JP2000066511A - Two-component system developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To optimize the arrangement of a developer stirring carrying member and a developer carrier by a magnetic pole arrangement which unnecessitates strict accuracy by specifying the positional relation between a stirring supplying member and the developer carrier and making the developer carrier have a magnetic field whose magnetic intensity in a specified direction is equal to or below a specified value a magnetic pole that is provided at the developer carrier and whose polarity is different. SOLUTION: A developer 34 is arranged to be separated by 2-5 mm from a first stirring member 36 at a position where it is raised by 40 deg.-70 deg. from the horizontal surface to the first stirring member 36. Magnetic poles (P4 pole and P5 pole) whose polarities are different from each other with respect to a line connecting the respective centers of the first stirring member 36 and the developing roller 34 are provided, and magnetic intensity in both horizontal and normal directions which is <=10 mT is provided on the upstream side of the rotation of the developing roller 34 of the P4 pole and the P5 pole. Here, the magnetic pole of the developing roller 34 is constituted of a P1 pole by which a developer is supplied, a P2 pole by which the developer is carried, a P3 pole by which the developer is stripped off, the P4 pole (S pole) by which the developer is attracted from the first stirring member 36 on the developer roller 34, the P5 pole (N pole) as a regulation magnetic pole and a P6 pole by which the developer is carried.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for developing an electrostatic latent image formed on an image carrier with a two-component developer in an image forming apparatus such as a printer, a facsimile, and a copying machine.

[0002]

2. Description of the Related Art In recent years, as image forming apparatuses have been reduced in size and space, it has become essential to reduce the size of each unit for image formation including a developing device. On the other hand, when developing a latent image formed by electrophotography, electrostatic recording, or the like, toner and carrier are used in terms of transferability, reproducibility of halftone, and stability of development characteristics with respect to temperature and humidity. Magnetic brush development using a two-component developer has become mainstream.

However, when the size of the developing device is reduced as described above, the developing device unit has a developer carrier (agent carrier, developing sleeve) for supplying toner to the opposing electrostatic latent image carrier. A developer stirring / conveying member for supplying the developer to the developer carrier with stirring, and a developer regulating member for regulating a layer thickness on the developer carrier, and an amount of developer accommodated therein. Is reduced as much as possible to suppress the unit volume, and a configuration in which the replenishment of the consumed toner is performed from an external toner magazine is adopted. In such a miniaturized developing device, it is difficult to sufficiently stir the replenished toner and the developer, and the toner concentration of the developer tends to be uneven, which tends to cause image density unevenness and density gradient. . Further, since the unit is small, the amount of the accommodated carrier is small, the deterioration with time is quick, and the concentration tends to decrease. When a toner containing a sharp-melt resin such as a polyester resin is used for the purpose of obtaining a high-quality full-color image, if a small toner is used, particularly for the purpose of improving the image quality, the developer deteriorates, and the image is deteriorated for a long time. When the formation is performed, there is a problem that the density is reduced and fog occurs.

[0004]

Therefore, for example, Japanese Patent No. 266050 proposes to regulate the rotation direction and magnetic force distribution of a developer stirring and conveying member (agent conveying member) and an agent carrier. This is because the strength of the magnetic field in the normal direction on the surface of the agent carrier between the first magnetic pole and the second magnetic pole adjacent to the first magnetic pole on the downstream side in the agent carrier moving direction and having the same polarity as the first magnetic pole. And the strength of the tangential magnetic field both have a low magnetic field region of 50 gauss or less, and the horizontal position at the center of this low magnetic field region is within the rotation range of the agent transport member and closer to the latent image carrier than the rotation center of the agent transport member. It is intended that the rotation direction of the agent transport member be the same as the rotation direction of the agent carrier.

However, in this proposed technique, it is not easy to pump up the developer to the developer carrier. In order to supply one side of the agent conveying member facing the agent carrier to the collection of the developer and the other side to supply the developer, in order to supply a large amount of the developer to the agent carrier, Accuracy is required for magnet arrangement. In view of the above-mentioned difficulties, the present invention realizes an appropriate arrangement of the developer stirring and conveying member and the developer carrier with a magnetic pole arrangement that does not require strict accuracy, and can obtain a stable quality image. It is an object to provide a developing device.

[0006]

According to the present invention, there is provided a developer carrier for visualizing a latent image, and a stirring / supplying member for supplying a developer to the developer carrier. In the two-component developing device comprising: the developer carrying member is positioned so as to be obliquely upward by 40 to 70 degrees with respect to the stirring and supplying member, and the distance between the developer carrying member and the stirring and supplying member is 2 mm to The developer carrier and the stirring and supply member are arranged so as to be 5 mm, and magnetic poles of different polarities are provided on the developer carrier with a line connecting each center of the developer carrier and the center of the stirring and supply member interposed therebetween. The problem can be solved by the developer carrier having a magnetic field having a magnetic force of 10 mT (millitesla) or less in the horizontal / normal direction on the upstream side in the rotation direction with respect to the magnetic pole.

It is preferable that the magnetic pole in the normal direction of the magnetic pole on the upstream side in the rotation direction among the magnetic poles of the different poles is not less than 30 mT and not more than 60 mT. It is also convenient that the magnetic pole in the normal direction of the magnetic pole on the downstream side in the rotational direction among the magnetic poles of the different poles is not less than 50 mT and not more than 80 mT.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described based on an example shown in the drawings. First, the entire photosensitive unit including the developing device according to the present invention will be described. In FIG. 1, a photosensitive member 1 serving as an electrostatic latent image carrier is charged uniformly on its surface by a charging roller 2, an electrostatic latent image is formed by exposure 4, and a toner image is formed by a developing unit 3. It has become. The toner image is transferred from the surface of the photoreceptor 1 to a transfer sheet by a transfer / separation unit (not shown). The transfer paper electrostatically attached to the photoconductor at the time of this transfer is separated from the photoconductor 1 by the separation discharge of the transfer separation section or the separation claw 6. The unfixed toner image on the transfer paper is fixed on the transfer paper by a fixing device (not shown).

On the other hand, the toner remaining on the photoreceptor without being transferred is scraped off by the cleaning blade 5,
The toner is collected by the developing unit 3 or a waste toner bottle (not shown) via the carry-out screw 7. The photoreceptor 1 from which the residual toner has been scraped off is initialized by the static elimination lamp 8 and used for the next image forming process. The photoconductor shutter 9 is configured to be openable and closable, and covers and protects the photoconductor 1 except when the photoconductor unit is set in the image forming apparatus main body (FIG. 1 shows the photoconductor). Is covered).

The structure of the developing section 3 will be described with reference to FIGS. The developing section 3 includes a developer carrying section 31 and a developer accommodating section 32. In the unused state, the developer carrying section 31 and the developer accommodating section 32 are separated by a seal member 33 provided therebetween. They are spatially separated (shown in FIG. 2 with the sealing member removed). The developer carrying section 31 includes a developing roller 34 which is a developer carrying body and a developing doctor 35 which controls a supply amount of the developer to the photoconductor. The developer accommodating section 32 stirs the developer and supplies the developer to the developing roller 34 with a first stirring member 36.
It comprises a second stirring member 37 and a toner concentration sensor 38 for magnetically detecting (permeability detection) the mixing ratio of toner and carrier in the developer, and contains a predetermined developer.
In this example, a developer composed of 50 μ carrier particles and 9 μ toner particles was used as the developer. However, the same applies to the case where the carrier particles have a size of 30 to 90 μ and the toner particles have a size of 5 to 10 μ. The result is derived.

Next, the vicinity of the photoconductor when the photoconductor unit is mounted on the image forming apparatus will be described.
As shown in FIG. 3, a toner hopper 10 for replenishing the consumed toner is provided on the side of the photoreceptor unit.
And the toner replenishing unit 11, and the above-described transfer separation unit 12 faces the photoreceptor 1 on the side opposite to the toner replenishing parts with respect to the photoreceptor unit. This transfer separation unit 1
Reference numeral 2 basically includes a transfer roller and a static elimination needle. A P sensor 13 serving as a toner density detection sensor is disposed closer to the developing roller 34 than the transfer / separation unit 12, and controls the toner supply to the developing unit based on the reflectance of the density pattern created on the photoconductor 1. ing. Therefore, the magnetic permeability detecting sensor 38 provided in the photoconductor unit
The toner supply is controlled by the value detected in step (1) and the value of the P sensor 13, and fresh toner is supplied from the toner supply unit 11 to the development unit via the toner hopper unit 10.

Referring to FIG. 4 showing details of the magnetic force, the configuration of the characteristic portion of the present invention will be exemplarily described. The developing roller 34 is disposed at a position rising from the horizontal plane by an angle θ with respect to the first stirring member 36 and separated from the first stirring member 36 by a distance δ. The magnetic force in the normal direction of the developing roller 34 by the built-in magnetic field generating means (magnet) is a P1 pole (developing magnetic pole, N pole) for supplying a developer for developing a latent image on the photoconductor, and a developer. A P2 pole (S pole) for transporting the developer to the storage section, a P3 pole for removing the developer on the developing roller with a magnetic force of 10 mT or less in both the horizontal and normal directions, and a first P3 pole.
P4 pole (S-pole), regulating magnetic pole P5 (N-pole) for adsorbing the developer onto the developing roller 34 from the stirring member 36,
It is composed of a P6 pole (S pole) for transporting the developer to one pole.

Various conditions in this embodiment are described below: Photoconductor 1: OPC drum φ30, rotation speed: 125 m
m / s Developing roller 34: φ16, rotation speed: 380 rpm Stirring member 36: screw type, φ19, rotation speed: 420r
pm, 12 mm pitch Magnetic force distribution: P1: magnetic force 83 mT, angle 7 ° P2: magnetic force 54 mT, angle 63 ° P3: magnetic force 4 mT, angle 114 ° P4: magnetic force 50 mT, angle 167 ° P5: magnetic force 60 mT, angle 235 ° P6: magnetic force 66mT, angle 306 °

The magnetic arrangement described above, that is, different magnetic poles (P4 pole and P5 pole in this embodiment) are provided for lines connecting the center of the developer stirring member and each center of the developing roller, A magnetic force of 10 mT or less in both the horizontal and normal directions is provided on the upstream side of rotation, and the distance between the developing roller and the developer stirring member is 2 to 5 mm and the inclination angle θ is 4
It has been found that the developer can be efficiently circulated at 0 to 70 degrees, in which the developer on the developing roller is peeled off and pumped up again.

In the above magnetic arrangement, when the distance between the developing roller and the developer stirring member was less than 2 mm, the positions were too close to each other and uneven developer supply of the stirring member appeared in the image. On the other hand, when the distance is more than 5 mm, it becomes difficult to sufficiently supply the developer to the developing roller, and a decrease in image density was confirmed.

Similarly, when the inclination angle is smaller than 40 degrees, the developer on the developing roller does not separate sufficiently, and the image density is reduced. On the other hand, if the angle is greater than 70 degrees, the amount of the developer attracted to the developing roller decreases, and the image density decreases. FIG. 5 shows these relationships.

In order to further increase the margin with respect to the above conditions, a study was conducted by focusing on the magnetic force of the P4 pole and the P5 pole facing the stirring member. As a result, the magnetic force of the P4 pole becomes 30
The margin was improved by setting the mT to 60 mT.
If the magnetic force of P4 is too low, the distance from the wall of the developer accommodating portion is increased (for example, 3 mm with respect to 2 mm in the embodiment).
As in the conventional case, the pumping of the developer tends to be insufficient, and if it is higher than 60 mT, the developer at the P3 pole is adsorbed, and the image density (ID) is reduced and pitch unevenness tends to occur.

With respect to the P5 pole, a margin of 50 mT to 80 mT improves the margin. If the magnetic force of P5 is too low, the pumping amount of the developer tends to be insufficient as described above.
If it is higher than 0 mT, the stress with the agent regulating member (doctor) is large, and the charge amount is increased, and as a result, a decrease in image density or pitch unevenness is likely to occur.

[0019]

According to the first aspect of the present invention, the developer carrying member is positioned so as to be obliquely upward by 40 to 70 degrees with respect to the stirring / supplying member for supplying the developer to the developer carrying member. And the distance between the developer carrier and the stirring / supplying member is 2 mm to 5 m.
m, and a magnetic pole having a different polarity is provided on the developer carrier with a line connecting the centers of the developer carrier and the stirring / supplying member interposed therebetween. The developer bearing member has a magnetic field having a magnetic force of 10 mT or less in the horizontal / normal direction on the upstream side in the rotation direction from the magnetic pole of, so that the magnetic force is stabilized without strictly restricting the magnetic force as in the related art. Images can be obtained.

The normal direction magnetic force of the magnetic pole on the upstream side in the rotational direction is 30 mT or more and 60 mT or less, and the normal magnetic force of the magnetic pole on the downstream side in the rotational direction is 50 mT or more and 80 mT or less. Thus, the above effect can be enhanced without being influenced by other factors such as the distance from the developer accommodating portion wall.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a photoconductor unit including a developing device according to the present invention.

FIG. 2 is a detailed configuration diagram of a developing device in FIG.

FIG. 3 is a detailed view of the vicinity of the photoconductor when the photoconductor unit of FIG. 1 is mounted on an image forming apparatus.

FIG. 4 is a diagram illustrating a magnetic force distribution of a developing roller.

FIG. 5 is a diagram illustrating a relationship between an angle and a distance between a stirring and conveying member and a developing roller.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoreceptor 31 Developer carrying part 32 Developer storing part 34 Developing roller 35 Developing doctor 36 First stirring member 37 Second stirring member

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Mizusawa 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Ken Amamiya 1-3-6 Nakamagome, Ota-ku, Tokyo Share Inside Ricoh Company (72) Inventor Toshitaka Yamaguchi 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Ricoh Company (72) Inventor Hideki Zennami 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Ricoh Company ( 72) Inventor Noriyuki Usui 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Mayumi Ohori 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (72) Invention Person Kenzo Tatsumi 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. (Reference) 2H031 AB01 AC08 AC14 AC19 AC20 BA04 BC03 2H077 AA11 AB18 AD02 AD06 DA1 0 DA54 DB02 EA03

Claims (3)

[Claims] 1. A two-component developing apparatus comprising: a developer carrier for visualizing a latent image; and a stirring supply member for supplying a developer to the developer carrier. The developer carrier is positioned so as to be obliquely upward by 40 to 70 degrees with respect to the supply member, and the developer carrier is agitated and supplied so that the distance between the developer carrier and the agitation supply member is 2 to 5 mm. A member is disposed, and a magnetic pole of a different polarity is provided on the developer carrier with a line connecting each center of the developer carrier and the center of the stirring / supplying member. Magnetic force in the normal direction is 1
A developing device, wherein the developer carrier has a magnetic field of 0 mT or less. 2. The developing device according to claim 1, wherein the magnetic pole in the normal direction of the magnetic pole on the upstream side in the rotation direction among the different magnetic poles is 30 mT or more and 60 mT or less. 3. The developing device according to claim 1, wherein the magnetic pole in the normal direction of the magnetic pole on the downstream side in the rotation direction among the magnetic poles of the different polarities is not less than 50 mT and not more than 80 mT.