JP5509157B2 - Developing device and image forming apparatus including the same - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile machine and a developing device used therefor, and more particularly, to a method for preventing leakage of developer from a developing device using a magnetic developer.

  In an image forming apparatus using an electrophotographic system such as a copying machine, a printer, and a facsimile, a powder developer is mainly used, and an electrostatic latent image formed on an image carrier such as a photosensitive drum is used as a developer. A general process is to perform a fixing process after visualizing and transferring the toner image onto a recording medium.

  Developers are broadly divided into two-component developers composed of toner and a magnetic carrier (hereinafter also simply referred to as carrier) and one-component developers composed only of magnetic toner, and a regulating blade (developer regulating member). Thus, triboelectric charging of the developer carried on the developing roller (developer carrying member) is promoted. As the regulating blade, there are known a configuration constituted by only a magnetic member, and a configuration in which a magnetic member is arranged in a portion (developer regulating portion) facing a developing roller based on a non-magnetic member.

  In such a developing device using a regulating blade, a part of the developer supplied to the developer regulating unit with the rotation of the developing roller passes through the regulating blade and forms a thin developer layer on the developing roller. However, most of the remaining developer rides on the regulating blade and is returned to the developing device. At this time, there exists a tendency for a developing agent to go to the longitudinal direction both ends of a developing roller and a control blade. Accordingly, it is necessary to prevent leakage of the developer from the developing device in this portion.

  Conventionally, as disclosed in Patent Document 1, a method for preventing leakage of a developer by providing a magnetic seal member at both longitudinal ends of a developing device has been proposed. This prevents leakage of developer using a magnetic brush formed between a magnetic seal member and a developing roller by a magnetic field between a fixed magnet body and a magnetic seal member arranged in the developer carrying body. It is.

  Patent Document 2 discloses a developing device in which a plurality of grooves are formed along the circumferential direction or the axial direction of the developing roller on the surface of the developing roller side of the magnetic seal member disposed at the end of the developing roller. Yes. According to this configuration, since the magnetic field concentrates on the edge portion of the groove and the magnetic binding force of the toner increases, the leakage of the developer can be effectively suppressed.

JP-A-2-262171 JP 2003-270941 A

  On the other hand, by increasing the peripheral speed of the developing roller accompanying the recent speeding up of the image forming process, making the developer finer for improving the image quality, and using a spherical carrier having a high circularity or apparent bulk density (AD), There is a tendency that leakage of the developer from the developing device tends to occur. Therefore, it is necessary to improve the sealing performance of the magnetic seal member in order to prevent leakage of the developer.

  However, even with the configuration of Patent Document 2, it has been difficult to obtain sufficient sealing performance that can withstand the increase in peripheral speed of the developing roller, finer developer, use of a spherical carrier, and the like. Further, as another method for improving the sealing performance, a method of increasing the magnetic field between the fixed magnet body and the magnetic seal member is conceivable, but there is a disadvantage that the cost of the magnetic seal member is increased.

  In view of the above problems, an object of the present invention is to provide a developing device that can improve the sealing performance of a magnetic seal member easily and at low cost, and an image forming apparatus including the developing device.

  To achieve the above object, the present invention provides a housing for storing a magnetic developer, a developer carrying member for carrying the developer by a magnet member that is rotatably supported by the housing and fixed inside. And a magnetic seal member disposed at a predetermined interval along the outer peripheral surface of both ends in the longitudinal direction of the developer carrier, wherein the magnetic seal member includes the developer carrier and the magnetic seal member. A plurality of circumferential grooves extending along the circumferential direction of the developer carrier, and a plurality of axial grooves connecting the plurality of circumferential grooves are formed on the opposite surface of the developer carrying member. The axial grooves adjacent to each other in the axial direction of the agent carrier are not formed on the same straight line parallel to the axial direction of the developer carrier.

  According to the present invention, in the developing device configured as described above, the axial groove includes an outermost first circumferential groove and an innermost second groove in the axial direction of the developer carrier among the plurality of circumferential grooves. It is characterized by being formed only between the circumferential grooves.

  According to the present invention, in the developing device configured as described above, the axial grooves adjacent to each other in the axial direction of the developer carrier are formed at different positions in the circumferential direction of the developer carrier.

  According to the present invention, in the developing device configured as described above, at least one of the axial grooves adjacent in the axial direction of the developer carrying member intersects the circumferential groove at a predetermined angle other than a right angle. It is characterized by.

  The present invention also provides an image forming apparatus including the developing device having the above-described configuration.

  According to the first configuration of the present invention, by providing the axial groove in addition to the plurality of circumferential grooves, a mesh-like convex portion is formed, and the edge peripheral length of the convex portion can be increased. Therefore, the region where the magnetic field is concentrated can be expanded, and a stronger sealing property can be secured. In addition, since each adjacent axial groove is discontinuous in the axial direction of the developer carrier, a large gap between the developer carrier and the magnetic seal member is generated continuously across the magnetic seal member. do not do. Accordingly, it is possible to prevent the magnetic binding force of the toner from being lowered by the magnetic seal member.

  Further, according to the second configuration of the present invention, in the developing device of the first configuration, the axial groove is formed such that the outermost first circumferential groove and the innermost second groove in the axial direction of the developer carrier. By forming only between the circumferential grooves, the first circumferential grooves and the first circumferential grooves are prevented from leaking out of the toner by magnetic brushes formed at the edge portions of the outer edges of the first circumferential grooves and the second circumferential grooves. The magnetic restraint force of the toner can be increased by the mesh-like convex portions formed inside the second circumferential groove.

  According to the third configuration of the present invention, in the developing device having the first or second configuration, the axial groove adjacent to the axial direction of the developer carrier differs in the circumferential direction of the developer carrier. By forming at the position, at least one convex part exists in any part in the circumferential direction of the magnetic seal member when viewed from the axial direction of the developer carrier, and is formed at the circumferential edge part of the convex part. The magnetic brush can effectively prevent the leakage of toner.

  According to the fourth configuration of the present invention, in the developing device having the first or second configuration, at least one of the axial grooves adjacent to the axial direction of the developer carrying member is perpendicular to the circumferential groove. By crossing at a predetermined angle other than, at least one convex portion exists in any part in the circumferential direction of the magnetic seal member when viewed from the axial direction of the developer carrier, and the circumferential direction of the convex portion The magnetic brush formed on the edge portion can effectively prevent toner leakage.

  Further, according to the fifth configuration of the present invention, by mounting the developing device having any one of the first to fourth configurations, the developer leaks from the developing device with a simple configuration over a long period of time. Thus, the image forming apparatus can be prevented.

Schematic sectional view of an image forming apparatus provided with the developing device of the present invention A plan view (FIG. 2A) and a front view (FIG. 2B) of the developing device of the present invention. Side sectional view of the developing device of the present invention Enlarged view around the developing roller in FIG. The perspective view which shows the state which extended the magnetic seal member of 1st Embodiment used for the image development apparatus of this invention in flat form. The perspective view which shows the other structural example of the magnetic seal member of 1st Embodiment. The perspective view which shows the state which extended the magnetic seal member of 2nd Embodiment used for the image development apparatus of this invention in flat form. The perspective view which shows the other structural example of the magnetic seal member of 2nd Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic sectional view of an image forming apparatus provided with the developing device of the present invention. In the image forming apparatus (for example, a monochrome printer) 100, when a printing operation is performed, an electrostatic latent image is formed based on document image data transmitted from a personal computer (PC) (not shown) in the image forming unit 9 in the apparatus main body. Then, the developing device 4 attaches toner to the electrostatic latent image to form a toner image. The toner is supplied to the developing device 4 from the toner container 5. In such an image forming apparatus 100, the image forming process for the photosensitive drum 1 is executed while rotating the photosensitive drum 1 clockwise in FIG.

  The image forming unit 9 includes a charging device 2, an exposure unit 3, a developing device 4, a transfer roller 6, a cleaning device 7, and a charge eliminating device (not shown) along the rotation direction (clockwise direction) of the photosensitive drum 1. ) Is arranged. The photosensitive drum 1 is formed, for example, by laminating a photosensitive layer on an aluminum drum, and the charging device 2 uniformly charges the surface. Then, an electrostatic latent image in which charging is attenuated is formed on the surface that has received a laser beam from the exposure unit 3 described later. The photosensitive layer is not particularly limited, and for example, amorphous silicon (a-Si) or OPC (organic photosensitive layer) is used.

  A charging device (charging charger) 2 uniformly charges the surface of the photosensitive drum 1. For example, the charging device 2 is a corona discharge device that discharges by applying a high voltage using a thin wire or the like as an electrode. Instead of the corona discharge device, a contact-type charging device that applies a voltage in a state where a charging member typified by a charging roller is in contact with the surface of the photoreceptor may be used. The exposure unit 3 irradiates the photosensitive drum 1 with a light beam (for example, a laser beam) based on the image data, and forms an electrostatic latent image on the surface of the photosensitive drum 1.

  The developing device 4 forms toner images by attaching toner to the electrostatic latent image on the photosensitive drum 1. In the present embodiment, a two-component developer (hereinafter also simply referred to as a developer) composed of toner and a magnetic carrier is accommodated in the developing device 4. Details of the developing device 4 will be described later. The cleaning device 7 includes a cleaning roller, a blade material, and the like that are in line contact with the longitudinal direction of the photosensitive drum 1 (the front and back sides in FIG. 1). After the toner image is transferred to the paper, the cleaning device 7 Toner remaining on the surface (residual toner) is removed.

  A sheet is conveyed from the sheet storage unit 10 to the image forming unit 9 at a predetermined timing via the sheet conveyance path 11 and the resist roller pair 13 toward the photosensitive drum 1 on which the toner image is formed as described above. . The transfer roller 6 transfers the toner image formed on the surface of the photosensitive drum 1 to the sheet conveyed through the sheet conveyance path 11 without disturbing the toner image. Thereafter, in preparation for the subsequent formation of a new electrostatic latent image, residual toner on the surface of the photosensitive drum 1 is removed by the cleaning device 7, and residual charges are removed by the static eliminator.

  Then, the sheet on which the toner image is transferred is separated from the photosensitive drum 1, conveyed to the fixing device 8, and heated and pressed to fix the toner image on the sheet. The paper that has passed through the fixing device 8 passes through the discharge roller pair 14 and is discharged to the paper discharge unit 15.

  2A and 2B are a plan view and a front view of a developing device according to an embodiment of the present invention, and FIG. 3 is a side sectional view of the developing device of the present invention. In FIG. 2A, for the sake of convenience, a state in which the top cover is removed and the inside can be seen is represented. As shown in FIGS. 2 and 3, the inside of the housing 20 of the developing device 4 is partitioned into a first storage chamber 21 and a second storage chamber 22 by a partition wall 20 a formed integrally with the housing 20. A first stirring screw 23 is disposed in the first storage chamber 21, and a second stirring screw 24 is disposed in the second storage chamber 22.

  Each of the first stirring screw 23 and the second stirring screw 24 has a configuration in which spiral blades are provided around a supporting shaft (rotating shaft), and is rotatably supported by the housing 20 in a state of being parallel to each other. . In addition, as shown to Fig.2 (a), the partition wall 20a does not exist in the both ends of the longitudinal direction of the housing 20 which is the axial direction of the 1st stirring screw 23 and the 2nd stirring screw 24, and the 1st stirring screw 23, the developer can be transferred between the second agitating screws 24. As a result, the first stirring screw 23 transports the developer in the first storage chamber 21 in the direction of arrow P while stirring the developer, and transports it to the second storage chamber 22. The developer conveyed to the chamber 22 is conveyed in the direction of arrow Q while being agitated and supplied to the developing roller 25.

  The developing roller 25 rotates in accordance with the rotation of the photosensitive drum 1 (see FIG. 1), thereby supplying toner to the photosensitive layer of the photosensitive drum 1. A fixed magnet body 27 made of a permanent magnet having a plurality of magnetic poles is fixed inside the developing roller 25. A magnetic brush is formed by attaching (carrying) developer to the surface of the developing roller 25 by the magnetic force of the fixed magnet body 27. The developing roller 25 is rotatably supported by the housing 20 in a state parallel to the first stirring screw 23 and the second stirring screw 24. The first stirring screw 23, the second stirring screw 24, and the developing roller 25 are rotationally driven by a motor (not shown).

  The regulating blade 29 is formed such that its longitudinal direction (left-right direction in FIG. 2) is larger than the maximum developing width, and is supplied to the photosensitive drum 1 by being arranged at a predetermined interval from the developing roller 25. A regulating unit 30 that regulates the toner amount is formed. As the material of the regulating blade 29, magnetic or non-magnetic SUS (stainless steel) or the like is used. Note that magnetism may be imparted by attaching a permanent magnet to the non-magnetic regulating blade 29.

  A toner concentration sensor (not shown) for detecting the toner concentration in the developer stored in the housing 20 is provided on the bottom surface of the second storage chamber 22 facing the second stirring screw 24. In accordance with the detection result of the toner density sensor, the toner stored in the toner container 5 (see FIG. 1) is supplied into the housing 20 through the toner supply port 20b provided in the upper part of the housing 20.

  DS rollers 31 a and 31 b are rotatably inserted on the rotation shaft of the developing roller 25. The DS rollers 31 a and 31 b strictly regulate the distance between the developing roller 25 and the photosensitive drum 1 by contacting both end portions of the outer peripheral surface of the photosensitive drum 1. The DS rollers 31a and 31b have built-in bearings, and the drum surface can be prevented from being worn by being rotated by being driven by the photosensitive drum 1. Further, magnetic seal members 33a and 33b for preventing the leakage of the developer from the gap between the housing 20 and the developing roller 25 are disposed at both ends of the developing roller 25.

  FIG. 4 is an enlarged view of the periphery of the developing roller in FIG. A method for regulating the amount of toner on the developing roller 25 will be described in detail with reference to FIG. As shown in FIG. 4, the fixed magnet body 27 has five magnetic poles 27a to 27e including N poles 27a and 27c and S poles 27b, 27d, and 27e. Since the N pole (regulation pole) 27 a of the fixed magnet body 27 faces the regulation blade 29, an S pole is induced at the tip of the regulation blade 29, and a magnetic field in a direction attracting the regulation portion 30 is generated.

  By this magnetic field, a magnetic brush in which a carrier and toner are connected is formed between the regulating blade 29 and the developing roller 25, and the layer is regulated to a desired height when the magnetic brush passes through the regulating unit 30. On the other hand, the developer not used for forming the magnetic brush stays along the upstream (right) side surface of the regulating blade 29. Thereafter, when the developing roller 25 rotates counterclockwise and the magnetic brush moves to a position facing the photosensitive drum 1, a magnetic field is applied by the south pole (main pole) 27 b. The electrostatic latent image is developed in contact with the surface of the substrate.

  When the developing roller 25 further rotates counterclockwise, a magnetic field attracted by the N pole 27c is applied this time, and the toner that has not been used to form the toner image together with the magnetic brush is collected in the housing 20. Further, since a repulsive magnetic field is applied by the S poles 27 d and 27 e (peeling poles), the magnetic brush is detached from the developing roller 25 in the housing 20. Then, after being stirred and conveyed by the second stirring screw 24, a magnetic brush is formed again on the developing roller 25 by the magnetic field of the south pole 27e.

  Magnetic seal members 33a and 33b are disposed on the housing 20 surrounding both ends of the developing roller 25, respectively. In FIG. 4, only the magnetic seal member 33a is shown. As shown in FIG. 4, the magnetic seal members 33a and 33b are disposed at both ends of the developing roller 25 in a non-contact state with the developing roller 25, that is, at a predetermined distance from the outer peripheral surface of the developing roller 25. Is done. The magnetic seal members 33a and 33b are disposed on the opposite side of the photosensitive drum 1 with the developing roller 25 interposed therebetween.

  Next, the two-component developer used in the developing device of the present invention will be described. The two-component developer contains a toner and a magnetic carrier. The weight ratio (T / C) between the toner and the magnetic carrier in the two-component developer is preferably 5 to 20 parts by weight, more preferably 8 to 15 parts by weight with respect to 100 parts by weight of the magnetic carrier.

  The toner is obtained by adding an external additive to toner base particles. The toner base particles contain a binder resin and a colorant. The toner base particles may contain a release agent, a charge control agent, magnetic powder and the like as necessary. The weight average particle diameter of the toner base particles is preferably 5 to 12 μm, and more preferably 6 to 10 μm. The weight average particle diameter of the toner base particles is measured by a particle size distribution measuring device (for example, Multisizer II type manufactured by Coulter, Inc.). The toner base particles are produced by a known method such as a pulverization classification method, a melt granulation method, a spray granulation method, or a polymerization method.

  Examples of the external additive include inorganic oxides such as silica, titanium oxide, and alumina, and metal soaps such as calcium stearate. The amount of the external additive is usually 0.1 to 5 parts by weight with respect to 100 parts by weight of the toner base particles.

  Examples of the magnetic carrier include magnetic particles or resin particles in which a magnetic material is dispersed in a binder resin. Examples of magnetic materials include magnetic metals such as iron, nickel, cobalt, and alloys thereof, or alloys containing rare earths, hematite, magnetite, manganese-zinc ferrite, nickel-zinc ferrite, manganese-magnesium. Soft ferrites such as lithium ferrite and lithium ferrite, iron oxides such as copper-zinc ferrite, and mixtures thereof.

  Examples of the binder resin include vinyl resins, polyester resins, epoxy resins, phenol resins, urea resins, polyurethane resins, polyimide resins, cellulose resins, polyether resins, and mixtures thereof. Magnetic particles are produced by a known method such as a sintering method or an atomizing method. The carrier may have a coating layer made of a coating resin on its surface.

  Here, in order to improve the mixing property of the toner in the two-component developer and the magnetic carrier, and smoothly circulate the developer in the developing device to reduce the driving torque of the first and second agitating screws 23 and 24. A spherical carrier having a circularity of 0.93 or more may be used. When such a spherical carrier is used, the magnetic brush on the developing roller 25 can be densely and uniformly formed, so that the image quality can be improved.

  Further, the spherical carrier may be defined by the apparent bulk density instead of the circularity. For example, in the case of a coated ferrite carrier in which a carrier core material composed of spherical ferrite particles is coated with a resin solution and then heat-treated, the apparent bulk density (AD) is 2.35 or more when the circularity is 0.93 or more. It becomes.

  However, when a carrier having a high degree of circularity or apparent bulk density is used, the adhesion between the carriers is weakened, so that leakage of the developer from the housing 20 is likely to occur. Therefore, it is necessary to improve the sealing performance of the magnetic seal members 33a and 33b.

  FIG. 5 is a perspective view showing a state in which the magnetic seal member of the first embodiment used in the developing device of the present invention is extended in a flat plate shape. In the following, the configuration of the magnetic seal member 33a will be described, but the same applies to the magnetic seal member 33b, and the description thereof will be omitted. As shown in FIG. 5, the magnetic seal member 33a of the present embodiment extends on the inner peripheral surface (the surface facing the developing roller 25) along the circumferential direction of the developing roller 25 (vertical direction in FIG. 5). A plurality (three in this case) of circumferential grooves 35 and a plurality of axial grooves 37 connecting the circumferential grooves 35 are formed.

  When a groove is formed in the inner peripheral surface of the magnetic seal member 33a, a magnetic field is concentrated on the edge portion of the convex portion 40 surrounded by the groove, so that the magnetic binding force of the toner is increased. As a result, the toner is difficult to leak. Further, by providing the axial grooves 37 in addition to the plurality of circumferential grooves 35, the mesh-shaped convex portions 40 are formed, and the edge circumferential length of the convex portions 40 can be increased. Therefore, the region where the magnetic field is concentrated can be expanded, and a stronger sealing property can be secured.

  Here, when the axial groove 37 is continuously formed on the same straight line parallel to the axial direction (arrow AA ′ direction) of the developing roller 25, the portion where the gap between the developing roller 25 and the magnetic seal member 33a is large is a magnetic seal. There is a concern that the magnetic binding force of the toner may decrease due to the continuous occurrence of crossing the member 33a. Therefore, as shown in FIG. 5, the axial grooves 37 adjacent to each other in the axial direction of the developing roller 25 are arranged so as to be shifted in the circumferential direction of the developing roller 25. Becomes discontinuous. Thus, at any part in the circumferential direction of the magnetic seal member 33a, at least one convex portion 40 exists as viewed from the axial direction of the developing roller 25, and is formed at the circumferential edge portion of the convex portion 40. The magnetic brush can effectively prevent toner leakage.

  The interval (pitch) between the circumferential groove 35 and the axial groove 37 is not particularly limited, but the convex portion 40 is finely partitioned when the interval between the circumferential groove 35 and the axial groove 37 is narrowed. The edge circumference can be made longer. On the other hand, since the convex portion 40 becomes smaller as the distance between the circumferential groove 35 and the axial groove 37 becomes narrower, chipping of the edge portion of the convex portion 40 is likely to occur. Accordingly, it is preferable to form the circumferential grooves 35 and the axial grooves 37 as many as possible by narrowing the interval within a range where the edge portion of the convex portion 40 is not chipped.

  On the other hand, if the depth and width of the circumferential groove 35 and the axial groove 37 are too large, the gap between the developing roller 25 and the magnetic seal member 33a becomes large, and the magnetic binding force of the toner is reduced. Therefore, the depth and groove width of the circumferential groove 35 and the axial groove 37 are preferably about 0.5 mm to 3 mm. In the present embodiment, a circumferential groove 35 and an axial groove 37 having a rectangular cross section with a groove width of 2 mm and a depth of 2 mm are formed.

As a material of the magnetic seal member 33a, for example, a ferromagnetic material made of iron, nickel, cobalt, or an alloy thereof is used. In the present embodiment, iron-based moldaroy having a magnetic permeability of 10 ⁻³ is used. Moldaroy is an alloy obtained by molding metal powder.

  The length L of the magnetic seal member 33a is determined according to the diameter of the developing roller 25 so that the magnetic seal member 33a can be arranged in an arc from the regulating blade 29 to the lower side of the developing roller 25 as shown in FIG. . Further, the width W and the thickness t of the magnetic seal member 33a may be determined according to the specifications of the developing device 4, respectively.

  FIG. 6 is a perspective view showing another configuration example of the magnetic seal member of the first embodiment. In FIG. 6, the axial groove 37 intersects the circumferential groove 35 at a predetermined angle that is not perpendicular. Also in the configuration of FIG. 6, the adjacent axial grooves 37 are not formed on the same straight line parallel to the axial direction of the developing roller 25, and the axial direction of the developing roller 25 in any part of the circumferential direction of the magnetic seal member 33 a. As a result, at least one convex portion 40 exists. Thereby, similarly to the configuration of FIG. 5, the leakage of toner can be effectively prevented by the magnetic brush formed at the circumferential edge portion of the convex portion 40.

  In FIG. 6, two axial grooves 37 adjacent to each other with one circumferential groove 35 interposed therebetween are inclined with respect to the circumferential groove 35 by the same angle so as to be line-symmetric, The angles of the two adjacent axial grooves 37 with respect to the circumferential groove 35 may be different. Further, it is only necessary that at least one of the two adjacent axial grooves 37 intersects with the circumferential groove 35 at a predetermined angle that is not a right angle.

FIG. 7 is a perspective view showing a state in which the magnetic seal member of the second embodiment used in the developing device of the present invention is extended in a flat plate shape. In the present embodiment, among the three circumferential grooves 35, the axial groove 37 is provided only between the outermost first circumferential groove 35 a and the innermost second circumferential groove 35 b in the axial direction of the developing roller 25. Forming. Further, as the material of the magnetic seal member 33a, iron-based moldaroy having a magnetic permeability of 10 ⁻⁶ is used. Since the configuration of other parts is the same as that of the first embodiment, description thereof is omitted.

  Also in this embodiment, the plurality of axial grooves 37 in addition to the plurality of circumferential grooves 35 are shifted in the circumferential direction so that the first magnetic brush formed on the circumferential edge portion of the convex portion 40 can be used. As in the first embodiment, a strong sealing property can be ensured. Further, since the axial groove 37 is not formed outside the outermost first circumferential groove 35a and inside the innermost second circumferential groove 35b, the first circumferential groove 35a and the second circumferential groove 35b are not formed. A mesh formed between the first circumferential groove 35a and the second circumferential groove 35b while restricting the movement of the toner in the axial direction of the developing roller 25 by a magnetic brush continuously formed on the edge portion of the outer edge. The magnetic restraint force of the toner can be increased by the convex portion 40 having a shape.

  FIG. 8 is a perspective view showing another configuration example of the magnetic seal member of the second embodiment. In FIG. 8, as in FIG. 6 of the first embodiment, the axial groove 37 intersects the circumferential groove 35 with a predetermined angle that is not perpendicular. Thus, the adjacent axial grooves 37 are not formed on the same straight line parallel to the axial direction of the developing roller 25, and at least any part of the magnetic seal member 33a in the circumferential direction is at least viewed from the axial direction of the developing roller 25. Since there is one convex portion 40, it is possible to effectively prevent the leakage of the toner by suppressing the decrease in the magnetic binding force of the toner.

  Further, by forming the axial groove 37 only between the first circumferential groove 35a and the second circumferential groove 35b, it is continuous with the edge portions of the outer edges of the first circumferential groove 35a and the second circumferential groove 35b. The movement of the toner in the axial direction of the developing roller 25 can be regulated by the magnetic brush formed in this manner.

  In addition, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the meaning of this invention. For example, the present invention is not limited to the developing device as shown in FIG. 2, but includes a magnetic roller (developer carrier) and a developing roller, and a toner is left on the developing roller while leaving a carrier on the magnetic roller. It can be applied in exactly the same manner to a seal structure at both ends of a magnetic roller in a developing device in which only a toner is transferred to form a thin toner layer and toner is attached to an electrostatic latent image on a photoreceptor by an alternating electric field.

  Further, the fixed magnet body 27 arranged inside the developing roller 25 is not limited to the five-pole configuration having the same pole portion (peeling pole) in which the S poles 27d and 27e are arranged as shown in FIG. A 6-pole configuration having no separation pole in which the S poles are alternately arranged by 3 poles may be used.

  Furthermore, the present invention is not limited to a developing device that uses a two-component developer including a toner and a carrier, but can be applied to a seal structure of a developing device that uses a magnetic one-component developer.

  The present invention can be used for a seal mechanism of a developing device using a magnetic developer. By using the present invention, a magnetic seal member magnetized to a relatively small magnetic flux density is used even in the case of high-speed printing where the peripheral speed of the developing roller is high or when a carrier having a small diameter and high circularity is used. A developing device capable of effectively preventing leakage of the developer can be provided. Further, by installing the developing device of the present invention, it is possible to provide a maintenance-free image forming apparatus that can prevent leakage of the developer over a long period of time with a simple configuration.

4 Developing device 9 Image forming unit 20 Housing (housing)
23 1st stirring screw 24 2nd stirring screw 25 Developing roller (developer carrier)
27 Fixed magnet body (magnet member)
29 regulating blades 33a, 33b magnetic seal member 35 circumferential groove 35a first circumferential groove 35b second circumferential groove 37 axial groove 100 image forming apparatus

Claims (5)

A housing for storing a magnetic developer;
A developer carrying member that carries the developer by a magnet member that is rotatably supported by the housing and fixed inside;
A magnetic seal member disposed at a predetermined interval along the outer peripheral surface of both longitudinal ends of the developer carrier;
In a developing device comprising:
The magnetic seal member includes a plurality of circumferential grooves extending along a circumferential direction of the developer carrying body and a plurality of shafts connecting the plurality of circumferential grooves on a surface facing the developer carrying body. And the axial groove adjacent to the axial direction of the developer carrier is not formed on the same straight line parallel to the axial direction of the developer carrier. apparatus.   The axial groove is formed only between the outermost first circumferential groove and the innermost second circumferential groove in the axial direction of the developer carrier among the plurality of circumferential grooves. The developing device according to claim 1.   The developing device according to claim 1, wherein the axial grooves adjacent to each other in the axial direction of the developer carrier are formed at different positions in the circumferential direction of the developer carrier.   The at least one of the axial grooves adjacent to each other in the axial direction of the developer carrying member intersects with the circumferential groove at a predetermined angle other than a right angle. The developing device described.   An image forming apparatus comprising the developing device according to claim 1.

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