JP5660456B2 - Developing device, and process cartridge and image forming apparatus including the same - Google Patents

Description

  The present invention relates to a developing device using a two-component developer including toner and a carrier, and a process cartridge and an image forming apparatus provided with the developing device.

  This type of developing device used in an image forming apparatus such as a printer, a facsimile machine, and a copying machine is generally transported along a developer carrying body in a developer supply carrying path extending in the direction of the developer carrying body rotation axis. A two-component developer (hereinafter simply referred to as “developer”) is carried on the surface of the rotating developer carrying member, and the developer is supplied to the developing region by the rotation of the developer carrying member. Some conventional developing devices employ a supply / recovery integrated system in which the developed developer on the surface of the developer carrying member that has consumed toner in the development region is returned to the developer supply / conveyance path. In this supply / collection-integrated developing device, the toner density of the developer flowing in the developer supply / conveyance path becomes lower toward the downstream side in the developer conveyance direction (hereinafter, simply referred to as “downstream”), and thus is supplied to the development region. In the developer, there is a drawback that unevenness of toner density occurs in the direction of the rotation axis of the developer carrier. Such toner density unevenness is likely to appear as density unevenness in the image formed on the recording material, and is therefore desired to be eliminated.

  As a developing device that can eliminate this drawback, the developed developer on the surface of the developer carrying member that has consumed toner in the developing region is collected in a developer collecting conveyance path that is a conveyance path different from the developer supply conveyance path. There is one that employs a supply / recovery separation system (for example, Patent Document 1). In the supply / separation type developing device, the toner concentration of the developer flowing in the developer supply / conveyance path is maintained constant over the developer conveyance direction. Therefore, in the developer supplied to the development area, toner density unevenness does not occur in the direction of the rotation axis of the developer carrying member, and the above-described drawbacks are solved.

  In the above-described supply / recovery separation type developing device, the developer is collected to the downstream end while collecting the developer from the developer carrier disposed along the developer collecting / conveying path in the developer collecting / conveying path. Be transported. Therefore, the amount of the developer flowing in the developer recovery conveyance path increases toward the downstream side. In addition, at the downstream end of the developer collection transport path, the developer is transferred to the upstream end of another transport path (hereinafter, the case where the separate transport path is a developer supply transport path will be described as an example). Therefore, the developer transport direction is changed greatly, and the developer transport speed is greatly reduced. Therefore, the developer existing at the downstream end of the developer recovery transport path is pushed by the developer transported later in the developer recovery transport path, and at the downstream end of the developer recovery transport path Becomes clogged.

  In particular, in a configuration in which the developer supply transport path is positioned above the developer recovery transport path, it is necessary to lift and transport the developer against the developer's own weight at the downstream end of the developer recovery transport path. For this reason, the drop in the developer conveyance speed at the downstream end of the developer collection conveyance path is large, and the degree of clogging of the developer at the downstream end of the developer collection conveyance path becomes large. In addition, in this configuration, the developer weight transferred from the downstream end of the developer recovery transport path to the upstream end of the developer supply transport path is added to the developer at the downstream end of the developer recovery transport path. The degree of clogging of the developer at the downstream end of the collection conveyance path is large.

In this way, in the above-described supply / recovery separation type developing device, the developer is clogged at the downstream end of the developer collecting / conveying path, so that a large stress is applied to the developer. In particular, during a period when the developer conveyance in the developing device is stopped during a non-image forming operation or the like, the air in the developer is released and the developer is tightened. In this case, the developer present at the downstream end of the developer recovery conveyance path is originally clogged, but when the developer conveyance stops, the degree of clogging further increases. As a result, when the developer conveyance is resumed, the developer having such a high degree of clogging is forcedly moved by applying a conveyance force by the conveyance member. Therefore, the developer present at the downstream end of the developer recovery transport path is subjected to very large stress when the developer transport is resumed. For this reason, the above-described developing device of the supply / recovery separation system has a problem that the deterioration of the developer easily proceeds.
Further, when the developer in such a high clogging state is forcibly moved by the conveying member when the developer conveyance is resumed, a large driving load torque is generated. For this reason, there is a problem that an excessive load is applied to the drive source of the conveying member, and the operation of the developing device stops and the image formation is interrupted.

  The present invention has been made in view of the above problems, and an object of the present invention is to be able to delay the progress of developer deterioration and to avoid applying an excessive load to the drive source. It is an object to provide a developing device of a possible supply / recovery separation system, and a process cartridge and an image forming apparatus including the same.

In order to achieve the above object, the invention of claim 1 includes a toner and a carrier that are transported in a developer supply transport path extending in the direction of the rotation axis of the developer support along the developer support. By carrying the component developer on the surface of the rotating developer carrier, the two-component developer carried on the surface of the developer carrier is transported to the development area, and the two components are developed in the development area. The toner in the developer is attached to the latent image on the surface of the latent image carrier to develop the latent image, and the two-component developer that has passed through the development area is transferred from the developer carrier to the developer supply conveyance path. In a developing device for collecting in a developer collecting and conveying path which is another conveying path, a spiral blade is provided around the rotation axis, and the rotation axis is driven to drive two-component development along the direction of the rotation axis. Transporting the developer downstream of the developer recovery transport path in the developer transport direction The two-component developer conveyed by the conveying member is a screw of the developer collection conveyance path to the current image agent conveyance direction downstream side end portion, or via other conveying path different from the developer collecting path By transporting the developer supply transport path to the upstream end in the developer transport direction without passing through the other transport path, a circulation transport mechanism for circulating and transporting the two-component developer, and driving of the transport member are performed. After stopping, the two-component developer present at the downstream end of the developer recovery transport path in the developer transport direction is displaced by displacing the transport member upstream of the developer recovery transport path in the developer transport direction. And a developer retracting means for retracting the developer recovery transport path upstream in the developer transport direction.
According to a second aspect of the present invention, in the developing device of the first aspect , the developer retracting means biases the conveying member in a direction in which the conveying member is displaced upstream in the developer conveying direction of the developer recovery conveying path. An urging means, and while the conveying member is being driven, the conveying member utilizes the driving force of the conveying member to resist the urging force of the urging means, and the conveying member is downstream of the developer collection conveying path in the developer conveying direction. It is characterized in that it is displaced.
According to a third aspect of the present invention, in the developing device of the first aspect , the developer retracting means displaces the conveying member by a magnetic force generated by a solenoid.
According to a fourth aspect of the present invention, in the developing device according to any one of the first to third aspects, the two-component developer present at the downstream end of the developer recovery transport path in the developer transport direction is provided. The other transport path or the developer supply transport path as described above is arranged above the developer recovery transport path.
According to a fifth aspect of the present invention, a two-component developer including a toner and a carrier that are conveyed in a developer supply conveyance path extending in a developer carrying member rotation axis direction along the developer carrying member is rotated. The two-component developer carried on the surface of the developer carrying member is transported to the development area by being carried on the surface of the developer carrying body, and the toner in the two-component developer is transferred to the development area. The latent image is developed by being attached to the latent image on the surface of the latent image carrier, and the two-component developer that has passed through the development area is transported from the developer carrier to a transport path different from the developer supply transport path. In the developing device that collects in a certain developer collection conveyance path, the two-component developer conveyed to the downstream end in the developer conveyance direction by the conveyance member in the developer collection conveyance path is referred to as the developer collection conveyance path. Through another different transport path or without the other transport path, It has a circulating transport mechanism for circulating and transporting the two-component developer by transporting it to the upstream end of the developer supply transport path in the developer transport direction, and downstream of the developer recovery transport path in the developer transport direction. The other transport path or the developer supply transport path, which is the transport destination of the two-component developer existing at the side end, is disposed above the developer recovery transport path, and the drive of the transport member is stopped. And a volume variable means for expanding the volume of the downstream end region in the developer transport direction of the developer recovery transport path and returning the expanded volume to the original volume after driving of the transport member is started. It is a feature.
According to a sixth aspect of the present invention, a two-component developer including a toner and a carrier that are conveyed in a developer supply conveyance path extending in the direction of the rotation axis of the developer carrier along the developer carrier is rotated. The two-component developer carried on the surface of the developer carrying member is transported to the development area by being carried on the surface of the developer carrying body, and the toner in the two-component developer is transferred to the development area. The latent image is developed by being attached to the latent image on the surface of the latent image carrier, and the two-component developer that has passed through the development area is transported from the developer carrier to a transport path different from the developer supply transport path. In the developing device that collects in a certain developer collection conveyance path, the two-component developer conveyed to the downstream end in the developer conveyance direction by the conveyance member in the developer collection conveyance path is referred to as the developer collection conveyance path. Through another different transport path or without the other transport path, It has a circulating transport mechanism for circulating and transporting the two-component developer by transporting it to the upstream end of the developer supply transport path in the developer transport direction, and downstream of the developer recovery transport path in the developer transport direction. The other transport path or the developer supply transport path, which is the transport destination of the two-component developer present at the side end, is disposed above the developer recovery transport path, and is connected to the developer recovery transport path. A portion of the conveyance path wall portion in the downstream end region in the developer conveyance direction is formed of a flexible member, and the flexible member is caused by an increase in the internal pressure of the developer existing in the downstream end region in the developer conveyance direction. By bending, the volume of the downstream end region in the developer conveyance direction is configured to be enlarged, and a predetermined time period including a deflection regulating member that regulates the deflection of the flexible member, and the start of driving of the conveyance member Cancels the regulation by the deflection regulating member, and the predetermined period During drive period conveying member excluding, due該撓seen regulating member is characterized in that provided a regulating control means for regulating the deflection of the flexible member.
Further, the invention according to claim 7 is the developing device according to claim 6 , wherein the toner concentration detecting means for detecting the toner concentration of the developer existing in the downstream end region in the developer transport direction of the developer recovery transport path Provided outside the developer collecting and conveying path, the toner concentration detecting means detects the toner concentration via the flexible member.
According to an eighth aspect of the present invention, in the developing device according to the seventh aspect , the toner density detecting means is mounted on the flexible member.
According to a ninth aspect of the present invention, there is provided a process in which the latent image carrier and the developing device for developing the latent image on the latent image carrier are integrally supported and detachably attached to the image forming apparatus main body. In the cartridge, the developing device according to any one of claims 1 to 8 is used as the developing device.
According to a tenth aspect of the present invention, there is provided a latent image bearing member, a latent image forming means for forming a latent image on the latent image bearing member, and a two-component developer containing a toner and a carrier. An image forming apparatus including: a developing device that develops a latent image; and a toner image formed on the latent image carrier by the developing device is finally transferred to a recording material to form an image on the recording material In the apparatus, the developing device according to any one of claims 1 to 8 is used as the developing device.

In the invention according to claim 1, after the driving of the conveying member which is the conveying screw is stopped, the developing member is displaced by the developer retracting means to the upstream side in the developer conveying direction of the developer collecting conveying path, thereby developing the developing member. agent the developer carrying direction of the developer of the collection conveyance path downstream end retracts in the opposite direction, it is possible to reduce the amount of developer the downstream end. As a result, the degree of clogging of the developer at the downstream end of the developer recovery conveyance path can be reduced, so that the stress applied to the developer at the start of driving of the conveyance member is reduced, and the progress of deterioration of the developer can be delayed. In addition, as a result of reducing the degree of developer clogging at the downstream end of the developer recovery conveyance path, the driving load torque at the start of driving the driving source of the conveying member is reduced, and the load applied to the driving source is reduced.

In the invention according to claim 5 , after the driving of the conveying member is stopped, the volume of the downstream end portion region of the developer recovery conveying path is enlarged by the volume varying means. As a result, the developer at the downstream end of the developer recovery conveyance path flows out to the enlarged region. Along with this, the developer accumulated at the upstream end of the transport destination transport path located above the developer recovery transport path falls and flows into the downstream end of the developer recovery transport path. . As a result, since the amount of developer at the upstream end of the transport destination transport path can be reduced, driving of the transport member is started and the developer at the downstream end of the developer recovery transport path is upstream of the transport destination transport path. When transporting toward the side end, the load of movement of the developer at the downstream end toward the transport destination transport path is reduced. Therefore, the stress applied to the developer at the start of driving of the conveying member is reduced, and the progress of deterioration of the developer can be delayed. In addition, as a result of the reduction of the movement load when the developer at the downstream end of the developer recovery conveyance path moves to the upstream end of the conveyance destination conveyance path, the driving load torque at the start of driving the drive source of the conveyance member is small. Thus, the load applied to the drive source is reduced.
Here, the expanded volume is returned to the original by the volume varying means after the driving of the conveying member is started. Since the developer that has been tightened during the drive stop period is immediately loosened by a small amount of conveyance at the start of driving of the conveying member, the degree of clogging of the developer is reduced after the driving of the conveying member is started. It has become. Therefore, even if the expanded volume is restored after the driving of the conveying member is started, an excessive stress is not applied to the developer, and an excessive load is not applied to the driving source.

  According to the present invention, it is possible to delay the progress of developer deterioration and to obtain an excellent effect that it is possible to avoid an excessive load being applied to the drive source.

1 is a schematic configuration diagram of a printer according to an embodiment. 2 is a schematic cross-sectional view showing an example of a developing device 3 applicable to the printer. FIG. FIG. 3 is an explanatory cross-sectional view in the vicinity of the rotation axis of each conveying screw when the developing device is viewed from the direction of arrow F in FIG. 2. FIG. 3 is a schematic diagram illustrating the flow of developer in a developing container of the developing device when the developing device is viewed from the direction of arrow F in FIG. 2. (A) is explanatory drawing which shows the internal structure and operation | movement of a developing container in developer conveyance. (B) is an explanatory view showing the internal configuration and operation of the developer container 33 while the developer conveyance is stopped. It is explanatory drawing which shows the attachment structure of the helical gear with respect to the rotating shaft of the collection | recovery screw in the developing device. It is explanatory drawing for demonstrating the force F which acts on a helical gear. (A) is a graph for explaining the relationship between the force F acting on the helical gear and the urging force F 'of the compression spring during driving of the developing device. (B) is a graph for explaining the relationship between the force F acting on the helical gear and the urging force F ′ of the compression spring while the driving of the developing device is stopped. (A) is explanatory drawing which shows the internal structure and operation | movement of the developing container in the conveyance of the developer in the modification 1. FIG. (B) is an explanatory view showing the internal configuration and operation of the developing container during the developer conveyance stop. 10 is a flowchart illustrating an outline of control contents of a control unit in Modification 1; It is a graph which shows the result of having compared the conventional structure with the drive torque which arises in the drive source of the image development apparatus in embodiment (including modification 1). (A) is explanatory drawing which shows the internal structure and operation | movement of the developing container in the developer conveyance in the modification 2. FIG. (B) is an explanatory view showing the internal configuration and operation of the developing container during the developer conveyance stop. (A) And (b) is explanatory drawing which shows the other example of the opening / closing mechanism of the door member in the modification 2. As shown in FIG. 10 is a graph showing a result of a comparison experiment of a driving torque generated in a driving source of a developing device in Modification 2 with a conventional configuration. (A) is explanatory drawing which shows the flow of the developer in the developer conveyance in the reference example 3. FIG. (B) is an explanatory view showing the flow of the developer during the developer return control performed while the developer conveyance is stopped. 10 is a graph showing a result of a comparison experiment of a driving torque generated in a driving source of a developing device in Reference Example 3 with a conventional configuration. (A) is explanatory drawing which shows the structure of the developing container in the developer conveyance in the modification 4. FIG. (B) is an explanatory view showing the configuration of the developer container immediately after the start of developer conveyance. (A) is explanatory drawing which shows the structure of the developing container in the developer conveyance in the modification 5. FIG. (B) is an explanatory view showing the configuration of the developer container immediately after the start of developer conveyance. (A) is explanatory drawing which shows the structure of the developing container in the developer conveyance in the modification 6. FIG. (B) is an explanatory view showing the configuration of the developer container immediately after the start of developer conveyance. (A) And (b) is explanatory drawing which shows the example which further provided the bending control member 71 of the modification 5 in the developing container of the modification 6. FIG.

  Hereinafter, an embodiment in which the present invention is applied to a printer 100 as an image forming apparatus will be described. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant description thereof will be simplified or omitted as appropriate.

FIG. 1 is a schematic configuration diagram of the printer 100.
The printer 100 is a color image forming apparatus that can form a full-color image using a tandem method, and forms toner images of each color of black, magenta, yellow, and cyan (hereinafter referred to as K, M, Y, and C, respectively). The image forming devices 17K, M, Y, and C are provided. Below these image forming devices 17K, 17M, 17C, and 17C, the recording paper P is carried on the surface and conveyed around the downstream stretching roller 18 and the upstream stretching roller 19, and each image forming device is conveyed. A transfer / conveying belt 15 that moves on the surface while facing the devices 17K, M, Y, and C is disposed. Transfer bias rollers 5K, M, Y, and C that face the image forming devices 17K, M, Y, and C with the transfer conveyance belt 15 interposed therebetween are provided.

  Further, a fixing device 24 that fixes unfixed toner on the recording paper P separated from the transfer conveyance belt 15 is provided downstream of the downstream tension roller 18 in the recording paper conveyance direction by the transfer conveyance belt 15. . In addition, a discharge tray 25 for stacking recording paper P that has passed through the fixing device 24 and has a toner image fixed thereon is provided at the top of the main body of the printer 100.

  A plurality of paper feed cassettes 20, 21, and 22 that store the recording paper P are provided below the transfer conveyance belt 15. Further, a paper feeding / conveying device 26 that supplies recording paper P as a recording material from each of the paper feeding cassettes 20, 21, and 22 to a transfer region where the transfer / conveying belt 15 and the image forming devices 17 </ b> K, M, Y, and C are opposed to each other. And a registration roller 23 for supplying the recording paper P conveyed from each of the paper feeding cassettes 20, 21, and 22 in accordance with the image forming timings of the image forming apparatuses 17K, 17M, 17C, and 17C.

  Further, in the printer 100 according to the present embodiment, the transfer conveyance belt 15 is disposed in an oblique direction so that the horizontal size in FIG. 1 can be reduced, and the conveyance direction of the recording paper P on the transfer conveyance belt 15 is set. As shown by the arrow in FIG. Accordingly, in the printer 100, the width of the housing in the left-right direction in FIG. 1 is slightly longer than the length in the longitudinal direction of the A3 size recording paper. With this configuration, the printer 100 according to the present embodiment can be configured to have a minimum size required to accommodate recording paper therein, and is greatly reduced in size.

  Each image forming device 17K, M, Y, C has a drum-shaped photoconductor 1K, M, Y, C as a latent image carrier. In order with respect to the rotation direction of the photoreceptors 1K, M, Y, and C, there are charging devices 2K, M, Y, and C, developing devices 3K, M, Y, and C, cleaning devices 6K, M, Y, and C, respectively. doing. Further, the writing light L is radiated from the exposure devices 16K, M, Y, C between the charging devices 2K, M, Y, C and the developing devices 3K, M, Y, C. The photoreceptors 1K, M, Y, and C may be belt-shaped instead of drum-shaped.

  In the printer 100 having such a configuration, each color toner image is formed by each image forming device 17K, M, Y, and C at the start of image formation. In each of the image forming devices 17K, M, Y, and C, the photoreceptors 1K, M, Y, and C are rotationally driven by a main motor (not shown) and are uniformly charged by the charging devices 2K, M, Y, and C. Thereafter, the exposure device 16K, M, Y, C emits the writing light L in accordance with the image information for each color obtained by color separation of the image, and an electrostatic latent image is formed. The electrostatic latent images formed on the photoreceptors 1K, M, Y, and C are developed by the developing devices 3K, M, Y, and C, and toner images of the respective colors are formed on the surfaces of the photoreceptors 1K, M, Y, and C. Is formed. On the other hand, the recording paper P fed and conveyed from any of the paper feeding cassettes 20, 21, and 22 is transferred by the registration roller 23 in accordance with the image forming timings of the image forming devices 17 K, M, Y, and C. Supplied on the surface. Then, the recording paper P carried on the transfer conveyance belt 15 is conveyed to the transfer area of each color by the surface movement of the transfer conveyance belt 15.

  The toner images formed on the photoconductors 1K, 1M, 1C, 1C are transferred to the transfer bias rollers 5K, 5M, 5B, and 5C, which are transfer bias means, at the facing portions of the photoconductors 1K, 1M, 1C, 1C and the transfer conveyance belt 15, respectively. The images are sequentially transferred onto the recording paper P carried on the transfer conveyance belt 15 by Y and C. In this way, the toner images formed on the photoreceptors 1K, M, Y, and C are transferred in the order of K, M, Y, and C, and a superimposed color toner image is formed on the recording paper P. The recording paper P onto which the toner image has been transferred is separated from the transfer conveyance belt 15 and conveyed to the fixing device 24 where the toner image is fixed and discharged to a paper discharge tray 25 outside the apparatus.

  On the other hand, after the toner image is transferred onto the recording paper P, the transfer residual toner is removed by the cleaning devices 6K, M, Y, and C, and the charge removal (not shown) is performed as necessary. After being neutralized by the lamp, the operation of being uniformly charged by the charging devices 2K, M, Y, and C is repeated again.

  Next, the developing device 3 will be described in detail. The developing devices 3K, M, Y, and C of the printer 100 according to the present embodiment use toners of different colors (K, M, Y, and C) as image forming materials, but the other configurations are the same. Yes. For this reason, hereinafter, the subscripts K, M, Y, and C are omitted unless otherwise required, and the developing device 3 will be described.

FIG. 2 is a schematic cross-sectional view showing an example of the developing device 3 applicable to the printer 100 of the present embodiment.
FIG. 3 is an explanatory cross-sectional view of the developing device 3 in the vicinity of the rotation axis of each conveying screw as seen from the direction of arrow F in FIG.
FIG. 4 is a schematic diagram illustrating the flow of the developer in the developing container 33 that is the casing of the developing device 3 when the developing device 3 is viewed from the direction of arrow F in FIG.
Note that the arrows in FIGS. 3 and 4 indicate the flow of the developer in the developing container 33.

  As shown in FIG. 2, the developing device 3 is disposed opposite to the photoreceptor 1, and the photoreceptor 1 is driven to rotate clockwise in FIG. 2 as indicated by an arrow a in the figure. A developer container 33 that is a casing of the developing device 3 contains a developer 32 that is a powdery two-component developer composed of a magnetic carrier and magnetic or non-magnetic toner. The developing device 3 carries the developer 32 in the developing container 33 to the developing area A where the toner is supplied to the electrostatic latent image formed on the surface of the photoreceptor 1 to perform development, and is transported by moving the surface. A developing sleeve 34a is provided as a developer carrying member. The developing sleeve 34a includes a magnet roller 34b as a magnetic field generating unit composed of a plurality of magnets fixed to the developing device 3, and the developing sleeve 34a and the magnet roller 34b constitute the developing roller 34. Further, a developing doctor 35 is provided as a developer regulating member for regulating the layer thickness of the developer carried on the developing sleeve 34a.

  The magnet roller 34b of the present embodiment includes three magnetic poles S1, N1, and N2 along the developing sleeve surface movement direction. The magnetic pole S1 is a developing magnetic pole having a function of causing the developer 32 passing through the developing area A to rise and bringing the toner held by the magnetic carrier into contact with the surface of the photoreceptor 1 for development. The magnetic pole N1 is a developer separating magnetic pole that ensures the transportability of the developer 32 by the rotation of the developing sleeve 34a and has a developer separating function for separating the developer from the surface of the developing sleeve 34a. The magnetic pole N2 functions as a pumping magnetic pole that moves the developer 32 in the supply conveyance path 37 to the buffer portion D and pumps it onto the developing sleeve, and controls the developer 32 that passes through the developing doctor 35 by applying a magnetic force. It is a pumping / regulating magnetic pole that also functions as a regulating magnetic pole that ensures the stability of the amount of developer passing through the gear.

  In the present embodiment, the supply screw 39 and the recovery screw 40 that is a conveying member are provided substantially parallel to the rotation axis direction of the developing sleeve 34a. As shown in FIG. 3, each conveying screw has a rotating shaft and a wing portion spirally provided on the rotating shaft, and develops in one direction along the axial direction of the rotating shaft by rotating. The agent 32 is conveyed. Inside the developing container 33, a supply conveyance path 37 as a developer supply conveyance path and a collection conveyance path 38 as a developer collection conveyance path are formed vertically with a partition plate 36 interposed therebetween.

  Moreover, as shown in FIG. 3, the opening part is provided in the both ends of the partition plate 36, respectively. Here, the opening 41 communicates the upstream side of the supply conveyance path 37 in the developer conveyance direction and the downstream side of the recovery conveyance path 38 in the developer conveyance direction. The opening 42 provided on the upstream side in the developer conveyance direction of the collection conveyance path 38 communicates with the end of the supply conveyance path 37 on the downstream side in the developer conveyance direction. A toner replenishing port 45 for replenishing replenished toner is disposed above the opening 42.

  Here, as shown in FIG. 2, the partition plate 36 is erected so that the end on the developing sleeve 34 a side wraps the supply screw 39 from below, and a barrier 43 is formed by this erected portion. The upper space of the developing sleeve 34a formed by the barrier 43, the inner wall of the developing device 3, and the upper peripheral surface of the developing sleeve 34a (pre-regulation space adjacent to the upstream side of the developing sleeve 35 in the moving direction of the developing sleeve) The developer 32 is sequentially supplied from the supply conveyance path 37. In the upper space of the developing sleeve 34a, the stored developer 32 comes into contact with the peripheral surface of the developing sleeve 34a, and the developer 32 that comes into contact with the peripheral surface of the developing sleeve 34a as the developing sleeve 34a rotates rotates. It is formed over the development width so as to be carried and conveyed over the entire width of the rotation axis direction 34a. The upper space of the developing sleeve 34a functions as a buffer portion D that is a storage portion for temporarily storing the developer 32 supplied from the supply conveyance path 37, and the stored developer 32 is stably supplied to the developing sleeve 34a. Supply.

  In the developing device 3 according to the present embodiment, as described later, the amount of the developer 32 in the supply conveyance path 37 tends to decrease as it goes downstream, so that the end of the barrier 43 follows the decrease in the amount. You may form so that height may become low as it goes downstream from upstream. As shown in FIG. 3, the developer 32 in the collection conveyance path 38 is conveyed by the collection screw 40 in the direction opposite to the conveyance direction of the supply screw 39. Further, the supply screw 39 rotates clockwise in FIG. 2, and the recovery screw 40 rotates counterclockwise similarly to the developing sleeve 34a. As shown in FIG. 4, the developer 32 in the developing container 33 is transported toward the transporting direction of the supply transporting path 37 and the recovery transporting path 38 by the rotation of the supply screw 39 and the recovery screw 40, so Circulate.

  The developer 32 is conveyed from the collection conveyance path 38 to the supply conveyance path 37 by the conveyance pressure of the developer 32 accumulated at the downstream end in the conveyance direction by the collection screw 40 provided in the collection conveyance path 38. The developer 32 is pushed upward in the vertical direction so as to pass through an opening 41 that communicates with the recovery conveyance path 38. The developer 32 transported in the supply transport path 37 sequentially passes the end of the barrier 43 between the supply screw 39 and the developing sleeve 34a by the rotation of the supply screw 39 along the developer transport direction, and the buffer section. To D. The developer 32 supplied to the buffer portion D is attracted to the developing sleeve 34a directly or by the magnetic force of the magnet roller 34b provided in the developing sleeve 34a, and is supplied to the developing sleeve 34a.

  The developer 32 supplied to the developing sleeve 34a via the buffer portion D is carried on the surface of the developing sleeve 34a by the rotation of the developing sleeve 34a and the magnetic force of the magnet roller 34b provided therein. 2 in the direction of arrow B. Then, a certain amount of the developer 32 supplied and carried to the developing sleeve 34a via the buffer portion D is carried on the developing sleeve 34a, while being carried on the developing sleeve 34a, as indicated by the arrow B, Passes through a regulation gap with the developing doctor 35. At this time, excessive developer out of the developer 32 carried on the surface of the developing sleeve 34a is blocked from passing by the developing doctor 35 when passing through the regulation gear gap, as shown by an arrow B1 in FIG. It remains in the buffer part D.

  The developer 32 that has passed through the regulation gear gap passes through the developing region A between the developing sleeve 34a and the photosensitive member 1 as shown by an arrow B2 in FIG. 2 and then leaves the developing sleeve 34a, and the bottom 33b of the developing container 33. To the collection conveyance path 38. More specifically, first, the developer 32 that has passed through the regulation gap is carried on the developing sleeve 34a, conveyed to the developing area A, and passes through the developing area A. Thereafter, the developer 32 remaining on the developing sleeve 34a without being supplied to the surface of the photoreceptor 1 in the developing region A is not collected again in the supply conveyance path 37 as the developing sleeve 34a rotates, but is collected. It is collected in the conveyance path 38. Then, the collected developer 32 is conveyed while being agitated in the collected conveyance path 38 with the replenished toner, and is transferred to the supply conveyance path 37 again. In this way, the developer 32 that has passed through the development region A circulates through the supply conveyance path 37 and the collection conveyance path 38 in the developing container 33, and therefore, the supply conveyance path 37 is always sufficiently agitated in the collection conveyance path 38. Only the developer is present.

  Further, since the developer 32 in the collection conveyance path 38 includes the developer 32 having passed through the development area A and having a lowered toner concentration, it is necessary to replenish the toner. Accordingly, the toner is supplied to the developer 32 on the upstream side of the recovery conveyance path 38 according to the toner consumption calculated from the image information of the latent image or according to the measurement result of the toner concentration of the developer 32 in the recovery conveyance path 38. Supply is made. As shown in FIG. 3, the toner replenished in the developing container 33 falls from the toner replenishing port 45 through the opening 42 to the upstream end of the collection transport path 38 in the transport direction. The dropped replenishment toner is replenished to the developer 32 in the collection conveyance path 38 and is agitated and conveyed in the collection conveyance path 38. In this way, the developer 32 having an appropriate toner concentration can be transferred to the supply conveyance path 37.

  In the developing device 3 of the present embodiment, the developer that has been supplied from the supply conveyance path 37 to the development sleeve 34 a and has passed through the development region A and has a decreased toner concentration is located at a position facing the recovery conveyance path 38 from the surface of the development sleeve 34 a. It separates and is collected in the collection conveyance path 38. The developer collected in the collection conveyance path 38 is agitated in the collection conveyance path 38 with the toner replenished at the upstream end in the conveyance direction in the collection conveyance path 38, and in a state where a desired toner concentration is obtained. It is supplied to the supply conveyance path 37. As described above, in the developing device 3 of the present embodiment, the developer whose toner density has decreased after passing through the developing region A is not collected in the supply conveyance path 37 and is supplied on the upstream side and the downstream side in the conveyance direction by the supply screw 39. The toner density of the developer 32 in the transport path 37 does not change.

  In the developing device 3 of the supply / recovery separation system as described above, the developer is clogged in the region surrounded by the broken line in FIG. This is due to the following reason. That is, in the supply and recovery separation type developing device, the developer 32 is transported to the downstream end while recovering the developer from the developing sleeve 34 a disposed along the recovery transport path in the recovery transport path 38. . Therefore, the amount of developer flowing in the collection conveyance path 38 increases toward the downstream side. In addition, since the developer transport direction is changed by 90 ° at the downstream end of the collection transport path 38 in order to transfer the developer to the upstream end of the supply transport path 37, the transport speed of the developer 32 is greatly reduced. Therefore, the developer present at the downstream end of the collection conveyance path 38 is pushed in by the developer conveyed later in the collection conveyance path 38. As a result, the developer present in the downstream end region C1 of the collection conveyance path 38 is clogged. In particular, in the present embodiment in which the supply conveyance path 37 is located above the collection conveyance path 38, it is necessary to lift and transfer the developer at the downstream end of the collection conveyance path 38. For this reason, the developer conveyance speed drops significantly at the downstream end of the collection conveyance path 38, and the degree of clogging of the developer at the downstream end of the collection conveyance path becomes large. In addition, a large amount of developer existing in the upstream end region C2 of the supply conveyance path 37 is applied to the developer present in the downstream end region C1 of the recovery conveyance path 38, so that the downstream end region C1 of the recovery conveyance path 38 is reached. The degree of clogging of the developer is large.

  When the driving of the developing device 3 is stopped during the non-image forming operation and the rotation of the collecting screw 40 is stopped, the air in the developer 32 is released during the stop period, and the developer is tightened. Therefore, the developer 32 existing in the downstream end region C1 of the collection conveyance path 38 is originally clogged, but the clogging is further increased by stopping the developer conveyance. As a result, when the rotation of the recovery screw 40 is started and the developer conveyance is resumed, the recovery screw 40 imparts a conveyance force to the developer 32 in such a high clogging state and forcibly moves it. become. Therefore, the developer 32 present in the downstream end region C1 of the collection conveyance path 38 is subjected to very large stress when the developer conveyance is resumed, and the deterioration of the developer greatly proceeds. Further, since the recovery screw 40 receives a large driving load torque when the developer conveyance is resumed, an excessive load is applied to the drive source of the recovery screw 40, the operation of the developing device 3 is stopped, and the image forming operation is interrupted. Things can happen.

FIG. 5A is an explanatory diagram showing the internal configuration and operation of the developer container 33 during developer conveyance.
FIG. 5B is an explanatory diagram showing the internal configuration and operation of the developer container 33 while the developer conveyance is stopped.
In the developing device 3 of the present embodiment, when a driving force from a driving source (not shown) is input to the driving input gear 52, the two helical gears 53 and 54 are thereby rotated. In the present embodiment, the first helical gear 53 is right-handed and the second helical gear 54 is left-handed. The first helical gear 53 is attached to one end of the rotary shaft 39b of the supply screw 39 and rotates integrally with the rotary shaft 39b. The second helical gear 54 is attached to one end of the rotary shaft 40b of the recovery screw 40 and rotates integrally with the rotary shaft 40b. Further, auxiliary gears 46 and 47 meshing with each other are attached to the other end portions of the rotary shafts 39b and 40b, respectively.

  The second helical gear 54 is attached to the rotating shaft 40b of the recovery screw 40 so as to be slidable along the axial direction. Specifically, as shown in FIG. 6, a cut surface 40 c is formed at the end of the rotation shaft 40 b of the recovery screw 40 to which the second helical gear 54 is attached, and the second helical gear 54 is formed. The shaft mounting hole has a shape that follows the cross-sectional shape of the rotating shaft portion on which the cut surface 40c is formed. As a result, the second helical gear 54 can slide along the rotation shaft 40b of the recovery screw 40, and when the second helical gear 54 rotates, its shaft mounting hole is hooked on the cut surface and rotates. A driving force is transmitted to the rotating shaft 40b, and can rotate integrally with the rotating shaft 40b.

FIG. 7 is an explanatory diagram for explaining the force acting on the second helical gear 54.
When the first helical gear 53 is driven to rotate, the second helical gear 54 from the tooth surface of the first helical gear 53 at the position where the first helical gear 53 and the second helical gear 54 are engaged. The force transmitted to the tooth surface includes an axial component F of the rotating shaft 40b indicated by an arrow in the drawing, in addition to a rotating component that rotates the second helical gear 54 around the rotating shaft 40b. Therefore, the second helical gear 54 receiving this force component (hereinafter referred to as “axial displacement force”) F is axially inward (left side in FIGS. 5A and 5B) along the rotation shaft 40b. Displace. Thereby, as shown in FIG. 6, the end surface of the second helical gear 54 comes into contact with the notch surface 40d of the rotary shaft 40b formed by the formation of the cut surface 40c, and the axial displacement force F is applied to the rotary shaft. 40b. As a result, when a driving force is input to the second helical gear 54, the second helical gear 54 is displaced inward in the axial direction, and the rotary shaft 40b is integrated with the second helical gear 54 in the collection conveyance path 38. Displaces downstream.

  On the other hand, a compression spring 50 is attached to the other end of the rotating shaft 40b as a biasing means for biasing the recovery screw 40 in the direction of displacing the recovery screw 40 to the upstream side of the recovery conveyance path 38. The urging force F ′ to the upstream side of the collection conveyance path 38 is always working. The compression spring 50 is supported by a side plate 51 used when assembling the photoreceptor housing and the development housing. The urging force F ′ is a force that acts on the rotation shaft 40 b of the recovery screw 40 in a direction opposite to the above-described axial displacement force F and is weaker than the axial displacement force F. Specifically, in this embodiment, as shown in FIG. 8A, the biasing force F ′ is approximately 0.3 [N], whereas the axial displacement force F is approximately 0.5 [N]. It is set to become. Therefore, when a driving force is input to the second helical gear 54, the shaft displacement force F generated in the second helical gear 54 is transmitted to the rotating shaft 40b, and the recovery screw 40 is downstream of the recovery conveyance path 38. To the state shown in FIG. On the other hand, when the driving force is no longer input to the second helical gear 54, the axial displacement force F becomes 0 [N] as shown in FIG. The collection screw 40 is returned to the upstream side of the collection conveyance path 38 by the urging force F ′. Since this urging force is transmitted to the second helical gear 54 from the notch surface 40d of the rotating shaft 40b, the second helical gear 54 is also integrated with the rotating shaft 40b to the upstream side of the collection conveyance path 38. Displacement takes place as shown in FIG.

  The axial displacement amount (displacement range) of the recovery screw 40 is regulated by a stopper (not shown). Specifically, even if the recovery screw 40 is displaced, the two auxiliary gears 46 and 47 having the same axial length are restricted so as not to disengage. In this embodiment, as shown in the drawing, the axial length of the second helical gear 54 is longer than that of the first helical gear 53. Thus, even if the second helical gear 54 is displaced in the axial direction while the recovery screw 40 is being driven, the entire tooth surface of the first helical gear 53 meshes with the second helical gear 54 at the meshing position. It is configured as follows. Therefore, even if the recovery screw 40 is displaced, a stable meshing state is ensured.

  With the above configuration, when a driving force from a driving source (not shown) is input to the drive input gear 52, the supply screw 39 is driven to rotate, and the recovery screw 40 is displaced by a certain amount to the downstream side of the recovery conveyance path 38. It is rotationally driven in the state (the state shown in FIG. 5A). As a result, the developer 32 is circulated and conveyed. When the input of the driving force to the drive input gear 52 is stopped, the rotation of the supply screw 39 is stopped, and the recovery screw 40 stops the rotation, and the urging force F ′ stops the rotation of the recovery conveyance path 38. Displacement to the upstream side results in the state shown in FIG. At this time, the developer 32 in the collection conveyance path 38 is pushed to the upstream side of the collection conveyance path 38 by the surface of the blade portion 40 a of the collection screw 40 that is displaced to the upstream side of the collection conveyance path 38. As a result, the developer clogged at the downstream end of the collection conveyance path 38 moves backward to the upstream side of the collection conveyance path 38 after the collection screw 40 is stopped. Therefore, according to the present embodiment, the developer amount at the downstream end of the collection conveyance path 38 is reduced compared to the conventional configuration in which the collection screw 40 is not displaced upstream of the collection conveyance path 38 after the drive is stopped. Can do. Further, the developer accumulated at the upstream end of the supply conveyance path 37 falls and flows into the downstream end of the recovery conveyance path. Since the amount of developer at the upstream end of the supply conveyance path that is weighted by the developer is reduced, the degree of clogging of the developer at the downstream end of the recovery conveyance path is reduced. In this way, the degree of clogging of the developer at the downstream end of the collection conveyance path is reduced, so that the stress applied to the developer 32 at the start of driving of the collection screw 40 is reduced, and the progress of deterioration of the developer is delayed. Can do. Further, as a result of reducing the degree of developer clogging at the downstream end of the collection conveyance path, the driving load torque at the start of driving of the driving source is reduced, and the load applied to the driving source is reduced.

[Modification 1]
Next, a modified example of the developing device 3 of the present embodiment (hereinafter, this modified example is referred to as “modified example 1”) will be described.
FIG. 9A is an explanatory diagram showing the internal configuration and operation of the developing container 33 during developer conveyance in the first modification.
FIG. 9B is an explanatory diagram showing the internal configuration and operation of the developing container 33 while the developer conveyance is stopped.
In the first modification, the developer clogged at the downstream end of the recovery conveyance path 38 is displaced to the upstream side of the recovery conveyance path after the drive is stopped by displacing the recovery screw 40 in the axial direction, similarly to the configuration of the above embodiment. The mechanism for displacing the recovery screw 40 is different. Specifically, the rotation shaft 40b in the recovery screw 40 of the first modification is made of metal, and the recovery screw is used by using a solenoid in which a coil 57 wound so that one end thereof is housed inside is disposed. 40 is displaced in the axial direction. A power source 58 is connected to the coil 57, and the power source 58 is controlled by a control unit (not shown). When a current flows from the power source 58 to the coil 57, a force that is displaced outward in the axial direction is generated on the metallic rotating shaft 40b by the action of the magnetic field generated thereby. Thereby, the recovery screw 40 can be displaced upstream of the recovery conveyance path 38.

FIG. 10 is a flowchart showing an outline of control contents of the control unit.
In the first modification, the control unit that has received a drive stop command for the developing device 3 issues a drive stop instruction to the drive source to stop the drive (S1), and controls the power source 58 to pass a current through the coil 57. (S2). As a result, the rotation of the supply screw 39 stops, and the magnetic field generated by the coil 57 in a state where the recovery screw 40 stops rotating is displaced upstream of the recovery conveyance path 38, as shown in FIG. 9B. It will be in the state shown. At this time, the developer 32 in the collection conveyance path 38 is pushed to the upstream side of the collection conveyance path 38 by the surface of the blade portion 40a of the collection screw 40 that is displaced to the upstream side of the collection conveyance path 38, as in the above embodiment. . Therefore, the developer clogged at the downstream end of the recovery conveyance path 38 moves backward to the upstream side of the recovery conveyance path 38 after the recovery screw 40 is stopped. Therefore, the developer amount at the downstream end of the collection conveyance path 38 can be reduced as compared with the conventional configuration in which the collection screw 40 is not displaced upstream of the collection conveyance path 38 after the drive is stopped. Further, the developer accumulated at the upstream end of the supply conveyance path 37 falls and flows into the downstream end of the recovery conveyance path. Since the amount of developer at the upstream end of the supply conveyance path that is weighted by the developer is reduced, the degree of clogging of the developer at the downstream end of the recovery conveyance path is reduced. In this way, the degree of clogging of the developer at the downstream end of the collection conveyance path is reduced, so that the stress applied to the developer 32 at the start of driving of the collection screw 40 is reduced, and the progress of deterioration of the developer is delayed. Can do. Further, as a result of reducing the degree of developer clogging at the downstream end of the collection conveyance path, the driving load torque at the start of driving of the driving source is reduced, and the load applied to the driving source is reduced.

  The control unit that has received a drive command for the developing device 3 issues a drive instruction to the drive source to start driving (S3), and controls the power supply 58 to stop the current flowing through the coil 57 (S4). . As a result, the supply screw 39 is driven to rotate, and the recovery screw 40 is displaced by a certain amount to the downstream side of the recovery conveyance path 38 due to the axial displacement force F generated at the meshing location of the two helical gears 53 and 54 (see FIG. 9 (a)). As a result, the developing device 3 is driven (S5), and the developer 32 is circulated and conveyed.

FIG. 11 is a graph showing the results of a comparison experiment with the conventional configuration of the drive torque generated in the drive source of the developing device in the present embodiment (including the first modification).
When the recovery screw 40 is displaced to the upstream side of the recovery conveyance path 38 after the drive is stopped as in the present embodiment (including the first modification example), the maximum drive is achieved as compared with the conventional configuration that does not displace in this way. It was confirmed that the torque can be reduced. According to this experiment, the maximum drive torque was 1.5 [N · m] in the conventional configuration, but could be reduced to 0.7 [N · m] in the configuration of this embodiment.

[Modification 2]
Next, another modified example of the developing device 3 of the present embodiment (hereinafter, this modified example is referred to as “modified example 2”) will be described.
FIG. 12A is an explanatory diagram showing the internal configuration and operation of the developing container 33 during developer conveyance in the second modification.
FIG. 12B is an explanatory diagram showing the internal configuration and operation of the developing container 33 while the developer conveyance is stopped.
In the second modification, instead of the recovery screw 40 not being displaced in the axial direction, a configuration is adopted in which the volume of the downstream end region of the recovery conveyance path 38 is increased after the drive is stopped.

  More specifically, in the second modification, the portion of the developing container 33 that constitutes the bottom surface of the downstream end of the collection conveyance path 38 is configured by a door member 60 that can rotate around a rotation shaft 60a. Yes. The door member 60 is supported by a movable mechanism 59 that can linearly advance and retract in the vertical direction in the figure by electrical control of a control unit (not shown). When the movable mechanism 59 retreats downward from the state shown in FIG. 12A, the door member 60 pivots about the rotation shaft 60a and opens. A bellows-like member 61 is hermetically sealed between the door member 60 and the developer container 33 so that the developer in the developer container 33 does not flow outside when the door member 60 is opened.

  In the second modification, the control unit that has received a drive stop command for the developing device 3 issues a drive stop instruction to the drive source to stop the drive, and controls the movable mechanism 59 to retract downward. As a result, the rotation of the supply screw 39 and the recovery screw 40 is stopped, and the door member 60 is opened, so that the volume at the downstream end of the recovery conveyance path 38 is expanded as shown in FIG. As a result, the developer at the downstream end portion of the recovery conveyance path 38 flows into the enlarged region, and the developer accumulated in the upstream end portion of the supply conveyance path 37 along with this flows into the downstream end of the recovery conveyance path. It falls into the part and flows in. As a result, the amount of developer at the upstream end of the supply conveyance path 37 can be reduced, so that the recovery screw 40 is started to drive the developer at the downstream end of the recovery conveyance path to the upstream side of the supply conveyance path 37. The transport load (moving load) when transporting toward the end is reduced. Therefore, the stress applied to the developer at the start of driving the recovery screw 40 is reduced, and the progress of deterioration of the developer can be delayed. Further, the driving load torque at the start of driving of the driving source is reduced, and the load applied to the driving source is reduced.

  Further, the control unit that has received the drive command for the developing device 3 issues a drive instruction to the drive source to start the drive. Thereby, the supply screw 39 and the recovery screw 40 are rotationally driven, and the developer 32 is circulated and conveyed. Then, at a predetermined timing after the start of driving, the movable mechanism 59 is controlled to advance upward. As a result, the door member 60 is closed, and the volume of the enlarged downstream end region of the collection conveyance path is restored as shown in FIG. Since the developer that has been tightened during the drive stop period is immediately loosened by the slight conveyance of the recovery screw 40 at the start of driving, the degree of clogging of the developer is reduced after the start of driving. Yes. Therefore, even if the expanded volume is restored after the start of driving, an excessive stress is not applied to the developer, and an excessive load is not applied to the driving source.

In the second modification, as the mechanism for opening and closing the door member 60, a movable mechanism 59 that can linearly advance and retreat in the vertical direction is adopted, but as shown in FIGS. 13A and 13B, Even if the door member 60 is opened and closed using the eccentric cam 62, the same effect can be obtained.
Specifically, the control unit that has received a drive stop command for the developing device 3 issues a drive stop instruction to the drive source to stop the drive, and rotates the eccentric cam 62 by a half circumference, thereby rotating the short shaft portion of the eccentric cam 62. Is brought into contact with the door member 60. As a result, the door member 60 is opened, and the volume of the downstream end of the collection conveyance path 38 is increased as shown in FIG. Further, the control unit that has received the drive command for the developing device 3 rotates the eccentric cam 62 by a half turn at a predetermined timing after issuing a drive instruction to the drive source and starting the drive, and the long axis of the eccentric cam 62 The part is brought into contact with the door member 60. As a result, the door member 60 is closed, and the volume of the enlarged downstream end region of the collection conveyance path is restored as shown in FIG.

FIG. 14 is a graph showing a result of a comparison experiment of the driving torque generated in the driving source of the developing device in Modification 2 with the conventional configuration.
When the volume at the downstream end of the collection conveyance path 38 is increased after the driving is stopped as in the second modification, it is confirmed that the maximum driving torque can be reduced as compared with the conventional configuration that does not increase in this way. It was done. According to this experiment, the maximum drive torque in the conventional configuration was 1.5 [N · m], but in the configuration of the second modification, it could be reduced to 0.8 [N · m].

[ Reference Example 3]
Next, a reference example of the developing device 3 of the present embodiment (hereinafter referred to as “ reference example 3”) will be described.
FIG. 15A is an explanatory diagram showing the flow of the developer during the developer conveyance in Reference Example 3.
FIG. 15B is an explanatory diagram illustrating the flow of the developer during the developer return control performed while the developer conveyance is stopped.
This reference example 3 employs a configuration in which the collection screw 40 is reversed instead of the collection screw 40 not being displaced in the axial direction and the volume of the downstream end region of the collection conveyance path 38 not being enlarged.

In the third reference example , the control unit that has received a drive stop command for the developing device 3 issues a drive stop instruction to the drive source to stop the drive, whereby the rotation of the supply screw 39 and the recovery screw 40 is stopped. After that, the control unit that receives the drive command of the developing device 3 issues a reverse drive instruction to the drive source for reverse rotation drive for a predetermined time before issuing a normal drive instruction to the drive source, and performs developer return control. Do. As a result, the collection screw 40 rotates in the reverse direction, and the developer 32 in the collection conveyance path 38 is reversely conveyed to the upstream side of the collection conveyance path 38 and downstream of the collection conveyance path 38 as shown in FIG. The amount of developer at the side end can be reduced.

In this reference example 3, since the supply screw 39 and the recovery screw 40 are driven by a single drive source, when the recovery screw 40 is rotated in the reverse direction, the supply screw 39 is also rotated in the reverse direction. Therefore, the developer is reversely conveyed from the downstream side of the supply conveyance path 37 to the upstream end portion of the supply conveyance path 37, and the developer amount at the upstream end portion of the supply conveyance path 37 increases. However, the amount by which the developer at the downstream end of the recovery conveyance path 38 is reversely conveyed by the recovery screw 40 is larger than the amount of the developer reversely conveyed by the supply screw 39 to the upstream end of the supply conveyance path 37. Enough enough. Accordingly, the developer at the upstream end of the supply conveyance path 37 drops and flows into the downstream end of the collection conveyance path 38 in which the developer amount has decreased due to the reverse conveyance of the collection screw 40, thereby The amount of developer at the upstream end of the supply conveyance path that is weighted by the developer at the downstream end is reduced. As a result, the degree of clogging of the developer at the downstream end of the collection conveyance path is reduced, so that the stress applied to the developer 32 when driving of the collection screw 40 is reduced, and the progress of deterioration of the developer can be delayed. . Further, the driving load torque at the start of driving of the driving source is reduced, and the load applied to the driving source is reduced.

  The control unit that has received the drive command for the developing device 3 performs the reverse rotation drive for a predetermined time as described above, and then issues a normal drive instruction to the drive source to start normal drive. As a result, the supply screw 39 and the recovery screw 40 are rotationally driven. As a result, as shown in FIG. 15A, the developer 32 is circulated and conveyed.

In the third reference example , the case where the drive instruction of the developing device 3 is received and the reverse rotation drive is performed immediately before the normal drive instruction is issued to the drive source has been described, but the drive is stopped and the drive is started. Any timing may be used as long as it is within this period. Therefore, for example, it may be the timing immediately after stopping the drive in response to the drive stop command of the developing device 3.
Further, if the recovery screw 40 is configured to be reversely driven separately from the supply screw 39, only the recovery screw 40 can be reversely rotated without reversely rotating the supply screw 39, and the downstream end portion of the recovery conveyance path The clogging state of the developer can be reduced more effectively.

FIG. 16 is a graph showing a result of a comparison experiment of the driving torque generated in the driving source of the developing device in Reference Example 3 with the conventional configuration.
When the recovery screw 40 is reversely rotated within a period from when the drive is stopped to when the drive is started as in the present reference example 3, the maximum drive torque is increased as compared with the conventional configuration in which the reverse rotation is not performed. It was confirmed that it could be reduced. According to this experiment, the maximum drive torque in the conventional configuration was 1.5 [N · m], but in the configuration of Reference Example 3, it could be reduced to 0.6 [N · m].

[Modification 4]
Next, still another modification of the developing device 3 of the present embodiment (hereinafter, this modification is referred to as “Modification 4”) will be described.
FIG. 17A is an explanatory diagram showing a configuration of the developing container 33 during the developer conveyance in the fourth modification.
FIG. 17B is an explanatory diagram showing the configuration of the developing container 33 immediately after the start of developer conveyance.
In the fourth modification, instead of the recovery screw 40 not being displaced in the axial direction, a configuration is adopted in which the volume of the downstream end region of the recovery conveyance path 38 is increased immediately after the start of driving.

  Specifically, in the fourth modification, the portion of the developing container 33 that constitutes the bottom surface of the downstream end portion of the collection conveyance path 38 is configured by the flexible member 70. In the fourth modification, when the control unit that has received a drive stop instruction for the developing device 3 issues a drive stop instruction to the drive source to stop the drive, the developer clogged at the downstream end of the collection conveyance path 38 The air gradually escapes and becomes more clogged. Thereafter, when the control unit that has received a drive start command for the developing device 3 issues a drive start instruction to the drive source to stop the drive, the developer is moved from the upstream side of the recovery conveyance path 38 to the downstream end of the recovery conveyance path 38. Will be transported. At this time, the developer present at the downstream end of the collection conveyance path 38 is in a very clogged state due to the escape of air, so the fluidity is poor. Therefore, immediately after the start of driving, the amount of developer entering from the upstream side of the recovery conveyance path 38 with respect to the downstream end portion of the recovery conveyance path 38 is greater than the supply conveyance path from the downstream end portion of the recovery conveyance path 38. It becomes larger than the amount of the developer that goes out to the upstream end of 37. As a result, immediately after the start of driving, the internal pressure of the developer present at the downstream end of the collection conveyance path 38 increases. If the volume at the downstream end of the collection conveyance path 38 is constant, the developer is subjected to very large stress due to an increase in the internal pressure of the developer, and an excessive load is applied to the drive source. However, in the fourth modification, when the internal pressure of the developer at the downstream end of the collection conveyance path 38 increases, the flexible member 70 bends as shown in FIG. The volume at the downstream end of the passage 38 is increased. Thereby, it is possible to suppress an increase in the internal pressure of the developer at the downstream end of the collection conveyance path 38 immediately after the start of driving. Therefore, immediately after the start of driving, an excessive stress is not applied to the developer at the downstream end portion of the collection conveyance path 38, and an excessive load is not applied to the driving source.

  As time elapses from the start of driving, the fluidity of the developer existing at the downstream end of the recovery conveyance path 38 is restored to the normal state, so that the internal pressure of the developer at the downstream end of the recovery conveyance path 38 is normally Go back to time. Thereby, the bending of the flexible member 70 also returns, and the flexible member 70 is in the state of FIG.

  Examples of the material of the flexible member 70 include urethane rubber and silicon rubber. However, any material may be used as long as it has toner resistance and can be stretched and contracted. However, as in the fourth modification, in the steady state during driving (the load torque of the driving source is stable and the distribution of the developer amount in the supply conveyance path 37 and the collection conveyance path 38 is stable). As shown in FIG. 17 (a), the flexible member 70 does not bend and its inner wall surface is maintained in a substantially flat state, and when the internal pressure immediately after the start of driving is high, as shown in FIG. 17 (b). In addition, in order to realize an operation in which the flexible member 70 is bent to suppress the increase in internal pressure, it is necessary to appropriately select a material that can realize such an operation.

[Modification 5]
Next, still another modification of the developing device 3 of the present embodiment (hereinafter, this modification is referred to as “modification 5”) will be described.
FIG. 18A is an explanatory diagram illustrating a configuration of the developing container 33 during the developer conveyance in the fifth modification.
FIG. 18B is an explanatory diagram showing the configuration of the developing container 33 immediately after the start of developer conveyance.
In the fifth modification, a deflection regulating member 71 that regulates the deflection of the flexible member 70 is provided in the configuration of the fourth modification.

  Specifically, in the fifth modification, the deflection regulating member 71 is provided so as to support the flexible member 70 provided in the portion of the developing container 33 that forms the bottom surface of the downstream end portion of the collection conveyance path 38. Is provided. This bending restricting member 71 is configured to be displaceable in the vertical direction in the figure by electrical control of a control unit (not shown). When the bending restricting member 71 is displaced downward from the state shown in FIG. 18A to the state shown in FIG. 18B, the bending restriction of the flexible member 70 is released, and the flexible member 70 bends. It becomes possible. On the other hand, when the bending restricting member 71 is displaced upward from the state shown in FIG. 18B to the state shown in FIG. 18A, the bending of the flexible member 70 is restricted, and the flexible member 70 is bent. I can't help.

  In the fifth modification, the control unit that has received a drive start command for the developing device 3 issues a drive start instruction to the drive source to start the drive, and displaces the deflection regulating member 71 downward. As a result, the flexible member 70 can be bent, and the flexible member 70 bends due to the increase in internal pressure immediately after the start of driving, as in the above-described fourth modification. The volume increases. Therefore, it is possible to suppress an increase in the internal pressure of the developer at the downstream end of the collection conveyance path 38 immediately after the start of driving, without applying excessive stress to the developer, and adding an excessive load to the driving source. There is nothing. After that, when a predetermined period (for example, a period until a steady state is reached), the control unit displaces the deflection regulating member 71 upward. Thereby, the flexible member 70 will be in the state by which bending was controlled, and the inner wall surface will be maintained in the substantially flat state.

  In the above-described modification example 4, in order to make the inner wall surface substantially flat without bending the flexible member 70 in a steady state during driving, the flexible member 70 is flexible so that such an operation can be realized. It is necessary to design the material and thickness of the member 70. On the other hand, according to the fifth modification, the flexible member 70 can be forced to not bend by the bending restricting member 71 (the inner wall surface is almost flat). There is an advantage that the degree of freedom in selecting the material and thickness of the conductive member 70 is high. In particular, according to the fifth modification, the flexible member 70 that is more easily bent can be adopted, so that it is possible to increase the volume expansion width immediately after the start of driving, and the stress applied to the developer can be further reduced. The load applied to the drive source can be further reduced.

[Modification 6]
Next, still another modification of the developing device 3 of the present embodiment (hereinafter, this modification is referred to as “Modification 6”) will be described.
FIG. 19A is an explanatory diagram illustrating a configuration of the developing container 33 during the developer conveyance in the sixth modification.
FIG. 19B is an explanatory diagram showing the configuration of the developing container 33 immediately after the start of developer conveyance.
In the sixth modification, a toner concentration sensor 72 as a toner concentration detecting means is provided on the outer wall surface of the flexible member 70 in the configuration of the fourth modification.

  More specifically, in the sixth modification, the toner concentration sensor 72 is attached to the outer wall surface of the flexible member 70 provided at the portion of the developing container 33 that forms the bottom surface of the downstream end portion of the collection conveyance path 38. It has been. The toner concentration sensor 72 is a magnetic permeability sensor that detects the toner concentration of the developer present at the downstream end of the collection conveyance path 38 from the outside. In the magnetic permeability sensor, the detection accuracy increases as the wall portion of the collection conveyance path 38 is thinner. Since the thickness of the flexible member 70 is thinner than other portions constituting the wall portion of the collection conveyance path 38, by providing the toner concentration sensor 72 on the flexible member 70, the toner concentration can be adjusted with high accuracy. Can be detected. Conventionally, in order to obtain high detection accuracy, a thin portion is provided on the wall portion of the developing container 33 and the toner concentration sensor 72 is disposed there. However, according to the sixth modification, such a thin portion is provided. Since it is not necessary to form, there is a merit in producing a mold for the developing container 33.

  In addition, as shown to Fig.20 (a) and (b), you may further provide the bending control member 71 demonstrated in the modification 5 mentioned above. At this time, it is also possible to use the toner concentration sensor 72 as the deflection regulating member 71.

As described above, the printer according to the embodiment, the first modification, and the third reference example includes the photosensitive member 1 as a latent image carrier and a charging device as a latent image forming unit that forms an electrostatic latent image on the photosensitive member 1. 2 and an exposure device 16, and a developing device 3 that develops the electrostatic latent image on the photoreceptor 1 with a two-component developer containing toner and carrier, and the toner formed on the photoreceptor 1 by the developing device 3 The image forming apparatus forms an image on the recording paper P by finally transferring the image to the recording paper P as a recording material. The developing device 3 rotates a developer 32 including toner and a carrier that are conveyed in a developer supply conveyance path 37 that extends in the direction of the rotation axis of the development sleeve along a development sleeve 34a as a developer carrier. The developer carried on the surface of the developing sleeve 34a is transported to the developing area A, and the toner in the developer is latent on the surface of the photoreceptor on the developing area A. The latent image is developed by being attached to the image, and the developer that has passed through the developing area A is collected from the developing sleeve 34 a to the developer collecting and conveying path 38 that is a conveying path different from the supply conveying path 37. In the developing device 3, the developer 32 conveyed to the downstream end by the collecting screw 40 serving as a conveying member in the collection conveying path 38 is not connected to another conveying path, and the upstream end of the supply conveying path 37 is used. The developer is circulated and conveyed. After the drive of the recovery screw 40 is stopped, as a developer retracting means for retracting the developer existing at the downstream end of the recovery transport path 38 to the upstream side of the recovery transport path 38, a compression spring 50, a power source 58, and A solenoid having a coil 57 and a controller for performing developer return control are provided. With this configuration, after the drive of the recovery screw 40 is stopped, the developer at the downstream end of the recovery transport path is retracted in the direction opposite to the developer transport direction, thereby reducing the amount of developer at the downstream end. it can. As a result, the degree of clogging of the developer at the downstream end of the collection conveyance path can be reduced, so that the stress applied to the developer at the start of driving is reduced and the progress of deterioration of the developer can be delayed. Further, the driving load torque at the start of driving of the driving source is reduced, and the load applied to the driving source is reduced.
In particular, in the above-described embodiment and Modification 1, the recovery screw 40 is provided with a spiral wing 40a around the rotation shaft 40b, and the rotation shaft 40b is driven to develop along the rotation shaft direction. This is a conveying screw that conveys the agent, and the developer present at the downstream end of the collecting and conveying path 38 is moved backward by displacing the collecting screw 40 to the upstream side of the collecting and conveying path 38. Accordingly, the developer can be retracted without driving the recovery screw 40 in the reverse rotation, and can be realized at a lower cost than the configuration in which the recovery screw 40 is driven in the reverse rotation to retract the developer.
In particular, in the above embodiment, the compression spring 50 is provided as an urging means for urging the recovery screw 40 in the direction of displacing the recovery screw 40 to the upstream side of the recovery conveyance path 38, and the helical gear 53, 54, the recovery screw 40 is displaced to the flow side of the recovery conveyance path 38 against the biasing force of the compression spring 50 by the driving force of the recovery screw 40. According to this configuration, the recovery screw 40 can be displaced to the upstream side of the recovery conveyance path 38 by the urging force of the compression spring 50 only by stopping the recovery screw 40, so that the developer is moved backward. The configuration is simple.
Moreover, even if it is the structure which displaces the collection | recovery screw 40 with the magnetic force which a solenoid generate | occur | produces like the said modification 1, it can implement | achieve cheaply.
Further, as in Reference Example 3 described above, the developer present at the downstream end of the collection conveyance path 38 may be retracted by reversely rotating the rotation shaft of the collection screw 40.
Further, in the developing devices in the above-described embodiment, the first modification, and the reference example 3, the supply conveyance path 37 that is the conveyance destination of the developer existing at the downstream end of the collection conveyance path 38 is located above the collection conveyance path 38. Because of the arrangement, the developer at the downstream end of the collection conveyance path 38 is likely to be clogged. However, with these developing devices, the developer is clogged even with such a disadvantageous configuration. The problem caused by becoming can be effectively solved.
Moreover, in the said modification 2, after the drive of the collection | recovery screw 40 stops, the volume of the downstream edge part area | region of the collection | recovery conveyance path 38 is expanded, and after the drive of the collection | recovery screw 40 is started, based on the expanded volume. As the volume changing means for returning, a mechanism for opening and closing the door member 60 constituting the bottom surface of the downstream end portion of the collection conveyance path 38 is provided. According to this configuration, the developer at the downstream end of the collection conveyance path 38 flows out to the enlarged area, and the developer collected at the upstream end of the supply conveyance path 37 is collected accordingly. It falls and flows into the downstream end of the conveyance path 38. As a result, the amount of developer at the upstream end of the supply conveyance path 37 can be reduced, so that driving is started and the developer at the downstream end of the collection conveyance path is directed toward the upstream end of the supply conveyance path 37. When transporting the developer, the developer transport load at the downstream end of the collection transport path is reduced. Therefore, the stress applied to the developer at the start of driving is reduced, and the progress of the deterioration of the developer can be delayed. Further, the driving load torque at the start of driving of the driving source is reduced, and the load applied to the driving source is reduced.

Further, in the above-described modified examples 4 to 6, a part of the conveyance path wall portion in the downstream end area of the collection conveyance path 38 is formed by the flexible member 70, and the internal pressure of the developer existing in the downstream end area is determined. The flexible member 70 is bent by the rise, so that the volume of the downstream end region can be increased. According to this configuration, it is possible to suppress an increase in the internal pressure of the developer in the downstream end region immediately after the start of driving. Therefore, the stress applied to the developer is reduced, the progress of deterioration of the developer can be delayed, and the load applied to the drive source is reduced by reducing the drive load torque.
Moreover, in the said modification 5, the bending control member 71 which controls the bending of the flexible member 70 is provided, and restriction | limiting by the bending control member 71 is cancelled | released for the predetermined period (predetermined period immediately after a drive start) at the time of a drive start. Then, during the driving period excluding the predetermined period, the bending restriction member 71 controls the bending of the flexible member 70. With such a configuration, the degree of freedom in selecting the material and thickness of the flexible member 70 can be increased. Further, since the flexible member 70 that is more flexible can be adopted, it is possible to increase the volume expansion width immediately after the start of driving, to further reduce the stress applied to the developer, and to further reduce the load applied to the driving source. it can.
In the sixth modified example, a toner concentration sensor 72 as a toner concentration detecting means for detecting the toner concentration of the developer present in the downstream end region of the collection conveyance path 38 is provided outside the collection conveyance path 38. The toner density sensor 72 is configured to detect the toner density via the flexible member 70. Usually, the thickness of the flexible member 70 constituting a part of the wall portion of the developing container 33 can be made thinner than other parts constituting the wall portion of the developing container 33. Therefore, by detecting the toner concentration by the toner concentration sensor 72 through the thin flexible member 70 as described above, the accuracy of detecting the toner concentration can be improved.
Further, as in Modification 6 above, by attaching the toner concentration sensor 72 on the flexible member 70, toner detection is always performed at a re-proximity distance to the developer regardless of the deflection of the flexible member 70. Therefore, it is possible to stably obtain high toner density detection accuracy.

In the above description, the recovery conveyance path 38 is disposed below the supply conveyance path 37, and the developer is circulated and conveyed on these two conveyance paths. However, the developer is conveyed on three or more conveyance paths. Even if it is the structure which carries out circulation conveyance of this invention, this invention is applicable.
Further, the present invention can be applied even if the developer transport destination transport path at the downstream end of the recovery transport path 38 is not disposed above the recovery transport path 38.

DESCRIPTION OF SYMBOLS 1 Photoconductor 3 Developing apparatus 16 Exposure apparatus 32 Developer 33 Developer container 34a Developing sleeve 37 Supply conveyance path 38 Collection conveyance path 39 Supply screw 40 Collection screw 40a Wing 40b Rotating shaft 45 Toner supply port 46, 47 Auxiliary gear 50 Compression spring 52 drive input gears 53, 54 helical gear 57 coil 58 power supply 59 movable mechanism 60 door member 61 bellows-like member 62 eccentric cam 70 flexible member 71 deflection regulating member 72 toner density sensor 100 printer

JP 11-84874 A

Claims (10)

A two-component developer containing toner and a carrier conveyed in a developer supply conveyance path extending in the direction of the developer carrier rotation axis along the developer carrier is transferred to the rotating developer carrier. By carrying the toner on the surface of the developer carrying member, the two-component developer carried on the surface of the developer carrying member is conveyed to the developing region, and in the developing region, the toner in the two-component developer is transferred onto the latent image carrier surface. The latent image is developed by adhering to the developer, and the two-component developer that has passed through the development area is collected from the developer carrying member into a developer collection conveyance path that is a conveyance path different from the developer supply conveyance path. In the developing device,
A conveying screw provided with a spiral wing around the rotation axis, and transporting the two-component developer downstream of the developer collection conveyance path along the rotation axis direction by driving the rotation axis. in a two-component developer conveyed to the developer collection conveyance path to the conveyance direction downstream side end portion current image agent by the conveying member, via other conveying path different from the developer collection conveyance path or the A circulation conveyance mechanism that circulates and conveys the two-component developer by conveying to the upstream end of the developer supply conveyance path in the developer conveyance direction without passing through another conveyance path;
After the driving of the conveying member is stopped, the conveying member is displaced to the upstream side in the developer conveying direction of the developer collecting conveying path, thereby existing at the downstream end of the developer collecting conveying path in the developer conveying direction. And a developer retracting means for retracting the two-component developer to be upstream of the developer collection transport path in the developer transport direction. The developing device according to claim 1 .
The developer retracting means includes biasing means for biasing the transport member in a direction to displace the developer recovery transport path upstream in the developer transport direction, and driving the transport member while the transport member is being driven. A developing device characterized in that the conveying member is displaced downstream in the developer conveying direction of the developer recovery conveying path by using force to resist the urging force of the urging means. The developing device according to claim 1 .
The developing device according to claim 1, wherein the developer retracting means displaces the conveying member by a magnetic force generated by a solenoid. The developing device according to any one of claims 1 to 3 ,
The other transport path or the developer supply transport path, which is the transport destination of the two-component developer existing at the downstream end of the developer recovery transport path in the developer transport direction, is located above the developer recovery transport path. A developing device which is arranged. A two-component developer containing toner and a carrier conveyed in a developer supply conveyance path extending in the direction of the developer carrier rotation axis along the developer carrier is transferred to the rotating developer carrier. By carrying the toner on the surface of the developer carrying member, the two-component developer carried on the surface of the developer carrying member is conveyed to the developing region, and in the developing region, the toner in the two-component developer is transferred onto the latent image carrier surface. The latent image is developed by adhering to the developer, and the two-component developer that has passed through the development area is collected from the developer carrying member into a developer collection conveyance path that is a conveyance path different from the developer supply conveyance path. In the developing device,
The two-component developer transported to the downstream end in the developer transport direction by the transport member in the developer recovery transport path is passed through another transport path different from the developer recovery transport path or the other transport. It has a circulation conveyance mechanism that circulates and conveys the two-component developer by conveying to the upstream end of the developer supply conveyance path in the developer conveyance direction without passing through the path,
The other transport path or the developer supply transport path, which is the transport destination of the two-component developer existing at the downstream end of the developer recovery transport path in the developer transport direction, is located above the developer recovery transport path. Has been placed,
After the driving of the conveying member is stopped, the volume of the downstream end portion region of the developer recovery conveying path in the developer conveying direction is enlarged, and the volume that returns the expanded volume after the driving of the conveying member is started is restored. And a developing unit. A two-component developer containing toner and a carrier conveyed in a developer supply conveyance path extending in the direction of the developer carrier rotation axis along the developer carrier is transferred to the rotating developer carrier. By carrying the toner on the surface of the developer carrying member, the two-component developer carried on the surface of the developer carrying member is conveyed to the developing region, and in the developing region, the toner in the two-component developer is transferred onto the latent image carrier surface. The latent image is developed by adhering to the developer, and the two-component developer that has passed through the development area is collected from the developer carrying member into a developer collection conveyance path that is a conveyance path different from the developer supply conveyance path. In the developing device,
The two-component developer transported to the downstream end in the developer transport direction by the transport member in the developer recovery transport path is passed through another transport path different from the developer recovery transport path or the other transport. It has a circulation conveyance mechanism that circulates and conveys the two-component developer by conveying to the upstream end of the developer supply conveyance path in the developer conveyance direction without passing through the path,
The other transport path or the developer supply transport path, which is the transport destination of the two-component developer existing at the downstream end of the developer recovery transport path in the developer transport direction, is located above the developer recovery transport path. Has been placed,
A portion of the transport path wall portion in the developer transport direction downstream end region of the developer recovery transport path is formed of a flexible member, and the internal pressure of the developer existing in the developer transport direction downstream end region is increased. The flexible member is bent by the above, so that the volume of the downstream end portion region in the developer transport direction can be increased ,
A deflection regulating member for regulating the deflection of the flexible member;
During the predetermined period including the start of driving of the conveying member, the restriction by the bending regulating member is released, and during the driving period of the conveying member except for the predetermined period, the bending of the flexible member by the bending regulating member. And a restriction control means for restricting the development. The developing device according to claim 6 .
A toner concentration detecting means for detecting the toner concentration of the developer existing in the downstream end portion region of the developer collecting conveyance path in the developer conveying direction is provided outside the developer collecting conveying path,
The developing device according to claim 1, wherein the toner density detecting means detects the toner density via the flexible member. The developing device according to claim 7 .
The developing device according to claim 1, wherein the toner density detecting means is mounted on the flexible member. In a process cartridge that integrally supports a latent image carrier and a developing device that develops a latent image on the latent image carrier and is configured to be detachable from the image forming apparatus main body,
As the developing apparatus, process cartridge characterized by using a developing apparatus according to any one of claims 1 to 8. A latent image carrier, a latent image forming unit that forms a latent image on the latent image carrier, and a developing device that develops the latent image on the latent image carrier using a two-component developer containing toner and a carrier. An image forming apparatus for forming an image on the recording material by finally transferring the toner image formed on the latent image carrier by the developing device to the recording material,
As the developing device, an image forming apparatus characterized by using the developing apparatus according to any one of claims 1 to 8.

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