Developing device

Abstract

This configuration provides a way to prevent the carrier from being collected by the duct 60. [Solution] The duct 60 has a suction port 60a for sucking up the developer scattered in the developing container 70, which is located downstream of the opposing portion 74 with respect to the rotational direction of the peeling sleeve 35. The duct 60 has a first duct wall 62 and a second duct wall 61 which are arranged to face a part of the peeling roller 32 with a gap between them. The peeling magnet 38 has a peeling pole 301 located downstream of the receiving pole 303 for peeling the developer from the peeling sleeve 35, and a transport pole 302 located downstream of the receiving pole 303 and upstream of the peeling pole 301, adjacent to the peeling pole 301. The peak position P1, which is the position of the maximum value of the normal component of the magnetic flux density of the peeling pole 301 on the peeling sleeve 35, is located downstream of the tip 62a on the suction port 60a side of the first duct wall 62 in the rotational direction of the peeling sleeve 35.

Description

[Technical Field]

[0001] The present invention relates to a developing apparatus for developing an electrostatic latent image formed on an image carrier using a developer. [Background technology]

[0002] A known developing apparatus includes a developing roller that develops an electrostatic latent image formed on an image carrier using a developer, and a peeling roller that peels and recovers the developer from the developing roller (Patent Document 1). The developing roller comprises a rotating developing sleeve and a non-rotating developing magnet placed inside the developing sleeve, and the developer is supported on the surface of the developing sleeve by the magnetic force of the developing magnet. Similarly, the peeling roller also comprises a rotating peeling sleeve and a non-rotating peeling magnet placed inside the peeling sleeve, and the developer is supported on the surface of the peeling sleeve by the magnetic force of the peeling magnet. The developer that has been supported and transported by the developing sleeve and developed the electrostatic latent image on the image carrier (used developer) is then supported on the surface of the peeling sleeve, and the developer is recovered from the developing roller by the peeling roller. Then, as the peeling sleeve rotates, the developer supported on the peeling sleeve is transported to the peeling position and the developer is peeled off the peeling sleeve. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2018-124338 [Overview of the project] [Problems that the invention aims to solve]

[0004] In the configuration described in Patent Document 1, the release sleeve rotates at the opposing portion facing the developing sleeve such that its surface moves in the opposite direction to the surface of the developing sleeve. At this time, during the process of transferring the developer from the developing sleeve to the release sleeve, there is a risk of toner scattering due to the tilting of the developer between the magnetic poles during transport as the release sleeve carries the developer received from the developing sleeve to the release position, and also due to toner scattering due to detachment during release.

[0005] In recent years, with the increasing speed of image forming machines, toner scattering from peeling rollers has become a problem, and many developing machines now include ducts to suck up the scattered toner within the developing unit. However, in such configurations, carriers scattered from the peeling roller along with the scattered toner are collected in the duct, which can cause the duct to become clogged with carriers. When carriers clog the duct in this way, the duct's ability to suck up scattered toner decreases, and there is a risk that toner scattering cannot be adequately suppressed.

[0006] The present invention aims to provide a configuration that can prevent carriers from being collected by the duct. [Means for solving the problem]

[0007] One aspect of the present invention includes a developing container for containing a developer containing toner and a carrier, a rotating developing sleeve, a developing roller for developing an electrostatic latent image formed on a rotating image carrier with the developer, the developing container having a developing container for containing a developer containing a toner and a carrier, a rotating developing sleeve, a developing magnet non-rotatingly positioned inside the developing sleeve and attracting the developer to the surface of the developing sleeve by magnetic force, a peeling sleeve for peeling off the developer from the developing roller after the electrostatic latent image on the image carrier has been developed by the developing roller, a peeling roller having a peeling magnet non-rotatingly positioned inside the peeling sleeve and attracting the developer to the surface of the peeling sleeve by magnetic force, and a suction port for sucking up scattered developer inside the developing container is located downstream of the opposing portion with respect to the rotation direction of the peeling sleeve, the duct extends downstream from the suction port in the rotation direction of the peeling sleeve and faces a part of the peeling roller with a gap between them. The developing apparatus comprises a duct having a first duct wall arranged so as to be positioned, and a second duct wall positioned opposite the first duct wall and forming a space between it and the first duct wall through which the developer drawn in from the suction port flows, wherein the developing magnet has a transfer pole which is a magnetic pole for transferring the developer from the developing roller to the peeling roller, and the peeling magnet has a receiving pole which is a magnetic pole for the peeling roller to receive the developer from the developing roller and is of the opposite pole to the transfer pole, a peeling pole which is a magnetic pole located downstream of the receiving pole with respect to the rotational direction of the peeling sleeve and for peeling the developer from the peeling sleeve, and a transport pole which is a magnetic pole located downstream of the receiving pole and upstream of the peeling pole with respect to the rotational direction of the peeling sleeve and adjacent to the peeling pole, wherein the peak position which is the position of the maximum value of the normal component of the magnetic flux density of the peeling pole on the peeling sleeve is located downstream of the tip of the first duct wall on the suction port side in the rotational direction of the peeling sleeve. [Effects of the Invention]

[0008] According to the present invention, it is possible to prevent the carrier from being collected by the duct. [Brief explanation of the drawing]

[0009] [Figure 1] Schematic cross-sectional view of the image forming apparatus according to the embodiment. [Figure 2] Schematic cross-sectional view of the developing device according to the embodiment. [Figure 3] Diagram showing the magnetic pole arrangement of the first developing roller according to the embodiment. [Figure 4] Diagram showing the magnetic pole arrangement of the second developing roller according to the embodiment. [Figure 5] Diagram showing the magnetic pole arrangement of the separation roller according to the embodiment. [Figure 6] Enlarged view of the periphery of the second developing roller, separation roller, and duct according to the embodiment. [Figure 7] Schematic cross-sectional view of the developing device according to the conventional example. [Figure 8] Enlarged view of the periphery of the separation roller showing the arrangement of the duct and the magnetic pole arrangement of the separation roller according to Example 1. [Figure 9] Enlarged view of the periphery of the separation roller showing the arrangement of the duct and the magnetic pole arrangement of the separation roller according to Comparative Example 1. [Figure 10] Enlarged view of the periphery of the separation roller showing the arrangement of the duct and the magnetic pole arrangement of the separation roller according to Example 2. [Figure 11] Graph showing the distribution of Fθ of the separation magnet near the tip of the first duct wall in Examples 1, 3, and 4. [Figure 12] Schematic cross-sectional view of the developing device according to Example 5. [Figure 13] Graph showing the distribution of Br near the separation pole of the separation magnet according to Example 5.

Embodiments for Carrying Out the Invention

[0010] The embodiments will be described with reference to FIGS. 1 to 6. First, the schematic configuration of the image forming apparatus of the present embodiment will be described with reference to FIG. 1.

[0011] [Image Forming Apparatus] The image forming apparatus 100 is a full-color image forming apparatus, and in this embodiment, for example, it is an MFP (Multi-Function Peripheral) having copy, printer, and scan functions. As shown in Figure 1, the image forming apparatus 100 is equipped with parallel image forming units PY, PM, PC, and PK, which each perform the image formation process for four toner colors: yellow, magenta, cyan, and black. In this embodiment, the image forming apparatus 100 is connected to the main body of the image forming apparatus (device body) by a document reading device or a host device such as a personal computer which is connected to the device body in a communication manner. Therefore, according to the image information from the host device, a four-color full-color image of yellow (Y), magenta (M), cyan (C), and black (K) can be formed on a recording material (recording paper, plastic sheet, cloth, etc.) using an electrophotographic method.

[0012] Each color image forming unit PY, PM, PC, and PK comprises a primary charger 21Y, 21M, 21C, 21K, a developing unit 1Y, 1M, 1C, 1K, an exposure unit 22Y, 22M, 22C, 22K, a photosensitive drum 28Y, 28M, 28C, 28K, and a cleaning unit 26Y, 26M, 26C, 26K. The image forming apparatus 100 also includes a transfer unit 2 and a fixing unit 3. Since the configurations of each color image forming unit PY, PM, PC, and PK are the same, the following explanation will use the image forming unit PY as a representative example.

[0013] The photosensitive drum 28Y, which serves as the image carrier, is a photoreceptor having a photosensitive layer made of a resin such as polycarbonate containing an organic photoconductor (OPC), and is configured to rotate at a predetermined speed. In this embodiment, the linear velocity of the surface of the photosensitive drum 28Y is set to 650 mm / s. The primary charger 21Y consists of corona discharge electrodes arranged around the photosensitive drum 28Y, and charges the surface of the photosensitive drum 28Y with the ions generated.

[0014] The exposure device 22Y incorporates a scanning optical device and, by exposing the photosensitive drum 28Y, which is charged based on image data, lowers the potential of the exposed area and forms a charge pattern (electrostatic latent image) corresponding to the image data. The developing device 1Y transfers the contained developer to the photosensitive drum 28Y and develops the electrostatic latent image formed on the photosensitive drum 28Y. The developer is a mixture of a carrier and toner corresponding to each color, and the electrostatic latent image is made visible by the toner.

[0015] The transfer device 2 includes primary transfer rollers 23Y, 23M, 23C, 23K, an intermediate transfer belt 24, and a secondary transfer roller 25. The intermediate transfer belt 24 is wound around the primary transfer rollers 23Y, 23M, 23C, 23K and multiple rollers and is supported so as to be able to move. The primary transfer rollers 23Y, 23M, 23C, 23K, which serve as primary transfer members, correspond to the colors Y (yellow), M (magenta), C (cyan), and K (black), respectively, from top to bottom in Figure 1. The secondary transfer roller 25 is positioned outside the intermediate transfer belt 24 and is configured so that the recording material can pass between it and the intermediate transfer belt 24.

[0016] The toner images of each color formed on the photosensitive drums 28Y, 28M, 28C, and 28K are sequentially transferred (primary transfer) onto the intermediate transfer belt 24 in the primary transfer section (primary transfer nip) T1 where the intermediate transfer belt 24 and the photosensitive drums 28Y, 28M, 28C, and 28K come into contact, by the action of a primary transfer bias applied to the primary transfer rollers 23Y, 23M, 23C, and 23K. For example, over time, when a four-color full-color image is created, the toner images are transferred onto the intermediate transfer belt 24 in order from the photosensitive drum 28Y, forming a color toner image with superimposed layers of yellow, magenta, cyan, and black.

[0017] Meanwhile, the recording material S, contained in the cassette 115 which serves as the recording material storage section, is transported to the transfer device 2 via the pickup roller 111 and the registration roller 112. The recording material S is transported to the secondary transfer section (nip section) T2, where the intermediate transfer belt 24 and the secondary transfer roller 25, which serves as the secondary transfer member, come into contact, in synchronization with the toner image on the intermediate transfer belt 24. The toner image formed on the intermediate transfer belt 24 is then secondarily transferred onto the recording material S in the secondary transfer section T2 by the action of the secondary transfer bias applied to the secondary transfer roller 25. The recording material on which the toner image has been transferred is then subjected to pressure and heat in the fixing device 3. This melts the toner on the recording material, fixing the color image to the recording material. After that, the recording material S is discharged from the machine.

[0018] When image formation is performed on both sides of the recording material, the recording material S that has passed through the fixing device 3 is transported to the inversion transport path 113, the inverted recording material S is transported to the registration roller 112 by the transport roller 114, and in the secondary transfer section T2, the toner image is transferred to the back surface of the recording material S in the same manner as described above. Then, the toner image is fixed to the back surface of the recording material S again in the fixing device 3.

[0019] After the primary transfer process, any toner or other deposits remaining on the photosensitive drums 28Y, 28M, 28C, and 28K are recovered by the cleaning devices 26Y, 26M, 26C, and 26K. This prepares the photosensitive drums 28Y, 28M, 28C, and 28K for the next image forming process. In addition, any toner or other deposits remaining on the intermediate transfer belt 24 after the secondary transfer process are removed by the intermediate transfer belt cleaner 29.

[0020] Furthermore, the image forming apparatus 100 of this embodiment can also form monochrome or multicolor images using a color image forming unit for a desired monochrome color or several of the four colors, such as a monochrome black image.

[0021] The developer storage units 27Y, 27M, 27C, and 27K are provided in accordance with the developing units 1Y, 1M, 1C, and 1K, respectively, and are loaded with replaceable bottles containing developer corresponding to the respective colors: yellow, magenta, cyan, and black, from top to bottom. The developer storage units 27Y, 27M, 27C, and 27K are configured to transport (replenish) the developer to the developing unit 1Y, 1M, 1C, and 1K corresponding to the color of the developer stored in them.

[0022] For example, the toner weight ratio of the developer stored in the bottle is 80-95%, while the toner weight ratio of the developer in developing units 1Y, 1M, 1C, and 1K is 5-10%. Therefore, when toner is consumed by developing in developing units 1Y, 1M, 1C, and 1K, developer containing an amount of toner corresponding to the consumption is replenished, and the toner weight ratio of the developer in developing units 1Y, 1M, 1C, and 1K is maintained at a constant level.

[0023] [Developing equipment] Next, developing units 1Y, 1M, 1C, and 1K will be described in detail using Figures 2 to 5. Since the configurations of developing units 1Y, 1M, 1C, and 1K are the same, developing unit 1Y will be described as a representative unit below. Figure 2 is a conceptual diagram illustrating developing unit 1Y shown in Figure 1, and Figures 3, 4, and 5 are conceptual diagrams illustrating the magnetic pole configuration of the first developing magnet (first magnet) 36, the second developing magnet (second magnet) 37, and the peeling magnet (third magnet) 38 arranged within developing unit 1Y.

[0024] As shown in Figure 2, the developing apparatus 1Y includes a first developing roller 30, a second developing roller 31, a stripping roller 32, a developer supply screw 42, a developer stirring screw 43, and a developer recovery screw 44, all of which are housed in a developing container 70. The developing container 70 contains a two-component developer containing a non-magnetic toner and a magnetic carrier.

[0025] The first developing roller 30 is a rotating developer carrier, positioned adjacent to the photosensitive drum 28Y, such that its axis of rotation is approximately parallel to the axis of rotation of the photosensitive drum 28Y. The first developing roller 30 includes a rotating first developing sleeve 33 and a first developing magnet (fixed magnet) 36 that is non-rotatingly positioned inside the first developing sleeve 33 and attracts the developer to the surface of the first developing sleeve 33 by magnetic force. The first developing roller 30 then attracts (carries) the developer drawn up from the developer supply screw 42 based on magnetic force and develops the electrostatic latent image formed on the rotating photosensitive drum 28Y (on the image carrier) with the developer.

[0026] Specifically, the first developing sleeve 33 and the second developing sleeve 34 (described later) of the developing device 1Y are subjected to a DC developing bias with the same polarity as the charging polarity of the primary charger 21Y, or a developing bias in which an AC voltage is superimposed with a DC voltage of the same polarity as the charging polarity of the primary charger 21Y. As a result, inverse development is performed in which toner charged with the same polarity as the charging polarity of the primary charger 21Y is deposited onto the electrostatic latent image formed on the photosensitive drum 28Y by the exposure device 22Y. In this embodiment, the charging polarity of the primary charger 21Y and the DC voltage of the developing bias are set to negative, and inverse development is performed in which negatively charged toner is deposited onto the electrostatic latent image.

[0027] The first developing sleeve 33 is a non-magnetic cylindrical member with an outer diameter of 25 mm (radius r1 = 12.5 mm) and is rotationally driven around a rotation axis 39. The rotation direction of the first developing sleeve 33 is clockwise, as indicated by the arrow in Figure 2, and in this embodiment, it is opposite to the rotation direction of the photosensitive drum 28Y. Therefore, the first developing sleeve 33 and the photosensitive drum 28Y rotate in the same direction (forward direction) at opposing positions (opposing parts). That is, the first developing sleeve 33 rotates such that the surface facing the photosensitive drum 28Y moves from the bottom vertically upward.

[0028] In this embodiment, the linear velocity on the surface of the first developing sleeve 33 is set to 1.0 times (=650 mm / s) the linear velocity on the surface of the photosensitive drum 28Y. Keeping the ratio of the linear velocity on the surface of the first developing sleeve 33 to the linear velocity on the surface of the photosensitive drum 28Y to approximately 1.0 to 1.2 times is advantageous in terms of toner degradation. On the other hand, there is a concern that the amount of toner supplied to the photosensitive drum 28Y will decrease, affecting the developability. However, this embodiment is equipped with two developing rollers 30 and 31, making it possible to maintain the amount of toner supplied to the photosensitive drum 28Y even when the linear velocity ratio is reduced.

[0029] The first developing magnet 36 is positioned inside the first developing sleeve 33 and has multiple magnetic poles 101 to 107, as shown in Figure 3. A space is provided between the inner circumference of the first developing sleeve 33 and the outer circumference of the first developing magnet 36 to allow rotation of the first developing sleeve 33.

[0030] The developer adsorbed on the first developing sleeve 33 is transported toward the photosensitive drum 28Y by the rotation of the first developing sleeve 33, and develops the latent image formed on the photosensitive drum 28Y. After developing the latent image formed on the photosensitive drum 28Y, the developer on the first developing sleeve 33 is transported toward the vicinity of the second developing roller 31 by the rotation of the first developing sleeve 33. Then, near the closest proximity point between the first developing roller 30 and the second developing roller 31, the developer is detached from the first developing sleeve 33 by the magnetic fields generated by the first developing magnet 36 contained in the first developing roller 30 and the second developing magnet 37 contained in the second developing roller 31, and the developer is transferred to the second developing sleeve 34. The first developing sleeve 33 and the second developing sleeve 34 are positioned with a 3 mm gap at their closest contact point.

[0031] The second developing roller 31, acting as a developing roller, is a rotating developer carrier positioned downstream of the first developing roller 30 in the direction of rotation of the photosensitive drum 28Y, and above the center of rotation of the first developing roller 30 in the vertical direction. Developer is transferred from the first developing roller 30 to the second developing roller 31 by magnetic force. Similar to the first developing roller 30, the second developing roller 31 is positioned adjacent to the photosensitive drum 28Y, with its axis of rotation approximately parallel to the axis of rotation of the photosensitive drum 28Y. Therefore, the axes of rotation of the second developing roller 31 and the first developing roller 30 are approximately parallel to each other.

[0032] Such a second developing roller 31 includes a rotating second developing sleeve 34 and a second developing magnet (fixed magnet) 37 that is positioned non-rotating inside the second developing sleeve 34 and attracts the developer to the surface of the second developing sleeve 34 by magnetic force. The second developing roller 31 receives the developer from the first developing roller 30 (first developing sleeve 33) based on magnetic force, attracts (carries) the developer, and develops the electrostatic latent image formed on the rotating photosensitive drum 28Y with the developer. A peeling roller 32, which will be described later, is located to the side of the second developing roller 31.

[0033] The second developing sleeve 34 is a non-magnetic cylindrical member with an outer diameter of 25 mm (radius r2 = 12.5 mm) and is rotationally driven around the rotation axis 40. The rotation direction of the second developing sleeve 34 is clockwise, as indicated by the arrow in Figure 2, and in this embodiment, it is opposite to the rotation direction of the photosensitive drum 28Y. Therefore, the second developing sleeve 34 and the photosensitive drum 28Y rotate in the same direction (forward direction) at opposing positions (opposing parts). That is, the second developing sleeve 34 rotates such that the surface facing the photosensitive drum 28Y moves from the bottom vertically upward. Also, the second developing sleeve 34 and the first developing sleeve 33 rotate in opposite directions at opposing positions. In this embodiment, the linear velocity of the surface of the second developing sleeve 34 is set to be 1.2 times (= 780 mm / s) the linear velocity of the surface of the photosensitive drum 28Y.

[0034] The second developing magnet 37 is located inside the second developing sleeve 34 and has, for example, a plurality of fan-shaped magnetic poles 201 to 207. A space is provided between the inner circumference of the second developing sleeve 34 and the outer circumference of the second developing magnet 37 to allow rotation of the second developing sleeve 34.

[0035] The developer adsorbed on the second developing sleeve 34 is transported toward the photosensitive drum 28Y by the rotational movement of the second developing sleeve 34, and develops the latent image formed on the photosensitive drum 28Y. After developing the latent image formed on the photosensitive drum 28Y, the developer remaining in the second developing sleeve 34 is transported toward the vicinity of the peeling roller 32 by the rotational movement of the second developing sleeve 34. Then, near the closest proximity position between the second developing roller 31 and the peeling roller 32, the developer is transferred from the second developing sleeve 34 to the peeling sleeve 35 of the peeling roller 32 by the magnetic fields generated by the second developing magnet 37 contained in the second developing roller 31 and the peeling magnet 38 contained in the peeling roller 32.

[0036] The peeling roller (recovery roller) 32 is positioned on the opposite side of the photosensitive drum 28Y from the rotation center of the second developing sleeve 34, and peels off the developer from the second developing roller 31 after the electrostatic latent image on the photosensitive drum 28Y has been developed by the second developing roller 31. Specifically, the peeling roller 32 is a rotating developer carrier, and is positioned between the second developing roller 31 and the developer recovery screw 44 such that its rotation center is above the rotation center of the second developing roller 31.

[0037] Furthermore, the peeling roller 32 is positioned such that its axis of rotation is approximately parallel to the axis of rotation of the second developing roller 31. This peeling roller 32 includes a rotating peeling sleeve 35 and a peeling magnet (fixed magnet) 38 that is positioned non-rotating inside the peeling sleeve 35 and attracts the developer to the surface of the peeling sleeve 35 by magnetic force, and is configured to transfer the developer from the second developing roller 31 based on magnetic force.

[0038] The peeling sleeve 35 is a non-magnetic cylindrical member with an outer diameter of 18 mm (radius of 9 mm) and is rotationally driven around the rotation axis 41. The rotation direction of the peeling sleeve 35 is clockwise, as indicated by the arrow in Figure 2, and in this embodiment, it is the same direction as the rotation direction of the second developing sleeve 34. Therefore, the peeling sleeve 35 and the second developing sleeve 34 rotate in opposite directions at their opposing positions (opposing parts). That is, the peeling sleeve 35 rotates such that its surface moves in the opposite direction to the surface of the second developing sleeve 34 at the opposing part facing the second developing sleeve 34.

[0039] The peeling magnet 38 is positioned inside the peeling sleeve 35 and has, for example, multiple magnetic poles 301 to 305. A space is provided between the inner circumference of the peeling sleeve 35 and the outer circumference of the peeling magnet 38 to allow rotation of the peeling sleeve 35.

[0040] The developer adsorbed onto the peeling sleeve 35 is transported downstream in the direction of rotation by the rotational movement of the peeling sleeve 35, and at a position close to the developer recovery screw 44, it is peeled off from the peeling sleeve 35 by the peeling magnet 38 enclosed in the peeling roller 32 and falls by its own weight toward the guide member 45 located vertically below. The developer that falls toward the guide member 45 is then guided by its own weight toward the developer recovery screw 44.

[0041] The guide member 45 and the developer recovery screw 44 constitute a developer recovery section 47, which is a recovery section for recovering the developer peeled off from the peeling sleeve 35 on the peeling roller 32. In the developer recovery section 47, the developer recovery screw 44 is located below the center of rotation of the peeling roller 32 in the vertical direction and conveys the developer received (recovered) from the peeling roller 32 while agitating it.

[0042] The guide member 45, acting as a guide, is positioned vertically below the rotation center of the peeling roller 32, and vertically above the center of the rotation axis 40 of the second developing roller 31 (rotation center) at the position on the guide member 45 where the guide member 45 and the peeling roller 32 are closest (nearest contact position C). The guide member 45 guides the developer peeled off by the peeling roller 32 toward the developer recovery screw 44. Such a guide member 45 has a slope 45a to allow the developer to slide down by its own weight, in order to more reliably guide the peeled developer toward the developer recovery screw 44. The slope 45a is inclined horizontally such that the developer recovery screw 44 side is lower than the position below the peeling roller 32.

[0043] The developer recovery screw 44, which serves as both a recovery member and a transport unit, transports the recovered developer to the developer circulation unit 46, which will be described below. In other words, the developer recovery screw 44 is a screw transport member used to transport the developer that has slid down the slope of the guide member 45 in one direction while agitating it.

[0044] The developer circulation unit 46 is a supply unit for supplying developer to the first developing roller 30, and the developer circulation unit 46 includes a regulating member 50, a developer supply screw 42, and a developer stirring screw 43. In the developer circulation unit 46, the developer is supplied to the first developing roller 30 while being agitated in the developer supply screw 42 and the developer stirring screw 43 and transported in a substantially horizontal direction. Also, as described above, the developer recovered by the developer recovery unit 47 falls by its own weight and is introduced into the developer circulation unit 46. That is, the developer circulation unit 46 is located below the developer recovery unit 47 in the vertical direction.

[0045] The developer supply screw 42, developer agitation screw 43, and developer recovery screw 44 are screw conveying members that convey the developer in one direction while agitating it. The developer supply screw 42 and developer agitation screw 43 are located below the rotation center of the developer recovery screw 44 in the vertical direction. Furthermore, these developer supply screw 42, developer agitation screw 43, and developer recovery screw 44 are arranged so that their rotation axes are approximately parallel to each other. The rotation axis of each of these screws is also approximately parallel to the rotation axis of the first developing roller 30.

[0046] The developer supply screw 42 is located between the first developing roller 30 and the developer agitation screw 43, and a partition wall 48 of the developing container 70 is positioned between the developer supply screw 42 and the developer agitation screw 43. The partition wall 48 of the developing container 70 extends along the rotation axis direction of the developer supply screw 42 and the developer agitation screw 43. The partition wall 48 is provided with a communication opening (not shown) that connects a first transport path 71 through which the developer is transported by the developer supply screw 42 and a second transport path 72 through which the developer is transported by the developer agitation screw 43.

[0047] The developer, agitated by the developer recovery screw 44, passes through a communication opening (not shown) formed in the partition wall 73 of the developing container 70 located between the developer recovery screw 44 and the developer supply screw 42, and falls towards the developer supply screw 42 by its own weight. The guide member 45 described above is formed integrally with the partition wall 73, and the developer recovery screw 44 is positioned above the partition wall 73.

[0048] The location of the communication port through which the developer agitated by the developer recovery screw 44 falls by its own weight and is introduced into the developer circulation section 46 is preferably positioned to avoid the area where the developer is supplied toward the first developing roller 30 (the intermediate portion with respect to the rotation axis direction of the developer supply screw 42). In this embodiment, the location of the communication port is set to include the downstream end (terminal end) in the developer transport direction of the first transport path 71 where the developer supply screw 42 is located.

[0049] The developer transport directions of the developer supply screw 42 and the developer agitation screw 43 are opposite to each other. The starting end (upstream end in the developer transport direction) and ending end (downstream end in the developer transport direction) of the first transport path 71 where the developer supply screw 42 is located, and the ending end and starting end of the second transport path 72 where the developer agitation screw 43 is located, are in communication via a communication port provided in the partition wall 48. Therefore, the developer circulates in the rotational direction of the developer supply screw 42 and the developer agitation screw 43, as indicated by the arrows in Figure 2, and in a substantially horizontal direction within the developing container 70, with a portion of it being supplied toward the first developing roller 30.

[0050] The developer supply port 51 (see Figure 2) is located above the developer agitation screw 43 in the developing container 70 and is connected to the developer storage section 27Y (see Figure 1). The developer supply port 51 is configured to supply the developer stored in the bottle loaded in the developer storage section 27Y to the second transport path 72 where the developer agitation screw 43 is located.

[0051] As described above, the toner weight ratio of the developer stored in the bottles of the developer storage unit 27Y is greater than the toner weight ratio of the developer in the developing device 1Y. Therefore, by adjusting the amount of developer supplied to the developer stirring screw 43, it is possible to maintain a constant toner weight ratio of the developer in the developing device 1.

[0052] The toner concentration detection sensor 49 (see Figure 2) is positioned to detect the toner concentration in the developer contained in the developer circulation unit 46. The toner concentration detection sensor 49 is a sensor that detects the magnetic permeability of the developer. The toner concentration corresponds to the amount of toner consumed in the developing device 1Y and is used to control the replenishment of developer from the developer storage unit 27Y. For example, if it is detected that the toner concentration has fallen below a predetermined value, developer is replenished from the developer storage unit 27Y. Since the magnetic permeability of the developer changes more than the toner concentration, it is possible to detect the toner concentration using the magnetic permeability.

[0053] The regulating member 50 is positioned adjacent to the first developing roller 30 and is used to regulate the amount of developer supplied from the developer circulation unit 46 to the first developing roller 30. The regulating member 50 can be configured to regulate the amount of developer adsorbed onto the first developing roller 30 based, for example, on the gap between the surface of the first developing sleeve 33 of the first developing roller 30 and the end of the regulating member 50.

[0054] The developer in the developing container 70 is transported in a substantially horizontal direction while being agitated in the developer circulation unit 46, and then supplied to the first developing roller 30. From the first developing roller 30, it is transferred to the upper second developing roller 31 based on magnetic force. Next, it is transferred from the second developing roller 31 to the peeling roller 32 on the side of the second developing roller 31, again based on magnetic force. After being peeled off the peeling roller 32 by a peeling magnet 38 embedded in the peeling roller 32, it is collected in the developer recovery unit 47 and then introduced back into the developer circulation unit 46.

[0055] Furthermore, as described above, in this embodiment, a two-component development method is used as the development method, and the developer is a mixture of a negatively charged non-magnetic toner and a magnetic carrier. The non-magnetic toner becomes negatively charged by triboelectric charging with the magnetic carrier, and the magnetic carrier becomes positively charged. The non-magnetic toner is made by encapsulating colorants, wax components, etc., in a resin such as polyester or styrene acrylic, and then crushing or polymerizing it into a powder, to which fine powders such as titanium dioxide and silica are added to the surface. The magnetic carrier is made by coating the surface of a core consisting of resin particles mixed with ferrite particles or magnetic powder with resin. In this embodiment, the toner concentration in the developer in the initial state (weight ratio of toner contained in the developer) is 8%.

[0056] Furthermore, the magnetic carriers are 40-80 Am at an applied magnetic field of 1000 Oersted. 2It is preferable to have a magnetization amount per unit weight of / kg. Reducing the magnetization amount of the magnetic carrier has the effect of suppressing scavenging by the magnetic brush, but it becomes difficult for the magnetic field generating part to adhere to the non-magnetic cylinder, which may cause image defects such as magnetic carrier adhesion to the photosensitive drum. Also, if the magnetization amount of the magnetic carrier is greater than the above range, image defects may occur due to the pressure of the magnetic brush as described above. In this embodiment, 63Am 2 Magnetic carriers with a magnetization amount per unit weight of / kg were used. The magnetization amount of the magnetic carriers was measured using a BHV-30 oscillating magnetic field type automatic magnetic property recorder manufactured by RIKEN Electron Co., Ltd. The magnetic property value of the magnetic carriers was determined by creating an external magnetic field of 1000 oorsted and determining the magnetization strength at that time. The magnetic carriers were packed tightly in a cylindrical plastic container. In this state, the magnetization moment was measured, and the actual weight with the sample placed inside was measured to determine the magnetization strength (Am 2 / kg).

[0057] The true specific gravity of the magnetic carrier is determined using a dry-type automatic density analyzer, AccuPic 1330, manufactured by Shimadzu Corporation. In this embodiment, the true specific gravity (density) is 4.6 g / cm³. 3 A magnetic carrier of the specified type was used. Furthermore, a magnetic carrier with a weight-average diameter of 35 μm (radius b = 17.5 μm) was employed.

[0058] Generally, two-component development systems using toner and carriers have the advantage of less stress on the toner than one-component development systems using a single-component developer, because they charge both the toner and carrier to a predetermined polarity by frictional contact. On the other hand, with prolonged use, the amount of dirt (spent) adhering to the carrier surface increases, and as a result, the ability to charge the toner gradually decreases. This results in problems such as fogging and toner scattering. Increasing the amount of carrier contained in the development unit could be considered to extend the lifespan of the two-component development unit, but this is undesirable because it would lead to a larger development unit.

[0059] To resolve the above-mentioned problems related to two-component developers, this embodiment employs an ACR (Auto Carrier Refresh) method. The ACR method is a method that suppresses the increase of degraded carriers by gradually supplying new developer from the developer storage unit 27Y into the developing device 1Y, and gradually discharging the developer with degraded charging performance from the discharge port (not shown) of the developing device 1Y. As a result, the degraded carriers in the developing device 1Y are gradually replaced with new carriers, making it possible to maintain the charging performance of the carriers in the developing device 1Y at a roughly constant level.

[0060] In the developing apparatus 1Y of this embodiment, the developer in the first transport path 71 is supplied to the first developing sleeve 33 by the developer supply screw 42. The developer supplied to the first developing sleeve 33 is carried on the first developing sleeve 33 in a predetermined amount by the magnetic field generated by the first developing magnet 36, forming a developer reservoir. As the first developing sleeve 33 rotates, the two-component developer on the first developing sleeve 33 passes through the developer reservoir and is thinly coated onto the surface of the first developing sleeve 33 by the regulating member 50, and then transported to the developing area facing the photosensitive drum 28Y. In the developing area, the developer on the first developing sleeve 33 rises up to form a magnetic pile.

[0061] In the first developing region where the first developing sleeve 33 and the photosensitive drum 28Y face each other, the developing bias applied to the first developing sleeve 33 makes the electrostatic latent image formed on the photosensitive drum 28Y visible. In this embodiment, the developing bias applied to the first developing sleeve 33 is a waveform in which both AC and DC electric fields are superimposed, but a developing bias of only a DC electric field may also be used.

[0062] The two-component developer is subjected to the development process in the first development area, then transferred to the second development sleeve 34 at a position close to the second development sleeve 34, and transported to the second development area opposite the second development sleeve 34 and the photosensitive drum 28Y. In the second development area, the same development bias as in the first development area is applied, and the toner image is uniformly adjusted by developing and supplementing the toner that is insufficient relative to the potential of the electrostatic latent image on the photosensitive drum 28Y, and recovering the toner that has been developed in excess. Here, the development bias applied to the first development sleeve 33 and the development bias applied to the second development sleeve 34 may have different waveforms.

[0063] The developer that has passed through the second developing region is then peeled off in the peeling magnetic field region formed by the second developing magnet 37 enclosed in the second developing sleeve 34. The developer peeled off from the second developing sleeve 34 is attracted to the surface of the peeling sleeve 35 by the magnetic field formed by the peeling magnet 38 enclosed in the peeling sleeve 35 of the peeling roller 32, and is conveyed along the rotational direction of the peeling sleeve 35. Then, due to the peeling magnetic field formed by the peeling magnet 38, it detaches from the surface of the peeling sleeve 35 and is collected in the developer recovery unit 47.

[0064] [About the magnetic poles of each magnet] Next, the magnetic pole configurations of the first developing magnet 36, the second developing magnet 37, and the peeling magnet 38, which are enclosed within the first developing roller 30, the second developing roller 31, and the peeling roller 32 shown in Figures 3, 4, and 5, will be described.

[0065] As shown in Figure 3, the first developing magnet 36 enclosed in the first developing roller 30 has multiple magnetic poles 101 (S1), 102 (N2), 103 (S2), 104 (N3), 105 (S3), 106 (N4), and 107 (N1) (S and N in parentheses indicate whether the magnetic pole is an S pole or an N pole, and the numbers are added to distinguish it from other magnetic poles. In this embodiment, the first developing magnet 36 has a total of 7 magnetic poles. The same applies to Figures 4 and 5). Of these, magnetic pole 106 is a transfer pole for transferring developer from the first developing roller 30 to the second developing roller 31. The magnetic poles 101 to 107 are arranged in numerical order in the rotational direction of the first developing sleeve 33.

[0066] Magnetic pole 106 is a magnetic pole that transfers developer from the first developing sleeve 33 to the second developing sleeve 34 by a magnetic field generated in conjunction with the second developing magnet 37 of the second developing roller 31, and may hereafter be referred to as the transfer pole 106. Magnetic pole 107 is an N pole and is used to attract the developer supplied from the developer supply screw 42 onto the first developing sleeve 33. Magnetic poles 101, 102, 103, 104 and 105 are S poles, N poles, S poles, N poles and S poles, and are used to transport the developer attracted by magnetic pole 107 upward as the first developing sleeve 33 rotates. Magnetic pole 106 is an N pole and, as described above, transfers developer from the first developing sleeve 33 to the second developing sleeve 34 facing the first developing sleeve 33 by a magnetic field generated in conjunction with magnetic pole 201 in the second developing magnet 37 enclosed in the second developing roller 31.

[0067] Furthermore, in this embodiment, a low-magnetic-force portion 110 is formed by a repulsive magnetic field generated in cooperation between a magnetic pole 107, which is positioned downstream of the magnetic pole 106 with respect to the rotational direction of the first developing sleeve 33 and is the same pole as the magnetic pole 106, and the magnetic pole 107, which is the same pole as the magnetic pole 106. This low-magnetic-force portion 110 facilitates the transfer of developer from the first developing sleeve 33 to the second developing sleeve 34. In this embodiment, the low-magnetic-force portion 110 has almost no magnetic force, but it may have a low magnetic force, for example, its magnetic force (the absolute value of the normal component Br of the magnetic flux density) may be 10 mT or less, or even 5 mT or less. The same applies to the low-magnetic-force portion 210 of the second developing magnet 37 shown in Figure 4, and the low-magnetic-force portion 310 of the peeling magnet 38 shown in Figure 5.

[0068] As shown in Figure 4, the second developing magnet 37 enclosed in the second developing roller 31 has multiple magnetic poles 201 (S4), 202 (N5), 203 (S5), 204 (N6), 205 (S6), 206 (N7), and 207 (S7) (a total of 7 poles). Of these, magnetic pole 201 is the receiving pole for the second developing roller 31 to receive developer from the first developing roller 30. Magnetic poles 201 to 207 are arranged in numerical order in the rotational direction of the second developing sleeve 34.

[0069] Magnetic pole 201 is a magnetic pole that attracts developer from the first developing sleeve 33 to the second developing sleeve 34 by the magnetic field generated in conjunction with the magnetic pole 107 of the first developing magnet 36 of the first developing roller 30, and may hereafter be referred to as the receiving pole 201. Magnetic pole 207 is a magnetic pole that transfers developer from the second developing sleeve 34 to the peeling sleeve 35 by the magnetic field generated in conjunction with the peeling magnet 38 of the peeling roller 32, and may hereafter be referred to as the transfer pole 207.

[0070] Furthermore, magnetic pole 201 is a south pole, opposite to magnetic pole 106, and is used to attract developer from the first developing roller 30 (first developing sleeve 33) onto the second developing sleeve 34, as described above. Magnetic poles 202, 203, 204, 205, and 206 are north poles, south poles, north poles, south poles, and north poles, and are used to transport the developer attracted by magnetic pole 201 upward as the second developing sleeve 34 rotates. Magnetic pole 207, acting as a transfer pole, is a south pole, and the developer that has passed through the developing area with the photosensitive drum 28Y corresponding to magnetic pole 203 is transferred from the second developing sleeve 34 to the peeling sleeve 35 facing the second developing sleeve 34 by a magnetic field generated in conjunction with magnetic pole 303 in the peeling magnet 38 enclosed in the peeling roller 32.

[0071] Furthermore, in this embodiment, a low-magnetic-force portion 210 is formed by a repulsive magnetic field generated in cooperation between a magnetic pole 207, which is positioned upstream of the magnetic pole 201 with respect to the rotational direction of the second developing sleeve 34 and is the same pole as the magnetic pole 201, and the magnetic force of the magnetic pole 207. This low-magnetic-force portion 210 facilitates the transfer of developer from the first developing sleeve 33 to the second developing sleeve 34. In addition, the low-magnetic-force portion 210 prevents the developer from being attracted to the closest point between the first developing sleeve 33 and the second developing sleeve 34, thereby suppressing the pressure on the developer.

[0072] As shown in Figure 5, the peeling magnet 38 enclosed in the peeling roller 32 has multiple magnetic poles 301 (N8), 302 (S8), 303 (N9), 304 (S9), and 305 (N10) (a total of 5 poles). The magnetic poles 301 to 305 are arranged in numerical order in the rotational direction of the peeling sleeve 35.

[0073] The magnetic pole 303, acting as a receiving pole, is a magnetic pole that attracts developer from the second developing sleeve 34 to the peeling sleeve 35 by the magnetic field generated in conjunction with the magnetic pole 207 of the second developing magnet 37 of the second developing roller 31, and may hereafter be referred to as the receiving pole 303. The magnetic pole 303 is an N pole, opposite to the magnetic pole 207, and is used to attract the developer peeled from the second developing sleeve 34 to the peeling sleeve 35 as described above. The magnetic poles 301, 302, and 304 are N pole, S pole, and S pole, and are used to transport the developer on the peeling sleeve 35 as the peeling sleeve 35 rotates. In particular, the magnetic pole 302 is used to transport the developer attracted by the magnetic pole 303 upward as the peeling sleeve 35 rotates. Hereafter, the magnetic pole 302 may be referred to as the transport pole 302. The magnetic pole 301 is a north pole and is a peeling pole used to peel off the developer adsorbed on the peeling sleeve 35 from the peeling sleeve 35 by the repulsive magnetic field generated in conjunction with the same pole, magnetic pole 305. Hereafter, it may be referred to as the peeling pole 301. A low-magnetic-force portion 310, in which the magnetic force is lower than that of magnetic pole 301, is formed between magnetic pole 301 and magnetic pole 305.

[0074] [duct] Next, we will describe the duct 60, which is a suction cleaning configuration for scattered toner generated by the second developing roller 31 and the peeling roller 32. Figure 6 is a cross-sectional view illustrating the arrangement of the second developing roller 31, the peeling roller 32, and the duct (scattered toner collection duct) 60 in this embodiment. The developing apparatus 1Y includes a duct 60 having a first duct wall 62 and a second duct wall 61, and an air suction device 69 (see Figure 2).

[0075] The first duct wall 62 covers a portion of the internal space of the developing container 70, where the first developing roller 30, the second developing roller 31, and the peeling roller 32 are installed and the developer is stored, preventing the developer from scattering from the internal space to the outside. In this embodiment, the first duct wall 62 covers the area above the peeling roller 32 and the developer recovery section 47. Specifically, the first duct wall 62 has a first wall portion 62b located above the vertical apex of the peeling roller 32, and a second wall portion 62c extending from the first wall portion 62b toward the upstream side in the rotational direction of the peeling sleeve 35, and positioned closer to the peeling roller 32 than the first wall portion 62b. That is, in this embodiment, the first duct wall 62 extends from a position above the peeling roller 32 toward the upstream side in the rotational direction of the peeling sleeve 35, and is formed to bend diagonally downward along the way. Furthermore, the end of the second wall portion 62c opposite to the first wall portion 62b is the end portion 62a of the first duct wall 62 on the side of the suction port 60a.

[0076] As described above, the first duct wall 62 covers the upper part of a portion of the internal space of the developing container 70, but a second duct wall 61 is provided on the outside of the first duct wall 62. In this embodiment, the second duct wall 61 constitutes a part of the outer wall of the developing container 70, but it may be separate from the outer wall of the developing container 70. The second duct wall 61 extends above the second developing roller 31, with its tip facing the photosensitive drum 28Y with a gap between them, and covering the area above the second developing roller 31. Specifically, the second duct wall 61 extends further toward the second developing roller 31 (developing roller side) than the tip 62a on the suction port 60a side of the first duct wall 62. In this embodiment, the second duct wall 61 extends from vertically above the first duct wall 62 to a position facing the second developing roller 31.

[0077] Furthermore, above the second developing roller 31, a suction port 60a of the duct 60, which consists of the first duct wall 62 and the second duct wall 61, is provided. Specifically, the suction port 60a is an opening at one end of the duct 60, formed between the tip 62a of the first duct wall 62 and a part of the second duct wall 61. With respect to the rotational direction of the peeling roller 32, the suction port 60a is located downstream of the opposing portion 74 where the second developing roller 31 and the peeling roller 32 face each other.

[0078] At the other end of duct 60, the ducts for each color developing device merge and are connected to an air suction device 69. The air suction device 69 is, for example, a fan, and by driving the air suction device 69, the developer that has been scattered inside the developing container during developing is sucked out through the duct 60 and the suction port 60a. This reduces the amount of developer that is scattered from inside the developing container 70 to the outside. When the image forming operation is performed, the air suction device 69 is operated to suck up the scattered developer. This suction operation is performed continuously during image forming.

[0079] As shown in Figure 6, the first duct wall 62 is positioned along the peeling roller 32. That is, the first duct wall 62 extends from the suction port 60a downstream in the rotational direction of the peeling sleeve 35 and is positioned opposite a part of the peeling roller 32 with a gap in between. Furthermore, the first duct wall 62 extends from the position opposite the peeling roller 32 to cover the area above the developer recovery section 47. Therefore, the suction path of the duct 60 is provided on the opposite side of the peeling roller 32, with the first duct wall 62 in between. In this embodiment, the nearest distance A between the peeling roller 32 and the first duct wall 62 is set to 1.5 mm.

[0080] The nearest proximity distance A is preferably in the range of 0.5 mm to 20 mm from the viewpoint of carrier recovery into the duct 60 and developer retention, as described later. In this embodiment, it is preferable that the nearest proximity distance A between the second wall portion 62c of the first duct wall 62 and the peeling roller 32 be 0.5 mm to 20 mm. If the nearest proximity distance A is large, the carrier is more easily recovered by the duct 60, and the duct 60 is more likely to become clogged with the carrier. Also, if the nearest proximity distance A is small, the developer will accumulate, making it difficult for the peeling roller 32 to properly transport the developer. In this case, backflow of the developer will occur, and the developer will return to the opposing portion 74, which can cause the developer to be carried around to the second developing roller 31, making image defects more likely. For this reason, it is preferable that the nearest proximity distance A between the peeling roller 32 and the duct 60 be 0.5 mm to 20 mm.

[0081] [Conventional example] Figure 7 shows the configuration of a conventional developing apparatus described in Patent Document 1. Similar to this embodiment, the conventional configuration also includes a first developing roller 30A, a second developing roller 31A, a stripping roller 32A, a developer supply screw 42A, a developer stirring screw 43A, and a developer recovery screw 44A. Furthermore, the first developing roller 30A, the second developing roller 31A, and the stripping roller 32A rotate in the direction of the arrows. However, unlike this embodiment, the conventional configuration does not have a duct 60 for sucking up the developer. Therefore, there is a risk that the developer scattered inside the developing container may scatter outside the developing container. This could lead to contamination of the image forming apparatus 100 with the developer, and furthermore, contamination of the output image.

[0082] [Regarding the suction and cleaning of scattered toner and clogging of the scattered toner carrier] Next, the relationship between the suction of scattered toner by the duct 60 and the clogging of the scattered carrier in the duct 60 will be explained using Figure 6. In this embodiment, as described above, the developer in the developing apparatus 1Y moves from the first developing sleeve 33 of the first developing roller 30 to the second developing sleeve 34 of the second developing roller 31, and then moves to the peeling sleeve 35 of the peeling roller 32. In recent years, image forming apparatuses have become faster, and the rotation speeds of the first developing roller 30, the second developing roller 31, and the peeling roller 32 have also increased. As a result, when the developer is transported on each sleeve, if the magnetic heads fall over between the magnetic poles, toner and carriers are more likely to detach from the sleeves and scatter. Therefore, in this embodiment, as a measure against toner scattering, the duct 60 is provided above the second developing roller 31 and the peeling roller 32, as described above. The scattered toner is then collected by the duct 60.

[0083] Furthermore, as described above, the high-speed rotation of the second developing sleeve 34 and the peeling sleeve 35 generates airflow, and carriers detached by centrifugal force, etc., are scattered by the airflow. The airflow flows in the direction of rotation of each sleeve, and the airflow near the peeling sleeve 35 flows along the direction of rotation of the peeling sleeve 35. The scattered carriers move along this flow and are sucked into the duct 60. Carriers sucked into the duct 60 can cause clogging of the duct 60, leading to a decrease in the efficiency of toner recovery. For this reason, it is necessary to suppress the recovery of carriers into the duct 60.

[0084] [Example 1] In this embodiment, Example 1, which is an example of a configuration that suppresses the scattering of carriers as described above, will be explained with reference to Figure 8. In Example 1, the relationship between the tip 62a position of the first duct wall 62, which is the end of the duct 60 on the suction port 60a side, and the magnetic pole of the peeling magnet enclosed in the peeling roller 32 is defined as shown in Figure 8.

[0085] In other words, in this embodiment, as shown in Figure 8, the peak position (pole position) P1, which is the position of the maximum value of the normal component of the magnetic flux density of the peeling pole 301 on the peeling sleeve 35, is positioned downstream in the rotational direction of the peeling sleeve 35 from the tip 62a on the suction port side of the first duct wall 62. Furthermore, the peak position P1 of the peeling pole 301 is located opposite the first duct wall 62. In this embodiment, the entire peeling pole 301 is located downstream in the rotational direction of the peeling sleeve 35 from the tip 62a and faces the first duct wall 62.

[0086] In this way, by positioning the peak position P1 of the peeling electrode 301 downstream of the tip 62a of the first duct wall 62 in the rotational direction of the peeling sleeve 35, the developer supported on the peeling sleeve 35 is peeled off from the peeling roller 32 downstream of the suction port 60a in the rotational direction of the peeling sleeve 35. As a result, the developer peeled off from the peeling roller 32 is less likely to be sucked into the duct 60, and the carrier scattered by the peeling of the developer is prevented from being collected by the duct 60.

[0087] Furthermore, in this embodiment, the peak position P2 of the transport pole 302, which is a magnetic pole adjacent to the peeling pole 301 and located downstream of the receiving pole 303 and upstream of the peeling pole 301 with respect to the rotational direction of the peeling sleeve 35, is also positioned downstream of the tip 62a. That is, the peak position (pole position) P2, which is the position of the maximum value of the normal component of the magnetic flux density of the transport pole 302 on the peeling sleeve 35, is located downstream of the tip 62a on the suction port side of the first duct wall 62 in the rotational direction of the peeling sleeve 35.

[0088] Although carrier scattering from the peeling roller 32 is less at the conveying electrode 302 compared to the peeling electrode 301, carrier scattering still occurs from the ear-falling position downstream of the conveying electrode 302. If this carrier is caught in the air of the duct 60, it will be collected by the duct 60. Therefore, as in this embodiment, by positioning the peak position P2 of the conveying electrode 302 downstream of the tip 62a of the first duct wall 62, carrier collection by the duct 60 can be suppressed more efficiently.

[0089] [Comparative Example 1] Figure 9 shows the configuration of Comparative Example 1. In Comparative Example 1, the peeling magnet 38 is rotated upstream in the rotational direction compared to the configuration of Example 1 shown in Figure 8, thereby shifting the position of the peak position P1 of the peeling pole 301 relative to Example 1. That is, in the configuration of Comparative Example 1, the peak position P1 of the peeling pole 301 is positioned upstream in the rotational direction of the peeling sleeve 35 from the tip 62a on the suction port side of the first duct wall 62.

[0090] In Comparative Example 1, the developer supported on the release sleeve 35 is detached from the release roller 32 upstream of the suction port 60a in the rotational direction of the release sleeve 35. As a result, the developer detached from the release roller 32 is more easily sucked into the duct 60, and the carrier scattered by the release of the developer is more easily collected by the duct 60. As a result, carrier clogging is more likely to occur in the duct 60, and when carrier clogging occurs, the suction capacity of the scattered toner by the duct 60 decreases, and toner scattering cannot be sufficiently suppressed.

[0091] In Comparative Example 1 shown in Figure 9, the peak position P1 of the peeling electrode 301 was positioned upstream of the tip 62a of the first duct wall 62 by rotating the peeling magnet 38. However, the same result can be obtained by changing the position of the tip 62a of the first duct wall 62 to position the peak position P1 of the peeling electrode 301 upstream of the tip 62a of the first duct wall 62.

[0092] Let's return to the configuration of Embodiment 1 in Figure 8 and explain. As described above, the peak position P1 of the peeling electrode 301 is located downstream of the tip 62a of the first duct wall 62. However, from the viewpoint of peelability of the developer from the peeling roller 32, it is preferable that the peak position P1 of the peeling electrode 301 be as follows. That is, it is preferable that the peak position P1 of the peeling electrode 301 be located downstream in the rotational direction of the peeling sleeve 35 from the vertical apex of the peeling roller 32. It is also preferable that the peak position P1 of the peeling electrode 301 be located vertically above the rotational center R of the peeling roller 32. By configuring it in this way, the peelability of the developer from the peeling roller 32 is improved, and image defects caused by the developer being carried along with the peeling roller 32 can be suppressed.

[0093] Table 1 shows the relationship between the peak position P1 of the peeling electrode 301 and carrier recovery to the duct 60 in the configurations of Example 1 in Figure 8 and Comparative Example 1 in Figure 9. In Table 1, the angle of the peak position P1 is expressed with the point on the side of the second developing roller 31, where the horizontal line H (Figure 8) passing through the rotation center R of the peeling roller 32 intersects the surface of the peeling sleeve 35, set to 0°, and clockwise (same direction as the rotation direction of the peeling sleeve 35) in Figures 8 and 9 is considered positive. In addition, Table 1 shows the results of investigating carrier recovery to the duct 60 when the peak position P1 is set at multiple angular positions, in addition to Comparative Example 1 and Example 1. [Table 1]

[0094] In Table 1, "◎" indicates that carrier recovery by the duct 60 was sufficiently suppressed. "〇" indicates that carrier recovery by the duct 60 was suppressed to the extent that carrier clogging did not occur. "×" indicates that carriers were recovered by the duct 60 and carrier clogging occurred. Furthermore, Comparative Example 1 is when the angle of the peak position P1 is 20°, and when the angle is 30°, the peak position P1 is located opposite the tip 62a. Also, when the angle of the peak position P1 is 90°, the peak position P1 is at the vertical apex of the peeling roller 32, and Example 1 is when the angle is 95°. Furthermore, when the angle is 180°, the peak position P1 is on the opposite side of the second developing roller 31 and at the same height as the rotation center R in the vertical direction, and when the angle is 270°, the peak position P1 is located vertically below the rotation center R. From Table 1, it was found that it is preferable for the peak position P1 to be between 30° and 270°, and more preferable for the peak position P1 to be between 90° and 180°.

[0095] Furthermore, the position of the tip 62a of the first duct wall 62 is preferably as follows from the viewpoint of suppressing carrier recovery into the duct 60. That is, the tip 62a of the first duct wall 62 is preferably located upstream of the vertical apex of the peeling roller 32 in the rotational direction of the peeling sleeve 35. Also, the tip 62a of the first duct wall 62 is preferably located vertically above the rotational center R of the peeling roller 32. By configuring it in this way, carrier recovery into the duct 60 can be further suppressed.

[0096] Table 2 shows the relationship between the position of the tip 62a of the first duct wall 62 and carrier recovery in the configuration of Example 1. In Table 2, as in Table 1, the angle of the position of the tip 62a is expressed with the point on the side of the second developing roller 31 as 0°, and clockwise (same direction as the rotation direction of the peeling sleeve 35) as positive, among the points where the horizontal line H (Figure 8) passing through the rotation center R of the peeling roller 32 intersects the surface of the peeling sleeve 35. Table 2 also shows the results of investigating carrier recovery to the duct 60 when the tip 62a is positioned at multiple angular positions. [Table 2]

[0097] The symbols "◎" and "〇" in Table 2 indicate the same things as explained in Table 1. From Table 2, it can be seen that it is preferable for the position of the tip 62a of the first duct wall 62 to be between -20° and 95°, and it is more preferable for the position of the tip 62a to be between 0° and 90°.

[0098] In Example 1, by positioning the peak position P1 of the peeling electrode 301 downstream of the tip 62a of the first duct wall 62 in the rotational direction of the peeling sleeve 35, it is possible to suppress the collection of scattered carriers by the duct 60. Furthermore, in Example 1, the peak position P2 of the transport electrode 302 is also positioned downstream of the tip 62a. As a result, carrier collection by the duct 60 can be suppressed more efficiently. Consequently, a decrease in the suction capacity of scattered toner by the duct 60 can be suppressed, and toner scattering can be suppressed over a long period of time.

[0099] [Example 2] In this embodiment, Example 2, which is an example of a configuration that suppresses carrier scattering, will be described with reference to Figure 10. In Example 2, the peeling magnet 38 is rotated upstream in the rotational direction compared to the configuration of Example 1 shown in Figure 8, thereby shifting the positions of the peak position P1 of the peeling pole 301 and the peak position P2 of the transport pole 302 compared to Example 1. That is, in Example 2, similar to Example 1, the peak position P1 of the peeling pole 301 is positioned downstream in the rotational direction of the peeling sleeve 35 from the tip 62a of the first duct wall 62. However, in Example 2, unlike Example 1, the peak position P2 of the transport pole 302 is positioned upstream in the rotational direction of the peeling sleeve 35 from the tip 62a of the first duct wall 62.

[0100] As in Example 1, if the peak position P2 of the transport electrode 302 is downstream in the rotational direction of the peeling sleeve 35 from the tip 62a of the first duct wall 62, carrier recovery by the duct 60 can be further suppressed. However, as in Example 2, if the peak position P1 of the peeling electrode 301 is downstream in the rotational direction of the peeling sleeve 35 from the tip 62a of the first duct wall 62, carrier recovery by the duct 60 can be suppressed, although to a lesser extent than in Example 1, even if the peak position P2 of the transport electrode 302 is upstream of the tip 62a.

[0101] Table 3 shows the relationship between the peak position P2 of the transport pole 302 and carrier recovery to the duct 60 in the configurations of Example 1 in Figure 8 and Example 2 in Figure 10. In Table 3, as in Table 1, the angle of the peak position P2 of the transport pole 302 is expressed with the point on the second developing roller 31 side of the horizontal line H (Figure 8) passing through the rotation center R of the peeling roller 32 intersecting the surface of the peeling sleeve 35 set to 0°, and clockwise in Figure 8 (the same direction as the rotation direction of the peeling sleeve 35) as positive. In addition to Examples 1 and 2, Table 3 also shows the results of investigating carrier recovery to the duct 60 when the peak position P2 faces the tip 62a (30°). [Table 3]

[0102] In Table 3, "◎" and "〇" indicate the same conditions as those explained in Table 1. From Table 3, it was found that it is preferable to set the peak position P2 of the transport pole 302 to 20° or more, and that carrier recovery can be sufficiently suppressed even if the peak position P2 faces the tip 62a. Furthermore, it was found that it is even more preferable to set the peak position P2 downstream of the tip 62a.

[0103] This embodiment 2 is effective, for example, when there are constraints on the positional relationship between the second developing roller 31, the peeling roller 32, and the first duct wall 62, making it difficult to position the peak position P2 of the transport electrode 302 downstream of the tip 62a. Even with such constraints, carrier recovery by the duct 60 can be suppressed by positioning the peak position P1 of the peeling electrode 301 downstream of the tip 62a.

[0104] [Examples 3 and 4] In this embodiment, Examples 3 and 4, which are examples of configurations that suppress carrier scattering, will be explained with reference to Figure 11. In Examples 3 and 4, confirmation was made in terms of Fθ, which is the magnetic force applied to the carrier at the tip 62a of the first duct wall 62.

[0105] Here, we will explain the magnetic flux density and magnetic force produced by the peeling magnet 38. For the purposes of this embodiment, Br, Bθ, Fr, and Fθ are defined as follows. Br: Magnetic flux density in the direction normal to (perpendicular to) the outer surface (surface) of the peeling sleeve 35 at a certain point. Bθ: Magnetic flux density in the tangential direction to the outer surface of the peeling sleeve 35 at a certain point. Fr: Magnetic force acting in the direction normal to the outer surface of the peeling sleeve 35 at a certain point (where the attractive direction (direction toward the peeling sleeve 35) is negative). Fθ: Magnetic force acting tangentially to the outer surface of the peeling sleeve 35 at a certain point (where the rotational direction of the peeling sleeve 35 is considered positive).

[0106] Unless otherwise specified, Br, Bθ, Fr, and Fθ refer to the magnetic flux density or magnetic force at a certain point on the peeling sleeve 35.

[0107] [Method for measuring magnetic force or magnetic flux density] Next, the method for measuring the magnetic force in this embodiment will be described. The magnetic force described in this embodiment can be calculated by the calculation method described below. The magnetic force acting on the carrier is obtained by the following equation (1). Here, μ0 is the magnetic permeability of vacuum, μ is the magnetic permeability of the carrier, b is the radius of the carrier, and B is the magnetic flux density.

[0108]

Equation

Equation

[0109] From this equation (2), if Br and Bθ are known, Fr and Fθ can be obtained. Here, the magnetic flux density Br was measured using the magnetic field measuring instrument "MS-9902" (trade name) manufactured by F.W.BELL as a measuring instrument, with the distance between the probe, which is a member of the measuring instrument, and the surface of the development sleeve set to approximately 100 μm.

[0110] Furthermore, Bθ can be obtained as follows. The vector potential A Z (R,θ) is obtained using the measured magnetic flux density Br,

Equation

Equation

Equation

[0111] By substituting the measured and calculated Br and Bθ into equation (1), Fr and Fθ can be derived. Furthermore, following the above equation, the magnetic flux density distribution that forms the Fr distribution required in this embodiment can be obtained.

[0112] In Example 3, when Fθ is the magnetic force acting tangentially on the peeling sleeve 35, and the force of Fθ that is in the same direction as the rotation direction of the peeling sleeve 35 is considered positive, and the force of Fθ that is in the opposite direction to the rotation direction of the peeling sleeve 35 is considered negative, then at the tip 62a of the first duct wall 62, Fθ is +1.5 × 10 -8 N was used. On the other hand, in Example 4, Fθ at the tip 62a of the first duct wall 62 was -1.5 × 10 -8 Let N be the value. Figure 11 shows graphs of the distribution of Fθ near the tip 62a of the first duct wall 62 in Examples 1, 3, and 4.

[0113] In Example 1, Fθ at the tip 62a was very small, close to 0. In Example 3, a peeling magnet 38 was used such that Fθ at the tip 62a was larger than in Example 1. In Example 4, a peeling magnet 38 was used such that Fθ at the tip 62a was smaller than in Example 1. Carrier recovery into the duct 60 was then confirmed in each example.

[0114] In Example 3, the Fθ at the tip 62a was increased, so the speed at which the developer moves at the tip 62a becomes faster than the rotational speed of the peeling roller 32. As a result, the centrifugal force acting on the carrier is large, and the carrier is more likely to separate from the peeling roller 32. Consequently, the carrier is more easily recovered by the duct 60 compared to Example 1.

[0115] On the other hand, in Example 4, because the Fθ at the position of the tip 62a was made small, the speed at which the developer moves at the position of the tip 62a became slower than the rotational speed of the peeling roller 32. As a result, the centrifugal force acting on the carrier is small, and the carrier does not easily separate from the peeling roller 32. However, because the developer moves slowly, the height of the developer on the peeling roller 32 tends to become high. As a result, in Example 4, the height of the developer on the peeling roller 32 exceeded the nearest-closest distance A between the peeling roller 32 and the first duct wall 62. Consequently, the developer accumulated at the nearest-closest distance A between the peeling roller 32 and the first duct wall 62, making it difficult for the peeling roller 32 to properly transport the developer, and causing backflow of the developer. Then, as the developer returned to the opposing part 74 side, the developer was carried around to the second developing roller 31, which easily resulted in image defects.

[0116] Based on the above, the configuration of Example 1 is less likely to cause developer stagnation at the nearest-nearest distance A, and most effectively suppresses carrier recovery into the duct 60.

[0117] Table 4 shows the relationship between Fθ at the position of tip 62a in the configurations of Examples 1, 3, and 4, and the retention of the developer and carrier recovery by the duct 60. In Table 4, in addition to Examples 1, 3, and 4, Fθ is also shown for Fθ of -1.0 × 10 -8 N(-1.0E-08), +1.0×10 -8 The case for N(1.0E-08) is also shown. Note that Fθ in Example 1 is +0.9 × 10 -9 N(0.9E-09), Fθ in Example 3 is +1.5×10 -8 N(1.5E-08), Fθ in Example 4 is -1.5×10 -8 N(-1.5E-08). [Table 4]

[0118] In Table 4, the "◎" and "〇" in the "Carrier Recovery" column indicate the same thing as explained in Table 1. Furthermore, "◎" in "Developer Retention" indicates that no developer retention occurred at nearest-closest distance A. "〇" indicates that some developer retention occurred at nearest-closest distance A, but the resulting image defects were within acceptable limits.

[0119] From Table 4, in terms of suppressing developer retention at the nearest-nearest distance A, Fθ at the tip 62a of the first duct wall should be set to +1.5 × 10 -8 It was found that it is preferable to keep N below 10⁻¹⁰. Furthermore, from the viewpoint of suppressing carrier recovery by duct 60, Fθ at the tip 62a of the first duct wall should be -1.5 × 10⁻¹⁰. -8 It was found that it is preferable to set N to ≥ . Furthermore, from the viewpoint of suppressing both the retention of the developer and the suppression of carrier recovery by the duct 60, Fθ at the tip 62a of the first duct wall should be -1.0 × 10 -8 N or more, +1.0×10 -8 It was found that it is preferable to keep N below a certain value.

[0120] In Example 3, the Fθ at the position of the tip 62a is larger than in Example 1, so the accumulation of developer at the nearest-nearest distance A can be suppressed more effectively than in Example 1. However, Example 1 suppresses developer accumulation and carrier recovery by the duct 60 more effectively than Example 3. Also, in Example 4, the Fθ at the position of the tip 62a is smaller than in Example 1, so the carrier is less likely to scatter, and the accumulation of developer and carrier recovery by the duct 60 can be suppressed in the same way as in Example 1, or even more effectively than in Example 1. However, Example 1 suppresses developer accumulation at the nearest-nearest distance A more effectively than in Example 4. Therefore, from the viewpoint of both suppressing developer accumulation and suppressing carrier recovery by the duct 60, Example 1 is the most preferable.

[0121] [Example 5] In this embodiment, Example 5, which is an example of a configuration that suppresses carrier scattering, will be described with reference to Figures 12 and 13. In Example 5, the position of the guide member 45 that guides the developer to the developer recovery screw 44 is changed from the configuration of Example 1. That is, when the normal component of the magnetic flux density on the peeling sleeve 35 is Br, in Example 4, as shown in Figure 12, the tip 45b of the guide member 45 on the peeling roller 32 side faces a region where the absolute value of Br is 10 mT or less, preferably 5 mT or less. The configuration of the peeling magnet 38 in the peeling roller 32 is the same as in Example 1.

[0122] As shown in Figure 12, the tip 45b of the guide member 45 is positioned close to the low-magnetic-force portion 310 of the peeling magnet 38. Since the low-magnetic-force portion 310 is the region where the developer is peeled off from the peeling sleeve 35, by positioning the tip 45b of the guide member 45 opposite the low-magnetic-force portion 310, as in Example 4, the peeling performance of the developer from the peeling roller 32 and the transport of the developer to the developer recovery screw 44 can be improved compared to the configuration of Example 1. As a result, the development is suppressed from moving around on the peeling roller 32, and the image quality of the output image can be improved.

[0123] Figure 13 shows a graph of the distribution of Br at the position of each magnetic pole of the magnetic field created by the peeling magnet 38 inside the peeling roller 32. When the tip 45b of the guide member 45 is positioned in the region where the absolute value of Br| is 10mT or less, the peelability of the developer from the peeling roller 32 can be improved.

[0124] Table 5 shows the relationship between the position of the tip 45b of the guide member 45 and the peelability of the developer from the peeling roller 32 in the configurations of Examples 1 and 5. In Table 5, as in Table 1, the angle of the position of the tip 45b of the guide member 45 is expressed with the point on the side of the second developing roller 31 being 0°, and clockwise (same direction as the rotation direction of the peeling sleeve 35) being considered positive, among the points where the horizontal line H (Figure 8) passing through the rotation center R of the peeling roller 32 intersects the surface of the peeling sleeve 35. In addition, Table 5 shows the results of investigating the peelability of the developer from the peeling roller 32 when the position of the tip 45b of the guide member 45 is a position other than that of Examples 1 and 5. [Table 5]

[0125] As shown in Table 5, "◎" indicates that the developer peeling performance from the peeling roller 32 was good. "〇" indicates that the developer peeling performance from the peeling roller 32 was slightly reduced, but not to the extent that it affected the output image. "△" indicates that the developer peeling performance from the peeling roller 32 was reduced, and there was a slight effect on the output image.

[0126] Table 5 shows that it is preferable to position the tip 45b of the guide member 45 within a range of 110° to 280°. Furthermore, it was found that it is even more preferable to position the tip 45b of the guide member 45 within a range of 110° to 200°.

[0127] In Example 5, the tip 45b of the guide member 45 on the peeling roller side is positioned facing a region where the absolute value of Br is 10 mT or less. Compared to the configuration in Example 1, this improves the peelability of the developer from the peeling roller 32. As a result, the development agent is suppressed from moving around on the peeling roller 32, improving the image quality of the output image.

[0128] [experiment] To confirm the effectiveness of each configuration of Examples 1 to 5, Comparative Example 1 (Figure 9), and the Conventional Example (Figure 7), the following experiment was conducted. The developing apparatus of each configuration was mounted on the image forming apparatus shown in Figure 1, and 5000 images were formed. For each configuration, toner scattering within the developing apparatus, carrier recovery into the duct 60, developer retention at the nearest distance A, and the peelability of the developer from the peeling roller 32 were checked and evaluated. In the case of the Conventional Example, since there was no duct 60, items other than toner scattering were not evaluated. In the case of Comparative Example 1, since the peak position P1 of the peeling electrode 301 is upstream of the tip 62a of the first duct wall 62 in the rotational direction of the peeling sleeve 35, developer retention was not evaluated. The experimental results are shown in Table 6. [Table 6]

[0129] As shown in Table 6, a "○" under "Toner scattering" indicates that toner scattering was sufficiently suppressed within the developing unit. A "×" indicates that toner scattering occurred within the developing unit. Also, "◎", "○", and "×" in the "Carrier recovery to the duct" column indicate the same as explained in Table 1. Furthermore, "◎" and "○" in the "Developer retention" column indicate the same as explained in Table 4. Furthermore, "◎" and "○" in the "Developer peelability" column indicate the same as explained in Table 5. Note that a "×" under "Developer peelability" indicates that the peelability of the developer from the peeling roller 32 decreased, affecting the output image.

[0130] Table 6 shows that in Comparative Example 1 and Examples 1-5, which are not the conventional example, toner scattering within the developing apparatus was sufficiently suppressed because they had a duct 60. In Comparative Example 1, the peak position P1 of the peeling electrode 301 was located upstream of the tip 62a of the first duct wall 62 in the rotational direction of the peeling sleeve 35, so it was evaluated lower in terms of carrier recovery into the duct and developer peelability compared to Examples 1-5. Regarding carrier recovery into the duct, Examples 1, 4, and 5 were evaluated highly among Examples 1-5. Regarding developer retention, all Examples except Example 4 were evaluated highly among Examples 1-5. Furthermore, regarding developer peelability, there were generally no problems in Examples 1-4, but Example 5 was evaluated highly.

[0131] [Other embodiments] Although the above embodiments describe a developing apparatus with two developing rollers, the present invention can also be applied to a configuration with only one developing roller. That is, the present invention can be applied to a configuration in which there is one developing roller for developing an electrostatic latent image on an image carrier such as a photosensitive drum, and a peeling roller for peeling the developed material from this developing roller.

[0132] The present invention is not limited to the configurations of the embodiments described above. For example, the image forming apparatus 100 is not limited to an MFP, but may be a copier, printer, or facsimile machine. Furthermore, the configurations of the developer supply screw 42, the developer agitation screw 43, and the developer recovery screw 44 are not particularly limited as long as they can transport the developer, and for example, spiral blades or paddle-shaped blades can be applied. [Explanation of symbols]

[0133] 1Y, 1M, 1C, 1K... Developing equipment 28Y, 28M, 28C, 28K... Photosensitive drum (image carrier) 30...First developing roller 31...Second developing roller (developing roller) 32... Stripping roller 33...First developing sleeve 34. Second developing sleeve (developing sleeve) 35...Removal sleeve 36...First developing magnet 37. Second developing magnet (developing magnet) 38... Peel-off magnet 44. Developer recovery screw (transport section) 45... Guide member 45b...tip 60...Duct 60a...Suction port 61...Second duct wall 62...First duct wall 62a...tip 62b...First Wall Section 62c...Second wall part 70... Developing container 74... Opposite section 100...Image forming apparatus 207...Delivery Pole 301... Stripping electrode 302... Transport pole 303... Receiving address

Claims

1. A developing container containing a developer including toner and carrier, A developing roller having a rotating developing sleeve, a developing magnet positioned non-rotating inside the developing sleeve and attracting developer to the surface of the developing sleeve by magnetic force, and developing an electrostatic latent image formed on a rotating image carrier with developer, The developing sleeve is opposed to the developing sleeve and includes a peeling sleeve that rotates so that its surface moves in the opposite direction to the surface of the developing sleeve, and a peeling magnet that is non-rotatingly positioned inside the peeling sleeve and attracts developer to the surface of the peeling sleeve by magnetic force, and a peeling roller that peels off the developer from the developing roller after the electrostatic latent image on the image carrier has been developed by the developing roller, A duct having a suction port for sucking up the developer scattered in the developing container, located downstream of the opposing portion with respect to the rotational direction of the peeling sleeve, comprising: a first duct wall extending downstream from the suction port in the rotational direction of the peeling sleeve and positioned to face a part of the peeling roller with a gap between them; and a second duct wall positioned opposite the first duct wall and forming a space between it and the first duct wall through which the developer sucked up from the suction port flows. The developing magnet has a transfer pole which is a magnetic pole for transferring the developer from the developing roller to the peeling roller. The peeling magnet has a receiving pole which is a magnetic pole for the peeling roller to receive developer from the developing roller and is opposite in polarity to the transfer pole, a peeling pole which is a magnetic pole located downstream of the receiving pole with respect to the rotational direction of the peeling sleeve and for peeling the developer from the peeling sleeve, and a transporting pole which is a magnetic pole located downstream of the receiving pole and upstream of the peeling pole with respect to the rotational direction of the peeling sleeve and adjacent to the peeling pole. The developing apparatus is characterized in that the peak position, which is the position of the maximum value of the normal component of the magnetic flux density of the peeling electrode on the peeling sleeve, is located downstream in the rotational direction of the peeling sleeve from the tip of the first duct wall on the suction port side.

2. The developing apparatus according to claim 1, characterized in that the peak position, which is the position of the maximum value of the normal component of the magnetic flux density of the transport pole on the peeling sleeve, is located downstream in the rotational direction of the peeling sleeve from the tip of the first duct wall on the suction port side.

3. When Fθ is the magnetic force acting tangentially on the peeling sleeve, and the force of Fθ that is in the same direction as the rotation direction of the peeling sleeve is considered positive, and the force of Fθ that is in the opposite direction to the rotation direction of the peeling sleeve is considered negative, At the tip of the first duct wall on the suction port side, Fθ is +1.5 × 10 －８ The developing apparatus according to claim 1, characterized in that N is less than or equal to N.

4. When Fθ is the magnetic force acting tangentially on the peeling sleeve, and the force of Fθ that is in the same direction as the rotation direction of the peeling sleeve is considered positive, and the force of Fθ that is in the opposite direction to the rotation direction of the peeling sleeve is considered negative, At the tip of the first duct wall on the suction port side, Fθ is -1.5 × 10 －８ The developing apparatus according to claim 1, characterized in that N is greater than or equal to N.

5. When Fθ is the magnetic force acting tangentially on the peeling sleeve, and the force of Fθ that is in the same direction as the rotation direction of the peeling sleeve is considered positive, and the force of Fθ that is in the opposite direction to the rotation direction of the peeling sleeve is considered negative, At the tip of the first duct wall on the suction port side, Fθ is +1.0 × 10 －８ The developing apparatus according to claim 1, characterized in that N is less than or equal to N.

6. When Fθ is the magnetic force acting tangentially on the peeling sleeve, and the force of Fθ that is in the same direction as the rotation direction of the peeling sleeve is considered positive, and the force of Fθ that is in the opposite direction to the rotation direction of the peeling sleeve is considered negative, At the tip of the first duct wall on the suction port side, Fθ is -1.0 × 10 －８ The developing apparatus according to claim 1, characterized in that N is greater than or equal to N.

7. A guide member for guiding the developer peeled off from the peeling roller, The system further comprises a transport unit that transports the developer guided by the aforementioned guide member, When the normal component of the magnetic flux density on the aforementioned peeling sleeve is Br, The developing apparatus according to claim 1, characterized in that the tip of the guide member on the peeling roller side faces a region where the absolute value of Br is 10 mT or less.

8. The developing apparatus according to claim 1, characterized in that the tip of the first duct wall on the suction port side is located upstream of the vertical apex of the peeling roller in the rotational direction of the peeling sleeve.

9. The developing apparatus according to claim 8, characterized in that the tip of the first duct wall on the suction port side is located vertically above the rotation center of the peeling roller.

10. The developing apparatus according to claim 1, characterized in that the peak position, which is the position of the maximum value of the normal component of the magnetic flux density of the peeling pole on the peeling sleeve, is located downstream in the rotational direction of the peeling sleeve from the vertical apex of the peeling roller.

11. The developing apparatus according to claim 10, characterized in that the peak position, which is the position of the maximum value of the normal component of the magnetic flux density of the peeling pole on the peeling sleeve, is located vertically above the rotation center of the peeling roller.

12. The first duct wall has a first wall portion located above the vertical apex of the peeling roller, and a second wall portion extending from the first wall portion toward the upstream side in the rotational direction of the peeling sleeve and positioned closer to the peeling roller than the first wall portion. The developing apparatus according to claim 1, characterized in that the tip of the second wall portion opposite to the first wall portion is the tip of the first duct wall on the suction port side.

13. The developing apparatus according to claim 12, characterized in that the closest proximity distance between the second wall portion and the peeling roller is 0.5 mm or more and 20 mm or less.

14. The developing apparatus according to claim 1, characterized in that the second duct wall extends further toward the developing roller than the tip of the first duct wall on the suction port side.

15. The developing apparatus according to claim 14, characterized in that the second duct wall extends from vertically above the first duct wall to a position facing the developing sleeve.

16. A first developing roller having a rotating first developing sleeve and a first developing magnet which is non-rotatingly positioned inside the first developing sleeve and attracts developer to the surface of the first developing sleeve by magnetic force, and which develops an electrostatic latent image formed on the rotating image carrier with developer, The system includes a supply unit for supplying developer to the first developing roller, The developing sleeve is a second developing sleeve, the developing magnet is a second developing magnet, and the developing roller is a second developing roller. The developing apparatus according to claim 1, wherein the second developing roller is positioned downstream of the first developing roller with respect to the rotation direction of the image carrier and above the rotation center of the first developing roller with respect to the vertical direction, and the developer is transferred from the first developing roller by magnetic force.

Images