JP2008250121A - Developing device, process cartridge and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device configured to prevent nonuniform image density by uniformizing a quantity of supplied developer without increasing cost, weight, consumption power, and so on. <P>SOLUTION: The developing device has a developing means for carrying developer thereon. The developing means 5 includes: a developing sleeve 5Y rotatable for carrying developer; a magnet roller 5Y1 having a plurality of magnetic poles, such as a development main pole, which are disposed within the developing sleeve 5Y along the circumference of the sleeve 5Y; and a blade 53 disposed to face the developing sleeve 5Y and used to regulate the thickness of the layer of developer carried on the developing sleeve 5Y. A quantity of developer carried on the middle of the developing sleeve 5Y is larger than a quantity of developer carried on each of the ends of developing sleeve 5Y in the axial direction of the sleeve 5Y. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a developing device, a process cartridge, and an image forming apparatus, and more particularly to a developer layer thickness defining structure using a magnetic brush developing system.

  As is well known, one of image forming methods is an electrophotographic method. In this system, when an electrostatic latent image formed on a photoconductor corresponding to a latent image carrier is subjected to visible image processing upon receiving toner from a developing device, the toner image is recorded on a recording medium such as recording paper. The transferred toner image is fixed by a melting / penetrating action using heat and pressure in a fixing device, and then discharged to form a copy or a printed output.

  As a developing device used for performing visible image processing, a configuration using either a one-component developer using magnetic toner or a two-component developer using magnetic carrier is known.

  The developer carried on the developing sleeve adheres to the electrostatic latent image on the photosensitive member by electrostatic attraction force from the electrostatic latent image. It is important to prevent occurrence of abnormal images such as uneven image density and fading. In view of this, the interval between the developing sleeve and the photosensitive member is accurately defined.

  Conventionally, as a developing sleeve configuration, a hollow cylindrical sleeve body capable of carrying a developer on its peripheral surface and a plurality of magnetic poles such as a developing main pole and a conveying magnetic pole are provided along the circumferential direction. There is a configuration having a magnet roller, and a configuration in which the developing sleeve is opposed to the photosensitive member with a predetermined interval is known (for example, Patent Document 1).

FIG. 6 is a diagram showing the configuration of the developing sleeve described above.
In the drawing, the developing sleeve 100 has both ends in the axial direction due to a sleeve main body 100A that can be rotated via a rotating shaft 100A1 and bearings 100C that are inserted into the sleeve main body 100A and provided at both ends in the axial direction of the sleeve main body 100A. And a magnet roller 100B having a supported spindle 100B1. The magnet roller 100B is supported by a bearing 100C in an immobile state independently of the rotation of the sleeve main body 100A, and can maintain the immobile state even when the sleeve main body 100A1 rotates and hold the magnetic pole in a predetermined position. Yes. The support shaft 100B1 is formed with a D-cut surface 100B2 cut by one unit in the axial direction, and is used for alignment of magnetic poles.

  As the sleeve body 100A rotates, the developing sleeve 100 can be rolled while the developer carried on the peripheral surface is opposed to the magnetic pole on the magnet roller 100B side, and at a position facing the developing main pole. A magnetic brush can be formed by the reached developer.

The developing sleeve 100 is driven by a gear 101 interlocked with the photosensitive member side by a support structure shown in FIG.
FIG. 7 is a view showing a main part of a support structure for the developing sleeve 100 and the photosensitive member 200. In FIG. Is provided inside.
In the process cartridge, the rotation shaft 100A1 of the sleeve main body 100A and the support shaft 100B1 of the magnet roller 100B are inserted into the developing unit casing member 150. The rotation shaft 100A1 is supported by the bearing 150A, and the support shaft 100B1 is The main electrode positioning member 151 attached to the developing unit casing member 150 is inserted into the D cut surface 100B2 of the support shaft 100B1.
A driving force transmission gear 101 is attached to the rotation shaft 100A1 of the sleeve main body 100A, and the shaft end is rotatably supported using a bearing 301 with respect to a restriction plate 300 described later.
The photosensitive member 200 is rotatably supported on the wall portion 400 of the process cartridge via the bearing 201.

A shaft support portion between the developing sleeve 100 and the photosensitive member 200 is provided with a defining plate 300 for defining a developing gap that is a distance between the two.
The regulation plate 300 is inserted into the end portion of the rotation shaft shaft of the sleeve body 100A and the end portion of the support shaft of the magnet roller 100B. This is a member for setting the inter-axis distance from the body 200 to a distance at which a predetermined development gap is obtained.
The shaft end of the support shaft 100B1 on the developing sleeve 100 side is inserted into the regulating plate 300 as it is, while the rotating shaft 100A and the rotating shaft 200A on the photosensitive member 200 side are rotatably supported via bearings 301 and 201. Has been.
A transmission mechanism 202 capable of transmitting a driving force is provided at one axial end of the rotation shaft on the photoconductor 200 side. Note that the regulation plate 300 and the side wall 400 of the process cartridge may be configured integrally.

Japanese Patent Laid-Open No. 8-179631

  The distance between the developing sleeve 100 and the photosensitive member 200, that is, the so-called developing gap is a state in which the developer is not carried on the developing sleeve 100, that is, the developer is not present on the peripheral surface facing the photosensitive member 200. However, the present inventors have confirmed that the development gap differs between the case where no developer is present and the case where the developer is transported on the development sleeve 100. did. In particular, the difference in the development gap often becomes a larger gap in the central portion than the both ends in the axial direction of the developing sleeve 100, so that the contact amount of the developer with respect to the photosensitive member, that is, the so-called developer supply amount is uniform. This causes a problem that the image density on the photoconductor is different.

  Such a problem due to the difference in the development gap is considered to be caused by the support structure of the development sleeve 100. That is, the developing sleeve 100 forms a both-end support beam supported at both ends in the axial direction by the support shaft 100B1 via the rotating shaft 100A1 and the bearing 100C, and has a structure in which the bending moment is maximized at the center in the axial direction. The bending deformation at the center in the axial direction becomes the largest due to the force acting on the developing sleeve 100.

In order to reduce the bending component in the developing sleeve 100, a method of adopting a material such as high-strength stainless steel as the sleeve main body 100A or increasing the thickness of the sleeve can be considered. Regarding materials, when comparing aluminum and stainless steel,
The inventor has confirmed that when the stainless steel is used, the gap can be expanded by about half that of aluminum.

  However, suppression of gap fluctuation due to the material is expensive, and for example, as surface treatment for efficiently carrying the developer, the surface roughness such as sandblasting or groove formation by cutting is performed. In some cases, the processing is difficult, which increases the cost.

On the other hand, in the method of increasing the thickness of the sleeve, the magnetic force from the built-in magnetic poles does not easily reach the developer, so that the magnetic force for supporting the developer may be weakened. It may be possible to strengthen this.
However, in this method, the magnet itself is expensive and the sleeve outer diameter increases due to the increase in thickness, which makes it difficult to reduce the size and increases the weight. There is a possibility that weight reduction and low power consumption cannot be achieved.

  In view of the above problems in the conventional developing device, the present invention does not cause unevenness in image density by uniformizing the amount of developer supplied without increasing costs, increasing weight, or increasing power consumption. It is an object of the present invention to provide a developing device and an image forming apparatus having a configuration that can be realized.

In order to achieve this object, the present invention has the following configuration.
(1) Visual development of the electrostatic latent image is possible by transporting the developer toward the electrostatic latent image formed on the latent image carrier using a developing unit carrying the developer. A developing device,
The developing means includes a rotatable developing sleeve for carrying the developer, a magnet roller having a plurality of magnetic poles including a developing main pole disposed along the circumferential direction in the developing sleeve, and the developing sleeve. A blade disposed oppositely and defining a layer thickness of the developer carried on the developing sleeve,
The developing sleeve is characterized in that when the amount of developer carried at the axial end is standard, the amount of developer carried at the central portion in the axial direction is larger than that at the axial end. apparatus.

  (2) The developer carrying amount at the central portion in the axial direction of the developing sleeve is such that the facing distance between the doctor and the developing sleeve facing the central portion in the axial direction is larger than the facing distance at the axial end portion. The developing device according to (1), wherein the amount of the developing device is larger than that of the end portion in the axial direction.

  (3) The developer carrying amount at the central portion in the axial direction of the developing sleeve is arranged in a region from the arrangement position of the blade on the magnet roller to the latent image carrier in the rotation direction of the developing sleeve. The developing device according to (1), wherein the amount of the magnetic pole is increased from that of the axial end portion by increasing the magnetic force at the central portion than the axial end portions of the magnetic pole.

  (4) The developer carrying amount at the center in the axial direction of the developing sleeve is an amount that compensates for the carrying amount that is smaller than the developer carrying amount at the axial end by the amount of bending deformation at the center in the axial direction of the developing sleeve. The developing device according to any one of (1) to (4), wherein the amount is increased.

  (5) The developing device according to (4), characterized in that the amount to be supplemented with the carrying amount is set to an amount that is about 10 to 30% larger than both ends in the axial direction.

  (6) The doctor facing the axial center of the developing sleeve is enlarged by 0.04 to 0.1 mm with respect to the spacing between the developing sleeve and the developing sleeve at the axial end (2). The developing device according to 1.

  (7) The surface of the developing sleeve is formed with a plurality of grooves intersecting with each other in the rotational thrust direction, and the distance between the intersections of the grooves is set in a range of 1.3 mm to 4.8 mm. (1) The development measure according to any one of (6).

  (8) A process cartridge comprising a latent image carrier, a charging unit, and a cleaning unit in addition to the developing device according to any one of (1) to (7) 6.

  (9) The facing distance between the developing sleeve of the developing device and the latent image carrier is 0.2 to 0.5 mm, and the developing bias with respect to the developing sleeve is a DC component (8) ) Process cartridge.

  (10) An image forming apparatus comprising the process cartridge according to (8) or (9).

  (11) The image forming apparatus according to (10), wherein the process cartridge is provided in each of image forming units for a plurality of color images.

  (12) As the toner used in the developing device, the shape factor SF-1 is set to 100 to 180, and the shape factor SF-2 is set to 100 to 180, respectively (10) or (11) The image forming apparatus described.

  According to the present invention, when the axial end portion of the developing sleeve is a standard developer carrying amount, the developing carrying amount is reduced due to the bending deformation of the developing sleeve by increasing the axial central portion more than that. Can be prevented. In particular, the amount of developer required for developing the electrostatic latent image on the latent image carrier becomes uniform by increasing the amount corresponding to the amount reduced by bending deformation with respect to the standard amount of developer carried. Further, image density unevenness due to lack of developer can be prevented. In particular, as a configuration used for increasing the amount of developer carried in the central portion in the axial direction, it can be performed only by using a doctor that defines the layer thickness of the developer or only by a magnetic pole that affects the carrying amount. Since it can be achieved by existing components without providing replenishing means or material correcting means, a uniform amount of developer can be supplied without causing an increase in cost.

The best mode for carrying out the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram illustrating an example of an image forming apparatus. The image forming apparatus illustrated in FIG. 1 is a color printer that uses a tandem method in which a plurality of image forming units that can independently form images of different colors are arranged side by side. is there.
In FIG. 1, the color printer 1 can form an image using yellow (Y), cyan (C), magenta (M), and black (Bk), which are toners of complementary colors with respect to color separation colors. Photosensitive drums 2Y, 2C, 2M, and 2Bk are juxtaposed on the same line in the horizontal direction.
Each photoconductor drum is provided in an image forming unit to be described later, and a belt having an extending surface parallel to the juxtaposing direction of the photoconductor drums 2Y, 2C, 2M, and 2Bk is used in the upper portion of the image forming unit. A transfer device 3 is arranged.

  The image forming unit constitutes a photosensitive drum and a process cartridge for performing an image forming process related to the photosensitive drum. The image forming unit includes therein a charging process, a developer supply member, among the image forming processes for the photosensitive drum. The devices 4, 5 and 6 for carrying out the developing process and the cleaning process for performing visible image processing by the developing sleeve are collectively accommodated.

Below the image forming unit, a scanning device 7 used for the writing process is arranged.
In FIG. 2, the reference numerals relating to the devices in the image forming unit are given only for yellow, but the devices for other colors have the same configuration.

  The transfer device 3 has a configuration in which a belt wound around a plurality of rollers is used as a transfer body, and a primary transfer process in which images of different colors are sequentially transferred onto a developing surface facing each photoconductor drum. And secondary transfer in which the images superimposed in the primary transfer step are collectively transferred to a sheet fed from the paper feeding device 8 (a case where a plurality of paper feeding cassettes 8A are provided is shown in FIG. 1). Are provided for performing the process.

  In the transfer device 3, primary transfer devices 9Y, 9C, 9M, and 9Bk constituted by rollers are arranged at positions facing the respective photosensitive drums, and a sheet is brought into contact with the transfer device 3 at the secondary transfer position. A conveying belt 10 and a secondary transfer device 112 are arranged while conveying.

In the color printer 1, an electrostatic latent image corresponding to writing scanning is formed after charging each photosensitive drum, and when the electrostatic latent image is subjected to visible image processing by the developing device 5, each photosensitive member is transferred to the transfer device 3. The color image from the drum is sequentially transferred through the primary transfer device 9 to form a superimposed image, and the superimposed image is collectively transferred to the sheet by the secondary transfer device 11.
The sheet on which the superimposed images are collectively transferred from the transfer device 3 is subjected to a fixing process by the fixing device 12 provided in the conveyance path to the paper discharge tray 1A and is discharged. In FIG. 1, reference numeral 13 indicates a belt cleaning device of the transfer device 3.

  FIG. 2 shows an image forming unit for a process cartridge capable of forming a yellow image. In FIG. 2, the image forming unit includes a charging device 4 and an optical path of writing light around the photosensitive drum 2Y. A slit ST, a developing device 5 and a cleaning device 6 are provided.

  The charging device 4 uses a charging roller that faces the photosensitive drum 2Y in a contact or non-contact state, and uniformly charges the photosensitive drum 2Y.

  The developing device 5 includes a developing sleeve 50 facing the photosensitive drum 2Y shown in FIG. 1 and a plurality of agitating and mixing screws 51 and 52, which are agitated and mixed while being circulated in a reciprocating direction and frictionally charged developer. A doctor blade 53 for defining the layer thickness, and a new toner introduction section 54 from a toner tank that forms a developer replenishment section (not shown) are provided. In FIG. 2, reference numeral 55 denotes a developer scattering prevention seal provided at a position where the developer conveyed by the developing sleeve 50 starts to face the photosensitive drum 2Y, and reference numeral S1 denotes a developer (toner) concentration. The sensor is shown.

  Although not shown in detail in the developing sleeve 5Y shown in FIG. 2, a plurality of grooves intersecting each other in the rotational thrust direction are formed, and the distance between the intersections of the grooves is set in a range of 1.3 mm to 4.8 mm. Yes. Thereby, unlike the case where the surface is smooth, the collecting action of the developer is enhanced.

On the other hand, the toner used in the developing device in this embodiment has the following specifications.
In the developing device, the toner has a volume particle diameter of 3 to 8 μm and a ratio (Dv / Dn) of the volume average particle diameter (Dv) to the number average particle diameter (Dn) is in the range of 1.00 to 1.40. Toner is used. This is intended to reproduce minute dots of 600 dpi or more. With such a setting, a toner having a small particle size distribution and a narrow particle size distribution has a uniform toner charge amount distribution and high quality with less background stains. An image can be obtained, and the transfer rate is increased in the electrostatic transfer system.

A toner in the range of 100 to 180 is used. The reason is as follows.
FIG. 3 is a diagram schematically illustrating the shape of the toner in order to explain the shape factor SF-1 and the shape factor SF-2.
The shape factor SF-1 indicates the ratio of the roundness of the toner shape and is represented by the following formula (1). This is a value obtained by dividing the square of the maximum length MXLNG of the shape formed by projecting the toner on a two-dimensional plane by the drawing area AREA and multiplying by 100π / 4.
SF-1 = {(MXLNG) ² / AREA} × (100π / 4) .. Formula (1)
When the value of SF-1 is 100, the shape of the toner is a true sphere, and becomes larger as the value of SF-1 increases.

The shape factor SF-2 indicates the ratio of the unevenness of the toner shape, and is represented by the following formula (2). A value obtained by dividing the square of the perimeter PERI of the figure formed by projecting the toner on the two-dimensional plane by the figure area AREA and multiplying by 100π / 4.
SF-2 = {(PERI) ² / AREA} × (100π / 4) Expression (2)
When the value of SF-2 is 100, the unevenness does not exist on the toner surface, and the unevenness of the toner surface becomes more remarkable as the value of SF-2 increases. Specifically, the shape factor is measured by taking a photograph of the toner with a scanning electron microscope (S-800: manufactured by Hitachi, Ltd.), introducing it into an image analyzer (LUSEX 3: manufactured by Nireco) and analyzing it. Calculated. When the shape of the toner is close to a spherical shape, the contact state between the toner and the toner or the toner and the photoconductor becomes point contact, so that the adsorbing force between the toners becomes weak and the fluidity increases, and the toner and the photoconductor The attraction force becomes weaker and the transfer rate becomes higher. If either of the shape factors SF-1 and SF-2 exceeds 180, the transfer rate is lowered, which is not preferable.

  In this embodiment, the interval between the developing sleeve 5Y and the photosensitive member 2Y is set to 0.2 to 0.5 mm, and a DC bias is used as the developing bias. This prevents the occurrence of abnormal images due to carrier adhesion and charge leakage when using the toner conditions described above. This reason is clearly demonstrated by experiments in Japanese Patent Application Laid-Open No. 2003-323050, which is a prior application of the present applicant.

Next, features of the present embodiment will be described.
In the developing device 5 in this embodiment, when the developer carrying amount in the axial direction of the developing sleeve 5Y is standard at both axial end portions, the developer carrying amount at the axial central portion is at the axial end portions. It has been more than that. In the present embodiment, an amount commensurate with the decrease in the developer carrying amount due to the amount of bending deformation that occurs in the axial direction of the developing sleeve 5Y is increased. The standard in this case corresponds to, for example, the developer carrying amount per unit area on one scanning line necessary to satisfy the required density in the main development electrode for the solid image formed on the photoreceptor 2Y. Yes.

  As a configuration for making the developer carrying amount in the axial direction in the developing sleeve 5Y different, the facing interval between the developing sleeve 5Y and the doctor blade 53 facing the developing sleeve 5Y is made larger in the axial central portion than in the axial both ends. In addition, in the magnet roller arranged in the developing sleeve 5Y, the axial direction of the magnetic pole arranged in the region from the position facing the doctor blade 53 to the photoconductor along the rotation direction of the developing sleeve 5Y. It is possible to use a configuration in which the magnetic force at the center portion is stronger than the axial end portions.

In the case of the former configuration, as shown in FIG. 4, in the distal end portion of the doctor blade 53 that faces the developing sleeve 5Y, a concave portion 53A that is recessed from the distal end positions of both axial end portions is formed in the axial center portion. As the maximum depth of the recess, 0.04 to 0.1 mm is selected. As the shape of the recess 53A, the axial center of both axial end regions where the standard developer carrying amount can be defined so as to correspond to the decrease in the developer carrying amount corresponding to the amount of bending of the developing sleeve 5Y in the axial direction. It can be in a curved shape with a maximum depth from the close end to the center, or can be a stepped portion.
The end of the doctor blade 53 to which the maximum depth in the case of forming the concave portion is applied is the case where the center in the thickness direction of the doctor blade 53 in FIG. 2 coincides with the normal line of the developing sleeve 5Y or the developing sleeve 5Y. When the corner of the end in the thickness direction located upstream in the rotation direction of the toner is opposed to each other, and the center of the thickness direction and the normal line of the developing sleeve 5Y coincide with each other, the dimension is set to the depth described above. Is set.

  In the case of the latter configuration, as shown in FIG. 5A, the developing magnetic pole 5Y2 provided on the magnet roller 5Y1 and the conveying magnetic pole 5YT facing the doctor blade 53 are targeted as shown in FIG. As shown, a configuration in which the magnetic force at the magnetic pole P2 positioned at the center is stronger than the magnetic pole P1 positioned at both ends in the longitudinal direction parallel to the axial direction of the developing sleeve 5Y is employed. As a divided configuration, it is conceivable that the magnetizing conditions are made different in the longitudinal direction of the magnetic pole parallel to the axial direction of the developing sleeve 5Y, or that the magnetic poles having different magnetic forces are arranged through a non-permeable material. . In FIG. 5, the magnitude of the magnetic force is schematically shown by the magnitude of the magnetic pole, but a ferromagnetic body made of a magnet material can also be used. When magnetic poles having different magnetic forces are used, the amount of developer carried can be made uniform while suppressing an increase in cost by reducing the amount of ferromagnetic material that tends to be expensive.

  The amount of increase in the case of using these configurations is set to an amount that increases by 10 to 30% with respect to the carrying amount at both ends in the axial direction. As a result, it has been confirmed by the inventors' experiment that a uniform carrying amount in the axial direction can be obtained.

  Since the present embodiment is configured as described above, when the developer carried on the developing sleeve 5Y has a layer thickness defined by the doctor blade 53, the distance between the two in the axial direction is different. In addition, the carrying amount at the central portion is larger than both axial end portions of the developing sleeve 5Y.

  Therefore, even when the axial center portion of the developing sleeve 5Y bends, even if the gap between the axial direction and the doctor blade 53 tends to increase, the decrease in the developer carrying amount due to the change is increased in advance. Therefore, the developer reject in the axial direction can be made uniform to prevent the occurrence of image density unevenness.

FIG. 3 is a schematic diagram for explaining a configuration of an image forming apparatus using the developing device according to the present invention. FIG. 2 is a schematic diagram for explaining a configuration of a process cartridge used in the image forming apparatus shown in FIG. 1. FIG. 2 is an explanatory diagram regarding a shape factor of toner used in a developing device provided in the image forming apparatus illustrated in FIG. 1. It is a figure for demonstrating the structure of the doctor blade used for a developing device. FIG. 3 is a diagram for explaining a magnetic pole structure in the developing sleeve shown in FIG. 2. It is a figure for demonstrating the conventional structure of a developing sleeve. FIG. 7 is a view for explaining a support structure of the developing sleeve shown in FIG. 6.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Color printer 2 Photoconductor 5 Developing apparatus 5Y Developing sleeve 5Y1 Magnet roller 5Y2, 5Y3 Magnetic pole 53 Doctor blade

Claims (12)

A developing device capable of performing visible image processing of the electrostatic latent image by conveying the developer toward the electrostatic latent image formed on the latent image carrier using a developing unit carrying the developer. There,
The developing means includes a rotatable developing sleeve for carrying the developer, a magnet roller having a plurality of magnetic poles including a developing main pole disposed along the circumferential direction in the developing sleeve, and the developing sleeve. A blade disposed oppositely and defining a layer thickness of the developer carried on the developing sleeve,
The developing sleeve is characterized in that when the amount of developer carried at the axial end is standard, the amount of developer carried at the central portion in the axial direction is larger than that at the axial end. apparatus.   The developer carrying amount at the central portion in the axial direction of the developing sleeve is such that the facing distance between the doctor facing the axial central portion and the developing sleeve is larger than the facing distance at the axial end portion. The developing device according to claim 1, wherein the amount of the developing device is larger than that of the end portion in the direction.   The developer carrying amount at the central portion in the axial direction of the developing sleeve is a magnetic pole arranged in a region from the arrangement position of the blade on the magnet roller to the latent image carrier in the rotation direction of the developing sleeve. 2. The developing device according to claim 1, wherein the amount of the developing device is increased by increasing the magnetic force at the center portion than at both end portions in the axial direction.   The developer carrying amount at the center in the axial direction of the developing sleeve is increased by an amount that compensates for the carrying amount that is smaller than the developer carrying amount at the end in the axial direction due to the amount of bending deformation at the center in the axial direction of the developing sleeve. The developing device according to claim 1, wherein the developing device is provided.   The developing device according to claim 4, wherein the amount to be supplemented to the carrying amount is set to an amount that is about 10 to 30% larger than both ends in the axial direction.   3. The doctor according to claim 2, wherein the doctor facing the center in the axial direction of the developing sleeve is enlarged by 0.04 to 0.1 mm with respect to the facing distance from the developing sleeve at the end in the axial direction. Development device.   The surface of the developing sleeve is formed with a plurality of grooves intersecting with each other in the rotational thrust direction, and the distance between the intersections of the grooves is set in a range of 1.3 mm to 4.8 mm. The developing measure according to any one of 5 to 5.   7. A process cartridge comprising a latent image carrier, a charging unit, and a cleaning unit in addition to the developing device according to claim 1.   8. The developing apparatus according to claim 7, wherein a facing distance between the developing sleeve of the developing device and the latent image carrier is 0.2 to 0.5 mm, and the developing bias with respect to the developing sleeve is a direct current component. Process cartridge.   An image forming apparatus comprising the process cartridge according to claim 7.   The image forming apparatus according to claim 9, wherein the process cartridge is provided in each of image forming units for a plurality of color images.   11. The image forming apparatus according to claim 9, wherein the shape factor SF-1 is set to 100 to 180 and the shape factor SF-2 is set to 100 to 180 as toner used in the developing device. .

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