JP5505606B2 - Developing device, process cartridge, and image forming apparatus - Google Patents

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 amount of the developer that is supplied by the first conveying member and carried (pumped) on the developing roller in the first conveying path is on the upstream side in the conveying direction. In comparison, there is a problem that the downstream side in the transport direction is reduced. This is because the developer is fed onto the developing roller while being transported in the longitudinal direction in the first transport path, so that the developer height (agent surface) in the first transport path is transported from the upstream side in the transport direction. It is because it becomes low as it goes to the direction downstream side. Such inconveniences 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).
Due to such inconvenience, there is a problem in that the absolute amount of developer pumped up on the developer roller on the downstream side in the transport direction is insufficient, and density deviation occurs in the toner image formed on the image carrier. It sometimes occurred.

  In order to solve such problems, the magnetic force of the pumping magnetic pole formed on the developing roller is sufficiently increased so that the absolute amount of developer pumped on the developer roller is insufficient on the downstream side in the transport direction. There is a way to avoid it. However, in that case, the absolute amount of developer pumped up on the developer roller on the upstream side in the transport direction becomes excessive, and when the amount of developer on the developer roller is regulated at the position of the doctor blade, The generated load becomes large, and the damage given to the developer regulated by the doctor blade becomes large. Further, the developer amount pumped up onto the developer roller on the upstream side in the transport direction increases, so that the height (agent surface) of the developer on the downstream side in the transport direction in the first transport path further decreases. Therefore, the expected effect may not be obtained.

  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. The amount of the developer that is installed so as to face the developer and the developer regulating member is disposed below the developer carrier, and is supplied by the first conveying member and carried on the developer carrier. SUMMARY OF THE INVENTION An object of the present invention is to provide a developing device, a process cartridge, and an image forming apparatus in which the problem that the downstream side in the transport direction is smaller than the upstream side in the transport direction is reduced.

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. And a developer carrying body having a plurality of magnetic poles formed around it, and arranged so as to face each other at a facing position below the developer carrying body and carried on the developer carrying body. A developer regulating member that regulates the amount of the developed 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 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; and disposed above the first carrying member. While facing the developer carrying member, A second conveying member that conveys the developer separated from the image carrier in the longitudinal direction, between the developer carrier and the first conveying member, and the developer regulating member A second developer that regulates the amount of the developer that is supplied by the first conveying member and carried on the developer carrying member at a position upstream of the developer carrying member in the rotation direction of the developer carrying member. The developer carrier further includes a pumping magnetic pole for pumping the developer flowing in the first transport path by the first transport member out of the plurality of magnetic poles onto the developer carrier. The second developer regulating member is formed from the position facing the first conveying member to the vicinity of the facing position with the developer regulating member, and the second developer regulating member is rotated in the rotation direction of the developer carrier at the pumping magnetic pole. Located at a position to block the upstream magnetic field It is intended.

The developing device according to a second aspect of the present invention is the developing device according to the first aspect, wherein the second developer regulating member is viewed in a cross section perpendicular to the rotation center axis of the developer carrier. Further, the cross-sectional area of the second developer regulating member on the downstream side in the transport direction of the developer in the first transport path by the first transport member is the cross-sectional area of the second developer regulating member on the upstream side in the transport direction. It is formed to be smaller than that.

The developing apparatus according to the invention of claim 3, wherein, in the invention described in claim 2, wherein the second developer regulating member, the developer developing the second along the rotational direction of the carrier The wall surface of the second developer regulating member located on the upstream side in the rotation direction of the developer carrier is such that the length of the developer regulating member gradually decreases from the upstream side in the carrying direction toward the downstream side in the carrying direction. The developer carrying member is formed to be inclined with respect to the rotation center axis.

According to a fourth aspect of the present invention, there is provided the developing device according to any one of the first to third aspects, wherein the second developer regulating member is made of a nonmagnetic material. is there.

According to a fifth aspect of the present invention, there is provided the developing device according to any one of the first to fourth aspects , wherein the first conveying member is provided at a position facing the developer carrying member. The image forming apparatus further includes a partition member that partitions a conveyance path and a second conveyance path by the second conveyance member, and the second conveyance member is a second member when viewed in a cross section perpendicular to the rotation center axis of the developer carrier. The position of the rotation center axis of the conveying member is disposed 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.

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

A process cartridge according to a seventh aspect of the present invention is a process cartridge that is detachably installed on the main body of the image forming apparatus, and the developing device according to any one of the first to sixth aspects. And the image carrier.

The image forming apparatus according to the invention of claim 8 is obtained by a said image bearing member and the developing device according to any one of claims 1 to 6.

  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. Since the second developer regulating member is disposed between the developer carrying body and the first transport member, the second developer regulating member is disposed below the carrier and is supplied by the first transport member. It is possible to provide a developing device, a process cartridge, and an image forming apparatus in which the problem that the amount of developer carried on the developer carrying member is less on the downstream side in the transport direction than on the upstream side in the transport direction is reduced. .

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 a figure which shows the state of the developer pumped up on a developing roller when not installing a control board. It is an enlarged view which shows a part of developing device in Embodiment 2 of this invention. It is a top view which shows separately the control board and developing roller in the developing device of FIG.

  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 (a cross-sectional view orthogonal to the rotation center axis of the developing roller 13a) showing the developing device, and the method of magnetic poles H1 to H6 formed on the developing roller 13a in the drawing. The magnetic force distribution of the linear component is also shown. Further, FIG. 6A is a diagram showing the state of the developer pumped up onto the developing roller 13a on the upstream side in the transport direction of the first transport path when the regulating plate 13k is not installed. FIG. FIG. 6 is a diagram showing a state of developer pumped up on the developing roller 13a on the downstream side in the transport direction of the first transport path when the regulating plate 13k is not installed.
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 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 the present embodiment, 225 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 carrier, conveying screws 13b1 and 13b2 (auger screws) as conveying members, a developer regulating member (first developer regulating member). A doctor blade 13c as a member), a regulating plate 13k as a second developer regulating member, a partition member 13d, 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 (developer regulating member) 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 repulsive magnetic field (a magnetic field acting in a direction away from the developing roller 13a in FIG. 7) 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, 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 polarity (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, a doctor blade 13c as a developer regulating member (first developer regulating member) is a non-magnetic plate-like member (a part of which is magnetically disposed below the developing roller 13a). It can also be made of a material. 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 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 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 5.8 μm, and is formed so that a toner having a particle diameter of 5 μm or less is 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. In the first embodiment, the carrier C formed so that the weight average particle diameter is 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 and operation of the developing device 13 according to the first embodiment will be described.
Referring to FIGS. 2 and 5, the developing device 13 according to the first embodiment includes a developing roller between the developing roller 13 a and the first conveying screw 13 b 1 and with respect to the position facing the doctor blade 13 c. A restricting plate 13k as a second developer restricting member is installed at a position upstream of the rotational direction of 13a. The regulating plate 23k (second developer regulating member) is for regulating the amount of the developer G supplied by the first conveying screw 13b1 and carried on the developing roller 13a.
In this way, by installing the regulation plate 13k, the deviation in the longitudinal direction of the amount of developer pumped up to the developer roller 13a (the amount of developer input to the position facing the doctor blade 13c) is reduced. Can be small.

Specifically, referring to FIG. 6A and FIG. 6B, when the restriction plate 13k is not installed, in the first transport path, the supply force by the first transport screw 13b1 and the magnetic force by the pumping magnetic pole H6 are used. As a result, the amount of the developer G pumped onto the developing roller 13a (the amount of developer input to the position of the doctor blade 13c) is smaller on the downstream side in the transport direction than on the upstream side in the transport direction. That is, on the upstream side in the transport direction, the amount of developer pumped up on the developing roller 13a is large as shown in FIG. 6A, whereas on the downstream side in the transport direction, the developing roller is shown in FIG. 6B. The amount of developer pumped on 13a is reduced. Note that the position of the broken line in FIG. 6B indicates the position of the developer on the upstream side in the transport direction.
As described above with reference to FIG. 4, since the developer is supplied to the developing roller 13a in the first transport path while transporting the developer in the longitudinal direction, the upstream side is directed to the downstream side. This is because the surface of the developer G is lowered.

On the other hand, in the first embodiment, since the regulating plate 13k (second developer regulating member) is installed between the developing roller 13a and the first conveying screw 13b1, the first conveying path The amount of developer pumped on the developing roller 13a on the upstream side in the transport direction (the right side in FIG. 4 and corresponding to FIG. 6A) (on the developing roller 13a at a position immediately before the doctor gap) The amount of the developer carried on the toner can be reduced to a suitable amount). As a result, the developer surface on the downstream side rises by the amount of the developer that has not been pumped upstream, so the amount of developer pumped on the developing roller 13a on the downstream side in the transport direction is larger than before. (Can be quantified). That is, the deviation between the amount of developer pumped on the developing roller 13a on the upstream side and the amount of developer pumped on the developing roller 13a on the downstream side is reduced, and the deviation is carried on the developing roller 13a from upstream to downstream. The balance of the amount of developer to be produced is made uniform.
As described above, in the first embodiment, the amount of developer pumped up on the developer roller 13a does not become excessive on the upstream side in the transport direction, so that the developer on the developer roller 13a at the position of the doctor blade 13c. It is possible to suppress the problem that the load generated when the amount is regulated increases and the torque of the apparatus increases, and the problem that the damage to the developer regulated by the doctor blade 13c increases and the life of the developer is shortened. it can.

Here, referring to FIG. 5, in the first embodiment, the regulating plate 13k (second developer regulating member) is on the upstream side of the pumping magnetic pole H6 (the upstream side in the rotation direction of the developing roller 13a). ) Is disposed at a position to block the magnetic field.
By taking such a layout of the regulating plate 13k, the inventor of the present application takes the developer amount pumped onto the developing roller 13a described above (the developer carried on the developing roller 13a at a position immediately before the doctor gap). It has been confirmed that the effect of reducing the deviation in the longitudinal direction is reliable.

Further, the regulation plate 13k is formed of a nonmagnetic material such as a resin material. As a result, the problem that the carrier, which is a magnetic material, is magnetically attracted to the regulating plate 13k and hinders the flow of the developer in the first transport path is suppressed.
Further, the restricting plate 13k has a confronting surface facing the developing roller 13a formed in a concave shape in accordance with the shape of the developing roller 13a, and a confronting surface facing the first conveying screw 13b1 is a screw portion of the first conveying screw 13b1. It is formed in a concave shape according to the outer diameter. Accordingly, it is possible to reduce a problem that the developer carried on the developing roller 13a and the developer conveyed to the first conveying screw 13b1 are subjected to excessive stress at a position facing the regulating plate 13k.

Further, with reference to FIG. 5 and the like, in the developing device 13 in the first 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 such that a gap CG between the facing surface 13d2 facing the developing roller 13a and the developing roller 13a is 2 mm or less (preferably 0.1 to 0.5 mm). In the first embodiment, the gap CG is set to 0.3 mm.
Although illustration is omitted, in the boundary region between the second transport path and the first transport path, the developing roller 13a (on the side of the first transport path) from the inside of the second transport path due to the influence of the fifth magnetic pole H5. A magnetic field toward 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 first 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. In addition, 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 is disposed in the range indicated by the double arrow M1.
Further, the position on the developing roller 13a that equally divides the two magnetic poles H3 and H5 forming the agent separating magnetic pole H4 when viewed in a cross section (FIG. 5) orthogonal to the rotation center axis of the developing roller 13a. K is formed so as to be above the virtual horizontal line S1 passing through the rotation center axis of the developing roller 13a. The position K described above passes through the straight line A3 passing through the peak magnetic force position of the third magnetic pole H3 and the center position of the developing roller 13a, and the peak magnetic force position of the fifth magnetic pole H5 and the center position of the developing roller 13a. The straight line drawn at an equal angle with the straight line A5 intersects the surface of the developing roller 13a (of the two points where the straight line and the surface of the developing roller 13a intersect, the one closer to the second conveying screw 13b2. ). In the first embodiment, the distance between the axes of the developing roller 13a and the second conveying screw 13b2 is set to about 26 mm.
With this configuration, the developer G after the development process carried on the developing roller 13a has a magnetic force 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 to a force (a magnetic force outward with respect to the developing roller 13a), a centrifugal force due to 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. become. As a result, the developer G after the development process carried on the developing roller 13a is efficiently separated from the developing roller 13a without causing a failure to separate from the developing roller 13a in the second quadrant of FIG. The separated developer G is smoothly collected in 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 first embodiment, the first magnetic pole H1 has a peak magnetic force of 100 mT, the second magnetic pole H2 has a peak magnetic force of 85 mT, the third magnetic pole H3 has a peak magnetic force of 52 mT, and the fifth magnetic pole H5. Is set to 35 mT, and the peak magnetic force of the sixth magnetic pole H6 is set to 78 mT.
The position (or position K) of the agent separating magnetic pole H4 (fourth magnetic pole) is variable by adjusting the position (half-value central angle) and the magnitude (peak magnetic force) of the third magnetic pole H3 and the fifth magnetic pole H5. can do. However, the peak magnetic force between the third magnetic pole H3 and the fifth magnetic pole H5 should be set to about 25 to 60 mT in order to surely prevent the rotation of the developer at the position of the agent separating magnetic pole H4 (separation failure). Is preferred.

Referring to FIG. 5, in the first embodiment, when viewed in a cross section orthogonal to the rotation center axis of the developing roller 13a, the tip of the partition member 13d is assumed to pass through the rotation center axis of the developing roller 13a. It is formed so as to be above the horizontal line S1 and below the position K. Accordingly, the developer G detached from the developing roller 13a is smoothly guided to the second transport path along the inclined surface of the partition member 13d at the position K or a position in the vicinity thereof.
Further, with reference to FIG. 5, in the first embodiment, when viewed in a cross section orthogonal to the rotation center axis of the developing roller 13a, the tip of the partition member 13d has the rotation center axis of the second transport screw 13b2. It is formed so as to be above the virtual horizontal line S2 that passes therethrough. As a result, it is possible to reduce a problem that the developer G collected in the second transport path flows over the partition member 13d and flows into the first transport path.

Further, in the first embodiment, the inclination angle (the angle formed with the horizontal plane) of the inclined surface (an inclined surface formed on the second transport path side) of the partition member 13d is the developer G. It is formed to be larger than the angle of repose. Here, the angle of repose of the developer is an angle formed by the ridge line of the developer crest that rises in a conical shape by dropping the developer on the horizontal plane and the horizontal plane. -S "(manufactured by Hosokawa Micron Corporation) can be used.
With such a configuration, the developer G detached from the developing roller 13a at the position of the agent separation magnetic pole H4 is smoothly guided to the second transport path without staying along the inclined surface of the partition member 13d. It is possible to reduce a problem that the developer after the separation is re-supported by the developing roller 13a.
In order to reliably prevent the developer having a small diameter with poor fluidity from staying on the inclined surface, it is preferable that the inclined angle of the inclined surface of the partition member 13d be 40 degrees or more. In the first embodiment, the inclination angle of the inclined surface is set to about 45 degrees.

Here, referring to FIG. 5, in the first embodiment, the position of the rotation center axis of the first conveyance screw 13b1 is the second conveyance screw when viewed in a cross section orthogonal to the rotation axis of the developing roller 13a. The first conveying screw 13b1 is between the virtual vertical line passing through the rotation center axis of 13b2 and the virtual vertical line passing through the rotation center axis of the developing roller 13a (between the range M2 in FIG. 5). 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 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). This is a case where the doctor blade 13c (developer regulating member) is disposed below the developing roller 13a so as to be opposed to each other, and between the developing roller 13a and the first conveying screw 13b1 (first conveying member). Since the regulating plate 13k (second developer regulating member) is installed between them, the amount of the developer G supplied by the first carrying screw 13b1 and carried on the developing roller 13a is on the upstream side in the carrying direction. In comparison, it is possible to reduce the problem that the downstream side in the transport direction is reduced.

  In the first embodiment, the regulating plate 13k (second developer regulating member) is installed over almost the entire area in the longitudinal direction. However, the amount of developer pumped up to the developer roller 13a is likely to be excessive. The restriction plate 13k can be installed only on the upstream side in the direction (the right side in FIG. 4). Such a range in which the regulating plate 13k is provided is preferably set so that the deviation in the longitudinal direction of the developer amount on the developing roller 13a on the upstream side of the doctor gap is as small as possible.

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. In particular, FIG. 7A is a cross-sectional view on the upstream side in the transport direction of the first transport path, and FIG. ) Is a cross-sectional view of the first transport path on the downstream side in the transport direction. FIG. 8 is a top view showing the regulating plate 13k (second developer regulating member) and the developing roller 13a separately.
In the developing device according to the second embodiment, the shape of the regulating plate 13k as the second developer regulating member is different from that of the first embodiment.

  Similarly to the first embodiment, the developing device 13 according to the second embodiment also has a developing roller 13a (developer carrying member), two conveying screws 13b1, 13b2 (conveying member), a doctor blade 13c (developer). A regulating member), a regulating plate 13k (second developer regulating member), a partition member 13d, and the like.

Here, the regulating plate 13k (second developer regulating member) in the second embodiment is downstream in the developer conveying direction in the first conveying path when viewed in a cross section orthogonal to the rotation center axis of the developing roller 13a. The cross-sectional area of the regulating plate 13k on the side is formed to be smaller than the cross-sectional area of the regulating plate 13k on the upstream side in the transport direction. That is, the cross-sectional area of the regulating plate 13k on the upstream side of the first conveyance path shown in FIG. 7A (the area of the shaded portion surrounded by the four wall surfaces 13k1 to 13k4) is shown in FIG. Are formed larger than the cross-sectional area of the regulating plate 13k on the downstream side of the first transport path shown in FIG.
Specifically, referring to FIG. 8, the regulating plate 13k is formed such that the length of the regulating plate 13k along the rotation direction of the developing roller 13a gradually decreases from the upstream side in the transport direction toward the downstream side in the transport direction. Yes. That is, the length W2 of the regulating plate 13k along the rotation direction of the developing roller 13a on the downstream side is made smaller than the length W1 of the regulating plate 13k along the rotation direction of the developing roller 13a on the upstream side. (W1> W2), and the length of the regulating plate 13k along the rotation direction of the developing roller 13a is gradually reduced from the upstream side to the downstream side.
Further, referring to FIG. 8, wall surface 13k1 of regulating plate 13k located on the upstream side in the rotation direction of developing roller 13a is a rotation center axis of developing roller 13a (a phantom line indicated by a one-dot chain line in FIG. 8). And inclined. That is, the wall surface 13k1 (side surface) on the upstream side of the regulation plate 13k is tapered in the longitudinal direction. A wall surface 13k2 (side surface) on the downstream side of the regulating plate 13k is formed in parallel to the rotation center axis of the developing roller 13a.

  With such a configuration of the regulating plate 13k, the amount of developer pumped on the developing roller 13a on the upstream side in the transport direction of the first transport path (the developer carried on the developing roller 13a at a position immediately before the doctor gap). The width of the restricting plate 13k (along the rotation direction of the developing roller 13a) becomes smaller toward the downstream side where the amount of the developer pumped on the developing roller 13a decreases. By gradually decreasing the length, which is the distance between the two side surfaces 13k1 and 13k2, the restriction on the developer amount by the restriction plate 13k can be gradually weakened. Therefore, the amount of developer pumped on the developing roller 13a can be made more uniform over the longitudinal direction from the upstream side to the downstream side.

  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. This is a case where the doctor blade 13c (developer regulating member) is disposed below the developing roller 13a and is disposed so as to face the roller 13a (developer carrying member). Since the regulating plate 13k (second developer regulating member) is installed between the first conveying screw 13b1 and the developer 13b1 (first conveying member), the developer carried on the developing roller 13a is supported. The problem that the amount of G is less on the downstream side in the transport direction than on the upstream side in the transport direction 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.
Even in those cases, the same effect as that of each of the above embodiments can be obtained by providing a restriction plate (second developer restriction member) between the first conveying screw (supply screw) and the developing roller. it can.

  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,
13k restriction plate (second developer restriction member),
H1 first magnetic pole (main magnetic pole), H2 second magnetic pole (conveying magnetic pole),
H3 3rd magnetic pole (agent separating pre-magnetic pole),
H4 4th magnetic pole (agent separating magnetic pole),
H5 Fifth magnetic pole (magnetic pole after agent separation),
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 (8)

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 oppose at a lower facing position of the developer carrying member, and that regulates the amount of 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
The first conveying member is positioned between the developer carrying member and the first conveying member at a position upstream of the developer regulating member in the rotation direction with respect to the opposed position of the developer regulating member. A second developer regulating member that regulates the amount of developer supplied and carried on the developer carrying member ;
The developer carrier has a pumping magnetic pole for pumping the developer flowing on the first transport path by the first transport member out of the plurality of magnetic poles onto the developer carrier. Is formed from the position facing to the vicinity of the position facing the developer regulating member,
The developing device, wherein the second developer regulating member is disposed at a position that blocks a magnetic field on the upstream side in the rotation direction of the developer carrier in the pumping magnetic pole . The second developer regulating member, when viewed in a cross section orthogonal to the rotation center axis of the developer carrying member, the second developer downstream in the developer conveying direction in the first conveying path by the first conveying member. The developing device according to claim 1, wherein a cross-sectional area of the developer restricting member is smaller than a cross-sectional area of the second developer restricting member on the upstream side in the transport direction. The second developer regulating member gradually decreases as the length of the second developer regulating member along the rotation direction of the developer carrying member moves from the upstream side in the transport direction to the downstream side in the transport direction. The wall surface of the second developer regulating member located upstream in the rotation direction of the developer carrying member is formed to be inclined with respect to the rotation center axis of the developer carrying member. Item 3. The developing device according to Item 2. The developing device according to claim 1, wherein the second developer regulating member is made of a nonmagnetic material. 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;
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 below a virtual horizontal line passing through the upper end of the developer carrier. The developing device according to claim 1, wherein the developing device is disposed so as to be above a virtual horizontal line passing through a lower end of the developer carrier. 6. The developing device according to claim 1, wherein the carrier has a weight average particle diameter of 20 to 60 [mu] m. A process cartridge that is detachably installed on the main body of the image forming apparatus,
7. 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