JPH05265324A - Developing device - Google Patents

Abstract

PURPOSE:To obtain a developing device provided with a replenishing means capable of separating a toner lump into individual toner grains and replenishing them, at low cost, in a reduced space. CONSTITUTION:The developing device developing a latent image on a latent image carrier 1 by using a two-component developer composed of toner and a carrier, and provided with a separator 40 separating the developer on the developer carrier 10, and circulating it to a developer housing room 50 and a toner replenishing mechanism 60 replenishing the toner into the developer in the developer housing room 50, an elastic plate 43 is provided in a location opposite to the toner replenishing part 61 of the toner replenishing mechanism 60, the toner replenished from the toner replenishing part 61 is collided with the elastic plate 43, and simultaneously, the toner after being collided is mixed with the developer flowing on the separator 40. Thus, the toner lump can be separated into individual grains and replenished, so that the static charge characteristic of the toner is improved, and the image of high image quality without having unevenness in a density and staining, can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used in an image forming apparatus such as a copying machine, a facsimile machine or a printer, and more particularly to a developing device using a two-component developer composed of toner and carrier.

[0002]

2. Description of the Related Art A developing device used in an image forming apparatus such as a copying machine, a facsimile or a printer develops a latent image on a latent image carrier such as a photoconductor using a two-component developer composed of toner and carrier. A developing device for visualizing is well known. Generally, in a developing device using a two-component developer, a developer consisting of a toner and a carrier is stirred by a stirring roller or the like in a developer accommodating chamber to charge the toner, and then the developer is carried and conveyed by the developing roller. , Electrostatically attracts toner to the electrostatic latent image on the photoreceptor to develop. Then, the developer after development is separated from the developing roller by the separator and circulated in the developer accommodating chamber. Further, in order to keep the toner concentration constant, a toner replenishing mechanism for replenishing the developer in the developer accommodating chamber is provided.

[0003]

In such a developing device, when the replenishment toner from the toner replenishing portion is replenished in the developer as a lump, it is not sufficiently stirred and remains on the developing roller as a lump. There is a problem in that the toner is conveyed and adsorbed to the latent image portion of the photoconductor to cause unevenness in printing density, or adheres to the photoconductor to cause scumming. Therefore, a technique of separating the lumps of toner into individual toner particles so that the toner and the carrier can efficiently contact each other in the developer becomes very important. Especially in a downsized developing device such as a disposable developing device, since the distance until the replenishment toner reaches the developing roller is short and the space is small, it is inevitable to reduce the diameter of the stirring roller. Since the ability is reduced and the ability to separate the toner lumps is also reduced, the density unevenness and the background stain as described above are likely to occur.

Conventionally, as a technique for solving the above problem, in a toner replenishing mechanism for replenishing the toner in the toner hopper with the toner replenishing roller into the developer in the developing device, the toner replenishing roller is a brush roller having a brush embedded therein. A toner replenishing mechanism has been proposed which is configured and is provided with a plate-shaped spring member that is in contact with the brush and separates a lump of toner falling from the toner replenishing roller into individual toner particles (Japanese Patent Laid-Open No. 64-42669). (See the official gazette).
However, in this toner replenishing mechanism, the toner replenishing roller is composed of a brush roller in which a brush is implanted, so that (1) the cost is high (the cost of the brush roller is high), and (2) the brush roller is arranged. There were problems such as taking up a lot of space. The present invention has been made in view of the above circumstances, and provides a developing device equipped with a toner replenishing means capable of separating a toner lump into individual toner particles and replenishing them at low cost and in a small space. Is the first purpose. A second object of the present invention is to provide a developing device which is provided with means for preventing an excessive amount of developer containing toner lumps from adhering to the developer bearing member, thereby preventing uneven density. And

[0005]

In order to achieve the above first object, in the invention of claim 1, a two-component developer comprising a toner and a carrier is carried by a developer carrier to a developing area.
A device that conveys and develops a latent image on a latent image carrier to visualize it, a separator that separates the developer on the developer carrier and circulates the developer in the developer accommodating chamber, and a developer in the developer accommodating chamber In a developing device having a toner replenishing mechanism for replenishing toner therein, an elastic plate member is provided at a position facing the toner replenishing section of the toner replenishing mechanism, and the replenishment toner from the toner replenishing section is made to collide with the elastic plate material. The toner after the collision is mixed with the developer flowing on the separator.

According to the second aspect of the invention, a two-component developer consisting of toner and carrier is carried and conveyed to a developing area by a developer carrier, and the latent image on the latent image carrier is developed and visualized. And a toner replenishing mechanism for replenishing the developer in the developer accommodating chamber with a separator for separating the developer on the developer carrier and circulating the developer in the developer accommodating chamber. , An elastic plate member is provided at a position facing the toner replenishing portion of the toner replenishing mechanism, and means for imparting vibration to the elastic plate member is provided, and the replenishment toner from the toner replenishing portion is collided with the elastic plate member and dropped after applying vibration. The toner is mixed with the developer flowing on the separator.

In the developing device of claim 3, the developing device of claim 2 is used.
In the developing device described above, a stirring roller that mixes and stirs the developer and the replenishment toner is provided, and a convex portion is provided at an end portion of the stirring roller, and the elastic portion is vibrated by the convex portion. .. Further, the developing device according to claim 4 is the developing device according to claim 2.
In the developing device described above, having ultrasonic vibration applying means,
Vibration is applied to the elastic plate material by the ultrasonic vibration applying means.

In order to achieve the second object, the invention according to claim 5
According to the invention, a two-component developer comprising a toner and a carrier is carried and conveyed to a development area by a developer carrier, and a latent image on the latent image carrier is developed and visualized. In a developing device equipped with a separator for separating the developer on the carrier and circulating it in the developer accommodating chamber, and a toner replenishing mechanism for replenishing the toner in the developer in the developer accommodating chamber, the developer carrier is The sleeve, a scooping pole (P ₃ pole) for scooping the developer in the developer accommodating chamber disposed in the developing sleeve onto the developing sleeve, and a main pole (P ₃ ) for forming a spike of the developer in the developing area. ₍₁ pole) and a magnet body forming each magnetic pole of a transport pole (P ₂ pole) for transporting the developer from the development area to the separator position, and the above-mentioned pumping pole (P ₃ pole) and transport pole (P ₂ pole) Magnetic force between poles is less than 50 G (Gauss) It is characterized by having done.

[0009]

In the developing device according to the first aspect of the present invention, the elastic plate member is provided at a position facing the toner replenishing unit, and the replenishment toner from the toner replenishing unit is caused to collide with the elastic plate member. It is possible to separate the lumps into individual toner particles and replenish them in the developer. Further, in the developing device of the second, third, and fourth aspects, since the elastic plate member is provided with the means for imparting vibration, the toner lumps are more effectively separated into individual toner particles and replenished in the developer. It becomes possible.

In the developing device of claim 5, the magnetic force between the pumping pole (P ₃ pole) and the transporting pole (P ₂ pole) of the developer carrying member is set to 50 G (gauss) or less, so that the pumping pole ( It is possible to prevent the excessive developer containing the toner lumps from being sucked onto the developing sleeve between the P ₃ pole) and the transport pole (P ₂ pole).

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to illustrated embodiments. FIG. 1 is a diagram showing an embodiment of the invention of claim 1, (a) is a schematic configuration diagram of an essential part showing an example of an image forming apparatus to which the present invention is applied, and (b) is (a). FIG. 3 is a perspective view of a main part of a toner supply unit of the developing device of the image forming apparatus shown in FIG. In FIG. 1, reference numeral 1 is a photosensitive drum that is an image bearing member, 2 is a developing device (developing unit), 3 is a cleaning device (cleaning unit), 110 is a charging charger, 120 is a transfer charger, and a copying process is executed. Then, the photosensitive drum 1 is rotated in the direction of the arrow, and the charging charger 11
After being charged by 0 and imagewise exposed by an exposing section (not shown), the developing section 2 develops the image. In addition, the transfer paper is fed from a paper feed cassette (not shown) of the paper feed unit at the same timing as the copying process and is conveyed to the transfer unit via the transfer conveyance unit. Then, after the transfer paper conveyed to the transfer unit is transferred with the image by the transfer charger 120,
It is separated from the photosensitive drum 1 by the separating section. And
After the image transfer, the photoconductor drum 1 continues to rotate, and the cleaning blade 80 of the cleaning unit 3 causes the photoconductor drum 1 to rotate.
The toner remaining on the top is removed, and the removed toner is stored in the storage portion 90. On the other hand, the transfer paper on which the image transfer is completed is conveyed to a fixing device (not shown) via a transfer paper conveying unit (not shown), the transfer image is fixed by the fixing device, and then discharged to the outside of the machine. .. In the case of the present embodiment, FIG.
As shown in (a), the photosensitive drum 1, the developing device (developing unit) 2, the cleaning device (cleaning unit) 3, and the charging charger 110 are integrated into a process magazine system, and the main body of the image forming apparatus is provided. On the other hand, it has a one-touch removable structure.

Next, the structure of the developing device (developing section) 2 will be described. In FIG. 1, a developing unit 2 is disposed in the vicinity of the photosensitive drum 1, and in the developing casing 2a of the developing unit 2, a developing sleeve 10 made of a cylindrical member as a developer carrying member is provided. A part of the developing sleeve 10 is exposed toward the photosensitive drum 1 side through an opening provided in the developing casing 2a. The developing sleeve 10 is made of a non-magnetic material such as aluminum in a hollow cylindrical shape.
A drive mechanism (not shown) is driven to rotate in the direction of the arrow, and a developing area is formed in a portion facing the photosensitive drum 1. Further, a magnet roller or a plurality of magnets are arranged in the developing sleeve 10, and magnetic poles P ₁ , P ₂ and P ₃ are formed at predetermined positions. Further, in the developer housing chamber (developer housing portion) 50 for housing the two-component developer consisting of toner and carrier in the developing casing 2a, the developer on the developing sleeve 10 is separated to be stored in the developer housing chamber 50. Circulating separator 40
And a stirring roller 30 for mixing and stirring the developer.

A toner cartridge (toner replenishing mechanism) 60 for replenishing toner is mounted on the developer accommodating chamber 50 side of the developing casing 2a, and the toner is replenished from the toner cartridge 60 to the developer accommodating chamber 50 (a replenishment method will be described later). The mixed toner is mixed and stirred with the developer by the stirring roller 30 in the developer storage chamber 50. The developer mixed and stirred by the stirring roller 30 is carried and carried on the developing sleeve 10 by the scooping pole (P ₃ pole) in the developing sleeve 10. The developer regulated to a certain amount by the developer amount regulating doctor 20 is used as the developing sleeve 1.
It is erected by the main pole (P ₁ pole) within 0, and the electrostatic latent image on the photosensitive drum 1 is visualized with toner by a so-called magnetic brush type developing system. Thereafter, the developer is transported by the transport electrode (P ₂ electrode) in the developing sleeve 10, and the sheet of the separator 40 (material such as polyester film) 4
It is scraped off from the developing sleeve 10 by 1 and circulated in the developer accommodating chamber 50.

Next, the toner supply section will be described. As shown in FIGS. 1 and 2, an agitator 70 having an elastic sheet 71 at its tip is provided in a cylindrical toner cartridge 60 containing replenishment toner, and the elastic sheet 71 at the tip is The agitator 70 is adapted to rotate while being pressed against the inner wall of the cartridge. Also,
An opening is provided in a slit shape at a replenishment position (toner replenishing portion) 61 on the cylinder of the toner cartridge 60, and the opening is provided outside by a polyester film 100 in which a plurality of small holes 101 are formed along the longitudinal direction of the opening. Is blocked from. Therefore, by rotating the agitator 70 in the toner cartridge 60 in the direction of the arrow in FIG. 2, the elastic sheet 71 at the tip of the agitator conveys the toner in a state of being in pressure contact with the inner wall of the cartridge, and the elastic sheet 71 causes the toner of the toner cartridge 60 to be conveyed. Due to the elastic force when passing through the step d of the opening in the replenishing portion 61, the toner is replenished so as to jump out from the small hole 101 having the diameter φ toward the developer accommodating chamber 50. That is, the elastic sheet 71 conveys the toner while being pressed against the inner wall of the cartridge by the rotation of the agitator 70.
As a result, the toner is released from the pressure contact state, and therefore the toner is repelled toward the small hole 101 by the elastic force at the time of opening. As a result, the toner is ejected from the small hole 101 toward the developer accommodating chamber 50.

The toner replenishing method of this system takes up less space and costs less than the replenishing method using the conventional toner replenishing roller, but the toner is forced from the small holes 101 to the elastic force of the elastic sheet 71. Since the toner is replenished by the toner, the toner is likely to be aggregated and replenished. Further, in the case of the integrated cartridge as in the present embodiment, the distance / time from the replenishment section until the replenishment toner reaches the developing area is short,
Since the stirring roller 30 has a relatively small diameter, the stirring ability between the carrier and the toner is small, and the ability to separate the toner from the lumps into individual particles is small. For this reason, the lump toner remains in the developer and is conveyed as it is onto the developing sleeve 10, so that an abnormal image such as uneven density or background stain is likely to occur. However, in order to use the brush roller for toner replenishment as disclosed in Japanese Patent Application Laid-Open No. 64-42669, (1) the cost is increased (especially, since the integrated cartridge is disposable, the cost should be kept low. Is important), and (2) there is no space for arranging the brush roller while ensuring the toner capacity.

Therefore, in the present invention, FIG. 1 (a), (b)
As shown in, the elastic plate member 43 is provided at a position facing the small hole 101 of the toner replenishing unit 61 of the separator 40. Further, the developer flowing on the separator 40 passes through the hole 44 provided in front of the elastic plate member 43 and the separator 4 is discharged.
The wall portion 42 extending downward from 0 is configured to flow in the direction of the arrow in FIG. With such a configuration, the replenishment toner jumped out from the small hole 101 of the toner replenishing portion 61 by the elastic force of the elastic sheet 71 collides with the elastic plate member 43, and one agglomerated toner is generated by the impact force at the time of collision. It is separated into one toner particle and falls downward due to gravity. Then, the dropped toner particles merge with the developer flowing through the separator 40 through the flow hole portion 44 and down the lower wall portion 42, and the stirring roller 3 in the developer accommodating chamber 50.
Mix and stir by 0. As a result, the replenishment toner is replenished to the developer as toner particles separated one by one, so that the toner and the carrier are efficiently brought into contact with each other during stirring, and the toner charging characteristic is also improved. That is,
By eliminating the above-mentioned problems and stabilizing the charging characteristics of the toner, it is possible to prevent the occurrence of density unevenness and scumming.

Next, an example in which the toner separation is promoted more positively will be described. FIG. 3 is a diagram showing an embodiment corresponding to claims 2 and 3, and in this embodiment, a vibration applying member 31 having a plurality of convex portions is provided at the end of the stirring roller 30 shown in FIG. The convex portion 32 contacts the end of the elastic plate material 43, and the rotation of the stirring roller 30 causes the convex portion 32 of the vibration imparting member 31 provided at the end of the elastic plate material 43 to repel the end portion of the elastic plate material 43 to give vibration. However, when the replenishment toner collides with the elastic plate member 43, a stronger impact is generated so that the replenishment toner can be separated into individual toner particles. FIG. 5 is a graph comparing the density unevenness occurrence rank in this embodiment with the density unevenness occurrence rank in the conventional example in which the elastic plate member 43 is not provided, and shows the effect of the present invention.

Next, FIG. 4 is a diagram showing an embodiment corresponding to claims 2 and 4, in which ultrasonic vibration applying means is provided, and the elastic plate member 4 is provided by the ultrasonic vibration applying means.
3 is an example in which vibration is applied to the replenishment toner so that the replenishment toner can be separated into individual toner particles by the impact and vibration when the replenishment toner collides with the elastic plate member 43. It is the same.

As described above, the elastic plate member is provided at a position facing the toner replenishing unit to collide the replenishment toner from the toner replenishing unit with the elastic plate member, so that the toner lumps are separated into individual toner particles by the impact force and vibration at the time of collision. I described the developing device that separated and replenished into the developer to prevent uneven density and scumming. Next, extra developer containing toner lumps adheres to the developer carrier. An embodiment of claim 5 will be described as a developing device in which density unevenness is prevented from occurring by means for preventing the above.

FIG. 6 is a schematic configuration diagram of an essential part showing an example of an image forming apparatus to which the invention of claim 5 is applied. In FIG. 6, components designated by the same reference numerals as those in FIG. 1A are similar components, and the configuration operation is as described above, and therefore the description thereof is omitted here. The structure of the toner replenishing mechanism is also the same as that shown in FIG. still,
The difference between FIG. 6 and FIG. 1A is that the separator plate 40 is not provided with the elastic plate member 43 in the apparatus of FIG. In FIG. 6, the developer carrying member 10 includes, as described above, a developing sleeve and a magnet roller or a plurality of magnets for forming the magnetic poles P ₁ , P ₂ , P ₃ at predetermined positions in the developing sleeve. It is configured. In this developer carrying member 10, the P ₁ pole is called the main pole and forms a spike in the developing region to contribute to visualization. The P ₂ pole is called a transport pole, and the developer is transported from the P ₁ pole in the developing area to the scraping position by the upper separator 40 by the magnetic force and the rotation of the developing sleeve against the gravity. The P ₃ pole is called a scooping pole, and scoops up the developer stirred in the developer accommodating chamber onto the developing sleeve.

By the way, the magnetic poles P ₁ , of the developer carrying member 10,
Force distributed by P _2, P ₃ is as shown in FIG. 8, in the illustrated example, N-pole P ₁ poles, but P _2, P ₃ poles are S poles, P ₂ poles and P ₃ Between the poles, there is a magnetic force that is naturally generated by the S pole of P ₂ pole and the S pole of P ₃ pole. on the other hand,
The toner replenished by the toner replenishing mechanism described with reference to FIG. 2 passes through the small holes 101 due to the elastic force of the elastic sheet 71, and thus is slightly lumped and blown off toward the developer accommodating chamber side. At this time, since the elastic plate member 43 is not provided in the apparatus example of FIG. 6, it falls to a point A in the developer accommodating chamber as shown in FIG. At this time, since the rotating direction of the stirring roller 30 is clockwise as shown by the arrow in the figure, most of the stirring roller 30 is carried by the stirring roller 30 and enters the developer in the developer accommodating chamber to be stirred. The toner is attracted to the point B on the developer carrying member 10 together with the carrier by the magnetic force between the P ₂ pole and the P ₃ pole. Then, the toner reaching the point B is conveyed by the rotation of the developing sleeve of the developer carrier 10, is mixed with the developer drawn up by the magnetic force of the P ₃ pole, and is conveyed to the developing area. In this case, since the developer in which the toner lumps are mixed is used for the development, density unevenness occurs in the image.

In this way, the P ₂ pole and P of the developer carrying member 10
₃ when the machining gap of a magnetic force is strong, there is an extra developer including the toner mass on the developing sleeve between the P ₂ poles and P ₃ pole is sucked, factors uneven density occurs one Become one
Therefore, when the relationship between the magnetic force between the P ₂ -P ₃ poles and the density unevenness is examined, as shown in FIG. 9, the magnetic force between the P ₂ -P ₃ poles is 50
It was found that the density unevenness rank can be increased by keeping the value below G (Gauss). Therefore, in the present invention, by setting the magnetic force between the P ₂ pole and the P ₃ pole of the developer carrier to be 50 G (gauss) or less, the P ₂ pole and P 3
It prevents the excessive developer containing toner lumps from being sucked onto the developing sleeve between the _three poles, and prevents the occurrence of density unevenness. In the present embodiment, the apparatus configuration of FIG. 6 has been described as an example, but if it is applied to the apparatus configuration of FIG. 1, uneven density can be further prevented.

[0023]

As described above, in the developing device according to the first aspect of the invention, the elastic plate member is provided at a position facing the toner replenishing unit, and the replenishment toner from the toner replenishing unit is made to collide with the elastic plate member, thereby causing a collision. Since it is possible to separate the toner lumps into individual toner particles and replenish them in the developer by the impact force or vibration at the time, the toner charging characteristics are improved even in the low-cost, space-saving toner replenishment system. In addition, it is possible to provide an image of high image quality without density unevenness or background stain. Further, in the developing device of the second, third, and fourth aspects, since the elastic plate member is provided with the means for imparting vibration, it becomes possible to more effectively separate and replenish the toner lumps into individual toner particles. It is possible to provide an image with high image quality, which has improved toner charging characteristics and is free from uneven density and background stains.

In the developing device of claim 5, the magnetic force between the pumping pole (P ₃ pole) and the transporting pole (P ₂ pole) of the developer carrier is set to 50 G (gauss) or less, so that the pumping pole is It is possible to prevent the excessive developer containing the toner lumps from being sucked onto the developing sleeve between the (P ₃ pole) and the transport pole (P ₂ pole). Therefore, it is possible to provide an image of high image quality without density unevenness or background stain.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the invention of claim 1;
(a) is a schematic configuration diagram of an essential part of an image forming apparatus to which the present invention is applied, and (b) is a perspective view of the essential part of a toner replenishing part of a developing device of the image forming device shown in (a). ..

FIG. 2 is an explanatory diagram of a toner replenishing mechanism of the developing device (developing section) shown in FIG.

FIG. 3 is a main part configuration diagram of a developing device showing an embodiment corresponding to claims 2 and 3.

FIG. 4 is a main part configuration diagram of a developing device showing an embodiment corresponding to claims 2 and 4.

5 is a density unevenness occurrence rank in the embodiment shown in FIG.
7 is a graph comparing the density unevenness occurrence ranks of a conventional example having no elastic plate material.

FIG. 6 is a schematic configuration diagram of an essential part showing an example of an image forming apparatus to which the invention of claim 5 is applied.

FIG. 7 is a schematic configuration diagram of a main part of a developing device portion of the image forming apparatus shown in FIG.

FIG. 8 is a diagram showing a magnetic force distribution of a developer carrying member of the developing device shown in FIGS. 6 and 7.

FIG. 9 is a diagram showing the relationship between magnetic force between P _{2 and} P ₃ poles and density unevenness.

[Explanation of Codes] 1 ... Photosensitive drum (latent image carrier) 2 ... Developing device 2a ... Developing casing 3 ... Cleaning device 10 ... Developer carrier (developing sleeve) 20. ..Doctor 30 ... Stirring roller 31 ... Vibration imparting member 32 ... Convex portion 40 ... Separator 41 ... Separator sheet portion 42 ... Separator lower wall portion 43 ... Elastic plate material 44 ... Separator hole 45 ... Ultrasonic vibration adding means 50 ... Developer accommodating chamber 60 ... Toner cartridge 61 ... Toner supply unit 70 ... Agitator 71 ... Elastic sheet 80・ ・ ・ Cleaning blade 100 ・ ・ ・ Polyester film 101 ・ ・ ・ Small hole 110 ・ ・ ・ Charging charger 120 ・ ・ ・ Transfer charger

Claims (5)

[Claims] 1. A device for developing and visualizing a latent image on a latent image carrier by carrying and transporting a two-component developer comprising a toner and a carrier to a development area by a developer carrier. In a developing device equipped with a separator for separating the developer on the developer carrier and circulating it in the developer accommodating chamber, and a toner replenishing mechanism for replenishing the toner in the developer in the developer accommodating chamber,
An elastic plate member is provided at a position facing the toner replenishing unit of the toner replenishing mechanism, collides the replenishment toner from the toner replenishing unit with the elastic plate member, and mixes the toner after the collision with the developer flowing on the separator. And developing device. 2. A device for developing and visualizing a latent image on a latent image carrier by carrying and transporting a two-component developer comprising a toner and a carrier to a development area by a developer carrier. In a developing device including a separator that separates the developer on the agent carrier and circulates the developer in the developer accommodating chamber and a toner replenishing mechanism for replenishing the toner in the developer in the developer accommodating chamber, the toner of the toner replenishing mechanism is used. An elastic plate member is provided at a position facing the replenishing unit, and means for imparting vibration to the elastic plate member is provided, and the replenishment toner from the toner replenishing unit is collided with the elastic plate member, and after the vibration is applied, the dropped toner flows on the separator. A developing device characterized by being mixed with a developer. 3. The developing device according to claim 2, further comprising a stirring roller for mixing and stirring the developer and the replenishment toner, the stirring roller having a convex portion at an end thereof, and the convex portion vibrates the elastic plate member. And a developing device. 4. The developing device according to claim 2, further comprising ultrasonic vibration applying means for applying vibration to the elastic plate member by the ultrasonic vibration applying means. 5. A device for developing and visualizing a latent image on a latent image carrier by carrying and transporting a two-component developer comprising a toner and a carrier by a developer carrier to a developing area. In a developing device including a separator for separating the developer on the agent carrier and circulating it in the developer chamber, and a toner replenishing mechanism for replenishing the toner in the developer chamber, the developer carrier is The developing sleeve, a pumping pole (P ₃ pole) for pumping the developer in the developer accommodating chamber, which is disposed in the developing sleeve, onto the developing sleeve, and a main pole (for forming a spike of the developer in the developing region). (P ₁ pole) and a magnet body forming each magnetic pole of a transport pole (P ₂ pole) for transporting the developer from the developing area to the separator position, and the above-mentioned pumping pole (P ₃ pole) and transport pole (P ₃ pole) Magnetic force between ₂ poles is 50 G (Gauss) or less A developing device characterized in that