JP2017003710A - Developing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device that can suppress unevenness in image density without applying strong stress to a developer, and an image forming apparatus including the same.SOLUTION: There is provided a developing device 14 comprising a developing sleeve 141 being a developer carrier that carries and conveys a developer with a magnetic force of a magnet roller 147 being magnetic field generation means; a developer storage part 149 that stores the developer carried on the developing sleeve 141; and a round-bar doctor 146 being a developer regulation member that regulates the thickness of the developer carried on the developing sleeve 141, the developing device including an airflow passage hole 110 being airflow generation means that generates an airflow in a draw-up area through which a developer to be drawn up from the inside of the developer storage part 149 onto the developing sleeve 141 passes.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a developing device and an image forming apparatus.

  The developing device includes a developer container that stores a two-component developer composed of a magnetic carrier and a toner, and a developer in the developer container that is supported on the outer peripheral surface by a magnetic force. A device having a developer carrier that transports to a facing portion is known (Patent Document 1, etc.). The developing device described in Patent Document 1 includes a transport screw that stirs and transports the developer in the developer container.

  When an image having a high image area ratio, such as a solid image, is developed with a developing device having a conveying screw in the developer accommodating portion, an image defect called screw pitch unevenness that causes image density unevenness with a pitch corresponding to the pitch of the screw blades occurs. Sometimes. The screw pitch unevenness is caused by a variation in developer density depending on the position of the transport screw in the transport direction in the developer container. If there is a variation in the density of the developer in the developer accommodating portion, the variation in density also occurs in the developer that has been pumped from there and pumped up on the developer carrier. When this developer is used for development, the image density becomes high when developed at a portion where the developer density is high on the developer carrier, and the image density when developed at a portion where the developer density is low. Becomes thin and uneven image density called screw pitch unevenness occurs.

  Patent Document 1 discloses that the developer carrying member is upstream of the developer carrying member with respect to the developer restricting portion that regulates the amount of the developer carried to the developing region that is the opposed portion between the developer carrying member and the latent image carrying member. A configuration is described in which a region having a strong magnetic force acting on the developer is provided. With such a configuration, it is considered that the density of the developer is increased by the strong magnetic force, the density variation occurring in the developer before being pumped is reduced, and the occurrence of uneven image density can be suppressed.

  However, if a strong magnetic force is applied to the developer to reduce the variation in the density of the developer, a large stress is constantly applied to the developer. When a large stress is applied to the developer, the life of the developer is reduced.

  In order to solve the above-mentioned problems, the invention of claim 1 contains a developer carrying member that carries and conveys the developer by the magnetic force of the magnetic field generating means, and a developer carried on the developer carrying member. Development that pumps the developer from the developer container onto the developer carrier, in a developing device having a developer container and a developer regulating member that regulates the layer thickness of the developer carried on the developer carrier It is characterized by comprising an airflow generating means for generating an airflow in a pumping area through which the agent passes.

  According to the present invention, there is an excellent effect that image density unevenness can be suppressed without applying a great stress to the developer.

1 is a schematic configuration diagram of a developing device and a photoreceptor according to an embodiment. 1 is a schematic configuration diagram of a printer according to an embodiment. 1 is a schematic configuration diagram of an image forming device. FIG. 2 is an explanatory diagram of the developing device shown in FIG. 1 and airflow around it. FIG. 6 is a schematic diagram of an air flow including scattered toner and an air flow not including scattered toner around the developing device. FIG. 3 is an enlarged explanatory view of a vicinity of a round bar doctor of the developing device. FIG. 10 is a schematic diagram of a developing device according to a modification. FIG. 6 is a schematic configuration diagram of a developing device according to Embodiment 4. FIG. 2 is a schematic configuration diagram of a developing device of Comparative Example 1; FIG. 6 is a schematic configuration diagram of a developing device of Comparative Example 2. Explanatory drawing which shows the relationship between a conveyance screw and screw pitch nonuniformity. FIG. 3 is a schematic explanatory diagram of a developing device that strengthens a magnetic force acting on a developer in a region upstream of a restriction position.

An embodiment in which the present invention is applied to an electrophotographic printer (hereinafter simply referred to as “printer”) as an image forming apparatus will be described below.
FIG. 2 is a schematic configuration diagram of the printer 100 according to the present embodiment. Y, C, M, and K indicate members for yellow, cyan, magenta, and black, respectively.
In the printer 100, image forming apparatuses 10 (Y, C, M, K) for four colors as process cartridges are detachable from an image forming station formed on the apparatus main body 1 side. These use Y, M, C, and K toners of different colors as the image forming material, but the other configurations are the same and are replaced when the lifetime is reached. The printer 100 further includes an optical unit 20, an intermediate transfer unit 30, a paper feed unit 40, a fixing unit 50, and the like as exposure means capable of irradiating laser light.

  The image forming device 10 (Y, C, M, K) includes a drum-shaped photoconductor 12 (Y, C, M, K) as a latent image carrier. Further, as process means acting on this, a charging device 13 (Y, C, M, K) for charging the photoconductor 12 (Y, C, M, K), and a photoconductor 12 (Y, C, M, K). The cleaning devices 15 (Y, C, M, K) for removing the toner remaining on the toner are integrally formed. Further, a developing device 14 (Y, C, M, K) that develops a latent image formed on the photosensitive member 12 (Y, C, M, K) is connected to this.

  The intermediate transfer unit 30 includes an intermediate transfer belt 31 as an intermediate transfer member, a plurality of (here, three) stretching rollers (32, 33, 34), a primary transfer roller 35 (Y, C, M, K) and a second transfer roller. A next transfer roller 36 is provided. The tension rollers (32, 33, 34) are tension members that rotatably support the intermediate transfer belt 31, and the four primary transfer rollers 35 (Y, C, M, K) are formed on the photoconductor 12. Primary transfer means for transferring the toner images to the intermediate transfer belt 31. The secondary transfer roller 36 is a secondary transfer unit that further transfers the toner image transferred onto the intermediate transfer belt 31 onto a recording paper P as a recording material.

  The paper supply unit 40 includes a paper supply roller 43 that conveys the recording paper P from the paper supply cassette 41 or the manual paper supply tray 42 to the secondary transfer region, a registration roller 44, and the like. The fixing unit 50 includes a fixing roller 51 and a pressure roller 52, and has a known configuration in which fixing is performed by applying heat and pressure to the toner image on the recording paper P.

  In addition, toner bottles 60 (Y, C, M, K) each storing toner to be supplied to a toner replenishing port 145, which will be described later, are placed on the upper portion of the apparatus main body 1, and the respective image forming apparatuses 10 (Y, C, M). , K) are detachably mounted from the apparatus main body 1 separately.

  In such a configuration, first, in the first color yellow image forming device 10Y, the yellow photoconductor 12Y is uniformly charged by the yellow charging device 13Y. Thereafter, a latent image corresponding to the yellow image is formed on the surface of the yellow image forming device 10Y by the laser light emitted from the optical unit 20 as the latent image forming means, and this latent image is developed by the yellow developing device 14Y. As a result, a Y toner image is formed.

  The Y toner image formed on the yellow photoreceptor 12Y is transferred onto the intermediate transfer belt 31 by the action of the yellow primary transfer roller 35Y. The yellow photoconductor 12Y after the primary transfer is cleaned by the yellow cleaning device 15Y to prepare for the next image formation. The residual toner collected by the yellow cleaning device 15Y is stored in a waste toner collection bottle 16 installed in the take-out direction of the image forming device 10 (the rotation axis direction of the photoreceptor 12). The waste toner collection bottle 16 is detachable from the apparatus main body 1 of the printer 100 so that it can be replaced when the storage amount is full.

  A similar image forming process is performed in each of the image forming apparatuses 10 (C, M, and K) for C, M, and K to form toner images of the respective colors, which are sequentially superimposed on the previously formed toner images. Transcribed. On the other hand, the toner image formed on the intermediate transfer belt 31 is transferred to the recording paper P conveyed from the paper feed cassette 41 or the manual paper feed tray 42 to the secondary transfer region by the action of the secondary transfer roller 36. . The recording paper P to which the toner image has been transferred is conveyed to the fixing unit 50, where the toner image is fixed at the nip portion between the fixing roller 51 and the pressure roller 52 of the fixing unit 50, and is discharged to the upper part of the apparatus by the paper discharge roller 55. The paper is discharged to the paper discharge tray 56.

Next, a specific configuration of the image forming apparatus will be described.
The four image forming apparatuses 10 (Y, C, M, and K) have the same configuration except that the color of the toner to be used is different. M, K) will be omitted for explanation.
FIG. 3 is a schematic configuration diagram showing one of the four image forming apparatuses 10.
The charging device 13 provided in the image forming apparatus 10 includes a charging roller 131 and a cleaning roller 132 that cleans the surface of the charging roller 131. The cleaning device 15 includes a cleaning brush 151 and a cleaning blade 152 that come into contact with the surface of the photoreceptor 12, and a toner recovery coil 153. The toner collection coil 153 conveys the toner scraped by the cleaning brush 151 and the cleaning blade 152 toward the waste toner collection bottle 16.

  The developing device 14 uses a two-component developer (hereinafter simply referred to as “developer”) made of a magnetic carrier and toner. The developing device 14 carries a developer and rotates counterclockwise in FIG. 3, thereby forming a hollow member of the developer carrying member that conveys the developer to a developing region facing the photoreceptor 12. A magnetic developing sleeve 141 is provided. Inside the developing sleeve 141, a magnet roller 147 is fixedly disposed as magnetic field generating means having a plurality of magnetic poles in the circumferential direction. The developing sleeve 141 and the magnet roller 147 constitute a developing roller that is a developer carrier. In this developing roller, the developer is carried and conveyed on the outer peripheral surface by the magnetic force of the magnet roller 147.

  Further, the developing device 14 is disposed to face the developing sleeve 141, and forms a doctor gap for regulating the layer thickness of the developer carried on the surface of the developing sleeve 141 between the developing sleeve 141 and the developing sleeve 141. A round bar doctor 146 as a developer regulating member is also provided. Further, the developing device 14 includes a first transport screw 142 and a second transport screw 143. These are agitating and conveying members for reciprocally conveying the magnetic carrier housed in the developing device 14 and the replenishing toner supplied from the toner replenishing port 145 in the axial direction of the photoreceptor 12 while agitating. These members are housed and supported in the developing case 144.

Next, the configuration of the developing device 14 provided in the printer 100 will be further described.
FIG. 1 is an explanatory diagram showing the distribution of the normal direction magnetic flux density (absolute value) on the surface of the developing sleeve 141 together with the schematic configuration of the developing device 14 and the photoreceptor 12 of the present embodiment.
The developing device 14 passes the developing region opposed to the photoreceptor 12 after the developer pumped and carried on the developing sleeve 141 by the magnetic force of the magnet roller 147 from the developer accommodating portion is regulated by the round bar doctor 146. Return to the developer container again.

  A developer container 149 is formed inside the developing device 14 by the developing case 144. The developer accommodating portion 149 is located below the developing sleeve 141 and extends in a direction parallel to the rotation axis of the developing sleeve 141 (hereinafter referred to as “axial direction”), and the supply chamber 149A has a supply chamber 149A. Adjacent to the stirring chamber 149B extending in the axial direction. The supply chamber 149 </ b> A and the stirring chamber 149 </ b> B are respectively provided with a first transport screw 142 and a second transport screw 143 that transport the developer in a direction parallel to the rotation axis of the developing sleeve 141. The developer transported to the downstream end (back side in FIG. 1) of the supply chamber 149A by the second transport screw 143 is transferred to the stirring chamber 149B, and the first transport screw 142 in the stirring chamber 149B causes the developer in the stirring chamber 149B. It is conveyed toward the downstream end (front side in FIG. 1). Then, the developer transported to the downstream end of the stirring chamber 149B is transferred to the supply chamber 149A and transported toward the downstream end of the supply chamber 149A by the second transport screw 143 in the supply chamber 149A. As described above, the developer is circulated and conveyed in the developer accommodating portion 149.

  Replenishment toner for replenishing the amount of toner consumed by development is supplied from the toner replenishment port 145 to the developer in the stirring chamber 149B. The developer in the supply chamber 149 </ b> A is pumped onto the developing sleeve 141 by the magnetic force of the magnet roller 147 (magnetic force due to the N3 pole) during conveyance by the second conveyance screw 143. After that, the developer pumped up on the developing sleeve 141 is regulated by the round bar doctor 146, passes through the developing region facing the photosensitive member 12, and returns to the developer containing portion 149 again.

  In the present embodiment, the developer pumped up from the supply chamber 149 </ b> A by the magnetic force (magnetic force) by the N3 pole and adsorbed on the developing sleeve 141 turns counterclockwise in FIG. 1 as the developing sleeve 141 rotates. Be transported. The developer controlled to a predetermined amount by the round bar doctor 146 is spiked by the magnetic force generated by the S1 pole in the development area, and the electrostatic latent image on the surface of the photoreceptor 12 is transferred from the spiked developer by a developing electric field. Toner is supplied and development processing is performed. The developed developer is transported as the developing sleeve 141 rotates while being held on the developing sleeve 141 by the magnetic force of the N1 pole, S2 pole, and N2 pole. After that, it receives the action of repulsive magnetic force (peeling force) and centrifugal force generated between the N2 pole and the N3 pole, and is detached (separated from the developer) on the developing sleeve 141, and in the supply chamber 149A of the developer accommodating portion 149 Fall into.

In the developing device 14 shown in FIG. 1, an airflow passage hole 110 is provided in the developing case 144 in order to suppress an increase in pressure inside the device, and the filter 8 prevents the developer from passing through the airflow passage hole 110. Is installed.
The air containing the toner inside the developing device 14 is configured so as to pass through the filter 8 to separate the toner and air, and to discharge only the air to the outside of the developing device 14.

  The round bar doctor 146 will be further described. The round bar doctor 146 of the present embodiment mainly functions to regulate the amount of developer conveyed to the development area to a certain amount. When the developer is regulated, the developer is regulated. The pressure is received by the round bar doctor 146. Therefore, this round bar doctor 146 generally has to secure a diameter of the cylinder of, for example, about 5 to 6 [mm] in order to ensure a certain level of strength, and its restricting portion (the developing sleeve 141). A straightness of about 0.05 [mm] is required at the end facing the surface.

If the round bar doctor 146 is a magnetic body, it will bend due to the influence of magnetic force, so it is difficult to maintain a straightness of 0.05 [mm]. On the other hand, if the round bar doctor 146 is non-magnetic, it is not affected by the magnetic force, so that it is possible to suppress the center part of the round bar doctor 146 from being bent by the magnetic force of the magnet roller 147. Therefore, it is possible to ensure the uniformity of the gap between the developing sleeve 141 and the round bar doctor 146 that has a great influence on the abrasion.
In this embodiment, the round bar doctor 146 is fixed to the side plate of the developing device 14 outside the image area on both ends in the longitudinal direction (direction parallel to the rotation axis of the developing sleeve 141).

Next, toner scattering that has occurred in a conventional developing device will be described.
The two-component developing device is a device that develops and visualizes an electrostatic latent image formed on a latent image carrier using a two-component developer composed of toner and carrier. The developer whose toner has been consumed after completion of the development process in the development area is collected, mixed with the replenished toner, stirred, and again developed. In order to obtain a stable toner image, the developer used in the developing device having such a configuration needs to maintain a constant toner density and charge amount. The toner density is adjusted by the amount of toner consumed during development and the amount of replenished toner, and the charge amount is given by frictional charging during mixing of the carrier and toner.

  The toner adsorbed on the carrier is affected by the electric field formed between the developer carrying member and the latent image carrying member in the developing region, and adheres to the electrostatic latent image (image portion) on the latent image carrying member. . The force received from the electric field in the developing area at this time exceeds the electrostatic force with the carrier, and the toner leaves the carrier and flies to the latent image carrier side.

  The toner that is powder is not uniform in physical properties, and some toners do not have sufficient charging ability. In addition, there are toners that become insufficiently charged due to insufficient frictional charging with the carrier, such as toner that stays in a part of the apparatus. Furthermore, the carrier in the developer in the developing device has a tendency to decrease the charging ability with long-term use, and the toner tends to be insufficiently charged. Since such a toner with insufficient charge is not easily restrained by an electric force, it floats in the apparatus by riding on an air current generated in the apparatus. The suspended toner further rides on the air current and scatters out of the developing device and contaminates the inside of the image forming apparatus.

In recent years, market needs for increasing the speed of image forming apparatuses have increased, and therefore it is necessary to drive the developing apparatus at a higher speed than in the past. However, as the speed of the developing device increases, the impact force that the toner separates from the carrier also increases, so the amount of toner scattering tends to increase.
The toner scattering from the developing device described above appears to be scattered from the surface of the developing sleeve, which is a developer carrier, to the outside of the developing device. This is because the toner scatters due to the impact of the rising and falling of the developer in the development area.

As a method for reducing toner scattering, a general method is to generate an air flow from the downstream side of the developing region to the inside of the developing device and collect the scattered toner again in the developing device. Since the scattered toner appears to be sucked into the developing device by this air current, it is called a suction air current. As a method of increasing the suction air flow for the purpose of reducing the amount of scattered toner, a method of narrowing the gap between the developing case and the developer carrying member is known.
However, the conventional airflow generation configuration has a problem that the range in which the airflow acts (the range in the vicinity of the entrance gap between the developing case and the developing sleeve) is narrow and toner scattering due to the increase in the speed of the developing device cannot be sufficiently suppressed.

  As a conventional developing device that generates an air current, there is one that suppresses scattered toner by increasing the flow velocity of the gap portion by narrowing the gap between the developing case and the developer carrying member. However, with the increase in the speed of the developing device, the separation force of the toner from the developer carrier increases, and there is a problem that toner scattered inside the device cannot be completely suppressed even with a sufficiently narrow gap. It was.

FIG. 4 is an explanatory diagram of the developing device 14 shown in FIG. 1 and the airflow around it.
The generation mechanism of scattered toner will be described. The magnetic brush formed on the developing sleeve 141 passes through the developing region (region “α” in FIG. 4) for developing the latent image on the photosensitive member 12, so that the developing region in the direction of surface movement of the developing sleeve 141. An air flow from the upstream side to the downstream side is generated. At this time, as shown in FIG. 4, when the rotation direction of the photoconductor 12 is opposite to the rotation direction of the developing sleeve 141 (the surface movement direction of the opposite surface in the development region is the same direction), the region “α” The airflow at becomes stronger.

  Further, the magnetic brush on the surface of the developing sleeve 141 after passing through the developing region moves so as to fall down due to the magnetic force of the magnet roller 147 in the developing sleeve 141. The force due to the airflow at this time, the centrifugal force due to the rotation of the developing sleeve 141, and the impact when the magnetic brush is tilted act on the toner, and toner scattering tends to occur on the downstream side of the developing region.

  In particular, the developing region is positioned substantially in the horizontal direction of the developing sleeve 141 and the downstream side of the developing region in the rotating direction of the developing sleeve 141 is positioned below the developing sleeve 141 (the rotating direction of the developing sleeve 141 is different from that in FIG. 4). In the developing device having the reverse configuration, the operation is as follows. That is, in addition to the force caused by the air current acting on the toner, the centrifugal force, and the impact force, gravity is further applied, so that the force for releasing the toner is increased, and as a result, toner scattering is more likely to occur. .

  The toner separated from the developing sleeve 141 in the developing region (region “α”) is divided as follows. That is, the toner heading toward the inside of the developing device 14 </ b> A with the accompanying airflow of the developing sleeve 141, and the clearance (region “β”) between the developing case 144 and the photosensitive member 12 with the accompanying airflow of the photoconductor 12. It is divided into the toner to go.

  Here, since the toner traveling toward the developing device inside 14A continues to circulate in the developing device inside 14A, the toner does not become scattered toner. On the other hand, in the region “β”, the accompanying airflow of the photosensitive member 12 that causes toner scattering and the airflow that returns the scattered toner to the inside 14A of the developing device (airflow toward the region “α”) are mixed. . In general, the effect of the rotating airflow of the rotating body decreases with increasing distance from the surface of the rotating body. For this reason, in the region “β”, the influence of the accompanying air current of the photosensitive member 12 is stronger than the suction air current to the developing device inside 14A due to the accompanying air current of the developing sleeve 141, and as a result, toner scattering occurs.

FIG. 5 is a schematic diagram relating to the airflow including the scattered toner and the airflow not including the scattered toner described so far. The broken-line arrows in FIG.
If all of the scattered toner generated in the region “α” can be sucked into the developing device inside 14A, the toner scattering does not occur. However, in actuality, there is an accompanying airflow of the photoconductor 12, so that it is difficult to completely prevent the toner scattered from the region “α” to the region “β”. As a result, the scattered toner floats on the air current, and finally the scattered toner contaminates the entire image forming apparatus (the entire interior of the printer 100).

  As described above, the scattered toner floats on the airflow, but when there are airflows in a plurality of directions in a certain region, vortices are generated, and the toner is likely to accumulate. That is, a part of the toner scattered in the region “β” having the opposite airflow direction tends to accumulate on the upper surface of the developing case 144 indicated by “γ” in FIG. When toner accumulates on the outer surface of the developing case 144 as described above, the accumulated toner falls and adheres to the photoreceptor 12 or the recording paper P, resulting in an abnormal image.

  To cope with such a problem, the developing device 14 of the present embodiment is provided with an airflow passage hole 110 so that the air inside the developing device 14A can be discharged to the outside of the device. As a result, the air flow from the developing area toward the developing device inside 14A can be strengthened, and the air flow toward the area “β” in FIGS. 4 and 5 can be weakened, so that toner accumulates on the outer surface of the developing case 144. It can be suppressed, and abnormal images resulting from this can also be suppressed.

  As the image forming apparatus increases in speed, the number of rotations of the developing sleeve 141 tends to increase. As the number of rotations of the developing sleeve 141 increases, the detachment force (centrifugal force) acting on the developer on the developing sleeve 141 increases, so that the toner scattering in the region “α” tends to increase. In order to suppress the toner scattering, a method of narrowing the gap between the developing case 144 and the developing sleeve 141 and improving the suction flow rate to suppress the toner scattering is generally used. In this method, only the tip of the magnetic spike formed by the developer carried on the developing sleeve 141 is slightly in contact with the inner wall of the developing case 144 by the magnetic pole of the magnet roller 147 disposed inside the developing sleeve 141. to make. Then, the air flow accompanying the developing sleeve 141 is taken into the developing device inside 14A together with the magnetic spikes (referred to as a pumping action).

  As the gap between the developing case 144 and the developing sleeve 141 is narrower, the suction airflow tends to be strengthened. However, as the suction airflow is strengthened, the flow rate sucked into the developing device inside 14A per unit time increases. The internal pressure of the developing device 14 also increases. When the internal pressure of the developing device 14 rises and exceeds the holding pressure limit of the developing device, the fluid (air) inside the developing device 14A flows in the direction opposite to the air flow around the developing sleeve 141, and from the developing opening of the developing case 144 In some cases, the liquid was ejected to the development area (area “α”). In that case, the amount of scattered toner increases. That is, even if the suction airflow is strengthened, the scattered toner cannot be suppressed unless the pressure holding property of the developing device 14 is also improved.

  Furthermore, if the gap between the developing case 144 and the developing sleeve 141 is narrowed to the limit, the suction airflow is strengthened, but the developer stays in the portion in front of the entrance of the developing case, resulting in degradation of image quality. There was also a problem of inviting. In other words, there is a limit to the suction airflow that can be strengthened by narrowing the gap.

  In the developing device 14 of this embodiment shown in FIG. 1, an airflow passage hole 110 is provided in the developing case 144, and a filter 8 that prevents passage of the developer is installed in the airflow passage hole 110. As a result, when the flow rate sucked into the developing device inside 14A per unit time increases and the internal pressure of the developing device 14 increases, the air inside the developing device 14A is discharged from the air flow passage hole 110 to the outside of the developing device 14. The Therefore, even if the suction airflow generated in the gap between the developing case 144 and the developing sleeve 141 on the downstream side in the surface movement direction of the developing sleeve 141 with respect to the developing region is increased, the increase in the pressure inside the developing device 14A is suppressed. Toner scattering can be suppressed.

  Further, in the developing device 14 shown in FIG. 1, the developer in the supply chamber 149A is pumped onto the developing sleeve 141 by the magnetic force of the magnet roller 147 (magnetic force due to the N3 pole) during the conveyance. Then, an airflow passage hole 110 as an opening is arranged in the developing case 144 at a position facing the pumping region through which the developer to be pumped passes. By arranging the airflow passage hole 110 at this position, when the air inside the developing device inside 14A is discharged from the airflow passage hole 110 to the outside of the developing device 14, an airflow is generated in the pumping area, and the airflow passage hole 110 is generated. Functions as an airflow generating means.

As a configuration that can suppress an increase in atmospheric pressure in the developing device, it is conceivable to provide an opening for pressure relief above the developer accommodating portion 149.
On the other hand, the developing device 14 shown in FIG. 1 is opposed to the pumping region on the upstream side in the direction of surface movement of the developer carrier relative to the restriction position where the gap between the developer carrier and the developer restriction member is the narrowest. The airflow passage hole 110 which is an opening is arranged at a position to be. By disposing the opening at this position and releasing the internal pressure, it is possible to release the internal pressure at a portion close to the regulation region where the pressure is easily related and air is easily ejected to the outside. Accordingly, it is possible to effectively suppress an increase in the internal pressure of the developing device inside 14A, and to suppress the generation of an air flow that is ejected from the developing device inside 14A to the outside in the vicinity of the developing region.

6 is an enlarged explanatory view of the vicinity of the round bar doctor 146 of the developing device 14 shown in FIG.
As shown in FIG. 6, the magnetic carrier in the developer is held by the magnetic force generated by the N3 pole of the magnet roller 147. The toner is held on the magnetic carrier by electrostatic force. For this reason, as shown in FIG. 1, even if the airflow passage hole 110 is provided at a position facing the pumping area, the magnetic carrier and toner constituting the developer can be prevented from going out of the airflow passage hole 110.

As shown in FIG. 1, a filter 8 may be provided in the airflow passage hole 110. As a result, it is possible to prevent the deteriorated carrier that cannot be held by the magnetic force or the weakly charged toner from leaking to the outside.
Further, as long as a configuration capable of collecting the carrier and toner that has passed through the airflow passage hole 110 can be provided, the airflow passage hole 110 may not be provided with the filter 8. Thus, deteriorated carriers that cannot be held by magnetic force, weakly charged toner, and the like can be discharged through the airflow passage hole 110 and collected.

Next, the image defect of screw pitch unevenness which has occurred by using a conventional developing device will be described.
When a monochromatic image with a large area ratio is formed using a developing device that stirs and conveys the developer in the supply chamber using a screw-shaped member, the image density unevenness in a direction oblique to the paper passing direction ( (Hereinafter referred to as “screw pitch unevenness”) may occur in a striped pattern, which may impair the aesthetic appearance.
FIG. 11 is an explanatory diagram showing the relationship between the screw-shaped conveying screw 108 and the screw pitch unevenness 112.

  In the solid image 111 shown in FIG. 11, the portion indicated by the relatively dense parallel oblique lines in the screw pitch unevenness 112 is the high density portion 113 having a relatively high image density, and the portion indicated by the relatively coarse parallel oblique lines is relatively high. The low density portion 114 has a low image density. The image density unevenness such as the screw pitch unevenness 112 has a high incidence with the recent decrease in the particle diameter of the magnetic carrier aiming at high image quality. This is due to changes in the bulk density, coverage rate, charging ability, and the like accompanying the reduction in particle size.

  The pitch “W1” of the screw pitch unevenness 112 shown in FIG. 11 is equal to the pitch “W2” of the blades of the conveying screw 108 in the developing device. FIG. 11 shows, as an example, a case where a portion corresponding to the mountain of the conveying screw 108 is thin (low concentration portion 114) and a portion corresponding to the valley is dark (high concentration portion 113).

  Image density unevenness such as screw pitch unevenness 112 is likely to occur when the developer pumping performance of the developing roller (developer carrier) is low (when the amount of developer adhering to the developing roller is small). Further, it is also likely to occur when a developer that has been released from the developing roller and has a low toner concentration is immediately adsorbed to the developing roller without being stirred by the conveying screw 108.

  When the wing portion of the conveying screw 108 is lower than the developer surface, the developer moving on the conveying screw 108 becomes higher at the peak (portion with the wing portion) of the conveying screw 108, and at the valley (the wing portion). Lower). For this reason, when the developer that has climbed over the mountain falls to the valley of the conveying screw 108, a space containing air is created and the developer becomes sparse. On the other hand, the crest portion of the conveying screw 108 is compressed by the conveying force of the screw, so that the developer becomes dense.

  When the blade portion of the conveying screw 108 is higher than the developer surface, the upper end portion of the blade portion protrudes from the agent surface, and the surface of the developing roller facing the portion protruding from the agent surface is developed. It is difficult to supply the agent. For this reason, when the wing portion is higher than the developer surface, the developer becomes sparse at the peak portion and becomes dense at the valley portion.

  As described above, in the supply chamber, the density of the developer is varied according to the pitch of the blades of the conveying screw 108. Then, when the developer in a state in which the developer is sparse and dense is carried on the developing roller and used for development in the development area, there is a problem that uneven image density such as screw pitch unevenness 112 occurs in the solid image 111. .

Further, as a configuration for eliminating the screw pitch unevenness 112, a configuration in which the developer pumping property is increased by making the magnetic force of the developer pumping magnetic pole of the magnet roller a high magnetic force can be considered. However, when the magnetic force of the developer-pumping magnetic pole is set to a high magnetic force, an excessive amount of developer is pumped up to the developing roller, and an excess of the developer is scraped off by the regulating blade. As a result, a wasteful stress is applied to the developer by the surplus, and there is a possibility that the deterioration of the developer is accelerated.
Further, in such a developing device, the developed developer separated from the developing roller is attracted to the high magnetic force pumping magnetic pole, and is quickly pumped up by the stirring screw and reattached to the developing roller. Problems may arise.

FIG. 12 is a schematic explanatory diagram of the developing device 14 that strengthens the magnetic force acting on the developer in a region upstream of the developing sleeve 141 in the surface movement direction with respect to the regulating position (hereinafter referred to as “regulating position upstream region”). is there.
In the developing device 14 shown in FIG. 12, the “S2 pole” that is the upstream electrode that has the same polarity and the “S3 pole” that is the drainage / pumping pole are disposed adjacent to each other. With this arrangement, an agent separation region R is formed between these magnetic poles, where a peeling force is applied to the developer on the development sleeve 141 in a direction away from the surface of the development sleeve 141.
As a result, the developer conveyed to the agent separation region R receives the peeling force due to the magnetic force of the “S2 pole” that is the upstream electrode that runs out of the agent and the “S3 pole” that is the agent running-out / pumping pole. It will be detached and taken into the developer in the supply chamber 149A of the developer accommodating portion 149.

Further, in the developing device 14 shown in FIG. 12, the developer pumped up on the developing sleeve 141 by the magnetic force of the “S3 pole” that is the agent running out / pumping pole is the tip of the developer regulating blade 146b that is the developer regulating member. Is regulated at a regulation position close to the developing sleeve 141.
In the developing device 14 shown in FIG. 12, there is an inflection point Q where the polarity of the magnetic force in the normal direction changes on the surface of the developing sleeve 141 from the agent separation region R to the regulation position. In the vicinity of such an inflection point Q, the magnetic force acting on the developer is relatively strong, and the normal direction magnetic flux density is so small that no spikes occur, so the developer density is high. ing.

  When a spike occurs, each magnetic spike that rises tries to separate from the adjacent magnetic spike, so the density decreases. However, at the inflection point Q, the spike does not occur. The density is likely to be high. In addition, at the inflection point Q, since the magnetic ears lie down and attract in the normal direction, it is considered that the total magnetic flux density becomes high and the magnetic force acting on the developer becomes relatively strong.

As in the developing device 14 shown in FIG. 12, by strengthening the magnetic force acting on the developer, in the portion where the density of the developer is low, the effect of filling the gaps between the particles of the developer works, and the density of the developer is increased. be able to. As a result, even when the density of the developer at the time of pumping is uneven, the density difference can be leveled, and the image density caused by the density difference of the developer carried on the surface of the developer carrying body such as screw pitch unevenness. There is a possibility that unevenness can be suppressed.
However, when the magnetic force acting on the developer is increased, useless stress is applied to the developer, and there is a possibility that the deterioration of the developer is accelerated.

  In the developing device 14 shown in FIG. 12, even if the developer that could not be separated from the developing sleeve 141 in the agent separation region R remains on the developing sleeve 141, the remaining developer remains at the inflection point Q on the developing sleeve 141. It is scraped off by a high density developer in the vicinity. For this reason, there is an advantage that accompanying rotation can be effectively prevented. However, as a result of the developer always having a high density in the vicinity of the inflection point Q, the airflow cannot pass through the agent.

In the developing device 14 of this embodiment shown in FIG. 1, the inflection point Q does not exist on the upstream side in the surface movement direction of the developing sleeve 141 with respect to the restriction position that is the closest position between the developing sleeve 141 and the round doctor 146. For this reason, since the developer does not stay much in the upstream region of the restriction position, the amount of the developer drawn up is reduced as compared with the developing device 14 shown in FIG.
In the developing device 14 shown in FIG. 1, the amount of pumping is reduced, but the image density unevenness (screw pitch unevenness) is generated by adopting a configuration in which the developer flow to be pumped and the airflow toward the airflow passage hole 110 intersect. Could be suppressed. This is thought to be due to the following reasons.

That is, in the portion where the density of the developer to be pumped is low, there is a gap between the developer particles and air is included. The carrier in the developer to be pumped is attracted to the developing sleeve by magnetic force, and the toner is attracted to the carrier by electrostatic force. For this reason, even if an air flow is passed through the flow of the developer to be pumped up, the carrier and toner are hardly flowed into the air flow and are unlikely to be separated from the flow of the developer to be pumped up.
On the other hand, almost no force acts on the air between the developer particles to keep the developer flow pumped up. For this reason, when an air flow is passed through the developer flow to be pumped, the air between the particles is easily flowed to the air flow and is easily separated from the developer flow to be pumped.

By separating the air from the flow of the developer to be pumped, the gap between the particles is narrowed, and the density of the developer to be pumped to the developing sleeve is increased.
In addition, when the air flow hits a portion where the developer density is high, the developer in a tight state is loosened, a gap is formed between particles, and the density of the developer pumped up to the developing sleeve may be reduced. Conceivable.
In this way, the air in the portion where the developer density is low escapes and the density increases, and in the portion where the density is high, gaps are formed and the density decreases, so that the density difference of the developer is leveled, and the developing sleeve 141 is leveled. Therefore, the difference in density of the developer pumped up can be reduced.
Thereby, it is considered that the density difference can be suppressed in the developer carried on the surface of the developing sleeve 141, and the occurrence of image density unevenness can be suppressed.
Further, in the developing device 14 of the present embodiment, since the occurrence of image density unevenness can be suppressed without setting the pumping magnetic pole to be a high magnetic force, the developer reattachment due to the fact that the pumping magnetic pole described above has a high magnetic force. It is possible to suppress the occurrence of image density unevenness while suppressing the occurrence of.

The developing device 14 of this embodiment is configured such that the developer on the agent separation region R is not scraped off by the developer in the supply chamber 149A unlike the developing device 14 shown in FIG. Therefore, the developer pumping amount can be further reduced as compared with the developing device 14 shown in FIG. 12 in which the agent separation region R is configured to contact the developer in the supply chamber 149A.
In the developing device 14 of this embodiment, the developer does not stay much in the upstream region of the regulation position, so that the air flow is easy to pass in a sparse developer density as compared with the developing device 14 shown in FIG. Therefore, the air current can be uniformly passed through the developer, and unevenness of the developer density due to the peaks and valleys of the second conveying screw 143 can be eliminated.

  As shown in FIG. 1, the developing device 14 of the present embodiment uses a round bar doctor 146 as a developer regulating member. As the developer regulating member, the developer regulating blade of the developing device 14 shown in FIG. A blade member may be used as in 146b.

However, in the blade member, the value of the moment of inertia in the cross section in the cross section shown in FIG. 12 is small, and if only the both end portions in the longitudinal direction are fixed, the central portion in the longitudinal direction is bent, and the gap at the restriction position is kept constant. I can't.
For this reason, it is necessary to provide a fixing portion for fixing the developer regulating member made of a blade member to the developing case 144 even in a range in the image area in the longitudinal direction, and the air flow passage hole 110 may be provided in the fixing portion. Can not.

  On the other hand, the round bar doctor 146 has a larger value of the moment of inertia in the cross section shown in FIG. 1 than that of the blade member, and can suppress the bending of the central portion in the longitudinal direction even when only the both ends in the longitudinal direction are fixed. The gap at the restriction position can be kept constant. For this reason, it is not necessary to provide a fixing portion for fixing the developer regulating member to the developing case 144 in a range that is within the image area in the longitudinal direction, and the air flow passage hole is located near the position where the developer regulating member regulates the developer. 110 can be provided. Accordingly, it is possible to provide the air flow passage hole 110 at a location closer to the pumping region through which the developer pumped up on the developing sleeve 141 passes, and the action of leveling the developer density difference by the air flow can be improved. .

[Modification]
Next, a modification of the developing device 14 according to this embodiment will be described.
FIG. 7 is a schematic diagram of a developing device 14 according to a modified example. A broken-line arrow in FIG. 7 indicates a path of airflow around the developing device 14.
The modified developing device 14 differs from the developing device 14 shown in FIG. 1 in which the airflow passage hole 110 is provided in the developing case 144 in that the airflow passage hole 110 is provided in the round bar doctor 146.
Also in the developing device 14 of the modified example, by discharging the air inside the developing device 14 from the airflow passage hole 110, it is possible to suppress an increase in the internal atmospheric pressure and to prevent toner scattering. Further, as shown in FIG. 7, the air flow toward the air flow passage hole 110 intersects the path of the developer pumped up to the developing sleeve 141, so that the developer pumped up is leveled, and the density of the developer is uneven. Can be resolved.

  In the configuration of the developing device 14 of the present embodiment described above, when the round bar doctor 146 is a magnetic body, a wide magnetic field concentration region (region indicated by “ε” in FIG. 6) is provided in the upstream region of the restriction position. It is formed. The width of the magnetic field concentration region ε is a value of the diameter of the round bar doctor 146 made of a magnetic material, the magnetic permeability of the round bar doctor 146 as the magnetic body, the normal magnetic flux density of the N3 pole, and the diameter of the magnet roller 147. As the value increases, it tends to increase.

  In the magnetic field concentration region ε, the developer is constrained by the magnetic force, and the developer that is pumped up by the magnetic force and moves toward the restriction position enters the magnetic field concentration region ε, and this entered developer enters the magnetic field concentration region ε. Collides with constrained developer. Therefore, as compared with a configuration in which such a wide magnetic field concentration region ε is not formed, the temperature of the developer is likely to rise in the upstream region of the restriction position. Therefore, since a problem due to the temperature rise of the developer is likely to occur, a configuration that suppresses the temperature rise is required.

  For this reason, the developing device 14 of the modification shown in FIG. 7 has the following configuration. That is, the round bar doctor 146 is a hollow cylindrical member, and the air flow passage hole 110 is provided so that both ends of the developing sleeve axial direction are open and extend in the longitudinal direction of the round bar doctor 146. . And the ventilation fan 148 as a ventilation means which sends air directly in the hollow area | region inside the round bar doctor 146 is provided.

  The airflow generated by the blower fan 148 generates an airflow in the hollow region of the round bar doctor 146, and the heat of the magnetic pole facing surface of the round bar doctor 146 is efficiently removed through the air in the hollow region. Therefore, the heat of the developer existing in the upstream region of the restriction position can be efficiently removed through the magnetic pole facing surface of the round bar doctor 146. As a result, the temperature rise of the developer in the upstream region of the restriction position can be effectively suppressed.

In the modified example, the configuration including the blower fan 148 which is a blowing unit that directly sends air into the hollow region of the round bar doctor 146 has been described. A suction means for directly sucking out air may be used.
Further, as the airflow passage hole 110 provided in the round bar doctor 146, the developer leaks even if the airflow passage hole 110 is arranged at an appropriate position in relation to the magnetic pole arrangement even if the filter is not provided. This can be prevented. However, a filter that inhibits the passage of the developer may be provided in the airflow passage hole 110.

[Experimental example]
Next, a description will be given of an experimental example in which the developing device 14 provided with the air flow passage hole 110 at a position facing the region through which the developer to be pumped passes is evaluated as different conditions as in the developing device 14 shown in FIG. To do.

[Example 1]
A test image was output on the recording paper P by a printer 100 having a developing device having the same configuration as the developing device 14 shown in FIG.
The outer diameter of the developing sleeve 141 is 18 [mm], the rotation speed of the developing sleeve 141 is 500 [rpm], the diameter of the round bar doctor 146 made of a solid round bar is 6 [mm], and the upstream region of the restriction position (agent) The inflection point Q does not exist in the region between the separation position and the restriction position. Further, an opening having a width (height) L1 of 5 [mm] and a length L2 of 300 [mm] is provided near the pumping region of the developing case 144 below the round bar doctor 146 as the airflow passage hole 110. Further, a filter 8 having a thickness of 5 [mm] (30 cells / 25 mm) is disposed in the opening. Then, a two-component developer composed of a polymerized toner having an average particle diameter of 5 [μm] and a magnetic carrier having an average particle diameter of 30 [μm] is used.

[Example 2]
A test image was output on the recording paper P under the same conditions as in Example 1 except that a filter with a thickness of 3 [mm] was used as the filter 8 provided in the opening serving as the airflow passage hole 110.

Example 3
A test image was output on the recording paper P under the same conditions as in Example 1 except that a filter with a thickness of 1 [mm] was used as the filter 8 provided in the opening that becomes the airflow passage hole 110.

Example 4
FIG. 8 is a schematic configuration diagram of the developing device 14 according to the fourth embodiment. The recording paper P was tested under the same conditions as in Example 3 except that a round cylindrical doctor 146 was a hollow cylindrical member having an outer diameter of 6 [mm], and a cylindrical member through which airflow passed through the hollow region. An image was output.

[Comparative Example 1]
FIG. 9 is a schematic configuration diagram of the developing device 14 of Comparative Example 1.
The developing device 14 shown in FIG. 9 has the same configuration as the developing device 14 of the first embodiment, except that the position of the opening serving as the airflow passage hole 110 provided with the filter 8 and the magnetic pole arrangement of the magnet roller 147 are different. . In Comparative Example 1, a test image was output on the recording paper P using the developing device 14 shown in FIG.

In the first embodiment, the airflow passage hole 110 is disposed at a position facing the pumping area, whereas in the first comparative example, the airflow passage hole 110 is disposed at a position facing the agent separation area R.
Further, the magnet roller 147 of the first embodiment has a magnetic pole arrangement in which the inflection point Q does not exist in the upstream region of the restriction position (the region between the agent separation position and the restriction position). The magnetic pole arrangement has an inflection point Q in the position upstream region.
Conditions such as the outer diameter of the developing sleeve 141, the number of revolutions, the diameter of the round doctor 146, the size of the opening of the airflow passage hole 110, the type and thickness of the filter 8, the developer to be used, and the like are the same as in the first embodiment. .

[Comparative Example 2]
FIG. 10 is a schematic configuration diagram of the developing device 14 of Comparative Example 2.
The developing device 14 shown in FIG. 10 has the same configuration as the developing device 14 of Comparative Example 1 except that the magnetic pole arrangement of the magnet roller 147 is different. That is, the airflow passage hole 110 is disposed at a position facing the agent separation region R, and is the same as that of the comparative example 1, and the other configuration is the same as that of the developing device 14 of the first embodiment.
In Comparative Example 2, a test image was output on the recording paper P using the developing device 14 shown in FIG.

  Under the conditions of Examples 1 to 4 and Comparative Examples 1 and 2, the toner scattering to the outside of the developing device, screw pitch unevenness of the output test image, the driving torque of the developing device, and the temperature of the developing device are not used. It was measured. Table 1 shows the evaluation results of this measurement.

  The evaluation criteria in Table 1 are “◯” for those that can withstand practical use, “◎” for excellent ones, and “Δ” that are within acceptable limits for practical use. Moreover, the thing which cannot endure practical use is set as "x".

  From Table 1, in Examples 1 to 3, the thinner the filter 8 is, the more the toner scattering and screw pitch unevenness tend to be improved. This is presumably because the pressure loss of the airflow passing through the airflow passage hole 110 decreases as the thickness of the filter 8 decreases, and the flow rate of the air discharged from the airflow passage hole 110 increases.

When the discharged flow rate increases, when the pressure in the developing device increases, the air in the developing device can be quickly discharged, and the increase in pressure in the developing device can be suppressed. It is considered that the suppression effect is improved.
In addition, if the discharged flow rate increases, the flow rate of the air flow that intersects with the developer flow that is pumped increases, and the effect of the air flow that equalizes the density difference of the developer is improved, improving the effect of suppressing screw pitch unevenness. I think that.
For this reason, it is possible to suppress screw pitch unevenness by minimizing the pressure loss in the airflow passage hole 110, such as by thinning the filter 8 within a range where the developer can be prevented from leaking from the airflow passage hole 110. It is thought to improve.
Moreover, in this experiment example, since the screw pitch unevenness was improved as the pressure loss at the airflow passage hole 110 was smaller, it was confirmed that the screw pitch unevenness was improved by flowing air through the pumping area.

  In Comparative Example 1, since the inflection point Q exists in the upstream region of the restriction position, the magnetic force acting on the developer is strengthened in the upstream region of the restriction position as in the developing device 14 described with reference to FIG. The density difference of the developer can be reduced by increasing the density of the developer. For this reason, the screw pitch unevenness can withstand practical use at the same level as in the first embodiment. However, since a large amount of developer stays in the upstream region of the restriction position, the rotational torque of the developing sleeve 141 increases, and the torque evaluation is not practical.

In Comparative Example 2, since the inflection point Q does not exist in the upstream region of the restriction position, the developer does not stay much in the upstream region of the restriction position, and the amount of developer pumped up is reduced compared to the developing device of Comparative Example 1. Torque is reduced. However, the amount of pumping is small, and the effect of increasing the density of the pumped-up developer does not occur, so that screw pitch unevenness occurs.
On the other hand, in the first to fourth embodiments, the air flow passage hole 110 is provided at a position facing the pumping region through which the developer pumped up on the developing sleeve 141 passes, and the density difference of the developer is leveled by the air flow. Improved screw pitch unevenness.

What was demonstrated above is an example, and there exists an effect peculiar for every following aspect.
(Aspect A)
A developer carrying member such as a developing sleeve 141 that carries and conveys the developer by the magnetic force of a magnetic field generating unit such as a magnet roller 147, a developer containing unit 149 that contains the developer carried on the developer carrying member, and the like. A developing device such as a developing device 14 having a developer containing portion and a developer regulating member such as a round doctor 146 that regulates the layer thickness of the developer carried on the developer carrying member. Airflow generating means such as an airflow passage hole 110 for generating an airflow in a pumping area through which the developer pumped up on the developer carrier is provided.
According to this, as described in the above embodiment, the image density unevenness is improved by generating an air flow in the pumping area. This is thought to be due to the following reasons. That is, even if the density of the developer before being pumped varies, the developer is unraveled by the airflow hitting the developer to be pumped up, and there is a difference in density between the high density part and the low density part. Leveled. As a result, the variation in density that has occurred in the developer before being pumped up is leveled, and the variation in the density of the developer carried on the developer carrier can be suppressed, and the density of the developer used for development can be reduced. Image density unevenness due to the variation can be suppressed. Further, it is not necessary to apply a strong magnetic force in order to suppress the density difference of the developer. Therefore, according to this aspect, it is possible to suppress image density unevenness without applying a large stress to the developer.

(Aspect B)
In the aspect A, the airflow passage hole 110 that communicates the inside and the outside of the developer accommodating portion at a position facing the pumping area in the developing case such as the developing case 144 that forms the developer accommodating portion such as the developer accommodating portion 149. Etc. are provided.
According to this, as described in the above embodiment, when the pressure in the developing device rises, an air flow is generated outward from the opening of the developing case facing the pumping region, and an air flow is generated in the pumping region. The configuration to be realized can be realized.
Furthermore, in this aspect, by providing the opening portion, when the air pressure in the developer accommodating portion rises, the air flow is discharged to the outside of the developing device, so that the increase in the air pressure in the developer accommodating portion can be suppressed. Thereby, it is possible to suppress the generation of an air flow that is ejected from the inside of the developing device to the outside in the vicinity of the developing region, and it is possible to suppress the occurrence of toner scattering due to the air flow.

(Aspect C)
In aspect B, a filter member such as a filter 8 that inhibits the developer from passing is provided in the opening of the airflow passage hole 110 or the like.
According to this, as described in the above-described embodiment, it is possible to prevent the developer from leaking from the opening where the air flow toward the outside is generated.

(Aspect D)
In aspect A, the developer regulating member such as the round bar doctor 146 is hollow, and the inside of the developer regulating member is disposed on the surface of the developer regulating member that faces the inside of the developer containing unit such as the developer containing unit 149. An opening such as an airflow passage hole 110 that communicates with the inside of the developer accommodating portion is provided, and an airflow generating means in the developer regulating member such as a blower fan 148 that generates an airflow inside the developer regulating member is provided.
According to this, as described in the modification, it is possible to realize a configuration in which an airflow is generated in the opening of the developer regulating member located in the vicinity of the pumping area and an airflow is generated in the pumping area.
Further, since the airflow passes through the hollow portion of the round bar-shaped developer regulating member, the temperature rise of the developer on the upstream side of the regulation position where the developer regulating member regulates the developer can be suppressed.

(Aspect E)
In any one of the aspects A to D, the magnetic field generating means such as the magnet roller 147 generates a magnetic force for separating the developer after passing through the developing area from the developer carrier such as the developing sleeve 141. Are adjacent to each other and have a first magnetic pole such as an N2 pole and a second magnetic pole such as an N3 pole. The second magnetic pole is located downstream of the first magnetic pole in the developer transport direction by the developer carrier. Of the developer carrying member that is disposed in the vicinity of the developer regulating member such as the round bar doctor 146, pumps up the developer from the developer accommodating portion such as the developer accommodating portion 149, and is regulated by the developer regulating member. A magnetic force for causing the developer on the surface to rise is generated.
According to this, since the inflection point such as the inflection point Q does not exist in the region between the agent separation position and the restriction position as described in the above embodiment, the restriction position where the developer restriction member restricts the developer. It is possible to prevent a large amount of developer from staying in the upstream region. As a result, the airflow easily passes through the pumping area, and the effect of leveling the developer density by the airflow can be improved.

(Aspect F)
In any one of the aspects A to E, the developer carrying member such as the developing sleeve 141 is configured to convey the developer carried on the surface thereof in the surface moving direction by rotating, such as a round bar doctor 146 or the like. The developer regulating member is a cylindrical member that extends in a direction parallel to the rotation axis of the developer carrier.
According to this, as described in the above embodiment, it is not necessary to provide a fixing portion required in the development direction in the longitudinal direction when the developer regulating member is a blade member. Accordingly, an opening such as the airflow passage hole 110 can be provided near the position where the developer regulating member regulates the developer. Furthermore, by making it cylindrical, the surface area for holding the developer by the magnetic force is widened.

(Aspect G)
In any one of the aspects A to F, the developer regulating member such as the round bar doctor 146 is disposed vertically below the developer carrier such as the developing sleeve 141.
According to this, as described in the above embodiment, an air flow is generated in the pumping region by providing an opening such as the air flow passage hole 110 in the developer regulating member or the developing case such as the developing case 144 below the developer regulating member. The configuration can be realized. In this embodiment, the entrance of the developing case through which the surface of the developer carrying member that has passed through the developing region passes is located above the developer carrying member. Since there is a lot of developer below the developer carrier, it is difficult to generate a suction airflow at the entrance of the development case, but since there is little developer above the developer carrier, it is easy to generate a suction airflow, The occurrence of toner scattering can be suppressed.

(Aspect H)
In any one of the aspects A to G, the developer regulating member such as the round bar doctor 146 is hollow, and the developer regulating member is cooled by moving the heat inside the hollow area to the outside of the hollow area. Cooling means such as a blower fan 148 is provided.
According to this, as described in the modification, it is possible to suppress the temperature rise of the developer on the upstream side of the restriction position where the developer restriction member restricts the developer.

(Aspect I)
In an image forming apparatus such as a printer 100 that includes a latent image carrier such as the photosensitive member 12 and a developing unit that develops the latent image formed on the latent image carrier with a developer, modes A to H are used as the developing unit. A developing device such as the developing device 14 according to any of the above is used.
According to this, as described in the above embodiment, it is possible to suppress the occurrence of image density unevenness in the formed image.

DESCRIPTION OF SYMBOLS 1 Device main body 8 Filter 10Y Image forming device 10 for yellow Image forming device 12Y Photoconductor 12 for yellow Photoconductor 13Y Charging device 13 for yellow 13 Charging device 14 Developing device 14Y Developing device 14A for yellow 15 Developing device 15 Cleaning device 15Y Cleaning for yellow Device 16 Waste toner collection bottle 20 Optical unit 30 Intermediate transfer unit 31 Intermediate transfer belt 35 Primary transfer roller 35Y Primary transfer roller for yellow 36 Secondary transfer roller 40 Paper feed unit 41 Paper feed cassette 42 Paper feed tray 43 Paper feed roller 44 Resist Roller 50 Fixing unit 51 Fixing roller 52 Pressure roller 55 Paper discharge roller 56 Paper discharge tray 60 Toner bottle 100 Printer 108 Transport screw 110 Airflow passage hole 111 Solid image 112 Screw pitch unevenness 113 High density portion 11 4 Low density portion 131 Charging roller 132 Cleaning roller 141 Developing sleeve 142 First conveying screw 143 Second conveying screw 144 Developing case 145 Toner supply port 146 Round bar doctor 146b Developer regulating blade 147 Magnet roller 148 Blower fan 149 Developer accommodating portion 149A Supply chamber 149B Agitation chamber 151 Cleaning brush 152 Cleaning blade 153 Toner recovery coil P Recording paper Q Inflection point R Agent separation region ε Magnetic field concentration region

JP 2010-015120 A

Claims (9)

A developer carrier that carries and conveys the developer by the magnetic force of the magnetic field generating means;
A developer accommodating portion for accommodating a developer carried on the developer carrying member;
In a developing device having a developer regulating member that regulates the layer thickness of the developer carried on the developer carrying body,
A developing device, comprising: an airflow generating means for generating an airflow in a pumping area through which the developer pumped from the developer containing portion passes onto the developer carrier. The developing device according to claim 1,
A developing device comprising: an opening that communicates the inside and the outside of the developer accommodating portion at a position facing the scooping area in a developing case that forms the developer accommodating portion. The developing device according to claim 2,
A developing device, wherein a filter member that inhibits the developer from passing is provided in the opening. The developing device according to claim 1,
The developer regulating member is hollow, and an opening that communicates the inside of the developer regulating member and the inside of the developer containing portion with a surface of the developer regulating member that faces the inside of the developer containing portion. Provided,
A developing device comprising an air flow generating means in the developer regulating member for generating an air flow inside the developer regulating member. In the developing device according to any one of claims 1 to 4,
The magnetic field generating means includes first and second magnetic poles having the same polarity adjacent to each other for generating a magnetic force for separating the developer after passing through the development region from the developer carrier.
The second magnetic pole is disposed downstream of the first magnetic pole in the developer transport direction by the developer carrier and in the vicinity of the developer regulating member, and draws up the developer from the developer containing portion, And a developing device for generating a magnetic force for causing the developer on the surface of the developer carrying member regulated by the developer regulating member to rise. The developing device according to any one of claims 1 to 5,
The developer carrier is configured to convey the developer carried on the surface thereof in the direction of surface movement by rotating,
The developing device, wherein the developer regulating member is a cylindrical member extending in a direction parallel to a rotation axis of the developer carrying member. The developing device according to any one of claims 1 to 6,
The developing device, wherein the developer regulating member is disposed vertically below the developer carrying member. The developing device according to any one of claims 1 to 7,
The developing device according to claim 1, wherein the developer regulating member is hollow, and has cooling means for cooling the developer regulating member by moving the heat in the hollow region inside the developer regulating member to the outside of the hollow region. A latent image carrier;
An image forming apparatus comprising: a developing unit that develops the latent image formed on the latent image carrier with a developer;
An image forming apparatus using the developing device according to claim 1 as the developing unit.

Images