JP2011150122A - Developing device and image forming apparatus provided with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device which can obtain satisfactory images without disturbance of a developer layer on a developing roller by reliably scraping off developer on the developing roller, and uniformly convey toner in a developing container, and to provide an image forming apparatus provided with the developing device. <P>SOLUTION: The developing device 14 includes: a regulating member 35 for forming a developer layer region H, where an amount of toner on the developing roller 27 is regulated, by means of the magnetic field formed with a magnetic pole opposite to a fixed magnet body 25 in a developing roller 27; and a magnetic-field generating member 50 for scraping off, on the upstream side of the regulating member 35 in the rotational direction of the developing roller, toner which is not used for development on the developing roller 27. The magnetic-field generating member 50 includes: magnetic-field generating ends 52m and 52n respectively facing the both-ends sides in the longitudinal direction of the developer layer region H; and a magnetic-field generating central portion 52p sandwiched in the longitudinal direction between the respective magnetic-field generating ends 52m and 52n. The magnetic force of the magnetic-field generating ends 52m and 52n is greater than the magnetic force of the magnetic-field generating central portion 52p. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  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.

  In an image forming apparatus, a latent image formed on a photoreceptor is developed by a developing device and visualized as a toner image. As one of such developing devices, a developing device using a magnetic single-component developer that is small and low in cost has been put into practical use. In this developing device, a fixed magnet body having a plurality of magnetic poles is provided inside a developing sleeve that is a toner carrier, and a regulating member that regulates the amount of toner on the developing sleeve is further provided between the regulating member and the developing sleeve. A predetermined amount of toner thin layer is carried on the developing sleeve.

  In the developing device as described above, in order to make the toner thin layer on the developing sleeve uniform, Patent Document 1 discloses the following developing device.

  In the developing device of Patent Document 1, the restricting member is provided with a predetermined interval from the developing sleeve, and includes a plate-like blade made of a magnetic material and a magnet. The magnetic pole on the opposite side of the magnet to the developing sleeve has the same polarity as the opposing magnetic pole of the fixed magnet body in the developing sleeve, and is attached to the upstream side of the blade with respect to the rotation direction of the developing sleeve. The tip of the blade is magnetized with the opposite polarity to the magnet by the magnetic force of the magnet. In such a configuration, the charged toner is transported in a state of adhering to the developing sleeve, and the layer thickness is regulated and thinned by the blade tip of the regulating member. Here, a magnetic field is formed between the blade tip and the developing sleeve by the fixed magnet body and the magnet, and further, a magnetic field is also formed between the blade tip and the magnet. In a substantially uniform state, a thin toner layer is formed on the developing sleeve through the blade tip and the developing sleeve.

  However, in the above-described prior art, the magnet of the regulating member and the fixed magnet body in the developing sleeve tend to have a smaller magnetic force on the end side in the longitudinal direction than on the central side, and thereby the regulating member. There is a risk that the magnetic field between the developing sleeve and the developing sleeve may be reduced on the end side compared to the central side in the longitudinal direction. When the magnetic field decreases on the end side, the toner regulating force on the end side decreases. The toner charge amount on the developing sleeve increases with the rotation of the developing sleeve. When the toner charge amount increases, the toner strongly adheres to the developing sleeve and is strongly adsorbed between the toners. Thus, when repeated development is performed, when toner passes between the regulating member and the developing sleeve, the toner regulating force is weak on the end side even if the toner layer has a predetermined thickness on the central side in the longitudinal direction. The toner layer thickness increases and the toner layer is likely to be disturbed. When such a toner layer disturbance appears remarkably and the toner is supplied to the photoconductor in a state where the toner layer thickness is uneven, there is a problem that a good toner image is not formed on the photoconductor.

  Therefore, in order to eliminate the toner layer disturbance described above, in Patent Document 2, a magnetic field generating member made of a magnet is provided, and the magnetic field generating member is located upstream of the regulating member in the rotation direction of the developing sleeve. The magnetic brush of toner is formed at a position facing the portion between the magnetic poles of the fixed magnet body. In this configuration, the toner remaining on the developing sleeve after development is peeled off from the developing sleeve by the magnetic brush. Again, toner is carried on the developing sleeve, and the carried toner is conveyed to the regulating member side.

JP 2003-167426 A (paragraphs [0040] to [0046], FIG. 3) Japanese Patent Laid-Open No. 9-34267 (paragraphs [0028], [0033] to [0035], FIG. 1)

  However, in Patent Document 2 described above, in order to sufficiently peel off the toner layer having a large layer thickness on the end side from the developing sleeve, the magnetic force of the magnetic field generating member is increased, or the magnetic field generating member and the developing sleeve surface It is necessary to reduce the gap between As described above, when the magnetic force is increased or the gap is reduced, the toner on the end side can be peeled off from the developing sleeve, but the toner layer thickness is relatively small on the central side and the toner layer thickness is increased. Since the toner is biased in the longitudinal direction, when the toner passes through the gap between the magnetic field generating member and the developing sleeve, the toner deteriorates due to stress, or the toner aggregates and damages the surface of the developing sleeve. There was a problem that an image was generated.

  In some toner agitation methods, toner is circulated and conveyed in two conveyance paths by rotation of two agitation members composed of spiral blades, and the agitated toner is supplied to the developing roller. In such a system, when a magnetic field generating member as shown in Patent Document 2 is disposed between the agitating member and the developing roller, a magnetic field is also applied to the toner circulating in the two conveyance paths. The magnetic force of the generating member acts. That is, a magnetic force acts on the toner transported in each transport path in a direction orthogonal to the toner movement direction, and the toner transport direction from one transport path to the other transport path Magnetic force acts in a parallel direction.

  Therefore, when the toner is transported to the other transport path, particularly when the toner is transported away from the magnetic field generating member, a magnetic force opposite to the transport direction acts on the toner by the magnetic field generating member. The toner flow becomes worse. As described above, the toner stays in the conveyance path where the toner flow is poor, and the staying toner may leak to the outside from the end of the developing container. In addition, when the toner flow is poor, the toner is not uniformly conveyed in the developing container, and the toner sensor cannot accurately detect the toner amount, and the toner to be replenished is excessive or insufficient due to the erroneous detection of the toner amount. There was a problem.

  The present invention has been made to solve the above-described problems. The developer is surely peeled off from the developing roller, and the developer layer is not disturbed on the developing roller, and a good image can be obtained. Another object of the present invention is to provide a developing device in which toner is uniformly conveyed in a developing container and an image forming apparatus including the developing device.

  In order to achieve the above object, the present invention provides a developing roller that supplies a developer to a developing region facing an image carrier and incorporates a fixed magnet body having a plurality of magnetic poles in the circumferential direction; A regulating member that forms a developer layer region in which the amount of developer on the developing roller is regulated by a magnetic field that is formed together with the magnetic pole, and on the developing roller upstream of the regulating member with respect to the rotation direction of the developing roller. In a developing device including a magnetic field generating member that strips off a developer that is not used for development, the magnetic field generating member includes a magnetic field generating end that opposes both ends in the longitudinal direction of the developer layer region, and each of the magnetic field generating members. A magnetic field generation center portion sandwiched between the end portions in the longitudinal direction, and the magnetic force of the magnetic field generation end portion is larger than the magnetic force of the magnetic field generation center portion.

  According to this configuration, even if the developer layer thickness in the developer layer region is larger on the end side than the center side in the longitudinal direction, the developer remains on the developing roller surface after development. The developer on the part side and the end part side is stripped off by the respective magnetic fields of the magnetic field generating member.

  According to a second aspect of the present invention, the magnetic field generating member has a magnetic body facing the surface of the developing roller and a counter magnetic pole facing the surface of the developing roller, facing the developing roller rotating direction. A magnet attached to the magnetic body, the opposing magnetic pole of the magnet has the same polarity as the magnetic pole of the opposing fixed magnet body, and the magnetic force of the magnet on the magnetic field generation end side is on the magnetic field generation center side of the magnet It is characterized by greater magnetic force.

  According to this configuration, the tip of the magnetic body is magnetized to a magnetic pole having a different polarity from the opposing magnetic pole of the magnet, and a magnetic field line passing between the tip of the magnetic body and the opposing magnetic pole of the magnet is formed. In addition, the magnetized magnetic pole at the tip of the magnetic body has a different polarity from the magnetic pole of the fixed magnet body, and a line of magnetic force passing between the tip of the magnetic body and the fixed magnet body is formed. In this way, two magnetic paths are formed by magnetic lines of force at the tip of the magnetic body and the surface of the developing roller, increasing the density of the magnetic lines of force. The magnetic field corresponding to the magnetic field lines is relatively small on the center side of the developer layer region and relatively large on the end side of the developer layer region, and remains on the developing roller surface after development by each magnetic field. Developer is stripped off.

  According to a third aspect of the present invention, the magnetic field generating member has a magnetic body facing the surface of the developing roller and a counter magnetic pole facing the surface of the developing roller, facing the developing roller rotating direction. A magnet attached to the magnetic body, the magnetic body extending to both ends in the longitudinal direction of the developer layer region, the magnet facing the both ends in the longitudinal direction of the developer layer region. The opposed magnetic poles of the magnets are the same in polarity as the magnetic poles of the opposed fixed magnet bodies.

  According to this configuration, on the end side of the developer layer region, the tip of the magnetic material is magnetized to a magnetic pole having a different polarity from the opposing magnetic pole of the magnet, and between the tip of the magnetic material and the opposing magnetic pole of the magnet. A passing magnetic field line is formed. In addition, the magnetized magnetic pole at the tip of the magnetic body has a different polarity from the magnetic pole of the fixed magnet body, and a line of magnetic force passing between the tip of the magnetic body and the fixed magnet body is formed. Magnetic fields corresponding to the two magnetic paths formed by these lines of magnetic force are formed at the tip of the magnetic body and the surface of the developing roller. On the other hand, on the central portion side of the developer layer region, the tip of the magnetic material is magnetized to a magnetic pole of a different polarity from the magnetic pole of the fixed magnet body, and the magnetic field between the tip of the magnetic material and the magnetic pole of the fixed magnet body is Formed on the surface of the developing roller and the surface of the developing roller. As described above, the magnetic field between the end portion side and the center portion side of the developer layer region is relatively small on the center portion side and relatively large on the end portion side, and the surface of the developing roller after development by each magnetic field. The developer remaining on is removed.

  According to a fourth aspect of the present invention, the magnetic body has a tip portion facing the developing roller and an opposite surface portion opposite to the tip portion, and the width of the tip portion in the circumferential direction of the developing roller. Is smaller than the opposite surface portion.

  According to this configuration, in the circumferential direction of the developing roller, the length of the opposite surface portion of the magnetic body is larger in the circumferential direction of the developing roller than the length of the tip portion. Magnetic field lines are formed.

  In the invention according to claim 5, the regulating member is sandwiched in the longitudinal direction between the end regulating portions opposed to both ends in the longitudinal direction of the developer layer region and the respective end regulating portions. A center restricting portion, and the magnetic force of the end restricting portion is larger than the magnetic force of the central restricting portion, and the magnetic field generating end of the magnetic field generating member includes the end restricting portion of the restricting member and the end restricting portion. And a developer layer region opposite to the boundary between the central portion and the central regulating portion.

  According to this configuration, when the developer layer is formed by the restricting member, if the magnetic force of the end restricting portion is larger than the magnetic force of the central restricting portion, the developer layer thickness on the end side of the developer layer region and its center Since a difference occurs in the thickness of the developer layer on the part side, a level difference of the developer layer occurs at the boundary between the end side and the center side of the developer layer region. However, when the developer remaining on the surface of the developing roller is peeled off after development, the magnetic field generating end of the magnetic field generating member includes the boundary between the end restricting portion of the restricting member and the central restricting portion on the developer layer region. Therefore, the magnetic field generating member is peeled off so as to eliminate the step of the developer layer.

  According to a sixth aspect of the present invention, the first stirring member that supplies the developer facing the developing roller, the second stirring member that stirs and conveys the developer together with the first stirring member, and the first A first conveyance path through which the developer is conveyed by the agitating member, a second conveyance path that is arranged in parallel with the first conveyance path, and that conveys the developer by the second agitating member, and the first conveyance A first communication part for passing the developer from the path to the second transport path, and a second communication part for passing the developer from the second transport path to the first transport path, wherein the magnetic field generating member comprises the developing roller And the first stirring member, and the first communication portion is disposed at a position not facing the magnetic field generating member.

  According to this configuration, the developer is transported from the upstream side to the downstream side in the developer transport direction in the first transport path while being stirred by the first stirring member. Next, when the developer moves from the first transport path to the second transport path via the first communication portion, the developer is transported without being greatly affected by the magnetic force of the magnetic field generating member.

  In the invention according to claim 7, the first stirring member is composed of a rotating shaft and a spiral blade formed around the rotating shaft, and is provided at a magnetic field generating end of the magnetic field generating member. The opposing spiral blades are formed such that the developer conveying force is increased.

  According to this configuration, the developer conveyed in the first conveyance path by the first agitating member receives the magnetic force of the magnetic field generation end, but the spiral blade facing the magnetic field generation end of the magnetic field generation end Is formed so that the developer conveying force is increased, the developer in the first conveying path is conveyed at substantially the same speed.

  According to an eighth aspect of the present invention, there is provided an image forming apparatus equipped with the developing device having the above configuration.

  According to the first aspect of the present invention, the developer layer thickness in the developer layer region becomes larger on the edge side than the central side in the longitudinal direction, and the developer remains on the developing roller surface after development. Even in this case, the developer on the center side and the end side is surely peeled off by the respective magnetic fields of the magnetic field generating member, and the developer layer is not disturbed on the developing roller, and a good image can be obtained.

  According to the second aspect of the present invention, the magnetic material tip is magnetized by the magnetic pole opposite to the opposite magnetic pole of the magnet and passes between the magnetic material tip and the opposite magnetic pole of the magnet. Is formed. In addition, the magnetized magnetic pole at the tip of the magnetic body has a different polarity from the magnetic pole of the fixed magnet body, and a line of magnetic force passing between the tip of the magnetic body and the fixed magnet body is formed. In this way, two magnetic paths are formed by magnetic lines of force at the tip of the magnetic body and the surface of the developing roller, increasing the density of the magnetic lines of force. The magnetic field corresponding to the magnetic field lines is relatively small on the center side of the developer layer region and relatively large on the end side of the developer layer region, and remains on the developing roller surface after development by each magnetic field. Developer is stripped off. Therefore, even if the developer layer thickness in the developer layer region increases on the end side with respect to the central portion in the longitudinal direction, the developer is surely retained even if the developer remains on the developing roller surface after development. As a result, the developer layer is not disturbed on the developing roller, and a good image can be obtained.

  According to the third aspect of the invention, on the end side of the developer layer region, the tip of the magnetic material is magnetized to a magnetic pole having a different polarity from the opposite magnetic pole of the magnet, and the tip of the magnetic material and the magnet Magnetic field lines passing between the opposite magnetic poles are formed. In addition, the magnetized magnetic pole at the tip of the magnetic body has a different polarity from the magnetic pole of the fixed magnet body, and a line of magnetic force passing between the tip of the magnetic body and the fixed magnet body is formed. Magnetic fields corresponding to the two magnetic paths formed by these lines of magnetic force are formed at the tip of the magnetic body and the surface of the developing roller. On the other hand, on the central portion side of the developer layer region, the tip of the magnetic material is magnetized to a magnetic pole of a different polarity from the magnetic pole of the fixed magnet body, and the magnetic field between the tip of the magnetic material and the magnetic pole of the fixed magnet body is Formed on the surface of the developing roller and the surface of the developing roller. As described above, the magnetic field between the end portion side and the center portion side of the developer layer region is relatively small on the center portion side and relatively large on the end portion side, and the surface of the developing roller after development by each magnetic field. The developer remaining on is removed. Therefore, even if the developer layer thickness in the developer layer region increases on the end side with respect to the central portion in the longitudinal direction, the developer is surely retained even if the developer remains on the developing roller surface after development. As a result, the developer layer is not disturbed on the developing roller, and a good image can be obtained.

  According to the invention described in claim 4, since the length of the opposite surface portion of the magnetic body is larger in the circumferential direction of the developing roller than the length of the tip portion in the circumferential direction of the developing roller, the opposite surface portion of the magnetic body, the magnet, A large number of magnetic field lines passing between the two are formed. Therefore, the magnetic force of the magnetic material is increased, a magnetic field can be generated efficiently at the tip of the magnetic material, and the developer attached to the surface of the developing roller is surely peeled off.

  According to the invention described in claim 5, when the developer layer is formed by the regulating member, if the magnetic force of the end regulating portion is larger than the magnetic force of the central regulating portion, Since there is a difference between the developer layer thickness and the developer layer thickness on the central portion side, a step difference of the developer layer occurs at the boundary between the end portion side and the central portion side of the developer layer region. However, when the developer remaining on the surface of the developing roller is peeled off after development, the magnetic field generating end of the magnetic field generating member includes the boundary between the end restricting portion of the restricting member and the central restricting portion on the developer layer region. Therefore, it is peeled off so that the level difference of the developer layer is eliminated. Therefore, the developer layer is not disturbed on the developing roller, and a good image can be obtained.

  According to the sixth aspect of the present invention, the developer is transported from the upstream side in the developer transport direction to the downstream side in the developer transport direction while being stirred by the first stirring member. Next, when the developer moves from the first transport path to the second transport path via the first communication portion, the developer is transported without being greatly affected by the magnetic force of the magnetic field generating member. Accordingly, the developer is peeled off from the developing roller by the magnetic field generating member, and the developer is uniformly circulated in the conveyance path, and the developer is supplied to the developing roller. Therefore, abnormalities such as a decrease in density and a ghost phenomenon are caused. There is no risk of image generation.

  According to the seventh aspect of the present invention, the developer transported in the first transport path by the first stirring member receives the magnetic force of the magnetic field generation end, but the magnetic field generation end of the magnetic field generation end. Since the spiral blades facing each other are formed so as to increase the developer conveying force, the developer in the first conveying path is conveyed at substantially the same speed. Accordingly, the developer circulates uniformly in the conveyance path and the developer is supplied to the developing roller, so that there is no possibility that an abnormal image such as a decrease in density or a ghost phenomenon occurs.

  According to the invention described in claim 8, the developer is surely peeled off from the developing roller, the developer layer is not disturbed on the developing roller, and a good image can be obtained. An image forming apparatus including a developing device that uniformly conveys toner can be obtained.

1 is a diagram showing a schematic configuration of an image forming apparatus equipped with a developing device according to a first embodiment of the present invention. Side surface sectional drawing which shows schematic structure of the developing device which concerns on 1st Embodiment. Side surface sectional drawing which shows the principal part structure of the image development apparatus concerning 1st Embodiment. Sectional enlarged view around the magnetic field generating member of the developing device according to the first embodiment. The top view which shows arrangement | positioning with the magnetic field generation member of the developing device which concerns on 1st Embodiment, a control member, and a developing roller. The top view which shows arrangement | positioning with the magnetic field generation member of the developing device which concerns on 2nd Embodiment of this invention, a control member, and a developing roller. The top view which shows arrangement | positioning with the magnetic field generation member of the developing device which concerns on 3rd Embodiment of this invention, a control member, and a developing roller. Plan sectional drawing which shows arrangement | positioning with the magnetic field generation member and stirring part of the developing device which concern on 4th Embodiment of this invention. Plan sectional drawing which shows arrangement | positioning with the magnetic field generation member and stirring part of the developing device which concern on 5th Embodiment of this invention.

  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.

(First embodiment)
FIG. 1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus 1 is provided with a sheet feeding unit 2 disposed in a lower portion thereof, a sheet conveying unit 3 disposed on a side of the sheet feeding unit 2, and an upper side of the sheet conveying unit 3. The image forming unit 4 includes a fixing unit 5 disposed on the discharge side of the image forming unit 4, and an image reading unit 6 disposed above the image forming unit 4 and the fixing unit 5.

  The paper feed unit 2 includes a plurality of paper feed cassettes 7 for containing paper 9, and the paper 9 is fed from the selected paper feed cassette 7 among the plurality of paper feed cassettes 7 by the rotation of the paper feed roller 8. Each sheet is surely sent out to the sheet transport unit 3.

  The paper 9 sent to the paper transport unit 3 is transported toward the image forming unit 4 via the paper supply path 10. The image forming unit 4 forms a toner image on a sheet 9 by an electrophotographic process. The image forming unit 4 includes a photosensitive member 11 rotatably supported in an arrow direction in FIG. A charging unit 12, an exposure unit 13, a developing device 14, a transfer unit 15, a cleaning unit 16, and a charge eliminating unit 17 are provided along the rotation direction.

  The charging unit 12 includes a charging wire to which a high voltage is applied. When a predetermined potential is applied to the surface of the photoconductor 11 by corona discharge from the charging wire, the surface of the photoconductor 11 is uniformly charged. Then, when light based on the image data of the original read by the image reading unit 6 is irradiated to the photoconductor 11 by the exposure unit 13, the surface potential of the photoconductor 11 is selectively attenuated, and the surface of the photoconductor 11 is irradiated. An electrostatic latent image is formed. Next, the developing device 14 develops the electrostatic latent image on the surface of the photoconductor 11, and a toner image is formed on the surface of the photoconductor 11. This toner image is transferred by the transfer unit 15 to the paper 9 supplied between the photoconductor 11 and the transfer unit 15.

  The sheet 9 on which the toner image has been transferred is conveyed toward the fixing unit 5 disposed on the downstream side of the image forming unit 4 in the sheet conveying direction. In the fixing unit 5, the sheet 9 is heated and pressed by the heating member 18 and the pressure roller 19, and the toner image is melted and fixed on the sheet 9. Next, the sheet 9 on which the toner image is fixed is discharged onto the discharge tray 21 by the discharge roller pair 20. After the transfer by the transfer unit 15, the toner remaining on the surface of the photoconductor 11 is removed by the cleaning unit 16, and the residual charge on the surface of the photoconductor 11 is removed by the charge eliminating unit 17. Then, the photosensitive member 11 is charged again by the charging unit 12 and image formation is performed in the same manner.

  Next, the developing device will be described with reference to FIG. FIG. 2 is a side sectional view showing a schematic configuration of the developing device and its peripheral devices used in the image forming apparatus 1.

  The developing device 14 includes a developing container 22 that contains a magnetic one-component developer, stirring members 43 and 44 that stir the developer (hereinafter, also referred to as “toner”), a developing roller 27, and a regulating member. 35. The toner tank 31 supplies toner to the developing device 14.

  The agitating members 43 and 44 are rotatably disposed in the developing container 22, and agitate and circulate the toner and supply the toner to the developing roller 27.

  The developing roller 27 includes a fixed magnet body 25 and a developing sleeve 26. The developing sleeve 26 is made of a cylindrical nonmagnetic material and is rotatably supported by the developing container 22 at a position adjacent to the stirring member 44. The fixed magnet body 25 is a permanent magnet fixed in the developing sleeve 26 and generates a magnetic field toward the developing sleeve 26. Further, the developing roller 27 is exposed from the opening of the developing container 22 and faces the photosensitive member 11 that is an image carrier at a predetermined interval. This facing area is a developing area D for supplying the toner carried on the developing sleeve 26 toward the photoreceptor 11. Further, a developing bias 29 in which alternating current is superimposed on direct current is applied to the developing sleeve 26 in order to supply toner to the photoreceptor 11.

  The regulating member 35 regulates the toner carried on the surface of the developing sleeve 26 to a predetermined layer thickness. The developing container 22 is spaced a predetermined distance from the surface of the developing sleeve 26 substantially above the developing sleeve 26. Attached to.

  The toner supplied from the stirring member 44 is carried on the surface of the developing sleeve 26 by the magnetic force of the fixed magnet body 25 in the developing sleeve 26. The carried toner is regulated to a predetermined layer thickness by the regulating member 35 and is conveyed toward the developing region D by the rotation of the developing sleeve 26 (rotation in the direction of the arrow in FIG. 2). When a developing bias 29 is applied to the developing sleeve 26, a potential difference is generated between the developing sleeve 26 and the photoconductor 11 in the developing region D, and the toner on the developing sleeve 26 is supplied to the photoconductor 11 and the photoconductor. The electrostatic latent image on 11 is developed into a toner image.

  Next, the configuration of the developing device 14 will be described in detail with reference to FIGS. 3 is a side cross-sectional view showing a configuration of a main part of the developing device, FIG. 4 is an enlarged cross-sectional view of the vicinity of the magnetic field generating member, and FIG. FIG.

  As shown in FIG. 3, the developer container 22 has a developer container 22 a that stores toner, a developer supply unit 22 p that stores toner and supplies the toner to the photoreceptor 11, Under the container 22, it has the adjacent part 22m interposed between the developer accommodating part 22a and the developer supply part 22p, and is formed with resin.

  Transport paths 22c and 22d are formed in the developer accommodating portion 22a, and two stirring members 43 and 44 are disposed in the transport paths 22c and 22d with the partition portion 22b interposed therebetween. The stirring members 43 and 44 include a support shaft that is rotatably supported by the developer accommodating portion 22a and blades that are formed in a spiral shape in the axial direction of the support shaft. The toner supplied from the toner tank 31 (see FIG. 2) to the conveyance path 22c is agitated by the rotation of the agitating member 43, and the agitated toner is conveyed through the openings provided at both ends of the partition portion 22b. It is conveyed to. Further, the toner circulates in the transport paths 22c and 22d while being stirred by the rotation of the stirring member 44 in the transport path 22d. The agitated toner is supplied to the developing sleeve 26 from the conveyance path 22d.

  A developing sleeve 26 is rotatably disposed in the developer supply unit 22p. The developing sleeve 26 is formed in a cylindrical shape with a nonmagnetic material such as aluminum and has a surface roughness Rz of 10 mμ or less. In the developing sleeve 26, the fixed magnet body 25 is fixedly supported by the developer supply unit 22p. The fixed magnet body 25 has S poles and N poles alternately arranged in the circumferential direction, and generates a magnetic field toward the surface of the developing sleeve 26.

  A magnetic pole S <b> 1 is arranged at a position facing the regulating member 35 of the fixed magnet body 25. In addition, a magnetic pole N2 is disposed at a position facing the development area D, and a magnetic pole S2 is disposed at the toner circulation area T where the residual toner after development is conveyed, and further at a position facing the adjacent portion 22m. Is provided with a magnetic pole N1.

  The restricting member 35 includes a restricting blade 36 made of a magnetic material such as stainless steel, and a plate magnet 37 which is a permanent magnet.

  The regulating blade 36 is attached to the developing container 22 at a predetermined distance from the surface of the developing sleeve 26 substantially above the developing sleeve 26. The front end portion of the regulating blade 36 forms an edge and faces the surface of the developing sleeve 26.

  The plate magnet 37 is attached to the upstream side of the regulating blade 36 in the rotation direction of the developing roller. The end of the plate magnet 37 facing the developing sleeve 26 is farther from the developing sleeve 26 than the tip of the regulating blade 36, and has the same S pole as the magnetic pole S1 of the fixed magnet body 25 in the developing sleeve 26. The opposite end is an N pole.

  With such a configuration, the front end portion of the regulating blade 36 is magnetized with a polarity (N pole) opposite to that of the opposing side end of the plate magnet 37 by the magnetic force of the plate magnet 37. Therefore, a magnetic field is formed between the tip of the regulating blade 36 and the developing sleeve 26 by the magnetic pole N 1 of the fixed magnet body 25 and the plate magnet 37, and a magnetic field is also formed between the tip of the regulating blade 36 and the plate magnet 37. Is done. By these magnetic fields, the toner passes almost between the tip of the regulating blade 36 and the developing sleeve 26 in a substantially uniform state, and a thin toner layer is formed on the developing sleeve 26. As shown in FIG. 5, in the longitudinal direction of the developing sleeve 26, a toner layer is formed in the developer layer region H corresponding to the width (length in the longitudinal direction) of the fixed magnet body 25 and the regulating member 35. It will be.

  As shown in FIG. 3, the adjacent portion 22 m has an attachment portion 22 n that is a surface to which the magnetic field generating member 50 is attached.

  When the magnetic field generating member 50 is attached to the attachment portion 22n, the magnetic field generating member 50 faces the developing sleeve 26 with a certain interval. The magnetic field generating member 50 faces the magnetic pole N1 of the fixed magnet body 25 via the developing sleeve 26 and generates a magnetic field between the magnetic pole N1 of the fixed magnet body 25.

  Next, the magnetic field generating member will be described in detail with reference to FIG. The magnetic field generating member 50 includes a magnet 51 and a magnetic body 52.

  The magnet 51 is a permanent magnet and opposes the surface of the developing sleeve 26 with a certain interval. Further, the magnet 51 has a counter magnetic pole 51 a that faces the magnetic pole N <b> 1 (N pole) of the fixed magnet body 25 via the developing sleeve 26, and a counter magnetic pole 51 b that is positioned on the opposite side of the developing sleeve 26. The opposing magnetic pole 51a has the same polarity (N pole) as the magnetic pole N1 of the fixed magnet body 25, and the opposite magnetic pole 51b becomes the S pole. Further, the magnet 51 has a rectangular parallelepiped shape with a rectangular cross section, and has a facing portion 51c positioned on the upstream side in the rotation direction of the developing roller.

  The magnetic body 52 is made of a magnetic material such as a stainless steel plate, and is fixed to the facing portion 51c of the magnet 51 with an adhesive. Moreover, the magnetic body 52 has the front-end | tip part 52a and the opposite surface part 52b. The tip 52a faces the surface of the developing sleeve 26 at substantially the same interval as the counter magnetic pole 51a of the magnet 51. This interval is set smaller than the interval between the developing sleeve 26 and the regulating member 35 (see FIG. 3). The opposite surface portion 52 b is located on the opposite side of the tip portion 52 a in the substantially normal direction of the developing sleeve 26, and is formed with the same planar height as the end surface of the opposite magnetic pole 51 b of the magnet 51. In this embodiment, the magnetic body 52 is attached to the upstream side of the magnet 51 with respect to the rotation direction of the developing roller. It may be attached downstream.

  With this configuration, the tip 52a of the magnetic body 52 is magnetized to the S pole, and the opposite surface 52b is magnetized to the N pole. Therefore, the magnetic body 52 forms a magnetic path by magnetic lines with the magnet 51, and the magnetic body 52 forms a magnetic path by magnetic lines with the fixed magnet body 25.

  That is, since the opposite surface portion 52b of the magnetic body 52 is magnetized to the north pole, a magnetic field line passing between the opposite surface portion 52b of the magnetic body 52 and the opposite magnetic pole (sole) 51b of the magnet 51 is formed. A magnetic field line passing between the opposite surface portion 52b of the magnetic body 52 and the magnetic pole (S pole) adjacent to the magnetic pole N1 of the fixed magnet body 25 is formed.

  Further, the width of the opposite surface portion 52b of the magnetic body 52 is set to be larger than the width of the front end portion 52a of the magnetic body 52 in the circumferential direction of the developing roller. As a result, a large number of magnetic field lines are formed between the opposite surface portion 52b of the magnetic body 52 and the opposite magnetic pole (S pole) 51b of the magnet 51, and the opposite surface portion 52b and the magnetic pole (S pole) of the fixed magnet body 25 In between, a large number of magnetic field lines are formed.

  Furthermore, since the tip 52a of the magnetic body 52 is magnetized to the S pole and has a relatively small width, the lines of magnetic force passing between the tip 52a and the opposing magnetic pole (N pole) 51a of the magnet 51 are concentrated. And magnetic field lines passing between the tip 52a and the magnetic pole N1 of the fixed magnet body 25 are formed in a concentrated manner. In this way, two magnetic paths are formed by magnetic lines of force in a narrow region between the tip 52a of the magnetic body 52 and the surface of the developing sleeve 26, and the density of the magnetic lines of force increases. A magnetic field corresponding to the lines of magnetic force is generated at the tip 52 a of the magnetic body 52 and the surface of the developing roller 27.

  Further, as shown in FIG. 5, the magnetic field generating member 50 has a different magnetic force in the longitudinal direction of the developer layer region H on the developing sleeve 26. That is, the magnet 51 has magnet end portions 51m and 51n and a magnet center portion 51p. The magnet end portions 51m and 51n are disposed on the end side in the longitudinal direction of the developer layer region H, and the magnetic force of the counter magnetic pole 51a of the magnet end portions 51m and 51n is set to be relatively large. On the other hand, the magnet central portion 51p is disposed on the central portion side in the longitudinal direction of the developer layer region H, and the magnetic force of the counter magnetic pole 51a of the magnet central portion 51p is set smaller than the magnet end portions 51m and 51n.

  The magnetic field generation end portions 52m and 52n of the magnetic body 52 face the magnet end portions 51m and 51n, and the magnetic field generation center portion 52p faces the magnet center portion 51p. Therefore, the magnetic force of the tip end portion 52a (see FIG. 4) of the magnetic field generation end portions 52m and 52n is larger than the magnetic force of the tip end portion 52a of the magnetic field generation center portion 52p.

  The toner in the developer layer region H is formed by the magnetic fields of different magnitudes formed on the magnetic layer generating member 50 and the magnetic pole N1 of the fixed magnet body 25 on the end side and the center side in the longitudinal direction of the developer layer region H. Is peeled off from the surface of the developing sleeve 26.

  Around the developing sleeve 26, a regulating member 35, a developing region D, a toner circulation region T, and a magnetic field generating member 50 are arranged in this order along the arrow direction (the rotating direction of the developing sleeve 26) in FIG. become.

  Usually, the fixed magnet body 25 in the developing roller 27 has a smaller magnetic force on the end side than the central side, and the plate magnet 37 of the regulating member 35 has a magnetic force on the end side compared to the central side. The toner charge amount increases on the end side, and the toner strongly adheres to the surface of the developing sleeve 26. Then, when repeated development is performed, when the toner passes between the regulating member 35 and the developing sleeve 26, the toner layer thickness is large on the end side even if the toner layer has a predetermined thickness on the central side in the longitudinal direction. Thus, the toner layer is disturbed.

  However, in the present embodiment, the toner on both end sides of the developer layer region H remaining on the developing sleeve 26 after development is the magnetic field generating end portions 52m and 52n of the magnetic field generating member 50 and the magnetic pole N1 of the fixed magnet body 25. Is peeled off from the surface of the developing sleeve 26 by a relatively large magnetic field formed by On the other hand, the residual toner on the central side of the developer layer region H is caused by the relatively small magnetic field formed by the magnetic field generating central portion 52p of the magnetic field generating member 50 and the magnetic pole N1 of the fixed magnet body 25, thereby developing the surface of the developing sleeve 26. Stripped from. Then, the toner is carried on the developing sleeve 26 in a state where the toner layer is not disturbed on the developing sleeve 26, and the carried toner is regulated to a predetermined layer thickness by the regulating member 35 and is uniformly formed on the surface of the developing sleeve 26. The adhered toner is supplied to the photoreceptor 11.

(Second Embodiment)
Next, a modified example of the magnetic field generating member will be described with reference to FIG. FIG. 6 is a plan view showing the arrangement of the magnetic field generating member, the regulating member, and the developing roller. In 2nd Embodiment, the magnet 51 of the magnetic field generation member 50 in 1st Embodiment differs. Henceforth, the same code | symbol is attached | subjected to the same part as 1st Embodiment, and description is abbreviate | omitted.

  As in the first embodiment, the magnetic body 52 of the magnetic field generating member 50 is made of a magnetic material such as a stainless steel plate, extends to both ends in the longitudinal direction of the developer layer region H, and is fixed on the surface of the developing sleeve 26. Opposes at intervals.

  The magnet 51 is a permanent magnet, and is opposed to the surface of the developing sleeve 26 with the same polarity as the magnetic pole N1 of the fixed magnet body 25 (see FIG. 3) with a certain interval. Further, the magnets 51 are disposed only on the both end sides of the developer layer region H. That is, each magnet 51 is arranged in a range corresponding to the magnet end portions 51m and 51n of the first embodiment. Furthermore, the magnet 51 is fixed to the downstream side surface of the magnetic body 52 with an adhesive with respect to the rotation direction of the developing roller. The magnet 51 may be attached to the upstream side surface of the magnetic body 52 with respect to the developing roller rotation direction.

  Therefore, on the end portion side of the developer layer region H, the magnetic field generating end portions 52m and 52n of the magnetic body 52 (see FIG. 4) are magnetized by the magnet 51, as in the first embodiment. A line of magnetic force is formed that passes between the tip end portions 52a of the generation end portions 52m and 52n and the opposing magnetic pole 51a of the magnet 51 (see FIG. 4). In addition, lines of magnetic force that pass between the tip portions 52a of the magnetic field generation end portions 52m and 52n and the fixed magnet body 25 are formed. A magnetic field corresponding to the magnetic field lines is formed on the front end portions 52a of the magnetic field generating end portions 52m and 52n and the surface of the developing sleeve 26.

  On the other hand, on the central portion side of the developer layer region H, the tip 52a (see FIG. 4) of the magnetic field generating central portion 52p of the magnetic body 52 is different from the magnetic pole N1 (see FIG. 4) of the fixed magnet body 25. The magnetic field lines passing between the tip 52a of the magnetic field generating central portion 52p and the magnetic pole N1 of the fixed magnet body 25 are formed. A magnetic field corresponding to the magnetic field lines is formed on the front end portion 52a of the magnetic field generation central portion 52p and the surface of the developing sleeve 26.

  As described above, the magnetic field between the end portion side and the center portion side of the developer layer region H is relatively small on the center portion side and relatively large on the end portion side, and the developing sleeve after development by each magnetic field. The developer remaining on the surface 26 is stripped off. Then, the toner is carried on the developing sleeve 26 in a state where the toner layer is not disturbed on the developing sleeve 26, and the carried toner is regulated to a predetermined layer thickness by the regulating member 35 and is uniformly formed on the surface of the developing sleeve 26. The adhered toner is supplied to the photoreceptor 11.

(Third embodiment)
FIG. 7 is a plan view showing the arrangement of the magnetic field generating member and the regulating member and the developing roller according to the third embodiment. In the third embodiment, the magnetic field generating member 50 is configured so as to correspond to the regulating member 35 in which the magnetic force on the end side is increased. The same parts as those in the first and second embodiments are denoted by the same reference numerals, and description thereof is omitted.

  As described above, the fixed magnet body 25 in the developing roller 27 and the plate magnet 37 of the regulating member 35 have a smaller magnetic force on the end portion side in the longitudinal direction than on the central portion side, and toner layer disturbance is likely to occur. In order to prevent this, as shown in FIG. 7, the magnetic force of the plate magnet end portions 37m and 37n formed on the end portion side of the plate magnet 37 is larger than that of the plate magnet center portion 37p formed on the center portion side. Is set.

  However, when setting the magnetic force of the plate magnet end portions 37m and 37n and the plate magnet central portion 37p, if the magnetic force of the plate magnet end portions 37m and 37n becomes too large, the end restriction portions 36m and 36n of the restriction blade 36 The magnetic force is too larger than the magnetic force of the center restricting portion 36p, and a step is generated between the toner layer on the end portion side of the developer layer region H and the toner layer on the central portion side.

  Therefore, the magnetic field generating member 50 of the present embodiment includes the magnetic member 52 and the magnet 51 as in the first embodiment, but the distance E in the longitudinal direction of the magnetic field generating end portions 52m and 52n of the magnetic body 52 is the plate magnet 37. Are set longer than the distance F in the longitudinal direction of the end regulating portions 36m and 36n. The distances E and F are both lengths based on the end of the developer layer region H.

  By setting the distances E and F in this way, on the developer layer region H, the boundary between the end restricting portions 36m and 36n of the restricting member 35 and the central restricting portion 36p is the magnetic field generating end 52m of the magnetic body 52. , 52n. And the magnetic force of the front-end | tip part 52a (refer FIG. 4) of the magnetic field generation | occurrence | production end parts 52m and 52n of the magnetic body 52 is large compared with the magnetic force of the front-end | tip part 52a of the magnetic field generation | occurrence | production center part 52p. As a result, when the toner remaining on the surface of the developing sleeve 26 is peeled off after the development, the magnetic field generating member 50 peels off so as to eliminate the toner layer step generated at the boundary portion.

  Note that the magnetic field generating member of the second embodiment (see FIG. 6) can be applied to eliminate the toner layer level difference. In this case, the two magnets 51 are attached to a range facing the magnetic field generation end portions 52m and 52n of the magnetic member 52, and the magnetic field generation end portions 52m and 52n are the ends of the regulating member 35 on the developer layer region H. The part restricting parts 36m, 36n and the center restricting part 36p are configured to be included.

(Fourth embodiment)
FIG. 8 is a plan sectional view showing the arrangement of the magnetic field generating member and the stirring unit according to the fourth embodiment. In the fourth embodiment, a stirrer such as a stirrer is appropriately disposed with respect to the magnetic field generating member 50.

  As described above, the developing container 22 is formed with the first transport path 22d, the second transport path 22c, the partition 22b, the first communication section 22f, and the second communication section 22e. The first conveyance path 22d and the second conveyance path 22c are arranged so as to be substantially parallel to the developing roller 27 in the horizontal direction.

  The partition 22b extends in the longitudinal direction of the developing container 22 and partitions the first transport path 22d and the second transport path 22c in parallel. A first communication portion 22f and a second communication portion 22e are provided on both ends of the partition portion 22b in the longitudinal direction, and the toner is supplied to the second conveyance path 22c, the second communication portion 22e, and the first conveyance. It is possible to circulate through the path 22d and the first communication part 22f.

  A first stirring member 44 is disposed in the first transport path 22d, and a second stirring member 43 is disposed in the second transport path 22c.

  The first stirring member 44 includes a rotating shaft 44b and first spiral blades 44a that are provided integrally with the rotating shaft 44b and formed in a spiral shape at a constant pitch in the axial direction of the rotating shaft 44b. The first spiral blade 44a extends to both ends in the longitudinal direction of the first transport path 22d, is provided to face the first and second communication portions 22f and 22e, and faces the developing roller 27. Is provided. The rotating shaft 44b is rotatably supported by the developing container 22.

  The second agitating member 43 is a blade that is provided integrally with the rotation shaft 43b and the rotation shaft 43b, and that faces in the opposite direction to the first spiral blade 44a at the same pitch as the first spiral blade 44a in the axial direction of the rotation shaft 43b. And a second spiral blade 43a formed in a spiral shape. Further, the second spiral blade 43a extends to both ends in the longitudinal direction of the second transport path 22c, and is provided to face the first and second communication portions 22f and 22e. The rotating shaft 43b is disposed in parallel with the rotating shaft 44b and is rotatably supported by the developing container 22.

  When the rotation shaft 43b is rotated by a drive source such as a motor (not shown), the second spiral blade 43a rotates, and the second spiral blade 43a transports the toner in the second transport path 22c in the direction of arrow P. Further, when the rotation shaft 44b interlocked with the rotation shaft 43b rotates, the first spiral blade 44a rotates, and the first spiral blade 44a transports the toner in the first transport path 22d in the arrow Q direction, and the toner is The second conveying path 22c is agitated while circulating through the second communication part 22e, the first conveying path 22d, and the first communication part 22f. Then, the agitated toner is supplied to the developing roller 27.

  The magnetic field generating member 50 is disposed between the developing roller 27 and the first stirring member 44 so as to face the developing roller 27 and also face the first stirring member 44.

  As described above, the magnetic field generating member 50 strips off the toner adhering to the developing roller 27. However, in order to generate a magnetic field around the magnetic field generating member 50, the stirring unit is affected by the magnetic field. .

  Therefore, in the present embodiment, the first communication portion 22 f is disposed at a position that does not face the magnetic field generating member 50. That is, the first conveyance path 22d extends further on the downstream side (right side in FIG. 8) in the toner conveyance direction from the portion where the magnetic field generating member 50 faces. The second conveyance path 22c also extends on the upstream side (the right side in FIG. 8) in the same manner as the first conveyance path 22d, and the first communication portion 22f is connected to the downstream end side of the first conveyance path 22d and the second conveyance path 22d. The upstream end side of the conveyance path 22c is communicated in a direction orthogonal to the toner conveyance directions P and Q.

  When the toner transported in the first transport path 22d is transported through the first communicating portion 22f, the first communicating portion 22f is separated from the magnetic field generating member 50, particularly the magnetic field generating end portion 52n having a relatively large magnetic force. Therefore, the magnetic force in the direction opposite to the toner moving direction does not act on the toner to suppress the toner movement, and the toner is smoothly conveyed by the first communication portion 22f.

(Fifth embodiment)
Next, another embodiment in which toner is smoothly conveyed by the stirring unit will be described. FIG. 9 is a plan sectional view showing the arrangement of the magnetic field generating member and the stirring unit. In the fifth embodiment, the first and second transport paths 22d and 22c and the first and second communication portions 22f and 22e have the same configuration as that of the fourth embodiment, and the first stirring member 44 is the same as that of the fourth embodiment. It is a different configuration.

  The first stirring member 44 transports the toner in the first transport path 22d in the direction of arrow Q by the first spiral blade 44a formed in a spiral shape. The magnetic force of the magnetic field generating member 50 acts on the toner in a direction orthogonal to the toner transport direction Q. A relatively small magnetic force acts on the magnetic field generation central portion 52p of the magnetic field generating member 50, and a relatively large magnetic force acts on the magnetic field generation end portion 52n. In the first transport path 22d facing the magnetic field generation end 52n, the toner moving speed is slower than in the first transport path 22d facing the magnetic field generation center 52p due to the influence of the magnetic field.

  Therefore, the blade outer diameter of the first spiral blade 44a is set larger at the portion facing the magnetic field generating end 52n of the magnetic field generating member 50 than at other portions. When the outer diameter of the first spiral blade 44a is increased, the toner conveying force is increased. By increasing the toner conveying force in this way, the toner opposes the magnetic field generating central portion 52p against the magnetic force of the magnetic field generating end 52n in the first conveying path 22d facing the magnetic field generating end 52n. It is transported at substantially the same speed as in the first transport path 22d, and is transported smoothly in the first transport path 22d. Note that the blade outer diameter of the first spiral blade 44a may be set to be large even at a portion facing the magnetic field generation end 52m of the magnetic field generation member 50. Further, the toner conveying force can be increased by increasing the blade pitch of the first spiral blade 44a.

  According to the above-described embodiment, the developing device 14 supplies toner to the developing region D facing the photoconductor 11, and includes the developing roller 27 including the fixed magnet body 25 having a plurality of magnetic poles in the circumferential direction, and the fixed magnet body. The developing member 27 forms a developer layer region H in which the toner amount on the developing roller 27 is regulated by a magnetic field formed with 25 opposing magnetic poles S1 and development on the upstream side of the regulating member 35 with respect to the developing roller rotation direction. And a magnetic field generating member 50 that strips off toner that is not used for development on the roller 27. The magnetic field generation member 50 includes magnetic field generation end portions 52m and 52n facing the both ends in the longitudinal direction of the developer layer region H, and a magnetic field generation central portion sandwiched between the magnetic field generation end portions 52m and 52n in the longitudinal direction. The magnetic force of the magnetic field generation end portions 52m and 52n is larger than the magnetic force of the magnetic field generation central portion 52p.

  According to this configuration, even if the toner layer thickness in the developer layer region H becomes larger on the end side than the central side in the longitudinal direction, the toner remains on the surface of the developing roller 27 after the development. The toner on the end side is surely peeled off by the respective magnetic fields of the magnetic field generating member 50, and the toner layer is not disturbed on the developing roller 27 and a good image is obtained.

  Further, according to the embodiment, the magnetic field generating member 50 includes the magnetic body 52 that extends in the longitudinal direction of the developer layer region H and faces the surface of the developing roller 27, and the counter magnetic pole that faces the surface of the developing roller 27. 51a and a magnet 51 attached to the magnetic body 52 so as to face the developing roller rotation direction. The opposing magnetic pole 51a of the magnet 51 has the same polarity as the magnetic pole N1 of the opposing fixed magnet body 25. The magnetic force of the end portions 51m and 51n is larger than the magnetic force of the magnet central portion 51p of the magnet 51.

  As a result, the tip 52a of the magnetic body 52 is magnetized to a magnetic pole having a different polarity from the counter magnetic pole 51a of the magnet 51, and a magnetic field line passing between the tip 52a of the magnetic body 52 and the counter magnetic pole 51a of the magnet 51 is formed. Is done. Further, the magnetized magnetic pole of the tip 52a of the magnetic body 52 has a different polarity from the magnetic pole N1 of the fixed magnet 25, and a magnetic line of force passing between the tip 52a of the magnetic 52 and the fixed magnet 25 is formed. The As described above, two magnetic paths are formed on the front end portion 52a of the magnetic body 52 and the surface of the developing roller 27, and the density of the magnetic force lines is increased. The magnetic field corresponding to the magnetic lines of force is relatively small on the center side of the developer layer region H and relatively large on the end side of the developer layer region H, and the surface of the developing roller 27 after development by each magnetic field. The remaining toner is stripped off. Therefore, even if the toner layer thickness of the developer layer region H becomes larger on the end side than the central side in the longitudinal direction, the toner is surely peeled off even if the toner remains on the surface of the developing roller 27 after development. As a result, the toner layer is not disturbed on the developing roller 27 and a good image can be obtained.

  Further, according to the embodiment, the magnetic field generating member 50 includes the magnetic body 52 that extends in the longitudinal direction of the developer layer region H and faces the surface of the developing roller 27, and the counter magnetic pole that faces the surface of the developing roller 27. 51a and a magnet 51 attached to the magnetic body 52 so as to face the developing roller rotation direction. The magnetic body 52 extends to both ends in the longitudinal direction of the developer layer region H, and the magnet 51 is a developer layer. The opposing magnetic pole 51a of the magnet 51 is disposed opposite to both end portions in the longitudinal direction of the region H, and has the same polarity as the magnetic pole N1 of the opposing fixed magnet body 25.

  As a result, on the end side of the developer layer region H, the tip 52 a of the magnetic body 52 is magnetized to a magnetic pole having a different polarity from the counter magnetic pole 51 a of the magnet 51, and the tip 52 a of the magnetic body 52 is opposed to the magnet 51. Magnetic field lines passing between the magnetic poles 51a are formed. Further, the magnetized magnetic pole of the tip 52a of the magnetic body 52 has a different polarity from the magnetic pole N1 of the fixed magnet 25, and a magnetic line of force passing between the tip 52a of the magnetic 52 and the fixed magnet 25 is formed. The Magnetic fields corresponding to the two magnetic paths due to these lines of magnetic force are formed on the tip 52 a of the magnetic body 52 and the surface of the developing roller 27. On the other hand, on the central side of the developer layer region H, the tip 52a of the magnetic body 52 is magnetized to a magnetic pole having a different polarity from the magnetic pole N1 of the fixed magnet 25, and the tip 52a of the magnetic 52 and the fixed magnet 25 A magnetic field with the magnetic pole N 1 is formed on the tip 52 a of the magnetic body 52 and the surface of the developing roller 27. As described above, the magnetic field between the end portion side and the center portion side of the developer layer region H is relatively small at the center portion side and relatively large at the end portion side, and the developing roller after development by each magnetic field. 27 The toner remaining on the surface is stripped off. Therefore, even if the toner layer thickness of the developer layer region H becomes larger on the end side than the central side in the longitudinal direction, the toner is surely peeled off even if the toner remains on the surface of the developing roller 27 after development. As a result, the toner layer is not disturbed on the developing roller 27 and a good image can be obtained.

  Further, according to the above-described embodiment, the regulating member 35 includes the end regulating portions 36m and 36n facing the both ends in the longitudinal direction of the developer layer region H, and the end regulating portions 36m and 36n in the longitudinal direction. And the end portion restricting portions 36m and 36n have a larger magnetic force than the center restricting portion 36p, and the magnetic field generating end portions 52m and 52n of the magnetic field generating member 50 are the ends of the restricting member 35. It is formed so as to face the developer layer region H that faces the part restricting portions 36m and 36n, and the boundary between the end restricting portions 36m and 36n and the central restricting portion 36p.

  Thus, when the developer layer H is formed by the regulating member 35, if the magnetic force of the end regulating portions 36m and 36n is larger than the magnetic force of the central regulating portion 36p, the toner layer thickness on the end side of the developer layer region H is increased. And a step is generated in the toner layer on the central side. However, after the development, when the toner remaining on the surface of the developing roller 27 is peeled off, the magnetic field generating end portions 52m and 52n of the magnetic field generating member 50 are located on the developer layer region H with the end restricting portions 36m and 36n of the restricting member 35. The magnetic field generating member 50 is peeled off so as to eliminate the step of the toner layer. Therefore, the toner layer is not disturbed on the developing roller 27 and a good image can be obtained.

  In addition, according to the above embodiment, the magnetic body 52 has the tip portion 52a facing the developing roller 27 and the opposite surface portion 52b opposite to the tip portion 52a, and the tip of the tip portion 52a in the circumferential direction of the developing roller. The width is smaller than the opposite surface portion 52b. Thereby, since the length of the opposite surface portion 52b of the magnetic body 52 is large, a large number of lines of magnetic force passing between the opposite surface portion 52b of the magnetic body 52 and the magnet 51 are formed. Accordingly, the magnetic force of the magnetic body 52 is increased, and a magnetic field can be efficiently generated at the tip 52a of the magnetic body 52, and the toner attached to the surface of the developing roller 27 is surely peeled off.

  In addition, according to the above-described embodiment, the developing device 14 includes the first stirring member 44 that supplies toner while facing the developing roller 27, the second stirring member 43 that stirs and conveys toner together with the first stirring member 44, A first transport path 22d through which toner is transported by the first stirring member 44; a second transport path 22c that is disposed in parallel with the first transport path 22d; and that transports toner by the second stirring member 43; A first communication portion 22f that passes toner from the first conveyance path 22d to the second conveyance path 22c and a second communication portion 22e that passes toner from the second conveyance path 22c to the first conveyance path 22d are provided. The magnetic field generating member 50 is disposed between the developing roller 27 and the first stirring member 44, and the first communication portion 22 f is disposed at a position not facing the magnetic field generating member 50.

  Thus, the toner is conveyed from the upstream side in the toner conveyance direction to the downstream side in the first conveyance path 22d while being agitated by the first agitating member 44. Next, when the toner moves from the first conveyance path 22d to the second conveyance path 22c via the first communication portion 22f, the toner is conveyed without being greatly affected by the magnetic force of the magnetic field generating member 50. Accordingly, the toner is peeled off from the developing roller 27 by the magnetic field generating member 50, and the toner is uniformly circulated in the first and second transport paths 22d and 22c, so that the toner is supplied to the developing roller 27. There is no risk of abnormal images such as density reduction or ghost phenomenon.

  Further, according to the above embodiment, the first stirring member 44 transports the toner by the spiral blade, and the spiral blade facing the magnetic field generation end portion 52n of the magnetic field generating member 50 has a large toner transport force. It is formed to become.

  As a result, the toner conveyed in the first conveyance path 22d by the first stirring member 44 receives the magnetic force of the magnetic field generation end 52n, but the spiral blade facing the magnetic field generation end 52n conveys the toner. Since the force is formed so as to increase, the toner in the first conveyance path 22d is conveyed at substantially the same speed. Therefore, the toner circulates uniformly in the first and second conveyance paths 22d and 22c and the toner is supplied to the developing roller 27, so that there is no possibility that an abnormal image such as a decrease in density or a ghost phenomenon occurs.

  In addition, if the magnetic force of the magnetic field generation | occurrence | production end parts 52m and 52n of the magnetic field generation member 50 is a structure larger than the magnetic force of the magnetic field generation | occurrence | production center part 52p, not only the said embodiment but the magnetic field generation member 50 consists only of the magnet 51, The opposed magnetic pole 51 a of 51 may have a different polarity with respect to the magnetic pole of the fixed magnet body 25 of the developing roller 27. Further, the magnetic field generating member 50 may be composed of only the magnet 51, and the opposing magnetic pole 51 a of the magnet 51 may have the same polarity as the magnetic pole of the fixed magnet body 25 of the developing roller 27. Further, the magnet 51 of the magnetic field generating member 50 is arranged between the magnetic pole N and the magnetic pole S of the fixed magnet body 25, and the magnetic force of the magnet 51 is made relatively strong. You may make it the structure formed. Even if the toner adhering to the surface of the developing roller 27 is peeled off by these magnetic fields, the same effect as in the above-described embodiment can be obtained.

  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.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 11 Photosensitive body (image carrier)
DESCRIPTION OF SYMBOLS 14 Developing apparatus 22 Developer container 22a Developer accommodating part 22b Partition part 22c 2nd conveying path 22d 1st conveying path 22e 2nd communicating part 22f 1st communicating part 22p Developer supply part 25 Fixed magnet body 26 Developing sleeve 27 Developing roller 35 Restriction member 36 Restriction blade 36m, 36n End restriction part 36p Central restriction part 37 Plate magnet 37m, 37n Plate magnet end part 37p Plate magnet center part 43 Second stirring member 43a Second spiral blade 44 First stirring member 44a First spiral Blade 50 Magnetic field generating member 51 Magnet 51a Opposing magnetic pole 51b Opposing magnetic pole 51c Face to face 51m, 51n Magnet end 51p Magnet central part 52 Magnetic body 52a Tip 52b Opposite face 52m, 52n Magnetic field generating end 52p Magnetic field generating central D H Developer layer area T Toner circulation area

Claims (8)

The developer roller is supplied to a developing region facing the image carrier and includes a developing roller containing a fixed magnet body having a plurality of magnetic poles in the circumferential direction, and a magnetic field formed together with the opposing magnetic poles of the fixed magnet body. A regulating member that forms a developer layer region that regulates the amount of the developer on the top, and a magnetic field generation that strips off the developer that is not used for development on the developing roller upstream of the regulating member with respect to the rotation direction of the developing roller In a developing device comprising a member,
The magnetic field generation member has a magnetic field generation end facing the both ends in the longitudinal direction of the developer layer region, and a magnetic field generation central portion sandwiched between the magnetic field generation ends in the longitudinal direction, The developing device according to claim 1, wherein the magnetic force at the magnetic field generation end is greater than the magnetic force at the magnetic field generation center.   The magnetic field generating member includes a magnetic body facing the surface of the developing roller, and a magnet having a counter magnetic pole facing the surface of the developing roller and facing the developing roller rotating direction and attached to the magnetic body. The opposing magnetic pole of the magnet has the same polarity as the magnetic pole of the opposing fixed magnet body, and the magnetic force on the magnetic field generation end side of the magnet is larger than the magnetic force on the magnetic field generation center side of the magnet. The developing device according to 1.   The magnetic field generating member includes a magnetic body facing the surface of the developing roller, and a magnet having a counter magnetic pole facing the surface of the developing roller and facing the developing roller rotating direction and attached to the magnetic body. The magnetic body extends to both ends in the longitudinal direction of the developer layer region, the magnet is disposed to face both ends in the longitudinal direction of the developer layer region, and the opposing magnetic pole of each magnet is The developing device according to claim 1, wherein the developing device has the same polarity as the magnetic poles of the opposed fixed magnet bodies.   The magnetic body has a tip portion facing the developing roller and an opposite surface portion opposite to the tip portion, and the width of the tip portion in the circumferential direction of the developing roller is smaller than the opposite surface portion. The developing device according to claim 2. The restricting member includes an end restricting portion facing both ends in the longitudinal direction of the developer layer region, and a central restricting portion sandwiched between the end restricting portions in the longitudinal direction. The magnetic force of the restriction part is larger than the magnetic force of the central restriction part,
The magnetic field generating end of the magnetic field generating member is formed to face an end portion restricting portion of the restricting member and a developer layer region facing the boundary between the end restricting portion and the central restricting portion. The developing device according to claim 1, wherein A first stirring member that faces the developing roller and supplies the developer, a second stirring member that stirs and transports the developer together with the first stirring member, and a first that transports the developer by the first stirring member. A transport path, a second transport path that is arranged in parallel with the first transport path, and transports the developer by the second stirring member; and the developer from the first transport path to the second transport path. A first communication part that passes through, and a second communication part that passes the developer from the second transport path to the first transport path,
2. The magnetic field generating member is disposed between the developing roller and the first stirring member, and the first communication portion is disposed at a position not facing the magnetic field generating member. The developing device according to claim 5.   The first agitating member includes a rotating shaft and a spiral blade formed around the rotating shaft, and the spiral blade facing the magnetic field generating end of the magnetic field generating member The developing device according to claim 6, wherein the developing device is formed to have a large conveying force.   An image forming apparatus on which the developing device according to claim 1 is mounted.

Images