JP4398709B2 - Developing device and image forming apparatus - Google Patents

Description

  The present invention relates to a developing device and an image forming apparatus, and more particularly to a configuration for preventing fouling caused by scattering of a developer.

  In an image forming apparatus such as a copying machine, a printer, or a facsimile machine, a visible image process is performed by developing an electrostatic latent image formed on a photosensitive member used as a latent image carrier with toner in a developer. Is called.

  In the developing device, a one-component or two-component developer is used, and in the case of using any developer, a developer sleeve which is a developer carrier, a developer agitating / mixing member, and a developer layer A thickness regulating member is provided, and each of these members is disposed in a housing that forms an outline of the developing device.

  The developing sleeve exposes a part of its surface from an opening provided in the housing, thereby bringing the developer carried on the surface into contact with the photosensitive member.

  By the way, when the electrostatic latent image formed on the photoreceptor is subjected to visible image processing, it is known that the charging characteristics of the supplied developer affect the reproducibility of image density and gradation. Yes. One of the causes for changing the charging characteristics of the developer is the environmental atmosphere, particularly humidity.

  On the other hand, as a problem that occurs during image formation, there is an adverse effect on the photosensitive member due to discharge products generated when the photosensitive member is charged. That is, when a discharge product such as NOx generated at the time of discharge adheres to the surface of the photoreceptor, the charging characteristics and the photosensitive characteristics are affected and the photoreceptor is degraded.

  Therefore, in order to solve such a problem, a configuration has been proposed in which air whose humidity is adjusted and managed is supplied into the developing device (for example, Patent Document 1).

On the other hand, in the developing device, the developing sleeve, the developer agitating / mixing member, and the layer thickness regulating member are housed in the housing, and only a part of the developing sleeve is exposed to the outside. Since the agent agitating / mixing member is a rotatable member, it is a member that generates airflow by moving the air of the surface layer portion with rotation. For this reason, the pressure in the housing changes and particularly tends to increase in pressure, so that the residual toner carried on the developing sleeve after passing through the developing area constituted by the area facing the photoconductor rises in the pressure in the housing. As a result, there is a risk of scattering from the opening of the housing to the outside.
The scattering of the toner from the housing side results in contamination of the peripheral portion including the photosensitive member.

  Conventionally, as a configuration for preventing the toner on the developing sleeve that has passed through the developing region from being scattered, the wall surface of the housing that accommodates the developing sleeve and the wall surface at the position facing the developing sleeve are separated from the developing sleeve. There is a configuration in which the gap is set larger than the gap between the wall surface of the housing and the photoconductor at a position facing the photoconductor (for example, Patent Document 2).

  In this configuration, the negative pressure tends to be caused by the area expansion that occurs when the toner on the developing sleeve that has passed through the developing region reaches the gap with the housing wall surface that is set larger than the gap with the photosensitive member. It is easy to be taken in the housing using.

  In addition to this configuration, a carrier recovery roller is provided at a rear position of the developing sleeve in the moving direction of the photosensitive member, and a rotation direction in which the carrier recovery roller moves in the same direction at a position facing the developing sleeve is set and the carrier recovery is performed. There is a configuration in which the gap between the roller and the photosensitive member is a gap through which air can flow (for example, Patent Document 3).

  In this configuration, the air flow generated by the rotation of the carrier recovery roller determines the opposing gap with the photosensitive member in the direction in which the air flows, thereby passing the developing area by making the opposing gap portion have a negative pressure tendency. The toner is sucked into the housing.

JP-A-6-19293 (paragraph "0011" column) JP 11-7191 A (paragraph "0016" column) JP 10-3220 A (paragraph “0025” column)

  When the toner that has passed through the developing area is sucked into the housing of the developing device due to a negative pressure tendency, if the toner in the developer that is supported on the surface of the developing sleeve in the form of a spike is all showing the same behavior Although suction by negative pressure is possible, actually, the behavior at the time of movement differs between the tip of the spike and the surface side of the developing sleeve.

FIG. 4 is a schematic diagram illustrating a state in which the developer moves while receiving a negative pressure from the housing side through the developing region.
In FIG. 4, the developer that has passed through the development region moves while being carried on the development sleeve B1, but the developer located at the tip of the ear is impacted by contact with the wall surface of the housing facing the development sleeve B1. May peel off.
The developer that is in a stand-up state on the surface of the developing sleeve generates a moment as the developing sleeve rotates. For this reason, the developer located at the tip of the ear has a larger impact force when contacting the wall surface of the housing than the base side of the ear, and part of the developer is easily peeled off when subjected to the impact.
When the charge amount of the toner contained in the developer decreases after passing through the development area, the toner is easily peeled off and easily floats by receiving an impact force. Such toner may be scattered from the housing to the outside due to the influence of the airflow described later.

  Although the air flow on the sleeve surface generated when the developing sleeve B1 rotates is a uniform flow on the developing sleeve surface side, the air that moves along the tip end side of the developer in the heading state contacts the wall surface of the housing. Due to the reaction force (collision force) applied to the flow, the flow becomes the reverse relationship. In particular, since there is an influence of the viscosity with the wall surface, the airflow when contacting the wall surface is different from the airflow on the developing sleeve surface side, and the speed may be canceled instantaneously.

  FIG. 5 shows that a negative pressure tendency occurs at the position where the developer that has passed through the development region enters the housing by the pumping action caused by the movement of the developer at the tip of the ear where such a phenomenon occurs. As described above, the developer flows backward toward the position where the developer enters the housing due to the negative pressure (indicated as a blown airflow in FIG. 5).

  At the position where the developer enters the housing, the peripheral air (air flow indicated by symbol PS in FIG. 4) is taken in by utilizing the pumping action of the developer carried on the developing sleeve, as shown in FIG. Because of the tendency, turbulent flow is likely to occur due to a mixture of air that moves with the developer that has flowed back on the surface of the developing sleeve B1 and air that is taken in, and the convective toner due to this turbulent flow causes the movement of the photoreceptor. When affected by the moving air (the air flow indicated by symbol PS1 in FIG. 5), the air is scattered outside the housing.

  As a result, a part of the toner contained in the developer that has passed through the development region may be scattered again from the housing, and the negative pressure for preventing the scattering may cause toner scattering instead.

  In view of the above problems in the conventional developing device, it is an object of the present invention to reliably prevent a part of the developer that passes through the developing region and is collected in the developing device from being scattered, and to form a latent image carrier background portion. It is an object of the present invention to provide a developing device and an image forming apparatus having a configuration capable of preventing the contamination of the peripheral portion including the contamination of the surface.

First aspect of the present invention, a housing constituting a substantially closed space except a position opposed to the image bearing member, a developing sleeve disposed to face the latent image bearing member within said housing, a toner A screw member that pumps the developer composed of a carrier toward the developing sleeve while stirring, a plurality of magnetic poles fixedly disposed in the developing sleeve, and the latent image carrying in the moving direction of the developer on the developing sleeve A film thickness regulating member disposed upstream of a position where the body and the developing sleeve face each other, and the plurality of magnetic poles are provided at least at a position where the latent image carrier and the developing sleeve face each other. A developing magnetic pole that forms a region, a conveying magnetic pole provided downstream of the developing magnetic pole in the rotation direction of the developing sleeve, and a repulsive magnetic field having the same polarity as the conveying magnetic pole and provided adjacent to the conveying magnetic pole In the developing device having the magnetic pole forming the formed region, the said housing is provided with a bypass passage,該迂circuit, movement the developer between the developing region and the conveyance pole before reaching to the conveying pole An opening provided in a position facing the developing sleeve on the upstream side in the direction to take in toner, and a wall surface at a position where the developer peeled off from the developing sleeve flows in the repulsive magnetic field forming region in the housing. It is characterized by communicating with the provided opening .

According to a second aspect of the present invention, in the developing device according to the first aspect, the wall surface at the position where the developer flows is a side wall surface adjacent to the screw member.
According to a third aspect of the invention, in the developing apparatus according to claim 1 Symbol mounting, opening for taking in the toner, characterized in that it is set the axial length more than a length in a longitudinal direction of the developing sleeve It is said.

According to a fourth aspect of the present invention, in the developing device according to any one of the first to third aspects, the opening for taking in the toner is in a direction opposite to the moving direction of the developing sleeve. It is characterized in that it is provided with a relationship capable of taking in the developer carried on the.

According to a fifth aspect of the present invention, in the developing device according to any one of the first to fourth aspects, the toner is taken in by being provided at a position facing the developing sleeve between the developing area and the conveying magnetic pole. The direction of the opening for performing the above operation is a tangential direction at a position where the conveyance magnetic pole of the developing sleeve is disposed, and is provided so as to face the direction opposite to the rotation direction of the developing sleeve. Yes.

According to a sixth aspect of the present invention, in the developing device according to any one of the first to fourth aspects, the wall surface of the housing facing the developing sleeve has a moving direction before the developer reaches the conveying magnetic pole. The facing gap between the upstream side and the downstream side in the developer moving direction is different from the opening for taking in the toner provided at a position facing the developing sleeve on the upstream side, and the opening is opposed to the facing side. provided the stepped portion gap changes is characterized in Rukoto.

Invention of claim 7, wherein, in the developing device according to claim 1, wherein said bypass passage, the area of the passage portion communicating in the developing device than the area of the opening for taking in the toner is larger It is characterized by.

According to an eighth aspect of the present invention, in the developing device according to the first or seventh aspect , a magnetic shield member is provided in a passage communicating with the developing device in the bypass .

According to a ninth aspect of the present invention, in the developing device according to any one of the first to eighth aspects, the gap between the entrance of the developer in the housing and the latent image carrier is G1, and the developing sleeve and G2 is a gap between the housing and the wall surface of the housing at a position before the developer passes through the opening for taking in the toner developer facing the developing sleeve, and for taking in the toner opposite to the developing sleeve. When the gap between the wall of the housing at the position where the developer has passed through the opening is G3,
G2 ≦ G3
This is characterized by the fact that the relationship is set .

According to a tenth aspect of the present invention, in the developing device according to any one of the first to seventh aspects, the gap between the entrance of the developer in the housing and the latent image carrier is G1, and the developing sleeve The gap between the housing wall surface at a position before the developer passes through the opening for taking in the toner opposite to this is G2, and the developing sleeve is opposed to this for taking in the toner. When the gap between the wall of the housing at the position where the developer has passed through the opening is G3 and the layer thickness of the developer carried on the developing sleeve that has passed through the developing region is t,
G1 ≧ G2-t
This is characterized by the fact that the relationship is set.

According to an eleventh aspect of the present invention, in the developing device according to any one of the first to seventh aspects, a gap between the entrance of the developer in the housing and the latent image carrier is G1, and the developing sleeve The gap between the housing wall surface at a position before the developer passes through the opening for taking in the toner opposite to this is G2, and the developing sleeve is opposed to this for taking in the toner. When the gap between the wall of the housing at the position where the developer has passed through the opening is G3 and the layer thickness of the developer carried on the developing sleeve that has passed through the developing region is t,
G2 <G3
This is characterized by the fact that the relationship is set.

The invention of claim 1 wherein, in the developing device according to one of claims 1 to 3, the gap between the inlet and the latent image bearing member on which the developer in the housing enters the G1, the developing sleeve opposite thereto and the gap between the wall surface of the housing at a position before the developer to the opening for taking in the toner passes G2, for capturing the toner faces the developing sleeve thereto When the gap between the wall of the housing at the position where the developer has passed through the opening is G3 and the layer thickness of the developer carried on the developing sleeve that has passed through the developing region is t,
G1> G2-t
This is characterized by the fact that the relationship is set.

The invention of claim 1 3, wherein, in the developing device according to one of claims 1 to 3, the openings in the positive position in the rotation direction of the screw member which is provided in the above developing apparatus- One of the openings is provided at a position where a negative pressure in the moving direction of the developing sleeve is provided.
A fourteenth aspect of the present invention is the developing device according to the thirteenth aspect, wherein the flow path includes one of openings provided at positions adjacent to the screw member and the layer thickness regulating member in the moving direction of the developer. And another one of the openings provided upstream of the developing region.
According to a fifteenth aspect of the present invention, in the developing device according to the fourteenth aspect of the present invention, one of the openings provided downstream of the layer thickness regulating member and upstream of the developing area in the moving direction of the developer is provided as an image. It is characterized in that a pipe communicating with a cleaning device provided in the forming apparatus is provided.
An invention according to claim 16 is an image forming apparatus using the developing device according to any one of claims 1 to 15 in an image forming apparatus.

According to the first, fifth , and sixth aspects of the present invention, the detour provided in the housing has the development on the upstream side in the movement direction before the developer reaches the conveyance magnetic pole between the development region and the conveyance magnetic pole. An opening provided at a position facing the sleeve to take in the toner and an opening provided on a wall surface at a position where the developer peeled off from the developing sleeve flows in the repulsive magnetic field forming region in the housing are communicated with each other. Therefore, it is possible to prevent the developer from being scattered by taking it in the opening for taking in the toner to be moved in the direction opposite to the moving direction of the developing sleeve and collecting it. In particular, in the invention described in claim 5, the wall surface of the housing that faces the developing sleeve is for taking in toner provided at a position facing the developing sleeve on the upstream side in the movement direction before the developer reaches the conveyance magnetic pole. Since the opposing gap between the upstream side and the downstream side in the developer moving direction is different from the opening of the developer, and the opening is provided at a step portion where the opposing gap changes, the developing sleeve moving direction The developer trying to move in the opposite direction can be collected and collected, so that the toner to be scattered can be captured well.

According to the third aspect of the present invention, since the opening for taking in the toner is longer than the axial length of the developing sleeve, it is possible to reliably prevent recovery leakage.

According to the fourth aspect of the present invention, since the opening for taking in the toner can take in the developer in a direction opposite to the moving direction of the developing sleeve, the negative pressure due to the pumping action generated by the movement of the developer is received. Since the developer that is about to be scattered can be collected on the side where the developer is about to be scattered, it is possible to reliably prevent the developer from being scattered outside.

According to the seventh aspect of the present invention, since the bypass route communicating with the opening is larger than the area of the opening, the developer entering the opening can be sucked by utilizing the pressure drop caused by the area expansion. Therefore, it is possible to prevent a decrease in recoverability.

According to the eighth aspect of the present invention, since the magnetic shield member is provided in the bypass route communicating with the inside of the developing device, a part of the developer peeled off from the developing sleeve is separated from the magnetic pole disposed on the developing sleeve. It is possible to prevent movement of the collected developer from being prevented from entering the detour due to the influence of the magnetic field lines.

According to the invention of claims 9 to 12 wherein, in the process of the developer is moved in the gap and the housing between the developing sleeve and the latent image bearing member at the time of reaching the entrance of the housing after the visible image processing By associating the gap between the developing sleeve and the housing, it is possible to dam the splash of the developer that moves into the housing, and it is possible to collect the developer at the dammed position. Thus, it is possible to reliably collect the developer to be scattered.

According to the second and thirteenth to fifteenth aspects of the present invention, the development is performed by utilizing the pressure form generated by the rotation of the screw member provided in the developing device or the rotating member provided in the cleaning device. It is possible to prevent a pressure increase in the apparatus and to generate a negative pressure to the opening.
According to the invention described in claim 16, the developer scattered after being able to surely prevent the developer entering the housing after finishing the visible image processing from being scattered in the direction opposite to the moving direction of the developing sleeve. It is possible to prevent contamination of the latent image carrier surface of the background and contamination of the peripheral portion.

  The best mode for carrying out the present invention will be described below with reference to the illustrated embodiments.

FIG. 1 shows an image forming apparatus to which a developing device according to an embodiment of the present invention is applied.
An image forming apparatus 1 shown in FIG. 1 has a tandem configuration in which a plurality of photoreceptors as latent image carriers capable of forming a color image corresponding to color separation are juxtaposed, and toner formed on each photoreceptor. The color printer is capable of forming a multicolor image by superimposing and transferring an image onto an intermediate transfer member and then transferring the superimposed image onto a sheet such as recording paper. In the present invention, the image forming apparatus is not limited to a color printer, but of course includes a color copying machine, a facsimile machine, and a printing machine.

In FIG. 1, in a color printer 1, an image forming unit 1A is positioned at a central portion in the vertical direction, a document feeding unit 1B is provided below the image forming unit 1A, and an original document table 1C1 is provided above the image forming unit 1A. Each of the scanning units 1C is arranged.
In the image forming unit 1A, a transfer unit composed of an intermediate transfer belt 2 having a horizontally extending surface is disposed. Above the intermediate transfer belt 2, an image of a color complementary to the color separation color is provided. The structure for forming is provided.

In the image forming unit 1A, photoreceptors 3B, 3Y, 3C, and 3M capable of carrying images of toners of complementary colors (yellow, magenta, cyan, and black) are juxtaposed along the extended surface of the intermediate transfer member 2. Has been. In the following description, in the case of contents common to all the photoconductors, the photoconductor is denoted by reference numeral 3.
Each of the photoconductors 3B, 3Y, 3C, and 3M is composed of a drum that can rotate in the same direction (counterclockwise in FIG. 1). A device 4, a writing device 5, a developing device 6, a primary transfer device 7 which is one of transfer bias applying means, and a cleaning device 8 are arranged (for the sake of convenience, the reference numerals of the respective devices are used for the photosensitive member 3B). B is shown).

  The intermediate transfer belt 2 constitutes a primary transfer portion to which a visible image from an image forming unit provided with each photoconductor is sequentially transferred. The intermediate transfer belt 2 is wound around a plurality of rollers 2A to 2C and is connected to the photoconductor. A roller 2C, which is configured to be movable in the same direction at the facing position and is different from the rollers 2A and 2B constituting the stretched surface, faces the secondary transfer device 9 with the intermediate transfer belt 2 interposed therebetween. In FIG. 1, reference numeral 10 indicates a cleaning device for the intermediate transfer belt 2.

The secondary transfer device 9 includes a transfer belt 9C that is wound around the charging drive roller 9A and the driven roller 9B and is movable in the same direction as the intermediate transfer belt 2 at the secondary transfer position where the secondary transfer device 9 is located. Yes.
In the secondary transfer device 9, the multi-color image superimposed on the intermediate transfer belt 2 is carried by batch transfer or carried in the process of conveying the recording sheet while electrostatically attracting the transfer belt 9 </ b> C by the charging drive roller 9 </ b> A. Each single color image can be transferred to a recording sheet.

A recording sheet is fed from the paper feeding unit 1B to the secondary transfer position.
The paper feed unit 1B includes a plurality of paper feed cassettes 1B1, a plurality of transport rollers 1B2 arranged in a transport path for recording sheets fed from the paper feed cassette 1B1, and a registration roller 1B3 positioned in front of the secondary transfer position. I have.
In this embodiment, in addition to the conveyance path of the recording sheet fed out from the sheet feeding tray 1B1, a recording sheet of a type not stored in the sheet feeding cassette 1B1 is fed to the sheet feeding unit 1B toward the secondary transfer position. A possible configuration is provided. As a configuration for this purpose, a manual feed tray 1A1 and a feeding roller 1A2 provided with a part of the wall surface of the image forming unit 1A so that it can be tilted are provided.
In the middle of the recording sheet conveyance path from the sheet feeding cassette 1B1 to the registration roller 1B3, the conveyance path of the recording sheet fed from the manual feed tray 1A1 joins, and the recording sheet fed from any of the conveyance paths is also a registration roller. Registration timing is set by 1B3.

  The writing device 5 (indicated by reference numeral 5B in FIG. 1 for convenience) has image information obtained by scanning a document on the document table 1C1 included in the document scanning unit 1C or an image output from a computer (not shown). The writing light is controlled by the information, and an electrostatic latent image corresponding to the image information is formed on the photoreceptors 3B, 3Y, 3C, and 3M.

The document scanning unit 1C is provided with a scanner 1C2 that exposes and scans the document on the document table 1C1, and an automatic document feeder 1C3 is disposed on the upper surface of the document table 1C1.
The automatic document feeder 1C3 has a configuration capable of reversing the document fed on the document table 1C1, and can perform scanning on both sides of the document.

  An electrostatic latent image formed on the photoconductor 3 (members indicated by reference numerals 3B, 3Y, 3C, and 3M in FIG. 1) formed by the writing device 5 is indicated by reference numeral 6B in FIG. 1 for convenience. ) To be subjected to a visible image processing and primary transfer to the intermediate transfer belt 2. When the toner images for the respective colors are superimposed and transferred onto the intermediate transfer belt 2, the secondary transfer device 9 performs secondary transfer on the recording sheet at once.

The unfixed image carried on the surface of the recording sheet that has been secondarily transferred is fixed by the fixing device 11.
Although not shown in detail, the fixing device 11 includes a belt fixing structure including a fixing belt heated by a heating roller and a pressure roller facing and abutting the fixing belt, and the contact between the fixing belt and the pressure roller. By providing the area, that is, the nip area, the heating area for the recording sheet can be expanded as compared with the fixing structure of another roller type.
The recording sheet that has passed through the fixing device 11 is switched in the transport direction by a transport path switching claw 12 disposed behind the fixing device 11, and is transported toward the paper discharge tray 13 and reversely transported. A transport direction is selected for the path RP.

  In the color printer 1 having the above-described configuration, the document placed on the document table 1C1 is exposed and scanned, or the image of the image information from the computer is used for statically charging the photosensitive member 3. After the electrostatic latent image is formed and the electrostatic latent image is subjected to visible image processing by the developing device 6, the toner image is primarily transferred to the intermediate transfer belt 2.

The toner image transferred to the intermediate transfer belt 2 is transferred as it is to the recording sheet fed out from the paper feed unit 1B in the case of a single color image, and the primary transfer is repeated in the case of a multicolor image. And then secondarily transferred to the recording sheet at once.
The recording sheet after the secondary transfer is fixed with an unfixed image by the fixing device 11 and then fed to the paper discharge tray 13 or reversed and fed again toward the registration roller 1B3.

  In FIG. 1, although not shown in detail, the intermediate transfer belt 2 includes a base layer composed of a base portion made of a material that hardly stretches, such as a fluorine-based resin with a small elongation or a rubber material with a large elongation, and a canvas, and the like. And an elastic layer made of fluorine-based rubber or acrylonitrile-butadiene copolymer rubber provided on the upper surface. The surface of the elastic layer is provided with a coat layer that is coated with a fluororesin to improve smoothness.

The intermediate transfer belt 2 is wound around at least a pair of support rollers 2A and 2B and a roller 2C having a backup function, and is driven by the counterclockwise rotation of the drive roller 2A.
A surface extended between the support rollers 2A and 2B, that is, a plane having no curvature, faces the photoreceptors 3B, 3Y, 3C, and 3M of each image forming unit.
A transfer roller 7 for electrostatically transferring a visible image on the photoconductor is disposed at a position facing each photoconductor with the intermediate transfer belt 2 interposed therebetween.

In the image forming apparatus 1 shown in FIG. 1, the photoconductor positioned in the image forming unit 1A is accommodated in the process cartridge shown in FIG.
FIG. 2 shows a process cartridge (indicated by reference numeral PCB for the sake of convenience) for the photosensitive member indicated by reference numeral 3B in the image forming section 1A shown in FIG. The constituting housing can be hermetically sealed except for a portion where the developing sleeve 6B1 facing the photoconductor 3B is exposed, and inside the charging device, the image forming process is performed for the photoconductor 3B and the like. 4B, a developing device 6B, and a cleaning device 8B (not shown in FIG. 2 for convenience) are accommodated.

The developing device 6B in the process cartridge PCB can form a magnetic brush using a two-component developer in which a toner and a magnetic carrier are mixed. As a configuration for this, a fixed magnetic pole is provided inside. And a pair of screw members 6B2 and 6B3 provided with an auger that makes the developer agitating and conveying direction opposite to each other. In this embodiment, a toner called a polymerization toner manufactured by a chemical method is used as the toner.
The developing sleeve 6B1 is exposed from the exposure opening formed in the housing so that the magnetic brush can come into contact with the photoreceptor 3B, and the developer before coming into contact with the photoreceptor 3B is pumped up by the screw member 6B2. It is designed to be carried on the surface.
The layer thickness of the magnetic brush carried on the peripheral surface of the developing sleeve 6B1 is regulated by the doctor blade 6B4 before reaching the developing region (developing nip) DP in contact with the electrostatic latent image on the photoreceptor 3B. It has become.

The fixed magnetic pole used for forming the magnetic brush on the peripheral surface of the developing sleeve 6B1 includes a magnetic pole for forming the transport region DT by adjoining different polarities for transporting the pumped developer, and a layer thickness. A magnetic pole (N pole in the figure) that constitutes the development area DP in which the regulated developer is maintained in a spiked state, and the same polarity at positions facing each other after passing through the development area DP (see FIG. In this case, the magnetic poles constituting the developer dropping repulsive magnetic field forming region DD adjacent to each other are used.

The developer pumped up by the screw member 6B2 and carried on the peripheral surface of the developing sleeve 6B1 is regulated in layer thickness by the blade 6B4 and then brought into contact with the electrostatic latent image on the photoreceptor 3B for visible image processing. Provided.
After passing through the developing area DP, the developer remaining in the developing sleeve 6B1 is peeled off from the developing sleeve 6B1 by the repelling magnetic field and falls when it reaches the repelling magnetic field forming area DD for dropping the developer.
The developing sleeve 6B1 again carries the developer on the peripheral surface by pumping up from the screw member 6B2, and thereafter repeats the layer thickness regulation and the passage of the developing region DP and the passage of the repelling magnetic field forming region DD for dropping the developer.

  A feature of the embodiment shown in FIG. 2 is that it has a configuration that prevents the developer entering the housing 6H of the developing device 6B after passing through the developing region DP from being scattered outside the developing device 6B. Hereinafter, this configuration will be described.

  In FIG. 2, the housing 6H of the developing device 6B faces the tip of the magnetic brush carried by the developing sleeve 6B1 that has passed the developing region DP after finishing the visible image processing on the wall surface facing the developing sleeve 6B1. An opening 6P1 is provided.

  As shown in FIG. 3, the opening 6P1 has an entrance through which the developer carried on the developing sleeve 6B1 that has passed through the developing region DP enters the housing 6H, and the conveying and adjacent homopolar poles disposed in the developing sleeve 6B1. Among the transfer magnetic poles constituting the developer dropping repulsive magnetic field forming region DD by the magnetic poles of the magnetic poles, the magnetic poles adjacent to the development main pole constituting the development region DP (for convenience, indicated by reference numeral S1 in FIG. 3) It is provided in between. That is, the opening 6P1 is located upstream in the moving direction of the developing sleeve 6B1 with respect to one repulsive magnetic field forming magnetic pole (S1) located downstream of the developing main pole in the moving direction of the developing sleeve 6B1. .

  A suction force acts on the opening 6P1, and as a configuration for that purpose, the opening 6P1 communicates with the inside of the developing device or the outside of the developing device (not shown).

  The embodiment shown in FIG. 3 shows a configuration in which the opening 6P1 communicates with the developing device 6B. In this configuration, the developer peeled off from the developing sleeve in the repulsive magnetic field forming region DD in the developing device 6B. The wall surface of the housing 6H corresponding to the flowing position (the position indicated by reference numeral 6H1 in FIG. 3) is communicated by a detour 6P3 having an opening 6P2.

Tei Ru opening 6P1 provided on the side facing the magnetic brush tip is carried on the developing sleeve 6B1 is provided to collect the toner in the magnetic brush tip. That is, the magnetic brush carried on the developing sleeve 6B1 that has passed through the developing region DP tends to have a negative pressure on the downstream side in the moving direction due to the pumping action that occurs when moving between the opposing wall surfaces of the housing 6H. . For this reason, the tip of the magnetic brush colliding with the wall surface of the housing 6H collapses due to the impact force, and a part of the toner contained in the magnetic brush moves toward the entrance side of the housing 6H due to the negative pressure tendency, and the developing device 6B It becomes easy to scatter outside .

  In this embodiment, the opening 6P1 is provided for the purpose of collecting the toner that is to be scattered due to such a phenomenon. Hereinafter, the installation conditions of the opening 6P1 will be described.

  First, the opening 6P1 is made longer than the axial length of the developing sleeve 6B1, and with respect to the position of the magnetic field (S1) for forming the repulsive magnetic field, which is the position where the height of the magnetic brush is highest. It is provided on the upstream side of the developer moving direction, and further at a position where the developer can be taken in a direction opposite to the moving direction of the developing sleeve 6B1.

  In the embodiment shown in FIG. 3, in order to set the position where the developer can be taken in, the gap between the entrance of the magnetic brush into the housing 6H and the photoreceptor 3B is G1, and the magnetic brush passes through the opening 6P1. The gap between the developing sleeve 6B1 and the wall surface of the housing 6H in the previous stage is G2, and the gap between the developing sleeve 6B1 and the housing at the position where the developer has passed through the opening 6P1 is G3. When the layer thickness of the magnetic brush carried on the developing sleeve 6B1 at the stage before reaching the magnetic field forming region DD is t, the relationship of G2 ≦ G3 and G1 ≧ G2-t is established.

  With this installation condition, as shown in FIG. 3, the opening 6P1 takes in the developer in a direction opposite to the moving direction of the developing sleeve 6B1 at the step formed on the front side of the repulsive magnetic field forming magnetic pole (S1). It is provided in a state where it can be.

  The installation position of the opening 6P1 corresponds to a position where the developer trying to move in the direction opposite to the moving direction of the developing sleeve 6B1 based on the negative pressure tendency is dammed up due to the above-described gap relationship. This makes it easier to take in the developer at the tip of the magnetic brush.

  The case where the equal sign is established in the relationship of the gaps indicated by reference numerals G1, G2, and G3 means that there is no step, and in this case, the development in which the opening 6P1 is located at the tip of the magnetic brush. It takes the form of a so-called pitfall that sucks and drops the agent.

On the other hand, the detour 6P3 having the opening 6P1 at one end has a larger area than the opening 6P1. As a result, the developer entering the opening 6P1 has a stronger negative pressure tendency due to a pressure drop in the detour having a larger area than the opening 6P1, and the suction action is enhanced. As a result, the efficiency of forcibly attracting scattered toner when the magnetic brush carried on the developing sleeve 6B1 that has passed through the developing region DP collides with the wall surface of the housing 6H and collapses can be enhanced.

  In the detour 6P3, a magnetic shield member DM (see FIG. 2) is provided in the vicinity of the opening 6P2 on the wall surface 6H1 side of the housing 6H corresponding to a position where the peeled developer flows. As a result, the influence of the magnetic lines of force from the repulsive magnetic field forming magnetic pole S1 can be prevented from reaching the detour 6P3, so that the recovery efficiency is prevented without hindering the movement of the developer moving in the detour 6P3. Can be prevented.

Since the present embodiment is configured as described above, the developer in the magnetic brush passing through the developing region DP and carried on the developing sleeve 6B1 enters from the entrance of the housing 6H of the developing device 6B, and the developing sleeve 6B1. It moves in the housing 6H opposite to.
When the magnetic brush that has entered the housing 6H collides with the wall surface of the housing 6H that faces the developing sleeve 6B1, the tip of the magnetic brush collapses, and the developer pumping action that occurs in the process in which the developer contained in the tip moves so far Scatters toward the rear in the direction of movement, which is a negative pressure-prone part.

The portion where the tip of the magnetic brush is most prominently collapsed is the position facing the repulsive magnetic field forming magnetic pole S1 corresponding to the position where the brush tip is the largest. Therefore, although the developer in the magnetic brush colliding with the wall surface of the housing 6H facing the magnetic pole S1 is scattered backward in the movement direction, an opening 6P1 having a suction action is provided at the rear position. It is taken in and collected by the opening 6P1.
The developer collected in the opening 6P1 is discharged into the developing device 6B through the bypass 6P3 due to the negative pressure tendency caused by the pressure drop generated in the opening 6P2 of the bypass 6P3. In particular, when the above-described gap relationship is used, the opening 6P1 is located at a step portion where the developer to be scattered can be dammed up. Will be taken in and recovered

  In the configuration of the embodiment shown in FIG. 3, in the housing 6H of the developing device 6B, the humidity is adjusted toward the position where the developer carried on the developing sleeve 6B1 that has passed through the developing region DP enters the housing 6H. A humidity control air flow path 6S1 through which air (humidity control air) can flow is provided, and the humidity control air can be taken in by utilizing the negative pressure due to the pumping action of the developer.

  The conditioned air is supplied to the periphery of the development area DP, and prevents the development efficiency from deteriorating due to a change in the charging characteristics of the developer. In addition, humidity-controlled air can be supplied not only in the vicinity of the development area DP but also to the peripheral surface of the photoreceptor 3B that has passed through the development area DP in the moving direction of the photoreceptor 3B. For this reason, a predetermined gap is provided in a part of the housing of the developing device 6B, that is, a range along the peripheral surface of the photoreceptor 3B that moves after passing through the developing region DP, and a flow path of the humidity control air is configured. In accordance with the movement of the photoconductor 3B, a shape in which the humidity-controlled air can move on the surface is set.

  Preliminary supply of humidity-controlled air greatly contributes to promoting stabilization of charging characteristics when the toner used in the developing device is a polymerized toner that is susceptible to humidity.

Further, as a configuration for obtaining the suction action with respect to the opening 6P1, as shown in FIG. 2 , one of the openings is provided at a position where the pressure is positive in the rotation direction of the screw member 6B2 used for stirring and mixing the developer. A flow path 6S2 having the other opening is provided at a position where the negative pressure is generated by the rotation of the developing sleeve 6B1, and a pipe PP is provided as a flow path for communicating the flow path 6S2 and a cleaning device (not shown). May be.

  By adopting such a configuration, the pressure form generated by the rotating member provided in the cleaning device is used to prevent the pressure in the developing device 6B from increasing, and at the same time, the suction negative pressure is generated in the opening 6P1. It can also be used as a source.

1 is a schematic diagram of an image forming apparatus to which a developing device according to an embodiment of the present invention is applied. It is a schematic diagram for explaining a process cartridge in which a developing device according to an embodiment of the present invention is incorporated. FIG. 3 is a partially enlarged view for explaining a main configuration of the developing device shown in FIG. 2. It is a schematic diagram for demonstrating the malfunction which arises in the conventional developing device. FIG. 5 is a schematic diagram for explaining the behavior of the developer in the developing device shown in FIG. 4.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 3B Photosensitive body 6B Developing apparatus 6B1 Developing sleeve 6B2, 6B3 Screw member 6H Housing 6H1 Wall surface from which developer peels 6P1 Opening 6P2 Other opening 6P3 Detour G1 Entrance of magnetic brush into housing 6H and photosensitive body 3B G2 G2 Gap between the developing sleeve 6B1 and the wall surface of the housing 6H before the magnetic brush passes through the opening 6P1 G3 Between the developing sleeve 6B1 and the housing at a position where the developer passes through the opening 6P1 The gap t of the magnetic brush carried on the developing sleeve 6B1 in the stage before reaching the repulsive magnetic field forming region DD DP developing region DD Developer repelling magnetic field forming region DM Magnetic shield member

Claims (16)

Stirring a developer comprising a housing that substantially forms a sealed space except for a position facing the latent image carrier, a developing sleeve disposed in the housing so as to face the latent image carrier, and a toner and a carrier. The screw member that pumps up toward the developing sleeve, a plurality of magnetic poles fixedly arranged in the developing sleeve, and the latent image carrier and the developing sleeve in the moving direction of the developer on the developing sleeve A film thickness regulating member disposed upstream of the position, and the plurality of magnetic poles are provided at least at a position where the latent image carrier and the developing sleeve face each other, and form a developing magnetic pole, A conveying magnetic pole provided downstream of the developing magnetic pole in the rotating direction of the developing sleeve, and a magnetic pole having the same polarity as the conveying magnetic pole and provided adjacent to the conveying magnetic pole to form a repulsive magnetic field forming region In the developing device having,
The housing is provided with a bypass,
The detour is provided at a position facing the developing sleeve on the upstream side in the movement direction before the developer reaches the transporting magnetic pole between the developing area and the transporting magnetic pole to take in the toner. A developing device, wherein the opening communicates with an opening provided in a wall surface at a position where the developer peeled off from the developing sleeve flows in the repulsive magnetic field forming region in the housing. The developing device according to claim 1,
The developing device according to claim 1, wherein a wall surface at a position where the developer flows is a side wall surface adjacent to the screw member. The developing device according to claim 1 or 2,
The developing device is characterized in that the opening for taking in the toner has a length in the longitudinal direction that is equal to or longer than the axial length of the developing sleeve. The developing device according to any one of claims 1 to 3,
The opening for taking in the toner is provided so as to be able to take in the developer carried on the developing sleeve in a direction opposite to the moving direction of the developing sleeve. Development device. The developing device according to claim 1,
The direction of the opening, which is provided at a position facing the developing sleeve between the developing area and the conveying magnetic pole and for taking in the toner, is a tangential direction at the position where the conveying magnetic pole of the developing sleeve is disposed. A developing device, wherein the developing device is provided so as to face in a direction opposite to a rotation direction of the developing sleeve. The developing device according to claim 1,
The wall surface of the housing facing the developing sleeve is bordered by an opening for taking in the toner provided at a position facing the developing sleeve on the upstream side in the movement direction before the developer reaches the transport magnetic pole. The developing device is characterized in that the opposing gap between the upstream side and the downstream side in the developer moving direction is different, and an opening for taking in the toner is provided in a step portion where the opposing gap changes. . The developing device according to claim 1,
The developing device according to claim 1, wherein the bypass route has an area of a passage portion communicating with the developing device larger than an area of an opening for taking in the toner. The developing device according to claim 1 or 6,
A developing device characterized in that a magnetic shield member is provided in a passage communicating with the developing device in the bypass. The developing device according to claim 1,
The gap between the entrance of the developer in the housing and the latent image carrier is G1, and the housing at a position before the developer passes through the developing sleeve and the opening for taking in the toner opposite to the developing sleeve. When the gap between the developing wall and the wall surface of the housing at the position where the developer has passed through the opening for taking in the toner opposite to the developing sleeve is G3,
G2 ≦ G3
A developing device characterized in that the relationship is established. The developing device according to claim 1,
The gap between the entrance of the developer in the housing and the latent image carrier is G1, and the housing at a position before the developer passes through the developing sleeve and the opening for taking in the toner opposite to the developing sleeve. G2 is the gap between the developing wall and G3, and the gap between the developing sleeve and the wall of the housing at the position where the developer has passed through the opening for taking in the toner is G3. When t is the layer thickness of the developer carried on the developing sleeve that has passed,
G1 ≧ G2-t
A developing device characterized in that the relationship is established. The developing device according to any one of claims 1 to 3,
The gap between the entrance of the developer in the housing and the latent image carrier is G1, and the housing at a position before the developer passes through the developing sleeve and the opening for taking in the toner opposite to the developing sleeve. G2 is the gap between the developing wall and G3, and the gap between the developing sleeve and the wall of the housing at the position where the developer has passed through the opening for taking in the toner is G3. When the layer thickness of the developer carried on the developing sleeve that has passed is t,
G2 <G3
A developing device characterized in that the relationship is established. The developing device according to any one of claims 1 to 3,
The gap between the entrance of the developer in the housing and the latent image carrier is G1, and the housing at a position before the developer passes through the developing sleeve and the opening for taking in the toner opposite to the developing sleeve. G2 is the gap between the developing wall and G3, and the gap between the developing sleeve and the wall of the housing at the position where the developer has passed through the opening for taking in the toner is G3. When t is the layer thickness of the developer carried on the developing sleeve that has passed,
G1> G2-t
A developing device characterized in that the relationship is established. The developing device according to any one of claims 1 to 3,
One opening is provided at a position where the positive pressure is provided in the rotation direction of the screw member provided in the developing device, and the other opening is provided at a position where the negative pressure is provided in the moving direction of the developing sleeve. A developing device comprising a flow path. The developing device according to claim 13, wherein
The flow path includes one of an opening provided at a position adjacent to the screw member, and an opening provided downstream of the layer thickness regulating member in the developer moving direction and upstream of the developing region. And a developing device. The developing device according to claim 14, wherein
A pipe is provided for communicating one of the openings provided downstream of the layer thickness regulating member in the moving direction of the developer and upstream of the developing region with a cleaning device provided in the image forming apparatus; A developing device.   An image forming apparatus using the developing device according to claim 1.

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