JP2019128424A - Developing device - Google Patents

Abstract

To provide a developing device with which it is possible to improve the performance of stirring a developer without lowering the performance of conveying a developer as much as possible.SOLUTION: A stirring screw 32 is composed of a multi-row screw, and stirring ribs 77a, 77b protruding in the radial direction are provided between its spiral blades 74a, 74b. The stirring ribs 77a, 77b do not touch a spiral blade 74 on the upstream side of the conveyance direction, and are in contact with the spiral blade 74 on the downstream side of the conveyance direction. The stirring ribs 77a, 77b include a stirring rib 77a whose height in the radial direction is low and a stirring rib 77b whose height in the radial direction is high, with a first region 80 where the stirring rib 77a is provided and a first region 80 where the stirring rib 77b is provided alternately arranged. Thus, it is possible to easily improve the performance of stirring a developer without lowering the performance of conveying a developer as much as possible.SELECTED DRAWING: Figure 4

Description

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

  An image forming apparatus such as a printer, a copier, a facsimile machine, or a multifunction machine includes a developing device that develops an electrostatic latent image formed on a photosensitive drum with a developer and visualizes it. In the developing device, a two-component developer (hereinafter, simply referred to as a developer) composed of toner and carrier is used. Then, in order to equalize the toner concentration in the developer or charge the toner to an appropriate charge amount, the developer is stirred and transported by the transport screw (Patent Documents 1 to 3). In order to improve the stirring property of the developer by the conveying screw, that is, in order to efficiently agitate the developer, in the device described in Patent Document 1, the spiral blade of the conveying screw is partially lost. In the described device, the transport screw is provided with a rib.

Patent No. 5434228 JP, 2006-337817, A JP 2012-3193 A

  Recently, there is a tendency to reduce the amount of developer stored in advance in the developing device in order to reduce the size and cost of the image forming apparatus. Further, as the amount of toner provided for development per unit time due to higher printing speed increases, the amount of toner replenished per unit time increases. Even in such a case, as described above, in order to equalize the toner concentration as quickly as possible and to charge the toner to an appropriate charge amount, the transport screw is provided with a rib, or the spiral blade of the transport screw May be partially lost. However, if a rib is provided on the transport screw, or a part of the spiral blade of the transport screw is lost, the developer's aggravability improves, while the developer's transportability decreases, so the developer's transport does not catch up. There has been a risk that a considerable amount of developer and thus toner can not be provided for development. In view of this, there has been a demand for a device that improves the developer agitation without reducing the developer transportability as much as possible, but such a device 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 device capable of improving the stirring property of the developer without lowering the transportability of the developer as much as possible.

  The developing device according to the present invention comprises a developing container for containing a developer containing toner and carrier, a rotary shaft provided in the developing container rotatably, and a plurality of spirals formed around the rotary shaft. A rib having a blade and a rib member protruding in a radial direction from the rotation shaft between the spiral blades, and a transport screw capable of transporting the developer in the transport direction while stirring the developer in the developer container. The member has a first rib member whose first radial height is the first height, and a second rib member whose second radial height is lower than the first height. And is not in contact with the spiral blade on the upstream side in the transport direction adjacent in the transport direction, but in contact with the spiral blade on the downstream side in the transport direction adjacent to the transport direction, and the transport screw is In the first region between adjacent spiral blades One rib member is provided, wherein the second rib member in the second region between the spiral blade adjacent different from the first region is provided, characterized in that.

  The developing device according to the present invention comprises a developing container for containing a developer containing toner and carrier, a rotary shaft provided in the developing container rotatably, and a plurality of spirals formed around the rotary shaft. A rib having a blade and a rib member protruding in a radial direction from the rotation shaft between the spiral blades, and a transport screw capable of transporting the developer in the transport direction while stirring the developer in the developer container. The member includes a first rib member having a first length in the transport direction and a second rib member having a second length in which the length in the transport direction is shorter than the first length. The spiral screw is provided so as not to contact the spiral blade on the upstream side in the transport direction adjacent in the direction, while being in contact with the spiral blade on the downstream side in the transport direction adjacent to the transport direction. The first rib member in the first region Provided, said second rib member in the second region between the spiral blade adjacent different from the first region is provided, characterized in that.

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

FIG. 1 is a schematic view showing a configuration of an image forming apparatus to which a developing device of the present embodiment is applied. FIG. 2 is a cross-sectional view showing the developing device of the present embodiment. FIG. 2 is a top cross-sectional view showing the developing device as viewed in a horizontal cross section including an axial direction. Schematic which shows a part of stirring screw of 1st embodiment. Schematic which shows a part of stirring screw of 2nd embodiment. Schematic which shows a part of stirring screw of 3rd embodiment. Schematic which shows a part of stirring screw of 4th embodiment.

[Image forming apparatus]
First, a schematic configuration of an image forming apparatus to which the developing device of this embodiment is applied will be described with reference to FIG. The image forming apparatus shown in FIG. 1 is a tandem full-color printer in which image forming units 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 1 a and transferred to the intermediate transfer belt 7. In the image forming portion Sb, a magenta toner image is formed on the photosensitive drum 1 b 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 images transferred to the intermediate transfer belt 7 are conveyed to the secondary transfer portion T2 and collectively secondarily 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 substantially the same except that the color of toner used in the developing devices 4a, 4b, 4c, and 4d is different from yellow, magenta, cyan, and black. Hereinafter, the configurations and operations 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 portion S, a primary charger 2, an exposure device 3, a developing device 4, a primary transfer roller 5, and a secondary charger 6 are disposed so as to surround the photosensitive drum 1 as an image carrier. The photosensitive drum 1 has a photosensitive layer, which is an organic photo semiconductor with negative charge characteristics, formed on the outer peripheral surface of an aluminum cylinder, and an arrow 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 to have, for example, 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 charging roller formed in a roller shape, and is applied with a charging voltage by a high voltage power source (not shown) to come into contact with the photosensitive drum 1, thereby making the photosensitive drum 1 a uniform negative-polarity dark portion. Charge to potential. The charging roller as the primary charger 2 is urged toward the photosensitive drum 1 by a pressure spring (not shown), and therefore, is driven to rotate by the photosensitive drum 1. As a charging voltage applied to the charging roller, for example, a superimposed voltage in which an AC voltage of peak voltage 1500 V is superimposed on a DC voltage of −900 V is applied. The charging roller is formed to have, for example, a diameter of 14 mm and a length of 320 mm in the rotation axis direction (longitudinal direction).

  The exposure device 3 generates, from a laser light emitting element (not shown), a laser beam in which scanning line image data obtained by developing separated color images of each color is ON-OFF modulated, scans this with a rotating mirror (not shown) and charges it. The electrostatic image of the image is written on the surface of the photosensitive drum 1 thus made. The secondary charger 6 disposed upstream of the primary charger 2 in the rotational direction of the photosensitive drum 1 is a charging assisting device that assists the charging of the primary charging device 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 disposed to face the photosensitive drum 1 with the intermediate transfer belt 7 interposed therebetween, and forms a primary transfer portion T1 of the toner image between the photosensitive drum 1 and the intermediate transfer belt 7. In the primary transfer portion T1, a 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 from a high voltage power source (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 and transferred.

  The intermediate transfer belt 7 is supported by being supported by the secondary transfer inner roller 8 and tension rollers 17 and 18, etc., and is driven by the secondary transfer inner roller 8 also serving as a driving roller to rotate in the direction of arrow R2 in FIG. Be done. The intermediate transfer belt 7 is rotated at substantially the same speed as the rotational speed (process speed) of the photosensitive drum 1. The secondary transfer portion T2 is a toner image transfer nip on the recording material P formed by bringing the secondary transfer outer roller 9 into contact with the intermediate transfer belt 7 supported by the secondary transfer inner roller 8. At the secondary transfer portion T2, a secondary transfer voltage is applied to the secondary transfer outer roller 9, whereby the toner image is secondarily transferred onto the recording material P conveyed from the intermediate transfer belt 7 to the secondary transfer portion T2. Ru. The recording material P is stored in a state of being stacked on the sheet feeding cassette 10, and is conveyed from the sheet feeding cassette 10 to the secondary transfer portion T2 by a sheet feeding roller, a conveyance roller, a registration roller, etc. not shown.

  The secondary transfer residual toner remaining on 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 rubs the cleaning blade on the intermediate transfer belt 7 to remove secondary transfer residual toner.

  The recording material P on which the four color toner images have been secondarily transferred at the secondary transfer portion T 2 is conveyed to the fixing device 13. The fixing device 13 contacts the fixing rollers 14 and 15 to form a fixing nip T3, and fixes the toner image onto the recording material P while conveying the recording material P at the fixing nip T3. In the fixing device 13, the fixing roller T5 is formed by pressing the fixing roller 15 against the fixing roller 14 which is internally heated by a lamp heater or the like (not shown) by an urging mechanism (not shown). The recording material P is nipped and conveyed by the fixing nip T3 to be heated / pressurized, 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 out of the machine body.

[Developer]
The developing device 4 of the present embodiment will be described with reference to FIGS. 2 and 3. As shown in FIG. 2, the developing device 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 nonmagnetic toner and magnetic carrier. That is, in this embodiment, a two-component developing method is used as a developing method, and a nonmagnetic toner of negative charging polarity and a magnetic carrier of positive charging polarity are mixed and used as a developer. The nonmagnetic toner is, for example, a resin such as polyester or styrene acryl, which contains a colorant, an external additive such as colloidal silica fine powder, a wax and the like, and is powdered or pulverized. The magnetic carrier is obtained, for example, by applying a resin coating to the surface layer of a core made of resin particles mixed with ferrite particles or magnetic powder.

  The developing container 41 is partially opened at the opposite side of the photosensitive drum 1, and the developing sleeve 30 is rotatably disposed so that a part is exposed at the opening. The developing sleeve 30 is formed in a cylindrical shape with a nonmagnetic material such as an aluminum alloy, and is driven to rotate at a predetermined process speed (for example, 250 mm / sec) in the direction of arrow R3 in FIG. The developing sleeve 30 has, for example, a diameter of 20 mm and a length in the rotational axis direction (longitudinal direction) of 334 mm. Inside the developing sleeve 30, a magnet roller 30a constituted by a plurality of magnetic poles is disposed non-rotatably.

  As shown in FIG. 2, the developing sleeve 30 rotates in the direction of the arrow R3, and carries the developer adsorbed at the position of the pumping magnetic pole N1 of the magnet roller 30a toward the regulating blade 42. The developer brushed by the regulating magnetic pole S1 is subjected to a 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 thereof is regulated. The developer layer is formed. The formed developer layer is carried and conveyed to the developing region facing the photosensitive drum 1, and develops the electrostatic latent image formed on the surface of the photosensitive drum 1 in a state where a magnetic brush is formed by the developing magnetic pole N2. The developer after being subjected to development is separated from the developing sleeve 30 by a non-magnetic force zone formed by the same poles adjacent to each other between the stripping pole N3 and the pumping pole N1.

  In the developing container 41, a developing chamber 21 and a stirring chamber 22 are formed, and between the developing chamber 21 and the stirring chamber 22, a partition wall 70 is provided which divides the developing chamber 21 and the stirring chamber 22. The partition wall 70 separates the developing chamber 21 and the agitating chamber 22 so as to protrude from the bottom surface portion 41 a into the developing container 41 (in the developing container). 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 in a substantially horizontal direction.

  As shown in FIG. 3, the partition wall 70 has a first communicating portion 23 and a second communicating portion 24 that respectively connect the developing chamber 21 and the stirring chamber 22 on both end sides in the longitudinal direction. The first communicating portion 23 is a path through which the developer is transferred from the stirring chamber 22 to the developing chamber 21, and the second communicating portion 24 is a path through which the developer is transferred from the developing chamber 21 to the stirring chamber 22.

  In the developing chamber 21, a developing screw 31 capable of transporting the developer in a predetermined first direction in the developing chamber 21 is disposed. 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. The developing screw 31 and the agitating screw 32 are formed by spirally forming the blades 73 and 74 around the rotating shafts 71 and 72, respectively, as described later in detail, and are rotatably supported with respect to the developing container 41. ing.

  The developing sleeve 30, the developing screw 31, and the stirring screw 32 are respectively connected and driven by a gear train (not shown), and rotate through a gear train from a drive motor (not shown). The developer is circulated and transported in the developing container 41 by the rotation of the developing screw 31 and the stirring screw 32. At this time, with respect to the developer conveying direction (second direction) of the agitating screw 32, the developer communicates from the agitating chamber 22 to the developing chamber 21 at the first communicating portion 23 on the downstream side in the conveying direction. In the portion 24, the developer is delivered from the developing chamber 21 to the stirring chamber 22, respectively. As a result, the developer chamber 21 and the stirring chamber 22 form a developer circulation path, and the developer circulates in this circulation path while being stirred and conveyed. In the following description, the direction of conveyance without particular notice refers to the developer conveyance direction (second direction) of the stirring screw 32.

<Replenishment and discharge of developer>
In the case of the developing device 4 of the present embodiment in which development is performed using a two-component developer, toner is consumed by development, so the toner concentration of the developer contained in the developing container 41 is in an appropriate range (for example, 6-9) %). When a developer whose toner density is lowered and falls outside the proper range is used, image defects are likely to occur. Therefore, in order to recover the toner concentration to an appropriate range, a replenishing developer (replenishing agent) in which, for example, the toner and the 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 with a replenishment amount corresponding to the amount of toner consumed.

  As shown in FIG. 3, on the upstream side of the second communicating part 24 of the agitating chamber 22 in the conveyance direction, the developing container 41 is provided with a replenishing part 60 for receiving the replenishing agent from the replenishing device (not shown). However, if the amount of the developer in the developing container 41 is too large due to the replenishment of the replenishing agent, the agitation of the developer is insufficient and an image defect tends to occur. In order to avoid this, a developer discharge portion 50 having a discharge port is provided in the developing container 41 such that, for example, the developer that has become excessive due to the replenishment of the developer is discharged from the developing container 41. It is formed downstream of the first communicating portion 23 in the transport direction. In addition, an inductance sensor 90 that is a concentration detection sensor for detecting the weight ratio of the developer toner to the carrier is disposed in the stirring chamber 22. The inductance sensor 90 is disposed at least on the downstream side of the center in the longitudinal direction of the stirring screw 32 in the conveying direction of the stirring screw 32.

  By the way, the replenishment agent (mainly toner) replenished to the stirring chamber 22 from a replenishing device (not shown) as described above is mixed with the developer remaining in the stirring chamber 22 to make the toner concentration uniform or to remove the toner. The toner is stirred and conveyed by the stirring screw 32 for charging and the like. In order to sufficiently stir the replenisher with the remaining developer, as will be described in detail later, the stirring screw 32 of the present embodiment is provided with stirring ribs 77 as rib members. It is preferable that the stirring rib 77 is disposed at least upstream of the longitudinal center of the stirring screw 32 in the conveying direction of the stirring screw 32. Furthermore, in the present embodiment, the stirring screw 32 is disposed downstream of the replenishment unit 60 in the conveyance direction. In this embodiment, in the region at least the upstream side of the longitudinal center of the stirring screw 32 in the conveyance direction of the stirring screw 32 in the stirring chamber 22, the stirring rib 77 is provided in the region between all the feathers of the stirring screw 32. Is provided. The stirrability is improved if the stirring rib 77 is provided in the region between the wings of at least half of the stirring screw 32 at least on the upstream side of the longitudinal center of the stirring screw 32 described above. Can be As shown in FIG. 3, in the present embodiment, the stirring rib 77 is provided over the entire area in the longitudinal direction of the stirring screw 32.

  As described above, recently, with the miniaturization of the image forming apparatus, there is a tendency to reduce the amount of developer stored in advance in the developing container 41. Also, with the speeding up of printing, 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 density uniform as quickly 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 the provision of the rib inevitably lowers the transportability of the developer. Therefore, the transport of the developer from the stirring chamber 22 to the developing chamber 21 can not catch up, and a sufficient amount of toner may not be provided for development.

  In view of the above points, in the present embodiment, in order to improve the developer's stirring property without lowering the developer's transportability as much as possible, the stirring screw 32 is formed of multiple threads as a transport screw In the configuration, a stirring rib 77 is provided at 32. In order to make the description easy to understand, the stirring screw 32 will be described as an example here, but the present embodiment is also applicable to the developing screw 31, and illustration and description of the developing screw 31 are omitted.

  About the stirring screw of this embodiment, the case where it is a double thread screw is demonstrated to an example. In each embodiment described below, the same reference numeral is given to the same configuration to simplify or omit the description. In addition, the stirring screw of this embodiment is not restricted to the thing of two streaks. Moreover, although the stirring screw demonstrates the example in which the outer diameter of each spiral blade was formed equally, it does not restrict to this, but the outer diameter of each spiral blade is conveyed so that the outer diameter of each spiral blade may differ. It may be formed to differ in direction.

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

  As shown in FIG. 4, the stirring screw 32 is arranged in the radial direction from the rotation shaft 72 in a first region 80 between the spiral blades as indicated by oblique lines in the drawing of the first spiral blade 74a and the second spiral blade 74b in the transport direction. The stirring ribs 77 a and 77 b are provided to project to the bottom. In other words, the stirring screw 32 has the first region 80 provided with the stirring ribs 77a and 77b, respectively. The first area 80 is an area 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 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 member having substantially no stirring function such as an extremely small protruding amount does not fall under the configuration of the present invention. In the present embodiment, the radial height (the amount of protrusion from the rotating shaft 72) of the stirring rib 77 is 1 mm or more.

  The stirring ribs 77a and 77b are provided so as not to be in contact with the spiral blade 74 on the upstream side in the transport direction adjacent to the transport direction, but in contact with the spiral blade 74 on the downstream side in the transport direction. Specifically, the stirring ribs 77a and 77b are not in contact with the conveyance surface 75 (surface) of the spiral vanes (74a and 74b) on the upstream side in the conveyance direction, and the spiral vanes (74b on the downstream side in the conveyance direction) , 74a) are in contact. The stirring ribs 77a and 77b are formed, for example, to have substantially the same length of 5 mm in the transport direction. The stirring ribs 77a and 77b are disposed continuously in the conveying direction in each of the first regions 80 between the spiral blades while maintaining a phase shift of 180 ° in the circumferential direction of the rotating shaft 72. Thus, a plurality of first regions 80 having the stirring ribs 77a and 77b are continuously arranged on the stirring screw 32. In addition, the conveyance direction length of the stirring ribs 77a and 77b is less than “P / N × 0.5”, where N is the number of spiral blades and P is the pitch of the spiral blades. Moreover, the phase shift at the time of arranging the stirring rib 77 in the circumferential direction is not limited to 180 °.

  In the case of this embodiment, the radial direction height (radial direction height which protruded from the surface of the rotating shaft 72, protrusion amount) differs between the stirring rib 77a and the stirring rib 77b. It is preferable that the radial height of the higher one of the radial heights of the stirring ribs 77b be such that the outer peripheral end does not extend largely in the radial direction than the outer peripheral end of the spiral blade 74 of the stirring screw 32. This is because the transportability of the developer can be impeded when the outer peripheral end of the higher stirring rib 77b in the radial direction largely protrudes outside the outer peripheral end of the spiral blade 74 of the stirring screw 32. However, even in the case of an overrun, it is desirable that the maximum overrun amount be within 1 mm. The height in the radial direction of the stirring ribs 77a and 77b is preferably equal to or less than half of the height protruding from the rotating shaft 72 of the spiral blade 74. However, in order to secure 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 greatly varies between the adjacent first regions 80, the difference in the radial height of the stirring rib 77a and the stirring rib 77b between the adjacent first regions 80 is as small as possible. It is preferable to do. For example, the difference in radial height between the stirring rib 77a and the stirring rib 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 this embodiment, in order to improve the stirring property of the developer, it is preferable that the radial height of the stirring ribs 77a and 77b is, for example, 1.0 to 1.3 mm or more. Specifically, the height of the stirring ribs 77a and 77b from the surface of the rotary shaft 72 is preferably a quarter or more of the height (4 mm) from the rotary shaft 72 of the spiral blade 74 (here, 1.). 0 to 1.3 mm).

  As described above, in the present embodiment, since the area of the developer conveyance surface 75 is larger than that in the case of the single screw screw, the stirring screw 32 is configured by the multiple screw with multiple spiral blades, The transportability of the developer can be improved. On the other hand, since the stirring ribs 77a and 77b are provided on the stirring screw 32 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 blade 74 on the upstream side in the transport direction adjacent in the transport direction, but in contact with the spiral blade 74 on the downstream side in the transport direction. When the stirring ribs 77a and 77b are in contact with the transport back surface 76 of the spiral blade 74 on the downstream side in the transport direction adjacent to each other, the developer agitating property 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, stirring ribs (77a, 77b) and stirring rib (77a, 77b) are spaced from the carrying surface 75 of the spiral blade 74 on the upstream side in the carrying direction, thereby making stirring ribs 77a, 77b. Transport of the developer on the transport surface 75 is less likely to be hindered. That is, it is possible to suppress the decrease in the developer transportability by the stirring ribs 77a and 77b. 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. The first region 80 provided with the stirring rib 77a and the stirring rib 77b are provided. The first regions 80 are alternately arranged. As described above, according to the present embodiment, it is possible to easily realize improvement of 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 developer transportability is inevitably lowered as compared with the case where the first region 80 is not continuously disposed. Therefore, in order to suppress a decrease in developer transportability, in the stirring screw of the second embodiment, a region having a stirring rib and a region having no stirring rib are provided. The stirring screw of such a 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 adjacent spiral blades in the transport direction, and between the first region 80 and the different adjacent spiral blades The stirring ribs 77 a to 77 c are not provided in the second region 81. In other words, stirring screw 32A has the 1st field 80 in which stirring ribs 77a-77c were provided, and the 2nd field 81 in which stirring ribs 77a-77c are not provided. A second area 81 indicated by oblique lines in the drawing is an area 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 be in contact with the spiral blade 74 on the upstream side in the transport direction adjacent in the transport direction, but in contact with the spiral blade 74 on the downstream side in the transport direction.

  In the case where the first region 80 is continuously present, the radial height varies so that the radial height gradually increases or decreases as it moves from the upstream to the downstream in the transport direction. The stirring ribs 77a to 77c may be arranged. This is preferable because the change in the developer transportability between adjacent first regions 80 in the continuous first region 80 is small, and the developer transportability is hardly reduced. Also, when the second area 81 is present, the diameter of the developer transportability in the first area 80 adjacent to the second area 81 does not largely deviate from the transportability of the developer in the second area 81. It is preferable to arrange stirring ribs with a low directional height. As an example, the radial height of the stirring rib 77c having the maximum radial height is 4 mm, the radial height of the stirring rib 77a having the minimum radial height is 2 mm, and the stirring rib 77b having the intermediate radial height is The radial height is 3 mm.

  As described above, in the stirring screw 32A according to the second embodiment, the first region 80 provided with the stirring ribs 77a to 77c different in height in the radial direction and the second region 81 not provided with the stirring ribs 77a to 77c. Is arranged. In this case, in the first region 80 where the stirring ribs 77a to 77c are provided, the developer stirring property is improved as compared with the second region 81, but the developer transportability is lowered. On the other hand, in the second region 81 where the stirring ribs 77a to 77c are not provided, the developer transportability is improved compared to the first region 80, while the developer stirring property is lowered. By disposing the first region 80 and the second region 81, it is possible to form a region having a good developer agitation and a region having a good developer transportability. Stirability of the developer can be improved without significantly reducing the transportability. As described above, also in the second embodiment, the same effect as the above-described first embodiment can be obtained in that it is possible to easily realize improvement in the stirring property of the developer without lowering the transportability of the developer as much as possible. Be

<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 carrying direction, the carrying direction of the stirring ribs The length may be different. Therefore, a stirring screw according to a third embodiment in which the lengths of the stirring ribs in the conveyance direction 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 blade 74 on the upstream side in the transport direction adjacent to the transport direction, but in contact with the spiral blade 74 on the downstream side in the 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 conveying direction length (first length) and the stirring having a short conveying direction length (second length). Preferably, the first regions 80 provided with the ribs 77a (second rib members) are alternately arranged.

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

<Fourth embodiment>
Also in the stirring screw according to the third embodiment described above, as in the second embodiment described above, the region having the stirring rib and the region not having the stirring rib are provided in order to suppress the decrease in the developer transportability. It is preferable. Such a stirring screw according to the fourth embodiment will be described with reference to FIG.

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

  When the first region 80 exists continuously, the transport direction length gradually increases or decreases as it moves from the upstream side to the downstream side in the transport direction, so that the transport direction lengths are different. The stirring ribs 77a to 77c may be arranged. This is preferable because the change in the developer transportability between adjacent first regions 80 in the continuous first region 80 is small, and the developer transportability is hardly reduced. When the second area 81 is present, the transportability of the developer in the first area 80 adjacent to the second area 81 does not largely deviate from the transportability of the developer in the second area 81. It is preferable to arrange a stirring rib with a short direction length. As an example, the conveyance direction length of the stirring rib 77c having the longest conveyance direction length is 7.5 mm (one half of the half pitch), the conveyance direction length of the stirring rib 77a having the smallest conveyance direction length is 3 mm, The conveying direction length of the stirring rib 77b having an intermediate conveying direction length is 5 mm.

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

  In the second and fourth embodiments (see FIGS. 5 and 7) described above, the four first areas 80 are continuously arranged, but the number of the first areas 80 arranged continuously is Not exclusively. In addition, the second regions 81 may be arranged continuously. In such a case, it is preferable to adjust the number of the first regions 80 and the second regions 81 arranged in series by setting emphasis on the agitability of the developer or on the developer transportability.

Other Embodiments
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 a replenishing screw that replenishes the replenisher from the replenishing device to the developing device 4, for example.

  The above-described embodiments are not limited to the lateral stirring type developing device in which the developing container 41 is divided into the developing chamber 21 and the stirring chamber 22 in the horizontal direction, for example, the developing container 41 may be the developing chamber 21 and the stirring chamber. The present invention is also applicable to a vertical agitation type developing device which is vertically divided into 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: First rib member (stirring rib) 80: first region 81: second region

Claims (6)

A developer container containing a developer including toner and carrier;
The developer container has a rotary shaft, a rotary shaft, a plurality of spiral blades formed around the rotary shaft, and a rib member radially projecting from the rotary shaft between the spiral blades. A conveying screw capable of being conveyed in the conveying direction while stirring the developer in the developing container,
The rib member has a first rib member having a first height at a radial height of the rotation shaft, and a second height at a second height where the height of the rotation shaft in a radial direction is lower than the first height. A rib member, provided in contact with the adjacent spiral blade on the downstream side in the transport direction while not in contact with the spiral blade on the upstream side in the transport direction adjacent to the transport direction,
In the transport screw, the first rib member is provided in a first region between adjacent spiral blades in the transport direction, and the second rib member is disposed in a second region between adjacent spiral blades different from the first region. Provided,
A developing device. The rib member has a height in the radial direction that is half or less of an outer diameter of the spiral blade.
The developing device according to claim 1. A developer container containing a developer including toner and carrier;
The developer container has a rotary shaft, a rotary shaft, a plurality of spiral blades formed around the rotary shaft, and a rib member radially projecting from the rotary shaft between the spiral blades. A conveying screw capable of being conveyed in the conveying direction while stirring the developer in the developing container,
The rib member includes a first rib member having a first length in the transport direction, and a second rib member having a second length in which the length in the transport direction is shorter than the first length. It is provided so as not to be in contact with the spiral blade on the upstream side in the transport direction adjacent in the transport direction, but in contact with the spiral blade on the downstream side in the transport direction adjacent thereto,
In the transport screw, the first rib member is provided in a first region between adjacent spiral blades in the transport direction, and the second rib member is disposed in a second region between adjacent spiral blades different from the first region. Provided,
A developing device. The multiple spiral blades are formed at the same pitch,
The rib member has a length in the conveyance direction of less than “P / N × 0.5”, where N is a number of the spiral blades and P is a pitch of the spiral blades.
The developing device according to claim 3. The conveying screw, the first region and the second region are alternately arranged in the conveying direction,
The developing device according to claim 1, wherein The plurality of first regions are continuously arranged in the conveyance direction in the conveyance screw.
The developing device according to claim 1, wherein

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