Developing unit and image formation device

Abstract

To efficiently collect floating toner in a developing unit unlike the situation that an electric field does not collect reverse polarity toner while collecting genuine electrode toner.SOLUTION: Provided is a developing unit 33 comprising: a developer holding body 334 that holds developer, which contains toner and carrier, to be supplied to an image holding body 31 that forms an electrostatic latent image; a first member 51 disposed downstream from a development position T0 which is a position where the developer held in the developer holding body 334 is supplied to the image holding body 31; and a second member 52 that has a surface 52a facing the developer holding body 334 between the developer holding body 334, the image holding body 31 and the first member 51, and to which an intermediate potential that is a potential between a potential applied to the developer holding body 334 and a potential applied to the first member 51, is applied.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a developing unit and an image forming apparatus. [Background technology]

[0002] For example, Patent Document 1 discloses a developing device for an image forming apparatus that uses a developer carrier having a developing magnetic pole and at least one transport magnetic pole arranged downstream of the developing magnetic pole, and in which the polarity of the transport magnetic pole arranged adjacent to the developing magnetic pole is different from the polarity of the developing magnetic pole, and forms a magnetic brush of a two-component developer composed mainly of toner and carrier on the developer carrier to develop an electrostatic latent image formed on a photosensitive member, in which a member for recovering carrier that has detached from the developer carrier is arranged close to the transport magnetic pole arranged adjacent to the developing magnetic pole, and a magnetic pole having the same polarity as the developing magnetic pole is provided within the carrier recovery member. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 6-11970 Summary of the Invention [Problem to be solved by the invention]

[0004] Here, when attempting to collect floating toner in the developing unit and prevent it from leaking to the outside, the floating toner consists of regular electrode toner and reverse polarity toner, which have different magnetic polarities. Therefore, the reverse polarity toner cannot be collected using the electric field that collects regular electrode toner, making it difficult to efficiently collect the floating toner. An object of the present invention is to efficiently collect floating toner in a developing device, as compared to a case where an electric field is provided that collects normal polarity toner but does not collect opposite polarity toner. [Means for solving the problem]

[0005] The invention described in claim 1 is a developing unit comprising: a developer holder that holds a developer containing toner and a carrier and that is supplied to an image holder that forms an electrostatic latent image; a first member that is provided downstream of a development position where the developer held in the developer holder is supplied to the image holder; and a second member that has a surface facing the developer holder between the developer holder, the image holder, and the first member, and to which an intermediate potential that is a potential between the potential applied to the developer holder and the potential applied to the first member is applied. The invention described in claim 2 is the developing device described in claim 1, characterized in that the developer holder has a magnet for forming a brush containing developer carrier toward the center of the first member. The invention described in claim 3 is the developing device described in claim 2, characterized in that the magnet is arranged upstream and downstream of the magnet in the developer holder and adjacent to a magnet of a different magnetic polarity from the magnet. The invention described in claim 4 is the developing device described in claim 2, characterized in that when the opposite polarity toner attracted by the second member is recovered by the developer that contacts the first member downstream of the position where the developer of the developer holder is supplied, the developer contacts the first member within a range where the upstream and downstream brushes of the brush are at a predetermined angle with respect to the central direction. The invention described in claim 5 is the developing unit described in claim 1, characterized in that the intermediate potential of the second member is set so that the potential difference between the closer distance between the second member and the developer holder and the closer distance between the second member and the first member is smaller than the longer distance. The invention described in claim 6 is the developing device described in claim 5, characterized in that the setting is performed according to the ratio of the distance between the second member and the developer holder and the distance between the second member and the first member. An invention recited in claim 7 is the developing unit recited in claim 1, characterized in that the second member is a polygon having an inclined surface. An eighth aspect of the present invention is the developing unit according to the seventh aspect, wherein the polygon has a surface facing the developer carrier at a position adjacent to the first member. An invention recited in claim 9 is the developing unit recited in claim 8, characterized in that the surface facing the developer carrier extends toward the center of the first member. The invention described in claim 10 is the developing device described in claim 7, characterized in that the inclined surface is arranged in a tangential direction of the developer holder so that the distance from the developer holder does not change even when moving from one end of the inclined surface to the other end. The invention described in claim 11 is an image forming apparatus including an image holder that forms an electrostatic latent image, a developing means that develops the electrostatic latent image formed on the image holder into a toner image, a transfer means that transfers the toner image by the developing means onto a recording material, and a fixing means that fixes the toner image transferred onto the recording material to the recording material, wherein the developing means is provided with a developer holder that holds a developer containing toner and a carrier and that is supplied to the image holder that forms the electrostatic latent image, a first member that is provided downstream of a development position where the developer held on the developer holder is supplied to the image holder, and a second member that has a surface facing the developer holder between the developer holder, the image holder, and the first member, and to which an intermediate potential that is a potential between the potential applied to the developer holder and the potential applied to the first member is applied. Effect of the Invention

[0006] According to the invention of claim 1, the floating toner in the developing device can be collected more efficiently than when an electric field is provided that collects normal polarity toner but does not collect opposite polarity toner. According to the invention of claim 2, the developer holder can improve the efficiency of recovery of the developer adhering to the first member compared to a case in which the developer holder does not have a configuration in which a brush containing the developer carrier has a magnet for forming the brush toward the center of the first member. According to the invention of claim 3, the magnet is arranged upstream and downstream of the magnet in the developer holder, and the efficiency of recovery of the developer adhering to the first member can be improved compared to a case in which a configuration is not adopted in which the magnet is adjacent to a magnet of a different magnetic polarity from the magnet. According to the invention of claim 4, the positioning accuracy of the first member relative to the developer holder can be reduced compared to a case in which a configuration is not adopted in which the developer contacts the first member within a range in which each of the upstream and downstream brushes is at a predetermined angle relative to the central direction. According to the invention of claim 5, the intermediate potential of the second member can suppress leakage of floating toner outside the container, compared to a case in which the intermediate potential of the second member is not set so that the potential difference at the closer distance between the second member and the developer holder and the distance between the second member and the first member is smaller than that at the farther distance. According to the invention of claim 6, the setting is made according to the ratio of the distance between the second member and the developer holder to the distance between the second member and the first member, thereby making it possible to suppress leakage of floating toner outside the container, compared to a case in which a configuration is not adopted in which the setting is made according to the ratio of the distance between the second member and the developer holder to the distance between the second member and the first member. According to the seventh aspect of the present invention, the second member can suppress leakage of floating toner to the outside of the container, compared to a case where the second member is not configured to have a polygonal shape with inclined faces. According to the invention of claim 8, the amount of floating toner collected can be increased compared to a case in which the polygon does not have a surface facing the developer carrier at a position adjacent to the first member. According to the invention of claim 9, the amount of floating toner collected can be increased compared to a case where the surface facing the developer carrier does not extend toward the center of the first member. According to the invention of claim 10, the amount of floating toner collected can be increased compared to a case in which the inclined surface is provided in the tangential direction of the developer carrier so that the distance from the developer carrier does not change even when moving from one end of the inclined surface to the other end. According to the invention of claim 11, the floating toner in the developing device can be collected more efficiently than when an electric field is provided that collects normal polarity toner but does not collect opposite polarity toner. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram illustrating an image forming apparatus. [Diagram 2] FIG. 2 is a diagram illustrating a developing device of the image forming apparatus. [Diagram 3] 1A and 1B are diagrams illustrating a developing unit in a first embodiment, in which (a) shows the developing unit together with a photosensitive drum, (b) shows the electrode member alone, and (c) shows the positional relationship between a seal roll and the electrode member. [Figure 4] FIG. 4 is a diagram for explaining the effect of a potential applied to an electrode member according to the first embodiment. [Diagram 5] 10A and 10B are diagrams illustrating the effect of a potential applied to an electrode member according to a comparative example. [Figure 6] 11 is a diagram illustrating a case where a developer held by a developing roll comes into contact with a seal roll. FIG. [Figure 7] FIG. 4 is a diagram illustrating a magnetic field of a developer layer held by a developing roll. [Figure 8] FIG. 2 is a diagram illustrating a magnetic brush of a developer layer held by a developing roll. [Figure 9] 5A and 5B are diagrams illustrating modified examples of the electrode member according to the first embodiment, where (a) shows one modified example and (b) shows another modified example. [Figure 10] FIG. 11 is a diagram illustrating a developing unit according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a diagram illustrating an image forming apparatus 1. As shown in FIG. The image forming apparatus 1 according to this embodiment includes a paper feed unit 1A, a printing unit 1B, and a paper discharge unit 1C. The paper feed unit 1A includes a first paper storage section 11 to a fourth paper storage section 14 for storing paper P as an example of a recording medium. The paper feed unit 1A also has feed rolls 15-18 that correspond to the first paper storage section 11 to the fourth paper storage section 14, respectively, and feed the paper P stored in each paper storage section to a transport path connected to the printing unit 1B.

[0009] The printing unit 1B includes an image forming section 20 that forms an image on a sheet P. The printing unit 1B also includes a control section 21 that controls each section of the image forming apparatus 1. The printing unit 1B also includes an image processing section 22. The image processing section 22 performs image processing on image data transmitted from the image reading device 4 and the personal computer (PC) 5. The printing unit 1B is also provided with a UI (User Interface) 23, which is configured with a touch panel or the like and notifies the user of information and receives information input from the user.

[0010] Image forming section 20, as an example of an image forming means, is provided with six image forming units 30T, 30P, 30Y, 30M, 30C, and 30K (hereinafter, sometimes simply referred to as "image forming units 30") arranged in parallel at regular intervals. Each image forming unit 30 includes a photosensitive drum 31 on which an electrostatic latent image is formed while rotating in the direction of arrow A, a charging roll 32 which charges the surface of the photosensitive drum 31, a developing device 33 which develops the electrostatic latent image formed on the photosensitive drum 31, and a drum cleaner 34 which removes toner and the like from the surface of the photosensitive drum 31. The photoconductor drum 31 is an example of an image carrier.

[0011] The image forming section 20 is also provided with a laser exposure device 26 that exposes the photoconductor drum 31 of each image forming unit 30 to laser light. The exposure of the photoconductor drum 31 by the laser exposure device 26 is not limited to using laser light. For example, a light source such as an LED (Light Emitting Diode) may be provided for each image forming unit 30, and the photoconductor drum 31 may be exposed using light emitted from the light source.

[0012] Each image forming unit 30 is configured similarly, except for the toner contained in the developer 33. The image forming units 30Y, 30M, 30C, and 30K form toner images of yellow (Y), magenta (M), cyan (C), and black (K), respectively. Further, the image forming units 30T and 30P form toner images using toner corresponding to a corporate color, foaming toner for Braille, fluorescent color toner, toner for improving gloss, etc. In other words, the image forming units 30T and 30P form toner images using toner of a special color.

[0013] The image forming section 20 is also provided with an intermediate transfer belt 41 onto which the toner images of each color formed on the photosensitive drums 31 of the image forming units 30 are transferred. The image forming section 20 is also provided with a primary transfer roll 42 that transfers the respective color toner images of the respective image forming units 30 onto the intermediate transfer belt 41 at a primary transfer portion T1. The image forming unit 20 is also provided with a secondary transfer roll 40 that transfers the toner image transferred onto the intermediate transfer belt 41 onto the paper P at a secondary transfer portion T2. Furthermore, the image forming section 20 is provided with a belt cleaner 45 that removes toner and the like from the surface of the intermediate transfer belt 41, and a fixing device 80 that fixes the secondarily transferred image onto the paper P. The developing device 33 is an example of a developing unit, the intermediate transfer belt 41 is an example of a transfer unit, and the fixing device 80 is an example of a fixing unit.

[0014] The image forming unit 20 performs an image forming operation based on a control signal from the control unit 21 . Specifically, in the image forming unit 20, first, image processing is performed on the image data input from the image reading device 4 or the PC 5 by the image processing unit 22, and the image data after image processing is supplied to the laser exposure device 26. Then, for example, in a magenta (M) image forming unit 30M, the surface of the photosensitive drum 31 is charged by the charging roll 32, and then the laser exposure device 26 irradiates the photosensitive drum 31 with laser light modulated by image data obtained from the image processing unit 22.

[0015] As a result, an electrostatic latent image is formed on the photoconductor drum 31 . The formed electrostatic latent image is developed by the developing unit 33, and a magenta toner image is formed on the photosensitive drum 31. Similarly, yellow, cyan and black toner images are formed in the image forming units 30Y, 30C and 30K, and special color toner images are formed in the image forming units 30T and 30P.

[0016] The respective color toner images formed in each image forming unit 30 are electrostatically transferred sequentially by a primary transfer roll 42 onto an intermediate transfer belt 41 rotating in the direction of arrow C in Figure 1, and superimposed toner images are formed on the intermediate transfer belt 41. The superimposed toner image formed on the intermediate transfer belt 41 is transported to a secondary transfer portion T2 constituted by a secondary transfer roll 40 and a backup roll 49 as the intermediate transfer belt 41 moves.

[0017] On the other hand, the paper P is taken out from the first paper storage unit 11 by, for example, the delivery roll 15, and then transported to the position of the registration roll 74 via the transport path. When the superimposed toner image is transported to the secondary transfer portion T2, a sheet of paper P is supplied from the registration roll 74 to the secondary transfer portion T2 in accordance with the transport timing. Then, in the secondary transfer portion T2, the superimposed toner images are electrostatically transferred onto the paper P all at once by the action of a transfer electric field formed between the secondary transfer roll 40 and the backup roll 49.

[0018] Thereafter, the paper P onto which the superimposed toner images have been electrostatically transferred is transported to a fixing device 80. In the fixing device 80, pressure and heat are applied to the paper P on which the unfixed toner image has been formed, and the toner image is fixed to the paper P. Then, the sheet P on which the fixing process has been performed passes through a curl correction section 81 provided in the sheet discharge unit 1C, and is then conveyed to a sheet stacking section (not shown).

[0019] FIG. 2 is a diagram illustrating the developing device 33 of the image forming apparatus 1. As shown in FIG. The developing unit 33 includes a storage unit 331 that stores a developer (not shown) therein. The storage unit 331 is made of a resin storage case 332. The developer is made of a magnetic carrier and a colored toner, and is a so-called two-component developer. The housing 332 of the developing device 33 is arranged to extend along a direction perpendicular to the paper surface of FIG. 2, which is the direction from the front side to the rear side of the image forming apparatus 1 (see FIG. 1), and has a front side member (not shown) on the front side and a rear side member (not shown) on the rear side.

[0020] An opening 333 is provided in the housing 332 at a location facing the photoconductor drum 31 (see FIG. 1). A developing roll 334 that adheres a developer to the surface of the photoconductor drum 31 is provided in this opening 333. The developing roll 334 holds the developer to be supplied to the photoconductor drum 31. The position where the developer from the developing roll 334 is supplied to the photoconductor drum 31 is sometimes referred to as a developing position T0 (see FIG. 3, for example). The developing roll 334, which is an example of a developer holder, is formed in a cylindrical shape and is arranged so as to extend along a direction from the front side to the rear side of the image forming apparatus 1. In addition, the developing roll 334 is arranged so as to extend along the longitudinal direction of the developing unit 33.

[0021] The developing roll 334 is provided with a developing sleeve 334A that is formed of a cylindrical body and that is driven to rotate, and a magnet roll 334B that is disposed inside the developing sleeve 334A. The developing sleeve 334A is made of a metal such as SUS, etc. The developing sleeve 334A rotates in the direction of the arrow D in the figure. The developing roll 334 is an example of a developer carrier.

[0022] Furthermore, in this embodiment, at the primary transfer portion T1 (see FIG. 1) between the developing roll 334 and the photosensitive drum 31, the developing sleeve 334A and the photosensitive drum 31 rotate so that they move in the same direction. The developing unit 33 is provided with a layer regulating member 335 that regulates the layer thickness of the developer held on the developing roll 334 .

[0023] As shown in FIG. 2, the developing device 33 is provided with a first transport member 336 and a second transport member 337 for transporting the developer. The first transport member 336 and the second transport member 337 are provided on the opposite side of the developing roll 334 to the side on which the photoconductor drum 31 (see FIG. 1) is installed. The first transport member 336 has a rotation axis aligned with the rotation axis of the developing sleeve 334A that is driven to rotate, and rotates around this rotation axis to transport the developer in the container 331.

[0024] In the developing device 33 configured in this manner, new toner or toner to which a very small amount of carrier has been added is circulated by being stirred and transported between the first transport member 336 and the second transport member 337. More specifically, by transferring the developer through connection ports formed at both ends of a partition wall extending in the axial direction, the developer stirred by the first transport member 336 is stirred by the second transport member 337, and can also be stirred by the first transport member 336. In the developing device 33, a circulation path is formed, which is a path that circulates in the axial direction by the rotation of each of the first transport member 336 and the second transport member 337.

[0025] The developing unit 33 is provided with a third transport member 338 adjacent to the second transport member 337. In addition, the developing unit 33 is provided with a pick-up roll 339 located above the third transport member 338. The transport path formed by the rotation of the third transport member 338 is connected to the circulation path described above, and receives the developer from the circulation path. The third transport member 338 supplies the developer to a pickup roll 339. The pickup roll 339 supplies the developer to the developing roll 334. For example, the first transport member 336 transports toward the front side of the paper, the second transport member 337 transports toward the back side of the paper, and the third transport member 338 transports toward the front side of the paper.

[0026] The developing roll 334, the layer regulating member 335, the first transport member 336, the second transport member 337, the third transport member 338 and the pickup roll 339 are disposed substantially parallel to the photoconductor drum 31 (see FIG. 1).

[0027] Next, a more specific configuration of the developing device 33 will be described. As such a specific configuration, a first embodiment and a second embodiment will be described. The developing device 33 according to the first embodiment includes a seal roll 51 as an example of a first member (see, for example, FIG. 3). The developing device 33 according to the second embodiment includes a carrier recovery roll 53 as an example of a first member (see, for example, FIG. 10).

[0028] FIG. 3 is a diagram illustrating the developing device 33 in the first embodiment, where (a) shows the developing device 33 together with the photosensitive drum 31, (b) shows the electrode member 52 alone, and (c) shows the positional relationship between the seal roll 51 and the electrode member 52. 3(a), the developing device 33 includes a seal roll 51 disposed to face the photosensitive drum 31 and the developing roll 334, and an electrode member 52 disposed to be surrounded by the photosensitive drum 31, the developing roll 334, and the seal roll 51. The seal roll 51 is an example of a first member, and the electrode member 52 is an example of a second member.

[0029] The seal roll 51 is located downstream of a development position T0 where the developer of the development roll 334 is supplied to the photosensitive drum 31, and rotates in a clockwise direction which is opposite to the counterclockwise direction of rotation of the development roll 334. The seal roll 51 has a smaller diameter than the photosensitive drum 31 and the development roll 334. The downstream side here refers to the downstream side in the rotation direction of the photosensitive drum 31 or the developing roll 334 with respect to the developing position T0.

[0030] The electrode member 52 is a fixed member, unlike the seal roll 51. In the present embodiment, the electrode member 52 has a shape based on a triangular shape that can be accommodated in the space formed by the developing roll 334, the photosensitive drum 31, and the seal roll 51, as shown in Fig. 3(a). The space here is an area surrounded by the tangents of the developing roll 334, the photosensitive drum 31, and the seal roll 51, and is an example of the space between the developer carrier, the image carrier, and the first member.

[0031] More specifically, the electrode member 52 has a surface 52a facing the developing roll 334 between the developing roll 334, the photosensitive drum 31, and the seal roll 51. The surface 52a is an example of a surface facing the developer carrier, and is an example of an inclined surface.

[0032] Describing the electrode member 52 in more detail, as shown in FIG. 3(b), the electrode member 52 has the above-mentioned surface 52a, a surface 52b formed adjacent to surface 52a so as to face the developing roll 334, a surface 52c formed adjacent to surface 52b so as to face the seal roll 51, and a surface 52d formed adjacent to surfaces 52c and 52a so as to face the photosensitive drum 31.

[0033] The surface 52a of the electrode member 52 is provided in a tangential direction of the developing roll 334 so that the distance from the developing roll 334 does not change even when moving from the upstream end to the downstream end of the surface 52a. Note that the surface 52a may be provided in a direction other than the tangential direction.

[0034] The electrode member 52 is a polygon in which a surface 52b is formed by cutting out one corner 52e of the triangular shape that is close to the developing roll 334 and the seal roll 51. The surface 52b of the electrode member 52 is an example of a surface facing the developer carrier.

[0035] 3(c), the surface 52b of the electrode member 52 is provided at a position adjacent to the seal roll 51 and extends in a direction toward the center 51a of the seal roll 51. As a result, the electrode member 52 is disposed so that the gap δ1 between the electrode member 52 and the seal roll 51 is small. The surface 52b is not limited to extending in the direction toward the center 51a of the seal roll 51, and may be configured to extend in another direction. The other direction referred to here is preferably a direction that becomes closer to the seal roll 51 as it approaches the seal roll 51.

[0036] Next, the potential applied to the electrode member 52 will be described. Figures 4 and 5 are diagrams for explaining the effect of the potential applied to the electrode member 52, with Figure 4 being the case of the first embodiment and Figure 5 being a comparative example. In Figures 4 and 5, the direction of the electric field is indicated by thin dashed arrows. In addition, in Figures 4 and 5, the developer layer 60 shown in Figures 6 and 7, which will be described later, is omitted for the sake of convenience of explanation. 4, in this embodiment, a potential of −500 V is applied to the developing roll 334, and a potential of −800 V is applied to the seal roll 51. A potential of −600 V, which is an intermediate potential between the potential of the developing roll 334 and the potential of the seal roll 51, is applied to the electrode member 52. This forms an electric field that collects the floating toner. The power supply to the electrode member 52 can be divided from the power supply of the seal roll 51 .

[0037] The photoconductor drum 31 has a potential of −200 to −620 V. More specifically, the portion of the photoconductor drum 31 on which an electrostatic latent image is formed is −200 V, and the portion on which an electrostatic latent image is not formed is −620 V.

[0038] The formation of an electric field for collecting floating toner will be described below. When the above-mentioned applied potential relationship is adopted, when attention is paid to the developing roll 334 and the electrode member 52, the positive (+) side is the developing roll 334. On the other hand, when attention is paid to the electrode member 52 and the seal roll 51, the electrode member 52 is the positive (+) side. The floating toner may contain negatively (-) charged normal electrode toner 60a (shown by white circles) as well as positively (+) charged reverse electrode toner 60b (shown by black circles). Although it is possible that the floating toner does not contain reverse electrode toner 60b, it may contain reverse electrode toner 60b. Comparing the amounts of regular electrode toner 60a and reverse electrode toner 60b in the floating toner, there is more regular electrode toner 60a than reverse electrode toner 60b. The ratio varies depending on various conditions such as the ratio of toner in the developer, such as a decrease in the charge amount and deterioration of the developer, but one example can be when the reverse electrode toner 60b accounts for about 10% of the floating toner.

[0039] Here, as the photoconductor drum 31 and the developing roll 334 rotate, an airflow is generated from the developing position T0 (see FIG. 6) toward the downstream side, and the floating toner moves on the airflow. More specifically, since the electrode member 52 is located downstream of the developing position T0, there are two types of airflow: an airflow passing between the photoconductor drum 31 and the electrode member 52, and an airflow passing between the developing roll 334 and the electrode member 52. To explain further, in the first embodiment, when comparing the gap δ2 between the photoconductor drum 31 and the electrode member 52 and the gap δ3 between the developing roll 334 and the electrode member 52, the gap δ2 is smaller than the gap δ3 (δ2<δ3). Therefore, the amount of airflow passing through the gap δ3 is large, and the amount of airflow passing through the gap δ2 is small. In addition, the surface 52a of the electrode member 52 faces the developing roll 334 so as to obstruct the airflow passing through the gap δ2 and promote the airflow passing through the gap δ3.

[0040] Furthermore, by applying the intermediate potential to the electrode member 52 described above, the regular electrode toner 60a among the floating toner particles is attracted toward the developing roll 334 by repelling the electrode member 52 and being attracted to the developing roll 334, as shown by the thick dashed arrow. The reverse electrode toner 60b is attracted toward the electrode member 52 by repelling the developing roll 334 and being attracted to the electrode member 52, as shown by the thick solid arrow. Due to the action of the intermediate potential of the electrode member 52, the floating toner is caused to move by the air current passing through the gap δ3.

[0041] A case will now be described in which a small amount of reverse electrode toner 60b compared to the regular electrode toner 60a rides on the air current passing through the gap δ2. Focusing on the photoconductor drum 31 and the electrode member 52, since the photoconductor drum 31 is on the positive (+) side, the reverse electrode toner 60b repels the photoconductor drum 31 and is attracted to the electrode member 52. As a result, it is assumed that the reverse electrode toner 60b is attracted to the electrode member 52 and adheres to, for example, the surface 52d.

[0042] Among the floating toner particles moving on the air current passing through the gap δ3, the negatively charged regular electrode toner particles 60a are attracted toward the developing roll 334 between the developing roll 334 and the electrode member 52, while the positively charged reverse electrode toner particles 60b repel the developing roll 334 and are attracted toward the electrode member 52.

[0043] Moreover, the positively charged opposite electrode toner 60b attracted toward the electrode member 52 is attracted toward the seal roll 51. Moreover, the surface 52b of the electrode member 52 extends toward the center of the seal roll 51 so that the gap δ4 between the electrode member 52 and the seal roll 51 does not become large. Therefore, the reverse electrode toner 60b attracted to the electrode member 52 is prevented from being carried by the air current passing through the gap δ2 from the gap δ4.

[0044] Note that even if the reverse electrode toner 60b moves on the air current passing through the gap δ2, it is assumed that it is attracted to the electrode member 52 and adheres to, for example, the surface 52d. This reduces the amount of reverse electrode toner 60b that leaks outside the device on the air current passing through the gap δ2 (arrow k in FIG. 4). Additionally, the relative sizes of the gaps δ1 to δ4 are not limited to those described above, and may be different from the relative sizes described above.

[0045] Here, a method for setting the intermediate potential to be applied to the electrode member 52, which is an example of the second member, will be described. In the present embodiment, as described above, a potential of −500 V is applied to the developing roll 334, a potential of −800 V is applied to the seal roll 51, and a potential of −600 V is applied as an intermediate potential to the electrode member 52. Due to this intermediate potential, the potential difference between the developing roll 334 and the electrode member 52 is 100 V, and the potential difference between the seal roll 51 and the electrode member 52 is 200 V. However, this potential difference is not limited to this.

[0046] For example, it is conceivable to associate the magnitude of the gap with the magnitude of the potential difference. Comparing the gap δ3 between the developing roll 334 and the electrode member 52 and the gap δ4 between the electrode member 52 and the seal roll 51, the potential difference of the closer gap may be set to be smaller than that of the farther gap. More specifically, in this embodiment, as shown in Fig. 4, the gap δ4 is smaller than the gap δ3 (δ4<δ3), and therefore the potential difference between the electrode member 52 and the seal roll 51 is set to be smaller than the potential difference between the developing roll 334 and the electrode member 52. That is, the intermediate potential applied to the electrode member 52 in this case is, for example, -700V.

[0047] In this case, the gap δ3 is the shortest distance between the developing roll 334 and the electrode member 52, and the gap δ4 refers to a position 60d (see FIG. 6) that is closest to the electrode member 52 among the contact positions when the developer layer 60 held by the developing roll 334 contacts the seal roll 51 (see FIG. 6). The position 60d here refers to the upstream end position of the developer layer 60 that contacts the seal roll 51 in the rotation direction of the seal roll 51. The above-mentioned gap δ3 is an example of the distance between the second member and the developer carrier, and the gap δ4 is an example of the distance between the second member and the first member.

[0048] Another method for setting the intermediate potential is to set the potential difference according to the gap ratio. For example, the ratio between the gap δ3 and the gap δ4 is calculated, and the intermediate potential is set by dividing the ratio. More specifically, if the potential difference between the developing roll 334 and the seal roll 51 is 300V and the ratio between the gap δ3 and the gap δ4 is 5:1, the potential difference for the gap δ3 is set to 250V, and the potential difference for the gap δ4 is set to 50V. That is, the intermediate potential applied to the electrode member 52 in this case is -750V.

[0049] Here, a comparative example to the first embodiment will be described. As such a comparative example, a configuration not including the electrode member 52 shown in Fig. 4 is shown in Fig. 5. The comparative example shown in Fig. 5 has the same configuration as that in Fig. 4 except for the configuration not including the electrode member 52, and the thick solid arrows, thick dashed arrows, thin dashed arrows, and k arrow are used in the same way as in Fig. 4. For ease of explanation, Fig. 5 shows the regular electrode toner 60a and reverse electrode toner 60b shown in Fig. 4, as well as the reverse electrode toner 60c not shown in Fig. 4.

[0050] 5, the regular electrode toner 60a is attracted to the developing roll 334, while the reverse electrode toner 60b is attracted to the seal roll 51, but the reverse electrode toner 60c moves on the air current passing between the photoconductor drum 31 and the seal roll 51. As a result, the reverse electrode toner 60c leaks outside the device, and the amount of leakage is not suppressed. In contrast, in the first embodiment shown in FIG. 4, as described above, an intermediate potential is applied to the electrode member 52 having the surface 52a facing the developing roll 334, thereby suppressing the amount of reverse electrode toner 60b leaking outside the device.

[0051] FIG. 6 is a diagram illustrating a case where the developer held by the developing roll 334 comes into contact with the seal roll 51. As shown in FIG. 6 shows the developer layer 60 held by the developing roll 334. The developer layer 60 contacts the photoconductor drum 31 at the development position T0, and also contacts the seal roll 51 at a downstream position. That is, the space between the developing roll 334 and the seal roll 51 is closed by the developer layer 60. Therefore, the regular electrode toner 60a and the reverse electrode toner 60b, which are floating toners moving on the air current passing through the gap δ3 between the developing roll 334 and the electrode member 52, are collected by the developer layer 60. This prevents the floating toners from leaking out of the developing device 33. Although FIG. 6 shows a state in which the developer layer 60 is in contact with the seal roll 51, the present invention is not limited to this, and the developer layer 60 may not be in contact with the seal roll 51.

[0052] FIG. 7 is a diagram illustrating the magnetic field of the developer layer 60 held by the developing roll 334. As shown in FIG. 7, the magnet roll 334B of the developing roll 334 is provided with a plurality of magnetic poles aligned in the circumferential direction. More specifically, the magnet roll 334B is provided with a plurality of magnetic poles, for example, an S pole 61 at a position corresponding to the developing position T0, and an N pole 62 at a position facing the seal roll 51 downstream of the S pole 61. An S pole 63 is provided further downstream.

[0053] The multiple magnetic poles cause the thickness of the developer layer 60 to vary depending on the circumferential position. In other words, the S pole 61 forms a layer thickness in contact with the photoconductor drum 31, and the N pole 62 forms a layer thickness in contact with the seal roll 51.

[0054] More specifically, magnetic lines of force are formed by the magnetic field of the developer layer 60. More specifically, as shown in Fig. 7, a magnetic brush 60e is formed by the magnetic lines of force in the developer layer 60 at the development position T0, and a magnetic brush 60f is formed by the magnetic lines of force in the developer layer 60 at a position facing the seal roll 51. The magnetic brushes 60e and 60f are formed by including the carrier of the developer layer 60.

[0055] The magnetic brush 60f stands up so as to overlap a dashed line 64 connecting the center 334C of the developing roll 334 and the center 51a of the seal roll 51. More specifically, the N pole 62 of the developing roll 334 is disposed toward the center 51a of the seal roll 51. The N pole 62 is a magnet for forming the magnetic brush 60f toward the center 51a of the seal roll 51. In other words, the magnet is arranged from the center 334C of the developing roll 334 toward the center 51a of the seal roll 51 so that the magnetic brush 60f from the developing roll 334 stands upright. The direction of the magnetic brushes 60e and 60f is the direction of the magnetic field lines.

[0056] Furthermore, on the upstream and downstream sides of the N pole 62 of the developing roll 334, S poles 61 and 63, which are magnetic poles different from the N pole 62, are arranged. In other words, the N pole 62 is adjacent to the S poles 61 and 63. The magnetic brushes other than the magnetic brushes 60e and 60f are inclined according to the magnetic field generated by such an adjacent arrangement. The N pole 62 is an example of a magnet, and the S poles 61 and 63 are examples of magnets with different poles. The arrangement of the multiple magnetic poles in the developing roll 334 is not limited to the above-mentioned magnet arrangement, and other magnet arrangements may be adopted.

[0057] Here, the tip of the magnetic brush 60f in the developer layer 60 moves faster than the other parts, and has a high ability to collect the opposite electrode toner 60b when it comes into contact with the seal roll 51. Therefore, even if the opposite electrode toner 60b that has gathered around the position 60d of the electrode member 52 due to the electric field formed by the electrode adheres to the seal roll 51, the frictional force between the magnetic brush 60f and the developer increases, and the opposite electrode toner 60b is collected in the developer layer 60.

[0058] More specifically, since the magnetic brushes 60f and 60g, 60h (see FIG. 8) stand along the direction of the magnetic lines of force, it is not necessary to increase the positioning accuracy of the seal roll 51 relative to the developing roll 334. In other words, even if the error in the distance between the developing roll 334 and the seal roll 51 is large, it is possible to collect the reverse electrode toner 60b adhering to the seal roll 51.

[0059] 8 is a diagram illustrating the magnetic brush of the developer layer 60 held by the developing roll 334. In this figure, for the convenience of calculating the magnetic field lines, a normal 334D of the developing roll 334 is shown instead of the outer circumferential surface of the developing roll 334. The normal 334D intersects with the line 64 (see FIG. 7).

[0060] 8, the contact state in which the developer layer 60 contacts the seal roll 51 is preferably such that the magnetic brushes 60f, 60g, and 60h are located within a range of a predetermined angle θ with respect to the line 64. More specifically, the angle θ is 30 degrees in this embodiment, and the magnetic brush 60g is inclined 30 degrees upstream with respect to the line 64, and the magnetic brush 60h is inclined 30 degrees downstream with respect to the line 64. The angle θ is determined by various boundary conditions, and is an example of a predetermined angle. As shown in FIG. 8, the developer in the developer layer 60 contacts the seal roll 51 within a range in which the upstream and downstream magnetic brushes 60g, 60h form an angle θ (30 degrees in this embodiment) with respect to a line 64. In such a contact state, the density of the tip of the magnetic brush is high, so that the reverse electrode toner 60b (see FIG. 7) on the surface of the seal roll 51 is rubbed, enhancing the cleaning effect.

[0061] FIG. 9 is a diagram illustrating modified examples of the electrode member 52 according to the first embodiment, where (a) shows one modified example and (b) shows another modified example. 9(a), the electrode member 52 has a triangular shape, and unlike the first embodiment (see FIG. 3), no notch is formed at the corner 52e. As in the other modifications, the electrode member 52 has a surface 52a facing the developing roll 334.

[0062] 9(b), the electrode member 52 is plate-shaped and has a rectangular cross section. In the case of the other modified example, the electrode member 52 also has a surface 52a facing the developing roll 334.

[0063] Fig. 10 is a diagram for explaining a developing device 33 according to the second embodiment, and corresponds to Fig. 6 among Figs. 3 to 9 for explaining the first embodiment. Therefore, the description of the parts common to Fig. 6 may be omitted. 10, the second embodiment includes a carrier recovery roll 53 as an example of a first member. More specifically, the developing device 33 according to the second embodiment does not include the seal roll 51 (see FIG. 3, for example) included in the developing device 33 according to the second embodiment, and the carrier recovery roll 53 is disposed at the position of the seal roll 51. In the description of the first embodiment, the seal roll 51 can be replaced with the carrier recovery roll 53. The carrier recovery roll 53 is an example of a first member.

[0064] The carrier recovery roll 53 includes a sleeve 53A that is formed of a cylindrical body and that is driven to rotate, and a magnet roll 53B that is disposed inside the sleeve 53A. The magnet roll 53B of the carrier recovery roll 53 is provided with a plurality of magnetic poles aligned in the circumferential direction. More specifically, the magnet roll 53B is provided with, as the plurality of magnetic poles, for example, an S pole 65 at a position where the developer layer 60 contacts the sleeve 53A, and an N pole 66 upstream of a position facing the electrode member 52. Furthermore, the magnet roll 53B is provided with, as the plurality of magnetic poles, an S pole 67 at a position shifted by 180 degrees from the position where the developer layer 60 contacts the sleeve 53A.

[0065] Here, a case where the opposite electrode toner 60i moves in a direction outside the device due to an airflow passing through the gap δ2 in the second embodiment shown in FIG. 10 will be described. Since the opposite electrode toner 60i is positively charged, it is easily attracted to the N pole 66 of the carrier recovery roll 53. Therefore, when the opposite electrode toner 60i adheres to the circumferential surface of the sleeve 53A, it is recovered into the developer layer 60 by the rotation of the sleeve 53A.

[0066] <Additional Notes> (((1))) a developer carrier for holding a developer containing a toner and a carrier and supplied to an image carrier for forming an electrostatic latent image; a first member provided downstream of a development position where the developer held on the developer holder is supplied to the image holder; a second member having a surface facing the developer carrier between the developer carrier, the image carrier, and the first member, and to which an intermediate potential between a potential applied to the developer carrier and a potential applied to the first member is applied; A developing device comprising: (((2))) The developer carrier has a magnet for forming a brush including a developer carrier toward the center of the first member. The developing device according to (((1))) above. (((3))) the magnet is disposed on the developer holder on the upstream side and downstream side of the magnet, and adjacent to magnets having a different magnetic pole from the magnet, The developing device according to (((2))) above. (((4))) In a case where the toner of the opposite polarity attracted by the second member is collected by the developer that is in contact with the first member downstream of the position where the developer of the developer carrier is supplied, the developer comes into contact with the first member within a range in which each of the brushes on the upstream side and the downstream side with respect to the central direction is at a predetermined angle; The developing device according to (((2))) above. (((5))) the intermediate potential of the second member is set such that a potential difference between a closer distance between the second member and the developer carrier and a longer distance between the second member and the first member is smaller than a potential difference between the closer distance between the second member and the developer carrier and a longer distance between the second member and the first member; The developing device according to (((1))) above. (((6))) the setting is performed according to a ratio of a distance between the second member and the developer carrier to a distance between the second member and the first member; The developing device according to (((5))) above. (((7))) The second member is a polygon having the surface as an inclined surface. The developing device according to any one of ((1))) to (((6))) above. (((8))) the polygon has a surface facing the developer carrier at a position adjacent to the first member; The developing device according to (((7))) above. (((9))) the surface facing the developer carrier extends toward the center of the first member; The developing device according to (((8))) above. (((10))) the inclined surface is provided in a tangential direction of the developer carrier so that the distance between the developer carrier and the inclined surface does not change even when moving from one end of the inclined surface to the other end of the inclined surface; The developing device according to any one of ((7)) to ((9)) above. (((11))) an image carrier for forming an electrostatic latent image; a developing means for developing the electrostatic latent image formed on the image carrier into a toner image; a transfer means for transferring the toner image produced by the developing means onto a recording material; a fixing unit for fixing the toner image transferred onto the recording material onto the recording material; Including, The developing means is a developer carrier for holding a developer containing a toner and a carrier and supplied to an image carrier for forming an electrostatic latent image; a first member provided downstream of a development position where the developer held on the developer holder is supplied to the image holder; a second member having a surface facing the developer carrier between the developer carrier, the image carrier, and the first member, and to which an intermediate potential between a potential applied to the developer carrier and a potential applied to the first member is applied; An image forming apparatus comprising:

[0067] According to the invention of (((1))), floating toner in the developing device can be collected more efficiently than when an electric field is provided that collects normal polarity toner but does not collect opposite polarity toner. According to the invention (((2))), the developer holder can improve the efficiency of recovering the developer adhering to the first member, compared to a case in which the developer holder does not have a configuration in which a brush containing the developer carrier has a magnet formed toward the center of the first member. According to the invention (((3))), the magnet is arranged upstream and downstream of the magnet in the developer holder, and the efficiency of recovery of the developer adhering to the first member can be improved compared to a case in which a configuration in which the magnet is adjacent to a magnet of a different magnetic polarity from the magnet is not adopted. According to the invention (((4))), the positioning accuracy of the first member relative to the developer holder can be reduced compared to a case in which a configuration is not adopted in which the developer contacts the first member within a range in which each of the upstream and downstream brushes is at a predetermined angle relative to the center direction. According to the invention (((5))), the intermediate potential of the second member can suppress leakage of floating toner outside the container, compared to a case in which the intermediate potential of the second member is not set so that the potential difference at the closer distance out of the distance between the second member and the developer holder and the distance between the second member and the first member is smaller than that at the farther distance. According to the invention (((6))), the setting is made according to the ratio of the distance between the second member and the developer holder to the distance between the second member and the first member, thereby making it possible to suppress leakage of floating toner outside the container, compared to a case in which a configuration is not adopted in which the setting is made according to the ratio of the distance between the second member and the developer holder to the distance between the second member and the first member. According to the invention (((7))), the second member can prevent floating toner from leaking out of the container, compared to a case in which the second member is not configured to have a polygonal shape with inclined faces. According to the invention (((8))), the polygon can increase the amount of floating toner collected compared to a case in which the polygon does not have a surface facing the developer carrier at a position adjacent to the first member. According to the invention (((9))), the amount of floating toner that is collected can be increased compared to a case in which the surface facing the developer carrier does not extend toward the center of the first member. According to the invention (((10))), the amount of floating toner collected can be increased compared to a case in which the inclined surface is provided in the tangential direction of the developer carrier so that the distance from the developer carrier does not change when moving from one end of the inclined surface to the other. According to the invention of (((11))), floating toner in the developing device can be collected more efficiently than when an electric field is provided that collects normal polarity toner but does not collect opposite polarity toner. [Explanation of symbols]

[0068] 1...image forming apparatus, 31...photoconductor drum, 33...developer, 41...intermediate transfer belt, 51...seal roll, 51a...center, 52...electrode member, 52a, 52b...surface, 53...carrier recovery roll, 60...developer layer, 60a...regular electrode toner, 60b, 60c, 60i...reverse electrode toner, 60e, 60f, 60g, 60h...magnetic brush, 61, 63, 65, 67...south pole, 62, 66...north pole, 64...line, 80...fixer, 334...developing roll, 334C...center, T0...developing position, δ1, δ2, δ3, δ4...gap, θ...angle

Claims

1. a developer carrier for holding a developer containing a toner and a carrier and supplied to an image carrier for forming an electrostatic latent image; a first member provided downstream of a development position where the developer held on the developer holder is supplied to the image holder; a second member having a surface facing the developer carrier between the developer carrier, the image carrier, and the first member, and to which an intermediate potential between a potential applied to the developer carrier and a potential applied to the first member is applied; A developing device comprising:

2. the developer carrier has a magnet for forming a brush including a developer carrier toward the center of the first member; 2. The developing device according to claim 1,

3. the magnet is disposed on the developer holder on the upstream side and downstream side of the magnet, and adjacent to magnets having a different magnetic pole from the magnet, 3. The developing device according to claim 2.

4. In a case where the toner of the opposite polarity attracted by the second member is collected by the developer that contacts the first member downstream of the position where the developer of the developer carrier is supplied, the developer comes into contact with the first member within a range in which each of the brushes on the upstream side and the downstream side with respect to the central direction forms a predetermined angle; 3. The developing device according to claim 2.

5. the intermediate potential of the second member is set such that a potential difference between a closer distance between the second member and the developer carrier and a longer distance between the second member and the first member is smaller than a potential difference between the closer distance between the second member and the developer carrier and a longer distance between the second member and the first member; 2. The developing device according to claim 1,

6. the setting is performed in accordance with a ratio of a distance between the second member and the developer carrier to a distance between the second member and the first member; 6. The developing device according to claim 5.

7. The second member is a polygon having an inclined surface.

2. The developing device according to claim 1,

8. the polygon has a surface facing the developer carrier at a position adjacent to the first member; 8. The developing device according to claim 7.

9. the surface facing the developer carrier extends toward the center of the first member; 9. The developing device according to claim 8.

10. the inclined surface is provided in a tangential direction of the developer carrier so that the distance between the developer carrier and the inclined surface does not change even when moving from one end of the inclined surface to the other end of the inclined surface; 8. The developing device according to claim 7.

11. an image carrier for forming an electrostatic latent image; a developing means for developing the electrostatic latent image formed on the image carrier into a toner image; a transfer means for transferring the toner image produced by the developing means onto a recording material; a fixing unit for fixing the toner image transferred onto the recording material onto the recording material; Including, The developing means is a developer carrier for holding a developer containing a toner and a carrier and supplied to an image carrier for forming an electrostatic latent image; a first member provided downstream of a development position where the developer held on the developer holder is supplied to the image holder; a second member having a surface facing the developer carrier between the developer carrier, the image carrier, and the first member, and to which an intermediate potential between a potential applied to the developer carrier and a potential applied to the first member is applied; An image forming apparatus comprising:

Images