JP2011248006A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To downsize a structure around a photoreceptor drum, and to remove discharge products such as nitrogen oxides generated when a photoreceptor drum surface is charged.SOLUTION: The image forming device comprises a cylindrical photoreceptor drum 3 forming an electrostatic latent image, a corona charger charging the photoreceptor drum 3, and an exhaust device 401 discharging air to the outside of a machine. In the photoreceptor drum 3, an intake port 309 is formed in a non-image area on an outer peripheral surface around a rotation axis for taking surrounding air into the inside space of the photoreceptor drum 3, and an exhaust port is formed on one end surface in the rotation axis direction for discharging air. Ozon and duct collection filters 307, 308 capturing discharge products due to corona discharge is provided between the intake port 309 and the exhaust port. The exhaust device 401 forms an air flow from the intake port 309 to the exhaust port through the filters.

Description

  The present invention relates to an image forming apparatus including a charging device that charges a photosensitive drum by a corona discharge method.

  In an electrophotographic image forming apparatus, a corona discharge type charging device is frequently used as a charging means for uniformly charging a photoreceptor on which an electrostatic latent image is formed. This type of charging device includes a shield case and a discharge electrode, the shield case has an opening facing the photoconductor, the discharge electrode is disposed inside the shield case, and the discharge surface is linear, sawtooth or It has a needle shape.

  The corona discharge charging device includes a so-called corotron that applies a high voltage to the discharge electrode to generate corona discharge to uniformly charge the photosensitive member, and a grid electrode between the discharge electrode and the photosensitive member. There is known a so-called scorotron that uniformly charges the photosensitive member by applying a desired voltage to the grid electrode.

In this type of charging device, in order to generate corona discharge, a discharge product such as nitrogen oxide (NOx) is generated. Specifically, due to the energy accompanying the discharge of electrons emitted from the charging device, nitrogen molecules (N ₂ ) present in the atmosphere dissociate into nitrogen atoms (N), which bind to oxygen molecules (O ₂ ). Thus, nitrogen oxides (nitrogen dioxide: NO ₂ ) are generated.

  The nitrogen oxides generated in this manner adhere to the photoreceptor as an ammonium salt (ammonium nitrate), causing abnormal images. In particular, when an organic photoreceptor (OPC) is used as the photoreceptor, there is a problem that image defects such as white spots and image flow are likely to occur due to nitrogen oxides.

  In order to solve such a problem, Patent Document 1 discloses an image forming apparatus having a configuration in which a brush roller containing zeolite is brought into contact with a photoconductor from above. Further, Patent Document 1 discloses an image forming apparatus having a configuration in which a plate-like member containing zeolite is arranged to face a photoconductor from above.

  According to the disclosure of Patent Document 1, the zeolite contained in the brush roller and the plate-like member has a property of adsorbing nitrogen oxide, ammonium nitrate, and the like. Therefore, the ammonium nitrate adhering to the surface of the photoreceptor can be adsorbed and removed while being rubbed with a brush roller, and discharge products such as nitrogen oxide floating in the air in the vicinity of the photoreceptor can be adsorbed and removed by the plate-like member. it can. As a result, it is possible to suppress the occurrence of image defects due to discharge products such as ammonium nitrate adhering to the photoreceptor and nitrogen oxides floating in the air in the vicinity of the photoreceptor.

  Further, Patent Document 2 discloses an image forming apparatus in which an activated carbon filter is built in a photosensitive drum, contaminated air sucked in the copying machine is guided into the photosensitive drum, purified by the activated carbon filter, and then discharged outside the apparatus. Is disclosed. According to the disclosure of Patent Document 2, the above-described configuration enables downsizing of the image forming apparatus.

JP 2003-122187 A (published April 25, 2003) Japanese Utility Model Publication No. 61-193461 (published on December 02, 1986)

  However, in the configuration disclosed in Patent Document 1, a brush roller containing zeolite adsorbs and removes ammonium nitrate adhering to the photoreceptor while rubbing. For this reason, there is a risk of scratches on the surface of the photoreceptor, and in this case, image defects due to the scratches occur. Further, in the configuration disclosed in Patent Document 1, a plate-like member containing zeolite is disposed on the upper side of the photoreceptor. Therefore, it is impossible to remove the discharge product flowing downward along the surface of the photoreceptor. For this reason, image defects such as white spots and image flow caused by discharge products such as nitrogen oxides cannot be sufficiently prevented.

  On the other hand, the configuration disclosed in Patent Document 2 requires a duct that guides sucked air into the photosensitive drum. For this reason, there is a problem that it is difficult to reduce the size of the process unit around the photosensitive drum.

  Further, in the configuration in which the discharge electrode is provided inside the shield case as in the corona discharge type charging device, the discharge product stays at a high concentration in the internal space of the shield case after the discharge operation. As described above, the discharge product adheres to the surface of the photoreceptor and causes an abnormal image. In addition, none of the above-mentioned documents discloses a configuration that can efficiently remove the discharge product without reducing the charging performance of the charging device.

  Therefore, according to the present invention, the configuration around the photosensitive drum can be reduced, and discharge products such as nitrogen oxides generated when charging the surface of the photosensitive drum can be reduced with the charging performance of the charging device. An object of the present invention is to provide an image forming apparatus that can be removed without being reduced, and thereby prevent occurrence of image defects such as white spots and image flow caused by discharge products.

  In order to solve the above-described problems, an image forming apparatus of the present invention includes a cylindrical photosensitive drum on which an electrostatic latent image is formed, a corona charger that charges the photosensitive drum by corona discharge, and image formation. In the image forming apparatus provided with an exhaust device that exhausts air inside the apparatus to the outside of the apparatus, the photosensitive drum has a non-image region on the outer peripheral surface around the rotation axis where the electrostatic latent image is not formed. An intake port for taking in the air around the photoconductive drum is formed in the internal space of the photoconductive drum, and an exhaust port for discharging the air in the internal space of the photoconductive drum is formed on one end surface in the rotation axis direction. A filter is provided between the intake port and the exhaust port in the internal space to capture a discharge product of the corona discharge contained in the air, and the exhaust device is connected to the intake port. It is characterized by forming a flow of air leading to the exhaust port through said filter.

  According to the above configuration, when the exhaust device is operated, air around the photosensitive drum is taken into the internal space of the photosensitive drum from the intake port of the photosensitive drum. This air passes through a filter provided in the internal space of the photosensitive drum and is discharged from the exhaust port of the photosensitive drum. When the air passes through the filter, discharge products and dust contained in the air are supplemented.

  As described above, in the present invention, the configuration for removing the discharge product from the air is accommodated in the photosensitive drum except for the exhaust device. For example, air around the photosensitive drum is taken directly into the photosensitive drum from an air inlet formed in a non-image area of the photosensitive drum. Therefore, a configuration added around the photosensitive drum such as an intake duct is unnecessary, and the configuration around the photosensitive drum can be reduced, and further, the size of the image forming apparatus can be reduced.

  In the above image forming apparatus, the photosensitive drum has the non-image areas on both sides of the image area where the electrostatic latent image is formed, and the non-image area far from the exhaust port includes the intake air. A first air inlet is formed as a mouth, and a second air inlet is formed as the air inlet in the non-image region closer to the air outlet, and the center point in the rotation axis direction of the photosensitive drum and the A first filter is provided as the filter between the first intake port, and a second filter is provided as the filter between the center point and the second intake port, A pipe member extending from the exhaust port through the second filter and extending in the second filter direction may be connected to the exhaust port.

  According to the above configuration, when the exhaust device is operated, air around the photosensitive drum is discharged from the first and second intake ports formed in the non-image areas on both sides of the image area of the photosensitive drum. Captured in the internal space. Air taken in from the first and second intake ports passes through the first filter and the second filter, respectively, passes through the pipe member, and is discharged from the exhaust port of the photosensitive drum. Therefore, the air around the photosensitive drum can be efficiently taken into the photosensitive drum from the first and second intake ports, and discharge products and dust contained in the air by the first and second filters. Can be efficiently supplemented.

  In the image forming apparatus, an adsorption layer that adsorbs a discharge product may be formed on the outer peripheral surface of the pipe member.

  According to the above configuration, when the discharge product contained in the air is not captured by the filter, the discharge product is adsorbed by the adsorption layer on the outer peripheral surface of the pipe member inside the photosensitive drum, and from the air. Removed. Therefore, the discharge product can be more efficiently removed even with a miniaturized configuration.

  In the above image forming apparatus, the end of the pipe member in the second filter direction has a plurality of vent holes extending in the rotation axis direction of the photosensitive drum, and the vent holes are arranged around the rotation axis. A cylindrical fin member having a fin closed between adjacent vent holes and having a closed end opposite to the pipe member side in the rotational axis direction is connected to the cylindrical fin member. It is good also as a structure by which the said adsorption layer is formed in the outer peripheral surface.

  According to the above configuration, when the discharge product contained in the air is not captured by the filter, the discharge product is adsorbed by the adsorption layer on the outer peripheral surface of the pipe member and the cylindrical fin member inside the photosensitive drum. And removed from the air. In this case, the air discharged from the exhaust port through the pipe member is taken into the pipe member after coming into contact with the fin having the adsorption layer of the cylindrical fin member. Therefore, the discharge product can be more efficiently removed even with a miniaturized configuration.

  In the image forming apparatus, the adsorption layer may include a zeolite.

  According to the above configuration, since zeolite can effectively decompose ozone as a discharge product contained in the air, the function of removing ozone as a discharge product contained in the air is further enhanced. Can do.

  As described above, in the present invention, the configuration for removing the discharge product from the air is accommodated in the photosensitive drum except for the exhaust device. For example, air around the photosensitive drum is taken directly into the photosensitive drum from an air inlet formed in a non-image area of the photosensitive drum. Therefore, a configuration added around the photosensitive drum such as an intake duct is unnecessary, and the configuration around the photosensitive drum can be reduced, and further, the size of the image forming apparatus can be reduced.

1 is a longitudinal sectional view showing a configuration of an image forming apparatus in an embodiment of the present invention. FIG. 2 is a block diagram illustrating an electrical configuration of the image forming apparatus illustrated in FIG. 1. FIG. 2 is a perspective view illustrating a photosensitive drum and a charging device illustrated in FIG. 1. FIG. 2 is an explanatory diagram illustrating an internal structure of the photosensitive drum illustrated in FIG. 1. FIG. 2 is a perspective view showing a drum boss portion and a cylindrical fin member of the photosensitive drum shown in FIG. 1. FIG. 2 is a perspective view showing a specific configuration of the charging device shown in FIG. 1 with a part thereof broken. It is explanatory drawing which shows the flow of the air generate | occur | produced by operation | movement of the exhaust apparatus shown in FIG. It is explanatory drawing which shows the experimental result investigated about the prevention function of the image defect by the adsorption layer which consists of a zeolite shown in FIG.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a longitudinal sectional view showing a configuration of an image forming apparatus 100 according to an embodiment of the present invention. The image forming apparatus 100 is a multifunction device including, for example, a scanner, a printer, and peripheral devices. Based on image data input from the outside or image data obtained by document reading, An apparatus for forming a monochrome image.

  The image forming apparatus 100 includes an automatic document feeder 101 at the top, and sequentially therebelow a document reading unit 102, a fixing unit 103, an image forming unit 104, an exposure unit 105, a manual sheet feeding unit 106, and an internal sheet feeding unit. 107.

  The automatic document feeder 101 automatically conveys the document placed on the document tray 93 onto the document placing table 92. The automatic document processor 120 is configured to be rotatable in the arrow M direction, that is, in the vertical direction around the rear end. Thus, the document placing table 92 can be opened, and the document can be placed by hand on the opened document placing table 92.

  The document reading unit 102 has the document placing table 92 made of transparent glass on which the document is placed on the upper surface, reads an image of the document placed on the document placing table 92, and acquires image data.

  The exposure unit 105 includes a laser scanning unit (LSU) including a laser emission unit, a polygon mirror, a converging lens, a reflection mirror, and the like. Laser light emitted from the laser emitting unit is deflected by a polygon mirror, converged by a converging lens, reflected by a reflecting mirror, and applied to the photosensitive drum 3 in the image forming unit 104. The surface of the photosensitive drum 3 is charged to a predetermined potential and polarity, and an electrostatic latent image corresponding to image data is formed by irradiating the laser beam. In addition to the laser scanning unit (LSU), the exposure unit 105 uses a writing device (for example, a writing head) in which light emitting elements such as EL (Electro Luminescence) and LED (Light Emitting Diode) are arranged in an array. You can also

  The image forming unit 104 supports black (K) and four hues of cyan (C), magenta (M), and yellow (Y), which are three subtractive primary colors obtained by color separation of a color image. The formed image data is used to form an image. For this purpose, the image forming unit 104 includes four toner image forming units 111 and an intermediate transfer unit 6.

  Each toner image forming unit 111 is provided corresponding to each color described above, and is arranged in a line in the moving direction (rotating direction) of the intermediate transfer belt 61 in the intermediate transfer unit 6. Each toner image forming unit 111 has the same configuration, and includes a developing unit 2, a cleaner unit 4, and a charging device 5 around the photosensitive drum 3.

  The charging device 5 extends along the rotational axis direction of the photosensitive drum 3 and is disposed so as to be separated from the surface of the photosensitive drum 3 with a predetermined gap. The charging device 5 is a charger type device, and uniformly charges the surface of the photosensitive drum 3 to a predetermined potential.

  The developing unit 2 is provided so as to face and press-contact the photosensitive drum 3, and supplies toner to the electrostatic latent image formed on the surface of the photosensitive drum 3 to develop the toner image. This toner image is transferred from the surface of the photosensitive drum 3 onto the intermediate transfer belt 61.

  The cleaner unit 4 removes and collects the toner remaining on the surface of the photosensitive drum 3 after development and transfer of the toner image to the intermediate transfer belt 61.

  The intermediate transfer unit 6 is disposed above each photosensitive drum 3 and has an intermediate transfer belt 61, an intermediate transfer belt driving roller 62, an intermediate transfer belt driven roller 63, a primary transfer roller 64, an intermediate transfer belt cleaning unit 65, and a secondary transfer belt. A transfer roller 10 is provided.

  The intermediate transfer belt 61 is an endless belt member that is stretched between an intermediate transfer belt driving roller 62 and an intermediate transfer belt driven roller 63 to form a loop-shaped movement path, and has a thickness of 100 μm to 100 μm. It is about 150 μm. A primary transfer roller 64 is disposed at a position facing the photosensitive drum 3 with the intermediate transfer belt 61 interposed therebetween. The position where the intermediate transfer belt 61 faces the photosensitive drum 3 is the primary transfer position.

  In order to transfer the toner image carried on the surface of the photosensitive drum 3 onto the intermediate transfer belt 61, a primary transfer bias having a polarity opposite to the toner charging polarity is applied to the primary transfer roller 64 by constant voltage control. . As a result, the toner images of the respective colors formed on the photosensitive drum 3 are sequentially transferred onto the outer peripheral surface of the intermediate transfer belt 61, and a full-color toner image is formed on the outer peripheral surface of the intermediate transfer belt 61. However, when image data of only a part of the hues of yellow, magenta, cyan, and black is input, the hue of the input image data is selected among the photosensitive drums 3 of the four toner image forming units 111. The electrostatic latent image and the toner image are formed only in the corresponding part. For example, when forming a monochrome image, an electrostatic latent image and a toner image are formed only on the photosensitive drum 3 corresponding to the black hue, and only the black toner image is transferred to the outer peripheral surface of the intermediate transfer belt 61. Is done.

  The primary transfer roller 64 is configured by covering the surface of a shaft made of a metal (for example, stainless steel) having a diameter of 8 to 10 mm with a conductive elastic material (for example, EPDM: ethylene-propylene copolymer rubber, urethane foam, or the like). A high voltage is uniformly applied to the intermediate transfer belt 61 by a conductive elastic material.

  The toner image transferred to the outer peripheral surface of the intermediate transfer belt 61 by the primary transfer roller 64 is conveyed to a secondary transfer position that is a position facing the secondary transfer roller 10 by the rotation of the intermediate transfer belt 61.

  The secondary transfer roller 10 is pressed against the outer peripheral surface of the intermediate transfer belt 61 whose inner peripheral surface is in contact with the peripheral surface of the intermediate transfer belt driving roller 62 at a predetermined nip pressure during image formation. The secondary transfer roller 10 has a toner charging polarity when a recording sheet fed from the internal paper feeding unit 107 or the manual paper feeding unit 106 passes between the secondary transfer roller 10 and the intermediate transfer belt 61. A high voltage having a polarity opposite to that of is applied. As a result, the toner image is transferred from the outer peripheral surface of the intermediate transfer belt 61 to the surface of the recording paper. Further, in order to constantly obtain the nip pressure at the secondary transfer position, one of the secondary transfer roller 10 and the intermediate transfer belt drive roller 62 is formed of a hard material made of metal or the like, and the other These rollers are made of a soft material made of elastic rubber, foamable resin, or the like.

  Of the toner adhering to the intermediate transfer belt 61 from a part or all of the photosensitive drum 3, the toner remaining on the intermediate transfer belt 61 without being transferred onto the recording sheet is prevented in order to prevent color mixing in the next step. It is removed and collected by the intermediate transfer belt cleaning unit 65. The intermediate transfer belt cleaning unit 65 includes a cleaning blade that contacts the intermediate transfer belt 61 and removes toner.

  The fixing unit 103 includes a heat roller 71 and a pressure roller 72. The recording sheet on which the toner image is transferred at the secondary transfer position is guided to the fixing unit 103 and is heated and pressed by passing between the heat roller 71 and the pressure roller 72. As a result, the toner image is firmly fixed on the surface of the recording paper. In the fixing unit 103, the heat roller 71 is provided in contact with an external fixing belt 73 that heats the heat roller 71 from the outside, and the heat roller 71 is based on temperature data detected by a temperature detector (not shown). Control is performed so as to achieve a predetermined fixing temperature. The recording sheet on which the toner image is fixed is discharged onto the discharge tray 91 by the transport roller 12b.

  In the image forming apparatus 100, the recording sheets stored in the internal paper feeding unit 107 and the manual paper feeding unit 106 are ejected between the secondary transfer roller 10 and the intermediate transfer belt 61 and via the fixing unit 103. A sheet conveyance path S extending in a substantially vertical direction for feeding to 91 is provided. In the vicinity of the sheet conveyance path S, pickup rollers 11a and 11b, a plurality of conveyance rollers 12a to 12d, and a registration roller 13 are arranged.

  The transport rollers 12 a to 12 d are small rollers for promoting and assisting the transport of the recording paper, and a plurality of the transport rollers 12 a to 12 d are provided along the paper transport path S. The pickup roller 11 a is provided in the vicinity of the end of the internal paper feed unit 107, picks up recording sheets from the internal paper feed unit 107 one by one, and supplies the recording paper to the paper transport path S. The pickup roller 11 b is provided near the end of the manual paper feed unit 106, picks up recording sheets one by one from the manual paper feed unit 106, and supplies the recording paper to the paper transport path S.

  The registration roller 13 temporarily holds the recording paper conveyed through the paper conveyance path S. The recording paper is transported between the secondary transfer roller 10 and the intermediate transfer belt 61 at the timing when the leading edge of the toner image on the intermediate transfer belt 61 is aligned with the leading edge of the recording paper.

  Further, in the image forming apparatus 100, in the case of double-sided printing in which images are formed on both sides of a recording sheet, the recording sheet that has finished single-sided printing and has passed through the fixing unit 103 is gripped by the conveyance roller 12b. In addition, the transport roller 12b rotates backward and is guided to the transport rollers 12c and 12d. The recording paper guided to the transport rollers 12 c and 12 d passes through the registration roller 13, the secondary transfer roller 10, and the fixing unit 103, is printed on the back surface, and is discharged to the paper discharge tray 91.

  Next, the electrical configuration of the image forming apparatus 100 will be described. FIG. 2 is a block diagram illustrating an electrical configuration of the image forming apparatus 100.

  As shown in FIG. 2, the image forming apparatus 100 includes an apparatus control unit 21, a storage device 22, a calculation unit 23, a display unit 24, an input unit 25, a USB / LAN 26, a reading unit 27, an image processing unit 28, and an image forming unit. 104 and a peripheral device control unit 29 are provided.

  The apparatus control unit 21 comprehensively controls an image forming operation in the image forming apparatus 100. The storage device 22 receives a print command input via an operation panel arranged on the upper surface of the image forming apparatus 100, detection results from various sensors arranged in various places inside the image forming apparatus 100, and USB / Image information input via the LAN 26, various setting values and data tables for controlling the operation of each unit in the image forming apparatus 100, programs for executing various controls, and the like are stored. The operation panel includes a display unit 24 and an input unit 25.

  As the storage device 22, for example, a read only memory (ROM), a random access memory (RAM), and a hard disk drive (HDD) can be used. The external device is an electrical device or an electronic device that can form or acquire image information and can be electrically connected to the image forming apparatus 100. For example, a computer, a digital camera, etc. are mentioned.

  The computing unit 23 takes out various data stored in the storage device 22, such as a print command, detection results and image information, and a program for executing various controls, and performs at least one of various detections and various determinations. The device control unit 21 controls each unit by transmitting a control signal to each unit according to various determination results and calculation results in the calculation unit 23.

  The device control unit 21 and the calculation unit 23 are processing circuits realized by, for example, a microcomputer or a microprocessor that includes a central processing unit (CPU).

  The peripheral device control unit 29 controls peripheral devices connected to the image forming apparatus 100. The peripheral device is, for example, a finisher or sorter as a post-processing device.

  Next, the photosensitive drum 3 and the charging device 5 shown in FIG. 1 will be described. 3 is a perspective view showing the photosensitive drum 3 and the charging device 5. FIG. 4 is an explanatory view showing the internal structure of the photosensitive drum 3. FIG. 5 shows the drum boss portion 306 and the cylindrical fin member 312 of the photosensitive drum 3. It is a perspective view shown.

  As shown in FIG. 3, the photosensitive drum 3 has a cylindrical drum shape, and is driven to rotate around a rotation axis by a driving device (not shown). The photosensitive drum 3 has a cylindrical conductive substrate 301 (see FIG. 4), and has a photosensitive layer 302 (see FIG. 3) on the surface of the conductive substrate 301. The surface of the photosensitive layer 302 is an image area where an electrostatic latent image is formed.

  The photosensitive drum 3 has cylindrical flange portions 303 and 304 adjacent to both ends of the photosensitive layer 302. The flange portion 303 is adjacent to one end portion of the photosensitive layer 302, and the flange portion 304 is adjacent to the other end portion of the photosensitive layer 302. The flange portions 303 and 304 are portions corresponding to non-image regions where an electrostatic latent image is not formed.

  Further, the photosensitive drum 3 has a gear portion 305 for rotationally driving the photosensitive drum 3 adjacent to the outer side of the one flange portion 303 in the rotational axis direction, and on the outer side of the other flange portion 304 in the rotational axis direction. There is a drum boss portion 306 adjacent thereto. A plurality of intake ports 309 are formed in the flange portions 303 and 304 in the circumferential direction of the flange portions 303 and 304. Through the intake port 309, the internal space and the external space of the photosensitive drum 3 communicate with each other.

  In the space inside the conductive substrate 301 of the photosensitive drum 3, ozone filters and dust collection filters 307 and 308 are located in the vicinity of both flange portions 303 and 304 and on the inner side of both flange portions 303. Is provided. The ozone filter / dust collection filter 307 is disposed in the vicinity of one flange portion 303, and the ozone filter / dust collection filter 308 is disposed in the vicinity of the other flange portion 304. These ozone filter / dust collection filters 307 and 308 are made of, for example, an activated carbon filter and capture discharge products and dust containing ozone.

  The drum boss part 306 has a boss part 310 and a pipe part (pipe member) 311. The boss portion 310 is located at the outer end portion on the flange portion 304 side in the rotation axis direction of the photosensitive drum 3. The pipe portion 311 extends along the rotation axis direction of the photosensitive drum 3 through the ozone filter / dust collection filter 308 from the surface on the flange portion 304 side of the boss portion 310 toward the gear portion 305 on the opposite side. Yes.

  A cylindrical fin member 312 is provided at the inner end of the pipe portion 311 in the rotation axis direction of the photosensitive drum 3. The cylindrical fin member 312 extends in the direction of the rotational axis of the photosensitive drum 3 from the end of the pipe portion 311 toward the gear portion 305 on the opposite side. In the cylindrical fin member 312, a large number of air holes 315 extending in the rotation axis direction of the photosensitive drum 3 are formed so as to be aligned in the circumferential direction of the cylindrical fin member 312. The vent hole 315 passes through the cylindrical fin member 312 and communicates with a gas flow path (not shown) inside the cylindrical fin member 312. In addition, fins 316 are formed between adjacent vent holes 315. Accordingly, the fins 316 are formed on the outer peripheral surface of the cylindrical fin member 312 in the rotational axis direction of the photosensitive drum 3 and have a predetermined height in the radial direction of the cylindrical fin member 312. Furthermore, the cylindrical fin member 312 has a shape in which an end portion on the opposite side to the pipe portion 311 side in the rotation axis direction is closed.

  As shown in FIG. 5, an exhaust port 313 extending in the rotation axis direction of the photosensitive drum 3 is formed at the center of the boss portion 310 of the drum boss portion 306, and this exhaust port 313 is a gas flow in the pipe portion 311. It communicates with the path 314. Further, the gas flow path 314 communicates with a gas flow path (not shown) in the cylindrical fin member 312. FIG. 5 shows a state where the pipe portion 311 and the cylindrical fin member 312 are separated.

  An adsorption layer 317 that adsorbs discharge products such as floating nitrogen oxide is formed on the outer peripheral surfaces of the pipe portion 311 and the cylindrical fin member 312. The discharge product is generated by the discharging operation of the charging device 5 when the photosensitive drum 3 is charged. The adsorption layer 317 is formed by, for example, applying zeolite to the surfaces of the pipe portion 311 and the cylindrical fin member 312.

  As the adsorbent for forming the adsorbing layer 317, in addition to the above zeolite, silica alumina type adsorbent, silica gel, alumina gel, or activated alumina can be used, but zeolite is preferable.

Zeolite is a material with excellent adsorption performance for discharge products such as nitrogen oxides. Therefore, if zeolite is used as the adsorption layer 317, the efficiency of adsorbing and removing discharge products can be improved. Zeolite has a three-dimensional network structure in which the TO ₄ tetrahedron (T = Si, Al) shares the apex oxygen (O) atom, and can be exchanged with zeolite water that can be desorbed without breaking the structure. Is a crystalline material of aluminosilicate, and has fine pores in the crystal.

  Examples of the method for forming the adsorption layer 317 made of zeolite on the pipe portion 311 and the cylindrical fin member 312 include the following two methods. The first method uses a mixed aqueous solution of silica / alumina gel and tetrapropylammonium salt to form an adsorbing layer 521 by precipitating crystals under a hydrothermal condition of 100 to 200 ° C. in a high pH region. It is. In the second method, the adsorption layer 521 is formed by a coating method using a paste-like dispersion liquid in which zeolite particles are dispersed in triethylene glycol (TEG).

  An exhaust device 401 including an exhaust fan 402 is provided at a position in the rotation axis direction of the photosensitive drum 3 on the drum boss portion 306 side. The exhaust device 401 forms a flow of air from the periphery of the photosensitive drum 3 to the outside of the image forming apparatus 100 through the inside of the photosensitive drum 3, and the air inside the image forming apparatus 100 is passed through the above-described path. The air is exhausted to the outside of the image forming apparatus 100.

  As shown in FIG. 3, the charging device 5 is disposed so as to face the photosensitive layer 302 of the photosensitive drum 3 with a predetermined interval. As shown in FIG. 6, the charging device 5 includes a discharge electrode 512, a holding member 515, a discharge electrode 512 and a shield case 511, and a grid electrode 514. FIG. 6 is a perspective view showing a specific configuration of the charging device 5 shown in FIG.

  The shield case 511 extends along a longitudinal direction parallel to the rotation axis of the photosensitive drum 3, and a region facing the photosensitive drum 3 is a shield opening 511 a. The shield case 511 is made of, for example, stainless steel, and has a rectangular parallelepiped outer shape and an internal space. A holding member 515 is provided on the bottom surface of the shield case 511, and the discharge electrode 512 is fixed to the holding member 515 with a screw 516.

  The discharge electrode 512 protrudes in a short direction from a flat plate portion 512a extending in the axial direction of the photosensitive drum 3 and one end surface of the flat plate portion 512a in a short direction (a direction perpendicular to the rotational axis direction of the photosensitive drum 3). And is formed in a plate shape. The material of the discharge electrode 512 can be used without particular limitation as long as corona discharge can be performed by applying a voltage and the sharp protrusion 512b can be formed. For example, stainless steel, aluminum, nickel, copper, iron Etc. Among these, stainless steel is preferable. The grid electrode 514 is provided in the shield opening 511 a of the shield case 511 and adjusts the charging potential on the surface of the photosensitive drum 3.

  In the charging device 5, the surface of the photosensitive drum 3 is charged by applying a voltage of several kV to the discharge electrode 512 and performing corona discharge. In this case, a predetermined grid voltage is applied to the grid electrode 514, whereby the charged state of the surface of the photosensitive drum 3 can be made uniform.

  In the above configuration, when corona discharge is performed in the charging device 5 in order to charge the surface of the photosensitive drum 3 to a predetermined potential, discharge products such as nitrogen oxides and ozone are generated. This discharge product drifts around the photosensitive drum 3, and particularly when nitrogen oxide adheres to the photosensitive drum 3, it causes an abnormal image.

  On the other hand, when the exhaust device 401 operates, the air inside the photosensitive drum 3 is sucked, and the air is discharged to the outside of the photosensitive drum 3 through the exhaust port 313 of the drum boss portion 306, and further, the image forming apparatus 100. It is discharged outside. Accordingly, the air around the photosensitive drum 3 is taken into the photosensitive drum 3 and then discharged to the outside of the image forming apparatus 100 through the same path as the air inside the photosensitive drum 3 described above. Hereinafter, this operation will be described in detail.

  FIG. 7 is an explanatory diagram showing the flow of air generated by the operation of the exhaust device 401. When the exhaust device 401 is operated, the air around the photosensitive drum 3 is taken into the photosensitive drum 3 from the air inlets 309 of the flange portions 303 and 304 (air flow F).

  The air taken into the photosensitive drum 3 passes through the ozone filter / dust collection filters 307 and 308 and is taken into the area between the ozone filter and dust collection filters 307 and 308 (air flow F). At this time, discharge products such as ozone and dust contained in the air are captured by the ozone filter / dust collection filters 307 and 308 and removed from the air.

  Next, the air taken into the region between both the ozone filter / dust collection filters 307 and 308 is taken into the space in the cylindrical fin member 312 from the vent hole 315 of the cylindrical fin member 312, and further the drum boss portion 306. Are discharged to the outside of the photosensitive drum 3 through the gas flow path 314 of the pipe portion 311 and the exhaust port 313 of the boss portion 310. The air discharged to the outside of the photosensitive drum 3 is further discharged to the outside of the image forming apparatus 100 by the exhaust device 401.

  Here, the discharge products contained in the air taken into the region between the ozone filters and dust collection filters 307 and 308 (those not captured by the ozone filters and dust collection filters 307 and 308) are piped. The adsorption layer 317 on the surface of the part 311 and the adsorption layer 317 on the surface of the fin 316 of the cylindrical fin member 312 are adsorbed. In this case, the air discharged from the exhaust port 313 through the pipe portion 311 comes into the pipe portion 311 after coming into contact with the fin 316 having the adsorption layer 317 of the cylindrical fin member 312, so that the discharge product is efficiently obtained. Can be removed. Therefore, the discharge product generated by the corona discharge of the charging device 5 does not adhere to the photosensitive layer 302 of the photosensitive drum 3 and is not discharged outside the image forming apparatus 100. As a result, image defects such as white spots and image flow caused by the discharge products adhering to the photosensitive layer 302 of the photosensitive drum 3 can be prevented.

  Moreover, the molecular weight of nitric oxide (NO) is 30.0 g / mol, the molecular weight of nitrogen dioxide (NO2) is 46.0 g / mol, and the molecular weight of air is 28.9 g / mol. Therefore, discharge products such as nitrogen oxides composed of nitrogen monoxide and nitrogen dioxide are heavier than air. Therefore, the discharge product generated when the charging device 5 charges the surface of the photosensitive drum 3 flows downward along the surface of the photosensitive drum 3 in the vertical direction.

  In other words, the discharge product does not rise in the air, but flows downward from the periphery of the photosensitive drum 3 in the vertical direction. Therefore, the photosensitive member is caused by the air flow from the intake port 309 of the flange portions 303 and 304 to the inside of the photosensitive drum 3. It can be taken into the drum 3 and efficiently removed by the ozone filter and dust collection filters 307 and 308 and the adsorption layer 317 inside the photosensitive drum 3.

  In addition, among the configurations for removing discharge products from the air, configurations other than the exhaust device 401 that generates an air flow can be accommodated in the photosensitive drum 3. Thus, the configuration around the photosensitive drum 3 and the size of the image forming apparatus can be reduced.

  FIG. 8 shows the experimental results of examining the function of preventing image defects by the adsorption layer 317 made of zeolite.

The conditions and measurement items in this experiment are as follows.
Samples of the photosensitive drum 3: Samples of the photosensitive drum 3 of 10 types (eight examples and two comparative examples) having different thicknesses of the adsorption layer 317 including a configuration in which the adsorption layer 317 is not provided are prepared. The image forming apparatus 100 is mounted.
Measurement item: After copying 50 sheets for each sample, after leaving for 1 hour, (1) White spot level at the circumferential length of the photoreceptor in an environment of temperature 25 ° C. and humidity 5% (measured image) Is an intermediate image), (2) The electrostatic latent image flow level (measured image is a character image) on the surface of the photoreceptor in an environment of a temperature of 35 ° C. and a humidity of 85% was examined. The total number of copies was 3000 sheets / month, and the above (1) and (2) were evaluated visually.
Exhaust device 401: The wind speed of the air flow generated by the exhaust device 401 was 3 m / sec, and the operation time of the exhaust device 401 was 60 seconds after the end of printing.

The meanings of “◎”, “◯”, “Δ”, and “X” in the evaluation results of FIG. 8 are as follows.
A: No image pitch unevenness / no text blur.
○: Image pitch unevenness is slightly present (light white stripes having a width of 10 mm in the horizontal direction of the image) / character blurring is slightly present (character blurring is slightly present).
Δ: Image pitch unevenness (white stripes up to a width of 20 mm in the horizontal direction of the image) / character blurring (character blurring slightly).
X: Image pitch unevenness is very high (white streaks with a width of more than 20 mm in the horizontal direction of the image) / character recognition is impossible.

  From the results of FIG. 8, it was found that the preferable thickness range of the adsorption layer 317 made of zeolite is 40 μm or more and 150 μm or less. In consideration of the adsorption capacity and cost of the discharge product, a more preferable range of the thickness of the adsorption layer 317 is 50 μm or more and 100 μm or less. That is, when the thickness of the adsorption layer 317 is 150 μm, the adsorption capability for the discharge product is good, but the cost increases due to the increase in the layer thickness. If the adsorption layer 317 is set to the above preferred range, the ability of the adsorption layer 317 to adsorb and remove discharge products in the air can be maintained over a long period of time.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

3 Photosensitive drum 5 Charging device 100 Image forming apparatus 101 Automatic document feeder 102 Document reading unit 103 Fixing unit 104 Image forming unit 105 Exposure unit 106 Manual sheet feeding unit 107 Internal sheet feeding unit 111 Toner image forming unit 302 Photosensitive layer
303,304 Flange part 305 Gear part 306 Drum boss part
307,308 Ozone filter and dust collecting filter 309 Intake port 310 Boss portion 311 Pipe portion 312 Cylindrical fin member 313 Exhaust port 314 Gas flow path 315 Vent 316 Fin 401 Exhaust device 402 Exhaust fan 511 Shield case 512 Discharge electrode 514 Grid electrode

Claims (5)

A cylindrical photosensitive drum on which an electrostatic latent image is formed;
A corona charger for charging the photosensitive drum by corona discharge;
In an image forming apparatus comprising an exhaust device that exhausts air inside the image forming apparatus to the outside of the apparatus,
The photosensitive drum is formed with an air inlet for taking in air around the photosensitive drum in the internal space of the photosensitive drum in a non-image area where the electrostatic latent image is not formed on the outer peripheral surface around the rotation axis. An exhaust port for discharging air in the internal space of the photosensitive drum is formed on one end surface in the rotation axis direction, and is included in the air between the intake port and the exhaust port in the internal space. A filter is provided for capturing discharge products from the corona discharge,
The image forming apparatus, wherein the exhaust device forms an air flow from the intake port to the exhaust port through the filter. The photoconductive drum has the non-image area on both sides of an image area where the electrostatic latent image is formed, and a non-image area far from the exhaust port has a first intake port as the intake port. Formed,
In the non-image area closer to the exhaust port, a second intake port is formed as the intake port,
A first filter is provided as the filter between a center point in the rotational axis direction of the photosensitive drum and the first air inlet, and between the center point and the second air inlet. A second filter is provided as the filter;
The image forming apparatus according to claim 1, wherein a pipe member that extends from the exhaust port through the second filter and extends in the first filter direction is connected to the exhaust port.   The image forming apparatus according to claim 2, wherein an adsorption layer that adsorbs discharge products is formed on an outer peripheral surface of the pipe member.   The end of the pipe member in the second filter direction has a plurality of vent holes extending in the rotation axis direction of the photosensitive drum. The vent holes are formed so as to be arranged around the rotation axis, and adjacent to each other. A fin is formed between the pores, and a cylindrical fin member having a closed end opposite to the pipe member side in the rotational axis direction is connected, and the suction surface is connected to an outer peripheral surface of the cylindrical fin member. The image forming apparatus according to claim 3, wherein a layer is formed.   The image forming apparatus according to claim 3, wherein the adsorption layer contains zeolite.

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