JP5376153B2 - Developing device, process cartridge, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device capable of preventing developer after a developing process in which the developer leaves a developer carrier in a second conveyance path from being carried on the developer carrier again, while preventing the rotational torque of the developer carrier from rising, when two conveyance members conveying the developer in the longitudinal direction and forming a circulation path are installed to oppose to the developer carrier and a developer regulation member is arranged below the developer carrier, and to provide a process cartridge and an image forming apparatus. <P>SOLUTION: The developing device includes a partition member 13d that partitions a first conveyance path formed by the first conveyance member 13b1 and a second conveyance path formed by the second conveyance member 13b2 from each other. The developing device also includes an opposing member 13k, facing a magnetic pole H4 on the upstream side among two magnetic poles H4, H6 forming a developer separating magnetic pole H5. <P>COPYRIGHT: (C)2011,JPO&amp;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. Developer regulation that regulates the amount of developer upstream of the development area, wherein at least two of the plurality of conveyance members that are conveyed to form a circulation path are arranged to face the developer carrier. The present invention relates to a developing device, a process cartridge, and an image forming apparatus in which members are disposed below a developer carrier.

  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. And a developer regulating member for regulating at least two conveying members in a vertical direction among a plurality of conveying members that form a circulation path by conveying in a direction, and for regulating a developer amount upstream of a developing region The technique of arrange | positioning below is known (for example, refer patent documents 1-3 grade | etc.,).

  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) installed below the developing roller, the toner in the two-component developer is transferred to the photosensitive drum (image carrier). To the latent image on the photosensitive drum at a position opposite to (). A magnet is fixed inside the developing roller, and a plurality of magnetic poles are formed around the developing roller by the magnet.

  In the developing device in Patent Document 1 or the like, a first conveying member (supply screw) and a second conveying member (collection screw) are installed in the vertical direction, and a developer circulation path is formed by these conveying members. ing. The first conveying member installed below supplies the developer to the developing roller at the position of the pumping magnetic pole while conveying the developer in the longitudinal direction. The second conveying member installed above conveys the developer separated from the developer roller at the position of the agent separating magnetic pole 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 unit. Then, the developer that has reached the downstream side of the first transport path stays at that position and is pushed up to reach the upstream side of the second transport 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 the second relay unit. Then, the developer that has reached the downstream side of the second conveyance path falls by its own weight on the second relay unit and is moved to the upstream side of the first conveyance path.

  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. 19 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 the developing device in which a plurality of conveying members are arranged in parallel in the horizontal direction (see, for example, FIG. 19 of Patent Document 2) and is carried on the developing roller in the developing process. Since the developer to be provided does not easily contain the developer after the development step, the density deviation of the toner image formed on the image carrier can be reduced.

  In addition, the image forming apparatus including the developing device in which the doctor blade (developer regulating member) is disposed below the developing roller as described above has a developing device (for example, a doctor blade disposed above the developing roller (for example, The length of the sheet conveyance path from the sheet feed unit (sheet storage unit) disposed below the image forming apparatus to the sheet discharge tray can be shortened as compared with the apparatus having the image forming apparatus (see FIG. 19 of Patent Document 2). Therefore, the first print time in the tandem type color image forming apparatus can be shortened (see, for example, FIG. 1 of Patent Document 2). Furthermore, since the layout in which the paper discharge tray is arranged above the image forming apparatus can be easily taken even if the paper transport path is relatively short, a tandem color image with a reduced horizontal size is provided. Often used in forming equipment.

In the developing devices described in Patent Documents 1 to 3 and the like described above, the developer after the developing process that has left the developing roller at the position of the agent separating magnetic pole in the second transport path may be carried again on the developing roller. there were. Such a problem is a problem that cannot be particularly ignored in the developing device in which the second transport path (collection path) is disposed above the first transport path (supply path).
When such a problem occurs, the developer carried on the developing roller and used for the developing step includes the developer after the developing step (the developer in which the toner is consumed). The toner image formed on the image carrier has a density deviation.

In order to suppress such a problem, the partition member that partitions the first transport path and the second transport path is made to face the developer carrier, and the position of the agent separation magnetic pole and the position of the second transport path are optimized. Measures can be considered. Further, in order to surely release the developer from the developing roller at the position of the agent separation magnetic pole, a method of setting the magnetic force of the two same-polarity magnetic poles forming the agent separation magnetic pole sufficiently large is conceivable.
However, in such a case, the developer separated from the developing roller at the position of the agent separating magnetic pole by the magnetic force of the upstream side of the two magnetic poles forming the agent separating magnetic pole is again carried (re-used) on the developing roller. There is a possibility that a problem will occur. If such a problem occurs, the load on the developing roller at the position where the developer is carried again increases, and the rotational torque of the developing roller increases.

  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 provided on the developer carrier. It is a case where the developer regulating member is disposed so as to be opposed to each other and disposed below the developer carrier, and the developer is reduced in the second transport path while reducing an increase in the rotational torque of the developer carrier. It is an object of the present invention to provide a developing device, a process cartridge, and an image forming apparatus that suppress the developer after the development process separated from the carrier from being carried on the developer carrier again.

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 developer carrying body facing the body and having a plurality of magnetic poles formed around it, and a developer carried on the developer carrying body and arranged to face the lower side of the developer carrying body A developer regulating member that regulates the amount of the developer, and a plurality of conveying members that convey the developer contained in the apparatus in the longitudinal direction to form a circulation path, wherein the plurality of conveying members are the developer A first conveying member facing the carrier and supplying the developer to the developer carrier while conveying the developer in the longitudinal direction; and the developer carrier disposed above the first conveying member. And the developer carrying member A second conveying member that conveys the developer separated from the developer in the longitudinal direction, and at a position facing the developer carrying member, the first conveying path by the first conveying member and the second conveying member. A partition member for separating the second transport path is further provided, and the developer carrying member has the same polarity as the agent separating magnetic pole for releasing the developer carried on the developer carrying member among the plurality of magnetic poles. The developer carrying member of the two magnetic poles is formed at a position upstream of the developer carrying member in the rotation direction with respect to the position where the partition member faces the developer carrying member. A counter member is provided opposite to the magnetic pole formed on the upstream side of the rotation direction of the body, and the counter member rotates in the direction of rotation of the developer carrier when viewed in a cross section perpendicular to the rotation center axis of the developer carrier. The tip located on the downstream side is the current In which extending downwardly from the virtual horizontal line passing through the rotational center axis of the carrying member.

  According to a second aspect of the present invention, there is provided the developing device according to the first aspect of the present invention, wherein the opposing member is the developer when viewed in a cross section perpendicular to the rotation center axis of the developer carrier. The facing surface facing the carrier is formed so as to be parallel to a virtual tangent passing through the closest point on the developer carrier relative to the facing member.

  According to a third aspect of the present invention, there is provided the developing device according to the second aspect, wherein the opposing member has a gap between the opposing surface and the closest point of the developer carrying member. It is formed so as to be equivalent to the gap between the regulating member and the developer carrier.

  The developing device according to a fourth aspect of the present invention is the developing device according to any one of the first to third aspects, wherein the opposing member is a tip located downstream in the rotation direction of the developer carrier. The part is extended toward the inside of the second transport path.

A developing device according to a fifth aspect of the present invention is the developing device according to any one of the first to fourth aspects, wherein the facing member is made of a nonmagnetic material.

  According to a sixth aspect of the present invention, in the developing device according to any one of the first to fifth aspects, the opposing member is formed integrally with the developing case.

  According to a seventh aspect of the present invention, there is provided the developing device according to any one of the first to sixth aspects, wherein the carrier has a weight average particle diameter of 20 to 60 μm. It is a thing.

The developing apparatus according to the invention of claim 8 is the invention according to any one of the claims 1 to 7, wherein the second conveying member is orthogonal to the central axis of rotation of said developer carrying member When viewed in cross section, the position of the rotation center axis of the second transport member is below a virtual horizontal line passing through the upper end of the developer carrier and above a virtual horizontal line passing through the lower end of the developer carrier. It is arrange | positioned so that it may become.

The developing apparatus according to the invention of claim 9, wherein, in the invention described in any one of the claims 1 to 8, wherein the first conveying member is perpendicular to the axis of rotation of said developer carrying member When viewed in cross section, the position of the rotation center axis of the first transport member is a virtual vertical line passing through the rotation center axis of the second transport member, and a virtual vertical line passing through the rotation center axis of the developer carrier. Are arranged so as to be in between.
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 the toner has a volume average particle diameter of about 5.8 μm. It has been done.
A process cartridge according to an eleventh aspect of the present invention is a process cartridge that is detachably installed on the apparatus main body of the image forming apparatus, and the process cartridge according to any one of the first to tenth aspects. The developing device and the image carrier are integrated.
An image forming apparatus according to a twelfth aspect of the present invention includes the developing device according to any one of the first to tenth 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, at least two conveying members among a plurality of conveying members that convey the developer in the longitudinal direction to form a circulation path are installed so as to face the developer carrying member, and the developer regulating member is the developer. The partition member is disposed below the carrier, and the partition member is opposed to the developer carrier, and an opposing member that is opposed to the upstream magnetic pole of the two magnetic poles forming the agent separation magnetic pole is provided. Therefore, it is possible to reduce the increase in the rotational torque of the developer carrier, and to prevent the developer after the development process separated from the developer carrier in the second transport path from being carried on the developer carrier again. A developing device, a process cartridge, and an image forming apparatus can be provided.

1 is an overall configuration diagram illustrating an image forming apparatus according to an embodiment 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 sectional drawing which shows a developing device. It is a schematic diagram which shows the magnetic field formed in the vicinity of a partition member and an opposing member. (A) Schematic diagram showing the developer flow in the vicinity of the agent separating magnetic pole when the opposing member is installed, and (B) Schematic diagram showing the developer flow in the vicinity of the agent separating magnetic pole when no opposing member is installed. And.

Embodiment.
Hereinafter, embodiments 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.

First, the configuration and operation of the entire image forming apparatus will be described with reference to FIG.
In FIG. 1, 1 is a main body of a tandem type color copier as an image forming apparatus, 3 is a document conveying unit that conveys a document to a document reading unit, 4 is a document reading unit that reads image information of a document, and 5 is an output image. , 7 is a paper feed 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, 11C, and 11BK are each color (yellow). , Magenta, cyan, and black), a photosensitive drum as an image carrier on which a toner image is formed, and a developing device 13 that develops electrostatic latent images formed on the photosensitive drums 11Y, 11M, 11C, and 11BK. , 14 is a transfer bias roller (primary transfer bias roller) for transferring the toner images formed on the photosensitive drums 11Y, 11M, 11C, and 11BK on the recording medium P in an overlapping manner. It is.
Reference numeral 17 denotes an intermediate transfer belt onto which a plurality of color toner images are transferred, 18 denotes a secondary transfer bias roller for transferring the color toner image on the intermediate transfer belt 17 onto the recording medium P, and 20 denotes a recording medium. A fixing device 28 for fixing an unfixed image on P, and a toner container for each color for supplying toner (toner particles) of each color (yellow, cyan, magenta, black) to the developing device 13.

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 is transported from the document table by the transport rollers of the document transport unit 3 and placed on the contact glass of the document reading unit 4. Then, the document reading unit 4 optically reads the image information of the document placed on the contact glass.

  Specifically, the document reading unit 4 scans an image of a document on the contact glass while irradiating light emitted from an illumination lamp. Then, the light reflected from the original is imaged on the color sensor via the mirror group and the lens. The color image information of the original is read for each color separation light of RGB (red, green, blue) 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, image information of each color of yellow, magenta, cyan, and black is transmitted to a writing unit (not shown). Then, a laser beam L (see FIG. 2) based on the image information of each color is emitted from the writing unit 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 (see FIG. 2) (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, laser beams corresponding to the image signals are emitted from the four light sources corresponding to the respective colors. 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 rotation 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 charged by the charging unit 12.

  Similarly, the laser beam corresponding to the magenta component is irradiated onto 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 photoconductive 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 counterclockwise in the drawing, and the secondary transfer bias roller 18 and 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 an intermediate transfer belt cleaning unit (not shown). Then, the untransferred toner attached on the intermediate transfer belt 17 is collected by the intermediate transfer belt cleaning unit, 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 thereafter. In the fixing device 20, the color image is fixed on the recording medium P at the nip between the fixing roller 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 discharge roller and stacked on the discharge tray 5 to complete a series of image forming processes.

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. 3A is a schematic cross-sectional view (horizontal cross-sectional view) of the upper portion of the developing device 13 (the position of the second transport screw 13b2 as the second transport member) in the longitudinal direction. (B) is a schematic cross-sectional view of the lower part of the developing device 13 (the position of the first conveying screw 13b1 as the first conveying member) 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 cross-sectional view showing the developing device (a cross-sectional view perpendicular to the rotation center axis of the developing roller 13a), and normal direction components of the magnetic poles H1 to H6 formed on the developing roller 13a. It also shows the distribution of magnetic force. Furthermore, FIG. 6 is a schematic diagram showing a magnetic field formed in the vicinity of the partition member 13d and the opposing member 13k. FIG. 7A is a schematic diagram showing the flow of the developer in the vicinity of the agent separating magnetic pole H5 when the counter member 13k is installed, and FIG. 7B is the agent when the counter member 13k is not installed. FIG. 6 is a schematic diagram illustrating a developer flow in the vicinity of a separation magnetic pole H5.
Since each image forming unit has substantially the same structure, the image forming unit and the developing device are illustrated in FIG. 2 to FIG. 7 except for alphabets (Y, C, M, BK).

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 photoconductor drum 11 as an image carrier is a negatively charged organic photoconductor having an outer diameter of about 30 mm, and is driven to rotate counterclockwise by a rotation drive 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 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. In this embodiment, 300 grams of developer G having a toner concentration of 7% by weight 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. 1, toner container 28 contains toner T to be supplied into developing device 13 therein. Specifically, toner conveyance (not shown) is performed based on information on the toner density (the ratio of toner in the developer G) detected by a magnetic sensor (not shown) installed in the developing device 13. The toner T is appropriately supplied from the toner supply port 13e from the toner container 28 into the developing device 13 through the tube.
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.

Hereinafter, the developing device 13 in the image forming apparatus will be described in detail.
2 to 6, the developing device 13 includes a developing roller 13a as a developer carrying member, conveying screws 13b1 and 13b2 (auger screws) as conveying members, a doctor blade 13c as a developer regulating member, and a partition. It is comprised by the member 13d, the opposing member 13k, etc.
A developing roller 13a as a developer carrying member is a developing roller having a small outer diameter of about 18 mm, and includes a sleeve 13a2 formed by forming a non-magnetic material such as aluminum, brass, stainless steel, or conductive resin into a cylindrical shape. It is configured to be rotated counterclockwise at about 150 to 600 rpm by a rotation driving mechanism (not shown). 3 and 5, a magnet 13a1 for forming a plurality of magnetic poles H1 to H6 is fixed on the peripheral surface of the sleeve 13a2 in the sleeve 13a2 of the developing roller 13a. The developer G carried on the developing roller 13a is conveyed as the developing roller 13a rotates in the direction of the arrow, and reaches the position of the doctor blade 13c. The developer G on the developing roller 13a is regulated to an appropriate amount at this position, and then conveyed to a position facing the photosensitive drum 11 (which is a developing region). The toner is attracted to the latent image formed on the photosensitive drum 11 by the electric field (developing electric field) formed in the developing area.

FIG. 5 shows a plurality of magnetic poles H1 to H6 formed around the developing roller 13a (sleeve 13a2) by the magnet 13a1. As shown in FIG. 5, the plurality of magnetic poles are a first magnetic pole H <b> 1 (main magnetic pole) formed at a position facing the photosensitive drum 11, a position on the downstream side of the first magnetic pole H <b> 1 and on the upper part of the developing case. The second magnetic pole H2 (conveying magnetic pole) formed on the second magnetic pole, the third magnetic pole (conveying magnetic pole) formed on the downstream side of the second magnetic pole H1 and upstream of the fourth magnetic pole H4 (pre-agent separating pre-magnetic pole), third A fifth magnetic pole H5 formed between the fourth magnetic pole H4 (agent separating pre-magnetic pole) formed downstream of the magnetic pole H3 and the fourth magnetic pole H4 and the sixth magnetic pole H6 and in the vicinity of the partition member 13d. (Agent separating magnetic pole), a sixth magnetic pole H6 (pumping magnetic pole) formed from a position facing the first conveying screw 13b1 to a position facing the doctor blade 13c, and the like.
First, the sixth magnetic pole H6 (pumping magnetic pole) acts on a carrier as a magnetic body, and the developer G accommodated in the first transport path is pumped onto the developing roller 13a. Part of the developer G carried on the developing roller 13a is scraped off at the position of the doctor blade 13c and returned to the first transport path. On the other hand, the developer G carried on the developing roller 13a through the doctor gap between the doctor blade 13c and the developing roller 13a at the position of the doctor blade 13c where the magnetic force by the sixth magnetic pole H6 acts is the first magnetic pole H1. It rises at the position of the (main magnetic pole) and becomes a magnetic brush in the developing region, and comes into sliding contact with the photosensitive drum 11. Thus, the toner T in the developer G carried on the developing roller 13 a adheres to the latent image on the photosensitive drum 11. Thereafter, the developer G that has passed the position of the first magnetic pole H1 is conveyed to the position of the fifth magnetic pole H5 (agent separating magnetic pole) by the second magnetic pole H2, the third magnetic pole H3, and the third magnetic pole H4. Then, at the position of the agent separating magnetic pole H5, a repulsive magnetic field (a magnetic field acting in a direction away from the developing roller 13a in FIG. 6) acts on the carrier, and after the developing process carried on the developing roller 13a. The developer G is detached from the developing roller 13a. The detached developer G falls into the second transport path and is transported downstream of the second transport path by the second transport screw 13b2.

  Here, with reference to FIG. 5, the above-mentioned six magnetic poles H1 to H6 have five poles magnetized on the magnet 13a1 of the developing roller 13a (in FIG. 5, the reference numeral “(N)” or “(S ) ”. That is, of the six magnetic poles H1 to H6, only the fifth magnetic pole H5 (agent separating magnetic pole) is not directly formed by the pole magnetized on the magnet 13a1, but is the same pole (in this embodiment). , S pole), and sandwiched between two magnetic poles (fourth magnetic pole H4 and sixth magnetic pole H6).

Referring to FIG. 2 and the like, the doctor blade 13c as a developer regulating member is a non-magnetic plate-like member disposed below the developing roller 13a (a part of which can be formed of a magnetic material). It is. The developing roller 13a rotates counterclockwise in FIG. 2, and the photosensitive drum 11 rotates clockwise in FIG.
With such a configuration, the photosensitive drum 11 is disposed below the intermediate transfer belt 17 for the purpose of shortening the conveyance path of the recording medium P and reducing the horizontal size of the image forming apparatus main body 1. Even so, since the rotation direction of the developing roller 13a can be the forward direction with respect to the photosensitive drum 11 in the developing gap, the doctor blade 13c is provided above the developing roller 13a and the photosensitive drum 11 is disposed. As compared with the case where the rotation direction of the developing roller 13a is opposite, the developing time in the developing gap can be sufficiently secured and the developing ability can be enhanced.

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. 3B). The developer G is supplied onto the developing roller 13a at the position of the pumping magnetic pole H6 (sixth magnetic pole) (the supply in the direction of the white arrow in FIG. 3B). .) The first transport screw 13b1 rotates counterclockwise in FIG.

The second conveying screw 13b2 as the second conveying member is disposed above the first conveying 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 separating magnetic pole H5 after the developing process, and separated in the direction of the white arrow in FIG. 3A. Is transported horizontally in the longitudinal direction (the transport in the right direction indicated by the broken-line arrow in FIG. 3A). In the present embodiment, the rotation direction of the second conveying screw 13b2 is set to be opposite to the rotation direction of the developing roller 13a (clockwise in FIG. 2).
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 the conveyance shown by the dashed-dotted arrow of FIG. 3).
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. Moreover, as for the two conveyance screws 13b1 and 13b2, both have a screw part (screw pitch: about 40 mm, number of threads: one or two) with a shaft part with a shaft diameter of about 6 to 10 mm and an outer diameter of about 20 mm. It is wound in a spiral. Moreover, the rotation speed of the two conveyance screws 13b1 and 13b2 is set to about 600 to 900 rpm.

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. The developer G that has reached the downstream side of the second conveyance path by the second conveyance screw 13b2 falls by its own weight at the second relay portion 13g and reaches the upstream side of the first conveyance path.
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 conveyance path by the first conveyance screw 13b1 stays in the vicinity of the first relay portion 13f and rises up, and then passes through the first relay portion 13f. It is transported (supplied) to the upstream side of the second transport path by the two transport screws 13b2.
In addition, in order to improve the transportability of the developer (transfer of the developer against the direction of gravity from the first transport path to the second transport path) in the first relay portion 13f, the first transport screw 13b1 A paddle-shaped portion or a screw portion in which the winding direction of the screw is formed in the reverse direction can be provided at a downstream position (a position corresponding to the first relay portion 13f).

  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, the toner container 28 is directed into the developing device 13 through the toner supply port 13e (located in the vicinity of the first relay portion 13f). New toner T is supplied.
3 and 4, the toner replenishing port 13e is located above the upstream side of the transport path by the second transport screw 13b2 and away from the developing area (the range in the longitudinal direction of the developing roller 13a). It is arranged outside.). By installing the toner replenishing port 13e in the vicinity of the first relay portion 13f in this way, the developer detached from the developing roller 13a falls from above the replenishment toner having a small specific gravity in the second transport path, and the second transport path. The replenishment toner can be sufficiently dispersed and mixed with respect to the developer over a relatively long time toward the downstream side.
In the present embodiment, the toner replenishing port 13e is disposed in the conveying path by the second conveying screw 13a2, but the position of the toner replenishing port 13e is not limited to this, and for example, in the first conveying path. It can also be arranged above the upstream side.

  Referring to FIG. 4, in the first transport path, in order to supply the developer to the developing roller 13a while transporting the developer in the longitudinal direction, the upstream side except for the vicinity of the first relay portion 13f. The developer surface of the developer G becomes lower as it goes downstream. On the other hand, in the second transport path, the developer surface of the developer G is directed from the upstream side toward the downstream side in order to collect the developer separated from the developing roller 13a while transporting the developer in the longitudinal direction. Is getting higher.

Hereinafter, the developer G used in the present embodiment will be briefly described.
The toner T (the toner in the developer G and the toner in the toner container 28) used in the present embodiment is a polymerized toner, and a styrene-acrylonitrile-acrylate copolymer as a binder resin. Styrenic resin (monopolymer or copolymer containing styrene or a styrene-substituted product), polyester resin, epoxy resin, or a composite of them can be used. In addition, as a production method (polymerization method) of these polymerized toners, bulk polymerization, solution polymerization, emulsion polymerization, suspension polymerization, and the like can be used.
Further, as the external additive of the toner T, it is preferable to use inorganic fine particles (for example, those having 1.0% by weight of silica and 0.5% by weight of titanium oxide). Furthermore, oxidized rice wax, low molecular weight polypropylene wax, carnauba wax and the like can be used as a release agent. Moreover, a charge control agent can be contained as required.
Further, the toner T used in the present embodiment has a volume average particle diameter of 5.8 μm, and the toner T having a particle diameter of 5 μm or less is formed to be 60 to 80% by number.
In this embodiment, polymerized toner is used, but pulverized toner can also be used.

The carrier C in the developer G used in the present embodiment is formed so that the weight average particle diameter is 20 to 60 μm. In the present embodiment, carrier C having a weight average particle diameter of 35 μm is used.
Specifically, the carrier C is formed by coating the ferrite particles serving as the core material with a methyl methacrylate resin (MMA) having a film thickness of 0.5 μm so as to have the above-described particle size. As the carrier C, a coating carrier having magnetite as a core material can also be used.
By using the carrier C having such a small particle diameter, the solid uniformity of the output image and the halftone image quality can be improved.

Hereinafter, a characteristic configuration / operation in the developing device 13 of the present embodiment will be described.
With reference to FIG. 5, FIG. 6, etc., in the developing device 13 in the present embodiment, a partition member 13d (separating plate) that partitions the first transport path and the second transport path at a position facing the developing roller 13a. Is provided. In other words, the developer G released from the developing roller 13a is reduced from being carried on the developing roller 13a again between the first conveying path and the second conveying path at a position facing the developing roller 13a. A partition member 13d is provided.
Specifically, the partition member 13d functions as a wall portion that separates the first conveyance path and the second conveyance path, and is formed to protrude toward the developing roller 13a. Further, the partition member 13d is formed integrally with a developing case (a case member indicated by hatching in FIG. 2). The partition member 13d is formed so that the gap between the facing surface facing the developing roller 13a and the developing roller 13a is 2 mm or less (preferably 0.1 to 0.5 mm). In the present embodiment, the gap between the partition member 13d and the developing roller 13a is set to 0.3 mm.
Referring to FIG. 6, the boundary region between the second conveyance path and the first conveyance path is from the inside of the second conveyance path to the developing roller 13a (on the first conveyance path side) due to the influence of the sixth magnetic pole H6. ) Is formed. By providing the partition member 13d at a position that blocks this magnetic field, it is possible to prevent a problem that the developer immediately after being collected in the second transport path is re-supported by the developing roller 13a. Further, since the partition member 13d is disposed so as to face the developing roller 13a in a non-contact manner, it is possible to reduce a problem that damages the surface of the developing roller 13a.
Since the partition member 13d is formed of a nonmagnetic material, the carrier, which is a magnetic body, is magnetically attracted to the partition member 13d to obstruct the flow of the developer in the second transport path. Problems such as promoting the movement of the developer to the transport path are reduced.

With reference to FIG. 5, in the present embodiment, the second transport screw 13b2 (second transport member) is viewed in a cross section (FIG. 5) perpendicular to the rotation center axis of the developing roller 13a. The position of the rotation center axis of the second transport screw 13b2 is disposed below the virtual horizontal line passing through the upper end of the developing roller 13a and above the virtual horizontal line passing through the lower end of the developing roller 13a. That is, the position of the rotation center axis of the second transport screw 13b2 (or the virtual horizontal line S2 passing therethrough) is disposed in the range indicated by the double arrow M1.
With this configuration, the developer G after the development process carried on the developing roller 13a has a magnetic force that works in the direction of positively separating the developer G from the developing roller 13a at the position of the agent separating magnetic pole H5. In addition to the force (the outward magnetic force indicated by the one-dot chain line in FIG. 6), the centrifugal force due to the rotation of the developing roller 13a, the pressure pushed by the developer on the downstream side, and the resultant force such as gravity act. Will do. As a result, the developer G after the development process carried on the developing roller 13a is efficiently separated from the developing roller 13a and separated at the position of the partition member 13d without causing a defect of separation from the developing roller 13a. The developer G is smoothly collected on the second transport path. Therefore, the developer G after the developing process separated from the developing roller 13a in the second transport path is hardly re-supported by the developing roller 13a immediately thereafter, and image density unevenness (density deviation) occurs on the output image. Defects are reliably reduced.

Referring to FIG. 5, in the present embodiment, the peak magnetic force of the first magnetic pole H1 is about 110 mT, the peak magnetic force of the second magnetic pole H2 is about 70 mT, the peak magnetic force of the third magnetic pole H3 is about 78 mT, The peak magnetic force of the magnetic pole H4 is set to about 45 mT, and the peak magnetic force of the sixth magnetic pole H6 is set to about 65 mT.
The position of the agent separating magnetic pole H5 (fifth magnetic pole) can be varied by adjusting the position (half-value central angle) and the magnitude (peak magnetic force) of the fourth magnetic pole H4 and the sixth magnetic pole H6. However, the peak magnetic force of the fourth magnetic pole H4 and the sixth magnetic pole H6 is sufficiently large to the above-mentioned magnitude in order to surely prevent the rotation of the developer at the position of the agent separating magnetic pole H5 (separation failure). It is preferable to set a large value.

Furthermore, referring to FIG. 5 and the like, in the present embodiment, the partition member 13d is positioned upstream of the position facing the developing roller 13a (on the upstream side in the rotation direction of the developing roller 13a). A counter member 13k (separation auxiliary plate) is provided to face the four magnetic poles H4 (the magnetic poles formed on the upstream side in the rotation direction of the developing roller 13a of the two magnetic poles H4 and H6 forming the agent separating magnetic pole H5). Yes.
Specifically, the facing member 13k functions as a wall portion that separates the position of the fourth magnetic pole H4 from the developing roller 13a and the second transport path. The opposing member 13k is formed integrally with a developing case (a case member indicated by hatching in FIG. 2).
Referring to FIG. 6, the upstream side of the agent separating magnetic pole H5 (in FIG. 6, the repulsive magnetic field acting in the direction away from the developing roller 13a) is affected by the fourth magnetic pole H4 (agent separating pre-magnetic pole). A magnetic field is formed toward the upstream side of the developing roller 13a. By providing the opposing member 13k at a position where the magnetic field is blocked, it is possible to prevent a problem that the developer detached from the developing roller 13a at the position of the agent separating magnetic pole H5 is again carried (reloaded) on the developing roller 13a. Can do.

That is, as shown in FIG. 7B, when the opposing member 13k is not installed, the agent separation is caused by the magnetic field toward the upstream side of the developing roller 13a due to the influence of the fourth magnetic pole H4 (agent separation pre-magnetic pole). A part of the developer (developer that moves in the direction of the white arrow) separated from the developing roller 13a at the position of the magnetic pole H5 moves to the upstream side of the developing roller 13a (the movement in the direction of the black arrow). As a result, it is re-supported on the developing roller 13a. If such a phenomenon occurs, the load on the developing roller 13a at the position where the developer is re-loaded increases, or the re-loaded developer is detached from the developing roller 13a at the position of the agent separating magnetic pole H5. The gap between the partition member 13d and the developing roller 13a enters the gap (or stays) without being closed, and the rotational torque of the developing roller 13a increases.
In contrast, in the present embodiment, as shown in FIG. 7A, since the opposing member 13k is installed at a position facing the fourth magnetic pole H4 (agent separating pre-magnetic pole), the fourth magnetic pole The magnetic field toward the upstream side of the developing roller 13a is blocked by the influence of H4, and the developer separated from the developing roller 13a at the position of the agent separating magnetic pole H5 moves to the upstream side of the developing roller 13a and moves on the developing roller 13a. The problem of being re-supported is reduced. That is, the developer separated from the developing roller 13a at the position of the agent separating magnetic pole H5 moves smoothly in the direction of the white arrow in FIG.
Since the opposing member 13k is made of a nonmagnetic material, the carrier, which is a magnetic material, is magnetically attracted to the opposing member 13k to inhibit the flow of the developer on the developing roller 13a, or the second conveyance. Problems such as hindering the movement of the developer to the path are reduced.
When the inventor of the present application conducted an experiment, the developing device 13 (in FIG. 7A) in the present embodiment is a developing device in which the opposing member 13k is not installed (in FIG. 7B). .)), It was confirmed that the rotational torque of the developing roller 13a can be reduced by about 15%.

Here, referring to FIG. 6 and the like, in the present embodiment, the facing member 13k has a facing surface 13k1 facing the developing roller 13a facing the developing roller 13a when viewed in a cross section perpendicular to the rotation center axis of the developing roller 13a. It is formed so as to be substantially parallel to a virtual tangent line S3 passing through the closest point Q on the developing roller 13a with respect to the member 13k.
With this configuration, the developer carried on the developing roller 13a does not stay at the position of the facing member 13k, and the developer carried on the developing roller 13a is directed toward the agent separating magnetic pole H5. Will be transported smoothly.

6 and the like, in the present embodiment, the opposing member 13k has a gap CG between the opposing surface 13k1 and the closest point Q of the developing roller 13a such that the gap between the doctor blade 13c and the developing roller 13a (doctor It is formed to be equivalent to the gap. Specifically, in the present embodiment, the gap CG between the facing member 13k and the developing roller 13a is set to about 0.5 mm.
With such a configuration, the height of the developer carried on the developing roller 13a at the position of the opposing member 13k (ear height) is set so that the developer carried on the developing roller 13a after the amount control is performed (the position of the doctor blade 13c). Therefore, it is possible to reduce the problem of applying stress to the developer carried on the developing roller 13a by the opposing member 13k. .

6 and the like, in the present embodiment, the opposing member 13k has a tip portion (a portion surrounded by a solid line circle in FIG. 6) located on the downstream side in the rotation direction of the developing roller 13a. , And bent at a right angle so as to extend toward the inside of the second transport path.
With such a configuration, the magnetic field toward the upstream side of the developing roller 13a can be surely cut off due to the influence of the fourth magnetic pole H4, and the developer separated from the developing roller 13a by the magnetic field is behind the opposing member 13k ( This is a surface opposite to the facing surface 13k1.

5 and 6 and the like, in the present embodiment, the opposing member 13k is a tip portion (a portion surrounded by a solid line circle in FIG. 6) located downstream in the rotation direction of the developing roller 13a. Is extended below the virtual horizontal line S1 passing through the rotation center axis of the developing roller 13a.
With such a configuration, the magnetic field toward the upstream side of the developing roller 13a can be reliably interrupted by the influence of the fourth magnetic pole H4.

Here, referring to FIG. 5, in the present embodiment, the position of the rotation center axis of the first conveyance screw 13b1 is the second conveyance screw 13b2 when viewed in a cross section orthogonal to the rotation axis of the developing roller 13a. The first conveying screw 13b1 is located between the virtual vertical line passing through the rotation center axis of the developing roller 13a and the virtual vertical line passing through the rotation center axis of the developing roller 13a (between the range M2 in FIG. 5). It is arranged.
Thus, the first conveying screw 13b1 can be brought close to the pumping magnetic pole H6 of the developing roller 13a, and the supply capability of the developer G to the developing roller 13a by the first conveying screw 13b1 can be improved.

  As described above, in the present embodiment, the two conveying screws 13b1 and 13b2 (conveying members) that convey the developer G in the longitudinal direction to form a circulation path face the developing roller 13a (developer carrier). The doctor blade 13c (developer regulating member) is disposed below the developing roller 13a, and the partition member 13d is opposed to the developing roller 13a so that the position of the agent separating magnetic pole H5 is And the position of the second transport path, and the opposing member 13k that opposes the upstream fourth magnetic pole H4 of the two magnetic poles H4 and H6 forming the agent separation magnetic pole H5 is provided. While reducing the increase in the rotational torque of the roller 13a, the developer G after the developing process separated from the developing roller 13a in the second transport path is again carried on the developing roller 13a. The case can be reliably reduced.

  In the present embodiment, the facing member 13k and the partition member 13d are formed integrally with the developing case, but the facing member and the partition member may be formed of a member different from the developing case. Specifically, for example, a plate-like facing member can be suspended from the developing case so as to face the fourth magnetic pole H4 of the developing roller 13a. In addition, a plate-like partition member can be attached to a wall portion that separates the first conveyance path and the second conveyance path in the developing case. In such a configuration, the accuracy of the parts of the developing case cannot be increased so much that the gap CG between the facing member and the developing roller 13a or the gap between the partition member and the developing roller 13a is to be set with high accuracy. Useful for.

  In this embodiment, the toner T is supplied from the toner container 28 toward the developing device 13, but the developer G (toner T and carrier C) is directed toward the developing device 13 from the toner container (developer container). It 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, the same effect as in the present embodiment can be obtained.

  Further, in the present embodiment, 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. In that case, the workability of maintenance of the image forming unit is improved.

In the present embodiment, 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 installed so as to face the developing roller 13a. In the present embodiment, the number of magnetic poles H1 to H6 formed around the developing roller 13a is six, but the number of magnetic poles formed around the developing roller 13a is five or less, or seven or more. You can also
In these cases, the same effect as in the present embodiment can be obtained by optimizing the position of the agent separation magnetic pole and the position of the second transport path.

  It should be noted that the present invention is not limited to the present embodiment, and it is obvious that the present embodiment can be modified as appropriate within the scope of the technical idea of the present invention, other than suggested in the present embodiment. is there. In addition, the number, position, shape, and the like of the constituent members are not limited to the present embodiment, and the number, position, shape, and the like suitable for implementing the present invention can be achieved.

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 partition member,
13e Toner supply port,
13f 1st relay part, 13g 2nd relay part,
13k facing member,
13k1 facing surface,
H1 first magnetic pole (main magnetic pole),
H2 second magnetic pole (conveying magnetic pole), H3 third magnetic pole (conveying magnetic pole),
H4 4th magnetic pole (agent separating pre-magnetic pole),
H5 5th magnetic pole (agent separating magnetic pole),
H6 6th magnetic pole (pumping magnetic pole),
G developer (two-component developer), T toner, C carrier.

Japanese Patent Laid-Open No. 11-174810 JP 2008-26408 A Japanese Patent No. 3950735

Claims (12)

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 having a plurality of magnetic poles formed around it;
A developer regulating member that is disposed so as to face the lower side of the developer carrying member and regulates the amount of the developer carried on the developer carrying member;
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 above the first conveying member to face the developer carrying member and convey the developer detached from the developer carrying member in the longitudinal direction;
Comprising
A partition member that partitions the first transport path by the first transport member and the second transport path by the second transport member at a position facing the developer carrier;
The developer carrying member is formed by being sandwiched between two magnetic poles having the same polarity as the agent separating magnetic pole for releasing the developer carried on the developer carrying member among the plurality of magnetic poles,
The partition member is formed at a position upstream of the developer carrying body in the rotation direction with respect to the position facing the developer carrying body, and is formed upstream of the two magnetic poles in the rotation direction of the developer carrying body. Provide a facing member that faces the magnetic pole ,
When the opposing member is viewed in a cross section orthogonal to the rotation center axis of the developer carrier, the tip located on the downstream side in the rotation direction of the developer carrier has the rotation center axis of the developer carrier. A developing device, wherein the developing device extends below a virtual horizontal line passing therethrough .   When the opposing member is viewed in a cross section perpendicular to the rotation center axis of the developer carrier, the opposing surface facing the developer carrier passes through the closest point on the developer carrier relative to the opposing member. The developing device according to claim 1, wherein the developing device is formed to be parallel to a virtual tangent.   The facing member is formed such that a gap between the facing surface and the closest point of the developer carrying member is equal to a gap between the developer regulating member and the developer carrying member. The developing device according to claim 2.   4. The counter member according to any one of claims 1 to 3, wherein a tip portion of the facing member that is located downstream in the rotation direction of the developer carrying member extends toward the inside of the second transport path. The developing device according to any one of the above. The developing device according to claim 1, wherein the facing member is made of a nonmagnetic material.   The developing device according to claim 1, wherein the facing member is formed integrally with a developing case.   The developing device according to claim 1, wherein the carrier has a weight average particle diameter of 20 to 60 μm. When the second transport member is viewed in a cross section orthogonal to the rotation center axis of the developer carrier, the position of the rotation center axis of the second transport member is a virtual horizontal line passing through the upper end of the developer carrier. 8. The developing device according to claim 1, wherein the developing device is disposed below and above a virtual horizontal line passing through a lower end of the developer carrying member. When the first transport member is viewed in a cross section orthogonal to the rotation center axis of the developer carrier, the position of the rotation center axis of the first transport member is an imaginary passage that passes through the rotation center axis of the second transport member. 9. The developing device according to claim 1, wherein the developing device is disposed so as to be between a vertical line and a virtual vertical line passing through a rotation center axis of the developer carrying member. . The developing device according to claim 1, wherein the toner has a volume average particle diameter of about 5.8 μm. A process cartridge that is detachably installed on the main body of the image forming apparatus,
11. A process cartridge in which the developing device according to claim 1 and the image carrier are integrated. An image forming apparatus comprising the developing device according to claim 1 and the image carrier.

Images