JPH07261547A - Developing device - Google Patents

Abstract

PURPOSE:To stably convey a developer for the conveyed quantity of a thin layer or above by arranging a developer layer thickness regulating member on the magnetic pole of a magnetic field generating means, and forming it with a magnet having a magnetic pole with the opposite polarity to the polarity of the magnetic pole of the magnetic field generating means. CONSTITUTION:A developing sleeve 70 serving as a developer carrier has a multi-pole permanent magnet 71 serving as a magnetic field generating means fixed inside and carrying and conveying a developer 74 constituted of a nonmagnetic toner and a magnetic carrier. A blade 80 serving as a developer layer thickness regulating member regulates the layer thickness of the developer 74 on the developing sleeve 70. The blade 80 is arranged on the magnetic pole S1 of the multi-pole permanent magnet 71 in no contact with the developing sleeve 70, and it forms a magnet having a magnetic pole (N pole) with the opposite polarity to the polarity of the magnetic pole (S pole) of the multi-pole permanent magnet 71. The action of large magnetic field is applied between the developing sleeve 70 and blade 80, and the developer with a thick layer, i.e., having a large conveyed quantity can be stably conveyed even when the distance between the developing sleeve 70 and blade 80 is increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device, and more particularly to a developing device used in an image forming apparatus.

[0002]

2. Description of the Related Art With a two-component developer (toner and carrier), it is necessary to circulate the developer more smoothly.
Due to the nature of the developer layer thickness regulating portion, the amount of developer passing through the developer layer thickness regulating member is set to be smaller than the amount of conveyed developer. For this reason, it is particularly necessary to smooth the circulation of the developer in this portion and send out the developer that does not pass through the developer layer thickness regulating member to the next position (for example, the stirring section). When the developer accumulates in this portion, the developer repeatedly collides with each other or with the side wall, and deterioration of the developer is accelerated. Further, the developer is likely to be in a packed state, and the carry amount is not stable.

In this type of image forming apparatus (electrophotographic apparatus), stabilization of the amount of developer conveyed is an important factor in reducing noise on an image. FIG. 9 is a diagram showing a configuration example of a conventional developing device (Japanese Patent Publication No. 59-8831). In the figure, 1 is a photosensitive drum as an electrostatic image holding means,
Reference numeral 70 is a developing sleeve provided facing the photosensitive drum 1, 71 is a multi-pole permanent magnet (fixed magnet roll) as a magnetic field generating means provided in the developing sleeve 70, and 72 is a supplied developer. This blade regulates the layer thickness of 74 (particularly toner).

Although the developer 74 adheres to the developing sleeve 70, the developing sleeve 70 rotates in the direction of the arrow in the figure and develops without contacting the surface of the photosensitive drum 1. The thickness of the toner layer 73 is regulated by the multipolar permanent magnet 71 and the blade 72. In the magnetic field, the developer 74 continues in the form of threads along the lines of magnetic force, and its density is smaller than in the usual case. Therefore, if the layer thickness of the developer is regulated by the blade 72 in the magnetic field, the developer can be stably transported.

Further, there is an invention described in Japanese Patent Application Laid-Open No. 60-176069 in which the inter-pole development is used in the non-contact development. Here, the development between magnetic poles is the development using a region where the magnetic force lines are horizontal between the magnetic poles. As a result of the developer layer being formed along the horizontal magnetic force lines, the developer layer can be made uniform.

[0006]

In the above-mentioned conventional apparatus, since the blade 72 regulates the conveyance of the developer 74 within the range of the magnetic field, there is a problem that the effect is not achieved within the range of the magnetic field. . In particular, when a two-component developer is used, the range of the magnetic field is when the carry amount is small, and when the developer amount is more than that, stable carrying cannot be performed.

This will be confirmed by experiments. FIG. 10 is a conceptual diagram of a conventional developing device. In the figure, 74 is 2
It is a component developer. In the developer, the toner is composed of non-magnetic insulating particles having a particle size of 8.5 μm, and the carrier is composed of magnetic particles having a particle size of 50 μm. 70 is a developing sleeve as a developer carrying member. Aluminum is used as the material of the developing sleeve 70, and the surface thereof is sandblasted. A blade 72 serves as a developer layer thickness regulating member. The blade 72 is made of a non-magnetic material or a magnetic material. Reference numeral 73 is a multi-pole permanent magnet provided in the developing sleeve 70 as a fixed magnetic field generating means. Reference numeral 1 is a photosensitive drum on which a toner layer is formed.
75 is a container for accommodating the two-component developer 74, and 76 and 77 are stirring screws for stirring the two-component developer 74 so as not to solidify.

Using such a developing device, the blade 7
The relationship between the distance between 2 and the developing sleeve 70 and the amount of developer conveyed was examined. FIG. 11 is a diagram showing the developer transport amount characteristic of the experimental apparatus. The vertical axis represents the developer transport amount [mg /
cm ² ], and the horizontal axis represents the distance between the developing sleeve and the blade. f1 shows the case where the blade 72 is a non-magnetic body, and f2 shows the case where the blade 72 is a magnetic body.

When the blade 72 is made of a non-magnetic material, the distance between the sleeve and the blade is substantially proportional to the carry amount. On the other hand, when the blade 72 is made of a non-magnetic material, the area where the distance between the sleeve and the blade is proportional to the carry amount (that is, the area where the carry amount can be controlled) is
The distance between the blades is up to 300 μm. When the distance between the sleeve and the blade is around 400 μm, the blade 72
The influence of the magnetic field is eliminated, and the conveyance amount control level is similar to that of the non-magnetic blade. When the distance between the sleeve and the blade is 300 μm, the amount of developer that can be carried is 10 m
It is about g / cm ² .

Therefore, in order to widen the range of the magnetic field applied to the blade 72, it is better to bring a magnetic pole of a multi-pole permanent magnet under the blade 72, and this magnetic pole should have a high magnetic force. As a result of studying this, it was possible to widen the range of the magnetic field up to around 450 μm. FIG. 12 is a diagram showing this experimental characteristic. f3 shows the characteristics after improvement. It can be seen that the proportional region, that is, the region where conveyance can be controlled, extends up to the sleeve-blade distance of 450 μm.

However, the carrying amount at this time is 15 mg.
/ Cm is ² mm, when the further conveyance amount set carry amount becomes unstable. It is necessary to develop a device that can stably convey the developer even under the setting condition of the conveying amount of 15 mg / cm ² or more.

Further, the above-mentioned Japanese Patent Laid-Open No. 176069/1985.
The apparatus described in the publication has an effect of making the developer uniform, but strictly speaking, a non-uniform portion still remains.
In particular, when the carrier particle size is 30 μm, the carrier magnetization σ ₁₀₀₀ is 20 emu / g or more, and the magnetic force between the magnetic poles is 500 G or more, the nonuniform portion becomes remarkable.

In this apparatus, when the developer layer is a single layer, a gap phenomenon occurs. FIG. 13 is an explanatory diagram of the gap phenomenon.
S and N are magnetic poles of a multi-pole permanent magnet. Development is performed in a region where the magnetic field is horizontal between the S pole and the N pole. In this case, it means a phenomenon in which the developer layer is uneven along the vertical direction of the drawing (direction of magnetic force line).

The present invention has been made in view of the above problems. First, it provides a developing device capable of stably carrying a developer even when the carrying amount is a thin layer or more. Secondly, it is an object of the present invention to provide a developing device capable of improving the uniformity of the developer in the developing section.

[0015]

A first invention for solving the above-mentioned problems is to carry a developer comprising a non-magnetic toner and a magnetic carrier, and to carry and carry a developer having a magnetic field generating means fixed inside. And a developer layer thickness regulating member for regulating the layer thickness of the developer on the developer carrier, wherein the developer layer thickness regulating member is in non-contact with the developer carrier and the magnetic field A second invention is a developer comprising a non-magnetic toner and a magnetic carrier, the magnet being disposed on the magnetic pole of the generating means and having a magnetic pole having a polarity opposite to that of the magnetic pole of the magnetic field generating means. Carrying and transporting,
A developing device comprising: a developer carrying member having a magnetic field generating means fixed inside; and a developer layer thickness regulating member for regulating the layer thickness of the developer on the developer carrying body, the developer layer comprising: In the case of performing the inter-pole development with a thickness of two or more layers, the holding member for holding the developer is arranged on the upstream magnetic pole of the magnetic field generating means for performing the inter-pole development.

[0016]

[Action]

(First invention) A developer layer thickness regulating member (blade) is arranged on the magnetic pole of the magnetic field generating means without contacting with the developer carrying member (developing sleeve), and at the same time as the magnetic pole of the magnetic field generating means. A magnet having a magnetic pole having a polarity opposite to the polarity is used. As a result, a large magnetic field acts between the developing sleeve and the blade, and the thick layer of the developer can be stably transported even if the distance between the developing sleeve and the blade is increased.

(Second Invention) The developer has two or more layers, and a holding member for holding the developer is arranged on the upstream magnetic pole of the magnetic field generating means for performing inter-magnetic pole development.
Thereby, the uniformity of the developer in the developing section can be improved.

[0018]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the first invention. The same parts as those in FIG. 10 are designated by the same reference numerals. In the figure, reference numeral 70 designates a developing sleeve as a developer carrier having a multi-pole permanent magnet 71 which is a magnetic field generating means fixed therein and carries a developer 74 composed of a non-magnetic toner and a magnetic carrier. The blade serves as a developer layer thickness regulating member that regulates the layer thickness of the developer 74 on the developing sleeve 70. As the blade 80, for example, H
A cut board is used. The blade 80 is arranged on the magnetic poles of the multi-pole permanent magnet 71 in a non-contact manner with the developing sleeve 70, and is composed of a magnet having a magnetic pole having a polarity opposite to that of the magnetic pole of the multi-pole permanent magnet 71. ing. For example, if the magnetic pole of the multi-pole permanent magnet 71 below the blade 80 is the S pole (S1), the magnetic pole of the blade 80 facing the developing sleeve 70 is the N pole. On the contrary, blade 8
If the magnetic pole of the multi-pole permanent magnet below 0 is the N pole, the magnetic pole of the blade 80 will be the S pole. There was no effect if the polarities of these opposing magnetic poles were the same.

The magnetic force of the magnet of the blade 80 is 20
The magnetic force of about 0 G and the magnetic force of the multi-pole permanent magnet 71 was about 500 G. The operation of the apparatus configured as described above will be described below.

The blade 80 is not in contact with the developing sleeve 70 and is disposed on the magnetic pole S1 of the multi-pole permanent magnet 71, and the polarity of the magnetic pole of the multi-pole permanent magnet 71 (S pole).
A magnet having a magnetic pole (N pole) having the opposite polarity to As a result, a large magnetic field acts between the developing sleeve 70 and the blade 80, and even if the distance between the developing sleeve 70 and the blade 80 is increased, a thick layer, that is, a large amount of the developer is stably conveyed. Will be able to enable.

FIG. 2 is a diagram showing an example of the transport characteristics of the present invention. The vertical axis represents the developer transport amount [mg / cm ² ] and the horizontal axis represents the sleeve-blade distance [μm]. F3 in the figure is the conventional characteristic shown in FIG. f4 is a characteristic of the present invention. As is clear from the figure, stable transport amount control characteristics are possible up to a transport amount of around 40 mg. At this time, the distance between the sleeve and the blade is 1200 μm. That is, although a large amount of developer is conveyed by increasing the distance between the sleeve and the blade, stable conveyance amount control cannot be performed as it is.
It has become possible to generate a high magnetic field during the period of time 0 and make the developer 74 act on this high magnetic field to stably control the conveyance of a large amount of the developer.

FIG. 3 is a diagram showing another configuration example of the blade 80. Instead of using the blade 80 as a magnet, a permanent magnet 81 is tied to the blade 80. As a result, a magnet having one end having an N pole and the other end having an S pole can be formed.

In the above embodiment, the multi-pole permanent magnet 71 is used.
Although 6 poles are used as the above, the present invention is not limited to this, and a permanent magnet having an arbitrary number of poles can be used. If the magnetic pole under the blade 80 is the N pole,
It goes without saying that the magnetic poles of the blade 80 are reversed to form the S pole.

FIG. 4 is a block diagram showing an embodiment of the second invention. The same parts as those in FIG. 1 are designated by the same reference numerals. In the figure, reference numeral 70 denotes a developer carrying member (developing sleeve) having a multi-pole permanent magnet 71 as a magnetic field generating means fixed therein for carrying and carrying a developer comprising a non-magnetic toner and a magnetic carrier, and 83 denotes the developing device. The blade serves as a developer layer thickness regulating member that regulates the layer thickness of the developer 74 on the sleeve 70. As the blade 83, for example, Hcu
A t-plate is used. The blade 83 may be the one having magnetism 80 used in the first invention, or FIG.
It may be the conventional blade 72 used in. The particle size of the two-component developer is about 8.5 μm for toner and 5 for carrier.
The carrier magnetization σ ₁₀₀₀ is 20 emu / g or more at about 0 μm.

This developing device is designed to perform the development between magnetic poles with a developer having a layer thickness of two or more layers. 82 is a developer 74
It is a pressing member for holding down the magnetic pole, and is arranged on the upstream magnetic pole of the multi-pole permanent magnet 71 for performing inter-magnetic pole development. As the material of the pressing member 82, PET, an aluminum plate,
A non-magnetic material such as a Sus rod is used. In the case of the figure,
The pressing member 82 is arranged above the S pole. The area for developing between the magnetic poles is on the horizontal magnetic field formed between the S pole and the N pole in the figure. The operation of the apparatus configured as described above will be described below.

First, in this embodiment, the reason why the developer 74 is 2
Explain whether it should be more than one layer. This is because when the developer 74 is a single layer, the gap phenomenon occurs as described with reference to FIG. Therefore, as shown in FIG. 5, the pressing member 82 is arranged on the upstream magnetic pole of one magnetic pole (S pole in the figure) so that the magnetic field between the N pole and the S pole is horizontal. This is to prevent the phenomenon from occurring. In addition, above the magnetic poles, the developer forms ears along the lines of magnetic force rising upward.

Here, it is assumed that the pressing member 82 is located in the direction toward the blade 83 as shown in FIG. In this case, there is no pressing member 82 on the magnetic pole S. Therefore, the developer 74 rises (forms a spike) on the magnetic pole S and becomes flat by the horizontal magnetic field, so that some nonuniformity occurs. Therefore, as shown in FIG. 5, a pressing member 82 is arranged above the magnetic pole.

Here, the blade 81 and the developing sleeve 70
Consider the relationship between the distance K1 and the distance K2 between the pressing member 82 and the developing sleeve 70. Figure 7 shows the blade
It is a figure which shows the relationship between the distance between a developing sleeve, and the distance between a pressing member and a developing sleeve. If K1> K2, the amount of the developer passing through the blade 81 is the pressing member 82.
Since the amount of the developer passing through the pressing member 82 is larger than that of the pressing member 82, some mechanism for transporting the developer that cannot pass through the pressing member 82 is required, which is complicated. Therefore, if K1 <K2, all the developer that has passed through the blade 81 can pass through the pressing member 82, so that a transport mechanism is not necessary and the mechanism is not complicated, which is desirable.

Returning to the explanation of the embodiment shown in FIG. The developer 74 that has passed through the blade 81 adheres to the developing sleeve 70 and moves in the direction of the arrow in the figure. And the pressing member 8
Pass 2. At this time, the pressing member 82 has the multi-pole permanent magnet 7
Since it is on the first magnetic pole (S pole in the figure), it rises along the magnetic field lines (becomes a spiked state), but it is pressed by the pressing member 82 and is formed between the S pole and the N pole. Returned to a horizontal magnetic field. Therefore, the developer 7 in this horizontal magnetic field
No. 4 is smooth as shown in FIG. 5, and good inter-magnetic pole development can be performed, and the uniformity of the developer in the developing section can be improved.

Here, the effect of the second invention has been confirmed by experiments, and will be described. The present invention was compared with the present invention as Comparative Example 1 where the pressing member was not provided and Comparative Example 2 where the pressing member was provided near the blade 83. Visual observation shows that the images of thin lines (8 lines / mm) are improved in the order of Comparative Example 1 <Comparative Example 2 <The present invention. In the case of solid images, there was no difference between the three.
In the case of a halftone image, the order of Comparative Example 1 <Comparative Example 2 <The present invention improves.

FIG. 8 is a diagram showing an example of the construction of a multicolor image batch transfer type color image forming apparatus using the developing device according to the present invention. In the figure, reference numeral 1 denotes a photosensitive drum which is an image bearing member, and is an OPC photosensitive member coated on the drum, which is electrically grounded and driven and rotated clockwise. 2 is a scorotron charger, which is attached to the peripheral surface of the photosensitive drum 1.
A uniform charge of potential VH is provided by corona discharge with a grid and corona discharge wire held at potential VG. Prior to charging by this scorotron charger 2,
In order to eliminate the history of the photoconductor up to the previous printing, the peripheral surface of the photoconductor is neutralized by performing exposure with an exposure device (for example, PCL) 3 using a light emitting diode or the like.

After the photosensitive body is uniformly charged, the image exposure means 10
Thus, image exposure is performed based on the image signal. The image exposure means 10 uses a laser diode (not shown) as a light emitting source, performs scanning while the optical path is bent by a reflecting mirror 12 via a rotating polygon mirror 11, fθ lens, etc., and rotation of the photosensitive drum 1 (sub scanning). Form an electrostatic latent image. Here, the character portion is exposed to form an inverted latent image in which the character portion has a lower potential VL.

At the periphery of the photosensitive drum 1, there is provided a developing device 20 in which a developer containing toner such as yellow (Y), magenta (M), cyan (C), black (K) and a carrier is incorporated. ing. The present invention is applied to the developing device 20, and enables stable and uniform supply of the developer. Then, the development of the first color is performed by the developing sleeve 21 which has a magnet built therein and holds the developer and rotates. The developer is composed of a carrier in which ferrite is used as a core and an insulating resin is coated around the core, and a toner in which a pigment as a main material and a charge control agent, silica, titanium oxide and the like are added, The developer is regulated to a layer thickness (developer) of 100 μm to 600 μm on the developing sleeve 21 by the layer forming means and is conveyed to the developing area.

The gap between the developing sleeve 21 and the photosensitive drum 1 in the developing area is larger than the layer thickness (developer) of 0.2.
The thickness is set to mm to 1.0 mm, and the AC bias having the voltage value VAC and the DC bias having the voltage value VDC are superimposed and applied during this period. Since VDC and VH and toner charge have the same polarity,
The toner that has been given the opportunity to leave the carrier by VAC does not adhere to the VH portion, which has a higher potential than VDC,
It adheres to the VL portion having a lower potential than VDC and is visualized (reversal development).

After the visualization of the first color is completed, the image forming process for the second color is started, the uniform charging is performed again by the scorotron charger 2, and the electrostatic latent image based on the image data of the second color is exposed by the image exposing means. Formed by 10. At this time, the charge removal by the exposure device 3 performed in the image forming process of the first color is not performed because the toner attached to the image portion of the first color scatters due to the rapid decrease in the potential around the image.

Again, an electrostatic latent image similar to that of the first color is formed on the portion of the photoconductor having the potential of VH all over the peripheral surface of the photoconductor drum without the image of the first color and developed. However, in the portion where the image with the first color image is developed again, the toner adhering to the first color shields light and an electrostatic latent image of potential VM is formed by the electric charge of the toner itself, so that VDC Development is performed according to the potential difference of VM. In the part where the images of the first and second colors overlap,
When the development of the first color is performed by forming an electrostatic latent image of VL, the balance between the first color and the second color is lost, so the exposure amount of the first color may be reduced to an intermediate potential of VH>VM> VL. is there.

An image forming process similar to that for the second color is performed for the third and fourth colors, and a visible image of four colors is formed on the peripheral surface of the photosensitive drum 1. On the other hand, the recording paper P carried out from the paper feeding cassette 15 via the half-moon roller 16 is temporarily stopped, and when the transfer timing is adjusted, the paper feeding roller 17
The paper is fed to the transfer area by the rotation operation of.

In the transfer area, the transfer roller 18 is pressed against the peripheral surface of the photosensitive drum 1 in synchronism with the transfer timing, and the fed recording paper P is nipped to transfer a multicolor image at once. To be done.

Next, the recording paper P is discharged at almost the same time by the separating brush 19 which is brought into a pressure contact state, separated by the peripheral surface of the photosensitive drum 1 and conveyed to the fixing device 30, where the heating roller 31 and the pressure roller 32 are heated. After the toner is fused by applying pressure, the toner is ejected to the outside of the apparatus through the paper ejection roller 41. Incidentally, the transfer roller 18 and the separation brush 1 described above.
After the recording paper P has passed through, 9 is retracted from the peripheral surface of the photosensitive drum 1 to prepare for the formation of the next toner image.

On the other hand, the photosensitive drum 1 from which the recording paper P is separated
Removes and cleans the residual toner by pressing the blade 51 of the cleaning device 50, and again receives the charge removal by the exposure device 3 and the charge by the scorotron charger 2 to start the next image forming process. The blade 51 moves immediately after cleaning the surface of the photoconductor and retracts from the peripheral surface of the photoconductor drum 1.

The image forming apparatus shown in the figure can also be manually fed in addition to being fed by the automatic paper feeding mechanism. The recording paper P manually fed by the manual feed tray 60 is conveyed by the rotation of the pickup roller 61,
The sheet is fed to the transfer area through the same process as the sheet feeding from the sheet feeding cassette 15 described above.

[0042]

As described above in detail, according to the present invention, the construction is such that the action of the high magnetic field is exerted between the developing sleeve and the blade. It is possible to provide a developing device that can stably convey the developer even at any time, and by providing the pressing member for pressing the developer on the upstream magnetic pole of the magnetic field generating means, secondly, in the developing section. It is possible to provide a developing device capable of improving the uniformity of the developer.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a first invention.

FIG. 2 is a diagram showing an example of transport characteristics of the present invention.

FIG. 3 is a diagram showing another configuration example of a blade.

FIG. 4 is a configuration diagram showing an embodiment of the second invention.

FIG. 5 is an explanatory view of suppressing a gap phenomenon by a pressing member.

FIG. 6 is a diagram showing an influence when a pressing member is provided near the blade.

FIG. 7 is a diagram showing the relationship between the distance between the blade and the developing sleeve and the distance between the pressing member and the developing sleeve.

FIG. 8 is a diagram showing a configuration example of a multi-color image batch transfer type color image forming apparatus using the developing device according to the present invention.

FIG. 9 is a diagram showing a configuration example of a conventional device.

FIG. 10 is a configuration diagram of a comparative example used in an experiment.

FIG. 11 is a diagram showing the developer transport characteristics of the experimental device.

FIG. 12 is a diagram showing the developer transport characteristics of the experimental device.

FIG. 13 is an explanatory diagram of a machining gap phenomenon.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor drum 72 Development sleeve 73 Multi-pole permanent magnet 74 Two-component developer 75 Container 76,77 Stirring screw 80 Blade

Claims (7)

[Claims] 1. A developer carrier having a fixed magnetic field generating means for carrying and carrying a developer comprising a non-magnetic toner and a magnetic carrier, and a layer thickness of the developer on the developer carrier are regulated. In the developing device having the developer layer thickness regulating member, the developer layer thickness regulating member is arranged on the magnetic pole of the magnetic field generating means in non-contact with the developer carrier, and A developing device comprising a magnet having a magnetic pole whose polarity is opposite to that of the magnetic pole. 2. The developing device according to claim 1, wherein a distance between the developer layer thickness regulating member and the developer carrying member is 450 μm or more. 3. The developing device according to claim 1, wherein a magnetic force of a magnetic pole below the developer regulating means in the magnetic field generating means is 300 G or more. 4. The particle size of the magnetic carrier is 20 μm to 8 μm.
The developing device according to claim 1, wherein the developing device has a range of 0 μm. 5. A developer carrier having a fixed magnetic field generating means for carrying and carrying a developer comprising a non-magnetic toner and a magnetic carrier, and a layer thickness of the developer on the developer carrier are regulated. And a developer layer thickness regulating member for performing magnetic pole-to-magnetic pole development with a developer layer thickness of two or more layers, wherein the pressing member for pressing the developer performs magnetic pole-to-magnetic pole development. A developing device arranged on the upstream magnetic pole of the magnetic field generating means. 6. The carrier particle size is 30 μm or more,
Carrier magnetization σ ₁₀₀₀ = 20emu / g or more, a developing apparatus according to claim 5, wherein the magnetic poles of the magnetic pole between the developing is both 500G or more. 7. The developing device according to claim 5, wherein the distance between the developer regulating member and the developer carrier is smaller than the distance between the pressing member and the developer carrier. .