Developing apparatus

Abstract

A developing apparatus includes a developing container, a first rotatable developing member, a first magnet non-rotatably and fixedly disposed inside the first rotatable developing member, a second rotatable developing member, a second magnet non-rotatably and fixedly disposed inside the second rotatable developing member, and a duct, the duct includes a suction port that is an inlet through which the developer scattered in the developing container is sucked. A position where an absolute value of a normal component of a magnetic flux density of a sixth magnetic pole of the second magnet becomes maximum on an outer peripheral surface of the second rotatable developing member is positioned downstream of an edge of the first duct wall of the duct on the suction port side with respect to a rotation direction of the second rotatable developing member.

Description

Technical Field

[0001] This disclosure relates to a developing apparatus that uses a developing agent to develop an electrostatic latent image formed on an image carrier member. Background Technology

[0002] As a developing apparatus, a configuration including a stripping roller has been proposed for stripping and collecting the developer from the developing roller that develops an electrostatic latent image formed on an image carrier member by the developer (Japanese Patent Application Publication No. 2018-124338). The developing roller includes a rotating developing sleeve and a developing magnet non-rotatably disposed inside the developing sleeve, wherein the developer is carried on the surface of the developing sleeve by the magnetic force of the developing magnet. Similarly, the stripping roller includes a rotating stripping sleeve and a stripping magnet non-rotatably disposed inside the stripping sleeve, wherein the developer is carried on the surface of the stripping sleeve by the magnetic force of the stripping magnet. The developer carried and fed by the developing sleeve and used to develop the electrostatic latent image on the image carrier member, i.e., the used developer, is carried on the surface of the stripping sleeve, whereby the developer on the developing roller is collected by the stripping roller. Then, by rotating the stripping sleeve, the developer carried on the stripping sleeve is conveyed to the stripping position, and the developer is stripped from the stripping sleeve.

[0003] According to the configuration disclosed in Japanese Patent Application Publication No. 2018-124338, the stripping sleeve rotates, causing the surface of the stripping sleeve to move in the opposite direction to the surface of the developing sleeve at the opposite portion to the developing sleeve. In this state, during the process of conveying the developer from the developing sleeve to the stripping sleeve, toner scattering may occur due to the magnetic tipping of the developer during the process of conveying the developer from the developing sleeve to the stripping sleeve and feeding it to the stripping position, and scattering of separated toner may also occur during stripping.

[0004] With the recent increase in the speed of image forming equipment, toner scattering from the stripping roller has become a problem, and many developing machines are equipped with pipes for drawing up the toner scattered within the developing machine. However, in this configuration, the carrier that scatters along with the toner from the stripping roller is collected by the pipes, which can cause the pipes to become clogged. When the pipes are clogged, their ability to draw up the scattered toner is reduced, making it possible that toner scattering cannot be adequately suppressed. Summary of the Invention

[0005] One aspect of this disclosure is to suppress the collection of carriers by the pipeline.

[0006] According to one aspect of this disclosure, a developing apparatus includes: a developing container, the developing container including a first chamber configured to contain a developer and a second chamber separated from the first chamber by a partition wall, the developer including a toner and a carrier; a first rotatable developing member, to which the developer is supplied, the first rotatable developing member being configured to carry the developer and feed the developer to a developing position, at which an electrostatic latent image formed on an image carrier is developed; a first magnet, the first magnet being non-rotatably and fixedly disposed inside the first rotatable developing member, the first magnet having a first magnetic pole, a second magnetic pole and a third magnetic pole, the first magnetic pole being disposed facing the image carrier at the developing position, the second magnetic pole being disposed downstream of the first magnetic pole in the rotational direction of the first rotatable developing member, the third magnetic pole being disposed downstream of and adjacent to the second magnetic pole relative to the rotational direction of the first rotatable developing member, and having the same magnetic polarity as the second magnetic pole; a second rotatable developing member, the second rotatable developing member being disposed facing the first rotatable developing member and configured to pass through the A first magnet generates a magnetic field to receive developer delivered from the first rotatable developing member. The second rotatable developing member is configured to carry developer after developing an electrostatic latent image and feed developer into a second chamber for collection of the developer in the second chamber. A second magnet is non-rotatably and fixedly disposed inside the second rotatable developing member. The second magnet has a fourth, fifth, sixth, and seventh magnetic pole. The fourth magnetic pole has a different magnetic polarity than the second magnetic pole. The fifth magnetic pole is positioned downstream of the fourth magnetic pole relative to the rotation direction of the second rotatable developing member. The sixth magnetic pole is positioned downstream of and adjacent to the fifth magnetic pole relative to the rotation direction of the second rotatable developing member and has a different magnetic polarity than the fifth magnetic pole. The seventh magnetic pole is positioned downstream of and adjacent to the sixth magnetic pole relative to the rotation direction of the second rotatable developing member and has the same magnetic polarity as the sixth magnetic pole. The developer after developing an electrostatic latent image is delivered from the first rotatable developing member to the second rotatable developing member by a magnetic field generated between the second magnetic pole and the fourth magnetic pole.The conduit includes: a suction port, which is an inlet through which developer dispersed in the developing container is drawn, the suction port being disposed downstream of the first rotatable developing member and the second rotatable developing member facing each other in the rotational direction of the second rotatable developing member; a first conduit wall, the first conduit wall being configured to extend downstream of the suction port in the rotational direction of the second rotatable developing member, the first conduit wall being configured to face a portion of the second rotatable developing member and forming a gap between the first conduit wall and the portion of the second rotatable developing member; and a second conduit wall, the second conduit wall being configured to face the first conduit wall and forming a space between the second conduit wall and the first conduit wall, through which developer drawn from the suction port flows, the second conduit wall being positioned further outward than the first conduit wall in a direction from the rotational center of the second rotatable developing member toward the position where the absolute value of the normal component of the magnetic flux density of the sixth magnetic pole on the outer peripheral surface of the second rotatable developing member becomes maximum, relative to the rotational center of the second rotatable developing member. At the position where the first and second rotatable developing members face each other, the rotation direction of the second rotatable developing member is opposite to that of the first rotatable developing member. The location where the absolute value of the normal component of the magnetic flux density of the sixth magnetic pole on the outer peripheral surface of the second rotatable developing member becomes maximum is located downstream of the edge of the first pipe wall on the suction port side, relative to the rotation direction of the second rotatable developing member.

[0007] The features of this disclosure will become clear from the following description of embodiments with reference to the accompanying drawings. The following description of the embodiments is given by way of example. Attached Figure Description

[0008] Figure 1 This is a schematic cross-sectional view illustrating the configuration of an image forming apparatus according to an embodiment.

[0009] Figure 2 This is a schematic cross-sectional view showing a developing apparatus according to an embodiment.

[0010] Figure 3 This is a view showing the magnetic pole arrangement of the first developing roller according to an embodiment.

[0011] Figure 4 This is a view showing the magnetic pole arrangement of the second developing roller according to an embodiment.

[0012] Figure 5 This is a view showing the magnetic pole arrangement of the stripping roller according to an embodiment.

[0013] Figure 6This is an enlarged view showing the periphery of the second developing roller, stripping roller, and conduit according to an embodiment.

[0014] Figure 7 This is a schematic cross-sectional view of a developing apparatus based on a standard example.

[0015] Figure 8 The enlarged view of the periphery of the stripping roller according to Example 1 shows the pipe arrangement and the magnetic pole arrangement of the stripping roller.

[0016] Figure 9 The enlarged view of the periphery of the stripping roller according to Comparative Example 1 shows the pipe arrangement and the magnetic pole arrangement of the stripping roller.

[0017] Figure 10 The enlarged view of the periphery of the stripping roller according to Example 2 shows the pipe arrangement and the magnetic pole arrangement of the stripping roller.

[0018] Figure 11 It is a graph showing the Fθ distribution near the edge of the first pipe wall for the stripped magnet according to Examples 1, 3 and 4.

[0019] Figure 12 It is a schematic cross-sectional view of the developing apparatus according to Example 5.

[0020] Figure 13 This is a graph showing the Br distribution near the stripped pole according to Example 5. Detailed Implementation

[0021] Reference Figures 1 to 6 An embodiment will be described. First, reference will be made to... Figure 1 A schematic configuration of the image forming apparatus of this embodiment is described.

[0022] Image forming equipment

[0023] The image forming apparatus 100 is a full-color image forming apparatus, and in this embodiment, it is, for example, a multi-functional peripheral device (MFP) with copying, printing, and scanning functions. Figure 1 As shown, the image forming apparatus 100 includes image forming units PY, PM, PC, and PK arranged in parallel, which respectively perform image forming processing for toner images of four colors: yellow, magenta, cyan, and black. The image forming apparatus 100 according to this embodiment has a document reading device connected to the image forming apparatus body (i.e., the apparatus body) or a host device such as a personal computer communicatively connected to the apparatus body. Therefore, based on image information received from the host device, a four-color panchromatic image of yellow (Y), magenta (M), cyan (C), and black (K) can be formed on recording materials such as recording paper, plastic sheets, and cloth using an electrophotographic system.

[0024] The image forming units PY, PM, PC, and PK for each color include primary chargers 21Y, 21M, 21C, and 21K; developing devices 1Y, 1M, 1C, and 1K; exposure devices 22Y, 22M, 22C, and 22K; photosensitive drums 28Y, 28M, 28C, and 28K; and cleaning devices 26Y, 26M, 26C, and 26K. The image forming apparatus 100 includes a transfer device 2 and a fixing device 3. Since the configurations of the image forming units PY, PM, PC, and PK for each color are similar, the image forming unit PY will be described as representative below.

[0025] The photosensitive drum 28Y, used as an image-carrying component, is a photosensitive component comprising a photosensitive layer made of a resin such as polycarbonate resin containing organic photoconductors (OPC), and is configured to rotate at a predetermined speed. According to this embodiment, the linear velocity of the surface of the photosensitive drum 28Y is set to 650 mm / s. The primary charger 21Y includes a corona discharge electrode disposed around the photosensitive drum 28Y and charges the surface of the photosensitive drum 28Y with the generated ions.

[0026] The exposure unit 22Y incorporates scanning optics and exposes the charged photosensitive drum 28Y based on image data to reduce the potential of the exposed portion, thereby forming a charge pattern (i.e., an electrostatic latent image) corresponding to the image data. The developing unit 1Y transfers the developer contained therein onto the photosensitive drum 28Y to develop the electrostatic latent image formed on the photosensitive drum 28Y. The developer is formed by mixing a carrier and a toner corresponding to each color, and the electrostatic latent image is visualized by the toner.

[0027] The transfer device 2 includes primary transfer rollers 23Y, 23M, 23C, and 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, and 23K, as well as the multiple rollers, and is supported to allow movement. Figure 1 Starting from the top, the primary transfer rollers 23Y, 23M, 23C, and 23K, which serve as primary transfer components, correspond sequentially to the colors yellow (Y), magenta (M), cyan (C), and black (K), respectively. The secondary transfer roller 25 is disposed outside the intermediate transfer belt 24 and is configured to allow recording material to pass between the secondary transfer roller 25 and the intermediate transfer belt 24.

[0028] At the primary transfer section (i.e., primary transfer clamping section) T1 where the intermediate transfer belt 24 and the photosensitive drums 28Y, 28M, 28C, and 28K abut against each other, the toner images of each color formed on the photosensitive drums 28Y, 28M, 28C, and 28K are sequentially transferred (i.e., primary transfer) onto the intermediate transfer belt 24 by applying a primary transfer bias to the primary transfer rollers 23Y, 23M, 23C, and 23K. For example, when forming a four-color full-color image, starting from the photosensitive drum 28Y, the toner images are sequentially transferred onto the intermediate transfer belt 24, thereby forming toner images of yellow, magenta, cyan, and black layered in an overlapping manner.

[0029] Simultaneously, the recording material S stored in the cartridge 115, which serves as the recording material receiving section, is conveyed toward the transfer device 2 via the pickup roller 111 and the alignment roller 112. The recording material S is conveyed at a timing synchronized with the toner image on the intermediate transfer belt 24 to the secondary transfer section (i.e., the clamping section) T2, where the intermediate transfer belt 24 and the secondary transfer roller 25, which serves as the secondary transfer component, abut against each other. At the secondary transfer section T2, the toner image formed on the intermediate transfer belt 24 is transferred onto the recording material S by applying a secondary transfer bias to the secondary transfer roller 25. Pressure and heat are applied to the recording material on which the toner image has been transferred at the fixing device 3. As a result, the toner on the recording material melts, and the color image is fixed onto the recording material. Afterward, the recording material S is discharged outside the device.

[0030] When images are formed on both sides of the recording material, the recording material S, which has already passed through the fixing device 3, is conveyed to the reversing transport channel 113, where it is reversed. The recording material S is then conveyed by the transport roller 114 to the alignment roller 112, and the toner image is transferred to the back side of the recording material S at the secondary transfer section T2 in a similar manner to the above. The toner image is then fixed again to the back side of the recording material S at the fixing device 3.

[0031] After the first transfer process, residues such as toner remaining on the photosensitive drums 28Y, 28M, 28C, and 28K are collected by cleaning devices 26Y, 26M, 26C, and 26K. Thus, the photosensitive drums 28Y, 28M, 28C, and 28K are ready for subsequent image forming processes. Furthermore, residues such as toner remaining on the intermediate transfer belt 24 after the second transfer process are removed by the intermediate transfer belt cleaner 29.

[0032] Alternatively, the image forming apparatus 100 according to this embodiment can use a desired monochrome (such as black) image forming unit or some of the image forming units of four colors to form a monochrome or multicolor image.

[0033] Developer reservoirs 27Y, 27M, 27C, and 27K are respectively provided corresponding to developing devices 1Y, 1M, 1C, and 1K, and bottles containing developers corresponding to yellow, magenta, cyan, and black are interchangeably loaded from top to bottom in a specified order. Developer reservoirs 27Y, 27M, 27C, and 27K are configured to transfer (i.e., replenish) developers to developing devices 1Y, 1M, 1C, and 1K corresponding to the colors of the developers they contain.

[0034] For example, the toner weight ratio of the developer contained in the bottle is 80 to 95%, and the toner weight ratio of the developer in each of the developing equipment 1Y, 1M, 1C, and 1K is 5 to 10%. Therefore, once the toner is consumed to perform development in the developing equipment 1Y, 1M, 1C, and 1K, developer containing toner is replenished to compensate for the consumption, and the toner weight ratio of the developer in each of the developing equipment 1Y, 1M, 1C, and 1K remains constant.

[0035] Developing equipment

[0036] Next, we will refer to Figures 2 to 5 The developing equipment 1Y, 1M, 1C, and 1K are described in detail. Since the developing equipment 1Y, 1M, 1C, and 1K have the same configuration, developing equipment 1Y will be described as representative below. Figure 2 It is shown Figure 1 The diagram shows a conceptual illustration of the developing equipment 1Y, and Figure 3 , Figure 4 and Figure 5 This is a conceptual diagram showing the magnetic pole configuration of the first developing magnet (i.e., the first magnet) 36, the second developing magnet (i.e., the second magnet) 37, and the stripping magnet (i.e., the third magnet) 38 disposed in the developing apparatus 1Y.

[0037] like Figure 2 As shown, 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 collecting screw 44, and these components are housed in a developing container 70. The developing container 70 contains a two-component developer comprising a non-magnetic toner and a magnetic carrier.

[0038] The first developing roller 30 is a developer-carrying member that is rotatably driven and is positioned adjacent to the photosensitive drum 28Y such that its axis of rotation is substantially parallel to the axis of rotation of the photosensitive drum 28Y. The first developing roller 30 includes a rotating first developing sleeve (third rotatable developing member) 33 and a first developing magnet (third magnet), i.e., a fixed magnet 36, which is non-rotatably disposed within the first developing sleeve 33 and attracts developer to the surface of the first developing sleeve 33 by magnetic force. Then, the first developing roller 30 attracts (i.e. carries) developer from the developer supply screw 42 based on magnetic force and develops the electrostatic latent image formed on the rotating photosensitive drum 28Y (i.e., on the image-carrying member) with the developer.

[0039] Specifically, for example, a DC developing bias voltage having the same polarity as the charging polarity of the primary charger 21Y, or a developing bias voltage having the same polarity as the charging polarity of the primary charger 21Y superimposed on an AC voltage, is applied to the first developing sleeve 33 and the second developing sleeve 34, described later, of the developing apparatus 1Y. As a result, reverse development is performed, wherein toner charged to the same polarity as the charging polarity of the primary charger 21Y adheres to the electrostatic latent image formed by the exposure apparatus 22Y on the photosensitive drum 28Y. In this embodiment, a configuration is adopted in which reverse development is performed, wherein the charging polarity of the primary charger 21Y and the DC voltage of the developing bias voltage are set to negative, and negatively charged toner adheres to the electrostatic latent image.

[0040] The first developing sleeve 33 is a non-magnetic cylindrical component with an outer diameter of 25 mm (radius r1 = 12.5 mm), and is driven to rotate around a rotation axis 39. The direction of rotation of the first developing sleeve 33 is as follows: Figure 2 The arrow indicates a clockwise direction, which is opposite to the rotation direction of the photosensitive drum 28Y in this embodiment. Therefore, the first developing sleeve 33 and the photosensitive drum 28Y rotate in the same direction (i.e., the forward direction) when they are facing each other. That is, the first developing sleeve 33 rotates such that the surface facing the photosensitive drum 28Y moves from bottom to top in the vertical direction.

[0041] In this embodiment, the linear velocity of the surface of the first developing sleeve 33 is set to 1.0 times (650 mm / s) the linear velocity of the surface of the photosensitive drum 28Y. From the viewpoint of toner degradation, it is advantageous to set the ratio of the linear velocity of the surface of the first developing sleeve 33 to the linear velocity of the surface of the photosensitive drum 28Y to be in the range of approximately 1.0 times to 1.2 times. While the toner dosage supplied to the photosensitive drum 28Y may decrease and image development performance may deteriorate, since this embodiment is equipped with two developing rollers 30 and 31, the toner dosage supplied to the photosensitive drum 28Y can be maintained even if the ratio of linear velocities is suppressed.

[0042] The first developing magnet 36 is disposed inside the first developing sleeve 33 and has multiple magnetic poles 101 to 107, such as Figure 3 As shown, 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 the first developing sleeve 33 to rotate.

[0043] The developer in the first developing sleeve 33 is attracted to the photosensitive drum 28Y by the rotation of the first developing sleeve 33, thereby developing the latent image formed on the photosensitive drum 28Y. After the latent image formed on the photosensitive drum 28Y is developed, the developer on the first developing sleeve 33 is fed to the vicinity of the second developing roller 31 by the rotation of the first developing sleeve 33. Then, near the closest position of the first developing roller 30 and the second developing roller 31, the developer is stripped from the first developing sleeve 33 by the magnetic field generated by the first developing magnet 36 in the first developing roller 30 and the second developing magnet 37 in the second developing roller 31, and is transported to the second developing sleeve 34. The first developing sleeve 33 and the second developing sleeve 34 are arranged with a 3 mm gap between them at their closest point.

[0044] The second developing roller 31, serving as a developing roller, is a developer-carrying member that is rotatably driven. It is positioned downstream of the first developing roller 30 in the rotational direction of the photosensitive drum 28Y and vertically positioned above the rotational center of the first developing roller 30. It receives developer delivered from the first developing roller 30 by magnetic force. Similar to the first developing roller 30, the second developing roller 31 is positioned adjacent to the photosensitive drum 28Y such that its axis of rotation is substantially parallel to the axis of rotation of the photosensitive drum 28Y. Therefore, the axis of rotation of the second developing roller 31 and the axis of rotation of the first developing roller 30 are substantially parallel to each other.

[0045] Such a second developing roller 31 includes a rotating second developing sleeve (first rotatable developing member) 34 and a second developing magnet (first magnet), i.e., a fixed magnet 37, which is non-rotatably disposed within 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 then receives the developer delivered from the first developing roller 30 (i.e., the first developing sleeve 33) based on magnetic force, attracts (i.e., carries) the developer, and develops the electrostatic latent image formed on the rotating photosensitive drum 28Y with the developer. The stripping roller 32, described below, is positioned to one side of the second developing roller 31.

[0046] The second developing sleeve 34 is a non-magnetic cylindrical component with an outer diameter of 25 mm (radius r2 = 12.5 mm), and is driven to rotate around the rotation axis 40. The rotation direction of the second developing sleeve 34 is as follows: Figure 2 The arrows indicate a clockwise direction, which is opposite to the rotation direction of the photosensitive drum 28Y in this embodiment. Therefore, the second developing sleeve 34 and the photosensitive drum 28Y rotate in the same direction at their facing positions (i.e., opposite portions). That is, the second developing sleeve 34 rotates such that the surface facing the photosensitive drum 28Y moves vertically from bottom to top. Furthermore, the second developing sleeve 34 and the first developing sleeve 33 rotate in opposite directions at their facing positions. In this embodiment, the linear velocity of the surface of the second developing sleeve 34 is set to 1.2 times the linear velocity of the surface of the photosensitive drum 28Y (=780mm / s).

[0047] The second developing magnet 37 is disposed inside the second developing sleeve 34 and has a plurality of sector-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 the second developing sleeve 34 to rotate.

[0048] The rotation of the second developing sleeve 34 attracts the developer to the photosensitive drum 28Y, thereby developing the latent image formed on the photosensitive drum 28Y. After the latent image on the photosensitive drum 28Y is developed, the developer remaining on the second developing sleeve 34 is fed to the vicinity of the stripping roller 32 by the rotation of the second developing sleeve 34. Then, near the closest position between the second developing roller 31 and the stripping roller 32, the developer is transported from the second developing sleeve 34 to the stripping sleeve 35 of the stripping roller 32 by the magnetic field generated by the second developing magnet 37 in the second developing roller 31 and the stripping magnet 38 in the stripping roller 32.

[0049] The stripping roller (i.e., the collection roller) 32 is positioned on the side opposite to the photosensitive drum 28Y relative to the rotation center of the second developing sleeve 34, and strips the developer from the second developing roller 31 after the electrostatic latent image has been developed on the photosensitive drum 28Y by the second developing roller 31. Specifically, the stripping roller 32 is a developer-carrying member that is rotatably driven and is positioned between the second developing roller 31 and the developer collection screw 44, such that its rotation center is positioned higher than the rotation center of the second developing roller 31.

[0050] The stripping roller 32 is configured such that its axis of rotation is substantially parallel to the axis of rotation of the second developing roller 31. The stripping roller 32 includes a rotating stripping sleeve (second rotatable developing member) 35 and a stripping magnet (second magnet), i.e., a fixed magnet 38, which is non-rotatably disposed within the stripping sleeve 35 and attracts developer to the surface of the stripping sleeve 35 by magnetic force. The stripping roller 32 is configured to receive developer delivered from the second developing roller 31 based on magnetic force.

[0051] The peeling sleeve 35 is a non-magnetic cylindrical component with an outer diameter of 18 mm (radius of 9 mm) and is rotatably driven about a rotation axis 41. The direction of rotation of the peeling sleeve 35 is as follows: Figure 2 The arrow indicates a clockwise direction, which is the same as the rotation direction of the second developing sleeve 34 in this embodiment. Therefore, the stripping sleeve 35 and the second developing sleeve 34 rotate in opposite directions at their facing positions (i.e., opposite portions). That is, the stripping sleeve 35 rotates such that its surface moves in the opposite direction to the surface of the second developing sleeve 34 in the opposite portion facing the second developing sleeve 34.

[0052] The stripping magnet 38 is disposed inside the stripping sleeve 35 and has multiple magnetic poles 301 to 305. A space is provided between the inner periphery of the stripping sleeve 35 and the outer periphery of the stripping magnet 38 to allow the stripping sleeve 35 to rotate.

[0053] The developer attracted to the stripper sleeve 35 is fed downstream in the rotational direction by the rotational operation of the stripper sleeve 35. Near the developer collection screw 44, it is stripped from the stripper sleeve 35 by the stripping magnet 38 within the stripper roller 32 and falls under its own weight toward the guide member 45 positioned vertically downwards. The developer falling onto the guide member 45 is then guided toward the developer collection screw 44 by its own weight.

[0054] The guide member 45 and the developer collecting screw 44 constitute a developer collecting section 47, which serves as a collection section for collecting the developer stripped from the stripping sleeve 35 of the stripping roller 32. In the developer collecting section 47, the developer collecting screw 44 is positioned vertically below the rotation center of the stripping roller 32 and conveys the developer delivered (i.e. collected) from the stripping roller 32 while agitating the developer.

[0055] The guide member 45, serving as a guide portion, is vertically positioned below the rotation center of the stripping roller 32, and arranged such that the closest position (i.e., closest position C) between the guide member 45 and the stripping roller 32 is vertically higher than the center (i.e., the rotation center) of the rotation axis 40 of the second developing roller 31. The guide member 45 guides the developer stripped by the stripping roller 32 toward the developer collection screw 44. This guide member 45 has an inclined surface 45a on which the developer slides down by its own weight, thus more reliably guiding the stripped developer toward the developer collection screw 44. The inclined surface 45a is inclined relative to the horizontal direction, such that the portion adjacent to the developer collection screw 44 is positioned below the stripping roller 32.

[0056] The developer collecting screw 44, which serves as both a collecting component and a conveying section, conveys the collected developer to the developer circulation section 46, as described below. Specifically, the developer collecting screw 44 is a screw conveying component that conveys the collected developer, which slides down the inclined surface of the guide member 45, in one direction while simultaneously agitating the developer.

[0057] The developer circulation section 46 is a supply section for supplying developer to the first developing roller 30, and includes a control member 50, a developer supply screw 42, and a developer stirring screw 43. In the developer circulation section 46, developer is supplied to the first developing roller 30 while being fed and stirred in a generally horizontal direction by the developer supply screw 42 and the developer stirring screw 43. As described above, the developer collected by the developer collection section 47 falls by its own weight and is introduced into the developer circulation section 46. That is, the developer circulation section 46 is positioned below the developer collection section 47 relative to the vertical direction.

[0058] The developer supply screw (first conveying section) 42, the developer stirring screw (third conveying section) 43, and the developer collecting screw (second conveying section) 44 are screw conveying members that convey developer in one direction while stirring it. The developer supply screw 42 and the developer stirring screw 43 are positioned vertically below the rotation center of the developer collecting screw 44. Furthermore, the developer supply screw 42, the developer stirring screw 43, and the developer collecting screw 44 are arranged such that their rotation axes are approximately parallel to each other. The rotation axis of each screw is approximately parallel to the rotation axis of the first developing roller 30.

[0059] The developer supply screw 42 is positioned between the first developing roller 30 and the developer stirring screw 43, and a partition wall 48 of the developing container 70 is disposed between the developer supply screw 42 and the developer stirring screw 43. The partition wall 48 of the developing container 70 extends in the direction of the rotation axis of the developer supply screw 42 and the developer stirring screw 43. The partition wall 48 has a communication port (not shown) for communication between the first conveying path (first chamber) 71 through which the developer is fed by the developer supply screw 42 and the second conveying path (third chamber) 72 through which the developer is fed by the developer stirring screw 43.

[0060] The developer, stirred by the developer collecting screw 44, passes through a communication opening (not shown) formed in the partition wall 73 of the developing container 70 between the developer collecting chamber (second chamber) 47a in which the developer collecting screw 44 is disposed and the first conveying path (first chamber) 71 in which the developer supply screw 42 is disposed, and falls toward the developer supply screw 42 by its own weight. The aforementioned guide member 45 is integrally formed with the partition wall 73, and the developer collecting screw 44 is disposed above the partition wall 73.

[0061] The developer, stirred by the developer collecting screw 44, falls under its own weight and is introduced into the communication port of the developer circulation section 46. The port is preferably positioned to avoid the area where the developer is supplied towards the first developing roller 30, i.e., the middle portion of the developer supply screw 42 in the direction of rotation. In this embodiment, it is assumed that the communication port is located within the downstream end portion (i.e., the end portion) of the first conveying path 71 in which the developer supply screw 42 is disposed in the developer conveying direction.

[0062] The developer supply screw 42 and the developer stirring screw 43 have opposite developer delivery directions. The starting end (i.e., upstream end in the developer delivery direction) and ending end (i.e., downstream end in the developer delivery direction) of the first delivery path 71 in which the developer supply screw 42 is located communicates with the ending end and starting end of the second delivery path 72 in which the developer stirring screw 43 is located via a communication port provided in the partition wall 48. Therefore, the developer is delivered by the developer supply screw 42 and the developer stirring screw 43... Figure 2 The arrows indicate the direction of rotation and the general horizontal direction of circulation inside the developing container 70, and a portion of the developer is supplied toward the first developing roller 30.

[0063] Developer replenishment port 51 (reference) Figure 2 The developer stirring screw 43 is positioned above the developer container 70 and connected to the developer reservoir 27Y (reference). Figure 1 The developer replenishment port 51 is configured to replenish the developer contained in the bottle loaded in the developer reservoir 27Y to the second conveying path 72 in which the developer stirring screw 43 is disposed.

[0064] As described above, since the toner weight ratio of the developer contained in the developer reservoir 27Y is higher than that of the developer in the developing apparatus 1Y, the toner weight ratio of the developer in the developing apparatus 1 can be kept constant by adjusting the developer added to the developer stirring screw 43.

[0065] A toner concentration detection sensor 49 is provided (reference) Figure 2 The toner concentration sensor 49 is used to detect the toner concentration in the developer contained in the developer circulation section 46. The toner concentration detection sensor 49 is a sensor that detects the permeability of the developer. Since the toner concentration corresponds to the amount of toner consumed in the developing equipment 1Y, the toner concentration is used to control the replenishment of developer from the developer storage 27Y. For example, when the toner concentration is detected to be below a predetermined value, developer is replenished from the developer storage 27Y. Since the permeability of the developer varies depending on the toner concentration, the permeability can be used to detect the toner concentration.

[0066] The control member 50 is disposed near the first developing roller 30 and is used to control the amount of developer supplied from the developer circulation section 46 to the first developing roller 30. For example, the control member 50 may be configured to control the amount of developer attracted to the first developing roller 30 based on the gap between the surface of the first developing sleeve 33 of the first developing roller 30 and the end portion of the control member 50.

[0067] In the developer circulation path within the developing container 70, the developer is fed in a generally horizontal direction while being agitated in the developer circulation section 46, and then supplied to the first developing roller 30. Based on magnetic force, it is then conveyed from the first developing roller 30 to a second developing roller 31 positioned above the first developing roller 30. The developer is then again conveyed by magnetic force from the second developing roller 31 to a stripping roller 32 positioned on the side surface of the second developing roller 31, and then stripped from the stripping roller 32 by a stripping magnet 38 within the stripping roller 32. It is further collected by the developer collection section 47 and reintroduced into the developer circulation section 46.

[0068] As described above, in this embodiment, a two-component developing system is used as the developing system, and a mixture of a negatively polarized non-magnetic toner and a magnetic carrier is used as the developing agent. The non-magnetic toner becomes negatively charged through frictional charging with the magnetic carrier, and the magnetic carrier becomes positively charged. The non-magnetic toner is obtained by incorporating colorant and wax components into a resin such as polyester resin or styrene-acrylic resin, pulverizing or polymerizing the resin into powder, and adding fine powders of titanium dioxide, silica, etc., to the surface. The magnetic carrier is obtained by applying a resin coating to the surface layer of a core formed of ferrite particles or resin particles kneaded with magnetic powder. The toner concentration in the developing agent in the initial state (i.e., the weight ratio of toner contained in the developing agent) is 8% in this embodiment.

[0069] It should be noted that the magnetic carrier preferably has a strength of 40 to 80 Am per unit weight under an applied magnetic field of 1000 Oersted. 2 The magnetization is / kg or less. When the magnetization of the magnetic carrier decreases, it has an effect of suppressing magnetic brush cleaning, but it becomes difficult for the magnetic carrier to partially adhere to the non-magnetic sleeve through the magnetic field, and image defects such as magnetic carrier adhesion to the photosensitive drum may occur. When the magnetization of the magnetic carrier exceeds the above range, image defects may occur due to the pressure of the magnetic brush as described above. In this embodiment, a magnetization of 63 Am per unit weight is used. 2 / kg of magnetic carrier. The magnetization of the magnetic carrier was measured using a vibration magnetic field type automatic magnetic property recording device BHV-30 manufactured by RIKEN Denshi Co., Ltd. For the magnetic property values ​​of the magnetic carrier, an external magnetic field of 1000 Oersted was generated, and the magnetization intensity at this point was obtained. The magnetic carrier was packaged in a cylindrical plastic container to ensure sufficient density. In this state, the magnetization moment was measured, the actual weight of the sample at the time of placement was measured, and the magnetization intensity (Am) was obtained. 2 / kg).

[0070] The true specific gravity of the magnetic carrier was determined using a dry-type automatic density meter, AccuPyc1330, manufactured by Shimadzu Corporation. In this embodiment, a true specific gravity (i.e., density) of 4.6 (g / cm³) was used. 3 The magnetic carrier is used. In addition, a magnetic carrier with a weight-average diameter of 35 μm (radius b = 17.5 μm) is used.

[0071] Typically, in two-component developing methods using toner and carrier, both the toner and carrier are charged to a predetermined polarity through frictional contact, resulting in less stress on the toner compared to single-component developing systems using single-component developers. However, prolonged use increases the accumulation of contaminants, or residue, on the carrier surface, gradually reducing the toner's ability to charge. This leads to problems such as fogging and toner scattering. While increasing the amount of carrier in the developing equipment could extend its lifespan, this configuration is undesirable due to the potential increase in equipment size.

[0072] To address the aforementioned issues related to two-component developers, an Automatic Carrier Replacement (ACR) method is employed in this embodiment. The ACR method suppresses the increase of degraded carriers by gradually replenishing the developer from the developer storage 27Y to the developing apparatus 1Y and gradually discharging degraded developer from the outlet (not shown) of the developing apparatus 1Y. As a result, the degraded carriers in the developing apparatus 1Y are gradually replaced by new carriers, and the charging performance of the carriers in the developing apparatus 1Y can be maintained substantially constant.

[0073] In the developing apparatus 1Y of this embodiment configured as described above, the developer in the first transport path 71 is supplied to the first developing sleeve 33 via the developer supply screw 42. A predetermined amount of developer supplied to the first developing sleeve 33 is carried on the first developing sleeve 33 by the magnetic field generated by the first developing magnet 36, forming a developer accumulation section. The two-component developer on the first developing sleeve 33 passes through the developer accumulation section due to the rotation of the first developing sleeve 33, forms a thin coating on the surface of the first developing sleeve 33 through the control member 50, and is transported to the developing area facing the photosensitive drum 28Y. In the developing area, the developer on the first developing sleeve 33 stands upright in a spike-like shape and forms a magnetic brush.

[0074] In a first developing region where the first developing sleeve 33 and the photosensitive drum 28Y face each other, an electrostatic latent image formed on the photosensitive drum 28Y is developed by applying a developing bias voltage to the first developing sleeve 33. In this embodiment, the developing bias voltage applied to the first developing sleeve 33 has a waveform in which both an AC electric field and a DC electric field are applied, but alternatively, the developing bias voltage may have only a DC electric field.

[0075] A two-component developer is used for development in the first developing region, and then delivered to the second developing sleeve 34 near the second developing sleeve 34, and then to the second developing region where the second developing sleeve 34 and the photosensitive drum 28Y face each other. In the second developing region, the same developing bias voltage as applied in the first developing region is applied, and toner with insufficient potential relative to the electrostatic latent image on the photosensitive drum 28Y is replenished and developed, while overdeveloped toner is collected to prepare a uniform toner image. Bias voltages with different waveforms can be applied as the developing bias voltage applied to the first developing sleeve 33 and the developing bias voltage applied to the second developing sleeve 34.

[0076] The developer that has passed through the second developing zone is stripped in the stripping magnetic field region formed by the second developing magnet 37 included in the second developing sleeve 34. The developer stripped from the second developing sleeve 34 is attracted to the surface of the stripping sleeve 35 by the magnetic field formed by the stripping magnet 38 included in the stripping sleeve 35 of the stripping roller 32, and is conveyed along the rotation direction of the stripping sleeve 35. Then, the developer is separated from the surface of the stripping sleeve 35 by the stripping magnetic field formed by the stripping magnet 38 and is collected in the developer collection section 47.

[0077] Magnetic poles of each magnet

[0078] Next, we will describe Figure 3 , Figure 4 and Figure 5 The magnetic pole configuration of the first developing magnet 36, the second developing magnet 37, and the stripping magnet 38 within the first developing roller 30, the second developing roller 31, and the stripping roller 32 is shown.

[0079] like Figure 3 As shown, the first developing magnet 36 within the first developing roller 30 has multiple magnetic poles 101 (S1), 102 (N2), 103 (S2), 104 (N3), 105 (S3), 106 (N4), and 107 (N1), where S and N indicate whether the magnetic pole is an S pole or an N pole, and the numbers are assigned to distinguish it from other magnetic poles. According to this embodiment, the first developing magnet 36 includes a total of seven magnetic poles. Figure 4 and Figure 5 Similarly, among these magnetic poles, magnetic pole 106 is the transport pole for conveying developer from the first developing roller 30 to the second developing roller 31. Magnetic poles 101 to 107 are arranged in numerical order in the direction of rotation of the first developing sleeve 33.

[0080] Magnetic pole 106 is used to transport developer from the first developing sleeve 33 to the second developing sleeve 34 by means of a magnetic field generated in cooperation with the second developing magnet 37 of the second developing roller 31, and may be referred to hereinafter as transport pole 106. Magnetic pole 107 is the N pole and is used to attract developer supplied from the developer supply screw 42 onto the first developing sleeve 33. Magnetic poles 101, 102, 103, 104, and 105 are the S pole, N pole, S pole, N pole, and S pole, respectively, and are used to feed the developer attracted by magnetic pole 107 upward as the first developing sleeve 33 rotates. Magnetic pole 106 is the N pole and, as described above, transports developer from the first developing sleeve 33 to the second developing sleeve 34 facing the first developing sleeve 33 by means of a magnetic field generated in cooperation with the magnetic pole 201 in the second developing magnet 37 within the second developing roller 31.

[0081] In this embodiment, a low-magnetic-force portion 110 with a lower magnetic force than magnetic pole 106 is formed by the repulsive magnetic field generated by the cooperation between magnetic pole 106 and magnetic pole 107 disposed downstream of magnetic pole 106 in the rotational direction of the first developing sleeve 33. Magnetic pole 107 has the same magnetic polarity as magnetic pole 106. The low-magnetic-force portion 110 facilitates the transport of developer from the first developing sleeve 33 to the second developing sleeve 34. It should be noted that in this embodiment, the low-magnetic-force portion 110 has almost no magnetic force, but can have a low magnetic force, and for example, can be a magnetic pole with a magnetic force (i.e., the absolute value of the normal component Br of the magnetic flux density) of 10 mT or less, or even 5 mT or less. This also applies to magnetic poles. Figure 4 The low magnetic force portion 210 of the second developing magnet 37 shown and Figure 5 The low magnetic force portion 310 of the stripped magnet 38 shown.

[0082] like Figure 4 As shown, the second developing magnet 37 within the second developing roller 31 has multiple magnetic poles 201 (S4), 202 (N5), 203 (S5), 204 (N6), 205 (S6), 206 (N7), and 207 (S7), for a total of seven magnetic poles. 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.

[0083] Magnetic pole 201 is used to attract developer from the first developing sleeve 33 to the second developing sleeve 34 by a magnetic field generated in cooperation with the magnetic pole 107 of the first developing magnet 36 of the first developing roller 30, and may be referred to hereinafter as receiving pole 201. Magnetic pole 207 is used to transport developer from the second developing sleeve 34 to the stripping sleeve 35 by a magnetic field generated in cooperation with the stripping magnet 38 of the stripping roller 32, and may be referred to hereinafter as transport pole 207.

[0084] Furthermore, the receiving pole 201 is an S pole with a different magnetic polarity than the magnetic pole 106, and is used to attract developer from the first developing roller 30 (i.e., the first developing sleeve 33) to the second developing sleeve 34, as described above. Magnetic poles 202, 203, 204, 205, and 206 are N poles, S poles, N poles, S poles, and N poles, respectively, and are used to feed the developer attracted by the magnetic pole 201 upward as the second developing sleeve 34 rotates. The magnetic pole 207, which serves as the transport pole, is an S pole, and is used by a magnetic field generated in cooperation with the magnetic pole 303 of the stripping magnet 38 in the stripping roller 32 to transport the developer that has passed through the developing area between the magnetic pole 203 and the photosensitive drum 28Y corresponding to the magnetic pole 203 from the second developing sleeve 34 to the stripping sleeve 35 facing the second developing sleeve 34.

[0085] In this embodiment, a low-magnetic-force portion 210 with a lower magnetic force than magnetic pole 207 is formed by the repulsive magnetic field generated by the cooperation between magnetic pole 201 and magnetic pole 207 disposed upstream of magnetic pole 201 in the rotational direction of the second developing sleeve 34. Magnetic pole 207 has the same magnetic polarity as magnetic pole 201. The low-magnetic-force portion 210 facilitates the transport of developer from the first developing sleeve 33 to the second developing sleeve 34. Furthermore, the low-magnetic-force portion 210 prevents developer from being attracted to the closest portion of the first developing sleeve 33 and the second developing sleeve 34, thereby suppressing the pressure applied to the developer.

[0086] like Figure 5 As shown, the stripping magnet 38 inside the stripping roller 32 has multiple magnetic poles 301 (N8), 302 (S8), 303 (N9), 304 (S9), and 305 (N10), for a total of five magnetic poles. Magnetic poles 301 to 305 are arranged in numerical order in the rotation direction of the stripping sleeve 35.

[0087] The magnetic pole 303, used as the receiving pole, is a magnetic pole that attracts developer from the second developing sleeve 34 to the stripping sleeve 35 through a magnetic field generated in cooperation with the magnetic pole 207 of the second developing magnet 37 of the second developing roller 31, and may be referred to hereinafter as the receiving pole 303. The magnetic pole 303 is an N pole with a polarity different from that of the magnetic pole 207, and is used to attract the developer stripped from the second developing sleeve 34 to the stripping sleeve 35, as described above. Magnetic poles 301, 302, and 304 are N, S, and S poles, respectively, and are used to feed the developer on the stripping sleeve 35 as the stripping sleeve 35 rotates. Specifically, the magnetic pole 302 is used to feed the developer attracted by the magnetic pole 303 upwards as the stripping sleeve 35 rotates. Hereinafter, the magnetic pole 302 may be referred to as the feed pole 302. Magnetic pole 301 is an N pole and is a stripping pole used to peel the developer attracted to the stripping sleeve 35 from the stripping sleeve 35 by a repulsive magnetic field generated in cooperation with magnetic pole 305 having the same magnetic polarity, and thereafter it may be referred to as stripping pole 301. A low magnetic force portion 310 having a lower magnetic force than magnetic pole 301 is formed between magnetic pole 301 and magnetic pole 305.

[0088] pipeline

[0089] Next, the conduit 60 will be described, which is a suction cleaning configuration for cleaning the scattered toner generated at the second developing roller 31 and the stripping roller 32. Figure 6 This is a cross-sectional view showing the arrangement of the second developing roller 31, the stripping roller 32, and the conduit (i.e., the toner collection conduit) 60 according to this embodiment. The developing apparatus 1Y is equipped with a conduit 60 including a first conduit wall 62 and a second conduit wall 61, and an air suction device 69 (see reference). Figure 2 ).

[0090] The first conduit wall 62 covers a portion of the internal space of the developing container 70, which houses the first developing roller 30, the second developing roller 31, and the stripping roller 32, and stores the developer, preventing the developer from escaping from the internal space to the outside. In this embodiment, the first conduit wall 62 covers the upper region of the stripping roller 32 and the developer collection portion 47. Specifically, the first conduit wall 62 includes a first wall portion 62b and a second wall portion 62c. The first wall portion is vertically positioned above the apex of the stripping roller 32, and the second wall portion extends upstream of the first wall portion 62b in the rotational direction of the stripping sleeve 35, and is positioned closer to the stripping roller 32 than the first wall portion 62b. That is, in this embodiment, the first conduit wall 62 is configured to extend upstream from above the stripping roller 32 in the rotational direction of the stripping sleeve 35, and bends downwards at an angle midway. Furthermore, the edge of the second wall portion 62c opposite to the first wall portion 62b is the edge 62a of the first conduit wall 62 on the suction port 60a side.

[0091] As described above, the first conduit wall 62 covers the upper portion of a portion of the internal space of the developing container 70, and the second conduit wall 61 is located outside the first conduit wall 62 relative to the rotation center of the stripping roller 32. In this embodiment, the second conduit wall 61 forms part of the outer wall of the developing container 70, but it can also be independent of the outer wall of the developing container 70. The second conduit wall 61 extends above the second developing roller 31, with its edge facing the photosensitive drum 28Y and forming a gap between them, and the second conduit wall covers the upper portion of the second developing roller 31. Specifically, the second conduit wall 61 extends more towards the side of the second developing roller 31 (i.e., the developing roller side) compared to the edge 62a of the first conduit wall 62 on the suction port 60a side. In this embodiment, the second conduit wall 61 extends from above the first conduit wall 62 in the vertical direction to a position facing the second developing roller 31.

[0092] Furthermore, the suction port 60a of the conduit 60, which is formed by the first conduit wall 62 and the second conduit wall 61, is disposed above the second developing roller 31. Specifically, the suction port 60a is an opening on the first end side of the conduit 60, which is formed between the edge 62a of the first conduit wall 62 and a portion of the second conduit wall 61. The suction port 60a is positioned downstream of the opposing portions 74 of the second developing roller 31 and the peeling roller 32 facing each other, relative to the rotational direction of the peeling roller 32.

[0093] At the second end of pipe 60, pipes for the developing equipment of each color are combined and 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, developer that has scattered inside the developer container during the developing operation is drawn in through pipe 60 and suction port 60a. This reduces the amount of developer that has scattered from the inside of the developing container 70 to the outside. When an image forming operation is performed, the air suction device 69 is activated to draw in the developer that is scattering. The suction operation is performed continuously during image forming.

[0094] like Figure 6 As shown, the first conduit wall 62 is arranged along the peeling roller 32. That is, the first conduit wall 62 extends downstream of the suction port 60a in the rotational direction towards the peeling sleeve 35, and is arranged to face a portion of the peeling roller 32, forming a gap between them. Furthermore, the first conduit wall 62 extends further from its position facing the peeling roller 32 to cover the upper region of the developer collection section 47. Therefore, the suction channel of the conduit 60 is disposed on the opposite side of the peeling roller 32, separated by the first conduit wall 62. In this embodiment, the closest distance A between the peeling roller 32 and the first conduit wall 62 is set to 1.5 mm.

[0095] From the viewpoint of carrier collection in the conduit 60 and developer retention, the closest distance A is preferably in the range of 0.5 mm to 20 mm. In this embodiment, the closest distance A between the second wall portion 62c of the first conduit wall 62 and the stripping roller 32 is preferably set to 0.5 mm to 20 mm. If the closest distance A is large, the carrier is easily collected by the conduit 60, and the conduit 60 may be easily blocked by the carrier. Furthermore, if the closest distance A is small, the developer may be retained, and the developer may not be easily conveyed by the stripping roller 32. In this case, backflow of the developer may occur, and the developer may return towards the opposite portion 74, which may cause co-rotation of the developer on the second developing roller 31, which may lead to image defects. Therefore, it is preferable to set the closest distance A between the stripping roller 32 and the conduit 60 to 0.5 mm to 20 mm.

[0096] Standard Example

[0097] Figure 7 The configuration of a developing apparatus according to a conventional example disclosed in Japanese Patent Application Publication No. 2018-124338 is shown. According to the conventional example, similar to this embodiment, the developing apparatus 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 collecting screw 44A. The first developing roller 30A, the second developing roller 31A, and the stripping roller 32A rotate in the direction of the arrows. However, the conventional example does not have a conduit 60 for drawing developer as in this embodiment. Therefore, developer that has splashed out of the developing container may splash to the outside of the developing container. Then, the inside of the image forming apparatus 100 may become contaminated with developer, or the output image may become contaminated.

[0098] Cleaning of scattered toners and clogging of scattered carriers

[0099] Next, we will refer to Figure 6This describes the relationship between the suction of scattered toner by the conduit 60 and the blockage of scattered carriers within the conduit 60. In this embodiment, as described above, the developer within the developing apparatus 1Y moves from the surface of the first developing sleeve 33 of the first developing roller 30 to the surface of the second developing sleeve 34 of the second developing roller 31, and then to the surface of the stripping sleeve 35 of the stripping roller 32. The processing speed of the image forming apparatus is increasing, and along with this, the rotational speeds of the first developing roller 30, the second developing roller 31, and the stripping roller 32 are also increasing. Therefore, while the developer is being transported on the respective sleeves, and with the magnetic spikes of the magnetic brush tilting between the magnetic poles, the toner and carriers may easily detach from the sleeves and scatter. Therefore, in this embodiment, as a countermeasure against toner scattering, the conduit 60 is provided above the second developing roller 31 and the stripping roller 32, as described above. The scattered toner is then collected by the conduit 60.

[0100] Furthermore, due to the airflow generated by the high-speed rotation of the second developing sleeve 34 and the stripping sleeve 35 as described above, the carrier that has been separated by centrifugal force may be scattered by the airflow. The airflow flows along the rotation direction of each sleeve, and the airflow near the stripping sleeve 35 flows along the rotation direction of the stripping sleeve 35. The scattered carrier moves with the airflow and is drawn into the pipe 60. The carrier drawn into the pipe 60 causes blockage of the pipe 60 and reduces the collection efficiency of the scattered toner. Therefore, it is necessary to prevent the carrier from being collected into the pipe 60.

[0101] Example 1

[0102] Reference Figure 8 Example 1 is described as an example of a configuration for suppressing carrier scattering as described above in this embodiment. In Example 1, the relationship between the position of the edge 62a of the first pipe wall 62 (which is the end portion on the suction port 60a side of the pipe 60) and the magnetic poles of the stripping magnet disposed inside the stripping roller 32 is as follows: Figure 8 Defined as shown.

[0103] That is, in this embodiment, such as Figure 8 As shown, the peak position (i.e., the pole position) P1 (which is the position where the normal component of the magnetic flux density of the stripping pole 301 on the stripping sleeve 35 reaches its maximum value) is located downstream of the edge 62a on the suction port side of the first pipe wall 62 in the rotational direction of the stripping sleeve 35. Furthermore, the peak position P1 of the stripping pole 301 is located facing the first pipe wall 62. According to this embodiment, the stripping pole 301 as a whole is located downstream of the edge 62a in the rotational direction of the stripping sleeve 35 and faces the first pipe wall 62.

[0104] As described above, by positioning the peak position P1 of the stripping electrode 301 downstream of the edge 62a of the first pipe wall 62 in the rotational direction of the stripping sleeve 35, the developer carried on the stripping sleeve 35 is stripped from the stripping roller 32 downstream of the suction port 60a in the rotational direction of the stripping sleeve 35. Therefore, the developer stripped from the stripping roller 32 is not easily sucked into the pipe 60, and the carrier scattered by the stripping of the developer can be prevented from being collected into the pipe 60.

[0105] According to this embodiment, the feed pole 302 (which is a magnetic pole adjacent to the stripping pole 301 and located downstream of the receiving pole 303 and upstream of the stripping pole 301 with respect to the rotation direction of the stripping sleeve 35) also has a peak position P2 located downstream of the edge 62a. That is, the peak position (i.e., pole position) P2 (which is the position of the maximum value of the normal component of the magnetic flux density of the feed pole 302 on the stripping sleeve 35) is located downstream of the edge 62a on the suction port side of the first pipe wall 62 in the rotation direction of the stripping sleeve 35.

[0106] Compared to the stripping pole 301, the feed pole 302 results in less carrier scattering from the stripping roller 32. However, carrier scattering occurs at the magnetic tipping position located downstream of the feed pole 302, and if the scattered carrier is captured in the airflow of the duct 60, the carrier will be collected into the duct 60. Therefore, according to this embodiment, the peak position P2 of the feed pole 302 is located downstream of the edge 62a of the first duct wall 62, making it possible to more effectively suppress the collection of carrier by the duct 60.

[0107] Comparative Example 1

[0108] Figure 9 The configuration of Comparative Example 1 is shown. In Comparative Example 1, the stripping magnet 38 is relative to... Figure 8 The configuration shown in Example 1 rotates upstream in the rotation direction, and the position of the peak position P1 of the stripping electrode 301 deviates from the position of Example 1. That is, in the configuration of Comparative Example 1, the peak position P1 of the stripping electrode 301 is located upstream of the edge 62a of the first pipe wall 62 on the suction port side in the rotation direction of the stripping sleeve 35.

[0109] In Comparative Example 1, the developer carried on the stripping sleeve 35 is stripped from the stripping roller 32 upstream of the suction port 60a in the rotational direction of the stripping sleeve 35. Therefore, the developer stripped from the stripping roller 32 is easily drawn into the conduit 60, and the carrier scattered by the stripping of the developer is easily collected in the conduit 60. Consequently, carrier blockage in the conduit 60 may easily occur, and when carrier blockage occurs, the conduit 60's ability to draw in scattered toner is reduced, and toner scattering may not be adequately suppressed.

[0110] exist Figure 9 In Comparative Example 1 shown, by rotating the stripping magnet 38, the peak position P1 of the stripping pole 301 is positioned upstream of the edge 62a of the first pipe wall 62. However, this also applies to the configuration in which the peak position P1 of the stripping pole 301 is positioned upstream of the edge 62a of the first pipe wall 62 by changing the position of the edge 62a of the first pipe wall 62.

[0111] Return to Figure 8 The configuration of Example 1 will be described below. As described above, the peak position P1 of the stripping electrode 301 is located downstream of the edge 62a of the first conduit wall 62. However, from the viewpoint of the stripping performance of the developer stripping from the stripping roller 32, it is preferable to set the peak position P1 of the stripping electrode 301 as follows: That is, preferably, the peak position P1 of the stripping electrode 301 is located downstream of the apex of the stripping roller 32 in the vertical direction in the rotation direction of the stripping sleeve 35. Furthermore, the peak position P1 of the stripping electrode 301 is preferably located above the rotation center R of the stripping roller 32 in the vertical direction. According to this configuration, the stripping performance of the developer from the stripping roller 32 is improved, making it possible to suppress image defects caused by the co-rotation of the developer and the stripping roller 32.

[0112] Table 1 shows the results according to... Figure 8 Example 1 and Figure 9 The peak position P1 of the stripping pole 301 in Comparative Example 1 is related to the collection of the carrier by the pipe 60. Table 1 shows the relationship between the peak position P1 and the peak position P1 of the stripping pole 301 in Comparative Example 1. The peak position P1 is shown on the horizontal line H passing through the rotation center R of the stripping roller 32. Figure 8 The point on the side of the second developing roller 31 is set to 0 degrees at the point where it intersects with the surface of the stripping sleeve 35, and the point on the side of the stripping roller 31 is set to 0 degrees. Figure 8 and Figure 9 The clockwise direction (i.e., the same direction as the rotation of the stripping sleeve 35) is defined as positive to represent the angle of the peak position P1. In addition, Table 1 shows, in addition to Comparative Example 1 and Example 1, the results of collecting the carrier with the pipe 60 in multiple angular positions with the peak position P1 arranged are also shown.

[0113] Table 1

[0114] *◎: Excellent: Effectively suppressed the collection of the carrier by pipe 60.

[0115] ○: Good: The collection of carriers in pipe 60 is suppressed to a level that will not cause carrier blockage.

[0116] ×: Poor: The carrier was collected by pipe 60 and carrier blockage has occurred.

[0117] In Table 1, "Very good" indicates that the collection of carrier by pipe 60 is sufficiently suppressed. "Good" indicates that the collection of carrier by pipe 60 is suppressed to a level that does not cause carrier blockage. "Poor" indicates that carrier is collected by pipe 60 and carrier blockage has occurred. Furthermore, the case where the angle of peak position P1 is 20° is Comparative Example 1, and the case where the angle is 30° is the position facing edge 62a. Furthermore, the case where the angle of peak position P1 is 90° is the peak position of the stripping roller 32 in the vertical direction, and the case where the angle is 95° is Example 1. Furthermore, the case where the angle is 180° is on the side opposite to the second developing roller 31 and is at the same height as the rotation center R in the vertical direction, while the case where the angle is 270° is the peak position P1 arranged below the rotation center R in the vertical direction. Based on Table 1, it can be understood that it is preferable to set the peak position P1 to 30° or more and 270° or less, and more preferably, to set the peak position P1 to 90° or more and 180° or less.

[0118] Furthermore, from the viewpoint of suppressing the collection of carriers into the pipe 60, the position of the edge 62a of the first pipe wall 62 is preferably set as follows: Specifically, the edge 62a of the first pipe wall 62 is preferably positioned upstream of the vertical apex of the peeling roller 32 in the rotational direction of the peeling sleeve 35. Furthermore, the edge 62a of the first pipe wall 62 is preferably positioned higher in the vertical direction than the rotation center R of the peeling roller 32. According to this configuration, the collection of carriers into the pipe 60 can be further suppressed.

[0119] Table 2 shows the relationship between the position of the edge 62a of the first pipe wall 62 according to the configuration of Example 1 and the collection of the carrier. In Table 2, similar to the case shown in Table 1, the carrier is collected along the horizontal line H passing through the rotation center R of the stripping roller 32. Figure 8 The point on the side of the second developing roller 31 is set to 0 degrees at the point where it intersects with the surface of the stripping sleeve 35, and the point on the side of the stripping roller 31 is set to 0 degrees. Figure 8 The clockwise direction (i.e., the same direction as the rotation of the stripping sleeve 35) is defined as positive to indicate the angle of the position of edge 62a. Furthermore, Table 2 shows the results of examining the collection of the carrier by the pipe 60 with edge 62a arranged in multiple angular positions.

[0120] Table 2

[0121] *◎: Excellent: Effectively suppressed the collection of the carrier by pipe 60.

[0122] ○: Good: The collection of carriers in pipe 60 is suppressed to a level that will not cause carrier blockage.

[0123] In Table 2, “very good” and “good” indicate the same state as described in Table 1. It can be understood from Table 2 that it is preferable to set the position of the edge 62a of the first pipe wall 62 to -20° or more and 95° or less, and more preferably, the position of the edge 62a to 0° or more and 90° or less.

[0124] In Example 1, by positioning the peak position P1 of the stripping electrode 301 downstream of the edge 62a of the first conduit wall 62 in the rotational direction of the stripping sleeve 35, the collection of scattered carrier into the conduit 60 can be suppressed. Furthermore, in Example 1, the peak position P2 of the feed electrode 302 is also positioned downstream of the edge 62a. Therefore, the collection of carrier by the conduit 60 can be suppressed more effectively. As a result, the reduction in the conduit 60's ability to absorb scattered toner can be suppressed, and toner scattering can be suppressed for a longer period.

[0125] Example 2

[0126] Reference Figure 10 Example 2 is described as an example of a configuration for suppressing carrier scattering in this embodiment. In Example 2, the stripping magnet 38 is relative to... Figure 8 The configuration of Example 1 shown rotates upstream in the rotational direction, causing the peak positions P1 of the stripping electrode 301 and P2 of the feed electrode 302 to shift relative to Example 1. That is, in Example 2, similar to Example 1, the peak position P1 of the stripping electrode 301 is positioned downstream of the edge 62a of the first pipe wall 62 in the rotational direction of the stripping sleeve 35. However, unlike Example 1, in Example 2, the peak position P2 of the feed electrode 302 is positioned upstream of the edge 62a of the first pipe wall 62 in the rotational direction of the stripping sleeve 35.

[0127] As in Example 1, if the peak position P2 of the feed electrode 302 is positioned downstream of the edge 62a of the first pipe wall 62 in the rotational direction of the stripping sleeve 35, the collection of the carrier by the pipe 60 can be further suppressed. However, as in Example 2, if the peak position P1 of the stripping electrode 301 is positioned downstream of the edge 62a of the first pipe wall 62 in the rotational direction of the stripping sleeve 35, the collection of the carrier by the pipe 60 can be suppressed even if the peak position P2 of the feed electrode 302 is positioned upstream of the edge 62a, although the effect is less than that of Example 1.

[0128] Table 3 shows the data based on... Figure 8 Example 1 and Figure 10The peak position P2 of the feed pole 302 in Example 2 configuration is related to the carrier being collected into the pipe 60. Table 3 shows a similar situation to Table 1, indicated by the horizontal line H (passing through the rotation center R of the stripping roller 32)... Figure 8 The point on the side of the second developing roller 31 is set to 0 degrees at the point where it intersects with the surface of the stripping sleeve 35, and the point on the side of the stripping roller 31 is set to 0 degrees. Figure 8 The clockwise direction (i.e., the same direction as the rotation of the stripper sleeve 35) is defined as positive to represent the angle of the peak position P2 of the feed pole 302. In addition, Table 3 shows, in addition to Examples 1 and 2, the results of the carrier being collected into the pipe 60 when the peak position P2 is facing the edge 62a (30°) are also shown.

[0129] Table 3

[0130] *◎: Excellent: Effectively suppressed the collection of the carrier by pipe 60.

[0131] ○: Good: The collection of carriers in pipe 60 is suppressed to a level that will not cause carrier blockage.

[0132] In Table 3, "Very good" and "Good" indicate the same states as described in Table 1. From Table 3, it can be understood that it is preferable to set the peak position P2 of the feed pole 302 to 20° or greater, and that carrier collection is sufficiently suppressed even when the peak position P2 faces the edge 62a. Furthermore, it can be understood that it is more preferable to arrange the peak position P2 downstream of the edge 62a.

[0133] Example 2 is effective when the positional relationship between the second developing roller 31, the stripping roller 32, and the first pipe wall 62 is limited, and it is difficult to position the peak position P2 of the feed pole 302 downstream of the edge 62a. Even with such limitations, the collection of the carrier by the pipe 60 can be suppressed by positioning the peak position P1 of the stripping pole 301 downstream of the edge 62a.

[0134] Example 3 and Example 4

[0135] In the configuration of this embodiment, reference will be made to Figure 11 Examples 3 and 4 are described as examples of configurations for suppressing toner scattering. In Examples 3 and 4, it is confirmed from the viewpoint of Fθ, which is the magnetic force applied to the carrier at the position of edge 62a of the first pipe wall 62.

[0136] The magnetic flux density and magnetic force generated by the stripped magnet 38 will be described below. In the description of this embodiment, Br, Bθ, Fr, and Fθ are defined as follows.

[0137] Br: Magnetic flux density at a point relative to the normal direction (i.e., the perpendicular direction) of the outer peripheral surface (i.e., the upper surface) of the stripping sleeve 35.

[0138] Bθ: Magnetic flux density at a point in the tangential direction relative to the outer peripheral surface of the stripping sleeve 35

[0139] Fr: The magnetic force applied at a point in the direction normal to the outer peripheral surface of the stripper sleeve 35, where the direction of attraction (i.e., the direction toward the stripper sleeve 35) is called the negative direction.

[0140] Fθ: The magnetic force applied at a point in the tangential direction relative to the outer peripheral surface of the stripping sleeve 35, where the direction of rotation of the stripping sleeve 35 is called the positive direction.

[0141] Unless otherwise specified, Br, Bθ, Fr and Fθ refer to the magnetic flux density or magnetic force at a point on the stripping sleeve 35.

[0142] Methods for measuring magnetic force or magnetic flux density

[0143] Next, a method for measuring magnetic force according to this embodiment will be described. The magnetic force according to this embodiment can be calculated by the calculation method described below. The magnetic force acting on the carrier can be obtained by the following expression (1). In this expression, μ0 represents the permeability of vacuum, μ represents the permeability of the carrier, b represents the radius of the carrier, and B represents the magnetic flux density.

[0144] Expression (1)

[0145]

[0146] therefore,

[0147] Expression (2)

[0148]

[0149] Based on expression (2), Fr and Fθ can be calculated by obtaining Br and Bθ. The magnetic flux density Br was measured using the magnetic field measuring instrument “MS-9902” (product name) manufactured by FW BELL and the distance between the probe (which is a component of the measuring instrument) and the upper surface of the developing sleeve was set to approximately 100 μm.

[0150] Furthermore, Bθ can be obtained using the following method. The vector potential A at the measurement location of the magnetic flux density Br can be obtained using the measured magnetic flux density Br through the following expression. z (R, θ).

[0151] Expression (3)

[0152]

[0153] By setting the boundary conditions to A z (R, θ) and solve the following expression to obtain A. z (r, θ),

[0154]

[0155] Then, Br and Bθ are obtained through the following expressions.

[0156] Expression (4)

[0157]

[0158] Expression (5)

[0159]

[0160] Fr and Fθ can be obtained by applying Br and Bθ, which are measured and calculated as described above, to expression (1). Furthermore, based on the above expression, the Fr distribution required according to this embodiment can be obtained.

[0161] In Example 3, when the magnetic force applied to the peeling sleeve 35 in the tangential direction is set to Fθ, the force of Fθ applied in the same direction as the rotation direction of the peeling sleeve 35 is set to positive, and the force of Fθ applied in the opposite direction to the rotation direction of the peeling sleeve 35 is set to negative, the Fθ on the peeling sleeve 35 corresponding to the edge 62a of the first pipe wall 62 is set to +1.5 × 10⁻⁶. -8 N. Meanwhile, in Example 4, the Fθ on the stripping sleeve 35 corresponding to the edge 62a of the first pipe wall 62 is set to -1.5 × 10⁻⁶. -8 N. Figure 11 A graph showing the distribution of Fθ near the location of the edge 62a of the first pipe wall 62 according to Examples 1, 3 and 4 is shown.

[0162] In Example 1, the Fθ corresponding to the position of edge 62a on the stripping sleeve 35 is approximately 0 and is very small. In Example 3, a stripping magnet 38 with a larger Fθ corresponding to the position of edge 62a on the stripping sleeve 35 than in Example 1 was used. In Example 4, a stripping magnet 38 with a smaller Fθ corresponding to the position of edge 62a on the stripping sleeve 35 than in Example 1 was used. For each example, collection of the carrier into the conduit 60 was confirmed.

[0163] In Example 3, the Fθ on the peeling sleeve 35 corresponding to the position of edge 62a is set to be relatively large, causing the developer to move faster on the peeling sleeve 35 at the position corresponding to edge 62a than the rotational speed of the peeling roller 32. Therefore, the centrifugal force acting on the carrier is large, and the carrier is easily released from the peeling roller 32. Thus, compared to Example 1, the carrier is more easily collected into the pipe 60.

[0164] Meanwhile, in Example 4, the Fθ corresponding to the position of edge 62a on the peeling sleeve 35 is set to be small, causing the developer to move at a slower speed on the peeling sleeve 35 at the position corresponding to edge 62a than the rotational speed of the peeling roller 32. Therefore, the centrifugal force acting on the carrier is small, and the carrier is less likely to be released from the peeling roller 32. However, the slow movement speed of the developer causes the height of the developer on the peeling roller 32 to tend to increase. Therefore, in Example 4, the height of the developer on the peeling roller 32 exceeds the closest distance A between the peeling roller 32 and the first pipe wall 62. Therefore, the developer remains at the closest distance A between the peeling roller 32 and the first pipe wall 62, and the developer cannot be properly conveyed by the peeling roller 32, resulting in developer backflow. By causing the developer to return to the opposite portion 74, co-rotation of the developer occurs on the second developing roller 31, and image defects tend to appear.

[0165] As described above, the configuration of Example 1 can suppress the retention of developer at the location closest to distance A and can minimize the collection of carrier into pipe 60.

[0166] Table 4 shows the relationship between Fθ on the peeling sleeve 35 corresponding to the position of edge 62a and the developer retention and carrier collection by the tube 60, corresponding to the configurations of Examples 1, 3, and 4. In addition to Examples 1, 3, and 4, Table 4 also shows Fθ as -1.0 × 10⁻⁶. -8 The case of N (-1.0E-08) and Fθ being +1.0×10 -8 The case of N (1.0E-08). In Example 1, Fθ is +0.9 × 10⁻⁸. -9 N(0.9E-09), Fθ in Example 3 is +1.5×10 -8 N(1.5E-08), and Fθ in Example 4 is -1.5×10 -8 N (-1.5E-08).

[0167] Table 4

[0168] *Carrier collection

[0169] ◎: Excellent: Effectively suppressed the collection of the carrier by pipe 60.

[0170] ○: Good: The collection of carriers in pipe 60 is suppressed to a level that will not cause carrier blockage.

[0171] *Developer residue

[0172] ◎: Excellent: No developer residue occurred at the location closest to point A.

[0173] ○: Good: Some developer retention occurred at the location closest to point A, but the accompanying image defects are within acceptable limits.

[0174] In Table 4, "Very Good" and "Good" in the "Carrier Collection" column indicate the same conditions as described in Table 1. Furthermore, "Very Good" in the "Developer Retention" column indicates that no developer retention has occurred at the location closest to distance A. "Good" indicates that some developer retention has occurred at the location closest to distance A, but the accompanying image defects are within acceptable limits.

[0175] Based on Table 4, it is recognized that, from the viewpoint of inhibiting developer retention at the position closest to distance A, it is preferable to set Fθ on the stripping sleeve 35 corresponding to the position of the edge 62a of the first conduit wall to +1.5 × 10⁻⁶. -8 N or less. Furthermore, from the viewpoint of suppressing the collection of the carrier by the conduit 60, it is preferable to set Fθ on the stripping sleeve 35 corresponding to the position of the edge 62a of the first conduit wall to -1.5 × 10⁻⁶. -8 N or greater. Furthermore, from the viewpoints of both suppressing developer retention and suppressing carrier collection by the tube 60, it is preferable to set Fθ on the stripping sleeve 35 corresponding to the position of the edge 62a of the first tube wall to -1.0 × 10⁻⁶. -8 N or more, +1.0×10 -8 Below N.

[0176] In Example 3, the Fθ corresponding to the position of edge 62a on the peeling sleeve 35 is set to be larger than in Example 1, thus suppressing developer retention at the position closest to distance A compared to Example 1. However, compared to Example 3, Example 1 is able to suppress developer retention and carrier collection by the tube 60. In Example 4, the Fθ corresponding to the position of edge 62a on the peeling sleeve 35 is set to be smaller than in Example 1, making the carrier less prone to scattering, and similarly suppressing developer retention and carrier collection by the tube 60 as in Example 1, or even suppressing developer retention and carrier collection by the tube 60 more than in Example 1. However, compared to Example 4, Example 1 is able to suppress developer retention at the position closest to distance A. Therefore, from the viewpoint of suppressing both developer retention and suppressing carrier collection by the tube 60, Example 1 is the most preferred.

[0177] Example 5

[0178] In the configuration of this embodiment, reference will be made to Figure 12 and Figure 13 Example 5 is described as an example of a configuration for suppressing carrier scattering. In Example 5, the position of the guide member 45 that guides the developer to the developer collection screw 44 is changed compared to the configuration of Example 1. That is, in Example 5, the normal component of the magnetic flux density on the stripping sleeve 35 is referred to as Br, as... Figure 12 As shown, the absolute value of the edge 45b of the guide member 45 facing Br on the peeling roller 32 side is 10 mT or less, preferably 5 mT or less. The peeling magnet 38 within the peeling roller 32 is configured the same as in Example 1.

[0179] like Figure 12 As shown, the edge 45b of the guide member 45 is arranged close to the low magnetic force portion 310 facing the stripping magnet 38. Since the low magnetic force portion 310 is the area where the developer is stripped from the stripping sleeve 35, by arranging the edge 45b of the guide member 45 at the position facing the low magnetic force portion 310 as in Example 4, the stripping performance of the developer from the stripping roller 32 can be improved compared to the configuration of Example 1, and the transfer performance of the developer to the developer collection screw 44 can also be improved. As a result, the co-rotation of the developer on the stripping roller 32 can be suppressed, and the image quality of the output image can be improved.

[0180] Figure 13 This is a graph showing the Br distribution at the positions of the individual magnetic poles of the magnetic field generated by the stripping magnet 38 inside the stripping roller 32. By setting the edge 45b of the guide member 45 in a region where the absolute value of Br |Br| is 10 mT or less, the stripping performance of the developer from the stripping roller 32 can be improved.

[0181] Table 5 shows the relationship between the position of the edge 45b of the guide member 45 according to the configurations of Examples 1 and 5 and the peelability of the developer from the stripping roller 32. In Table 5, similar to the case shown in Table 1, the relationship is indicated by the horizontal line H passing through the rotation center R of the stripping roller 32. Figure 8 The point on the side of the second developing roller 31 is set to 0 degrees at the point where it intersects with the surface of the stripping sleeve 35, and the point on the side of the stripping roller 31 is set to 0 degrees. Figure 8 The clockwise direction (i.e., the same direction as the rotation of the stripping sleeve 35) is defined as positive to represent the angle at the position of the edge 45b of the guide member 45. Furthermore, in Table 5, in addition to Examples 1 and 5, the results of examining the peelability of the developer from the stripping roller 32 when the position of the edge 45b of the guide member 45 is set differently than in Examples 1 and 5 are shown.

[0182] Table 5

[0183] *◎: Excellent: The developer peeling performance from stripping roller 32 is satisfactory.

[0184] ○: Good: The peelability of the developer from the stripping roller 32 has deteriorated somewhat, but is at a level that does not affect the output image.

[0185] △: Average: The peelability of the developer from the stripping roller 32 deteriorates, and the output image is somewhat affected.

[0186] In Table 5, "Very good" indicates that the developer peeling performance from the stripping roller 32 is satisfactory. "Good" indicates that the developer peeling performance from the stripping roller 32 is somewhat deteriorated but at a level that does not affect the output image. "Average" indicates that the developer peeling performance from the stripping roller 32 is deteriorated and the output image is somewhat affected.

[0187] Based on Table 5, it is understood that it is preferable to set the position of the edge 45b of the guide member 45 to be 110° or more and 280° or less. Furthermore, it is understood that it is more preferable to set the position of the edge 45b of the guide member 45 to be within the range of 110° or more and 200° or less.

[0188] In Example 5, since the absolute value of the edge 45b of the guide member 45 facing Br on the peeling roller side is 10mT or less, the peelability of the developer from the peeling roller 32 can be improved compared to the configuration of Example 1. As a result, the co-rotation of the developer on the peeling roller 32 is suppressed, and the image quality of the output image can be improved.

[0189] experiment

[0190] Perform the following experiments to confirm Examples 1 to 5 and Comparative Example 1 ( Figure 9) and regular examples ( Figure 7 The effects of each configuration. Attaching each configuration of the developing equipment to... Figure 1 The image forming apparatus shown was used to form images on 5000 sheets. In each configuration, toner scattering within the developing apparatus, carrier entry into conduit 60 collection, developer retention at the location closest to distance A, and developer stripping from the stripping roller 32 were identified and evaluated. For the conventional example, conduit 60 was not provided, thus items other than toner scattering were not evaluated. For Comparative Example 1, the peak position P1 of the stripping pole 301 was located upstream of the edge 62a of the first conduit wall 62 in the rotational direction of the stripping sleeve 35, thus developer retention was not evaluated. The experimental results are shown in Table 6.

[0191] Table 6

[0192] *Toner scattering

[0193] ○: Good: Toner dispersion in the developing equipment is adequately suppressed.

[0194] ×: Poor: Toner has spilled in the developing equipment.

[0195] *Collection of carrier into pipeline

[0196] ◎: Excellent: Effectively suppressed the collection of the carrier by pipe 60.

[0197] ○: Good: The collection of carriers in pipe 60 is suppressed to a level that will not cause carrier blockage.

[0198] ×: Poor: The carrier was collected by pipe 60 and carrier blockage has occurred.

[0199] *Developer residue

[0200] ◎: Excellent: No developer residue occurred at the location closest to point A.

[0201] ○: Good: Some developer retention occurred at the location closest to point A, but the accompanying image defects are within acceptable limits.

[0202] *Developer stripping properties

[0203] ◎: Excellent: The developer peeling performance from the stripping roller 32 is satisfactory.

[0204] ○: Good: The peelability of the developer from the stripping roller 32 has deteriorated somewhat, but is at a level that does not affect the output image.

[0205] △: Average: The peelability of the developer from the stripping roller 32 deteriorates, and the output image is somewhat affected.

[0206] In Table 6, "Good" in "Toner Spray" indicates that toner spray in the developing equipment is adequately suppressed. "Poor" indicates that toner spray has occurred in the developing equipment. Furthermore, "Very Good," "Good," and "Poor" in the "Carrier Collection into Pipeline" column indicate the same conditions as described in Table 1. "Very Good" and "Good" in the "Developer Retention" column indicate the same conditions as described in Table 4. "Very Good" and "Good" in the "Developer Stripping Properties" column indicate the same conditions as described in Table 5. "Poor" in "Developer Stripping Properties" indicates that the developer stripping properties from the stripping roller 32 have deteriorated and have affected the output image.

[0207] As can be seen from Table 6, in addition to the conventional examples, Comparative Examples 1 and Examples 1 to 5 include a conduit 60, which effectively suppresses toner dispersion within the developing apparatus. Furthermore, according to Comparative Example 1, the peak position P1 of the stripping electrode 301 is located upstream of the edge 62a of the first conduit wall 62 in the rotational direction of the stripping sleeve 35, resulting in a poorer evaluation of carrier collection into the conduit and developer stripping performance compared to Examples 1 to 5. Regarding carrier collection into the conduit, Examples 1, 4, and 5 have high evaluations among Examples 1 to 5. Regarding developer retention, all examples except Example 4 have high evaluations among Examples 1 to 5. Even further, while Examples 1 to 4 are acceptable in terms of developer stripping performance, Example 5 has a high evaluation.

[0208] Other embodiments

[0209] The various embodiments are described based on a developing apparatus including two developing rollers; however, this disclosure is also applicable to configurations having only one developing roller. That is, this disclosure applies to configurations in which a developing roller is provided for developing an electrostatic latent image on an image developing member (such as a photosensitive drum), and a stripping roller is provided for stripping developer from the developing roller.

[0210] The present invention is not limited to the configuration of each of the above embodiments. For example, the image forming apparatus 100 is not limited to an MFP, but can be a copier, printer, or fax machine. Furthermore, the configuration of the developer supply screw 42, the developer stirring screw 43, and the developer collecting screw 44 is not particularly limited, as long as developer can be fed, and for example, helical blades or paddle blades can be used.

[0211] According to this disclosure, the collection of the carrier by the pipeline can be suppressed.

[0212] While this disclosure has been described with reference to embodiments, it should be understood that this disclosure is not limited to the disclosed embodiments. The scope of the following claims should be interpreted in the broadest possible sense to include all such modifications and equivalent structures and functions.

Claims

1. A developing apparatus, comprising: A developing container, the developing container comprising a first chamber configured to contain a developer and a second chamber separated from the first chamber by a partition wall, the developer comprising a toner and a carrier; A first rotatable developing member is supplied with developer. The first rotatable developing member is configured to carry the developer and feed the developer to a developing position, where an electrostatic latent image formed on an image carrying member is developed. A first magnet is non-rotatably and fixedly disposed inside a first rotatable developing member. The first magnet has a first magnetic pole, a second magnetic pole, and a third magnetic pole. The first magnetic pole is disposed facing the image carrying member at the developing position. The second magnetic pole is disposed downstream of the first magnetic pole in the rotation direction of the first rotatable developing member. The third magnetic pole is disposed downstream of and adjacent to the second magnetic pole relative to the rotation direction of the first rotatable developing member, and has the same magnetic polarity as the second magnetic pole. A second rotatable developing member is arranged to face the first rotatable developing member and is configured to receive developer delivered from the first rotatable developing member by a magnetic field generated by the first magnet. The second rotatable developing member is configured to carry developer after developing an electrostatic latent image and to feed developer into a second chamber to collect the developer in the second chamber. A second magnet is non-rotatably and fixedly disposed inside the second rotatable developing member. The second magnet has a fourth, fifth, sixth, and seventh magnetic pole. The fourth magnetic pole has a different magnetic polarity than the second magnetic pole. The fifth magnetic pole is positioned downstream of the fourth magnetic pole relative to the rotation direction of the second rotatable developing member. The sixth magnetic pole is positioned downstream of and adjacent to the fifth magnetic pole relative to the rotation direction of the second rotatable developing member and has a different magnetic polarity than the fifth magnetic pole. The seventh magnetic pole is positioned downstream of and adjacent to the sixth magnetic pole relative to the rotation direction of the second rotatable developing member and has the same magnetic polarity as the sixth magnetic pole. The developing agent after developing the electrostatic latent image is transported from the first rotatable developing member to the second rotatable developing member by a magnetic field generated between the second magnetic pole and the fourth magnetic pole. as well as Pipeline, the pipeline comprising: The suction port, which is an inlet, is used to draw out the developer that has dispersed in the developing container. The suction port is located downstream of the first rotatable developing member and the second rotatable developing member, facing each other, in the rotational direction of the second rotatable developing member. A first conduit wall, configured to extend downstream of the suction port in the rotational direction of the second rotatable developing member, the first conduit wall being arranged to face a portion of the second rotatable developing member and forming a gap between the first conduit wall and said portion of the second rotatable developing member, and A second conduit wall, configured to face the first conduit wall and form a space between the second conduit wall and the first conduit wall, through which developer drawn from the suction port flows, is positioned further outward than the first conduit wall relative to the rotation center of the second rotatable developing member, in a direction from the rotation center of the second rotatable developing member toward the position where the absolute value of the normal component of the magnetic flux density of the sixth magnetic pole on the outer peripheral surface of the second rotatable developing member becomes maximum. Where the first rotatable developing member and the second rotatable developing member are positioned facing each other, the rotation direction of the second rotatable developing member is opposite to the rotation direction of the first rotatable developing member, and The location where the absolute value of the normal component of the magnetic flux density of the sixth magnetic pole on the outer peripheral surface of the second rotatable developing member becomes the largest is located downstream of the edge of the first pipe wall on the suction port side relative to the rotation direction of the second rotatable developing member.

2. The developing apparatus according to claim 1, The location where the absolute value of the normal component of the magnetic flux density of the fifth magnetic pole on the outer peripheral surface of the second rotatable developing member becomes the largest is located downstream of the edge of the first pipe wall on the suction port side relative to the rotation direction of the second rotatable developing member.

3. The developing apparatus according to claim 1 or 2, The magnetic force applied along the normal direction to the outer peripheral surface of the second rotatable developing member is called Fθ. Fθ is positive when its direction is the same as the rotation direction of the second rotatable developing member, and negative when its direction is opposite to the rotation direction of the second rotatable developing member. Fθ at the position on the outer peripheral surface of the second rotatable developing member corresponding to the edge of the first pipe wall on the suction port side is +1.5 × 10⁻⁶. -8 N or smaller.

4. The developing apparatus according to claim 3, Wherein, Fθ at the position corresponding to the edge of the first pipe wall on the suction port side on the outer peripheral surface of the second rotatable developing member is +1.0×10. -8 N or smaller.

5. The developing apparatus according to claim 1 or 2, The magnetic force applied along the normal direction to the outer peripheral surface of the second rotatable developing member is called Fθ. Fθ is positive when its direction is the same as the rotation direction of the second rotatable developing member, and negative when its direction is opposite to the rotation direction of the second rotatable developing member. Fθ at the position on the outer peripheral surface of the second rotatable developing member corresponding to the edge of the first pipe wall on the suction port side is -1.5 × 10⁻⁶. -8 N or greater.

6. The developing apparatus according to claim 5, The value of Fθ at the position corresponding to the edge of the first pipe wall on the suction port side on the outer peripheral surface of the second rotatable developing member is -1.0 × 10⁻⁶. -8 N or greater.

7. The developing apparatus according to claim 1 or 2, further comprising: A guiding portion, configured to face the second rotatable developing member and to guide developer stripped from the second rotatable developing member into the second chamber, The edge of the guide portion on the side of the second rotatable developing member is configured relative to the outer peripheral surface of the second rotatable developing member to face a region on the outer peripheral surface of the second rotatable developing member where the absolute value of the normal component of the magnetic flux density is 10 mT or less.

8. The developing apparatus according to claim 1 or 2, The edge of the first pipe wall on the suction port side is positioned upstream of the vertex of the second rotatable developing member in the vertical direction in the rotational direction of the second rotatable developing member.

9. The developing apparatus according to claim 8, The edge of the first pipe wall on the suction port side is positioned vertically above the rotation center of the second rotatable developing member.

10. The developing apparatus according to claim 1 or 2, The location where the absolute value of the normal component of the magnetic flux density of the sixth magnetic pole on the outer peripheral surface of the second rotatable developing member becomes the largest is located downstream of the vertex in the vertical direction of the second rotatable developing member in the rotational direction of the second rotatable developing member.

11. The developing apparatus according to claim 10, The position where the absolute value of the normal component of the magnetic flux density of the sixth magnetic pole on the outer peripheral surface of the second rotatable developing member becomes the largest on the outer peripheral surface of the second rotatable developing member is located in the vertical direction above the rotation center of the second rotatable developing member.

12. The developing apparatus according to claim 1 or 2, The second pipe wall is configured to extend further toward the first rotatable developing member than the edge of the first pipe wall on the suction port side.

13. The developing apparatus according to claim 1 or 2, further comprising: A transfer section is disposed in the second chamber and configured to transfer the developer within the second chamber; as well as A connecting portion, the connecting portion being configured to allow developer to communicate from the second chamber to the first chamber.

14. The developing apparatus according to claim 1 or 2, further comprising: A third chamber, the third chamber being configured to be separated from the first chamber by a separate partition wall different from the first chamber; A first transfer section is disposed in the first chamber and configured to transfer the developer in the first chamber; A second transfer section is disposed in the second chamber and configured to transfer the developer in the second chamber; A third transfer section is disposed in the third chamber and configured to transfer the developer in the third chamber; A first connecting portion, the first connecting portion being configured to allow developer to communicate from the third chamber to the first chamber; A second connecting portion is configured to allow developer to communicate from the first chamber to the third chamber; as well as A third connecting portion is configured to allow developer to communicate from the second chamber to the first chamber.

15. The developing apparatus according to claim 1 or 2, further comprising: A third rotatable developing member is configured to face the first rotatable developing member and to receive developer contained in the first chamber. The third rotatable developing member is configured to carry and feed developer to develop an electrostatic latent image. as well as A third magnet, which is non-rotatably and fixedly disposed inside the third rotatable developing member, Where the first rotatable developing member and the third rotatable developing member are positioned facing each other, the rotation direction of the first rotatable developing member is opposite to the rotation direction of the third rotatable developing member, and The first rotatable developing member is configured to receive developing agent delivered from the third rotatable developing member by means of a magnetic field generated by the third magnet.

Images