JP2007093705A - Developing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device capable of preventing the conveyance failure of a developer caused by the slipping of a magnetic brush (GB) when a two-component developer (G) containing a magnetic carrier (C) comprising spherical particles having smooth surfaces is conveyed by a developer carrier by forming the magnetic brush (GB), thereby performing a satisfactory development without decrease or unevenness of image density caused by the developer conveyance failure. <P>SOLUTION: A carrier body (21A, 21B) is used as the developer carrier (21) in the developing device (1), the body produced by uniformly distributing recesses (7) where the magnetic carrier (C) enters on the carrying surface (21a) of the body. Otherwise, a carrier body (21C, 21D) produced by uniformly distributing a magnetic material (8) on the carrying surface (21a) of the body is used as the developer carrier (21). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a developing device applied to an image forming apparatus such as a printer, a copying machine, or a multi-function machine that forms an image using a two-component developer composed of a toner and a carrier. The present invention relates to an improvement of a developing device using a two-component developer containing a magnetic carrier made of smooth spherical particles.

  In an image forming apparatus to which an electrophotographic system or an electrostatic recording system is applied, an electrostatic latent image formed on an image carrier such as a photoreceptor is developed with a two-component developer (actually toner) supplied from a developing device. After the toner image is formed, the toner image is transferred directly to a recording medium such as paper or via an intermediate transfer member, and further fixed to form an image made of toner.

  By the way, in a developing device applied to such an image forming apparatus, it is known to use a two-component developer containing a magnetic carrier composed of spherical particles having a smooth surface as a two-component developer (patent). Reference 1).

  When a two-component developer containing this type of magnetic carrier is used, the carrier surface is hard to wear, so that the developer life can be extended, or the carrier can be prevented from being destroyed. As a result, there is an advantage that the life of the cleaning blade in the blade type cleaning device for cleaning the surface of the image carrier can be extended.

  However, when a two-component developer containing this type of magnetic carrier is applied to a conventional two-component developing device as it is, the two-component developer is carried in the developing device to form a magnetic brush and conveyed to the developing area. As a developer carrying member such as a developing roll that rotates in such a manner, a general type in which the carrying surface is sandblasted to form fine irregularities is used.

  That is, in the developer carrying member with the fine irregularities formed thereon, the magnetic brush itself slips due to the magnetic carrier forming the magnetic brush on the carrying surface or causes displacement, and the developer carrying member rotates. A phenomenon in which the toner is not conveyed in the following occurs, and as a result, the developer may be poorly conveyed. This conveyance failure tends to be promoted by a decrease in conveyance force due to surface wear of the developer carrier. Such poor developer transport results in a decrease or unevenness in the amount of toner that is transported to the development area and contributes to the development process, and ultimately induces density reduction and unevenness in the developed image. become.

  Incidentally, in the past, there has been proposed a developer carrying body and a developing device in which irregularities by etching are formed on the surface for the purpose of allowing the developer to be carried and transported evenly and used for development (patent) Reference 2). According to this, the unevenness formed by etching on the support surface of the developer support can be made uniform, and as a result, the developer can be supported and transported without unevenness.

  However, in the developer carrier and the developing device according to this proposal, since the depth of the concave and convex portions is planned to be about 1/20 to 1/2 of the toner particle size, Is substantially the same as the developer carrying member on which irregularities are formed by sandblasting, and therefore it is difficult to eliminate the developer conveyance failure as described above.

  Further, the present applicant has also developed a first unevenness and a second unevenness smaller than the first unevenness for the purpose of providing a developing sleeve or the like that can hold a uniform developer layer on the surface. A sleeve or the like has been proposed (Patent Document 3). The first unevenness is, for example, a main conveyance groove that extends along the axial direction of the developing sleeve and that is formed at an interval in the rotation direction, and is located between the main conveyance grooves, and the main conveyance grooves are arranged before and after the rotation direction. It is a pattern provided with the sub conveyance groove | channel formed in the shape which is not parallel with any of the conveyance grooves (in the connected state or the state which is not connected). Further, when using a two-component developer, for example, the groove width of the first unevenness is 240 μm, and the groove depth is 60 μm.

  However, the developing sleeve according to this proposal and the developing apparatus using the same do not specify how the first unevenness is formed in relation to the carrier, so that the effect of preventing slipping of the magnetic brush and the like is prevented. Whether or not there is is unknown. Further, since the first unevenness has a sub-conveying groove extending in an oblique direction with respect to the axial direction of the developing sleeve, the magnetic brush slips obliquely backward with respect to the rotating direction of the developing sleeve. There is a possibility of causing a conveyance failure due to such slip. Therefore, it cannot be said that this also can solve the developer conveyance failure as described above.

JP-A-6-348063 JP-A-5-46007 JP 2005-164955 A

  The present invention has been made in view of the above problems. When a two-component developer including a magnetic carrier composed of spherical particles having a smooth surface is formed by a magnetic brush and conveyed by a developer carrier. In addition, it is possible to prevent the occurrence of developer conveyance failure due to the slip of the magnetic brush, and to perform good development without causing a decrease in image density and unevenness due to the developer conveyance failure. It is an object of the present invention to provide a developing device capable of performing the above.

  The developing device of the present invention (first invention) contains a two-component developer containing a magnetic carrier composed of spherical particles having a smooth surface, and a developing region in a state where a magnetic brush is formed by supporting the two-component developer. A developing device having a developer carrying member that is rotated so as to be conveyed to the carrying surface of the developer carrying member, wherein the concave portion into which the magnetic carrier enters is formed evenly on the carrying surface of the developer carrying member. It is.

  Here, the entry of the magnetic carrier in the recess means that at least one spherical particle as the carrier can enter. Further, that the concave portions are evenly arranged is a state in which the concave portions are uniformly arranged with no deviation with respect to the entire carrying surface of the developer carrying member. In addition, it is preferable that the form of the recessed part of a recessed part is a thing of the formation made into the steep slope which the carrier which entered the side part near opening especially did not go out easily. Moreover, it is preferable that the support surface in which this recessed part was formed performs the abrasion resistance provision process of a diamond coating, for example from a viewpoint of preventing the abrasion of the edge part of the recessed part, a defect | deletion, etc.

  Moreover, about the said recessed part, it is good to make the maximum depth into the value more than half of the volume average particle diameter of the said magnetic carrier. In this case, the maximum depth is usually the depth of the deepest part of the concave part itself, but depending on the shape of the concave part, it may be converted into the height of the part protruding from the concave part of the carry that has entered the concave part. Incidentally, the upper limit value of the maximum depth may be set to a value not more than three times the volume average particle diameter of the magnetic carrier. The volume average particle size of the magnetic carrier is generally 20 to 100 μm.

  In such a configuration, since the carrier that has entered the recess is in a state where more than half of the spherical particles are present in the recess, the carrier is held in the recess and is difficult to move (or to be easily pulled out), resulting in a positional shift. It is hard to wake up. As a result, the magnetic brush formed using the carrier that has entered the recess as a base point is also less likely to slip.

  Furthermore, it is preferable that the concave portion is a dot-shaped concave portion that is scattered independently, or a linear concave portion that extends along the axial direction of the developer carrying member and exists at equal intervals in the rotation direction.

The dot-shaped recess usually has a circular opening shape, but may have a rectangular, square, or elliptical shape. Also, point-like recess, the opening area of 300μm ² ~0.25mm ^2, density is preferably formed so as to satisfy the condition that 1 to 100 / mm ^2. However, the dot-like recesses are such that the total area does not exceed 50% of the effective area of the carrying surface. Such a point-like recess can be formed mainly by an etching process or an electric discharge machining method.

  On the other hand, the linear recess is preferably a straight groove. The linear recess satisfies the condition that the line width (length in the rotation direction of the developer carrying member) is 10 μm to 0.5 mm, and the pitch (interval in the rotation direction of the developer carrying member) is 20 μm to 0.5 mm. It is preferable to form as follows. However, the linear recess also has a total area that does not exceed 50% of the effective area of the carrying surface. Such a linear recess can be formed by a manufacturing method such as an etching process, but is preferably formed by a pultrusion molding method or an extrusion molding method.

  In the developing device of the present invention (second invention), in the developing device of the first invention, instead of forming the concave portion, the magnetic material portion is evenly arranged on the carrying surface of the developer carrying member. It is characterized by being formed.

  Here, the magnetic body portion aligns the magnetic moment along the direction of the magnetic field when receiving an external magnetic field from a magnetic field generating means such as a permanent magnet arranged to form a magnetic brush on the developer carrier. It is composed of materials with properties. In general, a ferromagnetic material exhibiting ferromagnetism can be used.

  Moreover, the said magnetic body part is taken as the magnetic body layer scattered independently, for example. This magnetic layer is formed by directly forming a magnetic part on a supporting surface using a magnetic material. For example, after forming a magnetic material layer on the entire supporting surface, an unnecessary portion is etched. It can be formed by removing by the method. In the case where the magnetic part made of the magnetic layer is employed, the magnetic part can be firmly formed on the support surface.

Magnetic part made of such a magnetic layer, the layer thickness of 5 to 100 [mu] m, the projection (surface) area of 300μm ² ~0.25mm ^2, density satisfy the condition that 1-50 / mm ² It is preferable to form. However, the total area of the magnetic layer should not exceed 50%, preferably 30%, of the effective area of the support surface.

  Moreover, the said magnetic body part is good also as adhesive magnetic powder which adhere | attached magnetic powder on the electroconductive adhesive layer distribute | arranged and apply | coated uniformly. When the magnetic part made of the adhesive magnetic powder is employed, the magnetic part can be formed relatively easily.

  The magnetic powder is a fine particle having a central particle diameter of 5 to 100 μm made of the magnetic material as described above. For example, magnetic powder made of a ferromagnetic material such as iron, cobalt, nickel or the like can be used. Moreover, as this magnetic powder, you may use the magnetic carrier which consists of a general or the said spherical particle. The conductive adhesive layer is applied to the region of the magnetic part to be formed by a coating method such as a printing method. The reason why the conductive adhesive is used is that the electric charge can move between the carrying surface of the developer carrying member and the magnetic powder. In addition, from the viewpoint of ensuring that the magnetic powder has sufficient conductivity, it is preferable that the surface of the magnetic powder is previously subjected to a conductive coating treatment.

  The “magnetic carrier comprising spherical particles with a smooth surface” used in the developing devices of the first and second inventions described above are, for example, spherical particles in which a magnetic core having voids is filled with a synthetic resin, or in a synthetic resin Spherical particles in which magnetic powder is dispersed. These can be produced by a conventionally known production method.

In addition, this “magnetic carrier composed of spherical particles having a smooth surface” represents SH1 of 100 to 130 and SH2 of 105 to 115 when expressed by shape factors SH1 and SH2, respectively. SH1 is represented by SH1 = (π / 4) · (ML ² / A) · 100.

SH2 is represented by SH2 = (1 / 4π) · (PERI ² / A) · 100. In each equation, “ML” is the maximum absolute length in the projected image of the carrier, “A” is the projected image area of the carrier, and “PERI” is the carrier circumference. In addition, “ML”, “A”, and “PERI” in the formula are images of a carrier image magnified 500 times using, for example, an optical microscope (Nikon: Microphoto-FXA), and the obtained image information Can be obtained by taking the image into an image analysis apparatus (manufactured by Nireco Corporation: Luzex III) and performing image analysis. The shape factors SH1 and SH2 are preferably average values obtained when, for example, 1000 randomly sampled carriers are measured.

  According to the developing devices of the first and second inventions, the two-component developer containing a magnetic carrier composed of spherical particles having a smooth surface enters the concave portion on the carrying surface of the developer carrying member. A magnetic brush is formed with the magnetic carrier adsorbed by the magnetic force as a base point.

  As a result, when transported by the developer carrier, the magnetic brush is securely transported without being slipped while being held by the magnetic carrier serving as the base point, which is caused by the slip phenomenon of the magnetic brush. It is possible to carry out satisfactory development without causing a developer conveyance failure and, consequently, a decrease in image density and unevenness due to the conveyance failure.

[Embodiment 1]
FIG. 1 shows a main part of a developing device according to Embodiment 1 of the present invention.

  The developing device 1 uses a two-component developer G containing a non-magnetic toner and a magnetic carrier. The developing device 1 is opened for development opposite to a housing portion 11 for housing the two-component developer G and the photosensitive drum 100. A container-shaped housing 10 having an opening 12 is provided. The developing roll 2 is installed in the developing opening 12 of the housing 10, and the developer G is agitated and conveyed into the container 11. Two conveyance augers 3 and 4 are installed in a state parallel to the axial direction of the developing roll 2. Further, a trimming member 5 for regulating the layer thickness of the two-component developer G carried on the developing roll 2 (actually the height of the head of the magnetic brush) to a lower side of the developing opening 12 of the housing 10. Is provided.

  The accommodating portion 11 is erected between the two transfer augers 3 and 4 with the partition plate 6 being spaced apart from the inner wall surface of the housing 40 by a predetermined distance. It has two accommodating areas 11a and 11b that communicate with each other at both ends. For this reason, in the accommodating part 11, when the developing device 1 is started, the developer G being accommodated is circulated between the accommodating areas 11a and 11b while being stirred by the conveying augers 3 and 4 respectively. To be conveyed. The transport augers 3 and 4 are formed with developer transport blades that spirally wind around the rotation shaft.

  The developing roll 2 has a cylindrical developing sleeve 21 made of aluminum, nonmagnetic stainless steel, etc., which is rotationally driven in the direction of the arrow, and a plurality of magnetic poles S, which are fixedly installed in the inner space of the developing sleeve 21 and made of permanent magnets. It is comprised with the magnet roll 22 which arrange | positions N suitably. Thus, the two-component developer G is carried by forming a magnetic brush on the developing sleeve 21 of the developing roll 2 by the magnetic force generated from the magnet roll 22. A developing bias voltage for forming a developing electric field between the developing sleeve 21 and the photosensitive drum 100 (developing region) is applied from a bias power source (not shown).

  Next, the developing operation by the developing device 1 will be described.

  First, the two-component developer G is agitated by the conveyance augers 3 and 4 in the storage unit 11 and the toner is conveyed while being frictionally charged. Subsequently, a part of the developer G is attracted to the outer peripheral surface of the developing sleeve 21 by the magnetic force of the magnet roll 22 when passing through the vicinity of the developing roll 2, and then the rotation of the developing sleeve 21 and the trimming member By the action of 5, the developer layer (magnetic brush) having an appropriate thickness is conveyed to the developing area facing the photosensitive drum 100. Finally, in this development region, development is performed by the developer G toner moving and adhering to the electrostatic latent image portion of the photosensitive drum 100 by a developing electric field formed between the developing sleeve 21 and the photosensitive drum 100. .

  In the developing device 1, since the two-component developer containing a magnetic carrier made of spherical particles having a smooth surface is used as the two-component developer G, the developing sleeve of the developing roll 2 as shown in FIGS. 21 (developing sleeve 21 </ b> A) formed with a large number of recesses 7 evenly arranged on the outer peripheral surface (developer carrying surface) 21 a is used.

As shown in FIGS. 2 to 4, the concave portion 7 in the developing sleeve 21 </ b> A has a circular opening shape that is recessed in a spherical shape, and is formed as a dot-shaped concave portion 71 that is formed to be scattered independently on the outer peripheral surface 21 a of the sleeve. It is. The point-shaped recess 71 has a maximum depth D of about 30 μm and an opening area of about 0.04 mm ^2. The point-shaped recess 71 is linearly spaced along the axial direction A of the developing sleeve 21 at regular intervals. The developing sleeves 21 are arranged so that the adjacent ones on the rotation direction B side of the developing sleeve 21 are positioned at the intermediate point, and are formed in a staggered arrangement pattern as a whole, and the density is about 9 / mm ^2. did. Further, the dot-like recesses 71 have a total opening area that occupies about 36% of the effective area on the outer peripheral surface 21a of the developing sleeve. The dot-shaped recess 71 was formed on the surface of the developing sleeve 21 made of aluminum by etching using a photoresist system.

  As the two-component developer G, a non-magnetic toner having a volume average particle diameter of about 7 μm made of a polyester resin and a pigment is used. As the magnetic carrier, a ferrite magnetic powder having a volume average particle size of about 35 μm was used. Further, this magnetic carrier has a shape factor SH1 of SH1 = 105 and a shape factor SH2 of SH2 = 110. For this reason, the maximum depth D of the point-like recess 71 is about 0.86 times the volume average particle diameter of the magnetic carrier.

  By using the developing sleeve 21A in which the concave portion 7 composed of such point-shaped concave portions 71 is formed, the developer conveyance during the development described above is performed as follows.

  That is, as shown in FIGS. 5 and 6, the two-component developer G adsorbed and carried on the developing sleeve 21 </ b> A of the developing roll 2 has a magnetic carrier (C- 1) that enters the point-like recess 71. The magnetic lines of force from the magnet roll 22 also extend from the magnetic carrier (C-1) that has entered the point-like recess 71, and other magnetic carriers (C-2, C-3, C-4, etc.) are chain-like. To form a magnetic brush (GB). At this time, the magnetic carrier (C-1) serving as a base point that has entered the point-like recess 71 fits into the recess of the recess 71 and does not move in the sleeve rotation direction B, and is in a state of being fixed in position. Therefore, the developing sleeve 21A moves following the rotation in the arrow B direction without slipping.

  For this reason, the two-component developer G in which the magnetic brush (GB) is formed on the developing sleeve 21A is stably and satisfactorily conveyed even if the magnetic carrier is composed of smooth spherical particles on the surface. become. As a result, a sufficient amount of toner is stably supplied to the development area, so that good development without reduction in density and unevenness is performed.

[Embodiment 2]
FIG. 7 shows a part (developing sleeve) of the developing device according to the second embodiment of the present invention.

  The developing device according to the second embodiment has the same configuration as the developing device according to the first embodiment, except that the developing sleeve 21B in which the linear recess 72 is formed as the recess 7 on the outer peripheral surface is used. It is. For this reason, in FIG. 7 and the like, the same reference numerals are given to the portions common to the developing device according to the first embodiment, and the description of the common components is omitted in the following (this) The same applies to the following embodiments).

  As shown in FIGS. 7 to 9, the concave portion 7 in the developing sleeve 21 </ b> B has a shape in which the opening shape is a long and thin linear shape and the cross section in the rotational direction B is recessed in a spherical shape, and is parallel to the axial direction A on the sleeve outer peripheral surface 21 a. And linear recesses (straight grooves) 72 formed so as to exist at equal intervals in the rotation direction B. The linear groove 72 has a maximum depth D of about 50 μm and a line width (length in the rotation direction B) W of about 100 μm. The linear groove 72 extends along the axial direction A of the developing sleeve 21. In addition to the formation, the pitches (intervals in the rotation direction B) P were arranged at equal intervals along the rotation direction B so that the pitch P was about 0.5 mm. Further, the linear groove 72 has a total opening area that occupies about 20% of the effective area on the outer peripheral surface 21a of the developing sleeve.

  The linear groove 72 was formed by a molding method for pulling out the developing sleeve 21 made of aluminum. Further, the maximum depth D of the linear recess 72 is about 0.6 times the volume average particle size (about 35 μm) of the magnetic carrier.

  By using the developing sleeve 21B in which the concave portion 7 composed of such a straight groove 72 is formed, the developer is conveyed in the developing device 1 as follows.

  That is, as shown in FIGS. 10 and 5, the two-component developer G adsorbed and carried on the developing sleeve 21 </ b> B of the developing roll 2 has a magnetic carrier (C- 1) that enters the linear groove 72. At this time, the magnetic carrier (C-1) exists in a state of being separated from each other by repelling the magnetic carrier chain (chain) of the adjacent magnetic brush in the linear recess 72. Magnetic field lines from the magnet roll 22 also extend from the magnetic carrier (C-1) that has entered the linear recess 72 as a starting point, and other magnetic carriers (C-2, C-3, C-4, etc.) are connected in a chain. A magnetic brush (GB) is formed (FIG. 5). At this time, the magnetic carrier (C-1) serving as a base point that has entered the linear groove 72 fits into the recess of the groove 72 so that it does not move in the sleeve rotation direction B and is fixed in position. The developer sleeve 21B moves following the rotation in the arrow B direction without slipping.

  Therefore, the two-component developer G in which the magnetic brush (GB) is formed on the developing sleeve 21B is the same as in the case of the first embodiment even if the magnetic carrier is composed of spherical particles having a smooth surface. , It will be transported stably and satisfactorily. As a result, a sufficient amount of toner is stably supplied to the development area, so that good development without reduction in density and unevenness is performed.

[Embodiment 3]
FIG. 11 shows a part (developing sleeve) of the developing device according to the second embodiment of the present invention.

  The developing device according to the third embodiment has the same configuration as the developing device according to the first embodiment, except that the developing sleeve 21C having the magnetic body portion 8 formed on the outer peripheral surface is used.

As shown in FIGS. 11 to 13, the magnetic body portion 8 in the developing sleeve 21 </ b> C has a circular planar shape, and is formed of a ferromagnetic material 81 made of a ferromagnetic material so as to be scattered independently on the outer peripheral surface 21 a of the sleeve. It is. The magnetic layer 81 has a layer thickness t of about 30 μm and a projected (planar) area of about 0.04 μm ^2. The magnetic layer 81 is linearly formed along the axial direction A of the developing sleeve 21. They are arranged at intervals and arranged so that those adjacent to the rotation direction B side of the developing sleeve 21 are positioned at the intermediate point, so that a staggered arrangement pattern is obtained as a whole, and the density is about 9 / mm ^2. Formed. In addition, the total opening area of the magnetic layer 8 occupies about 36% of the effective area on the outer peripheral surface 21a of the developing sleeve.

  The magnetic layer 8 is formed by first plating nickel, which is a ferromagnetic material, over the entire outer peripheral surface of the developing sleeve 21 to a thickness of about 30 μm, and then removing unnecessary portions of the plating layer (portions to be the magnetic layer 81). It was formed by removing by etching.

  By using the developing sleeve 21C in which the magnetic part 8 composed of the magnetic layer 81 is formed, the developer is conveyed during the development of the developing device 1 as follows.

  That is, as shown in FIGS. 14 and 15, the two-component developer G adsorbed and carried on the developing sleeve 21 </ b> C of the developing roll 2 passes through the magnetic layer 81 through the lines of magnetic force from the magnet roll 22. Therefore, there is a magnetic carrier (C-1) that adheres to the upper surface of the magnetic layer 81 by a magnetic force. Then, the magnetic lines of force from the magnet roll 22 extend from the magnetic carrier (C-1) adsorbed on the magnetic layer 81 as a base point, and other magnetic carriers (C-2, C-3, C-4, etc.) are chained. A magnetic brush (GB) is formed in the shape (FIG. 15). At this time, the magnetic carrier (C-1) serving as a base point adsorbed on the magnetic layer 81 is strongly adsorbed by the magnetic force generated by the magnetic force lines concentrated on the magnetic layer 81 and is difficult to move in the sleeve rotation direction B. Since it is in a fixed state, it moves following the rotation of the developing sleeve 21C in the direction of arrow B without slipping.

  For this reason, the two-component developer G in which the magnetic brush (GB) is formed on the developing sleeve 21C is the same as in the first embodiment, even if the magnetic carrier is composed of spherical particles with a smooth surface. , It will be transported stably and satisfactorily. As a result, a sufficient amount of toner is stably supplied to the development area, so that good development without reduction in density and unevenness is performed.

[Embodiment 4]
FIG. 16 shows a part (developing sleeve) of the developing device according to Embodiment 4 of the present invention.

  The developing device according to the fourth embodiment has the same configuration as the developing device according to the first embodiment, except that the developing sleeve 21D in which the adhesive magnetic powder 82 is formed as the magnetic body portion 8 on the outer peripheral surface is used. It will be.

  As shown in FIGS. 16 to 18, the magnetic body portion 8 in the developing sleeve 21 </ b> D includes a conductive adhesive layer 83 applied evenly on the sleeve outer peripheral surface 21 a and a magnetic powder adhered to the adhesive layer 83. 84. Adhesive magnetic powder 82. The adhesive magnetic powder 82 is present on the sleeve outer peripheral surface 21a in the form of islands in which the conductive adhesive is scattered in a staggered manner and uniformly evenly (similar to the magnetic layer 81 in the third embodiment). After the conductive adhesive layer 83 is formed by coating the magnetic powder 84, the magnetic powder 84 is adhered to the adhesive layer 83 before curing.

The conductive adhesive layer 83 was formed by applying a conductive adhesive in which conductive carbon was dispersed in a staggered pattern as described above by screen printing. Specifically, a conductive adhesive having a circular shape having a thickness of about 20 μm and a projected (planar) area of about 0.04 μm ² is linearly spaced along the axial direction A of the developing sleeve 21 at equal intervals. The developing sleeves 21 are arranged so that the adjacent ones on the rotation direction B side of the developing sleeve 21 are positioned at the intermediate point, and formed so as to form a staggered arrangement pattern having a density of about 9 / mm ^{2 as} a whole. . Magnetic powder 84 was sprinkled and adhered onto the conductive adhesive layer 83 formed by coating.

  By using the developing sleeve 21D on which the magnetic body portion 8 made of the adhesive magnetic powder 82 is formed, the developer is conveyed during the development of the developing device 1 as follows.

  That is, as shown in FIG. 19, the two-component developer G adsorbed and carried on the developing sleeve 21D of the developing roll 2 is magnetic carrier (C-1) adsorbed to the magnetic powder 84 of the adhesive magnetic powder 82 by magnetic force. Exists. And the magnetic line of force from the magnet roll 22 extends from the magnetic carrier (C-1) adsorbed to the magnetic powder 84 of the adhesive magnetic powder 82 as a base point, and other magnetic carriers (C-2, C-3, C-4, etc.) ) Are chained to form a magnetic brush (GB). At this time, the magnetic carrier (C-1) serving as a base point adsorbed on the magnetic powder 84 of the adhesive magnetic powder 82 is strongly adsorbed by the magnetic force generated by the magnetic force lines concentrated on the magnetic powder 84 and hardly moves in the sleeve rotation direction B. Since the position is fixed, the developing sleeve 21D moves following the rotation in the arrow B direction without slipping.

  For this reason, the two-component developer G in which the magnetic brush (GB) is formed on the developing sleeve 21D is the same as in the first embodiment, even if the magnetic carrier is composed of smooth spherical particles on the surface. , It will be transported stably and satisfactorily. As a result, a sufficient amount of toner is stably supplied to the development area, so that good development without reduction in density and unevenness is performed.

It is explanatory drawing which shows the principal part of the developing device which concerns on Embodiment 1 (and Embodiment 2-4). 3 is a perspective view illustrating a configuration of a developing sleeve in Embodiment 1. FIG. FIG. 3 is an enlarged perspective view showing a part of the developing sleeve of FIG. 2 in an enlarged manner. It is an expanded sectional view which follows the QQ line of FIG. FIG. 4 is an enlarged perspective view showing a state in which the two-component developer is carried and conveyed by the developing sleeve of FIGS. 2 and 3 (particularly, a state in which a magnetic carrier enters a dot-like recess). It is an expanded sectional view which follows the SS line of Drawing 5 (and Drawing 10). 6 is a perspective view illustrating a configuration of a developing sleeve in Embodiment 2. FIG. FIG. 8 is an enlarged perspective view showing a part of the developing sleeve of FIG. 7 in an enlarged manner. It is an expanded sectional view which follows the QQ line of FIG. FIG. 9 is an enlarged perspective view illustrating a state in which the two-component developer is carried and conveyed by the developing sleeve of FIGS. 7 and 8 (particularly, a state in which a magnetic carrier enters a linear groove). FIG. 10 is a perspective view illustrating a configuration of a developing sleeve in a third embodiment. FIG. 12 is an enlarged perspective view showing a part of the developing sleeve of FIG. 11 in an enlarged manner. It is an expanded sectional view which follows the QQ line of FIG. FIG. 13 is an enlarged perspective view showing a state in which the two-component developer is carried and conveyed by the developing sleeve of FIGS. 11 and 12 (particularly, a state in which a magnetic carrier is adsorbed to a magnetic layer). It is an expanded sectional view which follows the SS line | wire of FIG. FIG. 10 is a perspective view illustrating a configuration of a developing sleeve in a fourth embodiment. FIG. 17 is an enlarged perspective view showing a part of the developing sleeve of FIG. 16 in an enlarged manner. It is an expanded sectional view which follows the QQ line of FIG. FIG. 18 is an enlarged cross-sectional view illustrating a state in which the two-component developer is carried and conveyed by the developing sleeve of FIGS. 16 and 17 (particularly, a state in which the magnetic carrier is adsorbed to the adhesive magnetic powder).

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Developing device, 2 ... Developing roll, 7 ... Recessed part, 8 ... Magnetic part, 21A, 21B, 21C, 21D ... Developing sleeve (developer carrier), 21a ... Sleeve outer peripheral surface (carrying surface), 71 ... Point 72: linear groove (linear recess), 81: magnetic layer, 82: adhesive magnetic powder, 83: conductive adhesive layer, 84: magnetic powder, A: axial direction, B: rotational direction, C ... Carrier, D ... maximum depth, G ... two-component developer.

Claims (7)

A developer carrying member that contains a two-component developer containing a magnetic carrier composed of spherical particles having a smooth surface and rotates to carry the two-component developer to a developing region in a state where a magnetic brush is formed. A developing device comprising:
2. A developing device according to claim 1, wherein a concave portion into which said magnetic carrier enters is formed uniformly on the carrying surface of said developer carrying member.   The developing device according to claim 1, wherein the maximum depth of the concave portion is a value that is half or more of a volume average particle diameter of the magnetic carrier.   3. The image according to claim 1, wherein the concave portions are dot-shaped concave portions that are scattered independently, or linear concave portions that extend along the axial direction of the developer carrying member and are equally spaced in the rotation direction. Forming equipment. A developer carrying member that contains a two-component developer containing a magnetic carrier composed of spherical particles having a smooth surface and rotates to carry the two-component developer to a developing region in a state where a magnetic brush is formed. A developing device comprising:
2. A developing device according to claim 1, wherein a magnetic part is uniformly arranged on the carrying surface of the developer carrying member.   The developing device according to claim 4, wherein the magnetic part is a magnetic layer that is scattered independently.   5. The image forming apparatus according to 4, wherein the magnetic body part is an adhesive magnetic powder obtained by adhering magnetic powder to a conductive adhesive layer that is uniformly disposed and applied.   The developing device according to claim 1, wherein the magnetic carrier is a spherical particle in which a magnetic core having a gap is filled with a synthetic resin, or a spherical particle in which a magnetic powder is dispersed in a synthetic resin.

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