JP2009098595A - Developing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the insufficiency of the stirring of a developer, thereby suppressing the scatter of a toner, scumming, or the unevenness of image density. <P>SOLUTION: In a developing device, three conveyance members 42, 43 and 44 are separated by a partition 48 to form an independent conveyance path. The device includes: a first communicating opening 47-1 for transferring the developer from the vicinity of a downstream end in the conveyance direction of a first stirring conveyance member 43 to the vicinity of the upstream end of a supply conveyance member 42; a second communicating opening 47-2 for transferring the developer from the vicinity of the downstream end in the conveyance direction of the first stirring conveyance member 43 to the upstream end of a second stirring conveyance member 44; a third communicating opening 47-3 for transferring the developer from the vicinity of the downstream end of the supply conveyance member 42 to the vicinity of the upstream end in the conveyance direction of the first stirring conveyance member 43; and a fourth communicating opening 47-4 for transferring the developer from the vicinity of the downstream end of the second stirring conveyance member 44 to the vicinity of the upstream end in the conveyance direction of the first stirring conveyance member 43. In a developer storage, two developer circulation paths are formed at the supply conveyance member side and the second stirring conveyance member side around the first stirring conveyance member. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a developing device that develops an electrostatic latent image formed on a latent image carrier with a two-component developer composed of toner and a magnetic carrier, and a copier, printer, facsimile, or The present invention relates to an image forming apparatus using electrophotography that is configured as a multifunction machine having at least one of these functions.

  As a prior art related to the invention of the present application, for example, Patent Document 1 (Japanese Patent Laid-Open No. 6-167876) discloses a plurality of auxiliary mixed agitation for causing a turbulent flow state in a developer agitating member (screw). By attaching a plurality of members (plate-like vertical blades), a developing device that improves the mixing and stirring efficiency of the replenished toner and the developer and prevents a local decrease in the toner density in the developing roll is provided. Are listed.

  Patent Document 2 (Japanese Patent Application Laid-Open No. 2007-25638) includes a developer passage amount regulating means at an opening for delivering the developer from the downstream end of the replenishing side stirring chamber to the developing side stirring chamber. The developing device is configured to share the charging function to the stirring unit by regulating the developer conveyance amount. In this developing device, the developer passage amount regulating means is constituted by a shutter member, The cross-sectional area of the transfer part can be changed.

Patent Document 3 (Japanese Patent Laid-Open No. 2006-47456) includes a first stirring member that is provided adjacent to a developer carrying member and supplies the developer to the developer carrying member, a first stirring member, and a partition wall. A second agitating member that conveys the developer in the same direction as the first agitating member and a third agitating member that conveys the developer in the opposite direction are sandwiched between the path by the first agitating member and the second and second A developing device that circulates and conveys developer along a path of three agitating members is described. In this developing device, the developer conveying amount of the agitating member, the rotation direction, and the position of toner replenishment are defined.
Patent Document 4 (Japanese Patent Application Laid-Open No. 2007-101797) describes a developing device that uses three developer conveying members to convey the developer.

Japanese Patent Application Laid-Open No. 6-167876 JP 2007-25638 A JP 2006-47456 A JP 2007-101797 A

  Conventionally, a two-component developer containing a toner and a magnetic carrier has been used in an image forming apparatus configured as a copying machine, a printer, a facsimile, or a multifunction machine having at least one of these functions using electrophotography. An image forming apparatus having a so-called two-component developing type developing device is known. In the two-component development method, the toner is charged by the friction of the developer in the developing device, and the charged toner is moved by the electrostatic force generated by the electric field to develop the electrostatic latent image on the latent image carrier such as a photoconductor. .

  The developer is agitated and conveyed in the developer accommodating portion, and is frictionally charged by rubbing the toner and the carrier. A developer carrier such as a developing roller is composed of a rotating cylindrical sleeve and a magnetic field generating means having a plurality of magnetic poles (or a plurality of magnets) disposed inside the sleeve. -The developer that has been conveyed is pumped onto the sleeve by the magnetic force of the magnetic field generating means. The developer carried on the sleeve of the developer carrying member is conveyed to a developing region facing the latent image carrying member such as a photosensitive member by the magnetic force of the magnetic field generating means of the developer carrying member and the rotation of the sleeve.

  A regulating member (such as a doctor blade) that regulates the amount of developer is disposed upstream of the developing area, adjusts the developer conveyed to the developing area to a desired amount, and applies stress to the developer near the regulating member. This stabilizes the charge amount of the toner. The developer transported to the development area is sprinkled by a magnetic field generator to form a magnetic brush, and a developing bias is applied between the developer carrier and the latent image carrier to form an electric field. By applying electric power, toner is moved to the electrostatic latent image for development.

  When the electrostatic latent image on the latent image carrier is developed with toner, and the toner is consumed, the toner concentration of the developer in the developer storage portion decreases, so the output detected or developed by the toner concentration sensor In accordance with the amount of toner calculated from the number of pixels and the like, toner is supplied from the toner supply device to the developer storage portion through the toner supply port. The replenished toner is conveyed in the axial direction by an agitating / conveying member (for example, a conveying screw) and mixed and stirred with the existing developer, and gradually and uniformly dispersed. Approaching.

  When a large amount of toner is replenished, such as when printing a large image area, the replenished toner is not sufficiently agitated with the developer and is supplied to the developer carrier with the local toner density unevenness remaining. Appears in the image, resulting in uneven image density, and toner that is not sufficiently mixed may cause toner scattering or background smearing.

  In the prior art described in Patent Document 1 described above, the turbulent flow in the developer flow is achieved by providing a plate-like vertical blade member between the spiral blades of the conveyance screw. This creates a state and improves the mixing and stirring efficiency of the replenished toner and developer.

  However, the screw shape alone cannot prevent so-called upslip, in which the replenished toner is not mixed with the developer due to the difference in specific gravity between the toner and the carrier, and is transported on the developer surface. The toner transported by sliding up is not sufficiently agitated, so there is a large proportion of toner that becomes poorly charged, and the toner that is poorly charged causes uneven density in the image, dirt on the non-image area, and toner scattering. There is. Especially for high-speed machines with fast printing speed and small-sized machines with small developer capacity, high stirring ability is required because the time required for stirring from the toner replenishment position to the developer carrier is short and the amount of toner replenishment is large. It becomes.

  In the prior art described in Patent Document 2 described above as a countermeasure against top slip, a shutter is provided in the opening for delivering the developer, and a developer retention portion is created by restricting the amount of developer passing, thereby dispersibility of the replenishment toner. However, the staying portion simultaneously increases the stress on the developer.

In the prior art described in Patent Document 3 described above, a third stirring member is provided in order to improve the stirring ability, and the opposing portions of the two stirring members are used.
However, when viewed as a developer circulation path, the toner is circulated through a conveyance path on the side for supplying the developer to the developer carrying member and a conveyance path on the agitation side formed by two agitation members. However, the stirring distance until the toner reaches the developer carrying member is not longer than that in the prior art.
Further, in the prior art described in Patent Document 4, there is no communication port for transferring the developer from the vicinity of the downstream end of the first agitating and conveying member to the upstream end of the second agitating and conveying member, and each developer is conveyed. The arrangement of the members is also different from the configuration of the developing device of the present invention described later.

The present invention has been made in view of the above-described problems of the prior art, and improves toner agitation to prevent insufficient agitation of the replenishing toner, and stably conveys the developer, so that toner scattering, background contamination, and images can be obtained. An object of the present invention is to provide a developing device having a configuration capable of suppressing density unevenness.
Another object of the present invention is to provide an image forming apparatus that can suppress toner scattering, background contamination, and image density unevenness by using the developing device, and can perform high-quality image formation.

In order to achieve the above object, the present invention employs the following solutions.
According to a first aspect of the present invention, there is provided a developer carrying member that contains a magnetic field generating means and carries a two-component developer comprising a toner and a magnetic carrier in a developing region facing the latent image carrying member, and the developer carrying member. A developer storage portion for storing a developer to be supplied to the developer, and the developer carrying portion while being conveyed in the axial direction of the developer carrying member, which is housed in the developer housing portion and adjacent to the developer carrying member. A supply conveyance member that supplies the body, a first agitation conveyance member that is arranged in parallel to the supply conveyance member and conveys the developer in a direction opposite to the supply conveyance member, and is arranged in parallel to the first agitation conveyance member. A developing device having a second agitating and conveying member that conveys the developer in a direction opposite to the first agitating and conveying member, wherein the three conveying members are separated by a partition plate to form an independent conveying path; How to convey the first stirring and conveying member A first communication port for delivering the developer from the vicinity of the downstream end to the vicinity of the upstream end of the supply conveyance member; and the upstream end of the second agitation conveyance member from the vicinity of the downstream end in the conveyance direction of the first agitation conveyance member A second communication port for delivering the developer to the second communication port, a third communication port for delivering the developer from the vicinity of the downstream end portion of the supply conveyance member to the vicinity of the upstream end portion in the conveyance direction of the first agitation conveyance member, and the second A fourth communication port for delivering the developer from the vicinity of the downstream end of the agitating and conveying member to the vicinity of the upstream end of the first agitating and conveying member in the conveying direction, and the first agitating and conveying member in the developer accommodating portion Two developer circulation paths on the supply and conveyance member side and the second agitation and conveyance member side are formed around the center.

According to a second means of the present invention, in the developing device of the first means, the first communication port is disposed at a position lower than the second communication port.
According to a third means of the present invention, in the developing device of the first or second means, at least one of the first communication port and the second communication port has a variable opening area. .

According to a fourth means of the present invention, in the developing device of any one of the first to third means, the transport force of at least one transport member of the first stirring transport member or the second stirring transport member is variable. It is characterized by that.
According to a fifth means of the present invention, in the developing device of the fourth means, the first stirring and conveying member and the second stirring and conveying member are screws, and the conveying force is increased by changing the rotational speed of the screw. It is characterized by being variable.

According to a sixth means of the present invention, in the developing device of any one of the first to fifth means, the developer supplied to the developer carrier by the supply and transport member, and the developer that has passed through the development region is supplied and transported. It is returned to the path by the member.
According to a seventh means of the present invention, in the developing device of any one of the first to fifth means, the developer supplied to the developer carrying member by the supply conveying member, It is returned to the path by the second agitating and conveying member.
Further, an eighth means of the present invention is characterized in that in the developing device of any one of the first to seventh means, the toner is replenished to the developer circulation path by the second agitating and conveying member.

A ninth means of the present invention has a latent image carrier on which an electrostatic latent image is formed, and developing means using a two-component developer comprising a toner and a magnetic carrier, and the electrostatic image on the latent image carrier. In the image forming apparatus that develops the latent image with the toner of the developing unit and visualizes the latent image, the developing unit of any one of the first to eighth units is used as the developing unit.
According to a tenth means of the present invention, in the image forming apparatus of the ninth means, the image forming apparatus includes a plurality of image forming portions each having the latent image carrier and the developing device, and each image forming portion has a plurality of image forming portions on the latent image carrier. An image having a different toner color is formed, and an image of each color of each image forming unit is transferred onto a recording material or an intermediate transfer member so as to form a multicolor or full color image.

  In the developing device of the first means, the three transport members are separated by a partition plate to form an independent transport path, and from the vicinity of the downstream end in the transport direction of the first agitating transport member to the vicinity of the upstream end of the supply transport member A first communication port that delivers the developer to the second communication port, a second communication port that delivers the developer from the vicinity of the downstream end of the first agitating and conveying member to the upstream end of the second agitating and conveying member, and a supply conveying member A third communication port for delivering the developer from the vicinity of the downstream end to the vicinity of the upstream end of the first stirring and conveying member, and the upstream end of the first stirring and conveying member in the conveying direction from the vicinity of the downstream end of the second stirring and conveying member A fourth communication port for delivering the developer in the vicinity of the unit, and two developer circulation paths on the supply conveyance member side and the second agitation conveyance member side around the first agitation conveyance member in the developer storage unit Due to the configuration, the developer is supplied to the developer carrier. Since the circulation path of the separately stirred with circulation path of the image agent is formed, can take the stirring distance long, the margin of the stirring is increased, it is possible to improve the stirring properties.

In the developing device of the second means, in addition to the configuration and effects of the first means, the first communication port is disposed at a position lower than the second communication port, so that the replenishing toner does not mix and slips up. Since it passes through the second communication port at a high position and is conveyed to the circulation path on the stirring side, it does not affect the development area side, so that the stirring property is improved. It is possible to prevent soiling.
In the developing device of the third means, in addition to the configuration and effect of the first or second means, at least one of the first communication port and the second communication port has a variable opening area, so that the supply and conveyance Since the ratio of the conveyance amount between the path on the member side and the path on the second stirring and conveying member side can be changed, the developer is not conveyed more than necessary to the supply conveying member side, and the stress caused by the staying part in front of the regulating member is reduced. Since the influence can be reduced, it is possible to adjust the ratio of the conveyance amount in the circulation path between the supply side and the stirring side.

The developing device of the fourth means has a conveying force of at least one conveying member of the first agitating and conveying member or the second agitating and conveying member in addition to the configuration and effect of any one of the first to third means. Is variable, the ratio of the conveyance amount between the path on the supply conveyance member side and the path on the second stirring conveyance member side can be changed, so that the developer is not conveyed more than necessary to the supply conveyance member side, Since it is possible to reduce the influence of stress due to the staying portion before the regulating member, it is possible to adjust the ratio of the conveyance amount in the circulation path between the supply side and the stirring side.
Further, in the developing device of the fifth means, in addition to the configuration and the effect of the fourth means, the first stirring and conveying member and the second stirring and conveying member are screws, and the number of rotations of the screw is changed. By making the force variable, the ratio of the conveyance amount in the circulation path between the supply side and the stirring side can be adjusted with a simple configuration.

In the developing device of the sixth means, in addition to the configuration and effect of any one of the first to fifth means, the developer supplied to the developer carrying member by the supply conveying member and the developer passing through the developing region is supplied to the supply conveying member By returning to the path, it is possible to sufficiently stir on the stirring side and control the amount of developer transported, so that the state of the developer (developer amount, toner concentration) on the path on the supply transport member side can be stabilized. .
In addition, in the developing device of the seventh means, in addition to the configuration and effect of any one of the first to fifth means, the developer supplied to the developer carrying member by the supply conveying member and passed through the developing region is the first developer. 2 By returning to the path by the agitating and conveying member, sufficient agitation can be performed on the agitating side, and the developer conveyance amount can also be controlled, so that the developer state (developer amount and toner concentration) on the supply and conveying member side path is stable. Can be made.
Further, in the developing device of the eighth means, in addition to the configuration and effect of any one of the first to seventh means, the agitating distance can be increased by supplying toner to the second agitating / conveying member. Further improvement in sex can be achieved.

In the image forming apparatus of the ninth means, by using the developing device of any one of the first to eighth means as the developing means, it is possible to suppress toner scattering, background contamination, and image density unevenness, and to achieve high image quality. Image formation can be performed.
In the image forming apparatus of the tenth means, in addition to the configuration and effects of the ninth means, a plurality of image forming units having a latent image carrier and a developing device are provided, and each image forming unit has a toner color on the latent image carrier. Different images of each image forming unit, and transferring each color image of each image forming unit on a recording material or an intermediate transfer member to form a multicolor or full color image. Background stains and image density unevenness can be suppressed, and high-quality multicolor or full-color image formation can be performed.

  Hereinafter, the configuration, operation, and operation of the developing device and the image forming apparatus according to the present invention will be described in detail based on the illustrated embodiments.

[Example 1]
A schematic configuration and operation of the entire electrophotographic image forming apparatus to which the present invention is applied will be described with reference to FIG. Around the drum-shaped photoreceptor 1 as a latent image carrier, a charging device 2, an exposure device (for example, a laser scanning type writing device) 3, a developing device 4, a transfer device 5, and a cleaning device 6 are arranged in this order. ing. In addition, a sheet feeding / conveying device (not shown) that feeds a recording material (for example, transfer paper) P from a sheet feeding tray (not shown) toward a facing portion between the photosensitive member 1 and the transfer device 5, and a transfer sheet on which a toner image is transferred. And a fixing device 7 for fixing the toner onto the transfer paper P after P is separated from the photoreceptor 1.

  The photosensitive member 1 is formed by forming an organic photosensitive layer exhibiting photosensitivity on the surface of an element tube such as aluminum, and is driven to rotate in the direction of the arrow in the drawing by a driving means (not shown). The surface of the photosensitive member 1 thus rotationally driven is uniformly charged to a predetermined charging potential by the charging device 2, and then the laser beam modulated based on the image information from the exposure device 3 is scanned in the axial direction of the photosensitive member. And irradiated. Thereby, an electrostatic latent image is formed on the photoreceptor 1. The electrostatic latent image formed on the photosensitive member 1 is developed by attaching a toner charged by the developing device 4 in a developing area facing the developing device 4 and visualized to become a toner image.

  On the other hand, the transfer paper P is fed / conveyed by a paper feeding / conveying device (not shown), and is sent / conveyed to a transfer portion where the photosensitive member 1 and the transfer device 5 face each other at a predetermined timing. Then, the toner image formed on the photoconductor 1 is transferred to the transfer paper P by applying a charge having a polarity opposite to that of the toner image on the photoconductor 1 to the transfer paper P by the transfer device 5. Next, the transfer paper P is separated from the photoreceptor 1 and sent to the fixing device 7, and the toner image is fixed on the transfer paper P by the fixing roller 7 a and the pressure roller 7 b of the fixing device 7, and the transfer paper P after fixing is fixed. Is output to a paper discharge section (not shown) such as a paper discharge tray or a post-processing device.

  The surface of the photoreceptor 1 after the toner image is transferred by the transfer device 5 is cleaned by the cleaning device 6, and the toner remaining on the photoreceptor 1 is removed. The surface of the photosensitive member that has passed through the cleaning device 6 is then uniformly charged by the charging device 2 and the next image forming process is repeated.

Next, a characteristic configuration of the developing device 4 of the present invention will be described.
The developing device 4 according to the present invention includes a developer carrier 41 that contains a magnetic field generating means and carries a two-component developer composed of a toner and a magnetic carrier to a development region facing the latent image carrier, and a developer carrier 41. A developer container 40 for storing the developer to be supplied to the developer container, and a developer carrier while transporting the developer in the axial direction of the developer carrier 41, which is accommodated in the developer container 40 and adjacent to the developer carrier 41. A supply conveyance member 42 to be supplied to the body 41, a first agitation conveyance member 43 that is arranged in parallel to the supply conveyance member 42 and conveys the developer in a direction opposite to the supply conveyance member 42, and parallel to the first agitation conveyance member 43 And a second agitating / conveying member 44 that conveys the developer in the opposite direction to the first agitating / conveying member 43. Hereinafter, specific examples of the developing device 4 will be described.

  FIG. 2 is a schematic cross-sectional view of the developing device showing the first embodiment of the present invention. The developing device 4 has an opening at a portion facing the photoreceptor 1, and a part of a developer carrier (for example, a developing roller) 41 is exposed from the opening to face the photoreceptor 1. The developing roller as the developer carrying member 41 facing the photosensitive member 1 includes a cylindrical and nonmagnetic rotatable developing sleeve. Inside the developing sleeve, a magnet (a plurality of magnets or a magnet roller magnetized with a plurality of magnetic poles) is disposed as a fixed magnetic field generating means. Further, a developer accommodating portion (developing case) 40 that accommodates a developer 50 containing toner and a magnetic carrier, a supply conveying member (for example, a supply conveying screw) 42 that conveys the developer 50 in the developer accommodating portion 40, and a first one. A doctor blade as a regulating member that regulates the layer thickness of the developer 50 on the developing roller 41, a first agitating and conveying member (for example, a first agitating and conveying screw) 43 and a second agitating and conveying member (for example, a second agitating and conveying screw) 44 45.

  FIG. 3 is a view showing the flow (circulation path) of the developer in the developing device 4 shown in FIG. As shown in FIG. 3, in the developing device 4, the three conveying members 42, 43, 44 are separated by a partition plate 48 to form an independent conveying path, and the first stirring and conveying screw 43 has a downstream end in the conveying direction. A first communication port 47-1 for delivering the developer to the vicinity of the upstream end of the supply / conveying screw 42 from the vicinity of the first portion, and an upstream end of the second stirring / conveying screw 44 from the vicinity of the downstream end of the first stirring / conveying screw 43 in the conveying direction. A second communication port 47-2 for delivering the developer to the portion, and a third communication port 47 for delivering the developer from the vicinity of the downstream end portion of the supply conveyance screw 42 to the vicinity of the upstream end portion in the conveyance direction of the first agitation conveyance screw 43. 3 and a fourth communication port 47-4 for delivering the developer from the vicinity of the downstream end of the second agitating and conveying screw 44 to the vicinity of the upstream end of the first agitating and conveying screw 43 in the conveying direction. 1st agitation transport in section 40 Two developer circulation path of the crus 43 supply conveyance screw 42 side around the second stirring and conveying screw 44 side is configured with formed.

  Next, the developer circulation path will be described in more detail with reference to FIGS. A supply / conveying screw 42 that supplies the developer 50 to the developing roller 41 while conveying the developer 50 in the axial direction of the developing roller 41 is disposed adjacent to and parallel to the developing roller 41. A first agitating and conveying screw 43 that conveys the developer 50 in a direction opposite to the supplying and conveying screw 41 is disposed on the opposite side of the supplying and conveying screw 42 from the developing roller 41. Further, a second agitating and conveying screw 44 that conveys the developer 50 in the direction opposite to the first agitating and conveying screw 43 is disposed next to the first agitating and conveying screw 43.

  Between the supply conveyance screw 42, the 1st stirring conveyance screw 43, and the 2nd stirring conveyance screw 44, the partition plate 48 which separates each screw as an independent path | route is provided. Further, at both ends of each screw, an opening is provided in the partition plate 48 for transferring the developer to and from the adjacent screw, and the first, second, third, and fourth communication ports 47-1 and 47 are provided. -2, 47, 3, 47-4 are formed.

  The flow of the developer will be described in order. The developer 50 supplied onto the developing roller 41 while being conveyed in the axial direction by the supply conveying screw 42 is pumped up to the surface of the developing roller 41 by the magnetic force of the magnet in the developing roller 41. As the developing roller 41 rotates, it is conveyed in the same direction. The layer thickness of the developer 50 is regulated by a doctor blade 45 opposed to the surface of the developing roller 41 with a predetermined gap, and a certain amount of developer is carried on the developing roller 41 and is conveyed to the opening. 1 opposite. At the same time, passage through the doctor blade 45 is restricted, and stress is applied to the developer, thereby facilitating frictional charging of the toner in the developer.

  In the developing area facing the photoconductor 1, a magnetic brush is formed on the developing roller 41 by the magnetic force of the magnet, and is moved in the same direction as the moving direction of the photoconductor 1 and at a higher speed than the photoconductor 1. The photosensitive member 1 is passed through while being rubbed. At this time, a developing bias is applied to the developing roller 41 by a power source (not shown), and a developing potential acts on the toner at the tip of the magnetic brush that rubs against the photosensitive member 1, so that the photosensitive member 1 is exposed from the surface of the magnetic carrier. The toner image is formed by electrostatic transfer to the latent image portion. The magnetic brush that has passed through the developing area as the developing roller 41 rotates is returned to the supply / conveying screw 42 in the developer container 40 again.

  The developer conveyed to the end while being repeatedly supplied to the developing roller 41, collected from the developing roller 41, and conveyed in the axial direction by the supply conveying screw 42 to the first stirring and conveying screw 43 through the third communication port 47-3. Delivered. The transferred developer is transported in the opposite direction to the supply transport screw 42 while being mixed with the developer on the stirring side. When the first agitating and conveying screw 43 is conveyed to the end, it is transferred to the supply and conveying screw 42 through the first communication port 47-1, and the supply and conveying from the supplying and conveying screw 42 to the developing roller 41 are repeated. A circulation path on the transport side is formed. The first communication port 47-1 is provided with a shutter 46 that can change the opening area of the communication port so that the amount of developer delivered can be controlled.

  On the other hand, a second communication port 47-2 is provided on the opposite side of the first communication port 47-1, and the developer is transferred from the first stirring / transporting screw 43 to the second stirring / transporting screw 44. Toner replenishment position 49 at the upstream end of second agitating and conveying screw 44 is replenished with toner from a toner replenishing means (not shown). The replenished toner is conveyed in the axial direction while being mixed with the developer by the second agitating and conveying screw 44. The developer conveyed to the downstream end of the second agitating / conveying screw 44 is transferred to the first agitating / conveying screw 43 through the fourth communication port 47-4, and conveyed in the reverse direction by the first agitating / conveying screw 43. The agitating side conveyance path is formed.

  That is, the replenished toner is supplied to the developing roller 41 from the supply conveyance screw 42 only after passing through the second agitation conveyance screw 44 → the fourth communication port 47-4 → the first agitation conveyance screw 43 → the first communication port 47-1. Is done. For this reason, compared with the developing device circulating with two conventional conveying members, the stirring distance can be increased by one stirring and conveying screw.

  Incidentally, the stirring of the replenished toner has a problem of so-called upslip where the replenished toner is conveyed so as to slide on the developer surface without being mixed with the developer due to the difference in specific gravity between the toner and the carrier. The toner transported by sliding up is not sufficiently agitated, so that the ratio of the toner that becomes poorly charged is large, and the toner that is poorly charged causes image density unevenness, non-image area background contamination, and toner scattering.

  However, in the developing device 4 of this configuration, since the agitation conveyance distance is long as described above, the amount reaching the supply conveyance side while sliding upward is small, even if it is conveyed to the downstream of the first agitation conveyance screw 43. Since the opening position of the second communication port 47-2 of the transfer portion is formed at a position higher than the opening position of the first communication port 47-1, the replenishing toner that has slipped up passes through the second communication port 47-2. Then, it is conveyed to the circulation path on the stirring and conveying side. Therefore, the upslip toner does not reach the supply / conveyance side, and the image is not affected.

  Another problem is a change in the bulk of the developer. When the toner density of the developer changes due to toner consumption / replenishment, the developer volume also changes. As a method for extending the life of the developer by replenishing and collecting the carrier, there are a method in which the carrier is mixed with the replenished toner and a system in which the amount of the carrier is changed, such as replenishing the carrier by another means. In such a system, the range of change in the volume of the developer is further increased.

  When the volume of the developer changes, the pumping state from the supply / conveying screw 42 to the developing roller 41 and the amount of developer staying in front of the doctor blade 45 change, and the amount of the developer conveyed to the developing region varies. . When the bulk is low, it becomes difficult to pump up the developer, and the pumping amount becomes unstable, and density unevenness may occur in the image. On the other hand, when the bulk is increased, the developer is likely to be pumped up, and the amount of stay before the doctor blade 45 is increased, so that the developer becomes a compacted state and deterioration is promoted.

  In the developing device 4 configured as described above, the developer 50 is distributed and conveyed from the first agitating and conveying screw 43 to the supply conveying side and the agitating and conveying side through the first communication port 47-1 and the second communication port 47-2. Therefore, the ratio of the developer 50 distributed to both paths can be adjusted by the shutter 46 provided in the first communication port 47-1, so that the volume of the developer on the supply and transport screw 42 is kept in an appropriate range and pumped up. The amount is stable. The opening / closing of the shutter 46 may be controlled according to information such as the output of a toner density detecting means (not shown), the area of the image to be formed, the volume of the developer on the supply / conveying screw 42, and the like.

  By using the developing device 4 of this embodiment as described above, insufficient stirring of the replenishing toner can be prevented, and the developer 50 can be stably conveyed, thereby suppressing toner scattering, background contamination, and image density unevenness.

[Example 2]
FIG. 4 shows a second embodiment of the present invention. In this embodiment, the configuration of the image forming apparatus is substantially the same as that shown in FIG. In addition, about the structure which is common in Example 1, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted.
As shown in FIG. 4, a supply conveyance screw 42 is disposed adjacent to the developing roller 41, and a first agitation conveyance screw 43 is provided adjacent to the supply conveyance screw 42. A second agitating and conveying screw 44 is arranged further next to the first agitating and conveying screw 42. A different configuration from the first embodiment is that there is no shutter at the first communication port 47-1.

  FIG. 5 is a view showing the flow (circulation path) of the developer in the developing device 4 shown in FIG. The arrangement of each screw is the same as in Example 1, and the developer circulation path is the same. The second agitating and conveying screw 44 can control the rotation speed independently of other conveying screws, and can change the developer conveying force. By increasing the rotation speed of the second agitating and conveying screw 44, the ratio of the developer amount in the developer circulation path on the supply side can be increased. Conversely, if the rotation speed is decreased, the developer in the developer circulation path on the supply side is increased. The amount ratio can be lowered. For example, when the toner concentration is low, the bulk of the entire developer is reduced. However, if the rotation speed of the second agitating and conveying screw 44 is increased, the ratio of the developer amount in the developer circulation path on the supply side can be increased. The supply state from the transport screw 42 to the developing roller 41 can be stabilized.

  The first stirring and conveying screw 43 may also be configured to be able to independently control the rotation speed, and the ratio of the developer amount can be controlled by each rotation speed. Further, in this embodiment, the shutter is not provided at the communication port. However, in the configuration as in the first embodiment, the control of the developer conveying force based on the number of rotations of the screw and the opening / closing of the shutter may be combined to provide finer conveyance. The amount can be controlled and the stress on the developer can be adjusted. Increasing the screw rotation speed and narrowing the communication port with the shutter increases the stress on the developer.For example, such control is performed only when the charge amount of the developer is not sufficiently increased, such as immediately after the start of the apparatus. You may do it.

  When the amount of toner replenishment is large, the replenishment toner is rapidly stirred by increasing the rotation speed of the first stirring and conveying screw 43 and the second stirring and conveying screw 44 and increasing the conveying force to increase the circulation speed on the stirring side. In addition, since the charge amount is stabilized quickly, it is possible to obtain a stable developer state when reaching the circulation path on the supply side.

[Example 3]
FIG. 6 shows a third embodiment of the present invention. In this embodiment, the configuration of the image forming apparatus is the same as that in FIG. 1, but the arrangement of the conveying members of the developing device 4 is different. In addition, about the structure which is common in Example 1, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted.
As shown in FIG. 6, a supply conveyance screw 42 is disposed adjacent to the developing roller 41, and a second agitation conveyance screw 44 is provided above the supply conveyance screw 42. A first agitating and conveying screw 43 is arranged at a height between the supply conveying screw 42 and the second agitating and conveying screw 44 between the two. A shutter 46 is provided at each of the first communication port 47-1 and the second communication port 47-2 located at the downstream end of the first stirring and conveying screw 43 so that the opening area can be changed. Since the supply conveyance screw 42 and the second agitation conveyance screw 44 are arranged in almost two vertical stages, the width of the developing device 4 can be reduced by one screw compared to the first embodiment, and the size is reduced. Yes.

  FIG. 7 is a view showing the flow of developer (circulation path) of the developing device 4 shown in FIG. 6, in which three screws are shown side by side for easy understanding of the path, but the actual arrangement is shown. It is not a thing. Although the arrangement of each screw and the rotation direction of the developing roller 41 are different from those in the first embodiment, the flow is substantially the same when viewed in the developer circulation path. The delivery of the upstream portion of the first agitating and conveying screw 43 (the opposite end not shown in FIG. 6) is arranged such that the third communication port 47-3 and the fourth communication port 47-4 are shifted in the axial direction. There are a flow that is delivered slightly obliquely upward from the supply conveyance screw 42 to the first agitation conveyance screw 43, and a flow that is delivered from the second agitation conveyance screw 44 to the first agitation conveyance screw 43 by being dropped obliquely from above to below. I try not to interfere.

  In the first embodiment, the second embodiment, and the third embodiment, the developer path is pumped up from the supply / conveyance screw 42 to the developing roller 41, passes through the development region, and then returned to the supply / conveyance screw 42. Yes. The returned developer is pumped up again to the developing roller 41 while being conveyed downstream, so that the toner density becomes lower toward the downstream. For this reason, the image density on the downstream side is lowered, and density unevenness may occur. Therefore, examples of routes different from these are shown below.

[Example 4]
FIG. 8 shows a fourth embodiment of the present invention. In this embodiment, the configuration of the image forming apparatus is the same as that in FIG. 1, but the arrangement of the conveying members of the developing device 4 is different from those in the first to third embodiments. In addition, about the structure which is common in Examples 1-3, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted. FIG. 9 is a diagram showing the developer flow (circulation path) of the developing device 4 shown in FIG. 8 and shows three screws arranged side by side for easy understanding of the path. Not shown.

  As shown in FIG. 8, a supply and transport screw 42 is disposed obliquely above the developing roller 41, and a second stirring and transporting screw 44 is provided below the supply and transport screw 42. A first agitating and conveying screw 43 is arranged at a height between the supply conveying screw 42 and the second agitating and conveying screw 44 between the two. The developer is supplied from the supply / conveying screw 42 to the developing roller 41 by dropping from above, and the developer supplied to the developing roller 41 passes through the developing region and is collected by the second agitating / conveying screw 44.

  Unlike the first to third embodiments, the developer that has passed through the development region and used for development is collected by the second agitating and conveying screw 44, passed through the first agitating and conveying screw 43, and circulated once to the supply and conveying screw 42. To the developing roller 41 again. For this reason, the developer conveyed to the development area by the developing roller 41 is replenished with toner during one circulation and is sufficiently stirred, so that the toner concentration and charge amount are stable. On the other hand, since the developer that has passed through the development region is collected in a screw different from the supply side, the amount of the developer on the supply conveyance screw 42 decreases as it goes downstream. Since the distribution of the developer in the axial direction is deviated, it is severe with respect to the change in the volume of the developer due to the replenishment of the toner and carrier from Examples 1 to 3, but in this embodiment the second communication port By adjusting the shutter 46 provided on 47-2, the ratio of the developer conveyed to the supply conveyance side and the agitation conveyance side paths can be changed, so that the amount of the developer on the supply conveyance screw 42 is kept appropriate. be able to.

  As for the delivery part of the downstream part of the 1st stirring conveyance screw 43, although the direction of the 1st communication port 47-1 is arrange | positioned in the position higher than the 2nd communication port 47-2, as shown in FIG. Since the second communication port 47-2 is slightly upstream, even when the replenishment toner is transported by sliding up, it is easy to be guided from the second communication port 47-2 at the front to the path on the stirring and conveying side. ing. The first communication port 47-1 is also arranged to push the developer upward from the first agitation transport screw 43 to the supply transport screw 42, so that the vicinity of the first communication port 47-1 is filled with the developer. Therefore, the toner that has slipped up does not slide on the surface of the developer as it is and reaches the path on the supply and transport side.

[Example 5]
FIG. 10 shows a fifth embodiment of the present invention. In this embodiment, the configuration of the image forming apparatus is the same as that in FIG. 1, but the arrangement of the conveying members of the developing device 4 is different from those in the first to fourth embodiments. In addition, about the structure which is common in Examples 1-4, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted. FIG. 11 is a diagram showing the developer flow (circulation path) of the developing device 4 shown in FIG. 10 and shows three screws arranged side by side so that the path can be easily understood. Not shown.

  As shown in FIG. 10, a supply conveyance screw 42 is disposed below the developing roller 41, and a first agitation conveyance screw 43 and a second agitation conveyance screw 44 are provided next to the supply conveyance screw 42 in two vertical stages. 1 stirring conveyance screw 43 is arranged so that it may become down. With this configuration, the width of the developing device 4 can be further reduced as compared with the third and fourth embodiments.

  The doctor blade 45 is below the developing roller 41, and the rotation direction of the developing roller 41 is opposite to that of the third embodiment, and the developer flow is also reversed. However, as shown in FIG. 42, 43, 44 and the communication ports 47-1, 47-2, 47-3, 47-4, the circulation paths are almost the same.

  In the circulation type developing device as in the fourth and fifth embodiments, the developer that has passed through the developing region is returned to the second agitating / conveying screw 44, but the gap between the developing roller 41 and the developing case 40 is wide, or the developing is performed. In the case where the amount of toner replenishment is larger than the amount of agent, the toner replenished upstream of the second agitating and conveying screw 44 is ejected directly from the gap between the developing roller 41 and the case 40 before being mixed with the developer. May end up. In such a case, the toner replenishment position 49 may be provided near the downstream end of the second stirring and conveying screw 44 as in the fourth embodiment to replenish the toner. Although the stirring distance of the replenishment toner is shortened, it is possible to prevent the supply toner from being directly ejected from the gap.

  By using the developing device 4 of Examples 3 to 5 in the image forming apparatus having the configuration shown in FIG. 1, toner scattering, background contamination, and image density unevenness can be suppressed as in Example 1, and good image formation can be achieved. It can be performed.

[Example 6]
Although the direct transfer type image forming apparatus has been described in the above embodiments, the developing apparatus of the present invention can be applied to a tandem type color image forming apparatus as another type of image forming apparatus.
FIG. 12 shows an example thereof, and is a schematic configuration diagram of a tandem type color copying machine. This color copying machine has an image forming unit located in the center of the apparatus main body, a paper feeding unit located on the right side of the image forming unit, and an image reading unit (not shown) located above the image forming unit. Yes.

  An intermediate transfer belt 17 as an intermediate transfer member having a transfer surface extending in the horizontal direction is disposed in the image forming unit, and four image forming units for forming an image are formed on the upper surface of the intermediate transfer belt 17. Configurations of 10Y, 10M, 10C, and 10K are provided. That is, four photoconductors 11Y and 11M as image carriers capable of carrying images of four kinds of toners (yellow (Y), magenta (M), cyan (C), and black (K)) that form images. 11C and 11K are juxtaposed along the transfer surface of the intermediate transfer belt 17.

  The intermediate transfer belt 17 is wound around a driving roller 18, a support roller 19, and a secondary transfer counter roller 20, and has a configuration capable of moving in the same direction at the position facing each photoconductor 11Y, 11M, 11C, 11K. ing. A cleaning device 21 that cleans the surface of the intermediate transfer belt 17 is provided at a position facing the driving roller 18.

  The image forming units 10Y, 10M, 10C, and 10K provided with the respective photoreceptors 11Y, 11M, 11C, and 11K have the same configuration although the toner colors of images to be formed are different, and the black image forming unit 10K is an example. For example, a charging device 12, a writing device (for example, a laser scanning type writing device) 13, a developing device 14, and a primary transfer device (for example, 1) are disposed around the photosensitive member 11K, as in FIG. (Next transfer roller) 15 and cleaning device 16 are arranged in this order. The photosensitive member 11K is rotationally driven in a direction indicated by an arrow in the drawing by a driving unit (not shown), and the surface of the rotationally driven photosensitive member 11K is uniformly charged to a predetermined charging potential by the charging device 12, and then the writing device. A laser beam modulated based on the image information from 13 is scanned and irradiated in the photosensitive member axial direction. Thereby, an electrostatic latent image is formed on the photoreceptor 11K. The electrostatic latent image formed on the photoconductor 11K is developed by attaching toner charged by the developing device 14 in a developing area facing the developing device 14, and visualized to become a black toner image. The other image forming units 10Y, 10M, and 10C also perform image formation with the same configuration and operation, and yellow, magenta, and cyan toner images are formed on the photoreceptors 11Y, 11M, and 11C.

  The image forming units 10Y, 10M, 10C, and 10K for the respective colors are selectively used according to a single color or a plurality of color image forming modes, and the image forming units corresponding to the selected image forming mode. However, the image forming process described above is performed. As the developing device 14, the same one as the developing device 4 of each of the above-described embodiments (Examples 1 to 4) is used, and the configuration and operation around each photoconductor are almost the same as those of the above-described embodiment. However, the toner images of the respective colors formed on the respective photoreceptors are primarily transferred not on the recording material P such as transfer paper but on the intermediate transfer belt 17, and are monochromatic, multicolored or full color depending on the image forming mode. One of the images is formed.

  The paper feed unit separates and feeds a paper feed tray 22 on which recording materials such as transfer paper as a recording medium are stacked and a recording material P in the paper feed tray 22 one by one in order from the top. After the feeding roller 23, the conveying roller pair 24 that conveys the fed recording material P, and the recording material P are temporarily stopped and the oblique deviation is corrected, the leading edge of the image on the intermediate transfer belt and the conveying direction A registration roller pair 26 that is sent out toward the nip at a timing that coincides with a predetermined position, and a conveyance guide 25 are provided.

  The toner image T primarily transferred from the photoreceptors 11Y, 11M, 11C, and 11K onto the intermediate transfer belt 17 is conveyed by a bias applied to the secondary transfer roller 27 by a bias applying unit (not shown). Secondary transfer is electrostatically performed on P.

  The recording material P to which the image has been transferred passes through a conveyance guide 28 and is composed of a pair of rollers (fixing roller 29a and pressure roller 29b) having a nip formed therein, and is conveyed to a fixing device 29 controlled to a set temperature by a heater 29c. The toner image on the recording material is heated and pressurized, melted and fixed on the recording material P. The recording material P after the toner image is fixed is transported to a paper discharge section (discharge tray, post-processing device, etc.) (not shown) and output.

  Also in the tandem type color copying machine as described above, by using the developing device 4 having the configuration and operation described in the first to fifth embodiments as the developing device 14 of each of the image forming units 10Y, 10M, 10C, and 10K, Insufficient agitation of the replenishment toner can be prevented, and the developer transport is stable, so that toner scattering, background contamination, and image density unevenness can be suppressed, and high-quality multicolor or full-color image formation can be performed.

FIG. 12 shows an example of the configuration of an intermediate transfer type color image forming apparatus (copier) using the intermediate transfer belt 17, but instead of the intermediate transfer belt 17, a recording material transport belt is used for each image forming unit 10Y. , 10M, 10C, and 10K, the toner images of the respective colors formed on the photosensitive member by the image forming units 10Y, 10M, 10C, and 10K are directly transferred to the recording material conveyed by the recording material conveyance belt. It is also possible to provide a color image forming apparatus of this type.
In the embodiment, the color copying machine is used. However, by adding a communication function and connecting to a network such as a communication line or a LAN, a configuration of a multifunction machine having the functions of a copying machine, a printer, and a facsimile is provided. Can do.

1 is a schematic configuration diagram of an image forming apparatus showing a first embodiment of the present invention. 1 is a schematic sectional view of a developing device showing a first embodiment of the present invention. FIG. 3 is a diagram illustrating a developer circulation path in the developing device according to the first exemplary embodiment of the present invention. It is a schematic sectional drawing of the image development apparatus which shows the 2nd Example of this invention. It is a figure which shows the developer circulation path | route in the image development apparatus of the 2nd Example of this invention. It is a schematic sectional drawing of the image development apparatus which shows the 3rd Example of this invention. It is a figure which shows the developer circulation path | route in the image development apparatus of the 3rd Example of this invention. It is a schematic sectional drawing of the image development apparatus which shows the 4th Example of this invention. It is a figure which shows the developer circulation path | route in the image development apparatus of the 4th Example of this invention. It is a schematic sectional drawing of the image development apparatus which shows the 5th Example of this invention. It is a figure which shows the developer circulation path | route in the image development apparatus of the 5th Example of this invention. It is a schematic block diagram of the color image forming apparatus which shows the 6th Example of this invention.

Explanation of symbols

1: Photoconductor (image carrier)
2: Charging device 3: Exposure device (writing device)
4: Developing device 5: Transfer device 6: Cleaning device 7: Fixing device 10Y, 10M, 10C, 10K: Image forming unit 11Y, 11M, 11C, 11K: Photoconductor (image carrier)
12: Charging device 13: Writing device 14: Developing device 15: Primary transfer roller 16: Cleaning device 17: Intermediate transfer 18: Drive roller 19: Support roller 20: Secondary transfer counter roller 21: Cleaning device 22: Paper feed tray 23: Paper feeding roller 24: Conveying roller pair 26: Registration roller pair 27: Secondary transfer roller 29: Fixing device 40: Developer container (developing case)
41: Development roller (developer carrier)
42: Supply conveyance screw (supply conveyance member)
43: 1st stirring conveyance screw (1st stirring conveyance member)
44: 2nd stirring conveyance screw (2nd stirring conveyance member)
45: Doctor blade (regulating member)
46: Shutter 47-1: First communication port 47-2: Second communication port 47-3: Third communication port 47-4: Fourth communication port 48: Partition plate 49: Toner supply position P: Recording material (transfer) paper)
T: Toner image

Claims (10)

A developer carrier that contains a magnetic field generating means and carries a two-component developer composed of toner and a magnetic carrier in a development area facing the latent image carrier;
A developer accommodating portion for accommodating a developer to be supplied to the developer carrying member;
A supply and transport member that is housed in the developer housing section and feeds the developer to the developer carrier while transporting the developer in the axial direction of the developer carrier adjacent to the developer carrier;
A first stirring and conveying member that is arranged in parallel to the supply and conveying member and conveys the developer in a direction opposite to the supply and conveying member;
A second agitating and conveying member arranged in parallel to the first agitating and conveying member and conveying the developer in a direction opposite to the first agitating and conveying member;
In a developing device having
The three transport members are separated by a partition plate to form an independent transport path,
A first communication port that delivers developer from the vicinity of the downstream end of the first agitating and conveying member to the vicinity of the upstream end of the supply and conveying member;
A second communication port for transferring the developer from the vicinity of the downstream end of the first agitating and conveying member to the upstream end of the second agitating and conveying member;
A third communication port for delivering the developer from the vicinity of the downstream end portion of the supply conveyance member to the vicinity of the upstream end portion in the conveyance direction of the first stirring conveyance member;
A fourth communication port for delivering the developer from the vicinity of the downstream end of the second stirring and conveying member to the vicinity of the upstream end of the first stirring and conveying member in the conveying direction;
Provided,
2. A developing device according to claim 1, wherein two developer circulation paths are formed in the developer storage part, the supply and conveyance member side and the second agitation and conveyance member side centering on the first agitation and conveyance member. The developing device according to claim 1,
The developing device, wherein the first communication port is disposed at a position lower than the second communication port. The developing device according to claim 1 or 2,
At least one of the first communication port and the second communication port has a variable opening area. The developing device according to any one of claims 1 to 3,
The developing device, wherein a transport force of at least one transport member of the first stirring transport member or the second stirring transport member is variable. The developing device according to claim 4,
The developing device, wherein the first stirring and conveying member and the second stirring and conveying member are screws, and the conveying force is made variable by changing the number of rotations of the screw. The developing device according to any one of claims 1 to 5,
The developing device, wherein the developer supplied to the developer carrying member by the supply conveyance member and returned to the path by the supply conveyance member is passed through the development region. The developing device according to any one of claims 1 to 5,
The developing device, wherein the developer supplied to the developer carrying member by the supply conveyance member and passed through the development region is returned to the path by the second agitation conveyance member. The developing device according to any one of claims 1 to 7,
A developing device that replenishes toner to a developer circulation path by the second stirring and conveying member. A latent image carrier on which an electrostatic latent image is formed, and a developing unit using a two-component developer composed of toner and a magnetic carrier, and the electrostatic latent image on the latent image carrier with the toner of the developing unit In an image forming apparatus that develops and visualizes,
An image forming apparatus using the developing device according to claim 1 as the developing unit. The image forming apparatus according to claim 9.
A plurality of image forming units each having the latent image carrier and the developing device are provided, each image forming unit forms an image having a different toner color on the latent image carrier, and each color image of each image forming unit is recorded on a recording material. Alternatively, an image forming apparatus that forms a multicolor or full-color image by superimposing and transferring the intermediate transfer member.

Images