Developing device

Abstract

To provide a configuration that can prevent a variation in the amount of a developer regulated by a regulating member 25 in a magnetic flux density distribution in which a magnetic flux density in a normal direction of a regulating magnetic pole N1 arranged most proximate to the regulating member 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. An angle between the upstream peak P1 and the downstream peak P2 is 20° or more and less than 50°. The regulating magnetic pole N1 has, between the upstream peak P1 and the downstream peak P2, a position O where a magnetic flux density Bθ in a normal direction on an outer peripheral surface of a developing sleeve becomes zero. The regulating member 25 is arranged to face between the upstream peak P1 and the position O where the magnetic flux density Bθ in the normal direction becomes zero. The position O where the magnetic flux density Bθ in the normal direction becomes zero is located within a range of ±2° from a middle point of the upstream peak P1 and the downstream peak P2 or on the downstream side of the range.SELECTED DRAWING: Figure 8

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] However, the amount of developer regulated by the regulating member is affected not only by the magnetic flux density Br in the normal direction but also by the magnetic flux density Bθ in the tangential direction. If the rotation direction of the developing sleeve (downstream direction) is taken as the positive θ-axis (tangential direction), the tangential component Bθ of the magnetic flux density generally tends to be negative upstream of the magnetic pole, and positive downstream of the magnetic pole. This is because the magnetic flux lines extend radially from the peak position of the magnetic pole, so that the magnetic flux lines extend in the upstream direction (negative direction) upstream of the magnetic pole and in the downstream direction (positive direction) downstream of the magnetic pole.

[0007] According to the study by the present inventors, it was found that when the tangential magnetic flux density Bθ at the position facing the regulating member is positive, the developer amount tends to fluctuate more when the positional relationship with the regulating member is shifted than when it is negative. Therefore, even if the magnetic flux density Br in the normal direction of the regulating magnetic pole has two maximum values ​​(peaks), there is a risk that the amount of developer regulated by the regulating member will fluctuate more when the positional relationship between the magnetic flux density distribution of the magnet roller and the regulating member is shifted in relation to the tangential magnetic flux density Bθ.

[0008] The present invention aims to provide a configuration that can suppress fluctuations in the amount of developer regulated by a regulating member in a magnetic flux density distribution in which the magnetic flux density 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]

[0009] 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 A developing rotor, a magnet having a regulating pole, which is fixedly arranged inside the developing rotor and does not rotate, andTo The magnetic force of the developing rotor The amount of developer carried on the The regulatory department, 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 The minimum position where the degree of the rotation of the developing rotor is the minimum value is of The magnetic flux density in the normal direction to the outer periphery is Large value than the first maximum position where downstream and the magnetic flux density of the regulating pole in the normal direction to the outer circumferential surface of the developing rotor is greater than that of the second pole. Large value and the distance between the first maximum position and the second maximum position with respect to the rotation direction of the developing rotor is Angle between teeth, 20° or more and less than 50°, Developing Rotary Body Regarding the direction of rotation of In front of the regulatory pole Note For the outer peripheral surface of the developing rotor Tangential magnetic flux density is zero between the first maximum position and the second maximum position, and the opposing position where the regulating portion faces the outer circumferential surface of the developing rotor with respect to the rotation direction of the developing rotor is a position where the magnetic flux density of the regulating pole in the tangential direction with respect to the outer circumferential surface of the developing rotor is The place where is zero Placement Between and a rotation direction of the developing rotor is such that the regulating pole is in contact with the outer circumferential surface of the developing rotor. Tangential magnetic flux density Degree Zero position Place it in front Note 1st local maximum position and the above 2nd local maximum position ±2° range from the midpoint of Or the Below range In the flow Characterized by Developing device .

[0010] Books The 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 a developing rotor; 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; The amount of developer carried on the The regulatory department, The method comprises the steps of: With respect to the rotation direction of the developing rotor, the regulating pole is Magnetic flux density in the normal direction Extremely Small value The minimum position where the magnetic flux density of the regulating pole in the normal direction to the outer circumferential surface of the developing rotor is the first maximum position is closer to the first maximum position. downstream and the magnetic flux density of the regulating pole in the normal direction to the outer circumferential surface of the developing rotor is greater than that of the second pole. large a second maximum position at which the value of the developing roller is reached, Regarding the direction of rotation of The first maximum position and the second maximum position Angle between teeth, 20° or more and less than 50°, Developing Rotary Body Regarding the direction of rotation 、 The above In front of the regulatory pole Note Developing Rotary Body of For outer surface Tangential magnetic flux density Degree Zero position teeth , the above between the first maximum position and the second maximum position, Regarding the direction of rotation of The position where the regulating portion faces the outer circumferential surface of the developing rotor is the first maximum position and the developing rotor of the regulating pole. of For outer surface Tangential magnetic flux density Degree Zero position Placement Between and a magnetic flux density of the upstream magnetic pole in a normal direction to an outer circumferential surface of the developing rotor. The absolute maximum value of The value is , the downstream magnetic pole With respect to the outer peripheral surface of the developing rotor Magnetic flux density in the normal direction Degree Absolute maximum Value It is smaller than the above 1st pole large Value absolute The value is , the above 2nd pole large Value absolute Value It is also characterized by being smaller than Developing device .

[0011] Books The 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 a magnet having a developing rotor, a regulating pole fixedly disposed inside the developing rotor so as to be non-rotatable, and an upstream magnetic pole disposed 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 magnetic field generated by the regulating pole is applied to the developing rotor by the magnetic force of the regulating pole; The amount of developer carried on the Regulatory Department and With respect to the rotation direction of the developing rotor, of With respect to the outer peripheral surface of the developing rotor Magnetic flux density in the normal direction The minimum position where the degree of the rotation is the minimum is the outer circumferential surface of the developing rotor of the regulating pole. To The magnetic flux density in the normal direction to the first pole Large value than the first maximum position where downstream and the magnetic flux density of the regulating pole in the normal direction to the outer circumferential surface of the developing rotor is greater than that of the second pole. large a second maximum position at which the value of the developing roller is reached, Regarding the direction of rotation of 1st local maximum position and the above The second maximum position Angle between teeth, 20° or more and less than 50°, Developing Rotary Body Regarding the direction of rotation 、 The above Regulatory pole of With respect to the outer peripheral surface of the developing rotor Tangential magnetic flux density Degree Zero position teeth , the above between the first maximum position and the second maximum position, Regarding the direction of rotation of The regulating portion faces the outer circumferential surface of the developing rotor. position is a relationship between the first maximum position and the regulating pole and the outer circumferential surface of the developing rotor. Tangential magnetic flux density Degree Zero position Placement Between and the upstream magnetic pole is disposed on the outer peripheral surface of the developing rotor. Absolute maximum value of magnetic flux density in the normal direction teeth, The above 1st pole large Value absolute Value It is also characterized by being larger than Developing device .

[0012] Books The 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 a developing rotor; 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; The amount of developer carried on the The regulatory department, The method comprises the steps of: With respect to the rotation direction of the developing rotor, the regulating pole is Magnetic flux density in the normal direction Extremely Small value The minimum position where the magnetic flux density of the regulating pole in the normal direction to the outer circumferential surface of the developing rotor is the first maximum position is closer to the first maximum position. downstream and the magnetic flux density of the regulating pole in the normal direction to the outer circumferential surface of the developing rotor is greater than that of the second pole. large a second maximum position at which the value of the developing roller is reached, Regarding the direction of rotation of The first maximum position and the second maximum position Angle between teeth, 20° or more and less than 50°, Developing Rotary Body Regarding the direction of rotation 、 The above In front of the regulatory pole Note Developing Rotary Body of For outer surface Tangential magnetic flux density Degree Zero position teeth , the above between the first maximum position and the second maximum position, Regarding the direction of rotation of The position where the regulating portion faces the outer circumferential surface of the developing rotary body is the first maximum position. and The regulating pole is disposed on the outer circumferential surface of the developing rotor. Tangential magnetic flux density Degree Zero position Placement Between and the upstream magnetic pole is disposed on the outer peripheral surface of the developing rotor. Absolute maximum value of magnetic flux density in the normal direction teeth, The downstream magnetic pole With respect to the outer circumferential surface of the developing rotor Absolute maximum value of magnetic flux density in normal direction Value It is also characterized by being larger than Developing device . Effect of the Invention

[0013] According to the present invention, in a magnetic flux density distribution in which the magnetic flux density in the normal direction of the regulating magnetic pole located closest to the regulating member has two maximum values ​​(peaks), fluctuations in the amount of developer regulated by the regulating member can be suppressed. [Brief description of the drawings]

[0014] [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 about the region where the regulating member is disposed, the magnetic flux density Br in the normal direction, and the magnetic flux density Bθ in the tangential direction according to Example 1 and Comparative Example 1; [Figure 4] 11 is a graph showing the results of measuring the amount of developer on the developing sleeve after passing through a regulating member while changing the opposing position of the regulating member for the developing sleeves according to Example 1 and Comparative Example 1. [Diagram 5] FIG. 1A is a schematic diagram showing the behavior of magnetic brushes on a developing sleeve when a regulating member is placed opposite an area where the tangential magnetic flux density Bθ of the regulating magnetic pole of the developing sleeve is negative, and FIG. 1B is a schematic diagram showing a developer flow layer near a developer reservoir. [Figure 6] FIG. 1A is a schematic diagram showing the behavior of magnetic brushes on a developing sleeve when a regulating member is placed opposite an area where the tangential magnetic flux density Bθ of the regulating magnetic pole of the developing sleeve is positive, and FIG. 1B is a schematic diagram showing a developer flow layer near a developer reservoir. [Figure 7] 11 is a graph showing the relationship between the angle of the developing sleeve in Comparative Example 1 about the region where the regulating member is disposed, and the magnetic flux density Br in the normal direction and the magnetic flux density Bθ in the tangential direction. [Figure 8] 6 is a graph showing the relationship between the angle of the developing sleeve with respect to the regulating member arrangement area as the center and the magnetic flux density Br in the normal direction and the magnetic flux density Bθ in the tangential direction in the embodiment 1. [Figure 9] 13 is a graph showing the relationship between the angle of the developing sleeve centered on the regulating member arrangement area and the magnetic flux density Br in the normal direction and the magnetic flux density Bθ in the tangential direction according to Examples 2 and 2' and Comparative Example 1 in the second embodiment. [Figure 10] 13 is a graph showing the relationship between the angle of the developing sleeve centered on the regulating member arrangement area and the magnetic flux density Br in the normal direction and the magnetic flux density Bθ in the tangential direction according to Examples 3 and 3' and Comparative Example 1 in the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] <First embodiment> The first embodiment will be described with reference to Figures 1 to 8. In this embodiment, a developing device is applied to a tandem type full-color printer as an example of an image forming apparatus.

[0016] [Image forming equipment] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] [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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] [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) These are sometimes simply referred to as the upstream peak P1 and the downstream peak P2, respectively. Furthermore, the minimum position at which minimum value B occurs may simply be referred to as minimum value B.

[0050] 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 Example 1. FIG. 3 is a diagram showing the distribution of the magnetic flux density Br in the normal direction and the magnetic flux density Bθ in the tangential direction on the developing sleeve 24 by the magnet roller 24m. Note that the magnetic flux density Br refers to the component of the magnetic flux density B in the normal direction to the developing sleeve, to be precise. 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 Example 1 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.

[0051] 3 also shows the magnetic flux density Bθ in the tangential direction on the outer circumferential surface of the developing sleeve 24. The magnetic flux density Bθ in the tangential direction is calculated from the following formula 1 using the value of the magnetic flux density Br in the normal direction measured by the above method.

number

[0052] 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).

[0053] Also, although the magnetic flux density distribution is different from that of Example 1, Comparative Example 1 used a magnet roller using a regulating magnetic pole N1 having two peaks like Example 1. In the regulating magnetic pole N1 having 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.

[0054] 3 shows the magnetic flux density Br (solid line) in the normal direction of the regulating magnetic pole N1 of this embodiment as Example 1, and the magnetic flux density Br (dashed line) in the normal direction of Comparative Example 1. In addition, in FIG. 3, the magnetic flux density Bθ in each tangential direction when the rotation direction (downstream direction) of the developing sleeve 24 is set as the positive side of the θ axis (tangential direction) is also shown by a thick line.

[0055] In both Example 1 and Comparative Example 1, the shape (distribution) of the magnetic flux density Br in the normal direction of the regulating magnetic pole N1 is two-peaked, with an upstream peak P1 being a maximum value (peak) on the upstream side of the rotation direction of the developing sleeve 24 and a downstream peak P2 being a maximum value (peak) on the downstream side, and with a minimum value between the two peaks P1 and P2. That is, the shape of the magnetic flux density Br in the normal direction of the regulating magnetic pole N1 in Example 1 and Comparative Example 1 is two-peaked. By making the magnetic flux density Br in the normal direction of the regulating magnetic pole N1 have a two-peak magnetic flux density distribution shape, it is possible to further expand the area in which the change in the rotation direction of the developing sleeve 24 of the magnetic flux density distribution (change in the θ direction) is gentle. For this reason, by arranging the regulating member 25 so as to face between the two peaks of the magnetic flux density Br of the regulating magnetic pole N1, the magnetic flux density is less likely to change and the amount of developer is less likely to fluctuate even if the positional relationship with the regulating member 25 is shifted, compared to the case of a one-peak magnetic flux density Br shape. That is, it is possible to widen the latitude of the pole position (the positional relationship between the regulating magnetic pole N1 and the regulating member 25).

[0056] However, as described above, the amount of developer regulated by the regulating member 25 is affected not only by the magnetic flux density Br in the normal direction of the magnet roller 24m but also by the magnetic flux density Bθ in the tangential direction. As shown in FIG. 3, in both Example 1 and Comparative Example 1, the magnetic flux density Bθ in the tangential direction is negative on the upstream side of the regulating magnetic pole N1, and the magnetic flux density Bθ in the tangential direction is positive on the downstream side of the regulating magnetic pole N1. That is, in the regulating magnetic pole N1 as the first magnetic pole, there is a position where the magnetic flux density Bθ in the tangential direction on the outer circumferential surface of the developing sleeve 24 is 0 (zero) between the position of the upstream peak P1 and the position of the downstream peak P2 in the rotation direction of the developing sleeve 24 (requirement (B) described later). This is because the magnetic flux lines extend radially from the magnetic pole, so that the magnetic flux lines extend in the upstream direction (negative direction) upstream of the magnetic pole and in the downstream direction (positive direction) downstream of the magnetic pole.

[0057] 4 shows the results of measuring the amount of developer on the developing sleeve 24 after passing the regulating member 25 for each of the magnet rollers of Example 1 and Comparative Example 1 while changing the opposing position of the regulating member 25 in 10° increments. The following is a common feature of Example 1 and Comparative Example 1 that can be seen from FIG. 4. That is, when the regulating member 25 faces an area where the tangential magnetic flux density Bθ is negative on the upstream side (near 200°) of the regulating magnetic pole N1, the change in the developer amount with respect to the pole position is relatively small. On the other hand, when the regulating member 25 faces an area where the tangential magnetic flux density Bθ is positive on the downstream side (near 250°) of the regulating magnetic pole N1, the change in the developer amount with respect to the pole position is relatively large.

[0058] Such a difference in behavior is considered to be due to a difference in the behavior of the developer in the developer pool formed on the upstream side of the regulating member 25. This point will be explained with reference to Figs. 5 and 6. Fig. 5 shows the state of the developer near the developer pool when the regulating member 25 is opposed to an area where the magnetic flux density Bθ in the tangential direction of the regulating magnetic pole N1 is negative. Fig. 5(a) shows the behavior of the magnetic brush on the developing sleeve 24. Fig. 5(b) shows the boundary surface between the flowing layer in which the developer is moving in the developer pool and the stationary layer in which the developer is almost stationary, as in Fig. 5, with a dotted line. Fig. 6 shows the state of the developer near the developer pool when the regulating member 25 is opposed to an area where the magnetic flux density Bθ in the tangential direction of the regulating magnetic pole N1 is positive, as in Fig. 5.

[0059] As shown in Fig. 5(a), in the region where the magnetic flux density Bθ in the tangential direction of the regulating magnetic pole N1 is negative, the magnetic flux lines extend in the upstream direction, so that the magnetic brush of the developer is formed in a state where it lies down in the upstream direction (the closer to the tip of the magnetic brush, the more it is inclined upstream). The magnetic brush that lies down in the upstream direction is transported downstream, and behaves as if it gradually stands up as it approaches the regulating member 25. Reflecting this behavior of the developer, if the regulating member 25 is disposed opposite the region where the magnetic flux density Bθ in the tangential direction of the regulating magnetic pole N1 is negative, the narrow region closer to the developing sleeve 24 than the tip of the regulating member 25 becomes the developer flow layer, as shown in Fig. 5(b).

[0060] On the other hand, as shown in FIG. 6(a), in the region where the magnetic flux density Bθ in the tangential direction of the regulating magnetic pole N1 is positive, the magnetic flux lines extend in the downstream direction, so the magnetic brush of the developer is formed in a state where it is slightly tilted in the downstream direction (the closer to the tip of the magnetic brush, the more it is tilted downstream). The magnetic brush that is tilted in the downstream direction behaves in a more tilted manner as it is transported downstream. Reflecting this behavior of the developer, if a regulating member 25 is placed opposite the region where the magnetic flux density Bθ in the tangential direction of the regulating magnetic pole N1 is positive, the wider region on the upstream side of the regulating member 25 becomes the developer flow layer, as shown in FIG. 6(b).

[0061] One of the reasons why the amount of developer after regulation varies when the positional relationship between the magnetic flux density distribution and the regulating member 25 is shifted is thought to be the fluctuation of the developer flow layer. When the regulating member 25 is opposed to the position where the tangential magnetic flux density Bθ is negative, the developer flow layer is originally narrow, as shown in FIG. 5B, so the fluctuation of the developer flow layer when the positional relationship with the regulating member 25 is shifted is likely to be small. On the other hand, when the regulating member 25 is opposed to the position where the tangential magnetic flux density Bθ is positive, the developer flow layer is wide, as shown in FIG. 6B, so the fluctuation of the developer flow layer when the positional relationship with the regulating member 25 is shifted is likely to be large. Therefore, when the tangential magnetic flux density Bθ at the position where the regulating member 25 faces is positive, the fluctuation of the developer amount when the positional relationship with the regulating member 25 is shifted is more likely to be large than when it is negative.

[0062] As shown in Figure 4, when the regulating member 25 faces the region (near 200°) where the tangential magnetic flux density Bθ of the regulating magnetic pole N1 is negative, the change in developer amount with respect to pole position is relatively smaller than when the regulating member 25 faces the region (near 250°) where the tangential magnetic flux density Bθ of the regulating magnetic pole N1 is positive. This is believed to be due to the reasons described above.

[0063] Therefore, in order to suppress fluctuations in the amount of developer due to deviations in the positional relationship between the magnetic flux density distribution and the regulating member 25, it is preferable to position the regulating member 25 opposite an area where the magnetic flux density Br in the normal direction of the regulating magnetic pole N1 changes gradually and the magnetic flux density Bθ in the tangential direction is negative.

[0064] Therefore, in this embodiment, the regulating member 25 is disposed facing between two peaks P1 and P2 of the magnetic flux density Br in the normal direction of the regulating magnetic pole N1 and in an area where the magnetic flux density Bθ in the tangential direction of the regulating magnetic pole N1 is negative. In other words, the regulating member 25 is disposed facing between the upstream peak P1 of the magnetic flux density Br in the normal direction of the regulating magnetic pole N1 and a position O downstream of the upstream peak P1 where the magnetic flux density Bθ=0 in the tangential direction of the regulating magnetic pole N1 (requirement (C) described later). This makes it possible to minimize the change in the amount of developer after regulation with respect to the pole position.

[0065] In this case, if the angle between the upstream peak P1 and the position O where the tangential magnetic flux density Bθ is 0 is narrow, it is difficult to obtain a wide pole position latitude, as will be described in detail later. Therefore, in this embodiment, the angle between the upstream peak P1 and the position O where the tangential magnetic flux density Bθ is 0 is made wide.

[0066] Specifically, the configuration satisfies the requirements (A) to (H) as follows. Of these requirements, at least one of (D)' to (H) is also satisfied.

[0067] (A) 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°. (B) In the first magnetic pole (regulating magnetic pole N1), there is a position O between the position of the upstream peak P1 and the position of the downstream peak P2 in the rotational direction of the developing sleeve 24 where the tangential magnetic flux density Bθ on the outer peripheral surface of the developing sleeve 24 becomes 0. (C) The regulating member 25 is disposed so as to face, in relation to the rotational direction of the developing sleeve 24, between the position of the upstream peak P1 and the position O where the tangential magnetic flux density Bθ becomes zero. (D) The position O where the tangential magnetic flux density Bθ becomes 0 is located within a range of ±2° from the midpoint between the positions of the upstream peak P1 and the downstream peak P2 in the rotational direction of the developing sleeve 24 or downstream of this range. (D)' Position O where the tangential magnetic flux density Bθ becomes 0 is located downstream of the midpoint between the position of the upstream peak P1 and the position of the downstream peak P2 in relation to the rotation direction of the developing sleeve 24. (E) With respect to the rotation direction of the developing sleeve 24, the angle from the position of the upstream peak P1 to the position O where the tangential magnetic flux density Bθ becomes 0 is equal to or greater than 15° and less than 50°. (F) The absolute value |Br| of the upstream peak P1 is smaller than the absolute value |Br| of the downstream peak P2. (G) The difference between the absolute value |Br| of the upstream peak P1 and the absolute value |Br| of the normal magnetic flux density at the position O where the tangential magnetic flux density Bθ becomes 0 is 10 mT or less. (H) With respect to the rotation direction of the developing sleeve 24, the absolute value |Br| of the maximum value of the magnetic flux density Br in the normal direction of the upstream magnetic pole (pumping magnetic pole S1) is smaller than the absolute value |Br| of the maximum value of the magnetic flux density Br in the normal direction of the downstream magnetic pole (transporting magnetic pole S2).

[0068] Each of the above requirements will be described in detail. Note that requirement (B) has been described above. First, in order to explain Comparative Example 1, FIG. 7 simultaneously shows the magnetic flux density Br in the normal direction and the magnetic flux density Bθ in the tangential direction of Comparative Example 1. FIG. 7 also shows the midpoint M between the upstream peak P1 and the downstream peak P2 of the magnetic flux density Br in the normal direction of the regulating magnetic pole N1 of the magnet roller of Comparative Example 1. From FIG. 7, it can be seen that the position O where the magnetic flux density Bθ in the tangential direction of the regulating magnetic pole N1 of the magnet roller of Comparative Example 1 becomes 0 is located upstream of the midpoint M. Therefore, the angle between the upstream peak P1 of the magnetic flux density Br in the normal direction and the position O where the magnetic flux density Bθ=0 in the tangential direction is narrowed to 12°.

[0069] From this, it is expected that the magnetic roller of Comparative Example 1 does not obtain a pole position latitude as wide as expected, although the magnetic flux density Br in the normal direction has a two-peak shape. In fact, when FIG. 4 is checked, the region in which the developer amount varies gently with respect to the horizontal axis in Comparative Example 1 is relatively narrow. Therefore, the latitude for the developer amount variation when the positional relationship with the regulating member 25 is shifted is relatively narrow. Therefore, in Example 1, the position O where the magnetic flux density Bθ in the tangential direction becomes 0 is positioned downstream from Comparative Example 1.

[0070] [Position O where the tangential magnetic flux density Bθ is 0 (requirements (D), (D)')] For the explanation of Example 1, FIG. 8 simultaneously shows the magnetic flux density Br in the normal direction and the magnetic flux density Bθ in the tangential direction of Example 1. FIG. 8 also simultaneously shows the midpoint M between the upstream peak P1 and the downstream peak P2 of the magnetic flux density Br in the normal direction of the regulating magnetic pole N1 of the magnet roller 24m of Example 1. From FIG. 8, it can be seen that, unlike Comparative Example 1, the position O where the magnetic flux density Bθ in the tangential direction of the regulating magnetic pole N1 of the magnet roller 24m of Example 1 becomes 0 is located downstream of the aforementioned midpoint M. Therefore, the angle between the upstream peak P1 of the magnetic flux density Br in the normal direction and the position O where the magnetic flux density Bθ=0 in the tangential direction is wider than that of Comparative Example 1.

[0071] From this, it is expected that the magnet roller 24m of Example 1 can obtain a wider pole position latitude than Comparative Example 1. In fact, when checking Fig. 4, the region in which the developer amount varies more gently along the horizontal axis is wider in Example 1 than in Comparative Example 1. Therefore, Example 1 has achieved a configuration with a wider latitude for the developer amount variation when the positional relationship with the regulating member 25 is shifted.

[0072] From the above, it is considered that an index of the pole position latitude is whether the position O where the tangential magnetic flux density Bθ of the regulating magnetic pole N1 of the magnet roller 24m becomes 0 is located upstream or downstream of the midpoint M between the upstream peak P1 and downstream peak P2 of the magnetic flux density Br in the normal direction. Figures 7 and 8 show angles of main positions and values ​​of magnetic flux density Br in the normal direction for Comparative Example 1 and Example 1.

[0073] According to Fig. 7, the position O where the tangential magnetic flux density Bθ of the regulating pole N1 of the magnet roller 24m of Comparative Example 1 becomes 0 is located 5° upstream of the midpoint M between the upstream peak P1 and downstream peak P2 of the magnetic flux density Br in the normal direction. On the other hand, according to Fig. 8, the position O where the tangential magnetic flux density Bθ of the regulating pole N1 of the magnet roller 24m of Example 1 becomes 0 is located 3° downstream of the midpoint M between the upstream peak P1 and downstream peak P2 of the magnetic flux density Br in the normal direction.

[0074] To fully obtain the effect of increasing the pole position latitude by making the magnetic flux density Br in the normal direction of the regulating magnetic pole N1 have a two-peak shape, it is desirable that the position O where the magnetic flux density Bθ in the tangential direction of the regulating magnetic pole N1 of the magnet roller 24m becomes 0 is located near (within a range of ±2°) the midpoint M between the upstream peak P1 and downstream peak P2 of the magnetic flux density Br in the normal direction or further downstream (requirement (D)). More preferably, it should be located downstream of the midpoint M (requirement (D)'). With this configuration, it is possible to fully obtain the effect of increasing the pole position latitude by making the magnetic flux density Br in the normal direction of the regulating magnetic pole N1 have a two-peak shape.

[0075] [2 Peak shape] The magnetic roller 24m targeted in this embodiment has a two-peak magnetic flux density distribution in the normal direction of the regulating magnetic pole N1. By having two peaks, the magnetic flux density Br in the normal direction is unlikely to change even if the positional relationship between the regulating magnetic pole N1 and the regulating member 25 is shifted, the developer amount is unlikely to fluctuate, and the pole position latitude can be widened. Here, "the magnetic flux density distribution in the normal direction of the regulating magnetic pole N1 has two peaks P1 and P2, as shown in Figures 7 and 8, and has a concave minimum value B between the two peaks P1 and P2 (the maximum value and minimum value here refer to the maximum value and minimum value in absolute value). At this time, the maximum value and minimum value associated with measurement noise of 0.5 mT or less are ignored.

[0076] [Difference between the upstream peak P1 and the magnetic flux density Br at position O (requirement (G))] Here, if the minimum value B is too small compared to the two peaks P1 and P2, the magnetic flux density Br in the normal direction will fluctuate between the peaks P1 and P2, which may cause fluctuations in the amount of developer. As described above, in this embodiment, the regulating member 25 is disposed in the region between the upstream peak P1 of the magnetic flux density Br in the normal direction and the position O downstream of the peak P1 where the magnetic flux density in the tangential direction Bθ=0 (requirement (C)). Therefore, it is preferable that the difference between the maximum value and the minimum value B of the upstream peak P1 of the magnetic flux density Br in the normal direction be within 10 mT.

[0077] Also, the value of the magnetic flux density Br in the normal direction at the position O where the tangential magnetic flux density Bθ=0 may be greater than the magnetic flux density Br in the normal direction of the upstream peak P1. Therefore, more preferably, the fluctuation of the magnetic flux density Br in the normal direction between the upstream peak P1 and the position O where the tangential magnetic flux density Bθ=0 is within 10 mT (requirement (G)). In the first embodiment, the difference between the maximum value and the minimum value B of the upstream peak P1 of the magnetic flux density Br in the normal direction is 2 mT. Also, the value of the magnetic flux density Br in the normal direction at the position O where the tangential magnetic flux density Bθ=0 is 45 mT, and the fluctuation of the magnetic flux density Br in the normal direction between the upstream peak P1 and the position O where the tangential magnetic flux density Bθ=0 is 5 mT. Therefore, the first embodiment satisfies the above condition.

[0078] [Spacing requirement for two peaks (A)] 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 (A)), preferably 25° or more, and more preferably 30° or more, sufficient pole position latitude can be obtained. However, if it 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°. In particular, when the magnet roller 24m has seven or more magnetic poles as in this embodiment, the effect is more likely to be felt. In Example 1, the distance is 30°, which satisfies the above condition.

[0079] [Angle from upstream peak P1 to position O (requirement (E))] In the case of this embodiment, it is more important to increase the interval between the upstream peak P1 of the magnetic flux density Br in the normal direction and the position O where the magnetic flux density Bθ=0 in the tangential direction. The angle between the upstream peak P1 and the position O where the magnetic flux density Bθ=0 in the tangential direction in the comparative example 1 is 12°, and in the embodiment 1, it is 18°. In order to obtain a sufficient pole position latitude, it is preferable that it is 15° or more (requirement (E)). However, if the angle between the upstream peak P1 and the position O where the magnetic flux density Bθ=0 in the tangential direction 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 angle between the upstream peak P1 and the position O where the magnetic flux density Bθ=0 in the tangential direction is less than 50°. In particular, when the magnet roller 24m has seven or more magnetic poles as in this embodiment, the influence is more likely to occur.

[0080] As described above, the regulating magnetic pole N1 of the magnet roller 24m of the first embodiment achieves an area where the tangential magnetic flux density Bθ>0, where the developer amount fluctuation is relatively small, between two peaks of the magnetic flux density Br in the normal direction, in an angle range of 15° or more. Also, within this range, the magnetic flux density Br in the normal direction is within 10 mT. Furthermore, by arranging the regulating member 25 in the above area, it is possible to obtain a wide pole position latitude.

[0081] [Two peak magnetic flux density (requirement (F))] Here, the reason why the position O where the tangential magnetic flux density Bθ of the regulating magnetic pole N1 of the magnet roller 24m in the first embodiment becomes 0 can be located further downstream will be described. The position O where the tangential magnetic flux density Bθ becomes 0 means a state where the magnetic flux lines extend only in the normal direction (towards infinity). Normally, the magnetic flux lines extending from the magnetic pole extend radially toward the upstream and downstream magnetic poles, but at a position where the magnetic flux density Br in the normal direction of the magnetic pole is relatively large, it is relatively less affected by the upstream and downstream magnetic poles, and the magnetic flux lines tend to extend in the normal direction (towards infinity).

[0082] According to Fig. 7, the regulating magnetic pole N1 of the magnet roller 24m of Comparative Example 1 has an upstream peak P1 of 46mT and a downstream peak P2 of 43mT in the magnetic flux density Br in the normal direction, with the upstream peak P1 having a larger absolute value. Therefore, it is considered that the position where the magnetic flux line extends in the normal direction, that is, the position O where the tangential magnetic flux density Bθ=0, is likely to shift toward the upstream peak P1 where the magnetic flux density Br has a larger value. In fact, the position O where the tangential magnetic flux density Bθ of the regulating magnetic pole N1 of the magnet roller 24m of Comparative Example 1 becomes 0 is located 5° upstream of the midpoint M between the upstream peak P1 and the downstream peak P2 of the magnetic flux density Br in the normal direction.

[0083] On the other hand, according to FIG. 8, the regulating magnetic pole N1 of the magnet roller 24m of the first embodiment has an upstream peak P1 of 42mT and a downstream peak P2 of 53mT, with the downstream peak P2 having a larger absolute value. Therefore, it is considered that the position where the magnetic flux line extends in the normal direction, that is, the position O where the tangential magnetic flux density Bθ=0 is likely to shift toward the downstream peak P2 where the magnetic flux density Br is greater. Therefore, it is preferable that the absolute value |Br| of the magnetic flux density in the normal direction of the upstream peak P1 is smaller than the absolute value |Br| of the magnetic flux density in the normal direction of the downstream peak P2 (requirement (F)). In fact, the position O where the tangential magnetic flux density Bθ of the regulating magnetic pole N1 of the magnet roller 24m of the first embodiment becomes 0 is located 3° downstream of the midpoint M between the upstream peak P1 and the downstream peak P2 of the magnetic flux density in the normal direction.

[0084] In this way, regarding the magnetic flux density Br in the normal direction, by making the absolute value |Br| of the magnetic flux density in the normal direction of the downstream peak P2 larger than the absolute value |Br| of the magnetic flux density in the normal direction of the upstream peak P1, it is possible to position the position where the magnetic flux lines extend in the normal direction further downstream. Preferably, the absolute value |Br| of the magnetic flux density in the downstream peak P2 is made 2 mT or more larger than the absolute value |Br| of the magnetic flux density in the upstream peak P1. This is to prevent the magnitude relationship between the absolute value |Br| of the magnetic flux density in the upstream peak P1 and the absolute value |Br| of the magnetic flux density in the downstream peak P2 from being reversed depending on the component tolerance of the magnet roller. To obtain a further effect, it is preferable to make it 5 mT or more, more preferably 10 mT or more.

[0085] On the other hand, if the absolute value |Br| of the magnetic flux density of the downstream peak P2 is greater than the absolute value |Br| of the magnetic flux density of the upstream peak P1 by 25 mT or more, the fluctuation range of the magnetic flux density Br between the two peaks P1 and P2 becomes large, which may affect the pole position latitude. For this reason, it is preferable to keep it within 25 mT. In other words, it is preferable that the difference between the absolute value |Br| of the magnetic flux density of the upstream peak P1 and the absolute value |Br| of the magnetic flux density of the downstream peak P2 is greater than or equal to 2 mT and less than or equal to 25 mT. At this time, as mentioned above, it is preferable that the fluctuation of the magnetic flux density Br in the normal direction between the upstream peak P1 and the position O where the tangential magnetic flux density Bθ=0 is less than 10 mT.

[0086] [Relationship with adjacent poles of the regulating pole (requirement (H))] Here, the position where the magnetic flux lines of the regulating magnetic pole N1 extend in the normal direction is also greatly affected by the relationship with the magnetic pole adjacent to the regulating magnetic pole N1. This is because if the magnetic flux density of the adjacent magnetic pole is large, the magnetic flux lines tend to extend in that direction, but conversely, if the magnetic flux density of the adjacent magnetic pole is small, the magnetic flux lines do not extend as easily in that direction, in other words, they tend to extend in the normal direction. From the above, it is considered that the position where the magnetic flux lines of the regulating magnetic pole N1 extend in the normal direction is likely to shift toward the magnetic pole with a smaller absolute value Br of magnetic flux density in the normal direction when comparing the maximum values ​​of magnetic flux density Br in the normal direction of adjacent magnetic poles upstream and downstream of the regulating magnetic pole N1.

[0087] According to FIG. 7, in the magnet roller 24m of the comparative example 1, the absolute value |Br| of the maximum value of the magnetic flux density Br in the normal direction of the pumping pole S1 located upstream of the regulating pole N1 is 44 mT. On the other hand, the absolute value |Br| of the maximum value of the magnetic flux density Br in the normal direction of the transporting pole S2 located downstream of the regulating pole N1 is 88 mT. Therefore, the absolute value |Br| of the maximum value of the magnetic flux density Br in the normal direction of the pumping pole S1 is smaller than the absolute value |Br| of the maximum value of the magnetic flux density Br in the normal direction of the transporting pole S2. In other words, the absolute value |Br| of the maximum value of the magnetic flux density Br of the transporting pole S2 is larger than that of the pumping pole S1. Therefore, the position where the magnetic flux lines of the regulating pole N1 of the comparative example 1 extend in the normal direction is likely to shift to the upstream direction where the pumping pole S1, which has a smaller absolute value Br of the magnetic flux density in the normal direction, is located.

[0088] In fact, in comparative example 1, even though there is not much difference between the two peak values ​​of the magnetic flux density Br in the normal direction of the regulating magnetic pole N1, the position O where the tangential magnetic flux density Bθ=0 is shifted relatively significantly upstream, which is thought to be due to the above-mentioned reasons.

[0089] As shown in FIG. 8, in the magnet roller 24m of the first embodiment, as in the case of the comparative example 1, the absolute value |Br| of the maximum value of the magnetic flux density Br in the normal direction of the pumping magnetic pole S1 located upstream of the regulating magnetic pole N1 is 44 mT. On the other hand, the absolute value |Br| of the maximum value of the magnetic flux density Br in the normal direction of the transporting magnetic pole S2 located downstream of the regulating magnetic pole N1 is 88 mT. Therefore, the absolute value |Br| of the maximum value of the magnetic flux density Br in the normal direction of the pumping magnetic pole S1 is smaller than the absolute value |Br| of the maximum value of the magnetic flux density Br in the normal direction of the transporting magnetic pole S2 (requirement (H)). In other words, the absolute value |Br| of the maximum value of the magnetic flux density Br of the transporting magnetic pole S2 is larger than that of the pumping magnetic pole S1. Therefore, it can be said that the position where the magnetic flux line of the regulating magnetic pole N1 of the first embodiment extends in the normal direction is easily shifted to the upstream direction where the pumping magnetic pole S1, where the absolute value Br of the magnetic flux density in the normal direction is smaller, is located.

[0090] Despite this configuration, the magnet roller 24m of the first embodiment can shift the position O where the tangential magnetic flux density Bθ=0 to the downstream side by making the absolute value |Br| of the tangential magnetic flux density of the downstream peak P2 larger than the absolute value |Br| of the tangential magnetic flux density of the upstream peak P1 (requirement (F)). That is, as in this embodiment, when the absolute value of the maximum value of the normal magnetic flux density Br is larger for the downstream magnetic pole (the conveying magnetic pole S2 in this embodiment) than for the upstream magnetic pole (the pumping magnetic pole S1 in this embodiment) of the regulating magnetic pole N1 (requirement (H)), the position where the magnetic flux line of the regulating magnetic pole N1 extends in the normal direction can be shifted to the downstream side by making the absolute value |Br| of the downstream peak P2 larger than the absolute value |Br| of the magnetic flux density of the upstream peak P1 of the regulating magnetic pole N1 (requirement (F)). In this case, in order to obtain the desired effect, it is preferable that the absolute value |Br| of the magnetic flux density of the downstream peak P2 is greater than the absolute value |Br| of the magnetic flux density of the upstream peak P1 of the regulating magnetic pole N1 by 5 mT or more, more preferably by 10 mT or more.

[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 (C))] As already mentioned, by arranging the regulating member 25 between the upstream peak P1 of the magnetic flux density Br of the regulating magnetic pole N1 of the magnet roller 24m and the position O downstream thereof where the tangential magnetic flux density Bθ=0, the fluctuation in the amount of developer can be suppressed even if the position of the regulating member 25 is shifted. That is, the regulating member 25 is arranged so as to face, with respect to the rotational direction of the developing sleeve 24, between the upstream peak P1 and the position O where the tangential magnetic flux density Bθ is 0 (requirement (C)).

[0093] 8 illustrates the arrangement position of the regulating member 25 in Example 1. In Example 1, the regulating member 25 is arranged at approximately the midpoint (224°) between the upstream peak P1 (215°) of the magnetic flux density Br of the regulating magnetic pole N1 and a position O (233°) downstream thereof where the tangential magnetic flux density Bθ=0.

[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 cross-sectional shape of the regulating member 25 may not be square. Basically, the tip position of the regulating member 25 facing the developing sleeve 24 is regarded as the facing position, and when there are multiple tips in the rotation direction, the tip on the more upstream side is regarded as the facing position. For example, in the case of the regulating member 25 having a circular cross-sectional shape, the closest position to the developing sleeve 24 is regarded as the facing position.

[0096] 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).

[0097] In the case of this embodiment, by having the above-mentioned configuration, in a magnetic flux density distribution in which the regulating magnetic pole N1 arranged closest to the regulating member 25 has two maximum values ​​(peaks), the fluctuation of the developer amount regulated by the regulating member 25 can be suppressed. That is, if the above-mentioned requirements (A) to (D) are satisfied, the fluctuation of the developer amount regulated by the regulating member 25 can be suppressed even if the magnetic flux density distribution of the regulating magnetic pole N1 has a two-peak shape. In addition, by adding at least one of the requirements (D)' to (H), the fluctuation of the developer amount regulated by the regulating member 25 can be more preferably suppressed. However, when the requirement (H) is satisfied, it is preferable to satisfy the requirement (F). Alternatively, the fluctuation of the developer amount regulated by the regulating member 25 can be suppressed by satisfying the requirements (A), (B), (C), (F), and (H).

[0098] <Second embodiment> The second embodiment will be described with reference to FIG. 2 and FIG. 9. In the first embodiment, requirements (A) to (D) are satisfied. In contrast, in this embodiment, in addition to requirements (A) to (C), requirement (I) described below is satisfied. Since other configurations and functions are similar to those of the first embodiment described above, the same reference numerals are used to designate 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.

[0099] In the present embodiment, among the above-mentioned requirements (A) to (H), at least requirements (A) to (C) are satisfied. In addition, the following requirement (I) is satisfied. It is also preferable that the following requirement (J) and the above-mentioned requirements (F) and (H) are satisfied.

[0100] (I) The absolute value |Br| of the maximum value of the magnetic flux density in the normal direction of the upstream magnetic pole (pumping magnetic pole S1) is greater than the absolute value |Br| of the upstream peak P1. (J) The difference between the absolute value |Br| of the magnetic flux density in the normal direction of the upstream magnetic pole (pumping magnetic pole S1) and the absolute value |Br| of the upstream peak P1 is 5 mT or more.

[0101] The magnetic roller 24m of the present embodiment will be described in Example 2 and Example 2' in comparison with Comparative Example 1 (which appeared in the description of Example 1) as shown in Fig. 9. The image forming apparatus 1 and developing device 20 of Examples 2 and 2' are generally similar to those of Example 1, and therefore detailed description thereof will be omitted.

[0102] Fig. 9 shows the magnetic flux density Br (solid line) in the normal direction of the regulating magnetic pole N1 of this embodiment in Example 2, the magnetic flux density Br (dotted line) in the normal direction of Example 2', and the magnetic flux density Br (dashed line) in the normal direction of Comparative Example 1. Fig. 9 also shows, by a thick line, the magnetic flux density Bθ in each tangential direction when the downstream side in the rotation direction of the developing sleeve 24 is positive.

[0103] First, Example 2 satisfies the above-mentioned requirements (A), (B), (C), and (I), and preferably satisfies requirement (J). As shown in FIG. 9, Example 2 differs from Comparative Example 1 in the distribution of magnetic flux density Br in the normal direction of the pumping magnetic pole S1 arranged upstream of the regulating magnetic pole N1. Specifically, Example 2 has a larger maximum value of the pumping magnetic pole S1 than Comparative Example 1. The maximum value of the magnetic flux density Br in the normal direction of the pumping magnetic pole S1 in Example 2 is 59 mT. That is, the absolute value |Br| of the maximum value of the magnetic flux density in the normal direction of the pumping magnetic pole S1 is larger than the absolute value |Br| of the magnetic flux density in the normal direction of the upstream peak P1 (requirement (I)).

[0104] Comparing the tangential magnetic flux density Bθ between Comparative Example 1 and Example 2, it is found that the position where the tangential magnetic flux density Bθ=0 between two peaks P1 and P2 of the magnetic flux density Br in the normal direction of the regulating magnetic pole N1 (the position where the magnetic flux lines extend in the normal direction) is shifted downstream in Example 2. The results of considering the mechanism are explained below.

[0105] As described in the first embodiment, the position where the magnetic flux lines of the regulating magnetic pole N1 extend in the normal direction is also greatly affected by the relationship with the magnetic pole adjacent to the regulating magnetic pole N1. In the magnet roller 24m of the comparative example 1, the maximum value of the upstream peak P1 of the magnetic flux density Br in the normal direction of the regulating magnetic pole N1 is 46 mT, while the maximum value of the magnetic flux density Br in the normal direction of the pumping magnetic pole S1 adjacent to the upstream of the regulating magnetic pole N1 is 44 mT, and the maximum value of the upstream peak P1 of the regulating magnetic pole N1 is larger. Therefore, the magnetic flux lines near the upstream peak P1 of the regulating magnetic pole N1 are relatively difficult to extend in the direction of the upstream pumping magnetic pole S1, and conversely, are more likely to extend in the normal direction. As a result, it is considered that the position where the magnetic flux lines of the regulating magnetic pole N1 extend in the normal direction is more likely to shift to the upstream side where the upstream peak P1 is located.

[0106] On the other hand, in the magnet roller 24m of the second embodiment, the maximum value of the upstream peak P1 of the magnetic flux density Br in the normal direction of the regulating pole N1 is 46 mT, while the maximum value of the magnetic flux density Br in the normal direction of the pumping pole S1 adjacent to the upstream of the regulating pole N1 is 59 mT, so the maximum value of the upstream peak P1 of the regulating pole N1 is smaller. Therefore, the magnetic flux lines near the upstream peak P1 of the regulating pole N1 are relatively likely to extend in the direction of the upstream pumping pole S1, and conversely, are less likely to extend in the normal direction. As a result, it is considered that the position where the magnetic flux lines of the regulating pole N1 extend in the normal direction is more likely to shift downstream to the downstream peak P2.

[0107] If the position where the magnetic flux lines of the regulating magnetic pole N1 extend in the normal direction, that is, the position where the tangential magnetic flux density Bθ = 0, shifts downstream, the negative region of the tangential magnetic flux density Bθ, where the change in the amount of developer is small, can be increased, making it possible to widen the pole position latitude.

[0108] From the above, by making the maximum value of the magnetic flux density Br in the normal direction of the pumping pole S1 adjacent to the upstream of the regulating pole N1 larger than the maximum value of the upstream peak P1 of the magnetic flux density Br in the normal direction of the regulating pole N1, the area where the tangential magnetic flux density Bθ is negative, where the change in the amount of developer is small, can be increased, and further, by placing the regulating member 25 in this area, the pole position latitude can be expanded.

[0109] If the maximum value of the magnetic flux density Br in the normal direction of the pumping magnetic pole S1 adjacent to the upstream of the regulating magnetic pole N1 is larger than the maximum value of the upstream peak P1 of the magnetic flux density Br in the normal direction of the regulating magnetic pole N1, some effect can be obtained, but it is preferable to make it at least 5 mT or more larger to obtain a sufficient effect. It is more preferable to make it 10 mT or more larger to obtain a greater effect. That is, the difference between the absolute value |Br| of the magnetic flux density in the normal direction of the pumping magnetic pole S1 and the absolute value |Br| of the magnetic flux density in the normal direction of the upstream peak P1 is preferably 5 mT or more (requirement (J)), and more preferably 10 mT or more. In Example 2, it is 13 mT larger. As a result, in Example 2, it is possible to increase the area where the tangential magnetic flux density Bθ, where the developer amount change is small, is negative compared to Comparative Example 1, and by arranging the regulating member 25 in that area, it is possible to widen the pole position latitude.

[0110] Since there is a concern that the change in Bθ will be large if the maximum value of the magnetic flux density Br in the normal direction of the pumping pole S1 adjacent to the upstream of the regulating pole N1 is made too large relative to the maximum value of the upstream peak P1 of the magnetic flux density Br in the normal direction of the regulating pole N1, it is preferable to keep it within 50 mT. In other words, it is preferable to keep the difference between the absolute value |Br| of the magnetic flux density in the normal direction of the pumping pole S1 and the absolute value |Br| of the magnetic flux density in the normal direction of the upstream peak P1 50 mT or less.

[0111] In Example 2, the maximum value (43 mT) of the downstream peak P2 of the magnetic flux density Br in the normal direction of the regulating magnetic pole N1 was smaller than the maximum value (46 mT) of the upstream peak P1, as in Comparative Example 1. That is, Example 2 does not satisfy requirement (F).

[0112] Next, in addition to the above requirements (A), (B), (C), and (I), Example 2' satisfies requirement (F). It is preferable to additionally satisfy requirement (J). In this Example 2', the maximum value of the magnetic flux density Br in the normal direction of the pumping pole S1 adjacent to the upstream of the regulating pole N1 is made larger than the maximum value of the upstream peak P1 of the magnetic flux density Br in the normal direction of the regulating pole N1 as in Example 2 (requirement (I)). At the same time, the maximum value of the downstream peak P2 is made larger than the maximum value of the upstream peak P1 of the magnetic flux density Br in the normal direction of the regulating pole N1 as in Example 1 (requirement (F)). This is a difference from Example 2.

[0113] The maximum value of the upstream peak P1 of the magnetic flux density Br in the normal direction of the regulating magnetic pole N1 in Example 2' is 42 mT, and the maximum value of the downstream peak P2 is 53 mT. Incidentally, the maximum value of the magnetic flux density Br of the pumping magnetic pole S1 in Example 2' is 59 mT, which is the same as in Example 2.

[0114] Since Example 2' adds the effects described in Example 1 to Example 2, it is expected that the position where the tangential magnetic flux density Bθ=0 between the two peaks P1 and P2 of the magnetic flux density Br in the normal direction of the regulating magnetic pole N1 (the position where the magnetic flux lines extend in the normal direction) will be shifted further downstream than in Example 2. In fact, when comparing the tangential magnetic flux density Bθ of Example 2 and Example 2' in Fig. 9, it can be seen that the position where the tangential magnetic flux density Bθ=0 between the two peaks P1 and P2 of the magnetic flux density Br in the normal direction of the regulating magnetic pole N1, that is, the position where the magnetic flux lines extend in the normal direction, is shifted further downstream in Example 2'.

[0115] In this embodiment, by having the above-described configuration, it is possible to suppress fluctuations in the amount of developer regulated by the regulating member 25 in a magnetic flux density distribution in which the regulating pole N1 located closest to the regulating member 25 has two maximum values ​​(peaks).

[0116] <Third embodiment> The third embodiment will be described with reference to FIG. 2 and FIG. 10. In the first embodiment, requirements (A) to (D) are satisfied. In contrast, in this embodiment, in addition to requirements (A) to (C), requirement (K) described below is satisfied. Since 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, and the following description will focus on the points that are different from the first embodiment.

[0117] In the present embodiment, among the above-mentioned requirements (A) to (H), at least requirements (A) to (C) are satisfied. In addition, the following requirement (K) is satisfied. It is also preferable that the following requirement (L) and the above-mentioned requirement (F) are satisfied. However, the present embodiment does not satisfy the above-mentioned requirement (H).

[0118] (K) The absolute value |Br| of the maximum value of the magnetic flux density in the normal direction of the upstream magnetic pole (pumping magnetic pole S1) is greater than the absolute value |Br| of the maximum value of the magnetic flux density in the normal direction of the downstream magnetic pole (transporting magnetic pole S2). (L) The difference between the absolute value |Br| of the magnetic flux density in the normal direction of the upstream magnetic pole (pumping magnetic pole S1) and the absolute value |Br| of the magnetic flux density in the normal direction of the downstream magnetic pole (transporting magnetic pole S2) is 5 mT or more.

[0119] The magnetic roller 24m of the present embodiment will be described in Example 3 and Example 3' in comparison with Comparative Example 1 (which appeared in the description of Example 1) as shown in Fig. 10. The image forming apparatus 1 and developing device 20 of Example 3 and Example 3' are generally similar to those of Example 1, and therefore detailed description thereof will be omitted.

[0120] Fig. 10 shows the magnetic flux density Br (solid line) in the normal direction of the regulating magnetic pole N1 of this embodiment in Example 3, the magnetic flux density Br (dotted line) in the normal direction of Example 3', and the magnetic flux density Br (dashed line) in the normal direction of Comparative Example 1. Fig. 10 also shows, by a thick line, the magnetic flux density Bθ in each tangential direction when the downstream side in the rotation direction of the developing sleeve 24 is set to the positive side of the θ axis.

[0121] First, Example 3 satisfies the above-mentioned requirements (A), (B), (C), and (K), and preferably satisfies requirement (L). As shown in Fig. 10, Example 3 differs from Comparative Example 1 in the distribution of magnetic flux density Br in the normal direction of the pumping pole S1 arranged upstream of the regulating pole N1 and the conveying pole S2 arranged downstream of the regulating pole N1.

[0122] As described in the first embodiment, the position where the magnetic flux lines of the regulating magnetic pole N1 extend in the normal direction is also greatly affected by the relationship with the magnetic pole adjacent to the regulating magnetic pole N1. As described above, it is considered that the position where the magnetic flux lines of the regulating magnetic pole N1 extend in the normal direction (towards infinity) is likely to shift toward a magnetic pole with a smaller absolute value Br of magnetic flux density in the normal direction when comparing the maximum values ​​of magnetic flux density Br in the normal direction of the magnetic poles upstream and downstream of the regulating magnetic pole N1.

[0123] The magnet roller 24m of the comparative example 1 has a maximum magnetic flux density Br (44 mT) in the normal direction of the pumping magnetic pole S1 located upstream of the regulating magnetic pole N1, and the maximum magnetic flux density Br in the normal direction of the conveying magnetic pole S2 located downstream of the regulating magnetic pole N1 is smaller than the maximum magnetic flux density Br (44 mT) in the normal direction of the pumping magnetic pole S1 located upstream of the regulating magnetic pole N1. Magnetic flux The maximum value of the density Br (88 mT) is larger. Therefore, the position where the magnetic flux lines of the regulating magnetic pole N1 of Comparative Example 1 extend in the normal direction is likely to shift upstream to the pumping magnetic pole S1 where the absolute value of the magnetic flux density Br in the normal direction is smaller. In fact, in Comparative Example 1, the position O where the tangential magnetic flux density Bθ=0 is shifted relatively far upstream.

[0124] On the other hand, as shown in Fig. 10, the magnet roller 24m of the third embodiment is different from the comparative example 1 in that the maximum value (46 mT) of the magnetic flux density Br in the normal direction of the transport magnetic pole S2 located downstream of the regulating magnetic pole N1 is smaller than the maximum value (59 mT) of the magnetic flux density Br in the normal direction of the pumping magnetic pole S1 located upstream of the regulating magnetic pole N1. (Requirement (K)) Therefore, the position where the magnetic flux lines of the regulating magnetic pole N1 of the third embodiment extend in the normal direction is likely to shift downstream to the transport magnetic pole S2 where the absolute value of the magnetic flux density Br in the normal direction is smaller. In fact, as shown in Fig. 10, the position O where the tangential magnetic flux density Bθ = 0 is achieved in the third embodiment is significantly shifted downstream compared to the comparative example 1.

[0125] From the above, by making the maximum value of the magnetic flux density Br in the normal direction of the magnetic pole (in this embodiment, the transport magnetic pole S2) adjacent to the regulating pole N1 downstream smaller than the maximum value of the magnetic flux density Br in the normal direction of the magnetic pole (in this embodiment, the pumping magnetic pole S1) adjacent to the regulating pole N1 upstream, the area where the tangential magnetic flux density Bθ is negative, where the change in the developer amount is small, can be increased, and further, by placing the regulating member 25 in this area, the pole position latitude can be widened.

[0126] Although some effect can be obtained by making the maximum value of magnetic flux density Br in the normal direction of the magnetic pole (the conveying magnetic pole S2 in this embodiment) adjacent to the downstream of the regulating magnetic pole smaller than the maximum value of magnetic flux density Br in the normal direction of the magnetic pole (the pumping magnetic pole S1 in this embodiment) adjacent to the upstream side of the regulating magnetic pole N1, it is preferable to make it at least 5 mT smaller to obtain a sufficient effect (requirement (L)). To obtain a greater effect, it is more preferable to make it 10 mT smaller.

[0127] Next, in Example 3', in addition to the above requirements (A), (B), (C), and (K), requirement (F) is satisfied. In addition, it is preferable to satisfy requirement (L). FIG. 10 also shows the magnet roller 24m of Example 3'. In Example 3', the maximum value of the magnetic flux density Br in the normal direction of the magnetic pole (the conveying magnetic pole S2 in this embodiment) adjacent to the regulating magnetic pole N1 downstream is smaller than the maximum value of the magnetic flux density Br in the normal direction of the magnetic pole (the pumping magnetic pole S1 in this embodiment) adjacent to the regulating magnetic pole N1 upstream as in Example 3 (requirement (K)). At the same time, the absolute value |Br| of the magnetic flux density in the normal direction of the regulating magnetic pole N1 is set to be larger at the downstream peak P2 than at the upstream peak P1 as in Example 1 (requirement (F)). The maximum value of the upstream peak P1 of the magnetic flux density Br in the normal direction of the regulating magnetic pole N1 in Example 3' is 42 mT, and the maximum value of the downstream peak P2 is 53 mT.

[0128] In this embodiment, by having the above-described configuration, it is possible to suppress fluctuations in the amount of developer regulated by the regulating member 25 in a magnetic flux density distribution in which the regulating pole N1 located closest to the regulating member 25 has two maximum values ​​(peaks).

[0129] <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.

[0130] 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]

[0131] 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 a magnetic flux density of the regulating pole in a tangential direction to an outer circumferential surface of the developing rotor becomes zero with respect to a rotation direction of the developing rotor is between the first maximum position and the second maximum position; a position where the regulating portion faces the outer circumferential surface of the developing rotary body with respect to a rotation direction of the developing rotary body is between the first maximum position and a position where a magnetic flux density of the regulating pole in a tangential direction with respect to the outer circumferential surface of the developing rotary body becomes zero; With respect to the rotation direction of the developing rotor, a position where the magnetic flux density of the regulating pole in a tangential direction to the outer circumferential surface of the developing rotor becomes zero is within a range of ±2° with respect to a midpoint between the first maximum position and the second maximum position or is downstream of the range. A developing device characterized by the above.

2. With respect to the rotation direction of the developing rotor, a position where the magnetic flux density of the regulating pole in the tangential direction with respect to the outer circumferential surface of the developing rotor becomes zero is downstream of the midpoint between the first maximum position and the second maximum position.

2. The developing device according to claim 1,

3. With respect to the rotation direction of the developing rotor, an angle from the first maximum position to a position where the magnetic flux density in the tangential direction of the regulating pole with respect to the outer circumferential surface of the developing rotor becomes zero is equal to or greater than 15° and less than 50°.

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

4. A difference between an absolute value of the first maximum value and an absolute value of a magnetic flux density in a normal direction to the outer circumferential surface of the developing rotor at a position where a magnetic flux density in a tangential direction of the regulating pole to the outer circumferential surface of the developing rotor is zero is 10 mT or less.

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.

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

6. the magnet further includes an upstream magnetic pole disposed 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 disposed 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, the absolute value of the maximum value of the magnetic flux density of the upstream magnetic pole in the normal direction to the outer circumferential surface of the developing rotor is smaller than the absolute value of the maximum value of the magnetic flux density of the downstream magnetic pole in the normal direction to the outer circumferential surface of the developing rotor.

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

7. 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 rotary body 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 a magnetic flux density of the regulating pole in a tangential direction to an outer circumferential surface of the developing rotor becomes zero with respect to a rotation direction of the developing rotor is between the first maximum position and the second maximum position; a position where the regulating portion faces the outer circumferential surface of the developing rotary body with respect to a rotation direction of the developing rotary body is between the first maximum position and a position where a magnetic flux density of the regulating pole in a tangential direction with respect to the outer circumferential surface of the developing rotary body becomes zero; an absolute value of a maximum value of the magnetic flux density of the upstream magnetic pole in a normal direction to the outer circumferential surface of the developing rotor is smaller than an absolute value of a maximum value of the magnetic flux density of the downstream magnetic pole in a normal direction to the outer circumferential surface of the developing rotor; The absolute value of the first maximum value is smaller than the absolute value of the second maximum value. A developing device characterized by the above.

8. 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, and an upstream magnetic pole disposed adjacent to the regulating pole on the upstream side of the regulating pole with respect to 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, 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 a magnetic flux density of the regulating pole in a tangential direction to an outer circumferential surface of the developing rotor becomes zero with respect to a rotation direction of the developing rotor is between the first maximum position and the second maximum position; a position where the regulating portion faces the outer circumferential surface of the developing rotary body with respect to a rotation direction of the developing rotary body is between the first maximum position and a position where a magnetic flux density of the regulating pole in a tangential direction with respect to the outer circumferential surface of the developing rotary body becomes zero; The absolute value of the maximum value of the magnetic flux density of the upstream magnetic pole in the normal direction to the outer circumferential surface of the developing rotor is greater than the absolute value of the first maximum value. A developing device characterized by the above.

9. A difference between an absolute value of a maximum value of the magnetic flux density of the upstream magnetic pole in a normal direction to an outer circumferential surface of the developing rotor and an absolute value of the first maximum value is 5 mT or more.

9. The developing device according to claim 8.

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

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

11. the magnet further includes a downstream magnetic pole disposed adjacent to the regulating pole on the downstream side of the regulating pole with respect to a rotation direction of the developing rotor, The absolute value of the maximum value of the magnetic flux density of the upstream magnetic pole in the normal direction to the outer circumferential surface of the developing rotor is smaller than the absolute value of the maximum value of the magnetic flux density of the downstream magnetic pole in the normal direction to the outer circumferential surface of the developing rotor. The developing device according to claim 10 .

12. 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 rotary body 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 a magnetic flux density of the regulating pole in a tangential direction to an outer circumferential surface of the developing rotor becomes zero with respect to a rotation direction of the developing rotor is between the first maximum position and the second maximum position; a position where the regulating portion faces the outer circumferential surface of the developing rotary body with respect to a rotation direction of the developing rotary body is between the first maximum position and a position where a magnetic flux density of the regulating pole in a tangential direction with respect to the outer circumferential surface of the developing rotary body becomes zero; The absolute value of the maximum value of the magnetic flux density of the upstream magnetic pole in the normal direction to the outer circumferential surface of the developing rotor is greater than the absolute value of the maximum value of the magnetic flux density of the downstream magnetic pole in the normal direction to the outer circumferential surface of the developing rotor. A developing device characterized by the above.

13. A difference between an absolute value of a magnetic flux density of the upstream magnetic pole in a normal direction to the outer circumferential surface of the developing rotor and an absolute value of a magnetic flux density of the downstream magnetic pole in a normal direction to the outer circumferential surface of the developing rotor is 5 mT or more. The developing device according to claim 12 .

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

14. The developing device according to claim 12 or 13.

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