JP6565829B2 - Developing device and image forming apparatus including the same - Google Patents

Description

  The present invention relates to a developing device that supplies a developer to an image carrier and an electrophotographic image forming apparatus including the developing device.

  An electrophotographic image forming apparatus irradiates a peripheral surface of an image carrier (photosensitive drum) with light based on image information read from an original image or image information transmitted from an external device such as a computer. An electrostatic latent image is formed, toner is supplied from the developing device to the electrostatic latent image to form a toner image, and then the toner image is transferred to a sheet. The paper after the transfer process is subjected to a toner image fixing process and then discharged to the outside.

  By the way, in recent years, in the image forming apparatus, the configuration of the apparatus becomes complicated with the progress of color printing and high-speed processing, and the toner stirring member in the developing device is forced to rotate at high speed to cope with high-speed processing. . In particular, in a development method using a two-component developer including a magnetic carrier and a toner and using a magnetic roller (toner supply roller) that carries the developer and a development roller that carries only the toner, the development roller and the magnetic roller In the opposite portion, only the toner is carried on the developing roller by the magnetic brush formed on the magnetic roller, and the toner that has not been used for development is peeled off from the developing roller. Therefore, toner scattering is likely to occur in the vicinity of the facing portion between the developing roller and the magnetic roller, and the toner floating in the developing device accumulates around the earbrush blade (regulating blade), and the accumulated toner aggregates. If the toner adheres to the developing roller, the toner may be dropped and an image defect may occur.

  Therefore, for example, Patent Document 1 discloses a developing device that uses a two-component developer including a magnetic carrier and a toner and uses a magnetic roller that supports the developer and a developing roller that supports only the toner. Development provided with a toner receiving support member facing the roller, a toner receiving member that is disposed along the longitudinal direction of the toner receiving support member and that receives toner falling from the developing roller, and a vibration generating means that vibrates the toner receiving member An apparatus is disclosed.

  Patent Document 2 discloses a developing device in which a sheet-like vibration adjusting member is disposed at a predetermined distance from both ends of the toner receiving support member in the longitudinal direction. In this developing device, when the toner receiving member vibrates, the toner receiving member comes into contact with the vibration adjusting member, so that the free end of the toner receiving member vibrates so as to draw an arc and vibrates so as to accumulate on the free end side of the toner receiving member. Move the toner to the fulcrum side.

JP 2012-208469 A Japanese Patent Laying-Open No. 2014-6411

  By the way, the toner deposited on the toner receiving member is deteriorated and the charging ability is lowered, so that the fluidity is deteriorated. In addition, the fluidity of the toner changes depending on the usage environment of the image forming apparatus, the amount of toner consumed in the developing device, and the like. Therefore, as in Patent Documents 1 and 2, there is a problem that a sufficient toner recovery effect cannot be obtained by merely vibrating the toner receiving member for a certain period of time. In addition, the methods disclosed in Patent Documents 1 and 2 have a problem in that since a dedicated motor for vibrating the toner receiving member is used, the cost of parts increases and the noise level of the image forming apparatus increases.

  In view of the above problems, an object of the present invention is to provide a developing device that can efficiently collect toner dropped from a developing roller.

  In order to achieve the above object, a first configuration of the present invention is a developing device including a developing roller, a toner supply roller, a regulating blade, a casing, and a toner recovery mechanism. The developing roller is disposed to face the image carrier on which the electrostatic latent image is formed, and supplies toner to the image carrier in a region facing the image carrier. The toner supply roller is disposed to face the developing roller, forms a magnetic brush with a two-component developer including a magnetic carrier and toner on the outer peripheral surface, and supplies the toner to the developing roller in a region facing the developing roller. The regulating blade is disposed to face the toner supply roller at a predetermined interval. The casing houses a developing roller, a toner supply roller, and a regulating blade. The toner collecting mechanism includes an endless toner conveying belt that is disposed above the regulating blade and receives toner falling from the developing roller and conveys the toner toward the toner supply roller, and a driving roller around which the toner conveying belt is wound. A plurality of rollers, and a scraping member that scrapes off toner adhering to the toner conveying belt.

  According to the first configuration of the present invention, the toner dropped from the developing roller is transported to the toner supply roller by the toner transport member, scraped off from the toner transport belt by the scraping member, and then the magnetic brush of the toner supply roller. Collected. Thereby, toner accumulation on the top surface of the tip of the regulating blade can be suppressed. The toner immediately after dropping from the developing roller does not have a reduced charge amount, and even if it is collected by the toner supply roller and supplied again onto the developing roller, there is no possibility of adversely affecting the developing operation. Accordingly, it is possible to effectively suppress the occurrence of image defects due to toner dropping.

Schematic configuration diagram of a color printer 100 equipped with the developing devices 3a to 3d of the present invention Side sectional view of the developing device 3a according to the embodiment of the present invention mounted on the color printer 100. The perspective view which looked at the drive mechanism of the developing device 3a of this embodiment from the back side of FIG. Side sectional view around the toner recovery mechanism 35 Perspective view around the toner recovery mechanism 35 Side sectional view showing the developing device 3a of the present invention in which the arrangement of the toner supply roller 30 and the developing roller 31 is reversed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view of an image forming apparatus on which developing devices 3a to 3d of the present invention are mounted. Here, a tandem color printer is shown. In the main body of the color printer 100, four image forming portions Pa, Pb, Pc, and Pd are sequentially arranged from the upstream side in the transport direction (the right side in FIG. 1). These image forming portions Pa to Pd are provided corresponding to images of four different colors (cyan, magenta, yellow, and black), and cyan, magenta, and yellow are respectively performed by charging, exposure, development, and transfer processes. And a black image are sequentially formed.

  These image forming portions Pa to Pd are provided with photosensitive drums 1a, 1b, 1c and 1d for carrying visible images (toner images) of the respective colors, and further rotate clockwise in FIG. An intermediate transfer belt 8 is provided adjacent to each of the image forming portions Pa to Pd.

  When image data is input from a host device such as a personal computer, first, the surfaces of the photosensitive drums 1a to 1d are uniformly charged by the chargers 2a to 2d. Next, light is irradiated by the exposure device 5 according to the image data, and electrostatic latent images corresponding to the image data are formed on the respective photosensitive drums 1a to 1d. The developing devices 3a to 3d are filled with a predetermined amount of a two-component developer (hereinafter, also simply referred to as a developer) containing toners of cyan, magenta, yellow, and black by toner containers 4a to 4d. The toner in the developer is supplied onto the photosensitive drums 1a to 1d by 3a to 3d and electrostatically adheres. Thereby, a toner image corresponding to the electrostatic latent image formed by exposure from the exposure device 5 is formed.

  The primary transfer rollers 6a to 6d apply an electric field at a predetermined transfer voltage between the primary transfer rollers 6a to 6d and the photosensitive drums 1a to 1d, and cyan, magenta, yellow, and yellow on the photosensitive drums 1a to 1d. A black toner image is primarily transferred onto the intermediate transfer belt 8. Toner remaining on the surfaces of the photosensitive drums 1a to 1d after the primary transfer is removed by the cleaning devices 7a to 7d.

  The transfer paper P to which the toner image is transferred is accommodated in a paper cassette 16 disposed in the lower part of the image forming apparatus 100. The transfer paper P is transferred to a predetermined position via a paper feed roller 12a and a resist roller pair 12b. At a timing, the sheet is conveyed to the nip portion (secondary transfer nip portion) between the secondary transfer roller 9 provided adjacent to the intermediate transfer belt 8 and the intermediate transfer belt 8. The transfer sheet P on which the toner image is secondarily transferred is conveyed to the fixing unit 13.

  The transfer paper P conveyed to the fixing unit 13 is heated and pressed by the fixing roller pair 13a to fix the toner image on the surface of the transfer paper P, and a predetermined full-color image is formed. The transfer paper P on which the full-color image is formed is discharged to the discharge tray 17 by the discharge roller pair 15 as it is (or after being distributed to the reverse conveyance path 18 by the branching unit 14 and the image is formed on both sides).

  FIG. 2 is a side cross-sectional view of the developing device 3 a mounted on the color printer 100. 2 shows a state viewed from the back side of FIG. 1, and the arrangement of each member in the developing device 3a is opposite to that in FIG. Further, in the following description, the developing device 3a disposed in the image forming unit Pa of FIG. 1 is illustrated, but the configuration of the developing devices 3b to 3d disposed in the image forming units Pb to Pd is basically the same. Therefore, explanation is omitted.

  As shown in FIG. 2, the developing device 3a includes a developing container (casing) 20 in which a two-component developer (hereinafter simply referred to as a developer) is accommodated, and the developing container 20 is stirred and conveyed by a partition wall 20a. It is divided into a chamber 21 and a supply transfer chamber 22. In the agitating / conveying chamber 21 and the supply / conveying chamber 22, the agitating / conveying screw 25 a for supplying toner (positively charged toner) supplied from the toner container 4 a (see FIG. 1) with the carrier, agitating and charging, and the supplying and conveying Each screw 25b is rotatably arranged.

  Then, the developer is agitated by the agitating / conveying screw 25a and the supply / conveying screw 25b and conveyed in the axial direction (perpendicular to the paper surface of FIG. 2) to pass through the developer (not shown) formed at both ends of the partition wall 20a. It circulates between the stirring and conveying chamber 21 and the supply and conveying chamber 22 through the path. That is, a developer circulation path is formed in the developer container 20 by the agitating / conveying chamber 21, the supply / conveying chamber 22, and the developer passage.

  The developing container 20 extends obliquely upward to the right in FIG. 2. A toner supply roller 30 (developer carrying member) is disposed above the supply / conveying screw 25 b in the developing container 20. A developing roller 31 is disposed diagonally upward. The developing roller 31 faces the photosensitive drum 1a (see FIG. 1) on the opening side (the right side in FIG. 2) of the developing container 20, and the toner supply roller 30 and the developing roller 31 are shown in FIG. 2 rotates counterclockwise.

  In the agitating / conveying chamber 21, a toner density sensor 28 (not shown) is disposed so as to face the agitating / conveying screw 25a. The toner density sensor 28 detects the ratio (T / C) of the toner to the carrier in the developer. Based on the detection result of the toner density sensor 28, the toner is supplied from the toner container 4a to the agitating / conveying chamber 21 through a toner supply port (not shown). As the toner concentration sensor 28, for example, a magnetic permeability sensor that detects the magnetic permeability of a two-component developer composed of toner and a magnetic carrier in the developing container 20 is used.

  The toner supply roller 30 is composed of a non-magnetic rotating sleeve that rotates counterclockwise in FIG. 2 and a fixed magnet body having a plurality of magnetic poles contained in the rotating sleeve.

  The developing roller 31 includes a cylindrical developing sleeve that rotates counterclockwise in FIG. 2 and a developing roller side magnetic pole that is fixed in the developing sleeve. It faces with a predetermined gap at the facing position (facing position). The developing roller side magnetic pole has a different polarity from the opposing magnetic pole (main pole) of the fixed magnet body.

  Further, a spike cutting blade 33 is attached to the developing container 20 along the longitudinal direction of the toner supply roller 30 (a direction perpendicular to the paper surface of FIG. 2), and the spike cutting blade 33 rotates in the rotation direction of the toner supply roller 30. In the counterclockwise direction in FIG. 2, the developing roller 31 and the toner supply roller 30 are positioned on the upstream side. A slight gap (gap) is formed between the tip of the ear cutting blade 33 and the surface of the toner supply roller 30.

  A DC voltage (hereinafter referred to as Vslv (DC)) and an AC voltage (hereinafter referred to as Vslv (AC)) are applied to the developing roller 31, and a DC voltage (hereinafter referred to as Vmag (DC)) is applied to the toner supply roller 30. ) And an alternating voltage (hereinafter referred to as Vmag (AC)).

  As described above, the developer is agitated by the agitating / conveying screw 25a and the supply / conveying screw 25b, and the toner is charged by circulating through the agitating / conveying chamber 21 and the supplying / conveying chamber 22 in the developing container 20, and the supply / conveying screw 25b. The developer is conveyed to the toner supply roller 30. Then, a magnetic brush (not shown) is formed on the toner supply roller 30. After the layer thickness of the magnetic brush on the toner supply roller 30 is regulated by the earbrushing blade 33, the toner supply roller 30 and the developing roller 31 are separated. A thin toner layer is formed on the developing roller 31 by a potential difference ΔV between Vmag (DC) applied to the toner supply roller 30 and Vslv (DC) applied to the developing roller 31 and a magnetic field.

  The toner thin layer formed on the developing roller 31 by contact with the magnetic brush on the toner supply roller 30 is conveyed to a facing portion (facing region) between the photosensitive drum 1 a and the developing roller 31 by the rotation of the developing roller 31. The Since Vslv (DC) and Vslv (AC) are applied to the developing roller 31, the toner flies due to a potential difference with the photosensitive drum 1a, and the electrostatic latent image on the photosensitive drum 1a is developed. .

  Remaining toner that is not used for development is conveyed again to the opposite portion between the developing roller 31 and the toner supply roller 30 and is collected by the magnetic brush on the toner supply roller 30. The magnetic brush is peeled off from the toner supply roller 30 at the same polarity portion of the fixed magnet body, and then falls into the supply conveyance chamber 22.

  Thereafter, a predetermined amount of toner is replenished from a toner replenishing port (not shown) based on the detection result of the toner concentration sensor 28, and is uniformed again at an appropriate toner concentration while circulating through the supply conveyance chamber 22 and the agitation conveyance chamber 21. It becomes a charged two-component developer. This developer is again supplied onto the toner supply roller 30 by the supply agitating screw 25 b to form a magnetic brush, and is conveyed to the ear cutting blade 33.

  A toner collecting mechanism 35 that receives toner dropped from the developing roller 31 and collects it on a magnetic brush on the toner supply roller 30 is provided in the vicinity of the developing roller 31 on the right side wall in FIG. As shown in FIG. 2, the toner recovery mechanism 35 is disposed inside the developing container 20 so as to overlap the spike cutting blade 33.

  FIG. 3 is a partial perspective view showing a drive mechanism of the developing device 3a, and FIGS. 4 and 5 are a side sectional view and a perspective view of the periphery of the toner recovery mechanism 35. FIG. 3 to 5 show the developing device 3a as viewed from the back side of FIG. 2, and the arrangement of the toner supply roller 30, the developing roller 31, and the toner collecting mechanism 35 in the developing device 3 is shown in FIG. It is the opposite. The toner recovery mechanism 35 includes an endless toner conveyance belt 37, a driving roller 38 that rotates the toner conveyance belt 37, and a driven roller 39.

  As shown in FIG. 3, the first input gear 40 attached to one end of the toner supply roller 30 is formed with a fitting hole 40a into which a drive output coupling (not shown) on the main body side of the color printer 100 is fitted. The driving force is input to the developing device 3a through the first input gear 40. Idle gears 41 and 43 are connected to the first input gear 40. A second input gear 45 attached to one end of the developing roller 31 and a driving roller 38 of the toner collecting mechanism 35 are connected to the idle gear 41.

  With this configuration, the rotational driving force in the same direction as the first input gear 40 (clockwise direction in FIG. 3) is transmitted to the developing roller 31 and the driving roller 38 via the idle gear 41. Then, the toner conveying belt 37 wound around the driving roller 38 and the driven roller 39 rotates in the clockwise direction. The idle gear 43 is connected to a drive input gear (not shown) attached to one end of the agitating and conveying screw 25a and the supply and conveying screw 25b, and the agitating and conveying screw 25a and the supplying and conveying screw 25b are idle. A rotational driving force in the same direction as the first input gear 40 (clockwise direction in FIG. 3) is transmitted through the gear 43.

  Next, a collecting operation for collecting the toner dropped from the developing roller 31 by the toner collecting mechanism 35 will be described. As described above, the toner on the developing roller 31 that has not been used for development is peeled off from the developing roller 31 at a portion where the toner supply roller 30 and the developing roller 31 face each other, and is collected by the magnetic brush on the toner supply roller 30. . At this time, a part of the toner peeled off from the developing roller 31 falls without being collected by the magnetic brush. The dropped toner is deposited on the upper surface of the toner conveying belt 37 disposed above the ear cutting blade 33.

  As shown in FIG. 3, when the image is formed, the first input gear 40 that rotates the toner supply roller 30 rotates in the clockwise direction. Therefore, the idle gear 41 connected to the first input gear 47 is counterclockwise. The drive roller 38 connected to the idle gear 41 rotates in the clockwise direction and rotates in the clockwise direction. Along with the rotation of the driving roller 38, the toner conveying belt 37 wound around the driving roller 38 and the driven roller 37 also rotates in the clockwise direction.

  As a result, as shown in FIG. 4, the toner T accumulated on the toner conveying belt 37 moves to the driven roller 39 side in the direction of the arrow. Then, the toner conveying belt 37 to which the toner T is attached turns downward along the outer peripheral surface of the driven roller 39. Here, the driven roller 39 has an outer diameter smaller than that of the driving roller 38. That is, the toner conveyance belt 37 has a small radius of curvature (a large curvature) on the driven roller 39 side. Therefore, when the toner conveying belt 37 turns downward along the outer peripheral surface of the driven roller 39, the toner conveying belt 37 is largely bent outward. Accordingly, the toner T is easily separated from the surface of the toner conveying belt 37. In addition, by coating the outer peripheral surface of the toner conveying belt 37 with a fluorine-based resin, the toner T is more easily separated.

  Further, a sheet member 50 is disposed below the driven roller 39. The sheet member 50 is formed of a flexible sheet material such as polyethylene terephthalate (PET), and a lower end (base end portion) is fixed to the ear cutting blade 33, and a front end portion (swing end) is the toner conveying belt 37. It is arrange | positioned so that it may contact. As shown in FIG. 5, a large number of slits 50a are formed at the leading end of the sheet member 50 that contacts the toner conveying belt 37, and the leading end of the sheet member 50 is divided into a large number of swinging pieces. As a result, the rocking piece where the toner T adheres to the surface of the toner conveying belt 37 is partially bent and repels the toner T by the restoring force, so that the toner T adhering to the toner conveying belt 37 is efficiently scraped. Can be taken. The toner T adhering to the toner conveying belt 37 is scraped off by the sheet member 50 and is bounced to the toner supply roller 30 side (right direction in FIG. 4), and then collected by the magnetic brush of the toner supply roller 30.

  In addition, the leading end of the sheet member 50 that contacts the toner conveyance belt 37 is positioned higher than a horizontal straight line L that passes through the rotation axis center O of the toner supply roller 30. As a result, the toner T bounced by the sheet member 50 adheres to the upper half of the outer peripheral surface of the toner supply roller 30. Therefore, the toner T collected by the magnetic brush of the toner supply roller 30 is unlikely to fall from the toner supply roller 30 due to gravity, and the toner collection efficiency is improved.

  According to the configuration of the present embodiment, the toner dropped from the developing roller 31 is collected by the toner collecting mechanism 35 to the toner supply roller 30, so that toner accumulation on the top surface of the tip of the spike cutting blade 33 can be suppressed. . Since the toner immediately after dropping from the developing roller 31 does not have a reduced charge amount, there is no possibility of adversely affecting the developing operation even if the toner is recovered by the magnetic brush of the toner supply roller 30 and then supplied again on the developing roller 31. . Therefore, toner with a low charge amount deposited on the upper surface of the tip of the earbrushing blade 33 adheres to the magnetic brush of the toner supply roller 30 during image formation, and further adheres on the developing roller 31 to effectively cause toner drop. Can be suppressed.

  Further, since the toner collection mechanism 35 is driven using the drive mechanism of the toner supply roller 30 and the developing roller 31, it is not necessary to provide a separate motor for driving the toner collection mechanism 35, and the control path can be simplified. .

  In addition, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the meaning of this invention. For example, the shape and arrangement of the toner conveying belt 37 and the sheet member 50 constituting the toner collecting mechanism 35 shown in the above embodiment are merely examples, and are not particularly limited to the above embodiment. It can be set accordingly. For example, the toner conveying belt 37 may be wound around three or more rollers including the driving roller 38.

  In the above-described embodiment, the present invention uses a two-component developer, forms a magnetic brush on the toner supply roller 30, moves only the toner from the toner supply roller 30 to the development roller 31, and performs photosensitivity from the development roller 31. Although the present invention is applied to the developing devices 3a to 3d for supplying toner to the body drums 1a to 1d, as shown in FIG. 6, the development roller 31 and the toner supply roller 30 are arranged opposite to those in the above embodiment. Toner is supplied to the photosensitive drums 1a to 1d by a magnetic brush made of a two-component developer held on the surface of a roller 31 (in this configuration, a magnetic roller having the same configuration as the toner supply roller 30 of the above embodiment). The toner supply roller 30 is held on the surface of the toner supply roller 30 (in this configuration, the configuration is the same as the developing roller 31 of the above embodiment). It supplies the toner to the developing roller 31, to a developing device for collecting the surplus toner of the developing roller 31 surface with a toner supply roller 30 can be applied. Even in this configuration, it is possible to effectively suppress the toner dropped from the developing roller 31 from being accumulated around the regulating blade 33 facing the toner supply roller 30.

  The present invention can be used for an image forming apparatus including a developing device having a toner receiving member facing the developing roller between a region where the image carrier and the developing roller are opposed to each other and a regulating blade. By utilizing the present invention, it is possible to provide a developing device capable of efficiently collecting the toner dropped from the developing roller.

Pa to Pd Image forming section 1a to 1d Photosensitive drum (image carrier)
3a to 3d Developing device 4a to 4d Toner container 20 Developing container (casing)
30 Toner supply roller 31 Developing roller 33 Ear cutting blade (regulating blade)
35 Toner Collection Mechanism 37 Toner Conveying Belt 38 Drive Roller 39 Driven Roller 40 First Input Gear (Drive Input Gear)
41, 43 Idle gear 45 Second input gear 50 Sheet member (scraping member)
50a slit 100 color printer (image forming device)

Claims (8)

A developing roller that is disposed to face an image carrier on which an electrostatic latent image is formed, and that supplies toner to the image carrier in a region facing the image carrier;
A toner supply roller that is arranged to face the developing roller, forms a magnetic brush with a two-component developer including a magnetic carrier and toner on the outer peripheral surface, and supplies the toner to the developing roller in a region facing the developing roller When,
A regulating blade disposed opposite to the toner supply roller at a predetermined interval;
A casing that houses the developing roller, the toner supply roller, and the regulating blade;
In a developing device comprising:
A plurality of endless toner transport belts that are disposed above the regulating blade and receive toner falling from the developing roller and transport the toner toward the toner supply roller; and a drive roller around which the toner transport belt is wound A toner collecting mechanism having a roller and a scraping member that scrapes off the toner adhering to the toner conveying belt ,
The scraping member is a flexible sheet member, and the toner adhering to the toner conveying belt is scraped off by the sheet member, rebounded to the toner supply roller side, and then collected on the toner supply roller. developing device characterized in that it is.   The developing device according to claim 1, wherein the scraping member is in contact with the toner conveying belt at a position higher than a rotation axis center of the toner supply roller. The developing device according to claim 1 , wherein the sheet member has a plurality of slits formed at a front end portion that contacts the toner conveying belt . Wherein the drive roller, one of claims 1 to 3 driving force through the driving input gear for inputting the driving force to at least one of the developing roller or the toner supply roller, characterized in that it is transferred The developing device according to 1. The developing device according to claim 1 , wherein an outer peripheral surface of the toner conveying belt is coated with a fluorine-based resin . 6. The toner roller according to claim 1, wherein the toner supply roller is a magnetic roller that carries a two-component developer including toner and carrier by a plurality of magnetic poles provided therein. Development device. The developing roller includes a developing according to any one of claims 1 to 5, characterized in that a plurality of magnetic poles disposed inside a magnetic roller which carries a two-component developer containing toner and carrier apparatus. An image forming apparatus comprising the developing device according to claim 1 .

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