JP2015152905A - Developing device, and image forming apparatus including developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device that can uniformize an amount of developers drawn up to a developing roller without giving stress to the developer, and an image forming apparatus.SOLUTION: A developing device 41 includes a second stirring screw 62, a developing roller 63, a shield plate 120, a passage 122, and a regulating blade 65. The second stirring screw 62 is rotatably provided in a second stirring chamber 60C. The developing roller 63 is rotatably provided above the second stirring screw 62. The shield plate 120 is provided at an opposing position between the developing roller 63 and second stirring screw 62. The shield plate 120 is composed of a non-magnetic substance. The passage 122 guides a developer to the developing roller 63 and is provided on the upstream side in the direction of rotation of the second stirring screw 62 with respect to the opposing position. The shield plate 120 extends linearly from the regulating blade 65 toward the opposing position and has its lower surface in contact with the outer peripheral surface of the second stirring screw 62.

Description

  The present invention relates to a developing device that develops an electrostatic latent image on an image carrier, and an image forming apparatus including the developing device.

  A developing device is mounted on an image forming apparatus such as a copying machine or a printer that forms an image on a sheet by electrophotography. The developing device develops an electrostatic latent image formed on an image carrier such as a photosensitive drum with toner. The developing device includes a developing roller disposed at a predetermined gap from the image carrier. As a developing method, the developer is magnetically pumped from the developer accommodating chamber to the surface of the developing roller, and the electric field generated by the developing bias applied to the developing roller causes the developing roller to transfer the electrostatic latent image on the image carrier. There is known a system in which toner is deposited by adhesion.

  This type of developing device is provided with an agitating member for conveying the developer to a position facing the developing roller while agitating the developer accommodated in the developer accommodating chamber. As the stirring member, for example, a screw rotating member in which a spiral wing member is attached to a rotating shaft, a paddle rotating member in which a paddle-shaped wing member is attached to a rotating shaft, and the like are known. Regardless of the stirring member, there is a difference between the thickness of the developer when the wing member faces the developing roller and the thickness of the developer when the region not having the wing member faces the developing roller. Depending on the difference, there may be a difference in the amount of developer pumped up by the developing roller. For example, the amount of developer pumped up when a region not having the blade member faces the developing roller is larger than the amount of developer pumped up when the blade member faces the developing roller. Such a difference in the amount of pumping causes density unevenness in a striped pattern corresponding to the pitch of the wing members in the image. As a conventional device for reducing the density unevenness, a device that presses the developer against the surface of the developing roller using a pressing member provided downstream of the developer pumping position in the rotation direction of the developing roller (see Patent Document 1) There is known an apparatus (see Patent Document 2) that improves the ability of pumping developer to a developing roller by interposing an auxiliary member made of a magnetic material.

JP 2002-258605 A Japanese Patent Laid-Open No. 2005-292301

  However, in the conventional apparatus, it is necessary to newly provide the pressing member and the auxiliary member, which increases the number of parts of the developing device and becomes a factor of increasing the size of the developing device. In addition, the pressing member gives extra stress to the developer, which reduces the life of the toner contained in the developer and reduces the charging characteristics. In addition, even if the pumping performance is improved by the auxiliary member and the density unevenness is reduced as a result, the difference in the pumping amount of the developer is not completely eliminated, so the auxiliary member prevents the density unevenness. I can't do it.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a developing device and an image forming device capable of uniformizing the amount of developer drawn up to the developing roller without applying stress to the developer. To provide an apparatus.

  A developing device according to one aspect of the present invention includes a storage unit, a stirring member, a developing roller, a shielding plate, and a guide unit. The storage portion stores a developer. The agitating member is rotatably provided in the accommodating portion, and agitates the developer in the accommodating portion by being driven to rotate in a predetermined first rotation direction. The developing roller is rotatably provided above the stirring member, has a magnet for attracting the developer in the housing portion by magnetic force, and is driven to rotate in a predetermined second rotation direction. The shielding plate is provided at a position facing the developing roller and the stirring member. This shielding plate is made of a non-magnetic material. The guide portion is provided on the upstream side in the first rotation direction with respect to the facing position, and guides the developer from the housing portion to the developing roller side. The shielding plate extends linearly from the fixed portion provided on the downstream side in the second rotation direction toward the facing position, and is in contact with the outer peripheral surface of the stirring member.

  An image forming apparatus according to another aspect of the present invention includes the developing device.

  According to the present invention, it is possible to make the amount of developer drawn up to the developing roller uniform without giving stress to the developer.

1 is a schematic diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a vertical sectional view showing the configuration of the developing device according to the embodiment of the invention. 2 is a horizontal cross-sectional view illustrating a configuration of a developing device according to an embodiment of the present invention. It is a figure which shows the modification of the shielding board which concerns on embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings as appropriate. The embodiment described below is merely an example embodying the present invention, and the embodiment of the present invention can be changed as appropriate without departing from the scope of the present invention.

  FIG. 1 is a schematic diagram showing a schematic configuration of an image forming apparatus 10 (an example of an image forming apparatus of the present invention) according to an embodiment of the present invention. As shown in FIG. 1, the image forming apparatus 10 is a so-called tandem color image forming apparatus, and includes a plurality of image forming units 1 to 4, an intermediate transfer belt 5, a driving roller 7A, and a driven roller 7B. , A secondary transfer device 15, a fixing device 16, a control unit (not shown), a paper feed tray 17, a paper discharge tray 18, and exposure devices 31 and 32. Note that the image forming apparatus 10 according to the embodiment of the present invention is not limited to a tandem color image forming apparatus, but is a printer, a copier, a facsimile machine, or a composite device having these functions that can form a color image or a monochrome image. It may be a machine.

  The image forming units 1 to 4 form images based on an electrophotographic system. The image forming units 1 to 4 form toner images of different colors on the plurality of photosensitive drums 11 to 14 arranged in parallel, and sequentially superimpose the toner images on the running (moving) intermediate transfer belt 5. And transcribe. In the example shown in FIG. 1, in order from the downstream side in the moving direction (arrow 19 direction) of the intermediate transfer belt 5, an image forming unit 1 for black, an image forming unit 2 for yellow, an image forming unit 3 for cyan, The magenta image forming units 4 are arranged in a line in that order.

  Each of the image forming units 1 to 4 includes photosensitive drums 11 to 14, charging devices 21 to 24, developing devices 41 to 44 (an example of the developing device of the present invention), primary transfer devices 51 to 54, and the like. That is, the image forming apparatus 10 includes developing devices 41 to 44. The photoconductive drums 11 to 14 carry toner images on their surfaces. The charging devices 21 to 24 charge the surfaces of the corresponding photosensitive drums 11 to 14 to a predetermined potential. The exposure devices 31 and 32 are devices that form an electrostatic latent image by exposing the surfaces of the photosensitive drums 11 to 14 and scanning the light. The exposure device 31 exposes the surfaces of the photosensitive drums 11 and 12, and the exposure device 32 exposes the surfaces of the photosensitive drums 13 and 14. The developing devices 41 to 44 develop the electrostatic latent images on the photosensitive drums 11 to 14 formed by the exposure devices 31 and 32 with toner. The primary transfer devices 51 to 54 transfer the toner images on the rotating photosensitive drums 11 to 14 to the intermediate transfer belt 5. Although not shown in FIG. 1, each of the image forming units 1 to 4 includes a cleaning device that removes the toner image remaining on the photosensitive drums 11 to 14.

  The intermediate transfer belt 5 is an endless belt made of a material such as rubber or urethane. The intermediate transfer belt 5 is supported by a driving roller 7A and a driven roller 7B so as to be rotationally driven. The driving roller 7A is disposed at a position close to the fixing device 16 (right side in FIG. 1), and the driven roller 7B is disposed at a position away from the fixing device 16 (left side in FIG. 1). The surface of the drive roller 7A is formed of a material such as rubber or urethane in order to increase the frictional force with the intermediate transfer belt 5. By being supported by the driving roller 7A and the driven roller 7B, the intermediate transfer belt 5 can move (run) while the surface thereof is in contact with the surface of each of the photosensitive drums 11-14. Then, when the surface of the intermediate transfer belt 5 passes between the photosensitive drums 11 to 14 and the primary transfer devices 51 to 54, the toner images are sequentially superimposed and transferred from the photosensitive drums 11 to 14. .

  The secondary transfer device 15 transfers the toner image transferred to the intermediate transfer belt 5 onto the printing paper conveyed from the paper feed tray 17. The printing paper on which the toner image has been transferred is conveyed to the fixing device 16 by a conveying unit (not shown). The fixing device 16 includes a heating roller 16A heated to a high temperature, and a pressure roller 16B disposed to face the heating roller 16A. The printing paper conveyed to the fixing device 16 is conveyed while being sandwiched between the heating roller 16A and the pressure roller 16B, whereby the toner image is welded to the printing paper. Thereafter, the printing paper is discharged to the paper discharge tray 18.

  As described above, the image forming apparatus 10 transfers the color toner images on the intermediate transfer belt 5 by superimposing and transferring the toner images of the respective colors onto the running intermediate transfer belt 5 by the plurality of image forming units 1 to 4. Form on the surface. The color toner image is transferred from the intermediate transfer belt 5 to the printing paper by the secondary transfer device 15. Thereby, a color image is formed on the printing paper. A configuration in which the intermediate transfer belt 5 is used as a conveyance belt and a toner image is directly superimposed and transferred onto printing paper conveyed on the conveyance belt, or a roller-shaped intermediate transfer member is used instead of the intermediate transfer belt 5 The use of is also considered as another embodiment.

  FIG. 2 is a vertical cross-sectional view showing the configuration of the developing device 41 provided in the image forming unit 1. FIG. 3 is a horizontal sectional view showing the configuration of the developing device 41. Hereinafter, the configuration of the developing device 41 will be described with reference to FIGS. 2 and 3. Since the other developing devices 42 to 44 have the same configuration as the developing device 41, detailed description thereof is omitted.

  The developing device 41 is a device that develops the electrostatic latent image with toner by a developing method in which toner is electrostatically attached to the electrostatic latent image in a non-contact state with respect to the photosensitive drum 11. In general, the developer used for development includes a one-component developer mainly composed of magnetic toner or non-magnetic toner, and a two-component developer mainly composed of non-magnetic toner and magnetic carrier. In the present embodiment, a developing device 41 that performs development using a two-component developer is illustrated.

  As shown in FIG. 2, the developing device 41 includes a developing container 60 (an example of a storage unit of the present invention), a first stirring screw 61, a second stirring screw 62 (an example of a stirring member of the present invention), and a developing roller 63. (An example of the developing roller of the present invention), a shielding plate 120 (an example of the shielding plate of the present invention), and the like.

  The developing container 60 contains a two-component developer containing toner (hereinafter also simply referred to as a developer). The developing container 60 contains a developer and also serves as a housing for the developing device 41. The developing container 60 is formed in a long shape in the longitudinal direction of the developing device 41 (direction perpendicular to the paper surface in FIG. 2). The developing container 60 is partitioned into a first stirring chamber 60B and a second stirring chamber 60C by a partition wall 60A. A developer is accommodated in each of the first stirring chamber 60B and the second stirring chamber 60C. The first agitation chamber 60B and the second agitation chamber 60C are not completely partitioned, but are connected to both ends in the longitudinal direction of the developing device 41 as shown in FIG. Passages 112 and 113 are provided.

  A first stirring screw 61 is rotatably provided in the first stirring chamber 60B. A second stirring screw 62 is rotatably provided in the second stirring chamber 60C. Both the first stirring screw 61 and the second stirring screw 62 are rotatably supported on the side wall 60E (see FIG. 3) of the developing container 60. The bottom wall 60 </ b> G of the first stirring chamber 60 </ b> B provided with the first stirring screw 61 is formed in an arc shape corresponding to the outer periphery of the first stirring screw 61. The bottom wall 60 </ b> H of the second stirring chamber 60 </ b> C provided with the second stirring screw 62 is formed in an arc shape corresponding to the outer periphery of the second stirring screw 62. A density detection sensor 97 for measuring the toner density of the developer is attached to the bottom wall 60G.

  The rotational driving force from the motor is transmitted to the rotation shafts 61A and 62A of the first stirring screw 61 and the second stirring screw 62, respectively. Thereby, the 1st stirring screw 61 and the 2nd stirring screw 62 rotate in a predetermined direction. Specifically, the first stirring screw 61 and the second stirring screw 62 rotate in the counterclockwise rotation direction (an example of the first rotation direction of the present invention) indicated by arrows 93 and 94 in FIG.

  The developing container 60 has a replenishing port 60D. The supply port 60D is formed in the upper wall 60F that forms a flat wall surface on the upper side of the first stirring chamber 60B. The supply port 60D is a through hole that guides the toner supplied from a toner container (not shown) to the developing container 60.

  As shown in FIG. 3, the first stirring screw 61 has a spiral wing member 66 around its axis. The second stirring screw 62 has a spiral wing member 67 around its axis. As a result, when rotationally driven by the rotational driving force from the motor, the first stirring screw 61 and the second stirring screw 62 magnetize the toner supplied from the toner container (not shown) to the developing container 60 through the supply port 60D. It is mixed with the carrier and conveyed in the axial direction while stirring. Further, the developer is agitated by the first agitation screw 61 and the second agitation screw 62, whereby a charge is imparted to the toner. In the present embodiment, the developer is indicated by an arrow 96 (see FIG. 3) between the first stirring chamber 60B and the second stirring chamber 60C via the communication paths 112 and 113 (see FIG. 3) formed in the partition wall 60A. It is circulated and conveyed in the direction shown.

  As shown in FIG. 2, a developing roller 63 is rotatably provided in the developing container 60. Specifically, the developing roller 63 is provided above the second stirring screw 62 in the second stirring chamber 60C. Specifically, the developing roller 63 is provided on the photosensitive drum 11 side with respect to the second stirring screw 62 and in parallel with the second stirring screw 61. The developing roller 63 is disposed so as to face the second stirring screw 62 with a predetermined gap therebetween.

  The developing roller 63 includes a cylindrical developing sleeve 63A. The developing sleeve 63A is rotatably supported in the second stirring chamber 60C. The developing sleeve 63A is composed of an aluminum tube.

  The developing roller 63 faces the photosensitive drum 11 on the opening 64 side (right side in FIG. 2) of the developing container 60. That is, the developing roller 63 is arranged to face the outer peripheral surface of the photosensitive drum 11 with a predetermined gap therebetween. The developing roller 63 receives a rotational driving force from a motor (not shown) and is rotated in the counterclockwise direction (an example of the second rotational direction of the present invention) indicated by an arrow 91 in FIG. That is, the rotation direction of the developing roller 63 and the rotation direction of the second stirring screw 62 are the same rotation direction, and the developing roller 63 is rotated in the same rotation direction as the second stirring screw 62.

  The developing roller 63 includes a magnet unit 63B having a plurality of magnetic poles. The magnet unit 63B is provided inside the developing sleeve 63A. The magnet unit 63B is fixed in the developing sleeve 63A. In the present embodiment, the magnet unit 63 </ b> B has five magnetic poles, that is, a main pole 75, a transport pole 76, a peeling pole 77, a scooping pole 78, and a transport pole 79. Each magnetic pole 75-79 is comprised with the permanent magnet which generate | occur | produces magnetic force, for example.

  The main pole 75 is a magnetic pole that generates a peak magnetic force at a position facing the photosensitive drum 11. The main pole 75 is attached to the magnet unit 63B with its magnetic pole surface facing the photosensitive drum 11 side.

  The transport pole 76 is a magnetic pole having a different polarity from the main pole 75, generates a magnetic field in the circumferential direction of the developing sleeve 63A, holds the developer on the developing sleeve 63A, and transports it in the circumferential direction.

  The peeling pole 77 is a magnetic pole that forms a peeling area 89 having substantially zero magnetic flux density on the opposite side of the developing sleeve 63A from the photosensitive drum 11. When the developer is carried to the peeling area 89, the force for magnetically attracting the developer is lost, and the developer is peeled from the peeling area 89. The peeled developer falls on the second stirring screw 62 located below, is returned to the second stirring chamber 60C, and is conveyed while being stirred again by the second stirring screw 62. Then, after being stirred and transported by the first stirring screw 61 and the second stirring screw 62, the developer is uniformly pumped again onto the developing sleeve 63A by the pumping pole 78 as a uniformly charged developer with an appropriate toner concentration.

  The pumping pole 78 is a magnetic pole that generates a peak magnetic force at a position facing the second stirring screw 62. Specifically, the pumping pole 78 generates the peak magnetic force in the direction of a line segment connecting the rotation shaft 62A of the second stirring screw 62 and the rotation shaft of the developing roller 63. The developer is attracted by the magnetic force onto the surface of the developing sleeve 63A by the upper electrode 78 and is attracted by the magnetic force. As a result, the developer is carried on the surface of the developing sleeve 63A. In this state, the developing sleeve 63 </ b> A is rotated, so that the developer is carried to a position facing the photosensitive drum 11.

  The developing container 60 is provided with a regulating blade 65 (an example of the fixing portion and the regulating member of the present invention). The regulating blade 65 is made of a magnetic material, and is a metal plate member having magnetism, for example. The regulating blade 65 is attached along the longitudinal direction of the developing container 60 (direction perpendicular to the paper surface of FIG. 2). The regulating blade 65 is arranged on the downstream side in the rotation direction of the developing roller 63 with respect to the position where the developing roller 63 and the second stirring screw 62 are opposed in the rotating direction of the developing roller 63 (see arrow 91). A slight gap (gap) is formed between the leading end portion 65 </ b> A of the regulating blade 65 and the roller surface of the developing roller 63. The developer attached to the developing roller 63 is regulated to a thickness corresponding to the gap by the regulating blade 65. The transport pole 79 is a magnetic pole that holds the developer on the developing sleeve 63A and carries it in the circumferential direction while generating a peak magnetic force at a position on the developing sleeve 63A facing the regulating blade 65. The shielding plate 120 is fixed to the regulation blade 65. The shielding plate 120 will be described later.

  In the developing device 41 configured as described above, the developer unevenness in thickness corresponding to the pitch in the axial direction of the blade member 67 of the second stirring screw 62 occurs on the developing sleeve 63A. This uneven thickness is not necessarily made uniform uniformly by the regulating blade 65, and may be conveyed to a position facing the photosensitive drum 11 with the uneven thickness remaining. In this case, the thickness unevenness appears in the image as density unevenness. Specifically, the density unevenness of the stripe pattern corresponding to the pitch appears in the image. In order to prevent such density unevenness, the developing device 41 of this embodiment is provided with a shielding plate 120.

  Hereinafter, the configuration of the shielding plate 120 will be described with reference to FIGS. 2 and 3.

  As shown in FIG. 2, the shielding plate 120 is provided at a position where the developing roller 63 and the second stirring screw 62 face each other. The shielding plate 120 is a plate-like member made of a non-magnetic material. Specifically, the shielding plate 120 is an elastic film-like resin plate member (for example, a pet film) formed of a synthetic resin not having magnetism. The shielding plate 120 is formed in a long shape in the longitudinal direction of the developing container 60 (direction perpendicular to the paper surface of FIG. 2). The shielding plate 120 is linearly formed from a regulating member 65 as a fixed portion provided on the downstream side in the rotation direction of the developing roller 63 (arrow 91) toward a position where the developing roller 63 and the second stirring screw 62 are opposed to each other. It has been extended. Specifically, one end of the shielding plate 120 in the short direction is fixed to the regulating member 65. The shielding plate 120 extends from the regulating member 65 toward the facing position, and the lower surface 123 abuts on the outer peripheral surface of the second stirring screw 62.

  The shielding plate 120 is bent in a V shape along a fold 125 extending in the longitudinal direction of the resin plate member such as a pet film. The fold 125 is defined near the fixed end 120 </ b> A that is an end on the side fixed in the shielding plate 120. The fixed end portion 120 </ b> A is fixed to the side surface 65 </ b> B of the restriction member 65 so that the end edge is located on the tip end portion 65 </ b> A side of the restriction member 65. Here, the side surface 65 </ b> B is a side surface on the second stirring screw 62 side among the both side surfaces of the regulating member 65. Various methods such as adhesion, screwing, pressure bonding, and welding can be applied to the fixing end 120A.

  In the shielding plate 120, the extending portion 120 </ b> B opposite to the fixed end portion 120 </ b> A extends from the fold 125 toward the upper portion of the second stirring screw 62 in a state where the fixed end portion 120 </ b> A is fixed to the regulating member 65. The lower surface 123 is in contact with the outer peripheral surface of the second stirring screw 62. The extending end of the extending part 120B is not in contact with anywhere and reaches a position where the path from the peeling region 89 to the second stirring chamber 60C is not blocked. Specifically, the extending end of the extending part 120B is located in the vicinity of a vertical line passing through the rotating shaft 62A. In the present embodiment, when the shielding plate 120 is bent at the fold 125, the extending portion 120B tends to be displaced in the direction 124 away from the fixed end 120A with the fold 125 as a base point. The force to be displaced is based on the restoring force that the shielding plate 120 tries to return to the shape before deformation. The extension part 120B is arranged on the upper part of the second stirring screw 62 in a state where the extension part 120B is pulled toward the fixed end part 120A against the force to be displaced. Thereby, the extension part 120 </ b> B is elastically biased toward the outer peripheral surface of the second stirring screw 62 by the restoring force of the shielding plate 120. That is, the extension part 120 </ b> B is pressed against the outer peripheral surface of the second stirring screw 62 by the restoring force. The extending part 120B is in contact with the outer peripheral surface of the second stirring screw 62, but is not in contact with the roller surface of the developing roller 63.

  The shielding plate 120 is provided with a passage 122 (an example of the guide portion of the present invention) for guiding the developer. The passage 122 is formed in the extending portion 120B. The passage 122 is not provided at a position where the developing roller 63 and the second stirring screw 62 are opposed to each other, but is provided upstream of the facing position in the rotation direction of the second stirring screw 62. Specifically, the passage 122 is provided on the regulating member 65 side in the extending portion 120 </ b> B of the shielding plate 120. The passage 122 is an opening that penetrates the extension portion 120B. The passage 122 is an opening that is elongated in the longitudinal direction of the developing container 60. The developer stirred by the second stirring screw 62 is guided to the surface of the developing roller 63 through the passage 122.

  In the present embodiment, a stay space 99 is formed in a path from the second stirring screw 62 through the passage 122 to the roller surface of the developing roller 63. The retention space 99 is a space for retaining the developer conveyed from the second stirring screw 62. This staying space 99 is a space formed between the second stirring screw 62 and the regulating blade 65. By arranging the regulating blade 65 at a position separated from the second stirring screw 62 toward the downstream side in the rotation direction of the developing roller 63, a stay space 99 is formed between the second stirring screw 62 and the regulating blade 65. As shown in FIG. 2, the passage 122 is located approximately at the center of the stay space 99. Accordingly, the developer conveyed from the second agitating screw 62 to the staying space 99 stagnates as the movement toward the surface of the developing roller 63 relaxes before and after passing through the passage 122. The developer slowly moves toward the developing roller 63 while staying in the stay space 99. During this gentle movement, the difference in the developer pumping amount corresponding to the pitch of the wing members 67 that causes the unevenness of the developer thickness is made uniform.

  As described above, in the developing device 41 of the present embodiment, the shielding plate 120 is provided at a position where the developing roller 63 and the second stirring screw 62 are opposed to each other. Therefore, even when the developer is attracted by the drawing upper pole 78, the shortest distance path from the second stirring screw 62 to the developing roller 63, that is, the path passing through the line segment connecting the rotation shaft 62A and the rotation shaft of the developing roller 63. Therefore, the developer is not supplied to the developing roller 63 through the path. On the other hand, since the passage 122 is formed in the shielding plate 120, the developer is guided to the developing roller 63 from the second agitating screw 62 through the passage 122 while being attracted by the magnetic force generated by the pumping pole 78. That is, the developer is guided to the developing roller 63 through the passage 122 so as to bypass the facing position without passing through the facing position between the developing roller 63 and the second stirring screw 62. Thereby, the path | route until a developing agent reaches the developing roller 63 becomes long, and the cause of the thickness nonuniformity of a developing agent is eliminated while moving the path | route. As a result, the amount of developer pumped up to the developing roller 63 can be made uniform without giving stress to the developer. Further, the developer peeled off at the peeling region 89 is not hindered from dropping onto the second stirring screw 62.

  Further, by setting the fixed position of the fixed end 120 </ b> A of the shielding plate 120 as the regulating member 65, the shielding plate 120 can be easily attached in the developing container 60.

  In addition, the extended portion 120B of the shielding plate 120 is in contact with the outer peripheral surface at the upper portion of the second stirring screw 62, and is further elastically pressed against the outer peripheral surface by the restoring force of the shielding plate 120. The position of the protruding portion 120B is stabilized without shaking. Thereby, even if the repulsive force in the direction in which the shielding plate 120 separates from the second stirring screw 62 due to the rotation of the second stirring screw 62, the extending portion 120B does not contact the developing roller 63. Thereby, the developer pumped up by the developing roller 63 does not fall by contact, and the amount of the developer on the roller surface of the developing roller 63 is stabilized.

  Further, since the staying space 99 is formed in the developing container 60, the movement of the developer that has entered the staying space 99 through the passage 122 can be moderated. As a result, the developer becomes a uniform amount in the longitudinal direction of the staying space 99, and the amount of the developer pumped up to the developing roller 63 becomes uniform. Further, since the developer staying in the stay space 99 comes into contact with the roller surface of the developing roller 63, the developer is easily pumped up to the roller surface of the developing roller 63.

  In the above-described embodiment, the second agitating screw 62 having the spiral wing member 67 is exemplified. For example, the second stirring screw 62 extends in the axial direction of the rotating shaft 62A, and is perpendicular to the axial direction from the rotating shaft 62A. The present invention can be applied even to a stirring member having a paddle-shaped wing extending to the top. Moreover, although the structure which fixes 120 A of fixed ends of the shielding board 120 to the control member 65 was illustrated, this invention is not limited to this. The extending portion 120B may be fixed at any position as long as it can contact the upper portion of the second stirring screw 62. For example, the fixed end portion 120A may be fixed to the lower surface of the stay space 99. .

[Modification of Embodiment]
Hereinafter, with reference to FIG. 4, the shielding board 130 which is a modification of the shielding board 120 of the above-mentioned embodiment is demonstrated. Here, FIG. 4 is a cross-sectional view illustrating a configuration of the developing device 41 including the shielding plate 130. In addition, about the same structure as the above-mentioned embodiment, the description is abbreviate | omitted by attaching | subjecting a same sign.

  The shielding plate 130 shown in FIG. 4 is made of the same material as the shielding plate 120 of the above-described embodiment, that is, a film-like resin plate member (for example, a pet film) having elasticity and formed of a synthetic resin not having magnetism. Has been. The part where the shielding plate 130 is different from the shielding plate 120 is its shape, and the other parts are the same as the shielding plate 120. The shielding plate 130 is bent in an inverted L shape along the fold 125 extending in the longitudinal direction of the resin plate member such as a pet film. The fixed end portion 120 </ b> A has a regulation member 65 such that the fold 125 is located on the tip end portion 65 </ b> A side of the regulation member 65 and the end edge is located on the lower surface side of the staying space 99 on the opposite side to the tip portion 65 </ b> A of the regulation member 65. It is fixed to the side surface 65B. The extending portion 120B extends toward the upper portion of the second stirring screw 62 from the distal end portion 65A where the fold 125 is positioned in a state where the fixed end portion 120A is fixed to the regulating member 65. The lower surface 123 of the extending part 120 </ b> B is in contact with the outer peripheral surface of the second stirring screw 62. In the present embodiment, when the shielding plate 130 is strongly bent at the fold 125 and is plastically deformed into, for example, a V shape, the extending portion 120B is displaced in the direction 124 approaching the fixed end 120A with the fold 125 as a base point. And The force to be displaced is based on the restoring force that the shielding plate 120 tries to return to the deformed shape. An extending part 120B is arranged at the upper part of the second stirring screw 62 by separating the extending part 120B away from the fixed end part 120A against the force to be displaced. Thereby, the extension part 120 </ b> B is elastically biased toward the outer peripheral surface of the second stirring screw 62 by the restoring force of the shielding plate 120. That is, the extension part 120 </ b> B is pressed against the outer peripheral surface of the second stirring screw 62 by the restoring force.

  Even with the shielding plate 130 configured in this manner, the amount of developer pumped up to the developing roller 63 can be made uniform without applying stress to the developer. Further, the developer peeled off at the peeling region 89 is not hindered from dropping onto the second stirring screw 62. Moreover, the position of the extension part 120B of the shielding plate 130 can be stabilized.

10: Image forming apparatuses 11-14: Photoconductor drums 41-44: Developing apparatus 61: First stirring screw 62: Second stirring screw 63: Developing roller 63A: Developing sleeve 63B: Magnet unit 120, 130: Shield plate 122: aisle

Claims (9)

An accommodating portion for accommodating the developer;
An agitation member that is rotatably provided in the accommodating portion and is agitated in the accommodating portion by being driven to rotate in a predetermined first rotation direction;
A developing roller that is rotatably provided above the stirring member, has a magnet that draws the developer in the housing portion by magnetic force, and is driven to rotate in a predetermined second rotation direction;
A shielding plate made of a non-magnetic material provided at a position facing the developing roller and the stirring member;
A guide portion that is provided on the upstream side in the first rotation direction from the facing position and guides the developer from the housing portion to the developing roller side,
The developing device, wherein the shielding plate extends linearly from the fixed portion provided on the downstream side in the second rotation direction toward the facing position, and is in contact with the outer peripheral surface of the stirring member.   The developing device according to claim 1, wherein the shielding plate is pressed against an outer peripheral surface of the stirring member.   The developing device according to claim 1, wherein the guide portion is an opening formed in the shielding plate.   The developing device according to claim 1, wherein the fixing portion is a regulating member that is provided on the downstream side in the second rotation direction and regulates the thickness of the developer on the developing roller.   5. The developing device according to claim 1, wherein a retention space for retaining the developer is formed in a path from the guide portion to a roller surface of the developing roller.   The developing device according to claim 5, wherein the staying space is a gap formed between the stirring member and the regulating member.   The developing device according to claim 1, wherein the first rotation direction and the second rotation direction are the same rotation direction.   The developing device according to claim 1, wherein the developer includes toner and a magnetic carrier.   An image forming apparatus comprising the developing device according to claim 1.

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