JP5484183B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus that develops an electrostatic image on an image carrier by carrying the developer on the developer carrier, and more particularly to a structure that efficiently collects scattered toner associated with development.

  2. Description of the Related Art Image forming apparatuses that develop a static image on an image carrier by causing the developer carrier to carry the developer are widely used. In the image forming apparatus, when the electrostatic image potential and the toner charge amount change, the density of the developed toner image varies greatly. For this reason, an optical sensor that detects reflected light from the toner image may be disposed between the developing device along the rotation direction of the image carrier and the toner image transfer unit so as to face the image carrier. Yes (see FIG. 2). This is because the toner image density is measured using an optical sensor and fed back to the electrostatic image potential and the toner charge amount to ensure the reproducibility of the toner image density.

  However, if an optical sensor is disposed between the developing device and the toner image transfer portion, the optical sensor is easily affected by toner lump falling from the developing device and scattered toner generated during development. . When a toner lump or scattered toner enters the detection optical path of the optical sensor by riding on the airflow accompanying the rotation of the image carrier, the output noise of the optical sensor increases. When scattered toner adheres to the transparent window of the optical sensor, the measurement error of the toner applied amount becomes large. For this reason, various proposals have been made to reduce the influence of toner lump and scattered toner on the output of the optical sensor.

  In Patent Document 1, a mechanism that automatically cleans the transparent window of the optical sensor is provided periodically to clean the adhered toner. However, in this case, the toner image cannot be detected by the optical sensor during automatic cleaning, and the output of the optical sensor is affected by the toner lump and scattered toner during the toner image detection.

  Therefore, in Patent Document 2, air is constantly blown onto the transparent window of the optical sensor, and the adhering toner is removed by sucking the air.

JP 05-158318 A JP 2000-056443 A

  If the toner collected by the optical sensor is simply dropped, the dropped toner may cause new contamination. However, with the recent downsizing of developing devices, special structures such as Patent Documents 1 and 2 are provided in a narrow gap between the optical sensor and the image carrier, including the collected toner collecting structure. It has become difficult to provide. There is also an aspect against the reduction of the number of parts and the simplification of the mechanism.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus that efficiently collects toner lumps and scattered toner just before reaching an optical sensor, and that can always detect an accurate toner image by the optical sensor. Yes.

An image forming apparatus according to the present invention includes an image carrier, a developer carrier that carries a developer and develops an electrostatic image of the image carrier into a toner image, and is disposed below the developer carrier. Detecting means for optically detecting the toner image of the image carrier. Then, an exhaust means which exhausts to at least the developer and carrier side the overlying arranged cover member, one longitudinal end of said image bearing member air by sucking on said cover member of said detecting means, The cover member is provided such that a gap between the cover member and the image carrier is narrower than a gap between the detection means and the image carrier, and is arranged along a rotation direction of the image carrier. It is formed along the longitudinal direction of the image carrier so as to partition the developer carrier and the detection means.

  In the image forming apparatus of the present invention, a part of the airflow that moves around the photosensitive drum forms an airflow in the cylindrical space and stays in a state in which the toner is raised. The exhausting means sucks and exhausts the air containing the toner from the cylindrical space, so that the toner is not deposited on the floor of the cylindrical space. The toner can be efficiently collected between the two.

  Therefore, it is possible to efficiently collect the toner lump and the scattered toner just before reaching the optical sensor, and to always detect the accurate toner image by the optical sensor.

1 is an explanatory diagram of a configuration of an image forming apparatus. It is explanatory drawing of a structure of an image formation part. 2 is a block diagram of a control system of the image forming apparatus. FIG. 3 is a flowchart of image density control of the image forming apparatus. 3 is an explanatory diagram of a toner recovery structure of Embodiment 1. FIG. It is a partial perspective view of a developing device. 4 is an explanatory diagram of air flow in the toner recovery structure of Embodiment 1. FIG. It is explanatory drawing of the exhaust structure of a process cartridge. FIG. 6 is an explanatory diagram of a toner recovery structure of Example 2.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the present invention, as long as a cylindrical space in contact with the photosensitive drum is prepared between the developing sleeve and the optical sensor and exhaust is performed in the longitudinal direction, a part or all of the configuration of the embodiment can be used instead. Another embodiment in which the configuration is replaced can also be implemented.

  Therefore, not only the two-component developer but also a developing device using a one-component developer can be implemented. In a developing device using a two-component developer, not only a vertical type (FIG. 2) in which stirring screws are arranged vertically, but also a horizontal type developing device in which stirring screws are arranged horizontally can be implemented. Such a developing apparatus can be implemented without distinction in a tandem type / 1 drum type, intermediate transfer type / direct transfer type image forming apparatus.

  In the present embodiment, only main parts related to toner image formation will be described. However, the present invention includes a printer, various printing machines, a copier, a FAX, a multifunction machine, and the like in addition to necessary equipment, equipment, and a housing structure. The image forming apparatus can be used for various purposes.

  In addition, about the general matter of the image forming apparatus shown by patent document 1, 2, illustration is abbreviate | omitted and the overlapping description is abbreviate | omitted.

<Image forming apparatus>
FIG. 1 is an explanatory diagram of the configuration of the image forming apparatus. FIG. 2 is an explanatory diagram of the configuration of the image forming unit.

  As shown in FIG. 1, the image forming apparatus 20 is a tandem intermediate transfer type full-color printer in which yellow, magenta, cyan, and black image forming portions Py, Pm, Pc, and Pb are arranged along an intermediate transfer belt 7. is there.

  In the image forming unit Py, a yellow toner image is formed on the photosensitive drum 1 and transferred to the intermediate transfer belt 7. In the image forming unit Pm, a magenta toner image is formed on the photosensitive drum 1 and transferred to the intermediate transfer belt 7. In the image forming portions Pc and Pb, a cyan toner image and a black toner image are formed on the photosensitive drums 1 and 1, respectively, and transferred to the intermediate transfer belt 7.

  The intermediate transfer belt 7 is stretched around the driving roller 6a, the opposing roller 6b, and the tension roller 6c, and is rotated in the direction of the arrow R2 by the driving roller 6a. The four-color toner images transferred to the intermediate transfer belt 7 are conveyed to the secondary transfer portion Tn and secondarily transferred to the recording material P.

  The recording material P taken out from the recording material cassette 10 by the pickup roller 11 is separated one by one and fed to the registration roller 13. The registration roller 13 sends the recording material P to the secondary transfer portion Tn in synchronization with the toner image on the intermediate transfer belt 7.

  When an image is formed only on one side of the recording material P, the recording material P to which the toner image has been transferred is heated and pressurized by the fixing device 15 and fixed on the surface, and then discharged to the external tray 18. The On the other hand, when images are formed on both sides of the recording material P, the recording material P discharged from the fixing device 15 is guided to the lower reverse conveyance path 12b by the switching flapper 16. In the reverse conveyance path 12b, when the rear end of the recording material P reaches the reversal point Rp, the recording material P is switched back and sent to the double-side conveyance path 12c with the image carrying surface facing upward. In the double-side conveyance path 12c, the recording material P is conveyed to the registration roller 13 through the conveyance path 12a.

  Since the image forming portions Py, Pm, Pc, and Pb are substantially the same except that the toner colors used in the developing devices 4, 4, 4, and 4 are different, the image forming portion Py will be described below.

  As shown in FIG. 2, the image forming unit Py includes a corona charger 2, an exposure device 3, a developing device 4, a primary transfer roller 8, and a drum cleaning device 5 around the photosensitive drum 1. The image forming unit Py includes a sensor unit 100 that is disposed below the developing sleeve 42 and optically detects the toner image on the photosensitive drum 1 and is attached to the image forming apparatus 20 in a replaceable manner. It is a cartridge.

  A photosensitive drum 1, which is an example of an image carrier, is formed with a photosensitive layer having a negative charge polarity on the outer peripheral surface of an aluminum cylinder, and rotates in the direction of arrow R1 at a predetermined process speed. A corona charger 2 which is an example of a charging unit charges the surface of the photosensitive drum 1 to a uniform negative potential. An exposure apparatus 3 which is an example of an exposure unit scans a laser beam with a rotating mirror and writes an electrostatic image of an image on the surface of the charged photosensitive drum 1. The developing device 4, which is an example of a developing unit, develops an electrostatic image using a developer including toner and a carrier to form a toner image on the photosensitive drum 1.

  The primary transfer roller 8 presses the inner surface of the intermediate transfer belt 7 to form a primary transfer portion T <b> 1 between the photosensitive drum 1 and the intermediate transfer belt 7. By applying a positive DC voltage to the primary transfer roller 8, the negative toner image carried on the photosensitive drum 1 is primarily transferred to the intermediate transfer belt 7. The drum cleaning device 5 collects transfer residual toner remaining on the photosensitive drum 1 after escaping from the transfer to the recording material P.

  After the toner image is transferred, the transfer residual toner remaining on the surface of the intermediate transfer belt 7 is removed by the belt cleaner 9 and used for the next image formation.

<Developing device>
As shown in FIG. 2, a plurality of developing sleeves 41 and 42 are arranged in a state of facing each other along the rotation direction of the photosensitive drum 1. The developing device 4 develops the electrostatic image on the photosensitive drum 1 by supporting the two-component developer containing toner (non-magnetic) and carrier (magnetic) on the developing sleeves 41 and 42 which are examples of the developer-carrying member. .

  In the developing container 40, a developing chamber 45 and an agitating chamber 46 are vertically arranged with a partition wall 48 therebetween, and the developing chamber 45 and the agitating chamber 46 communicate with each other in the vertical direction through openings provided at both ends of the partition wall 48. ing. The developing screw 43 supplies the developer in the developing chamber 45 to the developing sleeve 41 while conveying the developer. The agitating screw 44 mixes the developer collected from the developing sleeve 42 and the developer in the agitating chamber 46, conveys it in the opposite direction to the developing screw 43, and circulates the developer between the developing chamber 45.

  The developing container 40 is provided with a pair of developing sleeves 41 and 42 rotatably arranged side by side, and non-rotating magnets 51 and 52 for attracting carriers (magnetism) are arranged inside the developing sleeves 41 and 42. Has been. A layer thickness regulating blade 47 is disposed upstream in the rotation direction of the developing area where the developing sleeve 41 faces the photosensitive drum 1, and regulates the thickness of the developer carried on the developing sleeve 41.

  The developer carried on the developing sleeve 41 is transferred to the developing sleeve 42 at the opposed portion of the developing sleeve 41 and the developing sleeve 42 after being involved in the development of the electrostatic image at the first developing portion facing the photosensitive drum 1. . The developer carried on the developing sleeve 42 is again collected in the developing container 40 after being involved in the development of the electrostatic image again in the second developing unit facing the photosensitive drum 1. As such, the magnetic poles of the magnets 51 and 52 inside the developing sleeves 41 and 42 are arranged.

<Optical sensor>
FIG. 3 is a block diagram of a control system of the image forming apparatus. FIG. 4 is a flowchart of image density control of the image forming apparatus.

  As shown in FIG. 1, in the electrophotographic image forming apparatus 20, a test patch toner image is formed on the photosensitive drum 1 in order to cope with a change in image density and color due to a change in temperature and a state of a developer. The concentration is detected. The control unit 19 detects the density of the test patch, controls the image forming conditions, and adjusts the image quality regarding the density and color of the image.

  As shown in FIG. 2, an optical sensor 101 that optically detects the toner image on the photosensitive drum 1 is installed below the developing sleeve 42 along the rotation direction of the photosensitive drum 1. The optical sensor 101 includes a density detection unit 102 including a light projecting unit and a light receiving unit, and is disposed so as to face the photosensitive drum 1.

  The density detection of the test patch is performed by the optical sensor 101 which is an example of a density detection unit. The density detection of the test patch is performed by forming a test patch on the photosensitive drum 1 by the image forming unit Py, measuring the reflected light by emitting measurement light from the light projecting unit of the density detection unit 102 to the test patch, and measuring the test patch. It is determined by the ratio between light and reflected light. For this reason, if the density detection unit 102 of the optical sensor 101 is contaminated with toner or the like, it causes a decrease in density detection accuracy and causes a change in density or color.

  As shown in FIG. 3, the control unit 19 includes a CPU and a memory such as a ROM and a RAM. When the control unit 19 receives a print command signal output from an external device (not shown) such as a host computer, the control unit 19 sequentially operates the image forming units Py, Pm, Pc, and Pb according to the image forming control sequence stored in the memory. To do.

  As shown in FIG. 4 with reference to FIG. 3, the control unit 19 writes the electrostatic image of the test patch by the exposure device 3 in the interval between the images at the timing for forming a predetermined number of images (YES in S <b> 11). . The electrostatic image of the test patch is developed by the developing device 4 and a test patch of each color is formed on the photosensitive drum 1 (S13). Each color test patch is detected by the optical sensor 101 provided in each of the image forming units Py, Pm, Pc, and Pb (S13). The control unit 19 sets an optimum image forming condition for each of the image forming units Py, Pm, Pc, and Pb based on the detection result of the optical sensor 101 (S14).

  More specifically, the toner charge amount is adjusted for each image formation to control the toner charge amount. When the amount of toner on the test patch is large (the image density is high), the amount of toner to be replenished is reduced, the chance of toner friction is increased, and the amount of charge is increased to increase the charge amount. Reduce the amount of toner adhering. On the other hand, when the amount of toner on the test patch is small (the image density is low), the amount of toner to be replenished is increased to reduce the amount of toner friction to reduce the charge amount, thereby reducing the amount of charge. Increase the amount of toner adhering to the electrostatic image.

  By the way, as shown in FIG. 2, when the optical sensor 101 detects a test patch on the photosensitive drum 1 during the density detection process, it is scattered between the photosensitive drum 1 and the density detector 102 of the optical sensor 101. Toner may pass through. At this time, the optical sensor 101 may erroneously recognize the scattered toner as a part of the test patch and generate an output indicating that the amount of applied toner is larger than the actual amount. In such a case, the original performance of the optical sensor 101 is impaired, and the density of the test patch cannot be detected accurately.

  In this regard, in Patent Document 1 (Japanese Patent Laid-Open No. 05-158318), a mechanism for automatically cleaning the window of the density detection unit is provided periodically to clean the toner or the like adhering to the window of the density detection unit. Further, in Patent Document 2 (Japanese Patent Application Laid-Open No. 2000-056443), air is blown onto the window of the density detection unit, and the air is sucked so that the toner adheres to the window of the density detection unit even if the toner is scattered. I try not to.

  However, in any of these conventional techniques, when the density detector detects the density of the test patch on the photosensitive drum 1, scattered toner may pass between the density detector and the test patch. At this time, the density detector erroneously detects scattered toner as part of the test patch, and the output value of the density detector and the density of the test patch may be different. When this happens, an incorrect image forming condition is set, which adversely affects changes in density and color.

  Therefore, in the following embodiments, an air suction structure for sucking scattered toner is provided, and a suction port is disposed in the vicinity of the optical sensor 101, so that the space between the density detection unit 102 of the optical sensor 101 and the photosensitive drum 1 is provided. The scattered toner is prevented from passing.

<Example 1>
FIG. 5 is an explanatory diagram of a toner recovery structure according to the first exemplary embodiment. FIG. 6 is a partial perspective view of the developing device. FIG. 7 is an explanatory diagram of the air flow in the toner recovery structure of the first embodiment.

  As shown in FIG. 5, in the toner recovery structure of Example 1, the photosensitive drum 1 side and the developing sleeve 42 side of the optical sensor 101 are covered with an integral upper cover 103. The edge of the upper surface of the upper cover 103 protrudes in a shelf shape toward the photosensitive drum 1, thereby forming a cylindrical space in contact with the upper surface of the upper cover 103 and the photosensitive drum 1 along the longitudinal direction of the photosensitive drum 1. Yes.

  The sensor unit 100 includes an optical sensor 101 and a sensor holder 105, and is attached to the lower side of the developing device 4 and assembled in an image forming unit (process cartridge) Py. In the optical sensor 101, the density detection unit 102 is opposed to the photosensitive drum 1 through a detection window 106 provided in the sensor holder 105. The density detector 102 irradiates the test patch formed on the photosensitive drum 1 with infrared light and detects the reflected light. The sensor holder 105 is formed by an upper cover 103 and a lower cover 104 that cover the optical sensor 101.

  As shown in FIG. 5, the sensor holder 105 is disposed so as to integrally cover the developing sleeve side (developer carrier side) and the photosensitive drum side (image carrier side) of the optical sensor 101. The sensor holder 105 faces the photosensitive drum 1 at a predetermined interval in a part in the longitudinal direction of the photosensitive drum 1.

  Between the upper surface of the sensor holder 105 and the density detection unit 102, a wind-cut wall 109 protruding in a shelf shape toward the photosensitive drum 1 is provided. The tip of the wind wall 109 divides the first space 111 on the upper surface of the sensor holder 105 and the second space between the density detection unit 102 and the photosensitive drum 1, and is narrow between the photosensitive drum 1. A gap is formed.

  As shown in FIG. 6, when the vicinity of the density detection unit 102 is viewed from the photosensitive drum 1 side, a duct 110 for sucking air on the upper surface of the sensor holder 105 is provided on the inner side of the sensor holder 105 in the longitudinal direction of the photosensitive drum 1. Be placed. The duct 110, which is an example of the exhaust pipe line, is placed in the cross section of the sensor holder 105 perpendicular to the longitudinal direction of the developing device 4 and is disposed at substantially the same height as the sensor holder 105.

  The duct 110 is disposed along the longitudinal direction of the photosensitive drum 1 so as to be within the cross section of the sensor holder 105 perpendicular to the longitudinal direction of the photosensitive drum 1, and the lower edge of the opening at the tip of the duct 110 and the upper surface of the sensor holder 105. And are connected on the slope. The duct 110 connects the bottom surface of the suction port 107 at the tip and the top surface of the sensor holder 105 with a slope 108 so that air on the top surface of the sensor holder 105 can be sucked. The suction port 107 is disposed so that the lower surface of the duct 110 extends longer than the upper surface and is inclined obliquely upward and has a slope 108 extending to the vicinity of the upper surface of the sensor holder 105.

  When the inclined surface 108 protrudes above the upper surface of the sensor holder 105, turbulence may occur in the airflow generated by air suction at the transfer portion between the inclined surface 108 and the upper surface of the sensor holder 105. For this reason, the end of the slope 108 is arranged to be slightly below the upper surface of the sensor holder 105.

  A first space 111 that is surrounded by the upper surface of the sensor holder 105, the developing device 4, and the photosensitive drum 1 in a cylindrical shape and communicates in the axial direction of the photosensitive drum 1 is formed, and the suction port 107 is located behind the sensor holder 105. It is arranged so as to hide.

  As shown in FIG. 5, the upper surface of the sensor holder 105 and the wind cutting wall 109 are flat and continuous, and the intersection angle between the upper surface of the sensor holder 105 and the photosensitive drum 1 is 90 degrees or more. For this reason, most of the airflow that includes the scattered toner and moves around the photosensitive drum 1 is scooped by the wind-cut wall 109, stays in a vortex in the first space 111, and hardly reaches the density detection unit 102. I ’m not going. Most of the airflow 122 generated by the rotation of the photosensitive drum 1 is diverted to the upper surface of the sensor holder 105 by the wind cutting wall 109, so that the airflow 122 flows toward the first space 111 and flows into the second space 112. Is very small.

  Since the gap between the photosensitive drum 1 and the wind cutting wall 109 is narrow, most of the airflow generated by suction through the suction port (107: FIG. 6) passes through the upper portion of the sensor holder 105 as indicated by a broken line. For this reason, the air entrained with the scattered toner and the accumulated toner hardly reaches the second space 112 between the detection window 106 and the photosensitive drum 1 formed under the wind cut wall 109. Even if it reaches, it passes through a position away from the detection window 106 by being blocked by the wind-cut wall 109, so that it is very rare to enter the sensor holder 105 from the detection window 106 and enter the concentration detection unit 102.

  Further, since the upper surface of the sensor holder 105 is exposed to a strong airflow generated with the rotation of the photosensitive drum 1, the toner does not fall down. The charged toner easily adheres to the wall surface or the floor surface, and toner with a small charge amount accumulates from the adhesion starting point, and may be separated into a lump and fall as the toner charge is attenuated. A strong air current is generated in the first space 111 as the photosensitive drum 1 rotates, and thus such adhesion and accumulation are avoided. Even a toner lump that has fallen from the direction of the developing sleeve 42 can stay in the first space 111 in a mixed and stirred state by an airflow vortex without being accumulated, and can be pushed away in the longitudinal direction of the photosensitive drum 1.

  As shown in FIG. 7, since the airflow including the scattered toner forms a vortex in the first space 111 and stays, the toner does not fall on the upper surface of the sensor holder 105, and the longitudinal direction of the photosensitive drum 1 can be obtained. Move to. The air staying in the first space 111 passes through the sensor holder 105 and is guided to the inclined surface 108 and guided to the suction port 107. The air in the first space 111 is sucked from the suction port 107 to form airflows 120 and 121 along the longitudinal direction of the photosensitive drum 1. The airflows 120 and 121 sucked from the suction port 107 merge to become an airflow 123 that passes through the duct 110.

  Therefore, the scattered toner generated from the developing device 4 is sucked into the suction port 107 by the air currents 120 and 121 when it passes through the first space 111. Further, the scattered toner scattered by the air flow 122 due to the rotation of the photosensitive drum 1 also travels toward the first space 111 along the air flow 122, so that the scattered toner reaching the second space 112 is greatly reduced.

As a result, the amount of scattered toner passing between the density detector 102 and the photosensitive drum 1 is reduced, and when the optical sensor 101 detects a test patch formed on the photosensitive drum 1, the scattered toner is erroneously recognized. It is possible to reduce the possibility. As a result, the density detection accuracy can be increased, and the image density and color can be further stabilized.
In the first embodiment, the diameter of the photosensitive drum 1 is 84 mm, the diameter of the upper developing sleeve 41 is φ24.5 mm, and the diameter of the lower developing sleeve 42 is φ20 mm. The facing distance between the edge of the upper surface of the upper cover 103 and the photosensitive drum 1 is set to 2.3 mm. The sensor holder 105 is formed such that the distance (clearance) between the protruding edge of the upper surface and the photosensitive drum 1 is 1.5 mm or more and 2.5 mm or less.

  In order to collect the scattered toner, the smaller the clearance, the better. However, in Example 1, since the photosensitive drum 1 has a relatively large diameter, the upper surface of the sensor holder 105 is left even if a gap of about 2.0 mm is left. A sufficient airflow can be diverted. Further, when the thickness is 1.5 mm or less, the possibility that the photosensitive drum 1 is in contact with the sensor holder 105 and is damaged at the time of assembly or disassembly is increased. When the distance between the wind-cut wall 109 and the photosensitive drum 1 is too short, there is a possibility that the toner may be blown off due to a pressure change on the surface of the photosensitive drum 1 when passing through the gap between the wind-cut wall 109. If it is 1.5 mm or more, the photosensitive drum 1 and the sensor holder 105 do not come into contact with each other when the photosensitive drum 1 is pulled out during maintenance as well as during rotation of the photosensitive drum 1.

  According to the first embodiment, it is possible to reduce the possibility that the optical sensor 101 detects the scattered toner as a part of the test patch, and the output value of the optical sensor 101 is different from the density of the test patch. It ’s less likely to happen. As a result, the control of the image forming conditions can be made more accurate, and the density and color of the image can be further stabilized.

  According to the first embodiment, there is a duct 110 that sucks toner scattered above a sensor holder 105 that is a cover member of the optical sensor 101, and the photosensitive drum 1 is disposed between the sensor holder 105 and the density detection unit 102. There is a wind wall 109 close to the wall. For this reason, it is possible to set so that most of the airflow caused by suction passes through the upper part of the sensor holder 105 and hardly passes in front of the density detection unit 102, and is scattered between the density detection unit 102 and the photosensitive drum 1. Toner can be reduced.

  According to the first exemplary embodiment, since there are two or more developing sleeves that supply toner, the amount of toner scattering itself tends to increase with respect to one developing unit. For this reason, the effect of reducing scattered toner passing between the density detection unit 102 and the photosensitive drum 1 is further increased.

  According to the first embodiment, since the gap between the wind-cut wall 109 and the photosensitive drum 1 is 2.5 mm or less, the performance of the image forming unit Py and the maintainability of the photosensitive drum 1 are not impaired, and the first space 111 is used. And the second space 112 can be more clearly distinguished. Among the airflows generated by the suction of air through the duct 110, the airflow flowing through the second space 112 can be further reduced, so that the effect of reducing scattered toner passing between the density detection unit 102 and the photosensitive drum 1 is further increased. Become.

  According to the first embodiment, by reducing the cross-sectional area of the first space 111 with respect to the cross-sectional area of the duct 110, most of the airflow generated by the suction port 107 passes through the duct 110.

<Process cartridge>
FIG. 8 is an explanatory view of the exhaust structure of the process cartridge. As shown in FIG. 8, the structure for sucking the air in the first space 111 of the developing device 4 includes the suction port 107, the slope 108, the duct 110, the toner filter 121, the fan 122, the ozone filter 123, and the exhaust port 124. Is done.

  The image forming unit (process cartridge) Py is provided with a duct 125 for sucking air from a charging region where the corona charger 2 and the photosensitive drum 1 face each other. The duct 110 is joined to the duct 125 in the image forming unit (process cartridge) Py. Since air sucked from the charging area contains scattered toner and ozone, the image forming apparatus 20 is provided with an ozone filter 123 in addition to the toner filter 121.

  According to the first embodiment, since the duct 110 is joined to the duct 125, piping, a fan, a filter, and the like for sucking only the air sucked from the suction port 107 are unnecessary. Connection of the pipelines when attaching the image forming unit (process cartridge) Py to the image forming apparatus 20 is reduced, and workability at the time of attachment / detachment is improved.

<Example 2>
FIG. 9 is an explanatory diagram of the toner recovery structure of the second embodiment. The second embodiment is configured in the same manner as the first embodiment except that the cylindrical electrode 53 is disposed in the first space 111 shown in FIG. Therefore, in FIG. 9, the same reference numerals as those in FIG.

  As shown in FIG. 9, the developing sleeve 42, which is an example of a developer carrying member, carries the developer and develops the electrostatic image on the photosensitive drum 1 into a toner image, and the developing container 40 includes the developing sleeve 42. The developer recovered from is circulated.

  A wind-cut wall 109, which is an example of a wall member, is disposed so as to protrude in a wall shape toward the photosensitive drum 1 below the developing sleeve 42 along the rotation direction of the photosensitive drum 1. A first space 111 communicating with the longitudinal direction of the photosensitive drum 1 is formed by being surrounded by the upper surface of the sensor holder 105 including the wind cut wall 109, the developing container 40, the developing sleeve 42, and the photosensitive drum 1.

  A duct (110: FIG. 6), which is an example of an exhaust unit, removes air staying on the upper surface of the sensor holder 105 in the longitudinal direction of the photosensitive drum 1 by being separated by the wind cutting wall 109 as the photosensitive drum 1 rotates. Suction and exhaust. A second space 112 in contact with the photosensitive drum 1 is formed below the wind cut wall 109.

  The columnar electrode member 53 is disposed in the first space 111 so as to face the developing sleeve 42, and is rotationally driven so that the surface facing the developing sleeve 42 rotates into the developing container. The power source D52 applies a positive voltage having a polarity opposite to the charging polarity of the toner to the electrode member 52. The rubber blade 54, which is an example of a collecting unit, separates the toner adsorbed on the electrode member 52 and collects it in the developing container 40.

  In the second embodiment, similarly to the first embodiment, air containing toner particles retained in a mixed and stirred state in the first space 111 is sucked through the duct 110 and discharged to one end side in the longitudinal direction of the photosensitive drum 1. At the same time, the toner charged in the normal charge polarity is taken out from the air staying in the first space 111 by being adsorbed to the electrode member 52, separated by the rubber blade 54, collected in the developing container 40, and again for development. Use.

  According to the second embodiment, the toner is saved as compared with the case where the toner is discharged only by using the duct 110. In addition, the amount of saving makes it difficult for the charged toner to adhere to the inner wall of the duct 110, and even if the air volume in the duct 110 is small, the toner is less likely to accumulate in the duct 110.

  In the second embodiment, a virtual transfer residual toner collecting duct continuous in the longitudinal direction in which the surface of the photosensitive drum 1 is taken in a part of the inner periphery is configured. As a result, a part of the air circulating around the photosensitive drum 1 is taken in to secure an air flow along the wall surface in the transfer residual toner recovery duct, thereby avoiding toner accumulation on the bottom surface of the transfer residual toner recovery duct. . By securing such an air flow, even if the velocity of the air flow in the longitudinal direction is low, toner accumulation on the bottom surface of the transfer residual toner collection duct is avoided, and scattered toner can be collected efficiently.

  Therefore, the transfer residual toner collecting duct configured by projecting the wind-cut wall 109 to the photosensitive drum 1 may be provided to extend outside the range of the optical sensor 101. The developing sleeve 42 is not limited to the central portion in the longitudinal direction, and may be provided so as to cover the entire longitudinal direction of the developing sleeve 42. You may provide in the developing device to which the optical sensor 101 is not attached.

  And it is good also as a structure which collects scattering toner only by the electrode member 53, without providing the duct 110. FIG. In the case of a developing device not provided with the optical sensor 101, the duct 110 may be communicated over the entire length in the longitudinal direction, and air including scattered toner in the transfer residual toner collecting duct may be sucked from a plurality of locations in the longitudinal direction. Good.

Py, Pm, Pc, Pb Image forming unit 1 Photosensitive drum, 2 Corona charger, 3 Exposure device 4 Developing device, 19 Control unit, 20 Image forming device 100 Sensor unit, 101 Optical sensor 105 Sensor holder, 107 Suction port, 108 slope 109 wind-cut wall, 110, 125 duct 111 first space, 112 second space

Claims (9)

An image carrier, a developer carrier that carries a developer and develops an electrostatic image of the image carrier into a toner image, and a toner image on the image carrier that is disposed below the developer carrier. In an image forming apparatus comprising a detection means for optical detection,
Comprising a cover member disposed over at least the side of the developer carrying member of said detecting means, and an exhaust means for air with suction to evacuate the one longitudinal end of said image bearing member on said cover member ,
The cover member is provided such that a gap between the cover member and the image carrier is narrower than a gap between the detection unit and the image carrier, and the developer along the rotation direction of the image carrier An image forming apparatus, wherein the image forming apparatus is formed along a longitudinal direction of the image carrier so as to partition the carrier and the detection unit. The cover member is disposed so as to integrally cover the image carrier side of the detection means,
The edge of the upper surface of the cover member protrudes in a wall shape toward the image carrier, so that a first space is formed in contact with the upper surface of the cover member,
The image forming apparatus according to claim 1, wherein a second space in which the cover member and the image carrier face each other is formed below an edge protruding in a wall shape on the upper surface of the cover member. . The cover member is opposed to the image carrier at a predetermined interval in a part of the longitudinal direction of the image carrier,
The exhaust means has an exhaust pipe line disposed along the longitudinal direction of the image carrier so as to be within a cross section of the cover member perpendicular to the longitudinal direction of the image carrier.
The image forming apparatus according to claim 2, wherein an opening at a distal end of the exhaust pipe communicates with the first space. 4. The image forming apparatus according to claim 3 , wherein the lower edge of the opening at the tip of the exhaust pipe line and the upper surface of the cover member are connected to each other by an inclined surface. It said cover member, the image forming according to any one of claims 2 to 4, characterized in that opposing distance of the image bearing member and the edge protruding like a wall is 1.5mm or more 2.5mm or less apparatus. The cover member covers the developer carrier side of the detection means to form an upper surface of the cover member;
The developer carrier is disposed in a space on the developer carrier side in contact with the upper surface of the cover member so as to face the developer carrier, and is rotationally driven so that the surface facing the developer carrier moves toward the developer container. A cylindrical electrode member,
A power source for applying a voltage having a polarity opposite to the charging polarity of the toner to the cylindrical electrode member;
The image forming apparatus according to claim 1 or 2, characterized in that and a recovery means for recovering the toner attracted to the cylindrical electrode member in the developing container. The cover member covers the developer carrier side of the detection means to form an upper surface of the cover member;
Before includes a charging means for charging the Kizo carrier, an exhaust pipe for discharging the air sucked from the space of the developer bearing member in contact with the upper surface of the cover member, the image bearing member by said charging means 7. The image forming apparatus according to claim 1, wherein the image forming apparatus is incorporated in an exhaust pipe for discharging air in a charging area. The image forming apparatus according to any one of claims 1 to 7 top cross angle between the image bearing member of said cover member is characterized in that at least 90 degrees. 9. The image forming apparatus according to claim 1 , wherein a plurality of the developer carrying members are arranged to face each other along a rotation direction of the image carrying member.

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