JPH1039613A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deterioration and resident of developing agent and supply efficient developing agent on a developing sleeve and provide an uniform layer thickness. SOLUTION: A draw pole N2 for carrying developing agent and a cut pole S2 for causing magnetic field in a restraining part for restraining amount of the developing agent are mounted in a developing sleeve 3 and satisfies a-b>60,0<θ1<25,θ2>84 when (a) (Gauss) is maximum flux density of the draw pole N2, (b) (Gauss) is maximum flux density of the cut pole S2, θ1 (degree) is angle of depression of the draw pole N2 from center of the developing sleeve 3 and θ2 (degree) is angle θ2 between the cut pole S2 and the draw pole N2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device which is used in an image forming apparatus such as a copying machine or a printer and develops an electrostatic image on an image carrier.

[0002]

2. Description of the Related Art FIG. 5 is a sectional view of a developing apparatus as a background in which the present invention is found.

In FIG. 5, a developing device 109 disposed opposite to a photosensitive drum 104 serving as an image carrier includes a developing container 108 and a developing sleeve 10 as a developer conveying means.
3. A developer return member 10 for regulating the developer reservoir 105
1. Blade 10 as ear height regulating member for developer
Two. The inside of the developing device 109 has a developing chamber 113 and a stirring chamber 114 formed by a partition 106 extending in the vertical direction.
Is divided into In the developing chamber 113 and the stirring chamber 114,
A two-component developer composed of a non-magnetic toner and a magnetic carrier is accommodated, and excess developer in the developing chamber 113 is collected in the stirring chamber 114 side.

The developing chamber 113 and the stirring chamber 114 are provided with first and second stirring screws 111 and 112, respectively.

The developing chamber 113 of the developing device 109 has an opening in a developing area facing the photosensitive drum 104, and a developing sleeve 103 is rotatably arranged so as to be partially exposed to the opening. The developing sleeve 103 is made of a non-magnetic material and rotates in the direction of the arrow in the drawing operation during the developing operation.
Has been fixed. A developing sleeve 103 having a built-in magnet 110 carries and conveys a two-component developer layer whose thickness is regulated by a blade 102 from a developer reservoir 105 to a developing area, and exposes the developer in a developing area opposed to the photosensitive drum 104. The electrostatic latent image formed on the photosensitive member is supplied to the drum 104 to be visualized. In order to improve the developing efficiency, a developing bias on which a direct current and / or an alternating electric field is superimposed is applied to the developing sleeve 103 from a power supply 115 provided on the image forming apparatus main body side.

The developing sleeve 103 and the magnet 11
Reference numeral 0 denotes a state in which the developer supplied to the surface of the developing sleeve 103 by the stirring screws 111 and 112 is held in a state of a magnetic brush by the magnetic force of the magnet 110, and is held on the photosensitive drum based on the rotation of the developing sleeve 103. The sheet is conveyed to a portion opposing the portion 104, that is, a developing area. Further, the developer return member 101 and the blade 102 appropriately maintain the amount of the developer transported to the developing area by cutting the magnetic brush.

[0007] More specifically, the magnet 110 is composed of five poles, and the developer stirred by the stirring screw 111 is supplied to the transport magnetic pole (pumping pole) N2 for pumping.
And is conveyed to the developer reservoir 105 by the rotation of the developing sleeve 103. The amount of the developer is regulated to some extent by the developer return member 101. In order to restrain a stable amount of the developer, the developer is sufficiently constrained by a transfer magnetic pole (cut pole) S2 having a magnetic force of a certain level or more. Conveyed while forming. Next, the magnetic brush is cut off by the blade 102 serving as a spike height regulating member to make the amount of the developer appropriate, and is conveyed to the developing area by the magnetic force of the conveying magnetic pole N1 and the rotation of the developing sleeve 103.

The developer conveyed to the developing area is charged by the developing pole S1 with the photosensitive drum 10
4, a developing bias is applied from a power supply 115, and the electrostatic latent image on the photosensitive drum 104 is visualized. That is, the development pole S1 is substantially opposed to the development area.

The developer after developing the electrostatic latent image on the photosensitive drum 104 in the developing area is transported from the developing area to the developing chamber 113 by the rotation of the developing sleeve 103 and the magnetic force of the transport magnetic pole N3 (take-in pole). Is done. Here, the take-in pole N3 and the pumping pole N2 are the same pole, and there is a region (repulsion pole) where the magnetic force is almost 0 Gauss between the two magnetic poles. As a result, the developer after developing the electrostatic latent image is stored in the developing chamber 113 without being confined by the pumping pole N2.

[0010] More specifically, the developer housed in the developing chamber 113 by the take-in pole N3 is mixed with the stirring screw 1
11 to the left (in FIG. 5). What is pumped by the pumping pole N2 is the developer on the right side (in FIG. 5) of the stirring screw 111.

Further, toner consumed in image formation is supplied from a toner supply layer (not shown). The toner newly replenished in this way is mixed and stirred with the developer in the stirring chamber 114 by the stirring screw 112, and the cut electrode S2
The toner is conveyed by the rotation of the developing sleeve 103 while being constrained by the toner, so that the toner in the developer and the carrier are rubbed. In this way, charging of the supplied toner is performed.

[0012]

From the viewpoint of frictional charging between the toner and the carrier and securing the amount of the developer in the developing region, a sufficient amount of the developer must be supplied to the developing sleeve by the pumping pole N2.

From this viewpoint, it is advantageous that the upper surface of the developer in the developing chamber is closer to the pumping pole N2.

However, when the level of the developer in the developing chamber 113 is so high that the stirring screw 111 is completely buried, the stirring of the developer in the developing chamber 113 by the stirring screw 111 becomes insufficient, and The toner density tends to be non-uniform. Further, the fact that the developer surface in the developing chamber 113 is so high that the stirring screw 111 is completely buried means that the developing sleeve 103 and the developer surface are closer to each other. This weakens the scraping effect of the developer at the repulsion pole between the intake pole N3 and the pumping pole N2,
The developer taken in at the take-in pole N3 is subsequently pumped up and restrained at the take-up pole N2. When such a twisting phenomenon occurs, for example, a developer in which a high-density image has been developed and the toner density has been reduced is used as it is for the next development, which leads to a decrease in image density.
Further, in the long term, a part of the developer is
Is continuously received, which promotes the deterioration of the developer.

Further, the position of the pumping pole N2 is
3 is also advantageous from the viewpoint of the pumping property, but in order to maintain the effect of the repelling pole formed with the take-in pole N3, the pumping pole N2 and the take-up pole N
The angle between 3 must be greater than a certain value. Thereby, the take-in pole N3 is on the upstream side, that is, the developing pole S
It will approach 1. However, as can be seen from the fact that the take-in pole N3 has a repulsion pole on the downstream side, the force for positively transporting the developer to the downstream side is weak. For this reason, the developer tends to stay on the upstream side of the take-in pole N3, that is, on the downstream side of the developing pole S1, which adversely affects the image such as disturbing the developed toner image.

Further, from the viewpoint of the pumping performance, it is effective to increase the magnetic flux density of the pumping pole N2. However, in consideration of the scraping at the repelling pole, this causes problems such as tangling. If the pumping pole N2 is not large, it also affects the adjacent opposite cut pole S2. If the cut pole S2 is too large, the rubbing in the developer reservoir 105 becomes strong, which promotes the deterioration of the developer.

When the developer deteriorates, problems such as fluctuations in image density, background fogging, and scattering of fine lines occur on the image.
The quality as an image is reduced. In addition, the deteriorated developer may change its fluidity compared to the initial stage, and this may cause the developer circulation in the developing container 108 to be out of balance. That is, a system that promotes the deterioration of the developer is not preferable from the viewpoint of the circulation of the developer, not to mention the image quality.

[0018]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a developing sleeve for carrying and transporting a developer having a toner and a carrier to a developing area facing an image carrier, and a developer amount on the developing sleeve. A regulating member for regulating the amount of the developer conveyed to the developing region, a regulating magnetic pole provided on the upstream side in the rotation direction of the developing sleeve from a regulating portion by the regulating member in the developing sleeve, and forming a magnetic field in the regulating portion; A supporting magnetic pole for supporting the developer on the developing sleeve, which is located below the central position of the developing sleeve in the sleeve and upstream of the regulating magnetic pole in the direction of rotation of the developing sleeve, for supporting the developer on the developing sleeve. Density a (Gauss),
When the maximum magnetic flux density b (Gauss) of the regulating magnetic pole is the depression angle θ ₁ (degree) of the carried magnetic pole from the center of the developing sleeve, and the angle θ ₂ (degree) formed between the carrying magnetic pole and the center of the developing sleeve and the regulating magnetic pole is:
ab> 60 and 0 <θ ₁ <25 and θ ₂ > 8
4 is satisfied.

[0019]

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

FIG. 2 is a sectional view of an image forming apparatus using the developing device of the present invention.

In FIG. 2, each station of YMCK forms a yellow, magenta, cyan, and black image of a full-color image, respectively. In the following description, for example, if there is the primary charger 21, the primary charger 21Y, the primary charger 21M,
It refers to the primary charger 21C and the primary charger 21K.

A photosensitive drum 4 serving as an image carrier is provided rotatably. The photosensitive drum 4 is uniformly charged by a primary charger 21 and is responsive to an information signal by a light emitting element 22 such as a laser. To form an electrostatic latent image. The electrostatic latent image is visualized as a toner image by the developing device 9 in a process described later. Next, the visible image is transferred to the transfer sheet 24 conveyed by the transfer sheet conveying sheet 27 by the transfer charger 23, and further fixed by the fixing device 25 to obtain a permanent image. The transfer residual toner on the photosensitive drum 4 is removed by the cleaning device 26.

FIG. 1 is a sectional view of a developing device according to an embodiment of the present invention.

In FIG. 1, a developing device 9 disposed opposite to a photosensitive drum 4 as an image bearing member includes a developing container 8, a developing sleeve 3 as a developer conveying means, and a developer reservoir 5.
And a blade 2 as a developer height control member. The inside of the developing device 9 is divided into a developing chamber 13 and a stirring chamber 14 by a partition 6 extending in the vertical direction. The developing chamber 13 and the stirring chamber 14 contain a two-component developer composed of a non-magnetic toner and a magnetic carrier, and the excess developer in the developing chamber 13 is collected in the stirring chamber 14.

First and second stirring screws 11 and 12 are disposed in the developing chamber 13 and the stirring chamber 14, respectively.

The developing chamber 13 of the developing device 9 includes the photosensitive drum 4
The developing sleeve 3 is rotatably disposed so as to be partially exposed at the opening. The developing sleeve 3 is made of a non-magnetic material, and its rotation direction is the direction of the arrow in FIG. 1, and a magnet 10 as a magnetic field generating means is fixed inside the developing sleeve 3. The developing sleeve 3 containing the magnet 10 carries the layer of the two-component developer, the thickness of which is regulated by the blade 2, from the developer reservoir 5 to the developing area, and exposes the developer in the developing area facing the photosensitive drum 4. The electrostatic latent image formed on the photoconductor is supplied to the drum 4 to be visualized. In order to improve the developing efficiency, a developing bias in which an AC voltage is superimposed on a DC voltage is applied to the developing sleeve 3 from a power supply 15 provided on the image forming apparatus main body side.

The developing sleeve 3 and the magnet 10 are
The developer supplied to the surface of the developing sleeve 3 by the stirring screws 11 and 12 according to the above configuration
It is held in a state of a magnetic brush with a magnetic force of 0, and is conveyed to a portion facing the photosensitive drum 4, that is, a developing area based on rotation of the developing sleeve 3. Further, the developer returning member 1 and the blade 2 cut the magnetic brush so as to appropriately maintain the amount of the developer transported to the developing area.

The developer conveyed to the developing area is opposed to the photosensitive drum 4 in a state of being raised by the developing pole S1, and a developing bias is applied from the power supply 15 to the electrostatic latent image on the photosensitive drum 4. Develop. That is, the developing pole S1
Is substantially opposed to the development area.

In this embodiment, the image forming stations for each color are arranged in the horizontal direction. When the developing pole S1 is viewed from the center of the developing sleeve 3, the developing pole S1 is directed to the lower left of the figure, and its depression angle (φ ₁ in FIG. ₁ ) is 18 degrees.
Similarly, when the center of the photosensitive drum 4 is viewed from the center of the developing sleeve 3, its depression angle (φ ₂ in FIG. 1) is 1
It is 8 degrees.

Further, toner consumed in image formation is supplied from a toner supply layer (not shown). The newly replenished toner is mixed and stirred with the developer in the stirring chamber 14 by the stirring screw 12, and is conveyed by the rotation of the developing sleeve 3 while being constrained by the cut pole N2. The toner and the carrier are rubbed. In this way, charging of the supplied toner is performed.

Next, the characteristic portions of this embodiment will be described in more detail.

The magnet 10 is composed of five poles, and the developer stirred by the stirring screw 11 is restrained on the developing sleeve 3 by the magnetic force of the transport magnetic pole (pumping pole) N2 for pumping. The developer is conveyed to the developer reservoir 5 by rotation. The developer amount is regulated to some extent by the developer return member 1, and is then sufficiently constrained by the transport magnetic pole (cut pole) S2 to be transported while forming a magnetic brush.
Next, the magnetic brush is cut off by the blade 2 serving as a spike height regulating member to make the amount of the developer appropriate, and is conveyed to the developing area by the magnetic force of the conveying magnetic pole N1 and the rotation of the developing sleeve 3.

The developer after developing the electrostatic latent image on the photosensitive drum 4 in the developing area is transported from the developing area to the developing chamber 13 by the magnetic force of the take-in pole N3 and the rotation of the developing sleeve 3. Here, the take-in pole N3 and the pumping pole N2 are the same pole, and there is a region (repulsion pole) where the magnetic force is almost 0 Gauss between the two magnetic poles. As a result, the developer after developing the electrostatic latent image is stored in the developing chamber 13 without being confined by the pumping pole N2.

More specifically, the developer accommodated in the developing chamber 13 by the take-in pole N3 is
To the left (in FIG. 1). Pumping pole N2
Pumped on the right side of the stirring screw 11 (FIG. 1).
).

Here, the absolute value a of the maximum magnetic flux density of the pumping pole N2 is 770 (gauss), and the absolute value b of the maximum magnetic flux density of the cut pole S2 is 670 (gauss). The depression angle (θ _{1 in} FIG. ₁ ) when viewing the pumping pole N2 from the center of the developing sleeve 3 is 10 degrees, and the angle when viewing the pumping pole N2 and the cutting pole S2 from the center of the developing sleeve 3 ( Θ ₂ ) in FIG. 1 is 90 degrees.

Numerous experiments of the present invention have led to the following conditional expressions: ab> 60 (gauss) (1) and 0 <θ ₁ <25 (2) and θ ₂ > 84 (3)

FIG. 3 shows the pumping pole N under this condition.
2 schematically illustrates the state of the magnetic lines of force around the cut pole S2 and the cut pole S2.

FIG. 3A shows that the absolute value a of the magnetic flux density of the pumping pole N2 of the developing device in this embodiment is 770 (gau).
ss), the absolute value b of the magnetic flux density of the cut pole S2 is 670
(Gauss) shows the state of the magnetic field lines.

FIG. 3B is a diagram for explaining the effect of this embodiment, and shows the state of the lines of magnetic force when a and b are both 770 (gauss).

Comparing FIGS. 3A and 3B, the developing chamber 1 has the same magnetic force at the pumping pole N2.
It can be seen that the extension of the lines of magnetic force to the three directions is different. That is, the limitation (770 in this embodiment) as in the above equation (1)
By performing (−670> 60), the degree of deviation of the magnetic field lines of the pumping pole N2 toward the cut pole S2 is reduced, and as a result, the magnetic field lines of the pumping pole N2 are efficiently directed to the developing chamber 13 side.

In the present embodiment, θ ₂ is 90 degrees,
Equation (3) above is satisfied. If θ ₂ does not satisfy Expression (3), that is, if θ ₂ is smaller than 84 degrees, the magnetic field lines of the pumping pole N2 are biased toward the cut pole S2 as in the case of FIG. The effect as in the embodiment cannot be obtained.

In the present embodiment, θ ₁ is 10 degrees,
Equation (2) is satisfied. Θ ₁ is smaller than 0 degree,
That is, when the pumping pole N2 is upward when viewed from the center of the developing sleeve 3, the magnetic field lines of the pumping pole N2 are not efficiently directed in the direction of the developer surface c as shown in FIG. No pumpability is obtained.

Further, since θ ₁ is smaller than 25 degrees, the angle between the pumping pole N2 and the take-in pole N3 is repulsive even when the developing pole S1 is below the horizontal as in the configuration of this embodiment. Is sufficient to form
When the developing roller 3 is too close to the developing pole S1, there is no adverse effect on the image such that the developer stays downstream of the developing pole S1 and disturbs the developed toner image.

As described above, according to the configuration of this embodiment, the developer surface c of the developing chamber 13 is
Even in a position where the stirring efficiency is not lowered by burying 1, the pumping force of the pumping pole N2 works sufficiently and stable pumping is performed. Thus, the developing device in the present embodiment can achieve the object of the present invention.

(Second Embodiment) Next, a developing device according to a second embodiment of the present invention will be described.

Here, the absolute value a of the magnetic flux density of the pumping pole N2 is 530 (gauss), and the absolute value b of the magnetic flux density of the cut pole S2 is 460 (gauss). The depression angle (θ _{1 in} FIG. ₁ ) when viewing the pumping pole N2 from the center of the developing sleeve 3 is 20 degrees, and the angle when viewing the pumping pole N2 and the cutting pole S2 from the center of the developing sleeve 3 ( Θ ₂ ) in FIG. 1 is 87 degrees. Accordingly, the developing device of the image forming apparatus according to the present embodiment satisfies the condition of the following expression b <650 (4) in addition to the expressions (1), (2), and (3) described in the first embodiment. Become.

The effect of satisfying this condition is to minimize the rubbing force of the developer due to the magnetic force of the cut pole S2 in the developer reservoir 105 and suppress the deterioration of the developer. As a result, fluctuations in image density, background fog,
It does not cause problems such as scattering of fine lines on the image, and does not break the balance of the developer circulation in the developing container 8 by changing the fluidity of the developer as compared with the initial stage. Therefore, with the image forming apparatus according to the present embodiment, the pumping by the magnetic force of the pumping pole N2 can be stabilized without the development of the object of the present invention, such as the twisting or the retention of the developer, which deteriorates the image quality. Is sufficient to keep the coating amount of the developer conveyed on the developing sleeve 103 uniform, and causes the image density to fluctuate, ground fogging, and scattering of fine lines on the image. By suppressing the deterioration of the developer, which is also a factor that disturbs the balance of circulation, image quality can be more stably guaranteed for a long period of time.

Although the two embodiments have been described above,
The size, angle, and the like of each magnetic pole need not necessarily be as described above, and the expression (1) described in the first embodiment is used.
(2) and (3), desirably, should satisfy Expression (4). According to numerous experiments by the inventor of the present invention, the following experimental results have been obtained for each equation.

Equations (1) and (3) will be described with reference to FIG.

FIG. 4 shows an absolute value a of the magnetic flux density of the pumping pole N2, an absolute value b of the magnetic flux density of the cut pole S2, and an absolute value b of the developing sleeve 3 using a developing device such as the conventional example or the embodiment according to the present invention. This is a result of an experiment on the developer pumping property when the angle θ ₂ when the pumping pole N2 and the cut pole N2 are viewed from the center is variously set. Incidentally, depression theta ₁ when viewed pole N2 pumped from the center of the developing sleeve 3 in this experiment satisfies the condition of formula (2).

In FIG. 4, the developer having a good pumping property is such that the developer surface c in the developing chamber 13 has the stirring screw 1
1 is completely buried, and the developer is stably and uniformly coated on the developing sleeve 3 without insufficient stirring of the developer or occurrence of twisting at the repulsion pole portion. Point to.

In addition, those with poor pumpability are:
Unless the stirring screw 11 is completely buried, the developer is not uniformly coated on the developing sleeve 3 or the coating of the developer becomes unstable due to a change in the fluidity of the developer unless the stirring screw 11 is completely buried. Point.

According to the experimental results shown in FIG. 4, the difference between the absolute value a of the magnetic flux density of the pumping pole N2 and the absolute value b of the magnetic flux density of the cut pole S2 is 60 (gauss) or more. Such effects can be obtained. Similarly, θ ₂ is 84
If it is higher than the degree, the effect as in the present invention can be obtained. On the contrary, unless these two conditions are both satisfied, the stirring of the developer becomes insufficient, the repulsion occurs in the repulsion pole portion, the developer is not uniformly coated on the developing sleeve 3, The developer coat becomes unstable with the change.

Regarding equation (2), as described in the first embodiment, when θ ₁ is smaller than 0 degree, the pumping pole N
The line of magnetic force No. 2 did not efficiently travel in the direction of the developer surface c as shown in FIG. 3, and the pumpability as obtained by the present invention was not obtained. Further, it has been confirmed that when θ ₁ is larger than 25 degrees, adverse effects as described in the related art occur. That is, the effect of the repulsion pole formed by the pumping pole N2 and the intake pole N3 cannot be maintained. Alternatively, if the effect of the repulsion pole is to be maintained, the take-in pole N3 approaches the development pole S1, and the development pole S1
The developer tends to stay on the downstream side of the toner image, and adversely affects the image such as disturbing the developed toner image.

As described in the second embodiment, with respect to the expression (4), by satisfying this condition, it is possible to suppress the deterioration of the developer, which is also a factor that disturbs the balance of the circulation of the developer, and to achieve a more stable operation. The effect of the present invention can be maintained for a long time.

[0056]

As described above, according to the present invention, the pumping by the magnetic force of the pumping pole N2 can be stably and sufficiently performed without the development that degrades the image quality, such as the twisting or stagnation of the developer. By keeping the coating amount of the developer conveyed on the developing sleeve uniform,
Image quality can be stably guaranteed over a long period of time.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a developing device according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating an image forming apparatus using the developing device according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating a developing device according to a first embodiment of the present invention in detail.

FIG. 4 is a diagram showing experimental results on conditional expressions (1) and (3) according to the present invention.

FIG. 5 is a diagram illustrating a conventional example.

[Explanation of symbols]

Reference Signs List 3 Development sleeve as developer conveying means 4 Photosensitive drum as image carrier 8 Developing container 9 Developing device 10 Magnet as magnetic field generating means 11 First stirring screw 13 Developing chamber S1 Development pole S2 Cut pole N2 Pumping pole N3 Import pole the absolute value of the depression angle (degrees) theta ₂ scooping pole and angle (degrees) of the cutting electrode a pumping magnetic flux density of the pole N2 when viewed pumping pole N2 from the center of theta ₁ developing sleeve 3 (gauss) b cut pole S2 Absolute value of magnetic flux density (gauss) c Developer surface

Continuing on the front page (72) Inventor Fumitake Hirobe 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Masami Izumizaki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Takao Ogata 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor ▲ Yoshi ▼ Tadanobu Kawasaki 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Kunihiko Kitayama 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc.

Claims (3)

[Claims] A developing sleeve that carries a developer having a toner and a carrier to a developing area facing the image carrier; and regulates an amount of the developer on the developing sleeve to keep the amount of the developer transported to the developing area constant. A regulating member, a regulating magnetic pole provided on the upstream side in the rotation direction of the developing sleeve from a regulating portion provided by the regulating member in the developing sleeve, and forming a magnetic field in the regulating portion. And a supporting magnetic pole for supporting the developer on the developing sleeve adjacent to the regulating magnetic pole on the upstream side in the rotation direction, wherein the maximum magnetic flux density a (Gauss) of the supporting magnetic pole and the maximum magnetic flux density b of the restricting magnetic pole (Gauss), the depression angle θ ₁ (degree) of the carried magnetic pole from the center of the developing sleeve, and the angle θ ₂ (degree) formed between the carried magnetic pole, the center of the developing sleeve, and the regulating magnetic pole, ab> 60 and 0 <θ ₁ <25 and θ ₂ > 8
4. A developing device satisfying item 4. 2. The developing device according to claim 1, further comprising a developing magnetic pole for causing the developer to spike in the developing area, wherein the developing magnetic pole is provided below a center position of the developing sleeve. 3. The developing device according to claim 1, wherein b <650.