JP5679509B2 - 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 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 process includes the developer after the developing process (the developer in which the toner is consumed). (This phenomenon is referred to as “developing with the developer”), resulting in a density deviation in the toner image formed on the image carrier.

  In order to prevent such a problem, a method of installing a partition member that partitions the first transport path and the second transport path is conceivable. However, even if an attempt is made to install the partition member so that the gap with the developing roller is very small, the desired gap cannot be secured due to variations in dimensional accuracy and assembly accuracy of various components including the partition member and the developing roller. In addition, there is a possibility of “developing the developer”. In addition, even if it is intended to make the tip of the partition member lightly contact the developing roller, due to variations in the dimensional accuracy and assembly accuracy of various components including the partition member and the developing roller, There is a possibility that the partition member abuts with a strong force, so that the surface of the developing roller is worn or the driving torque of the apparatus is increased.

  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. Even if there is a variation in the dimensional accuracy and assembly accuracy of the component parts when the developer regulating member is disposed below the developer carrying member and disposed so as to face each other, The developer after the development process separated from the developer carrying member in the second transport path is carried on the developer carrying member again without causing the problem of surface wear or increase in the driving torque of the apparatus. An object of the present invention is to provide a developing device, a process cartridge, and an image forming apparatus that are suppressed.

According to a first aspect of the present invention, there is provided a developing device for storing a developer having a carrier and a toner and developing a latent image formed on an image carrier, the image carrier. A developer carrying body facing the body and having a plurality of magnetic poles formed around it, and a developer carried on the developer carrying body and arranged to face the lower side of the developer carrying body A developer regulating member that regulates the amount of the developer, and a plurality of conveying members that convey the developer contained in the apparatus in the longitudinal direction to form a circulation path, wherein the plurality of conveying members are the developer A first conveying member facing the carrier and supplying the developer to the developer carrier while conveying the developer in the longitudinal direction; and the developer carrier disposed above the first conveying member. And the developer carrying member A second conveying member that conveys the developer separated from the developer in the longitudinal direction, and faces the developer carrying member, and includes a first conveying path by the first conveying member and a second conveying member by the second conveying member. (2) a partition member that partitions the conveyance path, and the partition member is pushed by an elastic force acting toward the developer carrying member so that a part or all of the tip end portion of the partition member contacts the developer carrying member. An elastic member to be contacted , wherein the partition member has a gap with the developer carrier at a position downstream in the developer transport direction in the second transport path, and the developer in the second transport path. It is formed so as to be smaller than the gap with the developer carrier at the upstream position in the transport direction .

  According to a second aspect of the present invention, there is provided the developing device according to the first aspect, wherein the partition member is in contact with the developer carrier at two positions spaced apart in the longitudinal direction. It is formed.

  According to a third aspect of the present invention, there is provided the developing device according to the first or second aspect, wherein the partition member is located outside the effective image forming area of the developer carrier. It is formed so as to come into contact with the carrier.

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 partition member has at least a contact portion that contacts the developer carrier. It is made of a low friction material.

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 partition member has at least a contact portion that contacts the developer carrier. The developer carrying member is made of a material having a lower hardness than the surface hardness.

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 includes a facing surface facing the developer carrier and the developer. It is formed so that the gap with the carrier is 2 mm or less.

A developing device according to a seventh aspect of the present invention is the developing device according to any one of the first to sixth aspects, wherein the partition member is detachable from the developing case. .

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

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

  In the present application, the “process cartridge” refers to a charging unit that charges the image carrier, a developing 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 application, the “effective image forming area” in the developer carrying member is defined as the range in the longitudinal direction in which the developer is carried on the developer carrying member.

  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. An elastic member that pushes the partition member toward the developer carrying member and causes a part or all of the tip end portion of the partition member to contact the developer carrying member even when disposed below the carrier Therefore, even if the dimensional accuracy and assembly accuracy of the component parts vary, the surface of the developer carrier does not wear or the driving torque of the device does not increase. It is possible to provide a developing device, a process cartridge, and an image forming apparatus in which the developer after the developing process separated from the developer carrying member is restrained from being carried on the developer carrying member again.

1 is an overall configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention. It is a block diagram which shows an image creation part. (A) The schematic sectional view which looked at the upper part of the developing device in the longitudinal direction, (B) The schematic sectional view which looked at the lower part of the developing device in the longitudinal direction. It is the schematic sectional drawing which looked at the circulation path of the developing device in the longitudinal direction. It is sectional drawing which shows a developing device. It is a figure which shows magnetic force distribution of the normal direction component of the magnetic pole formed on a developing roller. It is a schematic diagram which shows a partition member and a developing roller in a longitudinal direction. 4A is a cross-sectional view showing the vicinity of a non-contact portion and FIG. 5B is a cross-sectional view showing the vicinity of a contact portion in the partition member. It is a schematic diagram which shows the partition member of another form.

Embodiment.
Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

First, the configuration and operation of the entire image forming apparatus will be described with reference to FIG.
In FIG. 1, 1 is a main body of a tandem type color copier as an image forming apparatus, 3 is a document conveying unit that conveys a document to a document reading unit, 4 is a document reading unit that reads image information of a document, and 5 is an output image. , 7 is a paper feed unit that accommodates a recording medium P such as transfer paper, 9 is a registration roller that adjusts the conveyance timing of the recording medium P, and 11Y, 11M, 11C, and 11BK are each color (yellow). , Magenta, cyan, and black), a photosensitive drum as an image carrier on which a toner image is formed, and a developing device 13 that develops electrostatic latent images formed on the photosensitive drums 11Y, 11M, 11C, and 11BK. , 14 is a transfer bias roller (primary transfer bias roller) for transferring the toner images formed on the photosensitive drums 11Y, 11M, 11C, and 11BK on the recording medium P in an overlapping manner. It is.
Reference numeral 17 denotes an intermediate transfer belt onto which a plurality of color toner images are transferred, 18 denotes a secondary transfer bias roller for transferring the color toner image on the intermediate transfer belt 17 onto the recording medium P, and 20 denotes a recording medium. A fixing device 28 for fixing an unfixed image on P, and a toner container for each color for supplying toner (toner particles) of each color (yellow, cyan, magenta, black) to the developing device 13.

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

  Specifically, the document reading unit 4 scans an image of a document on the contact glass while irradiating light emitted from an illumination lamp. Then, the light reflected from the original is imaged on the color sensor via the mirror group and the lens. The color image information of the original is read for each color separation light of RGB (red, green, blue) by the color sensor, and then converted into an electrical image signal. Further, color conversion processing, color correction processing, spatial frequency correction processing, and the like are performed by the image processing unit based on the RGB color separation image signals to obtain yellow, magenta, cyan, and black color image information.

  Then, image information of each color of yellow, magenta, cyan, and black is transmitted to a writing unit (not shown). Then, a laser beam L (see FIG. 2) based on the image information of each color is emitted from the writing unit toward the corresponding photosensitive drums 11Y, 11M, 11C, and 11BK.

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

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

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

Thereafter, the surfaces of the photoconductive drums 11Y, 11M, 11C, and 11BK on which the electrostatic latent images of the respective colors are formed reach positions facing the developing device 13, respectively. Then, the respective color toners are supplied from the developing devices 13 onto the photosensitive drums 11Y, 11M, 11C, and 11BK, and the latent images on the photosensitive drums 11Y, 11M, 11C, and 11BK are developed (developing 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 diagram showing a magnetic force distribution of components in the normal direction of the magnetic poles H1 to H6 formed on the developing roller 13a. FIG. 7 is a schematic diagram showing the partition member 13d and the developing roller 13a in the longitudinal direction. 8A is a cross-sectional view showing the vicinity of the non-contact portion 13d2 in the partition member 13d, and FIG. 8B is a cross-sectional view showing the vicinity of the contact portion 13d1 in the partition member 13d.
Since each image forming unit has substantially the same structure, the image forming unit and the developing device are illustrated in FIGS. 2 to 8 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 driven to rotate counterclockwise by a rotation drive mechanism (not shown).

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

  The developing device 13 is disposed such that a developing roller 13a as a developer carrying member is close to the photosensitive drum 11, and a developing region (developing) where the photosensitive drum 11 and the magnetic brush are in contact with each other. Nip) is formed. A developer G (two-component developer) composed of toner T and carrier C is accommodated in the developing device 13. 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 8, the developing device 13 includes a developing roller 13a as a developer carrying member, conveying screws 13b1 and 13b2 (auger screws) as conveying members, a doctor blade 13c as a developer regulating member, and a partition. It is comprised by the member 13d.
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 of a nonmagnetic material such as aluminum, stainless steel, brass, or conductive resin in a cylindrical shape. It is configured to be rotated counterclockwise at about 150 to 600 rpm by a rotation driving mechanism (not shown). Referring to FIGS. 3, 5, and 6A, a magnet 13a1 that forms a plurality of magnetic poles H1 to H6 on the peripheral surface of the sleeve 13a2 is fixed 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.

5 and 6A show 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 applied to the first magnetic pole H1 (main magnetic pole) formed at a position facing the photosensitive drum 11, and on the downstream side of the first magnetic pole H1 and above the developing case 13r. The second magnetic pole H2 (conveying magnetic pole) formed at the position, 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 third magnetic pole H3 A fourth magnetic pole H4 (agent separating magnetic pole) formed between the five magnetic poles H5 and above the tip of the partition member 13d, and a fifth magnetic pole H5 (agent separating) formed above the first transport path. A rear 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. 6A, the above-mentioned six magnetic poles H1 to H6 are five poles ("N" or "S" in FIG. 6) 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 (in the present embodiment). , N pole.) Between the two magnetic poles (the third magnetic pole H3 and the fifth magnetic pole H5).
The six magnetic poles H1 to H6 will be described in more detail later.

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 present embodiment, the rotation direction of the second conveying screw 13b2 is set to be opposite to the rotation direction of the developing roller 13a (clockwise in FIG. 2).
Then, the second transport screw 13b2 has a second developer G circulated from the downstream side of the transport path by the first transport screw 13b1 via the first relay portion 13f to the upstream side of the transport path by the first transport member 13b1. It conveys via the relay part 13g (it is the conveyance shown by the dashed-dotted arrow of FIG. 3).
The two conveying screws 13b1 and 13b2 are arranged so that the rotation shaft is substantially horizontal, like the developing roller 13a and the photosensitive drum 11. Moreover, as for the two conveyance screws 13b1 and 13b2, both have a screw part (screw pitch: about 40 mm, number of threads: one or two) with a shaft part with a shaft diameter of about 6 to 10 mm and an outer diameter of about 20 mm. It is wound in a spiral. Moreover, the rotation speed of the two conveyance screws 13b1 and 13b2 is set to about 600 to 900 rpm.

The conveyance path (first conveyance path) by the first conveyance screw 13b1 and the conveyance path (second conveyance path) by the second conveyance screw 13b2 are isolated from each other by a wall portion.
3 and 4, the downstream side of the transport path (second transport path) by the second transport screw 13b2 and the upstream side of the transport path (first transport path) by the first transport screw 13b1 are 2 It communicates via the relay part 13g. The developer G that has reached the downstream side of the second conveyance path by the second conveyance screw 13b2 falls by its own weight at the second relay portion 13g and reaches the upstream side of the first conveyance path.
3 and 4, the downstream side of the conveyance path by the first conveyance screw 13b1 and the upstream side of the conveyance path by the second conveyance screw 13b2 communicate with each other via the first relay unit 13f. Yes. Then, the developer G that has not been supplied onto the developing roller 13a in the first conveyance path by the first conveyance screw 13b1 stays in the vicinity of the first relay portion 13f and rises up, and then passes through the first relay portion 13f. It is transported (supplied) to the upstream side of the second transport path by the two transport screws 13b2.
In addition, in order to improve the transportability of the developer (transfer of the developer against the direction of gravity from the first transport path to the second transport path) in the first relay portion 13f, the first transport screw 13b1 A paddle-shaped portion or a screw portion in which the winding direction of the screw is formed in the reverse direction can be provided at a downstream position (a position corresponding to the first relay portion 13f).

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

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

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

Hereinafter, the developer G used in the present embodiment will be briefly described.
The toner T (the toner in the developer G and the toner in the toner container 28) used in the present embodiment is a polymerized toner, and a styrene-acrylonitrile-acrylate copolymer as a binder resin. Styrenic resin (monopolymer or copolymer containing styrene or a styrene-substituted product), polyester resin, epoxy resin, or a composite of them can be used. In addition, as a production method (polymerization method) of these polymerized toners, bulk polymerization, solution polymerization, emulsion polymerization, suspension polymerization, and the like can be used.
Further, as the external additive of the toner T, it is preferable to use inorganic fine particles (for example, those having 1.0% by weight of silica and 0.5% by weight of titanium oxide). Furthermore, oxidized rice wax, low molecular weight polypropylene wax, carnauba wax and the like can be used as a release agent. Moreover, a charge control agent can be contained as required.
Further, the toner T used in the present embodiment has a volume average particle diameter of 6 μm, and is formed so that the particle diameter is 5 to 80 μm.
In this embodiment, polymerized toner is used, but pulverized toner can also be used.

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

Hereinafter, a characteristic configuration / operation in the developing device 13 of the present embodiment will be described.
Referring to FIGS. 5, 7, 8, and the like, the developing device 13 according to the present embodiment includes a partition member 13 d (partitioning member 13 d) that partitions the first transport path and the second transport path at a position facing the developing roller 13 a. Separation plate) 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 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. Further, the partition member 13d is detachable (separable) from the developing case 13r (a case member shown by hatching in FIG. 2).

7 and 8, in the developing device 13 in the present embodiment, the partition member 13d is pushed by the elastic force acting toward the developing roller 13a, and one end portion of the partition member 13d is pushed. An elastic member 13w is provided to bring the portion (both ends in the longitudinal direction) into contact with the developing roller 13a.
Specifically, referring to FIGS. 7 and 8B, elastic members 13w are attached to both ends in the longitudinal direction of the rear end of the partition member 13d (the side not facing the developing roller 13a). It is worn. This elastic member 13w is a sponge material such as polyurethane foam, and is interposed between the partition member 13d and the developing case 13r in the guide portion 13r1 (U-shaped groove) of the developing case 13r. With such a configuration, the partition member 13d is urged toward the developing roller 13a by the elastic force of the elastic member 13w in a state where both ends in the longitudinal direction are slidably held by the guide portion 13r1 ( FIG. 7 is an upward bias.)

On the other hand, a contact portion 13d1 (protrusion portion) that contacts the developing roller 13a by the elastic force of the elastic member 13w is provided at both ends in the longitudinal direction of the front end portion of the partition member 13d (the side facing the developing roller 13a). Is provided.
Specifically, with reference to FIG. 7 and FIG. 8B, the tip of the partition member 13d is developed as an abutting portion 13d1 at both ends (upstream and downstream) of the second transport path. It is comprised so that the roller 13a may be lightly contacted. In contrast, with reference to FIGS. 7 and 8A, at the center of the second transport path, the tip of the partition member 13d is configured not to contact the developing roller 13a as a non-contact portion 13d2. Has been.

  With such a configuration, the degree of variation in the gap CG between the developing roller 13a and the partition member 13d (opposite surface of the non-contact portion 13d2) is determined according to the component accuracy of the partition member 13d (mainly from the tip of the contact portion 13d1). It is a dimensional accuracy with respect to the length in the short direction to the tip of the non-contact portion 13d2. That is, even if the dimensional accuracy and assembly accuracy of components other than the partition member 13d (for example, the developing roller 13a and the developing case 13r) vary, the elastic member 13w partitions the outer peripheral surface of the developing roller 13a. The gap CG between the developing roller 13a and the partition member 13d (opposite surface of the non-contact portion 13d2) is determined in a state where the contact portion 13d1 of the member 13d is always in contact (the partition member 13d with respect to the development roller 13a). Will be positioned). As described above, since the gap CG between the developing roller 13a and the partition member 13d (opposing surface of the non-contact portion 13d2) can be determined only by the component accuracy of one component (the partition member 13d), the stacking is performed. Also from the viewpoint of tolerance, the variation in the gap CG between the developing roller 13a and the partition member 13d (non-contact portion 13d2) can be reduced. Accordingly, it is possible to reliably reduce the problem that the gap CG of the partition member 13d becomes larger than the target range and “developer rotation” occurs. Furthermore, the adjustment work of the gap CG of the partition member 13d becomes unnecessary.

  In the present embodiment, the non-contact portion 13d2 of the partition member 13d has a gap CG between the facing surface facing the developing roller 13a and the developing roller 13a of 2 mm or less (preferably 0.1 to 0.5 mm). Is set to be.) In the present embodiment, the gap CG is set to 0.3 mm. As a result, the occurrence of “developer rotation” is surely prevented.

Here, in the present embodiment, as shown in FIG. 7, the partition member 13d is formed so as to come into contact with the developing roller 13a at two positions spaced apart in the longitudinal direction. Specifically, the contact portions 13d1 (projections) of the partition member 13d are formed at both ends in the longitudinal direction (the left-right direction in FIG. 7).
With such a configuration, the partition member 13d is abutted (positioned) in a balanced manner with two-point support by the elastic force of the elastic member 13w. Furthermore, by setting the number of contact portions 13d1 of the partition member 13d that contacts the developing roller 13a to the minimum necessary, the partition member can be obtained without increasing the damage to the developing roller 13a and the driving torque of the developing device 13 so much. The variation in the gap CG of 13d can be suppressed, and “developer rotation” can be efficiently and reliably reduced.
In this embodiment, in order to further secure the above-described effect, the contact portion 13d1 is formed in a substantially hemispherical shape so as to be in point contact with the developing roller 13a.

Here, in the present embodiment, referring to FIG. 7, the partition member 13d (contact portion 13d1) is in the same range as the effective image forming area W (the longitudinal range of the magnet 13a1) in the developing roller 13a. .) Is formed so as to contact the developing roller 13a outside the region.
Since the effective image forming area W in the developing roller 13a is an area where the developer G is actually carried on the developing roller 13a (an area where an image may be formed), the above-described configuration is adopted. As a result, even if the contact portion of the developing roller 13a is worn due to sliding with the contact portion 13d1, the portion becomes a non-image region, so that the toner image (image) is hardly affected.

  In order to reduce the sliding resistance between the contact portion 13d1 of the partition member 13d and the developing roller 13a, at least the contact portion 13d1 is preferably formed of a low friction material. In that case, the entire partition member 13d can be formed of a low friction material, the entire contact portion 13d1 can be formed of a low friction material, or the contact surface of the contact portion 13d1 (on the developing roller 13a). It is also possible to form only the contact surface) with a low friction material by coating or the like. As the low friction material, fluorine resin such as Teflon (registered trademark), urethane resin, nylon resin, or the like can be used.

  Further, in order to reduce the problem that the surface of the developing roller 13a is worn by sliding with the contact portion 13d1 and affects the developing process, at least the contact portion 13d1 is placed on the surface of the developing roller 13a (sleeve 13a2). It is preferable to form with a material whose hardness is lower than the hardness. In that case, all of the partition member 13d can be formed of a low hardness material, or only the contact portion 13d1 can be formed of a low hardness material. As the low hardness material, fluorine resin such as Teflon (registered trademark), urethane resin, nylon resin, or the like can be used. Since the influence on the toner image is larger when the surface of the developing roller 13a is worn than when the contact portion 13d1 is worn, such a configuration is useful.

Further, in the present embodiment, the partition member 13d is detachably (replaceable) with respect to the developing case 13r with the elastic member 13w attached. Specifically, with respect to the developing device 13 in a state where the developing roller 13a is taken out, both ends in the longitudinal direction of the partition member 13d with the elastic member 13w attached are engaged with the holder portion 13r1 of the developing case 13r ( Alternatively, the partition member 13d is slid downward (or upward) in FIG. 7 so as to be disengaged), whereby mounting (or detachment) of the partition member 13d with respect to the developing case 13r is completed.
Thus, by forming the partition member 13d to be detachable (replaceable), the partition member 13d can be easily replaced with a new one even when the contact portion 13d1 is consumed by sliding with the developing roller 13a. Can be replaced (maintenance).

In the present embodiment, referring to FIG. 5, the developing roller 13a (first roller) is formed in the boundary area between the second conveyance path and the first conveyance path from the inside of the second conveyance path due to the influence of the fifth magnetic pole H5. A magnetic field directed toward the conveyance path) 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, in this partition member 13d, the range of the contact portion 13d1 that contacts the developing roller 13a is minimized, and the range of the non-contact portion 13d2 that faces the developing roller 13a in a non-contact manner is as long as possible. Therefore, it is possible to reduce a problem that the surface of the developing roller 13a is damaged or a driving torque of the developing device 13 is increased as compared with the case where the contact part is formed over the entire length direction.
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.

Referring to FIG. 5, in the present embodiment, the second transport screw 13b2 (second transport member) is viewed in a cross section (FIG. 5) perpendicular to the rotation center axis of the developing roller 13a. The position of the rotation center axis of the second transport screw 13b2 is disposed below the virtual horizontal line passing through the upper end of the developing roller 13a and above the virtual horizontal line passing through the lower end of the developing roller 13a. That is, the position of the rotation center axis of the second transport screw 13b2 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 present 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 the force, a centrifugal force caused 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, 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.

With reference to FIG. 6A, in the present embodiment, the half-value central angle of the first magnetic pole H1 (the central position of the region where the peak magnetic force is halved is the angle formed in the direction of the arrow in FIG. 6). Is -5 °, the median half angle of the second magnetic pole H2 is 58 °, the median half angle of the third magnetic pole H3 is 120 °, the median half angle of the fifth magnetic pole H5 is 212 °, and the median half angle of the sixth magnetic pole H6 is It is set to 280 °. 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, the fifth magnetic pole H5 has a peak magnetic force of 35 mT, and the sixth magnetic pole H6 has a peak magnetic force. It 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.
FIG. 6B shows a magnetic force distribution when the peak magnetic force of the fifth magnetic pole H5 is set to 65 mT. In such a case, the magnetic force acting on the vicinity of the partition member 13d (the magnetic force that attracts the carrier C toward the developing roller 13a) becomes strong.

Referring to FIG. 5, in the present embodiment, when viewed in a cross section orthogonal to the rotation center axis of the developing roller 13a, the virtual horizontal line where the tip of the partition member 13d passes through the rotation center axis of the developing roller 13a. It is formed so as to be above S1 and below 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, referring to FIG. 5, in the present embodiment, when viewed in a cross section orthogonal to the rotation center axis of developing roller 13a, the tip of partition member 13d passes through the rotation center axis of second transport screw 13b2. It is formed so as to be above the virtual horizontal line S2. 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 present embodiment, the inclination angle of the inclined surface of the partition member 13d (the angle formed with the horizontal plane) is formed to be larger than the repose angle of the developer G. 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 present embodiment, the inclination angle θ of the inclined surface of the partition member 13d is set to about 45 degrees.

Referring to FIG. 5, in the present embodiment, the position of the rotation center axis of the first conveyance screw 13b1 is the position of the second conveyance screw 13b2 when viewed in a cross section orthogonal to the rotation center axis of the developing roller 13a. The first conveying screw 13b1 is arranged so as to be between the virtual vertical line passing through the rotation center axis and the virtual vertical line passing through the rotation center axis of the developing roller 13a (between the range M2 in FIG. 5). It is installed.
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.

In the present embodiment, the gap CG between the developing roller 13a and the partition member 13d (non-contact portion 13d2) is configured to be uniform over the longitudinal direction.
On the other hand, as shown in FIG. 9, the gap CG1 with the developing roller 13a at the downstream side in the second transport path (the downstream side in the developer transport direction) is the upstream in the second transport path. The partition member 13d can be formed to be smaller than the gap CG2 with the developing roller 13a at the position on the side (upstream side in the developer transport direction) (CG1 <CG2). Specifically, in the two abutting portions 13d11 and 13d12 respectively provided at both ends of the partition member 13d, the protruding amount (developing roller 13a side) of the abutting portion 13d11 on the downstream side (the right side in FIG. 9). ) Is smaller than the protruding amount of the contact portion 13d12 on the upstream side (the left side in FIG. 9).
With this configuration, as described above with reference to FIG. 4, the developer amount on the downstream side in the second transport path is larger than that on the upstream side, and the position of the agent separation magnetic pole H <b> 4 in the second transport path. Although the developer G after the developing process separated from the developing roller 13a is easily carried on the developing roller 13a again, the gap CG1 of the partition member 13d is set to be extremely small at the downstream position. The problem that the developer G passes between the roller 13a and the partition member 13d and is mixed with the developer G pumped onto the developing roller 13a at the position of the pumping magnetic pole H6 (this phenomenon is referred to as “developer of developer”). Can be prevented in advance. That is, even if the developer G after the developing process separated from the developing roller 13a is carried on the developing roller 13a again at a position downstream of the second transport path, the developer is close to the developing roller 13a. The partition member 13d is mechanically scraped off into the second transport path.
On the other hand, although the gap CG2 of the partition member 13d is set to be relatively large on the upstream side in the second conveyance path, the developer amount is smaller on the upstream side in the second conveyance path than on the downstream side. There is almost no problem that the developer G after the developing process separated from the developing roller 13a at the position of the agent separating magnetic pole H4 in the path is carried again on the developing roller 13a.
In this way, the gap CG1 of the partition member 13d is set small (or lightly contacted) only on the downstream side of the second conveyance path where “developer accompanying” is likely to occur. By setting the gap CG2 of the partition member 13d large at other positions where it is difficult to occur, “developer rotation” can be efficiently and reliably reduced.

  As described above, in the present embodiment, the two conveying screws 13b1 and 13b2 (conveying members) that convey the developer G in the longitudinal direction to form a circulation path face the developing roller 13a (developer carrier). Even when the doctor blade 13c (developer regulating member) is disposed below the developing roller 13a, the partitioning member 13d is pushed toward the developing roller 13a to move the partitioning member 13d. Is provided with an elastic member 13w that abuts a part of the tip of the developing member 13a against the developing roller 13a. Therefore, even if the dimensional accuracy and assembly accuracy of the components vary, Without increasing the driving torque so much, 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. It is possible to reliably reduce the problem to be.

In the present embodiment, a sponge member is used as the elastic member 13w for pressing the partition member 13d against the developing roller 13a. However, a compression spring or a leaf spring may be used as the elastic member 13w. In the present embodiment, the two elastic members 13w are installed at both ends in the longitudinal direction. However, the number of installed elastic members 13w and the installation positions are not limited thereto, and, for example, three or more elastic members 13w. Can also be installed at equal intervals in the longitudinal direction.
In the present embodiment, the contact portion 13d1 has a substantially hemispherical shape, but the shape of the contact portion 13d1 is not limited to this.
Even in these cases, the same effect as in the present embodiment can be obtained.

  In the present embodiment, a part (two contact portions 13d1) of the front end portion of the partition member 13d is configured to contact the developing roller 13a. However, the entire front end portion of the partition member 13d is configured to be the developing roller 13a. It can also comprise so that it may contact | abut. In this case, even if the dimensional accuracy and assembly accuracy of components other than the partition member 13d (for example, the developing roller 13a and the developing case 13r) vary, the elastic member 13w causes the outer peripheral surface of the developing roller 13a to be The tip end of the partition member 13d can be lightly contacted with a desired contact pressure over the entire longitudinal direction. That is, the contact pressure between the developing roller 13a and the partition member 13d is determined only by the component accuracy of the partition member 13d.

  In this embodiment, the toner T is supplied from the toner container 28 toward the developing device 13, but the developer G (toner T and carrier C) is directed toward the developing device 13 from the toner container (developer container). It can also be supplied. In that case, a means for appropriately discharging excess developer from the developing device 13 is provided. Even in such a case, the same effect as in the present embodiment can be obtained.

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

In the present embodiment, the present invention is applied to the developing device 13 in which two conveying screws as conveying members are installed. However, three or more conveying screws are installed, and at least two conveying screws are included. The present invention can also be applied to a developing device installed so as to face the developing roller 13a. In the present embodiment, the number of magnetic poles H1 to H6 formed around the developing roller 13a is six, but the number of magnetic poles formed around the developing roller 13a is five or less, or seven or more. You can also
Also in those cases, the same effect as that of the present embodiment can be obtained by providing the partition member 13d with the contact portion 13d1 as in the present embodiment.

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

1 image forming apparatus body (apparatus body),
11, 11Y, 11C, 11M, 11BK Photosensitive drum (image carrier),
13 Developing device (developing part),
13a Development roller (developer carrier),
13b1 first conveying screw (first conveying member),
13b2 second conveying screw (second conveying member),
13c Doctor blade (developer regulating member),
13d partition member,
13d1 contact part, 13d2 non-contact part,
13r development case,
13w elastic member,
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 (9)

A developing device that contains a developer having a carrier and toner and that develops a latent image formed on an image carrier,
A developer carrying body facing the image carrying body and having a plurality of magnetic poles formed around it;
A developer regulating member that is disposed so as to face the lower side of the developer carrying member and regulates the amount of the developer carried on the developer carrying member;
A plurality of transport members that transport the developer contained in the apparatus in the longitudinal direction to form a circulation path;
With
The plurality of conveying members are:
A first conveying member facing the developer carrying member and supplying the developer to the developer carrying member while conveying the developer in the longitudinal direction;
A second conveying member disposed above the first conveying member to face the developer carrying member and convey the developer detached from the developer carrying member in the longitudinal direction;
Comprising
A partition member facing the developer carrying member and partitioning a first transport path by the first transport member and a second transport path by the second transport member;
An elastic member that pushes the partition member by an elastic force acting toward the developer carrying member so that a part or all of a tip end portion of the partition member contacts the developer carrying member;
Further comprising a,
The gap between the partition member and the developer carrier at a position downstream of the developer transport direction in the second transport path is at the upstream position of the developer transport direction in the second transport path. A developing device formed so as to be smaller than a gap with a developer carrying member .   The developing device according to claim 1, wherein the partition member is formed so as to abut on the developer carrier at two positions spaced apart in the longitudinal direction.   3. The developing device according to claim 1, wherein the partition member is formed so as to contact the developer carrying member outside an effective image forming region of the developer carrying member. The developing device according to claim 1, wherein at least a contact portion of the partition member that contacts the developer carrier is formed of a low friction material. 5. The partition member according to claim 1, wherein at least a contact portion that contacts the developer carrying member is formed of a material having a hardness lower than a hardness of a surface of the developer carrying member. The developing device according to any one of the above. 6. The partition member according to claim 1, wherein the partition member is formed so that a gap between a facing surface facing the developer carrier and the developer carrier is 2 mm or less. The developing device described. The developing device according to claim 1, wherein the partition member is detachable from the developing case. A process cartridge that is detachably installed on the main body of the image forming apparatus,
8. A process cartridge, wherein the developing device according to claim 1 and the image carrier are integrated. An image forming apparatus comprising the developing device according to claim 1 and the image carrier.

Images