JP4721426B2 - Developing device, process cartridge, and image forming apparatus - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus using an electrophotographic system such as a copying machine, a printer, a facsimile, or a complex machine thereof, and a developing device and a process cartridge installed therein, and particularly includes a toner and a carrier. The present invention relates to a developing device, a process cartridge, and an image forming apparatus using a two-component developer.

  Conventionally, in an image forming apparatus using an electrophotographic method such as a copying machine, a printer, a facsimile machine, or a combination machine thereof, a two-component developer composed of a non-magnetic toner and a magnetic carrier (when an additive is added) In other words, a developing device containing a large amount of a developing device is used (see, for example, Patent Document 1).

  In such a developing device using a two-component developer, the toner contained in the device is sufficiently charged with toner appropriately replenished in the device in order to supplement the toner consumed in the developing process. It is necessary to disperse and mix. If the replenishment toner is not sufficiently dispersed / mixed in the developer, the replenishment toner will be insufficiently triboelectrically charged, resulting in toner scattering or background contamination (on the non-image area on the photosensitive drum or on the output image). This is a phenomenon of adhesion. Such a phenomenon is particularly noticeable when images having a high image area ratio such as a solid image are continuously output.

  In order to solve such a problem, Patent Document 1 and the like disclose a technique of separately installing a developer blending unit (developer mixing unit) at a position different from the developing unit (developing unit). . Specifically, the toner and the carrier supplied from the storage means for storing the toner and the carrier to the developer blending means are agitated and mixed by the agitating member, and then conveyed to the developing means.

JP-A-11-143196

  In the technique disclosed in Patent Document 1 and the like described above, the developer that has been sufficiently stirred and mixed by the developer blending unit (developer mixing unit) disposed at a position different from the developing unit (developing unit) is developed by the developing unit. Therefore, an effect of suppressing the occurrence of toner scattering and background stains due to toner charging failure can be expected to some extent.

  However, in Patent Document 1 and the like, since the mixing of the developer in the developer blending means is performed by rotationally driving the stirring member, the driving energy for that amount is required and the structure is also complicated. It was. Furthermore, the developer may be stressed by being stirred by the stirring member.

  The present invention has been made to solve the above-described problems. The stress applied to the developer is small, the drive energy is consumed with a relatively simple configuration, and the replenishment toner is sufficiently dispersed in the developer. An object of the present invention is to provide a developing device, a process cartridge, and an image forming apparatus that are not mixed to cause problems such as toner scattering and background contamination.

The developing device according to the first aspect of the present invention contains a developer composed of toner and a carrier, a developing unit for developing a latent image formed on the image carrier, and a toner. Mixing the toner storage unit, the developer transported from the developing unit by the first transport unit and supplied through the developer supply port, and the toner supplied from the toner storage unit through the toner supply port A developer mixing unit that discharges the developer after being discharged from the developer discharge port; and a second transfer unit that transfers the developer discharged from the developer discharge port toward the developing unit. The agent mixing unit causes the developer supplied via the developer supply port and the toner supplied via the toner replenishing port to fall by their own weight, and the developer and the toner are mutually dropped in the dropping path. Colliding and dispersing / mixing Comprises a dispersing and mixing unit which, is provided with a toner density detecting means for detecting the toner density of the conveyed developer by the first conveyor in the vicinity of the developer feed inlet.

According to a second aspect of the present invention, there is provided a developing device containing a developer composed of toner and a carrier, a developing unit for developing a latent image formed on the image carrier, and a toner containing the toner. The container, the developer transported from the developing unit by the first transport unit and supplied through the developer supply port, and the toner supplied from the toner storage unit through the toner supply port are mixed. A developer mixing unit that discharges the developer after the developer from the developer discharge port; and a second transfer unit that transfers the developer discharged from the developer discharge port toward the developing unit. The mixing unit causes the developer supplied via the developer supply port and the toner supplied via the toner supply port to fall by their own weight, and the developer and the toner collide with each other in the dropping path. To be dispersed and mixed And dispersing and mixing unit, and the input means transport gas to fed the gas therein, those provided with the.

According to a third aspect of the present invention, there is provided a developing device containing a developer composed of toner and a carrier, a developing unit for developing a latent image formed on the image carrier, and a toner containing the toner. The container, the developer transported from the developing unit by the first transport unit and supplied through the developer supply port, and the toner supplied from the toner storage unit through the toner supply port are mixed. A developer mixing unit that discharges the developer after the developer from the developer discharge port; and a second transfer unit that transfers the developer discharged from the developer discharge port toward the developing unit. The mixing unit causes the developer supplied via the developer supply port and the toner supplied via the toner supply port to fall by their own weight, and the developer and the toner collide with each other in the dropping path. To be dispersed and mixed A plate-like member having a plurality of through-holes formed thereon, and a plate-like member arranged vertically above or below the plate-like member, having a through-hole at the bottom, and an inclined surface facing the through-hole. And an inclined member that is disposed below the inclined member in the vertical direction and whose apex is directed upward in the vertical direction.

According to a fourth aspect of the present invention, in the development device according to the third aspect, the developer mixing section includes a plurality of the plate-like members in the vertical direction, and the plurality of plate-like members are The plurality of through holes in the plate-like members adjacent in the vertical direction are disposed so as not to overlap each other in the vertical direction.

According to a fifth aspect of the present invention, there is provided the developing device according to the third or fourth aspect , wherein the developer mixing section is provided with a vibrating means for vibrating the plate-like member. It is.

The developing device according to a sixth aspect of the present invention is the developing device according to any one of the first to fifth aspects, wherein the developer supply port and the toner supply port are connected to the developer discharge port. Are arranged vertically above.

A developing device according to a seventh aspect of the present invention is the developing device according to any one of the first to sixth aspects, wherein the developing portion is disposed at a position separated from the developer mixing portion. In addition, it is configured to be detachable from the developer mixing section.

A developing device according to an eighth aspect of the present invention is the developing device according to any one of the first to seventh aspects, wherein a new carrier or developer is accommodated and the carrier or the developer is developed. It further includes a carrier accommodating portion that supplies the agent mixing portion.

The developing device according to the ninth aspect of the present invention is the developing device according to the eighth aspect, further comprising developer discharging means for discharging part or all of the developer in the device to the outside of the device. It is.

An image forming apparatus according to a tenth aspect includes the developing device according to any one of the first to ninth aspects and the image carrier.

  In the present application, the “process cartridge” refers to a charging unit that charges the image carrier, a developing unit that develops a latent image formed on the image carrier, and a cleaning unit that cleans the image carrier. Of these, at least one and the image carrier are defined as a unit that is integrated and detachable from the main body of the image forming apparatus.

  In the present invention, a developer mixing section is provided separately from the developing section, and the developer and toner are dropped by their own weight in the developer mixing section, and the developer and toner collide with each other in the dispersion / mixing section to be dispersed and mixed. ing. As a result, the stress applied to the developer is small, the consumption of driving energy is small with a relatively simple configuration, and the replenishment toner is sufficiently dispersed and mixed in the developer so as not to cause problems such as toner scattering and background stains. , A developing device, a process cartridge, and an image forming apparatus can be provided.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

Embodiment 1 FIG.
The first embodiment of the present invention will be described in detail with reference to FIGS.
First, the configuration and operation of the entire image forming apparatus will be described with reference to FIG.
In FIG. 1, 1 is an apparatus main body of a color copying machine as an image forming apparatus, 2 is a writing section (exposure section) that emits laser light based on input image information, and 20Y, 20M, 20C, and 20BK are colors (yellow, magenta). , Cyan, and black), 21 is a photosensitive drum as an image carrier accommodated in each of the process cartridges 20Y, 20M, 20C, and 20BK, 22 is a charging unit that charges the photosensitive drum 21, Reference numerals 23Y, 23M, 23C, and 23BK denote developing units for developing the electrostatic latent image formed on the photosensitive drum 21, and reference numeral 24 denotes a transfer bias for transferring the toner image formed on the photosensitive drum 21 to the intermediate transfer belt 27. A roller 25 indicates a cleaning unit that collects untransferred toner on the photosensitive drum 21.

  In addition, 27 is an intermediate transfer belt on which toner images of a plurality of colors are transferred in an overlapping manner, 28 is a second transfer bias roller for transferring the toner image formed on the intermediate transfer belt 27 to the recording medium P, and 29 is an intermediate transfer belt. 27 is an intermediate transfer belt cleaning unit that collects untransferred toner, 30 is a conveyance belt that conveys a recording medium P on which a four-color toner image has been transferred, 44Y, 44M, 44C, and 44BK are developing units 23Y and 23M. , 23C, and 23BK, a toner storage unit that stores toner of each color, 51 a document transport unit that transports the document D to the document reading unit 55, and 55 a document reading unit (scanner) that reads image information of the document D , 61 is a paper feeding unit for storing a recording medium P such as transfer paper, and 66 is a fixing unit for fixing an unfixed image on the recording medium P.

Here, each of the process cartridges 20Y, 20M, 20C, and 20BK is obtained by integrating the photosensitive drum 21, the charging unit 22, and the cleaning unit 25, respectively.
Image formation of each color (yellow, magenta, cyan, black) is performed on the photosensitive drum 21 in each of the process cartridges 20Y, 20M, 20C, and 20BK.

Hereinafter, an operation during normal color image formation in the image forming apparatus will be described.
First, the document D is transported from the document table in the direction of the arrow in the drawing by the transport roller of the document transport unit 51 and placed on the contact glass 53 of the document reading unit 55. Then, the document reading unit 55 optically reads the image information of the document D placed on the contact glass 53.

  Specifically, the document reading unit 55 scans the image of the document D on the contact glass 53 while irradiating light emitted from the illumination lamp. Then, the light reflected by the document D is imaged on the color sensor via the mirror group and the lens. The color image information of the document D is read for each RGB (red, green, blue) color separation light by the color sensor, and then converted into an electrical image signal. Further, an image processing unit (not shown) performs color conversion processing, color correction processing, spatial frequency correction processing, and the like on the basis of RGB color separation image signals, so that yellow, magenta, cyan, and black are processed. Get color image information.

  Then, the image information of each color of yellow, magenta, cyan, and black is transmitted to the writing unit 2. Then, laser light (exposure light) based on the image information of each color is emitted from the writing unit 2 toward the photosensitive drums 21 of the corresponding process cartridges 20Y, 20M, 20C, and 20BK.

On the other hand, the four photosensitive drums 21 rotate in the clockwise direction in FIG. First, the surface of the photosensitive drum 21 is uniformly charged at a position facing the charging unit 22 (a charging process). Thus, a charged potential is formed on the photosensitive drum 21. Thereafter, the surface of the charged photosensitive drum 21 reaches the irradiation position of each laser beam.
In the writing unit 2, laser light corresponding to the image signal is emitted from the light source corresponding to each color. The laser light is incident on the polygon mirror 3 and reflected, and then passes through the lenses 4 and 5. The laser light after passing through the lenses 4 and 5 passes through different optical paths for each of the yellow, magenta, cyan, and black color components (this is an exposure process).

  The laser beam corresponding to the yellow component is reflected by the mirrors 6 to 8 and then irradiated onto the surface of the photosensitive drum 21 of the first process cartridge 20Y from the left side of the drawing. At this time, the yellow component laser light is scanned in the rotation axis direction (main scanning direction) of the photosensitive drum 21 by the polygon mirror 3 that rotates at high speed. Thus, an electrostatic latent image corresponding to the yellow component is formed on the photosensitive drum 21 charged by the charging unit 22.

  Similarly, the laser beam corresponding to the magenta component is reflected by the mirrors 9 to 11 and then irradiated to the surface of the photosensitive drum 21 of the second process cartridge 20M from the left side of the paper, thereby causing an electrostatic latent image corresponding to the magenta component. An image is formed. The cyan component laser light is reflected by the mirrors 12 to 14 and then irradiated to the surface of the photosensitive drum 12 of the third process cartridge 20C from the left side of the drawing to form a cyan component electrostatic latent image. The black component laser light is reflected by the mirror 15 and then irradiated to the surface of the photosensitive drum 21 of the fourth process cartridge 20BK from the left side of the paper, thereby forming an electrostatic latent image of black component.

Thereafter, the surface of the photosensitive drum 21 on which the electrostatic latent images of the respective colors are formed reaches positions facing the developing units 23Y, 23M, 23C, and 23BK, respectively. Then, each color toner is supplied onto the photosensitive drum 21 from the developing units 23Y, 23M, 23C, and 23BK, and the latent image on the photosensitive drum 21 is developed (this is a developing step).
Thereafter, the surface of the photosensitive drum 21 after the development process reaches a position facing the intermediate transfer belt 27. Here, the transfer bias roller 24 is installed at each facing position so as to contact the inner peripheral surface of the intermediate transfer belt 27. Then, at the position of the transfer bias roller 24, the images of the respective colors formed on the photosensitive drum 21 are sequentially superimposed and transferred onto the intermediate transfer belt 27 (first transfer step).

Then, the surface of the photosensitive drum 21 after the first transfer process reaches a position facing the cleaning unit 25. The untransferred toner remaining on the photosensitive drum 21 is collected by the cleaning unit 25 (this is a cleaning process).
Thereafter, the surface of the photosensitive drum 21 passes through a static elimination unit (not shown), and a series of image forming processes on the photosensitive drum 21 is completed.

On the other hand, the surface of the intermediate transfer belt 27 on which the images of the respective colors on the photosensitive drum 21 are transferred in an overlapping manner travels in the direction of the arrow in the drawing and reaches the position of the second transfer bias roller 28. Then, the full-color image on the intermediate transfer belt 27 is secondarily transferred onto the recording medium P at the position of the second transfer bias roller 28 (second transfer step).
Thereafter, the surface of the intermediate transfer belt 27 reaches the position of the intermediate transfer belt cleaning unit 29. Then, the untransferred toner on the intermediate transfer belt 27 is collected by the intermediate transfer belt cleaning unit 29, and a series of transfer processes on the intermediate transfer belt 27 is completed.

Here, the recording medium P at the position of the second transfer bias roller 28 is transported from the paper feeding unit 61 via the transport guide 63, the registration roller 64, and the like.
Specifically, the transfer paper P fed by the paper feed roller 62 from the paper feed unit 61 that stores the recording medium P passes through the conveyance guide 63 and is guided to the registration roller 64. The recording medium P that has reached the registration roller 64 is conveyed toward the position of the second transfer bias roller 28 in synchronization with the toner image on the intermediate transfer belt 27.

Thereafter, the recording medium P on which the full-color image is transferred is guided to the fixing unit 66 by the conveyance belt 30. In the fixing unit 66, the color image is fixed on the recording medium P at the nip between the heating roller 67 and the pressure roller 68.
Then, the recording medium P after the fixing process is discharged as an output image by the paper discharge roller 69 to the outside of the apparatus main body 1, and a series of image forming processes is completed.

Next, the image forming unit of the image forming apparatus will be described in detail with reference to FIG. FIG. 2 is a cross-sectional view showing the image forming unit.
The four image forming units installed in the apparatus main body 1 have substantially the same structure except that the color of the toner T used in the image forming process is different. Therefore, the process cartridge and the developing device (developing unit, developer mixing unit) In the drawings, the alphabet (Y, M, C, BK) is omitted in the drawing.

  As shown in FIG. 2, the process cartridge 20 mainly contains a photosensitive drum 21 as an image carrier, a charging unit 22, and a cleaning unit 25 integrally in a case 26. The cleaning unit 25 is provided with a cleaning blade 25 a and a cleaning roller 25 b that are in contact with the photosensitive drum 21.

The developing device mainly includes a developing unit 23, a toner storage unit 44 (toner cartridge), a developer mixing unit 34, a recovery tube (first transport unit) 32, a supply tube (second transport unit) 33, and the like. .
The developing unit 23 is installed at a position separated from the developer mixing unit 34 and the toner storage unit 44, and is configured to be detachable from the developer mixing unit 34 (the recovery pipe 32 and the supply pipe 33). ing. That is, the degree of freedom of layout of each part of the developing device such as the developing unit 23 and the developer mixing unit 34 is high, and the maintenance workability for each part of the developing device is high.

  The developing unit 23 mainly includes a developing roller 23a facing the photosensitive drum 21, a supply screw 23b facing the developing roller 23a, a recovery screw 23c disposed below the supply screw 23b via a partition member, And a doctor blade 23d (developer regulating member) facing the developing roller 23a.

  The developing unit 23 is provided with a supply unit 23e and a recovery unit 23f separated by a partition member. The supply unit 23e is provided with a supply screw 23b for supplying the developer onto the developing roller 23a while conveying the developer G supplied from the supply pipe 33 in the longitudinal direction (the direction perpendicular to the paper surface in FIG. 2). Has been. The collection unit 23f is provided with a collection screw 23c that conveys the developer G after the development process separated from the developing roller 23a toward the inlet (located at the end in the longitudinal direction) of the collection tube 32. ing.

  The developing roller 23a includes a magnet that is fixed inside and forms a magnetic pole on the circumferential surface of the roller, and a sleeve that is made of a nonmagnetic material and rotates around the magnet. A plurality of magnetic poles (main pole, transport pole, pumping pole, agent cutting pole, etc.) are formed on the developing roller 23a (sleeve) by the magnet.

  The developing roller 23a (sleeve) is connected to a driving source installed in the apparatus main body 1 and is driven to rotate by the driving source. The developing roller 23a, the supply screw 23b, and the recovery screw 23c are drivingly connected by a gear train. Thereby, as the developing roller 23a is rotationally driven by the drive source, the supply screw 23b and the recovery screw 23c are also rotationally driven following the development roller 23a.

A two-component developer G composed of toner T and carrier C is accommodated in the developing unit 23.
The toner T (the toner in the developer G and the toner in the toner replenishing unit 32) in the first embodiment contains toner base particles and additives made of a resin and a colorant.
In addition, the toner T according to the first exemplary embodiment is synthesized by a polymerization reaction such as emulsion polymerization or suspension polymerization using a monomer, or by a method in which the resin itself is melted and sprayed to form fine particles. Alternatively, it can be produced by a method in which an additive is mixed and adhered to a base particle obtained by dispersing in water or the like to a predetermined particle size using a Henschel mixer or the like.

  As the resin contained in the toner T, styrene such as polystyrene, polychlorostyrene, polyvinyltoluene, and the like, and a substituted polymer thereof; styrene / p-chlorostyrene copolymer, styrene / propylene copolymer, styrene / vinyl Toluene copolymer, styrene / vinyl naphthalene copolymer, styrene / methyl acrylate copolymer, styrene / ethyl acrylate copolymer, styrene / butyl acrylate copolymer, styrene / octyl acrylate copolymer, styrene / Methyl methacrylate copolymer, styrene / ethyl methacrylate copolymer, styrene / butyl methacrylate copolymer, styrene / α-chloromethyl methacrylate copolymer, styrene / acrylonitrile copolymer, styrene / vinyl methyl ether Copolymer, styrene / vinyl ethyl Ether copolymer, styrene / vinyl methyl ketone copolymer, styrene / butadiene copolymer, styrene / isoprene copolymer, styrene / acrylonitrile / indene copolymer, styrene / maleic acid copolymer, styrene / maleic acid ester Styrene copolymers such as copolymers; polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, polyvinyl butyl butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin, A phenol resin, an aliphatic or alicyclic hydrocarbon resin, an aromatic petroleum resin, chlorinated paraffin, paraffin wax and the like can be used alone or in combination of two or more.

  As the black colorant used for the toner T, carbon black, aniline black, furnace black, lamp black, and the like are used. Examples of cyan colorants include phthalocyanine blue, methyllene blue, Victoria blue, methyl violet, aniline blue, and ultramarine blue. As the magenta colorant, rhodamine 6G lake, dimethylquinacridone, watching red, rose bengal, rhodamine B, alizarin lake and the like are used. As the yellow colorant, chrome yellow, benzidine yellow, hansa yellow, naphthol yellow, molybdenum orange, quinoline yellow, tartrazine and the like are used.

These toners T can contain a small amount of a charge imparting agent (for example, a dye or pigment, a polarity control agent, etc.) in order to impart the charge efficiently. As the polarity control agent, metal complex salts of monoazo dyes, nitrohumic acid and salts thereof, salicylic acid, naphthoic acid, metal complexes of dicarboxylic acid such as Co, Cr or Fe, organic dyes, quaternary ammonium salts and the like can be used.
The toner base particles and the average charge amount of the toner particles are measured by mixing and stirring the same carrier and the same conditions for any toner base particles and toner particles (after addition of the additive) by blow-off measurement. It is a thing.

  In addition, the toner T can contain abrasive fine particles such as alumina and zirconia. Thus, by containing abrasive fine particles (abrasive fine particles of complex oxide) in the toner T, the effect of scraping off the additive adhering to the carrier surface is improved.

Further, the additive contained in the toner T is set so that the addition amount is 0.5 to 5% by weight with respect to the toner base particles. As a result, a problem that the additive is buried in the toner or accumulated in the carrier is reduced, and a problem that the charging characteristics of the toner are deteriorated is reduced.
If the additive amount is 0.5% by weight or more based on the toner base particles, even if the toner continues to be stressed in the developing device, the additive is kept at a certain level. In contrast, when the additive amount is less than 0.5% by weight based on the toner base particles, most of the additive is embedded in the toner when the toner is stressed. The function as an agent will not be demonstrated.
When the additive amount is 5 wt% or less with respect to the toner base particles, the additive accumulation amount on the carrier surface is suppressed to a certain level. On the other hand, when the additive amount exceeds 5% by weight with respect to the toner base particles, the additive accumulation on the carrier surface is excessive even when stress is applied. It can no longer be scraped off enough.

As such an additive, an additive containing a plurality of inorganic fine particles having different particle diameters is preferably used. This further reduces the burying of the additive in the toner. In addition, when a plurality of inorganic fine particles (additives) are used in this way, the amount of the above-mentioned additive is the total amount of each additive.
Examples of inorganic fine particles used as additives include silica, alumina, titanium oxide, barium titanate, magnesium titanate, calcium titanate, strontium titanate, iron oxide, copper oxide, zinc oxide, tin oxide, silica sand, clay, Mica, wollastonite, diatomaceous earth, chromium oxide, cerium oxide, pengala, antimony trioxide, magnesium oxide, zirconium oxide, parium sulfate, barium carbonate, calcium carbonate, silicon carbide, silicon nitride, and the like can be used. Among these, when two types of silica and titanium oxide are used, the effect of suppressing the burying of the additive in the toner and the effect of stabilizing the charging of the toner are particularly exhibited.

Further, the carrier C in the developer G in the first embodiment is one in which a coating layer is formed on magnetic core particles.
As the core particles of the carrier C, ferromagnetic metals such as iron, cobalt and nickel, alloys such as magnetite, hematite and ferrite, or compounds thereof are used.

  Examples of the resin for forming the coating layer of the carrier C include polyolefin resins such as polyethylene, polypropylene, chlorinated polyethylene, and chlorosulfonated polyethylene; polyvinyl and polyvinylidene resins such as polystyrene, acrylic resin (eg, polymethyl methacrylate), Polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, polyvinyl ether and polyvinyl ketone; vinyl chloride / vinyl acetate copolymer; styrene / acrylic acid copolymer; straight silicone resin composed of organosiloxane bond Or modified products thereof (for example, modified products by alkyd resin, polyester, epoxy resin, polyurethane, etc.); fluorine resin, For example, polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, polychlorotrifluoroethylene; polyamide; polyester, such as polyethylene terephthalate; polyurethane; polycarbonate; amino resin, such as urea / formaldehyde resin; it can. Among these resins, acrylic resin, silicone resin or a modified product thereof, and fluorine resin are preferable from the viewpoint of preventing toner spent (particularly silicone resin or modified product thereof is preferable). As a method for forming the coating layer, a method in which a resin is applied to the surface of the carrier core particles by a spraying method, a dipping method or the like is used.

  In addition, a fine powder can be added to the coating layer to the carrier C in order to adjust the carrier resistance. The fine powder dispersed in the coating layer preferably has a particle size of about 0.01 to 5.0 μm. Moreover, it is preferable that 2-30 weight part (especially 5-20 weight part) is added with respect to 100 weight part of coating resin. As the fine powder, metal oxides such as silica, alumina and titania, and pigments such as carbon black can be used.

2 and 3, the developer mixing unit 34 communicates with the developing unit 23 via a recovery pipe 32 as a first transport unit and a supply pipe 33 as a second transport unit. Further, the developer mixing unit 34 communicates with the toner storage unit 44 through the toner supply port 34d.
The developer mixing unit 34 is newly replenished from the developing unit 23 through the recovery pipe 32 and supplied through the developer supply port 34a, and from the toner storage unit 44 through the toner supply port 34b. The toner T is mixed with the toner T to make the toner concentration (the ratio of the toner T in the developer G) uniform.

  The developer mixed in the developer mixing unit 34 and adjusted to an appropriate toner density is discharged from the developer discharge port 34c in a sufficiently frictionally charged state, and moves in the supply pipe 33 as the second transport unit. Then, it is supplied to the developing unit 23. The developer G supplied to the developing unit 23 is carried on the developing roller 23a while being transported in the longitudinal direction by the supply screw 23b. The developer carried on the developing roller 23a rotating counterclockwise in FIG. 2 reaches the position of the doctor blade 23d thereafter. The developer G on the developing roller 23a is adjusted to an appropriate amount at the position of the doctor blade 23d, and then reaches a position facing the photosensitive drum 21 (developing area).

  Thereafter, in the development area, the toner T in the developer G adheres to the electrostatic latent image formed on the surface of the photosensitive drum 21. Specifically, the toner T is latently exposed by the electric field formed by the potential difference (development potential) between the latent image potential (exposure potential) of the image area irradiated with the laser light L and the development bias applied to the development roller 23a. Adhere to the image.

  Thereafter, most of the toner T adhering to the photosensitive drum 21 in the developing process is transferred onto the intermediate transfer belt 27. The untransferred toner T remaining on the photosensitive drum 21 is collected in the cleaning unit 25 by the cleaning blade 25a and the cleaning roller 25b.

On the other hand, the developer (toner density is lowered) on the developing roller 23a that has passed through the developing region is separated from the developing roller 23a at the position of the recovery unit 23f. The developer G released from the developing roller 23a is recovered by the recovery screw 23c, and then transferred to the developer mixing unit 34 by the recovery pipe 32. The developer supplied to the developer mixing unit 34 is mixed with the replenishing toner supplied from the toner storage unit 44 and adjusted to an appropriate toner concentration, and then supplied to the developing unit 23 again. A series of such circulation cycles of the developer is repeated in the developing device.
For example, a discharge-type powder pump or a conveyance screw can be used as the recovery pipe 32 as the first conveyance unit and the supply pipe 33 as the second conveyance unit.

Here, the toner container 44 (toner cartridge) provided above the developer mixing unit 34 is configured to be replaceable, and the toner T (yellow, magenta, cyan, or black) is contained therein. Is housed).
The toner T in the toner storage unit 34 is appropriately supplied from the toner supply port 34b into the developer mixing unit 34 (developing device) as the toner T in the developing unit 23 is consumed. Consumption of the toner T in the developing unit 23 is detected by a magnetic permeability sensor 40 (toner density detecting means) installed on the collection pipe 32 and in the vicinity of the developer supply port 34a. The toner density (TC) is controlled to be within a predetermined range.

Specifically, when the output value of the magnetic permeability sensor 40 is less than or equal to a predetermined value, the toner supply from the toner storage unit 44 to the developer mixing unit 34 is performed according to the value, and the output value of the magnetic permeability sensor 40 When the toner value exceeds a predetermined value, the toner supply from the toner storage portion 44 to the developer mixing portion 34 is stopped.
In the first embodiment, since the magnetic permeability sensor 40 as the toner concentration detecting means is disposed in the vicinity of the outlet (developer supply port 34b) of the recovery tube 32, the toner is supplied to the developer mixing unit 34. The toner density of the developer can be accurately adjusted and controlled.

Hereinafter, the developer mixing unit 34 will be described in more detail with reference to FIGS.
The developer mixing unit 34 is configured such that the developer supplied via the developer supply port 34a and the toner supplied via the toner supply port 34b fall by their own weight. Specifically, the developer supply port 34a and the toner replenishment port 34b are disposed vertically above the developer discharge port 34c.
Further, the developer mixing portion 34 includes dispersion plates (plate-like members) 35A and 35B as dispersion / mixing portions for allowing the developer and the replenishment toner to collide with each other in the dropping path to be dispersed / mixed. is set up.

The dispersion plates 35A and 35B as the dispersion / mixing part are plate-like members in which a plurality of through holes 36 are formed. In the first embodiment, two dispersion plates 35 </ b> A and 35 </ b> B are installed in the developer mixing unit 34.
Referring to FIG. 4, two dispersion plates 35 </ b> A and 35 </ b> B (plate-like members that are adjacent to each other in the vertical direction with a predetermined distance) have a plurality of through holes 36 that overlap each other in the vertical direction. It is arranged so that the through holes 36 do not overlap each other when projected in the vertical direction. That is, after the developer that passes through the through hole 36 of the upper dispersion plate 36A and falls by its own weight collides with the lower dispersion plate 35B once without passing through the through hole 36 of the lower dispersion plate 35B. The positions of the through holes 36 of both of the dispersion plates 35A and 35B are shifted so that the weights drop downward from the through holes 36. As a result, the developer mixing unit 34 can improve the dispersibility and mixing properties of the developer supplied from the developing unit 23 and the toner supplied from the toner storage unit 44.

  The shape of the through hole 36 formed in the dispersion plate 35 can be a circle as shown in FIG. 5A, or a polygon (here, a rectangle as shown in FIG. 5B). .). Further, the plurality of through holes 36 in one dispersion plate 35 can be arranged alternately, can be arranged so as to draw a spiral, or can be arranged regularly at regular intervals. Further, a mesh or the like can be used as the dispersion plate 35.

In the first embodiment, the size of the through hole 36 formed in the dispersion plate 35 is set to be 5 to 20 times the particle size of the carrier C. Specifically, as shown in FIG. 5A, when the through hole 36 is circular, the diameter of the through hole 36 is set to be 5 to 20 times the particle size of the carrier C. In addition, as shown in FIG. 5B, when the through hole 36 is polygonal, the diameter of the inscribed circle of the through hole 36 is set to be 5 to 20 times the particle size of the carrier C. .
If the size of the through hole 36 is too small, the developer is clogged with the through hole 36, and if it is too large, the mixing ability of the dispersion plate 35 is reduced. When the inventor of the present application experimented with a combination of a carrier and a toner having different particle diameters, when the size of the through hole 36 is in the above range, the developer and the replenishment toner are positively contacted to mix the developer. It has been found that the state of charge of the developer supplied from the section 34 to the developing section 23 is good and the charge amount is made uniform.

  Here, the members constituting the developer mixing section 34 including the dispersion plates 35A and 35B are formed of a nonmagnetic material such as nonmagnetic stainless steel. As a result, since the constituent members of the developer mixing section 34 are not magnetized, the problem that the developer mainly composed of iron adheres and stays on the constituent members and blocks the developer flow is suppressed. Further, the constituent members of the developer mixing section 34 are preferably formed of a conductive material in order to reduce the influence on the charging of the toner.

Hereinafter, the mechanism in which the replenishment toner is dispersed and mixed in the developer by the developer mixing unit 34 will be described in detail.
First, from the developer supply port 34a and the toner supply port 34b disposed above (in the vertical direction above) the developer mixing unit 34, the developer (the developer whose toner concentration has decreased after the development step). ) And toner (replenishment toner) are supplied into the developer mixing section 34.

  Then, the supplied developer and replenishment toner drop by weight on the first dispersion plate 35A. The developer and the replenishment toner collide with the dispersion plate 35A, and a plurality of penetrating holes arranged at regular intervals around the periphery due to its own weight and the weight of the developer and the replenishment toner sequentially falling from above. It is divided (dispersed) toward the hole 46 (the movement in the direction of the arrow in FIG. 6A). Thereafter, in each through hole 46, the developer and the replenishment toner divided at a plurality of collision positions are merged (mixed) (moving in the direction of the arrow in FIG. 6B) and pass through the through hole 46. After that, it falls by its own weight onto the second dispersion plate 35B.

  The developer and the replenishment toner are also divided and combined (dispersed / mixed) on the second dispersion plate 35B as in the operation on the first dispersion plate 35A. At this time, since the through holes 36 of the two dispersion plates 35A and 35B arranged on the upper and lower sides are arranged so as not to overlap each other in the vertical direction, the developer that has passed through the first dispersion plate 35A is retained. It falls by its own weight and does not pass through the second dispersion plate 35B as it is. Therefore, dispersion / mixing of the developer is promoted.

  As described above, when the developer and the replenishment toner pass through the plurality of dispersion plates 35A and 35B, the replenishment toner is dispersed and mixed in the developer, and the developer discharge port of the developer mixing unit 34 is repeated. The developer discharged from 34c and supplied to the developing unit 23 has a uniform charge amount and toner density. That is, the charge amount and toner density of the developer used in the developing process are made uniform in the developing unit 23, and a high-quality image is stably output.

The replenished toner T replenished from the upper end of the developer mixing section 34 and the developer collected from the developing section 23 are uniformly mixed while falling and moving due to their own weight, adjusted to an appropriate toner concentration and developed. It is discharged from the agent discharge port 34c.
The developer mixing unit 34 is a system in which the developer and the replenishing toner are mixed by gravity without having a driving source. Therefore, driving energy is not consumed when the developer is mixed, and there is almost no failure. Since the developing device as a whole only needs to drive the developing roller 23a, the supply screw 23b, and the recovery screw 23c of the developing unit 23, the entire developing device can achieve high reliability, power saving, and noise reduction.
In addition, the developer mixing section 34 in the first embodiment has less developer stress compared to the mixing / stirring method using a screw (stirring member) or the like. Will extend.

Further, the developer mixing section 34 is united separately from the developing section 23 and is connected to the supply pipe 33, the collection pipe 32, and the toner storage section 44, so that there are few restrictions on the layout thereof. .
When the image forming is repeated, the carrier of the two-component developer is contaminated by the toner and additives adhering to the surface, or the film on the surface is displaced, and the charging ability deteriorates with time. Therefore, the durable life of the carrier is 5 to 130,000 sheets / kg. The developing device according to the first embodiment does not need to bother disassembling the developing unit when replacing the carrier (developer), and only removes the supply pipe 33 and the collecting pipe 32 of the developer mixing unit 34 to remove the developing unit 23. The developer contained in the can be easily discharged. Therefore, the developer replacement operation is made efficient and simplified.

  As described above, according to the first embodiment, the developer mixing unit 34 is provided separately from the developing unit 23, and the developer and toner are dropped by their own weight in the developer mixing unit 34, so that the dispersion plate 35A, In 35B (dispersion / mixing unit), the developer and the toner collide with each other to be dispersed and mixed. This reduces stress on the developer, reduces drive energy consumption with a relatively simple configuration, and ensures that supply toner is sufficiently dispersed and mixed in the developer to prevent problems such as toner scattering and background contamination. Can be reduced.

  In the first embodiment, the process cartridges 20Y, 20M, 20C, and 20BK are configured by integrating the photosensitive drum 21, the charging unit 22, and the cleaning unit 25, respectively. Further, each developing unit 23Y, 23M, 23C, 23BK is configured as a single unit. On the other hand, the developing units 23Y, 23M, 23C, and 23BK can be integrated with the process cartridges 20Y, 20M, 20C, and 20BK. That is, the process cartridge 20 can also be configured by the photosensitive drum 21, the charging unit 22, the developing unit 23, and the cleaning unit 25. Also in this case, the same effect as in the first embodiment is obtained. Furthermore, the maintainability of the image forming unit is improved.

Embodiment 2. FIG.
A second embodiment of the present invention will be described in detail with reference to FIG.
FIG. 7 is a cross-sectional view showing the developing device and its vicinity in the second embodiment. The developing device of the second embodiment is that the carrier accommodating portion 45 for supplying the carrier to the developing device and the developer discharging means for discharging the developer from the developing device are provided in the first embodiment. Is different.

As shown in FIG. 7, in the developing device according to the second embodiment, a carrier accommodating portion 45 is installed above the developer mixing portion 34 in addition to the toner accommodating portion 44. A new carrier (or developer) is accommodated in the carrier accommodating portion 45, and the carrier is appropriately supplied to the developer mixing portion 34 (developing device) via the carrier supply port 34d.
Further, at the bottom of the developer mixing section 34, as a developer discharging means, an opening for discharging a part or all of the developer in the developing device to the outside of the developing device, and a shutter 34e for opening and closing the opening, Is provided.

  When the carrier deteriorates over time, the shutter 34e is opened, the deteriorated developer is discharged from the developer mixing unit 34 (developing device), and a new carrier is supplied from the carrier containing unit 45. As a result, the carrier circulating in the developing device is appropriately replaced with a new carrier, so that a high-quality output image can be stably provided over time.

  As described above, also in the second embodiment, similarly to the first embodiment, the developer mixing section 34 is provided separately from the developing section 23, and the developer and toner are supplied to the developer mixing section 34. The developer and the toner collide with each other by the dispersion plates 35A and 35B (dispersion / mixing unit) and are dispersed and mixed by dropping by their own weight. This reduces stress on the developer, reduces drive energy consumption with a relatively simple configuration, and ensures that supply toner is sufficiently dispersed and mixed in the developer to prevent problems such as toner scattering and background contamination. Can be reduced.

Embodiment 3 FIG.
A third embodiment of the present invention will be described in detail with reference to FIG.
FIG. 8 is a cross-sectional view showing a part of the developer mixing portion of the developing device in the third embodiment, and corresponds to FIG. 4 in the first embodiment. The developing apparatus according to the third embodiment is different from that according to the first embodiment in that a vibrating means 46 that applies vibration to the dispersion plates 35A and 35B is provided.

In the third embodiment, a vibration unit 46 (vibration device) is installed in the developer mixing unit 34. The vibration means 46 oscillates the dispersion plates 35A and 35B in the direction of the arrow and applies vibration to the dispersion plates 35A and 35B.
With such a configuration, it is possible to suppress a problem that the developer is deposited on the dispersion plates 35A and 35B due to the deterioration of the developer over time. That is, by applying vibration to the dispersion plates 35A and 35B by the vibration means 46, the speed at which the developer passes through the dispersion plates 35A and 35B can be increased.

  As described above, also in the third embodiment, as in each of the above embodiments, the developer mixing unit 34 is provided separately from the developing unit 23, and the developer and toner are supplied to the developer mixing unit 34. The developer and the toner collide with each other by the dispersion plates 35A and 35B (dispersion / mixing unit) and are dispersed and mixed by dropping by their own weight. This reduces stress on the developer, reduces drive energy consumption with a relatively simple configuration, and ensures that supply toner is sufficiently dispersed and mixed in the developer to prevent problems such as toner scattering and background contamination. Can be reduced.

Embodiment 4 FIG.
A fourth embodiment of the present invention will be described in detail with reference to FIG.
FIG. 9 is a cross-sectional view showing a part of the developer mixing portion of the developing device in the fourth embodiment, and corresponds to FIG. 4 in the first embodiment. The developing apparatus of the fourth embodiment is different from that of the first embodiment in that gas feeding means 47 for feeding gas into the developer mixing section 34 is installed.

  As shown in FIG. 9, in the fourth embodiment, a gas feeding means 47 (air feeding device) is installed in the developer mixing unit 34. The gas feeding means 47 feeds air from the lower side to the upper side of the second dispersion plate 35 </ b> B in the developer mixing unit 34. As a result, convection occurs between the two dispersion plates 35A and 35B, and the developer falls after being lifted by the air current. At this time, since the weights of the toner and the carrier are different, the convection speeds are also different and the number of contact between the toner and the carrier is increased. Therefore, the friction between the toner and the carrier is promoted, and the chargeability of the developer finally discharged from the developer mixing unit 34 is improved.

  As described above, also in the fourth embodiment, similarly to the above-described embodiments, the developer mixing section 34 is provided separately from the developing section 23, and the developer and toner are supplied to the developer mixing section 34. The developer and the toner collide with each other by the dispersion plates 35A and 35B (dispersion / mixing unit) and are dispersed and mixed by dropping by their own weight. This reduces stress on the developer, reduces drive energy consumption with a relatively simple configuration, and ensures that supply toner is sufficiently dispersed and mixed in the developer to prevent problems such as toner scattering and background contamination. Can be reduced.

Embodiment 5. FIG.
A fifth embodiment of the present invention will be described in detail with reference to FIGS.
FIG. 10 is a cross-sectional view showing a part of the developer mixing portion of the developing device in the fifth embodiment, and corresponds to FIG. 4 in the first embodiment. FIG. 11 is a perspective view showing a part of the developer mixing section. The developing device of the fifth embodiment is different from that of the first embodiment in that a mortar-shaped member 37 and a conical member 38 are installed between two dispersion plates 35A and 35B.

  As shown in FIGS. 10 and 11, in the fifth embodiment, a mortar-shaped member 37 (inclined member) and a conical member 38 are installed in the developer mixing section 34. The mortar-shaped member 37 is disposed below the first dispersion plate 35A in the vertical direction, and a through hole 37a is formed at the bottom thereof. A plurality of conical members 38 are arranged below the mortar-shaped member 37 in the vertical direction and above the second dispersion plate 35B in the vertical direction. The plurality of conical members 38 are arranged such that their apexes face upward in the vertical direction (on the side of the mortar-shaped member 37).

  With such a configuration, the developer that has passed through the first dispersion plate 35 </ b> A gathers at the position of the through hole 37 a along the inclined surface of the mortar-shaped member 37. Then, the developer falls downward from the through holes 37a and is evenly distributed in the horizontal direction while colliding with the apexes of the plurality of conical members 38. As described above, in the developer mixing section 34 in the fifth embodiment, the developer in the vicinity of the wall surface of the developer mixing section 34 and the developer in the vicinity of the central portion are forcibly mixed. The mixed state of the developer discharged from the agent mixing unit 34 is further improved.

  As described above, also in the fifth embodiment, as in each of the above embodiments, the developer mixing section 34 is provided separately from the developing section 23, and the developer and toner are supplied to the developer mixing section 34. The developer and the toner collide with each other by the dispersion plates 35A and 35B (dispersion / mixing unit) and are dispersed and mixed by dropping by their own weight. This reduces stress on the developer, reduces drive energy consumption with a relatively simple configuration, and ensures that supply toner is sufficiently dispersed and mixed in the developer to prevent problems such as toner scattering and background contamination. Can be reduced.

  It should be noted that the present invention is not limited to the above-described embodiments, and within the scope of the technical idea of the present invention, the embodiments can be modified as appropriate in addition to those suggested in the embodiments. Is clear. In addition, the number, position, shape, and the like of the constituent members are not limited to the above embodiments, and can be set to a number, position, shape, and the like that are suitable for carrying out the present invention.

1 is an overall configuration diagram illustrating an image forming apparatus according to Embodiment 1 of the present invention. FIG. 2 is a cross-sectional view illustrating an image forming unit in the image forming apparatus of FIG. 1. It is a perspective view which shows a developing agent mixing part. It is sectional drawing which shows a part of developing agent mixing part. It is a top view which shows a dispersion | distribution / mixing part. It is a schematic diagram which shows the developer which passes a through hole. It is sectional drawing which shows the vicinity of the image development apparatus in Embodiment 2 of this invention. It is sectional drawing which shows a part of developer mixing part in Embodiment 3 of this invention. It is sectional drawing which shows a part of developer mixing part in Embodiment 4 of this invention. It is sectional drawing which shows a part of developer mixing part in Embodiment 5 of this invention. It is a perspective view which shows the developer mixing part of FIG.

Explanation of symbols

1 image forming apparatus body (apparatus body),
20, 20Y, 20M, 20C, 20BK Process cartridge,
21 Photosensitive drum (image carrier),
23, 23Y, 23M, 23C, 23BK Development section,
23a Developing roller, 23b Supply screw, 23c Recovery screw,
23d doctor blade, 23e supply unit, 23f recovery unit,
32 collection pipe (first transport section), 33 supply pipe (second transport section),
34 Developer mixing section,
34a developer supply port, 34b toner supply port,
34c Developer discharge port, 34d Carrier supply port,
34e shutter (developer discharging means),
35, 35A, 35B Dispersion plate (dispersion / mixing part, plate-like member), 36 Through hole,
37 mortar-shaped member, 37a through hole,
38 conical member, 40 permeability sensor (toner concentration detection means),
44, 44Y, 44M, 44C, 44B Toner container,
45 carrier accommodating portion, 46 excitation means, 47 gas feeding means,
G Two-component developer (developer), C carrier, T toner.

Claims (10)

A developer that contains a developer composed of a toner and a carrier, and that develops a latent image formed on the image carrier;
A toner container for containing toner;
The developer after mixing the developer conveyed from the developing unit by the first conveying unit and supplied through the developer supply port with the toner supplied from the toner storage unit through the toner replenishing port. A developer mixing section for discharging the developer from the developer discharge port;
A second transport unit that transports the developer discharged from the developer discharge port toward the developing unit;
With
The developer mixing unit causes the developer supplied via the developer supply port and the toner supplied via the toner supply port to fall by its own weight, and the developer and the toner in the dropping path. Equipped with a dispersion / mixing part that collides with each other and is dispersed / mixed,
A developing device comprising: a toner concentration detecting means for detecting a toner concentration of the developer conveyed by the first conveying unit in the vicinity of the developer supply port. A developer that contains a developer composed of a toner and a carrier, and that develops a latent image formed on the image carrier;
A toner container for containing toner;
The developer after mixing the developer conveyed from the developing unit by the first conveying unit and supplied through the developer supply port with the toner supplied from the toner storage unit through the toner replenishing port. A developer mixing section for discharging the developer from the developer discharge port;
A second transport unit that transports the developer discharged from the developer discharge port toward the developing unit;
With
The developer mixing part
The developer supplied through the developer supply port and the toner supplied through the toner replenishing port are dropped by their own weight, and the developer and the toner collide with each other in the dropping path to disperse / A dispersion / mixing section to be mixed;
Gas feeding means for feeding gas into the interior;
A developing device comprising: A developer that contains a developer composed of a toner and a carrier, and that develops a latent image formed on the image carrier;
A toner container for containing toner;
The developer after mixing the developer conveyed from the developing unit by the first conveying unit and supplied through the developer supply port with the toner supplied from the toner storage unit through the toner replenishing port. A developer mixing section for discharging the developer from the developer discharge port;
A second transport unit that transports the developer discharged from the developer discharge port toward the developing unit;
With
The developer mixing part
The developer supplied through the developer supply port and the toner supplied through the toner replenishing port are dropped by their own weight, and the developer and the toner collide with each other in the dropping path to disperse / A plate-like member in which a plurality of through holes are formed so as to be mixed;
An inclined member that is disposed vertically above or below the plate-like member, has a through hole at the bottom, and has an inclined surface facing the through hole,
A conical member disposed below the inclined member in the vertical direction and having a vertex directed upward in the vertical direction;
A developing device comprising: The developer mixing section includes a plurality of the plate-like members in the vertical direction,
The developing device according to claim 3, wherein the plurality of plate-like members are arranged such that the plurality of through holes in the plate-like members adjacent in the vertical direction do not overlap each other in the vertical direction.   5. The developing device according to claim 3, wherein the developer mixing unit includes a vibrating unit that applies vibration to the plate-like member.   6. The developing device according to claim 1, wherein the developer supply port and the toner supply port are disposed vertically above the developer discharge port.   7. The developing device according to claim 1, wherein the developing unit is disposed at a position separated from the developer mixing unit and is detachable from the developer mixing unit. The developing device according to any one of the above.   8. The apparatus according to claim 1, further comprising a carrier accommodating portion that accommodates a new carrier or developer and supplies the carrier or the developer to the developer mixing portion. Development device.   9. The developing device according to claim 8, further comprising developer discharging means for discharging a part or all of the developer in the apparatus to the outside of the apparatus. An image forming apparatus comprising the developing device according to claim 1 and the image carrier.

Images