JP2003241510A - Developing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device which is compact, whose life is long, and where density irregularity or the lowering of density is prevented to obtain a uniform image. <P>SOLUTION: The developing device is provided with a developing roll 1 having a magnet inside and carrying and feeding developer while rotating, and a pair of stirring members 3 and 4 arranged around the roll 1, having a rotary shaft parallel with the roll 1, and set to feed the developer 2 in a reverse direction to each other in the rotary shaft direction. The developer 2 is fed to a stirring member 4 on an upstream side from a stirring member 3 on a downstream side in the rotating direction of the roll 1 by the rotation of the roll 1. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used in an image forming apparatus such as an electrophotographic printer or a copying machine.

[0002]

2. Description of the Related Art Conventionally, as a two-component type developing device used in an electrophotographic image forming apparatus, a fixed magnet having a plurality of magnetic poles is disposed in the vicinity of or in contact with a latent image carrier. A two-component developer consisting of toner and a magnetic carrier is supplied onto a rotatable developing roll having a roller, the developing roll is rotated to convey the developer to a developing region, and the action of a bias voltage applied to the developing roll is exerted. A method of developing an electrostatic latent image on a latent image carrier is generally used.

As a conventional example, a developing device is shown in FIGS.
Shown in.

In the developing area, a bias voltage is applied to the developing roll, and the developing electric field generated causes the charged toner to move to the latent image carrier for development. The electric field generated by the developed toner cancels out the developing electric field, so when the amount of developing toner increases and the electric field balances with the developing electric field, the development ends at that point. Therefore, since a toner having a high charge amount has a large electric field generated by the toner, the amount of developable toner is small and the image density is low. On the contrary, since the toner having a low charge amount has a small electric field generated by the toner, the toner amount that can be developed is large and the image density is high.

The toner charge amount of the developer increases according to the stirring time and is saturated to a constant charge amount for a certain period of time, but the developer having a low toner concentration (toner ratio) has a saturated toner charge amount. , The image density becomes low, and conversely, a developer having a high toner density has a low toner charge amount, and toner stains and toner scattering easily occur on the image. Therefore, if the developer is agitated insufficiently or unevenly in the developing device, uneven toner concentration and uneven charge occur, which causes uneven image density and image density fluctuation.

As a method for solving this problem, a method is known in which a pair of stirring screws are provided as stirring members, and the developers are stirred and conveyed in opposite directions to each other by rotating the stirring screws. A developer delivery area is provided at both ends of the rotary shaft, and the developer moves from one stirring screw to the other stirring screw, and a conveying path is formed in which the developer circulates in both stirring screws. Since the developer is stirred and transported in the transport path and uniformly stirred and charged, an image having a constant and uniform image density is always obtained by the developer supplied from the stirring screw to the developing roll. In addition, the same amount of toner as the developed toner is newly supplied to the transport path and agitated with the developer in the transport path to maintain the developer at a constant toner concentration and charge amount, so that a stable image is always obtained. be able to.

[0007]

However, in order to smoothly and reliably move the developer in the transfer portion between the stirring screws, both stirring screws must be arranged substantially horizontally, and therefore the width of the developing device is wide. Therefore, there is a problem that miniaturization is difficult. That is, if a pair of stirring screws are arranged with a height difference between the upper and lower sides for downsizing, it becomes difficult to move the developer from the lower stirring screw to the higher stirring screw in the transfer area at the end, and This hinders conveyance and circulation, causes unevenness and clogging of the developer, and makes it impossible to stably stir the developer or supply it to the developing roll. That is, if the pair of stirring screws are arranged with a height difference, it becomes difficult to obtain a uniform and stable image.

In view of the above-mentioned circumstances, the present invention can reliably stir and convey the developer even with a stirring member having a difference in height, can be easily miniaturized, and has uniform density and no fluctuation in density. An object of the present invention is to provide a novel developing device capable of obtaining a stable image.

[0009]

The developing device of the present invention which achieves the above object has a developing agent having magnetism and a magnet inside, and is a developing device for developing an electrostatic latent image on a latent image carrier. To the area, a developing roll that rotates and carries the developer, and a developing roll that is arranged around the developing roll, has a rotation axis parallel to the developing roll, and stirs and conveys the developer in opposite directions in the rotation axis direction. It is characterized in that it has a pair of agitating members set, and that the developer can be conveyed from the agitating member on the downstream side in the rotating direction of the developing roll to the agitating member on the upstream side by the rotation of the developing roll.

Further, the developer is conveyed from the stirring member on the downstream side to the stirring member on the upstream side at an end portion in the axial direction of the developing roll.

A partition plate for partitioning the downstream stirring member and the upstream stirring member is provided.

Further, the developer is supplied to the developing roll from the downstream stirring member by the magnetic force of the magnet of the developing roll,
The developer conveyed by the rotation of the developing roll and subjected to layer regulation by the regulation member, and thereafter, the developer remaining without passing through the regulation member is agitated and conveyed in the axial direction by the rotation of the upstream stirring member, and is upstream at the axial end portion. It is configured such that it is dropped from the side stirring member to the downstream stirring member by gravity, and thereafter, it is stirred and conveyed by the downstream stirring member in a direction opposite to that of the upstream stirring member and is supplied to the developing roll. .

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

FIG. 1 is a schematic sectional view of a first embodiment of a developing device of the present invention. Further, FIG. 2 is a schematic configuration diagram of a stirring unit in the developing device shown in FIG.

The developing roll 1 is internally provided with a developing magnetic pole N1,
It has a fixed magnet in which five magnetic poles of a peeling magnetic pole S1, a scooping magnetic pole S2, a transport magnetic pole N2, and a transport magnetic pole S3 are arranged, and the developer 2 is carried and transported in the direction of arrow A by rotating. The separation magnetic pole S1 is separated from the separation magnetic pole S1 by a predetermined distance.
A pumping magnetic pole S2 having the same polarity as that of No. 1 is arranged, and a magnetic field is not formed on the sleeve surface between them. The developing roller 1 has an outer diameter of φ12 and is made of an aluminum sleeve having a surface with irregularities of several μm. The magnetic force of the fixed magnet inside is 95 mT for the developing magnetic pole N1 and 60 mT for the other magnetic poles.

In the developer 2, a magnetic carrier and a toner are mixed in a fixed ratio, the magnetic carrier is ferrite particles having a resin coating on the surface thereof and an average particle diameter of 35 μm, and the toner is particles such as polyester and the average particle diameter is 7 μm. is there.

As a regulating member for regulating the layer of the developer 2 on the developing roll 1, the regulating blade 5 is connected to the developing rolls 1 and 0.
They are arranged with a gap of 3 mm. The regulation blade 5 is made of aluminum having a thickness of 2 mm.

The stirring screws 3 and 4 each having a screw having an outer diameter of 12 mm and a pitch of 15 mm as a pair of stirring members.
Is arranged around and parallel to the developing roll 1, and the stirring screw 4 is arranged on the upstream side of the stirring screw 3 with respect to the rotation direction of the developing roll 1. A partition plate 8 integrally formed with the developing case 7 is provided between the stirring screws 3 and 4.

The partition plate 8 and the developing case 7 form transport paths 9 and 10 for stirring and transporting the developer. The conveying paths 9 and 10 have stirring screws 3 and 4, respectively, and since the side facing the developing roll 1 has an opening, it is between the developing roll 1 and the stirring screw 3 and between the developing roll 1 and the stirring screw 4. The developer can be moved by. The stirring screws 3 and 4 are rotated by a drive unit (not shown), and the developer 2 in the transport paths 9 and 10 is stirred and transported in the directions of arrow B in directions opposite to each other in the rotation axis direction.

The developer 2 is supplied from the downstream stirring screw 3 to the developing roll 1 by the magnetic force of the scooping magnetic pole S2 of the developing roll 1. Developer 2 supplied to developing roll 1
Is conveyed in the direction of arrow A by the rotation of the developing roller 1, the layer is regulated by the regulating blade 5, and then developed in the developing area. In the developing area, a bias voltage (not shown) is applied to the developing roll 1, and the developing electric field generated causes the toner to move to the latent image carrier 6 to develop the electrostatic latent image. After that, the developer moves from the developing roll 1 to the stirring screw 3 by the peeling magnetic pole S1, is collected, and is again mixed with the developer not used for the development and stirred and conveyed.

Here, from the stirring screw 3 to the developing roll 1
The developer 2 that is supplied to the developer and is conveyed by the rotation of the developing roller 1 but does not pass through the regulating blade 5 is blocked by the regulating blade 5 and enters the conveying path 10 having the upstream stirring screw 4 (arrow C ), And is agitated and conveyed in the axial direction by the rotation of the agitation screw 4. That is, by moving the developer 2 on the developing roll 1, it becomes possible to convey the developer 2 from the downstream stirring screw 3 to the upstream stirring screw 4.

There is no partition plate 8 at the end of the upstream stirring screw 4 in the developer conveying direction, and at this location, the developer falls from the upstream stirring screw 4 to the downstream stirring screw 3 by gravity. Then, the developer 2 is agitated and conveyed by the downstream stirring screw 3 in a direction opposite to that of the upstream stirring screw 4,
It is supplied to the developing roll 1 again. Therefore, the developer 2 is agitated and conveyed while being circulated in the conveyance paths 9 and 10 having the agitation screws 3 and 4, and the developer is successively supplied from the agitation screw 3 to the developing roll 1, so that a stable image can be obtained. it can.

Further, an amount of toner commensurate with the toner developed in the developing area is newly supplied to the conveying path 9 having the stirring screw 3 by the toner concentration detecting means and toner supplying means (not shown), and is mixed and stirred with the developer. Therefore, the toner concentration and the charge amount of the developer 2 are always kept constant.

In the first embodiment, the partition plate 8 is provided between the stirring screw 3 and the stirring screw 4 except the end of the stirring screw 4 in the developer conveying direction. An opening for moving from the stirring screw 4 to the stirring screw 3 may be provided in the partition plate 8, or even if the partition plate 8 itself is not provided, development from the downstream stirring screw 3 to the upstream stirring screw 4 The developer can be moved and the developer can be circulated and conveyed.

FIG. 3 is a schematic sectional view of the second embodiment of the developing device of the present invention. Further, FIG. 4 is a schematic configuration diagram of a stirring unit in the developing device shown in FIG.

In the second embodiment, the opening on the side of the developing roll 1 of the conveying path 10 having the stirring screw 4 is provided only at the end in the axial direction, and the developer is upstream from the downstream stirring screw 3 only at the end. It is configured to move to the side stirring screw 4. By moving the developer from the downstream stirring screw 3 to the upstream stirring screw 4 only at the end portion, the developer 2 is reliably circulated and stirred and conveyed, and more uniform stirring becomes possible, and the density is increased. Will be more stable.

In both the first and second embodiments, the downstream stirring screw 3 is used to both supply and recover the developer 2 to the developing roll 1. However, the present invention is not limited to this. The screw 4 may supply and collect the developer, or the developer 2 may be supplied from the upstream stirring screw 4 to the developing roll 1 and the developer may be recovered by the downstream stirring screw 3.

In the first embodiment, new toner is supplied to the conveying path 9 having the downstream stirring screw 3, but the conveying path 1 having the upstream stirring screw 4 is used.
The toner may be supplied to 0.

[0029]

As described above, according to the developing device of the present invention, it is possible to smoothly circulate and stir the developer even if the stirring member has a height difference, and as a result, the developing device can be downsized. Since the developing device can be made particularly small in width and the developer can be surely stirred and conveyed, a developing device that can obtain a stable image with uniform density can be realized.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a first embodiment of a developing device of the present invention.

2 is a schematic configuration diagram of a stirring unit in the developing device shown in FIG.

FIG. 3 is a schematic sectional view of a second embodiment of the developing device of the invention.

FIG. 4 is a schematic configuration diagram of a stirring unit in the developing device shown in FIG.

FIG. 5 is a schematic cross-sectional view of a conventional developing device.

6 is a schematic configuration diagram of a stirring unit of the conventional developing device shown in FIG.

[Explanation of symbols]

1 developing roll 2 developer 3 stirring screw 1 4 stirring screw 2 5 regulation blade 6 Electrostatic latent image carrier 7 Development case 8 partition boards 9 Developer transport path 1 10 developer transport path 2

Claims (4)

[Claims] 1. A developer having magnetism, a developing roll having a magnet therein, which rotates to carry and convey the developer to a developing area for developing an electrostatic latent image on a latent image carrier; It is arranged around the roll, the axis of rotation is parallel to the developing roll,
The developer has a pair of stirring members set to stir and convey the developer in opposite directions in the rotation axis direction, and the developer is rotated by the rotation of the developing roll from the stirring member on the downstream side in the rotation direction of the developing roll to the upstream side. A developing device that can be conveyed to a stirring member. 2. The developing device according to claim 1, wherein the developer is conveyed from the downstream stirring member to the upstream stirring member at an end portion in the developing roll axial direction. 3. The developing device according to claim 1, further comprising a partition plate for partitioning the downstream stirring member and the upstream stirring member. 4. The developer is supplied from the downstream stirring member to the developing roll by the magnetic force of the magnet of the developing roll, conveyed by the rotation of the developing roll, regulated by the regulating member, and then passes through the regulating member. The remaining developer is
The upstream stirring member is rotated and agitated and conveyed in the axial direction, and at the axial end portion, gravity falls from the upstream stirring member to the downstream stirring member, and thereafter, in the opposite direction to the upstream stirring member by the downstream stirring member. 4. The developing device according to claim 1, wherein the developing device is configured to be conveyed by stirring and supplied to a developing roll.