40, a stacked organic photoreceptor comprising a charge generation layer and a charge transport layer which are photosensitive layers formed on a conductive support can be mentioned. The conductive support exhibits conductivity with a volume resistance of 1010 Ωcm or less. For example, a metal oxide such as aluminum, nickel, chromium, nichrome, copper, silver, gold, platinum, metal oxide such as tin oxide, indium oxide, etc. The film is formed by vapor deposition or sputtering, film- or cylindrical plastic, paper-coated, pipes such as aluminum, aluminum alloy, nickel, and stainless steel are subjected to surface treatment by cutting, superfinishing, polishing, or the like.

  The charge generation layer is a layer mainly composed of a charge generation material. As the charge generation material, an inorganic or organic material is used, and typical examples include monoazo pigments, disazo pigments, trisazo pigments, perylene pigments, perinone pigments, quinacridone pigments, quinone condensed polycyclic compounds, squarics. Examples include acid dyes, phthalocyanine pigments, naphthalocyanine pigments, azulenium salt dyes, selenium, selenium-tellurium alloys, selenium-arsenic alloys, and amorphous silicon. These charge generation materials may be used alone or in combination of two or more.

  In this charge generation layer, the charge generation material as described above is dispersed by a ball mill, an attritor, a sand mill, etc., using a binder resin as appropriate and a solvent such as tetrahydrofuran, cyclohexanone, dioxane, 2-butanone, dichloroethane. It can be easily formed by applying the dispersion.

  The above-described charge generation layer can be applied by using a known technique such as dip coating, spray coating, or bead coating. Examples of the appropriately used binder resin include resins such as polyamide, polyurethane, polyester, epoxy, polyketone, polycarbonate, silicone, acrylic, polyvinyl butyral, polyvinyl formal, polyvinyl ketone, polystyrene, polyacryl, and polyamide. it can. Further, the amount of the binder resin is suitably 0 to 2 parts with respect to 1 part of the charge generating material on a weight basis. The charge generation layer can also be formed by a known vacuum thin film manufacturing method. The film thickness of the charge generation layer is usually 0.01 to 5 μm, preferably 0.1 to 2 μm.

  Further, the charge transport layer can be easily formed by dissolving or dispersing the charge transport material and the binder resin in an appropriate solvent, and applying and drying the solution. Moreover, a plasticizer, a leveling agent, etc. can also be added as needed. Among charge transport materials, low molecular charge transport materials include electron transport materials and hole transport materials.

  Examples of the electron transporting material include chloroanil, bromoanil, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2 , 4,5,7-tetranitroxanthone, 2,4,8-trinitrothioxanthone, 2,6,8-trinitro-4H-indeno [1,2-b] thiophene-4-one, 1,3,7- Examples thereof include electron accepting substances such as trinitrodibenzothiophene-5,5-dioxide. The electron transport material described above may be used alone or as a mixture of two or more.

  Examples of hole transport materials include oxazole derivatives, oxadiazole derivatives, imidazole derivatives, triphenylamine derivatives, 9- (p-diethylaminostyrylanthracene), 1,1-bis- (4-dibenzylaminophenyl) propane. , Styrylanthracene, styrylpyrazoline, phenylhydrazones, α-phenylstilbene derivatives, thiazole derivatives, triazole derivatives, phenazine derivatives, acridine derivatives, benzofuran derivatives, benzimidazole derivatives, thiophene derivatives, and the like.

  The hole transport material described above may also be used alone or as a mixture of two or more. The binder resin used in the charge transport layer together with the charge transport material described above includes polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, and chloride. Vinyl-vinyl acetate copolymer, polyvinyl acetate, polyvinylidene chloride, polyarylate, phenoxy, polycarbonate, cellulose acetate, ethyl cellulose, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, acrylic, silicone, epoxy, melamine, urethane, phenol, alkyd And other thermoplastic or thermosetting resins.

  Examples of the solvent used for the charge transport layer include tetrahydrofuran, dioxane, toluene, 2-butanone, monochlorobenzene, dichloroethane, methylene chloride, and the like. Furthermore, the thickness of the charge transport layer may be appropriately selected in accordance with desired photoreceptor characteristics within a range of 10 to 40 μm.

  Moreover, as a plasticizer added to the charge transport layer as desired, general-purpose plasticizers such as dibutyl phthalate and dioctyl phthalate can be used, and the amount used thereof is 0 to 0 based on the weight of the binder resin. About 30% is appropriate.

  Furthermore, as a leveling agent to be added to the charge transport layer as desired, silicone oils such as dimethyl silicone oil and methylphenyl silicone oil, polymers or oligomers having a perfluoroalkyl group in the side chain, and the amount used are About 0 to 1% is appropriate for the binder resin on a weight basis.

  In the present embodiment, the content of the charge transport material contained in the photosensitive layer is preferably 30% by weight or more of the charge transport layer. This is because if it is less than 30% by weight, sufficient light decay time in the high-speed electrophotographic process cannot be obtained in pulsed light exposure in laser writing on the photoreceptor 40, which is not preferable. In addition, an undercoat layer can be formed on the photoreceptor 40 between the conductive support and the photosensitive layer.

  The undercoat layer generally contains a resin as a main component. However, considering that the photosensitive layer is applied on the resin using a solvent, the subbing layer is a resin having high resistance to general organic solvents. It is desirable to do.

  Examples of such highly resistant resins include water-soluble resins such as polyvinyl alcohol, casein, and sodium polyacrylate, alcohol-soluble resins such as copolymer nylon and methoxymethylated nylon, polyurethane, melamine, and alkyd- Examples thereof include curable resins that form a three-dimensional network structure such as melamine and epoxy.

  Further, fine powder of metal oxide such as titanium oxide, silica, alumina, zirconium oxide, tin oxide, and indium oxide may be added to the undercoat layer in order to prevent moire and reduce residual potential.

  This undercoat layer can be easily formed using an appropriate solvent and a known coating method in the same manner as the above-described photosensitive layer. Furthermore, it is also useful to use a metal oxide layer formed by, for example, a sol-gel method using a silane coupling agent, a titanium coupling agent, a chromium coupling agent or the like as the undercoat layer.

In addition, the undercoat layer is made of anodized alumina (Al ₂ O ₃ ), organic matter such as polyparaxylylene (parylene), silica (SiO), tin oxide (SnO ₂ ), oxidized It is also effective to form an inorganic material such as titanium (TiO ₂ ), indium tin oxide (ITO), cerium oxide (CeO ₂ ) by a vacuum thin film manufacturing method. The thickness of the undercoat layer is suitably from 0 to 5 μm.

  Next, a protective layer may be formed on the outermost layer of the photosensitive layer for the purpose of protecting the photosensitive layer and improving durability. The protective layer is made by adding metal oxide fine particles such as alumina, silica, titanium oxide, tin oxide, zirconium oxide, and indium oxide to the binder resin for the purpose of improving wear resistance.

  Examples of the binder resin include styrene-acrylonitrile copolymer, styrene-butadiene copolymer, acrylonitrile-butadiene-styrene copolymer, olefin-vinyl monomer copolymer, chlorinated polyether, allyl, phenol, polyacetal, and polyamide. , Polyamideimide, polyacrylate, polyallylsulfone, polybutylene, polybutylene terephthalate, polycarbonate, polyethersulfone, polyethyne, polyethylene terephthalate, polyimide, acrylic, polymethylpentene, polypropylene, polyphenylene oxide, polysulfone, polyurethane, polyvinyl chloride, poly Examples of the resin include vinylidene chloride and epoxy.

  The amount of metal oxide fine particles added to the protective layer is usually 5 to 30% on a weight basis. The reason is that if the amount of the metal oxide fine particles is less than 5%, the wear is large and the effect of improving the wear resistance is small and the durability is inferior. If it exceeds 30%, the bright portion potential is significantly increased during exposure. This is because a decrease in sensitivity cannot be ignored.

  Moreover, as a formation method of a protective layer, it is good to employ | adopt normal coating methods, such as a spray method. The protective layer has a thickness of 1 to 10 μm, preferably about 3 to 8 μm. The reason is that if the protective layer is too thin, the durability is inferior, and if the protective layer is too thick, not only the productivity at the time of photoconductor production is reduced, but also the residual potential over time. This is because the increase in the price will increase.

Further, the particle size of the metal oxide particles added to the protective layer is suitably 0.1 to 0.8 μm. When the particle size of the metal oxide fine particles is too large, the unevenness of the surface of the protective layer becomes large and the cleaning property is deteriorated, and the exposure light is easily scattered by the protective layer, so that the resolution is lowered and the image quality is deteriorated. is there. Moreover, it is because abrasion resistance will be inferior when the particle size of metal oxide fine particles is too small.

In addition, a dispersing aid can be added to the protective layer in order to improve the dispersibility of the metal oxide fine particles in the base resin. As the added dispersion aid, those used for paints and the like can be used as appropriate, and the amount is usually 0.5 to 4% by weight based on the amount of metal oxide fine particles contained, preferably, It may be 1 to 2%.

  Further, by adding a charge transport material to the protective layer, the movement of charges in the protective layer can be promoted. As the charge transport material added to the protective layer, the same material as the charge transport layer may be used.

  Furthermore, in order to improve the environmental resistance, the photoreceptor 40 may be added with an antioxidant, a plasticizer, an ultraviolet absorber, a leveling agent, etc., in order to prevent a decrease in sensitivity and an increase in residual potential. .

(Peak voltage adjustment control)
Hereinafter, the peak-to-peak voltage adjustment control by the image forming apparatus of the present embodiment will be described. As described above, in a full-color copying machine, when a small charging gap is formed between the photosensitive member 40 and the charging roller 70, the charging gap is within a certain range as the photosensitive member 40 and the charging roller 70 rotate. Always fluctuates.

  In such a situation, in order to uniformly charge the photoconductor 40, it is effective to superimpose an AC bias voltage in addition to a DC voltage as a charging bias voltage applied to the resin layer 102 as a charging member.

  Here, when the frequency of the applied AC bias voltage is low, stripe-shaped charging unevenness is conspicuous. Therefore, it is desirable to set the frequency [Hz] at least 6 times the photosensitive member linear velocity [mm / s].

  On the other hand, when the frequency of the applied AC bias voltage is too high, excessive discharge occurs and the amount of wear of the photoconductor 40 increases, or filming of toner and toner external additives occurs on the photoconductor 40. It becomes easy. For this reason, it is desirable to set the frequency [Hz] which is 10 times or less the photosensitive member linear velocity [mm / s].

  By the way, when the AC bias voltage is superimposed on the charging member, the charging roller 70 disposed in contact with the photoreceptor 40 is less susceptible to fluctuations in roller resistance due to the environment by performing constant current control so that the AC current is constant. It is known that it can be done.

  On the other hand, when the charging roller 70 arranged in a non-contact manner on the photoconductor 40 is used, the charging gap varies as the photoconductor 40 and the charging roller 70 rotate. An abnormal image (horizontal stripe-like density unevenness) may occur due to overshooting or undershooting. Therefore, it is desirable that the AC voltage be constant voltage control.

  At this time, the necessary AC voltage varies depending on the environmental variation of the roller resistance and the size of the charging gap. The higher the roller resistance and the larger the charging gap, the larger the AC voltage is required.

  Therefore, in the image forming apparatus of the present embodiment, the alternating current detection unit (AC current detection unit) 91 notifies the control unit 90 that the alternating current value flowing through the charging roller 70 can be detected. The AC current detection unit 91 is a sensor (AC current value detection means) that detects a current value and notifies the control unit 90 of the current value.

  In addition, the control unit 90 stores a control target value of the alternating current value in advance, and the power supply unit 92 is connected to the power supply unit 92 so that the alternating current value notified from the alternating current detection unit 91 becomes the control target value. 92 adjusts the peak-to-peak voltage value of the AC voltage applied to the charging roller 70. The power supply unit 92 applies an AC voltage value based on the adjustment from the control unit 90 to the charging roller 70, thereby setting the AC voltage value to an appropriate AC voltage value without being affected by individual differences in roller resistance or charging gap. (Peak-to-peak voltage adjustment).

  The control unit 90 is realized by a microcomputer including a CPU as a calculation unit, a ROM and a RAM as storage units, and functions as the peak-to-peak voltage adjustment unit and the adjustment start voltage setting unit described later.

  In addition, the image forming apparatus according to the present exemplary embodiment includes an environment detection unit 93 as an environment detection unit capable of detecting at least one of temperature, relative humidity, and absolute humidity (referred to as environmental conditions) in the apparatus. The environment detection unit 93 notifies the control unit 90 of the detected temperature, relative humidity, absolute humidity, or a combination thereof (for example, temperature and relative humidity). In addition, the environment detection part 93 is comprised by a well-known temperature / humidity sensor, for example.

  Here, as described above, the appropriate peak-to-peak voltage is affected by the environment in which the image forming apparatus is installed, and is lower in the high temperature and high humidity environment and higher in the low temperature and low humidity environment than the normal temperature and humidity environment. The peak-to-peak voltage is appropriate.

  In particular, when the charging roller 70 is arranged in non-contact with the photoconductor 40, the charging gap slightly changes as the photoconductor 40 or the charging roller 70 rotates, so that the alternating current also changes according to the gap fluctuation. For this reason, in the peak-to-peak voltage adjustment operation, the average value of the detection results for one or more rotations of the photosensitive member at a predetermined sampling interval (for example, 10 msec) is used as the AC current detection value, and the difference between the charging AC current target value and the detection value The peak-to-peak voltage is gradually changed and adjusted so that the detected value approaches the target value. Therefore, if the target value and the detection value are far apart, detection and adjustment are repeated a plurality of times, and thus the peak-to-peak voltage adjustment operation takes time.

  The peak-to-peak voltage needs to be adjusted at a timing when the installation environment may change, for example, when the power is turned on, after leaving for a long time, or after outputting a predetermined number of sheets. .

  Therefore, in the image forming apparatus of the present embodiment, the control unit 90 adjusts the peak-to-peak voltage when performing the peak-to-peak voltage adjustment operation, and the environmental condition detected by the environment detection unit 93 at that time. When the peak-to-peak voltage adjustment operation is performed next, the environmental condition detected by the environment detection unit 93 at that time point is compared with the stored previous environmental condition to determine the environmental condition. If the fluctuation is within the specified range, the peak-to-peak voltage adjustment operation is started from the previous peak-to-peak voltage adjustment result. If the fluctuation of the environmental condition exceeds the predetermined range, the adjustment start set according to the environmental condition is started. The voltage adjustment operation between peaks is started from the voltage (adjustment start voltage setting).

  Here, the environmental conditions are classified into a plurality of environmental categories for each predetermined range with respect to temperature, humidity (relative humidity or absolute humidity), or a combination thereof, and during the previous and current peak-to-peak voltage adjustment operations. When the fluctuation of the environmental condition is within the same environmental category, start the peak-to-peak voltage adjustment operation from the previous adjustment result of the peak-to-peak voltage, and when the fluctuation of the environmental condition changes across different environmental categories, It is preferable to start the peak-to-peak voltage adjustment operation from a preset adjustment start voltage for each environmental category.

  In addition, as an adjustment start voltage preset for each environment category, for example, an average value of the peak-to-peak voltage adjustment result can be set in advance for each environment category. Thereby, voltage adjustment between peaks can be started from the adjustment start voltage according to the current installation environment.

  In consideration of the difference in the adjustment result due to variations in the charging roller 70 even if the installation environment is the same, if the environmental classification when the previous peak-to-peak voltage is applied and the current environmental classification are the same, the previous adjustment The result is the starting voltage for peak-to-peak voltage adjustment.

  According to the image forming apparatus according to the present embodiment described above, when adjusting the peak-to-peak voltage, it is set in advance according to the previous adjustment result of the peak-to-peak voltage or the environmental conditions in consideration of the change in the installation environment. By starting the peak-to-peak voltage adjustment operation from one of the adjustment start voltages, the peak-to-peak voltage adjustment time can be reduced and the standby time can be shortened. Therefore, the user can comfortably use the image forming apparatus with less waiting time.

  Further, as described above, the charging roller 70 as the charging unit is not in contact with the photosensitive member 40 as the image carrier, so that the charging unit can be made difficult to get dirty. Furthermore, by providing the gap holding members 103 at both ends of the charging roller 70, a stable charging gap can be formed even with time. In the present embodiment, an example in which the charging unit and the image carrier are not in contact with each other has been described.

  Further, since the AC current value is influenced not only by the charging roller 70 but also by the electrostatic capacity of the photoconductor 40, the electrostatic capacity changes when the photosensitive layer of the photoconductor 40 is worn, and the appropriate control target value also changes. End up. For this reason, it is desirable that the wear amount of the photoreceptor 40 be as small as possible.

  Therefore, it is preferable to form a protective layer on the surface of the organic photoreceptor as described above. As a result, the wear resistance of the photoreceptor can be greatly improved at low cost. Further, the change in the capacitance due to the wear of the photosensitive member is reduced, and the correction with respect to the change of the charging means with time can be effectively performed. Further, it is preferable to disperse the metal fine particles in the protective layer because the abrasion resistance of the organic photoreceptor can be further improved.

  The above-described embodiment is a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the gist of the present invention.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, this invention is not limited to these.

<Example>
In the embodiment, the full-color copying machine (image forming apparatus) shown in FIG. 1 is used. The photoreceptor 40 has an undercoat layer of 3.5 .mu.m, a charge generation layer of 0.15 .mu.m, a charge transport layer of 22 .mu.m, and a thickness of 5 .mu.m containing 10% by weight of alumina particles having a particle size of 0.3 .mu.m on the uppermost layer. The one in which a protective layer was formed was used.

  The charging roller 70 is made of a resin composition obtained by blending 60 parts by weight of polyether ester amide, which is an ion conductive material, with 40 parts by weight of ABS resin as a base resin on a core metal 101 made of stainless steel and having an outer diameter of 10 mm. The charging member (resin layer 102) was molded by injection molding, and a surface layer composed of an acrylic silicon resin, an isocyanate curing agent, and a conductive agent was applied to the surface of the charging member to produce an outer diameter of 12.7 mm.

  In addition, gap holding members 103 made of high molecular polyethylene were attached to both ends of the charging roller 70 so that the charging gap was about 70 μm.

  The process linear velocity of this image forming apparatus was 350 mm / s, and the DC component of the charging bias was a sine wave having a voltage V = −700 V and an AC frequency f = 2.5 kHz.

  In order to cope with the gap fluctuation between the photosensitive member 40 and the charging roller 70 when the charging roller 70 is arranged in non-contact with the photosensitive member 40, the result of detecting one or more rotations of the photosensitive member at a sampling interval of 10 msec in the peak-to-peak voltage adjustment operation. Was the AC current detection value.

  As described above, the difference between the target value and the detected value of the charging alternating current is obtained, and the peak-to-peak voltage is gradually changed and adjusted so that the detected value approaches the target value. For this reason, if the target value and the detection value are greatly separated from each other, detection and adjustment are repeated a plurality of times, so that the peak-to-peak voltage adjustment operation takes time.

In this image forming apparatus, a good image can be obtained regardless of the environment by adjusting the charging AC current to be 2.25 mA. At this time, the peak-to-peak voltage at which the charging AC current is 2.25 mA differs depending on the installation environment and the image forming station (image forming unit 18), and is as shown in Table 1. In addition, the environmental classification shown in Table 1 classifies the absolute humidity (g / m ³ ) in the apparatus detected by the temperature / humidity sensor within a predetermined range, and is classified into low temperature and low humidity (less than 5), slightly low temperature and low humidity ( 5 to 10 or less), normal temperature and normal humidity (10 to less than 18), slightly high temperature and high humidity (18 to less than 25), high temperature and high humidity (25 or more).

  The adjustment result of the peak-to-peak voltage is large at low temperature and low humidity, and the tendency to decrease at high temperature and high humidity is the same, but the slight difference between each image forming station is due to the resistance of the charging roller 70 and the variation of the gap. Conceivable.

  Therefore, as shown in Table 2, the adjustment start voltage is set for each environment category, and the environment category when the previous peak-to-peak voltage adjustment was performed is stored. When it is necessary to perform peak-to-peak voltage adjustment, the current environmental classification is compared with the environmental classification when the previous peak-to-peak voltage adjustment was performed. The peak-to-peak voltage adjustment was started, and when the environmental classification did not change, the peak-to-peak voltage adjustment was started from the previous adjustment result voltage.

  As shown in Table 2, for example, by setting an average value of the peak-to-peak voltage adjustment result for each environment category in advance as the adjustment start voltage, the peak-to-peak voltage can be changed from the adjustment start voltage according to the current installation environment. Adjustment can be started. Thus, it was confirmed that the adjustment of the peak-to-peak voltage can be completed in a short time even if the environmental conditions change.

  In addition, even if the installation environment is the same, there is a difference in the adjustment result due to variations in the charging roller 70. Therefore, if the environmental classification when the previous peak-to-peak voltage is applied is the same as the current environmental classification, the previous adjustment result is changed between the peaks. It was confirmed that the adjustment could be completed in a short time by using the voltage adjustment start voltage.

<Comparative Example 1>
In Comparative Example 1, by using the image forming apparatus having the same configuration as that of Example 1, the peak-to-peak voltage adjustment is performed from the average adjustment result of 2.2 kV at normal temperature and humidity regardless of the installation environment and the previous adjustment result. I started.

  When using in a normal temperature and humidity environment, the difference between the adjustment start voltage and the adjustment result is small, so the adjustment is completed in a short time.However, in the low temperature and low humidity environment and the high temperature and high humidity environment, the adjustment start voltage and the adjustment result It was confirmed that the adjustment took time because of the large difference.

<Comparative example 2>
In Comparative Example 2, peak-to-peak voltage adjustment is started from the previous adjustment result voltage using the image forming apparatus having the same configuration as in Example 1 regardless of the installation environment.

  When using continuously in the same environment, the adjustment is completed in a short time because the difference between the adjustment start voltage and the adjustment start voltage is small regardless of the installation environment. It was confirmed that the adjustment takes time because the difference between the adjustment start voltage and the adjustment result is large when the environment changes greatly.

  The effectiveness of the present invention could be confirmed by the above Examples and Comparative Examples 1 and 2.

DESCRIPTION OF SYMBOLS 10 Intermediate transfer belts 14, 15, 16 Support roller 17 Intermediate transfer belt cleaning devices 18, 18Y, 18C, 18M, 18BK Image forming unit 20 Tandem image forming device 21 Exposure device 22 Secondary transfer device 23 Roller 24 Secondary transfer belt 25 Fixing device 26 Fixing belt 27 Pressure roller 28 Reversing device 30 Document table 32 Contact glass 33 First traveling body 34 Second traveling body 35 Imaging lens 36 Reading sensor 40, 40Y, 40C, 40M, 40BK Photosensitive body (photosensitive roller) )
42 paper feed roller 43 paper feed table 44 paper feed cassette 45 separation rollers 46 and 48 paper feed path 47 transport roller 49 registration roller 50 paper feed roller 51 manual feed tray 52 separation roller 53 manual paper feed path 55 switching claw 56 discharge roller 57 discharge Paper tray 60, 60Y, 60C, 60M, 60BK Developing device 61 Developing roller 62, 63 Screw 64 Toner density sensor 65Y, 65C, 65M, 65BK Primary transfer roller 70 Charging roller 71 Potential sensor 72 Static elimination lamp 73 Brush roller 74 Lubricant supply Brush roller 75 Cleaning blade 76 Exposure light 78 Lubricant 79 Toner transfer coil 80 Case 80a Opening portion 81 Lubricant application blade 90 Control unit 91 AC current detection unit (AC current detection unit)
92 Power supply unit 93 Environment detection unit 100 Full-color copier body 101 Core metal 102 Resin layer 103 Gap holding member 200 Paper feed unit 300 Scanner unit 400 Automatic document feeder (ADF)

JP 2010-276822 A

Claims (7)

An image carrier;
Charging means for charging the image carrier;
A high voltage power source for applying a charging bias in which an AC voltage is superimposed on a DC voltage to the charging means;
Current detection means for detecting an alternating current output from the high-voltage power supply;
Peak-to-peak voltage adjusting means for adjusting the peak-to-peak voltage of the AC voltage so that the AC current detected by the current detecting means becomes a predetermined control target value;
Environmental detection means for detecting environmental conditions of the image forming apparatus;
The peak-to-peak voltage adjustment unit stores the peak-to-peak voltage adjustment result when the peak-to-peak voltage adjustment operation is performed, and the environmental condition detected by the environment detection unit, and
Next, when the peak-to-peak voltage adjustment unit performs the peak-to-peak voltage adjustment operation, the environmental condition detected by the environment detection unit at the time point is compared with the stored previous environmental condition,
When the fluctuation of the environmental conditions is within a predetermined range, the peak-to-peak voltage adjustment operation is started from the previous peak-to-peak voltage adjustment result,
An image forming apparatus comprising: an adjustment start voltage setting unit configured to start a peak-to-peak voltage adjustment operation from an adjustment start voltage set according to the environmental condition when the fluctuation of the environmental condition exceeds the predetermined range. .   The image forming apparatus according to claim 1, wherein the environmental condition is any one of a temperature detected by the environment detection unit, a relative humidity, an absolute humidity, or a combination thereof. The environmental conditions are divided into a plurality of environmental categories for each predetermined range,
If the fluctuations in environmental conditions are within the same environmental category, start the peak-to-peak voltage adjustment operation from the previous peak-to-peak voltage adjustment result,
3. The image formation according to claim 1, wherein when the environmental condition varies across different environmental classifications, the peak-to-peak voltage adjustment operation is started from the adjustment start voltage set for each environmental classification. apparatus. The charging means is a charging roller,
4. The image forming apparatus according to claim 1, wherein a charging area of the charging unit is not in contact with the image carrier. The charging roller is
A core bar which is at least a conductive support;
A charging member made of a resin material containing an ion conductive material;
And a gap holding member made of a resin material disposed at both ends of the charging member and in contact with the image carrier to form a gap between the image carrier and the charging member. 5. The image forming apparatus according to 4.   6. The image forming apparatus according to claim 1, wherein the image carrier is an organic photoreceptor, and a protective layer for reducing abrasion of the photoreceptor is formed on the outermost layer.   The image forming apparatus according to claim 6, wherein a metal oxide is dispersed in the protective layer of the organic photoreceptor.

Images