Developing device

Abstract

A developing device includes a first rotatable member, a first magnet, a second rotatable member, and a second magnet. When the position at which the pole magnetic flux density is maximum on the surface of the first rotatable member is point T, the downstream side position is point Hd and the upstream side position is point Hu in each position at which the pole magnetic flux density is half of the maximum. When an angle formed by a straight line L10 connecting a rotation center R1 of the first rotatable member and a point T and a straight line L12 connecting the rotation center R1 and a point Hu is w1, and an angle formed by L10 and a straight line L11 connecting R1 and Hd is w2, the following relationship is satisfied: w1-w2 > = 0.

Description

Technical Field

[0001] The present invention relates to a developing device for developing an electrostatic latent image formed on an image bearing member using a developer. Background Art

[0002] As a developing device, a configuration is proposed in which two developing rollers for developing an electrostatic latent image formed on an image bearing member with a developer are arranged side by side with respect to the rotation direction of the image bearing member (U.S. Patent Application Publication 2013 / 0330107). In the developing device having two developing rollers disclosed in US2013 / 0330107A1, the developer is supplied from a supply portion to a first developing roller located at a lower portion in the vertical direction, and the developer is delivered from the first developing roller located at the lower portion to a second developing roller located at an upper portion in the vertical direction.

[0003] As described in US2013 / 0330107A1, when the developer is delivered from the first developing roller to the second developing roller located at the upper part in the vertical direction, the developer is delivered by a magnetic field formed between the delivery pole of the first magnet provided in the first developing roller and the receiving pole of the second magnet provided in the second developing roller. The polarity of the delivery pole is opposite to that of the receiving pole. In this configuration, when the rotation direction of the second developing roller at a position where the second developing roller is opposite to the rotation direction of the first developing roller is opposite to that of the first developing roller, the polarity of the first magnetic pole adjacent to the delivery pole on the upstream side of the delivery pole is opposite to that of the second magnetic pole adjacent to the receiving pole on the downstream side of the receiving pole. Therefore, a magnetic field for attracting the developer to each developing roller is generated between the first magnetic pole and the second magnetic pole.

[0004] Therefore, a magnetic field for attracting the developer is generated between the first magnetic pole and the second magnetic pole, and the developer may move between the first magnetic pole and the second magnetic pole by the magnetic field. In addition, when the developer moves between the first magnetic pole and the second magnetic pole, the moved developer may float and then deposit on the image bearing member located near the first developing roller and the second developing roller. Therefore, when the developer is deposited on the image bearing member, image defects such as vertical streak-like fog occur on the output image. Summary of the invention

[0005] A main object of the present invention is to provide a developing device capable of suppressing the occurrence of image defects.

[0006] According to one aspect of the present invention, a developing device is provided, comprising: a developing container configured to contain a developer, the developer comprising a toner and a carrier; a first rotatable component, the developer contained in the developing container is supplied to the first rotatable component, and the first rotatable component carries and feeds the developer to a first developing position, and develops an electrostatic latent image formed on an image bearing component at the first developing position; a first magnet, which is non-rotatably and fixedly arranged in the first rotatable component, wherein the first magnet comprises a first developing pole arranged opposite to the image bearing component at the first developing position, a delivery pole arranged downstream of the first developing pole relative to a rotation direction of the first rotatable component, and a delivery pole arranged downstream of the first developing pole relative to a rotation direction of the first rotatable component. a first feeding pole disposed upstream of and adjacent to the feeding pole and having a magnetic polarity different from that of the feeding pole; a second rotatable member disposed opposite to the first rotatable member and delivering the developer from the first rotatable member to the second rotatable member by a magnetic field generated by the first magnet, wherein the second rotatable member carries and feeds the developer to a second developing position for developing an electrostatic latent image, wherein a rotation direction of the second rotatable member at a position on the outer circumferential surface of the second rotatable member where the second rotatable member is closest to the first rotatable member is opposite to a rotation direction of the first rotatable member at a position on the outer circumferential surface of the first rotatable member where the first rotatable member is closest to the second rotatable member; and a second magnet disposed non-rotatably and fixedly in the second rotatable member, wherein the second magnet includes a plurality of magnetic poles, the plurality of magnetic poles including a second developing pole arranged opposite to the image bearing member at the second developing position, a receiving pole arranged upstream of the second developing pole with respect to the rotation direction of the second rotatable member and having a magnetic polarity different from that of the delivering pole, and a second feeding pole arranged downstream of the receiving pole with respect to the rotation direction of the second rotatable member and adjacent to the receiving pole and having a magnetic polarity different from that of the receiving pole, the receiving pole being the magnetic pole arranged closest to the delivering pole among the plurality of magnetic poles; wherein, in the following case, that is, the position where the magnetic flux density of the delivering pole on the outer peripheral surface of the first rotatable member relative to the normal direction of the outer peripheral surface of the first rotatable member is the maximum is point T, and on the outer peripheral surface of the first rotatable member relative to the normal direction of the outer peripheral surface of the first rotatable member, the magnetic flux density of the delivering pole is the maximum at point T. The position on the downstream side relative to the rotation direction of the first rotatable component at each position where the delivery pole magnetic flux density normal to the outer peripheral surface of the first rotatable component is half the maximum value is point Hd, and the position on the upstream side relative to the rotation direction of the first rotatable component at each position where the delivery pole magnetic flux density normal to the outer peripheral surface of the first rotatable component is half the maximum value is point Hu, the angle formed by the straight line L10 connecting the rotation center R1 of the first rotatable component and point T and the straight line L12 connecting the rotation center R1 and point Hu is w1, and the angle formed by the straight line L10 and the straight line L11 connecting the rotation center R1 and point Hd is w2, satisfying the following relationship: w1-w2≥0.

[0007] According to another aspect of the present invention, a developing device is provided, comprising: a developing container configured to contain a developer, the developer comprising a colorant and a carrier; a first rotatable component, the developer contained in the developing container is supplied to the first rotatable component, and the first rotatable component carries and feeds the developer to a first developing position, and develops an electrostatic latent image formed on an image bearing component at the first developing position; a first magnet, which is non-rotatably and fixedly arranged in the first rotatable component, wherein the first magnet comprises a first developing pole arranged opposite to the image bearing component at the first developing position, a delivery pole arranged downstream of the first developing pole relative to the rotation direction of the first rotatable component, and a first feeding pole arranged upstream of the delivery pole relative to the rotation direction of the first rotatable component and adjacent to the delivery pole and having a magnetic polarity different from that of the delivery pole; a second rotatable component, which is arranged opposite to the first rotatable component, and delivers the developer from the first rotatable component to the second rotatable component by a magnetic field generated by the first magnet a rotating member, wherein the second rotatable member carries and feeds the developer to a second developing position for developing the electrostatic latent image, and wherein the rotation direction of the second rotatable member at a position on the outer peripheral surface of the second rotatable member where the second rotatable member is closest to the first rotatable member is opposite to the rotation direction of the first rotatable member at a position on the outer peripheral surface of the first rotatable member where the first rotatable member is closest to the second rotatable member; and a second magnet, non-rotatably and fixedly disposed in the second rotatable member, wherein the second magnet includes a plurality of magnetic poles, the plurality of magnetic poles including a second developing pole disposed opposite to the image bearing member at the second developing position, a receiving pole disposed upstream of the second developing pole with respect to the rotation direction of the second rotatable member and having a magnetic polarity different from that of the delivering pole, and a second feeding pole disposed downstream of the receiving pole with respect to the rotation direction of the second rotatable member and adjacent to the receiving pole and having a magnetic polarity different from that of the receiving pole, the receiving pole being a magnetic pole disposed closest to the delivering pole among the plurality of magnetic poles;wherein, in the following case, namely, the position on the outer peripheral surface of the first rotatable component where the delivery pole magnetic flux density relative to the normal direction of the outer peripheral surface of the first rotatable component is the maximum value is point T, the position on the downstream side relative to the rotation direction of the first rotatable component in each position on the outer peripheral surface of the first rotatable component where the delivery pole magnetic flux density relative to the normal direction of the outer peripheral surface of the first rotatable component is half the maximum value is point Hd, and the position on the upstream side relative to the rotation direction of the first rotatable component in each position on the outer peripheral surface of the first rotatable component where the delivery pole magnetic flux density relative to the normal direction of the outer peripheral surface of the first rotatable component is half the maximum value is point Hu, and wherein the vertical axis represents the delivery pole magnetic flux density relative to the normal direction of the outer peripheral surface of the first rotatable component and the horizontal axis represents the first rotatable component In the graph of the angle of the first rotatable component relative to the rotation direction of the first rotatable component, in the following case, that is, the straight line passing through the point T and parallel to the horizontal axis is the straight line HLt, the straight line passing through the points Hu and Hd and parallel to the horizontal axis is HLh, the straight line passing through the point Hd and parallel to the vertical axis is VL11, the straight line passing through the point Hu and parallel to the vertical axis is VL12, the area of ​​the rectangle surrounded by the straight lines VL11, VL12, HLt, HLh is the area S, and in the rectangular area, the area obtained by integrating the delivery pole magnetic flux density relative to the normal direction of the outer peripheral surface of the first rotatable component from the straight line VL11 to the straight line VL12 according to the angle of the first rotatable component relative to the rotation direction of the first rotatable component is the area Sa, and the following relationship is satisfied: Sa / S ≥ 75%. ;

[0008] According to another aspect of the present invention, a developing device is provided, comprising: a developing container configured to contain a developer, the developer comprising a colorant and a carrier; a first rotatable component, the developer contained in the developing container is supplied to the first rotatable component, and the first rotatable component carries and feeds the developer to a first developing position, and develops an electrostatic latent image formed on an image bearing component at the first developing position; a first magnet, which is non-rotatably and fixedly arranged in the first rotatable component, wherein the first magnet comprises a first developing pole arranged opposite to the image bearing component at the first developing position, a delivery pole arranged downstream of the first developing pole relative to the rotation direction of the first rotatable component, and a first feeding pole arranged upstream of the delivery pole relative to the rotation direction of the first rotatable component and adjacent to the delivery pole and having a magnetic polarity different from that of the delivery pole; a second rotatable component, which is arranged opposite to the first rotatable component, and delivers the developer from the first rotatable component to the second rotatable component by a magnetic field generated by the first magnet. two rotatable members, wherein the second rotatable member carries and feeds the developer to a second developing position for developing the electrostatic latent image, wherein the rotation direction of the second rotatable member at a position on the outer peripheral surface of the second rotatable member where the second rotatable member is closest to the first rotatable member is opposite to the rotation direction of the first rotatable member at a position on the outer peripheral surface of the first rotatable member where the first rotatable member is closest to the second rotatable member; and a second magnet, which is non-rotatably and fixedly arranged in the second rotatable member, wherein the second magnet includes a plurality of magnetic poles, the plurality of magnetic poles including a second developing pole arranged opposite to the image bearing member at the second developing position, a receiving pole arranged upstream of the second developing pole with respect to the rotation direction of the second rotatable member and having a magnetic polarity different from that of the delivering pole, and a second feeding pole arranged downstream of the receiving pole with respect to the rotation direction of the second rotatable member and adjacent to the receiving pole and having a magnetic polarity different from that of the receiving pole, the receiving pole being the magnetic pole arranged closest to the delivering pole among the plurality of magnetic poles;wherein, in the following case, namely, the position on the outer peripheral surface of the first rotatable component where the delivery pole magnetic flux density relative to the normal direction of the outer peripheral surface of the first rotatable component is the maximum value is point T, the position on the downstream side with respect to the rotation direction of the first rotatable component in each position on the outer peripheral surface of the first rotatable component where the delivery pole magnetic flux density relative to the normal direction of the outer peripheral surface of the first rotatable component is half the maximum value is point Hd, and in each position on the outer peripheral surface of the first rotatable component where the delivery pole magnetic flux density relative to the normal direction of the outer peripheral surface of the first rotatable component is half the maximum value, the position on the upstream side with respect to the rotation direction of the first rotatable component is point Hu, and wherein, in a graph in which the vertical axis represents the delivery pole magnetic flux density relative to the normal direction of the outer peripheral surface of the first rotatable component and the horizontal axis represents the angle of the first rotatable component relative to the rotation direction of the first rotatable component, in the following case, namely, the position on the upstream side with respect to the rotation direction of the first rotatable component in each position in which the delivery pole magnetic flux density relative to the normal direction of the outer peripheral surface of the first rotatable component is 10% of the maximum value of the delivery pole magnetic flux density relative to the normal direction of the outer peripheral surface of the first rotatable component is point Cu, in the horizontal axis, the angle of the first rotatable component relative to the rotation direction of the first rotatable component is angle Hu, and in the horizontal axis, the angle of the first rotatable component relative to the rotation direction of the first rotatable component is angle Cu, In each position where the delivery pole magnetic flux density normal to the outer peripheral surface of the first rotatable component is 10% of the maximum value of the delivery pole magnetic flux density normal to the outer peripheral surface of the first rotatable component, the position on the downstream side with respect to the rotation direction of the first rotatable component is point Cd, in each position where the delivery pole magnetic flux density normal to the outer peripheral surface of the first rotatable component is 90% of the maximum value of the delivery pole magnetic flux density normal to the outer peripheral surface of the first rotatable component, the position on the upstream side with respect to the rotation direction of the first rotatable component is point Cu, and in each position where the delivery pole magnetic flux density normal to the outer peripheral surface of the first rotatable component is 90% of the maximum value of the delivery pole magnetic flux density normal to the outer peripheral surface of the first rotatable component, the position on the upstream side with respect to the rotation direction of the first rotatable component is point Cu. The position on the downstream side with respect to the rotation direction of the first rotatable component in each position where the surface normal delivery pole magnetic flux density is 90% of the value of the maximum value of the surface normal delivery pole magnetic flux density with respect to the outer peripheral surface of the first rotatable component is point Cd, the angle formed by the straight line L11C connecting the rotation center R1 and point Cd and the straight line L12C connecting the rotation center R1 and point Cu is Wc, and the angle formed by the straight line L11D connecting the rotation center R1 and point Dd and the straight line L12D connecting the rotation center R1 and point Du is Wd, and the following relationship is satisfied: Wd / Wc≥45%. ;

[0009] Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a schematic cross-sectional view of the image forming apparatus in the first embodiment.

[0011] Figure 2 is a schematic cross-sectional view of a developing device according to a first embodiment.

[0012] Figure 3 Schematic diagram showing the arrangement of magnetic poles of the first developing roller in the first embodiment.

[0013] Figure 4 Schematic diagram showing the arrangement of magnetic poles of the second developing roller in the first embodiment.

[0014] Figure 5 Schematic diagram showing the arrangement of magnetic poles of the peeling roller in the first embodiment.

[0015] Figure 6 Schematic diagram showing the magnetic pole arrangement relationship between the first developing roller and the second developing roller in the first embodiment.

[0016] Figure 7 is a graph showing the magnetic characteristics of the first developing roller in the first embodiment.

[0017] Figure 8 Graph showing the magnetic characteristics of the periphery of the delivery pole of the first developing roller in the first embodiment.

[0018] Fig. 9 A schematic diagram for explaining the state of magnetic flux lines and magnetic flux density between the first developing roller and the second developing roller in the first embodiment.

[0019] Fig.10 is a graph showing the magnetic characteristics of the first developing roller in the comparative example.

[0020] Fig.11 is a graph showing the magnetic characteristics of the periphery of the delivery pole of the first developing roller in the comparative example.

[0021] Fig.12 A schematic diagram illustrating the state of magnetic flux lines and magnetic flux density between the first developing roller and the second developing roller in the comparative example.

[0022] Fig.13 is a graph showing the magnetic characteristics of the first developing roller in the second embodiment.

[0023] Fig.14 Schematic diagram showing the magnetic characteristics of the periphery of the delivery pole of the first developing roller in the second embodiment.

[0024] Fig.15 It is displayed in enlarged mode Fig.14 A graph of the magnetic properties of the delivery pole.

[0025] Fig.16 It is a graph showing the magnetic characteristics around three delivery poles with different area ratios Sa / S.

[0026] Fig.17 is a graph showing the magnetic characteristics of the periphery of the delivery pole of the first developing roller in the third embodiment.

[0027] Fig.18 It is displayed in enlarged mode Fig.17 A graph of the magnetic properties of the delivery pole.

[0028] Fig.19 is a graph showing in an enlarged manner the magnetic characteristics of the delivery pole of the first developing roller in the fourth embodiment.

[0029] Fig. 20 is a graph showing in an enlarged manner the magnetic characteristics of the delivery pole of the first developing roller in the fifth embodiment. DETAILED DESCRIPTION

[0030] [First embodiment]

[0031] Will use Figures 1 to 12 The first embodiment will be described. Figure 1 The schematic structure of the imaging apparatus in this embodiment is described.

[0032] [Imaging equipment]

[0033] The image forming apparatus 100 is a full-color image forming apparatus, and in the case of the present embodiment, the image forming apparatus 100 is, for example, an MFP (Multi-Function Peripheral) having a copy function, a printer function, and a scanner function. Figure 1 As shown, the image forming apparatus 100 includes image forming portions PY, PM, PC, and PK arranged in parallel for performing image forming steps of forming toner images of four colors, namely, yellow, magenta, cyan, and black, respectively.

[0034] The image forming units PY, PM, PC and PK of each color include primary chargers 21Y, 21M, 21C and 21K, developing devices 1Y, 1M, 1C and 1K, optical writing units (exposure devices) 22Y, 22M, 22C and 22K, photosensitive drums 28Y, 28M, 28C and 28K, and cleaning devices 26Y, 26M, 26C and 26K, respectively. In addition, the image forming apparatus 100 includes a transfer device 2 and a fixing device 3. Incidentally, the structures of the image forming units PY, PM, PC and PK are similar to each other, so the image forming unit PY will be used as a representative for description hereinafter.

[0035] The photosensitive drum 28Y as an image bearing member is a photosensitive member having a photosensitive layer formed of a resin such as polycarbonate containing an organic photoconductor (OPC) and configured to rotate at a predetermined speed. The primary charger 21Y includes a corona discharge electrode disposed around the photosensitive drum 28Y and charges the surface of the photosensitive drum 28Y by generating ions.

[0036] A scanning optical device is built into the optical writing section 22Y, and the potential of the exposed portion is lowered by exposing the charged photosensitive drum 28Y based on the image data, thereby forming a charge pattern (electrostatic latent image) corresponding to the image data. The developing device 1Y develops the electrostatic latent image formed on the photosensitive drum 28Y by transferring the developer contained therein to the photosensitive drum 28Y. The developer is prepared by mixing a carrier with a toner of a relevant color, and the electrostatic latent image is visualized (developed) using the toner.

[0037] 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 and a plurality of rollers, and is supported to be movable.

[0038] The primary transfer rollers 23Y, 23M, 23C and 23K are Figure 1 , which correspond to the colors of Y (yellow), M (magenta), C (cyan), and K (black), respectively. The secondary transfer roller 25 is provided outside the intermediate transfer belt 24, and is configured so that the recording material can pass between the secondary transfer roller 25 and the intermediate transfer belt 24. Incidentally, the recording material is a sheet such as paper, a plastic sheet, or the like.

[0039] The toner images of the respective colors formed on the photosensitive drums 28Y, 28M, 28C and 28K are sequentially transferred to the intermediate transfer belt 24 by the primary transfer rollers 23Y, 23M, 23C and 23K, respectively, thereby forming a color toner image including superimposed layers of yellow, magenta, cyan and black. The toner image thus formed is transferred to the recording material fed from the box accommodating the recording material by the secondary transfer roller 25. The recording material to which the toner image is transferred is pressurized and heated in the fixing device 3. Thereby, the toner on the recording material is melted, so that the color image is fixed on the recording material.

[0040] The developer storage sections 27Y, 27M, 27C, and 27K are provided corresponding to the developing devices 1Y, 1M, 1C, and 1K, respectively, and bottles containing developers corresponding to yellow, magenta, cyan, and black are replaceably installed in the developer storage sections in numerical order from the top, respectively. The developer storage sections 27Y, 27M, 27C, and 27K are configured so that the developer can be fed (supplied) from the developer storage sections to the developing devices 1Y, 1M, 1C, and 1K, respectively, corresponding to the colors of the stored developers.

[0041] For example, the toner weight ratio of the developer contained in each bottle is 80% to 95%, and the toner weight ratio of the developer in each of the developing devices 1Y, 1M, 1C, and 1K is 5% to 10%. Therefore, when the toner is consumed by development in each of the developing devices 1Y, 1M, 1C, and 1K, the developer containing the toner in an amount corresponding to the toner consumption is replenished so that the toner weight ratio of the developer in each of the developing devices 1Y, 1M, 1C, and 1K is maintained at a constant amount.

[0042] [Developing device]

[0043] Next, we will use Figures 2 to 5 The developing devices 1Y, 1M, 1C, and 1K are described in detail.

[0044] Incidentally, the developing devices 1Y, 1M, 1C, and 1K have the same structure, and therefore the developing device 1Y will be described as a representative hereinafter. Figure 2 It is shown Figure 1 The conceptual diagram of the developing device 1Y shown in FIG. Figures 3 to 5 1Y are conceptual diagrams respectively showing the magnetic pole structures of the first magnet 36 , the second magnet 37 , and the third magnet 38 provided inside the developing device 1Y.

[0045] like Figure 2 As shown, the developing device 1Y includes a first developing roller 30 , a second developing roller 31 , a peeling roller 32 , a developer supplying screw 42 , a developer stirring screw 43 , and a developer recovering screw 44 , and these components are accommodated in a developing container 60 .

[0046] The first developing roller 30 is a developer carrying member that is driven to rotate, and is disposed at a position adjacent to the photosensitive drum 28Y so that the rotation axis of the first developing roller is substantially parallel to the rotation axis of the photosensitive drum 28Y. The first developing roller 30 includes a rotatable first sleeve 33 and a first magnet (fixed magnet) 36 that is non-rotatably disposed inside the first sleeve 33 and is used to attract the developer to the surface of the first sleeve 33 by magnetic force. Then, the first developing roller 30 attracts (carries) the developer drawn from the developer supply screw 42 based on the magnetic force, and develops the electrostatic latent image formed on the rotating photosensitive drum 28Y (image carrying member) with the developer.

[0047] The first sleeve 33 is a non-magnetic cylindrical member, and is driven to rotate around the rotation axis 39. The rotation direction of the first sleeve 33 is as follows: Figure 2 The photosensitive drum 28Y rotates in the clockwise direction indicated by the arrow in the figure, and is the direction opposite to the rotation direction of the photosensitive drum 28. Therefore, the first sleeve 33 and the photosensitive drum 28Y rotate in the same direction at the positions opposite to each other. That is, normal (forward) development is performed in which the photosensitive drum 28 rotates vertically from bottom to top at the position opposite to the first sleeve 33.

[0048] The first magnet 36 is disposed in the first sleeve 33 and includes a plurality of sector-shaped magnetic poles 101 to 107. Figure 3 Between the inner periphery of the first sleeve 33 and the outer periphery of the first magnet 36, a space is provided to allow the first sleeve 33 to rotate.

[0049] The developer attracted to the first sleeve 33 is conveyed toward the photosensitive drum 28Y by the rotation operation of the first sleeve 33, so that the electrostatic latent image formed on the photosensitive drum 28Y is developed by the developer. After the electrostatic latent image formed on the photosensitive drum 28Y is developed by the developer, the developer on the first sleeve 33 is conveyed to the vicinity of the second developing roller 31 by the rotation operation of the first sleeve 33. Then, near the closest position between the first developing roller 30 and the second developing roller 31, the developer is peeled off from the first sleeve 33 by the magnetic field generated by the first magnet 36 included in the first developing roller 30 and the second magnet 37 included in the second developing roller 31, and then delivered to the surface of the second sleeve 34.

[0050] The second developing roller 31 is a developer bearing member driven to rotate, and is disposed downstream of the first developing roller 30 with respect to the rotation direction of the photosensitive drum 28Y, and the rotation center R2 of the second developing roller 31 is located above the rotation center R1 of the first developing roller 30 with respect to the vertical direction. The developer is delivered from the first developing roller 30 to the second developing roller 31 by magnetic force ( Figure 2 In the present embodiment, the entire second developing roller 31 is located above the rotation center R1 of the first developing roller 30 .

[0051] Similar to the first developing roller 30, the second developing roller 31 is disposed adjacent to the photosensitive drum 28Y so that the rotation axis of the second developing roller is substantially parallel to the rotation axis of the photosensitive drum 28Y. Therefore, the rotation axis of the second developing roller 31 and the rotation axis of the first developing roller 30 are substantially parallel to each other.

[0052] Such a second developing roller 31 includes a rotatable second sleeve 34 and a second magnet (fixed magnet) 37 which is non-rotatably provided inside the second sleeve 34 and is used to attract the developer to the surface of the second sleeve 34 by magnetic force. Then, based on the magnetic force, the developer is delivered from the first developing roller 30 (first sleeve 33) to the second developing roller 31, and the second developing roller 31 attracts (carries) the developer and develops the electrostatic latent image formed on the rotating photosensitive drum 28Y with the developer. Incidentally, a peeling roller 32 described later is located on the side of the second developing roller 31.

[0053] The second sleeve 34 is a non-magnetic cylindrical member, and is driven to rotate about the rotation axis 40. Similar to the first sleeve 33, the rotation direction of the second sleeve 34 is as follows: Figure 2The clockwise direction indicated by the arrow in the figure is the opposite direction to the rotation direction of the photosensitive drum 28 in this embodiment. Therefore, the second sleeve 34 and the photosensitive drum 28Y rotate in the same direction at the positions opposite to each other. That is, normal development is performed in which the photosensitive drum 28 rotates vertically from bottom to top at the position where the photosensitive drum 28 and the second sleeve 34 are opposite. In addition, the first sleeve 33 and the second sleeve 34 rotate in opposite directions at the positions opposite to each other.

[0054] The second magnet 37 is disposed in the second sleeve 34 and includes a plurality of sector-shaped magnetic poles 201 to 207. Figure 4 Between the inner periphery of the second sleeve 34 and the outer periphery of the second magnet 37, a space is provided to allow the second sleeve 34 to rotate.

[0055] The developer attracted on the second sleeve 34 is conveyed toward the photosensitive drum 28Y by the rotation operation of the second sleeve 34, so that the electrostatic latent image formed on the photosensitive drum 28Y is developed by the developer. After the electrostatic latent image formed on the photosensitive drum 28Y is developed by the developer, the developer remaining on the second sleeve 34 is conveyed to the vicinity of the peeling roller 32 by the rotation operation of the second sleeve 34. Then, in the vicinity of the closest position between the second developing roller 31 and the peeling roller 32, the developer is delivered from the second sleeve 34 to the third sleeve 35 of the peeling roller 32 by the magnetic field generated by the second magnet 37 included in the second developing roller 31 and the third magnet 38 included in the peeling roller 32.

[0056] The peeling roller 32 as a peeling portion is disposed on the side opposite to the photosensitive drum 28Y with respect to the rotation center of the second sleeve 34, and peels the developer from the second developing roller 31 after the electrostatic latent image on the photosensitive drum 28Y is developed by the second developing roller 31. Specifically, the peeling roller 32 is a developer bearing member driven to rotate, and is disposed between the second developing roller 31 and the developer recovery screw 44 so that the rotation center of the peeling roller is located above the rotation center R2 of the second developing roller 31.

[0057] In addition, the peeling roller 32 is arranged so that its rotation axis is substantially parallel to the rotation axis of the second developing roller 31. Such a peeling roller 32 includes a rotatable third sleeve 35 and a third magnet (fixed magnet) 38 which is non-rotatably arranged inside the third sleeve 35 and is used to attract the developer to the surface of the third sleeve 35 by magnetic force, and is configured so that the developer is delivered from the second developing roller 31 to the peeling roller based on the magnetic force.

[0058] The third sleeve 35 is a non-magnetic cylindrical member, and is driven to rotate around the rotation axis 41. The rotation direction of the third sleeve 35 is as follows: Figure 2The rotation direction is counterclockwise as indicated by the arrow in FIG. 3 , and is opposite to the rotation direction of the second sleeve 34. Therefore, the third sleeve 35 and the second sleeve 34 rotate in the same direction at positions opposite to each other.

[0059] The third magnet 38 is disposed in the third sleeve 35 and includes a plurality of sector-shaped magnetic poles 301 to 305. Figure 5 Between the inner periphery of the third sleeve 35 and the outer periphery of the third magnet 38, a space is provided to allow the third sleeve 35 to rotate.

[0060] The developer attracted to the third sleeve 35 is conveyed to the downstream side in the rotation direction by the rotation operation of the third sleeve 35, and is stripped from the third sleeve 35 by the third magnet 38 included in the stripping roller 32 at a position close to the developer recovery screw 44, so that the developer falls toward the guide member 45 located below with respect to the vertical direction by its own weight. Then, the developer that falls on the guide member 45 is guided toward the developer recovery screw 44 by its own weight.

[0061] The guide member 45 and the developer recovery screw 44 constitute a developer recovery section 47 as a recovery section for recovering the developer stripped from the third sleeve 35 on the stripping roller 32. In the developer recovery section 47, the developer recovery screw 44 is arranged so that its rotation center is located below the rotation center of the stripping roller 32 in the vertical direction, and conveys the developer delivered (recovered) from the stripping roller 32 while stirring it.

[0062] The guide member 45 as a guide portion is provided below the stripping roller 32 with respect to the vertical direction, and guides the developer stripped by the stripping roller 32 toward the developer recovery screw 44. Such a guide member 45 is provided with an inclined surface 45a along which the developer slides downward by its own weight, so as to reliably guide the stripped developer toward the developer recovery screw 44. The inclined surface 45a is inclined with respect to the horizontal direction so that its position on the developer recovery screw 44 side is lower than the lower position of the stripping roller 32.

[0063] The developer recovery screw 44 as a recovery member and a conveying (feeding) portion conveys the recovered developer to the developer circulation portion 46 described below. That is, the developer recovery screw 44 is a screw conveying (feeding) member for conveying in one direction while stirring the developer recovered by sliding downward along the inclined surface 45a of the guide member 45.

[0064] The developer circulation section 46 is a supply section for supplying developer to the first developing roller 30, and includes a regulating member 50, a developer supply screw 42, and a developer stirring screw 43. In the developer circulation section 46, the developer is supplied to the first developing roller 30 while being transported in a substantially horizontal direction while being stirred in the developer supply screw 42 and the developer stirring screw 43. In addition, as described above, the developer recovered by the developer recovery section 47 falls by its own weight and is guided to the developer circulation section 46.

[0065] The developer supply screw 42, the developer stirring screw 43 and the developer recovery screw 44 are screw conveying components for conveying the developer in one direction while stirring the developer, and the developer supply screw 42 and the developer stirring screw 43 are located below the developer recovery screw 44 with respect to the vertical direction. In addition, the developer supply screw 42, the developer stirring screw 43 and the developer recovery screw 44 are arranged so that their rotation axes are approximately parallel to each other. The rotation axes of these screws are also approximately parallel to the rotation axis of the first developing roller 30.

[0066] The developer supply screw 42 is located between the first developing roller 30 and the developer stirring screw 43, and a partition wall 48 of the developing container 60 is provided between the developer supply screw itself and the developer stirring screw 43. The partition wall 48 of the developing container 60 extends along the rotation axis direction of the developer supply screw 42 and the developer stirring screw 43. The partition wall 48 is provided with a communication port (not shown) for establishing communication between a first feeding path 61 along which the developer supply screw 42 feeds the developer and a second feeding path 62 along which the developer stirring screw 43 feeds the developer.

[0067] The developer stirred by the developer recovery screw 44 passes through a communication port (not shown) formed in a partition wall 63 of the developer container 60 between the developer recovery screw 44 and the developer supply screw 42, and then falls by its own weight toward the developer supply screw 42. The above-mentioned guide member 45 is formed integrally with the partition wall 63, and the developer recovery screw 44 is provided above the partition wall 63.

[0068] The position of the communication port through which the developer stirred by the developer recovery screw 44 falls by its own weight and is introduced into the developer circulation section 46 may preferably be set to avoid the region (the middle portion with respect to the rotation axis direction of the developer supply screw 42) where the developer is supplied to the first developing roller 30. In the present embodiment, the position of the communication port is such a position that the communication port position is included in the range of the downstream end portion (terminal portion) in the developer feeding direction with respect to the first feeding path 61 where the developer supply screw 42 is provided.

[0069] The developer feeding directions of the developer supply screw 42 and the developer stirring screw 43 are opposite to each other. In addition, the starting end side (upstream end side in the developer feeding direction) and the terminal end side (downstream end side in the developer feeding direction) of the first feeding path 61 provided with the developer supply screw 42 are connected to the terminal end side and the starting end side of the second feeding path 62 provided with the developer stirring screw 43 via the communication port provided in the partition wall 48. Figure 2 The developer supply screw 42 and the developer stirring screw 43 circulate in the rotation direction indicated by the middle arrow and circulate in the substantially horizontal direction in the developing container 60 , so that a part of the developer is supplied to the first developing roller 30 .

[0070] Developer supply port 51 (see Figure 2 ) is disposed above the developer stirring screw 43 in the developer container 60 and is connected to the developer storage portion 27Y (see Figure 1 ). In addition, the developer supply port 51 is configured to be able to supply the developer contained in the bottle mounted in the developer storage portion 27Y to the second feeding path 62 where the developer stirring screw 43 is provided.

[0071] As described above, the toner weight ratio of the developer contained in the bottle of the developer storage portion 27Y is greater than the toner weight ratio of the developer in the developing device 1Y. Therefore, by adjusting the amount of developer supplied to the developer stirring screw 43, the toner weight ratio of the developer in the developing device 1Y can be maintained at a certain level.

[0072] A toner concentration detection sensor 49 (see FIG. Figure 2 ) is used to detect the colorant concentration of the developer contained in the developer circulation section 46. The colorant concentration detection sensor 49 is a sensor for detecting magnetic permeability. The colorant concentration corresponds to the consumption of the colorant in the developing device 1Y, and is therefore used to control the supply of the developer from the developer storage section 27Y. For example, when it is detected that the colorant concentration is lower than a predetermined value, the developer is supplied from the developer storage section 27Y. In addition, the magnetic permeability varies according to the colorant concentration, and therefore the colorant concentration can be detected by utilizing the magnetic permeability.

[0073] The regulating member 50 is disposed adjacent to the first developing roller 30 for regulating the amount of developer supplied from the developer circulation portion 46 to the first developing roller 30. The regulating member 50 may be configured to regulate the amount of developer attracted to the first developing roller 30 based on a gap between the surface of the first sleeve 33 of the first developing roller 30 and the end of the regulating member 50.

[0074] The developer circulation path in the developing container 60 is such that the developer is fed in a substantially horizontal direction while being stirred in the developer circulation section 46, and then supplied to the first developing roller 30, and then delivered from the first developing roller 30 to the second developing roller 31 located above the first developing roller 30 based on the magnetic force. Then, the developer is delivered from the second developing roller 31 to the peeling roller 32 located beside the second developing roller 31 based on the magnetic force again, and then peeled from the peeling roller 32 by the third magnet 38 included in the peeling roller 32. In addition, the developer is recovered by the developer recovery section 47, and then guided to the developer circulation section 46 again.

[0075] In addition, as described above, in this embodiment, a two-component development type is adopted as a development type, and a developer obtained by mixing a non-magnetic colorant having a negatively charged property with a carrier having magnetism is used as a developer. The non-magnetic colorant is a colorant obtained by including a colorant, a wax component, etc. in a resin such as polyester, styrene acrylic resin, etc., forming a mixture in a powder form by pulverizing or polymerizing, and then adding micro powders such as titanium oxide and silicon dioxide to the surface of the powder. The magnetic carrier is a carrier obtained by coating a resin material on the surface layer of a core (which includes ferrite particles or resin particles obtained by kneading with magnetic powder). In this embodiment, the toner concentration in the developer (the weight ratio of the toner to the developer) is 8% in the initial state.

[0076] Generally speaking, the two-component development type using a toner and a carrier has a characteristic that the stress applied to the toner is less than the stress applied to the toner in the single-component development type using a single-component developer, because the toner and the carrier are charged to a predetermined polarity by making the toner and the carrier contact with frictional electrification. On the other hand, through long-term use, the amount of pollutants (waste) deposited on the surface of the carrier increases, so the charging ability of the toner gradually decreases. As a result, the problem of fogging and toner scattering arises. Although it is conceivable to increase the amount of the carrier contained in the developing device to extend the life of the two-component developing device, this leads to an increase in the size of the developing device and is therefore undesirable.

[0077] In order to solve the above-mentioned problem of the two-component developer, the ACR (Automatic Carrier Refresh) type is adopted in this embodiment. The ACR type is a type that suppresses the increase in the amount of deteriorated developer by not only supplying new developer little by little from the developer storage portion 27Y to the developing device 1Y, but also discharging the developer with deteriorated charging performance little by little through the discharge port (not shown) of the developing device 1Y. Thus, the deteriorated carrier in the developing device 1Y is replaced by the new carrier little by little, so that the charging performance of the carrier in the developing device 1Y can be maintained at an approximately constant level.

[0078] [Magnetic poles of a magnet]

[0079] Next, the magnetic pole configurations of the first magnet 36, the second magnet 37, and the third magnet 38 included in the first developing roller 30, the second developing roller 31, and the peeling roller 32, respectively, will be described. Figure 3 , Figure 4 and Figure 5 shown.

[0080] like Figure 3 As shown, the first magnet 36 included in the first developing roller 30 has a seven-pole magnetic pole configuration, including a plurality of magnetic poles 101, 102, 103, 104, 105, 106, and 107. Among these magnetic poles, the magnetic pole 106 is a delivery pole for delivering the developer from the first developing roller 30 to the second developing roller 31. The magnetic poles 101 to 107 are arranged in numerical order in the rotation direction of the first sleeve 33. The magnetic pole 101 is an S pole, is arranged at a position opposite to the regulating member 50 via the first sleeve 33, and adjusts the amount of the developer conveyed on the first sleeve 33 as described above. The magnetic pole 104 as the first developing pole is an N pole, is arranged at a position opposite to the photosensitive drum 28Y via the first sleeve 33, and is a magnetic pole for developing the electrostatic latent image formed on the photosensitive drum 28Y with the developer. Hereinafter, the magnetic pole 104 is referred to as the first developing pole 104 in some cases.

[0081] The magnetic pole 106 as a delivery pole is an N pole, is a magnetic pole for delivering the developer from the first sleeve 33 to the second sleeve 34 by generating a magnetic field in cooperation with the second magnet 37 of the second developing roller 31 , and is hereinafter referred to as the delivery pole 106 in some cases.

[0082] The magnetic pole 107 is an N pole for attracting the developer supplied by the developer supply screw 42 to the first sleeve 33. The magnetic poles 102, 103 and 105 are respectively an N pole, an S pole and an S pole, and serve as feed poles for feeding the developer attracted by the magnetic pole 107 upward with the rotation of the first sleeve 33. Among these magnetic poles, the magnetic pole 105 is the first magnetic pole upstream of and adjacent to the delivery pole 106 with respect to the rotation direction of the first sleeve 33, and is hereinafter referred to as the first feed pole 105 in some cases. With respect to the rotation direction of the first sleeve 33, the first development pole 104 is located upstream of and adjacent to the first feed pole 105.

[0083] In addition, relative to the rotation direction of the first sleeve 33, the magnetic pole 107 is arranged on the downstream side of the delivery pole 106 and has the same polarity as the delivery pole 106. The delivery pole 106 and the magnetic pole 107 form a low magnetic force portion 110 whose magnetic force is lower than that of the delivery pole 106 through the repulsive magnetic field that cooperates with each other. Through the low magnetic force portion 110, the developer is peeled off from the first sleeve 33, and the delivery of the developer from the first sleeve 33 to the second sleeve 34 is promoted. By the way, in the present embodiment, the low magnetic force portion 110 may have substantially no magnetic force, but may also have a low magnetic force, for example, it may be a magnetic pole whose magnetic force (normal component Br of magnetic flux density) is less than 5mT. The same applies to Figure 4 The low magnetic force portion 210 and the second magnet 37 shown Figure 5 The low magnetic force portion 310 of the third magnet 38 is shown.

[0084] like Figure 4 As shown, the second magnet 37 included in the second developing roller 31 has a seven-pole structure, including a plurality of magnetic poles 202, 203, 204, 205, 206 and 207. Among them, the magnetic pole 201 is a receiving pole for receiving the developer from the first developing roller 30 through the second developing roller 31. The magnetic poles 201 to 207 are arranged in numerical order in the rotation direction of the second sleeve 34.

[0085] The magnetic pole 201 is a magnetic pole for attracting the developer from the first sleeve 33 to the second sleeve 34 by cooperating with the magnetic pole 106 of the first magnet 36 of the first developing roller 30 to generate a magnetic field. The magnetic pole 207 is a magnetic pole for delivering the developer from the second sleeve 34 to the third sleeve 35 by cooperating with the third magnet 38 of the stripping roller 32 to generate a magnetic field.

[0086] In addition, the magnetic pole 201 is an S pole having a different polarity from the delivery pole 106, and is used to attract the developer from the first developing roller 30 (first sleeve 33) to the second sleeve 34 as described above. The magnetic pole 203 as the second developing pole is an S pole, and is a magnetic pole disposed at a position opposite to the photosensitive drum 28Y via the second sleeve 34, and is used to develop the electrostatic latent image formed on the photosensitive drum 28Y. Hereinafter, the magnetic pole 203 is referred to as the second developing pole 203 in some cases.

[0087] The magnetic poles 202, 204, 205, and 206 are N poles, N poles, S poles, and N poles, and are used to feed the developer attracted by the magnetic pole 201 upward with the rotation of the second sleeve 34. Among these magnetic poles, the magnetic pole 202 is a second magnetic pole located downstream and adjacent to the receiving pole 201 with respect to the rotation direction of the second sleeve 34, and is hereinafter referred to as the second feeding pole 202 in some cases. The second developing pole 203 is located downstream and adjacent to the second feeding pole 202 with respect to the rotation direction of the second sleeve 34. The magnetic pole 207 is an S pole, and by the magnetic field generated in cooperation with the magnetic pole 303 in the third magnet 38 included in the peeling roller 32, after the developer passes through the developing area of ​​the photosensitive drum 28Y and the magnetic pole 203 corresponding to each other, the developer is delivered from the second sleeve 34 to the third sleeve 35 opposite to the second sleeve 34.

[0088] In addition, the magnetic pole 207 is provided on the upstream side of the receiving pole 201 with respect to the rotation direction of the second sleeve 34, and has the same polarity as the receiving pole 201. The receiving pole 201 and the magnetic pole 207 form a low magnetic force portion 210 having a lower magnetic force than the magnetic pole 207 by the repulsive magnetic field generated by cooperation with each other. Through the low magnetic force portion 210, the developer is peeled off from the second sleeve 34, and the delivery of the developer from the first sleeve 33 to the second sleeve 34 is promoted. In addition, through the low magnetic force portion 210, the developer can be prevented from being attracted to the closest portion between the first sleeve 33 and the second sleeve 34, and the pressure applied to the developer can be suppressed.

[0089] like Figure 5 As shown, the third magnet 38 included in the peeling roller 32 is provided with a plurality of magnetic poles 301, 302, 303, 304, and 305. The magnetic poles 301 to 305 are arranged in numerical order in the rotation direction of the third sleeve 35.

[0090] The magnetic pole 303 is an N pole having a different polarity from the magnetic pole 207, and is used to attract the developer stripped from the second sleeve 34 as described above to the third sleeve 35. The magnetic poles 301, 302, and 304 are an N pole, an S pole, and an S pole, and are used to feed the developer on the third sleeve 35 as the third sleeve 35 rotates. In particular, the magnetic pole 304 is used to feed downward the developer attracted by the magnetic pole 303 as the third sleeve 35 rotates. The magnetic pole 305 is an N pole, and is a stripping pole, and is used to strip the developer attracted to the third sleeve 35 from the third sleeve 35 by generating a repulsive magnetic field in cooperation with the magnetic pole 301 having the same polarity as the magnetic pole 305.

[0091] [Magnetic pole arrangement relationship]

[0092] Next, we will use Figures 6 to 9 The magnetic pole arrangement relationship between the first magnet 36 and the second magnet 37 respectively provided inside the first developing roller 30 and the second developing roller 31 is described. Figure 6 1 is a conceptual diagram for explaining the arrangement of the first developing roller 30 and the second developing roller 31 in this embodiment, and particularly shows the layout of the first feeding pole 105 and the delivering pole 106 of the first magnet 36 of the first developing roller 30 and the receiving pole 201 and the second feeding pole 202 of the second magnet 37 of the second developing roller 31. Incidentally, due to complexity, the display of a part of the magnetic poles is omitted. In addition, Figure 7 and Figure 8 are graphs each showing the magnetic characteristic of the first magnet 36 of the first developing roller 30 . Fig. 9 It is a conceptual diagram for illustrating the magnetic field of the first developing roller 30 and the second developing roller 31 of this embodiment, and particularly shows the absolute values ​​of the magnetic flux density of the delivery pole 106, the first feed pole 105, the receiving pole 201 and the second feed pole 202 and the state of the magnetic flux lines formed by these poles.

[0093] In this embodiment, as described above, the developer in the developing device 1Y moves from the surface of the first sleeve 33 of the first developing roller 30 to the surface of the second sleeve 34 of the second developing roller 31 through the magnetic field of the delivery pole 106 in the first developing roller 30 and the receiving pole 201 in the second developing roller 31, and then moves to the surface of the third sleeve 35 of the stripping roller 32 after being used in the development step of the electrostatic latent image on the photosensitive drum 28Y.

[0094] The process of delivering the developer from the first sleeve 33 of the first developing roller 30 to the second sleeve 34 of the second developing roller 31 (arrow F1) will be described. Figure 6 and Fig. 9 As shown by the arrow F1 in FIG. 1 , the developer moves to the downstream side of the rotation direction 81 of the first sleeve 33 rotating around the rotation center R1 by the magnetic force along the magnetic flux lines extending from the first feed pole 105 to the delivery pole 106 of the first magnet 36. Then, the developer moves from the first sleeve 33 to the second sleeve 34 by the magnetic force along the magnetic flux lines extending from the delivery pole 106 to the receiving pole 201. In addition, the developer moves to the downstream side of the rotation direction 82 of the second sleeve 34 rotating around the rotation center R2 by the magnetic force along the magnetic flux lines extending from the receiving pole 201 to the second feed pole 202.

[0095] Here, the position (peak position) of the maximum value (peak value) of the normal component of the magnetic flux density of the delivery pole 106 on the surface of the first sleeve 33 is regarded as point T ( Figure 8 ). In addition, in the half-value position of the maximum value of the normal component of the magnetic flux density of the delivery pole 106, the downstream side position relative to the rotation direction of the first sleeve 33 is regarded as Hd, and the upstream side position relative to the rotation direction of the first sleeve 33 is regarded as Hu. In addition, by Figure 6 and Figure 8The straight lines L1, L2, L3, L4, L10, L11 and L12 represented by the dot-dash lines in are defined as follows:

[0096] L1: a horizontal line passing through the rotation center R1 of the first sleeve 33,

[0097] L2: a horizontal line passing through the rotation center R2 of the second sleeve 34,

[0098] L3: a vertical line passing through the rotation center R1 of the first sleeve 33,

[0099] L4: A straight line passing through the rotation center R1 and the rotation center R2,

[0100] L10: A straight line connecting the rotation center R1 and point T (the position of the peak magnetic flux density of the delivery pole 106) Figure 8 ),

[0101] L11: A straight line connecting the rotation center R1 and the point Hd (a downstream position of the half value of the peak value of the magnetic flux density of the delivery pole 106 with respect to the rotation direction 81 of the first sleeve 33) ( Figure 8 ),as well as

[0102] L12: A straight line connecting the rotation center R1 and the point Hu (the upstream position of the half value of the peak value of the magnetic flux density of the delivery pole 106 with respect to the rotation direction 81 of the first sleeve 33) ( Figure 8 ).

[0103] The developer is fed from the first feed pole 105 of the first sleeve 33 to the delivery pole 106 by the force generated by the rotation of the first sleeve 33 and the magnetic force along the magnetic flux line extending from the first feed pole to the delivery pole 106. The peak value of the magnetic flux density of the delivery pole 106 is not greater than the peak value (normal component maximum value) of the magnetic flux density of the receiving pole 201. In addition, the magnetic field (delivery magnetic field) formed by the delivery pole 106 and the receiving pole 201 and used to deliver the developer from the first sleeve 33 to the second sleeve 34 is configured so that: relative to the rotation direction 81 of the first sleeve 33, at the intersection P1 ( Figure 6 ) and within the range of the upstream side of the magnetic flux density peak position of the first feed pole 105 (the position of the maximum value of the normal component on the surface of the first sleeve 33), a repulsive force area is generated, in which the magnetic force in the direction of the rotation center R1 near the outer peripheral surface of the first sleeve 33 becomes negative polarity.

[0104] The delivery magnetic field is configured such that: relative to the rotation direction 82 of the second sleeve 34, at the intersection point P2 ( Figure 6) and the upstream side of the magnetic flux density peak position of the second feeding pole 202, an attraction area is generated in which the magnetic force in the direction of the rotation center R2 near the outer peripheral surface of the second sleeve 34 becomes positive. Through this magnetic force relationship, the developer is delivered from the first sleeve 33 to the second sleeve 34.

[0105] Incidentally, the magnetic flux lines extending from the first feed pole 105 are connected not only to the delivery pole 106 but also to the second feed pole 202 (composed of an N pole having a polarity different from that of the first feed pole 105) of the second developing roller 31. With regard to the magnetic force acting on the developer on the first sleeve 33 in the vicinity of the first feed pole 105, when the magnetic field between the first feed pole 105 and the second feed pole 202 becomes more dominant than the magnetic field between the first feed pole 105 and the delivery pole 106, then as shown in Figure 6 As shown by arrow F2 in FIG. 1 , movement of the developer occurs from the first feeding pole 105 to the second feeding pole 202 or from the second feeding pole 202 to the first feeding pole 105. Furthermore, the developer also contacts the photosensitive drum 28Y near these magnetic poles, thereby generating a vertically streaked fog image on the photosensitive drum 28Y.

[0106] In order to suppress such movement of the developer in the direction of the arrow F2, it is only necessary to weaken the magnetic field between the first feed pole 105 and the second feed pole 202 and to strengthen the magnetic field between the first feed pole 105 and the delivery pole 106. As one method for this, a method of increasing the peak value of the magnetic flux density of the delivery pole 106 can be considered. However, when the peak value of the magnetic flux density of the delivery pole 106 increases, the force for constraining the developer near the closest position between the first sleeve 33 and the second sleeve 34 becomes stronger, so that pressure is applied to the developer, so that the deterioration of the developer is accelerated. When the developer deteriorates, the charge amount of the colorant decreases, so there is a tendency that the electrostatic latent image cannot be developed on the photosensitive drum 28Y with an appropriate amount of colorant.

[0107] Furthermore, with respect to the rotation direction 81 of the first sleeve 33, within the range of the upstream side of the intersection point P1 between the straight line L4 and the first sleeve 33 and the downstream side of the magnetic flux density peak position of the first feed pole 105, the repulsive force region (in which the polarity of the magnetic force in the direction of the rotation center R1 near the outer peripheral surface of the first sleeve 33 becomes negative) is narrowed or eliminated, making it difficult to properly perform the delivery of the developer from the first sleeve 33 to the second sleeve 34 in some cases. When such poor delivery of the developer occurs, there is a possibility that the developer is carried and moved on the first sleeve 33, thereby causing uneven toner concentration of the developer on the first sleeve 33, and that the developer retention amount near the closest position between the first sleeve 33 and the second sleeve 34 gradually increases, thereby causing an overflow phenomenon that causes the developer supply amount to the second sleeve 34 to become excessive.

[0108] For the above reasons, it is not preferable to simply increase the peak value of the magnetic flux density of the delivery pole 106. Therefore, in this embodiment, the delivery pole 106 is set as follows. First, Figure 8 As shown, in the half-value width of the magnetic flux density peak of the delivery pole 106, the angle formed by the straight lines L10 and L12 (the width on the upstream side of the magnetic flux density peak position of the delivery pole 106) is taken as angle w1, and the angle formed by the straight lines L10 and L11 (the width on the downstream side of the magnetic flux density peak position of the delivery pole 106) is taken as w2. In addition, the angle difference (w1-w2) of angle w2 relative to angle w1 is Δw, that is, Δw=w1-w2. In this case, the delivery pole 106 is set to satisfy: Δw≥0.

[0109] As a result, the magnetic field between the first feed pole 105 and the second feed pole 202 is weakened, and the magnetic field between the first feed pole 105 and the delivery pole 106 is strengthened. In addition, the feeding characteristics of the developer from the first feed pole 105 of the first sleeve 33 to the delivery pole 106 are improved. As a result, the movement of the developer between the first feed pole 105 of the first developing roller 30 and the second feed pole 202 of the second developing roller 31 can be suppressed.

[0110] In this embodiment, the magnetic characteristics of the first magnet 36 are distributed as follows: Figures 7 to 9 shown. Figure 7 The graph shows the Figure 3 and Figure 6 The positions of the magnetic poles 101 to 107 in the first magnet 36 relative to the angular direction of the first sleeve 33 and the magnitude of the normal magnetic flux density are shown. Figure 7 In the figure, the horizontal axis represents the angle (denoted by Figure 6 Indicated by the arrow in the figure. Figure 7 , the vertical axis represents the measurement result of the normal magnetic flux density of the first magnet 36 at the relevant angle of the first magnet 36 relative to the rotation direction.

[0111] Figure 8 Shown in an enlarged manner Figure 7 The portion near the first feed pole 105 and the delivery pole 106, wherein the straight lines L1 to L4 and L10 to L12 on the first sleeve 33 are represented by dotted lines, and the angles w1 and w2 are represented by Figure 8Indicated by the double-headed arrow in . In the first magnet 36 of the present embodiment, the delivery pole 106 is set to provide an angle w1=11 degrees and an angle w2=6 degrees to satisfy the angle difference Δw=5 degrees. Here, the setting values ​​adopted in the present embodiment are examples, and the above-mentioned angle difference Δw may only need to satisfy the relationship of Δw≥0, and may preferably satisfy the relationship of Δw>0. By satisfying this relationship, the developer on the first sleeve 33 is easily fed from the first feed pole 105 to the delivery pole 106.

[0112] Fig. 9 Schematic diagram showing arrow F1 for indicating the movement of developer from the first feeding pole 105 on the first sleeve 33 to the second feeding pole 202 on the second sleeve 34, the state of magnetic flux lines formed by the first feeding pole 105, the delivery pole 106, the receiving pole 201 and the second feeding pole 202, and the absolute value of the normal magnetic flux density of these magnetic poles. In this embodiment, the first feeding pole 105 and the receiving pole 201 are composed of S poles, and the delivery pole 106 and the second feeding pole 202 are composed of N poles. The magnetic poles to which the first feeding pole 105 as an S pole is connected through the magnetic flux lines are the delivery pole 106 and the second feeding pole 202 as N poles.

[0113] Here, as described above, the shape of the magnetic flux density of the delivery pole 106 is set so that: in the half-value width of the peak value of the magnetic flux density of the delivery pole 106 in the normal direction of the delivery pole 106, the upstream side angle w1 is equal to or greater than the downstream side angle w2. Therefore, the upstream side angle w1 in the half-value width of the magnetic flux density of the delivery pole 106 close to the first feed pole 105 is widened, so that the magnetic field between the first feed pole 105 and the delivery pole 106 is enhanced and the magnetic field between the first feed pole 105 and the second feed pole 202 is weakened. In addition, the occurrence of the developer moving between the first feed pole 105 and the second feed pole 202 as shown by the arrow F2 is suppressed, so that the occurrence of abnormal images (vertical striped images) caused by this can be suppressed.

[0114] Furthermore, in order to weaken the magnetic field between the first feed pole 105 and the second feed pole 202, by adopting a structure in which only the upstream angle in the half-value width of the magnetic flux density of the delivery pole 106 close to the first feed pole 105 is increased so that the angle difference Δw ≥ 0, compared with simply increasing the peak value of the magnetic flux density of the delivery pole 106 in the normal direction of the delivery pole 106, it is possible to suppress an increase in the force for restraining the developer near the closest position between the first sleeve 33 and the second sleeve 34. Furthermore, in the range on the upstream side of the intersection P1 between the straight line L4 and the first sleeve 33 and on the downstream side of the peak position of the magnetic flux density of the first feed pole 105 with respect to the rotation direction 81 of the first sleeve 33, the repulsive force region in which the magnetic force polarity in the direction of the rotation center R1 near the outer peripheral surface of the first sleeve 33 is negative is not eliminated, thereby appropriately performing the delivery of the developer from the first sleeve 33 to the second sleeve 34.

[0115] Incidentally, a portion of the magnet forming the delivery pole 106 in the first magnet 36 with respect to the circumferential direction may be cut off, or a magnet having a different magnetic force may be embedded in the cut-off portion, thereby making the magnetic flux density distribution of the delivery pole 106 asymmetric as described above.

[0116] Next, we will use Figures 10 to 12 A comparative example for comparison with the present embodiment is described. In the comparative example, the magnetic property distribution of the delivery pole 106A is set so that the angle difference Δw satisfies Δw<0. Figures 10 to 12 The state of the magnetic field formed by the first feed pole 105 , the delivery pole 106A, the receiving pole 201 , and the second feed pole 202 in this comparative example is shown.

[0117] Fig.10 The graph shown is a magnetic characteristic in a comparative example, wherein the magnetic characteristics are shown as follows. Figure 3 and Figure 6 The disclosed position of the magnetic poles included in the first magnet 36 with respect to the angular direction and the magnitude of the magnetic flux density, and except for the delivery pole 106A, the curve diagram is similar to the above Figure 7 Graph of the curve. Fig.11 It is magnified Fig.10 Graph of the delivery pole 106A and the position near the first feed pole 105 in the embodiment, wherein the above-mentioned straight lines L1 to L4 and L10 to L12 on the first sleeve 33 are indicated by dot-dash lines, and the sizes of the angles w1 and w2 are indicated by double arrows. The delivery pole 106A of the first magnet 36 in the comparative example has the same peak value of the magnetic flux density as the above-mentioned delivery pole 106, and has a configuration of Δw<0, wherein the downstream side width of the half-value width is wider, and the angles w1 and w2 are set to w1=6 degrees and w2=11 degrees.

[0118] Fig.12A schematic diagram showing the arrow F1 used to represent the movement of the developer from the first feed pole 105 on the first sleeve 33 to the second feed pole 202 on the second sleeve 34, the state of the magnetic flux lines formed by the first feed pole 105, the delivery pole 106A, the receiving pole 201 and the second feed pole 202, and the absolute values ​​of the normal magnetic flux density of these magnetic poles.

[0119] As described above, the shape of the magnetic flux density of the delivery pole 106A in the comparative example is set so that the angle w1 is smaller than the angle w2. Therefore, in the structure where the angle w1 on the upstream side of the half-value width of the delivery pole 106A close to the first feed pole 105 is narrower, the magnetic field between the first feed pole 105 and the delivery pole 106A is weak, and the magnetic field between the first feed pole 105 and the second feed pole 202 cannot be sufficiently weakened. Therefore, the movement of the developer between the first feed pole 105 and the second feed pole 202 occurs, so that the above-mentioned vertical striped fog image occurs. That is, the unevenness of the developer coating state on the second sleeve 34 occurs, and an uneven image occurs on the output image. On the other hand, in the present embodiment, the magnetic properties of the first magnet 36 are as follows Figure 8 and Fig. 9 The characteristics shown can therefore suppress the occurrence of output image unevenness and vertical streak-like images as in the comparative example.

[0120] [experiment]

[0121] Next, an experiment for checking the occurrence of streak-like fog images (abnormal images) in the above-mentioned configuration will be described. In this example, the angle w1 and the angle w2 in the magnetic flux density distribution of the delivery pole 106 are changed, and images are output by an imaging device including the delivery poles under various conditions. Then, the occurrence of streak-like fog images on the output images is checked.

[0122] In the experiment, the occurrence of streak-like fog images on the output images was evaluated in the following manner.

[0123] A pure white image was formed on 10 A3-size sheets, and the number of vertical streaks on the output image was measured.

[0124] In the case where there were no vertical streaks on the pure white images on 10 A3 size sheets, pure white images were formed on 100 A3 size sheets and then vertical streaks were checked.

[0125] The results of this experiment are shown in Tables 1 and 2.

[0126] Table 1

[0127] w1(°),w2(°) (6,11) (6,8.5) (6,7.5) (6,6) (8.5,6) (11,6) (13.5,6) (16,6) Δw(w1-w2)(°) -5 -2.5 -1.5 0 2.5 5 7.5 10 <![CDATA[AI *1 ]]> × × × ○ ○ ○ ○ ○

[0128] *1: “AI” is an abnormal image.

[0129] Table 2

[0130] w1(°),w2(°) (4,10) (4,7) (4,5.5) (4,4) (6.5,4) (7.5,4) (9,4) (12,4) Δw(w1-w2)(°) -6 -3 -1.5 0 2.5 3.5 5 8 <![CDATA[AI *1 ]]> × × × △ ○ ○ ○ ○

[0131] *1: “AI” is an abnormal image.

[0132] The symbol in the abnormal image row in each of Table 1 and Table 2 is the evaluation result of the occurrence condition of the streak-like fog image (abnormal image), and the contents are as follows.

[0133] ×: On a single A3-size sheet, 10 or more vertical streaks were recognized.

[0134] △: On a single A3-size sheet, approximately one vertical streak was recognized.

[0135] ○: On 10 A3-size sheets, about one vertical streak was recognized.

[0136] In the development evaluation, "○" indicates a level at which substantially no abnormal image occurs.

[0137] The first developing roller 30 and the second developing roller 31 are constructed as follows. Figure 6 As shown. The magnetic characteristics are such that the peak value of the magnetic flux density of the delivery pole 106 is fixed to about 36 mT, and the shape of the magnetic flux density near the delivery pole 106 relative to the rotation angle of the first sleeve 33 is changed. As a method of changing the magnetic flux density, the magnetic flux density can be changed by changing the conditions when the delivery pole 106 carried on the first magnet 36 is magnetized or by cutting off a part of the magnet, etc. Incidentally, the magnetic poles other than the delivery pole 106 are Figures 7 to 10 shown.

[0138] Table 1 shows the results of increasing only the angle w1 or only the angle w2, with the upstream angle w1 and the downstream angle w2 being equal to each other at 6 degrees (°) as the center. In the case where the angle difference Δw (the difference between the angle w1 and the angle w2) is Δw<0, that is, in the case where the angle w1 is smaller than the angle w2, it is found that the occurrence of abnormal images cannot be suppressed. This is because, as in Fig.12 As in the comparative example shown, since the angle w1 adjacent to the first feed pole 105 is small, the magnetic field between the first feed pole 105 and the second feed pole 202 cannot be sufficiently weakened by the magnetic field between the first feed pole 105 and the delivery pole 106, so that the developer moves between the first feed pole 105 and the second feed pole 202. In addition, this can also be said to be that since the magnetic field between the first feed pole 105 and the delivery pole 106 cannot be enhanced even when the angle w2 not adjacent to the first feed pole 105 is increased, the magnetic field between the first feed pole 105 and the second feed pole 202 cannot be sufficiently weakened.

[0139] On the other hand, in the case of Δw ≥ 0, that is, in the case where the angle w1 is not less than the angle w2, it is found that the occurrence of abnormal images can be suppressed. This is because, as shown in FIG. Fig. 9 As described, the angle w1 adjacent to the first feed pole 105 is large, so the magnetic field between the first feed pole 105 and the delivery pole 106 becomes strong, thereby being able to weaken the magnetic field between the first feed pole 105 and the second feed pole 202. As a result, movement of the developer between the first feed pole 105 and the second feed pole 202 in the direction of arrow F2 can be suppressed, thereby suppressing the occurrence of abnormal images.

[0140] Table 2 shows the results of the case where only the angle w1 or only the angle w2 is increased, centered on the state where the upstream side angle w1 and the downstream side angle w2 are equal to each other at 4°. Similar to the results of Table 1, it is found that the occurrence of abnormal images can be suppressed by satisfying Δw ≥ 0. However, under the conditions of Table 2, in the case of the angle difference Δw = 0, the occurrence of abnormal images cannot be sufficiently suppressed compared with the results of Table 1. This is because: when the angle difference Δw = 0 in Table 1, the half-value width of the delivery pole 106 is 12 degrees, and when the angle difference Δw = 0 in Table 2, the half-value width of the delivery pole 106 is 8 degrees, which is narrower than 12 degrees. When the half-value width is narrow, due to the assembly tolerance of the first magnet 36 and the second magnet 37, some changes in the magnetic pole position caused by the influence of magnetization deviation, etc., the magnetic field between the delivery pole 106 and the first feed pole 105 changes in the weakening direction in some cases. In this case, the effect of weakening the magnetic field between the first feed pole 105 and the second feed pole 202 and suppressing the movement of the developer between the first feed pole 105 and the second feed pole 202 becomes smaller (weaker). Therefore, in the case where the half value width is narrow, it is preferable to satisfy the angle difference Δw>0. In addition, it is more preferable to satisfy Δw≥2.5 degrees.

[0141] As described above, according to the present embodiment, the occurrence of image defects can be suppressed. That is, in the developing device 1Y of the present embodiment, the developer is fed from the first feed pole 105 to the delivery pole 106 on the first sleeve 33, and is delivered to the second sleeve 34 based on the magnetic field between the delivery pole 106 and the receiving pole 201, and then fed from the receiving pole 201 to the second feed pole 202 on the second sleeve 34. In such a configuration, the developer moves by the magnetic force along the magnetic field from the first feed pole 105 to the second feed pole 202 in some cases. On the other hand, in the present embodiment, as described above, the delivery pole 106 satisfies Δw ≥ 0, and therefore, the magnetic field between the first feed pole 105 and the delivery pole 106 weakens the magnetic field between the first feed pole 105 and the second feed pole 202, so that the movement of the developer between the first feed pole 105 and the second feed pole 202 can be suppressed. Therefore, the occurrence of the above-mentioned streak-like fog image can be suppressed.

[0142] Specifically, even in an image forming apparatus having a high image forming speed (processing speed), movement of the developer between the first feed pole 105 and the second feed pole 202 can be suppressed, thereby suppressing the occurrence of the above-mentioned streak-like fog image. In addition, the developer is stably circulated from the first developing roller 30 and then through the second developing roller 31, the peeling roller 32 and the developer circulating portion 46, so that the developing device 1Y and the image forming apparatus that perform stable image output can be provided.

[0143] <Second Embodiment>

[0144] Will use Figures 13 to 16 A second embodiment is described. This embodiment is different from the first embodiment in the configuration of the delivery pole 106B of the first magnet 36 of the first developing roller 30. Other configurations and actions are similar to those in the first embodiment, so the description and illustration are omitted or briefly described by adding the same reference numerals or symbols for similar configurations, and the differences from the first embodiment will be mainly described below.

[0145] In the case of the first embodiment described above, if Figure 8 As shown, the magnetic flux density of the delivery pole 106 of the first magnet 36 included in the first developing roller 30 satisfies Δw ≥ 0. The angle w1 close to the first feed pole 105 is large, so the magnetic field between the first feed pole 105 and the delivery pole 106 can weaken the magnetic field between the first feed pole 105 and the second feed pole 202.

[0146] On the other hand, in this embodiment, if Fig.13 and Fig.14 As shown, a delivery pole 106B is provided at the position of the delivery pole 106 of the first magnet 36 used in the first embodiment. The magnetic flux density peak of the delivery pole 106B is the same as the magnetic flux density peak of the delivery pole 106. On the other hand, the shape of the magnetic flux density peak becomes a flat shape.

[0147] This flat shape will be described. Fig.15 The measurement result of the magnetic flux density of the delivery pole 106B in the normal direction of the delivery pole 106B is shown, wherein the rotation direction of the first sleeve 33 is used as the horizontal axis. That is, Fig.15 : is a graph showing the normal component of the magnetic flux density of the delivery pole 106B on the surface of the first sleeve 33, wherein the vertical axis represents the magnetic flux density and the horizontal axis represents the angle of the first sleeve 33 relative to the rotation direction of the first sleeve 33. Here, the values ​​Lt and Lh and the straight lines HLt, HLh, VL11 and VL12 are defined in the following manner:

[0148] Lt: peak value (normal component maximum value) of the magnetic flux density of the delivery pole 106B on the surface of the first sleeve 33,

[0149] Lh: half value of the peak value Lt of the magnetic flux density delivered to the pole 106B,

[0150] HLt: A straight line (dashed line) parallel to the horizontal axis and passing through the Lt value position.

[0151] HLh: A straight line (dashed line) parallel to the horizontal axis and passing through the Lh value position.

[0152] VL11: a straight line parallel to the longitudinal axis and passing through point Hd (dash-dot line), and

[0153] VL12: A straight line (dash-dot line) parallel to the longitudinal axis and passing through point Hu.

[0154] Incidentally, similarly to the first embodiment, Hd is a position on the downstream side of the half-value position of the maximum value of the normal component of the magnetic flux density of the delivery pole 106B with respect to the rotation direction of the first sleeve 33. Further, similarly to the first embodiment, Hu is a position on the upstream side of the half-value position of the maximum value of the normal component of the magnetic flux density of the delivery pole 106B with respect to the rotation direction of the first sleeve 33.

[0155] In addition, Fig.15 In the curve graph, the area of ​​the rectangle surrounded by the straight lines VL11, VL12, HLt and HLh is area S; and the area (shaded part) obtained by integrating the normal component of the magnetic flux density of the delivery pole 106B from the straight line VL11 to the straight line VL12 according to the angle relative to the rotation direction of the first sleeve 33 is area Sa.

[0156] As described above, in order to suppress the movement of the developer by weakening the magnetic field from the first feed pole 105 to the second feed pole 202, it is effective to enhance the magnetic field between the first feed pole 105 and the delivery pole 106B. For this reason, it can be considered to increase the peak value of the magnetic flux density of the delivery pole 106B, and thereby enhance the magnetic field between the delivery pole 106B and the first feed pole 105. However, the magnetic field that helps to deliver the developer from the first sleeve 33 to the second sleeve 34 is also greatly changed, and therefore, the enhanced magnetic field is likely to cause the developer to move with the rotation of the first sleeve 33 and cause the developer to deteriorate.

[0157] Therefore, in this embodiment, instead of increasing the peak value of the magnetic flux density of the delivery pole 106B, the area Sa is increased (not less than the integral value of the half value of the peak value of the magnetic flux density of the delivery pole 106B). Specifically, the portion near the peak position of the magnetic flux density of the delivery pole 106B is formed into a flat shape so that the area ratio Sa / S of the area Sa to the area S becomes 75% or more (Sa / S≥75%). As a result, the magnetic field between the first feed pole 105 and the delivery pole 106B is enhanced, so that the magnetic field between the first feed pole 105 and the second feed pole 202 can be weakened, so that the movement of the developer between the first feed pole 105 and the second feed pole 202 can be suppressed.

[0158] Incidentally, the flat shape of the delivery pole 106B near the peak value of the magnetic flux density is not limited to one peak value, but may be a plurality of peak values, and may only be configured to satisfy the area ratio Sa / S ≥ 75%. In addition, a flat magnetic flux density distribution such as the delivery pole 106B can be formed by cutting off a portion of the first magnet 36 forming the delivery pole 106B in the circumferential direction, or by embedding a magnet with a different magnetic force in the cut portion.

[0159] In addition, the delivery pole 106B in the present embodiment adopts a flat normal magnetic flux density that expands toward the upstream and downstream sides of the peak position of the normal magnetic flux density of the delivery pole 106 in the first embodiment. For this reason, the magnetic field between the delivery pole 106B and the receiving pole 201 is formed to be wider, so that the influence of the change in the magnetic field of the delivery pole 106B and the receiving pole 201 caused by the magnetization deviation and assembly tolerance of the first magnet 36 and the second magnet 37 becomes smaller. That is, in the present embodiment, compared with the first embodiment, the deviation of the magnetic pole arrangement relative to the first magnet 36 and the second magnet 37 can suppress the movement of the developer between the first feeding pole 105 and the second feeding pole 202 while widening the delivery range of the developer from the first sleeve 33 to the second sleeve 34.

[0160] [experiment]

[0161] Next, an experiment for checking the occurrence of streak-like fog images (abnormal images) in the above-mentioned configuration will be described. In the experiment, the area S and the area Sa were changed by adjusting the magnetic flux density of the delivery pole 106B, and images were output by an imaging device including delivery poles under various conditions. Then, the occurrence of streak-like fog images on the output images was checked.

[0162] The other conditions and evaluations of this experiment are the same as those of the experiment described in Example 1. The results of this experiment are shown in Table 3.

[0163] Table 3

[0164] Sa[rad.mt],S[rad.mt] (29,48) (36,56) (41,61) (46,66) (53,71) (59,76) Sa / S 60％ 65％ 67％ 70％ 75％ 78％ <![CDATA[AI *1 ]]> × × × × ○ ○

[0165] *1: “AI” is an abnormal image.

[0166] In this experiment, the first developing roller 30 and the second developing roller 31 are constructed as follows: Figure 6 As shown. Fig.16 As shown in FIG. 1 , the magnetic characteristics are such that the peak value of the magnetic flux density of the delivery pole 106B is fixed at about 36 mT, and the shape of the magnetic flux density near the delivery pole 106B changes stepwise from 60% to 78% according to the area ratio Sa / S. Fig.16 In the example, the magnetic properties when Sa / S is 60%, 70% and 78% are used as representatives. Fig.13 shown.

[0167] As is apparent from Table 3, when the area ratio Sa / S is 75% or more, the occurrence of abnormal images can be suppressed. This is an effect obtained by bringing the vicinity of the magnetic flux density peak of the delivery pole 106B close to the first feed pole 105, thereby enhancing the magnetic field between the first feed pole 105 and the delivery pole 106B and weakening the magnetic field between the first feed pole 105 and the second feed pole 202. On the other hand, when the area ratio Sa / S is less than 75%, the effect of weakening the magnetic field between the first feed pole 105 and the second feed pole 202 by the magnetic flux of the delivery pole 106B is low, so that the developer moves between the first feed pole 105 and the second feed pole 202, with the result that the abnormal images cannot be sufficiently suppressed.

[0168] As described above, according to the present embodiment, the occurrence of image defects can be suppressed. That is, in the developing device 1Y of the present embodiment, the developer is fed from the first feed pole 105 to the delivery pole 106B on the first sleeve 33, and is delivered to the second sleeve 34 based on the magnetic field from the delivery pole 106B to the receiving pole 201, and then fed from the receiving pole 201 to the second feed pole 202. In this configuration, in some cases, the developer moves by the magnetic force along the magnetic field from the first feed pole 105 to the second feed pole 202. On the other hand, in the present embodiment, the vicinity of the magnetic flux density peak is configured to have a flat shape in such a manner that the delivery pole 106B satisfies the area ratio Sa / S ≥ 75% as described above, so that the magnetic field between the first feed pole 105 and the delivery pole 106B weakens the magnetic field between the first feed pole 105 and the second feed pole 202, and thus the movement of the developer between the first feed pole 105 and the second feed pole 202 can be suppressed. Therefore, the occurrence of the above-mentioned streak-like fog image can be suppressed.

[0169] <Third Embodiment>

[0170] Will use Fig.17 and Fig.18A third embodiment is described. This embodiment is different from the first embodiment in the configuration of the delivery pole 106C of the first magnet 36 of the first developing roller 30. Other configurations and actions are similar to those in the first embodiment, so the description and illustration are omitted or briefly described by adding the same reference numerals or symbols for similar configurations, and the differences from the first embodiment will be mainly described below.

[0171] In the case of the second embodiment described above, if Fig.15 As shown, the integral value Sa of the half value of the peak value of the magnetic flux density of the delivery pole 106B of the first magnet 36 included in the first developing roller 30 increases, so that the area ratio Sa / S becomes greater than 75%, thereby enhancing the magnetic field between the first feed pole 105 and the delivery pole 106B, thereby weakening the magnetic field between the first feed pole 105 and the second feed pole 202.

[0172] On the other hand, in this embodiment, if Fig.17 As shown, a delivery pole 106C is provided at the position of the delivery pole 106 of the first magnet 36 used in the first embodiment. The peak value of the magnetic flux density of the delivery pole 106C is the same as the peak value of the magnetic flux density of the delivery pole 106. On the other hand, the shape of the peak value of the magnetic flux density is a shape close to a flat shape.

[0173] This flat shape will be described. Fig.18 The measurement result of the magnetic flux density of the delivery pole 106C in the normal direction of the delivery pole 106C is shown, wherein the rotation direction of the first sleeve 33 is used as the horizontal axis. Here, as described below, the values ​​C and D, the points Cd, Cu, Dd and Du, the straight lines L11C, L12C, L11D and L12D, and the angles Wc and Wd are defined. Incidentally, similar to the second embodiment, the value Lt is the peak value of the magnetic flux density of the delivery pole 106C.

[0174] C: value of 10% of Lt,

[0175] D: 90% of the value Lt,

[0176] Cd: the downstream position among the positions where the normal component of the magnetic flux density of the delivery pole 106C becomes the value C with respect to the rotation direction of the first sleeve 33,

[0177] Cu: the upstream position among the positions where the normal component of the magnetic flux density of the delivery pole 106C becomes the value C with respect to the rotation direction of the first sleeve 33,

[0178] Dd: the downstream position among the positions where the normal component of the magnetic flux density of the delivery pole 106C becomes the value D with respect to the rotation direction of the first sleeve 33,

[0179] Du: the upstream position among the positions where the normal component of the magnetic flux density of the delivery pole 106C becomes the value D with respect to the rotation direction of the first sleeve 33,

[0180] L11C: a straight line (dash-dot line) connecting the rotation center R1 of the first sleeve 33 and point Cd,

[0181] L12C: A straight line (dash-dot line) connecting the rotation center R1 and point Cu.

[0182] L11D: A straight line (dash-dot line) connecting the rotation center R1 and point Dd.

[0183] L12D: The straight line (dash-dot line) connecting the rotation center R1 and point Du.

[0184] Wc: the angle formed by the lines L11C and L12C, and

[0185] Wd: Angle formed by straight line L11D and straight line L12D.

[0186] As described above, in order to suppress the movement of the developer between the first feed pole 105 and the second feed pole 202 by weakening the magnetic field from the first feed pole 105 to the second feed pole 202, it is effective to enhance the magnetic field between the first feed pole 105 and the delivery pole 106C. For this reason, it can be considered to increase the peak value of the magnetic flux density of the delivery pole 106C, and thereby enhance the magnetic field between the delivery pole 106C and the first feed pole 105. However, the magnetic field that helps to deliver the developer from the first sleeve 33 to the second sleeve 34 is also greatly changed, and therefore, the enhanced magnetic field is likely to cause the developer to move with the rotation of the first sleeve 33 and cause the developer to deteriorate.

[0187] Therefore, in this embodiment, instead of increasing the peak value of the magnetic flux density of the delivery pole 106C, the angle Wd (i.e., the width of the 90% value of the peak value of the magnetic flux density of the delivery pole 106C) is increased. Specifically, the portion near the position of the peak value of the magnetic flux density of the delivery pole 106C is formed into a flat shape so that the angle ratio Wd / Wc of the angle Wd to the angle Wc (i.e., the width of the 10% value of the peak value of the magnetic flux density of the delivery pole 106C) becomes 45% or more (Wd / Wc≥45%). As a result, the magnetic field between the first feed pole 105 and the delivery pole 106C is enhanced, so that the magnetic field between the first feed pole 105 and the second feed pole 202 can be weakened, thereby suppressing the movement of the developer between the first feed pole 105 and the second feed pole 202.

[0188] Incidentally, the flat structure near the peak value of the magnetic flux density of the delivery pole 106C is not limited to one peak value, but may be a plurality of peak values, and may only be configured to satisfy the angle ratio Wd / Wc ≥ 75%. In addition, a magnetic flux density distribution having a flat shape like the delivery pole 106C may be formed by cutting off a portion of the first magnet 36 forming the delivery pole 106C in the circumferential direction or by embedding a magnet having a different magnetic force in the cut portion.

[0189] In addition, the delivery pole 106C in the present embodiment adopts a flat normal magnetic flux density that expands toward the upstream and downstream sides of the peak position of the normal magnetic flux density of the delivery pole 106 in the first embodiment. For this reason, the magnetic field between the delivery pole 106C and the receiving pole 201 is formed to be wider, so that the influence of the change in the magnetic field of the delivery pole 106C and the receiving pole 201 caused by the magnetization deviation and assembly tolerance of the first magnet 36 and the second magnet 37 becomes smaller. That is, in the present embodiment, compared with the first embodiment, the deviation of the magnetic pole arrangement relative to the first magnet 36 and the second magnet 37 can suppress the movement of the developer between the first feeding pole 105 and the second feeding pole 202 while widening the delivery range of the developer from the first sleeve 33 to the second sleeve 34.

[0190] [experiment]

[0191] Next, an experiment for checking the occurrence of streak-like fog images (abnormal images) in the above-mentioned configuration will be described. In the experiment, the angle Wc and the angle Wd were changed by adjusting the magnetic flux density of the delivery pole 106C, and images were output by an imaging device including delivery poles under various conditions. Then, the occurrence of streak-like fog images on the output images was checked.

[0192] The other conditions and evaluations of this experiment are the same as those of the experiment described in Example 1. The results of this experiment are shown in Table 4.

[0193] Table 4

[0194] Wd(°),Wc(°) (5.6,26) (7.6,27) (9.6,29) (11.6,29.3) (13.7,30.2) (15.6,30.8) Wd / Wc 22％ 28％ 33％ 40％ 45％ 51％ <![CDATA[AI *1 ]]> × × × × ○ ○

[0195] *1: “AI” is an abnormal image.

[0196] The structures of the first developing roller 30 and the second developing roller 31 in the experiment are as follows: Figure 6 The magnetic characteristics are such that the peak value of the magnetic flux density of the delivery pole 106C is fixed at about 36 mT, and the shape of the magnetic flux density of the delivery pole 106C changes stepwise from 22% to 51% according to the angle ratio Wd / Wc. The magnetic poles other than the delivery pole 106C are as follows Fig.13 shown.

[0197] As shown in Table 4, when the angle ratio Wd / Wc is 45% or more, the occurrence of abnormal images can be suppressed. This is an effect obtained by bringing the vicinity of the magnetic flux density peak of the delivery pole 106C close to the first feed pole 105, thereby enhancing the magnetic field between the first feed pole 105 and the delivery pole 106C and weakening the magnetic field between the first feed pole 105 and the second feed pole 202. On the other hand, when the angle ratio Wd / Wc is less than 45%, the effect of weakening the magnetic field between the first feed pole 105 and the second feed pole 202 by the magnetic flux of the delivery pole 106C is low, so that the developer moves between the first feed pole 105 and the second feed pole 202, and as a result, the abnormal images cannot be sufficiently suppressed.

[0198] As described above, according to the present embodiment, the occurrence of image defects can be suppressed. That is, in the developing device 1Y of the present embodiment, the developer is fed from the first feed pole 105 to the delivery pole 106C on the first sleeve 33, and is delivered to the second sleeve 34 based on the magnetic field between the delivery pole 106C and the receiving pole 201, and then fed from the receiving pole 201 to the second feed pole 202 on the second sleeve 34. In such a configuration, in some cases, the developer moves by the magnetic force along the magnetic field between the first feed pole 105 and the second feed pole 202. On the other hand, in the present embodiment, the vicinity of the magnetic flux density peak is configured to have a flat shape in such a manner that the delivery pole 106C satisfies the angle ratio Wd / Wc ≥ 45% as described above, so that the magnetic field between the first feed pole 105 and the delivery pole 106C weakens the magnetic field between the first feed pole 105 and the second feed pole 202, and thus the movement of the developer between the first feed pole 105 and the second feed pole 202 can be suppressed. Therefore, the occurrence of the above-mentioned streak-like fog image can be suppressed.

[0199] <Fourth Embodiment>

[0200] Will use Fig.19 A fourth embodiment is described. This embodiment is different from the first embodiment in the configuration of the delivery pole 106D of the first magnet 36 of the first developing roller 30. Other configurations and actions are similar to those in the first embodiment, and therefore, description and illustration are omitted or briefly described by adding the same reference numerals or symbols for similar configurations, and the differences from the first embodiment will be mainly described below.

[0201] In this embodiment, if Fig.19As shown, at the position of the delivery pole 106 of the first magnet 36 adopted in the first embodiment, a delivery pole 106D is provided. The peak value of the magnetic flux density of the delivery pole 106D is the same as the peak value of the magnetic flux density of the delivery pole 106. On the other hand, the present embodiment is characterized in that the shape of the peak value of the magnetic flux density of the delivery pole 106D is a shape close to a flat shape, and the upstream side width in its half value is wider than the downstream side width. Specifically, the construction that satisfies the angle difference Δw ≥ 0 described in the first embodiment and the area ratio Sa / S ≥ 70% described in the second embodiment. By the way, in the case of the present embodiment, unlike the second embodiment, Δw ≥ 0 is satisfied, and therefore, with respect to the area ratio Sa / S, it is only necessary to satisfy Sa / S ≥ 65%. However, it is preferred to satisfy Sa / S ≥ 70%.

[0202] In this case of the present embodiment, the magnetic flux density of the delivery pole 106D on the upstream side of the peak value of the magnetic flux density of the delivery pole 106D in the range close to the first feed pole 105 is larger than the magnetic flux density of the delivery pole in the same range in the first embodiment and the second embodiment. Therefore, the magnetic field between the first feed pole 105 and the delivery pole 106D is stronger, and the effect of weakening the magnetic field between the first feed pole 105 and the second feed pole 202 is higher than in the first embodiment and the second embodiment. Therefore, the effect of suppressing the movement of the developer between the first feed pole 105 and the second feed pole 202 becomes higher.

[0203] [experiment]

[0204] Next, an experiment for checking the occurrence of streak-like fog images (abnormal images) in the above-mentioned configuration will be described. In the experiment, the angle difference Δw and the area ratio Sa / S were changed by adjusting the magnetic flux density of the delivery pole 106D, and an image was output by an imaging device including the delivery poles under various conditions. Then, the occurrence of streak-like fog images on the output images was checked.

[0205] The other conditions and evaluations of this experiment are the same as those of the experiment described in Example 1. The results of this experiment are shown in Table 5.

[0206] Table 5

[0207] ΔW -3 -1 0 2 3 Sa / S 61％ 65％ 70％ 72％ 74％ <![CDATA[AI *1 ]]> × △ ○ ○ ○

[0208] *1: “AI” is an abnormal image.

[0209] The structures of the first developing roller 30 and the second developing roller 31 in the experiment are as follows: Figure 6 The magnetic characteristics are such that the peak value of the magnetic flux density of the delivery pole 106D is fixed at about 36 mT, and the angle difference Δw changes from -3 (°) to 3 (°), and at the same time, the shape of the magnetic flux density of the delivery pole 106D changes stepwise from 61% to 74% according to the area ratio Sa / S. The magnetic poles other than the delivery pole 106D are as shown in FIG. Figure 7 shown.

[0210] As can be seen from Table 5, when the angle difference Δw is 0 (°) or more and the area ratio Sa / S is 70% or more, the occurrence of abnormal images can be suppressed. This is an effect obtained by making the vicinity of the magnetic flux density peak of the delivery pole 106D close to the first feed pole 105, thereby strengthening the magnetic field between the first feed pole 105 and the delivery pole 106D and weakening the magnetic field between the first feed pole 105 and the second feed pole 202.

[0211] Furthermore, even in the case of the angle difference Δw=-1(°) and the area ratio Sa / S=65%, the effect of suppressing the occurrence of abnormal images was confirmed. However, under this condition, due to some changes in the magnetic pole position caused by the assembly tolerance of the first magnet 36 and the second magnet 37 and the influence of the magnetization deviation, the magnetic field between the delivery pole 106D and the first feed pole 105 changes in the weakening direction, so that the effect of weakening the magnetic field between the first feed pole 105 and the second feed pole 202 becomes lower in some cases. Therefore, it is preferable to satisfy Δw≥0, in which case, it is only necessary to satisfy Sa / S≥65%. However, it is more preferable to satisfy the angle difference Δw≥0 and the area ratio Sa / S≥70%.

[0212] As described above, according to the present embodiment, the occurrence of image defects can be suppressed. That is, in the developing device 1Y of the present embodiment, the developer is fed from the first feed pole 105 to the delivery pole 106C on the first sleeve 33, and is delivered to the second sleeve 34 based on the magnetic field between the delivery pole 106D and the receiving pole 201, and then fed from the receiving pole 201 to the second feed pole 202 on the second sleeve 34. In such a configuration, in some cases, the developer moves by the magnetic force along the magnetic field between the first feed pole 105 and the second feed pole 202. On the other hand, in the present embodiment, as described above, the magnetic flux density of the delivery pole 106D satisfies the angle difference Δw ≥ 0 and the area ratio Sa / S ≥ 65%, preferably the area ratio Sa / S ≥ 70%, so that the magnetic field between the first feed pole 105 and the delivery pole 106D weakens the magnetic field between the first feed pole 105 and the second feed pole 202, and thus the movement of the developer between the first feed pole 105 and the second feed pole 202 can be suppressed. Therefore, the occurrence of the above-mentioned streak-like fog image can be suppressed.

[0213] <Fifth Embodiment>

[0214] Will use Fig. 20A fifth embodiment is described. This embodiment is different from the first embodiment in the configuration of the delivery pole 106E of the first magnet 36 of the first developing roller 30. Other configurations and actions are similar to those in the first embodiment, and therefore, description and illustration are omitted or briefly made by adding the same reference numerals or symbols for similar configurations, and the differences from the first embodiment will be mainly described below.

[0215] In this embodiment, if Fig. 20 As shown, at the position of the delivery pole 106 of the first magnet 36 adopted in the first embodiment, a delivery pole 106E is provided. The peak value of the magnetic flux density of the delivery pole 106E is the same as the peak value of the magnetic flux density of the delivery pole 106. On the other hand, the present embodiment is characterized in that the shape of the peak value of the magnetic flux density of the delivery pole 106D is a shape close to a flat shape, and the upstream side width in its half value is wider than the downstream side width. Specifically, the construction that satisfies the angle difference Δw ≥ 0 described in the first embodiment and the angle ratio Wd / Wc ≥ 35% described in the third embodiment. Incidentally, in the case of the present embodiment, unlike the third embodiment, Δw ≥ 0 is satisfied, and therefore, with respect to the angle ratio Wd / Wc, it is only necessary to satisfy Wd / Wc ≥ 30%. However, it is preferred to satisfy Wd / Wc ≥ 35%.

[0216] In this case of the present embodiment, the magnetic flux density of the delivery pole 106E on the upstream side of the peak value of the magnetic flux density of the delivery pole 106D in the range close to the first feed pole 105 is greater than the magnetic field density of the delivery pole in the same range in the first embodiment and the third embodiment. Therefore, the magnetic field between the first feed pole 105 and the delivery pole 106E is stronger, and the effect of weakening the magnetic field between the first feed pole 105 and the second feed pole 202 is higher than in the first embodiment and the third embodiment. Therefore, the effect of suppressing the movement of the developer between the first feed pole 105 and the second feed pole 202 becomes higher.

[0217] [experiment]

[0218] Next, an experiment for checking the occurrence of streak-like fog images (abnormal images) in the above-mentioned configuration will be described. In the experiment, the angle difference Δw and the angle ratio Wd / Wc were changed by adjusting the magnetic flux density of the delivery pole 106E, and images were output by an imaging device including the delivery poles under various conditions. Then, the occurrence of streak-like fog images on the output images was checked.

[0219] The other conditions and evaluations of this experiment are the same as those of the experiment described in Example 1. The results of this experiment are shown in Table 6.

[0220] Table 6

[0221] ΔW -3 -1 0 2 3 Wd / Wc 25％ 30％ 35％ 41％ 46％ AI*1 × △ ○ ○ ○

[0222] *1: “AI” is an abnormal image.

[0223] The structures of the first developing roller 30 and the second developing roller 31 in the experiment are as follows: Figure 6 The magnetic characteristics are such that the peak value of the magnetic flux density of the delivery pole 106E is fixed at about 36 mT, and the angle difference Δw changes from -3 (°) to 3 (°), and at the same time, the shape of the magnetic flux density of the delivery pole 106E changes stepwise from 25% to 46% according to the angle ratio Wd / Wc. The magnetic poles other than the delivery pole 106E are as shown in FIG. Figure 7 shown.

[0224] As can be seen from Table 6, when the angle difference Δw is 0 (°) or more and the angle ratio Wd / Wc is 35% or more, the occurrence of abnormal images can be suppressed. This is an effect obtained by bringing the vicinity of the magnetic flux density peak of the delivery pole 106E close to the first feed pole 105, thereby strengthening the magnetic field between the first feed pole 105 and the delivery pole 106E and weakening the magnetic field between the first feed pole 105 and the second feed pole 202.

[0225] Furthermore, even in the case of the angle difference Δw=-1(°) and the angle ratio Wd / Wc=30%, the effect of suppressing the occurrence of abnormal images was confirmed. However, under this condition, due to some changes in the magnetic pole position caused by the assembly tolerance of the first magnet 36 and the second magnet 37 and the influence of the magnetization deviation, the magnetic field between the delivery pole 106E and the first feed pole 105 changes in the weakening direction, so that the effect of weakening the magnetic field between the first feed pole 105 and the second feed pole 202 becomes lower in some cases. Therefore, it is preferable to satisfy Δw≥0, in which case it is only necessary to satisfy Wd / Wc≥30%. However, it is more preferable to satisfy the angle difference Δw≥0 and the angle ratio Wd / Wc≥35%.

[0226] As described above, according to the present embodiment, the occurrence of image defects can be suppressed. That is, in the developing device 1Y of the present embodiment, the developer is fed from the first feed pole 105 to the delivery pole 106E on the first sleeve 33, and is delivered to the second sleeve 34 based on the magnetic field between the delivery pole 106E and the receiving pole 201, and then fed from the receiving pole 201 to the second feed pole 202 on the second sleeve 34. In such a configuration, in some cases, the developer moves by the magnetic force along the magnetic field between the first feed pole 105 and the second feed pole 202. On the other hand, in the present embodiment, the magnetic flux density of the delivery pole 106E satisfies the angle difference Δw ≥ 0 and the area ratio Wd / Wc ≥ 30%, preferably the angle ratio Sa / S ≥ 35%, as described above, so that the magnetic field between the first feed pole 105 and the delivery pole 106E weakens the magnetic field between the first feed pole 105 and the second feed pole 202, and thus the movement of the developer between the first feed pole 105 and the second feed pole 202 can be suppressed. Therefore, the occurrence of the above-mentioned streak-like fog image can be suppressed.

[0227] <Other embodiments>

[0228] The present invention is not limited to the configuration of the above-described embodiment. For example, the imaging device 100 is not limited to an MFP, but may be a copier, a printer, or a fax machine. In addition, as long as the configurations of the developer supply screw 42, the developer stirring screw 43, and the developer recovery screw 44 are capable of conveying the developer, these configurations are not particularly limited, and for example, a spiral blade, a paddle blade, etc. may be applied.

[0229] Furthermore, in the above embodiment, a configuration is described in which the first sleeve 33 and the photosensitive drum 28Y rotate in the same direction at positions opposing each other and the second sleeve 34 and the photosensitive drum 28Y rotate in the same direction at positions opposing each other, but the present invention is not limited thereto.

[0230] A structure may be adopted in which the rotation center R2 of the second developing roller 31 is located above the rotation center R1 of the first developing roller 30, the first sleeve 33 and the photosensitive drum 28Y rotate in opposite directions at positions relative to each other, and the second sleeve 34 and the photosensitive drum 28Y rotate in opposite directions at positions relative to each other. That is, in this structure, reverse development is performed so that the photosensitive drum 28 rotates from top to bottom in the vertical direction at the position where the photosensitive drum 28 is relative to the first developing roller 30 and the photosensitive drum 28 rotates from top to bottom in the vertical direction at the position where the photosensitive drum 28 is relative to the second developing roller 31. The present invention is also applicable to this structure. In addition, in the case where three or more developing rollers are provided, the present invention is also applicable to any two developing rollers.

[0231] While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all modifications and equivalent structures and functions.

Claims

1. A developing device, comprising: A developing container configured to contain a developer, the developer including a toner and a carrier; a first rotatable member to which a developer contained in a developing container is supplied, and the first rotatable member carries and feeds the developer to a first developing position at which an electrostatic latent image formed on an image bearing member is developed; a first magnet non-rotatably and fixedly disposed in the first rotatable member, wherein the first magnet includes a first developing pole disposed opposite to the image bearing member at a first developing position, a delivery pole disposed downstream of the first developing pole with respect to a rotational direction of the first rotatable member, and a first feeding pole disposed upstream of the delivery pole with respect to a rotational direction of the first rotatable member and adjacent to the delivery pole and having a magnetic polarity different from that of the delivery pole; a second rotatable member disposed opposite to the first rotatable member and delivering the developer from the first rotatable member to the second rotatable member by a magnetic field generated by the first magnet, wherein the second rotatable member carries and feeds the developer to a second developing position for developing the electrostatic latent image, wherein a rotation direction of the second rotatable member at a position on the outer peripheral surface of the second rotatable member where the second rotatable member is closest to the first rotatable member is opposite to a rotation direction of the first rotatable member at a position on the outer peripheral surface of the first rotatable member where the first rotatable member is closest to the second rotatable member; and a second magnet, which is non-rotatably and fixedly disposed in the second rotatable member, wherein the second magnet includes a plurality of magnetic poles, the plurality of magnetic poles including a second developing pole disposed opposite to the image bearing member at the second developing position, a receiving pole disposed upstream of the second developing pole with respect to the rotation direction of the second rotatable member and having a magnetic polarity different from that of the delivering pole, and a second feeding pole disposed downstream of the receiving pole with respect to the rotation direction of the second rotatable member and adjacent to the receiving pole and having a magnetic polarity different from that of the receiving pole, the receiving pole being a magnetic pole disposed closest to the delivering pole among the plurality of magnetic poles, Among them, in the following cases, namely, The position on the outer peripheral surface of the first rotatable element where the delivery pole magnetic flux density relative to the normal direction of the outer peripheral surface of the first rotatable element is the maximum is point T, At each position on the outer peripheral surface of the first rotatable element where the delivery pole magnetic flux density relative to the normal direction of the outer peripheral surface of the first rotatable element is half the maximum value, the position on the downstream side relative to the rotation direction of the first rotatable element is point Hd, and At each position on the outer peripheral surface of the first rotatable element where the delivery pole magnetic flux density relative to the normal direction of the outer peripheral surface of the first rotatable element is half the maximum value, the position on the upstream side relative to the rotation direction of the first rotatable element is point Hu, The angle formed by the straight line L10 connecting the rotation center R1 of the first rotatable element and the point T and the straight line L12 connecting the rotation center R1 and the point Hu is w1, and The angle formed by the straight line L10 and the straight line L11 connecting the rotation center R1 and the point Hd is w2, The following relations are satisfied: w1-w2≥0.

2. The developing device according to claim 1, wherein: The following relationship is also satisfied: w1-w2>0.

3. The developing device according to claim 1, wherein: The following relationship is also satisfied: w1-w2≥2.5 degrees.

4. The developing device according to claim 1 or 2, wherein: In a graph in which the vertical axis represents the delivery pole magnetic flux density relative to the normal direction of the outer peripheral surface of the first rotatable element and the horizontal axis represents the angle of the first rotatable element relative to the rotation direction of the first rotatable element, in the following case, that is: The straight line passing through point T and parallel to the horizontal axis is straight line HLt, The straight line passing through points Hu and Hd and parallel to the horizontal axis is HLh, The straight line passing through point Hd and parallel to the longitudinal axis is VL11, The straight line passing through point Hu and parallel to the longitudinal axis is VL12, The area of ​​the rectangle enclosed by the straight lines VL11, VL12, HLt, and HLh is area S, and In the rectangular region, the area obtained by integrating the delivery pole magnetic flux density with respect to the normal direction of the outer peripheral surface of the first rotatable element from the straight line VL11 to the straight line VL12 according to the angle of the first rotatable element with respect to the rotation direction of the first rotatable element is the area Sa, The following relations are satisfied: Sa / S≥65%.

5. The developing device according to claim 4, wherein: The following relationship is also satisfied: Sa / S≥70%.

6. The developing device according to claim 1 or 2, wherein: In a graph in which the vertical axis represents the delivery pole magnetic flux density relative to the normal direction of the outer peripheral surface of the first rotatable element and the horizontal axis represents the angle of the first rotatable element relative to the rotation direction of the first rotatable element, in the following case, that is: At each position where the delivery pole magnetic flux density with respect to the normal direction of the outer peripheral surface of the first rotatable element is 10% of the maximum value of the delivery pole magnetic flux density with respect to the normal direction of the outer peripheral surface of the first rotatable element, the position on the upstream side with respect to the rotation direction of the first rotatable element is point Cu, At each position where the delivery pole magnetic flux density with respect to the normal direction of the outer peripheral surface of the first rotatable element is 10% of the maximum value of the delivery pole magnetic flux density with respect to the normal direction of the outer peripheral surface of the first rotatable element, the position on the downstream side with respect to the rotation direction of the first rotatable element is point Cd, At each position where the delivery pole magnetic flux density with respect to the normal direction of the outer peripheral surface of the first rotatable element is 90% of the maximum value of the delivery pole magnetic flux density with respect to the normal direction of the outer peripheral surface of the first rotatable element, the position on the upstream side with respect to the rotation direction of the first rotatable element is point Du, At each position where the delivery pole magnetic flux density with respect to the normal direction of the outer peripheral surface of the first rotatable element is 90% of the maximum value of the delivery pole magnetic flux density with respect to the normal direction of the outer peripheral surface of the first rotatable element, the position on the downstream side with respect to the rotation direction of the first rotatable element is point Dd, The angle formed by the straight line L11C connecting the rotation center R1 and the point Cd and the straight line L12C connecting the rotation center R1 and the point Cu is Wc, and The angle formed by the straight line L11D connecting the rotation center R1 and the point Dd and the straight line L12D connecting the rotation center R1 and the point Du is Wd, The following relations are satisfied: Wd / Wc≥30%.

7. The developing device according to claim 6, wherein: The following relationship is also satisfied: Wd / Wc≥35%.

8. A developing device, comprising: A developing container configured to contain a developer, the developer including a toner and a carrier; a first rotatable member to which a developer contained in a developing container is supplied, and the first rotatable member carries and feeds the developer to a first developing position at which an electrostatic latent image formed on an image bearing member is developed; a first magnet non-rotatably and fixedly disposed in the first rotatable member, wherein the first magnet includes a first developing pole disposed opposite to the image bearing member at a first developing position, a delivery pole disposed downstream of the first developing pole with respect to a rotational direction of the first rotatable member, and a first feeding pole disposed upstream of the delivery pole with respect to a rotational direction of the first rotatable member and adjacent to the delivery pole and having a magnetic polarity different from that of the delivery pole; a second rotatable member disposed opposite to the first rotatable member and delivering the developer from the first rotatable member to the second rotatable member by a magnetic field generated by the first magnet, wherein the second rotatable member carries and feeds the developer to a second developing position where the electrostatic latent image is developed, and wherein a rotation direction of the second rotatable member at a position on the outer peripheral surface of the second rotatable member where the second rotatable member is closest to the first rotatable member is opposite to a rotation direction of the first rotatable member at a position on the outer peripheral surface of the first rotatable member where the first rotatable member is closest to the second rotatable member; and a second magnet, which is non-rotatably and fixedly disposed in the second rotatable member, wherein the second magnet includes a plurality of magnetic poles, the plurality of magnetic poles including a second developing pole disposed opposite to the image bearing member at the second developing position, a receiving pole disposed upstream of the second developing pole with respect to the rotation direction of the second rotatable member and having a magnetic polarity different from that of the delivering pole, and a second feeding pole disposed downstream of the receiving pole with respect to the rotation direction of the second rotatable member and adjacent to the receiving pole and having a magnetic polarity different from that of the receiving pole, the receiving pole being a magnetic pole disposed closest to the delivering pole among the plurality of magnetic poles, Among them, in the following cases, namely: The position on the outer peripheral surface of the first rotatable element where the delivery pole magnetic flux density relative to the normal direction of the outer peripheral surface of the first rotatable element is the maximum is point T, At each position on the outer peripheral surface of the first rotatable element where the delivery pole magnetic flux density with respect to the normal direction of the outer peripheral surface of the first rotatable element is half the maximum value, the position on the downstream side with respect to the rotation direction of the first rotatable element is point Hd, and In each position on the outer peripheral surface of the first rotatable element where the delivery pole magnetic flux density with respect to the normal direction of the outer peripheral surface of the first rotatable element is half the maximum value, the position on the upstream side with respect to the rotation direction of the first rotatable element is point Hu, and Wherein, in a graph in which the vertical axis represents the delivery pole magnetic flux density relative to the normal direction of the outer peripheral surface of the first rotatable element and the horizontal axis represents the angle of the first rotatable element relative to the rotation direction of the first rotatable element, in the following cases, that is: The straight line passing through point T and parallel to the horizontal axis is straight line HLt, The straight line passing through points Hu and Hd and parallel to the horizontal axis is HLh, The straight line passing through point Hd and parallel to the longitudinal axis is VL11, The straight line passing through point Hu and parallel to the longitudinal axis is VL12, The area of ​​the rectangle enclosed by the straight lines VL11, VL12, HLt, and HLh is area S, and In the rectangular region, the area obtained by integrating the delivery pole magnetic flux density with respect to the normal direction of the outer peripheral surface of the first rotatable element from the straight line VL11 to the straight line VL12 according to the angle of the first rotatable element with respect to the rotation direction of the first rotatable element is the area Sa, The following relations are satisfied: Sa / S≥75%.

9. A developing device, comprising: A developing container configured to contain a developer, the developer including a toner and a carrier; a first rotatable member to which a developer contained in a developing container is supplied, and the first rotatable member carries and feeds the developer to a first developing position at which an electrostatic latent image formed on an image bearing member is developed; a first magnet non-rotatably and fixedly disposed in the first rotatable member, wherein the first magnet includes a first developing pole disposed opposite to the image bearing member at a first developing position, a delivery pole disposed downstream of the first developing pole with respect to a rotational direction of the first rotatable member, and a first feeding pole disposed upstream of the delivery pole with respect to a rotational direction of the first rotatable member and adjacent to the delivery pole and having a magnetic polarity different from that of the delivery pole; a second rotatable member disposed opposite to the first rotatable member and delivering the developer from the first rotatable member to the second rotatable member by a magnetic field generated by the first magnet, wherein the second rotatable member carries and feeds the developer to a second developing position for developing the electrostatic latent image, wherein a rotation direction of the second rotatable member at a position on the outer peripheral surface of the second rotatable member where the second rotatable member is closest to the first rotatable member is opposite to a rotation direction of the first rotatable member at a position on the outer peripheral surface of the first rotatable member where the first rotatable member is closest to the second rotatable member; and a second magnet, which is non-rotatably and fixedly disposed in the second rotatable member, wherein the second magnet includes a plurality of magnetic poles, the plurality of magnetic poles including a second developing pole disposed opposite to the image bearing member at the second developing position, a receiving pole disposed upstream of the second developing pole with respect to the rotation direction of the second rotatable member and having a magnetic polarity different from that of the delivering pole, and a second feeding pole disposed downstream of the receiving pole with respect to the rotation direction of the second rotatable member and adjacent to the receiving pole and having a magnetic polarity different from that of the receiving pole, the receiving pole being a magnetic pole disposed closest to the delivering pole among the plurality of magnetic poles, Among them, in the following cases, namely: The position on the outer peripheral surface of the first rotatable element where the delivery pole magnetic flux density relative to the normal direction of the outer peripheral surface of the first rotatable element is the maximum is point T, At each position on the outer peripheral surface of the first rotatable element where the delivery pole magnetic flux density with respect to the normal direction of the outer peripheral surface of the first rotatable element is half the maximum value, the position on the downstream side with respect to the rotation direction of the first rotatable element is point Hd, and In each position on the outer peripheral surface of the first rotatable element where the delivery pole magnetic flux density with respect to the normal direction of the outer peripheral surface of the first rotatable element is half the maximum value, the position on the upstream side with respect to the rotation direction of the first rotatable element is point Hu, and Wherein, in a graph in which the vertical axis represents the delivery pole magnetic flux density relative to the normal direction of the outer peripheral surface of the first rotatable element and the horizontal axis represents the angle of the first rotatable element relative to the rotation direction of the first rotatable element, in the following cases, that is: At each position where the delivery pole magnetic flux density with respect to the normal direction of the outer peripheral surface of the first rotatable element is 10% of the maximum value of the delivery pole magnetic flux density with respect to the normal direction of the outer peripheral surface of the first rotatable element, the position on the upstream side with respect to the rotation direction of the first rotatable element is point Cu, At each position where the delivery pole magnetic flux density with respect to the normal direction of the outer peripheral surface of the first rotatable element is 10% of the maximum value of the delivery pole magnetic flux density with respect to the normal direction of the outer peripheral surface of the first rotatable element, the position on the downstream side with respect to the rotation direction of the first rotatable element is point Cd, At each position where the delivery pole magnetic flux density with respect to the normal direction of the outer peripheral surface of the first rotatable element is 90% of the maximum value of the delivery pole magnetic flux density with respect to the normal direction of the outer peripheral surface of the first rotatable element, the position on the upstream side with respect to the rotation direction of the first rotatable element is point Cu, At each position where the delivery pole magnetic flux density with respect to the normal direction of the outer peripheral surface of the first rotatable element is 90% of the maximum value of the delivery pole magnetic flux density with respect to the normal direction of the outer peripheral surface of the first rotatable element, the position on the downstream side with respect to the rotation direction of the first rotatable element is point Cd, The angle formed by the straight line L11C connecting the rotation center R1 and the point Cd and the straight line L12C connecting the rotation center R1 and the point Cu is Wc, and The angle formed by the straight line L11D connecting the rotation center R1 and the point Dd and the straight line L12D connecting the rotation center R1 and the point Du is Wd, The following relationship is satisfied: Wd / Wc≥45%.

Images