JP2006258842A - Developing device, processing cartridge, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device for reducing temporal deterioration of a developer by optimizing stress applied on the developer, and to provide a process cartridge and an image forming apparatus. <P>SOLUTION: When dynamic torque of the developing device 23 while the developer G is stored is W1(kgf cm), dynamic torque W0(kgf cm) of the developing device 23 while the developer G is not stored and a mass of toner T in the developer G stored in the developing device 23 is M(g), a condition of 4×10<SP>-2</SP><(W1-W0)/M<15×10<SP>-2</SP>is satisfied. <P>COPYRIGHT: (C)2006,JPO&NCIPI

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 Patent Document 1 and the like, the developing device includes a developing roller (developer carrier), two transport screws (a first transport member and a second transport member), and the like. The developer is supplied to the developing roller while the developer is circulated in the longitudinal direction of the developing device by two conveying screws.
Specifically, according to the consumption of toner in the apparatus, toner is appropriately supplied into the apparatus from a toner supply port provided at one end of the developing apparatus. The replenished toner is mixed with the developer in the developing device while being circulated in the device in the longitudinal direction (the same direction as the rotation axis of the developing roller) by two transport screws. A part of the mixed developer is supplied to the developing roller by the first conveying screw facing the developing roller. The developer carried on the developing roller is regulated to an appropriate amount by a doctor blade (developer regulating member), and then the toner in the developer is placed on the photosensitive drum at a position facing the photosensitive drum (image carrier). It adheres to the latent image.

  In such a two-component developing type developing apparatus, it is necessary to charge the toner in the developer satisfactorily. The charging of the toner is mainly caused by friction with the carrier, and in particular, the contribution of frictional charging due to friction between the doctor blade and the developing roller in the gap (doctor gap) is large.

  On the other hand, it is known that the rubbing of the developer performed at the position of the doctor blade places great stress on the toner. When the toner is subjected to great stress, a phenomenon occurs in which the additive on the toner surface is embedded in the toner base particles. When the additive is buried, the fluidity and charge controllability imparted by the additive are lost. As a result, problems such as background contamination (a phenomenon in which toner adheres to a non-image area on the photosensitive drum or the output image) and toner scattering occur.

On the other hand, in Patent Document 2 and the like, for the purpose of reducing the stress applied to the toner, the dynamic torque W (kgf · cm) received by the two-component developer when the developing device is driven and 22 A technique is disclosed in which the ratio W / M of the toner amount M (g) contained in the component developer is 4 × 10 ⁻² or less.

  On the other hand, Patent Document 3 discloses a technique for replenishing a new carrier with a replenishment toner at a certain ratio (this is a trickle development method) for the purpose of simplifying the work of replacing a deteriorated developer with a new developer. Is disclosed).

Japanese Patent Laid-Open No. 10-69155 JP 2003-263032 A Japanese Patent Publication No. 2-21591

  The conventional developing device described above cannot sufficiently suppress the deterioration of the developer over time.

In the technique disclosed in Patent Document 2 and the like, the stress applied to the developer becomes too small, and the additive composed of inorganic fine particles added to the toner adheres to the carrier.
That is, the inorganic fine particles adhering to the toner surface are released from the toner surface by being repeatedly stirred and conveyed in the developing device. The liberated inorganic fine particles adhere and accumulate on the outer periphery of the carrier that has been used for a long period of time together with a minute toner of less than 1 μm. Carriers in which such additives and fine toner are accumulated cannot sufficiently charge the toner. Such a phenomenon was prominent when the stress applied to the developer became too small.

  On the other hand, the technique described in Patent Document 3 described above merely extends the life of the developer in a pseudo manner by replacing a deteriorated carrier with a new carrier. Therefore, when the adhesive force of the additive to the toner is weak, the additive adheres to and accumulates on the carrier over time, and the toner cannot be sufficiently charged.

  The present invention has been made in order to solve the above-described problems. A developing device, a process cartridge, and an image forming apparatus capable of optimizing a stress applied to the developer and reducing deterioration with time of the developer. Is to provide.

The inventor of the present application has made researches to solve the above-described problems, and as a result, has come to know the following matters.
In other words, in order to charge the toner satisfactorily and stably, it is necessary to reduce the amount of the additive accumulated in the carrier and to prevent the additive from being buried in the toner. For this purpose, the stress applied to the developer needs to be optimized without being too large or too small. The stress applied to the developer can be characterized by the dynamic torque received by the developer from the developing device and the toner mass in the developer. Further, the deterioration of the developer can be further suppressed by limiting the configuration of the toner and additives.

The present invention is based on the above-described matters. That is, the developing device according to the first aspect of the present invention contains a developer composed of toner and a carrier and is formed on an image carrier. A developing device for developing the latent image to be developed, wherein the dynamic torque of the device in the state where the developer is accommodated is W1 (kgf · cm), and the dynamic torque of the device in the state where the developer is not accommodated is When W0 (kgf · cm) and the mass of the toner in the developer contained in the apparatus is M (g),
4 × 10 ⁻² <(W1-W0) / M <15 × 10 ⁻²
The relationship is established.

  According to a second aspect of the present invention, there is provided the developing device according to the first aspect, wherein the developer carrying member is opposed to the image carrier and carries the developer and is connected to a driving source. And a developer regulating member that opposes the developer carrying member and regulates the amount of the developer carried on the developer carrying member, and faces the developer carrying member and also carries the developer carrying member. A first conveying member that conveys the developer along the longitudinal direction of the body, and the developing member in a direction opposite to the conveying direction of the first conveying member while facing the first conveying member via a partition member A second conveying member that conveys the agent and forms a circulation path of the developer together with the first conveying member, and the first conveying member and the second conveying member are driven by the driving source. Following the developer carrier, Dynamic torque of location is to be detected in the drive source.

  The developing device according to a third aspect of the present invention is the developing device according to the first or second aspect, wherein the toner contains toner base particles composed of a resin and a colorant and an additive, The additive is formed so that the addition amount is 0.5 to 5% by weight with respect to the toner base particles.

  According to a fourth aspect of the present invention, there is provided the developing device according to the third aspect, wherein the additive contains a plurality of inorganic fine particles having different particle diameters.

  A developing device according to a fifth aspect of the present invention is the developing device according to any one of the first to fourth aspects, wherein the toner contains abrasive fine particles.

  According to a sixth aspect of the present invention, there is provided the developing device according to any one of the first to fifth aspects, wherein the discharging means discharges a part or all of the developer accommodated in the apparatus. And replenishment means for newly replenishing the developer or carrier in the apparatus.

The developing device according to a seventh aspect of the present invention is the developing device according to the sixth aspect, wherein the discharging means or / and the replenishing means are:
4 × 10 ⁻² <(W1-W0) / M <15 × 10 ⁻²
It is controlled so that the following relationship is established.

  The process cartridge according to an eighth aspect of the present invention is a process cartridge that is detachably installed on the main body of the image forming apparatus, and is according to any one of the first to seventh aspects. The developing device and the image carrier are integrated.

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

  In the present application, the “process cartridge” refers to a charging unit that charges the image carrier, a developing device (developing unit) that develops a latent image formed on the image carrier, and a cleaning on the image carrier. It is defined as a unit in which at least one of the cleaning units and the image carrier are integrated and configured to be detachable from the image forming apparatus main body.

  The present invention can provide a developing device, a process cartridge, and an image forming apparatus in which the deterioration of the developer over time is reliably reduced because the stress applied to the developer is optimized.

  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.
A 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 devices (developing units) that develop the electrostatic latent image formed on the photosensitive drum 21, and 24 denotes a toner image formed on the photosensitive drum 21 to the intermediate transfer belt 27. A transfer bias roller 25 for transferring represents a cleaning unit for collecting 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 is transferred, and 32Y, 32M, 32C, and 32BK are developing devices 23Y and 23M. , 23C and 23BK, a toner replenishing unit for replenishing each color toner, 51 a document conveying unit for conveying the document D to the document reading unit 55, 55 for a document reading unit (scanner) for reading image information of the document D, and 61 for transferring A paper feed unit 66 for storing a recording medium P such as paper, and a fixing unit 66 for fixing an unfixed image on the recording medium P are shown.

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 on 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 devices 23Y, 23M, 23C, and 23BK, respectively. Then, the respective color toners are supplied from the developing devices 23Y, 23M, 23C, and 23BK onto the photosensitive drum 21, 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 FIGS. FIG. 2 is a cross-sectional view showing the image forming unit, and FIG. 3 is a cross-sectional view in the longitudinal direction (vertical direction in FIG. 2) showing the developing device.
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. (Y, M, C, BK) is omitted for illustration.

  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 23 mainly includes a developing roller 23a as a developer carrying member facing the photosensitive drum 21, a first conveying screw 23b as a first conveying member facing the developing roller 23a, and a partition member 23e. A second conveying screw 23c as a second conveying member facing the first conveying screw 23b and a doctor blade 23d as a developer regulating member facing the developing roller 23a are configured.

  Further, the developing device 23 is provided with a first developer containing portion 23g and a second developer containing portion 23h separated by a partition member 23e. Referring to FIG. 3, the first developer accommodating portion 23g and the second developer accommodating portion 23h communicate with each other at both ends in the longitudinal direction (the range in which the partition member 23e is not interposed), and the developer circulation path. Is forming. A developing roller 23a, a first conveying screw 23b, and a doctor blade 23d are disposed in the first developer accommodating portion 23g. A second transport screw 23c and a magnetic sensor 40 are disposed in the second developer accommodating portion 23h.

  Referring to FIG. 3, the developing roller 23a includes a magnet 23a1 fixed inside and forming a magnetic pole on the roller peripheral surface, and a sleeve 23a2 made of a nonmagnetic material and rotating around the magnet 23a1. . A plurality of magnetic poles (main pole, transport pole, pumping pole, agent cutting pole, etc.) are formed on the developing roller 23a (sleeve 23a2) by the magnet 23a1.

The developing roller 23 a (sleeve 23 a 2) is connected to a drive source 43 installed in the apparatus main body 1 and is rotationally driven by the drive source 43. Although not shown, the developing roller 23a, the first transport screw 23b, and the second transport screw 23c are drivingly connected by a gear train. Thereby, as the developing roller 23a is rotationally driven by the drive source 43, the first transport screw 23b and the second transport screw 23c are also rotationally driven following the development roller 23a.
The drive source 43 is connected to a torque detector 44 that detects the dynamic torque (drive torque) of the developing device 23. Further, the torque detector 44 is connected to a controller 45 that controls the toner replenisher 32 and the like. These functions will be described in detail later.

In the developing device 23, a two-component developer G composed of toner T and carrier C is accommodated.
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 what.

  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.

The above-described image forming process will be described in more detail with a focus on the developing process.
The developing roller 23a rotates in the direction of the arrow in FIG. As shown in FIG. 3, the developer G in the developing device 23 is generated by the rotation of the first conveying screw 23 b and the second conveying screw 23 c arranged so as to interpose the partition member 23 e therebetween in the arrow direction. It circulates in the longitudinal direction while being agitated and mixed with the toner T replenished from the replenishing section 32 through the toner replenishing port 23f (circulation in the direction of the broken arrow in FIG. 3). The first transport screw 23b serving as the first transport member transports the developer G to the left side in FIG. 3, and the second transport screw 23c serving as the second transport member transports the developer G to the right side in FIG. It is conveyed in the direction opposite to the conveying direction of the conveying screw 23b.

  Then, the toner T that is frictionally charged and adsorbed on the carrier C is carried on the developing roller 23 a together with the carrier C. The developer G carried on the developing roller 23a then reaches the position of the doctor blade 23d. 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.

  Here, a toner replenishing unit 32 provided in the apparatus main body 1 includes a toner bottle 33 configured to be replaceable, and a toner hopper unit 34 that holds and rotates the toner bottle 33 and replenishes the developing device 23 with fresh toner T. And is composed of. The toner bottle 33 contains toner T (any one of yellow, magenta, cyan, and black). In addition, a spiral protrusion is formed on the inner peripheral surface of the toner bottle 33.

  The toner T in the toner bottle 33 is appropriately supplied into the developing device 23 from the toner supply port 23f as the toner T in the developing device 23 is consumed. Consumption of the toner T in the developing device 23 is detected by a magnetic sensor 40 (toner density detecting means) installed below the second conveying screw 23c of the developing device 23. Further, the toner replenishing port 23f is provided at one end in the longitudinal direction of the second transport screw 23c (the left-right direction in FIG. 3) and above the second transport screw 23c.

  Here, in the first embodiment, the toner density (TC) is controlled to be within a predetermined range. Specifically, the toner replenishing port 32 provides a toner replenishing port so that the detection result of the magnetic sensor 40 has an output value corresponding to the target toner density (the ratio of the toner T in the developer G). The toner is supplied to the developing device 23 via 23f.

Here, in the developing device 23 of the first embodiment, the dynamic torque received by the developer G from the developing device 23 and the mass of the toner T in the developer G are set so as to satisfy the following relationship. Has been.
That is, the dynamic torque of the developing device 23 in the state where the developer G is accommodated is W1 (kgf · cm), and the dynamic torque of the developing device 23 in the state where the developer G is not accommodated is W0 (kgf · cm). When the mass of the toner T in the developer G accommodated in the developing device 23 is M (g),
4 × 10 ⁻² <(W1-W0) / M <15 × 10 ⁻²
Is set to hold.

The above equation is derived as a result of repeated research by the present inventors. That is, the ratio ((W1-W0) / M) of the dynamic torque (W1-W0) received by the two-component developer G and the mass M of the toner T in the developer G when the developing device 23 is driven. When it is less than 4 × 10 ⁻² kgf · cm, accumulation of the additive in the carrier proceeds and the carrier deteriorates. On the other hand, when (W1−W0) / M exceeds 15 × 10 ⁻² kgf · cm, the additive is buried in the toner and the chargeability of the toner is lowered. Therefore, by satisfying the relationship of the above formula, the additive once adhered to the carrier can be scraped off and the burying of the additive in the toner can be reduced. As a result, good and stable toner chargeability can be maintained over time.

  Specifically, in order to satisfy the above formula, in the first embodiment, the magnetic pole arrangement of the developing roller 23a (magnet 23a1) in the developing device 23, the gap (doctor gap) between the doctor blade 23d and the developing roller 23a, The shape of the doctor blade 23d is optimized. Furthermore, the target values of the developer mass and toner concentration accommodated in the developing device 23 are also optimized.

  Note that the dynamic torques W 1 and W 0 of the developing device 23 in the above formula are detected by a torque detector 44 connected to the drive source 43. Specifically, the dynamic torque W0 of the developing device 23 in a state where the developer G is not accommodated is data at the time of factory shipment detected by the torque detector 44 and is stored in the memory of the controller 45. The dynamic torque W1 of the developing device 23 in the state where the developer G is accommodated is actual measurement data detected at the time of image formation by the torque detection unit 44.

  Then, the control unit 45 compares the actually measured data (W1) and the stored data (W0) to obtain the dynamic torque difference (W1-W0) of the above equation. Further, the toner replenishment amount supplied to the developing device is adjusted by the toner replenishing unit 32 so that the toner mass M satisfies the above formula. The adjustment of the toner replenishment amount by the toner replenishing unit 32 is performed in a range in which the toner density of the developer G is excessive or insufficient and does not cause problems such as an image density defect, toner scattering, and background contamination. That is, the toner mass M is adjusted so that the toner concentration of the developer G in the developing device 23 does not deviate from the predetermined range described above.

  As described above, according to the first embodiment, since the stress applied to the developer G is optimized, the deterioration of the developer G with time can be surely 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 device 23Y, 23M, 23C, 23BK is configured as a single unit. On the other hand, the developing devices 23Y, 23M, 23C, and 23BK can be integrated with the process cartridges 20Y, 20M, 20C, and 20BK. In other words, the process cartridge 20 can be configured by the photosensitive drum 21, the charging unit 22, the developing device 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 FIGS.
FIG. 4 is a cross-sectional view showing the developing device according to the second embodiment. The developing device 23 of the second embodiment is different from that of the first embodiment in that a discharging unit for discharging the developer and a supply unit for supplying the developer are provided.

As shown in FIG. 4, in the second embodiment, a discharging unit 23 j that discharges the developer G stored in the developing device 23 to the outside of the device, and a replenishing unit 47 that replenishes the developing device 23 with a fresh developer G. And are provided.
Specifically, a developer discharge port 23j as discharge means is provided below the second developer accommodating portion 23h. Then, the developer in the developing device 23 is discharged from the developer discharge port 23j at a predetermined timing. The developer discharged from the developer discharge port 23j is conveyed to a waste bottle via a discharge path (not shown).

On the other hand, a carrier replenishing portion 47 as a replenishing unit is provided above the second developer accommodating portion 23h, in addition to the toner replenishing portion 32. A developer G having a predetermined toner concentration is accommodated in the carrier replenishing section 47, and the developer G (a new developer) is fed into the developing device 23 at a predetermined timing via the toner replenishing port 23f. And replenish.
The toner replenishing unit 32 of the second embodiment uses a toner bottle that does not have a spiral protrusion unlike the one of the first embodiment.

In the developing device 23 configured as described above, the developer G (carrier C) is replaced by the control flow shown in FIG.
When the image forming process is repeatedly performed (steps S1 to S2), first, it is determined whether the number of times of image formation has reached a predetermined value (step S3). As a result, when it is determined that the number of times of image formation has not reached the predetermined value, it is determined that the developer G has not deteriorated, and the flow after step S2 is repeated.

  On the other hand, when it is determined that the number of times of image formation has reached the predetermined value, it is assumed that the developer G has deteriorated, and the discharge of the deteriorated developer from the developer discharge port 23j and the carrier A new developer is supplied from the supply unit 47 (step S4). Thereafter, the image forming process is repeatedly performed, and this control flow is ended (steps S5 to S6).

Thus, the ratio of the deteriorated developer in the developing device 23 decreases (or becomes zero) by discharging the developer by the discharging unit 23j and supplying the fresh developer by the supplying unit 47, and the developing device. The life of the developer accommodated in 23 is further increased.
In the second embodiment, the fresh developer G is supplied from the carrier supply unit 47, but only the fresh carrier C can be supplied from the carrier supply unit 47. In this case, the same effect as described above can be obtained.

Here, even when the developer is replaced, control is performed such that the stress applied to the developer G after the replacement is optimized.
That is, the dynamic torque of the developing device 23 in the state where the fresh developer G is accommodated is W1 (kgf · cm), and the dynamic torque of the developing device 23 in the state where the developer G is not accommodated is W0 (kgf · cm). ) And the mass of the toner T in the developer G accommodated in the developing device 23 is M (g),
4 × 10 ⁻² <(W1-W0) / M <15 × 10 ⁻²
Is set to hold. As a result, even after the replacement of the developer, as with the first embodiment, the deterioration with time of the developer G can be reliably reduced.

Further, in the second embodiment, in addition to the control flow of FIG. 5, in order to satisfy the relationship of the above formula, the developer replenishment from the carrier replenishment unit 47 and the developer discharge from the developer discharge port 23j are performed. The discharge and the toner supply from the toner supply unit 32 are appropriately performed.
Specifically, as in the first embodiment, the control unit 45 compares the actually measured data (W1) and the stored data (W0) obtained by the torque detection unit 44 to determine the dynamic torque difference (W1- W0) is determined. Further, the developer replenishment amount from the carrier replenishment unit 47, the developer discharge amount from the developer discharge port 23j, and the toner replenishment from the toner replenishment unit 32 so that the toner mass M satisfying the above equation is obtained. The amount is adjusted.

By performing such control, as in the case where an image with a low area ratio of about 1% is frequently formed, the replacement of the toner in the developer is small and the additive is embedded in the toner. Even when the fluidity of the developer is lowered and the dynamic torque is increased, toner oversupply can be prevented.
That is, when only the toner replenishment amount from the toner replenishing unit 32 is adjusted so that the toner mass M satisfies the above formula, the fluidity of the developer decreases and the dynamic torque increases. In addition, only toner replenishment is performed until the dynamic torque falls within a predetermined range. As a result, as the toner concentration of the developer in the developing device 23 increases, the coverage of the carrier increases, causing scumming due to toner scattering or a decrease in charge amount.

  On the other hand, in the second embodiment, in addition to the adjustment of the toner replenishment amount from the toner replenishment unit 32 so that the toner mass M satisfies the above formula, the developer replenishment amount from the carrier replenishment unit 47 Adjustment of (carrier replenishment amount) and adjustment of the developer discharge amount from the developer discharge port 23j are performed. As a result, when the fluidity of the developer decreases and the dynamic torque increases, the dynamic torque can be reduced to a predetermined range while suppressing the increase in toner density.

  As described above, according to the second embodiment, since the stress applied to the developer G is optimized as in the first embodiment, the deterioration with time of the developer G can be surely reduced. Can do.

Hereinafter, examples and comparative examples for confirming the effects in the above-described embodiments will be described with reference to FIG.
In Examples 1-8 and Comparative Examples 1-2, as shown in FIG. 6, the level of the above formula ((W1-W0) / M) is changed, and the developer replenishment (agent replenishment) by the carrier replenishment unit 47 is performed. The running test was performed by varying the presence / absence, doctor gap (GD), and the amount of additive (additive amount), and the occurrence of toner scattering and background contamination was evaluated.

That is, Examples 1 to 8 and Comparative Examples 1 and 2 use the image forming apparatus according to Embodiment 1 or 2 under the conditions shown in FIG. This is an evaluation of the state of occurrence of toner scattering and background contamination after sheet output. Here, the developing roller 23a linear velocity (sleeve linear velocity) in the developing region was 185 mm / sec. The toner density during running was set to maintain the initial value. Further, the charging potential was set to -700V, the image portion potential was set to -100V, and the non-image portion potential was set to -650V.
Then, the toner contamination in the vicinity of the developing device 23 and the image quality of the output image were checked to evaluate the degree of toner scattering and background contamination. The evaluations of toner scattering and background stain were both visually, and were ranked in five levels based on the limit sample (the best one was “5”, and the degree decreased with decreasing numbers). ). “5-3” in FIG. 6 is a good level, and “2-1” is an unacceptable level.

Other detailed conditions for Example 1 will be described.
(Carrier manufacturing conditions)
Silicone resin solution 100 parts Carbon black 4 parts Toluene 100 parts The formulation thus prepared was dispersed with a homomixer for 30 minutes to prepare a coating layer forming solution. Then, a carrier was prepared by forming a coating layer on the surface of 1000 parts of ferrite having a volume average particle size of 50 μm using the above-described coating layer forming liquid by a fluid bed type coating apparatus.
(Production of toner)
Polyester resin 80 parts Styrene-methyl acrylate copolymer 20 parts Carnauba wax 5 parts Carbon black 8 parts Metal-containing monoazo dye 3 parts These mixtures are sufficiently stirred and mixed in a Henschel mixer, and then heated to 130-140 ° C in a roll mill. And melt for about 30 minutes. Further, the kneaded product obtained after cooling to room temperature was pulverized and classified with a jet mill to obtain a toner base having an average particle size of 6 μm.
Further, as a fluidity imparting agent, 100 parts of the above-mentioned toner base and 2.0 parts of silica “AEROSIL TT600” (manufactured by Nippon Aerosil Co., Ltd.) (having an average primary particle size of 0.04 μm) are added to a Henschel mixer. To prepare a toner.
(Development of developer)
8.0 parts of the toner prepared as described above and 92.0 parts of the carrier were mixed by a ball mill to obtain a two-component developer having a toner concentration of 8% by weight.
The value of the above formula ((W1-W0) / M) in Example 1 was 6.8 × 10 ⁻² .

Other detailed conditions for the second embodiment will be described.
(Creation of carrier)
1. Core material Mn ferrite particles (weight average diameter: 35 μm) 5000 parts Coating material Toluene 450 parts Silicone resin 450 parts Aminosilane 10 parts Carbon black 10 parts This coating material is dispersed with a stirrer for 10 minutes to prepare a coating solution, and then the coating solution and the above-mentioned core material are put into a coating apparatus. The coating solution was applied onto the core material. And the obtained coating material was baked at 250 degreeC for 2 hours, and the carrier was created.
(Production of toner)
1. In a reaction vessel equipped with an organic fine particle emulsion synthesis stirring bar and thermometer, 683 parts of water, 11 parts of a sodium salt of ethylene oxide methacrylate adduct sulfate, 80 parts of styrene, 83 parts of methacrylic acid, 110 parts of butyl acrylate, Charge 12 parts of butyl thioglycolate and 1 part of ammonium persulfate and stir to obtain a white emulsion. Further, the emulsion was heated to raise the system temperature to 75 ° C. and reacted for 5 hours. Further, 30 parts of a 1% ammonium persulfate aqueous solution was added and aged at 75 ° C. for 5 hours to obtain an aqueous vinyl resin dispersion (hereinafter referred to as “fine particle dispersion A”). Further, a part of the fine particle dispersion A was dried to isolate the resin component.
2. 990 parts of aqueous phase adjustment water, 83 parts of fine particle dispersion A, 37 parts of a 48.5% aqueous solution of sodium dodecyldiphenylether disulfonate and 90 parts of ethyl acetate were mixed and stirred to obtain a milky white liquid (this was "Aqueous phase A").
3. In a reaction vessel equipped with a synthetic cooling tube, a stirrer, and a nitrogen introduction tube of low molecular weight polyester, 229 parts of bisphenol A ethylene oxide 2-mole adduct, 529 parts of bisphenol A propylene oxide 3-mole adduct, 208 parts of terephthalic acid, adipine 46 parts of acid and 2 parts of dibutyltin oxide were added and reacted at 230 ° C. under normal pressure for 8 hours. Furthermore, after reducing the pressure to 10 to 15 mmHg and reacting for 5 hours, 44 parts of trimellitic anhydride was put in a reaction vessel and reacted for 2 hours at 180 ° C. under normal pressure to obtain a polyester (this is referred to as “low molecular weight”). Polyester A ”).
4). In a reaction vessel equipped with an intermediate polyester synthetic cooling pipe, a stirrer, and a nitrogen introduction pipe, 682 parts of bisphenol A ethylene oxide 2 mol adduct, 81 parts of bisphenol A propylene oxide 2 mol adduct, 283 parts of terephthalic acid, 22 parts of trimellitic anhydride and 2 parts of dibutyltin oxide were added and reacted at 230 ° C. under normal pressure for 8 hours. Furthermore, the pressure was reduced to 10 to 15 mmHg, and the mixture was reacted for 5 hours to obtain a polyester (hereinafter referred to as “intermediate polyester A”).
Next, 410 parts of the intermediate polyester A, 89 parts of isophorone diisocyanate, and 500 parts of ethyl acetate are placed in a reaction vessel equipped with a cooling pipe, a stirrer, and a nitrogen introduction pipe, and reacted at 100 ° C. for 5 hours. (This is referred to as “Prepolymer A”.)
5. Into a reaction vessel equipped with a ketimine synthesis stir bar and thermometer, 170 parts of isophoronediamine and 75 parts of methyl ethyl ketone were charged and reacted at 50 ° C. for 5 hours to obtain a ketimine compound (this is “ketimine compound A”). And).
6). A master batch of 1200 parts of synthetic water, 540 parts of carbon black, and 1200 parts of a polyester resin were added and mixed with a Henschel mixer. Then, after kneading the mixture, rolling and cooling and pulverization were performed to obtain a master batch (hereinafter referred to as “master batch A”).
7). Preparation of oil phase In a container equipped with a stir bar and thermometer, 378 parts of low molecular weight polyester, 110 parts of carnauba wax, and 947 parts of ethyl acetate were charged, heated to 80 ° C. with stirring, and kept at 80 ° C. for 5 hours. After that, it was cooled to 30 ° C. at 1 hour. Thereafter, 500 parts of masterbatch A and 500 parts of ethyl acetate were charged in a container and mixed for 1 hour to obtain a mixed solution (this is referred to as “raw material solution A”).
Then, 1324 parts of the raw material solution A was transferred to a container, and carbon black and wax were dispersed using a bead mill. Next, 1324 parts of a 65% ethyl acetate solution of low molecular weight polyester A was added, and a dispersion was obtained with a bead mill (this is referred to as “Pigment / Wax Dispersion A”).
8). Emulsification, solvent removal pigment / wax dispersion A 749 parts, prepolymer A 115 parts, ketimine compound A 2.9 parts were mixed in a container, and then water phase A 1200 parts were added to the container and mixed to obtain an emulsion (this) ("Emulsified slurry A").
And the emulsified slurry A was thrown into the container which set the stirrer and the thermometer, and after carrying out solvent removal at 30 degreeC for 8 hours, aging was performed at 45 degreeC for 4 hours, and the dispersion | distribution slurry A was obtained.
9. After washing, drying, and filtering fluorinated dispersion slurry A 100 parts under reduced pressure,
(1) 100 parts of ion-exchanged water was added to the filter cake, followed by filtration after mixing.
(2) To the filter cake of (1), 100 parts of a 10% aqueous sodium hydroxide solution was added and mixed, and then filtered under reduced pressure.
(3) 100 parts of 10% hydrochloric acid was added to the filter cake of (2) and mixed, followed by filtration.
(4) 300 parts of ion-exchanged water was added to the filter cake of (3), mixed and then filtered twice to obtain a cake (hereinafter referred to as “filter cake A”).
Thereafter, 15 parts of filter cake A was added to 90 parts of water, and a fluorine compound was adhered to the surface of the toner particles, followed by drying at 45 ° C. for 48 hours. Thereafter, the resultant was sieved with a mesh having an opening of 75 μm to obtain toner base particles (hereinafter referred to as “toner base particles A”).
10. To 100 parts of the toner base particles A obtained at the external additive treatment destination, 2.0 parts of hydrophobic silica as an external additive and 1.0 part of hydrophobized titanium oxide are mixed and processed with a Henschel mixer. A toner was obtained.
(Development of developer)
7.0 parts of the toner prepared as described above and 93.0 parts of the carrier were mixed by a ball mill to obtain a two-component developer having a toner concentration of 7% by weight.
The value of the above formula ((W1-W0) / M) in Example 2 was 7.5 × 10 ⁻² .

Other detailed conditions for the third embodiment will be described.
The conditions were the same as in Example 2 except that the amount of developer accommodated in the developing device 23 was 200 g.
The value of the above formula ((W1-W0) / M) in Example 3 was 8.1 × 10 ⁻² .

Other detailed conditions for Example 4 will be described.
The conditions were the same as in Example 2 except that the amount of the fluidity-imparting agent used at the time of toner preparation was 1.2 parts.
The value of the above formula ((W1-W0) / M) in Example 4 was 7.3 × 10 ⁻² .

Other detailed conditions for the fifth embodiment will be described.
The conditions were the same as in Example 2 except that the amount of developer contained in the developing device 23 was 300 g and the toner concentration was 9% by weight.
The value of the above formula ((W1-W0) / M) in Example 5 was 4.1 × 10 ⁻² .

Other detailed conditions for the sixth embodiment will be described.
The conditions were the same as in Example 2 except that the amount of developer contained in the developing device 23 was 200 g and the toner concentration was 3% by weight.
The value of the above formula ((W1-W0) / M) in Example 6 was 14.8 × 10 ⁻² .

Other detailed conditions for Example 7 will be described.
The conditions were the same as in Example 1 except that the developer replenishment by the carrier replenishment unit 47 and the developer discharge by the developer discharge port 23j were performed (the developing device of the second embodiment).
The value of the above formula ((W1-W0) / M) in Example 7 was 7.3 × 10 ⁻² .

Other detailed conditions for the eighth embodiment will be described.
The conditions were the same as in Example 7 except that the amount of developer accommodated in the developing device 23 was 200 g.
The value of the above formula ((W1-W0) / M) in Example 8 was 8.1 × 10 ⁻² .

As shown in the results of FIG. 6, in Examples 1 to 6, toner scattering and background stains were good at levels of 3 to 4 even after 50,000 sheets of images were formed.
Further, when the developer was replaced as in Examples 7 to 8, the toner scattering and background stains were very good at a level of 4 to 5 even after 50,000 images were formed. It was.

Other detailed conditions for Comparative Example 1 with respect to Examples 1 to 8 will be described.
In Comparative Example 1, the conditions were the same as those in Example 1 except that the toner concentration was adjusted to 11% by weight when the toner was produced. The value of ((W1-W0) / M) in Comparative Example 1 was 3.9 × 10 ⁻² (outside the range of the above formula).
As shown in the results of FIG. 6, in Comparative Example 1, unacceptable toner scattering occurred after 20,000 sheets of images were formed. Furthermore, unacceptable background stains occurred after 50,000 images were formed.

Other detailed conditions for Comparative Example 2 will be described.
Comparative Example 2 was the same as Example 1 except that the doctor gap was set to 0.3 mm and the amount of developer accommodated in the developing device 23 was 200 g and the toner concentration was 5% by weight. Conditioned. The value of ((W1-W0) / M) in Comparative Example 1 was 15.1 × 10 ⁻² (outside the range of the above formula).
As shown in the results of FIG. 6, in Comparative Example 2, unacceptable toner scattering occurred after 20,000 images were formed. Furthermore, unacceptable background stains occurred after 50,000 images were formed.
As described above, the effects in the above-described embodiments were confirmed.

  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 sectional drawing which looked at the developing device to the longitudinal direction. It is sectional drawing which shows the developing device in Embodiment 2 of this invention. 6 is a flowchart showing developer replacement control performed by the developing device of FIG. 4. It is a graph which shows the conditions and result of the Example and comparative example which were performed in order to confirm an effect.

Explanation of symbols

1 image forming apparatus body (apparatus body),
20, 20Y, 20M, 20C, 20BK Process cartridge,
21 photosensitive drum (image carrier), 22 charging unit,
23, 23Y, 23M, 23C, 23BK Developing device (developing unit),
23a Development roller (developer carrier),
23b 1st conveyance screw (1st conveyance member),
23c 2nd conveyance screw (2nd conveyance member),
23d doctor blade (developer regulating member),
23e partition member, 23f toner supply port,
23g first developer accommodating portion, 23h second developer accommodating portion,
23j Developer outlet (discharge means),
32, 32Y, 32M, 32C, 32BK toner supply unit,
43 drive source, 44 torque detector, 45 controller,
47 Carrier replenishment section (replenishment means),
G Two-component developer (developer), C carrier, T toner.

Claims (9)

A developing device that contains a developer composed of a toner and a carrier and that develops a latent image formed on an image carrier,
The dynamic torque of the apparatus when the developer is accommodated is W1 (kgf · cm), and the dynamic torque of the apparatus when the developer is not accommodated is W0 (kgf · cm). When the mass of the toner in the developer is M (g),
4 × 10 ⁻² <(W1-W0) / M <15 × 10 ⁻²
A developing device characterized in that the following relationship is established. A developer carrying body facing the image carrying body and carrying the developer and connected to a driving source;
A developer regulating member facing the developer carrying body and regulating the amount of the developer carried on the developer carrying body;
A first conveying member facing the developer carrying member and carrying the developer along a longitudinal direction of the developer carrying member;
Opposite the first conveying member via a partition member, convey the developer in a direction opposite to the conveying direction of the first conveying member, and form a circulation path for the developer together with the first conveying member A second conveying member that
The first transport member and the second transport member are driven by the developer carrier driven by the drive source,
The developing device according to claim 1, wherein the dynamic torque of the device is detected by the driving source. The toner contains toner base particles composed of a resin and a colorant and an additive,
3. The developing device according to claim 1, wherein the additive is formed such that the additive amount is 0.5 to 5 wt% with respect to the toner base particles. The developing device according to claim 3, wherein the additive contains a plurality of inorganic fine particles having different particle diameters. The developing device according to claim 1, wherein the toner contains abrasive fine particles. Discharging means for discharging a part or all of the developer contained in the apparatus;
The developing device according to claim 1, further comprising a replenishing unit that newly replenishes the developer or carrier in the device. The discharging means or / and the replenishing means are:
4 × 10 ⁻² <(W1-W0) / M <15 × 10 ⁻²
The developing device according to claim 6, wherein the developing device is controlled so as to satisfy the following relationship. A process cartridge that is detachably installed on the main body of the image forming apparatus,
8. A process cartridge, wherein the developing device according to claim 1 and the image carrier are integrated. An image forming apparatus comprising the developing device according to claim 1 and the image carrier.

Images