JPH11174810A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device which prevents image hindrance, such as density increase or fog, resulting from developer deterioration. SOLUTION: In the developing device 9, a stirring chamber 17 is disposed vertically higher than a developing chamber 16, and besides a developer passage provided at the end of one side in a developing container 9a along which the developer is sent and received from the stirring chamber 17 to the developing chamber 16, a partition 6 is provided for separating the stirring chamber 17 and the developing chamber 16 from each other. The developing sleeve (developer carrier) 3 is composed so as to rotate in the direction where the developer subjected to bristle cutting in the developing chamber 16 is carried into the stirring chamber 17 through a developing area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for developing an electrostatic image on an image carrier.

[0002]

2. Description of the Related Art In an image forming apparatus using an electrophotographic system, a latent image formed on an image carrier is developed with a developer and visualized as a toner image. FIG. 6 shows an example of a conventional developing device used for such development.

FIG. 6 is a cross-sectional view of a conventional developing device 69. The developing device 69 collects the developer after passing through a developing area from a developer carrier and supplies the developer to a newly supplied developing device. And a stirring chamber 77 for mixing and stirring the developer, receiving the mixed and stirred developer from the stirring chamber 77, supplying the developer to the developing sleeve 63, and holding the magnetic brush ears of the developer carried on the developing sleeve 63 by a spike member. (Hodaka regulating member) 62
And a developing chamber 76 which cuts off to a predetermined height.

More specifically, the developing device 69 includes a developing container 69a containing a developer, and has a developing sleeve 63 in an opening of the developing container 69a facing the photosensitive drum 64. A developing chamber 76 and a stirring chamber 77 defined by a partition 66 are formed vertically above and below the opening in the developing container 69a, and a developer is provided in the developing chamber 76 and the stirring chamber 77. Screws 71 and 72 for agitating and transporting are respectively provided.

[0005] The developer contained in the developing container 69 a is supplied to the developing sleeve 63 by the conveying screws 71 and 72, and the magnetic force of the magnet roller 73 installed inside the developing sleeve 63 is applied to the magnetic brush. In this state, it is carried on the surface of the developing sleeve 63. The developer is conveyed to the developing area facing the photosensitive drum 64 with the rotation of the developing sleeve 63, and the amount of the developer on the developing sleeve 63 is conveyed by the developer returning member 61 in the upper part of the developing container 69 a during the conveyance. Is restricted, and the ear-cutting member 62
As a result, the amount of the developer that is cut off by the magnetic brush and conveyed to the development area is appropriately maintained.

Incidentally, the magnet roller 73 is
The developer transported by the transport screw 71 of the developing chamber 76 is constrained and carried on the surface of the developing sleeve 63 while forming a magnetic brush by the magnetic force of the pumping pole N2, and is rotated by the rotation of the developing sleeve 63. Developer pool 6
5 is conveyed. The developer conveyed to the developer reservoir 65 is sufficiently constrained by the cut pole S2 having a certain or more magnetic flux density to obtain a stable constraining force and conveyed in a state where a magnetic brush is formed. And the ear cutting member 62
, The magnetic brush is cut off, and is regulated to an appropriate amount. Then, the magnetic brush is conveyed to the developing area by the conveying pole N1.

In the developing area, the magnet roller 7
When the developer is a two-component developer due to the magnetic force of the third developing pole S1 and the developing bias in which the direct current and / or the alternating electric field applied from the bias power supply 75 provided on the image forming apparatus main body side to the developing sleeve 63 are superimposed. When the developer is transferred from the developer on the developing sleeve 63 to the electrostatic latent image on the photosensitive drum 64 and the developer is a one-component developer, the toner as the one-component developer is used as it is.
The image is transferred to the upper electrostatic latent image, and the latent image is visualized as a toner image.

In the developing chamber 76 and the stirring chamber 77, first and second conveying screws 71 and 72 are provided as developer stirring / conveying means, respectively. The first transport screw 71 transports the developer in the developing chamber 76 and the second transport screw 71
Under the control of the developer concentration controller, the toner supplied to the upstream side of the second transport screw 72 from the toner supply port into the stirring chamber 77 and the developer already in the stirring chamber 77. Is transported with stirring to make the toner concentration of the developer uniform.

Further, at both ends of the partition wall 66, a developer passage for communicating the developing chamber 76 and the stirring chamber 77 with each other is formed. The developer inside is moved into the stirring chamber 77 by the transport of the developing sleeve 63.

As shown in FIG. 7, the first transport screw 71 is disposed substantially parallel to the bottom of the developing chamber 76 along the axial direction (developing width direction) of the developing sleeve 63. A screw structure in which a blade member made of a non-magnetic material is provided in a spiral shape around a rotation shaft made of, and rotates so that the developer in the developing chamber 76 moves in the axial direction of the developing sleeve 73 at the bottom of the developing chamber 76. Along one direction.

Also, the second transport screw 72 has a screw structure in which the blade member is provided in a spiral shape around the rotation axis in a direction opposite to the first transport screw 71, similarly to the first transport screw 71. The first in the bottom of the stirring chamber 77
, And rotates in the same direction as the first conveying screw 71 to convey the developer in the stirring chamber 77 in the direction opposite to the first conveying screw 71. Thus, the first and second transport screws 7
As shown in FIG. 7, the developer is circulated between the developing chamber 76 and the agitating chamber 77 through the openings at both ends of the partition 66 as shown in FIG.

In the developing device 69, the developing chamber 7
6 and the stirring chamber 77 are arranged vertically, so that the developer flows from the developing chamber 76 to the stirring chamber 77 from top to bottom, as shown in FIG. The developer moves from bottom to top. In particular, the developer is delivered from the stirring chamber 77 to the developing chamber 76 such that the developer is pushed upward from below by the pressure of the developer collected at the end.

After being carried on the developing sleeve 63 and conveyed to the developing area, and subjected to the development, the remaining developer not subjected to the development in the developing area is transferred to the developing sleeve 63.
Is returned into the stirring chamber 77 with the rotation of the developing roller 6 and the developing sleeve 6 is repelled by the repulsive magnetic poles N3 and N2 of the magnet roller 73.
3 is scraped off from above and collected in the stirring chamber 77.

As described above, in the vertical stirring type developing device 69 shown in FIG. 6, since the developing chamber 76 and the stirring chamber 77 are arranged vertically, the space occupied in the horizontal direction is small. There is an advantage that it can be done. Further, the vertical stirring type developing device 69 has the following advantages.

That is, after being carried on the developing sleeve 63 and conveyed to the developing area and subjected to development, the remaining developer not subjected to development in the developing area is transferred to the developing sleeve 6.
Since the toner is not collected in the developing chamber 76 but is collected in the stirring chamber 77 with the rotation of 3, the developing chamber 76 always contains only the developer sufficiently stirred in the stirring chamber 77. For this reason, the developer having a uniform density is always supplied to the developing sleeve 63, and a uniform image free from image unevenness in the thrust direction and density difference can be obtained.

[0016]

However, in the configuration of the above-described conventional developing device 69, the stirring chamber 77 is moved from the developing chamber 7 to the developing chamber 7.
Since the developer is transferred to the side 6 by being pushed upward from the bottom by the pressure of the developer accumulated at the end, extra stress is applied to the developer, and this stress causes the developer to be quickly released. Deterioration causes image defects such as increased density and fog.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a developing device capable of preventing the occurrence of image disturbances such as an increase in density and fog due to deterioration of a developer. It is in.

[0018]

According to the first aspect of the present invention, there is provided a rotatable developer carrier for carrying a developer and transporting the developer to a development area facing the image carrier. And a magnet that is non-rotatably disposed in the developer carrier, and collects the developer after passing through the developing area from the developer carrier and mixes and agitates this with the newly supplied developer. A stirring chamber, receiving the mixed and stirred developer from the stirring chamber, supplying the developer onto the developer carrier, and cutting the magnetic brush ears of the developer carried on the developer carrier to a predetermined height; A developing chamber provided with an ear-cutting member disposed at a predetermined distance from the outer peripheral surface of the developer carrying member, the developing chamber and the stirring chamber are vertically arranged, and the magnet is , The developer conveyed through the developing area on the developer carrier In the developing device, the take-up pole and the pumping pole are configured to be a repelling pole configuration in order to drop the developer from the developer carrier into the stirring chamber, the stirring chamber is disposed vertically above the developing chamber, Except for a developer passage provided at one end in a developer container for transferring the developer from the developer chamber to the developing chamber, the developer carrier has a partition for partitioning the stirring chamber and the developing chamber, It is characterized in that the developer cut in the developing chamber rotates in a direction in which the developer is conveyed so that the developer passes through the developing area and is taken into the stirring chamber.

According to a second aspect of the present invention, in the first aspect of the present invention, a magnetic member is disposed at a leading end of a partition that divides the developing chamber and the stirring chamber, and the developer carrying member and its magnetic material are provided. It is characterized in that the developer in the stirring chamber is prevented from dropping into the developing chamber due to the magnetic restraining force with the member.

According to a third aspect of the present invention, in the first aspect of the present invention, a portion between the tip of a partition partitioning the developing chamber and the agitating chamber from an end portion of the repelling pole configuration of the developer carrier is provided. A scrape member is provided so as to be in contact with the scrape member.

[0021]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

<First Embodiment> FIG. 3 is a schematic sectional view of an image forming apparatus provided with a developing device according to a first embodiment of the present invention.

The present image forming apparatus is a four-station laser beam printer having a plurality of image forming stations, and includes an image forming station having image forming means around a photosensitive drum. , Are provided corresponding to four colors of yellow and black,
The toner image on the photosensitive drum formed at each station is transferred onto a transfer material conveyed by a transfer belt that moves in opposition to the photosensitive drum.

That is, magenta, cyan, yellow and black image forming stations Pm, Pc, Py and Pk
Are provided with photosensitive drums 4m, 4c, 4y, and 4k, respectively, and these photosensitive drums 4m, 4c, 4y, and 4k are rotated in the arrow direction (clockwise direction) in the figure. Around the photosensitive drums 4m, 4c, 4y, and 4k, corona chargers 46m, 46c, 46y, and 46k, scanning optical devices 47m, 47c, 47y, and 47k as optical scanning means, and developing devices 9m and 4m. 9c, 9y, 9k and cleaning device 48
m, 48c, 48y, and 48k are provided.

Further, a transfer section constituting a part of the image forming means includes a transfer belt 49a and photosensitive drums 4m to 4k which are commonly used in the image forming stations Pm to Pk.
For full-color image formation, the toner images formed on the photosensitive drums 4m to 4k are sequentially transferred onto a transfer material P formed on a transfer belt 49a for the transfer color chargers 49m, 49c, 49y, and 49k. This is achieved by:

On the other hand, the transfer material P is supplied from the paper supply cassette 50 onto the transfer belt 49a. When the transfer process is completed, the transfer material P is separated from the transfer belt 49a and discharged to the tray 52 via the fixing device 51.

The scanning optical devices 47m, 47c, 4
Reference numerals 7y and 47k denote a laser light source (not shown), a rotating polygon mirror that scans the laser light from the laser light source, an fθ lens that focuses the scanning beam on the generatrix of the surfaces of the photosensitive drums 4m to 4k, It comprises a reflecting mirror that deflects and a beam detector that detects a specific position of the scanning beam.

Here, the details of the developing device 9 (9m to 9k) will be described with reference to FIGS. FIG. 1 is a schematic sectional view of the developing device 9 (9 m to 9 k), and FIG. 2 is a plan view of the developing device 9.

The developing device 9 according to the present embodiment comprises a developing container 9a containing a two-component developer containing a non-magnetic toner and a magnetic carrier. The apparatus has a member 1 and an ear-cutting member 2 for regulating the ears of the developer carried on the developing sleeve 3. A substantially central portion in the developing container 9a is divided into a developing chamber (first chamber) 16 and a stirring chamber (second chamber) 17 by a partition wall 6 extending in a direction perpendicular to the paper surface. It is housed in the developing chamber 16 and the stirring chamber 17.

The developing chamber 16 and the stirring chamber 17 are provided with first and second conveying screws 11 and 12, respectively, as developer stirring / conveying means. The first transport screw 11 transports the developer in the developing chamber 16 and the second transport screw 11
Under the control of the developer concentration control device, the toner supplied to the upstream side of the second transport screw 12 from the toner supply port into the stirring chamber 17 and the developer already in the stirring chamber 17 Is transported with stirring to make the toner concentration of the developer uniform.

A developing chamber 16 is provided at one end of the partition 6.
A developer passage is formed for communicating the developer with the stirring chamber 17, and the developer that has passed through the developing region where the toner has been consumed and the toner concentration has decreased due to the development is moved into the stirring chamber 17 by transporting the developing sleeve 3. Let it.

Further, an opening is opened at a position corresponding to a developing region of the developing chamber 16 facing the photosensitive drum 4, and the developing sleeve 3 is partially exposed in the opening toward the photosensitive drum 4. It is arranged so that it can rotate. The developing sleeve 3 is made of a non-magnetic material, and a magnet roller 13 serving as a magnetic field generating means is installed in a non-rotating state inside the developing sleeve 3.
Reference numeral 3 denotes a developing pole N1 and magnetic poles S1, S2, and N for transporting the developer.
2, N3.

During development, the developing sleeve 3 rotates in the direction of the arrow as shown in the figure, and carries a two-component developer whose layer thickness is regulated by the cutting of the magnetic brush by the cutting member 2 and carries it on the photosensitive drum. The photosensitive drum 4 is conveyed to a developing area facing the photosensitive drum 4 and a developer is supplied to the latent image formed on the photosensitive drum 4 to develop the latent image. At this time, in order to improve the developing efficiency (that is, the rate of applying toner to the latent image), a developing bias voltage in which a DC voltage and an AC voltage are superimposed is applied from the power supply 15 to the developing sleeve 3.

The ear cutting member 2 is made of a non-magnetic material such as aluminum, and is disposed upstream of the photosensitive drum 4 in the rotation direction of the developing sleeve 3. Then, both the non-magnetic toner of the developer and the magnetic carrier pass between the front end of the ear cutting member 2 and the developing sleeve 3 and are sent to the developing area. Incidentally, by adjusting the gap between the ear cutting member 2 and the surface of the developing sleeve 3, the amount of the ear cutting of the developer magnetic brush carried on the developing sleeve 3 is regulated, and the amount of the developer conveyed to the developing area is reduced. Adjusted.

Incidentally, the first transport screw 11
As shown in FIG. 2, is disposed substantially parallel to the bottom of the developing chamber 16 along the axial direction (developing width direction) of the developing sleeve 3. In the present embodiment, the rotating member made of a ferromagnetic material is used. It has a screw structure in which a blade member made of a non-magnetic material is provided in a spiral shape around an axis, and rotates so that the developer in the developing chamber 16 moves along the axial direction of the developing sleeve 3 at the bottom of the developing chamber 16. Transport in the direction.

Further, the second transport screw 12 is also a first transport screw.
As in the case of the transfer screw 11, the screw structure is such that the blade member is provided in a spiral shape around the rotation axis in a direction opposite to that of the first transfer screw 11, and the first transfer screw 11 is provided at the bottom in the stirring chamber 17. Is arranged almost in parallel with
The stirring chamber 1 rotates in the same direction as the first conveying screw 11.
7 is conveyed in a direction opposite to the first conveying screw 11. In this way, by the conveyance by the rotation of the first and second conveyance screws 11 and 12, as shown in FIG. 2, the developer passes through one opening of the partition 6 to the developing chamber 16 and the stirring chamber 17, Circulated between

After being carried on the developing sleeve 3 and conveyed to the developing area and subjected to the development, the remaining developer not subjected to the development in the developing area is stirred again with the rotation of the developing sleeve 2. The developer is returned into the chamber 17, is scraped off from the developing sleeve 3 by the repulsive magnetic poles N3 and N2 of the magnet roller 13, and is collected into the stirring chamber 17.

On the other hand, the developer transported by the rotation of the first transport screw 11 is pumped up onto the developing sleeve 3 by one of the repulsive magnetic poles N2 in an amount proportional to the absolute value of the magnetic flux density. Note that the amount of the developer pumped up is determined by a magnetic restraining force acting on the center of the developing sleeve 3 formed by the magnetic field from the magnetic pole N2 and a conveying force acting on the rotating direction of the developing sleeve 3.

Thus, in the present embodiment, as shown in FIGS. 1 and 2, the circulation of the developer in the developing container 9a is as follows as compared with the conventional example.

First, since the stirring chamber 17 is arranged above the developing chamber 16, the developer is transferred from the stirring chamber 17 to the developing chamber 16 at one end of the partition 6 as shown in FIG. Down and down along the direction of gravity. In addition, the developer is cut off by the scribing member 2 on the developing sleeve 3 by the rotation of the developing sleeve 3, conveyed to a developing area opposed to the photosensitive drum 4, and further subjected to development, and then moved to the stirring chamber 17. By being taken in, the lower developing chamber 16
The developer is delivered to the upper stirring chamber 17 from above.

In the conventional developing device 69 shown in FIG. 6, the delivery of the developer from the agitating chamber 77 to the developing chamber 76 is reduced in the direction of gravity by the pressure of the developer accumulated at the end of the developing container 69a. However, in the present embodiment, there is no place that causes such a flow of the developer, and the developer flows from the lower developing chamber 16 to the upper stirring chamber 17. The transfer of the developer is performed only by the conveyance by rotation of the developing sleeve 3.

Accordingly, in this embodiment, no stress is applied to the developer in the circulation of the developer, and the deterioration of the developer can be extremely reduced. In this way, by suppressing the deterioration of the developer, a stable image can be output without causing an image failure such as an increase in density or fog over a long period of time, and until the developer needs to be replaced. (That is, the life of the developer) can be greatly extended.

In the present embodiment, an example is shown in which the rotation direction of the developing sleeve 3 and the photosensitive drum 4 in the developing area is opposite (counter development), but the rotation direction is the same (with development). Can obtain the same effect as the above.

Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 4 is a cross-sectional view of the developing device according to the second embodiment of the present invention. In FIG. 4, the same elements as those shown in FIG. 1 are denoted by the same reference numerals.

In the first embodiment, a gap is formed between the developing sleeve 3 and the tip of the partition 6. However, in the present embodiment, as shown in FIG. Are arranged in parallel with the developing sleeve 3 in the thrust direction, and the developer in the stirring chamber 17 is developed by the magnetic constraint force generated between the developing sleeve 3 and the magnetic member 18 from the gap between the developing sleeve 3 and the tip of the partition 6. It can be prevented from spilling into the chamber 16. As described above, since the gap can be filled without contacting the developing sleeve 3, the stirring chamber 17 can be sealed without increasing the rotational torque of the developing sleeve 3.

Third Embodiment Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 5 is a cross-sectional view of the developing device according to the third embodiment of the present invention. In FIG. 5, the same elements as those shown in FIG.

In the second embodiment, the magnetic member 18 is provided at the tip end of the partition wall 6.
As shown in FIG. 7, a scraping member 19 is extended from the tip end of the partition wall 6 toward the gap between the repulsion poles N2 and N3 of the developing sleeve 3 so as to contact the developing sleeve 3, and the stirring chamber 17 is provided.
The gap between the developing chamber 16 and the developing chamber 16 is filled.

Thus, as described above, the scrape member 19
The gap between the stirring chamber 17 and the developing chamber 16 can be completely buried in order to make the developer contact the developing sleeve 3.

In the first and second embodiments, the developer is stirred only by the repulsion poles N2 and N3 of the developing sleeve 3.
In the present embodiment, the developer on the developing sleeve 3 is mechanically peeled off by the scraping member 19, so that the developer is transferred from the developing sleeve 3 to the stirring chamber 17. Recovery can be complete.

[0050]

As is apparent from the above description, according to the present invention, the stirring chamber is disposed vertically above the developing chamber, and the developer is transferred from the stirring chamber to the developing chamber. Except for a developer passage provided at one end of the developing chamber, a partition partitioning the stirring chamber and the developing chamber is provided, and the developer carrier carries the developer cut off in the developing chamber through the developing area. The developer is rotated in the direction in which the developer is conveyed so that it is taken into the stirring chamber, so that stress is not applied to the developer in the circulation of the developer, and image defects such as density increase and fog due to the deterioration of the developer are prevented. The effect that generation can be prevented is obtained.

[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 sectional view of the developing device according to the first embodiment of the present invention.

FIG. 3 is a schematic sectional view of an image forming apparatus (laser beam printer) including a developing device according to the present invention.

FIG. 4 is a sectional view of a developing device according to a second embodiment of the present invention.

FIG. 5 is a sectional view of a developing device according to a third embodiment of the present invention.

FIG. 6 is a sectional view of a conventional developing device.

FIG. 7 is a plan view of a conventional developing device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 developer return member 2 spike member 3 developing sleeve (developer carrier) 4 photosensitive drum (image carrier) 6 partition 9 developing device 9a developing container 11, 12 transport screw 13 magnet roller (magnet) 16 developing chamber 17 stirring Chamber 18 Magnetic member 19 Scraping member

Claims (3)

[Claims] A rotatable developer carrier for carrying a developer and transporting the developer to a development area facing the image carrier; a magnet arranged non-rotatably in the developer carrier; A stirring chamber for collecting the developer after passing through the area from the developer carrier and mixing and stirring the developer with the newly supplied developer; and receiving the mixed and stirred developer from the stirring chamber to perform the development. The magnetic brush of the developer supplied on the developer carrier and the developer carried on the developer carrier is arranged at a predetermined distance from the outer peripheral surface of the developer carrier to cut the ears of the magnetic brush to a predetermined height. A developer chamber having an ear cutting member, wherein the developer chamber and the agitating chamber are vertically arranged, and the developer is conveyed through the developer area on the developer carrier. To drop the developer from the developer carrier into the stirring chamber. In a developing device in which the lift-up pole and the repelling pole configuration are arranged, the stirring chamber is disposed vertically above the developing chamber,
Except for a developer passage provided at one end in a developer container for transferring the developer from the stirring chamber to the developing chamber, the developer carrier has a partition that separates the stirring chamber from the developing chamber. The developing device rotates in a direction in which the developer is transported such that the developer cut off in the developing chamber passes through the developing area and is taken into the stirring chamber. 2. A magnetic member is provided at a tip end of a partition wall separating the developing chamber and the stirring chamber, and a developer on a stirring chamber side is driven by a magnetic binding force between the developer carrier and the magnetic member. 2. The developing device according to claim 1, wherein the developing device does not fall into the developing chamber. 3. A scraping member is provided so as to abut from a tip end of a partition partitioning the developing chamber and the stirring chamber to a gap between the repelling poles of the developer carrier. Item 2. The developing device according to Item 1.