JP2012047993A - Developing device and image forming apparatus equipped with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress bending of a path forming member which is arranged between a developing sleeve and a supply screw with an inexpensive constitution.SOLUTION: A partition wall 43 is made of the same synthetic resin material as a developing case and integrally formed with the developing case. On the other hand, a shield wall 44, which forms a slit 45 between the partition wall and itself for allowing a developer to move from a developer supply conveyance path 27 to a developing sleeve 22, is formed of a metal stay 46, which is supported only at both end areas in the rotary shaft direction of the developing sleeve. The metal stay 46 is made of a metal material more rigid than the partition wall 43.

Description

  In the present invention, the developer conveyed along the developer carrying member rotation axis direction is pumped up to the surface of the developer carrying member, and the developer is conveyed to the developing region by the rotation of the developer carrying member. The present invention relates to a developing device, and an image forming apparatus provided with the image forming device for forming an image by an electrophotographic method, a magnetic recording method, or the like, such as a copying machine, a facsimile, or a printer.

  As an image forming apparatus such as an electrophotographic copying apparatus, an electrostatic recording apparatus, or a magnetic recording apparatus, an electrostatic latent image formed on a latent image carrier is converted into a two-component developer (hereinafter, referred to as toner and magnetic carrier). A device using a developing device of a two-component development system that performs development processing using simply “developer”) is known. In this development processing, the developer is conveyed while being magnetically supported on the surface of a developer carrier rotatably attached to a developing device housing (development case) or the like, and the developer carrier and the latent image carrier In the developing area opposite to each other, magnetic force is applied to the developer to make it stand up. Then, the magnetic brush formed by the spikes is rubbed against the surface of the latent image carrier to attach toner to the electrostatic latent image on the surface of the latent image carrier to visualize the electrostatic latent image. . Such development processing generally requires magnetic field generating means such as a magnet having a plurality of magnetic poles arranged inside the developer carrier. An example of the magnetic pole generated by the magnetic field generating means is a pumping magnetic pole that generates a magnetic force for pumping up the developer on the developer carrier. In addition, the developer carried on the surface of the developer carrying member passes through a regulation gap for regulating the amount of the developer conveyed to the development region, so that the developer can be spiked. There is also a restriction magnetic pole that generates a restriction magnetic force. In addition, a developing magnetic pole that generates a developing magnetic force for causing the developer on the developer carrying member to rise in the developing region is also exemplified.

  Such a two-component developing system developing device is disclosed in, for example, Patent Document 1, and a developer supplied on the surface of a developer carrying member is moved in the direction of the developer carrying member rotation axis by a developer supply / conveying member. The developer in the developing device is circulated and conveyed along a developer circulation path including a developer supply conveyance path that is conveyed along the developer supply path. The developer supply conveyance path is disposed adjacent to the surface of the developer carrier, and the developer being conveyed exceeds the upper end of the side wall on the developer carrier side of the developer supply conveyance path and draws up the magnetic force. By the action, it is attracted to the surface of the developer carrier and is carried on the surface of the developer carrier. The developer thus carried on the developer carrier is transported in the direction of movement of the developer carrier as the developer carrier rotates, and the surface of the developer carrier and the developer regulating member face each other. Through the regulatory gap. During this passage, the developer carried at a distance close to the surface of the developer carrying body can pass through the regulation gap, but the developer carried at a distance far from the surface of the developer carrying body does not pass through the developer regulating member. It is blocked and cannot pass through the regulatory gap. In this developing device, a predetermined amount of developer is conveyed to the developing region by passing through the regulation gap. The developer whose passage through the regulation gap is prevented by the developer regulating member returns to the developer supply conveyance path side, is collected in the developer supply conveyance path, and is pumped up again to the developer carrier.

  Here, if characteristics such as developer fluidity change due to deterioration of the developer over time or environmental changes, the amount of developer passing through the regulation gap fluctuates, and a certain amount of developer is transported to the development area. May not be able to be performed, and the development ability may not be stably maintained. For such a problem, it is possible to reduce the problem by providing a restriction magnetic pole that generates a restriction magnetic force, and causing the developer passing through the restriction gap to act with the restriction magnetic force. Are known.

  However, when such a regulation magnetic pole is arranged, the regulation magnetic force acts on the developer that is prevented from passing through the regulation gap, and the space on the downstream side of the developer carrier surface movement direction of the developer regulation member (hereinafter, “ It is called “regulated retention space”). The developer staying in the restricted stay space (hereinafter referred to as “restricted stay developer”) rotates in the restricted stay space in the direction opposite to the direction of rotation of the developer carrier due to the surface movement of the developer carrier. It stays in the restricted stay space while (circulating movement). The regulated staying developer is rubbed and charged while circulating in the regulated staying space while receiving the restraining force of the regulated magnetic force, and compared with other developers circulating in the developing device, The toner charge amount is high. Therefore, there is a difference in developing ability (amount of toner attached per unit area that adheres to the electrostatic latent image during development) between the regulated staying developer and the other developers. Even with such developers with different development capabilities, if they are uniformly dispersed and mixed with each other, even if they are used for development, image density unevenness that can be recognized by humans will occur. There is no. However, if the developer is used in development in an insufficiently mixed state, image density unevenness that is recognizable by humans is generated and image quality is deteriorated. The conventional developing device as described in Patent Document 1 is used for development in a state where the regulated staying developer having an abnormally high toner charge amount is insufficiently mixed with other developer having a normal toner charge amount. There has been a problem that image density unevenness occurs and image quality is deteriorated.

  More specifically, the regulated staying developer that has escaped the restraint of the regulated magnetic force during the circulation movement is sequentially collected into the developer supply conveyance path. If the developer is collected in the developer supply conveyance path, the regulated staying developer is sufficiently mixed with the other developer and then pumped up again, and the above-described image quality deterioration problem does not occur. However, when the pumping magnetic pole having the opposite polarity to the regulation magnetic pole is arranged adjacent to the upstream side in the direction of movement of the developer carrying member as in the developing device described in Patent Document 1, the pumping with the regulation magnetic pole is performed. A magnetic field is formed such that the lines of magnetic force connecting to the magnetic poles pass through the restricted stay space where the restricted stay developer stays. In such a magnetic field, a part of the regulated staying developer, specifically, the part of the regulated staying developer that is closest to the pumping magnetic pole moves to the pumping magnetic pole side along the magnetic field line, and the surface of the developer carrier Be drawn to As a result, a part of the regulated staying developer is carried on the surface of the developer carrying member without being collected in the developer supply conveyance path.

  At this time, since the developer from the developer supply / conveyance path has already been pumped up on the surface of the developer carrying member, the regulated staying developer attracted by the pumping magnetic force is at a location where the pumping amount is sufficient. The developer is carried on the surface of the developer carrying member so as to overlap the developer from the developer supply conveyance path. In this case, since the regulated staying developer is carried in a region far from the surface of the developer carrying member, it cannot pass through the regulation gap by the developer regulating member and stays in the regulated staying space again without being transported to the development region. Will do. Therefore, in this case, image density unevenness does not occur and image quality deterioration does not occur.

  However, the regulated staying developer attracted by the pumping magnetic force obstructs the pumping of the developer from the developer supply conveyance path, and the amount of the developer pumped from the developer supply transport path is locally short. There is a case to let you. In particular, in a configuration in which the developer in the developer supply conveyance path is conveyed in the direction of the rotation axis by a conveyance screw having a blade portion provided in a screw shape on the rotation shaft, the developer is moved toward the developer carrier by the blade portion. Is not uniform in the direction of the rotation axis. For this reason, at locations where the force to feed the developer to the developer carrier side is weak, pumping of the developer from the developer supply conveyance path is hindered by the regulated staying developer attracted by the pumping magnetic force, and the developer supply conveyance path Insufficient amount of developer to be pumped. In locations where the amount of developer pumped up from the developer supply / conveyance path is locally insufficient, the regulated staying developer attracted by the pumping magnetic force is carried in a region close to the surface of the developer carrier, and the regulation gap is increased. It passes through and is transported to the development area. As a result, a developer layer in an insufficiently mixed state between a regulated staying developer with an abnormally high toner charge amount and another developer having a normal toner charge amount is fed into the development region, resulting in uneven image density. Causing image quality degradation.

  Therefore, the present inventors have secured the developer passage along the magnetic force lines of the regulated magnetic force while ensuring a supply passage for allowing the developer in the developer supply conveyance path to pass to the developer carrier side. A developing device has been developed that is provided with a blocking member (passage forming member) that prevents movement toward the surface side of the body. According to this developing device, by providing the blocking member, the restricted staying developer attracted by the pumping magnetic force does not hinder the pumping of the developer from the developer supply conveyance path. Therefore, it is difficult to generate a location where the amount of developer pumped up from the developer supply conveyance path is locally insufficient, and the surface of the developer carrier that allows the regulated staying developer attracted by the pumping magnetic force to pass through the regulation gap. It becomes difficult to be carried in an area close to. Therefore, it is possible to suppress the occurrence of a situation where a developer layer in an insufficiently mixed state between a regulated stay developer with an abnormally high toner charge amount and another developer having a normal toner charge amount is sent to the development region. Further, image quality deterioration due to image density unevenness is suppressed.

  As a method of providing such a blocking member (passage forming member), a through hole serving as the supply passage is formed on the side wall on the developer carrier side of the developer supply transport path, and the upper end side of the side wall from the through hole. A method using the portion as the blocking member is simple. However, an external force toward the developer carrying member is applied to the blocking member due to the movement of the developer passing through the supply passage. In addition, an external force is applied to the regulated staying developer that is attracted by the pumping magnetic force and presses it toward the developer carrier. Therefore, there is a possibility that the blocking member is bent toward the developer carrying member by these external forces. In particular, since the side wall of the developer supply / conveyance path is integrally formed with a developing case generally formed of a synthetic resin material, the blocking member is also formed of the same synthetic resin material as the developing case according to the above simple method. Will be. Since such a synthetic resin material has high flexibility and is easily bent, it is likely that the blocking member is bent toward the developer carrying member by the above-described simple method.

  Since such a blocking member is arranged close to the surface of the developer carrying member, when the blocking member is bent as described above, the developer carrying member near the center in the direction of the rotation axis of the developer carrying member and the developer carrying member. The gap with the surface is narrowed. When this gap is narrowed, the compressive force received when the developer on the developer carrier surface passes through the gap, the toner in the developer aggregates or adheres to the developer carrier surface, There arises a problem that an appropriate development process may be hindered. In particular, when toner aggregates, the toner aggregates adhere to the recording material and appear as black spots, or white spots appear due to the absence of toner around the toner aggregates.

  Even with the simple method described above, for example, if the configuration in which the blocking member is supported not only in the both ends of the developer carrying member in the rotation axis direction but also in the center region, the bending of the blocking member can be suppressed. In addition, if the rib is integrally formed with the developing case to support the central region of the blocking member, the rib and the blocking member can be integrally formed with the developing case, and an inexpensive configuration can be realized. However, when such a configuration is adopted, it has been confirmed that streaky image density unevenness occurs at a position corresponding to the support location in the central region. Therefore, it is necessary to adopt a configuration in which the blocking member is supported only at both end regions in the developer carrying member rotation axis direction.

  In the above description, the passage forming member that forms the supply passage between the side wall of the developer supply conveyance passage moves the regulated staying developer to the surface side of the developer carrier along the magnetic force line of the regulated magnetic force. The configuration arranged at a position where it can be prevented is described as an example. However, the above-described problem is not limited to such a configuration, and may be caused by a developing device in which a passage forming member that forms the supply passage is disposed between the side wall of the developer supply conveyance path. . In addition, this problem may occur in, for example, a two-component developing system or a one-component developing system.

  The present invention has been made in view of the above problems, and an object of the present invention is to suppress the bending of the passage forming member with an inexpensive configuration without causing the above-described streak-like image density unevenness and to develop the image. It is an object of the present invention to provide a developing device and an image forming apparatus provided with the developing device that can suppress the occurrence of a problem that toner in the agent aggregates or adheres to the surface of the developer carrying member.

In order to achieve the above object, the invention of claim 1 includes a developer carrying member that conveys the developer to a developing region facing the surface of the latent image carrying member by carrying and rotating the developer on the surface. A developing case having an opening for exposing a part of the developer carrying member accommodated in the outside to face the surface of the latent image carrying member, and carried on the surface of the developer carrying member. A developer regulating member that forms a regulating gap between the developer carrying member and the developer carrying member for regulating the amount of developer conveyed to the developing region by passing the developer; A developer supply that is arranged adjacent to the surface of the developer carrying member and that conveys the developer supplied on the surface of the developer carrying member along the direction of the rotation axis of the developer carrying member by a developer supply conveying member. A transport path, and the developer supply transport path In the developing device that supplies the developer in the developer supply transport path to the developer support side beyond the side wall on the image carrier support side, at least the development region is between the side wall of the developer supply transport path. Forming a supply passage for allowing the developer in the developer supply / conveyance path to pass to the developer carrier side over the entire region of the developer carrier rotation axis, and between the developer case and the inner wall of the developer case A passage forming member that forms a recovery passage for recovering the developer that has been blocked from passing through the restriction gap by the restriction member toward the developer supply conveyance path; and the sidewall of the developer supply conveyance path includes The same material as that of the developing case and formed integrally with the developing case, the passage forming member is formed of another material having higher rigidity than the side wall, and both end regions in the developer carrying member rotation axis direction And it is characterized in that it is supported by only.
According to a second aspect of the present invention, in the developing device of the first aspect, the different material forming the passage forming member is a metal.
According to a third aspect of the present invention, in the developing device of the first or second aspect, a developer containing toner and a magnetic carrier is used as the developer, and the developer is disposed inside the developer carrier, The another material having magnetic field generating means for generating a magnetic force to be carried on the surface of the developer carrying member and forming the passage forming member is a non-magnetic material.
According to a fourth aspect of the present invention, in the developing device according to any one of the first to third aspects, the outer surface portion of the passage forming member facing the supply passage and the surface of the developer carrying member are opposed. Each of the outer surface portions is a flat surface.
According to a fifth aspect of the present invention, in the developing device according to any one of the first to fourth aspects, an outer surface portion of the passage forming member facing the recovery passage and an outer surface facing the developer supply conveyance path. The portion is a convex curved surface.
According to a sixth aspect of the present invention, in the developing device according to any one of the first to fifth aspects, the passage forming member has a seam including a hollow portion extending along the direction of the rotation axis of the developer carrying member. It is a hollow-shaped member that does not exist.
According to a seventh aspect of the present invention, in the developing device according to any one of the first to fourth aspects, the passage forming member is orthogonal to the developer carrying member rotation axis direction and passes through the developing region. The flat plate member is bent so that the cross-sectional shape when cut along the imaginary plane is a square shape, and a closing port generated by the bending process is formed on the supply passage or the developer carrier. It is disposed so as to face the surface and to open in a direction perpendicular to the flow direction of the developer flowing through a portion adjacent to the closing port or in a direction toward the downstream side in the flow direction. To do.
The invention according to claim 8 is the developing device according to any one of claims 1 to 7, wherein both end portions of the passage forming member located outside the developing region in the direction of the rotation of the developer carrying member are in the center. The section extending from the portion toward the side wall of the developer supply conveyance path and orthogonal to the direction of the developer carrying member rotation axis is a U-shape, and the passage forming member is formed at the center portion. And attached to the side wall with the side wall of the developer supply / conveyance path inserted into each of the extended portions of the both ends so that the supply passage is secured between the side wall and the side wall. It is characterized by.
The invention according to claim 9 is the developing device according to claim 8, wherein the developer carrying member is rotated on the side wall of the developer supply transport path with respect to the extended portions of the both end portions of the passage forming member. A locking member is provided that contacts from the axial direction to lock the movement of the passage forming member in the direction of the rotation axis of the developer carrying member.
According to a tenth aspect of the present invention, in the developing device according to the eighth or ninth aspect, the inner surface of the extended portion of the both end portions of the passage forming member protrudes toward the side wall of the developer supply transport path. A protrusion is provided, and the protrusion is formed such that a distance between a tip of the protrusion and a facing portion facing the protrusion is smaller than a thickness of the side wall of the developer supply conveyance path. The passage forming member is attached to the side wall without using an adhesive by sandwiching the side wall of the developer supply conveyance path between the projecting portion and the opposed portion. To do.
The invention according to claim 11 is the developing device according to claim 10, wherein the protruding portion is formed at the both end portions of the passage forming member so as to open toward the outer surface portion of the passage forming member facing the recovery passage. A notch is formed in the extending portion, and the notched portion is formed by bending the notched portion toward the inner surface side of the extending portion.
According to a twelfth aspect of the present invention, in the developing device according to the tenth or eleventh aspect, a concave portion that engages with the protruding portion is formed on the side wall of the developer supply conveyance path at a position where the protruding portion contacts. It is characterized by being.
The invention of claim 13 is the developing apparatus according to any one of claims 10 to 12, wherein the same material as the developing case forming the side wall of the developer supply transport path is subjected to heat treatment. The passage forming member is formed of a deformable heat-deformable material, and the side wall of the developer supply / conveyance path is formed by the projecting portion formed at the extending portion of the both end portions of the passage forming member and the opposed portion. After sandwiching, the portion of the side wall with which the projecting portion abuts is deformed into the shape of the protruding portion by performing a heat treatment, thereby being attached to the side wall.
According to a fourteenth aspect of the present invention, in the developing device according to any one of the first to thirteenth aspects, a developer containing toner and a magnetic carrier is used as the developer, and the developer carrying member is disposed inside the developer carrier. And a magnetic field generating means for generating a magnetic force for supporting the developer on the surface of the developer carrier, wherein the magnetic field generating means takes at least the developer passing through the supply passage. A pumping magnetic pole for generating a pumping magnetic force for drawing to the surface of the developer carrying body by drawing it toward the carrier, and a regulation magnetic pole for generating a regulation magnetic force for causing the developer passing through the regulation gap to rise. The pumping magnetic pole and the regulating magnetic pole are adjacent to each other in the developer carrier surface movement direction and have opposite polarities, and the passage forming member is The developer that is prevented from passing through the regulation gap by the image material regulating member is disposed at a position that prevents the developer from moving to the surface side of the developer carrier along the magnetic force lines of the regulation magnetic force. It is what.
According to a fifteenth aspect of the present invention, there is provided a latent image on the latent image carrier by a latent image carrier, latent image forming means for forming a latent image on the latent image carrier, and a developer containing toner and carrier. An image forming apparatus for forming an image on the recording material by finally transferring the toner image formed on the latent image carrier to the recording material by the developing device. The developing device according to any one of claims 1 to 14 is used as the developing device.

In the present invention, there is provided a passage forming member that forms a supply passage for allowing the developer in the developer supply transport path to pass to the developer support body side between the developer supply transport path and the side wall on the developer support body side. The developer carrier is supported only at both end regions in the direction of the rotation axis. Therefore, since the passage forming member is not supported in the central region, streaky image density unevenness that occurs when the central region of the passage forming member is supported does not occur.
In the present invention, the side wall of the developer supply transport path is made of the same material as that of the developing case and is formed integrally with the developing case, so that the side wall is configured separately from the developing case. And can be manufactured at low cost. Here, if the passage forming member is also formed of the same material as the developing case and integrated with the developing case, the side wall and the passage forming member can be integrally formed with the developing case, and thus can be manufactured at a lower cost. However, the developing case is often formed of a highly flexible material such as a synthetic resin in order to simplify the manufacturing process and reduce the manufacturing cost. Therefore, when the passage forming member is also formed of the same material as that of the developing case and integrally formed with the developing case, the developer that passes through at least the supply passage in the configuration in which the passage forming member is supported only in the both ends of the developer carrier rotating shaft. The passage forming member is easily bent toward the developer carrying member by the external force received from the developer.
Therefore, in the present invention, the passage forming member is formed of a material different from the side wall having higher rigidity than the side wall of the developer supply conveyance path. Thereby, compared with the case where a channel formation member is integrally formed with the same material as a development case, the deflection of a channel formation member can be made small.

  As described above, according to the present invention, since the passage forming member is supported only in the both ends of the developer carrying member in the rotation axis direction, the above-described streaky image density unevenness does not occur, and this Since the deflection of the passage forming member, which is likely to occur in the configuration, is reduced by forming the passage forming member with a highly rigid material, the problem is that the toner in the developer aggregates or adheres to the surface of the developer carrier. It is possible to obtain an excellent effect that can be suppressed.

FIG. 2 is a schematic configuration diagram illustrating a main part of the printer according to the first embodiment. FIG. 2 is an explanatory diagram illustrating a schematic configuration of a developing unit in the printer. It is explanatory drawing which shows the relationship between the slit width and the largest image formation area width in the developing unit. FIG. 6 is a magnetic force distribution diagram schematically showing the direction of magnetic force at each point between the developing sleeve and the supply screw in a state where no developer is present in the developing unit. It is explanatory drawing of the synthetic force of the magnetic force and gravity which act on one magnetic carrier arrange | positioned at the developer supply conveyance path side edge part of a shielding wall lower surface. It is explanatory drawing of the synthetic force of the magnetic force and gravity which act on one magnetic carrier arrange | positioned at the developing sleeve side edge part of a partition wall upper surface. It is the perspective view of the state which removed the metal stay which comprises a shielding wall from the partition wall. FIG. 6 is a cross-sectional view showing a developing unit configuration in the vicinity of a shielding wall when cut along a plane orthogonal to the developing sleeve rotation axis direction so as to pass through a central region in the developing sleeve rotation axis direction of a metal stay constituting the shielding wall. is there. (A)-(c) is explanatory drawing which shows the state which attached the metal stay to the partition wall. (A)-(c) is explanatory drawing for demonstrating the structure which attaches a metal stay to a partition wall, without using the adhesive agent in a modification. It is explanatory drawing which shows the other structural example of the structure which attaches the metal stay in a modification to a partition wall. 10 is an enlarged view showing a developing unit in Embodiment 2. FIG. It is explanatory drawing which shows an example of the conventional image development unit in which the shielding wall is not provided. Explanatory drawing which shows the structure of the developing unit of the comparative example comprised so that the synthetic force of the magnetic force and gravity which act on the magnetic carrier located in the developer supply conveyance path side edge part of a shielding wall lower surface may face below a horizontal surface. It is. Explanatory drawing which shows the structure of the image development unit of the other comparative example comprised so that the synthetic force of the magnetic force and gravity which act on the magnetic carrier located in the image development sleeve side edge part of the partition wall upper surface might face down below a horizontal surface. It is. The configuration of the developing unit of still another comparative example is configured such that the developed developer peeled off from the sleeve surface due to the height of the partition wall is moved to the developer supply transport path side beyond the partition wall. It is explanatory drawing shown. FIG. 10 is an explanatory diagram showing a configuration of a developing unit of still another comparative example in which an intermediate magnetic pole having a polarity opposite to that of the pumping magnetic pole and the regulating magnetic pole is disposed.

Embodiment 1
Hereinafter, as an image forming apparatus to which the present invention is applied, an embodiment of an electrophotographic color laser printer (hereinafter simply referred to as “printer”) (hereinafter referred to as “embodiment 1”) will be described. To do.
FIG. 1 is a schematic configuration diagram illustrating a main part of the printer according to the first embodiment.
This printer includes four toner image forming units 1M, 1C, 1Y, and 1K for forming toner images of respective colors of magenta, cyan, yellow, and black (hereinafter referred to as M, C, Y, and K). ing. Further, a transfer unit 50 is provided on the side of the toner image forming portions 1M, 1C, 1Y, and 1K arranged in the vertical direction.

  The toner image forming units 1M, 1C, 1Y, and 1K have substantially the same configuration except that the color of the toner used is different. The M toner image forming unit 1M for forming an M toner image will be described. The toner image forming unit 1M includes a process unit 2M, an optical writing unit 10M, and a developing unit 20M.

  The process unit 2M for M has a uniform charging device 4M, a drum cleaning device 5M, a static elimination lamp 6M, etc. around a drum-shaped photoconductor 3M that is driven to rotate counterclockwise in the figure. These are held by a common casing and can be integrally attached to and detached from the printer main body. The photoreceptor 3M as a latent image carrier is obtained by coating an organic photosensitive layer on a base tube made of aluminum or the like.

  The uniform charging device 4M uniformly charges the surface of the photoreceptor 3M, which is driven to rotate counterclockwise in the drawing, to a negative polarity, for example, by corona charging.

  The optical writing unit 10M includes a light source composed of a laser diode or the like, a regular hexahedral polygon mirror, a polygon motor for rotationally driving the mirror, an fθ lens, a lens, a reflection mirror, and the like. A laser beam L emitted from a light source driven on the basis of image information sent from a personal computer (not shown) is reflected on the polygon mirror surface and deflected as the polygon mirror rotates, so that the photosensitive member 3M. To reach. As a result, the surface of the photoreceptor 3M is optically scanned, and an electrostatic latent image for M is formed on the surface of the photoreceptor 3M.

  The developing unit 20M for M, which is a developing device, has a developing roll 21M that exposes a part of the peripheral surface from an opening provided in the casing. The developing roll 21M includes a developing sleeve as a developer carrying member made of a non-magnetic pipe that is driven to rotate by a driving unit (not shown), and a magnet roller as a magnetic field generating unit (not shown) that is included so as not to rotate. have. In the developing unit 20M, an M developer (not shown) including a magnetic carrier and a negatively chargeable M toner is included. The M developer is agitated and conveyed by three conveying screws described later, and frictional charging of the M toner is promoted, and the magnetic force of the magnet roller in the developing roll 21M is applied to the surface of the developing sleeve rotated by the developing roll 21M. Adsorbed and pumped up. Then, with the rotation of the developing sleeve, the layer thickness is regulated when passing through the position facing the doctor blade 25M as the regulating member, and then the sheet is conveyed to the developing position facing the photoreceptor 3M.

  In this developing position, a negative M toner is applied from the sleeve side to the latent image between the developing sleeve to which a negative developing bias output from a power source (not shown) is applied and the electrostatic latent image on the photoreceptor 3M. The developing potential that causes electrostatic movement to the side acts. Further, a non-development potential that electrostatically moves negative M toner from the background side to the sleeve side acts between the developing sleeve and the uniformly charged portion (background portion) of the photoreceptor 3M. The M toner in the M developer on the developing sleeve is transferred onto the electrostatic latent image on the photoreceptor 3M by the action of the developing potential. By this transfer, the electrostatic latent image on the photoreceptor 3M is developed into an M toner image. The M developer that has consumed M toner by the development is returned to the casing as the developing sleeve rotates. Further, the M toner image on the photoreceptor 3M is intermediately transferred onto an intermediate transfer belt 51 of a transfer unit 50 described later.

  Further, the developing unit 20M has a toner concentration sensor (not shown) composed of a magnetic permeability sensor. The toner concentration sensor outputs a voltage having a value corresponding to the magnetic permeability of the M developer accommodated in a developer collection and conveyance path (described later) of the developing unit 20M. Since the magnetic permeability of the developer shows a good correlation with the toner concentration of the developer, the toner concentration sensor outputs a voltage having a value corresponding to the toner concentration. The value of the output voltage is sent to a toner supply control unit (not shown). This toner replenishment control unit is provided with storage means such as a RAM, in which M Vtref, which is a target value of the output voltage from the M toner density sensor, and toner density mounted in other developing units. Vtref data for C, Y, M, which is a target value of the output voltage from the sensor, is stored. For the M developing unit 20M, the output voltage value from the M toner density sensor is compared with the M Vtref, and an M toner density replenishing device (not shown) is driven for a time corresponding to the comparison result. As a result, M toner for replenishment is replenished into the developer collection transport path of the developing unit 20M. By controlling the driving of the M toner replenishing device in this way (toner replenishment control), an appropriate amount of M toner is replenished to the M developer whose M toner density has been reduced along with development, and the inside of the developing unit 20M. The M toner concentration of the M developer is maintained within a predetermined range. The same toner replenishment control is performed for the developing units 20C, 20Y, and 20K.

  The M toner image developed on the photoreceptor 3M is transferred to the front surface of an intermediate transfer belt 51 described later. The untransferred toner that has not been transferred onto the intermediate transfer belt 51 adheres to the surface of the photoreceptor 3M that has undergone the transfer process. This transfer residual toner is removed by the drum cleaning device 5K. The surface of the photoreceptor 3M from which the transfer residual toner has been removed in this manner is discharged by the discharging lamp 6M and then charged uniformly by the uniform charging device 5K.

  The toner image forming unit 1M for M has been described in detail. However, in the toner image forming units 1C, 1Y, and 1K for other colors, C, Y, and K toners are formed on the surfaces of the photoreceptors 3C, 3Y, and 3K by the same process. An image is formed.

  A transfer unit 50 is disposed on the right side of the toner image forming units 1M, 1C, 1Y, and 1K that are arranged in the vertical direction. The transfer unit 50 includes a driving roller 52, a tension roller 53, and a driven roller 54 inside a loop of an endless intermediate transfer belt 51. Then, while the intermediate transfer belt 51 is stretched by these three rollers, it is moved endlessly in the clockwise direction in the drawing by the rotational drive of the drive roller 52. The intermediate transfer belt 51 moved endlessly in this way has its front surface on the left side in the drawing applied to the M, C, Y, and K photoconductors 3M, 3C, 3Y, and 3K, respectively. In this way, primary transfer nips for M, C, Y, and K are formed.

  In addition to the three rollers described above, four transfer chargers 55M, 55C, 55Y, and 55K are disposed inside the loop of the intermediate transfer belt 51. These transfer chargers 55M, 55C, 55Y, and 55K are arranged on the back side of the primary transfer nip for M, C, Y, and K so as to apply charges to the back surface of the intermediate transfer belt 51. By applying this charge, the toner is transferred in the primary transfer nip for M, C, Y, and K in such a direction that the toner is electrostatically moved from the photoreceptor 3M, 3C, 3Y, 3K side to the belt front surface side. An electric field is formed. A transfer roller to which a transfer bias is applied may be used instead of the corona charge type transfer charger.

  The M, C, Y, and K toner images formed on the photoreceptors 3M, 3C, 3Y, and 3K of the respective colors are transferred from the photoreceptor side to the belt by the influence of the nip pressure and the transfer electric field in the primary transfer nip of each color. The image is moved to the surface side and transferred onto the intermediate transfer belt 51 in a superimposed manner. As a result, a four-color superimposed toner image (hereinafter referred to as “four-color toner image”) is formed on the intermediate transfer belt 51.

  A secondary transfer bias roller 56 is in contact with the driving roller 52 on the intermediate transfer belt 51 from the belt front surface side, thereby forming a secondary transfer nip. A secondary transfer bias is applied to the secondary transfer bias roller 56 by a voltage applying means including a power source and wiring (not shown). As a result, a secondary transfer electric field is formed between the secondary transfer bias roller 56 and the grounded driving roller 52. The four-color toner image formed on the intermediate transfer belt 51 enters the secondary transfer nip as the belt moves endlessly.

  The printer includes a paper feed cassette (not shown), and accommodates a recording paper bundle in which a plurality of recording papers P are stacked therein. Then, the uppermost recording paper P is sent out to the paper feed path at a predetermined timing. The fed recording paper P is sandwiched between the rollers of the registration roller pair 60 disposed at the end of the paper feed path.

  The registration roller pair 60 rotates both rollers in order to sandwich the recording paper P sent from the paper feed cassette between the rollers. However, as soon as the leading edge of the recording paper P is sandwiched, both rollers rotate. Stop. Then, the recording paper P is sent toward the secondary transfer nip at a timing at which the recording paper P can be synchronized with the four-color toner image on the intermediate transfer belt 51. In the secondary transfer nip, the four-color toner images on the intermediate transfer belt 51 are collectively transferred onto the recording paper P by the action of the secondary transfer electric field and the nip pressure. A full color image is formed in combination with the white color of the recording paper P. The recording paper P on which the full-color image is formed in this manner is discharged from the secondary transfer nip, and then sent to a fixing device (not shown) to fix the full-color image.

  The secondary transfer residual toner adhering to the surface of the intermediate transfer belt 51 after passing through the secondary transfer nip is removed from the belt surface by a belt cleaning device 57 that sandwiches the intermediate transfer belt 51 with the driven roller 54. Is done.

FIG. 2 is an explanatory diagram showing a schematic configuration of the developing unit 20 of the toner image forming unit 1.
In the figure, the graph of the magnetic flux density in the normal direction on the outer peripheral surface of the magnet roller 23 is displayed in an overlapping manner.
In the following description, description of color-coded codes M, C, Y, and K is omitted.

  In the figure, the drum-shaped photoconductor 3 is disposed in such a posture that its axial direction extends in a direction perpendicular to the drawing sheet. Inside the developing unit 20, a developer supply transport path 27 and a developer recovery transport path 28 are provided, and a developer (not shown) is accommodated in these. Further, a supply screw 32 as a developer supply / conveyance member is rotatably accommodated in the developer supply / conveyance path 27. A receiving screw 35 as a developer collecting / conveying member is rotatably accommodated in the developer collecting / conveying path 28.

  The developing roll 21 is disposed so that a part of the peripheral surface of the developing sleeve 22 is exposed from an opening formed in the casing on the side facing the photoreceptor 3. On the opposite side of the developing sleeve 22 from the side facing the photoreceptor 3, the developer supply / conveyance path 27 and the developer recovery / conveyance path 28 face each other over almost the entire area in the axial direction. The developer collection / conveyance path 28 is disposed below the developing roll 21, and the developer supply / conveyance path 27 is disposed at a position slightly shifted downward from the side of the developing roll 21.

The supply screw 32 accommodated in the developer supply / conveyance path 27 is made of a nonmagnetic material such as a resin, and has a posture extending in the horizontal direction like the photosensitive member 3 and the developing roll 21. Then, the rod-shaped rotating shaft member 33 and the screw blade 34 erected in a spiral shape on the peripheral surface thereof are integrated in a counterclockwise direction in the figure by driving means such as a motor or a drive transmission system (not shown). Is driven to rotate.
The receiving screw 35 accommodated in the developer collecting / conveying path 28 also takes a posture extending in the horizontal direction, like the photoconductor 3, the developing roll 21, and the supply screw 32. Then, the rotating shaft member 36 and the screw blade 37 made of a nonmagnetic material such as resin are integrally rotated in the clockwise direction in the drawing by a driving means (not shown).
The developer supply transport path 27 and the developer recovery transport path 28 are partitioned by a partition wall 43 that forms a side wall on the developing roll side of the developer supply transport path 27. An opening is formed in the wall 43, and the developer supply conveyance path 27 and the developer recovery conveyance path 28 communicate with each other through the opening.

  In the developer supply transport path 27, the developer G1 held in the blades of the supply screw 32 is transported from the front side to the back side in the direction orthogonal to the drawing sheet as the supply screw 32 rotates. The In the course of this conveyance, as indicated by a thick solid arrow in the drawing, the developer G1 is sequentially supplied to the developing sleeve 22 side over the upper end of the partition wall 43, and the magnetic force of the magnet roller 23 in the developing sleeve 22 ( Pumped up to the surface of the developing sleeve 22 by the pumping magnetic force). The developer G1 transported to the vicinity of the downstream end of the developer supply transport path 27 in the developer transport direction (near the rear end in the figure) without being drawn up by the developing sleeve 22 is developed through the opening of the partition wall 43. It falls into the agent recovery conveyance path 28.

  With the rotation of the developing sleeve 22, the developer G <b> 2 that has been transported to the above-described developing region and contributed to the development is then transported to a position facing the developer recovery transport path 28 with the rotation of the developing sleeve 22. . Then, it is peeled off from the sleeve surface due to the influence of the repulsive magnetic field formed by the magnet roller 23 and falls into the developer collecting and conveying path 28 as shown by a one-dot chain line arrow in the figure.

  In the developer collecting and conveying path 28, the developer G2 held in the blades of the receiving screw 35 is conveyed from the back side to the near side in the direction orthogonal to the drawing sheet as the receiving screw 35 rotates. . In this conveyance process, toner is supplied by the above-described toner supply device. Further, in the vicinity of the upstream end of the developer recovery transport path 28 in the developer transport direction (near the rear end in the figure), the development falling from the developer supply transport path 27 through the opening of the partition wall 43. Take in the agent. The developer transported to the vicinity of the downstream end in the developer transport direction by the receiving screw 35 (near the front end in the figure) passes through the opening of the partition wall 43 to supply the developer. It is lifted to the conveyance path 27.

  As shown in FIG. 2, the magnet roller 23 according to the first embodiment has a configuration in which five magnetic poles N1, S1, N2, S2, and S3 are arranged along the moving direction of the developing sleeve surface. The magnetic pole N1 is a developing magnetic pole that generates a developing magnetic force for causing the developer carried on the surface of the developing sleeve 22 to rise in the developing region. The magnetic pole S <b> 1 is a transport magnetic pole that generates a magnetic force for transporting the developer carried on the surface of the developing sleeve 22 to the developing region. The magnetic pole N2 is a regulation magnetic pole that generates a regulation magnetic force for causing the developer to rise when passing through a regulation gap formed between the surface of the developing sleeve 22 and a doctor blade 25 as a developer regulation member. is there. Examples of the magnetic pole S2 include a pumping magnetic pole that generates a magnetic force for pumping up the developer on the surface of the developing sleeve 22. The magnetic pole S <b> 3 is a magnetic pole for forming the repulsive magnetic field described above in cooperation with the magnetic pole S <b> 2, peeling the developer from the surface of the developing sleeve 22, and collecting it on the developer collecting conveyance path 28.

  In the printer of the first embodiment having the above basic configuration, the four photoconductors 3M, 3C, 3Y, and 3K each function as a latent image carrier that carries a latent image on a surface that moves endlessly by rotation. . Further, the optical writing units 10M, 10C, 10Y, and 10K function as a latent image forming unit that forms a latent image on the surface of the photoreceptor after uniform charging. The developing units 20M, 20C, 20Y, and 20K for the respective colors function as developing devices that develop the latent images on the surfaces of the photoreceptors 3M, 3C, 3Y, and 3K, respectively.

Next, the developing unit in the conventional image forming apparatus will be described.
FIG. 13 is an explanatory diagram showing an example of a conventional developing unit.
In this conventional developing unit 120, the upper end position of the partition wall 143 is higher than that of the developing unit 20 of the first embodiment shown in FIG. 2, and a shielding wall (described later) provided in the developing unit 20 of the first embodiment is provided. Blocking member) 44 is not provided.

  In the conventional developing unit 120 having such a configuration, the restriction magnetic force by the restriction magnetic pole N2 acts on the developer G3 blocked from passing through the restriction gap, and is adjacent to the downstream side of the doctor blade 25 in the developing sleeve surface movement direction. This causes a situation in which the developer G3 is retained in the restricted retention space. The restricted stay developer G3 staying in the restricted stay space rotates in the opposite direction to the rotation direction of the developing sleeve 22 in the restricted stay space by the surface movement of the developing sleeve 22 as indicated by the dotted arrow in the figure ( It stays in the restricted stay space while circulating). In some cases, the regulated staying developer G3 also takes in the developer G1 splashed by the supply screw 32. The regulated staying developer G3 is rubbed and charged while being circulated and moved in the regulated staying space while receiving the restraining force of the regulated magnetic force. Compared with the developer G1 in the developer supply transport path 27, the regulated staying developer G3 is charged with toner. The amount is abnormally high. Therefore, a difference occurs in the developing ability between the regulated staying developer G3 and the developer G1 in the developer supply conveyance path 27. Even with the developers G1 and G3 having different developing capabilities, even if they are in a state of being uniformly dispersed and mixed with each other, even if they are used for development, image density unevenness that can be recognized by human beings. Will not occur. However, if the developer G1 and G3 are used in development in a state where mixing of the developers G1 and G3 is insufficient, image density unevenness that can be recognized by humans is generated and image quality is deteriorated.

  In the conventional developing unit 120 shown in FIG. 13, the restricted staying developer G <b> 3 that has escaped the restriction of the restricting magnetic force during the circulating movement is collected into the developer supply conveyance path 27. If collected in the developer supply conveyance path 27, the regulated staying developer G3 is sufficiently mixed with the developer G1 and then pumped up again, so that the above-described image quality degradation problem does not occur. However, since the pumping magnetic pole S2 having a polarity opposite to that of the regulating magnetic pole N2 is arranged adjacent to the upstream side in the developing sleeve surface moving direction, the conventional developing unit 120 shown in FIG. A magnetic field is formed such that the magnetic field lines that come out wrap around the magnetic pole S2 that is pumped up through the restricted retention space. In such a magnetic field, the restricted staying developer portion that is closest to the pumping magnetic pole S2 of the restricted staying developer G3 (the portion that is close to the upper end of the partition wall 143) is drawn along the line of magnetic force S2 side. To the surface of the developing sleeve 22. As a result, a part of the restricted staying developer G3 is carried on the surface of the developing sleeve 22 without being collected in the developer supply conveyance path 27.

  At this time, if the developer G1 from the developer supply / conveying path 27 is sufficiently pumped on the surface of the developing sleeve 22, the regulated staying developer G3 attracted by the pumping magnetic force is placed on the developer G1. It is carried on the surface of the developing sleeve 22 so as to overlap. In this case, since the regulated staying developer G3 is carried in a region far from the surface of the developing sleeve, passage of the regulating gap is blocked by the doctor blade 25, and a developer layer composed only of the developer G1 is conveyed to the developing region. . Therefore, in this case, image density unevenness does not occur and image quality deterioration does not occur. However, in the conventional developing unit shown in FIG. 13, the restricted staying developer G <b> 3 attracted by the pumping magnetic force hinders the pumping of the developer G <b> 1 from the developer supply conveyance path 27. In particular, the development supplied to the developing sleeve side at a portion where the feeding force to the developing sleeve side by the screw blade 34 of the supply screw 32 is weak (a portion where the outer peripheral end portion of the screw blade 34 does not pass through the vicinity of the developing sleeve 22). The portion of the agent G1 is inhibited from being pumped by the restricted stay developer G3 attracted by the pumping magnetic force. As a result, in such a place, the regulated staying developer G3 attracted by the pumping magnetic force is carried in a region near the surface of the developing sleeve 22, and is transported to the developing region through the regulating gap. . Therefore, in the conventional developing unit shown in FIG. 13, there is a developer layer in an insufficiently mixed state between the regulated stay developer G3 having an abnormally high toner charge amount and the developer G1 having a normal toner charge amount. The image is sent to the development area, causing image density unevenness and image quality degradation.

  In particular, the conventional development unit shown in FIG. 13 uses a supply / recovery separation system for recovering the developer on the developing sleeve 22 that has passed through the development region to a developer recovery / conveyance path 28 different from the developer supply / conveyance path 27. Is a unit. In such a developing unit, the developer G1 in the developer supply transport path 27 is transported to the downstream end portion in the developer transport direction while being pumped up to the surface of the developing sleeve 22. Therefore, the amount of the developer G1 flowing in the developer supply transport path 27 is smaller toward the downstream side in the developer transport direction, so that the developer supply transport path 27 has a downstream end in the developer transport direction from the developer supply transport path 27. The amount of developer G1 supplied to the developing sleeve 22 side tends to be insufficient. For this reason, at the downstream end of the developer supply conveyance path 27 in the developer conveyance direction, pumping of the developer G1 is easily hindered by the regulated staying developer G3 attracted by the pumping magnetic force, and image quality deterioration due to image density unevenness occurs. It's easy to do.

  Therefore, in the developing unit 20 in the first embodiment, in order to suppress such image quality deterioration, as shown in FIG. 2, the upper end position of the partition wall 43 is lowered as compared with the conventional developing unit 120 shown in FIG. Thus, the height of the partition wall 43 is lowered, and a shielding wall 44 as a blocking member is provided. The shielding wall 44 is disposed at a position that prevents the regulated staying developer G3, which has been prevented from passing through the regulation gap by the doctor blade 25, from moving toward the surface of the developing sleeve 22 along the magnetic force lines of the regulation magnetic force. Yes.

  By providing such a shielding wall 44, the regulated staying developer G3 attracted by the pumping magnetic force does not hinder the pumping of the developer G1 from the developer supply conveyance path 27. Therefore, it is difficult to generate a portion where the amount of the developer G1 pumped up from the developer supply conveyance path 27 is locally insufficient, and the development stay sleeve G3 attracted by the pumping magnetic force can pass through the regulation gap. It becomes difficult to carry in a region close to the surface. Therefore, it is possible to suppress occurrence of a situation where a developer layer in an insufficiently mixed state between the regulated stay developer G3 having an abnormally high toner charge amount and the developer G1 having a normal toner charge amount is sent to the development region. Further, image quality deterioration due to image density unevenness is suppressed.

  Further, the shielding wall 44 of the first embodiment is a slit 45 that is a supply passage for allowing the developer G1 in the developer supply / conveyance path 27 to pass to the developing sleeve 22 side at least over the entire region of the developing sleeve in the rotation axis direction of the developing sleeve. Is formed between the upper end of the partition wall 43. Therefore, even if such a shielding wall 44 is provided, the operation of pumping up the developer G1 in the developer supply transport path 27 to the surface of the developing sleeve 22 is not hindered. In particular, in the first exemplary embodiment, the slit 45 is arranged at a position where a straight line connecting the rotation center position of the developing sleeve 22 and the rotation center position of the supply screw 32 passes through the slit 45 when viewed from the axial direction of the developing sleeve. Has been. Therefore, the developer G1 in the developer supply conveyance path 27 can be supplied to the surface of the developing sleeve 22 with the shortest distance.

  Further, the shielding wall 44 of the first embodiment has a recovery passage for recovering the regulated staying developer, which has been prevented from passing through the regulation gap by the doctor blade 25, to the developer supply conveyance path 27, and an upper inner wall of the developing case. Form between. Therefore, even when such a shielding wall 44 is provided, the operation of returning the regulated staying developer to the developer supply transport path 27 is not hindered.

  Further, the length of the slit 45 in the developing sleeve rotation axis direction in the first embodiment is set to be larger than the width of the maximum image forming area as shown in FIG. When the length of the slit 45 in the developing sleeve rotation axis direction is narrower than the maximum image forming area, the surface portion of the developing sleeve 22 corresponding to both ends of the developing sleeve rotating axis direction of the maximum image forming area passes through the slit 45 and develops. The developer G1 moved so as to go around in the sleeve rotation axis direction is carried. Therefore, the amount of the developer G1 carried on the surface portion of the developing sleeve 22 corresponding to both end portions in the developing sleeve rotation axis direction of the maximum image forming region tends to be insufficient. Therefore, in the surface portion of the developing sleeve 22, the shortage is compensated for by the restricted stay developer G <b> 3 in the restricted stay space. As a result, when image formation is performed using the entire maximum image forming region, image density unevenness occurs between the central portion and both end portions in the developing sleeve rotation axis direction, causing image quality degradation. In the first embodiment, since the length of the slit 45 in the developing sleeve rotation axis direction is set to be larger than the width of the maximum image forming area, such image quality degradation does not occur.

  The opening width of the slit 45 (the length in the direction of movement of the developing sleeve surface) is preferably 2 mm or more. If it is less than 2 mm, it becomes difficult for the developer G1 to smoothly pass through the slit 45 due to the action of the pumping magnetic force when a carrier having a volume average particle diameter of about 50 μm is used. If the developer G1 cannot smoothly pass through the slit 45, the amount of the developer G1 pumped up on the surface of the developing sleeve 22 is insufficient, and the regulated staying developer G3 is replenished in the insufficient portion and developed through the regulated gap. It will be transported to the area. In this case, the image quality may be deteriorated due to uneven image density. If it is 2 mm or more, even when a carrier having a volume average particle size of about 50 μm is used, the developer G1 can be passed smoothly through the slit 45. If it is a developer using a small particle size carrier, the developer G1 can pass through the slit 45 smoothly in a particularly stable manner. Therefore, it is possible to avoid the deterioration of the image quality due to the image density unevenness because the developer G1 cannot pass through the slit 45 smoothly.

  In addition, since fluctuations in the amount of developer conveyed to the development area have a great influence on the development capability, a specified amount of developer is stably sent to the development area by the regulation gap between the doctor blade 25 and the surface of the development sleeve 22. Is set to Here, when the shielding wall gap between the shielding wall 44 and the surface of the developing sleeve 22 (gap between the closest portions) is narrower than the regulation gap, the developer carried on the surface of the developing sleeve 22 and passing through the shielding wall gap. The amount will be less than the amount that passes through the regulatory gap. Therefore, even when the developer passing through the shielding wall gap includes only the developer G1 pumped up from the developer supply conveyance path 27 and does not include the regulated staying developer G3, the developer is regulated on the developer G1. The developer layer on which the staying developer G3 overlaps passes through the regulation gap. Even in this case, as long as the regulated staying developer G3 is uniformly dispersed in the developer layer passing through the regulation gap, the image quality deterioration due to the image density unevenness as described above does not occur. However, as a result of the developer layer containing a large amount of regulated staying developer having an abnormally high toner charge amount contributing to the development in the development region, there is a problem that a normal image density cannot be obtained.

  Therefore, in the first embodiment, the shielding wall gap between the shielding wall 44 and the surface of the developing sleeve 22 is set to be equal to or wider than the regulation gap. As a result, the developer layer passing through the regulation gap is the developer layer passing through the shielding wall gap, that is, the developer layer consisting only of the developer G1 having a normal toner charge pumped up from the developer supply conveyance path 27. It becomes. Therefore, the above-described problem that a normal image density cannot be obtained can be solved.

Here, as shown in FIG. 14, the magnetic force acting on the magnetic carrier located on the edge 44a ′ on the developer supply transport path 27 side of the end surface (lower surface) facing the slit 45 in the shielding wall 44 ′ and When the combined force F1 ′ of gravity is configured to be directed in the direction toward the inside of the slit 45, that is, the lower side of the horizontal plane, the regulated staying developer G3 is likely to enter the slit 45, and the regulated staying developer. There is a possibility that the effect of preventing the shielding wall 44 'from inhibiting the movement of G3 along the magnetic field lines of the regulating magnetic force to the surface side of the developing sleeve 22 may be insufficient. Therefore, in the first exemplary embodiment, one magnetic carrier is provided on the edge 44a on the developer supply transport path 27 side of the end surface (lower surface) facing the slit 45 in the shielding wall 44 in a state where the developer is not present in the developing unit 20. (Hereinafter referred to as “first specific magnetic carrier”.) The combined force F1 of the magnetic force F1 _M and the gravity F1 _G acting on the first characteristic magnetic carrier C1 when C1 is arranged is the direction away from the slit 45, that is, the horizontal plane. The configurations of the shielding wall 44 and the magnet roller 23 are adjusted so as to be parallel or to face upward from the horizontal plane.

FIG. 4 is a magnetic force distribution diagram schematically showing the direction of the magnetic force at each point between the developing sleeve 22 and the supply screw 32 in the state where the developer is not present in the developing unit 20.
In FIG. 4, the length of each arrow indicating the direction of the magnetic force does not indicate the magnitude of the magnetic force at that point.
FIG. 5 shows the magnetic force F1 _M and gravity F1 _G acting on one magnetic carrier C1 arranged on the edge 44a on the developer supply transport path 27 side of the end surface (lower surface) facing the slit 45 in the shielding wall 44. It is explanatory drawing of synthetic | combination force F1.
In order for the magnetic carrier present in the edge portion 44a to enter the inside of the slit 45, an external force that goes into the slit 45, that is, an external force that goes downward in the horizontal direction in the first embodiment needs to act. External force acting on the magnetic carrier to be present in the end 44a, the magnetic force F1 _M and the gravity F1 _G is dominant. In the first embodiment, as shown in FIGS. 4 and 5, the combined force F1 of the magnetic force F1 _M and the gravity F1 _G acting on the first characteristic magnetic carrier C1 is directed upward from the horizontal plane. The one-character magnetic carrier C1 does not enter the slit 45.

Here, actually, the developing unit 20 is filled with a developer, but when the developing unit 20 is filled with a developer, the magnetic carrier is magnetically adjacent to the magnetic carrier adjacent to the magnetic field line. A chain of magnetic carriers is formed by connecting with force. Therefore, the magnetic force component acting on one magnetic carrier is stronger when the developer is filled in the developing unit 20 than when the developer is not present in the developing unit 20. As a result, since the magnetic force F1 _M is relatively increased with respect to the gravity F1 _G , the resultant force F1 is directed further upward from the horizontal plane and is further away from the slit 45. Therefore, under the condition that the first specific magnetic carrier C1 does not enter the slit 45 in the state where the developer is not present in the developing unit 20, in the actual situation where the developer is filled in the developing unit 20, The magnetic carrier located at the same point as the first specific magnetic carrier C1 does not enter the slit 45. If the magnetic carrier located at the edge 44 a does not enter the slit 45, the restricted staying developer G <b> 3 can be sufficiently prevented from entering the slit 45.

Therefore, according to the first embodiment, the regulated staying developer G3 is effectively prevented from entering the slit 45 around the shielding wall 44, and the regulated staying developer G3 having an abnormally high toner charge amount is compared with the normal staying developer G3. Occurrence of a situation where a developer layer that is not sufficiently mixed with the developer G1 having a toner charge amount is sent to the development area is further suppressed, and image quality deterioration due to image density unevenness is further suppressed.
In this way, in order to effectively prevent the regulated staying developer G3 from entering the slit 45 around the shielding wall 44, at least the position of the end (lower end) facing the slit 45 in the shielding wall 44 is set. The developing sleeve surface needs to be set upstream of the straight line connecting the inflection point between the pumping pole S2 and the regulation magnetic pole N2 and the rotation center of the developing sleeve.

  In the first embodiment, as shown in FIG. 2, the shielding wall 44 is configured so that the developer G4 is pumped and carried by the action of the magnetic force on the surface of the shielding wall 44 on the developer supply / conveyance path 27 side. The shape and arrangement of the magnetic roller 23 and the configuration of the magnet roller 23 are adjusted. With such a configuration, the developer G4 raised on the shielding wall 44 by the pumping magnetic force becomes a wall, and the movement of the regulated staying developer G3 attracted to the slit 45 side by the pumping magnetic force is prevented. Can do. As a result, it is possible to prevent the restricted stay developer G3 from passing around the shielding wall 44 and passing through the slit 45, so that the stay with the regulated stay developer G3 having an abnormally high toner charge amount and a normal toner charge amount are developed. Occurrence of a situation where a developer layer that is not sufficiently mixed with the agent G1 is sent to the development area is further suppressed, and image quality deterioration due to image density unevenness is further suppressed.

  Even if the shape of the shielding wall 44 is changed in design and the same function as the wall of the developer G4 raised on the shielding wall 44 is realized by the shielding wall 44 itself, the same effect as described above can be obtained. can get. However, in this case, the size of the shielding wall 44 becomes large, and it is required to arrange the shielding wall 44 having such a large size in a narrow space between the developing sleeve 22 and the supply screw 32. Therefore, high accuracy is required for the component accuracy and assembly accuracy of the shielding wall 44, resulting in an increase in cost. Therefore, in terms of cost, it is more advantageous to form the wall with the developer G4 that is raised on the shielding wall 44 as in the first embodiment.

  Further, as described above, at the downstream end of the developer supply transport path 27 in the developer transport direction, the amount of the developer G1 is small, and the developer G1 supplied from the developer supply transport path 27 to the developing sleeve 22 side. The amount of is easy to run out. However, in the first embodiment, the height of the partition wall 43 is made lower than that of the conventional developing unit 120 shown in FIG. Therefore, in the conventional developing unit 120, the partition wall 43 is low even if the developer G1 is present in the developer supply transport path 27 so that the developer supply amount to the developing sleeve 22 is insufficient. With the developing unit 20 of the first embodiment, it is possible to avoid a shortage of the developer supply amount. Therefore, even at the downstream end of the developer supply transport path 27 in the developer transport direction, the mixing ratio between the regulated stay developer G3 having an abnormally high toner charge amount and the developer G1 having a normal toner charge amount is insufficient. Occurrence of a situation where the developer layer in the state is sent to the development area is suppressed, and image quality deterioration due to image density unevenness is suppressed.

  However, if the height of the partition wall 43 is too low, the developer G1 that has climbed over the upper end of the partition wall 43 may fall without being pumped up by the magnetic force. Specifically, as shown in FIG. 15, the combined force F2 ′ of the magnetic force and gravity acting on the magnetic carrier located at the edge 43a ′ on the developing sleeve 22 side on the upper end surface of the partition wall 43 ′ is the horizontal direction. If it faces downward, the developer G1 that has climbed over the upper end of the partition wall 43 'will be pumped up and dropped without being captured by the magnetic force. When such a drop occurs, the amount of the developer G1 supplied from the developer supply conveyance path 27 to the developing sleeve 22 side becomes insufficient, and the regulated staying developer G3 attracted by the pumping magnetic force becomes lower end of the shielding wall 44. There is a risk of being carried in a region close to the surface of the developing sleeve that can enter around and pass through the regulation gap.

Therefore, in the first embodiment, as shown in FIGS. 4 and 6, one magnetic element is formed on the edge 43 a on the developing sleeve 22 side on the upper end surface of the partition wall 43 in the state where the developer is not present in the developing unit 20. The combined force F2 of the magnetic force F2 _M and the gravity F2 _G acting on the second specific magnetic carrier C2 when the carrier (hereinafter referred to as “second specific magnetic carrier”) C2 is arranged is horizontal or higher than horizontal. The configuration of the partition wall 43 and the magnet roller 23 is adjusted so as to face the direction. In this case, since the second specific magnetic carrier C2 is pumped up to the magnetic force F2 _M gravity F2 surface against the _G developing sleeve 22 by the action of pumping, it does not fall. Here, actually, the developing unit 20 is filled with a developer, but when the developing unit 20 is filled with a developer, the magnetic carrier is magnetically adjacent to the magnetic carrier adjacent to the magnetic field line. A chain of magnetic carriers is formed by connecting with force. Therefore, the magnetic force component acting on one magnetic carrier is stronger when the developer is filled in the developing unit 20 than when the developer is not present in the developing unit 20. As a result, since the gravitational force F2 _G magnetic force F2 _M is strengthened relative to the synthetic force F2 will be directed more upward than the horizontal plane. Therefore, under the condition that the second specific magnetic carrier C2 does not fall in the state where the developer is not present in the developing unit 20, the second specific magnetic carrier C2 is used in the actual situation where the developer is filled in the developing unit 20. The magnetic carrier located at the same point as the magnetic carrier C2 does not fall.

Further, other magnetic carriers located closer to the surface of the developing sleeve 22 than the edge 43a (between the edge 43a and the developing sleeve surface) are pumped up more than the magnetic carrier located at the edge 43a. since the action of the magnetic force F2 _M is strong, if the condition in which the magnetic carrier is located in the edge 43a does not drop, it does not even fall the other of the magnetic carrier. Further, the other magnetic carrier positioned vertically above the edge 43a is closer to the peak point of the magnetic flux density in the normal direction of the magnetic pole S2 than the magnetic carrier positioned at the edge 43a. action of F2 _M is greater than the magnetic carrier is located in the edge 43a. Therefore, as long as the magnetic carrier located at the edge 43a does not fall, the other magnetic carrier does not fall. The other magnetic carrier positioned further above the peak point of the magnetic flux density in the normal direction of the pumping magnetic pole S2 is supported by the magnetic carrier positioned below, and thus does not fall.

Therefore, when the magnetic carrier (second specific magnetic carrier C2) is arranged on the edge 43a on the developing sleeve 22 side on the upper end surface of the partition wall 43 in the state where the developer is not present in the developing unit 20, the second is concerned. If the developing unit 20 of Embodiment 1 is adjusted such that the combined force F2 of the magnetic force F2 _M acting on the specific magnetic carrier C2 and the gravity force F2 _G is oriented in the horizontal direction or upward from the horizontal, The developer G1 that has passed over the upper end of the wall 43 is not trapped by the magnetic force and does not fall.

  Further, as shown in FIG. 16, if the height of the partition wall 43 ′ is too low, the developed developer G2 peeled off from the sleeve surface due to the influence of the repulsive magnetic field formed by the magnet roller 23 is separated from the partition wall 43 ′. May move toward the developer supply transport path 27 side. Since the developed developer G2 consumes toner in the development area, the toner density is low. When such developer G2 moves toward the developer supply / conveyance path 27 and is carried on the surface of the developing sleeve 22 as it is, the developer G1 pumped up from the developer supply / conveyance path 27 having a normal toner density There is a possibility that the developer G2 having a low toner concentration passes through the regulation gap in a state where the developer G2 is not sufficiently mixed and contributes to development. In this case as well, image quality deterioration due to image density unevenness occurs. Therefore, the height of the partition wall 43 needs to be such that the developed developer G2 can be prevented from moving to the developer supply transport path 27 side. For this purpose, the upper end position of the partition wall 43 is positioned downstream of the developing sleeve surface movement direction with respect to the peeling region where the peeling magnetic force for peeling the developed developer G2 from the surface of the developing sleeve 22 acts. Set to. Specifically, for example, it is set so as to be located downstream of the straight line connecting the inflection point between the pumping pole S2 and the magnetic pole S3 and the rotation center of the developing sleeve in the developing sleeve surface moving direction.

  In the first embodiment, the pumping magnetic pole S2 and the regulation magnetic pole N2 are arranged adjacent to each other in the developing sleeve surface movement direction. That is, there is no other magnetic pole between the pumping magnetic pole S2 and the regulating magnetic pole N2. With such a configuration, the developer carried on the surface of the developing sleeve 22 between the pumping magnetic pole S2 and the regulation magnetic pole N2 is in a state of lying along the magnetic field lines between the pumping magnetic pole S2 and the regulation magnetic pole N2. When the developer lies down, the developer is in a dense state. Therefore, even if the regulated staying developer G3 is attracted to the surface of the developing sleeve 22 with a strong force between the pumping magnetic pole S2 and the regulating magnetic pole N2, the developer G1 (developer supply / conveyance) already carried on the surface of the developing sleeve 22 By simply getting on the developer (provided from the path 27), the developer G1 is not pushed away and enters the vicinity of the surface of the developing sleeve. Therefore, the restricted stay developer G3 is prevented from being mixed into the developer passing through the restriction gap, and the development process can be performed only with the developer G1 having a normal toner charge amount.

  As shown in FIG. 17, when an intermediate magnetic pole N3 having a polarity opposite to that of the pumping magnetic pole S3 and the regulating magnetic pole S2 is disposed, the magnetic force between the intermediate magnetic pole N3 and the regulating magnetic pole S2 is followed. Thus, a magnetic force acts on the developer G3, and thereby the developer G3 stays. That is, the regulated staying developer G3 'is attracted toward the developing sleeve surface portion to which the intermediate magnetic pole N3 is opposed, not to the developing sleeve surface portion to which the pumping magnetic pole S3 is opposed. As a result, the place where the regulated staying developer G3 ′ is pumped up to the surface of the developing sleeve 22 is at a position far from the location where the developer G1 is pumped up from the developer supply conveyance path 27 on the downstream side of the developing sleeve surface movement direction. Become. Therefore, when the developer G1 from the developer supply / conveyance path 27 is pumped onto the surface of the developing sleeve 22, a situation in which the restricted staying developer G3 'interferes is unlikely to occur. Therefore, in the configuration in which the intermediate magnetic pole N3 is arranged, image quality deterioration due to the above-described image density unevenness hardly occurs.

  In addition, in the configuration of the developing unit as shown in FIG. 17, there is another reason that image quality deterioration due to image density unevenness due to the restricted staying developer G3 'is less likely to occur. In other words, the magnetic force chain (ear) of the developer carried on the surface of the developing sleeve 22 is formed along the lines of magnetic force, so that the head is raised at the position where the developing sleeve surface moving direction position is close to the magnetic pole. In addition, it is in a lying state at an intermediate position between the two magnetic poles. Therefore, the developer carried on the surface of the developing sleeve 22 (mostly the developer G1 pumped up from the developer supply transport path 27) is close to the intermediate magnetic pole N3 between the pumping magnetic pole S3 and the regulating magnetic pole S2. At this point, the spikes are once formed, and the developer density is sparse. Then, the developer G1 that has risen in this manner is in a state where the spike has fallen while passing further near the intermediate point between the intermediate magnetic pole N3 and the regulation magnetic pole S2 as the developing sleeve rotates. Due to such a series of behaviors of the developer G1, the regulated stay developer G3 ′ is taken into the developer G1 on the developing sleeve in a uniformly dispersed state, and the regulated stay developer G3 ′ in the regulated stay space is sequentially supplied. It will be consumed. As a result, the same developer is less likely to stay in the restricted stay space for a long period of time, so even if the restricted stay developer G3 ′ taken into the developer G1 on the developing sleeve is transported to the development region, it is not much. There is no image quality degradation.

However, even if the regulated staying developer G3 ′ is compared with the developer G1 pumped up from the developer supply conveyance path 27, the frictional charge is advanced and the toner charge amount is high. It is preferable not to use the staying developer G3 ′. In this respect, it can be said that the developing unit of the first embodiment is more advantageous than the developing unit as shown in FIG.
In addition, the developing unit of the first embodiment is advantageous in this respect because the magnetic pole arrangement is simple.

Next, the structure of the shielding wall 44 of the developing unit 20 that is a characteristic part of the present invention will be described.
FIG. 7 is a perspective view of the state in which the metal stay 46 constituting the shielding wall 44 in Embodiment 1 is removed from the partition wall 43.
In the developing unit 20 of the first embodiment, the metal stay 46 is supported on the developing case (specifically, the partition wall 43 which is a part of the developing case) by only the tab portions 47 provided at both end regions in the developing sleeve rotation axis direction. The central region of the stay 46 in the rotation axis direction of the developing sleeve is the shielding wall 44. In the central region of the metal stay 46 constituting the shielding wall 44 in the developing sleeve rotation axis direction, there is no support portion for the developing case. That is, in the first embodiment, such a long metal stay 46 is supported only at both ends in the longitudinal direction. This is because when a support portion is provided in the central region in the developing sleeve rotation axis direction of the metal stay 46 serving as the shielding wall 44, streaky image density unevenness occurs at a location corresponding to the support portion. This is to avoid it.

  Here, in the developing unit 20 of Embodiment 1, an external force toward the developing sleeve 22 is applied to the shielding wall 44 that is a passage forming member by the movement of the developer G1 that passes through the slit 45. Further, the restricted staying developer G3 attracted by the pumping magnetic force causes the shielding wall 44 to be pressed against the developing sleeve 22. Therefore, the shielding wall 44 supported only at both end regions in the developing sleeve rotation axis direction bends toward the developing sleeve, and the center in the developing sleeve rotation axis direction approaches the surface of the developing sleeve 22. Therefore, if the shielding wall 44 is integrally formed of the same material (synthetic resin material having high flexibility) as the developing case 43 for the purpose of cost reduction or the like, the shielding wall 44 is greatly bent. In particular, the space between the surface of the developing sleeve 22 where the shielding wall 44 is disposed and the supply screw 32 is very narrow. Therefore, the thickness of the shielding wall 44 in the facing direction of the surface of the developing sleeve 22 and the supply screw 32 must be reduced. In the developing unit 20 according to Embodiment 1, the closest distance between the surface of the developing sleeve 22 and the outer peripheral end of the screw blade of the supply screw 32 is approximately 5 mm. Therefore, the thickness of the shielding wall 44 needs to be, for example, 3 mm or less in consideration of margins such as manufacturing errors and assembly errors. Since the direction of the thickness of the shielding wall 44 substantially coincides with the above-described direction in which the external force or pressing force is applied, the thin shielding wall 44 is easily bent.

When the shielding wall 44 is greatly bent, the shielding wall gap between the vicinity of the center of the developing sleeve in the rotation axis direction of the shielding wall 44 and the surface of the developing sleeve becomes narrower than the vicinity of the end portion. Therefore, the developer amount on the developing sleeve passing through the shielding wall gap near the center of the developing sleeve rotation axis of the shielding wall 44 is insufficient, and the deficiency is replenished by the regulated retention developer G3 in the regulated residence space. As a result, a large amount of the restricted staying developer G3 is transported to the developing region in the vicinity of the center in the developing sleeve rotation axis direction, which may cause image quality deterioration due to uneven image density. Further, in a portion where the shielding wall 44 is greatly bent and the shielding wall gap is narrowed, the compressive force received when the developer on the surface of the developing sleeve 22 passes increases. For this reason, the toner in the developer aggregates or adheres to the surface of the developing sleeve 22, which may hinder proper development processing. In particular, when the toner aggregates, the toner aggregates adhere to the recording paper P and appear as black spots, or white spots appear due to the absence of toner around the toner aggregates. Cause image quality degradation.
Therefore, in the first embodiment, a metal stay 46 formed of a metal material having higher rigidity than the partition wall 43 made of a synthetic resin material integrally formed with the developing case is used as a member constituting the shielding wall 44. Yes.

FIG. 8 shows the developing unit in the vicinity of the shielding wall when cut along a plane orthogonal to the developing sleeve rotation axis direction so as to pass through the central region in the developing sleeve rotation axis direction of the metal stay 46 constituting the shielding wall 44. It is sectional drawing which shows a structure.
As shown in FIG. 8, the metal stay 46 according to the first embodiment has a substantially square shape in which the cross-sectional shape of the central region in the developing sleeve rotation axis direction constituting the shielding wall 44 is 3 mm × 3 mm. On the other hand, in the printer of the first embodiment, the developing area width in the developing sleeve rotation axis direction is secured to 300 mm or more, which is sufficiently larger than the A3 size. Specifically, printing on a recording paper having a width of 330 mm, which is equivalent to 13 inches, as a production printer is considered in consideration of printing white (considering that a margin is provided around the entire surface without printing). Assuming that it is necessary to secure a development area width of at least 320 mm or more. Therefore, the width of the slit 45 (the length in the developing sleeve rotation axis direction) of the first embodiment is also set to 320 mm or more.

  As described above, in the first embodiment, the width of the slit 45 to be secured is 320 mm or more, whereas the cross-sectional dimension of the shielding wall 44 forming the slit 45 is 3 mm × 3 mm. Since the shielding wall 44 is supported only at both ends in the developing sleeve rotation axis direction (width direction of the slit 45), it is difficult to ensure sufficient rigidity to suppress the deflection. Such high rigidity cannot be realized at low cost with the same synthetic resin material as that of the developing case. However, if it is a metal material having higher rigidity than the synthetic resin material, it can be realized at relatively low cost.

  As a material of the metal stay 46 of the first embodiment, stainless steel such as SUS304 and SUS316 is preferable. As the metal material, for example, nonmagnetic and highly rigid titanium or magnesium can be used. However, since the material is expensive, stainless steel is advantageous in terms of cost. As an inexpensive material, for example, aluminum can be used, but the rigidity is inferior to stainless steel. In the first embodiment, SUS304 is used as the material of the metal stay 46, and the amount of magnetism is made extremely small by processing. With such a small amount of magnetism, there is no inconvenience that causes the passage of the developer through the slit 45 to be inhibited when the metal stay 46 is made of a magnetic steel material. Therefore, it is possible to avoid a situation in which the amount of developer G1 drawn from the developer supply / conveyance path 27 is insufficient due to the passage of the developer through the slit 45 and the regulated staying developer G3 contributes to development.

  In the first embodiment, the outer shape of the shielding wall 44, that is, the outer shape of the central portion of the metal stay 46 in the developing sleeve rotation axis direction is the outer surface portion facing the slit 45 (hereinafter referred to as “slit forming surface”). 48c has a planar shape. Thereby, it is easy to ensure uniformity in the developing sleeve rotation axis direction with respect to the amount of the developer G1 passing through the slit 45. Further, an outer surface portion (hereinafter referred to as “sleeve facing surface”) 48 a facing the surface of the developing sleeve 22 has a planar shape. This makes it easy to ensure the uniformity of the developing sleeve rotation axis direction with respect to the shielding wall gap between the surface of the developing sleeve 22 and the shielding wall 44. By adopting such a configuration, the developer G1 supplied from the developer supply / conveying path 27 is pumped up to the surface of the developing sleeve through the slit 45 while ensuring uniformity in the developing sleeve rotating shaft direction, After that, even when passing through the shielding wall gap, the uniformity in the developing sleeve rotation axis direction is maintained. The uniformity of the developer amount passing through the slit 45 or the shielding wall gap in the direction of the developing sleeve rotation axis is ensured in a plane compared to the case where the slit 45 or the shielding wall gap is formed by a curved surface or a sharp portion. The degree of uniformity in the assembly accuracy of the stay 46 is high, and the assembly accuracy management becomes easy.

  In the first embodiment, the outer shape of the shielding wall 44, that is, the outer shape of the central region of the metal stay 46 in the developing sleeve rotation axis direction is the outer surface opposite to the sleeve facing surface, as shown in FIG. A portion (outer surface portion facing the recovery passage) 48d and an outer surface portion 48b facing the developer supply / conveyance path 27 are configured to have a convex curved surface. By adopting such a curved surface shape, since the entire curved surface becomes a processed surface by forming a curved surface, it is easy to benefit from work hardening, and thus it is easy to ensure the rigidity of the metal stay 46. Further, since the curved shape is used, the work hardening area is wide and the degree of processing is reduced, so there is no large bias in work hardening, and there is no difference in local hardening or deformation, so the slit forming surface 48c. And it becomes easy to ensure the plane accuracy of the sleeve facing surface 48a. Specifically, it becomes easy to correct the plane. Furthermore, the curved surface shape can suppress the amount of local deformation to a small extent, and as a result, the influence of magnetization due to tissue deformation due to work hardening can be reduced. Since the curved surface portion has little influence on the developer pumping operation to the developing sleeve 22, the developing sleeve has a large influence on the developer pumping operation to the developing sleeve 22 such as the slit forming surface 48 c and the sleeve facing surface 48 a. Uniformity in the direction of the rotation axis is not strictly required.

  Further, the metal stay 46 of the first embodiment has a structure in which the central region in the developing sleeve rotation axis direction constituting the shielding wall 44 is formed by bending a metal flat plate into a square shape. Thereby, since high rigidity is obtained by work hardening of a bending process, the highly inexpensive and cheap shielding wall 44 can be obtained.

  Here, when the central region in the developing sleeve rotation axis direction constituting the shielding wall 44 is formed by bending as in the first embodiment, a closing port 49 that closes the plate start end and the plate end is formed. . Such a closing port 49 is difficult to make the gap zero, and a small gap is opened, and there is a concern about the inflow of the developer from the closed 49. When the inflow of the developer occurs, the metal stay 46 becomes like a magnetic body when viewed from the outside, and there is a possibility that the passage of the developer through the slit 45 may be inhibited. That is, when the metal stay 46 behaves like a magnetic body, the developer is magnetically attached to the slit forming surface 48c facing the slit 45, and the passage of the developer through the slit 45 is inhibited. When the developer magnetically adheres to the slit forming surface 48c, the height of the slit 45 (the length in the moving direction of the developing sleeve surface) becomes substantially low. In the first embodiment, the target height of the slit 45 is 3 mm. However, if the height is substantially 2 mm or less, sufficient developer supply capability cannot be ensured, and the developer supply / conveyance path 27 is not secured. There is a situation in which the amount of the developer G1 pumped up is insufficient and the regulated staying developer G3 contributes to development. Further, when the developer magnetically adheres to the slit forming surface 48c, rubbing occurs between the adhered developer and the developer passing through the slit 45, and toner separation from the developer occurs, resulting in toner aggregation. There is also a risk of causing it.

  Therefore, in the first embodiment, a position where the closing port 49 between the end of the plate and the starting end of the plate in the B-shaped bending is opposed to the surface of the developing sleeve 22 and adjacent to the closing port 49. The metal stay 46 is arranged so that the closing port 49 is opened in the direction of the flow of the developer flowing through the developing sleeve, that is, in the direction perpendicular to the moving direction of the developing sleeve surface. Since the flow direction of the developer is stable in a certain direction (downstream of the developer surface movement direction) at a location facing the surface of the developing sleeve 22, the closing port 49 is opened in a direction orthogonal thereto. Thus, it is possible to effectively prevent the developer from entering the closing port 49.

Since the flow direction of the developer is also stable in the direction facing the slit 45 (direction toward the surface of the developer carrying member), the same applies even if the closing port 49 faces the slit 45. An effect is obtained.
Further, when closing the end of the plate so that it overlaps the top of the plate in the folding process of the square shape, the closing port is the closing port at a position facing the surface of the developing sleeve or a position facing the slit 45. The metal stay 46 may be disposed so as to open in a direction toward the downstream side in the flow direction of the developer flowing through the portion adjacent to the. In this case, the same effect can be obtained.
Further, the central region in the developing sleeve rotation axis direction of the metal stay 46 constituting the shielding wall 44 may be formed in a seamless tubular shape by, for example, pultrusion molding. In this case as well, the same effect can be obtained because the development can be prevented from entering.

  In the developing unit 20 of the first embodiment, when the shielding wall 44 is formed using the metal stay 46 made of SUS304, the shielding wall 44 is formed of the same resin molded product as that of the developing case. 1/50 or less of the amount of bending in the case. Specifically, when the shielding wall 44 is formed of a resin molded product, the shielding wall 44 is bent by 1 mm or more and comes into contact with the surface of the developing sleeve 22. However, the shielding wall 44 is shielded by using a metal stay 46 made of SUS304. In the first embodiment in which the wall 44 is formed, the amount of bending can be suppressed to about 50 μm.

9A to 9C are explanatory views showing a state in which the metal stay is attached to the partition wall. 9A is a front view, FIG. 9B is a side view, and FIG. 9C is a bottom view.
Further, the metal stay 46 is attached to the partition wall 43 which is a part of the developing case by tab portions 47 provided at both end regions in the developing sleeve rotation axis direction. The tab portions 47 are provided in both end regions of the metal stay 46 located outside the developing region in the developing sleeve rotation axis direction, and extend toward the partition wall 43 from the central portion in the developing sleeve rotation axis direction. The tab portion 47 has a U-shaped cross section as shown in FIG. 9B, which is perpendicular to the developing sleeve rotation axis direction. When the metal stay 46 is attached to the partition wall 43, the partition wall 43 is attached so as to be inserted into the U-shaped opening of the tab portion 47 of the metal stay 46. As a method for fixing the metal stay 46 to the partition wall 43, an adhesive method using an adhesive or the like is employed, but a method of mechanically fixing the engaging portions with each other may be used.

  Further, in the first embodiment, as shown in FIG. 9C, the partition wall 43 comes into contact with the tab portions 47 provided at both ends of the metal stay 46 from the inner side in the developing sleeve rotation axis direction. A step portion 43a as a locking member is provided. Since the stepped portions 43a are in contact with the tab portions 47 from the inside in the developing sleeve rotation axis direction, the movement of the metal stay 46 in the developing sleeve rotation axis direction is locked. Thereby, a slight external force is not applied to the metal stay 46, and the metal stay 46 does not move in the direction of the developing sleeve rotation axis.

  Since the partition wall 43 is integrally formed with the developing case, the positional relationship with the developing sleeve 22 and the supply screw 32 attached to the developing case can be determined with high accuracy. In the first embodiment, by attaching the metal stay 46 to the partition wall 43, the metal stay 46 can easily determine the positional relationship with respect to the developing sleeve 22 and the supply screw 32 with high accuracy.

  Further, the tab portion 47 of the metal stay 46 according to the first embodiment is formed by bending a metal flat plate similarly to the portion constituting the shielding wall 44, so that it can be manufactured at a low cost. The tab portion 47 can be formed by cutting a pipe material and molding it into a U-shape, or it can be formed by press molding.

[Modification]
Next, a modification of the developing unit in the first embodiment will be described.
As a method for fixing the metal stay 46 to the partition wall 43, when an adhesive method using a liquid adhesive or the like is employed as in the first embodiment, the partition wall to which the inner wall surface of the tab portion 47 or the tab portion 47 of the metal stay 46 is attached. The operation | work which attaches a liquid adhesive to the outer surface of 43 or both one by one is required, and it takes an effort. In addition, there may be a portion where the amount of liquid adhesive is insufficient, and the metal stay 46 may come off at such a portion. Further, it is difficult to fix the metal stay 46 so that the liquid adhesive does not protrude outside the adhesive surface, and toner may accumulate on the adhesive that protrudes outside the adhesive surface. In this case, if the accumulated portion is inside the slit 45, there is a possibility that the passage of the developer through the slit 45 may be inhibited. In addition, if the toner lump accumulated on the adhesive gets on the developer flow and is pumped up to the surface of the developing sleeve, the toner lump is clogged in the regulation gap and causes white streaks on the image. .

Therefore, in this modification, a configuration is adopted in which the metal stay 46 is fixed to the partition wall 43 without using an adhesive.
In the following description, the description of the same configuration as that of the first embodiment will be omitted, and only the configuration specific to this modification will be described.

FIGS. 10A to 10C are explanatory views for explaining a configuration in which a metal stay is attached to a partition wall without using an adhesive in the present modification. 10A is a front view, FIG. 10B is a side view, and FIG. 10C is a bottom view.
In this modification, both end portions in the developing sleeve rotation axis direction of the partition wall 43 to which the tab portion 47 of the metal stay 46 is attached are formed higher than the center portion as shown in FIG. The inside of the tab part 47 is inserted deeply. Further, as shown in FIG. 10A, two latches 47a as projecting portions projecting toward the partition wall 43 are provided on the inner surface of each tab portion 47 of the metal stay 46 so as to face each other. Yes. The interval between the two latches 47a facing each other is formed so as to be narrower than the thickness of the partition wall 43. Therefore, when the partition wall 43 is inserted into the tab portion 47, the partition wall 43 has two latches. 47a. This clamping force increases the fixing strength of the metal stay 46 with respect to the partition wall 43.

  Further, in this modification, the latch 47a is notched in the tab portion 47 so as to open toward the outer surface portion of the shielding wall 44 facing the recovery passage, that is, the upper surface of the shielding wall 44, and the notch It is formed by bending the portion toward the inner surface side of the tab portion. With such a configuration, when the metal stay 46 is attached to the partition wall 43, the latch 47a is displaced in the direction of the original bending, so that the partition wall 43 can be inserted into the tab portion 47 with little resistance. On the other hand, when the metal stay 46 is to be removed from the partition wall 43, a large frictional force is generated between the tip of the latch 47a and the outer peripheral surface of the partition wall 43, and the metal stay 46 cannot be easily removed. Therefore, the fixing strength of the metal stay 46 to the partition wall 43 can be increased while facilitating the work of attaching the metal stay 46 to the partition wall 43.

  In particular, as shown in FIG. 11, if a recess 43 b that engages with the latch 47 a is provided at a location where the latch 47 a contacts the partition wall 43, the tip of the latch 47 a is caught by the recess 43 c of the partition wall 43, and It becomes difficult to remove. Therefore, it is possible to further increase the fixing strength of the metal stay 46 to the partition wall 43 while facilitating the work of attaching the metal stay 46 to the partition wall 43.

[Embodiment 2]
Next, as an image forming apparatus to which the present invention is applied, another embodiment of an electrophotographic printer (hereinafter, this embodiment is referred to as “embodiment 2”) will be described.
Although the developing unit of Embodiment 1 (including the above-described modification) is a developing device including only one developer carrier (developing sleeve 22), the present invention includes a plurality of developer carriers. Also in a multi-stage developing type developing device that performs development processing on the electrostatic latent image formed on the surface of the photoreceptor 3 by the developer carried on the surface of the developer carrying body facing the photoreceptor 3. Can be applied as well.
In the following description, only the parts different from the first embodiment will be described, and the description of the same parts as the first embodiment will be omitted.

FIG. 12 is an enlarged view showing the developing unit 220 in the second embodiment.
The developing unit 220 according to the second exemplary embodiment includes a multi-stage provided with two developer carriers, a first developing roller 221A as a first developer carrier and a second developing roller 221B as a second developer carrier. This is a developing type developing device. The developing rolls 221A and 221B are arranged to face each other so as to be close to the surface of the photoreceptor 3, and the facing positions serve as development areas. In the development area, a magnetic brush made of a developer spiked on the surface of each of the developing rolls 221A and 221B contacts the surface of the photoreceptor 3. A developer G (two-component developer) containing toner T and magnetic carrier C is accommodated in the developing unit 220. The developing unit 220 performs a developing process for developing the electrostatic latent image formed on the photoconductor 3 into a toner image.

  Here, the developing unit 220 according to the second embodiment is of a premix developing type, and a new developer G is appropriately supplied into the developing unit 220 from an agent cartridge (not shown), and a deteriorated developer is used. G is discharged toward the agent storage container installed outside the developing unit 220. The agent cartridge contains developer G (toner T and carrier C) to be supplied into the developing unit 220 therein. The developer G is appropriately supplied from the agent cartridge toward the inside of the developing unit 220 based on the information on the toner density (ratio of toner in the developer G) detected by the magnetic sensor installed in the developing unit 220. The mixing ratio (toner concentration) of the toner T with respect to the carrier C in the developer G of the agent cartridge is set to be relatively high.

  In the developing device 220 according to the second exemplary embodiment, three developer transport paths 227, 228, and 229 that transport the developer G and form a circulation path are formed. Conveying screws 232, 235, and 238 are disposed in the developer conveying paths 227, 228, and 229, respectively, each of which has a screw portion formed in a spiral shape on the shaft portion. The developer G accommodated in the apparatus 220 is conveyed along the shaft portion. The supply screw 232 is disposed inside the developer supply conveyance path 227 and conveys the developer G in the developer supply conveyance path 227 in the longitudinal direction. While being conveyed by the supply screw 232, the developer G in the developer supply conveyance path 227 is sequentially pumped onto the surface of the first developing roll 221A. The receiving screw 235 is installed inside the developer collection conveyance path 228. The receiving screw 235 is located below the supply screw 232 in the vertical direction. The developed developer G separated from the second developing roll 221B and collected in the developer collection conveyance path 228 is conveyed in the developer collection conveyance path 228 in the longitudinal direction. The supply screw 232 and the receiving screw 235 are disposed so that the shaft portions thereof are substantially parallel to the rotation shafts of the developing rolls 221A and 221B.

  The stirring screw 238 is installed inside the developer stirring conveyance path 229. The agitating screw 238 is connected to the supply screw 232 and the receiving screw 235 so as to linearly connect the downstream portion of the developer recovery conveyance path 228 in the developer conveyance direction and the upstream portion of the developer supply conveyance path 227 in the developer conveyance direction. Are arranged diagonally. The agitation screw 238 conveys the developer G, which has been conveyed in the developer recovery conveyance path by the receiving screw 235, to the upstream side in the developer conveyance direction of the developer supply conveyance path 227. The agitating screw 238 is also transported to the downstream end in the developer transport direction of the developer supply transport path 227 by the supply screw 232, and the developer G that has passed through the dropping path is also upstream of the developer supply transport path 227 in the developer transport direction. Transport to the side.

Next, an image forming process performed on the photoreceptor 3 in the second embodiment will be described.
When the photosensitive member 3 is driven to rotate counterclockwise, the surface of the photosensitive member 3 is first uniformly charged at the position of the uniform charging device 4. Thereafter, the surface portion of the charged photoreceptor 3 is exposed by the optical writing unit 10 to form an electrostatic latent image. Thereafter, the surface portion of the photoreceptor 3 on which the electrostatic latent image is formed reaches a position facing the developing unit 220. The electrostatic latent image on the photoreceptor 3 is sequentially brought into contact with the magnetic brushes on the two developing rolls 221A and 221B, and the toner T in the magnetic brush is attached and visualized.

Specifically, the developer G pumped up on the first developing roll 221 </ b> A disposed at the upper side in the drawing is adjusted to an appropriate amount by a doctor blade 222 as a developer regulating member, and then is opposed to the photoreceptor 3. It is conveyed to a certain first development area. In the first developing region, the developer G on the first developing roll 221A is raised by the magnetic force of the developing magnetic pole in the first developing roll, and the surface of the photoreceptor 3 is rubbed with the magnetic brush formed thereby. . At this time, the toner T in the developer G is applied to the image on the photoreceptor 3 by the action of a developing electric field formed by a predetermined developing bias applied to the first developing roll 221A from a power supply unit (not shown). A toner image is formed by selectively adhering only to the portion. The developer G on the first development roll 221A that has passed through the first development area reaches the developer delivery area that faces the delivery magnetic pole disposed inside the second development roll 221B as the first development roll 221A rotates. Be transported. In this developer delivery region, a part or all of the developer G on the first development roll 221A is moved to the surface of the second development roll 221B by receiving the magnetic force (delivery magnetic force) of the delivery magnetic pole, 2 Supported on the surface of the developing roll 221B. In this way, the developer G carried on the second developing roll 221 </ b> B is transported to the second developing region facing the surface of the photoreceptor 3. Even in the second development area, the developer G on the second development roll 221B rises due to the magnetic force of the development magnetic pole in the second development roll, and the surface of the photoreceptor 3 is rubbed with the magnetic brush formed thereby. . At this time, the toner T in the developer G is applied to the image on the photoreceptor 3 by the action of a developing electric field formed by a predetermined developing bias applied to the second developing roll 221B from a power supply unit (not shown). A toner image is formed by selectively adhering only to the portion. Thereafter, the developer G on the second developing roller 221B that has passed through the second developing region is separated from the surface of the second developing roller 221B and returned to the developing unit 220.
The surface portion of the photoreceptor 3 on which the toner image is formed by the development processing in the first development area and the second development area undergoes an image forming process similar to that in the first embodiment.

Also in the developing unit 220 in the second embodiment, the shielding wall 244 is formed by the same metal stay 46 as in the first embodiment. Therefore, the deflection amount of the shielding wall 244 can be made smaller than the deflection amount when the shielding wall 244 is formed of the same resin molded product as the developing case. As a result, this bending makes it difficult for the shielding wall gap between the shielding wall 244 and the surface of the first developing roll 221A to narrow, and the toner in the developer aggregates or adheres to the surface of the first developing roll 221A. Thus, the occurrence of a situation that prevents proper development processing can be suppressed.
Needless to say, the above modification may be applied to the configuration of the second embodiment.

As described above, the printer according to the first embodiment (including modifications, the same applies hereinafter) and the second embodiment includes the photosensitive member 3 as a latent image carrier and a latent image forming an electrostatic latent image on the photosensitive member 3. The developing unit includes a uniform charging device 4 and an optical writing unit 10 as image forming means, and developing units 20 and 220 for developing the electrostatic latent image on the photoreceptor 3 with a developer containing toner and a carrier. 20 is an image forming apparatus that forms an image on the recording paper P by finally transferring the toner image formed on the photosensitive member 3 to the recording paper P as a recording material. The developing units 20 and 220 include a developing sleeve 22 as a developer carrying member that conveys the developer to a developing region facing the surface of the photosensitive member 3 by carrying the developer on the surface and rotating. A developer case having an opening for exposing a part of the accommodated developing sleeve 22 to the outside and facing the surface of the photoreceptor 3, and a developer carried on the surface of the developing sleeve 22 pass through. A doctor blade 25 as a developer regulating member that forms a regulating gap for regulating the amount of the developer conveyed to the developing region between the developing sleeve 22 and the surface of the developing sleeve 22 in the developing case. The developer that is arranged adjacently and is supplied onto the surface of the developing sleeve 22 is conveyed along the developing sleeve rotation axis direction by a supply screw 32 as a developer supplying and conveying member. A developer supply / conveyance path 27, and the developer in the developer supply / conveyance path 27 passes through partition walls 43 and 243 which are side walls of the developer supply / conveyance path 27 on the development sleeve 22 side. Is a developing device to be supplied. This developing unit is provided as a supply passage between the partition walls 43 and 243 for passing the developer in the developer supply / conveyance path to the developing sleeve 22 side at least over the entire area of the developing sleeve rotation axis in the developing region. A slit 45 is formed, and a collecting passage is formed between the inner wall of the developing case and the regulated staying developer G3, which is prevented from passing through the regulating gap by the doctor blade 25, toward the developer supply conveyance path 27. It has shielding walls 44 and 244 as passage forming members. The partition walls 43 and 243 are made of the same material as that of the developing case and are integrally formed with the developing case. However, the shielding walls 44 and 244 are made of another material having higher rigidity than the partition walls 43 and 243. In addition, it is formed by a metal stay 46 that is supported only at both end regions in the developing sleeve rotation axis direction. Thereby, the bending amount of the shielding walls 44 and 244 can be made smaller than the bending amount when the shielding walls 44 and 244 are formed of the same resin molded product as the developing case. As a result, it is difficult for the shielding wall gap to be narrowed by this bending, and it is possible to prevent the toner in the developer from aggregating or adhering to the surface of the developing sleeve to prevent proper development processing.
In the first and second embodiments, since the material forming the shielding walls 44 and 244 is a metal, it becomes easy to realize the shielding walls 44 and 244 having high rigidity and low cost.
The developing units of Embodiments 1 and 2 use a two-component developer containing toner and a magnetic carrier as a developer, and are arranged inside the developing sleeve 22 so that the developer is carried on the surface of the developing sleeve 22. A material for forming the shielding walls 44 and 244 is a non-magnetic material having the magnet roller 23 as a magnetic field generating means for generating a magnetic force to be generated. If the shielding walls 44 and 244 are made of a magnetic material, the developer adheres to the shielding walls 44 and 244 at times, and the movement of the developer passing through the slit 45 is hindered. As a result, the pumping amount of the developer G1 from the developer supply / conveyance path 27 is insufficient, and the regulated staying developer G3 may contribute to the development or may pass through the attached developer and the slit 45. Rubbing with the developer occurs, causing toner separation from the developer and causing problems such as toner aggregation. By using a non-magnetic material as the material for forming the shielding walls 44 and 244, such a problem can be prevented.
In the first and second embodiments, the slit forming surface 48c that is the outer surface portion facing the slit 45 in the shielding walls 44 and 244 and the sleeve facing surface 48a that is the outer surface portion facing the surface of the developing sleeve 22 are either Is also a plane. As a result, the developer G1 supplied from the developer supply / conveying path 27 passes through the slit 45 and is pumped up to the surface of the developing sleeve while ensuring uniformity in the developing sleeve rotation axis direction, and then passes through the shielding wall gap. Even in this case, the uniformity in the developing sleeve rotation axis direction is maintained. The uniformity of the developer amount passing through the slit 45 or the shielding wall gap in the direction of the developing sleeve rotation axis is ensured in a plane compared to the case where the slit 45 or the shielding wall gap is formed by a curved surface or a sharp portion. The degree of uniformity in the assembly accuracy of the stay 46 is high, and the assembly accuracy management becomes easy.
In the first and second embodiments, the outer surface portion (upper surface) facing the recovery passage and the outer surface portion facing the developer supply transport path 27 in the shielding walls 44 and 244 are convex curved surfaces. By using a curved surface in this way, the entire curved surface becomes a processed surface, so that a work hardening region can be widened and high rigidity is easily obtained. In addition, since the degree of processing is reduced, there is no large bias in work hardening, and there is no difference in local hardening or deformation, so that it is easy to ensure the planar accuracy of the slit forming surface 48c and the sleeve facing surface 48a.
Further, in the metal stays 46 of the first and second embodiments, the central portion constituting the shielding walls 44 and 244 is cut along a virtual plane that is orthogonal to the developing sleeve rotation axis direction and passes through the developing region. The metal flat plate, which is a flat plate member, is bent so that the cross-sectional shape becomes a square shape, and the closing port 49 generated by the bending process is opposed to the surface of the developing sleeve 22, and It arrange | positions so that it may open in the direction orthogonal to the flow direction of the developer which flows through the location adjacent to the closing port 49. FIG. With such a configuration, the developer that moves adjacent to the shielding walls 44 and 244 is less likely to enter the shielding walls 44 and 244.
Further, the metal stays 46 of the first and second embodiments extend toward the partition walls 43 and 243 from the central portion constituting the shielding walls 44 and 244 on the outer side in the developing sleeve rotation axis direction of the developing region, and A tab portion 47 having a U-shaped cross section orthogonal to the developing sleeve rotation axis direction is provided. Then, in a state in which the partition walls 43 and 243 are inserted in the respective tab portions 47 so that the slit 45 is secured between the central portion constituting the shielding walls 44 and 244 and the partition walls 43 and 243, the metal A stay 46 is attached to the partition walls 43 and 243. Accordingly, the metal stay 46 can be attached with high positional accuracy to the partition walls 43 and 243 that are integrally molded with the developing case, so that the positional accuracy of the metal stay 46 with respect to the developing sleeve 22 and the supply screw 32 is also high. Can be easily obtained.
In the first and second embodiments, the shielding walls 44 and 244 may be formed of a seamless hollow member having a hollow portion extending along the developing sleeve rotation axis direction. With this configuration, the developer moving adjacent to the shielding walls 44 and 244 does not enter the shielding walls 44 and 244.
In the first and second embodiments, the partition walls 43 and 243 are in contact with the tab portions 47 in both end regions of the metal stay 46 from the developing sleeve rotation axis direction, and the metal stay 46 is in the developing sleeve rotation axis direction. A stepped portion 43a is provided as a locking member for locking the movement to the. Thereby, a slight external force is not applied to the metal stay 46, and the metal stay 46 does not move in the direction of the developing sleeve rotation axis.
Further, in the developing unit according to the modified example, on the inner surface side of the tab portion 47 of the metal stay 46, latches 47a as protruding portions protruding toward the partition walls 43 and 243 are provided so as to face each other. The interval between the latches 47a is formed to be smaller than the thickness of the partition walls 43 and 243, and the metal stay 46 uses an adhesive by sandwiching the partition walls 43 and 243 between the latches 47a. It is attached to the partition walls 43 and 243. Thereby, the malfunction by using an adhesive agent can be eliminated.
Further, in the above modification, the tab 47 is notched so that the latch 47a opens toward the upper surface of the metal stay 46 facing the recovery passage, and the notch is formed on the inner surface side of the tab 47. It is formed by bending it. Thereby, the fixing strength of the metal stay 46 to the partition walls 43 and 243 can be increased while facilitating the work of attaching the metal stay 46 to the partition walls 43 and 243.
In particular, as shown in FIG. 11, if a concave portion that engages with the latch 47 a is formed at a position where the latch 47 a contacts the partition walls 43 and 243, the fixing strength of the metal stay 46 to the partition walls 43 and 243 can be further increased. Can be strengthened.
As a method for fixing the metal stay 46 to the partition walls 43 and 243, for example, when the partition walls 43 and 243 are formed of a heat-deformable material (for example, synthetic resin material) that can be deformed by heat treatment, the latch 47a is used. A method of attaching the metal stay 46 to the partition wall 43 by deforming the part of the partition wall 43 with which the latch 47a abuts into the shape of a latch by performing a heat treatment after the partition walls 43 and 243 are sandwiched.

2 Process unit 3 Photoconductor 4 Uniform charging device 10 Optical writing unit 20, 120, 220 Development unit 21, 221A, 221B Development roll 22 Development sleeve 23 Magnet roller 25, 225 Doctor blade 27, 227 Developer supply conveyance path 28 , 228 Developer collection conveyance path 43, 143, 243 Partition wall 43a Edge 44, 244 Shielding wall 44a Edge 45 Slit 46 Metal stay 47 Tab part 47a Latch 49 Closing port 51 Intermediate transfer belt 229 Developer stirring conveyance path 238 Stirring screw

JP 2008-256813 A

Claims (15)

A developer carrying member that conveys the developer to a developing region facing the surface of the latent image carrying member by carrying and rotating the developer on the surface; and
A developing case having an opening for exposing a part of the developer carrying member housed inside to be exposed to the surface of the latent image carrying member;
A regulation gap is formed between the surface of the developer carrying body and the surface of the developer carrying body to regulate the amount of the developer conveyed to the development area by passing the developer carried on the surface of the developer carrying body. A developer regulating member that
In the developing case, the developer is disposed adjacent to the surface of the developer carrying member and supplied onto the surface of the developer carrying member along the direction of the rotation axis of the developer carrying member by a developer supply / conveying member. A developer supply conveyance path for conveying,
In the developing device that supplies the developer in the developer supply transport path to the developer support side beyond the side wall on the developer support transport side in the developer supply transport path,
A supply passage for allowing the developer in the developer supply / conveyance path to pass to the developer carrier side over at least the entire area of the developer carrying member in the rotation axis direction of the developer region between the side walls of the developer supply / conveyance path. And a passage that forms a recovery passage for recovering the developer, which is blocked from passing through the restriction gap by the developer restriction member, to the developer supply transport path side, between the inner wall of the development case Having a forming member,
The side wall of the developer supply conveyance path is formed of the same material as the developing case and integrally with the developing case,
The developing device according to claim 1, wherein the passage forming member is formed of a different material having higher rigidity than the side wall and is supported only at both end regions in the developer carrying member rotation axis direction. The developing device according to claim 1.
The developing device according to claim 1, wherein the another material forming the passage forming member is a metal. The developing device according to claim 1 or 2,
As the developer, a developer containing toner and magnetic carrier is used,
A magnetic field generating means for generating a magnetic force that is disposed inside the developer carrying member and carries the developer on the surface of the developer carrying member;
The developing device, wherein the another material forming the passage forming member is a non-magnetic material. The developing device according to any one of claims 1 to 3,
The developing device according to claim 1, wherein an outer surface portion of the passage forming member facing the supply passage and an outer surface portion facing the surface of the developer carrier are both flat. The developing device according to any one of claims 1 to 4,
The developing device according to claim 1, wherein an outer surface portion facing the recovery passage and an outer surface portion facing the developer supply / conveying path in the passage forming member are convex curved surfaces. The developing device according to any one of claims 1 to 5,
The developing device according to claim 1, wherein the passage forming member is a seamless hollow member having a hollow portion extending along a rotation direction of the developer carrying member. The developing device according to any one of claims 1 to 4,
The passage forming member is formed by bending a flat plate member so that the cross-sectional shape is a square shape when cut along a virtual plane passing through the development region and orthogonal to the developer carrier rotation axis direction. The closing port generated by the bending process is opposed to the supply passage or the surface of the developer carrying member, and is orthogonal to the flow direction of the developer flowing through the portion adjacent to the closing port. The developing device is arranged so as to open in a direction or a direction toward the downstream side in the flow direction. In the developing device according to any one of claims 1 to 7,
Both end portions of the passage forming member located on the outer side of the developing region in the developer carrying member rotation axis extend from the center portion toward the side wall of the developer supply conveyance path, and the developer carrying member rotation shaft. The cross section perpendicular to the direction is U-shaped,
In the state where the side wall of the developer supply transport path is inserted into each of the extended portions of the both end portions so that the supply passage is secured between the central portion and the side wall. A developing device attached to the side wall. The developing device according to claim 8.
On the side wall of the developer supply / conveyance path, the developer carrying member rotating shaft of the passage forming member comes into contact with the extending portions of the both end portions of the passage forming member from the developer carrying member rotating shaft direction. A developing device comprising a locking member for locking movement in a direction. The developing device according to claim 8 or 9,
Protruding portions that protrude toward the side walls of the developer supply transport path are provided on the inner surface side of the extended portions of the both end portions of the passage forming member,
The protrusion is formed such that a distance between a tip of the protrusion and a facing portion facing the protrusion is narrower than a thickness of the side wall of the developer supply conveyance path.
The developing device characterized in that the passage forming member is attached to the side wall without using an adhesive by sandwiching the side wall of the developer supply / conveyance path between the projecting portion and the opposed portion. . The developing device according to claim 10.
The projecting portion has a notch formed in an extending portion of the both end portions of the passage forming member so as to open toward an outer surface portion of the passage forming member facing the recovery passage, and the notched portion is A developing device characterized in that the developing device is formed by bending toward the inner surface side of the extended portion. The developing device according to claim 10 or 11,
The developing device according to claim 1, wherein a concave portion that engages with the protruding portion is formed on the side wall of the developer supply / conveyance path at a position where the protruding portion contacts. The developing device according to any one of claims 10 to 12,
The same material as the developing case forming the side wall of the developer supply transport path is a heat deformable material that can be deformed by heat treatment,
The passage forming member is subjected to heat treatment after sandwiching the side wall of the developer supply / conveyance path between the projecting portion formed at the extending portion of the both end portions of the passage forming member and the opposed portion. The developing device is attached to the side wall by deforming the portion of the side wall with which the protruding portion abuts into the shape of the projection. The developing device according to any one of claims 1 to 13,
As the developer, a developer containing toner and magnetic carrier is used,
A magnetic field generating means for generating a magnetic force that is disposed inside the developer carrying member and carries the developer on the surface of the developer carrying member;
The magnetic field generating means includes at least a pumping magnetic pole for generating a pumping magnetic force for drawing the developer passing through the supply passage toward the developer carrying member and pumping it to the surface of the developer carrying member, and the regulation gap. And a regulation magnetic pole that generates a regulation magnetic force for causing the developer to pass through,
The pumping magnetic pole and the regulating magnetic pole are adjacent to each other in the developer carrier surface movement direction and have opposite polarities.
The passage forming member is located at a position where the developer blocked by the developer regulating member is prevented from moving toward the surface of the developer carrying member along a magnetic force line of the regulating magnetic force. A developing device which is arranged. A latent image carrier, latent image forming means for forming a latent image on the latent image carrier, and a developing device for developing the latent image on the latent image carrier with a developer containing toner and a carrier. In the image forming apparatus for finally transferring the toner image formed on the latent image carrier by the developing device to a recording material and forming an image on the recording material,
An image forming apparatus using the developing device according to claim 1 as the developing device.

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