JP2009300584A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: Toner goes up on a developer circulating in a first developer accommodating chamber for supplying the developer to the developer carrying member and a second developer accommodating chamber for stirring the developer. To prevent that.
A developing device includes a developer carrying member, a first developer containing chamber for containing a developer supplied to the developer carrying member, and a first opening and a first containing an adjacent developer. A second developer accommodating chamber 16 communicating with the first developer accommodating chamber 15 at two locations of the two openings 19, and the first developer conveying screw 12 and the second developer in the first developer accommodating chamber 15. The developer is circulated between the first developer accommodating chamber 15 and the second developer accommodating chamber 16 by the second developer conveying screw 13 in the accommodating chamber 16, and the toner is replenished in communication with the second developer accommodating chamber 16. A port 21 and an upstream prevention mechanism 30 for preventing the toner from going up on the circulating developer are provided upstream of the toner supply port 21 as viewed in the developer circulation direction.
[Selection] Figure 3

Description

  The present invention relates to a developing device using a two-component developer.

  2. Description of the Related Art Conventionally, various developing devices that are equipped in an electrophotographic image forming apparatus and perform development using a two-component developer containing toner and a magnetic carrier have been proposed (for example, see Patent Document 1). As one example, a biaxial transport type developing device is known (see, for example, Patent Document 2 and Patent Document 3).

  FIG. 7 shows an outline of such a biaxial transport type developing device 80, and FIG. 8 is a cross-sectional view taken along line III-III in FIG. 7 is a cross-sectional view obtained along the line IV-IV in FIG.

  The developing device 80 is configured such that a developing roller (sleeve) 81, a developer regulating member (doctor) 82, a supply / recovery screw 83, and a stirring / conveying screw 84 are accommodated in a developing tank 85. The developing tank 85 contains a two-component developer D (hereinafter referred to as developer D) containing toner and a magnetic carrier. A partition plate 86 is provided below the developing tank 85 and is divided into a supply / recovery chamber 87 (first developer accommodating chamber) and an agitating / conveying chamber 88 (second developer accommodating chamber). The partition plate 86 is provided with two openings (hereinafter referred to as a first opening 89 and a second opening 90 (see FIG. 8)) in the vicinity of both extending ends. Thus, the supply / recovery chamber 87 and the agitating / conveying chamber 88 communicate with each other.

  The developing roller 81 is a developer carrying member for attaching the toner of the developer D to a photosensitive drum (not shown), and a rotating cylindrical sleeve (not shown) and a magnet or magnet fixedly disposed in the sleeve. It consists of roles. The developer regulating member 82 regulates the amount of developer D on the developing roller 81 (on the sleeve located on the surface side).

  As shown in FIG. 8, the supply / recovery screw 83 is provided in the supply / recovery chamber 87, supplies the developer D in the supply / recovery chamber 87 to the developing roller 81 while conveying it, and the developer from the developing roller 81. A developer conveying member for collecting D. The agitating and conveying screw 84 is a developer conveying member that is provided in the agitating and conveying chamber 88 and conveys the developer D in the agitating and conveying chamber 88 while agitating. The supply / recovery screw 83 and the agitating / conveying screw 84 provided together convey the developer D in different directions. For this reason, in the developing tank 85, the screws 83 and 84 lead the stirring / conveying chamber 88 to the supply / recovery chamber 87 via the first opening 89 and the supply / recovery chamber 87 to the stirring / conveying chamber via the second opening 90. The developer D is circulated and conveyed so as to reach 88 (see arrow A9).

A toner supply port 91 is provided in the agitating and conveying chamber 88. The toner replenished from the toner replenishing port 91 is sufficiently charged by being agitated and conveyed together with the developer D in the agitating / conveying chamber 88 by the agitating / conveying screw 84 and contained in the developer D. Through one opening 89, it reaches the supply / recovery chamber 87 and is supplied to the developing roller 81.
JP 2005-031387 A JP 2007-218992 A JP 2008-039986 A

  However, in such a biaxial conveyance type developing device 80, a part of the toner replenished from the toner replenishing port 91 travels on the circulating developer D in the direction opposite to the circulation direction (see arrow A9). (Refer to the toner indicated by the symbol t and arrow A10). This is because the toner in the developer D is charged by being stirred together with the developer D (magnetic carrier), and the toner replenished from the toner replenishing port 91 is insufficiently charged. For this reason, a part of the toner replenished from the toner replenishing port 91 cannot be mixed with the developer D that circulates, and floats on the developer D or due to an impact that falls on the developer D or the like. This may be caused by jumping up and going up on the developer D that circulates.

  The toner going up in this way enters the supply / recovery chamber 87 through the second opening 90, reaches the developing roller 81 together with the supplied developer D, and moves to the photosensitive drum (not shown). May end up. The toner that has run up does not adhere properly to the photosensitive drum (not shown) (so that the electrostatic latent image can be properly visualized), causing toner scattering or abnormal image generation. Resulting in. This is because, as described above, the toner that has run up is insufficiently charged, so that it adheres appropriately to the photosensitive drum (not shown) on which the electrostatic latent image drawn by the potential potential is formed. Because it is not possible.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a developing device that can prevent the toner replenished from the toner replenishing port from going up on the circulating developer.

  Here, in the prior art described in Patent Document 1, the toner is supplied by providing a backflow restricting member in a developer retracting portion provided separately from the developer accommodating chamber for supplying the developer to the developer carrying member. The developer is prevented from flowing back from the toner storage portion to be supplied to the developer retracting portion, and some are similar in terms of preventing the developer from flowing back. However, since the flow of the developer itself is blocked in order to prevent the developer itself from flowing back to the developer retracting portion, the configuration and the concept of the present invention for preventing the toner from going up on the circulating developer are different. Different.

  In the prior art disclosed in Patent Document 2, an annular magnet is provided in the toner storage chamber for supplying toner to the second developer storage chamber, so that the first developer storage chamber is moved from the second developer storage chamber. The developer discharged to the top is prevented from flowing back into the toner storage chamber, and some of them are similar in terms of preventing the developer from flowing back. However, the flow of the developer itself is blocked in order to prevent the reverse flow of the developer itself to the toner storage chamber different from the circulation path, and the present invention prevents the toner from going up on the circulating developer. Structure and way of thinking are different.

  Furthermore, in the prior art described in Patent Document 3, a backflow prevention unit is provided in a delivery portion (first opening and second opening) that is a communication portion between the second developer storage chamber and the first developer storage chamber. As a result, the backflow of the developer that occurs at the delivery portion due to the rotation of the developer transport screw is prevented, and there are some similarities in terms of preventing the backflow of the developer. However, the flow of the developer itself is blocked in order to prevent the reverse flow of the developer itself due to the rotation of the developer conveying screw, and the present invention is configured to prevent the toner from going up on the circulating developer. And the way of thinking is different.

  The present invention has been made in view of the above problems, and includes a first developer accommodating chamber for supplying developer to the developer carrying member and a second developer accommodating chamber for stirring the developer. An object of the present invention is to provide a developing device capable of preventing the toner from going up on the developer circulated.

  In order to solve the above-mentioned problem, the invention according to claim 1 is a first developer containing a developer carrying member carrying a developer containing toner and a magnetic carrier, and containing the developer supplied to the developer carrying member. A developer storage chamber, a second developer storage chamber adjacent to the first developer storage chamber, storing the developer, and communicating with the first developer storage chamber at two locations, a first opening and a second opening. A first developer conveying screw rotated to convey the developer in the first developer accommodating chamber from the first opening side to the second opening side, and the second developer accommodating chamber The developer is rotated to be conveyed from the second opening side to the first opening side while stirring the developer, and in cooperation with the first developer conveying screw, the first developer accommodating chamber and the A second developer conveying screw for circulating the developer between the second developer accommodating chamber and the second developer; A toner replenishing port communicating with the image material storage chamber, and a run-up prevention mechanism for preventing the toner from going up on the circulating developer upstream of the toner replenishing port as viewed in the circulation direction of the developer. And.

  The invention according to claim 2 is the developing device according to claim 1, wherein the run-up prevention mechanism is viewed from the developer carrying member through the second opening as viewed in the circulation direction of the developer. It is provided so as not to hinder the circulation of the developer between the toner supply port.

  A third aspect of the present invention is the developing device according to the second aspect, wherein the anti-roll-up mechanism has a plate shape that contacts the surface layer of the developer so as not to hinder the circulation of the developer. It has the member.

  A fourth aspect of the present invention is the developing device according to the second or third aspect, wherein the run-up prevention mechanism is orthogonal to the circulation direction and the vertical direction on the developer through which the plate-shaped member circulates. The plate-like member is provided so as to be rotatable around an axis line, and is configured to be rotated in a direction for promoting circulation of the developer around the axis line by a driving mechanism.

  The invention according to claim 5 is the developing device according to claim 2 or claim 3, wherein the anti-raising mechanism is perpendicular to the circulation direction and the vertical direction on the developer through which the plate-like member circulates. The plate-like member is configured to be swingable about the axis by a drive mechanism.

  The invention according to claim 6 is the developing device according to claim 4 or 5, wherein the driving mechanism applies the driving force of the first developer conveying screw or the second developer conveying screw to the plate. It transmits to a shape member, It is characterized by the above-mentioned.

  The invention according to claim 7 is the developing device according to any one of claims 3 to 6, wherein the run-up prevention mechanism contacts a surface layer of the developer through which the plate-shaped member circulates. It is provided so as to be movable between a possible position and a position not in contact with the developer, and is a position where the toner can be contacted when the toner is supplied from the toner supply port.

  An invention according to an eighth aspect is the developing device according to any one of the first to seventh aspects, wherein the run-up prevention mechanism is provided in the second opening. To do.

  The invention according to claim 9 is a process cartridge in which the developing device according to any one of claims 1 to 8 is mounted.

  According to a tenth aspect of the present invention, there is provided an image forming apparatus equipped with the developing device according to any one of the first to eighth aspects.

  The developing device according to the present invention is provided with a mechanism for preventing the toner replenished upstream from the toner replenishing port as viewed in the developer circulation direction, thereby preventing the toner replenished from the toner replenishing port. Can do.

  In addition to the above-described configuration, the run-up prevention mechanism is configured so that, when viewed in the circulation direction of the developer, the developer does not pass between the developer carrier and the toner supply port through the second opening. If it is provided so as not to hinder the circulation, it is possible to prevent a part of the toner replenished from the toner replenishing port from going up to the developer carrying member.

  Further, since the circulation of the developer is not hindered by the anti-roll-up prevention mechanism, it is possible to prevent the adverse effects caused by the irregular circulation of the developer.

  In addition to the above-described configuration, if the anti-upward mechanism has a plate-like member that contacts the surface layer of the developer so as not to hinder the circulation of the developer, the development by the anti-upward mechanism Inhibition of the circulation of the developer can be prevented more reliably, so that the adverse effects caused by the irregular circulation of the developer can be more reliably prevented.

  In addition to the above-described configuration, the run-up prevention mechanism is provided on the developer through which the plate-like member circulates so as to be rotatable about an axis perpendicular to the circulation direction and the vertical direction, and the plate-like member is a drive mechanism. Is rotated in a direction that promotes circulation of the developer around the axis, and the toner is traced back on the developer while encouraging circulation of the developer by the rotated plate-like member. The top can be prevented.

  In addition to the above-described configuration, the run-up prevention mechanism is provided on the developer in which the plate member circulates so as to be swingable about an axis perpendicular to the circulation direction and the vertical direction, and the plate member is driven. If the mechanism is configured to be swung around the axis, it is possible to prevent the toner from going up on the developer while promoting the circulation of the developer by the swung plate-like member. .

  In addition to the above-described configuration, the driving mechanism transmits the driving force of the first developer conveying screw or the second developer conveying screw to the plate-like member. This can be realized without the need for a new drive source for the member.

  In addition to the above-described configuration, the run-up prevention mechanism is provided movably between a position where the plate-like member can contact the surface layer of the developer that circulates and a position where the plate member does not contact the developer, When the toner is replenished from the toner replenishing port, the plate member is brought into contact with the surface layer of the developer to be circulated only when the toner is replenished from the toner replenishing port. Therefore, it is possible to prevent the toner from going up on the developer while more reliably preventing the circulation of the developer.

  In addition to the above-described configuration, if the upstream prevention mechanism is provided in the second opening, the hindrance to the circulation of the developer can be further reduced. This is due to the following. In the agitating and conveying chamber and the supply / recovery chamber, the developer inside is conveyed so as to be pushed out by the rotation of the screw, so that the vertical movement of the surface layer of the developer becomes large. On the other hand, in the first opening and the second opening that connect the agitation transport chamber and the supply / recovery chamber, the developer is pushed out in the axial direction by the screw in the agitation transport chamber and the supply / recovery chamber. Since the developer is conveyed, the vertical movement of the surface layer of the developer is reduced. For this reason, it is possible to more reliably prevent the developer from being disturbed by providing a mechanism for preventing the developer from circulating in the second opening where the developer is circulated more stably.

  In the process cartridge equipped with the developing device described above, it is possible to provide a process cartridge that does not develop the toner that has been run up.

  An image forming apparatus equipped with the developing device described above can provide an image forming apparatus that forms a stable image.

  Embodiments of a developing device according to the present invention will be described below with reference to the drawings.

  First, the configuration of the developing device 10 according to the present invention will be described.

  1A and 1B are explanatory views schematically showing an image forming apparatus 50 in which the developing device 10 according to the present invention is used. FIG. 1A shows the entire image forming apparatus 50, and FIG. An example is shown.

  As shown in FIG. 1, the image forming apparatus 50 includes a photosensitive drum 51, a charging roller 52, a surface potential meter 53, a developing roller 54, a transfer roller 55, a cleaning device 56, a power pack 57, A fixing unit 58.

  The photosensitive drum 51 has a cylindrical shape, and an electrostatic latent image is formed. This photosensitive drum 51 obtains a driving force from a driving mechanism (not shown) and rotates in the direction of the arrow A1 about an axis extending in the illustrated depth direction. A charging roller 52 is provided opposite to the photosensitive drum 51.

  The charging roller 52 is charged by receiving power from the power pack 57, and uniformly charges the surface 51a of the opposing photosensitive drum 51 at a desired potential. At this time, since the photosensitive drum 51 rotates in the direction of arrow A1, the surface portion of the surface 51a of the photosensitive drum 51 that is on the downstream side in the rotational direction from the portion facing the charging roller 52 is rotated. Therefore, it is uniformly charged sequentially.

  Subsequently, on the uniformly charged surface of the photosensitive drum 51, the laser beam (or the original document) which is controlled to the amount of emitted light corresponding to the image information such as an image and characters obtained by reading from the original document or the image information stored in advance. The light L carrying the image information of the original such as reflected light or transmitted light is irradiated.

  At this time, the potential (negative potential) of the surface 51a of the photosensitive drum 51 is decreased by the irradiation of the laser light L (the absolute potential increases in a direction approaching 0 (zero)). Then, the width of the decreasing potential increases as the amount of light irradiated by the laser light L increases. Therefore, an electrostatic latent image having a potential distribution corresponding to the image information and the like is formed on the surface 51a of the photosensitive drum 51 by the irradiation of the laser light L carrying the image information and the like.

  In order to measure the surface potential of the photosensitive drum 51, a surface potential meter 53 is provided. The surface potential meter 53 detects the potential (potential distribution) of the electrostatic latent image formed on the surface 51 a of the photosensitive drum 51. The detection result of the potential is used for charging control of the charging roller 52 by the power pack 57 and exposure control of the laser beam L.

  A developing roller 54 is provided to attach toner to the electrostatic latent image on the photosensitive drum 51 formed by the laser light L. When a portion of the surface 51 a on which the electrostatic latent image of the photosensitive drum 51 is formed passes through the developing roller 54, an amount of toner according to the potential distribution of the electrostatic latent image adheres, and the surface 51 a of the photosensitive drum 51. The toner image having a density distribution corresponding to the electrostatic latent image is visually developed (developed). The developing roller 54 is provided in the developing device 10 (see FIG. 2) as will be described later.

  In order to transfer the toner image onto the recording paper S, a transfer roller 55 is provided. The recording sheet S fed to the photosensitive drum 51 at a predetermined timing passes through the toner image while being sandwiched between the photosensitive drum 51 and the transfer roller 55, so that the toner image is pressed onto the recording sheet S and transferred. Is done. Then, the recording sheet S on which the toner image is transferred is conveyed toward the fixing unit 58 in the arrow A2 direction.

  The fixing unit 58 includes a heat fixing roller 59 and a pressure roller 60. The heat fixing roller 59 is configured by providing an adhesion preventing layer made of a fluororesin layer or the like for preventing toner adhesion on the outer peripheral surface of a cored bar made of a hollow cylindrical body such as aluminum. Although not shown, the heat fixing roller 59 is provided with a heater such as a halogen lamp in the hollow portion of the core metal along the rotation center line, and the heat fixing roller 59 is heated from the inside by its radiant heat. . A pressure roller 60 is provided in parallel with the heat fixing roller 59 and so as to be in pressure contact with the heat fixing roller 59.

  The recording paper S conveyed to the fixing unit 58 is passed between the pressure roller 60 and the heat fixing roller 59, so that the toner adhering to the recording paper S is softened by the heat of the heat fixing roller 59. At the same time, the toner image is fixed on the recording paper S by being pressed by being sandwiched between the pressure roller 60 and the heat fixing roller 59. The fixing unit 58 may be a belt-type fixing unit 58 ′ as shown in FIG. The fixing unit 58 ′ is configured such that a fixing belt 61 is stretched between a fixing roller 62 and a heating roller 63, and a pressure roller 64 is pressed against the fixing belt 61.

  A cleaning device 56 is provided for cleaning the photosensitive drum 51 after the transfer process. After the toner image is transferred to the recording paper S, the photosensitive drum 51 is cleaned by removing the toner remaining on the surface 51a by the cleaning device 56 and removing the residual charge by a quenching lamp (not shown). Returning to the processing state, the next charging process is waited.

  In this image forming apparatus 50, the photosensitive drum 51, the charging roller 52, the surface potential meter 53, the developing roller 54 (developing apparatus 10 to be described later), and the cleaning apparatus 56 are integrated with a housing 65 indicated by a two-dot chain line. It may be housed in a cartridge and formed as a process cartridge.

  The developing roller 54 described above is provided in the developing device 10 as shown in FIG. Here, FIG. 2 is an explanatory view schematically showing the developing device 10 according to the present invention, and FIG. 3 is a cross-sectional view taken along the line II of FIG. FIG. 2 is a cross-sectional view obtained along the line II-II in FIG.

  In addition to the above-described developing roller (sleeve) 54, the developing device 10 is configured such that a developer regulating member (doctor) 11, a supply / recovery screw 12, and a stirring and conveying screw 13 are accommodated in a developing tank 14. Yes.

  The developing tank 14 contains a two-component developer D (hereinafter referred to as developer D) containing toner and a magnetic carrier. In this embodiment, the developer D is in a granular form including a toner having a particle diameter of 10 μm or less and a magnetic carrier having a particle diameter of 20 to 100 μm. A supply / recovery chamber 15 (first developer accommodating chamber) and an agitating / conveying chamber 16 (second developer accommodating chamber) are provided below the developing tank 14. The supply / recovery chamber 15 and the agitation transport chamber 16 are configured such that the lower part of the developing tank 14 is separated by a partition plate 17. As shown in FIG. 3, the partition plate 17 is provided with two openings (hereinafter referred to as a first opening 18 and a second opening 19) in the vicinity of both extending ends thereof. The supply / recovery chamber 15 and the agitating / conveying chamber 16 communicate with each other.

  As shown in FIG. 2, a developing roller 54 is provided above the developing tank 14. The developing roller 54 is a developer carrying member that carries the developer D so that the toner adheres to the photosensitive drum 51, and includes a rotating cylindrical developing sleeve 54a and a magnet 54b fixedly disposed in the developing sleeve 54a. (Magnet roll). The developing sleeve 54a is rotationally driven by a driving motor (not shown) or the like, and is rotationally driven at 280 RPM (rotation / minute) in this embodiment. The magnet 54 b is provided so as to radiate a magnetic field radially in a predetermined direction, magnetically attracts and holds the developer D on the surface of the rotationally driven developing sleeve 54 a, and magnetizes in the vicinity of the photosensitive drum 51. Form a brush. The toner attached to the surface of the magnetic carrier in the magnetic brush formed by the developer D adheres to the surface 51 a according to the potential distribution of the electrostatic latent image formed on the surface 51 a of the photosensitive drum 51. . As a result, a toner image having a density distribution corresponding to the electrostatic latent image is visualized (developed) on the surface 51a of the photosensitive drum 51.

  In order to make the magnetic brush formed on the surface of the developing sleeve 54a of the developing roller 54 appropriate, the developer regulating member 11 is provided. The developer regulating member 11 is provided at a predetermined interval from the developing roller 54 so that the developer D sucked and held on the developing sleeve 54a of the developing roller 54 by the magnetic force of the magnet 54b has a predetermined layer thickness. It has been.

  A supply and recovery screw 12 is provided in close proximity to the developing roller 54 in a parallel state. The supply / recovery screw 12 is rotatably provided in the supply / recovery chamber 15, has a spiral blade, and can rotate to convey the developer D in the axial direction thereof. The supply / recovery screw 12 is a first developer transport screw that supplies the developer D in the supply / recovery chamber 15 to the developing roller 54 while transporting the developer D and collects the developer D from the developing roller 54. In the present embodiment, the developer D in the supply / recovery chamber 15 is rotated by a drive mechanism (not shown) to move the developer D in the supply / recovery chamber 15 in the direction of arrow A3 (the direction from the first opening 18 toward the second opening 19). It is set to carry.

  A stirring and conveying screw 13 is provided in parallel with the supply and recovery screw 12. The agitating / conveying screw 13 is rotatably provided in the agitating / conveying chamber 16 and has a spiral blade. By rotating, the agitating / conveying screw 13 is developed in the direction opposite to the supply / recovery screw 12 provided in the axial direction. It is possible to transport the agent D. The conveyance in the reverse direction may be due to the reverse winding direction of the spiral blades or may be due to the reverse rotation direction. The agitating and conveying screw 13 is a second developer conveying screw that conveys the developer D in the agitating and conveying chamber 16 while agitating. In this embodiment, the developer D in the supply / recovery chamber 15 is rotated by a drive mechanism for driving the supply / recovery screw 12 (not shown), and the developer D in the supply / recovery chamber 15 is rotated in the direction indicated by the arrow A4 (from the second opening 19 side). It is set so as to be conveyed in the direction toward one opening 18.

  For this reason, in the lower part of the developing tank 14, the supply / recovery screw 12 and the stirring / transporting screw 13 provided so as to transport the developer D in mutually different directions are rotationally driven, so that from the stirring / transporting chamber 16. The developer D is circulated and conveyed through the first opening 18 to the supply / recovery chamber 15, and from the supply / recovery chamber 15 to the stirring and conveying chamber 16 via the second opening 19.

  In the circulated developer D, the toner density is lowered by supplying the toner to the photosensitive drum 51 by the supply and recovery screw 12. In the developing device 10, a toner concentration sensor 20 and a toner supply port 21 are provided in order to supplement such toner concentration. The toner concentration sensor 20 measures the toner concentration of the developer D accommodated in the developing tank 14. In this embodiment, the toner concentration sensor 20 is provided so that the toner concentration in the developer D in the supply / recovery chamber 15 can be measured. ing. The toner is replenished based on the measurement result by the toner density sensor 20. A toner supply port 21 is provided for supplying toner.

  The toner replenishing port 21 is provided so as to communicate with the stirring / conveying chamber 16 from above, and in this embodiment, as shown in FIG. 3, a position near the second opening 19 (the stirring / conveying chamber 16 as viewed in the circulation direction). At an upstream position). From the toner supply port 21, toner is supplied by a toner supply mechanism (not shown). The toner replenishing mechanism is driven and controlled to replenish an appropriate amount of toner based on the measurement result of the toner density sensor 20. The amount of toner to be replenished at one time varies depending on the model and configuration, but when it is large, it is about 30 to 100 mg. The toner replenished from the toner replenishing port 21 is sufficiently charged by being agitated and conveyed together with the developer D in the agitating and conveying chamber 16 by the agitating and conveying screw 13 and contained in the developer D. It reaches the supply / recovery chamber 15 through the opening 18 and is supplied to the developing roller 54. Thus, the developer D in the developing device 10 has a constant toner density regardless of the supply of toner to the photosensitive drum 51. The toner replenishing port 21 replenishes the developer D supplied to the developing roller 54 with toner, so that the agitating and conveying chamber 16 in which the developer D is circulated, the first opening 18, and the supply and recovery chamber. 15 and the second opening 19 may be used, and the present invention is not limited to the above-described embodiment.

  In the developing device 10 according to the present invention, a run-up prevention mechanism 30 is provided. The run-up prevention mechanism 30 prevents the toner from going up on the circulating developer D so that the circulation of the developer D is not hindered. Here, not to inhibit the circulation of the developer D means that the developer D is not intended to inhibit the circulation of the developer D like damming the developer D itself, This refers to suppressing the hindrance to the circulation of the developer D as much as possible.

  The anti-upward mechanism 30 prevents the toner that has run up from reaching the developing roller 54 together with the developer D supplied to the developing roller 54, so that the toner is viewed in the circulation direction of the developer D. What is necessary is just to provide upstream from the supply port 21. FIG. For this reason, in this embodiment, it is sufficient to provide the anti-back-up mechanism 30 between the developing roller 54 and the toner replenishing port 21 through the second opening 19 as viewed in the circulation direction of the developer D. In this example, the second opening 19 is provided.

  In the present embodiment, the anti-run-up mechanism 30 is configured by attaching a dam plate 31 to the ceiling portion 19a of the second opening 19. The weir plate 31 has a thin plate shape formed of PET (polyethylene terephthalate), and the developer whose one end 31a located on the ceiling portion 19a side is circulated when viewed in the circulation direction of the developer D (see arrow A5). It is attached to the ceiling portion 19a so as to be located upstream from the other end 31b side located on the D side. This dam plate 31 has a width dimension substantially equal to the width dimension of the second opening 19 (opening dimension seen in the extending direction of the partition plate 17), and on the surface layer of the developer D in which the other end 31b is circulated. The length is in contact.

  In the developing device 10 according to the present invention, when the developer D is circulated in the operating state and in the lower part of the developing tank 14, that is, in the stirring and conveying chamber 16, the first opening 18, the supply / recovery chamber 15, and the second opening 19. Since the weir plate 31 which is the upstream prevention mechanism 30 contacts the surface layer of the developer D so as to sweep over the developer D to be circulated, the circulation of the developer D is not hindered.

  Here, a part of the toner replenished from the toner replenishing port 21 in order to prevent a decrease in toner density cannot be mixed into the circulating developer D and floats on the developer D. Even when the developer D that circulates by jumping up due to an impact or the like falling on the developer D is run up, a weir plate 31 is provided in the second opening 19 as the rise-up prevention mechanism 30. For this reason, the run-up of the toner is stopped by the barrier plate 31 (see t in FIG. 2).

Therefore, in the developing device 10, it is possible to prevent the toner from going up on the circulating developer D. As a result, the developing device 10 can prevent the occurrence of toner scattering and abnormal images due to the toner going up.
[Modification 1]
Next, a first modification of the developing device 10 according to the embodiment will be described. Since the basic configuration of the developing device 101 of Modification 1 is the same as that of the developing device 10 (see FIGS. 2 and 3), detailed description of the same configuration is omitted. FIG. 4 is an explanatory diagram schematically showing the developing device 101.

  In the developing device 101 of the first modification, as shown in FIG. 4, a run-up prevention mechanism 301 having a configuration different from that of the developing device 10 is provided in the second opening 19.

  The run-up prevention mechanism 301 is configured by attaching a plurality of (six in this example) plate-like members 33 to the rotating shaft 32. The rotating shaft 32 extends on the developer D to be circulated along a direction perpendicular to a plane including the circulation direction and the vertical direction (a direction perpendicular to the paper surface of FIG. 4), and is rotatably provided. ing. In the first modification, the rotation shaft 32 is provided in the second opening 19 so as to bridge the developing tank 14 and the partition plate 17. Further, in the first modification, the rotating shaft 32 transmits the driving force of the agitating / conveying screw 13 and the supply / recovery screw 12 that are rotationally driven through a gear (not shown), so that The surface facing the developer D is rotated in the opposite direction (the direction of the arrow A6 in the illustrated example) with respect to the circulation direction of the developer D. In the first modification, the rotating shaft 32 is rotationally driven at a rotational speed (200 rpm to 400 rpm) comparable to that of the stirring and conveying screw 13 and the supply and recovery screw 12. Each plate member 33 is provided on the rotating shaft 32.

  Each plate-like member 33 has a thin plate shape formed of a resin material such as ABS (acrylonitrile butadiene styrene), and is provided on the rotary shaft 32 so as to extend radially from the rotation center of the rotary shaft 32. It has been. Each plate-like member 33 has a width dimension substantially equal to the width dimension of the second opening 19 (opening dimension seen in the extending direction of the partition plate 17), and the extending end 33a from the rotating shaft 32 circulates. The length of the developer D is in contact with the surface layer of the developer D.

  In the developing device 101 of the first modified example, when the developer D is circulated in the operating state and in the lower part of the developing tank 14, that is, in the stirring and conveying chamber 16, the first opening 18, the supply / recovery chamber 15, and the second opening 19. In the ascending prevention mechanism 301, the rotary shaft 32 is rotationally driven, and each plate-like member 33 is rotated around the rotary shaft 32. Since each of the plate-like members 33 slides on the developer D in a direction opposite to the circulation direction so as to sweep the developer D that is circulated while being bent lightly, the circulation of the developer D is prevented. Absent.

  Here, even if a part of the toner replenished from the toner replenishing port 21 goes up on the developer D in order to prevent the toner density from being lowered, the second opening 19 is prevented from going up. Each plate-like member 33 as the mechanism 301 slides so as to sweep over the developer D that is rotated around the rotating shaft 32 and circulates. It is stopped by 301 (each plate-like member 33) (see symbol t in FIG. 4).

  Therefore, in the developing device 101, it is possible to prevent the toner from going up on the circulating developer D. As a result, the developing device 101 can prevent the occurrence of toner scattering and abnormal images due to the toner going up.

In Modification 1, the anti-backlash mechanism 301 is configured with six plate members 33 provided on the rotating shaft 32. However, one or more plate members 33 may be provided. It is not limited to 1.
[Modification 2]
Next, a second modification of the developing device 10 according to the embodiment will be described. Since the basic configuration of the developing device 102 of Modification 2 is the same as that of the developing device 10 (see FIGS. 2 and 3), detailed description of the same configuration is omitted. FIG. 5 is an explanatory diagram schematically showing the developing device 102.

  In the developing device 102 of Modification 2, as shown in FIG. 5, the second opening 19 is provided with a run-up prevention mechanism 302 having a different configuration from the developing device 10 and the developing device 101.

  The back-up prevention mechanism 302 is configured by attaching a plate-like member 332 to the swing shaft 34. The swing shaft 34 extends on the developer D to be circulated along a direction perpendicular to the plane including the circulation direction and the vertical direction (a direction perpendicular to the paper surface of FIG. 5), and is provided so as to be swingable. It has been. In the second modification, the swing shaft 34 is provided in the second opening 19 so as to bridge the developing tank 14 and the partition plate 17. Further, in the second modification, the swing shaft 34 has a constant force when the driving force of the agitating and conveying screw 13 and the supply and recovery screw 12 that are rotationally driven is transmitted via a gear (not shown). It is rotated so as to reciprocate in the angular range (see arrow A7). In the second modification, the swing shaft 34 is swung at a frequency of about 10 Hz. A plate-like member 332 is provided on the swing shaft 34.

  The plate-like member 332 has a thin plate shape made of, for example, a PET film, and is provided on the swing shaft 34 so as to swing around the swing center of the swing shaft 34. In this embodiment, the plate-like member 332 is formed of Mylar (registered trademark) made of the material PET. The plate-like member 332 has a width dimension substantially equal to the width dimension of the second opening 19 (opening dimension seen in the extending direction of the partition plate 17), and the extending end 332a from the swing shaft 34 circulates. The length of the developer D is in contact with the surface layer of the developer D.

  In the developing device 102 of the modified example 2, when the developer D is circulated in the operation state and in the lower part of the developing tank 14, that is, in the stirring / conveying chamber 16, the first opening 18, the supply / recovery chamber 15 and the second opening 19. In the ascending prevention mechanism 302, the swing shaft 34 is rotated so as to reciprocate within a certain angular range, and the plate-like member 332 is swung around the swing shaft 34. The plate-like member 332 slides on the developer D so as to sweep the developer D circulated while being bent lightly (see the plate-like member 332 indicated by a two-dot chain line and an arrow A7). The circulation is not hindered.

  Here, even if a part of the toner replenished from the toner replenishing port 21 goes up on the developer D in order to prevent the toner density from being lowered, the second opening 19 is prevented from going up. Since the plate-like member 332 as the mechanism 302 slides so as to sweep over the developer D that is swung around the swinging shaft 34 and circulated, the toner ascending is prevented from moving up. It is stopped by 302 (plate member 332) (see symbol t in FIG. 5).

  Therefore, the developing device 102 can prevent the toner from going up on the circulating developer D. As a result, the developing device 102 can prevent toner scattering and abnormal image generation due to the toner going up.

In the second modification, the plate-like member 332 of the run-up prevention mechanism 302 is configured to slide so as to sweep over the circulated developer D, but the plate-like member is circulated developer. It may slide on the developer D so as to scoop up on D, and is not limited to the second modification.
[Modification 3]
Next, a third modification of the developing device 10 according to the embodiment will be described. Since the basic configuration of the developing device 103 of Modification 3 is the same as that of the developing device 10 (see FIGS. 2 and 3), detailed description of the same configuration is omitted. FIG. 6 is an explanatory diagram schematically showing the developing device 103.

  In the developing device 103 of Modification 3, as shown in FIG. 6, the ascending prevention mechanism 303 is configured by the same configuration as the ascending prevention mechanism 30 of the developing device 10, that is, by the inclined dam plate 313. This is different from the ascending prevention mechanism 30.

  The ascending prevention mechanism 303 is configured to translate in the vertical direction by a moving mechanism (not shown), that is, the dam plate 313 is translated in the vertical direction (see arrow A8). Specifically, in the third modification, the dam plate 313 is attached to a shaft member that spans the developing tank 14 and the partition plate 17 (not shown), and the shaft member can be translated in the vertical direction. The two openings 19 are configured to be held. In addition, this dam plate 313 may be the structure suspended from the ceiling part 19a of the 2nd opening part 19 so that a parallel movement is possible, and is not limited to this modification 3. FIG.

  The parallel movement of the ascending prevention mechanism 303 includes a position where the other end 313b of the dam plate 313 contacts the surface layer of the developer D to be circulated (refer to a dam plate 313 indicated by a solid line (hereinafter referred to as a retracted position)) and the other The end 313b is set so as to be between a position where it does not contact the surface layer of the developer D to be circulated (refer to a weir plate 313 indicated by a two-dot chain line (hereinafter referred to as a prevention position)). The movement mechanism (not shown) for the parallel movement of the ascent prevention mechanism 303 is driven and controlled so that the ascent prevention mechanism 303 is translated in accordance with the supply of toner by the toner supply mechanism (not shown). In other words, the ascending prevention mechanism 303 (the dam plate 313) is in the retracted position (see the dam plate 313 indicated by the solid line) in a normal state without toner replenishment, and the prevention position when the toner is replenished from the toner supply port 21. The back-up prevention mechanism 303 (the dam plate 313) is moved to (see the dam plate 313 indicated by the solid line), and when the toner supply is completed, the back-up prevention mechanism 303 (the dam plate 313 indicated by the two-dot chain line) is moved again. . The end of the toner supply may be when the toner supply from the toner supply port 21 has actually ended, or even when a certain time has elapsed since the end of the supply. What is necessary is just to set suitably so that it may correspond to the toner going up phenomenon on the circulating developer D.

  In the developing device 103 according to the third modification, even when the developer D is circulated in the operation state, the developer D is circulated in the lower part of the developing tank 14, that is, in the agitation transport chamber 16, the first opening 18, the supply / recovery chamber 15 and the second opening 19. In the ascending prevention mechanism 303, the other end 313b of the weir plate 313 is in a retracted position (see the weir plate 313 indicated by a two-dot chain line) that does not contact the surface layer of the developer D to be circulated. Circulation is not hindered.

  Here, when the toner is supplied from the toner replenishing port 21 to prevent the toner density from being lowered, the ascending prevention mechanism 303 is moved to the prevention position (see the weir plate 313 indicated by the solid line). Even when a part of the developer D circulates, the toner 313 rises as the anti-upward mechanism 303 exists in the second opening 19, so that the toner goes up. It is stopped by the dam plate 313 (see symbol t in FIG. 6).

  Therefore, the developing device 103 can prevent the toner from going up on the circulating developer D. As a result, the developing device 103 can prevent the occurrence of toner scattering and abnormal images due to the toner going up.

  In Modification 3, the ascending prevention mechanism 303 having the same configuration as the ascending prevention mechanism 30 of the developing device 10 is translated in the vertical direction by a moving mechanism (not shown). The ascending prevention mechanism 301 and the ascending prevention mechanism 302 of the second modification may be configured to move in parallel in the vertical direction, and are not limited to the third modification. .

  In the above-described embodiment, the ascending prevention mechanism prevents the ascending toner from reaching the developing roller 54 together with the developer D supplied to the developing roller 54. What is necessary is just to provide in the upstream rather than the toner replenishment port 21 seeing in the circulation direction, and is not limited to the above-mentioned embodiment. However, in the agitating and conveying chamber 16 and the supply / recovery chamber 15, the developer D is conveyed so that it is pushed out by the rotation of the screws (reference numerals 12 and 13) having spiral blades. Increases the vertical movement of. On the other hand, in the place (the 1st opening part 18 and the 2nd opening part 19) which connects the stirring conveyance chamber 16 and the supply collection chamber 15, a screw (code | symbols 12 and 13) in the stirring conveyance chamber 16 and the supply collection chamber 15 Since the developer D is conveyed by being pushed out by the developer D conveyed in the axial direction, the vertical movement of the surface layer of the developer D is reduced. For this reason, from the viewpoint of minimizing the hindrance to the circulation of the developer D, the run-up prevention mechanism communicates the stirring / conveying chamber 16 and the supply / recovery chamber 15 (in the above-described embodiment, the second opening 19). ) Is desirable.

  The present invention has been described in detail based on the embodiments. However, the present invention is not limited to this specific configuration, and design changes that do not depart from the spirit of the present invention are included in the technical scope of the present invention.

4A and 4B are explanatory views schematically showing an image forming apparatus using a developing device according to the present invention, in which FIG. 5A shows the entire image forming apparatus, and FIG. 5B shows another example of the fixing unit. It is explanatory drawing which shows typically the developing device which concerns on this invention. It is sectional drawing obtained along the II line of FIG. FIG. 10 is an explanatory diagram schematically illustrating a developing device according to a first modification. FIG. 10 is an explanatory diagram schematically illustrating a developing device according to a second modification. FIG. 10 is an explanatory diagram schematically illustrating a developing device according to Modification 3. It is explanatory drawing which shows typically the conventional biaxial conveyance type developing device. It is sectional drawing obtained along the III-III line of FIG.

Explanation of symbols

10, 101, 102, 103 Developing device 12 Supply / recovery screw (as first developer transport screw) 13 Stirring / transport screw 15 (as second developer transport screw) 15 (as first developer storage chamber) Supply / recovery chamber 16 Agitating and conveying chamber (as second developer storage chamber) 18 First opening portion 19 Second opening portion 21 Toner replenishing port 30, 301, 302, 303 Back-up prevention mechanism 31, 313 (as plate-like member) ) Weir plate 33, 332 Plate member 50 Image forming apparatus 54 Developing roller (as developer carrier) D Developer t Toner going up

Claims (10)

A developer carrying member carrying a developer containing toner and a magnetic carrier;
A first developer accommodating chamber for accommodating the developer supplied to the developer carrying member;
A second developer accommodating chamber adjacent to the first developer accommodating chamber and accommodating the developer and communicating with the first developer accommodating chamber at two locations, a first opening and a second opening;
A first developer conveying screw rotated to convey the developer in the first developer accommodating chamber from the first opening side to the second opening side;
The developer in the second developer storage chamber is rotated to transport the developer from the second opening side to the first opening side while stirring, and cooperates with the first developer transport screw to move the first developer. A second developer conveying screw that circulates the developer between one developer containing chamber and the second developer containing chamber;
A toner supply port communicating with the second developer storage chamber;
A developing device comprising: a upstream prevention mechanism for preventing the toner from going up on the circulating developer upstream of the toner supply port as viewed in the developer circulation direction.   The ascending prevention mechanism does not hinder the circulation of the developer from the developer carrying member through the second opening to the toner supply port as viewed in the developer circulation direction. The developing device according to claim 1, wherein the developing device is provided as described above.   The developing device according to claim 2, wherein the upstream prevention mechanism includes a plate-like member that contacts a surface layer of the developer so as not to hinder circulation of the developer.   The run-up prevention mechanism is provided on the developer through which the plate-like member circulates so as to be rotatable about an axis perpendicular to the circulation direction and the vertical direction, and the plate-like member is rotated around the axis by the drive mechanism. 4. The developing device according to claim 2, wherein the developing device is rotated in a direction that promotes circulation of the agent.   The run-up prevention mechanism is provided so as to be swingable about an axis perpendicular to the circulation direction and the vertical direction on the developer through which the plate-shaped member circulates, and the plate-shaped member is rocked about the axis by a drive mechanism. The developing device according to claim 2, wherein the developing device is configured to be moved.   The developing device according to claim 4, wherein the driving mechanism transmits a driving force of the first developer conveying screw or the second developer conveying screw to the plate-like member.   The back-up prevention mechanism is provided so as to be movable between a position where the plate-like member circulates can contact the surface layer of the developer and a position where the plate member does not contact the developer. 7. The developing device according to claim 3, wherein the developing device is in a position where it can be contacted when replenished.   8. The developing device according to claim 1, wherein the back-up prevention mechanism is provided in the second opening. 9.   A process cartridge equipped with the developing device according to claim 1. An image forming apparatus equipped with the developing device according to claim 1.