JP2012108234A - Developing device, process cartridge, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device that has at least two of plural conveyance members, which convey developer in a longitudinal direction and form a circulation path, installed to face opposite to a developer carrier; and reduces the occurrence of toner scattering due to rise of inner pressure of a first conveyance path disposed below a second conveyance path despite the above installation, as well as a process cartridge, and an image forming apparatus.SOLUTION: A developing device 13 includes a partition member 13d, which partitions a first conveyance path formed of a first conveyance member 13b1 and a second conveyance path formed of a second conveyance member 13b2, provided inside thereof with a ventilation passage 13d1 for ventilating air inside the first conveyance path from an opening 13d2 formed above the first conveyance path to the outside of the developing device 13.

Description

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

  2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine or a printer, a developing device that contains a two-component developer composed of a toner and a carrier (including a case where an additive or the like is added), and the developer is long. A technique is known in which at least two conveying members are installed in a vertical direction among a plurality of conveying members that are conveyed in a direction to form a circulation path (see, for example, Patent Documents 1 to 3).

  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). The developer carried on the developing roller is regulated to an appropriate amount by a doctor blade (developer regulating member) installed so as to face the developing roller, and then the toner in the two-component developer is transferred to the photosensitive drum (image). It adheres to the latent image on the photosensitive drum at a position facing the carrier.

  In the developing devices in Patent Documents 1 to 3 and the like, a first conveying member (supply screw) and a second conveying member (collection screw) are installed in the vertical direction, and these conveying members provide a developer circulation path. Forming. 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. In such a developing device, a doctor blade (developer regulating member) is disposed below the developing roller.

  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.

  On the other hand, Patent Document 4 and the like disclose a technique of providing a pressure relief opening in the upper part of the casing of the developing device in order to prevent toner scattering due to an increase in internal pressure inside the developing device. The opening is covered with a filter in order to prevent toner from leaking as air moves from the opening.

In the developing devices described in Patent Documents 1 to 3 and the like described above, the toner scatters from the gap between the developing roller and the case, and the inside of the image forming apparatus main body is stained, and the image formed on the recording medium is displayed. There was a case where a problem of soiling occurred.
As a result of repeated research, the inventor of the present application has found such a problem that the first transport path disposed below the second transport path is surrounded by the wall surface, the developing roller, and the developer, and the rotation of the developing roller. Accordingly, it has been found that there is a cause that air is sucked into the first transport path from the outside and the internal pressure in the first transport path tends to increase. In other words, toner scattering occurs due to an increase in the internal pressure of the first transport path disposed below the second transport path.

  Further, such a problem is common to a developing device in which a plurality of conveying members (a supply screw and a recovery screw) are arranged in the vertical direction, and a doctor blade (developer regulating member) is provided. The same occurs even when the supply screw is provided above the developing roller and the supply screw is provided above the recovery screw (see, for example, FIG. 6 of Patent Document 1).

  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 when installed so as to face each other, a developing device, a process cartridge, and a toner cartridge that reduce the occurrence of toner scattering due to an increase in internal pressure of the first transport path disposed below the second transport path, and An object is to provide an image forming apparatus.

  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 carrier having a plurality of magnetic poles formed on the periphery thereof, and an amount of the developer carried on the developer carrier and disposed so as to face the developer carrier 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 carrier. A first conveying member that conveys the developer in the longitudinal direction, and a first conveying member that is disposed above the first conveying member so as to face the developer carrier and convey the developer in the longitudinal direction. 2 transport members, and the development A partition member facing the carrier and partitioning the first transport path by the first transport member and the second transport path by the second transport member is further provided, and the partition member has the first transport in the interior thereof An air passage for ventilating the air inside the path from the opening formed above the first transport path toward the outside of the apparatus is provided.

  According to a second aspect of the present invention, there is provided the developing device according to the first aspect, wherein the developer regulating member is disposed so as to face a lower side of the developer carrying member. The conveying member supplies the developer to the developer carrying member while conveying the developer in the longitudinal direction, and the second conveying member conveys the developer separated from the developer carrying member in the longitudinal direction. It is.

  According to a third aspect of the present invention, in the developing device according to the second aspect, the opening formed in the partition member is formed such that the height of the upper end thereof is constant over the longitudinal direction. In addition, the height of the lower end is formed so that the upstream side is higher than the downstream side in the developer conveyance direction in the first conveyance path.

  According to a fourth aspect of the present invention, there is provided the developing device according to the first aspect, wherein the developer regulating member is disposed so as to face an upper side of the developer carrying member, and the second The conveying member supplies the developer to the developer carrying member while conveying the developer in the longitudinal direction, and the first conveying member conveys the developer detached from the developer carrying member in the longitudinal direction. It is.

  According to a fifth aspect of the present invention, in the developing device according to the fourth aspect, the opening formed in the partition member is formed such that the height of the upper end is constant over the longitudinal direction. In addition, the height of the lower end is formed so that the downstream side is higher than the upstream side in the developer conveyance direction in the first conveyance path.

  A 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, further comprising a filter that covers the opening of the partition member.

  A developing device according to a seventh aspect of the present invention is the developing device according to any one of the first to fifth aspects, wherein the developing device is formed on the downstream side of the ventilation passage of the partition member and is provided outside the apparatus. An exhaust port that communicates with the filter and a filter that covers the exhaust port are further provided.

  According to an eighth aspect of the present invention, there is provided the developing device according to the seventh aspect of the present invention, wherein a space isolated by a wall portion is provided between the air passage and the exhaust port.

  The developing device according to a ninth aspect of the present invention is the developing device according to any one of the first to eighth aspects, wherein the second transport path is formed on a ceiling portion of the second transport path. A second opening for ventilating the air toward the outside, and a filter covering the second opening.

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

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

  In the present application, the “process cartridge” refers to a charging unit that charges the image carrier, a developing unit (developing device) that develops a latent image formed on the image carrier, and a cleaning on the image carrier. At least one of the cleaning units and the image carrier are defined as a unit that is integrated and detachably installed on the image forming apparatus main body.

  In the present invention, even when a plurality of transport members that transport the developer in the longitudinal direction to form a circulation path are installed so that at least two transport members face the developer carrier, the first A developing device that reduces the occurrence of toner scattering due to an increase in internal pressure of the first transport path because the air passage is provided in the partition member that partitions the transport path and the second transport path disposed above the transport path. A process cartridge and an image forming apparatus can be provided.

1 is an overall configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention. It is a block diagram which shows an image creation part. (A) The schematic sectional view which looked at the upper part of the developing device in the longitudinal direction, (B) The schematic sectional view which looked at the lower part of the developing device in the longitudinal direction. It is the schematic sectional drawing which looked at the circulation path of the developing device in the longitudinal direction. It is sectional drawing which shows a developing device. It is a schematic perspective view which shows a part of partition member. It is sectional drawing which shows the image development apparatus of another form. It is sectional drawing which shows the image development apparatus of another form. It is a table | surface figure which shows an experimental result.

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, thereby forming an electrostatic latent image of the cyan component. The black component laser beam is applied to the surface of the fourth photosensitive drum 11BK from the left side of the paper, and an electrostatic latent image of the black component is formed.

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

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

On the other hand, the intermediate transfer belt 17 on which the toners of the respective colors on the photosensitive drums 11Y, 11M, 11C, and 11BK are transferred (carrying) are run counterclockwise in the drawing, and the secondary transfer bias roller 18 and Reach the opposite position. Then, a color toner image carried on the intermediate transfer belt 17 is transferred onto the recording medium P at a position facing the secondary transfer bias roller 18 (secondary transfer step).
Thereafter, the surface of the intermediate transfer belt 17 reaches the position of an intermediate transfer belt cleaning unit (not shown). Then, the untransferred toner attached on the intermediate transfer belt 17 is collected by the intermediate transfer belt cleaning unit, and a series of transfer processes in the intermediate transfer belt 17 is completed.

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

Then, the recording medium P on which the full color image is transferred is guided to the fixing device 20 thereafter. In the fixing device 20, the color image is fixed on the recording medium P at the nip between the fixing roller and the pressure roller.
Then, the recording medium P after the fixing step is discharged as an output image outside the apparatus main body 1 by a discharge roller and stacked on the discharge tray 5 to complete a series of image forming processes.

Next, the image forming unit in the image forming apparatus will be described in detail with reference to FIGS.
FIG. 2 is a configuration diagram illustrating the image forming unit. 3A is a schematic cross-sectional view (horizontal cross-sectional view) of the upper portion of the developing device 13 (the position of the second transport screw 13b2 as the second transport member) in the longitudinal direction. (B) is a schematic cross-sectional view of the lower part of the developing device 13 (the position of the first conveying screw 13b1 as the first conveying member) in the longitudinal direction. FIG. 4 is a schematic cross-sectional view (vertical cross-sectional view) of the circulation path of the developing device 13 as viewed in the longitudinal direction. FIG. 5 is a cross-sectional view showing the developing device (a cross-sectional view orthogonal to the rotation center axis of the developing roller 13a). Further, FIG. 6A is a perspective view showing a part of the partition member 13d (in the vicinity of the opening 13d2) obliquely from below, and FIG. 6B is a perspective view showing a modification thereof.
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 alphabets (Y, C, M, BK).

As shown in FIG. 2, the image forming unit includes a photosensitive drum 11 as an image carrier, a charging unit 12, a developing device 13 (developing unit), a cleaning unit 15, and the like.
The photoconductor drum 11 as an image carrier is a negatively charged organic photoconductor having an outer diameter of about 30 mm, and is 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. The developing device 13 develops the electrostatic latent image formed on the photosensitive drum 11 (forms a toner image). The configuration and operation of the developing device 13 will be described in detail later.

Referring to FIG. 1, toner container 28 contains toner T to be supplied into developing device 13 therein. Specifically, toner conveyance (not shown) is performed based on information on the toner density (the ratio of toner in the developer G) detected by a magnetic sensor (not shown) installed in the developing device 13. The toner T is appropriately supplied from the toner supply port 13e from the toner container 28 into the developing device 13 through the tube.
The supply of the toner T is not limited to the toner density information, but may be performed based on the image density information detected from the reflectance of the toner image formed on the photosensitive belt or the intermediate transfer belt. Good. Further, the implementation of the supply of the toner T may be determined by combining these different pieces of information.

Hereinafter, the developing device 13 in the image forming apparatus will be described in detail.
2 to 6, the developing device 13 includes a developing roller 13a as a developer carrying member, conveying screws 13b1 and 13b2 (auger screws) as conveying members, a doctor blade 13c as a developer regulating member, and a partition. It is comprised by the member 13d.
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). 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 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, the above-mentioned six magnetic poles H1 to H6 are formed by five poles magnetized by the magnet 13a1 of the developing roller 13a (indicated by “N” or “S” in FIG. 5). Is. 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).

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. 2 and 5, the developing device 13 in the present embodiment includes a partition member 13 d (separating plate) that partitions the first transport path and the second transport path at a position facing the developing roller 13 a. 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 formed integrally with the developing case 13r (a case member indicated by hatching in FIG. 2).
As described above, the cutting member 13d is provided between the first conveyance path and the second conveyance path at a position facing the development roller 13a, so that the developer G released from the development roller 13a is removed from the development roller. Inconveniences that are carried again on 13a (this phenomenon is referred to as “developer rotation”) are reduced.
In the present embodiment, 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). It is set to be. In the present embodiment, the gap (CG) is set to 0.3 mm. This reliably reduces the occurrence of “developer rotation”.

2 and 5 and the like, in the developing device 13 according to the present embodiment, air inside the first transport path is formed in the partition member 13d above the first transport path. A vent path 13d1 is provided for venting toward the outside of the developing device 13 from the opened opening 13d2.
Specifically, a part of the partition member 13d (developing case 13r) has a hollow structure, and an air passage 13d1 is provided from the opening 13d2 (intake port) to the exhaust port 13d3. Further, the opening 13d2 (intake port) of the air passage 13d1 is on the facing surface of the partition member 13d facing the first transport screw 13b1, and is a position above the first transport path (a position not buried in the developer). .). Further, the exhaust port 13d3 of the air passage 13d1 is disposed on the outer wall surface of the developing case 13r and at a position opening toward the outside of the developing device 13.

As described above, even in the developing device 13 in which the first transport path and the second transport path are arranged in the vertical direction, the ventilation path 13d1 is provided in the partition member 13d that separates the first transport path and the second transport path. By providing this, it is possible to reduce an increase in internal pressure in the first transport path disposed below the second transport path. That is, the air passage 13d1 serves as an air escape path in the first transport path, and the air flows from the first transport path to the outside of the apparatus through the air passage 13d1 (the flow in the direction of the white arrow in FIG. 5). ), The increase in the internal pressure of the first transport path can be reduced. Therefore, the occurrence of toner scattering due to an increase in the internal pressure of the first transport path can be reduced.
In particular, the first transport path is a path for supplying a developer (a developer having a high toner density before the development process) onto the developing roller 13a. In comparison, the degree of toner scattering increases when the internal pressure in the path increases. Therefore, it is significant to provide the air passage 13d1 for reducing the increase in internal pressure in the first transport path.

Here, referring to FIG. 3 and FIG. 5, in the present embodiment, a filter 13s that covers the opening 13d2 (intake port) of the partition member 13d is further installed.
Specifically, the filter 13s is a filter made of a nonwoven material or the like in which the mesh size is smaller than the toner particle size and the toner T can be collected. By installing the filter 13s in the opening 13d2, it is possible to suppress a problem that toner floating in the first conveyance path is discharged together with air to the outside of the developing device 13 through the ventilation path 13d1.

  In the present embodiment, the air inside the second transport path is directed to the outside of the developing device 13 at the ceiling of the second transport path (the position above the second transport path in the developing case 13r). A second opening 13w is provided for ventilation. Further, a filter 13t that covers the second opening 13w is provided. This can reduce the occurrence of toner scattering due to an increase in the internal pressure of the second transport path, and the toner floating in the second transport path can be removed from the developing device 13 through the second opening 13w together with the air. It is possible to suppress the problem of being discharged.

In the present embodiment, as shown in FIG. 6 (A), the opening 13d2 of the partition member 13d has a height A at the upper end that is constant over the longitudinal direction (the direction perpendicular to the plane of FIG. 3). The lower end height B1 was formed in a substantially rectangular shape so as to be constant over the longitudinal direction.
On the other hand, as shown in FIG. 6B, the opening 13d2 of the partition member 13d has an upper end height A that is constant over the longitudinal direction, and the downstream side (first transport path indicated by a white arrow in the figure). The lower end height B1 of the upstream side is higher than the lower end height B1 of the lower side of the developer conveying direction (in order to satisfy B1 <B2). You can also Specifically, the height of the lower end of the opening 13d2 is formed so as to gradually increase from the downstream side to the upstream side. As described above with reference to FIG. 4, this is because the surface of the developer G becomes lower in the first transport path from the upstream side toward the downstream side. That is, the lower end of the opening 13d2 is formed so as to match the change in the height of the developer surface in the first transport path. As a result, the opening 13d2 is not buried with the developer in the longitudinal direction, and the function of the air passage 13d1 for preventing an increase in the internal pressure of the first transport path is reliably ensured.

In the present embodiment, the filter 13s is installed at the position of the opening 13d2 (intake port) leading to the first conveyance path. However, as shown in FIG. 7, the filter 13s is formed on the downstream side of the ventilation path 13d1 and the developing device. The filter 13v can also be installed at the position of the exhaust port 13m1 communicating with the outside of 13 (or the position of the exhaust port 13d3 in FIG. 5).
In such a case, the filter 13v can be easily attached and detached from the outside of the developing device 13, so that the replacement work of the filter 13v can be easily performed when the filter 13v is clogged.
Further, as shown in FIG. 7, a space 13m (a space separated from the first transport path and the second transport path) is formed between the ventilation path 13d1 and the exhaust port 13m1 by a wall portion. You can also. That is, the air in the first transport path passes through the ventilation path 13d1 and the space 13m and is discharged to the outside of the developing device 13 through the filter 13v (the flow in the direction of the white arrow in FIG. 7). .) Even in such a case, it is possible to reduce the occurrence of toner scattering due to an increase in the internal pressure of the first conveyance path, and the toner floating in the first conveyance path together with the air via the exhaust port 13m1 can be developed. Can be prevented from being discharged to the outside. In particular, when the space 13m as described above is provided, the area of the filter 13v can be set large, so that the replacement frequency of the filter 13v can be lowered.

In the present embodiment, the present invention is applied to the developing device 13 that supplies the developer to the developing roller 13a in the first transport path and collects the developer from the developing roller 13a in the second transport path. Applied.
On the other hand, as shown in FIG. 8, the developer is supplied to the developing roller 13a in the second conveying path (conveying path by the second conveying screw 13b2), and the first conveying path (by the first conveying screw 13b1). The present invention can also be applied to the developing device 13 that collects the developer from the developing roller 13a in the transport path).
Specifically, as shown in FIG. 8, the doctor blade 13c (developer regulating member) is disposed above the developing roller 13a that rotates clockwise in FIG. The second conveying screw 13b2 (second conveying member) is disposed above the first conveying screw 13b1 (first conveying member), and supplies the developer to the developing roller 13a while conveying the developer in the longitudinal direction. To do. The first transport screw 13b1 transports the developer separated from the developing roller 13a in the longitudinal direction (the direction opposite to the transport direction by the second transport screw 13b2). A developer circulation path is formed by the second conveyance path by the second conveyance screw 13b2 and the first conveyance path by the first conveyance screw 13b1. 8 includes the rotation direction of the developing roller 13a and the photosensitive drum 11, the installation direction of the doctor blade 13c with respect to the developing roller 13a, the supply / recovery function of the first conveying screw 13b1 and the second conveying screw 13b2, Except for the difference, the configuration is almost the same as that of the present embodiment. Also in the developing device 13 of FIG. 8, as in the present embodiment, by providing the partition member 13d with the air passage 13d1, it is possible to obtain substantially the same effect as in the present embodiment.

  In the developing device 13 shown in FIG. 8, as described above with reference to FIG. 6, the opening 13d2 of the partition member 13d can be formed in a substantially right triangle shape. However, in this case, unlike the one in the present embodiment, the first transport path is a developer recovery path, and therefore, referring to the description of the second transport path in FIG. The developer surface of the developer G becomes higher toward the side. Therefore, in order to prevent a problem that the opening 13d2 is buried in the developer in the longitudinal direction, the height of the opening 13d2 of the partition member 13d is constant in the longitudinal direction, compared with the height of the lower end on the upstream side. It forms so that the height of the lower end in a downstream side may become high.

Finally, an experiment conducted to confirm the effect of the present invention for reducing the above-described toner scattering will be briefly described with reference to FIG.
Referring to FIG. 9, in this experiment, four types of developing devices (Examples 1 to 3 and comparative example) are prepared, and each is installed in the image forming apparatus main body 1 to print 10,000 sheets. This is a measurement of the amount of smoke (total amount of scattering) of the toner scattered from the developing device 13 after the operation. The developing device of Example 1 is the one in this embodiment (the developing device shown in FIGS. 3, 5, 6A, etc.), and the developing device of Example 2 is shown in FIG. The developing device of Example 3 is the same as that of the present embodiment, and the opening 13d2 is set in the shape of FIG. 6B. In the comparative example, the air passage 13d1 is formed in the partition member 13d. (This is a conventional developing device).
From the experimental results shown in FIG. 9, it can be seen that the amount of scattered toner is drastically reduced by providing the air passage 13d1 in the partition member 13d as in the first to third embodiments. In particular, when the shape of the opening 13d2 is set as shown in FIG. 6B as in the third embodiment, it can be seen that the toner scattering amount further decreases.

  As described above, in the present embodiment, the two conveying screws 13b1 and 13b2 (conveying members) that convey the developer in the longitudinal direction to form a circulation path face the developing roller 13a (developer carrier). Even in such a case, since the air passage 13d1 is provided in the partition member 13d that partitions the first transport path and the second transport path disposed above the first transport path, the internal pressure of the first transport path It is possible to reduce the occurrence of toner scattering due to the rise of the toner.

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

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

In the present embodiment, the present invention is applied to the developing device 13 in which two conveying screws as conveying members are installed. However, three or more conveying screws are installed, and at least two conveying screws are included. The present invention can also be applied to a developing device installed so as to face the developing roller 13a. In the present embodiment, the number of magnetic poles H1 to H6 formed around the developing roller 13a is six, but the number of magnetic poles formed around the developing roller 13a is five or less, or seven or more. You can also
In these cases, the same effect as in the present embodiment can be obtained by providing the air passage 13d1 in the partition member 13d 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 air passage, 13d2 opening (intake port),
13r development case,
13s, 13t, 13v filter,
13w second opening,
G developer (two-component developer), T toner, C carrier.

Japanese Patent Laid-Open No. 11-174810 JP 2008-26408 A Japanese Patent No. 3950735 Japanese Patent Laid-Open No. 9-236980

Claims (11)

A developing device that contains a developer having a carrier and toner and that develops a latent image formed on an image carrier,
A developer carrying body facing the image carrying body and having a plurality of magnetic poles formed around it;
A developer regulating member that is disposed so as to face the developer carrying member and regulates the amount of the developer carried on the developer carrying member;
A plurality of transport members that transport the developer contained in the apparatus in the longitudinal direction to form a circulation path;
With
The plurality of conveying members are:
A first conveying member facing the developer carrying member and conveying the developer in the longitudinal direction;
A second conveying member that is disposed above the first conveying member and faces the developer carrying member, and conveys the developer 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;
The partition member includes an air passage for allowing air inside the first transport path to vent toward the outside of the apparatus from an opening formed above the first transport path. A developing device. The developer regulating member is disposed so as to face the lower side of the developer carrier,
The first conveying member supplies the developer to the developer carrying member while conveying the developer in the longitudinal direction,
The developing device according to claim 1, wherein the second transport member transports the developer separated from the developer carrying member in a longitudinal direction.   The opening formed in the partition member is formed such that the height of the upper end is constant over the longitudinal direction, and the height of the lower end is on the downstream side in the developer transport direction in the first transport path. The developing device according to claim 2, wherein the developing device is formed so as to be higher on the upstream side. The developer regulating member is disposed so as to face above the developer carrier,
The second transport member supplies the developer to the developer carrier while transporting the developer in the longitudinal direction,
The developing device according to claim 1, wherein the first transport member transports the developer separated from the developer carrying member in a longitudinal direction.   The opening formed in the partition member is formed such that the height of the upper end is constant over the longitudinal direction, and the height of the lower end is on the upstream side in the developer transport direction in the first transport path. The developing device according to claim 4, wherein the developing device is formed so that the downstream side is higher than the developing device.   The developing device according to claim 1, further comprising a filter that covers the opening of the partition member. An exhaust port formed on the downstream side of the ventilation path of the partition member and leading to the outside of the device;
A filter covering the exhaust port;
The developing device according to claim 1, further comprising:   The developing device according to claim 7, further comprising a space isolated by a wall portion between the air passage and the exhaust port.   The second transport path includes a second opening for ventilating air inside the second transport path toward the outside and a filter covering the second opening in the ceiling portion. The developing device according to claim 1, wherein: A process cartridge that is detachably installed on the main body of the image forming apparatus,
10. A process cartridge in which the developing device according to claim 1 and the image carrier are integrated.   An image forming apparatus comprising the developing device according to claim 1 and the image carrier.

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