Developing device and image forming apparatus

Abstract

To provide a developing device that can improve dispersibility of developer without affecting the conveyance speed of the developer to prevent the occurrence of density unevenness.SOLUTION: A developing device 40 comprises a developer container 50, a first conveying member 42, a second conveying member 43, and a developing roller 44. The second conveying member 43 includes a regulating blade 43c that is formed on the downstream side of a second conveying blade 43b with respect to a second direction f2 that is a conveyance direction of developer, and conveys the developer in a direction opposite to the second conveying blade 43b. A developer supply port 50a is an opening formed in a top face of the developer container 50, and at least part of an opening length in the second direction f2 is included in a regulation area 53a that is an area in a second conveyance chamber 53 where the regulating blade 43c is arranged. The developer supplied from the developer supply port 50a at least partially drops into both a first conveyance chamber 52 and the regulation area 53a.SELECTED DRAWING: Figure 4

Description

Technical Field

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

Background Art

[0002] In electrophotographic image forming apparatuses such as copiers and printers, a toner image to be later transferred onto paper is formed by supplying toner to an electrostatic latent image formed on the outer peripheral surface of an image carrier such as a photoreceptor drum using a developing device. This developing device adopts, for example, a developing method using a two-component developer containing a magnetic carrier and toner, and is provided with a developing roller (developer carrier) for supplying the developer to the image carrier. The developer is stirred and conveyed in a developing container in which the developer is stored, and is supplied to the developing roller.

[0003] In a developing device using a two-component developing method, while the toner is consumed by the developing operation, the magnetic carrier remains in the developing container without being consumed. Therefore, the magnetic carrier stirred together with the toner in the developing container deteriorates due to mechanical stress as the stirring frequency increases. As a result, the charge imparting performance of the magnetic carrier to the toner gradually decreases. Thus, a developing device has been proposed that suppresses a decrease in charging performance by replenishing the developing container with a developer containing a magnetic carrier and toner, and discharging the surplus developer.

[0004] The conventional developing device disclosed in Patent Document 1 gradually replaces the deteriorated carrier in the developing container with a new carrier to keep the charging performance of the carrier in the developing container constant. And regarding the screw for conveying the developer, the number of spiral blades and the angle of the conveying surface of the blades are configured to be predetermined values. Thereby, both ensuring the conveyance property of the developer and ensuring the stirring property are achieved.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, when the number of blades is increased to compensate for the reduced transfer speed of the developer caused by the angle of the transfer surface of the blades configured to ensure the stirrability (dispersibility) of the developer, there is a problem in that density unevenness (concentration unevenness) is likely to occur due to an increase in the blade volume. As a result, there was a concern that suitable image formation could not be achieved.

[0007] The present invention has been made in view of the above points, and an object thereof is to provide a developing device and an image forming device capable of improving the dispersibility of a developer without affecting the transfer speed of the developer and suppressing the occurrence of density unevenness.

Means for Solving the Problems

[0008] To solve the above problems, the developing device of the present invention includes a developing container, a first conveying member, a second conveying member, and a developer carrier. The developing container includes a first conveying chamber and a second conveying chamber arranged in parallel with each other, a first partition wall that partitions the first conveying chamber and the second conveying chamber along the longitudinal direction, a communication portion that communicates the first conveying chamber and the second conveying chamber on both end sides in the longitudinal direction of the first partition wall, a developer supply port that supplies a developer including a magnetic carrier and toner, and a developer discharge port that is arranged at the downstream end of the second conveying chamber and from which the excess developer is discharged, and houses the developer. The first conveying member has a first rotating shaft and first conveying blades formed on the outer peripheral surface of the first rotating shaft, and stirs and conveys the developer in the first conveying chamber in a first direction. The second conveying member has a second rotating shaft and second conveying blades formed on the outer peripheral surface of the second rotating shaft, and stirs and conveys the developer in the second conveying chamber in a second direction, which is the opposite direction to the first direction. The developer carrier is rotatably supported by the developing container facing the image carrier, and supplies the toner in the second conveying chamber to the image carrier. The second conveying member includes a regulating blade and a discharging blade. The regulating blade is formed on the downstream side of the second conveying blade with respect to the second direction, and conveys the developer in a direction opposite to the second conveying blade. The discharging blade is formed on the downstream side of the regulating blade with respect to the second direction, conveys the developer in the same direction as the second conveying blade, and discharges the developer from the developer discharge port. The developer supply port is an opening formed on the upper surface of the developing container, and at least a part of the opening length in the second direction is included in a regulating region where the regulating blade in the second conveying chamber is arranged. At least a part of the developer supplied from the developer supply port falls into both the first conveying chamber and the regulating region.

Effect of the Invention

[0009] According to the configuration of the present invention, the developer replenished from the developer replenishment port falls into both the first transport chamber and the regulation region, and thus is dispersed into the first transport chamber and the second transport chamber and accommodated in the developer container. Thereby, the dispersibility of the developer can be improved without affecting the transport speed of the developer. Therefore, it is possible to suppress the occurrence of density unevenness.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the following content.

[0012] FIG. 1 is a schematic cross-sectional front view of the image forming apparatus 1 according to the embodiment. FIG. 2 is a schematic cross-sectional front view of the periphery of the image forming unit 20 of the image forming apparatus 1 in FIG. 1. As an example of the image forming apparatus 1 of the present embodiment, it is a tandem type color printer that transfers a toner image onto a sheet S using an intermediate transfer belt 31. The image forming apparatus 1 may be a so-called multifunction machine having functions such as printing, scanning (image reading), and facsimile transmission.

[0013] As shown in FIGS. 1 and 2, the image forming apparatus 1 includes a paper supply unit 3, a paper conveyance 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 provided in the main body 2 thereof.

[0014] The paper supply unit 3 is disposed at the bottom of the main body 2. The paper supply unit 3 stores a plurality of sheets S before printing and separates and feeds out the sheets S one by one during printing. The paper conveyance unit 4 extends vertically along the side wall of the main body 2. The paper conveyance unit 4 conveys the sheet S sent out from the paper supply unit 3 to the secondary transfer unit 33 and the fixing unit 6, and further discharges the sheet S after fixing from the paper discharge port 4a to the paper discharge unit 7. The exposure unit 5 is disposed above the paper supply unit 3. The exposure unit 5 irradiates the image forming unit 20 with laser light controlled based on image data.

[0015] The image forming unit 20 is disposed above the exposure unit 5 and below the intermediate transfer belt 31. The image forming unit 20 includes 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. Accordingly, in the following description, the identification symbols "Y", "C", "M", and "B" representing each color may be omitted unless particularly limited.

[0016] The image forming unit 20 includes a photosensitive drum (image carrier) 21 that is rotatably supported 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 along the rotation direction around the photosensitive drum 21. Note that a primary transfer unit 32 is arranged between the developing device 40 and the drum cleaning unit 23.

[0017] The photosensitive drum 21 is formed in a cylindrical shape extending in the horizontal direction and has a photosensitive layer formed of, for example, an amorphous silicon photoreceptor on its outer peripheral surface. The charging unit 22 charges the surface (outer peripheral surface) of the photosensitive drum 21 to a predetermined potential. The exposure unit 5 exposes the outer peripheral surface of the photosensitive drum 21 charged by the charging unit 22 to form an electrostatic latent image of the document image on the outer peripheral surface of the photosensitive drum 21. The developing device 40 supplies toner to this electrostatic latent image for development to form 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 toner and the like remaining on the outer peripheral surface of the photosensitive drum 21 after the toner image is primarily transferred to the outer peripheral surface of the intermediate transfer belt 31. In this way, the image forming unit 20 forms an image (toner image) to be transferred to the paper S later.

[0018] The transfer unit 30 includes an intermediate transfer belt 31, primary transfer units 32Y, 32C, 32M, 32B, a secondary transfer unit 33, and a belt cleaning unit 34. The intermediate transfer belt 31 is arranged above the four image forming units 20. The intermediate transfer belt 31 is an endless intermediate transfer member that is rotatably supported in a predetermined direction (counterclockwise in FIG. 1) and to 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 arranged in a so-called tandem method in a row from the upstream side to the downstream side in the rotation direction of the intermediate transfer belt 31.

[0019] The primary transfer units 32Y, 32C, 32M, and 32B are disposed above the image forming units 20Y, 20C, 20M, and 20B for respective colors, sandwiching the intermediate transfer belt 31. The secondary transfer unit 33 is disposed upstream of the fixing unit 6 with respect to the paper conveyance direction of the paper conveyance unit 4 and downstream of the four image forming units 20Y, 20C, 20M, and 20B with respect to the rotation direction of the intermediate transfer belt 31. The belt cleaning unit 34 is disposed downstream of the secondary transfer unit 33 with respect to the rotation direction of the intermediate transfer belt 31.

[0020] The primary transfer unit 32 transfers the toner image formed on the outer peripheral surface of the photosensitive drum 21 to the intermediate transfer belt 31. In other words, the toner image is primarily transferred to the outer peripheral surface of the intermediate transfer belt 31 in the primary transfer units 32Y, 32C, 32M, and 32B for respective colors. Then, as the intermediate transfer belt 31 rotates, the toner images of the four image forming units 20 are successively and continuously transferred and overlapped on the intermediate transfer belt 31 at a predetermined timing, whereby a color toner image in which toner images of yellow, cyan, magenta, and black are overlapped is formed on the outer peripheral surface of the intermediate transfer belt 31.

[0021] The color toner image on the outer peripheral surface of the intermediate transfer belt 31 is transferred to the paper S sent in synchronization by the paper conveyance unit 4 at the secondary transfer nip portion formed in the secondary transfer unit 33. The belt cleaning unit 34 removes and cleans deposits such as toner remaining on the outer peripheral surface of the intermediate transfer belt 31 after secondary transfer. In this way, the transfer unit 30 transfers (records) the toner image formed on the outer peripheral surface of the photosensitive drum 21 to the paper S.

[0022] The fixing unit 6 is disposed above the secondary transfer unit 33. The fixing unit 6 heats and presses the paper S onto which the toner image has been transferred to fix the toner image on the paper S.

[0023] The paper discharge unit 7 is disposed above the transfer unit 30. The paper S on which the toner image has been fixed and the printing has been completed is conveyed to the paper discharge unit 7. The paper discharge unit 7 allows the printed paper (printout) to be taken out from above.

[0024] The control unit 8 includes a CPU, an image processing unit, a storage unit, and other electronic circuits and components (all not shown). The CPU controls the operations of each component provided in the image forming apparatus 1 based on the control programs and data stored in the storage unit, and performs processes related to the functions of the image forming apparatus 1. Each of the paper supply unit 3, the paper conveyance unit 4, the exposure unit 5, the image forming unit 20, the transfer unit 30, and the fixing unit 6 receives individual commands from the control unit 8 and cooperates to perform printing on the paper S. The storage unit is composed of a combination of a non-volatile storage device such as a program ROM (Read Only Memory) and a data ROM, and a volatile storage device such as a RAM (Random Access Memory).

[0025] Subsequently, the configuration of the developing device 40 will be described with reference to FIG. 3 in addition to FIG. 2. FIG. 3 is a horizontal cross-sectional plan view of the developing device of the image forming unit in FIG. 2. Since the basic configurations of the developing devices 40 for each color are the same, the description and the identification symbols representing each color for the components are omitted. In this description, the "axial direction" represents the axial direction of rotation of each of the photosensitive drum 21, the first conveying member 42, the second conveying member 43, and the developing roller 44 that extend parallel to each other (the depth direction of the paper surface in FIG. 2, the left-right horizontal direction in FIG. 3).

[0026] The developing device 40 supplies toner to the outer peripheral surface of the photosensitive drum 21. The developing device 40 is, for example, detachable from the main body 2 of the image forming apparatus 1. The developing device 40 includes a developing container 50, a first conveying member 42, a second conveying member 43, a developing roller (developer carrier) 44, a regulating blade 45, and a toner density sensor 46.

[0027] The developing container 50 has an elongated shape extending along the axial direction of the photoreceptor drum 21, and is arranged with its longitudinal direction horizontal. That is, the longitudinal direction of the developing container 50 is parallel to the axial direction of the photoreceptor drum 21. The developing container 50 accommodates a two-component developer containing toner and a magnetic carrier as a developer containing toner to be supplied to the photoreceptor drum 21. A developer supply port 50a is opened on the upper surfaces of a first conveyance chamber 52 and a second conveyance chamber 53, which will be described later, of the developing container 50, and the developer is supplied into the developing container 50 through the developer supply port 50a.

[0028] The developing container 50 has a first partition wall 51A, a first conveyance chamber 52, a second conveyance chamber 53, a first communication part 54, and a second communication part 55.

[0029] The first partition wall 51A is provided at the lower part inside the developing container 50. The first partition wall 51A is disposed at a substantially central portion in a direction intersecting the longitudinal direction of the developing container 50 (the left-right horizontal direction in FIG. 2, the up-down direction in FIG. 3). The first partition wall 51A is formed in a substantially plate shape extending in the longitudinal direction and the up-down direction of the developing container 50. The first partition wall 51A divides the inside of the developing container 50 in a direction intersecting the longitudinal direction. In other words, the first partition wall 51A partitions the first conveyance chamber 52 and the second conveyance chamber 53 along the longitudinal direction.

[0030] The first conveyance chamber 52 and the second conveyance chamber 53 are provided inside the developing container 50. The first conveyance chamber 52 and the second conveyance chamber 53 are formed by partitioning the inside of the developing container 50 by the first partition wall 51A. The first conveyance chamber 52 and the second conveyance chamber 53 are arranged in parallel at substantially the same height.

[0031] The second conveyance chamber 53 includes the periphery of the arrangement region of the developing roller 44 in the developing container 50 and is arranged adjacent to the photoreceptor drum 21. The first conveyance chamber 52 is arranged in a region in the developing container 50 that is more separated from the photoreceptor drum 21 than the second conveyance chamber 53. In the first conveyance chamber 52, the developer is conveyed in a first direction f1 by a first conveying member 42. In the second conveyance chamber 53, the developer is conveyed in a second direction f2, which is the reverse direction of the first direction f1, by a second conveying member 43.

[0032] The first communication part 54 and the second communication part 55 are respectively arranged outside both longitudinal ends of the first partition wall 51A. The first communication part 54 and the second communication part 55 communicate the first transport chamber 52 and the second transport chamber 53 in a direction intersecting the longitudinal direction of the first partition wall 51A (the left - right horizontal direction in FIG. 2, the up - down direction in FIG. 3), that is, in the thickness direction of the first partition wall 51A which is substantially plate - shaped. In other words, the first communication part 54 and the second communication part 55 communicate the first transport chamber 52 and the second transport chamber 53 on both longitudinal end sides of the first partition wall 51A.

[0033] The first communication part 54 communicates the downstream end in the first direction f1 of the first transport chamber 52 and the upstream end in the second direction f2 of the second transport chamber 53. The first communication part 54 conveys the developer from the first transport chamber 52 side toward the second transport chamber 53 side. In other words, the first communication part 54 delivers the developer from the first transport chamber 52 to the second transport chamber 53 on the downstream side in the first direction f1.

[0034] The second communication part 55 communicates the downstream end in the second direction f2 of the second transport chamber 53 and the upstream end in the first direction f1 of the first transport chamber 52. The second communication part 55 conveys the developer from the second transport chamber 53 side toward the first transport chamber 52 side. In other words, the second communication part 55 delivers the developer from the second transport chamber 53 to the first transport chamber 52 on the downstream side in the second direction f2.

[0035] The first transport member 42 is arranged in the first transport chamber 52. The second transport member 43 is arranged in the second transport chamber 53. The first transport member 42 and the second transport member 43 are arranged in parallel at substantially the same height. The second transport member 43 extends in parallel close 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 in parallel with the developing roller 44.

[0036] The basic configurations of the first conveying member 42 and the second conveying member 43 are the same. The first conveying member 42 has first conveying vanes 42b formed in a spiral shape on the outer peripheral portion of a first rotating shaft 42a extending along the longitudinal direction of the developing container 50. In the present embodiment, the first conveying member 42 has two first conveying vanes 42b. The second conveying member 43 has second conveying vanes 43b formed in a spiral shape on the outer peripheral portion of a second rotating shaft 43a extending along the longitudinal direction of the developing container 50. In the present embodiment, the second conveying member 43 has two second conveying vanes 43b.

[0037] In the first conveying chamber 52, the first conveying member 42 conveys the developer while stirring it in a first direction f1 from the second communication portion 55 side toward the first communication portion 54 side along the axial direction of rotation. In the second conveying chamber 53, the second conveying member 43 conveys the developer while stirring it in a second direction f2 from the first communication portion 54 side toward the second communication portion 55 side along the axial direction of rotation. That is, the first conveying member 42 and the second conveying member convey the developer while stirring it in opposite directions in the longitudinal direction, and circulate it in a predetermined circulation direction.

[0038] The developing roller 44 is located above the second conveying member 43 in the developing container 50 and is disposed opposite to the photosensitive drum 21. The developing roller 44 is rotatably supported by the developing container 50 around an axis extending parallel to the axis of the photosensitive drum 21.

[0039] A part of the outer peripheral 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 the toner supplied to the outer peripheral surface of the photosensitive drum 21 in the facing region with the photosensitive drum 21 on its outer peripheral surface. The developing roller 44 carries the toner in the second conveying chamber 53 of the developing container 50 and supplies it to the photosensitive drum 21. In other words, the developing roller 44 attaches the toner in the second conveying chamber 53 to the electrostatic latent image on the outer peripheral surface of the photosensitive drum 21 to form a toner image.

[0040] The regulating blade 45 is disposed on the upstream side in the rotation direction of the developing roller 44 in the facing area between the developing roller 44 and the photoreceptor drum 21. The regulating blade 45 faces the developing roller 44 in proximity thereto, and is disposed with a predetermined gap provided between its tip and the outer peripheral surface of the developing roller 44. The regulating blade 45 extends over the entire axial direction of the developing roller 44. The regulating blade 45 regulates the layer thickness of the developer carried on the outer peripheral surface of the developing roller 44 that passes through the gap between the tip of the regulating blade 45 and the outer peripheral surface of the developing roller 44.

[0041] The toner density sensor 46 is disposed on the wall portion along the longitudinal direction (first direction f1) of the first conveyance chamber 52. For example, the toner density sensor 46 is located on the downstream side of the central portion in the longitudinal direction (first direction f1) of the first conveyance chamber 52 and on the upstream side of the first communication portion 54. The toner density sensor 46 is disposed to face the first conveyance member 42. In the present embodiment, a headless sensor is used as the toner density sensor 46. The toner density sensor 46, which is a headless sensor, has a detection surface buried in the inner wall surface of the first conveyance chamber 52. The toner density sensor 46 detects the toner density in the developer.

[0042] Specifically, the toner density sensor 46 is a permeability detection type sensor that obtains the toner density (mixing ratio of toner T to carrier C in the developer; T / C) by detecting the change in the magnetic permeability of the two-component developer. If the ratio of toner to carrier in the developer in the first conveyance chamber 52 changes, the magnetic permeability also changes, and accordingly, the output signal of the toner density sensor 46 also changes. The control unit 8 controls the start and stop of replenishment of the developer (toner and carrier) to the developing device 40 based on the output signal of the sensor received from the toner density sensor 46.

[0043] The developer in the developing container 50 circulates between the first transfer chamber 52 and the second transfer chamber 53 in a predetermined circulation direction through the first communication portion 54 and the second communication portion 55 due to the rotation of the first transfer member 42 and the second transfer member 43. At this time, the toner in the developing container 50 is agitated 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 conveyed to the facing region between the developing roller 44 and the photosensitive drum 21 by the rotation of the developing roller 44. When a predetermined developing voltage is applied to the developing roller 44, 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 facing region due to the potential difference from the potential of the surface (outer peripheral surface) of the photosensitive drum 21. Thereby, the electrostatic latent image on the outer peripheral surface of the photosensitive drum 21 is developed with toner.

[0044] 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 transfer chamber 53 in the second direction f2. The discharge portion 56 is connected to the second transfer chamber 53. The interiors of the discharge portion 56 and the second transfer chamber 53 communicate with each other. The inner diameter of the discharge portion 56 is smaller than the inner diameter of the second transfer chamber 53. The discharge portion 56 has a developer discharge port 561.

[0045] Note that the second rotation shaft 43a of the second transfer member 43 continuously extends into the discharge portion 56. One end in the axial direction of the second 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 transfer chamber 53.

[0046] The developer discharge port 561 is disposed at the downstream end of the discharge portion 56 with respect to the second direction f2 of the second transfer chamber 53. The developer discharge port 561 opens, for example, below the second rotation shaft 43a of the second transfer member 43. The developer discharge port 561 discharges excess developer in the developing container 50 to the outside.

[0047] The second conveying member 43 includes, in addition to the second conveying blade 43b, a regulating blade 43c and a discharging blade 43d. These three blades are provided in the order of the second conveying blade 43b, the regulating blade 43c, and the discharging blade 43d from the second conveying chamber 53 side toward the discharging portion 56. Similar to the second conveying blade 43b, the regulating blade 43c and the discharging blade 43d are provided integrally with the second rotating shaft 43a and are formed in a spiral shape along the axial direction on the outer peripheral portion of the second rotating shaft 43a.

[0048] The regulating blade 43c is formed on the downstream side of the second conveying blade 43b with respect to the second direction f2 of the second conveying chamber 53 and is disposed in the second conveying chamber 53. The regulating blade 43c is disposed in a regulating region 53a located at the downstream end portion of the second conveying chamber 53 with respect to the second direction f2 and faces the connection portion between the second conveying chamber 53 and the discharging portion 56 in the second direction f2.

[0049] The winding direction of the regulating blade 43c is opposite to that of the second conveying blade 43b. That is, the regulating blade 43c conveys the developer in a direction opposite to that of the second conveying blade 43b. Thereby, the regulating blade 43c blocks the developer conveyed to the downstream end portion in the second conveying chamber 53 and restricts the movement of the developer toward the discharging portion 56 side. Note that the pitch of the regulating blade 43c is smaller than the pitch of the second conveying blade 43b.

[0050] The outer peripheral portion of the regulating blade 43c has a predetermined interval (clearance) from the inner surface of the developing container 50. The developer that has reached a predetermined amount or more in the second conveying chamber 53 is conveyed as surplus developer from the gap between the outer peripheral portion of the regulating blade 43c and the inner surface of the developing container 50 toward the discharging portion 56.

[0051] The discharge blade 43d is formed on the downstream side of the regulating blade 43c with respect to the second direction f2 of the second conveyance chamber 53 and is disposed within the discharge portion 56. The discharge blade 43d has the same winding direction as the second conveyance blade 43b. That is, the conveyance direction of the developer within the discharge portion 56 is the same as the second direction f2 of the second conveyance chamber 53. Thereby, the discharge blade 43d conveys the surplus developer within the developing container 50 in the same direction as the second conveyance blade 43b, and discharges the developer from the developer discharge port 561. Note that the outer diameter of the discharge blade 43d is smaller than the outer diameters of the second conveyance blade 43b and the regulating blade 43c. The pitch of the discharge blade 43d is smaller than the pitch of the second conveyance blade 43b.

[0052] FIG. 4 is a partially enlarged view showing the periphery of the developer supply port 50a of the developing device 40 in FIG. 3. The developer supply port 50a drawn with a two-dot chain line in FIG. 4 indicates the position of the developer supply port 50a as viewed from above.

[0053] The developer supply port 50a is an opening formed in the upper surfaces of the first conveyance chamber 52 and the second conveyance chamber 53 of the developing container 50. At least a part of the opening length of the developer supply port 50a in the second direction f2 is included in a regulation region 53a which is a region where the regulating blade 43c within the second conveyance chamber 53 is disposed. The developer supply port 50a opens across both the first conveyance chamber 52 and the regulation region 53a of the second conveyance chamber 53 as viewed from above. At least a part of the developer supplied from the developer supply port 50a drops into both the first conveyance chamber 52 and the regulation region 53a.

[0054] According to the above configuration, the developer supplied from the developer supply port 50a drops into both the first conveyance chamber 52 and the regulation region 53a, and thus is divided into the first conveyance chamber 52 and the second conveyance chamber 53 and accommodated within the developing container 50. Thereby, the dispersibility of the developer can be improved without affecting the conveyance speed of the developer. Therefore, it becomes possible to suppress the occurrence of density unevenness.

[0055] Note that it is preferable that the entire opening length of the developer supply port 50a in the second direction f2 is included in the regulation area 53a which is the area where the regulation blade 43c in the second conveyance chamber 53 is disposed. According to this configuration, the developer is sufficiently agitated in the regulation area 53a, and it becomes possible to suppress the new developer from being directly discharged from the discharge portion 56. Thereby, the dispersibility and the dischargeability of the developer can be improved respectively.

[0056] Further, the developing container 50 has a second partition wall 51B. The second partition wall 51B is disposed on the downstream side of the second communication portion 55 with respect to the second direction f2. The second partition wall 51B is formed in a substantially plate shape extending in the longitudinal direction (second direction f2) and the vertical direction of the developing container 50, similarly to the first partition wall 51A. The second partition wall 51B is disposed on the extension line in the longitudinal direction of the first partition wall 51A and adjacent to the regulation area 53a of the second conveyance chamber 53. The second partition wall 51B partitions the first conveyance chamber 52 and the regulation area 53a.

[0057] The developer supply port 50a is disposed above the second partition wall 51B. The developer supply port 50a opens across both the first conveyance chamber 52 and the regulation area 53a of the second conveyance chamber 53 with the second partition wall 51B interposed therebetween when viewed from above. The dropping area of the developer supplied from the developer supply port 50a is divided by the second partition wall 51B into the first conveyance chamber 52 and the regulation area 53a.

[0058] According to the above configuration, the developer dropped into the developing container 50 from the developer supply port 50a hits the upper edge of the second partition wall 51B formed in a plate shape and drops into either the first conveyance chamber 52 or the regulation area 53a. Thereby, the developer supplied from the developer supply port 50a can be suitably divided and dropped into both the first conveyance chamber 52 and the regulation area 53a.

[0059] Also, it is preferable that the entire opening length of the developer supply port 50a in the second direction f2 is located downstream of the second communication portion 55 with respect to the second direction f2. According to this configuration, it is possible to prevent the developer supplied from the developer supply port 50a from falling into the second communication portion 55. That is, by enhancing the action of falling into both the first transport chamber 52 and the regulation region 53a, it becomes possible to effectively improve the dispersibility of the developer.

[0060] Further, it is preferable that the opening length of the developer supply port 50a in the second direction f2 is shorter than that of the second partition wall 51B. According to this configuration, it is possible to prevent the developer supplied from the developer supply port 50a from falling into the second communication portion 55 and also from falling toward the discharge portion 56 side. Thereby, it is possible to suppress the newly supplied developer from being directly discharged through the discharge portion 56 and the developer discharge port 561. Therefore, it becomes possible to effectively improve the dischargeability of the developer.

[0061] Subsequently, examples will be described. FIGS. 5 and 6 are first and second explanatory views showing an arrangement example of the developer supply port 50a of the developing device 40 in FIG. 4. FIGS. 7 and 8 are graphs showing the output variation ratio of the toner concentration sensor 46 and a graph showing the developer discharge amount in the developing devices 40 of the example and the comparative example. In each of the developing device of the example and the developing device of the comparative example, the influence of the arrangement of the developer supply port 50a on the output variation (concentration unevenness) of the toner concentration sensor and the developer discharge amount was evaluated. The configuration conditions related to the arrangement of the developer supply port 50a are shown in Table 1, FIGS. 5 and 6.

[0062]

Table 1

[0063] The "short-side direction" related to the arrangement of the developer supply port 50a shown in Table 1 is a direction perpendicular to the longitudinal direction of the developing container 50 (the second direction f2, the left-right horizontal direction in FIGS. 5 and 6), and is the up-down direction in FIGS. 5 and 6. Further, in this example, the developer supply port 50a is circular when viewed from the up-down direction (the depth direction of the paper surface in FIGS. 4, 5, and 6), and its diameter is 12 mm.

[0064] As shown in Table 1 and FIG. 5, the short-side direction position of the developer supply port H1 of the developing device 40 of Comparative Example 1 is above the first conveying member 42. As shown in Table 1, FIGS. 5, and 6, the short-side direction positions of the developer supply ports H2 and H3 of the developing devices 40 of Comparative Examples 2 and 3 are above the second partition wall 51B. The short-side direction positions of the developer supply ports 50a1 and 50a2 of the developing devices 40 of Examples 1 and 2 are above the second partition wall 51B.

[0065] The longitudinal direction position of the developer supply port H2 of Comparative Example 2 partially overlaps with the upstream portion of the regulation region 53a. The longitudinal direction position of the developer supply port 50a1 of Example 1 partially overlaps with the downstream portion of the regulation region 53a. The longitudinal direction positions of the developer supply port 50a2 of Example 2 and the developer supply port H3 of Comparative Example 3 are within the regulation region 53a.

[0066] The longitudinal length Le of the second partition wall 51B in Examples 1 and 2 and Comparative Examples 1 and 2 is 15 mm from the inner surface on the downstream side in the second direction f2 of the developing container 50. The longitudinal length Lc of the second partition wall 51B in Comparative Example 3 is 10 mm from the inner surface on the downstream side in the second direction f2 of the developing container 50. As a result, a part of the upstream side in the second direction f2 of the developer supply port H3 of Comparative Example 3 is located above the second communication portion 55.

[0067] Regarding the evaluation in FIGS. 7, 8, and Table 1, the output variation ratio of the toner density sensor 46 when 1000 sheets of printing are performed and the developer discharge amount per sheet of printing are compared. The output variation of the toner density sensor 46 calculates the ratio with the variation of Comparative Example 1 as the reference (100%). The smaller the output variation of the toner density sensor 46, the more uniformly the toner is dispersed in the developer.

[0068] In the case of Comparative Example 1, since the developer supply port H1 is above the first conveying member 42, new developer is not directly discharged from the discharge portion 56, and the evaluation of the dischargeability of the developer is "○ (good)". However, since the dispersibility of the developer depends on the screw shape of the first conveying member 42, the evaluation is "× (not acceptable)".

[0069] On the other hand, in the cases of Comparative Examples 2 and 3 and Examples 1 and 2, since each developer supply port is above the second partition wall 51B, as shown in FIG. 7, the dispersibility of the developer is improved.

[0070] In the case of Comparative Example 2, a part of the longitudinal position of the developer supply port H2 overlaps with the upstream portion of the regulation region 53a, and the other part is located on the second communication portion 55 side with respect to the regulation region 53a. As a result, a part of the developer dropped from the developer supply port H2 is not agitated by the regulating blade 43c in the regulation region 53a. Although the dispersibility of the developer is improved compared to Comparative Example 1, it is not sufficient, and the evaluation is "△ (acceptable)". The evaluation of the dischargeability of the developer is "○ (good)".

[0071] In the case of Comparative Example 3, since the length Lc in the longitudinal direction of the second partition wall 51B is shorter than the diameter of the developer supply port H3, the heaping up of the developer in the regulation region 53a by the second partition wall 51B becomes insufficient. As a result, the agitation of the developer in the regulation region 53a becomes insufficient, and the dispersibility and dischargeability of the developer are each evaluated as "△ (acceptable)".

[0072] In the case of Example 1, a part of the longitudinal position of the developer supply port 50a1 overlaps with the downstream portion of the regulation region 53a, and the other part is located on the discharge portion 56 side with respect to the regulation region 53a. As a result, a part of the developer dropped from the developer supply port 50a1 is easily discharged from the discharge portion 56 as it is, and the dischargeability of the developer is evaluated as "△ (acceptable)". The dispersibility of the developer is improved compared to Comparative Examples 1 and 2, and the evaluation is "○ (good)".

[0073] In the case of Example 2, the developer supply port 50a2 is accommodated within the regulation region 53a in the longitudinal direction, and the longitudinal length Le of the second partition wall 51B is longer than the diameter of the developer supply port 50a2. Since the heaping up of the developer in the regulation region 53a by the second partition wall 51B is sufficient, the developer is sufficiently agitated in the regulation region 53a, and it becomes possible to suppress the new developer from being directly discharged from the discharge portion 56. As a result, the dispersibility and dischargeability of the developer are each evaluated as "○ (good)".

[0074] As described above, the embodiments of the present invention have been explained, but the scope of the present invention is not limited to this, and various modifications can be made and implemented without departing from the gist of the invention.

[0075] For example, in the above embodiment, the image forming apparatus 1 is a so-called tandem type color printing image forming apparatus that sequentially superimposes images of a plurality of colors. However, the image forming apparatus is not necessarily limited to such a model. The image forming apparatus may be a color printing image forming apparatus that is not of the tandem type or a monochrome printing image forming apparatus.

Industrial Applicability

[0076] The present invention can be used in a developing device and an image forming apparatus.

Explanation of Reference Numerals

[0077] 1 Image forming apparatus 20 Image forming unit 21 Photoconductor drum (image carrier) 40 Developing device 42 First conveying member 42a First rotating shaft 42b First conveying blade 43 Second conveying member 43a Second rotating shaft 43b Second conveying blade 43c Regulation blade 43d Discharge blade 44 Developing roller (developer carrier) 45 Regulation blade 46 Toner density sensor 50 Developing container 50a, 50a1, 50a2 Developer supply port 51A First partition wall 51B Second partition wall 52 First conveyance chamber 53 Second conveyance chamber 53a Regulation region 54 First communication part 55 Second communication part 56 Discharge part 561 Developer discharge port f1 First direction f2 Second direction

Claims

1. A first transport chamber and a second transport chamber arranged in parallel with each other, a first partition wall that partitions the first transport chamber and the second transport chamber along the longitudinal direction, a communication portion that communicates the first transport chamber and the second transport chamber on both end sides in the longitudinal direction of the first partition wall, a developer supply port for supplying a developer containing a magnetic carrier and toner, a developer discharge port that is arranged at the downstream end of the second transport chamber and discharges the excess developer, a developing container having the above and accommodating the developer, a first transport member having a first rotating shaft and first transport blades formed on the outer peripheral surface of the first rotating shaft, and stirring and transporting the developer in the first transport chamber in a first direction, a second transport member having a second rotating shaft and second transport blades formed on the outer peripheral surface of the second rotating shaft, and stirring and transporting the developer in the second transport chamber in a second direction which is the reverse direction of the first direction, a developer carrier that is rotatably supported by the developing container so as to face the image carrier and supplies the toner in the second transport chamber to the image carrier, comprising, the second transport member, a regulating blade that is formed on the downstream side of the second transport blade with respect to the second direction and transports the developer in a direction opposite to the second transport blade, a discharge blade that is formed on the downstream side of the regulating blade with respect to the second direction and transports the developer in the same direction as the second transport blade to discharge the developer from the developer discharge port, comprising, the developer supply port is an opening formed on the upper surface of the developing container, and at least a part of the opening length in the second direction is included in a regulating region which is a region where the regulating blade in the second transport chamber is arranged, A developing apparatus, wherein at least a part of the developer supplied from the developer supply port falls into both the first transport chamber and the regulating region.

2. The developing apparatus according to claim 1, wherein the entire opening length in the second direction of the developer supply port is included in a regulating region which is a region where the regulating blade in the second transport chamber is arranged.

3. The communication portion, a first communication portion that delivers the developer from the first transport chamber to the second transport chamber on the downstream side in the first direction, a second communication portion that delivers the developer from the second transport chamber to the first transport chamber on the downstream side in the second direction, is composed of, The developing container is disposed adjacent to the regulation region on the downstream side of the second communication portion with respect to the second direction, and has a second partition wall that partitions the first conveyance chamber and the regulation region. The developer supply port is disposed above the second partition wall. The developing apparatus according to claim 1, wherein a dropping region of the developer supplied from the developer supply port is divided by the second partition wall into the first conveyance chamber and the regulation region.

4. The developing apparatus according to claim 3, wherein the entire opening length in the second direction of the developer supply port is located on the downstream side of the second communication portion with respect to the second direction.

5. The developing apparatus according to claim 4, wherein the opening length in the second direction of the developer supply port is shorter than that of the second partition wall.

6. An image forming apparatus comprising the developing apparatus according to any one of claims 1 to 5.

Images