JP2003057954A - Image forming device and developing means - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming means and a developing means which can always obtain stable images for a long period. SOLUTION: A developing means 1 is equipped with a development container 2 containing a developer having toner and carriers, a developer carrier 10, a magnetic field producing means 11 which is arranged fixedly in the developer carrier 10, and a restriction member 30 which restricts the layer thickness of the developer on the developer carrier 10 and also held rotatably by a holding means close to the image carrier 10; and the magnetic field producing means 11 is equipped with a 1st magnetic pole N2 and a 2nd magnetic pole N3 which is provided nearby the part opposite to the restricting member 30 adjacently on the downstream side of the 1st magnetic pole N2 in the moving direction of the developer carrier 11 and has the same polarity with the 1st magnetic pole N2 and moves the developing means 1 to a development part from below in the gravitation direction by the rotation of the holding means to perform developing operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-component developer that forms an electrostatic latent image on an image bearing member by, for example, an electrophotographic system or an electrostatic recording system, and the electrostatic latent image is a toner and a carrier. The present invention relates to an image forming apparatus, such as a printer, a facsimile or a copying machine, which forms a visible image (toner image) by the developing means used, and a developing means provided therein.

[0002]

2. Description of the Related Art Conventionally, an electrostatic latent image is formed on an image carrier,
In the image forming apparatus in which the electrostatic latent image is converted into a developed image (toner image) by the developing means, a developing means for developing using a magnetic brush of a two-component developer is used as the developing means.
An example thereof is shown in FIG.

In this embodiment, the developing means comprises a developing container 2 containing a two-component developer, and the developing container 2 has an opening facing the photosensitive drum 100, which is an image bearing member, in a developing sleeve which is a developer bearing member. A photosensitive drum 100 and a photosensitive drum 100 are rotatably installed with a predetermined gap therebetween.

The developing sleeve 10 is composed of a cylindrical body made of a non-magnetic material, and a magnet roller 11 as a magnetic field generating means is arranged inside the developing sleeve 10 so as not to rotate with respect to the rotation of the developing sleeve 10. The magnet roller 11 has five magnetic poles N1,
It has S1, N2, N3 and S2.

At the opening portion of the developing container 2 above the developing sleeve 10, a regulating blade 30 of a magnetic member is provided as a regulating member.
The regulation blade 30 is attached to the magnetic pole S which is located substantially at the uppermost point in the vertical direction of the magnet roller 11 in FIG.
The developing sleeve 10 is arranged so as not to contact the developing sleeve 10. The developer conveying screws 4 and 6 are arranged in the lower portion of the developing container 2.

The two-component developer housed in the developing container 2 is supplied to the developing sleeve 10 while being circulated in the container 2 by stirring and carrying by the carrying screws 4 and 6. The developing sleeve 10 conveys the developer from the position facing the regulating blade 30 at the opening of the developing container 2 to the outside of the developing container 2 and to the developing section facing the photosensitive drum 100. Therefore, the rotation direction c is the direction from the position facing the regulating blade 30 to the outside of the developing container 2 and to the developing unit facing the photosensitive drum 100, and in the case of the developing means shown in FIG. Rotate from the highest point,
It is exposed to the outside of the developing container 2 and then rotates in the direction c toward the developing portion facing the photosensitive drum 100, and the developing portion rotates from top to bottom in the counterclockwise direction in FIG.

The developer supplied to the developing sleeve 10 is
The magnetic pole N of the magnet roller 11 located in the developing container 2
3 is drawn up onto the developing sleeve 10 and, as the developing sleeve 10 rotates, it is conveyed from the magnetic pole S2 to the magnetic pole N1 which is the developing portion where the developing sleeve 10 and the photosensitive drum 100 face each other. During the transportation, the developer is magnetically regulated in layer thickness by the regulation blade 30 in cooperation with the magnetic pole S2, and a thin layer of the developer is formed on the developing sleeve 10.

Magnet roller 11 located in the developing section
The magnetic pole N1 is the main developing pole, and the developer conveyed to the developing unit stands up by the magnetic pole N1 and contacts the surface of the photosensitive drum 100, and the electrostatic latent image formed on the surface of the photosensitive drum 100 is formed. develop. The developer that has developed the latent image passes through the developing portion in the vertical direction from top to bottom in accordance with the rotation of the developing sleeve 10, is returned to the inside of the developing container 2 via the transport pole S1, and the magnetic pole N2 in the developing container 2 is It is removed from the developing sleeve 10 by the repulsive magnetic field of N3 and collected.

Therefore, the position of the magnetic pole of the magnet 11 is
In the developing means of FIG. 8 in which the photosensitive drum 100 is arranged on the left and the developing container 2 is arranged on the right, and the developing sleeve 10 rotates counterclockwise, the S2 pole at the uppermost vertical direction of the magnet 11 inside is the developing container. 2, the developer carried on the developing sleeve 10 is carried out with the layer thickness being regulated by the regulating blade 30, and the developer is carried to the opening of the developing container 2 at the N1 pole of the developing position, that is, the substantially lowermost vertical portion. After passing through the located S1 pole, it is carried into the developing container 2 again, and the N inside the developing container 2
It is configured to pass through the two poles in order and be guided to the lower side of the developing container 2 by the repulsive magnetic field of the N2 pole and the N3 pole.

That is, in FIG. 8, the positions of the magnetic poles of the magnet 11 are counterclockwise along the circumferential direction of the magnet 11, and the vertical uppermost portions S2, N1, S1 (lowermost portion), N
2 and N3 are arranged in this order.

[0011]

However, in the conventional developing means, the developer left over on the developing sleeve 10 due to the regulation by the regulating blade 30 is the magnetic pole N.
Due to the magnetic forces of 3 and S2, the developer is held so as to be stuck on the portion A near the upstream side in the rotation direction c of the developing sleeve 10 of the regulating blade 30, that is, the surface of the regulating blade 30 on the inner side of the developing container 2, and accumulates in a large amount.

The developer is successively conveyed by the developing sleeve 10 to the portion A where the developer is accumulated in the vicinity of the regulation blade 30 inside the developing container 2, so that a large pressure is applied to the developer accumulated in the portion A. This causes a phenomenon in which the magnetic carrier of the developer and the toner are pressed and fine particles such as silica (SiO ₂ ) externally added to the toner are embedded in the toner.

Further, due to the friction between the toner and the magnetic carrier, the particle shape of the toner itself becomes rounded and rounded. Further, when it is used for a long time, the toner adheres to the surface of the magnetic carrier and cannot be removed, so-called a spent phenomenon occurs.

When such deterioration of the developer occurs, the triboelectric charge amount of toner (so-called tribo) changes with use time, the developability of the toner changes to change the image density, and the magnetic carrier or the photosensitive drum. The adhesion of the toner to the toner increases, making it difficult to perform development and transfer corresponding to the electric field, resulting in image unevenness in which the toner is partially lost.

When a magnetic carrier having a relatively low magnetization is used as a carrier used for the two-component developer, the brush of the magnetic brush becomes soft and the developed toner image on the photosensitive drum is rubbed in the developing section. Since the force becomes weaker, it is advantageous for higher image quality, but the low magnetization weakens the magnetic transfer force, which deteriorates the developer and increases the degree of aggregation, and the amount of developer coated on the developing sleeve is small. Is likely to occur.

When this phenomenon occurs, the development is performed in a state where the magnetic brush and the photosensitive drum are not in contact with each other, so that the density around the surface image becomes high, so-called edge emphasis becomes remarkable, and in addition to the above-mentioned problems. The image quality was significantly deteriorated.

In order to solve such a problem, the amount of the two-component developer accumulated on the upstream side of the regulating blade in the developing container is reduced to prevent the developer from being conveyed one after another. There is a need for means for reducing the pressure applied to the developer and preventing the deterioration of the developer. As the means, a so-called light load developing means has been proposed and implemented.

FIG. 9 shows the developing means of this light load configuration.
Here, the regulation blade 30 is the magnet roller 11
Of the regulation blade 3 arranged so as to face the magnetic pole N3 of
A magnetic pole N3 near 0 is used as a second magnetic pole, and a first magnetic pole N2 having the same polarity is adjacent to the second magnetic pole N3 upstream of the developing sleeve 10 in the rotation direction c. Of the two first and second magnetic poles having the same polarity, the second magnetic pole located on the downstream side in the rotation direction c of the developing sleeve 10, here, the developer is regulated by the regulation blade 30 in the vicinity of the facing position of the N3 pole. As a result, of the remaining developer that has not been applied on the developing sleeve 10 and cannot be retained by the second magnetic pole, the repulsive magnetic field with the first magnetic pole promptly drops onto the conveying screws 4 and 6. Therefore, a large pool of developer does not occur in the vicinity of the upstream side of the regulating blade 30 in the rotation direction c of the developing sleeve 10.

Further, since the developer is dropped and removed between the repulsive poles B of the first and second magnetic poles, the developer is conveyed one after another as in the conventional case and a large pressure is applied to the developer. Absent. Therefore, it is possible to prevent the deterioration of the developer.

On the other hand, in the developing means having such a constitution, when the developer surface of the developer is lowered due to some factor, the developer dropped between the repulsion poles B is not stirred by the conveying screws 4 and 6 immediately. 3 is attracted to the second magnetic pole N3,
As will be described later with reference to (a) and (b), the developer tends to accompany. Therefore, in a solid image or a halftone image having a uniform density, image density unevenness due to the entrainment of the developer is likely to occur.
This tendency was particularly remarkable when the developer was used for a long period of time or was used in a high temperature and high humidity environment.

Therefore, an object of the present invention is to reduce the deterioration of the developer when a carrier having a low magnetization, which is advantageous for improving the image quality, is used and to prevent the developer from entraining the developer carrier. An object of the present invention is to provide an image forming apparatus and a developing unit capable of suppressing a decrease in the developer coating amount and edge enhancement, preventing image density unevenness, and always obtaining a stable image for a long period of time.

[0022]

The above objects can be achieved by the image forming apparatus and the developing means according to the present invention. In summary, the first aspect of the present invention relates to an image carrier, a developing container containing a developer containing a toner and a carrier, and a developer carrying and developing the latent image on the image carrier. Developing means including a developer carrying member conveyed to a portion, a magnetic field generating means fixedly arranged inside the developer carrying body to generate a magnetic field, and a regulating member for regulating the layer thickness of the developer on the developer carrying body. An image forming apparatus including: a holding unit that holds the developing unit rotatably in proximity to the image carrier,
The carrier is 3.0 × in a magnetic field of 100 mT.
The magnetic field generating means has a magnetization of 10 ⁴ A / m or more and 20 × 10 ⁴ A / m or less, and the magnetic field generating means is located downstream of the first magnetic pole in the moving direction of the developer carrier. A second magnetic pole that is adjacent to the first magnetic pole and has the same polarity as the first magnetic pole and that is provided in the vicinity of the facing portion of the first magnetic pole and the second magnetic pole. In the interval, the magnetic flux densities Br and Bθ by the magnetic field generating means are both 0 mT or more 1
It is 0 mT or less, and the image forming apparatus is characterized by performing the developing operation by moving the developing unit from the lower side in the direction of gravity to the developing unit by the rotation of the holding unit.

A second aspect of the present invention is a developing container for accommodating a developer containing a toner and a carrier, and a developer carrying member for carrying the developer for developing a latent image on an image carrier and carrying it to a developing section. A member, a magnetic field generating unit fixedly arranged inside the developer carrier to generate a magnetic field, and a regulating member for regulating the layer thickness of the developer on the developer carrier, In the developing unit rotatably held by a holding unit in proximity, the carrier has a magnetic field of 100 mT and is 3.0 × 10 ⁴ A / m or more and 20 × 10 ⁴ A / m or more.
The magnetic field generating means has the following magnetization, is adjacent to the first magnetic pole on the downstream side of the first magnetic pole in the rotation direction of the developer carrier, and is in the vicinity of the facing portion with the regulating member. And a second magnetic pole having the same polarity as the first magnetic pole,
Between the first magnetic pole and the second magnetic pole, the magnetic flux densities Br and Bθ by the magnetic field generating means are both 0 mT or more and 10 mT or less, and the developing means from below in the gravity direction by rotation of the holding means. Provided is a developing means which moves to a section and performs a developing operation.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION The image forming apparatus and developing means according to the present invention will now be described in more detail with reference to the drawings.
In the embodiment described below, the present invention will be described with reference to FIG.
However, the present invention is not limited to this.

Embodiment 1 FIG. 1 is a block diagram showing the form of an image forming apparatus according to the present invention. In this embodiment, as the holding unit of the developing unit, the rotating body 110 that is close to the photosensitive drum 100 that is an image carrier is used, and yellow, magenta, cyan, and
The developing means 1Y, 1M, 1C, 1K for each color of black are rotatably provided, and the developing means 1Y, 1M, 1C, 1K are moved to the position facing the photosensitive drum 100 by the rotation of the rotating body 110, and the photosensitive drum The electrostatic latent image formed on 100 is developed with toner of each color. Photosensitive drum 1
The developed images (toner images) of the respective colors developed on No. 00 are sequentially transferred onto the intermediate transfer drum 7, which is an intermediate transfer body, and then the secondary transfer bias applied to the secondary transfer means 9 records the paper or the like. It is configured to be collectively transferred to the medium P. The outline of image formation in this embodiment will be described below.

The photosensitive drum 100 has an arrow a shown in FIG.
The photosensitive drum 10 is rotatably supported in a rotating direction.
After 0 is uniformly charged by the primary charger 3, an exposure means 12 such as a laser beam exposure device first irradiates an optical image corresponding to a yellow portion obtained by color separation, and the peripheral surface of the photosensitive drum 100 is irradiated. An electrostatic latent image corresponding to the yellow portion is formed. At that time, as a developing means for developing the electrostatic latent image with the yellow toner as a developer, there is a developing means 1Y at a position facing the photosensitive drum 100, whereby the latent image in the yellow portion is formed by the yellow toner. It is developed.

In this embodiment, a two-component developer containing a non-magnetic toner and a magnetic carrier is used. In particular, a magnetic carrier having a relatively low magnetization is used to achieve a high image quality.

Next, the developed yellow toner image is transferred onto the intermediate transfer drum 7, and at the same time, the photosensitive drum 1 is transferred.
00 is uniformly charged by the primary charger 3 again,
This time, a light image corresponding to the magenta portion is irradiated, and an electrostatic latent image corresponding to the magenta portion is formed on the peripheral surface of the photosensitive drum 100.

During development of the electrostatic latent image on the magenta part,
By rotating the rotating body 110 in the direction b in which each developing unit moves from the lower side in the direction of gravity toward the position facing the rotating drum 100, the developing unit 1M faces the photosensitive drum 100, and the magenta portion is developed. The magenta toner image is transferred so as to be superposed on the yellow toner image on the intermediate transfer drum 7 which has been previously transferred.

The surface of the intermediate transfer drum 7 is formed of polyimide, and carbon is added to the surface of the intermediate transfer drum 7 to adjust the volume resistivity to about 10 ¹⁰ Ω · cm, whereby good transfer is obtained.

In this way, the cyan and black toner images are sequentially transferred onto the intermediate transfer drum 7 in an overlapping manner, and then all the colors are collectively transferred onto the recording medium P such as paper, and further applied by the fixing device 8. A full-color permanent image can be obtained by heating under pressure.

In this embodiment, the developing means 1Y, 1M, 1
As a magnetic carrier in the two-component developer housed in the C and 1K developing containers 2, a magnetic carrier of 3.0 mT in a magnetic field of 100 mT
It is characterized by using a relatively low magnetization having a magnetization of not less than × 10 ⁴ A / m and not more than 20 × 10 ⁴ A / m.

When a low-magnetization carrier is used as the magnetic carrier, the magnetic restraining force acting between the carriers is weakened, so that the ears of the magnetic brush formed by the carriers are softened, and the developing unit rubs against the photosensitive drum 100. The power to do becomes weak. As a result, the force of disturbing the toner image developed on the photosensitive drum 100 by the rubbing force of the ears of the magnetic brush is weakened, so that the feeling of the image is lessened and a high quality image can be obtained.

As the carrier having the above-mentioned magnetic characteristics, in this embodiment, a so-called magnetic substance-dispersed resin carrier in which a magnetic substance produced by a polymerization method is dispersed in a thermosetting binder resin is used. However, as long as the magnetic characteristics are within the above range, those manufactured by other manufacturing methods may be used.

When the magnetization of the magnetic carrier is less than the above range, the magnetic binding force with the developing sleeve 10, which is a developer carrying member for carrying and carrying the developer to the photosensitive drum 100, is too weak. Magnetic carrier is photosensitive drum 1
The phenomenon of adhesion to No. 00 became remarkable. Further, if the magnetization is more than the above range, the brush of the magnetic brush becomes too hard to obtain a desired high-quality image, so the magnetization of the magnetic carrier is limited to the above range.

Regarding the magnetization of the magnetic carrier, first, the magnetization (Am ² / kg) of the carrier packed in an external magnetic field of 100 mT was obtained using an oscillating magnetic field type magnetic characteristic automatic recording device manufactured by Riken Denshi Co., Ltd. Magnetization (A / m) was calculated by multiplying it by the true specific gravity (kg / m ³ ) of the carrier.

FIG. 2 shows a first embodiment of developing means for each color provided on the rotating body 110 used in the image forming apparatus of the present invention. Since the developing means 1Y, 1M, 1C, and 1K for each color have the same configuration, they are abbreviated as the developing means 1 here.

The developing means 1 of this embodiment comprises a developing container 2 containing a two-component developer containing a magnetic carrier and a non-magnetic toner, and the developing container 2 is a developer carrying member.
Development sleeve 1 made of non-magnetic material such as SUS
0 is provided so as to face the photosensitive drum 100 rotating in the direction of arrow a. The developing sleeve 10 is the photosensitive drum 10.
It rotates in the direction of arrow c so as to move in the same direction as the photosensitive drum 100 at the portion facing 0.

That is, the developing sleeve 10 and the photosensitive drum 10
The facing portion (developing portion) of 0 is located in the region of 0 ° to 180 ° in the upstream direction in the rotation direction c of the developing sleeve 10 from the lowest point in the vertical direction of the developing sleeve 10. The rotation direction c of the developing sleeve 10 is a direction that passes through the developing portion from the vertical direction to the lower side, and is the same direction as the developing sleeve 10 of the developing means of FIGS. 8 and 9 described in the conventional example.

In the developing sleeve 10, there are five magnetic poles, that is, the main developing pole arranged to face the photosensitive drum 100, the magnetic pole S1 in this embodiment, and the rotating direction c of the developing sleeve 10.
The magnet roller 11 which is a magnetic field generating means having magnetic poles of N2, N3, S2, and N1 is sequentially connected to the developing sleeve 10.
It is provided so as not to rotate with respect to.

The developing container 2 is divided into a first chamber 2a and a second chamber 2b by a partition wall 5, and developer conveying screws 4 and 6 are arranged in the first chamber 2a and the second chamber 2b, respectively.

A regulating blade 30, which is a regulating member, is provided above the first chamber 2a in the rotation direction c of the developing sleeve 10, and the developing sleeves 10 and 50 are located 5 ° downstream of the N3 pole.
It is arranged so that the closest contact is located at an interval of 0 μm. Developing sleeve 10 of the developing means of FIG.
In contrast, the regulation blade 30 is located at the uppermost portion in the vertical direction in the opening of the developing container 2, whereas in FIG.
In the developing means 1, the regulating blade 30 is provided further upstream, and the distance from the developer accommodating portion is shortened.

By configuring the regulation blade 30 only with the magnetic material, it is possible to widen the latitude of the developer layer thickness with respect to the variation of the gap (SB gap) between the regulation blade 30 and the developing sleeve 10, and in this embodiment. ,
It is formed in a plate shape having a thickness of 1.5 mm.

The developer in the developing container 2 is conveyed from the back side to the front side while being agitated by the developer conveying screw 4 provided in the developing container 2 and closer to the developing sleeve 10. Part of the developer is drawn up by the N3 pole (second magnetic pole) located in the lower semi-circular portion of the magnet roller 11 near the opening of the developing container 2. Here, the maximum magnetic flux density on the surface of the N3 pole developing sleeve 10 is 650 gauss,
The full width at half maximum of the magnetic flux density is 37 °. The drawn up developer is regulated to a layer thickness of about 30 mg / cm ² by the magnetic field between the regulation blade 30 and the N3 pole. It is carried from the N3 pole to the S2 pole located in the upper semi-circular portion of the magnet roller 11 in the developing container 2 and is located 5 ° downstream thereof to the regulating blade 30.
The layer thickness is regulated by.

That is, assuming that the lowermost point in the vertical direction of the developing sleeve 10 and the magnet roller 11 is 0 °, in the present embodiment, the regulating blade 30 is located at a position 85 ° downstream in the rotation direction c of the developing sleeve 10. is set up.

The developer whose layer thickness is regulated further passes through S2, is exposed from the developing container 2, and is conveyed to the N1 and S1 poles. In the vicinity of the S1 pole which is the developing pole, the latent image on the photosensitive drum 100 is conveyed. The image is developed.

The developer which has passed through the developing section is conveyed to the N2 pole (the magnetic flux density is, for example, 400 to 500 gauss), and the N3 pole is fed.
Delivered to the pole.

As described above, the developing means 1 of this embodiment has the light load structure described in the conventional example. That is, in addition to the second magnetic pole, which is the N3 pole in the present embodiment, which is arranged near the regulation blade 30, the first magnetic pole N3 and the first magnetic pole adjacent to the second magnetic pole N3 upstream in the rotation direction c of the developing sleeve 10 have the same polarity. It has a magnetic pole (N2 pole in this embodiment).

At that time, the first magnetic pole N2 and the second magnetic pole N
The vertical magnetic flux density Br on the developing sleeve 10 between the three poles is 0 mT or more and 10 mT or less, and the circumferential magnetic flux density Bθ is 0 mT or more and 10 mT or less, and the developer is the first magnetic pole. It falls from the developing sleeve 10 at a position between the repulsive poles B of the N3 pole and the second magnetic pole N2, and is conveyed to the inner side by the conveying screw 4 located below the developing sleeve 10 and conveyed through an opening (not shown). Handed over to 6.

The reason why the magnetic flux densities in the vertical and circumferential directions, that is, Br and Bθ, are set to be 0 mT or more and 10 mT or less is that the developer is most effectively stripped from the developing sleeve 10 in this range. Yes, and the first and second poles need not be opposite poles.

The magnetic flux densities Br and Bθ are F. W. BE
Using a magnetic field measuring device “MS-9902” (trade name) manufactured by LL, a probe and a developing sleeve 10 which are members of the measuring device.
The distance from the surface was set to about 100 μm for measurement.

According to the present embodiment, of the two first and second magnetic poles N2 and N3 having the same polarity, the second magnetic pole N3 located on the downstream side in the rotation direction c of the developing sleeve 10 faces each other. By regulating the developer by the regulating blade 30 near the position, among the developers not applied on the developing sleeve 10 and remaining on the developing sleeve 10, the developer that cannot be held at the N3 pole is promptly dropped onto the conveying screw 4. , Regulation blade 30
In the vicinity of the upstream side of the developing sleeve 10 inside the developing container 2 in the rotation direction c, a large pool of the developer unlike the portion A shown in FIG. 8 does not occur.

In this way, since the developer is dropped and removed between the repulsive poles B of the first magnetic pole N2 and the second magnetic pole N3,
Unlike the conventional case, the developer is conveyed one after another and a large pressure is not applied to the developer. As a result, it is possible to prevent the deterioration of the developer.

In particular, as in this embodiment, the developing sleeve 1
When 0 rotates in the direction of passing through the developing section from top to bottom,
By disposing the regulating blade 30 between 0 ° and 90 ° downstream in the rotation direction c of the developing sleeve 10 from the lowest point in the vertical direction of the developing sleeve 10 (85 ° downstream in this embodiment), N
The developer that cannot be held by the three poles is more likely to drop onto the conveying screw 4, and the pressure of the developer accumulated and receiving pressure can be further reduced.

According to the experiments conducted by the inventors, when a magnetic carrier having a magnetization in the range of 3.0 × 10 ⁴ A / m or more and 20 × 10 ⁴ A / m or less is used, the developing means is empty. When the developer deterioration level judged from the rotation time and the obtained image quality is compared with that of the conventional developing means shown in FIG. 8, the developing means of the present invention is about 4.5 in comparison with the conventional developing means.
With the double idling time, almost the same deterioration of the developer occurred.

However, when the developing means 1 of this embodiment is used as it is, the space between the repulsive poles B where the developer drops from the developing sleeve 10 and the second magnetic pole N3 which draws up the developer are close to each other. In addition, if the developer surface on the first chamber 2a side is lowered for some reason, a so-called entrainment phenomenon may occur in which the developer once dropped from the developing sleeve 10 is immediately pumped up. When the developer is accompanied by the developer, the developer is coated on the developing sleeve 10 in the state where the toner has uneven toner density, so that the uneven density tends to be conspicuous when a uniform image such as solid or halftone is formed. was there. This tendency was particularly remarkable when the developer was used for a long period of time or in a high temperature and high humidity environment.

Explaining this phenomenon in detail, FIG.
As shown in, the developer whose toner concentration has decreased after passing through the developing section is conveyed to the N2 pole near the opening of the developing container 2,
When it is carried into the developing container 2 through the opening, it falls from the developing sleeve 10 into the developing container first chamber 2a between the repulsive poles B of the N2 pole (first magnetic pole) and the N3 pole (second magnetic pole). .
Normally, the developer dropped from the sleeve 10 quickly rotates below the screw 4 as shown by the arrow by the rotation of the conveying screw 4, is taken into the lower part of the developing container 2, and is sufficiently stirred and then N3. Pumped up by the poles.

However, if the surface of the developer on the side of the first chamber 2a is lowered for some reason, as shown in FIG. 3 (b), the developer once dropped from the developing sleeve 10 moves to the upper portion of the conveying screw 4. It slips through and moves, and is pumped to the N3 pole without being sufficiently stirred. When such a phenomenon occurs, when the toner is used for development, the developer whose toner concentration has decreased is conveyed to the developing section in a state of being mixed with the developer whose toner concentration has not decreased in the developing container 2. As a result, uneven image density due to uneven toner density may occur on a uniform image such as solid or halftone.

Therefore, in the present embodiment, the developing means 1 is firmly fixed and accommodated in the accommodating portion so that the developing means 1 does not rattle or change its posture due to rotation of the developing means 1. The rotation of 110 rotates in the direction from the lower side in the direction of gravity toward the position facing the photosensitive drum 100, that is, in the direction toward the developing unit, that is, in the direction indicated by the arrow b in FIG. For example, the yellow developing means 1Y, which has completed the developing operation, rotates 90 ° in the direction of arrow b, and the magenta developing means 1M moves to the position facing the photosensitive drum 100.

At this time, the yellow developing means 1Y is shown in FIG.
As shown in (a), the developer hand pole S1 is vertically upward, and the developer on the first chamber 2a side is pressed against the partition wall 5 by the action of gravity. Then N2 pole and N
The developer dropped from the developing sleeve 10 between the repulsive poles B of the three poles is completely developed by the action of gravity.
It is in a state of being peeled off from 0.

As the cyan developing means 1C and the black developing means 1K are further moved from here to the developing position, the yellow developing means 1Y is completely opposite to the developing sleeve 10 at the time of developing as shown in FIG. 4B. When the developing container 2 is turned upside down and the developing container 2 is turned upside down, as shown in FIG. 4C, the developing sleeve 10 faces downward and the developing container 2 is laid sideways. To do.

The developer on the side of the first chamber 2a is agitated by the rotating operation of the developing means 1, and when the yellow developing means 1Y is moved to the developing position again, the developer dropped from the developing sleeve 10 during the previous developing operation. The developer is completely mixed with the developer in the first chamber 2a, so that the toner concentration becomes uniform and N
It will be pumped up to 3 poles. Therefore, it is possible to reliably prevent the unevenness of the image density due to the unevenness of the toner density of the developer coated on the developing sleeve 10.

Therefore, when a carrier with low magnetization is used as in the present embodiment, the rotating direction of the rotating body 110 is indicated by an arrow b in FIG. 1, that is, the developing means 1 contacts the photosensitive drum 100 from below in the gravity direction to the developing portion. By limiting to such a direction,
Immediately before the developing operation is performed, the rotating operation of the rotating body 110 is used to bring the position corresponding to the developing portion of the developing sleeve 10 downward, as shown in FIG. It can be sufficiently stored on the developing sleeve 10 in the vicinity of the regulation blade 30. As a result, even if the magnetization of the carrier was small, it was possible to prevent uneven thickness in the developer layer.

In order to make the developing sleeve 10 which is the developer carrying member face the photosensitive drum 100 when the developing means 1 is installed on the rotating body 110 and moved to the developing position by the rotation thereof, the developing sleeve 10 Will be installed in a state in which is directed to the outside of the circumference of the rotating body 110.

Therefore, when the rotating direction of the rotating body 110 is limited to the direction in which the rotating body 110 contacts the photosensitive drum 100 from below in the direction of gravity, the developing means 1 faces the photosensitive drum 100 like the developing means 1Y described above. By changing the posture of the developing means 1 by passing through the position and moving upward,
First, the developing sleeve 10 as shown in FIG.
4A and 4B, and then the developing sleeve 10 is positioned below the developing container 2 as shown in FIGS. 4B and 4C.

As a result, the developing sleeve 10 is first
It is possible to remove the developer by gravity from the inside, and then prepare to store the developer in the developing sleeve 10.

With respect to each of the magenta, cyan, and black developing means 1M, 1C, and 1K, the same effect can be obtained by stirring the developer by utilizing the rotating operation of the rotating body 110 in the direction of the arrow b in FIG. can get.

The main developing pole, each magnetic pole such as the first magnetic pole, the second magnetic pole and the like differ depending on the image forming apparatus and the developing means, and are not limited to those described in this embodiment.

As described above, in this embodiment, in the image forming apparatus and the developing means, the two-component developer containing the carrier of low magnetization is used, and the magnetic field generating means built in the developer carrier is used. The first magnetic pole, which has the same polarity as the second magnetic pole of the portion facing the regulating member, is provided upstream of the second magnetic pole, which is advantageous for agent deterioration, and the rotation of the rotating body in a predetermined direction. By agitating the developer using the operation, it is possible to prevent the entrainment phenomenon of the developer and the unevenness of the thickness of the developer layer, and to always provide a stable high-quality image with no unevenness in the image density. Became.

Embodiment 2 FIG. 5 shows a second embodiment of the developing means used in the image forming apparatus of the present invention. The overall configuration of the image forming apparatus is similar to that of the first embodiment. Since the developing means 1Y, 1M, 1C, and 1K for yellow, magenta, cyan, and black have the same configuration, they are abbreviated as developing means 1 here.

The developing means 1 of this embodiment is the developing sleeve 1
0 with respect to the photosensitive drum 100 rotating in the direction of arrow a,
The developing sleeve 10 is rotating in the direction of the arrow c so as to move in the opposite direction to the photosensitive drum 100 at the portion facing the photosensitive drum 100. That is, the developing sleeve 1
0 and the opposing portion (developing portion) of the photosensitive drum 100 are located between the lowermost point in the vertical direction of the developing sleeve 10 and 0 ° to 180 ° downstream in the rotation direction c of the developing sleeve 10.

That is, in the developing means 1 of this embodiment, the developing sleeve 10 rotates so as to pass through the developing section from the bottom to the top.

Inside the developing sleeve 10, five magnetic poles, that is, the main developing pole opposed to the photosensitive drum 100, the magnetic pole S1 in this embodiment, and the developing container 10 are sequentially exposed from the developing container 2 in the rotation direction c. N1 and S in the developing container 2
A magnet roller 11, which is a magnetic field generating means having magnetic poles of 2, N2, and N3 exposed from the developing container 2, is provided so as not to rotate with respect to the rotation of the developing sleeve 10.

Here, N3 arranged vertically below
A restricting blade 30, which is a restricting member, is arranged facing the pole, that is, the second magnetic pole, so that the closest contact point is located at a distance of 380 μm from the developing sleeve 10.

In the developing means 1 having such a structure,
The regulating blade 30 can be arranged in the vicinity of the lowermost point of the developing sleeve 10 in the vertical direction.
It is not necessary to pump up the developer against the gravity from the carrying screw 4 closer to 0, and the developer can be drawn up even if the amount of the developer existing on the carrying screw 4 is small.

That is, stable pumping can be carried out without depending on the amount of the developer in the developing container 2, so that the thickness unevenness of the regulated developer layer can be reduced.

Also in this embodiment, in order to realize high image quality, the magnetization is 3.0 × 10 as a magnetic carrier as in the first embodiment.
A relatively low magnetization of ⁴ A / m or more and 20 × 10 ⁴ A / m or less is used, but a two-component developer containing a low magnetization carrier has a weak magnetic attraction and is more disadvantageous for pumping. Therefore, the configuration of this embodiment is particularly effective.

However, the regulating blade 30 is replaced with the developing sleeve 1.
When it is arranged on the upstream side from the lowest point in the vertical direction of 0, the developer pool on the upstream side of the developing sleeve 10 receives pressure due to gravity, which is disadvantageous to the deterioration of the developer. Therefore, when the developing unit moves in the direction against gravity and the developer in the developing container 2 is stored below the developing sleeve 10 as in the configuration of the present embodiment, the regulating blade 30 causes the developing sleeve 10 to move. When the lowest point in the vertical direction is 0 °, it is preferable to arrange it at a position downstream of 0 ° to 90 ° in the rotation direction c of the developing sleeve 10. Of course, the developing section is located between 0 ° and 180 ° and downstream of the developing sleeve 30.

Also in this embodiment, the light load configuration is adopted, and in addition to the second magnetic pole, which is the N3 pole in this embodiment, which is arranged in the vicinity of the regulating blade 30, the second magnetic pole (N
3 poles) and a first magnetic pole (N2 pole in this embodiment) of the same polarity which is adjacent to the upstream side of the developing sleeve 10 in the rotation direction c. Then, of the two magnetic poles N2 and N3 having the same polarity, the regulating blade 30 is located near the facing position of the first magnetic pole (N3 pole) located on the downstream side in the rotation direction c of the developing sleeve 10.
By regulating the developer by the developing sleeve 1
The developer dropped from the top of the
Since it drops upward, a large pool of developer does not occur near the upstream side in the rotation direction c of the developing sleeve 10 of the regulation blade 30.

In this way, the developer is dropped and removed between the repulsive poles B of the first magnetic pole N2 pole and the second magnetic pole N3 pole, so that the developer is conveyed one after another as in the conventional case and becomes large. No pressure is applied to the developer. As a result, it is possible to prevent the deterioration of the developer.

The developing means of this embodiment is similar to that of the first embodiment.
When the developer surface on the side of the first chamber 2a lowers for some reason because the distance B between the repelling poles where the developer drops from the developing sleeve 10 and the N3 pole for drawing the developer are close, There is a case in which a so-called entrainment phenomenon occurs in which the developer that has fallen off is immediately attracted to the N3 pole.

Therefore, as in the first embodiment, the rotating member 11 which is a holding means for bringing this developing means close to the photosensitive drum 100.
0 and the developer is stirred by utilizing the operation of rotating the rotating body 110 in the direction of the arrow b in FIG. 1, thereby preventing the above-mentioned entrainment of the developer.

Also in this embodiment, the rotating direction of the rotary member 110 is limited to the direction in which the developing means 1 moves from the lower side in the gravity direction to the developing position, that is, the direction of arrow b in FIG. This is because when the rotator 110 is rotated in the direction opposite to the arrow b, the developing sleeve 30 faces upward, as shown in FIG. 6A, immediately before the developing means 1 moves to the developing position, and the developing container 2
Since the developer is located above the developing sleeve 10 in the vicinity of the regulating blade 30 as compared with the case of the first embodiment, the developer layer may be partially stripped. Is.

Then, by rotating the rotating body in the direction of arrow b in FIG. 1, the state shown in FIG. 6 (a) is obtained, and the developer is removed from the developing sleeve 10, and then the developing means 1 is moved to the developing position. 6B in which the developing sleeve 10 faces downward immediately before moving to, the developing sleeve 10 faces downward, the developer moves toward the developing sleeve 10, and The thickness of the developer layer could be stabilized.

The main developing pole and each magnetic pole such as the first magnetic pole and the second magnetic pole differ depending on the image forming apparatus and the developing means, and are not limited to those described in this embodiment.

As described above, with the structure of this embodiment, the first magnetic pole having the same polarity as the second magnetic pole in the portion facing the regulating member is provided upstream of the second magnetic pole. Therefore, even in an image forming apparatus using a developing unit that is advantageous in deterioration of the developer and that is easy to scoop up the developer, it is possible to stir the developer by utilizing the rotation operation of the rotating body in a predetermined direction. Therefore, it is possible to provide a stable image without the unevenness of the image density and the uneven development of the developer and the uneven thickness of the developer layer.

Embodiment 3 In this embodiment, the developer to be used, the constitution of the entire image forming apparatus, and the constitution of the developing means are the same as those of the first or second embodiment, but they are the holding means of the developing means. The rotating operation of the rotating body is controlled based on the video count number per unit area obtained by integrating the video count numbers of the density signals of the image information signals.

In the image forming apparatus using the developing means having the constitution advantageous for the deterioration of the agent as described in the first and second embodiments,
By stirring the developer by using the rotating motion of the rotating body,
It is possible to prevent the accompanying phenomenon of the developer.
When a full-color image is formed, the rotating body is rotated in order to move the developing means for each color to the position facing the photosensitive drum one after another. Therefore, the rotating operation at this time can be utilized for stirring the developer.

However, it is not necessary to replace the developing means at the time of forming a monochrome image, and the rotating body does not need to rotate to switch the developing means. The developer is agitated by using the rotating operation of the rotating body. Therefore, it was impossible to prevent the entrainment phenomenon of the developer as described above.

Therefore, in this embodiment, in order to solve this problem, the rotating operation of the rotating body is controlled based on the size of the video count number per unit area. A specific method will be described with reference to FIG.

The video count number of the density signal of the image information signal input from the image signal input means 101 is the counting means 1
02, and the integrated value is input to the calculating means 103. In addition to the video count number, the area of the original document on which an image is formed is simultaneously input to the calculating means 103, and the video count number per unit area is calculated by dividing the video count number by the original document area.

For example, if the video count number of a certain A4 size document is 390 × 10 ⁶ , the video count number per unit area is 390 × 10 ⁶ /62370=6.3×10 ³ (/ mm
² )

Since the video count number corresponds to the amount of toner consumed by the developing means 1 to form the toner image, the video count number per unit area corresponds to the image ratio of the original. That is, the larger the video count number per unit area is, the higher the image ratio of the original is, and the larger the amount of toner consumed per original is.

The video count number per unit area calculated by the calculation means 103 is sent to the CPU 104,
If it is determined that this value is larger than a predetermined value (for example, 4.8 × 10 ⁵ ), the image forming operation is temporarily suspended, and the rotary motor 105 of the rotary body is operated to move the rotary body to the arrow b in FIG. Direction, that is, the developing sleeve provided in the developing means accommodated in the rotating body is rotated once such that the developing sleeve faces upward with respect to the developing container and then faces downward, and then the image forming operation is restarted. . By the rotation operation of the rotating body, the developer is agitated, so that the entrainment of the developer can be prevented.

The reason why the rotating operation of the holding means is controlled based on the video count number per unit area is that the larger the video count number per unit area is, the more toner amount is consumed per one original, This is because the unevenness of the toner density of the developer becomes more conspicuous when the accompanying phenomenon of the developer occurs. Therefore, if the video count number per unit area is small, even if the developer entrainment phenomenon occurs, unevenness of the toner concentration of the developer is unlikely to occur. In that case, the rotating operation of the rotating body should not be performed. Control.

In the present embodiment, the above-mentioned value is used as the threshold value for the rotating operation of the rotating body, but it goes without saying that the optimum value is set depending on the image forming apparatus to which it is applied.

Further, this control is the same as in the case of a mode in which image formation is continuously performed without rotating the rotator in order to change the color of the developer, such as in the case of a monochrome color other than black only. It is valid.

By performing the control as in the present embodiment, even if the developing means is not replaced at the time of image formation, such as in the case of monochromatic black, the rotating member can be rotated in accordance with the image ratio of the original, so that the rotation can be performed. It is possible to stir the developer by utilizing the rotating motion of the body, to prevent the disadvantageous phenomenon of the developer accompanying especially when the image ratio of the original is high, and to always provide a stable image without uneven image density. It has become possible.

As described in Embodiments 1, 2 and 3, according to the present invention, the developer accumulated on the upstream side of the layer thickness regulating member of the developing container is used by using the developing means having a light load structure. By reducing the amount of toner and preventing the developer from being conveyed one after another, the pressure applied to the developer is reduced and the deterioration of the developer is prevented. It is possible to suppress the decrease in the coat amount and the edge enhancement. Further, it is possible to reliably prevent the uneven image density due to the entrainment of the developer, which is likely to occur in the developing unit having a light load structure, even when a carrier having a relatively low magnetization is used. In addition, by accommodating a plurality of the developing means in the rotating body and directing the developing means from the lower side in the moving direction toward the position facing the image carrier, good image characteristics can be provided.

[0100]

As described above, according to the image forming apparatus and the developing means of the present invention, the developing means has the developing container for containing the developer including the toner and the carrier, and the developing section carrying the developer. Holding a developer carrier to be conveyed to the image carrier, a magnetic field generating means fixedly arranged inside the developer carrier, and a regulation member for regulating the layer thickness of the developer on the developer carrier, The carrier is held by 10
3.0 × 10 ⁴ A / m or more in a magnetic field of 0 mT, 2
It has a magnetization of 0 × 10 ⁴ A / m or less, and the magnetic field generating means is
A first magnetic pole and a second magnetic pole that is adjacent to the downstream side of the first magnetic pole in the rotational direction of the developer carrier and is provided in the vicinity of a portion facing the regulating member, and has the same polarity as the first magnetic pole. ,,
Between the first magnetic pole and the second magnetic pole, the magnetic flux densities Br and Bθ by the magnetic field generating means are both 0 mT and 10 m.
Since it is less than T, the developing means is moved from the lower side in the direction of gravity to the developing portion by the rotation of the holding means to perform the developing operation.
Even if a developer containing a low-magnetization carrier is used, the developer is less likely to deteriorate, and by stirring the developer by utilizing the rotating operation of the rotating body in a predetermined direction, unevenness in the thickness of the developer layer, and It has become possible to prevent the entrainment phenomenon of the developer and to provide a stable high-quality image with no uneven image density.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an image forming apparatus of the present invention.

FIG. 2 is a sectional view showing an example of a developing unit of the present invention.

FIG. 3 is a cross-sectional view illustrating a phenomenon in which a developer is accompanied by a developing sleeve.

FIG. 4 is a cross-sectional view showing a state in which the developing means of the present invention is rotated.

FIG. 5 is a sectional view showing another example of the developing means of the present invention.

FIG. 6 is a sectional view showing a state in which a developing unit of another example of the present invention is rotated.

FIG. 7 is an explanatory diagram showing a control mechanism of the image forming apparatus according to the present invention.

FIG. 8 is a sectional view showing an example of conventional developing means.

FIG. 9 is a cross-sectional view showing another example of conventional developing means.

[Explanation of symbols]

1 developing means 2 Development container 4, 6 developer transport screw 5 partitions 10 Development sleeve (developer carrier) 11 Magnet (magnetic field generating means) 30 restriction blade (regulation member) 100 photosensitive drum (image carrier) 102 coefficient means 103 computing means 110 Rotating body (holding means)

Front page continuation (51) Int.Cl. ⁷ Identification symbol FI theme code (reference) G03G 15/08 503 G03G 9/10 331 F term (reference) 2H005 BA03 EA02 FA01 2H030 AD01 AD16 BB02 BB24 BB33 BB42 BB63 BB71 2H031 AB02 AB09 AC08 AC14 AC19 AC20 AC30 AC31 AC33 AD11 BA05 BA09 FA01 2H077 AB02 AB14 AC02 AD02 AD06 AD13 AD16 AD24 BA10 CA02 EA03 GA13

Claims (12)

[Claims] 1. An image carrier, and a developing container containing a developer containing a toner and a carrier,
A developer carrier that carries the developer and conveys it to a developing unit to develop the latent image on the image carrier, a magnetic field generating unit fixedly arranged inside the developer carrier and generating a magnetic field, and the developing unit. An image forming apparatus comprising: a developing unit that includes a regulating member that regulates the layer thickness of the developer on the agent carrier; and a retaining unit that rotatably retains the developing unit in proximity to the image carrier, The carrier is 3.0 × in a magnetic field of 100 mT.
The magnetic field generating means has a magnetization of 10 ⁴ A / m or more and 20 × 10 ⁴ A / m or less, and the magnetic field generating means has a first magnetic pole and a downstream side of the first magnetic pole in a rotation direction of the developer carrier. A second magnetic pole that is adjacent to the first magnetic pole and has the same polarity as the first magnetic pole and that is provided in the vicinity of the facing portion of the first magnetic pole and the second magnetic pole. In the interval, the magnetic flux densities Br and Bθ by the magnetic field generating means are both 0 mT or more 1
The image forming apparatus is 0 mT or less, and performs the developing operation by moving the developing unit to the developing unit from below in the direction of gravity by the rotation of the holding unit. 2. The image forming apparatus according to claim 1, wherein the carrier is a magnetic substance obtained by a polymerization method dispersed in a thermosetting binder resin. 3. The regulating member is composed only of a magnetic material, and regulates the layer thickness of the developer by a magnetic field formed between the regulating member and the second magnetic pole. 1 or 2 of the image forming apparatus. 4. The lowermost point of the developer carrying member in the vertical direction when the developer carrying member rotates in a direction passing vertically through the developing section from top to bottom and the developing means performs a developing operation. Is 0 ° and 0 ° to 9 ° in the rotation direction of the developer carrying member.
The front end of the regulation member is installed at a position of 0 ° downstream, and the developing unit is located at a position of 0 ° to 180 ° upstream in the rotation direction of the developer carrier. 1, 2, or 3 image forming apparatuses. 5. The lowermost point of the developer carrying member in the vertical direction when the developer carrying member rotates in a direction passing through the developing section from the lower side to the upper side in the vertical direction and the developing means performs a developing operation. Is 0 ° and 0 ° to 9 ° in the rotation direction of the developer carrying member.
The tip of the regulating member is installed at a position of 0 ° downstream, and in the rotation direction of the developer carrier, 0 ° to 180 ° downstream, at a position downstream of the position where the tip of the restricting member is installed. The image forming apparatus according to claim 1, wherein the developing unit is present. 6. The holding means further comprises: counting means for integrating a video count number of a density signal from image information; and computing means for converting the video count number into a video count number per unit area. The image forming apparatus according to any one of claims 1 to 5, wherein the rotating operation is controlled on the basis of the size of the video count number per unit area calculated by the arithmetic means. 7. The image forming apparatus according to claim 6, wherein when the number of video counts per unit area is larger than a predetermined number, the holding means is rotated to move the developing means. 8. A developing container containing a developer containing toner and a carrier, a developer carrier for carrying the developer for developing a latent image on the image carrier and transporting the developer to a developing section, and the developing device. A magnetic field generating unit that is fixedly arranged inside the agent carrier to generate a magnetic field, and a regulating member that regulates the layer thickness of the developer on the developer carrier, are provided by a holding unit that is close to the image carrier. In a developing unit that is rotatably held, the carrier has a magnetic field of 100 mT and is 3.0 ×
The magnetic field generating means has a magnetization of 10 ⁴ A / m or more and 20 × 10 ⁴ A / m or less, and the magnetic field generating means has a first magnetic pole and a downstream side of the first magnetic pole in a rotation direction of the developer carrier. A second magnetic pole that is adjacent to the first magnetic pole and has the same polarity as the first magnetic pole and that is provided in the vicinity of the facing portion of the first magnetic pole and the second magnetic pole. In the interval, the magnetic flux densities Br and Bθ by the magnetic field generating means are both 0 mT or more 1
The developing means is 0 mT or less, and the developing means performs the developing operation by moving from the lower side in the gravity direction to the developing portion by the rotation of the holding means. 9. The developing means according to claim 8, wherein the carrier is a magnetic material obtained by a polymerization method dispersed in a thermosetting binder resin. 10. The regulating member is composed only of a magnetic material, and regulates the layer thickness of the developer by a magnetic field formed between the regulating member and the first magnetic pole. 8 or 9 developing means. 11. The developer carrying member rotates in a direction passing through the developing unit in the vertical direction from top to bottom to perform a developing operation, and the vertical lowest point of the developer carrying member is set to 0 °. The tip of the regulating member is installed at a position downstream of 0 ° to 90 ° in the rotation direction of the developer carrier, and the development is performed at a position upstream of 0 ° to 180 ° in the rotation direction of the developer carrier. 10. The part is present, the part is present,
Or 10 developing means. 12. The developer carrying member rotates in a direction in which it passes through the developing section from the bottom to the top in the vertical direction, and when the developing operation is performed, the lowest point in the vertical direction of the developer carrying member is set to 0 °. A tip of the regulation member is installed at a position of 0 ° to 90 ° downstream in the rotation direction of the developer carrier, and the regulation member is located 0 ° to 180 ° downstream in the rotation direction of the developer carrier. 11. The developing means according to claim 8, 9, or 10, wherein the developing section is present at a position downstream of the position where the front end of the device is installed.