JP5983925B2 - Charging device and image forming apparatus - Google Patents

Description

  The present invention relates to a charging device and an image forming apparatus using the charging device. The image forming apparatus includes various apparatuses such as a copying machine, a printer, a facsimile machine, and a multifunction machine having these functions in a complex manner.

  2. Description of the Related Art Conventionally, in an image forming apparatus that employs an electrophotographic system, the surface of a photoconductor that is an image carrier is charged to a predetermined potential by a charging device, and then the surface of the photoconductor is exposed to electrostatic charge corresponding to image information. A latent image is formed. Then, after the electrostatic latent image is visualized as a toner image by a developing device, the toner image is transferred to a recording material directly or via an intermediate transfer member, and fixed to the recording material by heating and pressing.

  There are various types of charging devices, and those that charge the photoreceptor by corona discharge are widely used. When this type of charging device is used to charge the surface of the photoreceptor, discharge products such as ozone and nitrogen oxides are generated. If the discharge product adheres to the surface of the photosensitive member, it adversely affects image flow and density unevenness during image formation.

  In this regard, Patent Document 1 and Patent Document 2 disclose a technique in which an air flow is formed in a shield case of a charging device by an intake fan or an exhaust fan, and discharge products are discharged from the shield case by the air flow. Has been.

JP-A-62-283357 Japanese Patent No. 4126145

  However, in the techniques of Patent Documents 1 and 2, there is a tendency that the airflow is difficult to flow between the photosensitive member and the charging device, and the discharge product is biased downstream in the airflow direction in the shield case. The discharge product remains in the vicinity of the surface of the photoreceptor, and the discharge effect of the discharge product is limited.

  The present invention has been made in view of such a current situation, and it is a technical problem to be able to suppress the adverse effects on image formation by reducing the bias and residual discharge products in the charging device. Yes.

The invention according to claim 1 includes a discharge electrode that performs non-contact discharge with respect to the image carrier and a housing that houses the discharge electrode, and the discharge electrode and the housing rotate the image carrier. A charging device extending along an axis, wherein a plurality of air inlets for allowing air to flow into the housing are formed on one side in the longitudinal direction of the housing, and exhaust for allowing air in the housing to flow out to the outside An opening is formed in the other longitudinal direction of the casing, and an air guide member is provided in the casing for imparting a directionality of a flow toward the image carrier to the air flowing in from each of the intake ports. Provided at each position of the mouth, each of the air guide members is closer to the exhaust port, and the width dimension along the rotation direction of the image carrier is reduced .
According to a second aspect of the present invention, a discharge electrode that performs non-contact discharge with respect to the image carrier and a housing that houses the discharge electrode are provided, and the discharge electrode and the housing rotate the image carrier. A charging device extending along an axis, wherein a plurality of air inlets for allowing air to flow into the housing are formed on one side in the longitudinal direction of the housing, and exhaust for allowing air in the housing to flow out to the outside An opening is formed in the other longitudinal direction of the casing, and an air guide member is provided in the casing for imparting a directionality of a flow toward the image carrier to the air flowing in from each of the intake ports. It is provided for each location of the mouth, and each of the air guide members has a lower projection height toward the image carrier as it is closer to the exhaust port.

According to a third aspect of the present invention, in the charging device according to the first or second aspect , each of the air guide members is inclined so as to approach the surface of the image carrier as it goes from the intake port to the exhaust port. It is formed in the shape of a blade.

According to a fourth aspect of the present invention, in the charging device according to the first or second aspect , each of the air guide members is formed in a cylindrical shape extending from the air inlet toward the image carrier.

According to a fifth aspect of the present invention, in the charging device according to the first or second aspect , a front end portion of each of the air guide members closer to the image carrier is positioned lower than a discharge point of the discharge electrode. That's it.

A sixth aspect of the present invention relates to an image forming apparatus, comprising the charging device according to any one of the first to fifth aspects.

  According to the invention described in the claims of the present application, an air guide member that imparts a directivity of the flow toward the image carrier to the air flowing in from the intake port is provided for each position of the intake port in the housing. Therefore, the presence of the air guide members makes it easy to send the air flowing in from the intake ports to the surface side of the image carrier. For this reason, discharge products staying around the image carrier can be easily discharged from the exhaust port, and the presence of the discharge products can adversely affect image formation, that is, the discharge products adhere to the surface of the image carrier. Therefore, it is possible to suppress the possibility of causing image flow or density unevenness.

It is a schematic explanatory drawing of a printer. It is an expansion explanatory view of an image creation part. It is side surface sectional drawing which shows 1st Embodiment of a charging device. FIG. 4 is an enlarged sectional view taken along line IV-IV in FIG. 3. It is a top view of a charging device. It is side surface sectional drawing which shows 2nd Embodiment of a charging device. FIG. 7 is an enlarged sectional view taken along the line VII-VII in FIG. 6. It is a top view of a charging device. It is side surface sectional drawing which shows 3rd Embodiment of a charging device. FIG. 10 is an enlarged sectional view taken along line XX in FIG. 9. It is a top view of a charging device. It is side surface sectional drawing which shows 4th Embodiment of a charging device. FIG. 13 is an enlarged sectional view taken along line XIII-XIII in FIG. 12. It is a top view of a charging device. (A)-(e) is a graph of the experimental result which demonstrates the discharge | emission effect of the discharge product by an air guide member.

  Hereinafter, an embodiment embodying the present invention will be described with reference to the drawings when applied to a tandem color digital printer (hereinafter referred to as a printer) which is an example of an image forming apparatus. In addition, in the following description, when using a term indicating a specific direction or position (for example, “left / right”, “up / down”, etc.) as necessary, the direction orthogonal to the paper surface in FIG. ing. These terms are used for convenience of explanation, and do not limit the technical scope of the present invention.

(1). Overview of Printer First, an overview of the printer 1 will be described with reference to FIGS. 1 and 2. As shown in FIG. 1, the printer 1 includes an image processing device 3, a paper feeding device 4, a fixing device 5, and the like in an outer casing 2. Although not shown in detail, the printer 1 is connected to a network such as a LAN, and is configured to execute printing based on the command when receiving a print command from an external terminal (not shown). Yes.

  The paper feeding device 4 located in the lower part of the outer casing 2 includes a paper feeding cassette 21 that accommodates the recording material P, a pickup roller 22 that feeds the recording material P in the paper feeding cassette 21 from the uppermost layer, and a fed recording material. A pair of separation rollers 23 for separating P one by one and a pair of timing rollers 24 for conveying the recording material P separated into one sheet to the image processing apparatus 3 at a predetermined timing are provided. The recording material P in each paper feed cassette 21 is sent to the transport path 30 one by one from the top layer by the rotation of the pickup roller 22 and the separation roller 23. The conveyance path 30 passes from the paper feed cassette 21 of the paper feed device 4 to the outer casing 2 via the nip portion of the timing roller pair 24, the secondary transfer nip portion of the image processing device 3, and the fixing nip portion of the fixing device 5. It reaches the discharge roller pair 26 at the top.

  The recording material P in the paper feed cassette 21 is set to a center reference that is conveyed in the arrow S direction toward the conveyance path 30 with the center of the sheet passing width (width dimension orthogonal to the arrow S direction) as a reference. Although not shown, the paper feed cassette 21 is provided with a pair of side portion regulating plates for bringing the recording material P before paper feeding into the center reference. The pair of side part restricting plates are configured to move in close proximity to each other in the sheet passing width direction. By sandwiching the recording material P in the paper feed cassette 21 from both sides in the sheet passing width direction by the pair of side portion regulating plates, the recording material P in the paper feed cassette 21 is set to the center reference regardless of the standard. Therefore, the transfer process in the image processing apparatus 3 and the fixing process in the fixing apparatus 5 are also executed on the basis of the center.

  The image processing device 3 positioned above the paper feeding device 4 plays a role of transferring a toner image formed on a photosensitive drum 13 which is an example of an image carrier to a recording material P, and is an intermediate transfer member. And a total of four image forming sections 7 corresponding to the respective colors of yellow (Y), magenta (M), cyan (C) and black (K).

  The intermediate transfer belt 6 is an endless belt made of a conductive material, and is also an example of an image carrier. The intermediate transfer belt 6 is wound around a driving roller 8 located on the right side of the central portion in the outer casing 2 and a driven roller 9 located on the left side of the central portion. A secondary transfer roller 10 is disposed outside the portion of the intermediate transfer belt 6 that is wound around the drive roller 8. The intermediate transfer belt 6 rotates in the counterclockwise direction in FIG. 1 by rotating the driving roller 8 counterclockwise in FIG. 1 by power transmission from a main motor (not shown).

  A secondary transfer roller 10 is disposed on the outer peripheral side of the portion of the intermediate transfer belt 6 that is wound around the drive roller 8. The secondary transfer roller 10 is in contact with the intermediate transfer belt 6, and a portion between the intermediate transfer belt 6 and the secondary transfer roller 10 (contact portion) is a secondary transfer nip portion as a secondary transfer region. . The secondary transfer roller 10 rotates in the clockwise direction in FIG. 1 with the rotation of the intermediate transfer belt 6 or with the movement of the recording material P that is nipped and conveyed by the secondary transfer nip portion. A transfer belt cleaner 12 for removing untransferred toner on the intermediate transfer belt 6 is disposed on the outer peripheral side of the portion of the intermediate transfer belt 6 wound around the driven roller 9. The transfer belt cleaner 12 is in contact with the intermediate transfer belt 6.

  The four image forming units 7 are arranged along the intermediate transfer belt 6 in the order of yellow (Y), magenta (M), cyan (C), and black (K) from the left in FIG. They are arranged side by side. In FIG. 1, for convenience of explanation, symbols Y, M, C, and K are attached to each image forming unit 7 according to the reproduction color. Each image forming unit 7 includes a photosensitive drum 13 as an example of an image carrier that rotates clockwise in FIG. Around the photosensitive drum 13, a charging device 14, an exposure device 19, a developing device 15, a primary transfer roller 16, and a photosensitive cleaner 17 are arranged in this order along the clockwise rotation direction in FIG. 1.

  The photosensitive drum 13 is negatively charged and is configured to rotate clockwise in FIG. 1 by power transmission from the main motor. A charging bias voltage output at a predetermined timing from a charging power source (not shown) is applied to the charging device 14.

  The developing device 15 makes the electrostatic latent image formed on the photosensitive drum 13 visible by reversal development using toner having a negative polarity. As shown in detail in FIG. 2, the developing device 15 includes a developing roller 41 as a developer carrying member having a plurality of permanent magnets in a cylindrical developing sleeve 42, and a plurality of stirring members 43 having screw blades. I have. The developing roller 41 and the stirring member 43 are also configured to rotate by power transmission from the main motor, similarly to the driving roller 8 and the photosensitive drum 13. That is, the drive source of the intermediate transfer belt 6, the photosensitive drum 13, the developing roller 41, and the stirring member 43 are all the main motor and are common. In the developing device 15, a two-component developer containing toner and a carrier is accommodated. A developing bias voltage output from a developing power source (not shown) is applied to the developing sleeve 42. The developing bias voltage in this case is obtained by superimposing an AC component on a DC component. Needless to say, a development bias voltage consisting only of a DC component may be adopted.

  The primary transfer roller 16 is located on the inner peripheral side of the intermediate transfer belt 6 and faces the photosensitive drum 13 of the corresponding image forming unit 7 with the intermediate transfer belt 6 interposed therebetween. The primary transfer roller 16 also rotates counterclockwise in FIG. 1 as the intermediate transfer belt 6 rotates. Between the intermediate transfer belt 6 and the primary transfer roller 16 (contact portion) is a primary transfer nip portion as a primary transfer region. The photoreceptor cleaner 17 is for removing untransferred toner remaining on the photoreceptor drum 13, and is in contact with the photoreceptor drum 13. An exposure device 19 is disposed below the four image forming units 7. The exposure device 19 forms an electrostatic latent image on each photosensitive drum 13 by laser light based on image information from an external terminal or the like.

  The density of the toner image on the intermediate transfer belt 6 is detected on the most downstream side in the circumferential direction of the intermediate transfer belt 6, that is, between the image forming portion 7K closest to the secondary transfer roller 10 and the secondary transfer nip portion. An IDC sensor 20 is arranged. The IDC sensor 20 basically uses a reference pattern (a test toner image) for each color formed on the intermediate transfer belt 6 during image stabilization processing such as color misregistration, gradation, and image density reproduction correction. Good). A hopper (not shown) that accommodates toner to be supplied to each developing device 15 is disposed above the intermediate transfer belt 6.

  In each image forming unit 7, when a laser beam corresponding to an image signal is projected from the exposure device 19 onto the photosensitive drum 13 charged by the charging device 14, an electrostatic latent image is formed. The electrostatic latent image is reversely developed with toner supplied from the developing device 15 and becomes a toner image of each color. In this case, the toner in the developing device 15 is agitated and transferred by the plurality of agitating members 43 and conveyed to the outer peripheral surface of the developing sleeve 42. Then, the potential difference between the potential of the surface of the photosensitive drum 13 charged by the charging device 14 (hereinafter referred to as the photosensitive member potential) and the potential of the surface of the developing sleeve 42 to which the developing bias voltage is applied (hereinafter referred to as the developing potential). Then, the toner on the developing sleeve 42 is carried to the surface of the photosensitive drum 13 through the carrier in the state where the developing sleeve 42 is raised by magnetic force. As a result, the electrostatic latent image on the photosensitive drum 13 is developed (visualized) as a toner image. Only the toner is consumed from the developer by the development, and the carrier is not consumed. Therefore, the carrier is stored in advance in the developing device 15 and the consumed toner is replenished separately.

  The toner images on the respective photosensitive drums 13 are primarily transferred from the photosensitive drum 13 to the outer peripheral surface of the intermediate transfer belt 6 in the order of yellow, magenta, cyan, and black at the corresponding primary transfer nip portions, and are superimposed. . Untransferred toner remaining on the photosensitive drum 13 is scraped off by the photosensitive cleaner 17 and removed from the photosensitive drum 13. When the recording material P passes through the secondary transfer nip portion, the superimposed four color toner images are secondarily transferred onto the recording material P all at once. Untransferred toner remaining on the intermediate transfer belt 6 is scraped off by the transfer belt cleaner 12 and removed from the intermediate transfer belt 6.

  The fixing device 5 positioned above the secondary transfer roller 10 in the image processing apparatus 3 includes a fixing roller 31 incorporating a heat source such as a halogen lamp heater, and a pressure roller 32 facing the fixing roller 31. A contact portion between the fixing roller 31 and the pressure roller 32 is a fixing nip portion which is a fixing region. The recording material P on which the unfixed toner image is passed through the secondary transfer nip portion is heated and pressurized when passing through the fixing nip portion between the fixing roller 31 and the pressure roller 32, and the recording material P An unfixed toner image is fixed thereon. Thereafter, the recording material P is discharged onto the paper discharge tray 27 by the rotation of the discharge roller pair 26.

  A control unit 28 that performs overall control of the printer 1 is disposed between the image processing apparatus 3 and the sheet feeding apparatus 4 in the outer casing 2. The controller 28 incorporates a controller (not shown) that executes various arithmetic processes, storage, and control.

(2). First Embodiment of Charging Device Next, a first embodiment of the charging device 14 will be described with reference to FIGS. The charging device 14 is of a scorotron charging type, and includes a shield case 51 that is a long and narrow box-shaped housing that opens toward the photosensitive drum 13. The shield case 51 extends along the rotation axis of the photosensitive drum 13.

  Disposed within the shield case 51 is a discharge electrode 52 that charges the surface of the photosensitive drum 13 by corona discharge. The discharge electrode 52 extends in parallel with the rotational axis of the photosensitive drum 13 in the shield case 51. The discharge electrode 52 is a needle-like electrode provided with a strip-shaped conductive portion 53 and a plurality of needle-like portions 54. The needle-like portions 54 are integrally provided on the conductive portion 53 so as to be arranged at appropriate intervals along the longitudinal direction of the conductive portion 53. The tip of each needle-like portion 54 is a discharge point 55, and the tip side of each needle-like portion 54 is opposed to the surface of the photosensitive drum 13. When a charging bias voltage is applied to the discharge electrode 52, the discharge is performed so as to spread in a conical shape from each discharge point 55 toward the surface of the photosensitive drum 13.

  The opening 56 on the photosensitive drum 13 side in the shield case 51 is open over substantially the entire length of the shield case 51 in the longitudinal direction. A mesh plate-like grid electrode 57 is disposed in the opening 56 so as to be interposed between the surface of the photosensitive drum 13 and the discharge electrode 52 (discharge point 55 of each needle-like portion 54). Has been. The shield case 51, the discharge electrode 52, and the grid electrode 57 are made of a conductive material such as stainless steel. The grid electrode 57 is insulated from the shield case 51.

  A plurality of intake ports 61 through which air flows into the shield case 51 are formed on one side of the shield case 51 in the longitudinal direction of the bottom plate 60 on the side opposite to the opening 56. Further, an exhaust port 62 through which the air in the shield case 51 flows out to the outside is formed in the other longitudinal direction of the bottom plate 60. The intake ports 61 are formed at appropriate intervals along the longitudinal direction of the shield case 51 on the upstream side of the exhaust port 62 in the flow direction.

  One end side of an air intake duct 63 communicating with the air inlet 61 group is connected to the outer surface side of the bottom plate 60 in the shield case 51. An intake fan 65 for sending air into the shield case 51 is disposed on the other end side of the intake duct 63. Further, one end side of an exhaust duct 64 communicating with the exhaust port 62 is also connected to the outer surface side of the bottom plate 60 in the shield case 51. On the other end side of the exhaust duct 64, an exhaust fan 66 for discharging the air in the shield case 51 is disposed. By driving the intake fan 65 and the exhaust fan 66, an air flow A that flows from each intake port 61 toward the exhaust port 62 (from one longitudinal direction to the other longitudinal direction of the shield case 51) in the shield case 51. It is formed. Note that both the intake fan 65 and the exhaust fan 66 may be provided as in the first embodiment, or only one of them may be provided.

  In the shield case 51, that is, on the inner surface side of the bottom plate 60, an air guide member 70 is provided for each portion of the intake port 61 that imparts the direction of the flow toward the photosensitive drum 13 to the air flowing from each intake port 61. It has been. Each air guide member 70 of the first embodiment is formed in a blade plate shape that is inclined so as to approach the surface of the photosensitive drum 13 from the corresponding intake port 61 toward the exhaust port 62. That is, as shown in FIG. 3, each air guide member 70 is arranged in a posture inclined with respect to the bottom plate 60 by an angle θ. A notch groove 71 is formed in each wind guide member 70 at a portion where the conductive portion 53 of the discharge electrode 52 enters, so that interference between each wind guide member 70 and the conductive portion 73 is avoided.

  When configured as described above, the presence of each air guide member 70 makes it easy to send air flowing from each air inlet 61 to the surface side of the photosensitive drum 13. For this reason, the discharge product staying around the photosensitive drum 13 can be easily discharged from the exhaust port 62, and the presence of the discharge product may adversely affect image formation, that is, the discharge product may be on the surface of the photosensitive drum 13. It is possible to suppress the possibility of causing image flow or density unevenness due to adhesion to the surface. In addition, since a plurality of intake ports 61 are provided, the air from the intake ports 61 on the downstream side in the flow direction merges one after another in the shield case 50 as it approaches the exhaust port 62, and the flow rate of the air flowing in the shield case 51 is Increased (air flow rate can be secured). Accordingly, the discharge product discharge effect can be improved in this respect as well. Further, since each air guide member 70 is disposed in a posture inclined with respect to the bottom plate 60 by the mounting angle θ, the direction of the air flow A is appropriately adjusted with respect to the surface of the photosensitive drum 13 according to the mounting angle θ. It becomes possible.

  Each air guide member 70 is made of a material having electrical insulation. Each air guide member 70 may be configured separately from the shield case 51 as in the first embodiment, or a part of the bottom plate 60 is notched and the notch is bent into the shield case 51. The air guide member 70 may be provided integrally with the bottom plate 60. When a part of the bottom plate 60 is cut out, a hole formed in the bottom plate 60 at the cutout becomes the air inlet 61. When each wind guide member 70 is made of an electrically insulating material and configured separately from the shield case 51 as in the first embodiment, the shield case 51 itself does not need to be redesigned significantly from the conventional one, Since the freedom degree of the shape of each wind guide member 70 becomes high, it is easy to mass-produce and it contributes to cost control. Also, leakage from each discharge point 55 to the shield case 51 can be suppressed, which contributes to the ease of designing the charging device 14 itself.

  As shown in FIG. 5, the width dimension W of each air guide member 70 along the rotation direction of the photosensitive drum 13 (in the direction intersecting the longitudinal direction of the shield case 51) becomes smaller as it is closer to the exhaust port 62. ing. With this configuration, the closer to the exhaust port 62 in the shield case 50, the larger the air flow cross-sectional area in the shield case 50, and the easier it is to secure the flow rate because the air flow A can easily flow. Accordingly, the discharge product staying around the photosensitive drum 13 can be discharged from the exhaust port 62 more reliably and smoothly.

  As shown in FIG. 3, each air guide member 70 has a lower protrusion height H toward the photosensitive drum 13 as it is closer to the exhaust port 62. Even in such a configuration, the closer to the exhaust port 62 in the shield case 50, the larger the air flow cross-sectional area in the shield case 50, and the air flow A can easily flow, contributing to securing the flow rate. Further, the front end portion of each air guide member 70 on the side close to the photosensitive drum 13 is positioned lower than each discharge point 55 of the discharge electrode 52. In other words, the height position of the front end portion of each air guide member 70 on the side close to the photosensitive drum 13 is set to each discharge point 55 at the maximum. If comprised in this way, the fall of the charging performance with respect to the photoreceptor drum 13 can be suppressed. In particular, in the first embodiment, since the discharge electrode 52 is a needle-like electrode and the directionality of discharge is high, the charging performance is deteriorated in combination with the point of the tip portion height position of each air guide member 70. It is difficult and effective.

(3). Second Embodiment of Charging Device FIGS. 6 to 8 show a second embodiment of the charging device 14. Here, in another embodiment of the charging device described below, components having the same configuration and operation as those of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. In the charging device 14 of the second embodiment shown in FIGS. 6 to 8, each air guide member 70 is not in the form of a blade plate but in a cylindrical shape extending from each intake port 61 toward the photosensitive drum 13 (in the second embodiment). It is different from the first embodiment in that it is formed in a rectangular tube shape.

  Each rectangular tube-shaped air guide member 70 is erected on the inner surface side of the bottom plate 60 of the shield case 51 so as to surround the corresponding intake port 61. Moreover, as shown in FIG. 8, since the opening area of each intake port 61 is made the same, the width dimension W of each air guide member 70 is also the same. In each conductive member 70, notched grooves 71 are formed in both side plate portions located in the longitudinal direction of the shield case 51, so as to avoid interference between each air guide member 70 and the conductive portion 73.

  The charging device 14 of the second embodiment also has the same effects as those of the first embodiment, such as the air flowing in from the air inlets 61 can be easily sent to the surface side of the photosensitive drum 13 due to the presence of the air guide members 70. Play.

(4). Third Embodiment of Charging Device FIGS. 9 to 11 show a third embodiment of the charging device 14. The third embodiment is a modification of the first embodiment. In the charging device 14 according to the third embodiment shown in FIGS. 9 to 11, as a casing, an elongated box-shaped duct case 81 opened toward the photosensitive drum 13 is provided separately from the shield case 51. The shield case 51 is accommodated in the duct case 81. On the bottom plate 60 side of the shield case 51, a bottom opening 58 is formed that opens over substantially the entire length of the shield case 51 in the same manner as the opening 56 on the photosensitive drum 13 side.

  A plurality of air inlets 91 through which air flows into the duct case 81 and the shield case 51 are formed on one side of the duct case 81 in the longitudinal direction of the bottom plate 90. In addition, an exhaust port 92 through which air in the duct case 81 and the shield case 51 flows out is formed on the other side in the longitudinal direction of the bottom plate 90. The intake ports 91 are formed at appropriate intervals along the longitudinal direction of the duct case 81 on the upstream side of the exhaust port 92 in the flow direction.

  One end side of an intake duct 93 that communicates via an intake port 91 group is connected to the outer surface side of the bottom plate 90 in the duct case 81. An intake fan 95 that sends air into the duct case 81 and the shield case 51 is disposed on the other end side of the intake duct 93. One end side of an exhaust duct 94 communicating with the exhaust port 92 is also connected to the outer surface side of the bottom plate 60 in the duct case 81. An exhaust fan 96 that exhausts air in the duct case 81 and the shield case 51 is disposed on the other end side of the exhaust duct 94. By driving the intake fan 95 and the exhaust fan 96, the duct case 81 and the shield case 51 enter the exhaust ports 62 from the respective intake ports 91 through the bottom openings 58 (from the longitudinal direction of the duct case 81 to the longitudinal direction). A flowing air stream A is formed (towards the other).

  Inside the duct case 81, that is, on the inner surface side of the bottom plate 90, an air guide member 70 that imparts the direction of the flow toward the photosensitive drum 13 to the air flowing in from each intake port 91 is provided for each location of the intake port 91. Is provided. Similarly to the first embodiment, each air guide member 70 of the third embodiment is also a blade that is inclined so as to approach the surface of the photosensitive drum 13 from the corresponding intake port 91 to the exhaust port 92. It is formed in a shape. The front end side of each air guide member 70 is inserted into the shield case 51 through the bottom opening 58. A notch groove 71 is formed in each wind guide member 70 at a portion where the conductive portion 53 of the discharge electrode 52 enters, so that interference between each wind guide member 70 and the conductive portion 73 is avoided. Also in the charging device 14 of the third embodiment, the presence of each air guide member 70 makes it easy to send the air flowing in from each intake port 91 to the surface side of the photosensitive drum 13, and the same as in the first and second embodiments. Has an effect.

(5). Fourth Embodiment of Charging Device FIGS. 12 to 14 show a fourth embodiment of the charging device 14. The fourth embodiment is a modification of the first and third embodiments. The charging device 14 of the fourth embodiment shown in FIGS. 12 to 14 includes a duct case 81 similar to that of the third embodiment as a housing. As in the second embodiment, each air guide member 70 formed in a cylindrical shape (or a rectangular tube shape in the fourth embodiment) extending from each air inlet 91 toward the photosensitive drum 13 is employed. Each rectangular tube-shaped air guide member 70 is disposed on the inner surface side of the bottom plate 90 of the duct case 81 for each portion of the intake port 91. The front end side of each air guide member 70 is inserted into the shield case 51 through the bottom opening 58. Also in the charging device 14 of the fourth embodiment, the presence of each air guide member 70 makes it easy to send the air flowing in from each intake port 91 to the surface side of the photosensitive drum 13, and the same as in the first to third embodiments. There is an effect.

(6). Experimental Results FIGS. 15A to 15E show graphs of experimental results demonstrating the discharge product discharge effect by the air guide member 70. 15A to 15E, the horizontal axis represents the discharge product concentration, and the vertical axis represents the concentration measurement position in the shield case. In this experiment, the wind speed near the exhaust port 62 (92) was about 1.5 m / sec. FIG. 15A shows the result when the air guide member 70 is not provided (conventional structure). In this case, the closer to the surface of the photosensitive drum 13, the higher the discharge product concentration was detected. In addition, regarding the result of the sample printing, the image flow occurred regardless of the position of the charging device 14 in the longitudinal direction.

  FIG. 15B shows the result of the charging device 14 of the first embodiment. In this case, even near the surface of the photoconductor drum 13, the concentration of the discharge product was not so high but changed at a low concentration. This can be said to be proof that discharge products staying around the photosensitive drum 13 are steadily discharged from the exhaust port 62. As a result of sample printing, no image flow occurred.

  FIG. 15C shows the result of the charging device 14 of the third embodiment. In this case, near the surface of the photosensitive drum 13, the discharge product concentration was shifted at a lower density that was better than the result of the charging device 14 of the first embodiment shown in FIG. As a result of sample printing, no image flow occurred. FIG. 15D shows the result obtained by the charging device 14 of the fourth embodiment. Also in this case, similarly to the result in the charging device 14 of the third embodiment shown in FIG. 15C, the discharge product concentration was changed at a low concentration. As a result of sample printing, no image flow occurred.

  FIG. 15E shows the result when the discharge electrode 52 is not a needle electrode but a wire electrode in the charging device 14 of the first embodiment. In this case, the discharge product concentration is confirmed near the surface of the photosensitive drum 13 at a lower value than when the air guide member 70 is not provided, but the discharge product concentration is higher than the result shown in FIG. The concentration appeared high. The directivity of the wire electrode was lower than that of the needle electrode, and charging unevenness occurred. In addition, a slight image flow was seen as a result of sample printing. Therefore, it is understood that the discharge electrode 52 is more acicular when the discharge product 52 is more effectively discharged by the air guide member 70. Although not shown in detail, even when the tip of each air guide member 70 on the photosensitive drum 13 side is made higher than each discharge point 55, charging unevenness occurs on the photosensitive drum 13.

(7). Others The present invention is not limited to the above-described embodiment, and can be embodied in various forms. For example, a printer has been described as an example of the image forming apparatus. However, the image forming apparatus is not limited thereto, and may be a copier, a facsimile, or a complex machine having these functions in combination. In addition, the configuration of each unit is not limited to the illustrated embodiment, and various modifications can be made without departing from the spirit of the present invention.

1 Printer (image forming device)
13 Photoconductor (image carrier)
14 Charging device 51 Shield case (housing)
52 Discharge electrode 55 Discharge point 61, 91 Intake port 62, 92 Exhaust port 63, 93 Intake duct 64, 94 Exhaust duct 65, 95 Intake fan 66, 96 Exhaust fan 70 Air guide member 81 Duct case

Claims (6)

A discharge electrode that performs non-contact discharge with respect to the image carrier and a housing that accommodates the discharge electrode are provided, and the discharge electrode and the housing extend along a rotation axis of the image carrier. A charging device,
A plurality of intake ports for allowing air to flow into the housing are formed on one side in the longitudinal direction of the housing, while an exhaust port for allowing the air in the housing to flow out to the outside is formed on the other longitudinal direction of the housing. And
In the housing , a wind guide member is provided for each location of the air intake port to give the direction of the flow toward the image carrier to the air flowing in from each air intake port. The closer to the exhaust port, the smaller the width dimension along the rotation direction of the image carrier,
Charging device. A discharge electrode that performs non-contact discharge with respect to the image carrier and a housing that accommodates the discharge electrode are provided, and the discharge electrode and the housing extend along a rotation axis of the image carrier. A charging device,
A plurality of intake ports for allowing air to flow into the housing are formed on one side in the longitudinal direction of the housing, while an exhaust port for allowing the air in the housing to flow out to the outside is formed on the other longitudinal direction of the housing. And
In the housing, a wind guide member is provided for each location of the air intake port to give the direction of the flow toward the image carrier to the air flowing in from each air intake port. The closer to the exhaust port, the lower the protruding height toward the image carrier,
Charging device. Each of the air guide members is formed in a blade plate shape that is inclined so as to approach the surface of the image carrier as it goes from the intake port to the exhaust port.
The charging device according to claim 1 or 2 . Each of the air guide members is formed in a cylindrical shape extending from the air inlet toward the image carrier.
The charging device according to claim 1 or 2 . The tip of the air guide member on the side close to the image carrier is positioned lower than the discharge point of the discharge electrode.
The charging device according to claim 1 or 2 . The charging device according to claim 1 is provided.
Image forming apparatus .

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