JP4923699B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printer that employs an electrophotographic system.

  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, the generation of ozone and nitrogen oxides that have a negative effect on the human body and the global environment is a problem. On the other hand, the contact charging method in which the conductive charging roll is directly contacted with the image carrier to charge the image carrier has significantly less generation of ozone and nitrogen oxide, and the power supply efficiency is good. Recently it has become mainstream.

  Such a charging device of the contact charging method has a disadvantage that various deposits on the image bearing member are adsorbed and easily contaminated during charging. On the other hand, in Patent Document 1 or 2, a plate-shaped cleaning member is provided so as to be able to come into contact with and separate from the charging roll, and is brought into contact with the charging roll during cleaning.

In this apparatus, the cleaning member scrapes off the toner on the surface of the charging roller and drops it on the surface of the photosensitive drum, and collects the toner and the like attached on the surface of the photosensitive drum by a separate cleaning device However, the same portion of the cleaning member is always in contact with the charging roller in the axial direction, and there is a possibility that the cleaning performance varies in the axial direction of the charging roller.
Japanese Patent Laid-Open No. 5-273846 JP-A-10-90982

  In view of the above facts, an object of the present invention is to provide an image forming apparatus capable of obtaining a good cleaning performance of a charging roll.

In order to achieve the above object, according to a first aspect of the present invention, there is provided an image forming apparatus comprising: an image carrier that carries an image; a charging roll that is rotatably supported to charge the image carrier; A cleaning unit that contacts the roll and cleans the charging roll, the cleaning unit contacting the charging roll, and a contacting / separating unit that contacts and separates the cleaning member from the charging roll. Oscillation means for sliding the cleaning member along the axial direction of the charging roll, and the contacting / separating means moves the cleaning member moving downward by its own weight and moving away from the charging roll upward. And a first motor that rotates the first eccentric cam. A second eccentric cam that contacts the one end surface of the cleaning member and slides the cleaning member along the axial direction of the charging roll, and the other end surface of the cleaning member is disposed on the second eccentric cam side. And a second motor for rotating the second eccentric cam .

  In the first aspect of the present invention, the cleaning member that comes into contact with the charging roll has contact / separation means and oscillation means, the contact member separates the cleaning member from the charging roll, and the oscillation means removes the cleaning member. Slide along the axial direction of the charging roll.

  By bringing the cleaning member into and out of contact with the charging roll by the contact / separation means, the cleaning member can be separated from the charging roll during image formation, and the cleaning member can be brought into contact with the charging roll only during cleaning. The life of the cleaning member can be extended as compared with the case where the cleaning member is in contact with the roll.

  In addition, since the sliding member is slid along the axial direction of the charging roll by the oscillating means, a rubbing force acts in the circumferential direction and the axial direction of the charging roll, so that the cleaning member is simply applied to the surface of the charging roll. The cleaning performance can be improved as compared with the case of contact.

  Further, since the cleaning member slides along the axial direction of the charging roll, the position where the cleaning member contacts changes in the axial direction of the charging roller, thereby reducing variations in cleaning performance in the axial direction of the charging roller. Can do.

  Here, a first eccentric cam that contacts and separates the cleaning member with respect to the charging roll moves the cleaning member that moves downward by its own weight and moves away from the charging roll, and contacts the charging roll; And a first motor for rotating the first eccentric cam. That is, the cleaning member moves upward by the first eccentric cam and comes into contact with the charging roll, and moves downward by its own weight and moves away from the charging roll.

An oscillation means for sliding the cleaning member along the axial direction of the charging roll; and a second eccentric cam for contacting the one end face of the cleaning member and sliding the cleaning member along the axial direction of the charging roll; The spring includes a spring that urges the other end surface of the cleaning member toward the second eccentric cam, and a second motor that rotates the second eccentric cam. The stroke for pressing the cleaning member changes depending on the rotation angle of the second eccentric cam, and the cleaning member can be slid along the axial direction of the charging roll.

Charging an invention according to claim 2, in the image forming apparatus according to claim 1, during rotation of the charging roller, the first to drive the motor, the cleaning member is rotated the first eccentric cam It is characterized by being brought into and out of contact with a roll.

According to the second aspect of the present invention, when the charging roll is cleaned, the cleaning member is brought into contact with and separated from the charging roll, so that vibration is applied to the charging roll during cleaning. It can be floated on the surface, and the cleaning property can be improved.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect , the second motor is driven in a state where the cleaning member is in contact with the charging roll, and the second eccentric cam And the cleaning member is slid along the axial direction of the charging roll.

Invention according to claim 4, characterized in an image forming apparatus according to any one of claims 1 to 3, at least said cleaning member is brought into contact with the charging roll, that cleaning member is positioned And

According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the charging roll is a conductive rubber roll.

According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the charging roll is a conductive brush roll.

According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the fourth to sixth aspects, the cleaning member includes a shaft rotatably supported by a first support member that supports the cleaning member. A cleaning roll comprising a sponge layer provided on the outer peripheral surface of the shaft.

According to an eighth aspect of the present invention, in the image forming apparatus according to any one of the first to seventh aspects, the first support member and the second support member are disposed in one housing, and a cleaning member is provided. Is provided detachably with respect to the first support member.

In the invention according to claim 8, it is possible to replace only the cleaning member, which is very convenient.

According to a ninth aspect of the present invention, in the image forming apparatus according to any one of the first to eighth aspects, the detection means for detecting the operating status of the components of the apparatus main body, and the data detected by the detection means And a control means for operating at least the contact / separation means when a threshold value determined in accordance with an operating environment of the apparatus main body is exceeded.

In the ninth aspect of the invention, for example, the operating state of the apparatus main body, such as the image density obtained from the amount of toner used and the charging time of the charging roll, is detected by the detecting means, and the detected data is a predetermined threshold value. At this time, the control means operates at least the contact / separation means to perform cleaning of the charging roll in accordance with the contamination state of the charging roll, and to maintain the cleaning state of the charging roll in a substantially constant state. Can do.

  Since the present invention has the above-described configuration, it is possible to obtain good cleaning performance of the charging roll by the cleaning roll.

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

  The image forming apparatus 10 of the present embodiment shown in FIGS. 1 and 2 is a four-cycle full-color laser printer. As shown in the drawing, in the apparatus, a photosensitive drum 12 ( An image carrier) is rotatably arranged. As this photosensitive drum 12, for example, a drum made of a conductive cylinder having a diameter of about 47 mm and coated on a surface with a photosensitive layer made of OPC or the like is used. It is rotationally driven at a process speed of 150 mm / sec.

  The surface of the photosensitive drum 12 is charged to a predetermined potential by a charging roll 14 disposed almost directly below the photosensitive drum 12, and then exposed to a laser beam LB by an exposure device 16 disposed below the charging roll 14. Image exposure is performed, and an electrostatic latent image according to image information is formed.

  The electrostatic latent image formed on the photosensitive drum 12 has yellow (Y), magenta (M), cyan (C), and black (K) developing devices 18Y, 18M, 18C, and 18K in the circumferential direction. The toner is developed by a rotary developing device 18 disposed along the toner image to form a toner image of a predetermined color.

  At this time, charging, exposure, and development processes are repeated a predetermined number of times on the surface of the photosensitive drum 12 in accordance with the color of the image to be formed. In the developing process, the rotary developing device 18 rotates, and the corresponding color developing devices 18Y, 18M, 18C, and 18K move to a developing position facing the photosensitive drum 12.

  For example, when a full-color image is formed, the charging, exposing, and developing processes are performed on the surface of the photosensitive drum 12 in yellow (Y), magenta (M), cyan (C), and black (K) colors. The toner image corresponding to each color of yellow (Y), magenta (M), cyan (C), and black (K) is sequentially formed on the surface of the photosensitive drum 12. When the toner image is formed, the number of rotations of the photosensitive drum 12 varies depending on the size of the image. For example, in the case of A4 size, one image is obtained by rotating the photosensitive drum 12 three times. It is formed. That is, a toner image corresponding to each color of yellow (Y), magenta (M), cyan (C), and black (K) is formed on the surface of the photosensitive drum 12 every time the photosensitive drum 12 rotates three times. Is done.

  An intermediate transfer belt 20 is wound around the outer periphery of the photosensitive drum 12 for yellow (Y), magenta (M), cyan (C), and black (K) toner images sequentially formed on the photosensitive drum 12. At the primary transfer position, the images are transferred onto the intermediate transfer belt 20 by the primary transfer roll 22 while being superimposed on each other.

  The yellow (Y), magenta (M), cyan (C), and black (K) toner images transferred in multiple onto the intermediate transfer belt 20 are recorded on a recording sheet 24 fed at a predetermined timing. The images are collectively transferred by the secondary transfer roll 26.

  On the other hand, the recording paper 24 is fed out from a paper feed cassette 28 disposed at the lower part of the image forming apparatus 10 by a pickup roll 30 and is fed in a state of being fed one by one by a feed roll 32 and a retard roll 34. The toner image is transferred to the secondary transfer position of the intermediate transfer belt 20 in synchronization with the toner image transferred onto the intermediate transfer belt 20 by the registration roll 36.

  The intermediate transfer belt 20 includes a wrap-in roll 38 that specifies the wrap position of the intermediate transfer belt 20 on the upstream side in the rotational direction of the photosensitive drum 12 and a toner image formed on the photosensitive drum 12 as an intermediate transfer belt. A primary transfer roll 22 that is transferred onto the intermediate transfer belt 20, a wrap-out roll 40 that specifies the wrap position of the intermediate transfer belt 20 on the downstream side of the wrap position, and a backup that contacts the secondary transfer roll 26 via the intermediate transfer belt 20. The roll 42, the first cleaning backup roll 46 facing the cleaning device 44 of the intermediate transfer belt 20, and the second cleaning backup roll 48 are stretched with a predetermined tension, and have a predetermined process speed (about 150 mm / sec), for example, as the photosensitive drum 12 rotates. It is driven Te.

  Here, in order to reduce the size of the image forming apparatus 10, the intermediate transfer belt 20 is configured such that a cross-sectional shape on which the intermediate transfer belt 20 is stretched is a flat and elongated substantially trapezoidal shape.

  The intermediate transfer belt 20 includes a photosensitive drum 12, a charging roll 14, an intermediate transfer belt 20, a plurality of rolls 22, 38, 40, 42, 46, and 48 that stretch the intermediate transfer belt 20, and an intermediate transfer belt. The cleaning device 44 for 20 and the cleaning device 78 for the photosensitive drum 12 described later integrally form an image forming unit 52. Therefore, the entire image forming unit 52 can be removed from the image forming apparatus 10 by opening the upper cover 54 of the image forming apparatus 10 and lifting the handle (not shown) provided on the upper part of the image forming unit 52 by hand. It has become.

  On the other hand, the cleaning device 44 for the intermediate transfer belt 20 includes a scraper 58 disposed so as to come into contact with the surface of the intermediate transfer belt 20 stretched by the first cleaning backup roll 46, and a second cleaning backup roll 48. And a cleaning brush 60 disposed so as to be in pressure contact with the surface of the stretched intermediate transfer belt 20. Residual toner and paper dust removed by the scraper 58 and the cleaning brush 60 are contained in the cleaning device 44. It has come to be collected.

  The cleaning device 44 is disposed so as to be able to swing counterclockwise in the drawing with the swing shaft 62 as the center. Until the secondary transfer of the final color toner image is completed, the intermediate transfer belt is provided. It is configured to retreat to a position separated from the surface of the surface 20 and to contact the surface of the intermediate transfer belt 20 when the secondary transfer of the final color toner image is completed.

  Further, the recording paper 24 onto which the toner image has been transferred from the intermediate transfer belt 20 is conveyed to a fixing device 64 and is heated and pressurized by the fixing device 64 to fix the toner image on the recording paper 24. Thereafter, in the case of single-sided printing, the recording paper 24 on which the toner image has been fixed is discharged as it is onto a discharge tray 68 provided at the top of the image forming apparatus 10 by a discharge roll 66.

  On the other hand, in the case of double-sided printing, the recording paper 24 on which the toner image is fixed on the first surface (front surface) by the fixing device 64 is not directly discharged onto the discharge tray 68 by the discharge roll 66 but is discharged by the discharge roll 66. With the rear end portion of the recording paper 24 being held, the discharge roller 66 is reversed, the conveyance path of the recording paper 24 is switched to the double-sided paper conveyance path 70, and the double-sided paper conveyance path 70 is disposed. In the state where the front and back of the recording paper 24 are reversed by the transport roller 72 thus transferred, the recording paper 24 is again transported to the secondary transfer position of the intermediate transfer belt 20 and the toner image is transferred to the second surface (back surface) of the recording paper 24. . Then, the toner image on the second surface (back surface) of the recording paper 24 is fixed by the fixing device 64, and the recording paper 24 is discharged onto the discharge tray 68.

  Furthermore, a manual feed tray 74 can be attached to the side surface of the image forming apparatus 10 so as to be freely opened and closed. An arbitrary size and type of recording paper 24 placed on the manual feed tray 74 is fed by a paper feed roll 76, and a secondary transfer position of the intermediate transfer belt 20 via a transport roll 73 and a registration roll 36. The image can be formed on the recording paper 24 of any size and type.

  The surface of the photosensitive drum 12 after the toner image transfer process is completed is cleaned by the cleaning blade 80 of the cleaning device 78 disposed obliquely below the photosensitive drum 12 every time the photosensitive drum 12 rotates once. Residual toner, paper dust, and the like are removed to prepare for the next image forming process.

  As shown in FIG. 3, a roll-shaped charging roll 14 is disposed below the photosensitive drum 12 so as to be in contact with the photosensitive drum 12. The charging roll 14 has a conductive layer 14B formed around a conductive shaft 14A, and the shaft 14A is rotatably supported.

  A roll-shaped cleaning roll 100 that is in contact with the surface of the charging roll 14 is provided at a lower portion of the charging roll 14 opposite to the photosensitive drum 12. The cleaning roll 100 has a sponge layer 100B formed around a shaft 100A, and the shaft 100A is rotatably supported (described later).

  The cleaning roll 100 is pressed against the charging roll 14 with a predetermined load, and the sponge layer 100 </ b> B is elastically deformed along the peripheral surface of the charging roll 14 to form the nip portion 101. The photosensitive drum 12 is driven to rotate clockwise (in the direction of arrow 2) in FIG. 3 by a motor (not shown), and the charging roll 14 is driven to rotate in the direction of arrow 4 by the rotation of the photosensitive drum 12. Further, the roll-shaped cleaning roll 100 is driven to rotate in the direction of the arrow 6 by the rotation of the charging roll 14.

  Further, a charging power source is connected to the charging roll 14, and only a bias in which an alternating current is superimposed on a direct current or a direct current bias is applied. The cleaning roll 100 has the same potential as the charging roll 14.

  As the cleaning roll 100 is driven to rotate, dirt (foreign matter) such as toner and external additives attached to the surface of the charging roll 14 is cleaned by the cleaning roll 100. Then, when the foreign matter is taken into the cell of the sponge layer 100B and the foreign matter collected in the cell is aggregated to an appropriate size, it is returned from the cleaning roll 100 to the photosensitive drum 12 via the charging roll 14, It is considered that the cleaning performance is continuously maintained by being collected by the cleaning device 78 that cleans the photosensitive drum 12.

  In such a cleaning roll 100, free-cutting steel, stainless steel, or the like is used as the material of the shaft 100A, and the material and the surface treatment method are appropriately selected according to applications such as slidability. In addition, a non-conductive material 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 100 comes into contact with the charging roll 14 through the sponge layer 100B with an appropriate nip pressure, the shaft diameter having sufficient rigidity with respect to a material having a low bending strength or a shaft length. Is selected.

  The sponge layer 100B is formed of a foam having a cylindrical shape and a porous three-dimensional structure. The sponge layer 100B is selected from those made of a foamable resin or rubber such as polyurethane, polyethylene, polyamide, or polypropylene. The sponge layer 100B efficiently cleans foreign substances such as external additives by driven sliding rubbing with the charging roll 14, and at the same time does not damage the surface of the charging roll 14 due to rubbing of the sponge layer 100B. In order to prevent tearing and breakage, it is particularly preferable to use polyurethane that is strong in tearing and tensile strength. Note that the cleaning member of the cleaning roll 100 may be configured by a blade, a brush, a waste, or the like other than the sponge.

  The charging roll 14 is formed by sequentially forming a conductive elastic layer and a surface layer as a charging layer 14B on a conductive shaft 14A.

  As the material of the shaft 14A, 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 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 14B of the charging roll 14 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 14 </ 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 surface layer constituting the charging layer 14B is formed for the purpose of preventing 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.

  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 conductive metal oxide particles, which are conductive particles for adjusting the resistance value, are conductive particles such as tin oxide, tin oxide doped with antimony, zinc oxide, anatase titanium oxide, and ITO. Any conductive agent using electrons as charge carriers can be used without any particular limitation. These may be used alone or in combination of two or more. Any particle size may be used as long as the present invention is not inhibited. From the viewpoint of resistance value adjustment and strength, tin oxide, antimony-doped tin oxide, and anatase-type titanium oxide are preferable. Tin oxide and antimony-doped tin oxide are preferred.

  By performing resistance control with such a conductive material, the resistance value of the surface layer does not change depending on environmental conditions, and stable characteristics can be obtained.

  Further, a fluorine-based or silicone-based resin is used for the surface layer. In particular, it 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 adhesion of foreign matter to the charging roll 14. In addition, insulating particles such as alumina and silica are added to give unevenness to the surface of the charging roll 14, thereby reducing the burden at the time of rubbing against the photosensitive drum 12, and the charging roll 14 and the photosensitive drum. It is also possible to improve the mutual wear resistance.

  Next, the mounting structure of the charging roll 14 and the cleaning roll 100 will be described in detail.

  As shown in FIG. 4, in this embodiment, a frame 140 for supporting the photosensitive drum 12 is provided inside the main body of the image forming apparatus 10, and the photosensitive drum 12 can be supported by the frame 140. It is said that. At both ends in the longitudinal direction of the frame 140, shaft support portions 142 formed with bearing holes 142A are formed so as to face each other, and both end portions of the photosensitive drum 12 are rotatably supported in the bearing holes 142A. Has been. A substantially trapezoidal engagement piece 144 extends from the lower portion of the shaft support portion 142, and a notch portion 144 </ b> A is notched at the distal end portion of the engagement piece 144 along the extending direction. It is.

  A substantially box-shaped housing 146 can be attached to the lower part of the photoconductive drum 12 along the longitudinal direction of the photoconductive drum 12 inside the main body of the image forming apparatus 10. From the side wall (second support member) 148 at both ends in the longitudinal direction of the casing 146, an outer wall 147 having a substantially L-shaped cross section is provided from the lower side of the central portion of the side wall 148 to the tip. An engaging convex portion 147 </ b> A is convexly provided at the lower central portion of the outer surface of 147. This engagement convex part 147A can be engaged with the notch part 144A. The photosensitive drum 12, the charging roll 14, and the cleaning roll 100 are positioned in a state where the notch portion 144A is engaged with the engaging convex portion 147A.

  Here, the housing 146 is formed of a synthetic resin material such as polyacetal or polycarbonate having high rigidity, high slidability, and excellent wear resistance. In order to further improve the wear resistance, the synthetic resin material may contain glass fibers, carbon fibers, or the like.

  A bearing hole 150 is cut out at the tip of the side wall 148 so that both ends of the shaft 14A of the charging roll 14 are rotatably supported.

  A shaft plate (first support member) 152 is erected on the inner side of the side wall 148 so as to be parallel to the side wall 148 and lower than the side wall 148, and a bearing hole 154 is cut at the tip of the shaft plate 152. The shaft 100A of the cleaning roll 100 is pivotally supported so as to be rotatable.

  The cleaning roll 100 abuts against the charging roll 14 with the shaft 100A of the cleaning roll 100 rotatably supported by the bearing hole 154 and the shaft 14A of the charging roll 14 rotatably supported by the bearing hole 150. It becomes a state.

  Although not shown, a contact member is provided on the shaft 100A of the cleaning roll 100 or the shaft 14A of the charging roll 14, and the cleaning roll 100 is in a state where the corresponding contact member is in contact with the cleaning roll 100 side or the charging roll 14 side. May be positioned.

  By the way, inside the housing 146, as shown in FIG. 5 (note that FIG. 4 shows the housing 146 in a simplified manner), there is contact between the side wall 148 and the shaft plate 152. A stepping motor 156 constituting the means is disposed, and a stepping motor 168 constituting the oscillation means is disposed between the other side wall 148 and the shaft plate 152.

  The stepping motor 156 is rotatable at a pitch of 180 degrees, and a connecting shaft 160 that is slightly shorter than the cleaning roll 100 is connected to the shaft 158. On the other hand, a bearing hole 153 is formed in the shaft plate 152, and the connecting shaft 160 is rotatably supported by the bearing hole 153.

  Also, disc-shaped eccentric cams 162 (see FIG. 6, where FIG. 6 shows the right side of FIG. 5) are fixed to both ends of the connecting shaft 160. On the other hand, contact rings 166 are fixed to both ends of the shaft 100 </ b> A of the cleaning roll 100, and the outer peripheral surface of the contact ring 166 is in contact with the outer peripheral surface of the eccentric cam 162.

  For this reason, when the stepping motor 156 is driven and the eccentric cam 162 rotates via the shaft 158 and the connecting shaft 160, the rotation angle of the eccentric cam 162 causes the shaft 100 </ b> A of the cleaning roll 100 to pass through the contact ring 166. The height changes, and the cleaning roll 100 comes in contact with and separates from the charging roll 14 as shown in FIGS. When the cleaning roll 100 is separated from the charging roll 14, the cleaning roll 100 moves downward due to its own weight.

  8A, when the cleaning roll 100 is in contact with the charging roll 14, the sponge layer 100B is elastically deformed along the peripheral surface of the charging roll 14 to form the nip portion 101 (FIG. 3). reference). Thus, when the photosensitive drum 12 rotates, the charging roll 14 is driven to rotate with the rotation of the photosensitive drum 12 to charge the photosensitive drum 12, and further, the cleaning roll 100 is driven to rotate with the rotation of the charging roll 14. Then, the charging roll 14 is cleaned.

  On the other hand, the stepping motor 168 can rotate at a pitch of 180 degrees. As shown in FIGS. 6 and 7 (FIG. 7 shows the right side of FIG. 5), a disc-shaped eccentric cam 170 is fixed to the shaft 168A. The outer peripheral surface of the eccentric cam 170 is brought into contact with one end surface of the shaft 100A of the cleaning roll 100.

  Further, as shown in FIG. 5, one end portion of the coil spring 172 is brought into contact with the other end surface of the shaft 100A, and the other end portion of the coil spring 172 is brought into contact with the side wall 148. The power is biased to the 170 side.

  For this reason, when the eccentric cam 170 is rotated by driving the stepping motor 168, the stroke for pressing the shaft 100A of the cleaning roll 100 is changed depending on the rotation angle, and the shaft 100A is subjected to the biasing force of the coil spring 172 via the eccentric cam 170. It is pressed in the direction to resist and moves along the axial direction (see FIG. 9B).

  When the eccentric cam 170 rotates 180 degrees from this state, the cleaning roll 100 returns to the original position along the axial direction by the biasing force (force in the direction of the arrow) of the coil spring 172 (see FIG. 9A). . In this way, the cleaning roll 100 can be moved along the axial direction of the charging roll 14.

  Incidentally, the image forming apparatus 10 incorporates a control device 174 shown in FIG. 10 and is connected to a detection device 176 and stepping motors 156 and 168, respectively. The detection device 176 detects the amount of toner used (the image density is obtained from the amount of toner used) from the remaining amount of toner charged in the toner cartridge 178, and the detection result is transmitted to the control device 174. It is like that.

  Here, the detection device 176 that detects the remaining amount of toner is used. However, since the contamination state of the charging layer 14B of the charging roll 14 only needs to be known, it is only necessary to know the operating status of the components of the apparatus main body. For this reason, a detection device 176 other than the detection device 176 that detects the amount of toner used may be used.

  For example, a timer (not shown) is used as the detection device 176, and the charging time of the charging roll 14, the exposure time of the exposure device 16, or the rotation time of the photosensitive drum 12 is measured and transmitted to the control device 174. good.

  Further, an encoder (not shown) may be used as the detection device 176 to detect the rotational speed of the developing device 18 and transmit it to the control device 174, and a counter (not shown) may be used as the detection device 176. Alternatively, the number of prints on which an image is formed may be detected and transmitted to the control device 174.

  By the way, the contamination state of the charged layer 14B varies depending on the process speed, environmental temperature, humidity, and the like when an image is formed. For this reason, the process speed and the environmental temperature / humidity are measured and transmitted to the control device 174 together with the data detected by the detection device 176 so that the process speed and the environmental temperature / humidity are taken into consideration. Processing may be performed.

  That is, the control device 174 sets a threshold value in advance (for the toner usage amount in this case), and determines whether or not the accumulated value of the data (toner usage amount) detected and transmitted by the detection device 176 is equal to or greater than the threshold value ( However, this threshold value may be changed according to the environmental conditions such as the process speed, environmental temperature, and humidity.

  Next, the operation of this embodiment will be described.

  As shown in FIG. 5, in the present invention, stepping motors 156 and 168 are arranged in the housing 146, and the stepping motor 156 enables the cleaning roll 100 to contact and separate with respect to the radial direction of the charging roll 14. Thus, the cleaning roll 100 can be slid along the axial direction of the charging roll 14.

  As an example, a control method of the cleaning roll 100 by the control device 174 will be described based on the flowchart shown in FIG.

  In step 100, it is determined whether or not the accumulated toner usage amount transmitted from the detection device 176 is equal to or greater than the threshold value. The process is repeated until the cumulative value of the toner usage exceeds the threshold. When the cumulative value of the toner usage exceeds the threshold, the process proceeds to step 102.

  In step 102, the stepping motor 156 is driven and the shaft 158 is rotated 180 degrees. Thereby, the connecting shaft 160 rotates via the shaft 158, and the eccentric cam 162 rotates integrally with the connecting shaft 160. Due to the rotation of the eccentric cam 162, the connecting shaft 160 moves upward via the contact ring 166. Then, the cleaning roll 100 comes into contact with the surface of the charging roll 14 and is rotated by the rotation of the charging roll 14. Then, the process proceeds to step 104 and the driving of the stepping motor 156 is stopped.

  Next, at step 106, when a predetermined time has elapsed, the routine proceeds to step 108, where the stepping motor 168 is driven, the shaft 164 is rotated 180 degrees, and the eccentric cam 170 is rotated integrally with the shaft 164. As a result, the cleaning roll 100 is pressed in the direction against the urging force of the coil spring 172 and moves along the axial direction.

  That is, the cleaning roll 100 is moved (sliding operation (oscillation)) along the axial direction of the charging roll 14 while the cleaning roll 100 is in contact with the surface of the charging roll 14. Then, the process proceeds to step 110 and the driving of the stepping motor 168 is stopped.

  Next, in step 112, when a predetermined time has elapsed, the process proceeds to step 114 where the stepping motor 156 is driven and the connecting shaft 160 is rotated 180 degrees via the shaft 158 to separate the cleaning roll 100 from the charging roll 14. . Then, the process proceeds to step 116 and the driving of the stepping motor 156 is stopped.

  By the above control method, the cleaning roll 100 is slid along the axial direction of the charging roll 14 (oscillation) by the stepping motor 168 while the cleaning roll 100 is in contact with the charging roll 14. Since the rubbing force acts in the circumferential direction and the axial direction of the roll 14, the cleaning performance can be improved as compared with the case where the cleaning roll 100 is simply brought into contact with the surface of the charging roll 14.

  Further, since the cleaning roll 100 slides along the axial direction of the charging roll 14, the contact position of the cleaning roll 100 changes in the axial direction of the charging roll 14, and the cleaning performance is improved in the axial direction of the charging roll 14. Variations can be reduced.

  On the other hand, by bringing the cleaning roll 100 into and out of contact with the charging roll 14 by the stepping motor 156, the cleaning roll 100 is separated from the charging roll 14 during image formation, and the cleaning roll 100 is brought into contact with the charging roll 14 only during cleaning. Therefore, the life of the cleaning roll 100 can be extended as compared with the case where the cleaning roll 100 is always in contact with the charging roll 14.

  The cleaning roll 100 may be brought into contact with or separated from the charging roll 14 while the charging roll 14 is rotating. In this case, vibration is applied to the charging roll 14, and the toner or the like adhering to the charging roll 14 can be floated on the surface of the charging roll 14, so that the cleaning property can be improved.

  Here, the cleaning roll 100 is oscillated while the cleaning roll 100 is in contact with the charging roll 14, but as described above, for example, an image obtained from the accumulated toner usage amount. Only the stepping motor 156 is activated depending on the data that detects the operation status of the apparatus main body, such as the density and the charging time of the charging roll, and the stepping motor 168 is also activated when the data exceeds a threshold value. good. Thereby, cleaning of the charging roll 14 is performed according to the contamination state of the charging roll 14, and the cleaning state of the charging roll 14 can be maintained in a substantially constant state.

  By the way, the bearing hole 154 is notched in the shaft plate 152 of the housing 146, the shaft 100A of the cleaning roll 100 is pivotally supported, and the bearing hole 150 is notched in the side wall 148, and the shaft 14A of the charging roll 14 is pivotally supported. Thus, the charging roll 14 and the cleaning roll 100 can be easily detached from the housing 146. This makes it possible to replace only the cleaning roll 100, which is very convenient.

  In this embodiment, the stepping motor 156 and the eccentric cam 162 or the stepping motor 168 and the eccentric cam 170 are used. However, it is sufficient that the cleaning roll 100 can be moved toward and away from the charging roll 14 or moved in the axial direction. Therefore, it is not limited to this. For example, although not shown, a solenoid may be used, and the shaft connected to the solenoid may be directly brought into contact with the shaft 100A of the cleaning roll 100 to move the cleaning roll 100.

  Further, here, the roll-shaped charging roll 14 having conductivity is used. However, the present invention is not limited to this, and a brush roll 180 having conductivity may be used as shown in FIG.

  In the present embodiment, the cleaning roll 100 is used as the cleaning member and the sponge layer 100B is formed around the shaft 100A. However, the present invention is not limited to the roll-like sponge, but has a plate shape although not shown. A sponge member may be used. However, in this case, the sponge member is fixed to a holder provided facing the charging roll 14, and both ends of the holder are supported by the bearing holes 154 of the shaft plate 152 of the housing 146.

  As mentioned above, although it demonstrated in detail by embodiment of this invention, this invention is not limited to them, Various other forms can be implemented within the scope of the present invention.

  For example, in the present embodiment, the charging roll 14 is brought into contact with the lower part of the photosensitive drum 12 and the cleaning roll 100 is brought into contact with the lower part of the charging roll 14, but the photosensitive drum 12, the charging roll 14, and The positional relationship of the cleaning roll 100 is not limited to this. For example, the present invention can be applied to a configuration in which a charging roll is brought into contact with an upper portion of the photosensitive drum and a cleaning roll is brought into contact with the upper portion of the charging roll. Further, the present invention can be applied even when the charging roll 14 is not in contact with the photosensitive drum 12.

  The image forming apparatus to which the present invention is applied has a four-cycle configuration in which the toner image is formed on the photosensitive drum 12 four times using the rotary developer 18 as in the above-described embodiment. It is not limited to. For example, even in a tandem 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, the image forming unit is used as a photosensitive drum, a charging roll, and a cleaning roll of each image forming unit. The invention can be applied.

1 is a configuration diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a configuration diagram showing a schematic configuration of an image forming apparatus according to an embodiment of the present invention, and shows a state where an upper cover is opened and an image forming unit is removed. FIG. 3 is an enlarged view showing the arrangement of a photosensitive drum, a charging roll, and a cleaning roll of the image forming apparatus according to the embodiment of the present invention. FIG. 3 is an exploded perspective view showing a mounting structure of a photosensitive drum, a charging roll, and a cleaning roll of the image forming apparatus according to the embodiment of the present invention. FIG. 3 is a partial cross-sectional front view illustrating a mounting structure of a photosensitive drum, a charging roll, and a cleaning roll of the image forming apparatus according to the embodiment of the present invention. FIG. 3 is a partially enlarged exploded perspective view showing a mounting structure of a photosensitive drum, a charging roll, and a cleaning roll of the image forming apparatus according to the embodiment of the present invention. FIG. 3 is a partially enlarged perspective view showing a mounting structure of a photosensitive drum, a charging roll, and a cleaning roll of the image forming apparatus according to the embodiment of the present invention. 4A and 4B are partial cross-sectional front views illustrating an operation in which the cleaning roll of the image forming apparatus according to the embodiment of the present invention contacts and separates from the charging roll. 4A and 4B are partial cross-sectional front views illustrating an operation in which the cleaning roll of the image forming apparatus according to the embodiment of the present invention oscillates the charging roll. FIG. 2 is a block diagram illustrating a configuration of a control device that controls a cleaning roll of the image forming apparatus according to the exemplary embodiment of the present invention. 6 is a flowchart illustrating a method for controlling a cleaning roll of the image forming apparatus according to the exemplary embodiment of the present invention. FIG. 10 is an enlarged view showing a modification of the charging roll of the image forming apparatus according to the embodiment of the invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 12 Photosensitive drum (Image carrier)
14 Charging roll 100 Cleaning roll (cleaning member, cleaning means)
100A shaft (cleaning member, cleaning means)
100B sponge layer (cleaning member, cleaning means)
146 Housing 148 Side wall (first support member)
152 Shaft plate (second support member)
156 Stepping motor (first motor, contact / separation means, cleaning means)
162 Eccentric cam (first eccentric cam, contact / separation means, cleaning means)
168 Stepping motor (second motor, oscillation means, cleaning means)
170 Eccentric cam (second eccentric cam, oscillation means, cleaning means)
172 Coil spring (spring, oscillation means, cleaning means)
174 Control device 176 Detection device 180 Brush roll (cleaning member, cleaning means)

Claims (9)

An image carrier that carries an image, a charging roll that is rotatably supported to charge the image carrier, and a cleaning unit that contacts the charging roll and cleans the charging roll,
The cleaning means
A cleaning member in contact with the charging roll;
And moving means for contacting and separating against the cleaning member to the charging roller,
Oscillation means for sliding the cleaning member along the axial direction of the charging roll;
Equipped with a,
The contacting / separating means is
A first eccentric cam that moves downward by its own weight and moves away from the charging roll to contact the charging roll;
A first motor for rotating the first eccentric cam,
The oscillation means is
A second eccentric cam that contacts the one end surface of the cleaning member and slides the cleaning member along the axial direction of the charging roll;
A spring for urging the other end face of the cleaning member toward the second eccentric cam; a second motor for rotating the second eccentric cam;
An image forming apparatus characterized in that it is configured to include. 2. The image forming apparatus according to claim 1 , wherein the first motor is driven and the first eccentric cam is rotated while the charging roll is rotating to bring the cleaning member into contact with and away from the charging roll . In a state where the cleaning member is in contact with the charging roll, the second motor is driven to rotate the second eccentric cam to slide the cleaning member along the axial direction of the charging roll. The image forming apparatus according to claim 1. The image forming apparatus according to claim 1, wherein at least the cleaning member abuts on the charging roll to position the cleaning member . The image forming apparatus according to claim 1, wherein the charging roll is a rubber roll having conductivity . The image forming apparatus according to claim 1 , wherein the charging roll is a conductive brush roll . The cleaning member is a cleaning roll configured to include a shaft rotatably supported by a first support member that supports the cleaning member, and a sponge layer provided on an outer peripheral surface of the shaft. The image forming apparatus according to claim 4 , wherein the image forming apparatus is an image forming apparatus. A first support member that supports the cleaning member and a second support member that supports the charging roll are disposed in one housing, and the cleaning member is detachably provided to the first support member. The image forming apparatus according to any one of claims 1 to 7 . Detection means for detecting the operating status of the components of the apparatus body;
Control means for operating at least the contact / separation means when the data detected by the detection means is greater than or equal to a threshold value determined according to the operating environment of the apparatus body;
The image forming apparatus according to any one of claims 1-8, characterized in that it comprises a.

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