JP5332738B2 - Developing device, process cartridge, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device in which two conveying members configured to convey developer in a longitudinal direction and form a circulation path are disposed facing a developer carrier, and nonetheless toner-scattering is suppressed without causing side-effect even with a lapse of time, and to provide a process cartridge and an image forming apparatus. <P>SOLUTION: The developing device includes: a first relay section where the developer G reaching the downstream side of the first conveying path formed by the first conveying member 13b1 flows toward the upstream side of the second conveying path formed by the second conveying member 13b2; and a second relay section where the developer G reaching the downstream side of the second conveying path flows to the upstream side of the first conveying path. A ventilation path 13k leading from the second conveying path to the first conveying path is disposed between the first relay section and the second relay section. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an image forming apparatus using an electrophotographic system such as a copying machine, a printer, a facsimile, or a multifunction machine thereof, and a developing device and a process cartridge installed therein, and in particular, a developer in a longitudinal direction. The present invention relates to a developing device, a process cartridge, and an image forming apparatus in which two transport members that transport and form a circulation path are disposed so as 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), the developer being long A technique is known in which two transport members that transport in the direction to form a circulation path are installed in the vertical direction (see, for example, Patent Document 1 and Patent Document 2).

  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), the toner in the two-component developer is a latent image on the photosensitive drum at a position facing the photosensitive drum. Adhere 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 transport member (first agitation transport member) and a second transport member (second agitation transport member) are installed in the vertical direction, and development is performed by these two transport members. This forms a circulation route for the agent. The first conveying member installed above 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 below 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 conveyance path falls by its own weight on the first relay unit and reaches the upstream side of the second conveyance 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 transport path (the developer that has separated from the developing roller, the developer that has dropped from the first relay unit, the new toner replenished from the upstream side of the second transport path, and Is mixed and pushed up at that position and moved to the upstream side of the first transport path via the second relay section.

  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. 8 of Patent Document 1). 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. 8 of Patent Document 1) 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 the technique of Patent Document 1 and the like described above, in the second transport path, air is transported toward the downstream side together with the developer as the second transport member rotates, and the air stays in the vicinity of the second relay unit. There has been a case in which the developer loses the evacuation place and is scattered outside the developing device together with the toner floating in the second transport path.
Such a problem is a problem that cannot be particularly ignored when the developing device is downsized. This is because when the developing device is downsized, the amount of developer accommodated in the developing device decreases, the amount of replenishing toner per unit amount increases, and the transport member is reduced in diameter to transport the developer. This is because the capacity decreases, and the replenishment toner that floats without being mixed with the developer in the second transport path increases.

  In order to solve such problems, an exhaust port that directly communicates with the outside of the developing device from the second conveyance path is provided, and the exhaust port is provided with toner to prevent leakage of developer and toner from the exhaust port. It is possible to cover with a filter. However, in that case, the toner filter is clogged with toner over time, and the air cannot be exhausted from the exhaust port, causing the toner to scatter, or the toner filter is scraped off due to the collision of the developer. There is a possibility that a deficiency of debris mixed in the developer may occur.

  The present invention has been made to solve the above-described problems, and in the case where two transport members that transport the developer in the longitudinal direction to form a circulation path are disposed so as to face the developer carrier. An object of the present invention is to provide a developing device, a process cartridge, and an image forming apparatus capable of suppressing toner scattering without causing side effects over time.

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 which faces the body and carries the developer; and a first transport which faces the developer carrying body and supplies the developer to the developer carrying body while transporting the developer in the longitudinal direction. A member, a second conveying member that opposes the developer carrying member and conveys the developer separated from the developer carrying member in the longitudinal direction, and a downstream side of the first conveying path by the first conveying member. The first relay portion in which the reached developer flows upstream of the second transport path by the second transport member, and the developer that reaches the downstream side of the second transport path is on the upstream side of the first transport path. A second relay portion that flows, and Between the first relay unit and the second relay unit, in which the vent passage communicating with the first transport path from the second transport path has a plurality in the longitudinal direction.

  The developing device according to a second aspect of the present invention is the developing device according to the first aspect, wherein the vent of the vent path in the second transport path is above the rotation center axis of the second transport member. Are arranged.

  According to a third aspect of the present invention, in the developing device according to the first or second aspect, the vent of the vent path in the first transport path flows through the first transport path. It is disposed above the developer surface.

  A developing device according to a fourth aspect of the present invention is the developing device according to any one of the first to third aspects, wherein the vent of the vent path in the second transport path is the second transport path. It is arrange | positioned in the downstream of this.

  According to a fifth aspect of the present invention, there is provided the developing device according to the fourth aspect, wherein the vent hole of the vent path in the second transport path is disposed within a longitudinal range corresponding to the development area. It was established.

  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 an exhaust port communicating with the outside of the device from the first transport path. It is.

  A developing device according to a seventh aspect of the present invention is the developing device according to the sixth aspect, wherein a toner filter is covered on the exhaust port.

  The developing device according to an eighth aspect of the present invention is the developing device according to the sixth or seventh aspect, wherein the exhaust port is downstream of the vent hole of the vent path in the first transport path. Are arranged.

  A 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 air passage does not contact the first conveying member and the second conveying member. It is arranged like this.

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

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

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

  The present invention is a case where two transport members that transport the developer in the longitudinal direction to form a circulation path are installed so as to face the developer carrier, and the first relay unit and the second relay unit Provided are a developing device, a process cartridge, and an image forming apparatus that are provided with an air passage that leads from the second conveying path to the first conveying path, so that toner scattering is suppressed without causing side effects over time. can do.

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 a figure which shows magnetic force distribution of the magnetic pole formed on a developing roller. It is a figure which shows the state which the ventilation port of the 2nd conveyance path was buried with the developing agent. It is the schematic sectional drawing which looked at another developing device in the longitudinal direction. It is a block diagram which shows another developing device.

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, reference numeral 1 denotes an apparatus main body of a tandem color copier as an image forming apparatus, 2 a writing unit that emits laser light based on input image information, and 3 an original conveying unit that conveys an original D to an original reading unit 4. 4 is a document reading unit that reads image information of the document D, 7 is a paper feeding 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, and 11C. , 11BK is a photosensitive drum as an image carrier on which toner images of each color (yellow, magenta, cyan, black) are formed, 12 is a charging unit that charges the photosensitive drums 11Y, 11M, 11C, and 11BK, 13 Is a developing device for developing an electrostatic latent image formed on each of the photosensitive drums 11Y, 11M, 11C, and 11BK, and 14 is formed on each of the photosensitive drums 11Y, 11M, 11C, and 11BK. A transfer bias roller (primary transfer bias roller) for transferring the toner image superimposed on the recording medium P, and a cleaning unit 15 for collecting untransferred toner on the photosensitive drums 11Y, 11M, 11C, and 11BK. Show.

Reference numeral 16 denotes an intermediate transfer belt cleaning unit that cleans the intermediate transfer belt 17, 17 an intermediate transfer belt on which toner images of a plurality of colors are transferred and superimposed, and 18 a color toner image on the intermediate transfer belt 17 on the recording medium P. A secondary transfer bias roller 20 for transferring the toner image onto the recording medium P indicates a fixing device for fixing an unfixed image on the recording medium P.
Although not shown, each color toner (toner particles) that supplies toner (toner particles) of each color (yellow, cyan, magenta, black) to the developing device 13 is disposed above each of the photosensitive drums 11Y, 11C, 11M, and 11BK. Each container is installed.

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 D is transported from the document table in the direction of the arrow in the drawing by the transport rollers of the document transport unit 3 and placed on the contact glass 5 of the document reading unit 4. Then, the document reading unit 4 optically reads the image information of the document D placed on the contact glass 5.

  Specifically, the document reading unit 4 scans the image of the document D on the contact glass 5 while irradiating light emitted from an illumination lamp. Then, the light reflected by the document D is imaged on the color sensor via the mirror group and the lens. The color image information of the document D is read for each RGB (red, green, blue) color separation light 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, the image information of each color of yellow, magenta, cyan, and black is transmitted to the writing unit 2. The writing unit 2 emits laser light L (see FIG. 2) based on the image information of each color 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 (this is a 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 2, laser light corresponding to the image signal is emitted from the four light sources corresponding to each color. Each laser beam passes through a separate optical path for each of the yellow, magenta, cyan, and black color components (this is an exposure process).

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

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

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

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

On the other hand, the intermediate transfer belt 17 on which the toners of the respective colors on the photosensitive drums 11Y, 11M, 11C, and 11BK are transferred (carrying) are run in the clockwise direction in FIG. 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 the intermediate transfer belt cleaning unit 16. Then, the untransferred toner adhered on the intermediate transfer belt 17 is collected by the intermediate transfer belt cleaning unit 16, 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 by the transport belt. In the fixing device 20, the color image is fixed on the recording medium P at the nip between the fixing belt 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 paper discharge roller, and a series of image forming processes is completed.

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 and the toner container 28. 3A is a schematic cross-sectional view (horizontal cross-sectional view) of the upper portion of the developing device 13 (the position of the first transfer screw 13b1 as the first transfer member) in the longitudinal direction. (B) is a schematic sectional view of the lower part of the developing device 13 (the position of the second conveying screw 13b2 as the second conveying member) as viewed 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 diagram showing the magnitude of the normal direction magnetic flux density of the magnetic poles H1 to H4 formed on the developing roller 13a. Further, FIG. 6 is a diagram showing a state in which the vent hole 13k1 of the second transport path is buried with the developer G, and is a schematic cross-sectional view of the circulation path of the developing device 13 as seen in the longitudinal direction as in FIG. .
Since each image forming unit has almost the same structure and each toner container has almost the same structure, the image forming unit and the toner container in FIGS. 2 to 6 are denoted by alphabets (Y, C, M, BK) is shown in the figure.

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 brush (or 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. 2, toner container 28 contains toner T to be supplied into developing device 13 therein. Specifically, based on information on toner density (which is the ratio of toner in the developer G) detected by a magnetic sensor (not shown) installed in the developing device 13, the shutter driving unit performs shutter. The mechanism 80 is opened and closed, and the toner T is appropriately supplied from the toner container 28 into the developing device 13.
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.
The supply pipe 29 is for reliably guiding the toner T supplied from the toner container 28 into the developing device 13. That is, the toner T discharged from the toner container 28 is supplied into the developing device 13 through the supply pipe 29 from the toner supply port 13e.

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, ventilation. It comprises a passage 13k, an exhaust port 13m, and the like.
A developing roller 13a as a developer carrying member is a developing roller having a small outer diameter of 14 mm or less, and includes a sleeve 13a2 formed by forming a non-magnetic material such as aluminum, brass, stainless steel, or conductive resin into a cylindrical shape. It is configured to be rotated clockwise by a rotation drive mechanism (not shown). 3 and 5, a magnet 13a1 for forming magnetic poles H1 to H4 for generating a plurality of peak values of normal direction magnetic flux density is fixed on the peripheral surface of the sleeve 13a2 in the sleeve 13a2 of the developing roller 13a. It is installed. 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 the magnitude of the normal direction magnetic flux density by the plurality of magnetic poles H1 to H4 formed around the developing roller 13a (sleeve 13a2) by the magnet 13a1. As shown in FIG. 5, the plurality of magnetic poles are formed at positions facing the photosensitive drum 11, positions on the downstream side of the main magnetic pole H <b> 1 and a part of the inner wall surface of the second transport path. The conveying magnetic pole H2 formed on the second conveying path, the agent separating magnetic pole H3 formed above the second conveying path, and the pumping magnetic pole H4 formed from the position facing the first conveying screw 13b1 to the vicinity of the position facing the doctor blade 13c. (Doctor counter magnetic pole), etc.
First, the pumping magnetic pole H4 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 pumping magnetic pole H4 acts is the main magnetic pole H1. It rises at the position and becomes a magnetic brush in the developing region and slides on 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 through the position of the main magnetic pole H1 is transported to the position of the agent separating magnetic pole H3 by the transport magnetic pole H2. The repelling magnetic field acts on the carrier at the position of the agent separating magnetic pole H3, 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.

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. 3A). In addition, the developer G is supplied onto the developing roller 13a at the position of the pumping magnetic pole H4 (the supply in the direction of the white arrow in FIG. 3A).

The second conveyance screw 13b2 as the second conveyance member is disposed below the first conveyance 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 H3 after the developing process, and separated in the direction of the white arrow in FIG. 3B. Is transported horizontally in the longitudinal direction (the transport is in the left direction indicated by the broken-line arrow in FIG. 3B). In the present embodiment, the rotation direction of the second conveying screw 13b2 is set to be the same as the rotation direction of the developing roller 13a (the clockwise direction in FIG. 2). Further, the rotation direction of the first conveying screw 13b1 is set to be opposite to the rotation direction of the developing roller 13a (the counterclockwise direction in FIG. 2).
The second transport screw 13b2 is supplied with the developer G circulated (flowed) from the downstream side of the transport path (first transport path) by the first transport screw 13b1 via the first relay portion 13f. 13b1 is conveyed to the upstream side of the first conveyance path via the second relay unit 13g (this is the conveyance indicated by the one-dot chain line arrow in FIG. 3B).
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. The two conveying screws 13b1 and 13b2 are formed by spirally winding a screw portion having an outer diameter of 16 mm or less around a shaft portion.

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 second conveyance path by the second conveyance screw 13b2 and the upstream side of the first conveyance path by the first conveyance screw 13b1 communicate with each other via the second relay portion 13g. doing. Then, the developer G staying in the vicinity of the second relay part 13g in the second transport path by the second transport screw 13b2 is upstream of the first transport path by the first transport screw 13b1 via the second relay part 13g. It is conveyed (flowed) to the side.
3 and 4, the downstream side of the first conveyance path by the first conveyance screw 13b1 and the upstream side of the second conveyance path by the second conveyance screw 13b2 are connected via the first relay portion 13f. Communicate. 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 falls (flows) by its own weight in the first relay portion 13f, and is upstream of the second conveyance path. Will be reached.

  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 not shown, a magnetic sensor for detecting the toner concentration of the developer circulating in the apparatus is installed in the second transport path by the second transport 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 upstream of the second conveyance path by the second conveyance screw 13b2 and away from the development area (the longitudinal direction of the development roller 13a). It is outside the range.). 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 second transport path. However, the position of the toner replenishing port 13e is not limited to this, and is, for example, above the upstream side of the first transport path. It can also be arranged.

Hereinafter, a characteristic configuration / operation in the developing device 13 of the present embodiment will be described.
Referring to FIGS. 2 and 4, the developing device 13 according to the present exemplary embodiment includes a developing device 13 between the first relay portion 13 f and the second relay portion 13 g and on the back side of the developing device 13 (photosensitive drum). The air passage 13k that leads from the second transport path to the first transport path is provided on the side away from 11.
Thereby, even if the air is transported toward the downstream side (the left side in FIG. 4) together with the developer G by the rotation of the second transport screw 23b2 in the second transport path, the air is transported to the second relay portion 23g. The air is sent from the vent 13k2 of the first transport path to the first transport path through the vent 13k without losing the escape area by the developer G staying in the vicinity of the second transport. The problem that the toner floating in the path is scattered with the air from the second transport path to the outside of the developing device 13 is suppressed.

Here, the vent 13k1 of the vent path 13k in the second transport path is disposed above the rotation center axis of the second transport screw 13b2. In the normal state, as shown in FIG. 4, the vent 13k1 is in a position where it is not buried in the developer G in the second transport path, and the air in the second transport path passes through the vent 13k. It is configured to flow in one transport path.
In addition, the vent hole 13k2 of the vent path 13k in the first transport path is disposed above the developer surface of the developer flowing in the first transport path. Specifically, as shown in FIG. 4, the vent hole 13k2 is disposed considerably above the rotation center axis of the first transport screw 13b1. As a result, the problem that the developer in the first transport path flows backward to the second transport path via the ventilation path 13k is suppressed.
Referring to FIG. 2, even if the developer G enters the air passage 13k from the air vent 13b1, the air flows in the vicinity of the air vent 13b1 so that the developer returns into the second transport path according to gravity. An inclined surface is formed in the path 13k.

Referring to FIG. 4, in the second transport path, developer G collected from the developing roller 13a is transported to the downstream side (the left side in FIG. 4) by the second transport screw 13b2. The amount of developer increases. Further, in the first transport path, the developer G is transported to the downstream side (the right side in FIG. 4) while supplying the developer G to the developing roller 13a by the first transport screw 13b1, so that the developer G is transported to the downstream side. The amount of developer is decreasing.
Here, in the conventional developing device in which the air passage 13k is not provided, when the air is transported to the downstream side (the left side in FIG. 4) together with the developer G by the second transport screw 13b2 in the second transport path. The air loses its place due to the developer G blocked in the vicinity of the second relay portion 13g and flows to the outside through a gap below the developing roller 13a (a gap with the developing case). At this time, the problem is the toner replenished on the upstream side of the second transport path. The upstream side of the second conveyance path has a small amount of developer, and the replenishment toner cannot be mixed in the developer instantaneously and floats in the second conveyance path. The floated toner flows in the second conveyance path by riding on the air current formed by the second conveyance screw 13b2. Therefore, if the airflow is flowing toward the outside of the developing device on the downstream side of the second conveying path, the toner floating in the second conveying path is also carried on the airflow and flows to the outside of the developing device, causing toner scattering. End up.
On the other hand, in this embodiment, since the air passage 13k that leads from the second transport path to the first transport path is provided between the first relay section 13f and the second relay section 13g, the second transport The airflow that has lost its destination on the downstream side of the path can flow to the upstream side of the first transport path. Therefore, it is possible to suppress the occurrence of toner scattering from the second transport path to the outside of the developing device.

Here, as shown in FIGS. 2 and 4, the developing device 13 in the present embodiment is further provided with an exhaust port 13 m communicating with the outside of the developing device 13 from the first transport path. The exhaust port 13m is disposed above the downstream side (the right side in FIG. 4) with respect to the vent port 13k2 of the first transport path, and the exhaust port 13m has a toner filter (rather than the particle size of the toner). It is formed with a small mesh.)
With such a configuration, the air that has flowed into the first conveyance path from the second conveyance path via the ventilation path 13k is downstream (on the right side of FIG. 4) together with the developer G by the first conveyance screw 13b1 in the first conveyance path. Is discharged to the outside of the developing device 13 through the exhaust port 13m. That is, air flows in the direction indicated by the two-dot chain line arrow in FIG. Thereby, the malfunction which the internal pressure of a 1st conveyance path | route raises is suppressed. Further, since the exhaust port 13m is covered with a toner filter, the problem that only air is discharged from the exhaust port 13m to the outside and toner is ejected from the exhaust port 13m is suppressed. Note that the air that has not been discharged from the exhaust port 13m again flows into the second transport path via the first relay portion 13f.

As shown in FIG. 4, in the developing device 13 in the present embodiment, the vent hole 13k1 in the second transport path is disposed on the downstream side (the left side in FIG. 4) of the second transport path. . Specifically, the vent hole 13k1 is disposed slightly upstream from the region where the developer G stays in the vicinity of the second relay portion 13g. Thereby, the airflow formed by the 2nd conveyance screw 13b2 can be smoothly guide | induced to the ventilation path 13k.
Further, the vent hole 13k1 of the second transport path is disposed in a longitudinal range corresponding to the developing area (substantially equal to the magnetizing range of the magnet 13a1 of the developing roller 13a). In the second transport path, the longitudinal range corresponding to the development area is set so that the developer surface is lower than the position (the most downstream) of the second relay portion 13g, so the vent 13k1 is the developer. It becomes difficult to be buried in.

The inventor of the present application uses the developing device 13 in the present embodiment and a conventional developing device (the developing device in the present embodiment is not provided with the air passage 13k) to prevent toner scattering. An experiment was conducted to compare the effects.
In the experiment, the periphery of the developing roller (the opening facing the photosensitive drum) was covered with a film, and the amount of toner scattered from the developing device (the amount of toner attached to the film) was measured. At this time, 1.5 gram of toner (a considerably large amount of toner with respect to the upper limit of about 0.5 gram of the normal toner supply amount) was supplied from the toner supply port 13e. As a result, in the developing device 13 in the present embodiment, the amount of scattered toner from around the developing roller is reduced to ¼ compared to the conventional developing device.
Further, using the developing device 13 in the present embodiment and the conventional developing device, an experiment was performed in which a predetermined number of continuous sheets were passed by an actual machine and the degree of toner scattering from the developing device was visually confirmed. In the latter case, it was confirmed that the toner was evenly adhered to the outer wall of the developing device, but the former was not able to confirm any toner scattering around the developing device.

Here, in the developing device 13 in the present embodiment, a case where the developer amount in the device increases as the toner density of the developer increases will be described.
In the present embodiment, when the toner density of the developer rises to the vicinity of the upper limit value (or the range exceeding the upper limit) and the developer amount increases, the vent hole 13k1 of the second transport path is buried in the developer. The vent 13k1 is disposed at such a position. As described above, the toner density of the developer in the developing device 13 is detected by the magnetic sensor (toner density sensor), and when the toner density exceeds a certain threshold value (about 10% in the present embodiment). Control is performed so that toner supply to the developing device 13 is not performed.
Then, as shown in FIG. 6, when the toner density of the developer increases to the vicinity of the upper limit value (or the range exceeding the upper limit), the developer in the second transport path is compared with FIG. 4 showing the normal state. The amount increases. In this way, the state in which the amount of developer in the second transport path is increased is a state in which replenishment toner is more easily taken into the developer in the second transport path than in the normal state of FIG. And toner scattering is less likely to occur). In the present embodiment, in the state as shown in FIG. 6, since the vent hole 13b1 is buried in the developer G, the internal pressure of the second transport path is increased, and the second transport section 13g is passed to the first transport path. The amount of developer transferred increases. If a certain amount of developer does not collect on the downstream side of the second transport path, the developer cannot be moved to the first transport path through the second relay portion 13g. However, the developer is downstream of the second transport path. If too much is accumulated, a large amount of developer is accumulated up to the vicinity of the developing roller 13a, and the developer may leak from below the developing roller 13a. However, in this embodiment, when the developer has accumulated too much on the downstream side as shown in FIG. 6, the air passage 13k is blocked and the internal pressure in the second transport path increases, so that the developer at the second relay portion 13g. Since the transport amount increases, the problem that the developer leaks from below the developing roller 13a is suppressed.

In summary, when the toner density is not so high, the amount of carrier is not changed and the amount of toner is relatively small. Therefore, as shown in FIG. 4, the amount of developer in the second transport path is relatively small and replenishment is performed. The amount of developer for mixing the toner is reduced, and the replenishment toner is likely to float in the second transport path. Therefore, toner scattering from the second transport path to the outside of the developing device 13 can be reduced by positively flowing air from the second transport path to the first transport path via the ventilation path 13k.
On the other hand, when the toner density increases, the amount of carrier does not change and the amount of toner increases. Therefore, as shown in FIG. 6, the amount of developer in the second transport path increases and the replenishment toner is mixed. As a result, the amount of developer to be increased increases and the replenishment toner is less likely to float in the second transport path, but the developer amount is saturated on the downstream side of the second transport path and is likely to leak out of the developing device. Therefore, in such a case, the amount of developer that moves to the first transport path via the second relay portion 13g is increased by closing the air passage 13k with the increased developer and increasing the internal pressure in the second transport path. Thus, leakage of the developer to the outside due to the saturation of the developer amount on the downstream side of the second transport path is prevented.

In the present embodiment, only one air passage 13k is formed. However, as shown in FIG. 7A, a plurality of air passages 13k are provided between the first relay portion 13f and the second relay portion 13g. Can also be formed. In this case, in the air passage 13k on the upstream side of the second conveyance path, the air vent 13k1 is not filled with the developer even if the toner concentration increases. Therefore, the developer transfer amount in the second relay unit 13g is smaller than that in the present embodiment. However, in the case of a developing device in which the leakage of the developer from the second conveyance path does not easily occur even when the toner concentration increases, for example, control for stopping toner supply when the toner concentration is at the upper limit is performed. In such a case, as shown in FIG. 7A, a configuration in which a plurality of air passages 13k are formed between the first relay portion 13f and the second relay portion 13g is useful.
Further, as shown in FIG. 7B, the vent holes 13k1, 13k2 of the vent path 13k can be formed long in the longitudinal direction. Thus, the ventilation path 13k formed long in the longitudinal direction has substantially the same effect as the plurality of ventilation paths 13k shown in FIG.

  Further, in the present embodiment, as shown in FIG. 2, the air passage 13 k is formed so as to protrude to the back side of the developing device 13. On the other hand, as shown in FIG. 8, the air passage 13 k can be formed so as to be accommodated inside the developing device 13 without being formed so as to protrude from the developing device 13. In that case, it is necessary to arrange | position the ventilation path 13k so that it may not contact the 1st conveyance screw 13b1 and the 2nd conveyance screw 13b2. Accordingly, it is possible to reliably reduce the problem that the developing device 13 is enlarged by forming the air passage 13k while ensuring the effect of the present embodiment.

  As described above, in this 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 carrying member). Since the air passage 13k leading from the second transport path to the first transport path is provided between the first relay section 13f and the second relay section 13g, there is no side effect over time. It is possible to suppress toner scattering from the developing device 13 without the occurrence of toner.

  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 this embodiment, the number of magnetic poles H1 to H4 formed around the developing roller 13a is four. However, the number of magnetic poles formed around the developing roller 13a is three or less, or five or more. You can also Even in that case, the same effect as the present embodiment can be obtained.

  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),
13e Toner supply port,
13f 1st relay part, 13g 2nd relay part,
13k air passage,
13k1, 13k2 vents,
13m exhaust,
G developer (two-component developer), T toner, C carrier.

JP 2003-263012 A JP 2000-305359 A

Claims (11)

A developing device that contains a developer having a carrier and toner and that develops a latent image formed on an image carrier,
A developer carrying body facing the image carrying body and carrying a developer;
A first conveying member facing the developer carrying member and supplying the developer to the developer carrying member while conveying the developer in the longitudinal direction;
A second conveying member that faces the developer carrying member and conveys the developer detached from the developer carrying member in the longitudinal direction;
A first relay portion in which the developer that has reached the downstream side of the first transport path by the first transport member flows to the upstream side of the second transport path by the second transport member;
A second relay unit in which the developer that has reached the downstream side of the second transport path flows to the upstream side of the first transport path;
With
A developing device comprising a plurality of air passages extending in the longitudinal direction from the second transport path to the first transport path between the first relay section and the second relay section.   The developing device according to claim 1, wherein a vent of the vent path in the second transport path is disposed above a rotation center axis of the second transport member.   3. The vent according to claim 1, wherein a vent of the vent path in the first transport path is disposed above a developer surface of the developer that flows in the first transport path. Development device.   4. The developing device according to claim 1, wherein a vent of the vent path in the second transport path is disposed on a downstream side of the second transport path. 5.   The developing device according to claim 4, wherein a vent of the vent path in the second transport path is disposed in a longitudinal range corresponding to the developing area.   6. The developing device according to claim 1, further comprising an exhaust port communicating with the outside of the apparatus from the first transport path.   The developing device according to claim 6, wherein a toner filter is covered at the exhaust port.   The developing device according to claim 6, wherein the exhaust port is disposed on a downstream side with respect to a vent hole of the vent path in the first transport path.   The developing device according to claim 1, wherein the air passage is disposed so as not to contact the first transport member and the second transport member. 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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