JP2011128248A - Developing device, and process cartridge and image forming apparatus employing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device that has high accuracy in toner concentration detection, even when the size of the developing device is reduced and the numbers of rotations of a developer carrier and a stir conveyance member are increased, and to provide an image forming apparatus employing the same. <P>SOLUTION: The developing device includes: a developing sleeve 34a rotated while holding on its surface two-component developer 32 containing toner and magnetic carrier; a supply conveyance path 37 where a supply screw 39 is disposed for conveying the developer 32 along the axial direction of the developing sleeve 34a; a recovery conveyance path 38, disposed below the supply conveyance path 37, where a recovery screw 40 is disposed for conveying the developer 32 in a direction opposite to the direction in which the developer is conveyed by the supply screw 39; and a lift port 41 and a fall port 42 which make the supply conveyance path 37 and recovery conveyance path 38 communicate with each other. The developing device has: an agent receiving surface 44 formed to be inclined in order to receive the developer 32 falling from the fall port 42; and a magnetic permeability sensor 45 for detecting the toner concentration of the developer 32 on the agent receiving surface 44. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

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

  In a conventional electrophotographic image forming apparatus, as a means for downsizing a developing device using a two-component developer including toner and a carrier, two agitating and conveying members are arranged in the vertical direction, and the horizontal width is increased. A small configuration is known. In this configuration, for example, a developer conveying member is supplied from the developer carrying member to the developer carrying member by the first agitating and conveying member disposed above, and the developer conveying member is disposed to the developer by the second stirring and conveying member disposed below. And a recovery conveyance path for recovering. The downstream side of the supply conveyance path and the upstream side of the collection conveyance path communicate with each other through an opening, and the upstream side of the supply conveyance path and the downstream side of the collection conveyance path communicate with each other via an opening. Circulates. The developer that has been supplied from the supply conveyance path and has passed through the development area and has a reduced toner concentration is not returned to the supply conveyance path, but is collected in the collection conveyance path and is sufficiently stirred with new toner again. ) Will not return. Therefore, the toner density fluctuation on the developer carrying member can be reduced.

  In a developing device using a two-component developer, toner is appropriately supplied from a toner supply port provided in a part of the developing device according to toner consumption in the developing device. For example, the toner replenishment amount is controlled based on the toner concentration of the developer (ratio of toner to developer (toner + carrier)). The toner concentration can be estimated from the output result of measuring the amount of carriers having magnetization using a sensor for measuring magnetic permeability. In order to accurately detect the toner density, it is necessary to compress the developer near the sensor detection unit. For this purpose, for example, a means for raising a fin on the agitating / conveying member at a position close to the sensor detection unit and compressing the developer near the sensor detection unit is already known.

  Further, in Patent Document 1, for the purpose of detecting an appropriate toner density, an inclined surface is provided in the developer conveyance path between the developer carrying member and the agitation conveyance member, and the developer toner on the inclined surface is provided. A developing device provided with toner density detecting means for detecting density is disclosed. In this developing device, the developer stirring and conveying member always scrapes off the developer, so that the developer on the inclined surface does not flow down and stay. Therefore, it is possible to detect an appropriate developer toner concentration.

  Incidentally, in a developing device using a two-component developer, in order to reduce the size of the device and increase the process speed, it is necessary to increase the rotational speed of the developer carrier. Further, in order to establish a balance between the amount of developer consumed in the developing region and the amount of developer supplied to the developer carrying member, it is inevitably necessary to increase the rotational speed of the agitating and conveying member. However, if the rotational speed of the agitating and conveying member is increased, the void ratio (air ratio) in the developer increases and it becomes difficult to compress the developer, and there is a problem that the sensitivity of toner density detection becomes dull. When the rotation speed of the agitating / conveying member is increased, the porosity of the developer in the vicinity of the sensor detecting unit is increased even if the fin is set up on the agitating / conveying member at a position close to the sensor detecting unit.

  In the developing device disclosed in Patent Document 1, the toner concentration of the developer on the inclined surface is detected in order to detect an appropriate toner concentration. However, even in the developing device disclosed in Patent Document 1, when the number of rotations of the agitating and conveying member increases, the developer on the inclined surface in the developer conveying path is also affected by the conveying force by the agitating and conveying member, causing a gap. As a result, the toner density detection accuracy decreases.

  The present invention has been made in view of the above problems, and an object of the present invention is to develop with high toner density detection accuracy even if the developing device is downsized and the number of rotations of the developer carrier and the agitation transport member is increased. And an image forming apparatus using the same.

In order to solve the above-mentioned problems, the invention of claim 1 is the one in which a two-component developer containing a toner and a magnetic carrier is carried on the surface and rotated, and the latent image carrier is rotated at a position facing the latent image carrier. A developer carrying member for supplying toner to the latent image on the surface for development; a first carrying path in which a first agitation carrying member for carrying the developer along the axial direction of the developer carrying member is disposed; A second conveying path disposed below the first conveying path and having a second agitating and conveying member configured to convey the developer in a direction opposite to the conveying direction by the first agitating and conveying member; and conveying the first conveying path A first communication port that communicates between the upstream side in the conveyance direction and the downstream side in the conveyance direction of the second conveyance path, and a second communication port that communicates between the conveyance direction downstream side of the first conveyance path and the conveyance direction upstream side of the second conveyance path. A developing device provided with an inclination to receive the developer falling from the second communication port. And other agents receiving surface is configured to; and a toner concentration detecting means for detecting the toner concentration of the developer in the agent receiving surface.
According to a second aspect of the present invention, in the developing device according to the first aspect, the second stirring and conveying member has a conveying force that is reduced at a position close to the agent receiving surface compared to the downstream side in the conveying direction of the position. To do.
According to a third aspect of the present invention, in the developing device of the first aspect, the conveying force by the second agitating / conveying member does not reach the developer on the agent receiving surface.
According to a fourth aspect of the present invention, in the developing device according to the first, second, or third aspect, an inclination angle of the agent receiving surface from a horizontal plane is 30 degrees or more.
According to a fifth aspect of the present invention, in the developing device of the fourth aspect, an inclination angle of the agent receiving surface from a horizontal plane is 60 degrees or less.
According to a sixth aspect of the present invention, in the developing device of the first, second, third, fourth or fifth aspect, the toner replenishing position for replenishing toner to the developing device is downstream of the toner density detecting means in the developer transport direction. In addition, it is an upstream side in the developer conveyance direction of the collection conveyance path for collecting the developer from the developer carrying member.
According to a seventh aspect of the present invention, at least the latent image carrier and the developing means for developing the latent image on the latent image carrier are integrally supported, and the process cartridge is configured to be detachable from the image forming apparatus main body. In the above, the developing device of claim 1, 2, 3, 4, 5, or 6 is used as the developing means.
The invention of claim 8 includes at least a latent image carrier, charging means for charging the surface of the latent image carrier, latent image forming means for forming an electrostatic latent image on the latent image carrier, and the electrostatic An image forming apparatus having a developing unit that develops a latent image uses the developing device according to claim 1, 2, 3, 4, 5, or 6 as the developing unit.
In the present invention, the developer falling on the agent receiving surface always flows without staying on the agent receiving surface because the agent receiving surface is inclined. Then, the developer hitting on the agent receiving surface is compressed by dropping (gravity) and the porosity is reduced. Therefore, even if the rotation speed of the first agitation conveyance member and the second agitation conveyance member is increased to increase the porosity of the developer in the first conveyance path and the second conveyance path, the development dropped on the agent receiving surface. The agent has a reduced porosity. Since the toner concentration detection means detects the toner concentration of the developer having a reduced porosity on the agent receiving surface, the toner concentration can be detected with high accuracy.

  The present invention is excellent in that it can provide a developing device with high toner density detection accuracy and an image forming apparatus using the same even if the developing device is downsized and the rotation speed of the developer carrying member and the agitating and conveying member is increased. There is an effect.

1 is a configuration diagram illustrating a schematic configuration of a printer according to an embodiment. FIG. 2 is a configuration diagram illustrating a schematic configuration of a developing device of the printer. FIG. 3 is a schematic diagram for explaining the flow of the developer in the developer container, as seen from the direction of arrow C in FIG. FIG. 3 is a cross-sectional configuration diagram illustrating a configuration of the developing device viewed from an arrow C direction in FIG. 2. FIG. 3 is a schematic diagram illustrating the flow of a developer in the developing device. The characteristic view which shows the relationship between screw rotation speed and sensor output sensitivity in the developing device. The characteristic view which shows the relationship between the detection surface inclination | tilt angle of a magnetic permeability sensor, and a sensor output. FIG. 6A is a cross-sectional view illustrating the configuration near the dropping port (as viewed from the direction of arrow D shown in FIG. 5), and FIG. 6B is a perspective view illustrating the configuration near the dropping port. The block diagram explaining schematic structure of the developing device which concerns on another embodiment. The block diagram explaining schematic structure of the developing device which concerns on another embodiment. The block diagram explaining schematic structure of the developing device which concerns on another embodiment. FIG. 6 is a cross-sectional configuration diagram illustrating a configuration of a conventional developing device. The characteristic view which shows the relationship between screw rotation speed and sensor output sensitivity in the conventional developing device.

  Hereinafter, an embodiment in which the present invention is applied to a tandem printer as an image forming apparatus will be described. FIG. 1 is a configuration diagram illustrating a schematic configuration of a printer according to the present embodiment. As shown in FIG. 1, the printer includes four image forming units 10C, 10Y, 10M, and 10K that form toner images of yellow, magenta, cyan, and black (hereinafter subscripts C, Y, and M). , K represents cyan, yellow, magenta, and black, respectively). Each of the image forming units 10C, 10Y, 10M, and 10K includes photoreceptors 1C, 1Y, 1M, and 1K that are image carriers that carry toner images of respective colors. Around each of these photoreceptors 1 are charging devices 2C, 2Y, 2M, and 2K that uniformly charge the surface of each photoreceptor 1, and a developing device 3C that develops an electrostatic latent image formed on each photoreceptor 1 surface. 3Y, 3M, 3K, and photoconductor cleaning devices 4C, 4Y, 4M, 4K, etc. for cleaning the surface of each photoconductor 1 after the transfer of the toner image. The image forming units 10C, 10Y, 10M, and 10K are each an exposure device 5C that forms an electrostatic latent image by irradiating a uniformly charged surface of each photoreceptor 1 with laser light according to image information. 5Y, 5M, 5K. Note that the photoreceptor 1 may have a belt shape instead of a drum shape.

  Below the image forming units 10C, 10Y, 10M, and 10K, a transfer conveyance belt 8 is wound around the downstream tension roller 6 and the upstream tension roller 7 and carries the recording paper P on the surface and moves. It has. Transfer bias rollers 9C, 9Y, 9M, and 9K are provided at positions facing the photoconductors 1C, 1Y, 1M, and 1K of the image forming units 10 with the transfer conveyance belt 8 interposed therebetween. A fixing device 11 that fixes unfixed toner on the recording paper P separated from the transfer conveyance belt 8 is provided on the downstream side of the downstream tension roller 6 in the recording paper conveyance direction by the transfer conveyance belt 8. In addition, a discharge tray 12 for loading recording paper P that has passed through the fixing device 11 and has a toner image fixed thereon is provided at the top of the printer main body.

  A plurality of paper feed cassettes 13, 14, 15 for storing the recording paper P are provided below the transfer conveyance belt 8. Between the paper feed cassettes 13, 14, 15 and the transfer transport belt 8, each of the paper feed cassettes 13, 14, 14, toward the transfer region where the transfer transport belt 8 and the photoreceptors 1 </ b> C, 1 </ b> Y, 1 </ b> M, 1 </ b> K face each other. A paper feeding / conveying device 16 for supplying recording paper P from 15 is provided. A registration roller pair 17 is provided on the most downstream side in the paper conveyance direction of the paper feeding / conveying device 16 to supply the conveyed recording paper P in accordance with the image formation timing of the image forming units 10C, 10Y, 10M, and 10K. ing.

  In the printer, the transfer conveyance belt 8 is disposed in an oblique direction so that the printer is small in the left-right direction in FIG. 1, and the conveyance direction of the recording paper P is oblique. Thereby, 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. That is, the printer is greatly reduced in size by being the minimum size required to accommodate the recording paper P therein.

  In the printer having the above-described configuration, each color toner image is formed by the image forming units 10C, 10Y, 10M, and 10K at the start of image formation. In each of the image forming units 10C, 10Y, 10M, and 10K, the photoreceptors 1C, 1Y, 1M, and 1K are rotationally driven by a main motor (not shown) and uniformly charged by the charging devices 2C, 2Y, 2M, and 2K. From the exposure devices 5C, 5Y, 5M, and 5K, writing light L is irradiated according to 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 1C, 1Y, 1M, and 1K are developed by the developing devices 3C, 3Y, 3M, and 3K, and toner images of the respective colors are formed on the surfaces of the photoreceptors 1C, 1Y, 1M, and 1K. Is formed. On the other hand, the recording paper P fed and conveyed by the paper feeding / conveying device 16 from the selected paper feeding cassette among the paper feeding cassettes 13, 14, and 15 is registered by the image forming units 10 </ b> C, 10 </ b> Y, 10 </ b> M, and 10 </ b> K by the registration rollers 17. The toner is supplied onto the surface of the transfer conveyance belt 8 in accordance with the image forming timing. Then, the recording paper P carried on the transfer conveyance belt 8 is conveyed to the transfer area of each color by the surface movement of the transfer conveyance belt 8.

  The toner images formed on the photoconductors 1C, 1Y, 1M, and 1K are transferred to transfer bias rollers 9C, 9Y, and 9M in transfer regions that are opposed to the photoconductors 1C, 1Y, 1M, and 1K and the transfer conveyance belt 8, respectively. , 9K, and sequentially transferred onto the recording paper P carried on the transfer conveyance belt 8. In this way, the toner images formed on the photoreceptors 1C, 1Y, 1M, and 1K are transferred in the order of C (cyan), Y (yellow), M (magenta), and K (black) to superimpose color. A 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 8 and conveyed to the fixing device 11 where the toner image is fixed and discharged to a discharge tray 12 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 4C, 4Y, 4M, and 4K, and the static elimination (not shown) is performed as necessary. After being neutralized by the lamp, the operation of being uniformly charged by the charging devices 2C, 2Y, 2M and 2K is repeated again.

  Next, the developing device 3 that is a feature of the present invention will be described in detail. The developing devices 3C, 3Y, 3M, and 3K use toners of different colors as image forming materials, but have the same configuration except that. For this reason, hereinafter, the subscripts C, Y, M, and K are omitted, and the developing device 3 will be described. FIG. 2 is a configuration diagram illustrating a schematic configuration of the developing device. FIG. 3 is a schematic diagram for explaining the flow of the developer in the developing container when the developing device is viewed from the direction of arrow C in FIG. FIG. 4 is a cross-sectional configuration diagram illustrating a configuration of the developing device viewed from the direction of arrow C in FIG. FIG. 5 is a schematic diagram for explaining the distribution of the developer amount in the developing container when the developing device is viewed from the direction of the arrow in FIG.

  As shown in FIG. 2, the developing device 3 accommodates a developer 32 that is a two-component developer containing a magnetic carrier and magnetic or nonmagnetic toner in a developing container 33. The developing container 33 of the developing device 3 has an opening at a position facing the photosensitive member 1 that is rotationally driven in the direction of arrow A (clockwise direction) in FIG. The part is exposed. The developing roller 34 carries the developer 32 in the developing container 33 up to the developing region 31 where toner is supplied to the electrostatic latent image formed on the surface of the photoreceptor 1 and development is performed. A developing sleeve 34a is provided as a developer carrying member that moves in the counterclockwise direction. Further, inside the developing sleeve 34a, a magnet roller 34b composed of a plurality of magnets (N1, N2, S1) fixed to the developing device 3 is provided. Further, an opening of the developing container 33 has an agent regulating member 35 that regulates the layer thickness of the developer 32 carried on the developing sleeve 34a.

  In the developer container 33 for containing the developer 32, a supply conveyance path 37 as a first conveyance path and a supply conveyance path 38 as a second conveyance path are formed vertically by an inner wall and a partition plate 36. The supply conveyance path 37 includes a supply screw 39 that is a first agitation conveyance member that conveys the developer 32 along the axial direction of the developing sleeve 34a and supplies the developer 32 to the developing sleeve 34a. The collection conveyance path 38 includes a collection screw 40 that is a second stirring conveyance member that conveys the developer 32 collected from the developing sleeve 34 a after passing through the development region 31 in the direction opposite to the conveyance direction by the supply screw 39. The supply screw 39 is arranged slightly above the developing roller 5 and with the rotation axis parallel to the rotation axis of the developing sleeve 34a, and rotates in the clockwise direction in FIG. The collection screw 40 is disposed below the supply screw 39 and with the rotation axis parallel to the rotation axis of the developing sleeve 34a, and rotates counterclockwise in the same manner as the developing sleeve 34a. The supply screw 39 and the collection screw 40 convey the developer 32 in opposite directions. Further, a push-up port 41 as a first communication port and a drop port 42 as a second communication port are formed at both ends of the partition plate 36 in the rotation axis direction.

  As shown in FIG. 3, the developer 32 in the developing container 33 is transported by the supply screw 39 and the recovery screw 40, and the push-up port 41 provided in the partition plate 36 between the supply transport path 37 and the recovery transport path 38. And circulates through the drop opening 42. The developer 32 that has reached the downstream end in the transport direction of the supply screw 39 in the supply transport path 37 falls from the drop opening 42 and is delivered to the upstream end in the transport direction of the recovery screw 40 in the recovery transport path 38. The developer 32 that has reached the downstream end in the transport direction of the recovery screw 40 in the recovery transport path 38 is lifted from the push-up port 41 and delivered to the upstream end in the transport direction of the supply screw 39 in the supply transport path 37.

  The partition plate 36 is erected so that the end on the developing sleeve 34 a side surrounds the supply screw 39 to form a barrier 43 described later. An opening is formed on the developing sleeve 34a side by the end of the barrier 43 and the inner wall of the developing container 33, and the developer 32 in the supply conveyance path 37 is supplied from the opening to the developing sleeve 34a. The opening extends in the axial direction of the developing sleeve 34a, and the developer 32 can be supplied to the developing sleeve 34a over the developing width. In the developing device 3, as will be described later, the amount of the developer 32 in the supply conveyance path 37 tends to decrease toward the downstream side in the conveyance direction, so that the end portion of the barrier 43 follows the decrease in the amount. Is formed such that its height decreases from upstream to downstream in the transport direction.

  In the developing device 3 configured as described above, the developer 32 in the supply conveyance path 37 is supplied in such a manner as to fall from above onto the development sleeve 34 a over the barrier 43 while being conveyed in the axial direction by the supply screw 39. . The developer 32 transported to the downstream end in the transport direction of the supply screw 39 in the supply transport path 37 without being supplied to the developing sleeve 34a passes from the drop opening 42 provided in the partition plate 36 to the lower recovery transport path 38. It will fall. The developer 32 supplied to the developing sleeve 34a is carried on the surface of the developing sleeve 34a by the rotation of the developing sleeve 34a and the magnetic force of the pumping pole N1 of the magnet roller 34b provided therein, and the arrow in FIG. It is conveyed in the B direction. That is, a certain amount of the developer 32 supplied and carried on the developing sleeve 34a passes through the portion facing the agent regulating member 35 as shown by the arrow B direction while being carried on the developing sleeve 34a. At this time, the excess developer 32 out of the developer 32 carried on the surface of the developing sleeve 34a passes through the portion facing the agent regulating member 35 as indicated by an arrow B1 in FIG. Scraped by 35.

  An appropriate amount of the developer 32 that has passed through the portion facing the agent regulating member 35 passes through the developing region 31 between the developing sleeve 34a and the photosensitive member 1 as shown by an arrow B2 in FIG. , And flows to the bottom 33 b of the developing container 33 and is delivered to the collection conveyance path 38. That is, the developer 32 carried on the developing sleeve 34a and transported to the developing area 31 and remaining on the developing sleeve 34a without being supplied to the surface of the photoreceptor 1 in the developing area 31 is accompanied by the rotation of the developing sleeve 34a. In this case, it is not collected in the supply conveyance path 37 but is collected in the collection conveyance path 38.

  The developer 32 that has reached the downstream end of the supply conveyance path 37 and the developer 32 that has passed through the development region 31 and separated from the surface of the developing sleeve 34a are conveyed by the collection conveyance path 38 and are passed through the push-up opening in the supply conveyance path 37. Delivered to the upstream end. Since the developer 32 in the collection conveyance path 38 includes the developer 32 that has passed through the development region 31 and has a reduced toner concentration, it is necessary to replenish the toner. Therefore, as will be described later, toner is supplied into the collection conveyance path 38 by a toner supply mechanism (not shown) according to the detection result of the magnetic permeability sensor 45.

  In the collection conveyance path 38, the developer 32 that has reached the downstream end in the conveyance direction in the supply conveyance path 37 and has passed through the drop port 42 of the partition plate 36, the toner replenished from the toner replenishment port 46, and the surface of the development sleeve 34a. The developer 32 separated from the toner is conveyed while being agitated by the collection screw 40. The developer 32 that has reached the downstream end in the transport direction in the collection transport path 38 is lifted through a push-up port 41 provided in the partition plate 36 and transferred to the upstream end in the transport direction in the supply transport path 37. The movement of the developer 32 from the collection conveyance path 38 to the supply conveyance path 37 at the push-up port 41 is pushed upward from below by the pressure of the developer 32 accumulated at the downstream end in the conveyance direction in the collection conveyance path 38. Then, the developer 32 is delivered.

  As described above, in the developing device 3 shown in FIGS. 2 to 5, the developer 32 that is supplied from the supply conveyance path 37 to the developing sleeve 34 a and passes through the development region 31 and has a decreased toner concentration is separated from the collection conveyance path 38. At the opposite position, it is detached from the surface of the developing sleeve 34 a and is collected in the collection conveyance path 38. The developer 32 collected in the collection conveyance path 38 is agitated in the collection conveyance path 38 with toner replenished from a toner replenishing mechanism (not shown), and is supplied to the supply conveyance path 37 in a state where a desired toner concentration is obtained. Is done. That is, the developer 32 whose toner density has decreased after passing through the development region 31 is not collected in the supply conveyance path 37. Therefore, the toner concentration of the developer 32 in the supply conveyance path 37 does not change between the upstream side and the downstream side in the conveyance direction by the supply screw 39.

  In the developing device 3, not all of the developer 32 transferred from the recovery conveyance path 38 to the supply conveyance path 37 reaches the downstream end in the conveyance direction in the supply conveyance path 37. As indicated by an arrow B in FIG. 3, there is a component that is supplied to the surface of the developing sleeve 34 a while being transported in the supply transport path 37, passes through the developing region 31, and is recovered in the recovery transport path 38. To do. The delivery of the developer 32 to the surface of the developing sleeve 34a is performed over substantially the entire area in the axial direction of the developing sleeve 34a. For this reason, as shown in FIG. 5, the amount of the developer 32 transported by the supply screw 39 in the supply transport path 37 is transported from the upstream end to the downstream end in the supply transport path 37. There is a tendency to gradually decrease. On the other hand, the amount of the developer 32 that is conveyed with the conveying force applied by the circulation screw 40 in the collection conveyance path 38 tends to gradually increase from the upstream end to the downstream end in the collection conveyance path 38. That is, there is a deviation in the distribution of the amount of the developer 32 in the developing device 3.

  Next, the toner density detection of the developing device according to the present embodiment will be described in detail. In the developing device 3, as shown in FIG. 5, the developer 32 that has not been supplied from the supply conveyance path 37 to the developing sleeve 34 a falls into the collection conveyance path 38 by gravity from the drop opening 42 on the right side of the drawing. In the developing container 33 of the developing device 3, an inclined agent receiving surface 44 for receiving the developer 32 dropped from the dropping port 42 is formed. The developer container 33 is provided with a magnetic permeability sensor 45 serving as a toner concentration detecting means for detecting the toner concentration of the developer on the agent receiving surface 44.

  The developer 32 dropping from the drop opening 42 flows in such a manner that it strikes the inclined agent receiving surface 44 and slides down the agent receiving surface 44. Since the magnetic permeability sensor 45 uses the agent receiving surface 44 as a detection surface, it can detect the toner concentration of the developer 32 on the flowing agent receiving surface 44 without staying. When the agent receiving surface 44 that serves as the detection surface is not inclined, the developer 32 that has dropped first accumulates above the agent receiving surface 44, and the developer 32 that has fallen later accumulates on the first developer 32. And stay. Therefore, the magnetic permeability sensor 45 cannot detect the latest toner density. Usually, the magnetic permeability sensor 45 can detect only the developer 32 about 2 to 5 mm above the agent receiving surface 44.

  Further, since the developer 32 that has struck the agent receiving surface 44 is compressed by dropping (gravity), the porosity is smaller than that of the developer 32 conveyed through the supply conveyance path 37. Therefore, the magnetic permeability sensor 45 having the agent receiving surface 44 as a detection surface can detect the toner concentration without reducing the detection sensitivity. As described above, the porosity of the developer 32 on the agent receiving surface 44 can be reduced even if the rotation speed of the supply screw 39 and the recovery screw 40 is increased in order to reduce the size and speed of the developing device 3. Therefore, the magnetic permeability sensor 45 can accurately detect the toner concentration.

  Here, in the developing device 3 shown in FIGS. 4 and 5, the collection screw 40 is not formed with a blade portion at a position close to the agent receiving surface 44, and the conveyance force is reduced. Although it is desired to stabilize the toner concentration detection of the magnetic permeability sensor 45 by the inclination of the agent receiving surface 44, the toner concentration detection becomes unstable when the conveying force by the collection screw 40 reaches the agent receiving surface 44 (detection surface). Therefore, the influence of the conveying force of the collection screw 40 on the developer near the agent receiving surface 44 (detection surface) is reduced as much as possible.

  In the developing device 3 shown in FIGS. 4 and 5, the inclination of the agent receiving surface 44 ends near the axis of the recovery screw 40, but there is no problem even if the inclination continues to the bottom of the developing device 33. Further, the installation position of the magnetic permeability sensor 45 is not necessarily the same as that shown in FIG. 5 if it is installed at a position where the agent receiving surface 44 is used as a detection surface and does not contact the shaft of the recovery screw 40 and where the flow of the developer 32 can be detected. It doesn't have to be a position.

  Further, as shown in FIG. 5, the replenishment position of the toner T to be replenished to the developing device 3 is on the downstream side in the transport direction of the collection screw 40 with respect to the agent receiving surface 44 as indicated by a dotted line 46 in FIG. In addition, it is preferable to be upstream of the collection conveyance path 38. Thereby, the toner density detection by the magnetic permeability sensor 45 can be stably performed. A toner replenishing mechanism (not shown) can replenish an appropriate amount of toner based on the detection result of the magnetic permeability sensor 45. If the toner replenishment position is installed on or just before the agent receiving surface, there is a possibility that the replenishment toner is not yet completely mixed with the developer when the toner density is detected. Therefore, if the toner replenishment position is arranged on the agent receiving surface or immediately before, the detection result by the magnetic permeability sensor varies depending on the presence or absence of replenishment, and is not stable. The toner supply by a toner supply mechanism (not shown) is not limited to being performed based only on the detection result of the magnetic permeability sensor 45, and may be performed based on the toner consumption amount obtained from the image information of the latent image. Of course.

  Here, the relationship between the screw rotation speed and the toner density detection sensitivity in the developing device (conventional configuration) shown in FIG. 12 will be described. In FIG. 12, the same components as those of the developing device 3 are denoted by the same reference numerals, and the description thereof is omitted. In the developing device 100 shown in FIG. 12, the toner replenishing port 101 is installed above the dropping port 42, the developer receiving surface 44 is not formed in the developing device 33, and the magnetic permeability sensor 45 is installed on the downstream side of the collection conveyance path 38. Has been. FIG. 13 is a characteristic diagram showing the relationship between the screw rotation speed and the sensor output sensitivity in the developing device 100 shown in FIG. Since the permeability sensor 45 measures the magnetization of the carrier of the developer 32, the output increases as the toner concentration decreases (the proportion of the carrier increases). The toner concentration usage range was 4 wt% to 10 wt%. Since the magnetic permeability sensor 45 is installed to detect the toner concentration, the detection accuracy is higher when the sensor output is largely changed when the toner concentration is changed. Specifically, if the slope of the sensor output (hereinafter referred to as sensor output sensitivity) with respect to the change in toner density is 0.2 [V / wt%] or more, it can be used stably.

  As shown in FIG. 13, in the developing device 100 having the conventional configuration, when the screw rotation speed of the supply / recovery screws 39 and 40 is 500 rpm (500 rotations per minute), the sensor output sensitivity is 0.3 [V / wt%. ]there were. On the other hand, when the screw rotation speed was 1500 rpm, the sensor output sensitivity was 0.1 [V / wt%]. When the screw rotation speed of the supply / recovery screws 39 and 40 is 1500 rpm, the toner density cannot be detected. In this embodiment, since the screw rotation speed at the maximum linear speed is 1500 rpm, the toner density cannot be detected with the sensor output sensitivity as shown in FIG.

  Next, the relationship between the screw rotation speed and the sensor output sensitivity in the developing device (this embodiment) shown in FIGS. 2 to 5 will be described. FIG. 6 is a characteristic diagram showing the relationship between the screw rotation speed and the toner density detection sensitivity in the developing device shown in FIG. As shown in FIG. 6, in this example, when the screw rotation speed of the supply / recovery screws 39 and 40 was 1500 rpm, the sensor output sensitivity was 0.25 [V / wt%]. On the other hand, when the screw rotation speed is 500 rpm, the sensor output sensitivity is lowered to 0.27 [V / wt%], but the sensor output sensitivity of the toner density is at a level that does not cause any problem. In FIG. 6, the magnitude of the output value differs by about 0.2 to 0.3 V depending on the screw rotation speed. This is because the void rate immediately after dropping on the agent receiving surface 44 is slightly increased because the conveyance speed of the developer 32 is higher at higher screw rotation speeds. However, if the difference is such a level, it is possible to detect the accurate toner density by correcting the output value.

  FIG. 7 is a characteristic diagram showing the relationship between the detection surface inclination angle of the magnetic permeability sensor and the sensor output sensitivity. As shown in FIG. 7, if the inclination of the agent receiving surface 44 (detection surface) is increased, the sensor output sensitivity is lowered, and if it exceeds 60 degrees, the upper limit of the sensor output sensitivity is 0.2 [V / wt%]. . When the agent receiving surface 44 (detection surface) stands, the developer 32 easily moves due to gravity. However, the compression of the developer 32 due to dropping decreases, so the porosity increases, and the sensor output sensitivity decreases. End up. If the inclination angle of the agent receiving surface 44 is inclined by 35 degrees or more, the developer 32 flows without staying. This was measured by a method similar to the method described in Patent Document 1 (Japanese Utility Model Laid-Open No. 8-191). As a result, even when the drop height was zero, the developer 32 was retained if the agent receiving surface 44 was tilted 35 degrees or more. It has been confirmed that it flows without any damage.

  Next, a configuration of a developing device according to another embodiment will be described. Although the agent receiving surface 44 shown in FIG. 5 is inclined so that the developer 32 flows in the same direction as the conveying direction of the recovery screw 40, the inclination direction of the agent receiving surface is not limited to this. FIG. 8A is a cross-sectional view for explaining the configuration in the vicinity of the drop opening (viewed from the direction of arrow D shown in FIG. 5), and FIG. 8B is a perspective view for explaining the configuration in the vicinity of the drop opening. In FIG. 8, the same members as those of the developing device 3 are denoted by the same reference numerals, and description thereof is omitted. As shown in FIG. 8A, the developer container 50 is configured such that the agent receiving surface 51 is inclined in a direction orthogonal to the axial direction. However, since it is necessary to adopt a configuration in which the dropped developer 32 can move in the axial direction by tilting, the agent receiving surface 51 gradually becomes an arc shape shown by a dotted line as shown in FIGS. Thus, it is configured to have an inclination in the axial direction. With such a configuration, the developer 32 dropped on the agent receiving surface 51 flows without being retained by gravity, so that the magnetic permeability sensor 45 can detect the latest toner density. Although the developing sleeve 34a is illustrated by a dotted line in FIG. 6, it is preferable that the developing sleeve 34a is not provided near the drop opening 42. This is because the developer 32 falling from the developing sleeve 34a needs to be transported in the recovery transport path 38, but in this configuration, the transport capability of the recovery screw 40 in the vicinity of the drop opening 42 is small. This is because the developer 32 may accumulate.

  In addition, a configuration of a developing device according to another embodiment will be described. Although the agent receiving surface 44 shown in FIG. 5 is in the collection conveyance path 38, the agent reception surface may be formed in a dropping path between the supply conveyance path 37 and the collection conveyance path 38. The conveying member is not installed in the dropping path, and the conveying force of the conveying member does not reach. 9 and 10 are configuration diagrams illustrating a schematic configuration of a developing device according to another embodiment. In the developing device shown in FIG. 9, the axial length of the recovery screw 40 at the right end in the drawing is shorter than the axial length of the supply screw 39 and is inclined between the supply conveyance path 37 and the recovery conveyance path 38. A fall path 52 is formed. A magnetic permeability sensor 45 having one surface of the dropping path 52 as the agent receiving surface 53 and the agent receiving surface 53 as a detection surface is provided. Since the magnetic permeability sensor 45 uses the agent receiving surface 53 as a detection surface, it can detect the latest toner density as described above. Since the porosity of the developer 32 falling on the agent receiving surface 53 does not increase even if the rotation speed of the developing sleeve 34a and the supply / recovery screws 39 and 40 is increased, the magnetic permeability sensor 45 is accurate. The toner density can be detected well. Further, since the conveying force of the supply screw 39 and the recovery screw 40 does not reach the dropping path 52, the toner concentration can be detected stably. In the developing device shown in FIG. 9, since the influence of the stirring and conveying force of the collection screw 40 does not reach the developer 32 near the magnetic permeability sensor 45, the conveying force at the upstream end of the collecting screw 40 in the conveyance direction is reduced. This is the same as the part on the downstream side of the part.

  In the developing device shown in FIG. 10, a drop path 54 having a U-shaped cross section is formed between the supply conveyance path 37 and the collection conveyance path 38. A magnetic permeability sensor 45 having one surface of the dropping path 54 as the agent receiving surface 55 and the agent receiving surface 55 as a detection surface is provided. Since the magnetic permeability sensor 45 uses the agent receiving surface 55 as a detection surface, it can detect the toner concentration with high accuracy as described above. Even if the rotation speed of the developing sleeve 34a, the supply screw 39, and the recovery screw 40 is increased, the porosity of the developer 32 falling on the agent receiving surface 55 does not increase. The density can be detected. Further, since the conveying force of the supply screw 39 and the recovery screw 40 does not reach the dropping path 54, the toner density can be detected stably. In the developing device shown in FIG. 10, since the influence of the stirring and conveying force of the collecting screw 40 does not reach the developer 32 near the magnetic permeability sensor 45, the conveying force at the upstream end of the collecting screw 40 in the conveying direction is set to the end. This is the same as the part on the downstream side of the part.

  In the developing device shown in FIG. 5, the supply conveyance path 37 is on the upper side and the recovery conveyance path 38 is on the lower side. However, the vertical relationship between the supply conveyance path and the recovery conveyance path may be reversed. . FIG. 11 is a configuration diagram illustrating a schematic configuration of a developing device according to still another embodiment. In FIG. 11, the same members as those of the developing device 3 are denoted by the same reference numerals, and the description thereof is omitted. In the developing device 60 shown in FIG. 11, a collection conveyance path 38 for collecting the developer 32 on the developing sleeve 34a is configured above the supply conveyance path 37 for supplying the developer 32 to the developing sleeve 34a. In addition, there is a drop opening 42 on the right side of the figure for transporting the developer 32 using gravity. The magnetic permeability sensor 45 can detect the toner concentration with high accuracy by detecting the toner concentration using the agent receiving surface 44 formed in the drop opening 42 as a detection surface. As described above, the present invention is not limited to the configuration in which the direction of the developer 32 passing through the development region 31 is downward from the top as shown in FIGS. The present invention can also be applied to a configuration in which there is a region where the developer is conveyed.

As described above, in the developing device 3 according to the present embodiment, the inclined agent receiving surface 44 (51, 53, 55) for receiving the developer falling through the dropping port 42 as the second communication port is formed. The developer falling on the agent receiving surface 44 always flows without staying because the agent receiving surface 44 is inclined. Then, the developer hitting on the agent receiving surface 44 (51, 53, 55) is compressed by dropping (gravity) and the porosity is reduced. Therefore, even if the rotation speed of the supply screw 39 and the collection screw 40 is increased to increase the porosity of the developer in the supply conveyance path 37 and the collection conveyance path 38, the developer dropped on the agent receiving surface 44 is not void. The rate is reduced. Since the magnetic permeability sensor 45 detects the toner concentration of the developer having a reduced porosity on the agent receiving surface 33, the toner concentration can be detected with high accuracy.
In the developing device 3 according to this embodiment, the conveying force of the collection screw 40 is reduced in the vicinity of the agent receiving surfaces 44 and 51. Therefore, the developer in the vicinity of the agent receiving surfaces 44 and 51 is hardly affected by the conveying force (number of rotations) of the recovery screw 40, and the magnetic permeability sensor 45 can stably detect the toner density.
Further, in the developing device 3 according to the present embodiment, no transport screw is provided in the drop paths 52 and 54. Therefore, the developer on the agent receiving surfaces 53 and 55 is not affected by the conveying force (number of rotations) by the recovery screw 49, and the magnetic permeability sensor 45 can stably detect the toner density.
Further, in the developing device 3 according to the present embodiment, the inclination angle of the agent receiving surface 44 (51, 53, 55) from the horizontal plane is 30 degrees or more. As a result, the developer on the agent receiving surface 44 is constantly flowing without staying.
In the developing device 3 according to this embodiment, the inclination angle of the agent receiving surface 44 (51, 53, 55) from the horizontal plane is 60 degrees or less. Thereby, the porosity of the developer on the agent receiving surface 44 is reduced by dropping (gravity).
In the developing device 3 according to the present embodiment, the toner replenishment position 46 is downstream of the magnetic permeability sensor 45 in the developer transport direction and upstream of the recovery transport path 40 in the transport direction. Thereby, the magnetic permeability sensor 45 can stably detect the toner density without being affected by the toner supply.

3 Developing device 32 Developer 33 Developing container 34 Developing roller 34a Developing sleeve 35 Agent regulating member 36 Partition plate 37 Supply conveying path 38 Recovery conveying path 39 Supply screw 40 Recovery screw 41 Push-up opening 42 Falling opening 43 Barriers 44, 51, 53, 55 Agent receiving surface 45 Magnetic permeability sensors 52, 54 Fall path

Japanese Utility Model Publication No. 8-191

Claims (8)

A developer that rotates by supporting a two-component developer containing toner and a magnetic carrier on the surface, and supplies the toner to the latent image on the surface of the latent image carrier at a position facing the latent image carrier. A first conveying path in which a carrier, a first agitating and conveying member that conveys the developer along the axial direction of the developer carrier, and a developer is disposed below the first conveying path. A second conveying path in which a second agitating and conveying member that conveys in a direction opposite to the conveying direction by the first agitating and conveying member is disposed; an upstream side in the conveying direction of the first conveying path; and a downstream side in the conveying direction of the second conveying path. In a developing device, comprising: a first communication port that communicates; and a second communication port that communicates the downstream side in the transport direction of the first transport path and the upstream side in the transport direction of the second transport path.
Development comprising: an agent receiving surface formed to be inclined to receive the developer falling from the second communication port; and a toner concentration detecting means for detecting the toner concentration of the developer on the agent receiving surface. apparatus. The developing device according to claim 1.
The developing device, wherein the second agitating and conveying member has a conveying force that is reduced at a position close to the agent receiving surface as compared with a downstream side of the position in the conveying direction. The developing device according to claim 1.
2. A developing device according to claim 1, wherein the conveying force of the second agitating / conveying member does not reach the developer on the agent receiving surface. The invention of claim 4
4. The developing device according to claim 1, wherein an inclination angle of the agent receiving surface from a horizontal plane is 30 degrees or more. The invention of claim 5
5. The developing device according to claim 4, wherein an inclination angle of the agent receiving surface from a horizontal plane is 60 degrees or less. The developing device according to claim 1, 2, 3, 4 or 5.
The toner replenishment position for replenishing toner to the developing device is downstream in the developer transport direction with respect to the toner density detecting means, and the developer transport direction of the recovery transport path for recovering the developer from the developer carrier. A developing device which is on the upstream side. In a process cartridge in which at least a latent image carrier and a developing unit for developing a latent image on the latent image carrier are integrally supported and configured to be detachable from the image forming apparatus main body.
A process cartridge using the developing device according to claim 1, 2, 3, 4, 5, or 6 as the developing means. At least a latent image carrier, charging means for charging the surface of the latent image carrier, latent image forming means for forming an electrostatic latent image on the latent image carrier, and developing means for developing the electrostatic latent image In an image forming apparatus having
An image forming apparatus using the developing device according to claim 1, 2, 3, 4, 5, or 6 as the developing means.

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