JP2021157017A - Developing device - Google Patents

Abstract

To provide an image forming apparatus and a developing device that can prevent scattering of toner to the outside of the developing device.SOLUTION: An image forming apparatus has: a photoreceptor; a developing device that stores developer; a developing sleeve that rotates while carrying the developer to supply the developer to the photoreceptor in a supply area; an outer cover member that is arranged with a gap on the downstream side of the supply area A; and an inner cover member that is arranged further downstream with gaps respectively from the developing sleeve and the outer cover. In an exhaust path between the developing sleeve and the outer cover, the gaps near the ends are reduced compared with that near the center in the longitudinal direction of the developing sleeve.SELECTED DRAWING: Figure 8

Description

The present invention relates to an image forming apparatus that forms an image using an electrophotographic method, and is particularly applicable to an image forming apparatus such as a copier, a printer, a fax machine, or a multifunction device having a plurality of these functions. Regarding.

An image forming apparatus using an electrophotographic method called a laser printer or a laser multifunction device used in office or on-demand light printing generally forms an image by the following process.

After the surface of the photoconductor, which is the image carrier, is uniformly charged, it is exposed using a laser or an LED according to the image information input from a PC or the like. In the exposed region, the electric charge generated in the photoconductor cancels the charge, so that an electrostatic latent image corresponding to the image information is formed on the surface of the photoconductor. The formed electrostatic latent image is made to be visualized as a toner image by electrostatically adhering toner, which is a coloring resin, by a developing device. The developed toner image is transferred to a recording medium such as paper by a transfer device via an intermediate transfer body. Then, the toner image transferred to the recording medium is melt-fixed to the recording medium by using heat and pressure by the fixing device, and becomes a final output product. After the transfer, the photoconductor removes the residual toner with a static eliminator, and further cleans the surface of the photoconductor with a cleaning device to prepare for the next image forming process.

Among the developing devices of such image forming devices, some models that perform high-speed output and high-quality output employ a two-component developing method. The two-component developing device is a method in which toner and carriers, which are magnetic particles, are agitated and conveyed in the developing device to be triboelectrically charged, and only the toner is attached to the electrostatic latent image in the developing unit.

More specifically, the developing apparatus has two or more screws for stirring and transporting the toner and the carrier. The two screws are arranged in the developing apparatus so that the transport directions are opposite to each other. A wall surface is formed between the two screws, and the wall surfaces at both ends of the screws are removed. As a result, the developer circulates inside the developing apparatus.

In the image forming apparatus, high speed and high image quality of the output image are required, and maintenance is required to be simplified. One of the simplifications of this maintenance is the reduction of toner contamination inside the image forming apparatus. If the inside of the image forming apparatus is contaminated with toner, not only defects such as stains on the output image but also cleaning is required when replacing the developing unit and the photosensitive drum unit. Further, if it adheres to each drive system, slippage or the like may occur and accurate drive may not be possible.

As one of the causes of toner contamination inside the image forming apparatus, there is a problem that toner is scattered from the inside of the developing apparatus in the two-component development. Normally, since the toner and the carrier are triboelectrically charged as described above inside the developing apparatus, the toner adheres to the carrier by electrostatic force. However, some impact may release this adhesion, or toner with weak electrostatic adhesion may be released from the carrier. As the developing device operates, a pressure difference is generated between the inside and the outside, and when the pressure inside the developing device is high, this free toner is discharged together with air, and the inside of the device may be contaminated with toner.

As a countermeasure against the toner scattering, since the toner has an electric charge due to triboelectric charging, a method of removing the toner from the exhaust air by applying a voltage to the air discharge path from the inside of the developing device is effective. Prior art has been presented for this method.

In Patent Document 1, by providing a decompression unit that discharges the air of the developing container to the outside of the machine to reduce the internal pressure and a filter installed inside the decompression unit, the filter collects toner and does not contain free toner. It is proposed to suppress toner scattering by discharging the toner to the outside.

In Patent Document 2, a conductive member is arranged to face the developing sleeve, and a voltage having the same polarity as the triboelectric polarity of the developer is applied to the conductive member. As a result, a potential difference is generated between the conductive member and the developing sleeve, the toner is pressed toward the developing sleeve, and the toner is removed from the exhaust air. As a result, toner scattering can be effectively suppressed.

Japanese Unexamined Patent Publication No. 2009-22307 Japanese Unexamined Patent Publication No. 8-171282

However, in the configuration proposed in Patent Document 1, the decompression section and the exhaust section are installed, which causes an increase in size and the number of parts, and the decompression effect decreases as the toner accumulates in the filter. Replacement work is required.

Further, while the method as in Patent Document 2 is very effective, a dedicated substrate and a conductive path are required for applying a voltage to the conductive portion, which causes an increase in cost.

Therefore, an object of the present invention is to provide a developing apparatus capable of reducing toner scattering without increasing the size and cost of the apparatus.

In order to achieve the above object, the developing apparatus of the present invention includes a photoconductor and a developing apparatus, and the developing apparatus further includes a developing container containing a developing agent, a developing sleeve for supplying toner to the photoconductor, and developing. Includes a screw that stirs and conveys the agent and supplies the developer to the developing sleeve. The gap between the developing container and the wall surface closest to the developing container downstream of the toner supply region of the developing sleeve is characterized in that the gap is formed narrower at both ends in the axial direction of the developing sleeve than at the central portion.

According to the present invention, it is possible to provide an image forming apparatus and a developing apparatus capable of reducing toner scattering to the outside of the developing apparatus with an inexpensive configuration.

It is a schematic cross-sectional view which shows the whole structure of the image forming apparatus which concerns on this invention. It is a schematic cross-sectional view which shows the image forming part of the image forming apparatus which concerns on this invention. It is a front sectional view of the developing apparatus of the image forming apparatus which concerns on this invention. It is a top sectional view of the developing apparatus of the image forming apparatus which concerns on this invention. It is sectional drawing of the supply structure of the image forming apparatus which concerns on this invention. It is a schematic diagram of the airflow of the developing apparatus of the image forming apparatus which concerns on this invention. It is sectional drawing around the developing sleeve which concerns on this Example 1. It is sectional drawing around the central part of the developing sleeve which concerns on this Example 1. It is a schematic diagram of the air flow around the junction flow path which concerns on this Example 1. It is a top view of the developing apparatus which concerns on this Example 1. It is sectional drawing around the development sleeve end portion which concerns on this Example 1. FIG. It is sectional drawing around the central part of the developing sleeve which concerns on Example 2. FIG. It is sectional drawing around the end of the developing sleeve which concerns on Example 2. FIG.

Hereinafter, the image forming apparatus according to the present invention will be described in detail.

[Overall configuration and operation of the image forming apparatus]
First, the overall configuration and operation of the image forming apparatus of the present embodiment will be described. FIG. 1 shows an overall schematic view of an electrophotographic image forming apparatus. FIG. 2 shows a schematic configuration of an image forming unit. The image forming apparatus 100 of the present embodiment records according to image information from a document reading device connected to the image forming apparatus 100 main body or a host device such as a personal computer PC communicably connected to the image forming apparatus 100 main body. An image is formed on the material 10. For example, recording a four-color full-color image of yellow (Y), magenta (M), cyan (C), and black (K) on a recording sheet, plastic sheet, cloth, etc. using an electrophotographic image forming means described later. It is formed on the material 10.

The image forming apparatus 100 of the present embodiment is a quadruple tandem type image forming apparatus 100, and forms first, second, and third images of yellow, magenta, cyan, and black as a plurality of image forming portions, respectively. , Has a fourth image forming unit PY, PM, PC, PK. Then, while the intermediate transfer belt 51, which is the intermediate transfer body included in the transfer device 5, moves in the direction of the arrow in FIG. 1 and passes through the image forming portions PY to PK, each image forming portion PY is placed on the intermediate transfer belt 51. Images of each color are superimposed in ~ PK. Then, a recorded image is obtained by transferring the multiple toner images superimposed on the intermediate transfer belt 51 to the recording material 10.

In the following embodiments, the configurations of the image forming units PY, PM, PC, and PK are substantially the same except that the development colors are different. Hereinafter, when no particular distinction is required, the subscripts Y, M, C, and K given to the symbols to indicate that the elements belong to any of the image forming units PY to PK are omitted, and the image forming unit P is omitted. It will be explained comprehensively as follows.

The image forming unit P has a photosensitive drum 1 made of a drum-shaped photoconductor as an electrostatic latent image carrier that supports an electrostatic latent image according to image information. A charging roller 2 serving as a charging device, an exposure device 3 composed of a laser exposure optical system, a developing device 4, a transfer device 5, and a cleaning device 7 are provided on the outer periphery of the photosensitive drum 1. Reference numeral 8 is a toner cartridge. The transfer device 5 has an intermediate transfer belt 51 as an intermediate transfer body. The intermediate transfer belt 51 is hung around a plurality of rollers and rotates in the direction of the arrow in FIG. Further, the primary transfer member 52 is arranged at a position facing each photosensitive drum 1 via the intermediate transfer belt 51. Further, the secondary transfer member 53 is provided at a position facing one of the rollers around which the intermediate transfer belt 51 is hung.

At the time of image formation, first, the surface of the rotating photosensitive drum 1 is uniformly charged by the charging roller 2. Next, the surface of the charged photosensitive drum 1 is scanned and exposed by the exposure apparatus 3 according to the image information signal to form an electrostatic latent image on the photosensitive drum 1. The electrostatic latent image formed on the photosensitive drum 1 is visualized as a toner image by the toner of the developing agent using the developing device 4.

The toner image formed on the photosensitive drum 1 is displayed on the intermediate transfer belt 51 by the action of the primary transfer bias voltage applied to the primary transfer member 52 at the primary transfer nip portion where the intermediate transfer belt 51 and the photosensitive drum 1 abut. Primary transfer to. For example, when forming a four-color full-color image, a toner image is sequentially transferred from each photosensitive drum 1 onto the intermediate transfer belt 51 from the image forming unit PY, and the four-color toner images are superimposed on the intermediate transfer belt 51. Multiple toner images are formed.

On the other hand, the recording material 10 housed in the feed cassette 9 is brought into contact with the secondary transfer nip portion where the intermediate transfer belt 51 and the secondary transfer member 53 are brought into contact with each other by a pickup roller, a transfer roller, a resist roller, or the like. It is conveyed in synchronization with the toner image above. Then, the multiple toner image on the intermediate transfer belt 51 is transferred onto the recording material 10 by the action of the secondary transfer bias voltage applied to the secondary transfer member 53 at the secondary transfer nip portion.

After that, the recording material 10 separated from the intermediate transfer belt 51 is conveyed to the fixing device 6. The toner image transferred onto the recording material 10 is melt-mixed by being heated and pressurized by the fixing device 6, and is fixed on the recording material 10. After that, the recording material 10 is discharged to the outside of the machine.

The deposits such as toner remaining on the photosensitive drum 1 after the primary transfer step are collected by the cleaning device 7. As a result, the photosensitive drum 1 is prepared for the next image forming step. Further, deposits such as toner remaining on the intermediate transfer belt 51 after the secondary transfer step are removed by the intermediate transfer cleaner 54.

The image forming apparatus 100 of the present embodiment forms a monochromatic or multicolored image by using an image forming unit for some of desired monochromatic or four colors, such as a black monochromatic image. Is also possible.

[Basic configuration of developing device]
Next, the configuration of the developing apparatus 4 will be further described with reference to FIGS. 3 and 4.

The developing apparatus 4 has a developing container 41 that houses a two-component developer including a non-magnetic toner and a magnetic carrier. The developing container 41 is provided with a developing sleeve 44 as a developing agent carrier and a magnet roll 44a made of a magnet fixedly arranged in the developing sleeve 44 as a magnetic field generating means. Further, a developing blade 42 that forms a thin layer of the developing agent on the surface of the developing sleeve 44, and screw members 41d and 41e that agitate and convey the developing agent in the developing container 41 are arranged.

The inside of the developing container 41 is divided into a developing chamber 41a and a stirring chamber 41b by a partition wall 41c extending in the vertical direction. Then, the screw member 41d is arranged in the developing chamber 41a, and the screw member 41e is arranged in the stirring chamber 41b. At both ends of the partition wall 41c in the longitudinal direction (left side and right side in FIG. 3), delivery portions 41f and 41g are provided to allow the developing agent to pass between the developing chamber 41a and the stirring chamber 41b.

In the present embodiment, the screw members 41d and 41e are formed by providing spiral blades as transport portions around the shaft (rotational shaft) of the magnetic material, respectively. Further, in addition to the spiral blade, the screw member 41e is provided with a stirring rib 41e1 that protrudes from the shaft in the radial direction and has a predetermined width in the transport direction of the developer. The stirring rib 41e1 stirs the developer as the shaft rotates.

The screw member 41d stirs and conveys the developer in the developing chamber 41a. Further, the screw member 41e equalizes the toner concentration under automatic toner replenishment control (hereinafter referred to as "ATR: Automatic Toner Replenisher" control). That is, the toner supplied in the toner replenishment unit 46 and the developer already in the stirring chamber 41b and the developer composed of the magnetic carrier are stirred and conveyed to make the toner concentration uniform.

The screw members 41d and 41e are arranged substantially in parallel along the rotation axis direction of the developing sleeve 44. Then, the screw member 41d and the screw member 41e convey the developer in opposite directions along the rotation axis direction of the developing sleeve 44. In this way, the developing agent is circulated in the developing container 41 by the screw members 41d and 41e via the delivery portions 41f and 41g. That is, the developer in the developing chamber 41a whose toner is consumed in the developing process due to the conveying force of the screw members 41d and 41e and whose toner concentration is lowered is passed through one of the transfer portions 41f (left side in FIG. 3) to the stirring chamber. Move into 41b.

Further, a toner replenishment port 46 for replenishing toner is provided in the uppermost stream portion of the stirring chamber 41b, and the replenishment developer container 8 serving as a replenishment container for accommodating the replenishment toner shown in FIG. 5 is provided. I am in contact with. Then, according to the image ratio at the time of image formation, the inductance sensor 45 as the toner density sensor, and the density detection result of the patch image by the patch image density detection sensor (not shown) by the above-mentioned ATR control, the replenishing developer container 8 The operation is controlled, and the toner is replenished to the most upstream portion of the stirring chamber 41b.

Then, the developer in the stirring chamber 41b to which the toner is replenished and stirred moves to the developing chamber 41a via the other delivery portion 41g (right side in FIG. 3). Further, the developing chamber 41a of the developing apparatus 4 has an opening at a position corresponding to the developing region facing the photosensitive drum 1, and the developing sleeve 44 rotates so as to partially expose the opening of the developing container 41. Arranged as possible. In the present embodiment, the developing sleeve 44 is made of a non-magnetic material and rotates in the direction of the arrow in FIG. 4 during the developing operation. A magnet roll 44a having a plurality of magnetic poles is fixed inside the developing sleeve 44 along the circumferential direction as a magnetic field generating means.

The developer in the developing chamber 41a is supplied to the developing sleeve 44 by the screw member 41d, and the developer supplied to the developing sleeve 44 is predetermined on the developing sleeve 44 by the suction magnetic pole S2 generated by the magnet roll 44a. The amount is supported to form a developer pool. The two-component developer on the developing sleeve 44 passes through the developer pool as the developing sleeve 44 rotates, the layer thickness is regulated by the developing blade 42, and is conveyed to the developing region facing the photosensitive drum 1. Will be done. In the developing region, the developer on the developing sleeve 44 stands on the developing magnetic pole S1 to form magnetic spikes.

After that, the developer on the developing sleeve 44 maintains the adsorption of the developer on the surface of the developing sleeve 44 by the transport magnetic pole N2 and conveys the developer into the developer, and the developer is developed by the separating magnetic pole S3. Separated from the sleeve surface.

[Configuration of replenishment device]
FIG. 5 shows a cross section of the replenishment configuration.

This replenishment configuration is based on a configuration in which a replenishment transport path 83 extends from a discharge port 82 of the replenishment developer container 8 and is connected to a replenishment port 46 of the developing device 4.

First, a replenishment configuration using one replenishment transport path 83 as a conventional configuration will be described. In the developing apparatus 4 described above, the replenishment port 46 is provided at the uppermost stream of the stirring chamber 41b and outside the developing agent circulation path. There is almost no developer in the developer circulation path in the developer transport member in the vicinity of the replenishment port 46, and only the replenisher developer passes through.

The replenishment port 46 is connected to the lower end of the cylindrical member having a square cross section, which is the replenishment transport path 83. Further, the upper end portion, which is the other end portion of the tubular member, is connected to the discharge port 82 of the replenishing developer container 8.

The replenishing developer container 8 has a structure in which a spiral groove is dug in the inner wall of a cylindrical container, and the replenishing developer container 8 itself rotates to generate a conveying force in the longitudinal direction. Then, the replenishing developer is conveyed to the discharge port 82. The replenishing developer transported to the discharge port 82 is discharged to the replenishment transport path 83 through the discharge port 82 by the air pressure generated by the pump 81 having a variable volume in the developer container. Then, it reaches the replenishment port 46 of the developing device 4 through the replenishment transport path 83.

[Overview of toner scattering]
Next, the scattering of toner from the communication port inside the developing container 41 and the outside of the developing container 41, which is composed of the developing device top lid 41k and the developing sleeve 44, will be described with reference to FIG. The toner scattering here refers to the free toner generated in the developing container 4 due to the stirring / transporting of the developing agent and the replenishment of toner, which is discharged to the outside of the developing container through the communication port and cannot be completely collected in the developing container. ..

First, toner release will be described. The two-component developer contained in the developing container 41 is triboelectrically charged in the stirring chamber 41b and the developing chamber 41a, and the toner is transferred to the carrier by the electrostatic adhesive force generated by the triboelectric effect and the non-electrostatic adhesive force generated by the surface property. It is attached. When an impact or a shearing force is applied to the toner adhering to the carrier, the toner is peeled off from the carrier and released in the developing container. The impact and shear force at this time include the behavior of the developer when the developer is conveyed by the developing sleeve 44. As described above, the developing agent forms magnetic spikes having a chain-like structure along the magnetic field lines on the magnetic poles of the developing sleeve 44. The magnetic spike rises forward just before the magnetic pole, and when it passes over the magnetic pole, the magnetic spike tilts forward and collapses.

At this time, the rotation direction of the magnetic spike is the same as the direction of the developing sleeve 44. The toner is peeled off from the carrier by the impact or centrifugal force when the magnetic spikes fall, which causes the toner to be released. Of the developer transports in the developing sleeve 44, the one that contributes greatly to the release of toner is due to the separation magnetic pole S3 that generates a repulsive magnetic field. In this separation magnetic pole S3, since the developing agent is peeled from the developing sleeve 44, a magnetic force in the direction opposite to the rotation direction of the developing sleeve 44 is applied by the magnetic pole to reduce the speed of the developing agent and cause it to stay. At this time, since the length of the magnetic spikes becomes long, the impact and centrifugal force when the magnetic spikes fall down become large, and the amount of toner released tends to increase.

Further, when the toner from the toner replenishment port 46 is replenished by the replenishment, the toner that is blown up before being sufficiently agitated is also a factor of free toner in the developing container. As described above, the toner supplied at the toner supply port 46 is stirred and conveyed with the developer already in the stirring chamber 41b. At this time, the toner-developer mixing ratio temporarily increases in the mixing region of the replenishing toner and the developing agent. When the toner-developer mixing ratio is high, the amount of charge in the toner decreases, and the electrostatic adhesion between the toner and the carrier decreases. It is known that the replenishing toner that cannot be completely mixed with the developing agent is released as it is or by the impact of the screw members 41d and 41e during stirring and transportation of the developing agent, and the free toner is released in the developing container 44.

Further, when the replenishing developer container 8 discharged by the air pressure generated by the pump in the developing agent container is used, the air pressure propagates through the replenishment transport path 83, and the air pressure propagates from the toner replenishment port 46 to the developing container 41. May cause inflow of air. The airflow that flows in at this time winds up the free toner in the portion where the toner-developer mixing ratio is high in the vicinity of the toner supply port 46 into the developing container 41. Further, the air pressure propagation to the developing container 41 causes an unsteady increase in air pressure from the toner supply port 46 to the stirring chamber 41b. As will be described later, the inflow airflow accompanying this replenishment operation also causes the free toner to flow out to the outside of the developing container 41, and is one of the causes of toner scattering at the end of the side including the toner replenishment port 46 in the longitudinal direction. It has become.

Next, the air flow in the cross section near the developing apparatus 4 will be described with reference to FIG.

It is the developing sleeve 44 and the photosensitive drum 1 that generate the airflow in the vicinity of the developing device 4. Each will be described here.

Due to the rotation of the developing sleeve 44 and the behavior of the magnetic spikes on the magnetic poles, an air flow is generated in the same direction as the rotation of the developing sleeve. The air flow in the same direction as the developing sleeve has a contribution of taking in air into the developing container 41 from the communication port inside the developing container 41 and outside the developing container 41. Air also flows into the developing container 41 by replenishing the toner.

The longitudinal cross section of the developing device 4 is considered to be a substantially closed space. Since air is a fluid, the continuity equation can be applied. Assuming that the flow velocity of air is v and the density is ρ, there is no air coming out in the developing room, so ∂ρ / ∂t + ∇ρv = 0 ... (1)
Can be described as. Further, considering the steady state, the density ρ is substantially constant in each region in the developing container 41. Therefore, equation (1) can be described as follows.

ρ∇v = 0 ・ ・ ・ (2)
From this equation, the air flow rate ρv is preserved. In the longitudinal cross section near the developing device 4, the balance of the flow rate ρv becomes 0, and the same amount as the air flow rate flowing in by the development sleeve 44 and the replenishment is discharged to the outside of the developing device 4. Here, the air flow rate that flows into the developing container 4 as the developing sleeve 44 rotates through the communication port composed of the developing device top lid 41k and the developing sleeve 44 is Qa (sleeve inflow), and faces the flow taken in from the communication port. Assuming that the air flow rate discharged along the developer upper lid 41k side is Qb (sleeve discharge) and the air flow rate flowing in with the replenishment to the developing device is Qd (replenishment inflow), the following relationship is established.

Qa (sleeve inflow) + Qd (replenishment inflow) = Qb (sleeve discharge) ... (3)
In order for the airflow taken in by the developing sleeve and flowing along the developing sleeve to be discharged along the developer lid 41k side, it needs to be folded back in the developing apparatus. Generally, it is separated from the developing sleeve 44 at the developing agent retention portion of the separating magnetic pole S3 and then folded back. At this time, the free toner generated in the developing container 41 is contained and the toner is discharged.

There are mainly two steps in which the free toner contained in the Qb (sleeve discharge) is discharged to the outside of the developing container 41. First, Qb (sleeve discharge) discharged from the communication port to the outside of the developing device 4 is directly discharged from the gap between the developing device upper lid 41k and the photosensitive drum 1. Secondly, Qb (sleeve discharge) is mixed in the vicinity of the photosensitive drum 1, or the free toner is transferred to the air flow g generated by the photosensitive drum 1 by inertial force, so that the toner is discharged on the air flow generated by the photosensitive drum 1. Is to be done.

The scattered toner is discharged to the outside of the developing container 41 due to at least one of the above two factors, and contaminates the periphery of the developing device 1, the outer wall of the developing container 41, the photosensitive drum 1, the exposure device 3, and the transfer device 5. ..

Hereinafter, examples of reducing the scattered toner according to the present invention will be described.

Next, the detailed configuration of the developing apparatus 4 of the first embodiment will be described with reference to FIG. FIG. 7 is a cross-sectional view of the substantially central portion of the developing apparatus 4 in the longitudinal direction.

The angles θ1, θ2 ... In the figure indicate the angles formed when the horizontal plane is used as a reference.

The developing apparatus 4 has a developing device upper lid 41k so as to cover the developing sleeve 44 downstream of the developing region, and the developing device upper lid 41k is composed of an outer cover 47 and an inner cover 48. The outer cover 47 is formed at regular intervals L1 along the developing sleeve 44 in the regions θ1 to θ2 to form the flow path F1.

Further, in the region of the downstream θ2 to θ3, the gap L4 is gradually increased to form the combined flow path F4, and an inner cover 48 is provided between the outer cover 47 and the developing sleeve 44 in the region of the downstream θ3 to θ4. , A flow path F2 is formed between the inner cover 48 and the outer cover 47, and a flow path F3 is formed between the inner cover 48 and the developing sleeve 44.

Further, a branch path F5 between the flow path F2 and the flow path F3 is formed downstream of θ4. By doing so, an air flow as shown in FIG. 8 is generated in the vicinity of the developing sleeve 44.

As shown in FIG. 8, in the vicinity of the developing sleeve 44, an air flow a is generated so as to be involved in the container as the developing sleeve 44 rotates, and air flows into the developing container 41. As a result of the inflow, the internal pressure inside the developing container 41 increases, and an air flow b is generated from the inside of the developing container 41 toward the outside of the developing container so as to keep the internal pressure in an equilibrium state.

Here, an air flow c is generated along with the movement of the spikes of the separation magnetic pole S3, and the air taken into the inside of the developing container by the air flow c flows back by the air flow d and the air flow e.

As described in the section [Outline of Toner Scattering], the airflow d includes the scattered toner generated when the spikes of the separation magnetic pole S3 start to fall asleep.

Therefore, in this embodiment, an air flow e having a small amount of scattered toner is formed as an exhaust path by providing a range (θ3 to θ4) in which the inner cover covers the developing sleeve so as to include the position θ5 of the separation magnetic pole S3. Is possible.

Further, in order to increase the flow rate of the airflow e and decrease the flow rate of the airflow d, the cross-sectional area A3 of the flow path F3 and the cross-sectional area A2 of the flow path F2 are formed so that A3 <A2, and the flow path is formed. The pressure loss of F2 is made smaller than the pressure loss of the flow path F3.

However, if the cross-sectional area A3 is too small, the flow of the airflow c that takes in the scattered toner into the developing container 41 is obstructed, and the flow rate of the airflow e drops extremely. Therefore, in the implementation system, the distance L3 is set to 1.5 mm. It is set to ~ 3.0 mm, and the distance L2 is set to 2.0 mm to 3.5 mm.

Further, in the combined flow path F4, the cross-sectional area A1 of the first flow path is made smaller than the sum of the cross-sectional area A2 of the second flow path and the cross-sectional area A3 of the third flow path, so that the combined flow path is as shown in FIG. In addition, the airflow f becomes an air curtain, the airflow d can be returned to the flow of the airflow c, and the amount of scattered toner can be further reduced.

Further, the combined flow path F4 is arranged so as not to overlap the peak θ6 of the transport magnetic pole N2. The reason is that if the peaks of the confluent flow path F4 and the transport magnetic pole N2 overlap, the scattered toner generated when the spikes of the transport magnetic pole N2 start to fall asleep is diffused by the air flow f, and the effect of the air curtain is reduced. Because.

Further, although scattered toner easily adheres to the upstream end of the inner cover 48, by arranging the toner inside the developing container rather than vertically above the developing sleeve 44, when the toner adhering to the inner cover 48 drops, the developing sleeve 44 Since it is taken into the developing container as it rotates, it is possible to prevent image defects due to dropping of adhered toner.

Further, the flow path F6 can be generated by providing the flow path forming portion 47a along the photosensitive drum 1 at the tip of the outer cover 47 that covers the developing sleeve 44. By generating the flow path F6, the airflow h flows in from the outside air because the inflow and outflow are equivalent to the airflow discharged from the airflow g generated by the photosensitive drum 1. Further, the airflow h becomes an air curtain, and the airflow b merges with the nip portion of the photosensitive drum 1 and the developing sleeve 44 or the airflow a, so that the airflow h is less likely to be discharged to the outside air, and the amount of scattered toner can be reduced.

Further, since the floating toner adheres to the photoconductor drum 1 in a small amount in the vicinity of the photosensitive drum 1 of the air flow g, the scattered toner leaking to the outside can be reduced.

Further, since the amount of adhesion is such that it cannot be visually recognized on the image, the image quality is not deteriorated.

Next, the longitudinal shape of the developing apparatus 4 will be described. FIG. 11 is a cross-sectional view of the vicinity of B3 near the ends of the photoconductor drum 1 and the developing sleeve 44. In the vicinity of B3, as shown in FIG. 4, delivery portions 41f and 41g, which are routes for circulating the developing agent, are arranged. When the developing agent is circulated inside the developing container by a screw, an air flow F10 is generated due to the movement of the developing agent. Since the direction of the airflow F10 changes by 180 ° in the delivery portions 41f and 41g, the internal pressure due to the airflow F10 increases as compared with the vicinity of the central portion. Further, a toner supply port 46 is provided on the back side of the device. As described above, the toner supply causes air to flow into the developing container 41, and the internal pressure temporarily rises. Further, since this area is not sufficiently agitated by the toner that has just been replenished, it tends to fly up in the developing container, which tends to cause free toner. As described above, toner scattering is more likely to occur in the vicinity of the end portion of the developing apparatus 4 than in the vicinity of the center portion. Therefore, in this embodiment, the distance between the nearest contact portion, which is the tip end portion of the outer cover 47, and the developing sleeve 44 is changed between the vicinity of the center in the longitudinal direction and the vicinity of the end portion.

Specifically, the gap L1 near the center (FIG. 8) and the gap L7 near the end (FIG. 11) were formed so that L1> L7. By making the distance near the end smaller than the gap near the center and narrowing the opening in this way, air flow resistance is generated near the end and it becomes difficult to flow. On the contrary, in the vicinity of the center, the opening becomes relatively wide, and air flows more easily than in the fractional portion where the flow resistance is reduced.

In addition, the gap has a shape that gradually changes with a certain gradient from the end to the center. When the gap changes abruptly, a concentrated flow is generated at the place where the gap is expanded, and scattering occurs at that place. Therefore, it is desirable that this gradient is continuous and gentle, and in this embodiment, the gap is gently changed so that the rate of change is 1 mm or less in the gap direction with respect to 50 mm in the sleeve longitudinal direction.

By adopting such a configuration, the increase in the internal pressure generated near the end becomes a uniform pressure in the longitudinal direction near the opening where the air flows out, and the air circulation inside the developing apparatus described above is maintained. It is possible to reduce the amount of scattered toner leaking to the outside. Further, in this embodiment, the gap L1 near the center is set to 3 mm, and the gap L7 near the end is set to 2 mm.

In this embodiment, an example in a configuration without an inner cover (48) is shown. FIG. 12 is a cross-sectional view near the center of the photoconductor drum 1 and the developing sleeve 44 near the ends, and FIG. 13 is a cross-sectional view of the vicinity of B3. As described above, in the vicinity of B3, air flows into the developing container 41 due to toner replenishment, and the internal pressure temporarily rises. Further, since this area is not sufficiently agitated by the toner that has just been replenished, it tends to fly up in the developing container, which tends to cause free toner.

As described above, toner scattering is more likely to occur in the vicinity of the end portion of the developing apparatus 4 than in the vicinity of the center portion. Therefore, also in this embodiment, the distance between the closest contact portion, which is the tip end portion of the outer cover 47, and the developing sleeve 44 is changed between the vicinity of the center in the longitudinal direction and the vicinity of the end portion. Specifically, the gap L1 near the center (FIG. 12) and the gap L7 near the end (FIG. 13) were formed so that L1> L7. By making the distance near the end smaller than the gap near the center and narrowing the opening in this way, air flow resistance is generated near the end and it becomes difficult to flow. On the contrary, in the vicinity of the center, the opening becomes relatively wide, and air flows more easily than in the fractional portion where the flow resistance is reduced.

In addition, the gap has a shape that gradually changes with a certain gradient from the end to the center. When the gap changes abruptly, a concentrated flow is generated at the place where the gap is expanded, and scattering occurs at that place. Therefore, it is desirable that this gradient is continuous and gentle, and in this embodiment as well, the gap is gently changed so that the rate of change is 1 mm or less in the gap direction with respect to 50 mm in the sleeve longitudinal direction.

By adopting such a configuration as in the first embodiment, the pressure becomes uniform in the longitudinal direction in the vicinity of the opening where the air flows out, and the scattered toner leaking to the outside can be reduced. Further, in this embodiment, the gap L1 near the center is set to 3 mm, and the gap L7 near the end is set to 2 mm.

In the first and second embodiments, the gap L7 at the end is the same gap at the front and back. In Example 2, the gap between the central portion and the end portion was formed so that L71 <L72 with the gap L71 on the back side and the gap L72 on the front side while maintaining L1> L7. A toner supply port 46 is arranged on the back side of the developing device. When toner is replenished as described above, the internal pressure temporarily rises. In addition, the toner that has just been replenished is easily released because it is not sufficiently agitated. Therefore, since toner is more likely to scatter on the back side than on the front side, it is possible to reduce the scattered toner leaking to the outside by further reducing the back side gap L81. The effect is particularly large when the distance between the replenishment port 46 and the developer circulation path is short, or when the replenishment port is directly above the developer circulation path. In this embodiment, the gap L71 on the back side is set to 1.5 mm, and the gap on the front side is set to 2 mm.

1 Image carrier (photosensitive drum)
2 Charging device (charging roller)
3 Exposure device 4 Developing device 6 Fixing device 7 Cleaning device 8 Replenishing developer container (toner bottle)
9 Paper feed device 10 Recording material 41 Development container 41a First developer transfer path (development room)
41b Second developer transport path (stirring chamber)
41c partition wall 41d first developer transport member (first screw)
41e Second developer transport member (second screw)
41f Delivery section (2nd to 1st)
41g delivery section (1st to 2nd)
41k developer top lid 42 developer layer regulating member (developing blade)
44 Developer carrier (development sleeve)
44a Magnet roll 45 Developer concentration sensor (inductance sensor)
46 Supply port 47 Outer cover 48 Inner cover 51 Intermediate transfer body (intermediate transfer belt)
52 Primary transfer member 53 Secondary transfer member 54 Intermediate transfer cleaner 81 Pump 82 Discharge port 83 Replenishment transfer path 100 Image forming device P (PY, PM, PC, Pk) Image forming station

Claims (6)

A container containing the developer and a container
A rotating body that supplies the developer to the image carrier (1) in the supply region by rotating while carrying the developer, and a rotating body that supplies the developer to the image carrier (1) in the supply region.
A first flow path forming portion that covers the rotating body with a gap on the downstream side of the supply region that can be placed in the rotating direction of the rotating body.
A first flow path formed between the rotating body and the first flow path forming portion,
In a developing device with
The minimum gap between the rotating body and the flow path formed by the first flow path forming portion.
A developing apparatus characterized in that the central gap located near the central portion in the longitudinal direction of the rotating body is relatively wider than the end gap, which is a gap near the end portion in the longitudinal direction of the rotating body. The central gap (L1) and the end gap (L7) are
1.1 x L7 ≤ L1 ≤ 3 x L7
The developing apparatus according to claim 1, wherein the developing apparatus is characterized by the above. Claim 1 or 2 is characterized in that the gap between the rotating body and the flow path formed by the first flow path forming portion gradually widens toward the central portion at least in the magnetized region of the rotating body. The developing apparatus according to. A storage container containing the developer and
A rotating body that supplies the developer to the image carrier (1) in the supply region by rotating while carrying the developer, and a rotating body that supplies the developer to the image carrier (1) in the supply region.
A first flow path forming portion that covers the rotating body with a gap on the downstream side of the supply region in the rotation direction of the rotating body.
A first flow path formed between the rotating body and the first flow path forming portion,
A second flow path formed between the rotating body and the first flow path forming portion, arranged with a gap between them, and branching the first flow path into two flow paths at a first branch point. Placed in a developing device with a forming part,
In the gap of the flow path formed by the rotating body and the second flow path forming portion, the gap near the center portion is relatively wider than the gap near the end portion in the longitudinal direction of the rotating body. Further, the developing apparatus is characterized in that the end gap on the side near the developer supply port is narrower than the end gap on the far side. The end gap (L71) on the side closer to the developer supply port (46) and the end gap (L72) on the far side are
1.1 x L71 ≤ L72 ≤ 3 x L71
The developing apparatus according to claim 4, wherein the developing apparatus is characterized by the above. Any of claims 1 to 5, wherein the gap between the rotating body and the flow path formed by the first flow path forming portion continuously widens with a gradient of 1 mm or less in the gap direction with respect to 50 mm in the longitudinal direction. The developing apparatus according to item 1.

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