JP2008040224A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain filming from occurring on the surface of an electrifying roll since following rotation ability of the electrifying roll to an image holding body gets worse under low temperature environment. <P>SOLUTION: The image forming apparatus is provided with the electrifying roll 16 electrifying a photoreceptor drum 15, and a cleaning roll 68 coming into contact with the surface of the electrifying roll 16 and cleaning the electrifying roll 16. The photoreceptor drum 15 is driven to be rotated by a motor 62, and the electrifying roll 16 is rotated following the rotation of the photoreceptor drum 15, and then the cleaning roll 68 is rotated following the rotation of the electrifying roll 16. When temperature detected by a temperature sensor 66 is equal to or lower than a predetermined value, a control part 64 performs a mode for idling the photoreceptor drum 15 before image forming operation. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus including a charging roll that rotates following the rotation of an image carrier such as a photoconductor.

  Conventionally, as a charging device for an image forming apparatus such as a copying machine or a printer adopting an electrophotographic method, a device using a corona discharge phenomenon such as a scorotron charger has been widely used, but a charging device using a corona discharge phenomenon is used. In this case, generation of ozone and nitrogen oxides is a problem. In contrast, the contact charging method in which a conductive charging roll or the like is in direct contact with the photosensitive member to charge the photosensitive member generates less ozone and nitrogen oxides and is more power efficient. It has become mainstream.

  In such a contact charging method, a charging roll is brought into pressure contact with the surface of the photosensitive member, and is rotated by the rotation of the photosensitive member. A cleaning member that contacts the surface of the charging roll is provided to clean the surface of the charging roll.

  As this cleaning member, for example, a member that constantly presses a plate brush cleaner against a charging roll with a constant displacement (keep the distance constant) to clean the surface of the charging roll is disclosed (for example, Patent Document 1). See).

  Further, there has been disclosed a technique in which a roll brush cleaner is constantly pressed against a charging roll at a constant displacement, and the surface of the charging roll is cleaned by rotating the roll brush cleaner (see, for example, Patent Document 2).

Further, there is disclosed a technique in which a sponge roll cleaner is constantly pressed against a charging roll at a constant displacement, and the surface of the charging roll is cleaned by rotating the sponge roll cleaner (see, for example, Patent Document 1).
JP-A-2-272594 Japanese Patent Laid-Open No. 2004-101978

However, in a configuration using a plate brush cleaner or a roll brush cleaner, the bristle becomes hard in a low temperature environment, the nip pressure against the charging roll becomes excessive, and the followability of the charging roll due to the rotation of the photoconductor deteriorates. For this reason, troubles such as so-called filming that foreign matters such as toner and external additives adhere to the surface of the charging roll are likely to occur.
Further, in the configuration using the sponge roll cleaner, the sponge becomes hard in a low temperature environment and the nip pressure with respect to the charging roll becomes excessive, and the followability of the charging roll due to the rotation of the photosensitive member is deteriorated. For this reason, troubles such as filming are likely to occur on the surface of the charging roll.

  The present invention has been made in view of the above problems, and an image forming apparatus capable of suppressing the deterioration of driven rotation of the charging roll in a low temperature environment and suppressing the occurrence of filming on the surface of the charging roll. The purpose is to provide.

  In order to solve the above-described problem, an image forming apparatus according to the invention described in claim 1 has an image carrier that is rotationally driven, and has elasticity on the surface, and is rotated in contact with the image carrier, A charging roll that charges the surface of the image carrier, a cleaning member that contacts the charging roll to clean the surface of the charging roll, a temperature sensor that detects temperature, and a temperature detected by the temperature sensor is predetermined. And an idling mode control means for executing a mode for idling the image carrier prior to the image forming operation.

  According to the first aspect of the present invention, the image holding member is driven to rotate, and the charging roll contacting the image holding member rotates following the rotation of the image holding member. At that time, the surface of the charging roll is cleaned by the cleaning member that contacts the surface of the charging roll. In addition, when the temperature is detected by the temperature sensor and the detected temperature is equal to or lower than a predetermined temperature, the idling mode control unit executes a mode for idling the image carrier prior to the image forming operation. In general, in a low-temperature environment, there is a concern that the cleaning member becomes hard, the nip pressure to the charging roll becomes large, and the followability of the charging roll with respect to the rotation of the image carrier is deteriorated. In the present invention, since a mode in which the image carrier is idled when the temperature is equal to or lower than a predetermined temperature is implemented, the surface temperature of the charging roller rises due to friction between the charging roller and the image carrier, and the elasticity of the charging roller is restored. The gripping force between the charging roll and the image carrier increases. For this reason, even if the cleaning member becomes hard and the rotation torque of the charging roll increases, it is possible to maintain the driven rotation of the charging roll and to rotate it stably. For this reason, generation | occurrence | production of the filming on the surface of a charging roll is suppressed, and the trouble resulting from filming is suppressed.

  According to a second aspect of the present invention, there is provided an image forming apparatus having a rotationally driven image holding member and a surface having elasticity, being rotated in contact with the image holding member, and charging the surface of the image holding member. A charging roller; a cleaning member that contacts the charging roller to clean the surface of the charging roller; a temperature sensor that detects temperature; and a mode that idles the image carrier, and the temperature detected by the temperature sensor. And an idling number control means for increasing the idling number of the image carrier in the mode when the temperature is equal to or lower than a prescribed temperature.

  According to the second aspect of the present invention, the image holding member is driven to rotate, and the charging roll contacting the image holding member rotates following the rotation of the image holding member. At that time, the surface of the charging roll is cleaned by the cleaning member that contacts the surface of the charging roll. In addition, when the temperature is detected by the temperature sensor and the detected temperature is equal to or lower than the predetermined temperature, the idling number control means causes the image holding body to rotate in the idle rotation mode than when the temperature is higher than the predetermined temperature. Increase the number of idling. As a result, the surface temperature of the charging roll increases due to the friction between the charging roll and the image holding member, the elasticity of the charging roller is restored, and the gripping force between the charging roll and the image holding member increases. For this reason, even if the cleaning member becomes hard and the rotation torque of the charging roll increases, it is possible to maintain the driven rotation of the charging roll and to rotate it stably. For this reason, filming on the surface of the charging roll is suppressed, and troubles due to filming are suppressed.

  According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the image forming apparatus further comprises a temperature raising member that raises the temperature of the charging roll, and the temperature detected by the temperature sensor is a predetermined temperature. The temperature raising member is operated when the following is true.

  According to the third aspect of the present invention, the temperature raising member for raising the temperature of the charging roll is provided, and the temperature raising member is operated when the temperature detected by the temperature sensor is equal to or lower than the predetermined temperature. Increase the temperature of the charging roll. As a result, it is possible to reduce the time required for the mode in which the image carrier is idled, and it is possible to maintain stable image forming performance while minimizing a decrease in image formation productivity.

  According to a fourth aspect of the present invention, in the image forming apparatus according to the first or second aspect, a temperature raising member for increasing the temperature of the charging roll, and a surface temperature sensor for detecting the temperature of the surface of the charging roll. And when the temperature detected by the surface temperature sensor is equal to or lower than a predetermined temperature, the temperature raising member is operated, and the temperature of the surface of the charging roll detected by the surface temperature sensor is a specified value. It is characterized by keeping above.

  According to the invention described in claim 4, the temperature raising member for raising the temperature of the charging roll is provided, and the temperature detected by the surface temperature sensor for detecting the temperature of the surface of the charging roll is equal to or lower than a predetermined temperature. At some point, the temperature raising member is operated to raise the temperature of the charging roll. Then, the temperature of the surface of the charging roll detected by the surface temperature sensor is kept above a specified value. As a result, the elasticity of the charging roll makes it possible to more reliably maintain the follower rotation of the charging roll, and it is possible to maintain stable image forming performance while minimizing the decrease in image formation productivity. It becomes.

  According to a fifth aspect of the present invention, in the image forming apparatus according to the third or fourth aspect, the cleaning member also serves as the temperature raising member.

  According to the fifth aspect of the present invention, the cleaning member also serves as the temperature raising member, and it is possible to suppress the cleaning member from becoming hard and to maintain the follower rotation of the charging roll with respect to the rotation of the image carrier. Is possible. Further, space can be saved as compared with the case where a temperature raising member is separately provided.

  According to a sixth aspect of the present invention, in the image forming apparatus according to the fifth aspect, the cleaning member includes a metal pipe covered with a sponge or a brush, and the pipe includes a heater. It is characterized by.

  According to the sixth aspect of the present invention, the cleaning member is a metal pipe whose outer periphery is covered with a sponge or brush, and the surface of the cleaning member and the charging roll are raised by the heater provided in the pipe. Be warmed.

  According to a seventh aspect of the present invention, in the image forming apparatus according to the third or fourth aspect, the charging roll includes a metal shaft, and the temperature raising member is a heater disposed in the shaft. It is characterized by being.

  According to invention of Claim 7, the heater is arrange | positioned as a temperature rising member in the metal shaft of the charging roll. As a result, the temperature of the surface of the charging roll can be raised, and the follower rotation of the charging roll with respect to the rotation of the image carrier can be held more reliably. Further, space can be saved as compared with the case where a temperature raising member is separately provided.

  According to an eighth aspect of the present invention, in the image forming apparatus according to the third or fourth aspect, the temperature raising member heats the heat of the fixing device that fixes the toner image on the recording medium to the charging roll. It is characterized by having a conduction path.

  According to the eighth aspect of the present invention, the heat conduction path is provided to send heat of the fixing device for fixing the toner image on the recording medium to the charging roll, and the surface of the charging roll is heated by the heat sent from the fixing device. The temperature rises. For this reason, it is possible to maintain the driven rotation of the charging roll with respect to the rotation of the image carrier.

  According to a ninth aspect of the present invention, in the image forming apparatus according to any one of the first to eighth aspects, a humidity sensor that detects humidity is provided, and the humidity detected by the humidity sensor is a predetermined value. Controlling the idling of the image carrier or the operation of the temperature raising member is as follows.

  According to the ninth aspect of the invention, when the humidity detected by the humidity sensor is equal to or lower than the predetermined value, the idling of the image carrier or the operation of the temperature raising member is controlled, so that the image carrier can be used even in a low humidity environment. Therefore, it is possible to maintain the driven rotation of the charging roll with respect to the rotation of the charging roll.

  According to a tenth aspect of the present invention, in the image forming apparatus according to any one of the first to ninth aspects, the image forming apparatus includes a detection unit that detects a rotation speed of the charging roll, and the detection unit is in an idling mode. When the rotational speed detected in step (b) is equal to or lower than a predetermined value, an additional idling mode for idling the image carrier is performed.

  According to the tenth aspect of the present invention, there is provided detection means for detecting the rotation speed of the charging roll, and when the rotation speed detected by the detection means in the idling mode is not more than a predetermined value, the image carrier An additional idle mode is made to idle. Since the rotation speed of the charging roll is directly detected and the image carrier is idled, an additional idling mode can be performed when necessary to stabilize the driven rotation of the charging roll.

  An eleventh aspect of the present invention is the image forming apparatus according to any one of the third to ninth aspects, further comprising a detection unit that detects a rotation speed of the charging roll, and is detected by the detection unit. The temperature raising member is operated when the rotation speed is not more than a predetermined value.

  According to the eleventh aspect of the present invention, the detecting means for detecting the rotational speed of the charging roll is provided, and the temperature raising member is operated when the rotational speed detected by the detecting means is a predetermined value or less. Increase the temperature of the surface of the charging roll. Since the rotation speed of the charging roll is directly detected, it is possible to stabilize the driven rotation of the charging roll by operating the temperature raising member when necessary.

  According to a twelfth aspect of the present invention, in the image forming apparatus according to the tenth or eleventh aspect, the image forming apparatus includes a warning sound generating device that generates a warning sound, and is detected by the detecting unit after a predetermined time has elapsed from the start of the idling mode. A warning sound is generated by the warning sound generator when the rotation speed is not more than a predetermined value.

  According to the twelfth aspect of the present invention, there is provided a warning sound generating device for generating a warning sound, and when the rotational speed detected by the detecting means is less than or equal to a predetermined value after a predetermined time has elapsed from the start of the idling mode. In addition, a warning sound is generated by a warning sound generator. Thereby, it can be notified to the user that the driven roll of the charging roll is poor.

  ADVANTAGE OF THE INVENTION According to this invention, it can suppress that the driven rotation property of a charging roll deteriorates in a low-temperature environment, and generation | occurrence | production of filming etc. on the surface of a charging roll can be suppressed.

  Embodiments of an image forming apparatus according to the present invention will be described below with reference to the drawings.

  FIG. 1 shows an image forming apparatus 1 according to the first embodiment of the present invention.

The image forming apparatus 1 is a tandem digital color printer, and image data sent from an exposure apparatus for a manuscript (not shown), a personal computer, or the like is sent to an image processing apparatus 12 (for example, IPS: Image Processing System). And predetermined image processing is performed. Image data that has been subjected to predetermined image processing by the image processing device 12 is also processed by the image processing device 12 into 4 of yellow (Y), magenta (M), cyan (C), and black (K) (each 8 bits). As described below, the image forming units 13Y, 13M, 13C for each color of yellow (Y), magenta (M), cyan (C), and black (K) are converted into color original reproduction color material gradation data. It is sent to the 13K exposure device 14. In this exposure device 14, image exposure with laser light LB is performed in accordance with document reproduction color material gradation data of a predetermined color.
Inside the image forming apparatus 1, four image forming units 13Y, 13M, 13C, and 13K of yellow (Y), magenta (M), cyan (C), and black (K) are spaced at a constant interval in the horizontal direction. Are arranged in parallel. These four image forming units 13Y, 13M, 13C, and 13K are all configured in the same manner. The photosensitive drum 15 that is rotationally driven and the charging roll 16 that uniformly charges the surface of the photosensitive drum 15 are provided. An exposure device 14 that exposes an image corresponding to a predetermined color on the surface of the photosensitive drum 15 to form an electrostatic latent image, and an electrostatic latent image formed on the photosensitive drum 15 is converted to a predetermined color. A developing unit 17 that develops toner and a cleaning device 18 that cleans the surface of the photosensitive drum 15 are configured.

  The exposure device 14 is configured in common to the four image forming units 13Y, 13M, 13C, and 13K, and modulates four semiconductor lasers (not shown) in accordance with the original reproduction color material gradation data of each color. Laser light LB-Y, LB-M, LB-C, and LB-K are emitted from the semiconductor laser in accordance with the gradation data. Of course, the exposure device 14 may be individually configured for each of a plurality of image forming units. The laser beams LB-Y, LB-M, LB-C, and LB-K emitted from the semiconductor laser are irradiated to the polygon mirror 19 through an f-θ lens (not shown), and are deflected and scanned by the polygon mirror 19. The The laser beams LB-Y, LB-M, LB-C, and LB-K deflected and scanned by the polygon mirror 19 pass through an imaging lens (not shown) and a plurality of mirrors to an exposure point on the photosensitive drum 15. Then, scanning exposure is performed obliquely from below.

  Since the exposure device 14 scans and exposes an image on the photosensitive drum 15 from below, the exposure device 14 includes the developing units 17 of four image forming units 13Y, 13M, 13C, and 13K positioned above. There is a risk that the toner or the like may fall off and be soiled. Therefore, the periphery of the exposure apparatus 14 is hermetically sealed by a rectangular parallelepiped frame 20, and four laser beams LB-Y, LB-M, LB-C, and LB-K are applied to the upper portion of the frame 20. Transparent glass windows 21Y, 21M, 21C, and 21K as shield members are provided for exposure on the photosensitive drums 15 of the image forming units 13Y, 13M, 13C, and 13K.

  From the image processing device 12, an exposure device 14 is provided in common for the image forming units 13Y, 13M, 13C, and 13K for each color of yellow (Y), magenta (M), cyan (C), and black (K). The image data of each color is sequentially output. Laser beams LB-Y, LB-M, LB-C, and LB-K emitted from the exposure device 14 in accordance with image data are scanned and exposed on the surface of the corresponding photosensitive drums 15 to form an electrostatic latent image. Is done. The electrostatic latent image formed on the photoconductor drum 15 is developed by toners of yellow (Y), magenta (M), cyan (C), and black (K), respectively, by developing units 17Y, 17M, 17C, and 17K. Developed as an image.

  The yellow (Y), magenta (M), cyan (C), and black (K) toner images sequentially formed on the photosensitive drums 15 of the image forming units 13Y, 13M, 13C, and 13K On the intermediate transfer belt 25 of the transfer unit 22 arranged over the image forming units 13Y, 13M, 13C, and 13K, the images are transferred in multiple by the four primary transfer rolls 26Y, 26M, 26C, and 26K. These primary transfer rolls 26Y, 26M, 26C, and 26K are disposed on the back side of the intermediate transfer belt 25 corresponding to the photosensitive drums 15 of the image forming units 13Y, 13M, 13C, and 13K. A transfer bias power source (not shown) is connected to the primary transfer rolls 26Y, 26M, 26C, and 26K, and a transfer bias having a polarity opposite to a predetermined toner polarity (positive polarity in the present embodiment) is set at a predetermined timing. Applied.

  The intermediate transfer belt 25 is wound around the drive roll 27, the tension roll 24, and the backup roll 28 with a constant tension, and is rotated by a motor (not shown) by a drive roll 27 shown in the drawing. Circulation is driven around at a predetermined speed.

  The yellow (Y), magenta (M), cyan (C), and black (K) toner images transferred onto the intermediate transfer belt 25 in a multiple manner are transferred to the backup roll 28 by a secondary transfer roll 29. The recording paper 30 that has been secondarily transferred onto the recording paper 30 as a sheet and onto which the toner images of these colors have been transferred is conveyed to a fixing device 31 positioned above. The secondary transfer roll 29 is in pressure contact with the side of the backup roll 28 and is configured to secondary-transfer toner images of each color onto a recording paper 30 that is conveyed from below to above. The fixing device 31 includes a heating roll 56 heated to a predetermined temperature, and a pressure roll 58 pressed against the heating roll 56. The recording paper 30 onto which the toner images of the respective colors have been transferred undergoes a fixing process by heat and pressure at the pressure contact portion between the heating roll 56 and the pressure roll 58, and is then placed on the upper portion of the image forming apparatus 1 by the discharge roll 32. The paper is discharged onto a provided discharge tray 33.

  The recording paper 30 having a predetermined size from the paper feed cassette 34 is once transported to a registration roll 38 via a paper transport path 37 by a paper feed roller 35 and a pair of paper separating and transporting rollers 36 and stopped. . The paper transport path 37 of the fed recording paper 30 is directed upward in the vertical direction. The recording paper 30 supplied from the paper feed cassette 34 is sent to the secondary transfer position of the intermediate transfer belt 25 by a registration roll 38 that rotates at a predetermined timing.

  When the image forming apparatus 1 makes a full-color double-sided copy, the recording sheet 30 having an image fixed on one side is not directly discharged onto the discharge tray 33 by the discharge roll 32 but is not shown. To switch the transport direction and transport the paper to the duplex transport unit 40 via the pair of paper transport rollers 39. In the double-sided conveyance unit 40, the recording paper 30 is conveyed again to the registration roll 38 with the pair of conveyance rollers (not shown) provided along the conveyance path 41 being reversed. Then, after the image is transferred and fixed on the back surface of the recording paper 30, it is discharged onto the discharge tray 33.

  Further, residual toner, paper dust, and the like are removed from the surface of the photosensitive drum 15 after the toner image transfer process is completed by the cleaning device 18 to prepare for the next image forming process. The cleaning device 18 includes a cleaning blade (not shown), and removes residual toner, paper dust, and the like on the photosensitive drum 15 by the cleaning blade.

  Further, residual toner, paper dust, and the like are removed from the surface of the intermediate transfer belt 25 after the toner image transfer process is completed by the cleaning device 43 to prepare for the next image forming process. The cleaning device 43 includes a cleaning brush 43a and a cleaning blade 43b, and the cleaning brush 43a and the cleaning blade 42 remove residual toner, paper dust, and the like on the intermediate transfer belt 25.

  In addition, toner cartridges 44Y, 44M, 44C, and 44K that store yellow, magenta, cyan, and black toners are respectively provided in the upper part of the inside of the image forming apparatus 1. The color toner is supplied.

  Further, a manual feed tray 47 capable of stacking arbitrary sheets is attached to the side surface (left side surface in FIG. 1) of the image forming apparatus 1. A recording paper 52 as a sheet is set on the manual feed tray 47, and the recording paper 52 is fed by a paper feed roller 54 and conveyed to the registration roll 38. The recording sheet 52 is different in type and size from the recording sheet 30 described above.

  As shown in FIG. 2, a motor 62 is connected to the shaft of the photosensitive drum 15, and the drive of the motor 62 is controlled by the control unit 64. For example, a stepping motor is used as the motor 62. Further, a temperature sensor 66 for detecting the temperature is provided at a position facing the photosensitive drum 15. When the temperature detected by the temperature sensor 66 is equal to or lower than a predetermined temperature (for example, 15 ° C.), the controller 64 performs an idling mode in which the photosensitive drum 15 is idled a predetermined number of times prior to the image forming operation. Is set to In addition, about the range which can set the temperature which implements idling mode, an optimal setting value fluctuates between 12 degreeC-17 degreeC by the material of the member to be used, or accumulation use time.

  Further, the charging roll 16 is configured to come into contact with the surface of the photosensitive drum 15 and rotate in the arrow direction following the rotation of the photosensitive drum 15. In addition, a cleaning roll 68 that contacts the surface of the charging roll 16 and cleans the surface of the charging roll 16 is provided. The cleaning roll 68 has a sponge layer 68B formed on the peripheral surface of the shaft 68A, and is configured to rotate in the direction of the arrow following the rotation of the charging roll 16.

  Next, details of the charging roll 16 will be described.

  In the charging roll 16, a conductive elastic layer and a surface layer are sequentially formed as a charging layer 16B on a conductive shaft 16A.

  The diameter of the charging roll 16 is preferably 7 mm to 15 mm, more preferably 8 mm to 14 mm, and the thickness of the charging layer 16B is preferably 2 mm to 4 mm. If the diameter is 15 mm or more, the number of times of contact with the external additive per location on the peripheral surface is reduced, and the number of discharges is reduced. This is disadvantageous from the viewpoint of miniaturization, although it has excellent long-term stability against dirt and charging performance. . If the diameter is 7 mm or less, the image forming apparatus 1 can be downsized, which is advantageous. However, the number of times of contact with the external additive per peripheral surface increases and the number of discharges increases, which is disadvantageous for long-term stability. It becomes.

  Needless to say, the charging roll 16 is not limited to the following configuration as long as it has a predetermined charging performance.

  As the material of the shaft 16A, free-cutting steel, stainless steel or the like is used, and the material and surface treatment method are appropriately selected according to the use such as slidability, and the material having no conductivity is generally plated. It may be processed by an appropriate process and a conductive process may be performed.

  The conductive elastic layer constituting the charging layer 16B of the charging roll 16 may be, for example, an elastic material such as rubber having elasticity, a conductive material such as carbon black or ionic conductive material for adjusting the resistance of the conductive elastic layer, or the like. Accordingly, materials that can be usually added to rubber, such as softeners, plasticizers, curing agents, vulcanizing agents, vulcanization accelerators, anti-aging agents, and fillers such as silica and calcium carbonate, may be added. It is formed by coating the peripheral surface of the conductive shaft 16 </ b> A with a mixture in which materials usually added to rubber are added. As a conductive agent for the purpose of adjusting the resistance value, a material in which a material that conducts electricity using electrons and / or ions as a charge carrier, such as carbon black or an ionic conductive agent blended in a matrix material, is used. it can. The elastic material may be a foam.

  The elastic material constituting the conductive elastic layer is formed, for example, by dispersing a conductive agent in a rubber material. Rubber materials include isoprene rubber, chloroprene rubber, epichlorohydrin rubber, butyl rubber, urethane rubber, silicone rubber, fluorine rubber, styrene-butadiene rubber, butadiene rubber, nitrile rubber, ethylene propylene rubber, epichlorohydrin-ethylene oxide copolymer rubber, epichlorohydrin-ethylene oxide. -Allyl glycidyl ether copolymer rubber, ethylene-propylene-diene terpolymer rubber (EPDM), acrylonitrile-butadiene copolymer rubber, natural rubber and the like, and blended rubbers thereof. Among these, silicone rubber, ethylene propylene rubber, epichlorohydrin-ethylene oxide copolymer rubber, epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer rubber, acrylonitrile-butadiene copolymer rubber, and blended rubbers thereof are preferably used. These rubber materials may be foamed or non-foamed.

  As the conductive agent, an electronic conductive agent or an ionic conductive agent is used. Examples of electronic conductive agents include carbon blacks such as ketjen black and acetylene black; pyrolytic carbon, graphite; various conductive metals or alloys such as aluminum, copper, nickel, and stainless steel; tin oxide, indium oxide, titanium oxide Examples thereof include fine powders such as various conductive metal oxides such as tin oxide-antimony oxide solid solution and tin oxide-indium oxide solid solution; Examples of ionic conductive agents include perchlorates and chlorates such as tetraethylammonium and lauryltrimethylammonium; alkali metals such as lithium and magnesium; perchlorates and chlorates of alkaline earth metals Can be mentioned.

  The surface layer constituting the charging layer 16B is formed to prevent contamination by foreign matters such as toner, and the surface layer material may be any of resin, rubber, etc. It is not limited. Polyester, polyimide, copolymer nylon, silicone resin, acrylic resin, polyvinyl butyral, ethylene tetrafluoroethylene copolymer, melamine resin, fluoro rubber, epoxy resin, polycarbonate, polyvinyl alcohol, cellulose, polyvinylidene chloride, polyvinyl chloride, polyethylene And ethylene vinyl acetate copolymer. Of these, polyvinylidene fluoride, a tetrafluoroethylene copolymer, polyester, polyimide, and copolymer nylon are preferably used from the viewpoint of contamination of the external additive.

  The surface layer can contain a conductive material to adjust the resistance value. The conductive material preferably has a particle size of 3 μm or less. In addition, as a conductive agent for the purpose of adjusting the resistance value, it electrically conducts electrons and / or ions as charge carriers, such as carbon black, conductive metal oxide particles, or ionic conductive agent blended in the matrix material. What disperse | distributed material etc. can be used.

  The surface layer may be made of a fluorine-based or silicone-based resin, and is preferably composed of a fluorine-modified acrylate polymer. Further, fine particles may be added to the surface layer. As a result, the surface layer becomes hydrophobic and acts to prevent the foreign matter from adhering to the charging roll 16. Further, insulating particles such as alumina and silica are added to give unevenness to the surface of the charging roll 16, thereby reducing the burden at the time of rubbing against the photosensitive drum 15, and the charging roll 16 and the photosensitive drum. It is also possible to improve the mutual wear resistance.

  Next, the cleaning roll 68 will be described.

  As the material of the shaft 68A of the cleaning roll 68, free-cutting steel, stainless steel or the like is used, and the material and the surface treatment method are appropriately selected according to the use such as slidability, and the material does not have conductivity. May be processed by a general process such as a plating process and subjected to a conductive process, or may be used as it is. Further, since the cleaning roll 68 comes into contact with the charging roll 16 through the sponge layer 68B with an appropriate nip pressure, the shaft diameter having sufficient rigidity with respect to a material having a strength that does not bend at the nip or the shaft length is sufficient. Selected.

  The sponge layer 68B is made of a foam having a porous three-dimensional structure, has cavities and irregularities (hereinafter referred to as cells) inside and on the surface, and has elasticity. The sponge layer 68B is selected from materials made of foaming resin or rubber such as polyurethane, polyethylene, polyamide, olefin, melamine or polypropylene, NBR, EPDM, natural rubber, styrene butadiene rubber, chloroprene, silicone, nitrile, etc. Is done. Thereby, the sponge layer 68B having a large number of cells can be manufactured at low cost. The sponge layer 68B efficiently cleans foreign substances such as external additives by driven sliding rubbing with the charging roll 16, and at the same time, the surface of the charging roll 16 is not scratched by rubbing of the sponge layer 68B. In order to prevent tearing and breakage, it is particularly preferable to use polyurethane that is strong in tearing and tensile strength.

  It is not particularly limited as polyurethane, polyol such as polyester polyol, polyether polyester and acrylic polyol, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4-diphenylmethane diisocyanate, tolidine diisocyanate, It only needs to be accompanied by a reaction of an isocyanate such as 1,6-hexamethylene diisocyanate, and a chain extender such as 1,4-butanediol or trimethylolpropane is preferably mixed. In general, foaming is performed using a foaming agent such as water, azodicarbonamide, azo compounds such as azobisisobutyronitrile. Further, auxiliary agents such as foaming aids, foam stabilizers, catalysts, etc. may be added as necessary.

  The number of cells of the cleaning roll 68 is preferably 40 to 80/25 mm, and more preferably 45 to 75/25 mm. By setting the number of cells as described above, foreign matters such as toner and external additives can be easily taken into the cells, and foreign matters such as external additives taken in can be easily transferred to the charging roll 16 and the photosensitive drum 15. (This phenomenon will be described later). When the number of cells is more than 80/25 mm, the cell diameter is small, so the uptake of the external additive is reduced. Conversely, when the number of cells is less than 40/25 mm, the cell diameter becomes too large and the incorporated external additive. It is difficult to harden to an appropriate size for transferring the toner to the charging roll 16.

  Next, the operation of the image forming apparatus 1 having the above configuration will be described. As shown in FIG. 2, the photosensitive drum 15 is rotated by driving the motor 62, and the charging roll 16 that contacts the photosensitive drum 15 is rotated by the rotation of the photosensitive drum 15. The cleaning roll 68 rotates following the rotation of the charging roll 16, and the surface of the charging roll 16 is cleaned.

  In general, in a low-temperature environment, there is a concern that the cleaning roll becomes hard, the nip pressure to the charging roll increases, and the followability of the charging roll with respect to the rotation of the photosensitive drum deteriorates. In the present embodiment, when the temperature is detected by the temperature sensor 66 and the detected temperature is equal to or lower than a predetermined temperature (for example, 15 ° C.), the control unit 64 causes the photoconductor drum 15 to be predetermined before the image forming operation. The idling mode for idling the number of times is performed (for example, idling the photosensitive drum 15 20 times). In addition, about the range which can set the temperature which implements idling mode, an optimal setting value fluctuates between 12 degreeC-17 degreeC by the material of the member to be used, or accumulation use time.

  As a result, the surface temperature of the charging roll 16 increases due to friction between the charging roll 16 and the photosensitive drum 15, the elasticity of the charging roll 16 is restored, and the gripping force between the charging roll 16 and the photosensitive drum 15 increases. For this reason, even if the cleaning roll 68 becomes hard and the rotation torque of the charging roll 16 increases, the driven roll of the charging roll 16 can be maintained and can be rotated stably. For this reason, filming on the surface of the charging roll 16 can be suppressed, and trouble caused by filming can be suppressed.

  The control unit 64 may have an idle mode in which the photosensitive drum 15 idles a predetermined number of times, and may rotate the photosensitive drum 15 every time a predetermined number of copies are printed. Then, when the temperature detected by the temperature sensor 66 is equal to or lower than a predetermined temperature, the number of idling of the photosensitive drum 15 in the idling mode may be increased more than when the temperature is higher than the predetermined temperature. Thereby, the driven rotational property of the charging roll 16 can be further stabilized.

  In the image forming apparatus 1 shown in FIG. 1, an image printing test was performed with the amount of biting of the cleaning roll 68 set to 0.8 mm. It occurred at a rate (operating environment was 10 ° C., 15% RH). Further, when continuous printing was performed by repeating the printing of 10 sheets as it was, streaky white spots were seen on the entire sheet after about 1000 sheets, and white filming occurred on the surface of the charging roll 16.

  On the other hand, when the idling mode of the photoconductive drum 15 is performed before every image forming job (for example, 1 job = 10 sheets printed), and the photoconductive drum 15 is idled by 20 revolutions, the image is printed. Image quality defects due to slippage of the charging roll 16 did not occur, and filming of the charging roll 16 did not occur up to 200,000 prints that are the life of the photosensitive drum 15 even in continuous printing.

  However, in the same test in which the number of idling of the photosensitive drum 15 is reduced to 10 rotations and the same test in which the idling mode is reduced to a frequency of once every two jobs, both are about 3000 sheets and a streak-like white by filming. Omission occurred.

  Next, an image forming apparatus according to a second embodiment of the present invention will be described.

  In addition, the same code | symbol is attached | subjected to the member same as 1st Embodiment, and the overlapping description is abbreviate | omitted.

  As shown in FIG. 3, a non-contact radiant heater 72 as a temperature raising member for raising the temperature of the surface of the charging roll 16 is provided at a position facing the charging roll 16. When the temperature detected by the temperature sensor 66 is equal to or lower than a predetermined temperature, the control unit 64 causes the photosensitive drum 15 to idle (idle rotation) and simultaneously turns on the heater 72 (energizes). The heater 72 does not have a very large output (for example, 50 W). For example, a far infrared radiation heater such as a halogen heater or a ceramic heater is used.

  In such an image forming apparatus, when the temperature detected by the temperature sensor 66 is equal to or lower than a predetermined temperature, the heater 72 is turned on to increase the surface temperature of the charging roll 16. As a result, the time required for the idle rotation mode of the photosensitive drum 15 can be shortened, and stable image forming performance can be maintained while minimizing the decrease in productivity of image formation.

  Using the image forming apparatus shown in FIG. 3, a test was performed in which the heater 72 was turned on and the charging roll 16 was weakly warmed only when the photosensitive drum 15 was in the idling mode. Image quality defects due to slip and filming did not occur.

  Next, an image forming apparatus according to a third embodiment of the present invention will be described.

  In addition, the same code | symbol is attached | subjected to the member same as 1st and 2nd embodiment, and the overlapping description is abbreviate | omitted.

  As shown in FIG. 4, the photosensitive drum 85 rotates in the reverse direction (clockwise) with respect to FIG. 1, and the charging roll 86 and the charging roll 86 are arranged in the lateral direction of the photosensitive drum 85 sequentially from the upstream side in the rotational direction of the photosensitive drum 85. A developing unit 83 is provided below the photosensitive drum 85, and a cleaning device 88 is provided above the photosensitive drum 85. A cleaning roll 68 that contacts the charging roll 86 is provided in the lateral direction of the charging roll 86.

  Below the charging roll 86, a non-contact heat conduction type heater 92 having a low output (for example, about 50 W) is disposed. A temperature sensor 94 that detects the surface temperature of the charging roll 86 is provided at a position facing the surface of the charging roll 86. When the surface temperature detected by the temperature sensor 94 is equal to or lower than a predetermined temperature (for example, 18 ° C.), the control unit 96 turns on the heater 92 and defines the surface temperature of the charging roll 86 detected by the temperature sensor 94. It is comprised so that it may keep above a value (for example, 18 degreeC). In addition, about the range which can set the temperature which turns ON the heater 92, an optimal setting value fluctuates between 15 degreeC-20 degreeC by the material of the member to be used, or accumulation use time.

  In such an image forming apparatus, when the surface temperature of the charging roll 86 detected by the temperature sensor 94 is equal to or lower than a predetermined temperature, the heater 92 is turned on to increase the surface temperature of the charging roll 86. Then, the surface temperature of the charging roll 86 detected by the temperature sensor 94 is kept above a specified value. As a result, the driven rotation of the charging roll 86 can be further stabilized, and stable image forming performance can be maintained while minimizing the decrease in image formation productivity.

  Using the image forming apparatus shown in FIG. 4, a test was performed in which the heater 92 was turned on and the charging roll 86 was weakly warmed only when the photosensitive drum 85 was in the idle rotation mode. It was divided into cases where image quality defects due to slip and filming occurred and cases where they did not. When the idling rotation speed of the photosensitive drum 85 was set to 15 rotations, no image quality defect occurred.

  Next, an image forming apparatus according to a fourth embodiment of the present invention will be described.

  In addition, the same code | symbol is attached | subjected to the member same as 1st to 3rd embodiment, and the overlapping description is abbreviate | omitted.

  As shown in FIG. 5, a cleaning roll 102 is provided so as to contact the surface of the charging roll 86. The cleaning roll 102 is obtained by covering the outer periphery of a metal pipe 102A with a sponge layer 102B, and includes a heater 104 as a temperature raising member inside the pipe 102A. As the heater 104, a non-contact heat conduction type heater with a low output (for example, about 50 W) is used. The controller 96 is set to turn on the heater 104 simultaneously with the idling of the photosensitive drum 85 when the temperature detected by the temperature sensor 66 is equal to or lower than a predetermined temperature.

  In such an image forming apparatus, the surface of the cleaning roll 102 and the charging roll 86 are heated by the heater 104 provided in the pipe 102 </ b> A of the cleaning roll 102. As a result, the sponge layer 102 </ b> B of the cleaning roll 102 is suppressed from becoming hard, and the driven rotation of the charging roll 86 with respect to the rotation of the photosensitive drum 15 can be maintained. Further, the cleaning roll 102 also serves as a temperature raising member (heater), and space can be saved as compared with a case where a temperature raising member (heater) is separately provided.

  A test was performed using the image forming apparatus shown in FIG. 5 to heat the charging roll 86 weakly by turning on the heater 104 only when the photosensitive drum 85 is in the idling mode. Image quality defects due to slip and filming did not occur. When the output of the heater 104 was lowered to 30 W, there were cases where image quality defects occurred and cases where they did not occur.

  As shown in FIG. 6, in the image forming apparatus in which the charging roll 16 is disposed below the photosensitive drum 15, the cleaning roll having the heater 104 in the pipe 102A is used as a cleaning roll for cleaning the charging roll 16. 102 may be provided.

  Next, an image forming apparatus according to a fifth embodiment of the present invention will be described.

  In addition, the same code | symbol is attached | subjected to the member same as 1st-4th embodiment, and the overlapping description is abbreviate | omitted.

  As shown in FIG. 7, a charging roll 112 is provided so as to be in contact with the surface of the photosensitive drum 85. The charging roll 112 includes a charging layer 112B on the outer periphery of a metal pipe 112A, and a heater 114 as a temperature raising member inside the pipe 112A. As the heater 114, a non-contact heat conduction type heater having a low output (for example, about 50 W) is used. A cleaning roll 68 is provided so as to be in contact with the surface of the charging roll 112. The controller 96 is set to turn on the heater 114 at the same time as rotating the photosensitive drum 85 when the temperature detected by the temperature sensor 66 is equal to or lower than a predetermined temperature.

  In such an image forming apparatus, the temperature of the surface of the charging roll 112 is raised by the heater 114 provided in the pipe 112 </ b> A of the charging roll 112. Accordingly, the temperature of the cleaning roll 68 is also raised. As a result, the sponge layer 68 </ b> B of the cleaning roll 68 is suppressed from becoming hard, and the driven rotation of the charging roll 112 with respect to the rotation of the photosensitive drum 85 can be maintained. Further, the charging roll 112 also serves as a temperature raising member (heater), and space can be saved as compared with a case where a temperature raising member (heater) is separately provided.

  A test was performed using the image forming apparatus shown in FIG. 7 to heat the charging roller 112 weakly by turning on the heater 114 only when the photosensitive drum 85 is in the idling mode. Image quality defects due to slip and filming did not occur. Further, even when the output of the heater 114 was lowered to 30 W, no image quality defect occurred.

  Next, an image forming apparatus according to a sixth embodiment of the present invention will be described.

  In addition, the same code | symbol is attached | subjected to the member same as 1st to 5th embodiment, and the overlapping description is abbreviate | omitted.

  As shown in FIG. 8, a charging roll 122 is provided so as to come into contact with the photosensitive drum 85. The charging roll 122 includes a cylindrical shaft 122A and a charging layer 122B. Further, on the downstream side of the developing unit 83 in the rotation direction of the photosensitive drum 85, a transfer roll 124 for transferring the toner image formed on the photosensitive drum 85 to a recording sheet is disposed. On the downstream side of the transfer roll 124 in the recording sheet conveyance direction, a heating roll 126 and a pressure roll 128 are disposed as a fixing device for fixing the toner image on the recording sheet. A heater 127 is provided inside the heating roll 126.

  As shown in FIG. 9, a pipe 130 is provided as a heat conduction path so as to connect one end of the heating roll 126 and one end of the charging roll 122, and a fan 134 is provided on the pipe 130. It has been. In addition, a pipe 132 is provided as a heat conduction path so as to connect the other end of the heating roll 126 and the other end of the charging roll 122.

  In such an image forming apparatus, air is sent from the heating roll 126 through the pipe 130 in a fixed direction by the fan 134 and is sent into the cylindrical shaft 122 </ b> A of the charging roll 122. Then, the air that has passed through the shaft 122 </ b> A is returned to the heating roll 126 through the pipe 132. That is, the heat of the heater 127 in the heating roll 126 is refluxed into the shaft 122 </ b> A of the charging roll 122, so that the heat is transmitted to the charging roll 122. As a result, it is possible to maintain the driven rotation of the charging roll 122 with respect to the photosensitive drum 85.

  When the image formation test was performed using the image forming apparatus shown in FIGS. 8 and 9, there was no image quality defect due to slipping or filming of the charging roll 122 even when the idling rotation number of the photosensitive drum 85 was 10. .

  Next, an image forming apparatus according to a seventh embodiment of the present invention will be described.

  In addition, the same code | symbol is attached | subjected to the member same as 1st-6th embodiment, and the overlapping description is abbreviate | omitted.

  As shown in FIG. 10, the image forming apparatus includes a detection device 142 that detects the rotation speed of the charging roll 16. The detection device 142 detects a plurality of slits provided at the end of the charging roll 16 in the axial direction, measures the time from detection of one slit to detection of another slit, and the charging roll 16. The rotation speed is calculated. The control unit 64 performs an additional idle rotation mode for causing the photosensitive drum 15 to idle when the rotation speed detected by the detection device 142 in the idle rotation mode is equal to or less than a predetermined value. Further, the control unit 64 turns on the heater 72 when the rotation speed detected by the detection device 142 is equal to or less than a predetermined value.

  In this image forming apparatus, a speaker 144 is provided in a housing (not shown). The control unit 64 performs control such that a warning sound is generated from the speaker 144 when the rotation speed detected by the detection device 142 is equal to or less than a predetermined value after a predetermined time has elapsed from the start of the idling mode.

  In such an image forming apparatus, when the rotation speed of the charging roll 16 is detected by the detection device 142 and the detected rotation speed is equal to or less than a predetermined value, an additional idle rotation mode is performed in which the photosensitive drum 15 is idled. At the same time, the heater 72 is turned on. Thereby, the temperature of the surface of the charging roll 16 rises. By directly detecting the rotation speed of the charging roll 16, the surface temperature of the charging roll 16 can be raised only when necessary. Therefore, the charging roll 16 can be stably driven and rotated with respect to the photosensitive drum 15. In addition, the control unit 64 generates a warning sound from the speaker 144 when the rotation speed detected by the detection device 142 is equal to or less than a predetermined value after a predetermined time has elapsed since the start of the idling mode. Thereby, it can be notified to the user that the driven rotation of the charging roll 16 is poor.

  In the above embodiment, the temperature is detected by the temperature sensor. However, the present invention is not limited to this configuration, and the temperature and humidity sensor that detects the temperature and humidity is used to detect the photosensitive drum when the temperature is equal to or lower than a predetermined temperature and humidity. The idling of the heater, the energization of the heater, and the like may be controlled. In particular, since the cleaning roll is likely to be hard in a low-temperature and low-humidity environment, it is possible to suppress deterioration in the followability of the charging roll by detecting and controlling the temperature and humidity.

  In the above embodiment, the cleaning roll in which the sponge layer is brought into contact with the surface of the charging roll is used. However, the present invention is not limited to this configuration. For example, the same effect can be obtained by using a cleaning brush that contacts the surface of the charging roll. The cleaning member is not limited to a rotating member, and a fixed sponge member or brush member may be used.

  The image forming apparatus 1 of the present embodiment has a configuration in which image forming units of yellow, magenta, cyan, and black are arranged in parallel along the moving direction of the intermediate transfer belt. However, the present invention is not limited to this configuration. . For example, the present invention can also be applied to an image forming apparatus that repeatedly forms a toner image on a photosensitive drum by four cycles using a rotary developing device having four color developing devices. .

1 is a schematic configuration diagram illustrating an image forming apparatus according to a first embodiment of the present invention. FIG. 2 is a configuration diagram showing the vicinity of a photosensitive drum and a charging roll used in the image forming apparatus shown in FIG. 1. FIG. 6 is a configuration diagram showing the vicinity of a photosensitive drum and a charging roll used in an image forming apparatus according to a second embodiment of the present invention. FIG. 6 is a configuration diagram showing the vicinity of a photosensitive drum and a charging roll used in an image forming apparatus according to a third embodiment of the present invention. FIG. 10 is a configuration diagram showing the vicinity of a photosensitive drum and a charging roll used in an image forming apparatus according to a fourth embodiment of the present invention. It is a block diagram which shows the modification of the image forming apparatus which concerns on 4th Embodiment of this invention. FIG. 10 is a configuration diagram showing the vicinity of a photosensitive drum and a charging roll used in an image forming apparatus according to a fifth embodiment of the present invention. It is a block diagram which shows the circumference | surroundings of the photoconductive drum of the image forming apparatus which concerns on 6th Embodiment of this invention. FIG. 9 is a side view showing the vicinity of a charging roll and a heating roll of the image forming apparatus shown in FIG. 8. FIG. 10 is a configuration diagram showing the vicinity of a photosensitive drum and a charging roll used in an image forming apparatus according to a seventh embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 15 Photosensitive drum (Image holding body)
16 Charging roll 16A Shaft 16B Charging layer 62 Motor 64 Control unit (idling mode control means)
66 Temperature Sensor 68 Cleaning Roll (Cleaning Member)
68A Shaft 68B Sponge layer 72 Heater (temperature raising member)
85 Photosensitive drum (image carrier)
86 Charging roll 88 Cleaning device 92 Heater (temperature raising member)
92 Charging roll 94 Temperature sensor 96 Control unit (idling mode control means)
102 Cleaning roll (cleaning member)
102B Sponge layer 102A Pipe 104 Heater (temperature raising member)
112A Pipe 112 Charging roll 112B Charging layer 114 Heater (temperature raising member)
122A Shaft 122 Shaft 122 Charging roll 122B Charging layer 126 Heating roll (fixing device)
127 Heater 128 Pressure roll (fixing device)
130 Pipe (heat conduction path)
132 Pipe (heat conduction path)
134 Fan 142 Detection Device (Detection Means)
144 Speaker (warning sound generator)

Claims (12)

An image carrier that is rotationally driven;
A charging roll having elasticity on the surface, rotating in contact with the image carrier, and charging the surface of the image carrier;
A cleaning member that contacts the charging roll and cleans the surface of the charging roll;
A temperature sensor for detecting the temperature;
When the temperature detected by the temperature sensor is equal to or lower than a predetermined temperature, an idling mode control unit that implements a mode for idling the image carrier prior to an image forming operation;
An image forming apparatus comprising: An image carrier that is rotationally driven;
A charging roll having elasticity on the surface, rotating in contact with the image carrier, and charging the surface of the image carrier;
A cleaning member that contacts the charging roll and cleans the surface of the charging roll;
A temperature sensor for detecting the temperature;
A mode in which the image carrier is idled, and when the temperature detected by the temperature sensor is equal to or lower than a predetermined temperature, the number of idling of the image carrier in the mode is increased more than when the temperature is higher than the predetermined temperature. Idle speed control means;
An image forming apparatus comprising: A temperature raising member for raising the temperature of the charging roll;
The image forming apparatus according to claim 1, wherein the temperature raising member is operated when a temperature detected by the temperature sensor is equal to or lower than a predetermined temperature. A temperature raising member for raising the temperature of the charging roll;
A surface temperature sensor for detecting the temperature of the surface of the charging roll,
When the temperature detected by the surface temperature sensor is equal to or lower than a predetermined temperature, the temperature raising member is operated, and the surface temperature of the charging roll detected by the surface temperature sensor is maintained at a specified value or more. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   The image forming apparatus according to claim 3, wherein the cleaning member also serves as the temperature raising member.   6. The image forming apparatus according to claim 5, wherein the cleaning member has a metal pipe covered with a sponge or a brush, and a heater is provided in the pipe. The charging roll includes a metal shaft,
The image forming apparatus according to claim 3, wherein the temperature raising member is a heater arranged in the shaft.   The image forming apparatus according to claim 3, wherein the temperature raising member includes a heat conduction path that sends heat of a fixing device that fixes a toner image on a recording medium to the charging roll. It has a humidity sensor that detects humidity,
9. The method according to claim 1, wherein when the humidity detected by the humidity sensor is equal to or lower than a predetermined value, the idling of the image carrier or the operation of the temperature raising member is controlled. The image forming apparatus described in the item. A detection means for detecting the rotation speed of the charging roll;
The additional idling mode for idling the image carrier is performed when the rotation speed detected by the detection means is equal to or less than a predetermined value in the idling mode. 2. The image forming apparatus according to item 1. A detection means for detecting the rotation speed of the charging roll;
10. The image forming apparatus according to claim 3, wherein the temperature raising member is operated when a rotation speed detected by the detection unit is equal to or less than a predetermined value. 11. It has a warning sound generator that generates a warning sound,
12. The warning sound is generated by the warning sound generating device when the rotational speed detected by the detecting means is equal to or lower than a predetermined value after a predetermined time has elapsed from the start of the idling mode. The image forming apparatus described in 1.

Images