JP5224120B2 - Developing device, process cartridge, and image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus using an electrophotographic method 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, and particularly uses a two-component developer. The present invention relates to a developing device, a process cartridge, and an image forming apparatus.

  2. Description of the Related Art Conventionally, in a developing device in an image forming apparatus such as a copying machine or a printer, a plurality of developer conveying units in which a two-component developer composed of toner and a carrier (including cases where additives are added) are accommodated. There is known a technique in which a two-component developer is transported in the longitudinal direction and a circulation path is formed by a plurality of developer transport sections (see, for example, Patent Documents 1 to 4).

Specifically, the developing device includes a developing roller (developer carrying member), two developer conveying portions each including a conveying screw (including an auger), a doctor blade (developer regulating member), and the like. A two-component developer is accommodated in the interior.
Then, according to toner consumption in the developing device, toner is appropriately supplied into the device from a toner supply port provided at one end of the developing device. The replenished toner is mixed with the developer in the developing device while being circulated in the longitudinal direction (the same direction as the longitudinal direction of the developing roller) by the two conveying screws. A part of the mixed developer is carried on a developing roller facing a first conveying screw installed in the first developer conveying unit. After the developer carried on the developing roller is regulated to an appropriate amount by the doctor blade, the toner in the developer adheres to the latent image on the photosensitive drum at a position facing the photosensitive drum (image carrier). .

  Further, in such a developing device, the toner (replenishment toner) tends to float on the upper surface (agent surface) of the developer without being sufficiently stirred and mixed in the developer in the circulation path of the developer (such as This phenomenon is called “upslip” of toner), and there are known problems that background stains and density unevenness or toner scattering occurs due to poor charging of the toner on the output image (for example, patent document). 1, see Patent Document 2).

In order to solve such a problem, Patent Document 1 and the like disclose a technique for ejecting air from the upstream side of the toner supply port.
Patent Document 2 and the like disclose a technique for forming a partition wall around a conveying member (screw-shaped rotating member) in a cylindrical shape.
Patent Document 3 discloses a technique for forming a developer restraining region by installing a permanent magnet in the developer circulation path.
Japanese Patent Application Laid-Open No. H11-228561 discloses a technique for dropping the developer separated from the developing roller at the position of the doctor blade to the downstream side of the toner supply port.

JP 2008-26572 A JP 2006-106171 A JP 2006-58696 A JP 2006-58667 A

  In the conventional developing device described above, the toner (replenishment toner) is not sufficiently agitated and mixed in the developer in the developer circulation path under various conditions, and toner “slip” occurs, and the output image There is a possibility that background stains and density unevenness may occur on the top, and that the toner may be scattered outside the apparatus.

Specifically, in the technique of Patent Document 1 or the like, when the bulk density of the developer around the air ejection port varies depending on the image ratio of the output image, a change occurs in the agitation / mixing property of the developer by air. There was a possibility.
Further, in the techniques of Patent Document 2, Patent Document 3, and the like, the replenishment toner may not be sufficiently agitated and mixed in the developer unless the level of the developer surface is secured to some extent.
Further, the technique disclosed in Patent Document 4 or the like causes the developer to drop from the developer on which the replenishment toner floats, and the replenishment toner may not be sufficiently stirred and mixed in the developer by itself.

  The present invention has been made to solve the above-described problems, and the toner is sufficiently agitated and mixed in the developer in the developer circulation path, so that background dirt and density unevenness are generated on the output image. It is an object of the present invention to provide a developing device, a process cartridge, and an image forming apparatus, in which problems that occur and problems that cause toner scattering are reduced.

According to a first aspect of the present invention, there is provided a developing device for storing a developer having a carrier and a toner and developing a latent image formed on an image carrier, the image carrier. A developer carrying body that faces the body and carries the developer, and a first developer carrying unit that feeds the developer to the developer carrying body while carrying the developer in the longitudinal direction by the first carrying screw; The developer is disposed so as to face the first developer conveying portion via a partition member, and the developer fed from the downstream side in the conveying direction of the first developer conveying portion is longitudinally moved by the developer conveying means. And a second developer transport unit that transports the first developer transport unit to the upstream side in the transport direction of the first developer transport unit, and the developer transport means of the second developer transport unit includes a screw portion on the shaft portion. Is formed and rotates in a predetermined direction. And it screws, along with it the screw portion is formed on the shaft portion to rotate at the same rotational speed as the second conveyor screw, disposed in a position distant to the first developer conveying portion than the second conveying screw A third conveying screw, and the screw part of the third conveying screw overlaps the screw part of the second conveying screw when viewed in the direction of the rotation axis. The second transport screw and the third transport screw rotate in the same direction in a direction in which the uppermost portions thereof are away from the first developer transport portion, The second developer transport unit is a toner that detects the toner concentration of the developer at a downstream side in the transport direction and below a position approaching the first developer transport unit with respect to the rotation center of the second transport screw. Dark Those provided with the detection means.

According to a second aspect of the present invention, there is provided the developing device according to the first aspect, wherein the second developer conveying portion is upstream in the conveying direction and is at the rotation center of the third conveying screw. On the other hand, a toner replenishing port for replenishing toner is provided above the position away from the first developer conveying portion.

A process cartridge according to a third aspect of the present invention is a process cartridge that is detachably installed on the main body of the image forming apparatus, and the developing device and the image carrier according to the first or second aspect. Are integrated.

According to a fourth aspect of the present invention, an image forming apparatus includes the developing device according to the first or second aspect and the image carrier.

  In the present application, “process cartridge” means a charging unit (charging device) for charging an image carrier, a developing unit (developing device) for developing a latent image formed on the image carrier, and an image carrier. It is defined as a unit in which at least one of the cleaning unit (cleaning device) for cleaning the top and the image carrier are integrated and installed detachably with respect to the image forming apparatus main body.

  In the present application, “toner” replenished from the toner replenishing port is toner newly replenished to the developing device, and in addition to new toner, recycled toner (for example, toner collected by the cleaning unit). In the case where the developing device is resupplied to the developing device).

  The present invention provides a second developer conveying portion that forms a developer circulation path together with the first developer conveying portion, a second conveying screw that rotates in a predetermined direction, and a rotation shaft that is arranged in parallel with the second conveying screw. A rotating member having a projecting portion that projects toward the shaft portion of the second transport screw so as to overlap the screw portion of the second transport screw when viewed in the direction. As a result, the toner is sufficiently agitated and mixed in the developer in the developer circulation path, thereby reducing problems such as background stains and density unevenness on the output image and toner scattering. An apparatus, a process cartridge, and an image forming apparatus can be provided.

  Hereinafter, the best mode 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.
A 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.
As shown in FIG. 1, four toner containers 32Y, 32M, 32C, and 32K corresponding to the respective colors (yellow, magenta, cyan, and black) are attached to and detached from the toner container accommodating portion 31 above the image forming apparatus main body 100. It is installed freely (changeable).
An intermediate transfer unit 15 is disposed below the toner container housing 31. Image forming portions 6Y, 6M, 6C, and 6K corresponding to the respective colors (yellow, magenta, cyan, and black) are arranged in parallel so as to face the intermediate transfer belt 8 of the intermediate transfer unit 15.
Although illustration is omitted, toner replenishing devices are respectively disposed below the toner containers 32Y, 32M, 32C, and 32K. The toners stored in the toner containers 32Y, 32M, 32C, and 32K are respectively supplied (supplied) into the developing devices of the image forming units 6Y, 6M, 6C, and 6K by the toner replenishing device.

  Referring to FIG. 2, an image forming unit 6Y corresponding to yellow includes a photosensitive drum 1Y as an image carrier, a charging unit 4Y disposed around the photosensitive drum 1Y, and a developing device 5Y (developing unit). , A cleaning unit 2Y, a charge eliminating unit (not shown), and the like. Then, an image forming process (charging process, exposure process, developing process, transfer process, cleaning process) is performed on the photosensitive drum 1Y, and a yellow image is formed on the photosensitive drum 1Y.

  The other three image forming units 6M, 6C, and 6K have substantially the same configuration as that of the image forming unit 6Y corresponding to yellow except that the color of the toner used is different. A corresponding image is formed. Hereinafter, description of the other three image forming units 6M, 6C, and 6K will be omitted as appropriate, and only the image forming unit 6Y corresponding to yellow will be described.

Referring to FIG. 2, a photosensitive drum 1Y as an image carrier is rotationally driven in a clockwise direction in FIG. 2 by a drive motor (not shown). Then, the surface of the photosensitive drum 1Y is uniformly charged at the position of the charging unit 4Y (a charging process).
After that, the surface of the photosensitive drum 1Y reaches the irradiation position of the laser beam L emitted from the exposure device 7 (see FIG. 1), and the electrostatic latent image corresponding to yellow by exposure scanning at this position. Is formed (this is an exposure step).

Thereafter, the surface of the photosensitive drum 1Y reaches a position facing the developing device 5Y, and the electrostatic latent image is developed at this position to form a yellow toner image (developing process).
Specifically, referring to FIGS. 2 and 3, a two-component developer G composed of toner and a carrier (magnetic carrier) is accommodated in the developing device 5Y. The developer G in the developing device 5Y is adjusted so that the toner concentration (the ratio of the toner in the developer G) detected by the magnetic sensor 58Y as the toner concentration detecting means is within a predetermined range. . That is, according to the toner consumption in the developing device 5Y, the toner is replenished into the second developer conveying portion 54Y by the toner replenishing device via the toner replenishing port 64Y. The magnetic sensor 58Y (toner concentration detection means) is a sensor that detects the magnetic permeability of the developer flowing around it and detects the toner concentration of the developer from the magnitude of the magnetic permeability.
The toner replenishing device is connected to the toner container 32Y. Although not shown, the toner replenishing device is stored in a driving unit that rotates and drives the toner container 32Y (toner bottle), a toner tank unit that stores toner discharged from the toner container 32Y, and a toner tank unit. A toner conveying section that conveys the toner toward the toner dropping path, and a toner dropping path that causes the toner conveyed by the toner conveying section to fall by its own weight toward the developing device 5Y (second developer conveying section 54Y). Has been.

  Referring to FIGS. 2 and 3, the toner (supplemented toner) replenished into the second developer transporting part 54Y through the toner replenishing port 64Y is then transferred to three transporting screws 55Y to 57Y (screw-like rotating members). ) Circulates between the first developer conveying portion 53Y and the second developer conveying portion 54Y separated by the partition member 59Y while being mixed and stirred together with the developer G (in the circulation indicated by the broken line arrow in FIG. 3). is there.).

  Specifically, referring to FIG. 3, the developer G in the first developer transport portion 53Y is transported from the right side to the left side of the sheet by the first transport screw 55Y. Thus, a first transport path for transporting the developer G along the longitudinal direction of the developing roller 51Y is formed. On the other hand, the developer G in the second developer transport portion 54Y is transported from the left side to the right side of the sheet by the second transport screw 56Y and the third transport screw 57Y as developer transport means. Thus, a second transport path for transporting the developer G in the direction opposite to the first transport path is formed.

Further, the first developer transport portion 53Y in which the first transport path is formed and the second developer transport portion 54Y in which the second transport path is formed are partitions arranged in regions excluding both longitudinal ends. It is isolated by the member 59Y and communicates at both longitudinal ends where the partition member 59Y is not interposed. That is, the developer G transported by the first developer transport section 53Y flows to the upstream side of the second developer transport section 54Y in the first communication section A, and then the second developer transport section 54Y. It is transported by the second transport screw 56Y and the third transport screw 57Y (developer transport means). The developer G transported by the second developer transport section 54Y flows to the upstream side of the first developer transport section 53Y in the second communication section B, and then the first developer transport section 53Y first. It is conveyed by the conveyance screw 55Y. In other words, in the second developer conveying portion 54Y disposed so as to face the first developer conveying portion 53Y via the partition member 59Y, the first developer conveying portion 53Y is fed from the downstream side in the conveying direction. The developer G thus transported is transported in the longitudinal direction by the second transport screw 56Y and the third transport screw 57Y (developer transport means) and sent to the upstream side in the transport direction of the first developer transport section 53Y. Thus, a circulation path for the developer G is formed between the two developer transport portions 53Y and 54Y.
In the first embodiment, the second transport screw 56Y and the third transport screw 57Y installed in the second developer transport section 54Y are part of each screw section (blade) when viewed in the rotation axis direction. Are arranged so as to overlap, which will be described in detail later.

Thus, the toner in the developer G circulating in the circulation path is attracted to the carrier by frictional charging with the carrier and is carried together with the carrier on the developing roller 51Y in which a plurality of magnetic poles are formed.
Here, referring to FIG. 3, the developing roller 51Y includes a magnet 51b that is fixed inside and forms a plurality of magnetic poles on the circumferential surface of the roller, and a sleeve 51a that rotates around the magnet 23a1. . Then, when the sleeve 51a rotates around the magnet 51b on which a plurality of magnetic poles are formed, the developer G moves on the developing roller 51Y (on the sleeve 51a) with the rotation.

  The developer G carried on the developing roller 51Y as the developer carrying member is conveyed with the rotation of the developing roller 51Y in the direction of the arrow, and reaches the position of the doctor blade 52Y as the developer regulating member. Then, after the developer G on the developing roller 51Y is regulated to an appropriate amount at this position, the developer G is conveyed to a position facing the photosensitive drum 1Y (developing area). The toner is attracted to the latent image formed on the photosensitive drum 1Y by the electric field (developing electric field) formed in the developing area.

Specifically, a plurality of magnetic poles, such as a pumping magnetic pole, a main magnetic pole, a conveyance magnetic pole, and an agent separating magnetic pole, are formed around the developing roller 51Y (sleeve 51a) by the magnet 51b.
First, the pumping magnetic pole acts on a carrier as a magnetic material, and the developer G accommodated in the first developer transport portion 53Y is carried on the developing roller 51Y. A part of the developer G carried on the developing roller 51Y is scraped off at the position of the doctor blade 52Y (developer regulating member) and returned to the developer conveying portion 53Y. On the other hand, the developer G carried on the developing roller 51Y after passing through the doctor gap between the doctor blade 52Y and the developing roller 51Y rises at the position of the main magnetic pole and becomes a magnetic brush in the developing region. Touching 1Y. Thus, the toner in the developer G carried on the developing roller 51Y adheres to the latent image on the photosensitive drum 1Y. Thereafter, the developer G (toner concentration is low) that has passed through the position of the main magnetic pole (development region) is transported to the position of the agent separation magnetic pole by the transport magnetic pole. Then, the developer G after the developing process carried on the developing roller 51Y is detached from the developing roller 51Y at the position of the agent separating magnetic pole. The detached developer G is returned again to the first developer transport section 53Y and circulates in the two developer transport sections 53Y and 54Y. Such a flow of the developer G is repeated.
Here, the developer in the developing device 5Y is adjusted so that the toner ratio (toner concentration) in the developer is within a predetermined range. Specifically, according to the consumption of toner in the developing device 5Y, the toner stored in the toner bottle 32Y is replenished into the second developer conveying portion 54Y by the toner replenishing device via the toner replenishing port 64Y.

Referring to FIG. 2, after the development process described above, the surface of photoreceptor drum 1Y reaches a position facing intermediate transfer belt 8 and first transfer bias roller 9Y, and on this surface of photoreceptor drum 1Y. The toner image is transferred onto the intermediate transfer belt 8 (primary transfer process). At this time, a small amount of untransferred toner remains on the photosensitive drum 1Y.
Thereafter, the surface of the photosensitive drum 1Y reaches a position facing the cleaning unit 2Y, and untransferred toner remaining on the photosensitive drum 1Y at this position is mechanically collected by the cleaning blade 2a (in the cleaning process). is there.).
Finally, the surface of the photosensitive drum 1Y reaches a position facing a neutralization unit (not shown), and the residual potential on the photosensitive drum 1Y is removed at this position.
Thus, a series of image forming processes performed on the photosensitive drum 1Y is completed.

The image forming process described above is performed in the other image forming units 6M, 6C, and 6K in the same manner as the yellow image forming unit 6Y. That is, the laser beam L based on the image information is emitted from the exposure unit 7 disposed below the image forming unit onto the photosensitive drums of the image forming units 6M, 6C, and 6K. Specifically, the exposure unit 7 emits laser light L from a light source, and irradiates the photosensitive drum through a plurality of optical elements while scanning the laser light L with a polygon mirror that is rotationally driven.
Thereafter, the toner images of the respective colors formed on the respective photosensitive drums through the developing process are transferred onto the intermediate transfer belt 8 in an overlapping manner. In this way, a color image is formed on the intermediate transfer belt 8.

  Here, referring to FIG. 1, the intermediate transfer unit 15 includes an intermediate transfer belt 8, four primary transfer bias rollers 9Y, 9M, 9C, 9K, a secondary transfer backup roller 12, and a plurality of tension rollers 12-14. The intermediate transfer cleaning unit 10 and the like. The intermediate transfer belt 8 is stretched and supported by a plurality of roller members 12 to 14 and is endlessly moved in the direction of the arrow in FIG.

The four primary transfer bias rollers 9Y, 9M, 9C, and 9K respectively sandwich the intermediate transfer belt 8 with the photosensitive drums 1Y, 1M, 1C, and 1K to form a primary transfer nip. Then, a transfer bias reverse to the polarity of the toner is applied to the primary transfer bias rollers 9Y, 9M, 9C, and 9K.
The intermediate transfer belt 8 travels in the direction of the arrow and sequentially passes through the primary transfer nips of the primary transfer bias rollers 9Y, 9M, 9C, and 9K. In this way, the toner images of the respective colors on the photosensitive drums 1Y, 1M, 1C, and 1K are primarily transferred while being superimposed on the intermediate transfer belt 8.

  Thereafter, the intermediate transfer belt 8 on which the toner images of the respective colors are transferred in a superimposed manner reaches a position facing the secondary transfer roller 19. At this position, the secondary transfer backup roller 12 sandwiches the intermediate transfer belt 8 with the secondary transfer roller 19 to form a secondary transfer nip. The four-color toner images formed on the intermediate transfer belt 8 are transferred onto a recording medium P such as transfer paper conveyed to the position of the secondary transfer nip. At this time, untransferred toner that has not been transferred to the recording medium P remains on the intermediate transfer belt 8.

Thereafter, the intermediate transfer belt 8 reaches the position of the intermediate transfer cleaning unit 10. At this position, the untransferred toner on the intermediate transfer belt 8 is collected.
Thus, a series of transfer processes performed on the intermediate transfer belt 8 is completed.

Here, the recording medium P transported to the position of the secondary transfer nip is transported from a paper feeding unit 26 disposed below the apparatus main body 100 via a paper feeding roller 27, a registration roller pair 28, and the like. It is a thing.
Specifically, a plurality of recording media P such as transfer paper are stored in the paper supply unit 26 in a stacked manner. When the paper feed roller 27 is driven to rotate counterclockwise in FIG. 1, the uppermost recording medium P is fed toward the rollers of the registration roller pair 28.

  The recording medium P transported to the registration roller pair 28 temporarily stops at the position of the roller nip of the registration roller pair 28 whose rotation drive has been stopped. Then, the registration roller pair 28 is rotationally driven in synchronization with the color image on the intermediate transfer belt 8, and the recording medium P is conveyed toward the secondary transfer nip. In this way, a desired color image is transferred onto the recording medium P.

Thereafter, the recording medium P on which the color image is transferred at the position of the secondary transfer nip is conveyed to the position of the fixing unit 20. At this position, the color image transferred to the surface is fixed on the recording medium P by heat and pressure generated by the fixing roller and the pressure roller.
Thereafter, the recording medium P is discharged to the outside of the apparatus through the rollers of the discharge roller pair 29. The recording media P discharged to the outside of the apparatus by the discharge roller pair 29 are sequentially stacked on the stack unit 30 as an output image.
Thus, a series of image forming processes in the image forming apparatus is completed.

Hereinafter, the configuration and operation of the developing device 5Y, which are characteristic in the first embodiment, will be described in detail.
As shown in FIGS. 2 to 4, the developing device 5Y according to the first embodiment has two conveying screws (first screws) as developer conveying means for conveying the developer G in the longitudinal direction in the second developer conveying portion 54Y. 2 conveyance screw 56Y and 3rd conveyance screw 57Y). Referring to FIG. 4, the second transport screw 56Y and the third transport screw 57Y both have shaft portions 56Y2 and 57Y2 formed with screw portions 56Y1 and 57Y1 (blades), and have the same rotational speed. Rotate with.
The third transport screw 57Y is juxtaposed with the second transport screw 56Y and overlaps the screw portion 56Y1 of the second transport screw 56Y when viewed in the rotation axis direction (when viewed in the direction shown in FIG. 2). Thus, it functions as a rotating member having a protruding portion that protrudes toward the shaft portion 56Y2 of the second conveying screw 56Y. In other words, the third transport screw 57Y is juxtaposed with the second transport screw 56Y and to a position close to the shaft portion 56Y2 of the second transport screw 56Y so as not to contact the screw portion 56Y1 of the second transport screw 56Y. It functions as a rotating member having a protruding portion that protrudes. Here, the protruding portion of the rotating member (the protruding portion protruding toward the shaft portion 56Y2 of the second transport screw 56Y) becomes the screw portion 57Y1 of the third transport screw 57Y. In other words, the second transport screw 56Y and the third transport screw 57Y installed in the second developer transport portion 54Y overlap part of the screw portions 56Y1 and 57Y1 (blades) when viewed in the rotation axis direction. At the same time, the screw portions 56Y1 and 57Y1 are arranged so as not to interfere with each other (see FIG. 2).

More specifically, referring to FIG. 4, when the screw diameters of the screw parts 56Y1 and 57Y1 are a, the shaft diameters of the shaft parts 56Y2 and 57Y2 are b, and the distance between the axes is c, the two transport screws 56Y , 57Y overlap amount d is
d = ac
(However, 0 <d <c−b)
It becomes. In the first embodiment, the screw pitch N and screw diameter a of the screw portions 56Y1 and 57Y1 of the two conveying screws 56Y and 57Y, and the shaft diameter b of the shaft portions 56Y2 and 57Y2 are formed to be the same.

In the first embodiment, the screw diameters of the screw portions 56Y1 and 57Y1 and the shaft diameters of the shaft portions 56Y2 and 57Y2 of the two transport screws 56Y and 57Y are formed to be the same. On the other hand, when the screw diameters of the screw portions 56Y1 and 57Y1 and the shaft diameters of the shaft portions 56Y2 and 57Y2 are different, the overlap amount d of the two transport screws 56Y and 57Y is obtained by the following equation. The screw diameter of the screw portion 56Y1 of the second conveying screw 56Y as a _1, a screw diameter of the screw portion 57Y1 of the third conveying screw 57Y as a _2, a shaft diameter of the shaft portion 56Y2 of the second conveying screw 56Y as b ₁ the shaft diameter of the shaft portion 57Y2 of the third conveying screw 57Y is taken as b _{2,
d = (a 1/2 +} a 2/2) -c
(Where, 0 <d <c- (b 1/2 + b 2/2))
It becomes.

By configuring in this way, in the second developer conveying portion 54Y, the developer G pumped upward by the screw portion (blade) of one conveying screw (the third conveying screw 57Y or the second conveying screw 56Y) The screw part (blade) of the other transport screw (second transport screw 56Y or third transport screw 57Y) approaches and exerts a large force that shears the developer G in the vertical direction. As a result, the developer G transported in the second developer transport portion 54Y does not cause the replenishment toner replenished from the toner replenishing port 64Y to float on the upper surface of the developer G (without “sliding up”). It will be stirred and mixed efficiently and reliably in the vertical direction. Therefore, the toner density of the developer G is made uniform and the chargeability of the toner is improved.
In addition, by providing the two developer screws 56Y and 57Y in the second developer conveying portion 54Y, it is possible to improve the developer conveying property as compared with the case where one conveying screw is provided.
Further, by overlapping the screw portions 56Y1 and 57Y1 of the two conveying screws 56Y and 57Y, the developing device 5Y can be moved in the short direction (left and right in FIG. 2) as compared with the case where the two conveying screws 56Y and 57Y are not overlapped. Direction).).

FIG. 5A is a schematic diagram showing a state where the developer G in the second developer transport portion 54Y of the developing device 5Y is viewed from above in the first embodiment. FIG. 5B is a diagram illustrating a cross section taken along line XX in FIG. In FIG. 5A, a region H1 indicates a region where the surface of the developer G is high, a region H2 indicates a region where the surface of the developer G is low, and a white arrow indicates the conveyance direction of the developer G.
As shown in FIG. 5A, by causing the screw portions 56Y1 and 57Y1 of the two transport screws 56Y and 57Y to overlap, a difference in height occurs in the surface of the developer G in the second developer transport portion 54Y. Specifically, since the screw portions 56Y1 and 57Y1 move downward from above, the developer G is transported in a forward direction (downstream in the transport direction) of the screw portions 56Y1 and 57Y1, so that development is performed. A region H1 where the surface of the agent G is high is formed. On the other hand, since the developer G hardly enters behind the screw portions 56Y1 and 57Y1 (on the upstream side in the transport direction), an area H2 where the developer G has a low surface is formed.
Further, paying attention to the relationship between the rotation direction of the transport screws 56Y and 57Y and the movement of the developer G, the two transport screws 56Y and 57Y rotate in the counterclockwise direction of FIG. 5B, and therefore the transport screws 56Y and 57Y. In the region on the right side of the center of rotation, the developer G moves up from below, and in the region on the left side of the center of rotation of the transport screws 56Y and 57Y, the developer G sinks from above to below. Move to. In the region where the two conveying screws 56Y and 57Y overlap, a region where the developer G moves so as to spring out from below and a region where the developer G moves so as to sink under from above. And the developer G is agitated well and efficiently.
Further, by overlapping the two transport screws 56Y and 57Y, as shown in FIG. 5 (B), a large difference in height between the left and right agent surfaces occurs in the entire second developer transport section 54Y. Specifically, the right side of the second transport screw 56Y (the side closer to the first developer transport unit 53Y) is the highest, and the left side of the third transport screw 57Y (far from the first developer transport unit 53Y). Side)) is the lowest. In the second communication section B (see FIG. 2), the developer G is transferred from the second developer transport section 54Y to the first developer transport section 53Y while moving below the transport screws 56Y and 57Y. Therefore, the stirrability of the developer in the second communication part B is improved.

Here, with reference to FIGS. 2 to 4, the developing device 5 </ b> Y according to the first embodiment is configured so that the two transport screws (the second transport screw 56 </ b> Y and the third transport screw 57 </ b> Y) rotate in the same direction. It is configured. The second transport screw 56Y and the third transport screw 57Y are configured such that their uppermost portions rotate in a direction away from the first developer transport unit 53Y (or the first transport screw 55Y). That is, the second transport screw 56Y and the third transport screw 57Y rotate in the counterclockwise direction in FIG.
Although not shown, the gear train for rotationally driving the two transport screws 56Y and 57Y includes a gear installed on the shaft portion 56Y2 of the second transport screw 56Y and a gear installed on the shaft portion 57Y2 of the third transport screw 57Y. The idler gear meshes with these two gears (which is rotatably held by a stud (not shown) standing on the case of the developing device 5Y). This gear train, together with a gear train that rotationally drives the developing roller 51Y and the first conveying screw 55Y, is installed on the side of the case of the developing device 5Y (the region M surrounded by a broken line on the left side in FIG. 3). Thus, a driving force is received from a developing motor (not shown).
As described above, the second transport screw 56Y and the third transport screw 57Y are disposed so that the screw portions 56Y1 and 57Y1 are close to each other without contacting the shaft portions 56Y2 and 57Y2, and in the same direction. , And a large difference in level is generated on the surface of the developer G in the second developer transport section 54Y (the side closer to the first developer transport section 53Y is higher and the far side is lower). At the position where the two transport screws 56Y and 57Y are close to each other, the developer G pumped upward along the rotation of the third transport screw 57Y, and the developer G moved downward along the rotation of the second transport screw 56Y , Will be mixed up and down while colliding with each other. As a result, the “upslip” of the toner in the developing device 5Y (second developer conveying portion 54Y) is reduced, and the stirring property and charging property of the developer G are enhanced.

Further, in the first embodiment, referring to FIGS. 2 and 3, the second developer conveying portion 54Y is upstream in the conveying direction (the left side in FIG. 3), and the third conveying screw 57Y. The toner is replenished above a position away from the first developer conveyance portion 53Y with respect to the rotation center (a position on the left side with respect to the rotation center of the third conveyance screw 57Y indicated by a one-dot chain line in FIG. 2). A toner supply port 64Y is provided.
By disposing the toner replenishing port 64Y on the upstream side in the transport direction of the two developer transport section 54Y as described above, the replenishment toner is fed into the developer G by the two transport screws 56Y and 57Y in the second developer transport section 54Y. Sufficient time for stirring and mixing can be secured. That is, the replenishment toner is agitated and mixed in the developer G by taking a sufficient time to move along the path length of the second developer conveyance portion 54Y.
Further, by disposing the toner replenishing port 64Y on the left side with respect to the rotation center of the third conveying screw 57Y, the toner is replenished to a position where the developer surface is low. Then, the toner is submerged under the third transport screw 57Y so that the developer pumped up from the right side of the third transport screw 57Y is covered from above, and is transported toward the overlap portion with the second transport screw 56Y. Will be. Then, as described above, in the overlap portion, the force that shears the developer acts in a complicated manner, and a part of the developer is again transported around the third transport screw 57Y, and a part of the developer is transported. Enters under the second transport screw 56Y and is transported upward along the rotation of the second transport screw 56Y. Therefore, the toner is sufficiently agitated together with the developer, so that the dispersibility of the toner (replenishment toner) is enhanced and the toner is charged well. The developer that is well charged with a uniform toner density is transferred from the second developer conveying portion 54Y to the first developer conveying portion 53Y, and then pumped up to the developing roller 51Y to perform the developing process. Will be done. Therefore, it is possible to form a good output image with reduced background contamination and image density unevenness, and to reduce toner scattering from the developing device 5Y.

Further, in the first embodiment, with reference to FIGS. 2 and 3, the second developer conveying portion 54Y is located downstream in the conveying direction (the right side in FIG. 3), and the second conveying screw 56Y. Below the position approaching the first developer conveyance portion 53Y with respect to the rotation center (the position on the right side with respect to the rotation center of the second conveyance screw 56Y indicated by the one-dot chain line in FIG. 2), the toner density of the developer Is provided with a magnetic sensor 58Y (toner density detecting means).
By arranging the magnetic sensor 58Y on the downstream side in the transport direction of the two developer transport section 54Y in this way, the toner is sufficiently contained in the developer G by the two transport screws 56Y and 57Y in the second developer transport section 54Y. Since the toner concentration after stirring and mixing can be detected, the toner concentration can be detected accurately and with high accuracy. Therefore, highly accurate toner density control can be performed.
Furthermore, by disposing the magnetic sensor 58Y on the right side (the area where the developer surface of the developer is high) with respect to the rotation center of the second transport screw 56Y, a sufficient amount of developer is provided around the magnetic sensor 58Y. Therefore, the toner density can be detected accurately and with high accuracy. Therefore, highly accurate toner density control can be performed.

  As described above, in the first embodiment, the second developer screw 56Y that rotates in the predetermined direction is connected to the second developer transport unit 54Y that forms the circulation path of the developer G together with the first developer transport unit 53Y. , And a screw portion 57Y1 that is juxtaposed to the second conveying screw 56Y and protrudes toward the shaft portion 56Y2 of the second conveying screw 56Y so as to overlap the screw portion 56Y1 of the second conveying screw 56Y when viewed in the rotation axis direction. A third conveying screw 57Y (rotating member) having a protruding portion). As a result, the toner is sufficiently agitated and mixed in the developer G in the circulation path of the developer G, thereby reducing problems such as background stains and density unevenness on the output image and toner scattering.

  In the first embodiment, some or all of the image forming units 6Y, 6M, 6C, and 6K may be a process cartridge. Even in that case, the same effects as those of the first embodiment described above can be obtained.

In the first embodiment, the two developer screws 56Y and 57Y are installed in the second developer transport unit 54Y. However, three or more transport screws can be installed in the second developer transport unit 54Y. Even in that case, substantially the same effect as in the first embodiment can be obtained by overlapping a part of the screw part of at least two of the conveying screws installed in three or more.
In the first embodiment, the screw pitch N, screw diameter a, and shaft diameter b of the two conveying screws 56Y, 57Y are set to be equal, but the screw pitch N, screw diameter a of the two conveying screws 56Y, 57Y are set. Even if the shaft diameters b are not set to be equal, the present embodiment can be used as long as the two conveying screws 56Y and 57Y do not interfere with each other and part of the screw portions overlap each other. The effect similar to 1 can be obtained.

  In the first embodiment, the two developer screws 56Y and 57Y are installed in the second developer transport unit 54Y. However, a plurality of transport screws can also be installed in the first developer transport unit 53Y. Even in this case, substantially the same effects as those of the above embodiments can be obtained.

Embodiment 2. FIG.
6 and 7, the second embodiment of the present invention will be described in detail.
FIG. 6 is a configuration diagram illustrating the developing device 5Y according to the second embodiment. FIG. 7 is a schematic cross-sectional view of the developing device 5Y of FIG. 6 as viewed from above.
The developing device 5Y according to the second embodiment is the same as that of the first embodiment in the rotational directions of the second and third conveying screws 56Y and 57Y, and the positions of the toner replenishing port 64Y and the toner density detecting means 58Y. Is different.

As shown in FIGS. 6 and 7, the developing device 5Y according to the second embodiment also has a first developer conveying portion 53Y that forms a circulation path in the longitudinal direction of the developer, as in the first embodiment. And the 2nd developer conveyance part 54Y is provided. In the first developer conveying portion 53Y, a developing roller 51Y, a doctor blade 52Y, a first conveying screw 55Y, and the like are installed. The second developer conveying portion 54Y is provided with a second conveying screw 56Y, a third conveying screw 57Y (rotating member), a magnetic sensor 58Y (toner density detecting means), a toner supply port 64Y, and the like.
Also in the second embodiment, as in the first embodiment, when the second transport screw 56Y and the third transport screw 57Y installed in the second developer transport section 54Y are viewed in the rotation axis direction. It arrange | positions so that a part of mutual screw part (blade) may overlap. Further, the second transport screw 56Y and the third transport screw 57Y rotate in the same direction.

Here, the developing device 5Y according to the second embodiment is different from that of the first embodiment in that the second transport screw 56Y and the third transport screw 57Y have the uppermost portion of the first developer transport portion 53Y. (Or the first conveying screw 55Y) is configured to rotate in a direction approaching. That is, the second transport screw 56Y and the third transport screw 57Y rotate in the clockwise direction in FIG.
Since the two transport screws 56Y and 57Y rotate in the clockwise direction in FIG. 6, in the region on the left side of the rotation center of the transport screws 56Y and 57Y, the developer G moves so as to spring out from below, so that the transport screws In the region on the right side of the rotation centers of 56Y and 57Y, the developer G moves so as to be submerged from above to below. In the region where the two conveying screws 56Y and 57Y overlap, a region where the developer G moves so as to spring out from below and a region where the developer G moves so as to sink under from above. And the developer G is agitated well and efficiently. Therefore, the toner is sufficiently agitated together with the developer, and the toner (replenishment toner) does not slip up, so that the dispersibility of the toner is increased and the toner is charged well.
In the second embodiment, since the two transport screws 56Y and 57Y are rotationally driven in the opposite direction to the first embodiment, the right side of the second transport screw 56Y (the first developer transport section 53Y). ) Is the lowest, and the left side of the third conveying screw 57Y (the side far from the first developer conveying portion 53Y) is the highest.

In the second embodiment, referring to FIG. 6 and FIG. 7, the second developer transport portion 54Y is upstream in the transport direction (the left side in FIG. 7) and the second transport screw 56Y. A toner replenishing port 64Y is located above a position approaching the first developer conveyance section 53Y with respect to the rotation center (a position on the right side with respect to the rotation center of the second conveyance screw 56Y indicated by a one-dot chain line in FIG. 6). Provided.
By disposing the toner replenishing port 64Y on the right side with respect to the rotation center of the second conveying screw 56Y as described above, the toner is replenished to a position where the developer surface is low. Then, the toner is submerged under the second conveyance screw 56Y so that the developer pumped up from the left side of the second conveyance screw 56Y is covered from above, and is conveyed toward the overlap portion with the third conveyance screw 57Y. Will be. In the overlap portion, a force that shears the developer acts in a complicated manner, and a part of the developer is again transported around the second transport screw 56Y, and a part of the developer is transported in the third transport. It sinks under the screw 57Y and is conveyed upward along the rotation of the third conveying screw 57Y. Therefore, the toner is sufficiently agitated together with the developer, so that the dispersibility of the toner (replenishment toner) is enhanced and the toner is charged well. The developer that is well charged with a uniform toner density is transferred from the second developer conveying portion 54Y to the first developer conveying portion 53Y, and then pumped up to the developing roller 51Y to perform the developing process. Will be done. Therefore, it is possible to form a good output image with reduced background contamination and image density unevenness, and to reduce toner scattering from the developing device 5Y.

In the second embodiment, referring to FIGS. 6 and 7, the second developer conveying portion 54Y is located downstream in the conveying direction (the right side in FIG. 7), and the third conveying screw 57Y. A magnetic sensor 58Y (toner) below a position away from the first developer conveyance portion 53Y with respect to the rotation center (a position on the left side with respect to the rotation center of the third conveyance screw 57Y indicated by a one-dot chain line in FIG. 6). Density detecting means) is provided.
By disposing the magnetic sensor 58Y on the left side (the region where the developer surface of the developer is high) with respect to the rotation center of the third transport screw 57Y in this way, a sufficient amount of development is provided around the magnetic sensor 58Y. Since the agent can be secured, the toner concentration can be detected accurately and with high accuracy.

  As described above, also in the second embodiment, in the same manner as in the first embodiment, the second developer transport portion 54Y that forms the circulation path of the developer G together with the first developer transport portion 53Y has a predetermined direction. The second transport screw 56Y that rotates in parallel with the second transport screw 56Y and the shaft portion 56Y2 of the second transport screw 56Y so as to overlap the screw portion 56Y1 of the second transport screw 56Y when viewed in the rotational axis direction. And a third conveying screw 57Y (rotating member) having a screw part 57Y1 (protruding part) that protrudes toward the center. As a result, the toner is sufficiently agitated and mixed in the developer G in the circulation path of the developer G, thereby reducing problems such as background stains and density unevenness on the output image and toner scattering.

Embodiment 3 FIG.
A third embodiment of the present invention will be described in detail with reference to FIGS.
FIG. 8 is a configuration diagram illustrating the developing device 5Y according to the third embodiment, and corresponds to FIG. 6 according to the second embodiment. FIG. 9 is a schematic cross-sectional view of the developing device 5Y of FIG. 8 as viewed from above, and corresponds to FIG. 7 in the second embodiment. FIG. 10 is an enlarged top view showing the second transport screw 56Y and the third transport screw 57Y. FIG. 11 is a schematic diagram illustrating the state of the developer G in the second developer transport portion 54Y.
In the developing device 5Y according to the third embodiment, the third conveyance screw 57Y rotates in a direction different from the rotation direction of the second conveyance screw 56Y, and the positions of the toner replenishing port 64Y and the toner density detection means 58Y are described above. This is different from the first embodiment.

As shown in FIGS. 8 to 10, the developing device 5Y according to the third embodiment also has a first developer conveying portion 53Y that forms a circulation path in the longitudinal direction of the developer, as in the above-described embodiments. And the 2nd developer conveyance part 54Y is provided. In the first developer conveying portion 53Y, a developing roller 51Y, a doctor blade 52Y, a first conveying screw 55Y, and the like are installed. The second developer conveying portion 54Y is provided with a second conveying screw 56Y, a third conveying screw 57Y (rotating member), a magnetic sensor 58Y (toner density detecting means), a toner supply port 64Y, and the like.
Also in the third embodiment, as in the first embodiment, the second transport screw 56Y and the third transport screw 57Y installed in the second developer transport section 54Y are viewed when viewed in the rotation axis direction. A part of each screw part (blade) is arranged so as to overlap with an overlap amount d (see FIG. 10).

Here, the developing device 5Y in the third embodiment is different from that in the first embodiment in that the third transport screw 57Y has a screw direction of the screw portion 56Y1 of the second transport screw 56Y. It is formed in the direction opposite to the spiral direction and is configured to rotate in a direction different from the second transport screw 56Y. And the 2nd conveyance screw 56Y and the 3rd conveyance screw 57Y rotate so that a mutual proximity part may move toward the lower part from the upper part. That is, the second transport screw 56Y rotates in the counterclockwise direction of FIG. 8, and the third transport screw 57Y rotates at the same rotational speed in the clockwise direction of FIG.
Although not shown, the gear train for rotationally driving the two transport screws 56Y and 57Y is installed on the shaft 56Y2 of the second transport screw 56Y and the shaft 57Y2 of the third transport screw 57Y. And these two gears mesh with each other. This gear train, together with a gear train that rotationally drives the developing roller 51Y and the first conveying screw 55Y, is installed on the side of the case of the developing device 5Y (the region M surrounded by a broken line on the left side in FIG. 9). Thus, a driving force is received from a developing motor (not shown).

With such a configuration, the developer G moves in a region on the right side of the rotation center of the second conveyance screw 56Y and a region on the left side of the rotation center of the third conveyance screw 57Y so that the developer G springs up from below. . In the region where the two transport screws 56Y and 57Y overlap (the region between the rotation center of the second transport screw 56Y and the rotation center of the third transport screw 57Y), the developer G below The developer G is moved so as to be covered, and thus the developer G is well stirred. Therefore, the toner is sufficiently agitated together with the developer, and the toner (replenishment toner) does not slip up, so that the dispersibility of the toner is increased and the toner is charged well.
In the third embodiment, since the two transport screws 56Y and 57Y are rotationally driven so that their proximity portions move downward from above, the rotation center of the second transport screw 56Y and the third The agent surface between the rotation center of the conveyance screw 57Y is the lowest, the agent surface on the right side of the second conveyance screw 56Y (the side closer to the first developer conveyance unit 53Y) and the left side of the third conveyance screw 57Y ( The surface of the first developer transport portion 53Y is the farthest side.

  In particular, by rotating the two transport screws 56Y and 57Y in the opposite directions, large irregularities in the rotation axis direction correspond to the screw pitch on the surface (draft line) of the developer G in the second developer transport section 54Y. Formed periodically. As a result, the developer G moves from a high position (convex portion) to a low position (concave portion) like an avalanche, and the agitation of the developer G is further enhanced.

Further, in the third embodiment, referring to FIGS. 8 and 9, the second developer conveying portion 54Y is located upstream in the conveying direction (the left side in FIG. 9), and the second conveying screw 56Y. A toner replenishing port 64Y is provided above between the rotation center and the rotation center of the third conveying screw 57Y (a position sandwiched between two dashed lines in FIG. 8).
As described above, by disposing the toner replenishing port 64Y between the second transport screw 56Y and the third transport screw 57Y, the toner is replenished to a position where the developer surface is low. Then, the toner is submerged in an overlap portion of both the conveying screws 56Y and 57Y so that the developer pumped up from both the conveying screws 56Y and 57Y is covered from above. Then, in the overlap portion, as shown in FIG. 11, the developer is sheared so that the screw portion of the other transport screw 57Y enters the developer G transported downward from above by one transport screw 56Y. Such a force acts in a complicated manner. Thereafter, a part of the developer is transported along the rotation of the second transport screw 56Y, and a part of the developer is transported along the rotation of the third transport screw 57Y. Therefore, the toner is sufficiently agitated together with the developer, so that the dispersibility of the toner (replenishment toner) is enhanced and the toner is charged well. The developer that is well charged with a uniform toner density is transferred from the second developer conveying portion 54Y to the first developer conveying portion 53Y, and then pumped up to the developing roller 51Y to perform the developing process. Will be done. Therefore, it is possible to form a good output image with reduced background contamination and image density unevenness, and to reduce toner scattering from the developing device 5Y.

Further, in the third embodiment, referring to FIGS. 8 and 9, the second developer conveying portion 54Y is downstream in the conveying direction (the right side in FIG. 9), and the second conveying screw 56Y. A magnetic sensor 58Y (toner density detection means) is provided below a position that is outside the rotation center and the rotation center of the third transport screw 57Y. Specifically, the magnetic sensor 58Y is positioned away from the first developer conveyance portion 53Y with respect to the rotation center of the third conveyance screw 57Y (relative to the rotation center of the third conveyance screw 57Y indicated by the one-dot chain line in FIG. 8). (It is the position on the left side.)
As described above, the magnetic sensor 58Y is disposed at a position (a region where the developer surface of the developer is high) deviated between the rotation center of the second conveyance screw 56Y and the rotation center of the third conveyance screw 57Y. Since a sufficient amount of developer can be secured around the magnetic sensor 58Y, the toner density can be detected accurately and with high accuracy.
Note that the magnetic sensor 58Y is positioned closer to the first developer conveyance unit 53Y with respect to the rotation center of the second conveyance screw 56Y (a position on the right side with respect to the rotation center of the second conveyance screw 56Y indicated by the one-dot chain line in FIG. 8). The same effects as those described above can be obtained also in the case of being arranged in the above.

  As described above, also in the third embodiment, in the same manner as in each of the above embodiments, the second developer transport portion 54Y that forms the circulation path of the developer G together with the first developer transport portion 53Y has a predetermined direction. The second transport screw 56Y that rotates in parallel with the second transport screw 56Y and the shaft portion 56Y2 of the second transport screw 56Y so as to overlap the screw portion 56Y1 of the second transport screw 56Y when viewed in the rotational axis direction. And a third conveying screw 57Y (rotating member) having a screw part 57Y1 (protruding part) that protrudes toward the center. As a result, the toner is sufficiently agitated and mixed in the developer G in the circulation path of the developer G, thereby reducing problems such as background stains and density unevenness on the output image and toner scattering.

Embodiment 4 FIG.
A fourth embodiment of the present invention will be described in detail with reference to FIGS.
FIG. 12 is a configuration diagram illustrating the developing device 5Y according to the fourth embodiment, and corresponds to FIG. 6 according to the second embodiment. 13 is a schematic cross-sectional view of the developing device 5Y of FIG. 12 as viewed from above, and corresponds to FIG. 7 in the second embodiment. FIG. 14 is an enlarged top view showing the second transport screw 56Y and the stirring member 67Y.
The developing device 5Y according to the fourth embodiment is different from the first embodiment in that a stirring member 67Y is used as a rotating member instead of the third transport screw 57Y.

  As shown in FIGS. 12 to 14, the developing device 5 </ b> Y according to the fourth embodiment also has a first developer transport portion 53 </ b> Y that forms a circulation path in the longitudinal direction of the developer, as in the above-described embodiments. And the 2nd developer conveyance part 54Y is provided. In the first developer conveying portion 53Y, a developing roller 51Y, a doctor blade 52Y, a first conveying screw 55Y, and the like are installed. The second developer conveying portion 54Y is provided with a second conveying screw 56Y, an agitating member 67Y as a rotating member, a magnetic sensor 58Y (toner density detecting means), a toner replenishing port 64Y, and the like.

Here, the developing device 5Y according to the fourth embodiment has a second transport screw 56Y (which becomes a main transport unit) as a developer transport unit that transports the developer G in the longitudinal direction in the second developer transport unit 54Y. And a stirring member 67Y (which is a subordinate conveying means). Referring to FIG. 14, the stirring member 67Y is formed such that a plurality of rod-like parts 67Y1 rises in a spiral manner on the rotating shaft part 67Y2, and is the same as the second conveying screw 56Y. Rotates at the number of revolutions.
The stirring member 67Y is juxtaposed with the second transport screw 56Y and protrudes to a position close to the shaft portion 56Y2 of the second transport screw 56Y so as not to contact the screw portion 56Y1 of the second transport screw 56Y. It functions as a rotating member having a portion. Here, the protruding portion of the rotating member (the protruding portion that protrudes to a position close to the shaft portion 56Y2 of the second transport screw 56Y) becomes the rod-shaped portion 67Y1 of the stirring member 67Y. That is, the second conveying screw 56Y and the stirring member 67Y installed in the second developer conveying portion 54Y have an overlap amount d when the screw portion 56Y1 (blade) and the rod-shaped portion 67Y1 partially overlap when viewed in the rotation axis direction. (Refer to FIG. 14) and are arranged so as not to interfere with each other.

  With such a configuration, in the second developer conveying portion 54Y, the rod-shaped portion 67Y1 of the stirring member 67Y approaches the developer G pumped upward by the screw portion 56Y1 (blade) of the second conveying screw 56Y. A force that shears G up and down acts greatly. As a result, the developer G transported in the second developer transport section 54Y can move up and down without causing the toner replenished from the toner replenishing port 64Y to float on the upper surface of the developer G (without “sliding up”). It will be stirred and mixed efficiently and reliably in the direction. Therefore, the toner density of the developer G is made uniform and the chargeability of the toner is improved.

  Here, the inventor of the present application conducted an experiment to ensure the above-described effect. As a result, the position where the rod-like portion 67Y1 of the stirring member 67Y is close to the shaft portion 56Y2 of the second conveying screw 56Y is located on the stirring member 67Y. It has been found that it is preferable to dispose the tip portion of the approaching screw portion 56Y1 at a position shifted from the center position of the screw pitch N. Specifically, referring to FIG. 14, in the fourth embodiment, the screw pitch of the tip of the screw portion 56Y1 where the rod-like portion 67Y1 close to the shaft portion 56Y2 of the second transport screw 56Y approaches the stirring member 67Y is determined. It is configured to be shifted downstream from the center position of N by 1/4 pitch (N / 4).

Here, in the developing device 5Y according to the fourth embodiment, the second conveyance screw 56Y and the conveyance member 67Y rotate in the same direction, and the uppermost portion thereof is the first developer conveyance unit 53Y (or the first conveyance). It is configured to rotate in a direction away from the screw 55Y). That is, the second transport screw 56Y and the stirring member 67Y rotate in the counterclockwise direction in FIG.
Since the second transport screw 56Y rotates in the counterclockwise direction of FIG. 12, in the region on the right side of the rotation center of the second transport screw 56Y, the developer G moves so as to spring up from below to the second transport screw 56Y. In the region on the left side of the rotation center of the screw 56Y, the developer G moves so as to be submerged from above to below. In the region where the second transport screw 56Y and the stirring member 67Y overlap, the developer G moved downward by the second transport screw 56Y is moved upward by the rod-shaped portion 67Y1 (protruding portion) of the stirring member 67Y. A force that pushes up the toner acts on the developer G, whereby the developer G is well stirred. Therefore, the toner is sufficiently agitated together with the developer, and the toner (replenishment toner) does not slip up, so that the dispersibility of the toner is increased and the toner is charged well.
In the fourth embodiment, the agitating member 67Y is disposed at a position farther from the first developer conveying portion 53Y (or the first conveying screw 55Y) than the second conveying screw 56Y. Since the screw 56Y and the stirring member 67Y rotate counterclockwise in FIG. 12, as shown in FIG. 12, the right side of the second transport screw 56Y (the side closer to the first developer transport portion 53Y). Is the highest, and the left side of the stirring member 67Y (the side farther from the first developer conveying portion 53Y) is the lowest. Therefore, in the second communication portion B (see FIG. 13), the developer G is transferred from the second developer transport portion 54Y to the first developer transport portion 53Y while moving below the second transport screw 56Y. Therefore, the stirrability of the developer in the second communication part B is improved.

Further, in the fourth embodiment, with reference to FIGS. 12 and 13, the second developer transport portion 54Y is upstream in the transport direction (the left side in FIG. 13), and is the rotation center of the stirring member 67Y. On the other hand, a toner replenishing port 64Y is provided above a position away from the first developer conveying portion 53Y (a position on the left side with respect to the rotation center of the stirring member 67Y indicated by a one-dot chain line in FIG. 12).
By disposing the toner replenishing port 64Y on the left side with respect to the rotation center of the stirring member 67Y as described above, the toner is replenished at a position where the developer surface is low. Then, the toner is conveyed under the stirring member 67Y so as to be covered with the developer pumped up by the second conveying screw 56Y, and is conveyed toward the overlap portion with the second conveying screw 56Y. Become. In the overlap portion, a force that shears the developer acts in a complicated manner, and is then transported along the rotation of the second transport screw 56Y. Therefore, the toner is sufficiently agitated together with the developer, so that the dispersibility of the toner (replenishment toner) is enhanced and the toner is charged well. The developer that is well charged with a uniform toner density is transferred from the second developer conveying portion 54Y to the first developer conveying portion 53Y, and then pumped up to the developing roller 51Y to perform the developing process. Will be done. Therefore, it is possible to form a good output image with reduced background contamination and image density unevenness, and to reduce toner scattering from the developing device 5Y.

In the fourth embodiment, with reference to FIGS. 12 and 13, the second developer conveying portion 54Y is downstream in the conveying direction (the right side in FIG. 13), and the second conveying screw 56Y. A magnetic sensor 58Y (toner) below a position approaching the first developer conveyance portion 53Y with respect to the rotation center (a position on the right side with respect to the rotation center of the second conveyance screw 56Y indicated by a one-dot chain line in FIG. 12). Density detecting means) is provided.
In this way, by arranging the magnetic sensor 58Y on the right side (the region where the developer surface of the developer is high) with respect to the rotation center of the second transport screw 56Y, a sufficient amount of development is provided around the magnetic sensor 58Y. Since the agent can be secured, the toner concentration can be detected accurately and with high accuracy.

  As described above, in the fourth embodiment, the second developer screw 56Y that rotates in a predetermined direction is connected to the second developer transport portion 54Y that forms the circulation path of the developer G together with the first developer transport portion 53Y. The rod-shaped portion 67Y1 (which is arranged in parallel with the second transport screw 56Y and protrudes toward the shaft portion 56Y2 of the second transport screw 56Y so as to overlap the screw portion 56Y1 of the second transport screw 56Y when viewed in the rotation axis direction). And a stirring member 67Y (rotating member) having a protruding portion). As a result, the toner is sufficiently agitated and mixed in the developer G in the circulation path of the developer G, thereby reducing problems such as background stains and density unevenness on the output image and toner scattering.

Embodiment 5 FIG.
A fifth embodiment of the present invention will be described in detail with reference to FIGS.
FIG. 15 is a configuration diagram illustrating the developing device 5Y according to the fifth embodiment, and corresponds to FIG. 12 according to the fourth embodiment. 16 is a schematic cross-sectional view of the developing device 5Y of FIG. 15 as viewed from above, and corresponds to FIG. 13 in the fourth embodiment. FIG. 17 is an enlarged top view showing the second conveying screw 56Y and the agitating member 68Y, and corresponds to FIG. 14 in the fourth embodiment.
The developing device 5Y according to the fifth embodiment is different from the fourth embodiment in the configuration of a stirring member as a rotating member.

  As shown in FIGS. 15 to 17, the developing device 5 </ b> Y according to the fifth embodiment also has a first developer conveying portion 53 </ b> Y that forms a circulation path in the longitudinal direction of the developer, as in the fourth embodiment. And the 2nd developer conveyance part 54Y is provided. In the first developer conveying portion 53Y, a developing roller 51Y, a doctor blade 52Y, a first conveying screw 55Y, and the like are installed. The second developer conveying portion 54Y is provided with a second conveying screw 56Y, an agitating member 67Y as a rotating member, a magnetic sensor 58Y (toner density detecting means), a toner replenishing port 64Y, and the like.

Here, the developing device 5Y according to the fifth embodiment is a second transport screw 56Y (which becomes a main transport unit) as a developer transport unit that transports the developer G in the longitudinal direction in the second developer transport unit 54Y. And a stirring member 68Y (which is a subordinate conveying means). Referring to FIG. 17, the stirring member 68Y is formed with a plurality of crank portions 68Y1 that enter between the screw pitches N at the tip of the approaching screw portion 56Y1, and has the same rotational speed as the second transport screw 56Y. Rotate with.
The stirring member 68Y is juxtaposed with the second transport screw 56Y and protrudes to a position close to the shaft portion 56Y2 of the second transport screw 56Y so as not to contact the screw portion 56Y1 of the second transport screw 56Y. It functions as a rotating member having a portion. Here, the protruding portion of the rotating member (the protruding portion protruding to a position close to the shaft portion 56Y2 of the second conveying screw 56Y) becomes the crank portion 68Y1 of the stirring member 68Y. In other words, the second conveying screw 56Y and the stirring member 68Y installed in the second developer conveying portion 54Y are overlapped by a part d of the screw portion 56Y1 (blade) and the crank portion 68Y1 when viewed in the rotation axis direction. (Refer to FIG. 17) and are arranged so as not to interfere with each other. Specifically, the agitating member 68Y is configured such that the crank portion 68Y1 approaches the shaft portion 56Y2 of the second transport screw 56Y twice when rotated once (the crank portions 68Y1 are formed at intervals of 180 degrees). .

  With such a configuration, in the second developer conveying portion 54Y, the crank portion 68Y1 of the stirring member 68Y approaches the developer G pumped upward by the screw portion 56Y1 (blade) of the second conveying screw 56Y, and the developer A force that shears G up and down acts greatly. As a result, the developer G transported in the second developer transport section 54Y can move up and down without causing the toner replenished from the toner replenishing port 64Y to float on the upper surface of the developer G (without “sliding up”). It will be stirred and mixed efficiently and reliably in the direction. Therefore, the toner density of the developer G is made uniform and the chargeability of the toner is improved.

Here, in the developing device 5Y according to the fifth embodiment, the second conveyance screw 56Y and the conveyance member 68Y rotate in the same direction, and the uppermost portion thereof is the first developer conveyance unit 53Y (or the first conveyance). It is configured to rotate in a direction away from the screw 55Y). That is, the second conveying screw 56Y and the stirring member 68Y are rotated counterclockwise in FIG.
Since the second transport screw 56Y rotates counterclockwise in FIG. 15, in the region on the right side of the center of rotation of the second transport screw 56Y, the developer G moves so as to spring up from below to the second transport screw 56Y. In the region on the left side of the rotation center of the screw 56Y, the developer G moves so as to be submerged from above to below. In the region where the second conveying screw 56Y and the stirring member 68Y overlap, the developer G moved downward by the second conveying screw 56Y is moved upward by the crank portion 68Y1 (protruding portion) of the stirring member 68Y. A force that pushes up the toner acts on the developer G, whereby the developer G is well stirred. Therefore, the toner is sufficiently agitated together with the developer, and the toner (replenishment toner) does not slip up, so that the dispersibility of the toner is increased and the toner is charged well.
In the fifth embodiment, the agitating member 68Y is disposed at a position farther from the first developer conveying portion 53Y (or the first conveying screw 55Y) than the second conveying screw 56Y, and the second conveying screw 68Y. Since the screw 56Y and the stirring member 68Y rotate counterclockwise in FIG. 15, as shown in FIG. 15, the right side of the second transport screw 56Y (the side closer to the first developer transport portion 53Y). Is the highest, and the left side of the stirring member 68Y (the side farther from the first developer conveying portion 53Y) is the lowest. Therefore, in the second communication portion B (see FIG. 16), the developer G is transferred from the second developer transport portion 54Y to the first developer transport portion 53Y while moving below the second transport screw 56Y. Therefore, the stirrability of the developer in the second communication part B is improved.

Further, in the fifth embodiment, with reference to FIGS. 15 and 16, the second developer transport portion 54Y is upstream in the transport direction (the left side in FIG. 16), and is the rotation center of the stirring member 68Y. On the other hand, a toner replenishing port 64Y is provided above a position away from the first developer conveying portion 53Y (a position on the left side with respect to the rotation center of the stirring member 68Y indicated by a one-dot chain line in FIG. 15).
By disposing the toner replenishing port 64Y on the left side with respect to the rotation center of the stirring member 68Y in this way, the toner is replenished at a position where the developer surface is low. Then, the toner is transported toward the overlap portion with the second transport screw 56Y by dipping under the stirring member 68Y so that the developer pumped up by the second transport screw 56Y is covered from above. Become. In the overlap portion, a force that shears the developer acts in a complicated manner, and is then transported along the rotation of the second transport screw 56Y. Therefore, the toner is sufficiently agitated together with the developer, so that the dispersibility of the toner (replenishment toner) is enhanced and the toner is charged well. The developer that is well charged with a uniform toner density is transferred from the second developer conveying portion 54Y to the first developer conveying portion 53Y, and then pumped up to the developing roller 51Y to perform the developing process. Will be done. Therefore, it is possible to form a good output image with reduced background contamination and image density unevenness, and to reduce toner scattering from the developing device 5Y.

Further, in the fifth embodiment, with reference to FIGS. 15 and 16, the second developer conveying portion 54Y is downstream in the conveying direction (the right side in FIG. 16), and the second conveying screw 56Y. A magnetic sensor 58Y (toner) below a position approaching the first developer conveyance section 53Y with respect to the rotation center (a position on the right side with respect to the rotation center of the second conveyance screw 56Y indicated by a one-dot chain line in FIG. 15). Density detecting means) is provided.
In this way, by arranging the magnetic sensor 58Y on the right side (the region where the developer surface of the developer is high) with respect to the rotation center of the second transport screw 56Y, a sufficient amount of development is provided around the magnetic sensor 58Y. Since the agent can be secured, the toner concentration can be detected accurately and with high accuracy.

  As described above, in the fifth embodiment, the second developer screw 56Y that rotates in the predetermined direction is connected to the second developer transport portion 54Y that forms the circulation path of the developer G together with the first developer transport portion 53Y. The crank portion 68Y1 (which is arranged in parallel with the second transport screw 56Y and projects toward the shaft portion 56Y2 of the second transport screw 56Y so as to overlap the screw portion 56Y1 of the second transport screw 56Y when viewed in the rotation axis direction). And a stirring member 68Y (rotating member) having a protruding portion). As a result, the toner is sufficiently agitated and mixed in the developer G in the circulation path of the developer G, thereby reducing problems such as background stains and density unevenness on the output image and toner scattering.

  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 is an overall configuration diagram illustrating an image forming apparatus according to Embodiment 1 of the present invention. FIG. 2 is a configuration diagram illustrating an image forming unit in the image forming apparatus of FIG. 1. FIG. 3 is a schematic cross-sectional view of the developing device and the photosensitive drum as viewed from above. It is an enlarged top view which shows a 2nd conveyance screw and a 3rd conveyance screw. FIG. 6 is a schematic diagram illustrating a state of a developer in a second developer transport unit. It is a block diagram which shows the developing device in Embodiment 2 of this invention. FIG. 7 is a schematic cross-sectional view of the developing device of FIG. 6 as viewed from above. It is a block diagram which shows the developing device in Embodiment 3 of this invention. It is the schematic sectional drawing which looked at the developing device of Drawing 8 from the upper part. It is an enlarged top view which shows the 2nd conveyance screw of the developing device of FIG. 8, and a 3rd conveyance screw. FIG. 9 is a schematic diagram illustrating a state of a developer in a second developer transport unit of the developing device in FIG. 8. It is a block diagram which shows the developing device in Embodiment 4 of this invention. FIG. 13 is a schematic cross-sectional view of the developing device of FIG. 12 as viewed from above. It is an enlarged top view which shows the 2nd conveyance screw and stirring member of the image development apparatus of FIG. It is a block diagram which shows the developing device in Embodiment 5 of this invention. FIG. 16 is a schematic cross-sectional view of the developing device of FIG. 15 as viewed from above. FIG. 16 is an enlarged top view showing a second conveying screw and a stirring member of the developing device of FIG. 15.

Explanation of symbols

1Y photosensitive drum (image carrier),
5Y developing device,
51Y developing roller (developer carrier),
52Y Doctor blade (developer regulating member),
53Y first developer transport section,
54Y second developer transport section,
55Y first conveying screw,
56Y second conveying screw (developer conveying means),
56Y1 screw part, 56Y2 shaft part,
57Y third conveying screw (developer conveying means, rotating member),
57Y1 screw part (protruding part), 57Y2 shaft part,
58Y magnetic sensor (toner concentration detection means),
67Y stirring member (developer conveying means, rotating member),
67Y1 rod-shaped part (protruding part), 67Y2 shaft part,
68Y stirring member (developer conveying means, rotating member),
68Y1 crank part (protrusion part),
100 Image forming apparatus main body (apparatus main body).

Claims (4)

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 developer conveying section for supplying the developer to the developer carrying member while conveying the developer in the longitudinal direction by a first conveying screw;
The developer is disposed so as to face the first developer conveying portion via a partition member, and the developer fed from the downstream side in the conveying direction of the first developer conveying portion is longitudinally moved by the developer conveying means. A second developer transport section that transports the first developer transport section to the upstream side in the transport direction of the first developer transport section;
With
The developer conveying means of the second developer conveying unit is
A second conveying screw having a screw portion formed in the shaft portion and rotating in a predetermined direction;
A screw portion is formed in the shaft portion and rotates at the same rotational speed as the second conveying screw, and is arranged at a position farther from the first developer conveying portion than the second conveying screw. Screw,
Equipped with,
The screw portion of the third transport screw is formed to protrude toward the shaft portion of the second transport screw so as to overlap the screw portion of the second transport screw when viewed in the rotation axis direction,
The second transport screw and the third transport screw rotate in the same direction in the direction in which the uppermost part is away from the first developer transport unit,
The second developer transport unit detects the toner density of the developer downstream of the transport direction and below a position approaching the first developer transport unit with respect to the rotation center of the second transport screw. A developing device comprising toner density detecting means . The second developer transport unit is a toner supply port through which toner is replenished upstream of the transport direction and above a position away from the first developer transport unit with respect to the rotation center of the third transport screw. The developing device according to claim 1, comprising: A process cartridge that is detachably attached to the image forming apparatus main body,
3. A process cartridge in which the developing device according to claim 1 and the image carrier are integrated. An image forming apparatus comprising the developing device according to claim 1 and the image carrier.

Images