Developing device

Abstract

To provide a configuration that can prevent deterioration of a developer even in a magnetic flux density distribution in which the magnetic flux density in a normal direction of a regulating magnetic pole N1 arranged most proximate to a regulating member 25 has two maximum values (peaks).SOLUTION: The distribution of a magnetic flux density Br of the regulating magnetic pole N1 has an upstream peak P1 and a downstream peak P2. The regulating member 25 is arranged to face between the upstream peak P1 and the downstream peak P2. An angle between the upstream peak P1 and the downstream peak P2 is 20° or more and less than 50°. An absolute value B1 of the magnetic flux density of the upstream peak P1 is smaller than an absolute value B2 of the magnetic flux density in a normal direction of the downstream peak P2. An angle θ1 from a position on the upstream side of the upstream peak P1 where the magnetic flux density Br becomes a half value of the magnetic flux density Br of the upstream peak P1 to the upstream peak P1 is larger than an angle θ2 from a position on the downstream side of the downstream peak P2 where the magnetic flux density Br becomes a half value of the magnetic flux density Br of the downstream peak P2 to the downstream peak P2.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a developing device used in an image forming apparatus such as a copier, a printer, a facsimile, or a multifunction machine having a plurality of these functions. [Background technology]

[0002] Conventionally, there have been known developing devices that use a two-component developer (hereinafter, abbreviated as developer) containing non-magnetic toner particles and magnetic carrier particles. In such developing devices, the developer is carried on the surface of a developing sleeve (developer carrier) with a magnet roller disposed inside, and the developer is transported by rotating the developing sleeve. The developer is transported to a developing area facing a photosensitive drum (image carrier) with the amount of developer (layer thickness) regulated by a regulating member disposed close to the developing sleeve. Then, an electrostatic latent image formed on the photosensitive drum is developed by the toner in the developer.

[0003] In such a configuration, if the positional relationship between the magnetic flux density distribution of the magnet roller and the regulating member is misaligned, the amount of developer regulated by the regulating member and conveyed to the development section will change. Patent Document 1 describes a configuration in which, among the multiple magnetic poles of the magnet roller, the magnetic flux density Br in the normal direction of the regulating pole facing the regulating member has a magnetic flux density distribution with two maximum values ​​(peaks), and the regulating member is disposed facing between the two peak positions. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-146398 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the case of Patent Document 1, the magnetic flux density Br in the normal direction of the regulating magnetic pole has a magnetic flux density distribution with two maximum values ​​(peaks), so the distribution of the magnetic flux density Br in the normal direction of the regulating magnetic pole can be made gentle with respect to the rotation direction (θ direction) of the developing sleeve. Therefore, even if the positional relationship between the magnetic flux density distribution of the magnet roller and the regulating member is shifted, the fluctuation in the amount of developer regulated by the regulating member and transported to the developing section can be suppressed.

[0006] Here, in general, the magnetic attraction force Fr in the direction of the center of the developing sleeve induced in the carrier by the magnetic flux density is likely to be large when the absolute value of the magnetic flux density is large and the change in the magnetic flux density is large. When the regulating magnetic pole has a magnetic flux density distribution with two peaks as in the developing device of Patent Document 1, the absolute value of the magnetic flux density is large near the two peaks, and the change in the magnetic flux density is also likely to be large, so the magnetic attraction force of the carrier is likely to be large. In particular, when the magnetic attraction force of the carrier is large on the upstream side of the regulating member in the rotation direction of the developing sleeve, the developer is likely to be accumulated in the developer accumulation portion formed upstream of the regulating member. When the stagnation occurs, the torque increases, and there is a risk that the developer deterioration is likely to occur. In the recent trend of lowering the melting point of the toner due to the high speed of the image forming device, a new configuration capable of further suppressing such developer deterioration is desired.

[0007] The present invention aims to provide a configuration that can suppress developer deterioration even if the magnetic flux density distribution in the normal direction of the regulating magnetic pole located closest to the regulating member has two maximum values ​​(peaks). [Means for solving the problem]

[0008] The present invention One aspect teeth ,to The developer contains toner and carrier. A developing container for storing the developer and a developing position for storing the developer. Carry and transport Developing Rotary Body and, The developing rotor It is fixed and non-rotating inside the With a regulated pole A magnet and a regulating portion that regulates an amount of developer carried on the developing rotary body by a magnetic force of the regulating pole; The method comprises the steps of: With respect to the rotation direction of the developing rotor, the regulating pole Outer circumference For face Magnetic flux density in the normal direction Extremely Small value The minimum position whereis, with respect to the rotation direction of the the regulating pole is downstream of a first maximum position where the magnetic flux density in the normal direction to the outer circumferential surface of the developing rotor becomes a first maximum value, and the regulating pole is upstream of a second maximum position where the magnetic flux density in the normal direction to the outer circumferential surface of the developing rotor becomes a second maximum value, , the angle 1st local maximum position between the The second maximum position is 20° or more and less than 50°, and the teeth, is located upstream of the With respect to the rotation direction of the developing rotor, the regulating portion with respect to the The position facing the outer circumferential surface of the developing rotor is downstream of the first maximum position and upstream of the second maximum position, and is located 0.01 mm from the second maximum position to the first maximum position with respect to the rotation direction of the developing rotor. of the The developing rotor on the downstream side of the Outer surface to the The magnetic flux density in the normal direction to the position The angle to the first maximum position and is characterized in that the With respect to the outer peripheral surface of the developing rotor magnetic flux density in the normal direction Degree from the position where the 1st pole becomes half the maximum value Value to The first maximum position is smaller than the angle to small . Developing device .

[0009] Books The invention One aspect comprises a developer containing toner and a carrier ,to for carrying and transporting A developing container for storing the developer and a developing position for storing the developer. , and Developing Rotary Body a magnet fixedly arranged non-rotatably inside the The developing rotor , and With a regulated pole is provided with a regulating portion that regulates an amount of developer carried on the developing rotary body by a magnetic force of the regulating pole; . With respect to the rotation direction of the With respect to the rotation direction of the developing rotor, the regulating pole , the angle For face between the Extremely minimum value The minimum position where of the magnetic flux density in the normal direction of the outer circumference of the the regulating pole is downstream of a first maximum position where the magnetic flux density in the normal direction to the outer circumferential surface of the developing rotor becomes a first maximum value, and the regulating pole is upstream of a second maximum position where the magnetic flux density in the normal direction to the outer circumferential surface of the developing rotor becomes a second maximum value, is 20° or more and less than 50°, and the 1st local maximum position absolute value of which is B1 The second maximum position and the absolute value of the teeth, is B2. With respect to the rotation direction of the With respect to the rotation direction of the developing rotor, the regulating portion , when the angle at the The position facing the outer circumferential surface of the developing rotor is downstream of the first maximum position and upstream of the second maximum position, where the and the second maximum value magnetic flux density in the normal direction The developing rotor becomes half the maximum value is θ2, it is characterized in that B1 / θ1 < B2 / θ2 The amount of the developing roller 14 is larger than the amount of the first maximum value. . is defined as an angle from a position where the value of the first maximum value is half of the value of the first maximum value to the first maximum position, and the magnetic flux density in the normal direction to the outer circumferential surface of the developing rotor on the downstream side from the second maximum position to the second maximum value with respect to the rotation direction of the developing rotor is defined as θ1. . 2nd pole maximum Value half value position Place . Developing device .

[0010] Books The invention One aspect comprises a developer containing toner and a carrier ,to for carrying and transporting A developing container for storing the developer and a developing position for storing the developer. ​ Developing Rotary Body and, The developing rotor Fixed and non-rotating position inside Regulated very and the developing rotor. Regarding the direction of rotation Before Note The upstream side of the regulating pole is the regulating pole. an upstream magnetic pole disposed adjacent to said The regulating pole with respect to the rotation direction of the developing rotor The downstream side of the above regulation very and a downstream pole disposed adjacent to the and a regulating portion that regulates an amount of developer carried on the developing rotor by a magnetic force of the regulating pole, wherein a minimum position where the magnetic flux density of the regulating pole in the normal direction to the outer circumferential surface of the developing rotor becomes a minimum value with respect to a rotation direction of the developing rotor is downstream of a first maximum position where the magnetic flux density of the regulating pole in the normal direction to the outer circumferential surface of the developing rotor becomes a first maximum value and upstream of a second maximum position where the magnetic flux density of the regulating pole in the normal direction to the outer circumferential surface of the developing rotor becomes a second maximum value with respect to a rotation direction of the developing rotor, an angle between the first maximum position and the second maximum position is 20° or more and less than 50° with respect to the rotation direction of the developing rotor, and a facing position where the regulating portion faces the outer circumferential surface of the developing rotor is downstream of the first maximum position and upstream of the second maximum position with respect to the rotation direction of the developing rotor, Regarding the direction of rotation of 2nd local maximum position From before Below Flow side magnetic pole With respect to the outer peripheral surface of the developing rotor Magnetic flux density in the normal direction but Local maximum The angle to the position where of The magnetic flux density in the normal direction to the outer circumferential surface of the developing rotor is at a maximum value. From the position 1st local maximum position than the angle to small Characterized by Developing device . Effect of the Invention

[0014] According to the present invention, even if the magnetic flux density distribution in the normal direction of the regulating magnetic pole disposed closest to the regulating member has two maximum values ​​(peaks), developer deterioration can be suppressed. [Brief description of the drawings]

[0015] [Figure 1] 1 is a schematic cross-sectional view of an image forming apparatus according to a first embodiment. [Diagram 2] FIG. 2 is a schematic cross-sectional view of the developing device according to the first embodiment. [Diagram 3] 11 is a graph showing the relationship between the angle of the developing sleeve from the center of the regulating member arrangement area of ​​the developing sleeve according to Example 1 and Comparative Examples 1 and 2, and the magnetic flux density in the normal direction and the magnetic attractive force Fr in the developing sleeve center direction. [Figure 4] 11 is a graph showing the relationship between the angle around the regulating member arrangement area of ​​the developing sleeve according to Comparative Example 2 and the magnetic flux density in the normal direction. [Diagram 5] 6 is a graph showing the relationship between the angle centered on the regulating member arrangement area of ​​the developing sleeve in the first embodiment and the magnetic flux density in the normal direction. [Figure 6]13 is a graph showing the relationship between the angle of the developing sleeve from the center of the regulating member arrangement region of the developing sleeve according to Example 2 and Comparative Examples 2 and 3 in the second embodiment, and the magnetic flux density in the normal direction and the magnetic attraction force Fr in the developing sleeve center direction. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] <First embodiment> The first embodiment will be described with reference to Figures 1 to 5. In this embodiment, a developing device is applied to a tandem type full-color printer as an example of an image forming apparatus.

[0017] [Image forming device] First, a schematic configuration of the image forming apparatus 1 will be described with reference to Fig. 1. In this embodiment, the image forming apparatus 1 has an intermediate transfer belt 44b, and after the toner images of each color are primarily transferred from the photosensitive drums 81y to 81k to the intermediate transfer belt 44b, the composite toner images of each color are secondarily transferred collectively onto the sheet S. However, the present invention is not limited to this, and a method of directly transferring from the photosensitive drums to a sheet transported by a sheet transport belt may also be adopted.

[0018] In this embodiment, a two-component developer, which is a mixture of non-magnetic toner and magnetic carrier, is used as the developer. The toner is produced by pulverizing or polymerizing a resin such as polyester or styrene that contains coloring agents and wax components. The carrier is produced by applying a resin coating to the surface layer of a core made of resin particles kneaded with ferrite particles or magnetic powder.

[0019] 1, the image forming apparatus 1 includes an image forming apparatus main body (hereinafter, referred to as the apparatus main body) 10 serving as a housing. The apparatus main body 10 includes an image reading section 11, a sheet feeding section 30, an image forming section 40, a sheet conveying section 50, a sheet discharging section 60, and a control section 70. The sheet S, which is a recording material, is a material on which a toner image is formed, and specific examples thereof include plain paper, a resin sheet that is a substitute for plain paper, cardboard, and an overhead projector sheet.

[0020] The image reading unit 11 is provided on the upper part of the device body 10. The image reading unit 11 includes a platen glass (not shown) as a document placement platform, a light source (not shown) that irradiates light onto the document placed on the platen glass, an image sensor (not shown) that converts reflected light into a digital signal, and the like.

[0021] The sheet feeding section 30 is disposed at the bottom of the device main body 10 and is equipped with sheet cassettes 31a, 31b for loading and storing sheets S such as recording paper, and feeding rollers 32a, 32b, and feeds the stored sheets S to the image forming section 40.

[0022] The image forming section 40 includes an image forming unit 80, a toner hopper 41, a toner container 42, a laser scanner 43, an intermediate transfer unit 44, a secondary transfer section 45, and a fixing device 46. The image forming section 40 is capable of forming an image on the sheet S based on image information.

[0023] The image forming apparatus 1 of the present embodiment is a full-color image forming apparatus, and the image forming units 80y, 80m, 80c, and 80k are provided separately with the same configuration for each of the four colors, yellow (y), magenta (m), cyan (c), and black (k). Similarly, the toner hoppers 41y, 41m, 41c, and 41k and the toner containers 42y, 42m, 42c, and 42k are provided separately with the same configuration for each of the four colors, yellow (y), magenta (m), cyan (c), and black (k). For this reason, in FIG. 1, the configurations of the four colors are shown with the same reference numerals followed by color identifiers, but in FIG. 2 and in the specification, there are cases where the components are described only by reference numerals without the color identifiers.

[0024] The toner container 42 is, for example, a cylindrical bottle in which toner is stored, and is disposed above each image forming unit 80 and connected via a toner hopper 41. The laser scanner 43 exposes the surface of the photosensitive drum 81 charged by the charging roller 82 to light, and forms an electrostatic latent image on the surface of the photosensitive drum 81.

[0025] The image forming unit 80 includes four image forming units 80y, 80m, 80c, and 80k for forming four-color toner images. Each image forming unit 80 includes a photosensitive drum (image carrier) 81y, 81m, 81c, and 81k for forming a toner image, a charging roller 82y, 82m, 82c, and 82k, a developing device 20y, 20m, 20c, and 20k, and a cleaning blade 84y, 84m, 84c, and 84k. In addition, the photosensitive drums 81y, 81m, 81c, and 81k, the charging rollers 82y, 82m, 82c, and 82k, the developing devices 20y, 20m, 20c, and 20k, the cleaning blades 84y, 84m, 84c, and 84k, and the developing sleeve 24 described later are provided separately with the same configuration for each of the four colors, yellow (y), magenta (m), cyan (c), and black (k). For this reason, the configurations for each of the four colors are shown in FIG. 1 with the same reference numerals followed by a color identifier, but in FIG. 2 and in the specification, there are cases where the components are described using only the reference numerals without the color identifiers.

[0026] The photosensitive drum 81 as an image carrier has a photosensitive layer formed on the outer peripheral surface of an aluminum cylinder so as to have a negative charging polarity, and rotates in the direction of the arrow at a predetermined process speed (circumferential speed). A charging roller 82 as a charging member contacts the surface of the photosensitive drum 81 and charges the surface of the photosensitive drum 81 to, for example, a uniform negative dark potential. After charging, an electrostatic latent image is formed on the surface of the photosensitive drum 81 based on image information by a laser scanner 43 as an exposure device. The photosensitive drum 81 moves around while carrying the formed electrostatic latent image, and the image is developed with toner by the developing device 20. A detailed configuration of the developing device 20 will be described later.

[0027] The developed toner image is primarily transferred to an intermediate transfer belt 44b, which will be described later. After the primary transfer, the surface of the photosensitive drum 81 is neutralized by a pre-exposure unit (not shown). A cleaning blade 84 as a cleaning member is disposed in contact with the surface of the photosensitive drum 81, and cleans off residual matter such as transfer residual toner remaining on the surface of the photosensitive drum 81 after the primary transfer.

[0028] The intermediate transfer unit 44 is disposed above the image forming units 80y, 80m, 80c, and 80k. The intermediate transfer unit 44 includes a plurality of rollers (tension members) such as a drive roller 44a, a driven roller 44d, and primary transfer rollers 44y, 44m, 44c, and 44k, and an intermediate transfer belt 44b as an intermediate transfer body wound around these rollers. The primary transfer rollers 44y, 44m, 44c, and 44k are disposed opposite the photosensitive drums 81y, 81m, 81c, and 81k, respectively, and come into contact with the intermediate transfer belt 44b.

[0029] By applying a positive transfer bias to the intermediate transfer belt 44b by the primary transfer rollers 44y, 44m, 44c, and 44k, the toner images having negative polarity on the photosensitive drums 81y, 81m, 81c, and 81k are sequentially transferred in a multi-layer manner onto the intermediate transfer belt 44b. As a result, the intermediate transfer belt 44b moves in a circumferential direction with a full-color image formed on its outer circumferential surface.

[0030] The secondary transfer section 45 includes an inner secondary transfer roller 45a and an outer secondary transfer roller 45b. A positive secondary transfer bias is applied to the outer secondary transfer roller 45b to transfer the full-color image formed on the intermediate transfer belt 44b to the sheet S. The fixing device 46 includes a fixing roller 46a and a pressure roller 46b. The toner image transferred to the sheet S is heated and pressurized to be fixed to the sheet S by the sheet S being sandwiched and transported between the fixing roller 46a and the pressure roller 46b.

[0031] The sheet conveying section 50 includes a pre-secondary transfer conveying path 51, a pre-fixing conveying path 52, a discharge path 53, and a re-conveying path 54, and conveys the sheet S fed from the sheet feeding section 30 from the image forming section 40 to the sheet discharge section 60.

[0032] The sheet discharge section 60 includes a pair of discharge rollers 61 arranged downstream of the discharge path 53, and a discharge tray 62 arranged downstream of the pair of discharge rollers 61. The pair of discharge rollers 61 feeds the sheet S conveyed from the discharge path 53 from a nip portion, and discharges the sheet S onto the discharge tray 62 through a discharge port 10a formed in the apparatus body 10. The discharge tray 62 is a face-down tray, and stacks the sheet S discharged from the discharge port 10a in the direction of the arrow X.

[0033] The control unit 70 is configured by a computer, and includes, for example, a CPU, a ROM that stores programs that control each unit, a RAM that temporarily stores data, and an input / output circuit that inputs and outputs signals from and to the outside. The CPU is a microprocessor that is responsible for the overall control of the image forming apparatus 1, and is the main body of the system controller. The CPU is connected to the image reading unit 11, the sheet feeding unit 30, the image forming unit 40, the sheet conveying unit 50, the sheet discharging unit 60, and the operation unit via the input / output circuit, and exchanges signals with each unit and controls their operations.

[0034] Next, an image forming operation in the image forming apparatus 1 configured as above will be described. When the image forming operation starts, first, the photosensitive drum 81 rotates and the surface is charged by the charging roller 82. Then, the laser scanner 43 emits laser light to the photosensitive drum 81 based on image information, and an electrostatic latent image is formed on the surface of the photosensitive drum 81. Toner adheres to this electrostatic latent image, so that it is developed and visualized as a toner image, and then transferred to the intermediate transfer belt 44b.

[0035] Meanwhile, in parallel with such a toner image forming operation, the feed rollers 32a and 32b rotate to separate and feed the topmost sheet S of the sheet cassettes 31a and 31b. Then, in synchronization with the toner image on the intermediate transfer belt 44b, the sheet S is transported to the secondary transfer unit 45 via the secondary pre-transfer transport path 51. Furthermore, an image is transferred from the intermediate transfer belt 44b to the sheet S, and the sheet S is transported to the fixing device 46, where the unfixed toner image is heated and pressed to be fixed on the surface of the sheet S. The sheet S is then discharged from the discharge port 10a by the discharge roller pair 61 and stacked on the discharge tray 62.

[0036] [Developing device] Next, the developing device 20 will be described in detail with reference to Fig. 2. The developing device 20 has a developing container 21 that contains a developer, a first transport screw 22, a second transport screw 23, a developing sleeve 24, and a regulating member (a regulating blade in this embodiment) 25. The developing container 21 has an opening 21a at a position facing the photosensitive drum 81, through which the developing sleeve 24 is exposed.

[0037] Toner is supplied to the developing container 21 from a toner container 42 (see FIG. 1) filled with toner. The developing container 21 has a partition wall 27 extending in the longitudinal direction at approximately the center. The developing container 21 is horizontally partitioned into a developing chamber 21b and an agitating chamber 21c by this partition wall 27. Developer is contained in the developing chamber 21b and the agitating chamber 21c. The developing chamber 21b supplies developer to the developing sleeve 24. The agitating chamber 21c is connected to the developing chamber 21b and collects and agitates the developer from the developing sleeve 24.

[0038] The first transport screw 22 is disposed in the developing chamber 21b in the axial direction of the developing sleeve 24, approximately parallel to the developing sleeve 24, and transports the developer in the developing chamber 21b while stirring it. The second transport screw 23 is disposed in the stirring chamber 21c in the axis direction of the first transport screw 22, and transports the developer in the stirring chamber 21c in the opposite direction to the first transport screw 22. That is, the developing chamber 21b and the stirring chamber 21c form a circulation path for the developer that stirs and transports the developer. The toner is stirred by the screws 22 and 23, and rubs against the carrier, becoming negatively charged by friction.

[0039] The developer in the developing container 21 is carried on the developing sleeve 24 by a magnet roller 24m fixedly disposed inside the rotatable developing sleeve 24. Thereafter, the developer amount (layer thickness) on the developing sleeve 24 is regulated by a regulating member 25, and the developing sleeve 24 is transported to a developing area facing the photosensitive drum 81 as the developing sleeve 24 rotates. The developer is brought into contact with the photosensitive drum 81, and toner is supplied to the photosensitive drum 81, thereby developing the electrostatic latent image on the photosensitive drum 81 into a toner image. At this time, a developing bias in which a DC voltage and an AC voltage are superimposed is applied between the photosensitive drum 81 and the developing sleeve 24 so that the toner flies to the electrostatic latent image.

[0040] Developer Carrier (Developing Rotary Body) The developing sleeve 24 as a developing roller carries a developer having a non-magnetic toner and a magnetic carrier, and is disposed in a developing region facing the photosensitive drum 81. (Development position) The developing sleeve 24 is cylindrical and has a diameter of, for example, 25 mm, and is made of a non-magnetic material such as aluminum or non-magnetic stainless steel, and is made of aluminum in this embodiment.

[0041] As a regulatory department The regulating member 25 is a regulating magnetic pole of the magnet roller 24m. (Regulatory pole) It is provided in the developing container 21 to face N1. In other words, the regulating magnetic pole N1 is located inside the developing sleeve 24 at the opposing position where the regulating member 25 faces the outer circumferential surface of the developing sleeve 24.The regulating member 25 is disposed opposite the developing sleeve 24 in a non-contact manner, and regulates the amount of developer carried on the developing sleeve 24. That is, the regulating member 25 is fixed to the developing container 21 with its tip end kept at a predetermined gap from the developing sleeve 24, and regulates the layer thickness by cutting off the magnetic brushes of the developer carried on the surface of the developing sleeve 24 by the magnetic force (magnetic attraction force) of the regulating magnetic pole N1.

[0042] Such a regulating member 25 is made of a metal plate (e.g., a SUS plate) arranged in the longitudinal direction of the developing sleeve 24, and the developer passes between the tip of the regulating member 25 and the developing sleeve 24 to be sent to the development area. The regulating member 25 may be either a magnetic or non-magnetic member, but is preferably a magnetic member from the following viewpoint. In the case of a magnetic member, a magnetic field is formed between the tip of the regulating member 25 and the developing sleeve 24, and a magnetic attraction force acts on the surface of the regulating member 25. As a result, the developer is more easily scraped off. In addition, the gap between the tip of the regulating member 25 and the developing sleeve 24 can be made large, which has the advantage of making it less likely for foreign matter to clog.

[0043] On the other hand, in the case of a magnetic member, the developer is restrained by the magnetic field between the tip of the regulating member 25 and the developing sleeve 24, and there is a risk that developer deterioration due to friction may occur. Note that the regulating member may be a non-magnetic member to which a magnetic member is attached. In this way, the merits of the magnetic member are somewhat lost, but it is possible to suppress developer deterioration. In this embodiment, the regulating member 25 is made of only a magnetic member. Therefore, developer deterioration is a concern, but by using the magnet roller 24m of this embodiment described later in combination, it is possible to suppress developer deterioration.

[0044] A roller-shaped magnet roller (magnetic field generating means, magnet) 24m is fixedly installed inside the developing sleeve 24 in a non-rotating state relative to the developing container 21. The magnet roller 24m has a plurality of magnetic poles and generates a magnetic field for carrying the developer on the developing sleeve 24. In this embodiment, the magnet roller 24m has seven magnet pieces, each of which has a drawing-up magnetic pole S1, a regulating magnetic pole N1, a conveying magnetic pole S2, a developing magnetic pole N2, a conveying magnetic pole S3, a conveying magnetic pole N3, and a peeling magnetic pole S4 on its surface facing the developing sleeve 24. Note that, although a magnet roller with seven poles is used in this embodiment, it may have poles other than seven poles, and may have a magnet roller with five poles, for example.

[0045] However, when the magnet roller 24m has seven or more magnetic poles as in this embodiment, each magnet piece tends to be small, and the influence of the positional deviation of the regulating member with respect to the regulating magnetic pole tends to occur. Therefore, when the magnet roller 24m has seven or more magnetic poles as in this embodiment, the effect of adopting the configuration described below is enhanced.

[0046] The pumping magnetic pole S1 is disposed opposite the developing chamber 21b. The regulating magnetic pole N1 is disposed opposite the regulating member 25. The transporting magnetic pole S2 is disposed on the upstream side of the developing area in the rotation direction. The developing magnetic pole N2 is disposed opposite the developing area. The transporting magnetic pole S3 and the transporting magnetic pole N3 are disposed on the downstream side of the developing area in the rotation direction. The peeling magnetic pole S4 is disposed adjacent to the upstream side of the pumping magnetic pole S1 in the rotation direction. In particular, the regulating magnetic pole N1 as the first magnetic pole is disposed closest to the regulating member 25. Moreover, the pumping magnetic pole S1 as the second magnetic pole (upstream magnetic pole) is disposed adjacent to the regulating magnetic pole N1 on the upstream side of the regulating magnetic pole N1 with respect to the rotation direction of the developing sleeve 24. Furthermore, the transporting magnetic pole S2 as the third magnetic pole (downstream magnetic pole) is disposed adjacent to the regulating magnetic pole N1 on the downstream side of the regulating magnetic pole N1 with respect to the rotation direction of the developing sleeve 24.

[0047] Next, the operation of the developing sleeve 24 of this embodiment will be described with reference to Fig. 2. The developing sleeve 24 rotates in the direction of the arrow, and the developer contained in the developing chamber 21b is attracted by the drawing-up magnetic pole S1 facing the developing chamber 21b and transported toward the regulating member 25. The developer is made to stand upright by the regulating magnetic pole N1 facing the regulating member 25, and the layer thickness is regulated by the regulating member 25. The developer passes through the gap between the developing sleeve 24 and the regulating member 25, forming a developer layer of a predetermined thickness on the developing sleeve 24.

[0048] The developer layer is carried and transported through the transport magnetic pole S2 to the development area facing the photosensitive drum 81, and develops the electrostatic latent image formed on the surface of the photosensitive drum 81 in a state in which magnetic brushes are formed by the development magnetic pole N2 facing the development area.

[0049] The developer after being used for development passes through transport magnetic poles S3 and N3 arranged downstream in the rotation direction of the development region, and is peeled off from the developing sleeve 24 in the peeling region created by the repulsion of the peeling magnetic pole S4 and the pumping magnetic pole S1. The peeled off developer is stirred and transported in the stirring chamber 21c, and is supplied again to the developing sleeve 24 from the developing chamber 21b.

[0050] [Magnetic flux density distribution around the regulating pole] Next, the magnetic flux density distribution around the regulating magnetic pole N1 of the magnet roller 24m of this embodiment will be described. In the magnet roller 24m of this embodiment, the magnetic flux density Br in the normal direction on the outer circumferential surface of the developing sleeve 24 at the regulating magnetic pole N1 as the first magnetic pole is an upstream maximum value from the upstream side to the downstream side in the rotation direction of the developing sleeve 24. (First maximum value) P1, minimum B, and downstream maximum (Second maximum value)P2 are present in this order. Such a magnetic flux density distribution may be referred to as a two-peak distribution hereinafter. A magnetic flux density distribution of the regulating magnetic pole of a magnet roller having one maximum value may be referred to as a one-peak distribution hereinafter. In the present embodiment, a two-peak magnet roller 24m is used, and the regulating member 25 is disposed so as to face between the upstream maximum value P1 and the downstream maximum value P2. In the following, the upstream maximum value P1 and the downstream maximum value P2 are also referred to as the upstream peak P1 and the downstream peak P2, respectively. Also, the position of the upstream peak P1 (1st local maximum position) , the position of downstream peak P2 (2nd local maximum position) are sometimes simply referred to as the upstream peak P1 and the downstream peak P2, respectively. In addition, the positions of other maximum values, such as the position of the maximum value of the magnetic flux density Br, are sometimes simply referred to as the maximum value. Furthermore, the minimum position at which minimum value B occurs may simply be referred to as minimum value B.

[0051] Hereinafter, Example 1 having the regulating magnetic pole N1 of the magnet roller 24m of this embodiment will be described with reference to FIG. 3 in comparison with Comparative Examples 1 and 2. FIG. 3 is a diagram showing the distribution of the magnetic flux density Br on the developing sleeve 24 by the magnet roller 24m. More precisely, the magnetic flux density Br refers to the component of the magnetic flux density B in the normal direction to the developing sleeve. Hereinafter, the "magnetic flux density Br in the normal direction" may be simply called "magnetic flux density" according to convention. When simply referring to "magnetic flux density", it refers to the "magnetic flux density Br in the normal direction". The magnetic flux density Br (in the normal direction) of each magnet roller of Example 1 and Comparative Examples 1 and 2 was measured using a magnetic field measuring device (FWBELL's "MS-9902") with the distance between the probe, which is a component of the magnetic field measuring device, and the surface of the developing sleeve 24 being about 100 μm.

[0052] Figure 3 also shows an outline of the magnetic attraction force Fr that attracts the developer (carrier) toward the center of the developing sleeve 24. Hereinafter, the "magnetic attraction force Fr in the center direction of the developing sleeve" may be simply referred to as the "magnetic attraction force". When simply referred to as the "magnetic attraction force", it refers to the "magnetic attraction force Fr in the center direction of the developing sleeve". The magnetic attraction force Fr of the developing sleeve 24 can be derived from the magnetic flux density Br in the normal direction, and is expressed by the following formula 1.

number

[0053] In formula 1, μ is the magnetic permeability of the magnetic carrier, μ0 is the magnetic permeability of a vacuum, and b is the radius of the magnetic carrier. The magnetic flux density Bθ in the tangential direction is calculated from formula 2 below using the value of Br measured by the above method.

number

[0054] 3 also shows the regulating magnetic pole N1, as well as the pumping magnetic pole S1 on the upstream side of the regulating magnetic pole N1 in the rotation direction of the developing sleeve 24, and the transport magnetic pole S2 on the downstream side. Here, Example 1 uses the magnet roller 24m of this embodiment as the magnet roller 24m (i.e., uses a magnet roller using the regulating magnetic pole N1 consisting of two peaks).

[0055] Also, Comparative Example 1 used a magnet roller using a regulating magnetic pole N1 consisting of one peak, unlike Example 1, and Comparative Example 2 used a magnet roller using a regulating magnetic pole N1 consisting of two peaks, as in Example 1. In the regulating magnetic pole N1 consisting of two peaks, the magnetic flux density Br in the normal direction has a magnetic flux density distribution in which an upstream maximum value (upstream peak) P1, a minimum value B, and a downstream maximum value (downstream peak) P2 exist in this order from the upstream side to the downstream side in the rotation direction of the developing sleeve 24.

[0056] 3 shows the magnetic flux density Br (solid line) of the regulating pole N1 of the present embodiment as Example 1, the magnetic flux density Br (dotted line) of Comparative Example 1, and the magnetic flux density Br (dashed line) of Comparative Example 2. In addition, in FIG. 3, the magnetic attraction force Fr of each is also shown by a thick line.

[0057] The shape (distribution) of the magnetic flux density Br of the regulating pole N1 in Comparative Example 1 is one peak, whereas the shape of the magnetic flux density Br of the regulating pole N1 in Comparative Example 2 and Example 1 is two peaks. By making the magnetic flux density Br of the regulating pole N1 have a two-peak magnetic flux density distribution shape, it is possible to further expand the region in which the change in the rotation direction of the developing sleeve 24 (change in the θ direction) of the magnetic flux density distribution is gentle. Therefore, by arranging the regulating member 25 so as to face between the two peaks of the magnetic flux density Br of the regulating pole N1, the magnetic flux density is less likely to change even if the positional relationship with the regulating member 25 is shifted, and the developer amount is less likely to fluctuate, compared to the case of the magnetic flux density Br shape with one peak as in Comparative Example 1. That is, it is possible to widen the latitude of the pole position (the positional relationship between the regulating pole N1 and the regulating member 25).

[0058] On the other hand, when the magnetic attraction force Fr of Comparative Example 2 is compared with Comparative Example 1, there is a peak of the magnetic attraction force Fr on the upstream side of the regulating magnetic pole N1 that is not present in Comparative Example 1, and the magnetic attraction force Fr tends to be smaller overall on the upstream side of the regulating magnetic pole N1 in Comparative Example 1. As described above, when the magnetic attraction force Fr of the carrier increases especially on the upstream side of the regulating member 25 in the rotation direction of the developing sleeve 24, the developer is likely to be restrained and accumulated in the developer reservoir formed upstream of the regulating member 25. Therefore, there is a risk that developer deterioration will be more likely to occur due to an increase in torque.

[0059] The magnetic attraction force Fr on the upstream side of the regulating pole N1 in Comparative Example 2 is larger than that in Comparative Example 1 for the following reason. That is, the magnetic attraction force Fr that attracts the carrier toward the center direction (r direction) of the developing sleeve 24 is composed of the product of the magnitude of the magnetic flux density and its change in the r direction (partial differential) (see formula 1). The magnetic flux density distribution of the regulating pole N1 in Comparative Example 1 has a shape that gradually increases gently from the upstream side where the pumping pole S1 is located. In contrast, the magnetic flux density distribution of the regulating pole N1 in Comparative Example 2 has two peaks, and the upstream peak P1 is close to the upstream pumping pole S1, and has a shape that rapidly increases (has a steep gradient) from the pumping pole S1 to the upstream peak P1.

[0060] In regions where the magnetic flux density changes suddenly, the change in the r direction (partial differential) also tends to be large. As a result, in Comparative Example 2, which has a two-peak magnetic flux density distribution shape, the absolute value of the magnetic flux density is large, and the change in the r direction (partial differential) also tends to be large, and the magnetic attractive force Fr, which is the product of these, tends to be large. In fact, looking at Figure 3, it can be seen that the magnetic attractive force Fr is also large in areas where the change (gradient) in the θ direction of the magnetic flux density Br is large.

[0061] Next, Example 1 will be described. In Example 1, the magnetic flux density distribution of the regulating magnetic pole N1 has the same two-peak shape as Comparative Example 2, but in order to prevent the magnetic attraction force Fr from becoming large on the upstream side of the regulating magnetic pole N1 as in Comparative Example 2, the magnetic flux density distribution around the regulating magnetic pole N1 is configured to satisfy the requirements (A) to (F) as follows. Among these requirements, at least one of (C) to (F) is satisfied.

[0062] (A) The regulating member 25 is disposed between and opposite the position of the upstream peak P1 and the position of the downstream peak P2. (B) The angle between the position of the upstream peak P1 and the position of the downstream peak P2 with respect to the rotation direction of the developing sleeve 24 is equal to or greater than 20° and less than 50°. (C) The absolute value |Br| of the upstream peak P1 is smaller than the absolute value |Br| of the downstream peak P2. (D) θ1>θ2 Note that θ1 is the angle from the position where the magnetic flux density Br in the normal direction is half that of the upstream peak P1 upstream of the position of the upstream peak P1 with respect to the rotation direction of the developing sleeve 24 (rotation direction of the developer carrier) to the position of the upstream peak P1. Also, θ2 is the angle from the position where the magnetic flux density Br in the normal direction is half the value of the downstream peak P2 downstream of the position of the downstream peak P2 to the position of the downstream peak P2 with respect to the rotational direction of the developing sleeve 24. (D)´ B1 / θ1 <B2 / θ2 It should be noted that B1 is the absolute value of the upstream peak P1. Moreover, B2 is the absolute value of the downstream peak P2. (E) θ3>θ4 It should be noted that θ3 is an angle from the position of the maximum value of the magnetic flux density Br in the normal direction of the pumping magnetic pole S1 to the position of the upstream peak P1 with respect to the rotation direction of the developing sleeve 24. Also, θ4 is an angle from the position of the maximum value of the magnetic flux density Br in the normal direction of the transport magnetic pole S2 to the position of the downstream peak P2 with respect to the rotation direction of the developing sleeve 24. (F) With respect to the rotation direction of the developing sleeve 24, the angle from the position where the magnetic flux density Br in the normal direction is half that of the upstream peak P1 upstream of the upstream peak P1 to the position of the upstream peak P1 is greater than or equal to 13° and less than 50° (50°>θ1≧13°).

[0063] In addition to the above requirements, it is preferable to satisfy at least one of the following requirements. (H) The difference between the absolute value |Br| of the maximum value B, whichever of the upstream peak P1 and the downstream peak P2 has the smaller absolute value |Br| of the magnetic flux density in the normal direction, and the absolute value |Br| of the minimum value B is 10 mT or less. (I) The difference between the absolute value |Br| of the upstream peak P1 and the absolute value |Br| of the magnetic flux density of the downstream peak P2 is equal to or greater than 2 mT and equal to or less than 10 mT.

[0064] Each of the above requirements will be described in detail. As described above, in the portion where the change (gradient) of the magnetic flux density Br in the θ direction is large, the magnetic attraction force Fr is also large. In the comparative example 2, as a result of making the magnetic flux density shape of the regulating magnetic pole N1 two peaks, the change of the magnetic flux density Br in the θ direction is large on the upstream side of the regulating magnetic pole N1, and the magnetic attraction force Fr is also large. Therefore, in the embodiment 1, even if the magnetic flux density shape of the regulating magnetic pole N1 is made two peaks, the change of the magnetic flux density Br in the θ direction is not made large on the upstream side of the regulating magnetic pole N1. As a result, in the embodiment 1, the magnetic attraction force Fr is kept relatively small.

[0065] When the magnetic flux density distribution of the regulating pole N1 has a two-peak shape as in Comparative Example 2 and Example 1, the change (gradient) of the magnetic flux density Br on the upstream side of the regulating pole N1 tends to become large on the further upstream side of the upstream peak P1 of the regulating pole N1. This is because, by making it two peaks, the upstream peak P1 having a relatively high magnetic flux density Br value shifts toward the pumping pole S1 arranged upstream, so the gradient of the magnetic flux density Br tends to become large. Therefore, in Example 1, the gradient of the magnetic flux density Br on the upstream side of the upstream peak P1 of the magnetic flux density Br of the regulating pole N1 is made smaller than in Comparative Example 2.

[0066] [Regarding θ1 (requirement (F))] Here, as an index representing the gradient of the magnetic flux density Br on the upstream side of the upstream peak P1 of the magnetic flux density Br of the regulating magnetic pole N1, an angle θ1 from the upstream peak P1 position to the half-value of the magnetic flux density on the upstream side of the upstream peak P1 of the magnetic flux density Br of the regulating magnetic pole N1 is introduced. FIG. 4 shows the values ​​of Comparative Example 2, and FIG. 5 shows the values ​​of Example 1 together with the magnetic flux density distribution. The angle θ1 from the upstream peak P1 position to the half-value of the magnetic flux density Br on the upstream side of the upstream peak P1 of the magnetic flux density Br of the regulating magnetic pole N1 is 11.5° in Comparative Example 2 and 15° in Example 1. The larger this value is, the smaller the gradient of the magnetic flux density Br on the upstream side of the upstream peak P1 of the magnetic flux density Br of the regulating magnetic pole N1 becomes, and as a result, the magnetic attractive force Fr can be suppressed to a small value. In fact, as shown in FIG. 3, the magnetic attractive force Fr of Example 1 is suppressed to the same level as Comparative Example 1.

[0067] A developer deterioration test was performed in Comparative Example 1, Comparative Example 2, and Example 1. In the developing device using each magnet roller of Comparative Example 1, Comparative Example 2, and Example 1, after the image forming operation (initial image output) was performed first, only the stirring of the developer was performed for one hour, and the image forming operation (image output) was performed again under the same conditions as the first. Note that only the stirring of the developer means that the first transport screw 22 and the second transport screw 23 are driven to circulate and transport the developer in the developing container 21 while stirring it, without performing the developing operation of developing the electrostatic latent image on the photosensitive drum 81. At this time, the developing sleeve 24 is also driven. Of course, an electrostatic latent image is not formed on the photosensitive drum 81, and a developing bias is not applied. For this purpose, a jig that can be driven by the developing device alone may be created and used.

[0068] In Comparative Example 2, the density of the image formed by the image forming operation after stirring was decreased more than that of the image formed by the first image forming operation compared to Comparative Example 1. Therefore, it was found that the developer is easily deteriorated in the configuration of Comparative Example 2. On the other hand, Example 1 had a result almost equivalent to that of Comparative Example 1. From this, it can be said that although the magnetic flux density Br of the regulating magnetic pole N1 of the magnet roller 24m of Example 1 has a two-peak shape, the gradient of the magnetic flux density Br on the upstream side of the upstream peak P1 of the magnetic flux density Br of the regulating magnetic pole N1 was reduced, thereby suppressing the magnetic attraction force Fr and suppressing the deterioration of the developer.

[0069] In addition, a similar test was also performed on a magnetic roller in which the angle θ1 from the upstream peak P1 position of the magnetic flux density Br of the regulating magnetic pole N1 to the half value of the magnetic flux density Br was 13°. The result was that the developer was slightly more susceptible to deterioration than in Comparative Example 1 and Example 1, but the deterioration of the developer was suppressed compared to Comparative Example 2. Therefore, when the magnetic flux density distribution of the regulating magnetic pole N1 has a two-peak shape, by setting the angle θ1 from the upstream peak P1 position of the magnetic flux density Br of the regulating magnetic pole N1 to the half value of the magnetic flux density Br on the upstream side of the upstream peak P1 of the magnetic flux density Br of the regulating magnetic pole N1 to 13° or more (requirement (F)), more preferably 15° or more, it is possible to suppress the deterioration of the developer caused by the increase in the magnetic attractive force Fr, which is a problem when the magnetic flux density distribution has two peaks. That is, by satisfying the above-mentioned requirements (A), (B), and (F), the deterioration of the developer can be suppressed even if the magnetic flux density distribution of the regulating magnetic pole N1 has a two-peak shape. However, if the angle θ1 is 50° or more, it may be too wide and affect the degree of freedom in arranging other magnetic poles. Therefore, it is preferable to set the angle θ1 to less than 50°. In particular, when the magnet roller 24m has seven or more magnetic poles as in this embodiment, the effect is more likely to occur.

[0070] In addition, if the angle θ1 from the upstream peak P1 position to the point where the magnetic flux density Br reaches half its value is too large, the state where the absolute value of the magnetic flux density Br remains high over a wide range, which may induce a new increase in the magnetic attraction force Fr. Therefore, the angle θ1 from the upstream peak P1 position to the point where the magnetic flux density Br reaches half its value is preferably 30° or less (θ1≦30°). More preferably, it is 25° or less (θ1≦25°).

[0071] [Difference between maximum and minimum magnetic flux density (Requirement (H))] In the magnet roller 24m of this embodiment, the magnetic flux density distribution of the regulating magnetic pole N1 has a two-peak shape, and by having two peaks, even if the positional relationship between the regulating magnetic pole N1 and the regulating member 25 is shifted, the magnetic flux density Br is unlikely to change, the developer amount is unlikely to fluctuate, and the pole position latitude can be widened. Here, "the magnetic flux density distribution of the regulating magnetic pole N1 has a two-peak shape" refers to a shape in which the magnetic flux density of the regulating magnetic pole N1 has two maximum values, an upstream peak P1 and a downstream peak P2, and has a concave minimum value B between the two peaks P1 and P2, as shown in FIG. 5 (the maximum value and the minimum value here refer to the maximum value and the minimum value in absolute value). At this time, the maximum value and the minimum value associated with the measurement noise of 0.5 mT or less are ignored.

[0072] Here, if the minimum value B is too small compared to the two peaks P1 and P2, the magnetic flux density will fluctuate between the peaks P1 and P2, which may cause fluctuations in the amount of developer. Therefore, it is preferable that the difference between the peak with the smaller absolute value (maximum value) of the two peaks P1 and P2 and the minimum value B is within 10 mT (requirement (H)). It is more preferable that the difference between the peak with the larger absolute value of the two peaks P1 and P2 and the minimum value B is within 10 mT.

[0073] [Spacing between two peaks (Requirement (B))] The pole position latitude can be further increased by increasing the distance between the two peaks P1 and P2. Therefore, if the angle between the peaks P1 and P2 is at least 20° or more (requirement (B)), preferably 25° or more, and more preferably 30° or more, sufficient pole position latitude can be obtained. However, if the distance between the peaks P1 and P2 is 50° or more, it may be too wide and affect the degree of freedom of arrangement of other magnetic poles. Therefore, it is preferable that the distance between the peaks P1 and P2 is less than 50°. This effect is particularly likely to occur when the magnet roller 24m has seven or more magnetic poles as in this embodiment.

[0074] As shown in FIG. 5, the two peaks P1, P2, and the minimum value B of the regulating magnetic pole N1 of the magnet roller 24m of the first embodiment are the following values. Upstream peak P1: angle 216°, magnetic flux density 44mT, downstream peak P2: angle 250°, magnetic flux density 47mT, minimum value B: angle 230°, magnetic flux density 40mT. Therefore, in the regulating magnetic pole N1 of the magnet roller 24m of the first embodiment, the angle between the two peaks P1, P2 is 34°, the magnetic flux density difference between the upstream peak P1 and the minimum value B is 4mT, and the magnetic flux density difference between the downstream peak P2 and the minimum value B is 7mT, and the fluctuation width of the magnetic flux density Br is within 10mT in an angle range of 30° or more in the circumferential direction. Furthermore, by disposing the regulating member 25 in an area where the magnetic flux density change between the two peaks P1, P2 is suppressed, it is possible to obtain a pole position latitude.

[0075] In this embodiment, the magnetic attraction force Fr on the upstream side of the regulating member 25 is prevented from increasing by gradual change in the magnetic flux density Br on the upstream side of the upstream peak P1 of the two peaks P1 and P2 of the regulating magnetic pole N1, as described above, and developer deterioration is suppressed. If the change in the magnetic flux density Br on the upstream side of the upstream peak P1 is gradual, the following concerns arise. As can be seen by comparing Comparative Example 2 and Example 1 in FIG. 3, if the change in the magnetic flux density Br on the upstream side of the upstream peak P1 is gradual, the position of the upstream peak P1 is likely to shift downstream. If the position of the upstream peak P1 shifts downstream, the interval between the two peaks P1 and P2 becomes narrow, and there is a concern that the pole position latitude becomes narrow. Therefore, in this embodiment, the following configuration is adopted to obtain the wide interval between the two peaks P1 and P2 as described above.

[0076] [Changes in magnetic flux density upstream and downstream of the two peaks (requirements (C) and (D))] The reason why the change in the magnetic flux density Br on the upstream side of the upstream peak P1 is made gradual is that since the upstream peak P1 is located on the upstream side of the regulating member 25, there is a concern that if the magnetic attractive force Fr increases, the developer may deteriorate due to an increase in torque in the developer accumulation portion on the upstream side of the regulating member 25. On the other hand, since the vicinity of the downstream peak P2 is located on the downstream side of the regulating member 25, there is no concern of developer deterioration as in the upstream side even if the magnetic attractive force Fr increases. If the change in the magnetic flux density Br on the downstream side of the downstream peak P2 is made steep, it is possible to shift the downstream peak P2 further downstream. If the downstream peak P2 can be shifted further downstream, it is possible to widen the interval between the two peaks P1 and P2.

[0077] Therefore, in the magnet roller 24m of Example 1, the change in the magnetic flux density Br upstream of the upstream peak P1 of the regulating magnetic pole N1 is made gradual, while the change in the magnetic flux density Br downstream of the downstream peak P2 is made steep, thereby compensating for the shift of the upstream peak P1 downstream by also shifting the downstream peak P2 downstream, thereby obtaining the wide distance between the two peaks P1 and P2 as described above.

[0078] If the change in magnetic flux density Br downstream of the downstream peak P2 of the regulating pole N1 is made steeper than the change in magnetic flux density Br upstream of the upstream peak P1, a good balance can be achieved between suppressing developer deterioration and ensuring pole position latitude. Here, the change in magnetic flux density Br can be accurately expressed as a slope, (Δmagnetic flux density Br) / (Δangle). Therefore, the following can be done to make the slope of magnetic flux density Br downstream of the downstream peak P2 of the regulating pole N1 steeper than the slope of magnetic flux density Br upstream of the upstream peak P1.

[0079] First, regarding the Δ magnetic flux density Br, by increasing the Δ magnetic flux density Br, the slope of the magnetic flux density Br can be increased. If the absolute value |Br| (B2) of the magnetic flux density at the downstream peak P2 is made larger than the absolute value |Br| (B1) of the magnetic flux density at the upstream peak P1 (B1 < B2), the Δ magnetic flux density Br on the downstream side can be made larger than that on the upstream side (requirement (C)). Next, regarding the angle, by decreasing the Δ angle, the rate of change of the magnetic flux density can be increased. If the angle θ2 from the position of the downstream peak P2 until the magnetic flux density Br reaches half value on the downstream side of the downstream peak P2 is made smaller than the angle θ1 from the position of the upstream peak P1 until the magnetic flux density Br reaches half value on the upstream side of the upstream peak P1 (θ1 > θ2), the Δ angle on the downstream side can be made smaller than that on the upstream side (requirement (D)). By simultaneously satisfying the relationship between the two, it is always possible to make the change (slope) of the magnetic flux density on the downstream side of the downstream peak P2 of the regulated pole N1 steeper than the change (slope) of the magnetic flux density on the upstream side of the upstream peak P1.

[0080] As also shown in FIG. 5, Example 1 is set as follows based on the above viewpoints. First, regarding the magnetic flux density Br, as described above, the absolute value B1 of the magnetic flux density at the upstream peak P1 is 44 mT, while the absolute value B2 of the magnetic flux density at the downstream peak P1 is 47 mT, making the absolute value B2 of the magnetic flux density at the downstream peak P2 larger than the absolute value B1 of the magnetic flux density at the upstream peak P1 (B1 < B2).

[0081] Next, regarding the angle, the angle θ1 from the upstream peak P1 position to the half-value of the magnetic flux density Br on the upstream side of the upstream peak P1 is 15°, whereas the angle θ2 from the downstream peak P2 position to the half-value of the magnetic flux density Br on the downstream side of the downstream peak P2 is 12°. Therefore, the angle θ2 from the downstream peak P2 position to the half-value of the magnetic flux density Br on the downstream side of the downstream peak P2 is smaller than the angle θ1 from the upstream peak P1 position to the half-value of the magnetic flux density Br on the upstream side of the upstream peak P1 (θ1>θ2). In other words, the angle θ1 from the position where the magnetic flux density Br is half-value of the magnetic flux density Br of the upstream peak P1 on the upstream side of the upstream peak P1 to the upstream peak P1 is larger than the angle θ2 from the position where the magnetic flux density Br is half-value of the magnetic flux density Br of the downstream peak P2 on the downstream side of the downstream peak P2 to the downstream peak P2. Therefore, the relationship regarding both Δmagnetic flux density and Δangle is satisfied at the same time. As a result, in this embodiment, the wide interval between the two peaks P1 and P2 as described above is obtained.

[0082] [Difference between the magnetic flux densities of the two peaks (requirement (I))] In this embodiment, it is preferable that the absolute value B2 of the magnetic flux density of the downstream peak P2 is greater than the absolute value B1 of the magnetic flux density of the upstream peak P1 by 2 mT or more. That is, it is preferable that the difference between them is 2 mT or more. This is to prevent the magnitude relationship between the absolute value B1 of the magnetic flux density of the upstream peak P1 and the absolute value B2 of the magnetic flux density of the downstream peak P2 from being reversed depending on the component tolerance of the magnet roller. On the other hand, if it is greater than 10 mT, the fluctuation width of the magnetic flux density between the two peaks P1 and P2 becomes large, which may affect the pole position latitude, so it is preferable to keep it within 10 mT. That is, it is preferable that the difference between B1 and B2 is greater than or equal to 2 mT and less than or equal to 10 mT (requirement (I)).

[0083] Angle Range As for the angle, in this embodiment, it is more preferable that the angle θ2 from the downstream peak P2 position to the half-value of the magnetic flux density Br on the downstream side of the downstream peak P2 is smaller by 2° or more than the angle θ1 from the upstream peak P1 position to the half-value of the magnetic flux density Br on the upstream side of the upstream peak P1. That is, it is preferable that the difference between θ1 and θ2 is 2° or more. This is also to prevent the magnitude relationship from being reversed depending on the component tolerance of the magnet roller, as in the case of the absolute value |Br| of the magnetic flux density. On the other hand, if it is made smaller by 20° or more, the probability that the angle θ1 from the upstream peak P1 position to the half-value of the magnetic flux density Br will be 30° or more increases. As mentioned above, if the angle θ1 from the upstream peak P1 position to the half-value of the magnetic flux density Br is made too large, the state in which the absolute value of the magnetic flux density Br is high continues in a wide range, which may induce a new increase in the magnetic attraction force Fr. Therefore, the difference between the angle θ1 from the upstream peak P1 position to where the magnetic flux density Br reaches half its value on the upstream side of the upstream peak P1 and the angle θ2 from the downstream peak P2 position to where the magnetic flux density reaches half its value on the downstream side of the downstream peak P2 is preferably within 20°, more preferably within 15°. That is, the difference between θ1 and θ2 is preferably 2° or more and 20° or less, and further preferably 15° or less.

[0084] [Angle and magnetic flux density (requirement (D)')] Note that, as described above, instead of separately handling the absolute value of the magnetic flux density |Br| and the angle from the peak position of the magnetic flux density Br until the magnetic flux density Br becomes half value, the ratio of the absolute value of the magnetic flux density |Br| to the angle from the peak position of the magnetic flux density Br until the magnetic flux density Br becomes half value (the absolute value of the magnetic flux density |Br|) / (the angle from the peak position of the magnetic flux density Br until the magnetic flux density Br becomes half value) may be directly compared. In this case, if B1 (the absolute value of the magnetic flux density |Br| at the upstream peak P1) / θ1 (the angle from the peak P1 position until the magnetic flux density Br becomes half value on the upstream side of the upstream peak P1) can be made smaller than B2 (the absolute value of the magnetic flux density |Br| at the downstream peak P2) / θ2 (the angle from the peak P2 until the magnetic flux density Br becomes half value on the downstream side of the downstream peak P2), the upstream can have a gentle change (gradient) in the magnetic flux density, and the downstream can have a steep change (gradient) in the magnetic flux density.

[0085] That is, if B1 / θ1 < B2 / θ2 (requirement (D)') is satisfied, similar to the case where the above requirements (C) and (D) are satisfied, the change in the magnetic flux density Br on the upstream side of the upstream peak P1 of the regulating pole N1 can be made gentle, while the change in the magnetic flux density Br on the downstream side of the downstream peak P2 can be made steep. As a result, the downstream peak P2 also shifts downstream by the amount that the upstream peak P1 has shifted downstream to compensate, and the wide interval between the two peaks P1 and P2 as described above can be obtained.

[0086] When applied to Example 1, for B1 / θ1 = 44 mT / 15° = 2.93, B2 / θ2 = 47 mT / 12° = 3.91, and the above relationship is satisfied. In this embodiment, it is preferable from the viewpoints of both developer deterioration and pole position latitude with a clear contrast between the upstream and downstream that B1 / θ1 is 0.5 or more smaller than B2 / θ2.

[0087] [Relationship with the pole adjacent to the regulating pole (requirement (E))] Here, the gradient of the magnetic flux density Br of the regulating magnetic pole N1 is also greatly influenced by the relationship with the adjacent magnetic pole. In other words, it is possible to make the gradient of the magnetic flux density Br gentler or steeper by adjusting the relationship with the adjacent magnetic pole. The gradient of the magnetic flux density Br on the upstream side of the upstream peak P1 of the regulating magnetic pole N1 is greatly influenced by the relationship with the second magnetic pole (pumping magnetic pole S1 in this embodiment) arranged adjacent to the upstream side of the regulating magnetic pole N1. On the other hand, the gradient of the magnetic flux density Br on the downstream side of the downstream peak P2 of the regulating magnetic pole N1 is greatly influenced by the relationship with the third magnetic pole (transporting magnetic pole S2 in this embodiment) arranged adjacent to the downstream side of the regulating magnetic pole N1. In each case, the gradient tends to be gentler if the angle with the adjacent magnetic pole is large, and the gradient tends to be steeper if the angle with the adjacent magnetic pole is small.

[0088] Therefore, regarding the magnetic flux density Br, the absolute value B2 of the magnetic flux density of the downstream peak P2 is made larger than the absolute value B1 of the magnetic flux density of the upstream peak P1 of the regulating magnetic pole N1, and, regarding the angle, the angle θ4 from the downstream peak P2 of the regulating magnetic pole N1 to the downstream transport magnetic pole (peak) S2 is made smaller than the angle θ3 from the upstream peak P1 of the regulating magnetic pole N1 to the upstream pumping magnetic pole (peak) S1 (θ3>θ4) (requirement (E)). This makes it possible to make the change (gradient) of the magnetic flux density downstream of the downstream peak P2 of the regulating magnetic pole N1 steeper than the change (gradient) of the magnetic flux density upstream of the upstream peak P1.

[0089] As described above, in the first embodiment, the absolute value B1 of the magnetic flux density of the upstream peak P1 is 44 mT, whereas the absolute value B2 of the magnetic flux density of the downstream peak P1 is 47 mT, so that the absolute value B2 of the magnetic flux density of the downstream peak P2 is greater than the absolute value B1 of the magnetic flux density of the upstream peak P1. On the other hand, as for the angle, as shown in FIG. 5, the angle θ3 from the upstream peak P1 of the regulating pole N1 to the (peak of) the upstream pumping pole S1 is 44°, whereas the angle θ4 from the downstream peak P2 of the regulating pole N1 to the (peak of) the downstream conveying pole S2 is 38°, which is small. Therefore, the first embodiment simultaneously satisfies both relationships, and the above-mentioned effects can be obtained with such a configuration.

[0090] As mentioned above, the difference between the absolute value B1 of the magnetic flux density of the upstream peak P1 and the absolute value B2 of the magnetic flux density of the downstream peak P2 is preferably 2 mT or more and 10 mT or less. On the other hand, the difference between the angle θ3 from the upstream peak P1 of the regulating pole N1 to the (peak of) the upstream pumping pole S1 and the angle θ4 from the downstream peak P2 of the regulating pole N1 to the (peak of) the downstream conveying pole S2 is preferably 2° or more. This is also to prevent the magnitude relationship from being reversed depending on the component tolerance of the magnet roller.

[0091] The magnetic pole S2 arranged downstream of the regulating pole N1 is often a developing pole, but it is preferable that it is a transport pole as in this embodiment. This is because the developing pole is an important pole that determines the image in the developing process, and therefore has a low degree of freedom in terms of change, whereas the transport pole has a relatively high degree of freedom in terms of change. As already mentioned, the magnet roller 24m of this embodiment is made up of seven magnetic poles. Therefore, it is easy to make the magnetic pole arranged downstream of the regulating pole N1 the transport pole S2. However, this embodiment can be applied even if the magnetic pole arranged downstream of the regulating pole N1 is a developing pole.

[0092] [Layout of Regulatory Components (Requirement (A))] As for the position of the regulating member 25, as described above, the regulating member 25 is disposed so as to face between the upstream peak P1 and the downstream peak P2 of the magnetic flux density Br of the regulating magnetic pole N1 of the magnet roller 24m (requirement (A)). As a result, even if the position of the regulating member 25 is misaligned, the change in the magnetic flux density Br is gentle, so that the fluctuation in the amount of developer can be suppressed. In this embodiment, the absolute value B1 of the magnetic flux density of the upstream peak P1 is smaller than the absolute value B2 of the magnetic flux density of the downstream peak P2, so that the change is gentler upstream of the minimum value B between the two peaks P1 and P2. Therefore, it is preferable to dispose the regulating member 25 between the upstream peak P1 and the downstream peak P2 of the magnetic flux density Br of the regulating magnetic pole N1, and further upstream of the minimum value B.

[0093] 5 illustrates the position of the regulating member 25 in Example 1. In Example 1, the regulating member 25 was disposed 5° upstream of the minimum value B between the upstream peak P1 and downstream peak P2 of the magnetic flux density Br of the regulating magnetic pole N1.

[0094] Here, the line connecting the upstream end position of the tip of regulating member 25 facing developing sleeve 24 and the center of developing sleeve 24 will be referred to as the arrangement position of regulating member 25. The reason for calling it the upstream end is that it is the upstream side where regulating member 25 actually regulates the amount of developer, and therefore the arrangement of the upstream end is important.

[0095] The relationship between the position of the regulating member 25 and the magnetic flux density distribution can be measured as follows. Usually, the magnet roller 24m of the developing sleeve 24 has a shaft, the end of which has a so-called D-cut shape, and the D-cut portion is fixed to the developing device 20 by a pole determining member so as to achieve a desired magnetic pole arrangement. The distribution of magnetic flux density Br relative to the D-cut (planar angle) of the magnet roller 24m can be measured by the magnetic field measuring device described above. On the other hand, if the position of the regulating member 25 relative to the axial center of the magnet roller 24m is measured, the relationship between the position of the regulating member 25 and the magnetic flux density distribution can be known. The position of the regulating member 25 relative to the axial center of the magnet roller 24m may be measured using a measuring tool such as a protractor, but if you want to know the position accurately, you can use a general three-dimensional measuring machine (for example, Mitutoyo's three-dimensional measuring machine CRYSTA-ApexS series).

[0096] In the case of this embodiment, by having the above-mentioned configuration, it is possible to suppress developer deterioration even if the regulating magnetic pole N1 arranged closest to the regulating member 25 has a magnetic flux density distribution having two maximum values ​​(peaks). That is, among the above-mentioned requirements (A) to (F), (H), and (I), if one or more of requirements (C) to (F), (H), and (I) are satisfied in addition to requirements (A) and (B), developer deterioration can be suppressed even if the magnetic flux density distribution of the regulating magnetic pole N1 has a two-peak shape. For example, by satisfying any one of (A)+(B)+(C)+(D), (A)+(B)+(C)+(D)´, (A)+(B)+(C)+(E), (A)+(B)+(F), (A)+(B)+(C)+(I), developer deterioration can be suppressed even if the magnetic flux density distribution of the regulating magnetic pole N1 has a two-peak shape. Furthermore, by adding other requirements to each configuration, developer deterioration can be suppressed more favorably.

[0097] <Second embodiment> The second embodiment will be described using FIG. 6 with reference to FIG. 2. In the first embodiment, in addition to the requirements (A) and (B), one or more of the requirements (C) to (F), (H), and (I) are satisfied. In contrast, the present embodiment satisfies the following requirement (G). Since the other configurations and functions are similar to those of the first embodiment described above, the same reference numerals are used for similar configurations, and explanations and illustrations are omitted or simplified. The following description will focus on the points that are different from the first embodiment.

[0098] This embodiment also satisfies at least (A) to (C) of the above requirements (A) to (F), (H), and (I). In addition, it satisfies the following requirement (G). (G) With respect to the rotation direction of the developing sleeve 24, the position of the maximum value of the magnetic flux density Br in the normal direction of the pumping pole S1 as the upstream magnetic pole is located upstream of the half-value central position of the magnetic flux density Br in the normal direction of the pumping pole S1 (hereinafter referred to as the half-value central position of the pumping pole S1).

[0099] In addition to this requirement, it is preferable to satisfy at least one of (H) and (I), and further, it is acceptable to satisfy one or more of requirements (D) to (F).

[0100] Next, Example 2, which satisfies the requirements of the magnetic roller 24m of this embodiment, will be described in comparison with Comparative Example 2 (the same as Comparative Example 2 that appeared in the description of Example 1) and Comparative Example 3, as shown in Fig. 6. The image forming apparatus 1 and the developing device 20 of Example 2 are generally similar to those of Example 1.

[0101] FIG. 6 shows the magnetic flux density Br (dotted line) of the regulating pole N1 of Example 2 of this embodiment, the magnetic flux density Br (dashed line) of Comparative Example 2, and the magnetic flux density Br (solid line) of Comparative Example 3. FIG. 6 also shows the magnetic attraction force Fr of each of them with a thick line. As shown in FIG. 6, Example 2 and Comparative Example 3 have different distributions of the magnetic flux density Br of the pumping pole S1 arranged upstream of the regulating pole N1 compared to Comparative Example 2. Specifically, the magnetic flux density distribution of the pumping pole S1 has an asymmetric shape compared to Comparative Example 2, and the peak position of the magnetic flux density Br is shifted upstream. As a result, the magnetic roller 24m of Example 2 and Comparative Example 3 is expected to have a gentle change in the magnetic flux density Br on the upstream side of the regulating pole N1, and a smaller magnetic attraction force Fr. In fact, looking at the magnetic attraction force Fr shown at the same time in FIG. 6, the magnetic attraction force Fr is smaller on the upstream side of the regulating pole N1 in Example 2 and Comparative Example 3 compared to Comparative Example 2.

[0102] Regarding the asymmetry of the magnetic flux density Br in Example 2 and Comparative Example 3, the peak position (position of maximum value) of the upstream magnetic pole (pumping magnetic pole S1) arranged upstream of the regulating magnetic pole N1 is arranged upstream of the half-value central position of the upstream magnetic pole (pumping magnetic pole S1) (requirement (G)). Incidentally, it is almost 0° in Comparative Example 2. That is, in the case of Comparative Example 2, the peak position of the pumping magnetic pole S1 is almost the same position as the half-value central position. Considering the component tolerance as well, it is preferable that the peak position of the upstream magnetic pole (pumping magnetic pole S1) arranged upstream of the regulating magnetic pole N1 is arranged 2° or more upstream of the half-value central position of the upstream magnetic pole (pumping magnetic pole S1), preferably 3° or more, and more preferably 4° or more.

[0103] The magnitude of the magnetic attraction force Fr is smaller on the upstream side of the regulating magnetic pole N1 in Example 2 than in Comparative Example 3. This is because the magnetic flux density distribution of the regulating magnetic pole N1 is different between Example 2 and Comparative Example 3. That is, the regulating magnetic pole N1 has a two-peak magnetic flux density distribution in both Example 2 and Comparative Example 3. However, in Example 2, the absolute value B1 of the magnetic flux density in the normal direction of the upstream peak P1 is smaller than the absolute value B2 of the magnetic flux density in the normal direction of the downstream peak P2 (requirement (C)). In contrast, in Comparative Example 3, B1 is larger than B2.

[0104] Specifically, the absolute value |Br| of the magnetic flux density of the regulating pole N1 of the comparative example 3 is 47 mT for the upstream peak P1 and 44 mT for the downstream peak P2, with the downstream peak P2 being smaller than the upstream peak P1. On the other hand, the absolute value |Br| of the magnetic flux density of the regulating pole N1 of the embodiment 2 is 44 mT for the upstream peak P1 and 47 mT for the downstream peak P2, with the downstream peak P2 being larger than the upstream peak P1. Therefore, the magnetic flux density Br on the upstream side of the regulating pole N1 tends to change more gently in the embodiment 2. Furthermore, in the embodiment 2, the upstream magnetic pole (pumping magnetic pole S1) of the regulating pole N1 has an asymmetric shape such that the peak is shifted to the upstream side, and this makes it possible to make the magnetic flux density Br on the upstream side of the regulating pole N1 change more gently. As a result, the magnetic attraction force Fr on the upstream side of the regulating pole N1 can be made smaller than that of the comparative example 3.

[0105] Regarding the asymmetry of the magnetic flux density Br in Example 2, the peak position of the upstream magnetic pole (pumping magnetic pole S1) arranged upstream of the regulating magnetic pole N1 is arranged 2° upstream of the half-value central position of the upstream magnetic pole (pumping magnetic pole S1). In Comparative Example 3, the peak position is arranged 4° upstream of the half-value central position. Therefore, in Example 2, the amount of shift of the peak position upstream is smaller than that of Comparative Example 3. In this way, in Example 3, despite the small amount of shift of the peak position upstream, the magnitude of the magnetic attraction force Fr can be made smaller on the upstream side of the regulating magnetic pole N1 than in Comparative Example 3 by satisfying the above-mentioned requirement (C). This is because, unlike Comparative Example 3, in Example 2, the absolute value |Br| of the magnetic flux density of the regulating magnetic pole N1 can be made smaller at the upstream peak P1 than the downstream peak P2, and it is considered that an effect equal to or greater than that of Comparative Example 3 was obtained even though the asymmetry was somewhat smaller.

[0106] As described above, the peak position of the upstream magnetic pole (pumping magnetic pole S1) is preferably located 2° upstream of the half-value center position in consideration of component tolerances. Also, for the same reason as described in the first embodiment, the difference between the upstream peak P1 and the downstream peak P2 is preferably kept within the range of 2 mT to 10 mT.

[0107] In the case of this embodiment, by having the above-mentioned configuration, even if the regulating magnetic pole N1 arranged closest to the regulating member 25 has a magnetic flux density distribution having two maximum values ​​(peaks), developer deterioration can be suppressed.

[0108] <Other embodiments> In the above-described embodiments, the present invention has been described as being applied to a developing device used in a tandem-type image forming apparatus. However, the present invention can also be applied to developing devices used in other types of image forming apparatus. In addition, the image forming apparatus is not limited to being full-color, and may be monochrome or mono-color. Alternatively, by adding necessary devices, equipment, and housing structures, the present invention can be embodied in various applications such as printers, various printing machines, copiers, FAX machines, and multi-function machines.

[0109] In addition, the configuration of the developing device is not limited to the above-mentioned configuration in which the developing chamber and the stirring chamber are arranged horizontally, but may be configured such that the developing chamber and the stirring chamber are arranged vertically or inclined with respect to the horizontal direction. In addition, in Fig. 2, the developer is supplied from the developing chamber to the developing sleeve and the developer is collected from the developing sleeve in the developing chamber, but the developer may be supplied from the developing chamber to the developing sleeve and the developer is collected from the developing sleeve in the stirring chamber. [Explanation of symbols]

[0110] 20(20y, 20m, 20c, 20k)...Development device 24...Developing sleeve (developer carrier) 24m···Magnet roller (magnet) 25 Regulating member 81 (81y, 81m, 81c, 81k) - photosensitive drum (image carrier) N1 Regulating magnetic pole S1: Pumping pole (upstream pole) S2...Carrier magnetic pole (downstream magnetic pole) P1: The upstream peak of the magnetic flux density Br of the regulating magnetic pole (upstream maximum value) P2: Downstream peak of magnetic flux density Br of the regulating magnetic pole (downstream maximum value)

Claims

1. A developing container for accommodating a developer containing a toner and a carrier; a developing rotor that carries and transports the developer to a developing position; a magnet having a regulating pole, the magnet being fixedly disposed inside the developing rotor so as not to rotate; a regulating portion that regulates an amount of developer carried on the developing rotor by a magnetic force of the regulating pole, With respect to the rotation direction of the developing rotor, a minimum position where the magnetic flux density of the regulating pole in the normal direction to the outer circumferential surface of the developing rotor becomes a minimum value is downstream of a first maximum position where the magnetic flux density of the regulating pole in the normal direction to the outer circumferential surface of the developing rotor becomes a first maximum value, and is upstream of a second maximum position where the magnetic flux density of the regulating pole in the normal direction to the outer circumferential surface of the developing rotor becomes a second maximum value, an angle between the first maximum position and the second maximum position with respect to a rotation direction of the developing rotor is equal to or greater than 20° and smaller than 50°; a position where the regulating portion faces an outer circumferential surface of the developing rotary body in a rotation direction of the developing rotary body is downstream of the first maximum position and upstream of the second maximum position; An angle from the second maximum position to a position where the magnetic flux density in the normal direction to the outer circumferential surface of the developing rotor becomes half of the second maximum value on the downstream side of the second maximum position with respect to the rotation direction of the developing rotor is smaller than an angle from a position where the magnetic flux density in the normal direction to the outer circumferential surface of the developing rotor becomes half of the first maximum value on the upstream side of the first maximum position to the first maximum position. A developing device characterized by the above.

2. With respect to the rotation direction of the developing rotor, an angle from a position where a magnetic flux density in a normal direction to an outer peripheral surface of the developing rotor becomes half of the first maximum value on the upstream side of the first maximum position to the first maximum position is equal to or greater than 13° and less than 50°.

2. The developing device according to claim 1,

3. The magnet further has an upstream magnetic pole arranged adjacent to the regulating pole on the upstream side of the regulating pole with respect to the rotation direction of the developing rotor, and a downstream magnetic pole arranged adjacent to the regulating pole on the downstream side of the regulating pole with respect to the rotation direction of the developing rotor, With respect to the rotation direction of the developing rotor, an angle from the second maximum position to a position where the magnetic flux density of the downstream magnetic pole in the normal direction to the outer circumferential surface of the developing rotor becomes a maximum value is smaller than an angle from a position where the magnetic flux density of the upstream magnetic pole in the normal direction to the outer circumferential surface of the developing rotor becomes a maximum value to the first maximum position.

3. The developing device according to claim 1, wherein the developing device is a developing unit.

4. The absolute value of the first maximum value is smaller than the absolute value of the second maximum value.

4. The developing device according to claim 1, wherein the developing device is a developing unit.

5. The absolute value of the first maximum value is smaller than the absolute value of the second maximum value, The difference between the absolute value of the first maximum value and the absolute value of the first minimum value is 10 mT or less.

4. The developing device according to claim 1, wherein the developing device is a developing unit.

6. The absolute value of the first maximum value is smaller than the absolute value of the second maximum value, A difference between an absolute value of the first maximum value and an absolute value of the second maximum value is equal to or greater than 2 mT and equal to or less than 10 mT.

4. The developing device according to claim 1, wherein the developing device is a developing unit.

7. The magnet further has an upstream magnetic pole arranged adjacent to the regulating pole on the upstream side of the regulating pole with respect to the rotation direction of the developing rotor, With respect to the rotation direction of the developing rotor, a position where the magnetic flux density of the upstream magnetic pole in the normal direction to the outer circumferential surface of the developing rotor becomes a maximum value is located upstream of a half-value central position of the magnetic flux density of the upstream magnetic pole in the normal direction to the outer circumferential surface of the developing rotor.

7. The developing device according to claim 1, wherein the developing device is a developing unit.

8. With respect to the rotation direction of the developing rotor, the opposing position where the regulating portion faces the outer circumferential surface of the developing rotor is located upstream of the minimum position.

8. The developing device according to claim 1, wherein the developing device is a developing unit.

9. A developing container for accommodating a developer containing a toner and a carrier; a developing rotor that carries and transports the developer to a developing position; a magnet having a regulating pole, the magnet being fixedly disposed inside the developing rotor so as not to rotate; a regulating portion that regulates an amount of developer carried on the developing rotor by a magnetic force of the regulating pole, With respect to the rotation direction of the developing rotor, a minimum position where the magnetic flux density of the regulating pole in the normal direction to the outer circumferential surface of the developing rotor becomes a minimum value is downstream of a first maximum position where the magnetic flux density of the regulating pole in the normal direction to the outer circumferential surface of the developing rotor becomes a first maximum value, and is upstream of a second maximum position where the magnetic flux density of the regulating pole in the normal direction to the outer circumferential surface of the developing rotor becomes a second maximum value, an angle between the first maximum position and the second maximum position with respect to a rotation direction of the developing rotor is equal to or greater than 20° and smaller than 50°; a position where the regulating portion faces an outer circumferential surface of the developing rotary body in a rotation direction of the developing rotary body is downstream of the first maximum position and upstream of the second maximum position; The absolute value of the first maximum value is B1, The absolute value of the second maximum value is B2, With respect to the rotation direction of the developing rotor, an angle from a position at which the magnetic flux density in the normal direction to the outer circumferential surface of the developing rotor becomes half of the first maximum value on the upstream side of the first maximum value to the first maximum position is defined as θ1; With respect to the rotation direction of the developing rotor, when an angle from the second maximum position to a position downstream of the second maximum value where the magnetic flux density in the normal direction to the outer circumferential surface of the developing rotor is half of the second maximum value is defined as θ2, B1 / θ1 < B2 / θ2 Fulfill A developing device characterized by the above.

10. Satisfying 13°≦θ1<50° 10. The developing device according to claim 9.

11. The magnet further has an upstream magnetic pole arranged adjacent to the regulating pole on the upstream side of the regulating pole with respect to the rotation direction of the developing rotor, and a downstream magnetic pole arranged adjacent to the regulating pole on the downstream side of the regulating pole with respect to the rotation direction of the developing rotor, With respect to the rotation direction of the developing rotor, an angle from the second maximum position to a position where the magnetic flux density of the downstream magnetic pole in the normal direction to the outer circumferential surface of the developing rotor becomes a maximum value is smaller than an angle from a position where the magnetic flux density of the upstream magnetic pole in the normal direction to the outer circumferential surface of the developing rotor becomes a maximum value to the first maximum position.

11. The developing device according to claim 9 or 10.

12. The absolute value of the first maximum value is smaller than the absolute value of the second maximum value.

12. The developing device according to claim 9, wherein the developing device is a developing unit.

13. The absolute value of the first maximum value is smaller than the absolute value of the second maximum value, The difference between the absolute value of the first maximum value and the absolute value of the first minimum value is 10 mT or less.

12. The developing device according to claim 9, wherein the developing device is a developing unit.

14. The absolute value of the first maximum value is smaller than the absolute value of the second maximum value, A difference between an absolute value of the first maximum value and an absolute value of the second maximum value is equal to or greater than 2 mT and equal to or less than 10 mT.

12. The developing device according to claim 9, wherein the developing device is a developing unit.

15. The magnet further has an upstream magnetic pole arranged adjacent to the regulating pole on the upstream side of the regulating pole with respect to the rotation direction of the developing rotor, With respect to the rotation direction of the developing rotor, a position where the magnetic flux density of the upstream magnetic pole in the normal direction to the outer circumferential surface of the developing rotor becomes a maximum value is located upstream of a half-value central position of the magnetic flux density of the upstream magnetic pole in the normal direction to the outer circumferential surface of the developing rotor.

15. The developing device according to claim 9, wherein the developing device is a developing unit.

16. With respect to the rotation direction of the developing rotor, the opposing position where the regulating portion faces the outer circumferential surface of the developing rotor is located upstream of the minimum position.

16. The developing device according to claim 9, wherein the developing device is a developing unit.

17. A developing container for accommodating a developer containing a toner and a carrier; a developing rotor that carries and transports the developer to a developing position; a magnet having a regulating pole fixedly disposed inside the developing rotor so as to be non-rotatable, an upstream magnetic pole disposed adjacent to the regulating pole on the upstream side of the regulating pole in the rotation direction of the developing rotor, and a downstream magnetic pole disposed adjacent to the regulating pole on the downstream side of the regulating pole in the rotation direction of the developing rotor; a regulating portion that regulates an amount of developer carried on the developing rotor by a magnetic force of the regulating pole, a minimum position where the magnetic flux density of the regulating pole in the normal direction to the outer circumferential surface of the developing rotor becomes a minimum value with respect to the rotation direction of the developing rotor is downstream of a first maximum position where the magnetic flux density of the regulating pole in the normal direction to the outer circumferential surface of the developing rotor becomes a first maximum value, and is upstream of a second maximum position where the magnetic flux density of the regulating pole in the normal direction to the outer circumferential surface of the developing rotor becomes a second maximum value, an angle between the first maximum position and the second maximum position with respect to a rotation direction of the developing rotor is equal to or greater than 20° and smaller than 50°; a position where the regulating portion faces an outer circumferential surface of the developing rotary body in a rotation direction of the developing rotary body is downstream of the first maximum position and upstream of the second maximum position; With respect to the rotation direction of the developing rotor, an angle from the second maximum position to a position where the magnetic flux density of the downstream magnetic pole in the normal direction to the outer circumferential surface of the developing rotor becomes a maximum value is smaller than an angle from a position where the magnetic flux density of the upstream magnetic pole in the normal direction to the outer circumferential surface of the developing rotor becomes a maximum value to the first maximum position. A developing device characterized by the above.

18. The absolute value of the first maximum value is smaller than the absolute value of the second maximum value.

20. The developing device according to claim 17,

19. The absolute value of the first maximum value is smaller than the absolute value of the second maximum value, The difference between the absolute value of the first maximum value and the absolute value of the first minimum value is 10 mT or less.

20. The developing device according to claim 17,

20. The absolute value of the first maximum value is smaller than the absolute value of the second maximum value, A difference between the absolute value of the first maximum value and the absolute value of the second maximum value is equal to or greater than 2 mT and equal to or less than 10 mT.

20. The developing device according to claim 17,

21. With respect to the rotation direction of the developing rotor, a position where the magnetic flux density of the upstream magnetic pole in the normal direction to the outer circumferential surface of the developing rotor becomes a maximum value is upstream of a half-value central position of the magnetic flux density of the upstream magnetic pole in the normal direction to the outer circumferential surface of the developing rotor.

21. The developing device according to claim 17, wherein the developing device is a developing unit.

22. With respect to the rotation direction of the developing rotor, the opposing position where the regulating portion faces the outer circumferential surface of the developing rotor is located upstream of the minimum position.

22. The developing device according to claim 17, wherein the developing device is a developing unit.

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