JP2012047984A - Development device and image forming apparatus having the device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a development device and an image forming apparatus having the device for stabilizing the transportation amount of developer on a developer carrier and reducing a stress to the developer caused by a regulation member.SOLUTION: A development device 2 includes a magnetic roller 21 having a magnetic member 21c therein and rotating while carrying a developer on the surface, a magnetic regulation member 24 having a regulating end face 24a facing the surface of the magnetic roller 21 for regulating a layer thickness of the developer on the magnetic roller 21, and a magnetic reinforcement member 51 disposed opposite to and upstream side of the regulation member 24 relative to the rotating direction of the magnetic roller 21. Further, the reinforcement member 51 has an inclined face 51a formed so as to depart from the surface of the magnetic roller 21 toward upstream side thereof and a curved surface 51b that is formed at a surface closest to the surface of the magnetic roller 21 and that is separate more from the surface of the magnetic roller 21 than from the regulating end face 24a.

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used in an image forming apparatus such as a copying machine, a printer, a facsimile, or a composite machine using an electrophotographic system, and an image forming apparatus including the developing device. The present invention relates to a developing device that carries a developer having a layer thickness and an image forming apparatus including the developing device.

  Conventionally, in an image forming apparatus using an electrophotographic method, a developing device includes a magnetic one-component developing method using a magnetic toner, and a developing method using a developer composed of a magnetic carrier and a non-magnetic toner. Both are provided with a developer carrying member containing a magnetic member. The developer carrier is supported and transported on the surface of the developer carrier by a built-in magnetic member, and is regulated to have a constant layer thickness by a regulating member. The regulating member forms a certain gap with the surface of the developer carrier, and the developer passes through the gap so as to have a certain layer thickness. When the layer thickness of the developer is kept constant, stress such as compression or rubbing is given to the developer by the regulating member, and the developer is deteriorated.

  Therefore, in Patent Document 1, the regulating member is opposed to the magnetic pole of the magnetic member built in the developer carrier, and is arranged with a predetermined gap from the surface of the developer carrier, and is formed of a nonmagnetic material. The Magnetic members are respectively disposed facing the restriction member at upstream and downstream positions in the developer conveyance direction with respect to the restriction member. As described above, the regulation end surface of the regulation member is a non-magnetic material, and by arranging the magnetic material on the upstream side and the downstream side, the magnetic force on the regulation end surface of the regulation member is weakened, and the stress on the developer is reduced. .

JP 2009-3076 A (paragraphs [0027], [0028], FIG. 3)

  However, in the above-described prior art, since the non-magnetic material is used as the regulating member, the transport amount of the developer carried on the surface of the developer carrying member depends on the magnetic force of the opposing magnetic member and the developer carrying member. The amount of developer transport is not stable if there is a change in the magnetic force due to the displacement of the magnetic member or an environmental change such as temperature and humidity. There is a problem that image defects such as a decrease in image density occur.

  The present invention has been made to solve the above-described problems, and a developing device that stabilizes the transport amount of the developer on the developer carrying member and reduces stress on the developer by the regulating member, and the developing device An object of the present invention is to provide an image forming apparatus including the above.

  In order to achieve the above object, a developing device according to a first aspect of the present invention comprises a developer carrying member having a built-in magnetic member and carrying a developer on the surface and rotating, and the developer facing the surface of the developer carrying member. A regulating member made of a magnetic body having a regulating end face that regulates the layer thickness of the developer on the carrier, and a magnetic body attached facing the upstream side of the regulating member with respect to the rotation direction of the developer carrier. The reinforcing member is formed with an inclined surface that is separated from the surface of the developer carrier toward the upstream side in the rotation direction of the developer carrier. The surface closest to the surface is formed as a curved surface, and the curved surface is separated from the surface of the developer carrying member than the regulating end surface.

  In the second invention, in the above developing device, when the curvature radius of the curved surface is represented by R and the curvature radius of the peripheral surface of the developer carrier is represented by T, 0.05 ≦ R / T. It is a feature.

  The third invention is characterized in that 0.1 ≦ R / T ≦ 0.5 in the developing device.

  According to a fourth aspect of the present invention, in the developing device, the reinforcing member is formed by bending the plate member to form the inclined surface and an attachment surface that extends from the inclined surface at an acute angle and contacts the regulating member. The curved surface is formed at a portion where the inclined surface and the mounting surface intersect.

  According to a fifth aspect of the invention, there is provided an image forming apparatus including the developing device having the above-described configuration.

  According to the first invention, when the developer supplied from the stirring unit approaches the regulating member, the developer supply area is narrowed by the inclined surface of the reinforcing member, and the density of the developer gradually increases. Even if there is an environmental change such as temperature and humidity, the developer conveyance amount in the vicinity of the regulating member is stabilized by increasing the density of the developer. In addition, since the surface of the reinforcing member that is closest to the surface of the developer carrying member is formed as a curved surface, a space for storing developer between the curved surface of the reinforcing member and the opposing surface of the regulating member that faces the reinforcing member ( A developer reservoir) is formed. The developer immediately before being regulated by the regulating member is accumulated in this gap, so that the stress of the developer is released. Accordingly, a good image can be obtained without lowering the image density, and deterioration of the developer after printing can be suppressed.

  According to the second aspect of the present invention, when the curvature radius R of the curved surface formed on the reinforcing member is 0.05 ≦ R / T, the stress of the developer immediately before being regulated by the regulating member is developed. Since it is released by the agent reservoir, the deterioration of the developer after printing is suppressed.

  According to the third aspect of the present invention, the developer immediately before being restricted by the restricting member when the curvature radius R of the curved surface formed on the reinforcing member is 0.1 ≦ R / T ≦ 0.5. Is released in the developer pool, so that deterioration of the developer after printing is suppressed. Furthermore, the magnetic field formed by the regulating member and the reinforcing member spreads on the surface of the developer carrying member, and the developer transport amount is further stabilized.

  According to the fourth aspect of the invention, since the reinforcing member is formed of a plate material, the curved surface of the reinforcing member can be easily formed.

  According to the fifth aspect of the present invention, an image forming apparatus including a developing device that stabilizes the transport amount of the developer on the developer carrying member and reduces stress on the developer by the regulating member can be provided. .

1 is a diagram schematically showing an image forming apparatus equipped with a developing device according to an embodiment of the present invention. Sectional drawing which shows schematically the developing device which concerns on embodiment Sectional drawing which shows schematically the reinforcement member of the developing device which concerns on embodiment Sectional drawing which shows the reinforcement member of a comparative example schematically

  Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to these embodiments. Further, the use of the invention and the terms shown here are not limited thereto.

  FIG. 1 is a diagram schematically showing a configuration of an image forming apparatus equipped with a developing device according to an embodiment of the present invention. The image forming apparatus 1 is a tandem type color printer, and the rotatable photoreceptors 11a to 11d use an organic photoreceptor (OPC photoreceptor) as a photosensitive material for forming a photosensitive layer, and are magenta, cyan, and yellow. , And black. Around each of the photoreceptors 11a to 11d, developing devices 2a to 2d, an exposure unit 12, chargers 13a to 13d, and cleaning devices 14a to 14d are disposed.

  The developing devices 2a to 2d are arranged to face the right sides of the photoconductors 11a to 11d, respectively, and supply toner to the photoconductors 11a to 11d. The chargers 13a to 13d are arranged on the upstream side of the developing devices 2a to 2d with respect to the rotation direction of the photoconductors 11a to 11d so as to face the surfaces of the photoconductors 11a to 11d. Charge like this.

  The exposure unit 12 scans and exposes each of the photoconductors 11a to 11d based on image data such as characters and patterns input from a personal computer or the like to an image input unit (not shown). The developing device 2a ~ 2d below. The exposure unit 12 is provided with a laser light source and a polygon mirror, and a reflection mirror and a lens are provided corresponding to each of the photoreceptors 11a to 11d. Laser light emitted from the laser light source is applied to the surfaces of the photoconductors 11a to 11d from the downstream side in the photoconductor rotation direction of the chargers 13a to 13d via the polygon mirror, the reflection mirror, and the lens. Electrostatic latent images are formed on the surfaces of the photoreceptors 11a to 11d by the irradiated laser light, and the electrostatic latent images are developed into toner images by the developing devices 2a to 2d.

  The endless intermediate transfer belt 17 is stretched around the tension roller 6, the driving roller 25, and the driven roller 27. The driving roller 25 is rotationally driven by a motor (not shown), and the intermediate transfer belt 17 is circulated and driven by the rotation of the driving roller 25.

  The photoreceptors 11a to 11d are arranged below the intermediate transfer belt 17 so as to be in contact with the intermediate transfer belt 17 along the conveying direction (arrow direction in FIG. 1). The primary transfer rollers 26a to 26d face the photoconductors 11a to 11d with the intermediate transfer belt 17 interposed therebetween, and press contact with the intermediate transfer belt 17 to form a primary transfer portion. In the primary transfer portion, the toner images on the photoconductors 11a to 11d are sequentially transferred to the intermediate transfer belt 17 at a predetermined timing as the intermediate transfer belt 17 rotates. As a result, a toner image is formed on the surface of the intermediate transfer belt 17 by superimposing four color toner images of magenta, cyan, yellow, and black.

  The secondary transfer roller 34 is opposed to the driving roller 25 with the intermediate transfer belt 17 interposed therebetween, and presses against the intermediate transfer belt 17 to form a secondary transfer portion. In this secondary transfer portion, the toner image on the surface of the intermediate transfer belt 17 is transferred to the paper P. After the transfer, the belt cleaning device 31 cleans the toner remaining on the intermediate transfer belt 17.

  A paper feed cassette 32 that stores paper P is disposed below the image forming apparatus 1, and a stack tray 35 that supplies manually fed paper is disposed to the right of the paper feed cassette 32. On the left side of the paper feed cassette 32, a first paper transport path 33 for transporting the paper P fed from the paper feed cassette 32 to the secondary transfer portion of the intermediate transfer belt 17 is disposed. Further, on the left side of the stack tray 35, a second paper transport path 36 for transporting paper fed from the stack tray 35 to the secondary transfer unit is disposed. Further, on the upper left side of the image forming apparatus 1, a fixing unit 18 that performs a fixing process on the sheet P on which an image is formed, and a third sheet transport that transports the sheet on which the fixing process has been performed to the sheet discharge unit 37. A path 39 is provided.

  The paper feed cassette 32 can be replenished by pulling it out of the apparatus (the front side of the paper surface in FIG. 1). The paper P stored therein is picked up by the pickup roller 33b and the separating roller 33a one by one. It is fed out to the first paper transport path 33 side.

  The first paper transport path 33 and the second paper transport path 36 merge before the registration roller 33c, and the registration roller 33c takes the timing of the image forming operation and the paper feeding operation on the intermediate transfer belt 17, The paper P is conveyed to the secondary transfer unit. The sheet P conveyed to the secondary transfer unit is secondarily transferred with the toner image on the intermediate transfer belt 17 by the secondary transfer roller 34 to which a bias potential is applied, and is conveyed to the fixing unit 18.

  The fixing unit 18 includes a fixing belt heated by a heater, a fixing roller in contact with the fixing belt, a pressure roller disposed in pressure contact with the fixing roller with the fixing belt interposed therebetween, and a toner image is transferred. The fixing process is performed by heating and pressurizing the sheet P. After the toner image is fixed by the fixing unit 18 on the paper P, the toner image is reversed by the fourth paper conveyance path 40 as necessary, and the toner image is secondarily transferred to the back surface of the paper by the secondary transfer roller 34 to be fixed. Fixing is performed at the portion 18. The sheet on which the toner image is fixed passes through the third sheet conveyance path 39 and is discharged to the sheet discharge unit 37 by the discharge roller 19a.

  FIG. 2 is a cross-sectional view showing a configuration of a developing device used in the image forming apparatus 1 described above. In the following description, the configuration and operation of the developing device 2a corresponding to the photoconductor 11a shown in FIG. 1 will be described. However, the configuration and operation of the developing devices 2b to 2d are the same as those of the developing device 2a. Omitted, and reference numerals a to d indicating developing devices and photoconductors of the respective colors are omitted.

  As shown in FIG. 2, the developing device 2 includes a developing roller 20, a magnetic roller 21 that is a developer carrier, a stirring unit 42, a regulating member 24, a reinforcing member 51, a developing container 22, and the like. Yes.

  The developing container 22 constitutes the outline of the developing device 2, and is partitioned into a first transport path 22d and a second transport path 22c by a partition member 22b at a lower portion thereof. The first transport path 22d and the second transport path 22c contain a developer composed of a magnetic carrier and toner. Further, the developing container 22 rotatably holds the stirring unit 42, the magnetic roller 21, and the developing roller 20. Further, the developing container 22 is formed with an opening 22 a that exposes the developing roller 20 toward the photoconductor 11.

  The stirring unit 42 is provided at the bottom of the developing container 22 and includes two members, a first stirring member 44 and a second stirring member 43. The first stirring member 44 is provided in the first transport path 22d, and the second stirring member 43 is provided in the second transport path 22c adjacent to the right side of the first stirring member 44.

  The first and second stirring members 44 and 43 stir the developer to charge the toner in the developer to a predetermined level. Thus, the toner is held on the magnetic carrier. Further, communication portions (not shown) are provided on both end sides in the longitudinal direction (front and back direction of the paper surface of FIG. 2) of the partition member 22b that partitions the first transport path 22d and the second transport path 22c. 2 When the agitating member 43 rotates, the charged developer is transported into the first transport path 22d from one communicating portion provided in the partition member 22b, and circulates in the first transport path 22d and the second transport path 22c. To do. Then, the developer is supplied from the first stirring member 44 to the magnetic roller 21.

  The magnetic roller 21 is disposed above the first stirring member 44 so as to carry and carry the developer supplied from the first stirring member 44 and supply only the toner to the developing roller 20. A regulating member 24 is disposed to face the peripheral surface of the magnetic roller 21.

  The restricting member 24 is formed in a plate shape with a magnetic material such as stainless steel, and is fixedly held in the developing container 22 obliquely to the left of the magnetic roller 21. The front end of the regulating member 24 faces the surface of the magnetic roller 21 with a predetermined interval, and regulates the layer thickness of the developer carried on the surface of the magnetic roller 21.

  The magnetic roller 21 includes a rotating sleeve 21b made of a nonmagnetic material, a magnetic pole member 21c, and a roller shaft 21a.

  The magnetic pole member 21 c is composed of a plurality of magnets having different polarities on the outer peripheral portion, and has a regulation pole 21 d composed of N poles at a position facing the regulation member 24. The magnetic pole member 21c is fixed to the roller shaft 21a by adhesion or the like, and the roller shaft 21a is supported by the developing container 22 so as not to rotate. The rotating sleeve 21b has a predetermined distance from the magnetic pole member 21c and is rotatably supported by the developing container 22. The rotating sleeve 21b is rotated in the direction of arrow C by a drive mechanism including a motor and gears (not shown), and a bias 56 is applied in which the AC voltage 56b is superimposed on the DC voltage 56a. On the surface of the rotating sleeve 21b, the charged developer is carried by forming a magnetic brush by the magnetic force of the magnetic pole member 21c, and the magnetic brush is adjusted to a predetermined height by the regulating member 24 and the regulating pole 21d. The rotating sleeve 21b further rotates, and the magnetic brush is conveyed to the developing roller 20 side.

  The developing roller 20 is configured to include a developing sleeve 20c, a magnetic pole member 20b, a fixed shaft 20a, and the like, facing the magnetic roller 21 with a certain interval left obliquely above the magnetic roller 21.

  The developing sleeve 20 c is formed of a nonmagnetic material in a cylindrical shape and is rotatably supported by the developing container 22. The magnetic pole member 20b is fixed to the fixed shaft 20a by bonding or the like at a position facing the magnetic roller 21 with a predetermined distance from the developing sleeve 20c. The fixed shaft 20a is supported by the developing container 22 so as not to rotate. Further, the developing sleeve 20c is opposed to the photoconductor 11 and is disposed on the right side of the photoconductor 11 with a certain interval, and is a development that supplies toner to the photoconductor 11 at a position close to the photoconductor 11. Region D is formed. The developing sleeve 20c is rotated in the direction of arrow B by a drive mechanism including a motor and gears (not shown). Further, a developing bias 55 in which an AC voltage 55b is superimposed on a DC voltage 55a is applied to the developing sleeve 20c.

  Therefore, when the magnetic brush carried on the magnetic roller 21 rises at a position facing the magnetic pole member 20b of the developing roller 20 and contacts the developing roller 20, only the toner of the magnetic brush is biased 56 applied to the magnetic roller 21. Accordingly, the toner is supplied to the developing sleeve 20c. When the developing bias 55 is applied in the developing region D, the toner carried on the developing sleeve 20 c flies to the photosensitive member 11 due to the potential difference between the developing bias potential and the potential of the exposed portion of the photosensitive member 11. The flying toner sequentially adheres to the exposed portion on the photoconductor 11 rotating in the direction of arrow A, and the electrostatic latent image on the photoconductor 11 is developed.

  In the present embodiment, a reinforcing member 51 is disposed on the regulating member 24.

  The reinforcing member 51 collects the developer on the regulating member 24 side, stabilizes the developer conveyance amount, and releases the stress generated in the developer, and is bent into a V shape with a magnetic material such as a steel plate. Formed on the upstream side of the regulating member 24 with respect to the rotation direction of the magnetic roller 21 (the direction of arrow C), and is attached to the opposing surface of the regulating member 24 with screws or the like.

  The reinforcing member 51 will be described in detail with reference to FIG. FIG. 3 is a cross-sectional view schematically showing the reinforcing member.

  The reinforcing member 51 is formed on an attachment surface 51c for attaching to the opposing surface 24b of the regulating member 24, an inclined surface 51a inclined at an acute angle with respect to the attachment surface 51c, and a portion intersecting the attachment surface 51c and the inclined surface 51a. And a curved surface 51b to be formed.

  The inclined surface 51a is inclined so as to be separated from the surface of the magnetic roller 21 toward the upstream side in the rotation direction (arrow C direction) of the magnetic roller 21, and in a range of 40 to 60 ° with respect to the mounting surface 51c. It is inclined. Therefore, the inclined surface 51a gathers together the developer supplied from the stirring unit 42 (see FIG. 2) between the regulating end surface 24a of the regulating member 24 and the surface of the rotating sleeve 21b together with the surface of the rotating sleeve 21b. When the developer is gathered together and moves toward the regulating member 24, the density of the developer gradually increases, and the developer transport amount is stabilized in the vicinity of the regulating member 24.

  The curved surface 51b is formed with a radius of curvature R, faces the rotating sleeve 21b, and further faces the regulating pole 21d via the rotating sleeve 21b. The regulating end surface 24a of the regulating member 24 forms a predetermined gap H with the surface of the rotating sleeve 21b, but the curved surface 51b is disposed at a position separated from the regulating end surface 24a with respect to the surface of the rotating sleeve 21b. A gap G is formed between the curved surface 51 b and the facing surface 24 b of the regulating member 24. The developer gathered toward the gap H on the inclined surface 51a is collected in the gap G (developer pool), and the stress applied to the gathered developer is released.

Here, assuming that the radius of curvature of the rotating sleeve 21b is T, if the radius of curvature R of the curved surface 51b is in the range of the following formula (1), the stress of the developer immediately before being regulated by the regulating member 24 is caused by this development. Since it is opened in the agent reservoir G, the deterioration of the developer after printing is suppressed. When the value of R / T is below the lower limit of the expression (1), the curvature radius R of the curved surface 51b becomes too small with respect to the curvature radius T of the rotating sleeve 21b, and sufficient developer can be stored in the developer reservoir G. It becomes difficult and it becomes difficult to release the stress of the developer.
0.05 ≦ R / T (1)

More preferably, when the radius of curvature R of the curved surface 51b is in the range of the following formula (1A), the stress of the developer is released as described above, and the magnetic field generated by the regulating member 24 and the reinforcing member 51 is further reduced. It spreads on the surface of the rotating sleeve 21b, and the amount of developer transport is further stabilized. When the value of R / T is below the lower limit of the formula (1A), the radius of curvature R of the curved surface 51b becomes too small with respect to the radius of curvature T of the rotating sleeve 21b, and the range of the magnetic field formed with the regulation pole 21d becomes narrow. In addition, the developer transport amount is not stable. On the other hand, if the upper limit of the expression (1A) is exceeded, the curvature radius R of the curved surface 51b becomes too large with respect to the curvature radius T of the rotation sleeve 21b, and the surface close to the rotation sleeve 21b spreads in the circumferential direction of the rotation sleeve 21 and develops. Degradation of the agent proceeds.
0.1 ≦ R / T ≦ 0.5 (1A)

  According to the above-described embodiment, the developing device 2 includes the magnetic member 21c, the magnetic roller 21 that rotates while supporting the developer on the surface, and the developer layer on the magnetic roller 21 that faces the surface of the magnetic roller 21. A regulating member 24 made of a magnetic body having a regulating end face 24 a that regulates the thickness, and a reinforcing member 51 made of a magnetic body that is attached facing the upstream side of the regulating member 24 with respect to the rotation direction of the magnetic roller 21 are provided. The reinforcing member 51 is formed with an inclined surface 51a that is separated from the surface of the magnetic roller 21 toward the upstream side in the rotation direction of the magnetic roller 21, and a surface closest to the surface of the magnetic roller 21 is formed by a curved surface 51b. In addition, the curved surface 51b is separated from the surface of the magnetic roller 21 than the regulating end surface 24a.

  According to this configuration, when the developer supplied from the stirring unit 42 approaches the regulating member 24, the developer supply area is narrowed by the inclined surface 51 a of the reinforcing member 51, and the developer density gradually increases. Even if there is an environmental change such as temperature and humidity, the developer conveyance amount in the vicinity of the regulating member 24 is stabilized by increasing the developer density. Further, since the surface of the reinforcing member 51 that is closest to the surface of the magnetic roller 21 is formed by a curved surface 51b, a gap G (development) that collects developer between the curved surface 51b and the facing surface 24b of the regulating member 24 is formed. Agent reservoir) is formed. When the developer immediately before being restricted by the restriction member 24 is accumulated in the gap G, the stress of the developer is released. Accordingly, a good image can be obtained without lowering the image density, and deterioration of the developer after printing can be suppressed.

  In the above embodiment, the example in which the developer carrying member is applied to the magnetic roller 21 has been described. However, the present invention is not limited to this, and the developer is carried on the developing roller, and the carried developer is used as a regulating member. The developing device may be applied to the developing roller in a developing device that regulates the thickness to a predetermined level and supplies only the toner from the developer carried on the developing roller toward the photosensitive member.

  Examples 1 and 2 and Comparative Examples 3 and 4 that further embody the embodiment of the present invention will be described below. In addition, this invention is not limited only to a following example.

  The magnetic roller 21 used in Examples 1 and 2 and Comparative Examples 3 and 4 has an outer diameter of 16 mm (curvature radius T; 8 mm), and the regulation pole 21d in the magnetic roller 21 has a magnetic flux density of 60 mT. It is disposed at a position of 29 ° on the lower side. The material of the restricting member 24 is SUS403, and the distance between the restricting end surface 24a of the restricting member 24 and the surface of the rotating sleeve 21b is 0.3 mm. The developer used was a positively charged toner having a particle size of 6.8 μm and a specific gravity of 1.2, a carrier particle size of 35 μm and a specific gravity of 4.5.

  The reinforcing member 51 in Examples 1 and 2 is made of SECC (electrogalvanized steel plate) and has a thickness of 1 mm. In Example 1, the curvature radius R of the curved surface 51b is 0.4 mm (R / T = 0). .05), in Example 2, the radius of curvature R of the curved surface 51b was 1 mm (R / T = 0.125). On the other hand, the reinforcing member 51 is not provided in the comparative example 3, and the reinforcing member 51 shown in FIG. 4 is provided in the comparative example 4. As shown in FIG. 4, in the comparative example 4, the reinforcing member 51 is disposed at the same position as the first and second embodiments with respect to the regulating member 24, and the reinforcing member 51 facing the magnetic roller 21 does not have the curved surface 51b. It is bent at an acute angle.

For Examples 1 and 2 and Comparative Examples 3 and 4 configured as described above, the image density with respect to environmental changes, the image fog after printing durability, and the developer transport characteristics against the displacement of the regulation electrode 21d were evaluated. The evaluation results are shown in Table 1.

(A) Image density with respect to environmental changes A low temperature and low humidity environment with a temperature of 10 ° C and a humidity of 15%, a normal temperature and humidity environment with a temperature of 25 ° C and a humidity of 30%, and a high temperature of 32 ° C and a humidity of 85% The change in the reflection density of the printed solid image was evaluated under each environment of high humidity. In Table 1, ◎ indicates that the difference between the maximum value and minimum value of image density (ID; image density) is 0 or more and 0.2 or less, and X indicates the difference between the maximum value and minimum value of image density. Is greater than 0.2.

  According to this result, compared with Comparative Example 3, Examples 1, 2 and Comparative Example 4 are more stable in image density against environmental changes. This is because the developer supply path is restricted by the inclined surface 51a of the reinforcing member 51 as the developer approaches the regulating member 24, the developer density gradually increases, and the developer transport amount is stable. It is shown that.

(B) Image fog after printing durability The image fog after printing 50,000 sheets was visually inspected using a chart with a printing rate of 5%. In Table 1, “◎” indicates that no image fog is recognized, “◯” indicates that image fog is recognized but within an allowable range, and “×” indicates that image fog is clearly recognized and is not acceptable.

  According to this result, Examples 1 and 2 were better than Comparative Examples 3 and 4, and Example 2 was better than Example 1. In the first and second embodiments, the developer reservoir G is formed on the curved surface 51 b of the reinforcing member 51. By forming the developer pool G, the developer immediately before being regulated by the regulating member 24 is released from stress, and deterioration of the developer after printing durability is suppressed. Furthermore, the larger the radius of curvature R of the curved surface 51b of the reinforcing member 51 is in the range of the formulas (1) and (2), the greater the effect.

(C) Conveyance property of developer with respect to deviation of regulating electrode 21d When the regulating electrode 21d facing the regulating member 24 and the reinforcing member 51 is deviated from a predetermined position by ± 5 °, the developer conveyance amount varies from a predetermined value. Evaluated. In Table 1, the symbol ◎ indicates that the amount of variation in the transport amount is 2 mg / cm ² or less, the symbol ◯ indicates that the amount of variation in the transport amount is greater than 2 mg / cm ^{2 and not} more than 5 mg / cm ² , The amount of variation in the transport amount is greater than 5 mg / cm ² .

  According to this result, Examples 1 and 2 were better than Comparative Examples 3 and 4, and Example 2 was better than Example 1. In the first and second embodiments, a magnetic field is formed by the reinforcing member 51 and the regulating pole 21d by the curved surface 51b of the reinforcing member 51. This magnetic field spreads on the rotating sleeve 21b and compensates for the positional deviation of the regulating pole 21d. The developer transport amount is stable. Furthermore, the larger the radius of curvature R of the curved surface 51b of the reinforcing member 51 is in the range of the formulas (1) and (2), the greater the effect.

  INDUSTRIAL APPLICABILITY The present invention can be used for a developing device used in an image forming apparatus such as a copying machine, a printer, a facsimile, and a composite machine using the electrophotographic method, and an image forming apparatus including the developing device. The present invention can be used in a developing device that carries a developer having a predetermined layer thickness on a body and an image forming apparatus including the developing device.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2a-2d, 2 Developing apparatus 11a-11d, 11 Photoconductor 20 Developing roller 20b Magnetic pole member 20c Developing sleeve 21 Magnetic roller (Developer carrier)
21b Rotating sleeve 21c Magnetic pole member 21d Restricting pole 22 Developer container 24 Restricting member 24a Restricting end surface 24b Opposing surface 51 Reinforcing member 51a Inclined surface 51b Curved surface 51c Mounting surface

Claims (5)

A developer carrier that contains a magnetic member and rotates with the developer carried on the surface;
A regulating member made of a magnetic body facing the surface of the developer carrying body and having a regulating end face that regulates the layer thickness of the developer on the developer carrying body;
A reinforcing member made of a magnetic body that is attached to the upstream side of the regulating member with respect to the rotation direction of the developer carrier,
The reinforcing member is formed with an inclined surface that is separated from the surface of the developer carrier toward the upstream side in the rotation direction of the developer carrier, and the surface closest to the surface of the developer carrier is A developing device, wherein the developing device is formed in a curved surface, and the curved surface is separated from the surface of the developer carrying member than the regulating end surface. When the radius of curvature of the curved surface is represented by R and the radius of curvature of the peripheral surface of the developer carrier is represented by T,
0.05 ≦ R / T
The developing device according to claim 1, wherein: 0.1 ≦ R / T ≦ 0.5
The developing device according to claim 2, wherein:   The reinforcing member is formed by bending the plate member to form the inclined surface and an attachment surface that extends from the inclined surface at an acute angle and contacts the regulating member, and the inclined surface and the attachment surface intersect each other. The developing device according to claim 1, wherein the curved surface is formed on the developing device.   An image forming apparatus comprising the developing device according to claim 1.

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