JP2004258569A - Development device and electrostatic recording device using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device that can print an image of high quality having a small difference of toner density in an axial direction, makes it easy to discharge a developer, and has good operability, and an electrostatic recording device using the same. <P>SOLUTION: The developing device is characterized in that an agitating mechanism part is provided with at least two conveyance members, which convey a developer along the axis by rotation horizontally and partition walls 41a and 41b projecting from the bottom part of the agitating mechanism part are provided between the conveyance members along its axis of rotation. Further, the conveyance members have their rotation axis centers high on sides far away from a development part, and the partition walls 41a and 41b are set short at their center parts and both ends; and a developer discharge opening is provided to the conveyance member end close to the development part, and the conveyance members are rotated during developing operation so that the conveyance member close to the development part moves the developer toward the development part and the conveyance member at a distance from the development part moves it to the partition walls. When the developer is discharged, the conveyance members are rotated in the opposite directions from those in the developing operation. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
[Field of the Invention]
The present invention relates to an electrostatic recording device such as an electrophotographic printer and a copying machine, and more particularly, to a stirring mechanism of a developing device using a magnetic developer.
[0002]
[Prior art]
With reference to FIG. 5, a schematic configuration of a conventional electrostatic recording device will be described.
[0003]
In electrostatic recording devices such as copiers and printers, a developing device attaches toner to an electrostatic latent image formed on a photoreceptor, transfers the toner image to paper, and then heats and fixes the image to form an image. Form.
[0004]
The developing device 4 includes a developing roller 31 disposed close to the photoconductor 1, a stirring mechanism 34 for mixing and stirring the developer including the toner 21 and the carrier, and a toner replenishment for replenishing the stirring mechanism 34 with the toner 21. A section 200 is provided.
[0005]
The developer mixed and stirred by the stirring mechanism unit 34 is supplied to the developing roller 31, and rubs the photosensitive member 1 on the developing roller 31, thereby causing the toner 21 to adhere to the electrostatic latent image on the photosensitive member 1. . The developer that has consumed the toner 21 by the development is returned to the stirring mechanism 34 and supplied with the toner 21 from the toner supply unit 200.
[0006]
The replenished toner 21 is mixed with the developer by the stirring mechanism 34 and the developer having a predetermined toner concentration is conveyed to the developing roller 31.
[0007]
As described above, in the stirring mechanism unit 34 that mixes and stirs the toner and the carrier and transports the developer, a member that performs the mixing and stirring while moving the developer in the axial direction represented by the auger is widely used.
[0008]
Normally, 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 toner is supplied to the developer conveyed by the auger located far from the developing roller, The developer replenished with the toner is delivered to the auger located near the developing roller.
[0009]
[Problems to be solved by the invention]
As described above, in the developing device having the pair of members for transporting the developer in the axial direction in the stirring mechanism, the developer is sequentially transported in the axial direction by the auger closer to the developing roller. It is delivered to the roller and transported to the developing unit.
[0010]
The developer that has consumed the toner in the developing unit is returned to the auger near the developing roller again, mixed with the developer being transported in the axial direction, and transported downstream by the auger.
[0011]
In the process of being conveyed to the downstream side, the developer is repeatedly transferred to the developing roller, consumes the toner, and returns to the auger.Therefore, the toner concentration decreases toward the downstream side in the developer feeding direction. Become.
[0012]
This decrease in toner concentration is caused by the fact that the higher the printing density (printing area per unit area), the wider the printing width, the faster the printing speed is, and the more the developer is consumed in the developing area while moving the unit length in the axial direction. The larger the amount of toner, the more noticeable the appearance.
[0013]
If there is a difference in the toner density in the axial direction, a density difference appears in the axial direction, that is, in the width direction of the paper, in the print image, and the print quality is reduced.
[0014]
As a method for preventing this, there is disclosed a method in which a developer is delivered at the center of the auger in the feeding direction by using an auger in which the winding direction of the feed blade is reversed at the center (for example, Patent Documents 1 and 2). reference.). According to this method, since the flow of the developer becomes two in the stirring mechanism, 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 and the like
[Problems to be solved by the invention]
However, in a developing device having an agitating mechanism for transporting the developer in the axial direction, the developer is discharged by rotating the auger in a direction opposite to that during the developing operation when the developer reaches a replacement time, thereby discharging the developer. In many cases, the developer is conveyed in the direction opposite to the normal circulation direction, and the developer is discharged from a discharge port provided at the end in the auger axial direction. When the developer flow is formed, the developer circulating near the outlet is quickly discharged, but the developer circulating far from the outlet is difficult to reach the outlet, and until all the developer is discharged. There is a problem that it takes a lot of time.
[0016]
[Means for Solving the Problems]
The above object is achieved by providing at least two conveying members for conveying the developer in the axial direction by rotation in the stirring mechanism section in the horizontal direction, and stirring the developer along the rotation axis direction between the conveying members. In a developing device provided with a partition protruding from the bottom of the mechanism unit, the position of the rotation axis of the transport member is arranged higher in a portion farther from the developing unit, and the height of the partition is set lower in the center and both ends, A developer outlet is provided at an end of the conveying member closer to the developing unit, and the rotation direction of the conveying member during the developing operation is shifted toward the developing unit toward the developing unit at the conveying member closer to the developing unit. The direction of the transfer member is farther from the developing unit than the developing unit. The direction of rotation of the transfer member is opposite to that during the developing operation when the developer is discharged.
BEST MODE FOR CARRYING OUT 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 of a developing device used in the present invention. In the stirring mechanism 34, the two augers 36a and 36b, which are the conveying members, are positioned such that the outer periphery of the auger is at an appropriate distance from the bottom and side portions of the developing device 4, and the auger 36b is higher in axial center than the auger 36a. It is provided in. At the bottom of the developing device 4 below the auger 36b, the toner density sensor 45 is arranged so that the detection surface thereof comes into contact with the developer accumulated under the auger 36b. Between the two augers, a partition 41a protrudes from the lower portion of the developing machine 4, and further a partition 41b protrudes toward the developing roller (not shown) on the left side of the auger 36a to form a region for accumulating the developer in a lower region of each auger. ing. A partition plate 37 is provided between the augers.
[0019]
Above the stirring mechanism 34, a toner hopper 39 filled with the toner 21 therein and a replenishing roller 38 for replenishing the filled toner 21 are provided. The stirring mechanism 34 stirs the developer by moving the augers 36a and 36b in the front-rear direction in the drawing.
[0020]
In this embodiment, the auger 36a rotates clockwise to convey the developer to the back side in the figure, and the developer flows into the auger 36b side at the end of the developing machine 4 (not shown), and the auger 36b rotates clockwise in the figure to the front. To the side. At this time, the partition 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 41a and the bottom portion of the developing machine 4, so that the development accumulated in this region. The developer is pushed in the axial direction and the rotational direction by the winding direction and the rotation direction of the feed blades of the augers 36a and 36b, and the auger 36b moves the accumulated developer toward the developing roller toward the developing roller while moving the auger 36b backward. Then, the developer is transported to the near side while approaching the partition 41 on the left side of the drawing.
[0021]
Therefore, the auger 36a conveys the developer toward the rear side in the drawing while moving the developer toward the partition wall 41b, and the developer is sequentially conveyed toward the developing roller in the conveying process. The toner density sensor 45 detects the toner density value of the developer being conveyed by the auger 36b, and in a toner density control circuit (not shown), detects this detected value when the developer having the specified toner density is being conveyed. If it is detected that the toner density is low as compared with the reference value, the supply roller 38 is rotated for a specified time according to a command from the toner density control circuit, so that the toner 21 is supplied from the toner hopper 39 to the stirring mechanism 34. .
[0022]
FIG. 2 is a top view showing a schematic configuration of a stirring mechanism section according to one 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. Further, a projection 362 that functions to move the developer in the auger rotation direction is provided on a part of the shaft 360 portion without the feed blade 361. Further, fins 363 are provided at the downstream end of each auger in the developer feeding direction.
[0024]
The auger 36a may have the same interval between the feed blades 361 in all regions, but it is preferable to reduce the interval (pitch) between the feed blades 361 at the center.
[0025]
FIG. 4 is a side view showing the positional relationship between the auger and the partition.
[0026]
The partition wall 41a at the center of the augers 36a and 36b has a lower partition wall height at both ends and a central portion of the auger 36a than in other regions, and has lower end portions at the both ends than the central portion. I have. The region where the feed blade 361 pitch 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 stirring mechanism 34 is provided with an opening for discharging the developer at the upstream end (the right side in the figure) 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 transported leftward by the rotation of the auger 36a. At this time, the feed blade 361 rotates so as to push out the developer in the lower right direction in the figure, so that the developer is conveyed rightward 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 the developer accumulated between the auger blades increases in this region, and a part of the developer is reduced from the region where the partition height at the central portion of the partition 41a is reduced. Is passed to the auger 36b. The developer not transferred to the auger 36b in this area is further transported by the auger 36a, and the partition 41a at the right end in the figure reaches a lower area and is transferred to the auger 36b. The developer conveyed by the auger 36b is conveyed to the left side in the figure by the rotation of the auger 36b. At this time, the developer is conveyed while being moved toward the lower left in the figure by the rotation of the feed blade 361, so that the developer that has passed the partition 41b during the conveyance is sequentially arranged at the lower part of the figure with a developing roller (not shown) or It is delivered to the transport rollers. The developer that has been developed by the developing roller is transported to the auger 36b by a guide member (not shown).
[0028]
Therefore, since the developer is delivered to the auger 36b from the central portion and the end portion, even in the case where printing with large toner consumption is performed, high-quality printing is performed without greatly lowering the toner density on the downstream side of the auger 36b. It becomes possible.
[0029]
FIG. 3 is a diagram showing the flow of the developer when the auger is rotated in the reverse direction for discharging the developer. Due to the rotation of the auger 36a, the developer is conveyed while being moved to the upper left in FIG. The lowermost partition is transferred to the auger 36b at the lowered portion. In the auger 36b, the developer is conveyed while being moved toward the partition wall 41a. At this time, even in the lower part of the partition wall at the center or right side, since the auger 36b is at a lower position than the auger 36a, the brought developer is not conveyed in the direction of the auger 36a, and the developer is supplied to the right end of the auger 36b. To the discharge port. As described above, the amount of the developer circulated through the auger and conveyed to the discharge port is reduced, so that the discharge does not take a long time, 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 can perform high-quality printing with a small difference in toner concentration in the axial direction, and can easily discharge the developer and have good operability. An electrostatic recording device can be provided.
[Brief description of the drawings]
FIG. 1 is a side view showing a schematic configuration of a stirring mechanism of a developing device of the present invention.
FIG. 2 is a top view showing an embodiment of a stirring mechanism section according to the present invention.
FIG. 3 is a top view illustrating a flow of the developer when the auger is rotated in reverse for discharging the developer according to the 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 device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Photoconductor 3 Exposure device 4 Developing device 20 Developing agent 21 Toner 25 Carrier 30 Magnet roller 31 Developing roller 34 Stirring mechanism parts 36a, 36b Auger 41a Partition wall

Claims (4)

At least two conveying members for conveying the developer in the axial direction by rotation are arranged in the stirring mechanism in the horizontal direction, and between the conveying members, along the rotation axis direction, from the bottom of the stirring mechanism. In the developing device provided with the protruding partition, the rotational axis position of the conveying member is disposed higher in a portion farther from the developing unit, and the height of the partition is set lower in the center and both ends, and the side closer to the developing unit is set. A developer discharge port is provided at an end of the conveying member, and the rotation direction of the conveying member during the developing operation is set to a direction in which the developer at the bottom of the conveying member close to the developing unit is moved toward the developing unit. And a rotating direction of the conveying member when the developer is discharged is rotated in a direction opposite to that during the developing operation. The developing device according to claim 1, wherein the conveying member disposed at a position far from the developing unit reduces a feed speed of the developer in an axial direction near a position where a partition wall in a central part is lowered. . The developing device according to claim 1, wherein a height of the partition wall is lower at an end portion than at a center position. An electrostatic recording device comprising the developing device according to claim 1.

Images