JP2660050B2 - Developing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for forming an electrostatic latent image on an image carrier and developing the latent image.

[Conventional technology]

The magnetic brush developing method using a two-component developer having toner and magnetic particles (carrier) is a simple developing method that can perform stable development and is suitable for non-black or full-color developing, but the change in magnetic particle surface (spent) Toner, etc.).

Therefore, as a means for solving the above problem of the two-component magnetic brush developing method, the present applicant has proposed the invention of Japanese Patent Application Laid-Open No. Sho 62-153882.

The invention of Japanese Patent Application Laid-Open No. Sho 62-153882 is a developing device for developing an electrostatic latent image on an electrostatic latent image carrier as illustrated in FIG. 3, wherein toner particles 128 and magnetic particles 127 are developed. And a developer unit for supplying toner particles 128 to the electrostatic latent image carrier 1 facing the electrostatic latent image carrier 1 and forming a developing unit facing the electrostatic latent image carrier 1. A developer carrying member 21 that carries and transports the developer to the developing unit; and a tip of a regular portion that is located upstream of the developing unit in the rotation direction of the developer carrying member 21 and is separated from the surface of the developer carrying member. A developer regulating member 9 having: and a developer that has passed through the portion of the developer regulating member 9 and further has passed through the developing section and has been conveyed on the developer carrying member 21 at a downstream of the developing section. The developer is conveyed into the developer container 2, and the developer is conveyed to the developer container 2 by the developer regulating member 9. A developing device having a conveying stirring member (Sukuriyu) 23, 24 to be mixed with the inverted developer into container 21.

[Problems to be solved by the invention]

However, the order in the conventional example are taking a structure to prevent the developer deterioration by the developer that is naturally circulated in the developing container 21, S ₂ be each other great pains provided repelling pole S _2, S _3, S _Three
Since the circulation of the agent in the part is not effectively used, the conveyance and stirring in the axial direction cannot be sufficiently performed, and the toner concentration in the developer is biased, resulting in uneven image density and density gradient, resulting in a uniform image. It is difficult to get stable. Further, when a toner containing a resin such as a polyester resin is used for the purpose of obtaining a high-quality full-color image, the use of a toner having a volume average particle diameter of less than 12 μm particularly for the purpose of improving the image quality results in deterioration of the developer. As a result, there has been a problem that when image formation is performed for a long period of time, density reduction and fogging occur.

[Means for solving the problem]

The present invention solves the above-mentioned problems, and a developer container containing a developer having toner particles and magnetic particles, and a developing unit formed to face a latent image carrier that carries a latent image, and the developer is supplied from the container. A developer carrying member to be conveyed to the developing unit, a second magnetic pole provided in the developer carrying member and adjacent to the first magnetic pole and the first magnetic pole on the downstream side in the moving direction of the developer carrying member, and having the same polarity as the first magnetic pole; And a transport rotator for transporting and agitating the developer dropped from the developer carrying member between the first magnetic pole and the second magnetic pole. Both the normal magnetic field strength _Br and the tangential magnetic field strength B _θ have a low magnetic field area of 50 Gauss or less on the surface of the agent carrier, and the horizontal position at the center of this low magnetic field area is transported and rotated. Within the rotation range of the body and on the side of the latent image It is characterized in that the direction of rotation of the rotary body was set to the same direction as the rotational direction of the developer carrying member.

(Operation of the present invention)

With the above configuration, the developer conveyed from the developing unit is surely taken into the conveying member on the side closer to the developing unit of the developing stirring and conveying member, and forms a pool of the developer dropped from the developer carrier. Nothing. Further, the developer is sufficiently stirred with the developer being conveyed in the container by the conveying member, and is then pumped up by the second magnetic field generating means. Thus, the circulation of the agent becomes very efficient. For this reason, the conventional problems of image density unevenness and problems such as deterioration when image formation is performed for a long time are eliminated, and a high-definition image can be stably obtained for a long time. Was.

〔Example〕

An embodiment of the present inventor will be described below with reference to the accompanying drawings.

FIG. 1 is a longitudinal sectional view of a developing device according to the present invention, and FIG. 2 is a diagram supplementarily explaining the principle of agent circulation of FIG.

The developing device develops a latent image formed on a latent image carrier 1 such as a photoconductor or a dielectric by electrophotography, electrostatic recording, or the like. It includes a developing sleeve 21 as a developer carrier, a blade 9 as a developer layer regulating member, and the like. That is, an opening is formed in the developing container 2 at a position close to the latent image carrier 1, and the developing sleeve 21 is rotatably provided in this opening, and the developing sleeve 21 is provided above the developing sleeve 21. The blade 9 is attached with a predetermined gap.

Incidentally, the developing sleeve 21 is formed of a nonmagnetic material, at the time of developing operation rotates in a direction shown by the arrow, the inside is fixed a magnet 3 is magnetic field generating means, described later magnet 3 and the developing magnetic pole S ₁ pole N ₁ for conveying the developer 4, N ₂ has a magnetic pole N ₂ for pumping magnetic pole S ₂ for regulating, N _2, N ₃ in providing once stripped repulsion to be used for development recovered agent from the sleeve 3 . The blade 4 is made of a magnetic material such as SUS or aluminum, and is attached with a predetermined gap between the blade 4 and the surface of the developing sleeve 21 as described above. The amount of the developer 4 transported to the developer, specifically, the thickness of the developer on the developing sleeve 21 is regulated. Therefore, in this embodiment, both the non-magnetic toner and the magnetic particles pass between the tip of the blade 9 and the surface of the developing sleeve 21 and are sent to the developing unit.

By the way, inside the developing container 2, a developing chamber B is formed by the partition walls 14a, 14b and the opening 8 formed between the partition walls 14a, 14b in a direction perpendicular to the paper surface of FIG.
The toner supply port 13 is formed above the stirring chamber A, and an amount of toner corresponding to the amount of toner consumed through the supply port 13 is dropped into the stirring chamber A and supplied. Is done. Further, in the developing chamber B and the stirring chamber A, the developer 4
Is housed. Among the developers 4, a non-magnetic toner having an average volume particle size of 8 μm was used.

 Next, a method for measuring the particle size distribution in the present invention will be described.

As a measurement installation, a Coulter Counter TA-II type (manufactured by Coulter) was used, and an interface (manufactured by Nikkaki) for outputting a number average distribution and a volume average distribution and a CX-1 personal computer (manufactured by Canon) were connected. As the solution, a 1% aqueous NaCl solution is prepared using primary sodium chloride.

As a measurement method, 0.1 to 5 ml of a surfactant, preferably an alkylbenzene sulfonate, is added as a dispersant to 100 to 150 ml of the aqueous electrolytic solution, and 0.5 to 50 mg of a measurement sample is further added.

The electrolytic solution in which the sample was suspended was subjected to a dispersion treatment for about 1 to 3 minutes by an ultrasonic disperser, and a 100 μm aperture was used as the aperture by the Coulter Counter TA-II.
The particle size distribution of 4040 μm particles is measured to determine the volume average distribution. The volume average particle size is obtained from the obtained volume average distribution.

In the end of the front side and the rear side of the first view of the developing container 2, the partition wall 14a, not 14b is formed, as seen in Figure 5, stirred with the developing chamber S ₁ in this opposite end portions Room A
The openings 25 and 26 are formed so as to communicate with each other. The circulation of the developer 18 will be described with reference to FIG. 5, which is a schematic sectional view taken along the arrow direction in FIG. 1. Toner supplied from the toner supply port 13 is dropped into the stirring chamber A, The developer 8 is agitated by the first transporting means 23 (hereinafter referred to as a screw 23) and transported from left to right in the direction of the arrow.
Through the opening 25, it is delivered to the developing chamber s _2. The developing chamber S _2, be in substantially the same horizontal position as the Sukuriyu 23, while supplying the developer 8 which is passed through the opening 25 in the sleeve 21, is conveyed from right to left (arrow). The developer supplied to the sleeve 3 moves in the direction of the arrow with the rotation of the sleeve 3, and a thin layer is formed at a predetermined height by the cutting blade 9. As a result, the toner is consumed, and is recovered as it is in the developing device 2 with the rotation of the sleeve 3, conveyed by the screw 24, and contributes to development.

While the developer is circulated as described above, the rotary developing unit 11 rotates, and the toner of each color is developed.
Due to the centrifugal force of the rotation of the rotary developing unit 11, the developer 4 is pressed in the direction of the sleeve. However, the rotation of the sleeve 3 and the restriction of the cutting blade 9 and the carrier return 5 circulate as indicated by the arrow in the drawing. Yields
When the centrifugal force acts due to the rotation of the rotary developing unit 11 and the developer in the developing chamber A is likely to aggregate, the developer is discharged to the stirring chamber A as indicated by the arrow from the interval 8 between the partition walls 14a and 14b.
Aggregation and stress of the developer in the developing chamber A can be reduced. This also increases the developer circulation speed,
Even in solid development in which a large amount of toner is consumed, the toner supply is sufficiently performed,
Conversely, even if the development with a small amount of toner consumption is repeated, the toner charge gap can be reduced.

Here, the transport screw and the repulsion pole, which are the features of the present invention,
The relationship between N ₂ and N ₃ will be described.

As a result of conducting various experiments as a method to eliminate the inconvenience of inefficient circulation of the agent, we found that the positional relationship between the repulsive magnetic poles N ₂ and N ₃ and the stirring screw was very important. One is that the point where the force acting on the developer on the sleeve surface becomes almost zero is located before the rotation center of the stirring screw.

Conditions under which the force acting on the developer becomes almost zero include:
The vertical and horizontal magnetic flux densities on the sleeve surface are less than 50 Gauss. In the case of the configuration of the repulsion poles N ₁ and N ₂ , if the magnetic flux density in the vertical direction is near zero, the horizontal direction is also near zero, and the force acting on the developer there is almost zero. FIG. 2 is a diagram in which data of the magnetic flux density in the vertical direction of the sleeve surface is superimposed on the magnet portion of the developer.

According to the above description, since the force for restraining the developer on the sleeve at the point 11 becomes almost zero, the developer drops. The horizontal position of the center 11 of this low magnetic field region is within the rotation range of the screw 24, and on the latent image carrier side from the rotation center of the screw 24, and the screw 24 is in the C direction in the same direction as the rotation direction of the developer carrier. The developer can be sufficiently mixed and stirred with the developer inside the developing container without falling again on the developer used for development and dropped from the developer carrying member.

The following important is the position of the poles N ₂ scooping developer. The relationship between the force Fγ exerted on the sleeve acting on the sleeve surface and the magnetic flux density Bγ in the vertical direction on the sleeve surface is represented by the repulsion magnetic pole
In the vicinity of N ₃ and N ₂ , it was found that the results were almost the same from both the experiment and the simulation. Therefore, the vicinity of the maximum value 12 of the magnetic flux density Bγ in the vertical direction becomes the maximum value of Fγ, and the agent is pumped around this maximum value.
It is important to be behind the rotation center of the developing unit. If this position is before the center of rotation of the screw, the agent removed from the sleeve will be pumped again into the sleeve before being taken into the screw and will not have sufficient circulation.

The screw and repulsive magnetic poles N ₂ , N ₃
As a result, the circulation and stirring of the agent can be sufficiently performed, and a high-quality image can be stably obtained.

 Hereinafter, various conditions in this example will be described.

Photosensitive pair 1: OPC drum 80φ Sleeve 21: Forward movement with 32φ drum 280mm / sec Mag roll S pole inside sleeve S ₁ Bγ 1000 gauss Half width 35 ゜ S ₂ Bγ 790 gauss Half width 43 ゜ N ₁ Bγ 500 gauss Half width 32 ₂ N ₂ Bγ 500 Gauss Half width 38 ゜ N ₃ Bγ 500 Gauss Half width 38 As another embodiment, a developing device having the same configuration as that of the first embodiment except that the stirring assist member 16 is provided on the shafts of the screws 23 and 24 is described.

By providing the stirring assist member, it is possible to effectively take in the developer dropped at the point 11 in FIG. 2 and to pump up the developer to the point 12 in FIG. 2, which is an object of the present invention. The agent circulation can be performed more smoothly.

〔The invention's effect〕

As described above, by adopting the configuration of the magnetic pole arrangement and the screw arrangement in which the developer is completely removed from the sleeve before the rotation center of the stirring screw and the agent is pumped up behind the rotation center of the stirring screw. Even in a small developing device, sufficient circulation of the agent can be obtained, and even if the particle size is smaller than 12 μm in volume average with a toner such as polyester toner, a uniform image without unevenness can be obtained. It can be obtained stably for a long time.

[Brief description of the drawings]

FIG. 1 is a sectional view of a developing device according to an embodiment of the present invention, FIG. 2 is a view for explaining the principle of the embodiment of the present invention, FIG. 3 is a sectional view of a conventional developing device, and FIG. FIG. 5 is a view of the screw of FIG. 1 and a sleeve portion viewed from above, 1 is a latent image carrier, 3 is a magnet, 21 is a sleeve, and 23 and 24 are screws.

Claims (1)

(57) [Claims] An image forming apparatus includes: a developer container for storing a developer having toner particles and magnetic particles; and a developing unit formed opposite to a latent image carrier for carrying a latent image, and the developer is conveyed from the container to the developing unit. Member having a first magnetic pole provided in the developer holding member, and a second magnetic pole having the same polarity as the first magnetic pole, the first magnetic pole being adjacent to the first magnetic pole on the downstream side in the moving direction of the developer holding member. And a transport rotator that transports and agitates the developer dropped from the developer bearing member between the first magnetic pole and the second magnetic pole. The developer bearing surface between the first magnetic pole and the second magnetic pole. Both the normal magnetic field strength _Br and the tangential magnetic field strength _Bθ are 50
A low magnetic field region of Gauss or less, the horizontal position at the center of the low magnetic field region is within the rotation range of the transport rotator and the latent image carrier side of the rotation center of the transport rotator, and the rotation direction of the transport rotator is the developer. A developing device, wherein the rotating direction is the same as the rotating direction of the carrier.