Developing device and image forming apparatus

Abstract

To suppress the change of the discharge amount of a developer.SOLUTION: A developer 10 includes a first conveyance screw 60 for conveying a developer, in a first room 51. The first conveyance screw 60 includes: a conveyance unit 610 having a first spiral blade 61; a discharge unit 620 having a second spiral blade 62, the discharge unit being arranged in a discharge room; and a reverse winding unit 630 having a third spiral blade 63 between the conveyance unit 610 and the discharge unit 620, the third spiral blade winding in a reverse direction to that of the first spiral blade 61. The third spiral blade 63 has an outer diameter which is smaller on the conveyance unit 610 side than the discharge unit 620 side.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a developing device and an image forming apparatus equipped with the developing device, and more particularly to a developing device and an image forming apparatus using a two-component developer. [Background technology]

[0002] As a two-component developing device using a developer containing toner and a non-magnetic carrier, a trickle developing device is known in which new developer is replenished into the developing device while a portion of the developer is discharged from a discharge port. In this type of developing device, the developer is circulated in a circulation chamber by being agitated by a plurality of transport screws and transported in a predetermined transport direction. The circulation chamber is connected to a supply section that supplies the developer and a discharge section that discharges the developer.

[0003] The fluidity of the developer changes depending on the conditions of use, etc., and there is a risk of clogging or stagnation during the process of being transported to the discharge section. If developer stagnation occurs, the amount of developer discharged from the discharge section decreases, and the amount of developer in the circulation chamber increases, or the pressure of the developer increases, which can cause problems such as the developer not being stirred and transported smoothly.

[0004] For example, Patent Document 1 discloses a developing device including an agitating and transporting member for agitating and transporting developer, a discharge section disposed at the downstream end of the agitating and transporting member in the developer transport direction, and a regulating member for regulating the amount of developer discharged. The agitating and transporting member has a helical structure for transporting developer and a reverse helical structure adjacent to the helical structure on the downstream side. The regulating member is intended to regulate the amount of developer flowing from the helical structure to the reverse helical structure in the agitating and transporting member rotating at high speed. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-118715 A Summary of the Invention [Problem to be solved by the invention]

[0006] Normally, the fluidity of a deteriorated developer or a developer in a high humidity environment is easily reduced. In such a case, in the conventional developing device, a transport force acts on the developer with reduced fluidity that flows from the spiral structure to the reverse spiral structure in the opposite direction to the discharge section, making it difficult for the developer to be discharged. Furthermore, combined with the action of the regulating member, the excess developer increases in the developing device, causing a problem that the developer cannot be discharged smoothly.

[0007] In addition, a reverse spiral structure is provided on the path to the discharge section, so that a transport force in the opposite direction to the discharge section acts on the developer. However, when the fluidity of the developer increases, the developer is more likely to scatter into the space above it, and is transported excessively to the discharge section, which causes a problem of an increase in the amount of developer discharged.

[0008] The present invention has been made in consideration of the above-mentioned problems, and its object is to provide a developing device that can suppress fluctuations in the amount of developer discharged and stabilize the amount of developer in the developing device, and an image forming apparatus equipped with such a developing device. [Means for solving the problem]

[0009] The solution of the present invention for achieving the above object is directed to a developing device having a circulation chamber that transports and agitates a developer to be supplied to a developer carrier in an axial direction of the developer carrier, the circulation chamber having a first chamber equipped with a first transport member that transports the developer in one direction in the axial direction, and a second chamber equipped with a second transport member that transports the developer in the other direction in the axial direction and supplies the developer to the developer carrier, the first chamber and the second chamber being connected via communication ports that are respectively arranged at both ends of the second transport member. The first chamber is connected to an outlet chamber having a developer outlet at an end in the one direction, and the first transport member has a transport section having a spiral first blade for transporting the developer in the one direction, a discharge section having a spiral second blade and disposed in the discharge chamber for transporting the developer to the outlet, and a reverse winding section provided between the transport section and the discharge section and having a spiral third blade wound in the opposite direction to the first blade, and the third blade has an outer diameter smaller on the transport section side than on the discharge section side.

[0010] In the developing device having the above-described configuration, it is preferable that the third blade has an outer diameter on the transport portion side smaller than an outer diameter of the first blade.

[0011] In the developing device having the above-described structure, it is preferable that the third blade has a constant outer diameter over at least one helical pitch on the discharge portion side.

[0012] In the developing device having the above-described structure, a peripheral wall member may be provided on the discharge chamber side of the first chamber, the peripheral wall member covering at least an upper portion of the third blade.

[0013] In the developing device having the above-described structure, it is preferable that the peripheral wall member has a length in the axial direction that corresponds to at least one helical pitch of the third blade.

[0014] In the developing device having the above-described structure, it is preferable that the peripheral wall member is disposed with a gap provided relative to the outer periphery of the third blade, and the gap is set to 0.5 mm or less.

[0015] Furthermore, in the developing device having the above configuration, the peripheral wall member may have a protrusion that protrudes between the first chamber and the second chamber, and may be a sheet-like member having elasticity.

[0016] Furthermore, in the developing device having the above configuration, the first transport member may be provided with a boundary portion between the reverse winding portion and the discharge portion that does not have a spiral blade, and a regulating member having a through hole with an inner diameter smaller than the outer diameter of the third blade is provided at the end of the first chamber on the discharge chamber side, so that the boundary portion is disposed within the through hole.

[0017] In the developing device having the above-described configuration, it is preferable that the helical pitch of the first blade is larger than the helical pitch of the third blade.

[0018] Further, an image forming apparatus using a developing device having the above-mentioned configuration is also within the scope of the technical concept of the present invention.

[0019] According to the above-described configuration, even if the fluidity of the developer fluctuates, the developer can be prevented from accumulating or being discharged in excess, and the amount of developer in the developing device can be stabilized. Effect of the Invention

[0020] According to the present invention, it is possible to suppress fluctuations in the amount of developer discharged and stabilize the amount of developer within the developing device. [Brief description of the drawings]

[0021] [Figure 1] 1 is a cross-sectional view showing a schematic configuration of an image forming apparatus according to a first embodiment of the present invention. [Diagram 2] 1 is a perspective view showing a developing device according to a first embodiment of the present invention. [Diagram 3] 1 is a cross-sectional view showing a developing device according to a first embodiment of the present invention. [Figure 4] 4 is a cross-sectional view taken along the line AA in FIG. [Diagram 5]5 is a cross-sectional view taken along line BB in FIG. [Figure 6] FIG. 2 is an enlarged perspective view of a front portion of the developing device, with a portion cut away; [Figure 7] 4 is a perspective view showing a front portion of a first transport screw provided in the developing device. FIG. [Figure 8A] FIG. 4 is a perspective view showing a mounting structure of a peripheral wall member in the developing device; [Figure 8B] FIG. 4 is a perspective view showing a state in which a peripheral wall member is attached to the developing device. [Figure 9A] FIG. 4 is a perspective view showing an attachment structure of a regulating member in the developing device. [Figure 9B] FIG. 4 is a perspective view showing a state in which a regulating member is attached to the developing device. [Figure 10] FIG. 4 is a cross-sectional view illustrating a flow of developer in the developing device. [Figure 11] 5 is a cross-sectional view illustrating a flow of developer in a comparative example of the present embodiment. FIG. [Figure 12A] FIG. 11 is a perspective view showing a front portion of a developing device according to a second embodiment of the present invention. [Figure 12B] FIG. 2 is a perspective view showing a front portion of the developing device. [Figure 13] FIG. 11 is an explanatory diagram showing an enlarged view of a front portion of a developing device according to a third embodiment of the present invention. [Figure 14] FIG. 2 is a perspective view showing the developing device as viewed obliquely from above. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] A developing device according to an embodiment of the present invention and an image forming apparatus including the developing device will be described with reference to the drawings.

[0023] (Overall configuration of image forming apparatus) 1 is a cross-sectional view showing a schematic configuration of an image forming apparatus 1 according to an embodiment of the present invention. In the embodiment, a case in which the present invention is applied to a color multifunction peripheral that forms a color image on a sheet will be described as an example of the image forming apparatus 1.

[0024] The image forming apparatus 1 can be applied to various image forming apparatuses including a color printer, a monochrome multifunction machine, a monochrome printer, etc. As the recording medium sheet, paper, an overhead projector sheet, etc. can be used. In addition, when the image forming apparatus 1 is viewed from the front as shown in the figure, in the front-to-rear direction X, the front side (near side) of the image forming apparatus 1 is the front direction X1, the back side (rear side) of the image forming apparatus 1 is the rear direction X2, and in the left-to-right direction Y, the left side is the left direction Y1, and the right side is the right direction Y2, in the following description.

[0025] The image forming device 1 is a multifunction device having a scanner function, a copy function, a printer function, a facsimile function, etc., and transmits an image of an original document read by the image reading device 18 to the outside (corresponding to the scanner function), and also forms an image of the read original document or an image received from the outside on a sheet in color or monochrome (corresponding to the copy function, printer function, and facsimile function).

[0026] The image forming apparatus 1 includes a charging device 12, an optical scanning device 11, a developing device 10, a photosensitive drum 13, a drum cleaning device 14, an image transfer section 15, a paper feeding device 17, an image reading device 18, a fixing device 27, a sheet transport path 31, and the like.

[0027] The image forming apparatus 1 handles image data corresponding to color images using the colors black (K), cyan (C), magenta (M), and yellow (Y), or monochrome images using a single color (e.g., black). The image reading device 18 reads an original document or an original document conveyed from an original document conveying section (ADF) to generate image data. The image transfer section 15 of the image forming apparatus 1 is provided with four developing devices 10, four photoconductor drums 13, four drum cleaning devices 14, and four charging devices 12 for forming four types of toner images, and four image stations Pa, Pb, Pc, and Pd are configured so that the image stations correspond to black, cyan, magenta, and yellow, respectively.

[0028] The drum cleaning device 14 removes and collects residual toner on the surface of the photoreceptor drum 13. The charging device 12 charges the surface of the photoreceptor drum 13. The optical scanning device 11 exposes the surface of the photoreceptor drum 13 to light to form an electrostatic latent image. The developing device 10 develops the electrostatic latent image on the surface of the photoreceptor drum 13 to form a toner image on the surface of the photoreceptor drum 13. Through this series of operations, a toner image of each color is formed on the surface of each photoreceptor drum 13.

[0029] Above the photoconductor drums 13, intermediate transfer rollers 16 are disposed with intermediate transfer belt 21 interposed therebetween. The intermediate transfer belt 21 is an image carrier on which a toner image is formed, and is stretched around a transfer drive roller 22 and a transfer driven roller 23, rotating (moving in a circular motion) in the direction of arrow C. The toner images of each color formed on the surface of each photoconductor drum 13 are transferred (primary transfer) and superimposed, forming a color toner image on the surface of the intermediate transfer belt 21.

[0030] A transfer roller 26 of the secondary transfer unit 25 forms a nip area (secondary transfer position) between itself and the intermediate transfer belt 21, and conveys the sheet conveyed through the sheet conveying path 31 by pinching it therebetween. When the sheet passes through the nip area, the toner image on the surface of the intermediate transfer belt 21 is transferred to the sheet, and the sheet is conveyed to the fixing device 27. Toner and the like remaining on the intermediate transfer belt 21 are collected by the belt cleaning device 24.

[0031] The fixing device 27 includes a fixing roller 28 and a pressure roller 29 that rotate while sandwiching the sheet. The fixing device 27 sandwiches the sheet, on which the toner image has been transferred, between the fixing roller 28 and the pressure roller 29 and applies heat and pressure to fix the toner image to the sheet.

[0032] The paper feeder 17 stores sheets used for image formation, and is provided below the optical scanning device 11. The sheet is pulled out from the paper feeder 17 by a pickup roller 33, transported through a sheet transport path 31, and transported to a paper output tray 37 via a paper output roller 36 after passing through a secondary transfer unit 25 and a fixing device 27. Various pairs of rollers are arranged in the sheet transport path 31, such as a registration roller 35 that temporarily stops the sheet, aligns the leading edge of the sheet, and then starts transporting the sheet in accordance with the transfer timing of the color toner image in the nip area between the intermediate transfer belt 21 and the transfer roller 26, a plurality of transport rollers 34 that promote the transport of the sheet, and a paper output roller 36.

[0033] When an image is to be formed on the back side as well as the front side of the sheet, the sheet is transported in the reverse direction from the discharge rollers 36 to the sheet reversing transport path 32 to invert the sheet, and the sheet is guided again to the registration rollers 35, where an image is formed on the back side in the same manner as on the front side, and the sheet is transported to the discharge tray 37.

[0034] (Embodiment 1) FIG. 2 is a perspective view of the developing device 10 according to the first embodiment of the present invention as viewed from the front left side, and FIG.

[0035] The developing device 10 supplies non-magnetic toner contained in a two-component developer (developer) onto the surface of the photosensitive drum 13 by a development electric field formed between the photosensitive drum 13 and the developing device 10. As shown in FIG. 2, the developing device 10 has a housing 41 that is long in the front-rear direction X. As shown in FIG. 3, the housing 41 of the developing device 10 has an opening at a position facing the photosensitive drum 13. The photosensitive drum 13 is attached to a positioning portion 131 provided outside the housing 41 as shown in FIG. 2, and is disposed facing this opening.

[0036] The developing roller 44 is a magnet roller that functions as a developer carrier, and is disposed in a position facing the photosensitive drum 13 in the housing 41. The developing roller 44 includes a sleeve portion that is formed in a non-magnetic cylindrical shape (not shown) and is rotatable around a rotation shaft 441, and a magnetic roll portion that is cylindrical and disposed inside the sleeve portion and has magnetic properties. A plurality of magnetic poles, each of which has a single polarity, are formed on the circumferential surface of the developing roller 44 due to the magnetism of the magnetic roll portion. In the illustrated embodiment, the developing roller 44 is provided so that the sleeve portion rotates in a rotation direction R3 around the rotation shaft 441 disposed along the front-rear direction X. The developing roller 44 carries the developer on its surface and transports the toner contained in the carried developer to the surface of the photosensitive drum 13. The developer carried on the surface is regulated to a predetermined thickness by a regulating blade 45.

[0037] A rotation direction R3 of the developing roller 44 is set to be the same as a rotation direction R4 of the photosensitive drum 13 at a position facing the photosensitive drum 13. In a development region where the photosensitive drum 13 and the developing roller 44 face each other, an electrostatic latent image formed on the surface of the photosensitive drum 13 is developed with toner.

[0038] As shown in FIG. 3, the developing device 10 has a first chamber 51 and a second chamber 52 provided in the housing 41 as circulation chambers that transport and agitate the developer to be supplied to the developing roller 44 in the axial direction of the developing roller 44. The first chamber 51 and the second chamber 52 form a long space along the front-rear direction X in which the developer is accommodated. The first chamber 51 is provided with a first transport screw (first transport member) 60 that transports the developer in one direction, the front-rear direction X, which is the axial direction of the developing roller 44. The second chamber 52 is provided with a second transport screw (second transport member) 70 that transports the developer in the other direction of the front-rear direction X.

[0039] Fig. 4 is a cross-sectional view taken along line AA in Fig. 3, and Fig. 5 is a cross-sectional view taken along line BB in Fig. 4. As shown in Fig. 4, the first chamber 51 and the second chamber 52 are provided adjacent to each other and are connected to each other via communication ports 541, 541 respectively disposed at both ends of the second conveying screw 70. These communication ports 541, 541 are formed at both ends of a partition wall 54 provided in the housing 41 and extending in the front-rear direction X.

[0040] In the illustrated embodiment, the first transport screw 60 transports the developer in a forward direction X1 while stirring the developer, and the second transport screw 70 transports the developer in a backward direction X2 opposite to the transport direction of the first transport screw 60 while stirring the developer.

[0041] Therefore, the developer contained in the first chamber 51 is transported in the first transport direction D1 while being stirred by the first transport screw 60, and reaches the second chamber 52 from the first chamber 51 by passing through the communication port 541 provided in the forward direction X1. The developer contained in the second chamber 52 is transported in the second transport direction D2 while being stirred by the second transport screw 70, and reaches the first chamber 51 from the second chamber 52 by passing through the communication port 541 provided in the rear direction X2. In this way, the developer is transported so as to circulate between the first chamber 51 and the second chamber 52.

[0042] Further, the first chamber 51 is provided with a discharge chamber 53 at an end in the forward direction X1 in communication with the first chamber 51. As shown in FIG. 5, the discharge chamber 53 is provided at a downstream end in the first chamber 51 in the developer transport direction (first transport direction D1). As shown in FIGS. 2 and 5, a discharge section cover 43 is provided on the outside of the discharge chamber 53. The discharge chamber 53 is provided with a developer discharge port 531. A recovery container (not shown) is connected to the discharge port 531. Excess developer among the developer accommodated in the first chamber 51 is discharged from the discharge chamber 53 through the discharge port 531 to the recovery container.

[0043] As shown in FIG. 4, the second conveying screw 70 disposed in the second chamber 52 includes a helical blade 71 formed in a helical shape around a rotating shaft portion 72. The helical blade 71 rotates together with the rotating shaft portion 72 to send the developer in the second chamber 52 in the second conveying direction D2. On the other hand, the first conveying screw 60 disposed in the first chamber 51 includes a first helical blade (first blade) 61 and a second helical blade (second blade) 62 that are helically provided around a rotating shaft portion 64, and a third helical blade (third blade) 63 that is helically provided in a reverse winding shape to the first helical blade 61 and the second helical blade 62. The first helical blade 61, the second helical blade 62, and the third helical blade 63 are each integrally provided on the rotating shaft portion 64.

[0044] 6 is an enlarged perspective view, with a part cut away, of the front portion of the developing device 10, and FIG. 7 is a perspective view showing the front portion of the first transport screw 60. As shown in FIG.

[0045] More specifically, the first transport screw 60 includes a transport section 610 having a first helical blade 61 and transporting the developer in a first transport direction D1 (forward direction X1), a discharge section 620 having a second helical blade 62 and disposed in the discharge chamber 53 and transporting the developer in the first transport direction D1, which is the direction of the discharge port 531, and a reverse winding section 630 having a third helical blade 63 and applying a transport force to the developer in a second transport direction D2 (rear direction X2) opposite to the first transport direction D1. The transport section 610 is provided on the rear direction X2 side of a rotating shaft section 64 extending in the front-rear direction X, and the discharge section 620 is provided on the front direction X1 side. The reverse winding section 630 is provided on the rear direction X2 side between the transport section 610 and the discharge section 620. Furthermore, between the reverse winding portion 630 and the discharge portion 620, a boundary portion 640 is provided which is made up of only the rotating shaft portion 64 and does not have any spiral blades.

[0046] As shown in FIG. 7, the helical pitch P1 of the first helical blade 61 is set to be larger than the helical pitch P4 of the second helical blade 62 and larger than the helical pitches P2 and P3 of the third helical blade 63. In particular, the helical pitches P2 and P3 of the third helical blade 63 are smaller than the helical pitch P1 of the first helical blade 61, and are set at approximately 1 / 4 to 1 / 2 of the helical pitch P1. The helical pitches P1 to P4 relate to the distance the developer is transported when the first transport screw 60 rotates once, and a larger helical pitch can increase the transport force. In the illustrated embodiment, the helical pitch P2 and the helical pitch P3 are equal.

[0047] Among the first helical blade 61, the second helical blade 62, and the third helical blade 63, the first helical blade 61 has the greatest number of helical threads, followed by the second helical blade 62. In the illustrated embodiment, the third helical blade 63 has the fewest number of helical threads, with three threads as shown. The developer enters between these helical blades, and the helical blades form the developer flow, so it can be said that the greater the number of threads, the greater the developer transport force.

[0048] Furthermore, the second helical blade 62 has an outer diameter S4 smaller than the outer diameter S1 of the first helical blade 61 and the outer diameters S3 and S2 of the third helical blade 63. The third helical blade 63 has an outer diameter S3 larger than the outer diameter S1 of the first helical blade 61. In the first transport screw 60, the difference between the outer diameter S1 of the first helical blade 61 and the outer diameter (shaft diameter) S5 of the rotating shaft portion 64 is related to the area of ​​the first helical blade 61, so it can be said that the larger the outer diameter of the first helical blade 61, the greater the developer transport force.

[0049] Further, the third spiral blade 63 has an outer diameter S2 that is smaller on the transport section 610 side than on the discharge section 620 side. That is, as shown in FIG. 7, the third spiral blade 63 has a reverse-wound small diameter portion 631 having a small outer diameter S2 on the upstream side of the developer transport direction (first transport direction D1) from the transport section 610, and has a reverse-wound large diameter portion 632 having an outer diameter S3 on the downstream side. The outer diameter S2 of the reverse-wound small diameter portion 631 is smaller than the outer diameter S3 of the reverse-wound large diameter portion 632. Furthermore, the outer diameter S2 of the third spiral blade 63 on the transport section 610 side is smaller than the outer diameter S1 of the first spiral blade 61. Further, the rotating shaft portion 64 in the reverse-wound portion 630 is provided with an outer diameter S6 that is smaller than the outer diameter S5 of the rotating shaft portion 64 in the transport section 610.

[0050] Further, the reverse-wound large diameter portion 632 of the third spiral blade 63 is provided on the discharge portion 620 side so as to have an outer diameter S3 that is equal to at least one pitch of the spiral pitch P2. As shown in Fig. 7, the reverse-wound large diameter portion 632 and the reverse-wound small diameter portion 631 are connected via a step 633 having a size equivalent to the difference in the outer diameters. The reverse-wound large diameter portion 632 is provided with a spiral pitch P2, and the reverse-wound small diameter portion 631 is provided with a spiral pitch P3 equal to the spiral pitch P2. The reverse-wound large diameter portion 632 and the reverse-wound small diameter portion 631 may be connected in a shape that gradually decreases continuously from the outer diameter S3 to the outer diameter S2 without a step.

[0051] As a result, in the third spiral blade 63 of the reverse wound portion 630, the conveying force acting on the developer in the second conveying direction D2 is weaker in the reverse wound small diameter portion 631 of the outer diameter S2 than in the reverse wound large diameter portion 632. In addition, since the third spiral blade 63 has the reverse wound small diameter portion 631 on the conveying portion 610 side, as shown in Fig. 6, the outer periphery of the reverse wound small diameter portion 631 has a space (gap) larger than the outer periphery of the reverse wound large diameter portion 632. Therefore, the developer conveyed in the first conveying direction D1 through the conveying portion 610 by the first conveying screw 60 is easily allowed to enter the third spiral blade 63 due to the space in the outer periphery of the reverse wound small diameter portion 631 on the conveying portion 610 side of the reverse wound portion 630.

[0052] On the other hand, the third spiral blade 63 acts to transport the developer in a second transport direction D2 opposite to the first transport direction D1. Since a space is also generated above the outer periphery of the reversely wound small diameter portion 631, the developer is likely to wrap around when the developer has high fluidity. Therefore, as shown in FIG. 6, a peripheral wall member 81 and a regulating member 83 are provided on the discharge chamber 53 side of the first chamber 51 to prevent the developer from being excessively discharged. The peripheral wall member 81 is provided so as to cover at least the upper part of the outer periphery of the third spiral blade 63. The regulating member 83 is also provided at the boundary portion 640 of the first transport screw 60.

[0053] 8A and 8B are perspective views showing the mounting structure of the peripheral wall member 81, and Fig. 9A and 9B are perspective views showing the mounting structure of the regulating member 83. In Fig. 8A and 8B, in order to make the drawings easier to see, the second conveying screw 70 disposed in the second chamber 52 across the partition wall 54 is omitted.

[0054] As shown in FIG. 8B, the peripheral wall member 81 is a protruding block body that protrudes between the first chamber 51 and the second chamber 52. In the illustrated embodiment, as shown in FIG. 8A, the peripheral wall member 81 has a cylindrical surface 811 that is arranged to face the outer periphery of the third spiral blade 63 of the first conveying screw 60, and a fixing portion 812 is provided above the cylindrical surface 811. The cylindrical surface 811 is formed in a curved shape having an inner diameter that can secure a gap between the outer diameter S3 of the reverse-wound large diameter portion 632 of the third spiral blade 63. In this case, the cylindrical surface 811 is provided on two surfaces so as to face both the first chamber 51 side and the second chamber 52 side.

[0055] The fixing portion 812 is attached to the inner surface of the mounting member 46 provided above the third spiral blade 63, and the peripheral wall member 81 is fixed thereto. Note that the peripheral wall member 81 is not limited to being provided above the third spiral blade 63 as shown in Fig. 8B, but may be provided so that two peripheral wall members 81 are arranged above and below with their protrusions butted against each other, as shown in Fig. 9A, to integrally cover one side of the outer periphery of the third spiral blade 63 from above to below.

[0056] 9A, the restricting member 83 is a plate-like member having a through hole 831. The through hole 831 is formed with an inner diameter smaller than the outer diameter S3 of the reverse-wound large diameter portion 632 of the third spiral blade 63.

[0057] The regulating member 83 is fitted in the front-rear direction X from the second helical blade 62 side to the first conveying screw 60 arranged in parallel to the second conveying screw 70 via the partition wall 54. As shown in FIG. 9B, after the regulating member 83 is attached, a discharge case 532 having a discharge port 531 is fitted onto the second helical blade 62. The discharge chamber 53 is provided in the internal space of this discharge case 532. As shown in FIG. 6, the regulating member 83 is disposed at the end of the first chamber 51 on the discharge chamber 53 side. The boundary portion 640 of the first conveying screw 60 is disposed within the through hole 831.

[0058] 10 is a cross-sectional explanatory view showing the flow of developer in the developing device 10 according to embodiment 1. As shown in the figure, the peripheral wall member 81 has a length L1 in the axial direction (front-rear direction X) of the rotating shaft portion 64 that is long enough to cover the reversely wound large diameter portion 632 of the third spiral blade 63. The peripheral wall member 81 is preferably provided over at least one spiral pitch of the third spiral blade 63 (spiral pitches P2 and P3 shown in FIG. 7).

[0059] The cylindrical surface 811 on the inner surface of the peripheral wall member 81 is disposed with a gap G1 from the outer periphery of the third spiral blade 63. For example, this gap G1 is preferably set to 0.5 mm or less. Furthermore, at a minimum, a gap G2 is provided between the bottom surface of the first chamber 51 and the third spiral blade 63 and from the outer periphery of the reverse-wound large diameter portion 632.

[0060] A restricting member 83 is provided adjacent to the peripheral wall member 81 in the forward direction X1. As shown in Fig. 10, a through hole 831 of the restricting member 83 is formed with an inner diameter smaller than the outer diameter of the reverse-wound large diameter portion 632 of the third spiral blade 63, and is disposed on the outer periphery of the boundary portion 640.

[0061] FIG. 11 is a cross-sectional explanatory view showing the flow of developer in a comparative example for this embodiment in which neither the peripheral wall member 81 nor the regulating member 83 is provided.

[0062] The fluidity of the developer changes depending on the usage conditions such as humidity. In particular, when the fluidity decreases, as shown in Fig. 11, the developer transported in the first transport direction D1 by the first spiral blade 61A becomes easily clogged, and even if it reaches the reverse-wound third spiral blade 63A, it becomes difficult for the developer to advance in the direction of the third spiral blade 63A.

[0063] 11, when the third spiral blade 63A is formed with a constant outer diameter without having a large diameter portion and a small diameter portion, the gap at the outer periphery of the third spiral blade 63A becomes narrow (the outer diameter S3 of the third spiral blade 63 is larger than the outer diameter S1 of the first spiral blade 61), and therefore, when the fluidity of the developer deteriorates, the developer tends to stagnate D11. As a result, the amount of developer sent to the second spiral blade 62A decreases, and the amount of developer discharged from the discharge chamber 53A may decrease.

[0064] On the other hand, developer with increased fluidity tends to float. Since a space is created above the third spiral blade 63A that does not have the peripheral wall member 81, developer with high fluidity tends to wrap around from above D12. As shown in FIG. 11, since no regulating member 83 is provided in the rear direction X2 of the discharge chamber 53A, the wrapped around developer tends to enter the discharge chamber 53A. In such a case, there is a risk that the amount of developer discharged from the discharge chamber 53A will increase.

[0065] In this way, if neither the peripheral wall member 81 nor the regulating member 83 is provided, the amount of developer discharged will fluctuate due to the influence of the fluidity of the developer, and the amount of developer in the device will not be stable.

[0066] 10, in the developing device 10 according to the present embodiment, a peripheral wall member 81 is provided on the outer periphery of the third spiral blade 63, so that even if the developer has high fluidity, the floating developer can be prevented from wrapping around or scattering from above the third spiral blade 63, and the developer can be prevented from flowing excessively toward the discharge portion 620. In addition, a regulating member 83 is provided between the reverse winding portion 630 and the discharge portion 620, so that a through hole 831 having an inner diameter smaller than the outer diameter of the third spiral blade 63 acts as a resistance to the developer entering the discharge chamber 53, and the developer can be prevented from being excessively sent to the discharge chamber 53.

[0067] Furthermore, since the third spiral blade 63 is configured with a reverse-wound small diameter portion 631 and a reverse-wound large diameter portion 632, even if the fluidity of the developer decreases, the developer transported in the first transport direction D1 can be prevented from stagnating or clogging in the reverse-wound portion 630.

[0068] For example, the outer periphery of the third spiral blade 63 is provided with a gap G1 between the peripheral wall member 81 and a gap G2 between the peripheral wall member 81 and the bottom surface of the first chamber 51, and these gaps allow the developer with reduced fluidity to flow from the third spiral blade 63 toward the second spiral blade 62 without stagnation. That is, the developer transported in the first transport direction D1 by the first spiral blade 61 and entering the space in the outer periphery of the reverse-wound small diameter portion 631 on the transport section 610 side of the reverse-wound portion 630 and the developer transported in the second transport direction D2 from the reverse-wound large diameter portion 632 of the third spiral blade 63 collide with each other at the outer periphery of the reverse-wound small diameter portion 631, forming a circulating flow D10. Therefore, a shear force due to the flow D10 acts on the developer, and the developer does not aggregate even if the developer has reduced fluidity, so that a constant amount of developer is always sent through the gap G2 in the first transport direction D1. That is, it becomes possible to always discharge a constant amount of developer from the discharge chamber 53A regardless of the fluidity of the developer.

[0069] As described above, the outer diameter (S6) of the rotating shaft portion 64 at the reverse winding portion 630 and the discharge portion 620 is set smaller than the outer diameter (S5) at the transport portion 610. This also makes it possible to secure as large a space as possible for the developer to enter, making it easier for the developer to enter in the direction of the discharge portion 620.

[0070] Therefore, regardless of whether the fluidity of the developer decreases or increases, it is possible to maintain the amount of developer discharged at an appropriate level, and the amount of developer circulating in the first chamber 51 and the second chamber 52 can be stabilized.

[0071] (Embodiment 2) 12A and 12B are perspective views showing a front portion of a developing device 10 according to the second embodiment.

[0072] The peripheral wall member 81 provided on the discharge chamber 53 side of the first chamber 51 is preferably configured to cover at least the upper part of the outer periphery of the third spiral blade 63, and is not limited to the configuration shown in the above-mentioned embodiment 1. For example, as shown in FIG. 12A, the peripheral wall member 81 may be provided with a curved cylindrical surface 813 that covers one side of the outer periphery of the third spiral blade 63 from the upper to the lower part. In this case, the peripheral wall member 81 has cylindrical surfaces 813 symmetrically provided on both sides. In addition, fixing parts 814 are provided above and below the peripheral wall member 81. The cylindrical surface 813 has a length of at least one helical pitch of the third spiral blade 63 in the front-rear direction X.

[0073] 12B, the peripheral wall member 81 is fitted and attached from the second helical blade 62 side of the first conveying screw 60 to the side of the third helical blade 63. The peripheral wall member 81 narrows the gap at the outer periphery of the third helical blade 63 of the first conveying screw 60.

[0074] Even in this configuration, as in the first embodiment, even if the fluidity of the developer increases, the floating developer can be prevented from flowing around or scattering from above or to the sides of the third spiral blade 63, and the developer can be prevented from flowing excessively toward the discharge section 620.

[0075] (Embodiment 3) FIG. 13 is an explanatory diagram showing an enlarged view of the peripheral wall member 82 in the developing device 10 according to the third embodiment together with the front portion of the first transport screw 60, and FIG. 14 is a perspective view showing the peripheral wall member 82 as viewed obliquely from above.

[0076] In the first and second embodiments, the block-shaped peripheral wall member 81 is provided on the outer periphery of the first transport screw 60. The developing device 10 according to the present invention is not limited to this configuration, and the peripheral wall member 82 may be an elastic sheet-like member.

[0077] As shown in Fig. 13, the peripheral wall member 82 made of a sheet-like member is provided adjacent to the discharge chamber 53 in the rear direction X2 of the discharge chamber 53. Also, as shown in Fig. 14, the peripheral wall member 82 is provided in a substantially cylindrical shape so as to surround the third helical blade 63 of the first conveying screw 60. An inner circumferential surface 821 of the peripheral wall member 82 is disposed with a gap provided between it and the third helical blade 63. It is preferable that the length L2 of the peripheral wall member 82 in the front-rear direction X is set to a length covering at least one pitch of the third helical blade 63 in the forward direction X1 (for example, equivalent to the helical pitch P2 of the reverse-wound large diameter portion 632 shown in Fig. 7).

[0078] Even in this configuration, as in the first and second embodiments, it is possible to prevent floating developer from wrapping around or scattering from above or around the sides of the third spiral blade 63, and it is possible to prevent the developer from flowing excessively toward the discharge section 620.

[0079] With the above-mentioned configuration, in the developing device 10, even if the fluidity of the developer changes, it is possible to suppress fluctuations in the amount of developer discharged from the discharge chamber 53. As a result, it is possible to stabilize the amount of developer in the first chamber 51 and the second chamber 52 of the developing device 10, and the developer pressure is appropriately maintained, which contributes to high-quality image formation.

[0080] The present invention is not limited to the above-described embodiments, and can be embodied in various other forms. For example, the shapes of the peripheral wall members 81, 82 are not limited to those shown in the above-described embodiments. The helical pitch and number of threads of the second helical blade 62 and the third helical blade 63 are also not limited, and may be configured in any way. Therefore, the above-described embodiments are merely illustrative in every respect and should not be interpreted as being restrictive. The scope of the present invention is defined by the claims, and is not bound by the description. Furthermore, all modifications and changes within the scope of the claims are within the scope of the present invention. [Explanation of symbols]

[0081] 1. Image forming device 10 Developing device 11 Optical scanning device 12 Charging device 13 Photoconductor drum 44 Developing roller (developer carrier) 441 Rotational axis 51 Room 1 (Circulation room) 52 2nd room (circulation room) 53 Discharge chamber 531 Outlet 54 Partition Wall 541 Connecting port 60 First conveying screw (first conveying member) 61 First spiral blade (first blade) 62 Second spiral blade (second blade) 63 3rd spiral blade (3rd blade) 631 Reverse winding small diameter section 632 Reverse winding large diameter section 64 Rotating shaft 610 Conveyor 620 Discharge section 630 Reverse winding section 640 Boundary 70 Second conveying screw (second conveying member) 71 Spiral Blade 72 Rotating shaft 81, 82 Peripheral wall member 811, 813 Cylindrical surface 812, 814 Fixed part 83 Regulatory Materials 831 Through hole

Claims

1. A developing device having a circulation chamber that conveys and agitates a developer to be supplied to a developer carrier in an axial direction of the developer carrier, the circulation chamber includes a first chamber including a first transport member that transports the developer in one direction in the axial direction, and a second chamber that includes a second transport member that transports the developer in the other direction in the axial direction and supplies the developer to the developer carrier; the first chamber and the second chamber are connected via communication ports disposed at both ends of the second conveying member, a discharge chamber having a developer discharge port is provided at an end of the first chamber in communication with the end of the first chamber, The first conveying member is a transport section including a spiral first blade for transporting the developer in the one direction; a discharge portion provided in the discharge chamber and including a spiral second blade for feeding the developer in the one direction; a reverse winding portion provided between the conveying portion and the discharge portion and including a third blade having a spiral shape that is reverse wound to the first blade, the third blade has an outer diameter that is smaller on the conveying section side than on the discharge section side, A developing device characterized in that an outer diameter of the third blade closest to the discharge portion is larger than an outer diameter of the first blade, and an outer diameter of a rotating shaft portion of the third blade is smaller than an outer diameter of a rotating shaft portion of the first blade.

2. 2. The developing device according to claim 1, The developing device, wherein the third blade has an outer diameter on the transport portion side smaller than an outer diameter of the first blade.

3. 3. The developing device according to claim 1, The developing device, wherein the third blade has a constant outer diameter over at least one helical pitch on the discharge portion side.

4. In the developing device according to any one of claims 1 to 3, a peripheral wall member that covers at least an upper portion of an outer periphery of the third blade, the peripheral wall member being provided on the discharge chamber side of the first chamber.

5. 5. The developing device according to claim 4, a peripheral wall member having a length in the axial direction that is at least equivalent to one helical pitch of the third blade;

6. 6. The developing device according to claim 4, a developing device, the peripheral wall member being disposed with a gap provided relative to an outer periphery of the third blade, the minimum gap being set to 0.5 mm or less.

7. In the developing device according to any one of claims 4 to 6, The developing device according to claim 1, wherein the peripheral wall member has a protruding portion protruding between the first chamber and the second chamber.

8. In the developing device according to any one of claims 4 to 6, The developing device according to claim 1, wherein the peripheral wall member is a sheet-like member having elasticity.

9. The developing device according to any one of claims 1 to 8, the first conveying member includes a boundary portion between the reverse winding portion and the discharge portion that does not have a spiral blade, A developing device characterized in that a regulating member having a through hole with an inner diameter smaller than the outer diameter of the third blade is provided at the end of the first chamber on the discharge chamber side, and the boundary portion is disposed within the through hole.

10. The developing device according to any one of claims 1 to 9, A developing device, wherein the helical pitch of the first blade is larger than the helical pitch of the third blade.

11. An image forming apparatus comprising the developing device according to any one of claims 1 to 10.

Images