JP5858329B2 - Developing device, image forming apparatus, and process cartridge - Google Patents

Description

  The present invention relates to a developing device, an image forming apparatus, and a process cartridge.

  Conventionally, supply / recovery provided with a supply conveyance path for supplying the developer to the developer carrier and a collection conveyance path for collecting the developed developer on the surface of the developer carrier that has consumed toner in the development region A separation-type developing device is known (for example, Patent Document 1). In the developing device described in Patent Document 1, a recovery conveyance path is arranged in parallel below a supply conveyance path extending in the direction of the rotation axis of the developer carrier along the developer carrier. The downstream side of the supply conveyance path and the upstream side of the collection conveyance path communicate with each other through an opening, and the upstream side of the supply conveyance path and the downstream side of the collection conveyance path communicate with each other through an opening, and a developer Circulates. The developed developer that has passed through the development area and has a reduced toner concentration is collected in the collection conveyance path. The developed developer recovered to the recovery transport path is transported toward the opening downstream of the recovery transport path while being stirred by the recovery transport member in the recovery transport path, and is transported to the developer supply transport path.

  The developed developer collected in the collection conveyance path may fly by the stirring force of the collection conveyance member until it is conveyed to the opening by the collection conveyance member, and may reattach to the developer carrier. As described above, when the developed developer in the recovery conveyance path is reattached, the developed developer having the reduced toner density is transported to the development area, and an image of a portion developed by the developed developer is obtained. The image density is lowered, and image density unevenness occurs.

  In the developing device described in Patent Document 1, the partition member that partitions the collection transport path and the supply transport path is opposed to the developer carrying member with a gap of 0.2 mm to 1 mm, and is separated by the partition member. By scraping off the developed developer that has reattached to the developer carrying member, the developer that has reattached to the developer carrying member is prevented from being conveyed to the development region.

  However, in the configuration in which the partition member is opposed to the developer carrying member with a gap of 0.2 mm to 1 mm, the re-deposited developed developer cannot be sufficiently scraped off. Further, if the partition member is brought into contact with the developer carrying member, the reattached developer can be scraped off favorably, and the reattached developer can be prevented from being conveyed to the development region. However, in this case, since the surface of the developer carrying member is rubbed against the partition member, there arises a problem that the surface of the developer carrying member is damaged.

  The present invention has been made in view of the above problems, and the purpose of the present invention is to convey the developed developer reattached to the developer carrying member to the developing region without damaging the surface of the developer carrying member. To provide a developing device, an image forming apparatus, and a process cartridge that can be suppressed.

In order to achieve the above object, a first aspect of the present invention includes a magnetic field generating means having a plurality of magnetic poles, and a developer containing toner and a magnetic carrier is carried on the surface and rotated, and a latent image carrier. A developer carrying member for developing the latent image on the surface of the latent image carrying member in a developing region facing the developer, and a developer carrying member arranged opposite to the developer carrying member, and in an axial direction of the developer carrying member And a developer conveyance unit that supplies the developer to the developer carrying member while conveying the developer by a supply conveyance member, and the developer is supplied from the development conveyance region from the development region of the developer carrier. The developer is disposed opposite to the region up to the supply region, and the developer after passing through the development region is collected from the developer carrier, and is collected from the developer carrier along the axial direction of the developer carrier. Recovery transport path for transporting developer by the recovery transport member A first communication portion that communicates the downstream end of the supply transport path with respect to the developer transport direction and the upstream end of the recovery transport path with respect to the developer transport direction; the upstream end of the supply transport path with respect to the developer transport direction; A developing device that circulates and conveys the developer between the supply conveyance path and the recovery conveyance path; and a second communication portion that communicates with the downstream end of the conveyance path in the developer conveyance direction. A reattachment suppression magnet that magnetically attracts the developer so as to remain in the recovery transport path and suppresses the developer in the recovery transport path from reattaching to the developer carrying member is provided in the recovery transport path. And a partition member that partitions the supply conveyance path .

According to the present invention, the developer that wants to fly toward the developer carrying member by the stirring force of the collecting and conveying member can remain in the developer collecting and conveying path by the magnetic attraction force of the reattachment suppression magnet. Therefore, it is possible to suppress the developer in the developer recovery path from adhering to the developer material carrier by flying toward the developer carrier by the stirring force of the recovery conveyance member. As a result, it is possible to suppress the developed developer recovered to the developer recovery path from flying due to the stirring force of the recovery conveyance member and reattaching to the developer carrying member. As a result, the reattached developer can be suppressed from being conveyed to the development area.
In addition, the developer carrying member is brought into contact with the developer carrying member so that the partition member that separates the recovery carrying path and the supply carrying path is brought into contact with the developer carrying member so that the developer reattached to the developer carrying member is not conveyed to the developing region. In comparison, the developer carrier surface can be prevented from being damaged.

1 is a schematic configuration diagram of a printer according to an embodiment. 1 is a schematic configuration diagram of an image forming device. Explanatory drawing of the image development apparatus and photoreceptor to which normal flux density distribution was added. Sectional explanatory drawing of the cross section parallel to the rotating shaft direction of a developing roller. FIG. 4 is an explanatory diagram of a developing device and a photosensitive member in which a normal magnetic flux density distribution of a developing roller including five magnets MG inside a developing sleeve 302c and including a magnet roller that generates five magnetic poles MP (magnetic force distribution) is added. 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. Explanatory drawing of the communicating port part of a developing device. The perspective view which shows the modification of a circulation path. The disassembled perspective view of the circulation path of the modification. Sectional drawing of the back | inner side of the developing device provided with the circulation path of the modification. The figure explaining the malfunction of the conventional image development apparatus. The schematic block diagram of the image development apparatus provided with the reattachment suppression magnet. FIG. 3 is an external perspective view of a main part of a developing device in which a reattachment suppression magnet is provided only on the downstream side in the developer conveyance direction in a developing roller facing region of a collection chamber. The figure which shows the relationship between the amount of developer pumping, and the amount of magnetic flux density fluctuation | variation of a developer control member opposing magnetic pole. The figure which shows the polarity of the magnetic pole made to oppose the collection | recovery chamber of a reattachment suppression magnet, and the polarity of each magnetic pole of a magnet roller. The schematic block diagram of the developing apparatus of the modification which provided the reattachment suppression magnet between the collection | recovery chamber and the supply chamber. The figure which shows the polarity of the magnetic pole made to oppose the collection | recovery chamber of the reattachment suppression magnet of the developing device of the modification, and the polarity of each magnetic pole of a magnet roller. FIG. 9 is an external perspective view of the main part of the developing device in which a reattachment suppression magnet is provided only on the downstream side in the developer transport direction in the developing roller facing region of the recovery chamber of the developing device according to the modification. 1 is a schematic configuration diagram of a conventional developing device.

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. 1 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). An image forming device 17 (K, M, Y, C) is provided. Below these image forming devices 17 (K, M, Y, 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. A transfer conveyance belt 15 that moves while facing the image forming devices 17 (K, M, Y, C) is disposed. A transfer bias roller 5 (K, M, Y, C) facing each image forming device 17 (K, M, Y, C) is provided with the transfer conveyance belt 15 interposed therebetween.
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. 1, the transfer conveyance belt 15 is disposed in an oblique direction so that the printer 100 is small in the left-right direction in FIG. 1, 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 housing in the left-right direction in FIG. 1 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. A charging device 2 (K, M, Y, C) as a charging unit and a developing device 3 (K, M, Y) as a developing unit in order with respect to the rotation direction of the photoreceptor 1 (K, M, Y, C). , C), a cleaning device 6 (K, M, Y, C), and the like. The image forming device 17 (K, M, Y, C) is configured to be detachable from the apparatus body as a process cartridge integrally including the photosensitive member 1, the charging device 2, the developing device 3, the cleaning device 6, and the like. Has been. Further, an exposure device 16 (K, M, or C) that uses the writing light L as a latent image forming means between the charging device 2 (K, M, Y, or C) and the developing device 3 (K, M, Y, or C). 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 the plurality of paper feed cassettes 20 is matched with the image forming timing by the image forming device 17 (K, M, Y, C) by the registration roller pair 23. Supplied on the surface of the transfer / conveying belt 15. Then, the transfer paper P carried on the transfer conveyance belt 15 is conveyed to the transfer area 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.
In the printer 100 shown in FIG. 2, four image forming apparatuses are arranged in the order of K (black), M (magenta), Y (yellow), and C (cyan) from the upstream side in the conveyance direction along the conveyance direction of the transfer conveyance belt 15. 17 (K, M, Y, C) are arranged, but the order of arranging the image forming devices 17 (K, M, Y, C) of the respective colors 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. 2 is a schematic configuration diagram of the image forming device 17 including the developing device 3 as developing means 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. 2 as indicated by an arrow a in FIG.
A charging device 2 serving as charging means 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 the writing light L from the exposure device 16 (see FIG. 1) which is a latent image forming unit. Is formed. The electrostatic latent image moves downstream as the photosensitive member 1 rotates and reaches the developing device 3. The developing device 3 is disposed on the right side of the photoreceptor 1.
The developing device 3 includes a casing 301 and a rotating member such as a supply chamber conveying member 304 and a recovery chamber conveying member 305 for agitating and conveying the developer 320, a developing roller 302 as a developer carrying member, and other members.
The developing roller 302 is disposed in the vicinity of 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. To be transported to. The toner in the developer 320 adheres to the electrostatic latent image formed on the surface of the photoreceptor 1 in the development area α, 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.
The cleaning device 6 is disposed at the 10 o'clock position with respect to the photoreceptor 1 in FIG. 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. 2, 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. 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. 3 is an explanatory diagram of the developing device 3 and the photosensitive member 1 in which the normal magnetic flux density distribution of the magnetic field formed around the developing roller 302 is added.
As shown in FIG. 3, 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, and a magnet roller 302d that is formed integrally with the fixed shaft 302a and serves as a columnar magnetic field generating unit. And a developing sleeve 302c covering the periphery of the magnet roller 302d through a gap, a rotating shaft 302e integrally formed with the developing sleeve 302c, and the like. The rotation shaft 302e is rotatable with respect to the fixed shaft 302a via a bearing 302f, and the rotation shaft 302e is driven to rotate by receiving power from a rotation driving means (not shown). The developing roller 302 preferably has a diameter of 14 mm or less in order to reduce the size of the developing device 3.
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.
Various configurations can be applied as the magnet roller 302d. However, in the developing device 3 of the present embodiment, as shown in FIG. 3, the developing sleeve 302c includes three magnets MG, and three magnetic poles MP ( A magnetic roller 302d for generating a magnetic force distribution).
As shown in FIG. 3, a position facing the photoreceptor 1 on an imaginary 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 on the main magnetic pole MP1 in the developing region α. Further, a second magnet MG2 that forms the casing opposing magnetic pole MP2 and a third magnet MG3 that forms the developer regulating member opposing magnetic pole MP3 are arranged in the counterclockwise direction in FIG. 3 with respect to the main magnetic pole MP1.

In the developing device 3 of this embodiment, the main magnetic pole MP1 is an N pole, and the casing opposing magnetic pole MP2 and the developer regulating member opposing magnetic pole MP3 are S poles. The polarity of each magnetic pole is opposite to that of each magnetic pole. May be. The main magnetic pole MP1 faces the photoreceptor 1, the casing opposing magnetic pole MP2 faces the casing, and the developer regulating member opposing magnetic pole MP3 faces the developer regulating member 303.
In the development region 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 maintaining 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.

  Further, as shown in FIG. 5, the developing sleeve 302c may include five magnets MG and a magnet roller 302d that generates five magnetic poles MP (magnetic force distribution). In the magnet roller 302d shown in FIG. 5, a fourth magnet MG4 is disposed between the main magnetic pole MP1 and the casing counter magnetic pole MP2, and a developed developer transporting magnetic pole MP4 is formed. In addition, a fifth magnet is disposed between the main magnetic pole MP1 and the developer regulating member opposing magnetic pole MP3 to form a pre-development developer transport magnetic pole MP5. In FIG. 5, the main magnetic pole MP1 is the N pole, the developed developer transport magnetic pole MP4 is the S pole, the casing facing magnetic pole MP2 and the developer regulating member facing magnetic pole MP3 are the N pole, and the developer transporting magnetic pole MP5 before development is the S pole. However, these poles may have opposite polarities. As shown in FIG. 5, on the developing roller 302, each pole is centered, the main magnetic pole MP1 is 8 o'clock on the dial, the developed developer transport magnetic pole MP4 is 7 o'clock, and the casing counter magnetic pole MP2 is 5 o'clock. At this time, the developer regulating member opposing magnetic pole MP3 is substantially located at the same position as that at 1 o'clock, and the pre-development developer transporting magnetic pole MP5 is located at 10 o'clock.

  A grounding bias power source (not shown) is connected to the fixed shaft 302 a constituting the developing roller 302 of the developing device 3. A voltage from a power source connected to the fixed shaft 302a is applied to the developing sleeve 302c through 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, an 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 potential difference between the developing sleeve 302c and the electrostatic latent image formed on the surface of the photosensitive member 1 is formed. Thus, the toner can be moved toward the photoreceptor 1 side.

  The developing device 3 according to 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 as shown in FIGS. 1 and 2. In order to uniformly apply negative charges on the surface of the photosensitive member 1 by the charging device 2 and to lower the negative potential, the image portion is exposed with the writing light L, and the image portion (electrostatic potential) in which the potential is lowered (static 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 the developing region α is carried on the developing sleeve 302c by the magnetic force of the casing opposing magnetic 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 opposing magnetic pole MP2 and the developer regulating member opposing magnetic pole MP3 have the same polarity. As shown in FIGS. 3 and 4, the surface movement direction of the developing sleeve 302c is downstream of the position facing the casing opposing magnetic pole MP2. In the region on the surface of the developing sleeve 302c that is upstream of the position facing the developer regulating member counter magnetic 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 are laid down, and the “agent releasing” that separates the developer 320 that has been drawn on the surface of the developing sleeve 302c until then from the developing roller 302 is performed. Works. The region on the surface of the developing sleeve 302c where the ear is lying is downstream from the position facing the casing opposing magnetic pole MP2 and upstream from the position facing the developer regulating member opposing magnetic pole MP3. 3 and 4, the peak of the peak of the normal magnetic flux density distribution is an extremely low region compared to other regions, and this region separates the developer 320 from the developing sleeve 302c, the agent separating region γ ( (Shown in FIG. 2).

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 carried on the surface of the developing sleeve 302c that has passed through the developing area α is separated from the developing roller 302 in the agent releasing area γ. The developer separated from the developing roller 302 is collected in the collecting 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 opposed magnetic pole MP3, and is located at the peak position of the developer regulating member opposed magnetic pole MP3. By passing through a portion facing 303, it 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 opposing magnetic pole MP3 functions as a transport pole for transporting the developer 320.

FIG. 6 is an internal perspective view of a main part of the developing device 3, and FIG. 7 is an external perspective view of the main part of the developing device 3. FIG. 8 is an explanatory view of a portion where the communication holes are provided in the plate-like partition members 306 at both ends in the longitudinal direction of the developing device 3 as viewed from above.
Arrows D1 to D4 in FIG. 6 indicate the flow of the developer 320 in the casing 301.

  As shown in FIGS. 2 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. 2 and 3. 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. 6, the supply chamber conveying member 304 has a screw shape with a spiral wing around the rotation axis, and the 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. 2 and 3 around the line O-304. By this rotation, as shown by an arrow D4 in the figure, the developer 320 is conveyed along the supply screw center line O-304 while stirring the developer 320 from the front side FS in the longitudinal direction of the developing device 3 toward the back side BS. . 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. 2 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. 2 and 3. Are arranged. As shown in FIG. 6, the recovery chamber transport member 305 has a screw shape with a spiral wing around the rotation axis, and a recovery screw center line O-305 parallel to the developing roller center line O-302a. 2 and 3 in the clockwise direction indicated by the arrow g in FIGS. By this rotation, as shown by an arrow D2 in the figure, the developer 320 is conveyed along the recovery screw center line O-305 while stirring the developer 320 from the longitudinal side BS in the longitudinal direction of the developing device 3 toward the near side FS. . 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 member 306.
As shown in FIGS. 6 and 7, the front end of the supply chamber transport member 304 and the collection chamber transport member 305 is set to be located slightly in front of the front end of the developing roller 302, and development is performed. 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. 2 and 3, a partition member 306 that spatially partitions the supply chamber 304 a and the recovery chamber 305 a is supported inside the casing 301 between the supply chamber transfer member 304 and the recovery chamber transfer member 305. Has been. Communication ports (41 and 42) are provided at both ends in the longitudinal direction of the partition member 306, respectively.
The developer 320 transported from the back side BS in the longitudinal direction to the near side FS (in the direction of arrow D2 in the figure) by the recovery chamber transport member 305 is cut off on the side wall of the casing 301 at the end in the transport direction, so It rises along. The developer 320 that has reached the downstream end in the transport direction in the collection chamber 305a due to this swell is formed at the front end in the longitudinal direction of the communication ports provided at both ends in the longitudinal direction of the partition member 306 described above. It passes through the lifting port provided (arrow D3 in the figure) and is delivered to the supply chamber 304a. The developer 320 transferred 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 the figure) by the supply chamber transport member 304.
As in the case of the recovery chamber 305a, the developer 320 transported from the front side FS in the longitudinal direction to the back side BS (in the direction of arrow D4 in the figure) by the supply chamber transport member 304 is the end of the casing 301 at the transport direction end. The path is cut off by the side wall. The developer 320 that has reached the downstream end in the conveyance direction in the supply chamber 304a falls at the end in the longitudinal direction of the communication ports provided at both ends in the longitudinal direction of the partition member 306 described above. It falls from the mouth and is delivered to the collection chamber 305a.

  As described above, the developing device 3 includes the developing roller 302, the supply chamber transport member 304, the collection chamber transport member 305, the partition member 306, and the like. The developing roller 302 carries the developer 320 and rotates 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 conveyance 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 to be supplied. The chamber conveying member 304 conveys the developer 320 in a direction opposite to the direction in which the developer 320 is conveyed while stirring. The partition member 306 is between the supply chamber transport member 304 and the recovery chamber transport 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 the drawing.

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 shown in FIG. 20, the conventional developing device 3 has a configuration in which two developer agitating / 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). There is something. As described above, the developing device 3 of the present embodiment can reduce the size of the device in the horizontal direction (horizontal direction) as compared to the configuration in which the two developer stirring 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 member 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.

  9 to 11 are diagrams showing modified examples of the circulation path. In this modification, as shown in FIG. 10, the developer in the supply chamber 304a is transported from the back side BS to the front side FS (arrow D4 ′), and the developer in the recovery chamber 305a is transferred from the front side FS. It is configured to be transported to the back side BS (arrow D2 ′). FIG. 11 is a cross-sectional view of the back side BS of the developing device.

  As shown in FIGS. 9 to 11, in this modification, a portion facing the lifting port 307 of the collection chamber transport member 305 is not a spiral screw shape, but a plurality of plate-like wings extending in the axial direction are provided. The impeller 308 is used. With the rotation of the collection chamber transport member 305, the developer 320 jumps upward by the impeller 308, so that the developer 320 passes through the lifting port 307 (arrow D3 in the figure) and is received by the supply chamber 304a. Passed.

  As shown in FIG. 11, the center O-304 of the supply chamber transfer member 304 and the center O-305 of the recovery chamber transfer member 305 are on substantially the same vertical line, and the impeller 308 rotates in the counterclockwise direction, The developer 320 is flipped up along the inner wall of the casing 301. The lifting port 307 does not obstruct the path of the developer due to the jumping up, and the center O-304 and the center O-305 are prevented so that the developer jumped up does not fall into the collection chamber transport member 305. It is formed so as to extend from a position slightly closer to the casing inner wall to a casing inner wall portion (upstream side in the 304 rotation direction) than a substantially vertical line connecting the two. That is, as shown in FIG. 10, the lifting port 307 is formed in a state where a hole is formed in a part of the partition member 306, and the developing roller side portion corresponding to the lifting port 307 has a center in the developing roller axial direction. Like the part, the partition member is configured to exist. By the remaining partition member portion 306 ′, the developer that has moved from the bottom to the top through the lifting port 307 is transported by the supply chamber transport member 304 without being dropped again, or is attracted to the developing roller 302. Since the toner is conveyed to the developing area, efficient developer circulation can be performed.

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 supply port 309 (see FIG. 7) in the vicinity of the end of the back side BS in the longitudinal direction, and supplies toner from the outside through the toner supply port 309. Further, in the modification examples of the circulation path shown in FIGS. 9 to 11, the toner supply port 309 is provided in the vicinity of the end portion of the front side FS in the longitudinal direction. That is, the toner replenishing port 309 is provided in the vicinity of the downstream end in the transport direction in the supply chamber 304 a that supplies the developer to the developing roller 302. As a result, the toner replenished from the toner replenishing port 309 is not immediately supplied for development, but is supplied to the recovery chamber 305a through the dropping port. The toner supplied to the recovery chamber 305a is mixed and agitated with the developer 320 by the recovery chamber transport member 305 and received from the lifting port to the supply chamber 304a in a state of being contained in the developer 320 having a predetermined toner concentration. Passed to be developed. The collection chamber 305 a in which the collection chamber conveyance member 305 is disposed collects and conveys the developer 320 separated from the surface of the developing roller 302, and does not supply the developer 320 to the developing roller 302. For this reason, it is possible to prevent the developer 320 having a non-uniform toner density, which has not been sufficiently agitated by newly supplying toner from the toner supply port 309, from being used for development.
The toner replenished from the toner replenishing port 309 passes through the dropping port and is supplied to the recovery chamber 305a. The toner is separated from the developing roller 302 and is recovered together with the developer 320 recovered in the recovery chamber 305a as the toner density decreases. It is conveyed while being stirred and mixed by the chamber conveying member 305. The newly replenished toner and the developer 320 whose toner concentration has been reduced are normalized in toner concentration before being transported to the downstream end in the transport direction in the recovery chamber 305a, and the supply chamber 304a is supplied from the lifting port. It is handed over to. In the supply chamber 304a, the developer 320 is supplied to the developing roller 302 and used for development while being transported to the supply chamber transport member 304.

  In the developing device 3, a toner concentration sensor (not shown) is disposed below the lifting port in the collection chamber 305a. The toner concentration sensor 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, 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 is appropriate from the carrier density, and determines the amount of toner to be replenished. To do.

Next, features of the developing device 3 of the present embodiment will be described.
When the amount of developer in the collection chamber 305a is large or when the number of rotations of the collection chamber transport member 305 is too fast, as shown by an arrow K in FIG. The amount of developer flying toward 302 increases. When this developer reaches the surface of the developing sleeve 302c, the developer adheres to the surface of the developing sleeve 302c due to the magnetic force of the magnet roller 302d or the surface friction, and is conveyed to the developing region by the developing sleeve 302c. Such flying toner includes developed developer in which toner is consumed in the development area and the toner density is not recovered. When the developed developer having such a lowered toner density adheres to the surface of the developing sleeve and is transported to the developing area, the developing ability of that portion is lowered, resulting in uneven image density.

  Therefore, as shown in FIG. 13, in this embodiment, a reattachment suppression magnet 340 is provided at a location facing the developing roller 302 of the collection chamber 305 a and a location on the opposite side across the collection chamber transport member 305. Specifically, a reattachment suppression magnet 340 is provided outside the casing 301 in which the recovery chamber 305a is formed. By providing the reattachment suppression magnet 340, the developer 320 in the recovery chamber 305 a can be retained in the recovery chamber 305 a by the magnetic attraction force of the reattachment suppression magnet 340, and development is performed from the recovery chamber 305 a toward the developing roller 302. The agent can be prevented from flying. In particular, a developed developer having a lowered toner concentration has a higher magnetic carrier density, and has a larger magnetic attraction force received from the reattachment suppression magnet 340 than a developer having a prescribed toner concentration. Therefore, the flying of the developed developer having a reduced toner concentration can be reliably suppressed. Further, the developer can be retained in the recovery chamber 305a by the magnetic attraction force by the reattachment suppression magnet 340, and the function of dispersing the developer and charging the toner in the recovery chamber can be enhanced.

  The height direction in which the reattachment suppression magnet 340 is provided is preferably disposed above the axis of the recovery chamber transport member 305. By arranging the reattachment suppression magnet 340 above the axis of the recovery chamber transport member 305, the developer in the recovery chamber 305a is developed by the magnetic attraction force of the reattachment suppression magnet 340 as shown in FIG. The bulkiness on the side away from the roller 302 is higher than the bulkiness on the development roller side. As a result, as shown in FIG. 13, the distance between the developer in the collection chamber and the developing roller 302 can be increased, and the developer 320 in the collection chamber can be further suppressed from adhering to the surface of the developing sleeve. . Even if the developer 320 in the collection chamber 305 a is somewhat larger, the developer 320 in the collection chamber 305 a does not contact the developing roller 302. Therefore, the developer can be transported by reducing the rotation speed of the recovery chamber transport member 305, and the load on the bearing that supports the recovery chamber transport member 305 and the seal member that seals the developer from entering the bearing is reduced. The lifetime of the device can be improved. Moreover, the temperature rise of the developing device 3 can be suppressed, and damage to the developer can also be suppressed.

  The longitudinal direction of the reattachment suppression magnet 340 is the same as the length of the developing roller 302 and covers the entire area of the collection chamber 305a facing the developing roller 302. Of course, it may be longer than the developing roller 302 so as to cover the entire recovery chamber 305a, but the cost increases.

  Further, the developer 320 in the collection chamber 305a is most likely to fly on the downstream side in the developer conveyance direction of the collection chamber 305a. This is because the supply chamber 304a is located above the recovery chamber 305a, and therefore it is necessary to lift and transfer the developer 320 against the dead weight of the developer 320 at the downstream end of the recovery chamber 305a. For this reason, the developer conveyance speed drops significantly at the downstream end of the recovery chamber 305a, and the developer 320 stays at the downstream end of the recovery chamber 305a. As a result, in the vicinity of the downstream end of the recovery chamber 305a, the bulk of the developer 320 is higher than that on the upstream side, and the distance between the developer 320 in the recovery chamber 305a and the developing roller 302 is reduced. As a result, when the developer 320 flies, it tends to adhere to the developing roller 302. On the other hand, the upstream side of the collection chamber 305a in the developer conveyance direction is difficult to adhere to the developing roller 302 even if it flies because the bulk of the developer 320 is low and the distance from the developing roller 302 is long. Further, since the amount of developer is small, the amount of flying toner is small. Therefore, as shown in FIG. 14, the reattachment suppression magnet 340 may be provided only at the downstream side in the developer transport direction of the region G facing the developing roller 302 of the collection chamber 305 a. Thereby, cost can be suppressed and adhesion to the developing roller 302 can be suppressed.

  The reattachment suppression magnet 340 is preferably a permanent magnet. By using a permanent magnet, the developer 320 in the collection chamber 305a can be magnetically attracted with a simple configuration, and the flying of the developer 320 can be suppressed, thereby reducing the cost.

Further, the re-adhesion suppression magnet 340 affects the developer regulating member opposing magnetic pole MP3, and the magnetic flux density fluctuates. When the magnetic flux density fluctuates, the amount of rising of the developer when passing through the developer regulating member 303 fluctuates, and the amount of image agent drawn up fluctuates. Here, the amount of developer drawn up is the amount of developer per unit area that has passed through the developer regulating member 303.
FIG. 15 is a diagram showing the relationship between the pumping amount and the fluctuation amount of the developer regulating member opposing magnetic pole MP3 by the reattachment suppressing magnet 340. As shown in the figure, it can be seen that if the fluctuation amount of the developer regulating member opposing magnetic pole MP3 by the reattachment suppressing magnet 340 is 0.5 mT or less, the pumping amount is hardly affected.

  Therefore, the reattachment suppression magnet 340 is disposed at a position where the fluctuation amount of the normal magnetic flux density of the developer regulating member opposing magnetic pole MP3 is within 0.5 mT. In addition, as shown in FIG. 16, the magnetic poles of the reattachment suppression magnet 340 have two magnetic poles (casing facing magnetic pole MP2 and adjacent magnetic poles) that are adjacent to each other and generate a magnetic field for separating from the surface of the developing sleeve 302c. The polarity is opposite to that of the developer regulating member opposing magnetic pole MP3). This makes it possible to form a magnetic field (a magnetic field that attracts the developer into the collection chamber) between the re-adhesion suppression magnet 340 and the casing opposing magnetic pole MP2 so that the developer is easily peeled off from the developing roller. In addition, since a repulsive magnetic field is not formed between the reattachment suppression magnet 340 and the developer regulating member opposing magnetic pole MP3, fluctuations in the normal magnetic flux density of the developer regulating member opposing magnetic pole MP3 can be suppressed.

  Further, it has been found by experiments by the present inventors that when the magnetic flux density of the reattachment suppression magnet 340 is made higher than the magnetic flux density of the main magnetic pole MP1, the pumping amount to the developing sleeve surface increases. Specifically, when an experiment is performed with a magnetic flux density of 150 mT of the reattachment suppression magnet 340 with respect to a magnetic flux density of 100 mT of the main magnetic pole MP1, when passing through the developer regulating member 303, the spikes of the developer lie down and pump up. The amount has increased. Further, since the magnetic flux density of the reattachment suppression magnet 340 is strong, the magnetic attraction force received by the developer in the recovery chamber 305a from the reattachment suppression magnet 340 increases, and the torque of the recovery chamber transport member 305 increases, resulting in an increase in temperature. I also noticed an inconvenience of rising and driving load. On the other hand, when the magnetic flux density of the reattachment suppression magnet 340 is set to 100 mT or less, which is smaller than the magnetic flux density of the main magnetic pole MP1, an increase in the pumping amount is prevented. Therefore, by setting the magnetic flux density of the re-adhesion suppression magnet 340 to be equal to or less than the magnetic flux density of the main magnetic pole MP1, it is possible to prevent an increase in the amount of developer conveyed to the development area and to suppress the increase in image density. can do. Moreover, by setting it as 100 mT or less, it is not necessary to use the rare earth (neodymium) with strong magnetic force as the reattachment suppression magnet 340, and the apparatus can be made inexpensive.

  As shown in FIG. 13, in the case where the re-adhesion suppression magnet 340 is provided at a location opposite to the developing roller 302 of the recovery chamber 305 a and a location opposite to the recovery chamber transport member 305, the casing 301 is provided. The re-adhesion suppression magnet 340 is provided on the outer side, and the length of the developing device 3 in the horizontal direction (lateral direction in the drawing) becomes long. As a result, as shown in FIG. 1, in a tandem type color image forming apparatus in which a plurality of developing devices 3 are arranged in the horizontal direction, the horizontal length of the apparatus becomes long.

  Therefore, as shown in FIG. 17, a reattachment suppression magnet 340 may be disposed between the recovery chamber 305a and the supply chamber 304a. Further, since the reattachment suppression magnet 340 is disposed between the recovery chamber 305a and the supply chamber 304a, the partition member 306 that partitions the recovery chamber 305a and the supply chamber 304a is not a plate but a box shape having a hollow portion. And the reattachment suppression magnet 340 is disposed therein. With this configuration, the reattachment suppression magnet 340 can be disposed inside the casing 301, and an increase in the size of the developing device 3 can be suppressed. Even if the reattachment suppression magnet 340 is disposed between the recovery chamber 305a and the supply chamber 304a, the magnetic attraction force of the reattachment suppression magnet 340 causes the developer 320 in the recovery chamber 305a to fly toward the developing roller. Can be suppressed.

  Further, in this case, a part of the developer 320 in the recovery chamber 305a adheres to the upper surface (partition member 306) of the recovery chamber 305a by the magnetic attraction force of the reattachment suppression magnet 340, so that the developer in the recovery chamber 305a. The bulkiness of 320 can be kept low, the distance between the developing roller 302 and the developer in the collection chamber can be increased, and it can be further suppressed that the developer 320 in the collection chamber is prevented from reattaching. Further, since the bulk of the developer 320 in the collection chamber can be kept low, the developer 320 in the collection chamber 305a does not contact the developing roller 302 even if the developer 320 in the collection chamber 305a is somewhat large. . Therefore, the developer 320 can be transported at a reduced rotational speed of the recovery chamber transport member 305, and the load on the bearing that bears the recovery chamber transport member 305 and the seal member that seals the developer from entering the bearing. Can be reduced, and the lifetime of the apparatus can be improved. Moreover, the temperature rise of the developing device 3 can be suppressed, and damage to the developer 320 can also be suppressed. In order to attract more developer 320, it is desirable to provide a reattachment suppression magnet above the axis of the collection chamber transport member 305.

  Further, even when the reattachment suppression magnet 340 is disposed between the recovery chamber 305a and the supply chamber 304a, as shown in FIG. 18, the polarity of the magnetic pole of the reattachment suppression magnet 340 facing the recovery chamber 305a is set to the above development. It is preferable that the polarity is opposite to two magnetic poles (casing facing magnetic pole MP2 and developer regulating member facing magnetic pole MP3) that are adjacent to each other and have the same polarity that generate a magnetic field to be separated from the surface of the agent carrier. Thus, a magnetic field (a magnetic field that attracts the developer to the recovery chamber 305a) is formed between the re-adhesion suppressing magnet 340 and the developer regulating member opposing magnetic pole MP3 so that the developer is easily separated from the developing roller. Can do.

  Also in this case, as shown in FIG. 19, the reattachment suppression magnet 340 is attached only to the downstream side in the developer transport direction of the region G facing the developing roller 302 of the collection chamber 305a. It may be provided. Thereby, cost can be suppressed and adhesion to the developing roller 302 can be suppressed.

What has been described above is merely an example, and the present invention has specific effects for each of the following aspects (1) to (12).
(1)
A developing region that includes magnetic field generating means such as a magnet roller 302d having a plurality of magnetic poles, and that supports and rotates a developer containing toner and a magnetic carrier on the surface, and faces a latent image carrier such as the photosensitive member 1 And a developer carrying member such as a developing roller 302 that supplies toner to the latent image on the surface of the latent image carrying member and develops the developer carrying member so as to face the developer carrying member, and the axial direction of the developer carrying member A supply conveyance path such as a supply chamber 304a for supplying the developer to the developer carrier while conveying the developer by a supply conveyance member such as the supply chamber conveyance member 304, and the development region of the developer carrier. To the region from the supply conveyance path to the supply region to which the developer is supplied, and collects the developer after passing through the development region from the developer carrier, and in the axial direction of the developer carrier Along with the current A recovery transport path such as a recovery chamber 305a for transporting the developer recovered from the developer carrier by a recovery transport member such as a recovery chamber transport member 305, a downstream end in the developer transport direction of the supply transport path, and the recovery transport path A first communication portion such as a drop port that communicates with the upstream end of the developer conveying direction, a lifting end that communicates the upstream end of the supply conveying path with respect to the developer conveying direction, and the downstream end of the recovery conveying path with respect to the developer conveying direction. A developing device that circulates and conveys the developer between the supply conveyance path and the recovery conveyance path, and the developer in the recovery conveyance path is placed in the recovery conveyance path. A reattachment suppression magnet 340 is provided that suppresses reattachment of the developer in the recovery conveyance path to the developer carrying member by magnetic attraction so as to stay.
By providing such a configuration, as described above, it is possible to prevent the developed developer collected in the collection conveyance path from reattaching to the developer carrying member, and the developed developer that has been reattached to the development region. It is possible to suppress the developer from being conveyed. As a result, the density unevenness of the developed image can be suppressed.

(2)
Further, in the developing device according to the aspect described in (1) above, the re-adhesion suppression magnet is provided at a location opposite to the developer carrying member of the recovery transport path and a location on the opposite side of the recovery transport member. As a result, the magnetic attraction force of the reattachment suppression magnet can be applied to the developer that is about to fly toward the developer carrying member from the collection conveyance path, and can be reattached to the developer carrying member. Can be suppressed.
Further, the developer in the recovery transport path is collected by the magnetic attraction force of the reattachment suppression magnet at a position opposite to the developer carrying member of the recovery transport path and a position on the opposite side across the recovery transport member. Therefore, the bulkiness of the developer on the developer carrying member side in the recovery conveyance can be made lower than the portion on the opposite side across the recovery conveyance member. As a result, the distance between the developer in the recovery conveyance and the developer carrying member can be increased, and the developer in the collection conveyance path can be further suppressed from adhering to the developer carrying member.

(3)
Further, in the developing device according to the aspect described in (1) above, a reattachment suppression magnet is provided between the recovery conveyance path and the supply conveyance path.
Even in such a configuration, the magnetic attraction force of the re-adhesion suppression magnet can be applied to the developer that is about to fly from the recovery conveyance path toward the developer carrier, and can be re-attached to the developer carrier. Can be suppressed.
Further, when the collection conveyance path is vertically below the supply conveyance path, a part of the developer in the collection conveyance path is removed from the upper surface of the collection conveyance path by the magnetic attraction force of the reattachment suppression magnet. Can be attached to. As a result, the bulk of the developer in the recovery conveyance path is reduced, and the distance between the developer in the recovery conveyance path and the development carrier can be increased, and the developer in the recovery conveyance path can be separated from the developer carrier. Can be further suppressed.
Further, since the reattachment suppression magnet can be provided in the casing of the developing device, the developing device can be made compact.

(4)
In the developing device according to any one of the above (1) to (3), the developer carrying member surface is opposed to the developer carrying member surface with a predetermined gap between the supply conveyance path and the developing region. And a developer regulating member for regulating the developer carried on the developer carrying member, and a change in the normal direction magnetic flux density by the reattachment inhibiting magnet at a position facing the developer regulating member of the magnetic field generating means. The said reattachment suppression magnet was arrange | positioned so that quantity might be 0.5 mT or less.
By providing such a configuration, as shown in FIG. 15, it is possible to suppress the amount of developer passing through the developer regulating member from being changed by the reattachment suppression magnet, and a developed image having a specified image density. Can be obtained.

(5)
In the developing device according to any one of (1) to (4), the magnetic field generating means generates a magnetic field for separating the developer that has passed through the developing area from the surface of the developer carrying member. Two magnetic poles having the same polarity that are generated adjacent to each other (in this embodiment, a developer regulating member opposing magnetic pole MP3 and a casing opposing magnetic pole MP2) are provided, and are opposed to the developer recovery path of the reattachment suppression magnet. The magnetic poles to be opposed to the recovery conveyance path of the reattachment suppression magnets are opposite in polarity to two adjacent magnetic poles having the same polarity that generate a magnetic field for separating from the surface of the developer carrier. did.
By providing such a configuration, it is possible to suppress the formation of a repulsive magnetic field between the two magnetic poles and the reattachment suppression magnet. Thus, the developed developer on the surface of the developer carrier can be separated from the developer carrier by the magnetic field for separating from the surface of the developer carrier, and can be collected in the collection conveyance path.

(6)
In the developing device according to any one of (1) to (5), the reattachment suppression magnet is provided in the vicinity of the second communication portion.
In the vicinity of the second communication portion, the developer that has been transported through the collection transport path stays in order to pass through the second communication portion. For this reason, since the amount of the developer is large in the vicinity of the second communication portion, the amount of toner flying toward the developer carrier increases. Further, the bulk of the developer is high, the distance between the developer carrying member and the developer in the collection conveyance path is close, and the flying toner is likely to be reattached to the developer carrying member.
Therefore, by providing a re-adhesion suppression magnet in the vicinity of the second communicating portion where the developer easily re-adheres to the developer carrying member as described above, the re-adhesion of the developer to the developer carrying member can be well suppressed. it can.

(7)
In the developing device according to any one of (1) to (6), a permanent magnet is used as the reattachment suppression magnet.
By providing such a configuration, the structure can be simplified and the apparatus can be made inexpensive as compared with the case where an electromagnet is used as the reattachment suppression magnet.

(8)
In the developing device according to any one of the above (1) to (7), the magnetic field generating unit has a main magnetic pole disposed at a position facing the developing region, and the reattachment suppression is performed. The magnetic flux density of the magnet was made lower than the magnetic flux density of the main magnetic pole.
By providing such a configuration, it is possible to suppress the influence of the magnetic flux density in the region facing the developer regulating member of the magnetic field generating unit, and to suppress an increase in the amount of development conveyed to the development region. It can suppress that the density of an image becomes darker than a regulation.

(9)
In addition, a toner image obtained by developing a latent image formed on the surface of the latent image carrier using a developer with a developing device is finally transferred onto a recording material, whereby an image is formed on the recording material. In the process cartridge which is configured to be detachable from the image forming apparatus for forming the image and integrally supports at least the latent image carrier and the developing device, the developing device is any one of (1) to (8). Was used.
By providing such a configuration, it is possible to provide a process cartridge capable of obtaining a good image without density unevenness.

(10)
Further, at least a latent image carrier, a charging unit such as a charging device 2 for charging the surface of the latent image carrier, and a latent image forming unit such as an exposure device 16 for forming an electrostatic latent image on the latent image carrier. And a developing device for developing the electrostatic latent image, the developing device according to any one of (1) to (8) is used as the developing device.
By providing such a configuration, it is possible to obtain a good image without density unevenness.

(11)
The image forming apparatus according to the above aspect (10) further includes a process cartridge that integrally supports the latent image carrier and the developing device and is detachable from the device.
With this configuration, the latent image carrier and the developing device can be easily replaced.

(12)
The image forming apparatus according to the aspect described in (10) or (11) includes a plurality of the developing devices or the process cartridges.
By providing such a configuration, a color image without density unevenness can be obtained.

1: Photoconductor 2: Charging device 3: Developing device 16: Exposure device 301: Casing 302: Developing roller 302c: Developing sleeve 302d: Magnet roller 303: Developer regulating member 304: Supply chamber conveying member 304a: Supply chamber 305: Collection Chamber conveying member 305a: Collection chamber 306: Partition member 307: Lifting port 309: Toner replenishing port 320: Developer 340: Reattachment suppression magnet MP1: Main magnetic pole MP2: Casing counter magnetic pole MP3: Developer regulating member counter magnetic pole MP3 Developer Regulating member counter magnetic pole α: Development area

JP 2003-263012 A

Claims (10)

A magnetic field generating means having a plurality of magnetic poles is included, a developer containing toner and a magnetic carrier is carried on the surface and rotated, and the latent image on the surface of the latent image carrier is developed in a development region facing the latent image carrier. A developer carrier for developing the toner by supplying toner to the image;
A supply conveyance path that is disposed to face the developer carrying member and supplies the developer to the developer carrying member while conveying the developer by a supply conveying member along the axial direction of the developer carrying member;
The developer carrying member is disposed opposite to a region from the developing region to the supply region where the developer is supplied from the supply conveyance path, and collects the developer after passing the developing region from the developer carrying member. A recovery transport path for transporting the developer recovered from the developer support by a recovery transport member along the axial direction of the developer support;
A first communicating portion that communicates the downstream end of the supply transport path in the developer transport direction and the upstream end of the recovery transport path in the developer transport direction;
A second communication portion that communicates the upstream end of the supply transport path with respect to the developer transport direction and the downstream end of the recovery transport path with respect to the developer transport direction;
In the developing device that circulates and conveys the developer between the supply conveyance path and the recovery conveyance path,
A reattachment suppression magnet that magnetically attracts the developer in the recovery transport path so as to remain in the recovery transport path and prevents the developer in the recovery transport path from reattaching to the developer carrier. Is provided on a partition member that partitions the recovery conveyance path and the supply conveyance path . The developing device according to claim 1 .
There is a developer regulating member that faces the developer carrying member surface with a predetermined gap between the supply conveyance path and the developing region, and regulates the developer carried on the developer carrying member. ,
The reattachment suppression magnet is arranged such that the amount of change by the reattachment suppression magnet in the normal direction magnetic flux density at a position facing the developer regulating member of the magnetic field generating means is 0.5 mT or less. A developing device. The developing device according to claim 1 or 2 ,
The magnetic field generating means includes two magnetic poles having the same polarity adjacent to each other for generating a magnetic field for separating the developer that has passed through the development region from the surface of the developer carrier,
The magnetic pole of the re-adhesion suppression magnet facing the recovery conveyance path is opposite in polarity to two adjacent magnetic poles of the same polarity that generate a magnetic field for separating from the surface of the developer carrier. A developing device. The developing device according to any one of claims 1 to 3 ,
A developing device, wherein the reattachment suppression magnet is provided in the vicinity of the second communication portion. In the developing device according to any one of claims 1 to 4 ,
A developing device using a permanent magnet as the reattachment suppression magnet. The developing device according to any one of claims 1 to 5 ,
The magnetic field generating means has a main magnetic pole disposed at a location facing the development region,
2. A developing device according to claim 1, wherein a magnetic flux density of the reattachment suppressing magnet is set to be equal to or lower than a magnetic flux density of the main magnetic pole. An image is formed on the recording material by finally transferring the toner image obtained by developing the latent image formed on the surface of the latent image carrier onto the recording material using a developer. In a process cartridge that is configured to be detachable from the image forming apparatus and that integrally supports at least the latent image carrier and the developing device,
As the developing apparatus, a process cartridge, which comprises using one of the developing apparatus according to claim 1 to 6. 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, and a developing device for developing the electrostatic latent image In an image forming apparatus having
As the developing device, an image forming apparatus characterized by using any of the developing apparatus according to claim 1 to 6. The image forming apparatus according to claim 8 .
An image forming apparatus comprising a process cartridge that integrally supports a latent image carrier and a developing device and is configured to be detachable from the device. The image forming apparatus according to claim 8 or 9 ,
An image forming apparatus comprising a plurality of the developing device or the process cartridge.

Images