JP4512997B2 - Charger, process cartridge, and image forming apparatus - Google Patents

Description

  The present invention relates to a charger, a process cartridge, and an image forming apparatus.

Conventionally, in an image forming apparatus such as a laser printer, a photoconductor is charged by performing corona discharge with a charger. In this type of charger, a casing in which an opening is provided in a casing that houses a discharge electrode is known (Patent Document 1). The purpose of this is to prevent contaminants such as silica contained in the toner from adhering to the discharge electrode during corona discharge. That is, when the inside of the casing is in a negative pressure state due to corona discharge, fresh air flows from the opening into the casing. This makes it difficult for dirty air to enter the casing.
Moreover, in order to make fresh air flow easily in a casing, the opening leg which protrudes outward is formed in the opening part.
JP-A-9-160349 (FIG. 2)

In the above structure, since the opening leg 210 protrudes outward, as shown in FIG. Most of them are dispersed in the casing 200. Therefore, once silica or the like adheres to the discharge electrode 205, it cannot be removed well, and there is room for improvement.
The present invention has been completed based on the above-described circumstances, and an object thereof is to provide a charger, a process cartridge, and an image forming apparatus that can prevent dirt from adhering to a discharge electrode. .

As a means for achieving the above object, the invention of claim 1 is to generate a corona discharge in a casing comprising a pair of counter electrodes and a wall body arranged so as to bridge between the counter electrodes. A charger containing a discharge electrode for charging the photosensitive member, wherein the discharge electrode is installed in a direction of a support shaft of the photosensitive member with respect to the casing, and the wall member is located at a position facing the discharge electrode. An air intake opening is formed, the air intake opening is formed in a direction in which the discharge electrode is erected, and protrudes toward the discharge electrode at an edge portion of the air intake opening through the air intake opening. the guide portion of the air taken into the casing for guiding toward the discharge electrode is provided, wherein the guide portion extends in the erection direction of the discharge electrode, it is formed over the entire length of said air intake Having the features in place are.

According to a second aspect of the invention, there is provided a connector described in claim 1, in which the photosensitive member is rotatably supported in the circumferential direction around the support shaft, the counter electrode are both of the support shaft The plate extends in the axial direction, and is arranged with one end of the end along the support shaft facing the photoconductor. The wall extends in the form of a plate extending along the support and It is characterized in that an end of the electrode opposite to the side facing the photoconductor is provided on both ends along the support shaft.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the guide portion includes a pair of opposed pieces extending toward the discharge electrode. It is characterized by a shape in which the facing interval becomes narrower toward.

  According to a fourth aspect of the present invention, in the method according to any one of the first to third aspects, the wall body is made of an insulating resin material, and the opposing piece is integrally formed on the wall body. It has a characteristic where it exists.

  According to a fifth aspect of the present invention, the discharge electrode according to the third or fourth aspect is formed with a dimension such that the discharge electrode is continuous over the entire axial direction of a cylindrical photosensitive drum as the photosensitive member. The air intake port and the opposing piece are characterized in that they are formed so as to be continuous over the entire axial direction of the discharge electrode.

  According to a sixth aspect of the present invention, in the cross section obtained by cutting the photoconductor in a direction intersecting with the support shaft, the opposite piece has a tip at the opposite electrode. Of these, it is characterized in that it is formed with a protruding height so as to be located on a line connecting between the discharge electrode and the edge portion continuous with the wall body.

  A seventh aspect of the invention is characterized in that the discharge electrode is a wire according to any one of the first to sixth aspects.

  According to an eighth aspect of the present invention, in the apparatus according to any one of the first to seventh aspects, the casing is located between the photoconductor and the discharge electrode, and ions of the photoconductor are charged. It is characterized in that a grid for controlling the quantity is provided.

  The invention according to claim 9 is characterized in that the photoconductor and the charger according to any one of claims 1 to 8 are provided.

  A tenth aspect of the invention is characterized in that an image is formed by using the charger according to the first to eighth aspects or the process cartridge according to the ninth aspect.

  The invention of claim 11 is characterized in that, in the invention of claim 10, one end is open and the other end is provided with a duct connected to the air intake port.

  The invention of claim 12 is characterized in that, in the invention of claim 11, a blowing means for blowing air into the casing is provided on one end side of the duct.

  According to a thirteenth aspect of the present invention, in the invention according to the twelfth aspect, only the one end and the other end of the duct are opened, and the opening width of the air intake port is wider toward the side closer to the blowing means. However, it has characteristics.

<Invention of Claims 1, 9, 10>
According to the first, ninth, and tenth aspects of the present invention, the air (fresh air) taken into the casing through the air intake port is guided to the discharge electrode by the guide portion. Accordingly, air is intensively blown onto the discharge electrode, and dirt is difficult to adhere to the discharge electrode.

<Invention of Claim 2>
According to the second aspect of the present invention, a box-shaped casing along the spindle of the photosensitive member is formed by the discharge electrode and the wall.

<Invention of Claim 3>
According to the invention of claim 3, the flow of air taken into the charger from the air intake port becomes smooth.

<Invention of Claim 4>
According to the invention of claim 4, since the wall body and the opposing piece are integrally formed, the number of parts can be reduced as compared with the case where these both members are constituted by separate parts.

<Invention of Claim 5>
According to the fifth aspect of the present invention, air can be taken in substantially uniformly over the entire axial direction of the discharge electrode.

<Invention of Claim 6>
According to the invention of claim 6, the outside air can be effectively led to the discharge electrode without affecting the corona discharge.

<Invention of Claim 7>
According to the invention of claim 7, the discharge electrode is a wire.

<Invention of Claim 8>
According to the eighth aspect of the present invention, the charge amount of ions attached to the photosensitive member can be adjusted.

<Invention of Claim 11>
According to the eleventh aspect of the present invention, the amount of air taken in can be adjusted.
<Invention of Claim 12>
According to the twelfth aspect of the present invention, air can be actively taken into the casing.

<Invention of Claim 13>
According to the invention of claim 13, the air pressure in the duct tends to be lower as the air blowing means is provided, but if the opening width of the portion where the air pressure is low is widened, the air in the same portion is also reduced. The flow is smooth and balanced with the high pressure part.

Next, Embodiment 1 which is one embodiment of the present invention will be described with reference to FIGS.
As shown in FIG. 1, the laser printer 1 includes a main body casing 2, a feeder section 4 for feeding paper 3 as a recording medium accommodated in the main body casing 2, and an image on the fed paper 3. The image forming unit 5 and the like are provided.

  An attachment / detachment opening 6 for attaching / detaching a process cartridge 20 described later is formed on one side wall of the main casing 2, and a front cover 7 for opening / closing the attachment / detachment opening 6 is provided. The front cover 7 is rotatably supported by a cover shaft (not shown) inserted through the lower end portion thereof. As a result, when the front cover 7 is closed around the cover shaft, as shown in FIG. 1, the attachment / detachment opening 6 is closed by the front cover 7 and when the front cover 7 is opened with the cover shaft as a fulcrum (when tilted), As shown in FIG. 2, the attachment / detachment opening 6 is opened, and the process cartridge 20 can be attached / detached to / from the main casing 2 through the attachment / detachment opening 6. In the laser printer 1, the main body portion other than the process cartridge 20 is the apparatus main body 1a.

  In the following description, the side on which the front cover 7 is provided in FIG. 1 is referred to as “front side”, and the opposite side is referred to as “rear side”.

  The feeder unit 4 includes a paper feed tray 9 that is detachably attached to the bottom of the main casing 2, a paper feed roller 10 and a separation pad 11 that are provided above the front end of the paper feed tray 9, and a paper feed roller 10, a pickup roller 12 provided on the rear side of the paper feed roller 10, a pinch roller 13 disposed oppositely on the lower front side of the paper feed roller 10, a paper dust removing roller 8 disposed oppositely on the upper front side of the paper feed roller 10, And a registration roller 14 provided on the upper rear side of the roller 10.

  Inside the paper feed tray 9 is provided a paper pressing plate 15 on which the paper 3 can be stacked. The sheet pressing plate 15 is supported so as to be swingable at the rear end portion, so that the front end portion is disposed below, the placement position along the bottom plate 16 of the sheet feeding tray 9 and the front end portion are disposed above. Oscillating and displaceable to the inclined transport position.

  A lever 17 for lifting the front end portion of the paper pressing plate 15 upward is provided at the front end portion of the paper feed tray 9. The lever 17 is formed in a substantially L-shaped cross section so as to go from the front side to the lower side of the paper pressing plate 15, and its upper end is attached to a lever shaft 18 provided at the front end of the paper feed tray 9. The rear end portion is in contact with the front end portion of the lower surface of the paper pressing plate 15. Accordingly, when a clockwise rotational driving force in the drawing is input to the lever shaft 18, the lever 17 rotates about the lever shaft 18, and the rear end portion of the lever 17 lifts the front end portion of the paper pressing plate 15. The paper pressing plate 15 is positioned at the transport position.

  When the sheet pressing plate 15 is positioned at the transport position, the sheet 3 on the sheet pressing plate 15 is pressed by the pickup roller 12 and is directed between the sheet feeding roller 10 and the separation pad 11 by the rotation of the pickup roller 12. The transport is started.

  On the other hand, when the paper feed tray 9 is detached from the main casing 2, the front end of the paper pressing plate 15 moves downward due to its own weight, and the paper pressing plate 15 is positioned at the placement position. When the paper pressing plate 15 is positioned at the mounting position, the paper 3 can be stacked on the paper pressing plate 15.

  When the sheet 3 sent out between the sheet feeding roller 10 and the separation pad 11 by the pickup roller 12 is sandwiched between the sheet feeding roller 10 and the separation pad 11 by the rotation of the sheet feeding roller 10. Each sheet is reliably fed and fed. The fed paper 3 passes between the paper feed roller 10 and the pinch roller 13, and after the paper dust is removed by the paper dust removing roller 8, it is conveyed to the registration roller 14.

  The registration roller 14 is composed of a pair of rollers. After registration of the sheet 3, the registration roller 14 is positioned between a photosensitive member 29 and a transfer roller 32, which will be described later, at a transfer position where a toner image on the photosensitive member 29 is transferred to the sheet 3. Transport.

  The image forming unit 5 includes a scanner unit 19, a process cartridge 20, a fixing device 21, and the like.

  The scanner unit 19 is provided in the upper part of the main casing 2 and includes a laser light source (not shown), a polygon mirror 22 that is driven to rotate, an fθ lens 23, a reflecting mirror 24, a lens 25, a reflecting mirror 26, and the like. The laser beam based on the image data emitted from the laser light source is deflected by the polygon mirror 22 as shown by the chain line, passes through the fθ lens 23, the optical path is turned back by the reflecting mirror 24, and further passes through the lens 25. Thereafter, the light path is further bent downward by the reflecting mirror 26, so that the light is irradiated onto the surface of the photosensitive drum 34 of the photosensitive member 29 described later of the process cartridge 20.

  The process cartridge 20 is detachably attached to the main casing 2 below the scanner unit 19. The process cartridge 20 includes upper and lower frames 27 and 28 that are divided into upper and lower parts as a casing. Inside the photosensitive member 29, a scorotron charger 30 (hereinafter simply referred to as a charger 30), a developing cartridge 31, and a transfer roller 32 are provided. , And a cleaning brush 33.

  The upper frame 27 is made of synthetic resin (insulating), and as shown in FIG. 7, the left and right edges of the substrate wall 56 have downward side walls (hereinafter, the left side wall is the left side wall 54 and the right side wall is the right side wall. A right side wall 55). Further, as shown in FIG. 5, a drum shaft (corresponding to a support shaft of the present invention) 35 for supporting the photosensitive member 29 described below is mounted between the side walls 54 and 55 so as to be freely rotatable. Yes. On the other hand, the lower frame 28 is made of synthetic resin, like the upper frame 27, and is formed by connecting a pair of side walls 92 rising upward by a connecting wall 95.

  The photoconductor 29 includes a photoconductive drum 34 formed of a positively chargeable photoconductive layer having a cylindrical shape and having an outermost layer made of polycarbonate or the like. The photosensitive drum 34 is fitted on the drum shaft 35 and is rotated integrally with the drum shaft 35. A motor (not shown) is provided in the main casing 2, and a power transmission gear is interposed between the motor and the drum shaft 35. For this reason, when the power transmission gear is driven to rotate in accordance with the driving of the motor, the drum shaft 35 and, consequently, the photosensitive drum 34 rotate integrally. The surface of the photoconductor 29 is uniformly positively charged by the charger 30 and then exposed by high-speed scanning of the laser beam from the scanner unit 19 to form an electrostatic latent image corresponding to the image to be formed on the paper 3. The

  A transfer roller 32 is arranged alongside the drum shaft 35. The transfer roller 32 is formed by coating the outer peripheral portion of the roller shaft 108 provided between the side walls 92 of the lower frame 28 with a conductive rubber material. The roller shaft 108 and the drum shaft 35 are connected by a gear, and when the drum shaft (photosensitive drum) 35 is driven, the roller shaft (transfer roller) 108 rotates in the opposite direction. Yes. As shown in FIG. 1, the transfer roller 32 is arranged so as to face and contact the photoconductor 29 in the vertical direction so as to form a nip with the photoconductor 29, and a transfer bias is applied during transfer.

Next, the charger 30 will be described. As shown in FIG. 6, a pair of support walls 59 project toward the photoconductor 29 at a position near the rear portion of the substrate wall 56 of the upper frame 27 and face the photoconductor 29. On the inner side, a positioning projection 67 is formed so as to project toward the photosensitive member 29, and an attachment groove is formed between the positioning projection 67 and the support wall 59. The mounting groove is formed along the axial direction of the photosensitive member 29, and the counter electrode 61 is fitted therein. Both of the counter electrodes 61 have a horizontally long plate shape extending along the axial direction of the photoconductor 29. The counter electrode 61 constitutes a frame-shaped casing 30A together with the substrate wall 56 of the upper frame 27, and a discharge wire (corresponding to the discharge electrode of the present invention) 37 is accommodated therein. As shown in FIG. 7, the discharge wire 37 has one end locked to the left side wall 54 of the upper frame 27 and the other end connected to a torsion coil spring 121 as an urging means. 27 between the side walls 54 and 55 of the 27.
Note that the end portion (the upper end portion in FIG. 6) fitted in the mounting groove in the counter electrode 61 is on the opposite side of the both end portions along the support shaft in the present invention from the side facing the photoconductor. Corresponds to the end.

  Further, as shown in FIG. 11, the wall surface (corresponding to the wall body of the present invention, which forms the ceiling portion of the charger 30) among the substrate walls 56 of the upper frame 27, hereinafter referred to as the ceiling wall 58. .) Is formed with an air intake 58A at a position facing the discharge wire 37. The air intake port 58 </ b> A is formed over the entire axial direction of the photoconductor 29 and functions to take in the outside air into the charger 30.

  On the other hand, as shown in FIG. 9, the side of the casing 30 </ b> A that faces the ceiling wall 58 is a discharge port 66, in which the counter electrode 61 is installed between the discharge wire 37 and the photosensitive member 29. A grid 38 for controlling the discharge amount is arranged. In the charger 30, a bias voltage is applied to the grid 38, and at the same time, a high voltage is applied to the discharge wire 37 to cause corona discharge in the casing 30A. Then, ions generated by corona discharge flow out from the discharge port 66 to the photoconductor 29, so that the surface of the photoconductor 29 is uniformly charged to a positive polarity.

  The charger 30 is provided with a wiper (not shown) for cleaning the discharge wire 37, and the discharge wire 37 is cleaned by sliding the wiper along the discharge wire 37. I can do it.

  Next, the developing cartridge 31 is formed in a box shape whose rear side is released, and is detachably attached to the lower frame 28. In the developing cartridge 31, a toner storage chamber 39, a supply roller 40, a developing roller 41, and a layer thickness regulating blade 42 are provided (see FIGS. 1 and 2).

  The toner storage chamber 39 is formed as an internal space on the front side of the developing cartridge 31 partitioned by the partition plate 43. The toner storage chamber 39 is filled with positively charged non-magnetic one-component toner as a developer. Examples of the toner include polymerizable monomers such as styrene monomers such as styrene, and acrylic monomers such as acrylic acid, alkyl (C1 to C4) acrylate, and alkyl (C1 to C4) methacrylate. Polymerized toner obtained by copolymerization by suspension polymerization or the like is used. Such a polymerized toner has a substantially spherical shape, has extremely good fluidity, and can achieve high-quality image formation.

  Such a toner is blended with a colorant such as carbon black, wax, or the like, and an external additive such as silica is added to improve fluidity. The average particle size of the toner is about 6 to 10 μm.

  An agitator 44 is provided in the toner storage chamber 39. The toner in the toner storage chamber 39 is agitated by the agitator 44 and discharged toward the supply roller 40 from the opening 45 communicating in the front-rear direction below the partition plate 43.

  The supply roller 40 is disposed behind the opening 45 and is rotatably supported by the developing cartridge 31. The supply roller 40 is configured by covering a metal roller shaft with a roller made of a conductive foam material. The supply roller 40 is rotationally driven by power input from a motor (not shown).

  The developing roller 41 is rotatably supported by the developing cartridge 31 in a state where the developing roller 41 is in contact with the supplying roller 40 so as to be compressed with respect to the rear side of the supplying roller 40. Further, the developing roller 41 is opposed to and contacts the photosensitive member 29 in a state where the developing cartridge 31 is mounted on the lower frame 28. The developing roller 41 is configured by covering a metal roller shaft 96 with a roller made of a conductive rubber material. The roller shaft 96 protrudes outward in the width direction perpendicular to the front-rear direction from the side surface of the developing cartridge 31 at the rear end of the developing cartridge 31 (see FIGS. 3 and 4). In the roller of the developing roller 41, the surface of a roller body made of conductive urethane rubber or silicone rubber containing carbon fine particles or the like is coated with a coating layer of urethane rubber or silicone rubber containing fluorine. A developing bias is applied to the developing roller 41 during development. The developing roller 41 is rotationally driven in the same direction as the supply roller 40 by the input of power from a motor (not shown).

  The layer thickness regulating blade 42 includes a pressing portion 47 having a semicircular cross section made of insulating silicone rubber at the tip of a blade body 46 made of a metal leaf spring material. The layer thickness regulating blade 42 is supported by the developing cartridge 31 above the developing roller 41, and the pressing portion 47 is pressed onto the developing roller 41 by the elastic force of the blade body 46.

  The toner discharged from the opening 45 is supplied to the developing roller 41 by the rotation of the supply roller 40, and at this time, the toner is positively frictionally charged between the supply roller 40 and the developing roller 41. The toner supplied onto the developing roller 41 enters between the pressing portion 47 of the layer thickness regulating blade 42 and the developing roller 41 as the developing roller 41 rotates, and is further charged to form a thin layer having a constant thickness. It is carried on the developing roller 41.

  The electrostatic latent image formed on the surface of the photosensitive member 29 when the positively charged toner carried on the developing roller 41 comes into contact with the photosensitive member 29 by the rotation of the developing roller 41. In other words, the surface of the photoconductor 29 that is uniformly positively charged is supplied to an exposed portion exposed to a laser beam and having a lowered potential. As a result, the electrostatic latent image on the photoconductor 29 is visualized, and a toner image by reversal development is carried on the surface of the photoconductor 29.

  Thereafter, the toner image carried on the surface of the photoconductor 29 is passed through the transfer position between the photoconductor 29 and the transfer roller 32 as shown in FIG. In the meantime, the image is transferred to the paper 3 by a transfer bias applied to the transfer roller 32. The sheet 3 on which the toner image is transferred is conveyed to the fixing device 21.

  Note that the untransferred toner remaining on the photoconductor 29 after the transfer is collected by the developing roller 41. Further, paper dust from the paper 3 adhering to the photoconductor 29 after the transfer is collected by the cleaning brush 33. The cleaning brush 33 is attached to the lower frame 28, and is disposed on the rear side of the photoconductor 29 so as to face and contact the photoconductor 29.

Further, a laser beam incident window 124 for allowing the laser beam LB scanned at high speed from the scanner unit 19 to enter the process cartridge 20 and an air passage 125 for discharging the air in the charger 30 after corona discharge is performed. Is provided.
More specifically, as shown in FIG. 6, an air passage 125 is formed on the substrate wall 56 of the upper frame 27 and on the front side of the charger 30 (between the charging position P0 and the exposure position P1). Further, a laser beam incident window 124 is provided on the front side of the air passage 125. Both the air passage 125 and the laser light incident window 124 penetrate the upper frame 27 vertically, and the opening width of the laser light incident window 124 is set wider than that of the air passage 125. In addition, as shown in FIG. 7, the air passage 125 is provided intermittently along the axial direction of the photosensitive member 29, but the laser light incident window 124 is continuous without interruption throughout the entire axial direction of the photosensitive member 29. is doing.
Here, the charging position P0 is a position where ions are sprayed onto the photoconductor 29, and the exposure position P1 is an irradiation position of the laser beam LB.

  As shown in FIG. 1, a fixing device 21 including a heating roller 49 and a pressure roller 50 is provided in the fixing frame 48 on the rear side of the process cartridge 20. The heating roller 49 includes a metal tube whose surface is coated with a fluororesin, and a halogen lamp for heating in the metal tube, and is rotated by input of power from a motor (not shown).

  The pressure roller 50 is disposed below the heating roller 49 so as to press the heating roller 49. The pressure roller 50 is configured by covering a metal roller shaft with a roller made of a rubber material, and is driven in accordance with the rotational drive of the heating roller 49.

  In the fixing device 21, the toner transferred onto the paper 3 at the transfer position is thermally fixed while the paper 3 passes between the heating roller 49 and the pressure roller 50. The sheet 3 on which the toner is fixed is conveyed to a sheet discharge path 51 that extends in the vertical direction toward the upper surface of the main casing 2. The sheet 3 conveyed to the sheet discharge path 51 is discharged onto a sheet discharge tray 53 formed on the upper surface of the main body casing 2 by a sheet discharge roller 52 provided on the upper side.

  By the way, when the corona discharge occurs, the inside of the charger 30 is in a negative pressure state. On the other hand, as described above, the developing roller 41 and the cleaning brush 33 are provided around the charger 30, so that dust such as toner is scattered around the charger 30. 30 flows in. In this case, if the inflowing dust (especially silica contained in the toner) adheres to the discharge wire 37, corona discharge hardly occurs at that portion, and there is a possibility that the image quality is deteriorated. Therefore, in the present embodiment, the charger 30 is provided with a duct 70 for supplying fresh outside air that does not contain dust and the like, and a counter piece 65 that guides the outside air taken in through the duct 70 to the discharge wire 37. Yes.

  More specifically, as shown in FIG. 6, an upper closing piece 62 having an L-shaped cross section is provided at a position facing the charger 30 in the apparatus main body 1a with one piece facing downward. On the other hand, a lower closing piece 64 protruding upward from the rear end portion of the lower frame 28 of the process cartridge 20 is provided. Both the closing pieces 62 and 64 surround the ceiling wall 58 of the charger 30, and form a duct 70 between the ceiling wall 58.

  As shown in FIG. 10, the duct 70 is formed along the axial direction of the photoconductor 20 (in the left-right direction in the figure). The left end of the duct 70 shown in the figure is located slightly inside (the center side in the figure) from the left end of the upper frame 27 and is closed by a side wall 63 provided in the apparatus main body 1a. On the other hand, the right end in the figure is not closed but is open. The opening 70A side of the duct 70 protrudes outward (right side in the figure) from the left end portion of the upper frame 27 and faces the frame 172 constituting the apparatus main body 1a. On the other hand, a ventilation hole 172A is opened at a position facing the duct 70 in the frame 172 so as to penetrate the frame 172 to the left and right, and there is a blower fan (corresponding to the blowing means of the present invention) 175. Is housed.

  For this reason, once the fan 175 is driven, outside air outside the apparatus is taken into the charger 30 through the duct 70 and the air intake 58A. The duct 70 is completely closed except for the opening 70A and the air intake port 58A. Further, as shown in FIG. 6, a hanging droop 62A and a lower closing piece 64 constituting the upper closing piece 62 are provided. Is formed with a height dimension that overlaps in the vertical direction. With such a configuration, the outside air blown by the fan 175 flows into the air intake 58A without leakage.

  Further, as shown in FIG. 11, the air intake port 58A is formed gently so that the opening width (A dimension shown in FIG. 11) increases from the left side to the right side in FIG. This is because the pressure inside the duct 70 tends to be lower as the side where the fan 175 is provided (the convection is generated by the side wall 63 at a position far from the fan 175 and the pressure is higher). By widening the opening width of the portion where the pressure is low, the air flow is smooth even in this portion, and it is possible to balance with the portion where the atmospheric pressure is high.

Next, the facing piece 65 will be described.
As shown in FIG. 9, a pair of facing pieces 65 protrude into the charger 30 from the edge of the air intake port 58 </ b> A. These opposing pieces 65 extend while being inclined slightly toward the discharge wire 37, and the opposing interval is narrowed from the proximal end 65B side to the distal end 65A side (inverted C-shaped). Further, the tip 65A of the opposing piece 65 is at a position that substantially intersects the line L connecting the discharge wire 37 and the edge 61A of the opposing electrode 61, as shown in FIG. If the protruding amount of the facing piece 65 is small and the tip 65A is on the front side (upper side in FIG. 9) of the line L, the outside air flowing in from the air intake port 58A is dispersed in the charger 30, and the discharge wire However, with the above configuration, the outside air supplied into the charger 30 through the air intake port 58 </ b> A is intensively blown directly onto the discharge wire 37.
Further, when the tip 65A extends across the line L (lower side in FIG. 9), the peripheral portion of the discharge wire 37 is surrounded by the resin, so that corona discharge hardly occurs. However, if the tip 65A is on the line L, the peripheral portion of the discharge wire 37 is not surrounded by the opposing piece 65, so that corona discharge is not hindered. As a result, the facing piece 65 can be extended toward the discharge wire 37 within a range that does not hinder corona discharge, and the outside air can be effectively blown onto the discharge wire 37.

  Moreover, as shown in FIG. 8, the opposing piece 65 is formed over the full length regarding the longitudinal direction of 58 A of air intakes. With such a configuration, outside air is blown over the entire length of the discharge wire 37. In addition, since the opposing piece 65 is formed integrally with the upper frame 27, the material thereof is resin. By adopting such a configuration, even if the opposing piece 65 is disposed close to the discharge wire 37, discharge is prevented from occurring toward the opposing piece 65 from the discharge wire 37. If the opposing piece 65 is made of metal, a strong electric field is generated between the discharge wire 37 and the opposing piece 65, and spark discharge occurs there.

Then, the effect of this embodiment is demonstrated.
When a bias voltage is applied to the grid 38 to expose the photoconductor 29 and at the same time, a high voltage is applied to the discharge wire 37, a corona discharge is generated in the charger 30, and the photoconductor 29 is discharged from the charger 30 by this corona discharge. A so-called ion wind (spontaneous air flow due to corona discharge) is generated. As a result, ions generated by corona discharge flow through the discharge port 66 toward the photoconductor 29 and charge the photoconductor 29. The air containing ions flowing out of the charger 30 flows in a U-turn shape near the outer peripheral surface 34 a of the photoconductor 29 and is led out through the air passage 125. As a result, the outflowing air is discharged without charging the exposed portion again.

  Further, since the inside of the charger 30 becomes negative pressure due to the corona discharge described above, air containing dust such as silica flows into the charger 30 from the discharge port 66. However, fresh external air is constantly taken into the charger 30 by taking the duct 70 and the air intake 58A by driving the fan 175. Then, fresh outside air taken into the charger 30 is guided to the discharge wire 37 by the facing piece 65 and is intensively blown against the discharge wire 37. Therefore, it becomes difficult for dust such as silica to adhere to the discharge wire 37, and even if it adheres, it can be easily dropped. For this reason, since the corona discharge occurs without any spots over the entire length of the discharge wire 37, the photosensitive member 29 is charged without any spots.

  In addition, if the driving speed of the fan 175 is adjusted according to the amount of dust entering the charger 30, the amount of air blown against the discharge wire 37 can be adjusted, and a large amount of dust is generated. Even if it flows in, it can be discharged out of the charger 30 without being attached to the discharge wire 37. Furthermore, since the facing piece 65 is formed integrally with the upper frame 27, the number of parts can be reduced as compared with the case where the facing piece 65 is formed of a separate member.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention, and further, within the scope not departing from the gist of the invention other than the following. Various modifications can be made.

  (1) In the above-described embodiment, the opposing piece 65 is configured to be inclined in the shape of a letter C. However, if the opposing piece 65 projects from the ceiling wall 58 toward the discharge wire 37, both plates extend in parallel. There may be.

  (2) In the above embodiment, the outside air is forcibly sent into the charger 30 by the fan 175 and the duct 70. However, instead of this, the outside air may be taken in using ion wind.

  (3) In the above embodiment, the discharge electrode is constituted by the wire 37, but may be a needle-type electrode.

Sectional drawing of the laser printer which concerns on one Embodiment of this invention Sectional drawing which shows the state which removed the process cartridge from the laser printer Top view of laser printer Side view showing process cartridge installation Sectional view of the periphery of the photoconductor Sectional view enlarging the periphery of the photoconductor Perspective view of upper frame Diagram showing the shape of the facing piece AA line sectional view of FIG. Sectional view showing the positional relationship between the duct and charger Diagram showing the shape of the air intake opening Cross section of conventional example

30 ... Charger 30A ... Casing 58 ... Ceiling wall 58A ... Air intake 65 ... Counterpiece

Claims (13)

A charger containing a discharge electrode for charging a photoconductor by generating a corona discharge in a casing formed of a pair of counter electrodes and a wall disposed so as to be installed between the counter electrodes;
The discharge electrode is installed in the direction of the spindle of the photosensitive member with respect to the casing,
The wall has an air intake opening that opens at a position facing the discharge electrode;
The air intake port is formed in the construction direction of the discharge electrode,
Wherein the rim of the air inlet guide portion is provided for guiding toward the air taken in the casing through the air inlet and protrudes toward the discharge electrode to the discharge electrode,
The charger is characterized in that the guide portion extends in the construction direction of the discharge electrode and is formed over the entire length of the air intake port . In what the photosensitive member is rotatably supported in the circumferential direction around the support shaft,
Both of the counter electrodes have a plate shape extending in the axial direction of the support shaft, and are arranged with one side of an end portion along the support shaft directed to the photoconductor,
The wall has a plate-like shape extending along the support shaft, and has an end opposite to the side facing the photoconductor among both ends of the counter electrode along the support shaft. The charger according to claim 1. The said guide part consists of a pair of opposing piece extended toward the said discharge electrode, These both opposing pieces are the shapes where an opposing space | interval becomes narrow toward a front end side from a base end side. The charger according to claim 2. The charger according to any one of claims 1 to 3, wherein the wall body is made of an insulating resin material, and the opposing piece is integrally formed on the wall body. The discharge electrode is formed with a dimension that is continuous over the entire axial direction of a cylindrical photosensitive drum that is the photoreceptor.
5. The charger according to claim 3, wherein the air intake port and the facing piece are formed so as to be continuous over the entire axial direction of the discharge electrode. 6. In the cross-section obtained by cutting the photoconductor in a direction intersecting the support shaft, the opposing piece is on a line connecting the discharge electrode with the edge of the counter electrode that is continuous with the wall body. 6. The charger according to claim 3, wherein the charger is formed to have a protruding height so as to be positioned. The charger according to claim 1, wherein the discharge electrode is a wire. 2. The grid according to claim 1, wherein a grid is provided between the photosensitive member and the discharge electrode to control an amount of ions charged on the photosensitive member. The charger according to any one of 7. A photoreceptor,
A process cartridge comprising the charger according to claim 1. An image forming apparatus configured to form an image using the charger according to claim 1 or the process cartridge according to claim 9. The image forming apparatus according to claim 10, further comprising a duct having one end opened and the other end connected to the air intake port. The image forming apparatus according to claim 11, wherein a blowing unit for blowing air into the casing is provided on one end side of the duct. 13. The image forming apparatus according to claim 12, wherein only one end and the other end of the duct are opened, and an opening width of the air intake port is wider toward a side closer to the blowing unit.

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