JP2010210942A - Developing device, process cartridge, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device that prevents such a fault leading to density deviation or density decrease of an output image and that can be further reduced in size, and to provide a process cartridge and an image forming apparatus. <P>SOLUTION: The developing device includes: conveying members 13b1 and 13b2 for longitudinally conveying a developer while facing a developer carrier 13a; and a developer-regulating member 13c for regulating an amount of developer G held on the developer carrier 13a. Among a plurality of magnetic poles H1 to H6 formed in the developer carrier 13a, a plurality of magnetic poles formed from the position facing the image carrier 11 to the position facing the developer-regulating member 13c include at least two pairs of magnetic pole groups (H2-H3 and H4 and H5) in which magnetic poles adjacent to each other become the same polarity. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus using an electrophotographic system, such as a copying machine, a printer, a facsimile machine, or a multifunction machine thereof, and a developing device and a process cartridge installed therein. The present invention relates to a developing device, a process cartridge, and an image forming apparatus in which a conveying member that conveys in a direction is installed.

  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 a plurality of conveying members that are conveyed in a direction to form a circulation path are installed in a vertical direction or a horizontal direction (see, for example, Patent Document 1).

  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, two transport members (a first stirring transport member and a second stirring transport member) are installed in the vertical direction, and a developer circulation path is formed by the two transport members. ing. The 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 conveying member installed below conveys the developer separated from the developing roller at the position of the agent separation magnetic pole in the longitudinal direction (the direction opposite to the conveying direction by the upper conveying member). The downstream side of the conveyance path (first conveyance path) by the upper conveyance member and the upstream side of the conveyance path (second conveyance path) by the lower conveyance member communicate with each other via a relay unit. The developer that has reached the downstream side of the first transport path falls by its own weight on the relay unit and reaches 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. Further, 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 (the developer separated from the developing roller, the developer that has dropped from the relay portion, and the new toner replenished from the upstream side of the second conveyance path are mixed. ) Stays at that position and is pushed up and moved to the upstream side of the first transport path via the second relay section.

  Further, FIG. 8 and the like of Patent Document 1 disclose a developing device in which two conveying members (first screw and second screw) are installed in the horizontal direction. The conveying member facing the developing roller supplies the developer to the developing roller at the position of the pumping magnetic pole while conveying the developer in the longitudinal direction, and lengthens the developer separated from the developing roller at the position of the agent separating magnetic pole. Transport in the direction. A downstream side of a transport path (first transport path) by a transport member (first transport member) facing the developing roller, and a second transport member (a transport member facing the developing roller via the first transport member). To the upstream side of the transport path (second transport path) via the relay section. Then, the developer that has reached the downstream side of the first transport path reaches the upstream side of the second transport path via the relay unit. Here, a toner supply port is provided on the upstream side of the second conveyance path, and new toner is appropriately supplied. Further, 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 is moved to the upstream side of the first transport path via the second relay unit.

  In this way, the developing device having a conveying member that stirs and mixes the developer while conveying the developer in the longitudinal direction is a conveying member that agitates and mixes the developer while conveying the developer in the short direction and the longitudinal direction. Compared to a developing device (for example, see JP-A-6-348124), the apparatus can be downsized and the number of components can be reduced.

  In the conventional developing device described above, the conveying member facing the developing roller (the lower conveying member when there are two conveying members in the vertical direction) is located at a lower position than the developing roller and is somewhat to the developing roller. Otherwise, the developer that has separated from the developing roller will be pumped up again on the developing roller before it is sufficiently stirred and mixed with the replenishing toner, resulting in insufficient toner chargeability. In some cases, the toner image formed on the carrier may have a density deviation or a decrease in density. This makes it difficult to further reduce the size of the developing device.

  The present invention has been made in order to solve the above-described problems, and is free from problems such as density deviation and density reduction in an output image, and can further reduce the size of the developing device, process cartridge, and Another 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 carrying body facing the body and having a plurality of magnetic poles formed around it, and one or a plurality of conveyances carrying the developer contained in the apparatus in the longitudinal direction while facing the developer carrying body A member and a developer regulating member that regulates the amount of the developer before the developer carried on the developer carrying body reaches a position facing the image carrying body. Among the plurality of magnetic poles, a pair of magnetic poles formed between the position facing the image carrier and the position facing the developer regulating member is a pair in which adjacent magnetic poles are the same. To have at least two magnetic pole groups They have been made.

  A developing device according to a second aspect of the present invention is the developing device according to the first aspect, wherein the conveying members are arranged in the vertical direction so as to face each other and are accommodated in the device. Two conveying members that convey the agent in the longitudinal direction to form part or all of the circulation path, wherein the pair of magnetic pole groups is formed at a position facing the lower conveying member of the two conveying members. The other pair of magnetic pole groups is formed at a position facing the upper conveying member of the two conveying members, and the other pair of magnetic pole groups is formed on the conveying path by the lower conveying member. It is formed so that a part of the magnetic force extends upward.

  According to a third aspect of the present invention, there is provided the developing device according to the first aspect, wherein the conveying member is one conveying member adjacent to the developer carrying member, and the one conveying member. Is formed such that one magnetic pole of the pair of magnetic pole groups and one magnetic pole of the other pair of magnetic pole groups are adjacent to each other.

  A developing device according to a fourth aspect of the present invention is the developing device according to the third aspect, wherein the developing device is opposed to the developer carrying member via the one conveying member and is installed in the apparatus together with the one conveying member. Is further provided with a second conveying member that conveys the developer accommodated in the longitudinal direction to form part or all of the circulation path.

  A developing device according to a fifth aspect of the present invention is the developer according to any one of the first to fourth aspects, wherein the developer agent is transported in a transport path by the transport member when the apparatus is in operation. The surface is formed so as to be above the lowermost position of the developer carrying member.

  According to a sixth aspect of the present invention, there is provided a process cartridge according to any one of the first to fifth aspects, wherein the process cartridge is detachably installed on the main body of the image forming apparatus. The developing device and the image carrier are integrated.

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

  In the present application, the “process cartridge” means 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, the conveying member that conveys the developer in the longitudinal direction is disposed so as to face the developer carrier, and the plurality of magnetic poles formed around the developer carrier is optimized. It is possible to provide a developing device, a process cartridge, and an image forming apparatus that are free from problems such as density deviation and density reduction in an output image and that can further reduce the size of the apparatus.

1 is an overall configuration diagram illustrating an image forming apparatus according to Embodiment 1 of the present invention. It is a block diagram which shows an image creation part. (A) The schematic sectional view which looked at the upper part of the developing device in the longitudinal direction, (B) The schematic sectional view which looked at the lower part of the developing device in the longitudinal direction. It is the schematic sectional drawing which looked at the circulation path of the developing device in the longitudinal direction. It is a figure which shows magnetic force distribution of the magnetic pole formed on a developing roller. It is a figure which shows the flow of the developer in the one side edge part of a developing device. It is sectional drawing which shows the developing device in Embodiment 2 of this invention. It is sectional drawing which shows another developing device.

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

Embodiment 1 FIG.
The first embodiment of the present invention will be described in detail with reference to FIGS.
First, the configuration and operation of the entire image forming apparatus will be described with reference to FIG.
In FIG. 1, 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 photoconductor drum 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, the image processing unit performs color conversion processing, color correction processing, spatial frequency correction processing, and the like 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 magnetic force distribution of the magnetic poles H1 to H6 formed on the developing roller 13a. Further, FIG. 6 is a diagram showing the flow of the developer G at one end portion of the developing device (in the vicinity of the second relay portion 13g in FIG. 4).
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 driven to rotate counterclockwise by a rotation drive mechanism (not shown).

The charging unit 12 is a charging roller having elasticity in which a foamed urethane layer having a medium resistance in which a urethane resin, carbon black as conductive particles, a sulfurizing agent, a foaming agent, and the like are formed in a roller shape on a core metal. The material of the middle resistance layer of the charging unit 12 is urethane, ethylene-propylene-diene polyethylene (EPDM), butadiene acrylonitrile rubber (NBR), silicone rubber, isoprene rubber, etc. It is also possible to use a rubber material in which a conductive material such as the above is dispersed or a foamed material of these materials.
The cleaning unit 15 is provided with a cleaning 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, a developing device 13 includes a developing roller 13a as a developer carrying member, two conveying screws 13b1 and 13b2 (auger screws) as conveying members, and a doctor blade 13c as a developer regulating member. , Etc.
The developing roller 13a as the developer carrying member has an outer diameter of about 18 mm, and a sleeve 13a2 formed of a nonmagnetic material such as aluminum, brass, stainless steel or conductive resin in a cylindrical shape is rotationally driven (not shown). It is configured to be rotated clockwise by the mechanism. 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 doctor blade 13c is a plate-like member made of aluminum, stainless steel or the like, and the amount of the developer G is adjusted before the developer G carried on the developing roller 13a reaches the position facing the photosensitive drum 11. Regulate to an appropriate amount. The toner is attracted to the latent image formed on the photosensitive drum 11 by the electric field (developing electric field) formed in the developing area.

FIG. 5 shows a plurality of magnetic poles H1 to H6 formed around the developing roller 13a (sleeve 13a2) by the magnet 13a1. As shown in FIG. 5, the plurality of magnetic poles are a first magnetic pole H <b> 1 (main magnetic pole) formed at a position facing the photoconductive drum 11, an inner wall surface of the second transport path on the downstream side of the first magnetic pole H <b> 1. The second magnetic pole H2 formed at a position over a part of the second magnetic pole, the third magnetic pole H3 formed above the second transport path, and the position opposite to the first transport screw 13b1 adjacent to the third magnetic pole H3. The fourth magnetic pole H4, the fifth magnetic pole H5 formed at the position facing the doctor blade 13c (doctor facing magnetic pole), the sixth magnetic pole H6 formed between the fifth magnetic pole H5 and the first magnetic pole H1, etc. Composed.
First, the fifth magnetic pole H5 acts on a carrier as a magnetic body, and the developer G accommodated in the first transport path is pumped onto the developing roller 13a. Part of the developer G carried on the developing roller 13a is scraped off at the position of the doctor blade 13c (developer regulating member) and returned to the first transport path. On the other hand, the developer G carried on the developing roller 13a through the doctor gap between the doctor blade 13c and the developing roller 13a at the position of the doctor blade 13c where the magnetic force by the fifth magnetic pole H5 acts is the sixth magnetic pole H6. Then, after being conveyed to the position of the first magnetic pole H1, it rises at the position of the first magnetic pole H1 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 first magnetic pole H1 is conveyed by the second magnetic pole H2 to a position between the third magnetic pole H3 (formed in the same polarity as the second magnetic pole H2). . Then, the repulsive magnetic field formed between the second magnetic pole H2 and the third magnetic pole H3 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. It is. 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 conveying screw 13b1 as an upper conveying member is disposed at a position facing the developing roller 13a, and conveys the developer G horizontally in the longitudinal direction (rotating axis direction) (see FIG. 3A). In addition, the developer G is supplied onto the developing roller 13a at the position of the fifth magnetic pole H5 (in the direction indicated by the white arrow in FIG. 3A).

The second conveying screw 13b2 as a lower conveying member is disposed below the first conveying screw 13b1 and at a position facing the developing roller 13a. Developer G separated from the developing roller 13a (developer G forcibly separated from the developing roller 13a by the repulsive magnetic field formed by the second magnetic pole H2 and the third magnetic pole H3 after the developing step, 3) is transported horizontally in the longitudinal direction (the transport in the left direction indicated by the broken-line arrow in FIG. 3B). In the first embodiment, the rotation direction of the second conveying screw 13b2 is set to be opposite to the rotation direction of the developing roller 13a (counterclockwise 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 conveyance shown by the dashed-dotted arrow of FIG. 3 (B)).
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. Further, the two conveying screws 13b1 and 13b2 are formed by spirally winding a screw portion 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 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. Then, the developer G that has risen and stayed in the vicinity of the second relay portion 13g in the transport path by the second transport screw 13b2 is transported to the upstream side of the transport path by the first transport screw 13b1 via the second relay portion 13g ( Supply).
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 conveying path by the first conveying screw 13b1 falls by its own weight at the first relay portion 13f and reaches the upstream side of the second conveying path. become.

  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 the developer over a relatively long time toward the downstream side.
In the first embodiment, the toner replenishment port 13e is disposed in the conveyance path by the second conveyance screw 13a2, but the position of the toner replenishment port 13e is not limited to this, and for example, the first conveyance path It can also be arranged above the upstream side.

Hereinafter, a characteristic configuration and operation of the developing device 13 according to the first embodiment will be described.
As described above with reference to FIG. 5, six magnetic poles (first magnetic pole H1, second magnetic pole H2, third magnetic pole H3, fourth magnetic pole H4, fourth magnetic pole H4, and second magnetic pole H4 are formed around the developing roller 13a (sleeve 13a2) by the magnet 13a1. Five magnetic poles H5 and a sixth magnetic pole H6) are formed. Here, in the first embodiment, among the six magnetic poles H1 to H6 formed around the developing roller 13a, it is between the position facing the photosensitive drum 11 and the position facing the doctor blade 13c. The plurality of magnetic poles formed are formed to include at least two pairs of magnetic pole groups in which adjacent magnetic poles are the same. Specifically, five magnetic poles (first magnetic pole H1 and second magnetic pole H2) are required from the position facing the photosensitive drum 11 to the position facing the doctor blade 13c along the rotation direction of the developing roller 13a. , A third magnetic pole H3, a fourth magnetic pole H4, and a fifth magnetic pole H5) are formed, and two magnetic pole groups in which adjacent magnetic poles are the same are formed. Adjacent magnetic poles have the same polarity. One magnetic pole group is a second magnetic pole H2 and a third magnetic pole H3, which are set to N poles, and the other magnetic pole group is a fourth magnetic pole H4 and a fifth magnetic pole H5. And are set to S poles. The polarities of the other magnetic poles are set such that the first magnetic pole H1 is the S pole and the sixth magnetic pole H6 is the N pole.
More specifically, a pair of magnetic pole groups H2 and H3 are formed at a position facing the second transport screw 13b2 (lower transport member), and another one is positioned at a position facing the first transport screw 13b1 (upper transport member). A pair of magnetic pole groups H4 and H5 is formed. The magnetic pole groups H4 and H5 facing the first transport screw 13b1 (upper transport member) are partially magnetic (fourth magnetic pole H4) above the transport path (second transport path) by the second transport screw 13b2. It is formed so as to reach.

With such a configuration, referring to FIG. 5, in the second transport path, the positions excluding the downstream side in the transport direction (the center in the width direction and the right end in the width direction in FIG. At a relatively low position), the developer G after the developing process carried on the developing roller 13a is separated from the developing roller 13a by the repulsive magnetic poles of one of the magnetic pole groups H2 and H3 and collected in the second transport path. However, the magnetic force of the third magnetic pole H3 and the magnetic force of the fourth magnetic pole H4 out of the other magnetic pole groups H4 and H5 do not act on the collected developer G, and the pumping to the developing roller 13a does not occur.
On the other hand, referring to FIG. 6, in the second transport path, the position downstream of the transport direction (the left end in the width direction in FIG. 4 and in the vicinity of the second relay portion 13g, the developer agent) In this case, the developer G after the developing process carried on the developing roller 13a by the repulsive magnetic poles of the magnetic pole groups H2 and H3 is collected in the second transport path and the third magnetic poles. The magnetic force of H3 and the magnetic force of the fourth magnetic pole H4 of the other magnetic pole groups H4 and H5 act on the collected developer G to pump up the developer to the developing roller 13a and transport the developer on the developing roller 13a. (Developer flow in the direction of the arrow in FIG. 6). The developer pumped up to the developing roller 13a on the downstream side of the second conveying path is separated from the developing roller 13a by the repulsive magnetic poles of the other magnetic pole groups H4 and H5 and collected in the first conveying path. It is again carried on the developing roller 13a by the fifth magnetic pole H5 (the flow of developer in the direction of the arrow in FIG. 6).

In this way, on the downstream side of the second transport path, since the developer delivery from the second transport path to the first transport path is actively promoted, development from the second transport path to the first transport path is facilitated. Density deviation and density reduction of the output image due to insufficient delivery of the developer and insufficient developer in the first transport path are reduced. In addition, the developer on the developing roller 13a that has moved from the second conveying path to the first conveying path is once surely separated from the developing roller 13a and is sufficiently stirred and mixed in the first conveying path. Further, it is possible to reduce density deviation and density reduction of the output image caused by poor stirring / mixing of the developer transferred from the second transport path to the first transport path. Further, since the developer on the developing roller 13a that has moved from the second conveying path to the first conveying path is once surely separated from the developing roller 13a by the repulsive magnetic force, the first developing roller 13a is not affected. The conveyance screw 13b1 (or the second conveyance screw 13b2) can be brought close to each other, and the developing device 13 can be further downsized.
Referring to FIG. 5, in the first embodiment, the position of the developer surface conveyed in the first conveyance path by the first conveyance screw 13b1 during the operation of the developing device 13 is the position of the developing roller 13a. It will be above the lowest position.

  As described above, in the first embodiment, the first conveying screw 13b1 and the second conveying screw 13b2 (conveying member) that convey the developer G in the longitudinal direction are opposed to the developing roller 13a (developer carrying member). Since the plurality of magnetic poles H1 to H6 formed around the developing roller 13a are optimized, there is no problem such as a density deviation or a density drop in the output image. Miniaturization is possible.

  In the first 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). 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 first embodiment can be obtained.

  In the first 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 the first 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 in which (conveying member) is installed in the vertical direction. In the first 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 not limited to this. Absent.
In these cases as well, the same effect as in the first embodiment can be obtained by optimizing the plurality of magnetic poles H1 to H6 formed around the developing roller 13a as in the first embodiment.

Embodiment 2. FIG.
7 and 8, the second embodiment of the present invention will be described in detail.
FIG. 7 is a cross-sectional view showing the developing device in the second embodiment, and corresponds to FIG. 5 in the first embodiment. FIG. 8 is a cross-sectional view showing another developing device different from that shown in FIG.
The developing device according to the second embodiment is provided with two transport members 13b1 and 13b2 facing the developer carrier 13a in that there is one transport member 13b10 facing the developer carrier 13a. This is different from that of the first embodiment.

  As shown in FIG. 7, the developing device 13 according to the second embodiment includes a developing roller 13a as a developer carrying member, a first conveying screw 13b10 as a conveying member, and a second conveying screw 13b20 as a second conveying member. And a doctor blade 13c as a developer regulating member. In the sleeve of the developing roller 13a, a magnet for forming a plurality of magnetic poles H1 to H6 is fixed on the peripheral surface of the sleeve. 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 (not shown). The toner is attracted to the latent image formed on the photosensitive drum by the electric field formed in the development area.

As shown in FIG. 7, a plurality of magnetic poles H1 to H6 formed around the developing roller 13a are formed of a first magnetic pole H1 (main magnetic pole) and a first magnetic pole H1 formed at positions facing the photosensitive drum. On the downstream side, the second magnetic pole H2 formed at a position on the tip of the inner wall surface of the first transport path, the third magnetic pole H3 formed at a position facing the first transport screw 13b10, and the third magnetic pole H3 A fourth magnetic pole H4 formed at a position adjacent to the first conveying screw 13b1 and a fifth magnetic pole H5 (doctor counter magnetic pole) formed at a position facing the doctor blade 13c, a fifth magnetic pole H5 and the first magnetic pole. A sixth magnetic pole H6 formed between H1 and the like.
First, the fourth 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 (developer regulating member) and returned to the first transport path. On the other hand, the developer G carried on the developing roller 13a through the doctor gap between the doctor blade 13c and the developing roller 13a at the position of the doctor blade 13c where the magnetic force by the fifth magnetic pole H5 acts is the sixth magnetic pole H6. Then, after being conveyed to the position of the first magnetic pole H1, it rises at the position of the first magnetic pole H1 and becomes a magnetic brush in the developing region and slides on the photosensitive drum. Thus, the toner T in the developer G carried on the developing roller 13a adheres to the latent image on the photosensitive drum. Thereafter, the developer G that has passed through the position of the first magnetic pole H1 is conveyed by the second magnetic pole H2 to a position between the third magnetic pole H3 (formed in the same polarity as the second magnetic pole H2). . Then, the repulsive magnetic field formed between the second magnetic pole H2 and the third magnetic pole H3 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. It is. The detached developer G falls into the first transport path and is transported downstream of the first transport path by the first transport screw 13b10.

The two conveying screws 13b10 and 13b20 are agitated and mixed while circulating the developer G accommodated in the developing device 13 in the longitudinal direction (the direction perpendicular to the paper surface of FIG. 7).
The first conveying screw 13b10 as a conveying member facing the developing roller 13a conveys the developer G horizontally in the longitudinal direction (rotational axis direction), and on the developing roller 13a at the position of the fourth magnetic pole H4. Supply. The first transport screw 13b10 is disposed so as to be close to the developing roller 13a.

The second conveying screw 13b20 as the second conveying member is disposed at a position facing the developing roller 13a via the first conveying screw 13b10. Then, the developer G separated from the developing roller 13a and delivered from the downstream side of the first transport path is transported horizontally in the longitudinal direction (the direction opposite to the transport direction by the first transport screw 13b10).
Then, the second transport screw 13b20 is configured so that the developer G circulated from the downstream side of the transport path by the first transport screw 13b10 via the first relay portion (not shown) is transported by the first transport member 13b10. To the upstream side through a second relay section (not shown).

The conveyance path (first conveyance path) by the first conveyance screw 13b10 and the conveyance path (second conveyance path) by the second conveyance screw 13b20 are separated from each other by a wall portion.
Although illustration is omitted, the downstream side of the first conveyance path by the first conveyance screw 13b10 and the upstream side of the second conveyance path by the second conveyance screw 13b20 communicate with each other via the first relay unit. Further, the downstream side of the transport path (second transport path) by the second transport screw 13b20 and the upstream side of the transport path (first transport path) by the first transport screw 13b10 communicate with each other via the second relay unit. ing.
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 transport screws 13b10 and 13b20.

  Although illustration is omitted, a magnetic sensor for detecting the toner concentration of the developer circulating in the apparatus is installed in the second conveyance path by the second conveyance screw 13b20. Then, based on the toner density information detected by the magnetic sensor, the inside of the developing device 13 is passed from the toner container through a toner supply port (not shown, but disposed in the vicinity of the first relay unit). A new toner T is supplied toward.

Here, also in the developing device 13 according to the second embodiment, as shown in FIG. 7, the doctor blade from the position facing the photosensitive drum among the six magnetic poles H1 to H6 formed around the developing roller 13a. The plurality of magnetic poles formed until reaching the position facing 13c is formed to include at least two pairs of magnetic pole groups in which adjacent magnetic poles are the same. Specifically, five magnetic poles (a first magnetic pole H1, a second magnetic pole H2, and a second magnetic pole H2, from the position facing the photosensitive drum to the position facing the doctor blade 13c along the rotation direction of the developing roller 13a). A third magnetic pole H3, a fourth magnetic pole H4, and a fifth magnetic pole H5) are formed, and two magnetic pole groups in which adjacent magnetic poles are the same are formed. Adjacent magnetic poles have the same polarity. One magnetic pole group is a second magnetic pole H2 and a third magnetic pole H3, which are set to N poles, and the other magnetic pole group is a fourth magnetic pole H4 and a fifth magnetic pole H5. And are set to S poles. The polarities of the other magnetic poles are set such that the first magnetic pole H1 is the S pole and the sixth magnetic pole H6 is the N pole.
More specifically, one magnetic pole H3 of the pair of magnetic pole groups H2 and H3 and one of the other pair of magnetic pole groups H4 and H5 are disposed at positions facing the conveying screw 13b10 (conveying member). The magnetic pole H4 is formed so as to be adjacent.

  With such a configuration, with reference to FIG. 7, in the first transport path, a part of the developer G after the developing process carried on the developing roller 13a by the repulsive magnetic poles of the one magnetic pole group H2, H3 is developed roller. The developer roller 13a is separated from the first conveyance path and is collected in the first conveyance path, and a part of the developer G pumped up onto the developing roller 13a by the fourth magnetic pole H4 is repelled by the other magnetic pole groups H4 and H5. The developer G in the first transport path is separated from the first transport path and collected in the first transport path, and further between the two pairs of magnetic pole groups (between the third magnetic pole H3 and the fourth magnetic pole H4). And the developer G carried on the developing roller 13a collide with each other (the developer flows in the direction of the arrow in FIG. 7).

As described above, in the first transport path, the first transport screw 13b10 is brought close to the developing roller 13a so that the first repulsive magnetic field is located (between the second magnetic pole H2 and the third magnetic pole H3). Even if there is a developer G after the development process that does not completely separate from the developing roller 13a, as described above, the position of the second repulsive magnetic field (between the fourth magnetic pole H4 and the fifth magnetic pole H5). Thus, the developer G is separated from the developing roller 13a, and the developer G and the developer in the first transport path are developed between the two pairs of magnetic pole groups (between the third magnetic pole H3 and the fourth magnetic pole H4). Since the developer G carried on the roller 13a is made to collide positively, it is possible to reduce density deviation and density reduction of the output image caused by developer agitation / mixing failure in the first transport path. . Further, since the first conveying screw 13b10 can be brought close to the developing roller 13a, the size of the developing device 13 in the horizontal direction (the horizontal direction in FIG. 7) and the vertical direction (the vertical direction in FIG. 7). )) Can be reduced in size.
Referring to FIG. 7, in the second embodiment, the position of the developer surface conveyed in the first conveying path by the first conveying screw 13b10 when the developing device 13 is operated is the position of the developing roller 13a. It will be above the lowest position. This is the vertical direction of the developing device 13 (up and down direction in FIG. 7) as compared with the conventional developing device (the first conveying screw is disposed below the developing roller 13). ) Means that the size has been reduced.

In the second embodiment, the present invention is applied to the developing device 13 provided with the second transport screw 13b20 as the second transport member. However, as shown in FIG. 8, the second transport screw 13b20 is used. The present invention can also be applied to the developing device 13 in which is not installed.
Also in this case, by forming the plurality of magnetic poles H1 to H6 formed around the developing roller 13a in the same manner as that in FIG. 7, it is possible to obtain substantially the same effect as in the second embodiment. However, unlike the one in FIG. 7, the developing device 13 in FIG. 8 does not actively circulate the developer in the longitudinal direction by using a plurality of conveying screws, and therefore, in the conveying path by the conveying screw 13b10. It is preferable that the toner replenishing port 13e for replenishing replenished toner is opened in a range substantially corresponding to the developing region in the longitudinal direction (the direction perpendicular to the paper surface in FIG. 8).

  As described above, also in the second embodiment, similarly to the first embodiment, the first conveying screw 13b10 (conveying member) that conveys the developer G in the longitudinal direction is used as the developing roller 13a (developer carrier). Since the plurality of magnetic poles H1 to H6 formed around the developing roller 13a are optimized so as to be opposed to the developing roller 13a, there is no problem such as density deviation or density reduction in the output image, and the developing device 13 can be further downsized.

  It should be noted that the present invention is not limited to the above-described embodiments, and within the scope of the technical idea of the present invention, the embodiments can be modified as appropriate in addition to those suggested in the embodiments. Is clear. In addition, the number, position, shape, and the like of the constituent members are not limited to the above embodiments, and can be set to a number, position, shape, and the like that are suitable for carrying out the present invention.

1 image forming apparatus body (apparatus body),
11, 11Y, 11C, 11M, 11BK Photosensitive drum (image carrier),
13 Developing device (developing part),
13a Development roller (developer carrier),
13b1 first conveying screw (conveying member),
13b2 second conveying screw (conveying member),
13b10 first conveying screw (conveying member),
13b20 second transport screw (second transport member),
13c Doctor blade (developer regulating member),
H1 first magnetic pole (main magnetic pole), H2 second magnetic pole,
H3 3rd magnetic pole, H4 4th magnetic pole,
H5 5th magnetic pole, H6 6th magnetic pole,
G developer (two-component developer), T toner, C carrier.

JP 2003-263012 A

Claims (7)

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;
One or a plurality of conveying members that face the developer carrying member and convey the developer accommodated in the apparatus in the longitudinal direction;
A developer regulating member that regulates the amount of the developer before the developer carried on the developer carrying body reaches a position facing the image carrying body;
With
The developer carrier has a plurality of magnetic poles formed between the position facing the image carrier and the position facing the developer regulating member, and the adjacent magnetic poles are among the plurality of magnetic poles. A developing device characterized by comprising at least two pairs of magnetic pole groups having the same polarity. The conveying members are two conveying members that are arranged in the vertical direction so as to face each other and that form a part or all of the circulation path by conveying the developer contained in the apparatus in the longitudinal direction. And
The pair of magnetic pole groups is formed at a position facing the lower transport member of the two transport members, and the other pair of magnetic poles at a position facing the upper transport member of the two transport members. 2. The developing according to claim 1, wherein a group is formed, and the other pair of magnetic pole groups is formed so that a part of the magnetic force extends above a conveying path by the lower conveying member. apparatus. The transport member is one transport member close to the developer carrying member,
One magnetic pole of the pair of magnetic pole groups and one magnetic pole of the other pair of magnetic pole groups are formed adjacent to each other at a position facing the one conveying member. The developing device according to claim 1.   The developer is opposed to the developer carrying member via the one conveying member, and the developer contained in the apparatus together with the one conveying member is conveyed in the longitudinal direction to form part or all of the circulation path. The developing device according to claim 3, further comprising two conveying members.   The developer surface of the developer transported in the transport path by the transport member when the apparatus is in operation is formed so as to be above the lowest position of the developer carrier. The developing device according to claim 1. A process cartridge that is detachably installed on the main body of the image forming apparatus,
6. 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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