JP2003295602A - Developing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device where carrier means for stirring and carrying a developer in the developing device are vertically arranged, and by which the developer is prevented from following a development sleeve even when spherical toner or toner with low flowability, etc., is used, and the toner density distribution of the developer to be supplied to the development sleeve is substantially uniform in an axial direction, so as to form an uniform image without an image defect such as nonuniformity in density, and to provide an image forming apparatus. <P>SOLUTION: The developing device includes: a first developer carrier 8 which is rotatable to perform carrying to a development area facing an image carrier 10; a development chamber 3 for supplying the developer T to the first developer carrier 8; and carrier means 5 and 6 for circulating the developer T between the development chamber 3 and a stir chamber 4. The developing device 1 stores the developer for developing a latent image formed on the image carrier 10. The device 1 comprises a second developer carrier 11 which is rotatable in a direction being the same as that of the first carrier 8. <P>COPYRIGHT: (C)2004,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 for adhering a developer to a latent image formed on an image carrier to form a visible image, and an electrophotographic system or an electrostatic recording system provided with the developing device. The present invention relates to an image forming apparatus such as a copying machine and a laser beam printer using the.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine using an electrophotographic method or an electrostatic recording method, an electrostatic latent image formed on an image bearing member such as a photosensitive drum can be applied with a developer. Visualize. FIG. 5 shows an example of a conventional developing device used for such development that uses a two-component developer containing a toner and a carrier.

In the developing device 101 using a two-component developer as shown in FIG. 5, a first conveying screw 5 and a second conveying screw 6 which are conveying means for conveying the two-component developer T while stirring. Many of them are arranged horizontally. The first conveying screw 5 installed in the developing chamber 3 provided by partitioning the developing container 2 in the horizontal direction by the partition 7 supplies the developer to the developer carrier (developing sleeve) 8 and passes through the developing area. After that, the developer is collected. Similarly, the second conveying screw 6 installed in the stirring chamber 4, which is the other accommodation section partitioned by the partition wall 7, separates the developer collected from the developing sleeve 8 and the newly replenished developer. Mix and stir.

On the other hand, in recent years, in an image forming apparatus using an electrophotographic system such as a copying machine or a printer, there is a strong demand for downsizing of the main body of the apparatus in order to achieve space saving. In the image forming apparatus,
Since a plurality of developing devices are used, there is a strong demand for downsizing.

In order to solve this problem, Japanese Patent Laid-Open No. 5-33
6391 and the like, the developing device 10 as shown in the sectional view in the direction intersecting the axial direction of FIG. 6 and the axial sectional view of FIG.
2 is proposed. The developing device 102 shown in FIGS. 6 and 7 is characterized in that two conveying screws 5 and 6 for stirring and conveying the developer are arranged vertically above and below.

More specifically, the developing device 102 includes a developing container 2 containing a developer T, and a developing sleeve 8 at the opening of the developing container 2 facing the photosensitive drum 10. Further, a developing chamber 3 and an agitating chamber 4 which are partitioned by a partition wall 7 are vertically formed on the side opposite to the opening in the developing container 2, and the developing chamber 3 and the agitating chamber 4 are provided with a developer. The first and second conveying screws 5 and 6 are respectively installed as a stirring and conveying means. The first conveying screw 5 conveys the developer in the developing chamber 3, and the second conveying screw 6 conveys the developer from a toner supply port (not shown) to the stirring chamber 4.
The toner supplied to the upstream side of the second conveying screw 6 and the developer already in the stirring chamber 4 are conveyed while being stirred, and the toner concentration of the developer T is made uniform.

As described above, in the vertical stirring type developing device 102 shown in FIG. 6, since the developing chamber 3 and the stirring chamber 4 are arranged in the vertical direction, the space occupied in the horizontal direction is small. The advantage is that the color image forming apparatus of a tandem type in which a plurality of developing devices are mounted in parallel in the horizontal direction can be downsized.

Further, the vertical stirring type developing device also has the following advantages.

That is, the partition wall 7 is located at the upper and lower center of the developing sleeve 8, and the developing sleeve 8 is rotated in the direction in which the developing area moves vertically from the upper side to the lower side. Therefore, the developer T supplied from the developing chamber 3 located above according to the arrow a.
Is carried on the developing sleeve 8 and conveyed to the developing area for development, but the developer T left undeveloped in the developing area remains as shown in FIG. 5 as the developing sleeve 8 rotates. Instead of being collected in the developing chamber 3 side as in the illustrated lateral stirring type developing device 101, it is collected in the lower stirring chamber 4 side according to the arrow b. After that, in the stirring chamber 4, it is stirred and conveyed by the conveying screw 6 in the direction of arrow d in FIG. 7, and is conveyed to the developing chamber 3 from the communicating portions 71 provided on both sides of the developing container 2 of the partition wall 7. Therefore, in the developing chamber 3, there is always only the developer T sufficiently stirred in the stirring chamber 4. Therefore, the developer T having a uniform density is always supplied to the developing sleeve 8, and a uniform image having no image unevenness in the thrust direction and a density difference can be obtained.

[0010]

However, the structure of the vertical stirring type developing device 102 has the following problems.

As shown in FIGS. 6 and 7, the first conveying screw 5 as the conveying means is substantially parallel to the bottom of the developing chamber 3 along the axial direction of the developing sleeve 8 as the developer carrying member. It is arranged and rotates to convey the developer T in the developing chamber 3 in one direction along the axial direction. Further, the second conveying screw 6 which is a conveying means is arranged at the bottom of the stirring chamber 4 substantially in parallel with the first conveying screw 5 so that the developer in the stirring chamber 4 is directed in the opposite direction to the first conveying screw 5. Transport to. In this way, the developer T is conveyed by the rotation of the first and second conveying screws 5 and 6, and the developer T passes through the communicating portions 71 and 72 opened at both ends of the partition wall 7 and the developing chamber 3
And the stirring chamber 4.

By the way, in the main developing device 102, since the developing chamber 3 and the agitating chamber 4 are arranged vertically above and below,
As shown in FIGS. 6 and 7, the developer T from the developing chamber 3 to the stirring chamber 4 moves from top to bottom, and the developer T from the stirring chamber 4 to the developing chamber 3 moves from bottom to top. At this time, the stirring chamber 4 to the developing chamber 3
The developer T is handed over to the above as being pushed up from below by the pressure of the developer T accumulated at the end of the stirring chamber 4.

The agent circulation path d at this time is shown in FIG. 7. All of the developer T transferred from the stirring chamber 4 to the developing chamber 3 is smoothly transported in the axial direction in the developing chamber 3 and the first There is a component that is supplied to the developing sleeve 8 on the way and does not reach the downstream end of the conveying screw 5 and is recovered in the stirring chamber 4 after passing through the developing area.

The delivery of the developer to the developing sleeve 8 is carried out over almost the entire area of the developing sleeve 8 in the thrust direction. Therefore, the amount of the developer T carried by the first carrying screw 5 in the developing chamber 3 tends to gradually decrease from the upstream end to the downstream end. On the other hand, the amount of the developer T carried by the second carrying screw 6 in the stirring chamber 4 tends to gradually increase from the upstream end to the downstream end. That is, the distribution of the developer T in the developing device 102 is very likely to be offset as shown in FIG.

In particular, in the vicinity of the communicating portion 71 at the inner end of the agitating chamber 4 where the developer T amount in the agitating chamber 4 is deviated and the developer T amount is maximum, as shown in FIG. When the developer has accumulated up to this point, the developer having a low toner concentration which normally passes through the developing area and is collected in the stirring chamber 4 side according to the arrow b travels with the developing sleeve 8 and the partition 7 and the developing sleeve. A phenomenon occurs in which the toner is conveyed from the gap between the nozzles 8 and 8 to the developing chamber 3 according to the arrow c, and then to the developing area again.

As a result, in the region where such a rotation is generated, the developer T used for the development is not collected in the stirring chamber 4, that is, is not stirred, so that the toner concentration is lowered, Image density decreases. Stirring room 4
Occurs mainly in the end region of the developing container 2 in which the amount of developer T increases, and hardly occurs in other regions.
The developer T having a non-uniform toner concentration is supplied to the developing sleeve 8, image unevenness in the thrust direction occurs, and the advantages of the vertical stirring type developing device are lost.

In order to cope with the above-mentioned accompanying rotation phenomenon as described above, the developing sleeve 8 can be used especially for high-speed copying machines and printers.
It becomes noticeable when the peripheral speed of is increased. It is considered that this is because the developer conveying force of the developing sleeve 8 and the kinetic energy of the developer, that is, the entrainment force increased due to the increased peripheral speed. Therefore, it is considered that the above problems will become more and more important in the recent trend toward higher speeds of printers and copiers using the electrophotographic method. Specifically, when the rotation speed of the developing sleeve exceeds 350 mm / sec, further 500 m
If it is more than m / sec, it becomes a serious problem.

As a measure against the above problem, as in the developing device 103 shown in FIG. 8, a developer is provided above the second conveying screw 6 in the stirring chamber 4 in the direction opposite to the second conveying screw 6. A third conveying screw 70 for conveying is provided to reduce the deviation of the developer in the stirring chamber 4 (Japanese Patent Laid-Open No. 6-
Japanese Patent No. 51634) is proposed.

However, in such a structure, the structure is not a structure that directly eliminates the entrainment, but is a structure that indirectly eliminates the entrainment by reducing the deviation. It is not effective when the degree of deviation is severe, such as when the above toner is used.

Therefore, an object of the present invention is to provide a low fluidity toner in a high-speed image forming apparatus such as a copying machine or a printer, in which conveying means for agitating and conveying the developer in the developing apparatus are arranged vertically. Even when using a spherical toner or the like, the developer is prevented from entraining the developing sleeve,
It is an object of the present invention to provide a developing device and an image forming apparatus that form a uniform image in which the toner concentration distribution of the developer supplied to the developing sleeve is substantially uniform in the axial direction and image defects such as density unevenness do not occur.

[0021]

The above object is achieved by the developing device and the image forming apparatus according to the present invention. In summary, the first aspect of the present invention is directed to a rotatable first developer carrier that carries a developer and conveys the developer to a developing area facing the image carrier, and the first developer carrier. A developing chamber for supplying the developer to the developing chamber, a stirring chamber arranged vertically below the developing chamber for collecting the developer after passing through the developing area, and a developing chamber between the developing chamber and the developing chamber. And a conveying unit that circulates the developer, and stores a developer that develops the latent image formed on the image carrier, in a downstream direction of the developing region in a rotation direction of the first developer carrier. At a position close to this, a second developer carrier which is rotatable in the same direction as the first developer carrier is provided, and the second developer carrier is moved from the first developer carrier to the second developer carrier. A feature that the developer after passing through the developing area is delivered to the developer carrier. To provide a developing device which.

According to one embodiment of the first aspect of the present invention, the second developer carrying member faces the image carrying member and is used for development.

According to another embodiment of the first aspect of the present invention, inside the first developer carrying member, a first developer carrying member is provided downstream of the developing region in the rotation direction of the first developer carrying member. A first magnetic pole, and a second magnetic pole that is adjacent to the first magnetic pole on the downstream side in the rotation direction of the first developer carrier and that is provided inside the developing device main body and has the same polarity as the first magnetic pole. A first magnetic field generating means is provided, and inside the second developer carrying member, a third magnetic pole provided in a region substantially opposite to the first magnetic pole, and the second developing of the third magnetic pole are provided. A second magnetic field generating unit having a fourth magnetic pole having the same polarity as the third magnetic pole is provided adjacent to the upstream side in the rotation direction of the agent carrier and inside the developing device main body.

A second aspect of the present invention is provided with an image carrier on which a latent image is formed, and a developing device of the first aspect of the present invention.
Provided is an image forming apparatus characterized by forming an image on a recording material.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION A developing device and an image forming apparatus according to the present invention will be described below in more detail with reference to the drawings. still,
The developing device of the present invention is used, for example, in an image forming apparatus as described below, but is not necessarily limited to this form.

Embodiment 1 FIG. 1 shows a developing device 1 facing a photosensitive drum 10 in each image forming portion (station) of Y, M, C, and K in a full-color image forming device as shown in FIG. It is a thing. Each station of Y, M, C, K
Each has substantially the same configuration, and forms a yellow (Y), magenta (M), cyan (C), and black (K) image in a full-color image, respectively. In the following description, for example, if there is the developing device 1, the developing device 1 in each of the Y, M, C and K stations shown in FIG.
Y, the developing device 1M, the developing device 1C, and the developing device 1K are commonly referred to. The same applies to other devices and members.

First, the operation of the entire image forming apparatus will be described with reference to FIG.

The photosensitive drum 10 as an image carrier is rotatably provided, and the photosensitive drum 10 is connected to the primary charger 2
A light emitting element 2 such as a laser that is uniformly charged by 1
An electrostatic latent image is formed by exposure with light that is modulated by 2 according to the information signal. The electrostatic latent image is developed by the developing device 1.
It is visualized as a developer image (toner image) in the process described below. Then, the visible image is transferred by a transfer charger 23 onto a transfer paper 27 which is a recording material conveyed by a transfer paper conveying sheet 24, and further fixed by a fixing device 25 to obtain a permanent image. Further, the transfer residual toner on the photosensitive drum 10 is removed by the cleaning device 26.
Further, the toner consumed in the image formation is replenished from the toner replenishing tank 20 provided in the upper part of the developing device 1 here. Further, here, the photosensitive drums 10M, 10C, 10
Although a method of directly transferring from Y and 10K to the transfer sheet 27 which is a recording material conveyed to the transfer sheet conveying sheet 24 is adopted, an intermediate transfer member is provided in place of the transfer sheet conveying sheet 24, and the photosensitive drums 10M of respective colors are provided. The present invention can also be applied to an image forming apparatus having a configuration in which toner images of respective colors are primarily transferred from 10C, 10Y, and 10K to an intermediate transfer member, and then composite toner images of respective colors are collectively secondarily transferred to a transfer paper.

Next, the operation of the developing device 1 will be described with reference to FIG. In the developing device 1 of the present embodiment, a developing sleeve 2 as a first developer carrying member is provided in a developing container 2 in which a two-component developer containing a non-magnetic toner and a magnetic carrier is contained as a developer T. And a brush cutting member 9 for controlling the brush of the developer carried on the developing sleeve 8. And
A substantially central portion in the developing container 2 is vertically divided into an upper developing chamber 3 and a lower stirring chamber 4 by a partition wall 7 extending in an axial direction of the developing container 2, that is, a vertical direction on the paper surface of FIG. The developer T is contained in the developing chamber 3 and the stirring chamber 4. Here, the partition wall 7 is located substantially vertically in the center of the developing sleeve 8 in the vertical direction.

In the developing chamber 3 and the agitating chamber 4, first and second conveying screws 5 and 6 are respectively arranged as a developer agitating / conveying means. The first conveying screw 5 is arranged at the bottom of the developing chamber 3 substantially parallel to the axial direction of the developing sleeve 8 and rotates to convey the developer in the developing chamber 3 in one direction along the axial direction. To do. Further, the second conveying screw 6 is arranged at the bottom of the stirring chamber 4 substantially in parallel with the first conveying screw 5, and conveys the developer in the stirring chamber 4 in the direction opposite to the first conveying screw 5. In this way
By the conveyance by the rotation of the first and second conveying screws 5 and 6, the developer T is opened (communication portion) at both ends of the partition wall 7 provided in the same manner as shown in FIG. It is circulated between the developing chamber 3 and the stirring chamber 4 through the parts 71, 72).

Further, a position corresponding to the developing area of the developing container 2 facing the photosensitive drum 10 is opened, and the developing sleeve 8 is opened in this opening and the direction in which the photosensitive drum 10 is installed in the image forming apparatus. It is rotatably arranged so that a part of it is exposed. As described above, the developing container 2 is divided into the upper developing chamber 3 and the lower stirring chamber 4 by the partition wall 7 in the substantially upper and lower center of the developing sleeve 8. The developing sleeve 8 is rotated in a direction that passes through a developing area, which is a portion facing the photosensitive drum 10, in a vertical direction from top to bottom. Therefore,
The developer is supplied from the upper developing chamber 3 and the developing sleeve 8 is rotated in such a direction as to return the developed developer to the lower stirring chamber 4.

The developing sleeve 8 is a cylindrical body made of a non-magnetic material, and a magnet roller 8'which is a first magnetic field generating means is installed inside the developing sleeve 8 in a non-rotating state. The roller 8'has a developing pole S2 and magnetic poles S1, N1, N2, N3 for carrying the developer.
Of these, the first magnetic pole N3 and the second magnetic pole N1 which are the same poles are installed adjacent to each other inside the developing container 2, a repulsive magnetic field is formed between the poles, and a barrier against the developer T. Is formed, and the developer T is separated in the stirring chamber 4.

During development, the developing sleeve 8 rotates in the direction of the arrow shown in the drawing, which moves the developing area vertically from top to bottom, and the layer thickness is regulated by the brush cutting of the magnetic brush by the brush cutting member 9. The two-component developer T is carried and conveyed to the developing area facing the photosensitive drum 10, and the developer T is supplied to the latent image formed on the photosensitive drum 10 to develop the latent image. At this time, in order to improve the development efficiency (that is, the toner application rate to the latent image), a developing bias voltage in which a DC voltage and an AC voltage are superimposed is applied to the developing sleeve 8 from a power source.

The bristle-cutting member 9 is made of a non-magnetic member such as aluminum and has a developing sleeve 8 rather than the photosensitive drum 10.
It is arranged on the upstream side in the rotation direction. Then, both the non-magnetic toner of the developer and the magnetic carrier pass through the space between the tip of the spike-cutting member 9 and the developing sleeve 8 and are sent to the developing area. By adjusting the gap between the brush cutting member 9 and the surface of the developing sleeve 8, the brush cutting amount of the developer magnetic brush carried on the developing sleeve 8 is regulated, and the amount of the developer conveyed to the developing area is controlled. Adjusted.

The first conveying screw 5 is arranged substantially parallel to the bottom of the developing chamber 3 along the axial direction (developing width direction) of the developing sleeve 8. In this embodiment, it is made of a ferromagnetic material. It has a screw structure in which a blade member made of a non-magnetic material is spirally provided around a rotating shaft to be rotated, and the developer T in the developing chamber 3 is rotated and the developer T in the developing chamber 3 is rotated at the bottom of the developing sleeve 8. Transport along the axial direction.

The second conveying screw 6 has a screw structure in which a blade member is provided in a spiral shape around the rotary shaft in the opposite direction to the first conveying screw 5 like the first conveying screw 5. , Is arranged at the bottom of the stirring chamber 4 substantially parallel to the first conveying screw 5 and rotates in the same direction as the first conveying screw 5 to transfer the developer T in the stirring chamber 4 to the first conveying screw 5. Transport in the opposite direction.

By the rotation of the first and second conveying screws 5 and 6, the developer T is transferred to the developing chamber 3 and the stirring chamber 4.
In the present developing device 1, the developing chamber 3 and the agitating chamber 4 are arranged vertically in the vertical direction, and the developer from the developing chamber 3 to the agitating chamber 4 moves from top to bottom, The developer from the stirring chamber 4 to the developing chamber 3 moves from bottom to top. In particular, the stirring chamber 4
To the developing chamber 3 is transferred by being pushed up from below by the pressure of the developer accumulated at the end.

At this time, as described in the conventional example, the stirring chamber 4
From the developing chamber 3 to the developing chamber 3 in the vicinity of the communicating portion 71, the developer is likely to accumulate in the agitating chamber 4 and the T surface of the developer becomes high. As a result, the developer T having a reduced toner concentration after passing through the developing area is the developing sleeve. It is likely that the phenomenon of being pumped up to the developing chamber 3 along with 8 and conveyed again to the developing area occurs.

Therefore, in the developing device of the present invention, the developing device 1 of the present embodiment will be described. Further, a second developer carrying means is provided in a region of the lower part of the developing sleeve 8 facing the developing sleeve 8. The conveying sleeve 11 is arranged rotatably in the direction of the arrow shown, that is, in the same direction as the developing sleeve 8.

The carrying sleeve 11 is made of a non-magnetic material, and like the developing sleeve 8, a magnet roller 11 'which is a second magnetic field generating means is installed in the non-rotating state inside the sleeve. 11 'is the magnetic pole S
It has three poles of 3, S4 and N4. Of these, the third magnetic pole S3 and the fourth magnetic pole S4, which are the same pole, are adjacent to each other, and a repulsive magnetic field is formed between them to form a barrier against the developer. The magnetic poles S3 and S forming this repulsive magnetic field
Of the four, the third magnetic pole S3 on the downstream side in the rotation direction of the sleeve 11
The pole is the first of the magnet 8'included in the developing sleeve 8.
The sleeves 8 and 11 face the magnetic pole N3 in the vicinity of the position where the sleeves 8 and 11 are closest to each other. Here, the N3 pole of the magnet 8'is the upstream side in the rotation direction of the sleeve 8 of the magnetic poles N1 and N3 forming the repulsive magnetic pole on the developing sleeve 8 side described above.

The flow of the developer T will be described below with reference to an enlarged view (FIG. 3) near the developing sleeve 8 and the conveying sleeve 11. As described above, a repulsive magnetic field is formed between the first magnetic pole N3 pole and the second magnetic pole N1 pole in the developing sleeve 8, and the third magnetic pole S3 pole and the fourth magnetic pole S4 pole of the transport sleeve 11 are formed. A repulsive magnetic field is also formed between them. The repulsive magnetic fields of the N1 pole and the N3 pole in the developing sleeve 8 and the repulsive magnetic fields of the S3 pole and the S4 pole in the transport sleeve 11 are directed to the same side, and are directed to the inside of the developing container 2. Therefore, the developer T conveyed on the developing sleeve 8 and passing through the developing area is
It reaches the position of the first magnetic pole N3 pole of the magnet 8 ', and by the repulsive magnetic field with the downstream second magnetic pole N1 pole, it passes through the closest position where the sleeves 8 and 11 face each other and passes as shown by arrow e. That is, the developer T cannot be entrained in the developing sleeve 8, and the direction from the N3 pole on the developing sleeve 8 side to the third magnetic pole S3 pole of the magnet 11 'on the conveying sleeve 11 side as indicated by arrow f. It moves to the side of the conveying sleeve 11 according to the extending magnetic force line, and is conveyed to the second conveying screw 5 in the stirring chamber 4 on the conveying sleeve 11.

In the conventional system composed of one sleeve 8 as shown in FIG. 6, the developer T is contained in the developing container 2
After being conveyed in the order of N1 → S1 → N2 → S2 → N3 so as to pass through the developing area from the inside to the outside and return to the inside of the developing container 2, N3 → N1 as shown by an arrow c in FIG.
As described above, there is a high possibility that the developer T will be accompanied, but as in the present embodiment, at the opening portion of the developing container 2 facing the photosensitive drum 10, the conveying sleeve faces the developing sleeve 8. By providing 11, the developer T
Flow from the developing sleeve 8 to the outside of the developing container 2 is N1 → S1.
After being transported in the order of → N2 → S2 → N3, the developer T on the developing sleeve 8 is blocked by the repulsive magnetic field of the sleeves 8 and 11, so that the developer T does not slip through the gap between the closest portions of the sleeves 8 and 11. , Moves to the conveying sleeve 11, is conveyed on the conveying sleeve 11 in the order of S3 → N4 → S4, and is agitated while being blocked by the repulsive magnetic field with the third magnetic pole S3 pole in the developing container 2 by the fourth magnetic pole S4. The developer T is stripped off into the chamber 4. In this way, by completely stripping the developer T on the developing sleeve 8 by the transport sleeve 11, it is possible to prevent accompanying rotation.

In order to completely peel off the developer T from the developing sleeve 8 by the carrying sleeve 11, as in this embodiment, the poles having opposite polarities in the vicinity of the closest positions of both sleeves 8 and 11, that is, It is better to make the attracting polarities face each other. As a result, the developer can be prevented from slipping through the closest portions of the sleeves 8 and 11.

At this time, in this embodiment, the magnetic poles of opposite polarities (N3 pole and S3 pole) are made to face each other in the vicinity of the closest portion, but the same stripping effect can be obtained even if the same poles are made to face each other. To be In addition, the developer T that has been peeled off and then conveyed on the conveying sleeve 11 returns to the developing sleeve 8 again and is prevented from being conveyed, so that the developer T is peeled off from the conveying sleeve 11; It is better that the other magnetic pole, that is, the fourth magnetic pole S4 in this embodiment, is farther from the developing sleeve 8.

That is, the distance between the same poles forming the repulsive magnetic field of the carrier sleeve 11, that is, the distance between the S3 pole and the S4 pole in the present embodiment, is better, the angle is 100 ° or more, more preferably 150 degrees. It is good that it is at least °, more preferably at least 180 °. Further, the larger the diameter of the conveying sleeve 11 is, the longer the distance becomes. Therefore, the diameter is preferably 15 mm or more, more preferably 20 mm or more. Although not shown, it is also effective to provide two or more transport sleeves and sequentially transfer the developer.

In general, the entrainment phenomenon appears remarkably when the peripheral speed of the developing sleeve is increased to cope with a high-speed copying machine or printer. Specifically, when the rotation speed of the developing sleeve exceeds 350 mm / sec, it becomes 500 mm / sec or more, which is a particular problem. Generally, the rotation of the developing sleeve is 1000 mm /
If it is set to sec or more, toner scattering due to centrifugal force from the developing sleeve becomes a problem. Therefore, in the present invention, the peripheral speed of the developing sleeve is 350 mm / sec or more and 1000 mm / sec.
It can be said that it is effective for the following high speed developing devices.

As described above, the transport means for stirring and transporting the developer in the developing device is arranged vertically, and the developer is supplied from the developing chamber with the developing sleeve above and the developer after the developing is supplied to the stirring chamber below. When rotating in a direction to recover
By providing a conveying sleeve, which is a second developer carrying member, which rotates in the same direction as the developing sleeve, in a region where the developing sleeve, which is the first developer carrying member, opposes, and the developer on the developing sleeve is peeled off. To provide a developing device in which the developer does not follow the developing sleeve and the toner concentration distribution of the developer supplied to the developing sleeve is substantially uniform in the axial direction, and the occurrence of image defects such as uneven density can be prevented. You can

Example 2 Next, a second embodiment of the present invention shown in FIG. 4 will be described.

This embodiment has almost the same structure as the first embodiment, but in this embodiment, a conveying sleeve 11 which is a second developer carrying member provided facing the developing sleeve 8 is
The feature is that it is also close to the photosensitive drum 10. Furthermore,
By applying a developing bias voltage to the carrying sleeve 11, the developer on the carrying sleeve 11 is also developed by using the N4 pole as a developing pole.

As a result, the number of times of development is the development sleeve 8
The development is carried out twice and the carrying sleeve 11 develops twice, and it is possible to improve the development efficiency by increasing the number of developments. Although only the DC voltage may be applied as the developing bias to the carrying sleeve 11, the developing efficiency can be further improved by applying the voltage in which the DC voltage and the AC voltage are superposed like the developing bias applied to the developing sleeve 8. Becomes In summary, it is preferable to apply an AC voltage to either the developing sleeve or the conveying sleeve, more preferably both.

At this time, the developing sleeve 8 and the conveying sleeve 11 do not have to be the same as long as they are a voltage obtained by superimposing a DC voltage and an AC voltage, but by making them the same, the power source can be shared and the cost and the like can be improved. There are merits from a viewpoint.

Even in such an image forming apparatus provided with a developing device for developing twice with two developer carrying members, the developer does not follow the developing sleeve and the toner of the developer supplied to the developing sleeve. It is possible to provide a developing device in which the density distribution is substantially uniform in the axial direction and the occurrence of image defects such as density unevenness can be prevented.

Incidentally, in the present invention, the developing is configured such that the developer is supplied to the first developer carrying member in the developing chamber located vertically above and the developer after the development is collected in the lower stirring chamber. It is about the device.

Further, the construction of dividing the developing container into the developing chamber and the stirring chamber, which is a feature of the developing device of the present invention, is generally executed for a two-component developing device, but the developer is a two-component developing device. The developer is not limited to the agent, and a one-component developer containing toner but not carrier may be used. In the case of a one-component developer, the present invention can be applied particularly for the purpose of suppressing the deterioration of the agent due to entrainment.

[0055]

As described above, according to the present invention, the rotatable first developer carrier for carrying the developer and transporting the developer to the developing area facing the image carrier, and the first developing device A developing chamber for supplying the developer to the agent carrier, a stirring chamber arranged vertically below the developing chamber for collecting the developer after passing through the developing area, and a developing chamber between the developing chamber and the stirring chamber for collecting the developer. In a developing device containing a developer for developing the latent image formed on the image bearing member, the circulating transporting means is provided downstream of the developing region in the rotation direction of the first developer bearing member. A second developer carrying member that is rotatable in the same direction as the first developer carrying member is provided at a position close to the first developer carrying member, and the second developer carrying member develops from the first developer carrying member to the second developer carrying member. Developing device for delivering the developer after passing through the area, and image forming apparatus including the developing device Therefore, when the conveying means for stirring and conveying the developer in the developing device is arranged above and below, the developer does not follow the developing sleeve and the toner concentration distribution of the developer supplied to the developing sleeve is axial. Almost uniform in the direction,
An effect that a uniform image can be provided without occurrence of image defects such as density unevenness can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a developing device according to the present invention.

FIG. 2 is a schematic configuration diagram showing an example of an image forming apparatus according to the present invention.

FIG. 3 is an enlarged cross-sectional view showing the configurations of a first developer carrier and a second developer carrier according to the present invention.

FIG. 4 is a sectional view showing another example of the developing device according to the present invention.

FIG. 5 is a sectional view showing an example of a conventional developing device.

FIG. 6 is a sectional view showing another example of a conventional developing device.

FIG. 7 is an axial sectional view showing another example of a conventional developing device.

FIG. 8 is a sectional view showing another example of a conventional developing device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 developing device 2 developing container 3 developing chamber 4 stirring chamber 5 first conveying screw (conveying means) 6 second conveying screw (conveying means) 7 partition wall 8 developing sleeve (first developer carrying member) 8'magnet roller (First Magnetic Field Generating Means) 9 Ear Cutting Member 10 Photosensitive Drum (Image Carrier) 11 Conveying Sleeve (Second Developer Carrier) 11 'Magnet Roller (Second Magnetic Field Generating Means)

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2H031 AA11 AB02 AB09 AC04 AC08                       AC14 AC15 AC18 AC19 AD03                       AE01 BA05 BA09 DA01 FA01                 2H077 AB02 AB14 AB15 AB18 AC12                       AC16 AD02 AD06 BA03 EA01                       FA19 GA13                 2H300 EA08 EB04 EB07 EB12 EF02                       EF06 EF07 EH16 EJ02 EJ09                       EJ21 EJ22 EJ23 EJ30 EJ31                       EJ33 EJ35 EJ43 EJ52 EJ58                       EJ59 FF05 GG01 GG02 GG11                       HH15 HH19

Claims (8)

[Claims] 1. A rotatable first developer carrier that carries a developer and conveys the developer to a developing area facing the image carrier, and supplies the developer to the first developer carrier. A developing chamber, a stirring chamber arranged vertically below the developing chamber for collecting the developer after passing through the developing area, and a conveying means for circulating the developer between the developing chamber and the stirring chamber. ,
A developing device containing a developer for developing the latent image formed on the image carrier, the position being close to the first developer carrier in the rotation direction in the downstream direction of the developing area. Is provided with a second developer carrying body rotatable in the same direction as the first developer carrying body, and the first developer carrying body is provided with the second developer carrying body. A developing device, wherein the developer is transferred after passing through the developing area. 2. The developing device according to claim 1, wherein the second developer carrier faces the image carrier and is used for development. 3. A first magnetic pole provided downstream of the developing region in the rotation direction of the first developer carrier inside the first developer carrier, and the first magnetic pole of the first magnetic pole. A first magnetic field generating means having a first magnetic pole and a second magnetic pole having the same polarity as that of the first magnetic pole, which is adjacent to the downstream side of the developer carrier in the rotation direction and is provided inside the developing device main body; Inside the second developer carrier, a third magnetic pole provided in a region that is substantially close to and opposed to the first magnetic pole and is adjacent to the third magnetic pole on the upstream side in the rotation direction of the second developer carrier. 3. The developing device according to claim 1, further comprising a second magnetic field generating unit having a fourth magnetic pole having the same polarity as the third magnetic pole inside the developing device main body. 4. The developing device according to claim 3, wherein the first magnetic pole and the third magnetic pole have opposite polarities. 5. The developing device according to claim 1, further comprising a developer containing a toner and a magnetic carrier. 6. The peripheral speed of the first developer carrying member is 350.
The developing device according to claim 1, wherein the developing device has a diameter of not less than mm / sec and not more than 1000 mm / sec. 7. An image carrier on which a latent image is formed and a developing device according to claim 1 are provided, and an image is formed on a recording material. Image forming apparatus. 8. An image forming apparatus according to claim 7, further comprising a plurality of the image bearing members, and the developing device according to any one of claims 1 to 6 provided for each of the image bearing members. .