JP2004233597A - Developing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device by which two-component dry developer is sufficiently stirred and also the unevenness of the density of a formed image is eliminated. <P>SOLUTION: The developing device 1 is provided with a stirring chamber 12 and a developing chamber 13 at the inside of a developing container 10. A magnet roller 15 which is a developer carrier is arranged at the aperture part 14 of the developing chamber 13 so that one side is exposed in the developing chamber 13 and the other side is made opposed to a photoreceptor drum 16 that is an image carrier. Developer is fed from one end of the stirring chamber 12 to the developing chamber 13 by a stirring screw 20 in the stirring chamber 12, and the developer is fed to the other end of the developing chamber 13 while bringing into contact with the magnet roller 15 by a feeding screw 30 in the developing chamber 13, and developer that does not stick to the magnet roller 15 is returned to the stirring chamber 12. The flowing speed of the developer in the stirring chamber 12 is lower than that of the developer in the developing chamber 13, and also the diameter of the stirring screw 20 is larger than that of the feeding screw 30. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a developing device using a two-component dry developer.
[0002]
[Prior art]
Among image forming apparatuses such as printers, copiers, and facsimile machines, the mainstream adopts a developing process using a two-component dry developer. In a developing device, which is a main part of the image forming apparatus, the electrostatic latent image formed on the surface of the image carrier must be developed so as not to cause an excess, deficiency or unevenness of the developer. In general, a technique is employed in which a developer is attached to a roll-shaped developer carrier, and the developer is transferred from the developer carrier to the image carrier. An example of such a developing device can be found in Patent Document 1.
[0003]
FIGS. 4 and 5 show a schematic configuration of a developing device described in Patent Document 1. FIG. FIG. 4 is a sectional view, and FIG. 5 is a plan view. The developing container 131 contains a two-component dry developer 135 composed of a non-magnetic toner and a magnetic carrier, and is internally partitioned by a partition 144 into a developing chamber R1 and a stirring chamber R2. An opening is provided in the developing container 131 at a position close to the photosensitive drum 103 serving as an image carrier, and a developing sleeve 139 serving as a developer carrier is arranged in this opening. A magnet roller 142 is disposed inside the developing sleeve 139, and the toner adsorbed on the surface of the developing sleeve 139 is transferred to the photosensitive drum 103 by the magnetic field of the magnet roller 142 to develop the electrostatic latent image. The consumed toner is replenished from a toner storage chamber (not shown) into the stirring chamber R2.
[0004]
The developing chamber R1 contains a stirring screw 136, and the stirring chamber R2 contains a stirring screw 137. When the stirring screw 136 rotates, the developer 135 is conveyed along the longitudinal direction of the developing sleeve 139 while being in contact with the surface of the developing sleeve 139. When the stirring screw 137 rotates, the developer 135 in the stirring chamber R2 is transported in a direction opposite to the transport direction by the stirring screw 136. In the partition 144, openings are formed on the near side and the back side in FIG. The supplied developer 135 is delivered to the stirring screw 136 at the other opening.
[0005]
[Patent Document 1]
JP 2001-83784 A
[Problems to be solved by the invention]
In a developing device such as a developing device described in Patent Literature 1, in which a developer is circulated between a stirring chamber and a developing chamber, the diameter of a stirring screw, a rotation speed, or a screw pitch is adjusted in order to balance circulation. In many cases, the stirring chamber and the developing chamber are almost the same. Patent Document 1 also proposes that the rotation speed of the stirring screw on the stirring chamber side is made faster than the rotation speed of the stirring screw on the developing chamber side.
[0007]
However, from the viewpoint of sufficiently agitating the non-magnetic toner and the magnetic carrier to form a uniform developer and uniformly depositing the same on the developer carrier, the above design does not always lead to a good result. Absent. As described above, the developer enters the developing chamber from one end of the developing chamber, and advances along the developer carrier to the other end of the developing chamber. Since the toner is consumed during the process, the toner concentration in the developer differs between when the toner enters the developing chamber and when the toner leaves the developing chamber. This appears as a density difference in the image. Further, in the stirring chamber, it is desired that the toner and the carrier are sufficiently mixed.
[0008]
The present invention has been made in view of the above points, and an object of the present invention is to provide a developing device which can sufficiently stir a two-component dry developer and does not cause an imbalance in the density of an image to be formed. To provide.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, in the present invention, the developing device is configured as follows.
[0010]
(1) A stirring chamber with a built-in stirring screw and a developing chamber with a built-in transport screw are arranged in parallel with each other so as to communicate at both ends, and the developer in the stirring chamber is supplied to the developing chamber by the stirring screw. The developer is fed to one end, and the fed developer is sent to the other end of the developing chamber by the transport screw while being in contact with the surface of the developer carrier exposed in the developing chamber. In the developing device in which the developer is returned to the stirring chamber, the flow rate of the developer in the stirring chamber is reduced while maintaining the transport amount between the stirring chamber and the developing chamber substantially equal. Slower than the speed.
[0011]
According to this configuration, sufficient stirring can be performed while the developer flows in the stirring chamber at a relatively low speed. On the other hand, since the developer flows in the developing chamber at a relatively high speed, the developer having a high toner concentration reaches a portion of the developer carrier that is located away from the developer supply start point. Therefore, there is little difference in image density depending on which side of the developer carrier is closer to the end. In addition, since the transport amount is maintained substantially equal between the stirring chamber and the developing chamber, the flow of the developer does not stagnate.
[0012]
(2) In the developing device as described above, the rotational speed of the stirring screw is made lower than the rotational speed of the transport screw to obtain a difference in the flow speed of the developer.
[0013]
According to this configuration, by adjusting the rotation speed ratio between the stirring screw and the transport screw, the difference in the flow speed of the developer can be easily adjusted.
[0014]
(3) In the developing device as described above, the difference in the flow speed of the developer is obtained by setting the screw pitch of the stirring screw to be smaller than the screw pitch of the transport screw.
[0015]
According to this configuration, by providing a difference in the screw pitch between the stirring screw and the conveying screw, a difference in the flow velocity of the developer can be reliably obtained.
[0016]
(4) In the developing device as described above, the rotation speed of the stirring screw is made slower than the rotation speed of the transport screw, and the screw pitch of the stirring screw is made smaller than the screw pitch of the transport screw. Thereby, a difference in the flow velocity of the developer is obtained.
[0017]
According to this configuration, the rotational speed ratio between the stirring screw and the transport screw is adjusted, and the difference in the screw pitch between the agitating screw and the transport screw is provided, so that a difference in the flow speed of the developer can be easily and reliably obtained. .
[0018]
(5) In the developing device as described above, the diameter of the stirring screw is larger than the diameter of the transport screw.
[0019]
According to this configuration, although there is a difference in the speed of the developer, the developer conveying capacity of the stirring screw is substantially equal to the developer conveying capacity of the conveying screw so that the supply of the developer from the stirring chamber to the developing chamber is not interrupted. Can be
[0020]
(6) In the developing device as described above, a stirring rib is formed between the protrusions of the stirring screw.
[0021]
According to this configuration, the developer can be sufficiently stirred while the developer flows in the stirring chamber.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a sectional view of the developing device, and FIG. 2 is a front view showing the structure of a stirring screw and a transport screw. FIG. 2 is drawn with the middle part omitted.
[0023]
The developing device 1 of the image forming apparatus includes a developing container 10. The developing container 10 has an elongated shape in the depth direction of the paper of FIG. 1 and is arranged with its longitudinal direction being horizontal. The inside of the developing container 10 is partitioned by a horizontal partition 11 into two upper and lower sections parallel to each other. The upper section is the stirring chamber 12, and the lower section is the developing chamber 13. Similarly to the image forming apparatus described in Patent Document 1, the developing container 10 contains a two-component dry developer composed of a non-magnetic toner and a magnetic carrier. The developer circulates between the stirring chamber 12 and the developing chamber 13. To make this possible, openings are provided at both ends of the partition 11, so that the stirring chamber 12 and the developing chamber 13 communicate with each other. (See FIG. 2).
[0024]
A stirring screw 20 is arranged in the stirring chamber 12, and a transport screw 30 is arranged in the developing chamber 13 so that their axes are horizontal and parallel to each other. The structures of the stirring screw 20 and the transport screw 30 will be described later in detail.
[0025]
The developing chamber 13 has an opening 14 at the front. The opening 14 is provided with a magnet roller 15 as a developer carrier. One side of the magnet roller 15 is exposed to the inside of the developing chamber 13, and the other side is exposed to the outside of the developing chamber 13 and faces the photosensitive drum 16 as an image carrier. The magnet roller 15 and the photosensitive drum 16 have a positional relationship close to or in contact with each other, and the toner adsorbed on the surface of the magnet roller 15 is transferred to the photosensitive drum 16 by a magnetic field to develop an electrostatic latent image. The consumed toner is supplied to the stirring chamber 12 from a toner storage chamber (not shown). An opening 18 for toner replenishment is formed in a lid 17 that covers the upper opening of the stirring chamber 12.
[0026]
The stirring screw 20 and the conveying screw 30 are designed as follows. That is, the flow velocity of the developer in the stirring chamber 12 is set to be lower than the flow velocity of the developer in the development chamber 13. In addition, the transport amount between the stirring chamber 12 and the developing chamber 13 is maintained substantially equal. Here, the “conveyance amount” refers to an amount of the developer that passes through a specific cross section of the stirring chamber 12 or the developing chamber 13 in a unit time.
[0027]
In the first embodiment, the screw shape itself is different. That is, the stirring screw 20 is a single-thread screw and has a smaller screw pitch than the conveying screw 30. The transport screw 30 is a two-start thread and has a larger screw pitch than the stirring screw 20. Accordingly, when the stirring screw 20 and the conveying screw 30 are rotated at the same rotation speed, the flow speed of the stirring screw 20 to the developer is relatively slow, and the flow speed of the conveying screw 30 to the developer is relatively low. Be faster.
[0028]
In the first embodiment, a difference is also made in the rotation speed of the screw. That is, the rotation speed (the number of rotations per unit time) of the stirring screw 20 is set lower than the rotation speed of the transport screw 30. Thereby, there is a further difference between the flow rate of the stirring screw 20 applied to the developer and the flow rate of the transport screw 30 applied to the developer.
[0029]
According to the configuration of the first embodiment, the flow rate of the developer in the stirring chamber 12 is determined by the difference in the screw pitch between the stirring screw 20 and the transport screw 30 and the difference in the rotation speed between the stirring screw 20 and the transport screw 30. A sufficient difference can be made between the flow rate of the developer in the developing chamber 13 and the flow rate of the developer in the developing chamber 13. Accordingly, while sufficient stirring can be performed while the developer flows in the stirring chamber 12 at a relatively low speed, the developer flows in the developing chamber 13 at a relatively high speed. The developer having a high toner density reaches a portion located away from the supply start point of the developer. Therefore, there is little difference in image density depending on which side of the magnet roller 15 is closer to the end.
[0030]
If the transport amount per unit time by the stirring screw 20 is smaller than the transport amount per unit time by the transport screw 30, the transport of the developer by the transport screw 30 is interrupted somewhere. That is, there is a portion where the developer does not contact the magnet roller 15. This directly results in image unevenness.
[0031]
The stirring screw 20 is configured as follows in order to make the transport amount of the developer per unit time substantially equal to that of the transport screw 30 irrespective of the lower flow rate of the developer applied to the developer than the transport screw 30. That is, the diameter of the stirring screw 20 is made larger than the diameter of the transport screw 30, and the cross-sectional area of the ridge of the screw for feeding the developer is made to have a sufficient difference to compensate for the difference in the flow speed of the developer (FIG. 1).
[0032]
With such a configuration, the developer carrying capacity of the stirring screw 20 is made substantially equal to the developer carrying capacity of the carrying screw 30 so that the supply of the developer from the stirring chamber 12 to the developing chamber 13 is not interrupted. it can.
[0033]
FIG. 3 shows a second embodiment of the present invention. FIG. 3 is a front view showing the structure of the stirring screw and the transport screw as in FIG. 2, and is drawn with the middle part omitted.
[0034]
The structures of the stirring screw 20 and the transport screw 30 of the second embodiment are basically the same as those of the first embodiment. What is different is that the stirring ribs 21 are formed at appropriate intervals between the protrusions of the stirring screw 20. Thereby, the developer can be further agitated while the developer flows in the stirring chamber 12.
[0035]
Although the embodiments of the present invention have been described, other various modifications can be made without departing from the spirit of the present invention.
[0036]
【The invention's effect】
According to the present invention, a stirring chamber containing a stirring screw and a developing chamber containing a transport screw are arranged in parallel with each other and communicate with each other at both ends, and the developer in the stirring chamber is supplied to the developing chamber by the stirring screw. The developer is fed to one end, and the fed developer is sent to the other end of the developing chamber by a transport screw while being in contact with the surface of the developer carrier exposed in the developing chamber, and the developer that has not adhered to the developer carrier is again removed. In the developing device that is returned to the stirring chamber, the flow rate of the developer in the stirring chamber is made lower than the flow rate of the developer in the developing chamber while maintaining the transport amount between the stirring chamber and the developing chamber substantially equal. Therefore, sufficient stirring can be performed while the developer flows in the stirring chamber at a relatively low speed. On the other hand, since the developer flows in the developing chamber at a relatively high speed, the developer having a high toner concentration reaches a portion of the developer carrier that is located away from the developer supply start point. Therefore, there is little difference in image density depending on which side of the developer carrier is closer to the end. Since the transport amount is maintained substantially equal between the stirring chamber and the developing chamber, there is no stagnation in the flow of the developer. By making the diameter of the stirring screw larger than the diameter of the conveying screw, the developer conveying capacity of the stirring screw is almost equal to that of the conveying screw, although there is a difference in the speed of the developer. The supply of the developer from the developer to the developing chamber can be prevented from being interrupted.
[Brief description of the drawings]
FIG. 1 is a sectional view of a developing device according to a first embodiment of the present invention; FIG. 2 is a front view showing a structure of a stirring screw and a transport screw of the developing device of the first embodiment; FIG. FIG. 4 is a front view showing the structure of a stirring screw and a transport screw of the developing device according to the embodiment. FIG. 4 is a cross-sectional view showing a schematic configuration of a conventional developing device. FIG. 5 is a plan view of the developing device in FIG.
Reference Signs List 1 developing device 10 developing container 11 partition 12 stirring chamber 13 developing chamber 14 opening 15 magnet roller (developer carrier)
16 Photosensitive drum (image carrier)
20 stirring screw 21 stirring rib 30 transport screw

Claims (6)

A stirring chamber with a built-in stirring screw and a developing chamber with a built-in transport screw are arranged in parallel with each other and communicate with each other at both ends, and the developer in the stirring chamber is sent to one end of the developing chamber by the stirring screw. The developer fed is sent to the other end of the developing chamber by the transport screw while contacting the surface of the developer carrier exposed in the developing chamber, and the developer not attached to the developer carrier is again removed. In the developing device configured to return to the stirring chamber,
A developing apparatus, wherein the flow rate of the developer in the stirring chamber is made slower than the flow rate of the developer in the developing chamber while maintaining the transport amount between the stirring chamber and the developing chamber substantially equal. The developing device according to claim 1, wherein a difference in the flow speed of the developer is obtained by setting a rotation speed of the stirring screw to be lower than a rotation speed of the transport screw. The developing device according to claim 1, wherein a difference in the flow speed of the developer is obtained by setting a screw pitch of the stirring screw to be smaller than a screw pitch of the transport screw. The rotation speed of the stirring screw is made slower than the rotation speed of the conveyance screw, and the screw pitch of the stirring screw is made smaller than the screw pitch of the conveyance screw, thereby reducing the flow speed difference of the developer. The developing device according to claim 1, wherein the developing device is obtained. The developing device according to claim 1, wherein a diameter of the stirring screw is larger than a diameter of the transport screw. The developing device according to claim 1, wherein a stirring rib is formed between protrusions of the stirring screw.

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