JP2009003076A - Developing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device for developing a latent image on an image carrier which suppresses deterioration in the developer, will not cause image fogging, and allows proper image to be formed over a long period, and to provide an image forming apparatus. <P>SOLUTION: A regulating member, disposed adjacent to a developer carrier, for regulating the layer thickness of the developer carried on the surface of the developer carrier, is constituted of a non-magnetic member and two magnetic members separately, disposed upstream and downstream from the non-magnetic member in the direction of conveying the developer on the developer carrier, and the part approaching closest to the developer carrier becomes the non-magnetic member. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a developing device and an image forming apparatus for developing a latent image on an image carrier.

  2. Description of the Related Art Conventionally, in an image forming apparatus using an electrophotographic method, a method of developing an image carrier surface on which an electrostatic latent image is formed by a developing device using a developer containing a magnetic component is known.

  As such a developing device, there are a magnetic one-component developing system using magnetic toner and a two-component developing system using non-magnetic toner and a magnetic carrier, both of which include a developer carrier having a plurality of magnets inside. I have.

  The developer carrying member carries the developer on its surface by a built-in magnet and is regulated to have a constant layer thickness by a regulating member. The regulating member is generally arranged with a certain gap between it and the surface of the developer carrier, and by adjusting the gap, a layer thickness of the required developer amount is formed on the developer carrier. The amount of developer is regulated.

  By the way, when such a developing device is used for a long time, there is a problem that the developer deteriorates.

  Specifically, the developer deterioration is an alteration of the developer surface. For example, in a two-component developing device, there is carrier deterioration. One of the carrier deteriorations is a phenomenon in which fine particles or toner fine particles that have been externally added to the toner over a long period of time accumulate in the developing device and adhere to the carrier surface. Such adhesion of foreign matter to the surface of the carrier obstructs contact between the toner and the carrier and reduces the charge amount of the toner. The carrier is generally a resin coated core material such as ferrite or magnetite. These coating materials are processed in order to adjust the resistance of the carrier and to make the toner easy to be charged. Wear of the coating layer also causes carrier deterioration, resulting in a decrease in the charge amount of the toner. The developer deterioration not only deteriorates the carrier but also the toner. The toner surface is externally added for the purpose of improving fluidity and adjusting the chargeability. However, as the toner is used, it is detached or buried in the surface of the toner base material, and the charge amount of the toner decreases. To do. It has been found that the main cause of the deterioration of the developer is a restriction member provided on the developer carrier, and stress such as compression or rubbing is applied to the developer in the restriction portion.

  There is a demand for a developing device that can suppress the deterioration of the developer by reducing the stress of the restricting portion and obtain a stable toner charge amount over a long period of time.

In Patent Document 1, a magnetic member is used for the restricting portion, and the tip surface of the magnetic member facing the developer carrier is moved closer to the developing sleeve surface toward the downstream side in the rotation direction of the developing sleeve. It has been proposed as a method that can widen the area of the magnetic brush formed between the front end surface and the developing sleeve and reduce stress on the developer.
JP-A-11-161007

  However, even with the method of Patent Document 1, a sufficiently durable developing device cannot be obtained, and image fogging due to poorly charged toner caused by developer deterioration occurs due to long-term use.

  The present invention provides a developing device that develops a latent image on an image bearing member, suppresses the deterioration of the developer, does not cause image fogging, and can perform good image formation over a long period of time, and an image forming device. Objective.

  In order to solve the above problems, the present invention has the following features.

1.
A developer carrying body having a magnet inside and carrying a developer on the surface;
A regulating member that is disposed close to the developer carrying member and regulates the layer thickness of the developer carried on the surface of the developer carrying member;
The regulating member is a non-magnetic member,
Two magnetic members disposed on the upstream side and the downstream side in the developer transport direction on the developer carrier relative to the non-magnetic member,
The developing device characterized in that a portion closest to the developer carrying member is the nonmagnetic member.

2.
A tip portion where the non-magnetic member faces the surface of the developer carrier has a surface that approaches the surface of the developer carrier toward the downstream side of the developer carrier in the developer transport direction. 2. The developing device according to 1.

3.
3. The developing device according to 2, wherein the tip end part is composed of two surfaces whose tip end angle is an obtuse angle.

4).
3. The developing device according to 2, wherein the tip portion is a convex curved surface.

5).
The surface of the magnetic member disposed on the upstream side of the non-magnetic member that faces the developer carrying member approaches the surface of the developer carrying member toward the downstream in the developer carrying direction of the developer carrying member. 5. The developing device according to any one of 1 to 4, which has a surface.

6).
6. An image carrier, an electrostatic latent image forming unit that forms an electrostatic latent image on the image carrier, and any one of 1 to 5 for developing the electrostatic latent image on the image carrier An image forming apparatus comprising: the developing device described above.

  According to the present invention, the regulating member that is disposed in proximity to the developer carrying member and regulates the layer thickness of the developer carried on the surface of the developer carrying member includes the nonmagnetic member and the developer carrying member with respect to the nonmagnetic member. And two magnetic members disposed on the upstream side and the downstream side in the developer conveying direction on the body, and the portion closest to the developer carrying member is a non-magnetic member. By doing so, it is possible to reduce stress on the developer when the developer on the developer carrying member is regulated by the regulating member, to suppress the deterioration of the developer, and to prevent image fogging for a long period of time. And stable toner charge amount. Therefore, it is possible to provide a long-life developing device and image forming apparatus capable of forming a good image.

  FIG. 1 shows an embodiment of an image forming apparatus according to the present invention. This image forming apparatus is a printer that forms an image by transferring a toner image formed on an image carrier 1 to a transfer medium P such as paper by an electrophotographic method. This image forming apparatus has an image carrier 1 for carrying an image, and a charging member 3 as a charging unit for charging the image carrier 1 and an image carrier around the image carrier 1. A developing device 2 that develops an electrostatic latent image on 1, a transfer roller 4 for transferring a toner image on the image carrier 1, and a cleaning member 5 for removing residual toner on the image carrier 1 include an image carrier. It arranges in order along the rotation direction of the body 1.

  The image carrier 1 is charged by the charging member 3 and then exposed by an exposure device 6 equipped with a laser emitter or the like at the position E in the figure, and an electrostatic latent image is formed on the surface thereof. . The developing device 2 develops the electrostatic latent image into a toner image. The transfer roller 4 transfers the toner image on the image carrier 1 onto the transfer medium P, fixes it with the fixing device 90, and discharges it in the direction of the arrow in the figure. The cleaning member 5 removes the residual toner on the image carrier 1 after the transfer by the mechanical force. The image carrier 1, the charging member 3, the transfer roller 4, the cleaning blade 5, the exposure device 6, and the like used in the image forming apparatus may arbitrarily use a known electrophotographic technique. For example, although a charging roller is shown in the drawing as the charging means, a charging device that is not in contact with the image carrier 1 may be used. For example, the cleaning member may not be provided.

  Next, the developing device used in the image forming apparatus of the present invention will be described in more detail with reference to FIG. In the present embodiment, the developing device 2 includes a developer tank 13 that contains a two-component developer 12 including a carrier and toner, and a developer carrier that supports and conveys the developer supplied from the developer tank 13 to the surface. A developing roller 9 and a regulating member 11 arranged with a certain distance from the developing roller 9 are provided.

  The developing roller 9 includes a magnet roller 8 inside, and a cylindrical sleeve roller 7 having a diameter of 18 is provided outside thereof so as to be rotatable independently of the magnet roller 8. The magnet roller 8 has five magnetic poles (N1, S1, N2, S2, N3) on the peripheral surface and is fixed, and the sleeve roller 7 is made of a nonmagnetic material such as aluminum.

  The developer 12 in the developer tank 13 is agitated by the agitating members 14 and 15 and conveyed toward the regulating member 11. The conveyed developer 12 is attracted to the magnetic pole N <b> 1 of the developing roller 9 and is attracted to the surface of the developing roller 9.

  Of the five magnetic poles of the magnet roller 8, the main magnetic pole S <b> 2 is disposed at a position facing the image carrier 1, and has the same polarity for generating a repulsive magnetic field for peeling off the developer on the sleeve roller 7. The portions N1 and N3 are disposed at positions facing the developer tank 13 side of the developer tank 13.

  The developer adsorbed on the surface of the sleeve roller 7 by the magnetic pole N1 is regulated by the regulating member 11 having a predetermined gap from the surface of the sleeve roller 7 to regulate the developer amount. The magnetic flux density in the normal direction of the surface of the sleeve roller 7 facing N1 can be determined as appropriate, but in this embodiment, it is 50 mT.

  Further, the peripheral speed of the image carrier 1 and the peripheral speed of the sleeve roller 7 may be determined as appropriate, but in this embodiment, the peripheral speed of the image carrier is 100 mm / s and the peripheral speed of the sleeve roller 7 is 150 mm / s. It was.

  The restriction member 11 will be described with reference to FIG. The restricting member 11 faces the magnetic pole N1 of the magnet roller 8 included in the developing roller 9 and is disposed with a predetermined distance d from the sleeve roller 7. The restricting member 11 includes a nonmagnetic member 113 and two magnetic members 111 and 112 disposed on the upstream side and the downstream side in the developer transport direction on the developing roller 9 with respect to the nonmagnetic member 113. The member corresponding to the distance d closest to the developing roller 9 is a nonmagnetic member 113. As the material of the magnetic members 111 and 112, SUS430 was used, and the plate thickness of the upstream magnetic member 112 was 0.3 to 1.0 mm. As the nonmagnetic member 113, SUS304 was used, and the plate thickness was 1.0 to 3.0 mm. The plate thickness of the magnetic member on the downstream side was 1.0 to 3.0 mm. The material of the magnetic member is not limited to SUS430, and any material having magnetism may be used. Also, the nonmagnetic material is not limited to SUS304, and any nonmagnetic material can be used. The plate | board thickness of the magnetic members 111 and 112 and the nonmagnetic member 113 should just be in the said range.

  By using such a restricting member 11, it is possible to reduce stress on the developer in the restricting portion and to stably regulate the developer amount. This is presumably because the trimming position at the restricting portion is a non-magnetic material, and the magnetic force at the trimming position is weakened by disposing the magnetic material on the upstream and downstream sides, thereby reducing the stress on the developer. Further, in order to weaken the magnetic force on the developer, the magnetic flux density of N1 may be lowered. However, the amount of developer that can be attracted to the upstream side of the regulating portion is reduced, and a stable developer can be conveyed. become unable. According to the regulating member 11 of the present invention, it is possible to reduce stress at the regulating portion without weakening the developer conveying force.

  Further, it is preferable that the tip portion of the nonmagnetic member 113 facing the surface of the developing roller 9 has a surface that approaches the surface of the developing roller 9 toward the downstream side in the developer transport direction of the developing roller 9.

  With such a shape, the developer filling density increases toward the position where the ears are cut, and the amount of the developer can be regulated more stably. At this time, the angle θ1 of the tip of the nonmagnetic member 113 is preferably composed of two surfaces 113a and 113b having obtuse angles as shown in FIG. Moreover, it is preferable that a front-end | tip part consists of a convex-shaped curved surface like FIG.

  Further, as shown in FIG. 5, the regulating member 11 is developed such that the surface of the magnetic member 112 disposed on the upstream side of the nonmagnetic member 113 that faces the developing roller 9 is developed downstream in the developer transport direction of the developing roller 9. It is preferable to have a surface 112a (inclination angle θ2) that approaches the surface of the roller 9. By having such an inclined surface, the developer pool on the upstream side of the regulating portion can be formed more stably, and the amount of the stable developer can be regulated. In addition, if the length of the inclined surface is too short, there is no effect, and if it is too long, the dead space increases. In FIG. 5, the magnetic member is bent to form the surface. However, for example, the tip of a 5 mm magnetic plate may be cut obliquely.

  Returning to FIG. 2, the developer tank 13 is formed of a casing 19, and contains stirring members 14 and 15 for stirring the developer 12 therein. An ATDC (Automatic Toner Density Control) sensor 18 for detecting toner density is disposed at a position of the casing 19 facing the stirring member 15.

  The developing device 2 usually has a replenishing unit 16 for replenishing the developer tank 13 with the toner consumed by the development. The replenishment toner 17 is appropriately replenished through the replenishment unit 16 according to the output from the ATDC sensor.

  The mixing ratio of the toner and the carrier may be adjusted so as to obtain a desired toner charge amount. The toner ratio is 3 to 50% by mass based on the total amount of the toner and the carrier. Although depending on the ratio of the surface area to be used, 5 to 20% by mass is preferable.

  As a developer used in the developing device, a two-component developer including a carrier and a toner is used.

  The toner is not particularly limited, and a commonly used known toner can be used. The binder resin contains a colorant or, if necessary, a charge control agent or a release agent, and is added externally. What processed the agent can be used. The toner particle diameter is not limited to this, but is preferably about 3 to 15 μm.

  In manufacturing such a toner, it can be manufactured by a publicly known method, for example, a pulverization method, an emulsion polymerization method, a suspension polymerization method, or the like.

  The binder resin used in the toner is not limited to this. For example, styrene resin (monopolymer or copolymer containing styrene or a styrene-substituted product), polyester resin, epoxy resin, vinyl chloride Resins, phenol resins, polyethylene resins, polypropylene resins, polyurethane resins, silicone resins and the like can be mentioned. It is preferable to use those having a softening temperature in the range of 80 to 160 ° C. and those having a glass transition point in the range of 50 to 75 ° C., depending on the resin alone or the composite.

  Moreover, as a coloring agent, the publicly known well-known thing can be used, for example, carbon black, aniline black, activated carbon, magnetite, benzine yellow, permanent yellow, naphthol yellow, phthalocyanine blue, first sky blue, ultra Marine blue, rose bengal, lake red, or the like can be used, and it is generally preferable to use 2 to 20 parts by mass with respect to 100 parts by mass of the binder resin.

  As the charge control agent, known ones can be used. Examples of the charge control agent for positively chargeable toners include nigrosine dyes, quaternary ammonium salt compounds, triphenylmethane compounds, imidazoles. System compounds and polyamine resins. Examples of the charge control agent for negatively chargeable toners include metal-containing azo dyes such as Cr, Co, Al, and Fe, salicylic acid metal compounds, alkyl salicylic acid metal compounds, and curlyx arene compounds. In general, the charge control agent is preferably used at a ratio of 0.1 to 10 parts by mass with respect to 100 parts by mass of the binder resin.

  In addition, as the above-mentioned mold release agent, known ones that are generally used can be used. For example, polyethylene, polypropylene, carnauba wax, sazol wax and the like can be used alone or in combination of two or more. In general, it is preferably used at a ratio of 0.1 to 10 parts by mass with respect to 100 parts by mass of the binder resin.

  Also, as the above external additives, publicly known ones can be used, and as fluidity improvers, for example, inorganic fine particles such as silica, titanium oxide, aluminum oxide, acrylic resins, styrene resins, Resin fine particles such as a silicone resin and a fluororesin can be used, and it is particularly preferable to use one that has been hydrophobized with a silane coupling agent, a titanium coupling agent, silicon oil, or the like. Such a fluidizing agent is added at a ratio of 0.1 to 5 parts by mass with respect to 100 parts by mass of the toner. The number average primary particle size of the external additive is preferably 10 to 100 nm. Further, as the external additive, both those charged to the same polarity as the toner and those charged to the opposite polarity to the toner can be used.

  The carrier is not particularly limited, and a commonly used carrier can be used, and a binder type carrier, a coat type carrier, and the like can be used. Although it is not limited to this as a carrier particle size, 15-100 micrometers is preferable.

  The binder type carrier is obtained by dispersing magnetic fine particles in a binder resin, and positive or negative chargeable fine particles can be fixed to the carrier surface or a surface coating layer can be provided. Charging characteristics such as polarity of the binder type carrier can be controlled by the material of the binder resin, the chargeable fine particles, and the type of the surface coating layer.

  Examples of the binder resin used for the binder-type carrier include thermoplastic resins such as vinyl resins, polyester resins, nylon resins, polyolefin resins, and the like typified by polystyrene resins, and curable resins such as phenol resins. .

  Magnetic fine particles of the binder type carrier include spinel ferrite such as magnetite and gamma iron oxide, and magnets such as spinel ferrite and barium ferrite containing one or more metals other than iron (Mn, Ni, Mg, Cu, etc.). Plumbite type ferrite, iron or alloy particles having an oxide layer on the surface can be used. The shape may be granular, spherical, or needle-shaped. In particular, when high magnetization is required, it is preferable to use iron-based ferromagnetic fine particles. In consideration of chemical stability, it is preferable to use ferromagnetic fine particles of magnetoplumbite type ferrite such as spinel ferrite and barium ferrite containing magnetite and gamma iron oxide. A magnetic resin carrier having a desired magnetization can be obtained by appropriately selecting the type and content of the ferromagnetic fine particles. The magnetic fine particles are suitably added in an amount of 50 to 90% by mass in the magnetic resin carrier.

  Silicone resin, acrylic resin, epoxy resin, fluorine resin, etc. are used as the surface coating material of the binder type carrier, and these resins are coated on the surface and cured to form a coating layer, thereby providing a charge imparting ability. Can be improved.

  For example, the charging fine particles or the conductive fine particles can be fixed to the surface of the binder type carrier by, for example, mixing the magnetic resin carrier and the fine particles uniformly and adhering the fine particles to the surface of the magnetic resin carrier. By applying a strong impact force and fixing the fine particles so as to be driven into the magnetic resin carrier. In this case, the fine particles are not completely embedded in the magnetic resin carrier, but are fixed so that a part thereof protrudes from the surface of the magnetic resin carrier. As the chargeable fine particles, organic or inorganic insulating materials are used. Specifically, organic insulating fine particles such as polystyrene, styrene copolymers, acrylic resins, various acrylic copolymers, nylon, polyethylene, polypropylene, fluororesin, and cross-linked products thereof may be used as the organic type. Regarding the charge level and polarity, a desired level of charge and polarity can be obtained by a material, a polymerization catalyst, a surface treatment or the like. Further, as the inorganic type, negatively charged inorganic fine particles such as silica and titanium dioxide, and positively charged inorganic fine particles such as strontium titanate and alumina are used.

  On the other hand, a coated carrier is a carrier in which a carrier core particle made of a magnetic material is coated with a resin, and in a coated carrier, similarly to a binder-type carrier, positive or negatively chargeable fine particles are fixed to the carrier surface. it can. Charging characteristics such as polarity of the coat type carrier can be controlled by the type of the surface coating layer and the chargeable fine particles, and the same material as the binder type carrier can be used. In particular, the coating resin can be the same resin as the binder resin of the binder type carrier.

  The flow of the developer 12 in the developing device 2 will be described. The developer 12 inside the developer tank 13 is agitated by the agitating members 14 and 15 and conveyed to the developing roller 9 side. The developer 12 transported to the developing roller 9 side is attracted by the magnetic pole N1 and creates a developer pool upstream of the regulating member 11. When the sleeve roller 7 rotates, the developer on the developing roller 9 is regulated to a predetermined amount of developer when passing through the gap d at the closest portion of the regulating member 11. At this time, by using the regulating member 11 according to the present invention, the developer can be regulated with low stress and the amount can be regulated stably.

  The developer on the developing roller 9 regulated to a certain amount in this way is conveyed to the developing unit facing the image carrier 1 by the rotation of the sleeve roller 7, and the spike is formed by the developing pole S2, The electrostatic latent image on the image carrier 1 is developed to form a toner image.

  Next, the image forming operation will be described in order.

  The surface of the image carrier 1 is charged to about −900 to −500 V by the charging member 3, and then the image portion is exposed by the exposure device 6 to set the potential of the image portion to −10 to −100 V. In this way, an electrostatic latent image is formed on the surface of the image carrier 1.

  The electrostatic latent image formed in this way moves to a position (developing unit) facing the developing roller 9 and is developed by the developing device 2. A developing bias for developing is applied from the power source 100 to the developing roller 9 of the developing device 2. Since the toner in the developer is negatively charged, the developing bias is set between the potential of the image portion and the potential of the background portion. For example, the DC voltage is set to -400V. In order to improve the developing performance, an AC bias may be superimposed on the DC voltage.

  Thus, the toner image on the image carrier 1 developed by the developing device 2 of the present invention was transferred onto the transfer paper P by the transfer roller 4. The transferred toner image on the transfer paper P was fixed on the transfer paper P by the fixing device 90.

  Although the image forming operation as described above was repeated for a long period of time, there was no occurrence of image fogging due to developer deterioration, and a stable and high-quality image could be formed.

  Embodiments of a developing device in an image forming apparatus using electrophotography to which the present invention is applied will be described below.

  Using the developing device 2 having the configuration shown in FIG. 2, a printing durability test was performed using an image forming apparatus in which bizhub C350 manufactured by Konica Minolta was modified. As a developer, a carrier for bizhub C350 (volume average particle diameter of about 33 μm) and toner (volume average particle diameter of about 6.5 μm) manufactured by Konica Minolta Business Technologies, Inc. were used. The surface of the carrier is coated with 3% by mass (about 1 μm) of acrylic resin as a coating agent. The toner ratio in the developer was 8% by mass. However, the toner ratio is the ratio of toner to the total amount of developer.

  A rectangular wave developing bias having an amplitude of 1.4 kV, a DC component of −400 V, a duty ratio of 50%, and a frequency of 2 kHz was applied to the developing roller 9. The background portion potential of the electrostatic latent image formed on the image carrier 1 was −550V, and the image portion potential was −60V. The gap at the closest part between the image carrier 1 and the developing roller 9 was 0.35 mm. As shown in FIG. 6, the magnet roller 8 has a magnetic flux density N1 of 50 mT, S1 of 60 mT, N2 of 60 mT, S2 (development pole) of 110 mT, and N3 of 60 mT as shown in FIG. As the sleeve roller 7, an aluminum roller having an outer diameter of 18 mm was used. The angle between the line connecting the closest part of the regulating member 11 and the center of the developing roller 9 and the line connecting the center of the N1 pole and the center of the developing roller 9 is such that N1 is the sleeve roller 7 as shown in the figure. It was arrange | positioned so that it might become 15 degree | times upstream of the rotation direction.

The regulating members used in the developing device 2 were those in Examples 1 to 6 and Comparative Examples 1 to 5 shown in FIG. As the magnetic members 111 and 112, SUS430 material was used, and as the nonmagnetic member 113, SUS304 material was used. The gap and thickness of the closest part are shown in the figure. The system speed of the image forming apparatus was 100 mm / sec, and the rotational speed of the sleeve roller 7 of the developing roller 9 was 150 mm / sec.
(Example 1)
The restricting member of Example 1 includes a nonmagnetic member having a thickness of 2 mm, a magnetic member having a thickness of 0.3 mm on the upstream side in the rotation direction of the developing roller, and a magnetic member having a thickness of 1 mm on the downstream side. The closest part between the regulating member and the developing roller is the upstream edge of the non-magnetic member in the developing roller rotation direction, the tip shape is flat, and the gap with the developing roller widens toward the downstream in the developing roller rotation direction. did.

In the durability test, an A4 chart with an image area ratio of 5% was copied on 30,000 sheets (A4 landscape paper), and the abrasion of the coat layer of the carrier was evaluated as an index of developer deterioration.
(Example 2)
As Example 2, in Example 1, the closest part is an edge on the downstream side in the developing roller rotation direction of the nonmagnetic member, and the tip part is narrower toward the downstream side in the developing roller rotation direction with a narrow gap with the developing roller. The surface was inclined by 30 degrees. Others were evaluated in the same manner as in Example 1.
(Example 3)
As Example 3, the tip part of the nonmagnetic member in Example 2 was composed of two surfaces with a tip angle of 80 degrees, and the closest part to the developing roller was the tip edge. Others were evaluated in the same manner as in Example 2.
Example 4
As Example 4, in Example 3, the tip portion of the nonmagnetic member was formed from two surfaces having a tip angle of 120 degrees. Others were evaluated in the same manner as in Example 3.
(Example 5)
As Example 5, the tip portion of the nonmagnetic member in Example 4 was an arc-shaped convex curved surface having a radius of 2 mm. Others were evaluated in the same manner as in Example 4.
(Example 6)
As Example 6, in Example 4, the tip of the magnetic member on the upstream side in the developing roller rotation direction has an inclination angle of 30 degrees so that the gap with the developing roller becomes narrower toward the downstream side in the developing roller rotation direction. And having a surface with a length of 5 mm. Others were evaluated in the same manner as in Example 4.
(Comparative Example 1)
As Comparative Example 1, the restricting member in Example 1 was only a magnetic member. Others were evaluated in the same manner as in Example 1.
(Comparative Example 2)
As Comparative Example 2, in Example 1, only the nonmagnetic member was used as the regulating member, and the gap with the developing roller was 0.35 mm. Others were evaluated in the same manner as in Example 1.
(Comparative Example 3)
As Comparative Example 3, the magnetic member on the downstream side in the rotation direction of the developing roller in Example 1 was removed. Others were evaluated in the same manner as in Example 1.
(Comparative Example 4)
As Comparative Example 4, the configuration in Example 2 was made by removing the magnetic member on the upstream side in the rotation direction of the developing roller. Others were evaluated in the same manner as in Example 2.
(Comparative Example 5)
As Comparative Example 5, the magnetic member on the downstream side in the rotation direction of the developing roller in Example 2 was removed. Others were evaluated in the same manner as in Example 2.

  As the wear evaluation of the carrier coat layer, the carrier before and after endurance was cultivated in an oven at 200 ° C., and the mass difference before and after the calcination was taken as the amount of wear of the coat layer, and calculated by the mass ratio with respect to the carrier. Further, after printing, an image including a character image and a solid black image was printed, and fogging evaluation and image density variation were evaluated. In the fogging evaluation, the level where fogging was recognized and not acceptable was evaluated as x, the level allowed but allowed as Δ, and the level where fogging was not recognized as good. For evaluation of variation in image density, four solid image portions of A4 paper were measured with a reflection densitometer (model 310) manufactured by X-RITE, and evaluated by a difference ΔID between the maximum value and the minimum value of the measured values. ΔID is 0 to 0.1 or less, ◯, 0.1 to 0.2 or less, ◯, 0.2 to 0.3 or less, Δ, 0.3.

  The evaluation results are shown in Table 1.

  From the results in Table 1, the regulating member is composed of a non-magnetic member and two magnetic members disposed on the upstream side and the downstream side in the developer transport direction on the developer carrier relative to the non-magnetic member. It can be seen that the amount of wear of the coat layer on the carrier surface is reduced by the nonmagnetic member being the closest part to the agent carrier. This indicates that the stress of the regulation section is reduced. It can also be seen from the image fog evaluation that the toner charge amount is stable. Further, in the second to second embodiments, the front end portion of the nonmagnetic member has a closer surface as compared to the first embodiment, which is a surface having a shape that is separated from the surface of the image carrier with respect to the developer carrying direction of the developer carrier. It can be seen that the remaining amount of the coating agent No. 6 is large and the deterioration is less.

  Further, from the evaluation result of the image density difference, the image density difference of Example 4 is smaller than that of Example 3. This is thought to be because the developer filling state at the restriction portion of the nonmagnetic member gradually changes upstream and downstream of the restriction position, so that the developer amount can be stably regulated. It can be said that it is preferable that the front end angle is constituted by two surfaces having an obtuse angle.

  Further, when Example 4 and Example 6 are compared, Example 6 has a smaller image density difference. In Example 6, since the shape of the tip of the magnetic member on the upstream side in the developing roller rotation direction has a surface that approaches the surface of the developing roller toward the downstream side in the developing roller rotation direction, the stable developer amount is regulated. This is probably because the member can be supplied to the upstream side of the developing roller rotation direction.

  As described above, according to the present invention, it is possible to provide a developing device and an image forming apparatus capable of suppressing the deterioration of the developer, causing no image fogging, and performing good image formation over a long period of time.

1 is a schematic diagram illustrating a main part of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a schematic diagram illustrating a main part of a developing device according to the present invention. It is the schematic which shows the control member which concerns on this invention. It is the schematic which shows the control member which concerns on this invention. It is the schematic which shows the control member which concerns on this invention. It is the schematic which shows the magnetic flux density distribution of a magnet roller, and arrangement | positioning of a control member. It is the schematic which shows the control member used for the Example and the comparative example.

Explanation of symbols

1 Image carrier (photosensitive drum)
DESCRIPTION OF SYMBOLS 2 Developing device 3 Charging device 4 Transfer roller 5 Cleaning blade 6 Exposure device 7 Sleeve roller 8 Magnet roller 9 Developing and developing roller 11 Restricting member 12 Developer 13 Developer tank 14, 15 Stirring member 16 Toner replenishing portion 17 Replenishing toner 18 ATDC sensor 19 Casing 90 Fixing device 100 Power supply P Transfer body E Exposure position

Claims (6)

A developer carrying body having a magnet inside and carrying a developer on the surface;
A regulating member that is disposed close to the developer carrying member and regulates the layer thickness of the developer carried on the surface of the developer carrying member;
The regulating member is a non-magnetic member,
Two magnetic members disposed on the upstream side and the downstream side in the developer transport direction on the developer carrier relative to the non-magnetic member,
The developing device characterized in that a portion closest to the developer carrying member is the nonmagnetic member. A tip portion where the non-magnetic member faces the surface of the developer carrier has a surface that approaches the surface of the developer carrier toward the downstream side of the developer carrier in the developer transport direction. The developing device according to claim 1. The developing device according to claim 2, wherein the tip portion includes two surfaces having a blunt tip angle. The developing device according to claim 2, wherein the tip portion is formed of a convex curved surface. The surface of the magnetic member disposed on the upstream side of the non-magnetic member that faces the developer carrying member approaches the surface of the developer carrying member toward the downstream in the developer carrying direction of the developer carrying member. The developing device according to claim 1, further comprising a surface. 6. An image bearing member, an electrostatic latent image forming unit that forms an electrostatic latent image on the image bearing member, and an electrostatic latent image on the image bearing member for developing the electrostatic latent image. An image forming apparatus.

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