JP4243116B2 - Developing device and electrostatic recording apparatus using the same - Google Patents

Description

[0001]
[Field of the Invention]
The present invention relates to an electrostatic recording apparatus such as an electrophotographic printer or a copying machine, and more particularly to a stirring mechanism portion of a developing apparatus using a magnetic developer.
[0002]
[Prior art]
A schematic configuration of a conventional electrostatic recording apparatus will be described with reference to FIG.
[0003]
In an electrostatic recording apparatus such as a copying machine or a printer, toner is attached to an electrostatic latent image formed on a photosensitive member by a developing device, the toner image is transferred to a sheet, and then heated to fix the image. Form.
[0004]
The developing device 4 includes a developing roller 31 disposed in the vicinity of the photoreceptor 1, a stirring mechanism unit 34 that mixes and stirs the developer composed of toner 21 and a carrier, and toner replenishment that replenishes the stirring mechanism unit 34 with the toner 21. Part 200 is provided.
[0005]
The developer mixed and stirred by the stirring mechanism unit 34 is supplied to the developing roller 31, and the toner 21 is attached to the electrostatic latent image on the photosensitive member 1 by rubbing the photosensitive member 1 on the developing roller 31. . The developer that has consumed the toner 21 by the development is returned to the stirring mechanism unit 34 and is replenished with the toner 21 from the toner replenishment unit 200.
[0006]
The replenished toner 21 is mixed with the developer by the stirring mechanism 34 and the developer having a predetermined toner density is conveyed to the developing roller 31.
[0007]
As described above, in the stirring mechanism unit 34 for mixing and stirring the toner and the carrier and transporting the developer, a member that performs the mixing and stirring while moving the developer in the axial direction typified by an auger is widely used.
[0008]
Usually, the two augers are rotated so that the developer moving directions are different from each other, the developer is circulated in the stirring mechanism, and the toner is replenished in the developer conveyed by the auger located at a position far from the developing roller, The developer replenished with toner is delivered to an auger located near the developing roller.
[0009]
[Problems to be solved by the invention]
As described above, in the developing device having a pair of axially conveying members for the developer in the stirring mechanism portion, the developer is sequentially developed in the process of being conveyed in the axial direction by the auger closer to the developing roller. It is delivered to the roller and conveyed to the developing unit.
[0010]
The developer that has consumed toner in the developing unit is returned again to the auger near the developing roller, mixed with the developer conveyed in the axial direction, and conveyed downstream by the auger.
[0011]
The developer is transferred to the developing roller again in the process of being conveyed downstream, and the operation of consuming the toner and returning to the auger is repeated. Therefore, the toner concentration decreases toward the downstream in the developer feeding direction. Become.
[0012]
This decrease in toner density is consumed in the development area while the printing density (printing area per unit area) is higher, the printing width is wider, the printing speed is faster, and the developer moves unit length in the axial direction. The more the toner amount, the more noticeable.
[0013]
If there is a difference in toner density in the axial direction as described above, a density difference also appears in the print image in the axial direction, that is, in the width direction of the paper, and print quality deteriorates.
[0014]
As a method for preventing this, a method is disclosed in which a developer is delivered at the central portion in the feed direction of the auger by using an auger in which the winding direction of the feed blade is reversed at the central portion (for example, Patent Documents 1 and 2). reference.). According to this method, since there are two developer flows in the stirring mechanism portion, it is possible to suppress a decrease in the toner concentration in the axial direction.
[Patent Document 1]
JP-A-7-152235 [Patent Document 2]
JP-A-7-175306 etc.
[Problems to be solved by the invention]
However, in a developing device having an agitation mechanism that transports developer in the axial direction, the developer is removed by rotating the auger in the direction opposite to that during the developing operation when the developer is discharged when the replacement time is reached. In many cases, the developer is transported in a direction opposite to the normal circulation direction, and the developer is discharged from a discharge port provided at the end portion in the auger axial direction. When the developer flow is formed, the developer that circulates closer to the discharge port is quickly discharged, but the developer that circulates farther from the discharge port is difficult to reach the discharge port until all the developer is discharged. There was a problem that it took a lot of time.
[0016]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention provides at least two conveying members arranged in the horizontal direction in the agitating mechanism portion, each having a feeding blade that conveys developer in the axial direction by rotation, and is arranged between the conveying members. In a developing device provided with a partition wall protruding from the bottom of the stirring mechanism along the direction of the rotation axis, the position of the rotation axis of the conveying member is located farther from the development unit, and the height of the partition is increased. A developer discharge port is provided at the end on the upstream side during the developing operation of the conveying member near the developing unit , which is set low at the center and both ends, and the rotation direction during the developing operation of the conveying member In the transport member located near the developing unit, the developer at the bottom is moved in the direction toward the developing unit, and the transport member located far from the developing unit is moved in the direction toward the partition, and transported at a position far from the developing unit. member in the central region of the partition Corresponding to parts, and feed has become narrow blade pitch, also at the time of the developer discharge is characterized by rotating in the opposite direction as during the developing operation of the rotation direction of the conveying member.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the embodiments shown in FIGS.
[0018]
FIG. 1 is a side view showing a schematic configuration of a stirring mechanism portion of a developing device used in the present invention. The stirring mechanism section 34, the two augers 36a is conveying member, 36b the auger periphery at appropriate intervals and the bottom portion and the side portion of the developing apparatus 4, the auger 36 a high axial center than the auger 36 b It is provided in the position. The bottom portion of the auger 36 a lower portion of the developing device 4, the detection surface of the toner density sensor 45 is placed in contact with the developer stored in the auger 36 a bottom. A partition wall 41a protrudes from the lower portion of the developing machine 4 between the two augers, and the partition wall 41b also protrudes in the direction of the developing roller (not shown ) on the left side of the auger 36b to form an area for accumulating developer in each lower auger area. is doing. A partition plate 37 is provided between the two augers.
[0019]
Above the agitation mechanism 34, a toner hopper 39 filled with the toner 21 and a replenishing roller 38 for replenishing the filled toner 21 are provided. The agitating mechanism 34 agitates the developer by moving the augers 36a and 36b in the front-rear direction of the drawing.
[0020]
In this embodiment, the auger 36 b is rotated in the clockwise direction to convey the developer to FIG far side, pouring a developer to auger 36 a side in the developing machine end (not shown), the auger 36 a in the clockwise direction in FIG. Rotates and conveys developer to the near side. At this time, a partition wall 41a protrudes from below between the augers 36a and 36b, and the lower portion of the periphery of the augers 36a and 36b is surrounded by the partition wall 41a and the bottom of the developing device 4, so that the development accumulated in this region agent auger 36a, by the rotation direction winding direction of the feed blades of 36b is pushed in the axial direction and the rotational direction, the illustrated back side while submitted to a direction closer to auger 36 b in the stored developer to the developing roller direction, the auger while attracted to a partition wall 41 a on the left side of 36 a in FIG conveys the developer to the front side.
[0021]
Therefore, the developer is conveyed to FIG rear side while attracted to the auger 36 b in the developer in the partition wall 41b direction, sequentially developer its conveying process will be conveyed to the developing roller direction. The toner concentration sensor 45 detects the toner concentration value of the developer will be carried in the auger 36 a, the toner density control circuit (not shown), the detected value, when the developer toner concentration specified is conveyed If the toner density is detected to be low, the toner 21 is replenished from the toner hopper 39 to the agitating mechanism 34 by rotating the replenishing roller 38 for a specified time according to a command from the toner density control circuit. To do.
[0022]
FIG. 2 is a top view illustrating a schematic configuration of a stirring mechanism unit according to an embodiment of the present invention.
[0023]
The augers 36a and 36b are provided with a feed blade 361 in a spiral shape on a shaft 360, and a protrusion 362 that functions to move the developer in the auger rotation direction to a part of the shaft 360 without the feed blade 361. Furthermore, a fin 363 is provided at the downstream end of each auger in the developer feeding direction.
[0024]
The auger 36a may have the same spacing between the feeding blades 361 in all regions, but it is preferable to narrow the spacing (pitch) between the feeding blades 361 at the center.
[0025]
FIG. 4 is a side view showing the positional relationship between the auger and the partition wall.
[0026]
The partition wall 41a at the center of the augers 36a and 36b has a partition wall height lower than that of the other regions at both ends and the center of the auger 36a, and both ends are lower than the center portion. Yes. The region where the pitch of the feed blades 361 of the auger 36a is short is provided so as to correspond to the region where the partition wall height at the center is low. The agitating mechanism 34 is provided with an opening for discharging the developer at the upstream end (right side in the drawing) of the auger 36b.
[0027]
The flow of the developer in the stirring mechanism 34 will be described with reference to FIG. The developer is conveyed leftward by the rotation of the auger 36a. At this time, since the feed blade 361 rotates to push the developer in the lower right direction in the figure, the developer is conveyed in the right direction in the figure while being moved toward the partition wall 41a. At this time, since the auger pitch is narrow in the central portion, the amount of developer accumulated between the auger blades increases in this region, and a part of the developer starts from the region where the partition wall height in the central portion of the partition wall 41a is reduced. Is delivered to the auger 36b. The developer that has not been delivered to the auger 36b in this region is further conveyed by the auger 36a, and reaches the region where the partition wall 41a at the right end of the figure is low and is delivered to the auger 36b. The developer conveyed by the auger 36b is conveyed to the left side of the drawing by the rotation of the auger 36b. At this time, since the developer is transported while being moved in the diagonally lower left direction in the drawing by the rotation of the feed blade 361, the developer that has exceeded the partition wall 41b in the middle of the transport is sequentially arranged at the lower side of the drawing roller (not shown) It is delivered to the transport roller. The developer that has been developed by the developing roller is conveyed to the auger 36b by a guide member (not shown).
[0028]
Therefore, since the developer is transferred to the auger 36b from the center and the end, even when printing with high toner consumption is performed, high-quality printing is performed without greatly reducing the toner density on the downstream side of the auger 36b. It becomes possible.
[0029]
FIG. 3 is a diagram illustrating the flow of the developer when the auger is rotated in reverse to discharge the developer. Due to the rotation of the auger 36a, the developer is conveyed while being moved obliquely upward to the left in the figure. At the part where the partition wall on the most downstream side is lowered, it is delivered to the auger 36b. In the auger 36b, the developer is conveyed while being moved toward the partition wall 41a. At this time, since the auger 36b is located at a position lower than the auger 36a even in the central region or the lower region of the right partition wall, the collected developer is not conveyed in the direction of the auger 36a, and the developer is not fed to the right end of the auger 36b. To the discharge port. In this way, the amount of developer that is circulated through the auger and conveyed to the discharge port is reduced, so that it does not take time to discharge, and the developer can be discharged in a short time.
[0030]
【The invention's effect】
According to the present invention, a developing device using a two-component developer, capable of high-quality printing with little difference in toner density in the axial direction, easy to discharge the developer, and easy to operate, and An electrostatic recording apparatus can be provided.
[Brief description of the drawings]
FIG. 1 is a side view showing a schematic configuration of a stirring mechanism portion of a developing device of the present invention.
FIG. 2 is a top view showing an embodiment of a stirring mechanism section in the present invention.
FIG. 3 is a top view showing the flow of the developer when the auger is reversely rotated for discharging the developer in one embodiment of the present invention.
FIG. 4 is a side view showing a positional relationship between an auger and a partition wall in one embodiment of the present invention.
FIG. 5 is a schematic configuration diagram of a conventional electrostatic recording apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Photoconductor 3 Exposure apparatus 4 Developing apparatus 20 Developer 21 Toner 25 Carrier 30 Magnet roller 31 Developing roller 34 Agitation mechanism part 36a, 36b Auger 41a Partition

Claims (3)

At least two transport members having feed blades for transporting the developer in the axial direction by rotation in the agitating mechanism section are arranged in parallel in the horizontal direction, and the stirring is performed between the transport members along the rotational axis direction. In the developing device provided with a partition wall protruding from the bottom of the mechanism unit,
The rotational axis position of the transport member is arranged higher at a position farther from the developing unit, the height of the partition wall is set lower at the center and both ends , and upstream during the developing operation of the transport member on the side closer to the developing unit. A developer discharge port is provided at the end which becomes the side, and the rotation direction during the developing operation of the transport member is set to a direction in which the developer at the bottom of the transport member close to the developing unit is moved toward the developing unit, The transport member at a position far from the developing unit is in the direction approaching the partition, and the transport member at a position far from the developing unit has a central area corresponding to the central part of the partition and a narrowing blade pitch. The developing device is characterized in that when the developer is discharged, the rotation direction of the conveying member is rotated in the direction opposite to that during the developing operation.   The developing device according to claim 1, wherein the partition wall has a lower height at an end position than at a center position.   An electrostatic recording apparatus comprising the developing device according to claim 1.

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