Development device

Abstract

The present application relates to a developing device. With respect to the rotation direction of a rotatable developing member of the developing device, a relative position of a regulating portion of the developing device relative to an outer peripheral surface of the rotatable developing member is between a first maximum position and a position where a tangential magnetic flux density of a regulating pole relative to the outer peripheral surface of the rotatable developing member is zero. With respect to the rotation direction of the rotatable developing member, the position where a tangential magnetic flux density of a regulating pole relative to the outer peripheral surface of the rotatable developing member is zero is within a range of ±2° of a midpoint between the first maximum position and a second maximum position, or downstream of the range.

Description

Technical Field

[0001] The present invention relates to a developing device used in an image forming apparatus such as a copying machine, a printer, a facsimile machine, and a multifunctional machine having multiple functions of these machines. Background Art

[0002] Among the developing devices, a conventionally known developing device uses a two-component developer (hereinafter, the two-component developer is referred to as the developer) containing a colorant (including non-magnetic particles) and a carrier (including magnetic particles). In this developing device, the developer is carried on the surface of a developing sleeve (developer carrying member) having a built-in magnetic roller, and the developer is fed by the rotation of the developing sleeve. The developer amount (layer thickness) of the developer is regulated by a regulating member arranged close to the developing sleeve, and then the developer is fed to a developing area opposite to a photosensitive drum (image carrying member). Then, the colorant in the developer is used to develop the electrostatic latent image formed on the photosensitive drum.

[0003] In the case of such a structure, when the positional relationship between the magnetic flux density distribution of the magnetic roller and the regulating member deviates, the amount of developer regulated by the regulating member and fed to the developing section changes. In US Patent Publication US2017 / 0235248, a structure is disclosed in which the magnetic flux density distribution is formed so that the normal magnetic flux density Br of the regulating pole opposite to the regulating member among the plurality of magnetic poles of the magnetic roller has two maximum values ​​(peak values), and the regulating member is arranged opposite to a position between the two positions.

[0004] In the structure disclosed in US2017 / 0235248, the magnetic flux density distribution of the normal magnetic flux density Br of the control pole includes two maximum values ​​(peak values), so that the magnetic flux density distribution can be made gentle with respect to the rotation direction (θ direction) of the developing sleeve. Therefore, even when the positional relationship between the magnetic flux density distribution of the magnetic roller and the control member deviates, the fluctuation of the amount of the developer (developer coating) controlled by the control member and fed to the developing section can be suppressed.

[0005] However, the developer amount regulated by the regulating member is affected not only by the normal magnetic flux density Br, but also by the tangential magnetic flux density Bθ. Here, when the developing sleeve rotation direction (downstream direction) is the positive direction of the θ axis (tangential direction), the tangential component of the magnetic flux density Bθ on the upstream side of the magnetic pole is usually easy to become negative, and the tangential component of the magnetic flux density Bθ on the downstream side of the magnetic pole is easy to become positive. This is because: the magnetic flux lines extend radially from the peak position of the magnetic pole, so the magnetic flux lines extend in the upstream direction (negative direction) on the upstream side of the magnetic pole and extend in the downstream direction (positive direction) on the downstream side of the magnetic pole.

[0006] According to the research of the present inventors, it was found that when the tangential magnetic flux density Bθ at the position where the regulating member and the regulating magnetic pole are opposite is positive, the fluctuation of the developer amount is likely to become larger when the positional relationship with respect to the regulating member deviates, compared with the case where the tangential magnetic flux density Bθ is negative. Therefore, even in the magnetic flux density distribution in which the normal magnetic flux density Br of the regulating magnetic pole has two maximum values ​​(peaks), in relation to the tangential magnetic flux density Bθ, when the positional relationship between the magnetic flux density distribution of the magnetic roller and the regulating member deviates, the fluctuation of the developer amount regulated by the regulating member may become larger. Summary of the invention

[0007] A main object of the present invention is to provide a developing device capable of stabilizing the developer coating amount in a structure in which the normal magnetic flux density of the regulating magnetic pole has two maximum values.

[0008] According to one aspect of the present invention, there is provided a developing device, comprising:

[0009] a developing container configured to contain a developer including a toner and a carrier;

[0010] a rotatable developing member configured to carry a developer and feed the developer to a developing position;

[0011] a magnet non-rotatably and fixedly disposed within the rotatable developing member and having a regulated pole; and

[0012] a regulating portion configured to regulate the amount of the developer carried on the rotatable developing member by the magnetic force of the regulating pole;

[0013] wherein, with respect to the rotation direction of the rotatable developing member, a minimum position at which the normal magnetic flux density of the control pole relative to the outer peripheral surface of the rotatable developing member is a minimum value is located downstream of a first maximum position at which the normal magnetic flux density of the control pole relative to the outer peripheral surface of the rotatable developing member is a first maximum value, and is located upstream of a second maximum position at which the normal magnetic flux density of the control pole relative to the outer peripheral surface of the rotatable developing member is a second maximum value;

[0014] wherein an angle between the first maximum position and the second maximum position is greater than 20° and less than 50° relative to a rotation direction of the rotatable developing member;

[0015] wherein, relative to the rotation direction of the rotatable developing member, the position at which the tangential magnetic flux density of the pipe pole relative to the outer peripheral surface of the rotatable developing member is zero is between the first maximum position and the second maximum position;

[0016] wherein, relative to the rotation direction of the rotatable developing member, the relative position of the regulating portion relative to the outer peripheral surface of the rotatable developing member is between a first maximum position and a position where the tangential magnetic flux density of the regulating pole relative to the outer peripheral surface of the rotatable developing member is zero; and

[0017] Wherein, relative to the rotation direction of the rotatable developing member, the position where the tangential magnetic flux density of the control pole relative to the outer peripheral surface of the rotatable developing member is zero is within the range of ±2° of the midpoint between the first maximum position and the second maximum position, or downstream of this range.

[0018] According to another aspect of the present invention, there is provided a developing device, comprising:

[0019] a developing container configured to contain a developer including a toner and a carrier;

[0020] a rotatable developing member configured to carry a developer and feed the developer to a developing position;

[0021] a magnet non-rotatably and fixedly disposed in the rotatable developing member and having a control pole, an upstream magnetic pole disposed adjacent to the control pole on the upstream side of the control pole relative to the rotation direction of the rotatable developing member, and a downstream magnetic pole disposed adjacent to the control pole on the downstream side of the control pole relative to the rotation direction of the rotatable developing member; and

[0022] a regulating portion configured to regulate the amount of the developer carried on the rotatable developing member by the magnetic force of the regulating pole;

[0023] wherein, with respect to the rotation direction of the rotatable developing member, the minimum position at which the normal magnetic flux density of the control pole relative to the outer peripheral surface of the rotatable developing member is the minimum value is located downstream of the first maximum position at which the normal magnetic flux density of the control pole relative to the outer peripheral surface of the rotatable developing member is the first maximum value, and is located upstream of the second maximum position at which the normal magnetic flux density of the control pole relative to the outer peripheral surface of the rotatable developing member is the second maximum value;

[0024] wherein an angle between the first maximum position and the second maximum position is greater than 20° and less than 50° relative to a rotation direction of the rotatable developing member;

[0025] wherein, relative to the rotation direction of the rotatable developing member, the position at which the tangential magnetic flux density of the pipe pole relative to the outer peripheral surface of the rotatable developing member is zero is between the first maximum position and the second maximum position;

[0026] wherein, relative to the rotation direction of the rotatable developing member, the relative position of the regulating portion relative to the outer peripheral surface of the rotatable developing member is between a first maximum position and a position where the tangential magnetic flux density of the regulating pole relative to the outer peripheral surface of the rotatable developing member is zero;

[0027] wherein, with respect to the rotation direction of the rotatable developing member, an absolute value of a maximum value of a normal magnetic flux density of a magnetic pole on an upstream side relative to an outer peripheral surface of the rotatable developing member is smaller than an absolute value of a maximum value of a normal magnetic flux density of a magnetic pole on a downstream side relative to the outer peripheral surface of the rotatable developing member; and

[0028] The absolute value of the first maximum value is smaller than the absolute value of the second maximum value.

[0029] According to another aspect of the present invention, there is provided a developing device, comprising:

[0030] a developing container configured to contain a developer including a toner and a carrier;

[0031] a rotatable developing member configured to carry a developer and feed the developer to a developing position;

[0032] a magnet non-rotatably and fixedly disposed in the rotatable developing member and having a regulating pole and an upstream side magnetic pole disposed adjacent to the regulating pole on an upstream side of the regulating pole with respect to the rotation direction of the rotatable developing member; and

[0033] a regulating portion configured to regulate the amount of developer carried on the rotatable developing member by the magnetic force of the regulating pole,

[0034] wherein, with respect to the rotation direction of the rotatable developing member, the minimum position at which the normal magnetic flux density of the control pole relative to the outer peripheral surface of the rotatable developing member is the minimum value is located downstream of the first maximum position at which the normal magnetic flux density of the control pole relative to the outer peripheral surface of the rotatable developing member is the first maximum value, and is located upstream of the second maximum position at which the normal magnetic flux density of the control pole relative to the outer peripheral surface of the rotatable developing member is the second maximum value;

[0035] wherein an angle between the first maximum position and the second maximum position is greater than 20° and less than 50° relative to a rotation direction of the rotatable developing member;

[0036] wherein, relative to the rotation direction of the rotatable developing member, the position at which the tangential magnetic flux density of the pipe pole relative to the outer peripheral surface of the rotatable developing member is zero is between the first maximum position and the second maximum position;

[0037] wherein, relative to the rotation direction of the rotatable developing member, the relative position of the regulating portion relative to the outer peripheral surface of the rotatable developing member is between a first maximum position and a position where the tangential magnetic flux density of the regulating pole relative to the outer peripheral surface of the rotatable developing member is zero; and

[0038] Here, an absolute value of a maximum value of the normal magnetic flux density of the upstream magnetic pole relative to the outer peripheral surface of the rotatable developing member is greater than an absolute value of the first maximum value.

[0039] According to another aspect of the present invention, there is provided a developing device, comprising:

[0040] a developing container configured to contain a developer including a toner and a carrier;

[0041] a rotatable developing member configured to carry a developer and feed the developer to a developing position;

[0042] a magnet non-rotatably and fixedly disposed in the rotatable developing member and having a control pole, an upstream magnetic pole disposed adjacent to the control pole on the upstream side of the control pole relative to the rotation direction of the rotatable developing member, and a downstream magnetic pole disposed adjacent to the control pole on the downstream side of the control pole relative to the rotation direction of the rotatable developing member; and

[0043] a regulating portion configured to regulate the amount of developer carried on the rotatable developing member by the magnetic force of the regulating pole,

[0044] wherein, with respect to the rotation direction of the rotatable developing member, the minimum position at which the normal magnetic flux density of the control pole relative to the outer peripheral surface of the rotatable developing member is the minimum value is located downstream of the first maximum position at which the normal magnetic flux density of the control pole relative to the outer peripheral surface of the rotatable developing member is the first maximum value, and is located upstream of the second maximum position at which the normal magnetic flux density of the control pole relative to the outer peripheral surface of the rotatable developing member is the second maximum value;

[0045] wherein an angle between the first maximum position and the second maximum position is greater than 20° and less than 50° relative to a rotation direction of the rotatable developing member;

[0046] wherein, relative to the rotation direction of the rotatable developing member, the position at which the tangential magnetic flux density of the pipe pole relative to the outer peripheral surface of the rotatable developing member is zero is between the first maximum position and the second maximum position;

[0047] wherein, relative to the rotation direction of the rotatable developing member, the relative position of the regulating portion relative to the outer peripheral surface of the rotatable developing member is between a first maximum position and a position where the tangential magnetic flux density of the regulating pole relative to the outer peripheral surface of the rotatable developing member is zero; and

[0048] Among them, relative to the rotation direction of the rotatable developing member, the absolute value of the maximum normal magnetic flux density of the upstream magnetic pole relative to the outer peripheral surface of the rotatable developing member is greater than the absolute value of the maximum normal magnetic flux density of the downstream magnetic pole relative to the outer peripheral surface of the rotatable developing member.

[0049] Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1is a schematic structural sectional view of the image forming apparatus according to the first embodiment.

[0051] Figure 2 is a schematic structural sectional view of the developing device according to the first embodiment.

[0052] Figure 3 : is a graph showing the relationship among the developing sleeve angle centered on the regulating member arrangement region, the normal magnetic flux density Br, and the tangential magnetic flux density Bθ according to each of Embodiment 1 and Comparative Example 1.

[0053] Figure 4 is a graph showing, for the developing sleeve according to each of Embodiment 1 and Comparative Example 1, a result of measuring the amount of the developer on the developing sleeve after passing through the regulating member while changing the relative position of the regulating member.

[0054] Figure 5 (a) and (b) are schematic diagrams showing a situation where the regulating member is arranged opposite to a region where the tangential magnetic flux density Bθ of the regulating magnetic pole of the developing sleeve is negative, wherein (a) shows the behavior of the magnetic flux on the developing sleeve, and (b) shows the developer flow layer near the retained developer.

[0055] Figure 6 (a) and (b) are schematic diagrams showing a situation where the regulating member is arranged opposite to a region where the tangential magnetic flux density Bθ of the regulating magnetic pole of the developing sleeve is positive, wherein (a) shows the behavior of the magnetic flux on the developing sleeve, and (b) shows the developer flow layer near the retained developer.

[0056] Figure 7 is a graph showing the relationship among the developing sleeve angle centered on the regulating member arrangement region according to Comparative Example 1, the normal magnetic flux density Br, and the tangential magnetic flux density Bθ.

[0057] Figure 8 Graph showing the relationship among the developing sleeve angle, the normal magnetic flux density Br, and the tangential magnetic flux density Bθ centered on the regulating member arrangement region according to Embodiment 1. FIG.

[0058] Fig. 9 is a graph showing the relationship among the developing sleeve angle centered on the regulating member arrangement region, the normal magnetic flux density Br, and the tangential magnetic flux density Bθ according to each of Embodiments 2 and 2′ and Comparative Example 1 in the second embodiment.

[0059] Fig.10 is a graph showing the relationship among the developing sleeve angle centered on the regulating member arrangement region, the normal magnetic flux density Br, and the tangential magnetic flux density Bθ according to each of Embodiments 3 and 3′ and Comparative Example 1 in the third embodiment. DETAILED DESCRIPTION

[0060] <First Embodiment>

[0061] Will use Figures 1 to 8 Description of the First Embodiment Incidentally, in this embodiment, description is given of the case where the developing device is applied to a tandem full-color printer as an example of an image forming apparatus.

[0062] [Imaging equipment]

[0063] First, we will use Figure 1 A schematic structure of the imaging apparatus 1 is described.

[0064] In the present embodiment, the image forming apparatus 1 is of a type in which an intermediate transfer belt 44b is provided, and the toner images of the respective colors are primarily transferred from the photosensitive drums 81y to 81k onto the intermediate transfer belt 44b, and then the composite toner images of the respective colors are secondarily transferred from the intermediate transfer belt 44b onto the sheet S. However, the image forming apparatus is not limited thereto, but may also adopt a type in which the toner images are directly transferred from the photosensitive drums onto the sheet fed by the sheet feeding belt.

[0065] In addition, in this embodiment, a two-component developer is used as a developer, which is a mixture of a non-magnetic toner and a magnetic carrier. The toner is formed by pulverizing or polymerizing a resin material (such as polyester or styrene) containing a colorant, a wax component, etc. The carrier is formed by resin coating the surface layer of a core composed of a mixture of resin particles and ferrite particles or magnetic powder.

[0066] like Figure 1 As shown, the image forming apparatus 1 includes an image forming apparatus main body (hereinafter referred to as the apparatus main body) 10 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 feeding (conveying) section 50, a sheet discharging section 60, and a controller 70. A toner image is to be formed on a sheet S as a recording material, and specific examples of the sheet S may include ordinary paper, a resin material sheet as an alternative to ordinary paper, thick paper, a sheet for a projector, and the like.

[0067] The image reading section 11 is provided at the upper part of the apparatus body 10. The image reading section 11 includes components such as a platen glass not shown as a document mounting table, a light source not shown for irradiating the document placed on the platen glass with light, and an image sensor not shown for converting reflected light into a digital signal.

[0068] The sheet feeding section 30 is provided at the lower portion of the apparatus body 10 , includes sheet cassettes 31 a and 31 b for stacking and accommodating sheets S such as recording paper, includes feed rollers 32 a and 32 b , and feeds the accommodated sheets S to the image forming section 40 .

[0069] 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 can form an image on a sheet S based on image information.

[0070] Incidentally, the imaging device 1 in this embodiment satisfies full-color imaging, and the imaging units 80y, 80m, 80c, and 80k have similar structures to be used for the four colors of yellow (y), magenta (m), cyan (c), and black (k) respectively and are provided separately. In addition, similarly, the toner hoppers 41y, 41m, 41c, and 41k and the toner containers 42y, 42m, 42c, and 42k have the same structure to be used for the four colors of yellow (y), magenta (m), cyan (c), and black (k), respectively, and are provided separately. Therefore, in Figure 1 The components for each of the four colors are represented by color identifiers, but in Figure 2 And in the specification, description is made using only reference numerals without adding color identifiers in some cases.

[0071] The toner container 42 is, for example, a cylindrical bottle and contains toner; the toner container 42 is connected to each imaging unit 80 via the toner hopper 41 and is arranged above each imaging unit 80. The laser scanner 43 exposes the surface of the photosensitive drum 81 charged by the charging roller 82, thereby forming an electrostatic latent image on the surface of the photosensitive drum 81.

[0072] The imaging unit 80 includes four imaging units 80y, 80m, 80c, 80k for forming toner images of four colors. The imaging units 80y, 80m, 80c, 80k include photosensitive drums (image bearing members) 81y, 81m, 81c, 81k for forming toner images, charging rollers 82y, 82m, 82c, 82k, developing devices 20y, 20m, 20c, 20k, and cleaning blades 84y, 84m, 84c, 84k. In addition, the photosensitive drums 81y, 81m, 81c, 81k, the charging rollers 82y, 82m, 82c, 82k, the developing devices 20y, 20m, 20c, 20k, the cleaning blades 84y, 84m, 84c, 84k, and the developing sleeve 24 described later have the same structure for the four colors of yellow (y), magenta (m), cyan (c), and black (k), respectively, and are provided separately. Figure 1 Each component used for the four colors is represented by a color identifier, but in Figure 2 And in the specification, description is made using only reference numerals without adding color identifiers in some cases.

[0073] The photosensitive drum 81 as an image bearing member includes a photosensitive layer having a negative charging polarity formed on the outer peripheral surface of an aluminum cylinder, and rotates in the direction of the arrow at a predetermined process speed (peripheral speed). The 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 respective surface of each photosensitive drum 81 by a laser scanner 43 as an exposure device based on image information. Each photosensitive drum 81 carries the formed electrostatic image and moves in a circular motion, and the electrostatic latent image is developed with a toner by the developing device 20. The details of the structure of the developing device 20 will be described later.

[0074] The toner image obtained by developing the electrostatic image is primarily transferred onto the intermediate transfer belt 44b described later. The surface of the photosensitive drum 81 is discharged by a front exposure section not shown after the primary transfer. A cleaning blade 84 as a cleaning member is provided to contact the surface of the photosensitive drum 81 and removes residues such as transfer residual toner remaining on the surface of the photosensitive drum 81 after the primary transfer.

[0075] 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 driving roller 44a, a driven roller 44d, primary transfer rollers 44y, 44m, 44c, and 44k, and an intermediate transfer belt 44b wound around these rollers as an intermediate transfer member. The primary transfer rollers 44y, 44m, 44c, and 44k are arranged to be opposed to the photosensitive drums 81y, 81m, 81c, and 81k, respectively, and are arranged to be in contact with the intermediate transfer belt 44b.

[0076] A positive transfer bias is applied to the intermediate transfer belt 44b by primary transfer rollers 44y, 44m, 44c, and 44k, so that toner images having negative polarity are sequentially transferred from the photosensitive drums 81y, 81m, 81c, and 81k to the intermediate transfer belt 44b in a superimposed manner. In this way, the intermediate transfer belt 44b is rotated with a full-color image formed on its outer peripheral surface.

[0077] The secondary transfer section 45 includes a secondary transfer inner roller 45a and a secondary transfer outer roller 45b. By applying a positive polarity secondary transfer bias to the secondary transfer outer roller 45b, the full color image formed on the intermediate transfer belt 44b is transferred to the sheet S. The fixing device 46 includes a fixing roller 46a and a pressure roller 46b. The sheet S is sandwiched and fed between the fixing roller 46a and the pressure roller 46b so that the toner image transferred on the sheet S is heated and pressurized, thereby fixing on the sheet S.

[0078] The sheet feeding section 50 includes a pre-secondary transfer feeding path 51 , a pre-fixing feeding path 52 , a discharge path 53 , and a re-feeding path 54 , and feeds the sheet S fed from the sheet feeding section 30 from the image forming section 40 to the sheet discharge section 60 .

[0079] The sheet discharge section 60 includes a discharge roller pair 61 provided on the downstream side of the discharge path 53 and a discharge tray 62 provided on the downstream side of the discharge roller pair 61. The discharge roller pair 61 feeds the sheet S fed from the discharge path 53 via its nip portion, and discharges the sheet S via the discharge port 10a formed on the apparatus body 10. The discharge tray 62 is a tray facing downward, and the sheets S discharged via the discharge port 10a in the arrow X direction are stacked on the discharge tray 62.

[0080] The controller 70 is composed of a computer, for example, including a CPU, a ROM for storing programs used to control each part, a RAM for temporarily storing data, and an input-output circuit for inputting and outputting signals in relation to an external device. The CPU is a microprocessor for realizing overall control of the imaging device 1, and is a main part of the system controller. The CPU is connected to each of the image reading section 11, the sheet feeding section 30, the imaging section 40, the sheet feeding section 50, the sheet discharging section 60, and the operating section via the input-output circuit, and transmits signals to each section and controls the operation of each section.

[0081] Next, the image forming operation in the image forming apparatus 1 configured as described above will be described.

[0082] When the image forming operation starts, first, the photosensitive drum 81 rotates, and its surface is charged by the charging roller 52. Then, the laser scanner 43 emits laser light to the surface of the photosensitive drum 81 based on image information, thereby forming an electrostatic latent image on the surface of the photosensitive drum 81. Toner is deposited on the electrostatic latent image, so that the electrostatic latent image is developed (visualized) into a toner image, and then the toner image is transferred onto the intermediate transfer belt 44b.

[0083] On the other hand, in parallel with this toner image forming operation, the feed rollers 32a and 32b rotate and feed the uppermost sheet S in the sheet cassettes 31a and 31b while separating the sheet S. Then, in synchronization with the toner image on the intermediate transfer belt 44b, the sheet S is fed to the secondary transfer portion 45 via the pre-secondary transfer feed path 51. Then, the toner image is transferred from the intermediate transfer belt 44b to the sheet S, and the sheet S is fed to the fixing device 46, where the unfixed toner image is heated and pressurized, thereby being fixed on the surface of the sheet S. The sheet S is discharged through the discharge port 10a by the discharge roller pair 61, and is stacked on the discharge tray 62.

[0084] [Developing device]

[0085] Next, we will refer to Figure 2 The developing device 20 is described in detail. The developing device 20 includes a developing (developer) container 21 that contains a developer, a first screw 22 and a second feeding screw 23, a developing sleeve 24, and a regulating member (regulating blade in this embodiment) 25. The developing container 21 has an opening 21a at which the developing sleeve 24 is exposed at a position opposite to the photosensitive drum 81.

[0086] From the toner container 42 ( Figure 1 ) supplies toner to the developing container 21. The developing container 21 includes a partition wall 27 extending in the longitudinal direction substantially in the center portion. The developing container 21 is divided into a developing chamber 21b and a stirring chamber 21c in the horizontal direction by the partition wall 27. The developer is contained in the developing chamber 21b and the stirring chamber 21c. In the developing chamber 21b, the developer is fed to the developing sleeve 24. The stirring chamber 21c is connected to the developing chamber 21b, and the developer is recovered from the developing sleeve 24 and stirred.

[0087] The first feeding screw 22 is arranged in the developing chamber 21b along the axial direction of the developing sleeve 24 and is substantially parallel to the developing sleeve 24. The second feeding screw 23 is arranged in the stirring chamber 21c substantially parallel to the axis of the first feeding screw 22, and feeds the developer in the stirring chamber 21c in a direction opposite to the feeding direction of the first feeding screw 22. That is, the developing chamber 21b and the stirring chamber 21c constitute a circulation path of the developer, and the developer is fed along the circulation path while being stirred. The toner is frictionally charged to a negative polarity by sliding relative to the carrier by being stirred by each of the screws 22 and 23.

[0088] The developer in the developing container 21 is carried on the developing sleeve 24 by the magnetic roller 24m fixedly provided in the rotatable developing sleeve 24. Thereafter, the developer on the developing sleeve 24 is regulated in amount (layer thickness) by the regulating member 25, and is fed to a developing area opposite to the photosensitive drum 81 by the rotation of the developing sleeve 24. The developer contacts the photosensitive drum 81, thereby supplying the toner to the photosensitive drum 81, so that the electrostatic latent image on the photosensitive drum 81 is developed into a toner image. At this time, a developing bias including a superposition of a DC voltage and an AC voltage is applied between the photosensitive drum 81 and the developing sleeve 24, so that the toner jumps onto the electrostatic latent image.

[0089] The developing sleeve 24 as a developer carrying member carries the developer (the developer includes a non-magnetic toner and a magnetic carrier) and rotatably feeds the developer to a developing area opposed to the photosensitive drum 81. For example, the developing sleeve 24 has a diameter of 20 mm, has a cylindrical shape, and is composed of a non-magnetic material (such as aluminum or non-magnetic stainless steel), and is formed of aluminum in this embodiment.

[0090] The regulating member 25 is opposite to the regulating magnetic pole N1 of the magnetic roller 24m and is provided on the developing container 21. In addition, the regulating member 25 includes a regulating portion which is opposite to the developing sleeve 24 without contact and is used to regulate the amount of the developer carried on the developing sleeve 24. That is, the regulating member 25 is fixed to the developing container 21 in a state where its free end (regulating portion) is separated from the developing sleeve 24 by a predetermined interval, and the layer thickness of the developer is regulated by cutting the magnetic chain of the developer carried on the surface of the developing sleeve 24 by the magnetic force (magnetic attraction) of the regulating magnetic pole N1. Such a regulating member 25 is composed of a metal plate (for example, a SUS plate) arranged in the longitudinal direction of the developing sleeve 24, and the developer passes between the free end (regulating portion) of the regulating member 25 and the developing sleeve 24 and is sent to the developing area Da. By the way, the regulating member 25 may be a magnetic member or a non-magnetic member, but the regulating member 25 may be preferably a magnetic member from the following viewpoint. In the case of the magnetic member, a magnetic field is formed between the free end (regulating portion) of the regulating member 25 and the developing sleeve 24, and a magnetic attraction force acts on the surface of the regulating member 25. Therefore, the developer is easily cut. In addition, there is an advantage that the interval between the free end (regulating portion) of the regulating member 25 and the developing sleeve 24 can be made larger, so foreign matter is not easily blocked.

[0091] On the other hand, in the case of a magnetic member, the developer is easily constrained by the magnetic field between the free end of the regulating member 25 and the developing sleeve 24, and is therefore easily degraded by friction. Incidentally, the regulating member 25 may also be a regulating member in which the magnetic member is attached to a portion of the non-magnetic member. By doing so, the advantage of the magnetic member is lost, but the developer degradation can be suppressed. In this embodiment, as the regulating member 25, a regulating member consisting only of a magnetic member is used. Therefore, there is a possibility of developer degradation, but the developer degradation can be suppressed by using the magnetic roller 24m in combination.

[0092] In the developing sleeve 24, a roller-shaped magnetic roller (magnetic field generating device, magnet) 24m is fixedly arranged in a non-rotatable state relative to the developing container 21. The magnetic roller 24m includes a plurality of magnetic poles, and generates a magnetic field for carrying the developer on the developing sleeve 24. The magnetic roller 24m includes seven magnetic members, each of which has a surface opposite to the developing sleeve 24, namely, an extraction magnetic pole S1, a control magnetic pole N1, a feed magnetic pole S2, a developing magnetic pole N2, a feed magnetic pole S3, a feed magnetic pole N3 and a stripping magnetic pole S4. By the way, in the present embodiment, a magnetic roller consisting of seven magnetic poles is used, but the magnetic roller may also include magnetic poles other than the seven magnetic poles. For example, a magnetic roller consisting of five magnetic poles may be used.

[0093] However, as in the present embodiment, when the magnetic roller 24m includes seven or more magnetic poles, each magnetic piece tends to become smaller, so that the influence of the position deviation of the regulating member on the regulating magnetic poles is likely to occur. Therefore, as in the present embodiment, when the magnetic roller 24m includes seven or more magnetic poles, the effect of adopting the structure described later becomes better.

[0094] The drawing magnetic pole S1 is arranged opposite to the developing chamber 21b. The developing magnetic pole N1 is arranged opposite to the regulating member 25. The feeding magnetic pole S2 is arranged on the upstream side of the developing area with respect to the rotation direction. The developing magnetic pole N2 is arranged opposite to the developing area. The feeding magnetic pole S3 and the feeding magnetic pole N3 are arranged on the downstream side of the developing area Da with respect to the rotation direction. The stripping magnetic pole S4 is arranged adjacent to the drawing magnetic pole S1 and upstream of the drawing magnetic pole S1 with respect to the rotation direction. In particular, the regulating magnetic pole N1 as the first magnetic pole is arranged closest to the regulating member 25. In addition, the drawing magnetic pole S1 as the second magnetic pole (upstream side magnetic pole) is arranged adjacent to the regulating magnetic pole N1 and on the upstream side of the regulating magnetic pole N1 with respect to the rotation direction of the developing sleeve 24. In addition, the feeding magnetic pole S2 as the third magnetic pole (downstream side magnetic pole) is arranged adjacent to the regulating magnetic pole N1 and on the downstream side of the regulating magnetic pole N1 with respect to the rotation direction of the developing sleeve 24.

[0095] Next, according to Figure 2 The operation of the developing sleeve in this embodiment is described. 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 magnetic pole S1 opposite to the developing chamber 21b and fed to the regulating member 25. The developer is erected by the regulating magnetic pole N1 opposite to the regulating member 25, and the layer thickness of the developer is regulated by the regulating member 25, and the developer passes through the gap (interval) between the developing sleeve 24 and the regulating member 25, thereby forming a developer layer with a predetermined layer thickness on the developing sleeve 24.

[0096] The developing layer passes through the feeding magnetic pole S2 and is carried and fed to the developing area opposite to the photosensitive drum 81, and then develops the electrostatic latent image formed on the surface of the photosensitive drum 81 in a state where magnetic linkage is formed by the developing magnetic pole N2 opposite to the developing area.

[0097] The developer after development (electrostatic latent image) passes through the feed magnetic poles S3 and N3 arranged downstream of the development area with respect to the rotation direction, and is peeled off from the development sleeve 24 in the peeling area formed by the repulsion of the peeling magnetic pole S4 and the drawing magnetic pole S1. The peeled developer is stirred and fed in the stirring chamber 21c, and then supplied to the development sleeve 24 again from the development chamber 21b.

[0098] [Magnetic flux density distribution around the control pole]

[0099] Next, the magnetic flux density distribution around the regulated magnetic pole N1 of the magnetic roller 24m in the present embodiment will be described. The magnetic roller 24m has the following magnetic flux density distribution, so that: in the regulated magnetic pole N1 as the first magnetic pole, the normal magnetic flux density Br of the developing sleeve 24 relative to the outer peripheral surface of the developing sleeve 24 has an upstream maximum value P1, a minimum value B, and a downstream maximum value P2 in a specified order from the upstream side to the downstream side relative to the rotation direction of the developing sleeve 24. In some cases, such a magnetic flux density distribution is hereinafter referred to as two peaks. By the way, in some cases, the magnetic flux density distribution of the regulated magnetic pole of the magnetic roller with one maximum value is hereinafter referred to as one peak. In the case of the present embodiment, a magnetic roller 24m with two peaks is used, and the regulated member 25 is arranged to be opposite to the position between the upstream maximum value P1 and the downstream maximum value P2. By the way, in the following, the upstream maximum value P1 and the downstream maximum value P2 are also referred to as the upstream peak value P1 and the downstream peak value P2, respectively. In addition, the position of the upstream peak P1 and the position of the downstream peak P2 are also referred to as the upstream peak P1 and the downstream peak P2, respectively.

[0100] In the following, while comparing with Comparative Example 1, reference Figure 3 Embodiment 1 including the magnet roller 24m having the regulated magnetic pole N1 in this embodiment is described. Figure 3 It is a schematic diagram schematically showing the distribution of the normal magnetic flux density Br and the tangential magnetic flux density Bθ on the developing sleeve 24 caused by the magnetic roller 24m. Incidentally, the magnetic flux density Br exactly represents the normal component of the magnetic flux density B relative to the developing sleeve. Hereinafter, in some cases, "normal magnetic flux density Br" is referred to as "magnetic flux density" according to convention. In the case where the magnetic flux density is referred to as magnetic flux density, the magnetic flux density refers to the "normal magnetic flux density Br". The magnetic flux density Br of each magnetic roller (relative to the normal direction) in Example 1 and Comparative Example 1 was measured using a magnetic field measuring device ("MS-9902", manufactured by FWBELL), wherein the distance between the probe as a component of the magnetic field measuring device and the surface of the developing sleeve 24 was approximately 100 μm.

[0101] exist Figure 3 , the tangential magnetic flux density Bθ with respect to the outer peripheral surface of the developing sleeve 24 is also shown together. The magnetic flux density Bθ is obtained from the following Formula 1 by using the value of the normal magnetic flux density Br measured by the above method.

[0102]

[0103] exist Figure 3, in addition to the regulated magnetic pole N1, an upstream side suction magnetic pole S1 and a downstream side feed magnetic pole S2 are also shown relative to the rotation direction of the developing sleeve 24. In this case, as the magnetic roller 24m, the magnetic roller 24m in this embodiment is used in Embodiment 1 (that is, a magnetic roller using the regulated magnetic pole N1 including two peaks).

[0104] Furthermore, although the magnetic flux density distribution is different from that in Embodiment 1, a magnet roller using a regulated magnetic pole N1 including two peaks is used in Comparative Example 1 similarly to Embodiment 1. In the regulated magnetic pole N1 including two peaks, the normal magnetic flux density Br has a magnetic flux density distribution such that an upstream maximum value (upstream peak value) P1, a minimum value B, and a downstream maximum value (downstream peak value) P2 are in the specified order from the upstream side to the downstream side with respect to the rotation direction of the developing sleeve 24.

[0105] exist Figure 3 In FIG. 1 , the normal magnetic flux density Br (solid line) of the regulated magnetic pole N1 in this embodiment, which is the same as that in the first embodiment, and the normal magnetic flux density Br (broken line) in the first comparative example are shown. Figure 3 , the tangential magnetic flux density Bθ in each of Example 1 and Comparative Example 1 is shown together by a bold (thick) line, with the developing sleeve 24 rotating direction (downstream direction) regarded as the forward direction.

[0106] In both Embodiment 1 and Comparative Example 1, the shape (distribution) of the magnetic flux density Br of the regulated magnetic pole is two peaks, so that the minimum value appears between the two peaks P1 and P2, which are composed of the upstream peak P1 (upstream maximum value (peak value)) and the downstream peak P2 (downstream maximum value (peak value)). That is, in each of Embodiment 1 and Comparative Example 1, the shape of the normal magnetic flux density Br of the regulated magnetic pole N1 is two peaks. By adopting such a magnetic flux density distribution that the normal magnetic flux density Br of the regulated magnetic pole N1 has two peaks, the area where the change (θ direction change) of the magnetic flux density distribution relative to the rotation direction of the developing sleeve 24 is gentle can be further expanded. Therefore, compared with the case where the shape of the magnetic flux density Br is one peak, by arranging the regulating member 25 to be opposite to the position between the two peaks of the magnetic flux density Br of the regulated magnetic pole N1, even when the positional relationship relative to the regulating member 25 deviates, the magnetic flux density is not easy to change, and therefore the developer amount is not easy to fluctuate. That is, the range of the pole position (the positional relationship between the regulated magnetic pole N1 and the regulating member 25) can be expanded.

[0107] However, as described above, the developer amount of the developer regulated by the regulating member 25 is affected not only by the normal magnetic flux density Br of the magnetic roller 24m but also by the tangential magnetic flux density Bθ of the magnetic roller 24m. Figure 3As shown, in both Example 1 and Comparative Example 1, the tangential magnetic flux density Bθ is a negative value on the upstream side of the regulated magnetic pole N1 and is a positive value on the downstream side of the regulated magnetic pole N1.

[0108] That is, in the regulated magnetic pole N1 as the first magnetic pole, there is a position where the tangential magnetic flux density Bθ relative to the outer peripheral surface of the developing sleeve 24 becomes 0 (zero) 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 (requirement (B) described later). This is because: the magnetic flux lines extend radially from the magnetic poles, so the magnetic flux lines extend in the upstream direction (negative direction) on the upstream side of the magnetic poles, and extend in the downstream direction (positive direction) on the downstream side of the magnetic poles.

[0109] Figure 4 The results shown represent the amount of developer on the developing sleeve 24 after passing through the regulating member 25, measured with respect to the magnet rollers of each of Example 1 and Comparative Example 1, when the relative position of the regulating member 25 was changed in 10° increments. Figure 4 The features that are understood and are common to Example 1 and Comparative Example 1 are as follows. That is, in the case where the regulating member 25 is opposite to the region (at about 200°) where the tangential magnetic flux density Bθ is negative on the upstream side of the regulating magnetic pole N1, the change in the developer amount relative to the pole position is relatively small. On the other hand, in the case where the regulating member 25 is opposite to the region (at about 250°) where the tangential magnetic flux density Bθ is positive on the downstream side of the regulating magnetic pole N1, the change in the developer amount relative to the pole position is relatively large.

[0110] This behavior difference can be considered to be caused by the difference in behavior of the developer at the developer stagnation portion formed on the upstream side of the regulating member 25. This point will be explained using Figure 5 and Figure 6 Give a description. Figure 5 (a) and (b) show the state of the developer near the retained developer in the case where the regulating member 25 is arranged to be opposite to the region where the tangential magnetic flux density Bθ of the regulating magnetic pole N1 is negative. Figure 5 In FIG. 1 , (a) schematically shows the behavior of the magnetic flux on the developing sleeve 24, and (b) schematically shows the interface between the flowing layer (the developer moves in the developer retention portion) and the stationary layer (the developer is substantially stationary) by means of a broken line. Figure 5 (a) and (b) are similar. Figure 6 (a) and (b) schematically show the state of the developer near the retained developer in the case where the regulating member 25 is arranged to oppose the region where the tangential magnetic flux density Bθ of the regulation magnetic pole N1 is positive.

[0111] like Figure 5As shown in (a), in the region where the tangential magnetic flux density Bθ of the regulated magnetic pole N1 is negative, the magnetic flux lines extend in the upstream direction, so the magnetic flux of the developer is formed in a state where the magnetic flux is inclined in the upstream direction (that is, as the magnetic flux portion approaches its free end, the magnetic flux is inclined more toward the upstream side). The behavior of the magnetic flux having an upstream-inclined shape causes the magnetic flux to feed toward the downstream side and gradually increase as the magnetic flux approaches the regulated member 25. This developer behavior is reflected so that when the regulated member 25 is arranged opposite to the region where the tangential magnetic flux density Bθ of the regulated magnetic pole N1 is negative, as shown in FIG. Figure 5 As shown in (b) of FIG. 2 , a narrow area closer to the developing sleeve 24 than the free end portion of the regulating member 25 constitutes a developer flow layer.

[0112] On the other hand, Figure 6 As shown in (a), in the area where the tangential magnetic flux density Bθ of the regulated magnetic pole N1 is positive, the magnetic flux lines extend toward the downstream direction, so the magnetic flux of the developer is formed in a state where the magnetic flux is slightly inclined toward the downstream direction (that is, as the magnetic flux portion approaches its free end, the magnetic flux is inclined toward the downstream side). The behavior of the magnetic flux having a shape inclined toward the downstream direction makes the magnetic flux more inclined as it feeds toward the downstream side. This developer behavior is reflected so that when the regulated member 25 is arranged opposite to the area where the tangential magnetic flux density Bθ of the regulated magnetic pole N1 is positive, as shown in FIG. Figure 6 As shown in (b), a wide area located on the upstream side of the regulating member 25 constitutes a developer flow layer.

[0113] The fluctuation of the developer flow layer is considered to be one of the factors causing the developer amount to fluctuate after regulation when the magnetic flux density distribution and the positional relationship between the regulating member 25 are deviated. Figure 5 As shown in (b), when the regulating member 25 is arranged opposite to the position where the tangential magnetic flux density Bθ is negative, the developer flow layer is narrow, and thus the developer flow layer fluctuation is likely to be small when the positional relationship relative to the regulating member 25 is deviated. Figure 6 As shown in (b), when the regulating member 25 is arranged to oppose the position where the tangential magnetic flux density Bθ is positive, the developer flow layer is wide, so that the developer flow layer fluctuation is likely to become larger when the positional relationship with respect to the regulating member 25 is deviated. Therefore, when the tangential magnetic flux density Bθ at the position where the regulating member 25 is arranged to oppose is positive, when the positional relationship with respect to the regulating member 25 is deviated, the developer amount fluctuation is likely to become larger than when the tangential magnetic flux density Bθ at the above relative position is negative.

[0114] like Figure 4As shown, when the regulating member 25 is arranged opposite to the area where the tangential magnetic flux density Bθ of the regulated magnetic pole N1 is negative (at about 200°), the change in the developer amount relative to the pole position is relatively small compared to the case where the regulating member 25 is arranged opposite to the area where the tangential magnetic flux density Bθ of the regulated magnetic pole N1 is positive (at about 250°). It can be considered that such behavior is exhibited due to the above-mentioned reasons.

[0115] Therefore, in order to suppress the developer amount fluctuation with respect to the deviation of the magnetic flux density distribution and the positional relationship between the regulating member 25, preferably, not only the normal magnetic flux density Br of the regulating pole N1 changes gently, but also the regulating member 25 is arranged opposite to the region where the tangential magnetic flux density Bθ is negative.

[0116] Therefore, in this embodiment, the regulating member 25 is arranged not only to be opposite to the position between the two peaks P1 and P2 of the normal magnetic flux density Br of the regulated magnetic pole N1, but also to be opposite to the region where the tangential magnetic flux density Bθ of the regulated magnetic pole N1 is negative. In other words, the regulating member 25 is arranged to be opposite to the position between the upstream peak P1 of the normal magnetic flux density Br of the regulated magnetic pole N1 and the downstream position O of the upstream peak P1 (at which the tangential magnetic flux density Bθ of the regulated magnetic pole N1 is zero) (requirement (C) described later). By doing so, the variation of the developer amount with respect to the pole position (after regulation) can be suppressed.

[0117] At this time, when the angle between the upstream peak P1 and the position O where the tangential magnetic flux density Bθ becomes 0 (zero) is narrow (small), it is not easy to obtain a wider pole position range. Therefore, in this embodiment, the angle between the upstream peak P1 and the position O where the tangential magnetic flux density Bθ becomes 0 is increased.

[0118] Specifically, a configuration satisfying requirements (A) to (H) is adopted as follows. Incidentally, among these requirements, at least one of requirements (D)′ to (H) is satisfied.

[0119] (A) With respect to the rotation direction of the developing sleeve 24 , the angle between the position of the upstream peak P1 and the position of the downstream peak P2 is 20° or more and 50° or less.

[0120] (B) In the first magnetic pole (regulated magnetic pole N1), relative to the rotation direction of the developing sleeve 24, the position O where the tangential magnetic flux density Bθ relative to the outer peripheral surface of the developing sleeve 24 is 0 is arranged between the position of the upstream peak P1 and the position of the downstream peak P2.

[0121] (C) With respect to the rotation direction of the developing sleeve 24 , the regulating member 25 is arranged to oppose a position between the position of the upstream peak P1 and the position O where the tangential magnetic flux density Bθ is 0 (zero).

[0122] (D) With respect to the rotation direction of the developing sleeve 24, the position O where the tangential magnetic flux density Bθ is 0 is located within the range of ±2° relative to the midpoint between the upstream peak P1 position and the downstream peak P2 position, or on the downstream side of the range.

[0123] (D)' With respect to the rotation direction of the developing sleeve 24, the position O where the tangential magnetic flux density Bθ is 0 is located on the downstream side of the midpoint between the upstream peak P1 position and the downstream peak P2 position.

[0124] (E) With respect to the rotation direction of the developing sleeve 24 , the angle from the upstream peak P1 position to the position O where the tangential magnetic flux density Bθ is 0 is 15° or more and less than 50°.

[0125] (F) The absolute value |Br| of the upstream peak P1 is smaller than the absolute value |Br| of the downstream peak P2.

[0126] (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 is 0 is 10 mT or less.

[0127] (H) With respect to the rotation direction of the developing sleeve 24, the absolute value |Br| of the normal magnetic flux density Br of the upstream magnetic pole (the extraction magnetic pole S1) is smaller than the absolute value |Br| of the normal magnetic flux density Br of the downstream magnetic pole (the feed magnetic pole S2).

[0128] The above requirements will be described in detail. Incidentally, requirement (B) has been described above. First, in order to explain Comparative Example 1, Figure 7 In the figure, the normal magnetic flux density Br and the tangential magnetic flux density Bθ in Comparative Example 1 are shown together. Figure 7 In FIG. 1 , the midpoint M between the upstream peak value P1 and the downstream peak value P2 of the normal magnetic flux density Br of the regulated magnetic pole N1 of the magnet roller in Comparative Example 1 is also shown. Figure 7 It can be understood that in Comparative Example 1, the position O where the tangential magnetic flux density Bθ of the regulated magnetic pole N1 of the magnet roller is 0 is located upstream of the midpoint M. Therefore, the angle between the upstream peak P1 of the normal magnetic flux density Br and the position O where the tangential magnetic flux density Bθ is 0 is 12°, which is very narrow (small).

[0129] It can be seen from this that although the magnet roller in Comparative Example 1 has a shape that gives the normal magnetic flux density Br two peaks, it is expected that the assumed wide pole position range cannot be obtained. Figure 4 , in Comparative Example 1, the region where the developer amount fluctuation is gentle with respect to the abscissa is relatively narrow. Therefore, when a deviation occurs in the positional relationship with respect to the regulating member 25, the range of the developer amount fluctuation is relatively narrow. Therefore, the position O where the tangential magnetic flux density Bθ is 0 in Embodiment 1 is positioned on the downstream side of the position O in Comparative Example 1.

[0130] [Position O where the tangential magnetic flux density Bθ is 0 (requires (D), (D)')]

[0131] To explain Example 1, Figure 8 In the figure, the normal magnetic flux density Br and the tangential magnetic flux density Bθ in Example 1 are shown together. Figure 8 In the figure, the midpoint M between the upstream peak value P1 and the downstream peak value P2 of the normal magnetic flux density Br of the regulated magnetic pole N1 of the magnet roller 24m in Embodiment 1 is also shown. Figure 8 It can be understood that, unlike Comparative Example 1, the position O where the tangential magnetic flux density Bθ of the regulated magnetic pole N1 of the magnet roller 24m is 0 in Embodiment 1 is located downstream of the midpoint M. Therefore, the angle between the upstream peak P1 of the normal magnetic flux density Br and the position O where the tangential magnetic flux density Bθ is 0 is larger than the relevant angle in Comparative Example 1.

[0132] It can be seen from this that the magnetic roller 24m in Example 1 is expected to provide a wider range of pole positions than the range of pole positions in Comparative Example 1. Figure 4 , in Embodiment 1, the region where the developer amount fluctuation is gentle with respect to the abscissa is wider than that in Comparative Example 1. Therefore, in Embodiment 1, a structure where the developer amount fluctuation range is wide when the positional relationship with respect to the regulating member 25 deviates can be realized.

[0133] From the above, it can be seen that whether the position O where the tangential magnetic flux density Bθ of the control magnetic pole N1 of the magnetic roller 24m is 0 is located upstream or downstream of the midpoint between the upstream peak P1 and the downstream peak P2 of the normal magnetic flux density Br constitutes an indicator of the magnetic pole position range. Figure 7 and Figure 8 , the angles at main positions and the values ​​of the normal magnetic flux density Br in Comparative Example 1 and Example 1 are shown respectively.

[0134] like Figure 7 As shown in FIG. 1 , the position O where the tangential magnetic flux density Bθ of the regulated magnetic pole N1 of the magnetic roller 24m is 0 is located 5° upstream of the midpoint M between the upstream peak value P1 and the downstream peak value P2 of the normal magnetic flux density Br. Figure 8 As shown, the position O where the tangential magnetic flux density Bθ of the regulated magnetic pole N1 of the magnet roller 24m in Embodiment 1 is 0 is located 3° downstream of the midpoint M between the upstream peak P1 and the downstream peak P2 of the normal magnetic flux density Br.

[0135] In order to fully obtain the effect of increasing the pole position range by regulating the two peak shapes of the normal magnetic flux density Br of the magnetic pole N1, the position O where the tangential magnetic flux density Bθ of the regulated magnetic pole N1 of the magnetic roller 24m is 0 may preferably be located near the midpoint M between the upstream peak P1 and the downstream peak P2 of the normal magnetic flux density Br (within the range of ±2°), or downstream of the midpoint M (requirement (D)). More preferably, the position O is located downstream of the midpoint M (requirement (D)'). By adopting this structure, the effect of increasing the pole position range by regulating the two peak shapes of the normal magnetic flux density Br of the magnetic pole N1 can be fully obtained.

[0136] [Two peak shapes]

[0137] The magnetic roller 24m as the object of this embodiment makes the normal magnetic flux density distribution of the regulated magnetic pole N1 have a two-peak shape; by adopting the two-peak shape, even if the positional relationship relative to the regulating member 25 deviates, the normal magnetic flux density Br is not easy to change, so the developer amount is difficult to fluctuate, thereby making the pole position range wider. Here, "the two-peak shape of the normal magnetic flux density distribution of the regulated magnetic pole N1" refers to Figure 7 and Figure 8 The shape shown makes the normal magnetic flux density Br of the control pole N1 have two peaks P1 and P2, and there is a concave minimum value B between the two peaks P1 and P2 (in this case, the maximum and minimum values ​​refer to absolute values). At this time, the maximum and minimum values ​​accompanied by measurement noise below 0.5mT are ignored.

[0138] [Difference in magnetic flux density Br between upstream peak P1 and position O]

[0139] Here, the minimum value B is too small relative to the two peak values ​​P1 and P2, and the normal magnetic flux density Br fluctuates, thus causing the developer amount to fluctuate. As described above, in this embodiment, the regulating member 25 is arranged in the region between the upstream peak value P1 of the normal magnetic flux density Br and the downstream position O of the upstream peak value P1 (where the tangential magnetic flux density Bθ is 0) (requirement (C)). Therefore, the difference between the maximum value and the minimum value B of the upstream peak value P1 of the normal magnetic flux density Br can be preferably 10 mT or less.

[0140] In addition, the normal magnetic flux density Br value at the position O where the tangential magnetic flux density Bθ is 0 may also be greater than the normal magnetic flux density Br of the upstream peak P1. Therefore, the normal magnetic flux density Br fluctuation between the upstream peak P1 and the position O where the tangential magnetic flux density Bθ is 0 may preferably fall within a range of 10mT or less (requirement (G)). In Embodiment 1, the difference between the maximum and minimum values ​​of the upstream peak P1 of the normal magnetic flux density Br is 2mT.

[0141] Furthermore, the value of the normal magnetic flux density Br at the position O where the tangential magnetic flux density Bθ is 0 is 45 mT, and the fluctuation of the normal magnetic flux density Br at the position between the upstream peak P1 and the position O where the tangential magnetic flux density Bθ is 0 is 5 mT. Therefore, Example 1 satisfies the above conditions.

[0142] [Requirement for the interval between two peaks (A)]

[0143] For the interval between the two peaks P1 and P2, the pole position range can be widened by increasing the interval. Therefore, when the angle between the peaks P1 and P2 is at least 20° (requirement (A)), preferably above 25°, and more preferably above 30°, a sufficient pole position range can be obtained. However, when the angle is above 50°, the interval is too wide, so that the interval may affect the arrangement freedom of other magnetic poles. Therefore, the interval (angle) between the peaks P1 and P2 may preferably be less than 50°. In particular, in the case where the magnetic roller 24m includes magnetic poles with more than 7 poles as in the present embodiment, it is easier to have an impact. In Example 1, the angle (interval) is 30°, so that Example 1 meets the above conditions.

[0144] [Angle from upstream peak P1 to position O (required (E))]

[0145] In the case of the present embodiment, it is more important to increase the interval between the upstream peak P1 of the normal magnetic flux density Br and the position O where the tangential magnetic flux density Bθ is 0. In Comparative Example 1, the angle between the upstream peak P1 and the position O is 12°, and in Embodiment 1 it is 18°. The angle may preferably be greater than 15° to obtain a sufficient pole position range (requirement (E)). However, when the angle between the upstream peak P1 of the normal magnetic flux density Br and the position O where the tangential magnetic flux density Bθ is 0 is greater than 50°, the angle is too large, and thus the large angle may affect the arrangement freedom of other magnetic poles. Therefore, the angle between the upstream peak P1 and the position O may preferably be less than 50°. In particular, in the case where the magnetic roller 24m includes magnetic poles with more than 7 poles, the influence is more likely to occur.

[0146] As described above, for the regulated magnetic pole N1 of the magnetic roller 24m in Embodiment 1, a region where the tangential magnetic flux density Bθ is greater than 0 (Bθ>0) (in which the developer amount fluctuation is relatively small) can be realized within an angle range of 15° or more between two peaks of the normal magnetic flux density Br. Moreover, within this range, the normal magnetic flux density Br is 10 mT or less. Furthermore, the regulating member 25 is arranged in this region, so that a wider pole position range can be obtained.

[0147] [Magnetic flux density of two peaks (required (F))]

[0148] Here, the reason why the position O where the tangential magnetic flux density Bθ of the regulated magnetic pole N1 of the magnetic roller 24m in Embodiment 1 is 0 can be arranged on the further downstream side will be described. The position O where the tangential magnetic flux density Bθ is 0 represents a state where the magnetic flux lines extend only in the normal direction (infinite distance direction). Generally, the magnetic flux lines extending from the magnetic poles extend radially toward the upstream magnetic poles and the downstream magnetic poles, but are not easily affected by the relative influence of the upstream magnetic poles and the downstream magnetic poles at a location where the normal magnetic flux density Br of the magnetic poles is relatively large, so that the magnetic flux lines are easy to extend in the normal direction (infinite distance direction).

[0149] according to Figure 7 , for the regulated magnetic pole N1 of the magnetic pole 24m in Comparative Example 1, the upstream peak value P1 of the normal magnetic flux density Br is 46mT, and the downstream peak value P2 is 43mT, so that the upstream peak value P1 is greater than the downstream peak value P2 in terms of absolute value. Therefore, it can be considered that the position where the magnetic flux line extends along the normal direction (i.e., the position O where the tangential magnetic flux density Bθ is 0) is easily offset in the direction of the upstream peak value P1 (i.e., the larger value of the magnetic flux density Br). In fact, the position O where the tangential magnetic flux density Bθ of the regulated magnetic pole N1 of the magnetic roller 24m in Comparative Example 1 is 0 is located 5° upstream of the midpoint M between the upstream peak value P1 and the downstream peak value P2 of the normal magnetic flux density Br.

[0150] On the other hand, according to Figure 8 For the regulated magnetic pole N1 of the magnetic pole 24m in Example 1, the upstream peak P1 value of the normal magnetic flux density Br is 42mT, and the downstream peak P2 value is 45mT, so that in terms of absolute value, the downstream peak P2 is greater than the upstream peak P1. Therefore, it can be considered that the position where the magnetic flux line extends along the normal direction (i.e., the position O where the tangential magnetic flux density Bθ is 0) is prone to shift in the direction of the downstream peak P2 (larger value of the magnetic flux density Br). Therefore, the absolute value of the normal magnetic flux density of the upstream peak P1 |Br| can be preferably smaller than the absolute value of the normal magnetic flux density of the downstream peak P2 |Br| (requirement (F))). In fact, the position O where the tangential magnetic flux density Bθ of the regulated magnetic pole N1 of the magnetic roller 24m in Example 1 is 0 is located 3° downstream of the midpoint M between the upstream peak P1 and the downstream peak P2 of the normal magnetic flux density Br.

[0151] Therefore, for the normal magnetic flux density Br, the absolute value |Br| of the downstream peak P2 normal magnetic flux density is made greater than the absolute value |Br| of the upstream peak P1 normal magnetic flux density, so that the position where the magnetic flux lines extend in the normal direction can be arranged on the further downstream side.

[0152] Preferably, the absolute value of the downstream peak P2 magnetic flux density |Br| is greater than the absolute value of the upstream peak P1 magnetic flux density |Br| by more than 2mT. This is to prevent the magnitude relationship between the absolute value of the upstream peak P1 magnetic flux density |Br| and the absolute value of the downstream peak P2 magnetic flux density |Br| from being reversed due to the tolerance of the magnetic roller parts. In order to achieve further effects, the absolute value of the downstream peak P2 magnetic flux density |Br| may preferably be greater than the absolute value of the upstream peak P1 magnetic flux density |Br| by more than 5mT, more preferably by more than 10mT.

[0153] On the other hand, when the absolute value |Br| of the downstream peak P2 magnetic flux density is greater than the absolute value |Br| of the upstream peak P1 magnetic flux density by more than 25mT, the fluctuation range of the magnetic flux density Br between the two peaks P1 and P2 becomes larger, so that the large fluctuation range may have an impact on the pole position range. Therefore, the fluctuation range (difference) between the absolute values ​​|Br| of the magnetic flux density of the upstream peak P1 and the downstream peak P2 may preferably be less than 25mT. That is, 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 may preferably be greater than 2mT and less than 25mT. At this time, as described above, the fluctuation of the normal magnetic flux density Br at the position between the upstream peak P1 and the position O where the tangential magnetic flux density Bθ is 0 may preferably be less than 10mT.

[0154] [Regulate the relationship between the magnetic pole and the adjacent magnetic pole (requirement (H))]

[0155] Here, the position where the magnetic flux lines of the regulated magnetic pole N1 extend in the normal direction is also greatly affected by the magnetic poles adjacent to the regulated magnetic pole N1. This is because: when the magnetic flux density of the adjacent magnetic pole is large, the magnetic flux lines tend to extend in the direction of the magnetic flux density, and when the magnetic flux density of the adjacent magnetic pole is small, the magnetic flux lines do not tend to extend in the direction of the magnetic flux density, that is, the magnetic flux lines tend to extend in the normal direction. From the above, it can be seen that when the maximum values ​​of the normal magnetic flux density Br are compared between the upstream magnetic pole and the downstream magnetic pole adjacent to the regulated magnetic pole N1, the position where the magnetic flux lines of the regulated magnetic pole N1 extend in the normal direction tends to deviate toward the direction of the magnetic pole with the smaller absolute value of the normal magnetic flux density Br.

[0156] according to Figure 7For the magnetic roller 24m in Comparative Example 1, the absolute value |Br| of the maximum value of the normal magnetic flux density Br of the extraction magnetic pole S1 located upstream of the regulated magnetic pole N1 is 44mT. On the other hand, the absolute value of the maximum value of the normal magnetic flux density Br of the feed magnetic pole S2 located downstream of the regulated magnetic pole N1 is 88mT. Therefore, the absolute value |Br| of the maximum value of the normal magnetic flux density Br of the extraction magnetic pole S1 is smaller than the absolute value |Br| of the maximum value of the normal magnetic flux density Br of the feed magnetic pole S2. In other words, the absolute value |Br| of the normal magnetic flux density Br of the feed magnetic pole S2 is larger than the absolute value |Br| of the normal magnetic flux density Br of the extraction magnetic pole S1. Therefore, in Comparative Example 1, the position where the magnetic flux lines of the regulated magnetic pole N1 extend along the normal direction tends to deviate toward the upstream direction (where there is an extraction magnetic pole S1 with a smaller absolute value |Br| of the normal magnetic flux density).

[0157] In fact, in Comparative Example 1, although there is no large difference between the two peaks of the normal magnetic flux density Br of the pipe pole N1, the position O where the tangential magnetic flux density Bθ is 0 is relatively largely shifted to the upstream side, which is considered to be caused by the above reason.

[0158] like Figure 8 As shown, for the magnetic roller 24m in Example 1, similar to the case of Comparative Example 1, the absolute value |Br| of the maximum value of the normal magnetic flux density Br of the extraction magnetic pole S1 located upstream of the regulated magnetic pole N1 is 44mT. On the other hand, the absolute value of the maximum value of the normal magnetic flux density Br of the feed magnetic pole S2 located downstream of the regulated magnetic pole N1 is 88mT. Therefore, the absolute value |Br| of the maximum value of the normal magnetic flux density Br of the extraction magnetic pole S1 is smaller than the absolute value |Br| of the maximum value of the normal magnetic flux density Br of the feed magnetic pole S2 (requirement (H)). In other words, the absolute value |Br| of the normal magnetic flux density Br of the feed magnetic pole S2 is larger than the absolute value |Br| of the normal magnetic flux density Br of the extraction magnetic pole S1. Therefore, the position where the magnetic flux lines of the regulated magnetic pole N1 in Example 1 extend in the normal direction can be said to be a position that is easily offset toward the upstream direction (where there is an extraction magnetic pole S1 with a smaller absolute value |Br| of the normal magnetic flux density).

[0159] Although such a structure is adopted, for the magnetic roller 24m in the first embodiment, with respect to the normal magnetic flux density Br, the absolute value |Br| of the normal magnetic flux density of the downstream peak P2 is made greater than the absolute value |Br| of the normal magnetic flux density of the upstream peak P1 (requirement (F)), so that the position O where the tangential magnetic flux density Bθ is 0 can be shifted to the downstream side. That is, as in the present embodiment, when the absolute value |Br| of the maximum value of the normal magnetic flux density Br of the downstream side magnetic pole (the feed magnetic pole S2 in the present embodiment) is greater than the absolute value |Br| of the maximum value of the normal magnetic flux density Br of the upstream side magnetic pole (the extraction magnetic pole S1 in the present embodiment) (requirement (H)), the absolute value |Br| of the magnetic flux density of the downstream peak P2 is made greater than the absolute value |Br| of the magnetic flux density of the upstream peak P1 (requirement (F)), so that the position where the magnetic flux line of the control magnetic pole N1 extends in the normal direction can be shifted to the downstream side. In this case, in order to achieve the effect, the absolute value |Br| of the peak P2 magnetic flux density downstream of the regulation pole N1 may preferably be greater than the absolute value |Br| of the peak P1 magnetic flux density upstream of the regulation pole N1 by 5 mT or more, more preferably greater by 10 mT or more.

[0160] Incidentally, the magnetic pole S2 disposed downstream of the control magnetic pole N1 is a developing magnetic pole in many cases, but it may also be preferably a feeding magnetic pole as in the present embodiment. This is because: the developing magnetic pole is an important magnetic pole that determines the image in the developing step, and therefore has a low degree of freedom to change, while the degree of freedom to change the feeding magnetic pole is relatively high. As described above, the magnetic roller 24m in the present embodiment includes seven magnetic poles. Therefore, the magnetic pole disposed downstream of the control magnetic pole N1 can be easily set as the feeding magnetic pole S2. However, even when the magnetic pole disposed downstream of the control magnetic pole N1 is a developing magnetic pole, the present embodiment is also applicable to the developing magnetic pole.

[0161] [Layout of control components (requirements (C))]

[0162] As for the arrangement position of the regulating member 25, it has been described above that by arranging the regulating member 25 at a position between the upstream peak P1 of the magnetic flux density Br of the regulated magnetic pole N1 of the magnet roller 24m and the downstream position O of the upstream peak P1 (at which the tangential magnetic flux density Bθ is 0), even when the position of the regulating member 25 deviates, the developer amount fluctuation can be suppressed. That is, with respect to the rotation direction of the developing sleeve 24, the regulating member 25 is arranged to oppose the position between the upstream peak P1 and the position O at which the tangential magnetic flux density Bθ is 0 (requirement (C)).

[0163] exist Figure 8, the arrangement position of the pipe member 25 in Embodiment 1 is shown. In Embodiment 1, the pipe member 25 is arranged substantially at the midpoint (224°) between the upstream peak P1 (215°) of the magnetic flux density Br of the regulated magnetic pole N1 and the downstream position O (233°) of the upstream peak P1 (where the tangential magnetic flux density Bθ is 0).

[0164] Here, a line connecting the upstream end position of the free end (regulating portion) of the regulating member 25 opposite to the developing sleeve 24 and the center of the developing sleeve 24 is referred to as the arrangement position of the regulating member 25. The reason for using the upstream end is that the developer amount is actually regulated by the regulating member 25 on the upstream side, and the arrangement of the upstream end of the regulating member 25 is important.

[0165] There are also cases where the cross-sectional shape of the regulating member 25 is not rectangular. Basically, the position of the free end of the regulating member 25 relative to the developing sleeve 24 is called the relative position; and in the case where the regulating member 25 has a plurality of free ends relative to the rotation direction of the developing sleeve 24, the position of the free end on the most upstream side is called the relative position. For example, in the case where the cross-sectional shape of the regulating member 25 is circular, the position of the regulating member 25 closest to the developing sleeve 24 is called the relative position.

[0166] The relationship between the arrangement position and the magnetic flux density distribution can be measured in the following manner. Generally, the magnetic roller 24m of the developing sleeve 24 has an axis, the end of the axis has a so-called D-cut shape, and the D-cut portion is fixed to the developing device 20 by a pole determining member to achieve the desired magnetic pole arrangement. The magnetic flux density distribution relative to the D-cut portion (plane angle) of the magnetic roller 24m can be measured by the above-mentioned magnetic field measuring device. On the other hand, when the arrangement position of the regulating member 25 relative to the axial center of the magnetic roller 24m is measured, the relationship between the arrangement position of the regulating member 25 and the magnetic flux density distribution can be known. The arrangement position of the regulating member 25 relative to the axial center of the magnetic roller 24m can be measured using a measuring instrument such as a protractor, but in the case of accurately determining the arrangement position, a general-purpose three-dimensional measuring machine (for example, "CRYSTA-Apex S Series" manufactured by Mitutoyo Corporation) can be used.

[0167] In the case of the present embodiment, by adopting the above-mentioned structure, in the magnetic flux density distribution in which the regulated magnetic pole N1 arranged closest to the regulating member 25 has two maximum values ​​(peak values), the fluctuation of the developer amount regulated by the regulating member 25 can be suppressed. That is, in the case where the above-mentioned requirements (A) to (D) are satisfied, even when the magnetic flux density distribution of the regulated magnetic pole N1 has a two-peak shape, the fluctuation of the developer amount regulated by the regulating member 25 can be suppressed. 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 preferably suppressed. However, in the case where 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 also be suppressed by satisfying the requirements (A), (B), (C), (F) and (H).

[0168] <Second Embodiment>

[0169] In reference Figure 2 At the same time, we will use Fig. 9 The second embodiment is described. In the first embodiment, requirements (A) to (D) are satisfied. On the other hand, in this embodiment, in addition to requirements (A) to (C), requirement (I) described later is also satisfied. Other constructions and actions are similar to those in the first embodiment described above, so descriptions and illustrations of similar constructions are omitted, or are briefly described by adding the same figure marks. In the following, the differences from the first embodiment will be mainly described.

[0170] In the case of this embodiment, among the above requirements (A) to (H), at least requirements (A) to (C) are satisfied. In addition, the following requirement (I) is also satisfied. In addition, it is preferred to satisfy the following requirement (J) and the above requirements (F) and (H).

[0171] (I) The absolute value |Br| of the maximum normal magnetic flux density of the upstream magnetic pole (the extraction magnetic pole S1) is greater than the absolute value |Br| of the upstream peak value P1.

[0172] (J) The difference between the absolute value |Br| of the maximum normal magnetic flux density of the upstream magnetic pole (drawing magnetic pole S1) and the absolute value |Br| of the upstream peak P1 is 5 mT or more.

[0173] like Fig. 9 Embodiment 2 and Embodiment 2' of regulating the magnetic pole N1 in this embodiment will be described while comparing with Comparative Example 1 (described in Embodiment 1). The outlines of the image forming apparatus 1 and the developing device 20 in Embodiment 2 and Embodiment 2' are similar to those in Embodiment 1, so detailed description will be omitted.

[0174] exist Fig. 9In the figure, the normal magnetic flux density Br (solid line) of the regulated magnetic pole N1 in the embodiment 2, the normal magnetic flux density (dotted line) of the regulated magnetic pole N1 in the embodiment 2', and the normal magnetic flux density Br (broken line) in the comparative example 1 are shown. Fig. 9 In the figure, the tangential magnetic flux density Bθ of Example 2, Example 2′ and Comparative Example 1 are also shown together by a bold solid line, a bold dotted dashed line and a bold broken dashed line, respectively, when the downstream side in the rotation direction of the developing sleeve 24 is regarded as the positive side.

[0175] First, Example 2 satisfies the above requirements (A), (B), (C) and (I), and can preferably further satisfy requirement (J). Fig. 9 As shown, the difference between Example 2 and Comparative Example 1 is that the distribution of the normal magnetic flux density Br of the extraction pole S1 arranged upstream of the control pole N1 is different from that in Comparative Example 1.

[0176] Specifically, the maximum value of the extraction pole S1 is larger in Example 2 than in Comparative Example 1. The maximum value of the normal magnetic flux density Br of the extraction pole S1 in Example 2 is 59 mT. That is, the absolute value |Br| of the maximum value of the normal magnetic flux density of the extraction pole S1 is greater than the absolute value |Br| of the magnetic flux density of the upstream peak P1 (requirement (I)).

[0177] When the tangential magnetic flux density Bθ in Comparative Example 1 is compared with the tangential magnetic flux density Bθ in Example 2, it can be seen that the position where the tangential magnetic flux density Bθ is 0 (the position where the magnetic flux line extends in the normal direction) between the two peaks P1 and P2 of the normal magnetic flux density Br of the control pole N1 in Example 2 is offset toward the downstream direction. The results of the investigation of its mechanism will be described below.

[0178] As described in the first embodiment, the position where the magnetic flux lines of the regulated magnetic pole N1 extend in the normal direction is also greatly affected by the relationship between the regulated magnetic pole N1 and the magnetic poles adjacent to the regulated magnetic pole N1. For the magnetic roller 24m in the comparative example 1, the maximum value of the upstream peak P1 of the normal magnetic flux density Br of the regulated magnetic pole N1 is 46mT. On the other hand, the maximum value of the normal magnetic flux density Br of the extraction magnetic pole S1 arranged upstream and adjacent to the regulated magnetic pole N1 is 44mT, so that the maximum value of the upstream peak P1 of the regulated magnetic pole N1 is greater than the maximum value of the extraction magnetic pole S1. Therefore, the magnetic flux lines near the upstream peak P1 of the regulated magnetic pole N1 are relatively difficult to extend toward the upstream extraction magnetic pole S1, but are easy to extend in the normal direction. Therefore, it can be considered that the position where the magnetic flux lines of the regulated magnetic pole N1 extend in the normal direction is easy to deviate to the upstream side where the upstream peak P1 is located.

[0179] On the other hand, for the magnetic roller 24m in Example 2, the maximum value of the upstream peak P1 of the normal magnetic flux density Br of the regulated magnetic pole N1 is 46mT, while the maximum value of the normal magnetic flux density Br of the extraction magnetic pole S1 arranged upstream and adjacent to the regulated magnetic pole N1 is 59mT, so that the maximum value of the upstream peak P1 of the regulated magnetic pole N1 is smaller than the maximum value of the extraction magnetic pole S1. Therefore, the magnetic flux lines near the upstream peak P1 of the regulated magnetic pole N1 are more likely to extend toward the upstream extraction magnetic pole S1, and are not easy to extend in the normal direction. Therefore, it can be considered that the position where the magnetic flux lines of the regulated magnetic pole N1 extend in the normal direction is likely to shift to the downstream side where the downstream peak P2 is located.

[0180] When the position where the magnetic flux lines of the regulated magnetic pole N1 extend along the normal direction (i.e., the position where the tangential magnetic flux density Bθ is 0) is offset toward the downstream side, the area where the tangential magnetic flux density Bθ is negative (in which the developer amount changes less) can be enlarged, thereby expanding the pole position range.

[0181] From the above, it can be seen that the maximum value of the normal magnetic flux density Br of the adjacent extraction pole S1 located upstream of the regulated magnetic pole N1 is greater than the maximum value of the upstream peak P1 of the normal magnetic flux density Br of the regulated magnetic pole N1, thereby increasing the area where the developer amount variation is small and the tangential magnetic flux density Bθ is negative, and the pole position range can be expanded by arranging the regulated member 25 in this area.

[0182] When the maximum value of the normal magnetic flux density Br of the adjacent extraction pole S1 located upstream of the control pole N1 is greater than the maximum value of the upstream peak P1 of the normal magnetic flux density Br of the control pole N1, a certain effect can be obtained; but in order to obtain a sufficient effect, the former maximum value can preferably be greater than the latter maximum value by more than 5mT, and more preferably greater than 10mT to obtain a further effect. That is, the difference between the absolute value |Br| of the normal magnetic flux density of the extraction pole S1 and the absolute value |Br| of the normal magnetic flux density of the upstream peak P1 can be preferably greater than 5mT (requirement (J)), and further preferably greater than 10mT. In Example 2, the difference is 13mT. In this way, in Example 2, compared with Comparative Example 1, the area where the developer amount changes little and the tangential magnetic flux density Bθ is negative can be increased, and the pole position range can be expanded by arranging the control member 25 in this area.

[0183] When the maximum value of the normal magnetic flux density Br of the adjacent extraction magnetic pole S1 located upstream of the control magnetic pole N1 is too large compared to the maximum value of the upstream peak P1 of the normal magnetic flux density Br of the control magnetic pole N1, the change of Bθ may become large, so it is preferable to suppress the above difference to a range below 50mT. In other words, the difference between the absolute value |Br| of the normal magnetic flux density of the extraction magnetic pole S1 and the absolute value |Br| of the normal magnetic flux density of the upstream peak P1 can be preferably 50mT or less.

[0184] Incidentally, in Example 2, similarly to Comparative Example 1, the maximum value of the downstream peak P2 (43 mT) is smaller than the maximum value of the upstream peak P1 (46 mT) for the normal magnetic flux density Br of the pipe pole N1. That is, Example 2 does not satisfy requirement (F).

[0185] Next, in addition to satisfying the above-mentioned requirements (A), (B), (C) and (I), embodiment 2' also satisfies requirement (F). Incidentally, in addition to this, embodiment 2' may preferably further satisfy requirement (J). In such embodiment 2', similar to embodiment 2, the maximum value of the normal magnetic flux density Br of the adjacent extraction magnetic pole S1 located upstream of the regulated magnetic pole N1 is greater than the maximum value of the upstream peak P1 of the normal magnetic flux density Br of the regulated magnetic pole N1 (requirement (I)). At the same time, as in embodiment 1, for the normal magnetic flux density Br of the regulated magnetic pole N1, the maximum value of the downstream peak P2 is greater than the maximum value of the upstream peak P1 (requirement (F)). This is different from embodiment 2.

[0186] For the normal magnetic flux density Br of the control pole N1 in embodiment 2', the maximum value of the upstream peak P1 is 42mT, and the maximum value of the downstream peak P2 is 53mT. Incidentally, the maximum value of the magnetic flux density Br of the extraction pole S1 in embodiment 2' is 59mT, which is the same as that in embodiment 2.

[0187] In Example 2', the effect of Example 1 is added to the effect of Example 2, so it is expected that the position where the tangential magnetic flux density Bθ is 0 between the two peaks P1 and P2 of the normal magnetic flux density Br of the control magnetic pole N1 (the position where the magnetic flux lines extend along the normal direction) will be further shifted toward the downstream direction. Fig. 9 By comparing the tangential magnetic flux density Bθ between Example 2 and Example 2', it can be seen that in the case of Example 2', the position where the tangential magnetic flux density Bθ is 0 between the two peak values ​​P1 and P2 of the normal magnetic flux density Br of the regulated magnetic pole N1 (i.e., the position where the magnetic flux lines extend along the normal direction) is further offset toward the downstream direction.

[0188] With the above-described embodiment, by adopting the above-described structure, in the magnetic flux density distribution in which the regulating magnetic pole N1 disposed closest to the regulating member 25 has two maximum values ​​(peaks), fluctuations in the developer amount regulated by the regulating member 25 can be suppressed.

[0189] <Third Embodiment>

[0190] In reference Figure 2 At the same time, we will use Fig.10The third embodiment is described. In the first embodiment, requirements (A) to (D) are satisfied. On the other hand, in this embodiment, in addition to satisfying requirements (A) to (C), requirement (K) described later is also satisfied. Other constructions and actions are similar to those in the first embodiment described above, so descriptions and illustrations of similar constructions are omitted, or are briefly described by adding the same figure marks. In the following, the differences from the first embodiment will be mainly described.

[0191] In the case of the present embodiment, among the above requirements (A) to (H), at least requirements (A) to (C) are satisfied. In addition, the following requirement (K) is also satisfied. In addition, it is preferred to satisfy the following requirement (L) and the above requirement (F). However, in the present embodiment, the above requirement (H) is not satisfied.

[0192] (K) The absolute value |Br| of the maximum normal magnetic flux density of the upstream magnetic pole (the extraction magnetic pole S1) is greater than the absolute value |Br| of the normal magnetic flux density of the downstream magnetic pole (the feed magnetic pole S2).

[0193] (L) The difference between the absolute value |Br| of the maximum normal magnetic flux density of the upstream magnetic pole (the extraction magnetic pole S1) and the absolute value |Br| of the normal magnetic flux density of the downstream magnetic pole (the feed magnetic pole S2) is 5 mT or more.

[0194] In such Fig.10 While comparing with Comparative Example 1 (described in Embodiment 1), Embodiment 3 and Embodiment 3' of regulating the magnetic pole N1 in this embodiment will be described. The outlines of the image forming apparatus 1 and the developing device 20 in Embodiment 3 and Embodiment 3' are similar to those in Embodiment 1, so detailed description will be omitted.

[0195] exist Fig.10 In FIG. 1 , the normal magnetic flux density Br (solid line) of the regulated magnetic pole N1 of the present embodiment in the embodiment 3, the normal magnetic flux density (dotted line) of the regulated magnetic pole N1 of the present embodiment in the embodiment 3′, and the normal magnetic flux density Br (broken line) in the comparative example 1 are shown. Fig.10 In the figure, when the downstream side in the rotation direction of the developing sleeve 24 is taken as the positive side of the θ axis, the tangential magnetic flux density Bθ of Example 3, Example 3′ and Comparative Example 1 are also shown together by a bold solid line, a bold dotted line and a bold broken line.

[0196] First, Example 3 satisfies the above requirements (A), (B), (C) and (K), and can preferably further satisfy requirement (L). Fig.10 As shown, the difference between Example 3 and Comparative Example 1 is that the normal magnetic flux density Br distribution of each of the extraction pole S1 arranged upstream of the control pole N1 and the feed pole S2 arranged downstream of the control pole N1 is different from the relevant distribution in Comparative Example 1.

[0197] As described in the first embodiment, the position where the magnetic flux lines of the regulated magnetic pole N1 extend in the normal direction is also greatly affected by the relationship between the regulated magnetic pole N1 and the magnetic poles adjacent to the regulated magnetic pole N1. As described above, it can be considered that when the maximum values ​​of the normal magnetic flux density Br of the magnetic poles arranged upstream and downstream of the regulated magnetic pole N1 are compared with each other, it can be seen that the position where the magnetic flux lines of the regulated magnetic pole N1 extend in the normal direction (infinite distance direction) is easily offset in the direction where the magnetic pole with a smaller absolute value of the normal magnetic flux density Br is located.

[0198] For the magnet roller 24m in Comparative Example 1, the maximum value (88mT) of the normal magnetic flux density Br of the feed magnetic pole S2 located downstream of the control magnetic pole N1 is greater than the maximum value (44mT) of the normal magnetic flux density Br of the extraction magnetic pole S1 located upstream of the control magnetic pole N1. Therefore, the position where the magnetic flux lines of the control magnetic pole N1 in Comparative Example 1 extend in the normal direction tends to shift toward the upstream direction where the extraction magnetic pole S1 with a smaller absolute value of the normal magnetic flux density Br is located. In fact, in Comparative Example 1, the position O where the tangential magnetic flux density Bθ is 0 is relatively largely shifted to the upstream side.

[0199] On the other hand, Fig.10 As shown, for the magnet roller 24m in the third embodiment, unlike the case of the first comparative example, the maximum value of the normal magnetic flux density Br (46mT) of the feed magnetic pole S2 located downstream of the control magnetic pole N1 is smaller than the maximum value of the normal magnetic flux density Br (50mT) of the extraction magnetic pole S1 located upstream of the control magnetic pole N1 (requirement (K)). Therefore, the position where the magnetic flux lines of the control magnetic pole N1 in the third embodiment extend in the normal direction is easily offset to the downstream direction where the feed magnetic pole S2 with a smaller absolute value of the normal magnetic flux density Br is located.

[0200] In fact, if Fig.10 As shown, in Example 3, compared with the case of Comparative Example 1, the position O where the tangential magnetic flux density Bθ is 0 is shifted to the downstream side to a greater extent.

[0201] From the above, it can be seen that the maximum value of the normal magnetic flux density Br of the magnetic pole (the feed magnetic pole S2 in this embodiment) located downstream of the regulated magnetic pole N1 and adjacent to it is smaller than the maximum value of the normal magnetic flux density Br of the magnetic pole (the extraction magnetic pole S1 in this embodiment) located upstream of the regulated magnetic pole N1 and adjacent to it, so that the area where the developer amount changes little and the tangential magnetic flux density Bθ is negative can be increased, and by arranging the regulated member 25 in this area, the pole position range can be expanded.

[0202] When the maximum value of the normal magnetic flux density Br of the adjacent magnetic pole (the feed magnetic pole S2 in the present embodiment) arranged downstream of the regulated magnetic pole N1 is smaller than the maximum value of the normal magnetic flux density Br of the regulated magnetic pole N1, a certain effect can be obtained; however, in order to obtain a sufficient effect, the maximum value of the former can preferably be made smaller than the maximum value of the latter by more than 5mT (requirement (L)), and more preferably by more than 10mT to obtain further effect.

[0203] Next, in addition to the above-mentioned requirements (A), (B), (C), and (K), embodiment 3' also satisfies requirement (F). Incidentally, in addition to this, embodiment 3' may preferably further satisfy requirement (L). Incidentally, in Fig.10 , the magnetic roller 24m in the embodiment 3' is shown. In the embodiment 3', similar to the embodiment 3, the maximum value of the normal magnetic flux density Br of the magnetic pole (the feed magnetic pole S2 in this embodiment) disposed downstream and adjacent to the regulated magnetic pole N1 is smaller than the maximum value of the normal magnetic flux density Br of the magnetic pole (the extraction magnetic pole S1 in this embodiment) disposed upstream and adjacent to the regulated magnetic pole N1 (requirement (K)). At the same time, as in the embodiment 1, for the absolute value |Br| of the normal magnetic flux density of the regulated magnetic pole N1, the downstream peak value P2 is made greater than the upstream peak value P1 (requirement (F)).

[0204] For the normal magnetic flux density Br of the pipe magnetic pole N1 in Example 3', the maximum value of the upstream peak P1 is 42 mT, and the maximum value of the downstream peak P2 is 53 mT.

[0205] With the above-described embodiment, by adopting the above-described structure, in the magnetic flux density distribution in which the regulating magnetic pole N1 disposed closest to the regulating member 25 has two maximum values ​​(peaks), fluctuation in the developer amount regulated by the regulating member 25 can be suppressed.

[0206] <Other embodiments>

[0207] In the above-mentioned embodiments, the present invention is described as being applied to a developing device used in a tandem imaging device. However, the present invention may also be applicable to developing devices used in other types of imaging devices. In addition, the imaging device is not limited to an imaging device for full-color images, but may also be an imaging device for monochrome images or an imaging device for single-color (single-color) images. Alternatively, by adding necessary devices, equipment, and housing structures, etc., the imaging device may be implemented in various applications, such as printers, various printing presses, copiers, fax machines, and multifunction machines.

[0208] While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all modifications and equivalent structures and functions.

Claims

1. A developing device, comprising: a developing container configured to contain a developer including a toner and a carrier; a rotatable developing member configured to carry a developer and feed the developer to a developing position; a magnet non-rotatably and fixedly disposed within the rotatable developing member and having a pipe pole; and a regulating portion configured to regulate the amount of the developer carried on the rotatable developing member by the magnetic force of the regulating pole; wherein, with respect to the rotation direction of the rotatable developing member, a minimum position at which the normal magnetic flux density of the control pole relative to the outer peripheral surface of the rotatable developing member is a minimum value is located downstream of a first maximum position at which the normal magnetic flux density of the control pole relative to the outer peripheral surface of the rotatable developing member is a first maximum value, and is located upstream of a second maximum position at which the normal magnetic flux density of the control pole relative to the outer peripheral surface of the rotatable developing member is a second maximum value; wherein an angle between the first maximum position and the second maximum position is greater than 20° and less than 50° relative to a rotation direction of the rotatable developing member; wherein, relative to the rotation direction of the rotatable developing member, the position at which the tangential magnetic flux density of the pipe pole relative to the outer peripheral surface of the rotatable developing member is zero is between the first maximum position and the second maximum position; wherein, relative to the rotation direction of the rotatable developing member, the relative position of the regulating portion relative to the outer peripheral surface of the rotatable developing member is between a first maximum position and a position where the tangential magnetic flux density of the regulating pole relative to the outer peripheral surface of the rotatable developing member is zero; and Wherein, relative to the rotation direction of the rotatable developing member, the position where the tangential magnetic flux density of the control pole relative to the outer peripheral surface of the rotatable developing member is zero is within the range of ±2° of the midpoint between the first maximum position and the second maximum position, or downstream of this range.

2. The developing device according to claim 1, wherein: With respect to the rotation direction of the rotatable developing member, a position where the pipe pole tangential magnetic flux density relative to the outer peripheral surface of the rotatable developing member is zero is located downstream of a midpoint between the first maximum position and the second maximum position.

3. The developing device according to claim 1 or 2, wherein: With respect to the rotation direction of the rotatable developing member, an angle from the first maximum position to a position where the pipe pole tangential magnetic flux density relative to the outer peripheral surface of the rotatable developing member is zero is 15° or more and less than 50°.

4. The developing device according to claim 1 or 2, wherein: The difference between the absolute value of the first maximum value and the absolute value of the pipe pole normal magnetic flux density relative to the outer peripheral surface of the rotatable developing member at a position where the pipe pole tangential magnetic flux density relative to the outer peripheral surface of the rotatable developing member is zero is 10 mT or less.

5. The developing device according to claim 1 or 2, wherein: The absolute value of the first maximum value is smaller than the absolute value of the second maximum value.

6. The developing device according to claim 1 or 2, wherein: The magnet also includes an upstream magnetic pole disposed adjacent to the control pole on the upstream side of the control pole relative to the rotation direction of the rotatable developing member, and a downstream magnetic pole disposed adjacent to the control pole on the downstream side of the control pole relative to the rotation direction of the rotatable developing member; as well as Among them, relative to the rotation direction of the rotatable developing member, the absolute value of the maximum normal magnetic flux density of the upstream side magnetic pole relative to the outer peripheral surface of the rotatable developing member is smaller than the absolute value of the maximum normal magnetic flux density of the downstream side magnetic pole relative to the outer peripheral surface of the rotatable developing member.

7. A developing device, comprising: a developing container configured to contain a developer including a toner and a carrier; a rotatable developing member configured to carry a developer and feed the developer to a developing position; a magnet non-rotatably and fixedly disposed in the rotatable developing member and having a control pole, an upstream magnetic pole disposed adjacent to the control pole on the upstream side of the control pole relative to the rotation direction of the rotatable developing member, and a downstream magnetic pole disposed adjacent to the control pole on the downstream side of the control pole relative to the rotation direction of the rotatable developing member; and a regulating portion configured to regulate the amount of the developer carried on the rotatable developing member by the magnetic force of the regulating pole; wherein, with respect to the rotation direction of the rotatable developing member, the minimum position at which the normal magnetic flux density of the control pole relative to the outer peripheral surface of the rotatable developing member is the minimum value is located downstream of the first maximum position at which the normal magnetic flux density of the control pole relative to the outer peripheral surface of the rotatable developing member is the first maximum value, and is located upstream of the second maximum position at which the normal magnetic flux density of the control pole relative to the outer peripheral surface of the rotatable developing member is the second maximum value; wherein an angle between the first maximum position and the second maximum position is greater than 20° and less than 50° relative to a rotation direction of the rotatable developing member; wherein, relative to the rotation direction of the rotatable developing member, the position at which the tangential magnetic flux density of the pipe pole relative to the outer peripheral surface of the rotatable developing member is zero is between the first maximum position and the second maximum position; wherein, relative to the rotation direction of the rotatable developing member, the relative position of the regulating portion relative to the outer peripheral surface of the rotatable developing member is between a first maximum position and a position where the tangential magnetic flux density of the regulating pole relative to the outer peripheral surface of the rotatable developing member is zero; wherein, with respect to the rotation direction of the rotatable developing member, an absolute value of a maximum value of a normal magnetic flux density of a magnetic pole on an upstream side relative to an outer peripheral surface of the rotatable developing member is smaller than an absolute value of a maximum value of a normal magnetic flux density of a magnetic pole on a downstream side relative to the outer peripheral surface of the rotatable developing member; and The absolute value of the first maximum value is smaller than the absolute value of the second maximum value.

8. A developing device, comprising: a developing container configured to contain a developer including a toner and a carrier; a rotatable developing member configured to carry a developer and feed the developer to a developing position; a magnet non-rotatably and fixedly disposed in the rotatable developing member and having a control pole and an upstream side magnetic pole disposed adjacent to the control pole on an upstream side of the control pole relative to the rotation direction of the rotatable developing member; and a regulating portion configured to regulate the amount of developer carried on the rotatable developing member by the magnetic force of the regulating pole, wherein, with respect to the rotation direction of the rotatable developing member, the minimum position at which the normal magnetic flux density of the control pole relative to the outer peripheral surface of the rotatable developing member is the minimum value is located downstream of the first maximum position at which the normal magnetic flux density of the control pole relative to the outer peripheral surface of the rotatable developing member is the first maximum value, and is located upstream of the second maximum position at which the normal magnetic flux density of the control pole relative to the outer peripheral surface of the rotatable developing member is the second maximum value; wherein an angle between the first maximum position and the second maximum position is greater than 20° and less than 50° relative to a rotation direction of the rotatable developing member; wherein, relative to the rotation direction of the rotatable developing member, the position at which the tangential magnetic flux density of the pipe pole relative to the outer peripheral surface of the rotatable developing member is zero is between the first maximum position and the second maximum position; wherein, relative to the rotation direction of the rotatable developing member, the relative position of the regulating portion relative to the outer peripheral surface of the rotatable developing member is between a first maximum position and a position where the tangential magnetic flux density of the regulating pole relative to the outer peripheral surface of the rotatable developing member is zero; and Here, an absolute value of a maximum value of the normal magnetic flux density of the upstream magnetic pole relative to the outer peripheral surface of the rotatable developing member is greater than an absolute value of the first maximum value.

9. The developing device according to claim 8, wherein: A difference between an absolute value of the normal magnetic flux density of the upstream magnetic pole with respect to the outer peripheral surface of the rotatable developing member and an absolute value of the first maximum value is 5 mT or more.

10. The developing device according to claim 8, wherein: The absolute value of the first maximum value is smaller than the absolute value of the second maximum value.

11. The developing device according to claim 10, wherein: The magnet further includes a downstream side magnetic pole disposed adjacent to the regulating pole on the downstream side of the regulating pole with respect to the rotation direction of the rotatable developing member; and The absolute value of the maximum value of the normal magnetic flux density of the upstream magnetic pole relative to the outer peripheral surface of the rotatable developing member is smaller than the absolute value of the maximum value of the normal magnetic flux density of the downstream magnetic pole relative to the outer peripheral surface of the rotatable developing member.

12. A developing device, comprising: a developing container configured to contain a developer including a toner and a carrier; a rotatable developing member configured to carry a developer and feed the developer to a developing position; a magnet non-rotatably and fixedly disposed in the rotatable developing member and having a control pole, an upstream magnetic pole disposed adjacent to the control pole on the upstream side of the control pole relative to the rotation direction of the rotatable developing member, and a downstream magnetic pole disposed adjacent to the control pole on the downstream side of the control pole relative to the rotation direction of the rotatable developing member; and a regulating portion configured to regulate the amount of developer carried on the rotatable developing member by the magnetic force of the regulating pole, wherein, with respect to the rotation direction of the rotatable developing member, the minimum position at which the normal magnetic flux density of the control pole relative to the outer peripheral surface of the rotatable developing member is the minimum value is located downstream of the first maximum position at which the normal magnetic flux density of the control pole relative to the outer peripheral surface of the rotatable developing member is the first maximum value, and is located upstream of the second maximum position at which the normal magnetic flux density of the control pole relative to the outer peripheral surface of the rotatable developing member is the second maximum value; wherein an angle between the first maximum position and the second maximum position is greater than 20° and less than 50° relative to a rotation direction of the rotatable developing member; wherein, relative to the rotation direction of the rotatable developing member, the position at which the tangential magnetic flux density of the pipe pole relative to the outer peripheral surface of the rotatable developing member is zero is between the first maximum position and the second maximum position; wherein, relative to the rotation direction of the rotatable developing member, the relative position of the regulating portion relative to the outer peripheral surface of the rotatable developing member is between a first maximum position and a position where the tangential magnetic flux density of the regulating pole relative to the outer peripheral surface of the rotatable developing member is zero; and Among them, relative to the rotation direction of the rotatable developing member, the absolute value of the maximum normal magnetic flux density of the upstream magnetic pole relative to the outer peripheral surface of the rotatable developing member is greater than the absolute value of the maximum normal magnetic flux density of the downstream magnetic pole relative to the outer peripheral surface of the rotatable developing member.

13. The developing device according to claim 12, wherein: The difference between the absolute value of the normal magnetic flux density of the upstream magnetic pole relative to the outer peripheral surface of the rotatable developing member and the absolute value of the normal magnetic flux density of the downstream magnetic pole relative to the outer peripheral surface of the rotatable developing member is 5 mT or more.

14. The developing device according to claim 12, wherein: The absolute value of the first maximum value is smaller than the absolute value of the second maximum value.

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