JP6838699B2 - Developing equipment, process cartridges, and image forming equipment - Google Patents

Description

The present invention relates to a developing apparatus for developing a latent image formed on the surface of an image carrier, and a process cartridge and an image forming apparatus including the developing apparatus.

Conventionally, in a developing device installed in an image forming device using an electrophotographic method such as a copier, a printer, a facsimile, or a multifunction device thereof, the first is so as to face a developing agent carrier (developing roller). A transport path (first transport member) is arranged, a second transport path (second transport member) is arranged so as to face the first transport path via a wall portion, and development is performed by those transport paths. Those that form a circulation pathway for agents are known (see, for example, Patent Documents 1 and 2).

Specifically, in the developing apparatus of Patent Document 1, a first transport path is arranged so as to face below the developing roller (developer carrier), and a first transport path is provided below the first transport path via a wall portion. Two transport paths are arranged. A first transport member (first transport screw) for transporting the developer from one end side in the longitudinal direction to the other end side in the longitudinal direction is installed in the first transport path. A second transport member (second transport screw) that transports the developer from the other end side in the longitudinal direction to the one end side in the longitudinal direction is installed in the second transport path. Further, the upstream side of the first transport path and the downstream side of the second transport path communicate with each other, and the downstream side of the first transport path and the upstream side of the second transport path communicate with each other.
In the developing apparatus configured in this way, a circulation path for transporting the developer in the longitudinal direction is formed by the first transport path and the second transport path, and the developer is supplied to the developing roller by the first transport member. At the same time, the developer separated from the developing roller is recovered.

On the other hand, Patent Document 2 describes the first transfer from the second transfer path for the purpose of preventing the height of the agent surface of the developer from changing significantly in the first transfer path for supplying the developer to the developing roller. A pool (a space opened upward) in which the developer can stay in the vicinity of the opening (communication portion) through which the developer is delivered toward the path and on the upstream side of the first transport path. Disclosed is a technique for forming a developer to suppress a change in the surface height of the developer.

The above-mentioned conventional developing apparatus develops when the surface of the developing agent in the first transport path becomes too high due to fluctuations in the toner concentration of the contained developer or environmental fluctuations. The developer after the developing process, which was separated from the agent carrier (development roller), was re-supported on the developer carrier, which sometimes caused abnormal images such as uneven image density and whiteout images. ..
Further, even if a pool portion is provided on the upstream side of the first transport path as in Patent Document 2 so that the surface of the developer in the first transport path does not become high, the developer above the pool portion is the first. It stays in the transport path without being agitated, and there is a difference in toner concentration and charge amount from the developer that is agitated and transported. Since a part of the retained developer also travels downstream of the first transport path, the image quality is abnormal due to the difference in toner concentration and charge amount from the appropriately agitated developer.

The present invention has been made to solve the above-mentioned problems, and provides a developing apparatus, a process cartridge, and an image forming apparatus in which the surface of the developing agent in the first transport path does not rise and an abnormal image does not occur. To provide.

The developing device in the present invention is a developing device that develops a latent image formed on the surface of an image carrier by accommodating a developer, and is a developer carrier that supports the developer in opposition to the image carrier. The first transport member that supplies the developer to the developer carrier while transporting the developer from one end side in the longitudinal direction to the other end side in the longitudinal direction facing the developer carrier, and the developer. A second transport member that transports from the other end side in the longitudinal direction toward one end side in the longitudinal direction, a developer on the upstream side of the first transport member, and a developer on the downstream side of the second transport member flow so as to flow. A communicating portion formed on one end side in the longitudinal direction is provided, and the non-image forming region of the developer carrier is formed so as to reach the communicating portion in the longitudinal direction, and the developing agent in the non-image forming region. The pumping amount of the developer on the carrier is larger than the pumped amount of the developer on the developer carrier in the image-forming region .

According to the present invention, it is possible to provide a developing device, a process cartridge, and an image forming device, in which the surface of the developing agent in the first transport path is not high and abnormal images are unlikely to occur.

It is an overall block diagram which shows the image forming apparatus in embodiment of this invention. It is a block diagram which shows the image-forming part. It is a schematic cross-sectional view which looked at the developing apparatus in the longitudinal direction, and is the schematic which shows the positional relationship in the longitudinal direction with a photoconductor drum. In a conventional developing apparatus, (A) a schematic cross-sectional view showing a state when the bulk density of a developer is large in the longitudinal direction, and (B) a schematic cross-sectional view showing a state when the bulk density of a developer is low in the longitudinal direction. And. It is the schematic which shows the behavior of the developer separated from the developing roller. As the first modification, (A) a schematic view showing a developing roller and (B) an enlarged cross-sectional view showing the surface of the developing roller. It is the schematic which shows the developing roller as a modification 2. In the developing apparatus as the third modification, there are (A) a cross-sectional view showing an image-forming area and (B) a cross-sectional view showing a non-image-forming area. In the developing apparatus as the modification 4, (A) a cross-sectional view showing an image-forming area and (B) a cross-sectional view showing a non-image-creating area. In the developing apparatus as the modification 5, (A) a cross-sectional view showing an image-forming area and (B) a cross-sectional view showing a non-image-creating area. FIG. 6 is a schematic cross-sectional view of the developing apparatus viewed in the longitudinal direction as a modification 6, and is a schematic view showing the positional relationship with the photoconductor drum in the longitudinal direction.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In each figure, the same or corresponding parts are designated by the same reference numerals, and the duplicated description thereof will be appropriately simplified or omitted.

First, FIG. 1 describes the overall configuration and operation of the image forming apparatus 1.
In FIG. 1, 1 is a tandem color copier as an image forming apparatus, 3 is a document conveying unit that conveys a document to a document reading unit, 4 is a document reading unit that reads image information of a document, and 5 is loaded with an output image. A paper ejection tray, 7 indicates a paper feeding unit in which a recording medium P such as transfer paper is housed.
Reference numeral 9 denotes a resist roller for adjusting the transport timing of the recording medium P, and 11Y, 11M, 11C, and 11BK are photoconductor drums as an image carrier on which toner images of each color (yellow, magenta, cyan, black) are formed. Is shown.
Further, 13 is a developing device for developing an electrostatic latent image formed on the surface of each of the photoconductor drums 11Y, 11M, 11C, 11BK, and 14 is a toner formed on each of the photoconductor drums 11Y, 11M, 11C, 11BK. A primary transfer bias roller, in which an image is superimposed and transferred on a recording medium P, is shown.
Further, 17 is an intermediate transfer belt on which toner images of a plurality of colors are superimposed and transferred, 18 is a secondary transfer bias roller for transferring a color toner image on the intermediate transfer belt 17 onto a recording medium P, and 20 is a recording medium. A fixing device for fixing the unfixed image on P, 28 indicates a toner container of each color for supplying toner (toner particles) of each color (yellow, cyan, magenta, black) to the developing device 13.

Hereinafter, the operation of the image forming apparatus during normal color image forming will be described.
Note that FIG. 2 can also be referred to for the image forming process performed on the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK.
First, the original is conveyed from the platen by the transfer roller of the original transfer unit 3 and placed on the contact glass of the original reading unit 4. Then, the document reading unit 4 optically reads the image information of the document placed on the contact glass.

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

Then, the image information of each color of yellow, magenta, cyan, and black is transmitted to the writing unit. Then, a laser beam L (see FIG. 2) based on the image information of each color is emitted from the writing unit toward the surfaces of the corresponding photoconductor drums 11Y, 11M, 11C, and 11BK, respectively.

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

The laser beam corresponding to the yellow component irradiates the surface of the photoconductor drum 11Y, which is the first from the left side of the paper surface. At this time, the laser beam of the yellow component is scanned in the rotation axis direction (main scanning direction) of the photoconductor drum 11Y by the polygon mirror rotating at high speed. In this way, an electrostatic latent image corresponding to the yellow component is formed on the photoconductor drum 11Y after being charged by the charging unit 12.

Similarly, the laser beam corresponding to the magenta component is applied to the surface of the photoconductor drum 11M, which is the second from the left on the paper surface, to form an electrostatic latent image corresponding to the magenta component. The cyan component laser beam is applied to the surface of the photoconductor drum 11C, which is the third from the left on the paper surface, to form an electrostatic latent image of the cyan component. The laser beam of the black component is applied to the surface of the photoconductor drum 11BK, which is the fourth from the left on the paper surface, to form an electrostatic latent image of the black component.

After that, the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK on which the electrostatic latent images of each color are formed reach the positions facing the developing device 13, respectively. Then, toner of each color is supplied from each developing device 13 onto the photoconductor drums 11Y, 11M, 11C, 11BK, and the latent image on the photoconductor drums 11Y, 11M, 11C, 11BK is developed (development step). .).
After that, the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK after the developing step reach the facing portions with the intermediate transfer belt 17, respectively. Here, a primary transfer bias roller 14 is installed on each of the opposing portions so as to abut on the inner peripheral surface of the intermediate transfer belt 17. Then, at the position of the primary transfer bias roller 14, the toner images of each color formed on the photoconductor drums 11Y, 11M, 11C, and 11BK are sequentially superimposed and transferred on the intermediate transfer belt 17 (primary transfer). It is a process.).

Then, the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK after the transfer step reach the positions facing the cleaning unit 15, respectively. Then, the cleaning unit 15 collects the untransferred toner remaining on the photoconductor drums 11Y, 11M, 11C, and 11BK (this is a cleaning step).
After that, the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK pass through the static elimination unit, and a series of image forming processes on the photoconductor drums 11Y, 11M, 11C, and 11BK are completed.

On the other hand, the intermediate transfer belt 17 on which the toners of the respective colors on the photoconductor drums 11Y, 11M, 11C, and 11BK are superimposed and transferred (supported) travels in the counterclockwise direction of FIG. Reach the opposite position of. Then, the color toner image supported on the intermediate transfer belt 17 is transferred onto the recording medium P at the position facing the secondary transfer bias roller 18 (the secondary transfer step).
After that, the surface of the intermediate transfer belt 17 reaches the position of the intermediate transfer belt cleaning portion. Then, the untransferred toner adhering to the intermediate transfer belt 17 is collected by the intermediate transfer belt cleaning unit, and a series of transfer processes on the intermediate transfer belt 17 is completed.

Here, the recording medium P conveyed between the intermediate transfer belt 17 and the secondary transfer bias roller 18 (which is the secondary transfer nip) is conveyed from the paper feed unit 7 via the resist roller 9 and the like. It is a thing.
Specifically, the recording medium P fed by the paper feed roller 8 is guided to the resist roller 9 from the paper feed unit 7 that houses the recording medium P after passing through the transport guide. The recording medium P that has reached the resist 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 subsequently guided to the fixing device 20. In the fixing device 20, the color image is fixed on the recording medium P by the nip of the fixing roller and the pressurizing roller.
Then, the recording medium P after the fixing step is discharged as an output image to the outside of the apparatus main body 1 by the paper ejection roller, and is stacked on the paper ejection tray 5, and a series of image forming processes is completed.

Next, the image forming portion in the image forming apparatus of FIG. 1 will be described in detail with reference to FIGS. 2, 3 and the like.
FIG. 2 is a configuration diagram showing an image-creating portion, and is a view seen in a cross section orthogonal to the rotation axis of the photoconductor drum 11. FIG. 3 is a schematic cross-sectional view (longitudinal cross-sectional view) of the developing device 13 viewed in the longitudinal direction, and is a schematic view showing the positional relationship in the longitudinal direction with the photoconductor drum 11.
Since each image processing unit has almost the same structure, in FIGS. 2 and 3 (and FIGS. 4 to 11 described later), the image forming unit and the developing device have alphabetic symbols (Y, C, M, respectively. BK) is excluded from the illustration.

As shown in FIG. 2, the image forming unit is composed of a photoconductor 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, and is rotationally driven clockwise by a rotation drive mechanism.

The charging portion 12 is an elastic charging roller in which a medium-resistance urethane foam layer in which urethane resin, carbon black as conductive particles, a sulfide agent, a foaming agent, etc. are formulated on a core metal in a roller shape. The material of the medium resistance layer of the charged portion 12 is urethane, ethylene-propylene-diene polyethylene (EPDM), butadiene acrylonitrile rubber (NBR), silicone rubber, isoprene rubber, etc., and carbon black or metal oxide for resistance adjustment. A rubber material in which a conductive substance such as the above is dispersed, or a foamed material thereof can also be used.
The cleaning unit 15 is provided with a cleaning blade that is in sliding contact with the photoconductor drum 11, and mechanically removes and recovers the untransferred toner on the photoconductor drum 11.

The developing apparatus 13 is arranged such that the developing roller 13a as the developing agent carrier faces the photoconductor drum 11 with a slight gap through the opening A (formed in the developing case 13j). .. A developing region is formed in a portion where the developing roller 13a and the photoconductor drum 11 face each other, in which the photoconductor drum 11 and the magnetic brush (the developing agent G in a raised state) come into contact with each other. A developer G (two-component developer) composed of toner T and carrier C is housed in the developing apparatus 13. Then, the developing device 13 develops an electrostatic latent image formed on the surface of the photoconductor drum 11 (forms a toner image). The configuration and operation of the developing device 13 will be described in detail later.

With reference to FIG. 1, the toner container 28 houses the toner T to be supplied into the developing apparatus 13 inside the toner container 28. Specifically, based on the information of the toner concentration (the ratio of the toner in the developer G) detected by the magnetic sensor installed in the developing device 13, the developing is performed from the toner container 28 via the toner transport tube. Toner T is appropriately supplied from the supply port 13d (see FIG. 3) toward the inside of the device 13.

Hereinafter, the developing apparatus 13 in the image forming apparatus will be described in detail.
With reference to FIGS. 2 and 3, the developing apparatus 13 includes a developing roller 13a as a developing agent carrier, a supply screw 13b1 as a first conveying member, a conveying screw 13b2 as a second conveying member, and a developer regulating member. The round bar doctor 13c, the partition member 13e as a wall portion, the filter 13k covering the exhaust port 13j1 of the developing case 13j, and the like. These members 13a, 13b1, 13b2, 13c, 13e, 13k are included in the developing case 13j (housing).

In the developing roller 13a as a developing agent carrier, a sleeve 13a2 formed of a non-magnetic material such as aluminum, brass, stainless steel, or a conductive resin in a cylindrical shape is supplied by a rotation drive mechanism, together with a screw 13b1 and a transport screw 13b2. It is configured to rotate in the direction of the arrow shown in.
With reference to FIG. 3, a magnet 13a1 forming a plurality of magnetic poles (S1 pole, N1 pole, S2 pole, N2 pole, N3 pole) is fixedly formed in the sleeve 13a2 of the developing roller 13a on the peripheral surface of the sleeve 13a2. Has been done.
The developer G carried on the developing roller 13a is conveyed along with the rotation of the developing roller 13a in a predetermined rotation direction (counterclockwise in FIG. 2), and is carried by the round bar doctor 13c (developer regulating member). ) Is reached. Then, 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 photoconductor drum 11 (a developing region). Then, the toner is adsorbed on the latent image formed on the photoconductor drum 11 by the electric field (developing electric field) formed in the developing region.

With reference to FIG. 2 (and FIG. 3), the plurality of magnetic poles formed around the developing roller 13a (sleeve 13a2) by the magnet 13a1 are N1 poles (mainly) formed at positions facing the photoconductor drum 11. (Magnet), S2 pole (conveying magnetic pole) formed on the downstream side of N1 pole (downstream side in the rotation direction of the developing roller 13a) and above the development case 13j, downstream side of S2 pole and developing roller N2 pole (agent separation pre-magnet) formed diagonally above 13a, agent separation magnetic pole (N pole) formed above the first transport path B1 at a position sandwiched between N2 pole and N3 pole, agent. The N3 pole (magnetic pole after agent separation) formed on the downstream side of the separation magnetic pole and above the first transport path B1 was formed from the position facing the supply screw 13b1 to the vicinity of the facing position with the round bar doctor 13c. It is composed of S1 pole (pumping magnetic pole), etc.
First, the S1 pole (pumping magnetic pole) acts on the carrier as a magnetic material, and the developer G contained in the first transport path B1 is pumped onto the developing roller 13a. A part of the developer G supported on the developing roller 13a is scraped off at the position of the round bar doctor 13c as the developing agent regulating member, and is returned to the first transport path B1. On the other hand, at the position of the round bar doctor 13c on which the magnetic force due to the S1 pole acts, the developer G carried on the developing roller 13a through the doctor gap between the round bar doctor 13c and the developing roller 13a is N1 pole (mainly). It stands at the position of the magnetic pole) and becomes a magnetic brush in the developing area and slides into contact with the photoconductor drum 11. In this way, the toner T in the developer G supported on the developing roller 13a adheres to the latent image on the photoconductor drum 11. After that, the developer G that has passed through the position of the N1 pole is conveyed to the position of the agent separation magnetic pole (N pole) by the S2 pole and the N2 pole. Then, at the position of the agent separating magnetic pole, a repulsive magnetic field (a magnetic field acting in a direction away from the developing roller 13a) acts on the carrier, and the developing agent G after the developing step supported on the developing roller 13a is released. It is detached from the developing roller 13a. The desorbed developer G falls into the first transport path B1, is collected by the supply screw 13b1, and is transported toward the downstream of the first transport path B1.

The six magnetic poles described above are formed by five poles (S1 pole, N1 pole, S2 pole, N2 pole, and N3 pole) magnetized on the magnet 13a1 of the developing roller 13a. Of the six magnetic poles, only the agent-separated magnetic pole (N pole) is not directly formed by the pole magnetized on the magnet 13a1, but is the same pole (in the present embodiment, the N pole). It is formed by being sandwiched between two magnetic poles (N2 pole and N3 pole) that serve as (.).
It should be noted that the above-mentioned five poles can also form the S pole and the N pole in the opposite direction.

With reference to FIG. 2, the round bar doctor 13c as the developer regulating member is a magnetic columnar member arranged below the developing roller 13a. Then, the developing roller 13a rotates in the counterclockwise direction of FIG. 2, and the photoconductor drum 11 rotates in the clockwise direction of FIG.
With such a configuration, the photoconductor drum 11 is arranged below the intermediate transfer belt 17 in order to shorten the transport path of the recording medium P and to reduce the size of the image forming apparatus main body 1 in the horizontal direction. There is. Then, in the development gap, the rotation direction of the developing roller 13a is the forward direction with respect to the photoconductor drum 11. By setting the forward direction in this way, development in the development gap is performed as compared with the case where the round bar doctor 13c is arranged above the development roller 13a and the rotation direction of the development roller 13a with respect to the photoconductor drum 11 is opposite. Sufficient time can be secured and the developing ability can be enhanced.

In the developing apparatus of FIG. 2, as shown in FIG. 3, two transporting members (supplied screw 13b1 and transporting screw 13b2) use the developer G housed in the developing apparatus 13 in the longitudinal direction (paper surface of FIG. 2). Stir and mix while circulating in the vertical direction (the left-right direction in FIG. 3).
The supply screw 13b1 as the first transport member is disposed below the developing roller 13a and at a position facing the developing roller 13a, and horizontally conveys the developer G in the longitudinal direction (rotational axis direction). (Transport from right to left as shown by the broken arrow in FIG. 3), the developer G is supplied onto the developing roller 13a at the position of the pumping magnetic pole (S1 pole), and the agent separating magnetic pole (N pole). ), The developer G that has fallen off from the developing roller 13a is conveyed toward the downstream side in the axial direction. The supply screw 13b1 rotates counterclockwise in FIG.

The transport screw 13b2 as the second transport member is arranged at a position below the supply screw 13b1 and facing the developing roller 13a via the supply screw 13b1. Then, the developer G is horizontally transported in the longitudinal direction in the second transport path B2 (transportation from the left to the right indicated by the broken line arrow in FIG. 3). In the present embodiment, the rotation direction of the transport screw 13b2 is set to be opposite to the rotation direction of the supply screw 13b1 (clockwise in FIG. 2).

Gears are installed on one end side (the right end portion in FIG. 3) of the shaft portion of the developing roller 13a (sleeve 13a2), the supply screw 13b1, and the transport screw 13b2, and these are gears. A row is formed to rotate the developing roller 13a, the supply screw 13b1, and the transport screw 13b2 in the rotation direction described above.
When the transfer screw 13b2 is rotated counterclockwise in FIG. 2 to change the position of the upper transfer by the transfer screw 13b2, the idler is interposed between the gears of the supply screw 13b1 and the transfer screw 13b2, and the transfer screw 13b2 The direction of the blades may be reversed.
Further, in both the supply screw 13b1 and the transport screw 13b2, the shaft portions at both ends thereof are rotatably held in the developing case 13j via a bearing (in this embodiment, a sliding bearing). Further, in order to prevent the toner T (developer G) from entering the bearing inside the bearing holding the supply screw 13b1 and the transport screw 13b2 in the developing case 13j (on the inner side of the developing apparatus 13). (In this embodiment, it is a G seal) is installed.

Then, in the transport screw 13b2, the developer is circulated from the axially downstream side of the first transport path B1 by the supply screw 13b1 via the second communication portion 13 g (second relay portion) not partitioned by the partition member 13e. .. Then, the transport screw 13b2 is a first communication portion 13f (first relay portion) as a communication portion that is not partitioned by the partition member 13e on the axially upstream side of the first transport path B1 by the supply screw 13b1. (The transport is shown by the broken line arrow in FIG. 3).
Both the supply screw 13b1 and the transport screw 13b2 are arranged so that the rotation axes are substantially horizontal, like the developing roller 13a and the photoconductor drum 11. Further, both the supply screw 13b1 and the transport screw 13b2 are those in which a screw portion (which is formed with a predetermined screw pitch and a number of threads of 1) is spirally wound around a shaft portion. Is. The screw portion may have a plurality of threads in order to stabilize the transport of the developer, and in particular, the screw portion of the supply screw 13b1 may have a plurality of threads.

The first transport path B1 by the supply screw 13b1 and the second transport path B2 by the transport screw 13b2 are separated by a partition member 13e (wall portion) except for both ends.
With reference to FIG. 3, the upstream side of the first transport path B1 by the supply screw 13b1 and the downstream side of the second transport path B2 by the transport screw 13b2 communicate with each other via the first communication section 13f as a communication section. ing. In other words, the first developer on one end side in the longitudinal direction so that the developer on the upstream side of the supply screw 13b1 (first transport member) and the developer on the downstream side of the transport screw 13b2 (second transport member) circulate. The communication portion 13f is formed. The developer G that has reached the downstream side of the second transport path by the transport screw 13b2 stays in the vicinity of the first communication portion 13f (communication portion) and rises, and the first by the supply screw 13b1 via the first communication portion 13f. It will be transported (supplied) to the upstream side of the transport path B1.
Further, referring to FIG. 3, the downstream side of the first transport path B1 by the supply screw 13b1 and the upstream side of the second transport path B2 by the transport screw 13b2 communicate with each other via the second communication portion 13g. .. In other words, the developer on the downstream side of the supply screw 13b1 (first transport member) and the developer on the upstream side of the transport screw 13b2 (second transport member) are distributed on the other end side in the longitudinal direction. A double communication portion 13 g is formed. Then, the developer G that has reached the downstream side of the first transport path B1 by the supply screw 13b1 (the developer G that was not supplied onto the developing roller 13a in the first transport path B1 and the agent separating magnetic pole in the developing roller 13a). The developer G that has separated and dropped from the developing roller 13a at the position (N pole) falls by its own weight at the second communication portion 13g and reaches the upstream side of the second transport path B2.
In the developing apparatus 13 of the present embodiment, the non-image forming region portion N is located at the position of the developing roller 13a on one end side (right side in FIG. 3) of the developing roller 13a in the longitudinal direction. The non-image-creating region portion N has a configuration extended to a position facing the first communication portion 13f, which will be described in detail later.

Here, in the present embodiment, the amount of the developer G transported per unit time by the transport screw 13b2 (second transport member) is the amount of the developer G transported per unit time by the supply screw 13b1 (first transport member). It is configured to be larger than the amount transported to.
Specifically, in the present embodiment, the pitch of the blades of the transport screw 13b2 is set to be longer than the pitch of the blades of the supply screw 13b1.
As a result, the upper transfer of the developer G against the direction of gravity from the second transport path B2 to the first transport path B1 in the first communication section 13f (communication section) is promoted.
By configuring the transfer screw 13b2 so that the rotation speed of the transfer screw 13b2 is higher than the rotation speed of the supply screw 13b1, it is possible to provide a difference in the transfer amount of the developer G.
Further, in order to improve the transportability of the developer in the first communication portion 13f (upward transfer of the developer G against the direction of gravity from the second transport path B2 to the first transport path B1), the transport screw is used. A paddle-shaped portion or a screw portion in which the winding direction of the screw is formed in the opposite direction may be provided at a position on the downstream side of 13b2 (a position corresponding to the first communication portion 13f).

With such a configuration, the two transport members (supply screw 13b1 and transport screw 13b2) form a circulation path for circulating the developer G in the longitudinal direction in the developing apparatus 13. That is, when the developing apparatus 13 is operated, the developing agent G contained in the developing apparatus 13 flows in the direction of the broken line arrow in FIG.
Then, in this way, the developing apparatus is formed by forming the circulation path of the developer G (the first transport path B1 and the second transport path B2) with respect to the developing roller 13a in the vertical direction instead of the horizontal direction. The horizontal size of 13 can be reduced (it can be vertically long). In particular, in the tandem type color image forming apparatus 1 in which a plurality of developing devices 13 (image forming portions) are arranged side by side in the horizontal direction, the size of the plurality of developing devices 13 (image forming portions) in the horizontal direction can be reduced. , The overall horizontal size can be effectively reduced.

A magnetic sensor for detecting the toner concentration of the developer G circulating in the apparatus is installed in the transport path by the transport screw 13b2. Then, based on the toner concentration information detected by the magnetic sensor, the toner container 28 (see FIG. 1) is developed through the supply port 13d arranged on the outer side in the longitudinal direction with respect to the second communication portion 13 g. A new toner T is supplied toward the inside of the device 13.
Further, referring to FIG. 3, the replenishment port 13d (toner replenishment port) is above the upstream side of the second transport path B2 by the transport screw 13b2 and is located away from the developing region (longitudinal direction of the developing roller 13a). It is arranged outside the range of.). Then, the new toner T discharged from the toner container 28 is appropriately replenished from the replenishment port 13d toward the inside of the developing device 13 (replenishment in the direction of the white arrow in FIG. 3). By installing the replenishment port 13d in the vicinity of the second communication portion 13g in this way, the developer G supplied by dropping its own weight from the second communication portion 13g toward the downstream side in the second transport path B2. On the other hand, the replenishing toner can be sufficiently dispersed and mixed over a relatively long time.
In the present embodiment, the supply port 13d is arranged in the second transport path B2, but the position of the supply port 13d is not limited to this, and for example, the first transport path B1 is extended in the longitudinal direction. It can also be placed above the downstream side.

The toner T (toner in the developer G, toner in the toner container 28) used in the present embodiment is a polymerized toner having a volume average particle size of about 5.0 to 6.0 μm. Small diameter toner can also be used.
Further, as the carrier C in the developer G, a small-diameter carrier formed so that the weight average particle size is 20 to 60 μm can also be used.

Hereinafter, the characteristic configuration and operation of the developing apparatus 13 according to the present embodiment will be described.
As described above with reference to FIG. 3 and the like, the developing apparatus 13 in the present embodiment has a first transport path B1 in which a supply screw 13b1 as a first transport member is installed, and a second transport member. A second transport path B2 in which the transport screw 13b2 is installed is provided.
The first transport path B1 is arranged so as to face the developing roller 13a (developer carrier). Further, in the supply screw 13b1 (first transport member), the developer G is directed from one end side in the longitudinal direction (right side in FIG. 3) to the other end side in the longitudinal direction (left side in FIG. 3). The developer is supplied to the developing roller 13a while being conveyed, and the developer G separated from the developing roller 13a is recovered.
The second transport path B2 is arranged below the first transport path B1 so as to face each other via a partition member 13e as a wall portion, and forms a circulation path for the developer G together with the first transport path B1. ing. Further, in the transport screw 13b2 (second transport member), the developer G is directed from the other end side in the longitudinal direction (left side in FIG. 3) to one end side in the longitudinal direction (right side in FIG. 3). It is to be transported.

Then, the first communication portion 13f as a communication portion is on one end side in the longitudinal direction so as to communicate the upstream side of the first transport path B1 and the downstream side of the second transport path B2. Similarly, a non-image-creating region portion N is formed on one end side of the developing roller 13a, and the non-image-creating region portion N has a configuration extending to the first communication portion 13f in the longitudinal direction.

Here, in the specification of the present application and the like, the image forming region M is defined as the photoconductor drum by the developing apparatus 13 within the range (magnetic force effective range) in which the developing agent in the longitudinal direction is supported by the magnet 13a1 of the developing roller 13a. It is a region in the developing roller 13a facing a region (maximum image region) in the longitudinal direction (rotational axis direction) on which a toner image can be formed on the surface of 11 (image carrier). In the conventional developing apparatus, the effective magnetic field range of the developing roller and the maximum image region forming the toner image of the photoconductor drum 11 are substantially the same.
Further, in the specification of the present application and the like, the non-image forming region is a region on the end side in the longitudinal direction with respect to the image forming region M of the developing roller 13a, and the developing agent in the longitudinal direction of the magnet of the developing roller 13a is used. Within the supported range (effective magnetic force range), a region in the longitudinal direction (rotational axis direction) of the developing roller 13a in which a toner image cannot be formed on the surface of the photoconductor drum 11 (image carrier) by the developing device 13. Is. In the present embodiment, the non-image-forming region N and the boundary portion R, which will be described later, are formed in the non-image-forming region on one end side in the longitudinal direction of the developing roller 13a.

Here, referring to FIG. 3, in the developing apparatus 13 of the present embodiment, the non-image forming region of the developing roller 13a (developer carrier) extends to the first communicating portion 13f (communication portion) in the longitudinal direction. It is formed to reach.
Specifically, the sleeve 13b2 of the developing roller 13a is formed so that the position on one end side in the longitudinal direction reaches from the image forming region M to the position facing the first communication portion 13f. Therefore, in the present embodiment, the position of the developing roller 13a (sleeve 13a2) on one end side in the longitudinal direction is formed in the non-image forming region and at a position sufficiently distant from the image forming region M. Become. The first communication portion 13f is formed at a position in the longitudinal direction corresponding to the non-image forming region of the developing roller 13a in accordance with the position on one end side in the longitudinal direction of such a developing roller 13a (sleeve 13a2). ..

More specifically, as shown in FIG. 3, the magnet 13a1 of the developing roller 13a is formed so as to extend not only to the image forming region M but also to the non-image forming region. The non-image-forming region here includes a boundary portion R and a non-image-forming region portion N. The magnet 13a1 is integrally formed from the image-forming area M to the non-image-forming area, and is configured as described above with reference to FIG. 2 without distinguishing between the image-forming area M and the non-image-forming area. ing. Therefore, on the surface (outer peripheral surface) of the developing roller 13a (sleeve 13a2), a plurality of magnetic poles (main magnetic pole, carrier magnetic pole, agent release pre-magnetic pole, agent release magnetic pole) are provided by the magnet 13a1 from the image formation region M to the non-image formation region. , The magnetic pole after the agent is separated and the pumping magnetic pole.) Will be formed.

With such a configuration, in the developing apparatus 13, even in the non-image forming region N, the developer G in the first transport path B1 is transferred to the developing roller 13a at the position of the pumping magnetic pole, as in the image forming region M. After being carried and the developer G moves along the rotation of the developing roller 13a (sleeve 13a2), it is separated from the developing roller 13a at the position of the agent release magnetic pole and returned to the first transport path B1. Become. However, unlike the image-forming area M, the non-image-forming area portion N does not perform the developing step (the transfer of toner to the photoconductor drum 11) at the position of the main magnetic pole. Therefore, in the non-image forming region N, unlike the image forming region M, the characteristics (toner concentration and charge amount) of the developer G pumped up by the developing roller 13a at the position of the pumping magnetic pole and the agent separation. At the position of the magnetic pole, the characteristics of the developer G separated from the developing roller 13a are substantially the same.

Here, in the present embodiment, the developing roller 13a is formed with a boundary portion R on the non-image area side of the boundary between the non-image area and the image area M on one end side in the longitudinal direction. That is, the developing roller 13a is provided with a boundary portion R between the image forming region M and the non-image forming region portion N. The boundary portion R is formed in the non-image-forming region, and is formed so that the range in the longitudinal direction is shorter than that in the image-forming region M and the non-image-forming region N.
The boundary portion R is a region on the developing roller 13a on which a toner image cannot be formed on the surface of the photoconductor drum 11 as in the non-image forming region portion N, but is different from the non-image forming region portion N. Is a region in which the developer G is not supported on the developing roller 13a.

Hereinafter, the developing roller 13a (magnet) is sufficiently distant from the image forming region M so that the developer G can be supported on the non-image forming region N of the developing roller 13a in the vicinity of the first communication portion 13f. The reason for extending and forming 13a1) will be described.
FIG. 4 is a diagram showing a conventional developing apparatus 130 in which a developing roller 13a (magnet 13a1) is formed so that a range in the longitudinal direction substantially coincides with the image forming region M, unlike the one of the present embodiment. .. Even if the developer G having the same weight is initially accommodated in the developing apparatus 130, the toner density of the developing agent G fluctuates or the environment fluctuates after that, so that the fluidity of the developing agent G further increases. As shown in FIG. 4, the developer G housed in the developing apparatus 130 can be changed due to a change or a variable process linear velocity (conveying speed of the recording medium P) depending on the type of the recording medium P or the like. The bulk density changes and the height of the agent surface also changes.
Specifically, when the toner concentration of the developer G is low, the charge amount of the toner T decreases in a high temperature and high humidity environment, or when the process linear velocity is set to be high, the developing roller 13a and the supply screw 13b1 When the number of rotations of the transport screw 13b2 becomes large or the like, as shown in FIG. 4 (A), the bulk density of the developer G becomes large and the developer G becomes dense, and the surface of the developer G becomes low as a whole. Become. On the other hand, when the toner concentration of the developer G is high, the charge amount of the toner T is high in a low temperature and low humidity environment, or the process linear speed is set to be slow, the developing roller 13a and the supply screw 13b1 Or when the rotation speed of the transport screw 13b2 becomes small, as shown in FIG. 4B, the bulk density of the developing agent G becomes small and the bulk density becomes sparse, and the surface of the developing agent G becomes high as a whole. Become.

Then, as shown in FIG. 4, in the conventional developing apparatus 130 in which only the image forming region M is formed on the developing roller 13a, when the surface of the developing agent G in the first transport path B1 is high, the developing agent G is separated from the developing roller 13a. The developer G after the developed development step is re-supported on the developing roller 13a, and an abnormal image such as an image density unevenness or a white band image is generated.
For details, with reference to FIG. 5, the developer G after the developing step carried on the developing roller 13a is separated from the developing roller 13a at the position of the agent separating magnetic pole as shown by the broken line arrow, and is separated from the developing roller 13a. It will be returned to B1. At that time, when the surface of the developer G in the first transport path B1 is lower than the predetermined height, the distance from the developing roller 13a (pumping magnetic pole) is so large that the developing roller 13a (pumping magnetic pole) is not re-supported. The developer G (in a state where the toner concentration is lowered by the developing step) after the developing step, which is separated from the developing roller 13a without being re-supported on the roller 13a, moves as shown by the white arrow. Then, while being sufficiently mixed with the developer G conveyed by the supply screw 13b1 (while the decrease in the toner concentration is eliminated), the developer G is conveyed toward the downstream side in the conveying direction. On the other hand, in the conventional developing apparatus 130, when the surface of the developing agent G in the first transport path B1 is high (when the height exceeds a predetermined height), the developing roller 13a (pumping magnetic pole) is used. Since the distance between the two is close, the developer G after the developing step (which is in a state where the toner concentration is lowered by the developing step) separated from the developing roller 13a moves as shown by the black arrow. Therefore, it is not sufficiently mixed with the developer G conveyed by the supply screw 13b1 and is re-supported on the developing roller 13a. Then, the developer G having a low toner concentration is re-supported on the developing roller 13a in this way, so that the toner image formed on the photoconductor drum 11 (or the output image formed on the recording medium P). In addition, abnormal images such as uneven image density and whiteout images will occur.

The phenomenon that the surface of the developer G becomes too high in the first transport path B1 is likely to occur on the upstream side of the first transport path B1 (on the right side in FIG. 4). This is because, as shown in FIG. 4, the developer G transferred from the second transport path B2 to the first transport path B1 tends to stay in the vicinity of the first communication section 13f, and the first transport path B1 However, even in the second transport path B2, the surface of the developer G becomes higher as it is closer to the first communication portion 13f.

In response to such a defect, in the present embodiment, as shown in FIG. 3, the developer G can be supported in the non-image area portion N of the developing roller 13a in the vicinity of the first communication portion 13f. The developing roller 13a (magnet 13a1) is extended to a position sufficiently distant from the image region M.
As a result, even if the surface of the developer G is likely to become too high in the vicinity of the first communication portion 13f in the first transport path B1, a part of the developer G is not imaged on the developing roller 13a. Since it is supported on the region portion N, the height of the drug surface can be made relatively low. Further, the developer G carried on the non-image-forming region portion N of the developing roller 13a is returned to the first transport path B1 again at the position of the agent separation magnetic pole, but the developer G is developed. Since the process has not been performed, the toner concentration and the amount of charge of the developer G are the same as those at the time of pumping as described above. This is the same even if the developer G is re-supported on the developing roller 13a in the non-image-forming region portion N, because the developing step is not performed on the developing agent G. Therefore, even if the developer G having no such change in characteristics is subsequently pumped into the image forming region M, the toner concentration and the amount of charge of the developer G are uniform and stable, and thus the photosensitive agent G is exposed to light. An abnormal image such as an image density unevenness or a whiteout image does not occur in the toner image (or the output image formed on the recording medium P) formed on the body drum 11.

Further, in the range of the first transport path B1 corresponding to the image forming region M of the developing roller 13a, the condition that the height of the agent surface of the developing agent G is high (the condition that the toner concentration is high, the condition that the environment is low temperature and low humidity). , And the condition that the process linear velocity is increased.) Even if the image density unevenness and the image density unevenness are not made even if the difficult setting for adjusting the agent surface of the developer G in the image forming region M is not made. Abnormal images such as whiteout images do not occur.
In other words, in the present embodiment, there are three conditions that the height of the surface of the developer G is high (a condition that the toner concentration is high, a condition that the environment is low temperature and low humidity, and a condition that the process linear velocity is high). There is), and the maximum region where the developer G may be re-supported on the developing roller 13a is set as the non-image-creating region portion N.
In particular, in the present embodiment, the height of the surface of the developer G is sufficiently secured even on the downstream side (the other end side in the longitudinal direction) of the first transport path B1 facing the image forming region M for development. The height of the surface of the developer G is inevitably high on the upstream side (one end side in the longitudinal direction) of the first transport path B1 so that the supply of the developer G to the roller 13a is not insufficient. Therefore, the configuration of the present invention becomes useful.

Further, when the swelling of the developer is small in the vicinity of the first communication portion 13f (for example, when the toner concentration is low), the developer is supported on the non-image area portion N above the supply screw 13b1. Since the amount of the developer G is reduced, the amount of the developer in the image forming region M is not reduced, and the agent height is appropriate in the range of the first transport path B1 corresponding to the image forming region M, and no abnormal image is generated.

Further, in the present embodiment, as shown in FIG. 3, the photoconductor drum 11 faces the image forming region M of the developing roller 13a and does not face the non-image forming region N of the developing roller 13a. , The range in the longitudinal direction is defined.
With such a configuration, it is physically impossible for the developer G carried on the non-image area portion N of the developing roller 13a to form a toner image on the surface of the photoconductor drum 11, as described above. The effect of suppressing the occurrence of abnormal images such as uneven image density and whiteout images will be further exerted.

In the present embodiment, as shown in FIG. 3, the maximum image region X (the region substantially coincides with the longitudinal range of the maximum recording medium P capable of passing paper) in the photoconductor drum 11 is. It is configured within the image forming region M of the developing roller 13a. With such a configuration, the image forming process described above with reference to FIGS. 1, 2 and the like can be normally performed.
The maximum image area X and the image-creating area M can be configured to coincide with each other.

Here, in the present embodiment, the surface roughness of the surface of the developing roller 13a (developer carrier) in the non-image area on one end side in the longitudinal direction is higher than the surface roughness of the surface in the image area. It is formed to be rough.
Specifically, the outer peripheral surface of the developing roller 13a (sleeve 13a2) is formed so that the surface thereof is roughened as a whole by subjecting a solid state to sound blasting or the like. The outer peripheral surface of the developing roller 13a (sleeve 13a2) is formed so that the surface roughness of the non-image-creating region portion N is larger than the surface roughness of the image-forming region M.
As a result, the amount (pumping amount) of the developer G supported on the surface of the developing roller 13a at the position of the pumping magnetic pole is larger in the non-image forming region N than in the image forming region M. Therefore, the height of the surface of the developer G becomes relatively low in the vicinity of the first communication portion 13f in the first transport path B1 described above.

Further, referring to FIG. 3, in the present embodiment, the developing roller 13a (developing agent carrier) is a boundary portion between the non-image forming region portion N on one end side in the longitudinal direction and the image forming region M. In R, the surface is formed like a mirror surface.
Specifically, the outer peripheral surface of the boundary portion R of the developing roller 13a (sleeve 13a2) is mirror-finished, and the surface roughness thereof is smaller than that of the image forming region M and the non-image forming region portion N. It is formed so that it becomes smooth.
As a result, the developer G is hardly supported on the surface of the boundary portion R of the developing roller 13a, or even if it is supported, the amount is extremely small. Therefore, in the developing roller 13a, the developer G supported on the non-image-forming region N shifts to the image-forming region M, and the developer G supported on the image-forming region M shifts to the non-image-forming region N. The problem of squeezing is reduced, and the function of the non-image-creating region portion N described above is further exhibited.

<Modification example 1>
FIG. 6A is a schematic view showing a developing roller 13a as a modification 1, and FIG. 6B is an enlarged cross-sectional view showing the surface of the developing roller 13a.
As shown in FIG. 6, in the developing apparatus 13 of the first modification, a plurality of grooves 13a20 are periodically formed on the surface of the developing roller 13a (sleeve 13a2) excluding the boundary portion R in the circumferential direction. Then, in the developing roller 13a, the depth H of the plurality of grooves 13a20 periodically formed in the circumferential direction on the surface of the non-image-forming region portion N of the non-image-forming region on one end side in the longitudinal direction is formed in the image-forming region M. It is formed so as to be deeper than the depth H of the plurality of grooves 13a20 formed periodically in the circumferential direction on the surface. The surface of the boundary portion R of the developing roller 13a (sleeve 13a2) is mirror-finished without forming a plurality of grooves as described above.
With such a configuration, the amount (pumping amount) of the developer G supported on the surface of the developing roller 13a at the position of the pumping magnetic pole is surely larger in the non-image forming region N than in the image forming region M. Will be. Therefore, the height of the surface of the developer G becomes relatively low in the vicinity of the first communication portion 13f in the first transport path B1 described above.

<Modification 2>
FIG. 7 is a schematic view showing a developing roller 13a as a modification 2.
As shown in FIG. 7, in the developing apparatus 13 of the second modification, a sealing member 13a3 made of urethane or the like is attached to the boundary portion R of the developing roller 13a in the circumferential direction. The thickness of the seal member 13a3 is thicker than the layer thickness of the developer G regulated and supported by the round bar doctor 13c as the developer regulating member on the developing roller 13a without hindering the rotation of the developing roller 13a. It is preferable that it is one. Further, it is preferable that the seal member 13a3 has a smooth surface and is less likely to support the developer G than the non-image-forming region N and the image-forming region M.
As a result, in the developing roller 13a, the developer G supported on the non-image-forming region N shifts to the image-forming region M, and the developer G supported on the image-forming region M moves to the non-image-forming region N. The trouble of migration is further reduced, and the function of the non-image area portion N described above is further exhibited.

<Modification example 3>
FIG. 8A is a cross-sectional view showing an image forming region M in the developing apparatus 13 as a modification 3, and FIG. 8B is a sectional view showing a non-image forming region portion N in the developing apparatus 13. is there.
As described above with reference to FIG. 2 and the like, also in the developing apparatus 13 of the modified example 3, the developing agent regulation that regulates the amount of the developing agent G carried on the surface of the developing roller 13a facing the developing roller 13a. A round bar doctor 13c as a member is installed.
Then, in the third modification, the round bar doctor 13c (developer regulating member) has a gap W2 (doctor gap) with the developing roller 13a in the non-image area (non-image area N) on one end side in the longitudinal direction. It is formed so as to be larger than the gap W1 (doctor gap) with the developing roller 13a in the image forming region M (W2> W1). In order to realize such a configuration, the round bar doctor 13c is formed in a stepped manner so that the outer diameter in the image-forming region and the outer diameter in the non-image-creating region are different with the same axis. There is.
With such a configuration, the amount of the developer G supported on the surface of the developing roller 13a and passing through the position of the round bar doctor 13c is larger in the non-image forming region N than in the image forming region M. Therefore, the amount of the developer supported in the non-image-forming region N in the developing roller 13a increases, and the height of the surface of the developer G in the vicinity of the first communication portion 13f in the first transport path B1 is relatively high. It gets lower.

<Modification example 4>
FIG. 9 (A) is a cross-sectional view showing an image forming region M in the developing apparatus 13 as the modified example 4, and is the same as FIG. 8 (A) in the modified example 3. Further, FIG. 9B is a cross-sectional view showing a non-image-creating region portion N in the developing apparatus 13.
As shown in FIG. 9, in the developing apparatus 13 in the modified example 4, the round bar doctor 13c (developer regulating member) is placed on the developing roller 13a in the non-image area (non-image area N) on one end side in the longitudinal direction. It is formed so as not to face each other. That is, the range of the round bar doctor 13c in the longitudinal direction is set so that the round bar doctor 13c faces only the image forming region M without facing the non-image forming region portion N of the developing roller 13a (the developing roller 13a has. It is set to be shorter than that).
In this configuration, the amount of the developer G supported on the surface of the developing roller 13a in the non-image forming region N is not regulated by the round bar doctor 13c. Therefore, the amount of the developer supported in the non-image-forming region N in the developing roller 13a increases, and the height of the surface of the developer G in the vicinity of the first communication portion 13f in the first transport path B1 is relatively high. It gets lower. Further, since the stress generated when the developer G carried on the developing roller 13a passes through the doctor gap with the round bar doctor 13c does not occur, the problem that the developer G housed in the developing device 13 deteriorates earlier is suppressed. be able to.

<Modification 5>
FIG. 10 (A) is a cross-sectional view showing an image forming region M in the developing apparatus 13 as the modified example 5, and is the same as FIG. 8 (A) in the modified example 3. Further, FIG. 10B is a cross-sectional view showing a non-image-creating region portion N in the developing apparatus 13.
As shown in FIG. 10, the developing apparatus 13 in the modified example 5 is integrated with the wall portion 13j2 (integrated with the developing case 13j) so that the developing roller 13a does not face the photoconductor drum 11 through the opening in the non-image forming region portion N. The developing roller 13a is covered with the formed portion (the opening is closed).
With such a configuration, toner does not adhere to the surface of the photoconductor drum 11 due to the developer G supported on the non-image-forming region N of the developing roller 13a. Further, the toner scattering from the developing device 13 is reduced.

<Modification 6>
FIG. 11 is a schematic cross-sectional view of the developing device 13 as a modification 6 in the longitudinal direction, and is a schematic view showing the positional relationship with the photoconductor drum 11 in the longitudinal direction. It is a figure equivalent to FIG. 3 in the form of.
As shown in FIG. 11, in the modification 6, the photoconductor drum 11 is extended to one end side in the longitudinal direction in which the non-image-creating region portion N is formed in accordance with the range in the longitudinal direction of the developing roller 13a. , The range in the longitudinal direction is defined. Specifically, in the photoconductor drum 11, the maximum image region X1 is formed so as to face the image forming region M of the developing roller 13a, and the developing roller 13a is not formed on one end side in the longitudinal direction with respect to the maximum image region X1. The image forming region portion N is formed so as to face the non-image region X2. In the photoconductor drum 11, a photosensitive layer is also formed in the non-image region X2 in the same manner as in the maximum image region X1.
Further, the charging portion 12 (see FIG. 2) has a longitudinal range of the photoconductor drum 11 so that the non-image region X2 can be charged in addition to the maximum image region X1 of the photoconductor drum 11. It is formed so as to almost match the range of directions. Further, the laser beam L (see FIG. 2) from the writing unit (exposure device) that forms an electrostatic latent image on the surface of the photoconductor drum 11 is a maximum image without exposing the non-image region X2 of the photoconductor drum 11. The exposure range in the longitudinal direction (main scanning direction) is defined so that only the region X1 can be exposed.
With such a configuration, even when the range in the longitudinal direction of the photoconductor drum 11 is set according to that of the developing roller 13a, normal image formation is performed in the maximum image region X1 of the photoconductor drum 11. In the non-image region X2, the background potential (background portion) is always formed and the image is not formed.
Therefore, it is possible to reduce the occurrence of abnormal images in the maximum image region X1 as in the case of the above-described embodiment.

As described above, the developing apparatus 13 in the present embodiment is supplied with the developing agent G, which faces the developing roller 13a (developer carrier) and is conveyed from one end side in the longitudinal direction to the other end side in the longitudinal direction. Development on the upstream side of the screw 13b1 (first transport member) and on the downstream side of the transport screw 13b2 (second transport member) that transports the developer G from the other end side in the longitudinal direction toward one end side in the longitudinal direction. A first communication portion 13f (communication portion) is formed on one end side in the longitudinal direction so that the agent G and the agent G can flow. The non-image forming region of the developing roller 13a is formed so as to reach the first communication portion 13f in the longitudinal direction.
As a result, the surface of the developer G in the first transport path B1 does not rise, and an abnormal image can be less likely to occur.

In the present embodiment, the present invention has been applied to an image forming apparatus configured as a unit in which the developing apparatus 13 is attached to and detached from the image forming apparatus main body by itself. 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 portion is made into a process cartridge. In that case, the workability of maintenance of the image forming unit is improved.
Here, in the present application, the "process cartridge" refers to a charged portion that charges the image carrier, a developing device (developing unit) that develops a latent image formed on the image carrier, and cleaning on the image carrier. It is defined as a unit in which at least one of the cleaning unit (cleaning device) and the image carrier are integrated and detachably installed with respect to the main body of the image forming apparatus.

Further, in the present embodiment, the first transport path B1 is arranged above the second transport path B2, and the second transport path B2 is arranged so as to face the developing roller 13a via the first transport path B1. The present invention was applied to the provided developing apparatus 13. However, the developing apparatus to which the present invention is applied is not limited to this, and the present embodiment is appropriately modified in addition to the disclosure in the present embodiment within the scope of the technical idea of the present invention. It is clear to get. Further, the number, position, shape, etc. of the constituent members are not limited to the present embodiment, and can be a suitable number, position, shape, etc. for carrying out the present invention.

1 Image forming apparatus (image forming apparatus main body),
11, 11Y, 11C, 11M, 11BK Photoreceptor drum (image carrier),
13 Developing equipment (development unit),
13a Development roller (developer carrier),
13a3 seal member,
13a20 groove,
13b1 Supply screw (first transport member),
13b2 transport screw (second transport member),
13c Round bar doctor (developer regulating member),
13e Partition member (wall part),
13f 1st communication section (communication section),
13g 2nd communication part,
B1 1st transport route, B2 2nd transport route,
M image area, N non-image area, R boundary,
G developer (two-component developer), T toner, C carrier.

Japanese Unexamined Patent Publication No. 2015-132803 Japanese Patent No. 5907376

Claims (11)

A developing device that contains a developer and develops a latent image formed on the surface of an image carrier.
A developer carrier that supports the developer on the image carrier and
A first transport member that supplies the developer to the developer carrier while transporting the developer from one end side in the longitudinal direction to the other end side in the longitudinal direction facing the developer carrier.
A second transport member that transports the developer from the other end side in the longitudinal direction toward one end side in the longitudinal direction,
A communication portion formed on one end side in the longitudinal direction so that the developer on the upstream side of the first transport member and the developer on the downstream side of the second transport member flow through.
With
The non-image area of the developer carrier is formed so as to reach the communication portion in the longitudinal direction .
A developing apparatus characterized in that the amount of the developer of the developer-supported body pumped up in the non-image-forming region is larger than the amount of the developer of the developer-supported body pumped up in the image-forming region. A developing device that contains a developer and develops a latent image formed on the surface of an image carrier.
A developer carrier that supports the developer on the image carrier and
A first transport member that supplies the developer to the developer carrier while transporting the developer from one end side in the longitudinal direction to the other end side in the longitudinal direction facing the developer carrier.
A second transport member that transports the developer from the other end side in the longitudinal direction toward one end side in the longitudinal direction,
A communication portion formed on one end side in the longitudinal direction so that the developer on the upstream side of the first transport member and the developer on the downstream side of the second transport member flow through.
A developer regulating member that regulates the developer supported on the surface of the developer carrier facing the developer carrier, and a developer regulating member.
With
The non-image area of the developer carrier is formed so as to reach the communication portion in the longitudinal direction.
The developer regulating member was formed so that the gap with the developer carrier in the non-image-forming region on one end side in the longitudinal direction was larger than the gap with the developer carrier in the image-forming region. A developing device characterized by this. A developing device that contains a developer and develops a latent image formed on the surface of an image carrier.
A developer carrier that supports the developer on the image carrier and
A first transport member that supplies the developer to the developer carrier while transporting the developer from one end side in the longitudinal direction to the other end side in the longitudinal direction facing the developer carrier.
A second transport member that transports the developer from the other end side in the longitudinal direction toward one end side in the longitudinal direction,
A communication portion formed on one end side in the longitudinal direction so that the developer on the upstream side of the first transport member and the developer on the downstream side of the second transport member flow through.
With
The non-image area of the developer carrier is formed so as to reach the communication portion in the longitudinal direction.
In the developer carrier, the depths of a plurality of grooves periodically formed on the surface of the non-image-forming region on one end side in the longitudinal direction are periodically formed on the surface of the image-forming region in the circumferential direction. A developing device characterized in that it is formed so as to be deeper than the depth of a plurality of grooves. A developing device that contains a developer and develops a latent image formed on the surface of an image carrier.
A developer carrier that supports the developer on the image carrier and
A first transport member that supplies the developer to the developer carrier while transporting the developer from one end side in the longitudinal direction to the other end side in the longitudinal direction facing the developer carrier.
A second transport member that transports the developer from the other end side in the longitudinal direction toward one end side in the longitudinal direction,
A communication portion formed on one end side in the longitudinal direction so that the developer on the upstream side of the first transport member and the developer on the downstream side of the second transport member flow through.
With
The non-image area of the developer carrier is formed so as to reach the communication portion in the longitudinal direction.
The developer carrier is developed so that the surface roughness of the surface in the non-image-forming region on one end side in the longitudinal direction is rougher than the surface roughness of the surface in the image-forming region. apparatus. A developing device that contains a developer and develops a latent image formed on the surface of an image carrier.
A developer carrier that supports the developer on the image carrier and
A first transport member that supplies the developer to the developer carrier while transporting the developer from one end side in the longitudinal direction to the other end side in the longitudinal direction facing the developer carrier.
A second transport member that transports the developer from the other end side in the longitudinal direction toward one end side in the longitudinal direction,
A communication portion formed on one end side in the longitudinal direction so that the developer on the upstream side of the first transport member and the developer on the downstream side of the second transport member flow through.
With
The non-image area of the developer carrier is formed so as to reach the communication portion in the longitudinal direction.
The developer carrier has a boundary portion on the non-image-forming region side of the boundary between the non-image-forming region and the image-forming region on one end side in the longitudinal direction.
The boundary portion is a developing apparatus characterized in that the amount of the developer pumped from the developer carrier is smaller than the amount of the developer pumped from the developer carrier in the image-forming region. The developer carrier has a boundary portion on the non-image-forming region side of the boundary between the non-image-forming region and the image-forming region on one end side in the longitudinal direction.
The boundary portion according to any one of claims 1 to 5, wherein the surface is formed in a mirror surface shape, or a sealing member is attached to the surface in the circumferential direction. Developer. A developer regulating member that regulates the developer supported on the surface of the developer carrier facing the developer carrier is provided.
The developer according to any one of claims 1 and 3 to 6, wherein the developer regulating member is formed so as not to face the developer carrier in the non-image forming region on one end side in the longitudinal direction. The developing device described. The first transport member is disposed above the second transport member, and supplies the developer to the developer carrier while transporting the developer from one end side in the longitudinal direction to the other end side in the longitudinal direction. At the same time, the developer separated from the developer carrier was recovered.
A second communication portion formed on the other end side in the longitudinal direction is provided so that the developer on the downstream side of the first transport member and the developer on the upstream side of the second transport member can flow. The developing apparatus according to any one of claims 1 to 7. The feature is that the amount of the developer transported per unit time by the second transport member is larger than the amount of the developer transported per unit time by the first transport member. The developing apparatus according to any one of claims 1 to 8. A process cartridge that is detachably installed with respect to the main body of the image forming apparatus.
A process cartridge comprising the developing apparatus according to any one of claims 1 to 9 and the image carrier integrally. An image forming apparatus comprising the developing apparatus according to any one of claims 1 to 9 and the image carrier.

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