Developing device and image forming apparatus

Abstract

To provide a developing device that can improve dispersibility of developer in a developer container to realize uniform image formation with suppressed density unevenness.SOLUTION: A developing device 40 comprises a developer container 50, a first conveying member 42 and a second conveying member 43, and a developing roller 44. The first conveying member 42 has a rotation shaft 42a, a first conveying blade 42b, a cut-out part 42c, and a holding part 42e. The cut-out part 42c is a portion where the first conveying blade 42b is partially cut out in a longitudinal direction. The holding part 42e is formed on an outer peripheral part of the rotation shaft 42a opposite to the cut-out part 42c, and extends in a radial direction of the rotation shaft 42a, and has a peripheral end surface 42f having an area larger than the cross sectional area of the first conveying blade 42b.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a developing device and an image forming apparatus. [Background technology]

[0002] Electrophotographic image forming devices such as copiers and printers widely use devices that supply toner to an electrostatic latent image formed on the outer peripheral surface of an image carrier such as a photosensitive drum, thereby developing the image and forming a toner image that is later transferred to paper.In order to continuously form uniform images, the image forming device conveys a developer containing toner contained in a developer container while stirring it within the developer container.

[0003] The developer stirring and transporting member of a conventional developing device disclosed in Patent Document 1 has multiple helical blades formed to extend in a spiral shape around a rotation shaft, and a discontinuous portion where the helical blades are divided into opposing first and second helical blades so that they are discontinuous in the extension direction. This creates turbulence in the developer, preventing the developer from sticking or accumulating. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-134619 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the prior art, the turbulence of the developer caused by the end face (cross section) of the spiral blade adjacent to the discontinuous portion had a low stirring effect on the developer, and there was a risk that sufficient stirring (dispersibility) could not be ensured, which raised concerns that it would be impossible to achieve a uniform image with reduced density unevenness.

[0006] The present invention has been made in consideration of the above points, and aims to provide a developing device and an image forming device that can improve the dispersibility of developer in a developing container and achieve uniform image formation with suppressed density unevenness. [Means for solving the problem]

[0007] In order to solve the above problems, the developing device of the present invention includes a developer container, a transport member, and a developer carrier. The developer container contains a developer containing toner to be supplied to an image carrier. The transport member is rotatably supported in the developer container and transports the developer while stirring it. The developer carrier is rotatably supported in the developer container facing the image carrier and supplies the toner in the developer container to the image carrier. The transport member has a rotation shaft, a transport blade, a cutout portion, and a dispersion portion. The rotation shaft extends along the longitudinal direction of the developer container. The transport blade is formed in a spiral shape on the outer periphery of the rotation shaft. The cutout portion is formed by partially cutting out the transport blade in the longitudinal direction. The dispersion portion is formed on the outer periphery of the rotation shaft facing the cutout portion, extends in the radial direction of the rotation shaft, and has a dispersion surface with an area larger than the cross-sectional area of ​​the transport blade. [Effects of the Invention]

[0008] According to the configuration of the present invention, the area of ​​the dispersion surface is larger than the cross-sectional area of ​​the transport blade, so that the dispersion section can send out the developer in a direction different from the direction of transport of the developer by the transport blade. In other words, the dispersion section can promote dispersion (agitation) of the developer. This improves the dispersibility of the developer in the developer container, making it possible to achieve uniform image formation with reduced density unevenness. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic cross-sectional front view of an image forming apparatus according to an embodiment of the present invention; [Figure 2] 2 is a schematic cross-sectional front view of the periphery of an image forming unit of the image forming apparatus of FIG. 1. [Figure 3]3 is a horizontal cross-sectional plan view of the developing device of the image forming unit of FIG. 2. [Figure 4] 4 is a partial side view of a first conveying member of the developing device of FIG. 3. FIG. [Figure 5] 5 is a partial side view of the first conveying member as seen from the opposite side to FIG. 4. FIG. [Figure 6] FIG. 5 is a partial perspective view of the first conveying member of FIG. 4. [Figure 7] FIG. 10 is a partial side view of a first conveying member of Modified Example 1. [Figure 8] 8 is a partial side view of the first conveying member of the first modified example as viewed from the opposite side of FIG. 7. FIG. [Figure 9] FIG. 10 is a partial side view of a first conveying member of Modified Example 2. [Figure 10] 10 is a partial side view of a first conveying member of Modification 2 as viewed from the opposite side of FIG. 9. FIG. [Figure 11] FIG. 11 is a partial side view of a first conveying member of Modified Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings, but the present invention is not limited to the following.

[0011] Fig. 1 is a schematic cross-sectional front view of an image forming apparatus 1 according to an embodiment. Fig. 2 is a schematic cross-sectional front view of the periphery of an image forming unit 20 of the image forming apparatus 1 shown in Fig. 1. An example of the image forming apparatus 1 according to this embodiment is a tandem color printer that transfers a toner image onto paper S using an intermediate transfer belt 31. The image forming apparatus 1 may be a so-called multifunction device that has functions such as printing, scanning (image reading), and facsimile transmission.

[0012] As shown in Figures 1 and 2, the image forming apparatus 1 includes a paper supply unit 3, a paper transport unit 4, an exposure unit 5, an image forming unit 20, a transfer unit 30, a fixing unit 6, a paper discharge unit 7, and a control unit 8, which are provided in its main body 2.

[0013] The paper supply unit 3 is located at the bottom of the main body 2. The paper supply unit 3 stores multiple sheets of paper S before printing, and separates and sends out the sheets S one by one during printing. The paper transport unit 4 extends vertically along the side wall of the main body 2. The paper transport unit 4 transports the paper S sent out from the paper supply unit 3 to the secondary transfer unit 33 and the fixing unit 6, and then ejects the paper S after fixing from the paper outlet 4a to the paper ejection unit 7. The exposure unit 5 is located above the paper supply unit 3. The exposure unit 5 irradiates the image forming unit 20 with laser light controlled based on image data.

[0014] The image forming units 20 are disposed above the exposure unit 5 and below the intermediate transfer belt 31. The image forming units 20 include an image forming unit 20Y for yellow, an image forming unit 20C for cyan, an image forming unit 20M for magenta, and an image forming unit 20B for black. These four image forming units 20 have the same basic configuration. Therefore, in the following description, the identification symbols "Y," "C," "M," and "B" representing each color may be omitted unless otherwise specified.

[0015] The image forming unit 20 includes a photosensitive drum (image carrier) 21 that is supported so as to be rotatable in a predetermined direction (clockwise in FIGS. 1 and 2). The image forming unit 20 further includes a charging unit 22, a developing device 40, and a drum cleaning unit 23 that are arranged around the photosensitive drum 21 along the direction of rotation of the photosensitive drum 21. A primary transfer unit 32 is arranged between the developing device 40 and the drum cleaning unit 23.

[0016] The photosensitive drum 21 is formed in a cylindrical shape extending horizontally, and has a photosensitive layer formed of, for example, an amorphous silicon photosensitive material on its outer circumferential surface. The charging unit 22 charges the surface (outer circumferential surface) of the photosensitive drum 21 to a predetermined potential. The exposure unit 5 exposes the outer circumferential surface of the photosensitive drum 21 charged by the charging unit 22 to light, forming an electrostatic latent image of the original image on the outer circumferential surface of the photosensitive drum 21. The developing device 40 supplies toner to this electrostatic latent image to develop it into a toner image. Each of the four image forming units 20 forms a toner image of a different color. The drum cleaning unit 23 removes and cleans any toner remaining on the outer circumferential surface of the photosensitive drum 21 after the toner image has been primarily transferred to the outer circumferential surface of the intermediate transfer belt 31. In this way, the image forming unit 20 forms an image (toner image) that will later be transferred to paper S.

[0017] The transfer unit 30 includes an intermediate transfer belt 31, primary transfer units 32Y, 32C, 32M, and 32B, a secondary transfer unit 33, and a belt cleaning unit 34. The intermediate transfer belt 31 is disposed above the four image forming units 20. The intermediate transfer belt 31 is supported so as to be rotatable in a predetermined direction (counterclockwise in FIG. 1), and is an endless intermediate transfer body onto which the toner images formed by each of the four image forming units 20 are sequentially superimposed and primarily transferred. The four image forming units 20 are disposed in a so-called tandem arrangement, lined up in a row from the upstream side to the downstream side in the rotation direction of the intermediate transfer belt 31.

[0018] Primary transfer units 32Y, 32C, 32M, and 32B are disposed above image forming units 20Y, 20C, 20M, and 20B of the respective colors, with intermediate transfer belt 31 sandwiched between them. Secondary transfer unit 33 is disposed upstream of fixing unit 6 in the paper conveying direction of paper conveying unit 4, and downstream of four image forming units 20Y, 20C, 20M, and 20B in the rotation direction of intermediate transfer belt 31. Belt cleaning unit 34 is disposed downstream of secondary transfer unit 33 in the rotation direction of intermediate transfer belt 31.

[0019] The primary transfer unit 32 transfers the toner image formed on the outer circumferential surface of the photosensitive drum 21 onto the intermediate transfer belt 31. In other words, the toner image is primarily transferred onto the outer circumferential surface of the intermediate transfer belt 31 at the primary transfer units 32Y, 32C, 32M, and 32B for each color. Then, as the intermediate transfer belt 31 rotates, the toner images of the four image forming units 20 are successively superimposed and transferred onto the intermediate transfer belt 31 at a predetermined timing, thereby forming a color toner image on the outer circumferential surface of the intermediate transfer belt 31 in which toner images of four colors, yellow, cyan, magenta, and black, are superimposed.

[0020] The color toner image on the outer circumferential surface of intermediate transfer belt 31 is transferred to paper S, which has been synchronously fed by paper transport unit 4, at a secondary transfer nip formed in secondary transfer unit 33. Belt cleaning unit 34 removes and cleans toner and other adhering matter remaining on the outer circumferential surface of intermediate transfer belt 31 after secondary transfer. In this way, transfer unit 30 transfers (records) the toner image formed on the outer circumferential surface of photosensitive drum 21 onto paper S.

[0021] The fixing unit 6 is disposed above the secondary transfer unit 33. The fixing unit 6 fixes the toner image to the paper S by applying heat and pressure to the paper S onto which the toner image has been transferred.

[0022] The paper discharge section 7 is disposed above the transfer section 30. The paper S on which the toner image has been fixed and printing has been completed is transported to the paper discharge section 7. The paper discharge section 7 takes out the printed paper (printed matter) from above.

[0023] The control unit 8 includes a CPU, an image processing unit, a memory unit, and other electronic circuits and electronic components (none of which are shown). The CPU controls the operation of each component provided in the image forming apparatus 1 based on control programs and data stored in the memory unit to perform processing related to the functions of the image forming apparatus 1. The paper supply unit 3, paper transport unit 4, exposure unit 5, image forming unit 20, transfer unit 30, and fixing unit 6 each receive individual commands from the control unit 8 and work together to print on the paper S. The memory unit is configured by a combination of a non-volatile storage device such as a program ROM (Read Only Memory) or a data ROM, and a volatile storage device such as a RAM (Random Access Memory).

[0024] Next, the configuration of the developing device 40 will be described using FIG. 3 in addition to FIG. 2. FIG. 3 is a horizontal cross-sectional plan view of the developing device 40 of the image forming unit 20 of FIG. 2. Note that the developing devices 40 for each color have the same basic configuration, so the identification symbols representing each color and their descriptions will be omitted. In addition, in this description, the "axial direction" refers to the axial direction of rotation of the photosensitive drum 21, first transport member 42, second transport member 43, and developing roller 44, which extend parallel to one another (the direction into the paper in FIG. 2, the direction to the left and right in FIG. 3).

[0025] The developing device 40 supplies toner to the outer peripheral surface of the photosensitive drum 21. The developing device 40 is detachable from, for example, the main body 2 of the image forming apparatus 1. The developing device 40 includes a developer container 50, a first transport member 42, a second transport member 43, a developing roller (developer carrier) 44, a regulating blade 45, a toner concentration sensor 46, a scraper 47, and a holding portion (dispersion portion) 42e.

[0026] The developing container 50 has an elongated shape extending along the axial direction of the photosensitive drum 21, and is disposed with its longitudinal direction horizontal. In other words, the longitudinal direction of the developing container 50 is parallel to the axial direction of the photosensitive drum 21. The developing container 50 contains, as the developer containing toner to be supplied to the photosensitive drum 21, for example, a two-component developer containing toner and a magnetic carrier.

[0027] The developing container 50 has a partition portion 51, a first transport chamber 52, a second transport chamber 53, a first communication portion 54, and a second communication portion 55.

[0028] The partition portion 51 is provided at the lower part inside the developing container 50. The partition portion 51 is disposed at approximately the center in a direction intersecting the longitudinal direction of the developing container 50 (the horizontal direction in FIG. 2, the vertical direction in FIG. 3). The partition portion 51 is formed in a generally plate shape extending in the longitudinal direction and the vertical direction of the developing container 50. The partition portion 51 divides the inside of the developing container 50 in a direction intersecting the longitudinal direction.

[0029] The first transport chamber 52 and the second transport chamber 53 are provided inside the developing container 50. The first transport chamber 52 and the second transport chamber 53 are formed by dividing the inside of the developing container 50 by a partition 51. The first transport chamber 52 and the second transport chamber 53 are arranged in parallel at approximately the same height.

[0030] The second transport chamber 53 is located adjacent to the photosensitive drum 21 and includes the periphery of the region where the developing roller 44 is disposed within the developing container 50. The first transport chamber 52 is located in a region within the developing container 50 that is farther away from the photosensitive drum 21 than the second transport chamber 53. A developer supply port 52a is opened in the first transport chamber 52, and developer is replenished into the developing container 50 through the developer supply port 52a. In the first transport chamber 52, the developer is transported in a first direction f1 by the first transport member 42. In the second transport chamber 53, the developer is transported in a second direction f2 opposite to the first direction f1 by the second transport member 43.

[0031] The first communication portion 54 and the second communication portion 55 are disposed on the outside of both longitudinal end portions of the partition portion 51. The first communication portion 54 and the second communication portion 55 communicate the first transfer chamber 52 and the second transfer chamber 53 in a direction intersecting the longitudinal direction of the partition portion 51 (the horizontal direction in FIG. 2, the vertical direction in FIG. 3), i.e., in the thickness direction of the approximately plate-shaped partition portion 51. In other words, the first communication portion 54 and the second communication portion 55 communicate the first transfer chamber 52 and the second transfer chamber 53 with each other at both longitudinal end sides thereof.

[0032] The first communication section 54 communicates the downstream end of the first transport chamber 52 in the first direction f1 with the upstream end of the second transport chamber 53 in the second direction f2. The first communication section 54 transports the developer from the first transport chamber 52 side toward the second transport chamber 53 side. The second communication section 55 communicates the downstream end of the second transport chamber 53 in the second direction f2 with the upstream end of the first transport chamber 52 in the first direction f1. The second communication section 55 transports the developer from the second transport chamber 53 side toward the first transport chamber 52 side.

[0033] The first transport member 42 is disposed in the first transport chamber 52. The second transport member 43 is disposed in the second transport chamber 53. The first transport member 42 and the second transport member 43 are disposed in parallel with each other at approximately the same height. The second transport member 43 extends in close proximity to and parallel to the developing roller 44. The first transport member 42 and the second transport member 43 are supported by the developing container 50 so as to be rotatable about an axis extending horizontally parallel to the developing roller 44.

[0034] The first transport member 42 and the second transport member 43 have the same basic configuration. The first transport member 42 has a spirally formed first transport blade 42b on the outer periphery of a rotation shaft 42a extending along the longitudinal direction of the developing container 50. In this embodiment, the first transport member 42 has two first transport blades 42b. The second transport member 43 has a spirally formed second transport blade 43b on the outer periphery of a rotation shaft 43a extending along the longitudinal direction of the developing container 50. In this embodiment, the second transport member 43 has two second transport blades 43b.

[0035] The first transport member 42 transports the developer while stirring it in a first direction f1 from the second communicating portion 55 side toward the first communicating portion 54 side along the rotation axis direction within the first transport chamber 52. The second transport member 43 transports the developer while stirring it in a second direction f2 from the first communicating portion 54 side toward the second communicating portion 55 side along the rotation axis direction within the second transport chamber 53. That is, the first transport member 42 and the second transport member 43 transport the developer while stirring it in opposite longitudinal directions, and circulate the developer in a predetermined circulation direction.

[0036] The developing roller 44 is located above the second conveying member 43 inside the developing container 50 and is disposed opposite the photosensitive drum 21. The developing roller 44 is supported by the developing container 50 so as to be rotatable about an axis extending parallel to the axis of the photosensitive drum 21.

[0037] A portion of the outer circumferential surface of the developing roller 44 is exposed from the developing container 50, and faces and is close to the photosensitive drum 21. The developing roller 44 carries toner on its outer circumferential surface to be supplied to the outer circumferential surface of the photosensitive drum 21 in the region facing the photosensitive drum 21. The developing roller 44 carries toner in the second transport chamber 53 of the developing container 50 and supplies it to the photosensitive drum 21. In other words, the developing roller 44 causes the toner in the second transport chamber 53 to adhere to the electrostatic latent image on the outer circumferential surface of the photosensitive drum 21, thereby forming a toner image.

[0038] The regulating blade 45 is disposed upstream in the rotation direction of the developing roller 44 in the opposing region between the developing roller 44 and the photosensitive drum 21. The regulating blade 45 is disposed closely opposing the developing roller 44 with a predetermined gap between its tip and the outer circumferential surface of the developing roller 44. The regulating blade 45 extends over the entire area of ​​the developing roller 44 in the axial direction. The regulating blade 45 regulates the layer thickness of the developer carried on the outer circumferential surface of the developing roller 44 that passes through the gap between the tip of the regulating blade 45 and the outer circumferential surface of the developing roller 44.

[0039] The toner concentration sensor 46 is disposed on a wall portion along the longitudinal direction (first direction f1) of the first transport chamber 52. The toner concentration sensor 46 is disposed opposite the first transport member 42. In this embodiment, a headless sensor is used as the toner concentration sensor 46. The toner concentration sensor 46, which is a headless sensor, has a detection surface embedded in the inner wall surface of the first transport chamber 52. The toner concentration sensor 46 detects the toner concentration in the developer.

[0040] More specifically, the toner concentration sensor 46 is a magnetic permeability detection sensor that obtains the toner concentration (the mixture ratio of toner T to carrier C in the developer; T / C) by detecting changes in the magnetic permeability of the two-component developer. If the ratio of toner to carrier in the developer in the first transport chamber 52 changes, the magnetic permeability also changes, and the output signal of the toner concentration sensor 46 changes accordingly. Based on the sensor output signal received from the toner concentration sensor 46, the control unit 8 controls the start and stop of replenishment of the developer (toner and carrier) to the developing device 40.

[0041] With respect to the toner concentration sensor 46, a scraper 47 is attached to the first conveying member 42. The scraper 47 is fixed to the rotation shaft 42a of the first conveying member 42 via a holding portion 42e in an area facing the toner concentration sensor 46. Details of the area around the scraper 47 will be described later.

[0042] The developer in the developing container 50 circulates in a predetermined circulation direction between the first transport chamber 52 and the second transport chamber 53 through the first communication portion 54 and the second communication portion 55 due to the rotation of the first transport member 42 and the second transport member 43. At this time, the toner in the developing container 50 is stirred and charged, and is carried on the outer peripheral surface of the developing roller 44. The developer carried on the outer peripheral surface of the developing roller 44 has its layer thickness regulated by the regulating blade 45, and is then carried to the opposing region between the developing roller 44 and the photosensitive drum 21 due to the rotation of the developing roller 44. When a predetermined development voltage is applied to the developing roller 44, the toner in the developer carried on the outer peripheral surface of the developing roller 44 moves to the outer peripheral surface of the photosensitive drum 21 in the opposing region due to the potential difference between the developing roller 44 and the surface (outer peripheral surface) of the photosensitive drum 21. As a result, the electrostatic latent image on the outer peripheral surface of the photosensitive drum 21 is developed with the toner.

[0043] The developing container 50 further has a discharge portion 56. The discharge portion 56 is provided further downstream than the downstream end of the second transport chamber 53 in the second direction f2. The discharge portion 56 is connected to the second transport chamber 53. The inside of the discharge portion 56 and the second transport chamber 53 are in communication with each other. The inner diameter of the discharge portion 56 is smaller than the inner diameter of the second transport chamber 53. The discharge portion 56 has a developer discharge port 561.

[0044] The rotation shaft 43a of the second transport member 43 extends continuously into the discharge portion 56. One axial end of the rotation shaft 43a is rotatably supported by the developing container 50 at the downstream end of the discharge portion 56 with respect to the second direction f2 of the second transport chamber 53.

[0045] The developer discharge port 561 is disposed at the downstream end of the discharge portion 56 in the second direction f2 of the second transport chamber 53. The developer discharge port 561 opens, for example, below the rotation shaft 43a of the second transport member 43. The developer discharge port 561 discharges excess developer in the developing container 50 to the outside.

[0046] The second conveying member 43 further includes a regulating blade 43c and a discharge blade 43d in addition to the second conveying blade 43b. These three blades are provided in the order of second conveying blade 43b, regulating blade 43c, and discharge blade 43d from the second conveying chamber 53 side toward the discharge section 56. Like the second conveying blade 43b, the regulating blade 43c and discharge blade 43d are provided integrally with the rotating shaft 43a and are formed in a spiral shape along the axial direction on the outer periphery of the rotating shaft 43a.

[0047] The regulating blade 43c is located downstream of the second conveying blade 43b in the second direction f2 of the second conveying chamber 53, and is disposed within the second conveying chamber 53. The regulating blade 43c faces the connection portion between the second conveying chamber 53 and the discharge section 56 in the axial direction of the rotation shaft 43a.

[0048] The regulating blade 43c has a winding direction opposite to that of the second transport blade 43b. As a result, the regulating blade 43c blocks the developer transported to the vicinity of the downstream end of the second transport chamber 53, and regulates the movement of the developer toward the discharge portion 56. The pitch of the regulating blade 43c is smaller than the pitch of the second transport blade 43b.

[0049] The outer periphery of the regulating blade 43c has a predetermined gap (clearance) between it and the inner surface of the developing container 50. When the amount of developer in the second conveying chamber 53 exceeds a predetermined amount, the developer is conveyed as excess developer through the gap between the outer periphery of the regulating blade 43c and the inner surface of the developing container 50 toward the discharge section 56.

[0050] The discharge blade 43d is located downstream of the regulating blade 43c in the second direction f2 of the second transport chamber 53, and is disposed within the discharge section 56. The discharge blade 43d has the same winding direction as the second transport blade 43b. That is, the transport direction of the developer within the discharge section 56 is the same as the second direction f2 of the second transport chamber 53. As a result, the discharge blade 43d transports excess developer within the discharge section 56 toward the developer discharge port 561. The outer diameter of the discharge blade 43d is smaller than the outer diameters of the second transport blade 43b and the regulating blade 43c. The pitch of the discharge blade 43d is smaller than the pitch of the second transport blade 43b.

[0051] Next, a more detailed configuration of the developing device 40 will be described using Figures 4, 5, and 6 in addition to Figure 3. Figure 4 is a partial side view of the first conveying member 42 of the developing device 40 in Figure 3. Figure 5 is a partial side view of the first conveying member 42 as seen from the opposite side of Figure 4. Figure 6 is a partial perspective view of the first conveying member 42 in Figure 4.

[0052] 4, 5, and 6, the first conveying member 42 has a cutout 42c. As shown in FIG. 3, the cutout 42c is formed in an area facing the toner concentration sensor 46. The first conveying blade 42b is partially cut out along the longitudinal direction (first direction f1) at the cutout 42c located in the area facing the toner concentration sensor 46. In this embodiment, the two first conveying blades 42bA, 42bB are cut out at different lengths in the axial direction of the rotation shaft 42a (the left-right lateral direction in FIGS. 4 and 5) at the cutout 42c.

[0053] According to the above configuration, the first transport blade 42b has the cutout portion 42c in the area facing the toner concentration sensor 46, so that even if the transport speed of the developer increases, the developer tends to accumulate near the toner concentration sensor 46. This makes it possible to stabilize the detected value of the toner concentration and maintain an appropriate amount of toner in the developing container 50.

[0054] The scraper 47 is fixed to the rotating shaft 42a of the first conveying member 42 at the cutting portion 42c via the mounting portion 42d. As shown in Fig. 6, the scraper 47 is formed in a fan shape when viewed from the axial direction of the rotating shaft 42a. The scraper 47 is arranged so that its inclination with respect to the axial direction of the rotating shaft 42a is approximately the same as that of the spiral first conveying blade 42b.

[0055] Scraper 47 is made by laminating a fiber sheet such as felt or nonwoven fabric on the surface of a base material made of a flexible film (elastic material) such as a PET (Polyethylene Terephthalate) film. Scraper 47 rotates together with rotary shaft 42a to move the developer facing toner concentration sensor 46. New developer is then sent into the area facing toner concentration sensor 46.

[0056] According to the above configuration, by providing the scraper 47 in the cutout portion 42c, it is possible to prevent excessive accumulation of developer near the toner concentration sensor 46. Therefore, it becomes possible to properly detect the toner concentration in the developing container 50.

[0057] Similar to the scraper 47, the mounting portion 42d is disposed at approximately the same inclination as the spiral first conveying blade 42b with respect to the axial direction of the rotating shaft 42a. The mounting portion 42d is integrally formed on the outer periphery of the rotating shaft 42a at the cutting portion 42c. Note that although the mounting portion 42d is integral with the rotating shaft 42a in this embodiment, it may be provided as a separate member from the rotating shaft 42a.

[0058] At both axial end portions of the mounting portion 42d, there are formed holding portions (dispersion portions) 42e for holding the scraper 47. The holding portions 42e sandwich and hold the scraper 47 in the approximate axial direction of the rotary shaft 42a.

[0059] The holding portion (dispersion portion) 42e has a peripheral end surface (dispersion surface) 42f extending radially of the rotating shaft 42a at each of both circumferential ends of the rotating shaft 42a. In other words, the peripheral end surface (dispersion surface) 42f is formed on the outer periphery of the rotating shaft 42a opposite the cutout portion 42c and extends radially of the rotating shaft 42a. As shown in FIG. 5, the area of ​​the peripheral end surface 42f is larger than the cross-sectional area of ​​the first conveying blade 42b (42bA).

[0060] According to the above configuration, the area of ​​the peripheral end surface 42f, which is the dispersion surface, is larger than the cross-sectional area of ​​the first transport blade 42b. Therefore, in the holding portion 42e, which is the dispersion portion, the developer can be sent out in a direction (for example, the circumferential direction of the rotation shaft 42a) different from the developer transport direction (first direction f1) by the first transport blade 42b. In other words, the dispersion (stirring) of the developer can be promoted in the holding portion 42e. This improves the dispersibility of the developer in the developing container 50, making it possible to form a uniform image with reduced density unevenness.

[0061] 5, the peripheral end surface 42f is formed parallel to the axial direction of the rotary shaft 42a and faces in a direction substantially perpendicular to the axial direction of the rotary shaft 42a. With this configuration, in the holding portion 42e, which is a dispersion portion, the developer can be sent out in a direction perpendicular to the developer transport direction (first direction f1) by the first transport blade 42b, i.e., in the circumferential direction of the rotary shaft 42a. This makes it possible to more effectively promote dispersion (agitation) of the developer in the holding portion 42e.

[0062] The peripheral end surface 42f is disposed on the edge of the holding portion 42e that holds the scraper 47, facing the cutting portion 42c.

[0063] According to the above configuration, the holding portion 42e that holds the scraper 47 has a peripheral end surface (dispersion surface) 42f, and the peripheral end surface 42f that moves with the rotation of the rotary shaft 42a can enhance the effect of moving the developer near the toner concentration sensor 46. This makes it possible to prevent excessive accumulation of developer near the toner concentration sensor 46. Therefore, in addition to being able to improve the dispersion of the developer in the developing container 50, it becomes possible to properly detect the toner concentration.

[0064] Furthermore, by using the holding portion 42e of the scraper 47 as a dispersion portion for improving the dispersion of the developer, it is possible to ensure a sufficient installation area for the holding portion 42e, thereby improving the holding strength of the scraper 47.

[0065] Next, the effects of this embodiment will be described. Table 1 shows the evaluation results of the developer transport speed and dispersibility in the developing devices of the example and the comparative example. For each of the developing device 40 of the example and the developing device of the comparative example, the influence of the area magnification of the dispersion surface (cross-sectional area of ​​the transport blade = 1.0) on the developer transport speed and dispersibility was evaluated.

[0066] [Table 1]

[0067] The area magnification of the dispersion surface of the first transport member of the developing device of Comparative Example 1 is 1.0 times the cross-sectional area of ​​the first transport blade of the first transport member, i.e., the same area. The area magnification of the dispersion surface (circumferential end surface 42f) of the first transport member 42 of the developing device 40 of Examples 1, 2, 3, and 4 is 1.5, 3.0, 6.0, and 9.0 times the cross-sectional area of ​​the first transport blade 42b of the first transport member 42, respectively. The area magnification of the dispersion surface of the first transport member of the developing device of Comparative Example 2 is 10.0 times the cross-sectional area of ​​the first transport blade of the first transport member.

[0068] Regarding Table 1, when printing was performed with an image ratio per sheet of paper of 40%, if the amount of developer replenishment exceeded a satisfactory developer transport speed, the developer transport speed was evaluated as "good (○)." If the developer transport speed was lower than that, the developer transport speed was evaluated as "poor (×)." Furthermore, when a predetermined amount of developer was replenished from the developer replenishment port 52a of the developing device 40, if the difference between the toner to carrier mixture ratio (T / C) in the developer that reached the downstream portion of the first transport member 42 in the developer transport direction (the location of the toner concentration sensor 46) and the T / C after complete dispersion was within 1%, the developer dispersibility was evaluated as "good (○)." If the difference in T / C was 1% or more, the developer dispersibility was evaluated as "poor (×)."

[0069] According to Table 1, in the configuration of Comparative Example 1, the area ratio of the dispersion surface of the first transport member is the same as the cross-sectional area of ​​the first transport blade, so the developer transport speed is sufficient, but the developer dispersibility is not good. Furthermore, in the configuration of Comparative Example 2, the area ratio of the dispersion surface of the first transport member is 10.0 times the cross-sectional area of ​​the first transport blade, so the developer dispersibility is sufficient, but the developer transport speed is not good. This is because the dispersion surface configuration clogs the gap between adjacent transport blades in the axial direction, making it difficult for the developer to pass in the transport direction, and the developer transport speed is extremely reduced.

[0070] In addition, the evaluation results for both the developer transport speed and developer dispersibility were good in the configurations of Examples 1, 2, 3, and 4. That is, by making the area of ​​the dispersion surface (circumferential end surface 42f) of the first transport member 42 1.4 to 9 times the cross-sectional area of ​​the first transport blade 42b, sufficient developer dispersibility can be ensured without adversely affecting the developer transport speed.

[0071] Next, a modified example of the developing device 40 will be described.

[0072] Fig. 7 is a partial side view of the first conveying member 42 of Modified Example 1. Fig. 8 is a partial side view of the first conveying member 42 of Modified Example 1 as viewed from the opposite side of Fig. 7. In the first conveying member 42 of Modified Example 1, the holding portion (dispersion portion) 42e of the scraper 47 is formed only on one end side of the scraper 47 in the axial and circumferential directions of the rotating shaft 42a, i.e., on the right side in Fig. 7 (left side in Fig. 8). In other words, the peripheral end surface (dispersion surface) 42f is formed at one location in the axial direction of the rotating shaft 42a.

[0073] In the configuration of the above-described modified example 1, dispersion (agitation) of the developer can be promoted in the holding portion 42e, as in the previous embodiment described with reference to Figures 4, 5, and 6. This improves the dispersibility of the developer in the developing container 50, and makes it possible to form a uniform image with reduced density unevenness.

[0074] If developer dispersion surfaces (dispersion portions) are provided in three or more locations, it is necessary to provide many cutout portions 42c in the first transport member 42, which increases the number of divided locations in the first transport blade 42b. This may result in a decrease in developer transportability. In order to ensure both the developer transport speed and developer dispersibility in a favorable manner, it is preferable to form developer dispersion surfaces (dispersion portions) in one or two locations along the axial direction of the rotation shaft 42a.

[0075] Furthermore, when the conveying member is provided with the scraper 47, it is preferable to arrange the holding portions (dispersion portions) 42e at both axial end portions of the scraper 47. This makes it possible to improve the holding strength of the scraper 47.

[0076] Fig. 9 is a partial side view of a first conveying member 42 of Modified Example 2. Fig. 10 is a partial side view of a first conveying member 42 of Modified Example 2 as seen from the opposite side of Fig. 9. The first conveying member 42 of Modified Example 2 has two first conveying blades 42bA, 42bB, and a cutout portion 42c and an attachment portion 42d (holding portion 42e) are provided for one first conveying blade 42bB, but not for the other first conveying blade 42bA. In the installation area of ​​the cutout portion 42c and the attachment portion 42d (holding portion 42e) of the first conveying blade 42bB, the first conveying blade 42bA extends continuously in the axial direction.

[0077] In the configuration of the above-described modified example 2, dispersion (agitation) of the developer can be promoted in the holding portion 42e, as in the previous embodiment described with reference to Figures 4, 5, and 6. This improves the dispersibility of the developer in the developing container 50, and makes it possible to form a uniform image with reduced density unevenness.

[0078] 11 is a partial side view of a first conveying member 42 of Modified Example 3. The first conveying member 42 of Modified Example 3 does not have the scraper 47 and mounting portion 42d (holding portion 42e) seen in the previous embodiment. Furthermore, the first conveying member 42 of Modified Example 3 has two first conveying blades 42bA, 42bB, and a cutout portion 42c is provided on one first conveying blade 42bA but not on the other first conveying blade 42bB. The first conveying blade 42bB extends continuously in the axial direction.

[0079] The cutouts 42c are formed at two locations spaced apart in the axial direction of the first conveying blade 42bA. The first conveying blade 42bA has two dispersion portions 42g, each having a dispersion surface 42h arranged opposite the two cutouts 42c. The two dispersion surfaces 42h are formed at both axial ends of the region of the first conveying blade 42bA sandwiched between the two cutouts 42c.

[0080] The two dispersion surfaces 42h are formed on the outer periphery of the rotating shaft 42a, extend in the radial direction of the rotating shaft 42a, and have a cross-sectional area larger than that of the remaining portions of the first conveying blade 42bA. The dispersion surfaces 42h are formed so as to be perpendicular to the extension direction of the spirally extending first conveying blade 42bA. In other words, the dispersion surfaces 42h are formed so as to be inclined with respect to the axial direction of the rotating shaft 42a.

[0081] In the configuration of the above-described modified example 3, dispersion (agitation) of the developer can be promoted in the dispersion section 42g, as in the previous embodiment described with reference to Figures 4, 5, and 6. This improves the dispersibility of the developer in the developing container 50, and makes it possible to form a uniform image with reduced density unevenness.

[0082] The developer dispersion portion 42g (dispersion surface 42h) may be formed on only one side in the axial direction. Also, in the region of the first transport blade 42bA sandwiched between the two cutouts 42c in the axial direction, a cutout may also be formed on the other first transport blade 42bB, leaving an area where the first transport blade 42bB is not provided.

[0083] Although the embodiments of the present invention have been described above, the scope of the present invention is not limited to these, and various modifications can be made without departing from the spirit of the invention.

[0084] For example, in the above embodiment, the image forming apparatus 1 is a so-called tandem type image forming apparatus for color printing that forms images of multiple colors by sequentially overlapping them, but the image forming apparatus is not limited to this type. The image forming apparatus may be a non-tandem type image forming apparatus for color printing or a monochrome image forming apparatus. [Industrial Applicability]

[0085] The present invention can be used in developing devices and image forming apparatuses. [Explanation of symbols]

[0086] 1. Image forming device 2 Main unit 20 Image forming unit 21 Photosensitive drum (image carrier) 40 Developing device 42 first conveying member 42a Rotation axis 42b, 42bA, 42bB First conveying blade 42c Excision 42d Mounting part 42e Holding section (distribution section) 42f Peripheral end surface (dispersion surface) 42g dispersion section 42h dispersion surface 43 second conveying member 43a Rotation axis 43b Second conveying blade 44 Developing roller (developer carrier) 45 Regulatory Blade 46 Toner density sensor 47 Scraper 50 Developer container 51 Partition 52 Transport Room 1 52a Developer supply port 53 Transport Room 2

Claims

1. a developer container that contains a developer containing toner to be supplied to an image carrier; a conveying member that is rotatably supported by the developing container and conveys the developer while stirring it; a developer carrier that is rotatably supported by the developing container and faces the image carrier, and that supplies the toner in the developing container to the image carrier; Equipped with The conveying member is a rotation shaft extending along the longitudinal direction of the developing container; a conveying blade formed in a spiral shape on the outer periphery of the rotating shaft; a cutout portion in which the conveying blade is partially cut out in the longitudinal direction; a dispersion portion formed on an outer periphery of the rotating shaft opposite the cutout portion, extending in a radial direction of the rotating shaft, and having a dispersion surface with an area larger than a cross-sectional area of ​​the conveying blade; A developing device comprising:

2. 2. The developing device according to claim 1, wherein the area of ​​the dispersion surface is 1.4 to 9 times the cross-sectional area of ​​the transport blade.

3. 2. The developing device according to claim 1, wherein the dispersion surface is formed on an end surface of the transport blade that faces the cutout portion.

4. 2. The developing device according to claim 1, wherein the dispersion surface is formed parallel to the axial direction of the rotation shaft.

5. 2. The developing device according to claim 1, wherein the dispersion surface is formed at one or two locations in the axial direction of the rotation shaft.

6. a toner concentration sensor disposed on a wall portion of the developing container along the longitudinal direction, facing the conveying member, for detecting a toner concentration in the developer; The conveying member is the cutout portion formed in an area facing the toner concentration sensor; a scraper fixed to the rotary shaft at the cutting portion and configured to move the developer facing the toner concentration sensor; A holding portion that is the dispersion portion formed on the rotating shaft at the cutting portion and holds the scraper; and 2. The developing device according to claim 1, wherein the holding portion extends in a radial direction of the rotary shaft at both circumferential ends of the rotary shaft, and the dispersion surface is located on an edge facing the cutout portion.

7. An image forming apparatus comprising the developing device according to any one of claims 1 to 6.

Images