JP2015230344A - Developing device and image forming apparatus using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress scattering of toner from a development downstream area even when a large amount of toner is at the development downstream area.SOLUTION: A developing device includes airflow increasing means for driving to rotate a rotating body 71 that is arranged at a position closer to a photoreceptor 1 than a passage space E between the surface of a developer carrier 50 and an inner wall of a development case arranged opposite to the developer carrier with a predetermined gap to extend along the surface of the developer carrier, so as to increase a sucking airflow that sucks a toner at a development downstream area adjacent to the downstream side in the direction of surface movement of the developer carrier in a development area to an inner space of the development case through the gap E.

Description

  The present invention relates to a developing device that develops a latent image formed on a latent image carrier to form a toner image, and an image forming apparatus such as a copying machine, a facsimile, and a printer including the developing device.

  In this type of developing device, it is known that toner scattering occurs from a region adjacent to the downstream side of the developer carrying surface in the developing region (hereinafter referred to as “developing downstream region”) to the outside (inside the image forming apparatus). It has been.

  In the conventional developing device, a suction air flow from the downstream development area to the internal space of the development case is generated as the surface of the developer carrying member moves, and the toner in the downstream development area is collected in the internal space of the development case by this suction air flow. ing. There is also known a developing device that employs a configuration in which a passage space between the inner wall of the developing case through which the suction airflow passes and the surface of the developer carrier is narrowed in order to increase the suction airflow. Specifically, the inner wall of the developing case is formed so as to face each other with a small gap along the surface of the developer carrying member.

  When the developer carrying member moves on the surface, the surface of the developer carrying member itself or the developer carried on the surface moves, thereby generating a follower airflow that flows in the direction of the developer carrying member. The momentum of the accompanying airflow becomes stronger as the surface of the developer carrier is closer. Therefore, if the passage space is narrowed as in the conventional developing device, the influence of the accompanying airflow of the developer carrier on the airflow generated in the passage space is increased, and the suction airflow can be increased. However, if the toner in the downstream area of the development increases as the speed of the image forming operation increases, the airflow that is sufficient to collect the toner in the downstream area of the development into the internal space of the development case only by moving the surface of the developer carrier. Can not cause.

  Note that Patent Document 1 discloses a developing device including a carrier recovery roller in the vicinity of a development downstream region. In this developing device, the carrier attached to the latent image carrier is attached to the surface of the carrier recovery roller by the action of a magnetic field by a fixed magnet in the carrier recovery roller, and is recovered in the internal space of the developing case. In this developing apparatus, the carrier recovery roller has a function of increasing the suction airflow because the surface of the carrier recovery roller moves in the direction of the developer carrying member. However, this developing device does not include a configuration for increasing the suction airflow by narrowing the passage space between the inner wall of the developing case through which the suction airflow passes and the surface of the developer carrier.

  In order to solve the above-described problems, the present invention provides a developer carrier that carries a developer containing toner on the surface and moves, and a portion of the surface of the developer carrier in the developer carrier surface movement direction. An opening that is exposed to the outside in order to face the surface of the moving latent image carrier, and a developing case that contains the developer in an internal space; and the developer carrier and the latent image carrier In a developing device that develops a latent image on the latent image carrier with a developer carried on the developer carrier in a developing region facing each other to form a toner image, the developer is placed along the surface of the developer carrier. The outer peripheral surface is exposed in a part of the passage space between the inner wall of the developing case and the surface of the developer carrying member facing each other with a predetermined gap, and the outer peripheral surface is not exposed in the inner space of the developing case. Or from the passage space By rotating and driving a rotating body disposed at a position close to the surface of the latent image carrier, the toner existing in the development downstream region adjacent to the developer carrier surface movement direction downstream of the development region is developed through the passage space. It is characterized by having an air flow increasing means for increasing the suction air flow sucked into the internal space of the case.

  According to the present invention, there is an excellent effect that toner scattering from the downstream development area can be suppressed even under a situation where there is a large amount of toner in the downstream development area.

FIG. 3 is a partially enlarged view of the developing device 5 according to the first embodiment. 1 is a schematic configuration diagram of a copier according to a first embodiment. FIG. 3 is an enlarged explanatory diagram of one of four image forming units in the copier. FIG. 2 is an explanatory cross-sectional view of the developing device. It is explanatory drawing for demonstrating a general image development apparatus and the airflow around it. It is a schematic diagram for demonstrating a general image development apparatus and the airflow around it. FIG. 2 is an explanatory diagram for describing a developing device and airflow around the developing device in Embodiment 1. FIG. 10 is a partial enlarged view of a developing device according to Modification 1. FIG. 10 is a partially enlarged view of a developing device according to Modification 2. It is an example of the computer screen which shows the result of the generation | occurrence | production simulation of the airflow in the image development apparatus of a comparative example. 10 is a graph showing an estimated value of toner scattering amount calculated by using a predetermined arithmetic expression from the above-described simulation results for Comparative Example, Embodiment 1 and Modification Example 1. 4 is a partially enlarged explanatory view for explaining a relationship between a gap between an airflow generation roller and a photosensitive member and a toner scattering amount in the developing device of Embodiment 1. FIG. In the developing device according to the first exemplary embodiment, the toner is generated when the gap between the airflow generation roller and the photosensitive member is wider (gap wide) than when the gap between the developing roller surface and the inner wall of the casing is narrowed (gap narrow). It is a graph which shows the result of having calculated the estimated value of the amount of scattering. It is explanatory drawing for demonstrating an airflow when a suction | inhalation airflow is insufficient in a general developing device. It is a schematic diagram for demonstrating the airflow in case a suction | inhalation airflow is insufficient in a general developing device. FIG. 6 is a partial enlarged view of a developing device in Embodiment 2. FIG. 10 is a partial enlarged view of a developing device according to Modification 3. FIG. 10 is a partial enlarged view of a developing device according to Modification 4. 10 is a graph showing an estimated value of the amount of scattered toner calculated using a predetermined arithmetic expression from the above-described simulation results for Comparative Example, Embodiment 2, and Modification 4.

Embodiment 1
Hereinafter, an embodiment (hereinafter referred to as “embodiment 1”) of a tandem type color copying machine (hereinafter referred to as a copying machine 500) as an image forming apparatus to which the developing device according to the present invention is applied. explain.
FIG. 2 is a schematic configuration diagram of the copying machine 500 in the present embodiment.
The copying machine 500 includes a document reading unit 4 and a document conveying unit 3 above a printer unit 100 as a main body unit of the image forming apparatus, and a sheet feeding unit 7 below the printer unit 100. The document conveying unit 3 conveys the document to the document reading unit 4, and the document reading unit 4 reads image information of the conveyed document. The paper supply unit 7 is a recording material storage unit that stores the transfer paper P, which is a recording material. The paper supply unit 26 that stores the transfer paper P, and the transfer paper P in the paper supply cassette 26 to the printer unit 100. And a paper feed roller 27 that feeds out. A one-dot chain line in FIG. 2 indicates a conveyance path of the transfer paper P in the copying machine 500.

  An upper portion of the printer unit 100 is a paper discharge tray 30 on which transfer paper P on which an output image is formed is stacked. The printer unit 100 includes four image forming units 6Y, 6M, 6C, and 6K as image forming units that form toner images of respective colors (yellow, magenta, cyan, and black), and an intermediate transfer unit 10. Each of the image forming units 6Y, 6M, 6C, and 6K is formed on a drum-shaped photoreceptor 1Y, 1M, 1C, and 1K as a latent image carrier on which each color toner image is formed, and on the surface of each photoreceptor. And developing devices 5Y, 5M, 5C, and 5K for developing the electrostatic latent image.

  The intermediate transfer unit 10 includes an intermediate transfer belt 8 and primary transfer bias rollers 9Y, 9M, 9C, and 9K. The intermediate transfer belt 8 is an intermediate transfer body serving as a transfer body on which the color toner images formed on the surfaces of the photoreceptors 1Y, 1M, 1C, and 1K are transferred in a superimposed manner, and a color toner image is formed on the surface. It is. The primary transfer bias rollers 9Y, 9M, 9C, and 9K are primary transfer units that transfer the toner images formed on the surfaces of the photoreceptors 1Y, 1M, 1C, and 1K to the intermediate transfer belt 8.

  The printer unit 100 includes a secondary transfer bias roller 19 for transferring the color toner image on the intermediate transfer belt 8 onto the transfer paper P. Also, the transfer of the transfer paper P sent out by the paper feed roller 27 is stopped once, and the registration roller pair 28 that adjusts the timing at which the intermediate transfer belt 8 and the secondary transfer bias roller 19 are transported to the opposing secondary transfer nip. Is provided. Further, the printer unit 100 includes a fixing device 20 that fixes an unfixed toner image on the transfer paper P above the secondary transfer nip.

  In addition, toner containers 11Y, 1M, 1C, and 1K for the respective colors are disposed below the paper discharge tray 30 and above the intermediate transfer unit 10 in the printer unit 100. The toner containers 11Y, 1M, 1C, and 1K for the respective colors store the respective color toners supplied to the developing devices 5Y, 5M, 5C, and 5K.

FIG. 3 is an enlarged explanatory view of one of the four image forming units 6Y, 6M, 6C, 6K.
The four image forming units 6Y, 6M, 6C, and 6K have substantially the same configuration and operation except for the color of the toner used in the image forming process. Therefore, in the following description, reference numerals indicating the corresponding colors are used. In the description, Y, M, C, and K are omitted as appropriate.

  As shown in FIG. 3, the image forming unit 6 is a process cartridge that integrally supports the photoreceptor 1 and the developing device 5, and this process cartridge is detachable from the copying machine 500 main body. . This facilitates exchange of the developing device 5 in the main body of the copying machine 500 provided with the developing device 5, and improves the maintainability of the copying machine 500.

  The image forming unit 6 includes a photoconductor cleaning device 2, a lubricant application device 41, and a charging device 40 in addition to the developing device 5 around the photoconductor 1. In the image forming unit 6 of the present embodiment, the photoreceptor cleaning device 2 is configured to be cleaned by the cleaning blade 2a, and the charging device 40 is configured to be charged by the charging roller 4a.

Hereinafter, an operation during normal color image formation in the copier 500 of the present embodiment will be described.
First, when a start button (not shown) is pressed in a state where the document is set on the document table of the document conveyance unit 3, the document is conveyed from the document table by the conveyance roller of the document conveyance unit 3, and the document reading unit 4. Placed on the contact glass. Then, the document reading unit 4 optically reads the image information of the document placed on the contact glass.

  Specifically, the document reading unit 4 scans an image of a document on the contact glass while irradiating light emitted from an illumination lamp. Then, the light reflected from the original is imaged on the color sensor via the mirror group and the lens. The color image information of the original is read for each color separation light of RGB (red, green, blue) by the color sensor, and then converted into an electrical image signal. Further, color conversion processing, color correction processing, spatial frequency correction processing, and the like are performed by the image processing unit based on the RGB color separation image signals to obtain yellow, magenta, cyan, and black color image information.

  Then, image information of each color of yellow, magenta, cyan, and black is transmitted to a writing unit (not shown). Then, laser light L based on the image information of each color is emitted from the writing unit toward the corresponding photoreceptors 1Y, 1M, 1C, and 1K.

  On the other hand, the four photoconductors 1Y, 1M, 1C, and 1K rotate in the clockwise direction in FIGS. First, the surfaces of the photoreceptors 1Y, 1M, 1C, and 1K are uniformly charged at a portion facing the charging roller 4a of the charging device 40 (charging process). Laser beams L corresponding to image signals are emitted from the four light sources onto the surfaces of the charged photoreceptors 1Y, 1M, 1C, and 1K from the writing unit. Each laser beam L passes through a different optical path for each color component of yellow, magenta, cyan, and black, and is irradiated on the surface of each of the photoreceptors 1Y, 1M, 1C, and 1K (exposure process).

  The laser beam L corresponding to the yellow component is applied to the surface of the first yellow photoconductor 1Y from the left side in FIG. At this time, the yellow component laser light L is scanned in the rotational axis direction (main scanning direction) of the yellow photoconductor 1Y by a polygon mirror that rotates at high speed. By scanning the laser beam L in this manner, an electrostatic latent image corresponding to the yellow component is formed on the surface of the yellow photoreceptor 1Y after being charged by the charging device 40.

  Similarly, the laser beam L corresponding to the magenta component is irradiated onto the surface of the second magenta photoreceptor 1M from the left in FIG. 2, and an electrostatic latent image corresponding to the magenta component is formed. The cyan component laser light L is applied to the surface of the third cyan photoconductor 1C from the left in FIG. 2 to form an electrostatic latent image of the cyan component. The black component laser beam L is applied to the surface of the fourth black photoconductor 1K from the left in FIG. 2 to form a black component electrostatic latent image.

  Thereafter, the surfaces of the photoreceptors 1Y, 1M, 1C, and 1K on which the electrostatic latent images of the respective colors are formed reach positions facing the developing device 5, respectively. Then, the respective color toners are supplied onto the surfaces of the photoreceptors 1Y, 1M, 1C, and 1K from the developing devices 5Y, 5M, 5C, and 5K that store the developer including the toners and magnetic carriers, and the photoreceptors 1Y and 1M. , 1C, 1K are developed (development process).

  The surfaces of the photoreceptors 1Y, 1M, 1C, and 1K after passing through the portion facing the developing device 5 (development region) reach the portion facing the intermediate transfer belt 8 (primary transfer region). Here, in each primary transfer region, primary transfer bias rollers 9Y, 9M, 9C, and 9K are installed so as to be in contact with the inner peripheral surface of the intermediate transfer belt 8. The photosensitive drums 1Y, 1M, 1C, and 1K and the primary transfer bias rollers 9Y, 9M, 9C, and 9K face each other with the intermediate transfer belt 8 interposed therebetween, thereby forming a primary transfer nip. In the primary transfer nip, the toner images of the respective colors formed on the photoreceptors 1Y, 1M, 1C, and 1K are sequentially transferred onto the intermediate transfer belt 8 (primary transfer process).

  The surfaces of the photoconductors 1Y, 1M, 1C, and 1K after passing through the primary transfer nip reach positions facing the photoconductor cleaning device 2, respectively. Then, untransferred toner remaining on the photoconductor is scraped and collected by the cleaning blade 2a at a position facing the photoconductor cleaning device 2 (photoconductor cleaning process).

  The surfaces of the photoconductors 1Y, 1M, 1C, and 1K that have passed through the portion facing the photoconductor cleaning device 2 pass through a charge removal unit that is opposed to a charge removal unit (not shown), and residual charges are discharged. The image forming process is completed, and the next image forming operation is prepared.

  The color toner images on the four photoconductors 1Y, 1M, 1C, and 1K are superimposed and transferred, and the intermediate transfer belt 8 that carries the color toner images moves in the counterclockwise direction in FIG. It reaches the secondary transfer nip which is a position facing the bias roller 19. On the other hand, the transfer paper P fed by the paper feed roller 27 from the paper feed cassette 26 containing the transfer paper P is guided to the registration roller pair 28 after passing through the conveyance guide, and hits the registration roller pair 28. Stop once. The transfer paper P that has struck the registration roller pair 28 is conveyed toward the secondary transfer nip in accordance with the timing at which the color toner image formed on the intermediate transfer belt 8 is directed to the secondary transfer nip. Then, the color toner image carried on the intermediate transfer belt 8 at the secondary transfer nip is transferred onto the transfer paper P (secondary transfer step).

  The surface of the intermediate transfer belt 8 that has passed through the secondary transfer nip reaches a portion facing an intermediate transfer belt cleaning device (not shown). At this facing portion, the transfer residual toner adhering to the intermediate transfer belt 8 is collected by an intermediate transfer belt cleaning device (not shown), and a series of transfer processes in the intermediate transfer belt 8 is completed.

  The transfer paper P on which the color toner image is transferred at the secondary transfer nip is guided to the fixing device 20. In the fixing device 20, a color image is fixed on the transfer paper P by heat and pressure at a fixing nip formed by a fixing roller and a pressure roller (fixing step). The transfer paper P that has passed through the fixing device 20 is discharged as an output image outside the printer unit 100 by the paper discharge roller pair 25 and stacked on the paper discharge tray 30 to complete a series of image forming processes.

FIG. 4 is a cross-sectional explanatory view of the developing device 5 of the present embodiment.
The developing device 5 of the present embodiment includes a casing 58 as a developing case for containing a developer in an internal space. The casing 58 includes a developing lower case 58a, a developing upper case 58b, and a developing cover 58c. . The developing device 5 includes a developing roller 50 as a developer carrying member that forms a developing region facing the photoreceptor 1, a supply screw 53 that is a supply conveyance member, a collection screw 54 that is a collection conveyance member, and a developer regulating member. A doctor blade 52 and a partition member 57 are provided. The supply screw 53 and the recovery screw 54 are screw members provided with a spiral blade on the rotation shaft, and convey the developer G in the axial direction of the rotation shaft by rotating.

In the casing 58, a developing opening 58e is formed as an opening so that a part of the surface of the developing roller 50 is exposed in a developing region where the developing roller 50 faces the photoreceptor 1.
The doctor blade 52 is disposed so as to face the developing roller 50 and regulates the amount of the developer G carried on the surface of the developing roller 50.

  The supply screw 53 and the recovery screw 54 are conveying members that form a circulation path by stirring and conveying the developer G accommodated in the internal space of the casing 58 in the longitudinal direction. The supply screw 53 is disposed to face the developing roller 50 and supplies the developer G to the developing roller 50 while conveying the developer G in the longitudinal direction. The collection screw 54 receives the developer G on the developing roller 50 that has passed through the development area, and conveys the replenished toner and the developer G while mixing and stirring them.

  Of the internal space of the casing 58, the supply conveyance path 53 a in which the supply screw 53 is arranged and the collection conveyance path 54 a in which the collection screw 54 is arranged are spatially partitioned by a partition member 57. In addition, the partition member 57 has an end portion in a cross section orthogonal to the axial direction (cross section shown in FIG. 4) facing the surface of the developing roller 50 and is disposed close to the surface of the developing roller 50. It also functions as a separation plate that promotes the detachment of the developer G from above. Due to the function of the partition member 57 as a separation plate, the developer G carried on the developing roller 50 and having passed through the developing region is prevented from reaching the supply conveyance path 53a, and is not delayed toward the collection conveyance path 54a. Can be moved.

  The developing roller 50 includes a magnet roller 55 composed of a plurality of magnets fixed inside, and a developing sleeve 51 that rotates around the magnet roller 55. The developing sleeve 51 is a cylindrical member that includes a magnet roller 55 and is made of a rotatable nonmagnetic material. On the surface of the developing sleeve 51, as a plurality of magnetic poles, a first magnetic pole P1 (S pole), a second magnetic pole P2 (N pole), a third magnetic pole P3 (S pole), a fourth magnetic pole P4 (N pole), In addition, five magnetic poles of the fifth magnetic pole P5 (N pole) are formed by the magnet roller 55. Note that P1 to P5 in FIG. 4 indicate the distribution of the normal direction magnetic flux density (absolute value) on the surface of the developing sleeve 51 of the magnetic field formed by each magnetic pole.

  In the present embodiment, development that is carried on the surface of the developing roller 50 toward the developing region on the upstream side in the surface movement direction of the developing roller 50 with respect to the developing region that is a facing portion between the photosensitive member 1 and the developing roller 50. A doctor blade 52 that regulates the amount of the agent is disposed below the developing roller 50. In the present embodiment, a filter 59 is installed to reduce the pressure in the internal space of the casing 58. The air containing the toner in the internal space of the casing 58 is separated from the toner and air by passing through the filter 59, and only the air is discharged to the outside of the casing 58.

  Since the developing device 5 uses a two-component developer G (including the case where an additive or the like is added) composed of toner and carrier, a part of the casing 58 is used in accordance with the toner consumption in the developing device 5. The toner is appropriately replenished to the internal space of the casing 58 from a toner replenishing port (not shown) provided in the casing 58. The replenished toner is agitated and mixed with the developer G in the casing 58 while being conveyed by the recovery screw 54 and the supply screw 53.

  A developing voltage is applied to the developing sleeve 51 of the developing roller 50 from a developing power source (not shown), and toner charged to a normal polarity (for example, a negative polarity) is charged into the electrostatic latent image on the surface of the photoreceptor 1 in the developing region. A developing electric field that is moved toward the image portion is formed. By this developing electric field, in the developing area, the toner in the developer G on the surface of the developing roller 50 adheres to the electrostatic latent image on the surface of the photoreceptor 1, and the electrostatic latent image is converted into a toner image.

  The developer G in the casing 58 is conveyed in the longitudinal direction by a supply screw 53 provided in parallel and close to the surface of the developing roller 50, and the developing roller 50 is acted on by the magnetic field of the fifth magnetic pole P <b> 5 of the magnet roller 55. Is supplied to the outer circumferential surface. The developer G transferred to the surface of the developing roller 50 is regulated by the doctor blade 52 as the developing sleeve 51 rotates counterclockwise as shown by an arrow in FIG. To reach.

  The electrostatic latent image on the photosensitive member 1 is developed by a developing electric field formed in the developing region by applying a developing voltage to the developing sleeve 51 from a developing power source (not shown). The developer G on the surface of the developing roller 50 after passing through the developing region is returned to the internal space of the casing 58 as the developing sleeve 51 rotates, and the fourth magnetic pole P4 and the fifth magnetic pole P5 having the same polarity. It is separated from the surface of the developing roller 50 under the action of the repulsive magnetic field. The developer G separated from the surface of the developing roller 50 falls on the upper surface of the partition member 57 and slides down, and is collected by the collecting screw 54.

Next, a mechanism that causes toner scattering from the development downstream area will be described.
FIG. 5 is an explanatory diagram for explaining a general developing device and airflow around it.
When the developer on the surface of the developing roller 50 passes through the developing region, the developer is raised by the action of the magnetic field by the first magnetic pole P1 to form a magnetic brush, and the surface of the photoreceptor 1 is slid by the tip of the magnetic brush. Rub. Due to the movement of the developer, an air flow is generated from the upstream side to the downstream side in the developing roller rotation direction in the developing region. In the present embodiment, since the surface movement direction of the photosensitive member 1 is a direction that rotates around the developing roller 50, the airflow is strong.

  Further, the developer after passing through the developing region shows a movement such that the magnetic brush that rises up falls due to the magnetic field of the magnet roller 55 in the developing roller 50. Impacts due to this movement, the momentum of the air flow generated in the developing area, the centrifugal force due to the rotation of the developing roller 50, and the like act on the toner in the developer on the developing roller, so that the developing downstream area (in FIG. 5) In area A), the toner is detached from the developer. In particular, when the development downstream area A is located laterally or below the surface of the developing roller 50, the gravity acting on the toner in the developer on the developing roller also acts as a force for releasing the toner.

  The toner released from the developing roller 50 in the downstream development area A is carried by an air current that rotates with the rotation of the developing roller 50 and travels toward the inside of the casing 58 from the gap between the inner wall of the casing 58 and the surface of the developing roller 50; The air travels as the photoconductor 1 rotates, and is divided into toner that travels toward the gap (region B in FIG. 5) between the opening edge 58f of the casing 58 and the surface of the photoconductor 1.

  Here, since the toner which goes to the inside of the casing 58 is accommodated in the internal space of the casing 58, it does not cause toner scattering. On the other hand, in the region B, the accompanying airflow of the photoconductor 1 flowing on the side close to the surface of the photoconductor 1 and the return airflow flowing toward the developing region on the side close to the opening edge 58f of the casing 58 are mixed. Yes. This return airflow is generated due to the influence of the accompanying airflow of the developing roller 50 (the suction airflow toward the inside of the casing 58 by the accompanying airflow of the developing roller 50) and the like. In general, the accompanying air current of the rotating body such as the photosensitive member 1 and the developing roller 50 becomes weaker as the distance from the surface of the rotating body increases. For this reason, in the region B, the follower airflow of the photosensitive member 1 is more strongly influenced than the follower airflow of the developing roller 50, and most of the toner flowing into the region B moves downstream in the surface movement direction of the photoreceptor 1. Head.

  As a result, the toner that has moved from the region B to the downstream side in the photosensitive member surface movement direction flows into the upstream region of the transfer region in the photosensitive member surface movement direction (hereinafter referred to as “transfer upstream region”). In this upstream transfer region (region C in FIG. 5), the accompanying airflow of the photoconductor 1 and the accompanying airflow of the intermediate transfer belt 8 collide with each other and become high pressure. As a result, an air flow from the upstream transfer area C to the gap (area D in FIG. 5) between the upper outer wall of the casing 58 of the developing device 5 and the intermediate transfer belt 8 and the area B is generated.

  Of the toner that has flowed into the transfer upstream area C, the toner that has been on the return airflow from the transfer upstream area C to the area B returns to the development downstream area A and rides on the suction airflow toward the inside of the casing 58, or The air travels along with the photosensitive member 1 and travels to the region B again. On the other hand, of the toner that has flowed into the transfer upstream area C, a part of the toner that has flowed toward the area D is returned again to the area C by the accompanying airflow of the intermediate transfer belt 8, but the rest is relatively It flows out toward the area inside the low-pressure image forming apparatus. This causes toner scattering.

FIG. 6 is a schematic diagram for explaining a general developing device and airflow around it.
If all the toner separated in the development downstream area A can be sucked into the casing 58, the toner scattering from the development downstream area A will not occur. However, in reality, the separated toner moves from the development downstream area A to the transfer upstream area C through the area B due to the influence of the accompanying airflow of the photosensitive member 1, and further, due to the high pressure in the transfer upstream area C, the transfer upstream area C. To the inside of the image forming apparatus through the region D.

Next, a configuration for suppressing the above-described toner scattering, which is a characteristic part of the present invention, will be described.
FIG. 1 is a partially enlarged view of the developing device 5 according to the first embodiment.
In the developing device 5 according to the first embodiment, an airflow generation roller 71 that is an external rotating body is disposed at a position that does not face the internal space of the casing 58. Specifically, the air flow generation roller 71 of the present embodiment is positioned on the outside of the casing 58 facing the surface of the photosensitive member 1 and the surface of the intermediate transfer belt 8, more specifically, the opening edge 58f of the casing 58 and the photosensitive member. It is arranged between the surface of the body 1. The air flow generating roller 71 is supported by being rotatably supported at both ends of the rotating shaft 71a by the axially outer casing 58 portion.

  In addition, a guide plate 72 as an airflow guide member for guiding the accompanying airflow of the airflow generation roller 71 to the gap E between the surface of the developing roller 50 and the inner wall of the casing 58 is provided at the opening edge portion 58 f of the casing 58. Yes. One end of the guide plate 72 is attached to the opening edge portion 58 f of the casing 58, and the other end is disposed so as to contact the surface of the air flow generation roller 71. The guide plate 72 is preferably composed of a sheet member made of a flexible material such as urethane in order to suppress wear of the guide plate 72 and the airflow generation roller 71 at the contact portion with the airflow generation roller 71.

  The air flow generation roller 71 is driven in the direction of the arrow in the figure by a driving means (not shown), that is, the rotation direction with respect to the surface movement direction of the intermediate transfer belt 8 and the movement direction with respect to the surface movement direction of the photoreceptor 1. It is driven to rotate in the direction opposite to the direction of rotation (counter direction). When the air flow generating roller 71 is driven to rotate, the detaching toner existing in the development downstream area A is increased by the suction air flow sucked into the internal space of the casing 58 through the gap E between the surface of the developing roller 50 and the inner wall of the casing 58. Can do. The rotational drive of the airflow generation roller 71, the photosensitive member 1, and the intermediate transfer belt 8 is started at the same timing, and the accompanying airflow of the photosensitive member 1 and the intermediate transfer belt 8 is generated, and at the same time, the accompanying airflow of the airflow generation roller 71 is generated. Is configured to do.

FIG. 7 is an explanatory diagram for explaining the developing device 5 and the airflow around it in the present embodiment.
The dotted line arrows in FIG. 7 indicate the airflow direction in each region. As the airflow generation roller 71 rotates, a follower airflow is generated near the surface of the airflow generation roller 71. The accompanying airflow generated by the airflow generating roller 71 is an airflow opposite to the accompanying airflow generated by the photosensitive member 1 in the area B ′ between the development downstream area A and the transfer upstream area C. Therefore, the accompanying airflow of the photoreceptor 1 can weaken the momentum of the airflow from the development downstream area A to the transfer upstream area C in the area B ′. As a result, it is possible to suppress the separated toner in the development downstream area A from going to the upstream transfer area C via the area B ′. As a result, the transfer upstream area C to the inside of the image forming apparatus via the area D can be prevented. The toner can be prevented from scattering.

  Further, since the accompanying airflow generated by the airflow generation roller 71 flows toward the transfer upstream area C in the area D, the pressure in the transfer upstream area C increases, and at first glance, it may be considered to promote toner scattering. However, since the momentum of the airflow from the upstream transfer area C to the development downstream area A through the area B ′ increases due to the accompanying airflow of the airflow generation roller 71, the pressure in the transfer upstream area C does not increase, but temporarily increases. Even a few. Therefore, the scattering of toner is not promoted by the accompanying airflow of the airflow generation roller 71.

  In the present embodiment, the accompanying airflow generated by the airflow generation roller 71 flows along the guide plate 72 and travels toward the opening 58 e of the casing 58. Therefore, the toner returned to the development downstream area A from the area B ′ by the accompanying air current generated by the airflow generation roller 71 is guided along the guide plate 72 to the opening 58 e of the casing 58, and the development roller 50 rotates. The air is sucked in and collected from the gap E into the internal space of the casing 58.

[Modification 1]
Next, a modified example of the developing device according to the first embodiment described above (hereinafter, this modified example is referred to as “modified example 1”) will be described.
When the image forming operation of the copying machine 500 becomes faster, the surface moving speed (number of rotations) of the photoconductor 1 increases, and the flow velocity of the accompanying airflow of the photoconductor 1 increases. Therefore, only the accompanying airflow of the airflow generation roller 71 cannot suppress the momentum of the airflow from the development downstream area A to the transfer upstream area C in the area B ′, and the toner scattering may not be sufficiently suppressed. In the first modification, an auxiliary roller 73 as an auxiliary rotating body is provided separately from the airflow generation roller 71.

FIG. 8 is a partially enlarged view of the developing device 5 in the first modification.
The auxiliary roller 73 in Modification 1 is disposed at a position closer to the transfer area than the airflow generation roller 71 and at a position outside the casing 58 facing the surface of the photoreceptor 1 and the surface of the intermediate transfer belt 8. ing. That is, the auxiliary roller 73 is disposed in the transfer upstream area C. Similarly to the air flow generation roller 71, the auxiliary roller 73 is also supported by being rotatably supported at both ends of the rotating shaft by a portion of the casing 58 that is axially outward.

  The auxiliary roller 73 is driven by a driving means (not shown) in the direction of the arrow in the drawing, that is, in the counter direction with respect to the surface movement direction of the intermediate transfer belt 8 and in the rotating direction with respect to the surface movement direction of the photoreceptor 1. To rotate. When the auxiliary roller 73 is driven to rotate, the airflow flowing into the transfer upstream area C by the accompanying airflow of the photosensitive member 1 is intermediate in the gap between the auxiliary roller 73 and the intermediate transfer belt 8 by the accompanying airflow of the auxiliary roller 73. It flows in the direction opposite to the surface movement direction of the transfer belt 8. The airflow collides with the accompanying airflow of the intermediate transfer belt 8 at a location upstream of the auxiliary transfer roller 73 in the intermediate transfer belt surface movement direction, and weakens the force of the accompanying airflow of the intermediate transfer belt 8. Also weaken the momentum. In this portion, a flow toward the air flow generation roller 71 is generated by the accompanying air flow of the auxiliary roller 73. Therefore, the force of the air flow from the region B ′ to the development downstream region A is generated by the accompanying air current of the air generation roller 71. Increase.

  When such an air flow is generated by the auxiliary roller 73, the pressure in the transfer upstream region C is reduced, the momentum of the air flow from the transfer upstream region C to the region D is weakened, and the air flows on the air flow and is scattered inside the image forming apparatus. The amount of toner is reduced.

[Modification 2]
Next, another modification of the developing device according to the first embodiment described above (hereinafter, this modification is referred to as “modification 2”) will be described.
Since the airflow generation roller 71 generates a follower airflow on which the release toner in the development downstream area A is placed, the surface thereof is always exposed to the airflow including the release toner. Therefore, the detached toner is likely to adhere to the surface of the airflow generation roller 71. In the first embodiment described above, the toner adhering to the surface of the airflow generation roller 71 is scraped off by the guide plate 72 in contact with the surface. At this time, the toner gradually accumulates at the contact portion between the surface of the airflow generation roller 71 and the guide plate 72 and may eventually fall as a toner aggregate. When such a toner agglomerate falls from this contact portion, it moves downward by its own weight without being collected by the air current or the developer on the developing roller 50, and enters the developing area from the developing downstream area A. Sometimes. When such toner agglomerates enter the development region, there arises a problem that image quality is deteriorated.

Even when the guide plate 72 is not provided, the toner gradually accumulates on the surface of the airflow generation roller 71, and the accumulated toner may fall from the airflow generation roller 71 in a lump and cause the same problem. is there.
Further, since the guide surface of the guide plate 72 (surface on the surface side of the photosensitive member 1) is always exposed to the air flow including the separation toner, the toner gradually accumulates on the guide surface, and the accumulated toner is a lump. There is a possibility of falling from the guide plate 72 and causing the same problem.

In order to solve this problem, the second modification adopts the following configuration.
FIG. 9 is a partially enlarged view of the developing device 5 according to the second modification.
In general, the main cause of toner detachment from the developer in the development downstream area A is that the electrostatic adsorption force with the magnetic carrier in the developer is insufficient, and thus many of such detachment toners are used. Is a low-charge toner with a small charge amount. The low charge toner here includes not only a toner charged to a normal charge polarity but also a reverse charge toner charged to a polarity opposite to the normal charge polarity. Therefore, in the second modification, at least one of the surface of the airflow generation roller 71 ′ and the guide surface of the guide plate 72 ′ is a surface having a function of hindering the adhesion of low-charged toner. Specifically, for example, a minute uneven shape is provided on the surface of the airflow generation roller 71 ′ and the guide surface of the guide plate 72 ′. As a result, the amount of low-charged toner adhering to the surfaces of the airflow generation roller 71 ′ and the guide plate 72 ′ can be reduced, and the occurrence of a situation in which a lump of toner enters the development region and causes deterioration in image quality is suppressed. can do. In addition, as a method of providing the concavo-convex shape, there are, for example, a method of manufacturing a rotating member with a material capable of surface concavo-convex processing, and a method of attaching a sheet having concavo-convex properties to the surface of a relatively low cost substrate. Further, the size of the surface irregularities is preferably substantially the same size as the additive on the toner surface, and a height of about 50 nm is suitable.

  On the other hand, when the image forming speed of the copying machine 500 is high and the surface moving speed (rotation speed) of the developing roller 50 is high, not only the above-mentioned low-charged toner but also a sufficient charge amount with the normal charging polarity. Highly charged toner is also easily detached from the developer in the downstream development area A. Since most of the toner contained in the developer is a highly charged toner, the ratio of the highly charged toner contained in the detached toner gradually increases as the speed increases, and when the image formation speed becomes higher than a certain level, the highly charged toner May adhere to the surfaces of the airflow generation roller 71 and the guide plate 72 and enter the developing area as a lump, which may be more serious than a lump of low-charged toner.

  In such a case, it is preferable that at least one of the surface of the airflow generation roller 71 ′ and the guide surface of the guide plate 72 ′ be a surface having a function of inhibiting the adhesion of the highly charged toner. Specifically, for example, a surface treatment for imparting hydrophilicity is applied to the surface of the airflow generation roller 71 ′ and the guide surface of the guide plate 72 ′, and the surface is connected to the ground. Alternatively, for example, the surface of the airflow generation roller 71 ′ and the guide surface of the guide plate 72 ′ are formed of a conductive material such as a conductive plastic having a relatively low surface resistance value, and the surfaces are connected to the ground. Also good.

  As a result, the charge amount of the highly charged toner adhering to the surfaces of the airflow generation roller 71 ′ and the guide plate 72 ′ can be reduced, and the electrostatic adhesion force of the highly charged toner can be weakened. As a result, the highly charged toner adhering to the surfaces of the airflow generation roller 71 ′ and the guide plate 72 ′ can be separated from the surfaces by the action of centrifugal force or airflow before becoming a lump. Therefore, it is possible to suppress the occurrence of a situation in which a mass of highly charged toner falls to the development area.

Next, the effect confirmation test of the first embodiment and the first modification will be described.
In this effect confirmation test, a computer system is used for the developing device of the first embodiment, the developing device of the modified example 1, and the developing device of the comparative example that does not include the airflow generation roller 71 and the auxiliary roller 73 described above. The simulation of airflow generation was performed. FIG. 10 is an example of a computer screen showing the result of airflow generation simulation in the developing device of the comparative example.

FIG. 11 is a graph showing an estimated value of the amount of scattered toner calculated by using a predetermined arithmetic expression from the simulation results described above for the comparative example, the first embodiment, and the first modification.
As can be seen from this graph, compared to the comparative example that does not include the airflow generation roller 71, the estimated value of the toner scattering amount is smaller in the first embodiment and the modification 1 that include the airflow generation roller 71. This is because the momentum of the airflow flowing out from the region D into the image forming apparatus is suppressed by providing the airflow generation roller 71.

  In particular, the modified example 1 including not only the airflow generation roller 71 but also the auxiliary roller 73 has a smaller estimated amount of toner scattering than the first embodiment in which the auxiliary roller 73 is not provided. This is because the momentum of the airflow flowing out from the region D into the image forming apparatus is further suppressed by providing the auxiliary roller 73.

Next, the relationship between the gap between the airflow generation roller 71 and the photosensitive member 1 and the toner scattering amount will be described.
FIG. 12 is an explanatory diagram in which the developing device 5 in the first embodiment described above is partially enlarged in order to explain the relationship between the gap between the airflow generation roller 71 and the photoreceptor 1 and the toner scattering amount.
In general, as the gap Gp1 between the airflow generation roller 71 and the photosensitive member 1 is narrower, the accompanying airflow of the airflow generation roller 71 increases the momentum of the airflow from the region C to the development downstream region A via the region B ′. This is advantageous for suppressing toner scattering. However, if the gap Gp1 is too narrow, the pressure loss in the gap Gp1 becomes excessive, and the momentum of the air flow from the region C to the development downstream region A via the region B ′ is reduced to reduce the toner scattering. It is disadvantageous for restraint.

FIG. 13 shows a case where the gap Gp1 between the airflow generation roller 71 and the photoreceptor 1 is wider than the gap GP2 between the surface of the developing roller 50 and the inner wall of the casing 58 in the developing device 5 of the first embodiment described above (gap). It is a graph which shows the result of having computed the estimated value of the amount of toner scattering about the case where it is narrow (gap narrow).
The estimated value of the toner scattering amount was calculated in the same manner as in the effect confirmation test described above.

  The gap GP2 between the surface of the developing roller 50 and the inner wall of the casing 58 is generally wide enough to suppress pressure loss to the extent that a suction airflow can be secured, and the surface of the developing roller 50 and the inner wall of the casing 58 are wide. In addition, the gap is set so as to prevent the toner from flowing out from the gap. That is, the gap GP2 is normally set to a minimum size that can secure the suction airflow.

  Therefore, if the gap Gp1 between the airflow generating roller 71 and the photosensitive member 1 is set to be narrower than the gap GP2 between the surface of the developing roller 50 and the inner wall of the casing 58, the pressure loss becomes excessive, and the region C to the region B The momentum of the airflow toward the development downstream area A via 'decreases. As a result, as shown in FIG. 13, the amount of scattered toner is relatively large.

  On the other hand, if the gap Gp1 between the airflow generation roller 71 and the photoreceptor 1 is set wider than the gap GP2 between the surface of the developing roller 50 and the inner wall of the casing 58, the pressure loss does not become excessive. Therefore, the original function of increasing the momentum of the airflow from the region C to the development downstream region A via the region B ′ by the accompanying airflow of the airflow generation roller 71 is exhibited. As shown in FIG. The amount of scattering is relatively small.

[Embodiment 2]
Next, another embodiment in which the developing device according to the present invention is applied to the same copier 500 as in the first embodiment (hereinafter, this embodiment is referred to as “second embodiment”) will be described.
In the second exemplary embodiment, toner scattering caused by a shortage of the suction air flow for sucking the separated toner in the downstream development area into the casing 58 of the developing device 5 is suppressed. Since the basic configuration of the copier 500 in the second embodiment is the same as that in the first embodiment, the description below will focus on a configuration that is different from the first embodiment.

FIG. 14 is an explanatory diagram for explaining the airflow when the suction airflow is insufficient in a general developing device.
FIG. 15 is a schematic diagram for explaining the air flow when the suction air flow is insufficient in a general developing device.
As the image forming speed increases, the amount of toner released from the developer tends to increase in the downstream development area A. To suck the released toner from the downstream development area A into the casing 58, the developing roller 50 is rotated. There is a case where the momentum of the airflow is insufficient only by the suction airflow. Further, since the pressure in the internal space of the casing 58 tends to increase due to the increase in the image forming speed, the outside of the casing opposite to the suction airflow passes through the gap E between the surface of the developing roller 50 and the inner wall of the casing 58. There may be an air flow toward. As a result, toner scattering increases as the image forming speed increases, and means for suppressing this is required.

FIG. 16 is a partially enlarged view of the developing device 5 according to the second embodiment.
In the developing device 5 of the second embodiment, a suction airflow reinforcing roller 74 that is an internal rotating body is disposed at a position that does not face the internal space of the casing 58. Specifically, the suction airflow reinforcing roller 74 is disposed on the wall portion of the casing 58 so that a part of the rotation direction of the surface thereof is exposed to the gap E. The suction airflow reinforcing roller 74 is supported by being rotatably supported at both ends of the rotating shaft 71a by a portion of the casing 58 that is axially outward.

  The suction airflow reinforcing roller 74 is opposed to the surface of the developing roller 50 by exposing a part of the surface of the suction airflow reinforcing roller 74 in the rotational direction from the space F provided in the wall portion of the casing 58 for installation. At the opening edge of the space F, a guide plate 75 is provided as an airflow guide member for guiding the accompanying airflow of the suction airflow reinforcing roller 74 to the internal space of the casing 58. One end of the guide plate 75 is attached to the opening edge on the downstream side in the direction of movement of the developing roller surface in the space F, and the other end is disposed so as to contact the surface of the suction airflow reinforcing roller 74. The guide plate 75 is preferably composed of a sheet member made of a flexible material such as urethane in order to suppress wear of the guide plate 75 and the suction airflow reinforcement roller 74 at the contact portion with the suction airflow reinforcement roller 74.

  In the present embodiment, one end of the rectifying plate 76 is attached to the opening edge on the upstream side of the developing roller surface moving direction in the space F, and the other end of the rectifying plate 76 is on the surface of the suction airflow reinforcing roller 74. It arrange | positions so that it may contact | abut. Thus, the suction airflow near the opening 58e of the casing 58 is prevented from being disturbed by the rotation of the suction airflow reinforcing roller 74.

  The suction airflow reinforcing roller 74 is driven to rotate in the direction indicated by the arrow in the drawing, that is, along with the moving direction of the surface of the developing roller 50 by driving means (not shown). When the suction airflow reinforcing roller 74 is driven to rotate, the suction airflow flowing through the gap E can be increased. The rotational driving of the suction airflow reinforcing roller 74 and the developing roller 50 is started at the same timing, and the accompanying airflow of the developing roller 50 is generated and the accompanying airflow of the suction airflow reinforcing roller 74 is generated.

  In the conventional developing device, normally, the gap E between the surface of the developing roller 50 and the inner wall of the casing 58 is narrowed, and the accompanying airflow of the developing roller 50 acts on the entire gap E to generate the suction airflow. It was. At this time, the force of the accompanying airflow of the developing roller 50 decreases as the distance from the surface of the developing roller 50 decreases, so that the force of the suctioned airflow is weak near the inner wall of the casing 58 in the gap E. For this reason, the pressure in the internal space of the casing 58 increases due to the increase in the image forming speed, so that a blowout airflow that passes through the vicinity of the inner wall of the casing 58 in the gap E and is directed to the outside of the casing may be generated. When such a blown airflow is generated, the momentum of the sucked airflow that sucks the toner into the casing 58 is weakened, and the amount of separated toner outside the developing device increases, resulting in an increase in toner scattering.

  In the second embodiment, an airflow in the same direction as the suction airflow can be generated in the vicinity of the inner wall of the casing 58 in the gap E where the blown airflow can occur due to the accompanying airflow of the suction airflow reinforcing roller 74. As a result, even in a situation where a blown air flow can occur due to an increase in the pressure of the internal space of the casing 58 due to an increase in image formation speed, a blown air flow does not occur in the vicinity of the inner wall of the casing 58, and the gap E A suction airflow can be generated throughout. Therefore, an increase in toner scattering due to an increase in the speed of the image forming operation can be suppressed.

  In the second embodiment, the surfaces of the suction airflow reinforcing roller 74, the guide plate 75, and the rectifying plate 76 are always exposed to the suction airflow including the separation toner, and thus the separation toner is likely to adhere. As in the case of the second modification in the first exemplary embodiment, the surface may have a function that inhibits the adhesion of low-charged toner, or the surface may have a function that inhibits the adhesion of highly-charged toner.

[Modification 3]
Next, a modified example of the developing device in the above-described second embodiment (hereinafter, this modified example is referred to as “modified example 3”) will be described.
Depending on the magnetic pole arrangement of the magnet roller 55 in the developing roller 50, the developer may rise up in the gap E between the surface of the developing roller 50 and the inner wall of the casing 58 to form a magnetic brush. The toner on the suction airflow reinforcing roller 74 is blocked by the contact portion with the guide plate 75. When a magnetic brush of developer is formed in the gap E, the toner blocked by the contact portion is magnetically formed. It tends to be a toner agglomerate when pressed by a brush. Such a toner agglomerate eventually falls from the contact portion between the suction airflow reinforcing roller 74 and the guide plate 75, and moves to the internal space of the casing 58 by the rotation of the developing roller 50. In some cases, the toner agglomerates are caught in the gap between the developing roller 50 and the doctor blade 52. In this case, the image quality is deteriorated.

FIG. 17 is a partially enlarged view of the developing device 5 according to the third modification.
In the developing device 5 of Modification 3, the contact portion H between the suction airflow reinforcing roller 74 and the guide plate 75 is located farther from the surface of the developing roller 50 than the inner wall surface of the casing 58 that forms the gap E. It is configured to be arranged. More preferably, the surface of the suction airflow reinforcing roller 74 is arranged at a position farther from the surface of the developing roller 50 than the inner wall surface of the casing 58 forming the gap E.

  According to the third modification, the force with which the toner blocked by the contact portion between the suction airflow reinforcing roller 74 and the guide plate 75 is pressed by the magnetic brush in the gap E can be weakened or can not be pressed. be able to. As a result, it is possible to prevent the toner in the contact portion from moving into the internal space of the casing 58 as a toner agglomerate and causing deterioration in image quality.

  Further, in the third modification, as shown in FIG. 17, the rectifying plate 76 is omitted from the developing device of the second embodiment described above. In the configuration in which the surface of the suction airflow reinforcing roller 74 is arranged at a position farther from the surface of the developing roller 50 than the inner wall surface of the casing 58 that forms the gap E as in the third modification, the effect of the rectifying plate 76 is obtained. It tends to be thinner. Therefore, in the third modification, the configuration is simplified and the manufacturing cost is reduced without installing the current plate 76.

[Modification 4]
Next, another modified example of the developing device in the above-described second embodiment (hereinafter, this modified example is referred to as “modified example 4”) will be described.
In the second embodiment described above, the suction airflow reinforcing roller 74 is arranged on the wall portion of the casing 58 so that a part of the rotation direction of the surface is exposed to the gap E, and the suction airflow flowing through the gap E is reinforced. If all the toner separated in the development downstream area A can be sucked into the casing 58, the toner scattering from the development downstream area A will not occur. However, in actuality, as described above, the separated toner moves from the development downstream area A to the transfer upstream area C through the area B due to the influence of the accompanying airflow of the photosensitive member 1, and further, the influence of the high pressure in the transfer upstream area C. As a result, the transfer upstream area C, the area D, and the inside of the image forming apparatus are scattered. That is, there is a possibility that toner scattering cannot be sufficiently suppressed only by enhancing the suction airflow.

FIG. 18 is a partially enlarged view of the developing device 5 according to the fourth modification.
The suction airflow reinforcing roller 74 ′ in the fourth modification example is arranged so that the surface of one part in the rotation direction faces the surface of the developing roller 50 and the surface of the other part in the rotation direction faces the surface of the intermediate transfer belt 8. ing. Specifically, in the space F ′ provided in the wall portion of the casing 58 for installing the suction airflow reinforcing roller 74 ′, a location facing the surface of the developing roller 50 and a location facing the surface of the intermediate transfer belt 8. An opening is provided at each of the openings, and a part of the surface of the suction airflow reinforcing roller 74 ′ is exposed from each opening. The suction airflow reinforcing roller 74 ′ is supported by being rotatably supported at both ends of the rotating shaft by a portion of the casing 58 that is axially outward.

  The suction airflow reinforcing roller 74 ′ in the fourth modification is driven in the direction indicated by the arrow in the drawing by a driving unit (not shown), that is, along the surface movement direction of the developing roller 50 and the surface movement direction of the intermediate transfer belt 8. Even in the accompanying direction, it is rotationally driven.

  A guide plate 75 and a current plate 76 are provided at the opening edge of the space F ′ facing the surface of the developing roller 50 as in the second embodiment. Two rectifying plates 77A and 77B are provided at the opening edge of the space F ′ facing the surface of the intermediate transfer belt 8. One end of each of the two rectifying plates 77A and 77B is attached to the upstream and downstream opening edges of the intermediate transfer belt surface moving direction in the space F ′, and the other end is in contact with the surface of the suction airflow reinforcing roller 74. Are arranged as follows. The rectifying plates 77A and 77B are formed of a sheet member made of a flexible material such as urethane in order to suppress wear of the rectifying plates 77A and 77B and the suction airflow reinforcing roller 74 ′ at the contact portion with the suction airflow reinforcing roller 74 ′. Is preferred.

  Due to the effect of the high pressure in the transfer upstream region C, an air flow toward the region D and an air flow toward the region B are generated from the transfer upstream region C. When the toner in the upstream transfer area C moves on the air flow toward the area D, the toner scatters from the area D to the inside of the image forming apparatus. Here, in the vicinity of the surface of the intermediate transfer belt 8, the influence of the accompanying airflow of the intermediate transfer belt 8 is great, and an airflow from the region D toward the transfer upstream region C is generated. On the other hand, at the location away from the surface of the intermediate transfer belt 8, that is, the location near the outer wall surface of the casing 58 of the developing device 5, the influence of the accompanying airflow of the intermediate transfer belt 8 is small. Therefore, the air flow from the transfer upstream region C to the region D due to the high pressure in the transfer upstream region C flows through the vicinity of the outer wall surface of the casing 58 of the developing device 5.

  In the fourth modification, the direction of the surface of the intermediate transfer belt 8 that moves in the vicinity of the outer wall surface of the casing 58 of the developing device 5 in the region D, that is, from the region D due to the accompanying airflow of the suction airflow reinforcing roller 74 ′. It is possible to generate an air flow in the direction toward the transfer upstream region C, or to weaken the momentum of the air flow from the transfer upstream region C to the region D. As a result, the amount of toner in the upstream transfer area C moving to the area D can be reduced, and toner scattering inside the image forming apparatus can be suppressed.

  Incidentally, the accompanying airflow of the suction airflow reinforcing roller 74 ′ may increase the pressure in the transfer upstream area C, and the momentum of the airflow from the transfer upstream area C to the area D may be increased. However, even if the pressure in the transfer upstream area C increases, the airflow from the transfer upstream area C to the area D is hindered by the influence of the accompanying airflow of the suction airflow reinforcing roller 74 ′ and the accompanying airflow of the intermediate transfer belt 8. . Therefore, the increase in the pressure in the transfer upstream area C has the effect of enhancing the momentum of the airflow from the transfer upstream area C to the area B. If the momentum of the airflow from the transfer upstream area C to the area B becomes strong, the amount of toner in the transfer upstream area C moved from the area B to the development downstream area A increases, and the toner recovery to the inside of the casing 58 by the suction airflow Increases efficiency.

  In particular, in the fourth modification, the suction airflow from the development downstream area A to the inside of the casing 58 is enhanced by the accompanying airflow of the suction airflow reinforcing roller 74 '. Therefore, even if the pressure in the transfer upstream area C increases, the air flow from the transfer upstream area C to the area B flows without a stagnation into the development downstream area A, and merges with the suction air flow and can flow into the casing 58. .

Next, the effect confirmation test of Embodiment 2 and Modification 4 described above will be described.
In this effect confirmation test, a computer system is used for the developing device of the second embodiment, the developing device of the modified example 4, and the developing device of the comparative example that does not include the suction airflow reinforcing rollers 74 and 74 ′ described above. The simulation of airflow generation was performed. The contents of this simulation are the same as the simulation in the first embodiment described above.

FIG. 19 is a graph showing an estimated value of the amount of scattered toner calculated using a predetermined arithmetic expression from the above-described simulation results for the comparative example, the second embodiment, and the modified example 4.
As can be seen from this graph, in contrast to the comparative example that does not include the suction airflow reinforcement rollers 74 and 74 ′, in the second embodiment and the modification 4 that include the suction airflow reinforcement rollers 74 and 74 ′, the estimated value of the toner scattering amount is Less. This is because the momentum of the suction airflow into the casing 58 is strengthened by providing the suction airflow reinforcing rollers 74 and 74 ′.

  In this simulation, the result of the toner scattering is larger in the modified example 4 than in the second embodiment. This is considered to be due to the difference in the layout of the suction airflow reinforcing rollers 74 and 74 '. Specifically, when the suction airflow is strengthened by using the accompanying airflow of the suction airflow reinforcement rollers 74 and 74 ′, the narrower the gap between the surface of the suction airflow reinforcement rollers 74 and 74 ′ and the surface of the developing roller 50, the more the suction is performed. There is a tendency to increase the momentum of the airflow. In the case of the modified example 4, the configuration is such that the accompanying airflow of the suction airflow reinforcing roller 74 ′ is applied to the region D so as to face the surface of the intermediate transfer belt 8. The layout is limited, and there is a possibility that the gap between the surfaces of the suction airflow reinforcing rollers 74 and 74 ′ and the surface of the developing roller 50 cannot be set sufficiently narrow. The result of this simulation is considered to be that the toner scattering amount is larger than that in the second embodiment due to this influence.

  However, if the gap between the surfaces of the suction airflow reinforcing rollers 74 and 74 ′ and the surface of the developing roller 50 is too narrow, the pressure loss in the gap becomes excessive, which results in weakening the momentum of the suction airflow. Therefore, the gap between the surfaces of the suction airflow reinforcing rollers 74 and 74 ′ and the surface of the developing roller 50 is appropriately set in consideration of this. Specifically, for example, the gap GP2 between the surface of the developing roller 50 and the inner wall of the casing 58 is preferably set to 1/2 to 2 times.

  In the above description, the intermediate transfer type image forming apparatus that transfers the toner image on the photosensitive member 1 to the intermediate transfer belt 8 has been described as an example. However, the recording is performed by carrying the recording material on the surface and moving the surface. The same applies to a direct transfer type image forming apparatus that directly transfers a toner image on the photosensitive member 1 to a recording material on a material carrier.

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 developer carrying member such as a developing roller 50 that carries a developer G containing toner on its surface and moves on the surface, and a photosensitive member 1 that moves part of the surface of the developer carrying member in the developer carrying member surface moving direction, etc. A developing case such as a casing 58 in which the developer is accommodated in an internal space, and an opening 58e that is exposed to the outside so as to face the surface of the latent image carrier. In the developing device 5 for developing the latent image on the latent image carrier with the developer carried on the developer carrier in the developing region facing the image carrier, the toner carrier is developed. The outer peripheral surface is exposed in a part of the passage space between the inner wall of the developing case and the surface of the developer carrying member facing each other with a predetermined gap along the surface of the developing case, and the outer periphery is exposed to the inner space of the developing case. The face is not exposed, or The developer carrier in the development region is driven by rotating and rotating a rotating body such as the airflow generating roller 71 and the suction airflow reinforcing rollers 74 and 74 ′ disposed closer to the surface of the latent image carrier than the passage space E. An air flow increasing means is provided for increasing a suction air flow for sucking toner existing in the developing downstream area A adjacent to the downstream side of the body surface moving direction into the internal space of the developing case through the passage space E.
In this embodiment, the passage space between the inner wall of the developing case and the surface of the developer carrying member is a flow path from the developing downstream region to the inner space of the developing case. The inner wall of the developing case forming the passage space is opposed to the surface of the developer carrying member with a predetermined gap so as to be along the surface of the developer carrying member, and the flow passage cross-sectional area is narrowed. . As a result, the suction airflow increases, and the toner in the development downstream region can be efficiently collected into the internal space of the development case. However, if there is a large amount of toner in the downstream area of the development to be collected in the internal space of the developing case by being placed on the suction airflow, the suction airflow may be insufficient. According to this aspect, since the suction airflow is increased by the airflow increasing means, it is possible to sufficiently secure the suction airflow and improve the efficiency of collecting the toner in the development downstream region into the internal space of the development case. Therefore, even when there is a large amount of toner in the development downstream area to be collected, the toner in the development downstream area can be sufficiently collected in the internal space of the development case, and toner scattering from the development downstream area A into the image forming apparatus can be suppressed. it can.

(Aspect B)
In the aspect A, the developer is a two-component developer including toner and a magnetic carrier, and the rotating body is an airflow generating roller 71 that rotates without generating a magnetic field that attracts the magnetic carrier, and a suction airflow reinforcement. It includes a rotating body such as rollers 74 and 74 '.
According to this aspect, since the magnetic carrier does not adhere to the rotating body, the magnetic carrier on the rotating body is rotated to collect it in the internal space of the developing case like the carrier collecting roller disclosed in Patent Document 1. It is not necessary to employ a configuration in which the body is opposed to the internal space of the developing case. In addition, according to the rotating body of this aspect, it is not necessary to arrange a fixed magnet for attaching the carrier on the latent image carrier to the surface of the rotating body by the action of magnetic force. Therefore, it is possible to reduce the size of the rotating body and easily suppress the increase in the size of the developing device.

(Aspect C)
In the above-described aspect A or B, the rotating body includes a surface of the latent image carrier and a surface of a member to be transferred such as an intermediate transfer belt 8 onto which a toner image formed on the surface of the latent image carrier is transferred. The toner image is disposed at a position outside the developing case opposite to the surface of the recording material conveying member that conveys the recording material to which the toner image is transferred, and is associated with the moving direction of the surface of the transfer object or the recording material conveying member. It includes an external rotating body such as an airflow generating roller 71 that rotates in the rotating direction and in the direction opposite to the rotating direction with respect to the surface movement direction of the latent image carrier.
According to this, the accompanying airflow of the external rotating body generates an airflow in a direction opposite to the accompanying airflow of the latent image carrier in the area B ′ between the development downstream area A and the transfer upstream area C. Therefore, the momentum of the airflow from the development downstream area A to the transfer upstream area C in the area B ′ can be weakened by the accompanying airflow of the latent image carrier. As a result, it is possible to suppress the separated toner in the development downstream area A from going to the upstream transfer area C via the area B ′. As a result, the transfer upstream area C to the inside of the image forming apparatus via the area D can be prevented. The toner can be prevented from scattering.
Further, since the accompanying airflow of the external rotating body flows toward the transfer upstream area C in the area D, the pressure in the transfer upstream area C increases, and at first glance, it may be considered to promote toner scattering. However, since the momentum of the airflow from the upstream transfer area C to the development downstream area A through the area B ′ increases due to the accompanying airflow of the external rotating body, the pressure in the transfer upstream area C does not increase, but temporarily increases. Even a few. Accordingly, toner scattering is not promoted by the accompanying airflow of the airflow generation roller 71.

(Aspect D)
In the aspect C, the gap Gp1 between the external rotating body and the latent image carrier is wider than the gap Gp2 in the passage space E.
According to this, since the pressure loss in the gap Gp1 between the external rotating body and the latent image carrier does not become excessive, the developing downstream area A from the transfer upstream area C via the area B ′ due to the accompanying airflow of the external rotating body. The original function of increasing the momentum of the airflow toward the can be maintained.

(Aspect E)
In the aspect C or D, the rotating body is separate from the external rotating body with respect to a transfer area for transferring a toner image formed on the surface of the latent image carrier to the transfer target or the first recording material. It is disposed at a position closer to the rotating body and at a position outside the developing case facing the surface of the latent image carrier and the surface of the transferred body or the surface of the recording material conveying member, and the transferred body or the An auxiliary rotator such as an auxiliary roller 73 that rotates in the direction opposite to the follow direction with respect to the surface movement direction of the recording material conveying member and in the follow direction with respect to the surface move direction of the latent image carrier. It is characterized by including.
According to this, the pressure in the transfer upstream area C is reduced by the airflow generated by the auxiliary rotating body, and the momentum of the airflow from the transfer upstream area C to the area D is weakened and is scattered in the image forming apparatus along this airflow. The amount of toner is reduced.

(Aspect F)
In any one of the aspects C to E, an air flow guide member such as a guide plate 72 that guides the air flow generated by the external rotating body to the passage space E is provided.
According to this, the accompanying airflow of the external rotating body is guided by the airflow guide member and flows from the passage space E to the internal space of the developing case. By such an air flow, the toner can be efficiently sucked into the internal space of the developing case.

(Aspect G)
In the aspect F, the airflow guide member is arranged so that one end is attached to the edge 58f of the opening 58e of the developing case and the other end is in contact with the surface of the external rotating body. And
According to this, the toner adhered on the surface of the external rotating body can be removed by the airflow guide member. The removed toner can be collected on the airflow flowing along the airflow guide surface of the airflow guide member into the internal space of the developing case, and the toner scattering suppression effect is high.

(Aspect H)
In the aspect F or G, the airflow guide surface of the airflow guide member has a surface that inhibits adhesion of toner with a small charge amount.
According to this, when the ratio of the toner with a small amount of charge contained in the separated toner in the downstream development area is high, the toner adhering to the air flow guide surface of the air flow guide member becomes a toner aggregate and falls to the development area. Or image quality deterioration caused by being collected in the developing case.

(Aspect I)
In the aspect F or G, the airflow guide surface of the airflow guide member has a surface that inhibits adhesion of toner having a large charge amount.
According to this, when the ratio of the toner with a large amount of charge contained in the separated toner in the downstream development area is high, the toner adhering to the airflow guide surface of the airflow guide member falls as a toner agglomerate and falls to the development area. Or image quality deterioration caused by being collected in the developing case.

(Aspect J)
In any one of the aspects A to I, the rotating body is disposed on the wall portion of the developing case so that a part of the rotation direction of the surface of the rotating body is exposed to the passage space E, and the surface of the developer carrier is moved. It includes an internal rotating body such as suction airflow reinforcing rollers 74 and 74 ′ that are driven to rotate in a rotational direction with respect to the direction.
According to this, in the vicinity of the inner wall of the developing case in the passage space E where the blown airflow can occur, an airflow in the same direction as the suction airflow can be generated by the accompanying airflow of the internal rotating body. Thereby, even in a situation where a blown airflow may be generated due to an increase in the pressure of the internal space of the developing case due to an increase in the image forming speed or the like, the blown airflow is not generated or the momentum of the blown airflow is reduced. it can. Therefore, it is possible to suppress the toner from flowing out of the developing device by riding on the blowing airflow, and to suppress toner scattering.

(Aspect K)
The aspect J is characterized by having an air flow guide member such as a guide plate 75 for guiding an air flow generated by the internal rotating body to the internal space of the developing case.
According to this, the momentum of the airflow flowing through the passage space E toward the internal space of the developing case can be increased, and the toner can be efficiently sucked into the internal space of the developing case.

(Aspect L)
In the above aspect J or K, a part of the surface of the internal rotator in the rotation direction is transferred to the surface of the transfer medium or the toner image onto which the toner image formed on the surface of the latent image carrier is transferred. The recording material conveying member that conveys the recording material to be conveyed is disposed so as to face the surface of the recording material conveying member, and is rotated with respect to the surface moving direction of the developer carrying member and the surface moving direction of the transfer target or the recording material conveying member It is characterized in that it is driven to rotate in the following direction.
According to this, as described in the modification 4, the surface movement of the transfer medium or the recording material conveying member in the vicinity of the outer wall surface of the casing 58 of the developing device 5 in the region D due to the accompanying airflow of the internal rotating body. It is possible to generate an airflow in the direction along the direction, that is, in the direction from the region D to the transfer upstream region C, or to weaken the momentum of the airflow from the transfer upstream region C to the region D. As a result, the amount of toner in the upstream transfer area C moving to the area D can be reduced, and toner scattering inside the image forming apparatus can be suppressed.

(Aspect M)
In any one of the aspects J to L, the gap RG between the internal rotator and the developer carrier is 0.5 ≦ (RG / CG) ≦ 2 with respect to the gap CG in the passage space. It is characterized by satisfying the relationship.
According to this, since the pressure loss in the gap RG between the internal rotator and the developing carrier is not excessive, it is possible to maintain the original function of enhancing the suction airflow by the accompanying airflow of the internal rotator.

(Aspect N)
In any one of the aspects A to M, the surface of the rotating body has a surface that inhibits adhesion of toner with a small charge amount.
According to this, when the ratio of the toner with a small charge amount contained in the detached toner in the downstream development area is high, the toner adhering to the surface of the rotating body falls as a toner agglomerate and falls into the development area or the development case. It is possible to suppress deterioration in image quality caused by being collected inside.

(Aspect O)
In any one of the aspects A to M, the surface of the rotating body has a surface that inhibits adhesion of toner having a large charge amount.
According to this, when the ratio of the toner with a large charge amount contained in the detached toner in the development downstream area is high, the toner adhering to the surface of the rotating body becomes a toner agglomerate and falls into the development area or the development case. It is possible to suppress deterioration in image quality caused by being collected inside.

(Aspect P)
In the aspect I or O, the surface that inhibits adhesion of toner having a large charge amount is a surface having conductivity.
According to this, the electrostatic charge can be reduced by reducing the charge amount of the toner having a large charge amount, and the adhesion of the toner having a large charge amount can be easily inhibited.

(Aspect Q)
A copying machine for finally transferring a toner image obtained by developing a latent image formed on a latent image carrier such as the photoreceptor 1 by a developing means into a toner image onto a recording material such as transfer paper P In an image forming apparatus such as 500, the developing device 5 according to any one of the aspects A to P is used as the developing unit.
According to this, toner scattering from the development downstream area to the inside of the image forming apparatus can be suppressed even under a situation where the toner in the development downstream area is large.

DESCRIPTION OF SYMBOLS 1 Photoconductor 5 Developing device 6 Image forming unit 8 Intermediate transfer belt 9 Primary transfer bias roller 19 Secondary transfer bias roller 20 Fixing device 50 Developing roller 51 Developing sleeve 52 Doctor blade 55 Magnet roller 58 Casing 58e Opening portion 58f Opening edge portion 71 Airflow generating rollers 72, 75 Guide plate 73 Auxiliary roller 74 Airflow reinforcing rollers 74, 74 'Airflow reinforcing rollers 76, 77A, 77B Rectifying plate 100 Printer unit 500 Copier A Development downstream region C Transfer upstream region E Clearance H Contact portion

Japanese Patent Laid-Open No. 10-3220

Claims (17)

A developer carrying body that carries a developer containing toner on the surface and moves on the surface;
A developer having an opening that exposes a part of the surface of the developer carrier in the direction of movement of the developer carrier to the outside so as to face the surface of the latent image carrier that moves on the surface, and contains the developer in an internal space. With a case,
A developing device that develops a latent image on the latent image carrier with a developer carried on the developer carrier in a development region where the developer carrier and the latent image carrier are opposed to each other to form a toner image. In
The outer peripheral surface is exposed in a part of the passage space between the inner wall of the developing case and the surface of the developer carrying member facing each other with a predetermined gap along the surface of the developer carrying member, and the developing case It is arranged so that the outer peripheral surface is not exposed in the internal space of the image forming apparatus, or by rotating the rotating body arranged closer to the surface of the latent image carrying body than the passage space, A developing device comprising air flow increasing means for increasing a suction air flow for sucking toner existing in a developing downstream area adjacent to the downstream side of the body surface moving direction into the internal space of the developing case through the passage space. The developing device according to claim 1,
The developer is a two-component developer containing a toner and a magnetic carrier,
The developing device according to claim 1, wherein the rotating body includes a rotating body that is driven to rotate without generating a magnetic field that attracts the magnetic carrier. The developing device according to claim 1 or 2,
The rotating body is a recording medium that conveys a surface of the latent image carrier, a surface of a transfer medium to which a toner image formed on the surface of the latent image carrier is transferred, or a recording material to which the toner image is transferred. It is arranged at a position outside the developing case opposite to the surface of the material conveying member, and is in a rotating direction with respect to the surface moving direction of the transfer target or the recording material conveying member and the surface moving direction of the latent image carrier In contrast, the developing device includes an external rotating body that is driven to rotate in a direction opposite to the rotation direction. The developing device according to claim 3,
The developing device according to claim 1, wherein a gap between the external rotating body and the latent image carrier is wider than a gap in the passage space. The developing device according to claim 3 or 4,
The rotating body is located at a position closer to the transfer area for transferring the toner image formed on the surface of the latent image carrier to the transfer target body or the first recording material, separately from the external rotating body. The surface of the latent image carrier and the surface of the transferred body or the surface of the recording material transport member are arranged at positions outside the developing case, and the surface of the transferred body or the recording material transport member is moved. A developing device comprising an auxiliary rotator that rotates in a direction opposite to the direction of rotation with respect to the direction and in the direction of rotation with respect to the surface movement direction of the latent image carrier. The developing device according to any one of claims 3 to 5,
A developing device comprising an airflow guide member for guiding an airflow generated by the external rotating body to the passage space. The developing device according to claim 6,
The developing device according to claim 1, wherein one end of the airflow guide member is attached to an edge of the opening of the developing case, and the other end is in contact with the surface of the external rotating body. The developing device according to claim 6 or 7,
The developing device according to claim 1, wherein the airflow guide surface of the airflow guide member has a surface that inhibits adhesion of toner having a small charge amount. The developing device according to claim 6 or 7,
The developing device according to claim 1, wherein the airflow guide surface of the airflow guide member has a surface that inhibits adhesion of toner having a large charge amount. The developing device according to any one of claims 1 to 9,
The rotating body is disposed on the wall of the developing case so that a part of the rotating direction of the surface is exposed to the passage space, and is internally rotated to rotate in a rotating direction with respect to the surface moving direction of the developer carrier. A developing device comprising a body. The developing device according to claim 10,
A developing device comprising an air flow guide member for guiding an air flow generated by the internal rotating body to an internal space of the developing case. The developing device according to claim 10 or 11,
The internal rotating body has a part of the rotation direction of the surface of the latent image carrier. The recording medium transports the surface of the transfer target to which the toner image formed on the surface of the latent image carrier is transferred or the recording material to which the toner image is transferred. It is arranged so as to face the surface of the material conveying member, and is rotated in the direction of movement with respect to the surface of the developer carrier and in the direction of rotation with respect to the direction of movement of the surface of the transfer medium or recording material conveying member. A developing device that is rotationally driven. The developing device according to any one of claims 10 to 12,
The developing device characterized in that a gap RG between the internal rotating body and the developer carrying member satisfies a relationship of 0.5 ≦ (RG / CG) ≦ 2 with respect to the gap CG of the passage space. The developing device according to any one of claims 1 to 13,
The developing device according to claim 1, wherein the surface of the rotating body has a surface that inhibits adhesion of toner having a small charge amount. The developing device according to any one of claims 1 to 13,
The developing device according to claim 1, wherein the surface of the rotating body has a surface that inhibits adhesion of toner having a large charge amount. The developing device according to claim 9 or 15,
The developing device according to claim 1, wherein the surface that inhibits adhesion of toner having a large amount of charge is a conductive surface. In an image forming apparatus for finally transferring a toner image obtained by developing a latent image formed on a latent image carrier with a developing unit into a toner image onto a recording material,
An image forming apparatus using the developing device according to claim 1 as the developing unit.