JP2011027880A - Developing device, process cartridge and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device having at least two of a plurality of conveying members for conveying a developer in a longitudinal direction and forming a circulation path, which faces a developer carrier, and preventing the developer separated from the developer carrier from being carried on the developer carrier again in a second conveying path; and to provide a process cartridge and an image forming apparatus. <P>SOLUTION: A partitioning member 13d for partitioning between a first conveying path by a first conveying member 13b1 and a second conveying path by a second conveying member 13b2 is disposed in a position facing the developer carrier 13a. Then, the partitioning member 13d is covered with a sheet-like member 13m which travels in a predetermined direction to guide the developer separated from the developer carrier 13a to the second conveying path. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a multifunction machine or a direct plate making machine thereof, and a developing device and a process cartridge installed therein, and in particular, conveys a developer in a longitudinal direction. In particular, the present invention relates to a developing device, a process cartridge, and an image forming apparatus in which at least two conveying members among a plurality of conveying members forming a circulation path are arranged to face 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.

  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. A developing device that suppresses the developer after the development process separated from the developer carrying member in the second transport path from being carried on the developer carrying member again when installed so as to face each other; A process cartridge and an image forming apparatus are provided.

  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 that faces the body and that carries the developer, and a developer that is disposed so as to face the developer carrying body and that regulates the amount of the developer carried on the developer carrying body. And a plurality of conveying members that convey the developer accommodated in the apparatus in the longitudinal direction to form a circulation path, and the plurality of conveying members face the developer carrier. A first conveying member that supplies the developer to the developer carrying member while conveying the developer in the longitudinal direction; and a developer that is opposed to the developer carrying member and that is separated from the developer carrying member in the longitudinal direction. Second conveying member that conveys in the direction And 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 carrying member, the partition member comprising: The sheet is covered with a sheet-like member that guides the developer, which has traveled in a predetermined direction and separated from the developer carrying member, to the second transport path.

  According to a second aspect of the present invention, in the developing device according to the first aspect, the sheet-like member travels in the same direction as the rotation direction of the developer carrier.

  A developing device according to a third aspect of the present invention is the developing device according to the first or second aspect, wherein the sheet-like member is formed with a plurality of holes.

  A developing device according to a fourth aspect of the present invention is the developing device according to the first or second aspect, wherein the sheet-like member has irregularities formed on the outer peripheral surface thereof.

  The 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 sheet-like member is formed of a fiber material at least on the outer peripheral surface thereof. is there.

  The developing device according to a sixth aspect of the present invention is the developing device according to any one of the first to fifth aspects, wherein the partition member faces the developer carrier via the sheet-like member. A magnetic material is provided at the position where

  A developing device according to a seventh aspect of the invention is the developing device according to any one of the first to fourth aspects, wherein the sheet-like member is formed of a magnetic material.

  The developing device according to an eighth aspect of the present invention is the developing device according to any one of the first to seventh aspects, wherein the developer regulating member faces the lower side of the developer carrier. The first transport member is disposed below the second transport member.

  The developing device according to a ninth aspect of the present invention is the developing device according to any one of the first to eighth aspects, wherein the carrier is formed such that a weight average particle diameter thereof is 20 to 60 μm. It is a thing.

  A process cartridge according to a tenth aspect of the present invention is a process cartridge that is detachably attached to the apparatus main body of the image forming apparatus, and is according to any one of the first to ninth aspects. The developing device and the image carrier are integrated.

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

  In the present application, the “process cartridge” refers to a charging unit that charges the image carrier, a developing unit (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.

  The present invention relates to a case where 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, Since the sheet-like member that positively conveys the developer separated from the developer carrying member toward the second conveyance path is installed in the partition member facing the body, the developer carrying in the second conveyance path It is possible to provide a developing device, a process cartridge, and an image forming apparatus that suppress the developer after the developing process released from the body from being carried again on the developer carrying member.

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 sectional drawing which shows a developing device. It is the schematic which shows a sheet-like member. It is an enlarged view which shows a part of developing device in Embodiment 2 of this invention.

  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.

Embodiment 1 FIG.
The first embodiment of the present invention will be described in detail with reference to FIGS.
First, the configuration and operation of the entire image forming apparatus will be described with reference to FIG.
In FIG. 1, 1 is 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 orthogonal to the rotation center axis of the developing roller 13a). Further, FIG. 6 is a schematic view showing the sheet-like member 13m.
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. 6 without the alphabet (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 rotated clockwise 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. 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 composed of a member 13d, a sheet-like member 13m, a driving roller 13n, and the like.
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 top of the developing case. The second magnetic pole H2 (conveying magnetic pole) formed on the second magnetic pole H3, the third magnetic pole H3 (agent separating pre-magnetic pole) formed downstream of the second magnetic pole H1 and above the developing roller 13a, the third magnetic pole H3 and the fifth magnetic pole H3 A fourth magnetic pole H4 (agent separating magnetic pole) formed between the magnetic pole H5 and above the tip of the partition member 13d, and a fifth magnetic pole H5 formed above the first transport path (after agent separation). Magnetic pole), a sixth magnetic pole H6 (pumping magnetic pole) formed from the position facing the first conveying screw 13b1 to the vicinity of the 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 fourth magnetic pole H4 (agent separating magnetic pole) by the second magnetic pole H2 and the third magnetic pole H3. Then, at the position of the agent separating magnetic pole H4, a repelling magnetic field (a magnetic field acting in a direction away from the developing roller 13a) acts on the carrier, and the developer G after the developing process carried on the developing roller 13a. 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, referring to FIG. 5, the above-described six magnetic poles H1 to H6 are five poles ("(N)" or "(S)" in the figure) magnetized on the magnet 13a1 of the developing roller 13a. This is the displayed part.) That is, out of the six magnetic poles H1 to H6, only the fourth magnetic pole H4 (agent separating magnetic pole) is not directly formed by the pole magnetized on the magnet 13a1, but the same pole (the first embodiment). Then, it is formed between two magnetic poles (the third magnetic pole H3 and the fifth magnetic pole H5).

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 H4 after the developing process, and is 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 first embodiment, the rotation direction of the second conveying screw 13b2 is set to be opposite to the rotation direction of the developing roller 13a (the clockwise direction 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 first embodiment, the toner replenishment port 13e is disposed in the conveyance path by the second conveyance screw 13a2, but the position of the toner replenishment port 13e is not limited to this, and for example, the first conveyance path It can also be arranged above the downstream 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 Embodiment 1 will be briefly described.
The toner T (the toner in the developer G and the toner in the toner container 28) used in the first embodiment is a polymerized toner, and a styrene-acrylonitrile-acrylic acid ester copolymer is used as a binder resin. Styrenic resins (monopolymer or copolymer containing styrene or styrene-substituted product), polyester resins, epoxy resins, or composites thereof 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 first embodiment has a volume average particle diameter of 6 μm, and the toner T having a particle diameter of 5 μm or less is formed to be 60 to 80% by number.
In the first embodiment, polymerized toner is used, but pulverized toner can also be used.

The carrier C in the developer G used in Embodiment 1 is formed so that the weight average particle diameter is 20 to 60 μm.
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 and operation of the developing device 13 according to the first embodiment will be described.
Referring to FIG. 5, the developing device 13 according to the first embodiment is provided with 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. ing. 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 part of a wall portion that separates the first conveyance path and the second conveyance path, and is formed so as to protrude toward the developing roller 13a. The partition member 13d is fixed so as to be sandwiched between the side walls at both ends of the developing case. The partition member 13d is formed so that the gap with the developing roller 13a is 2 mm or less (preferably 0.1 to 0.5 mm). In the first embodiment, the gap between the partition member 13d and the developing roller 13a is set to 0.3 mm. Moreover, the partition member 13d is formed of a resin material, like other wall portions that separate the first transport path and the second transport path.

Here, referring to FIG. 5, in Embodiment 1, partition member 13d is covered with sheet-like member 13m that travels in a predetermined direction (the counterclockwise direction in FIG. 5). The sheet-like member 13m is for guiding the developer separated from the developing roller 13a (developer carrier) to the second transport path.
Specifically, the sheet-like member 13m is an endless belt-like member made of PET (polyethylene terephthalate) having a thickness of about 0.1 mm. And the sheet-like member 13m is installed so that the partition member 13d may be covered. Furthermore, the driving roller 13n is installed so as to contact the inner peripheral surface of the sheet-like member 13m, and the driving roller 13n rotates counterclockwise in FIG. 13m rotates (runs) in the counterclockwise direction of FIG. 5 (the same direction as the rotation direction of the developing roller 13a).
Since the gap between the partition member 13d and the developing roller 13a is set to 0.3 mm, and the thickness of the sheet-like member 13m is set to about 0.1 mm, the sheet-like member 13m and the developing roller 13a are set. The gap is about 0.2 mm.

With such a configuration, the developer G separated from the developing roller 13a is positively transported toward the second transport path by the traveling of the sheet-like member 13m in the arrow direction. Therefore, the problem that 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 is reduced.
More specifically, the developer G after the development process carried on the developing roller 13a has a magnetic force (outward facing) acting in a direction in which the developer G is positively separated from the developing roller 13a at the position of the agent separating magnetic pole H4. In addition, a centrifugal force generated by the rotation of the developing roller 13a, a pressure pushed by the developer on the downstream side, and a resultant force such as gravity act. As a result, a part of the developer G after the developing process carried on the developing roller 13a detaches vigorously from the developing roller 13a and directly flies toward the second transport path. On the other hand, among the developer G after the developing process carried on the developing roller 13a, the other developer G does not fly directly into the second transport path, but the partition member 13d (sheet-like). It falls on the upper surface of the member 13m). However, the developer G that has fallen on the upper surface of the partition member 13d is positively conveyed toward the second conveyance path by traveling of the sheet-like member 13m without stagnation at that position. Further, the developer G that has reached the position where the partition member 13d and the developing roller 13a face each other without being completely separated from the developing roller 13a and being carried on the developing roller 13a is also along the traveling direction of the sheet-like member 13m. Then, after being scraped from the facing position, the sheet-like member 13m is positively transported toward 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.

  In order to smoothly move the developer G carried on the developing roller 13a onto the partition member 13d (sheet-like member 13m), the partition member 13d (sheet-like member) at a position where the partition member 13d and the developing roller 13a face each other. The tip of the member 13m) is preferably pointed (a smaller R is preferred). That is, if the R shape at the tip of the partition member 13d is too large, the developer easily enters the gap between the partition member 13d and the developing roller 13a. However, if the R shape at the tip of the partition member 13d is too small, there is a possibility that the running failure of the sheet-like member 13m may occur or the sheet-like member 13m may be damaged. In the first embodiment, considering these points, the shape of the tip of the partition member 13d is set to about R0.5 mm.

  In the first embodiment, the developer G that has fallen on the upper surface of the partition member 13d is not transported into the second transport path by sliding on the inclined surface, but by traveling of the sheet-like member 13m. Since the sheet is positively conveyed toward the second conveyance path, even if the inclination angle of the upper surface of the partition member 13d is not set so large (for example, in a state close to the horizontal), the partition member 13d The developer G that has fallen on the upper surface can be reliably conveyed toward the second conveyance path. Therefore, the degree of freedom in designing the layout such as the position of the agent separating magnetic pole H4 of the developing roller 13a, the positions of the transport screws 13b1 and 13b2, the position of the partition member 13d, and the like is increased.

  2 and 5 and the like, for the sake of simplicity, the sheet-like member 13m and the wall portion that separates the first conveyance path and the second conveyance path are illustrated so as to have a gap. However, in order to prevent the movement of the developer from this gap (the movement of the developer from the second conveyance path to the first conveyance path), the sheet-like member 13m is formed between the sheet-like member 13m and the wall portion. It is preferable to install a seal member on the surface.

  In the first embodiment, it is preferable to improve the transportability of the sheet-like member 13m with respect to the developer G in order to ensure the above-described effect. A specific example will be described below with reference to FIG. 6A1 to 6D1 are top views illustrating the respective sheet-like members 13m, and FIGS. 6A2 to 6D2 are cross-sectional views illustrating the respective sheet-like members 13m.

  As a first specific example, as shown in FIGS. 6A1 and 6A2, a plurality of holes 13m1 (through holes) are formed in the sheet-like member 13m. However, the hole diameter of the plurality of holes 13m1 is sufficiently smaller than the particle diameter of the carrier C. With such a configuration, since the developer G is held so as to fit into the plurality of holes 13m1 on the sheet-like member 13m, the transportability of the sheet-like member 13m with respect to the developer G is improved.

  As a 2nd specific example, as shown to FIG. 6 (B1) and FIG. 6 (B2), the unevenness | corrugation is formed in the outer peripheral surface of the sheet-like member 13m. Specifically, a plurality of hemispherical recesses 13m2 are formed on the outer peripheral surface of the sheet-like member 13m. The outer diameter and pitch of the plurality of recesses 13m2 are formed to be equal to or smaller than the particle diameter of the carrier C. With such a configuration, the developer G is held so as to fit into the plurality of recesses 13m2 on the sheet-like member 13m, so that the transportability of the sheet-like member 13m with respect to the developer G is improved.

  In the third specific example, as shown in FIGS. 6C1 and 6C2, irregularities are formed on the outer peripheral surface of the sheet-like member 13m. Specifically, a plurality of grooves 13m3 are formed on the outer peripheral surface of the sheet-like member 13m. The widths and pitches of the plurality of grooves 13m3 are equal to or smaller than the particle size of the carrier C. With such a configuration, the developer G is held so as to fit into the plurality of grooves 13m3 on the sheet-like member 13m, so that the transportability of the sheet-like member 13m to the developer G is improved.

  As a fourth specific example, as shown in FIG. 6 (D1) and FIG. 6 (D2), the outer peripheral surface of the sheet-like member 13m is formed of a fiber material. Specifically, the sheet-like member 13m has a two-layer structure, and a fiber layer 13ma formed of a fiber material is provided on the outer peripheral surface side, and a PET layer 13mb formed of PET is provided on the inner peripheral surface side. Yes. The mesh of the fiber layer 13ma is formed equal to or less than the particle size of the carrier C. With such a configuration, the developer G is held so as to fit into the fiber layer 13ma on the sheet-like member 13m, so that the transportability of the sheet-like member 13m to the developer G is improved. Moreover, since the partition member 13d comes into sliding contact with the PET layer 13mb of the sheet-like member 13m, the frictional resistance of both the members 13d and 13m can be reduced. Furthermore, the fiber layer 13ma is bonded to the PET layer 13mb, whereby deformation such as expansion and contraction and twist of the fiber layer 13ma can be prevented.

  Although not shown, the sheet-like member 13m can be formed of a magnetic material. Specifically, since the developer G is magnetically held on the sheet-like member 13m by forming the sheet-like member 13m with a magnetic material such as a magnet, the transportability of the sheet-like member 13m to the developer G is improved. Will be improved.

  As described above, in 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 connected to the developing roller 13a (developer carrier). In this case, the sheet-like member 13m that positively conveys the developer G detached from the developing roller 13a toward the second conveying path to the partition member 13d that faces the developing roller 13a. Therefore, it is possible to reliably reduce a problem that the developer G after the developing process separated from the developing roller 13a in the second transport path is carried on the developing roller 13a again.

Embodiment 2. FIG.
A second embodiment of the present invention will be described in detail with reference to FIG.
FIG. 7 is an enlarged view showing a part of the developing device 13 according to the second embodiment and showing the vicinity of the partition member 13d. The developing device in the second embodiment is different from that in the first embodiment in that a magnetic body 13d1 is installed at the tip of the partition member 13d.

  Similarly to the first embodiment, the developing device 13 according to the second embodiment also has a developing roller 13a (developer carrier), two transport screws 13b1 and 13b2, a doctor blade 13c (developer regulating member), It is composed of a partition member 13d, a sheet-like member 13m, a driving roller 13n, and the like.

Here, as shown in FIG. 7, the partition member 13d of the developing device 13 according to the second embodiment is provided with a magnetic body 13d1 at a position facing the developing roller 13a via the sheet-like member 13m. Specifically, the magnetic body 13d1 is a magnet, and is provided at the tip of the partition member 13d that faces the developing roller 13a.
With such a configuration, in the region K1 shown in FIG. 7, the developer has reached the position where the partition member 13d and the developing roller 13a are opposed to each other while being held on the developing roller 13a without being separated from the developing roller 13a. After G is attracted to the sheet-like member 13m by the magnetic body 13d1 and scraped out from the opposing position along the traveling direction of the sheet-like member 13m, the sheet-like member 13m actively moves toward the second transport path. Will be transported.
Further, in the region K2 shown in FIG. 7, the developer G carried on the developing roller 13a without being completely separated from the developing roller 13a is attracted to the sheet-like member 13m by the magnetic body 13d1, and the partition member 13d (sheet-like member). It becomes easy to fall on the upper surface of 13m). Then, the developer G dropped on the upper surface of the partition member 13d (sheet-like member 13m) is positively conveyed toward the second conveyance path by the traveling of the sheet-like member 13m.
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.

  As described above, also in the second embodiment, as in 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 developed. In the case where it is installed so as to face the roller 13a (developer carrying member), the developer G separated from the developing roller 13a is directed to the partition member 13d facing the developing roller 13a toward the second transport path. Since the sheet-like member 13m that actively conveys is installed, it is ensured that the developer G after the developing process separated from the developing roller 13a in the second conveying path is again carried on the developing roller 13a. Can be 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. In that case, the workability of maintenance of the image forming unit is improved.

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 installed so as to face the developing roller 13a. In each of the above embodiments, the number of magnetic poles H1 to H6 formed around the developing roller 13a is six. However, the number of magnetic poles formed around the developing roller 13a is five or less, or seven or more. It can also be. Furthermore, in each of the above embodiments, the present invention is applied to the developing device in which the first transport path is disposed below the second transport path. However, the first transport path is above the second transport path. The present invention can also be applied to the developing device provided.
Also in those cases, the same effect as in the above-described embodiments can be obtained by installing the sheet-like member 13m at the position of the partition member 13d.

  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 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,
13d1 magnetic material,
13e Toner supply port,
13f 1st relay part, 13g 2nd relay part,
13m sheet-like member,
13n driving roller,
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 (11)

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 developer regulating member that is disposed so as to face 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 that faces the developer carrying member and conveys 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 developing device according to claim 1, wherein the partition member is covered with a sheet-like member that travels in a predetermined direction and guides the developer separated from the developer carrying member to the second transport path.   The developing device according to claim 1, wherein the sheet-like member travels in the same direction as a rotation direction of the developer carrying member.   The developing device according to claim 1, wherein the sheet-like member has a plurality of holes formed therein.   The developing device according to claim 1, wherein the sheet-like member has irregularities formed on an outer peripheral surface thereof.   The developing device according to claim 1, wherein at least an outer peripheral surface of the sheet-like member is formed of a fiber material.   The developing device according to claim 1, wherein the partition member includes a magnetic body at a position facing the developer carrier through the sheet-like member.   The developing device according to claim 1, wherein the sheet-like member is made of a magnetic material. The developer regulating member is disposed so as to face the lower side of the developer carrier,
The developing device according to claim 1, wherein the first transport member is disposed below the second transport member.   The developing device according to claim 1, wherein the carrier has a weight average particle diameter of 20 to 60 μm. A process cartridge that is detachably installed on the main body of the image forming apparatus,
10. 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