JP7039300B2 - Developer - Google Patents

Description

The present invention relates to a developing apparatus suitable for an image forming apparatus using electrophotographic technology such as a printer, a copying machine, a facsimile or a multifunction device.

An image forming apparatus such as a printer, a copying machine, a facsimile or a multifunction device includes a developing apparatus for developing an electrostatic latent image formed on a photosensitive drum with a developing agent to make a visible image. In the developing apparatus, a two-component developing agent (hereinafter, simply referred to as a developing agent) composed of toner and a carrier is used. Then, in order to make the toner concentration in the developer uniform or to charge the toner to an appropriate charge amount, the developer is agitated and conveyed by the conveying screw (Patent Documents 1 to 3). In order to improve the stirring property of the developer by the transfer screw, that is, to efficiently agitate the developer, the spiral blade of the transfer screw is partially missing in the apparatus described in Patent Document 1, and Patent Documents 2 and 3 describe it. In the device described, the transfer screw is provided with a rib.

Japanese Patent No. 5434228 Japanese Unexamined Patent Publication No. 2006-337817 Japanese Unexamined Patent Publication No. 2012-3193

By the way, recently, in order to reduce the size and cost of an image forming apparatus, there is a tendency to reduce the amount of a developer previously stored in the developing apparatus. Further, as the amount of toner used for development per unit time increases due to the increase in printing speed, the amount of toner replenished per unit time increases. Even in such a case, as described above, the transfer screw may be provided with ribs or the spiral blades of the transfer screw in order to equalize the toner concentration as soon as possible and to charge the toner to an appropriate charge amount. Can be partially missing. However, if the transfer screw is provided with ribs or a part of the spiral blade of the transfer screw is missing, the agitation property of the developer is improved, but the transfer property of the developer is lowered, so that the transfer of the developer cannot catch up sufficiently. There was a risk that a large amount of developer and thus toner would not be used for development. Therefore, an apparatus having improved the stirring property of the developer without lowering the transportability of the developer as much as possible has been desired, but such an apparatus has not yet been proposed.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a developing apparatus capable of improving the stirring property of a developing agent without lowering the transportability of the developing agent as much as possible.

The developer according to an embodiment of the present invention includes a developer carrier that carries a developer containing a toner and a carrier, a first chamber for supplying the developer to the developer carrier, and the first chamber. A second chamber partitioned by a partition wall, a first series of passages through which the developer can be communicated from the second chamber to the first chamber, and a developer can be communicated from the first chamber to the second chamber. A developing container having a second communication unit for accommodating the developing agent, a developing agent replenishing unit for supplying the developing agent to the developing container, and a rotatably provided in the first chamber, the developing agent is provided in the first chamber. Is rotatably provided in the second chamber and formed around the rotation shaft and the rotation shaft, and a first transfer screw that conveys the spiral from the first series passage portion to the second communication portion in the first direction. It has a first spiral blade and a second spiral blade that form a multi-row spiral blade, and the developer is applied in the second chamber in the second direction from the second communication portion to the first series communication portion. A second transport screw for transporting is provided, the second transport screw having a plate-shaped first protrusion on the rotation axis between the first spiral blade and the second spiral blade in the second direction. A plate-like shape on the rotation axis between the first spiral blade and the second spiral blade, which is adjacent to the first region downstream of the first region provided with the portion and the first region. The plate-shaped first protrusion provided in the first region has a second region provided with the second protrusion of the above, and the plate-shaped first protrusion is provided with a spiral blade adjacent to the spiral blade on the upstream side in the second direction. The plate-shaped second protruding portion provided in the second region , which is not in contact with the spiral blade which is in contact with the adjacent spiral blade on the downstream side, is a spiral blade which is adjacent on the upstream side in the second direction. It is characterized in that the first protruding portion and the second protruding portion have different shapes because they are not in contact with the spiral blade and are in contact with the adjacent spiral blade on the downstream side.

According to the present invention, it is possible to easily improve the stirring property of the developer without lowering the transportability of the developer as much as possible.

The schematic diagram which shows the structure of the image forming apparatus to which the developing apparatus of this embodiment is applied. The cross-sectional view which shows the developing apparatus of this embodiment. Top sectional view showing a developing apparatus as seen in a horizontal cross section including an axial direction. The schematic which shows a part of the stirring screw of 1st Embodiment. The schematic which shows a part of the stirring screw of the 2nd Embodiment. The schematic which shows a part of the stirring screw of 3rd Embodiment. The schematic which shows a part of the stirring screw of 4th Embodiment.

[Image forming device]
First, a schematic configuration of an image forming apparatus to which the developing apparatus of the present embodiment is applied will be described with reference to FIG. The image forming apparatus shown in FIG. 1 is a tandem type full-color printer in which image forming portions Sa, Sb, Sc, and Sd are arranged along an intermediate transfer belt 7.

In the image forming unit Sa, a yellow toner image is formed on the photosensitive drum 1a and transferred to the intermediate transfer belt 7. In the image forming unit Sb, a magenta toner image is formed on the photosensitive drum 1b and transferred to the intermediate transfer belt 7. In the image forming portions Sc and Sd, a cyan toner image and a black toner image are formed on the photosensitive drums 1c and 1d, respectively, and transferred to the intermediate transfer belt 7. The four-color toner image transferred to the intermediate transfer belt 7 is conveyed to the secondary transfer unit T2 and collectively secondary transferred to the recording material P (paper, sheet material such as OHP sheet, etc.).

The image forming portions Sa, Sb, Sc, and Sd are configured to be substantially the same except that the toner colors used in the developing devices 4a, 4b, 4c, and 4d are different from those of yellow, magenta, cyan, and black. Hereinafter, the configuration and operation of the image forming units Sa to Sd will be described by omitting a, b, c, and d at the end of the reference numerals indicating the distinction between the image forming units Sa, Sb, Sc, and Sd.

In the image forming unit S, a primary charging device 2, an exposure device 3, a developing device 4, a primary transfer roller 5, and a secondary charging device 6 are arranged so as to surround the photosensitive drum 1 as an image carrier. The photosensitive drum 1 has a photosensitive layer, which is an organic optical semiconductor having negative charging characteristics, formed on the outer peripheral surface of an aluminum cylinder, and is indicated by an arrow shown in FIG. 1 at a predetermined process speed (for example, 250 mm / sec) by a motor (not shown). It is rotated in the R1 direction. The photosensitive drum 1 is formed, for example, to have a diameter of 30 mm and a length in the rotation axis direction (longitudinal direction) of 360 mm.

The primary charger 2 is, for example, a roller-shaped charging roller, and when a charging voltage is applied by a high-voltage power source (not shown) and comes into contact with the photosensitive drum 1, the photosensitive drum 1 is brought into contact with a uniform negative electrode dark portion. Charge to electric potential. Since the charging roller as the primary charging device 2 is urged toward the photosensitive drum 1 by a pressure spring (not shown), the charging roller is driven to rotate. As the charging voltage applied to the charging roller, for example, a superimposed voltage obtained by superimposing an AC voltage having a peak voltage of 1500V on a DC voltage of −900V is applied. The charging roller is formed, for example, to have a diameter of 14 mm and a length in the rotation axis direction (longitudinal direction) of 320 mm.

The exposure apparatus 3 generates a laser beam obtained by ON-OFF modulation of scanning line image data obtained by developing separated color images of each color from a laser light emitting element (not shown), and scans this with a rotating mirror (not shown) to charge the laser beam. An electrostatic image of an image is written on the surface of the photosensitive drum 1. The secondary charger 6 arranged upstream of the primary charger 2 in the rotational direction of the photosensitive drum 1 is a charging aid that assists the charging of the primary charger 2. The developing device 4 supplies toner to the photosensitive drum 1 to develop an electrostatic image into a toner image. The details of the developing device 4 will be described later (see FIGS. 2 and 3).

The primary transfer roller 5 is arranged to face the photosensitive drum 1 with the intermediate transfer belt 7 interposed therebetween, and forms a toner image primary transfer portion T1 between the photosensitive drum 1 and the intermediate transfer belt 7. In the primary transfer unit T1, the toner image is primarily transferred from the photosensitive drum 1 to the intermediate transfer belt 7 by applying a primary transfer voltage to the primary transfer roller 5 by a high-voltage power supply (not shown). That is, when a primary transfer voltage having a polarity opposite to the charging polarity of the toner is applied to the primary transfer roller 5, the toner image on the photosensitive drum 1 is electrostatically attracted to the intermediate transfer belt 7 to perform transfer.

The intermediate transfer belt 7 is supported by being hung on rollers such as the secondary transfer inner roller 8, tension rollers 17, and 18, and is driven by the secondary transfer inner roller 8 that also serves as a drive roller to rotate in the direction of arrow R2 in FIG. Will be done. The intermediate transfer belt 7 is rotated at substantially the same speed as the rotation speed (process speed) of the photosensitive drum 1. The secondary transfer unit T2 is a toner image transfer nip unit formed by abutting the secondary transfer outer roller 9 on the intermediate transfer belt 7 supported by the secondary transfer inner roller 8 to the recording material P. In the secondary transfer unit T2, the toner image is secondarily transferred from the intermediate transfer belt 7 to the recording material P transferred to the secondary transfer unit T2 by applying the secondary transfer voltage to the secondary transfer outer roller 9. Toner. The recording material P is stored in a state of being loaded on the paper feed cassette 10, and is conveyed from the paper feed cassette 10 to the secondary transfer unit T2 by a paper feed roller, a transfer roller, a resist roller, or the like (not shown).

The secondary transfer residual toner that remains attached to the intermediate transfer belt 7 after the secondary transfer is removed by the belt cleaning device 11 rubbing the intermediate transfer belt 7. The belt cleaning device 11 removes the secondary transfer residual toner by rubbing the cleaning blade against the intermediate transfer belt 7.

The recording material P to which the four-color toner image is secondarily transferred by the secondary transfer unit T2 is conveyed to the fixing device 13. In the fixing device 13, the fixing rollers 14 and 15 come into contact with each other to form the fixing nip T3, and the toner image is fixed to the recording material P while the recording material P is conveyed by the fixing nip T3. In the fixing device 13, the fixing roller 15 is pressed against the fixing roller 14 heated from the inside by a lamp heater or the like (not shown) by an urging mechanism (not shown) to form a fixing nip T3. The recording material P is heated / pressurized by being sandwiched and conveyed by the fixing nip T3, and the toner image is fixed to the recording material P. The recording material P on which the toner image is fixed by the fixing device 13 is discharged to the outside of the machine body.

[Developer]
The developing apparatus 4 of this embodiment will be described with reference to FIGS. 2 and 3. As shown in FIG. 2, the developing apparatus 4 includes a developing container 41, a regulating blade 42, a developing sleeve 30, a developing screw 31, a stirring screw 32, and the like.

The developing container 41 contains a two-component developer containing a non-magnetic toner and a magnetic carrier. That is, in this embodiment, a two-component developing method is used as the developing method, and a non-magnetic toner having a negative charge polarity and a magnetic carrier having a positive charge polarity are mixed and used as a developer. The non-magnetic toner is obtained by encapsulating a resin such as polyester or styrene acrylic with a colorant, an external additive such as colloidal silica fine powder, or wax, and pulverizing or polymerizing the toner into a powder. The magnetic carrier is, for example, a core coated with a resin on the surface layer of a core made of resin particles obtained by kneading ferrite particles or magnetic powder.

A part of the developing container 41 facing the photosensitive drum 1 is open, and the developing sleeve 30 is rotatably arranged so that a part is exposed in this opening. The developing sleeve 30 is formed of a non-magnetic material such as an aluminum alloy in a cylindrical shape, and is rotationally driven at a predetermined process speed (for example, 250 mm / sec) in the direction of arrow R3 in FIG. The developing sleeve 30 is formed, for example, to have a diameter of 20 mm and a length in the rotation axis direction (longitudinal direction) of 334 mm. Inside the developing sleeve 30, a magnet roller 30a composed of a plurality of magnetic poles is non-rotatably arranged.

As shown in FIG. 2, the developing sleeve 30 rotates in the direction of arrow R3, and carries and conveys the developer adsorbed at the position of the pumping magnetic pole N1 pole of the magnet roller 30a in the direction of the regulation blade 42. The amount of the developer sprouting by the regulating magnetic pole S1 pole receives shearing force by the regulating blade 42 when passing through the gap between the developing sleeve 30 and the regulating blade 42, and the amount is regulated, and a predetermined layer thickness is applied on the developing sleeve 30. The developer layer is formed. The formed developer layer is carried and carried on a developing region facing the photosensitive drum 1, and develops an electrostatic latent image formed on the surface of the photosensitive drum 1 in a state where magnetic spikes are formed by the developing magnetic poles N2 poles. The developer after being subjected to development is peeled off from the developing sleeve 30 by a magnetic force band formed by adjoining the same poles between the stripping magnetic pole N3 pole and the pumping magnetic pole N1 pole.

In the developing container 41, a developing chamber 21 and a stirring chamber 22 are formed, and a partition wall 70 for partitioning the developing chamber 21 and the stirring chamber 22 is provided between the developing chamber 21 and the stirring chamber 22. The partition wall 70 separates the developing chamber 21 and the stirring chamber 22 into the developing container 41 (inside the developing container) so as to protrude from the bottom surface portion 41a. Further, the partition wall 70 extends in the rotation axis direction (longitudinal direction) of the developing sleeve 30, and divides the inside of the developing container 41 so that the developing chamber 21 and the stirring chamber 22 are arranged substantially horizontally.

As shown in FIG. 3, the partition wall 70 has a first communication section 23 and a second communication section 24 for communicating the developing chamber 21 and the stirring chamber 22 on both ends in the longitudinal direction, respectively. The first communication section 23 is a route through which the developer is delivered from the stirring chamber 22 to the developing chamber 21, and the second communication section 24 is a route through which the developer is delivered from the developing chamber 21 to the stirring chamber 22.

The developing chamber 21 is provided with a developing screw 31 capable of transporting the developing agent in a predetermined first direction in the developing chamber 21. The stirring chamber 22 is provided with a stirring screw 32 capable of transporting the developer in the second direction opposite to the first direction in the stirring chamber 22. As will be described in detail later, the developing screw 31 and the stirring screw 32 are configured by spirally forming blades 73 and 74 around the rotating shafts 71 and 72, respectively, and are rotatably supported by the developing container 41. ing.

The developing sleeve 30, the developing screw 31, and the stirring screw 32 are each connected and driven by a gear train (not shown), and rotate via a gear train from a drive motor (not shown). By rotating the developing screw 31 and the stirring screw 32, the developing agent is circulated and conveyed in the developing container 41. At this time, with respect to the developer transport direction (second direction) of the stirring screw 32, the developer is communicated from the stirring chamber 22 to the developing chamber 21 at the first series communication portion 23 on the downstream side in the transport direction, and the second communication on the upstream side in the transport direction. In the unit 24, the developer is delivered from the developing chamber 21 to the stirring chamber 22, respectively. As a result, the developing chamber 21 and the stirring chamber 22 form a circulation path for the developer, and the developer circulates through this circulation path while being stirred and conveyed. In the following description, the transport direction is referred to as the developer transport direction (second direction) of the stirring screw 32 without particular notice.

<Replenishment and discharge of developer>
In the case of the developing apparatus 4 of the present embodiment in which development is performed using a two-component developing agent, toner is consumed by the development, so that the toner concentration of the developing agent contained in the developing container 41 is in an appropriate range (for example, 6 to 9). %) Can be lower than. When a developer whose toner concentration is lowered and is out of the proper range is used, image defects are likely to occur. Therefore, in order to restore the toner concentration to an appropriate range, for example, a replenishing developer (replenishing agent) in which toner and carrier are mixed at a weight ratio of 9: 1 from a replenishing device (not shown) connected to the developing device 4. Is controlled to recover the toner concentration. The replenisher is appropriately replenished according to the amount of toner consumed.

As shown in FIG. 3, in the developing container 41, a replenishment unit 60 for receiving a replenisher from a replenishment device (not shown) is formed on the upstream side in the transport direction of the second communication unit 24 of the stirring chamber 22. However, if the amount of the developing agent in the developing container 41 becomes too large due to the replenishment of the replenishing agent, the stirring of the developing agent becomes insufficient and image defects are likely to occur. In order to avoid this, the developer 50 having a discharge port in the developing container 41 is provided, for example, in the stirring chamber 22 so that the developer surplus due to the replenishment of the replenishing agent is discharged from the developing container 41. It is formed on the downstream side in the transport direction from the first series passage portion 23. Further, an inductance sensor 90, which is a concentration detection sensor for detecting the weight ratio of the toner of the developer and the carrier, is arranged in the stirring chamber 22. The inductance sensor 90 is arranged at least downstream of the center in the longitudinal direction of the stirring screw 32 in the transport direction of the stirring screw 32.

By the way, the replenisher (mainly toner) replenished to the stirring chamber 22 from the replenishing device (not shown) as described above is mixed with the developer remaining in the stirring chamber 22 to equalize the toner concentration or to add toner. It is stirred and conveyed by the stirring screw 32 because it is charged or the like. In order to sufficiently stir the replenisher with the remaining developer, the stirring screw 32 of the present embodiment is provided with a stirring rib 77 as a rib member, as will be described in detail later. The stirring rib 77 is preferably arranged at least upstream of the center in the longitudinal direction of the stirring screw 32 in the transport direction of the stirring screw 32. Further, in the present embodiment, the stirring screw 32 is arranged on the downstream side of the replenishment unit 60 in the transport direction. In the present embodiment, in the region at least upstream of the longitudinal center of the stirring screw 32 in the transport direction of the stirring screw 32 in the stirring chamber 22, the stirring rib 77 is formed in the region between all the wings of the stirring screw 32. Is provided. In the region at least upstream of the center of the stirring screw 32 in the longitudinal direction, if the stirring rib 77 is provided in the region between the blades of at least half of the stirring screw 32, the stirring performance is improved. Can be planned. As shown in FIG. 3, in the present embodiment, the stirring rib 77 is provided over the entire longitudinal direction of the stirring screw 32.

As already described, recently, with the miniaturization of the image forming apparatus, there is a tendency to reduce the amount of the developer previously stored in the developing container 41. In addition, as the printing speed increases, the amount of toner replenished per unit time is increasing. Even in such a case, it is necessary to further improve the stirring property of the developer in order to make the toner concentration uniform as soon as possible or to charge the toner to an appropriate charge amount. Therefore, it is conceivable to provide a rib on the stirring screw, but if the rib is provided, the transportability of the developer is inevitably lowered. Therefore, the transfer of the developer from the stirring chamber 22 to the developing chamber 21 cannot catch up, and there is a possibility that a sufficient amount of toner cannot be used for development.

In view of the above points, in the present embodiment, in order to improve the stirring property of the developer without lowering the transportability of the developer as much as possible, the stirring screw 32 is formed as a transport screw by the multi-row screw, and the multi-row stirring screw is used. 32 is provided with a stirring rib 77. In order to make the explanation easier to understand, the stirring screw 32 will be described here as an example, but this embodiment can also be applied to the developing screw 31, and the illustration and description of the developing screw 31 are omitted.

The stirring screw of the present embodiment will be described by taking the case of a double-row screw as an example. In each of the embodiments described below, the same configurations are designated by the same reference numerals to simplify or omit the description. The stirring screw of the present embodiment is not limited to the one having two threads. Further, the stirring screw will be described as an example in which the outer diameter of each spiral blade is formed to be the same, but the present invention is not limited to this, and the outer diameter of each spiral blade is different, or the outer diameter of each spiral blade is conveyed. It may be formed so as to be different in the direction.

<First Embodiment>
The stirring screw of the first embodiment will be described with reference to FIG. The stirring screw 32 shown in FIG. 4 is a double-threaded screw in which two spiral blades 74a and a second spiral blade 74b are formed as a multi-row spiral blade 74 around a rotating shaft 72. For example, the outer diameter of the stirring screw 32 is 14 mm, and the pitches of the first spiral blade 74a and the second spiral blade 74b are formed to be the same pitch of 30 mm. The diameter of the rotating shaft 72 is, for example, 6 mm.

As shown in FIG. 4, the stirring screw 32 is radially located in the first region 80 between the spiral blades as shown by the diagonal lines in the figure of the first spiral blade 74a and the second spiral blade 74b in the transport direction from the rotation shaft 72. Stirring ribs 77a and 77b protruding from the surface are provided. In other words, the stirring screw 32 has a first region 80 provided with stirring ribs 77a and 77b, respectively. The first region 80 is a region below the rotation axis 72 between the spiral blades. In the case of the present embodiment, the first region 80 provided with the stirring rib 77a and the first region 80 provided with the stirring rib 77b are provided in order to change the stirring property of the developer between the continuous first regions 80. They are arranged alternately. In the present embodiment, the outer peripheral end of the stirring rib 77 is inside the outer peripheral end of the spiral blade 74. Although the stirring rib 77 protrudes from the rotating shaft 72, a stirring rib 77 having almost no stirring function such that the amount of protrusion is extremely small does not fall under the configuration of the present invention. In the present embodiment, the height of the stirring rib 77 in the radial direction (the amount of protrusion from the rotating shaft 72) is 1 mm or more.

The stirring ribs 77a and 77b are provided so as not to be in contact with the spiral blades 74 on the upstream side in the adjacent transport direction with respect to the transport direction, but to be in contact with the spiral blades 74 on the downstream side in the adjacent transport direction. Specifically, these stirring ribs 77a and 77b do not come into contact with the transport surface 75 (surface) of the adjacent spiral blades (74a and 74b) on the upstream side in the transport direction, and the spiral blades (74b) on the downstream side in the adjacent transport direction do not come into contact with each other. , 74a) is in contact with the transport back surface 76. The stirring ribs 77a and 77b are formed to have substantially the same length, for example, having a length of 5 mm in the transport direction. Further, the stirring ribs 77a and 77b are continuously arranged in each of the first regions 80 between the spiral blades in the transport direction while maintaining a phase shift of 180 ° in the circumferential direction of the rotating shaft 72. In this way, a plurality of first regions 80 having stirring ribs 77a and 77b are continuously arranged on the stirring screw 32. The length of the stirring ribs 77a and 77b in the transport direction is less than "P / N × 0.5" when the number of spiral blades is N and the pitch of the spiral blades is P. Further, the phase shift when the stirring rib 77 is arranged in the circumferential direction is not limited to 180 °.

In the case of the present embodiment, the stirring rib 77a and the stirring rib 77b have different radial heights (diametrical height protruding from the surface of the rotating shaft 72, protrusion amount). The radial height of the stirring rib 77b, which has a higher radial height, is preferably such that the outer peripheral end thereof does not protrude more in the radial direction than the outer peripheral end of the spiral blade 74 of the stirring screw 32. This is because if the outer peripheral end of the stirring rib 77b having the higher radial height protrudes more outward than the outer peripheral end of the spiral blade 74 of the stirring screw 32, the transportability of the developer may be hindered. However, even if it protrudes, it is desirable that the maximum amount of protrusion is within 1 mm. The radial height of the stirring ribs 77a and 77b is preferably half or less of the height protruding from the rotating shaft 72 of the spiral blade 74. However, in order to ensure the stirring property of the developer, it is better to be as high as possible. Further, since it is not preferable that the transportability of the developer differs greatly between the adjacent first regions 80, the difference in radial height between the stirring ribs 77a and the stirring ribs 77b between the adjacent first regions 80 is made as small as possible. It is preferable to do so. For example, the difference in radial height between the stirring ribs 77a and the stirring ribs 77b between the adjacent first regions 80 is preferably 2 mm or more and 4 mm or less.

As an example, the radial height (second height) of the stirring rib 77a (second rib member) is 2 mm, and the radial height (first height) of the stirring rib 77b (first rib member) is 4 mm. .. In the case of the present embodiment, in order to improve the stirring property of the developer, the radial heights of the stirring ribs 77a and 77b are preferably 1.0 to 1.3 mm or more, for example. Specifically, the height of the stirring ribs 77a and 77b from the surface of the rotating shaft 72 is preferably one-fourth or more of the height (4 mm) of the spiral blade 74 from the rotating shaft 72 (here, 1. 0-1.3 mm).

As described above, in the present embodiment, the stirring screw 32 is composed of a multi-row screw having a multi-row spiral blade, which has a larger area of the developer transport surface 75 than the case where the stirring screw 32 is a single-thread screw. The transportability of the developer can be improved. On the other hand, since the stirring screws 32 are provided with stirring ribs 77a and 77b between the spiral blades, the stirring property of the developer can be improved. The stirring ribs 77a and 77b are provided so as not to be in contact with the spiral blades 74 on the upstream side in the transport direction adjacent to each other in the transport direction, but to be in contact with the spiral blades 74 on the downstream side in the adjacent transport direction. When the stirring ribs 77a and 77b are in contact with the transport back surface 76 of the adjacent spiral blade 74 on the downstream side in the transport direction, the stirring property of the developer is improved as compared with the case where the stirring ribs 77a and 77b are not in contact with the transport back surface 76. On the other hand, by leaving a gap between the stirring ribs (77a, 77b) and the transport surface 75 of the adjacent spiral blade 74 on the upstream side in the transport direction, the stirring ribs 77a, 77b are compared with the case where they are in contact with the transport surface 75. The transport of the developer on the transport surface 75 is less likely to be hindered. That is, it is possible to suppress a decrease in the transportability of the developer due to the stirring ribs 77a and 77b. Further, the stirring ribs 77a and 77b include a stirring rib 77a having a low radial height and a stirring rib 77b having a high radial height, and the first region 80 provided with the stirring rib 77a and the stirring rib 77b are provided. The first regions 80 are arranged alternately. In this way, according to the present embodiment, it is possible to easily improve the stirring property of the developer without lowering the transportability of the developer as much as possible.

<Second embodiment>
In the stirring screw of the first embodiment described above, the first region 80 is continuously arranged, but the present invention is not limited to this. When the first region 80 having the stirring ribs is continuously arranged, the transportability of the developer is inevitably lowered as compared with the case where the first region 80 is not provided. Therefore, in order to suppress the deterioration of the transportability of the developer, the stirring screw of the second embodiment is provided with a region having a stirring rib and a region having no stirring rib. The stirring screw of the second embodiment will be described with reference to FIG.

In the stirring screw 32A shown in FIG. 5, stirring ribs 77a to 77c having different radial heights are provided in the first region 80 between the spiral blades adjacent to each other in the transport direction, and the stirring ribs 77a to 77c having different radial heights are provided between the adjacent spiral blades different from the first region 80. The stirring ribs 77a to 77c are not provided in the second region 81. In other words, the stirring screw 32A has a first region 80 provided with stirring ribs 77a to 77c and a second region 81 not provided with stirring ribs 77a to 77c. The second region 81 shown by diagonal lines in the figure is a region below the rotation axis 72 between the spiral blades. In the first region 80, the stirring ribs 77a to 77c are provided so as not to contact the spiral blades 74 on the upstream side in the transport direction adjacent to each other in the transport direction, but to contact the spiral blades 74 on the downstream side in the adjacent transport direction.

When the first region 80 is continuously present, the radial height is different so that the radial height gradually increases or decreases as the first region 80 moves from the upstream to the downstream in the transport direction. Stirring ribs 77a to 77c may be arranged. This is preferable because the change in the decrease in the transportability of the developer between the adjacent first regions 80 in the continuous first region 80 is small, and the transportability of the developer is less likely to be extremely reduced. Further, when the second region 81 is present, the diameter of the developer so that the transportability of the developer in the first region 80 adjacent to the second region 81 does not greatly deviate from the transportability of the developer in the second region 81. It is preferable to arrange a stirring rib having a low directional height. As an example, the stirring rib 77c having the maximum radial height has a radial height of 4 mm, the stirring rib 77a having the minimum radial height has a radial height of 2 mm, and the stirring rib 77b having an intermediate radial height. The radial height is 3 mm.

As described above, in the stirring screw 32A of the second embodiment, the first region 80 provided with the stirring ribs 77a to 77c having different radial heights and the second region 81 not provided with the stirring ribs 77a to 77c. Is placed. In this case, in the first region 80 provided with the stirring ribs 77a to 77c, the stirring property of the developer is improved as compared with the second region 81, but the transportability of the developer is lowered. On the other hand, in the second region 81 not provided with the stirring ribs 77a to 77c, the transportability of the developer is improved as compared with the first region 80, while the stirring property of the developer is lowered. By arranging the first region 80 and the second region 81, it is possible to form a region having good agitation of the developer and a region having good transportability of the developer, and it is possible to form a region having good transportability of the developer. The agitability of the developer can be improved without significantly reducing the transportability. As described above, also in the second embodiment, the same effect as that of the first embodiment described above can be easily realized that the stirring property of the developer can be easily improved without lowering the transportability of the developer as much as possible. Be done.

<Third embodiment>
In the first and second embodiments described above, a stirring screw provided with stirring ribs having different radial heights is shown as an example, but in order to change the stirring property of the developer in the transport direction, the transport direction of the stirring ribs is shown. The length may be different. Therefore, the stirring screw of the third embodiment in which the lengths of the stirring ribs in the transport direction are different will be described with reference to FIG.

The stirring screw 32B shown in FIG. 6 is provided with two types of stirring ribs 77a and 77b having different lengths in the transport direction in the first region 80, respectively. The stirring ribs 77a and 77b are provided so as not to be in contact with the spiral blades 74 on the upstream side in the adjacent transport direction with respect to the transport direction, but to be in contact with the spiral blades 74 on the downstream side in the adjacent transport direction. In the case of the present embodiment, the first region 80 provided with the stirring rib 77b (first rib member) having a long transport direction length (first length) and the stirring having a short transport direction length (second length). It is preferable that the first region 80 provided with the rib 77a (second rib member) is alternately arranged.

As an example, the length of the stirring rib 77b having the longer transport direction is 5 mm (one-third of the half pitch), and the length of the stirring rib 77a having the shorter transport direction is 3 mm (half pitch). 1/5).

<Fourth Embodiment>
In the stirring screw of the third embodiment described above, similarly to the second embodiment described above, a region having a stirring rib and a region having no stirring rib are provided in order to suppress a decrease in the transportability of the developer. Is preferable. The stirring screw of the fourth embodiment will be described with reference to FIG. 7.

In the stirring screw 32C shown in FIG. 7, stirring ribs 77a to 77c having different lengths in the transport direction are provided in the first region 80 between the spiral blades adjacent to each other in the transport direction, and the stirring ribs 77a to 77c having different lengths in the transport direction are provided between the adjacent spiral blades different from the first region 80. The stirring ribs 77a to 77c are not provided in the second region 81. Then, in the first region 80, the stirring ribs 77a to 77c are provided so as not to be in contact with the spiral blades 74 on the upstream side in the transport direction adjacent to each other in the transport direction, but to be in contact with the spiral blades 74 on the downstream side in the adjacent transport direction.

When the first region 80 is continuously present, the length in the transport direction is different so that the length in the transport direction gradually increases or decreases as the first region 80 moves from the upstream to the downstream in the transport direction. Stirring ribs 77a to 77c may be arranged. This is preferable because the change in the decrease in the transportability of the developer between the adjacent first regions 80 in the continuous first region 80 is small, and the transportability of the developer is less likely to be extremely reduced. Further, when the second region 81 is present, the transportability of the developer in the first region 80 adjacent to the second region 81 is not significantly different from the transportability of the developer in the second region 81. It is preferable to arrange a stirring rib having a short directional length. As an example, the length of the stirring rib 77c having the longest length in the transport direction is 7.5 mm (half the pitch), and the length of the stirring rib 77a having the smallest length in the transport direction is 3 mm. The length in the transport direction of the stirring rib 77b having an intermediate length in the transport direction is 5 mm.

Even in the case of the third and fourth embodiments described above, it is possible to easily improve the stirring property of the developer without lowering the transportability of the developer as much as possible, which is the same effect as that of the first embodiment described above. Is obtained.

In the second and fourth embodiments described above (see FIGS. 5 and 7), the case where the four first regions 80 are continuously arranged is shown, but the number of continuously arranging the first regions 80 is the same. Not exclusively. Further, the second region 81 may be continuously arranged. In such a case, the number of the first region 80 and the second region 81 to be continuously arranged can be adjusted depending on whether the stirring property of the developer is emphasized or the transportability of the developer is emphasized, which is preferable.

<Other embodiments>
It should be noted that each of the above-described embodiments is not limited to the application to the stirring screw 32 or the developing screw 31, and may be applied to, for example, a replenishing screw for replenishing the replenishing agent from the replenishing device to the developing device 4.

In addition, each of the above-described embodiments is not limited to the horizontal stirring type developing apparatus in which the developing container 41 is horizontally partitioned into the developing chamber 21 and the stirring chamber 22, and for example, the developing container 41 is the developing chamber 21 and the stirring chamber. It is also applicable to a vertical stirring type developing device which is partitioned vertically with 22.

32 (32A, 32B, 32C) ... Conveying screw (stirring screw), 41 ... Developing container, 72 ... Rotating shaft, 74 ... Spiral blade, 77 ... Rib member (stirring rib), 77a ... Second rib member (stirring rib) , 77b ... 1st rib member (stirring rib), 80 ... 1st region, 81 ... 2nd region

Claims (5)

A developer carrier that supports a developer containing toner and carriers, and
A first chamber for supplying the developer to the developer carrier, a second chamber partitioned from the first chamber by a partition wall, and a second chamber in which the developer can communicate from the second chamber to the first chamber. A developing container for accommodating a developer, which has a communication unit and a second communication unit through which the developer can communicate from the first chamber to the second chamber.
A developer replenishing unit that replenishes the developing agent to the developing container,
A first transport screw rotatably provided in the first chamber and transporting the developer in the first direction from the first communication section to the second communication section in the first chamber.
The second chamber is rotatably provided with a rotation shaft, and has a first spiral blade and a second spiral blade formed around the rotation shaft to form a multi-row spiral blade. A second transport screw for transporting the developer in the second direction from the second communication portion to the first series communication portion is provided.
The second transfer screw has a first region provided with a plate-shaped first protrusion on the rotation axis between the first spiral blade and the second spiral blade in the second direction. A second plate-shaped second protrusion is provided on the rotation axis between the first spiral blade and the second spiral blade, which is adjacent to the first region downstream of the first region. Has an area of
The plate-shaped first protrusion provided in the first region is not in contact with the adjacent spiral blade on the upstream side in the second direction, but is in contact with the adjacent spiral blade on the downstream side, and is in contact with the adjacent spiral blade. ,
The plate-shaped second protrusion provided in the second region is not in contact with the adjacent spiral blade on the upstream side in the second direction, but is in contact with the adjacent spiral blade on the downstream side.
The first protrusion and the second protrusion have different shapes.
A developing device characterized by that. The maximum length of the portion of the second protruding portion protruding from the rotating shaft is shorter than the maximum length of the portion of the first protruding portion protruding from the rotating shaft.
The developing apparatus according to claim 1. The maximum length of the portion of the second protruding portion protruding from the rotation axis is half or less of the outer diameter of the first spiral blade.
The developing apparatus according to claim 2. The maximum length of the second protrusion in the second direction is shorter than the maximum length of the first protrusion in the second direction.
The developing apparatus according to any one of claims 1 to 3. In the second transfer screw, the first region and the second region are alternately arranged in the second direction.
The developing apparatus according to any one of claims 1 to 4 .

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