JP2013076980A - Developing device, and image forming apparatus using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress developer from separating off from a developer carrier between a scattering suppressing member arranged in a scattering suppression target area and the outer peripheral surface of the developer carrier, and thereby suppressing scattering of developer.SOLUTION: A magnet roller 82 arranged inside a developing sleeve 81 rotates along a rotation direction of the developing sleeve, and a scattering suppressing member 85 is provided in a scattering suppression target area that is adjacent to the downstream side in the rotation direction of the developing sleeve in a developing area. The scattering suppressing member has a developing sleeve opposing surface 85a that is opposite to the outer peripheral surface of the developing sleeve and curves along the curved surface of the outer peripheral surface of the developing sleeve.

Description

  The present invention relates to a developing device that develops a latent image on a latent image carrier with a two-component developer containing toner and a magnetic carrier, and an image forming apparatus such as a copying machine, a printer, and a facsimile machine using the developing device.

  In general, a developing device using a two-component developer (hereinafter simply referred to as “developer”) includes a developing case that contains the developer, an agitating and conveying member that agitates and conveys the developer in the developing case, It is composed of a developer carrying member that carries and carries the developer. The developer carrier is generally composed of a rotatable developing sleeve, and a magnetic field generating means is disposed inside the developing sleeve. In the developing case, the developer circulates while being agitated and conveyed by the agitating / conveying member, and a part of the developer is supplied onto the developing sleeve, and a magnetic field generated by the magnetic field generating means inside the developing sleeve is applied to the developing sleeve. It is carried on the outer peripheral surface. The developer carried on the outer peripheral surface of the developing sleeve is conveyed in the developing sleeve rotating direction as the developing sleeve rotates, and passes through a region (developing region) facing the latent image carrier. When the developer on the outer peripheral surface of the developing sleeve passes through the developing region, the developing process is performed by attaching toner to the electrostatic latent image on the latent image carrier, and then collected again in the developing case.

  The developer carried on the outer peripheral surface of the developing sleeve forms a magnetic brush in a direction corresponding to the surrounding magnetic flux distribution. In the development area, the toner in the magnetic brush is turned into an electrostatic latent image on the latent image carrier by raising the magnetic brush in the direction normal to the outer peripheral surface of the development sleeve and rubbing the surface of the latent image carrier. Adhere.

  In a magnet fixing method that is generally used well, the magnetic field generating means is fixedly arranged inside the developing sleeve. This magnetic field generating means has a magnetic pole in the vicinity of the developing area, and this allows the magnetic brush to rise in the developing area and rub the latent image carrier. In such a magnet fixing system, the toner that can move to the electrostatic latent image on the latent image carrier in the development area is in contact with or close to the surface of the latent magnetic carrier surface of the raised magnetic brush (the tip portion of the magnetic brush). Only the toner adhering to (). Therefore, when the linear velocity on the outer peripheral surface of the developing sleeve is approximately the same as the linear velocity on the surface of the latent image carrier, the amount of developer facing until the electrostatic latent image on the latent image carrier passes through the development region. And the amount of toner adhering to the electrostatic latent image is insufficient.

  Therefore, in many cases, in the magnet fixing method, the developing sleeve outer peripheral surface linear velocity is set to be larger than the surface linear velocity of the latent image carrier. As a result, the amount of developer facing the electrostatic latent image on the latent image carrier increases until it passes through the development area, and the shortage of the amount of toner adhering to the electrostatic latent image can be solved. However, when the speed difference between the developer on the developing sleeve and the latent image carrier increases in the development region, the toner once adhered to the electrostatic latent image on the latent image carrier is transported later. The image quality deterioration such as blurring of the image becomes serious.

  On the other hand, there is also known a magnet rotation method in which the magnetic field generating means is rotated inside the developing sleeve and a plurality of magnetic poles in which the N pole and the S pole are alternately arranged along the developing sleeve rotating direction are moved in the developing sleeve rotating direction. (Patent Document 1). The developing method using the magnet rotation method is a developing method called MS development. By rotating the magnetic field generating means during image formation, the developer on the developing sleeve causes the developing sleeve to repeat the rising and falling of the magnetic brush. It is transported along with the rotation.

  In the magnet rotation method, each magnetic pole of the magnetic field generating means sequentially passes through a position facing the developing area, so that the developer repeats the rising and falling of the magnetic brush in the developing area. Even in the magnet rotation method, when the magnetic brush rises in the developing region, the toner at the tip of the magnetic brush adheres to the electrostatic latent image on the latent image carrier and is consumed. However, when the magnetic brush is tilted, the portion that consumes toner mixes with the portion that does not consume toner, and when the magnetic brush rises again, the tip of the magnetic brush is sufficiently replenished with toner. . As a result, even if the speed difference between the developer on the developing sleeve and the latent image carrier in the development area is reduced, the magnetic brush is raised while the electrostatic latent image on the latent image carrier passes through the development area. By repeating the tilting, a sufficient amount of toner can be attached to the electrostatic latent image. Therefore, it is possible to solve the problem of image quality degradation such as image blurring caused by a large speed difference between the developer on the developing sleeve and the latent image carrier in the developing region.

However, the magnet rotation method has the following disadvantages compared to the magnet fixing method.
When toner or carrier (hereinafter, collectively referred to as “developer” in some cases) detaches from the developing sleeve in a region adjacent to the downstream side of the developing sleeve in the developing sleeve rotation direction, the developer is scattered outside the developing device. Developer scattering occurs, causing problems such as carrier adhesion. The carrier adhesion is a phenomenon in which the carrier detached from the developing sleeve adheres to the surface of the latent image carrier. When the carrier adheres to the surface of the latent image carrier, the carrier generally has a larger particle size than the toner. Therefore, if the carrier adheres to the toner image on the latent image carrier, the toner image on the latent image carrier is intermediate. When transferring onto a transfer body or a recording material, the toner around the carrier is not transferred, causing a problem that white spots of the image occur.

  Such developer scattering that causes problems such as carrier adhesion tends to become worse as the image forming apparatus increases in speed. This is because, in order to increase the speed of the image forming apparatus, it is necessary to increase the number of rotations of the developing sleeve. As a result, the centrifugal force applied to the developer carried and conveyed on the developing sleeve increases. This is because the developer is easily detached.

  In the developer scattering, the developer is separated from the developing sleeve to the extent that the magnetic restraint force that restrains the developer on the developing sleeve is not exerted by the magnetic field generated by the magnetic field generating means in the developing sleeve outside the developing device. Occurs. However, in the area adjacent to the upstream side in the developing sleeve rotation direction of the developing area in the outer peripheral surface portion of the developing sleeve exposed to the outside of the developing device, the scattering of the developer is not a problem.

This is because the toner in the developer on the developing sleeve in this area has not yet been subjected to the action of the developing electric field in the developing area, and the state where the toner adheres to the carrier is appropriately maintained. Difficult to detach from the sleeve. Further, even if the toner is detached in this area, it is electrostatically attracted and attached to the electrostatic latent image portion on the surface of the latent image carrier, and then to the development area as the latent image carrier rotates. It is sent. In the developing area, the developer forms a magnetic brush and rubs the surface of the latent image carrier, so that the toner separated from the developing sleeve and adhering to the surface of the latent image carrier by this rubbing In the developer. Therefore, in the area adjacent to the upstream side of the developing area in the rotation direction of the developing sleeve, a problem due to toner scattering hardly occurs.
Further, even if the carrier is separated from the developing region in the region adjacent to the upstream side of the developing sleeve rotation direction, there is no problem. This is because even if the carrier released in this region adheres to the surface of the latent image carrier, it is sent to the development region as the latent image carrier rotates. Therefore, since the magnetic brush is rubbed in the developing area and taken into the developer on the developing sleeve, problems such as carrier adhesion due to scattering of the carrier hardly occur.

On the other hand, when the developer scatters in a region adjacent to the downstream side in the developing sleeve rotation direction of the developing region, there is a problem.
That is, the toner present in this region is affected by the development electric field when passing through the development region, and the charge amount is reduced, and the electrostatic adhesion with the carrier is reduced. Easy to leave. In addition, since the toner has already adhered to the electrostatic latent image portion on the surface of the latent image carrier, the force that electrostatically attracts the toner that has separated from the developing sleeve to the electrostatic latent image portion is weak. For this reason, the toner released from the developing sleeve in this region is likely to be scattered outside the developing device without adhering to the surface of the latent image carrier. Further, when the carrier is detached from the developing sleeve in this region, if the carrier adheres to the surface of the latent image carrier, the carrier is no longer brought into the developing device by the magnetic field action by the magnetic field generating means in the developing sleeve. The image cannot be collected and is transferred to the surface of the latent image carrier. Therefore, when carrier scattering occurs in this region, problems such as white spots due to carrier adhesion are likely to occur. Hereinafter, a region adjacent to the downstream side of the developing region in the rotation direction of the developing sleeve is referred to as a scattering suppression target region.

  In the magnet rotation method, the magnetic brush rises at any location on the developing sleeve in the developing sleeve rotating direction. Therefore, the magnetic brush rises also in a region adjacent to the developing region in the downstream direction of the developing sleeve rotation, that is, the scattering suppression target region. When the magnetic brush rises, the developer on the outer peripheral surface of the developing sleeve moves in a direction away from the sleeve surface, so that the developer is easily detached from the developing sleeve due to the centrifugal force due to the rotation of the developing sleeve. In the case of the magnet fixing method, since the region (scattering suppression target region) adjacent to the downstream side in the developing sleeve rotation direction of the development region exists between the magnetic poles, the magnetic brush is always tilted in the scattering suppression target region. It becomes. On the other hand, in the magnet rotation method, the magnetic brush rises even in the scattering suppression target region as described above. Therefore, the toner and the carrier in the developer are more easily separated from the developing sleeve in the scattering suppression target region than in the magnet fixing method. . Therefore, the magnet rotation method has a disadvantage that developer scattering is more likely to occur than the magnet fixing method.

  In Patent Document 1, a recovery plate (scavenger plate) is opposed to a photoreceptor (photoconductor) in a region adjacent to the downstream side of the development sleeve rotation direction of the development zone (development zone) in order to suppress problems due to carrier adhesion. A developing device is disclosed. In this developing device, the recovery plate has an end extending toward the development region, and the carrier adhered to the photoconductor by the action of an electric field or a magnetic field formed between the recovery plate and the photoconductor. Can be recovered.

  According to the description of Patent Document 1, the collection plate collects carriers by the action of an electric field or a magnetic field that has adhered to the photoreceptor as described above. The collection plate is as follows. It is thought that it also functions as a proper scattering suppression member.

  That is, even in the region adjacent to the downstream side in the developing sleeve rotation direction of the developing region, that is, the scattering suppression target region, the region close to the outer peripheral surface of the developing sleeve, specifically, the region where the magnetic binding force by the magnetic field generating means is applied. In the case of (restraint region), the developer does not detach, or even if it detaches, the developer is immediately restrained on the developing sleeve, so that the developer is not scattered. On the other hand, in a region away from the outer peripheral surface of the developing sleeve, specifically, in a region where the magnetic restraining force by the magnetic field generating means is not exerted (non-constraining region), the developer is easily separated from the developing sleeve, and It becomes difficult to pull the detached developer back to the developing sleeve, and the developer is likely to be scattered.

  The collection plate is disposed in a part of such a non-restraining region, and limits the size (height) of the space in which the developer on the developing sleeve that has passed through the developing region is conveyed. As a result, the developer on the developing sleeve after passing through the developing region is returned to the developing device through a gap between the outer peripheral surface of the developing sleeve and the inner wall surface of the collecting plate (the wall surface facing the outer peripheral surface of the developing sleeve). . In the case where the recovery plate is provided, the non-restraining region becomes narrower than in the configuration in which the recovery plate does not exist, so that the developer scattering hardly occurs. That is, the collection plate has a function of suppressing the scattering of the developer.

  However, the developing device described in Patent Document 1 does not consider the function of suppressing the scattering of the developer by the recovery plate, and does not define the distance between the outer peripheral surface of the developing sleeve and the inner wall surface of the recovery plate. However, the distance between the outer peripheral surface of the developing sleeve and the inner wall surface of the recovery plate is an important parameter for obtaining the effect of suppressing the scattering of the developer. This is because if the distance between the outer peripheral surface of the developing sleeve and the inner wall surface of the collecting plate exceeds the range where the magnetic binding force by the magnetic field generating means reaches, the distance between the outer peripheral surface of the developing sleeve and the inner wall surface of the collecting plate An unconstrained region exists in the gap. As a result, the developer separated from the developing sleeve is generated in the gap, which floats on the airflow, blows out of the developing device from the gap at the end of the developing sleeve in the rotation axis direction, and the like, Causes scattering.

  The present invention has been made in view of the above background. The object of the present invention is to provide a developer between a scattering suppression member disposed in a scattering suppression target region and the outer peripheral surface of the developer carrier. It is an object of the present invention to provide a developing device that can prevent the developer from scattering by suppressing separation from the carrier, and an image forming apparatus using the developing device.

  In order to achieve the above-mentioned object, the present invention has a two-component developer containing a magnetic carrier and toner carried on an outer peripheral surface by the action of a magnetic field generated by a plurality of magnetic poles. Having a rotating cylindrical developer carrier, the toner in the two-component developer carried on the outer peripheral surface of the developer carrier is attached to the electrostatic latent image formed on the latent image carrier. Thus, in the developing device for developing the electrostatic latent image, the magnetic field generating means rotates the plurality of magnetic poles along the rotation direction of the developer carrier, and the developer carrier and the latent image A scattering suppression member is provided in a scattering suppression target region adjacent to the downstream side in the developer carrying member rotation direction of the developing region facing the carrier, and the scattering suppression member is opposed to the outer peripheral surface of the developer carrier. The developer carrying member facing surface And characterized in that curved along the curved surface of the outer peripheral surface of the body.

  When the developer carrying member facing surface of the scattering suppressing member is not curved along the curved surface of the outer peripheral surface of the developer carrying member (for example, when it is a flat surface), the closest contact between the scattering suppressing member and the outer peripheral surface of the developer carrying member. Even if the portion is brought close to the limit, the developer carrying member-facing surface of the scattering suppressing member may not be brought close to the developer carrying member outer peripheral surface to the extent that the magnetic restraining force reaches other portions. In the present invention, the developer carrying member facing surface of the scattering restraining member provided in the scattering restraining target region is curved along the curved surface of the outer peripheral surface of the developer carrying member. The distance from the outer peripheral surface of the developer carrying member can be reduced over the entire surface. Therefore, the entire area of the developer carrying member facing surface of the scattering suppressing member can be brought close to the outer circumferential surface of the developer carrying member to the extent that the magnetic restraint force by the magnetic field generating means inside the developer carrying member reaches. As a result, it is possible to suppress the generation of the developer that separates from the developer carrying member between the developer carrying member facing surface of the scattering suppressing member and the outer peripheral surface of the developer carrying member.

  As described above, according to the present invention, it is possible to prevent the developer from separating from the developer carrying member by suppressing the developer from separating between the scattering restraining member disposed in the scattering suppression target region and the outer peripheral surface of the developer carrying member. An excellent effect that it can be suppressed is obtained.

1 is an explanatory diagram illustrating a schematic configuration of a copier according to an embodiment. FIG. 4 is an explanatory view showing a developing device and a photosensitive drum respectively provided in four process cartridges. FIG. 6 is a perspective cross-sectional view of the developing device for explaining the flow of the developer in the developer transport path. FIG. 2 is an external perspective view of the developing device for explaining a position for supplying toner. It is explanatory drawing to which the periphery of the developing roller of the developing device was enlarged. It is a graph which shows the magnetic flux density on a carrier recovery sleeve when a block magnet is a rare earth bonded magnet. It is a graph which shows the magnetic flux density on a carrier recovery sleeve when a block magnet is a rare earth sintered magnet. It is a graph which shows the experimental result about the relationship between the magnetic flux density on a photoconductor drum, and a carrier recovery rate. FIG. 6 is a perspective view when the vicinity of a developing region is viewed from the photosensitive drum side. It is a graph which shows the result of the confirmation test of the developer scattering suppression effect by having provided the scattering suppression member. It is a graph which shows the result of the confirmation test of the carrier adhesion inhibitory effect by having provided the scattering suppression member. FIG. 10 is an explanatory diagram in which a vicinity of a development area of a development device according to Modification 1 is enlarged. It is a graph which shows the result of the background stain | pollution | contamination evaluation in the effect confirmation test of the developing device. FIG. 10 is an explanatory diagram in which a vicinity of a development region of a development device according to Modification 2 is enlarged. It is a graph which shows the evaluation result of the amount of developer scattering in the effect check test of the developing device.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram illustrating an outline of a full-color copying machine (hereinafter referred to as “copying machine”) 500 according to the present embodiment. In the present embodiment, “parts” used as the amount of a substance all represent parts by weight.

  The copying machine 500 includes a printer unit 100, a paper feeding device 200 on which the printer unit 100 is mounted, a scanner 300 fixed on the printer unit 100, and the like. An automatic document feeder 400 is fixed on the scanner 300.

  The printer unit 100 is an image forming unit including four sets of process cartridges 18Y, 18M, 18C, and 18K for forming images of each color of yellow (Y), magenta (M), cyan (C), and black (K). 20 is provided. Y, M, C, and K added after the numbers of the respective symbols indicate yellow, magenta, cyan, and black members (the same applies hereinafter). In addition to the process cartridges 18Y, 18M, 18C, and 18K, an optical writing unit 21, an intermediate transfer unit 17, a secondary transfer device 22, a resist roller pair 49, a belt fixing type fixing device 25, and the like are disposed. . The optical writing unit 21 includes a light source (not shown), a polygon mirror, an f-θ lens, a reflection mirror, and the like, and irradiates the surface of the photosensitive drum 1 described later with laser light based on image data.

  The process cartridges 18Y, 18M, 18C, and 18K include a drum-shaped photosensitive drum 1, a charger, a developing device 4, a drum cleaning device, a static eliminator, and the like. The yellow process cartridge 18Y will be described below.

  The surface of the photosensitive drum 1Y is uniformly charged by a charger as charging means. The surface of the photosensitive drum 1Y subjected to the charging process is irradiated with laser light modulated and deflected by the optical writing unit 21. Thereby, the potential of the surface of the photosensitive drum 1Y of the irradiation part (exposure part) is attenuated. Due to the attenuation of the surface potential, an electrostatic latent image for Y is formed on the surface of the photosensitive drum 1Y. The formed electrostatic latent image for Y is developed by the developing device 4Y as developing means to become a Y toner image.

  The Y toner image formed on the Y photosensitive drum 1Y is primarily transferred to an intermediate transfer belt 110 described later. The surface of the photosensitive drum 1Y after the primary transfer is cleaned of residual transfer toner by a drum cleaning device. In the Y process cartridge 18Y, the photosensitive drum 1Y cleaned by the drum cleaning device is discharged by the charge eliminator. Then, it is uniformly charged by the charger and returns to the initial state. The series of processes as described above is the same for the other process cartridges 18M, 18C, and 18K.

Next, the intermediate transfer unit 17 will be described.
The intermediate transfer unit 17 includes an intermediate transfer belt 110, a belt cleaning device 70, and the like. Further, it also includes a tension roller 14, a driving roller 15, a secondary transfer backup roller 16, four primary transfer bias rollers 62Y, 62M, 62C, and 62K. The intermediate transfer belt 110 is tensioned by a plurality of rollers including the tension roller 14. Then, it is endlessly moved clockwise in the drawing by the rotation of the driving roller 15 driven by a belt driving motor (not shown).

  The four primary transfer bias rollers 62Y, 62M, 62C, and 62K are arranged so as to be in contact with the inner peripheral surface side of the intermediate transfer belt 110, respectively, and receive a primary transfer bias from a power source (not shown). Further, the intermediate transfer belt 110 is pressed toward the photosensitive drums 1Y, 1M, 1C, and 1K from the inner peripheral surface side to form primary transfer nips. In each primary transfer nip, a primary transfer electric field is formed between the photosensitive drum 1 and each primary transfer bias roller 62Y, 62M, 62C, 62K due to the influence of the primary transfer bias.

  The above-described Y toner image formed on the Y photosensitive drum 1Y is primarily transferred onto the intermediate transfer belt 110 due to the influence of the primary transfer electric field and nip pressure. On the Y toner image, the M, C, and K toner images formed on the M, C, and K photoconductive drums 1M, 1C, and 1K are sequentially superimposed and primarily transferred. By this primary transfer of superposition, a four-color superposed toner image (hereinafter referred to as “four-color toner image”) as a multiple toner image is formed on the intermediate transfer belt 110.

  The four-color toner image superimposed and transferred onto the intermediate transfer belt 110 is secondarily transferred to a transfer sheet (not shown) as a recording material at a secondary transfer nip described later. Transfer residual toner remaining on the surface of the intermediate transfer belt 110 after passing through the secondary transfer nip is cleaned by a belt cleaning device 70 that sandwiches the belt with the driving roller 15 on the left side in the drawing.

Next, the secondary transfer device 22 will be described.
Below the intermediate transfer unit 17 in the figure, a secondary transfer device 22 is disposed in which a paper conveying belt 24 is stretched by two stretching rollers 23. The paper transport belt 24 is moved endlessly in the counterclockwise direction in the figure as the at least one tension roller 23 is driven to rotate. One of the two stretching rollers 23 arranged on the right side in the drawing sandwiches the intermediate transfer belt 110 and the paper transport belt 24 between the secondary transfer backup roller 16 of the intermediate transfer unit 17. It is out. By this sandwiching, a secondary transfer nip is formed in which the intermediate transfer belt 110 of the intermediate transfer unit 17 and the paper transport belt 24 of the secondary transfer device 22 are in contact with each other. A secondary transfer bias having a polarity opposite to that of the toner is applied to the one stretching roller 23 by a power source (not shown).

  By applying this secondary transfer bias, the four-color toner image on the intermediate transfer belt 110 of the intermediate transfer unit 17 is electrostatically moved from the belt side toward the one stretching roller 23 side in the secondary transfer nip. A next transfer electric field is formed. The transfer paper fed into the secondary transfer nip so as to synchronize with the four-color toner image on the intermediate transfer belt 110 by a registration roller pair 49 to be described later has four colors affected by the secondary transfer electric field and nip pressure. The toner image is secondarily transferred. Instead of the secondary transfer method in which the secondary transfer bias is applied to one of the stretching rollers 23 as described above, a charger for charging the transfer paper in a non-contact manner may be provided.

  In the paper feeding device 200 provided at the lower part of the copying machine 500, a plurality of paper feeding cassettes 44 in which a plurality of transfer sheets can be stacked and accommodated in a bundle of sheets are arranged so as to overlap each other in the vertical direction. It is installed. Each paper feed cassette 44 presses the paper feed roller 42 against the uppermost transfer paper in the paper bundle. Then, by rotating the paper feed roller 42, the uppermost transfer paper is sent out toward the paper feed path 48.

  The paper feed path 48 that receives the transfer paper delivered from the paper feed cassette 44 has a plurality of conveying roller pairs 47 and a registration roller pair 49 provided near the end in the paper feed path 48. Then, the transfer paper is conveyed toward the registration roller pair 49. The transfer sheet conveyed toward the registration roller pair 49 is sandwiched between the rollers of the registration roller pair 49. On the other hand, in the intermediate transfer unit 17, the four-color toner image formed on the intermediate transfer belt 110 enters the secondary transfer nip as the belt moves endlessly. The registration roller pair 49 sends out the transfer paper sandwiched between the rollers at a timing at which the transfer paper can be brought into close contact with the four-color toner image at the secondary transfer nip.

  Thereby, in the secondary transfer nip, the four-color toner image on the intermediate transfer belt 110 is in close contact with the transfer paper. Then, it is secondarily transferred onto the transfer paper and becomes a full color image on the white transfer paper. The transfer paper on which the full-color image is formed in this manner exits the secondary transfer nip as the paper transport belt 24 moves endlessly, and then is sent from the paper transport belt 24 to the fixing device 25.

  The fixing device 25 includes a belt unit that moves the fixing belt 26 endlessly while being stretched by two rollers, and a pressure roller 27 that is pressed toward one roller of the belt unit. The fixing belt 26 and the pressure roller 27 are in contact with each other to form a fixing nip, and the transfer paper received from the paper transport belt 24 is sandwiched therebetween. Of the two rollers in the belt unit, the roller that is pressed from the pressure roller 27 has a heat source (not shown) inside, and heats the fixing belt 26 by the generated heat. The heated fixing belt 26 heats the transfer paper sandwiched in the fixing nip. The full color image is fixed on the transfer paper by the influence of the heating and the nip pressure.

  The transfer paper subjected to the fixing process in the fixing device 25 is stacked on the stack portion 57 provided outside the left side plate in the drawing of the printer housing, or forms a toner image on the other surface. Any one of the transport modes to be returned to the secondary transfer nip is selected.

  When a document is copied, for example, a bundle of sheet documents is set on the document table 30 of the automatic document feeder 400. However, for example, when the original is a single-sided original closed in a main form, the original is set on the contact glass 32. Prior to this setting, the automatic document feeder 400 is opened with respect to the copying machine main body, and the contact glass 32 of the scanner 300 is exposed. Thereafter, the single-bound original is pressed by the closed automatic document feeder 400.

  When a copy start switch (not shown) is pressed after the document is set in this way, the document reading operation by the scanner 300 starts. However, when a sheet document is set on the automatic document feeder 400, the automatic document feeder 400 automatically moves the sheet document to the contact glass 32 prior to the document reading operation. In the document reading operation, first, the first traveling body 33 and the second traveling body 34 both start traveling, and light is emitted from a light source provided in the first traveling body 33. Then, the reflected light from the document surface is reflected by a mirror provided in the second traveling body 34, passes through the imaging lens 35, and then enters the reading sensor 36. The reading sensor 36 constructs image information based on the incident light.

  In parallel with such document reading operation, each device in each of the process cartridges 18Y, 18M, 18C, and 18K, the intermediate transfer unit 17, the secondary transfer device 22, and the fixing device 25 start driving. Based on the image information constructed by the reading sensor 36, the optical writing unit 21 is driven and controlled so that Y, M, C, and K toner images are formed on the photosensitive drums 1Y, 1M, 1C, and 1K. It is formed. These toner images become four-color toner images superimposed and transferred on the intermediate transfer belt 110.

  Further, almost simultaneously with the start of the document reading operation, the paper feeding operation is started in the paper feeding device 200. In this paper feeding operation, one of the paper feeding rollers 42 is selectively rotated, and the transfer paper is sent out from one of the paper feeding cassettes 44 accommodated in the paper bank 43 in multiple stages. The fed transfer paper is separated one by one by the separation roller 45 and enters the paper feed path 48, and is then transported toward the secondary transfer nip by the transport roller pair 47. In some cases, paper feeding from the manual feed tray 51 is performed instead of such paper feeding from the paper feeding cassette 44. In this case, after the manual feed roller 50 is selectively rotated to feed the transfer paper on the manual feed tray 51, the separation roller 52 separates the transfer paper one by one and feeds it to the manual feed path 53 of the printer unit 100. Make paper.

  When the copier 500 forms a multicolor image composed of toners of two or more colors, the intermediate transfer belt 110 is stretched so that the upper stretched surface thereof is substantially horizontal, and all the upper stretched surface is placed on the upper stretched surface. The photosensitive drums 1Y, 1M, 1C, and 1K are brought into contact with each other. On the other hand, when forming a monochrome image consisting of only K toner, the intermediate transfer belt 110 is tilted to the lower left in the drawing by a mechanism (not shown) and the upper stretched surface is set to Y, M, C. The photosensitive drums 1Y, 1M, and 1C are separated from each other. Of the four photosensitive drums 1Y, 1M, 1C, and 1K, only the K photosensitive drum 1K is rotated counterclockwise in the drawing to form only the K toner image. At this time, for Y, M, and C, the driving of not only the photosensitive drum but also the developing device is stopped to prevent unnecessary consumption of each member of the photosensitive drum and the developing device and the developer in the developing device. .

  The copier 500 includes a control unit (not shown) composed of a CPU and the like that controls each device in the copier 500, and an operation display unit (not shown) composed of a liquid crystal display, various key buttons, and the like. . The operator sends a command to the control unit by a key input operation on the operation display unit, so that one of the three modes is selected from the three-sided print mode, which is a mode for forming an image only on one side of the transfer paper. You can choose one. The three single-sided printing modes include a direct discharge mode, a reverse discharge mode, and a reverse decal discharge mode.

  FIG. 2 is a diagram for explaining the developing device 4 and the photosensitive drum 1 provided in each of the four process cartridges 18Y, 18M, 18C, and 18K. The four process cartridges 18Y, 18M, 18C, and 18K have substantially the same configuration except that the toner colors to be handled are different from each other. Therefore, the subscripts Y, M, C, and K are omitted in FIG. ing.

  As shown in FIG. 2, the surface of the photosensitive drum 1 is charged by a charging device (not shown) while rotating in the direction of arrow G in the drawing. The surface of the charged photosensitive drum 1 is irradiated with laser light from the optical writing unit 21 to form an electrostatic latent image, and toner is supplied from the developing device 4 to the electrostatic latent image. A toner image is formed. The developing device 4 has a developing roller 5 that supplies toner to the electrostatic latent image on the surface of the photosensitive drum 1 and develops it while conveying the developer in the direction of arrow I in the figure. The developing roller 5 includes a developing sleeve 81 as a rotatable developer carrying member, and includes a magnet roller 82 as a magnetism generating unit that is composed of a plurality of magnetic poles and can rotate in the direction of arrow A in the figure.

  A carrier recovery roller 13 as a carrier recovery member is provided on the downstream side of the developing area in the rotation direction of the photosensitive drum so as to be close to both the developing roller 5 and the photosensitive drum 1. Similarly to the developing roller 5, the carrier recovery roller 13 also includes a rotatable carrier recovery sleeve 90 and includes a carrier recovery magnet roller 91 as a magnetism generating unit including a plurality of fixed magnetic poles. The carrier attached to the photosensitive drum 1 is collected on the carrier collecting roller 13 by the magnetic force of the carrier collecting magnet roller 91, and returned to the developing device 4 by the rotation of the carrier collecting sleeve 90.

  Further, while supplying the developer to the developing roller 5, the back side of the paper surface of FIG. 2 along the axial direction of the developing roller 5 (hereinafter, sometimes referred to as the back side in the drawing or the back side in FIG. 2 for convenience). A supply screw 8 is provided as a supply / conveyance member that conveys the developer toward the substrate. Further, a doctor blade 12 as a developer regulating means for regulating the developer supplied to the developing roller 5 to a thickness suitable for development is provided on the downstream side in the developing sleeve rotation direction from the portion facing the supply screw 8. Yes.

  Further, on the downstream side in the developing sleeve rotation direction with respect to the developing area, the collection conveyance path 7 that collects the developed developer that has passed through the developing area and separated from the surface of the developing sleeve inside the developing device faces the developing roller 5. . The collection conveyance path 7 is a collection conveyance member that conveys the collected developer collected in the same direction as the supply screw 8 along the axial direction of the developing roller 5. I have. A supply conveyance path 9 including a supply screw 8 is provided above the developing roller 5, and a collection conveyance path 7 including a recovery screw 6 is provided below the development roller 5.

  The developing device 4 is provided with a stirring conveyance path 10 in parallel with the supply conveyance path 9 and the collection conveyance path 7. The agitation conveyance path 10 is inclined so as to be substantially the same height as the collection conveyance path 7 on the back side and the supply conveyance path 9 on the near side. The stirring conveyance path 10 is in the direction opposite to the supply screw 8 while stirring the developer along the axial direction of the developing roller 5 (referred to as the front side in the drawing for the sake of convenience). In some cases, as a stirring and conveying member that conveys toward the surface, a helical stirring screw 11 is provided that is inclined in the axial direction.

  The supply conveyance path 9 and the stirring conveyance path 10 are partitioned by a first partition wall 133 as a partition wall. The supply conveyance path 9 and the agitation conveyance path 10 of the first partition wall 133 have an opening on the front side in the figure, and the supply conveyance path 9 and the agitation conveyance path 10 communicate with each other. The supply conveyance path 9 and the collection conveyance path 7 are partitioned by a second partition wall 134. The supply conveyance path 9 and the collection conveyance path 7 of the second partition wall 134 have an opening on the back side in the drawing, and the supply conveyance path 9 and the collection conveyance path 7 communicate with each other. In addition, the two developer conveyance paths of the agitation conveyance path 10 and the collection conveyance path 7 are partitioned by a third partition wall 135 as a partition member. The third partition wall 135 has an opening on the back side in the figure, and the stirring conveyance path 10 and the collection conveyance path 7 communicate with each other.

  The supply screw 8, the recovery screw 6, and the stirring screw 11, which are developer conveying members, are made of resin or metal screws. Each screw diameter is φ26 [mm] for the supply screw 8 and the recovery screw 6 and φ30 [mm] for the stirring screw 11. The screw pitch is a double winding of 54 [mm] for the supply screw, a double winding of 36 [mm] for the recovery screw 6, and a double winding of 54 [mm] for the stirring screw 11. All the rotation speeds are set to about 600 [rpm]. The diameter of the developing roller 5 is φ40 [mm], and the gap between the doctor blade 12 and the photosensitive drum 1 is about 0.3 [mm].

  The developer carried on the developing roller 5 is thinned by a doctor blade 12 made of stainless steel, and then transported to the developing area for development. The developer after development is collected in the collection conveyance path 7, conveyed to the back side in FIG. 2, and developed to the agitation conveyance path 10 at the opening of the third partition wall 135 provided in the non-image area portion. The agent is transferred. As shown in FIG. 4, a toner replenishing port 19 to be described later is formed near the opening of the second partition wall 134 on the downstream side in the developer conveyance direction in the supply conveyance path 9 and above the supply conveyance path 9. Has been.

FIG. 3 is a perspective sectional view of the developing device 4 for explaining the flow of the developer in the developer transport path. Each arrow in the figure indicates the moving direction of the developer.
In the supply conveyance path 9 that receives the developer supplied from the agitation conveyance path 10, the developer is supplied in contact with the developing roller 5 while moving. The surplus developer that has not been supplied to the developing roller 5 and has moved to the downstream end in the transport direction of the supply transport path 9 is supplied to the recovery transport path 7 from the surplus opening of the second partition wall 134 (arrow E in FIG. 3). ).

  On the other hand, the developer supplied to the developing roller 5 is used for development in the developing region, and is then transported to the inside of the developing device again. Then, the developer is stripped from the developing roller 5 in the predetermined stripping region, and the collection transport path 7 Is passed on. The developer (recovered developer) delivered to the collection conveyance path 7 is conveyed to the downstream end in the conveyance direction of the collection conveyance path 7 by the collection screw 6, and is transferred to the stirring conveyance path 10 from the collection opening of the third partition wall 135. Supplied (arrow F in FIG. 3). In the agitation transport path 10, excess developer supplied from the supply transport path 9, recovered developer recovered in the recovery transport path 7, and toner replenished from a toner replenishment port 19 (see FIG. 4) described later. While being stirred, the developer is transported downstream in the developer transport direction by the stirring screw 11 and supplied to the supply transport path 9 from the supply opening of the first partition wall 133 (arrow D in FIG. 3).

  A toner concentration sensor (not shown) including a magnetic permeability sensor is provided at the bottom of the agitation transport path 10, and a toner supply control device (not shown) is operated by the sensor output to supply toner from a toner storage unit (not shown). ing.

  In the developing device 4 shown in FIG. 3, a supply conveyance path 9 and a collection conveyance path 7 are provided, and developer supply and collection are performed in different developer conveyance paths, so that developed developer is supplied to the supply conveyance path 9. There is no contamination. For this reason, the developer in the supply conveyance path 9 can be maintained at a constant toner concentration over the entire supply conveyance path. Further, since the recovery conveyance path 7 and the agitation conveyance path 10 are provided and the developer recovery and agitation are performed in different developer conveyance paths, the developed developer is not mixed in the middle of the agitation conveyance path. Thereby, since the developer with insufficient stirring is not supplied to the supply conveyance path 9, it is possible to suppress the developer supplied onto the developing roller 5 from being insufficiently stirred.

FIG. 4 is an external perspective view illustrating a position where toner is supplied.
As shown in FIG. 4, the toner replenishing port 19 for replenishing toner is provided above the downstream end portion in the developer conveyance direction of the supply conveyance path 9 including the supply screw 8. Since the toner replenishing port 19 is an upper portion of the excessive opening (arrow E in FIG. 3) of the second partition wall 134, the toner is easily mixed with the excessive developer and the collected developer. By replenishing at this position, the developer can be more efficiently stirred.

FIG. 5 is an enlarged view illustrating the periphery of the developing roller 5 of the developing device.
The developing roller 5 includes a cylindrical developing sleeve 81 that carries a developer and a magnet roller 82 that is included in the developing sleeve 81 and serves as a magnetic field generating unit that attracts the developer by magnetic force. The developing sleeve 81 can be selected from non-magnetic and conductive materials such as aluminum, austenitic stainless steel, and magnesium. However, in a high speed / high durability machine, austenitic stainless steel is suitable for preventing heat generation by electromagnetic induction and improving durability. The surface may be smooth, but in a high-speed machine, the following roughening treatment / processing may be performed to suppress developer slip.
(A) Groove extrusion processing such as V-groove or U-groove, machining of various concave shapes or laser processing or edging processing (B) Blasting processing (C) Thermal spraying processing of metal or ceramic

  The magnet roller 82 is rotatably provided in the direction of arrow A opposite to the developing sleeve rotation direction I, and has an even number of magnets 83 arranged at equal intervals (in the configuration of the present embodiment, 16 magnets are provided). ), And the polarity is configured to be opposite between adjacent magnets. In the present embodiment, the rotation direction of the magnet roller 82 and the developing sleeve 81 can be selected either in the same direction or in the opposite direction. As for the relationship between these rotational directions, the rotational speed of the magnet roller 82 and the developing sleeve 81 is also taken into consideration, and the number of passes between the developer carried on the outer peripheral surface of the developing sleeve 81 and each magnet 83 of the magnet roller 82 increases. It is set as appropriate on the condition. The increase in the number of times the developer passes the magnet 83 of the magnet roller 82 increases the number of repetitions of a phenomenon in which a spike is formed when the developer is opposed to the magnetic pole, and the spike is broken when the developer is separated from the magnetic pole. . This repetition increases the chance of frictional contact between the toner and the carrier, so that the charging characteristics of the toner can be improved.

  As the magnet 83 of the magnet roller 82, a conventional inexpensive ferrite magnet can be used. However, a stronger rare earth magnet such as a samarium cobalt magnet or a neodymium magnet can be used for downsizing and speeding up. The magnet 83 may be supported on the magnet holder 84 by adhesion, and the outer periphery thereof may be protected by a heat shrinkable tube or the like (not shown). If the magnet holder 84 is made of a magnetic material, the magnetic force of the magnet 83 can be slightly improved. However, the cost is high, and in general, a magnetic material containing iron as a main component has a high specific gravity, so that the moment of inertia increases during high-speed rotation, which may cause a problem in the durability of the drive unit. Therefore, although the magnetic force of the magnet 83 is slightly reduced, nonmagnetic and light specific gravity aluminum or magnesium may be used as a material.

  In FIG. 5, the rotation center P ′ of the magnet roller 82 in this embodiment is eccentrically positioned at a position away from the rotation center P of the developing sleeve 81 by a distance T. The direction of eccentricity is set in a direction toward the development area. Further, the amount of eccentricity is an amount that can be closest to the inner surface of the developing sleeve 81. The amount of eccentricity and the magnetic force of the magnet 83 are appropriately set so that the carrier can be prevented from moving to the photosensitive drum 1 in the developing region by the action of the magnetic field.

  On the other hand, the magnetic force is kept low on the outer peripheral surface of the developing sleeve 81 on the side opposite to the eccentric direction. Therefore, the developer carried on the outer peripheral surface of the developing sleeve 81 can be smoothly peeled inside the developing device. Therefore, the developer can be easily peeled off from the developing sleeve 81 only by adopting the eccentric structure as described above without using a mechanical external force from the outside.

Next, the movement of the developer in this embodiment will be described.
The developer supplied from the supply screw 8 to the flange portion 9 ′ is attracted onto the developing sleeve 81 by the magnetic force of the magnet roller 82, and is conveyed in the developing sleeve rotating direction as the developing sleeve 81 rotates. The developer on the developing sleeve is regulated to a certain amount when passing through the doctor blade 12. The developer that has passed through the doctor blade 12 is arranged along the lines of magnetic force generated by the magnet roller 82. In other words, the magnetic brush rises at a position facing each magnet 83 as shown by reference numeral B1 in FIG. 5, and the magnetic brush falls down at a position between the magnet 83 and magnet 83 as shown by reference numeral B2. Become.

  While the developer that has passed through the doctor blade 12 is conveyed to the developing region as the developing sleeve 81 rotates, the attracting force to the developing sleeve 81 gradually increases due to the eccentricity of the magnet roller 82. The higher the rotational speed of the magnet roller 82, the higher the development efficiency because the developer magnetic brush is repeatedly raised and tilted in the development region. As the developing sleeve 81 continues to rotate, the developer that has passed through the developing region is conveyed to the inside of the developing device while gradually decreasing the attractive force to the developing sleeve 81 due to the eccentricity of the magnet roller 82. Then, the developed developer on the developing sleeve is peeled off from the developing sleeve 81 and collected by its own weight into the collection conveyance path 7 (arrow K, arrow L).

  The carrier recovery magnet roller 91 of the carrier recovery roller 13 is formed by attaching a composite magnet 93 and a block magnet 94 to a shaft 92 made of a nonmagnetic material such as aluminum, austenitic stainless steel, magnesium, or various resin materials. The composite magnet 93 uses Sr ferrite or Ba ferrite as magnet powder, and PA (polyamide) material such as 6PA or 12PA as a polymer compound, EEA (ethylene / ethyl copolymer) or EVA (ethylene / vinyl copolymer). An ethylene compound such as coalescence), a chlorine material such as CPE (chlorinated polyethylene), and a rubber material such as NBR can be used. The carrier recovery magnet roller 91 has a cross-sectional shape orthogonal to the axial direction formed in a half-moon shape, and has three magnetic poles by magnetization. The notch where the composite magnet 93 does not exist is arranged on the developing roller 5 side, and does not have a magnetic pole on the side facing the developing roller 5.

  The block magnet 94 requires a higher magnetic force with a smaller volume than the composite magnet 93 in order to recover the carrier attached to the photosensitive drum 1. Therefore, it is desirable to use a material of Br> 0.5 [T], and most of them are Ne-based (such as Ne—Fe—B) or Sm-based (Sm—Co, Sm—Fe—N) rare earth sintered magnets. Alternatively, a rare earth bonded magnet obtained by mixing these magnet powders with a polymer compound can be used. In addition, rare earth magnet powders include isotropic and anisotropic magnet powders. Anisotropic magnet powders can provide higher magnetic force, but depending on the desired magnetic properties, either type can be used. It doesn't matter. Then, the block magnet 94 having a width of 3 [mm] and a thickness of 3 [mm] is formed by, for example, sintering, extrusion molding / injection molding, or in-mold compression molding of magnetic powder and binder. create. The length is 346 [mm], which is about 10 [mm] longer than the magnet roller 82, so that the carrier can be reliably recovered to the end.

FIG. 6 is a graph showing the magnetic flux density on the carrier recovery sleeve 90 when the block magnet 94 is a rare earth bonded magnet. The circumferential position of this graph corresponds to the rotational position on the carrier recovery sleeve 90.
As shown in FIG. 6, with the magnetic pole P21 corresponding to the block magnet 94, a high magnetic flux density of 150 [mT] was obtained. The other magnetic poles were a magnetic pole P22 of 100 [mT], a magnetic pole P23 of 70 [mT], and a magnetic pole P24 of 40 [mT]. The magnetic flux density by the magnetic pole P21 corresponding to the block magnet 94 was 140 [mT] on the surface of the photosensitive drum 1 that was 0.5 [mm] away from the surface of the carrier recovery roller 13.

FIG. 7 is a graph showing the magnetic flux density on the carrier recovery sleeve 90 when the block magnet 94 is a rare earth sintered magnet. The circumferential position of this graph corresponds to the rotational position on the carrier recovery sleeve 90.
As shown in FIG. 7, in the magnetic pole P21 corresponding to the block magnet 94, an even higher magnetic flux density of 230 [mT] was obtained. As for the other magnetic poles, the magnetic pole P22 was 110 [mT], the magnetic pole P23 was 70 [mT], and the magnetic pole P24 was 40 [mT]. The magnetic flux density by the magnetic pole P21 corresponding to the block magnet 94 was 200 [mT] on the surface of the photosensitive drum 1 that was 0.5 [mm] away from the surface of the carrier recovery roller 13.

Here, an experiment conducted for selecting the magnetic flux density of the block magnet 94 will be described.
The number of carriers per unit area on the photosensitive drum 1 after the development process and before the transfer process was counted with and without the carrier recovery roller 13, and the ratio was defined as the carrier recovery rate. The gap between the carrier recovery roller 13 and the photosensitive drum 1 was 0.5 [mm], and the relationship between the magnetic flux density on the photosensitive drum 1 and the carrier recovery rate was investigated.

<Experimental conditions>
・ Carrier: 35 [μm] ferrite carrier for Ricoh Imagio MP C7500 ・ Toner: PxP polymerization toner for Ricoh Imagio MP C7500 ・ Toner concentration: 4 [wt%]
-Charge amount: -24 [μC / g]
・ Development potential: 114 [V]
・ Skin potential: 150 [V]
-Photoconductor drum linear speed: 600 [mm / s]
・ Developing sleeve linear velocity: 750 [mm / s]
・ Development gap: 0.4 [mm]

FIG. 8 is a graph showing the results of an experiment regarding the relationship between the magnetic flux density on the photosensitive drum 1 and the carrier recovery rate.
The higher the magnetic flux density on the photosensitive drum 1 is, the higher the carrier recovery rate tends to be. To make the carrier recovery rate 98% or more, which does not normally cause a problem, the magnetic flux density on the photosensitive drum 1 is 140 [mT]. It is necessary to be above. When the magnetic flux density on the photosensitive drum 1 is 200 [mT] or more, the carrier recovery rate is close to 100 [%].

  Setting the magnetic flux density on the photosensitive drum 1 to 140 [mT] can be achieved even if the block magnet 94 is made of a rare earth bonded magnet, but the magnetic flux density on the photosensitive drum 1 is set to 200 [mT]. For this purpose, the block magnet 94 must be made of an expensive rare earth sintered magnet. The material of the block magnet 94 is preferably selected from the cost and the problem level of carrier adhesion.

The carrier recovery sleeve 90 is made of a nonmagnetic and conductive material such as aluminum, austenitic stainless steel, or magnesium. In order to convey the carrier adsorbed on the carrier recovery sleeve 90 by the magnetic field action of the magnetic flux P21 having a high magnetic flux density as described above to the relatively low magnetic flux density magnetic pole P22 by the rotation of the carrier recovery sleeve 90, the carrier It is desirable to subject the surface of the collection sleeve 90 to the following roughening treatment / processing.
(A) Groove extrusion processing such as V-groove or U-groove, machining of various concave shapes or laser processing or edging processing (B) Blasting processing (C) Thermal spraying processing of metal or ceramic

About the said process (A), the depth of a groove | channel and a recessed part is about 0.05 [mm]-0.5 [mm], and can use well-known techniques, such as a shape and a number.
About the said process (B), the roughness is the range which can manufacture Rz7 [micrometer]-Rz50 [micrometer], and can prevent the slip of a carrier.
About the said process (C), the roughness is the range which can manufacture Rz40 [micrometer]-Rz90 [micrometer], and can prevent the slip of a carrier.

  In the present embodiment, the carrier recovery roller 13 rotates in the direction of the symbol J in FIG. 2 or FIG. That is, the carrier recovery roller 13 rotates in the same direction as the developing roller 5. The carrier adhering to the photosensitive drum 1 is conveyed to a region facing the carrier recovery roller 13 as the photosensitive drum 1 rotates as indicated by a broken line arrow in FIG. It is attracted and collected on the carrier collecting roller 13 by the magnetic field action of the magnetic pole P21 having the density. In this embodiment, since the surface of the carrier recovery sleeve 90 is roughened, the carrier on the carrier recovery roller 13 is transported as the carrier recovery roller 13 rotates without slipping. A part of the carrier on the carrier recovery roller 13 falls to the recovery conveyance path 7 by its own weight as indicated by a symbol M in FIG. 5 at a position where the region facing the inner wall of the lower casing 95 ends.

  However, the carrier remaining on the carrier recovery roller 13 without being peeled off at this point is further transported along with the rotation of the carrier recovery sleeve 90 and is transported to a portion facing the developing roller 5. At the opposing portion of the carrier recovery roller 13 and the developing roller 5, the developer on the developing roller 5 repeats the rising and falling of the magnetic brush, and the surface of the carrier recovery roller 13 is rubbed by this magnetic brush. In addition, there is no magnetic pole on the carrier recovery roller 13 side in the facing portion between the carrier recovery roller 13 and the developing roller 5. Therefore, the carrier on the carrier recovery roller 13 conveyed to the portion facing the developing roller 5 is taken in and recovered by the developer on the developing roller 5 as indicated by the symbol N in FIG. 5 (arrow N). .

  By setting the gap between the carrier recovery roller 13 and the photosensitive drum 1 as narrow as 0.5 [mm], for example, the magnetic flux density on the photosensitive drum 1 is 10 [mT] than the magnetic flux density on the carrier recovery sleeve 90. It is suppressed to about 30 [mT] attenuation. Thereby, the carrier adhering to the photosensitive drum 1 can be more reliably collected. In addition, since the carrier collection | recovery roller 13 of this embodiment is controlled to rotate intermittently at very low speed, the carrier adhering on the carrier collection | recovery roller 13 hardly scatters with a centrifugal force.

  If the gap between the carrier recovery roller 13 and the developing roller 5 is set to be as narrow as 2 mm, for example, the magnetic brush B3 on the developing roller 5 is brought into contact with the carrier recovery roller 13 as shown in FIG. Can do. Thereby, the carrier adhering on the carrier recovery roller 13 can be separated from the carrier recovery roller 13 by the magnetic brush B3 on the developing roller 5, and the carrier recovery from the carrier recovery roller 13 can be performed appropriately. Further, since the gap between the developing roller 5 and the carrier recovery roller 13 is blocked by the magnetic brush B3, the developer floating in the developing device is suppressed from flowing out of the developing device to the outside of the developing device.

  Further, by setting the gap between the inner wall of the lower casing 95 facing the carrier recovery roller 13 on the side opposite to the developing roller 5 and the carrier recovery roller 13 to be as narrow as 1.5 [mm], for example, the magnetic field action of the magnetic pole P24. The magnetic brush B <b> 4 that rises due to contact with the inner wall of the lower casing 95. Thereby, the carrier or developer attached on the inner wall of the lower casing 95 can be collected by the magnetic brush on the carrier collecting roller 13, and the accumulation of the carrier and developer on the inner wall of the lower casing 95 can be suppressed. Further, since the gap between the carrier recovery roller 13 and the inner wall of the lower casing is closed by the magnetic brush B4, the developer floating in the developing device is suppressed from flowing out of the developing device to the outside of the developing device.

Next, the scattering suppression member 85 which is a characteristic part of the present invention will be described in detail.
If the developer is inside the developing device, the developer hardly flows out of the developing device even if the developer floats without being subjected to the magnetic restraint force by the magnet roller 82 inside the developing sleeve 81. In particular, in the present embodiment, the gap between the developing roller 5 and the carrier recovery roller 13 is closed by the magnetic brush B3 as shown in FIG. 5, and the gap between the carrier recovery roller 13 and the inner wall of the lower casing 95 is blocked. Since the gaps are also blocked by the magnetic brush B4 as shown in FIG. 5, the developer does not flow out from these gaps.

  However, an area adjacent to the downstream side of the developing area in the rotation direction of the developing sleeve (an area to be scattered), specifically, the outer peripheral surface of the developing sleeve 81, the surface of the photosensitive drum 1, and the surface of the carrier recovery roller 13 When a developer that does not reach the magnetic restraint force by the magnet roller 82 inside the developing sleeve 81 is generated in the region surrounded by, the developer flows out of the developing device and causes the developer to scatter. Specifically, the developer that has escaped the magnetic restraining force in this scattering suppression target area flows to the end of the developing sleeve rotation axis in the airflow, and blows out of the developing device through the gap at the end. Causes the developer to scatter. In particular, in the case of the magnet rotation method in which the magnet roller 82 rotates as in the present embodiment, the magnetic brush rises in the scattering suppression target area by the developer on the developing sleeve 81. Thus, in addition to the centrifugal force generated by the rotation of the developing sleeve 81, the developer on the developing sleeve 81 is easily released from the magnetic restraint force within the scattering suppression target region due to the momentum generated by the rising of the magnetic brush.

FIG. 9 is a perspective view of the vicinity of the developing area as viewed from the photosensitive drum side.
In this embodiment, the scattering suppression member 85 is arrange | positioned in this scattering suppression object area | region. By thus filling the scattering suppression target area with the scattering suppression member 85, the area away from the outer peripheral surface of the developing sleeve 81, that is, the area where the magnetic restraint force by the magnet roller 82 does not reach (unrestrained area) can be reduced. it can. Thereby, it is possible to suppress the generation of the developer that escapes from the magnetic restraining force in the scattering suppression target area.

  In general, if the gap in the scattering suppression target area is wide, the surrounding airflow is not stable, and the flow rate of the airflow that leaks out of the developing device increases, which also causes the developer scattering to deteriorate. As in the present embodiment, by arranging the scattering suppression member 85 in the scattering suppression target area, the air gap in the scattering suppression target area is narrowed. As a result, the surrounding airflow is stabilized, and development by rotation of the developing sleeve 81 is performed. Inhalation airflow into the device is also likely to occur. This also functions to suppress the scattering of the developer.

  However, when the developing sleeve facing surface 85a of the scattering suppressing member 85 is not curved along the curved surface of the outer peripheral surface of the developing sleeve 81 (for example, when it is a flat surface), the closest contact between the scattering suppressing member 85 and the developing sleeve outer peripheral surface. Even if the portion is brought close to the limit, the developing sleeve facing surface of the scattering suppressing member 85 may not be brought close to the outer peripheral surface of the developing sleeve to the extent that the magnetic restraining force reaches the other portion.

  Therefore, in the scattering suppression member 85 of the present embodiment, the developing sleeve facing surface 85a is curved along the curved surface of the outer peripheral surface of the developing sleeve. As a result, the developing sleeve facing surface 85a can be brought close to the developing sleeve outer peripheral surface over the entire area of the developing sleeve facing surface 85a of the scattering suppressing member 85 to the extent that the magnetic restraint force by the magnet roller 82 inside the developing sleeve is reached. . Therefore, it is possible to suppress the generation of the developer that separates from the developing sleeve 81 between the developing sleeve facing surface 85a of the scattering suppressing member 85 and the developing sleeve outer peripheral surface.

  The scattering suppressing member 85 of the present embodiment includes a plate 86 and a stay 87. The plate 86 is fixedly supported on the surface of the stay 87 facing the photosensitive drum. The plate 86 is disposed so that the plate surface faces the photosensitive drum 1, and the plate edge portion on the development area side is disposed close to the development area. The closer the plate edge portion is to the development area, the higher the effect of preventing the developer scattering. In addition, the gap between the plate edge portion and the developing sleeve 81 is preferably optimized so that a suction air flow from the gap into the developing device is appropriately generated. Even if the developer is separated in the scattering suppression target area due to the suction air flow, the developer can be collected into the developing device, and the developer scattering can be suppressed. However, if the plate edge portion is too close to the development area, there is a risk of causing a problem in the development process or developer conveyance by the development sleeve 81, and therefore, the adjustment is made as long as such a problem does not occur. Specifically, when the plate edge portion of the plate 86 contacts the magnetic brush on the developing sleeve 81, the developer enters the gap between the scattering suppression member 85 and the photosensitive drum 1, and develops outside the developing device. Since the agent may overflow, adjustment is made so that such a problem does not occur.

  In the stay 87, the developing sleeve facing surface 85 a is curved along the curved surface of the outer peripheral surface of the developing sleeve 81. As the stay 87 comes closer to the outer peripheral surface of the developing sleeve 81, the non-restraining region is narrowed, so that the effect of suppressing the scattering of the developer increases. At this time, if the gap between the developing sleeve facing surface 85a of the stay 87 and the outer peripheral surface of the developing sleeve 81 is constant, the effect of stabilizing the surrounding airflow is higher. However, the shape is not necessarily constant, and the shape can be appropriately changed according to other requirements.

  Further, in the stay 87, the collection roller facing surface 85 b that faces the carrier collection roller 13 is curved along the curved surface of the surface of the carrier collection roller 13. The closer the stay 87 is to the surface of the carrier collection roller 13, the narrower the gap between the collection roller facing surface 85b of the stay 87 and the surface of the carrier collection roller 13, and the higher the effect of suppressing the developer scattering. At this time, if the gap between the collection roller facing surface 85b of the stay 87 and the surface of the carrier collection roller 13 is constant, the effect of stabilizing the surrounding airflow is higher. However, the shape is not necessarily constant, and the shape can be appropriately changed according to other requirements.

  In the present embodiment, the connecting side between the recovery roller facing surface 85b of the stay 87 and the photosensitive drum facing surface (the surface on which the plate 86 is fixed) of the stay 87 is a corner (not rounded). Thus, a stay 87 is configured. Since such a corner portion is provided in the stay 87, it becomes easy to obtain the processing accuracy of the stay 87 and the measurement accuracy of the dimension based on the corner portion. As a result, gaps when the scattering suppressing member 85 is assembled to the developing device, specifically, the gap between the outer peripheral surface of the developing sleeve 81 and the developing sleeve facing surface 85a of the scattering suppressing member 85, the surface of the carrier recovery roller 13, and the like. Accuracy such as a gap between the scattering suppressing member 85 and the recovery roller facing surface 85b is improved, which leads to stabilization of the suction airflow.

  Here, assuming that the plate 86 and the stay 87 are made of a single component, the scattering suppressing member 85, it is difficult to achieve a shape that can reduce the developer scattering by the scattering suppressing member 85 to the maximum due to restrictions in processing parts. Met. On the other hand, as shown in the present embodiment, the scattering suppression member 85 is composed of two components, the plate 86 and the stay 87, so that the shape of each part and the gap with the surroundings can be optimized according to each request. It becomes. However, this does not limit the number of parts constituting the scattering suppressing member 85 at all.

  As a specific example of this embodiment, the gap between the plate edge portion of the plate 86 and the outer peripheral surface of the developing sleeve 81 is 1 [mm], and the gap between the developing sleeve facing surface 85 a of the stay 87 and the outer peripheral surface of the developing sleeve 81 is set. Is 1.5 [mm], and the gap between the recovery roller facing surface 85b of the stay 87 and the surface of the carrier recovery roller 13 is 1.5 [mm]. The plate 86 is made of a sheet metal having a thickness of 0.2 [mm] so that the plate edge portion is as close as possible to the development region. However, these conditions are not necessarily limited, and may be optimized according to the configuration of the image forming apparatus and the developing apparatus to be used, operating conditions, and the like.

  In order to enhance the effect of reducing the developer scattering by the scattering suppressing member 85, it is better to bring the scattering suppressing member 85 closer to the developing sleeve 81 as described above. Further, as described above, by reducing the developer scattering, it is possible to prevent the scattered carrier from adhering to the surface of the photosensitive drum 1 and causing carrier adhesion. However, the carrier adhesion suppressing effect by the scattering suppressing member 85 is only for the carriers scattered after passing through the developing area, and the carrier adhesion generated in the developing area cannot be prevented. Therefore, in order to suppress the carrier adhesion generated in the development region by the scattering suppression member 85, it is considered to add a function of magnetically collecting the carrier adhered to the photosensitive drum 1 to the scattering suppression member 85. It is done.

  However, in the magnet rotation method in which the magnet roller 82 rotates as in the present embodiment, when the scattering suppression member 85 disposed in the vicinity of the developing sleeve 81 generates a strong magnetic field, the rotating magnet roller 82 and the magnetic field interference. To generate vibration. When the developing device vibrates, the developing gap between the developing sleeve 81 and the photosensitive drum 1 changes, and the strength of the developing electric field generated in the developing region changes. Since the amount of toner adhering to the electrostatic latent image on the photosensitive drum 1 varies depending on the intensity of the developing electric field, when vibration occurs, unevenness corresponding to the vibration cycle appears on the image. That is, if it is attempted to achieve both the reduction of developer scattering and the effect of carrier recovery with a single scattering suppression member, this causes a problem that image density unevenness corresponding to such a vibration cycle occurs.

  Therefore, in the present embodiment, the scattering suppression member 85 and the carrier recovery roller 13 are provided separately, and the scattering suppression member 85 is made non-magnetic, thereby achieving both the reduction of developer scattering and the effect of carrier recovery. Occurrence of image density unevenness corresponding to the vibration period is suppressed. In order to provide the carrier recovery roller 13 having high carrier recovery efficiency and high magnetic force, it is necessary to install the carrier recovery roller 13 away from the developing sleeve 81 so as not to cause vibration in the magnet roller 82 inside the developing sleeve. However, in this case, a large gap is generated between the developing sleeve 81 and the carrier recovery roller, that is, in the scattering suppression target area. Therefore, as it is, the non-restraining region where the magnetic field action of the magnet roller 82 does not reach is wide, and the developer that is detached from the developing sleeve 81 is likely to be generated. According to the present embodiment, the developer that separates from the developing sleeve 81 by reducing the non-restraining region where the magnetic field action of the magnet roller 82 does not reach by filling the gaps in such a wide scattering suppression target region with the scattering suppression member 85. Can be prevented, and developer scattering can be suppressed. Even if the carrier recovery roller 13 is installed away from the developing sleeve 81 as described above, the scattering of the developer is suppressed by the function of the scattering suppression member 85. Thus, the carrier recovery efficiency can be increased.

  Further, when the potential of the scattering suppression member 85 is in a float state, toner may adhere and accumulate. In order to prevent this, the toner of this embodiment in which the normal charging polarity is negative is set between the scattering suppressing member 85 and the developing sleeve 81 by setting the potential of the scattering suppressing member to be lower than the potential of the developing sleeve 81. It is preferable that an electric field to be moved toward the developing sleeve 81 is formed. Specifically, a voltage is applied by connecting a power source as a voltage applying means to the scattering suppressing member 85. For example, toner is accumulated on the scattering suppression member 85 by configuring the potential of the scattering suppression member 85 to be the same as that of the non-image portion (background portion) on the photosensitive drum during the image forming process. Can be suppressed. Thus, in order to adjust the potential of the scattering suppression member 85, the scattering suppression member 85 needs to be conductive.

  However, if the scattering suppression member 85 is made of metal in order to obtain conductivity, an eddy current is generated in the scattering suppression member 85 by an alternating magnetic field generated by the rotating magnet roller 82, and induction magnetic field generation or induction heating is generated. Detrimental effects may occur. When an induced magnetic field is generated, magnetic field interference occurs with the rotating magnet roller 82 to generate vibration, and the above-described image density unevenness occurs. Further, when the scattering suppressing member 85 generates heat due to induction heating, the surrounding temperature may rise, and the toner may be softened and fixed, or a lump of toner may fall on the image.

  In order to prevent such a problem, in this embodiment, nonmagnetic SUS is used as the material of the plate 86 and the stay 87 of the scattering suppressing member 85. With such a scattering suppression member 85, it is possible to suppress the accumulation of toner by applying a voltage to the scattering suppression member 85, and there is no problem in the operation of the image forming apparatus such as generation of an induction magnetic field or induction heating. It can be suppressed to the level.

FIG. 10 is a graph showing the results of a confirmation test of the developer scattering suppression effect obtained by providing the scattering suppression member 85.
In this test, only the developing device is removed from the image forming apparatus, the developing device is driven under predetermined conditions, the developer scattered from the developing sleeve 81 of the developing device is collected, and the amount of developer scattered per minute is collected. Was measured. As a result, when the scattering suppression member 85 is not provided, the developer scattering amount per minute is 3.5 [mg]. When the scattering suppression member 85 is provided, this is 1.0 [ mg], and the amount of developer scattering could be reduced to 1/3 or less.

FIG. 11 is a graph showing the results of the confirmation test of the carrier adhesion suppression effect by providing the scattering suppression member 85.
In this test, an image was output using the copying machine of the present embodiment, and the number of white spots appearing on the image was counted as the number of adhered carriers. As a result, by using the scattering suppression member 85, the number of carrier adhesion occurrences could be reduced to 1/3 or less. In this test, a dot pattern having the highest number of occurrences of carrier adhesion was used as an output image pattern. In addition, the horizontal axis of the graph shown in FIG. 11 is the non-image portion potential, and the larger the value is, the less the toner smears in the non-image portion. Usually, the region around 50 to 250 [V] is used. . Further, if the number of occurrences of carrier adhesion is usually less than about 150, the image quality is not problematic. However, these standards are for reference only.

The main conditions of the above test are as follows.
-Image formation speed: equivalent to 135 A4 plates / min.-Developing sleeve: SUS sleeve of φ40.-Surface linear velocity of developing sleeve: 630 [mm / s]
-Number of magnetic poles of magnet roller: 20 poles-Number of rotations of magnet roller: 1400 [rpm]
Developer: Ricoh Co., Ltd. RICOH Pro C901 developer

[Modification 1]
Next, a modified example of the developing device in the above-described embodiment (hereinafter, this modified example is referred to as “modified example 1”) will be described.
FIG. 12 is an explanatory diagram enlarging the vicinity of the developing region of the developing device in which the developer movement inhibiting member, which is a characteristic part of the first modification, is arranged.
In the embodiment described above, the closest portion between the developing sleeve 81 and the carrier recovery roller 13 is set narrow as described above, and suppresses the developer from flowing out of the developing device. On the other hand, an electric field is formed by the potential difference between the developing sleeve 81 and the carrier recovery roller 13, and an electrostatic force that attracts the carrier on the developing sleeve 81 toward the carrier recovery roller 13 may occur. The carrier on the developing sleeve 81 is restrained on the developing sleeve 81 by a magnetic field generated by the magnet roller 82 inside the developing sleeve. For example, a carrier having a relatively low magnetic susceptibility among the carriers on the developing sleeve 81 is a magnet. The magnetic restraint force by the roller 82 is small. Therefore, such a carrier may move from the developing sleeve 81 to the carrier recovery roller 13 due to the influence of the electrostatic force described above.

  In particular, in the first modification, a developer including a negatively charged toner and a positively charged carrier is used, and a negative voltage is applied to both the developing sleeve 81 and the carrier recovery roller 13. By applying a negative voltage to the carrier recovery roller 13, the carrier attached to the photosensitive drum 1 can be recovered by electrostatic force, and the carrier recovery capability is enhanced. At this time, the potential of the carrier recovery roller 13 is set to suppress the negatively charged toner from moving from the carrier recovery roller 13 to the photosensitive drum 1 or from the developing sleeve 81 to the carrier recovery roller 13. The electrostatic latent image potential (exposure portion potential) on the photosensitive drum 1 and the developing bias must be the same potential or lower. However, since the carrier carried on the developing sleeve 81 is positively charged, setting the potential of the carrier recovery roller 13 in this way generates an electric field in a direction that attracts the carrier toward the carrier recovery roller 13. End up. Therefore, a situation where the carrier moves from the developing sleeve 81 to the carrier collecting roller 13 is likely to occur.

  Further, when the carrier moving from the developing sleeve 81 to the carrier collecting roller 13 comes into contact with the toner scattered around, the electrostatic force generated between the positively charged carrier and the negatively charged toner. Thus, the toner is bound to the carrier. In this case, not only the carrier but also the toner is restrained by the carrier recovery roller 13.

  Normally, the toner or carrier (developer) moved from the developing sleeve 81 to the carrier recovery roller 13 is constrained by the carrier recovery roller 13, and the opposite portion between the carrier recovery roller 13 and the photosensitive drum 1 is moved. It passes through and is collected into the developing device. However, there is an upper limit on the amount of developer per unit time that can be conveyed by the carrier recovery roller 13. For this reason, when an amount of developer exceeding the upper limit is input from the photosensitive drum 1 and the developing sleeve 81, the closest to the photosensitive drum 1 where the strongest magnetic pole P21 is installed in the carrier recovery roller 13 is provided. In this portion, excess developer cannot follow the rotation of the carrier recovery roller 13 and stays there. When the staying developer exceeds a certain amount, the staying developer rises due to the magnetic force of the magnetic pole P 21, and the magnetic brush of the developer formed thereby comes into contact with the photosensitive drum 1. As a result, when this magnetic brush comes into contact with the image portion on the photosensitive drum 1, blurring of the image appears, and when the magnetic brush comes into contact with the background portion (non-image portion), a problem such as the occurrence of traces of stains occurs.

  Therefore, in the first modification, as shown in FIG. 12, the developer carried on the developing sleeve 81 is inhibited from moving to the carrier collecting roller 13 in a region where the carrier collecting roller 13 and the developing sleeve 81 are opposed to each other. A developer movement inhibiting member 88 is provided. The developer movement inhibiting member 88 is disposed so as to be present at the closest portion between the developing sleeve 81 and the carrier recovery roller 13, and the developer moving from the developing sleeve 81 to the carrier recovery roller 13 is carrier recovered. It functions to prevent direct contact with the roller 13. As a result, even if the positively charged carrier is attracted to the carrier recovery roller 13 side at the opposed portion (mainly the closest portion) between the developing sleeve 81 and the carrier recovery roller 13, the carrier is closest to the carrier. It moves to the carrier recovery roller 13 at the part and does not come into contact. Accordingly, the amount of developer input from the developing sleeve 81 to the carrier recovery roller 13 can be reduced, and various problems associated with the increase in the amount of developer input to the carrier recovery roller 13 as described above can be suppressed.

  Further, the developer movement inhibiting member 88 of the first modification is attached at one end to the scattering suppressing member 85, and the other end (free end) in the direction away from the scattering suppressing target region from the one end is the carrier. It arrange | positions so that the surface of the collection | recovery roller 13 may be contacted. Thus, the developer movement inhibiting member 88 can function as a seal member that prevents the developer in the developing device from flowing out of the developing device through the gap between the scattering suppressing member 85 and the carrier recovery roller 13. it can.

  Further, the developer movement-inhibiting member of Modification 1 is formed of a thin plate member. As a result, the gap between the developing sleeve 81 and the carrier recovery roller 13 can be kept narrow, and the gap between the developing roller 5 and the carrier recovery roller 13 is closed by the magnetic brush B3. Therefore, the effect of suppressing the developer in the developing device from flowing out of the developing device through the gap with the developing device 13 can be maintained.

  Further, the developer movement inhibiting member 88 of the first modification is arranged so that its free end extends to a position farther from the scattering suppression target region than the closest portion between the developing sleeve 81 and the carrier recovery roller 13. Yes. Thereby, it is possible to suppress the occurrence of a problem that the developer movement inhibiting member 88 is turned by friction between the rotating carrier recovery roller 13 and the developer movement inhibiting member 88.

  In addition, the developer movement inhibiting member 88 of the first modification example is disposed so as to extend outward in the developing sleeve rotation axis direction from the region over the developing sleeve rotating shaft direction in the region where the developing sleeve 81 carries the developer. ing. Thereby, the effect of the developer movement inhibiting member can be exhibited over the entire image forming area.

A specific configuration of the developer movement inhibiting member 88 in Modification 1 will be described.
In the first modification, a sheet-shaped member having a thickness of 0.2 [mm] manufactured by PET (Polyethylene terephthalate) is used as the developer movement inhibiting member 88, and its position end portion is connected to the developing sleeve 81 of the scattering suppressing member 85. It is installed by adhering to the opposed developing sleeve facing surface 85a. Further, the developer movement inhibiting member 88 has its free end (end on the downstream side in the developing sleeve rotation direction) extending about 1 [mm] from the contact portion with the carrier recovery roller 13 to the inside of the developing device. Are arranged as follows.

  However, the installation method, fixing method, shape, and the like of the developer movement inhibiting member 88 are not limited to the first modification. In the first modification, the location where the developer movement inhibiting member 88 is in contact with the carrier recovery roller 13 is set so as to coincide with the closest portion between the developing sleeve 81 and the carrier recovery roller 13. , Not necessarily coincident. In the first modification, PET is used as the material of the developer movement inhibiting member 88, but other materials may be used. In addition to PET, any known material used as a seal member of a developing device, such as polyurethane resin, is less likely to cause problems such as toner adhesion, and is suitable as a material for the developer movement inhibiting member 88.

Next, a test for confirming the effect of using the developer movement inhibiting member 88 of Modification 1 will be described.
In this test, output images were compared between the case where the developing device described in Modification 1 was set in the image forming apparatus body and the developer movement inhibiting member 88 was removed and attached. As a result, the image blur that occurred when the developer movement inhibiting member 88 was removed could be eliminated by attaching the developer movement inhibiting member 88.

  In addition, for the traces of the traces in the form of traces, the transition of the background stain density was compared with the potential of the non-image area as a parameter depending on the presence or absence of the developer movement inhibiting member 88. As a result, as shown in FIG. 13, by providing the developer movement inhibiting member 88, it was confirmed that the background density was lowered. In general, if the background density is 0.01 [-] or less, there is no problem in image quality. However, by providing the developer movement inhibiting member 88, the background is improved to a level lower than this standard. I was able to.

Other conditions when this test was conducted are as follows.
・ Carrier: 35 [μm] ferrite carrier manufactured by Ricoh Co., Ltd. ・ Toner: PxP polymerization toner for Ricoh ProC901 ・ Toner concentration: 8 [wt%]
Toner charge amount: -20 to -30 [μC / g]
Photoconductor linear velocity: 630 [mm / s]
・ Developing sleeve linear velocity: 540 [mm / s]
・ Development gap: 0.25 [mm]
Development bias: -200 to -400 [V]
Non-image part potential: -300 to -500 [V]
Carrier recovery roller potential: -500 to -800 [V]

[Modification 2]
Next, another modified example of the developing device in the above-described embodiment (hereinafter, this modified example is referred to as “modified example 2”) will be described.
FIG. 14 is an explanatory diagram enlarging the vicinity of the developing region of the developing device in which the seal member, which is a characteristic part of the second modification, is arranged.
As described above, the provision of the scattering suppression member 85 makes it difficult for the developer on the downstream side of the developing region to escape from the restraint of the developing roller. Further, since the gap between the scattering suppressing member 85 and the developing sleeve 81 is set narrow, as shown by the symbol O in the figure, a suction air flow toward the inside of the developing device is generated, and the developer on the outer peripheral portion of the developing sleeve 81 is generated. Is guided into the developing device.

  On the other hand, at the facing portion between the scattering suppressing member 85 and the carrier recovery roller 13, as described above, the magnetic restraint force by the carrier recovery roller 13 is as much as possible in order to suppress interference with the alternating magnetic field by the magnet roller 82 in the developing sleeve 81. It is set to be smaller. Therefore, the developer scattered on the facing portion flows out to the outside of the developing device through the gap between the scattering suppressing member 85 and the carrier recovery roller 13 as indicated by a symbol P in the figure without being restricted by the surrounding magnetic field. There are things to do.

  Therefore, in the second modification, as shown in FIG. 14, a seal member 89 that closes the gap between the carrier recovery roller 13 and the scattering suppression member 85 is provided. When the opening between the scattering suppressing member 85 and the carrier recovery roller 13 is blocked by the seal member 89, the developer released from the restraint of the developing sleeve 81 leaks to the outside through the opening while floating. Can be suppressed. If the leakage of the floating developer is suppressed, the developer is restrained again when approaching the developing sleeve 81 and the carrier recovery roller 13, so that development is performed by the conveying force of the developing sleeve 81 and the carrier recovery roller 13. It is collected inside the device.

A specific configuration of the seal member 89 in Modification 2 will be described.
In the second modification, one end of the seal member 89 is bonded to the plate 86 of the scattering suppression member 85. The other end of the seal member 89 is a free end and is not fixed, but is in contact with the carrier recovery roller 13. Thereby, the opening part between the carrier collection | recovery roller 13 and the scattering suppression member 85 is block | closed. The position where the free end and the carrier recovery roller 13 are in contact is set on the upstream side in the rotation direction of the carrier recovery roller 13 with respect to the closest portion between the carrier recovery roller 13 and the photosensitive drum 1. If the seal member 89 is interposed at the closest portion between the carrier recovery roller 13 and the photosensitive drum 1, it is hindered to recover the carrier on the photosensitive drum 1 to the carrier recovery roller 13. However, regarding the installation of the seal member 89, for example, one end of the seal member 89 may be fixed to the stay 87 instead of the plate 86, and the carrier recovery without disturbing the functions of the carrier recovery roller 13 and the scattering suppression member 85 is possible. What is necessary is just to become the structure which plugs up the clearance gap between the roller 13 and the scattering suppression member 85. FIG.

  Further, the seal member 89 of the second modification is formed of a thin plate member. Accordingly, since the seal member 89 does not occupy a narrow space in the vicinity of the developing region, it is possible to suppress the side effects on the function of the developing device.

  Further, by using a flexible material for the seal member 89 of the second modification, an elastic force in a direction in which the seal member 89 is pressed against the carrier collection roller 13 at the free end in contact with the carrier collection roller 13 is obtained. Can work. Thereby, the effect which plugs the said opening part over a long period can be maintained.

  Further, the seal member 89 according to the second modification example is disposed so as to extend outward in the developing sleeve rotation axis direction from the region over the developing sleeve rotation axis direction in the region where the developing sleeve 81 carries the developer. Thereby, the effect of the seal member 89 can be exhibited over the entire image forming area.

A specific configuration of the seal member 89 in Modification 2 will be described.
In the second modification, a sheet-like member having a thickness of 0.1 [mm] made of polyurethane-based resin is used as the seal member 89, and an area of about 2 [mm] from the lower end of the plate 86 of the scattering prevention member 85 is used. It is made to adhere to. Further, the free end of the seal member 89 is in contact with the surface of the carrier recovery roller 13. At this time, the carrier recovery roller 13 is installed with an amount of biting of about 1 [mm] by the elasticity of the seal member. The force of the direction pushed to the side works properly.

  However, the installation method, fixing method, shape, and the like of the seal member 89 are not limited to the second modification. In the second modification, polyurethane-based resin is used as the material of the seal member 89. However, other than this, any known material used as a seal member of the developing device such as PET can be used for fixing the toner. It is less likely to cause problems and is suitable as a material for the seal member 89.

Next, a test for confirming the effect of using the seal member 89 of the second modification will be described.
In this test, the amount of developer per unit time scattered outside the developing device is compared between when the developing device described in Modification 2 is set in the image forming apparatus main body and the seal member 89 is removed and attached. did. Note that the amount of developer scattered per unit time is small, and in order to suppress the influence of measurement errors, the developer scattered in one hour was collected and measured in this test.

  As shown in FIG. 15, it was confirmed that the amount of the developer scattered outside the developing device is reduced by attaching the seal member 89 as compared with the case where the seal member 89 is removed. From this result, it may seem that the amount of scattering per unit time and the improvement effect by the seal member 89 are negligible. However, since the purpose of this test was a relative comparison, the amount of developer scattering increased. There are also usage conditions. In view of the operational lifetimes of the image forming apparatus and the developing apparatus, this difference is a significant effect. Specifically, since the developer that should be scattered outside the developing device can be collected in the developing device, waste of the developer can be suppressed, so that cost performance is improved and environmental load is reduced. In addition, the developer scattered outside the developing device for each color is collected in a common dust collection tank in the image forming apparatus and is periodically discarded, but the frequency of dust collection tank replacement can be reduced. Become.

Other conditions when this test was conducted are as follows.
・ Carrier: 35 [μm] ferrite carrier manufactured by Ricoh Co., Ltd. ・ Toner: PxP polymerization toner for Ricoh ProC901 ・ Toner concentration: 8 [wt%]
Toner charge amount: -20 to -30 [μC / g]
Photoconductor linear velocity: 630 [mm / s]
・ Developing sleeve linear velocity: 540 [mm / s]
・ Development gap: 0.25 [mm]

In addition, the following developers can be used in the present embodiment (including the above-described modifications. The same applies hereinafter).
The toner used in this embodiment contains at least a binder resin and a colorant, and if necessary, a release agent, a charge control agent, and other components. In addition to the above-mentioned additives, a fluidity improver and other components are added as necessary. For these materials, all known materials are possible. Examples of the binder resin include styrene, parachlorostyrene, vinyl toluene, vinyl chloride, vinyl acetate, vinyl propionate, methyl (meth) acrylate, ethyl (meth) tacrylate, propyl (meth) acrylate, (meth ) N-butyl acrylate, isobutyl (meth) acrylate, dodecyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, (meth) Hydroxypropyl acrylate, 2-chloroethyl (meth) acrylate, (meth) acrylonitrile acid, (meth) acrylamide, (meth) acrylic acid, vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether. Examples include a weight body of monomers such as vinyl methyl ketone, N-vinyl pyrrolidone, N-vinyl pyridine and butadiene, a copolymer composed of two or more of these monomers, or a mixture thereof. In addition, polyester resin, polyol resin, polyurethane resin, polyamide resin, epoxy resin, rosin, modified rosin, terbene resin, phenol resin, hydrogenated petroleum resin, ionomer resin, silicone resin, ketone resin, xylene resin, etc. alone or in combination Can be used.

  As the colorant, all known dyes and pigments can be used. For example, carbon black, nigrosine dye, iron black, naphthol yellow S, Hansa yellow (10G, 5G, G), cadmium yellow, yellow iron oxide, ocher, Yellow lead, Titanium yellow, Polyazo yellow, Oil yellow, Hansa yellow (GR, A, RN, R), Pigment yellow L, Benzidine yellow (G, GR), Permanent yellow (NCG), Vulcan fast yellow (5G, R) ), Tartrazine Lake, Quinoline Yellow Lake, Anthrazan Yellow BGL, Isoindolinone Yellow, Bengala, Red Dan, Lead Zhu, Cadmium Red, Cadmium Mercury Red, Antimon Zhu, Permanent Red 4R, Para Red, Phi Se Red, Parachlor Ortonito Aniline Red, Resol Fast Scarlet G, Brilliant Fast Scarlet, Brilliant Carmin Min BS, Permanent Red (F2R, F4R, FRL, FRLL, F4RH), Fast Scarlet VD, Belkan Fast Rubin B, Brilliant Scarlet G, Resol Rubin GX, Permanent Red F5R, Brilliant Carmine 6B, Pigment Scarlet 3B, Bordeaux 5B, Tolujing Maroon, Permanent Bordeaux F2K, Helio Bordeaux BL, Bordeaux 10B, Bon Maroon Light, Bon Maroon Medium, Eosin Lake, Rhodamine Lake B, Rhodamine Lake Y, Alizarin Lake , Thioindigo red B, thioindigo maroon, oil red, quinacridone red, pyrazolone red, Riazo Red, Chrome Vermillion, Benzidine Orange, Perinone Orange, Oil Orange, Cobalt Blue, Cerulean Blue, Alkaline Blue Lake, Peacock Blue Lake, Victoria Blue Lake, Metal Free Phthalocyanine Blue, Phthalocyanine Blue, Fast Sky Blue, Indanthrene Blue (RS, BC), indigo, ultramarine blue, bitumen, anthraquinone blue, fast violet B, methyl violet lake, cobalt purple, manganese purple, dioxane violet, anthraquinone violet, chrome green, zinc green, chromium oxide, pyridian, emerald green, pigment Green B, Naphthol Green B, Green Gold, Acid Green Lake, Malachite Green Lake, Phthalo Cyanine green, anthraquinone green, titanium oxide, zinc white, litbon and mixtures thereof can be used. The amount used is generally 0.1 to 50 parts by weight per 100 parts by weight of the binder resin.

  Examples of the charge control agent include nigrosine dyes, triphenylmethane dyes, chromium-containing metal complex dyes, molybdate chelate pigments, rhodamine dyes, alkoxy amines, quaternary ammonium salts (including fluorine-modified quaternary ammonium salts). .), Alkylamide, phosphorus simple substance or compound, tungsten simple substance or compound, fluorine-based activator, salicylic acid metal salt, metal salt of salicylic acid derivative, and the like. The amount of charge control agent used is determined by the type of binder resin, the presence or absence of additives used as necessary, and the toner production method including the dispersion method, and is not uniquely limited. Preferably, it is used in the range of 0.1 to 10 parts by weight with respect to 100 parts by weight of the binder resin. The range of 2 to 5 parts by weight is preferable. If the amount is less than 0.1 parts by weight, the toner is not practically negatively charged. When the amount exceeds 10 parts by weight, the chargeability of the toner is too high, and the electrostatic attraction force with the carrier increases, leading to a decrease in developer fluidity and a decrease in image density.

  Examples of release agents include low molecular weight polyolefin waxes such as low molecular weight polyethylene and low molecular weight polypropylene, synthetic hydrocarbon waxes such as Fischer-Tropsch wax, beeswax, carnauba wax, candelilla wax, rice wax, and montan wax. Natural waxes such as paraffin wax, petroleum wax such as microcrystalline wax, higher fatty acids such as stearic acid, palmitic acid, myristic acid, metal salts of higher fatty acids, higher fatty acid amides, and various modified waxes thereof. Can be mentioned.

  These can be used alone or in combination of two or more, but it is preferable to use those having a melting point in the range of 70 [° C.] to 125 [° C.]. By setting the melting point to 70 [° C.] or more, a toner having excellent transferability and durability can be obtained, and by setting the melting point to 125 [° C.] or less, the toner melts quickly at the time of fixing and has a reliable release effect. Can demonstrate. The amount of these release agents used is preferably 1 [wt%] to 15 [wt%] based on the toner. If it is less than 1 [wt%], the effect of preventing offset is insufficient, and if it is 15 wt% or more, transferability and durability are lowered.

As the additive (external additive), at least fine particles having a volume average particle diameter of 50 [nm] to 500 [nm] and a bulk density of 0.3 [g / cm ³ ] or more are added. The amount of external addition is preferably 0.2% by weight to 3% by weight with respect to the toner base. If it is less than this range, the effect of forming an appropriate gap between the toners or between the toner and the others will not be exhibited. On the other hand, when the amount is large, fluidity is inhibited, or the amount of desorption increases, so that aggregates of external additives are formed, and image quality is deteriorated. In addition to the above-mentioned additives, additives outside this range can be added, and it is preferable to add fine particles having a small volume average particle diameter for the purpose of improving fluidity.

In the additive in the present embodiment, as the inorganic _{compound, SiO 2, TiO 2, Al} 2 O 3, MgO, CuO, ZnO, SnO 2, CeO 2, Fe 2 O 3, BaO, CaO, K 2 O, Examples include Na ₂ O, ZrO ₂ , CaO · SiO ₂ , K ₂ O (TiO ₂ ) n, Al ₂ O ₃ · 2SO ₂ , CaCO ₃ , MgCO ₃ , BaSO ₄ , MgSO ₄ , SrTiO _{3 and the} like. Of these, SiO ₂ , TiO ₂ , and Al ₂ O ₃ are preferable. In particular, these inorganic compounds may be hydrophobized with various coupling agents, hexamethyldisilazane, dimethyldichlorosilane, octyltrimethoxysilane, and the like. Further, the organic compound additive may be a thermoplastic resin or a thermosetting resin, for example, vinyl resin, polyurethane resin, epoxy resin, polyester resin, polyamide resin, polyimide resin, silicon resin, phenol resin, melamine resin. , Urea resin, aniline resin, ionomer resin, polycarbonate resin and the like. As the resin fine particles, two or more of the above resins may be used in combination. Of these, vinyl resins, polyurethane resins, epoxy resins, polyester resins, and combinations thereof are preferred because an aqueous dispersion of fine spherical resin particles is easily obtained.

  Specific examples of vinyl resins include polymers obtained by homopolymerization or copolymerization of vinyl monomers, such as styrene- (meth) acrylic acid ester copolymers, styrene-butadiene copolymers, (meth) acrylic acid. -Acrylic ester copolymer, styrene-acrylonitrile copolymer, styrene-maleic anhydride copolymer, styrene- (meth) acrylic acid copolymer, and the like.

  The additive (fine particles) in this embodiment is excellent as a toner for the developer in the developing device 4. That is, the contact area between the toner particles, the photosensitive drum 1 and the charge imparting member is very small and evenly contacted, so that the effect of reducing the adhesion is great and effective in improving the development / transfer efficiency. Further, since it plays the role of a roller, toner particles can be removed even when the cleaning blade and the photosensitive drum 1 are cleaned under high stress (high load, high speed, etc.) without wearing or damaging the photosensitive drum 1. Therefore, it is difficult to embed in a metal or can be detached and restored even if it is buried a little, so that stable characteristics can be obtained over a long period of time. Further, the toner is moderately detached from the surface of the toner and accumulated at the tip of the cleaning blade, and the so-called dam effect has an effect of preventing a phenomenon that the toner passes from the blade.

  As a method for producing the toner in the present embodiment, a method obtained by melting and kneading a toner constituent material and then pulverizing and classifying is generally used as a conventional method, but is not limited to this method. A method is possible.

  As the polymerization method, a suspension polymerization method, an emulsion polymerization method, a dispersion polymerization method, and the like are possible. Although different from the polymerization method, in addition to a dissolution suspension method, a polymer suspension method, etc., an extension reaction method or the like can be used. .

  Other than the conventional method is preferable in that the toner having the above-described particle size range and circularity can be easily obtained. Further, the circularity may be adjusted by subjecting the toner after pulverization and classification to heat treatment.

  The method for adding the additive in the present embodiment is not particularly limited, and a method in which the toner base particles and the additive are mechanically mixed and adhered using various known mixing devices, or a toner base in a liquid phase. There is a method in which particles and additives are uniformly dispersed with a surfactant or the like, and after an adhesion treatment, dried.

  The particle size distribution of the toner described above can be measured by using a toner particle size distribution measuring apparatus by the Coulter counter method. Examples of these devices include Coulter Counter TA-II and Coulter Multisizer II (both manufactured by Coulter). The measurement method is described below.

  First, 0.1 [ml] to 5 [ml] of a surfactant (preferably alkylbenzene sulfonate) is added as a dispersant to 100 [ml] to 150 [ml] of the electrolytic aqueous solution. Here, the electrolytic solution is prepared by preparing a 1% NaCl aqueous solution using primary sodium chloride, and for example, ISOTON-II (manufactured by Coulter) can be used. Here, 2 [mg] to 20 [mg] of the measurement sample is further added. The electrolyte in which the sample is suspended is subjected to a dispersion treatment with an ultrasonic disperser for about 1 to 3 minutes, and the weight and number of toner particles or toner are measured using the 100 [μm] aperture as the aperture by the above-described measuring apparatus. Is measured to calculate the weight distribution and the number distribution. From the obtained distribution, the weight average particle diameter (D4) and the number average particle diameter (D1) of the toner can be obtained.

  As channels, 2.00 [μm] to less than 2.52 [μm]; 2.52 [μm] to less than 3.17 [μm]; 3.17 [μm] to less than 4.00 [μm]; 4 0.000 [μm] to less than 5.04 [μm]; 5.04 [μm] to less than 6.35 [μm]; 6.35 [μm] to less than 8.00 [μm]; 8.00 [μm] ≦ 10.08 [μm]; 10.08 [μm] to less than 12.70 [μm]; 12.70 [μm] to less than 16.00 [μm]; 16.00 [μm] to 20.20 [ <20 μm]; less than 20.20 [μm] to less than 25.40 [μm]; 25.40 [μm] to less than 32.00 [μm]; 13 less than 32.00 [μm] to less than 40.30 [μm] A channel is used and particles having a particle size of 2.00 [μm] or more and less than 40.30 [μm] are targeted.

Hereinafter, the carrier used in this embodiment will be described supplementarily.
The carrier used in the present embodiment is formed so that the weight average particle diameter is 20 [μm] to 60 [μm] (preferably 20 [μm] to 45 [μm]). This particle size range is also excellent as a carrier for the developer in the developing device 4.

  If the average particle size of the carrier is less than 20 [μm], fine particles are increased in the distribution of the carrier particles, and the magnetization per particle is lowered, which may cause carrier scattering. On the other hand, if the average particle diameter of the carrier exceeds 45 [μm], the carrier spikes during the development process become rough, and the uniformity of solid and halftone may be inferior (particularly, the average particle diameter is It becomes remarkable when it exceeds 60 [μm]). In addition, since the specific surface area is reduced, toner scattering may occur in a small particle size toner.

  The carrier is not particularly limited except for the particle diameter, and can be appropriately selected according to the purpose. However, a carrier having a core material and a resin layer covering the core material is preferable.

As the material of the core material is not particularly limited, can be appropriately selected from those known in the art, for ^{example, 50 × 4π × 10 -4 ~90} × 4π × 10 -4 [A / m] (50~90 [Emu / g]) manganese-strontium (Mn-Sr) -based material, manganese-magnesium (Mn-Mg) -based material and the like are preferable, and iron powder (100 [emu / g] or more in view of securing image density) ) And magnetite (75 × 4π × 10 ^{−4 to} 120 × 4π × 10 ⁻⁴ [A / m] (75 to 120 [emu / g])) are preferable. In addition, the copper-zinc (Cu—Zn) -based (30 × 4π × 10 ⁻⁴ to 80) is advantageous in that it can weaken the contact with the photosensitive drum 1 in which the toner is in a spiked state and is advantageous in improving the image quality. A weakly magnetized material such as × 4π × 10 ⁻⁴ [A / m] (30 to 80 [emu / g])) is preferable. These may be used alone or in combination of two or more.

  The material for the resin layer of the carrier is not particularly limited and can be appropriately selected from known resins according to the purpose. Examples thereof include amino resins, polyvinyl resins, polystyrene resins, and halogenated olefin resins. Polyester resin, polycarbonate resin, polyethylene resin, polyvinyl fluoride resin, polyvinylidene fluoride resin, polytrifluoroethylene resin, polyhexafluoropropylene resin, copolymer of vinylidene fluoride and acrylic monomer, fluoride Examples thereof include a copolymer of vinylidene and vinyl fluoride, a fluoroterpolymer such as a terpolymer of tetrafluoroethylene, vinylidene fluoride, and a non-fluorinated monomer, and a silicone resin. These may be used individually by 1 type and may use 2 or more types together.

  The resin layer may contain conductive powder or the like as necessary. Examples of the conductive powder include metal powder, carbon black, titanium oxide, tin oxide, and zinc oxide. The average particle diameter of these conductive powders is preferably 1 [μm] or less. When the average particle diameter exceeds [1 μm], it may be difficult to control the electrical resistivity.

  The carrier resin layer is prepared, for example, by dissolving the silicone resin in a solvent to prepare a coating solution, and then uniformly coating the coating solution on the surface of the core by a known coating method, drying, and baking. It can form by performing. Examples of the application method include a dipping method, a spray method, and a brush coating method.

  The amount of the resin layer in the carrier is preferably 0.01 [mass%] to 5.0 [mass%]. If the amount of the resin layer is less than 0.01 [mass%], a uniform resin layer may not be formed on the surface of the core material. If the amount exceeds 5.0 [mass%], the resin layer Becomes too thick and granulation of carriers occurs, and uniform carrier particles may not be obtained.

  The developer (initial agent) stored in advance in the developing device 4 is also a mixture of the above-described toner and carrier. There is no restriction | limiting in particular as content (carrier density | concentration) of the carrier in a developing agent, According to the objective, it can select suitably. For example, 90 [mass%] to 98 [mass%] is preferable, and 93 [mass%] to 97 [mass%] is more preferable.

What has been described above is merely an example, and the present invention has a specific effect for each of the following modes.
(Aspect A)
A developing sleeve 81 that rotates while carrying a two-component developer including a magnetic carrier and toner on the outer peripheral surface by the action of a magnetic field generated from a plurality of magnetic poles by a magnetic field generating means such as a magnet roller 82 disposed therein. An electrostatic latent image formed on a latent image carrier such as the photosensitive drum 1 with toner in a two-component developer carried on the outer peripheral surface of the developer carrier having a cylindrical developer carrier. In the developing device 4 that develops the electrostatic latent image by attaching it to an image, the magnetic field generating means moves the plurality of magnetic poles around the rotation direction of the developer carrier, and the developer carrier A scattering suppression member 85 is provided in a scattering suppression target region adjacent to the developer carrier rotating direction downstream side of the developing region where the body and the latent image carrier are opposed to each other, and the scattering suppression member 85 includes the developer Opposite the outer peripheral surface of the carrier In which the image-carrying member facing surface 85a is curved along the curved surface of the outer peripheral surface of the developer carrying member.
According to this, as described above, the distance from the outer peripheral surface of the developer carrying member can be reduced in the entire area of the developer carrying member facing surface 85a of the scattering suppressing member 85. Therefore, the entire area of the developer carrying member facing surface 85a of the scattering suppressing member 85 can be brought close to the outer circumferential surface of the developer carrying body to the extent that the magnetic restraint force by the magnetic field generating means inside the developer carrying body reaches. As a result, it is possible to suppress the generation of the developer that separates from the developer carrying member between the developer carrying member facing surface 85a of the scattering suppressing member 85 and the outer peripheral surface of the developer carrying member, and the developer scattering can be reduced.

(Aspect B)
In the above aspect A, in the region adjacent to the downstream side in the moving direction of the latent image carrier surface of the development region, the magnetic carrier attached on the surface of the latent image carrier is applied to the outer surface by the action of a magnetic field or an electric field or both. And a carrier recovery member such as a carrier recovery roller 13 that is attracted to and recovered.
As described above, since the scattering suppression member 85 is disposed close to the developer carrier, the magnetic carrier generated by the scattering suppression member 85 and attached to the surface of the latent image carrier is transferred to the scattering suppression member 85. If it is configured to collect, vibration is generated by magnetic field interference with the magnetic field of the magnetic field generating means inside the developer carrier. When such vibration occurs, problems such as density unevenness occur on the image. As in the present aspect B, by providing a carrier recovery member that recovers the magnetic carrier adhering to the surface of the latent image carrier separately from the scattering suppression member 85, the latent image can be generated without causing such a problem. It is possible to recover the magnetic carrier attached on the surface of the image carrier.
In particular, when a carrier recovery member having a high magnetic force is provided to increase carrier recovery efficiency, the carrier recovery member is removed from the developer carrier so as not to generate vibration due to magnetic field interference with the magnetic field generating means inside the developer carrier. It is necessary to install in a distant position. In this case, a large gap is generated in the scattering suppression target area, and as it is, a non-restraining area where the magnetic field action of the magnetic field generating unit does not reach is wide, so that it is easy to generate a developer that separates from the developer carrier. However, in the present aspect B, it is possible to suppress the generation of the developer that fills the gap in the wide scattering suppression target region with the scattering suppression member 85 and separates from the developer carrier. Therefore, even if a carrier recovery member having a high magnetic force is employed to increase the carrier recovery efficiency, vibrations are not generated and developer scattering is suppressed.

(Aspect C)
In the above aspect B, the carrier recovery member is a rotating body such as a carrier recovery roller 13 that attaches a magnetic carrier to the outer peripheral surface, and the scattering suppression member 85 is a carrier recovery member that faces the outer peripheral surface of the carrier recovery member. The facing surface 85b is curved along the curved surface of the outer peripheral surface of the carrier recovery member.
According to this, as described above, the entire region of the carrier recovery member facing surface 85b of the scattering suppression member 85 can be brought close to the outer peripheral surface of the carrier recovery member. As a result, the developer can be prevented from scattering from the gap between the carrier recovery member facing surface 85b of the scattering suppression member 85 and the outer peripheral surface of the carrier recovery member.

(Aspect C ′)
In the aspect C, the carrier recovery member facing surface 85b of the scattering suppression member 85 and the outer peripheral surface of the carrier recovery member are configured to be parallel.
According to this, as described above, since the gap between the carrier recovery member facing surface 85b of the scattering suppression member 85 and the outer peripheral surface of the carrier recovery member is constant, the airflow passing through the gap is stabilized and development is performed. Contributes to the improvement of the effect of the agent scattering.

(Aspect D)
In the above aspect B or C, the developer movement inhibition that inhibits the developer carried on the developer carrying member from moving to the carrier collecting member in a region where the carrier collecting member and the developer carrying member are opposed to each other. A member 88 is provided.
According to this, even if the carrier is attracted to the carrier recovery member side at the facing portion between the developer carrier and the carrier recovery member, the carrier is inhibited from moving to the carrier recovery member. As a result, the amount of developer input from the developer carrier to the carrier recovery member can be reduced, and defects such as image blurring and traces of background stains associated with an increase in the amount of developer input to the carrier recovery member. Can be suppressed.

(Aspect E)
In the aspect D, the developer movement inhibiting member 88 is disposed so as to be present at the closest portion between the developer carrying member and the carrier recovery member.
According to this, the amount of developer input from the developer carrier to the carrier recovery member can be reduced at the closest portion where the input from the developer carrier to the carrier recovery member is most actively performed. Therefore, the amount of developer input from the developer carrier to the carrier recovery member can be effectively reduced.

(Aspect F)
In the above aspect D or E, the electric field for moving the toner charged to the normal charging polarity such as negative polarity to the carrier collecting member side is formed between the carrier collecting member and the developer carrying member. A voltage application member for a carrier recovery member such as a power source 96 for applying a voltage to the carrier recovery member is provided.
According to this, it is possible to suppress the toner from being input to the carrier recovery member from the developer carrier, and the toner input to the carrier recovery member is transported to a portion facing the latent image carrier to remove the background stain. Generation | occurrence | production of malfunctions, such as generating, can be suppressed.

(Aspect G)
In the aspect F, the voltage application member for the carrier recovery member applies a voltage to the carrier recovery member so that the potential of the carrier recovery member is the same as the non-image portion potential of the latent image carrier.
According to this, even when a voltage is applied to the carrier recovery member, this prevents the ability to recover the carrier attached to the non-image portion on the latent image carrier to the carrier recovery member.

(Aspect H)
In the aspect F, the voltage application member for the carrier recovery member moves the carrier attached to the non-image part to the carrier recovery member side between the carrier recovery member and the non-image part of the latent image carrier. A voltage is applied to the carrier recovery member so that an electric field is formed.
According to this, the ability to collect the carrier adhering to the non-image part on the latent image carrier to the carrier collecting member is improved by the voltage applied to the carrier collecting member.

(Aspect I)
In any one of the above embodiments D to H, the developer movement inhibiting member 88 is a thin plate member.
According to this, even if the developer movement preventing member is arranged at the facing portion between the developer carrying member and the carrier recovery member, the gap between the facing portions can be minimized or the amount to be widened can be minimized. Side effects due to the arrangement of the agent movement prevention member can be reduced. In particular, by keeping the gap between the developer carrying member and the carrier recovery member narrow and obtaining the effect of suppressing the outflow of the developer through the gap, even if the developer movement prevention member is disposed, The effect is not disturbed.

(Aspect J)
In the aspect I, the developer movement inhibiting member 88 has one end attached to the scattering suppression member 85 and the other end in a direction away from the scattering suppression target area from the one end. It arrange | positions so that it may contact the surface of.
According to this, the developer movement inhibiting member as a seal member that suppresses the developer in the developing device from flowing out of the developing device through the gap formed between the developer carrying member and the carrier recovery member. 88 can be used.

(Aspect K)
In the above aspect J, the developer movement inhibiting member 88 is extended so that the other end extends to a position farther from the scattering suppression target region than the closest portion between the developer carrying member and the carrier recovery member. Is arranged.
According to this, it is possible to suppress the occurrence of a problem that the developer movement inhibiting member 88 is turned up due to friction between the rotating carrier recovery member and the developer movement inhibiting member 88.

(Aspect L)
In any one of the above embodiments D to K, the developer movement inhibiting member 88 is located more in the developer carrier than in the region of the developer carrier over the rotation direction of the developer carrier in the region where the developer is carried. It is arranged to extend outward in the direction of the rotation axis.
According to this, the effect of the developer movement inhibiting member can be exhibited over the entire image forming area.

(Aspect M)
In any one of the above aspects B to L, a seal member 89 that closes a gap between the carrier recovery member and the scattering suppression member 85 is provided.
According to this, it is possible to suppress the developer in the developing device from flowing out of the developing device through the gap between the scattering suppressing member 85 and the carrier recovery member.

(Aspect N)
In the aspect M, the seal member 89 is a thin plate member.
According to this, the side effect by having arrange | positioned the sealing member 89 can be decreased.

(Aspect O)
In the aspect N, the seal member 89 has flexibility, and is arranged so that an end portion that comes into contact with the carrier recovery member is pressed against the carrier recovery member.
According to this, the sealing effect can be maintained over a long period of time.

(Aspect P)
In any one of the above embodiments M to O, the seal member 89 extends in the direction of the developer carrying member rotation axis of the developer carrying member over the direction of the developer carrying member rotation axis of the region carrying the developer. It is arranged to extend outward.
According to this, the effect of the seal member 89 can be exhibited over the entire image forming area.

(Aspect Q)
In any one of the above aspects A to P, the developer carrying member facing surface 85a of the scattering suppressing member 85 and the outer peripheral surface of the developer carrying member are configured to be parallel to each other.
According to this, as described above, the gap between the developer carrying member facing surface 85a of the scattering suppressing member 85 and the outer peripheral surface of the developer carrying member is constant, so that the suction airflow passing through the gap is stable. To do. As a result, the efficiency with which the developer separated from the scattering suppression target area is sucked into the airflow and collected into the developing device is increased, and the effect of suppressing the developer scattering is increased.

(Aspect R)
The developing apparatus according to any one of the above aspects A to Q, wherein the scattering suppressing member 85 is nonmagnetic.
According to this, as described above, since the scattering suppressing member 85 disposed close to the developer carrying member is non-magnetic, magnetic field interference between the magnetic field generating means and the scattering suppressing member 85 inside the developer carrying member. There is no vibration due to magnetic field interference. As a result, it is possible to suppress the occurrence of image density unevenness due to the vibration. Further, the eddy current generated in the scattering suppression member 85 due to the magnetic field effect by the magnetic poles of the rotating magnetic field generating means is reduced, and the heat generation of the scattering suppression member 85 due to induction heating is suppressed, so that problems such as toner softening can be suppressed. .

(Aspect S)
In any one of the above aspects A to R, the scattering suppressing member 85 has electrical conductivity, and the toner charged with a normal charging polarity between the scattering suppressing member 85 and the developer carrier is developed. A voltage application member such as a power source for applying a voltage to the scattering suppression member 85 is provided so that an electric field to be moved toward the agent carrier is formed.
According to this, as described above, it is possible to suppress the toner from being accumulated on the scattering suppression member 85.

(Aspect T)
In any one of the above aspects A to S, the scattering suppressing member 85 includes a thin plate-like member such as the plate 86 disposed so as to face the surface of the latent image carrier, and the surface of the latent image carrier. The thin plate-like member facing the latent image carrier facing surface of the thin plate-like member, and a rod-like member such as a stay 87 having the developer carrier facing surface 85a. The development region side end of the plate-like member or the like protrudes toward the development region from the development region side end of the rod-shaped member.
In order to bring the end portion on the development area side of the scattering suppressing member 85 closer to the developing area, it is necessary to make the scattering suppressing member 85 taper toward the developing area. It is actually very difficult to create such a shape with a single member because of constraints such as part processing. On the other hand, with the present aspect G, the scattering suppressing member 85 that tapers toward the developing region can be created relatively easily.

(Aspect U)
In the above aspect T, the rod-shaped member has at least one corner extending in the direction of the rotation axis of the developer carrying member.
According to this, as described above, it becomes easy to obtain the processing accuracy of the rod-shaped member and the measurement accuracy of the dimensions with reference to the corner portion. As a result, the accuracy of each gap or the like when the scattering suppressing member 85 is assembled to the developing device is improved, leading to stabilization of the suction airflow, and the effect of suppressing the developer scattering can be enhanced.

(Aspect V)
In any one of the above aspects A to U, the scattering suppression member 85 includes the developer carrying member rotating shaft in the developer carrying region on the outer peripheral surface of the developer carrying member and the developer carrying member rotating shaft. It is comprised so that the area | region of a direction outer side may be opposed.
According to this, the gap near the end portion of the developer carrying member in the rotation axis direction can be filled with the scattering suppressing member 85, and the developer scattering generated near the end portion can be effectively suppressed.

(Aspect W)
The latent image carrier such as the photosensitive drum 1, latent image forming means such as an optical writing unit 21 that forms a latent image on the latent image carrier, and a two-component developer containing toner and a magnetic carrier. A developing device 4 for developing the latent image on the image carrier, and the toner image formed on the latent image carrier by the developing device is finally transferred to a recording material such as transfer paper, In an image forming apparatus that forms an image on a recording material, the developing device according to any one of the above aspects A to V is used as the developing device.
According to this, it is possible to suppress problems such as the occurrence of white spots due to carrier adhesion caused by developer scattering.

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 4 Developing device 5 Developing roller 6 Collection screw 7 Collection conveyance path 8 Supply screw 9 Supply conveyance path 10 Stirring conveyance path 11 Stirring screw 12 Doctor blade 13 Carrier collection roller 81 Development sleeve 82 Magnet roller 85 Scatter suppression member 85a Development Sleeve facing surface 85b Recovery roller facing surface 86 Plate 87 Stay 90 Carrier recovery sleeve 91 Carrier recovery magnet roller 95 Lower casing

US Patent Application Publication No. 2009/0136267

Claims (23)

It has a cylindrical developer carrying body that rotates by carrying a two-component developer containing a magnetic carrier and toner on the outer peripheral surface by the action of a magnetic field generated from a plurality of magnetic poles by a magnetic field generating means arranged inside. And a developing device for developing the electrostatic latent image by attaching toner in the two-component developer carried on the outer peripheral surface of the developer carrying member to the electrostatic latent image formed on the latent image carrying member. In
The magnetic field generating means is for rotating the plurality of magnetic poles along the rotation direction of the developer carrier.
A scattering suppression member is provided in a scattering suppression target region adjacent to the developer carrier rotating direction downstream side of the developing region where the developer carrier and the latent image carrier are opposed to each other,
The developing device according to claim 1, wherein the scattering suppressing member has a developer bearing member facing surface that faces the outer circumferential surface of the developer bearing member and is curved along a curved surface of the outer circumferential surface of the developer bearing member. The developing device according to claim 1.
In a region adjacent to the developing region on the downstream side in the moving direction of the latent image carrier, the magnetic carrier adhering to the surface of the latent image carrier is attracted to the outer surface by a magnetic field or an electric field or both, and collected. A developing device having a carrier recovery member. The developing device according to claim 2.
The carrier recovery member is a rotating body that attaches a magnetic carrier to the outer peripheral surface,
The developing device according to claim 1, wherein the scattering suppressing member has a carrier recovery member facing surface facing the outer peripheral surface of the carrier recovery member curved along a curved surface of the outer peripheral surface of the carrier recovery member. The developing device according to claim 2 or 3,
A developer movement inhibiting member that inhibits the developer carried on the developer carrying member from moving to the carrier collecting member in a region opposite to the carrier collecting member and the developer carrying member; Developing device. The developing device according to claim 4.
The developing device, wherein the developer movement inhibiting member is disposed so as to be present at a closest portion between the developer carrying member and the carrier recovery member. The developing device according to claim 4 or 5,
A carrier recovery member that applies a voltage to the carrier recovery member so that an electric field is formed between the carrier recovery member and the developer carrier to move the toner charged with a normal charging polarity toward the developer carrier. A developing device provided with a voltage applying member. The developing device according to claim 6.
The voltage application member for the carrier recovery member applies a voltage to the carrier recovery member so that the potential of the carrier recovery member is the same as the non-image portion potential of the latent image carrier. apparatus. The developing device according to claim 6.
The voltage application member for the carrier recovery member has an electric field between the carrier recovery member and the non-image portion of the latent image carrier to move the carrier attached to the non-image portion toward the carrier recovery member. Thus, a developing device characterized by applying a voltage to the carrier recovery member. In the developing device according to any one of claims 4 to 8,
The developing device according to claim 1, wherein the developer movement inhibiting member is a thin plate member. The developing device according to claim 9.
One end of the developer movement inhibiting member is attached to the scattering suppression member, and the other end in a direction away from the scattering suppression target area from the one end contacts the surface of the carrier recovery member. And a developing device. The developing device according to claim 10.
The developer movement inhibiting member is disposed so that the other end extends to a position farther from the scattering suppression target region than a closest portion between the developer carrying member and the carrier recovery member. A developing device. The developing device according to any one of claims 4 to 11,
The developer movement-inhibiting member is disposed so as to extend in the direction of the developer carrying member rotation axis in the region where the developer carrying member carries the developer, and to extend outward in the developer carrying member rotation axis direction from the region. A developing device. The developing device according to any one of claims 2 to 12,
A developing device comprising a seal member that closes a gap between the carrier recovery member and the scattering suppression member. The developing device according to claim 13,
The developing device according to claim 1, wherein the sealing member is a thin plate member. The developing device according to claim 14, wherein
The developing device according to claim 1, wherein the seal member has flexibility and is arranged so that an end portion in contact with the carrier recovery member is pressed against the carrier recovery member. The developing device according to any one of claims 13 to 15,
The seal member is arranged so as to extend in the direction of the developer carrying member rotation axis of the region where the developer carrying member carries the developer, and to extend outward from the region in the direction of the developer carrying member rotation axis. A developing device. The developing device according to any one of claims 1 to 16,
A developing device characterized in that a developer carrying member facing surface of the scattering suppressing member and an outer peripheral surface of the developer carrying member are parallel to each other. The developing device according to any one of claims 1 to 17,
The developing device according to claim 1, wherein the scattering suppression member is non-magnetic. The developing device according to any one of claims 1 to 18,
The scattering suppression member has conductivity,
Voltage application for applying a voltage to the scatter suppressing member so that an electric field is formed between the scatter suppressing member and the developer carrying member so as to move the toner charged to the normal charging polarity toward the developer carrying member. A developing device comprising a member. The developing device according to any one of claims 1 to 19,
The scattering suppressing member is opposite to the thin plate-like member disposed so as to face the surface of the latent image carrier and the surface opposite to the latent image carrier-facing surface of the thin plate member facing the surface of the latent image carrier. A rod-shaped member provided on the side surface and having the developer-carrying member facing surface,
2. A developing device according to claim 1, wherein an end portion of the thin plate member on the developing area side protrudes further toward the developing area side than an end portion of the rod-shaped member on the developing area side. The developing device according to claim 20,
The developing device according to claim 1, wherein the rod-shaped member has at least one corner portion extending in a developer carrying member rotation axis direction. The developing device according to any one of claims 1 to 21,
The scattering suppression member is configured to face the entire region of the developer carrying region in the developer carrying member rotation axis direction and the region outside the developer carrying member rotation axis direction on the outer peripheral surface of the developer carrying member. A developing device. A latent image carrier, a 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 two-component developer containing toner and a magnetic carrier; An image forming apparatus that finally transfers a toner image formed on the latent image carrier by the developing device to a recording material and forms an image on the recording material.
23. An image forming apparatus using the developing device according to claim 1 as the developing device.

Images