JP2010256701A - Developing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide, at a low price, a developing device that has a long life and copes with various developer stirring conveyance speeds. <P>SOLUTION: The developing device has: a developing chamber 14 serving as a first chamber capable of storing developer; a stirring chamber 15 connected to the developing chamber 14 to thereby form a circulation path for circulation of developer, and serving as a second chamber capable of storing developer; first and second developer stirring conveyance screws 5 and 6 serving as conveying means for conveying developer in the developing chambers 14 and the stirring chamber 15; a developer exhaust port 8, for ejecting developer, disposed outside the circulation path on the downstream side in the direction of developer conveyance in the stirring chamber 15; a rotation shaft 10a rotatably disposed in a developer conveyance path between the circulation path and the developer exhaust port 8; an exhaust screw 9 disposed on the rotation shaft 10a, and serving as a spiral conveying portion for conveying developer, which is directed to the developer exhaust port 8, toward the circulation path; and a brim member 11 disposed on upstream portion in the conveying direction of the exhaust screw 9, and serving as an annular projection which projects in the radial direction of the rotation shaft 10a so as to be continuous in the circumferential direction of the rotation shaft 10a. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a developing device provided in an image forming apparatus such as a copying machine, a laser printer, and a facsimile machine.

  10 to 12 are schematic views showing a conventional developing device 30. FIG. In the drawing, in the developing container 32, a first developer stirring and conveying screw 5 provided in the developing chamber 14 and a second developer stirring and conveying screw 36 provided in the stirring chamber 15 are installed. The developer is agitated and mixed by the screws 5 and 36, and is conveyed and circulated in the developing container 32. The developer transport direction is transported and circulated in the directions of arrows B and C in FIG.

  A partition wall 7 is provided between the first developer stirring and conveying screw 5 and the second developer stirring and conveying screw 36. Further, as shown in FIG. 10, openings 7a and 7b for delivering the developer are provided on the back side and the near side of the partition wall 7 so that the developer is smoothly circulated between the screws 5 and 36. .

  Next, the replenishment and recovery of the developer in the conventional developing device 30 will be described in detail. As shown in FIG. 11, a developer discharge port 8 is provided on the downstream side of the second developer agitating and conveying screw 36 of the developing device 30 in the developer conveying direction. Between the developer discharge port 8 and the developer container 32, a developer discharge screw 9 for discharging the developer and a return screw 10 for pushing back the developer are provided.

  Further, as the replenishment developer, a developer containing a carrier in a certain ratio (about 10% by weight) in the toner is used. The ratio is not limited to this. As described above, the toner consumed by the image formation is supplied to the second developer agitating and conveying screw 36 of the developing container 32 according to the rotation of a supply screw (not shown) as a supply developer containing a carrier at a certain ratio. Replenishment is performed from the upstream side in the developer conveyance direction. The replenishment developer is supplied to the developing device 30 from a replenishment developer hopper (not shown) and received from a replenishment port (not shown) above the developing container 32.

  The replenishment amount of toner and carrier is roughly determined by the rotation speed of a replenishment screw (not shown), and this rotation speed is determined by a toner replenishment amount control means (not shown).

  When replenishment is performed so that the toner density of the developer inside the developing container 32 is kept constant, the amount of the developer in the developing container 32 increases with image formation. Since the replenishment developer is 90% toner and 10% carrier, the toner is consumed by the image formation, but the carrier is not consumed and remains in the developing container 32, and the replenishment is repeated and the amount of the developer increases. . When the amount of developer increases, the developer passes over the return screw 10 and is conveyed to the developer discharge port 8 by the developer discharge screw 9. The developer transported to the developer discharge port 8 is discharged from the developer discharge port 8, transported to a recovery container (not shown) by a developer recovery means (not shown), and collected and stored.

  Referring to FIG. 13A, the developer is conveyed as indicated by an arrow R, passes over the return screw 10, and is discharged by the discharge screw 9. In FIG. 13B, H1 is a normal developer height on the line, and H2 is a developer height at which the developer height increases and the developer automatic discharge function works. Although the developer of H1 or more and H2 or less is discharged, since the return screw 10 is present, the developer is discharged only from the shaded portion S1 shown in FIG. However, the return screw 10 has a screw end portion 10b, and the discharge amount differs depending on the position of the screw end portion 10b. For example, the position of the screw terminal portion 10b shown in FIG. 13B is a position where it is easy to be discharged because it is lower than the developer height H2 at which the developer automatic discharge function works. Further, as shown in FIG. 13C, when the returning screw terminal portion 10b is at a position higher than the developer height H2, the consumed toner is replenished by the replenishment developer as described above. At the same time, the two-component developer is automatically and gradually replaced so as to keep the developer in the developer container 32 constant while discharging the excess developer, and an automatic developer discharge function is realized. To do.

  Japanese Patent Laid-Open No. 2002-72686 (Patent Document 1) proposes an automatic developer discharging configuration as described above.

JP 2002-72686 A

  However, if the stirring and conveying speed in the developing container 32 is always constant, the two-component developer can be replaced without any problem as described above. However, when a plurality of different stirring and conveying speeds such as 1/2 and 1/3 of the agitating and conveying speed are to be performed by the same developing device 30, the balance between the conveying forces of the second developer agitating and conveying screw 36 and the return screw 10 is balanced. Collapses. Then, excessive developer is discharged by spilling from the break of the blade of the return screw 10. FIG. 13 shows a state in which excessive developer spills from the breaks of the blades of the return screw 10. As a result, there is a problem that an appropriate developer discharge amount cannot be ensured at all stirring and conveying speeds.

  In other words, if a sufficient discharge speed cannot be obtained, the developer in the developing container 32 becomes excessive, and the developer is clogged or the developer overflows. On the other hand, if the discharge speed is too high, the developer is reduced too much, which causes a problem that a development failure occurs and an image is not placed on the transfer material or the density becomes low.

  Accordingly, an object of the present invention is to provide a developing device that can appropriately control the discharge amount of developer conveyed at different conveying speeds.

  The developing device according to the present invention includes a first chamber capable of storing a developer, a circulation path for circulating the developer by communicating with the first chamber, a second chamber capable of storing the developer, Conveying means for conveying the developer in the first chamber and the second chamber, and a discharge port for discharging the developer provided in the second chamber outside the circulation path on the downstream side in the developer conveying direction. A rotation shaft rotatably provided in the developer conveyance path between the circulation path and the discharge port, and a developer that is provided on the rotation shaft and that is directed toward the discharge port is conveyed toward the circulation path. And a ring-shaped protruding portion that is provided upstream in the conveying direction of the conveying portion and projects in the radial direction of the rotating shaft continuously in the circumferential direction of the rotating shaft. And

  According to the present invention, the discharge amount of the developer transported at different transport speeds is provided in the upstream portion in the transport direction of the transport unit, and the annular shape projects in the radial direction of the rotation shaft continuously in the circumferential direction of the rotation shaft. It can control appropriately by a projection part.

1 is a diagram illustrating a configuration of an image forming apparatus equipped with a developing device according to the present invention. 1 is a schematic diagram illustrating a configuration of a first embodiment of a developing device according to the present invention. 1 is a cross-sectional view illustrating a configuration of a first embodiment of a developing device according to the present invention. It is sectional drawing which shows the structure of the 2nd developer stirring conveyance means of 1st Embodiment of the developing device which concerns on this invention. It is the schematic which shows the 2nd developer stirring conveyance means of 1st Embodiment of the developing device which concerns on this invention. It is the schematic which shows the 2nd developer stirring conveyance means, reverse conveyance means, collar part, and developer discharge means of 1st Embodiment of the developing device which concerns on this invention. It is the schematic which shows the structure of 2nd Embodiment of the developing device which concerns on this invention. It is sectional drawing which shows the structure of 2nd Embodiment of the developing device which concerns on this invention. It is the schematic which shows the developing container of 2nd Embodiment of the developing device which concerns on this invention. It is the schematic which shows the structure of the conventional image development apparatus. It is sectional drawing which shows the structure of the conventional image development apparatus. It is sectional drawing which shows the conventional developer stirring conveyance screw. FIG. 5 is a schematic diagram showing a state in which excessive developer spills out due to a difference in height of an end portion of a return screw. It is a schematic diagram showing the behavior of the developer whose discharge amount is adjusted by the flange member regardless of the difference in the height of the end portion of the return screw.

  Embodiments of the present invention will be described below.

<Overall configuration of image forming apparatus>
First, an overall configuration of an electrophotographic printer will be described with reference to FIG. 1 as an example of an image forming apparatus including a developing device according to the present invention. FIG. 1 is an explanatory diagram of the overall configuration of the image forming apparatus. The image forming apparatus 24 according to the present embodiment is an electrophotographic printer (hereinafter simply referred to as “printer”), and includes an image forming unit that forms an unfixed image on a sheet S by an electrophotographic method based on image information.

  The image forming means is based on an electrophotographic method, and a laser beam is applied from a writing unit 37 to a photosensitive drum 29 serving as an image forming means whose surface is uniformly charged by applying a bias to the charging roller 35 based on image data. Irradiate to form an electrostatic latent image. The electrostatic latent image is developed with toner by the developing device 1 to be visualized.

  The sheet S loaded in the sheet cassette 39 mounted on the lower part of the apparatus main body 31 is conveyed to the nip portion between the photosensitive drum 29 and the transfer roller 34 by the feeding roller 38 and the conveying roller 33 so as to synchronize with the formation of the toner image. To do. The toner image on the photosensitive drum 29 is transferred to the sheet S by bias application to the transfer roller 34 to form an image.

  The sheet S on which the unfixed image composed of the toner image is transferred is sent to the nip portion between the fixing roller 41 and the pressure roller 42, and the toner image is fixed by heating and pressing, and then the discharge roller 45 Is discharged to the discharge section 44. The developing device 1 according to the present invention can be applied to a single color image forming apparatus or an image forming apparatus that forms a full color image by various methods such as a tandem method.

  2 to 6 are schematic views showing the configuration of the first embodiment of the developing device of the present invention. The developing device 1 will be described in detail with reference to FIGS. The developing device 1 contains a two-component developer composed of a nonmagnetic toner and a magnetic carrier in a developing container 2, and the mixing ratio of the toner and carrier is about 1: 9 by weight. This ratio should be adjusted appropriately depending on the charge amount of the toner, the particle size of the carrier, the configuration of the image forming apparatus 24, etc., and does not necessarily have to follow this value.

  The developing device 1 is a developer in which a portion of a developing region facing the photosensitive drum 29 of the developing container 2 is opened, and a magnet 4 is disposed in a non-rotating manner so as to be partially exposed to the opening. A developing sleeve 3 serving as a carrier is rotatably installed.

  The developing sleeve 3 is made of a non-magnetic material and rotates in the direction of arrow A in FIG. 3 during the developing operation to hold the two-component developer in the developing container 2 in a layered form and transport it to the developing area. A developer is supplied to 29 to develop the electrostatic latent image formed on the photosensitive drum 29. The developer after developing the latent image is collected in the developing container 2 as the developing sleeve 3 rotates.

  In the developing container 2, a developing chamber 14 serving as a first chamber capable of storing the developer and a circulation path for circulating the developer are formed by communicating with the developing chamber 14, so that the developer can be stored. Two stirring chambers 15 are provided. First and second developer agitating and conveying screws 5 and 6 are provided as conveying means for conveying the developer in the developing chamber 14 and the agitating chamber 15 (second chamber). A replenishment port (not shown) for replenishing the agitation chamber 15 with developer having toner and carrier is provided. And as shown in FIG. 4, the developer discharge port 8 for discharging the developer provided in the stirring chamber 15 is provided. The developer discharge port 8 is provided outside the circulation path on the downstream side in the developer transport direction in the stirring chamber 15 serving as the second chamber. The developer discharge amount limiting means is formed by a surface continuous in a direction intersecting with the developer discharge direction for blocking the developer upstream of the developer discharge port 8 and restricting the discharge amount. A flange member 11 is provided on the rotary shaft 10a of the second developer stirring and conveying screw 6. The rotary shaft 10a is rotatably provided in the developer transport path between the circulation path and the developer discharge port 8. Then, the two-component developer is stirred and mixed by these screws 5 and 6 and conveyed and circulated in the developing container 2. The developer transport direction is transported and circulated in the directions of arrows B and C in FIG.

  The rotary shaft 10a is provided with a discharge screw 9 serving as a spiral conveyance unit that conveys the developer toward the developer discharge port 8 toward the circulation path. Further, a flange member 11 serving as an annular projecting portion protruding in the radial direction of the rotary shaft 10a is provided at the upstream portion in the transport direction of the discharge screw 9 in the circumferential direction of the rotary shaft 10a. The flange member 11 limits the developer discharge amount regardless of the number of rotations of the second developer agitating and conveying screw 6 serving as a conveying means provided in the agitating chamber 15 due to its shape.

  A partition wall 7 is provided between the first developer stirring and conveying screw 5 and the first developer stirring and conveying screw 6. Further, as shown in FIG. 2, openings 7a and 7b for delivering the developer are provided on the back side and the near side of the partition wall 7 so that the developer is smoothly circulated between the screws 5 and 6. . FIG. 3 shows a cross section of the developing device 1 as viewed from the back side of the image forming apparatus main body 31, and the front side of FIG. 3 corresponds to the back side of the apparatus main body 31.

  Next, the developer supply and recovery, which is a characteristic part of the present embodiment, will be described in detail. As shown in FIG. 4, a developer discharge port 8 is provided on the downstream side of the second developer agitating and conveying screw 6 of the developing device 1 in the developer conveying direction. As shown in FIGS. 4 to 6, a discharge screw 9 serving as a developer discharge means is provided between the developer discharge port 8 and the developer container 2. Between the second developer stirring and conveying screw 6 and the developer discharging screw 9, a return screw 10 serving as a reverse conveying means is provided. A circular eaves member 11 serving as a developer discharge amount limiting means is provided at a terminal position downstream of the return screw 10 in the developer conveying direction by the second developer stirring and conveying screw 6. The eaves member 11 is formed with a surface continuous in a direction intersecting with the developer discharge direction that dams up the developer upstream of the developer discharge port 8 and restricts the discharge amount.

  The two-component developer is continuously discharged to the two-component developer conveyance path 12 in which the second developer agitating and conveying screw 6 is provided on the downstream side of the second developer agitating and conveying screw 6 in the conveying direction of the two-component developer. A discharge path 13 is provided. The height level of the bottom surface 13a of the discharge path 13 is set higher than the height level of the bottom surface 12a of the transport path 12. A developer discharge screw 9 that discharges an excess of the two-component developer to the developer discharge port 8 is provided in the discharge path 13.

  The second developer agitating and conveying screw 6 has a return screw 10 having a conveying force opposite to the conveying direction of the two-component developer on the downstream side in the conveying direction of the two-component developer. A return screw 10 is provided around the shaft 10a of the return screw 10 at a terminal position downstream of the two-component developer in the conveying direction of the second developer agitating and conveying screw 6 to dam the two-component developer. It has a hook member 11. On the downstream side in the conveying direction of the two-component developer by the second developer agitating and conveying screw 6 of the collar member 11, the conveying force in the same direction as the conveying direction of the two-component developer by the second developer agitating and conveying screw 6 was provided. A developer discharge screw 9 is provided. The eaves member 11 is formed in a circular shape when viewed from the conveying direction of the two-component developer of the second developer agitating and conveying screw 6. The eaves member 11 is configured as a part of the second developer stirring and conveying screw 6.

  Further, as the replenishment developer, a developer containing a carrier in a certain ratio (about 10% by weight) in the toner is used. The ratio is not limited to this. As described above, the toner consumed by the image formation is used as a replenishment developer containing a carrier at a constant rate, and the developer of the second agitating and conveying screw 6 of the developing container 2 is rotated according to the rotation of a replenishment screw (not shown). Replenished from the upstream side in the transport direction. The replenishment developer is supplied to the developing device 1 from a replenishment developer hopper (not shown) and received from a replenishment port (not shown) on the upper side of the developing container 2.

  The amount of toner and carrier replenishment is roughly determined by the number of rotations of the replenishment screw, and this number of rotations is determined by a toner replenishment amount control means (not shown).

  When replenishment is performed so as to keep the toner density of the developer inside the developing container 2 constant, the amount of the developer in the developing container 2 increases with image formation. Since the replenishment developer is 90% toner and 10% carrier, the toner is consumed by the image formation, but the carrier is not consumed and remains in the developing container, and the replenishment is repeated and the amount of the developer increases. . When the amount of the developer increases, the developer passes over the return screw 10 and the flange member 11 and is conveyed to the developer discharge port 8 by the developer discharge screw 9. The developer transported to the developer discharge port 8 is discharged from the developer discharge port 8, transported to a recovery container (not shown) by developer recovery means (not shown), and collected and stored.

  As described above, two-component development is performed so that the consumed toner is replenished by the replenishment developer, and at the same time, the developer in the developing container 2 is kept constant while discharging the excess developer. The replacement of the developer is automatically performed gradually to realize an automatic developer discharging function.

  Next, an automatic developer discharging function corresponding to a plurality of stirring and conveying speeds that is characteristic in the present invention will be described. In some cases, the developer agitation conveyance speed has a plurality of conveyance speeds, for example, an equal speed such as 300 rpm, 150 rpm, and 100 rpm, a 1/2 speed, and a 1/3 speed. In this case, the developer is conveyed by the second developer agitating and conveying screw 6 and is fed to a terminal portion (hereinafter simply referred to as “terminated portion”) 10 b of the returning screw 10 on the downstream side in the developer conveying direction by the second developer agitating and conveying screw 6. The amount of developer that spills from the blade breaks up to.

  When the developer transport speed is the same speed, the developer speed is higher than when the developer speed is low, so the inertial force of the developer increases. And spills from the cuts of the blades to reach the end portion 10b.

  However, since the developer that has reached the end portion 10b of the return screw 10 collides with the flange member 11 and is decelerated, the inertial force of the developer conveyed by the second developer agitating and conveying screw 6 is also reduced, and the speed dependency. Is also greatly reduced. Moreover, although the eaves member 11 is rotating, since it is disk-shaped, it can always be shielded as a disk-shaped wall regardless of the rotation speed. 14A, the developer advances in the direction of arrow P, but collides with the flange member 11. Only the developer that has passed over the flange member 11 as indicated by the arrow Q reaches the discharge screw 9. In FIG. 14B, H1 is a normal developer height on the line, and H2 is a developer height at which the developer height increases and the developer automatic discharge function works. Only the developer having a height of H1 or more and H2 or less is discharged. However, since the collar member 11 is present, the developer is actually discharged only from the shaded portion S2. The structure is not affected by the phase shift difference caused by the rotation of the developer stirring and conveying screw 6. Therefore, regardless of the speed difference from the uniform speed to the 1/3 speed, the amount of developer that reaches the developer discharge screw 9 over the flange member 11 becomes constant, and the development from the developer discharge port 8 is constant. The discharge amount of the agent can be made constant.

  As described above, in the present invention, the apparatus configurations such as the developer container 2, the first developer agitating / conveying screw 5, and the second developer agitating / conveying screw 6 are the same. The developer amount can be kept constant even at a plurality of stirring and conveying speeds.

  An annular protrusion provided upstream of the discharge screw 9 in the conveying direction and projecting in the radial direction of the rotary shaft 10a continuously in the circumferential direction of the rotary shaft 10a. Various other shapes are conceivable. For example, one of the upstream sides in the developer discharge direction may be a conical surface. Further, both sides may be conical surfaces (the shape of abacus balls). Further, it may be a spherical shape, a cylindrical shape whose diameter gradually increases in a step shape in the rotation axis direction, or a disk shape. Further, the present invention can be similarly applied even when a plurality of fine holes are formed in a part of the disk.

  Next, a second embodiment of the developing device according to the present invention will be described with reference to FIGS. FIG. 7 is a schematic view showing the developing device of this embodiment. The developing device 1 of the present embodiment will be described in detail with reference to FIGS. In addition, about the structure similar to the said 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  In the present embodiment, the annular screw is provided upstream of the discharge screw 9 in the conveying direction and protrudes in the radial direction of the rotary shaft 10a continuously in the circumferential direction of the rotary shaft 10a. A collar member 21 is provided as a protrusion. The flange member 21 is fixed to the wall surface of the developing container 2 around the shaft 10a of the return screw 10 in order to block the two-component developer. The flange member 21 is configured to have a smaller diameter than the diameter of the developer discharge port 8. The flange member 21 of the present embodiment is provided with a leg portion on the side surface, and the leg portion is fixed to the wall surface of the developing container 2. Since the developing container 2 and the developer automatic discharging function are the same as those in the first embodiment, description thereof will be omitted.

  Next, a developer automatic discharging function corresponding to a plurality of stirring and conveying speeds that is characteristic of the present embodiment will be described. As in the developing device 1 of the present embodiment, the developer agitation transport speed may have a plurality of transport speeds such as an equal speed such as 300 rpm, 150 rpm, and 100 rpm, a 1/2 speed, and a 1/3 speed. In this case, the amount of developer that is conveyed by the second developer agitating and conveying screw 6 and reaches the end of the return screw 10 varies.

  When the developer transport speed is the same speed, the developer speed is higher than when the developer speed is low, so the inertial force of the developer increases. To the end of.

  However, the developer that has reached the end portion of the return screw 10 collides with the flange member 21 and is decelerated, so that the inertial force of the conveyed developer is also reduced, and the speed dependency is greatly reduced. Further, the flange member 21 has a disk shape and is fixed to the developing container 22. For this reason, it can always be shielded as a wall regardless of the rotation speed. Therefore, the amount of developer that reaches the developer discharge screw 9 over the flange member 21 is constant regardless of the speed difference from the uniform speed to 1/3 speed, and the developer discharge from the developer discharge port 8 is constant. The amount can be constant. The flange member 21 of the present embodiment is not limited to a disk shape as long as the developer amount can be made constant.

  As described above, in the present embodiment, the apparatus configurations such as the developer container 2, the first developer agitating / conveying screw 5, and the second developer agitating / conveying screw 6 can be the same. In addition, the discharged developer amount can be kept constant even at a plurality of different developer stirring and conveying speeds.

  As an application example of the present invention, the present invention can be applied to a developing device provided in an image forming apparatus such as a copying machine, a laser printer, and a facsimile.

5 ... 1st developer stirring conveyance screw (conveyance means)
6 ... Second developer stirring and conveying screw (conveying means)
8: Developer outlet (exhaust)
9: Discharge screw (conveying part)
10a: Rotating shaft
11… 鍔 member (protrusion)
14 ... Development chamber (first chamber)
15: Stirring chamber (second chamber)

Claims (1)

A first chamber in which developer can be stored;
Forming a circulation path for circulating the developer by communicating with the first chamber, and a second chamber capable of storing the developer;
Conveying means for conveying the developer in the first chamber and the second chamber;
In the second chamber, provided outside the circulation path on the downstream side in the transport direction of the developer, a discharge port for discharging the developer,
A rotating shaft rotatably provided in the developer transport path between the circulation path and the discharge port;
A spiral conveyance unit that is provided on the rotation shaft and conveys the developer toward the discharge port toward the circulation path;
A developing device, comprising: an annular projecting portion provided upstream of the transporting portion in the transporting direction and projecting in a radial direction of the rotating shaft continuously in a circumferential direction of the rotating shaft.

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