JP5362505B2 - Corona charging device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a corona electrifier capable of preventing dust from adhering to a discharge tip of a saw-toothed electrode, and an image forming apparatus. <P>SOLUTION: The corona electrifier 32A includes a case 52A, the saw-toothed electrode 53A, an exhaust duct 62A, and a guiding member 64A. The case 52A has an opening surface 524A open toward a photoreceptor drum 31A. The saw-toothed electrode 53A is arranged in the case 52A. The exhaust duct 62A is arranged adjacently to the case 52A, and has a receiving port 65A receiving air discharged from the opening surface 524A and an exhaust port 63A arranged at one end in a longitudinal direction of the exhaust duct 62A. The guiding member 64A is arranged in the exhaust duct 62A, and guides the air received from the receiving port 65A toward the exhaust port 63A. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a corona charging device including a non-contact type sawtooth electrode for charging a photosensitive member in an electrophotographic image forming process, and an image forming apparatus including the corona charging device.

  Some image forming apparatuses that perform electrophotographic image forming processing include a corona charging device that charges the surface of a photoreceptor to a predetermined potential. In order to form a high-quality image, it is important to uniformly charge the surface of the photoreceptor.

  Some conventional corona charging devices include a shield case having a sawtooth electrode disposed therein, an opening surface that opens toward the photoreceptor, and a base formed with a slit (for example, Patent Document 1). reference.). This corona charging device takes in air from the slit and generates an air flow from the slit to the opening surface using ion wind generated during discharge, so that dust entering from the outside adheres to the discharge tip of the sawtooth electrode. We are trying to prevent this.

Japanese Patent Laid-Open No. 9-230668

  However, the air taken in from the slit of the shield case and discharged from the opening surface may pass through the vicinity of the surface of the photoreceptor, and may contain a lot of dust such as silica particles and toner particles. For this reason, if the air discharged from the opening surface cannot be discharged smoothly to a place away from the slit, air containing a large amount of dust stays around the corona charging device and is taken into the shield case again from the slit. Dust easily adheres to the discharge tip of the sawtooth electrode. If dust adheres to the discharge tip of the sawtooth electrode, discharge unevenness may occur, and the surface of the photoreceptor may not be uniformly charged.

  An object of the present invention is to provide a corona charging device and an image forming apparatus capable of preventing dust from adhering to a discharge tip of a sawtooth electrode.

  The corona charging device of the present invention includes a case, a sawtooth electrode, an exhaust duct, and a guide member. The case has an opening surface that opens toward the photoreceptor. The sawtooth electrode has a plurality of projection-shaped discharge tips arranged in one direction, and is disposed in the case with the discharge tips facing the opening, and charges the surface of the photoreceptor when a voltage is applied. The exhaust duct is disposed adjacent to the case in a direction orthogonal to the arrangement direction of the discharge tips so as to extend along the arrangement direction of the discharge tips, and receives the air discharged from the opening surface while facing the photoreceptor. And an exhaust port disposed at one end in the longitudinal direction of the exhaust duct. The guide member guides air received from the receiving port toward the exhaust port. The guide member is provided on the side wall of the exhaust duct so that a side away from the receiving port is inclined in a direction approaching the exhaust port side with respect to a direction orthogonal to the longitudinal direction of the exhaust duct.

  In this configuration, the exhaust duct is long along the arrangement direction of the discharge tips. The air that is discharged from the opening surface of the case in a direction perpendicular to the arrangement direction of the discharge tips and enters the exhaust duct from the receiving port flows along the guide member. Since the guide member is inclined so that the side away from the receiving port is closer to the exhaust port side, the flow of air entering the exhaust duct is reliably directed to the exhaust port side by the guide member, and the air is directed to the exhaust port. Flows smoothly toward. For this reason, the air containing a large amount of dust after passing through the vicinity of the surface of the photosensitive member after being discharged from the opening surface does not stay around the corona charging device, and is prevented from entering the case.

  In the above-described configuration, the guide member can be provided on the first side wall which is the side wall far from the case. Since the exhaust duct is disposed adjacent to the case, the air discharged from the opening surface of the case tends to pass through the first side wall which is the side wall far from the case. For this reason, by providing a guide member in the 1st side wall, the air discharged | emitted from the opening surface flows more smoothly toward an exhaust port.

  In addition, at least a part of the second side wall that is the side wall facing the first side wall of the exhaust duct can be constituted by a third side wall that is the side wall on the exhaust duct side of the case. By using at least a part of the second side wall of the exhaust duct also as the third side wall of the case, the structure is simplified and the manufacturing cost can be reduced.

  Further, the guide member can be constituted by a plate member standing on the side wall of the exhaust duct. The air that has entered the exhaust duct from the receiving port flows along the plate member. Since the plate member is inclined so that the side away from the receiving port approaches the exhaust port side, the flow of air entering the exhaust duct is reliably directed to the exhaust port side by the plate member, and the air is directed to the exhaust port. Flows smoothly toward.

  Further, the guide member can be constituted by a cylindrical member provided on the side wall of the exhaust duct. The air that has entered the exhaust duct from the receiving port flows through the cylindrical member. Since the cylindrical member is inclined in a direction in which the side away from the receiving port approaches the exhaust port side, the flow of air entering the exhaust duct is more reliably directed to the exhaust port side by the cylindrical member, and the air is It flows more smoothly toward the exhaust port via the tubular member.

  Further, it can be configured to further include a blade that presses against the surface of the photoreceptor on the opposite side of the exhaust duct with respect to the case. Since the air discharged from the opening surface is blocked by the blade from the flow on the side opposite to the exhaust duct, it becomes easier to flow into the exhaust duct. For this reason, the air containing a large amount of dust passing through the vicinity of the surface of the photosensitive member does not stay around the corona charging device, and is prevented from entering the case.

  An image forming apparatus according to the present invention includes a photoreceptor and a corona charging device configured as described above. It is possible to prevent dust from adhering to the discharge tip of the sawtooth electrode and prevent discharge unevenness. For this reason, the surface of the photoreceptor can be uniformly charged, and a high-quality image can be formed.

  According to the present invention, there is provided a corona charging device and an image forming apparatus capable of preventing dust from adhering to a discharge tip of a sawtooth electrode.

1 is a front sectional view showing a schematic configuration of an image forming apparatus including a corona charging device according to an embodiment of the present invention. (A) is front sectional drawing of the unit containing a corona charging device, (B) is a left view of the unit containing a corona charging device, (C) is a figure which shows an inlet port. (A) is front sectional drawing of the charging part of a corona charging device, (B) is a side view of a serrated electrode. It is a figure which shows the airflow in a charging part, Comprising: (A) is a comparative example and (B) is an Example. It is a perspective view of a guide member. It is a right view of a guide member. It is a perspective view of the guide member which concerns on other embodiment.

  Embodiments of the present invention will be described below with reference to the drawings.

  As shown in FIG. 1, the image forming apparatus 1 is a tandem color image forming apparatus including four image forming units 101A to 101D. The four image forming units 101A to 101D form toner images having hues of black, cyan, magenta, and yellow, respectively. The image forming units 101B to 101D are configured substantially the same as the image forming unit 101A.

  For example, the image forming unit 101A includes a corona charging device 32A, an LSU (laser scanning unit) 33A, a developing device 34A, a primary transfer roller 35A as a transfer device, and a cleaner unit 36A around the photosensitive drum 31A. Yes. A corona charging device 32A, an LSU (laser scanning unit) 33A, a developing device 34A, a primary transfer roller 35A as a transfer device, and a cleaner unit 36A are arranged along the rotation direction indicated by an arrow K on the photosensitive drum 31A. Are arranged in the order of the symbols.

  Above the image forming units 101A to 101D, an intermediate transfer belt 105 constituted by an endless belt is disposed. The intermediate transfer belt 105 is stretched around the support roller 106A and the support roller 106B, and rotates in the direction of arrow R. A secondary transfer roller 108 is disposed to face the support roller 106A. Further, a belt cleaning unit 110 is disposed so as to face the support roller 106B.

  On the inner peripheral side of the intermediate transfer belt 105, primary transfer rollers 35A to 35D are respectively installed facing the photosensitive drums of the image forming units 101A to 101D.

  Each of the image forming units 101A to 101D operates as follows. For example, in the case of the image forming unit 101A, the corona charging device 32A charges the photosensitive drum 31A, and the LSU 33A forms an electrostatic latent image. Then, the developing device 34A supplies toner to the photosensitive drum 31A, and visualizes the electrostatic latent image into a toner image. The primary transfer roller 35 </ b> A transfers a single color toner image onto the intermediate transfer belt 105. The cleaner unit 36A cleans the surface of the photosensitive drum 31A after transferring the toner image.

  The single color toner images formed by the image forming units 101A to 101D are transferred so as to be superimposed on the intermediate transfer belt 105, thereby forming one color image.

  Below the image forming units 101A to 101D, a tray 114 for storing paper is disposed. The plurality of paper feed rollers 113 </ b> A to 113 </ b> D feed out the paper in the tray 114 and transport the paper in the paper transport direction P toward the secondary transfer position where the secondary transfer roller 108 faces the intermediate transfer belt 105.

  The color image formed on the intermediate transfer belt 105 is transferred onto a sheet as an example of a recording medium by the support roller 106A and the secondary transfer roller 108.

  The surface of the intermediate transfer belt 105 after the color image is transferred is cleaned by the belt cleaning unit 110.

  In the paper transport direction P, a fixing unit 115 and a paper discharge roller 116 are installed on the downstream side of the secondary transfer roller 108. The fixing unit 115 fixes the color image transferred onto the paper on the paper. The paper discharge roller 116 discharges the paper on which the color image is fixed from the conveyance path.

  Next, details of the corona charging device 32A of the image forming unit 101A will be described. The corona charging devices 32B to 32D are configured substantially the same as the corona charging device 32A.

  2A to 2C show, as an example, a unit 30A in which a photosensitive drum 31A, a corona charging device 32A, and a cleaner unit 36A are integrated. The holder 303A of the unit 30A holds the photosensitive drum 31A, the corona charging device 32A, and the cleaner unit 36A. Holder 303A includes side walls 301A and 302A.

  As shown in FIG. 2A, the corona charging device 32A is disposed on the downstream side of the cleaner unit 36A in the rotation direction of the photosensitive drum 31A. The corona charging device 32A extends long along the rotation axis direction of the photosensitive drum 31A.

  The corona charging device 32A includes an intake part 41A, a charging part 51A, and an exhaust part 61A.

  The charging unit 51A includes a case 52A, a sawtooth electrode 53A, an electrode holder 54A, a guide plate holder 55A, a guide plate 56A, an air barrier 57A, and a grid electrode 58A. The case 52A has a U-shaped cross section, and has an opening surface 524A that opens toward the photosensitive drum 31A, and a bottom surface 521A that faces the opening surface 524A. The bottom surface 521A has an opening 525A at the center. Air is taken into the case 52A from the outside through the opening 525A. The charging unit 51A is arranged so that the opening surface 524A of the case 52A opens toward the photosensitive drum 31A.

  The intake portion 41A is disposed on the opposite side of the photosensitive drum 31A with respect to the charging portion 51A. The intake portion 41A includes an intake port 42A and an intake duct 43A. The air inlet 42A is provided at an end portion on the side away from the photosensitive drum 31A. The intake duct 43A includes a side wall 301A of the unit 30A and an elastic partition sheet 44A, and extends from the intake port 42A to the opening 525A of the charging unit 51A. The intake duct 43A sends the air taken from the intake port 42A into the case 52A through the opening 525A.

  The exhaust unit 61A is disposed adjacent to the charging unit 51A on the opposite side of the cleaner unit 36A in the direction along the rotation direction of the photosensitive drum 31A, that is, on the downstream side of the charging unit 51A in the rotation direction of the photosensitive drum 31A. . A blade 361A of the cleaner unit 36A is disposed on the upstream side of the charging unit 51A in the rotation direction of the photosensitive drum 31A. The blade 361A is in pressure contact with the surface of the photoreceptor drum 31A.

  The exhaust part 61A includes an exhaust duct 62A, an exhaust port 63A (see FIG. 2B), and a guide member 64A. The exhaust duct 62A is disposed so as to be adjacent to the case 52A in a direction orthogonal to the rotation axis direction of the photosensitive drum 31A. The intake duct 43A and the exhaust duct 62A are partitioned by one side wall of the case 52A and the left side wall 522A disposed downstream in the rotation direction of the photosensitive drum 31A, and a partition sheet 44A. The exhaust duct 62A includes a side wall 302A on the downstream side of the unit 30A in the rotation direction of the photosensitive drum 31A, a left side wall 522A of the case 52A, and a partition sheet 44A.

  The exhaust duct 62A has a receiving port 65A that receives the air discharged from the opening surface 524A of the case 52A. The receiving port 65A faces the photosensitive drum 31A. The exhaust portion 61A has an air flow restriction sheet 66A on the side wall 302A on the downstream side of the receiving port 65A in the rotation direction of the photosensitive drum 31A. The air flow restriction sheet 66A extends from the side wall 302A toward the photosensitive drum 31A. The airflow restriction sheet 66A is disposed closer to the photosensitive drum 31A than the left side wall 522A of the case 52A. The air flow restriction sheet 66A guides the air discharged from the opening surface 524A of the case 52A into the exhaust duct 62A from the receiving port 65A. The guide member 64A will be described later.

  As shown in FIG. 2B, the air inlet 42A is provided at the bottom of the corona charging device 32A, which is the end away from the photosensitive drum 31A, in the rotational axis direction of the photosensitive drum 31A, that is, the corona charging device 32A. It is formed over the entire area in the longitudinal direction. The exhaust duct 62A extends along the longitudinal direction of the corona charging device 32A. The exhaust port 63A is provided at one end in the longitudinal direction of the exhaust duct 62A.

  An airflow generator (for example, a fan) 631A that generates an airflow that flows from the intake port 42A to the exhaust port 63A is attached to the exhaust port 63A. Note that the airflow generation device 631A can also be provided at the air inlet 42A.

  2C is a view of the air inlet 42A as viewed from the direction of the arrow T shown in FIG. 2B, that is, from the bottom side of the corona charging device 32A. The intake port 42A is provided with a plurality of ribs 421A at predetermined intervals.

  As shown in FIG. 3A, the case 52A of the charging portion 51A has a U-shaped cross section as described above, and has a right side 523A in addition to the bottom 521A, the left side 522A, and the opening 524A. doing. In the direction of the rotation axis of the photosensitive drum 31A, the case 52A has a length that substantially matches the length of the photosensitive drum 31A. The case 52A is composed of a conductive shield plate. Further, as described above, the bottom surface 521A has the opening 525A at the center. The opening 525A opens over the entire length of the corona charging device 32A.

  A grid electrode 58A is provided between the opening surface 524A of the case 52A, that is, between the end 522AT of the left side 522A and the end 523AT of the right side 523A.

  An electrode holder 54A having a narrower width than the opening 525A is installed at a central portion of the case 52A at a predetermined interval from the opening 525A. The electrode holder 54A has an L-shaped cross section, and the sawtooth electrode 53A is disposed on the bottom surface 521A and the grid electrode 58A so that the tip 531A which is the discharge tip of the sawtooth electrode 53A is disposed toward the opening surface 524A. Holds it vertically. The tip portion 531A of the sawtooth electrode 53A is disposed so as to be separated from the grid electrode 58A by a predetermined distance. The bottom of the sawtooth electrode 53A and the lower half of the right side surface are held by the electrode holder 54A. The sawtooth electrode 53A is a thin plate made of metal (for example, stainless steel), and is attached to the electrode holder 54A with an adhesive or a screw (not shown).

  As shown in FIG. 3B, the sawtooth electrode 53A has a plurality of tip portions 531A formed in a sharp projection shape like a saw blade edge. The front end portions 531A are arranged in one direction at regular intervals along the rotation axis direction of the photosensitive drum 31A, that is, the longitudinal direction of the corona charging device 32A. The arrangement direction of the tip portion 531A of the sawtooth electrode 53A, the rotational axis direction of the photosensitive drum 31A, the longitudinal direction of the corona charging device 32A, and the longitudinal direction of the exhaust duct 62A are the same.

  The sawtooth electrode 53A charges the surface of the photosensitive drum 31A when a voltage is applied. The grid electrode 58A is disposed between the sawtooth electrode 53A and the photosensitive drum 31A, and controls the charging potential on the surface of the photosensitive drum 31A.

  The guide plate holder 55A has an L-shaped cross section, and its bottom part is in contact with the bottom surface 521A. Further, the guide plate holder 55A is installed with a predetermined space that allows ventilation between the guide plate holder 55A and the electrode holder 54A in a state where a part of the side portion faces the electrode holder 54A. A guide plate 56A is attached to the holding surface of the guide plate holder 55A so as to be inclined at an inclination angle γ with respect to the bottom surface 521A.

  The guide plate 56A constitutes a guide member, and is arranged so that an extension line of the guide plate 56A indicated by a broken line in FIG. 3A intersects the tip portion 531A of the sawtooth electrode 53A. The guide plate 56A is spaced from the sawtooth electrode 53A by a predetermined distance that allows ventilation.

  The air barrier 57A constitutes a guide member, has an L-shaped cross section, and a bottom portion is in contact with the bottom surface 521A of the case 52A. Further, the air barrier 57A is disposed so that a side portion thereof faces the electrode holder 54A and the sawtooth electrode 53A and has a predetermined space that allows ventilation. The upper surface 571A of the air barrier 57A is inclined at a predetermined angle α with respect to the bottom surface 521A so that an extension line of the upper surface 571A shown by a broken line in FIG. 3A intersects the tip portion 531A of the sawtooth electrode 53A. Yes.

  Further, the end of the air barrier 57A on the side facing the sawtooth electrode 53A, the end closer to the opening surface 524A is inclined toward the sawtooth electrode 53A.

  The tip portion 531A of the sawtooth electrode 53A is higher in height than the tip portion 561A of the guide plate 56A and the upper surface 571A of the air barrier 57A, and the tip portion 531A of the sawtooth electrode 53A is between the guide plate 56A and the air barrier 57A. Stick out.

  The grid electrode 58A is, for example, a metal mesh such as stainless steel that can be ventilated and connected to a power source (not shown). The sawtooth electrode 53A is connected to a high voltage power supply (not shown).

  When a negative high voltage of about −5000 V, for example, is applied to the sawtooth electrode 53A from a high voltage power supply (not shown), an electric field concentrates on the tip portion 531A of the sawtooth electrode 53A, and a discharge occurs from the tip portion 531A of the sawtooth electrode 53A. Begins. In the discharge region, oxygen in the air is ionized to generate negatively charged ions (charged particles) and ozone in which oxygen is dissociated and bonded. Ions generated in the discharge region move along the electric field. At this time, when a negative voltage having a smaller absolute value than the voltage applied to the sawtooth electrode 53A, for example, about −650 V, is applied to the grid electrode 58A from a power supply (not shown), ions are supplied from the sawtooth electrode 53A to the grid electrode 58A. Move towards. Some of the ions flow to the grid electrode 58A, and the remaining ions pass through the grid electrode 58A and reach the photosensitive drum 31A, so that the surface of the photosensitive drum 31A is negatively charged. As ions move from the vicinity of the sawtooth electrode 53A toward the grid electrode 58A according to the electric field, an air flow called an ion wind is generated.

  When the charging unit 51A is configured as described above and a voltage is applied to the sawtooth electrode 53A and the grid electrode 58A, as shown in FIG. 4B, a part of the ion wind S1 is generated in the upper left part of the case 52A, That is, it flows from the downstream end of the opening surface 524A to the outside of the case 52A in the rotation direction of the photosensitive drum 31A. The other part of the ion wind J1 passes through the grid electrode 58A, flows to the right side along the surface of the photosensitive drum 31A, that is, upstream in the rotational direction of the photosensitive drum 31A, and hits the blade 361A. 52A flows along the right side 523A and the upper surface 571A of the air barrier 57A. That is, a circulating air flow G1 is generated.

  When the upper surface 571A of the air barrier 57A is perpendicular to the sawtooth electrode 53A (angle α = 0 degrees) as shown in FIG. 4A and is lower than the tip portion 531A of the sawtooth electrode 53A, the circulating airflow G1 is After passing through the upper surface 571A of the air barrier 57A, it hits the tip 531A of the sawtooth electrode 53A.

  When the circulating airflow G1 passes near the surface of the photosensitive drum 31A, there is a high possibility that the circulating airflow G1 will contain dust such as silica and toner that could not be completely removed by the blade 361A. For this reason, when the circulating airflow G1 hits the tip portion 531A of the sawtooth electrode 53A, dust may adhere to the tip portion 531A of the sawtooth electrode 53A.

  Therefore, in the corona charging device 32A, as shown in FIGS. 3A and 4B, air is taken into the case 52A from the intake portion 41A through the opening 525A. The guide plate 56A and the air barrier 57A guide the airflow around the tip 531A of the sawtooth electrode 53A, and allow the airflows N1 and N2 to pass around the tip 531A of the sawtooth electrode 53A. Since the passage widths of the airflows N1 and N2 are made smaller than the width of the case 52A by the guide plate 56A and the air barrier 57A, they are urged more than when there is no guide plate 56A and the air barrier 57A. As a result, the tip 531A of the sawtooth electrode 53A is encased in the airflows N1 and N2, so that the circulating airflow G1 does not hit the tip 531A of the sawtooth electrode 53A. Therefore, it is possible to suppress dust from adhering to the tip portion 531A of the sawtooth electrode 53A.

  Further, since the end of the air barrier 57A on the side facing the saw-tooth electrode 53A, the end closer to the opening surface 524A is inclined toward the saw-tooth electrode 53A, the passage width of the airflows N1 and N2 is sawtooth. In the vicinity of the distal end portion 531A of the electrode 53A, the momentum of the airflows N1 and N2 is further increased in the vicinity of the distal end portion 531A of the sawtooth electrode 53A. Therefore, it is possible to further suppress dust from adhering to the tip portion 531A of the sawtooth electrode 53A.

  The upper surface 571A of the air barrier 57A is inclined so that the circulating airflow G1 does not hit the tip portion 531A of the sawtooth electrode 53A. The angle α at which the upper surface 571A of the air barrier 57A is inclined can be set to an angle at which the extended line of the upper surface 571A intersects the tip portion 531A of the sawtooth electrode 53A or larger. The circulating airflow G1 flows along the upper surface 571A of the air barrier 57A, and the airflows N1 and N2 vigorously flow around the tip portion 531A of the sawtooth electrode 53A. Therefore, the circulating airflow G1 flows to the tip portion 531A of the sawtooth electrode 53A. It is possible to prevent dust from adhering to the tip portion 531A.

  In addition, it is preferable to set the speed of airflow N1, N2 to about 1.0 m / s-3.0 m / s, for example. This is because if the air flow speed is too slow, the tip portion 531A may not be protected by the air flows N1 and N2, and if the air flow speed is too fast, the charging of the photosensitive drum 31A may be adversely affected.

  As shown in FIG. 2A, the corona charging device 32A passes clean air currents N1 and N2 that do not include dust around the tip portion 531A of the sawtooth electrode 53A. An intake portion 41A is provided on the bottom surface 521A side. By providing the air intake portion 41A, air can be taken into the case 52A of the charging portion 51A from a location further away from the surface of the photosensitive drum 31A as compared with the case where air is directly taken in from the opening portion 525A. . Since the dust such as silica and toner is not floating as far from the surface of the photosensitive drum 31A, clean air that does not contain dust is taken in from the intake port 42A and sent to the charging unit 51A via the intake duct 43A. be able to.

  The air inlet 42A can be formed so as to open only at one end in the longitudinal direction of the corona charging device 32A. As a result, it is possible to take in air that does not contain dust from the outside of the image forming apparatus 1. For example, an air inlet 42A may be provided on the front side (front side in FIG. 1) of the image forming apparatus 1 so that air flows to the charging unit 51A via the air intake duct 43A.

  It is preferable to attach a filter to the air inlet 42A so as to prevent dust from entering the air intake duct 43A.

  The intake port 42A and the exhaust port 63A are preferably disposed at ends opposite to each other in the longitudinal direction of the corona charging device 32A. For example, when the air inlet 42A is provided on the front side (front side in FIG. 1) of the image forming apparatus 1, the air outlet 63A is provided on the rear side. Accordingly, it is possible to suppress the air containing dust such as silica discharged from the exhaust port 63A from being taken in from the intake port 42A and attached to the tip portion 531A of the sawtooth electrode 53A.

  In the corona charging device 32A, as described above, for example, a fan is attached to the intake port 42A or the exhaust port 63A as the airflow generation device 631A, and therefore, from the intake port 42A via both sides of the tip portion 531A of the sawtooth electrode 53A. It is possible to suppress stagnation of air toward the exhaust port 63A. For this reason, it can suppress that dust adheres to tip part 531A. Further, ozone generated in the charging unit 51A can be forcibly discharged to the outside of the corona charging device 32A.

  Next, the guide member 64A of the exhaust part 61A will be described. As described above, the exhaust duct 62A extends along the longitudinal direction of the corona charging device 32A, and is disposed so as to be adjacent to the case 52A in a direction orthogonal to the arrangement direction of the tip portions 531A of the sawtooth electrodes 53A. Yes.

  As shown in FIGS. 5 and 6, a guide member 64A is arranged in the exhaust duct 62A. 5 and 6 show a state in which a part of the configuration is cut away for convenience of explanation.

  The guide member 64A guides the air received from the receiving port 65A toward the exhaust port 63A. The guide member 64A is configured by a plate member provided upright on the side wall of the exhaust duct 62A.

  As an example, the guide member 64A is provided on the side wall 302A farther from the case 52A. That is, the guide member 64A is provided on the side wall 302A constituting the edge portion on the side away from the opening surface 524A among the edge portions constituting the receiving port 65A.

  Since the exhaust duct 62A is disposed adjacent to the case 52A in the direction along the rotation direction of the photosensitive drum 31A, the air discharged from the opening surface 524A of the case 52A travels on the side of the side wall 302A farther from the case 52A. Easy to pass. For this reason, by providing the guide member 64A on the side wall 302A far from the case 52A, the air discharged from the opening surface 524A flows more smoothly toward the exhaust port 63A.

  As an example, the guide member 64A is formed lower with respect to the side wall 302A at the end closer to the receiving port 65A and higher at the end spaced apart from the receiving port 65A. Accordingly, it is possible to efficiently guide the air corresponding to the spread of the air entering from the receiving port 65A and traveling through the exhaust duct 62A.

  At least a part of the exhaust duct 62A is constituted by the left side wall 522A of the case 52A. Specifically, in the rotation direction of the photosensitive drum 31A, at least a part of the side wall facing the downstream side wall 302A of the exhaust duct 62A, that is, the upstream side wall is defined by the left side wall 522A of the case 52A on the exhaust duct 62A side. It is configured. In this embodiment, as described above, the side wall facing the side wall 302A of the exhaust duct 62A is constituted by the left side wall 522A of the case 52A and the partition sheet 44A. By using at least a part of the side wall facing the side wall 302A of the exhaust duct 62A as the left side wall 522A of the case 52A, the structure is simplified and the manufacturing cost is reduced.

  The guide member 64A is inclined with respect to the direction perpendicular to the longitudinal direction of the exhaust duct 62A so that the side away from the receiving port 65A (the lower side in FIG. 5) approaches the exhaust port 63A.

  The air discharged from the opening surface 524A flows in a direction orthogonal to the arrangement direction of the tip portions 531A of the sawtooth electrode 53A and is received by the receiving port 65A. The air that has entered the exhaust duct 62A from the receiving port 65A flows along the guide member 64A. Since the guide member 64A is inclined in such a direction that the side away from the receiving port 65A is closer to the exhaust port 63A, the flow of air entering the exhaust duct 62A is reliably directed to the exhaust port 63A side by the guide member 64A. The air flows smoothly toward the exhaust port 63A. For this reason, air that may pass through the vicinity of the surface of the photosensitive drum 31A after being discharged from the opening surface 524A and contain a large amount of dust does not stay around the corona charging device 32A, and enters the case 52A. Is prevented. Therefore, it is possible to prevent dust from adhering to the tip portion 531A of the sawtooth electrode 53A.

  Further, as described above, the blade 361A that is in pressure contact with the surface of the photosensitive drum 31A is disposed on the opposite side of the exhaust duct 62A with respect to the case 52A. Since the air discharged from the opening surface 524A is blocked by the blade 361A from flowing to the side opposite to the exhaust duct 62A, the air is more likely to flow into the exhaust duct 62A. For this reason, the air containing a large amount of dust that passes near the surface of the photosensitive drum 31A does not stay around the corona charging device 32A, and is prevented from entering the case 52A.

  A filter for filtering dust can be attached to the exhaust port 63A. As a result, the amount of dust discharged from the exhaust duct 62A can be suppressed. Therefore, even when the air exhausted from the exhaust port 63A is taken in again from the intake port 42A, the amount of dust entering the charging unit 51A can be suppressed.

  As shown in FIG. 7, the guide member 641A can also be configured by a cylindrical member. In FIG. 7, for convenience of explanation, a state in which a part of the configuration is cut out is shown.

  The guide member 641A is provided on the side wall 302A. One end of the guide member 641A opens toward the receiving port 65A, and the other end opens to the side away from the receiving port 65A.

  The guide member 641A is inclined with respect to the direction perpendicular to the longitudinal direction of the exhaust duct 62A so that the side away from the receiving port 65A is closer to the exhaust port 63A.

  The air that has entered the exhaust duct 62A from the receiving port 65A flows through the guide member 641A. Since the guide member 641A is inclined in a direction in which the side away from the receiving port 65A is closer to the exhaust port 63A, the flow of air entering the exhaust duct 62A is more reliably directed to the exhaust port 63A side by the guide member 641A. The air flows more smoothly toward the exhaust port 63A via the guide member 641A.

  The above description of the embodiment is to be considered in all respects as illustrative and not restrictive. The scope of the present invention is shown not by the above embodiments but by the claims. Furthermore, the scope of the present invention is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

1 Image forming apparatus 30A unit 302A side wall (first side wall)
31A to 31D Photosensitive drums 32A to 32D Corona charging device 41A Intake section 42A Inlet 43A Intake duct 44A Partition sheet 51A Charging section 52A Case 521A Bottom 522A Left side wall (third side wall)
524A opening surface 525A opening 53A sawtooth electrode 531A tip (discharge tip)
54A Electrode holder 55A Guide plate holder 56A Guide plate 57A Air barrier 58A Grid electrode 61A Exhaust part 62A Exhaust duct 63A Exhaust port 64A, 641A Guide member 65A Receptacle 66A Airflow restriction sheet 101A-101D Image forming unit

Claims (6)

A case having an opening surface that opens toward the photoreceptor;
A sawtooth electrode having a plurality of projecting discharge tips arranged in one direction and arranged in the case with the discharge tips facing the opening, and charging the surface of the photoreceptor when a voltage is applied;
An exhaust duct disposed adjacent to the case in a direction orthogonal to the arrangement direction so as to extend along the arrangement direction of the discharge tips, and air discharged from the opening surface while facing the photoconductor An exhaust duct having a receiving inlet and an exhaust port disposed at one longitudinal end;
A guide member that guides air received from the receiving port toward the exhaust port, and a side away from the receiving port is inclined in a direction toward the exhaust port with respect to a direction orthogonal to the longitudinal direction. A guide member provided on a side wall of the exhaust duct,
The guide member is formed by a cylindrical member provided on the side wall of the exhaust duct, and is lower at the end closer to the reception port than the side wall of the exhaust duct, and is separated from the reception port. A corona charging device that is formed higher at the end .   2. The corona charging device according to claim 1, wherein the guide member is provided on a side wall constituting an edge portion on a side away from the opening surface among edge portions constituting the receiving port.   The corona charging device according to claim 1, wherein a side wall of the case constitutes at least a part of the exhaust duct. Corona charging device according to any one of claims 1-3, further comprising a blade pressed against the surface of the photosensitive member at the opposite side of the exhaust duct with respect to the casing in a direction along the rotational direction of the photosensitive member. A charging unit for charging the photosensitive member, an intake unit for taking in air to be sent to the charging unit, and an exhaust unit for receiving and exhausting air discharged from the charging unit;
The charging unit includes the case and the sawtooth electrode,
The exhaust part includes the exhaust duct and the guide member,
The intake unit has an intake duct that sends the taken-in air to the charging unit, and is disposed on the opposite side of the photoconductor from the charging unit,
5. The corona charging device according to claim 1, wherein the exhaust duct and the intake duct are disposed adjacent to each other, and the exhaust duct and the intake duct are partitioned by an elastic partition sheet. The photoreceptor;
An image forming apparatus comprising: the corona charging device according to claim 1.

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