JP2020046577A - Conveyance mechanism, development device and image formation apparatus - Google Patents

Abstract

To suppress the variation in a conveyance amount per one rotation of a shaft part in powder conveyed to a downstream side in a conveyance direction of a large diameter section.SOLUTION: A conveyance mechanism includes: a housing which stores powder; a shaft part which is arranged in the housing and has a large diameter section that has a large diameter portion in the axial direction; a projection part which is formed on the inner wall of the housing and projects toward the large diameter section from the outer side in the radial direction with respect to the large diameter section; a first blade which is formed in the spiral shape on the outer peripheral surface of the large diameter section, and conveys the powder to one side in the axial direction with the rotation of the shaft part; a second blade which is formed in the spiral shape on the outer peripheral surface of an immediately upstream portion with respect to the large diameter section in the shaft part and conveys the powder to one side with the rotation of the shaft part; and a third blade which is formed in the spiral shape on the outer peripheral surface of the upstream portion with respect to the immediately upstream portion in the shaft part and conveys the powder to one side with the rotation of the shaft part. At least one of the first blade and the second blade has at least one of the strip number and the spiral pitch smaller than the strip number and the spiral pitch of the third blade.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a transport mechanism, a developing device, and an image forming device.

  Patent Literature 1 discloses a configuration in which a stirring and conveying unit that has a spiral blade member and conveys a developer has a spiral pitch of an intake unit shorter than a spiral pitch of a stirring unit.

JP 2007-304202 A

  Here, as the transport mechanism, a shaft having a large-diameter portion having a large diameter in a part of the axial direction, a first blade spirally formed on the outer peripheral surface of the large-diameter portion, and a large A second blade spirally formed on an outer peripheral surface of a portion immediately upstream of the radial portion, and a third blade spirally formed on an outer peripheral surface of an upstream portion of the shaft portion with respect to the immediately upstream portion; A configuration in which the powder is conveyed by the first blade, the second blade, and the third blade by the rotation of the unit is conceivable. In this configuration, furthermore, a protruding portion that protrudes from the radially outer side to the large diameter portion with respect to the large diameter portion is provided, and per rotation of the shaft portion of the powder conveyed to the downstream side in the conveying direction of the large diameter portion. A configuration for quantifying the transport amount of the image is conceivable.

  In the configuration with the overhang portion, for example, when the rotation speed of the shaft portion is increased, the powder does not stay on the upstream side in the transport direction of the large diameter portion, and the downstream side in the transport direction by the large diameter portion and the overhang portion. Since the amount of the powder whose movement is restricted is not stable, the amount of powder conveyed per rotation of the shaft portion in the powder conveyed downstream in the conveying direction of the large diameter portion may fluctuate.

  In the present invention, in both the first blade and the second blade, both the number of rows and the helical pitch are the same as the number of rows and the helical pitch of the third blade. It is an object of the present invention to suppress a variation in a transport amount per rotation of a shaft portion in powder to be produced.

  The invention according to claim 1 is a housing in which powder is stored, a shaft portion having a large-diameter portion disposed inside the housing and having a large diameter in a part in the axial direction, A projecting portion formed on the inner wall and projecting from the radially outer side of the large-diameter portion toward the large-diameter portion, and a spirally formed outer peripheral surface of the large-diameter portion; A first blade that conveys the body to one side in the axial direction, and a spiral formed on an outer peripheral surface of a portion of the shaft portion immediately upstream of the large-diameter portion, and rotating the shaft portion moves the powder to the one side. A second blade for conveying, and a third blade formed in a spiral shape on an outer peripheral surface of an upstream portion of the shaft portion with respect to the immediately upstream portion, and conveying the powder to the one by rotation of the shaft portion. At least one of the first blade and the second blade has a small number of strips and a helical pitch. Even less than the number of threads and the helical pitch of one of the third blade.

  In the invention according to claim 2, both the first blade and the second blade have at least one of the number of rows and the helical pitch smaller than the number of rows and the helical pitch of the third blade.

  In the invention of claim 3, both the first blade and the second blade both have a smaller number of rows and a helical pitch than the number of rows and the helical pitch of the third blade.

  In the invention according to claim 4, the second blade has an outer diameter smaller than the outer diameter of the first blade.

  In the invention of claim 5, the thickness of the second blade in the axial direction is greater than the thickness of the first blade in the axial direction.

  In the invention according to claim 6, in the second blade, the length of the space between the blades along the axial direction is shorter than the length of the space between the blades of the first blade along the axial direction.

  In the invention of claim 7, the first blade is formed continuously with the second blade.

  In the invention of claim 8, the first blade is formed so as to reach an outer peripheral surface of a portion of the shaft portion immediately downstream of the large-diameter portion.

  In the invention of claim 9, the first blade reaches downstream from a downstream end of the overhang portion.

  In the invention according to claim 10, the length of the overhang portion along the axial direction is equal to or longer than the length of the large diameter portion along the axial direction.

  In the invention of claim 11, at least one of the upstream end and the downstream end of the projecting portion extends in the axial direction more than at least one of the upstream end and the downstream end of the large diameter portion.

  A twelfth aspect of the present invention is provided with a holder which is arranged along the shaft above the immediately upstream portion and holds the powder staying in the immediately upstream portion on the outer periphery.

  In the invention according to claim 13, the second blade is disposed in at least a region from a center in the axial direction to a downstream end in a holding region in which the holding body holds the powder.

  According to a fourteenth aspect of the present invention, the toner as the powder is replenished into the housing at an upstream side of the large-diameter portion, and the developer containing the toner is transported. And a supply member for supplying the developer transported by the transport mechanism to the latent image.

  In the invention of claim 15, the transport mechanism is the transport mechanism according to claim 12 or 13, wherein the toner is replenished through a passage, wherein the holding member transports the held developer to the passage. The replenishment of the toner is stopped by closing the passage with the developer.

  According to a sixteenth aspect of the present invention, there is provided a latent image holding member for holding a latent image, the developing device according to the fourteenth or fifteenth aspect for developing the latent image, and transferring an image developed by the developing device to a recording medium. A transfer unit.

  According to the configuration of claim 1 of the present invention, in both the first blade and the second blade, both the number of rows and the helical pitch are larger than the configuration in which the number of rows and the helical pitch of the third blade are the same. It is possible to suppress the variation in the transport amount per rotation of the shaft portion in the powder transported downstream in the transport direction of the section.

  According to the configuration of claim 2 of the present invention, in only one of the first blade and the second blade, at least one of the number of rows and the helical pitch is smaller than the number of rows and the helical pitch of the third blade. Variations in the transport amount per rotation of the shaft portion in the powder transported downstream in the transport direction of the large diameter portion can be suppressed.

  According to the configuration of claim 3 of the present invention, in both the first blade and the second blade, only one of the number of rows and the helical pitch is larger than the number of rows and the helical pitch of the third blade. Variations in the transport amount per rotation of the shaft portion in the powder transported downstream in the transport direction of the diameter portion can be suppressed.

  According to the configuration of claim 4 of the present invention, as compared with the configuration in which the outer diameter of the second blade is the same as the outer diameter of the first blade, the shaft portion in the powder conveyed downstream in the conveying direction of the large-diameter portion Of the transport amount per one rotation can be suppressed.

  According to the configuration of claim 5 of the present invention, the thickness along the axial direction of the second blade is transported to the downstream side in the transport direction of the large-diameter portion, compared to the same configuration as the thickness along the axial direction of the first blade. The variation in the transport amount per rotation of the shaft portion in the powder can be suppressed.

  According to the configuration of claim 6 of the present invention, the length of the space between the blades along the axial direction of the second blade is the same as the length of the space between the blades of the first blade along the axial direction. In comparison, fluctuations in the transport amount per rotation of the shaft portion in the powder transported downstream in the transport direction of the large diameter portion can be suppressed.

  According to the configuration of claim 7 of the present invention, the amount of retained powder can be reduced as compared with the configuration in which the first blade and the second blade are separated.

  According to the configuration of claim 8 of the present invention, compared to the configuration in which the first blade is formed only in the large-diameter portion, per rotation of the shaft portion in the powder conveyed downstream in the conveyance direction of the large-diameter portion. Variations in the transport amount can be suppressed.

  According to the configuration of claim 9 of the present invention, the downstream end of the first blade is transported to the downstream side in the transport direction of the large-diameter portion, compared to a configuration in which the downstream end of the first blade is disposed upstream of the downstream end of the overhang. Fluctuation in the amount of conveyance per rotation of the shaft portion of the powder can be suppressed.

  According to the configuration of claim 10 of the present invention, the length of the overhanging portion along the axial direction is less than the length of the large-diameter portion along the axial direction, and the downstream of the large-diameter portion in the transport direction. Fluctuation in the amount of powder conveyed per rotation in the shaft portion in the powder conveyed to the side can be suppressed.

  According to the configuration of claim 11 of the present invention, compared with the configuration in which the overhang portion is arranged only in the range from the upstream end to the downstream end of the large diameter portion, the large diameter portion is transported downstream in the transport direction of the large diameter portion. Fluctuation in the amount of conveyance per rotation of the shaft portion of the powder can be suppressed.

  According to the configuration of claim 12 of the present invention, the variation in the amount of powder held by the holder in the axial direction is suppressed as compared with the case where the holder is disposed above only the upstream portion with respect to the immediately upstream portion. You.

  According to the configuration of the thirteenth aspect of the present invention, compared to the case where the second blade is arranged only in the region on the downstream end side of the holding region of the holding member with respect to the axial center, the powder held by the holding portion is Variations in the holding amount in the axial direction are suppressed.

  According to the configuration of claim 14 of the present invention, in both the first blade and the second blade, the configuration is provided with a transport mechanism in which both the number of rows and the helical pitch are the same as the number of rows and the helical pitch of the third blade. In comparison, fluctuations in the toner concentration of the developer can be suppressed.

  According to the configuration of claim 15 of the present invention, in comparison with the configuration in which the holding body includes the transport mechanism disposed only above the upstream portion with respect to the immediately upstream portion, the amount of developer retained in the passage in the axial direction is reduced. Variation is suppressed.

  According to the configuration of claim 16 of the present invention, in both the first blade and the second blade, the developing device having the transport mechanism in which both the number of rows and the helical pitch are the same as the number of rows and the helical pitch of the third blade The image quality defect can be suppressed as compared with the configuration including.

FIG. 1 is a schematic diagram illustrating a configuration of an image forming apparatus according to an embodiment. FIG. 2 is a plan view illustrating the developing device according to the exemplary embodiment in a state where an upper wall of a housing is omitted. FIG. 2 is a front sectional view illustrating a configuration of a developing device according to the exemplary embodiment. It is a side view showing the composition of the stirring auger concerning this embodiment. It is a perspective view which expands and shows a part of structure of the stirring auger concerning this embodiment. FIG. 6 is a side cross-sectional view (a cross-sectional view along line 6-6 in FIG. 3) showing a part of the developing device according to the exemplary embodiment.

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

  The arrow UP shown in the figure indicates the upper part of the apparatus (vertically above), and the arrow DO indicates the lower part of the apparatus (vertically below). The arrow LH shown in the figure indicates the left side of the device, and the arrow RH indicates the right side of the device. Further, an arrow FR shown in the drawing indicates the front of the device, and an arrow RR indicates the rear of the device. These directions are directions defined for the sake of convenience of description, and thus the device configuration is not limited to these directions.

  The directions along the upper and lower sides of the device may be referred to as the vertical direction of the device. Further, directions along the left and right sides of the device may be referred to as left and right directions of the device. The horizontal direction of the device is also the width direction (horizontal direction) of the device. The directions along the front and rear of the device may be referred to as the front-back direction of the device. The front-back direction of the device is also the depth direction (horizontal direction) of the device. It should be noted that the term "device" may be abbreviated in each direction of the device. That is, for example, “above the device” may be simply referred to as “above”.

  In addition, a symbol in which “x” is described in “o” in the drawing means an arrow heading from the front to the back of the paper. In addition, a symbol in which “•” is described in “」 ”in the drawing means an arrow pointing from the back of the paper to the front.

<Image forming apparatus 10>
First, the image forming apparatus 10 according to the present embodiment will be described. FIG. 1 is a schematic diagram illustrating a configuration of the image forming apparatus 10.

  As shown in FIG. 1, the image forming apparatus 10 includes a paper storage unit 12 that stores paper P, a transport unit 14 that transports paper P, and an image forming unit 16 that forms an image on paper P. Have.

(Paper storage unit 12)
The sheet accommodating section 12 is provided with an accommodating member 12A that can be pulled out forward from the housing 10A of the image forming apparatus 10, and sheets P are stacked on the accommodating member 12A. Further, the paper storage unit 12 is provided with a delivery roll 14B that sends out the paper P stacked on the storage member 12A to a transport path 14A constituting the transport unit 14. Here, the sheet P is an example of a recording medium.

(Transport unit 14)
The transport unit 14 includes a delivery roll 14B that transports the paper P from the storage member 12A along the transport path 14A, and a plurality of transport rolls 14C that transport the paper P to the paper discharge unit 10B via the image forming unit 16. , Is provided.

(Image forming unit 16)
The image forming section 16 has an image forming unit 18 that forms a black toner image. The image forming unit 18 includes a photosensitive drum 20 as an example of a latent image holding member that holds a latent image, an exposing device 26, a charging roll 24 as a charging device, and a developing device 30.

  In the image forming unit 18, the charging roll 24 charges the photosensitive drum 20. Further, the exposure device 26 exposes the photosensitive drum 20 charged by the charging roll 24 to form an electrostatic latent image (an example of a latent image). The developing device 30 develops the electrostatic latent image formed on the photosensitive drum 20 by the exposure device 26 to form a toner image (an example of an image). The specific configuration of the developing device 30 will be described later.

  Further, the image forming unit 16 includes a transfer roll 22 as an example of a transfer unit that transfers the toner image developed by the developing device 30 to the sheet P, and a fixing device 28 that fixes the toner image to the sheet P by heat and pressure. And

[Developing device 30]
Next, the developing device 30 will be described with reference to FIGS.

  As shown in FIGS. 2 and 3, the developing device 30 transports the developer G containing the toner TN and transports the developer G transported by the transport mechanism 31 to the electrostatic latent image on the photosensitive drum 20. And a replenishing mechanism 39 for replenishing the transport mechanism 31 with the toner TN.

  As shown in FIG. 3, the transport mechanism 31 includes a housing 32, a supply auger 38 for supplying the developer G to the developing roll 34, a stirring auger 90 for stirring the developer G, an overhang portion 80, It has. Note that the developer G in the present embodiment is a two-component developer mainly including the toner TN and the magnetic carrier. Here, the toner TN and the developer G are an example of a powder.

  Hereinafter, the specific configuration of each part of the transport mechanism 31 (the housing 32, the supply auger 38, the stirring auger 90, and the overhang portion 80), the developing roll 34, and the replenishment mechanism 39 will be described.

[Housing 32]
The housing 32 contains the developer G as shown in FIG. The housing 32 is disposed next to (to the left of) the photoconductor drum 20. In the housing 32, a portion facing the photoconductor drum 20 has an opening 32 </ b> A that opens the inside of the housing 32 in the front-rear direction. It is formed to extend. On the opposite side of the photosensitive drum 20 across the opening 32A, a delivery path 32B in which the developing roll 34 is disposed is formed to extend in the front-rear direction.

  Further, a supply path 32D in which a supply auger 38 is disposed extends obliquely below the delivery path 32B so as to extend in the front-rear direction. On the opposite side of the delivery path 32B across the supply path 32D, a stirring path 32C in which a stirring auger 90 is disposed is formed to extend in the front-rear direction.

  Further, the wall surface forming the supply path 32D and the stirring path 32C has a U-shaped cross section as shown in FIG. Further, a partition wall 32E that partitions the supply path 32D and the stirring path 32C is formed between the supply path 32D and the stirring path 32C.

  As shown in FIG. 2, in the housing 32, a supply auger 38 is arranged from the front side to the rear side of the supply path 32D. In FIG. 2, only the left and right end portions of the supply auger 38 are shown.

  Further, a stirring auger 90 is arranged from the front side to the rear side of the stirring path 32C. The stirring path 32C and the supply path 32D are connected to each other at the front end and the rear end, respectively, and the developer G is configured to circulate through the stirring path 32C and the supply path 32D. The partition wall 32E is disposed between a connection portion at the front end and a connection portion at the rear end of the stirring path 32C and the supply path 32D in the front-rear direction.

[Developing roll 34]
The developing roll 34 is arranged in the delivery path 32B as shown in FIG. The developing roll 34 faces the photosensitive drum 20 through the opening 32A of the housing 32. A gap (developing gap) for transferring the developer G from the developing roll 34 to the photosensitive drum 20 is formed between the developing roll 34 and the photosensitive drum 20.

  The developing roll 34 is configured to include a magnet roll 34A having a circular cross section, and a rotating sleeve 34B that covers the magnet roll 34A and rotates around the magnet roll 34A.

  Rotational force is transmitted from a drive source (not shown) to the rotary sleeve 34B, and the rotary sleeve 34B rotates in the direction of arrow A (clockwise) in the figure.

[Supply Auger 38]
The supply auger 38 is arranged in the supply path 32D as shown in FIG. That is, the supply auger 38 is arranged inside the housing 32. The supply auger 38 functions as a transport member that transports the developer G in the supply path 32D. Specifically, the supply auger 38 has a function of transporting the developer G from the rear side to the front side. Therefore, in the supply path 32D, the rear side is the upstream side in the transport direction of the developer G, and the front side is the downstream side in the transport direction of the developer G. The “upstream side in the transport direction” may be simply referred to as “upstream side”, and the “downstream side in the transport direction” may be simply referred to as “downstream side”.

  The supply auger 38 includes a supply shaft 38A extending in the front-rear direction, and a spiral supply blade 38B formed on the outer peripheral surface of the supply shaft 38A. Both ends of the supply shaft 38A are rotatably supported by walls of the housing 32, and the supply shaft 38A is rotated by a driving source (not shown).

  In this configuration, the rotating supply auger 38 supplies the developer G to the developing roll 34 while transporting the developer G in the supply path 32D from the rear side (upstream side) to the front side (downstream side). ing. Further, the rotating supply auger 38 transfers the developer G conveyed to the downstream side (front side) of the supply path 32D to the stirring auger 90 of the stirring path 32C upstream (front side) of the stirring path 32C.

[Stirring auger 90]
The stirring auger 90 is disposed in the stirring path 32C as shown in FIGS. That is, the stirring auger 90 is disposed inside the housing 32. The stirring auger 90 functions as a transport member that transports the developer G in the stirring path 32C. Specifically, the stirring auger 90 has a function of transporting the developer G from the front side to the rear side. Therefore, in the stirring path 32C, the front side is the upstream side in the transport direction of the developer G, and the rear side is the downstream side in the transport direction of the developer G.

  Specifically, as shown in FIG. 4, the stirring auger 90 includes a stirring shaft 98, a first blade 91, a second blade 92, a third blade 93, a fourth blade 94, and a pair of protrusions. And a fifth blade 95 (see FIG. 2). The stirring shaft 98 is an example of a shaft.

  The stirring auger 90 is driven by rotation of a stirring shaft 98 by a drive source (not shown), so that a first blade 91, a second blade 92, a third blade 93, a fourth blade 94, a pair of protrusions 99, and a The five blades 95 transport the toner TN replenished from the replenishing mechanism 39 to the stirring path 32C and the developer G from the supply path 32D while stirring.

  Hereinafter, a specific configuration of each part of the stirring auger 90 (the stirring shaft 98, the first blade 91, the second blade 92, the third blade 93, the fourth blade 94, the pair of protrusions 99, and the fifth blade 95) will be described. I do.

<Stirring shaft 98>
The stirring shaft 98 is arranged along the longitudinal direction of the stirring path 32C, as shown in FIG. That is, the stirring shaft 98 is arranged inside the housing 32 along the front-back direction. Both ends in the axial direction of the stirring shaft 98 are rotatably supported by the wall of the housing 32. The stirring shaft 98 is rotated in one direction (the counterclockwise direction in FIG. 3) by transmitting a rotational force from a driving source (not shown).

  Further, as shown in FIGS. 2 and 4, the stirring shaft 98 has a large-diameter portion 98A having a large diameter at a part in the axial direction. Specifically, the large diameter portion 98A has a larger diameter than other portions of the stirring shaft 98. The large-diameter portion 98A is provided coaxially with other portions.

  The large-diameter portion 98A projects outward in the radial direction of the stirring shaft 98, so that the upstream end and the downstream end in the transport direction of the large-diameter portion 98A are respectively located on the upstream side in the transport direction as shown in FIG. An upstream end face 98X facing (front side) and a downstream end face 98Y facing downstream (rear side) in the transport direction are formed. As shown in FIG. 6, the large-diameter portion 98 </ b> A is disposed on the rear side (downstream in the transport direction) with respect to the rotating roll 50 described later in the front-rear direction (the transport direction in the stirring path 32 </ b> C). The outer diameter of the stirring shaft 98 is, for example, 9 mm in the large-diameter portion 98A, and 6 mm in other portions. That is, the outer diameter of the large-diameter portion 98A is, for example, 1.5 times the outer diameter of the other portions. The size of the upstream end face 98X and the downstream end face 98Y along the radial direction of the stirring shaft 98 is, for example, 1.5 mm. FIG. 6 shows a side cross section of the housing 32 and the overhang portion 80, and also shows a side surface of the stirring auger 90 and the rotating roll 50.

  Furthermore, as shown in FIG. 4, the stirring shaft 98 has a portion 98B immediately upstream of the large diameter portion 98A. The immediately upstream portion 98B is a part of the stirring shaft 98 provided continuously to the large diameter portion 98A on the upstream side in the transport direction of the developer G with respect to the large diameter portion 98A. Further, the immediately upstream portion 98B is set in a part of the upstream portion of the stirring shaft 98 in the transport direction with respect to the large diameter portion 98A. The axial length of the immediately upstream portion 98B is longer than the axial length of the large-diameter portion 98A, and is, for example, 1.5 times or less the axial length of the large-diameter portion 98A.

  Further, the stirring shaft 98 has an upstream portion 98C with respect to the immediately upstream portion 98B. The upstream portion 98C is a part of the stirring shaft 98 provided continuously to the immediately upstream portion 98B on the upstream side in the transport direction of the developer G with respect to the immediately upstream portion 98B. Note that the axial length of the upstream portion 98C is longer than the axial length of the immediately upstream portion 98B.

  Further, the stirring shaft 98 has a portion 98D immediately downstream of the large diameter portion 98A. The immediately downstream portion 98D is a part of the stirring shaft 98 provided continuously to the large diameter portion 98A downstream of the large diameter portion 98A in the transport direction of the developer G. Further, the immediately downstream portion 98D is set in a partial range of a portion on the downstream side in the transport direction with respect to the large diameter portion 98A of the stirring shaft 98. Note that the axial length of the immediately downstream portion 98D is shorter than the axial length of the large diameter portion 98A.

  Further, the stirring shaft 98 has a downstream portion 98E with respect to the immediately downstream portion 98D. The downstream portion 98E is a part of the stirring shaft 98 provided on the downstream side in the transport direction of the developer G with respect to the immediately downstream portion 98D and continuously to the immediately downstream portion 98D. Note that the axial length of the downstream portion 98E is longer than any of the axial length of the immediately downstream portion 98D, the axial length of the large diameter portion 98A, and the upstream portion 98C.

<First wing 91>
The first blade 91 is spirally formed on the outer peripheral surface of the large diameter portion 98A, as shown in FIG. The first blade 91 conveys the developer G rearward (one example in the axial direction) by rotation of the stirring shaft 98.

  In other words, the first blade 91 is wound around the axis of the stirring shaft 98 in a direction opposite to the rotation direction of the stirring shaft 98 toward one of the axial directions of the stirring shaft 98. Specifically, the first blade 91 is wound around the axis of the stirring shaft 98 in a clockwise direction as viewed from the rear.

  Further, the first blade 91 is formed so as to reach the outer peripheral surface of the portion 98 </ b> D immediately downstream of the stirring shaft 98. In other words, the first blade 91 conveys the developer G to the rear side beyond the large diameter portion 98A. Note that, in the immediately downstream portion 98D, the dimension of the first blade 91 along the radial direction becomes longer as the outer diameter of the stirring shaft 98 becomes smaller.

  Further, as shown in FIG. 6, the first blade 91 reaches a downstream side (rear side) from a downstream end (a downstream end surface 84 described later) of the overhang portion 80. In other words, the first blade 91 conveys the developer G beyond the downstream end of the overhang portion 80 to the rear side.

  As shown in FIG. 4, the first blade 91 is specifically composed of a single blade. The spiral pitch P1 of the first blade 91 is, for example, 8 mm. The outer diameter D1 of the first blade 91 is, for example, 12 mm.

  The helical pitch refers to the axial length of the blade per 360 degrees (one rotation) of the stirring shaft 98 in the circumferential direction.

  The first blade 91 is formed in the large-diameter portion 98A of the stirring shaft 98, for example, in a range of 360 degrees in the circumferential direction of the stirring shaft 98. That is, the first blades 91 are formed within a range of one pitch in the large diameter portion 98A of the stirring shaft 98. In other words, the large-diameter portion 98A of the stirring shaft 98 has an axial length of one pitch of the first blade 91.

  Further, the first blade 91 is formed in a range of 180 degrees in a circumferential direction of the stirring shaft 98 in a portion 98D immediately downstream of the stirring shaft 98, for example. That is, the first blade 91 is formed in a range of a half pitch (0.5 pitch) in a portion 98D immediately downstream of the stirring shaft 98. In other words, the portion 98D immediately downstream of the stirring shaft 98 has an axial length of 0.5 pitch of the first blade 91.

  The portion formed on the large-diameter portion 98A of the stirring shaft 98 in the first blade 91 is regarded as the first blade 91, and the portion formed on the portion 98D immediately downstream of the stirring shaft 98 in the first blade 91 is referred to as the sixth blade. It may be grasped as a wing (other wing). In this case, the sixth blade is grasped as, for example, a blade formed continuously with the first blade 91 and having the same diameter and the same pitch as the first blade 91.

<Second wing 92>
As shown in FIG. 4, the second blade 92 is spirally formed on the outer peripheral surface of a portion 98 </ b> B immediately upstream of the stirring shaft 98. The second blade 92 conveys the developer G rearward (one example in the axial direction) by rotation of the stirring shaft 98.

  In other words, the second blade 92 is wound around the axis of the stirring shaft 98 in a direction opposite to the rotation direction of the stirring shaft 98 toward one of the axial directions of the stirring shaft 98. Specifically, the second blade 92 is wound around the axis of the stirring shaft 98 in a clockwise direction as viewed from the rear. In other words, the second blade 92 has a spiral shape wound in the same direction as the first blade 91.

  The second blade 92 is formed continuously with the first blade 91 as shown in FIG. That is, the first blade 91 is formed continuously with the second blade 92. In other words, the front end (upstream end) of the first blade 91 and the rear end (downstream end) of the second blade 92 are connected. In other words, the developer G transported by the second blade 92 is continuously transported by the first blade 91. In FIG. 5, a connecting portion between the first blade 91 and the second blade 92 is indicated by reference numeral 912.

  As shown in FIG. 4, the second blade 92 is specifically composed of a single blade. The spiral pitch P2 of the second blade 92 is, for example, 8 mm. The outer diameter D2 of the second blade 92 is, for example, 10 mm. The second blade 92 is formed, for example, in a range of 540 degrees in a circumferential direction of the stirring shaft 98. That is, the second blades 92 are formed in a range of 1.5 pitches. In other words, the immediately upstream portion 98B of the stirring shaft 98 has an axial length of 1.5 pitches of the second blade 92. The relationship between the number of blades of each blade in the stirring auger 90, the helical pitch, the outer diameter, and the like will be described later.

<Third blade 93>
As shown in FIG. 4, the third blade 93 is spirally formed on the outer peripheral surface of the upstream portion 98C of the stirring shaft 98. The third blade 93 conveys the developer G backward by rotation of the stirring shaft 98.

  The third blade 93 is specifically composed of a plurality of blades. More specifically, the third blade 93 includes two blades 93A and 93B. Therefore, in the third blade 93, the rotation of the stirring shaft 98 causes the two blades 93A and 93B to transport the developer G backward.

  In other words, the blades 93A and 93B are wound around the axis of the stirring shaft 98 in one direction in the axial direction of the stirring shaft 98 in a direction opposite to the rotation direction of the stirring shaft 98. Specifically, the blades 93A and 93B are wound around the stirring shaft 98 in a clockwise direction as viewed from the rear. In other words, the blades 93A and 93B have a spiral shape wound in the same direction as the first blade 91 and the second blade 92.

  The downstream end (rear end) of the third blade 93 is separated from the upstream end (front end) of the second blade 92. Specifically, the third blade 93 is disposed apart from the second blade 92 in the circumferential direction and the axial direction of the stirring shaft 98. In other words, the third blade 93 has a gap with respect to the second blade 92 in the circumferential direction and the axial direction.

  The helical pitch P3 of the blades 93A and 93B is, for example, 24 mm. The outer diameter D3 of the blades 93A and 93B is, for example, 12 mm.

<Fourth blade 94>
The fourth blade 94 is formed on the outer peripheral surface of the downstream portion 98E of the stirring shaft 98, as shown in FIG. The fourth blade 94 conveys the developer G backward by the rotation of the stirring shaft 98.

  The fourth blade 94 is specifically composed of a plurality of blades. More specifically, the fourth blade 94 includes two blades 94A and 94B. The plurality of (for example, nine) fourth blades 94 are arranged in the axial direction of the stirring shaft 98.

  Therefore, in the fourth blade 94, the rotation of the stirring shaft 98 causes the plurality of two blades 94A and 94B to transport the developer G backward. In other words, the blades 94A and 94B are wound around the axis of the stirring shaft 98 in one direction in the axial direction of the stirring shaft 98 in a direction opposite to the rotation direction of the stirring shaft 98. Specifically, the blades 94A and 94B are wound around the stirring shaft 98 in a clockwise direction as viewed from the rear. In other words, the blades 94A and 94B have a spiral shape wound in the same direction as the first blade 91, the second blade 92, and the third blade 93.

  Each of the blades 94A and 94B arranged in the axial direction of the stirring shaft 98 has an upstream end (front end) and a downstream end (rear end) separated from each other. Specifically, the blades 94A and 94B are arranged continuously in the axial direction of the stirring shaft 98 while being spaced apart in the circumferential direction of the stirring shaft 98. In other words, each of the blades 94A and 94B has a gap in the circumferential direction of the stirring shaft 98 and is arranged without a gap in the axial direction of the stirring shaft 98. The blades 94A and 94B may have a gap in the axial direction as long as the transport of the developer G is not hindered (the developer G is not accumulated).

  The upstream end (front end) of the fourth blade 94 is separated from the downstream end (rear end) of the first blade 91. Specifically, the fourth blade 94 is arranged in the axial direction of the stirring shaft 98 while being spaced apart from the first blade 91 in the circumferential direction of the stirring shaft 98. In other words, the fourth blade 94 has a gap with respect to the first blade 91 in the circumferential direction of the stirring shaft 98 and is arranged without a gap in the axial direction of the stirring shaft 98. The fourth blade 94 may have a gap in the axial direction with respect to the first blade 91 as long as the transport of the developer G is not hindered (the developer G cannot be accumulated).

  Each blade 94A, 94B of the fourth blade 94 is formed, for example, in a range of 360 degrees in the circumferential direction of the stirring shaft 98. That is, each of the blades 94A and 94B is formed in a range of one pitch. The helical pitch P4 of each blade 94A, 94B is, for example, 24 mm. The outer diameter D4 of the blades 94A and 94B is, for example, 12 mm.

<Protrusion 99>
As shown in FIG. 4, the pair of protrusions 99 is formed on the outer peripheral surface of the downstream portion 98E of the stirring shaft 98. The pair of protrusions 99 protrude radially outward of the stirring shaft 98. Further, the pair of protrusions 99 also protrude radially outward of the stirring shaft 98 on the side opposite to the position illustrated in FIG. The pair of protrusions 99 are arranged at predetermined intervals in the axial direction of the stirring shaft 98. The pair of protrusions 99 are arranged, for example, at intervals of two pitches of the fourth blade 94.

<Fifth blade 95>
As shown in FIG. 2, the fifth blade 95 is spirally formed on the outer peripheral surface of the downstream end (rear end) of the stirring shaft 98 in the transport direction. The fifth blade 95 has a single spiral shape wound in the reverse direction of the first blade 91, the second blade 92, the third blade 93, and the fourth blade 94. The fifth blade 95 conveys the developer G forward by the rotation of the stirring shaft 98. The fifth blade 95 suppresses the retention of the developer G at the downstream end (rear end) of the stirring path 32C, and promotes the movement of the developer G from the stirring path 32C to the supply path 32D.
<Relationship between number of threads and spiral pitch in each blade>
Here, at least one of the first blade 91 and the second blade 92 shown in FIG. 4 has at least one of the number of rows and the spiral pitch smaller than the number of rows and the spiral pitch of the third blade 93. Specifically, in both the first blade 91 and the second blade 92, at least one of the number of rows and the spiral pitch is smaller than the number of rows and the spiral pitch of the third blade 93. More specifically, in both the first blade 91 and the second blade 92, both the number of rows and the helical pitch are smaller than the number of rows and the helical pitch of the third blade 93. Hereinafter, a specific configuration will be described for each of the relationship between the number of rows of each blade and the relationship between the spiral pitches of each blade.

<Relationship between the number of rows of each blade>
The number of lines of the first blade 91 and the second blade 92 shown in FIG. 4 is smaller (smaller) than the number of lines of the third blade 93. Specifically, the number of the first blades 91 and the number of the second blades 92 are the same and smaller than the number of the third blades 93. More specifically, the number of the first blades 91 and the number of the second blades 92 are smaller than the number of the third blades 93 by one. More specifically, as described above, the third blade 93 is formed of, for example, two lines, whereas the first blade 91 and the second blade 92 are formed of, for example, one line.

  Note that the number of lines of the first blade 91 and the second blade 92 may be smaller than the number of lines of the third blade 93, and the number of lines of the first blade 91 and the number of lines of the second blade 92 may be different. Good. The number of the first and second blades 91 and 92 may be less than the number of the third blade 93, and may be two or more less than the number of the third blade 93. Further, the number of rows of the first blade 91 and the second blade 92 may be less than the number of rows of the third blade 93, and may be plural.

  Further, the number of rows of the first blade 91 and the second blade 92 is smaller than the number of rows of the fourth blade 94. More specifically, the number of lines of the first blade 91 and the number of second blades 92 is smaller than the number of lines of the fourth blade 94 by one line. More specifically, as described above, the fourth blade 94 is formed of, for example, two lines, whereas the first blade 91 and the second blade 92 are formed of, for example, one line. Note that the third blade 93 and the fourth blade 94 have the same number of lines.

<Relationship of spiral pitch of each blade>
The spiral pitch P1 of the first blade 91 and the spiral pitch P2 of the second blade 92 shown in FIG. 4 are smaller than the spiral pitch P3 of the blades 93A and 93B of the third blade 93. Specifically, the helical pitch P1 of the first blade 91 and the helical pitch P2 of the second blade 92 are the same pitch and smaller than the helical pitch P3 of the blades 93A and 93B of the third blade 93. More specifically, as described above, the spiral pitch P3 of the blades 93A and 93B of the third blade 93 is, for example, 24 mm, whereas the spiral pitch P1 of the first blade 91 and the spiral pitch P2 of the second blade 92 are different. Are set to, for example, 8 mm.

  The helical pitch P1 of the first blade 91 and the helical pitch P2 of the second blade 92 may be smaller than the helical pitch P3 of the blades 93A and 93B of the third blade 93. The spiral pitch P2 of the blade 92 may be different.

  The helical pitch P1 of the first blade 91 and the helical pitch P2 of the second blade 92 are smaller than the helical pitch P4 of the blades 94A and 94B of the fourth blade 94. More specifically, as described above, the spiral pitch P4 of each of the blades 94A and 94B of the fourth blade 94 is, for example, 24 mm, while the spiral pitch P1 of the first blade 91 and the second blade Each of the helical pitches 92 is, for example, 8 mm. The spiral pitch P3 of the blades 93A and 93B of the third blade 93 and the spiral pitch P4 of each of the blades 94A and 94B of the fourth blade 94 are the same.

<Relationship of outer diameter of each blade>
The outer diameter D2 of the second blade 92 shown in FIG. 4 is smaller than the outer diameter D1 of the first blade 91. Specifically, the outer diameter D2 of the second blade 92 is larger than the outer diameter of the large diameter portion 98A of the stirring shaft 98 and smaller than the outer diameter D1 of the first blade 91. More specifically, as described above, the outer diameter D1 of the first blade 91 is 12 mm, and the outer diameter of the large diameter portion 98A of the stirring shaft 98 is 9 mm, whereas the outer diameter D1 is 9 mm. Has an outer diameter D2 of 10 mm.

  The second dimension of the second blade 92 along the radial direction is larger than the first dimension of the first blade 91 along the radial direction. Specifically, the first dimension is, for example, 1.5 mm (radius of the first blade 91 is 6 mm-radius of the large-diameter portion 98A is 4.5 mm), but the second dimension is, for example, 2 mm (the (The radius of the two blades 92 is 5 mm-the radius of the stirring shaft 98 is 3 mm).

  The outer diameter D2 of the second blade 92 is smaller than the outer diameter D3 of the third blade 93 and the outer diameter D4 of the fourth blade 94. More specifically, as described above, the outer diameter D3 of the third blade 93 and the outer diameter D4 of the fourth blade 94 are 12 mm, whereas the outer diameter D2 of the second blade 92 is 10 mm. It has been. Thus, the outer diameter D1 of the first blade 91, the outer diameter D3 of the third blade 93, and the outer diameter D4 of the fourth blade 94 are the same.

<Relationship between thickness of first blade 91 and second blade 92>
As shown in FIG. 4, the second blade 92 has a thickness T2 along the axial direction of the stirring shaft 98 greater than the thickness T1 of the first blade 91 along the axial direction. Specifically, at least when the thickness T1 of a part of the first blade 91 in the radial direction is compared with the thickness T2 of a part of the second blade 92 in the radial direction, the thickness T2 of the second blade 92 is obtained. Are thicker than the thickness T1 of the first blade 91. In the present embodiment, the thickness T2 at the radially outer end of the second blade 92 is greater than the thickness T1 at the radially outer end of the first blade 91. Further, the thickness T2 at the radially inner end of the second blade 92 is also greater than the thickness T1 at the radially inner end of the first blade 91.

<Relationship of space between blades in first blade 91 and second blade 92>
In the second blade 92, the length of the space between the blades along the axial direction of the stirring shaft 98 is shorter than the length of the space between the blades of the first blade 91 along the axial direction. Specifically, as shown in FIG. 4, when the stirring auger 90 is viewed in the radial direction (for example, the left-right direction), the length L2 along the axial direction of the space between the blades constituting the second blade 92 is determined. The length between the blades constituting the first blade 91 along the axial direction of the space between the blades is shorter than L1. The length L2 corresponds to the length from the rear surface of the first blade constituting the second blade 92 to the front surface of the second blade (the blade on the rear side of the first blade). The length L1 corresponds to the length from the rear surface of the first blade constituting the first blade 91 to the front surface of the second blade (the blade on the rear side of the first blade).

  Specifically, the length L2 of at least a part of the second blade 92 in the radial direction is shorter than the length L1 of a part of the first blade 91 in the radial direction. In the present embodiment, the length L2 of the space at the radially outer end of the second blade 92 is shorter than the length L1 of the space at the radially outer end of the first blade 91. Further, the length L2 of the space at the radially inner end of the second blade 92 is also shorter than the length L1 of the space at the radially inner end of the first blade 91.

[Overhang part 80]
As shown in FIGS. 3 and 6, the overhang portion 80 is formed on the inner wall of the housing 32 and projects from the radially outer side of the large diameter portion 98A of the stirring shaft 98 toward the large diameter portion 98A. I have. Specifically, as shown in FIG. 3, the projecting portion 80 projects from a radially outer side of the large-diameter portion 98A toward the large-diameter portion 98A in a part of a circumferential direction of the large-diameter portion 98A. . More specifically, the projecting portion 80 projects downward from the upper wall 32X of the housing 32 toward the large-diameter portion 98A. More specifically, the lower surface of the overhang portion 80 (the surface facing the large-diameter portion 98A) is formed in an arc shape along the outer peripheral surface of the large-diameter portion 98A when viewed in the axial direction of the stirring shaft 98. I have.

  In other words, the overhang portion 80 has a function of narrowing the width of the large-diameter portion 98A and the periphery of the stirring path 32C. In addition, the overhang portion 80 has a function of reducing the volume (volume) of the large-diameter portion 98A and the stirring path 32C around the large-diameter portion 98A.

  As shown in FIG. 6, an upstream end face 82 facing the upstream side (front side) in the transport direction and a downstream side (rear side) in the transport direction ) Is formed.

  The length of the overhang portion 80 along the axial direction is equal to or greater than the length of the large diameter portion 98A along the axial direction. Specifically, the length of the overhang portion 80 along the axial direction is longer than the length of the large-diameter portion 98A along the axial direction.

  Further, at least one of the upstream end and the downstream end of the overhang portion 80 extends in the axial direction more than at least one of the upstream end and the downstream end of the large-diameter portion 98A. Specifically, the overhang portion 80 extends axially at one of the upstream end and the downstream end more than one of the upstream end and the downstream end of the large-diameter portion 98A. More specifically, the overhang portion 80 extends forward only at the upstream end from the upstream end of the large diameter portion 98A. That is, the upstream end surface 82 of the overhang portion 80 is disposed upstream (frontward) of the upstream end surface 98X of the large-diameter portion 98A. At the downstream end of the overhang portion 80, the downstream end surface 84 of the overhang portion 80 does not extend rearward than the downstream end of the large diameter portion 98A, and is arranged along the downstream end surface 98Y of the large diameter portion 98A. I have. In other words, in the front-rear direction, the downstream end surface 84 of the overhang portion 80 and the downstream end surface 98Y of the large-diameter portion 98A are arranged at the same position.

  Note that the overhang portion 80 may extend axially beyond both the upstream end and the downstream end of the large-diameter portion 98A at both the upstream end and the downstream end. Further, the overhang portion 80 may extend rearward beyond the downstream end of the large-diameter portion 98A only at the downstream end. In the case where the downstream end of the overhang portion 80 extends rearward from the downstream end of the large-diameter portion 98A, the downstream end is disposed, for example, in the range of the immediately downstream portion 98D.

  Further, a configuration may be employed in which the length of the overhang portion 80 along the axial direction is the same as the length of the large-diameter portion 98A along the axial direction. In the case of this configuration, for example, at the upstream end and the downstream end of the overhang portion 80, it does not extend in the axial direction than the upstream end and the downstream end of the large-diameter portion 98A, and the upstream end surface 82 and the downstream end of the overhang portion 80 do not extend. Each of the end faces 84 is disposed along each of the upstream end face 98X and the downstream end face 98Y of the large diameter portion 98A. Further, in the case of the configuration, the overhang portion 80 may be configured to extend in the axial direction at one of the upstream end and the downstream end more than the upstream end and the downstream end of the large-diameter portion 98A.

[Replenishment mechanism 39]
The replenishing mechanism 39 is a mechanism that replenishes the toner TN to the stirring path 32C. Specifically, as shown in FIG. 3, the replenishment mechanism 39 has a toner cartridge 62, a replenishment path 40, a rotating roll 50, a first path 44, and a second path 46. .

  As illustrated in FIG. 1, the toner cartridge 62 functions as a storage unit that stores the toner TN. This toner cartridge 62 is formed in a cylindrical shape with both axial ends closed. As shown in FIG. 3, the toner cartridge 62 has a replenishing port 62A for dropping the toner TN inside and replenishing the toner TN toward the stirring path 32C.

  The replenishment path 40 is a path for replenishing toner from the toner cartridge 62 toward the stirring path 32C. The replenishment path 40 is formed on the upper wall 32X of the housing 32 as shown in FIG. Specifically, the replenishment path 40 opens at a position obliquely above the housing 32 on the side opposite to the supply path 32D with respect to the stirring path 32C, and is a replenishment port for the toner cartridge 62 disposed above the housing 32. 62A.

  Further, as shown in FIG. 6, the replenishment passage 40 is opened on the upstream side (front side) of the large diameter portion 98A of the stirring shaft 98. Specifically, the replenishment path 40 is open on the upstream side (front side) with respect to the overhang portion 80. Specifically, the replenishment passage 40 is opened at the upstream portion 98B and the upstream portion 98C of the stirring shaft 98.

  Therefore, in the present embodiment, the toner TN is replenished into the housing 32 (specifically, the stirring path 32C) on the upstream side (front side) of the large diameter portion 98A of the stirring shaft 98.

  As shown in FIG. 3, the rotating roll 50 includes a magnet roll 50A having a circular cross section, and a rotating sleeve 50B that covers the outer periphery of the magnet roll 50A and rotates along the outer periphery of the magnet roll 50A. ing. Further, the magnet roll 50A is fixed to the housing 32, and the rotating sleeve 50B is rotated around the magnet roll 50A in the direction of arrow B by driving means (not shown).

  The magnet roll 50A has a first magnetic pole G1, a second magnetic pole G2, and a third magnetic pole G3 housed inside. In the present embodiment, for example, the polarity of the first magnetic pole G1 is set to the S pole, the polarity of the second magnetic pole G2 is set to the N pole, and the magnetic pole of the third magnetic pole G3 is set to the S pole. The rotating roll 50 holds the developer G on the outer periphery of the rotating sleeve 50B by a magnetic field formed by the first magnetic pole G1, the second magnetic pole G2, and the third magnetic pole G3.

  The rotating roll 50 holds the developer G in a holding area 51 (see FIG. 6) disposed at a central portion in the axial direction of the rotating sleeve 50B. In the holding region 51 of the rotating sleeve 50B, as shown in FIG. 6, a concave portion 52 and a convex portion 53 are formed on the outer peripheral surface. The concave portions 52 and the convex portions 53 are formed alternately in the circumferential direction of the rotating roll 50. The concave portion 52 and the convex portion 53 are formed so as to extend along the axial direction of the rotating roll 50, respectively. Note that the first magnetic pole G1, the second magnetic pole G2, and the third magnetic pole G3 of the magnet roll 50A are arranged in a range of the holding area 51.

  The rotating roll 50 is arranged below the replenishment path 40 as shown in FIG. In plan view, the size of the opening at the downstream end of the replenishment path 40 is set smaller than the outer dimensions of the rotating roll 50, and the rotating roll 50 is arranged at a position that closes the opening.

  When viewed from the axial direction of the rotating roll 50 and the stirring auger 90, the lower end of the rotating roll 50 is disposed at a position lower than the upper end of the stirring auger 90. Further, the right end of the rotating roll 50 is disposed on the right side of the left end of the stirring auger 90. That is, the rotating roll 50 and the stirring auger 90 are arranged so as to overlap in both the vertical and horizontal directions.

  In addition, as shown in FIG. 6, the rotating roll 50 is disposed along the stirring shaft 98 above the immediately upstream portion 98 </ b> B of the stirring shaft 98. Specifically, the rotating roll 50 is disposed so as to straddle the upstream portion 98B and the upstream portion 98B of the stirring shaft 98.

  The second blade 92 is disposed in at least a region 51A from the axial center to the downstream end in the holding region 51 of the rotating roll 50.

  In FIG. 6, in order to make it easy to understand the positional relationship between the rotating roll 50 and the large-diameter portion 98 </ b> A of the stirring auger 90 in the axial direction, the rotating roll 50 is conveniently arranged vertically so as not to overlap the stirring auger 90. It is illustrated.

  As shown in FIG. 3, the first path 44 connects the stirring path 32 </ b> C and the replenishment path 40 on the upstream side of the replenishment path 40 in the rotation direction B of the rotating roll 50. The second path 46 connects the stirring path 32C and the replenishment path 40 downstream of the replenishment path 40 in the rotation direction B of the rotating roll 50. The replenishment path 40 and the first path 44 are examples of a path.

  In the rotating roll 50, the rotating sleeve 50B is constantly rotated in the direction of arrow B. Then, in the rotating roll 50, the magnetic field formed by the first magnetic pole G1, the second magnetic pole G2, and the third magnetic pole G3 causes the large-diameter portion 98A of the stirring shaft 98 to be located upstream (directly upstream) at the position of the first magnetic pole G1. The developer G remaining in the portion 98B and the upstream portion 98C) is held on the outer periphery of the rotating sleeve 50B. Then, by the rotation of the rotary sleeve 50B, the developer G is transported to the third magnetic pole G3, and the holding is released at the position of the third magnetic pole G3.

  That is, the rotating roll 50 holds the developer G that is retained on the upstream side of the large-diameter portion 98A of the stirring shaft 98, and passes the held developer G through the first path 44 and the second path 46. . The rotating roll 50 is an example of a holder.

  When the amount of the developer G in the stirring path 32C decreases due to the consumption of the developer G, the amount of the developer G staying upstream of the large-diameter portion 98A of the stirring shaft 98 decreases. The amount of the developer G held by the rotating roll 50 decreases, and the second path 46 and the replenishment path 40 are opened. Thus, the toner TN is supplied to the stirring path 32C through the second path 46 and the supply path 40.

  On the other hand, when the amount of the developer G in the stirring path 32 </ b> C increases due to the replenishment of the toner TN, the amount of the developer G stagnating upstream of the large-diameter portion 98 </ b> A of the stirring shaft 98 increases. The amount of the developer G held by the rotating roll 50 increases, and the second path 46 and the replenishment path 40 are closed by the developer G. Thereby, the supply of the toner TN to the stirring path 32C through the second path 46 and the supply path 40 is stopped.

(Developing operation of the developing device)
Next, the operation of the developing device 30 will be described.

  Inside the housing 32 of the developing device 30, the rotating supply auger 38 and the rotating stirring auger 90 circulate the developer G between the supply path 32D and the stirring path 32C while stirring (see FIG. 3). .

  By stirring the developer G, the toner TN in the developer G and the magnetic carrier are rubbed, and the toner TN is frictionally charged to a predetermined polarity.

  As shown in FIG. 3, the developer G is supplied to the developing roll 34 by the rotating supply auger 38, and the developer G supplied to the developing roll 34 is applied to the surface of the developing roll 34 by the magnetic force of the magnet roll 34A. Is held in a state where a magnetic brush (not shown) is formed.

  The rotating sleeve 34 </ b> B conveys the developer G to a position facing the photosensitive drum 20.

  The toner TN contained in the developer G transported to the developing gap of the photosensitive drum 20 adheres to the electrostatic latent image formed on the photosensitive drum 20, and the electrostatic latent image is developed as a toner image.

  As described above, the developing device 30 supplies the developer G for forming an image on the paper P to the photosensitive drum 20.

  In the developing device 30, when the amount of the developer G in the stirring path 32C decreases due to the consumption of the developer G, the amount of the developer G staying upstream of the large-diameter portion 98A of the stirring shaft 98 decreases. In the mechanism 39, the amount of the developer G held by the rotating roll 50 decreases, and the second path 46 and the replenishment path 40 are opened. Thus, the toner TN is supplied to the stirring path 32C through the second path 46 and the supply path 40.

  On the other hand, when the amount of the developer G in the stirring path 32 </ b> C increases due to the replenishment of the toner TN, the amount of the developer G stagnating upstream of the large-diameter portion 98 </ b> A of the stirring shaft 98 increases. The amount of the developer G held by the rotating roll 50 increases, and the second path 46 and the replenishment path 40 are closed by the developer G. Thus, the supply of the toner to the stirring path 32C through the second path 46 and the supply path 40 is stopped.

<Operation of the present embodiment>
Next, the operation according to the present embodiment will be described.

  In the present embodiment, when the stirring shaft 98 is rotated, in the upstream portion 98C of the stirring shaft 98, the blades 93A and 93B of the third blade 93 convey the developer G to the immediately upstream portion 98B. In a portion 98B immediately upstream of the stirring shaft 98, the second blade 92 conveys the developer G toward the large-diameter portion 98A.

  At this time, the movement of a part of the developer G toward the downstream side (rearward) in the transport direction is restricted by the upstream end surface 82 of the overhang portion 80. The movement of the developer G transported to the upstream end of the large-diameter portion 98A in the transport direction is partially restricted by the upstream end surface 98X of the large-diameter portion 98A. The developer G that has moved to the large-diameter portion 98A without being restricted by the upstream end surface 98X of the large-diameter portion 98A is transported by the first blade 91 to the downstream side (rearward side) in the transport direction of the large-diameter portion 98A.

  In this way, a part of the movement of the developer G is restricted by the upstream end face 82 of the overhanging part 80 and the upstream end face 98X of the large diameter part 98A, so that the developer G is transported downstream in the transport direction of the large diameter part 98A. Fluctuation in the transport amount of the developer G per rotation of the stirring shaft 98 is suppressed.

  Here, in the configuration (first configuration) in which the number of rows and the spiral pitches P1 and P2 of the first blade 91 and the second blade 92 are the same as the number of rows and the spiral pitch P3 of the third blade 93, for example, When the number of rotations is increased, or when used in a state where the rear side is inclined so as to be disposed below the front side, the amount of the developer G transported to the large diameter portion 98A and the immediately downstream portion 98D is reduced. More. Therefore, the developer G may be conveyed downstream of the large-diameter portion 98A in the conveying direction without staying in the immediately upstream portion 98B. That is, the developer G may be conveyed downstream of the large-diameter portion 98A in the conveyance direction without being restricted by the upstream end surface 82 of the overhang portion 80 and the upstream end surface 98X of the large-diameter portion 98A. . As a result, the transport amount of the developer G transported downstream of the large-diameter portion 98A in the transport direction becomes unstable, and the transport amount of the developer G transported downstream of the large-diameter portion 98A in the transport direction per rotation of the stirring shaft 98. Is likely to fluctuate.

  In contrast, in the present embodiment, as described above, at least one of the first blade 91 and the second blade 92 has at least one of the number of threads and the helical pitch smaller than the number of threads and the helical pitch of the third blade 93. Has been made smaller. Accordingly, the transport amount per one rotation of the stirring shaft 98 in the upstream portion 98B and the large diameter portion 98A of the stirring shaft 98 is smaller than in the first configuration, and the developer G stays in the upstream portion 98B of the stirring shaft 98. Therefore, the state in which the bulk of the developer G in the immediately upstream portion 98B is high is maintained.

  Therefore, for example, even when the rotation speed of the stirring shaft 98 is increased or when the rear side is used in a state of being inclined so as to be disposed below the front side, the developer G can be compared with the first configuration. However, while being restricted by the upstream end surface 82 of the overhang portion 80 and the upstream end surface 98X of the large-diameter portion 98A, the state of being transported downstream in the transport direction of the large-diameter portion 98A is maintained. Thus, compared to the first configuration, the fluctuation of the transport amount per one rotation of the stirring shaft 98 in the developer G transported downstream in the transport direction of the large-diameter portion 98A is suppressed. Note that the first configuration is a configuration in which the first blade 91 and the second support portion 72 are not provided, and the third blade 93 is formed so as to reach the immediately upstream portion 98B and the large-diameter portion 98A from the upstream portion 98C. It may be grasped.

  More specifically, in this embodiment, at least one of the number of rows and the helical pitch of both the first blade 91 and the second blade 92 is smaller than the number of rows and the helical pitch of the third blade 93. Thus, in only one of the first blade 91 and the second blade 92, at least one of the number of rows and the helical pitch is smaller than the number of rows and the helical pitch of the third blade 93 (second configuration). The amount of conveyance per rotation of the stirring shaft 98 in the immediately upstream portion 98B and the large diameter portion 98A of the shaft 98 is small, and the developer G easily stays in the immediately upstream portion 98B of the stirring shaft 98. The state in which the bulk of the developer G is high is maintained.

  For this reason, for example, even when the rotation speed of the stirring shaft 98 is increased or when the rear side is used in a state of being inclined so as to be disposed below the front side, the developer G can be compared with the second configuration. However, while being restricted by the upstream end surface 82 of the overhang portion 80 and the upstream end surface 98X of the large-diameter portion 98A, the state of being transported downstream in the transport direction of the large-diameter portion 98A is maintained. Thus, compared to the second configuration, fluctuations in the transport amount of the developer G transported downstream of the large-diameter portion 98A in the transport direction per rotation of the stirring shaft 98 are suppressed.

  More specifically, in this embodiment, both the first blade 91 and the second blade 92 have both the number of rows and the helical pitch smaller than the number of rows and the helical pitch of the third blade 93. That is, the number of lines of the first blade 91 and the second blade 92 is smaller than the number of lines of the third blade 93, and the helical pitch P1 of the first blade 91 and the helical pitch P2 of the second blade 92 are the third blade. The helical pitch P3 of the 93 blades 93A and 93B is smaller than the helical pitch P3. Accordingly, in both the first blade 91 and the second blade 92, the stirring shaft is smaller than the configuration (third configuration) in which only one of the number of rows and the helical pitch is smaller than the number of rows and the helical pitch of the third blade 93. Since the amount of conveyance per rotation of the stirring shaft 98 in the upstream portion 98B and the large diameter portion 98A of the stirring shaft 98 per rotation is small, and the developer G easily stays in the upstream portion 98B of the stirring shaft 98, development in the upstream portion 98B is performed. The state where the bulk of the agent G is high is maintained.

  Therefore, for example, even when the rotation speed of the stirring shaft 98 is increased, or when the stirring shaft 98 is used in a state where the rear side is inclined downward so as to be disposed below the front side, the developer G is smaller than the third configuration. However, while being restricted by the upstream end surface 82 of the overhang portion 80 and the upstream end surface 98X of the large-diameter portion 98A, the state of being transported downstream in the transport direction of the large-diameter portion 98A is maintained. Thus, compared to the third configuration, the fluctuation of the transport amount per one rotation of the stirring shaft 98 in the developer G transported to the downstream side in the transport direction of the large diameter portion 98A is suppressed.

  In the present embodiment, the outer diameter D2 of the second blade 92 is smaller than the outer diameter D1 of the first blade 91. For this reason, compared with the configuration (fourth configuration) in which the outer diameter D2 of the second blade 92 is the same as the outer diameter D1 of the first blade 91, the outer diameter D2 of the second blade 92 is more radially outward than the large-diameter portion 98A. Since the area of the protruding portion is reduced, the force for pushing the developer G downstream of the large-diameter portion 98A in the transport direction is reduced. Therefore, compared to the fourth configuration, the developer G easily stays in the immediately upstream portion 98B, and the state in which the bulk of the developer G in the immediately upstream portion 98B is high is effectively maintained.

  Thus, for example, even when the rotation speed of the stirring shaft 98 is increased, or when the stirring shaft 98 is used in a state where the rear side is inclined so as to be disposed below the front side, the developer G can be compared with the fourth configuration. However, while being restricted by the upstream end surface 82 of the overhang portion 80 and the upstream end surface 98X of the large-diameter portion 98A, the state of being transported downstream in the transport direction of the large-diameter portion 98A is maintained. Thus, compared to the fourth configuration, fluctuations in the transport amount of the developer G transported downstream of the large-diameter portion 98A in the transport direction per rotation of the stirring shaft 98 are suppressed.

  In this embodiment, the thickness T2 of the second blade 92 along the axial direction of the stirring shaft 98 is larger than the thickness T1 of the first blade 91 along the axial direction. Thereby, the second blade 92 has a stirring shaft in comparison with the configuration (fifth configuration) in which the thickness T2 along the axial direction of the stirring shaft 98 is the same as the thickness T1 of the first blade 91 along the axial direction. The space on the outer periphery of the portion 98 </ b> B immediately upstream of 98 is filled with the second blade 92. For this reason, the volume of the space on the outer periphery of the immediately upstream portion 98B of the stirring shaft 98 is smaller than in the fifth configuration, and the state in which the bulk of the developer G in the immediately upstream portion 98B is high is maintained.

  Thereby, for example, even when the rotation speed of the stirring shaft 98 is increased or when the rear side is used in a state of being inclined so that the rear side is disposed below the front side, the developer G can be compared with the fifth configuration. However, while being restricted by the upstream end surface 82 of the overhang portion 80 and the upstream end surface 98X of the large-diameter portion 98A, the state of being transported downstream in the transport direction of the large-diameter portion 98A is maintained. Thus, compared to the fifth configuration, fluctuations in the transport amount of the developer G transported downstream of the large-diameter portion 98A in the transport direction per rotation of the stirring shaft 98 are suppressed.

  In the present embodiment, the length of the space between the blades along the axial direction of the stirring shaft 98 is longer than the length of the space between the blades of the first blade 91 along the axial direction. It has been shortened. Accordingly, the second blade 92 has a configuration in which the length of the space between the blades along the axial direction of the stirring shaft 98 is the same as the length of the space between the blades of the first blade 91 along the axial direction (the sixth blade). Configuration), the volume of the space on the outer periphery of the immediately upstream portion 98B of the stirring shaft 98 is reduced, and the state in which the bulk of the developer G in the immediately upstream portion 98B is high is maintained.

  Accordingly, for example, even when the rotation speed of the stirring shaft 98 is increased, or when the rear side is used in a state where the rear side is inclined so as to be disposed below the front side, the developer G is smaller than in the sixth configuration. While being restricted by the upstream end surface 82 of the overhang portion 80 and the upstream end surface 98X of the large-diameter portion 98A, the state in which the large-diameter portion 98A is transported downstream in the transport direction is maintained. Thus, compared to the sixth configuration, the fluctuation of the transport amount per one rotation of the stirring shaft 98 in the developer G transported downstream in the transport direction of the large-diameter portion 98A is suppressed.

  In the present embodiment, the first blade 91 is formed to reach the outer peripheral surface of the portion 98D immediately downstream of the stirring shaft 98. As a result, the developer G flows directly downstream of the stirring shaft 98 as compared with a configuration in which the first blade 91 is formed only in the large-diameter portion 98A and the fourth blade 94 is formed directly downstream of the stirring shaft 98 (seventh configuration). It is easy to stay at 98D. As a result, as compared with the seventh configuration, the developer G tends to stay in the immediately upstream portion 98B of the stirring shaft 98, and the bulk of the developer G in the immediately upstream portion 98B is maintained high.

  Thus, for example, even when the rotation speed of the stirring shaft 98 is increased or when the rear side is used in a state where the rear side is inclined so as to be disposed below the front side, the developer G is smaller than the seventh configuration. However, while being restricted by the upstream end surface 82 of the overhang portion 80 and the upstream end surface 98X of the large-diameter portion 98A, the state of being transported downstream in the transport direction of the large-diameter portion 98A is maintained. Thus, compared to the seventh configuration, the fluctuation of the transport amount of the developer G transported downstream of the large-diameter portion 98A in the transport direction per rotation of the stirring shaft 98 is suppressed.

  Further, in the present embodiment, the first blade 91 reaches downstream (rearward side) from the downstream end (downstream end surface 84 described later) of the overhang portion 80. For this reason, the first blade 91 is disposed upstream (front side) of the downstream end (downstream end surface 84) of the overhang portion 80, and the fourth blade is located downstream from the downstream end (downstream end surface 84) of the overhang portion 80. As compared with the configuration in which the blades 94 are formed (eighth configuration), the developer G tends to stay on the downstream side of the overhang portion 80. As a result, as compared with the eighth configuration, the developer G easily stays in the immediately upstream portion 98B of the stirring shaft 98, and the state in which the bulk of the developer G in the immediately upstream portion 98B is high is maintained.

  Accordingly, for example, even when the rotation speed of the stirring shaft 98 is increased or when the rear side is used in a state where the rear side is inclined so as to be disposed below the front side, the developer G is smaller than in the eighth configuration. However, while being restricted by the upstream end surface 82 of the overhang portion 80 and the upstream end surface 98X of the large-diameter portion 98A, the state of being transported downstream in the transport direction of the large-diameter portion 98A is maintained. Thus, compared to the eighth configuration, a variation in the transport amount of the developer G transported downstream of the large-diameter portion 98A in the transport direction per rotation of the stirring shaft 98 is suppressed.

  In the present embodiment, as shown in FIG. 6, the length of the overhang portion 80 along the axial direction is equal to or greater than the length of the large-diameter portion 98A along the axial direction. For this reason, compared with the configuration (ninth configuration) in which the length of the overhang portion 80 along the axial direction is less than the length of the large diameter portion 98A along the axial direction (ninth configuration), the stirring at the large diameter portion 98A and its periphery is performed. The width of the road 32C is reduced. As a result, as compared with the ninth configuration, the developer G tends to stay in the immediately upstream portion 98B of the stirring shaft 98, and the bulk of the developer G in the immediately upstream portion 98B is maintained high.

  Thus, for example, even when the rotation speed of the stirring shaft 98 is increased, or when the developer is used in a state where the rear side is inclined so as to be disposed below the front side, compared to the ninth configuration, the developer G However, while being restricted by the upstream end surface 82 of the overhang portion 80 and the upstream end surface 98X of the large-diameter portion 98A, the state of being transported downstream in the transport direction of the large-diameter portion 98A is maintained. Thus, compared to the ninth configuration, fluctuations in the transport amount of the developer G transported downstream of the large-diameter portion 98A in the transport direction per rotation of the stirring shaft 98 are suppressed.

  In this embodiment, as shown in FIG. 6, the upstream end of the overhang portion 80 extends in the axial direction from the upstream end of the large-diameter portion 98A. For this reason, compared with the configuration (tenth configuration) in which the overhang portion 80 is arranged in the range from the upstream end to the downstream end of the large-diameter portion 98A, the path width of the large-diameter portion 98A and the stirring path 32C around it is reduced. Narrows. As a result, compared to the tenth configuration, the developer G tends to stay in the immediately upstream portion 98B of the stirring shaft 98, and the bulk of the developer G in the immediately upstream portion 98B is maintained high.

  Accordingly, for example, even when the rotation speed of the stirring shaft 98 is increased or when the rear side is used in a state where the rear side is inclined so as to be disposed below the front side, the developer G is smaller than the tenth configuration. However, while being restricted by the upstream end surface 82 of the overhang portion 80 and the upstream end surface 98X of the large-diameter portion 98A, the state of being transported downstream in the transport direction of the large-diameter portion 98A is maintained. Thus, compared to the tenth configuration, fluctuations in the transport amount of the developer G transported downstream in the transport direction of the large-diameter portion 98A per rotation of the stirring shaft 98 are suppressed.

  In the present embodiment, the first blade 91 is formed continuously with the second blade 92. Therefore, the developer G is more easily conveyed from the upstream portion 98B of the stirring shaft 98 to the large-diameter portion 98A as compared with the configuration (the eleventh configuration) in which the first blade 91 and the second blade 92 are separated. . Therefore, as compared with the eleventh configuration, it is easier to adjust the amount of stay such that the amount of stay in the upstream portion 98B of the developer G is reduced. That is, it can be used as an adjustment factor (adjustment allowance) for adjusting the amount of stagnation of the developer G in the immediately upstream portion 98B.

  In the present embodiment, as shown in FIG. 6, the rotating roll 50 is disposed along the stirring shaft 98 above the immediately upstream portion 98 </ b> B of the stirring shaft 98. Here, in the configuration in which the rotating roll 50 is disposed only above the upstream portion 98C (twelfth configuration), the developer G that exists in the upstream portion 98C where the developer G is less likely to stay than the immediately upstream portion 98B is held. Therefore, the holding amount of the developer G held by the rotating roll 50 may not be stable in the axial direction, and the holding amount may vary in the axial direction.

  On the other hand, in the present embodiment, since the rotating roll 50 is disposed along the stirring shaft 98 above the immediately upstream portion 98B of the stirring shaft 98, the development in the bulky state is performed as compared with the twelfth configuration. The agent G is held on the rotating roll 50. Therefore, compared to the twelfth configuration, the variation in the amount of the developer G held by the rotating roll 50 in the axial direction is suppressed.

  In the present embodiment, the second blade 92 is disposed in at least a region 51 </ b> A from the center in the axial direction to the downstream end in the holding region 51 of the rotating roll 50. For this reason, the developer G in a bulky state rotates as compared with the configuration (the thirteenth configuration) in which the second blades 92 are disposed in the holding area 51 of the rotating roll 50 in the area on the downstream end side with respect to the axial center. It is held by the roll 50. Therefore, compared to the thirteenth configuration, the variation in the amount of the developer G held by the rotating roll 50 in the axial direction is suppressed.

  As described above, the variation in the amount of the developer G held by the rotating roll 50 in the axial direction is suppressed, so that the developer G retained in the first path 44, the second path 46, and the replenishment path 40 is retained. The variation in the amount in the axial direction is suppressed. As a result, the first path 44, the second path 46, and the replenishment path 40 are blocked by the developer G from one end to the other end in the axial direction, and the replenishment of the toner TN is appropriately stopped.

  As described above, in the present embodiment, the fluctuation in the amount of the developer G conveyed per rotation of the stirring shaft 98 in the conveying direction downstream of the large-diameter portion 98A is suppressed. Is suppressed. As a result, development defects are suppressed, and image defects due to the development defects are suppressed.

(Modification)
In the present embodiment, both the first blade 91 and the second blade 92 have both the number of rows and the spiral pitches P1 and P2 smaller than the number of rows of the third blade 93 and the spiral pitch P3. Not limited to For example, both the first blade 91 and the second blade 92 may have at least one of the number of rows and the helical pitches P1 and P2 smaller than the number of rows and the helical pitch P3 of the third blade 93. Of the four values of the spiral pitch P1 of the first blade 91, the spiral pitch P2 of the second blade 92, the number of lines of the first blade 91, and the number of lines of the second blade 92, one or more of the values What is necessary is just to be smaller than the value of the three blades 93.

  Further, in the present embodiment, the outer diameter D2 of the second blade 92 is smaller than the outer diameter D1 of the first blade 91, but is not limited thereto. For example, the outer diameter D2 of the second blade 92 may be the same as the outer diameter D1 of the first blade 91.

  In the present embodiment, the thickness T2 of the second blade 92 along the axial direction of the stirring shaft 98 is larger than the thickness T1 of the first blade 91 along the axial direction. I can't. For example, the second blade 92 may have a configuration in which the thickness T2 along the axial direction of the stirring shaft 98 is the same as the thickness T1 of the first blade 91 along the axial direction.

  In the present embodiment, the length of the space between the blades along the axial direction of the stirring shaft 98 is longer than the length of the space between the blades of the first blade 91 along the axial direction. Although it was shortened, it is not limited to this. For example, the second blade 92 may have a configuration in which the length of the space between the blades along the axial direction of the stirring shaft 98 is the same as the length of the space between the blades of the first blade 91 along the axial direction. Good.

  Further, in the present embodiment, the first blade 91 is formed so as to reach the outer peripheral surface of the portion 98 </ b> D immediately downstream of the stirring shaft 98, but is not limited to this. For example, a configuration in which the first blade 91 is formed only in the large-diameter portion 98A may be employed. In this case, for example, the fourth blade 94 is formed in a portion 98D immediately downstream of the stirring shaft 98.

  Further, in the present embodiment, the first blade 91 reaches the downstream side (rear side) from the downstream end (downstream end surface 84) of the overhang portion 80, but is not limited thereto. For example, the first blade 91 is disposed on the upstream side (front side) of the downstream end (downstream end surface 84) of the overhang portion 80 and the fourth blade is located downstream from the downstream end (downstream end surface 84) of the overhang portion 80. The configuration in which the 94 is formed may be used.

  Further, in the present embodiment, as shown in FIG. 6, the length of the overhang portion 80 along the axial direction is equal to or greater than the length of the large-diameter portion 98A along the axial direction. Not limited. For example, the configuration may be such that the length of the overhang portion 80 along the axial direction is less than the length of the large diameter portion 98A along the axial direction.

  Further, in the present embodiment, as shown in FIG. 6, the upstream end of the overhang portion 80 extends in the axial direction from the upstream end of the large-diameter portion 98A, but is not limited thereto. For example, the configuration may be such that the overhang portion 80 is arranged in a range from the upstream end to the downstream end of the large diameter portion 98A.

  Further, in the present embodiment, the first blade 91 is formed continuously with the second blade 92, but is not limited to this. For example, a configuration in which the first blade 91 and the second blade 92 are separated may be used.

  Further, in the present embodiment, as shown in FIG. 6, the rotating roll 50 is disposed along the stirring shaft 98 above the immediately upstream portion 98B of the stirring shaft 98, but is not limited thereto. For example, a configuration in which the rotating roll 50 is disposed above only the upstream portion 98C may be employed.

  Further, in the present embodiment, the second blade 92 is disposed at least in the region 51A from the center in the axial direction to the downstream end in the holding region 51 of the rotating roll 50, but is not limited thereto. For example, a configuration may be adopted in which the second blade 92 is arranged in a region on the downstream end side of the axial center of the holding region 51 of the rotating roll 50.

  In the present embodiment, the toner TN and the developer G are used as the powder, but the present invention is not limited to this. As the powder, any powder may be used.

  The present invention is not limited to the above embodiment, and various modifications, changes, and improvements can be made without departing from the gist of the present invention. For example, the above-described modifications may be appropriately combined with each other.

10 Image Forming Apparatus 20 Photoconductor Drum (Example of Latent Image Holder)
22 Transfer Roll (Example of Transfer Unit)
Reference Signs List 30 developing device 31 transport mechanism 32 housing 34 developing roll (an example of a supply body)
50 rotating roll (example of holder)
51 holding area 51A area 80 overhang portion 91 first blade 92 second blade 93 third blade 98 stirring shaft (an example of a shaft portion)
98A Large diameter portion 98B Immediately upstream portion 98C Upstream portion 98D Immediately downstream portion G Developer (an example of powder)
TN toner (an example of powder)
P paper (an example of a recording medium)

Claims (16)

A housing containing the powder,
A shaft portion disposed inside the housing and having a large-diameter portion that has a large diameter at a part in the axial direction,
An overhanging portion formed on the inner wall of the housing and extending from the radially outer side of the large diameter portion toward the large diameter portion,
A first blade that is formed in a spiral shape on the outer peripheral surface of the large-diameter portion and that conveys the powder in one of the axial directions by rotation of the shaft portion,
A second blade that is spirally formed on the outer peripheral surface of the shaft portion immediately upstream of the large-diameter portion and conveys the powder to the one by rotation of the shaft portion,
A third blade that is formed in a spiral shape on an outer peripheral surface of an upstream portion of the shaft portion with respect to the immediately upstream portion, and conveys the powder to the one by rotation of the shaft portion,
With
A transport mechanism in which at least one of the first blade and the second blade has at least one of the number of rows and the spiral pitch smaller than the number of rows and the spiral pitch of the third blade.   2. The transport mechanism according to claim 1, wherein at least one of the number of rows and the helical pitch of both the first blade and the second blade is smaller than the number of rows and the helical pitch of the third blade. 3.   3. The transport mechanism according to claim 2, wherein both the first blade and the second blade have a smaller number of rows and a spiral pitch than the number of rows and the spiral pitch of the third blade. 4.   The transport mechanism according to claim 1, wherein an outer diameter of the second blade is smaller than an outer diameter of the first blade.   5. The transport mechanism according to claim 1, wherein the second blade has a thickness along the axial direction that is greater than a thickness of the first blade along the axial direction. 6.   The length of the space between the blades along the axial direction of the second blade is shorter than the length of the space between the blades along the axial direction of the first blade. The transport mechanism according to the item.   The transport mechanism according to claim 1, wherein the first blade is formed continuously with the second blade.   The transport mechanism according to claim 1, wherein the first blade is formed so as to reach an outer peripheral surface of a portion of the shaft portion immediately downstream of the large-diameter portion.   The transport mechanism according to claim 8, wherein the first blade reaches a downstream side of a downstream end of the overhang portion. The transport mechanism according to any one of claims 1 to 9, wherein the length of the overhang portion along the axial direction is equal to or longer than the length of the large diameter portion along the axial direction. The transport mechanism according to claim 10, wherein at least one of an upstream end and a downstream end of the overhang portion extends in the axial direction than at least one of an upstream end and a downstream end of the large-diameter portion. The transport mechanism according to any one of claims 1 to 11, further comprising: a holding body that is arranged along the shaft portion above the immediately upstream portion and that holds the powder staying in the immediately upstream portion on the outer periphery. . The second blade is
The transport mechanism according to claim 12, wherein the holding body is arranged at least in a region from a center in the axial direction to a downstream end in a holding region for holding the powder. The transport mechanism according to any one of claims 1 to 13, wherein the toner as the powder is replenished into the housing on an upstream side with respect to the large-diameter portion, and transports a developer containing the toner.
A supply body for supplying the developer transported by the transport mechanism to the latent image,
A developing device comprising: 14. The transport mechanism according to claim 12, wherein the transport mechanism replenishes the toner through a passage.
The developing device according to claim 14, wherein the holding member conveys the held developer to the passage, closes the passage with the developer, and stops replenishment of the toner. A latent image holder for holding a latent image,
The developing device according to claim 14 or 15, which develops the latent image,
A transfer unit that transfers an image developed by the developing device to a recording medium,
An image forming apparatus comprising: