JP2009192962A - Developing device, process cartridge, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide: a developing device in which even in the setting of two conveying members, one above the other, which convey developer in a lengthwise direction and form a circulation path, developer separated from a developer carrier in the conveying path defined by the second conveying member is sufficiently mixed and stirred; a process cartridge; and an image forming apparatus. <P>SOLUTION: The developing device includes: the first conveying member 13b1 that supplies developer G to the developer carrier 13a while conveying developer G in the lengthwise direction; and the second conveying member 13b2 that is disposed below the first conveying member 13b2 and conveys developer G separated from the developer carrier 13a, in the lengthwise direction. The conveying path defined by the second conveying member 13b2 has a scattering member 13d by which developer separated from the developer carrier 13a is scattered prior to being mixed with developer in the conveying path. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus using an electrophotographic system such as a copying machine, a printer, a facsimile, or a multifunction machine thereof, and a developing device and a process cartridge installed therein, and in particular, a developer in a longitudinal direction. The present invention relates to a developing device, a process cartridge, and an image forming apparatus in which at least two transport members among a plurality of transport members that transport and form a circulation path are installed in the vertical direction.

  2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine or a printer, a developing device that contains a two-component developer composed of a toner and a carrier (including a case where an additive or the like is added), and the developer is long. A technique is known in which at least two transport members among a plurality of transport members that transport in the direction to form a circulation path are installed in the vertical direction (see, for example, Patent Document 1 and Patent Document 2).

  In a developing device using a two-component developer, toner is appropriately replenished into the developing device from a toner replenishing port provided in a part of the developing device according to toner consumption in the developing device. The replenished toner is agitated and mixed together with the developer in the developing device by a conveying member (agitating and conveying member) such as a conveying screw. Part of the stirred and mixed developer is supplied to a developing roller (developer carrier). After the developer carried on the developing roller is regulated to an appropriate amount by a doctor blade (developer regulating member), the toner in the two-component developer is a latent image on the photosensitive drum at a position facing the photosensitive drum. Adhere to.

  In the developing device in Patent Document 1 or the like, a first transport member (first agitation transport member) and a second transport member (second agitation transport member) are installed in the vertical direction, and development is performed by these two transport members. This forms a circulation route for the agent. The first conveying member installed above supplies the developer to the developing roller while conveying the developer in the longitudinal direction. The second conveying member installed below conveys the developer separated from the developer roller in the longitudinal direction (the direction opposite to the conveying direction by the first conveying member). The downstream side of the conveyance path (first conveyance path) by the first conveyance member and the upstream side of the conveyance path (second conveyance path) by the second conveyance member communicate with each other via the first relay portion (opening). Then, the developer that has reached the downstream side of the first conveyance path falls by its own weight on the first relay unit and reaches the upstream side of the second conveyance path. Here, a toner supply port is provided on the upstream side of the second conveyance path, and new toner is appropriately supplied. In addition, the upstream side of the first transport path and the downstream side of the second transport path communicate with each other via a second relay unit (opening). Then, the developer that has reached the downstream side of the second transport path (the developer that has separated from the developing roller, the developer that has dropped from the first relay unit, the new toner replenished from the upstream side of the second transport path, and Is mixed and pushed up at that position and moved to the upstream side of the first transport path via the second relay section.

  As described above, the developing device in which the plurality of conveying members are arranged in the vertical direction is more developed than the developing device in which the plurality of conveying members are arranged in the horizontal direction (see, for example, FIG. 4 of Patent Document 2). The device can be made compact in the horizontal direction. Therefore, a tandem type color image forming apparatus in which a plurality of developing devices are arranged in parallel in the horizontal direction is often used. In addition, a plurality of transport members are arranged in the vertical direction, and a developer supply path (first transport path) to the developer carrier and a developer recovery path (second transport path) that separates from the developer carrier. ) Is separated from a developing device in which a plurality of conveying members are arranged in a horizontal direction (for example, see FIG. 4 of Patent Document 2). The density deviation can be reduced.

  On the other hand, Patent Document 2 discloses a developing device in which a first conveying member and a second conveying member are arranged in the vertical direction, and a developer near the end of a second conveying path (lower stirring chamber). In order to prevent the accumulation of the toner, a technique for installing a third auger between the developer carrier and the second transport member is disclosed. The third auger is configured to transport the developer in a direction opposite to the direction in which the second transport member transports the developer.

JP 2003-263012 A Japanese Patent No. 3127594

The technology disclosed in Patent Document 1 and the like described above includes a developer that is dropped from the downstream side of the first conveyance path via the first relay unit and supplied to the upstream side of the second conveyance path in the second conveyance path, There is a problem that the developer separated from the developing roller is not sufficiently stirred and mixed with the new toner replenished from the upstream side of the two conveying paths.
Such inconvenience occurs because the developer separated from the developing roller falls intensively on the same part of the second transport path as seen in the cross section perpendicular to the rotation axis direction (transport direction) of the second transport member. It is because it is easy to do.

In this way, the developer that is not sufficiently stirred and mixed and has low dispersibility of new toner (replenishment toner) reaches the downstream side of the second transport path and passes through the second relay portion to the first transport path. If the toner is further supplied to the developing roller, image density unevenness occurs on the output image. Such a problem becomes more prominent when the developer starts to deteriorate over time.
Furthermore, the circulation path is formed only by the second conveyance path and the first conveyance path as compared with the developing device in which another conveyance path is provided between the second conveyance path and the first conveyance path to form the circulation path. Since the developing device cannot sufficiently take the stirring and mixing time of the developer until it is supplied to the first transport path, the above-mentioned problems are not particularly negligible.

  On the other hand, in the developing device described in Patent Document 2 and the like described above, the developer is transported between the developer carrier and the second transport member in a direction opposite to the direction in which the second transport member transports the developer. The purpose of the third auger is to prevent the developer from being deposited near the end of the second transport path, and does not solve the above-described problems.

  The present invention has been made to solve the above-described problems, and at least two of the plurality of transport members that transport the developer in the longitudinal direction to form a circulation path are installed in the vertical direction. Even in such a case, it is an object of the present invention to provide a developing device, a process cartridge, and an image forming apparatus in which the developer separated from the developer carrying member is sufficiently stirred and mixed in the transport path by the second transport member.

  According to a first aspect of the present invention, there is provided a developing device for storing a developer having a carrier and a toner and developing a latent image formed on an image carrier, the image carrier. A plurality of conveying members that are opposed to the body and that carry a developer, and a plurality of conveying members that convey the developer contained in the apparatus in the longitudinal direction to form a circulation path. The member faces the developer carrying member and supplies the developer to the developer carrying member while conveying the developer in the longitudinal direction. The member is below the first carrying member and is located below the developing member. A second transport member that is disposed at a position facing the developer carrier and transports the developer detached from the developer carrier in the longitudinal direction, and a transport path by the second transport member is: Removed from the developer carrier. The developer is obtained by including a diffusing member which diffuses prior to mixing the developer in the conveying path.

  A developing device according to a second aspect of the present invention is the developing device according to the first aspect, wherein the diffusing member is disposed between the developer carrying member and the second transport member and a plurality of the diffusing members are disposed. A plate-like member having a hole or / and a slit is formed.

According to a third aspect of the present invention, there is provided the developing device according to the second aspect, wherein the area of the hole or / and slit of the plate member is M, and the volume average particle diameter of the carrier is N1. Assuming that the volume average particle diameter of the toner is N2,
M ≧ π · [(N1 + N2 × 2) / 2] ²
This relationship is established.

  According to a fourth aspect of the present invention, in the developing device according to the second or third aspect, the plate-like member has a constant area of each of the plurality of holes or / and slits. It is formed as follows.

  The developing device according to a fifth aspect of the present invention is the developing device according to any one of the second to fourth aspects, wherein the plate-like member has a side closer to the developer carrier on the developer carrier. It is arranged to be inclined so as to be lower than the far side.

  The developing device according to a sixth aspect of the present invention is the developing device according to any one of the second to fifth aspects, wherein the plate-like member has a thickness closer to the developer carrier. It is formed so as to be thicker than the thickness on the side farther from the developer carrier.

  A developing device according to a seventh aspect of the present invention is the developing device according to any one of the second to sixth aspects, wherein the plate-like member is located on the upstream side of the conveying path by the second conveying member. The two conveying members are disposed so as to be lower than the downstream side of the conveying path.

  The developing device according to an eighth aspect of the present invention is the developing device according to any one of the second to seventh aspects, wherein the plate-like member has a thickness on the upstream side of the conveyance path by the second conveyance member. Is formed to be thicker than the thickness on the downstream side of the transport path by the second transport member.

  A developing device according to a ninth aspect of the present invention is the developing device according to any one of the second to eighth aspects, wherein the plate-like member is formed between the developer carrier and the second conveying member. A plurality of them are installed between them.

  A developing device according to a tenth aspect of the present invention is the developing device according to any one of the first to ninth aspects, wherein a part or all of the diffusion member is formed of a conductive material. It is.

  The developing device according to an eleventh aspect of the present invention is the developing device according to the tenth aspect, wherein the diffusion member has a portion formed of the conductive material grounded.

  A developing device according to a twelfth aspect of the present invention is the developing device according to any one of the first to eleventh aspects, wherein the carrier has a volume average particle diameter of 20 to 60 μm. It is a thing.

A developing device according to a thirteenth aspect of the present invention is the developing device according to any one of the first to twelfth aspects, wherein the toner has an average primary particle size of 5 to 50 nm with respect to the toner base. The inorganic fine particles are coated so that the coverage A is 40 to 200,
The coverage A is
A = (inorganic fine particle input amount [wt%] / 100) × inorganic fine particle projected area Sa [m ² / g] / ((1−inorganic fine particle input amount [wt%] / 100) × toner surface area Sc [m ² / g]) × 100
Is obtained by the following formula,
In the above formula, the toner surface area Sc and the inorganic fine particle projected area Sa are:
Sc = 3 / (toner volume average particle diameter [m] × toner specific gravity [g / m ³ ])
Sa = 3 / (4 × average particle size of inorganic fine particles [m] × specific gravity of inorganic fine particles [g / m ³ ])
Is obtained by the following formula.

A developing device according to a fourteenth aspect of the present invention is the developing device according to any one of the first to thirteenth aspects, wherein the developer has the coverage B of the toner on the surface of the carrier. It is coated so as to be 40-90,
The coverage B is
B = (toner input amount [wt%] / 100) × toner projected area Sb [m ² / g] / ((1−toner input amount [wt%] / 100) × carrier surface area Sd [m ² / g]) × 100
Is obtained by the following formula,
In the above formula, the carrier surface area Sd and the toner projected area Sb are:
Sd = 3 / (carrier volume average particle size [m] × carrier specific gravity [g / m ³ ])
Sb = 3 / (4 × toner volume average particle diameter [m] × toner specific gravity [g / m ³ ])
Is obtained by the following formula.

  A developing device according to a fifteenth aspect of the present invention is the developing device according to any one of the first to fourteenth aspects, wherein the second conveying member conveys from the downstream side of the conveying path by the first conveying member. A first relay unit that drops the developer toward the upstream side of the path is provided, and the amount of developer dropped in the first relay unit is configured to be 5 to 10 g / second.

A developing device according to a sixteenth aspect of the invention is the developing device according to any one of the first to fifteenth aspects, wherein the developing device is supplied by the first conveying member and carried on the developer carrying member. A developer regulating member for regulating the amount of the developer, and the amount of the developer carried on the developer carrying member after passing through the position of the developer regulating member is 30 to 70 mg / cm ^2; It is composed.

  A developing device according to a seventeenth aspect of the present invention is the developing device according to any one of the first to sixteenth aspects, wherein the developer exceeding the wall portion of the conveying path by the first conveying member is the developing device. It is configured to fall on the developer carrier and to be carried on the developer carrier.

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

  An image forming apparatus according to a nineteenth aspect of the present invention includes the developing device according to any one of the first to seventeenth 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 (developing device) that develops a latent image formed on the image carrier, and a cleaning on the image carrier. At least one of the cleaning units and the image carrier are defined as a unit that is integrated and detachably installed on the image forming apparatus main body.

  In the present invention, even when at least two conveying members among the plurality of conveying members that convey the developer in the longitudinal direction to form a circulation path are installed in the vertical direction, the development separated from the developer carrier Since the diffusion member that diffuses before the developer is mixed with the developer in the conveyance path by the second conveyance member is installed, the developer separated from the developer carrier in the conveyance path by the second conveyance member is sufficiently A developing device, a process cartridge, and an image forming apparatus that are stirred and mixed 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.
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, reference numeral 1 denotes an apparatus main body of a tandem color copier as an image forming apparatus, 2 a writing unit that emits laser light based on input image information, and 3 an original conveying unit that conveys an original D to an original reading unit 4. 4 is a document reading unit that reads image information of the document D, 7 is a paper feeding unit that accommodates a recording medium P such as transfer paper, 9 is a registration roller that adjusts the conveyance timing of the recording medium P, and 11Y, 11M, and 11C. , 11BK is a photosensitive drum as an image carrier on which toner images of each color (yellow, magenta, cyan, black) are formed, 12 is a charging unit that charges the photosensitive drums 11Y, 11M, 11C, and 11BK, 13 Is a developing device for developing an electrostatic latent image formed on each of the photosensitive drums 11Y, 11M, 11C, and 11BK, and 14 is formed on each of the photosensitive drums 11Y, 11M, 11C, and 11BK. A transfer bias roller (primary transfer bias roller) for transferring the toner image superimposed on the recording medium P, and a cleaning unit 15 for collecting untransferred toner on the photosensitive drums 11Y, 11M, 11C, and 11BK. Show.

Reference numeral 16 denotes an intermediate transfer belt cleaning unit that cleans the intermediate transfer belt 17, 17 an intermediate transfer belt on which toner images of a plurality of colors are transferred and superimposed, and 18 a color toner image on the intermediate transfer belt 17 on the recording medium P. A secondary transfer bias roller 20 for transferring the toner image onto the recording medium P indicates a fixing device for fixing an unfixed image on the recording medium P.
Although not shown, each color toner (toner particles) that supplies toner (toner particles) of each color (yellow, cyan, magenta, black) to the developing device 13 is disposed above each of the photosensitive drums 11Y, 11C, 11M, and 11BK. Each container is installed.

Hereinafter, an operation during normal color image formation in the image forming apparatus will be described. Note that FIG. 2 can also be referred to for the image forming process performed on the photosensitive drums 11Y, 11M, 11C, and 11BK.
First, the document D is transported from the document table in the direction of the arrow in the drawing by the transport rollers of the document transport unit 3 and placed on the contact glass 5 of the document reading unit 4. Then, the document reading unit 4 optically reads the image information of the document D placed on the contact glass 5.

  Specifically, the document reading unit 4 scans the image of the document D on the contact glass 5 while irradiating light emitted from an 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, color conversion processing, color correction processing, spatial frequency correction processing, and the like are performed by the image processing unit based on the RGB color separation image signals to obtain yellow, magenta, cyan, and black color image information.

  Then, the image information of each color of yellow, magenta, cyan, and black is transmitted to the writing unit 2. The writing unit 2 emits laser light L (see FIG. 2) based on the image information of each color toward the corresponding photosensitive drums 11Y, 11M, 11C, and 11BK.

On the other hand, the four photosensitive drums 11Y, 11M, 11C, and 11BK are rotated clockwise in FIG. First, the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK are uniformly charged at a portion facing the charging unit 12 (this is a charging process). Thus, a charged potential is formed on the photosensitive drums 11Y, 11M, 11C, and 11BK. Thereafter, the charged surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK reach the irradiation positions of the respective laser beams.
In the writing unit 2, laser light corresponding to the image signal is emitted from the four light sources corresponding to each color. Each laser beam passes through a separate optical path for each of the yellow, magenta, cyan, and black color components (this is an exposure process).

  Laser light corresponding to the yellow component is irradiated on the surface of the first photosensitive drum 11Y from the left side of the drawing. At this time, the yellow component laser light is scanned in the rotational axis direction (main scanning direction) of the photosensitive drum 11Y by a polygon mirror that rotates at high speed. Thus, an electrostatic latent image corresponding to the yellow component is formed on the photosensitive drum 11Y after being charged by the charging unit 12.

  Similarly, the laser beam corresponding to the magenta component is irradiated to the surface of the second photosensitive drum 11M from the left side of the paper, and an electrostatic latent image corresponding to the magenta component is formed. The cyan component laser light is applied to the surface of the third photosensitive drum 11C from the left side of the paper, and an electrostatic latent image of the cyan component is formed. The black component laser beam is applied to the surface of the fourth photosensitive drum 11BK from the left side of the paper, and an electrostatic latent image of the black component is formed.

Thereafter, the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK on which the electrostatic latent images of the respective colors are formed reach positions facing the developing device 13, respectively. Then, the respective color toners are supplied from the developing devices 13 onto the photosensitive drums 11Y, 11M, 11C, and 11BK, and the latent images on the photosensitive drums 11Y, 11M, 11C, and 11BK are developed (development process). .)
Thereafter, the surfaces of the photoconductive drums 11Y, 11M, 11C, and 11BK after the development process reach the facing portions of the intermediate transfer belt 17, respectively. Here, a transfer bias roller 14 is installed at each facing portion so as to contact the inner peripheral surface of the intermediate transfer belt 17. Then, the toner images of the respective colors formed on the photosensitive drums 11Y, 11M, 11C, and 11BK are sequentially superimposed and transferred onto the intermediate transfer belt 17 at the position of the transfer bias roller 14 (in the primary transfer process). is there.).

Then, the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK after the transfer process reach positions facing the cleaning unit 15, respectively. Then, the untransferred toner remaining on the photosensitive drums 11Y, 11M, 11C, and 11BK is collected by the cleaning unit 15 (this is a cleaning process).
Thereafter, the surfaces of the photoconductive drums 11Y, 11M, 11C, and 11BK pass through a neutralization unit (not shown), and a series of image forming processes on the photoconductive drums 11Y, 11M, 11C, and 11BK is completed.

On the other hand, the intermediate transfer belt 17 on which the toners of the respective colors on the photosensitive drums 11Y, 11M, 11C, and 11BK are transferred (carrying) are run in the clockwise direction in the drawing and are connected to the secondary transfer bias roller 18. Reach the opposite position. Then, a color toner image carried on the intermediate transfer belt 17 is transferred onto the recording medium P at a position facing the secondary transfer bias roller 18 (secondary transfer step).
Thereafter, the surface of the intermediate transfer belt 17 reaches the position of the intermediate transfer belt cleaning unit 16. Then, the untransferred toner adhered on the intermediate transfer belt 17 is collected by the intermediate transfer belt cleaning unit 16, and a series of transfer processes in the intermediate transfer belt 17 is completed.

Here, the recording medium P transported between the intermediate transfer belt 17 and the secondary transfer bias roller 18 (secondary transfer nip) is transported from the paper supply unit 7 via the registration roller 9 and the like. It is a thing.
Specifically, the recording medium P fed by the paper feeding roller 8 from the paper feeding unit 7 that stores the recording medium P is guided to the registration roller 9 after passing through the conveyance guide. The recording medium P that has reached the registration roller 9 is conveyed toward the secondary transfer nip at the same timing.

Then, the recording medium P on which the full-color image is transferred is guided to the fixing device 20 by the transport belt. In the fixing device 20, the color image is fixed on the recording medium P at the nip between the fixing belt and the pressure roller.
Then, the recording medium P after the fixing step is discharged as an output image outside the apparatus main body 1 by a paper discharge roller, and a series of image forming processes is completed.

Next, the image forming unit in the image forming apparatus will be described in detail with reference to FIGS.
FIG. 2 is a configuration diagram illustrating the image forming unit and the toner container 28. 3A is a schematic cross-sectional view (horizontal cross-sectional view) of the upper portion of the developing device 13 (the position of the first transfer screw 13b1 as the first transfer member) in the longitudinal direction. (B) is a schematic sectional view of the lower part of the developing device 13 (the position of the second conveying screw 13b2 as the second conveying member) as viewed in the longitudinal direction. FIG. 4 is a schematic cross-sectional view (vertical cross-sectional view) of the circulation path of the developing device 13 as viewed in the longitudinal direction. FIG. 5 is a front view showing the diffusing member 13 d installed in the developing device 13.
Since each image forming unit has substantially the same structure and each toner container has almost the same structure, the image forming unit and the toner container are denoted by alphabets (Y, C, M, BK) is shown in the figure.

As shown in FIG. 2, the image forming unit includes a photosensitive drum 11 as an image carrier, a charging unit 12, a developing device 13 (developing unit), a cleaning unit 15, and the like.
The photosensitive drum 11 as an image carrier is a negatively charged organic photosensitive member, and is rotated counterclockwise by a rotation driving mechanism (not shown).

The charging unit 12 is a charging roller having elasticity in which a foamed urethane layer having a medium resistance in which a urethane resin, carbon black as conductive particles, a sulfurizing agent, a foaming agent, and the like are formed in a roller shape on a core metal. The material of the middle resistance layer of the charging unit 12 is urethane, ethylene-propylene-diene polyethylene (EPDM), butadiene acrylonitrile rubber (NBR), silicone rubber, isoprene rubber, etc. It is also possible to use a rubber material in which a conductive material such as the above is dispersed or a foamed material of these materials.
The cleaning unit 15 is provided with a cleaning brush (or a cleaning blade) that is in sliding contact with the photosensitive drum 11, and mechanically removes and collects untransferred toner on the photosensitive drum 11.

  The developing device 13 is disposed such that a developing roller 13a as a developer carrying member is close to the photosensitive drum 11, and a developing region (developing) where the photosensitive drum 11 and the magnetic brush are in contact with each other. Nip) is formed. A developer G (two-component developer) composed of toner T and carrier C is accommodated in the developing device 13. The developing device 13 develops the electrostatic latent image formed on the photosensitive drum 11 (forms a toner image). The configuration and operation of the developing device 13 will be described in detail later.

Referring to FIG. 2, toner container 28 contains toner T to be supplied into developing device 13 therein. Specifically, based on information on toner density (which is the ratio of toner in the developer G) detected by a magnetic sensor (not shown) installed in the developing device 13, the shutter driving unit performs shutter. The mechanism 80 is opened and closed to appropriately supply the developer G from the toner container 28 into the developing device 13.
The supply of the toner T is not limited to the toner density information, but may be performed based on the image density information detected from the reflectance of the toner image formed on the photosensitive belt or the intermediate transfer belt. Good. Further, the implementation of the supply of the toner T may be determined by combining these different pieces of information.

  The supply pipe 29 is for reliably guiding the toner T supplied from the toner container 28 into the developing device 13. That is, the toner T discharged from the toner container 28 is supplied into the developing device 13 from the supply port 13e (toner supply port) via the supply pipe 29.

Hereinafter, the developing device 13 in the image forming apparatus will be described in detail.
2 to 5, the developing device 13 includes a developing roller 13 a as a developer carrying member, conveying screws 13 b 1 and 13 b 2 (auger screws) as conveying members, a doctor blade 13 c as a developer regulating member, diffusion It is comprised by the member 13d.
The developing roller 13a as the developer carrying member is configured such that a sleeve formed of a nonmagnetic material such as aluminum, brass, stainless steel, conductive resin or the like in a cylindrical shape is rotated clockwise by a rotation driving mechanism (not shown). It is configured. Referring to FIG. 3, a magnet 13 a 1 that forms a magnetic field is fixed in the sleeve 13 a 2 of the developing roller 13 a so as to cause the developer G to rise on the peripheral surface of the sleeve. The carrier C in the developer G rises in a chain shape on the sleeve 13a2 so as to follow the normal line of magnetic force emitted from the magnet 13a1. The charged toner T is attached to the carrier C that is spiked in a chain shape to form a magnetic brush. The magnetic brush is transferred in the same direction (clockwise) as the sleeve 13a2 by the rotation of the sleeve 13a2. Then, the toner T in the developer G carried on the developing roller 13 a is exposed to the photosensitive drum 11 by an electric field (developing electric field) formed between the developing roller 13 a and the photosensitive drum 11 in the developing region N. It will fly toward the electrostatic latent image above.
The doctor blade 13c as a developer regulating member is installed on the upstream side of the developing area, and regulates the developer G on the developing roller 13a to an appropriate amount.

The two conveying screws 13b1 and 13b2 (conveying members) stir and mix the developer G accommodated in the developing device 13 while circulating in the longitudinal direction (the direction perpendicular to the paper surface of FIG. 2).
The first transport screw 13b1 as the first transport member is disposed at a position facing the developing roller 13a, and transports the developer G horizontally in the longitudinal direction (rotation axis direction) (see FIG. 3A). In addition, the developer G is supplied onto the developing roller 13a (in the direction of the white arrow in FIG. 3A).

The second conveyance screw 13b2 as the second conveyance member is disposed below the first conveyance screw 13b1 and at a position facing the developing roller 13a. Then, the developer G separated from the developing roller 13a (the developer G forcibly separated from the developing roller 13a by the agent separation pole after the developing step, and separated in the direction of the white arrow in FIG. 3B). Is horizontally transported in the longitudinal direction (the transport is in the left direction indicated by the dashed arrow in FIG. 3B).
Then, the second transport screw 13b2 has a second developer G circulated from the downstream side of the transport path by the first transport screw 13b1 via the first relay portion 13f to the upstream side of the transport path by the first transport member 13b1. It conveys via the relay part 13g (it is conveyance shown by the dashed-dotted arrow of FIG. 3 (B)).
The two conveying screws 13b1 and 13b2 are arranged so that the rotation shaft is substantially horizontal, like the developing roller 13a and the photosensitive drum 11. Further, the two conveying screws 13b1 and 13b2 are formed by spirally winding a screw portion around a shaft portion.

The conveyance path (first conveyance path) by the first conveyance screw 13b1 and the conveyance path (second conveyance path) by the second conveyance screw 13b2 are isolated from each other by a wall portion.
3 and 4, the downstream side of the transport path (second transport path) by the second transport screw 13b2 and the upstream side of the transport path (first transport path) by the first transport screw 13b1 are 2 It communicates via the relay part 13g. Then, the developer G that has risen and stayed in the vicinity of the second relay portion 13g in the transport path by the second transport screw 13b2 is transported to the upstream side of the transport path by the first transport screw 13b1 via the second relay portion 13g ( Supply).
3 and 4, the downstream side of the conveyance path by the first conveyance screw 13b1 and the upstream side of the conveyance path by the second conveyance screw 13b2 communicate with each other via the first relay unit 13f. Yes. Then, the developer G that has not been supplied onto the developing roller 13a in the first conveying path by the first conveying screw 13b1 falls by its own weight at the first relay portion 13f and reaches the upstream side of the second conveying path. become.

  With such a configuration, a circulation path for circulating the developer G in the longitudinal direction in the developing device 13 is formed by the two conveying screws 13b1 and 13b2. That is, when the developing device 13 is operated, the developer G accommodated in the device flows in the direction of the broken line arrow in FIGS. 3 and 4. Thus, the developer G supply path (the first transport path by the first transport screw 13a1) to the developing roller 13a and the developer G recovery path (second transport screw) separated from the developing roller 13a. 13a2), the density deviation of the toner image formed on the photosensitive drum 11 can be reduced.

Although illustration is omitted, a magnetic sensor for detecting the toner concentration of the developer circulating in the apparatus is installed in the conveyance path by the second conveyance screw 13b2. Then, based on the toner density information detected by the magnetic sensor, new toner T is supplied from the toner container 28 into the developing device 13 through the supply port 13e.
3 and 4, the replenishment port 13e (toner replenishment port) is located upstream of the upstream side of the transport path by the second transport screw 13b2 and away from the development region (on the development roller 13a). Outside the longitudinal range). In the first embodiment, the replenishment port 13e is disposed in the transport path by the second transport screw 13a2, but the position of the replenishment port 13e is not limited to this, for example, upstream of the first transport path. It can also be arranged above the side.

Hereinafter, a characteristic configuration and operation of the developing device 13 according to the first embodiment will be described.
2 to 4, in the second transport path (the transport path by the second transport screw 13 b 2), the developer separated from the developing roller 13 a is transferred to the developer ( The developer dropped from the downstream side of the first transport path via the first relay portion 13f and supplied to the upstream side of the second transport path, and the new article replenished from the supply port 13e on the upstream side of the second transport path. A developer 13d mixed with toner) is installed before being mixed with the toner.
Specifically, the diffusing member 13d is disposed between the developing roller 13a and the second conveying screw 13b2 and above the developer surface in the second conveying screw. Referring to FIG. 5, the diffusion member 13d is a plate-like member in which a plurality of holes are formed in a mesh shape by punching. With such a configuration, the developer separated from the developing roller 13a is widely dispersed and mixed with the developer in the second transport path. That is, the developer separated from the developing roller 13a collides with the developer in the second conveyance path after colliding with the diffusion member 13d and dispersed from the plurality of holes and falling into the second conveyance path. become. Then, the developer in which the developer separated from the developing roller 13a in the second transport path is sufficiently stirred and mixed moves to the upstream side of the first transport path via the second relay portion 13g, and further the first The toner is supplied onto the developing roller 13a through the conveyance path. As a result, it is possible to suppress a problem in which unevenness in image density is caused on the output image due to poor stirring and mixing of the developer.

Here, in the first embodiment, when the area of the hole of the diffusion member 13d (plate member) is M, the volume average particle diameter of the carrier C is N1, and the volume average particle diameter of the toner T is N2. ,
M ≧ π · [(N1 + N2 × 2) / 2] ²
Is set to hold.
Thus, by setting the hole of the diffusing member 13d to be sufficiently large with respect to the developer, it is possible to suppress a problem that the developer detached from the developing roller 13a is clogged in the hole of the diffusing member 13d.

In the first embodiment, the area of each of the plurality of holes formed in the diffusing member 13d is set to be constant. As a result, the developer separated from the developing roller 13a is uniformly diffused from the plurality of holes of the diffusion member 13d.
In the first embodiment, since the plurality of mesh holes formed in the diffusion member 13d are formed by punching, the mesh diffusion member is formed by combining a plurality of linear members in three dimensions. Compared with the case of forming the step, a step is less likely to occur inside the hole. Therefore, it is possible to suppress a problem that the developer is clogged in the hole of the diffusion member 13d.

Here, in the first embodiment, the diffusion member 13d is formed of a conductive material such as a metal or a conductive resin, and is further grounded (grounded).
Thereby, when the developer separated from the developing roller 13a passes through the diffusion member 13d, the charge (counter charge) of the carrier C is removed, and the charging ability and holding ability of the carrier with respect to the toner can be restored. it can. Thus, new toner (replenishment toner) can be quickly dispersed when mixed with the developer in the second transport path.
Even when the diffusing member 13d formed of a conductive material is not grounded, the charging ability and holding ability of the carrier with respect to the toner can be restored to some extent. This is because even if a counter charge remains locally at the carrier where the toner has been removed in the development process, the carrier is charged with another carrier via the diffusion member 13d formed of a conductive material. This is to give and receive. As a result, the counter charge is averaged among the carriers in the developer, and the holding capacity of the replenishing toner is improved as a whole.
In the first embodiment, a coating layer made of a conductive material can be provided on the surface of the diffusion member 13d. In that case, although the coating layer is required to have abrasion resistance that can withstand repeated collisions of the developer, the same effect as described above can be obtained.

  As described above, it is desirable to remove the counter charge of the carrier in the developer released from the developing roller 13a as quickly as possible to improve the toner holding ability. However, if all the counter charge of the carrier is removed, the charge capacity of the carrier is restored too much, so that the toner charge amount of the developer in the developing device 13 becomes too large. In this case, since the adhesion force between the toner and the carrier is increased, a desired toner adhesion amount cannot be obtained in the development process. Therefore, it is necessary to keep the counter charge of the carrier removed by the diffusing member 13d within a range not exceeding a predetermined amount. Specifically, only a part of the diffusing member 13d is formed of a conductive material, or the resistance value of the conductive material is optimized.

Hereinafter, the developer G (toner T, carrier C) used in the developing device 13 (image forming apparatus 1) according to the first embodiment will be described in detail.
<About Carrier C>
In Embodiment 1, a carrier having a small particle diameter and having a volume average particle diameter of 20 to 100 μm (preferably 20 to 60 μm) is used. Thereby, since the carrier surface area in the developer becomes relatively large, the replenishment toner is easily dispersed in the developer. Further, by using a carrier having a small particle diameter, it is possible to reduce the developer pumping amount without lowering the developing ability, and it is possible to reduce the amount of developer circulating in the developing device. In particular, since the amount of the developer passing through the doctor blade 23c is reduced, the stress applied to the developer is reduced, which contributes to a longer life of the developer. Further, since the capacity of the carrier can be reduced, the developing device can be reduced in size. Further, since the magnetic brush in the development area becomes denser, high image quality and stability of image quality are achieved.
On the other hand, if the carrier particle size is too small, the surface area of the carrier increases, so that the stress applied to the toner increases, and the deterioration of the developer and fluidity are promoted. Thereby, the dispersibility at the time of toner replenishment deteriorates.
The volume average particle size of the carrier is measured using a “Microtrack particle size analyzer (SRA type)” (manufactured by Nikkiso Co., Ltd.) with a range setting of 0.7 [μm] or more and 125 [μm] or less. Can be done.

<About Toner T>
In the first embodiment, toner T having a small diameter and having a volume average particle diameter (Dv) of 3 to 10 μm (preferably 3 to 6 μm) is used. Further, the toner T having a value obtained by dividing the volume average particle diameter (Dv) by the number average particle diameter (Dn) is 1.4 or less.
By using a toner having a small particle size and a sharp particle size distribution in this way, the gap between the toner particles is reduced, so that the necessary amount of toner can be reduced without impairing the color reproducibility. Therefore, the density fluctuation in the developing process can be reduced. In addition, the stable reproducibility of a minute dot image is improved, and a stable high image quality can be obtained for a long time. When the volume average particle diameter (Dv) is less than 3 μm, problems such as a decrease in transfer efficiency and a decrease in cleaning properties are likely to occur. When the volume average particle size (Dv) exceeds 8 μm, the fluidity of the developer deteriorates, and it is difficult to suppress scattering of characters and lines, and it is difficult to stably maintain image quality for a long period of time.
The average circularity of the toner T in the first embodiment is set to 0.94 to 0.98. Thereby, the amount of the external additive adhering to the toner 1 particle can be increased, and the inorganic fine particles for protecting the toner base surface from external stress due to collision with the carrier or the like can be increased.
In the toner T according to the first embodiment, the shape factor SF-1 is set to 100 to 180, and SF-2 is set to 100 to 150. Thereby, the amount of the external additive adhering to the toner 1 particle can be increased, and the inorganic fine particles for protecting the toner base surface from external stress due to collision with the carrier or the like can be increased.
In addition, the toner T in the first exemplary embodiment contains 30% or less of a toner derivative of 2 μm or less. If the toner contains more than 30% of the toner fine powder, the number of inorganic fine particles adhering to one toner particle decreases, so that the cohesive force between the toners increases and the fluidity of the developer deteriorates. End up. Then, the dispersibility of the replenishment toner in the developer is deteriorated.

<Particle size measurement method>
The volume average particle diameter (Dv) and the number average particle diameter (Dn) of the toner described above were measured with a particle size measuring device “Multisizer III” (manufactured by Beckman Coulter, Inc.) with an aperture diameter of 100 μm. Beckman Coulter Multisizer 3 Version 3.51 "was analyzed.
Specifically, 0.5 ml of 10 wt% surfactant “alkylbenzene sulfonate Neogen SC-A” (Daiichi Kogyo Seiyaku Co., Ltd.) is added to a 100 ml glass beaker, and 0.5 g of each toner is added. The mixture was stirred with a micropartel, and then 80 ml of ion-exchanged water was added. The resulting dispersion was subjected to a dispersion treatment for 10 minutes with an ultrasonic disperser “W-113MK-II” (manufactured by Honda Electronics Co., Ltd.). Further, the dispersion was measured using the above-mentioned Multisizer III and “Isoton III” (manufactured by Beckman Coulter, Inc.) as the measurement solution.
In the measurement, the above-described toner sample dispersion was dropped so that the concentration indicated by the apparatus was 8 ± 2%. In this measuring method, it is important that the above-mentioned concentration is 8 ± 2% from the viewpoint of the reproducibility of the particle size. Within this concentration range, no error occurs in the particle size.

<Measuring method of average circularity, measuring method of particle diameter of 2 μm or less>
The average circularity of the toner and the particle ratio of 2 μm or less can be measured by a flow type particle image analyzer “FPIA-2000” (manufactured by Toa Medical Electronics Co., Ltd.).
As a specific measuring method, 0.1 to 0.5 ml of a surfactant, preferably alkylbenzene sulfonate, is added as a dispersant to 100 to 150 ml of water from which impure solids have been previously removed, and further measurement is performed. Add about 0.1-0.5g of sample. The suspension in which the sample is dispersed is obtained by performing a dispersion treatment with an ultrasonic disperser for about 1 to 3 minutes and measuring the shape and distribution of the toner with the above-mentioned apparatus at a dispersion concentration of 3000 to 10,000 / μl. It is done.

<About the shape factors SF-1 and SF-2>
The shape factor SF-1 described above indicates the ratio of the roundness of the toner shape, and the square of the maximum length MXLNG of the shape formed by projecting the toner onto a two-dimensional plane is divided by the graphic area AREA to give 100π / 4. The value multiplied by. That is, it can be expressed by the following formula.
SF-1 = {(MXLNG) 2 / AREA} × (100π / 4)
When the value of SF-1 is 100, the shape of the toner is a true sphere, and becomes irregular as the value of SF-1 increases.
The shape factor SF-2 indicates the ratio of irregularities in the shape of the toner. The square of the perimeter PERI of the figure formed by projecting the toner onto the two-dimensional plane is divided by the figure area AREA to obtain 100 / 4π. The value multiplied by. That is, it can be expressed by the following formula.
SF-2 = {(PERI) 2 / AREA} × (100 / 4π)
When the value of SF-2 is 100, there is no unevenness on the toner surface, and the unevenness of the toner surface becomes more prominent as the value of SF-2 increases.
Specifically, the shape factor is measured by taking a photograph of the toner with a scanning electron microscope “S-800” (manufactured by Hitachi, Ltd.) and introducing it into an image analyzer “LUSEX3” (manufactured by Nireco) for analysis. And calculated.

In producing a toner having these properties, a polymerization method is more suitable as a toner production method than a pulverization method in order to obtain the optimum particle size and shape.
A method for producing toner using a polymerization method will be described below. The following toner manufacturing method is one specific example, and the toner manufacturing method applied to the present invention is not limited to the following.
(A) A toner material solution is prepared by dispersing a colorant, unmodified polyester, a polyester prepolymer having an isocyanate group, and a release agent in an organic solvent.
The organic solvent is preferably volatile with a boiling point of less than 100 ° C. from the viewpoint of easy removal after toner base particle formation. Specifically, toluene, xylene, benzene, carbon tetrachloride, methylene chloride, 1,2-dichloroethane, 1,1,2-trichloroethane, trichloroethylene, chloroform, monochlorobenzene, dichloroethylidene, methyl acetate, ethyl acetate, methyl ethyl ketone, Methyl isobutyl ketone or the like can be used alone or in combination of two or more. In particular, aromatic solvents such as toluene and xylene and halogenated hydrocarbons such as methylene chloride, 1,2-dichloroethane, chloroform and carbon tetrachloride are suitable.
The usage-amount of an organic solvent is 0-300 weight part normally with respect to 100 weight part of polyester prepolymers, Preferably it is 0-100 weight part, More preferably, it is 25-70 weight part.
(B) The toner material liquid is emulsified in an aqueous medium in the presence of a surfactant and resin fine particles.
The aqueous medium may be water alone or an organic solvent such as alcohol (methanol, isopropyl alcohol, ethylene glycol, etc.), dimethylformamide, tetrahydrofuran, cellosolves (methyl cellosolve, etc.), lower ketones (acetone, methyl ethyl ketone, etc.). It may be included.
The amount of the aqueous medium used relative to 100 parts by weight of the toner material liquid is usually 50 to 2000 parts by weight, preferably 100 to 1000 parts by weight. If the amount is less than 50 parts by weight, the dispersion state of the toner material liquid is poor and toner particles having a predetermined particle diameter cannot be obtained. If it exceeds 20000 parts by weight, it is not economical.
Further, in order to improve the dispersion in the aqueous medium, a dispersant such as a surfactant and resin fine particles is appropriately added.
As surfactants, anionic surfactants such as alkylbenzene sulfonates, α-olefin sulfonates, phosphate esters, alkylamine salts, amino alcohol fatty acid derivatives, polyamine fatty acid derivatives, amine salt types such as imidazoline, Quaternary ammonium salt type cationic surfactants such as alkyltrimethylammonium salts, dialkyldimethylammonium salts, alkyldimethylbenzylammonium salts, pyridinium salts, alkylisoquinolinium salts, benzethonium chloride, fatty acid amide derivatives, polyhydric alcohols Nonionic surfactants such as derivatives, for example, amphoteric surfactants such as alanine, dodecyldi (aminoethyl) glycine, di (octylaminoethyl) glycine and N-alkyl-N, N-dimethylammonium betaine It is below.
Moreover, the effect can be exhibited in a very small amount by using a surfactant having a fluoroalkyl group. Suitable anionic surfactants having a fluoroalkyl group include fluoroalkylcarboxylic acids having 2 to 10 carbon atoms and metal salts thereof, disodium perfluorooctanesulfonyl glutamate, 3- [ω-fluoroalkyl (C6-C11). Oxy] -1-alkyl (C3-C4) sodium sulfonate, 3- [ω-fluoroalkanoyl (C6-C8) -N-ethylamino] -1-propanesulfonic acid sodium, fluoroalkyl (C11-C20) carboxylic acid And metal salts, perfluoroalkyl carboxylic acids (C7 to C13) and metal salts thereof, perfluoroalkyl (C4 to C12) sulfonic acids and metal salts thereof, perfluorooctane sulfonic acid diethanolamide, N-propyl-N- (2 -Hydroxyethyl) perfluorooctane Sulfonamide, perfluoroalkyl (C6-C10) sulfonamidopropyltrimethylammonium salt, perfluoroalkyl (C6-C10) -N-ethylsulfonylglycine salt, monoperfluoroalkyl (C6-C16) ethyl phosphate, etc. .
Product names include Surflon S-111, S-112, S-113 (Asahi Glass Co., Ltd.), Florard FC-93, FC-95, FC-98, FC-129 (Sumitomo 3M Co., Ltd.), Unidyne DS-101. DS-102 (manufactured by Daikin Industries, Ltd.), Megafac F-110, F-120, F-113, F-191, F-812, F-833 (manufactured by Dainippon Ink, Inc.), Xtop EF-102, 103, 104, 105, 112, 123A, 123B, 306A, 501, 201, 204 (manufactured by Tochem Products), and Fgentent F-100, F150 (manufactured by Neos).
In addition, as the cationic surfactant, aliphatic quaternary ammonium salts such as aliphatic primary, secondary or secondary amine acids having a fluoroalkyl group, and perfluoroalkyl (C6-C10) sulfonamidopropyltrimethylammonium salts. , Benzalkonium salt, benzethonium chloride, pyridinium salt, imidazolinium salt, trade names include Surflon S-121 (manufactured by Asahi Glass), Florard FC-135 (manufactured by Sumitomo 3M), Unidyne DS-202 (Daikin Industries) Manufactured), MegaFuck F-150, F-824 (manufactured by Dainippon Ink, Inc.), X-Top EF-132 (manufactured by Tochem Products), and Footgent F-300 (manufactured by Neos).
The resin fine particles are added to stabilize the toner base particles formed in the aqueous medium. For this reason, it is preferable to add so that the coverage existing on the surface of the toner base particles is in the range of 10 to 90%.
For example, polymethyl methacrylate fine particles 1 μm and 3 μm, polystyrene fine particles 0.5 μm and 2 μm, poly (styrene-acrylonitrile) fine particles 1 μm, trade names are PB-200H (manufactured by Kao), SGP (manufactured by Soken), Techno Examples include polymer SB (manufactured by Sekisui Chemical Co., Ltd.), SGP-3G (manufactured by Sokensha), and micropearl (manufactured by Sekisui Fine Chemical Co., Ltd.).
In addition, inorganic compound dispersants such as tricalcium phosphate, calcium carbonate, titanium oxide, colloidal silica, and hydroxyapatite can also be used.
As a dispersant that can be used in combination with the above-described resin fine particles and inorganic compound dispersant, the dispersed droplets may be stabilized by a polymer protective colloid.
For example, acrylic acid, methacrylic acid, α-cyanoacrylic acid, α-cyanomethacrylic acid, itaconic acid, crotonic acid, fumaric acid, maleic acid or maleic anhydride and other (meth) acrylic monomers containing hydroxyl groups Bodies such as acrylic acid-β-hydroxyethyl, methacrylic acid-β-hydroxyethyl, acrylic acid-β-hydroxypropyl, methacrylic acid-β-hydroxypropyl, acrylic acid-γ-hydroxypropyl, methacrylic acid-γ-hydroxy Propyl, acrylic acid-3-chloro-2-hydroxypropyl, methacrylic acid-3-chloro-2-hydroxypropyl, diethylene glycol monoacrylate, diethylene glycol monomethacrylate, glycerol monoacrylate, glycerol monomethacrylate Acid esters, N-methylol acrylamide, N-methylol methacrylamide, etc., vinyl alcohol or ethers with vinyl alcohol, such as vinyl methyl ether, vinyl ethyl ether, vinyl propyl ether, etc., or compounds containing vinyl alcohol and a carboxyl group Esters such as vinyl acetate, vinyl propionate, vinyl butyrate, acrylamide, methacrylamide, diacetone acrylamide or their methylol compounds, acid chlorides such as acrylic acid chloride, methacrylic acid chloride, vinyl pyridine, vinyl pyrrolidone, vinyl imidazole , Nitrogen-containing compounds such as ethyleneimine, or homopolymers or copolymers such as those having a heterocyclic ring thereof, polyoxyethylene, polyoxypropylene , Polyoxyethylene alkylamine, polyoxypropylene alkylamine, polyoxyethylene alkylamide, polyoxypropylene alkylamide, polyoxyethylene nonyl phenyl ether, polyoxyethylene lauryl phenyl ether, polyoxyethylene stearyl phenyl ester, polyoxyethylene nonyl Polyoxyethylenes such as phenyl esters, celluloses such as methyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose can be used.
The dispersion method is not particularly limited, and any of known methods such as a low-speed shear method, a high-speed shear method, a friction method, a high-pressure jet method, and an ultrasonic wave can be applied.
Among these, the high-speed shearing method is preferable in order to make the particle size of the dispersion 2 to 20 μm. When a high-speed shearing disperser is used, the rotational speed is not particularly limited, but is usually 1000 to 30000 rpm, preferably 5000 to 20000 rpm. The dispersion time is not particularly limited, but in the case of a batch method, it is usually 0.1 to 5 minutes. The temperature during dispersion is usually 0 to 150 ° C. (under pressure), preferably 40 to 98 ° C.
(C) At the same time as the preparation of the emulsion, the amines (B) are added to cause a reaction with the polyester prepolymer (A) having an isocyanate group.
This reaction involves molecular chain crosslinking and / or elongation. The reaction time is selected depending on the reactivity between the isocyanate group structure of the polyester prepolymer (A) and the amines (B), but is usually 10 minutes to 40 hours, preferably 2 to 24 hours. The reaction temperature is generally 0 to 150 ° C, preferably 40 to 98 ° C. Moreover, a well-known catalyst can be used as needed. Specific examples include dibutyltin laurate and dioctyltin laurate.
(D) After completion of the above reaction, the organic solvent is removed from the emulsified dispersion (reactant), washed and dried to obtain toner base particles.
In order to remove the organic solvent, the temperature of the entire system is gradually raised in a laminar stirring state, and after giving strong stirring in a certain temperature range, a spindle-shaped toner base particle can be produced by removing the solvent. .
Further, when an acid such as calcium phosphate salt or an alkali-soluble material is used as the dispersion stabilizer, the calcium phosphate salt is dissolved from the toner base particles by a method such as washing with water after dissolving the calcium phosphate salt with an acid such as hydrochloric acid. Remove. It can also be removed by an operation such as degradation with an enzyme.

Here, the toner T used in Embodiment 1 is obtained by coating inorganic fine particles having an average primary particle diameter of 5 to 50 nm on the toner base so that the coverage A is 40 to 200. .
Here, the coverage A is
A = (inorganic fine particle input amount [wt%] / 100) × inorganic fine particle projected area Sa [m ² / g] / ((1−inorganic fine particle input amount [wt%] / 100) × toner surface area Sc [m ² / g]) × 100
It is calculated by the following formula.
In the above formula, the toner surface area Sc and the inorganic fine particle projected area Sa are:
Sc = 3 / (toner volume average particle diameter [m] × toner specific gravity [g / m ³ ])
Sa = 3 / (4 × average particle size of inorganic fine particles [m] × specific gravity of inorganic fine particles [g / m ³ ])
It is calculated by the following formula.
With such a configuration, even when the developer is stirred and mixed for a long time, the dispersibility of the replenishment toner can be improved from the initial stage over time without decreasing the fluidity of the developer. Also, by setting the above-described coverage ratio range, it becomes difficult for the inorganic fine particle film to be formed on the carrier surface, and the replenishment toner is easily attached to the carrier surface, and the dispersibility of the replenishment toner is enhanced.

As inorganic fine particles coated on the toner base, SiO2, TiO2, Al2O3, MgO, CuO, ZnO, SnO2, CeO2, Fe2O3, BaO, CaO, K2O, Na2O, ZrO2, CaO.SiO2, K2O (TiO2) n, Al2O3. 2SiO2, CaCO3, MgCO3, BaSO4, MgSO4, SrTiO3, etc. can be used, and SiO2, TiO2, Al2O3 are preferable. In particular, these inorganic compounds may be hydrophobized with various coupling agents, hexamethyldisilazane, dimethyldichlorosilane, octyltrimethoxysilane, and the like.
More specifically, silica oxide (H3004, H2000, H1303) manufactured by Clariant Japan can be used for SiO2, and titanium oxide (JMT150IB, SMT150AI, SMT150AFM) manufactured by Teika can be used for TiO2. it can.

In order to reduce the adhesion between the toner and the photosensitive drum 11, fine particles having an average primary particle size of 60 to 500 nm may be added to the toner described above. When fine particles having an average primary particle size of 60 to 500 nm are inorganic fine particles, SiO2, TiO2, Al2O3, MgO, CuO, ZnO, SnO2, CeO2, Fe2O3, BaO, CaO, K2O, Na2O, ZrO2, CaO.SiO2 , K2O (TiO2) n, Al2O3 · 2SiO2, CaCO3, MgCO3, BaSO4, MgSO4, SrTiO3, etc., preferably SiO2, TiO2 and Al2O3. In particular, these inorganic compounds may be hydrophobized with various coupling agents, hexamethyldisilazane, dimethyldichlorosilane, octyltrimethoxysilane, and the like. More specifically, for SiO2, silica oxide (X24) made by Shin-Etsu Chemical, silica oxide made by Denka (UFP30HH, UFP35HH, UFP40HH), silica oxide made by Tokuyama (NHM-3N), etc. can be used. .
Further, when fine particles having an average primary particle size of 60 to 600 nm are resin fine particles, they may be thermoplastic resins or thermosetting resins. For example, vinyl resins, polyurethane resins, epoxy resins, polyester resins, polyamide resins, polyimides Examples thereof include resins, silicon-based resins, phenol resins, melamine resins, urea resins, aniline resins, ionomer resins, and polycarbonate resins. As the resin fine particles, two or more of the above-described resins may be used in combination. Of these, vinyl resins, polyurethane resins, epoxy resins, polyester resins, and combinations thereof are preferred because an aqueous dispersion of fine spherical resin particles is easily obtained. Specific examples of vinyl resins include polymers obtained by homopolymerization or copolymerization of vinyl monomers, such as styrene- (meth) acrylic acid ester copolymers, styrene-butadiene copolymers, (meth) acrylic acid. -Acrylic ester copolymer, styrene-acrylonitrile copolymer, styrene-maleic anhydride copolymer, styrene- (meth) acrylic acid copolymer, and the like. More specifically, acrylic non-crosslinked monodispersed resin particles (MP-1451, MP300, MP2200, MP2701, MP5000, MP5500, MP4009) manufactured by Soken Chemical Co., Ltd. can be used.

The developer G used in the first embodiment is obtained by coating the surface of the carrier C with the toner T so that the coverage B is 40 to 90.
Here, the coverage B is
B = (toner input amount [% by weight] / 100) × toner projected area Sb [m ² / g] / ((1−toner input amount [% by weight] / 100) × carrier surface area Sd [m ² / g]) × 100
It is calculated by the following formula.
In the above equation, the carrier surface area Sd and the toner projected area Sb are:
Sd = 3 / (carrier volume average particle size [m] × carrier specific gravity [g / m ³ ])
Sb = 3 / (4 × toner volume average particle diameter [m] × toner specific gravity [g / m ³ ])
It is calculated by the following formula.
If the coverage B is less than 40, the number of toners present between the carriers decreases, so that the stress applied to the toner particles increases and the toner tends to deteriorate. For this reason, the fluidity of the developer tends to deteriorate, and the dispersibility of the replenishment toner deteriorates.
On the other hand, if the coverage B exceeds 90, the retention ability of the carrier with respect to the toner is extremely reduced, so that the toner that could not be retained adheres to the photosensitive drum 11 as scattered toner. The image quality of the output image is degraded.

Here, in the first embodiment, the developer dropping amount in the first relay portion 13f is set to be 5 to 10 g / second.
The greater the amount of developer dropped at the first relay portion 13f, the more effective the dispersed toner is dispersed in the developer. However, if the amount of the developer dropped from the first relay portion 13f is too large, the range for establishing the conditions for circulating the developer (such as the rotation speed of the transport screw) is narrowed, and the developing device is stable. The margin for performing the process will be reduced.
As a result of an experiment conducted by the inventor of the present application, it was confirmed that stable development was performed when the amount of developer dropped at the first relay portion 13f was 5 to 10 g / sec. If the developer drop amount is less than 5 g / sec, the replenishability of the replenished toner is extremely deteriorated. If the developer drop amount exceeds 10 g / sec, the rotation speed of the conveying screw must be set high in order to circulate the developer, and the deterioration of the developer is accelerated by the heat generated from the bearing portion of the conveying screw. It has been done.

In the first embodiment, the amount of developer (pumping amount) carried on the developing roller 13a after passing through the position of the doctor blade 13c is set to 30 to 70 mg / cm ² . .
The greater the amount of developer pumped, the greater the surface area of the carrier contained in the developer, and the greater the effect of dispersing the replenishment toner. However, if the amount of developer pumped up is too large, the range for establishing the conditions for circulating the developer (such as the number of rotations of the conveying screw) is narrowed, and the margin for stable development as a developing device Will fall.
When the inventor of the present application conducted an experiment, it was confirmed that stable development was performed when the developer pumped amount was 30 to 70 mg / cm ² . When the developer pumping amount is less than 30 mg / cm ² , the carrier surface that can hold the replenished toner cannot be secured, and the dispersibility of the replenished toner deteriorates. When the developer pumping amount exceeds 70 mg / cm ² , the rotation speed of the conveying screw must be set high in order to circulate the developer, and the developer deteriorates due to the heat generated from the bearing portion of the conveying screw. Has been promoted.

Further, referring to FIG. 2, the developing device 13 according to the first embodiment causes the developer G that has exceeded the wall portion of the first conveying path by the first conveying screw 13b1 to fall on the developing roller 13a and develop the developing roller. It is comprised so that it may carry | support by magnetic force on 13a.
With such a configuration, the developer is supported on the developing roller 13a only by the magnetic force of the magnet, and a large compressive force is not applied to the developer when passing through the position of the doctor blade 13c. The stress applied to the developer can be reduced while maintaining the increased amount. Therefore, since deterioration of the developer and fluidity can be reduced, stable replenishment toner replenishment can be ensured over time.

  As described above, in the first embodiment, even when the two conveying screws 13b1 and 13b2 (conveying members) that convey the developer G in the longitudinal direction to form a circulation path are installed in the vertical direction. The diffusion member 13d that diffuses before the developer G separated from the developing roller 13a (developer carrier) is mixed with the developer G in the second conveyance path by the second conveyance screw 13b2 (second conveyance member) is provided. Since it is installed, the developer G separated from the developing roller 13a in the second transport path can be sufficiently stirred and mixed.

  In the first embodiment, the diffusing member 13d is disposed so as to face the entire longitudinal direction of the developing roller 13a. However, the range of the diffusing member 13d in the longitudinal direction is not limited to this, and the second conveyance is performed. It can be installed only on the upstream side of the path, can be installed only on the downstream side of the second transport path, or can be installed only on the inner part of the second transport path.

Embodiment 2. FIG.
6 and 7, the second embodiment of the present invention will be described in detail.
FIG. 6 is a configuration diagram illustrating the developing device according to the second embodiment, and corresponds to FIG. 2 according to the first embodiment. In the developing device in the second embodiment, the shape of the diffusion member 13d is different from that in the first embodiment.

  Referring to FIG. 6, the developing device 13 according to the second embodiment also has a developing roller 13a (developer carrier), two transport screws 13b1, 13b2, and a doctor blade 13c (development) as in the first embodiment. Agent regulating member), diffusion member 13d (plate-like member), and the like.

Here, in the diffusion member 13d (plate-like member) in Embodiment 2, the side closer to the developing roller 13a (the right side in FIG. 6) is the side farther from the developing roller 13a (the left side in FIG. 6). It is inclined and arranged so as to be lower.
Thereby, the distance between the developer surface in the second transport path (the side closer to the developing roller 13a is lower than the side farther from the developing roller 13a) and the diffusion member 13d is almost the same on either side. The developer can be kept uniform to improve the diffusibility of the developer, and the balance of the developer can be made uniform. In addition, since the diffusion member 13d is less likely to come into contact with the developer surface in the second conveyance path, the load for rotating the second conveyance screw 13b2 can be reduced.
Note that the inclination angle of the diffusing member 13d depends on the position of the developing roller 13a, the position of the developer separated from the developing roller 13a, the position of the second transport screw 13b2, the state of the developer surface in the second transport path, replenishment This is determined in consideration of the toner position and the like.

Further, referring to FIG. 7, diffusion member 13d of the second embodiment includes a first conductive region 13d1 formed of a conductive resin having a relatively high electrical resistance, and a metal having a relatively low electrical resistance. And a second conductive region 13d2 formed in (1). The first conductive region 13d1 is disposed on the downstream side of the second transport path, and the second conductive region 13d2 is disposed on the upstream side of the second transport path.
On the upstream side of the second conveyance path, since there is a large amount of replenishment toner that is insufficiently dispersed in the collected developer, the toner holding ability of the carrier in the detached developer is sufficiently restored. There is a need. On the other hand, since the replenishment toner is dispersed in the developer on the downstream side of the second conveyance path, the dispersibility after that even if the toner holding ability of the carrier in the detached developer is not high. Therefore, it is not necessary to sufficiently restore the toner holding ability of the carrier. Therefore, by providing a difference in electrical resistance depending on the position in the longitudinal direction of the diffusing member 13d, it is possible to efficiently distribute the replenishment toner along the longitudinal direction.
In the first embodiment, a difference is provided in the electrical resistance depending on the position in the longitudinal direction of the diffusing member 13d. However, a difference in the electrical resistance may be provided depending on the position in the short direction of the diffusing member 13d. Specifically, the electrical resistance of the diffusing member 13d on the side closer to the developing roller 13a (the right side in FIG. 6) is that of the diffusing member 13d on the side farther from the developing roller 13a (the left side in FIG. 6). It can also be set to be lower than the electrical resistance. Even in such a case, the replenishment toner can be efficiently dispersed.

  As described above, also in the second embodiment, similarly to the first embodiment, the two conveying screws 13b1 and 13b2 (conveying members) that convey the developer G in the longitudinal direction to form a circulation path are moved up and down. Even when installed in the direction, the developer G released from the developing roller 13a (developer carrier) is mixed with the developer G in the second transport path by the second transport screw 13b2 (second transport member). Since the diffusing member 13d that diffuses before installation is provided, the developer G that has separated from the developing roller 13a in the second transport path can be sufficiently stirred and mixed.

Embodiment 3 FIG.
A third embodiment of the present invention will be described in detail with reference to FIG.
FIG. 8 is a configuration diagram illustrating the developing device according to the third embodiment, and corresponds to FIG. 6 according to the second embodiment. In the developing device according to the third embodiment, the shape of the diffusion member 13d is different from that of the second embodiment.

  Referring to FIG. 8, similarly to the second embodiment, the developing device 13 according to the third embodiment also has a developing roller 13a (developer carrying member), two transport screws 13b1, 13b2, and a doctor blade 13c (developing). Agent regulating member), diffusion member 13d (plate-like member), and the like. Also in the third embodiment, the diffusion member 13d (plate-like member) has a side closer to the developing roller 13a (the right side in FIG. 6) and a side farther from the developing roller 13a (the left side in FIG. 6). ) And are arranged so as to be lower.

Here, the diffusion member 13d (plate-like member) in the third embodiment is disposed so that the side far from the developing roller 13a abuts the upper wall of the second conveyance path.
Accordingly, since the space in the height direction of the second transport path is effectively used, the developing device 13 can be made compact in the height direction.

  As described above, also in the third embodiment, the two transport screws 13b1 and 13b2 (conveying members) that transport the developer G in the longitudinal direction to form a circulation path are moved up and down in the same manner as in the above embodiments. Even when installed in the direction, the developer G released from the developing roller 13a (developer carrier) is mixed with the developer G in the second transport path by the second transport screw 13b2 (second transport member). Since the diffusing member 13d that diffuses before installation is provided, the developer G that has separated from the developing roller 13a in the second transport path can be sufficiently stirred and mixed.

Embodiment 4 FIG.
A fourth embodiment of the present invention will be described in detail with reference to FIG.
FIG. 9 is a schematic cross-sectional view in the longitudinal direction of the circulation path of the developing device in the fourth embodiment, corresponding to FIG. 4 in the first embodiment. In the developing device in the fourth embodiment, the shape of the diffusion member 13d is different from that in the first embodiment.

  Referring to FIG. 9, similarly to the first embodiment, the developing device 13 according to the fourth embodiment also has a developing roller 13a (developer carrier), two conveying screws 13b1, 13b2, and a doctor blade 13c (developing). Agent regulating member), diffusion member 13d (plate-like member), and the like.

Here, in the diffusion member 13d (plate-like member) according to the fourth embodiment, the upstream side of the second transport path (the right side in FIG. 9) is the downstream side of the second transport path (the left side in FIG. 9). .) Is arranged so as to be lower.
As a result, the distance between the developer surface in the second transport path whose upstream side is lower than that of the downstream side and the diffusion member 13d is kept substantially uniform on both sides, thereby making the developer diffusible. In addition to the improvement, the balance of the developer can be made uniform. In addition, since the diffusion member 13d is less likely to come into contact with the developer surface in the second conveyance path, the load for rotating the second conveyance screw 13b2 can be reduced.
Note that the inclination angle of the diffusing member 13d depends on the position of the developing roller 13a, the position of the developer separated from the developing roller 13a, the position of the second transport screw 13b2, the state of the developer surface in the second transport path, replenishment This is determined in consideration of the toner position and the like.

  As described above, in the fourth embodiment as well, the two conveying screws 13b1 and 13b2 (conveying members) that convey the developer G in the longitudinal direction to form a circulation path are moved up and down in the same manner as in the above embodiments. Even when installed in the direction, the developer G released from the developing roller 13a (developer carrier) is mixed with the developer G in the second transport path by the second transport screw 13b2 (second transport member). Since the diffusing member 13d that diffuses before installation is provided, the developer G that has separated from the developing roller 13a in the second transport path can be sufficiently stirred and mixed.

Embodiment 5 FIG.
A fifth embodiment of the present invention will be described in detail with reference to FIGS.
FIG. 10 is a configuration diagram illustrating the developing device according to the fifth embodiment, and corresponds to FIG. 6 according to the second embodiment. FIG. 11 is a schematic cross-sectional view of a circulation path of a developing device different from the developing device of FIG. 10 in the longitudinal direction.
In the developing device according to the fifth embodiment, the shape of the diffusing member 13d is different from those of the respective embodiments.

As shown in FIG. 10, the diffusion member 13d (plate-like member) in Embodiment 5 has a side closer to the developing roller 13a (the right side in FIG. 10) and a side farther from the developing roller 13a (see FIG. 10). 10 is the left side of 10).
As a result, the distance between the developer surface of the developer in the second transport path and the diffusion member 13d can be kept substantially uniform on either side, improving the diffusibility of the developer, and The balance can be made uniform. Further, since the diffusion member 13d is less likely to come into contact with the developer surface in the second transport path, the load for rotating the second transport screw 13b2 can also be reduced.

In addition, as shown in FIG. 11, the thickness of the diffusion member 13d on the upstream side (the right side in FIG. 11) of the second transport path is the downstream side (the left side in FIG. 11) of the second transport path. It can also be formed to be thicker than the thickness.
Thus, the distance between the developer surface of the developer in the second transport path and the diffusion member 13d can be kept substantially uniform on either side, and the developer balance can be made uniform. Further, since the diffusion member 13d is less likely to come into contact with the developer surface in the second transport path, the load for rotating the second transport screw 13b2 can also be reduced.

  As described above, in the fifth embodiment, similarly to the above-described embodiments, the two conveying screws 13b1 and 13b2 (conveying members) that convey the developer G in the longitudinal direction to form a circulation path are moved up and down. Even when installed in the direction, the developer G released from the developing roller 13a (developer carrier) is mixed with the developer G in the second transport path by the second transport screw 13b2 (second transport member). Since the diffusing member 13d that diffuses before installation is provided, the developer G that has separated from the developing roller 13a in the second transport path can be sufficiently stirred and mixed.

Embodiment 6 FIG.
A sixth embodiment of the present invention will be described in detail with reference to FIGS.
FIG. 12 is a configuration diagram illustrating the developing device according to the sixth embodiment, and corresponds to FIG. 6 according to the second embodiment. FIG. 13 is a block diagram showing a developing device in a form different from the developing device of FIG. FIG. 14 is a schematic cross-sectional view of a circulation path of a developing device of another form different from the developing device of FIG. 12 as viewed in the longitudinal direction.
The developing device according to the sixth embodiment is different from those of the respective embodiments in that a plurality of diffusion members are provided.

  As shown in FIG. 12, in the developing device 13 according to the sixth embodiment, a plurality of diffusion members 13da and 13db (plate-like members) are installed between the developing roller 13a and the second transport screw 13b2. If the diffusibility of the developer is insufficient by installing only one diffusing member, a plurality of diffusing members 13da and 13db are installed along the falling direction of the developer to be detached, thereby providing a desired developer. Diffusivity can be obtained. In particular, by optimizing the installation positions and angles of the respective diffusion members 13da and 13db, the separated developer can be dispersed over a wide range at the target position on the developer in the second transport path.

As shown in FIG. 13, among the plurality of diffusion members 13da and 13db, one diffusion member 13db is closer to the developing roller 13a (on the right side in FIG. 13) and is far from the developing roller 13a. It can also be formed to be thicker than the thickness of the side (the left side in FIG. 13).
Further, as shown in FIG. 14, among the plurality of diffusion members 13da and 13db, one diffusion member 13db is arranged on the upstream side of the second conveyance path (the right side in FIG. 14) on the downstream side of the second conveyance path. (It is the left side of FIG. 14).

  As described above, also in the sixth embodiment, the two conveying screws 13b1 and 13b2 (conveying members) that convey the developer G in the longitudinal direction to form a circulation path are moved up and down in the same manner as in the above embodiments. Even when installed in the direction, the developer G released from the developing roller 13a (developer carrier) is mixed with the developer G in the second transport path by the second transport screw 13b2 (second transport member). Since the diffusing members 13da and 13db that diffuse before being installed are installed, the developer G separated from the developing roller 13a in the second transport path can be sufficiently stirred and mixed.

Embodiment 7 FIG.
A seventh embodiment of the present invention will be described in detail with reference to FIGS.
FIG. 15 is a plan view showing a diffusing member 13d installed in the developing device in the seventh embodiment, and corresponds to FIG. 5 in the first embodiment. 16 is a cross-sectional view showing the vicinity of the hole H formed in the diffusion member 13d of FIG. FIG. 17 is a plan view showing a diffusing member of a form different from that of FIG. FIG. 18 is a plan view showing a diffusing member of another form different from the diffusing member of FIG.
In the developing device according to the seventh embodiment, the shape of the diffusing member 13d is different from those of the respective embodiments.

As shown in FIG. 15, the diffusing member 13d in the seventh embodiment has a plurality of circular holes H formed therein. As shown in FIG. 16, the hole H of the scattering member 13d is chamfered to improve the developer passage.
The hole H formed in the diffusing member 13d is not limited to a circular shape, and for example, an elliptical hole H can be formed as shown in FIG.
Further, as shown in FIG. 18, the diffusion member 13d may be comb-shaped having a plurality of slits.

  As described above, also in the seventh embodiment, the two conveying screws 13b1 and 13b2 (conveying members) that convey the developer G in the longitudinal direction to form the circulation path are moved up and down in the same manner as in the above embodiments. Even when installed in the direction, the developer G released from the developing roller 13a (developer carrier) is mixed with the developer G in the second transport path by the second transport screw 13b2 (second transport member). Since the diffusing member 13d that diffuses before installation is provided, the developer G that has separated from the developing roller 13a in the second transport path can be sufficiently stirred and mixed.

Embodiment 8 FIG.
The eighth embodiment of the present invention will be described in detail with reference to FIG.
FIG. 19 is a plan view showing a diffusing member 13d installed in the developing device in the eighth embodiment, and corresponds to FIG. 5 in the first embodiment. In the developing device according to the eighth embodiment, the shape of the diffusing member 13d is different from those of the respective embodiments.

  As shown in FIG. 19, the diffusion member 13d according to the eighth embodiment has a plurality of rectangular holes H formed therein. Although not shown, the corners of the rectangular hole H are formed in an R shape to reduce damage to the developer and improve the developer passage.

  As described above, in the eighth embodiment, similarly to the above-described embodiments, the two conveying screws 13b1 and 13b2 (conveying members) that convey the developer G in the longitudinal direction to form a circulation path are moved up and down. Even when installed in the direction, the developer G released from the developing roller 13a (developer carrier) is mixed with the developer G in the second transport path by the second transport screw 13b2 (second transport member). Since the diffusing member 13da that diffuses before being installed is installed, the developer G separated from the developing roller 13a in the second transport path can be sufficiently stirred and mixed.

Embodiment 9 FIG.
A ninth embodiment of the present invention will be described in detail with reference to FIG.
FIG. 20 is a plan view showing a diffusing member 13d installed in the developing device in the ninth embodiment, and corresponds to FIG. 5 in the first embodiment. In the developing device according to the ninth embodiment, the shape of the diffusing member 13d is different from those of the respective embodiments.

  As shown in FIG. 20, the diffusing member 13d according to the ninth embodiment has a plurality of linear members arranged in parallel in the short direction, and has a plurality of slits. Since the diffusion member 13d formed in this way is unlikely to have a step in the developer passage direction, a problem that the developer is clogged in the slit of the diffusion member 13d is suppressed.

  As described above, also in the ninth embodiment, similarly to the above embodiments, the two conveying screws 13b1 and 13b2 (conveying members) that convey the developer G in the longitudinal direction to form a circulation path are moved up and down. Even when installed in the direction, the developer G released from the developing roller 13a (developer carrier) is mixed with the developer G in the second transport path by the second transport screw 13b2 (second transport member). Since the diffusing member 13da that diffuses before being installed is installed, the developer G separated from the developing roller 13a in the second transport path can be sufficiently stirred and mixed.

Embodiment 10 FIG.
A tenth embodiment of the present invention will be described in detail with reference to FIG.
FIG. 21 is a plan view showing a diffusing member 13d installed in the developing device in the tenth embodiment, and corresponds to FIG. 5 in the first embodiment. In the developing device according to the tenth embodiment, the shape of the diffusing member 13d is different from those of the above-described embodiments.

  As shown in FIG. 21, the diffusing member 13d according to the tenth embodiment has a plurality of linear members arranged in an oblique direction, and has a plurality of slits. Since the diffusion member 13d formed in this way is unlikely to have a step in the developer passage direction, a problem that the developer is clogged in the slit of the diffusion member 13d is suppressed.

  As described above, also in the tenth embodiment, the two conveying screws 13b1 and 13b2 (conveying members) that convey the developer G in the longitudinal direction to form a circulation path are moved up and down in the same manner as in the above embodiments. Even when installed in the direction, the developer G released from the developing roller 13a (developer carrier) is mixed with the developer G in the second transport path by the second transport screw 13b2 (second transport member). Since the diffusing member 13da that diffuses before being installed is installed, the developer G separated from the developing roller 13a in the second transport path can be sufficiently stirred and mixed.

Experimental result.
With reference to FIG. 22, an experiment conducted to confirm the effects described in the above embodiments will be described.
FIG. 22 shows the evaluation results of the output images using 23 types of developing devices 13 (Examples 1 to 16, Comparative Examples 1 to 7). The experiment was performed according to the following procedures and conditions.
(1) The toner T and the image forming apparatus 1 used in the experiment are left in an environmental room at 25 ° C. and 50% for one day.
(2) 400 g of developer G is charged into the developing device 13.
(3) The linear velocity of the developing roller 13a is set to 600 mm / second, and only the developing device 13 is idled for 1 minute.
(4) The linear velocity of the developing roller 13a is set to 600 mm / second, the linear velocity of the photosensitive drum 11 is set to 300 mm / second, and the toner adhesion amount on the photosensitive drum 11 is 0.45 ± 0.05 mg / cm ^2. The charging potential and the developing bias are adjusted so that
(5) Under the above development conditions, the transfer current is adjusted so that the transfer rate is 96 ± 2%.
(6) A toner amount (about 0.56 g) equivalent to the output of two A3 size solid images is supplied to the upstream side of the second conveying screw 13b2, and the image area ratio is 100% using the above set value. Print two A3 full face images in succession.
(7) The image density IDs at the left end, the center, and the right end within 1 cm of the rear end side of the second image are measured by X-Rite.
(8) The deviation of the image density (ID) at the three locations described above is obtained, and when the difference between the IDs is within 0.1, ◎, when the difference is within 0.2, ○, 0.2 or more When it is, it evaluates as x.

The toner used in the experiment was manufactured by the following manufacturing method.
229 parts of bisphenol A ethylene oxide 2-mole adduct, 529 parts of bisphenol A propion oxide 3-mole adduct, 208 parts of terephthalic acid, 46 parts of adipic acid and dibutyltin oxide 2 parts were added and reacted at 230 ° C. under normal pressure for 8 hours. Next, after reacting under reduced pressure of 10 to 15 mmHg for 5 hours, 44 parts of trimellitic anhydride was added to the reaction vessel and reacted at 180 ° C. for 2 hours under normal pressure to synthesize an unmodified polyester resin. .
The obtained unmodified polyester resin had a number average molecular weight of 2500, a weight average molecular weight of 6700, a glass transition temperature of 43 ° C., and an acid value of 25 mgKOH / g.
1200 parts of water, 540 parts of carbon black “Printex35” (manufactured by Dexa; DBP oil absorption = 42 ml / 100 mg, pH = 9.5) and 1200 parts of unmodified polyester resin were used with a Henschel mixer (manufactured by Mitsui Mining). Mixed. The resulting mixture was kneaded at 150 ° C. for 30 minutes using two rolls, then rolled and cooled, and pulverized with a pulverizer (manufactured by Hosokawa Micron Corporation) to prepare a master batch.
In a reaction vessel in which a stir bar and a thermometer were set, 378 parts of unmodified polyester resin, 110 parts of carnauba wax, 22 parts of a salicylic acid metal complex “E-84” (manufactured by Orient Chemical Co., Ltd.) and 947 parts of ethyl acetate were charged. While stirring, the temperature was raised to 80 ° C., held at 80 ° C. for 5 hours, and then cooled to 30 ° C. over 1 hour. Next, 500 parts of a master batch and 500 parts of ethyl acetate were charged into the reaction vessel and mixed for 1 hour to obtain a raw material solution.
1324 parts of the resulting raw material solution was transferred to a reaction vessel and filled with 80% by volume of 0.5 mm zirconia beads using “Ultra Visco Mill” (manufactured by AIMEX Co., Ltd.), a liquid feed rate of 1 kg / hour. 3 passes under the condition that the disk peripheral speed is 6 m / sec. I. Pigment Red and carnauba wax were dispersed to obtain a wax dispersion.
Next, 1324 parts of a 65 wt% ethyl acetate solution of unmodified polyester resin was added to the wax dispersion. A layered inorganic mineral montmorillonite (Clayton APA Southern Clay modified at least partly with a quaternary ammonium salt having a benzyl group) was added to 200 parts of a dispersion obtained by one pass using Ultraviscomil under the same conditions as above. 3 parts of Products (manufactured by Products) were added, and the mixture was stirred for 30 minutes using “TK Homo Disperser” (manufactured by Tokushu Kika Kogyo Co., Ltd.) to obtain a toner material dispersion.
Then, the viscosity of the obtained dispersion of toner material was measured as follows.
Using a parallel plate type rheometer AR2000 (made by D.A. Instruments Japan Co., Ltd.) equipped with a parallel plate with a diameter of 20 mm, the gap was set to 30 μm, and the toner material dispersion was at 25 ° C. After applying a shear force at a shear rate of 30000 seconds-1 for 30 seconds, the viscosity (viscosity A) when the shear rate was changed from 0 seconds-1 to 70 seconds-1 in 20 seconds was measured. Further, using a parallel plate rheometer AR2000, the viscosity (viscosity B) when a shearing force was applied to the dispersion liquid of the toner material at 25 ° C. at a shear rate of 30000 sec-1 for 30 seconds was measured.
In a reaction vessel equipped with a cooling tube, a stirrer and a nitrogen introduction tube, 682 parts of bisphenol A ethylene oxide 2-mole adduct, 81 parts of bisphenol A propylene oxide 2-mole adduct, 283 parts of terephthalic acid, 22 parts of trimellitic anhydride And 2 parts of dibutyltin oxide were added and reacted at 230 ° C. for 8 hours under normal pressure. Next, it was made to react under reduced pressure of 10-15mHg for 5 hours, and the intermediate polyester resin was synthesize | combined.
The obtained intermediate polyester resin had a number average molecular weight of 2,100, a weight average molecular weight of 9,500, a glass transition temperature of 55 ° C., an acid value of 0.5 mgKOH / g, and a hydroxyl value of 51 mgKOH / g.
Next, 410 parts of the intermediate polyester resin, 89 parts of isophorone diisocyanate, and 500 parts of ethyl acetate are charged into a reaction vessel equipped with a cooling pipe, a stirrer, and a nitrogen introduction pipe, and reacted at 100 ° C. for 5 hours. Was synthesized. The free isocyanate content of the obtained prepolymer was 1.53% by weight. In a reaction vessel equipped with a stir bar and a thermometer, 170 parts of isophoronediamine and 75 parts of methyl ethyl ketone were charged and reacted at 50 ° C. for 5 hours to synthesize a ketimine compound. The amine value of the obtained ketimine compound was 418 mgKOH / g.
In a reaction container, 749 parts of a dispersion of toner material, 115 parts of a prepolymer and 2.9 parts of a ketimine compound are charged and mixed at 5000 rpm for 1 minute using a “TK homomixer” (manufactured by Tokushu Kika Co., Ltd.). An oil phase mixture was obtained.
In a reaction vessel equipped with a stirring bar and a thermometer, 683 parts of water, 11 parts of reactive emulsifier (sodium salt of sulfuric acid ester of methacrylic acid ethylene oxide adduct), Eleminol RS-30 (manufactured by Sanyo Chemical Industries), styrene 83 Parts, 83 parts of methacrylic acid, 110 parts of butyl acrylate and 1 part of ammonium persulfate were stirred at 400 rpm for 15 minutes to obtain an emulsion. The emulsion was heated, heated to 75 ° C. and reacted for 5 hours. Next, 30 parts of a 1% by weight aqueous ammonium persulfate solution was added and aged at 75 ° C. for 5 hours to prepare a resin particle dispersion.
Hereinafter, the particle size of the dispersoid particles in the toner material liquid and the distribution of the dispersed particle size will be described.
The measurement of the dispersoid particle size and dispersion particle size distribution of the toner material liquid was performed using “Microtrac UPA-150” (manufactured by Nikkiso Co., Ltd.), and the analysis software “Microtrac Particle Size Analyzer-Ver. -016EE "(manufactured by Nikkiso Co., Ltd.) was used for analysis. Specifically, the toner material liquid and then the solvent used for preparation of the toner material liquid were added to a glass 30 ml sample bottle to prepare a 10 mass% dispersion. The obtained dispersion was subjected to a dispersion treatment for 2 minutes with an “ultrasonic wave disperser W-113MK-II” (Honda Electronics Co., Ltd.).
After measuring the background with the solvent used for the toner material liquid to be measured, the dispersion was dropped, and the dispersed particle size was measured under the condition that the sample loading value of the measuring device was in the range of 1-10. In this measurement method, it is important to measure under the condition that the sample loading value of the measuring device is in the range of 1 to 10 from the viewpoint of measurement reproducibility of the dispersed particle size. In order to obtain the sample loading value, it is necessary to adjust the dripping amount of the dispersion.
Measurement and analysis conditions were set as follows.
Distribution display: volume, particle size classification selection: standard, number of channels: 44, measurement time: 60 sec, number of measurements: once, particle permeability: transmission, particle refractive index: 1.5, particle shape: non-spherical, density: The value of the solvent used for the toner material liquid among the values described in “Guidelines on Input Conditions at Measurement” published by Nikkiso Co., Ltd. was used as the value of 1 g / 3 cm 3 and the solvent refractive index.
990 parts of water, 83 parts of resin particle dispersion, 37 parts of a 48.5% by weight aqueous solution of dodecyl diphenyl ether disulfonate, Eleminol MON-7 (manufactured by Sanyo Kasei Kogyo Co., Ltd.), 1% by weight aqueous solution of sodium carboxymethylcellulose polymer dispersant 135 parts of BS-H-3 (Daiichi Kogyo Seiyaku Co., Ltd.) and 90 parts of ethyl acetate were mixed and stirred to obtain an aqueous medium.
To 1200 parts of the aqueous medium, 867 parts of the oil phase mixed liquid was added and mixed for 20 minutes at 13000 rpm using a TK homomixer to prepare a dispersion (emulsified slurry).
Next, the emulsified slurry was charged into a reaction vessel in which a stirrer and a thermometer were set, and after removing the solvent at 30 ° C. for 8 hours, aging was performed at 45 ° C. for 4 hours to obtain a dispersed slurry. After filtering 100 parts of the dispersion slurry under reduced pressure, 100 parts of ion-exchanged water was added to the filter cake, followed by mixing at 12000 rpm for 10 minutes using a TK homomixer, followed by filtration.
To the obtained filter cake, 10 wt% hydrochloric acid was added to adjust the pH to 2.8, and the mixture was mixed at 12000 rpm for 10 minutes using a TK homomixer, followed by filtration.
Furthermore, 300 parts of ion-exchanged water was added to the obtained filter cake, mixed for 10 minutes at 12000 rpm using a TK homomixer, and then filtered twice to obtain a final filter cake.
The obtained final filter cake was dried at 45 ° C. for 48 hours using a circulating dryer, and sieved with a mesh having a mesh size of 75 μm to produce a toner. The obtained toner base has a volume average particle diameter (Dv) of 5.8 μm, a Dv / Dn of 1.3, a fine particle content of 2 μm or less, 13.4%, an average circularity of 0.9570, a shape factor SF. -1- is 138 and SF-2ga127.
To this toner base, 1.0 part of inorganic fine particles having an average primary particle diameter of 12 nm (silica oxide silica H2000 manufactured by Clariant Japan), and 0 part of inorganic fine particles having an average primary particle diameter of 15 nm (titanium oxide SMT150AI manufactured by Teika) were 0. The toner A was obtained by adding 5 parts and mixing using a Henschel mixer so that the toner surface coverage with the inorganic fine particles was about 93%.
The carrier used in the experiment has a volume average particle size of 35 μm, and the toner and the carrier were mixed so that the carrier coverage of the toner was about 55%, and prepared as a developer used in the experiment.

Hereinafter, the structure of 23 types of developing devices 13 (Examples 1 to 16 and Comparative Examples 1 to 7) will be described.
(Example 1)
The developing device 13 in the first embodiment is used. The diffusion member 13d is formed by forming a mesh-like hole in a copper plate, and the size of the hole is 3 mm × 3 mm. Further, R of 0.3 mm was provided inside the hole, and the thickness of the diffusing member 13d was set to 1 mm. The amount of developer pumped on the developing roller 13a was set to 45 mg / cm ² , and the amount of developer dropped from the first relay portion 13f was set to 7 g / second.
(Example 2)
The developing device 13 in Embodiment 2 (the diffusing member 13d is disposed at an inclination) was used. The configuration of the diffusing member 13d, the amount of developer drawn on the developing roller 13a, and the amount of developer dropped from the first relay portion 13f were set to be the same as those in the first embodiment.
(Example 3)
The developing device 13 in Embodiment 3 was used. The configuration of the diffusing member 13d, the amount of developer drawn on the developing roller 13a, and the amount of developer dropped from the first relay portion 13f were set to be the same as those in the first embodiment.
Example 4
The developing device 13 in Embodiment 4 was used. The configuration of the diffusing member 13d, the amount of developer drawn on the developing roller 13a, and the amount of developer dropped from the first relay portion 13f were set to be the same as those in the first embodiment.
(Example 5)
The developing device 13 in the fifth embodiment (shown in FIG. 10) was used. The configuration of the diffusing member 13d, the amount of developer drawn on the developing roller 13a, and the amount of developer dropped from the first relay portion 13f were set to be the same as those in the first embodiment.
(Example 6)
A developing device in which the developing device of FIG. 8 and the developing device of FIG. 9 are combined (the diffusing member 13d is disposed inclining in the longitudinal direction and the lateral direction) was used. The configuration of the diffusing member 13d, the amount of developer drawn on the developing roller 13a, and the amount of developer dropped from the first relay portion 13f were set to be the same as those in the first embodiment.
(Example 7)
In the developing device shown in Example 5, the one provided with the diffusing member 13d of the seventh embodiment (shown in FIG. 7) was used. The diffusion member 13d is formed by forming a hole H having a diameter of 2 mm on a copper plate so that the distance between the centers is 4 mm. The diffusion member 13d was also grounded.
(Example 8)
In the developing device shown in Example 5, the one provided with the diffusion member 13d of the eighth embodiment was used. The diffusing member 13d is formed by forming a rectangular hole H of 2 mm × 4 mm in a copper plate so that the distance between the holes is 3 mm in both length and width. The diffusion member 13d was also grounded.
Example 9
In the developing device shown in Example 5, the one provided with the diffusion member 13d of the ninth embodiment was used. The diffusing member 13d is a member in which linear members having a thickness of 0.5 mm are juxtaposed in the short direction at intervals of 2 mm. The diffusion member 13d was also grounded.
(Example 10)
In the developing device shown in Example 5, the one provided with the diffusion member 13d of the tenth embodiment was used. The diffusing member 13d is a linear member having a thickness of 0.5 mm that is inclined by 45 degrees at intervals of 2 mm. The diffusion member 13d was also grounded.
Example 11
In the developing device shown in Example 8, a carrier having a volume average particle diameter of 25 μm was used. However, the carrier coating was not changed, and the toner and the carrier were mixed so that the carrier coverage of the toner was about 55%.
Example 12
In the developing device shown in Example 8, the toner A was classified and changed to a toner having a toner volume average particle size of 4.0 μm and Dv / Dn of 1.34. However, the inorganic fine particles were added to the toner so that the toner surface coverage with the inorganic fine particles was about 93%.
(Example 13)
In the developing device shown in Example 8, the one in which silica oxide was added to 1.85 parts so that the value of the toner coverage A of the inorganic fine particles was about 150% was used.
(Example 14)
In the developing device shown in Example 8, a mixture of toner and carrier was used so that the carrier coverage of the toner was about 85%.
(Example 15)
In the developing device shown in Example 8, the developer pumping amount on the developing roller 13a was changed to 60 mg / cm ² .
(Example 16)
In the developing device shown in Example 8, a developing device in which the amount of developer dropped from the first relay portion 13f was changed to 9 g / second was used.

(Comparative Example 1)
The experiment was conducted without installing the diffusion member 13d. As shown in FIG. 22, the evaluation result was x. This is presumably because the carrier surface area in the developer that can substantially contact the replenishing toner is reduced by not installing the diffusing member 13d.
(Comparative Example 2)
In the developing device shown in Example 8, a carrier having a volume average particle diameter of 18 μm was used. However, the carrier coating was not changed, and the toner and the carrier were mixed so that the carrier coverage of the toner was about 55%.
As shown in FIG. 22, the evaluation result was x. This is probably because the surface area of the carrier is increased, the deterioration of the developer is greatly promoted, the fluidity is deteriorated, and the dispersibility of the replenishment toner is deteriorated.
(Comparative Example 3)
In the developing device shown in Example 8, the toner A was classified and changed to a toner having a toner volume average particle size of 2.6 μm and Dv / Dn of 1.38. However, the inorganic fine particles were added to the toner so that the toner surface coverage with the inorganic fine particles was about 93%.
As shown in FIG. 22, the evaluation result was x. It is considered that the toner particle size is too small, the cohesive force between the toners is increased, the developer fluidity is deteriorated, and the replenishment toner dispersibility is deteriorated.
(Comparative Example 4)
In the developing device shown in Example 8, the one in which 0.15 part of silica oxide was added so that the value of the toner coverage A of the inorganic fine particles was about 36.4% was used.
As shown in FIG. 22, the evaluation result was x. This is probably because the coating amount of the inorganic fine particles is too small, so that the flowability of the developer is poor and the dispersibility of the replenishing toner is deteriorated.
(Comparative Example 5)
In the developing device shown in Example 8, a mixture of toner and carrier was used so that the carrier coverage of the toner was about 100%.
As shown in FIG. 22, the evaluation result was x. This is probably because there was no carrier surface area that could hold the replenishment toner, and the replenishment toner could not be dispersed.
(Comparative Example 6)
In the developing apparatus shown in Example 8, a developer whose pumping amount of developer on the developing roller 13a was changed to 25 mg / cm ² was used.
As shown in FIG. 22, the evaluation result was x. This is presumably because the surface area of the carrier contained in the collected developer has decreased.
(Comparative Example 7)
In the developing device shown in Example 8, a developer whose amount of developer dropped from the first relay portion 13f was changed to 3 g / sec was used.
As shown in FIG. 22, the evaluation result was x. This is probably because the amount of developer dropped from the first relay portion 13f was small and the carrier surface area was reduced.

  As can be seen from the evaluation results in FIG. 22, the developer G detached from the developing roller 13a (developer carrier) is transferred to the developer G in the second transport path by the second transport screw 13b2 (second transport member). By installing the diffusion member 13da that diffuses before mixing, the developer G detached from the developing roller 13a in the second transport path can be sufficiently stirred and mixed, and image density unevenness occurs on the output image. The trouble is reduced.

  In each of the above embodiments, the toner T is supplied from the toner container 28 toward the developing device 13. However, the developer G (toner T and carrier C) is directed toward the developing device 13 from the toner container (developer container). Can also be supplied. In that case, a means for appropriately discharging excess developer from the developing device 13 is provided. Even in such a case, it is possible to obtain the same effects as those of the above embodiments.

  In each of the above embodiments, the present invention is applied to an image forming apparatus in which the developing device 13 is configured as a unit that is detachably attached to the main body of the image forming apparatus. However, the application of the present invention is not limited to this, and the present invention can naturally be applied to an image forming apparatus in which a part or all of the image forming unit is formed as a process cartridge.

  Further, in each of the above embodiments, the present invention is applied to the developing device 13 in which two conveying screws as conveying members are installed. However, three or more conveying screws are installed, and at least two conveying screws are included. The present invention can also be applied to a developing device in which is installed in the vertical direction. Further, in each of the above embodiments, the present invention is applied to the developing device 13 in which one developing roller 13a is installed. However, the present invention is also applied to a developing device in which a plurality of developing rollers 13a are installed in the vertical direction. Can be applied. In those cases, the same effects as those of the above-described embodiments can be obtained by installing the diffusion member 13d in the second transport path.

  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. It is a block diagram which shows an image creation part. (A) The schematic sectional view which looked at the upper part of the developing device in the longitudinal direction, (B) The schematic sectional view which looked at the lower part of the developing device in the longitudinal direction. It is the schematic sectional drawing which looked at the circulation path of the developing device in the longitudinal direction. It is a top view which shows a diffusion member. It is a block diagram which shows the developing device in Embodiment 2 of this invention. It is a top view which shows the diffusion member installed in the developing device of FIG. It is a block diagram which shows the developing device in Embodiment 3 of this invention. It is the schematic sectional drawing which looked at the circulation path of the developing device in Embodiment 4 of this invention in the longitudinal direction. It is a block diagram which shows the developing device in Embodiment 5 of this invention. It is the schematic sectional drawing which looked at the circulation path of the developing device of the form different from the developing device of Drawing 10 in the longitudinal direction. It is a block diagram which shows the developing device in Embodiment 6 of this invention. It is a block diagram which shows the developing device of a form different from the developing device of FIG. FIG. 13 is a schematic cross-sectional view of a developing device in another form different from the developing device of FIG. 12 as viewed in the longitudinal direction. It is a top view which shows the diffusion member installed in the developing device in Embodiment 7 of this invention. It is sectional drawing which shows the vicinity of the hole formed in the diffusion member of FIG. It is a top view which shows the diffusion member of a form different from the diffusion member of FIG. It is a top view which shows the diffusion member of another form from the diffusion member of FIG. It is a top view which shows the diffusion member installed in the developing device in Embodiment 8 of this invention. It is a top view which shows the diffusion member installed in the developing device in Embodiment 9 of this invention. It is a top view which shows the diffusing member installed in the developing device in Embodiment 10 of this invention. It is a table | surface figure which shows an experimental result.

Explanation of symbols

1 image forming apparatus body (apparatus body),
11, 11Y, 11C, 11M, 11BK Photosensitive drum (image carrier),
13 Developing device (developing part),
13a Development roller (developer carrier),
13b1 first conveying screw (first conveying member),
13b2 second conveying screw (second conveying member),
13c Doctor blade (developer regulating member),
13d, 13da, 13db diffusion member (plate-like member),
G developer (two-component developer), T toner, C carrier.

Claims (19)

A developing device that contains a developer having a carrier and toner and that develops a latent image formed on an image carrier,
A developer carrying body facing the image carrying body and carrying a developer;
A plurality of transport members that transport the developer contained in the apparatus in the longitudinal direction to form a circulation path;
With
The plurality of conveying members are:
A first conveying member facing the developer carrying member and supplying the developer to the developer carrying member while conveying the developer in the longitudinal direction;
A second conveying member disposed below the first conveying member and facing the developer carrying member and conveying the developer detached from the developer carrying member in the longitudinal direction;
Comprising
2. A developing apparatus according to claim 1, wherein the transport path by the second transport member comprises a diffusing member that diffuses the developer separated from the developer carrying member before being mixed with the developer in the transport path.   2. The plate member according to claim 1, wherein the diffusing member is a plate-like member that is disposed between the developer carrying member and the second conveying member and has a plurality of holes or / and slits. The developing device described. When the area of the hole or / and slit of the plate-like member is M, the volume average particle diameter of the carrier is N1, and the volume average particle diameter of the toner is N2,
M ≧ π · [(N1 + N2 × 2) / 2] ²
The developing device according to claim 2, wherein the following relationship is established.   The developing device according to claim 2, wherein the plate-like member is formed so that each of the plurality of holes and / or slits has a constant area.   5. The plate member according to claim 2, wherein the plate-like member is disposed so as to be inclined such that a side closer to the developer carrier is lower than a side far from the developer carrier. The developing device according to 1.   6. The plate-like member according to claim 2, wherein the plate-like member is formed so that a thickness on a side close to the developer carrier is thicker than a thickness on a side far from the developer carrier. The developing device according to any one of the above.   The plate-like member is disposed so as to be inclined so that the upstream side of the transport path by the second transport member is lower than the downstream side of the transport path by the second transport member. The developing device according to claim 6.   The plate-like member is formed so that a thickness on an upstream side of a transport path by the second transport member is thicker than a thickness on a downstream side of the transport path by the second transport member. The developing device according to claim 2.   The developing device according to claim 2, wherein a plurality of the plate-like members are installed between the developer carrier and the second transport member.   The developing device according to claim 1, wherein a part or all of the diffusion member is formed of a conductive material.   The developing device according to claim 10, wherein a portion of the diffusion member formed of the conductive material is grounded.   12. The developing device according to claim 1, wherein the carrier has a volume average particle diameter of 20 to 60 [mu] m. The toner is obtained by coating inorganic fine particles having an average primary particle size of 5 to 50 nm on a toner base so that the coverage A is 40 to 200,
The coverage A is
A = (inorganic fine particle input amount [wt%] / 100) × inorganic fine particle projected area Sa [m ² / g] / ((1−inorganic fine particle input amount [wt%] / 100) × toner surface area Sc [m ² / g]) × 100
Is obtained by the following formula,
In the above formula, the toner surface area Sc and the inorganic fine particle projected area Sa are:
Sc = 3 / (toner volume average particle diameter [m] × toner specific gravity [g / m ³ ])
Sa = 3 / (4 × average particle size of inorganic fine particles [m] × specific gravity of inorganic fine particles [g / m ³ ])
The developing device according to claim 1, wherein the developing device is calculated by: The developer is obtained by coating the surface of the carrier with the toner so that the coverage B is 40 to 90,
The coverage B is
B = (toner input amount [wt%] / 100) × toner projected area Sb [m ² / g] / ((1−toner input amount [wt%] / 100) × carrier surface area Sd [m ² / g]) × 100
Is obtained by the following formula,
In the above formula, the carrier surface area Sd and the toner projected area Sb are:
Sd = 3 / (carrier volume average particle size [m] × carrier specific gravity [g / m ³ ])
Sb = 3 / (4 × toner volume average particle diameter [m] × toner specific gravity [g / m ³ ])
The developing device according to claim 1, wherein the developing device is calculated by: A first relay unit that drops the developer from the downstream side of the transport path by the first transport member toward the upstream side of the transport path by the second transport member;
The developing device according to claim 1, wherein the amount of developer dropped in the first relay portion is 5 to 10 g / second. A developer regulating member that regulates the amount of developer that is supplied by the first conveying member and carried on the developer carrying member;
16. The constitution in which the amount of developer carried on the developer carrying member after passing through the position of the developer regulating member is 30 to 70 mg / cm ^2. The developing device according to any one of the above.   The developer exceeding the wall portion of the transport path by the first transport member falls on the developer carrier and is supported on the developer carrier. The developing device according to claim 16. A process cartridge that is detachably installed on the main body of the image forming apparatus,
18. 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.

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