JP2005266511A - Developing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a component change from causing degradation in the image quality of an image formed on an image carrier, by sufficiently minimizing the component change of developer in a main flow passage which occurs due to the effect of replenishment developer supplied from outside. <P>SOLUTION: In the developing device 10, the counter fin 64 of a supply auger 32 causes trickle developer supplied into a replenishment path 58 through an inlet 62 to flow to the main flow passage 22, while stirring it. The trickle developer is combined with developer flowing near the downstream end of the main flow passage 22. Thus, the direction in which the trickle developer supplied into the main flow passage 22 via the replenishment path 58 by the counter fin 64 can be switched to an almost opposite direction (main flow direction) in which developer flows while circulating in the main flow passage 22 by the supply auger 32. In addition, stirring force that is extremely great can be made to act on the trickle developer combined with the developer near the downstream end of the main flow passage 22. Accordingly, the trickle developer supplied from outside can efficiently and uniformly be diffused into the developer circulating in the device. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention is applied to an image forming apparatus such as a copying machine, a printer, a facsimile, or a composite machine that forms an image using an electrophotographic system, and develops an electrostatic latent image formed on an image carrier with a developer. The present invention relates to a developing device.

  2. Description of the Related Art Conventionally, image forming apparatuses such as copying machines, printers, facsimiles, and composite machines using this type of electrophotographic system are, for example, developing devices filled with a two-component developer composed of toner and a magnetic carrier. I have. In the image forming apparatus, the developing device is disposed to face the photosensitive drum, and the developing device transfers toner charged to a predetermined polarity from the developing roll to the electrostatic latent image formed on the photosensitive drum. The electrostatic latent image is visualized with toner to form an image.

  For example, Patent Document 1 discloses an example of an image forming apparatus applied to an image forming apparatus using an electrophotographic system. The developing device 200 disclosed in Patent Document 1 is as shown in FIG. 5. In this developing device 200, a magnet roll 203 and two spiral augers 202 and 204 can be rotated by a developing device body 201. The two spiral augers 202 and 204 are rotated in the opposite directions.

  A partition wall 206 is formed in the developing device main body 201 along the longitudinal direction of the developing device main body 201, and the inside of the developing device main body 201 is partitioned into a space 208 and a space 210. A spiral auger 202 is disposed in the space 208, and a spiral auger 204 is disposed in the space 210. Further, communication ports 212 and 213 are respectively provided at both ends of the developing device main body 201 so that the space 208 and the space 210 are communicated.

  A developer inlet 214 to which a developer is supplied is provided on the space 210 side, and the developer that has entered the space 210 from the developer inlet 214 is recirculated while being stirred in the space 210 by the spiral auger 204. It is conveyed in the direction (arrow N direction), guided to the space 208 through the communication port 213, and then conveyed in the main flow direction (arrow M direction) while being stirred by the spiral auger 202, and circulates in the space 208. The toner in the developer is attracted by the magnet roll 203.

  Here, the developing device 200 as described above normally has a magnetic permeability for measuring the toner concentration (= (toner / toner + carrier) × 100) of the developer that circulates in the two spaces 206 and 208. In the image forming apparatus in which the sensor (ATC sensor) is arranged and the developing device 200 is mounted, the developer supply device replenishes the toner according to the toner density detected by the ATC sensor and the toner consumption amount accompanying the developing operation. Developer (hereinafter referred to as “trickle developer”) is supplied to the developer inlet 214. The trickle developer is supplied into the space 210 of the developing device 200 and joins the developer conveyed in the backward flow direction by the spiral auger 204 in the space 210. The trickle developer has a toner and carrier composition adjusted so that the toner concentration is significantly higher than that of the developer circulating in the spaces 208 and 210. As a result, it is possible to supply toner substantially equal to the amount of toner consumed by the developing operation into the spaces 208 and 210 while keeping the carrier amount in the spaces 208 and 210 substantially constant. It is possible to keep the toner concentration of the developer circulating in the substantially constant.

  Japanese Patent Application Laid-Open No. 2004-228688 discloses a developer container that stores a developer, a developer replenishing device that replenishes a two-component developer into the developer container according to consumption of toner by a developing operation, and a toner consumption amount from the developer container. The toner consumption detecting means for detecting toner and the developer discharging auger according to the toner consumption detected by the toner consumption detecting means are rotated to discharge the excess developer in the developer container to the developer collecting container. A developing device including a developer discharging means is disclosed.

The developing devices described in Patent Document 1 and Patent Document 2 described above employ a developer replenishing method called a so-called trickle developing method, and in this trickle developing method, the developing device circulates in the developing device. By replenishing the developer with trickle developer according to the toner concentration, toner consumption, etc., the deteriorated developer inside the device is gradually replaced with new developer, and development such as developer charging performance in the developing device The characteristics can be kept constant, and the deterioration of copy image quality can be suppressed.
JP 2003-337515 A JP-A-10-90991

  However, in the developing device 200 described in Patent Document 1, the supply direction of the trickle developer supplied into the space 210 through the developer inlet 214 coincides with the return flow direction of the developer in the space 210 by the spiral auger 204. Therefore, it is difficult to uniformly diffuse the trickle developer into the developer in the space 210, and the toner density distribution of the developer supplied to the space 208 through the communication port 212 and conveyed by the spiral auger 208 is mainly used. There may be non-uniformity along the flow direction, that is, the toner concentration locally increases. When the toner density fluctuates beyond the predetermined allowable range in the space 208 facing the magnet roll in this manner, the toner image on the photosensitive drum developed by the developing device 200 is fogged or part of the toner is transferred to the carrier. There is a risk that image quality deteriorates due to occurrence of white spots (BCO) or the like caused by the replacement.

  In the developing device described in Patent Document 2, the developer discharging auger is rotationally driven in accordance with the toner consumption detected by the toner consumption detection means, so that the developer circulating in the developing container can be accurately and constant. It is possible to easily optimize the discharge amount of the deteriorated developer discharged from the developer circulating in the developing container to the outside while maintaining the sensor, the developer for constituting the toner consumption detecting means, and the developer A discharging auger, a torque transmission mechanism for rotationally driving the developer discharging auger, and the like are required, which complicates the structure of the apparatus and increases the manufacturing cost of the apparatus.

  In view of the above facts, the object of the present invention is to sufficiently reduce the component variation of the developer in the main flow path caused by the influence of the replenishment developer supplied from the outside, and to the image carrier by this component variation. An object of the present invention is to provide a developing device capable of preventing the image quality from being deteriorated in the formed image.

  A developing device according to claim 1 of the present invention is provided in a main flow passage for allowing a developer to flow in a predetermined main flow direction, and in the main flow passage, while the developer in the main flow passage is agitated while the main flow passage is stirred. A supply auger that circulates in the flow direction, a return passage that is provided in the housing so as to be adjacent to the main flow passage, and circulates the developer in a reverse flow direction substantially opposite to the main flow direction; An admixing auger provided in the return passage and configured to flow the developer in the main flow passage in the return flow direction while stirring; an end on the downstream side of the main flow passage; and an upstream side of the return passage A first communication port that connects the end portion, a second communication port that connects a downstream end portion of the return flow passage and an upstream end portion of the main flow passage, and the main flow direction Provided by the supply auger. A developer supply member that develops a latent image formed on the image carrier by the developer into a visible image while adsorbing the developer flowing in the passage, and an extension of the main flow passage along the main circulation direction One end is a supply port that opens toward the downstream end of the main flow passage, and the other end is a reception port that opens to the outside of the apparatus. The replenishment developer and the replenishment developer supplied into the replenishment passage through the receiving port are circulated to the supply port side while stirring, and the replenishment developer is downstream of the main flow passage through the supply port. And a feeding member that joins the developer that flows in the vicinity of the end portion.

  In the developing device according to the first aspect, the replenishment developer supplied to the replenishment path through the receiving port is fed to the supply port side while the supply member is agitated, and the replenishment developer is passed through the supply port. By joining the developer flowing near the downstream end of the main flow passage, the replenishment developer supplied from the outside through the replenishment path is fed into the main flow passage, and the replenishment developer is fed into the main flow in the apparatus. Since the developer circulating in the passage and the return passage can be replenished, even if the developer is consumed during the developing operation, a replenishment developer corresponding to the consumed amount of the developer is developed in the apparatus. The developer can be replenished so that the circulation amount of the developer in the main flow passage and the return flow passage can be kept substantially constant at all times, and if the developer is a two-component system including toner and carrier, the replenishment A predetermined ratio of carrier to If the amount of developer corresponding to the amount of developer replenished from the outside is discharged from the inside of the apparatus, the deteriorated carrier contained in the developer flowing through the main flow passage and the return flow passage is little by little. By replacing the carrier contained in the replenishment developer, it is possible to effectively prevent a decrease in charging performance of the toner due to the deterioration of the carrier.

  Here, the replenishment developer supply path is provided so as to extend along the main flow direction on the extension line of the main flow path, and the supply port of the replenishment path faces the downstream end of the main flow path. The flow direction of the replenishment developer supplied into the main flow path by the feeding member through the supply port of the replenishment path, and the flow direction of the developer flowing in the main flow path by the supply auger (main flow direction). ) And a remarkably large stirring force can be applied to the replenishment developer that merges with the developer in the vicinity of the downstream end of the main flow path. The developer can be mixed so as to diffuse uniformly into the developer circulating efficiently in the apparatus.

  Further, the developer mixed with the replenishment developer near the downstream end of the main flow passage flows immediately into the return passage through the first communication passage without being adsorbed by the developer supply member. Admixed to the developer mixed with replenishment developer since it flows in the backward flow direction while being stirred by the admix auger over the entire length of the flow path and then flows into the main flow path through the second communication port. Since the stirring time by the auger can be secured sufficiently long, the developer mixed with the replenishment developer is stirred for a sufficient time to give high uniformity, and then this developer is connected to the second communication. It can be fed into the mainstream passage through the mouth.

  As a result, it is possible to effectively suppress local TC fluctuations occurring in the developer flowing in the main flow path after the replenishment developer is supplied from the outside, and therefore, due to local TC fluctuations of the developer in the main flow path. It is possible to prevent the image quality from being deteriorated in the image formed on the image carrier.

  A developing device according to a second aspect of the present invention is the developing device according to the first aspect, wherein the developer supply member is provided in the first communication port and the second communication port respectively along the main flow direction. It arrange | positions on the outer side of the one end and other end of this.

  According to a third aspect of the present invention, there is provided a developing apparatus according to the first or second aspect, wherein the developer that has become excessive in the apparatus in accordance with the replenishment of the developer from the replenishment path is discharged to the outside. An outlet and an opposing conveying member that is provided at a downstream end in the return passage and that circulates the developer in the return passage in an opposite direction opposite to the return flow direction; The discharge port is opened to the side of the counter conveying member.

  A developing device according to a fourth aspect of the present invention is the developing device according to the first, second, or third aspect, wherein a concentration sensor that detects the concentration of toner contained in the developer is disposed along the backward flow direction. It is arranged at the downstream end of the return flow passage.

  A developing device according to a fifth aspect of the present invention is the developing device according to any one of the first to fourth aspects, wherein the admix auger includes a shaft portion extending along the backward flow direction, A fin portion extending in a spiral shape around the shaft portion is provided, and a scraping portion is provided between the fin portions facing the second communication port so as to extend in the axial direction. The mix auger rotates in a predetermined driving direction by a torque transmitted from the outside, and applies a conveying force in the backward flow direction to the developer in the backward flow path by the fin portion. A conveying force that scoops out the developer near the bottom of the return flow path to the main flow path side is applied to the portion facing the two communication ports.

  In the developing device according to claim 6 of the present invention, the main flow passage is provided with a sub-communication port communicating with the return flow passage on the upstream side of the first communication port along the main flow direction. Features.

  The developing device according to claim 7 of the present invention is the developing device according to claim 6, wherein the main flow passage extends from the downstream end thereof to the upstream side of the first communication port along the main flow direction. In addition, a throttle part having a reduced cross-sectional area is provided with respect to the other part of the main flow passage, and the communication port is arranged in front of the throttle part along the main flow direction.

  As described above, according to the image forming apparatus of the present invention, the component variation of the developer in the main flow path caused by the influence of the replenishment developer supplied from the outside is sufficiently reduced, and the image carrier is thereby supported by the component variation. It is possible to prevent the image quality from being deteriorated in the image formed on the body.

  Hereinafter, a developing device according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 shows a developing device according to an embodiment of the present invention and a photosensitive drum in an image forming apparatus to which the developing device is applied. The developing device 10 is applied to an image forming apparatus that forms an image (toner image) using a so-called electrophotographic system such as a copying machine, a laser printer, a facsimile machine, or a multifunction machine, and is applied to a photosensitive drum 12 that is an image carrier. The formed electrostatic latent image is developed with toner, and a toner image is formed on the photosensitive drum 12.

  First, an image forming apparatus to which the developing device according to the present embodiment is applied will be briefly described.

  In the image forming apparatus, a cylindrical photosensitive drum 12 (see FIG. 1) is provided as a toner image carrier, and a developing device 10 is disposed on the outer peripheral side of the photosensitive drum 12. The outer circumferential surface of the photosensitive drum 12 is an image carrying surface 14 on which an image is formed based on an electrophotographic process, and the developing device 10 uses a two-component developer D containing toner and a carrier. The development is performed by a conventional development process. A charger (not shown) is disposed on the upstream side of the developing device 10 along the rotation direction (arrow RD direction) on the outer peripheral side of the photosensitive drum 12, and a transfer roll is disposed on the downstream side of the developing device 10. A cleaning device or the like is arranged. In the image forming apparatus, a laser scanner (not shown) is disposed above the photosensitive drum 12, and this laser scanner is charged to a predetermined potential by a laser beam L modulated based on image information. The image bearing surface 14 of the photosensitive drum 12 is scanned to form an electrostatic latent image on the image bearing surface 14.

  In the image forming apparatus, the developing device 10 selectively attaches toner to the electrostatic latent image formed by exposure on the photosensitive drum 12 to form a toner image, and this toner image is transferred to a recording paper, intermediate transfer Transfer to the body. At this time, the transfer roll causes the electrostatic attraction force to act on the toner image on the image carrying surface 14 via the recording medium or the like to transfer (transfer) the toner image (toner) to the recording medium. The cleaning device removes and collects toner (residual toner) remaining on the image carrying surface 14 after the transfer is completed from the image carrying surface 14. The image bearing surface 14 from which the residual toner has been cleaned is charged by a charger to prepare for a new image forming process.

  Next, the developing device 10 according to the present embodiment will be described in detail.

  The developing device 10 is a so-called trickle developing system (in order to prevent the charging performance of the developer from being lowered and extend the interval for changing the developer, the developer is gradually replenished with a replenishing developer (trickle developer). On the other hand, it is a developing method that develops while discharging excess developer (including many deteriorated carriers), so that the deteriorated developer is collected in a collection container (not shown). It has become.

  As shown in FIG. 1, the developing device 10 is provided with a housing 16 that is supported so as to face the photosensitive drum 12, and the housing 16 is connected to the image carrying surface 14 of the photosensitive drum 12. An opening 18 is formed to face and open. A developing roll 20 is disposed in the housing 16 near the opening 18. The housing 16 is provided with a main flow passage 22 and a double flow passage 24 in which the developer D is accommodated on the lower side thereof. These flow passages 22 and 24 are respectively open upward. The cross-sectional shape is a substantially semicircular shape opened upward. As shown in FIG. 3, the main flow passage 22 and the return flow passage 24 are formed to be elongated along the axial direction of the photosensitive drum 12 (direction of arrow S). A partition wall 26 is erected from the bottom surface of the housing 16, and the partition wall 26 connects the main flow passage 22 and the return flow passage 24 in the width direction (arrow W direction) of the device orthogonal to the axial direction. It is divided along. The partition wall 26 has a first communication port 28 that communicates the downstream end of the main flow passage 22 to the upstream end of the return passage 24 at one end along the longitudinal direction of the flow passages 22 and 24. And a second communication port 30 for communicating the downstream end of the return passage 24 to the upstream end of the main flow passage 22 is formed at the other end.

  As shown in FIG. 2, a screw shaft-like supply auger 32 and an admix auger 34 are arranged in the main flow passage 22 and the return flow passage 24, respectively. The supply auger 32 is provided with support shaft portions 36 that are smaller in diameter than the center side at both ends in the axial direction. These support shaft portions 36 are bearings 40 embedded in both side walls of the housing 16. It is supported by. The admix auger 34 is also provided with support shaft portions 38 having a diameter smaller than that of the center side at both axial end portions thereof, and these support shaft portions 38 are embedded in both side walls of the housing 16, respectively. It is supported by a bearing 42. Thus, the supply auger 32 and the admix auger 34 are rotatably supported by the housing 16. Here, the shaft centers S <b> 1 and S <b> 2 that are the rotation centers of the supply auger 32 and the admixing auger 34 are parallel to the longitudinal directions of the main flow passage 22 and the return flow passage 24.

  As shown in FIG. 2, the supply auger 32 is provided with a round bar-shaped main shaft portion 44 at the center along the axis S <b> 1, and a rib-shaped spiral extending from the outer peripheral surface of the main shaft portion 44. Fins 46 are integrally formed. The spiral fin 46 is disposed in a portion of the main flow passage 22 excluding one end portion on the first communication port 28 side, and is provided so as to have a constant inclination angle with respect to the axial direction of the main shaft portion 44 at an arbitrary portion. It has been. As a result, the spiral fin 46 is formed in a spiral shape that travels along the axial direction while circling the outer peripheral side of the main shaft portion 44. The spiral fin 46 has an outer diameter slightly shorter than the inner diameter on the bottom side of the main flow passage 22. The spiral fin 46 is arranged so that one end side thereof extends from the other end of the first communication port 28 toward the one end side by about ½ pitch along the axial direction.

  The admix auger 34 is also provided with a round bar-shaped main shaft portion 48 at the center along the axis S2, and a rib-shaped spiral fin 50 extending from the outer peripheral surface of the main shaft portion 48 is integrally formed. Has been. The spiral fin 50 is disposed in a portion of the return passage 24 excluding the other end portion on the second communication port 30 side, and has a constant inclination angle with respect to the axial direction of the main shaft portion 48 at an arbitrary portion. Is provided. Thereby, the spiral fin 50 is also formed in a spiral shape that moves along the axial direction while circling the outer peripheral side of the main shaft portion 48. The outer diameter of the spiral fin 50 is slightly shorter than the inner diameter of the return passage 24 on the bottom side. The spiral fin 50 is formed so that the other end side extends from one end of the second communication port 30 to the other end side by about ½ pitch along the axial direction.

  As shown in FIG. 2, the admix auger 34 is provided with a plate-like scraping portion 52 at a portion corresponding to one pitch on the other end side of the spiral fin 50 in the main shaft portion 48. The scraping portion 52 extends along the radial direction from the outer peripheral surface of the main shaft portion 48, and extends in the axial direction to close the gap between the spiral fins 50. Since the developer D in the vicinity of the bottom surface in the return passage 24 is scooped upward by the scraping portion 52 and pushed out toward the second communication port 30, the bottom surface portion in the return passage 24 is passed through the second communication port 30. The developer D present in the vicinity can be reliably fed into the main flow passage 22.

  The admix auger 34 is provided with a counter fin 54 having an inclination angle opposite to that of the spiral fin 50 at the other end side of the main shaft portion 48 with respect to the spiral fin 50. The counter fin 54 has a pitch along the axial direction shorter than that of the spiral fin 50 and an inclination angle with respect to the axis S <b> 2 smaller than that of the spiral fin 50.

  As shown in FIG. 2, the housing 16 is integrally provided with a cylindrical receiving portion 56 that protrudes outward along the axis S <b> 1 of the supply auger 32 on the side plate portion of the first communication port 28. . A pipe-shaped supply path 58 is formed in the receiving portion 56 so as to extend along the axis S1. One end of the supply path 58 along the axial direction is a side plate portion of the housing 16. The other end portion is provided with a supply port 60 that opens into the main flow passage 22. Further, as shown in FIG. 3, a receiving port 62 connected to one end portion of the supply path 58 is opened on the upper surface portion of the receiving portion 56. Here, the cross-sectional area of the supply path 58 is smaller than that of the main flow passage 22 and the return flow passage 24.

  The main shaft portion 44 of the supply auger 32 is inserted into the supply path 58 through the supply port 60, and one of the support shaft portions 36 is pivotally supported by a bearing 40 disposed on the axially outer side with respect to the supply path 58. ing. The supply auger 32 is provided with a counter fin 64 having an inclination angle opposite to that of the spiral fin 46 on one end side inserted into the supply path 58 in the main shaft portion 44. The counter fin 64 has a pitch along the axial direction shorter than that of the spiral fin 46 and an outer diameter smaller than that of the spiral fin 46.

  As shown in FIG. 3, the housing 16 is a throttle that covers the upper surface side of one end side of the main flow passage 22 and the return flow passage 24 and reduces the cross-sectional areas of the main flow passage 22 and the return flow passage 24 more than other portions. A portion 66 is provided. The partition wall 26 that divides the main flow passage 22 and the return flow passage 24 is provided with a sub-communication port 68 adjacent to the throttle portion 66 along the axial direction. The main flow passage 22 communicates with the return flow passage 24. In the housing 16, a discharge port 72 is formed in the rear plate portion on the opposite side to the photosensitive drum 12 (see FIG. 1) to communicate the counterflow portion 70 of the return passage 24 to the outside of the housing 16. The discharge port 72 is disposed on the side of the counter fin 54 along the width direction of the apparatus (the direction of the arrow W).

  In the developing device 10, torque is transmitted to the supply auger 32 and the admix auger 34 when the developing roll 20 rotates, and the developing roll 20 rotates. At this time, the supply auger 32 rotates in a predetermined feeding direction (arrow FM direction in FIG. 2), and the admix auger 34 feeds in a direction opposite to the supply auger 32 (arrow FN direction in FIG. 2). Rotate to. As a result, the developer D stored in the main flow passage 22 is stirred by the spiral fins 46 of the supply auger 32, and the main flow direction (arrow M direction) from the second communication port 30 side to the first communication port 28 side. ).

  On the other hand, the developer D stored in the return passage 24 is agitated by the spiral fin 50 in the area where the spiral fin 50 is provided in the admix auger 34, and from the first communication port 28 side to the second communication port 28. In the countercurrent portion 70 that is conveyed in the backward flow direction (arrow N direction) toward the 30 side and provided with the counter fin 54, the counter flow direction is opposite to the reverse flow direction while being stirred by the counter fin 54. It is conveyed in the direction of arrow C. At this time, the conveyance amount (conveyance capability) per unit time for the developer D by the counter fin 54 is smaller than the conveyance capability for the developer D by the spiral fin 50. Further, the developer D carrying ability by the spiral fin 46 of the supply auger 32 and the developer D carrying ability by the spiral fin 50 of the admix auger 34 are substantially equal.

  In the developing device 10, when the developing roll 20 rotates, the developer D is transported in the main flow passage 22 by the supply auger 32, so that it is transported to the downstream end of the main flow passage 22 along the main flow direction. The developer D flows into the return passage 24 through the first communication port 28, and the developer D is conveyed in the return passage 24 by the admix auger 34, whereby the return passage along the return flow direction. The developer D conveyed to the downstream end of 24 flows into the main flow passage 22 through the second communication port 30. As a result, in the housing 16 of the developing device 10, the developer D circulates between the main flow passage 22 and the return flow passage 24 when the developing roll 20 rotates.

  As shown in FIG. 2, an ATC sensor 74 is attached to the housing 16 so as to face the inside of the main flow passage 22 at the rear plate portion. The ATC sensor 74 is disposed on the side of the scraping portion 52 of the admix auger 34 along the axial direction, and detects the magnetic permeability of the developer D stored in the return passage 24. A detection signal corresponding to the composition of developer D is output to a control unit (not shown) of the image forming apparatus. The image forming apparatus is provided with a developer supply device (not shown) for supplying a replenishment developer (hereinafter referred to as “trickle developer”) into the replenishment path 58 through the receiving port 62. When the developer supply device receives a replenishment signal from the control unit, the developer supply device supplies an amount of trickle developer instructed by the replenishment signal into the replenishment path 58. The trickle developer supplied into the supply path 58 is conveyed by the counter fin 64 of the supply auger 32 in the supply direction opposite to the main flow direction, and is sent out into the main flow path 22 through the supply port 60. The trickle developer joins the developer D conveyed in the main flow direction in the vicinity of the downstream end portion in the main flow passage 22 by the supply auger 32.

  In the developing device 10, the toner concentration (TC) of the developer D circulating in the device is controlled within a range of approximately 8% ± 2%.

  Here, the control unit of the image forming apparatus determines a toner replenishment amount to the developing device 10 based on a detection signal from the ATC sensor 74 and a toner consumption amount calculated from the image information, and corresponds to this toner replenishment amount. A replenishment signal is output to the developer supply device when the supply auger 32 and the admix auger 34 are rotated.

  As shown in FIGS. 1 and 4, the developing roll 20 is located above the main flow path 22, and its roll surface 21 is close to the outer peripheral portion of the supply auger 32, and on the image carrying surface 14 of the photosensitive drum 12. It is supported so as to face each other with a predetermined minute interval. Further, when the developing device 10 is mounted on the main body portion of the image forming apparatus, the developing roll 20 is connected to a torque transmission mechanism provided on the main body portion and is driven in a direction (arrow RR direction) driven by the photosensitive drum 12. Rotate. The rotation speed of the developing roll 20 is set so that the linear velocity is 1.6 times the linear velocity of the photosensitive drum 12. Here, the developing roll 20 is configured as a magnet roll containing a magnet inside, and the toner in the developer D flowing through the main flow path 22 is adsorbed by the roller surface 21 when the photosensitive drum 12 rotates. .

  In the housing 16, a plate-shaped trimmer bar 80 is disposed above the developing roll 20, and the developing roll 20 is disposed between the front end of the trimmer bar 80 and the roll surface 21 of the developing roll 20. A gap having a predetermined minute width is formed along the radial direction. As a result, the toner in the developer D adsorbed on the roll surface 21 as the developing roll 20 rotates is thinned by the trimmer bar 80 and then moved to the developing position close to the image carrying surface 14 of the photosensitive drum 12. To do. At this time, when an electrostatic latent image is formed on the image bearing surface 14 of the photosensitive drum 12, the toner charged to a predetermined polarity (usually negative (−) polarity) is electrostatically charged. Due to the force, the toner image is transferred from the roll surface 21 of the developing roll 20 to the image carrying surface 14 at the developing position, and selectively adheres to the electrostatic latent image to form a toner image on the image carrying surface 14.

  As shown in FIG. 1, a plate-like sealing material 76 having elasticity is attached to the peripheral portion of the opening 18 in the housing 16, and the sealing material 76 has a tip portion of the photosensitive drum 12. It is in close contact with the image carrying surface 14. As a result, the toner that has been peeled off from the developing roll 20 or the photoconductive drum 12 to be clouded is prevented from being scattered and flowing out from between the housing 16 and the photoconductive drum 12.

  In the housing 16, a seal roll 78 is rotatably disposed below the developing roll 20, and the roll surface of the seal roll 78 has a predetermined minute distance from the image carrying surface 14 of the photosensitive drum 12. It is supported so as to face each other. The seal roller 78 is also configured to rotate in the driven direction when the developing roller 20 rotates. When the developing device 10 is operated, a voltage having a polarity opposite to that of the toner is applied to the cored bar. When the developing device 10 is operated, a voltage having the same potential as the developing bias is applied, thereby adsorbing the cloud toner having the opposite polarity that is peeled off from the developing roll 20 and the photosensitive drum 12. In the housing 16, a scraper 82 is disposed between the seal roll 78 and the supply auger 32, and the scraper 82 is in contact with or close to the roll surface of the seal roll 78. As a result, the toner adsorbed by the seal roll 78 is peeled and removed by the scraper 82, falls from the scraper 82 into the main flow path 22, and is collected.

  Next, the operation and action of the developing device 10 according to the present embodiment configured as described above will be described.

  In the developing device 10, when the photosensitive drum 12 in the image forming apparatus rotates and formation of an electrostatic latent image on the image bearing surface 14 of the photosensitive drum 12 is started, the supply auger 32 and the admixing auger 34 are moved. The developing roll 20 is rotated in the driven direction with respect to the photosensitive drum 12 while being rotated in the feeding direction. As a result, the developer D stored in the main flow passage 22 flows in the main flow direction while being stirred, and the developer D stored in the return flow passage 24 flows in the return flow direction while being stirred. At this time, in the housing 16, the developer D that has flowed to the downstream end portion of the main flow passage 22 flows into the upstream end portion of the return flow passage 24 through the first communication port 28, and the return flow passage 24. The developer D that has flowed to the downstream end of the toner flows into the upstream end of the main flow passage 22 through the second communication port 30, so that the developer D circulates in the main flow passage 22 and the return flow passage 24. To do. The developing roll 20 rotates while adsorbing toner in the developer D flowing in the main flow passage 22 in the main flow direction onto the roll surface 21 by magnetic force, and the toner adsorbed on the roller surface 21 is trimmer bar 80. To make it thinner. Thereafter, the developing roll 20 moves the toner thinned on the roll surface 21 to a developing position close to the image carrying surface 14 of the photosensitive drum 12, and the toner is exposed to the image carrying surface 14 at this developing position. A toner image is formed by selectively transferring to the formed electrostatic latent image. After completion of the toner image formation, the developing roll 20 temporarily causes the toner remaining on the roll surface 21 to temporarily move on the roll surface 21 by the action of the repulsive pole located above the main flow path 22 in the magnet disposed inside the roll. To be recirculated into the main flow passage 22.

  In the developing device 10, the magnetic permeability of the developer D flowing through the return passage 24 is detected by the ATC sensor 74 when the above developing operation is performed, and a detection signal corresponding to the toner concentration of the developer D is sent to the image forming apparatus. To the control unit. Upon receiving this detection signal, the control unit keeps the amount (level) of the developer D circulating through the developing device 10 based on the toner consumption amount and the detected toner density by the developing operation substantially constant, and the developer D The trickle developer is introduced from the receiving port 62 into the replenishment path 58 by the developer supply device so that the toner density is maintained within a predetermined appropriate range (for example, 8% ± 2%). The trickle developer charged into the supply path 58 is conveyed to the supply port 60 side while being stirred by the counter fin 64 of the supply auger 32, and is supplied into the main flow passage 22 through the supply port 60.

  Further, in the return passage 24, the spiral fin 50 of the admix auger 34 applies a conveying force in the backward flow direction to the developer D on the upstream side of the counterflow portion 70, and the counter fin 54 has the counterflow portion 70. The conveying force in the counterflow direction is applied to the developer D in the inside. Thereby, in the return passage 24, a part of the developer D conveyed in the backward flow direction by the spiral fin 50 on the upstream side of the reverse flow portion 70 is blocked by the counter fin 54 and in the reverse flow portion 70. The remaining developer D that has flowed into is conveyed in the counterflow direction by the counter fin 54, and the flow of the developer D collides with the flow of the developer D conveyed by the spiral fin 50. As a result, in the return passage 24, the developer D is blocked by the counter fin 54, so that the level of the developer D is near the area immediately before the counterflow portion 70, that is, near the area where the ATC sensor 74 is disposed. Increases as compared with other regions, and the flow rate of the developer D decreases.

  In the countercurrent portion 70, the developer D is always conveyed (discharged) upstream by the counter fin 54, so that the level of the developer D is lower than the upstream side. As the trickle developer is supplied into the main flow passage 22 by the developer supply device and the level of the developer D stored in the return flow passage 24 increases, the amount of the developer D flowing into the counterflow portion 70 gradually increases. And the level of the developer D in the countercurrent portion 70 also increases. As a result, the level of the developer D in the countercurrent portion 70 is stably raised and lowered so as to correspond to the increase / decrease of the circulating developer D in the developing device 10. At this time, when the total amount of the developer D in the developing device 10 increases and the level of the developer D in the countercurrent portion 70 rises above the level of the discharge port 72, the developer D is discharged to the outside through the discharge port 72. As a result, the total amount of the developer D in the developing device 10 gradually decreases, the level of the developer D in the countercurrent portion 70 converges to the level of the discharge port 72, and the total amount of the developer D in the developing device 10 also increases. It becomes almost constant.

  In the developing device 10 according to the present embodiment described above, the counter fin 64 of the supply auger 32 causes the trickle developer supplied into the supply path 58 through the receiving port 62 to be circulated to the supply port 60 side while stirring. The trickle developer is fed into the main flow passage 22 through the replenishment path 58 by joining the trickle developer to the developer D flowing in the vicinity of the downstream end of the main flow path 22 through the opening 60. Since the trickle developer can be replenished into the developer D circulating in the main flow passage 22 and the return flow passage 24, even if the developer D is consumed during the developing operation, the consumption of the developer D can be accommodated. The amount of trickle developer to be replenished to the developer D in the apparatus, and the circulation amount of the developer D in the main flow passage 22 and the return flow passage 24 can always be kept substantially constant, Since the trickle developer is replenished into the apparatus, the developer D in an amount corresponding to the replenishment amount of the trickle developer containing a predetermined ratio of carrier can be discharged to the outside through the discharge port 72. 22 and the deteriorated carrier contained in the developer D flowing through the return passage 24 are gradually replaced with the carrier contained in the trickle developer, so that it is possible to effectively prevent a decrease in charging performance of the toner due to the deterioration of the carrier. .

  Here, a trickle developer supply path 58 is provided so as to extend on an extension line of the main flow path 22 along the main flow direction, and a supply port 60 of the supply path 58 is provided at the downstream end of the main flow path 22. Since the opening faces the portion, the direction of flow of trickle developer supplied into the main flow passage 22 by the counter fin 64 through the supply port 60 of the replenishment passage 58 is determined. The direction in which the agent D flows (main flow direction) can be made in a substantially opposite direction, and an extremely large stirring force can be applied to the trickle developer that merges with the developer D in the vicinity of the downstream end of the main flow passage 22. Therefore, the trickle developer supplied from the outside can be mixed so as to diffuse uniformly into the developer D circulating efficiently in the apparatus.

  Further, the developer D mixed with trickle developer near the downstream end of the main flow passage 22 flows into the return passage 24 through the first communication port 28 without being immediately adsorbed by the developing roll 20. After being circulated while being stirred in the backward flow direction by the admix auger 34 over the entire length of the flow passage 24, it flows into the main flow passage 22 through the second communication port 30, so that the developer D mixed with trickle developer is mixed. Since the stirring time by the admix auger 34 can be secured sufficiently long, the developer D mixed with the trickle developer is stirred for a sufficient time to give high uniformity, and then the second communication port The developer D can be fed into the main flow passage 22 through 30.

  As a result, since the local TC fluctuation generated in the developer D flowing in the main flow passage 22 after the trickle developer is supplied from the outside can be effectively suppressed, the local TC of the developer D in the main flow passage 22 can be suppressed. It can be prevented that the image quality is deteriorated in the image formed on the photosensitive drum 12 due to the fluctuation.

  Further, in the developing device 10 according to the present embodiment, the second communication port 30 is disposed outside the other end of the developing roll 20 along the main flow direction, so that the developer D can be reliably extended to the entire length of the return passage 24. After being stirred by the admix auger 34, the developer D can be supplied to the main flow passage 22 through the second communication port 30. Therefore, the developer D having high uniformity with little fluctuation in toner density is supplied to the main flow passage 22, and this developer. D can be supplied from the main flow path 22 to the developing roll 20, and the first communication port 28 is arranged outside the one end of the developing roll 20 along the main flow direction, so that the replenishment path 58 supplies the main roll path 22. The developer D containing the trickle developer is prevented from being directly supplied to the developing roll 20, and after the developer D containing the trickle developer flows through the return passage 24, the developer D containing the trickle developer passes through the second communication port 30. Therefore, even when the trickle developer is supplied through the replenishment path 58, the developer D having high uniformity with little fluctuation in toner density is supplied to the main flow path 22, and this developer D is supplied to the main flow path 22. It can be supplied from the main flow path 22 to the developing roll 20.

  Further, in the developing device 10 according to the present embodiment, the return passage 24 is provided with a discharge port 72 for discharging the developer D that becomes surplus in the device according to the supply of trickle developer from the supply path 58 to the outside. The level of the developer D in the counterflow portion 70 circulates in the developing device 10 by opening the side of the counter fin 54 of the admix auger 34 disposed in the counterflow portion 70 in the developing device 10. Therefore, when the total amount of the developer D in the developing device 10 increases due to the replenishment of the trickle developer, the developer D in the countercurrent portion 70 is increased. The level rises corresponding to the amount of increase. As a result, for example, when the level of the developer D in the countercurrent portion 70 rises above the level of the discharge port 72, the developer D is discharged to the outside through the discharge port 72, and the total amount of the developer D in the developing device 10 is also increased. The developer D gradually decreases, the level of the developer D in the countercurrent portion 70 converges to the level of the discharge port 72, and the total amount of the developer D in the developing device 10 becomes substantially constant, so that the developing device 10 is circulated. The total amount of the developer D can be accurately maintained at the target amount.

  Further, in the developing device 10 according to the present embodiment, the ATC sensor 74 that detects the toner concentration of the developer D is disposed immediately before the counter fin 54 in the return passage 24 along the return flow direction. In the path 24, the developer D is blocked by the counter fin 54, and the level of the developer D rises in the vicinity of the area immediately before the counterflow portion 70, that is, in the vicinity of the area where the ATC sensor 74 is disposed, as compared with other areas. At the same time, the phenomenon that the flow rate of the developer D decreases occurs, so that the pressing force and the moving speed of the developer D with respect to the ATC sensor 74 can be stabilized, and as a result, the accuracy of toner density detection by the ATC sensor 74 can be improved.

  Further, in the developing device 10 according to this embodiment, the main flow passage 22 is provided with a sub-communication port 68 communicating with the return flow passage 24 immediately before the first communication port 28 in the main flow direction, that is, immediately before the throttle portion 56. As a result, the trickle developer is replenished into the vicinity of the downstream end portion of the main flow passage 22 through the replenishment passage 58, and the amount of the developer D rapidly increases near the downstream end portion of the main flow passage 22. However, since the developer D on the upstream side flows into the return passage 24 through the sub-communication port 68 and flows into the vicinity of the downstream end portion of the main flow passage 22, the throttle portion of the main flow passage 22 is avoided. It is effective that more developer D than can flow into 66 flows in and clogs developer D or the level of developer D rises locally on the upstream side of the throttle 66 in the main flow passage 22. Can be prevented.

FIG. 2 is a side cross-sectional view illustrating a configuration of a developing device and a photosensitive drum according to an embodiment of the present invention. FIG. 2 is a plan sectional view of a portion including a supply path in the developing device shown in FIG. 1. FIG. 2 is a plan sectional view of a part including a seal roll in the developing device shown in FIG. 1. FIG. 2 is a plan sectional view of a part including a developing roll in the developing device shown in FIG. 1. FIG. 11 is a plan sectional view showing a conventional example of a developing device disclosed in Japanese Patent Laid-Open No. 2003-337515.

Explanation of symbols

10 Development Device 12 Photosensitive Drum (Image Carrier)
20 Development roll (developer supply member)
22 Main flow passage 24 Return flow passage 28 First communication port 30 Second communication port 32 Supply auger 34 Admix auger 46 Spiral fin 50 Spiral fin (fin part)
52 Scraping section 54 Counter fin (opposite conveying member)
58 Supply path 60 Supply port 64 Counter fin (feeding member)
66 Restriction section 68 Sub-communication port 70 Counterflow section 72 Discharge port 74 ATC sensor (concentration sensor)

Claims (7)

A main flow path for flowing the developer in a predetermined main flow direction;
A supply auger that is provided in the main flow passage and circulates in the main flow direction while stirring the developer in the main flow passage;
A return passage provided in the housing adjacent to the main flow passage, for allowing the developer to flow in a return flow direction substantially opposite to the main flow direction;
An admixing auger that is provided in the return flow passage and circulates in the return flow direction while stirring the developer in the main flow passage;
A first communication port connecting the downstream end of the main flow passage and the upstream end of the return flow passage;
A second communication port connecting the downstream end of the return flow passage and the upstream end of the main flow passage;
Development that is provided so as to extend along the main flow direction and that develops a latent image formed on the image carrier by the developer while adsorbing the developer flowing through the main flow passage by the supply auger. An agent supply member;
It is provided so as to extend on the extension line of the main flow passage along the main flow direction, and one end portion is a supply port that opens to face the downstream end portion of the main flow passage, and the other end portion is A replenishment passage that is open to the outside of the apparatus, and
The replenishment developer supplied into the replenishment path through the receiving port is circulated to the supply port side while stirring, and the replenishment developer is circulated through the supply port near the downstream end of the main flow passage. A feeding member that joins the developer to be
A developing device comprising:   The developing device according to claim 1, wherein the first communication port and the second communication port are arranged outside one end and the other end of the developer supply member along the main flow direction, respectively. . A discharge port for discharging the developer remaining in the apparatus to the outside in response to the replenishment of the developer from the replenishment path, and a downstream end in the return passage, and the development in the return path is provided. An opposing conveying member that circulates in a facing direction opposite to the backward flow direction while stirring the agent,
The developing device according to claim 1, wherein the discharge port is opened to a side of the opposite conveying member.   The density sensor for detecting the density of toner contained in the developer is disposed immediately before the opposing conveying member in the return flow path along the return flow direction. 3. The developing device according to 3. The admix auger is provided with a shaft portion extending along the backward flow direction, and a fin portion extending in a spiral shape with the shaft portion as a center, and facing the second communication port. A scraping portion is provided so as to extend in the axial direction between the fin portions,
While the admix auger rotates in a predetermined driving direction by torque transmitted from the outside, the fin portion applies a conveying force in the backward flow direction to the developer in the backward flow path, A conveying force that scoops out the developer near the bottom of the return flow path to the main flow path side is applied by the scraping portion at a portion facing the second communication port. The developing device according to claim 1.   6. The sub-communication port that communicates with the return flow passage is provided in the main flow passage immediately before the first communication port along the main flow direction. 6. Development device. A throttle portion extending from the downstream end of the main flow passage to the upstream side of the first communication port along the main flow direction and having a reduced cross-sectional area with respect to other portions of the main flow passage. Provided,
The developing device according to claim 6, wherein the communication port is disposed immediately before the throttle portion along the main flow direction.

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