JP2008134361A - Developer conveying device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably maintain a developer conveying ability. <P>SOLUTION: A developer conveying part 55 includes: a storage part 551 in which a discharge port 553 is arranged and stores residual developer peeled from the surface of a developing roller; and a conveying part 552 which is disposed in the storage part 551, and conveys the developer toward the discharge port 553. The conveying part 552(=spring screw) is disposed so that the position of the lower end thereof may be lower than the position of the lower end of the discharge port 553. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a developer transport device and an image forming apparatus that transport a developer toward a discharge port in order to collect the peeled residual developer. In particular, the present invention relates to a developer transport device used for a copying machine, a facsimile, a printer, and the like.

  Formed on a photosensitive drum in an image forming apparatus (so-called wet image forming apparatus) such as a copying machine or a printer that forms an image by transferring to a recording paper by an electrophotographic method using a developer composed of a carrier liquid and a toner. From the viewpoint of ensuring image quality, it is necessary to peel off the developer remaining on the developing roller (hereinafter referred to as “residual developer”) after supplying the developer to the electrostatic latent image.

Further, it is advantageous from the viewpoint of cost to collect and reuse the residual developer peeled off from the developing roller or the like, and also from the viewpoint of environmental protection. Therefore, various developer transport devices that transport the residual developer toward the discharge port have been proposed. For example, a developer transport device that collects residual developer by a screw conveyor disposed in a transport pipe is disclosed (see FIG. 4 of Patent Document 1).
JP-A-11-102122

  However, in the developer conveying device, particularly when the image forming apparatus is not in operation (= the residual developer peeled off from the developing roller does not flow into the conveying pipe), the screw conveyor in the conveying pipe. When the upper surface of the developer is exposed to the atmosphere from the liquid level of the developer to be conveyed, the toner contained in the developer may adhere to the screw conveyor and the conveying capacity of the screw conveyor may be reduced.

  SUMMARY An advantage of some aspects of the invention is that it provides a developer transport device and an image forming apparatus capable of stably maintaining a developer transport capability.

  In order to solve the above problem, the developer transport device according to claim 1 is a developer transport device that transports the developer toward a discharge port in order to recover the peeled residual developer. A storage means for storing the peeled residual developer, and a transport means disposed in the storage means for transporting the developer toward the discharge port. The conveying means is arranged such that a lower end position thereof is located below a lower end position of the discharge port.

  According to a second aspect of the present invention, there is provided the developer conveying apparatus according to the first aspect, wherein the conveying means is disposed so that the upper end position is lower than the lower end position of the discharge port. It is characterized by being.

  The developer transport device according to claim 3 is the developer transport device according to claim 1 or 2, wherein the transport means is formed in a spiral shape and rotates around a central axis of the spiral shape. It is characterized by comprising a driven spring screw and drive means for rotationally driving the spring screw.

  According to a fourth aspect of the present invention, there is provided the developer conveying apparatus according to the third aspect, wherein the spring screw has a substantially circular cross section.

  The developer transport device according to claim 5 is the developer transport device according to claim 3 or 4, wherein the spring screw is formed of a material whose surface has lower surface free energy than the developer. It is characterized by being.

  A developer conveying device according to a sixth aspect is the developer conveying device according to the fifth aspect, wherein the spring screw has a surface formed of a fluorine-based material.

  The developer transport device according to claim 7 is the developer transport device according to any one of claims 3 to 6, wherein the driving means sets a rotation speed of the spring screw to a predetermined value. It is characterized by being changed step by step at each time.

  The developer transport device according to claim 8 is the developer transport device according to any one of claims 3 to 7, wherein the peeled residual developer is peeled off from the surface of the rotating body. The discharge port is disposed at a substantially central position in the axial direction of the rotating body in the storage unit, and the spring screw is used to transport the developer toward the discharge port. In the position opposite to, the spiral shape is formed in the opposite direction.

  The image forming apparatus according to claim 9 is a liquid developing type image forming apparatus that forms an image on recording paper by transferring toner contained in the developer onto the recording paper. Any one of the developer transport devices described above is provided, and the developer collected via the developer transport device is reused.

  According to the developer transport device of the first aspect, the position of the lower end of the transport unit that is disposed in the storage unit that stores the peeled residual developer and transports the developer toward the discharge port is stored. Since it is arranged to be lower than the position of the lower end of the discharge port provided in the means, the developer stays in the storage means below the position of the lower end of the discharge port, and is conveyed to the retained developer. Since at least a part of the means is immersed, sticking of toner to the conveying means is suppressed, and the developer conveying ability can be stably maintained.

  According to the developer transport device of the second aspect, the position of the upper end of the transport unit that is disposed in the storage unit that stores the separated residual developer and transports the developer toward the discharge port is stored. Since it is arranged to be lower than the position of the lower end of the discharge port provided in the means, the developer stays in the storage means below the position of the lower end of the discharge port, and is conveyed to the retained developer. Since the entire means is immersed, the toner is prevented from sticking to the conveying means, and the developer conveying ability can be more stably maintained.

  According to the developer transport device of claim 3, since the developer is transported by rotating the spring screw formed in a spiral shape around the center axis of the spiral shape, to the spring screw. The toner can be prevented from sticking, and the developer conveying ability can be maintained more stably.

  That is, the spring screw has a smaller area on the surface to which the toner adheres than the screw having a cylindrical central axis, and thus the toner is prevented from adhering.

  According to the developer conveying device of the fourth aspect, since the cross section of the spring screw is formed in a substantially circular shape, it is possible to more reliably prevent the toner from adhering to the spring screw.

  That is, since the toner is more likely to adhere to a flat surface (having a larger radius of curvature), the cross section of the spring screw is formed in a circular shape with a constant curvature (= the curvature of the surface of the spring screw is substantially constant). In this case, the toner can be more reliably prevented from sticking.

  According to the developer transport device of claim 5, since the surface of the spring screw is formed of a material having a surface free energy lower than that of the developer, the developer is in contact with the surface of the spring screw. However, it is difficult to adhere to the surface of the spring screw, and even if it adheres, it can be easily peeled off with a slight external force, so that it is possible to more reliably prevent the toner from adhering to the spring screw.

  According to the developer transport device of claim 6, since the surface of the spring screw is formed of a fluorine-based material, the surface of the spring screw can be used even when the developer contacts the surface of the spring screw. Further, even if it adheres, it can be easily peeled off with a slight external force, so that it is possible to more reliably prevent the toner from adhering to the spring screw.

  According to the developer transport device of the seventh aspect, since the rotational speed of the spring screw is changed stepwise every predetermined time set in advance, the acceleration (or decrease) when the step change is made. Since the developer adhering to the spring screw is peeled off by the speed), it is possible to more reliably prevent the toner from adhering to the spring screw.

  According to the developer transport device of claim 8, the residual developer is peeled off from the surface of the rotating body, and the discharge port is disposed at a substantially central position in the axial direction of the rotating body in the storage unit. In order to convey the developer toward the discharge port, the spiral screw is formed in a reverse direction at a position facing the discharge port, so that the developer stored in the storage means is discharged to the discharge port. Since the distance to be conveyed toward is short, the developer conveying ability can be improved.

  According to the image forming apparatus of the ninth aspect, since the developer collected through the developer conveying device according to any one of the first to eighth aspects is reused, the developer is stably conveyed. Thus, an image forming apparatus that can be reused can be realized.

  Hereinafter, an image forming apparatus according to the present invention will be described with reference to the drawings. Although the case where the image forming apparatus is a wet tandem color printer will be described here, another image forming apparatus may be used. For example, the image forming apparatus may be a wet copying machine, a facsimile machine, or a multifunction machine.

  FIG. 1 is a longitudinal sectional view showing an example of a schematic structure of a printer 100 according to the present invention. The printer 100 includes a paper feeding unit 1, a conveyance path 2, a belt conveyance unit 3, an image forming unit 4 (4Y, 4C, 4M, and 4B), a developing unit 5 (5Y, 5C, 5M, and 5B), and a secondary transfer unit 6. , A fixing unit 7, and a discharge tray 71.

  The paper feeding unit 1 is configured to stack recording papers and sequentially feed them to the conveyance path 2. The conveyance path 2 conveys the recording paper sent from the paper feeding unit 1 to the secondary transfer unit 6. The belt conveyance unit 3 includes an intermediate transfer belt 31 that is rotated in the direction of an arrow. On the intermediate transfer belt 31, yellow (Y), cyan (C), and magenta are formed by image forming units 4Y, 4C, 4M, and 4B. The toner images of each color (M) and black (B) are sequentially transferred to form a color image.

  Each of the image forming units 4Y, 4C, 4M, and 4B includes a photosensitive drum 41, and each of the yellow (Y), cyan (C), magenta (M), and black (B) toner images is transferred to the photosensitive drum 41. And is formed on the intermediate transfer belt 31. Note that the image forming units 4Y, 4C, 4M, and 4B have substantially the same configuration, and are therefore referred to as the image forming unit 4 in the following description unless otherwise limited.

  The developing units 5Y, 5C, 5M, and 5B are respectively provided with yellow (Y), cyan (C), magenta (M), and black (B) colors on the photosensitive drums 41 of the image forming units 4Y, 4C, 4M, and 4B. The toner image is formed. Since the developing units 5Y, 5C, 5M, and 5B have substantially the same configuration, they are referred to as the developing unit 5 in the following description unless otherwise limited.

  The secondary transfer unit 6 secondarily transfers the color toner image formed on the intermediate transfer belt 31 onto the recording paper conveyed from the paper feeding unit 1 via the conveyance path 2, and forms the color image on the recording paper. To form. The fixing unit 7 heat-fixes the color image secondarily transferred by the secondary transfer unit 6 onto the recording paper. The discharge tray 71 is for stacking and placing recording sheets on which color images have been thermally fixed by the fixing unit 7.

  FIG. 2 is a longitudinal sectional view showing an example of a schematic structure of the developing unit 5 shown in FIG. The developing unit 5 includes a scooping roller 51, an anilox roller 52, a developing roller 53, a sweep roller 54, a developer transport unit 55, and a developer tank 56. Here, the draw-up roller 51, the anilox roller 52, and the developing roller 53 are rotationally driven by a motor or the like (the arrow in each roller in FIG. 2 indicates the direction of rotation).

  The developer tank 56 is a tank that is composed of toner and a carrier liquid that is an insulating liquid, and stores the developer that is stirred and mixed to a predetermined concentration. The scooping roller 51 is disposed in the developer tank 56 so that a part of the roller is immersed in the developer, and pumps up the developer in the developer tank 56 and applies the developer to the anilox roller 52. . The anilox roller 52 is disposed in contact with the pumping roller 51 above the pumping roller 51, and applies the developer from the pumping roller 51 and also applies the developer to the developing roller 53.

  The developing roller 53 (corresponding to a rotating body) is disposed above the anilox roller 52 in contact with the anilox roller 52, and is applied with the developer from the anilox roller 52 and is formed on the photosensitive drum 41. The toner contained in the developer is attached to the electrostatic latent image to form a toner image.

  The sweep roller 54 is disposed on the downstream side in the rotation direction of the developing roller 53 with respect to the photosensitive drum 41 and is disposed above the developing roller 53 and in a direction opposite to the developing roller 53 (here, counterclockwise). The developer that is driven to rotate and peels off the developer remaining on the developing roller 53 is caused to flow down to the developer transport section 55 (see FIG. 5).

  The cleaning blade 541 is disposed on the downstream side in the rotation direction of the developing roller 53 with respect to the sweep roller 54, and the cleaning blade 541 is disposed in contact with the surface of the developing roller 53. The remaining developer is peeled off and allowed to flow down to the developer transport section 55. The cleaning blade 541 is disposed so that the upper surface of the cleaning blade 541 is inclined downward toward the side away from the developing roller 53 (the right side in the drawing), and the developer separated by the sweep roller 54 and the cleaning blade 541 is removed. The cleaning blade 541 is arranged so as to flow down the upper surface of the cleaning blade 541 and to flow into the developer conveying section 55 (see FIG. 5).

  Next, the developing solution circulation mechanism connected to the developing unit 5 shown in FIG. 2 will be described with reference to the drawings. FIG. 3 is a configuration diagram illustrating an example of a schematic configuration of the developer circulation mechanism 8. In FIG. 3, a part of the configuration of the developing unit 5 is omitted. The developer circulating mechanism 8 collects the developer discharged from the developer transport section 55, adjusts the density, and supplies the adjusted developer to the developer tank 56. , A pump 82, a redispersion device 83, a carrier tank 84, a reservoir tank 85, and a developer supply device 86.

  The redispersing device 83 collects and stores the developer discharged from the developer transporting unit 55 via the conduit 81 and the pump 82, and collects the collected developer and the carrier supplied from the carrier tank 84. The mixture is stirred so as to uniformly mix the liquid, and the aggregate of toner particles in the developer is redispersed.

  The carrier tank 84 stores unused carrier liquid, and supplies the carrier liquid to the redispersing device 83 via the pipe line 81 and the pump 82.

  The reservoir tank 85 is supplied from the re-dispersing device 83 via the pipe line 81 and the pump 82, and preliminarily stores a developer adjusted to a predetermined toner concentration set in advance.

  The developer supply device 86 is connected to a developer replenishing port (not shown) of the developing unit 5, and is supplied from the reservoir tank 85 through the conduit 81 and the pump 82 to the adjusted developer to the developer tank 56. To supply.

  FIG. 4 is a perspective view showing an example of the configuration of the developer transport section 55 according to the present invention. (A) is a perspective view of the entire developer transport section 55, and (b) is a perspective view of the transport section 552 provided in the developer transport section 55. FIG. 5 is a top view and a cross-sectional view showing an example of the developer transport section 55 according to the present invention. (A) is a top view of the developer transport part 55, and (b) and (c) are cross-sectional views of the developer transport part 55. (C) is an enlarged view of a part of (b).

  The configuration of the developer transport unit 55 will be described with reference to FIGS. 4 and 5. The developer transport section 55 (corresponding to the developer transport device) pipes the residual developer separated from the developing roller 53 by the sweep roller 54 and the cleaning blade 541 shown in FIG. 2 to the redispersing device 83 shown in FIG. It conveys via the channel | path 81 and the pump 82, Comprising: The storage part 551 and the conveyance part 552 are provided.

  The storage section 551 (corresponding to storage means) is provided with a discharge port 553 and stores residual developer separated from the developing roller 53. Moreover, the storage part 551 is provided with the inclination member 551a and the bowl-shaped member 551b. The inclined member 551a is a plate-like member inclined toward the flange-shaped member 551b, receives the transport liquid that has been peeled off from the developing roller 53 by the sweep roller 54 and the cleaning blade 541, and has flowed down the upper surface of the cleaning blade 541. It flows down to the bowl-shaped member 551b.

  The bowl-shaped member 551b stores the transport liquid flowing down from the inclined member 551a, and has a discharge port 553 formed on the side surface (here, the right side surface in FIG. 5). The developer is sent to the dispersion device 83. In addition, the bowl-shaped member 551b is provided with a transport section 552 therein. The discharge port 553 is disposed at a substantially central position in the axial direction (vertical direction in FIG. 5) of the developing roller 53 in the bowl-shaped member 551b.

  The transport unit 552 (corresponding to a transport unit) is formed in a spiral shape and includes a spring screw that is driven to rotate about the central axis of the spiral shape. Both ends of the spring screw are rotatably engaged with end faces of the hook-shaped member 551b (here, the upper left and lower right ends in FIG. 4 and the upper and lower ends in FIG. 5), and one end is a motor (drive not shown). (Corresponding to the means) and the like.

  Further, as shown in FIG. 4B, the spring screw of the transport unit 552 has a substantially circular cross section, and the discharge port 553 is configured to transport the developer toward the discharge port 553. At opposite positions (= substantially central position in the length direction), the spiral direction is formed in reverse. That is, the spring screw has a first spiral portion 552a formed in a counterclockwise spiral shape from the upper left end to the lower right end in the drawing, and a clockwise spiral shape from the upper left end in the drawing toward the lower right end. A second spiral portion 552b formed.

  Further, the spring screw of the conveying unit 552 is formed of a material whose surface free energy is lower than that of the developer (here, a fluorine-based material). That is, the spring screw has a surface free energy lower than that of the developer (the surface free energy of the developer is, for example, 30 to 50 mN / m), a fluorine-based coating, or PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether). (Polymer) The tube is coated to improve the peelability of the developer. Note that the material of the spring screw of the conveying unit 552 itself may be a fluorine-based resin.

  In addition, the rotational speed of the spring screw of the transport unit 552 is changed and driven step by step every predetermined time (for example, 10 sec). For example, the spring screw has a rotation speed every 10 sec between a preset first rotation speed (for example, 10 rpm) and a preset second rotation speed (for example, 20 rpm) greater than the first rotation speed. It is changed and driven step by step.

  Further, as shown in FIGS. 5B and 5C, the spring screw of the transport unit 552 is disposed so that the position of the upper end is below the position of the lower end of the discharge port 553. That is, the spring screw is disposed so that the whole spring screw is immersed in the developer stored in the flange-shaped member 551b.

  In this way, the upper end of the transport unit 552 (= spring screw) is disposed in the storage unit 551 that stores the residual developer separated from the developing roller 53 and transports the developer toward the discharge port 553. Since the position is disposed so as to be lower than the position of the lower end of the discharge port 553 disposed in the storage unit 551 (the bowl-shaped member 551b), the discharge port 553 is disposed in the storage unit 551 (the bowl-shaped member 551b). Since the developer stays below the lower end position of the toner, and the entire transport unit 552 (= spring screw) is immersed in the retained developer, the toner is prevented from sticking to the transport unit 552 (= spring screw). Further, the developer conveying ability can be stably maintained.

  Further, since the developer is transported by rotating the spring screw 552 formed in a spiral shape around the central axis of the spiral shape, the toner is prevented from sticking to the spring screw, and the developer solution The conveyance capability can be maintained more stably.

  That is, since the area of the surface to which the toner adheres is smaller than that of the screw 552b (see FIG. 6B) having a cylindrical central axis, the spring screw 552 prevents the toner from adhering.

  In addition, since the cross section of the spring screw 552 is formed in a substantially circular shape, it is possible to more reliably prevent toner from being fixed to the spring screw 552.

  That is, since the toner is more likely to adhere to a flat surface (having a larger radius of curvature), when the cross section of the spring screw 552 is formed in a circular shape with a constant curvature (= the surface curvature of the spring screw 552 is equal). If it is substantially constant), the toner can be more reliably prevented from sticking.

  Further, since the surface of the spring screw 552 is made of a fluorine-based material, even when the developer contacts the surface of the spring screw, it is difficult to adhere to the surface of the spring screw 552, and further, for example Even in such a case, the toner can be easily peeled off with a slight external force, so that the toner can be more securely prevented from adhering to the spring screw 552.

  Further, since the rotational speed of the spring screw 552 is changed stepwise every predetermined time (10 sec in this case), the spring screw 552 is accelerated by the acceleration (or deceleration) when changed stepwise. Since the developer adhering to 552 is peeled off, it is possible to more reliably prevent the toner from adhering to the spring screw 552.

  In addition, a discharge port 553 is disposed at a substantially central position in the axial direction of the developing roller 53 in the storage portion 551 (the bowl-shaped member 551b), and the spring screw 552 conveys the developer toward the discharge port 553. At the position facing the discharge port 553, the spiral shape is formed in the opposite direction, so the distance for transporting the developer stored in the storage unit 551 (the bowl-shaped member 551b) toward the discharge port 553 is short. Further, the developer conveying ability can be improved.

The present invention can also be applied to the following forms.
(A) In this embodiment, the position of the upper end of the transport unit 552 (= spring screw) is disposed as much as possible below the position of the lower end of the discharge port 553 disposed in the storage unit 551 (the hook-shaped member 551b). However, at least the position of the lower end of the transport unit 552 (= spring screw) should be lower than the position of the lower end of the discharge port 553 provided in the storage unit 551 (the bowl-shaped member 551b). Any form may be used.

  The position of the lower end of the transport unit 552 (= spring screw) is below the position of the lower end of the discharge port 553 provided in the storage unit 551 (saddle-shaped member 551b), and the transport unit 552 (= spring screw). When the position of the upper end of the storage unit 551 is arranged to be higher than the position of the lower end of the discharge port 553 provided in the storage unit 551 (the bowl-shaped member 551b) (for example, in the conveyance unit 552 (= spring screw)). When the central axis is disposed at the position of the lower end of the discharge port 553), the bowl-shaped member 551b can be made shallower, so that the storage portion 551 can be reduced in size.

  (B) In this embodiment, although the conveyance part 552 demonstrated the case where the cross section was provided with the spring screw with a circular cross section, the form provided with the screw of another form may be sufficient as the conveyance part 552. FIG. 6 is a perspective view showing another type of screw. (A) is a spring screw 552a having a substantially rectangular cross section, and (b) is a screw 552b having a cylindrical central axis. In these forms, since the surface which conveys a developing solution is wide compared with the spring screw with a circular cross section, high conveyance capability is realizable.

  (C) Although the present embodiment has been described with respect to the case where the discharge port 553 is disposed at a substantially central position in the axial direction of the developing roller 53 in the storage section 551 (the bowl-shaped member 551b), the storage section 551 (the bowl-shaped member). The discharge port 553 may be disposed at the axial end of the developing roller 53 in 551b). In this case, since the conveying direction of the developer by the conveying unit 552 (= spring screw) is one direction, the spiral shape of the spring screw is one direction, so that the spring screw can be easily manufactured. .

  (D) In the present embodiment, the case where the developer transport device transports the residual developer separated from the developing roller 53 has been described. However, the surface of another rotating body (for example, the photosensitive drum 41 and the intermediate transfer belt 31). The form which conveys the residual developing solution peeled from may be sufficient.

These are the longitudinal cross-sectional views which show an example of schematic structure of the printer which concerns on this invention. These are longitudinal cross-sectional views which show an example of schematic structure of the image development part shown in FIG. These are block diagrams which show an example of schematic structure of a developing solution circulation mechanism. These are perspective views which show an example of a structure of the developing solution conveyance part which concerns on this invention. These are the top view and sectional drawing which show an example of the developing solution conveyance part which concerns on this invention. FIG. 5 is a perspective view showing another form of screw.

Explanation of symbols

100 printer (image forming apparatus)
4 Image forming section 41 Photosensitive drum 5 Developing section 51 Uplift roller 52 Anilox roller 53 Developing roller (rotating body)
54 Sweep roller 55 Developer transport unit (Developer transport device)
551 Reserving part (reserving means)
551a Inclined member 551b Hook-like member 552 Conveying section (conveying means, spring screw)
553 Discharge port 56 Developer tank 8 Developer circulation mechanism

Claims (9)

A developer transport device that transports the developer toward the discharge port in order to collect the peeled residual developer,
A storage means for storing the discharged residual developer and the discharge port;
A conveying means disposed in the storage means for conveying the developer toward the discharge port;
With
The developer conveying apparatus, wherein the conveying means is disposed so that a lower end position thereof is lower than a lower end position of the discharge port.   2. The developer conveying apparatus according to claim 1, wherein the conveying unit is disposed so that a position of an upper end thereof is lower than a position of a lower end of the discharge port. The conveying means is formed in a spiral shape and is rotated around a central axis of the spiral shape;
Drive means for rotationally driving the spring screw;
The developer transport device according to claim 1, wherein the developer transport device is provided.   4. The developer conveying device according to claim 3, wherein the spring screw has a substantially circular cross section.   5. The developer transport device according to claim 3, wherein a surface of the spring screw is formed of a material having a surface free energy lower than that of the developer.   6. The developer conveying device according to claim 5, wherein the surface of the spring screw is made of a fluorine-based material.   7. The developer conveying device according to claim 3, wherein the driving unit changes the rotational speed of the spring screw stepwise at predetermined time intervals. 7. . The peeled residual developer is a residual developer peeled from the surface of the rotating body,
The discharge port is disposed at a substantially central position in the axial direction of the rotating body in the storage means,
8. The spiral screw is formed in a reverse direction at a position facing the discharge port so that the spring screw conveys the developer toward the discharge port. A developer transport device according to any one of the above. A liquid developing type image forming apparatus that forms an image on a recording paper by transferring toner contained in the developer onto the recording paper,
The developer transport device according to claim 1,
An image forming apparatus, wherein the developer collected via the developer transport device is reused.

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