JP2013083742A - Developing device, image forming apparatus and process cartridge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device capable of suppressing the occurrence of density unevenness caused by staining of the surface of a developer carrier, an image forming apparatus having the developing device and a process cartridge.SOLUTION: A developing device 3 comprises a developing roller 302 including a magnet roller 302d having a plurality of magnetic poles inside a developing sleeve 302c, a supply chamber 304a and a recovery chamber 305a, wherein a drawing up region η and a separating region γ are formed by a magnetic field of the magnet roller 302d and a developing bias having the same polarity as the electrification polarity of toner is applied to the developing sleeve 302c by a power source for developing bias 302g. A grounded conductive grounding member 50 is disposed at a position contacting with a developer 320 near a surface of the developing sleeve 302c, which is a position on the downstream side in a surface moving direction of the developing sleeve 302c to a developing region α and on the upstream side to the drawing up region η.

Description

  The present invention relates to a developing device used for a copying machine, a facsimile, a printer, and the like, and an image forming apparatus and a process cartridge using the developing device.

Conventionally, an image forming apparatus including a developing device using a two-component developer including toner and a magnetic carrier has been widely used.
In this type of developing device, a magnetic field generating means is provided inside a surface member such as a developing sleeve that forms a developer carrier such as a developing roller, and the surface of the surface member of the developer carrier is generated by the magnetic field generated by the magnetic field generating means. To form a magnetic brush of developer. In the developing region where the developer carrier and the latent image carrier are close to each other, a surface member to which a developing bias having the same polarity as the charging polarity of the toner is applied, and a latent image formed on the surface of the latent image carrier. The toner in the developer forming the magnetic brush is transferred to the latent image. As a result, the latent image on the surface of the latent image carrier is developed by the developing device, and a toner image is formed on the surface of the latent image carrier.

Conventionally, in a developing device using a two-component developer, the developed toner image has uneven density due to “developer carrying member surface contamination” in which toner adheres directly to the surface of the surface member of the developer carrying member. It sometimes occurred.
Regarding the density unevenness problem, first, “developer carrier surface contamination” that causes the problem will be described.

  When the developer carrying member conveys the developer, the developer is conveyed while moving relative to the surface member. Specifically, the magnetic brush of the developer on the surface of the surface member is brought into a sprouting state or a lying state by the magnetic field generated by the magnetic field generating means. Since the developer is transported on the surface of the surface member while repeating the state where the magnetic brush is standing up or sleeping, the change from the standing state to the sleeping state, or from the sleeping state to the standing state An impact is applied to the developer forming the magnetic brush at a timing such as a change in. Due to this impact, the toner may leave the carrier and adhere directly to the surface of the surface member, which becomes the developer carrier surface contamination.

  The toner is charged with a predetermined polarity (hereinafter referred to as a negative polarity but may be a positive polarity as an example) due to frictional charging with the carrier before being carried as a developer on the developer carrying member. The toner forming the surface of the carrier is also charged with a negative polarity. A developing bias having the same polarity (negative polarity) as the charging polarity of the toner is applied to the surface member, but the surface of the developer carrying member is contaminated by the negative charge of the toner at the portion where the developer carrier surface is stained. The upper potential increases to negative polarity. For this reason, the developer carrying member surface is contaminated, and the portion where the toner adheres to the surface of the surface member has a stronger electric field strength of the developing electric field in the developing region than in other portions. Therefore, in the portion where the toner is attached to the surface of the surface member, more toner is transferred to the latent image of the latent image carrier, and adheres to the portion where the toner is attached on the surface of the surface member. Density unevenness occurs in areas that are not exposed.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a developing device capable of suppressing the occurrence of density unevenness due to contamination on the surface of the developer carrying member, and image formation including the developing device. An apparatus and a process cartridge are provided.
Is to provide.

  In order to achieve the above object, a first aspect of the present invention is to carry a latent image in a developing region facing a latent image carrier by carrying a two-component developer comprising toner and a magnetic carrier on an endlessly moving surface. A developer carrying body for supplying toner to the latent image on the surface of the carrying body and developing; and a developer containing portion for containing the developer to be supplied to the developer carrying body, the developer carrying body comprising: A magnetic field generating means having a plurality of magnetic poles inside the surface member that moves endlessly, and the developer supplied from the developer accommodating portion is placed on the surface of the developer carrier by the magnetic field generated by the magnetic field generating means. And a developer separating portion for separating the developer that has passed through the developing area from the surface of the developer carrying member, and a developing bias having the same polarity as the charging polarity of the toner. In the developing device to which A developer in the vicinity of the surface of the developer carrying member that is located downstream of the region in the surface moving direction of the developer carrying member and upstream of the pumping portion in the surface moving direction of the developer carrying member; A grounded conductive member is disposed at a position in contact with.

  When the developer carrier surface contamination of the surface member reaches the pumping unit and the developer is supplied, the developer supplied by the pumping unit onto the toner that forms the developer carrier surface contamination. The magnetic brush of the agent is formed, and the electric field strength of the developing electric field becomes stronger in the developing region than in other parts. That is, if the developer carrying member surface contamination is not generated on the surface member in the pumping portion, it is possible to prevent density unevenness due to the developer carrying member surface contamination.

  In the present invention, the conductive member is grounded, and a developing bias having the same polarity as the charging polarity of the toner is applied to the surface member. Therefore, an electric field is formed between the surface member and the conductive member, and this electric field is formed in a direction in which the toner charged to a predetermined polarity moves to the conductive member. Due to this electric field, the toner in the developer existing between the surface member and the conductive member moves in the direction of the conductive member. At this time, the toner adhering to the surface of the surface member is separated from the surface member and taken into the developer existing between the surface member and the conductive member.

  Further, since the toner in the developer existing between the surface member and the conductive member moves in the direction of the conductive member, it is considered that the toner concentration in the developer changes. For this reason, when the conductive member is disposed at a position downstream of the pumping portion in the surface movement direction of the developer carrier and upstream of the development region in the surface movement direction of the developer carrier, The toner density of the developer adjusted to a desired toner density before being supplied to the toner changes, and there is a possibility that a developer having a state different from the desired toner density is supplied to the development area. On the other hand, in the present invention, the conductive member is disposed at a position downstream of the developer carrying member in the surface movement direction with respect to the developing region and at a position upstream of the pumping portion in the surface movement direction of the developer carrying member. The conductive member is not disposed between the drawing-up portion and the development region. Therefore, the developer supplied onto the developer carrier at the scooping section is conveyed to the development area without changing the toner density.

  According to the present invention, the toner that may form the developer carrying member surface stain at the pumping portion can be separated from the surface of the surface member of the developer carrying member. There is an excellent effect that the occurrence of density unevenness can be suppressed.

FIG. 2 is a schematic configuration diagram of a developing device of the present embodiment. 1 is a schematic configuration diagram of a printer according to an embodiment. 1 is a schematic configuration diagram of an image forming device. Sectional explanatory drawing of the cross section parallel to the rotating shaft direction of a developing roller. The internal perspective view of the principal part of a developing device. FIG. 3 is an external perspective view of a main part of the developing device. FIG. 3 is a schematic diagram illustrating the flow of a developer in a developing container. Explanatory drawing of the communicating port part of a developing device. Explanatory drawing which shows typically the opposing part of a developing sleeve and a conductive grounding member. The graph which compared the level of "image tip darkness" by the presence or absence of a conductive grounding member. FIG. 9 is an explanatory diagram illustrating a schematic configuration of a developing device according to a first modification and a photosensitive member. FIG. 9 is an explanatory diagram illustrating a schematic configuration of a developing device according to a second modification and a photosensitive member. FIG. 4 is an explanatory diagram of a developing device in which two developer agitating and conveying members are arranged side by side in a direction away from the developing roller. FIG. 3 is an explanatory diagram schematically showing a facing portion between a developing sleeve and a photoreceptor in which sleeve contamination occurs on a part of the surface. The image figure of the image which "image tip darkness" generate | occur | produced.

Hereinafter, an embodiment in which the present invention is applied to a printer (hereinafter referred to as a printer 100) as an image forming apparatus will be described.
FIG. 2 is a schematic configuration diagram of the printer 100. The printer 100 is a color image forming apparatus that can form a full color image by adopting a tandem method, and forms toner images of respective colors of black, magenta, yellow, and cyan (hereinafter referred to as K, M, Y, and C). Four image forming devices 17 (K, M, Y, C) are provided.

Below the four image forming devices 17 (K, M, Y, and C), the transfer paper P is carried on the surface and conveyed around the downstream tension roller 18 and the upstream tension roller 19, and conveyed. An endless belt-like transfer conveyance belt 15 that moves while facing the image forming devices 17 (K, M, Y, C) is disposed.
One of two rollers, a downstream tension roller 18 and an upstream tension roller 19 that stretch the transfer conveyance belt 15, is a drive roller that is rotationally driven by a rotational drive transmitted from a drive source. The transfer conveyance belt 15 moves endlessly in the direction of arrow A in FIG. The other of the two rollers is a driven roller that rotates following the endless movement of the transfer conveyance belt 15.
Further, a transfer bias roller 5 (K, M, Y, C) facing each image forming device 17 (K, M, Y, C) with the transfer conveyance belt 15 interposed therebetween is provided.
In addition, a fixing device 24 that fixes unfixed toner on the transfer paper P separated from the transfer conveyance belt 15 is provided downstream of the downstream tension roller 18 in the transfer paper conveyance direction by the transfer conveyance belt 15. . Further, an upper portion of the printer 100 is provided with a paper discharge tray 25 for stacking transfer paper P that has passed through the fixing device 24 and has a toner image fixed thereon.

  Below the transfer conveyance belt 15, a plurality of paper feed cassettes 20 for storing transfer paper P are provided. In addition, a paper feeding / conveying device 26 as a transfer paper feeding unit that feeds the transfer paper P from each paper feeding cassette 20 to a transfer region where the transfer / conveying belt 15 and the image forming device 17 (K, M, Y, C) face each other. And a registration roller pair 23 that supplies the transfer paper P conveyed from the paper feed cassette 20 in accordance with the image forming timing of the image forming device 17 (K, M, Y, C).

  In FIG. 2, the transfer conveyance belt 15 is arranged in an oblique direction so that the printer 100 is small in the left-right direction in FIG. 2, and the conveyance direction of the transfer paper P indicated by an arrow A is an oblique direction. Accordingly, in the printer 100, the width of the casing in the left-right direction in FIG. 2 is slightly longer than the length in the longitudinal direction of the A3 size transfer sheet. That is, the printer 100 is greatly reduced in size by being the minimum size required to accommodate the transfer paper therein.

  Each image forming device 17 (K, M, Y, C) has a drum-shaped photosensitive member 1 (K, M, Y, C) as a latent image carrier. The charging device 2 (K, M, Y, C), the developing device 3 (K, M, Y, C), and the cleaning device 6 (in order with respect to the rotation direction of the photoreceptor 1 (K, M, Y, C), respectively. K, M, Y, C), etc. Further, between the charging device 2 (K, M, Y, C) and the developing device 3 (K, M, Y, C), the writing light L is exposed to an exposure device 16 (K, M, Y, C) is a well-known configuration. The photoreceptor 1 (K, M, Y, C) may be a belt shape instead of a drum shape.

  In the printer 100 having such a configuration, each color toner image is formed by each image forming device 17 (K, M, Y, C) at the start of image formation. In each image forming device 17 (K, M, Y, C), the photoreceptor 1 (K, M, Y, C) is rotationally driven by a main motor (not shown), and the charging device 2 (K, M, Y, C). ), The exposure device 16 (K, M, Y, C) irradiates the writing light L according to the image information for each color obtained by color separation of the image, and forms an electrostatic latent image. Is done. The electrostatic latent image formed on the photoreceptor 1 (K, M, Y, C) is developed by the developing device 3 (K, M, Y, C), and each photoreceptor 1 (K, M, Y, C) is developed. Each color toner image is formed on the surface of C).

  On the other hand, the transfer paper P fed and conveyed from one of a plurality of paper feed cassettes 20 is temporarily kept waiting at the position of the registration roller pair 23, and then the image forming device 17 (K, M, Y, C). The toner is supplied from the registration roller pair 23 onto the surface of the transfer conveyance belt 15 in accordance with the image forming timing. The transfer paper P supplied onto the surface of the transfer / conveying belt 15 is attracted to the transfer / conveying belt 15 by electrostatic adsorption and is carried on the transfer / conveying belt 15. The transfer paper P carried on the transfer conveyance belt 15 is sequentially conveyed to the transfer area by the image forming devices 17 (K, M, Y, C) of each color by the surface movement of the transfer conveyance belt 15.

The toner image formed on each photoconductor 1 (K, M, Y, C) is transferred as a transfer bias means at a facing portion between the photoconductor 1 (K, M, Y, C) and the transfer conveyance belt 15. The image is sequentially transferred onto the transfer paper P carried on the transfer conveyance belt 15 by the bias roller 5 (K, M, Y, C). In this way, the toner images formed on the respective photoreceptors 1 (K, M, Y, C) are transferred in the order of K (black), M (magenta), Y (yellow), and C (cyan). A superimposed color toner image is formed on the transfer paper P. The transfer paper P onto which the toner image has been transferred is separated from the transfer conveyance belt 15 and conveyed to the fixing device 24, where the toner image is fixed and discharged to a discharge tray 25 outside the apparatus.
On the other hand, the photoreceptor 1 (K, M, Y, C) after the toner image is transferred onto the transfer paper P is removed by the cleaning device 6 (K, M, Y, C) to remove the transfer residual toner. In response to the above, after being neutralized by a neutralizing lamp (not shown), the operation of being uniformly charged by the charging device 2 (K, M, Y, C) is repeated again.
Further, in the printer 100 of the present embodiment, a unit is configured by integrally supporting a plurality of members constituting the image forming device 17, and is configured to be removable from the printer 100 main body as a process cartridge. The image forming device 17 is not necessarily configured as a unit.

  In the printer 100 shown in FIG. 2, K (black), M (magenta), and Y (yellow) from the upstream side in the conveyance direction along the surface movement direction (conveyance direction) of the transfer conveyance belt 15 that conveys the transfer paper P. , C (cyan), four image forming devices 17 (K, M, Y, C) are arranged. However, the order in which the image forming devices 17 (K, M, Y, C) for the respective colors are arranged is not limited to this. For example, a black image forming device 17K is arranged on the most downstream side in the transport direction, and four image forming devices 17 (M, Y) in the order of M (magenta), Y (yellow), C (cyan), and K (black). , C, K) may be arranged.

  Next, the image forming device 17 will be described in detail. The image forming device 17 (K, M, Y, C) of the printer 100 of the present embodiment uses toners of different colors (K, M, Y, C) as image forming materials in the developing device 3. Other than that, the configuration is the same. Therefore, hereinafter, the subscripts K, M, Y, and C are omitted, and the image forming device 17 will be described.

FIG. 3 is a schematic configuration diagram of the image forming device 17 including the developing device 3 applicable to the printer 100 of the present embodiment.
The developing device 3 is disposed to face the photoconductor 1, and the photoconductor 1 is rotated in the clockwise direction in FIG. 3 as indicated by an arrow a in FIG.
The charging device 2 is disposed above the photosensitive member 1 at a position of approximately 11 o'clock of the photosensitive member 1 in FIG. In this example, the charging device 2 is composed of a rotating body that is rotated at the same surface moving speed as that of the photosensitive member 1.

The surface of the photosensitive member 1 is uniformly charged in the dark by the charging device 2 and then irradiated with writing light L from an exposure device 16 which is writing means not shown in FIG. Is formed. The electrostatic latent image moves to the downstream side of the surface movement direction of the photoconductor 1 along with the rotation of the photoconductor 1, and reaches a developing region α that is a portion facing the developing device 3. In FIG. 3, the developing device 3 is disposed on the right side of the photoreceptor 1.
The developing device 3 includes a supply chamber conveyance member 304 and a collection chamber conveyance member 305 for agitating and conveying the developer 320 in the casing 301, and other members such as a developing roller 302 and other members.
The developing roller 302 is close to and opposed to the photosensitive member 1 at a position between 2 o'clock and 3 o'clock of the photosensitive member 1 in FIG. Closely arranged. A portion of the casing 301 corresponding to the portion facing the photoconductor 1 is opened to expose the developing roller 302.

As the developing roller 302 moves in the direction of arrow b in FIG. 3, the developer 320 in the casing 301 is carried on the surface of the developing roller 302 and is conveyed in the direction of arrow B in FIG. It is conveyed to. In the developing area α, the toner in the developer 320 adheres to the electrostatic latent image formed on the surface of the photoreceptor 1 and is visualized as a toner image.
The toner image moves to the downstream side of the surface movement direction of the photoconductor 1 along with the rotation of the photoconductor 1, and reaches a transfer region β that is a portion facing the transfer bias roller 5 of the transfer device. The transfer bias roller 5 is disposed below the photoconductor 1 and at the 6 o'clock position of the photoconductor 1 in FIG. The transfer device of the present embodiment is configured to include the transfer bias roller 5 made of a rotating body as a transfer member, but the transfer member is not limited to the rotating body and may be a corona discharge type.

  The toner image on the photoreceptor 1 is transferred to the transfer paper P in the transfer region β, and becomes an image on the transfer paper P. The printer 100 according to the present embodiment is configured to directly transfer a toner image formed on the photoreceptor 1 onto the transfer paper P. As a configuration for transferring the toner image formed on the photosensitive member 1 to the transfer paper P, the toner image on the photosensitive member is temporarily transferred to an intermediate transfer member (such as an intermediate transfer belt), and each color toner image is transferred onto the intermediate transfer member. The developing device of the present invention can also be applied to an intermediate transfer body type image forming apparatus that superimposes to form a multicolor toner image and then transfers the multicolor toner image to a transfer sheet in a lump. In this case, the toner on the photosensitive member is transferred to the intermediate transfer member (intermediate transfer belt) in the transfer region β.

The surface of the photoreceptor 1 that has passed through the transfer region β moves to the downstream side in the surface movement direction along with the rotation of the photoreceptor 1 and reaches a portion facing the cleaning device 6.
In FIG. 3, the cleaning device 6 is disposed at the 10 o'clock position with respect to the photoreceptor 1. The cleaning device 6 removes the toner remaining on the surface of the photoreceptor 1 without being completely transferred onto the transfer paper P in the transfer region β by the cleaning blade 601. The surface of the photoreceptor 1 that has passed through the portion facing the cleaning device 6 is then uniformly charged by the charging device 2, and the next image forming process is repeated.

Next, the developing device 3 will be described in detail.
As shown in FIG. 3, the developing device 3 includes a developing roller 302, a supply chamber transport member 304, a collection chamber transport member 305, and a developer regulating member 303 inside the casing 301, and stirs and transports the developer 320. And circulating. In the developing device 3 of the present embodiment, a screw member in which a helical screw blade is fixed to the rotating shaft is used as the supply chamber transfer member 304 and the recovery chamber transfer member 305, and the outer diameter of the screw blade is 16. [Mm] The following is used.

FIG. 1 is an explanatory diagram showing a schematic configuration of the developing device 3 and the photosensitive member 1 according to the present embodiment, in which a normal magnetic flux density distribution of a magnetic field formed around the developing roller 302 is additionally written.
As shown in FIG. 1, the developing roller 302 includes a magnet roller 302d in which a plurality of magnets MG (MG1 to MG3) are arranged in the circumferential direction, and a cylindrical developing sleeve 302c is provided around the rotation shaft 302e. And is configured to rotate integrally.
The developing sleeve 302c is made of a nonmagnetic metal such as aluminum. The magnet roller 302d is fixed to an immovable member such as the casing 301 so that each magnet MG faces a predetermined direction, and the developing sleeve 302c rotates around the periphery of the magnet roller MG to convey the developer 320 attracted by the magnet MG. I will do it.

FIG. 4 is a cross-sectional explanatory diagram of a cross section parallel to the rotation axis direction of the developing roller 302.
As shown in FIG. 4, the developing roller 302 includes a fixed shaft 302a fixed to a casing 301 that is a stationary member, a magnet roller 302d that is formed integrally with the fixed shaft 302a, has a cylindrical shape, and a magnet roller. The developing sleeve 302c covers the periphery of 302d through a gap, and a rotating shaft 302e integrally formed with the developing sleeve 302c. The rotating shaft 302e is rotatable with respect to the fixed shaft 302a via a bearing 302f. The rotating shaft 302e is driven to rotate by receiving power from a rotation driving means (not shown).
A plurality of magnets MG are fixed to the outer periphery of the magnet roller 302d at a predetermined interval as shown in FIG. The developing sleeve 302c rotates around these magnets MG.

The plurality of magnets MG disposed on the magnet roller 302d are for forming a magnetic field so that the developer 320 can be spiked on the peripheral surface of the developing sleeve 302c, and can be cut off. Magnetic carriers are gathered to form a magnetic brush along the normal magnetic field lines emitted from these magnets MG.
Although various configurations can be applied as the magnet roller 302d, the developing device 3 of the present embodiment has three magnets MG inside the developing sleeve 302c as shown in FIG. A magnetic roller 302d for generating a magnetic force distribution).
As shown in FIG. 1, the position facing the photoreceptor 1 on a virtual straight line connecting the developing roller center line O-1 that is the center of the developing roller 302 and the photoreceptor center O-2 that is the center of the photoreceptor 1. The first magnet MG1 is disposed in the developing magnetic field MP1, and the developing magnetic pole MP1 for causing the developer 320 to rise on the peripheral surface of the developing sleeve 302c in the developing region α is formed. Further, the second magnet MG2 that forms the casing counter pole MP2 and the third magnet that forms the developer regulating member counter pole MP3 in the counterclockwise direction (the rotation direction of the developing sleeve 302c) in FIG. 1 with respect to the developing magnetic pole MP1. Magnet MG3 is arranged.

In the developing device 3 of the present embodiment, the developing magnetic pole MP1 is an N pole, and the casing counter pole MP2 and the developer regulating member counter pole MP3 are S poles. The polarities of the magnetic poles are opposite to those of the magnetic poles. May be. The developing magnetic pole MP1 faces the photoreceptor 1, the casing counter pole MP2 faces the casing 301, and faces the developer regulating member opposing pole MP3 developer regulating member 303.
In the development area α, the surface of the developing roller 302 and the surface of the photoreceptor 1 are not in direct contact with each other, and are opposed to each other while holding a development gap GP that is a constant interval suitable for development. The developing device 3 causes the developer 320 to rise on the surface of the developing roller 302 and brings the developer 320 into contact with the photosensitive member 1, thereby attaching toner to the electrostatic latent image on the surface of the photosensitive member 1 to be a visible image. Turn into.

  A development bias power supply 302g, which is grounded, is connected to a fixed shaft 302a constituting the developing roller 302 of the developing device 3. The developing bias power supply 302g applies a predetermined voltage having the same polarity as the charged polarity of the normally charged toner to the developing sleeve 302c via the conductive bearing 302f and the conductive rotating shaft 302e shown in FIG. On the other hand, the lowermost conductive support constituting the photoreceptor 1 is grounded. With such a configuration, a developing electric field for moving the toner separated from the carrier to the photosensitive member 1 side is formed in the developing region α, and the developing sleeve 302 c and the electrostatic latent image formed on the surface of the photosensitive member 1 are formed. The toner can be moved toward the photosensitive member 1 by the potential difference.

  As shown in FIGS. 2 and 3, the developing device 3 of the present embodiment is combined with an image forming apparatus that writes a latent image on the surface of the photosensitive member 1 with writing light L. The charging device 2 uniformly applies a negative charge on the surface of the photoconductor 1 and exposes the image portion with the writing light L to reduce the writing amount. A so-called reversal development method is employed in which the latent image is developed with negative polarity toner. This is merely an example, and as a configuration to which the developing device including the characteristic portion of the present invention is applied, the polarity of the charged charge placed on the surface of the photoreceptor 1 is not a big problem.

The developer 320 carried on the surface of the developing sleeve 302c that has passed through the developing region α is carried on the developing sleeve 302c by the magnetic force of the casing facing pole MP2, and is conveyed downstream in the surface movement direction along with the rotation of the developing sleeve 302c. Then, it is drawn into the casing 301.
The casing facing pole MP2 and the developer regulating member facing pole MP3 have the same polarity, and as shown in FIG. 1, the surface movement direction of the developing sleeve 302c is downstream of the position facing the casing facing pole MP2, and In the region on the surface of the developing sleeve 302c that is upstream of the position facing the developer regulating member counter pole MP3, a magnetic field that causes the developer 320 to rise is not formed. For this reason, on the surface of the developing sleeve 302c in this region, the ears of the developer 320 lie down, and the developer 320 that has been drawn on the surface of the developing sleeve 302c upstream from this region is removed from the developing roller 302. The action of “agent release” that separates works. In this way, on the surface of the developing sleeve 302c in which the ears are lying down, it is on the downstream side from the position facing the casing facing pole MP2 and upstream from the position facing the developer regulating member facing pole MP3. As shown in FIG. 1, the region has an extremely low peak of the normal magnetic flux density distribution as compared with the other regions. This region separates the developer 320 from the developing sleeve 302c, and the agent separating region γ (FIG. 3).

The developer 320 having the toner adhered to the photoreceptor 1 has a lower toner concentration in the developer 320. For this reason, if the developer 320 having a lowered toner density is transported again to the development area α without being separated from the developing roller 302 and used for development, there is a problem that the target image density cannot be obtained. End up.
As a configuration for preventing this, in the developing device 3 of the present embodiment, the developer 320 carried on the surface of the developing sleeve 302c that has passed through the developing region α is separated from the developing roller 302 in the agent releasing region γ. The developer 320 separated from the developing roller 302 is collected in the collection chamber 305a, and then sufficiently stirred and mixed in the casing 301 so that the target toner concentration and toner charge amount are obtained. In this way, the developer 320 having the target toner concentration and charge amount is supplied from the supply chamber 304a to the developer storage space ε by the supply chamber conveyance member 304.

  The developer 320 supplied to the developer storage space ε is carried on the surface of the developing sleeve 302c by the magnetic force of the developer regulating member counter pole MP3, and is located immediately downstream of the peak position of the developer regulating member counter pole MP3. By passing through a portion facing the developer regulating member 303, the thickness is adjusted to a predetermined thickness. The developer 320 that has passed through the portion facing the developer regulating member 303 is conveyed to the development region α while forming a magnetic brush. Further, the developer regulating member counter electrode MP3 functions as a transport pole for transporting the developer 320. Further, the region where the developer 320 in the developer storage space ε is carried on the surface of the developing sleeve 302c by the magnetic force of the developer regulating member counter pole MP3 is the agent scooping region η.

FIG. 5 is an internal perspective view of a main part of the developing device 3, and FIG. 6 is an external perspective view of the main part of the developing device 3. FIG. 7 is a schematic diagram illustrating the flow of the developer 320 in the casing 301 when the developing device 3 is viewed from the direction of arrow E in FIG. FIG. 8 is an explanatory view of a portion provided with a communication hole in the partition plate 306 at both ends in the longitudinal direction of the developing device 3 as viewed from above.
Arrows D1 to D4 in FIGS. 5 and 7 indicate the flow of the developer 320 in the casing 301.

  As shown in FIGS. 1 and 3, the supply chamber conveying member 304 is positioned around the developing roller 302 and is arranged in the 2 o'clock direction of the developing roller 302 in FIGS. 3 and 1. This position is also on the upstream side in the surface movement direction of the developing roller 302 with respect to the portion facing the developer regulating member 303. As shown in FIG. 5, the supply chamber conveying member 304 has a screw shape with a spiral wing around the rotation axis, and a supply screw center parallel to the developing roller center line O-302a of the developing roller 302. It rotates in the clockwise direction indicated by the arrow f in FIGS. 1 and 3 around the line O-304. By this rotation, as shown by an arrow D4 in FIG. 5, the developer 320 is conveyed while being stirred from the front side FS in the longitudinal direction of the developing device 3 toward the back side BS along the supply screw center line O-304. To do. That is, the supply chamber conveyance member 304 conveys the developer 320 in the axial direction, from the near side FS to the back side BS, by inputting rotational drive to the rotation axis.

  As shown in FIGS. 1 and 3, the collection chamber transport member 305 is positioned around the developing roller 302 and in the vicinity of the agent separation region γ in the direction of 4 o'clock of the developing roller 302 in FIGS. 1 and 3. Is arranged. Further, as shown in FIG. 5, the recovery chamber transport member 305 has a screw shape provided with a spiral blade around the rotation axis, and the recovery screw center line O parallel to the developing roller center line O-302a. It rotates in the counterclockwise direction indicated by the arrow g in FIGS. 1 and 3 around −305. As a result of this rotation, as shown by an arrow D2 in FIG. 5, the developer 320 is conveyed while being stirred from the back side BS in the longitudinal direction of the developing device 3 toward the front side FS along the recovery screw center line O-305. To do. That is, the recovery chamber transport member 305 transports the developer 320 from the back side BS opposite to the transport direction by the supply chamber transport member 304 toward the front side FS when the rotational drive is input to the rotation shaft.

The supply chamber transfer member 304 is positioned above the recovery chamber transfer member 305, and the supply chamber 304 a that is a space around the supply chamber transfer member 304 in the casing 301, and the recovery chamber transfer member 305. The collection chamber 305a, which is the surrounding space, is adjacent to the partition plate 306.
As shown in FIGS. 5 and 6, the front end of the supply chamber transport member 304 and the collection chamber transport member 305 is set so as to be located slightly in front of the front end of the developing roller 302. The supply of the developer 320 from the inside of the supply chamber 304a to the near end of the roller 302 is ensured. Further, the back side end portions of the supply chamber transport member 304 and the collection chamber transport member 305 are set to be located on the back side with respect to the back side end portion of the developing roller 302. As a result, a space for supplying toner, which will be described later, is secured. The length in the longitudinal direction of the developer regulating member 303 is set according to the length of the developing roller 302.

As shown in FIGS. 1, 3, and 7, a partition plate 306 that spatially partitions the supply chamber 304 a and the recovery chamber 305 a is provided between the supply chamber transfer member 304 and the recovery chamber transfer member 305 of the casing 301. Supported on the inside. Communication ports (41 and 42) are provided at both ends in the longitudinal direction of the partition plate 306, respectively.
The developer 320 transported from the back side BS in the longitudinal direction to the front side FS (in the direction of arrow D2 in FIG. 5) by the collection chamber transport member 305 is cut off from the path at the side wall of the casing 301 at the end in the transport direction. It rises along. As a result of this swell, the developer 320 that has reached the downstream end in the transport direction in the collection chamber 305a reaches the end on the near side in the longitudinal direction of the communication ports provided at both ends in the longitudinal direction of the partition plate 306 described above. It passes through the provided lifting opening 41 (arrow D3 in FIG. 5) and is delivered to the supply chamber 304a.

The developer 320 delivered to the supply chamber 304a is transported in the supply chamber 304a from the near side FS in the longitudinal direction to the back side BS (in the direction of arrow D4 in FIG. 5) by the supply chamber transport member 304.
As in the case of the recovery chamber 305a, the developer 320 conveyed from the front side FS in the longitudinal direction to the back side BS (in the direction of arrow D4 in FIG. 5) by the supply chamber conveyance member 304 is the casing 301 at the end in the conveyance direction. The path is cut off by the side wall. The developer 320 that has reached the downstream end in the transport direction in the supply chamber 304a falls at the end in the longitudinal direction among the communication ports provided at both ends in the longitudinal direction of the partition plate 306 described above. It falls from the opening 42 and is delivered to the collection chamber 305a.

  As described above, the developing device 3 includes the developing roller 302, the supply chamber conveyance member 304, the collection chamber conveyance member 305, the partition plate 306, and the like. The developing roller 302 carries the developer 320 and moves on the surface to visualize the electrostatic latent image formed on the photosensitive member 1. The supply chamber conveyance member 304 rotates about a supply screw center line O-304 parallel to the developing roller center line O-302a of the developing roller 302, and the longitudinal direction of the developing device 3 along the supply screw center line O-304. The developer 320 is conveyed in the direction while being stirred. The collection chamber transport member 305 is disposed in the vicinity of the agent separation region γ that separates the developer 320 from the developing roller 302, and rotates around a collection screw center line O-305 parallel to the developing roller center line O-302a. The supply chamber transport member 304 transports the developer 320 in a direction opposite to the direction in which the developer 320 is transported while stirring the developer 320. The partition plate 306 is between the supply chamber transfer member 304 and the recovery chamber transfer member 305, partitions the space between the supply chamber 304a and the recovery chamber 305a, and has communication ports at both ends in the longitudinal direction. With such a configuration, the developing device 3 forms a circulation path of the developer 320 along the arrows D1 to D4 in FIG.

Further, two developer agitating / conveying members (304 and 305) for circulating the developer 320 in the developing device 3 of the present embodiment are arranged side by side on the side of the developing roller 302.
As a conventional developing device 3, as shown in FIG. 13, two developer agitating and conveying members (supply / recovery screw 404, circulation screw 405) are arranged side by side in a direction away from the developing roller 302 (horizontal direction). is there. As described above, the developing device 3 of the present embodiment can reduce the size of the apparatus in the horizontal direction (horizontal direction) as compared with the configuration in which the two developer agitating and conveying members are arranged side by side in the horizontal direction.

Further, in the developing device 3 of the present embodiment, the space from the supply chamber 304a and the recovery chamber 305a is partitioned by the partition plate 306. For this reason, only the developer 320 in which the toner and the carrier are sufficiently agitated and mixed is supplied to the developing roller 302 by the supply chamber conveying member 304, and the developer 320 whose toner density has decreased immediately after the development is exclusively collected. It is agitated and conveyed by the conveying member 305 and is not immediately supplied to the developing roller 302. Therefore, only the developer 320 including the toner having the target charge amount and having the target toner density is supplied to the developing roller 302 and used for development, so that high image quality can be obtained.
As described above, the developing device 3 according to the present embodiment can obtain high image quality while achieving compactness in the horizontal direction.

Next, toner supply in the developing device 3 will be described.
Since the developer 320 in the developing device 3 consumes toner while repeating the developing operation, it is necessary to supply the toner to the developer 320 in the device from the outside of the developing device 3. The developing device 3 of the present embodiment includes a toner replenishing port 309 in the vicinity of the end of the back side BS in the longitudinal direction, and the toner replenishment from the outside as indicated by an arrow T in FIG. I do. In the developing device 3 of the present embodiment, the vicinity of the end on the far side BS in the longitudinal direction is near the end on the downstream side in the transport direction in the supply chamber 304a for supplying the developer to the developing roller 302. The replenished toner is not immediately used for development, but is supplied to the recovery chamber 305a through the drop opening 42. The toner supplied to the recovery chamber 305a is mixed and agitated with the developer 320 by the recovery chamber transport member 305 and contained in the developer 320 having a predetermined toner concentration, and then the toner is supplied from the lifting port 41 to the supply chamber 304a. And delivered for development.

  Further, the collection chamber 305a in which the collection chamber conveyance member 305 is disposed is conveyed to the back side BS (in the direction of arrow D4 in FIG. 5) in the longitudinal direction of the developing device 3 by the supply chamber conveyance member 304 separated from the surface of the developing roller 302. While being supplied to the developing roller 302, it is used for development.

Next, the toner density sensor 201 will be described.
As shown in FIG. 7, in the developing device 3, a toner concentration sensor 201 is disposed below the lifting port 41 in the collection chamber 305a. The toner concentration sensor 201 of this embodiment is a sensor that measures magnetic permeability, and can detect the carrier concentration (= 100−toner concentration) of the developer. Based on the detection result of the toner density sensor 201, a control unit (not shown) determines whether or not the toner density of the developer 320 in the detection area of the toner density sensor 201 is appropriate from the carrier density, and the amount of toner to be replenished To decide.

Below the lifting port 41 where the toner concentration sensor 201 is disposed is a downstream end portion in the transport direction of the recovery chamber transport member 305 in the recovery chamber 305a.
The flow of the developer 320 in the developing device 3 is as indicated by arrows D1 to D4 in FIG. 5 and arrows in FIG. In the supply chamber 304a, a large amount of the developer 320 is supplied to the developing roller 302 and used for development before being transported to the end of the back side BS by the supply chamber transport member 304, and is received by the recovery chamber 305a. Passed. For this reason, in the collection chamber 305a, the amount of the developer 320 is increased toward the front side FS that is the downstream side in the conveyance direction of the collection chamber conveyance member 305, and the developer 320 tends to accumulate near the front side FS end. Therefore, like the developing device 3 of the present embodiment, the toner density sensor 201 is disposed at the downstream end in the transport direction of the recovery chamber transport member 305 in the recovery chamber 305a, so that the development is performed above the toner density sensor 201. The agent 320 is always filled, and stable carrier concentration detection is possible.

  As shown in FIG. 2, the printer 100 according to this embodiment includes a photosensitive device 1 arranged in the horizontal direction for each color of black, magenta, yellow, and cyan, and a charging device 2 and a developing device 3 are provided on each photosensitive member 1. This is a tandem type color image forming apparatus that forms an electrostatic latent image, visualizes it, and sequentially transfers it onto a transfer paper P to obtain a full color image. In such an image forming apparatus, the developing device 3 (K, M, Y, C) is provided for each of the photoreceptors 1 (K, M, Y, C) arranged in the horizontal direction. In order to save the space, it is required to narrow the interval between the photoreceptors 1. In order to reduce the interval between the photoconductors 1, the developing devices 3 are also required to be reduced in horizontal size (lateral direction).

  By using the developing device 3 as shown in FIG. 1 as a plurality of developing devices provided in the printer 100, the lateral dimension of one developing device 3 can be made smaller than the conventional one shown in FIG. Miniaturization in the horizontal direction can be achieved. Further, as described above, the developing device 3 (K, M, Y, C) of the present embodiment has the agent separating area γ, the agent pumping area η, the supply chamber conveying member 304, the recovery chamber conveying member 305, the partition plate 306, and the like. Therefore, toner having a target charge amount is used for development, and high image quality can be obtained. Further, since the developer 320 that has passed through the development region α is not immediately used for re-development, deterioration of the developer 320 can be suppressed, and the performance of the developer 320 can be stably maintained over a long period of time. Therefore, it is possible to provide a developing device having a long life and high durability. Such a benefit is not unique to the tandem full-color image forming apparatus, but can be obtained in a single-color image forming apparatus.

Next, the characteristic part of the developing device 3 of the present invention will be described.
As shown in FIG. 1, the developing device 3 includes the developing sleeve 302 c at a downstream side in the rotation direction of the developing sleeve 302 c with respect to the developing region α and a portion facing the developer storage space ε serving as the pumping region η. A conductive grounding member 50, which is a conductive member grounded, is disposed on the inner wall of the casing 301 that is a portion facing the casing counter pole MP2 that is located upstream in the rotational direction. A conductive grounding member 50 shown in FIG. 1 is a non-magnetic metal member, and is a cylindrical metal bar extending in parallel with the rotation axis direction of the developing roller 302.

Here, a phenomenon such as “density unevenness” or “image tip darkness”, which is a problem occurring in a conventional developing device that does not include the conductive grounding member 50, will be described.
First, sleeve contamination that causes these phenomena will be described. When the developing sleeve 302c conveys the developer 320, the developer 320 is conveyed while moving with respect to the developing sleeve 302c. That is, when the magnetic flux density on the surface of the developing sleeve 302c is perpendicular to the surface of the developing sleeve 302c, the developer 320 rises, and when the magnetic flux density is tangential, the developer 320 is Go to sleep. Since the developer 320 is conveyed by repeating this, an impact is applied to the developer 320 at a timing such as a change from the standing state to the sleeping state or a change from the sleeping state to the standing state. Due to this impact, the toner may be separated from the carrier and adhere to the surface of the developing sleeve 302c, which becomes the sleeve dirt.

The toner has a negative polarity charge due to frictional charging with the carrier before being transferred to the developing sleeve 302c. Naturally, the toner attached to the surface of the developing sleeve 302c also has a negative polarity charge.
FIG. 14 is an explanatory diagram schematically showing a facing portion between the developing sleeve 302c and the photosensitive member 1 in which sleeve contamination occurs on a part of the surface.
In the state shown in FIG. 14, the toner T adheres to the end portion of the surface of the developing sleeve 302 c, and the apparent potential of the developing sleeve 302 c increases to a negative polarity due to the negative charge of the adhered toner T. . As a result, the electric field is stronger than the desired developing electric field in the region 1A in FIG. 14 where the toner adheres to the surface of the developing sleeve 302c in the developing region α where the developer 320 and the photoreceptor 1 are in contact. On the other hand, in a region 1B in FIG. 14 where toner is not attached to the surface of the developing sleeve 302c, a desired developing electric field is obtained.

  Due to the potential increase of the developing sleeve 302c, the effective developing bias is increased by the potential of the toner T attached to the developing sleeve 302c to the desired developing bias. Therefore, the portion where the toner is attached to the developing sleeve 302c is more than intended. However, the amount of toner T to be developed increases. Therefore, when the sleeve is soiled, density unevenness occurs between the portion where the toner T is attached and the portion where the toner T is not attached on the surface of the developing sleeve 302c.

Here, when the portion (region 1A) where the toner T adheres to the surface of the developing sleeve 302c passes through the developing region α and development is performed using the developer 320 in this portion, the developing sleeve 302c is developed by the developing bias. A force in the direction toward the photosensitive member 1 also acts on the toner T adhering to the surface of the toner. As a result, the toner T is detached from the surface of the developing sleeve 302c corresponding to the region 1A, and a state similar to that in the region 1B is obtained.
For this reason, when a solid image is formed in a state where the sleeve is smeared, the developing sleeve 302c starts rotating, and after the solid image is developed on the photosensitive member 1, the density becomes dark only for one round of the developing sleeve 302c. A kind of unevenness occurred. Hereinafter, this phenomenon is referred to as “dark image tip”. FIG. 15 is an image diagram of an image in which “high image tip” has occurred. As shown in FIG. 15, when all the solid images are output in a state where the sleeve is smeared, the image density is increased by one round of the developing sleeve 302 c at the leading end of the image, and the image density is decreased after the second round ( The desired concentration).

In order to suppress the occurrence of density unevenness due to sleeve contamination as described above, it is required to reduce the amount of toner that becomes attached to the surface of the developing sleeve 302c.
In the developing device described in Patent Document 1, a retaining member that retains a part of the developer is provided between the magnetic poles. However, in the present invention, the toner adheres to the developing sleeve when stirring, but there is no effect of suppressing the toner adhering to the sleeve by the electric field.
On the other hand, in the developing device 3 of the present embodiment, by providing the conductive grounding member 50, the amount of toner that is attached to the surface of the developing sleeve 302c is reduced.
Hereinafter, the principle will be described with reference to FIG.

FIG. 9 is an explanatory diagram schematically showing a facing portion between the developing sleeve 302c and the conductive grounding member 50 in the developing device 3 of the present embodiment.
The conductive grounding member 50 is grounded, and a developing bias having a negative polarity is applied to the developing sleeve 302c. Accordingly, an electric field is formed between the developing sleeve 302 c and the conductive grounding member 50, and this electric field is formed in the direction in which the negatively charged toner T moves to the conductive grounding member 50. Due to this electric field, the toner T existing between the developing sleeve 302 c and the conductive grounding member 50 moves toward the conductive grounding member 50.
At this time, the toner T2 adhering to the carrier as the developer 320 adheres to the conductive grounding member 50, and the toner T1 adhering to the surface of the developing sleeve 302c separates from the surface of the developing sleeve 302c, and the developer T Is taken in.

  Thus, the toner T adhering to the developing sleeve 302c is separated from the developing sleeve 302c by the electric field between the developing sleeve 302c and the conductive grounding member 50. As a result, the toner T that has caused the density unevenness is separated from the surface of the developing sleeve 302c, so that it is possible to suppress the occurrence of density unevenness (in the case of a solid image, “dark image front end”).

  As described above, the toner T charged to negative polarity adheres to the conductive ground member 50 by the electric field formed between the developing sleeve 302 c and the conductive ground member 50. If the toner T continues to adhere to the conductive grounding member 50, a negative charge is accumulated on the surface of the conductive grounding member 50 due to the adhered toner T, so that the electric field between the developing sleeve 302c and the conductive grounding member 50 becomes weak. When the electric field is not formed between the developing sleeve 302c and the conductive grounding member 50 by the toner T adhering to the conductive grounding member 50, the toner T is not moved.

As a configuration that can solve such a problem, in the developing device 3 of the present embodiment, the conductive grounding member 50 is disposed on the inner wall of the casing 301 that is a portion facing the casing facing pole MP2, and the conductive grounding member 50 is The magnetic brush formed by the casing counter pole MP2 is in contact with the surface.
With such a configuration, there is a developer 320 that forms a magnetic brush around the conductive grounding member 50, and the developer 320 is moved by the surface movement of the developing sleeve 302c. The carrier in the developer 320 that is moving is positively charged. Further, when the carrier 320 contacts with the conductive grounding member 50, it is triboelectrically charged with the toner T attached to the conductive grounding member 50. The toner adhering to the toner 50 can be scraped off by the developer 320. As a result, the toner T adhering to the conductive grounding member 50 is changed, so that the electric field between the developing sleeve 302 c and the conductive grounding member 50 is not lost in the developing device 3.

  Here, in order to scrape off the toner adhering to the conductive grounding member 50 with the developer 320, it is desirable that the conductive grounding member 50 is nonmagnetic. When the conductive grounding member 50 is a magnetic substance, the conductive grounding member 50 is magnetized by the magnetic field generated by the magnet roller 302d. When the conductive grounding member 50 is magnetized, the carrier contained in the developer 320 existing around the conductive grounding member 50 is adsorbed by the conductive grounding member 50 and the developer 320 around the conductive grounding member 50 does not move. . Since the developer 320 around the conductive grounding member 50 moves and has the effect of stripping off the toner T adhering to the conductive grounding member 50, if the developer 320 around the conductive grounding member 50 stops moving, There is no possibility that the toner T adhering to the conductive grounding member 50 is replaced, and the electric field between the developing sleeve 302c and the conductive grounding member 50 may be lost.

  Further, the arrangement of the conductive ground member 50 is required to be in the developer 320. Even if the conductive grounding member 50 is not in the developer 320, an electric field is initially formed between the developing sleeve 302 c and the conductive grounding member 50. However, if the conductive grounding member 50 is not in the developer 320, there is nothing to remove the toner T adhering to the conductive grounding member 50, so the electric field between the developing sleeve 302c and the conductive grounding member 50 becomes zero. The toner T continues to adhere to the conductive grounding member 50 until the state. In this state, since the effect of separating the toner T adhering to the developing sleeve 302c by the electric field is lost, density unevenness such as “dark image tip” cannot be suppressed.

For example, the developer regulating member 303 is made of a nonmagnetic metal member (nonmagnetic conductive member). However, even if the developer regulating member 303 is grounded, there is a portion that is not in contact with the developer 320 (the left side portion of the developer regulating member 303 in FIG. 1). Resulting in. For this reason, even if the developer regulating member 303 is grounded, it is not sufficient as a configuration for suppressing density unevenness such as “dark image tip”. In the developing device 3 of the present embodiment, the developer regulating member 303 is used in a float state.
In the developing device 3 of the present embodiment, SUS303, which is a nonmagnetic metal material, is used as the conductive ground member 50. However, the present invention is not limited to this as long as it is a nonmagnetic conductive material.

  FIG. 10 is a graph comparing the levels of “dark image tip” with and without the conductive grounding member 50. The vertical axis of the graph in FIG. 10 represents the density difference between the image density of the first round of the developing sleeve and the image density of the second round in the solid image. The smaller this value is, the better the level of “dark image tip” is. The image density is an image density measurement value obtained by a reflection spectral densitometer “X-rite 938”. From the graph of FIG. 10, it can be seen that the level of “dark image tip” is improved by providing the conductive grounding member 50.

It is desirable that the closest distance between the conductive grounding member 50 and the developing sleeve 302 c is longer than the closest distance between the developing sleeve 302 c and the photosensitive member 1. This is due to the following reason.
That is, when the electric field formed between the developing sleeve 302c and the conductive grounding member 50 becomes stronger than the electric field formed between the developing sleeve 302c and the photosensitive member 1, the developing sleeve 302c and the conductive grounding member. This is because there is a case where a leak occurs between the two. When the leak occurs, the potential of the developing sleeve 302c drops, and the development of the latent image on the photoreceptor 1 becomes unstable. Therefore, it is desirable that the closest distance between the conductive grounding member 50 and the developing sleeve 302 c is longer than the closest distance between the developing sleeve 302 c and the photosensitive member 1.

  Further, if the closest distance between the conductive grounding member 50 and the developing sleeve 302c is too short, there is no space for the developer 320 to pass through, causing a problem of agent leakage that causes the developer 320 to go out of the casing 301. End up. For this reason as well, it is desirable that the closest distance between the conductive grounding member 50 and the developing sleeve 302 c is longer than the closest distance between the developing sleeve 302 c and the photosensitive member 1.

  The developing device 3 of the present embodiment has a portion facing the casing counter pole MP2 on which the conductive grounding member 50 is disposed, on the downstream side in the rotation direction of the developing sleeve 302c with respect to the developing region α, and the agent separation region γ. It is upstream in the rotational direction. For this reason, the toner that has moved into the developer 320 from the surface of the developing sleeve 302c at the portion facing the conductive grounding member 50 is separated from the developing sleeve 302c in a state of being contained in the developer 320 in the agent separation region γ. Thereby, the toner adhering to the surface of the developing sleeve 302c can be separated from the developing sleeve 302c. Thereafter, the developer 320 in the developer storage space ε is carried on the surface of the developing sleeve 302c in the pumping region η, so that the developer 320 can be supplied to the surface of the developing sleeve 302c without the sleeve contamination. The resulting density unevenness can be more reliably suppressed.

  In the developing device 3 of the present embodiment, the magnetic pole MP formed by the magnet roller 302d, which is a magnetic field generating unit, has three configurations. The number of magnetic poles formed by the magnetic field generating means is not limited to three, but includes a plurality of magnetic poles such as a pentapole, a developing magnetic pole that forms a magnetic brush at least in the developing region, and includes a pumping portion and an agent separating portion. Any structure that can be formed is acceptable.

[Modification 1]
Next, a first modified example (hereinafter referred to as modified example 1) of the developing device 3 to which the present invention is applied will be described.
FIG. 11 is an explanatory diagram illustrating a schematic configuration of the developing device 3 and the photosensitive member 1 according to the first modification.
The developing device 3 shown in FIG. 11 has a configuration in which a metal plate is attached as a conductive grounding member 50 at a position facing the developing sleeve 302 c on the inner wall surface of the casing 301. As the conductive ground member 50, a metal rod may be arranged as shown in FIG. 1, but the same effect can be obtained even in a configuration in which a metal plate is arranged as shown in FIG.

[Modification 2]
Next, a second modified example (hereinafter referred to as modified example 2) of the developing device 3 to which the present invention is applied will be described.
FIG. 12 is an explanatory diagram illustrating a schematic configuration of the developing device 3 according to the second modification and the photoreceptor 1.
The developing device 3 of Modification 2 is obtained by applying a configuration in which the conductive grounding member 50 that is a characteristic part of the present invention is disposed to the conventional developing device 3 in which the apparatus shown in FIG. 13 is enlarged in the horizontal direction.

  In the developing device 3 according to the second modified example, as in the developing device 3 according to the embodiment and the developing device 3 according to the first modified example, the storage unit for the developer 320 supplied to the developing roller 302 and the developer 320 collected from the developing roller 302 are used. Therefore, density unevenness in the rotation axis direction of the developing roller 302 cannot be suppressed. Further, since the two developer agitating / conveying members are arranged in the horizontal direction, the space in the horizontal direction of the developing device 3 cannot be reduced. However, it is located downstream of the developing region 302 in the surface movement direction of the developing roller 302, upstream of the drawing region η in the surface movement direction, and further upstream of the agent separation region γ in the surface movement direction. By arranging the conductive grounding member 50, density unevenness due to sleeve contamination can be suppressed.

What has been described above is merely an example, and the present invention has a specific effect for each of the following modes.
[Aspect A]
A two-component developer such as developer 320 composed of toner and a magnetic carrier is carried on a surface that moves endlessly, and the toner is applied to the latent image on the surface of the latent image carrier in a development region facing the latent image carrier. A developer carrying member such as a developing roller 302 for supplying and developing; and a developer containing unit such as a supply chamber 304a and a collecting chamber 305a for containing the developer supplied to the developer carrying member. The body includes magnetic field generating means such as a magnet roller 302d having a plurality of magnetic poles inside a surface member such as a developing sleeve 302c that moves endlessly, and is supplied from the developer accommodating portion by a magnetic field generated by the magnetic field generating means. A pumping area such as a pumping area η that pumps the developer onto the surface of the developer carrier, and an agent separation area γ that separates the developer after passing through the developing area such as the developing area α from the surface of the developer carrier. In the developing device such as the developing device 3 in which a developing bias having the same polarity as the charging polarity of the toner is applied to the surface member. Further, a conductive member such as a grounded conductive grounding member 50 is provided at a position in contact with the developer in the vicinity of the surface of the developer carrying member that is located upstream of the pumping portion in the surface moving direction of the developer carrying member. It is arranged. According to this, as described in the above embodiment, Modification 1 and Modification 2, it is possible to suppress the occurrence of density unevenness due to developer carrier surface contamination such as sleeve contamination.
[Aspect B]
In [Aspect A], the conductive member such as the conductive grounding member 50 is a nonmagnetic material such as a nonmagnetic metal substance containing SUS303. According to this, as described in the above embodiment, the conductive member is magnetized and the peripheral developer is prevented from staying, and the replacement of the developer around the conductive member is not hindered. The removal of the toner from the conductive member by the agent is promoted, and it is possible to prevent the electric field between the conductive member and the surface member from being weakened due to the toner continuously adhering to the conductive member.
[Aspect C]
In [Aspect A] or [Aspect B], the conductive member such as the conductive grounding member 50 is disposed downstream of the developing area such as the developing area α in the surface movement direction of the developer carrier such as the developing roller 302 and the like. The developer carrier is disposed at a position in the vicinity of the surface of the developer carrier that is upstream of the developer carrier in the surface movement direction with respect to the agent separation part such as the agent separation region γ. According to this, as described in the above embodiment, the developer scraped off the toner adhering to the conductive member before the agent separating portion is removed from the developer carrier at the agent separating portion together with the scraped toner. break away. On the other hand, when the conductive member is disposed after the agent separating portion, the toner scraped off from the conductive member in a lump state is conveyed to the development area, and is transferred to the latent image carrier to obtain an abnormal image. There is a risk. In [Aspect C], even if the toner scraped off from the conductive member includes a lump state, the toner scraped off from the developer carrying member together with the developer is separated from the developer carrying member. It is possible to suppress the occurrence of an abnormal image.
[Aspect D]
In [Aspect C], a magnetic brush made of the developer is formed on the surface of the surface member such as the developing sleeve 302c by the magnetic field generated by the magnetic field generating means, and the conductive material is in contact with the developer forming the magnetic brush. Conductive members such as the ground member 50 are disposed. According to this, as described in the above embodiment, the developer that forms the magnetic brush always moves while the surface member moves, so that the conductive material is conductive while the developing device is driven. The developer in contact with the adhesive member is always in a moving state. Since the developer around the conductive member moves to remove the toner attached to the conductive member, if the developer around the conductive member stops moving, the toner attached to the conductive member may be replaced. The electric field between the surface member and the conductive member may be lost. On the other hand, in [Aspect D], since the developer that contacts the conductive member is constantly in a moving state, the replacement of the toner adhering to the conductive member can be maintained, and the surface member and the conductive member can be maintained. Therefore, it is possible to stably remove toner on the surface member, and thus it is possible to stably suppress density unevenness due to contamination on the surface of the developer carrying member.
[Aspect E]
In [Aspect C] or [Aspect D], the developer accommodating portion conveys the developer while supplying the developer to the developer carrying member such as the developing roller 302 in the pumping portion such as the agent pumping area η. And a collection conveyance unit such as a collection chamber 305a that conveys the developer while collecting the developer separated from the developer carrying member at the agent separation part such as the agent separation region γ. Get ready. According to this, as described in the above embodiment, the toner scraped from the conductive member such as the conductive grounding member 50 is collected together with the developer into the collection conveyance unit and sufficiently mixed with the other developer. Then, the toner is supplied to the developer carrying member via the supply / conveying unit and is conveyed to the developing region. Therefore, it is possible to prevent the toner adhering to the conductive member from being conveyed to the developing region with insufficient stirring, and to prevent the occurrence of abnormal images due to the use of toner with insufficient stirring for development. I can do it.
[Aspect F]
At least a latent image carrier such as the photosensitive member 1, a charging means such as a charging device 2 for charging the surface of the latent image carrier, an exposure device 16 for forming an electrostatic latent image on the latent image carrier, and the like. In the image forming apparatus such as the printer 100 having the latent image forming means and the developing means for developing the electrostatic latent image into a toner image, any one of [Aspect A] to [Aspect E] is used as the developing means. The developing device of one embodiment is used. According to this, as described in the embodiment, the first modification, and the second modification, it is possible to suppress the occurrence of density unevenness due to the developer carrier surface dirt such as the sleeve dirt, and an image with high image quality. Can be provided.
[Aspect G]
At least a latent image carrier and a developing unit in an image forming apparatus such as a printer 100 including a latent image carrier such as the photosensitive member 1 that carries the latent image and a developing unit that develops the latent image on the latent image carrier. In a process cartridge such as the image forming device 17 that is held on a common holding body as a unit and is detachable from the main body of the image forming apparatus, any one of [Aspect A] to [Aspect E] is used as a developing unit. One embodiment of the developing device is used. According to this, as described in the embodiment, it is possible to improve the exchangeability of the developing device that can suppress the occurrence of density unevenness with respect to the image forming apparatus main body.

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charging device 3 Developing device 5 Transfer bias roller 6 Cleaning device 16 Exposure device 17 Image forming device 24 Fixing device 50 Conductive grounding member 100 Printer 201 Toner density sensor 301 Casing 302 Developing roller 302a Fixed shaft 302c Developing sleeve 302d Magnet Roller 302e Rotating shaft 302f Bearing 302g Development bias power supply 303 Developer regulating member 304 Supply chamber conveying member 304a Supply chamber 305 Recovery chamber conveying member 305a Collection chamber 306 Partition plate 320 Developer MP1 Developing magnetic pole MP2 Casing counter pole MP3 Developer regulating member Counter electrode P Transfer paper α Development area β Transfer area γ Agent release area ε Developer storage space η Agent pumping area

JP 2007-003864 A JP 2010-204639 A

Claims (7)

A two-component developer composed of toner and a magnetic carrier is carried on an endlessly moving surface, and toner is supplied to the latent image on the surface of the latent image carrier for development in a development area facing the latent image carrier. A developer carrier;
A developer accommodating portion for accommodating a developer to be supplied to the developer carrying member,
The developer carrying member includes a magnetic field generating unit having a plurality of magnetic poles inside a surface member that moves endlessly, and the developer supplied from the developer accommodating portion is generated by the magnetic field generated by the magnetic field generating unit. A pump-up portion that pumps up on the surface of the developer-carrying member, and an agent separating part that separates the developer after passing through the development region from the surface of the developer-carrying member,
In the developing device in which a developing bias having the same polarity as the charging polarity of the toner is applied to the surface member,
In the vicinity of the surface of the developer carrier that is located downstream of the development region in the surface movement direction of the developer carrier and upstream of the pumping portion in the surface movement direction of the developer carrier. A developing device, wherein a grounded conductive member is disposed at a position in contact with the developer. The developing device according to claim 1.
The developing device according to claim 1, wherein the conductive member is a non-magnetic material. The developing device according to claim 1 or 2,
The development is such that the conductive member is positioned downstream of the development region in the surface movement direction of the developer carrier and upstream of the developer separation portion in the surface movement direction of the developer carrier. A developing device, wherein the developing device is disposed at a position near the surface of the agent carrier. The developing device according to claim 3.
A magnetic brush made of developer is formed on the surface of the surface member by a magnetic field generated by the magnetic field generating means,
A developing apparatus comprising the conductive member disposed at a position in contact with a developer forming the magnetic brush. The developing device according to claim 3 or 4,
The developer container includes a supply transport unit that transports the developer while supplying the developer to the developer carrier at the pumping unit, and a developer that is separated from the developer carrier at the agent separation unit. A developing device comprising: a collecting and conveying unit that conveys the developer in a state of being spatially partitioned. At least a latent image carrier;
Charging means for charging the surface of the latent image carrier;
Latent image forming means for forming an electrostatic latent image on the latent image carrier;
In an image forming apparatus having developing means for developing the electrostatic latent image into a toner image,
An image forming apparatus using the developing device according to claim 1 as the developing unit. In an image forming apparatus comprising a latent image carrier that carries a latent image and a developing unit that develops the latent image on the latent image carrier, at least the latent image carrier and the developing unit are shared as one unit. In the process cartridge that is held by the holding body and is detachable from the image forming apparatus main body,
6. A process cartridge using the developing device according to claim 1 as the developing means.