JP6701015B2 - Conveyor screw and developing device - Google Patents

Description

  The present invention relates to a conveying screw that conveys a developer, and a developing device that includes the conveying screw.

  There is a developing device that includes a first conveying screw that supplies a developer containing a toner and a magnetic carrier to a developer carrier, and a second conveying screw that conveys the developer separated from the developer carrier. In this developing device, a partition member (partition wall) for partitioning the transport path (supply route) of the first transport screw and the transport route (recovery route) of the second transport screw is projected toward the developer carrier. (See Patent Document 1).

  In the developing device described in Patent Document 1, the developer transferred from the recovery path is supplied to the developer carrier through the supply path, and the developer separated from the developer carrier is recovered through the recovery path and recovered. The developed developer is transferred from the recovery path to the supply path. As described above, the development in which the function of collecting the developer separated from the developer carrier in the recovery path and the function of supplying the developer transferred from the recovery path to the developer carrier in the supply path are separated from each other The apparatus is hereinafter referred to as a function-separated type developing apparatus. In the function-separated type developing device, the developer is sequentially supplied to the developer carrier from the upstream side to the downstream side of the developer conveying direction in the supply path. Therefore, the developer amount in the supply path of the function-separated type developing device tends to be smaller on the downstream side in the transport direction than on the upstream side.

  In the developing device described in Patent Document 1, the outer diameter of the rotating shaft of the first conveying screw is increased from the upstream side to the downstream side in the conveying direction of the first conveying screw.

JP, 2011-158577, A

  The conveying screw that conveys the developer includes a core metal, a resin layer that covers the outer periphery of the core metal, and a blade portion that is provided on the outer periphery of the resin layer and integrally molded with the resin layer. By making the outer diameter of the core metal uniform along the longitudinal direction of the conveying screw and increasing the thickness of the resin layer from one end to the other end of the conveying screw in the longitudinal direction, the conveying screw is conveyed from one longitudinal end to the other end. It is assumed that the cross sectional area of the screw is increased. In such a case, since the thickness of the resin layer is different between the one end and the other end in the longitudinal direction of the conveying screw, a difference occurs in the degree of heat shrinkage of the resin layer after molding the conveying screw with the resin. The warp and runout of the layers will increase.

  On the other hand, the clearance between the outer diameter of the conveying screw and the inner wall of the developing container is set to a predetermined distance so that the developer in the developing container is sufficiently agitated by the blade portion of the conveying screw. If the warp or runout of the resin layer of the conveying screw is large, the clearance between the outer diameter of the conveying screw and the inner wall of the developing container will be smaller than the specified distance, and the outer diameter of the conveying screw will interfere with the inner wall of the developing container. There is a risk of doing it. Therefore, if the clearance between the blade of the conveying screw and the inner wall of the developing container is made larger than a predetermined distance in advance by considering the warp amount and the amount of deflection of the resin layer of the conveying screw, the inner wall of the conveying screw and the developing container is A large amount of developer stays between and. If the developer staying in the developing container is supplied to the developer carrying area of the developer carrying member without being sufficiently stirred by the blade portion of the conveying screw, there is a possibility that image defects such as density unevenness may occur.

  The present invention has been made in view of the above problems. An object of the present invention is to reduce warpage and runout of a resin layer in a conveying screw that conveys a developer including a resin layer and a blade portion provided on the outer periphery of the resin layer and integrally formed with the resin layer. With the goal.

  In order to achieve the above object, a conveying screw according to one aspect of the present invention has the following configuration. That is, in a carrying screw for carrying a developer, which comprises a cored bar, a resin layer covering the outer periphery of the cored bar, and a blade part provided on the outer periphery of the resin layer and integrally molded with the resin layer, The outer diameter of the core metal at one end in the longitudinal direction of the conveying screw is larger than the outer diameter of the core metal at the other end in the longitudinal direction of the conveying screw, and the resin extends from one end to the other end in the longitudinal direction of the conveying screw. It is characterized in that the layers have substantially the same thickness.

  Further, in order to achieve the above object, the developing device according to one aspect of the present invention has the following configuration. That is, a developer carrying member that carries a developer and develops an electrostatic latent image, a core metal, a resin layer that covers the outer periphery of the core metal, and a resin layer that is provided on the outer periphery of the resin layer and integrally molded with the resin layer. And a conveying screw for conveying the developer to be supplied to the developer carrying body, the developing device having at least a region where the developer is carried on the developer carrying body. In the region of the carrying screw to be, the outer diameter of the core metal on the downstream side in the carrying direction of the developer by the carrying screw is larger than the outer diameter of the core metal on the upstream side in the carrying direction of the developer by the carrying screw. It is characterized in that the thickness of the resin layer is substantially the same from the upstream side to the downstream side in the developer conveying direction by the conveying screw.

  ADVANTAGE OF THE INVENTION According to this invention, in the conveyance screw which conveys the developer provided with the resin layer and the blade part integrally formed with the resin layer provided in the outer periphery of the resin layer, the warp and shake of the resin layer are reduced. You can

FIG. 3 is a cross-sectional view showing the configuration of the image forming apparatus. FIG. 3 is a cross-sectional view showing a configuration of a developing device. It is a schematic diagram showing a configuration of a developing device. FIG. 6 is a cross-sectional view showing a configuration of a developer discharging mechanism. FIG. 3 is a cross-sectional view showing a configuration of a developing device (separated function type). FIG. 3 is a schematic diagram showing a configuration of a developing device (separated function type). FIG. 3 is a schematic diagram showing a developer surface in a developing device (separate function type). It is a schematic diagram which shows the shape of the conveyance screw which concerns on 1st Embodiment. It is a schematic diagram which shows the shape of the conveyance screw which concerns on 2nd Embodiment. It is a schematic diagram which shows the shape of the conveyance screw which concerns on 3rd Embodiment. It is a schematic diagram which shows the shape of the conveyance screw which concerns on 4th Embodiment. It is a schematic diagram which shows the shape of the conventional conveyance screw.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the present invention according to the claims, and all combinations of the features described in the present embodiments are not necessarily essential to the solving means of the present invention. . The present invention can be implemented in various applications such as printers, various printing machines, copiers, fax machines, and multifunction machines.

[First Embodiment]
(Structure of image forming apparatus)
First, the configuration of the image forming apparatus according to the first embodiment of the present invention will be described with reference to the sectional view of FIG.

  As shown in FIG. 1, the image forming apparatus includes an endless intermediate transfer belt (ITB) 7 as an intermediate transfer member, and an upstream side to a downstream side along the rotation direction of the intermediate transfer belt 7 (direction of arrow R7). Four image forming sections S (Sa, Sb, Sc, Sd) are provided.

  The image forming portions S (Sa, Sb, Sc, Sd) form toner images of Y (yellow), M (magenta), C (cyan), and Bk (black), respectively.

  The image forming unit S (Sa, Sb, Sc, Sd) includes a rotatable photosensitive drum 1 (1a, 1b, 1c, 1d) as an image carrier.

  Each of the photosensitive drums 1 (1a, 1b, 1c, 1d) is rotationally driven in the arrow R (Ra, Rb, Rc, Rd) direction (clockwise). Around the photosensitive drum 1 (1a, 1b, 1c, 1d), along the rotation direction of the photosensitive drum 1 (1a, 1b, 1c, 1d), a charging roller 2 (2a, 2b, 2c, 2d) are provided. Further, around the photosensitive drum 1 (1a, 1b, 1c, 1d), along the rotation direction of the photosensitive drum 1 (1a, 1b, 1c, 1d), an exposure device 3 ( 3a, 3b, 3c, 3d) are provided.

  Further, around the photosensitive drum 1 (1a, 1b, 1c, 1d), a developing device 4 (4a, 4b, 4c, 4d) as a developing unit and a primary transfer roller 5 (5a, 5b) as a primary transferring unit. 5c, 5d) are provided. Further, around the photoconductor drum 1 (1a, 1b, 1c, 1d), a photoconductor cleaning blade 6 (6a, 6b, 6c, 6d) as a photoconductor cleaner is arranged.

  Each of the developing devices 4 is attachable to and detachable from the image forming apparatus. Each of the developing devices 4 (4a, 4b, 4c, 4d) includes a developing container 41 (41Y, 41M, 41C, 41K) that contains a two-component developer (hereinafter simply referred to as a developer) containing toner and a magnetic carrier. ) Has.

  The intermediate transfer belt 7 is stretched around a primary transfer roller 5 (5a, 5b, 5c, 5d), a secondary transfer counter roller 8, a tension roller 17, and a tension roller 18. The secondary transfer counter roller 8 also functions as a drive roller.

  The intermediate transfer belt 7 is pressed by the primary transfer rollers 5 (5a, 5b, 5c, 5d) from the back surface side of the intermediate transfer belt 7.

  The surface of the intermediate transfer belt 7 is brought into contact with the photosensitive drums 1 (1a, 1b, 1c, 1d). As a result, a primary transfer nip portion T1 (T1a, T1b, T1c, T1d) as a primary transfer portion is formed between the photosensitive drum 1 (1a, 1b, 1c, 1d) and the intermediate transfer belt 7. There is.

  Further, as the secondary transfer counter roller 8 rotates in the direction of arrow R8 (counterclockwise), the intermediate transfer belt 7 rotates in the direction of arrow R7. The rotation speed of the intermediate transfer belt 7 is set to be substantially the same as the rotation speed (process speed) of each of the photoconductor drums 1 (1a, 1b, 1c, 1d).

  A secondary transfer roller 9 as a secondary transfer unit is arranged at a position corresponding to the secondary transfer counter roller 8 on the surface of the intermediate transfer belt 7. The intermediate transfer belt 7 is sandwiched between a secondary transfer counter roller 8 and a secondary transfer roller 9. As a result, a secondary transfer nip portion T2 as a secondary transfer portion is formed between the secondary transfer roller 9 and the intermediate transfer belt 7.

  A belt cleaner 11 as an intermediate transfer member cleaner is in contact with the surface of the intermediate transfer belt 7 at a position corresponding to the tension roller 17.

  A sheet P (for example, paper or transparent film) used for image formation by the image forming unit S (Sa, Sb, Sc, Sd) is stored in a state of being stacked on a feeding cassette 10 serving as a sheet storage unit. There is. Then, the sheet P is supplied to the secondary transfer nip portion T2 by a feeding/conveying device having a feeding roller, a conveying roller, a registration roller, and the like. A fixing device 13 having a fixing roller 14 and a pressure roller 15 is disposed downstream of the secondary transfer nip portion T2 in the sheet P transport direction. Further, a discharge tray for stacking the sheets P discharged outside the machine is disposed on the downstream side of the fixing device 13 in the conveying direction of the sheets P.

(Structure of image forming unit)
The photosensitive drum 1 (1a, 1b, 1c, 1d) is a cylindrical (drum type) electrophotographic photosensitive member having a photosensitive layer which is an organic photo-semiconductor having negative charging characteristics. The photosensitive drum 1 (1a, 1b, 1c, 1d) has, for example, a diameter of 30 mm, a longitudinal length of 360 mm, and a process speed (peripheral speed) of 250 mm/sec. Further, at the time of image formation, the photosensitive drum 1 (1a, 1b, 1c, 1d) is rotationally driven in the forward direction (arrow R (Ra, Rb, Rc, Rd) direction) by the motor.

  The charging roller 2 (2a, 2b, 2c, 2d) is in contact with the photoconductor drum 1 (1a, 1b, 1c, 1d) and is directed toward the photoconductor drum 1 (1a, 1b, 1c, 1d) by a pressure spring. Is being urged. During image formation, the charging roller 2 (2a, 2b, 2c, 2d) is driven and rotated by the photoconductor drum 1 (1a, 1b, 1c, 1d). The charging roller 2 (2a, 2b, 2c, 2d) has a diameter of 14 mm and a longitudinal length of 320 mm, for example. A charging bias (DC voltage: -900V, AC peak-to-peak voltage: 1500V) is applied to the charging roller 2 (2a, 2b, 2c, 2d) from, for example, a high voltage power source as an applying unit. As a result, the photosensitive drums 1 (1a, 1b, 1c, 1d) are uniformly charged.

  The exposure device 3 (3a, 3b, 3c, 3d) is a laser beam provided with a semiconductor laser for irradiating the photosensitive drum 1 (1a, 1b, 1c, 1d) charged by the charging roller 2 with a laser beam. It is a scanner. The exposure device 3 (3a, 3b, 3c, 3d) has a photosensitive drum 1 (1a, 1a, 1a, 1b) charged by a charging roller 2 (2a, 2b, 2c, 2d) based on an image signal input to the image forming apparatus. 1b, 1c, 1d) to form an electrostatic latent image.

  The developing device 4 (4a, 4b, 4c, 4d) forms the electrostatic latent image formed on the photosensitive drum 1 (1a, 1b, 1c, 1d) by the exposure device 3 (3a, 3b, 3c, 3d). Develop with a developer (toner). As a result, toner adheres to the exposed portion (laser light irradiation portion) on the photosensitive drum 1 (1a, 1b, 1c, 1d), and a visible image is formed.

  The transfer device has a primary transfer section having a primary transfer roller 5 (5a, 5b, 5c, 5d) and a secondary transfer section having a secondary transfer roller 9.

  The primary transfer rollers 5 (5a, 5b, 5c, 5d) are pressed against the surface of the intermediate transfer belt 7 sandwiched between the photosensitive drums 1 (1a, 1b, 1c, 1d) with a predetermined pressing force. .. As a result, the primary transfer nip portion T1 (T1a, T1b, T1c, T1d) as the primary transfer portion is formed.

  Further, the secondary transfer roller 9 is pressed against the surface of the intermediate transfer belt 7 sandwiched between the secondary transfer counter roller 8 with a predetermined pressing force. As a result, the secondary transfer nip portion T2 as the secondary transfer portion is formed.

  A transfer bias is applied to the primary transfer rollers 5 (5a, 5b, 5c, 5d), and the toner image formed on the photosensitive drums 1 (1a, 1b, 1c, 1d) is transferred onto the intermediate transfer belt 7. To be done. The transfer residual toner slightly left on the photosensitive drum 1 (1a, 1b, 1c, 1d) after the primary transfer is scraped and collected by the photosensitive member cleaning blade 6 (6a, 6b, 6c, 6d). .

  The recording material P fed from the feeding cassette 10 is fed to the secondary transfer portion by the registration roller. A transfer bias is applied to the secondary transfer roller 9, and the toner image formed on the intermediate transfer belt 7 is transferred onto the recording material P. The transfer residual toner slightly left on the intermediate transfer belt 7 after the secondary transfer is scraped off by the belt cleaner 11 and collected.

  The fixing device 13 fixes the toner image transferred on the recording material P. The recording material P that has undergone the fixing process by the fixing device 13 is discharged to a discharge tray.

  The series of image forming processes by the image forming unit as described above is completed, and the apparatus is ready for the next image forming operation.

(Structure of developing device)
Next, the configuration of the developing device 4 will be described with reference to the sectional view of FIG. 2 and the schematic view of FIG.

  In the developing container 41, a developing sleeve 44 as a developer carrier for carrying a developer, a magnet roll 44a including a magnet as a magnetic field generating means, and a thin layer of the developer are formed on the surface of the developing sleeve 44. A developing blade 42 as a developer regulating member is provided.

  The developing sleeve 44 is made of a non-magnetic material. The developing sleeve 44 has, for example, a diameter of 20 mm and a longitudinal length of 334 mm, and rotates in the arrow direction shown in FIG. 2 at the process speed (peripheral speed) of 425 mm/sec during the developing operation.

  Inside the developing sleeve 44, a magnet roll 44a having a plurality of magnetic poles is fixedly arranged along the circumferential direction of the developing sleeve 44. The width of the developer carried on the developing sleeve 44 in the axial direction of the rotation axis of the developing sleeve 44 (hereinafter referred to as the longitudinal direction of the developing sleeve 44) (hereinafter referred to as the developer carrying area) is a magnet roll. The width is substantially the same as the width of 44a in the longitudinal direction.

  As shown in FIG. 2, the developing container 41 is provided with a developing chamber 41a and a stirring chamber 41b. Each of the developing chamber 41a and the stirring chamber 41b can store a developer. The developer transferred from the stirring chamber 41b is supplied to the developing sleeve 44 in the developing chamber 41a. Further, the developer separated from the developing sleeve 44 is collected in the developing chamber 41a, and the collected developer is supplied again to the developing sleeve 44 in the developing chamber 41a. An opening is provided in the developing chamber 41a at a position corresponding to a region of the developing sleeve 44 facing the photosensitive drum 1 in the longitudinal direction of the developing sleeve 44 (hereinafter referred to as a developing region). The developing sleeve 44 is rotatably arranged in this opening so that a part of the developing sleeve 44 is exposed.

  Further, the developing container 41 is provided with a first carrying screw 71 as a first carrying member and a second carrying screw 72 as a second carrying member. The first transport screw 71 has a rotating shaft 73 made of a magnetic material. In addition, the second conveying screw 72 has a rotating shaft 74 formed of a magnetic body shaft.

  The first transport screw 71 stirs and transports the developer in the developing chamber 41a. The second transport screw 72 stirs and transports the toner supplied by the developer replenishing mechanism (hopper) for replenishing the developer and the developer already existing in the stirring chamber 41b.

  As shown in FIG. 3, the first conveying screw 71 is provided with a spiral blade portion 75 as a conveying portion around the rotary shaft 73. The first conveying screw 71 is arranged substantially parallel to the longitudinal direction of the developing sleeve 44. Further, the second conveying screw 72 is provided with a spiral blade portion 76 as a conveying portion around the rotary shaft 74. The second carrying screw 72 is arranged substantially parallel to the longitudinal direction of the developing sleeve 44.

  In addition, the second conveying screw 72 has the stirring rib 12 having a predetermined width in the developer conveying direction by the second conveying screw 72 (hereinafter, referred to as the second conveying screw 72 conveying direction), and the rotating shaft 74. It is formed so as to project from the rotary shaft 74 in the radial direction of. The stirring rib 12 stirs the developer in a direction orthogonal to the transport direction of the second transport screw 72 as the rotation shaft 74 of the second transport screw 72 rotates. As shown in FIG. 3, the stirring rib 12 is provided between the fins which are the blade portions 76, and the stirring rib 12 has a plate shape.

  The developer in the developing chamber 41 a is supplied to the developing sleeve 44 by the first carrying screw 71. When the developer is supplied to the developing sleeve 44, a predetermined amount of the developer is carried on the developing sleeve 44 by the magnetic field generated by the magnet roll 44a. At this time, a developer pool is formed on the developing sleeve 44. Then, the developer carried on the developing sleeve 44 passes through the developer reservoir as the developing sleeve 44 rotates, and the layer thickness is regulated by the developing blade 42. Then, the developer carried on the developing sleeve 44 is conveyed to the developing area.

  In the developing area, the developer carried on the developing sleeve 44 stands up to form magnetic ears. The magnetic brush is brought into contact with the photoconductor drum 1 and toner is supplied to the photoconductor drum 1, whereby the electrostatic latent image formed on the photoconductor drum 1 is developed as a toner image. In order to improve the toner application rate (developing efficiency) to the electrostatic latent image formed on the photosensitive drum 1, the developing sleeve 44 is provided with a DC voltage and an AC voltage from a developing bias power source as a voltage applying unit. Is applied to the developing bias voltage.

  The developer on the developing sleeve 44 after supplying the toner to the photosensitive drum 1 is peeled off from the developing sleeve 44 by the repulsive magnetic field as the developing sleeve 44 rotates. The repulsive magnetic field is formed by arranging the magnetic poles arranged on the magnet roll 44a (the magnetic pole for stripping the developer and the magnetic pole for scooping up the developer) in the same pole.

  As shown in FIG. 2, the developing container 41 is provided with a partition wall 70 for partitioning the inside of the developing container 41 into a developing chamber 41a and a stirring chamber 41b. The partition wall 70 extends in the longitudinal direction of the first transport screw 71. The partition wall 70 extends in the longitudinal direction of the second conveying screw 72.

  Further, as shown in FIG. 3, in the longitudinal direction of the partition wall 70, a first delivery portion 41c is provided at one end portion of the partition wall 70, and a second delivery portion 41d is provided at the other end portion of the partition wall 70. .. The 1st delivery part 41c plays a role of a communicating part for making a developer communicate with the stirring chamber 41b from the developing chamber 41a. That is, the developer can be communicated from the developing chamber 41a to the stirring chamber 41b via the first delivery section 41c. On the other hand, the second delivery section 41d serves as a communication section for communicating the developer from the stirring chamber 41b to the developing chamber 41a. That is, the developer can be communicated from the stirring chamber 41b to the developing chamber 41a via the second delivery section 41d.

  The first carrying screw 71 and the second carrying screw 72 carry the developer in the developing container 41 in opposite directions along the longitudinal direction of the developing sleeve 44. As a result, the developer in the developing container 41 is circulated in the developing container 41 via the first transfer section 41c and the second transfer section 41d by the first transfer screw 71 and the second transfer screw 72. In the developing step of adhering the developer carried on the developing sleeve 44 to the electrostatic latent image formed on the photoconductor drum 1, the developer on the developing sleeve 44 whose toner concentration has decreased due to consumption of toner is It is peeled off from the sleeve 44 and collected in the developing chamber 41a. Then, the collected developer is supplied again to the developing sleeve 44 in the developing chamber 41a.

  On the other hand, the developer in the developing chamber 41a not carried by the developing sleeve 44 is conveyed by the first conveying screw 71, moves in the developing chamber 41a, and then is received by the stirring chamber 41b via the first transfer portion 41c. Passed.

  Next, the developer discharging mechanism 43 for discharging the developer in the developing container 41 to the outside of the developing device 4 will be described with reference to the schematic diagram of FIG.

  As shown in FIG. 4, a developer discharge mechanism 43 is provided at the most downstream side of the stirring chamber 41b. Further, at the most downstream in the transport direction of the second transport screw 72, a return transport unit 72a for transporting the developer in a direction opposite to the transport direction (forward direction) of the second transport screw 72 is provided. The return transport unit 72a includes fins that are wound in the opposite direction to the winding direction of the fins that are the blades 76 of the second transport screw 72, and delivers the developer that has been transported in the forward direction to the developing chamber 41a side.

  As the image forming operation progresses, only the toner is consumed in the image forming operation, while the replenishing developer containing the toner and the magnetic carrier is supplied by the developer replenishing mechanism. That is, as the image forming operation proceeds, the amount of developer in the developing container 41 tends to gradually increase. Therefore, the height of the developer surface of the developer in the developing container 41 increases as the amount of developer increases. When the developer surface exceeds a predetermined height, the carrying capacity of the return conveying unit 72a is exceeded, and the developer in the stirring chamber 41b gets over the return conveying unit 72a.

  On the other hand, a discharge transport unit 43b having a forward transport capability is provided downstream of the return transport unit 72a. Therefore, the developer that has passed over the return transport unit 72a is transported to the developer discharge port 43a by the discharge transport unit 43b, falls into a recovery container for recovering the developer, and is collected. By this series of operations, the magnetic carrier of the developer circulating in the developing container 41 and the magnetic carrier of the replenishment developer newly supplied by the developer replenishing mechanism are exchanged.

  Next, the configuration of the function-separated type developing device 4 will be described with reference to the sectional view of FIG. 5 and the schematic view of FIG. The function-separated type developing device 4 has a function of collecting the developer separated from the developing sleeve 44 in a collecting path (stirring chamber 41b) and a supply path of the developer passed from the collecting path (developing chamber 41a). Is a developing device separated from the function of supplying the developing sleeve 44 with.

  As shown in FIG. 5, in the developing process, the toner on the developing sleeve 44 in which the toner is consumed and the toner concentration is lowered is peeled off from the developing sleeve 44 and collected in the stirring chamber 41b. Then, the developer collected in the stirring chamber 41b is transported by the second transport screw 72 and moves in the stirring chamber 41b. Then, the developer separated from the developing sleeve 44 moves in the stirring chamber 41b, and then is transferred from the stirring chamber 41b to the developing chamber 41a via the second transfer portion 41d. As described above, in the function-separated type developing device 4, the stirring chamber 41b plays a role of collecting the developer separated from the developing sleeve 44, and is therefore referred to as a collecting chamber.

  The developer peeled off from the developing sleeve 44 falls on the slope 70b of the partition wall 70 and is then collected in the stirring chamber 41b. The inclined surface 70b is formed on the outer wall surface of the partition wall 70 facing the second conveying screw 72 in the longitudinal direction of the second conveying screw 72.

  For this reason, in the stirring chamber 41b, the developer delivered from the developing chamber 41a via the first delivery unit 41c, the developer stripped from the developing sleeve 44 with a reduced toner concentration, and the developer And the developer replenished from the replenishment mechanism. These developers are stirred in the stirring chamber 41b by the second transport screw 72 and transported in the transport direction of the second transport screw 72. Then, these developers stirred in the stirring chamber 41b move in the stirring chamber 41b, and then are transferred to the developing chamber 41a via the second transfer unit 41d.

  As shown in FIG. 6, there are two routes in the circulation route from the developing chamber 41a to the stirring chamber 41b. That is, a path for circulating the developer from the developing chamber 41a to the stirring chamber 41b via the first delivery section 41c, and the developer peeled off from the developing sleeve 44 falls on the slope 70b and is collected in the stirring chamber 41b. It is one of the two routes. On the other hand, the circulation path from the stirring chamber 41b to the developing chamber 41a is one of the paths via the second transfer section 41d. As described above, in the function-separated type developing device 4, since the number of paths through which the developer is transferred to the stirring chamber 41b is different from the number of paths through which the developer is transferred to the developing chamber 41a, the circulation of the developer is performed. The distribution of the developer amount is not uniform in the path.

  On the other hand, from the upstream side to the downstream side of the developer conveying direction of the first conveying screw 71 (hereinafter, referred to as the conveying direction of the first conveying screw 71), the developing sleeve 44 is uniformly developed in the developer carrying region. The developer in the chamber 41a is supplied onto the developing sleeve 44. Therefore, as shown in FIG. 7, the amount of the developer in the developing chamber 41a gradually decreases from the upstream side to the downstream side in the conveying direction of the first conveying screw 71, and the developer surface in the developing chamber 41a decreases. Lowers the height.

  On the other hand, the developer collected from the developing sleeve 44 is added to the stirring chamber 41b by dropping the developer separated from the developing sleeve 44 onto the slope 70b. For this reason, the amount of the developer in the stirring chamber 41b gradually increases and the height of the developer surface in the stirring chamber 41b increases as the amount of the developer in the stirring chamber 41b increases from the upstream side to the downstream side in the conveying direction.

  As described above, in the function-separated type developing device 4, the developer is sequentially supplied to the developer carrier from the upstream side to the downstream side in the developer conveying direction in the supply path (developing chamber 41a). Therefore, the amount of the developer in the supply path of the function-separated type developing device 4 tends to be smaller on the downstream side in the transport direction of the first transport screw 71 than on the upstream side.

  Therefore, in the first embodiment, in the first carrying screw 71, at least the cross-sectional area of the first carrying screw 71 at a portion facing the developer carrying area of the developing sleeve 44 is set to the upstream side in the carrying direction of the first carrying screw 71. Increase from the side to the downstream side. As a result, the occupancy rate of the first carrying screw 71 in the developing chamber 41a is increased from the upstream side to the downstream side of the first carrying screw 71 in the carrying direction. In other words, by compensating for the decrease in the amount of developer on the downstream side of the first conveying screw 71 in the conveying direction by increasing the cross-sectional area of the first conveying screw 71, the developer agent on the downstream side of the first conveying screw 71 in the conveying direction can be obtained. Make the height of the surface higher than before.

(Conveyor screw shape)
First, the conventional shape of the first conveying screw 71 will be described with reference to the schematic diagrams of FIGS. 12(A) and 12(B).

  As shown in FIGS. 12A and 12B, the rotating shaft 73 of the first conveying screw 71 is a cored bar 73a made of metal. The core metal 73a as the rotary shaft 73 of the first conveying screw 71 needs to have a core metal diameter 73d of at least 2 mm or more, more preferably 4 mm or more, from the viewpoint of strength.

  The 1st conveyance screw 71 is provided in the outer periphery of the core metal 73a (core metal part), and is equipped with the spiral blade part 75 shape|molded by resin. Further, the first conveying screw 71 includes a resin layer 73b which is provided between the core metal 73a and the blade portion 75 and which is integrally molded with the blade portion 75 by resin.

  In the example of FIG. 12A, the outer diameter of the cored bar 73a (hereinafter referred to as the cored bar diameter 73d) is uniform over the longitudinal direction of the first conveying screw 71. Further, the outer diameter of the first conveying screw 71 (hereinafter, referred to as screw diameter 71d) is uniform over the longitudinal direction of the first conveying screw 71.

  In the example of FIG. 12B, the core metal diameter 73d is uniform over the longitudinal direction of the first conveying screw 71. On the other hand, the screw diameter 71d at the central portion of the first conveying screw 71 is larger than the screw diameter 71d at both ends of the first conveying screw 71.

  As described above, in both the examples of FIG. 12A and FIG. 12B, when the first conveying screw 71 is divided into two parts at the central portion, the weight ratio of each of the two divided rotary shafts 73 is It is almost even. Further, in both examples of FIG. 12(A) and FIG. 12(B), when the first conveying screw 71 is divided into two parts at the central portion, the weight ratios of the two divided resin layers 73b are substantially equal. It has become. In such a case, since the warp and shake of the resin layer 73b due to the thermal contraction of the resin layer 73b after the first conveying screw 71 is molded (injection molded) with the resin are reduced, the molding balance is the first conveying. It becomes good in the longitudinal direction of the screw 71.

  On the other hand, in the function separation type developing device 4, as described above, it is necessary to increase the occupancy rate of the first conveying screw 71 in the developing chamber 41a from the upstream side to the downstream side of the first conveying screw 71 in the conveying direction. is there. Therefore, in the first carrying screw 71, at least the cross-sectional area of the first carrying screw 71 at a portion facing the developer carrying region of the developing sleeve 44 is increased from the upstream side to the downstream side in the carrying direction of the first carrying screw 71. Is desirable.

  Therefore, it is assumed that the core metal diameter 73d is made uniform over the longitudinal direction of the first conveying screw 71 and the thickness of the resin layer 73b is increased from the upstream side to the downstream side in the conveying direction of the first conveying screw 71. In such a case, since the thickness of the resin layer 73b is different between the upstream side and the downstream side of the first conveying screw 71 in the conveying direction, the thermal contraction of the resin layer 73b after the first conveying screw 71 is molded with resin. Of the resin layer 73b, the warp and shake of the resin layer 73b become large.

  On the other hand, the clearance between the screw diameter 71d of the first conveying screw 71 and the partition wall 70 of the developing container 41 is set so that the developer in the developing container 41 is sufficiently stirred by the blade portion 75 of the first conveying screw 71. Is a predetermined distance (for example, 1 mm). If the warp or runout of the resin layer 73b of the first conveying screw 71 is large, the clearance between the screw diameter 71d and the partition wall 70 becomes smaller than a predetermined distance, and the blade portion 75 and the partition wall 70 may interfere with each other. There is. Therefore, when the clearance between the screw diameter 71d and the partition wall 70 is made larger than a predetermined distance in advance in consideration of the warp amount and the shake amount of the resin layer 73b, the retention between the first conveying screw 71 and the partition wall 70 occurs. The amount of developer used increases. If the developer staying in the developing container 41 is supplied to the developer carrying region of the developing sleeve 44 without being sufficiently stirred by the blade portion 75, there is a possibility that image defects such as density unevenness may occur.

  Therefore, in the first embodiment, at least the core metal diameter 73d and the thickness of the resin layer 73b in the region of the first conveying screw 71 facing the developer carrying region of the developing sleeve 44 are defined. That is, at least in the area of the first carrying screw 71 facing the developer carrying area of the developing sleeve 44, the core metal diameter 73d on the downstream side in the carrying direction of the first carrying screw 71 is the core metal diameter on the upstream side in the carrying direction. It is larger than 73d. Further, at least in the area of the first carrying screw 71 facing the developer carrying area of the developing sleeve 44, the thickness of the resin layer 73b is made substantially the same from the upstream side to the downstream side in the carrying direction of the first carrying screw 71. .. Thus, the warp of the resin layer 73b in the first conveying screw 71 that conveys the developer including the resin layer 73b and the blade portion 75 that is provided on the outer periphery of the resin layer 73b and integrally formed with the resin layer 73b. This is to reduce shake. The details will be described below.

  First, the shape of the first conveying screw 71 according to the first embodiment will be described with reference to the schematic diagram of FIG. 8.

  As shown in FIG. 8, the screw diameter 71d is continuously increased from the upstream side to the downstream side of the first conveying screw 71 in the conveying direction.

  In the example of FIG. 8, in the longitudinal direction of the first conveying screw 71, the screw diameter 71d is divided into three substantially evenly, and the screw diameter 71d is 6 mm, 8 mm, and in order from the upstream side in the conveying direction of the first conveying screw 71. It is changed in 3 steps of 10 mm.

  When the screw diameter 71d increases, the ratio of the cross-sectional area of the first carrying screw 71 to the cross-sectional area within the developing chamber 41a (that is, the developing chamber 41a when viewed in a cross section perpendicular to the carrying direction of the developing chamber 41a). The occupancy rate of the first conveying screw 71 in the inside increases. As a result, the area ratio of the developer existing in the developing chamber 41a relatively decreases, and as a result, the developer surface of the developer rises. That is, since the developer surface of the developer rises in the downstream region of the developing chamber 41a, the developer surface of the developer in the downstream region of the developing chamber 41a is introduced into the circulation path in order to raise the developer surface as compared with the conventional case. It is not necessary to increase the amount of developer itself.

  Further, as shown in FIG. 8, the core metal diameter 73d is continuously increased from the upstream side to the downstream side of the first transport screw 71 in the transport direction.

  In the example of FIG. 8, the core metal diameter 73d is divided into three substantially evenly in the longitudinal direction of the first conveying screw 71, and the core metal diameter 73d is 4 mm and 6 mm in order from the upstream side in the conveying direction of the first conveying screw 71. , And 8 mm in 3 steps.

  That is, since the core metal diameter 73d is also changed stepwise as the screw diameter 71d is changed stepwise, the thickness of the resin layer 73b should be substantially the same in the longitudinal direction of the first conveying screw 71. You can In the example of FIG. 8, the thickness of the resin layer 73b is 1 mm, which is substantially the same in the longitudinal direction of the first conveying screw. In other words, the thickness of the resin layer 73b does not substantially differ between the upstream side and the downstream side of the first conveying screw 71 in the conveying direction.

  The ratio of the thickness of the resin layer 73b at the other longitudinal end of the first transport screw 71 to the thickness of the resin layer 73b at one longitudinal end of the first transport screw 71 is 80% or more and 120% or less. For example, it is assumed that the resin layers 73b have substantially the same thickness. For example, when the thickness of the resin layer 73b is designed to be 1 mm, the difference between the thickness of the resin layer 73b at one end of the first conveying screw 71 in the longitudinal direction and the thickness of the resin layer 73b at the other end is within 0.2 mm. For example, it is assumed that the resin layers 73b have substantially the same thickness.

  Therefore, the warp and runout of the resin layer 73b due to the thermal contraction of the resin layer 73b after molding (injection molding) the first conveying screw 71 with resin are reduced, so that the balance of molding is less than that of the first conveying screw 71. Good in the longitudinal direction.

  In the longitudinal direction of the first conveying screw, the screw diameter 71d and the core metal diameter 73d are substantially evenly divided into three parts, and the screw diameter 71d and the core metal diameter 73d are changed in three steps. I can't. If the thickness of the resin layer 73b is substantially the same in the longitudinal direction of the first conveying screw 71, the number of divisions of the screw diameter 71d and the core metal diameter 73d and the division position may be an integer of 2 or more.

  As described above, in the first embodiment, the core metal diameter 73d and the thickness of the resin layer 73b are defined at least in the region of the first conveying screw 71 facing the developer carrying region of the developing sleeve 44. That is, in at least the area of the first carrying screw 71 facing the developer carrying area of the developing sleeve 44, the core metal diameter 73d on the downstream side of the carrying direction of the first carrying screw 71 is set to the direction of the carrying direction of the first carrying screw 71. The diameter was made larger than the core metal diameter 73d on the upstream side. Further, at least in the area of the first carrying screw 71 facing the developer carrying area of the developing sleeve 44, the thickness of the resin layer 73b is made substantially the same from the upstream side to the downstream side in the carrying direction of the first carrying screw 71. . As a result, the warp and runout of the resin layer 73b due to the heat shrinkage of the resin layer 73b after the first conveyance screw 71 is molded (injection-molded) with resin is reduced, so that the molding balance is maintained. Is good in the longitudinal direction.

[Second Embodiment]
In the above-described first embodiment, the core metal diameter 73d is increased stepwise from the upstream side to the downstream side of the first conveying screw 71 in the conveying direction, and the resin layer 73b extends from the upstream side to the downstream side in the conveying direction. The example in which the thickness is made substantially the same has been described.

  On the other hand, in the second embodiment, the configuration of the first conveying screw 71 is different from that of the first embodiment. Therefore, the configuration of the first conveying screw 71 according to the second embodiment will be described with reference to the schematic diagram of FIG. 9. In the second embodiment, the same members as those in the first embodiment are designated by the same reference numerals, and the description of the same components and functions as those in the first embodiment will be omitted.

  In the second embodiment, as shown in FIG. 9, at least in the region of the first conveying screw 71 facing the developer carrying region of the developing sleeve 44, the screw diameter 71d is set to the upstream side in the conveying direction of the first conveying screw 71. It becomes larger continuously from the downstream side. On the other hand, in at least the area of the first carrying screw 71 facing the developer carrying area of the developing sleeve 44, the core metal diameter 73d according to the second embodiment is provided from the upstream side to the downstream side of the carrying direction of the first carrying screw 71. It is gradually increasing as it goes to.

  In other words, the shape of the first carrying screw 71 according to the second embodiment is a conical shape over the longitudinal direction of the first carrying screw 71. In the example of FIG. 9, the screw diameter 71d continuously increases from 6 mm to 10 mm from the upstream side to the downstream side of the first conveying screw 71 in the conveying direction. In addition, in the example of FIG. 9, the shape of the first conveying screw 71 is a conical shape in the longitudinal direction of the first conveying screw 71, but the shape is not limited to this. As a modified example of the shape of the first conveying screw 71, the first conveying screw 71 has a cylindrical shape from the upstream portion to the central portion in the conveying direction, and the first conveying screw 71 has a cylindrical portion from the central portion to the downstream portion in the conveying direction. It may be changed to a conical shape.

  Further, in the example of FIG. 9, the core metal diameter 73d is divided into two in the longitudinal direction of the first conveying screw, and the core metal diameter 73d is changed in two steps, but the invention is not limited to this. The number of divisions of the core metal diameter 73d and the division positions may be integers of 2 or more.

  Alternatively, a modification in which the shape of the core metal 73 a is a conical shape in the longitudinal direction of the first conveying screw 71, like the shape of the first conveying screw 71, may be used. That is, at least in the area of the first carrying screw 71 facing the developer carrying area of the developing sleeve 44, the core metal diameter 73d is continuously increased from the upstream side to the downstream side in the carrying direction of the first carrying screw 71. It may be a modified example.

[Third Embodiment]
In the third embodiment, the configuration of the first conveying screw 71 is different from that of the first and second embodiments. Therefore, the configuration of the first conveying screw 71 according to the third embodiment will be described with reference to the schematic diagram of FIG. 10. In the third embodiment, the same members as those in the first and second embodiments are designated by the same reference numerals, and those having the same configurations and functions as those in the first and second embodiments are described. Will not be described.

  The first conveying screw 71 according to the first embodiment and the second embodiment is injection molded by a normal injection molding method. On the other hand, the first conveying screw 71 according to the third embodiment is injection-molded by the gas injection method.

  As shown in FIG. 10, the first carrying screw 71 according to the third embodiment does not have the core metal 73a. The inside of the first conveying screw 71 (the portion between the resin layers 73b and 73b) is a hollow portion 73c having a hollow shape. That is, when the first carrying screw 71 is viewed in a cross section perpendicular to the carrying direction of the developing chamber 41a, the inside of the first carrying screw 71 is hollow.

  Further, as shown in FIG. 10, at least in the area of the first conveying screw 71 facing the developer carrying area of the developing sleeve 44, the screw diameter 71d is changed from the upstream side to the downstream side in the conveying direction of the first conveying screw 71. It grows continuously as it goes. Further, at least in the region of the first conveying screw 71 facing the developer carrying region of the developing sleeve 44, the average value of the inner diameters of the hollow portions 73c (hereinafter referred to as the hollow inner diameter 73e) is conveyed by the first conveying screw 71. It is continuously increased from the upstream side to the downstream side in the direction. The shape of the first conveying screw 71 is conical and the shape of the hollow portion 73c is conical over the longitudinal direction of the first conveying screw 71.

  That is, in at least the area of the first carrying screw 71 facing the developer carrying area of the developing sleeve 44, the thickness of the resin layer 73b on the upstream side in the carrying direction of the first carrying screw 71 is the resin layer on the downstream side in the carrying direction. Substantially the same as the thickness of 73b.

  The ratio of the thickness of the resin layer 73b at the other longitudinal end of the first conveying screw 71 to the thickness of the resin layer 73b at one longitudinal end of the first conveying screw 71 is 80% or more and 120% or less. For example, it is assumed that the resin layers 73b have substantially the same thickness. For example, when the thickness of the resin layer 73b is designed to be 1 mm, the difference between the thickness of the resin layer 73b at one end of the first conveying screw 71 in the longitudinal direction and the thickness of the resin layer 73b at the other end is within 0.2 mm. For example, it is considered that the resin layers 73b have substantially the same thickness.

In addition, in the third embodiment, the hollow portion 73c is molded by gas injection type injection molding, but the method of molding the hollow portion 73c is not limited to this. For example,
When injection molding is performed by a normal injection molding method, first, the hollow portion 73c may be molded by molding with the pin inserted from the end and then pulling out the pin after molding.

  Incidentally, in the third embodiment, the hollow portion 73c is formed over at least substantially the entire area of the first conveying screw 71 facing the developer carrying area of the developing sleeve 44, but the present invention is not limited to this. A hollow portion 73c may be partially formed in at least the area of the first conveying screw 71 facing the developer carrying area of the developing sleeve 44.

[Fourth Embodiment]
In the first to third embodiments described above, the shape of the first conveying screw 71 has been described. That is, in at least the area of the first conveying screw 71 facing the developer carrying area of the developing sleeve 44, the screw diameter 71d is gradually or continuously increased from the upstream side to the downstream side in the conveying direction of the first conveying screw 71. An example of increasing the size has been described. Furthermore, in at least the area of the first carrying screw 71 facing the developer carrying area of the developing sleeve 44, the core metal diameter 73d is gradually or continuously increased from the upstream side to the downstream side in the carrying direction of the first carrying screw 71. The example has been described. Alternatively, in at least the region of the first conveying screw 71 facing the developer carrying region of the developing sleeve 44, the hollow inner diameter 73e is continuously increased from the upstream side to the downstream side in the conveying direction of the first conveying screw 71. I explained an example.

  On the other hand, in the fourth embodiment, the shape of the second conveying screw 72 will be described with reference to the schematic diagrams of FIGS. 11(A) and 11(B).

  In the function-separated type developing device 4, the developer separated from the developing sleeve 44 is collected in the collecting path (stirring chamber 41b), so that the amount of the developer in the collecting path (stirring chamber 41b) is upstream in the transport direction. The side tends to be less than the downstream side. Therefore, it is necessary to increase the occupation rate of the second conveying screw 72 in the stirring chamber 41b from the downstream side to the upstream side in the conveying direction of the second conveying screw 72.

  Therefore, in at least the area excluding the most downstream portion of the second conveying screw 72 (the returning conveying portion 72a and the discharging conveying portion 43b), the cross-sectional area of the second conveying screw 72 is set from the downstream side in the conveying direction of the second conveying screw 72. It is desirable to increase to the upstream side.

  The second conveying screw 72 shown in FIG. 11(A) is injection molded by a normal injection molding method. On the other hand, the second conveying screw 72 shown in FIG. 11(B) is injection-molded by the gas injection method.

  In the example of FIG. 11A, the rotating shaft 74 of the second conveying screw 72 is a cored bar 74a made of metal. The second conveying screw 72 is provided on the outer periphery of the cored bar 74a (cored bar part) and includes a spiral blade part 76 formed of resin. The second conveying screw 72 includes a resin layer 74b that is provided between the cored bar 74a and the blade portion 76 and that is integrally molded with the blade portion 76 by resin.

  Then, in at least the region excluding the most downstream portion of the second conveying screw 72 (returning conveying portion 72a and discharge conveying portion 43b), the screw diameter 72d is increased from the downstream side in the conveying direction of the second conveying screw 72 toward the upstream side. It is continuously increasing. In addition, at least in the region excluding the most downstream portion of the second conveyor screw 72 (return conveyor portion 72a, discharge conveyor portion 43b), the screw diameter 72d is increased from the downstream side in the conveying direction of the second conveyor screw 72 toward the upstream side. A modification in which the size is increased stepwise may be used.

  Further, in the example of FIG. 11A, the core metal diameter 74d is conveyed by the second conveyance screw 72 at least in the region excluding the most downstream portion of the second conveyance screw 72 (return conveyance section 72a, discharge conveyance section 43b). It is gradually increased from the downstream side to the upstream side in the direction. In addition, at least in the region excluding the most downstream portion of the second conveying screw 72 (returning conveying portion 72a, discharge conveying portion 43b), the core metal diameter 74d is directed from the downstream side in the conveying direction of the second conveying screw 72 to the upstream side. It may be a modified example in which the size is continuously increased according to the above.

  On the other hand, in the example of FIG. 11B, the second conveying screw 72 does not have the cored bar 74a. The inside of the second conveying screw 72 (the portion between the resin layers 74b and 74b) is a hollow portion 74c having a hollow shape. That is, when the second conveying screw 72 is viewed in a cross section perpendicular to the conveying direction of the stirring chamber 41b, the inside of the second conveying screw 72 is hollow.

  Then, in at least the region excluding the most downstream portion of the second conveying screw 72 (returning conveying portion 72a and discharge conveying portion 43b), the screw diameter 72d is increased from the downstream side in the conveying direction of the second conveying screw 72 toward the upstream side. It is continuously increasing. Further, in the example of FIG. 11B, the average value of the inner diameters of the hollow portions 74c (hollow inner diameters 74e) in the conveying direction of the second conveying screw 72 is at least in the region excluding the most downstream portion of the second conveying screw 72. It continuously increases from the downstream side to the upstream side.

  That is, the thickness of the resin layer 74b substantially extends from one end to the other end in the longitudinal direction of the second transport screw 72 in at least the region excluding the most downstream portion of the second transport screw 72 (the return transport unit 72a, the discharge transport unit 43b). Is the same as

  The ratio of the thickness of the resin layer 74b at the other longitudinal end of the second conveying screw 72 to the thickness of the resin layer 74b at one longitudinal end of the second conveying screw 72 is 80% or more and 120% or less. For example, it is considered that the resin layers 74b have substantially the same thickness. For example, when the thickness of the resin layer 74b is designed to be 1 mm, the difference between the thickness of the resin layer 74b at one end of the second conveying screw 72 in the longitudinal direction and the thickness of the resin layer 74b at the other end is within 0.2 mm. For example, it is considered that the resin layers 74b have substantially the same thickness.

(Other embodiments)
The present invention is not limited to the above-described embodiments, and various modifications (including organic combinations of the embodiments) are possible based on the gist of the present invention, which are excluded from the scope of the present invention. is not.

  In the above embodiment, each of the first transport screw 71 and the second transport screw 72 is described as a transport screw provided in the function separation type developing device 4, but the invention is not limited to this. Each of the first carrying screw 71 and the second carrying screw 72 according to the above-described embodiment is also applicable to a carrying screw provided in a non-functional separation type developing device. Incidentally, in the non-functional separation type developing device, the function of collecting the developer separated from the developer carrier through the recovery path and the developer transferred from the recovery path are supplied to the developer carrier through the supply path. The function to do is not separated.

  Further, in the above embodiment, an example in which the intermediate transfer belt 7 is used as an image carrier has been described. However, the present invention is not limited to this, and the present invention can also be applied to an image forming apparatus having a configuration in which the recording material P is brought into direct contact with the photosensitive drums 1 (1a, 1b, 1c, 1d) in order to perform transfer. In that case, the photosensitive drums 1 (1a, 1b, 1c, 1d) form a rotatable image carrier that carries a toner image.

  In the above embodiment, the case where the developing chamber 41a and the stirring chamber 41b are arranged side by side in the horizontal direction has been described, but the present invention is not limited to this. For example, the developing chamber 41a and the stirring chamber 41b can be applied to a configuration in which the developing chamber 41a and the stirring chamber 41b are vertically arranged with respect to the direction of gravity.

71 1st conveyance screw 71d Screw diameter 73a Core metal 73b Resin layer 73d Core metal diameter 75 Blade part

Claims (14)

A core screw, a resin layer covering the outer periphery of the core metal, and a blade provided on the outer periphery of the resin layer and integrally formed with the resin layer, and a conveying screw for conveying a developer,
The outer diameter of the core metal at one end in the longitudinal direction of the conveying screw is larger than the outer diameter of the core metal at the other end in the longitudinal direction of the conveying screw,
The conveying screw, wherein the thickness of the resin layer is substantially the same from one end to the other end in the longitudinal direction of the conveying screw. The transport screw according to claim 1, wherein the outer diameter of the core metal increases stepwise from one end to the other end in the longitudinal direction of the transport screw. The conveying screw according to claim 1, wherein the outer diameter of the core metal increases continuously from one end to the other end in the longitudinal direction of the conveying screw. The ratio of the thickness of the resin layer at the other end in the longitudinal direction of the conveying screw to the thickness of the resin layer at one end in the longitudinal direction of the conveying screw is 80% or more and 120% or less. The conveying screw according to any one of 1 to 3. A developer carrier that carries a developer and develops an electrostatic latent image;
It has a core metal, a resin layer covering the outer periphery of the core metal, and a blade portion provided on the outer periphery of the resin layer and integrally formed with the resin layer, and conveys the developer to be supplied to the developer carrier. A developing device including a conveying screw,
At least in the region of the conveying screw facing the region where the developer is carried on the developer carrying member, the outer diameter of the core metal on the downstream side in the conveying direction of the developer by the conveying screw is the development by the conveying screw. It is larger than the outer diameter of the core metal on the upstream side in the agent conveying direction, and the thickness of the resin layer is substantially the same from the upstream side to the downstream side in the developer conveying direction by the conveying screw. Developing device. At least in the region of the conveying screw facing the region where the developer is carried on the developer carrying body, the outer diameter of the core metal is increased from the upstream side to the downstream side of the developer conveying direction by the conveying screw. The developing device according to claim 5, wherein the developing device has a large size. At least in the region of the carrying screw facing the region where the developer is carried on the developer carrying body, the outer diameter of the core metal is continuous from the upstream side to the downstream side in the carrying direction of the developer by the carrying screw. The developing device according to claim 5, wherein the developing device has a large size. At least in the area of the conveying screw facing the area where the developer is carried on the developer carrying body, the developer by the carrying screw with respect to the thickness of the resin layer on the upstream side in the carrying direction of the developer by the carrying screw The developing device according to any one of claims 5 to 7, wherein a ratio of the thickness of the resin layer on the downstream side in the transport direction is 80% or more and 120% or less. In a carrying screw for carrying a developer, which comprises a resin layer and a blade portion provided on the outer periphery of the resin layer and integrally formed with the resin layer,
A hollow portion is formed between the resin layer and the resin layer from one end to the other end in the longitudinal direction of the conveying screw,
The average value of the inner diameter of the hollow portion at one end in the longitudinal direction of the conveying screw is larger than the average value of the inner diameter of the hollow portion at the other end in the longitudinal direction of the conveying screw,
The conveying screw, wherein the thickness of the resin layer is substantially the same from one end to the other end in the longitudinal direction of the conveying screw. The conveying screw according to claim 9, wherein an average value of the inner diameters of the hollow portions continuously increases from one end to the other end in the longitudinal direction of the conveying screw. The ratio of the thickness of the resin layer at the other end in the longitudinal direction of the conveying screw to the thickness of the resin layer at one end in the longitudinal direction of the conveying screw is 80% or more and 120% or less. The conveying screw according to 9 or 10. A developer carrying member carrying a developer and carrying a developer;
A developing device comprising: a resin layer; and a conveying screw that has a blade portion that is provided on the outer periphery of the resin layer and that is integrally molded with the resin layer, and that conveys a developer to be supplied to the developer carrier. hand,
A hollow portion is formed between the resin layer and the resin layer from one end to the other end in the longitudinal direction of the conveying screw,
At least in the area of the conveying screw facing the area where the developer is carried on the developer carrying body, the average value of the inner diameter of the hollow portion on the downstream side in the carrying direction of the developer by the carrying screw is the carrying screw. Is larger than the average value of the inner diameter of the hollow portion on the upstream side in the longitudinal direction, and the thickness of the resin layer is substantially the same from the upstream side to the downstream side in the developer conveying direction by the conveying screw. And developing device. At least in the area of the carrying screw facing the area where the developer is carried on the developer carrying body, the average value of the inner diameter of the hollow portion from the upstream side to the downstream side in the carrying direction of the developer by the carrying screw. The developing device according to claim 12, wherein the developing amount is continuously increased. At least in the area of the conveying screw facing the area where the developer is carried on the developer carrying body, the developer by the carrying screw with respect to the thickness of the resin layer on the upstream side in the carrying direction of the developer by the carrying screw The developing device according to claim 12 or 13, wherein a ratio of the thickness of the resin layer on the downstream side in the transport direction is 80% or more and 120% or less.

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