JP2011175095A - Developing device and image forming apparatus including the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact developing device which has a simple structure and in which a surplus developer is stably discharged from a developing container and a developer amount in the developing container is accurately maintained to a desired amount, and an image forming apparatus including the developing device. <P>SOLUTION: The developing device 2 includes a first stirring member 44 that has a first helical blade 44a extending in an axial direction around a rotary shaft 44b, and stirs and conveys the developer to be supplied to a developing roller 20. The developing container 22 includes a developer discharge port 22h from which the surplus developer is discharged. The first stirring member 44 includes a regulating part 52 arranged to face the developer discharge port 22h, for regulating movement of the developer to the developer discharge port 22h side. The regulating part 52 has a reverse helical blade 52a helically formed on a reverse phase with respect to the first helical blade 44a, and the outer diameter Db of the reverse helical blade 52a is larger than the outer diameter Da of the first helical blade 44a. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used in an image forming apparatus such as a copying machine, a printer, a facsimile, or a composite machine using an electrophotographic system, and an image forming apparatus including the developing device. The present invention relates to a developing device that replenishes developer and discharges excess developer, and an image forming apparatus including the developing device.

  In an image forming apparatus, a latent image formed on an image carrier made of a photoreceptor or the like is developed by a developing device and visualized as a toner image. As one of such developing devices, a two-component developing system using a two-component developer is employed. In this type of developing device, a developer composed of a carrier and toner is accommodated in a developer container, a developing roller for supplying the developer to the image carrier is disposed, and the developer inside the developer container is conveyed and stirred. However, a stirring member for supplying the developing roller is provided.

  In this developing device, the toner is consumed by the developing operation, while the carrier is not consumed and remains in the developing device. Therefore, the carrier stirred together with the toner in the developing container deteriorates as the stirring frequency increases, and as a result, the charge imparting performance of the carrier with respect to the toner gradually decreases.

  In view of this, there has been proposed a developing device in which a developer containing a carrier is replenished in a developing container and a surplus developer is discharged to suppress a decrease in charging performance.

  For example, in Patent Document 1, two stirring members each having a rotation shaft and a spiral blade formed in a spiral shape on the outer periphery thereof are arranged in parallel in each conveyance path. A partition portion is provided between the conveyance paths, and communication portions for delivering the developer are provided at both ends of the partition portion. A developer discharge port is formed on the downstream side of the conveyance path with respect to the developer conveyance direction, and a spiral shape is formed between the stirring member and the developer discharge port in a phase opposite to the spiral blade of the stirring member. The reverse spiral blade is integrally provided on the rotating shaft as a restricting portion. In this configuration, when the developer is supplied into the developing container, the developer is conveyed to the downstream side of the conveyance path while being agitated by the rotation of the agitating member. When the reverse spiral blade rotates in the same direction as the agitating member, the developer is blocked and becomes bulky on the downstream side of the conveyance path, so that excess developer moves over the reverse spiral blade and moves to the developer discharge port. And discharged to the outside.

JP 2001-265098 A (paragraphs [0020] to [0024], [0028], FIG. 4)

  However, in the above-described prior art, even when the developer is not newly replenished, the developer conveyed by the spiral blade of the stirring member moves to the downstream side of the conveyance path so as to follow the outer periphery of the spiral blade. It will collide with the regulation part. When the developer collides with the restricting portion, the volume of the developer differs from the outer periphery of the restricting portion depending on the axial position of the spiral blade with respect to the restricting portion. When the developer collides with the restricting portion at a position where the developer volume is high, the developer moves over the restricting portion and moves to the developer discharge port due to the momentum of the collision, and the developer is excessively discharged. . This may cause the developer amount in the developing container to be unstable. In particular, in an apparatus for forming an image at a high speed, the stirring member also rotates at a high speed together with the photosensitive member, and a disadvantage that the developer is excessively discharged occurs remarkably.

  In order to prevent the developer from being excessively discharged in this way, the restricting portion is lengthened in the axial direction, for example, a configuration in which the number of reverse spiral blades is increased, or the restricting portion is separated from the communication portion. Arrangements are made to move the developer before being transported from the communicating part to the other conveyance path, but in these configurations, the restriction part and the developer discharge port are separated from the conveyance path. There is a disadvantage that the apparatus becomes larger in the axial direction.

  The present invention has been made to solve the above-described problems, and with a simple configuration, the excess developer can be stably discharged from the developing container, and the amount of developer in the developing container can be accurately determined. It is an object of the present invention to provide a developing device that is small in size, and an image forming apparatus including the developing device.

  In order to achieve the above object, the present invention has a developer container for containing a developer, a developing roller for supplying the developer to the image carrier, and a spiral blade extending in the axial direction around the rotation axis. A plurality of agitating members for agitating and conveying the developer supplied to the developing roller, and the developer container includes a partition unit that divides a plurality of conveying paths through which the developer is circulated by the agitating members; Provided on the downstream side of any one of the plurality of transport paths, a communication section for communicating the transport paths on both ends in the longitudinal direction of the partition section, a developer supply port for supplying developer, and the plurality of transport paths A developer discharge port through which excess developer is discharged, and the first agitating member disposed in the first conveyance path upstream of the developer discharge port has a connection to the developer discharge port. In a developing device provided with a regulating portion that regulates the movement of the developer The restricting portion has a reverse spiral blade formed in a spiral shape in reverse phase with respect to the spiral blade of the first stirring member, and the outer diameter of the reverse spiral blade is the outer diameter of the spiral blade of the first stirring member. It is characterized by being larger.

  According to this configuration, the developer is supplied into the developing container from the developer supply port, and the developer is conveyed while being stirred by the stirring member. Then, the developer to be transported moves to the downstream side of the first transport path and is blocked by the reverse spiral blade, and excess developer that is bulky than the reverse spiral blade is removed from the outer peripheral portion of the reverse spiral blade. Overflow to the outlet. On the other hand, when the developer is not newly replenished, the conveyed developer moves to the downstream side of the first conveying path so as to follow the outer periphery of the spiral blade of the stirring member, and collides with the reverse spiral blade. When the bulky developer that moves in a undulating manner collides with the reverse spiral blade, the outer diameter of the reverse spiral blade is larger than the outer diameter of the spiral blade. Never get over.

  In the invention according to claim 2, when the outer diameter of the spiral blade of the first stirring member is represented by Da and the outer diameter of the reverse spiral blade is represented by Db, 1.1 <Db / Da <1.3 ( Formula 1) is characterized by being.

  In the invention according to claim 3, the interval between the outer peripheral portion of the reverse spiral blade and the inner peripheral surface of the first transport path is such that the outer peripheral portion of the spiral blade and the inner peripheral surface of the first transport path are It is characterized by being substantially the same as the interval.

  According to a fourth aspect of the present invention, there is provided an image forming apparatus equipped with the developing device having the above configuration.

  According to the first aspect of the present invention, the developer is supplied into the developing container from the developer supply port, and the developer is conveyed while being stirred by the stirring member. Then, the developer to be transported moves to the downstream side of the first transport path and is blocked by the reverse spiral blade, and excess developer that is bulky than the reverse spiral blade is removed from the outer peripheral portion of the reverse spiral blade. Overflow to the outlet. Accordingly, it is possible to stably discharge the excess developer from the developer discharge port to the outside of the developing container. On the other hand, when the developer is not newly replenished, the conveyed developer moves to the downstream side of the first conveying path so as to follow the outer periphery of the spiral blade of the stirring member, and collides with the reverse spiral blade. When the bulky developer that moves in a undulating manner collides with the reverse spiral blade, the outer diameter of the reverse spiral blade is larger than the outer diameter of the spiral blade. Never get over. Accordingly, the amount of developer in the developing container can be accurately maintained at a desired amount, and the reverse spiral blade need not be separated from the stirring member, and the apparatus can be miniaturized. Furthermore, the developing device of this embodiment can also be applied to a high-speed image forming apparatus.

  According to the second aspect of the present invention, when the outer diameter ratio Db / Da of the spiral blade is below the lower limit, there is a risk that the outer periphery of the reverse spiral blade may be overcome when the developer is not newly replenished. In other words, it becomes difficult to keep the amount of developer in the developing container at a desired amount. On the other hand, if the upper limit of the outer diameter ratio Db / Da of the spiral blade is exceeded, the outer diameter of the reverse spiral blade becomes too large, and the developer stays near the boundary between the reverse spiral blade and the spiral blade, Larger equipment. When the outer diameter ratio Db / Da of the spiral blade is in the numerical range of Formula 1, the amount of developer in the developing container can be maintained at a desired amount, and the apparatus can be downsized.

  According to the invention described in claim 3, the distance between the outer peripheral portion of the reverse spiral blade and the inner peripheral surface of the first transport path is the distance between the outer peripheral portion of the spiral blade and the inner peripheral surface of the first transport path. Are approximately the same size. If the spacing is substantially the same, even if the outer diameter of the reverse spiral blade is increased and the developer transport force by the reverse spiral blade is increased, the respective developer transports by the reverse spiral blade and the spiral blade. Since the forces are substantially the same, the amount of developer in the developing container can be accurately maintained at a desired amount.

  According to the invention described in claim 4, the development is small in size with a simple configuration, stably discharging excess developer from the developing container, and maintaining the amount of developer in the developing container at a desired amount with high accuracy. The image forming apparatus can be provided with the apparatus.

1 is a side view schematically showing an overall configuration of an image forming apparatus equipped with a developing device according to an embodiment of the present invention. Sectional side view schematically showing a developing device according to an embodiment Sectional top view which shows the stirring part of the developing device which concerns on embodiment Sectional top view which shows the principal part of the stirring part of the image development apparatus concerning embodiment. Sectional drawing which shows typically the spiral blade and reverse spiral blade in the developing container of the developing device according to the embodiment The figure which shows the developer scattering of the developer discharge part which concerns on an Example and a comparative example

  Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to these embodiments. Further, the use of the invention and the terms shown here are not limited thereto.

  FIG. 1 is a side view schematically showing a configuration of an image forming apparatus equipped with a developing device according to an embodiment of the present invention. The image forming apparatus 1 is a tandem type color printer, and the rotatable photoconductors 11a to 11d use an organic photoconductor (OPC photoconductor) as a photosensitive material for forming a photosensitive layer, and are black, yellow, cyan. , And magenta. Around each of the photoreceptors 11a to 11d, developing devices 2a to 2d, an exposure unit 12, chargers 13a to 13d, and cleaning devices 14a to 14d are disposed.

  The developing devices 2a to 2d are arranged to face the right sides of the photoconductors 11a to 11d, respectively, and supply toner to the photoconductors 11a to 11d. The chargers 13a to 13d are arranged on the upstream side of the developing devices 2a to 2d with respect to the rotation direction of the photosensitive member and opposed to the surfaces of the photosensitive members 11a to 11d, and uniformly charge the surfaces of the photosensitive members 11a to 11d. .

  The exposure unit 12 scans and exposes each of the photoconductors 11a to 11d based on image data such as characters and patterns input from a personal computer or the like to an image input unit (not shown). The developing device 2a ~ 2d below. The exposure unit 12 is provided with a laser light source and a polygon mirror, and a reflection mirror and a lens are provided corresponding to each of the photoreceptors 11a to 11d. Laser light emitted from the laser light source is applied to the surfaces of the photoconductors 11a to 11d from the downstream side in the photoconductor rotation direction of the chargers 13a to 13d via the polygon mirror, the reflection mirror, and the lens. Electrostatic latent images are formed on the surfaces of the photoreceptors 11a to 11d by the irradiated laser light, and the electrostatic latent images are developed into toner images by the developing devices 2a to 2d.

  The endless intermediate transfer belt 17 is stretched around the tension roller 6, the driving roller 25, and the driven roller 27. The driving roller 25 is rotationally driven by a motor (not shown), and the intermediate transfer belt 17 is circulated and driven by the rotation of the driving roller 25.

  The photoreceptors 11a to 11d are arranged below the intermediate transfer belt 17 so as to be in contact with the intermediate transfer belt 17 along the conveying direction (arrow direction in FIG. 1). The primary transfer rollers 26a to 26d face the photoconductors 11a to 11d with the intermediate transfer belt 17 interposed therebetween, and press contact with the intermediate transfer belt 17 to form a primary transfer portion. In the primary transfer portion, the toner images on the photoconductors 11a to 11d are sequentially transferred to the intermediate transfer belt 17 at a predetermined timing as the intermediate transfer belt 17 rotates. As a result, a full-color toner image is formed on the surface of the intermediate transfer belt 17 in which toner images of four colors of magenta, cyan, yellow, and black are superimposed.

  The secondary transfer roller 34 is opposed to the driving roller 25 with the intermediate transfer belt 17 interposed therebetween, and presses against the intermediate transfer belt 17 to form a secondary transfer portion. In this secondary transfer portion, the toner image on the surface of the intermediate transfer belt 17 is transferred to the paper P. After the transfer, the belt cleaning device 31 cleans the toner remaining on the intermediate transfer belt 17.

  A paper feed cassette 32 that stores paper P is disposed below the image forming apparatus 1, and a stack tray 35 that supplies manually fed paper is disposed to the right of the paper feed cassette 32. On the left side of the paper feed cassette 32, a first paper transport path 33 for transporting the paper P fed from the paper feed cassette 32 to the secondary transfer portion of the intermediate transfer belt 17 is disposed. Further, on the left side of the stack tray 35, a second paper transport path 36 for transporting paper fed from the stack tray 35 to the secondary transfer unit is disposed. Further, on the upper left side of the image forming apparatus 1, a fixing unit 18 that performs a fixing process on the sheet P on which an image is formed, and a third sheet transport that transports the sheet on which the fixing process has been performed to the sheet discharge unit 37. A path 39 is provided.

  The paper feed cassette 32 can be replenished by pulling it out of the apparatus (the front side in FIG. 1). The paper P stored therein is first fed one by one by the pick-up roller 33b and the separating roller 33a. The paper is fed out to the paper conveyance path 33 side.

  The first paper transport path 33 and the second paper transport path 36 merge before the registration roller 33c, and the registration roller 33c takes the timing of the image forming operation and the paper feeding operation on the intermediate transfer belt 17, The paper P is conveyed to the secondary transfer unit. The full-color toner image on the intermediate transfer belt 17 is secondarily transferred to the sheet P conveyed to the secondary transfer unit by the secondary transfer roller 34 to which a bias potential is applied, and is conveyed to the fixing unit 18.

  The fixing unit 18 includes a fixing belt heated by a heater, a fixing roller in contact with the fixing belt, a pressure roller disposed in pressure contact with the fixing roller with the fixing belt interposed therebetween, and a toner image is transferred. The fixing process is performed by heating and pressurizing the sheet P. After the toner image is fixed by the fixing unit 18 on the paper P, the toner image is reversed by the fourth paper conveyance path 40 as necessary, and the toner image is secondarily transferred to the back surface of the paper by the secondary transfer roller 34 to be fixed. Fixing is performed at the portion 18. The sheet on which the toner image is fixed passes through the third sheet conveyance path 39 and is discharged to the sheet discharge unit 37 by the discharge roller 19a.

  FIG. 2 is a cross-sectional side view showing the configuration of the developing device used in the image forming apparatus 1 described above. In the following description, the configuration and operation of the developing device 2a corresponding to the photoconductor 11a shown in FIG. 1 will be described. However, the configuration and operation of the developing devices 2b to 2d are the same as those of the developing device 2a. Omitted, and reference numerals a to d indicating developing devices and photoconductors of the respective colors are omitted.

  As shown in FIG. 2, the developing device 2 includes a developing roller 20, a magnetic roller 21, a regulating blade 24, a stirring member 42, a developing container 22, and the like.

  The developing container 22 constitutes an outline of the developing device 2, and a lower portion of the developing container 22 is partitioned into a first transport path 22d and a second transport path 22c by a partition portion 22b. The first transport path 22d and the second transport path 22c contain a developer composed of a carrier and toner. Further, the developing container 22 rotatably holds the stirring member 42, the magnetic roller 21, and the developing roller 20. Further, the developing container 22 is formed with an opening 22 a that exposes the developing roller 20 toward the photoconductor 11.

  The developing roller 20 faces the photoconductor 11 and is disposed on the right side of the photoconductor 11 with a certain interval. Further, the developing roller 20 forms a developing area D for supplying toner to the photoconductor 11 at a facing position close to the photoconductor 11. The magnetic roller 21 is opposed to the developing roller 20 with a certain interval, and is disposed diagonally to the right of the developing roller 20. Further, the magnetic roller 21 supplies toner to the developing roller 20 at a facing position close to the developing roller 20. The regulating blade 24 is fixedly held in the developing container 22 obliquely to the left of the magnetic roller 21. The stirring member 42 is disposed substantially below the magnetic roller 21.

  The stirring member 42 includes two members, a first stirring member 44 and a second stirring member 43. A first stirring member 44 is provided in the first conveyance path 22d below the magnetic roller 21, and a second stirring member 43 is provided in the second conveyance path 22c adjacent to the right side of the first stirring member 44. It is done.

  The first and second stirring members 44 and 43 stir the developer to charge the toner in the developer to a predetermined level. As a result, the toner is held on the carrier. In addition, communication portions (not shown) are provided at both ends in the longitudinal direction (front and back surfaces in FIG. 2) of the partition 22b that partitions the first transport path 22d and the second transport path 22c, and the second stirring When the member 43 rotates, the charged developer is transported into the first transport path 22d from one communicating portion provided in the partition portion 22b, and the developer in the first transport path 22d and the developer in the second transport path 22c. Circulate. Then, the developer is supplied from the first stirring member 44 to the magnetic roller 21.

  The magnetic roller 21 includes a roller shaft 21a, a magnetic pole member M, and a rotating sleeve 21b made of a nonmagnetic material. The magnetic roller 21 carries the developer supplied by the stirring member 42 and supplies only the toner from the carried developer to the developing roller 20. To do. In the magnetic pole member M, a plurality of magnets with different polarities on the outer peripheral portion formed in a sector shape are alternately arranged, and are fixed to the roller shaft 21a by adhesion or the like. The roller shaft 21a is supported by the developing container 22 in a non-rotatable manner in the rotating sleeve 21b with a predetermined interval between the magnetic pole member M and the rotating sleeve 21b. The rotating sleeve 21b is rotated in the same direction as the developing roller 20 (clockwise direction in FIG. 2) by a driving mechanism including a motor and a gear (not shown), and a bias 56 in which the AC voltage 56b is superimposed on the DC voltage 56a is applied. The On the surface of the rotating sleeve 21 b, the charged developer is carried by forming a magnetic brush by the magnetic force of the magnetic pole member M, and the magnetic brush is adjusted to a predetermined height by the regulating blade 24.

  When the rotary sleeve 21b rotates, the magnetic brush is carried on the surface of the rotary sleeve 21b by the magnetic pole member M and conveyed. When the magnetic brush contacts the developing roller 20, only the magnetic brush toner is applied to the bias 56 applied to the rotary sleeve 21b. Accordingly, the toner is supplied to the developing roller 20.

  The developing roller 20 includes a fixed shaft 20a, a magnetic pole member 20b, a developing sleeve 20c formed in a cylindrical shape with a nonmagnetic metal material, and the like.

  The fixed shaft 20a is supported by the developing container 22 so as not to rotate. A developing sleeve 20c is rotatably held on the fixed shaft 20a. Further, a magnetic pole member 20b made of a magnet is fixed to the developing sleeve 20c at a position facing the magnetic roller 21, and is fixed by adhesion or the like. The The developing sleeve 20c is rotated in an arrow direction (clockwise direction) in FIG. 2 by a driving mechanism including a motor and gears (not shown). Further, a developing bias 55 in which an AC voltage 55b is superimposed on a DC voltage 55a is applied to the developing sleeve 20c.

  When the developing bias 55 is applied in the developing region D, the toner carried on the surface of the developing sleeve 20 c flies to the photosensitive member 11 due to the potential difference between the developing bias potential and the potential of the exposed portion of the photosensitive member 11. The flying toner sequentially adheres to the exposed portion on the photoconductor 11 rotating in the direction of arrow A (counterclockwise direction), and the electrostatic latent image on the photoconductor 11 is developed.

  Next, the stirring unit of the developing device will be described in detail with reference to FIG. FIG. 3 is a cross-sectional plan view showing the stirring unit.

  As described above, the developing container 22 includes the first transport path 22d, the second transport path 22c, the partition 22b, the upstream communication section 22e, and the downstream communication section 22f. A developer supply port 22g, a developer discharge port 22h, an upstream side wall portion 22i, and a downstream side wall portion 22j are formed. In the second transport path 22c, the left side of FIG. 2 is the upstream side, the right side of FIG. 2 is the downstream side, and the first transport path 22d is the upstream side of FIG. 2 and the left side of FIG. And Therefore, the communication part and the side wall part are called upstream and downstream with reference to the first transport path 22d.

  The partition 22b extends in the longitudinal direction of the developing container 22 and partitions the first transport path 22d and the second transport path 22c in parallel. The right end portion in the longitudinal direction of the partition portion 22b forms the upstream communication portion 22e together with the inner wall portion of the upstream side wall portion 22i, while the left end portion in the longitudinal direction of the partition portion 22b is the inner wall portion of the downstream side wall portion 22j. At the same time, a downstream communication portion 22f is formed. The developer can circulate in the second conveyance path 22c, the upstream communication section 22e, the first conveyance path 22d, and the downstream communication section 22f.

  The developer supply port 22g is an opening for supplying new toner and carrier into the developer container 22 from a developer supply container (not shown) provided in the upper part of the developer container 22, and the second supply path 22c. Arranged on the upstream side (left side in FIG. 2).

  The developer discharge port 22h is an opening for discharging the developer remaining in the first and second transport paths 22d and 22c due to the replenishment of the developer. The developer discharge port 22h is located downstream of the first transport path 22d. It is provided continuously in the longitudinal direction of one conveyance path 22d.

  A first stirring member 44 is disposed in the first transport path 22d, and a second stirring member 43 is disposed in the second transport path 22c.

  The second agitating member 43 includes a rotation shaft 43b and second spiral blades 43a that are provided integrally with the rotation shaft 43b and formed in a spiral shape at a constant pitch in the axial direction of the rotation shaft 43b. Further, the second spiral blade 43a extends to both end portions in the longitudinal direction of the second transport path 22c, and is provided to face the upstream and downstream communication portions 22e and 22f. The rotating shaft 43b is rotatably supported by the upstream side wall portion 22i and the downstream side wall portion 22j of the developing container 22.

  The first stirring member 44 has a rotation shaft 44b and a first spiral blade 44a provided integrally with the rotation shaft 44b. The first spiral blade 44a is formed in a spiral shape with blades having the same pitch as the second spiral blade 43a in the axial direction of the rotation shaft 44b and facing in the opposite direction (in reverse phase) to the second spiral blade 43a. The first spiral blade 44a has a length equal to or longer than the axial length of the magnetic roller 21, and further extends to a position facing the upstream communication portion 22e and the downstream communication portion 22f. The rotation shaft 44b is disposed in parallel with the rotation shaft 43b, and is rotatably supported by the upstream side wall portion 22i and the downstream side wall portion 22j of the developing container 22.

  In addition, a regulating portion 52 and a discharge blade 53 are integrally disposed on the rotation shaft 44b together with the first spiral blade 44a.

  The restricting unit 52 blocks the developer conveyed downstream in the first conveyance path 22d, and conveys the developer that has become a predetermined amount or more in the first conveyance path 22d to the developer discharge port 22h. It is possible to do. The restricting portion 52 includes a rotating shaft 44b and a reverse spiral blade 52a provided on the rotating shaft 44b.

  The reverse spiral blade 52a is formed in a spiral shape with a blade facing in the opposite direction to the first spiral blade 44a (in reverse phase), and is formed larger than the outer diameter of the first spiral blade 44a. Further, the reverse spiral blade 52a is formed of blades having a pitch smaller than that of the first spiral blade 44a and 2 to 3 turns so as not to be elongated in the axial direction. The reverse spiral blade 52a is disposed between the first spiral blade 44a and the developer discharge port 22h with a distance from the inner peripheral surface of the first conveyance path 22d in the downstream side wall portion 22j. Accordingly, the restricting portion 52 can discharge excess developer in the first conveyance path 22d to the developer discharge port 22h beyond the outer peripheral portion of the reverse spiral blade 52a.

  The rotating shaft 44b extends into the developer discharge port 22h. A discharge blade 53 is provided on the rotating shaft 44b in the developer discharge port 22h. The discharge blades 53 are formed of spiral blades that face the same direction as the first spiral blades 44a, but have a smaller pitch than the first spiral blades 44a and an outer diameter of the blades smaller than that of the first spiral blades 44a. Therefore, when the rotating shaft 44b rotates, the discharge blade 53 also rotates, and the excess developer that has passed over the reverse spiral blade 52a and is conveyed into the developer discharge port 22h is sent to the left side of FIG. It is designed to be discharged outside. The discharge blade 53, the reverse spiral blade 52a, and the first spiral blade 44a are integrally molded with the rotary shaft 44b by a synthetic resin.

  Gears 61 to 64 are disposed on the outer wall of the developing container 22. The gears 61 and 62 are fixed to the rotation shaft 43b, the gear 64 is fixed to the rotation shaft 44b, and the gear 63 and a gear (not shown) are rotatably held by the developing container 22 and mesh with the gears 62 and 64. .

  Accordingly, during development without newly replenishing the developer, when the gear 61 is rotated by a driving source such as a motor, the second spiral blade 43a is rotated together with the rotating shaft 43b, and the developer is removed by the second spiral blade 43a. Then, it is transported in the direction of arrow P in the second transport path 22c, and then transported into the first transport path 22d through the upstream communication portion 22e. Further, when the rotating shaft 44b that is linked to the rotating shaft 43b rotates, the developer is transported in the direction of arrow Q in the first transport path 22d by the rotation of the first spiral blade 44a. By the rotation of the first and second spiral blades 44a and 43a, the developer follows the outer periphery of the first and second spiral blades 44a and 43a, and the developer is conveyed while greatly changing its bulkiness. Since the outer diameter is larger than the outer diameter of the first spiral blade 44a, the developer is transported to the second transport path 22c through the downstream communication section 22f without overcoming the regulating section 52 in the first transport path 22d. Is done.

  Thus, the developer is agitated while circulating from the second conveyance path 22c to the upstream communication part 22e, the first conveyance path 22d, and the downstream communication part 22f, and the agitated developer is applied to the magnetic roller 21. Supplied.

  Next, a case where developer is supplied from the developer supply port 22g will be described. When the toner is consumed by the development, the developer including the carrier is supplied from the developer supply port 22g into the second transport path 22c.

  The replenished developer is transported in the direction of the arrow P by the second spiral blade 43a in the direction of arrow P by the second spiral blade 43a, and then passes through the upstream communication portion 22e in the first transport path 22d. To be transported. Further, the developer is transported in the direction of arrow Q in the first transport path 22d by the first spiral blade 44a. When the reverse spiral blade 52a rotates with the rotation of the rotating shaft 44b, the reverse spiral blade 52a imparts a developer with a transport force in a direction opposite to the developer transport direction by the first spiral blade 44a. By the reverse spiral blade 52a, the developer in the first conveyance path 22d in the vicinity of the reverse spiral blade 52a is blocked and bulky, and excess developer passes over the reverse spiral blade 52a and passes through the developer discharge port 22h. Then, it is discharged out of the developing container 22.

  Next, the detailed structure of the control part 52 is demonstrated based on FIG. 4, FIG. FIG. 4 is a plan view showing the first spiral blade 44a, the reverse spiral blade 52a, and the periphery thereof. FIG. 5A is a cross-sectional view schematically showing the first spiral blade 44a in the developing container 22, and FIG. 5B is a cross-sectional view schematically showing the reverse spiral blade 52a in the developing container 22. .

  As shown in FIG. 4, a gap Ka is formed between the outer peripheral portion of the first spiral blade 44a and the inner peripheral surface 22m of the first transport path 22d. The interval Ka is formed by the lower and left and right inner peripheral surfaces of the developing container 22 shown in FIG. 5A and the outer peripheral portion of the first spiral blade 44a. In FIG. 5A and FIG. 5B, M represents the developer surface.

  In addition, as shown in FIG. 4, the reverse spiral blade 52a is opposed to the first spiral blade 44a in the axial direction, and is provided close to the first spiral blade 44a. As described above, the outer diameter of the reverse spiral blade 52a is larger than the outer diameter of the first spiral blade 44a, and further, between the outer peripheral portion of the reverse spiral blade 52a and the inner peripheral surface 22m of the first transport path 22d. Is formed with an interval Kb. The interval Kb is formed by the lower and left and right inner peripheral surfaces in the developing container 22 shown in FIG. 5B and the outer peripheral portion of the reverse spiral blade 52a. And this space | interval Kb is set to the substantially same magnitude | size as the space | interval Ka formed by the outer peripheral part of the 1st spiral blade 44a.

  Thus, when the interval Ka and the interval Kb are approximately the same size, even if the outer diameter of the reverse spiral blade 52a is increased and the toner conveying force by the reverse spiral blade 52a is increased, the reverse spiral blade 52a and the reverse spiral blade 52a Since the conveying force of each toner by one spiral blade 44a is substantially the same, the amount of toner in the developing container 22 can be accurately maintained at a desired amount.

Next, when the outer diameter of the first spiral blade 44a is represented by Da as shown in FIG. 5 (a) and the outer diameter of the reverse spiral blade 52a is represented by Db as shown in FIG. 5 (b),
1.1 <Db / Da <1.3 Formula 1
It is better to satisfy the relationship.

  If the lower limit of Equation 1 is not reached, the outer diameter of the reverse spiral blade 52a becomes substantially the same as the outer diameter of the first spiral blade 44a, and the toner is reverse spiral even when no new toner is supplied. There is a risk of overcoming the outer periphery of the blade 52a, and it becomes difficult to keep the toner amount in the developing container 22 at a desired amount. On the other hand, when the upper limit of Equation 1 is exceeded, the interval Ka and the interval Kb are greatly different, or if the interval Ka and the interval Kb are the same, the reverse spiral blade 52a on the inner peripheral surface 22m shown in FIG. Since a step is formed at the boundary with the blade 44a, toner stays and stable toner discharge becomes difficult. However, when the outer diameter ratio Db / Da of the spiral blade is in the numerical range of Formula 1, the amount of developer in the developing container 22 can be maintained at a desired amount, and the apparatus can be downsized.

  According to the embodiment, the developing device 2 extends along the axial direction around the rotation shafts 43b and 44b, the developing container 22 that stores the developer, the developing roller 20 that supplies the developer to the photosensitive member 11, and the rotating shafts 43b and 44b. The first and second agitating members 44 and 43 have first and second spiral blades 44a and 43a, and agitate and convey the developer supplied to the developing roller 20. The developing container 22 includes a partition portion 22b that partitions the first and second transport paths 22d and 22c through which the developer is circulated and transported by the stirring members 44 and 43, and the first and second end portions in the longitudinal direction of the partition portion 22b. The upstream and downstream communication portions 22e and 22f for communicating the first and second transport paths 22d and 22c, the developer supply port 22g for supplying the developer, and the first transport path 22d are provided on the downstream side. Developer outlet 22h through which the developer is discharged. The first agitating member 44 is provided with a restricting portion 52 that is disposed to face the developer discharge port 22h and restricts the movement of the developer toward the developer discharge port 22h. The restricting portion 52 has a spiral blade 52a formed in a spiral shape in an opposite phase with respect to the first spiral blade 44a, and the outer diameter Db of the reverse spiral blade 52a is larger than the outer diameter Da of the first spiral blade 44a.

  According to this configuration, the developer is supplied into the developing container 22 from the developer supply port 22g, and this developer is conveyed while being stirred by the first and second stirring members 44 and 43. Then, the conveyed developer moves downstream of the first conveyance path 22d and is blocked by the reverse spiral blade 52a, and the excess developer that is bulkier than the reverse spiral blade 52a is the outer periphery of the reverse spiral blade 52a. Overflows into the developer discharge port 22h. Therefore, the excess developer can be stably discharged out of the developer container 22 from the developer discharge port 22h.

  On the other hand, when the developer is not newly replenished, the conveyed developer moves to the downstream side of the first conveying path 22d so as to follow the outer peripheral portion of the first spiral blade 44a, and is moved to the reverse spiral blade 52a. collide. When the bulky developer moving in a undulating manner collides with the reverse spiral blade 52a, the outer diameter Db of the reverse spiral blade 52a is larger than the outer diameter Da of the first spiral blade 44a, so the first spiral blade 44a rotates at high speed. Even if it does not get over the outer periphery of the reverse spiral blade 52a. Therefore, the amount of developer in the developing container 22 can be accurately maintained at a desired amount, and the reverse spiral blade 52a need not be separated from the first spiral blade 44a, and the apparatus can be miniaturized. Further, the developing device 2 of the present embodiment can be applied to a high-speed image forming apparatus.

  In the above embodiment, the developing roller 20 and the magnetic roller 21 are provided, a magnetic brush is carried on the magnetic roller 21, only the toner is supplied to the developing roller 20, and the toner on the developing roller 20 flies to the photoconductor 11. However, the present invention is not limited to this, and the developer is pumped directly from the stirring member to the developing roller, and only the toner from the developer on the developing roller incorporating the magnet is photoreceptord. You may apply to the developing device supplied to.

  Moreover, in the said embodiment, although the 1st stirring member 44 was arrange | positioned in the 1st conveyance path 22d, the 2nd stirring member 43 was arrange | positioned in the 2nd conveyance path 22c, The present invention is not limited to this, and the third stirring member 44 may be disposed in the third transport path. In this case as well, the same effects as in the above embodiment can be obtained.

  Hereinafter, Example 1 which further embodies the embodiment of the present invention and Comparative Example 1 will be described. In addition, this invention is not limited only to a following example.

  The developing roller 20 used in Example 1 and Comparative Example 1 has an outer diameter of 16 mm and a rotation number of 878 rpm, and the magnetic roller 21 has an outer diameter of 20 mm and a rotation number of 700 rpm. In the second stirring member 43, the outer diameter of the second spiral blade 43a is 18 mm, the blade pitch is 30 mm (double winding), the shaft diameter of the rotating shaft 43b is 7 mm, and the rotational speed is 500 rpm. is there. On the other hand, the outer diameter Da of the first spiral blade 44a of the first stirring member 44 is 18 mm, the blade pitch is 30 mm (two windings), and the shaft diameter of the rotating shaft 44b is 7 mm. The blade 43a rotates in the reverse direction, and the rotation speed is 500 rpm. The restricting member 52 is formed of a spiral blade having a phase opposite to that of the first spiral blade 44a.

  In Example 1, the outer diameter Db of the reverse spiral blade 52a of the regulating member 52 is 20 mm, and the number of blades is 2.5. On the other hand, in Comparative Example 1, the outer spiral blade 52a has an outer diameter Db of 18 mm and the number of blades is 2.5.

  The toner in the developing container 22 of Example 1 and Comparative Example 1 has an average particle diameter of 6.8 μm, the carrier has an average particle diameter of 35 μm, and the weight ratio of the toner to the carrier is 9%. The weight ratio of the carrier to the toner of the new developer replenished in the developing container 22 was 10%. 400 g of developer is accommodated in the developer container 22 (first and second transport paths 22d and 22c), and this amount is a predetermined amount that does not include excess developer in the developer container 22.

  In Example 1 and Comparative Example 1 configured as described above, the amount of developer splattering in the discharge portion was evaluated. The developer scattering amount is the amount of developer conveyed from the first and second conveyance paths 22d and 22c to the developer discharge port 22h.

  FIG. 6 shows the evaluation results of the developer scattering amount of Example 1 and Comparative Examples 1 and 2. FIG. 6 is a graph in which the horizontal axis represents the stirring time, and the vertical axis represents the developer scattering amount.

  In Comparative Example 1, the amount of developer splattering increased as the stirring time increased. However, in Example 1, there was almost no developer splattering even when the stirring time was long.

  INDUSTRIAL APPLICABILITY The present invention can be used for a developing device used in an image forming apparatus such as a copying machine, a printer, a facsimile, and a composite machine using the electrophotographic method, and an image forming apparatus including the developing device. Can be used for a developing device that replenishes the two-component developer and discharges excess developer and an image forming apparatus equipped with the developing device.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2a-2d, 2 Developing apparatus 11a-11d, 11 Photoconductor 20 Developing roller 21 Magnetic roller 22 Developing container 22b Partition part 22c Second conveyance path 22d First conveyance path 22e Upstream communication part (communication part)
22f Downstream communication part (communication part)
22g Developer supply port 22h Developer discharge port 22i Upstream side wall 22j Downstream side wall 22m Inner peripheral surface 42 Stirring member 43 Second stirring member 43a Second spiral blades 43b and 44b Rotating shaft 44 First stirring member 44a First spiral blade (Spiral feather)
52 Regulating portion 52a Reverse spiral blade Da Outer diameter Db of second spiral blade Outer diameter Ka, Kb interval of reverse spiral blade

Claims (4)

A developer container for containing the developer, a developing roller for supplying the developer to the image carrier, and a spiral blade extending in the axial direction around the rotation axis, and stirring the developer supplied to the developing roller; A plurality of agitating members to be conveyed, and the developer container includes a partition portion that divides a plurality of conveying paths through which the developer is circulated and conveyed by the respective agitating members, and at both ends in the longitudinal direction of the partition portion. A development unit that communicates each conveyance path, a developer supply port that supplies developer, and a downstream side of any one of the plurality of conveyance paths, and discharges excess developer. The first agitating member that is provided in the first conveyance path upstream of the developer discharge port is provided with a restriction unit that restricts the movement of the developer to the developer discharge port. In the developing device
The restricting portion has a reverse spiral blade formed in a spiral shape in reverse phase with respect to the spiral blade of the first stirring member, and the outer diameter of the reverse spiral blade is the outer diameter of the spiral blade of the first stirring member. Larger developing device. When the outer diameter of the spiral blade of the first stirring member is represented by Da and the outer diameter of the reverse spiral blade is represented by Db,
1.1 <Db / Da <1.3
The developing device according to claim 1, wherein the developing device is provided.   The distance between the outer peripheral part of the reverse spiral blade and the inner peripheral surface of the first transport path is substantially the same as the distance between the outer peripheral part of the spiral blade and the inner peripheral surface of the first transport path. The developing device according to claim 1 or 2.   An image forming apparatus on which the developing device according to claim 1 is mounted.

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