JPH10207216A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device equipped with a developer supply roller capable of suppressing the aggregation of the developer with a simple constitution, but without imparting a large stress on the developer, and capable of uniformly supplying the developer to a developer carrier in the axial direction and also capable of obtaining an image hardly generating density gradient. SOLUTION: The developing device is provided with the developer supply rollers 4 and 5 which are formed to a conical shape so that the diameter of each roller may be nearly continuously changed from one end to the other end, and the developer supply rollers 4 and 5 are arranged so that the rotary shafts may be parallel and also the large diameter end part may be placed opposite to the small diameter part respectively. And, the developer supply rollers 4 and 5 are respectively rotated in opposite directions, and the developer in a hopper 2 is carried toward a developing roller 3, and simultaneously, a carrying force is imparted also in the axial direction of the developer supply rollers 4 and 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device applicable to a copying machine, a printer, a facsimile, etc. for forming an image by electrophotography, and more particularly to a developing device using a one-component developer.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus, a two-component developing method using a developer comprising a toner and a carrier has been widely used as a dry developing apparatus for developing an electrostatic latent image. . A typical two-component developing method is a magnetic brush developing method in which a carrier is raised by a magnetic field generating means and development is performed with toner held on the surface of the carrier. Although the magnetic brush developing method using such a toner and a carrier can sufficiently withstand practical use, recently, due to downsizing of the apparatus and ease of maintenance, etc., a one-component developer composed of only toner has been used. Is widely studied.

Conventionally, as a developing device using a one-component developer (hereinafter simply referred to as a developer), there has been known a developing device in which a developer supply member is arranged close to or in contact with a developer carrier. For example, as shown in FIG. 9, the developing device is provided opposite to the photoreceptor 61 and has a developer carrier 62 capable of adhering and transporting a developer on the surface, and a developer carrier 62 on the developer carrier 62. A developer regulating member 64 for regulating and thinning the developer, a developer supply roller 63 for supplying the developer to the developer carrier 62, and a hopper 65 for storing the developer to be supplied to the developer carrier 62; It has.

In such a developing device, the developer in the hopper 65 is stably supplied to the developer carrier 62 by rotating the developer supply roller 63 in contact with or in proximity to the developer carrier 62. The developer regulating member 64 forms an even thin layer. The thinned developer is conveyed to a developing area where the developer carrier 62 and the photoconductor 61 come into contact with each other by the rotation of the developer carrier 62, and the developer is transferred to the photoconductor in the development area. The latent image is visualized by transferring to the upper latent image.

When high-speed copying or a high-density image is performed by a developing device using such a one-component developer, the developer carrier 62
Since the developer on the surface is consumed in a large amount, it is important to supply the developer efficiently.

In order to enhance the developer supply capability, for example, Japanese Patent Publication No. 6-16210 discloses a developer supply roller made of a foaming elastic material such as a sponge roller. A technique for efficiently supplying a developer to a developing roller is disclosed.

[0007]

However, in the above-mentioned conventional configuration, the developer supply roller and the developer roller are brought into contact with each other, and the developer supply roller is rotated by using a cylindrical roller. Since the developer powder is conveyed by pressing force only in the rotation direction in the situation, the developer tends to gather more at both ends of the developing roller than at the axial center side. For this reason, it is impossible to uniformly supply the developer without generating a density gradient, and there is a problem that inconvenience such as density unevenness is likely to occur in image formation. Further, as described above, since more developer is collected at both ends of the developing roller, there is also a problem that it is necessary to enhance the sealing effect of the developer. Further, there is a problem that the developer is easily condensed because the transport direction of the developer is one direction.

[0008] As means for avoiding the above-mentioned problems, there is a device using a screw member or a member provided with a helical conveying blade on a rotating shaft for conveying the developer. It is conveyed toward the center in the direction to suppress density unevenness (JP-A-5-72894, JP-A-6-301286, etc.).

However, in this type of method, the structure becomes complicated in any case, and a new concentration gradient is generated due to the complicated member, and the developer is transported by rotating the spiral member. In such a case, the developer can be transported by a small member, but a large stress is applied to the developer, and the external additive is deteriorated due to peeling or deformation, and the charging characteristics of the developer are changed. A point occurs.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to suppress the aggregation of the developer with a simple structure without applying a large stress to the developer, and to provide a developer supporting member. It is an object of the present invention to provide a developing device including a developer supply roller capable of supplying a uniform developer without bias in an axial direction, and capable of obtaining an image in which a density gradient hardly occurs.

[0011]

According to the present invention, there is provided a developing device comprising:
The developer stored in the developer storage section is transported by a developer carrier, and the developer is attached to the electrostatic latent image formed on the surface of the electrostatic latent image carrier to display the electrostatic latent image. In order to solve the above-mentioned problem, at least one developer supply roller that supplies a developer to the developer carrier is provided in the developer storage unit in the vicinity of the developer carrier. Each of the developer supply rollers has a substantially conical portion in which the diameter of the roller continuously changes.

According to the above arrangement, the developer supply roller for supplying the developer to the developer carrier has a substantially conical portion in which the diameter of the roller changes continuously. For this reason, the developer in the developer storing portion is not only moved in the direction toward the developer carrier but also in the direction of the rotation axis of the developer supply roller by the rotation of the developer supply roller in the substantially conical portion. Also receives a conveying force in a direction from the thick end to the narrow end of the above-mentioned substantially conical portion.

Therefore, if the developer supply roller is provided with a conical portion having a narrow central portion and a thick end portion, the developer is sufficiently supplied even in the central portion where the developer tends to be insufficient. Thus, the developer can be supplied stably and uniformly in the axial direction of the developer carrying member.

According to a second aspect of the present invention, in addition to the configuration of the first aspect, the developing device further includes a plurality of the developer supply rollers, and each of the developer supply rollers has one end having a diameter at the other end. A set of developer supply rollers having a larger conical shape, the rotation axes of the developer supply rollers being substantially parallel, and the thicker and narrower ends being opposed to each other; Is provided at least one.

According to the above arrangement, the developer supply roller for supplying the developer to the developer carrier has a substantially conical shape in which one end has a larger diameter than the other end. For this reason, the developer in the developer storage section is not only moved toward the developer carrier by the rotation of the developer supply roller, but also in the direction of the rotation axis of the developer supply roller from the thicker end. The transport force is applied in the direction toward the narrow end.

At this time, the two developer supply rollers are arranged such that the rotation axes are parallel and the thick end and the thin end face each other, and are conveyed in the rotation axis direction. The developer is conveyed more at the thicker end than at the narrower end, and is conveyed from the end of the developer supply roller to the center.

As a result, the developer can be supplied stably and uniformly in the axial direction of the developer carrier, and a stable high-quality copy image without a density gradient can be obtained.

According to a third aspect of the present invention, in addition to the configuration of the first aspect, the developer supply roller has a substantially conical conical region that becomes narrower from the end in the direction of the rotation axis toward the center. It is characterized by having on both sides.

According to the above arrangement, the developer supply roller for supplying the developer to the developer carrier has substantially conical conical areas on both sides in the direction of the rotation axis, which taper from the end toward the center. doing. For this reason, the developer in the developer storage section is moved from the end to the center not only in the direction toward the developer carrier but also in the rotation axis direction of the developer supply roller by the rotation of the developer supply roller. And the transport force in the direction toward.

As a result, the developer can be supplied stably and uniformly in the axial direction of the developer carrier, and a stable high-quality copy image without a density gradient can be obtained.

According to a fourth aspect of the present invention, in addition to the configuration of the third aspect, the developer supply roller is provided between the conical regions on both sides in the direction of the rotation axis and has a diameter equal to the center of the conical region. It has a cylindrical region having a diameter.

With the above arrangement, the developer in the developer storage receives a transport force in a direction from the end in the direction of the rotation axis toward the center by the rotation of the developer supply roller.
Further, the flow of the developer is changed depending on the central cylindrical region, so that the stirring efficiency is increased, whereby the aggregation of the developer can be suppressed.

According to a fifth aspect of the present invention, in addition to the configuration of the third aspect, the diameter between the conical regions on both sides in the rotation axis direction of the developer supply roller is larger than the diameter on the center side of the conical region. A stirring member having a substantially cylindrical shape having the following.

According to the above configuration, the developer in the developer storage section receives a conveying force in a direction from the end in the direction of the rotation axis toward the center by the rotation of the developer supply roller.
Furthermore, since the developer can be more efficiently stirred by the central stirring member, aggregation of the developer can be suppressed.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

As shown in FIG. 1, the developing device according to the present embodiment includes a drum-shaped photosensitive member 1 as an electrostatic latent image carrier and a hopper 2 as a developer storing section for storing a developer. Further, inside the hopper 2, a developing roller 3 as a developer carrier and a developer supply roller 4 for supplying the developer stored in the hopper 2 to the developing roller 3 are provided.・ 5 is provided. Further, the hopper 2 is provided with a developer regulating member 6 which is pressed against the surface of the developing roller 3 and forms a thin layer of developer on the surface of the developing roller 3 by regulating the amount of developer attached. ing.

The hopper 2 is provided with a toner supply port for supplying a developer, and the photosensitive member 1 is disposed outside the hopper 2 near the toner supply port, and inside the hopper 2. The developing roller 3 is arranged. The photoreceptor 1 and the developing roller 3 rotate while being in contact with each other, and no slip occurs at the contact portion. Further, in the hopper 2, the developer supply rollers 4.5 are arranged substantially vertically and near the side of the development roller 3 and are arranged close to each other.
5 rotate in opposite directions (in FIG. 1, the developer supply roller 4 is in the direction of arrow A, and the developer supply roller 5 is in the direction of arrow B), so that the developer in the hopper 2
The sheet is transported in a direction toward the developing roller 3.

The developer adhered to the developing roller 3 is conveyed to the outside of the hopper 2 by the rotation of the developing roller 3, and the developer is partially scraped off by the developer regulating member 6, and the surface of the developing roller 3 is removed. A thin layer of developer having a uniform thickness is formed. The thin layer of the developer formed on the surface of the developing roller 3 adheres to the electrostatic latent image formed on the surface of the photoconductor 1 when the developing roller 3 comes into contact with the photoconductor 1, and the electrostatic latent image Are visualized.

The two developer supply rollers 4 and 5 are covered with a foaming elastic material such as a sponge roller having a good developer transportability around the rotation axis. The outer diameter is formed so that the diameter of one end is different from the diameter of the other end, and the outer diameter is a conical shape in which the diameter changes almost continuously from the one end to the other end. That is, the developer supply roller 4
The diameter of the larger diameter end (hereinafter referred to as a large diameter end) is C ₁ , the diameter of the smaller diameter end (hereinafter referred to as a small diameter end) is C ₂ , and C _1> is a C _2. Also,
The developer supply roller 5 has a large-diameter end having a diameter D ₁ , a small-diameter end having a diameter D ₂ , and D ₁ > D ₂ .

As shown in FIG. 2, the two developer supply rollers 4 and 5 are arranged such that their rotation axes are parallel and their large-diameter end and small-diameter end face each other. When the developer supply rollers 4 and 5 rotate in the opposite directions in this state, the developer supply rollers 4 and 5 rotate.
During the rotation of the developing roller 3
In addition to being transported in the direction toward (see FIG. 1), the developer transporting force acts along the axis from the large-diameter end to the small-diameter end of the developer supply roller. That is, the developer in the vicinity of the developer supply roller 4 receives the conveying force in the direction of arrow C, and the developer in the vicinity of the developer supply roller 5 moves in the direction of arrow D.
In the direction of.

As described above, the developer conveying force also acts in the direction from the large-diameter end to the small-diameter end of the developer supply roller for the following reason.

The two developer supply rollers 4 and 5 arranged as described above
Is rotated, as shown in FIG. 3, the developer between the developer supply rollers 4.5 is removed from the developer supply rollers 4.5.
And receives a conveying force F ′ in a direction substantially perpendicular to a plane including the two rotation axes. At this time, the developer supply rollers 4 and 5
The developer particles 7 in the vicinity of the conical surface receive a conveying force F in a direction substantially parallel to the conveying force F ′.

When the conveying force F acts in a direction to press the developer particles 7 against the developer supply rollers 4.5, as shown in FIG.
Component force F in the generatrix direction of the component force F ₁ of the conical surface, the direction normal to the contact surface of the conical side surfaces tangential component force F ₂ of the circle is a cross section of the conical surface, and the generatrix tangent Divided into _three . At this time, the component force F ₁ is applied to the developer supply roller 4.
5 acts in the direction from the large-diameter end to the small-diameter end, so that the developer particles 7 near the conical surface of the developer supply rollers 4.5 are separated from the large-diameter end of the developer supply rollers 4.5. Is conveyed in the direction toward the small-diameter end.

On the upper side of the developer supply rollers 4 and 5, a force acts in a direction of pressing the developer particles 7 against the developer supply rollers 4 and 5 by the weight of the developer. Also in this case, for the reasons described above, the component force in the generatrix direction of the conical surfaces of the developer supply rollers 4 and 5 acts in the direction from the large-diameter end to the small-diameter end of the developer supply rollers 4 and 5. The developer particles 7 are conveyed from the large-diameter ends of the developer supply rollers 4 and 5 toward the small-diameter ends.

At this time, on the small-diameter end side of the developer supply roller, the developer is conveyed from the center to the end in the rotation axis direction by the above-described operation, but the amount of the developer conveyed in the axial direction is Is substantially proportional to the surface area of the developer supply roller, so that the amount of the developer transported at the large-diameter end of the other developer supply roller disposed opposite to the other is larger. The developer inside is transported from the end to the center in the rotation axis direction of the developer supply rollers 4 and 5.

In the present embodiment, there is only one set of two conical developer supply rollers arranged so that the large-diameter end and the small-diameter end face each other.
It is also possible to make a plurality of sets. When the combination of the developer supply rollers is two or more, a certain 1
Different pairs of developer supply rollers may be shared. In this case, for example, by setting the taper of the conical surface of each developer supply roller, even if the number of developer supply rollers is an odd number, the transport amount of the developer in the axial direction can be adjusted.

As shown in FIG. 5, only one developer supply roller 8 may be used. At this time, the developer supply roller 8 is arranged near the side of the developing roller 3 and close to the developing roller 3.

When only one developer supply roller 8 is used, as shown in FIG. 6, the used developer supply roller 8 has a large diameter at the end and a small diameter at the center.
It becomes the shape which connected two truncated cones. That is, the developer supply roller 8 has two conical regions 8a, 8a having the smallest diameter at the center and gradually increasing in diameter from the center to both ends. The above two conical regions 8
The diameters E1 and E3 of the large-diameter end of the a.8a are almost equal,
Further, assuming that the diameter of the central portion (the diameter of the small diameter end of the conical region 8a) is E2, E1> E2 and E3> E2.

By rotating the developer supply roller 8 in one direction, for example, in the direction of arrow B in FIG. 5, the rotation direction is changed in the same manner as when the developer supply rollers 4 and 5 shown in FIG. 2 are used. In addition, the developer conveying force acts in the axial direction from both ends in the center direction, and it is possible to supply the developer uniformly and stably without aggregation in the axial direction.

In place of the developer supply roller 8, a developer supply roller 9 or 10 as shown in FIG. 7 or 8 can be used. The developer supply roller 9 shown in FIG. 7 has a cylindrical region 9b whose diameter does not change at the center thereof.
It has two conical regions 9a having a conical shape whose diameter gradually increases from the center to the end. In the developer supply roller 9, the diameter of the cylindrical region 9b is equal to the diameter of the small diameter end of the conical region 9a. Also according to the above configuration, the developer conveying force acts on the conical regions 9a in a direction (arrows C and D in FIG. 7) from the end to the center along the rotation axis. In this case, the developer is sent to the developing roller 3 in the cylindrical region 9b, and at the same time, the flow of the developer transport changes in the cylindrical region 9b, so that the developer can be more sufficiently stirred.

Further, the developer supply roller 10 shown in FIG. 8 has a stirring member 10b whose diameter does not change at the center thereof. Both ends of the stirring member 10b extend from the center to the end. It has two conical regions 10a, 10a having a conical shape whose diameter gradually increases. In the developer supply roller 10, the diameter of the stirring member 10b is larger than the diameter of the small diameter end of the conical region 10a.
In this case, the turning radius of the stirring member 10b is set to the conical region 10a.
Is larger than the radius of the small-diameter end portion, the stirring efficiency of the developer is increased, and the aggregation of the developer can be suppressed.

In this embodiment, the case where only one developer supply roller 8 to 10 is used is shown, but a plurality of developer supply rollers 8 to 10 may be provided. When a plurality of developer supply rollers are provided, the developer supply rollers 8 to 10 may be used in any combination. further,
The conical portions of the developer supply rollers 4 and 5 or the developer supply rollers 8 to 10 described in the present embodiment are:
It is not necessary to have a perfect conical shape, and it may be a substantially conical shape having a curved generatrix.

In addition to the above configuration, it is conceivable to apply a bias to the two developer supply rollers. In this case, charge injection into the developer becomes possible, and it becomes possible to carry the developer to the developing roller after precharging the developer. For example, in the structure shown in FIG. 1, the bias voltages applied to the developer supply rollers 4 and 5 are V ₁ and V ₂ , respectively, and the bias voltage applied to the development roller 3 is V ₃ .

Here, assuming that the charging polarity of the developer is positive, the polarity of the applied bias voltage is both positive and V ₁
By setting <V ₂ or V ₁ > V ₂ , charge injection is performed between the developer supply rollers 4 and 5. Further, V ₁ >
By setting V ₃ , V ₂ > V ₃ , the developer supply roller 4.
5 and the developing roller 3 generate an electrostatic force,
The developer is more efficiently supplied to the developing roller 3.

With the above configuration, in the developing device according to the present embodiment, since the developer supply roller has the conical area, the developer is conveyed from the large-diameter end to the small-diameter end of the conical area. You. That is, the developer of the hopper 2 is
In addition to being conveyed in the direction toward the developing roller 3, the developer is conveyed from the end to the center in the rotation axis direction of the developer supply roller, so that the developer can be uniformly supplied in the axial direction.
Further, since the developer in the hopper 2 is conveyed from the end to the center in the direction of the rotation axis of the developer supply roller, a phenomenon in which a large amount of the developer is collected at the end of the hopper 2 can be avoided. The reliability of the seal for preventing the problem is improved.

Further, in the developing device according to the present embodiment, a part of the force for pressing the developer particles 7 against the developer supply roller is transported to transport the developer particles 7 in the axial direction of the developer supply roller. Since the force is converted into a force, stress applied to the developer in the hopper 2 is reduced, and aggregation of the developer is suppressed. Further, for example, as compared with a conventional developing device that transports the developer in the axial direction by rotating the spiral member, the stress of the developer is further reduced, and the aggregation of the developer is suppressed.

When the developer is transported using two developer supply rollers, the rotation direction of the developer supply roller is reversed, and the developer in the hopper 2 moves in the direction toward the development roller 3. Aggregation of the developer can be suppressed by being conveyed. That is, since the developer can surely pass between the two developer supply rollers provided close to each other, the developer can be conveyed to the developing roller after the aggregation of the developer is released.

[0048]

As described above, in the developing device according to the first aspect of the present invention, at least one developer supply roller for supplying the developer to the developer carrier is provided in the developer reservoir. And each of the developer supply rollers is
In this configuration, the roller has a substantially conical portion in which the diameter of the roller changes continuously.

Therefore, the developer in the developer storage section is substantially conical in the substantially conical portion not only in the direction toward the developer carrier but also in the direction of the rotation axis of the developer supply roller. The transfer force is applied in a direction from the thick end to the thin end of the portion.

Thus, if the developer supply roller is provided with a conical portion having a narrow central portion and a thick end portion, the developer can be sufficiently supplied even in the central portion where the developer tends to be insufficient. And stable and uniform supply of the developer over the axial direction of the developer carrier.
This produces an effect that a stable high-quality copy image without a density gradient can be obtained. Further, since the developer in the developer storage is conveyed from the end to the center in the rotation axis direction of the developer supply roller, a phenomenon that a large amount of the developer is collected at the end of the developer storage can be avoided, and This also has the effect of improving the reliability of the seal for preventing leakage of the agent.

According to a second aspect of the present invention, as described above, in addition to the configuration of the first aspect, a plurality of the developer supply rollers are provided, and each of the developer supply rollers has one end. The developer supply roller has a substantially conical shape whose diameter is larger than the diameter of the other end, and the rotation axes of the developer supply rollers are substantially parallel, and the thicker end and the thinner end are arranged so as to face each other. And at least one set of developer supply rollers.

Therefore, in addition to the effect of the configuration of the first aspect, the developer in the developer storage section is moved not only in the direction toward the developer carrier by the rotation of the developer supply roller but also in the developer supply section. Also in the direction of the rotation axis of the roller, a conveying force is applied in a direction from the thick end to the thin end.

As a result, the developer can be supplied stably and uniformly in the axial direction of the developer carrying member, and an effect of obtaining a stable high-quality copy image without a density gradient can be obtained. Further, since the developer in the developer storage is conveyed from the end to the center in the direction of the rotation axis of the developer supply roller, it is possible to avoid a phenomenon that a large amount of developer collects at the end of the developer storage, and This also has the effect of improving the reliability of the seal for preventing leakage of the agent.

According to a third aspect of the present invention, as described above, in addition to the configuration of the first aspect, the developer supply roller has a substantially conical shape tapered from an end in the rotation axis direction toward the center. Are formed on both sides in the rotation axis direction.

Therefore, in addition to the effect of the first aspect, the developer in the developer storage section is moved not only in the direction toward the developer carrier by the rotation of the developer supply roller but also in the developer supply section. Also in the direction of the rotation axis of the roller, the roller receives a conveying force in a direction from the end to the center.

As a result, the developer can be supplied stably and uniformly in the axial direction of the developer carrying member, so that a stable and high-quality copy image having no density gradient can be obtained. Further, since the developer in the developer storage is conveyed from the end to the center in the direction of the rotation axis of the developer supply roller, it is possible to avoid a phenomenon that a large amount of developer collects at the end of the developer storage, and This also has the effect of improving the reliability of the seal for preventing leakage of the agent.

According to a fourth aspect of the present invention, as described above, in addition to the configuration of the third aspect, the developer supply roller is provided between the conical regions on both sides in the rotation axis direction. Is a configuration having a cylindrical region having a diameter equal to the diameter of the center side.

Therefore, in addition to the effect of the structure of the third aspect, the flow of the developer is changed by the central cylindrical region, so that the stirring efficiency is increased, whereby the aggregation of the developer can be suppressed. It works.

According to a fifth aspect of the present invention, as described above, in addition to the configuration of the third aspect, the center of the conical area is located between the conical areas on both sides in the rotation axis direction of the developer supply roller. This is a configuration in which a substantially cylindrical stirring member having a diameter larger than the diameter of the side is provided.

Therefore, in addition to the effect of the structure of the third aspect, the developer can be more efficiently stirred by the central stirring member, so that the aggregation of the developer can be suppressed.

[Brief description of the drawings]

FIG. 1 illustrates one embodiment of the present invention, and is a schematic configuration diagram illustrating a configuration of a developing device.

FIG. 2 is a perspective view illustrating an example of a developer supply roller used in the developing device.

FIG. 3 is an explanatory diagram showing a conveying force acting when the developer supply roller rotates.

FIG. 4 is an explanatory diagram showing a force acting on developer particles on the developer supply roller.

FIG. 5 illustrates another embodiment of the present invention, and is a schematic configuration diagram illustrating a configuration of a developing device.

FIG. 6 is a perspective view illustrating an example of a developer supply roller used in the developing device.

FIG. 7 is a perspective view showing another example of a developer supply roller used in the developing device.

FIG. 8 is a perspective view showing still another example of a developer supply roller used in the developing device.

FIG. 9 is a schematic configuration diagram illustrating a configuration of a conventional developing device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photoconductor (electrostatic latent image carrier) 2 hopper (developer storage unit) 3 developing roller (developer carrier) 4.5.8-10 developer supply roller 8a-10a conical area 9b cylindrical area 10b stirring member

Claims (5)

[Claims] The developer stored in a developer storage section is transported by a developer carrier, and the developer is adhered to an electrostatic latent image formed on the surface of the electrostatic latent image carrier to form the electrostatic latent image. In a developing device for visualizing an electro-latent image, at least one developer supply roller for supplying a developer to the developer carrier is provided in the developer reservoir, in proximity to the developer carrier. A developing device, wherein each of the developer supply rollers has a substantially conical portion in which the diameter of the roller changes continuously. 2. The image forming apparatus according to claim 1, further comprising a plurality of developer supply rollers, wherein each of the developer supply rollers has a substantially conical shape in which one end diameter is larger than the other end diameter. The image forming apparatus according to claim 1, further comprising at least one set of developer supply rollers whose rotation axes are substantially parallel and whose thick and thin ends face each other. 2. The developing device according to 1. 3. The developing device according to claim 1, wherein the developer supply roller has a substantially conical conical area on both sides which becomes narrower from an end in the rotation axis direction toward the center. 4. The developer supply roller according to claim 3, further comprising a cylindrical region between the conical regions on both sides in the rotation axis direction, the cylindrical region having a diameter equal to the diameter of the conical region on the center side.
The developing device as described in the above. 5. A substantially cylindrical agitating member having a diameter larger than a diameter of a center side of the conical area is provided between conical areas on both sides in the rotation axis direction of the developer supply roller. The developing device according to claim 3, wherein: